Liquid water beneath Martian south polar cap?

A Southwest Research Institute scientist measured the properties of ice-brine mixtures as cold as -145 degrees Fahrenheit to help confirm that salty water likely exists between grains of ice or sediment under the ice cap at Mars' south pole. Laboratory measurements conducted by SwRI geophysicist Dr. David Stillman support oddly bright reflections detected by the MARSIS subsurface sounding radar aboard ESA's Mars Express orbiter.

With a 130-foot antenna, MARSIS flies over the planet, bouncing radio waves over a selected area and then receiving and analyzing the echoes or reflections. Any near-surface liquid water should send a strong bright signal, whereas the radar signal for ice and rock would be much smaller.

Because conventional models assume the Mars south polar cap experiences temperatures much lower than the melting point of water, many scientists have questioned the presence of liquid water. Clay, hydrated salts and saline ices have been proposed as potential explanations for the source of the bright basal reflections. The Italian-led team investigating the proposed phenomena used previously published data, simulations and new laboratory measurements.

"Lakes of liquid water actually exist beneath glaciers in Arctic and Antarctic regions, so we have Earth analogs for finding liquid water below ice," said Stillman, a specialist in detecting water in any format -- liquid, ice or absorbed -- on planetary bodies and co-author of a paper describing these findings. "The exotic salts that we know exist on Mars have amazing 'antifreeze' properties allowing brines to remain liquid down to -103 degrees Fahrenheit. We studied these salts in our lab to understand how they would respond to radar."

Stillman has over a decade of experience measuring the properties of materials at cold temperatures to detect and characterize subsurface ice, unfrozen water and the potential for life throughout the solar system. For this project, Stillman measured the properties of perchlorate brines in an SwRI environmental chamber that produces near-liquid-nitrogen temperatures at Mars-like pressures.

"My Italian colleagues reached out to see if my laboratory experiment data would support the presence of liquid water beneath the Martian ice cap," Stillman said. "The research showed that we don't have to have lakes of perchlorate and chloride brines, but that these brines could exist between the grains of ice or sediments and are enough to exhibit a strong dielectric response. This is similar to how seawater saturates grains of sand at the shoreline or how flavoring permeates a slushie, but at -103 degrees Fahrenheit below a mile of ice near the South Pole of Mars."

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Researchers provide insight into how the brain multitasks while walking

New research turns the old idiom about not being able to walk and chew gum on its head. Scientists with the Del Monte Institute for Neuroscience at the University of Rochester have shown that the healthy brain is able to multitask while walking without sacrificing how either activity is accomplished.

"This research shows us that the brain is flexible and can take on additional burdens," said David Richardson, an MD/PhD student in his fifth year in the Pathology & Cell Biology of Disease Program, and first author of the study recently published in the journal NeuroImage. "Our findings showed that the walking patterns of the participants improved when they performed a cognitive task at the same time, suggesting they were actually more stable while walking and performing the task than when they were solely focused on walking."

During these experiments, researchers used a Mobile Brain/Body Imaging system, or MoBI, located in the Del Monte Institute's Frederick J. and Marion A. Schindler Cognitive Neurophysiology Lab. The platform combines virtual reality, brain monitoring, and motion capture technology. While participants walk on a treadmill or manipulate objects on a table, 16 high speed cameras record the position markers with millimeter precision, while simultaneously measuring their brain activity.

The MoBI was used to record the brain activity of participants as they walked on a treadmill and were cued to switch tasks. Their brain activity was also recorded as they performed these same tasks while sitting. Brain changes were measured between the cued tasks and showed that during the more difficult the tasks the neurophysiological difference was greater between walking and sitting -- highlighting the flexibility of a healthy brain and how it prepares for and executes tasks based on difficulty level.

"The MoBI allows us to better understand how the brain functions in everyday life," said Edward Freedman, Ph.D., lead author on the study. "Looking at these findings to understand how a young healthy brain is able to switch tasks will give us better insight to what's going awry in a brain with a neurodegenerative disease like Alzheimer's disease."

