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The COVID-19 pandemic has caused a dramatic reduction in travel, especially to other countries. Figures show that in the second quarter of this year, airlines suffered an 80% fall in income compared to 2019, as the passenger fleet was brought to a virtual standstill, according to data from the International Air Transport Association.

Pere Suau-Sanchez is the research leader of the Sustainability and Management Research Group (SUMA) at the Universitat Oberta de Catalunya (UOC) Faculty of Economics and Business and an expert in air transport. According to his estimates, "COVID-19 has caused the biggest crisis in aviation history. For 2020, there will be a 50% fall in seat numbers for the airline industry, representing almost 3 billion fewer passengers and 400 billion dollars in loss of income".

Although these shocking figures affect the whole industry, low-cost airlines have proven more adaptable to this uncertain outlook, as Suau-Sanchez reports in his research published in the Journal of Transport Geography, in conjunction with Edgar Jimenez, from Cranfield University (United Kingdom).

According to the study, these airlines have shown greater resilience than traditional ones, due to their lower exposure to international long-haul traffic, which has been considerably disrupted by the health crisis.

Indeed, the fall in seat numbers offered in March and April 2020 was much sharper in traditional airlines than low-cost ones, while the recovery is similar in both, as travel restrictions are gradually lifted.

According to the UOC researcher, "Low-cost airlines operate in regional (intracontinental) markets and are therefore less exposed to the dynamics of long-haul (intercontinental) markets, which were the first to be grounded in early February and have remained inactive for longer due to government restrictions".

Exponential growth in less than a decade

The research is using new metrics to analyse the long-term effects of low-cost airlines on European airports. It also identifies the airports that have benefited most from the consolidation of these companies since 2001.

Generally, discussions on air traffic tend to use absolute figures, which fail to show the real situation of the airport, thus the authors have developed two new metrics. The first measures the offer of low-cost seats as a proportion of the total for the airport, i.e. the market share of these companies.

The second metric standardizes the low-cost market share in each individual airport in relation to the airport offering the highest number of low-cost seats. According to Suau-Sanchez, "this allows us to compare different years with a standard, comparable measurement".

After analysing all scheduled flights in Europe from 2001 to 2019, the research shows that in 2001 low-cost airlines represented 5.3% of total seats available on the market, or 37 million out of a total of 701 million seats.

Between 2001 and 2019, European air travel doubled its offer and the low-cost market grew exponentially: it increased its size by up to 14 times, so that by 2019 the companies represented 37.3% of total seats on offer, or 534 million out of a total of 1.43 billion seats.

Democratizing air transport

The research also shows how market concentration decreases once low-cost airlines arrive. The expert pointed out that "low-cost companies have democratized air transport in Europe and led the way in developing traffic in European airports".

The study also shows that the 2008 financial crisis marked a break in the growth of these companies. Furthermore, the data shows that eastern European countries saw the expansion in these airlines some years after the rest of Europe.

The UOC researcher said: "The later development of low-cost traffic in eastern Europe was linked to some of these countries joining the European Union in 2004 and 2007."

With regard to the future, bearing in mind this new post-pandemic scenario, Suau-Sanchez foresees the air industry having fewer companies, focusing its business on larger markets, with fewer business passengers. By way of conclusion, he said: "It should focus on economic and environmental sustainability in order to cope with an increasing number of changes."

Below please find a summary of a new article that will be published today in Annals of Internal Medicine. Annals summaries are not intended to substitute for the full articles as a source of information.

1. ACP Leaders Urge Consideration of Presidential Candidates' Proposals for a Better U.S. Health Care System
Full text: https://www.acpjournals.org/doi/10.7326/M20-7089

As voters cast their ballots, it is important for them to know the health care proposals of the two presidential candidates and how they will address and improve the U.S. health care system especially in light of the problems with the system that have been underscored this year during the COVID-19 pandemic, say leaders from the American College of Physicians (ACP). In an opinion piece published in Annals of Internal Medicine today, they compared the proposals of President Donald Trump and former Vice-President Joe Biden, to ACP's comprehensive framework for improving health care in the U.S.

Better Is Possible: The American College of Physicians' Vision for the U.S. Health Care System was published (https://www.acpjournals.org/toc/aim/172/2_Supplement) earlier this year and lays out ACP's comprehensive, interconnected set of recommendations for systematic health care reforms. The series begins with an overview paper that seeks to answer the question, "what would a better health care system for all Americans look like?" An additional set of ACP policy papers address issues related to coverage and cost of care, health care payment and delivery systems, barriers to care and social determinants of health, and more.

The new piece begins by stating that "Health care in the United States costs too much, is unaffordable for too many, spends too much on administration, produces outcomes that are unfavorable compared to other countries, misaligns incentives with patient interests, and undervalues primary care and public health." It further notes that while ACP is a non-partisan physician-led member organization, they believe it is important to identify key differences in the candidates' policies on health care issues that affect patients. Throughout, they reference how the COVID-19 pandemic has shone a light on why these improvements need to be made.

