Brain

Sound waves reveal the unique properties of an ultracold quantum gas, a model system for describing certain superconductors and forms of nuclear matter. A new Australian study examines the propagation of energy as sound waves in a quantum gas, revealing for the first time strong variations in the nature of the sound wave as a function of temperature.

At low energies, this energy travels via the collective movement of many particles moving in sync - essentially, as sound waves -quantified using quasiparticles known as phonons.

Below the superfluid transition temperature Tc these sound waves in a unitary Fermi gas can propagate without collisions and are driven by ripples in the phase of the superfluid order parameter (wave-function)--this mode is known as the Bogoliubov-Anderson (BA) phonon.

Above Tc, the sound waves become more strongly-damped, and collisions play a dominant role.

Strong similarities were identified in the temperature dependence of sound in the unitary Fermi gas and the behaviour of phonons in liquid helium, which was one of the first superfluids identified historically.

This study provides quantitative benchmarks for dynamical theories of strongly-correlated fermions.

MORE ABOUT THE STUDY

The ultracold atomic gases formed and studied in Prof Chris Vale's lab at Swinburne allow very precise tuning of interactions between atoms.

"We cooled and confined a highly dilute gas of Li6 atoms, realising a unitary Fermi gas, which exhibits the strongest interactions allowed by quantum mechanics with a contact potential," explains Prof Vale.

In a unitary gas, elastic collisions become resonant and the thermodynamic properties of the gas become universal functions of the temperature and density. Unitary Fermi gases allow precise testing of theories of interacting fermions.

The team then studied excitations in the gas above and below the superfluid phase transition Tc using two-photon Bragg spectroscopy.

"We measured excitation spectra at a momentum of approximately half the Fermi momentum, both above and below the superfluid critical temperature Tc," explains study author Dr Carlos Kuhn.

Two, focused laser pulses (approx 1.2 milliseconds in duration) intersecting within the gas create a periodic perturbation for the lithium atoms.

Immediately after the twin laser pulse, the confining optical trap is swiTched off and the momentum of atoms is measured after 4 milliseconds of expansion, and can be mapped as a function of laser frequency.

The finite duration and size of the Bragg beams lead to a Fourier-limited spectral resolution of approximately 1:25 kHz FWHM which is well below the typical Fermi energies, EF 11 kHz, used in the experiments.

Washington, DC, April 14, 2020 - The Journal of the American Academy of Child and Adolescent Psychiatry (JAACAP), published by Elsevier, reports on a study following a four year effort to change the stigma of mental illness at Indiana University, which drew the attention of students and faculty; increased awareness of discrimination and prejudice; and decreased prejudice and increased inclusion.

The study evaluated the effectiveness of the "U Bring Change to Mind" (UBC2M) campaign -- a student led program designed to reduce the stigma of mental health problems. While initial stigma levels among college students were much lower than levels reported in the general population, the study documented a significant reduction in the stigmatizing attitudes and beliefs, and a greater willingness to interact with others on campus who face mental health challenges. Results of the UBC2M campaign showed an 11 to 14 percent reduction in stigma documented by the study. This rivals well-funded, national programs, while requiring minimal support for sustainability.

"The development of UBC2M was different from the start," said Dr. Bernice Pescosolido, Chair of the Scientific Advisory Council of Bring Change to Mind, the advocacy group founded by actor Glen Close to end stigma by starting the conversation. "The students read the science of change, developed principles for their club, and built a broad coalition of support organizations across the campus including the campus cinema, classes and professors.

"The New Student Orientation program, and even the Office of Enrollment Management got involved," Dr. Pescosolido added. In collaboration with Ms. Close, Indiana University was chosen as the national pilot site and engaged professors in evaluating the effort from its beginning.

Wiith new studies of college campuses showing an unexpectedly high level of mental health challenges among US college students, more parents and college administrators have raised concerns about how to respond. Many higher education institutions have reconsidered their campus mental health services but have found that the degree of service need is beyond what current resources are already able to address.

Following changes in attitudes, behaviors and engagement among the 2019 entering class through their junior year, Dr. Pescosolido and her team worked with UBC2M students to administer a web-based survey. The survey asked students about their general ideas about mental illness and their opinions about interacting with students, faculty and staff who face mental health challenges.

Over 1,000 students completed both waves of surveys with over 80 percent reporting that they were aware of the anti-stigma effort. As students' level of participation increased, they reported greater decreases in stigma. Those who had only heard about UBC2M reported no change in prejudice, however they did report a more favorable perception of campus culture overall.

"We are very excited about the results, especially after seeing the comparatively low levels of stigma among entering students. This is a sustainable, scalable approach that builds stability into student clubs that often face the wonderful but inevitable changes in student involvement with minimal, but critical, 'skin in the game' from the campus," concluded Dr. Pescosolido.

Some apps highlight when a person is online -- and then share that information with their followers. When a user logs in to a website or app that uses online status indicators, a little green (or orange or blue) dot pops up to alert their followers that they're currently online.

Researchers at the University of Washington wanted to know if people recognize that they are sharing this information and whether these indicators change how people behave online.

After surveying smartphone users, the team found that many people misunderstand online status indicators but still carefully shape their behavior to control how they are displayed to others. More than half of the participants reported that they had suspected that someone had noticed their status. Meanwhile, over half reported logging on to an app just to check someone else's status. And 43% of participants discussed changing their settings or behavior because they were trying to avoid one specific person.

These results will be published in the Proceedings of the 2020 ACM CHI conference on Human Factors in Computing Systems.

"Online status indicators are an unusual mechanism for broadcasting information about yourself to other people," said senior author Alexis Hiniker, an assistant professor in the UW Information School. "When people share information by posting or liking something, the user is in control of that broadcast. But online status indicators are sharing information without taking explicit direction from the user. We believe our results are especially intriguing in light of the coronavirus pandemic: With people's social lives completely online, what is the role of online status indicators?"

