Tech

Scientists from the Physikalisch-Technische Bundesanstalt (PTB) have implemented a novel pressure measurement method, quasi as a byproduct of the work on the "new" kelvin. In addition to being new, this procedure is a primary method, i.e. it only depends on natural constants. As an independent method, it can be used to check the most accurate pressure gauges, for which PTB is known as the world leader. Checking such instruments was formerly possible in the range of up to 100 000 pascals only; now 7 million pascals are feasible. A comparison between mechanical and electrical pressure measurements has thus been carried out for the first time with a relative uncertainty of less than 5 × 10-6. Moreover, this new method offers unique possibilities to investigate helium - an important model system for the fundamentals of physics. The scientists have reported their work in the current issue of Nature Physics.

Have you ever been stepped on by a person wearing stilettos? If you are familiar with this kind of pain, you may have already considered that pressure corresponds to a force per unit of surface, or, to be more precise, that it is the result of a force applied vertically onto a surface. This is also the principle according to which the most accurate methods of pressure measurement work. When using a pressure balance, you measure the pressure of the gas under a piston of an exactly known surface by determining the gravitational force exerted onto the piston. PTB's pressure balances are currently the most accurate piston gauges in the world - high-precision instruments, each of them manufactured with great effort. As there are, however, pressure ranges in which even the best pressure balances do not measure as accurately as metrologists would like them to. There had been endeavors to develop alternative pressure measurement methods for a long time. "Our new method is actually very simple: it is based on measuring the density of the measuring gas helium by means of a capacitance measurement. It means that we measure to what degree the gas changes the capacitance of a special, highly stable capacitor between the electrodes," explains Christof Gaiser, physicist at PTB. This method only refers to one universal property of helium gas, which is expressed via the dielectric constant; it is therefore a primary method.

Gaiser and his colleagues have thus succeeded in realizing a groundbreaking theoretical approach for the first time in practice. As early as 1998, Mike Moldover of the US American metrology institute NIST had voiced his idea of measuring pressure via an electrical (capacitance) measurement using theoretical calculations of the gas properties of helium. In the following years, however, implementing this thought proved to be a real challenge. Both the precision capacitance measurement and the highly stable capacitors needed for this purpose, as well as the theoretical calculations using solely natural constants (ab initio calculations) were not yet possible with the required accuracy. Moreover, there was no accurate possibility to compare them with conventional pressure balances.

Each of the experimental obstacles has been removed at PTB over the last decade. Due to activities carried out within the scope of the new definition of the base unit kelvin, which reached its apex on 20 May this year with the introduction of an enhanced system of units, conventional pressure measurements both with pressure balances and via capacitance measurements were raised to an unprecedented level worldwide. Thanks to the latest theoretical calculations achieved by diverse research groups across the globe, it has now become possible to measure a pressure of 7 million pascals (i.e. 70 times normal pressure) with a relative uncertainty of less than 5 × 10-6. This measurement has been confirmed by comparison with a conventional pressure balance. It was the first comparison on an equal footing between mechanical and electrical pressure measurements.

Thus, a second method is now available to calibrate pressure with high accuracy. The method itself and the direct comparison with the conventional pressure standard offer, for one thing, the possibility to verify theoretical calculations of helium - an important model system in atomic physics. For another, they also allow other gases to be measured and thus, both theory and gas metrology to be further developed.
(es/ptb)

One of the main challenges in materials science research is to achieve high tunability of the optical properties of semiconductors at room temperature. These properties are governed by "excitons", which are bound pairs of negative electrons and positive holes in a semiconductor.

Excitons have become increasingly important in optoelectronics and the last years have witnessed a surge in the search for control parameters - temperature, pressure, electric and magnetic fields - that can tune excitonic properties. However, moderately large changes have only been achieved under equilibrium conditions and at low temperatures. Significant changes at ambient temperatures, which are important for applications, have so far been lacking.

This has now just been achieved in the lab of Majed Chergui at EPFL within the Lausanne Centre for Ultrafast Science, in collaboration with the theory groups of Angel Rubio (Max-Planck Institute, Hamburg) and Pascal Ruello (Université de Le Mans). Publishing in Science Advances, the international team shows, for the first time, control of excitonic properties using acoustic waves. To do this, the researchers launched a high-frequency (hundreds of gigahertz), large-amplitude acoustic wave in a material using ultrashort laser pulses. This strategy further allows for the dynamical manipulation of the exciton properties at high speed.

This remarkable result was reached on titanium dioxide at room temperature, a cheap and abundant semiconductor that is used in a wide variety of light-energy conversion technologies such as photovoltaics, photocatalysis, and transparent conductive substrates.

"Our findings and the complete description we offer open very exciting perspectives for applications such as cheap acousto-optic devices or in sensor technology for external mechanical strain," says Majed Chergui. "The use of high-frequency acoustic waves, as those generated by ultrashort laser pulses, as control schemes of excitons pave a new era for acousto-excitonics and active-excitonics, analogous to active plasmonics, which exploits the plasmon excitations of metals."

"These results are just the beginning of what can be explored by launching high-frequency acoustic waves in materials," adds Edoardo Baldini, the lead author of the article who is currently at MIT. "We expect to use them in the future to control the fundamental interactions governing magnetism or trigger novel phase transitions in complex solids".

When Bruce Beutler won the Nobel Prize for Medicine in 2011, he reminisced about his grandmother, telling how she had once explained this distinguished award to him. Her grandson's Nobel Prize directed medical historians' attention to the Beutler family. The life of a Jewish pediatrician who emigrated from Nazi Germany to the United States in 1935 leads through a century of political turmoil, scientific progress, and prejudices.

Drawing on the personal recollections of Bruce Beutler and his family as well as autobiographical manuscripts and archival sources, Professor Sabine Hildebrandt from the Harvard Medical School and four other authors illustrate how these circumstances and conditions shaped the life of the physician before and after her emigration. Their study, entitled "Dr. Käthe Beutler, 1896 - 1999," has now been published in the Medizinhistorisches Journal ("Medicine and the Life Sciences in History"). One of the co-authors, Dr. Thomas Kammertöns, is a researcher at the Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC). Kammertöns, together with Professor Gerhard Gaedicke and other colleagues at the Charité, initiated in 2016 a symposium on the fate of Jewish physicians in general and on the Beutler family in specific. "There wasn't even a Wikipedia entry for Käthe Beutler in 2011," says Kammertöns. "The study is the first article in the field of medical history to extensively examine the life of Käthe Beutler and her family."