The article compares ACP's healthcare vision to the views and public records of the candidates on eight different challenges facing the U.S. health care system including:

Achieving universal health care coverage.

Ensuring coverage for those with pre-existing conditions.

All insurance plans including an essential health care benefit package emphasizing high-value care.

Expansion of Medicaid to lower-income persons in all states.

Prescription drug pricing.

Physician payment reform that appropriately values primary care and cognitive care services.

Decreasing health care administrative requirements and standardizing and streamlining billing and reporting.

Equitable access to care regardless of an individual's personal characteristics or life circumstances.

CORVALLIS, Ore. - Oregon State University researchers have found that a type of common gut bacteria sometimes associated with inflammation, abscesses, bowel disease and cancer has a major silver lining: It seems to help prevent cardiovascular disease.

The findings suggest the possibility of probiotic treatments for atherosclerosis, the dangerous buildup of fats, cholesterol and other substances in arteries that cause strokes and heart attacks and is linked to smoking, diet, age and a range of genetic causes.

Diets heavy in animal-based foods have long been considered a risk factor for cardiovascular disease as such diets are a major source of TMA - trimethylamine - which is converted by the liver to another compound, TMAO, that promotes the buildup of fatty plaque in arteries. TMAO is short for trimethylamine-N-oxide.

"The connection between TMAO and cardiovascular disease has tended to focus the conversation on how animal-based diets cause negative health consequences," said Veronika Kivenson, the study's lead author and a postdoctoral fellow in the OSU College of Science. "But in analyzing data from foundational gut microbiome studies, we uncovered evidence that one type of bacteria associated with meat consumption can take the TMA, as well as precursors to TMA, and metabolize them without producing any TMAO. That means those bacteria are in effect severing a key link in the cardiovascular disease chain."

The bacteria are of the Bilophila genus and evidence suggests an expanded genetic code enables their metabolism, via a demethylation pathway, to avoid making TMAO. Furthermore, Kivenson said, research shows animal-based diets cause a rapid increase in Bilophila in the gut.

"The organisms in your stomach have been shown to affect the development of myriad disease states," said co-author Steve Giovannoni, distinguished professor of microbiology at OSU. "But the mechanisms - what is actually happening behind the connections among diet, health and microbiota - have generally been hard to pin down. More research into Bilophila cell biology and ecology is needed, but our study presents a clearly defined mechanism with potential for a big impact on human health."

Identified only 31 years ago, in an infected appendix, Bilophila is a gram-negative anaerobic rod that's classified as a pathobiont - an organism that normally has a symbiotic relationship with its host but can become disease-causing under certain circumstances. It's commonly present in the microbiomes of people who are healthy.

"The data we reviewed show significantly more Bilophila in the microbiomes of healthy people compared to those with cardiovascular disease, and that Bilophila numbers go up in response to a diet based on meat compared to a plant-based diet," Kivenson said. "Our findings suggest Bilophila's role in the microbiome and human health might depend on the specific context and that their potential as a probiotic that mitigates animal products' role in heart disease should be studied further."

Motorists with smartphones could help highway chiefs maintain road quality by sending 'crowdsourced' data from their mobiles that would allow engineers to assess when carriageway repairs are needed, according to a new study.

Road roughness is an important measure of condition and ride quality, but many agencies around the world with large road networks lack the resources to regularly check the state of their highways and make informed maintenance decisions.

Using high resolution three-axis accelerometers and GPS tracking already built into smartphones - together with a low-cost app - to record how a vehicle moves vertically in relation to the carriageway can provide a useful measure of road roughness for civil engineers.

Researchers at the University of Birmingham have studied the feasibility of using smartphones in this way, publishing their findings in Journal of Infrastructure Systems.

On most road networks, road roughness is usually used as the measure of functional condition because it can be related readily to road use costs and measurement can be automated.

Co-author Dr. Michael Burrow, Senior Lecturer at the University of Birmingham, commented: "The most accurate automated methods of assessing road roughness use vehicles fitted with lasers, but even assessing the roughness of a reasonably sized network can be costly.

An attractive solution is to use acceleration sensors built into most smartphones - because smartphone ownership and use are widespread, we can foresee an approach where the condition of road networks is assessed using crowdsourced data from these mobile devices."

Maintaining roads at an appropriate standard encourages economic development and minimises road use costs such as travel time, fuel efficiency, vehicle repairs and accidents. It also provides social benefit and reduces the environmental impact of transport.

In order to make best use of scarce resources, road agencies worldwide prioritise maintenance according to the socio-economic returns - achieving this by regularly assessing road surface and structural condition. #

The International Roughness Index (IRI) is the most commonly used measure of road roughness, but even assessing the roughness of a reasonably-sized road network can be costly using 'traditional' technology.

