Tech

Skoltech scientists conducted a study of milk lipids and described the unique features of human breast milk as compared to bovids, pigs, and closely related primates. Their findings could be indicative of co-evolution of milk composition and the specific needs of the developing organism.

Milk is a source of nutrients for growth and development of all mammals. Its composition can adjust to the needs of the baby's organism depending on the habitat, physiology, and reproductive strategy. The main lipids in milk ? triglycerides ? are composed of three fatty acids and show high diversity depending on the lactation stage, season, and the mother's diet. The baby's body uses fatty acids both as a source of energy and as building blocks for cell membranes, which is particularly important for the brain. Thus, the evolution of milk composition could occur concurrently with the evolution of the brain, and interspecific differences in mammalian milk are of special interest to scientists.

Researchers from Philipp Khaitovich's lab at Skoltech conducted mass spectrometric analysis of milk lipid samples of humans, two species of macaques, cows, pigs, goats and yaks, and made comparisons for their 472 components. The differences in the lipid composition were then compared to the known evolutionary distances between the species, and the majority of samples displayed a good match, except for pig milk. The analysis of triglycerides showed that saturated and monounsaturated fatty acids prevail in the milk of even-toed mammals, while primate milk is rich in unsaturated fatty acids. Pig milk contains a large amount of polyunsaturated fatty acids, which may be indicative of the adaptation to the short lactation period. Human milk, unlike primate milk, also contains a lot of polyunsaturated fatty acids. As both primates and humans have rather long lactation periods, scientists attribute the differences in milk composition to increased needs of the more complex human brain. Polyunsaturated fatty acids, especially omega-3 and omega-6, mostly come from food and are known to play an important role in the functioning of the nervous system.

"This is the first study that describes lipid composition of milk of seven mammalian species, including humans and primates. Our results show that milk composition differs not only between primates and cows, which was to be expected, but also between humans and monkeys. This means that breast milk is evolving, with its composition reflecting the changing needs of the entire body and the extensively growing brain. As the next step, we want to compare the interspecific differences in the composition of milk and brain," says Aleksandra Mitina, the first author of the paper.

WASHINGTON, July 7, 2020 -- Sensors placed in the environment spend long periods of time outdoors through all weather conditions, and they must continuously power themselves in order to collect data. Many, like photovoltaic cells, use the sun to produce electricity, but powering outdoor sensors at night is a challenge.

Thermoelectric devices, which use the temperature difference between the top and bottom of the device to generate power, offer some promise for harnessing naturally occurring energy. But, despite being more efficient than photovoltaics, many thermoelectric devices flip the sign of their voltage, meaning the electrical current changes the direction of its flow, when environmental temperatures change, so the voltage drops to zero at least twice a day.

"The sign of the thermoelectric device depends on the temperature difference between the top and bottom of the device," author Satoshi Ishii said. "Cooling can be used to create a temperature difference compared to the ambient temperature, and if there is a temperature difference, thermoelectric generation is possible."

In a study published this week in Applied Physics Letters, by AIP Publishing, the authors tested a thermoelectric device made up of a wavelength-selective emitter that constantly cools the device during the day using radiative cooling, the dispersion of thermal energy from the device into the air. As a result, the top of the device is cooler than the bottom, causing a temperature difference that creates constant voltage through day and night and various weather conditions.

The authors compared a broadband emitter with a selective emitter, showing the selective emitter avoids the problem of the voltage dropping to zero during environmental changes in temperature.

"For the selective emitter, it is best to have emissivity close to unity in the atmospheric window, approximately 8 to 13 micrometers, where the atmospheric transmittance is high and thermal emission can effectively radiate into space, which in turn cools the device," Ishii said.

The device they tested is comprised of a 100-nanometer-thick aluminum film on the bottom of a glass substrate. The authors discovered that other sources of heat, such as the roof where a sensor might be mounted, can augment its ability to generate voltage.

"A large temperature difference results in a large thermoelectric voltage," Ishii said. "Using the heat on the backside of the device makes the temperature difference between the bottom and top larger, so heat from behind the device is beneficial for thermoelectric generation."

WASHINGTON, July 7, 2020 -- Utility-scale photovoltaics, ground-mounted projects larger than 5 megawatts of alternating current, are the largest sector of the overall solar market within the U.S. and the fastest-growing form of renewable power generation.

This fleet of utility-scale photovoltaic projects is relatively young and hasn't been operating long enough to establish a lengthy history of operational field service. The first utility-scale photovoltaic projects in the U.S. came online in 2007, and most projects have been operating for only a few years.

In the Journal of Renewable and Sustainable Energy, from AIP Publishing, Mark Bolinger and colleagues from the U.S. Department of Energy's Lawrence Berkeley National Laboratory and the National Renewable Energy Laboratory assess the performance of a fleet of 411 utility-scale photovoltaic projects built within the U.S. from 2007 through 2016.

This fleet produced more than half of all of the solar electricity generated within the U.S. in 2017.

After correcting for variations in weather and curtailment, the group found, on average, the first-year performance of these systems was largely as expected, and that newer projects have degraded at a slower rate than older ones. This suggests photovoltaics technology has improved over time. Interestingly, they also confirmed that projects in hotter climates tend to degrade faster than those in cooler climates.

"A large and rapidly growing market that lacks a lengthy operating history means that investors are fronting a lot of money -- $6.5 billion for projects built within the U.S. in 2018 alone -- based on as-yet untested assumptions about the long-term performance of these projects," said Bolinger.

Photovoltaic cells degrade in efficiency and performance over time due to a variety of factors.

"Most photovoltaic module manufacturers warrant that their modules' performance won't degrade by more than a certain percentage, for example, losing 0.5% per year, during a 25-year period," he said. "But module degradation is only part of the story, because the other components of a utility-scale photovoltaic system -- the inverter, tracking system, fuses, wiring -- can also negatively affect output."

Many existing studies so far have explored module-level degradation, but the total system-level performance and degradation is what truly affects the bottom line.

"To our knowledge, our study is the first use of fixed effects regression techniques to analyze photovoltaic performance degradation," Bolinger said. "Unlike other approaches commonly used, fixed effects regression is compatible with low-frequency generation data."

Because low-frequency generation data tends to be publicly available, in contrast to high-frequency data, which is often proprietary, this new approach is more accessible to researchers and enables large-sample or even fleetwide analyses.

