Tech

Nanometers are one billionth of a meter, a metric typically used to measure molecules and scientific building blocks not visible to the human eye. Materials of tens and/or several hundred nanometers in diameter have unique properties, and thus have been widely used in diagnosing and treating various human diseases. One major challenge to use these nano-sized materials is how to deliver them into cells and reach their sites of action.

Traditional methods include linking them to short fragments of proteins called peptides, which are structural components of cells and tissues, hormones, toxins, antibiotics and enzymes. These peptides, by interacting with cells, will lead nanomaterial into cells. The impact of these interactions on other cellular activities remains poorly understood, plus this peptide coupling introduces additional complexity in nanomaterial manufacturing, and may change their functionality as well.

In a study published in Nature Communications, University of Minnesota researchers discovered a novel cellular process that can engulf nanomaterial without direct peptide functionalization, and its activity is regulated by Cysteine surrounding the cells. The research team termed this cellular process of engulfing bystander NPs as 'bystander uptake.'

"By simply mixing two types of nano-sized material, we discover a novel cellular process that offers an easy solution for nanomaterial entry into cells," said Hongbo Pang, corresponding author, an assistant professor in the College of Pharmacy and a member of the Masonic Cancer Center. "Moreover, it opens up a new avenue of cell biology that interconnects several fundamental elements of living cells. Further understanding of this process will aid in both cell biology and nanotechnology development."

The study revealed the following unique properties:

the bystander uptake only allows the cells to engulf nano-sized materials, but not other substances surrounding the cells (e.g. fluids);

the activity of this bystander uptake is stimulated by the existence of one of 20 natural amino acids, Cysteine, surrounding the cells.

These phenomena have been validated with a wide variety of cells, nanoparticles (aka nanomaterials), and under various physiological conditions.

The study findings included:

co-administration with TAT-NP, a peptide and nanomaterial fusion, enables cells to engulf nano-sized materials in a bystander manner;

this bystander uptake is specific to nanomaterial, but not other substances surrounding the cells;

cysteine in the cell culture medium greatly stimulates the activity of this bystander uptake.

Eating disorder researchers at The University of Texas Health Science Center at Houston (UTHealth) have discovered a neurocircuit in mice that, when activated, increased their stress levels while decreasing their desire to eat. Findings appear in Nature Communications.

The scientists believe their research could aid efforts to develop treatments for a serious eating disorder called anorexia nervosa, which has the highest mortality rate of any mental disorder, according to the National Institute of Mental Health. People with anorexia nervosa avoid food, severely restrict food, or eat very small quantities of only certain foods. Even when they are dangerously underweight, they may see themselves as overweight.

"We have identified a part of the brain in a mouse model that controls the impact of emotions on eating," said Qingchun Tong, PhD, the study's senior author and an associate professor in the Center for Metabolic and Degenerative Disease at McGovern Medical School at UTHealth.

Because mice and humans have similar nervous systems, Tong, the Cullen Chair in Molecular Medicine at UTHealth, believes their findings could shed light on the part of the human brain that regulates hunger.

The investigators believe they are among the first to demonstrate the role of this neurocircuit in the regulation of both stress and hunger.

While previous research has established that stress can both reduce and increase a person's desire to eat, the neural mechanisms that act on the regulation of eating by stress-related responses largely remain a mystery.

Tong's team focused on a neurocircuit connecting two parts of the mouse brain: the paraventricular hypothalamus, an eating-related zone in the brain, and the ventral lateral septum, an emotional zone in the brain. The neurocircuit acts as an on/off switch.

When researchers activated the neurocircuit, there was an increase in anxiety levels and a decrease in appetite. Conversely, when the investigators inhibited the neurocircuit, anxiety levels dropped and hunger increased.

The scientists used a research technique called optogenetics to turn the neurons in question on and off.

Yuanzhong Xu, PhD, the study's lead author and an instructor at McGovern Medical School, said additional preclinical tests are needed to confirm their findings.

Bottom Line: This observational study analyzed survey data from 1,652 active-duty military personnel to examine associations between firearm ownership and storage practices with suicidal thoughts and behaviors. More than one-third (35.7%) of military personnel reported having a firearm in or around their homes, with 32.2% indicating their firearms were safely stored unloaded and locked up. Study authors report that although service members with recent thoughts about death or self-harm were less likely to report having firearms at home, safe storage practices were less common among those with a history of suicidal thoughts or behaviors who had firearms. Limitations of the study include self-reported information.

Authors: Craig J. Bryan, Psy.D., A.B.P.P., University of Utah, Salt Lake City, and coauthors

(doi:10.1001/jamanetworkopen.2019.9160)

Editor's Note: The article includes conflict of interest and funding/support disclosures. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

The "Landau-level laser" is an exciting concept for an unusual radiation source. It has the potential to efficiently generate so-called terahertz waves, which can be used to penetrate materials as well as for future data transmission. So far, however, nearly all attempts to make such a laser reality have failed. An international team of researchers has now taken an important step in the right direction: In the journal Nature Photonics (DOI: 10.1038/s41566-019-0496-1), they describe a material that generates terahertz waves by simply applying an electric current. Physicists from the German research center Helmholtz-Zentrum Dresden-Rossendorf (HZDR) played a significant role in this project.

Like light, terahertz waves are electromagnetic radiation, in a frequency range between microwaves and infrared radiation. Their properties are of great technological and scientific interest, as they allow fundamental researchers to study the oscillations of crystal lattices or the propagation of spin waves. Simultaneously "terahertz waves are of interest for technical applications because they can penetrate numerous substances that are otherwise opaque, such as clothing, plastics and paper," HZDR researcher Stephan Winnerl explains. Terahertz scanners are already used today for airport security checks, detecting whether passengers are concealing dangerous objects under their clothing - without having to resort to harmful X-rays.

