Astronomers at the University of California, Riverside, have discovered that powerful winds driven by supermassive black holes in the centers of dwarf galaxies have a significant impact on the evolution of these galaxies by suppressing star formation.
Dwarf galaxies are small galaxies that contain between 100 million to a few billion stars. In contrast, the Milky Way has 200-400 billion stars. Dwarf galaxies are the most abundant galaxy type in the universe and often orbit larger galaxies.
The team of three astronomers was surprised by the strength of the detected winds.
"We expected we would need observations with much higher resolution and sensitivity, and we had planned on obtaining these as a follow-up to our initial observations," said Gabriela Canalizo, a professor of physics and astronomy at UC Riverside, who led the research team. "But we could see the signs strongly and clearly in the initial observations. The winds were stronger than we had anticipated."
Canalizo explained that astronomers have suspected for the past couple of decades that supermassive black holes at the centers of large galaxies can have a profound influence on the way large galaxies grow and age.
"Our findings now indicate that their effect can be just as dramatic, if not more dramatic, in dwarf galaxies in the universe," she said.
Study results appear in The Astrophysical Journal.
The researchers, who also include Laura V. Sales, an assistant professor of physics and astronomy; and Christina M. Manzano-King, a doctoral student in Canalizo's lab, used a portion of the data from the Sloan Digital Sky Survey, which maps more than 35% of the sky, to identify 50 dwarf galaxies, 29 of which showed signs of being associated with black holes in their centers. Six of these 29 galaxies showed evidence of winds -- specifically, high-velocity ionized gas outflows -- emanating from their active black holes.
"Using the Keck telescopes in Hawaii, we were able to not only detect, but also measure specific properties of these winds, such as their kinematics, distribution, and power source -- the first time this has been done," Canalizo said. "We found some evidence that these winds may be changing the rate at which the galaxies are able to form stars."
Manzano-King, the first author of the research paper, explained that many unanswered questions about galaxy evolution can be understood by studying dwarf galaxies.
"Larger galaxies often form when dwarf galaxies merge together," she said. "Dwarf galaxies are, therefore, useful in understanding how galaxies evolve. Dwarf galaxies are small because after they formed, they somehow avoided merging with other galaxies. Thus, they serve as fossils by revealing what the environment of the early universe was like. Dwarf galaxies are the smallest galaxies in which we are directly seeing winds -- gas flows up to 1,000 kilometers per second -- for the first time."
Manzano-King explained that as material falls into a black hole, it heats up due to friction and strong gravitational fields and releases radiative energy. This energy pushes ambient gas outward from the center of the galaxy into intergalactic space.
"What's interesting is that these winds are being pushed out by active black holes in the six dwarf galaxies rather than by stellar processes such as supernovae," she said. "Typically, winds driven by stellar processes are common in dwarf galaxies and constitute the dominant process for regulating the amount of gas available in dwarf galaxies for forming stars."
Astronomers suspect that when wind emanating from a black hole is pushed out, it compresses the gas ahead of the wind, which can increase star formation. But if all the wind gets expelled from the galaxy's center, gas becomes unavailable and star formation could decrease. The latter appears to be what is occurring in the six dwarf galaxies the researchers identified.
"In these six cases, the wind has a negative impact on star formation," Sales said. "Theoretical models for the formation and evolution of galaxies have not included the impact of black holes in dwarf galaxies. We are seeing evidence, however, of a suppression of star formation in these galaxies. Our findings show that galaxy formation models must include black holes as important, if not dominant, regulators of star formation in dwarf galaxies."
Next, the researchers plan to study the mass and momentum of gas outflows in dwarf galaxies.
"This would better inform theorists who rely on such data to build models," Manzano-King said. "These models, in turn, teach observational astronomers just how the winds affect dwarf galaxies. We also plan to do a systematic search in a larger sample of the Sloan Digital Sky Survey to identify dwarf galaxies with outflows originating in active black holes."
Read more at Science Daily
Oct 12, 2019
Drug reverses signs of liver disease in people living with HIV
Researchers at the National Institutes of Health and their colleagues at Massachusetts General Hospital (MGH) in Boston report that the injectable hormone tesamorelin reduces liver fat and prevents liver fibrosis (scarring) in people living with HIV. The study was conducted by the National Institute of Allergy and Infectious Diseases (NIAID) and the National Cancer Institute, both parts of NIH. The findings were published online today in The Lancet HIV.
"Many people living with HIV have overcome significant obstacles to live longer, healthier lives, though many still experience liver disease," said NIAID Director Anthony S. Fauci, M.D. "It is encouraging that tesamorelin, a drug already approved to treat other complications of HIV, may be effective in addressing non-alcoholic fatty liver disease."
Non-alcoholic fatty liver disease, or NAFLD, frequently occurs alongside HIV, affecting as many as 25% of people living with HIV in the developed world. However, no effective treatments currently exist to treat the condition, which is a risk factor for progressive liver disease and liver cancer. Investigators led by Colleen M. Hadigan, M.D., senior research physician in NIAID's Laboratory of Immunoregulation, and Steven K. Grinspoon, M.D., Chief of the Metabolism Unit at MGH, tested whether tesamorelin could decrease liver fat in men and women living with both HIV and NAFLD. Among the participants enrolled, 43% had at least mild fibrosis, and 33% met the diagnostic criteria for a more severe subset of NAFLD called nonalcoholic steatohepatitis (NASH). Thirty-one participants were randomized to receive daily 2-mg injections of tesamorelin, and 30 were randomized to receive identical-looking injections containing a placebo. Researchers provided nutritional counseling to all participants, as well as training in self-administering the daily injections. Researchers then compared measures of liver health in both groups at baseline and 12 months.
After one year, participants receiving tesamorelin had better liver health than those receiving placebo, as defined by reduction in hepatic fat fraction (HFF) -- the ratio of fat to other tissue in the liver. The healthy range for HFF is less than 5%. Thirty-five percent of study participants receiving tesamorelin achieved a normal HFF, while only 4% of those on placebo reached that range with nutritional advice alone. Overall, tesamorelin was well-tolerated and reduced participants' HFF by an absolute difference of 4.1% (corresponding to a 37% relative reduction from the beginning of the study). While nine participants receiving placebo experienced onset or worsening of fibrosis, only two participants in the tesamorelin group experienced the same. Additionally, levels of several blood markers associated with inflammation and liver damage -- including the enzyme alanine aminotransferase (ALT) -- decreased more among those taking tesamorelin compared to those on a placebo, particularly among those with increased levels at the beginning of the study.
Given these positive results, investigators suggest expanding the indication for tesamorelin to include people living with HIV who have been diagnosed with NAFLD. They also recommend additional research to determine if tesamorelin could contribute to long-term protection against serious liver disease in people without HIV.
"Our hope is that this intervention may help people living with HIV, as well as benefit HIV-negative people with liver abnormalities," said Dr. Hadigan. "Further research may inform us of the potential long-term benefits of this approach and develop formulations that can benefit everyone with liver disease, regardless of HIV status."
Egrifta (tesamorelin) was approved in 2010 by the U.S. Food and Drug Administration to reduce excess abdominal fat in HIV patients with lipodystrophy -- a complication characterized by an abnormal distribution of body fat initially associated with older classes of HIV medications. The most commonly reported side effects in previous clinical trials evaluating Egrifta included joint pain (arthralgia), skin redness and rash at the injection site (erythema and pruritis), stomach pain, swelling, and muscle pain (myalgia). Worsening blood sugar control occurred more often in trial participants treated with Egrifta than with placebo.
"Because tesamorelin proved effective in treating abnormal fat build-up in the abdomens of people in the context of HIV and related medication use, we hypothesized that the drug might also reduce fat that accrues in the liver and causes damage in a similar population," said Dr. Grinspoon.
While liver disease is often associated with heavy alcohol use, NAFLD occurs when excess fat builds up in the liver without alcohol as a contributing factor. This condition may progress to liver damage, cirrhosis or cancer that could be life-threatening and necessitate liver transplantation.
Read more at Science Daily
"Many people living with HIV have overcome significant obstacles to live longer, healthier lives, though many still experience liver disease," said NIAID Director Anthony S. Fauci, M.D. "It is encouraging that tesamorelin, a drug already approved to treat other complications of HIV, may be effective in addressing non-alcoholic fatty liver disease."
Non-alcoholic fatty liver disease, or NAFLD, frequently occurs alongside HIV, affecting as many as 25% of people living with HIV in the developed world. However, no effective treatments currently exist to treat the condition, which is a risk factor for progressive liver disease and liver cancer. Investigators led by Colleen M. Hadigan, M.D., senior research physician in NIAID's Laboratory of Immunoregulation, and Steven K. Grinspoon, M.D., Chief of the Metabolism Unit at MGH, tested whether tesamorelin could decrease liver fat in men and women living with both HIV and NAFLD. Among the participants enrolled, 43% had at least mild fibrosis, and 33% met the diagnostic criteria for a more severe subset of NAFLD called nonalcoholic steatohepatitis (NASH). Thirty-one participants were randomized to receive daily 2-mg injections of tesamorelin, and 30 were randomized to receive identical-looking injections containing a placebo. Researchers provided nutritional counseling to all participants, as well as training in self-administering the daily injections. Researchers then compared measures of liver health in both groups at baseline and 12 months.
After one year, participants receiving tesamorelin had better liver health than those receiving placebo, as defined by reduction in hepatic fat fraction (HFF) -- the ratio of fat to other tissue in the liver. The healthy range for HFF is less than 5%. Thirty-five percent of study participants receiving tesamorelin achieved a normal HFF, while only 4% of those on placebo reached that range with nutritional advice alone. Overall, tesamorelin was well-tolerated and reduced participants' HFF by an absolute difference of 4.1% (corresponding to a 37% relative reduction from the beginning of the study). While nine participants receiving placebo experienced onset or worsening of fibrosis, only two participants in the tesamorelin group experienced the same. Additionally, levels of several blood markers associated with inflammation and liver damage -- including the enzyme alanine aminotransferase (ALT) -- decreased more among those taking tesamorelin compared to those on a placebo, particularly among those with increased levels at the beginning of the study.
Given these positive results, investigators suggest expanding the indication for tesamorelin to include people living with HIV who have been diagnosed with NAFLD. They also recommend additional research to determine if tesamorelin could contribute to long-term protection against serious liver disease in people without HIV.
"Our hope is that this intervention may help people living with HIV, as well as benefit HIV-negative people with liver abnormalities," said Dr. Hadigan. "Further research may inform us of the potential long-term benefits of this approach and develop formulations that can benefit everyone with liver disease, regardless of HIV status."
Egrifta (tesamorelin) was approved in 2010 by the U.S. Food and Drug Administration to reduce excess abdominal fat in HIV patients with lipodystrophy -- a complication characterized by an abnormal distribution of body fat initially associated with older classes of HIV medications. The most commonly reported side effects in previous clinical trials evaluating Egrifta included joint pain (arthralgia), skin redness and rash at the injection site (erythema and pruritis), stomach pain, swelling, and muscle pain (myalgia). Worsening blood sugar control occurred more often in trial participants treated with Egrifta than with placebo.
"Because tesamorelin proved effective in treating abnormal fat build-up in the abdomens of people in the context of HIV and related medication use, we hypothesized that the drug might also reduce fat that accrues in the liver and causes damage in a similar population," said Dr. Grinspoon.
While liver disease is often associated with heavy alcohol use, NAFLD occurs when excess fat builds up in the liver without alcohol as a contributing factor. This condition may progress to liver damage, cirrhosis or cancer that could be life-threatening and necessitate liver transplantation.
Read more at Science Daily
Oct 11, 2019
The Milky Way kidnapped several tiny galaxies from its neighbor
Just like the moon orbits the Earth, and the Earth orbits the sun, galaxies orbit each other according to the predictions of cosmology.
For example, more than 50 discovered satellite galaxies orbit our own galaxy, the Milky Way. The largest of these is the Large Magellanic Cloud, or LMC, a large dwarf galaxy that resembles a faint cloud in the Southern Hemisphere night sky.
A team of astronomers led by scientists at the University of California, Riverside, has discovered that several of the small -- or "dwarf" -- galaxies orbiting the Milky Way were likely stolen from the LMC, including several ultrafaint dwarfs, but also relatively bright and well-known satellite galaxies, such as Carina and Fornax.
The researchers made the discovery by using new data gathered by the Gaia space telescope on the motions of several nearby galaxies and contrasting this with state-of-the-art cosmological hydrodynamical simulations. The UC Riverside team used the positions in the sky and the predicted velocities of material, such as dark matter, accompanying the LMC, finding that at least four ultrafaint dwarfs and two classical dwarfs, Carina and Fornax, used to be satellites of the LMC. Through the ongoing merger process, however, the more massive Milky Way used its powerful gravitational field to tear apart the LMC and steal these satellites, the researchers report.
"These results are an important confirmation of our cosmological models, which predict that small dwarf galaxies in the universe should also be surrounded by a population of smaller fainter galaxy companions," said Laura Sales, an assistant professor of physics and astronomy, who led the research team. "This is the first time that we are able to map the hierarchy of structure formation to such faint and ultrafaint dwarfs."
