It costs more than a new iPhone XS, and it's made out of hazelnut shrub stems. Traditional baby baskets of Northern California's Yurok and Karuk tribes come at a premium not only because they are handcrafted by skilled weavers, but because the stems required to make them are found only in forest understory areas experiencing a type of controlled burn once practiced by the tribes but suppressed for more than a century.
A new Stanford-led study with the U.S. Forest Service in collaboration with the Yurok and Karuk tribes found that incorporating traditional techniques into current fire suppression practices could help revitalize American Indian cultures, economies and livelihoods, while continuing to reduce wildfire risks. The findings could inform plans to incorporate the cultural burning practices into forest management across an area one and a half times the size of Rhode Island.
"Burning connects many tribal members to an ancestral practice that they know has immense ecological and social benefit especially in the aftermath of industrial timber activity and ongoing economic austerity," said study lead author Tony Marks-Block, a doctoral candidate in anthropology who worked with Lisa Curran, the Roger and Cynthia Lang Professor in Environmental Anthropology.
"We must have fire in order to continue the traditions of our people," said Margo Robbins, a Yurok basket weaver and director of the Yurok Cultural Fire Management Council who advised the researchers. "There is such a thing as good fire."
The study, published in Forest Ecology and Management, replicates Yurok and Karuk fire treatments that involve cutting and burning hazelnut shrub stems. The approach increased the production of high-quality stems (straight, unbranched and free of insect marks or bark blemishes) needed to make culturally significant items such as baby baskets and fish traps up to 10-fold compared with untreated shrubs.
Reducing fuel load
Previous studies have shown that repeated prescribed burning reduces fuel for wildfires, thus reducing their intensity and size in seasonally dry forests such as the one the researchers studied in the Klamath Basin area near the border with Oregon. This study was part of a larger exploration of prescribed burns being carried out by Stanford and U.S. Forest Service researchers who collaborated with the Yurok and Karuk tribes to evaluate traditional fire management treatments. Together, they worked with a consortium of federal and state agencies and nongovernmental organizations across 5,570 acres in the Klamath Basin.
The consortium has proposed expanding these "cultural burns" -- which have been greatly constrained throughout the tribes' ancestral lands -- across more than 1 million acres of federal and tribal lands that are currently managed with techniques including less targeted controlled burns or brush removal.
Tribes traditionally burned specific plants or landscapes as a way of generating materials or spurring food production, as opposed to modern prescribed burns that are less likely to take these considerations into account. The authors argue that increasing the number of cultural burns could ease food insecurity among American Indian communities in the region. Traditional food sources have declined precipitously due in part to the suppression of prescribed burns that kill acorn-eating pests and promote deer populations by creating beneficial habitat and increasing plants' nutritional content
"This study was founded upon tribal knowledge and cultural practices," said co-author Frank Lake, a research ecologist with the U.S. Forest Service and a Karuk descendant with Yurok family. "Because of that, it can help us in formulating the best available science to guide fuels and fire management that demonstrate the benefit to tribal communities and society for reducing the risk of wildfires."
The researchers write that it would be easy and efficient to include traditional American Indian prescribed burning practices in existing forest management strategies. For example, federal fire managers could incorporate hazelnut shrub propane torching and pile burning into their fuel reduction plans to meet cultural needs. Managers would need to consult and collaborate with local tribes to plan these activities so that the basketry stems could be gathered post-treatment. Larger-scale pile burning treatments typically occur over a few days and require routine monitoring by forestry technicians to ensure they do not escape or harm nearby trees. As these burn, it would be easy for a technician to simultaneously use a propane torch to top-kill nearby hazelnut shrubs. This would not require a significant increase in personnel hours.
Read more at Science Daily
Aug 27, 2019
Arms race between parasites and their victims
Acanthocephala are parasitic worms that reproduce in the intestines of various animals, including fish. However, only certain species of fish are suitable as hosts. A study by the University of Bonn now shows how the parasites succeed in preferably infecting these types. The results will be published in the journal Behaviour, but are already available online.
The parasitic worm Pomphorhynchus laevis does not have an easy life: In order to reproduce, the parasite must first hope that its eggs will be eaten by a freshwater shrimp. The larvae hatching from the eggs then need a change of scenery: They can only develop into adult worms if they are swallowed by a fish. However, not every fish species is suitable as a final host. Some species have defense mechanisms that kill the parasite before it can mate and release new eggs into the water through the fish intestine.
In order to improve their chances of reproduction, the worms have developed several sophisticated strategies in the course of evolution. "For example, parasite-infected shrimp change their behavior," explains Dr. Timo Thünken from the Institute for Evolutionary Biology and Ecology at the University of Bonn. "They no longer avoid certain fish species and are therefore eaten more frequently." Another thesis was so far controversial: Freshwater shrimp are beige-brownish; their body shell is also relatively transparent. They therefore barely stand out from their surroundings. Pomphorhynchus laevis larvae, on the other hand, are bright orange. It is therefore possible to see with the naked eye whether a shrimp is infected: Its parasitic cargo is marked by an orange spot.
Infected shrimp attract more attention
It may be that the shrimp are less well camouflaged as a result and are more frequently eaten by fish. Study director Prof. Dr. Theo Bakker already investigated this thesis several years ago. He was indeed able to determine that shrimp with an orange mark more frequently ended up in the stomachs of sticklebacks. Yet this finding was not confirmed in studies with brown trout.
However, the brown trout, in contrast to the stickleback, is not a suitable final host for Pomphorhynchus laevis. Its immune system usually prevents a successful infection with Pomphorhynchus laevis. "It is therefore possible that the orange coloring attracts particular those fish that are especially suitable for the parasite's further reproduction," Thünken suspects. "We have now conducted experiments to put this thesis to the test."
The biologists marked the shrimp with an orange dot in order to simulate larval infestation. Then they tested how often the shrimp in question were eaten by different fish in comparison to unmarked species. The mark did in fact increase the risk of being eaten -- but only in some types of fish: Barbels and sticklebacks were particularly interested in the marked freshwater shrimp; the dot made no difference to brown trout.