Family and professional life in Berlin

"Do something!" was one of her favorite things to say. And Käthe Beutler truly adhered to this dictum: As one of 251 women among a total of 2,560 medical students, she began her studies at Friedrich-Wilhelm-Universität in 1918, where she earned her doctorate, became a researcher, and worked as a physician at the Charité with renowned professors of the day, including Finkelstein and Czerny. Among her main interests were infant nutrition and social medicine, and she published an article in a medical journal about the effectiveness of a medication against congenital syphilis when combined with good nutrition and care of children with the disease.

Käthe Beutler married the Jewish internist Dr. Alfred Beutler in 1925, and they had three children: Friedrich, Ernst, and Ruth. The Beutlers were among those secular Jewish households who at Christmastime displayed the menorah and the Christmas tree side by side. The upbringing and education of her children were very important to Käthe Beutler. Her eldest son originally attended a Montessori school, which was an unusual choice at the time. After the Nazi regime closed the school, Käthe Beutler sent her children to a Zionist school, probably to protect them from anti-Semitic hostility, where they learned Hebrew and more about their Jewish heritage. It is likely that Käthe Beutler considered settling in Palestine at the time, but she kept other options open: She hired a British nanny so that her children could learn English.

Although Alfred Beutler was the chief breadwinner in the family, Käthe Beutler continued her profession after marriage. Around a year after her first son was born, she opened her own, initially private, pediatric practice in Berlin under her maiden name of Italiener - thus asserting her independence. She also treated children from prominent non-Jewish families, such as Harald Quandt, Magda Goebbels' son from her first marriage.

While Hildebrandt was studying the life of Käthe Beutler, she was surprised to learn that there was a period in Germany, specifically in the 1920s in Berlin, when a woman like Beutler was able to freely live out the roles of doctor, wife, and mother. "That possibility was completely taken away from most women, especially Jewish women, in 1933 by the National Socialists," says Hildebrandt. "Many decades passed before this freedom was restored, though it may not yet have returned to the same level."

This period in which Käthe Beutler was able - as a professional woman, mother of three children, and member of the German-Jewish bourgeoisie - to develop herself personally and professionally ended abruptly in 1933. She saw no chance under the National Socialist regime for securing an adequate education for her children. She had to witness how her mentors Otto Pick and Heinrich Finkelstein were forced into retirement because of their Jewish heritage and how family members were interrogated by the Gestapo. She lost her statutory health insurance accreditation and was only allowed to treat private patients. When a mother refused to let the pediatrician treat her children because she was Jewish, Käthe Beutler became the driving force behind her family's emigration from Germany.

Alfred Beutler was willing to listen to his wife and was also soon convinced of the need to emigrate. He chose the United States, where a cousin of his living in Milwaukee sponsored the family. Faced with the financial restrictions imposed on Jewish emigrants by the Nazi state, Käthe Beutler smuggled around 10,000 Reichsmarks out of the country in order to rescue at least a portion of the family's money. The couple even managed to take their piano and part of their medical equipment with them, though they had to leave a number of assets behind. On January 1, 1936, Käthe Beutler arrived in New York Harbor with her children, where Alfred Beutler, who had left several months earlier, was waiting for them.

In their new homeland

The Beutler family settled in Milwaukee. Alfred Beutler was soon able to practice medicine again, thanks to the fact that the accreditation requirements for foreign medical personnel were less restrictive in Wisconsin than in most other U.S. states. He passed the necessary examinations, and it wasn't long before his practice was running as well as it had in Berlin. Käthe Beutler also opened her own private pediatric practice in 1937. According to the study, this was an exception among dual-doctor marriages: In only three of nine such marriages were both spouses able to return to their previous professions in their new homeland. As a female physician in the United States, and a Jew and foreigner to boot, Beutler found herself fighting double and triple prejudices. She received support from neither male colleagues nor the other emigrants living there. On top of this came the foreign language, plus she had to do household chores and look after her three children, tasks that in Europe had been handled in part by hired help. Although Käthe Beutler the physician never resumed her former level of activity, she never stopped identifying with her profession. According to her son Ernst, when someone would mistake her for a nurse, she would reply, "No, I'm a doctor."

Hildebrandt says that what she admires about Käthe Beutler was her ability to adjust to new circumstances over and over again, without sacrificing her priorities, which mainly included her family. Käthe Beutler proved this once again at the age of 65, when she decided to leave Milwaukee after the death of her husband in 1962. She sold the practices and the mink farm and moved to California, where her children Ruth and Ernst lived with their families. She never practiced medicine again, but instead tended to Bruce and her nine other grandchildren, giving them piano lessons and helping them with their career paths. "She was the force that held the family together, the ultimate matriarch who made sure we came together and kept our family bonds strong," recalls her great-granddaughter Rhian Beutler. She passed on her scientific curiosity to her children and grandchildren - for example, to Friedrich, Ernst, and Bruce, who all pursued careers in research and became leading figures in their fields. She learned to use a computer when she was 80 years old and managed her finances herself. Käthe Beutler died in 1999 at the age of 103.

Berlin commemorates an extraordinary woman

Käthe Beutler was a married pediatrician who succeeded in reestablishing her medical practice in her new homeland. Despite this rare achievement, the history of the Beutler family had not previously been thoroughly researched. Hildebrandt and her colleagues chronicle the story of Käthe Beutler's life and the experiences of her family members in the context of the social situation which Jews faced in the Weimar Republic, during the Nazi regime, and as emigrants in the United States. The team of authors also examines the professional career of Alfred Beutler, the family's origins, and the fate of family members who remained in Germany. "The study expands our knowledge of the life of female physicians before and after their emigration from Nazi Germany," writes the research team.

A new research facility on the Berlin-Buch campus will carry the name of Käthe Beutler. Researchers of the Berlin Institute of Health (BIH) will move into the Käthe Beutler Building in 2020. Kammertöns and other Berlin scientists initiated the installation of commemorative plaques in front of Käthe Beutler's former Berlin practice and apartment, at what is today Theodor-Heuss-Platz 2. These so-called Stolpersteine - literally, stumble stones - are memorials to the building's former residents: Käthe, Alfred, their sons Friedrich and Ernst and their daughter Ruth. Berlin was also where the idea for a book about the Beutler family was born. With the support of her co-authors, Hildebrandt published a German biography of Käthe Beutler in 2019 with the publisher Hentrich & Hentrich.