For example, the cost of collecting road roughness data in the United States is between $1.4 and $6.2 per kilometre, depending on the state - in Illinois, which has 224,719 km of roads, the annual cost of data collection is $1.4 million.

Decision-making using roughness data collected using a smartphone system could allow road agencies to:

Produce a regular low-cost summary of the entire road network's condition;

Use network-level models to evaluate and compare maintenance policies, as well as assessing road use and road agency costs; and

Screen roads to identify and prioritise road sections requiring maintenance .

"Routine inspection of the condition of a road network could be achieved using low-cost data collection systems on smartphones with similar characteristics inside a fleet of vehicles of similar types, travelling at normal traffic speeds," noted Dr. Burrow.

"Vertical acceleration data from smartphones could be analysed using machine learning algorithms to enable IRI to be predicted to a similar accuracy as would be expected from a visual inspection, but with improved repeatability and reproducibility.

"A particularly useful application could be the assessment of the condition of low-volume rural road networks in developing countries where the majority of rural roads are constructed from either gravel or earth and where smartphone ownership is surprisingly high."

Insight into energy losses that affect the conversion of light into electricity could help enhance organic solar cell efficiencies. A KAUST-led team of organic chemists, materials engineers, spectroscopists and theoretical physicists from six research groups has extensively evaluated efficiency-limiting processes in organic photovoltaic systems.

To harvest light, cutting-edge organic solar cells rely on bulk heterojunctions, blends of light-responsive electron donor and acceptor materials. When light strikes the heterojunction, the resulting excited states are pairs of electrons and positively charged holes that need to be separated to make electric current. During charge separation, the donor gives electrons to the acceptor, and the acceptor transfers holes to the donor. Therefore, the efficiency of the solar cells depends on two key factors: the electron affinity offset between these materials, which corresponds to the ability of the acceptor to gain an electron and drives electron transfer; and the ionization energy offset, which represents the propensity of the donor to release an electron, facilitating hole transfer.

Nonfullerene acceptors (NFAs) have recently yielded solar cells with conversion efficiencies nearing 20 percent, outperforming fullerene-based acceptors that had previously dominated. "Key to these record efficiencies is the design and synthesis of materials that combine efficient charge generation with minimal energy losses," explains team leader Frédéric Laquai. "However, the precise role of the energy offsets and their related processes is unclear, which has stalled the development of design rules for NFA-based systems" he adds.

To address this, the multidisciplinary team devised an approach to monitor the photophysical processes that influence charge generation in 23 different NFA-based systems. "With our collaborator, Denis Andrienko from the Max Planck Institute for Polymer Research in Germany, we developed a concise model that enabled us to correlate our experimental observations to physical parameters and chemical structures," says research scientist, Julien Gorenflot.

The researchers discovered that, contrary to recent reports, substantial ionization energy offsets were needed to generate charges. In contrast, electron affinity offsets failed to induce charge separation regardless of their magnitude. These unexpected findings result from a process known as Förster resonance energy transfer, which appears to compete with electron transfer. Postdoc Catherine De Castro explains that "this is an immediate consequence of the design principle of the blends, where donor and acceptor present overlapping emission and absorption, which facilitates energy transfer."

The team plans to design new materials combining enhanced charge generation efficiencies with lower energy losses. "This will help reduce the efficiency gap to other emerging photovoltaic technologies and bring organic photovoltaics closer to maturity and application," Gorenflot says.

This is the first report for the syntheses of water-soluble polyimides which are Interestingly derived from bio-based resources, showing high transparency, tunable mechanical strength and the highest thermoresistance in water-soluble polymers reported ever.

Water-soluble polymers are of great interest in many areas of soft materials. These soft materials have been widely used in application related to aqueous solutions, such as dispersants, aggregation agents, thickeners, moisturizers, binders, and hydrogels. With increase in global awareness about environmental concerns, the importance of water-soluble materials has been highlighted and thereby have expanded their application windows to electronics, functional coatings, advanced adhesives and biomedical materials. Most of natural polymers such as polysaccharides, polypeptides, or their derivatives are water-soluble while synthetic water-soluble polymers are also available such as poly(ethylene oxide), poly(vinyl alcohol), polyacrylates, polyacrylamide, and their derivatives. However, the conventional water-soluble polymers have limited applications due to their low thermal distortion temperatures (ca. 200 °C). On the other hand, polymers exhibiting ultrahigh thermal stability, such as polyimides, possess poor solubility. Particularly, in literature there is little effective molecular engineering strategy for designing the polyimide with water solubility features due to the rigid polymer backbone and study interchain interactions and thereby limits processability and post-polymerization functionalization. A precise molecular engineering induced in the polyimide backbone through multifunctional monomers could play a game changer role in developing water-soluble polymers with ultrahigh thermal stability.