In another experiment, the researchers fed their fish exclusively with larvae-infested shrimp. "We were able to show that this diet often led to infection in barbels and sticklebacks, but very rarely in brown trout," explains Thünken. Evidently, their conspicuous coloring ensures that the larvae end up mainly in the stomach of suitable final hosts. However, it is unclear whether they have acquired their orange hue in the course of evolution in order to reach precisely these hosts. "Perhaps over time they have simply adapted better to the digestive tract of those fish that responded particularly strongly to the orange color," says Thünken.
Read more at Science Daily
The parasitic worm Pomphorhynchus laevis does not have an easy life: In order to reproduce, the parasite must first hope that its eggs will be eaten by a freshwater shrimp. The larvae hatching from the eggs then need a change of scenery: They can only develop into adult worms if they are swallowed by a fish. However, not every fish species is suitable as a final host. Some species have defense mechanisms that kill the parasite before it can mate and release new eggs into the water through the fish intestine.
In order to improve their chances of reproduction, the worms have developed several sophisticated strategies in the course of evolution. "For example, parasite-infected shrimp change their behavior," explains Dr. Timo Thünken from the Institute for Evolutionary Biology and Ecology at the University of Bonn. "They no longer avoid certain fish species and are therefore eaten more frequently." Another thesis was so far controversial: Freshwater shrimp are beige-brownish; their body shell is also relatively transparent. They therefore barely stand out from their surroundings. Pomphorhynchus laevis larvae, on the other hand, are bright orange. It is therefore possible to see with the naked eye whether a shrimp is infected: Its parasitic cargo is marked by an orange spot.
Infected shrimp attract more attention
It may be that the shrimp are less well camouflaged as a result and are more frequently eaten by fish. Study director Prof. Dr. Theo Bakker already investigated this thesis several years ago. He was indeed able to determine that shrimp with an orange mark more frequently ended up in the stomachs of sticklebacks. Yet this finding was not confirmed in studies with brown trout.
However, the brown trout, in contrast to the stickleback, is not a suitable final host for Pomphorhynchus laevis. Its immune system usually prevents a successful infection with Pomphorhynchus laevis. "It is therefore possible that the orange coloring attracts particular those fish that are especially suitable for the parasite's further reproduction," Thünken suspects. "We have now conducted experiments to put this thesis to the test."
The biologists marked the shrimp with an orange dot in order to simulate larval infestation. Then they tested how often the shrimp in question were eaten by different fish in comparison to unmarked species. The mark did in fact increase the risk of being eaten -- but only in some types of fish: Barbels and sticklebacks were particularly interested in the marked freshwater shrimp; the dot made no difference to brown trout.
In another experiment, the researchers fed their fish exclusively with larvae-infested shrimp. "We were able to show that this diet often led to infection in barbels and sticklebacks, but very rarely in brown trout," explains Thünken. Evidently, their conspicuous coloring ensures that the larvae end up mainly in the stomach of suitable final hosts. However, it is unclear whether they have acquired their orange hue in the course of evolution in order to reach precisely these hosts. "Perhaps over time they have simply adapted better to the digestive tract of those fish that responded particularly strongly to the orange color," says Thünken.
Read more at Science Daily
Skin creams aren't what we thought they were
Anyone who has gone through the stress and discomfort of raw, irritated skin knows the relief that comes with slathering on a creamy lotion. Topical creams generally contain a few standard ingredients, but manufacturers know little about how these components interact to influence the performance of the product. Now, researchers report the first direct glimpse of how a cream or lotion is structured on the molecular scale, and it's not quite what they expected.
The researchers will present their results today at the American Chemical Society (ACS) Fall 2019 National Meeting & Exposition.
"The long-term stability and clinical properties of a cream are determined by its fundamental structure," says Delaram Ahmadi, the graduate student who performed the study. "If we can understand the chemical microstructure of the cream and relate that to the structure of the skin, then perhaps we can better repair the compromised skin barrier."
One of Ahmadi's research advisors, David Barlow, Ph.D., adds, "We wanted to improve the science around cream formulation so that companies could more rationally formulate them to get exactly what they want. The most significant thing we found is that the textbook picture of the structure of a cream is very naïve."
Formulators have mostly inferred the structure of these emulsions based on indirect measurements, Barlow explains. But his group took a direct approach, with Ahmadi analyzing the cream using X-ray and neutron scattering techniques to determine how the ingredients were dispersed. Ahmadi and Barlow are at King's College London, and their co-investigator, Jayne Lawrence, Ph.D., is at Manchester University.
Cream is usually thought of as stacks of lamellae, or membranes, composed of surfactants and co-surfactants that maintain oil droplets dispersed within water (or vice versa). To reveal a cream's true structure, the researchers started with an aqueous cream formulation from the British Pharmacopoeia that contains two co-surfactants and a sodium dodecyl sulfate (SDS) surfactant. They also incorporated a diol known to act as a preservative. One by one, Ahmadi replaced each ingredient with heavier isotopic versions. The researchers then scattered X-rays and neutrons off the selectively isotope-labelled samples and, from the resulting patterns of scattering, determined the location of each ingredient and the aggregate it formed within the cream.
The results were surprising. Although they observed co-surfactants in the lamellar layers as predicted, the surfactant was not there. "The surfactant peak profile suggested that the molecule formed micelles in the cream," Ahmadi says. In addition, the preservative was not found in the aqueous layer, where scientists have always presumed it would be. It was, in fact, residing in the lamellae. Preservatives have an antimicrobial effect, thereby prolonging shelf-life. Formulators had assumed that to be an effective antimicrobial, the preservative had to be dissolved in the water layer. So, Ahmadi says this finding could mean the creams are essentially self-preserving.
The team is currently performing computer experiments to model the behavior of the preservatives in a bilayer system like a cream to understand why they are in the membrane layer. And they want to better understand the structure of the surfactant micelles dispersed in the layers. "I don't think anybody else has considered that there would be these micelles in the system at all," Barlow says. "This is new, and we need to think about where they are in the structure and what they are doing."
Read more at Science Daily
The researchers will present their results today at the American Chemical Society (ACS) Fall 2019 National Meeting & Exposition.