Because terahertz waves have a higher frequency than the radio waves we use today, they could also be harnessed for data transmission one day. Current WLAN technology, for instance, operates at frequencies of two to five gigahertz. Since terahertz frequencies are about a thousand times higher, they could transmit images, video, and music much faster, albeit across shorter distances. However, the technology is not yet fully developed. "There has been a lot of progress in recent years," Winnerl reports. "But generating the waves is still a challenge - experts speak of a veritable terahertz gap." A particular issue is the lack of a terahertz laser that is compact, powerful, and tunable at the same time.

Flexible frequencies

Laser light is generated by the electrons in the laser material. According to the quantum effect, energized electrons emit light, but they cannot absorb just any random amount of energy, only certain portions. Accordingly, light is also emitted in portions, in a specific color and as a focused beam. For some time now, experts have set their sights on a specific concept for a terahertz laser: the "Landau-level laser". It is special because it can use a magnetic field to flexibly adjust the electrons' energy levels. These levels, in turn, determine the frequencies that are emitted by the electrons, which makes the laser tunable - a huge advantage for many scientific and technical applications.

There is just one issue: Such a laser does not exist yet. "So far, the problem has been that the electrons pass their energy on to other electrons instead of emitting them as the desired light waves," Winnerl explains. Experts call this physical process the "Auger effect". To their chagrin, this phenomenon also occurs in graphene, a material that they deemed particularly promising for a "Landau-level laser". This two-dimensional form of carbon showed strong Auger scattering in HZDR experiments.

A question of material

The research team therefore tried another material: a heavy metal alloy of mercury, cadmium, and tellurium (HgCdTe) that is used for highly sensitive thermal imaging cameras, among other things. The special feature of this material is that its mercury, cadmium, and tellurium contents can be very precisely chosen, which makes it possible to fine-tune a certain property that experts call the "band gap".

As a result, the material showed properties similar to graphene, but without the issue of strong Auger scattering. "There are subtle differences to graphene that avoid this scattering effect," says Stephan Winnerl. "Put simply, the electrons can't find any other electrons that could absorb the right amount of energy." Therefore, they have no choice but to get rid of their energy in the form that the scientists want: terahertz radiation.

The project was an international team effort: Russian partners had prepared the HgCdTe samples, which the project's lead group in Grenoble then analyzed. One of the pivotal investigations took place in Dresden-Rossendorf: Using the free-electron laser FELBE, experts fired strong terahertz pulses at the sample and were able to observe the electrons' behavior in temporal resolution. The result: "We noticed that the Auger effect that we had observed in graphene had actually disappeared," Winnerl is happy to report.

LED for Terahertz

Lastly, a work group in Montpellier observed that the HgCdTe compound actually emits terahertz waves when electric current is applied. By varying an additional magnetic field of only about 200 millitesla, the experts were able to vary the frequency of the emitted waves in a range of one to two terahertz - a tunable radiation source. "It's not quite a laser yet, but rather like a terahertz LED," Winnerl describes. "But we should be able to extend the concept to a laser, even though it will take some effort." And that's exactly what the French partners want to tackle next.

There is one limiting factor, however: Up to now, the principle has only worked when cooled to very low temperatures, just above absolute zero. "This is certainly a hindrance for everyday applications," Winnerl summarizes. "But for use in research and in certain high-tech systems, we should be able to make it work with this kind of cooling."

PHILADELPHIA - Violence toward first responders is widespread and can face a felony charge in Pennsylvania, yet new research shows that victims often feel they do not receive legal justice. Now a study of victim cases and interviews with district attorneys in Philadelphia offers three solutions to help educate first responders and legal professionals to participate constructively in the legal system intended to prevent incidents from occurring and deliver justice. The findings, from researchers at the Dornsife School of Public Health at Drexel University, are published today in the American Journal of Industrial Medicine.

The Drexel team conducted in-person, in-depth interviews of five Philadelphia district attorneys on specific cases of first responders attacked on the job. The team sought to learn about job demands and pressure experienced by the DAs, how they prosecute these types of cases and their experiences with perpetrators of the assaults.

"This study uncovers a tension between society's desire to turn perpetrators of crimes into productive citizens and providing justice to victims," said senior author Jennifer Taylor, PhD, MPH, CPPS, an associate professor of Environmental and Occupational Health at Drexel's Dornsife School of Public Health. "This study listened to those who have prosecuted these cases to come up with practical, scalable solutions that respect all stakeholders and improve how the system serves injured first responders."

In interviews, DAs shared factors that can prevent an assault from ending in a felony charge, such as prosecutorial merit. For example, DAs reported that cases can "fall out" at the preliminary hearing due to lack of evidence or because a municipal court judge says the case is not "serious enough to go to the Court of Common Pleas for a felony trial," as one DA noted. Respondents also said it may be difficult to prove intent - that the offender had a mens rea, or guilty mind.

Compounding the problem, victims may have very limited involvement with the court process, because of physical or emotional pain, not being able to afford taking leave from work, among other reasons.

DAs also discussed what factors they perceive could influence a judge's sentencing decision, including concern for the future well-being of the defendant, the view that violence is an acceptable "part of the job" of a first responder and the belief that the justice system is more focused on rehabilitating the offender than the victim.

Using this feedback, the researchers came up with three solutions:

Educate DAs, judges, and defense attorneys that violence against first responders is not an expected "part of the job" by informing them about how the violence impacts an EMS worker.

Train EMS responders whom have experienced violence on how to prepare for a court appearance, in collaboration with the DA's office, leadership from the fire department and labor union.