"Understanding how a young healthy brain can successfully 'walk and talk' is an important start, but we also need to understand how these findings differ in the brains of healthy older adults, and adults with neurodegenerative diseases," said Richardson. "The next stage is expanding this research to include a more diverse group of brains."

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Redefining alcohol use disorder

Researchers at the University of Missouri have developed a new framework that they believe will help identify people previously overlooked for alcohol use disorder (AUD). This framework focuses on 13 risk factors, such as impulsive behavior, reward sensitivity, and punishment sensitivity, that could lead to someone developing an AUD.

"We know from decades of research that there are a lot of different pathways to alcohol use disorder," said Cassie Boness, a former graduate student at MU in the Department of Psychological Sciences. "So, we want to make sure that we are targeting people's specific pathways as accurately as possible in order to be most effective in identifying and treating AUD."

Throughout her career, Boness has been interested in the causes, diagnosis and assessment of substance use disorders, including AUD, a chronic medical condition characterized by ongoing alcohol use despite adverse consequences. For Boness, it's personal -- after seeing her loved ones stigmatized for their addiction to alcohol, and then watching them struggle to get connected with treatment, she wanted to help reduce the amount of suffering people may experience with AUD.

While today's assessment tools, such as the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) can help health care professionals diagnose someone with AUD, Boness believes the current methods are too narrowly focused on the consequences of someone's actions, rather than incorporating a broad list of potential risk factors that may lead to an AUD diagnosis.

Boness, who is now a research assistant professor at the University of New Mexico, hopes their framework can be a step forward toward a comprehensive diagnosis of AUD throughout the health care community. However, she stresses that this tool is not meant to be the only solution, but rather a way for other researchers like her to build upon and enhance the existing research on the subject.

"Eventually, we'd like to see assessment tools that more comprehensively capture the factors articulated in our framework so that we can identify individual profiles of risk and potentially intervene during earlier stages of addiction," Boness said.

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Using the eye as a window into heart disease

Scientists have developed an artificial intelligence (AI) system that can analyse eye scans taken during a routine visit to an optician or eye clinic and identify patients at a high risk of a heart attack.

Doctors have recognised that changes to the tiny blood vessels in the retina are indicators of broader vascular disease, including problems with the heart.

In the research, led by the University of Leeds, deep learning techniques were used to train the AI system to automatically read retinal scans and identify those people who, over the following year, were likely to have a heart attack.

Deep learning is a complex series of algorithms that enable computers to identify patterns in data and to make predictions.

Writing in the journal Nature Machine Intelligence, the researchers report that the AI system had an accuracy of between 70% and 80% and could be used as a second referral mechanism for in-depth cardiovascular investigation.

The use of deep learning in the analysis of retinal scans could revolutionise the way patients are regularly screened for signs of heart disease.

Professor Alex Frangi, who holds the Diamond Jubilee Chair in Computational Medicine at the University of Leeds and is a Turing Fellow at the Alan Turing Institute, supervised the research. He said: "Cardiovascular diseases, including heart attacks, are the leading cause of early death worldwide and the second-largest killer in the UK. This causes chronic ill-health and misery worldwide.

"This technique opens-up the possibility of revolutionising the screening of cardiac disease. Retinal scans are comparatively cheap and routinely used in many optician practices. As a result of automated screening, patients who are at high risk of becoming ill could be referred to specialist cardiac services.

"The scans could also be used to track the early signs of heart disease."

The study involved a worldwide collaboration of scientists, engineers and clinicians from the University of Leeds; Leeds Teaching Hospitals' NHS Trust; the University of York; the Cixi Institute of Biomedical Imaging in Ningbo, part of the Chinese Academy of Sciences; the University of Cote d'Azur, France; the National Centre for Biotechnology Information and the National Eye Institute, both part of the National Institutes for Health in the US; and KU Leuven in Belgium.

The UK Biobank provided data for the study.

Chris Gale, Professor of Cardiovascular Medicine at the University of Leeds and a Consultant Cardiologist at Leeds Teaching Hospitals NHS Trust, was one of the authors of the research paper.