"But the flip side is that lower-frequency data often results in greater uncertainty around degradation estimates," Bolinger said. "By focusing on system-level rather than module-level performance, our approach provides a more holistic and realistic estimate of long-term investment risk."

Quantum information scientists have introduced a new method for machine learning classifications in quantum computing. The non-linear quantum kernels in a quantum binary classifier provide new insights for improving the accuracy of quantum machine learning, deemed able to outperform the current AI technology.

The research team led by Professor June-Koo Kevin Rhee from the School of Electrical Engineering, proposed a quantum classifier based on quantum state fidelity by using a different initial state and replacing the Hadamard classification with a swap test. Unlike the conventional approach, this method is expected to significantly enhance the classification tasks when the training dataset is small, by exploiting the quantum advantage in finding non-linear features in a large feature space.

Quantum machine learning holds promise as one of the imperative applications for quantum computing. In machine learning, one fundamental problem for a wide range of applications is classification, a task needed for recognizing patterns in labeled training data in order to assign a label to new, previously unseen data; and the kernel method has been an invaluable classification tool for identifying non-linear relationships in complex data.

More recently, the kernel method has been introduced in quantum machine learning with great success. The ability of quantum computers to efficiently access and manipulate data in the quantum feature space can open opportunities for quantum techniques to enhance various existing machine learning methods.

The idea of the classification algorithm with a nonlinear kernel is that given a quantum test state, the protocol calculates the weighted power sum of the fidelities of quantum data in quantum parallel via a swap-test circuit followed by two single-qubit measurements (see Figure 1). This requires only a small number of quantum data operations regardless of the size of data. The novelty of this approach lies in the fact that labeled training data can be densely packed into a quantum state and then compared to the test data.

The KAIST team, in collaboration with researchers from the University of KwaZulu-Natal (UKZN) in South Africa and Data Cybernetics in Germany, has further advanced the rapidly evolving field of quantum machine learning by introducing quantum classifiers with tailored quantum kernels.

The input data is either represented by classical data via a quantum feature map or intrinsic quantum data, and the classification is based on the kernel function that measures the closeness of the test data to training data.

Dr. Daniel Park at KAIST, one of the lead authors of this research, said that the quantum kernel can be tailored systematically to an arbitrary power sum, which makes it an excellent candidate for real-world applications.

Professor Rhee said that quantum forking, a technique that was invented by the team previously, makes it possible to start the protocol from scratch, even when all the labeled training data and the test data are independently encoded in separate qubits.

Professor Francesco Petruccione from UKZN explained, "The state fidelity of two quantum states includes the imaginary parts of the probability amplitudes, which enables use of the full quantum feature space."

To demonstrate the usefulness of the classification protocol, Carsten Blank from Data Cybernetics implemented the classifier and compared classical simulations using the five-qubit IBM quantum computer that is freely available to public users via cloud service. "This is a promising sign that the field is progressing," Blank noted.

Optical singularities are key elements in modern optics and have been widely researched. In particular, phase and polarization singularities have been manipulated in various applications, such as imaging and metrology, nonlinear optics, optical tweezers, sensing, quantum information, and optical communication. In theory, both singularities can be detected simultaneously if one can detect the topological charge and photon spin at the same time. Several methods have been proposed to detect the topological charge of the OAM in recent years, including holography, metasurfaces, optical transformation, and photonic circuits. However, these methods have drawbacks including the need to align the beam precisely with the structure, the need for complex detection processes, such as near-field microscopy, and the low diffraction efficiencies of some elements. These drawbacks strongly limit their applications in new optical systems with optical fibres or integrated on-chip devices.

In a new paper published in Light Science & Application, a team of scientists, led by Professor Changjun Min, Xiaocong Yuan, Mike Somekh from Nanophotonics Research Center, Shenzhen Key Laboratory of Micro-Scale Optical Information Technology, Shenzhen University, Shenzhen 518060, China and co-workers have developed an on-chip plasmonic spin-Hall nanograting for simultaneously detecting phase and polarization singularities. They have designed a symmetry-breaking nanograting structure first to unidirectionally launch the SPP wave according to the sign of the topological charge of the incident wave. The propagation angle of the generated SPP increases with the value of the topological charge. The topological charge value of the incident beam can be accurately determined by placing an output coupling grating on both sides of the nanograting to couple the generated SPP wave to the far field and analysing the far-field optical microscopy image. Additionally, a spin-Hall structure is integrated onto the nanograting so that the nanograting can respond to the spin of the incident beam. This combined structure directionally couples the incident OAM beam to different positions depending on the polarization and topological charge of the beam. It is proved experimentally that the structure detects the polarization singularity and phase singularity of the incident CVB beam simultaneously. This device is very promising for achieving a highly compact photonic integrated circuit. These scientists summarize the operational principle of their structure:

"We design a SPP based meta-surface which can detect simultaneously phase and polarization singularities of the incident wave for two purposes in one: (1) to rapidly and simultaneously detect the phase and polarization singularities with single shot image; (2) to enable optical communication with photonics singularities of electromagnetic waves."

"This device is very promising for achieving a highly compact photonic integrated circuit. It has shown great potential in large-scale photonic integrated circuits and would benefit diverse applications such as optical on-chip information processing and optical communications. We are now trying to intergrate an additional coupound phase modulation structure onto the device to cancel the diffraction effect of the SPP wave during generation. This would further enhance the resolution and detection limit of the system." they added

"The presented technique can be used for new generation of optical communication. As photonic singularities are new degree of freedom which can carry far more information compare to what the intensity modulation, frequency modulation we use now. The tiny volum of the device and its capacity of information processing will open a new gate to modern communication in both classic regime and quantum regime." The scientists forecast.

Many animals, including dogs, cats and various species of monkeys, will move their ears to better focus their attention on a novel sound. That humans also have this capability was not known until now. A research team based in Saarland has demonstrated for the first time that we make minute, unconscious movements of our ears that are directed towards the sound want to focus our attention on. The team discovered this ability by measuring electrical signals in the muscles of the vestigial motor system in the human ear. The results have now been published in the journal eLife.