Enact non-punitive leave policies to encourage injured EMS responders to attend court appearances.

"EMS providers are often among the first on the scene to respond to fires, crimes, and a range of other disasters, and can face spitting, biting, verbal abuse and sometimes even stabbings or shootings," said Taylor, who is also director and principal investigator of the Center for Firefighter Injury Research and Safety Trends (FIRST), established at Drexel to collect and analyze data for the United States Fire and Rescue Service. "This paper unveils simple steps to address the frustration and dissatisfaction of assaulted first responders."

Previous studies report that the majority -- some suggesting up to 90 percent -- of EMS first responders have been verbally or physically attacked at least once during their career. In addition to the effects of the attacks, such incidents result in lost productivity and stress that can impair the EMS worker's ability to perform their job. A 2016 study by the Drexel team illuminated concerns shared by victims about the legal system.

Organic solar cells are made of cheap and abundant materials, but their efficiency and stability still lag behind those of silicon-based solar cells. A Chinese-German team of scientists has found a way to enhance the electric conductivity of organic solar cells, which increases their performances. Doping the metal oxide interlayer, which connected the electrode and active layer, with a modified organic dye boosted both the efficiency and stability, the study published in the journal Angewandte Chemie revealed.

Organic solar cells convert light into electric current. The heart of the cells is the active organic layer made of specially designed organic molecules. Here, electrons and holes, the positive counterparts of the electrons, are generated by light and travel to the electrodes to form the electric current. A recurrent problem in organic solar cell design is the matching of the material types. The electrodes are made of inorganic materials, but the active layer is organic. To join the two materials, metal oxide interlayers are introduced in many organic cell types. But in most designs, the resulting conductivities are not optimal.

Frank Würthner at the University of Würzburg, Germany, and Zengqi Xie at the South China University of Technology (SCUT), Guangzhou, China, investigated the idea of making a zinc oxide interlayer slightly more organic and photoconductive to reduce the contact resistance when irradiated with sunlight. The scientists prepared an organic dye in such a way that it formed stable complexes with the zinc ions present in the zinc oxide layer. Under sunlight, this modified dye called hydroxy-PBI would then inject electrons into the zinc oxide interlayer, which would increase its conductivity.

The scientists then assembled the organic solar cell, which consisted of an indium tin oxide glass (ITO) electrode, the zinc oxide layer doped with the hydroxy-PBI dye, the active layer made of a polymer as the electron donor and an organic molecule as the acceptor, another metal oxide interlayer, and an aluminum electrode as the positive electrode. This architecture, which is called an inverted bulk heterojunction cell, is that of a state-of-the-art organic solar cell, which achieves a maximum 15 percent power conversion efficiency.

The interlayer doping was beneficial in several ways. Depending on the dye--the scientists checked the performance of several dyes with slightly different structures-- conversion efficiencies of almost 16 percent were achieved. And the dye-doped zinc oxide interlayer also appeared to be more stable than one without the doping. The authors said that it was important that the PBI dye was modified to its hydroxy-PBI form, which gave rise to tight complexes with the zinc ions. Only then could an inorganic-organic hybrid structure evolve to form a good contact with the active materials.

Dr Antony Dodd, Senior Lecturer in the School of Biological Sciences and senior author of the paper, said: "This proof of concept research suggests that, in future, we might be able to refine the use of some chemicals that are used in agriculture by taking advantage of the biological clock in plants. Approaches of this type, combining biotechnology with precision agriculture, can provide economic and environmental benefits."

Just like human jet lag, plants have body clocks that are crucial for their life in a world that has day and night. Plant biological clocks make a crucial contribution to their growth and the responses of crops to their fluctuating environments.

In a new paper, published today [Friday 16 August] in the journal Nature Communications, the researchers found that the death of plant tissue and slow-down in growth resulting from the herbicide glyphosate depends upon the time that the herbicide is applied and also the biological clock.

Crucially, the biological clock also led to a daily change in the minimum amount of herbicide that is needed to affect the plant, so less herbicide was needed at certain times of day. This provides an opportunity to reduce the quantity of herbicides used, saving farmers time, money and reducing environmental impacts.

In medicine, "chronotherapy" considers the body clock when deciding the best time to give a medicine or treatment. This new research suggests that a similar approach could be adopted for future agricultural practice, with crop treatments being applied at times that are most appropriate for certain species of weed or crop. By employing a form of agricultural chronotherapy might have a future role in the sustainable intensification of agriculture required to feed the growing population.

Have you ever wondered how marine animals smell the world, and how the olfactory system evolved from aquatic to terrestrial animals? There are two different classes of odorant receptor (OR) genes that can be expressed in olfactory sensory neurons: "class I" first identified in fish and frogs and then found to be common to all vertebrates, and "class II", which is specific to terrestrial animals. How does the olfactory sensory neuron know which class of OR to express?

"Decision between two classes of ORs is critical to both the anatomical and functional organization of olfactory system." explains Prof. Junji Hirota from the Tokyo Institute of Technology, "However, while we have known that two classes of ORs exist for more than 20 years, the mechanisms that regulate the OR class choice have remained an open question." To understand the OR selection process, he and a group of investigators set out to unveil the factors that make the decision between two classes of ORs.

The researchers discovered for the first time that Bcl11b, a transcription factor, determines which class of OR gene is expressed in olfactory neurons. In the absence of Bcl11b, olfactory neurons are fated to class I. But the fate can be switched to class II in the presence of Bcl11b. This also corroborates the idea that class I OR is the default OR, which undergoes a transcriptional switch in the presence of Bcl11b.