The findings have important implications for the total mass of the LMC and also on the formation of the Milky Way.
"If so many dwarfs came along with the LMC only recently, that means the properties of the Milky Way satellite population just 1 billion years ago were radically different, impacting our understanding of how the faintest galaxies form and evolve," Sales said.
Study results appear in the November 2019 issue of the Monthly Notices of the Royal Astronomical Society.
Dwarf galaxies are small galaxies that contain anywhere from a few thousand to a few billion stars. The researchers used computer simulations from the Feedback In Realistic Environments project to show the LMC and galaxies similar to it host numerous tiny dwarf galaxies, many of which contain no stars at all -- only dark matter, a type of matter scientists think constitutes the bulk of the universe's mass.
"The high number of tiny dwarf galaxies seems to suggest the dark matter content of the LMC is quite large, meaning the Milky Way is undergoing the most massive merger in its history, with the LMC, its partner, bringing in as much as one third of the mass in the Milky Way's dark matter halo -- the halo of invisible material that surrounds our galaxy," said Ethan Jahn, the first author of the paper and a graduate student in Sales' research group.
Jahn explained that the number of tiny dwarf galaxies the LMC hosts may be higher than astronomers previously estimated, and that many of these tiny satellites have no stars.
"Small galaxies are hard to measure, and it's possible that some already-known ultrafaint dwarf galaxies are in fact associated with the LMC," he said. "It's also possible that we will discover new ultrafaints that are associated with the LMC."
Dwarf galaxies can either be satellites of larger galaxies, or they can be "isolated," existing on their own and independent of any larger object. The LMC used to be isolated, Jahn explained, but it was captured by the gravity of the Milky Way and is now its satellite.
"The LMC hosted at least seven satellite galaxies of its own, including the Small Magellanic Cloud in the Southern Sky, prior to them being captured by the Milky Way," he said.
Next, the team will study how the satellites of LMC-sized galaxies form their stars and how that relates to how much dark matter mass they have.
Read more at Science Daily
For example, more than 50 discovered satellite galaxies orbit our own galaxy, the Milky Way. The largest of these is the Large Magellanic Cloud, or LMC, a large dwarf galaxy that resembles a faint cloud in the Southern Hemisphere night sky.
A team of astronomers led by scientists at the University of California, Riverside, has discovered that several of the small -- or "dwarf" -- galaxies orbiting the Milky Way were likely stolen from the LMC, including several ultrafaint dwarfs, but also relatively bright and well-known satellite galaxies, such as Carina and Fornax.
The researchers made the discovery by using new data gathered by the Gaia space telescope on the motions of several nearby galaxies and contrasting this with state-of-the-art cosmological hydrodynamical simulations. The UC Riverside team used the positions in the sky and the predicted velocities of material, such as dark matter, accompanying the LMC, finding that at least four ultrafaint dwarfs and two classical dwarfs, Carina and Fornax, used to be satellites of the LMC. Through the ongoing merger process, however, the more massive Milky Way used its powerful gravitational field to tear apart the LMC and steal these satellites, the researchers report.
"These results are an important confirmation of our cosmological models, which predict that small dwarf galaxies in the universe should also be surrounded by a population of smaller fainter galaxy companions," said Laura Sales, an assistant professor of physics and astronomy, who led the research team. "This is the first time that we are able to map the hierarchy of structure formation to such faint and ultrafaint dwarfs."
The findings have important implications for the total mass of the LMC and also on the formation of the Milky Way.
"If so many dwarfs came along with the LMC only recently, that means the properties of the Milky Way satellite population just 1 billion years ago were radically different, impacting our understanding of how the faintest galaxies form and evolve," Sales said.
Study results appear in the November 2019 issue of the Monthly Notices of the Royal Astronomical Society.
Dwarf galaxies are small galaxies that contain anywhere from a few thousand to a few billion stars. The researchers used computer simulations from the Feedback In Realistic Environments project to show the LMC and galaxies similar to it host numerous tiny dwarf galaxies, many of which contain no stars at all -- only dark matter, a type of matter scientists think constitutes the bulk of the universe's mass.
"The high number of tiny dwarf galaxies seems to suggest the dark matter content of the LMC is quite large, meaning the Milky Way is undergoing the most massive merger in its history, with the LMC, its partner, bringing in as much as one third of the mass in the Milky Way's dark matter halo -- the halo of invisible material that surrounds our galaxy," said Ethan Jahn, the first author of the paper and a graduate student in Sales' research group.
Jahn explained that the number of tiny dwarf galaxies the LMC hosts may be higher than astronomers previously estimated, and that many of these tiny satellites have no stars.
"Small galaxies are hard to measure, and it's possible that some already-known ultrafaint dwarf galaxies are in fact associated with the LMC," he said. "It's also possible that we will discover new ultrafaints that are associated with the LMC."
Dwarf galaxies can either be satellites of larger galaxies, or they can be "isolated," existing on their own and independent of any larger object. The LMC used to be isolated, Jahn explained, but it was captured by the gravity of the Milky Way and is now its satellite.
"The LMC hosted at least seven satellite galaxies of its own, including the Small Magellanic Cloud in the Southern Sky, prior to them being captured by the Milky Way," he said.
Next, the team will study how the satellites of LMC-sized galaxies form their stars and how that relates to how much dark matter mass they have.
Read more at Science Daily
Sharing data for improved forest protection and monitoring
Although the mapping of aboveground biomass is now possible with satellite remote sensing, these maps still have to be calibrated and validated using on-site data gathered by researchers across the world. IIASA contributed to the establishment of a new global database to support Earth Observation and encourage investment in relevant field-based measurements and research.
Forest biomass is an essential indicator for monitoring the Earth's ecosystems and climate. It also provides critical input to greenhouse gas accounting, estimation of carbon losses and forest degradation, assessment of renewable energy potential, and for developing climate change mitigation policies. Although satellite remote sensing technology now allows researchers to produce extensive maps of aboveground biomass, these maps still require reliable, up-to-date, on-site data for calibration and validation. Collecting data in the field by measuring trees and documenting species is, however, a very labor intensive, expensive, and time-consuming exercise and it would therefore make sense to bring together the many extant data sets to provide real added value for a number of applications. In terms of policy applications, doing so can also lead to improved biomass products and better monitoring of forest resources, which could in turn lead to more effective forest protection measures.
In a new paper published in the journal Scientific Data, 143 researchers involved in this type of data collection in the field, explored whether it was possible to build a network that openly shares their data on biomass for the benefit of different communities. They particularly wanted to see if they could bring together as much on-site data on biomass as possible to prepare for new satellite missions, such as the European Space Agency's BIOMASS mission, with a view to improving the accuracy of current remote sensing based products, and developing new synergies between remote sensing and ground-based ecosystem research communities. Their efforts have resulted in the establishment of the Forest Observation System (FOS) -- an international, collaborative initiative that aims to establish a global on-site forest aboveground biomass database to support Earth Observation and to encourage investment in relevant field-based measurements and research.
"Keeping in mind that this paper is a data descriptor and not a conventional paper with hypotheses, the whole idea behind this study is a new open database on biomass data. This is important for the following reasons: First, it represents a way to link the ecological/forestry and remote sensing communities. It also overcomes existing data sharing barriers, while promoting data sharing beyond small, siloed communities. Lastly, it provides recognition to the people working in the field, including those who collect the data, which is why there are 143 coauthors on this paper, as they are all contributors to the database," explains study lead author Dmitry Shchepashchenko, a researcher in the IIASA Ecosystems Services and Management Program.
The researchers collected data from 1,645 permanent forest sample plots from 274 locations distributed around the globe. This data has now been made available for download via the FOS website. The initiative represents the first attempt at bringing this type of data together from different networks in a single location. The researchers point out that their work in this regard is ongoing and there are plans to continue adding more data sets and networks to the FOS. In addition to promoting data sharing, the system also promotes a new leading network on biomass data (through the FOS), which IIASA is leading and will continue to grow into the future.
Apart from the obvious benefits that data sharing hold for the scientific community, the data are also essential for training various models at IIASA such as the BioGeoChemistry Management Model (BGC-MAN) and the Global Forest Model (G4M). Several on-going IIASA projects, as well as other ecological-, biophysical-, and economic models and projects outside of IIASA will also benefit, which means that providing access to the data can improve models and understanding of biomass more generally.
Read more at Science Daily
Forest biomass is an essential indicator for monitoring the Earth's ecosystems and climate. It also provides critical input to greenhouse gas accounting, estimation of carbon losses and forest degradation, assessment of renewable energy potential, and for developing climate change mitigation policies. Although satellite remote sensing technology now allows researchers to produce extensive maps of aboveground biomass, these maps still require reliable, up-to-date, on-site data for calibration and validation. Collecting data in the field by measuring trees and documenting species is, however, a very labor intensive, expensive, and time-consuming exercise and it would therefore make sense to bring together the many extant data sets to provide real added value for a number of applications. In terms of policy applications, doing so can also lead to improved biomass products and better monitoring of forest resources, which could in turn lead to more effective forest protection measures.
In a new paper published in the journal Scientific Data, 143 researchers involved in this type of data collection in the field, explored whether it was possible to build a network that openly shares their data on biomass for the benefit of different communities. They particularly wanted to see if they could bring together as much on-site data on biomass as possible to prepare for new satellite missions, such as the European Space Agency's BIOMASS mission, with a view to improving the accuracy of current remote sensing based products, and developing new synergies between remote sensing and ground-based ecosystem research communities. Their efforts have resulted in the establishment of the Forest Observation System (FOS) -- an international, collaborative initiative that aims to establish a global on-site forest aboveground biomass database to support Earth Observation and to encourage investment in relevant field-based measurements and research.
"Keeping in mind that this paper is a data descriptor and not a conventional paper with hypotheses, the whole idea behind this study is a new open database on biomass data. This is important for the following reasons: First, it represents a way to link the ecological/forestry and remote sensing communities. It also overcomes existing data sharing barriers, while promoting data sharing beyond small, siloed communities. Lastly, it provides recognition to the people working in the field, including those who collect the data, which is why there are 143 coauthors on this paper, as they are all contributors to the database," explains study lead author Dmitry Shchepashchenko, a researcher in the IIASA Ecosystems Services and Management Program.
The researchers collected data from 1,645 permanent forest sample plots from 274 locations distributed around the globe. This data has now been made available for download via the FOS website. The initiative represents the first attempt at bringing this type of data together from different networks in a single location. The researchers point out that their work in this regard is ongoing and there are plans to continue adding more data sets and networks to the FOS. In addition to promoting data sharing, the system also promotes a new leading network on biomass data (through the FOS), which IIASA is leading and will continue to grow into the future.
Apart from the obvious benefits that data sharing hold for the scientific community, the data are also essential for training various models at IIASA such as the BioGeoChemistry Management Model (BGC-MAN) and the Global Forest Model (G4M). Several on-going IIASA projects, as well as other ecological-, biophysical-, and economic models and projects outside of IIASA will also benefit, which means that providing access to the data can improve models and understanding of biomass more generally.
Read more at Science Daily
Habitual tea drinking modulates brain efficiency: Evidence from brain connectivity evaluation
The researchers recruited healthy older participants to two groups according to their history of tea drinking frequency and investigated both functional and structural networks to reveal the role of tea drinking on brain organization.
The suppression of hemispheric asymmetry in the structural connectivity network was observed as a result of tea drinking.
The authors did not observe any significant effects of tea drinking on the hemispheric asymmetry of the functional connectivity network.
Dr. Junhua Li and Dr. Lei Feng said, "Tea has been a popular beverage since antiquity, with records referring to consumption dating back to the dynasty of Shen Nong (approximately 2700 BC) in China."
Tea is consumed in diverse ways, with brewed tea and products with a tea ingredient extremely prevalent in Asia, especially in China and Japan.
Although individual constituents of tea have been related to the roles of maintaining cognitive abilities and preventing cognitive decline, a study with behavioural and neurophysiological measures showed that there was a degraded effect or no effect when a constituent was administered alone and a significant effect was observed only when constituents were combined.
The superior effect of the constituent combination was also demonstrated in a comparative experiment that suggested that tea itself should be administered instead of tea extracts; a review of tea effects on the prevention of Alzheimers disease, found that the neuroprotective role of herbal tea was apparent in eight out of nine studies.
It is worth noting that the majority of studies thus far have evaluated tea effects from the perspective of neurocognitive and neuropsychological measures, with direct measurement of brain structure or function less-well represented in the extant literature.
These studies focusing on brain regional alterations did not ascertain tea effects on interregional interactions at the level of the entire brain.
The Li/Feng Research team concluded, "In summary, our study comprehensively investigated the effects of tea drinking on brain connectivity at both global and regional scales using multi-modal imaging data and provided the first compelling evidence that tea drinking positively contributes to brain structure making network organization more efficient."
From Science Daily
The suppression of hemispheric asymmetry in the structural connectivity network was observed as a result of tea drinking.
The authors did not observe any significant effects of tea drinking on the hemispheric asymmetry of the functional connectivity network.