"The long-term stability and clinical properties of a cream are determined by its fundamental structure," says Delaram Ahmadi, the graduate student who performed the study. "If we can understand the chemical microstructure of the cream and relate that to the structure of the skin, then perhaps we can better repair the compromised skin barrier."
One of Ahmadi's research advisors, David Barlow, Ph.D., adds, "We wanted to improve the science around cream formulation so that companies could more rationally formulate them to get exactly what they want. The most significant thing we found is that the textbook picture of the structure of a cream is very naïve."
Formulators have mostly inferred the structure of these emulsions based on indirect measurements, Barlow explains. But his group took a direct approach, with Ahmadi analyzing the cream using X-ray and neutron scattering techniques to determine how the ingredients were dispersed. Ahmadi and Barlow are at King's College London, and their co-investigator, Jayne Lawrence, Ph.D., is at Manchester University.
Cream is usually thought of as stacks of lamellae, or membranes, composed of surfactants and co-surfactants that maintain oil droplets dispersed within water (or vice versa). To reveal a cream's true structure, the researchers started with an aqueous cream formulation from the British Pharmacopoeia that contains two co-surfactants and a sodium dodecyl sulfate (SDS) surfactant. They also incorporated a diol known to act as a preservative. One by one, Ahmadi replaced each ingredient with heavier isotopic versions. The researchers then scattered X-rays and neutrons off the selectively isotope-labelled samples and, from the resulting patterns of scattering, determined the location of each ingredient and the aggregate it formed within the cream.
The results were surprising. Although they observed co-surfactants in the lamellar layers as predicted, the surfactant was not there. "The surfactant peak profile suggested that the molecule formed micelles in the cream," Ahmadi says. In addition, the preservative was not found in the aqueous layer, where scientists have always presumed it would be. It was, in fact, residing in the lamellae. Preservatives have an antimicrobial effect, thereby prolonging shelf-life. Formulators had assumed that to be an effective antimicrobial, the preservative had to be dissolved in the water layer. So, Ahmadi says this finding could mean the creams are essentially self-preserving.
The team is currently performing computer experiments to model the behavior of the preservatives in a bilayer system like a cream to understand why they are in the membrane layer. And they want to better understand the structure of the surfactant micelles dispersed in the layers. "I don't think anybody else has considered that there would be these micelles in the system at all," Barlow says. "This is new, and we need to think about where they are in the structure and what they are doing."
Read more at Science Daily
Gene mutations coordinate to drive malignancy in lung cancer
Scientists have shown exactly how mutations in two different genes coordinate to drive the development of malignant lung tumors, according to a new report in the open-access journal eLife.
The study in novel genetically engineered mice looked at the characteristics of lung tumors from when they are invisibly small to when they are larger and potentially deadly. The results shed new light on the mechanisms of tumor progression and will help researchers currently developing drugs for lung tumors.
There are many types of lung cancer: non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death globally, and lung adenocarcinoma is the most common subtype of NSCLC. Around 75% of lung adenocarcinomas have mutations that affect two important control mechanisms for cell growth -- the MAP kinase pathway, and the PI3'-kinase pathway. Each pathway alone is not sufficient to cause lung cancer; they need to coordinate to make this happen.
"We knew that mutations in the MAP kinase pathway promote the growth of benign lung tumors, but that PI3'-kinase mutations alone do not kickstart tumor formation in the same cells," explains lead author Ed van Veen, former Postdoctoral Fellow in senior author Martin McMahon's laboratory at Huntsman Cancer Institute (HCI) at the University of Utah (U of U), Salt Lake City, US. "The pathways instead cooperate to drive the growth of malignant tumors, but we didn't know what molecular changes occurred as a result of this cooperation and how the lung cells lose their characteristics as cancer develops."
The team studied mice with mutations that were only active in lung cells called Type 2 pneumocytes. They analyzed the effects of these mutations on the genes and protein molecules in individual cells at different stages of tumor development. When they looked at the gene expression of the MAP and PI3'-kinase-driven tumors, they found that the tumor cells had reduced levels of genes that are hallmarks of a Type 2 pneumocyte, suggesting that these lung cells had lost their identity.
Next, the team looked at which molecules were responsible for coordinating the MAP and PI3'- kinase pathways together. Fluorescent labeling of molecules already known to be involved in lung cell specialization showed some surprising results -- these molecules did not play a role in the loss of lung cell identity that contributes to tumor progression. Rather, a molecule called PGC1? appeared to be involved.
To investigate if PGC1? directly controls the loss of Type 2 pneumocyte identity during lung tumor development, the team studied mice with a silenced version of the molecule, alongside mutations in the MAP kinase pathway. They found that silencing PGC1? causes lung cells to lose their specialized characteristics by cooperating with two other molecules that are required for this specialization.
Read more at Science Daily
The study in novel genetically engineered mice looked at the characteristics of lung tumors from when they are invisibly small to when they are larger and potentially deadly. The results shed new light on the mechanisms of tumor progression and will help researchers currently developing drugs for lung tumors.
There are many types of lung cancer: non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death globally, and lung adenocarcinoma is the most common subtype of NSCLC. Around 75% of lung adenocarcinomas have mutations that affect two important control mechanisms for cell growth -- the MAP kinase pathway, and the PI3'-kinase pathway. Each pathway alone is not sufficient to cause lung cancer; they need to coordinate to make this happen.
"We knew that mutations in the MAP kinase pathway promote the growth of benign lung tumors, but that PI3'-kinase mutations alone do not kickstart tumor formation in the same cells," explains lead author Ed van Veen, former Postdoctoral Fellow in senior author Martin McMahon's laboratory at Huntsman Cancer Institute (HCI) at the University of Utah (U of U), Salt Lake City, US. "The pathways instead cooperate to drive the growth of malignant tumors, but we didn't know what molecular changes occurred as a result of this cooperation and how the lung cells lose their characteristics as cancer develops."
The team studied mice with mutations that were only active in lung cells called Type 2 pneumocytes. They analyzed the effects of these mutations on the genes and protein molecules in individual cells at different stages of tumor development. When they looked at the gene expression of the MAP and PI3'-kinase-driven tumors, they found that the tumor cells had reduced levels of genes that are hallmarks of a Type 2 pneumocyte, suggesting that these lung cells had lost their identity.