A similar mechanism takes place in frogs. In tadpoles, olfactory neurons express class I ORs in the so called "water-nose" until they undergo metamorphosis, when a part of their olfactory epithelium starts expressing Bcl11b, and thus start expressing class II ORs, which becomes "air-nose" in adult frogs.

Further, the scientists demonstrated that genetically manipulating Bcl11b expression in mice not only altered the class of OR gene, but it also changed the corresponding neural wiring, altering odor perception in the animals.

By manipulating the expression of this gene in mice, the researchers generated mice with "class I-dominant" and "class II-dominant" noses. Interestingly, because these two different OR classes are linked to the entire odor perception mechanism of the animal, the mutant mice perceived aversive odors differently, i.e., "class I-dominant" mice become hyper-sensitive to decayed food odor but less sensitive to predator's odor.

"Our findings unveil a long-standing mystery in OR gene regulation, a molecular mechanism of the OR class choice as well as an essential role of Bcl11b for the functional organization of olfactory system by integrating genetic, cellular, and behavioral analyses, and provide important insights on the terrestrial adaption of olfaction during evolution," concludes Prof. Hirota.

In the battle of the sexes, males appear to have the innovative edge--from a genetic standpoint, at least. Scientists are finding that the testes are more than mere factories for sperm; these organs also serve as hotspots for the emergence of new genes, the raw material for the evolution of species.

Using fruit flies, a Rockefeller team has gained key insight into how nature's attempts at innovation play out during the development of sperm. In research described August 16 in eLife, they mapped the presence of mutations to DNA at the single-cell level, and the activity of new genes arising from such changes.

"Our work offers an unprecedented perspective on a process that enables living things to adapt and evolve, and that ultimately contributes to the diversity of life on Earth," says assistant professor Li Zhao, who led the research.

High stakes

In recent years, studies in animals from flies to humans have turned up a number of young genes that originated in the testes. These and other discoveries suggest the testes rank among the most productive sites in the body--male or female--for genetic innovation.

This mass production of genetic novelties comes with significant risks, however. In humans, for example, a father's sperm acquires two to three times more new mutations than do a mother's eggs in the course of normal development, leaving the sperm riddled with genetic mistakes. In some cases, such mistakes may harm his offspring, or even derail the prospect of fatherhood altogether.

In other words, the male stands to lose the one thing that matters in the game of evolution: the opportunity to propagate his gene pool into the next generation.

But whatever the potential downside genetic experimentation has for individual males and their offspring, the dynamics of reproduction nevertheless encourage it. Potential fathers face intense pressure to attract females and fend off competitors. Any advantage, such as brighter plumage or hardier sperm, for example, can make all the difference.

At the molecular level, this pressure drives an abundance of new genes within the testes. Scientists think that if these newcomers contribute to males' ability to father healthy offspring, they rapidly acquire a fixed place in the genome and may even go on to contribute elsewhere in the body.

Searching cell by cell

Looking a little closer, however, the picture gets blurry. Scientists haven't yet understood the dynamics by which genetic innovation occurs within the precursor cells from which sperm develops.

To find out more, Zhao and researchers in her lab tagged individual cells from fly testes, then identified and decoded the RNA sequences each contained. This approach allowed them to see how the activity of specific genes changed throughout the developmental stages. Within the RNA sequences isolated from stem cells and five intermediary cell types, the researchers examined innovation from two perspectives: that of mutations and that of genes.

Mutations known as substitutions, in which one letter of DNA's code is swapped for another, are most abundant early on in the development of sperm, then decrease, they found. The sperm cells' DNA-repair machinery follows a similar pattern--it is most active early on, then tapers off--which makes sense, according to Zhao, since the machinery is responsible for fixing errors like these.

Starting from scratch

Within the RNA sequences, Zhao's team hunted for a particular type of young gene--one that arises from scratch rather than through duplication of an existing gene. For Zhao, these so-called de novo genes, which originate from sequences that originally did not code for protein, are the most interesting new genes from an evolutionary perspective. Her team found no less than 184 de novo genes, drawn from a set they had previously identified.

When they examined these de novo genes, the scientists uncovered complex patterns, with certain genes showing up primarily in certain cell types, but not in others. About 15 percent of these genes appeared early on, including in the stem cell stage--which is surprising, Zhao says, because scientists previously thought that new genes rarely show up at the start of development as this phase is tightly controlled. The most active period for de novo genes occurred midstream, however, in the so-called spermatocyte phase of developing sperm.

The scientists are now interested in understanding what purpose, if any, de novo genes serve when they first arise. And although it's possible that some essentially fire at random, making no particular contribution, Zhao suspects that in many cases, these new genes play roles in the maturation of sperm cells.

"Precisely what these de novo genes are doing to move development along is an exciting open question," Zhao says.

High-temperature superconductors, which carry electricity with zero resistance at much higher temperatures than conventional superconducting materials, have generated a lot of excitement since their discovery more than 30 years ago because of their potential for revolutionizing technologies such as maglev trains and long-distance power lines. But scientists still don't understand how they work.

One piece of the puzzle is the fact that charge density waves - static stripes of higher and lower electron density running through a material - have been found in one of the major families of high-temperature superconductors, the copper-based cuprates. But do these charge stripes enhance superconductivity, suppress it or play some other role?

In independent studies, two research teams report important advances in understanding how charge stripes might interact with superconductivity. Both studies were carried out with X-rays at the Department of Energy's SLAC National Accelerator Laboratory.

Exquisite detail

In a paper published today in Science Advances, researchers from the University of Illinois at Urbana-Champaign (UIUC) used SLAC's Linac Coherent Light Source (LCLS) X-ray free-electron laser to observe fluctuations in charge density waves in a cuprate superconductor.