Dr. Junhua Li and Dr. Lei Feng said, "Tea has been a popular beverage since antiquity, with records referring to consumption dating back to the dynasty of Shen Nong (approximately 2700 BC) in China."
Tea is consumed in diverse ways, with brewed tea and products with a tea ingredient extremely prevalent in Asia, especially in China and Japan.
Although individual constituents of tea have been related to the roles of maintaining cognitive abilities and preventing cognitive decline, a study with behavioural and neurophysiological measures showed that there was a degraded effect or no effect when a constituent was administered alone and a significant effect was observed only when constituents were combined.
The superior effect of the constituent combination was also demonstrated in a comparative experiment that suggested that tea itself should be administered instead of tea extracts; a review of tea effects on the prevention of Alzheimers disease, found that the neuroprotective role of herbal tea was apparent in eight out of nine studies.
It is worth noting that the majority of studies thus far have evaluated tea effects from the perspective of neurocognitive and neuropsychological measures, with direct measurement of brain structure or function less-well represented in the extant literature.
These studies focusing on brain regional alterations did not ascertain tea effects on interregional interactions at the level of the entire brain.
The Li/Feng Research team concluded, "In summary, our study comprehensively investigated the effects of tea drinking on brain connectivity at both global and regional scales using multi-modal imaging data and provided the first compelling evidence that tea drinking positively contributes to brain structure making network organization more efficient."
From Science Daily
Slower walkers have older brains and bodies at 45
The walking speed of 45-year-olds, particularly their fastest walking speed without running, can be used as a marker of their aging brains and bodies.
Slower walkers were shown to have "accelerated aging" on a 19-measure scale devised by researchers, and their lungs, teeth and immune systems tended to be in worse shape than the people who walked faster.
"The thing that's really striking is that this is in 45-year-old people, not the geriatric patients who are usually assessed with such measures," said lead researcher Line J.H. Rasmussen, a post-doctoral researcher in the Duke University department of psychology & neuroscience.
Equally striking, neurocognitive testing that these individuals took as children could predict who would become the slower walkers. At age 3, their scores on IQ, understanding language, frustration tolerance, motor skills and emotional control predicted their walking speed at age 45.
"Doctors know that slow walkers in their seventies and eighties tend to die sooner than fast walkers their same age," said senior author Terrie E. Moffitt, the Nannerl O. Keohane University Professor of Psychology at Duke University, and Professor of Social Development at King's College London. "But this study covered the period from the preschool years to midlife, and found that a slow walk is a problem sign decades before old age."
The data come from a long-term study of nearly 1,000 people who were born during a single year in Dunedin, New Zealand. The 904 research participants in the current study have been tested, quizzed and measured their entire lives, mostly recently from April 2017 to April 2019 at age 45.
The study appears Oct. 11 in JAMA Network Open.
MRI exams during their last assessment showed the slower walkers tended to have lower total brain volume, lower mean cortical thickness, less brain surface area and higher incidence of white matter "hyperintensities," small lesions associated with small vessel disease of the brain. In short, their brains appeared somewhat older.
Adding insult to injury perhaps, the slower walkers also looked older to a panel of eight screeners who assessed each participant's 'facial age' from a photograph.
Gait speed has long been used as a measure of health and aging in geriatric patients, but what's new in this study is the relative youth of these study subjects and the ability to see how walking speed matches up with health measures the study has collected during their lives.
"It's a shame we don't have gait speed and brain imaging for them as children," Rasmussen said. (The MRI was invented when they were five, but was not given to children for many years after.)
Read more at Science Daily
Slower walkers were shown to have "accelerated aging" on a 19-measure scale devised by researchers, and their lungs, teeth and immune systems tended to be in worse shape than the people who walked faster.
"The thing that's really striking is that this is in 45-year-old people, not the geriatric patients who are usually assessed with such measures," said lead researcher Line J.H. Rasmussen, a post-doctoral researcher in the Duke University department of psychology & neuroscience.
Equally striking, neurocognitive testing that these individuals took as children could predict who would become the slower walkers. At age 3, their scores on IQ, understanding language, frustration tolerance, motor skills and emotional control predicted their walking speed at age 45.
"Doctors know that slow walkers in their seventies and eighties tend to die sooner than fast walkers their same age," said senior author Terrie E. Moffitt, the Nannerl O. Keohane University Professor of Psychology at Duke University, and Professor of Social Development at King's College London. "But this study covered the period from the preschool years to midlife, and found that a slow walk is a problem sign decades before old age."
The data come from a long-term study of nearly 1,000 people who were born during a single year in Dunedin, New Zealand. The 904 research participants in the current study have been tested, quizzed and measured their entire lives, mostly recently from April 2017 to April 2019 at age 45.
The study appears Oct. 11 in JAMA Network Open.
MRI exams during their last assessment showed the slower walkers tended to have lower total brain volume, lower mean cortical thickness, less brain surface area and higher incidence of white matter "hyperintensities," small lesions associated with small vessel disease of the brain. In short, their brains appeared somewhat older.
Adding insult to injury perhaps, the slower walkers also looked older to a panel of eight screeners who assessed each participant's 'facial age' from a photograph.
Gait speed has long been used as a measure of health and aging in geriatric patients, but what's new in this study is the relative youth of these study subjects and the ability to see how walking speed matches up with health measures the study has collected during their lives.
"It's a shame we don't have gait speed and brain imaging for them as children," Rasmussen said. (The MRI was invented when they were five, but was not given to children for many years after.)
Read more at Science Daily
Oct 10, 2019
Milky Way raids intergalactic 'bank accounts'
Our Milky Way is a frugal galaxy. Supernovas and violent stellar winds blow gas out of the galactic disk, but that gas falls back onto the galaxy to form new generations of stars. In an ambitious effort to conduct a full accounting of this recycling process, astronomers were surprised to find a surplus of incoming gas.
"We expected to find the Milky Way's books balanced, with an equilibrium of gas inflow and outflow, but 10 years of Hubble ultraviolet data has shown there is more coming in than going out," said astronomer Andrew Fox of the Space Telescope Science Institute, Baltimore, Maryland, lead author of the study to be published in the Astrophysical Journal.
Fox said that, for now, the source of the excess inflowing gas remains a mystery.
One possible explanation is that new gas could be coming from the intergalactic medium. But Fox suspects the Milky Way is also raiding the gas "bank accounts" of its small satellite galaxies, using its considerably greater gravitational pull to siphon away their resources. Additionally, this survey, while galaxy-wide, looked only at cool gas, and hotter gas could play a role, too.
The new study reports the best measurements yet for how fast gas flows in and out of the Milky Way. Prior to this study, astronomers knew that the galactic gas reserves are replenished by inflow and depleted by outflow, but they did not know the relative amounts of gas coming in compared to going out. The balance between these two processes is important because it regulates the formation of new generations of stars and planets.
Astronomers accomplished this survey by collecting archival observations from Hubble's Cosmic Origins Spectrograph (COS), which was installed on the telescope by astronauts in 2009 during its last servicing mission. Researchers combed through the Hubble archives, analyzing 200 past ultraviolet observations of the diffuse halo that surrounds the disk of our galaxy. The decade's worth of detailed ultraviolet data provided an unprecedented look at gas flow across the galaxy and allowed for the first galaxy-wide inventory. The gas clouds of the galactic halo are only detectable in ultraviolet light, and Hubble is specialized to collect detailed data about the ultraviolet universe.
"The original Hubble COS observations were taken to study the universe far beyond our galaxy, but we went back to them and analyzed the Milky Way gas in the foreground. It's a credit to the Hubble archive that we can use the same observations to study both the near and the more distant universe. Hubble's resolution allows us to simultaneously study local and remote celestial objects," noted Rongmon Bordoloi of North Carolina State University in Raleigh, North Carolina, a co-author on the paper.
Because the galaxy's gas clouds are invisible, Fox's team used light from background quasars to detect these clouds and their motion. Quasars, the cores of active galaxies powered by well-fed black holes, shine like brilliant beacons across billions of light-years. When the quasar's light reaches the Milky Way, it passes through the invisible clouds.
The gas in the clouds absorbs certain frequencies of light, leaving telltale fingerprints in the quasar light. Fox singled out the fingerprint of silicon and used it to trace the gas around the Milky Way. Outflowing and inflowing gas clouds were distinguished by the Doppler shift of the light passing through them -- approaching clouds are bluer, and receding clouds are redder.
Currently, the Milky Way is the only galaxy for which we have enough data to provide such a full accounting of gas inflow and outflow.
"Studying our own galaxy in detail provides the basis for understanding galaxies across the universe, and we have realized that our galaxy is more complicated than we imagined," said Philipp Richter of the University of Potsdam in Germany, another co-author on the study.
Read more at Science Daily
"We expected to find the Milky Way's books balanced, with an equilibrium of gas inflow and outflow, but 10 years of Hubble ultraviolet data has shown there is more coming in than going out," said astronomer Andrew Fox of the Space Telescope Science Institute, Baltimore, Maryland, lead author of the study to be published in the Astrophysical Journal.
Fox said that, for now, the source of the excess inflowing gas remains a mystery.
One possible explanation is that new gas could be coming from the intergalactic medium. But Fox suspects the Milky Way is also raiding the gas "bank accounts" of its small satellite galaxies, using its considerably greater gravitational pull to siphon away their resources. Additionally, this survey, while galaxy-wide, looked only at cool gas, and hotter gas could play a role, too.
The new study reports the best measurements yet for how fast gas flows in and out of the Milky Way. Prior to this study, astronomers knew that the galactic gas reserves are replenished by inflow and depleted by outflow, but they did not know the relative amounts of gas coming in compared to going out. The balance between these two processes is important because it regulates the formation of new generations of stars and planets.
Astronomers accomplished this survey by collecting archival observations from Hubble's Cosmic Origins Spectrograph (COS), which was installed on the telescope by astronauts in 2009 during its last servicing mission. Researchers combed through the Hubble archives, analyzing 200 past ultraviolet observations of the diffuse halo that surrounds the disk of our galaxy. The decade's worth of detailed ultraviolet data provided an unprecedented look at gas flow across the galaxy and allowed for the first galaxy-wide inventory. The gas clouds of the galactic halo are only detectable in ultraviolet light, and Hubble is specialized to collect detailed data about the ultraviolet universe.
"The original Hubble COS observations were taken to study the universe far beyond our galaxy, but we went back to them and analyzed the Milky Way gas in the foreground. It's a credit to the Hubble archive that we can use the same observations to study both the near and the more distant universe. Hubble's resolution allows us to simultaneously study local and remote celestial objects," noted Rongmon Bordoloi of North Carolina State University in Raleigh, North Carolina, a co-author on the paper.
Because the galaxy's gas clouds are invisible, Fox's team used light from background quasars to detect these clouds and their motion. Quasars, the cores of active galaxies powered by well-fed black holes, shine like brilliant beacons across billions of light-years. When the quasar's light reaches the Milky Way, it passes through the invisible clouds.
The gas in the clouds absorbs certain frequencies of light, leaving telltale fingerprints in the quasar light. Fox singled out the fingerprint of silicon and used it to trace the gas around the Milky Way. Outflowing and inflowing gas clouds were distinguished by the Doppler shift of the light passing through them -- approaching clouds are bluer, and receding clouds are redder.
Currently, the Milky Way is the only galaxy for which we have enough data to provide such a full accounting of gas inflow and outflow.
"Studying our own galaxy in detail provides the basis for understanding galaxies across the universe, and we have realized that our galaxy is more complicated than we imagined," said Philipp Richter of the University of Potsdam in Germany, another co-author on the study.
Read more at Science Daily
Koala epidemic provides lesson in how DNA protects itself from viruses
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| Koala |
earRetroviruses, including pathogens like HIV, incorporate into the chromosomes of host cells as part of their infectious lifecycle. Retroviruses don't usually infect the germ cells that produce sperm and eggs and are therefore usually not passed from generation to generation, but this has happened several times during evolution. Out of the entire 3 billion nucleotides of the human genome, only 1.5% of the sequence forms the 20,000 genes that code for proteins -- and 8% of the human genome comes from fragments of viruses. These pathogen invasions of the genome have sometimes been beneficial. For example, a gene "co-opted" from a virus is required for formation of the placenta in all mammals, including humans.
Retroviral infection of germ cells has been a rare but important driving force in human evolution. But how the germ cells in mammals respond to pathogen invasion has not been previously described and might be quite different than other cells of the body. KoRV-A is a retrovirus sweeping through the wild koala population of Australia and is associated with susceptibility to infection and cancer. KoRV-A spreads between individual animals, like most viruses. Surprisingly, KoRV-A also infects the germline cells, and most wild koalas are born with this pathogen as part of the genetic material of every cell in the body. The team used this system to see how germ cells respond to a retrovirus. Their findings suggest that that germ cells recognize an essential step in the viral life cycle and turn it against the invader to suppress genome infection. These studies shed new light on interactions between viruses and the genetic "blueprint," written in the genome.