Here we have reported the preparation of a new diamine 4,4'-diamino truxillic acid as photodimer of bio-derived amino acid, 4-aminocinnamic acid, with a series of dianhydrides. The article demonstrates that a super-engineering plastic with very high thermo-mechanical properties bearing unprotected carboxylic acid groups can be utilized to incept the water solubility in the polymer. The synthesized biopolyimide were treated with alkaline metal hydroxide (or ammonium hydroxide) to yield biopolyimide salts. The resultant biopolyimide salts were dissolved in water to give an optically clear solution. The ion exchange reaction between monovalent cation with multivalent cation or with proton resulted in insoluble biopolyimide formation. The degradation temperatures of biopolyimide salts were found to keep very high temperatures (nearly= 366 °C), which is much higher than conventional water-soluble polymers. Furthermore, it was observed that biopolyimide salt self-standing film exhibited high transparency and an interesting trend for greater cationic size of the metal ion yielding more elastic film. In other words, change in cation size provides an opportunity for precise tuning of the tensile properties. The synthesized water-soluble biopolyimide are attractive building blocks for the soft materials and may be utilized for specialty applications such as drug delivery, polychelatogens etc. A preliminary study into polyureas and polyamides by following similar strategy also resulted the induction of water-solubility features, which indicates the wide versatility of this building block methodology.

Professor Tatsuo Kaneko of JAIST said that "I and Dr. Sumant Dwivedi developed the ideation process and then led experiments with very hardworker students and researchers to synthesize these wonderful materials with plausible waterborne applications, like coatings, biomedical device etc."

SINGAPORE, 27 October 2020 - Bats act as reservoirs of numerous zoonotic viruses, including SARS-CoV, MERS CoV, Ebola virus, and--most likely--SARS-CoV-2, the pathogen behind the ongoing coronavirus pandemic. However, the molecular mechanisms bats deploy to tolerate pathogenic viruses has remained unclear.

Now scientists from Duke-NUS Medical School, Singapore, have discovered novel molecular mechanisms that allow bats to tolerate zoonotic viruses without getting sick. Published this week in the Proceedings of the National Academy of Sciences (PNAS), the study suggests that bats adopt unique strategies to prevent overactive immune responses, which protects them against diseases caused by zoonotic viruses.

The team examined three bat species--Pteropus alecto (black fruit bat), Eonycteris spelaea (cave nectar bat), and Myotis davidii (David's myotis bat)--and identified mechanisms that balance the activity of key proteins that play a major role in mediating immunity and inflammatory responses in mammals. These mechanisms enable bats to harbour and transmit zoonotic pathogens without setting off the detrimental consequences of immune activation.

One of the mechanisms bats use is to reduce the levels of caspase-1, a protein that triggers a key inflammatory cytokine protein, interleukin-1 beta (IL-1β). Another mechanism they employ hampers the maturation of IL-1β cytokines through a finely-tuned balancing between caspase-1 and IL-1β.

"Suppression of overactive inflammatory responses improves longevity and prevents age-related decline in humans. Our findings may offer potential insights to the development of new therapeutic strategies that can control and treat human infectious diseases," said Professor Wang Linfa, senior and corresponding author of the study from Duke-NUS' Emerging Infectious Diseases (EID) Programme.

"This study exemplifies the world-class research led by our talented faculty to advance fundamental scientific knowledge. Professor Wang's research is all the more important in the context of COVID-19, by contributing to a greater understanding of how zoonotic diseases persist in nature, and potentially aiding new approaches to managing future outbreaks," said Professor Patrick Casey, Senior Vice-Dean for Research, Duke-NUS Medical School.

The ocean plays a key role in the current climate change, as it absorbs a considerable part of the atmospheric carbon dioxide emitted by mankind. On the one hand, this slows down the heating of the climate, and on the other hand, the dissolution of CO2 in seawater leads to acidification of the oceans. This has far-reaching consequences for many marine organisms and thus also for the oceanic carbon cycle. One of the most important mechanisms in this cycle, is called the biological carbon pump. Part of the biomass that phytoplankton forms in the surface ocean through photosynthesis sinks to the depths in the form of small carbonaceous particles. As a result, the carbon is stored for a long time in the deep sea. The ocean thus acts as a carbon sink in the climate system. How strongly this biological pump acts varies greatly from region to region and depends on the composition of species in the ecosystem.

The study, which has now been published in the journal Nature Climate Change, is one of the most comprehensive studies so far on the effects of ocean acidification on marine ecosystems. Scientists at the GEOMAR Helmholtz Centre for Ocean Research in Kiel have now been able to show for the first time that ocean acidification influences the carbon content of sinking organic material, and thus the biological pump. Surprisingly, the observed changes were highly variable. The carbon content of sinking particles increased or decreased significantly with increasing CO2, depending on the composition of species and the structure of the food web. Since the underlying data cover a wide range of ocean regions, this seems to be a global phenomenon. These findings allow a completely new assessment of the effects of ocean acidification.