People need to be aware of everything they are sharing about themselves online, the researchers said.

"Practicing good online security and privacy hygiene isn't just a matter of protecting yourself from skilled technical adversaries," said lead author Camille Cobb, a postdoctoral researcher at Carnegie Mellon University who completed this research as a UW doctoral student in the Paul G. Allen School of Computer Science & Engineering. "It also includes thinking about how your online presence allows you to craft the identities that you want and manage your interpersonal relationships. There are tools to protect you from malware, but you can't really download something to protect you from your in-laws."

The team recruited 200 participants ages 19 to 64 through Amazon Mechanical Turk to fill out an online survey. Over 90% of the participants were from the U.S., and almost half of them had completed a bachelor's degree.

The researchers asked participants to identify apps that they use from a list of 44 that have online status indicators. The team then asked participants if those apps broadcast their online status to their network. Almost 90% of participants correctly identified that at least one of the apps they used had online status indicators. But for at least one app they used, 62.5% answered "not sure" and 35.5% answered "no." For example, of the 60 people who said they use Google Docs regularly, 40% said it didn't have online status indicators and 28% were not sure.

Then the researchers asked the participants to time themselves while they located the settings to turn off "appearing online" in each app they used regularly. For the apps that have settings, participants gave up before they found the settings 28% of the time. For apps that don't have these settings, such as WhatsApp, participants mistakenly thought they had turned the settings off 23% of the time.

"When you put some of these pieces together, you're seeing that more than a third of the time, people think they're not broadcasting information that they actually are," Cobb said. "And then even when they're told: 'Please go try and turn this off,' they're still not able to find it more than a quarter of the time. Just broadly we're seeing that people don't have a lot of control over whether they share this information with their network."

Finally the team asked participants a series of questions about their own experiences online. These questions touched on whether participants noticed when others were online, if they thought others noticed when they were online and whether they had changed their own behavior because they did or didn't want to appear online.

"We see this repeated pattern of people adjusting themselves to meet the demands of technology -- as opposed to technology adapting to us and meeting our needs," said co-author Lucy Simko, a UW doctoral student in the Allen School. "That means people are choosing to go online not because they want to do something there but because it's important that their status indicator is projecting the right thing at the right time."

Now that most states have put stay-at-home orders in place to try to combat the coronavirus pandemic, many people are working from home and socializing only online. This could change how people use online status indicators, the team says. For example, employees can use their online status to indicate that they are working and available for meetings. Or people can use a family member's "available" status as an opportunity to check up on them and make sure they are OK.

"Right now, when a lot of people are working remotely, I think there's an opportunity to think about how future evolutions of this technology can help create a sense of community," Cobb said. "For example, in the real world, you can have your door cracked open and that means 'interrupt me if you have to,' you can have it wide open to say 'come on in' or you can have your door closed and you theoretically won't get disturbed. That kind of nuance is not really available in online status indicators. But we need to have a sense of balance -- to create community in a way that doesn't compromise people's privacy, share people's statuses when they don't want to or allow their statuses to be abused."

An international team of researchers, in a paper published today in Nature Astronomy, highlights a new way novae light up the sky: this is indeed shocks from an explosion that create the novae that cause most of the its brightness.

A nova, or stella nova the Latin word for "new star," is an explosion which occurs on the surface of a star. The explosion produces an incredible amount of energy resulting in an increase in the star's brightness by thousands or even millions of times. Sometimes a nova is so bright that it appears as a new naked-eye star, a star that is suddenly there where there wasn't one before. Thus, the name nova.

These novae occur in stars called white dwarfs, which are part of a binary system; that is, two stars orbiting one another. What happens is the white dwarf strips material from the companion star, and this material piles up on the white dwarf's surface where the density becomes so high that it undergoes an explosive nuclear fusion.

While for many years, astronomers have thought that nuclear burning of material on the surface of the white dwarf directly powers all the light from the explosion, more recently astronomers started debating that "shocks" from the explosion might power most of the brightness.

Now, an international team of researchers, among which Professor Anthony Moffat from Université de Montréal and member of the Centre for Research in Astrophysics of Quebec (CRAQ), has found that it is indeed shocks that cause most of the nova's brightness. The research is detailed in a paper published in the journal Nature Astronomy titled "Direct evidence for shock-powered optical emission in a nova."

"This is a new way of understanding the origin of the brightness of novae and other stellar explosions," said Elias Aydi, a research associate in Michigan State University's Department of Physics and Astronomy and lead author of the paper. "Our findings present the first direct observational evidence, from unprecedented space observations, that shocks play a major role in powering these events."

So, what are shocks and how do they form? Picture a supersonic jet airplane. When the jet exceeds the speed of sound, it produces a shock which leads to a loud sonic boom. In a nova explosion, the shocks produce light rather than sound. When material blasts out from the white dwarf it is ejected in multiple phases and at different speeds. These ejections collide with one another and create shocks, which heat the ejected material producing much of the light.

Another side effect of astronomical shocks are gamma-rays, the highest-energy kind of electromagnetic radiation. The astronomers detected bright gamma-rays from the star, known as nova V906 Carinae (ASASSN-18fv), whose explosion in the constellation Carina was first detected in March 2018.

Using NASA's Fermi Gamma-ray Space Telescope, they showed that V906 Car had the brightest gamma-rays ever observed for a nova, proving that it hosts energetic shocks.

But the real surprise came because an optical satellite - one of the six nanosatellites that make up a collection of satellites operated by an international consortium called the BRITE constellation of cube-sats - just happened to be looking at the part of the sky where the nova occurred. Comparing the gamma-ray and optical data, the astronomers noted that every time there was a fluctuation in gamma-rays, the light from the nova fluctuated as well. This means that both emissions are originating from shocks and that shocks are indeed responsible for most of the brightness of the event.