"KoRV-A infection of the koala germline is happening now, and lets us look at genome evolution in real time," says William E. Theurkauf, PhD, professor of molecular medicine at UMass Medical School, a senior author of the study.
"What we are seeing with koalas is something that every organism on the planet has gone through. Animals get infected by retroviruses that enter the germline cells. These viruses multiply and insert into the chromosomes, altering host genome organization and function, and the process continues until the invader is tamed by the host. At the end of this infection cycle, the host has changed," says co-senior author Zhiping Weng, professor in the Program of Bioinformatics and Integrative Biology at UMass Medical School.
"What we've uncovered, we believe, is an "innate" genome immune system that can tell a virus from one of your genes," says Theurkauf. "We think this is getting at how your genome says, 'This is something we want; this is a gene.' And, 'That is something we don't want; that's a virus'."
Most host genes are interrupted by spacer sequences called introns, which are removed in a process called splicing, to produce functional mRNAs that can make proteins. Splicing is a hallmark of normally cellular genes. Retroviruses also have introns, which are removed to make a protein that forms the envelope that surrounds the virus particle. However, these invaders also have to produce an "unspliced" RNA, which is essential to replication and infection. The appears to be critical, as germ cells recognize these virus-specific RNAs and chop them into a distinct class of small RNAs, called "sense" piRNAs, which block the formation of the virus. Preliminary studies suggest that this process is conserved from insects to mammals.
The team is working to expand their findings. "First, we're trying to figure out is how the virus got into the germline in the first place," says Weng. She and Theurkauf will conduct addition experiments to determine the machinery in the cells that recognize the difference in viral RNA, and, finally, they hope to better understand the process of chopping up the unspliced RNA transcripts, so they are no longer functional.
Read more at Science Daily
Prehistoric humans ate bone marrow like canned soup 400,000 years ago
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| Illustration of prehistoric human with animal skeleton. |
The research provides direct evidence that early Paleolithic people saved animal bones for up to nine weeks before feasting on them inside Qesem Cave.
The study, which was published in the October 9 issue of Science Advances, was led by Dr. Ruth Blasco of TAU's Department of Archaeology and Ancient Near Eastern Civilizations and Centro Nacional de Investigación Sobre la Evolución Humana (CENIEH) and her TAU colleagues Prof. Ran Barkai and Prof. Avi Gopher. It was conducted in collaboration with Profs. Jordi Rosell and Maite Arilla of Universitat Rovira i Virgili (URV) and Institut Català de Paleoecologia Humana i Evolució Social (IPHES); Prof. Antoni Margalida of University of Lleida, University of Bern, and the Institute for Game and Wildlife Research (IREC); and Prof. Daniel Villalba of University of Lleida.
"Bone marrow constitutes a significant source of nutrition and as such was long featured in the prehistoric diet," explains Prof. Barkai. "Until now, evidence has pointed to immediate consumption of marrow following the procurement and removal of soft tissues. In our paper, we present evidence of storage and delayed consumption of bone marrow at Qesem Cave."
"This is the earliest evidence of such behavior and offers insight into the socioeconomics of the humans who lived at Qesem," adds Dr. Blasco. "It also marks a threshold for new modes of Paleolithic human adaptation."
"Prehistoric humans brought to the cave selected body parts of the hunted animal carcasses," explains Prof. Rosell. "The most common prey was fallow deer, and limbs and skulls were brought to the cave while the rest of the carcass was stripped of meat and fat at the hunting scene and left there. We found that the deer leg bones, specifically the metapodials, exhibited unique chopping marks on the shafts, which are not characteristic of the marks left from stripping fresh skin to fracture the bone and extract the marrow."
The researchers contend that the deer metapodials were kept at the cave covered in skin to facilitate the preservation of marrow for consumption in time of need.
The researchers evaluated the preservation of bone marrow using an experimental series on deer, controlling exposure time and environmental parameters, combined with chemical analyses. The combination of archaeological and experimental results allowed them to isolate the specific marks linked to dry skin removal and determine a low rate of marrow fat degradation of up to nine weeks of exposure.
"We discovered that preserving the bone along with the skin, for a period that could last for many weeks, enabled early humans to break the bone when necessary and eat the still nutritious bone marrow," adds Dr. Blasco.
"The bones were used as 'cans' that preserved the bone marrow for a long period until it was time to take off the dry skin, shatter the bone and eat the marrow," Prof. Barkai emphasizes.
Until recently, it was believed that the Paleolithic people were hunter gatherers who lived hand-to-mouth (the Stone Age version of farm-to-table), consuming whatever they caught that day and enduring long periods of hunger when food sources were scarce.
"We show for the first time in our study that 420,000 to 200,000 years ago, prehistoric humans at Qesem Cave were sophisticated enough, intelligent enough and talented enough to know that it was possible to preserve particular bones of animals under specific conditions, and, when necessary, remove the skin, crack the bone and eat the bone marrow," Prof. Gopher explains.
According to the research, this is the earliest evidence in the world of food preservation and delayed consumption of food. This discovery joins other evidence of innovative behaviors found in Qesem Cave including recycling, the regular use of fire, and cooking and roasting meat.
Read more at Science Daily
Humans have salamander-like ability to regrow cartilage in joints
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| Salamander |
Publishing online Oct. 9 in the journal Science Advances, the researchers identified a mechanism for cartilage repair that appears to be more robust in ankle joints and less so in hips. The finding could potentially lead to treatments for osteoarthritis, the most common joint disorder in the world.
"We believe that an understanding of this 'salamander-like' regenerative capacity in humans, and the critically missing components of this regulatory circuit, could provide the foundation for new approaches to repair joint tissues and possibly whole human limbs," said senior author Virginia Byers Kraus, M.D., Ph.D., a professor in the departments of Medicine, Pathology and Orthopedic Surgery at Duke.
Kraus and colleagues, including lead author Ming-Feng Hsueh, Ph.D., devised a way to determine the age of proteins using internal molecular clocks integral to amino acids, which convert one form to another with predictable regularity.
Newly created proteins in tissue have few or no amino acid conversions; older proteins have many. Understanding this process enabled the researchers to use sensitive mass spectrometry to identify when key proteins in human cartilage, including collagens, were young, middle-aged or old.
They found that the age of cartilage largely depended on where it resided in the body. Cartilage in ankles is young, it's middle-aged in the knee and old in the hips. This correlation between the age of human cartilage and its location in the body aligns with how limb repair occurs in certain animals, which more readily regenerate at the furthest tips, including the ends of legs or tails.
The finding also helps explain why injuries to people's knees and, especially, hips take a long time to recover and often develop into arthritis, while ankle injuries heal quicker and less often become severely arthritic.
The researchers further learned that molecules called microRNA regulate this process. Not surprisingly, these microRNAs are more active in animals that are known for limb, fin or tail repair, including salamanders, zebrafish, African fresh water fish and lizards.
These microRNAs are also found in humans -- an evolutionary artifact that provides the capability in humans for joint tissue repair. As in animals, microRNA activity varies significantly by its location: it was highest in ankles compared to knees and hips and higher in the top layer of cartilage compared to deeper layers of cartilage.
"We were excited to learn that the regulators of regeneration in the salamander limb appear to also be the controllers of joint tissue repair in the human limb," Hsueh said. "We call it our 'inner salamander' capacity."
The researchers said microRNAs could be developed as medicines that might prevent, slow or reverse arthritis.
Read more at Science Daily
Oct 9, 2019
How do the strongest magnets in the universe form?
How do some neutron stars become the strongest magnets in the Universe? A German-British team of astrophysicists has found a possible answer to the question of how these so-called magnetars form. The researchers used large computer simulations to demonstrate how the merger of two stars creates strong magnetic fields. If such stars explode in supernovae, magnetars could result. Scientists from Heidelberg University, the Max Planck Society, the Heidelberg Institute for Theoretical Studies, and the University of Oxford were involved in the research. The results were published in Nature.
Our Universe is threaded by magnetic fields. The Sun, for example, has an envelope in which convection continuously generates magnetic fields. "Even though massive stars have no such envelopes, we still observe a strong, large-scale magnetic field at the surface of about ten percent of them," explains Dr Fabian Schneider from the Centre for Astronomy of Heidelberg University, who is the first author of the study in "Nature." Although such fields were already discovered in 1947, their origin has remained elusive so far.
Over a decade ago, scientists suggested that strong magnetic fields are produced when two stars collide. "But until now, we weren't able to test this hypothesis because we didn't have the necessary computational tools," says Dr Sebastian Ohlmann from the computing centre of the Max Planck Society in Garching near Munich. This time, the researchers used the AREPO code, a highly dynamic simulation code running on compute clusters of the Heidelberg Institute for Theoretical Studies (HITS), to explain the properties of Tau Scorpii (τ Sco), a magnetic star located 500 light years from Earth.
Already in 2016, Fabian Schneider and Philipp Podsiadlowski from the University of Oxford realised that τ Sco is a so-called blue straggler. Blue stragglers are the product of merged stars. "We assume that Tau Scorpii obtained its strong magnetic field during the merger process," explains Prof. Dr Philipp Podsiadlowski. Through its computer simulations of τ Sco, the German-British research team has now demonstrated that strong turbulence during the merger of two stars can create such a field.
Stellar mergers are relatively frequent: Scientists assume that about ten percent of all massive stars in the Milky Way are the products of such processes. This is in good agreement with the occurrence rate of magnetic massive stars, according to Dr Schneider. Astronomers think that these very stars could form magnetars when they explode in supernovae.
Read more at Science Daily
Our Universe is threaded by magnetic fields. The Sun, for example, has an envelope in which convection continuously generates magnetic fields. "Even though massive stars have no such envelopes, we still observe a strong, large-scale magnetic field at the surface of about ten percent of them," explains Dr Fabian Schneider from the Centre for Astronomy of Heidelberg University, who is the first author of the study in "Nature." Although such fields were already discovered in 1947, their origin has remained elusive so far.
Over a decade ago, scientists suggested that strong magnetic fields are produced when two stars collide. "But until now, we weren't able to test this hypothesis because we didn't have the necessary computational tools," says Dr Sebastian Ohlmann from the computing centre of the Max Planck Society in Garching near Munich. This time, the researchers used the AREPO code, a highly dynamic simulation code running on compute clusters of the Heidelberg Institute for Theoretical Studies (HITS), to explain the properties of Tau Scorpii (τ Sco), a magnetic star located 500 light years from Earth.
Already in 2016, Fabian Schneider and Philipp Podsiadlowski from the University of Oxford realised that τ Sco is a so-called blue straggler. Blue stragglers are the product of merged stars. "We assume that Tau Scorpii obtained its strong magnetic field during the merger process," explains Prof. Dr Philipp Podsiadlowski. Through its computer simulations of τ Sco, the German-British research team has now demonstrated that strong turbulence during the merger of two stars can create such a field.
Stellar mergers are relatively frequent: Scientists assume that about ten percent of all massive stars in the Milky Way are the products of such processes. This is in good agreement with the occurrence rate of magnetic massive stars, according to Dr Schneider. Astronomers think that these very stars could form magnetars when they explode in supernovae.
Read more at Science Daily
Dietary supplement from tomatoes discovered to boost sperm quality
Sperm quality can be improved with a simple diet supplement containing a compound found in cooked tomatoes, according to new research by the University of Sheffield.
The discovery could transform the outlook for men with fertility problems and lead to better ways to reduce the damaging impact of modern living on reproductive health. Of all infertility cases, approximately 40 to 50 per cent are due to "male factor" infertility.
The first ever double-blind randomised controlled trial to assess the impact of giving men a dietary compound called LactoLycopene, was led by Allan Pacey, Professor of Andrology Reproduction and Head of the University of Sheffield's Department of Oncology and Metabolism, and Dr Liz Williams, a leading specialist in Human Nutrition at the University of Sheffield. The team discovered it is possible to increase the proportion of healthy shaped sperm (sperm morphology) and boost 'fast swimming' sperm by around 40 per cent.
Lycopene can be found in some fruits and vegetables, but the main source in the diet is from tomatoes. Lycopene is a pigment that gives tomatoes their red colour, but dietary Lycopene is poorly absorbed by the human body, so the compound used for the trial was a commercially available formulation called LactoLycopene; designed by FutureYou Cambridge to improve bioavailability.
The 12-week trial designed by Dr Williams involved 60 healthy volunteers aged 19 to 30. Half took LactoLycopene supplements and the other half took identical placebo (dummy pills) every day for 12 weeks. Neither the researchers nor the volunteers knew who was receiving the LactoLycopene treatment and who was receiving the placebo. Sperm and blood samples were collected at the beginning and end of the trial.
"We didn't really expect that at the end of the study there would be any difference in the sperm from men who took the tablet versus those who took the placebo. When we decoded the results, I nearly fell off my chair," said Professor Pacey, a world expert in male reproduction.
"The improvement in morphology -- the size and shape of the sperm, was dramatic. We used a computer system to make these measurements, which takes a lot of the human error out of the results. Also, the person using the computer didn't know who had taken LactoLycopene and who had taken the dummy pills either.
"This was the first properly designed and controlled study of the effect of LactoLycopene on semen quality, and it has spurred us to want to do more work with this molecule."