They disturbed the charge density waves with pulses from a conventional laser and then used RIXS, or resonant inelastic X-ray scattering, to watch the waves recover over a period of a few trillionths of a second. This recovery process behaved according to a universal dynamical scaling law: It was the same at all scales, much as a fractal pattern looks the same whether you zoom in or zoom out.

With LCLS, the scientists were able to measure, for the first time and in exquisite detail, exactly how far and how fast the charge density waves fluctuated. To their surprise, the team discovered that the fluctuations were not like the ringing of a bell or the bouncing of a trampoline; instead, they were more like the slow diffusion of a syrup - a quantum analog of liquid crystal behavior, which had never been seen before in a solid.

"Our experiments at LCLS establish a new way to study fluctuations in charge density waves, which could lead to a new understanding of how high-temperature superconductors operate," says Matteo Mitrano, a postdoctoral researcher in professor Peter Abbamonte's group at UIUC.

This team also included researchers from Stanford University, the National Institute of Standards and Technology and Brookhaven National Laboratory.

Hidden arrangements

Another study, reported last month in Nature Communications, used X-rays from SLAC'S Stanford Synchrotron Radiation Lightsource (SSRL) to discover two types of charge density wave arrangements, making a new link between these waves and high-temperature superconductivity.

Led by SLAC scientist Jun-Sik Lee, the research team used RSXS, or resonant soft X-ray scattering, to watch how temperature affected the charge density waves in a cuprate superconductor.

"This resolves a mismatch in data from previous experiments and charts a new course for fully mapping the behaviors of electrons in these exotic superconducting materials," Lee says.

"I believe that exploring new or hidden arrangements, as well as their intertwining phenomena, will contribute to our understanding of high-temperature superconductivity in cuprates, which will inform researchers in their quest to design and develop new superconductors that work at warmer temperatures."

As the microelectronic industry is now shifting toward wearable electronic gadgets and electronic (e-)textiles, the comprising electronic materials, such as ferroelectrics, should be integrated with our clothes. Nylons, a family of synthetic polymers, were first introduced in the 1920s' for women's stockings and are nowadays among the most widely used synthetic fibers in textiles. They consist of a long chain of repeated molecular units, i.e. polymers, where each repeat unit contains a specific arrangement of hydrogen, oxygen, and nitrogen with carbon atoms.

Besides the use in textiles, it was discovered that some nylons also exhibit so called "ferroelectric properties". This means that positive and negative electric charges can be separated and this state can be maintained. The ferroelectric materials are used in sensors, actuators, memories and energy harvesting devices. The advantage in using polymers is that they can be liquified using adequate solvents and therefore processed from solution at low cost to form flexible thin-films which are suitable for electronic devices such as capacitors, transistors and diodes. This makes ferroelectric polymers a viable choice for integration with e-textiles. Although nylon polymers have found over the years significant commercial applications in fabrics and fibers, their application in electronic devices was hindered because it was impossible to create high quality thin films of ferroelectric nylons by solution processing.

Scientists at the MPI-P, in collaboration with researchers from the Johannes Gutenberg University of Mainz and Lodz University of Technology, have now solved this forty year old problem, and developed a method to fabricate ferroelectric nylon thin-film capacitors by dissolving nylon in a mixture of trifluoroacetic acid and acetone and solidifying it again in vacuum. They were able to realize thin nylon films that are typically only a few 100 nanometers thick, several 100 times thinner than human hair. "Using this method, we have produced extremely smooth thin-films. This is very important because it prevents electrical break down of for example capacitors and destroying the electronic circuits. At the same time, the smoothness allows for having transparent thin-films and eventually transparent electronic devices," says Dr. Kamal Asadi, group leader at the MPI-P.

By using their newly developed method, the group around Kamal Asadi was able to produce high performance nylon capacitors. The scientists subjected the prototypes of the capacitors to extended stress cycles and demonstrated robustness of ferroelectric nylons under millions of operation cycles. The thin nylon films could become an important component for use in flexible electronics in the future and find applications in bendable electronic devices or for electronics in clothing. These new findings pave the way towards multi-functional fabrics that serve as cloth for covering our body and at the same time can generate electricity from our body movement.

One of the greatest mysteries in condensed matter physics is the exact relationship between charge order and superconductivity in cuprate superconductors. In superconductors, electrons move freely through the material--there is zero resistance when it's cooled below its critical temperature. However, the cuprates simultaneously exhibit superconductivity and charge order in patterns of alternating stripes. This is paradoxical in that charge order describes areas of confined electrons. How can superconductivity and charge order coexist?

Now researchers at the University of Illinois at Urbana-Champaign, collaborating with scientists at the SLAC National Accelerator Laboratory, have shed new light on how these disparate states can exist adjacent to one another. Illinois Physics post-doctoral researcher Matteo Mitrano, Professor Peter Abbamonte, and their team applied a new x-ray scattering technique, time-resolved resonant soft x-ray scattering, taking advantage of the state-of-the-art equipment at SLAC. This method enabled the scientists to probe the striped charge order phase with an unprecedented energy resolution. This is the first time this has been done at an energy scale relevant to superconductivity.

The scientists measured the fluctuations of charge order in a prototypical copper-oxide superconductor, La2?xBaxCuO4 (LBCO) and found the fluctuations had an energy that matched the material's superconducting critical temperature, implying that superconductivity in this material--and by extrapolation, in the cuprates--may be mediated by charge-order fluctuations.