He said: "The AI system has the potential to identify individuals attending routine eye screening who are at higher future risk of cardiovascular disease, whereby preventative treatments could be started earlier to prevent premature cardiovascular disease."

Deep learning

During the deep learning process, the AI system analysed the retinal scans and cardiac scans from more than 5,000 people. The AI system identified associations between pathology in the retina and changes in the patient's heart.

Once the image patterns were learned, the AI system could estimate the size and pumping efficiency of the left ventricle, one of the heart's four chambers, from retinal scans alone. An enlarged ventricle is linked with an increased risk of heart disease.

With information on the estimated size of the left ventricle and its pumping efficiency combined with basic demographic data about the patient, their age and sex, the AI system could make a prediction about their risk of a heart attack over the subsequent 12 months.

Currently, details about the size and pumping efficiency of a patient's left ventricle can only be determined if they have diagnostic tests such as echocardiography or magnetic resonance imaging of the heart. Those diagnostic tests can be expensive and are often only available in a hospital setting, making them inaccessible for people in countries with less well-resourced healthcare systems -- or unnecessarily increasing healthcare costs and waiting times in developed countries.

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Tug of sun, moon could be driving plate motions on ‘imbalanced’ Earth

A study led by geophysicist Anne M. Hofmeister in Arts & Sciences at Washington University in St. Louis proposes that imbalanced forces and torques in the Earth-moon-sun system drive circulation of the whole mantle.

The new analysis provides an alternative to the hypothesis that the movement of tectonic plates is related to convection currents in the Earth's mantle. Convection involves buoyant rise of heated fluids, which Hofmeister and her colleagues argue does not apply to solid rocks. They argue that force, not heat, moves large objects. The new research is published in a special paper of the Geological Society of America, as part of a forthcoming collection assembled in honor of geologist Warren B. Hamilton.

Earth's internal workings are popularly modeled as dissipating heat generated by internal radioactivity and from leftover energy created during collisions when our planet formed. But even mantle convection proponents recognize that that amount of internal heat-energy is insufficient to drive large-scale tectonics. And there are other problems with using convection to explain observed plate motions.

Instead, Earth's plates might be shifting because the sun exerts such a strong gravitational pull on the moon that it has caused the moon's orbit around Earth to become elongated.

Over time, the position of the barycenter -- the center of mass between the orbiting bodies of the Earth and the moon -- has moved closer to Earth's surface and now oscillates 600 km per month relative to the geocenter, Hofmeister said. This sets up internal stresses, as the Earth continues to spin.

"Because the oscillating barycenter lies ~4600 km from the geocenter, Earth's tangential orbital acceleration and solar pull are imbalanced except at the barycenter," Hofmeister said. "The planet's warm, thick and strong interior layers can withstand these stresses, but its thin, cold, brittle lithosphere responds by fracturing."

Daily spin flattens the Earth from a perfect spherical shape, which contributes to this brittle failure of the lithosphere. These two independent stresses create the mosaic of plates observed in the outer shell, the authors suggest. The variety of plate motions comes from the changes in size and direction of the imbalanced gravitational forces with time.

But how to test this alternative? Hofmeister suggested: "One test would be a detailed examination of the tectonics of Pluto, which is too small and cold to convect, but has a giant moon and a surprisingly young surface."

The study includes a comparison of rocky planets that shows that the presence and longevity of volcanism and tectonism depend on the particular combination of moon size, moon orbital orientation, proximity to the sun and rates of body spin and cooling.

Earth is the only rocky planet with all the factors needed for plate tectonics, Hofmeister noted.

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Scientists identify new genus and species of legume, now mysteriously extinct

Oregon State University researchers have described a new legume tree from flowers embedded in several lumps of amber recovered from deep within an amber mine in the mountains of the Dominican Republic.

OSU's George Poinar Jr. and Kenton Chambers placed the 20- to 30-million-year-old flowers in a novel genus and species, Salpinganthium hispaniolanum, in the family Fabaceae.