"We were surprised by the improvement in sperm quality shown by the results," said Dr Williams.
"This was a small study and we do need to repeat the work in bigger trials, but the results are very encouraging. The next step is to repeat the exercise in men with fertility problems and see if LactoLycopene can increase sperm quality for those men and whether it helps couples conceive and avoid invasive fertility treatments."
Her team, which included three other researchers Madeleine Park, Aisling Robinson and Sophie Pitt, is hoping to embark on the new study as soon as possible.
Read more at Science Daily
The discovery could transform the outlook for men with fertility problems and lead to better ways to reduce the damaging impact of modern living on reproductive health. Of all infertility cases, approximately 40 to 50 per cent are due to "male factor" infertility.
The first ever double-blind randomised controlled trial to assess the impact of giving men a dietary compound called LactoLycopene, was led by Allan Pacey, Professor of Andrology Reproduction and Head of the University of Sheffield's Department of Oncology and Metabolism, and Dr Liz Williams, a leading specialist in Human Nutrition at the University of Sheffield. The team discovered it is possible to increase the proportion of healthy shaped sperm (sperm morphology) and boost 'fast swimming' sperm by around 40 per cent.
Lycopene can be found in some fruits and vegetables, but the main source in the diet is from tomatoes. Lycopene is a pigment that gives tomatoes their red colour, but dietary Lycopene is poorly absorbed by the human body, so the compound used for the trial was a commercially available formulation called LactoLycopene; designed by FutureYou Cambridge to improve bioavailability.
The 12-week trial designed by Dr Williams involved 60 healthy volunteers aged 19 to 30. Half took LactoLycopene supplements and the other half took identical placebo (dummy pills) every day for 12 weeks. Neither the researchers nor the volunteers knew who was receiving the LactoLycopene treatment and who was receiving the placebo. Sperm and blood samples were collected at the beginning and end of the trial.
"We didn't really expect that at the end of the study there would be any difference in the sperm from men who took the tablet versus those who took the placebo. When we decoded the results, I nearly fell off my chair," said Professor Pacey, a world expert in male reproduction.
"The improvement in morphology -- the size and shape of the sperm, was dramatic. We used a computer system to make these measurements, which takes a lot of the human error out of the results. Also, the person using the computer didn't know who had taken LactoLycopene and who had taken the dummy pills either.
"This was the first properly designed and controlled study of the effect of LactoLycopene on semen quality, and it has spurred us to want to do more work with this molecule."
"We were surprised by the improvement in sperm quality shown by the results," said Dr Williams.
"This was a small study and we do need to repeat the work in bigger trials, but the results are very encouraging. The next step is to repeat the exercise in men with fertility problems and see if LactoLycopene can increase sperm quality for those men and whether it helps couples conceive and avoid invasive fertility treatments."
Her team, which included three other researchers Madeleine Park, Aisling Robinson and Sophie Pitt, is hoping to embark on the new study as soon as possible.
Read more at Science Daily
Genes play a role in dog breed differences in behavior
Given the dazzling array of dog breeds, from dachshunds to mastiffs, from poodles to bloodhounds, it's easy to forget that most of that diversity arose only in the last few centuries or so, thanks to human tinkering. People have bred dogs for their looks, but the lion's share of breeding efforts have taken aim at eliciting particular behaviors, according to the University of Pennsylvania's James A. Serpell.
"If you look at the evolution of the dog, selection has been primarily for behaviors: hunting behaviors, guarding behaviors, or giving companionship to humans," he says.
In a new study, Serpell and colleagues Evan L. MacLean of the University of Arizona, Noah Snyder-Mackler of the University of Washington, and Bridgett M. vonHoldt of Princeton University offer strong evidence to support what scientists have long suspected: that some of the behaviors that help characterize breeds -- a drive to chase, for example, or aggression toward strangers -- are associated with distinct genetic differences between them. Their findings were published in the Proceedings of the Royal Society B.
"Dogs present a good model for understanding what portion of the variation in their behavior is attributable to differences in genetics, and how much to their environment and experiences," says Snyder-Mackler, who earned his undergraduate and doctoral degrees from Penn.
What seems obvious -- that genes can influence an individual's behaviors -- has not always been easy to support with evidence, in large part because behaviors are complex traits. Tendencies such as aggression, anxiety, or a compulsion to chase anything that moves are governed by many genes, not just one.
But dog breeds, being highly inbred, have allowed researchers to make progress in this area. Serpell and his colleagues recognized that, if a dog breed is associated with a particular behavior that distinguishes it from other breeds, it might be easier to detect the genetic variants contributing to that behavior if you compared that breed's genome to a host of others.
It helped that Serpell was in possession of a treasure-trove of behavior data from C-BARQ, short for Canine Behavioral Assessment and Research Questionnaire, a survey that more than 50,000 dog owners have filled out about their pets. C-BARQ returns a result on 14 behavioral "factors" about each dog surveyed, giving a measure of traits such as stranger-directed aggression, excitability, energy level, and predatory chasing drive.
For this study, the researchers pulled 14,020 of those entries that included information about pure-bred dogs. To look for associations with genetics, they borrowed data from two earlier studies, together representing 5,697 dogs, for which 172,000 points in the genome had been sequenced.
They found that about half of the variation in the 14 measured behaviors across breeds could be attributed to genetics -- a greater proportion that previous studies have found.
"This was based on breed-average behaviors," notes MacLean, "because we didn't have behavioral and genetic information from the same animals."
What stood out to the researchers was that the traits with the highest rates of heritability -- in other words, those that seemed to be most influenced by genetic factors rather than environmental ones -- were behaviors such as trainability, predatory chasing, stranger-directed aggression, and attention seeking. For these traits, genetics explained 60 to 70 percent of variation across breeds.
"These are exactly the types of traits that have been selected for in particular breeds of dogs," says Serpell. "So for trainability, you're thinking of breeds like border collies that have to respond to human signals to accomplish complicated tasks; for chasing behavior you can think of something like a greyhound, which is innately predisposed to chase anything that runs; and for stranger-directed aggression you might focus on some of the guard dog breeds that are highly protective and tend to respond in a hostile way to unfamiliar people."
Taking advantage of their vast pool of genomic data, the researchers looked for genetic variants associated with breed differences in the 14 C-BARQ traits. They found 131 variants tightly linked to these behaviors. Some were located in genes that have been implicated in influencing behavior, including in humans. But many were unknown and provide fodder for future study.
"This gives us an encouraging start and places to look," says MacLean. "We have ongoing projects where we've obtained genetic and behavioral data from the same individuals, so we'll be able to dive deeper into some of these traits and variants to see if the patterns we found here hold up."
If these genetic differences influence behavior, a good assumption would be that they somehow affect the brain. So, as a final step, the team looked to see where the genes in which key variants appeared were expressed in the body. Their analysis showed the genes were much more likely to be expressed in the brain than in other tissues in the body.
Of note, however, is that the researchers' results also leave plenty of room for individual differences and an animal's environment in influencing behavior.
Read more at Science Daily
"If you look at the evolution of the dog, selection has been primarily for behaviors: hunting behaviors, guarding behaviors, or giving companionship to humans," he says.
In a new study, Serpell and colleagues Evan L. MacLean of the University of Arizona, Noah Snyder-Mackler of the University of Washington, and Bridgett M. vonHoldt of Princeton University offer strong evidence to support what scientists have long suspected: that some of the behaviors that help characterize breeds -- a drive to chase, for example, or aggression toward strangers -- are associated with distinct genetic differences between them. Their findings were published in the Proceedings of the Royal Society B.
"Dogs present a good model for understanding what portion of the variation in their behavior is attributable to differences in genetics, and how much to their environment and experiences," says Snyder-Mackler, who earned his undergraduate and doctoral degrees from Penn.
What seems obvious -- that genes can influence an individual's behaviors -- has not always been easy to support with evidence, in large part because behaviors are complex traits. Tendencies such as aggression, anxiety, or a compulsion to chase anything that moves are governed by many genes, not just one.
But dog breeds, being highly inbred, have allowed researchers to make progress in this area. Serpell and his colleagues recognized that, if a dog breed is associated with a particular behavior that distinguishes it from other breeds, it might be easier to detect the genetic variants contributing to that behavior if you compared that breed's genome to a host of others.
It helped that Serpell was in possession of a treasure-trove of behavior data from C-BARQ, short for Canine Behavioral Assessment and Research Questionnaire, a survey that more than 50,000 dog owners have filled out about their pets. C-BARQ returns a result on 14 behavioral "factors" about each dog surveyed, giving a measure of traits such as stranger-directed aggression, excitability, energy level, and predatory chasing drive.
For this study, the researchers pulled 14,020 of those entries that included information about pure-bred dogs. To look for associations with genetics, they borrowed data from two earlier studies, together representing 5,697 dogs, for which 172,000 points in the genome had been sequenced.
They found that about half of the variation in the 14 measured behaviors across breeds could be attributed to genetics -- a greater proportion that previous studies have found.
"This was based on breed-average behaviors," notes MacLean, "because we didn't have behavioral and genetic information from the same animals."
What stood out to the researchers was that the traits with the highest rates of heritability -- in other words, those that seemed to be most influenced by genetic factors rather than environmental ones -- were behaviors such as trainability, predatory chasing, stranger-directed aggression, and attention seeking. For these traits, genetics explained 60 to 70 percent of variation across breeds.
"These are exactly the types of traits that have been selected for in particular breeds of dogs," says Serpell. "So for trainability, you're thinking of breeds like border collies that have to respond to human signals to accomplish complicated tasks; for chasing behavior you can think of something like a greyhound, which is innately predisposed to chase anything that runs; and for stranger-directed aggression you might focus on some of the guard dog breeds that are highly protective and tend to respond in a hostile way to unfamiliar people."
Taking advantage of their vast pool of genomic data, the researchers looked for genetic variants associated with breed differences in the 14 C-BARQ traits. They found 131 variants tightly linked to these behaviors. Some were located in genes that have been implicated in influencing behavior, including in humans. But many were unknown and provide fodder for future study.
"This gives us an encouraging start and places to look," says MacLean. "We have ongoing projects where we've obtained genetic and behavioral data from the same individuals, so we'll be able to dive deeper into some of these traits and variants to see if the patterns we found here hold up."
If these genetic differences influence behavior, a good assumption would be that they somehow affect the brain. So, as a final step, the team looked to see where the genes in which key variants appeared were expressed in the body. Their analysis showed the genes were much more likely to be expressed in the brain than in other tissues in the body.
Of note, however, is that the researchers' results also leave plenty of room for individual differences and an animal's environment in influencing behavior.
Read more at Science Daily
Special occasion drinking during pregnancy may cause harm
If you thought a glass or two of alcohol on special occasions was safe during pregnancy, think again. Research in the Journal of Physiology shows even small amounts of alcohol consumed during pregnancy can cause insulin-resistance, which increases the likelihood of diabetes, in male rat offspring.
The study mimicked 'special occasion drinking', such as a family barbeque or birthday party, where a pregnant mother might be encouraged to have one or two alcoholic drinks. Male rats exposed to this low level of prenatal alcohol showed signs of becoming diabetic at around six months old. The researchers only gave alcohol to the mother rats on two days during their pregnancy.
The rats' blood alcohol concentration only reached 0.05%, and yet their male offspring became almost diabetic, with insulin levels reaching higher than expected to maintain normal blood sugar levels.
Another interesting finding was that insulin-resistance was sex-specific, occurring only in the male rats. There are a couple of potential reasons for this, one being that during pregnancy, the placenta adapts to a prenatal stress differently depending on if it's a male or female fetus, and this can impact on fetal growth and development.
The other factor is hormone changes as offspring grow into adulthood. In this case, estrogen protects against insulin-resistance, and because males don't have high oestrogen, they don't experience the same protection.
Commenting on the study University of Queensland researcher Lisa Akison, senior author on the study, said:
"Even a small amount of alcohol during pregnancy can be harmful, so if you're planning on getting pregnant don't drink. Families, partners and friends should support a woman's choice not to drink alcohol during pregnancy. If a woman accidentally becomes pregnant, and unknowingly drinks alcohol during the first part of their pregnancy, the important thing once they know is to stop drinking, have a good diet and take care of themselves throughout the remainder of the pregnancy."
From Science Daily
The study mimicked 'special occasion drinking', such as a family barbeque or birthday party, where a pregnant mother might be encouraged to have one or two alcoholic drinks. Male rats exposed to this low level of prenatal alcohol showed signs of becoming diabetic at around six months old. The researchers only gave alcohol to the mother rats on two days during their pregnancy.
The rats' blood alcohol concentration only reached 0.05%, and yet their male offspring became almost diabetic, with insulin levels reaching higher than expected to maintain normal blood sugar levels.
Another interesting finding was that insulin-resistance was sex-specific, occurring only in the male rats. There are a couple of potential reasons for this, one being that during pregnancy, the placenta adapts to a prenatal stress differently depending on if it's a male or female fetus, and this can impact on fetal growth and development.