"I'm especially impressed at the synergy between two entirely different approaches to reveal something entirely new, like here the correlated shocks in gamma and optical, with surprisingly little coming in X-rays, all observed simultaneously from space," said Professor Moffat. "The BRITE-Constellation mission is one of the cheapest astronomical satellite projects ever conceived and first realized by a collaboration among Canadian, Austrian and Polish astronomers, resulting in such a precious discovery, even if serendipitous," he added.

The team estimates that V906 Car is about 13,000 light years from Earth. This means that when the nova was first detected in 2018, it had actually happened 13,000 years ago.

This new information may also help explain how large amounts of light are generated in other stellar events, including supernovae and stellar mergers, when two stars collide with one another.

As one of the world's most densely populated regions, eastern China has been plagued by air pollution. The future projection of atmospheric diffusion conditions conducive to extreme haze events over eastern China is therefore of great importance for government emission regulations and public human health.

"Under the RCP8.5 scenario (a high emissions scenario), while the warming caused by the increase of greenhouse gases dominates, the effects induced by aerosol emissions reduction cannot be ignored. The effects of global change on China's atmospheric diffusion conditions have been widely studied in recent years. But, studies on the effects of aerosol emissions reduction on atmospheric diffusion conditions is still lacking," explains Weiyang Feng, from the group of Prof. Minghuai Wang, Nanjing University.

In order to fill this knowledge gap, Feng and her coauthors studied the changes of atmospheric diffusion conditions under the RCP8.5 scenario on the basis of three sets of single-model ensemble experiments from 2006-2100, and further explored the contributions from aerosol emissions reduction and increased greenhouse gases. The results have been recently published in Atmospheric and Oceanic Science Letters.

"Output from the Community Earth System Model large ensemble experiments allows us to examine the changes of extreme events under different future emission scenarios," Feng says.

They found that the relative strength of haze events in the North China Plain region have increased under the RCP8.5 scenario, induced by a stronger and longer-lasting anticyclone anomaly in eastern China. The strengthened anticyclone anomaly is mainly induced by increased northern wave train convergence and the longer duration of the anticyclone anomaly is mainly induced by stronger local feedback from the basic state. It was found that the climate effects induced by aerosol reduction plays a leading role in the anticyclone change in eastern China, while the effects from increased greenhouse gases are small.

"Future aerosol emissions reduction can induce deteriorating diffusion conditions, suggesting more stringent regulations on aerosol emissions in China are needed to meet air quality standards," Feng concludes.

A common thread in many inflammatory and neurodegenerative diseases, including multiple sclerosis (MS), is damage caused by oxidative stress. Oxidative stress occurs when cells produce toxic substances known as reactive oxygen species, which are damaging nerve cells and other cells in the body.

In patients with progressive MS, brain immune cells called microglia are now recognized to be early contributors to oxidative stress and the ensuing damage to the brain. This oxidative stress also contributes to neurotoxicity in many other diseases, including Alzheimer's disease, Parkinson's disease, ALS, epilepsy, stroke, and traumatic brain injury. In addition, oxidative stress is a key contributor to autoimmune and infectious diseases. Yet, how immune cells regulate and turn on their production of reactive oxygen species remains unknown.

Now, researchers at Gladstone Institutes have identified a comprehensive molecular profile or "atlas" of the toxic immune cells that damage the brain. Reporting in Nature Immunology, they demonstrate the value of this atlas by using it to identify a potential new drug target for MS and, possibly, many other diseases.

"We now have a map of the toxic immune cells in the brain that drastically changes our understanding of how disease develops and how it can be treated" said Katerina Akassoglou, PhD, senior investigator at Gladstone Institutes, who led the study. "The map of toxic immune cells can be used to guide the discovery of new drugs to protect the brain from deleterious immune responses."

Adding a Functional Layer to Single-Cell Gene Expression Analysis

To understand how oxidative stress-producing immune cells inflict damage on the central nervous system, the researchers developed a method called Tox-seq. Tox-seq integrates single-cell RNA-sequencing technology with selective labeling of cells that produce oxidative stress and reveals which genes are "on" or "off," specifically in the cells that cause damage in the central nervous system.

"Single-cell gene expression analysis is very useful to identify different types of cells in a tissue, but it doesn't directly tell you what the cells are doing," explained postdoctoral scholar Andrew Mendiola, PhD, co-first author of the study. "We developed Tox-seq to link gene expression with function in single cells."

The research team applied Tox-seq to immune cells from the central nervous system of a mouse model of MS, revealing which subtypes of the cells produce toxic reactive oxygen species and express a distinct gene signature associated with oxidative stress.

Surprisingly, Tox-seq showed that only one sub-group of microglia, approximately 10 percent of the cells, caused oxidative stress, together with sub-groups of immune cells from the periphery that entered the brain. And importantly, the gene expression signature of those microglia in the mouse model matched the pattern observed in cells that had previously been suspected of causing damage in progressive MS patients.

In addition, Tox-seq showed that the pattern of gene expression associated with oxidative stress in the mouse cells includes genes involved in coagulation, the process of blood clotting.

In many neurodegenerative diseases, the blood vessels in the brain become leaky. Akassoglou and her team previously established that leakage of the coagulation factor fibrinogen into the brain activates microglia and promotes production of reactive oxygen species.

The Tox-seq data showed that, in turn, toxic microglia express genes that induce coagulation. "This is the first time we have evidence that coagulation and oxidative stress are at work in the same immune cells in the brain," said Akassoglou, who is also a professor of neurology at UC San Francisco. "It's a vicious cycle between the two processes."

From Tox-seq to a Novel Treatment Strategy

Next, the scientists explored how they could apply the Tox-seq results to identify strategies for combatting oxidative stress in the central nervous system.

To start, they used a technique known as high throughput screening to test the ability of 1,907 drug-like chemicals (or "compounds") to suppress activation of microglia induced by the blood coagulation protein fibrin. This approach narrowed the list to 128 compounds that suppressed microglial activation, but did not identify which of the compounds specifically affect oxidative stress.