Asking children to 'perk up their ears' means asking them to listen intently. Nobody seriously thinks that kids literally move their ears the way that cats, dogs or horses do. But the fact is, they do, as researchers at the Systems Neuroscience & Neurotechnology Unit (SNNU) have now shown. The research team, led by Professor Danial Strauss, has shown that the muscles around the ear become active as soon as novel, unusual or goal-relevant sounds are perceived. 'The electrical activity of the ear muscles indicates the direction in which the subject is focusing their auditory attention,' says neuroscientist and computer scientist Strauss. 'It is very likely that humans still possess a rudimentary orientation system that tries to control the movement of the pinna (the visible outer part of the ear). Despite becoming vestigial about 25 million years ago, this system still exists as a "neural fossil" within our brains,' explains Professor Strauss. The question why pinna orienting was lost during the evolution of the primate lineage has still not been completely resolved.

The researchers were able to record the signals that control the minute, generally invisible, movements of the pinna using a technique known as surface electromyography (EMG). Sensors attached to the subject's skin detected the electrical activity of the muscles responsible for moving the pinna or altering its shape. Two types of attention were examined. To assess the reflexive attention that occurs automatically when we hear unexpected sounds, the participants in the study were exposed to novel sounds coming at random intervals from different lateral positions while they silently read a monotonous text. To test the goal-directed attention that we show when actively listening, the participants were asked to listen to a short story coming from one laterally positioned speaker, while ignoring a 'competing' story from a speaker located on the opposite side. Both experiments showed that muscle movements in the vestigial pinna-orienting system indicate the direction of the subject's auditory attention.

To better characterize these minute movements of the ear, the team also made special high-definition video recordings of the subjects during the experiments. The subtle movements of the ears were made visible by applying computer-based motion magnification techniques. Depending on the type of aural stimulus used, the researchers were able to observe different upward movements of the ear as well as differences in the strength of the rearward motion of the pinna's upper-lateral edge.

'Our results show that electromyography of the ear muscles offers a simple means of measuring auditory attention. The technique is not restricted to fundamental research, it also has potential for a number of interesting applications," explains Professor Strauss. One area of great practical relevance would be in developing better hearing aids. 'These devices would be able to amplify the sounds that the wearer is trying to hear, while suppressing the noises that they are trying to ignore. The device would function in a way that reflects the user's auditory intention.' The hearing aid would almost instantaneously register and interpret the electrical activity in the ear muscles. A miniature processor would gauge the direction the user is trying to direct their attention towards and then adjust the gain on the device's directional microphones accordingly.

The research project was conducted by researchers at the Systems Neuroscience & Neurotechnology Unit (SNNU), which is affiliated to both the Medical Faculty at Saarland University and to the School of Engineering at the University of Applied Sciences in Saarland (htw saar). External project partners were Dr. Ronny Hannemann from the hearing aid manufacturer Sivantos GmbH and Steven A. Hackley, Professor of Psychology at the University of Missouri-Columbia, who in 2015 first postulated the existence of a vestigial pinna-orienting system in humans.

The air around us is still getting more and more polluted. No wonder many scientists strive to find a way to purify it. Thanks to the work of an international team led by prof. Juan Carlos Colmenares from the Institute of Physical Chemistry, Polish Academy of Sciences, we are a big step closer to achieve this goal. They found a way to make an efficient reactive adsorbent able to purify the air from various toxic compounds, cheaply, and effectively.

"Most important is the material we made at the laboratory," says prof. Colmenares. "It not only adsorbs toxic vapors from the air but also, thanks to its photocatalytic properties, can break them into less toxic elements." Material made by the team consists of two quite cheap and easy to acquire compounds: titanium dioxide and graphite oxide. "We intended to make it widely available," explains the professor, and "environmentally friendly." The innovation here was to use ultrasound to make the two counterparts - one organic and one inorganic - to co-operate. The organic counterpart catches the toxic particles, and the inorganic one destroys them by photocatalysis. Ultrasonic manipulation also significantly widens the active surface and chemical heterogeneity of the new material, allowing for higher detoxification efficiency against the "bad guys" from the air. "Thanks to the ultrasound waves, we get excellent dispersion and the layer of graphite oxide sort of rests on the surface of titanium dioxide," says prof. Colmenares. Initially, researchers planned to incorporate this material as an additional filter layer for soldiers' gas masks, or into fabrics, making uniforms that would protect a soldier from toxic gaseous chemicals on the combat field. All this, providing the day, was sunny, and garment had additional LED lights activating photocatalysis. However, high absorptance can be achieved even in the dark.

However, although the invention has been tested on warfare agents, its potential applications are much broader and more peaceful.

One could, for example, make industrial suits for workers exposed to toxic vapors daily. "Just milligrams in a suit would be sufficient," says professor, "if only dispersed properly. The only downside is that potential fabrics should be artificial polymers rather than natural cotton or flax," he smiles lightly. Scientists would also have to find a way to fasten their nanomaterial to the carrier fabric more securely as clothes get washed. We know that nearly 35% of microplastic found in the environment comes from synthetic clothes and washed linen. "We would not like our nanomaterial to end in rivers and seas," says the professor. "We aim for being environmentally friendly all the way, not only at the level of destroying air toxins." Although, as shown earlier by Dimitrios A. Giannakoudakis, the first author of the current work published in the Chemical Engineering Journal and other members of the international team, by ultrasonication, the active phases can be anchored quickly and stably both on cotton and carbon textiles.

If adequately modified, the same technology could help purify not only air but also water and soil. "We have not examined these possibilities yet," says prof. Colmenares, "but it mainly depends on whether we would safely deposit our nanomaterial on possible future carriers/substrates. While purifying water from toxins, we would not like to pollute it with these oxides; we would not want nanotoxicity, although in theory neither TiO2 nor graphite oxide is toxic to humans," explains the scientist. "After all, who was not chewing on a pencil while at school?"

If we resolved this issue, we could say, "sky is the limit." New material could detoxify sewage in paper and coke industries or even neutralize highly toxic remnants of World War II, lying deep in the Baltic Sea. "For now, we aim at sewage plants," says the professor. "Photocatalysis and nanocomposites can help where microbes cannot because the environment is too toxic for them."

Photocatalysis of the soil is the greatest challenge. However, even this is imaginable with proper mixing, lighting, and a proper photocatalyst, for example, to remove herbicides or pesticides.

Cleaner air is within active reach. For cleaner water and soil, we would have to wait a little longer for an optimum solution, but scientists from IPC PAN are just starting their quest for a better, cleaner environment by sustainable approaches for us all.

People who work in jobs that require less physical activity - typically office and desk-based jobs - are at a lower risk of subsequent poor cognition than those whose work is more physically active, suggests new research from the University of Cambridge.