Called the "second secret of life", allostery is one of the most fundamental processes of biology and has been a central focus among scientists across the life sciences spectrum, from fundamental biology to drug development.

But what is allostery? In the never-ending dance of regulation inside the cell, allostery is the process by which proteins - and other biological molecules - can indirectly regulate the activity of other biomolecules like receptors.

The key here is "indirectly". Normally, proteins and other ligands will bind their target molecule, e.g. a receptor or enzyme, on a main region called the "active site". Once bound, the ligand triggers a biochemical domino that results in a particular effect.

But in allostery, ligands bind enzymes or receptors on sites other than the active site, and cause different effects. For example, allosteric binding can reduce or even stop the activity of a receptor altogether. The advantage here for fields like drug development is that allosteric ligands don't have to compete for the active site, but rather exerts their effects through a "side door".

Now, the lab of Patrick Barth at EPFL's Institute of Bioengineering has developed a computational method for predicting and even designing allosteric functions in proteins. Published in Nature Chemical Biology, the scientists show that their method can be used for predictably designing signaling functions into receptors that belong to the large family of G protein-coupled receptors (GPCRs).

The scientists began with molecular dynamics simulations, a computer technique that models the physical movements of atoms and molecules. Using this to model GPCRs, they were able to identify allosteric sites on the dopamine receptor, a GPCR in the nervous system that is activated by the neurotransmitter dopamine. Dopamine is involved in functions like motor control, motivation, arousal, reinforcement, reward, lactation, sexual gratification, and nausea.

They then applied a new method developed in the lab that can rapidly evolve in silico protein sequences for specific dynamic and allosteric properties. This allowed the scientists to design allosteric variants of a GPCR: receptors with small differences in the locations of their structure where ligands can bind allosterically.

These locations are called "microswitches" and can change the entire behavior of the receptor. "We were able to engineer novel amino-acid microswitches at these sites, which can reprogram specific allosteric signaling properties," says Barth.

The researchers produced no less than 36 variants of the dopamine receptor D2, which regulates cognitive flexibility in humans and is the main target for most antipsychotic drugs. In one case, the scientists were able to entirely repurpose the D2 receptor into a serotonin biosensor, essentially making it susceptible to an entirely new neurotransmitter.

After binding serotonin, the redesigned receptor showed potent signaling responses that matched the predictions that the scientists made using their computational method. This accuracy wasn't only limited to the one variant; the researchers were able to predict the effects of more than a hundred known mutations on the signaling activities of several GPCRs.

Finally, it is important to note that the new method afford what chemists and bioengineers call "rational design": a strategy that uses computer modeling to predict how the new molecule's structure and dynamics will affect its behavior.

"So far, protein design has mostly focused on engineering stable protein structures and interactions lacking dynamics," says Barth. "Our work demonstrates the development and validation of the first computational approach that enables the prediction and rational design of protein allosteric dynamic functions; it sets the stage for designing signaling receptors with precise functions for cell-engineering approaches and predicting the effects of genetic variations on protein functions for personalized medicine, as well as designing new allosteric proteins and better drugs from scratch."

Imperial College London scientists have created a new type of membrane that could improve water purification and battery energy storage efforts.

The new approach to ion exchange membrane design, which is published today in Nature Materials, uses low-cost plastic membranes with many tiny hydrophilic ('water attracting') pores. They improve on current technology that is more expensive and difficult to apply practically.

Current ion exchange membranes, known as Nafion, are used to purify water and store renewable energy output in fuel cells and batteries. However, the ion transport channels in Nafion membranes are not well defined and the membranes are very expensive.

In contrast, low-cost polymer membranes have been widely used in the membrane industry in various contexts, from removal of salt and pollutants from water, to natural gas purification - but these membranes are usually not conductive or selective enough for ion transport.

Now, a multi-institutional team led by Imperial's Dr Qilei Song and Professor Neil McKeown at the University of Edinburgh has developed a new ion-transport membrane technology that could reduce the cost of storing energy in batteries and of purifying water.

They developed the new membranes using computer simulations to build a class of microporous polymers, known as polymers of intrinsic microporosity (PIMs), and alter their building blocks for varying properties.

Their invention could contribute to the use and storage of renewable energy, and boost the availability of clean drinking water in developing nations.

Lead author Dr Song, of Imperial's Department of Chemical Engineering, said: "Our design hails a new generation of membranes for a variety of uses - both improving lives and boosting storage of renewable energy such as solar and wind power, which will help combat climate change."

Fusilli backbones

The polymers are made of rigid and twisted backbones, like fusilli pasta. They contain tiny pores known as 'micropores' that provide rigid, ordered channels through which molecules and ions travel selectively based on their physical sizes.

The polymers are also soluble in common solvents so they can be cast into super-thin films, which further speeds up ion transport. These factors mean the new membranes could be used in a wide range of separation process and electrochemical devices that require fast and selective ion transport.

Water

To make PIMs more water-friendly, the team incorporated water-attracting functional groups, known as Tröger's base and amidoxime groups, to allow small salt ions to pass while retaining large ions and organic molecules.

The team demonstrated that their membranes were highly selective when filtering small salt ions from water, and when removing organic molecules and organic micropollutants for municipal water treatment. Dr Song said: "Such membranes could be used in water nanofiltration systems and produced at a much larger scale to provide drinking water in developing countries."

They are also specific enough to filter out lithium ions from magnesium in salt water - a technique that could reduce the need for expensive mined lithium, which is the major source for lithium ion batteries.

Dr Song said: "Perhaps now we can get sustainable lithium from seawater or brine reservoirs instead of mining under the ground, which would be less expensive, more environmentally friendly, and help the development of electric vehicles and large-scale renewable energy storage."

Batteries

Batteries store and convert energy made by renewable sources like wind and solar, before the energy feeds into the grid and powers homes. The grid can tap into these batteries when renewable sources run low, such as when solar panels are not collecting energy at night.

Flow batteries are suitable for such large-scale long-term storage but current commercial flow batteries use expensive vanadium salts, sulfuric acid, and Nafion ion-exchange membranes, which are expensive and limit the large-scale applications of flow batteries.

A typical flow battery consists of two tanks of electrolyte solutions which are pumped past a membrane held between two electrodes. The membrane separator allows charge-carrying ions to transport between the tanks while preventing the cross-mixing of the two electrolytes. The cross-mixing of materials can lead to battery performance decay.