Dr. Jan Taucher, marine biologist and main author of the study, says: "Interestingly, we found that bacterial and animal plankton, such as small crustaceans, play a key role in how the carbon cycle and biological pump respond to ocean acidification. Until now, it has been widely held that biogeochemical changes are mainly driven by reactions of phytoplankton. Therefore, even modern Earth system models do not take into account the interactions we observe between the marine food web and the carbon cycle. Our findings thus help to make climate models more realistic and improve climate projections".

Up to now, most of the knowledge on this topic has been based on idealized laboratory experiments, which only represent ecological interactions and the dynamics of the complex marine food web in a highly simplified way. This makes it difficult to transfer such results to real ocean conditions and project them into the future. In order to gain a more realistic insight, the study summarizes several field experiments that were conducted with large-volume test facilities, so-called mesocosms, in different ocean regions, from arctic to subtropical waters.

Mesocosms are, so to speak, oversized test tubes in the ocean, in which changes in environmental conditions in a closed but otherwise natural ecosystem can be studied. For the present study, a large amount of data from five mesocosm experiments was synthesized to provide a more precise picture of plankton communities and biogeochemical processes within the ecosystem. A total of over ten thousand data points were included in the analysis.

The newly gained knowledge can now be used to implement the complex ecological interactions in Earth system models, thus contributing to further improve climate projections.

"When eco-friendly, inexpensive, versatile, and efficient solar cells are developed, all thermal and nuclear power plants will disappear, and solar cells installed over the ocean or in outer space will power our world," says Professor Dong-Seon Lee of the Gwangju Institute of Science and Technology in Korea. His highly optimistic view of the future mirrors the visions of many researchers involved in the effort to improve solar cells.

Over time, in this effort, scientists have come to realize that doping--distorting a crystal structure by introducing an impurity--polycrystalline solar cells made by melting together crystals called CZTSSe with earth-abundant and eco-friendly alkali metals, such as sodium and potassium, can improve their light to electricity conversion efficiency while also leading to the creation of inexpensive flexible thin-film solar cells which, needless to say, could find many applications in a society that is increasingly making wearable electronics commonplace. But why doping improves performance is yet unknown.

In a recent paper published in Advanced Science, Prof Lee and team reveal one part of this unknown. Their revelations come from their observations of composition and electric charge transport properties of CZTSSe cells doped with layers of sodium fluoride of varying thicknesses.

Upon analyzing these doped cells, Prof Lee and team saw that the amount of dopant determined the path that charge carriers took between electrodes, making the cell either more or less conductive. At an optimal doped-layer thickness of 25 nanometer, the charges flowed through the crystal via pathways that allowed for maximum conductivity. This in turn, the scientists hypothesized, affected the "fill factor" of the cell, which indicates the light-to-electricity conversion efficiency. At 25 nanometers, a record fill factor of 63% was obtained, a notable improvement over the previous limit of 50%. The overall performance was also competitive with this amount of doping.

These findings provide insight into CZTSSe and other polycrystalline solar cells, paving the way for improving them further and realizing a sustainable society. But the competitive performance of the solar cell that yielded these findings gives it real-world applications more tangible to us common folks, as Prof Lee explains: "We have developed flexible and eco-friendly solar cells that will be useful in many ways in our real lives, from building-integrated photovoltaics and solar panel roofs, to flexible electronic devices". And given the bold vision that Prof Lee carries, perhaps a green economy is not too far away.

WASHINGTON, October 26, 2020 -- The continued increase in COVID-19 infection around the world has led scientists from many different fields, including biomedicine, epidemiology, virology, fluid dynamics, aerosol physics, and public policy, to study the dynamics of airborne transmission.

In Physics of Fluids, by AIP Publishing, researchers from Johns Hopkins University and the University of Mississippi used a model to understand airborne transmission that is designed to be accessible to a wide range of people, including nonscientists.

Employing basic concepts of fluid dynamics and the known factors in airborne transmission of diseases, the researchers propose the Contagion Airborne Transmission (CAT) inequality model. While not all factors in the CAT inequality model may be known, it can still be used to assess relative risks, since situational risk is proportional to exposure time.

Using the model, the researchers determined protection from transmission increases with physical distancing in an approximately linear proportion.

"If you double your distance, you generally double your protection," said author Rajat Mittal. "This kind of scaling or rule can help inform policy."

The scientists also found even simple cloth masks provide significant protection and could reduce the spread of COVID-19.

"We also show that any physical activity that increases the breathing rate and volume of people will increase the risk of transmission," said Mittal. "These findings have important implications for the reopening of schools, gyms, or malls."

The CAT inequality model is inspired by the Drake equation in astrobiology and develops a similar factorization based on the idea that airborne transmission occurs if a susceptible person inhales a viral dose that exceeds the minimum infectious dose.