Lack of physical activity and exercise are known risk factors for major health conditions, including cognitive impairments such as memory and concentration problems. However, evidence as to whether physical activity actually protects against cognitive decline has often been mixed and inconclusive.

Researchers at the University of Cambridge examined patterns of physical activity among 8,500 men and women who were aged 40-79 years old at the start of the study and who had a wide range of socioeconomic backgrounds and educational attainment. The individuals were all part of the EPIC-Norfolk Cohort. In particular, the team were able to separate physical activity during work and leisure to see if these had different associations with later life cognition.

"The often used mantra 'what is good for the heart, is good for the brain' makes complete sense, but the evidence on what we need to do as individuals can be confusing," said Shabina Hayat from the Department of Public Health and Primary Care at the University of Cambridge. "With our large cohort of volunteers, we were able to explore the relationship between different types of physical activity in a variety of settings."

As part of the study, participants completed a health and lifestyle questionnaire, including information on the level of physical activity during both work and leisure, and underwent a health examination. After an average 12 years, the volunteers were invited back and completed a battery of tests that measured aspects of their cognition, including memory, attention, visual processing speed and a reading ability test that approximates IQ.

While many studies have only been able to report cross-sectional findings, the ability to follow up EPIC-Norfolk participants over a long period allowed the researchers to examine data prospectively. This helped them rule out any bias resulting from people with poor cognition - possibly as a result of cognitive impairment or early dementia - being less likely to be physically active due to poor cognition, rather than poor cognition being a result of physical inactivity.

Among their findings, published today in the International Journal of Epidemiology, the researchers report:

Individuals with no qualifications were more likely to have physically active jobs, but less likely to be physically active outside of work.

A physically inactive job (typically a desk-job), is associated with lower risk of poor cognition, irrespective of the level of education. Those who remained in this type of work throughout the study period were the most likely to be in the top 10% of performers.

Those in manual work had almost three times increased risk of poor cognition than those with an inactive job.

"Our analysis shows that the relationship between physical activity and cognitive is not straightforward," explained Hayat. "While regular physical activity has considerable benefits for protection against many chronic diseases, other factors may influence its effect on future poor cognition.

"People who have less active jobs - typically office-based, desk jobs - performed better at cognitive tests regardless of their education. This suggests that because desk jobs tend to be more mentally challenging than manual occupations, they may offer protection against cognitive decline."

It was not possible to say conclusively that physical activity in leisure time and desk-based work offer protection against cognitive decline. The researchers say that to answer this question, further studies will be required to include a more detailed exploration of the relationship of physical activity with cognition, particularly on inequalities across socio-economic groups and the impact of lower education.

With high-resolution microscopy, it is theoretically possible to image cell structures with a resolution of a few nanometres. However, this has not yet been possible in practice.

The reason for this is that antibodies carrying a fluorescent dye are usually used to label cell structures. Therefore, the dye is not located directly at the target structure, but about 17.5 nanometres away from it. Partly because of this distance error, the theoretically achievable resolution could not be achieved so far.

Publication in Nature Communications

An international research team has now overcome this hurdle. This was achieved by combining the super-resolution microscopy methods dSTORM and expansion microscopy (ExM). The journal Nature Communications presents the results.

The publication was led by a team from the Biocenter of Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany: Professor Markus Sauer, Head of the Department of Biotechnology and Biophysics, with PhD students Fabian Zwettler and Sebastian Reinhard. Professors Paul Guichard from the University of Geneva (Switzerland) and Toby Bell from Monash University (Australia) also played a key role.

Obstacles to combining dSTORM and ExM

The dSTORM method, developed in Professor Sauer's group, achieves an almost molecular resolution of about 20 nanometers. To further increase the resolution, a combination with expansion microscopy, which has been available for a few years now, seemed promising.

In ExM, the sample to be examined is cross-linked into a swellable polymer. Then the interactions of the molecules in the sample are destroyed and the sample is allowed to swell in water. This leads to an expansion: the molecules to be imaged drift spatially apart by a factor of four.

Why the two methods could not be combined until now:

The fluorescent dyes used for dSTORM to label the molecules did not survive the polymerization of the aqueous gel.

A buffer solution is needed for dSTORM, but the expanded sample shrinks to its original size in such buffers.

Distance error significantly reduced

"By stabilizing the gel and immune staining only after expansion, we could overcome these hurdles and successfully combine the two microscopy methods," says Markus Sauer. As a result, the distance error melts to just five nanometers when expanded 3.2 times. This makes fluorescence imaging with molecular resolution possible for the first time.

The researchers used centrioles and structures that are composed of the protein tubulin to show how well their method works. They were able to visualise tubulin tubes as hollow cylinders with a diameter of 25 nanometres. The researchers succeeded in sharply imaging groups of three made up of tubulin structures at a distance of 15 to 20 nanometres at the centrioles. The centrioles are cell structures that play an important role in cell division.

Professor Sauer's conclusion: "For many important cell components, the combination of ExM and dSTORM now enables us to gain detailed insights into molecular function and architecture for the first time. The team therefore plans to apply the method to different structures, organelles and multiprotein complexes of the cell.

In physics, they are currently the subject of intensive research; in electronics, they could enable completely new functions. So-called topological materials are characterised by special electronic properties, which are also very robust against external perturbations. This material group also includes tungsten ditelluride. In this material, such a topologically protected state can be "broken up" using special laser pulses within a few trillionths of a second ("picoseconds") and thus change its properties. This could be a key requirement for realising extremely fast, optoelectronic switches. For the first time physicists at Kiel University (CAU), in cooperation with researchers at the Max Planck Institute for Chemical Physics of Solids (MPI-CPfS) in Dresden, Tsinghua University in Beijing and Shanghai Tech University, have been able to observe changes to the electronic properties of this material in experiments in real-time. Using laser pulses, they put the atoms in a sample of tungsten ditelluride into a state of controlled excitation, and were able to follow the resulting changes in the electronic properties "live" with high-precision measurements. They published their results recently in the scientific journal Nature Communications.

"If these laser-induced changes can be reversed again, we essentially have a switch that can be activated optically, and which can change between different electronic states," explained Michael Bauer, professor of solid state physics at the CAU. Such a switching process has already been predicted by another study, in which researchers from the USA were recently able to directly observe the atomic movements in tungsten ditelluride. In their study, the physicists from the Institute of Experimental and Applied Physics at the CAU now focused on the behaviour of the electrons, and how the electronic properties in the same material can be altered using laser pulses.