Using their new-generation PIMs, the researchers designed cheaper, easily processed membranes with well-defined pores that let specific ions through and keep others out. They demonstrated the applications of their membranes in organic redox flow batteries using low-cost organic redox-active species such as quinones and potassium ferrocyanide. Their PIM membranes showed higher molecular selectivity towards ferrocyanide anions, and hence low 'crossover' of redox species in the battery, which could lead to longer lifetime of the battery.

Co-first author Rui Tan, a PhD researcher at the Department of Chemical Engineering, said: "We are looking into a wide range of battery chemistries that can be improved with our new generation of ion-transport membranes, from solid-state lithium-ion batteries to low-cost flow batteries."

What's next?

The design principles of these ion-selective membranes are generic enough that they can be extended to membranes for industrial separation processes, separators for future generations of batteries such as sodium and potassium ion batteries, and many other electrochemical devices for energy conversion and storage including fuel cells and electrochemical reactors.

Co-first author Anqi Wang, also a PhD researcher at the Department of Chemical Engineering, said: "The combination of fast ion transport and selectivity of these new ion-selective membrane makes them attractive for a wide range of industrial applications."

Next, the researchers will scale up this type of membrane to make filtration membranes. They will also look into commercialising their products in collaboration with industry, and are working with RFC power, a spin-out flow-battery company founded by Imperial co-author Professor Nigel Brandon.

Since 2015 Malaria has resurged and typical bednets treated with insecticide are losing their efficiency due to insecticide resistance in some mosquito species.

The bednets were previously crucial in reducing transmission and bites from mosquitoes in countries where Malaria is most common.

However, imaging systems developed at the University of Warwick working in collaboration with entomologists at Liverpool School of Tropical Medicine have discovered new mosquito behaviours leading to the barrier bednet design that is 100% effective, restoring the efficiency of bed nets and protecting from a resurgence of Malaria in Africa.

According to the Center for Disease Control and Prevention in 2016 an estimated 445,000 people died of malaria, most were young children in sub-Saharan Africa.

The resurgence of Malaria in high risk areas calls for new methods to combat the potentially dangerous situation. A collaboration between researchers at the University of Warwick and Liverpool School of Tropical Medicine have found adding a barrier above a bednet can significantly improve the bednet's performance, reduce the quantity of insecticide while expanding the range of insecticides that can be safely delivered via a bednet.

The project was led by Prof Philip McCall at Liverpool School of Tropical Medicine and in this study the team was joined by scientists at Imperial College and field specialists in Burkina Faso to demonstrate improvements to the efficiency of the traditional bednet method and mathematically predict reductions in clinical malaria.

In the paper 'Novel bednet design targets malaria vectors and expands the range of usable insecticides', published today, 2nd December in the Journal Nature Microbiology, the team investigated a simple method to safeguard the role of bednets in malaria control for the future.

Sleeping under a long-lasting insecticidal net is currently the most effective way of preventing malaria in Africa. However since 2015 these nets have been losing the ability to protect from more resistant mosquitoes carrying malaria.

Professor David Towers, from the School of Engineering at the University of Warwick comments:

"By 2017 an increase of 3.5 million malaria cases in the ten highest burden African countries revealed a serious reversal. Our imaging systems had revealed that mosquitoes tend to bounce across the top of a bednet, probing and attempting to get to the person sleeping beneath it and hence to blood feed."

From this new understanding, Prof McCall introduced the barrier bednet design - mounted in the bednet roof, the barrier is confined to a spatial region where the insecticide is beyond the reach of children, never touched by the bednet's occupants and rarely touched by anyone during routine human activity.

Professor David Towers from the School of Engineering at the University of Warwick continues:

"The imaging systems were used to evaluate the barrier net design revealing that contact durations with the barrier are relatively short, less than 20 seconds, but still sufficient to deliver a lethal dose of insecticide. They also revealed that a unique behaviour change in the mosquitoes occurred in the presence of a barrier that may have contributed to its effect and merits further investigation."

Tested against pyrethroid resistant malaria vectors in Burkina Faso, bednets with barriers achieved significantly higher killing rates than bednets alone.

"The tracking data fed into a mathematical model of mosquito-barrier interactions and identified other barrier designs that are predicted to further increase the barrier's performance."

Professor David Towers, from the School of Engineering at the University of Warwick continues:

"Minimal change from existing long-lasting insecticidal net processes and behaviour are required to place barrier bednets as an appropriate, safe and affordable method to extend the life of bednets in the fight against malaria in sub-Saharan Africa."

"In countries such as Burkina Faso in Africa, where malaria incidence has stubbornly remained high despite reductions in many other countries, a control tool such as the barrier bednet offers a realistic, affordable solution to the challenge of insecticide resistance that could be implemented in the short term and help reduce the number of deaths from malaria in affected communities."

Physicists at the Center for Integrated Nanostructure Physics (CINAP), within the Institute for Basic Science (IBS, South Korea), have discovered an intriguing phenomenon, known as carrier multiplication (CM), in a class of semiconductors with incredible thinness, outstanding properties, and possible applications in electronics and optics. Published in Nature Communications, these new findings have the potential to boost the photovoltaics and photodetector fields, and could improve the efficiency of solar cells produced with these ultrathin materials to up to 46%.

An interesting class of 2D materials, the van der Waals layered transition metal dichalcogenides (2D-TMDs), are expected to create the next-generation of optoelectronic devices, such as solar cells, transistors, light emitting diodes (LED), etc. They consist of individual thin layers separated by very weak chemical bonds (van der Waals bonds), and have unique optical properties, high light absorption, and high carrier (electron and hole) mobility. Beyond allowing the option to tune their band gap by changing composition and layer thickness, these materials also offer an ultrahigh internal radiative efficiency of >99%, promoted by the elimination of surface imperfections and large binding energy between carriers.

Absorption of sunlight in semiconducting 2D-TMD monolayers reaches typically 5-10%, which is an order of magnitude larger than that in most common photovoltaic materials, like silicon, cadmium telluride, and gallium arsenide. Despite these ideal characteristics, however, the maximum power conversion efficiency of 2D-TMDs solar cells has remained below 5% due to losses at the metal electrodes. The IBS team in collaboration with researchers at the University of Amsterdam aimed to overcome this drawback by exploring the CM process in these materials.