The researchers further demonstrated that, if the charge order melts, the electrons in the system will reform the striped areas of charge order within tens of picoseconds. As it turns out, this process obeys a universal scaling law. To understand what they were seeing in their experiment, Mitrano and Abbamonte turned to Illinois Physics Professor Nigel Goldenfeld and his graduate student Minhui Zhu, who were able to apply theoretical methods borrowed from soft condensed matter physics to describe the formation of the striped patterns.

These findings were published on August 16, 2019, in the online journal Science Advances.

Cuprates have stripes

The significance of this mystery can be understood within the context of research in high-temperature superconductors (HTS), specifically the cuprates--layered materials that contain copper complexes. The cuprates, some of the first discovered HTS, have significantly higher critical temperatures than "ordinary" superconductors (e.g., aluminum and lead superconductors have a critical temperature below 10 K). In the 1980s, LBCO, a cuprate, was found to have a superconducting critical temperature of 35 K (-396°F), a discovery for which Bednorz and Müller won the Nobel Prize.

That discovery precipitated a flood of research into the cuprates. In time, scientists found experimental evidence of inhomogeneities in LBCO and similar materials: insulating and metallic phases that were coexisting. In 1998, Illinois Physics Professor Eduardo Fradkin, Stanford Professor Steven Kivelson, and others proposed that Mott insulators--materials that ought to conduct under conventional band theory but insulate due to repulsion between electrons--are able to host stripes of charge order and superconductivity. La2CuO4, the parent compound of LBCO, is an example of a Mott insulator. As Ba is added to that compound, replacing some La atoms, stripes form due to the spontaneous organization of holes--vacancies of electrons that act like positive charges.

Still, other questions regarding the behavior of the stripes remained. Are the areas of charge order immobile? Do they fluctuate?

"The conventional belief is that if you add these doped holes, they add a static phase which is bad for superconductivity--you freeze the holes, and the material cannot carry electricity," Mitrano comments. "If they are dynamic--if they fluctuate--then there are ways in which the holes could aid high-temperature superconductivity."

Probing the fluctuations in LBCO

To understand what exactly the stripes are doing, Mitrano and Abbamonte conceived of an experiment to melt the charge order and observe the process of its reformation in LBCO. Mitrano and Abbamonte reimagined a measurement technique called resonant inelastic x-ray scattering, adding a time-dependent protocol to observe how the charge order recovers over a duration of 40 picoseconds. The team shot a laser at the LBCO sample, imparting extra energy into the electrons to melt the charge order and introduce electronic homogeneity.

"We used a novel type of spectrometer developed for ultra-fast sources, because we are doing experiments in which our laser pulses are extremely short," Mitrano explains. "We performed our measurements at the Linac Coherent Light Source at SLAC, a flagship in this field of investigation. Our measurements are two orders of magnitude more sensitive in energy than what can be done at any other conventional scattering facility."

Abbamonte adds, "What is innovative here is using time-domain scattering to study collective excitations at the sub-meV energy scale. This technique was demonstrated previously for phonons. Here, we have shown the same approach can be applied to excitations in the valence band."

Hints of a mechanism for superconductivity

The first significant result of this experiment is that the charge order does in fact fluctuate, moving with an energy that almost matches the energy established by the critical temperature of LBCO. This suggests that Josephson coupling may be crucial for superconductivity.

The idea behind the Josephson effect, discovered by Brian Josephson in 1962, is that two superconductors can be connected via a weak link, typically an insulator or a normal metal. In this type of system, superconducting electrons can leak from the two superconductors into the weak link, generating within it a current of superconducting electrons.

Josephson coupling provides a possible explanation for the coupling between superconductivity and striped regions of charge order, wherein the stripes fluctuate such that superconductivity leaks into the areas of charge order, the weak links.

Obeying universal scaling laws of pattern formation

After melting the charge order, Mitrano and Abbamonte measured the recovery of the stripes as they evolved in time. As the charge order approached its full recovery, it followed an unexpected time dependence. This result was nothing like what the researchers had encountered in the past. What could possibly explain this?

The answer is borrowed from the field of soft condensed matter physics, and more specifically from a scaling law theory Goldenfeld had developed two decades prior to describe pattern formation in liquids and polymers. Goldenfeld and Zhu demonstrated the stripes in LBCO recover according to a universal, dynamic, self-similar scaling law.

Goldenfeld explains, "By the mid-1990s, scientists had an understanding of how uniform systems approach equilibrium, but how about stripe systems? I worked on this question about 20 years ago, looking at the patterns that emerge when a fluid is heated from below, such as the hexagonal spots of circulating, upwelling white flecks in hot miso soup. Under some circumstances these systems form stripes of circulating fluid, not spots, analogous to the stripe patterns of electrons in the cuprate superconductors. And when the pattern is forming, it follows a universal scaling law. This is exactly what we see in LBCO as it reforms its stripes of charge order."

Through their calculations, Goldenfeld and Zhu were able to elucidate the process of time-dependent pattern reformation in Mitrano and Abbamonte's experiment. The stripes reform with a logarithmic time dependence--a very slow process. Adherence to the scaling law in LBCO further implies that it contains topological defects, or irregularities in its lattice structure. This is the second significant result from this experiment.

Zhu comments, "It was exciting to be a part of this collaborative research, working with solid-state physicists, but applying techniques from soft condensed matter to analyze a problem in a strongly correlated system, like high-temperature superconductivity. I not only contributed my calculations, but also picked up new knowledge from my colleagues with different backgrounds, and in this way gained new perspectives on physical problems, as well as new ways of scientific thinking."

In future research, Mitrano, Abbamonte, and Goldenfeld plan to further probe the physics of charge order fluctuations with the goal of completely melting the charge order in LBCO to observe the physics of stripe formation. They also plan similar experiments with other cuprates, including yttrium barium copper oxide compounds, better known as YBCO.