Next, the team looked at which molecules were responsible for coordinating the MAP and PI3'- kinase pathways together. Fluorescent labeling of molecules already known to be involved in lung cell specialization showed some surprising results -- these molecules did not play a role in the loss of lung cell identity that contributes to tumor progression. Rather, a molecule called PGC1? appeared to be involved.
To investigate if PGC1? directly controls the loss of Type 2 pneumocyte identity during lung tumor development, the team studied mice with a silenced version of the molecule, alongside mutations in the MAP kinase pathway. They found that silencing PGC1? causes lung cells to lose their specialized characteristics by cooperating with two other molecules that are required for this specialization.
Read more at Science Daily
Aug 26, 2019
How plants measure their carbon dioxide uptake
When water is scarce, plants can close their pores to prevent losing too much water. This allows them to survive even longer periods of drought, but with the majority of pores closed, carbon dioxide uptake is also limited, which impairs photosynthetic performance and thus plant growth and yield.
Plant accomplish a balancing act -- navigating between drying out and starving in dry conditions -- through an elaborate network of sensors. An international team of plant scientists led by Rainer Hedrich, a biophysicist from Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany, has now pinpointed these sensors. The results have been published in the journal Nature Plants.
Microvalves control photosynthesis and water supply
When light is abundant, plants open the pores in their leaves to take in carbon dioxide (CO2) which they subsequently convert to carbohydrates in a process called photosynthesis. At the same time, a hundred times more water escapes through the microvalves than carbon dioxide flows in.
This is not a problem when there is enough water available, but when soils are parched in the middle of summer, the plant needs to switch to eco-mode to save water. Then plants will only open their pores to perform photosynthesis for as long as necessary to barely survive. Opening and closing the pores is accomplished through specialised guard cells that surround each pore in pairs. The units comprised of pores and guard cells are called stomata.
Guard cells have sensors for CO2 and ABA
The guard cells must be able to measure the photosynthesis and the water supply to respond appropriately to changing environmental conditions. For this purpose, they have a receptor to measure the CO2 concentration inside the leaf. When the CO2 value rises sharply, this is a sign that the photosynthesis is not running ideally. Then the pores are closed to prevent unnecessary evaporation. Once the CO2 concentration has fallen again, the pores reopen.
The water supply is measured through a hormone. When water is scarce, plants produce abscisic acid (ABA), a key stress hormone, and set their CO2 control cycle to water saving mode. This is accomplished through guard cells which are fitted with ABA receptors. When the hormone concentration in the leaf increases, the pores close.
Analysing the CO2-ABA network
The JMU research team wanted to shed light on the components of the guard cell control cycles. For this purpose, they exposed Arabidopsis species to elevated levels of CO2 or ABA. They did so over several hours to trigger reactions at the level of the genes. Afterwards, the stomata were isolated from the leaves to analyse the respective gene expression profiles of the guard cells using bioinformatics techniques. For this task, the team took Tobias Müller and Marcus Dietrich on board, two bioinformatics experts at the University of Würzburg.
The two experts found out that the gene expression patterns differed significantly at high CO2 or ABA concentrations. Moreover, they noticed that excessive CO2 also caused the expression of some ABA genes to change. These findings led the researchers to take a closer look at the ABA signalling pathway. They were particularly interested in the ABA receptors of the PYR/PYL family (pyrabactin receptor and pyrabactin-like). Arabidopsis has 14 of these receptors, six of them in the guard cells.
ABA receptors under the microscope
"Why does a guard cell need as many as six receptors for a single hormone? To answer this question, we teamed up with Professor Pedro Luis Rodriguez from the University of Madrid, who is an expert in ABA receptors," says Hedrich. Rodriguez's team generated Arabidopsis mutants in which they could study the ABA receptors individually.
"This enabled us to assign each of the six ABA receptors a task in the network and identify the individual receptors which are responsible for the ABA- and CO2-induced closing of the stomata," Peter Ache, a colleague of Hedrich's, explains.
Read more at Science Daily
Plant accomplish a balancing act -- navigating between drying out and starving in dry conditions -- through an elaborate network of sensors. An international team of plant scientists led by Rainer Hedrich, a biophysicist from Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany, has now pinpointed these sensors. The results have been published in the journal Nature Plants.
Microvalves control photosynthesis and water supply
When light is abundant, plants open the pores in their leaves to take in carbon dioxide (CO2) which they subsequently convert to carbohydrates in a process called photosynthesis. At the same time, a hundred times more water escapes through the microvalves than carbon dioxide flows in.
This is not a problem when there is enough water available, but when soils are parched in the middle of summer, the plant needs to switch to eco-mode to save water. Then plants will only open their pores to perform photosynthesis for as long as necessary to barely survive. Opening and closing the pores is accomplished through specialised guard cells that surround each pore in pairs. The units comprised of pores and guard cells are called stomata.
Guard cells have sensors for CO2 and ABA
The guard cells must be able to measure the photosynthesis and the water supply to respond appropriately to changing environmental conditions. For this purpose, they have a receptor to measure the CO2 concentration inside the leaf. When the CO2 value rises sharply, this is a sign that the photosynthesis is not running ideally. Then the pores are closed to prevent unnecessary evaporation. Once the CO2 concentration has fallen again, the pores reopen.
The water supply is measured through a hormone. When water is scarce, plants produce abscisic acid (ABA), a key stress hormone, and set their CO2 control cycle to water saving mode. This is accomplished through guard cells which are fitted with ABA receptors. When the hormone concentration in the leaf increases, the pores close.
Analysing the CO2-ABA network
The JMU research team wanted to shed light on the components of the guard cell control cycles. For this purpose, they exposed Arabidopsis species to elevated levels of CO2 or ABA. They did so over several hours to trigger reactions at the level of the genes. Afterwards, the stomata were isolated from the leaves to analyse the respective gene expression profiles of the guard cells using bioinformatics techniques. For this task, the team took Tobias Müller and Marcus Dietrich on board, two bioinformatics experts at the University of Würzburg.