CM is a very efficient way to convert light into electricity. A single photon usually excites a single electron, leaving behind an 'empty space' (hole). However, it is possible to generate two or more electron-hole pairs in particular semiconductors if the energy of the incident light is sufficiently large, more specifically, if the photon energy is twice the material's bandgap energy. While the CM phenomenon is rather inefficient in bulk semiconductors, it was expected to be very efficient in 2D materials, but was not proved experimentally due to some technical limitations, like proper 2D-TMD synthesis and ultrafast optical measurement. In this study, the team observed CM in 2D-TMDs, namely 2H-MoTe2 and 2H-WSe2 films, for the first time; a finding that is expected to improve the current efficiency of 2D-TMD solar cells, even going beyond the Shockley-Queisser limit of 33.7%.

"Our new results contribute to the fundamental understanding of the CM phenomenon in 2D-TMD. If one overcomes the contact losses and succeeds in developing photovoltaics with CM, their maximum power conversion efficiency could be increased up to 46%," says Young Hee Lee, CINAP director. "This new nanomaterial engineering offers the possibility for a new generation of efficient, durable, and flexible solar cells."

Osaka, Japan - An Osaka University research team has introduced a new terahertz detector that allows extremely rapid wireless data communication and highly sensitive radar by using a frequency range that has previously been very difficult to work with. Their approach combined sensitive electronics and a novel method for handling high frequencies to achieve the long-sought goal of using terahertz radiation for sending and receiving wireless data. The record 30 gigabit per second real-time error-free transmission they obtained may lead the way for next-generation (6G) cellular network technology.

Wireless data is in great demand. Not only do mobile phones need high speeds to stream videos on the go, but some people living in rural areas rely entirely on wireless for their home broadband connections. Terahertz radiation—electromagnetic waves with frequencies around 1012 cycles per second—has long been tempting scientists and cell phone companies alike. The high frequency of terahertz radiation would allow more data to be transmitted per second, compared with the current standard of about 800 MHz. However, a practical terahertz receiver has remained elusive, for two main reasons. First, the electromagnetic oscillations are just too fast for conventional electronics to handle, and both the terahertz oscillator and detector have poor efficiency. Second, the thermal noise of the room-temperature detector obscures the received signals above.

Now, researchers at Osaka University have invented a novel receiver that not only overcomes these obstacles, it also set the record for the fastest error-free real-time transmission speed to date. They used a special electronic component called a resonant tunneling diode. In contrast with normal electronics - for which the current always increases at larger voltages - in a resonant tunneling diode, there is a specific "resonant" voltage that yields the peak current. Thus, there exists a region in which the current actually falls with increasing voltage. This nonlinear behavior allows the scientists to synchronize the rapid received terahertz signals with an internal electronic oscillator in the device, and then separate the data from the carrier wave. In the end, the sensitivity was enhanced by a factor of 10,000. "Among all electronic-based systems, ours achieved the highest error-free wireless transmission data rate," says first author Yousuke Nishida.

Cell phone towers are not the only places you might find terahertz radiation in the future. "This technology can be put to work in a wide range of applications, in addition to next-generation 6G wireless communication. These include spectroscopic sensing, non-destructive inspection, and high-resolution radar," adds corresponding author Masayuki Fujita.

Osaka, Japan - With more and more couples seeking assistance to conceive, the steps required for fertilization are being put under the microscope to identify factors that could enhance fertility. In a study published in the journal PNAS, a team led by researchers from Osaka University describe an exciting breakthrough that may aid in future fertility treatments.

When it comes down to it, sperm have only one job: to fertilize the egg. To do this though, they must first make their way to the fallopian tube, propelled by long tails called flagella. When they near their destination, the sperm become turbo-charged in a process known as capacitation, allowing them to race towards the egg. This enhanced motility is triggered by an influx of calcium ions into the flagellum. While researchers have known for some time that an electrical signal-sensing protein called VSP is expressed in sperm of many animal species, the actual physiological role of this protein was unknown.

Lead author of the study Takafumi Kawai explains, "Determining the physiological role of VSP was the main aim of our study. To do this, we generated a VSP-deficient mouse line so that we could examine VSP-deficient sperm from these animals."

The first thing the researchers noticed was that the VSP-deficient sperm had a greatly reduced ability to fertilize eggs in vitro. Closer inspection showed that the sperm were swimming around in circles during capacitation, meaning that fewer sperm actually made it to their destination. Defective motility suggested a problem with the flagellum, prompting the researchers to examine these structures in more detail.

"Surprisingly, in normal sperm, a lipid molecule called PIP2 is concentrated near the top of the flagellum, closer to the head," says Dr Kawai. "In the VSP-deficient sperm, PIP2 was both more abundant and more widely dispersed throughout the flagellum. We also recorded much higher concentrations of calcium ions in the VSP-deficient sperm."

These findings suggested that VSP plays a major role in ion channel regulation, which ultimately affects motility. The researchers proposed a mechanism whereby VSP is responsible for the polarized distribution of PIP2 in the flagellum. PIP2 then activates potassium ion channels, which indirectly causes a localized influx of calcium ions, enhancing motility. In the VSP-deficient sperm, the dispersed PIP2 causes excessive calcium ion influx which decreases the flexibility of the flagellum, affecting motility.

According to senior author of the study Yasushi Okamura, the discovery of VSP-based regulation of sperm motility has significant implications for male fertility. "We predict that our findings will lead to the development of fertility treatments that enhance sperm motility, increasing the chances of fertilization."

Sweet potatoes (Ipomoea batatas) are becoming more and more popular: Whether in soup or as fries, they increasingly compete with "regular" potatoes which, surprisingly, are only distantly related. Although economically not as important as the potato world-wide, the sweet potato has a higher nutritional value and is richer in vitamins. Particularly in Asia, the crop is an important source of nutrients. As with potatoes, there are different cultivars of sweet potatoes available, all displaying their own characteristics. Even cultivars grown in the field under similar conditions may differ strikingly with respect to insect attack. In previous studies, a cultivar known as Tainong 57 had demonstrably higher resistance to field herbivores in comparison to the cultivar known as Tainong 66. When attacked, the plants' leaves emit a distinct odor bouquet. Researchers at the Max Planck Institute for Chemical Ecology in Jena, Germany, and at the National Taiwan University wanted to find out whether the high insect resistance in one cultivar was related to this odor. They especially wanted to know whether sweet potatoes have mechanisms to activate defense responses via volatile signals, as described in other plant species.