Goldenfeld sees this and future experiments as ones that could catalyze new research in HTS: "What we learned in the 20 years since Eduardo Fradkin and Steven Kivelson's work on the periodic modulation of charge is that we should think about the HTS as electronic liquid crystals," he states. "We're now starting to apply the soft condensed matter physics of liquid crystals to HTS to understand why the superconducting phase exists in these materials."

Excess heat given off by smartphones, laptops and other electronic devices can be annoying, but beyond that it contributes to malfunctions and, in extreme cases, can even cause lithium batteries to explode.

To guard against such ills, engineers often insert glass, plastic or even layers of air as insulation to prevent heat-generating components like microprocessors from causing damage or discomforting users.

Now, Stanford researchers have shown that a few layers of atomically thin materials, stacked like sheets of paper atop hot spots, can provide the same insulation as a sheet of glass 100 times thicker. In the near term, thinner heat shields will enable engineers to make electronic devices even more compact than those we have today, said Eric Pop, professor of electrical engineering and senior author of a paper published Aug. 16 in Science Advances.

"We're looking at the heat in electronic devices in an entirely new way," Pop said.

Detecting sound as heat

The heat we feel from smartphones or laptops is actually an inaudible form of high-frequency sound. If that seems crazy, consider the underlying physics. Electricity flows through wires as a stream of electrons. As these electrons move, they collide with the atoms of the materials through which they pass. With each such collision an electron causes an atom to vibrate, and the more current flows, the more collisions occur, until electrons are beating on atoms like so many hammers on so many bells - except that this cacophony of vibrations moves through the solid material at frequencies far above the threshold of hearing, generating energy that we feel as heat.

Thinking about heat as a form of sound inspired the Stanford researchers to borrow some principles from the physical world. From his days as a radio DJ at Stanford's KZSU 90.1 FM, Pop knew that music recording studios are quiet thanks to thick glass windows that block the exterior sound. A similar principle applies to the heat shields in today's electronics. If better insulation were their only concern, the researchers could simply borrow the music studio principle and thicken their heat barriers. But that would frustrate efforts to make electronics thinner. Their solution was to borrow a trick from homeowners, who install multi-paned windows - usually, layers of air between sheets of glass with varying thickness - to make interiors warmer and quieter.

"We adapted that idea by creating an insulator that used several layers of atomically thin materials instead of a thick mass of glass," said postdoctoral scholar Sam Vaziri, the lead author on the paper.

Atomically thin materials are a relatively recent discovery. It was only 15 years ago that scientists were able to isolate some materials into such thin layers. The first example discovered was graphene, which is a single layer of carbon atoms and, ever since it was found, scientists have been looking for, and experimenting with, other sheet-like materials. The Stanford team used a layer of graphene and three other sheet-like materials - each three atoms thick - to create a four-layered insulator just 10 atoms deep. Despite its thinness, the insulator is effective because the atomic heat vibrations are dampened and lose much of their energy as they pass through each layer.

To make nanoscale heat shields practical, the researchers will have to find some mass production technique to spray or otherwise deposit atom-thin layers of materials onto electronic components during manufacturing. But behind the immediate goal of developing thinner insulators looms a larger ambition: Scientists hope to one day control the vibrational energy inside materials the way they now control electricity and light. As they come to understand the heat in solid objects as a form of sound, a new field of phononics is emerging, a name taken from the Greek root word behind telephone, phonograph and phonetics.

"As engineers, we know quite a lot about how to control electricity, and we're getting better with light, but we're just starting to understand how to manipulate the high-frequency sound that manifests itself as heat at the atomic scale," Pop said.

BUFFALO, N.Y. -- Higher levels of blood high-density lipoprotein (HDL) -- or good cholesterol -- may improve fatigue in multiple sclerosis patients, according to a new University at Buffalo-led study.

The pilot study, which investigated the effects of fat levels in blood on fatigue caused by multiple sclerosis, found that lowering total cholesterol also reduced exhaustion.

The results, published recently in PLOS ONE and led by Murali Ramanathan, PhD, professor in the UB School of Pharmacy and Pharmaceutical Sciences, highlight the impact that changes in diet could have on severe fatigue, which impacts the majority of those with multiple sclerosis.

Fatigue is a frequent and debilitating symptom for people with multiple sclerosis that affects quality of life and ability to work full time. Despite its prevalence and the severity of its impact, treatment options for fatigue are limited. The medications used to treat severe fatigue often come with unwanted side effects.

"Fatigue in people with multiple sclerosis has been viewed as a complex and difficult clinical problem with contributions from disability, depression and inflammation. Our study implicates lipids and fat metabolism in fatigue," said Ramanathan. "This is a novel finding that may open doors to new approaches for treating fatigue."

In previous studies, Terry Wahls, MD, clinical professor of internal medicine and neurology and creator of the Wahls Protocol diet, and her team of researchers at the University of Iowa, showed that a diet-based intervention accompanied by exercise, stress reduction and neuromuscular electrical stimulation (NMES) is effective at lowering fatigue. However, the physiological changes underlying the improvements were unknown.

The researchers examined changes in body mass index (BMI), calories, total cholesterol, HDL, triglycerides, and low-density lipoprotein (LDL) -- commonly known as bad cholesterol. Fatigue was measured on the Fatigue Severity Scale.

The study followed 18 progressive multiple sclerosis patients over the course of a year who were placed on the Wahls diet, which is high in fruits and vegetables. The diet encourages the consumption of meat, plant protein, fish oil and B vitamins. Gluten, dairy and eggs are excluded.