The two experts found out that the gene expression patterns differed significantly at high CO2 or ABA concentrations. Moreover, they noticed that excessive CO2 also caused the expression of some ABA genes to change. These findings led the researchers to take a closer look at the ABA signalling pathway. They were particularly interested in the ABA receptors of the PYR/PYL family (pyrabactin receptor and pyrabactin-like). Arabidopsis has 14 of these receptors, six of them in the guard cells.
ABA receptors under the microscope
"Why does a guard cell need as many as six receptors for a single hormone? To answer this question, we teamed up with Professor Pedro Luis Rodriguez from the University of Madrid, who is an expert in ABA receptors," says Hedrich. Rodriguez's team generated Arabidopsis mutants in which they could study the ABA receptors individually.
"This enabled us to assign each of the six ABA receptors a task in the network and identify the individual receptors which are responsible for the ABA- and CO2-induced closing of the stomata," Peter Ache, a colleague of Hedrich's, explains.
Read more at Science Daily
A lack of background knowledge can hinder reading comprehension
The purpose of going to school is to learn, but students may find certain topics difficult to understand if they don't have the necessary background knowledge. This is one of the conclusions of a research article published in Psychological Science, a journal of the Association for Psychological Science.
"Background knowledge plays a key role in students' reading comprehension -- our findings show that if students don't have sufficient related knowledge, they'll probably have difficulties understanding text," says lead researcher Tenaha O'Reilly of Educational Testing Service (ETS)'s Center for Research on Human Capital in Education. "We also found that it's possible to measure students' knowledge quickly by using natural language processing techniques. If a student scores below the knowledge threshold, they'll probably have trouble comprehending the text."
Previous research has shown that students who lack sufficient reading skills, including decoding and vocabulary, fare poorly relative to their peers. But the research of O'Reilly and ETS colleagues Zuowei Wang and John Sabatini suggests that a knowledge threshold may also be an essential component of reading comprehension.
The researchers examined data from 3,534 high-school students at 37 schools in the United States. The students completed a test that measured their background knowledge on ecosystems. For the topical vocabulary section of the test, the students saw a list of 44 words and had to decide which were related to the topic of ecosystems. They also completed a multiple-choice section that was designed to measure their factual knowledge.
Then, after reading a series of texts on the topic of ecosystems, the students completed 34 items designed to measure how well they understood the texts. These comprehension items tapped into their ability to summarize what they had read, recognize opinions and incorrect information, and apply what they had read to reason more broadly about the content.
The researchers used a statistical technique called broken-line regression -- often used to identify an inflection point in a data set -- to analyze the students' performance.
The results revealed that a background-knowledge score of about 33.5, or about 59% correct, functioned as a performance threshold. Below this score, background knowledge and comprehension were not noticeably correlated; above the threshold score, students' comprehension appeared to increase as their background knowledge increased.
Additional results indicated that the pattern could not be fully explained by the level of students' knowledge on a different topic -- what mattered was their background knowledge of ecosystems.
The researchers found that students' ability to identify specific keywords was a fairly strong predictor whether they would perform above or below the threshold. That is, correctly identifying ecosystems, habitat, and species as topically relevant was more strongly linked with students' comprehension than was identifying bioremediation, densities, and fauna.
The findings underscore the importance of having reached a basic knowledge level to be able to read and comprehend texts across different subjects:
"Reading isn't just relevant to English Language Arts classes but also to reading in the content areas," says O'Reilly. "The Common Core State Standards highlight the increasing role of content area and disciplinary reading. We believe that the role of background knowledge in students' comprehension and learning might be more pronounced when reading texts in the subject areas."
The researchers plan to explore whether a similar kind of knowledge threshold emerges in other topic areas and domains; they note that it will be important to extend the research by focusing on diverse measures and populations.
If the pattern holds, the findings could have important applications for classroom teaching, given the availability of knowledge assessments that can be administered without taking valuable time away from instruction.
Read more at Science Daily
"Background knowledge plays a key role in students' reading comprehension -- our findings show that if students don't have sufficient related knowledge, they'll probably have difficulties understanding text," says lead researcher Tenaha O'Reilly of Educational Testing Service (ETS)'s Center for Research on Human Capital in Education. "We also found that it's possible to measure students' knowledge quickly by using natural language processing techniques. If a student scores below the knowledge threshold, they'll probably have trouble comprehending the text."
Previous research has shown that students who lack sufficient reading skills, including decoding and vocabulary, fare poorly relative to their peers. But the research of O'Reilly and ETS colleagues Zuowei Wang and John Sabatini suggests that a knowledge threshold may also be an essential component of reading comprehension.
The researchers examined data from 3,534 high-school students at 37 schools in the United States. The students completed a test that measured their background knowledge on ecosystems. For the topical vocabulary section of the test, the students saw a list of 44 words and had to decide which were related to the topic of ecosystems. They also completed a multiple-choice section that was designed to measure their factual knowledge.
Then, after reading a series of texts on the topic of ecosystems, the students completed 34 items designed to measure how well they understood the texts. These comprehension items tapped into their ability to summarize what they had read, recognize opinions and incorrect information, and apply what they had read to reason more broadly about the content.
The researchers used a statistical technique called broken-line regression -- often used to identify an inflection point in a data set -- to analyze the students' performance.
The results revealed that a background-knowledge score of about 33.5, or about 59% correct, functioned as a performance threshold. Below this score, background knowledge and comprehension were not noticeably correlated; above the threshold score, students' comprehension appeared to increase as their background knowledge increased.
Additional results indicated that the pattern could not be fully explained by the level of students' knowledge on a different topic -- what mattered was their background knowledge of ecosystems.
The researchers found that students' ability to identify specific keywords was a fairly strong predictor whether they would perform above or below the threshold. That is, correctly identifying ecosystems, habitat, and species as topically relevant was more strongly linked with students' comprehension than was identifying bioremediation, densities, and fauna.
The findings underscore the importance of having reached a basic knowledge level to be able to read and comprehend texts across different subjects:
"Reading isn't just relevant to English Language Arts classes but also to reading in the content areas," says O'Reilly. "The Common Core State Standards highlight the increasing role of content area and disciplinary reading. We believe that the role of background knowledge in students' comprehension and learning might be more pronounced when reading texts in the subject areas."