"At this point, our solution was to computationally overlay the oxidative stress gene signature identified by Tox-seq with previously published drug-target pathways," said co-first author Jae Kyu Ryu, PhD, staff research scientist at Gladstone Institutes and assistant professor of neurology at UC San Francisco. "This type of overlay had never been done before for oxidative stress pathways."

By comparing the known targets of the hits from the screen with the Tox-seq data, the scientists were able to prioritize drugs relevant to toxic immune pathways. They found that one of the hits, a drug called acivicin, works by inhibiting an enzyme that degrades an antioxidant called glutathione. Glutathione neutralizes reactive oxygen species. So, acivicin may decrease oxidative stress by blocking glutathione degradation.

Acivicin also blocked microglial activation in cell culture and prevented the development of symptoms in a mouse model of MS. Remarkably, acivicin treatment suppressed symptoms even when administered to mice with well-established, chronic progressive disease.

"This was exciting because it told us that oxidative stress may be a key driver in maintaining the clinical severity of MS, not just in the initial nerve damage," said Ryu.

Originally developed as a cancer drug, acivicin itself may not hold promise as a therapy for MS patients because it can cause toxic side effects. But the discovery revealed that the glutathione degradation pathway plays a critical role in regulating oxidative stress production in immune cells relevant to MS. The work also demonstrates the exciting potential for gene expression studies to be integrated with pharmacological studies to accelerate the discovery of drugs that can inhibit disease-related pathways.

"This interdisciplinary tour-de-force nicely illustrates the kinds of transformative advances that can emerge from combining leading-edge biotechnologies with deep understanding of disease mechanisms," said Lennart Mucke, MD, who directs the Gladstone Institute of Neurological Disease and is also a professor of neurology and neuroscience at UC San Francisco. "We are eager to see Katerina and her team advance these discoveries into better treatments for MS and other devastating diseases of the nervous system."

Opening New Frontiers

As oxidative stress is a common pathological process in neurological, autoimmune, and infectious conditions, Tox-seq may allow researchers to investigate mechanisms and find therapeutic targets in many types of diseases. The researchers have made their methods publicly available, and the full oxidative stress immune cell atlas has been published online for other researchers to access.

"We hope that Tox-seq will open the way to more disease-relevant transcriptomics. Information captured in genes can now be more readily related to a disease process, which will accelerate drug discovery" said Akassoglou.

ANN ARBOR--Synthetic microparticles more intricate than some of the most complicated ones found in nature have been produced by a University of Michigan-led international team. They also investigated how that intricacy arises and devised a way to measure it.

The findings pave the way for more stable fluid-and-particle mixes, such as paints, and new ways to twist light--a prerequisite for holographic projectors.

The particles are composed of twisted spikes arranged into a ball a few microns, or millionths of a millimeter, across.

Biology is a great creator of complexity on the nano- and microscales, with spiky structures such as plant pollen, immune cells and some viruses. Among the most complex natural particles on the scale of the new synthetic particles are spiky coccolithophores. A few microns in diameter, this type of algae is known for building intricate limestone shells around themselves. To better understand the rules that govern how particles like these grow, scientists and engineers try to make them in the lab. But until now, there was no formalized way to measure the complexity of the results.

"Numbers rule the world, and being able to rigorously describe spiky shapes and put a number on complexity enables us to use new tools like artificial intelligence and machine learning in designing nanoparticles," said Nicholas Kotov, the Joseph B. and Florence V. Cejka Professor of Engineering at U-M, who led the project.

The team--which includes researchers at the Federal University of São Carlos and the University of São Paulo in Brazil, as well as the California Institute of Technology and the University of Pennsylvania--used the new framework to demonstrate that their particles were even more complicated than coccolithophores.

The computational arm of the team, led by André Farias de Moura, professor of chemistry at the Federal University, investigated the quantum properties of the particles and the forces acting on the nanoscale building blocks.

One of the key players in producing complexity can be chirality--in this context, the tendency to follow a clockwise or counterclockwise twist. They introduced chirality by coating nanoscale gold sulfide sheets, which served as their particle building blocks, with an amino acid called cysteine. Cysteine comes in two mirror-image forms, one driving the gold sheets to stack with a clockwise twist, and the other tending toward a counterclockwise twist. In the case of the most complex particle, a spiky ball with twisted spines, each gold sheet was coated with the same form of cysteine.

The team also controlled other interactions. By using flat nanoparticles, they created spikes that were flat rather than round. They also used electrically charged molecules to ensure that the nanoscale components built themselves into larger particles, bigger than a few hundred nanometers across, due to repulsion.

"These laws often conflict with each other, and the complexity emerges because these communities of nanoparticles have to satisfy all of them," said Kotov, professor of materials science and engineering and macromolecular science and engineering.

And that complexity can be useful. Nanoscale spikes on particles like pollen keep them from clumping together. Similarly, the spikes on these particles made by the research team help them disperse in virtually any liquid, a property that is useful for stabilizing solid/liquid mixtures such as paints.

The microparticles with twisted spikes also take in UV light and emit twisted--or circularly polarized--visible light in response.

"The understanding of these emissions was one of the hardest parts of the investigation," de Moura said.

From the results of the experiments and simulations, it appears that UV energy was absorbed into the hearts of the particles and transformed through quantum mechanical interactions, becoming circularly polarized visible light by the time it left through the curved spikes.

The researchers believe that the tactics they have uncovered can help scientists engineer particles that improve biosensors, electronics and the efficiency of chemical reactions.