The other factor is hormone changes as offspring grow into adulthood. In this case, estrogen protects against insulin-resistance, and because males don't have high oestrogen, they don't experience the same protection.
Commenting on the study University of Queensland researcher Lisa Akison, senior author on the study, said:
"Even a small amount of alcohol during pregnancy can be harmful, so if you're planning on getting pregnant don't drink. Families, partners and friends should support a woman's choice not to drink alcohol during pregnancy. If a woman accidentally becomes pregnant, and unknowingly drinks alcohol during the first part of their pregnancy, the important thing once they know is to stop drinking, have a good diet and take care of themselves throughout the remainder of the pregnancy."
From Science Daily
Nobel Prize in Chemistry 2019: Lithium-ion batteries
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| Lithium-ion batteries concept |
They created a rechargeable world
The Nobel Prize in Chemistry 2019 rewards the development of the lithium-ion battery. This lightweight, rechargeable and powerful battery is now used in everything from mobile phones to laptops and electric vehicles. It can also store significant amounts of energy from solar and wind power, making possible a fossil fuel-free society.
Lithium-ion batteries are used globally to power the portable electronics that we use to communicate, work, study, listen to music and search for knowledge. Lithiumion batteries have also enabled the development of long-range electric cars and the storage of energy from renewable sources, such as solar and wind power.
The foundation of the lithium-ion battery was laid during the oil crisis in the 1970s. Stanley Whittingham worked on developing methods that could lead to fossil fuel-free energy technologies. He started to research superconductors and discovered an extremely energy-rich material, which he used to create an innovative cathode in a lithium battery. This was made from titanium disulphide which, at a molecular level, has spaces that can house -- intercalate -- lithium ions.
The battery's anode was partially made from metallic lithium, which has a strong drive to release electrons. This resulted in a battery that literally had great potential, just over two volts. However, metallic lithium is reactive and the battery was too explosive to be viable.
John Goodenough predicted that the cathode would have even greater potential if it was made using a metal oxide instead of a metal sulphide. After a systematic search, in 1980 he demonstrated that cobalt oxide with intercalated lithium ions can produce as much as four volts. This was an important breakthrough and would lead to much more powerful batteries.
With Goodenough's cathode as a basis, Akira Yoshino created the first commercially viable lithium-ion battery in 1985. Rather than using reactive lithium in the anode, he used petroleum coke, a carbon material that, like the cathode's cobalt oxide, can intercalate lithium ions.
The result was a lightweight, hardwearing battery that could be charged hundreds of times before its performance deteriorated. The advantage of lithium-ion batteries is that they are not based upon chemical reactions that break down the electrodes, but upon lithium ions flowing back and forth between the anode and cathode.
Read more at Science Daily
Oct 8, 2019
The deeper these octopuses live, the wartier their skin
Deep beneath the ocean's surface, surprisingly cute warty pink octopuses creep along the seafloor. But not all these octopuses look alike. While we humans love a good "Is your skin oily, dry, or combination?" quiz, members of one octopus species take variations in skin texture to a whole new level. Some have outrageous warts, while others appear nearly smooth-skinned. Scientists weren't sure if these octopuses were even members of the same species, and they didn't know how to explain the differences in the animals' looks. But in a new study, scientists cracked the case: the deeper in the ocean the octopuses live, the bumpier their skin and the smaller their bodies. DNA revealed even though the octopuses looked different, they were the same species.
"If I had only two of these animals that looked very different, I would say, 'Well, they're different species, for sure.' But variation inside animal species can sometimes fool you," says Janet Voight, associate curator of zoology at the Field Museum and the lead author of the paper in the Bulletin of Marine Science. "That's why we need to look at multiple specimens of species to see, does that first reaction based on two specimens make sense?"
To figure out if the smooth and warty octopuses were the same species, the scientists examined 50 specimens that were classified as Graneledone pacifica -- the Pacific warty octopus. Plunging deep into the ocean in ALVIN, a human-occupied submersible vehicle, Voight collected some of the octopuses from the Northeast Pacific Ocean. The team also studied specimens loaned from the University of Miami Marine Laboratory and the California Academy of Sciences. They looked at specimens from up and down the Pacific, from as far north as Washington State to as far south as Monterey, California, and from depths ranging from 3,660 feet to more than 9,000 feet below the ocean's surface.
The researchers counted the number of warts in a line across each octopus's back and its head and the number of suckers on their arms. They found that the octopuses from deeper in the ocean looked different from their shallower counterparts. The deep-sea specimens were smaller, with fewer arm suckers, and, most noticeably, bumpier skin than those from shallower depths. The thing is, there weren't two distinct groups; the animals' appearances changed according to how deep they live. Comparing the octopuses' DNA sequences revealed only minor differences, supporting the idea that they were all the same species, despite looking so different.
Sometimes when animals look different from each other, scientists can be tempted to jump the gun and declare them separate species -- especially in the deep sea, where very little is known about animal life and scientists often don't have many specimens to compare. But looking different doesn't necessarily mean that animals are members of different species; take chihuahuas and Great Danes, which are both the same species of Canis lupus familiaris.Dogs' different appearances are due to selective breeding by humans, but in the case of the warty octopuses in this study, their different appearances seem to result from environmental influences, because their appearance changes depending on where the octopuses are from.
Scientists aren't sure why the variations in skin texture occur with depth. But they do have a hunch about the size difference.
Voight thinks that these octopuses usually eat creatures from the sediment on the ocean floor, passing food from sucker to sucker and then crushing their prey like popcorn. "There's less food as you get deeper in the ocean. So these animals have to work harder to find food to eat. And that means at the end of their lives, they'll be smaller than animals who have more food. If you're a female who's going to lay eggs at the end of your life, maybe your eggs will be smaller" says Voight. Smaller eggs mean smaller hatchlings.
Support for this hypothesis comes from the number of suckers on the males' arm that transfers sperm packets to females. Earlier research by Voight found that male hatchlings have a full-formed arm with all its suckers in place. The researchers documented that the number of suckers on this arm was way smaller in males from greater depth, and Voight hypothesizes it relates to egg size.
"The octopus hatchlings in shallower water, only 3,660 feet, are bigger. Their eggs had more yolk. As the embryos grew, they developed farther inside the egg than the ones from 9,000 feet, who were developing in smaller eggs. They had less energy to fuel their growth before they left the egg, so they made fewer suckers," says Voight. Seeing these physical manifestations of octopuses' food limitation provides a hint of how they might fare as climate change progresses and the octopuses' food supply fluctuates.
Voight notes that this study, which shows that different-looking octopuses can still be the same genetic species, could help researchers down the line trying to identify life forms in the deep sea. Remotely operated vehicles collect video footage of the ocean floor, and it can be used to estimate the number of species present -- if we know what they look like. That's why, Voight says, it's so important to examine specimens in person and use characteristics you can't see on video to identify species boundaries.
Read more at Science Daily
"If I had only two of these animals that looked very different, I would say, 'Well, they're different species, for sure.' But variation inside animal species can sometimes fool you," says Janet Voight, associate curator of zoology at the Field Museum and the lead author of the paper in the Bulletin of Marine Science. "That's why we need to look at multiple specimens of species to see, does that first reaction based on two specimens make sense?"
To figure out if the smooth and warty octopuses were the same species, the scientists examined 50 specimens that were classified as Graneledone pacifica -- the Pacific warty octopus. Plunging deep into the ocean in ALVIN, a human-occupied submersible vehicle, Voight collected some of the octopuses from the Northeast Pacific Ocean. The team also studied specimens loaned from the University of Miami Marine Laboratory and the California Academy of Sciences. They looked at specimens from up and down the Pacific, from as far north as Washington State to as far south as Monterey, California, and from depths ranging from 3,660 feet to more than 9,000 feet below the ocean's surface.
The researchers counted the number of warts in a line across each octopus's back and its head and the number of suckers on their arms. They found that the octopuses from deeper in the ocean looked different from their shallower counterparts. The deep-sea specimens were smaller, with fewer arm suckers, and, most noticeably, bumpier skin than those from shallower depths. The thing is, there weren't two distinct groups; the animals' appearances changed according to how deep they live. Comparing the octopuses' DNA sequences revealed only minor differences, supporting the idea that they were all the same species, despite looking so different.
Sometimes when animals look different from each other, scientists can be tempted to jump the gun and declare them separate species -- especially in the deep sea, where very little is known about animal life and scientists often don't have many specimens to compare. But looking different doesn't necessarily mean that animals are members of different species; take chihuahuas and Great Danes, which are both the same species of Canis lupus familiaris.Dogs' different appearances are due to selective breeding by humans, but in the case of the warty octopuses in this study, their different appearances seem to result from environmental influences, because their appearance changes depending on where the octopuses are from.
Scientists aren't sure why the variations in skin texture occur with depth. But they do have a hunch about the size difference.
Voight thinks that these octopuses usually eat creatures from the sediment on the ocean floor, passing food from sucker to sucker and then crushing their prey like popcorn. "There's less food as you get deeper in the ocean. So these animals have to work harder to find food to eat. And that means at the end of their lives, they'll be smaller than animals who have more food. If you're a female who's going to lay eggs at the end of your life, maybe your eggs will be smaller" says Voight. Smaller eggs mean smaller hatchlings.
Support for this hypothesis comes from the number of suckers on the males' arm that transfers sperm packets to females. Earlier research by Voight found that male hatchlings have a full-formed arm with all its suckers in place. The researchers documented that the number of suckers on this arm was way smaller in males from greater depth, and Voight hypothesizes it relates to egg size.
"The octopus hatchlings in shallower water, only 3,660 feet, are bigger. Their eggs had more yolk. As the embryos grew, they developed farther inside the egg than the ones from 9,000 feet, who were developing in smaller eggs. They had less energy to fuel their growth before they left the egg, so they made fewer suckers," says Voight. Seeing these physical manifestations of octopuses' food limitation provides a hint of how they might fare as climate change progresses and the octopuses' food supply fluctuates.
Voight notes that this study, which shows that different-looking octopuses can still be the same genetic species, could help researchers down the line trying to identify life forms in the deep sea. Remotely operated vehicles collect video footage of the ocean floor, and it can be used to estimate the number of species present -- if we know what they look like. That's why, Voight says, it's so important to examine specimens in person and use characteristics you can't see on video to identify species boundaries.
Read more at Science Daily
Pressure runs high at edge of solar system
Out at the boundary of our solar system, pressure runs high. This pressure, the force plasma, magnetic fields and particles like ions, cosmic rays and electrons exert on one another when they flow and collide, was recently measured by scientists in totality for the first time -- and it was found to be greater than expected.
Using observations of galactic cosmic rays -- a type of highly energetic particle -- from NASA's Voyager spacecraft scientists calculated the total pressure from particles in the outer region of the solar system, known as the heliosheath. At nearly 9 billion miles away, this region is hard to study. But the unique positioning of the Voyager spacecraft and the opportune timing of a solar event made measurements of the heliosheath possible. And the results are helping scientists understand how the Sun interacts with its surroundings.
"In adding up the pieces known from previous studies, we found our new value is still larger than what's been measured so far," said Jamie Rankin, lead author on the new study and astronomer at Princeton University in New Jersey. "It says that there are some other parts to the pressure that aren't being considered right now that could contribute."
On Earth we have air pressure, created by air molecules drawn down by gravity. In space there's also a pressure created by particles like ions and electrons. These particles, heated and accelerated by the Sun create a giant balloon known as the heliosphere extending millions of miles out past Pluto. The edge of this region, where the Sun's influence is overcome by the pressures of particles from other stars and interstellar space, is where the Sun's magnetic influence ends. (Its gravitational influence extends much farther, so the solar system itself extends farther, as well.)
In order to measure the pressure in the heliosheath, the scientists used the Voyager spacecraft, which have been travelling steadily out of the solar system since 1977. At the time of the observations, Voyager 1 was already outside of the heliosphere in interstellar space, while Voyager 2 still remained in the heliosheath.
"There was really unique timing for this event because we saw it right after Voyager 1 crossed into the local interstellar space," Rankin said. "And while this is the first event that Voyager saw, there are more in the data that we can continue to look at to see how things in the heliosheath and interstellar space are changing over time."
The scientists used an event known as a global merged interaction region, which is caused by activity on the Sun. The Sun periodically flares up and releases enormous bursts of particles, like in coronal mass ejections. As a series of these events travel out into space, they can merge into a giant front, creating a wave of plasma pushed by magnetic fields.
When one such wave reached the heliosheath in 2012, it was spotted by Voyager 2. The wave caused the number of galactic cosmic rays to temporarily decrease. Four months later, the scientists saw a similar decrease in observations from Voyager 1, just across the solar system's boundary in interstellar space.
Knowing the distance between the spacecraft allowed them to calculate the pressure in the heliosheath as well as the speed of sound. In the heliosheath sound travels at around 300 kilometers per second -- a thousand times faster than it moves through air.
The scientists noted that the change in galactic cosmic rays wasn't exactly identical at both spacecraft. At Voyager 2 inside the heliosheath, the number of cosmic rays decreased in all directions around the spacecraft. But at Voyager 1, outside the solar system, only the galactic cosmic rays that were traveling perpendicular to the magnetic field in the region decreased. This asymmetry suggests that something happens as the wave transmits across the solar system's boundary.