First the scientists examined what happens in a plant after it has been attacked by herbivores. Plants of the resistant cultivar synthesize a plant hormone in the wounded leaves that is important for activating defense mechanisms. These plants also emit a bouquet of odors. As a result, a substance (sporamin) is formed in Tainong 57 leaves that are not directly affected by attack. Sporamin inhibits digestive enzymes in the attacking insects and causes the herbivores to completely lose their appetite. At the same time, sporamin is the dominant storage protein in the tuber and the reason why sweet potatoes must be cooked before being consumed. In the odor bouquet, only a single substance, DMNT, is responsible for this defense response: "DMNT is a terpene compound and smells almost a bit like herbal balm. One could imagine it as a fragrance used in a sauna," says Anja Meents, first author of the study and doctoral researcher at the MPI for Chemical Ecology, describing the scent. DMNT triggers the formation of the defense protein not only in the affected plant but also in neighboring plants that have not yet been attacked by herbivores. These plants are able to perceive the smell quickly and efficiently in order to prepare themselves to meet the impending threat.

"To our surprise, only one single volatile is enough to induce a specific defense reaction in a sweet potato plant of the Tainong 57 cultivar. Moreover, the same substance is simultaneously used by the plant for communication with neighboring plants in order to transmit important information," points out Axel Mithöfer, head of the Research Group Plant Defense Physiology. Interestingly, only plants of the resistant Tainong 57 cultivar released DMNT in high concentrations and were able to perceive the odor. Plants of the Tainong 66 cultivar, in contrast, released significantly less DMNT; even when the level of DMNT was increased, plants of this herbivore-susceptible sweet potato cultivar were unable to improve the effectiveness of their defense response.

"Our results are of great agricultural importance, because the consistent cultivation of resistant cultivars, such as Tainong 57, could help to considerably reduce the damage caused by herbivores in a natural way," Meents explains, indicating the practical potential of the study. The development of cultivars that release higher amounts of DMNT and which can perceive DMNT more efficiently compared to the cultivars in the study could further minimize the use of pesticides.

In further studies, the team of researchers would like to examine more closely how Tainong 57 perceives DMNT and transfers the signal into a defense response.

Researchers from LSTM have designed a new bednet that can kill mosquitoes more efficiently than existing nets, in a way that increases the choice of insecticide used, while minimising risk to the person inside the bednet.

The team, led by LSTM's Professor Philip McCall, designed what they call the Barrier Bednet as a solution to the increasing problem of resistance in African mosquito populations to pyrethroids, the main insecticide class currently used on bednets. Using video tracking systems developed with engineers from the University of Warwick, the team had already mapped the behaviour of malaria mosquitoes around bednets, which allowed them to explore how and where mosquitoes could be targeted. From this came the barrier net design, simply an extra panel of netting positioned above a standard bednet's roof, where mosquitoes collide with it as they fly back and forth above the net.

Results from initial studies, published today in the journal Nature Microbiology, show that Barrier Bednets with an appropriate treatment were highly effective against wild insecticide resistant Anopheles gambiae vectors in Burkina Faso. Remarkably, this was the case even when the bednet was untreated and only the barrier carried insecticide. Despite the apparent simplicity, the results are quite significant. Professor McCall explained: "Ensuring that long-lasting insecticidal bednets (LLINs) remain effective despite insecticide resistance is a global health priority and a research goal for those looking for effective tools to prevent the spread of malaria. Putting insecticide on the panel above the roof of the net means that is beyond the reach of children, doesn't come into contact with those sleeping inside the net and is rarely touched during routine daily activity. This paves the way to use insecticides previously unavailable for bednets because of possible health risks from direct contact. Plus, if we only use the effective insecticide on the barrier panel, it means that manufacturing nets would cost a lot less, as would the over-the-counter price for the people that need them. It also means we could consider additional insecticides that might have been ruled out previously as too expensive."

Mathematical modelling of malaria epidemiology by the Imperial College colleagues looked at the likely impacts on malaria in Burkina Faso if existing bednets were replaced by barrier bednets. Results indicated that barrier bednets should perform at least as well as the next-generation bednets currently being recommended by WHO for use where pyrethroid resistance occurs.

The team hopes that this simple design can safeguard the central role of bednets in malaria control for many years. "Insecticide-treated bednet are by far the most important method for preventing malaria in Africa and we cannot afford to lose them" continued Professor McCall. "Recent trial results have shown that insecticide combinations are effective against pyrethroid-resistant mosquitoes but toxicity restrictions on risk to occupants, especially children, and the higher cost of these nets continue to reduce options. We believe that barrier bednets can match the efficacy of WHO's currently recommended nets and with minor modification, possibly become even more effective. Importantly, because we can use current insecticides and production technology, functional Barrier Bednets could be ready for household deployment in at-risk communities in the very near future."

Plant scientists are striving to cultivate crops that can cope with saline soils in the hope that this may help feed the world's growing population, particularly in the face of climate change. Now, KAUST researchers have applied a newly developed robust statistical technique to examine how different barley plant traits affect yields grown in saline and nonsaline conditions.

"The problem with traditional regression analyses is that they focus on finding the average, or mean, of a given distribution," says Gaurav Agarwal, who worked on the project under the guidance of his supervisor Ying Sun and in collaboration with plant scientists Stephanie Saade and Mark Tester.

"In plant science, this incomplete picture can be frustrating because we're often more interested in details at the extreme ends of the distribution and what these data can tell us about optimizing crops," says Agarwal.

The two research groups turned to new advanced quantile regression techniques to analyze the traits that influence salt tolerance and yield in barley plants. The team modeled the saline and nonsaline conditions jointly, dividing up the data into different "quantiles" to build up a more detailed picture of the entire distribution. In this way, they could focus their analyses on those plant groups that displayed higher yields and greater tolerance and then examine the main influencing factors.

The team's results provide interesting insights into barley's responses and could inform future crop decisions, particularly in arid parts of the world.

Two key traits help gain high yield under saline conditions. Firstly, the plants' flowering time should not occur too late in the growing season. Late flowering may mean that the plant is affected by increased heat as the season progresses, reducing its ability to produce seeds.