The researchers plan to explore whether a similar kind of knowledge threshold emerges in other topic areas and domains; they note that it will be important to extend the research by focusing on diverse measures and populations.
If the pattern holds, the findings could have important applications for classroom teaching, given the availability of knowledge assessments that can be administered without taking valuable time away from instruction.
Read more at Science Daily
The flavor of chocolate is developed during the processing of the cocoa beans
Just as we have seen an increase in the number of microbreweries making specialty beers, the market for chocolate has also developed, so there are more high-end chocolate manufacturers who are trying to stand out by fine tuning the taste and making several different varietals. Therefore, there is a need to know how you can address this during the processing of the noble cocoa.
The research was conducted on so-called noble cocoa (the varieties Criollo and Trinitario). Since the vast majority of the world's cocoa production is of the Forastero varietal, much more research has been done on this variety than on the two aforementioned varietals.
"Criollo cocoa is less bitter than Forastero, but is still more aromatic. You could call it the Pinot Noir of cocoa. But Criollo is a hassle to cultivate and it is difficult to grow in Africa, which is why it is almost exclusively grown in Central America, South America and Madagascar," says Professor with Special Responsibilities at the Department of Food Science at the University of Copenhagen (UCPH FOOD) Dennis Sandris Nielsen and continues:
"In this study we have, together with colleagues from Belgium and Nicaragua, examined for the first time how different conditions during fermentation affect the composition and activity of the microorganisms naturally present on the Criollo beans and how this affects the flavour of the finished fermented beans.
It has long been known that the processing, including the fermentation and drying of the cocoa, is important in relation to the final quality of the cocoa.
"Our research confirms this and we have also learned how to fine tune the cocoa by fine tuning the process itself, which means that you can get a higher quality out of your raw materials if you understand these processes," says Dennis Sandris Nielsen.
Part of the flavour is formed in the fermentation
A cocoa fruit is the size of a small honey melon and contains 30-40 cocoa beans, which are surrounded by a pulp. If you take a raw cocoa bean and try to make chocolate from it, it does not taste good -- you need fermentation to release the flavour potential.
The fermentation is done by opening the cocoa fruit, removing the beans and allowing them to ferment -- for example, in a box (see picture).
The pulp surrounding the beans is inoculated with various microorganisms from the surroundings, equipment, etc. The pulp is very acidic (pH 3-3.5) and has a high sugar content (about 10%), and in such an environment only a small number of microorganisms can grow. This is why the fermentation usually goes well, even if it is not inoculated with a starter culture. There is a natural selection of microorganisms that positively affect the taste.
Initially, it is mainly yeast that grows and then lactic acid bacteria. The yeast forms alcohol, while the lactic acid bacteria eat some of the citric acid that is naturally present. This means that the pH rises, making the environment more favourable for acetic acid bacteria, which converts some of the alcohol that has been formed into vinegar.
The processes generate a lot of heat -- reaching approx. 45-48 degrees. The alcohol and vinegar penetrate the beans and kill the germ in the cocoa beans so that they can no longer germinate. The cell walls are broken down, which means that different substances can react with each other and this is where the flavour development evolves.
Flavour development continues as the beans dry in the sun, where they are dried until they are microbially stable. Here ends the process for the cocoa farmers who can now sell the fermented and dried beans on. The producers are responsible for roasting the beans, where the substances formed during fermentation and drying react with each other, leading to the well-known and beloved flavour and aroma of cocoa.
Read more at Science Daily
The research was conducted on so-called noble cocoa (the varieties Criollo and Trinitario). Since the vast majority of the world's cocoa production is of the Forastero varietal, much more research has been done on this variety than on the two aforementioned varietals.
"Criollo cocoa is less bitter than Forastero, but is still more aromatic. You could call it the Pinot Noir of cocoa. But Criollo is a hassle to cultivate and it is difficult to grow in Africa, which is why it is almost exclusively grown in Central America, South America and Madagascar," says Professor with Special Responsibilities at the Department of Food Science at the University of Copenhagen (UCPH FOOD) Dennis Sandris Nielsen and continues:
"In this study we have, together with colleagues from Belgium and Nicaragua, examined for the first time how different conditions during fermentation affect the composition and activity of the microorganisms naturally present on the Criollo beans and how this affects the flavour of the finished fermented beans.
It has long been known that the processing, including the fermentation and drying of the cocoa, is important in relation to the final quality of the cocoa.
"Our research confirms this and we have also learned how to fine tune the cocoa by fine tuning the process itself, which means that you can get a higher quality out of your raw materials if you understand these processes," says Dennis Sandris Nielsen.
Part of the flavour is formed in the fermentation
A cocoa fruit is the size of a small honey melon and contains 30-40 cocoa beans, which are surrounded by a pulp. If you take a raw cocoa bean and try to make chocolate from it, it does not taste good -- you need fermentation to release the flavour potential.
The fermentation is done by opening the cocoa fruit, removing the beans and allowing them to ferment -- for example, in a box (see picture).
The pulp surrounding the beans is inoculated with various microorganisms from the surroundings, equipment, etc. The pulp is very acidic (pH 3-3.5) and has a high sugar content (about 10%), and in such an environment only a small number of microorganisms can grow. This is why the fermentation usually goes well, even if it is not inoculated with a starter culture. There is a natural selection of microorganisms that positively affect the taste.
Initially, it is mainly yeast that grows and then lactic acid bacteria. The yeast forms alcohol, while the lactic acid bacteria eat some of the citric acid that is naturally present. This means that the pH rises, making the environment more favourable for acetic acid bacteria, which converts some of the alcohol that has been formed into vinegar.
The processes generate a lot of heat -- reaching approx. 45-48 degrees. The alcohol and vinegar penetrate the beans and kill the germ in the cocoa beans so that they can no longer germinate. The cell walls are broken down, which means that different substances can react with each other and this is where the flavour development evolves.
Flavour development continues as the beans dry in the sun, where they are dried until they are microbially stable. Here ends the process for the cocoa farmers who can now sell the fermented and dried beans on. The producers are responsible for roasting the beans, where the substances formed during fermentation and drying react with each other, leading to the well-known and beloved flavour and aroma of cocoa.