Weyl semimetals with unusual electronic properties

"Some of the electrons in tungsten ditelluride are highly mobile, so they are excellent information carriers for electronic applications. This is due to the fact that they behave like so-called Weyl fermions," said doctoral researcher Petra Hein to explain the unusual properties of the material, also known as a Weyl semimetal. Weyl fermions are massless particles with special properties and have previously only been observed indirectly as "quasi-particles" in solids like tungsten ditelluride. "For the first time, we were now able to make the changes in the areas of the electronic structure visible, in which these Weyl properties are exhibited."

Excitations of the material changes its electronic properties

To capture the barely-visible changes in the electronic properties a highly-sensitive experimental design, extremely precise measurements and an extensive analysis of the data obtained were required. During the past years the Kiel research team was able to develop such an experiment with the necessary long-term stability. With the generated laser pulses they put the atoms inside a sample of tungsten ditelluride into a state of vibrational excitation. Different overlapping vibrational excitations arose, which in turn changed the electronic properties of the material. "One of these atomic vibrations was known to change the electronic Weyl properties. We wanted to find out exactly what this change looks like," said Hein to describe one of the key goals of the study.

Series of snapshots shows how properties change

In order to observe this specific process, the research team irradiated the material with a second laser pulse after a few picoseconds. This released electrons from the sample, which allowed drawing conclusions about the electronic structure of the material - the method is known as "time-resolved photoelectron spectroscopy". "Due to the short exposure time of only 0.1 picoseconds, we get a snapshot of the electronic state of the material. We can combine many of these individual images into a film and thereby observe how the material reacts to the excitation by the first laser pulse," said Dr Stephan Jauernik to explain the measurement method.

Recording a single data set on the extremely short modification process typically took one week. The Kiel research team evaluated a large number of such data sets using a newly developed analytical approach and was thus able to visualize the changes in the electronic Weyl properties of tungsten ditelluride.

Extremely short switching processes conceivable

"Our results demonstrate the sensitive and highly-selective interplay between the vibrations of the atoms of the solid and the unusual electronic properties of tungsten ditelluride," summarised Bauer. Follow-up research aims at investigating whether such electronic switching processes can be triggered even faster - directly by the irradiating laser pulse - as has already been theoretically predicted for other topological materials.

Researchers at the Center for Cognition and Sociality, within the Institute for Basic Science (IBS), Gwangju Institute of Science and Technology (GIST), and Korea Institute of Science and Technology (KIST) have discovered a new mechanism to explain the effects of subcortical strokes and a new possible therapeutic approach.

Every year, 15 million people worldwide suffer from stroke according to the World Health Organization. Five million of those die and another five million are permanently disabled. Stroke is one of the most commonly reported causes of death and greatly impacts patients' quality of life. However, despite its prevalence and negative impact, there are no direct medical treatments for recovery after stroke and patients rely on rehabilitation.

A stroke occurs when the blood supply is interrupted or reduced due to bleeding or occlusion of blood vessels in some part of the brain. Brain cells subsequently begin to die within minutes, causing a regional brain damage. In addition, the stroke leads to a loss of function, called diaschisis, in other brain regions connected to the damaged area. Proposed 115 years ago, diaschisis worsens symptoms and prognosis of stroke patients. However, despite the broad clinical interest, diaschisis' molecular and cellular mechanisms are still unknown.

In this study, the researchers reported that diaschisis in the cortex of the mouse brain with subcortical stroke is caused by the decline of neuronal activity, due to the reduction in neuronal glucose uptake. They showed that this is dependent on pathological changes of astrocytes, the most abundant cell type in the brain. "Astrocytes respond to the presence of any chemical disregulation, caused by stroke. They become reactive, proliferate and increase in size," says C. Justin Lee, Director of the Cognitive Glioscience Group, at the IBS Center for Cognition and Sociality and co-corresponding author of this research. The researchers discovered that reactive astrocytes synthesize and release an excessive amount of GABA, an inhibitory neurotransmitter, that affects the activity of neighboring motor neurons.

They also demonstrated that the diaschisis is significantly alleviated by the treatment with KDS2010, which efficiently blocks astrocytic GABA synthesis. developed by the same group, KDS2010 is currently licensed out to the pharmaceutical company, Neurobiogen. It works by inhibiting MAO-B, one of the key enzymes in the production of GABA. They further reported that rehabilitation training of the animals with stroke was not effective to recover the motor function. However, the treatment with KDS2010 accompanied by rehabilitation training dramatically mitigated the motor impairment due the stroke.

"Our findings demonstrate that astrocytic GABA-mediated cortical diaschisis impedes functional recovery after white matter stroke," explains NAM Min-Ho, researcher at KIST and first author of the study.

"Diaschisis is observed in migraine, glioblastoma, traumatic brain injury in addition to stroke. This study will provide a novel therapeutic approach for those diseases as well," adds KIM Hyoung-Ihl, researcher at GIST and co-corresponding author of the study.

In conclusion, the researchers suggest that blocking astrocytic GABA synthesis with KDS2010 alleviates cortical diaschisis, and stimulates rehabilitation-aided functional recovery in white matter stroke.

The spectacular leaps of gazelles, group living in deer and monkeys, and fast flight in many insects are all linked by a common phenomenon?predation. In its various forms, predation has driven the evolution of a plethora of specialized structures (morphology) and behaviours among organisms. Insects, being especially vulnerable because of their small size, have evolved various strategies to avoid predators. For example, butterflies may either accumulate toxins (aposematism), mimic other toxic species (mimicry), avoid detection by predators by remaining inconspicuous (crypsis or camouflage), or look like inedible plant parts (masquerade) to escape predators.

Butterflies of the family Lycaenidae, popularly known as Blues and Hairstreaks, have gone in a completely unexpected direction to deal with their predators. Caterpillars and pupae of the majority of the approx. 5,200 lycaenid species do not avoid predatory ants at all. In fact, they seek and closely associate with ants, becoming strange bedfellows! Ants not only do not eat these caterpillars and pupae, but they actually care for them and aggressively protect them from other predators and parasitoids, thus creating an enemy-free space. Many of these associations have been perfected over millions of years via an evolutionary arms-race between the caterpillars and ants. How are these strange associations between predator and potential prey species sustained?