Ants are excellent navigators and always find their way back to the nest. But how do they react when an obstacle or a predator blocks their path? An international team including Antoine Wystrach, a CNRS researcher at the Research Centre on Animal Cognition (CNRS/Université Toulouse III - Paul Sabatier), has shown that ants are capable of changing their familiar route to avoid traps thanks to an aversive learning mechanism: by associating visual cues with negative experiences, they can memorise potentially dangerous routes. This was discovered when scientists "trapped" desert ants1 by placing a pit trap with slippery walls in their path; a small bridge hidden by twigs was their only exit. On the first attempt, all ants rushed - at almost 1 m/s - towards the nest and fell into the hole. However, on the second attempt they had already adapted their behaviour: as they ap-proached the trap, some ants stopped to scan their environment before making a quick detour and continuing safely to the nest. The researchers demonstrated that the ants' visual memories experi-enced a few seconds before falling had been retrospectively associated with the fall. The goal for scientists is to now implement these learning mechanisms into their neural models in order to better understand the complexity of the insect nervous system. The results are published in Current Biology (April 9 2020).

Digital cameras as well as many other electronic devices need light-sensitive sensors. In order to cater for the increasing demand for optoelectronic components of this kind, industry is searching for new semiconductor materials. They are not only supposed to cover a broad range of wavelengths but should also be inexpensive. A hybrid material, developed in Dresden, fulfils both these requirements. Himani Arora, a physics PhD student at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), demonstrated that this metal-organic framework can be used as a broadband photodetector. As it does not contain any cost-intensive raw materials, it can be produced inexpensively in bulk.
 

In the last twenty years, metal-organic frameworks (MOFs) have become a coveted material system. So far, these highly porous substances, up to 90 percent of which are composed of empty space, have largely been used to store gases, for catalysis or to slowly release drugs in the human body. "The metal-organic framework compound developed at TU Dresden comprises an organic material integrated with iron ions," explains Dr. Artur Erbe, head of the "Transport in Nanostructures" group at HZDR's Institute of Ion Beam Physics and Materials Research. "The special thing about it is that the framework forms superimposed layers with semiconducting properties, which makes it potentially interesting for optoelectronic applications."
 

The group had the idea of using the new semiconducting two-dimensional MOF as a photodetector. In order to pursue it further, Himani Arora investigated the semiconductor's electronic properties. She explored, among others, to what extent the light sensitivity was dependent on temperature and wavelength - and came to a promising conclusion: From 400 to 1,575 nanometers, the semiconductor could detect a broad range of light wavelengths. The spectrum of radiation thus goes from ultraviolet to near infrared. "This is the first time we have proved such a broadband photodetection for a photodetector completely based on MOF layers," the doctoral candidate notes. "These are ideal properties for using the material as an active element in optoelectronic components."
 

Small bandgap makes for efficiency

The spectrum of wavelengths a semiconducting material can cover and transform into electrical signals essentially depends on the so-called bandgap. Experts use this term to describe the energetic distance between the valence band and the conduction band of a solid state material. In typical semiconductors, the valence band is completely full, so the electrons cannot move around. The conduction band, on the other hand, is largely empty, so the electrons can move around freely and influence the current flow. While the bandgap in insulators is so big that the electrons cannot jump from the valance band to the conduction band, metal conductors have no such gaps. A semiconductor's bandgap is just big enough to raise the electrons to the higher energy level of the conduction band by using the light waves. The smaller the bandgap, the lesser the energy required to excite an electron. "As the bandgap in the material we explored is very small, only very little light energy is required to induce the electricity," Himani Arora explains. "This is the reason for the large range of the detectable spectrum."
 

By cooling the detector down to lower temperatures, the performance can be improved yet further because the thermal excitation of the electrons is suppressed. Other improvements include optimizing the component configuration, producing more reliable contacts and developing the material further. The results suggest that the MOF-based photodetectors will have a bright future. Thanks to their electronic properties and inexpensive manufacturing, MOF layers are promising candidates for a raft of optoelectronic applications.
 

"The next step is to scale the layer thickness," says Artur Erbe, looking forward. "In the study, 1.7 micrometer MOF films were used to build the photodetector. To integrate them into components, they need to be significantly thinner." If possible, the aim is to reduce the superimposed layers to 70 nanometers, that is, 25 times smaller than their size. Down to this layer thickness the material should exhibit comparable properties. If the group can prove that the functionality remains the same in these significantly thinner layers, they can then embark on developing it to the production stage.
 

Acyl fluorides are organic compounds that contain a fluorine atom in their structure. These compounds have recently gained much attention in transition-metal catalysis due to their stability and selective reactivity. However, their commercial production remains a challenge. A group of researchers in Tokyo have found a way to generate complex acyl fluorides from widely available acyl fluorides through a reversible reaction, with the rare metal palladium at the core of this process.

In organic chemistry, metals have recently gained attention for their roles as catalysts of a variety of reactions where two different starting materials are joined together, generally known as cross-coupling reactions. Acyl fluorides are a special type of carbon compounds that contain fluorine in their structure. They are very important in various cross-coupling reactions due to their stability and reactivity, as evidenced by the increasing amount of research reporting their relevance.

Because of their central role in these reactions, synthesis of acyl fluorides is an important research topic explored by chemists worldwide. Scientists have already devised several techniques to synthesize acyl fluorides using metal catalysts, but using a simple acyl fluoride as a reagent for the synthesis of complex acyl fluorides is not explored.

Junior Assoc Prof Yohei Ogiwara, Prof Norio Sakai, and Shintaro Hosaka, a group of scientists from the Tokyo University of Science, had previously identified a variety of techniques to transform acyl fluorides using palladium as a catalyst, including a technique involving the manipulation of the acyl C-F bond. As a result of detailed experiments, they found that palladium can help cleave the acyl C-F bond of acyl fluoride. What was more fascinating was that this reaction was reversible, meaning that the presence of palladium also catalyzed the formation of this bond.