Read more at Science Daily
Even scientists have gender stereotypes ... which can hamper the career of women researchers
However convinced we may be that science is not just for men, the concept of science remains much more strongly associated with masculinity than with femininity in people's minds. This automatic bias, which had already been identified among the general public, also exists in the minds of most scientists, who are not necessarily aware of it. And, in certain conditions, it may lead to otherwise careful scientific evaluation committees putting women at a disadvantage during promotion rounds involving men and women researchers. These are the findings of a study conducted by behavioural scientists from the Social and cognitive psychology laboratory (CNRS/Université Clermont Auvergne), the Laboratory of Cognitive Psychology (CNRS/Aix-Marseille Université), and the University of British Columbia (Canada), with the support of the CNRS Mission for the place of women. The study is published in the journal Nature Human Behaviour on 26 August 2019.
Women remain underrepresented in scientific research: at the French National Centre for Scientific Research (CNRS), across all disciplines, the average percentage of female researchers is 35%. And the higher the scientific research position, the more this percentage declines. Several reasons have been cited to explain these disparities: differences in levels of motivation, self-censorship ... but is discrimination also part of the story?
To find out, scientists in social and cognitive psychology studied 40 evaluation committees tasked with evaluating applications for research director positions at the CNRS over a period of two years. This is the first time that a research institution has carried out such a scientific study of its practices in the course of an annual nationwide competition covering the entire scientific spectrum.
This study shows that, from particle physics to the social sciences, most scientists, whether male or female, associate "science" and "masculine" in their semantic memory (the memory of concepts and words). This stereotype is implicit, which is to say that most often it is not detectable at the level of discourse. And it is equivalent to that observed among the general population.
Yet does this implicit stereotype have consequences on the decisions made by evaluation committees? Yes, when committees deny or minimise the existence of bias against women. Here, this is the case for around half of the committees. In these committees, the stronger the implicit stereotypes, the less often women are promoted. In contrast, when committees acknowledge the possibility of bias, implicit stereotypes, however strong they may be, have no influence.
Even if disparities between men and women in science have multiple causes and start at school (as the same authors have shown in other publications), this study indicates for the first time the existence of implicit gender stereotypes among male and female researchers across all disciplines -- stereotypes that can harm the careers of women scientists.
Read more at Science Daily
Women remain underrepresented in scientific research: at the French National Centre for Scientific Research (CNRS), across all disciplines, the average percentage of female researchers is 35%. And the higher the scientific research position, the more this percentage declines. Several reasons have been cited to explain these disparities: differences in levels of motivation, self-censorship ... but is discrimination also part of the story?
To find out, scientists in social and cognitive psychology studied 40 evaluation committees tasked with evaluating applications for research director positions at the CNRS over a period of two years. This is the first time that a research institution has carried out such a scientific study of its practices in the course of an annual nationwide competition covering the entire scientific spectrum.
This study shows that, from particle physics to the social sciences, most scientists, whether male or female, associate "science" and "masculine" in their semantic memory (the memory of concepts and words). This stereotype is implicit, which is to say that most often it is not detectable at the level of discourse. And it is equivalent to that observed among the general population.
Yet does this implicit stereotype have consequences on the decisions made by evaluation committees? Yes, when committees deny or minimise the existence of bias against women. Here, this is the case for around half of the committees. In these committees, the stronger the implicit stereotypes, the less often women are promoted. In contrast, when committees acknowledge the possibility of bias, implicit stereotypes, however strong they may be, have no influence.
Even if disparities between men and women in science have multiple causes and start at school (as the same authors have shown in other publications), this study indicates for the first time the existence of implicit gender stereotypes among male and female researchers across all disciplines -- stereotypes that can harm the careers of women scientists.
Read more at Science Daily
Aug 25, 2019
Bioprinting complex living tissue in just a few seconds
Tissue engineers create artificial organs and tissues that can be used to develop and test new drugs, repair damaged tissue and even replace entire organs in the human body. However, current fabrication methods limit their ability to produce free-form shapes and achieve high cell viability.
Researchers at the Laboratory of Applied Photonics Devices (LAPD), in EPFL's School of Engineering, working with colleagues from Utrecht University, have come up with an optical technique that takes just a few seconds to sculpt complex tissue shapes in a biocompatible hydrogel containing stem cells. The resulting tissue can then be vascularized by adding endothelial cells.
The team describes this high-resolution printing method in an article appearing in Advanced Materials. The technique will change the way cellular engineering specialists work, allowing them to create a new breed of personalized, functional bioprinted organs.
Printing a femur or a meniscus
The technique is called volumetric bioprinting. To create tissue, the researchers project a laser down a spinning tube filled with a stem-cell-laden hydrogel. They shape the tissue by focusing the energy from the light at specific locations, which then solidify. After just a few seconds, a complex 3D shape appears, suspended in the gel. The stem cells in the hydrogel are largely unaffected by this process. The researchers then introduce endothelial cells to vascularize the tissue.
The researchers have shown that it's possible to create a tissue construct measuring several centimeters, which is a clinically useful size. Examples of their work include a valve similar to a heart valve, a meniscus and a complex-shaped part of the femur. They were also able to build interlocking structures.
"Unlike conventional bioprinting -- a slow, layer-by-layer process -- our technique is fast and offers greater design freedom without jeopardizing the cells' viability," says Damien Loterie, an LAPD researcher and one of the study's coauthors.
Replicating the human body
The researchers' work is a real game changer. "The characteristics of human tissue depend to a large extent on a highly sophisticated extracellular structure, and the ability to replicate this complexity could lead to a number of real clinical applications," says Paul Delrot, another coauthor. Using this technique, labs could mass-produce artificial tissues or organs at unprecedented speed. This sort of replicability is essential when it comes to testing new drugs in vitro, and it could help obviate the need for animal testing -- a clear ethical advantage as well as a way of reducing costs.
"This is just the beginning. We believe that our method is inherently scalable towards mass fabrication and could be used to produce a wide range of cellular tissue models, not to mention medical devices and personalized implants," says Christophe Moser, the head of the LAPD.