The model includes variables that can added at each of the three stages of airborne transmission: the generation, expulsion, and aerosolization of the virus-containing droplets from the mouth and nose of an infected host; the dispersion and transport via ambient air currents; and the inhalation of droplets or aerosols and the deposition of the virus in the respiratory mucosa in a susceptible person.

The researchers hope to look more closely at face mask efficiency and the transmission details in high-density outdoor spaces. Beyond COVID-19, this model based on the CAT inequality could apply to the airborne transmission of other respiratory infections, such as flu, tuberculosis, and measles.

Actin is among the most abundant proteins in cells, and it has many jobs--from giving the cell its very shape and structure to managing networks of proteins crucial to numerous cellular functions. Without it, the fragile fundamental unit of life would crumble. 

A good deal of actin's activity is based on mechanical signaling; it appears to somehow sense physical feedback from the environment and respond accordingly. Now, a new study in eLife describes how this mechanical signaling works. By literally stretching individual actin filaments, the researchers determined a process by which actin transmits cellular mechanical messages to other proteins. Because hundreds of different proteins bind actin filaments, the implications of this discovery are far-reaching and may ultimately explain how cells mechanically control movement--including how cardiac cells contract or how motile cells move. 

"The idea that actin filaments could potentially be tiny stretchy tension sensors in the cell has been banging around in the literature for a while, but I think we really proved it here," says Gregory M. Alushin, assistant professor and head of the Laboratory of Structural Biophysics and Mechanobiology. "We're just now beginning to understand the nuances of mechanical signaling in the cell."   

In search of a mechanical signal

The lifecycle of a cell is intimately tied to chemical signaling, in which well-studied networks of ligands and receptors feed information to the cell and determine whether it grows, divides, migrates, or dies. But physical forces also pass crucial signals onto cells through an entirely different phenomenon in which molecules push and pull on each other, perpetually coming together and dissociating. 

While decades of research have shed light on the chemical signaling process, the particulars of mechanical signaling are still poorly understood. It is clear, for instance, that when a cell clings to the bottom of a petri dish or makes contact with neighboring cells, its interaction with its surroundings is driven by actin, which binds to so-called adhesion proteins in the cell's outer rim.

But it remained unclear how cells pass a mechanical signal from their environment along to actin, and how actin then relays that signal to either beckon adhesion proteins or push them away.

"We've known about actin-binding adhesion proteins for many years," says Lin Mei, a graduate fellow in chemical biology at Rockefeller. "But before our study, there was no research proving that stretching actin conveys a mechanical signal to proteins that can sense this mechanical force."

A "floppy tail" receives the transmission

To further investigate, Alushin and Mei stretched actin--quite literally. 

In collaboration with Rockefeller's Shixin Liu, the researchers undertook the painstaking task of suspending a single actin filament, which measures about 1/15,000th the width of a human hair, between two microscopic beads that anchor each end of the filament. They then exposed the filament to an adhesion protein known as α-catenin, and used an innovative technology called laser tweezers to pull on the actin protein just enough to mimic the minute tension it might experience in a cell.

They observed that actin bound α-catenin better while they were pulling on it, implying that actin was transmitting a mechanical signal to α-catenin, and that α-catenin had the capacity to receive this signal. 

But a similar adhesion protein, vinculin, proved to be signal-deaf. With the help of advanced electron microscopy techniques, the researchers homed in on the crucial difference between α-catenin and vinculin. "There was this one peptide in α-catenin protein, a floppy little tail that partially folds only when it is bound to actin directly," Alushin says. "All other parts of the two proteins were essentially the same."

He and his co-workers suspected that actin was relaying a perfectly good mechanical signal, but that only the floppy tail of α-catenin was prepared to receive it. Vinculin, bereft of floppy tail, was simply missing actin's call. To test this theory, they engineered a version of vinculin with an α-catenin tail transplanted onto it--and the floppy-tailed vinculin began binding better when actin was stretched. Actin was the signal transmitter; the floppy tail, the receiver.

Alushin notes that, while α-catenin and its floppy tail may eventually become an appealing target for clinical therapies, the new findings are first and foremost a coup for the burgeoning field of mechanobiology, which studies how mechanical forces drive crucial processes at the cellular level. "We know that α-catenin is critical in brain development and frequently mutated in cancer, but most of what we know about it is that, if you get rid of it, everything else in the cell breaks," he says. "By precisely defining the force-detector in α-catenin, we will enable researchers to figure out exactly what its function is in mechanical signaling."

"We suspect that there are hundreds of other proteins that directly sense force transmitted by actin," adds Mei. "Our work provides the foundation and the molecular details to begin searching for all of the other force-sensitive proteins."

A simple process for depositing silicon oxide onto silicon wafers could be a great step forward for making silicon-based solar cells. Researchers at KAUST have used a method called plasma processing in a chamber filled with carbon dioxide gas.