"Trying to understand why the change in the cosmic rays is different inside and outside of the heliosheath remains an open question," Rankin said.
Read more at Science Daily
Using observations of galactic cosmic rays -- a type of highly energetic particle -- from NASA's Voyager spacecraft scientists calculated the total pressure from particles in the outer region of the solar system, known as the heliosheath. At nearly 9 billion miles away, this region is hard to study. But the unique positioning of the Voyager spacecraft and the opportune timing of a solar event made measurements of the heliosheath possible. And the results are helping scientists understand how the Sun interacts with its surroundings.
"In adding up the pieces known from previous studies, we found our new value is still larger than what's been measured so far," said Jamie Rankin, lead author on the new study and astronomer at Princeton University in New Jersey. "It says that there are some other parts to the pressure that aren't being considered right now that could contribute."
On Earth we have air pressure, created by air molecules drawn down by gravity. In space there's also a pressure created by particles like ions and electrons. These particles, heated and accelerated by the Sun create a giant balloon known as the heliosphere extending millions of miles out past Pluto. The edge of this region, where the Sun's influence is overcome by the pressures of particles from other stars and interstellar space, is where the Sun's magnetic influence ends. (Its gravitational influence extends much farther, so the solar system itself extends farther, as well.)
In order to measure the pressure in the heliosheath, the scientists used the Voyager spacecraft, which have been travelling steadily out of the solar system since 1977. At the time of the observations, Voyager 1 was already outside of the heliosphere in interstellar space, while Voyager 2 still remained in the heliosheath.
"There was really unique timing for this event because we saw it right after Voyager 1 crossed into the local interstellar space," Rankin said. "And while this is the first event that Voyager saw, there are more in the data that we can continue to look at to see how things in the heliosheath and interstellar space are changing over time."
The scientists used an event known as a global merged interaction region, which is caused by activity on the Sun. The Sun periodically flares up and releases enormous bursts of particles, like in coronal mass ejections. As a series of these events travel out into space, they can merge into a giant front, creating a wave of plasma pushed by magnetic fields.
When one such wave reached the heliosheath in 2012, it was spotted by Voyager 2. The wave caused the number of galactic cosmic rays to temporarily decrease. Four months later, the scientists saw a similar decrease in observations from Voyager 1, just across the solar system's boundary in interstellar space.
Knowing the distance between the spacecraft allowed them to calculate the pressure in the heliosheath as well as the speed of sound. In the heliosheath sound travels at around 300 kilometers per second -- a thousand times faster than it moves through air.
The scientists noted that the change in galactic cosmic rays wasn't exactly identical at both spacecraft. At Voyager 2 inside the heliosheath, the number of cosmic rays decreased in all directions around the spacecraft. But at Voyager 1, outside the solar system, only the galactic cosmic rays that were traveling perpendicular to the magnetic field in the region decreased. This asymmetry suggests that something happens as the wave transmits across the solar system's boundary.
"Trying to understand why the change in the cosmic rays is different inside and outside of the heliosheath remains an open question," Rankin said.
Read more at Science Daily
Believing in climate change doesn't mean you are preparing for climate change
Believing in climate change has no effect on whether or not coastal homeowners are protecting their homes from climate change-related hazards, according to a new study from the University of Notre Dame.
Funded by Notre Dame's Global Adaptation Initiative (ND-GAIN), the study analyzed data from a 2017 Coastal Homeowner Survey of 662 respondents in one of the most frequently exposed U.S. coastal communities, New Hanover County, North Carolina. Just one year after the survey, the county was affected by Hurricane Florence and was nearly missed by Hurricane Dorian in September.
The survey asked homeowners whether they believed in climate change, in human causation of climate change, or in God having a role in controlling the weather or climate. Coastal homeowners were also questioned about their knowledge of climate-related hazards, their knowledge of warming oceans and their perception of the seriousness of the impact of climate change.
"We found that climate change attitudes have little to no statistically significant effect on coastal homeowners' actions towards home protection, homeowner action or homeowner intentions to act in the future," said Tracy Kijewski-Correa, the Leo E. and Patti Ruth Linbeck Collegiate Chair and associate professor of civil and environmental engineering and earth sciences, associate professor of global affairs and co-author of the study. "This is despite the fact that with climate change, U.S. coastlines have experienced increased frequency and intensity of tropical storms and sea level rise, which has further heightened their vulnerability to waves, storm surge and high-tide flooding."
According to the study published in Climatic Change, 81.5 percent of survey respondents believed climate change is "probably happening," with varying degrees of confidence. The Notre Dame research team also measured for partisanship and ideology with the intention to control for questions about climate change that can tap into identity and prior political beliefs. However, after controlling for partisanship, the findings were unaffected.
"Despite persistent differences between Democrat and Republican ideologies in regards to climate change, the behavior of people from either party appears relatively similar. Neither has or intends to take action to improve the structural vulnerabilities of their homes," said Debra Javeline, associate professor of political science at Notre Dame and lead author of the study. "Homeowners' knowledge about climate change also held no significance, showing that providing more information and understanding may not be the main driver of convincing homeowners to reduce the vulnerabilities of their coastal homes."
The research team found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage. Javeline says this may be a reflection of the limited communication about home vulnerabilities from other key stakeholders, like insurance companies, government agencies or sellers of home improvement products.
Read more at Science Daily
Funded by Notre Dame's Global Adaptation Initiative (ND-GAIN), the study analyzed data from a 2017 Coastal Homeowner Survey of 662 respondents in one of the most frequently exposed U.S. coastal communities, New Hanover County, North Carolina. Just one year after the survey, the county was affected by Hurricane Florence and was nearly missed by Hurricane Dorian in September.
The survey asked homeowners whether they believed in climate change, in human causation of climate change, or in God having a role in controlling the weather or climate. Coastal homeowners were also questioned about their knowledge of climate-related hazards, their knowledge of warming oceans and their perception of the seriousness of the impact of climate change.
"We found that climate change attitudes have little to no statistically significant effect on coastal homeowners' actions towards home protection, homeowner action or homeowner intentions to act in the future," said Tracy Kijewski-Correa, the Leo E. and Patti Ruth Linbeck Collegiate Chair and associate professor of civil and environmental engineering and earth sciences, associate professor of global affairs and co-author of the study. "This is despite the fact that with climate change, U.S. coastlines have experienced increased frequency and intensity of tropical storms and sea level rise, which has further heightened their vulnerability to waves, storm surge and high-tide flooding."
According to the study published in Climatic Change, 81.5 percent of survey respondents believed climate change is "probably happening," with varying degrees of confidence. The Notre Dame research team also measured for partisanship and ideology with the intention to control for questions about climate change that can tap into identity and prior political beliefs. However, after controlling for partisanship, the findings were unaffected.
"Despite persistent differences between Democrat and Republican ideologies in regards to climate change, the behavior of people from either party appears relatively similar. Neither has or intends to take action to improve the structural vulnerabilities of their homes," said Debra Javeline, associate professor of political science at Notre Dame and lead author of the study. "Homeowners' knowledge about climate change also held no significance, showing that providing more information and understanding may not be the main driver of convincing homeowners to reduce the vulnerabilities of their coastal homes."
The research team found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage. Javeline says this may be a reflection of the limited communication about home vulnerabilities from other key stakeholders, like insurance companies, government agencies or sellers of home improvement products.
Read more at Science Daily
2019 Nobel Prize in Physics: Evolution of the universe and discovery of exoplanet orbiting solar-type star
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| Illustration of exoplanet orbiting star. |
New perspectives on our place in the universe
This year's Nobel Prize in Physics rewards new understanding of the universe's structure and history, and the first discovery of a planet orbiting a solar-type star outside our solar system.
James Peebles' insights into physical cosmology have enriched the entire field of research and laid a foundation for the transformation of cosmology over the last fifty years, from speculation to science. His theoretical framework, developed since the mid-1960s, is the basis of our contemporary ideas about the universe.
The Big Bang model describes the universe from its very first moments, almost 14 billion years ago, when it was extremely hot and dense. Since then, the universe has been expanding, becoming larger and colder. Barely 400,000 years after the Big Bang, the universe became transparent and light rays were able to travel through space. Even today, this ancient radiation is all around us and, coded into it, many of the universe's secrets are hiding. Using his theoretical tools and calculations, James Peebles was able to interpret these traces from the infancy of the universe and discover new physical processes.
The results showed us a universe in which just five per cent of its content is known, the matter which constitutes stars, planets, trees -- and us. The rest, 95 per cent, is unknown dark matter and dark energy. This is a mystery and a challenge to modern physics.
In October 1995, Michel Mayor and Didier Queloz announced the first discovery of a planet outside our solar system, an exoplanet, orbiting a solar-type star in our home galaxy, the Milky Way. At the Haute-Provence Observatory in southern France, using custom-made instruments, they were able to see planet 51 Pegasi b, a gaseous ball comparable with the solar system's biggest gas giant, Jupiter.
This discovery started a revolution in astronomy and over 4,000 exoplanets have since been found in the Milky Way. Strange new worlds are still being discovered, with an incredible wealth of sizes, forms and orbits. They challenge our preconceived ideas about planetary systems and are forcing scientists to revise their theories of the physical processes behind the origins of planets. With numerous projects planned to start searching for exoplanets, we may eventually find an answer to the eternal question of whether other life is out there.
Read more at Science Daily
Oct 7, 2019
Nobel Prize in Physiology or Medicine 2019: How cells sense and adapt to oxygen availability
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| Marathon runners |
Animals need oxygen for the conversion of food into useful energy. The fundamental importance of oxygen has been understood for centuries, but how cells adapt to changes in levels of oxygen has long been unknown.
William G. Kaelin Jr., Sir Peter J. Ratcliffe and Gregg L. Semenza discovered how cells can sense and adapt to changing oxygen availability. They identified molecular machinery that regulates the activity of genes in response to varying levels of oxygen.
The seminal discoveries by this year's Nobel Laureates revealed the mechanism for one of life's most essential adaptive processes. They established the basis for our understanding of how oxygen levels affect cellular metabolism and physiological function. Their discoveries have also paved the way for promising new strategies to fight anemia, cancer and many other diseases.
Oxygen at center stage
Oxygen, with the formula O2, makes up about one fifth of Earth's atmosphere. Oxygen is essential for animal life: it is used by the mitochondria present in virtually all animal cells in order to convert food into useful energy. Otto Warburg, the recipient of the 1931 Nobel Prize in Physiology or Medicine, revealed that this conversion is an enzymatic process.
During evolution, mechanisms developed to ensure a sufficient supply of oxygen to tissues and cells. The carotid body, adjacent to large blood vessels on both sides of the neck, contains specialized cells that sense the blood's oxygen levels. The 1938 Nobel Prize in Physiology or Medicine to Corneille Heymans awarded discoveries showing how blood oxygen sensing via the carotid body controls our respiratory rate by communicating directly with the brain.
HIF enters the scene
In addition to the carotid body-controlled rapid adaptation to low oxygen levels (hypoxia), there are other fundamental physiological adaptations. A key physiological response to hypoxia is the rise in levels of the hormone erythropoietin (EPO), which leads to increased production of red blood cells (erythropoiesis). The importance of hormonal control of erythropoiesis was already known at the beginning of the 20th century, but how this process was itself controlled by O2 remained a mystery.
Gregg Semenza studied the EPO gene and how it is regulated by varying oxygen levels. By using gene-modified mice, specific DNA segments located next to the EPO gene were shown to mediate the response to hypoxia. Sir Peter Ratcliffe also studied O2-dependent regulation of the EPO gene, and both research groups found that the oxygen sensing mechanism was present in virtually all tissues, not only in the kidney cells where EPO is normally produced. These were important findings showing that the mechanism was general and functional in many different cell types.
Semenza wished to identify the cellular components mediating this response. In cultured liver cells he discovered a protein complex that binds to the identified DNA segment in an oxygen-dependent manner. He called this complex the hypoxia-inducible factor (HIF) . Extensive efforts to purify the HIF complex began, and in 1995, Semenza was able to publish some of his key findings, including identification of the genes encoding HIF. HIF was found to consist of two different DNA-binding proteins, so called transcription factors, now named HIF-1α and ARNT. Now the researchers could begin solving the puzzle, allowing them to understand which additional components were involved and how the machinery works.
VHL: an unexpected partner
When oxygen levels are high, cells contain very little HIF-1α. However, when oxygen levels are low, the amount of HIF-1α increases so that it can bind to and thus regulate the EPO gene as well as other genes with HIF-binding DNA segments. Several research groups showed that HIF-1α, which is normally rapidly degraded, is protected from degradation in hypoxia. At normal oxygen levels, a cellular machine called the proteasome, recognized by the 2004 Nobel Prize in Chemistry to Aaron Ciechanover, Avram Hershko and Irwin Rose, degrades HIF-1α. Under such conditions a small peptide, ubiquitin, is added to the HIF-1α protein. Ubiquitin functions as a tag for proteins destined for degradation in the proteasome. How ubiquitin binds to HIF-1α in an oxygen-dependent manner remained a central question.