"The flowers are quite striking with their spreading sepals and petals, along with the 10 extended stamens," said Poinar, an international expert in using plant and animal life forms preserved in amber to learn about the biology and ecology of the distant past. "While now darkened with age, the petals were probably white, yellow or even pink, which are the petal colors of the closely related purpleheart tree, whose strong, durable, purplish wood is prized by artists, ship builders, furniture makers and other crafts people."

Groves of purpleheart trees continue to grow along rivers in tropical rain forests in Central and South America, particularly in the Amazon basin, said Poinar, professor emeritus in the Oregon State College of Science.

Poinar and Chambers, professor emeritus in the OSU College of Agricultural Sciences, derived the name of the genus from the Greek words for tube, trumpet and flower. The species name is based on the Caribbean island, Hispaniola, where the fossil originated.

"While purpleheart trees are still with us, Salpinganthium trees have disappeared," said Poinar. "We can only speculate about why these fossil trees have become extinct."

They could have succumbed to some unique biological and/or physical events, such as the loss of a pollinator, presence of a pathogen or climatic change that ravaged populations throughout their entire range, Poinar said. Finding their flowers in five separate pieces of amber shows that they were well established in the Dominican amber forest, he added.

Poinar and Chambers placed Salpinganthium hispaniolanum, the latest in a number of flowers described by the authors from Dominican amber mines, in the resin-producing tribe Detarieae; the tribe's members have sepals and petals dotted with glands.

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Transparency in butterflies, from A-Z: It’s more of a superpower than we thought

Like invisibility in legends, transparency in nature is a powerful tool. Most transparent animals live in the ocean, where a close visual match with the water renders them almost invisible to predators.

On land, transparency is rare and difficult to achieve, but some butterflies and moths (Lepidoptera) do have transparent wings. And a new study indicates transparency can serve not only to camouflage them, but in other cases to signal and warn predators, "Don't eat me! I'm toxic."

This flexible weapon for self-defense is one of many findings from a multiyear study spanning the physics, biology, ecology, and evolution of transparency in Lepidoptera conducted by several groups, including the lab of Nipam Patel, director of the Marine Biological Laboratory (MBL).

"This is one of those interdisciplinary studies you dream about, where you want to understand [a biological structure] from its physics to its development and ecology," says Patel of the international study, which began as a project in the MBL Embryology course and ended up being funded by the Human Frontier Science Program. Ph.D. candidate Aaron Pomerantz in Patel's lab is also on the team.

Mimicry for Self-Defense

The group's latest paper adds a unique perspective on Lepidoptera self-defense. In some species, vivid wing coloration indicates the presence of chemical defenses that make the butterfly unpalatable or toxic, and predators learn to avoid them. Accordingly, palatable species can evolve to mimic the toxic ones, so predators leave them alone, too. In addition, multiple unpalatable species may converge in their warning colorations, thereby sharing in the benefits of the warning coloration process. Large "mimicry rings" can even form containing both toxic and nontoxic species, all displaying strikingly similar patterns and color combinations.

"The most amazing place to see this is the Amazon," Patel says. "You'll find a group of species that are distantly related to each other, yet they've all converged on a similar wing pattern."

Surprisingly, mimicry rings have also been found among clear-wing species in the Amazon. "So we asked, 'Wait, why would a species be transparent and unpalatable at the same time?'" Patel says. And, structurally, how would a clear-wing species accomplish that trick?

The team looked at the optical and structural properties of transparent butterfly wings within mimicry rings to see if they were convergent, and found in some rings, they were.

"In one transparency ring we studied (see photo 1, middle row), the key unpalatable butterfly doesn't have an anti-glare coating on its transparent wing, so in sunlight, it's really easy to see," Patel says. "It may be signaling a warning pattern to predators when it's in bright sun, and it's camouflaged when in shadows. So it kind of cheats: it has the best of both worlds."