These findings encouraged the scientists to now develop a novel strategy for the synthesis of acyl fluorides. "We envisioned reversibility of the acyl C−F bond cleavage/formation may be the answer to the conundrum of acyl fluoride synthesis," states Dr Ogiwara, lead scientist of the study. In their recent report published in Organometallics, they detail the palladium/phosphine-catalyzed synthesis of a variety of acyl fluorides from a simple and commercially available acyl fluoride―called the benzoyl fluoride―as a fluoride source.

This novel method involves an "acyl-exchange reaction," whereby a reaction is induced between benzoyl fluoride and benzoic anhydride by palladium. Benzoic anhydride is a part of a larger subclass of compounds known as acid anhydrides, which are composed of two acyl groups bonded to the same oxygen atom. Therefore, this compound was a perfect supplier of acyl groups.

The researchers found that this reaction resulted in the production of adequate amounts of complex acyl fluorides as desired. By testing out various catalysts and substrates (the chemicals undergoing the reaction), they confirmed that benzoyl fluoride, benzoic anhydride, and palladium indeed provide the best results. However, the preferred complex acyl fluoride can be obtained by playing around with the substrates. This reaction is thus efficient and allows for the preparation of a variety of more complex acyl fluorides. "At its core," reports Prof Sakai, "this reaction proceeds through the cleavage and formation of the acyl C−F bond at the palladium center."

Using this method, Dr Ogiwara and his team succeeded in obtaining 10 or more types of acyl fluoride from benzoyl fluoride, demonstrating the efficiency of this technique. An added bonus is that through this technique, acyl fluoride presents an attractive source of fluorine. "This study represents the first practical protocol to use commercially available acyl fluoride as a fluorination reagent for the catalytic generation of a variety of value-added acyl fluorides," reports Prof Sakai. The reversibility of the breaking and formation of the C-F bond is the highlight of this study, and it could potentially find many industrial applications.

Reference

Titles of original paper
　:
Benzoyl Fluorides as Fluorination Reagents: Reconstruction of Acyl
Fluorides via Reversible Acyl C−F Bond Cleavage/Formation in
Palladium Catalysis

Journal
　:
Organometallics

DOI
　:
10.1021/acs.organomet.0c00028

About The Tokyo University of Science

Tokyo University of Science (TUS) is a well-known and respected university, and the largest science-specialized private research university in Japan, with four campuses in central Tokyo and its suburbs and in Hokkaido. Established in 1881, the university has continually contributed to Japan's development in science through inculcating the love for science in researchers, technicians, and educators.

With a mission of "Creating science and technology for the harmonious development of nature, human beings, and society", TUS has undertaken a wide range of research from basic to applied science. TUS has embraced a multidisciplinary approach to research and undertaken intensive study in some of today's most vital fields. TUS is a meritocracy where the best in science is recognized and nurtured. It is the only private university in Japan that has produced a Nobel Prize winner and the only private university in Asia to produce Nobel Prize winners within the natural sciences field.

Website: https://www.tus.ac.jp/en/mediarelations/

About Dr Yohei Ogiwara from Tokyo University of Science

Dr Yohei Ogiwara is a Junior Associate Professor at the Department of Pure and Applied Chemistry, Tokyo University of Science. Having completed his doctoral studies in 2014 from Keio University, he went on to serve as an Assistant Professor at TUS before progressing to his current role. His key research interest is organic chemistry, with a focus on organometallic and synthetic chemistry. He is a recipient of many prestigious awards, most recently including the research grant from TOBE MAKI Scholarship Foundation in 2019.
https://www.tus.ac.jp/en/fac/p/index.php?69c1

Journal

Organometallics

DOI

10.1021/acs.organomet.0c00028

WEST LAFAYETTE, Ind. - A new tool for medical professionals may help shed more light on tumors in the body and how the brain operates.

Purdue University researchers created technology that uses optical imaging to better help surgeons map out tumors in the body and help them understand how certain diseases affect activity in the brain. The work is published in the journal IEEE Transactions on Medical Imaging.

"We are using light to extract new information from tissue to inform doctors and assist them in designing and carrying out surgeries to remove tumors," said Brian Bentz, a Purdue alumnus, who worked on the technology with Kevin Webb, a professor of electrical and computer engineering at Purdue. "It is a localization method where our technology helps the surgeon pinpoint precise information about the depth and location of tumors. Such information is not easily accessible with current technologies."

The Purdue technology uses contrast in the absorption of light and fluorescent agents that are introduced into the body to find tumors and/or blood vessels within the tissue. The same technology can be used to study neuron activation in the brain, which can help doctors detect diseases such as Parkinson's.

Bentz said the Purdue technology overcomes one of the major challenges with fluorescence imaging - the light becomes highly scattered and that limits the information that a surgeon receives.

"Our technology aims to provide more detailed information about tumors for surgeons and neuron activity in the brain, both of which can improve outcomes for patients," Bentz said.

The innovators are working with the Purdue Research Foundation Office of Technology Commercialization to patent the technology.

There is plenty of scientific evidence that the health of a mother can impact the health of her child. Now a Northwestern University study flips that relationship around: Researchers have discovered the health of the fertilized embryo determines the functional health of the mother, which has implications for healthy aging, stress resilience and suppression of protein damage.

Essentially, a bad egg does good by protecting the mother from cellular stress, ensuring she lives longer and is healthy enough to produce the next generation.

Led by molecular biologist Richard I. Morimoto and postdoctoral fellow Ambre J. Sala, the research team studied maternal health span using a popular research tool, the transparent roundworm C. elegans. This animal, whose cellular properties and protective mechanisms are similar to that of humans, is used by scientists to better understand aspects of human biology, such as aging and neurodegenerative disease.

Using the power of a genetic screen, the researchers discovered that if the eggshell of a fertilized egg is damaged, a molecular signal is sent to the mother that protects her from the negative effects of a human protein associated with neurodegeneration. They found that this signal also protects the mother from environmental stress, allowing her to better survive adverse conditions. This gives her a longer functional health span so she has more time to produce healthy eggs.