The lycaenid caterpillars are far from vulnerable in this association. Over tens of millions of years of evolution, this butterfly group has evolved a range of adaptations that have tamed their ferocious ant predators into protectors and providers. Lycaenid caterpillars typically have at least four types of specialized organs that produce chemical concoctions that modulate the nature of their ant associations, ranging from facultative to obligate, and mutually beneficial to behaviourally manipulative and parasitic. First, the body surface of lycaenid caterpillars has clusters of pheromone-secreting glands called pore cupolae. Pore cupolae are thought to secrete chemicals that secure favorable recognition by the ants, thereby subduing their aggression.

Next, two other organs, called dew patches in some species and nectar glands in others, produce carbohydrate-rich secretions to attract and reward the tending ants. For the most part, these sugary secretions, which ants drink readily, keeps the ants interested in tending and protecting the caterpillars. Ants can sometimes be seen stroking the caterpillars with their antennae to encourage them to produce these secretions, and the caterpillars often comply. So this association can be beneficial for both parties. However, caterpillars can sometimes deceive the ants by luring them with these secretions but then reabsorbing the secretions before ants can take them. One supposes that the caterpillars have to juggle between keeping the tending ants happy so that they continue to receive protection, while minimizing the energetic cost of producing these nutritious secretions. Who isn't tempted to skim off some profits from business partners once in a while?

In some species, the secretions of dew patches and nectar glands have been shown to alter the levels of neurotransmitters, particularly dopamine, in the brains of their attendant ants, causing them to slow their locomotory activity. This also makes the ants more faithful to the caterpillars and increase the level of aggression toward their parasites and predators. In cases like these, it is better to consider these apparently mutualistic interactions to be reciprocal parasitisms, where natural selection may turn the strategies used by each partner to outwit the other into a sophisticated coevolutionary arms race.

Finally, caterpillars deter the ants by rhythmically everting a pair of tentacle organs or tactile organs when the density of tending ants increases too much, or when the caterpillar wants to move. Ciliary tufts at the tips of these organs also contain receptors of ant pheromones, and act as a compass to direct caterpillars toward ant aggregations.

Additionally, caterpillars may produce substrate-borne vibrations to draw the attention of specific species of ants. In some species, caterpillars have evolved to mimic the characteristic smell, sounds and certain behaviours of ant larvae and even ant queens. These incredible adaptations mean that worker ants sometimes carry their caterpillar guests inside the nests, keeping them among their brood, caring for them and feeding them like their own.

Thus, these caterpillars manipulate ant behaviour with multimodal signals involving chemical, acoustic, and tactile means. These modes of interaction are deployed selectively in specific interactions with ants. Together, these ant-associated organs and behaviours of caterpillars orchestrate a 'push and pull' mechanism to manipulate ant behavior to the advantage of caterpillars.

These fascinating caterpillar-ant associations have been studied for many decades, generating a detailed understanding of their evolution and ecology. The presence of the ant-associated organs of these caterpillars, variation in their positions on the body, and their relative development with respect to the nature of ant associations are also well known. However, how these organs actually work (i.e., their functional morphology) has been poorly understood. This is because the native structures of these organs inside the body and their relative positions with connecting muscles and nerves get destroyed in traditional methods of dissection and staining. It is difficult to understand the functional significance of these organs and associated muscles and nerves when they are out of their native context inside the body. Dipendra Nath Basu, a PhD student, and his advisor Dr. Krushnamegh Kunte at the National Centre for Biological Sciences, Bengaluru, found this problem both peculiar and fascinating. To find out how these critically important organs function in sustaining these caterpillar-ant associations, they turned to X-ray microtomography, or MicroCT (remember that CT-scanning is used widely in hospitals). MicroCT has recently emerged as a valuable tool for studying organ development and functional morphology of smaller animals such as lizards and insects. Using MicroCT, we can map the entire internal structure of the body in great detail, without the need to dissect and disrupt the organs in their native states. Also, with a single scan, any structures inside the body can be studied either in isolation or in relation to other structures. This is precisely the kind of technology that can shed light on the functional morphology of the ant-associated organs, so Dipendra got busy mastering it.

Around the same time, another set of naturalists was occupied with studying the natural history and ecology of a rare species of butterfly in the Bengaluru area. Nitin Ravikanthachari, still an undergraduate student, had rediscovered a population of the Lilac Silverline (Apharitis lilacinus) a few years earlier. This butterfly had not been seen in India for over a hundred years, but Nitin stumbled upon it while photographing butterflies at Hesaraghatta lake. His subsequent observations revealed that this suburban wildland had a stable breeding population of this butterfly. Excited by this rare discovery, Nitin, along with fellow naturalists Ashok Sengupta and Girish Kumar G. S., started making regular visits to Hesaraghatta, learning everything they could about the biology of this species.

They soon discovered that the Lilac Silverline caterpillars have an obligate association with a single species of cocktail ant (named so because they often hold their heart-shaped gasters or 'tails' up when they are alarmed), called Crematogaster hodgsoni. Females of the Lilac Silverline deposit eggs at the entrance of cocktail ant nests, sometimes on sand and away from plants. Caterpillars are completely dependent on ants after hatching from eggs, and they are constantly attended by their hosts. Indeed, they live inside the ant nests, often among the ant broods, and are cared for by the tending ants just like the rest of their own brood. As far as known, caterpillars exclusively feed on regurgitated food provided by ants; they have not been observed so far feeding on plant tissue, like most other caterpillars do. As expected from their close relationship, the caterpillars possess all the main ant-associated organs that have been described in other obligate ant-associates, and these organs are very well developed in this species.

Dipendra took advantage of this fascinating species occurring in close proximity of Bengaluru. His MicroCT scan of the caterpillar provided high resolution and three-dimensional reconstruction that enabled the detailed characterization of hard as well as soft tissues such as muscles and nerves in their native states inside the body. This revealed the functional morphology of the ant-associated organs of this caterpillar in unprecedented detail. The MicroCT scan revealed how surrounding muscles may contract and relax, enabling the caterpillar to control the release and reabsorption of secretory droplets from dew patches and nectar glands that lure and sometimes deceive ants. Dew patches, for example, operate on a 'lasso bag' control mechanism using surrounding muscles. Dew patches are assemblages of multiple gland lobules opening in a common cavity, which is guarded above with an external orifice resembling a bag/sac in cross-section. The cavity and the orifice on their inner surfaces are attached to sets of retractor muscles that control the opening and closing of dew patches similar to a lasso. The lasso bag mechanism is known to operate glands in a few other organisms as well, and its use in dew patches makes sense since it offers a greater control over the release and reabsorption of secretions. The scans also suggested how muscle action and haemolymph pressure, controlled by abdominal ganglia, might cause the rhythmic motions of the tactile organs.