Previously, the team reported on the developmental origins of transparency in a clear-wing species, Greta oto. They also compared wing transparency across 123 Lepidoptera species for its structural basis, optical properties, and biological relevance in relation to concealment, thermoregulation, and protection against UV. Those results showed a wide diversity of solutions to achieve transparency, suggesting that transparency has likely evolved multiple times independently.

Approaching transparency from multiple disciplines brought emergent knowledge and interesting new questions, Patel said. "Now that we've identified different Lepidoptera groups that have found different ways to achieve transparency, we can ask, how did they actually do this? Or, alternatively, if two very distant lineages have come up with the same solution for transparency, did they solve the problem in the same way?"

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My heart will go on: Patient-derived heart cells mimic disease in vitro

How can you mend a broken heart? According to researchers from Japan, in some cases gene replacement therapy just might do the trick.

In a study published in January in Stem Cell Reports, researchers from Osaka University report that heart cells from a patient with an inherited heart disease called arrhythmogenic cardiomyopathy do not contract correctly when grown in the laboratory, and that replacing the mutated gene responsible for this effect fixes this defect.

Arrhythmogenic cardiomyopathy occurs due to mutations in genes involved in desmosomes, which form 'welds' between cells that help them communicate and move in a coordinated way. One of these genes, PKP2, encodes a protein known as plakophilin-2 that is crucial to maintaining heart cell structure.

"Previous studies carried out in cardiomyocytes have shown that mutations in PKP2 play a pathological role in arrhythmogenic cardiomyopathy," says lead author of the study Hiroyuki Inoue. "However, the cells used in those experiments were derived from healthy individuals and were not assessed for contractile function."

To investigate how cells derived from patients behave in the laboratory, the researchers first took a blood sample from a young patient with arrhythmogenic cardiomyopathy, induced some of the blood cells to become stem cells, and then differentiated these stem cells into heart cells. They then modified this original batch of heart cells into three different cell lines with precisely adjusted PKP2 expression based on how many mutated or intact copies of the gene were present.

"The cells with two mutated copies of PKP2 clearly exhibited reduced contractility and impaired desmosome assembly due to plakophilin-2 deficiency," explains Shuichiro Higo, senior author. "These effects were also observed in cells with only one mutated copy of PKP2, although they were less severe."

Replacing the mutated PKP2 with an intact copy of the gene repaired the defects in both cell contraction and desmosome assembly, which the researchers were able to observe using a time-lapse approach and fluorescently labeled desmosomes.

"These findings suggest that our cardiomyocyte cell lines recapitulate the pathology of arrhythmogenic cardiomyopathy and provide a rapid and convenient platform for developing gene-based therapies for this disease," says Higo.

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Sidewinding young stellar jets spied by Gemini South

Sinuous stellar jets meander lazily across a field of stars in new images captured from Chile by the international Gemini Observatory, a Program of NSF's NOIRLab. The gently curving stellar jets are the outflow from young stars, and astronomers suspect their sidewinding appearances are caused by the gravitational attraction of companion stars. These crystal-clear observations were made using the Gemini South telescope's adaptive optics system, which helps astronomers counteract the blurring effects of atmospheric turbulence.

Young stellar jets are a common by-product of star formation and are thought to be caused by the interplay between the magnetic fields of rotating young stars and the disks of gas surrounding them. These interactions eject twin torrents of ionized gas in opposite directions, such as those pictured in two images captured by astronomers using the Gemini South telescope on Cerro Pachón on the edge of the Chilean Andes. Gemini South is one half of the international Gemini Observatory, a Program of NSF's NOIRLab, that comprises twin 8.1-meter optical/infrared telescopes on two of the best observing sites on the planet. Its counterpart, Gemini North, is located near the summit of Maunakea in Hawai'i.

The jet in the first image, named MHO 2147, is roughly 10,000 light-years from Earth, and lies in the galactic plane of the Milky Way, close to the boundary between the constellations Sagittarius and Ophiuchus. MHO 2147 snakes across a starry backdrop in the image -- an appropriately serpentine appearance for an object close to Ophiuchus. Like many of the 88 modern astronomical constellations, Ophiuchus has mythological roots -- in ancient Greece it represented a variety of gods and heroes grappling with a serpent. MHO 1502, the jet pictured in the second image, is located in the constellation of Vela, approximately 2000 light-years away.