"The success and future of any species is about the quality of its progeny," Morimoto said. "Now we know that progeny quality ensures maternal health."

Morimoto is an expert on how organisms sense and respond to physiologic and environmental stress on the molecular and cellular level in biology, aging and neurodegenerative disease. He is the Bill and Gayle Cook Professor of Molecular Biosciences and director of the Rice Institute for Biomedical Research in Northwestern's Weinberg College of Arts and Sciences.

This communication between child and parent is about protein quality control. Specifically, the researchers found that when the eggshell's vitelline layer is damaged, that's when the fertilized egg sends a signal that restores stress resilience and protein homeostasis, or proteostasis, in the mother.

The vitelline layer, found in all metazoans that use eggs, including humans, is the extracellular coat that surrounds and protects the developing embryo. Proteostasis is the processes by which cells maintain protein health, keeping important proteins folded and functional, for good overall health.

The study was published online recently by the journal Genes and Development. It also will appear in the May 2020 print issue of the journal. Morimoto is the corresponding author, and Sala is the first author.

These findings build on an earlier study by the Morimoto lab that looked at the regulation of proteostasis by an animal's reproductive system. In that 2015 study, the researchers found that adult cells in C. elegans abruptly begin their downhill slide when an animal reaches reproductive maturity. After the animal starts to reproduce, germline stem cells throw a genetic switch that starts the aging process by turning off protective cell stress responses that protect against molecular damage as occurs in Alzheimer's disease, Parkinson's disease, Huntington's disease and other diseases of protein conformation.

In this new study, Morimoto's team shows that communication between the embryo and mother in reproductive adults also regulates proteostasis, stress resilience and the mother's health span. An implication of these results is that unhealthy progeny promotes the health span of the mother by preventing the occurrence of protein damage associated with proteins that cause neurodegeneration in humans.

"Aging is about a lack of protein quality control," Morimoto said. "We found if the eggshell is damaged, the mother survives longer and has time to have good eggs and healthy offspring."

Greek and Norwegian researchers have conducted a study on the health conditions in six refugee camps in Greece.

"We found high levels of trauma," says Professor Terje A. Eikemo.

He heads the Centre for Global Health Inequalities Research (CHAIN) at the Norwegian University of Science and Technology (NTNU). CHAIN collaborated with the National Center for Social Research in Athens, and others, to survey refugee health.

"It's important to systematically map the health situation and needs of the refugees in the camps. We know way too little and this is slowing down the asylum processes," Eikemo says.

But what we do know is disturbing, especially now, with the onset of the COVID-19 pandemic.

Problems increase with time

The longer people spend in refugee camps, the more the problems increase, especially for vulnerable groups.

Two-thirds of refugees are plagued by memories of scary and painful events. About half of the refugees report being extremely disturbed by such events.

Sleep problems and concentration difficulties are common, as are being frightened and having strong reactions when reminded of past events.

CHAIN is working to monitor global health. One of their goals is to provide knowledge that can reduce social health disparities in and between countries.

Huge number of refugees in Greece

Since 2014 Greece has become the transit country for many refugees in connection with unrest in the Middle East. Due to its geographical location, the country has received a disproportionate number of migrants.

Numbers peaked in 2015, when a total of 857 000 refugees arrived in Greece. They were largely accommodated in refugee camps, where tens of thousands still live. Life in the camps is wreaking havoc on the health of many refugees.

"People lack any sense of security," says Eikemo.

Children, the elderly and women

Being physically safe in a camp doesn't mean that people find peace. Seven out of ten migrants have children, who are more susceptible to trauma than adults. The children are especially prone to worsening health the longer they are in the camps.

"Unfortunately, we're seeing a connection between how long the children have been in the camps and their health situation," says Eikemo.

This finding is based on parents' assessment of their children. More than half of the parents report that their children have suffered from significantly worse health since their journey began. It is also worrisome that most of the respondents do not feel safe in the camps, and that a large proportion of the refugees do not have access to shelters that provide privacy or clean facilities.

"Although most refugees have access to free food, toilets, showers and mattresses, that is not enough to prevent the children's declining health over time," says Eikemo.

The elderly in refugee camps also have a harder time getting their health needs met than others. Women who lack shelter that offers some privacy are another particularly vulnerable group.

Feel the symptoms later

In particular, the refugees highlight neck and back problems, allergies, extreme headaches and other chronic conditions, often in combination. The more time they've spent in the camps, the more refugees report these types of health issues.

One reason may be that the early health surveys in the camps concentrated on other health conditions, such as infectious diseases. Still, only four out of ten refugees report that they have been examined by a doctor.

"Once people are physically safe in refugee camps after fleeing, they start to feel the symptoms," Eikemo says.

Upon arrival at the camps, the proportion of people with ailments is about the same as the European average. Over time, the percentage of chronic illnesses increases dramatically.

"Our findings indicate that staying in the camps is destroying the health of both children and adults. It is simply the wrong place to be for people who have been through such traumatizing experiences. Good health is a human right. It's incomprehensible from a public health and human rights perspective that families - and especially children - are still in these camps," says Eikemo.

He says the researchers have not had the opportunity to follow up with the participants again to see how things turned out for them later.

Challenging work

The survey was conducted on two occasions in 2016. The work was challenging because it required the approval of both the authorities and aid organizations, which was given at short notice. Boats and interpreters had to be at the ready, and the researchers were allowed to spend only a limited amount of time in the camps.

The researchers interviewed one person from every three tents or households in order to obtain the most representative sampling possible.

Researchers wanted to find out why people had fled and whether they had experienced traumatizing or discriminatory experiences before, during or after fleeing, as well as to identify needs, the reception conditions in the camps and refugees' health situations.

The researchers used their own trauma index, developed by Harvard University researchers who also participated in the project. A total of 367 people were surveyed, which accounted for approximately four per cent of the refugees in the six camps.