The semiconducting element silicon is the material of choice for around 90 percent of solar cell production. When the silicon is doped with selected impurities, the energy from sunlight can kick electrons into generating a flow of electric current.

A technical challenge arises, however, at the exposed surface of the silicon, described by Areej Alzahrani, a KAUST Ph.D. student, as the problem of "dangling bonds." She explains that the reduced availability of silicon atoms to bond together at the surface leaves scope for electrons ejected by light energy to recombine with the positively charged "holes" that the departing electrons leave behind.

This problem can be resolved by generating a layer of silicon oxide at the surface regions used to form electrical contacts in a chemical process called passivation. Several methods can achieve this, but they all come with difficulties and limitations. They also introduce an additional and costly fabrication step. "The problems with existing methods challenged us to find a more simple and practical process," says Alzahrani.

The solution involves exposing the silicon to carbon dioxide in plasma--a low temperature ionized gas. This allows controlled deposition of silicon oxide, followed by the overlaying of another silicon layer, as required for the architecture of a solar cell. Achieving both these steps in the same chamber offers a significant reduction in production costs. "This straightforward and simple process could be of great use to the solar cell industry," Alzahrani concludes.

She points out that the team was surprised by the control that the method achieves over the deposition of an ultrathin silicon oxide layer with the required microstructure. It also generates oxide films that are more stable at high temperatures, overcoming another problem with existing methods. Tests revealed the procedure permits high voltages and low electrical resistance, as required for efficient performance.

Now the team has demonstrated the basic technique, it plans to move to develop its commercial potential. "A first step will be to integrate this process into a complete and working solar cell, while also exploring improved light-capturing designs," says research group leader, Stefaan De Wolf.

Increasingly, biologists are turning to computational modeling to make sense of complex systems. In neuroscience, researchers are adapting the kinds of algorithms used to forecast the weather or filter spam from your email to seek insight into how the brain's neural networks process information.

New research from Cold Spring Harbor Laboratory Assistant Professor Tatiana Engel offers crucial guidance to biologists using such models. Testing various computational models of the nervous system, she and postdoctoral researcher Mikhail Genkin have found that just because a model can make good predictions about data does not mean it reflects the underlying logic of the biological system it represents. Relying on such models without carefully evaluating their validity could lead to wrong conclusions about how the actual system works, they say.

The work, published October 26, 2020 in Nature Machine Intelligence, concerns a type of machine learning known as flexible modeling, which gives users the freedom to explore a wide range of possibilities without formulating specific hypotheses beforehand. Engel's lab has turned to such models to investigate how signaling in the brain gives rise to decision-making.

When it comes to forecasting the weather or predicting trends in the stock market, any model that makes good predictions is valuable. But Engel says that for biologists, the goals are different:

"Because we are interested in scientific interpretation and actually discover hypotheses from the data, we not only need to fit the model to the data, but we need to analyze or understand the model which we get, right? So we want to look, as I said, we want to look into model structure and the model mechanism to make inference that this is maybe how the brain works."

It's possible to make good predictions using wrong assumptions, Engel said, pointing to the ancient model of the solar system that accurately predicted the movements of celestial bodies while positing that those bodies revolved around the Earth, not the Sun. So it was important to consider how well particular models of neural networks could be trusted.

By building and comparing several models of neural signaling, Engel and Genkin found that good predictive power does not necessarily indicate that a model is a good representation of real neural networks. They found that the best models were instead those that were most consistent across multiple datasets. This approach won't necessarily work for all situations, however, and biologists may need alternative methods of evaluating their models. Most importantly, Genkin said, "We shouldn't take anything for granted. We should check every assumption we have."

SAN ANTONIO -- Oct. 26, 2020 -- A new study authored by Southwest Research Insti-tute planetary scientist Dr. Tracy Becker discusses several new views of the asteroid 16 Psyche, including the first ultraviolet observations. The study, which was published today in The Planetary Science Journal and presented at the virtual meeting of the American Astronomical Society's Division for Planetary Sciences, paints a clearer view of the asteroid than was previously available.

At about 140 miles in diameter, Psyche is one of the most massive objects in the main asteroid belt orbiting between Mars and Jupiter. Previous observations indicate that Psyche is a dense, largely metallic object thought to be the leftover core of a planet that failed in formation.

"We've seen meteorites that are mostly metal, but Psyche could be unique in that it might be an asteroid that is totally made of iron and nickel," Becker said. "Earth has a metal core, a mantle and crust. It's possible that as a Psyche protoplanet was forming, it was struck by another object in our solar system and lost its mantle and crust."

Becker observed the asteroid at two specific points in its rotation to view both sides of Psyche completely and delineate as much as possible from observing the surface at ul-traviolet (UV) wavelengths.

"We were able to identify for the first time on any asteroid what we think are iron oxide ultraviolet absorption bands," she said. "This is an indication that oxidation is happen-ing on the asteroid, which could be a result of the solar wind hitting the surface."