"A more surprising result was that the salinity tolerance of plants increased linearly as the ear number per plant increased," says Agarwal. "However, tolerance then faltered when a plant grew more than three ears. A possible explanation is that the plant can cope with salt stress while producing seeds, but only up to a point, after which generating seeds comes at the expense of salinity tolerance."

"We are keen to expand on these initial results," adds Sun. "Our insights may also help further understanding of mechanisms of salt tolerance in barley and other crops."

Scientists are developing a new way to identify the unique chemical 'fingerprints' for different types of breast cancers.

These new chemical footprints will be used to train AI software - creating a new tool for rapid and accurate diagnosis of breast cancers.

The team of researchers from Lancaster University and Airedale NHS Foundation Trust are using a specialised chemical analytical technique called Raman Spectroscopy on biopsies to identify the molecular structure of different types of breast cancer, as well as variations within each cancer cell group.

Raman analysis is able to provide real-time information on cells and can be used to check how the cells are behaving, spreading and emerging elsewhere in the body.

After identifying the chemical fingerprints of breast cancer cells, and observing how they change, the researchers used this information to train complex machine learning algorithms to identify four subtypes of cancer.

The algorithms successfully predicted diagnostic patterns for each subtype with a high level of accuracy ranging between 70 per cent and 100 per cent.

Similar versions of these algorithms have previously been used to identify other forms of caners and diseases such as skin, oral and lung cancers.

The next stage of the research will look at creating databases of the chemical structures of many more different types of breast cancer cells and the forms they can take.

These databases will be then used to train more artificial intelligent algorithms using machine learning - eventually leading to a new diagnostic tool to sit alongside mammograms and MRI scans.

The new algorithms promise to provide rapid information to help medical specialists to make quicker diagnosis.

In addition, the approach will help to determine the state of the disease at various points in its progression and will become critical in planning the therapeutic approach of individual patients.

Professor Ihtesham Rehman, Chair in Bioengineering at Lancaster University and senior author of the study, said: "This research is an important step in developing a new way to identify the chemical structures of different types of breast cancers. We have been able to use these 'fingerprints' to develop complex algorithms that are accurately able to identify cells of four different types of cancer types.

"Vibrational spectroscopy combined with data mining and machine learning has the potential to offer a real-time analysis in biological samples, including cancer, with excellent accuracy - creating a powerful new tool to sit alongside existing techniques and helping medical specialists deliver accurate and timely diagnosis for their patients, and for monitoring the progression of the disease."

Manufacturing - Lightning strike out

Researchers at Oak Ridge National Laboratory demonstrated that an additively manufactured polymer layer, when applied to carbon fiber reinforced plastic, or CFRP, can serve as an effective protector against aircraft lightning strikes. CFRP is usually used on an airplane's exterior because it's lighter than traditional metal. Although lightweight, CFRP has a drawback - low electrical conductivity and heat resistance, making it vulnerable to lightning strikes. "We printed a novel, easy to apply adhesive material for CFRP," ORNL's Vipin Kumar said. "The polymer's chain-like structure makes the resulting material electrically conductive and structurally strong with thermal treatment." In a study, the research team conducted simulated lightning strike tests on polymer protected CFRP versus unprotected. "The polymer-protected sample showed minimal damage upon visual inspection and enabled much more uniform heat dissipation," Kumar said. "Our results proved that the polymer layer provided a continuous path to effectively distribute the lightning current." [Contact: Jennifer Burke, (865) 576-3212; burkejj@ornl.gov]

Image: https://www.ornl.gov/sites/default/files/2019-11/Lightning%20strike%20test%201.jpg

Credit: Researchers conducted simulated lightning strike tests on additively manufactured polymeric material applied to carbon fiber reinforced plastic, or CFRP. The test revealed minimal damage to the polymer protected CFRP compared to the unprotected material. Credit: Vipin Kumar/Oak Ridge National Laboratory, U.S. Dept. of Energy

Fusion - Argon calling

As scientists study approaches to best sustain a fusion reactor, a team led by Oak Ridge National Laboratory investigated injecting shattered argon pellets into a super-hot plasma, when needed, to protect the reactor's interior wall from high-energy runaway electrons. Other pellet materials, frozen from room-temperature gasses, have successfully reduced the plasma's thermal energy, but argon was most effective at runaway electron dissipation. Using fuel pellet injection technology - which literally shoots cryogenic pellets of fuel into the plasma to raise its density - the team used an injector optimized for argon during a series of tests at the DIII-D National Fusion Facility. "Now that we have demonstrated argon's effectiveness, our next step is to determine how many pellets and pellet injectors are needed for a solution that's applicable," said ORNL's Larry Baylor. This research may be scaled up for possible application on ITER, the international experimental reactor. [Contact: Sara Shoemaker, (865) 576-9219; shoemakerms@ornl.gov]

Image: https://www.ornl.gov/sites/default/files/2019-11/13966_ar_20degree_enhanced.jpg

Video: https://youtu.be/0sQIdmn6EQo

Caption: Scientists tested ORNL-developed pellet injection technology with shattered argon pellets shot out of a bent shatter tube in a lab at ORNL. The technology was later tested on an experimental fusion plasma to mitigate runaway electrons, preventing interior wall damage. Credit: Trey Gebhart/Oak Ridge National Laboratory, U.S. Dept. of Energy

Biology - Honoring a genetics pioneer

The life and legacy of Dr. Liane Russell - world-renowned for her groundbreaking genetics research in mice - will be celebrated during a symposium on December 20 beginning at 8:30 a.m. at Oak Ridge National Laboratory. The event will feature past and current recipients of the Liane B. Russell Distinguished Early Career Fellowship, as well as select guests who were influenced by Russell's work and life. She was lauded for her contributions to mammalian genetics, including the chromosomal basis of sex determination in mammals and the effect of radiation on embryos. Findings by Russell and her husband, the late William L. Russell, about the vulnerability of embryos to radiation led to changes in radiological practices for female patients of child-bearing age. Known as "Lee," Russell was also an active conservationist, as a founder of the Tennessee Citizens for Wilderness Protection. Visitors to the symposium must contact ORNL in advance to make arrangements. [Contact: Sara Shoemaker, (865) 576-9219; shoemakerms@ornl.gov]

Image: https://www.ornl.gov/sites/default/files/2019-07/LianeRussell40s200_1.jpg

Caption: The life and legacy of pioneering geneticist Dr. Liane Russell will be celebrated during a symposium on December 20 at Oak Ridge National Laboratory. Credit: Oak Ridge National Laboratory, U.S. Dept. of Energy

If you ask Northwestern Engineering's Michael Jewett, the potential of cell-free gene expression has always made sense. Rip off the wall of the cell, collect its insides, and teach the cell catalyst to produce new kinds of molecules and biological processes without the evolutionary constraints of using intact living cells.