The research project involved approximately 60 researchers from several countries. It was led by Terje Andreas Eikemo of CHAIN/ NTNU and Theoni Stathopoulou of the National Center for Social Research in Athens, who is also affiliated with the Harvard Program in Refugee Trauma in the United States.

Infrared radiation, which is invisible yet highly utilizable, is used in various fields and for various purposes, such as for coronavirus detection (i.e. through thermal imaging cameras and biosensors). A Korean research team has developed a technology that visualizes infrared radiation and expands its application range.

The Korea Institute of Science and Technology (KIST, Acting President Yoon Seok-jin) announced that Dr. Kwon Seok-joon's research team at the Nanophotonics Research Center has developed a multi-functional luminescent film that can visualize near-infrared light through *wavelength conversion that converts near-infrared light to visible light. The research was jointly conducted by the KIST team and Ko Doo-hyun, a professor of applied chemistry at Kyung Hee University (President Han Gyun-tae).

*Wavelength conversion: A process of down-conversion in which shorter-wave ultraviolet light is converted into longer-wave visible light or a process of up-conversion in which longer-wave near-infrared light is converted into shorter-wave visible light

The conversion of invisible infrared or ultraviolet light into visible light allows us to intuitively see the data contained in the light, and thus enables the use of infrared or ultraviolet light for displays or imaging devices. Quantum dots, recently used for high-definition TVs, can be seen as a type of wavelength conversion technology that converts ultraviolet light into visible light in displays.

Ultraviolet light is high in energy, which makes its conversion into visible light relatively easy and enables high conversion efficiency. In contrast, **near-infrared light is low in energy, and at least two near-infrared ***photons are absorbed and converted into one higher-energy photon. The conversion efficiency of converting near-infrared light into visible light is extremely low and is about 1/100 to 1/1000 the efficiency of converting quantum dots into visible light. This was a major stumbling block in making the near-infrared-to-visible light conversion more realistic for wider application in various fields in the form of sensors, displays, and imaging devices.

**Near-infrared light: Infrared light with the shortest wavelength among all the different types of infrared light

***Photon: A type of elementary particle or quantum that comprises all electromagnetic waves including visible lights. It also acts as a carrier of electromagnetic forces.

The research team at KIST made a square lattice array of oxidized silicon (silica) microbeads decorated with up-conversion nanoparticles and metal structures. This configuration maximizes both the absorption of near-infrared light and the luminescence of visible light, thus increasing the efficiency of near-infrared-to-visible light conversion by nearly 1,000 times.

The lattice configuration of silica microbeads developed by the research team can easily be transferred to a transparent film. This type of film was found to be flexible, foldable, and even washable with the light intensity maintained after wavelength conversion.

"Existing infrared sensors can only collect one type of data, but this technology can be used to collect various types of data all at once and visualize them," said Dr. Kwon Seok-joon from KIST, who led the research. "Since this technology has various advantages in processing, such as foldability, washability, and transferability into other films, its application can be extended throughout various fields, and it can be used for foldable devices, wearable sensors, and flexible wavelength conversion imaging devices."

Nipple-sparing mastectomy is gaining ground as a treatment or preventive measure for breast cancer, given the understandable desire among patients to preserve natural appearance as much as possible. But the precise risk of preserving the nipple is not known as the cancer can spread along mammary ducts and to the nipple. A three-dimensional picture of the nipple structure can elucidate much more clearly than conventional reconstructions whether, where, and how much the cancer has spread to the nipple.

Conventional reconstruction from multiple two-dimensional tissue slices is a laborious process, is invasive, and does not give a clear understanding of the 3D structure of the nipple. Thus, the search for better imaging techniques continues.

Recently, Associate Professor Sunaguchi from Nagoya University and his colleagues saw the potential of X-ray dark-field computed tomography (or XDFI-CT) as a promising alternative to existing nipple-exploration methods, such as needle biopsy or ductoscopy. XDFI-CT is a technique that can create a 3D rendering of a structure based on the distribution of its electron density and refractive index. Sunaguchi and team hypothesized that XDFI-CT could provide a 3D reconstruction of the human nipple that is at least as precise as images built from 2D slices, with the added benefit that the proposed approach leaves the nipple intact and therefore has wider applications.

"In this study, which has been published in Breast Cancer Research and Treatment, we examined 51 human nipples by XDFI-CT and visualized the 3D arrangements of the nipple ducts," explains Assoc. Prof. Sunaguchi. First, XDFI-CT was used to obtain 2D sections of the nipple so as to compare them with conventional tissue sections observed through light microscopy. The results showed that the 2D CT slices were structurally compatible with the ones obtained through the conventional approach, giving a first demonstration of the capabilities of the method.

The CT-derived 2D slices were afterwards easily turned into full 3D renderings of the nipples, allowing the researchers to count the number of milk ducts and analyze the overall ductal structure, which varied from patient to patient. "Using 3D volume renderings of the 51 samples, we discovered three different types of duct arrangements," comments Assoc. Prof. Sunaguchi. These three types of arrangements were "convergent," in which the ducts converged in a bowl shape centered at the tip of the nipple; "straight." where the ducts grew parallelly from the base to the tip; and "divergent," where the ducts diverged as they came closer to the tip.

The findings of this study also provided evidence for "sick lobe theory," which postulates that non-invasive ductal carcinoma (DCIS) begins in a single mammary lobe. In one particular sample, the researchers noted that three seemingly separate ducts with DCIS converged into a single opening near the tip of the nipple, implying that the three DCIS-ridden ducts were derived from the same cancerous mammary lobe.

Overall, the proposed strategy is very promising not only for analyzing the structure of the nipple but also for scanning other soft tissues or organs. Though there are some technical limitations to currently implementing XDFI-CT for diagnostic or exploratory purposes, the approach employed in the present study will certainly become very relevant once these hurdles are overcome.