Participants also engaged in a home-based exercise program that included stretches and strength training, NMES to stimulate muscle contraction and movement, and meditation and self-massages for stress reduction. However, adherence to the diet was the main factor associated with reductions in fatigue.

"Higher levels of HDL had the greatest impact on fatigue," said Ramanathan, "possibly because good cholesterol plays a critical role in muscle, stimulating glucose uptake and increasing respiration in cells to improve physical performance and muscle strength."

Patients consumed fewer calories and experienced decreases in BMI and triglyceride and LDL levels as well. However, these factors were found unrelated to changes in fatigue.

The results provide the basis for a larger study that could examine the effects of metabolic changes on fatigue.

A potentially useful material for building quantum computers has been unearthed at the National Institute of Standards and Technology (NIST), whose scientists have found a superconductor that could sidestep one of the primary obstacles standing in the way of effective quantum logic circuits.

Newly discovered properties in the compound uranium ditelluride, or UTe2, show that it could prove highly resistant to one of the nemeses of quantum computer development -- the difficulty with making such a computer's memory storage switches, called qubits, function long enough to finish a computation before losing the delicate physical relationship that allows them to operate as a group. This relationship, called quantum coherence, is hard to maintain because of disturbances from the surrounding world.

The compound's unusual and strong resistance to magnetic fields makes it a rare bird among superconducting (SC) materials, which offer distinct advantages for qubit design, chiefly their resistance to the errors that can easily creep into quantum computation. UTe2's exceptional behaviors could make it attractive to the nascent quantum computer industry, according to the research team's Nick Butch.

"This is potentially the silicon of the quantum information age," said Butch, a physicist at the NIST Center for Neutron Research (NCNR). "You could use uranium ditelluride to build the qubits of an efficient quantum computer."

Research results from the team, which also includes scientists from the University of Maryland and Ames Laboratory, appear today in the journal Science. Their paper details UTe2's uncommon properties, which are interesting from the perspectives of both technological application and fundamental science.

One of these is the unusual way the electrons that conduct electricity through UTe2 partner up. In copper wire or some other ordinary conductor, electrons travel as individual particles, but in all SCs they form what are called Cooper pairs. The electromagnetic interactions that cause these pairings are responsible for the material's superconductivity. The explanation for this kind of superconductivity is named BCS theory after the three scientists who uncovered the pairings (and shared the Nobel Prize for doing so).

What's specifically important to this Cooper pairing is a property that all electrons have. Known as quantum "spin," it makes electrons behave as if they each have a little bar magnet running through them. In most SCs, the paired electrons have their quantum spins oriented in a single way -- one electron's points upward, while its partner points down. This opposed pairing is called a spin singlet.

A small number of known superconductors, though, are nonconformists, and UTe2 looks to be among them. Their Cooper pairs can have their spins oriented in one of three combinations, making them spin triplets. These combinations allow for the Cooper-pair spins to be oriented in parallel rather than in opposition. Most spin-triplet SCs are predicted to be "topological" SCs as well, with a highly useful property in which the superconductivity would occur on the surface of the material and would remain superconducting even in the face of external disturbances.

"These parallel spin pairs could help the computer remain functional," Butch said. "It can't spontaneously crash because of quantum fluctuations."

All quantum computers up until this point have needed a way to correct the errors that creep in from their surroundings. SCs have long been understood to have general advantages as the basis for quantum computer components, and several recent commercial advances in quantum computer development have involved circuits made from superconductors. A topological SC's properties -- which a quantum computer might employ -- would have the added advantage of not needing quantum error correction.

"We want a topological SC because it would give you error-free qubits. They could have very long lifetimes," Butch said. "Topological SCs are an alternate route to quantum computing because they would protect the qubit from the environment."

The team stumbled upon UTe2 while exploring uranium-based magnets, whose electronic properties can be tuned as desired by changing their chemistry, pressure or magnetic field -- a useful feature to have when you want customizable materials. (None of these parameters are based on radioactivity. The material contains "depleted uranium," which is only slightly radioactive. Qubits made from UTe2 would be tiny, and they could easily be shielded from their environment by the rest of the computer.)

The team did not expect the compound to possess the properties they discovered.

"UTe2 had first been created back in the 1970s, and even fairly recent research articles described it as unremarkable," Butch said. "We happened to make some UTe2 while we were synthesizing related materials, so we tested it at lower temperatures to see if perhaps some phenomenon might have been overlooked. We quickly realized that we had something very special on our hands."??

The NIST team started exploring UTe2 with specialized tools at both the NCNR and the University of Maryland. They saw that it became superconducting at low temperatures (below -271.5 degrees Celsius, or 1.6 kelvin). Its superconducting properties resembled those of rare superconductors that are also simultaneously ferromagnetic - acting like low-temperature permanent magnets. Yet, curiously, UTe2 is itself not ferromagnetic.

"That makes UTe2 fundamentally new for that reason alone," Butch said.

It is also highly resistant to magnetic fields. Typically a field will destroy superconductivity, but depending on the direction in which the field is applied, UTe2 can withstand fields as high as 35 tesla. This is 3,500 times as strong as a typical refrigerator magnet, and many times more than most low-temperature topological SCs can endure.

While the team has not yet proved conclusively that UTe2 is a topological SC, Butch says this unusual resistance to strong magnetic fields means that it must be a spin-triplet SC, and therefore it is likely a topological SC as well. This resistance also might help scientists understand the nature of UTe2 and perhaps superconductivity itself.

"Exploring it further might give us insight into what stabilizes these parallel-spin SCs," he said. "A major goal of SC research is to be able to understand superconductivity well enough that we know where to look for undiscovered SC materials. Right now we can't do that. What about them is essential? We are hoping this material will tell us more."