But less than 20 years ago, this burgeoning field within synthetic biology still had much to prove.

"People thought we were crazy," said Jewett, professor of chemical and biological engineering at the McCormick School of Engineering. "When I was a graduate student, the idea of making a protein therapeutic was so obscure. At best, it was something that wasn't going to be cost effective enough to be useful, or the system wasn't going to produce enough protein to do anything worthwhile."

In a review paper published on November 29 in the journal Nature Reviews Genetics, Jewett, director of Northwestern's Center for Synthetic Biology, explores how cell-free engineering evolved from a specialized research tool to the backbone of a variety of applications in synthetic biology that stand to dramatically impact society, from the environment to medicine to education.

Now, synthetic biology garners wide interest. "Commercial industries are popping up around these technologies. Granting agencies are seeing the importance," he said. "The time for cell-free systems is here. It's now."

A technical renaissance

While cell-free gene expression has been used as a research tool for more than 50 years, its transformative potential has been limited by several constraints, including low and variable protein synthesis yields, short reaction durations, and small reaction scale. Researchers also battled against doubts that controlling the reaction environment within cells would remain beyond reach.

However, in the last 20 years, synthetic biology researchers have gradually peeled back the curtain of cell-free gene expression's potential, uncovering new insights in the lab that have led to new efficiencies and applications outside of it -- from biosensors to measure and monitor environmental contaminants in natural resources to targeted therapeutics to treat disease.

Jewett and collaborators, for example, recently developed a high-yielding one-pot cell-free protein synthesis platform derived from a genomically recoded strain of Escherichia coli. The system is not only optimized to produce the highest batch reaction expression yield of a protein to date, but the platform can make proteins with non-canonical amino acids, expanding the genetically encoded chemistry available to proteins and opening the door to create new types of enzymes, materials, and therapeutics.

"By having a platform that enables high-level gene expression in a one-pot use, the process becomes a lot more democratized," Jewett said. "That's exciting, because it will hopefully make it easier for other labs to use cell-free gene expression systems."

Northwestern at the forefront

As cell-free synthetic biology has grown in importance, so too has Northwestern's Center for Synthetic Biology. Launched in 2016 to bring together the brightest minds in the field and to provide a supportive ecosystem for research and education, the center has quickly established itself as a leader of cell-free systems research and technological development.

"The center has organically grown into one of leading centers in synthetic biology in the United States, and perhaps the world," said Jewett, Charles Deering McCormick Professor of Teaching Excellence. "As our team has come together, we've thought about research themes that not only connect us, but also position Northwestern as having a particular strength -- and cell-free systems has emerged."

Recent advances by center faculty have pushed the boundaries of cell-free engineering even further. Jewett and Milan Mrksich, Henry Wade Rogers Professor of Biomedical Engineering, for example, collaborated on a method to rapidly produce enzymes and analyze their reactions. The system, which combines Jewett's cell-free protein synthesis technology with Mrksich's SAMDI mass spectrometry platform, will help synthetic biologists design more complex molecules faster than ever.

Neha Kamat, assistant professor of biomedical engineering, recently demonstrated the first instance of using cell-free systems to selectively drive the fusion of lipid nanoparticles -- an emerging carrier for drug-delivery -- opening the door to new and complex types of biochemical reactions. Danielle Tullman-Ercek, associate professor of chemical and biological engineering, is uncovering new rules governing the function of microcompartment systems like viruses, which could serve as vessels to deliver protein therapeutics derived from cell-free systems to targeted locations in the body. Joshua Leonard, associate professor of chemical and biological engineering, is studying the interface of synthetic biology and systems biology to achieve design-driven medicine. Earlier this year, he chaired the Sixth International Mammalian Synthetic Biology Workshop hosted at Northwestern.

The center's work also touches the startup space. Stemloop was born out of the lab of Julius Lucks, associate professor of chemical and biological engineering. The company applies Lucks's research mission to understand how cellular systems sense and respond to their environments through a platform of technologies, including one focused on environmental water quality monitoring. Jewett also recently started SwiftScale Biologics, which seeks to accelerate a drug's arrival to the market using cell-free systems.

Sherlock Biosciences, started by Center for Synthetic Biology advisory board member James Collins, uses engineering biology platforms to create better, faster, and affordable medical diagnostic tests.

"The technology is ready to be applied outside the lab to address societal issues, and companies are emerging to give them a fair shake in the marketplace," Jewett said. "What people thought was once completely impossible is proving to be more than possible."

A glimpse of what's to come

The next decade will welcome even greater milestones, thanks in part to growing research collaborations, Jewett said.

Northwestern is working with clean-energy startup LanzaTech and Oak Ridge National Laboratory on a multi-year project supported by the Department of Energy to leverage clostridia, a bacterium that metabolizes carbon, to produce sustainable fuels. Jewett and his lab, joined by Keith Tyo, associate professor of chemical and biological engineering, and Linda Broadbelt, Sarah Rebecca Roland Professor of Chemical and Biological Engineering, are using computational design algorithms and cell-free engineering to rapidly prototype thousands of potential biosynthetic pathway designs that could optimize clostridia's production of biofuels.

"What would take LanzaTech months to engineer and test, our lab can do in days, thanks to cell-free systems," Jewett said.

Jewett also envisions an expansion of synthetic biology education through experiential learning opportunities in middle school and high school classrooms. Hundreds of schools around the world want to incorporate his suite of BioBits educational kits -- developed in collaboration with MIT and the Wyss Institute at Harvard -- into science curriculums. The interactive kits, now used in dozens of Evanston and Chicago classrooms, equip students to conduct synthetic and molecular biology experiments by adding water and simple reagents to freeze-dried cell-free reactions.

"It's critically important that we provide training opportunities to students, so they're excited about supporting and contributing to the emerging bio-economy," he said.

And what about the first FDA-approved therapeutic supported by a cell-free system? As companies improve the ability to scale the production of engineered proteins, Jewett is hopeful that engineered therapeutics will move into clinics.

"An FDA-approved product will certainly be a watershed moment," he said, "and I believe it is coming in the next decade."