The answer came from an unexpected direction. At about the same time as Semenza and Ratcliffe were exploring the regulation of the EPO gene, cancer researcher William Kaelin, Jr. was researching an inherited syndrome, von Hippel-Lindau's disease (VHL disease). This genetic disease leads to dramatically increased risk of certain cancers in families with inherited VHL mutations. Kaelin showed that the VHL gene encodes a protein that prevents the onset of cancer. Kaelin also showed that cancer cells lacking a functional VHL gene express abnormally high levels of hypoxia-regulated genes; but that when the VHL gene was reintroduced into cancer cells, normal levels were restored. This was an important clue showing that VHL was somehow involved in controlling responses to hypoxia. Additional clues came from several research groups showing that VHL is part of a complex that labels proteins with ubiquitin, marking them for degradation in the proteasome. Ratcliffe and his research group then made a key discovery: demonstrating that VHL can physically interact with HIF-1α and is required for its degradation at normal oxygen levels. This conclusively linked VHL to HIF-1α.
Oxygen sHIFts the balance
Many pieces had fallen into place, but what was still lacking was an understanding of how O2 levels regulate the interaction between VHL and HIF-1α. The search focused on a specific portion of the HIF-1α protein known to be important for VHL-dependent degradation, and both Kaelin and Ratcliffe suspected that the key to O2-sensing resided somewhere in this protein domain. In 2001, in two simultaneously published articles they showed that under normal oxygen levels, hydroxyl groups are added at two specific positions in HIF-1α. This protein modification, called prolyl hydroxylation, allows VHL to recognize and bind to HIF-1α and thus explained how normal oxygen levels control rapid HIF-1α degradation with the help of oxygen-sensitive enzymes (so-called prolyl hydroxylases). Further research by Ratcliffe and others identified the responsible prolyl hydroxylases. It was also shown that the gene activating function of HIF-1α was regulated by oxygen-dependent hydroxylation. The Nobel Laureates had now elucidated the oxygen sensing mechanism and had shown how it works.
Oxygen shapes physiology and pathology
Thanks to the groundbreaking work of these Nobel Laureates, we know much more about how different oxygen levels regulate fundamental physiological processes. Oxygen sensing allows cells to adapt their metabolism to low oxygen levels: for example, in our muscles during intense exercise. Other examples of adaptive processes controlled by oxygen sensing include the generation of new blood vessels and the production of red blood cells. Our immune system and many other physiological functions are also fine-tuned by the O2-sensing machinery. Oxygen sensing has even been shown to be essential during fetal development for controlling normal blood vessel formation and placenta development.
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Saturn surpasses Jupiter after the discovery of 20 new moons
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| Saturn illustration |
A team led by Carnegie's Scott S. Sheppard has found 20 new moons orbiting Saturn. This brings the ringed planet's total number of moons to 82, surpassing Jupiter, which has 79. The discovery was announced Monday by the International Astronomical Union's Minor Planet Center.
Each of the newly discovered moons is about five kilometers, or three miles, in diameter. Seventeen of them orbit the planet backwards, or in a retrograde direction, meaning their movement is opposite of the planet's rotation around its axis. The other three moons orbit in the prograde -- the same direction as Saturn rotates.
Two of the prograde moons are closer to the planet and take about two years to travel once around Saturn. The more-distant retrograde moons and one of the prograde moons each take more than three years to complete an orbit.
"Studying the orbits of these moons can reveal their origins, as well as information about the conditions surrounding Saturn at the time of its formation," Sheppard explained.
The outer moons of Saturn appear to be grouped into three different clusters in terms of the inclinations of the angles at which they are orbiting around the planet. Two of the newly discovered prograde moons fit into a group of outer moons with inclinations of about 46 degrees called the Inuit group, as they are named after Inuit mythology. These moons may have once comprised a larger moon that was broken apart in the distant past. Likewise, the newly announced retrograde moons have similar inclinations to other previously known retrograde Saturnian moons, indicating that they are also likely fragments from a once-larger parent moon that was broken apart. These retrograde moons are in the Norse group, with names coming from Norse mythology. One of the newly discovered retrograde moons is the farthest known moon around Saturn.
"This kind of grouping of outer moons is also seen around Jupiter, indicating violent collisions occurred between moons in the Saturnian system or with outside objects such as passing asteroids or comets," explained Sheppard.
The other newly found prograde moon has an inclination near 36 degrees, which is similar to the other known grouping of inner prograde moons around Saturn called the Gallic group. But this new moon orbits much farther away from Saturn than any of the other prograde moons, indicating it might have been pulled outwards over time or might not be associated with the more inner grouping of prograde moons.
If a significant amount of gas or dust were present when a larger moon broke apart and created these clusters of smaller moon fragments, there would have been strong frictional interactions between the smaller moons and the gas and dust, causing them to spiral into the planet.
"In the Solar System's youth, the Sun was surrounded by a rotating disk of gas and dust from which the planets were born. It is believed that a similar gas-and-dust disk surrounded Saturn during its formation," Sheppard said. "The fact that these newly discovered moons were able to continue orbiting Saturn after their parent moons broke apart indicates that these collisions occurred after the planet-formation process was mostly complete and the disks were no longer a factor."
The new moons were discovered using the Subaru telescope atop Mauna Kea in Hawaii. The observing team included Sheppard, David Jewitt of UCLA, and Jan Kleyna of the University of Hawaii.
"Using some of the largest telescopes in the world, we are now completing the inventory of small moons around the giant planets," says Scott Sheppard. "They play a crucial role in helping us determine how our Solar System's planets formed and evolved."
Last year, Sheppard discovered 12 new moons orbiting Jupiter and Carnegie hosted an online contest to name five of them.
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NASA's Curiosity Rover finds an ancient oasis on Mars
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| NASA's Curiosity Mars rover took this selfie on May 12, 2019. |
Imagine ponds dotting the floor of Gale Crater, the 100-mile-wide (150-kilometer-wide) ancient basin that Curiosity is exploring. Streams might have laced the crater's walls, running toward its base. Watch history in fast forward, and you'd see these waterways overflow then dry up, a cycle that probably repeated itself numerous times over millions of years.
That is the landscape described by Curiosity scientists in a Nature Geoscience paper published today. The authors interpret rocks enriched in mineral salts discovered by the rover as evidence of shallow briny ponds that went through episodes of overflow and drying. The deposits serve as a watermark created by climate fluctuations as the Martian environment transitioned from a wetter one to the freezing desert it is today.
Scientists would like to understand how long this transition took and when exactly it occurred. This latest clue may be a sign of findings to come as Curiosity heads toward a region called the "sulfate-bearing unit," which is expected to have formed in an even drier environment. It represents a stark difference from lower down the mountain, where Curiosity discovered evidence of persistent freshwater lakes.
Gale Crater is the ancient remnant of a massive impact. Sediment carried by water and wind eventually filled in the crater floor, layer by layer. After the sediment hardened, wind carved the layered rock into the towering Mount Sharp, which Curiosity is climbing today. Now exposed on the mountain's slopes, each layer reveals a different era of Martian history and holds clues about the prevailing environment at the time.
"We went to Gale Crater because it preserves this unique record of a changing Mars," said lead author William Rapin of Caltech. "Understanding when and how the planet's climate started evolving is a piece of another puzzle: When and how long was Mars capable of supporting microbial life at the surface?"
He and his co-authors describe salts found across a 500-foot-tall (150-meter-tall) section of sedimentary rocks called "Sutton Island," which Curiosity visited in 2017. Based on a series of mud cracks at a location named "Old Soaker," the team already knew the area had intermittent drier periods. But the Sutton Island salts suggest the water also concentrated into brine.
Typically, when a lake dries up entirely, it leaves piles of pure salt crystals behind. But the Sutton Island salts are different: For one thing, they're mineral salts, not table salt. They're also mixed with sediment, suggesting they crystallized in a wet environment -- possibly just beneath evaporating shallow ponds filled with briny water.
Given that Earth and Mars were similar in their early days, Rapin speculated that Sutton Island might have resembled saline lakes on South America's Altiplano. Streams and rivers flowing from mountain ranges into this arid, high-altitude plateau lead to closed basins similar to Mars' ancient Gale Crater. Lakes on the Altiplano are heavily influenced by climate in the same way as Gale.
"During drier periods, the Altiplano lakes become shallower, and some can dry out completely," Rapin said. "The fact that they're vegetation-free even makes them look a little like Mars."
Signs of a Drying Mars
Sutton Island's salt-enriched rocks are just one clue among several the rover team is using to piece together how the Martian climate changed. Looking across the entirety of Curiosity's journey, which began in 2012, the science team sees a cycle of wet to dry across long timescales on Mars.
"As we climb Mount Sharp, we see an overall trend from a wet landscape to a drier one," said Curiosity Project Scientist Ashwin Vasavada of NASA's Jet Propulsion Laboratory in Pasadena, California. JPL leads the Mars Science Laboratory mission that Curiosity is a part of. "But that trend didn't necessarily occur in a linear fashion. More likely, it was messy, including drier periods, like what we're seeing at Sutton Island, followed by wetter periods, like what we're seeing in the 'clay-bearing unit' that Curiosity is exploring today."
Up until now, the rover has encountered lots of flat sediment layers that had been gently deposited at the bottom of a lake. Team member Chris Fedo, who specializes in the study of sedimentary layers at the University of Tennessee, noted that Curiosity is currently running across large rock structures that could have formed only in a higher-energy environment such as a windswept area or flowing streams.
Wind or flowing water piles sediment into layers that gradually incline. When they harden into rock, they become large structures similar to "Teal Ridge," which Curiosity investigated this past summer.
"Finding inclined layers represents a major change, where the landscape isn't completely underwater anymore," said Fedo. "We may have left the era of deep lakes behind."
Curiosity has already spied more inclined layers in the distant sulfate-bearing unit. The science team plans to drive there in the next couple years and investigate its many rock structures. If they formed in drier conditions that persisted for a long period, that might mean that the clay-bearing unit represents an in-between stage -- a gateway to a different era in Gale Crater's watery history.
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The last mammoths died on a remote island
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| Woolly mammoth illustration. |
During the last ice age -- some 100,000 to 15,000 years ago -- mammoths were widespread in the northern hemisphere from Spain to Alaska. Due to the global warming that began 15,000 years ago, their habitat in Northern Siberia and Alaska shrank. On Wrangel Island, some mammoths were cut off from the mainland by rising sea levels; that population survived another 7000 years.
The team of researchers from Finland, Germany and Russia examined the isotope compositions of carbon, nitrogen, sulfur and strontium from a large set of mammoth bones and teeth from Northern Siberia, Alaska, the Yukon, and Wrangel Island, ranging from 40,000 to 4,000 years in age. The aim was to document possible changes in the diet of the mammoths and their habitat and find evidence of a disturbance in their environment. The results showed that Wrangel Island mammoths' collagen carbon and nitrogen isotope compositions did not shift as the climate warmed up some 10,000 years ago. The values remained unchanged until the mammoths disappeared, seemingly from the midst of stable, favorable living conditions.
This result contrasts with the findings on woolly mammoths from the Ukrainian-Russian plains, which died out 15,000 years ago, and on the mammoths of St. Paul Island in Alaska, who disappeared 5,600 years ago. In both cases, the last representatives of these populations showed significant changes in their isotopic composition, indicating changes in their environment shortly before they became locally extinct.
Earlier aDNA studies indicate that the Wrangel Island mammoths suffered mutations affecting their fat metabolism. In this study, the team found an intriguing difference between the Wrangel Island mammoths and their ice age Siberian predecessors: the carbonate carbon isotope values indicated a difference in the fats and carbohydrates in the populations' diets. "We think this reflects the tendency of Siberian mammoths to rely on their reserves of fat to survive through the extremely harsh ice age winters, while Wrangel mammoths, living in milder conditions, simply didn't need to," says Dr. Laura Arppe from the Finnish Museum of Natural History Luomus, University of Helsinki, who led the team of researchers. The bones also contained levels of sulfur and strontium that suggested the weathering of bedrock intensified toward the end of the mammoth population's existence. This may have affected the quality of the mammoths' drinking water.
Why then did the last woolly mammoths disappear so suddenly? The researchers suspect that they died out due to short-term events. Extreme weather such as a rain-on-snow, i.e. an icing event could have covered the ground in a thick layer of ice, preventing the animals from finding enough food. That could have led to a dramatic population decline and eventually to extinction. "It's easy to imagine that the population, perhaps already weakened by genetic deterioration and drinking water quality issues could have succumbed after something like an extreme weather event," says professor Hervé Bocherens from the Senckenberg Center for Human Evolution and Palaeoenvironment at the University of Tübingen, a co-author of the study.
Another possible factor could have been the spread of humans. The earliest archaeological evidence of humans on Wrangel Island dates to just a few hundred years after the most recent mammoth bone. The chance of finding evidence that humans hunted Wrangel Island mammoths is very small. Yet a human contribution to the extinction cannot be ruled out.
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