Since the nutrient-rich rewards and other chemical investments aimed at keeping the ants engaged are energetically likely very expensive, caterpillars must produce and release them judiciously. Naturally, the best way to keep your partners engaged is to let them know about the potential rewards, but then dish out the expensive good stuff in small doses in a controlled manner. The detailed insights into the functional morphology of the ant-associated organs and the mechanisms of gland operations indicate how caterpillars may be able to have a fine control over when they reward ants, and how much, thus optimizing their investments and returns.

MicroCT scans also revealed additional adaptations of these obligate ant-associates. The caterpillars have a thick skin or 'dermis' with chitinous thoracic and abdominal plates, which shield their front and rear ends from ants should they become momentarily aggressive. Internal morphology also revealed a narrow foregut missing most of the musculature that is required in caterpillars of other species to digest tough plant tissue. Since the Lilac Silverline caterpillars only eat food regurgitated by ants, which is presumably easily digested, they have largely lost the musculature around the foregut. On the other hand, even in a detailed MicroCT analysis, the team could not detect any special morphological features in the pupa that might facilitate its association with ants. It is possible that the pupae maintain their close association with ants purely via chemical signals.

Prof. Naomi Pierce of Harvard University, a leading expert on caterpillar-ant associations who was not involved in this study, is impressed and excited about these findings. "This work opens up the wonderful world of caterpillar-ant associations for Indian biologists and naturalists", she remarked, observing that the vast number of Blues and Hairstreaks that occur in India should provide ample opportunities to study not only the diversity of caterpillar structures and behaviours, but also their species-specific associations with ants that might have evolved over millions of years across India's biodiversity hotspots.

"While caterpillar-ant interactions have been explored as fine examples of multi-partner interactions, i.e. between caterpillars, ants and potential predators, what is important and novel about this study is the study of the mechanisms that facilitate these fascinating interactions", agreed Prof. Renee Borges of the Centre for Ecological Sciences, Indian Institute of Science, who is an expert on plant-animal and other inter-specific interactions. She continued, "It will be very exciting to study how the evolutionary arms race between ants and caterpillars has shaped the functional nature of the interactions between these vastly different insects, including adaptions and counter-adaptations in anatomy, physiology, behaviour and chemistry. What determines the fine balance between mutualism and exploitation in these close associations? A new generation of evolutionary biologists in India will have to find out."

"Guess we have a lot of exciting work cut out for us", Dipendra and Nitin say with a smile. They are looking forward to diving further into the dynamics of evolution of interspecific interactions. "We are incredibly fortunate to be able to inspire young people to find out something very cool and fascinating about the superb biodiversity and nature around us", said Dr. Kunte, with a touch of pride for his students.

Solar cells based on perovskite compounds could soon make electricity generation from sunlight even more efficient and cheaper. The laboratory efficiency of these perovskite solar cells already exceeds that of the well-known silicon solar cells. An international team led by Stefan Weber from the Max Planck Institute for Polymer Research in Mainz has found microscopic structures in perovskite crystals that can guide the charge transport in the solar cell. Clever alignment of these electron highways could make perovskite solar cells even more powerful.

When solar cells convert sunlight into electricity, the electrons of the material inside the cell absorb the energy of the light. Traditionally, this light-absorbing material is silicon, but perovskites could prove to be a cheaper alternative. The electrons excited by the sunlight are collected by special contacts on the top and bottom of the cell. However, if the electrons remain in the material for too long, they can lose their energy again. To minimize losses, they should therefore reach the contacts as quickly as possible.

Microscopically small structures in the perovskites - so-called ferroelastic twin domains - could be helpful in this respect: They can influence how fast the electrons move. An international research group led by Stefan Weber at the Max Planck Institute for Polymer Research in Mainz discovered this phenomenon. The stripe-shaped structures that the scientists investigated form spontaneously during the fabrication of the perovskite by mechanical stress in the material. By combining two microscopy methods, the researchers were able to show that electrons move much faster parallel to the stripes than perpendicular to them. "The domains act as tiny highways for electrons," compares Stefan Weber.

Possible applications in light-emitting diodes and radiation detectors

For their experiments, the researchers first had to visualize the stripe-shaped domains. They succeeded in doing this with a piezo force microscope (PFM). Five years ago, Weber and his colleagues discovered the domains for the first time in a perovskite crystal using this method. "Back then, we already wondered whether the structures had an influence on the operation of a perovskite solar cell," Weber explains. "Our latest results now show that this is the case."

The breakthrough came when the researchers compared their PFM images with data obtained from another method called photoluminescence microscopy. "Our photoluminescence detector works like a speed trap," explains Ilka Hermes, researcher in Weber's group and first author of the study. "We use it to measure the speed of electrons in different directions at the microscopic level." Hermes discovered that along the stripes the electrons moved about 50 to 60 percent faster than perpendicular to them. "If we were able to make the stripes point directly to the electrodes, a perovskite solar cell could become much more efficient", concludes Hermes.

With the new results, not only solar cells could be improved. Other optoelectronic applications such as light-emitting diodes or radiation detectors could also benefit from directed charge transport. "In general, it is an advantage if we can direct the electrons in the right direction," explains Stefan Weber. The researchers' idea: to put perovskite crystals under mechanical stress during their production. This so-called strain engineering would enable an optimized orientation of the electron highways.

The molecular gas in galaxies is organised into a hierarchy of structures. The molecular material in giant molecular gas clouds travels along intricate networks of filamentary gas lanes towards the congested centres of gas and dust where it is compressed into stars and planets, much like the millions of people commuting to cities for work around the world.

To better understand this process, a team of astronomers led by Jonathan Henshaw at Max Planck Institute for Astronomy (MPIA) have measured the motion of gas flowing from galaxy scales down to the scales of the gas clumps within which individual stars form. Their results show that the gas flowing through each scale is dynamically interconnected: while star and planet formation occurs on the smallest scales, this process is controlled by a cascade of matter flows that begin on galactic scales. These results are published today in the scientific journal Nature Astronomy.