Most stellar jets are straight but some can be wandering or knotted. The shape of the uneven jets is thought to be related to a characteristic of the object or objects that created them. In the case of the two bipolar jets MHO 2147 and MHO 1502, the stars which created them are obscured from view.

In the case of MHO 2147, this young central star, which has the catchy identifier IRAS 17527-2439, is embedded in an infrared dark cloud -- a cold, dense region of gas that is opaque at the infrared wavelengths represented in this image. The sinuous shape of MHO 2147 is caused because the direction of the jet has changed over time, tracing out a gentle curve on either side of the central star. These almost unbroken curves suggest that MHO 2147 has been sculpted by continuous emission from its central source. Astronomers found that the changing direction (precession) of the jet may be due to the gravitational influence of nearby stars acting on the central star. Their observations suggest that IRAS 17527-2439 could belong to a triple star system separated by more than 300 billion kilometers (almost 200 billion miles).

MHO 1502, on the other hand, is embedded in a totally different environment -- an area of star formation known as an HII region. The bipolar jet is composed of a chain of knots, suggesting that its source, thought to be two stars, has been intermittently emitting material.

These detailed images were captured by the Gemini South Adaptive Optics Imager (GSAOI), an instrument on the 8.1-meter-diameter Gemini South telescope. Gemini South is perched on the summit of Cerro Pachón, where dry air and negligible cloud cover provide one of the best observing sites on the planet. Even atop Cerro Pachón, however, atmospheric turbulence causes the stars to blur and twinkle.

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In visual memory, size matters

Every day we encounter images on the wall, in newspapers, books, and electronic devices. Some become etched in our memory and some don't. The elements influencing whether we remember one image and not the other aren't yet known, but researchers have assumed that image size and memory aren't connected to one another, since we usually understand what appears in an image, whether it is large or small.

A new study led by Dr. Sharon Gilaie-Dotan, of Bar-Ilan University's School of Optometry and Vision Science and Gonda (Goldschmied) Multidisciplinary Brain Research Center, sought to determine whether large images are better remembered than small ones during natural daily behavior. Her assumption was based on the fact that large images require the visual system to utilize greater resources for processing them.

The results of the study, just published in the journal Proceedings of the National Academy of Sciences, show for the first time that in natural vision, visual memory of images is affected by the size of the image on the retina. These findings can have many implications, including on the use of different types of electronic screens and the quality of information processing when we rely on large vs. small screens.

Shaimaa Masarwa and Olga Kreichman, PhD students in Dr. Gilaie-Dotan's lab, examined what happens to visual memory when participants were asked to look at pictures without knowing anything about a memory task to come. Each participant was shown different pictures in different sizes, each presented to them just once.

One hundred eighty-two subjects participated in seven different experiments. Time and time again the researchers found that the large images were better remembered (1.5 times more) than the small images. This phenomenon was not dependent on specific stimuli, the order in which the images appeared, their resolution, or the amount of information they contained.

To understand whether this result was determined by size rather than amount of detail, the researchers also examined whether large, blurred images are better etched in memory than clear, small images, where the large images contained the same details as the small images. To their surprise, they found that even in this case, the participants remembered the large, blurry images better than the small, clear images.

They also found that most images were better remembered when they were presented as bigger relative to when they were presented as smaller.

"In areas of the brain that represent the retinal image, more resources will be directed to processing large images than to processing small images because the processing is determined by the area of the retina that the image stimulates," says Dr. Gilaie-Dotan. She points out that additional factors may contribute to remembering large images, such as different eye movements, and more attention and interest that large images elicit.

The study was conducted on young adults aged 18-40, ages in which vision is completely developed but has not yet begun to age. Different ages may be affected by the size of the stimuli in a different way, since both age and experience with screens are quite different between young and old.

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