Read more at Science Daily
Researchers at the Laboratory of Applied Photonics Devices (LAPD), in EPFL's School of Engineering, working with colleagues from Utrecht University, have come up with an optical technique that takes just a few seconds to sculpt complex tissue shapes in a biocompatible hydrogel containing stem cells. The resulting tissue can then be vascularized by adding endothelial cells.
The team describes this high-resolution printing method in an article appearing in Advanced Materials. The technique will change the way cellular engineering specialists work, allowing them to create a new breed of personalized, functional bioprinted organs.
Printing a femur or a meniscus
The technique is called volumetric bioprinting. To create tissue, the researchers project a laser down a spinning tube filled with a stem-cell-laden hydrogel. They shape the tissue by focusing the energy from the light at specific locations, which then solidify. After just a few seconds, a complex 3D shape appears, suspended in the gel. The stem cells in the hydrogel are largely unaffected by this process. The researchers then introduce endothelial cells to vascularize the tissue.
The researchers have shown that it's possible to create a tissue construct measuring several centimeters, which is a clinically useful size. Examples of their work include a valve similar to a heart valve, a meniscus and a complex-shaped part of the femur. They were also able to build interlocking structures.
"Unlike conventional bioprinting -- a slow, layer-by-layer process -- our technique is fast and offers greater design freedom without jeopardizing the cells' viability," says Damien Loterie, an LAPD researcher and one of the study's coauthors.
Replicating the human body
The researchers' work is a real game changer. "The characteristics of human tissue depend to a large extent on a highly sophisticated extracellular structure, and the ability to replicate this complexity could lead to a number of real clinical applications," says Paul Delrot, another coauthor. Using this technique, labs could mass-produce artificial tissues or organs at unprecedented speed. This sort of replicability is essential when it comes to testing new drugs in vitro, and it could help obviate the need for animal testing -- a clear ethical advantage as well as a way of reducing costs.
"This is just the beginning. We believe that our method is inherently scalable towards mass fabrication and could be used to produce a wide range of cellular tissue models, not to mention medical devices and personalized implants," says Christophe Moser, the head of the LAPD.
Read more at Science Daily
Big brains or big guts: Choose one
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| Ptarmigan |
A global study comparing 2,062 birds finds that, in highly variable environments, birds tend to have either larger or smaller brains relative to their body size. Birds with smaller brains tend to use ecological strategies that are not available to big-brained counterparts. Instead of relying on grey matter to survive, these birds tend to have large bodies, eat readily available food and make lots of babies.
The new research from biologists at Washington University in St. Louis appears Aug. 23 in the journal Nature Communications.
"The fact is that there are a great many species that do quite well with small brains," said Trevor Fristoe, formerly a postdoctoral researcher at Washington University, now at the University of Konstanz in Germany.
"What's really interesting is that we don't see any middle ground here," Fristoe said. "The resident species with intermediate brain size are almost completely absent from high latitude (colder and more climatically variable) environments. The species that don't go all in on either of the extreme strategies are forced to migrate to more benign climates during the winter."
"Having a large brain is typically associated with strong energetic demands and a slower life-history," said Carlos Botero, assistant professor of biology in Arts & Sciences and co-author of the paper. "Free from these constraints, species with small brains can exhibit traits and lifestyles that are never seen in larger-brained ones.
"What we found is that alternative ecological strategies that either increase or decrease investments in brain tissue are equally capable of coping with the challenges of living in high-latitude environments," he said.
Because the brain is such a costly organ to develop and maintain, biologists have long been interested in understanding how large brain size -- in all species -- could have evolved.
One hypothesis is based around the idea that one of the main advantages of possessing a big brain is that it allows for a high degree of behavioral flexibility. With flexibility comes the ability to respond to different conditions -- such as wide swings in temperature, or changes in food availability.
The so-called cognitive buffer hypothesis is not the only possible explanation for the evolution of brain size -- but it is an important and influential one.
Relative brain size is a measure of the size of the brain as compared to the body -- think: an ostrich's brain might be much bigger than a chickadee's brain, but so is the ostrich's body. Predictably, the global distribution of relative brain size of birds follows a bell curve, with most species landing squarely in the middle, and only a handful of outliers with relatively large or relatively small brains.
Previous studies had found general trends towards larger relative brain sizes in higher latitudes, where conditions are more variable -- consistent with the cognitive buffer hypothesis. Fristoe and Botero's new study is different because it looks at the full distribution of brain sizes across environments, allowing them to test whether different sizes are over- or under-represented.
Excluding contributions from migrants -- the birds that live in polar or temperate environments only during more favorable times of the year -- the researchers found that at high latitudes, bird brain size appears to be bimodal. This morphological pattern means that bird brains are significantly more likely to be relatively large, or relatively small, compared to body size.
What was going on here? Fristoe, born in Alaska, had a few ideas.
In fact, Fristoe suggests that the Alaska state bird, the ptarmigan, might be a good poster child for the small-brained species. Endearing though she is -- with her plushy bosom, feathered feet and unusual chuckling call -- she's not exactly known for her smarts. The ptarmigan can, however, chow down on twigs and willow leaves with the best of them.
"In our paper, we find that small-brained species in these environments employ strategies that are unachievable with a large brain," Fristoe said. "First, these species are able to persist by foraging on readily available but difficult to digest resources such as dormant plant buds, the needles of conifers, or even twigs.
"These foods can be found even during harsh winter conditions, but they are fibrous and require a large gut to digest," he said. "Gut tissue, like brain tissue, is energetically demanding, and limited budgets mean that it is challenging to maintain a lot of both.
"We also found that these species have high reproductive rates, producing many offspring every year," Fristoe said. "This would allow their populations to recover from high mortality during particularly challenging conditions. Because big-brained species tend to invest more time in raising fewer offspring, this is a strategy that is not available to them."
In other words, maybe big brains are not all that.
"Brains are not evolving in isolation -- they are part of a broader suite of adaptations that help organisms be successful in their lives," Botero said. "Because of trade-offs between different aspects of that total phenotype, we find that two different lineages may respond to selection from environmental oscillations in completely different ways.
Read more at Science Daily
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