The molecular gas in galaxies is set into motion by physical mechanisms such as galactic rotation, supernova explosions, magnetic fields, turbulence, and gravity, shaping the structure of the gas. Understanding how these motions directly impact star and planet formation is difficult, because it requires quantifying gas motion over a huge range in spatial scale, and then linking this motion to the physical structures we observe. Modern astrophysical facilities now routinely map huge areas of the sky, with some maps containing millions of pixels, each with hundreds to thousands of independent velocity measurements. As a result, measuring these motions is both scientifically and technologically challenging.

In order to address these challenges, an international team of researchers led by Jonathan Henshaw at the MPIA in Heidelberg set out to measure gas motions throughout a variety of different environments using observations of the gas in the Milky Way and a nearby galaxy. They detect these motions by measuring the apparent change in the frequency of light emitted by molecules caused by the relative motion between the source of the light and the observer; a phenomenon known as the Doppler effect. By applying novel software designed by Henshaw and Ph.D. student Manuel Riener (a co-author on the paper; also at MPIA), the team were able to analyse millions of measurements. "This method allowed us to visualise the interstellar medium in a new way," says Henshaw.

The researchers found that cold molecular gas motions appear to fluctuate in velocity, reminiscent in appearance of waves on the surface of the ocean. These fluctuations represent gas motion. "The fluctuations themselves weren't particularly surprising, we know that the gas is moving," says Henshaw. Steve Longmore, co-author of the paper, based at Liverpool John Moores University, adds, "What surprised us was how similar the velocity structure of these different regions appeared. It didn't matter if we were looking at an entire galaxy or an individual cloud within our own galaxy, the structure is more or less the same."

To better understand the nature of the gas flows, the team selected several regions for close examination, using advanced statistical techniques to look for differences between the fluctuations. By combining a variety of different measurements, the researchers were able to determine how the velocity fluctuations depend on the spatial scale.

"A neat feature of our analysis techniques is that they are sensitive to periodicity," explains Henshaw. "If there are repeating patterns in your data, such as equally spaced giant molecular clouds along a spiral arm, we can directly identify the scale on which the pattern repeats." The team identified three filamentary gas lanes, which, despite tracing vastly different scales, all seemed to show structure that was roughly equidistantly spaced along their crests, like beads on a string, whether it was giant molecular clouds along a spiral arm or tiny "cores" forming stars along a filament.

The team discovered that the velocity fluctuations associated with equidistantly spaced structure all showed a distinctive pattern. "The fluctuations look like waves oscillating along the crests of the filaments, they have a well-defined amplitude and wavelength," says Henshaw adding, "The periodic spacing of the giant molecular clouds on large-scales or individual star-forming cores on small-scales is probably the result of their parent filaments becoming gravitationally unstable. We believe that these oscillatory flows are the signature of gas streaming along spiral arms or converging towards the density peaks, supplying new fuel for star formation."

In contrast, the team found that the velocity fluctuations measured throughout giant molecular clouds, on scales intermediate between entire clouds and the tiny cores within them, show no obvious characteristic scale. Diederik Kruijssen, co-author of the paper based at Heidelberg University explains: "The density and velocity structures that we see in giant molecular clouds are 'scale-free', because the turbulent gas flows generating these structures form a chaotic cascade, revealing ever smaller fluctuations as you zoom in - much like a Romanesco broccoli, or a snowflake. This scale-free behaviour takes place between two well-defined extremes: the large scale of the entire cloud, and the small scale of the cores forming individual stars. We now find that these extremes have well-defined characteristic sizes, but in between them chaos rules."

"Picture the giant molecular clouds as equally-spaced mega-cities connected by highways," says Henshaw. "From a birds eye view, the structure of these cities, and the cars and people moving through them, appears chaotic and disordered. However, when we zoom in on individual roads, we see people who have travelled from far and wide entering their individual office buildings in an orderly fashion. The office buildings represent the dense and cold gas cores from which stars and planets are born."

Over the past few decades, medical technology seen various advances in terms of the scope and efficiency of implant devices. For example, developments in medical research have led to the emergence of electronic implants, such as pacemakers to regulate the heart rate and cerebral spinal shunts to control the flow of spinal fluid. Most of these medical devices, including the pacemaker, require a constant source of energy to operate. Naturally, this causes some limitations: batteries, which provide an energy source for the implants, have a finite lifespan. Once the battery power gets exhausted, there is no other option but to perform invasive surgery to replace the battery, which poses a risk of surgical complications, such as bruising, infections, and other adverse events.

In a new study published in PNAS, a research group from South Korea, led by Professor Jongho Lee at GIST, dug deeper to find a solution: they attempted to develop a strategy to recharge the internal battery of devices without invasive surgery or risky penetrative procedures. Prof Lee explains, "One of the greatest demands in biomedical electronic implants is to provide a sustainable electrical power for extended healthy life without battery replacement surgeries." Although this is a tricky concept, Prof Lee believes that the answer lies in the "translucency" of living tissue.

This can be explained through an interesting phenomenon. When you hold your hand up to a powerful light, you can see that the edges of your hand glow as the light passes through your skin. Taking inspiration from this, Prof Lee and his team developed an "active photonic power transfer" method, which can generate electrical power in the body. This novel system consisted of two parts: a skin-attachable micro-LED source patch--which can generate photons that would penetrate through the tissues--and a photovoltaic device integrated into a medical implant--which can capture the photons and generate electrical energy. This system provides a sustainable way of supplying the medical implant device with enough power to avoid any high-risk replacement methods. Prof Lee says, "Currently, a lack of a reliable source of power limits the functionality and performance of implant devices. If we can secure enough electrical power in our body, new types of medical implants with diverse functions and high performance can be developed."

When the scientists tested this power system in mice, they found that this wireless power transfer system is easy to use, regardless of weather, clothes, indoor or outdoor conditions, etc. The light photons emitted from the source patch successfully penetrated live tissues in mice and recharged the device in a wireless and convenient manner. "These results enable the long-term use of currently available implants, in addition to accelerating emerging types of electrical implants that require higher power to provide diverse, convenient diagnostic and therapeutic functions in human bodies," says Prof Lee, pleased with the efforts of his team and already looking forward to furthering their experiments. He concludes, "Our device would probably not work for 'Iron Man,' but it can provide enough power for medical implants."