Becker's study comes as NASA is preparing to launch the spacecraft Psyche, which will travel to the asteroid as part of an effort to understand the origin of planetary cores. The mission is set to launch in 2022. Metal asteroids are relatively rare in the solar system, and scientists believe Psyche could offer a unique opportunity to see inside a planet.

"What makes Psyche and the other asteroids so interesting is that they're considered to be the building blocks of the solar system," Becker said. "To understand what really makes up a planet and to potentially see the inside of a planet is fascinating. Once we get to Psyche, we're really going to understand if that's the case, even if it doesn't turn out as we expect. Any time there's a surprise, it's always exciting."

Becker also observed that the asteroid's surface could be mostly iron, but she noted that the presence of even a small amount of iron could dominate UV observations. Howev-er, while observing Psyche, the asteroid appeared increasingly reflective at deeper UV wavelengths.

"This is something that we need to study further," she said. "This could be indicative of it being exposed in space for so long. This type of UV brightening is often attributed to space weathering."

Boulder, Colo., USA: Microplastics (plastics While microplastics in groundwater likely affect human health, only a handful of studies have examined the abundance and movement of microplastics in groundwater. This gap means the potential for adverse health effects remains largely unknown.

At the Geological Society of America's 2020 Annual Meeting today at 1:30, Teresa Baraza Piazuelo, a Ph.D. candidate at Saint Louis University, will help fill that knowledge gap by presenting new research on groundwater microplastics in a karst aquifer. "There hasn't been that much research looking at [micro]plastics and groundwater," Baraza says. "It's a very new topic. There's been a boom of research on microplastics in the ocean, even in soils... but to fully understand something, you have to explore it in all its aspects."

Microplastics pose multiple physical and chemical risks to the ecosystems where they're present, and those risks are exacerbated by plastics' longevity in natural environments. "Since they're plastic, they're very durable," Baraza says, "which is why plastic is great. But it doesn't degrade easily." Microplastics' ability to linger in their environments for decades or longer likely has cumulative detrimental effects on both the organisms and quality of the ecosystem. Their chemical threat stems largely from their ability to transport harmful compounds on their surfaces; when organisms at the base of the food chain ingest microplastics, they ingest the toxins, too. As larger organisms consume the smaller ones, the toxins can build up (a process called bioaccumulation), eventually resulting in responses like organ dysfunction, genetic mutation, or death. "Cave ecosystems are known for being super fragile to begin with," she explains. "All the cave organisms -- salamanders, blind fish -- are sensitive, so any contaminants that are introduced could damage those ecosystems."

Groundwater can stay in the same aquifer for tens to hundreds of years, or even longer. Combining that long residence time with plastics' resistance to degradation means that those chemical effects could effectively build up in the water and in any organisms within it, increasing the likelihood of toxic bioaccumulation. Together, these could result in long-term contamination of water sources with poorly-understood health effects and ecosystem damage.

To understand where microplastics in groundwater come from and how they move through aquifers, Baraza and her Ph.D. advisor have been sampling groundwater from a Missouri cave weekly, all year long, and analyzing its chemistry and microplastics load. Because previous groundwater-microplastics studies have been limited to low-rainfall conditions, they're also studying how flooding events affect microplastics concentrations in groundwater.

So far, they've found that while microplastics do increase in groundwater during a flood event, there's also a second peak in microplastics after the flooding has begun to wane. Their explanation is that there are two sources of microplastics for groundwater: those that are already in the subsurface, and those that are newly delivered from the surface. "Finding so much plastic later on in the flood, thinking that it could be coming from the surface... is important to understand the sourcing of microplastics in the groundwater," Baraza says. "Knowing where the plastic is coming from could help mitigate future contamination."

Their current flood results are only based on one event, but Baraza will continue sampling through the rest of the year -- weather permitting. "Flood sampling is hard," she says, "especially in St. Louis, where the weather is so unpredictable. Sometimes we think it's going to rain and then it doesn't rain, and then sometimes it doesn't seem like it's going to rain, but it does... we caught a flood a week ago, and we are expecting to catch a couple more floods." The effort is worth it to determine if flooding events -- which are becoming more common under climate change -- are highly-effective deliverers of microplastics in groundwater reservoirs.

Session No. 23 - T191. New frontiers in cave and karst research I

Monday, 26 Oct.: 1:30 to 5:30 p.m. EDT
Presentation time: 1:30 to 1:45 p.m. EDT
Session Link: https://gsa.confex.com/gsa/2020AM/meetingapp.cgi/Session/50065
Paper 23-1: Quantifying microplastic debris sourcing and transport for a karst aquifer
Abstract Link: https://gsa.confex.com/gsa/2020AM/meetingapp.cgi/Paper/355066
Contact: Teresa Baraza Piazuelo, Saint Louis University, Missouri; teresa.barazapiazuelo@slu.edu.