Tech

Solar cells made of perovskite are at the center of much recent solar research. The material is cheap, easy to produce and almost as efficient as silicon, the material traditionally used in solar cells. However, perovskite cells have a love-hate-relationship with the sun. The light that they need to generate electricity, also impairs the quality of the cells, severely limiting their efficiency and stability over time. Research by scientists at the Eindhoven University of Technology and universities in China and the US now sheds new light on the causes of this degradation and paves the way for designing new perovskite compositions for the ultimate stable solar cells.

Perovskite is an attractive alternative to silicon, because it's abundant and easy to produce. What's more, over the past decade, the performance of perovskite solar cells has improved dramatically, with efficiency rates reaching more than 25 percent, which is close to the state-of-art for silicon solar cells.

The new research focuses on perovskite solar cells made from formamidinium-cesium lead iodide, a halide compound that has become increasingly popular as it combines high efficiency and reasonable heat resistance with low manufacturing costs.

Love-hate

However, solar panels made of this particular compound have a rather ambivalent relationship with sunlight, a problem that is well-known in the field, but barely understood. While the light of the sun feeds it with the much-wanted energy to convert into electricity, it also impairs the stability of the cells. Over time this affects their performance.

To understand why this is the case, the researchers at TU/e, Peking University and University of California San Diego did both practical experiments - monitoring the photovoltaic performance of the panels over 600 hours of exposure and characterizing the degraded perovskites - and theoretical analysis.

From this they conclude that sunlight generates charged particles in the perovskite, which tend to flow to places in the solar panel where the band gap (the minimum amount of energy needed for generating the free electrons) is lowest, in this case the formamidinium perovskite. The resulting energy differences make the mixed compounds that worked together so well to make the cell efficient, fall apart into separate clusters. It appears that especially the cesium-heavy clusters (the green dots in the image) are photoinactive and current-blocking, limiting the performance of the device.

Solutions

According to Shuxia Tao, who together with PhD candidate Zehua Chen and her colleague Geert Brocks was responsible for the TU/e part of the research, the new findings are one step further to finding the way to possible solutions.

"By combining macroscopic tests, microscopic materials characterization and atomistic modelling, we were able to thoroughly understand the instability of halide perovskites that are intrinsic to device operation. This opens the possibility for designing new perovskite compositions for the ultimate stable solar cells."

Possible strategies include using additives to enhance the chemical interaction inside the materials in the panels, tuning the band gaps by using other elements like bromide and rubidium instead of iodide and cesium, or modifying the energy levels to extract photo-carriers more efficiently.

Tao stresses that more research is needed to see what solution works best. In addition, separation of halide compounds is not the only cause for perovskite degradation. These additional causes require separate analysis.

Scientists are a step closer to developing a fast and cost effective camera that utilises terahertz radiation, potentially opening the opportunity for them to be used in non-invasive security and medical screening.

A research team led by Professor Emma Pickwell-Macpherson from the University of Warwick Department of Physics and involving Rayko Ivanov Stantchev and scientists from the Department of Electronic Engineering at The Chinese University of Hong Kong has reached a crucial milestone towards developing single-pixel terahertz imaging technology for use in biomedical and industrial applications.

Their single-pixel terahertz camera reached 100 times faster acquisition than the previous state-of-the-art without adding any significant costs to the entire system or sacrificing the sub-picosecond temporal resolution needed for the most sought-after applications.

The breakthrough has been published in the journal Nature Communications.

The potentials and problems of Terahertz radiation

Terahertz (THz) radiation, or T-rays, sit in-between infrared and WiFi on the electromagnetic spectrum. T-rays have different properties from other electromagnetic waves, most notably they can see through many common materials such as plastics, ceramics and clothes, making them potentially useful in non-invasive inspections. Another quality is that the low-energy photons of T-rays are non-ionizing, making them very safe in biological settings including security and medical screening. They are also highly sensitive to water and can observe minute changes to the hydration state of biological matter. This means that diseases perturbing the water content of biological matter, such as skin cancer, can potentially be detected using T-rays in vivo without any histological markers.

Efficient detection and generation of T-rays has been possible in laboratory settings for the last 25 years. However, THz technology is still not widely used in commercial settings as the cost, robustness and/or ease of use is still lagging behind for commercial adoption in industrial settings.

For biomedical applications, very few clinical trials have been performed most notably due to the equipment not being user-friendly and imaging being too slow due to the need for measuring multiple terahertz frequencies (for accurate diagnosis). Finally, equipment and running costs need to be within hospital budgets. As a result, a lot of research into terahertz technology is currently focused on developing the equipment to improve imaging speed, without reducing diagnosis accuracy or incurring large costs. As a result, we have to explore alternative imaging techniques to those currently used in modern day smart phones.

The advantages of single-pixel cameras

Professor Emma Pickwell-Macpherson, from the Department of Physics at the University of Warwick, said: "We use what is called 'a single-pixel camera' to obtain our images. In short, we spatially modulate the THz beam and shine this light onto an object. Then, using a single-element detector, we record the light that is transmitted (or reflected) through the object we want to image. We keep doing this for many different spatial patterns until we can mathematically reconstruct an image of our object."

The researchers have to keep changing the shape of the THz beam many times which means this method is usually slower compared to multi-pixel detector arrays. However, multi-pixel arrays for the terahertz regime usually lack sub-picosecond temporal resolution, require cryogenic temperatures to operate or incur large equipment costs (>US$ 350,000). The setup developed by the Warwick team, which is based on a single-element detector, is reasonably priced (~US$20,000), robust, has sub-picosecond temporal resolution (needed for accurate diagnosis) and operates at room temperature.

Professor Pickwell-Macpherson adds: "Our latest work improves upon the acquisition rate of single-pixel terahertz cameras by a factor of 100 from the previous state-of-the-art, acquiring a 32x32 video at 6 frames-per-second. We do this by firstly determining the optimal modulation geometry, secondly by modelizing the temporal response of our imaging system for improvement in signal-to-noise, and thirdly by reducing the total number of measurements with compressed sensing techniques. In fact, part of our work shows that we can reach a five times faster acquisition rate if we have sufficient signal-to-noise ratio."

The researchers have previously developed several THz devices including THz modulators that make use of the total internal reflection geometry to achieve high MDs across a broadband frequency range and a new approach for amplitude and phase modulation exploiting the Brewster angle. They are also working to improve the resolution of single pixel THz imaging through signal processing approaches. Future work will focus on improving the signal-to-noise and optimizing the software needed for accurate medical diagnosis, with the ultimate goal being to use single pixel THz imaging for in vivo cancer diagnosis.

Dull. Slow. Unchanging. Like watching paint dry. 

But take a closer look at that paint—all the way down to the nanoscale—and there’s a lot more going on than you might think.  

Researchers in the Gilchrist Laboratory in Lehigh University’s P.C. Rossin College of Engineering and Applied Science are observing the evolution of coatings as they dry with groundbreaking microscale precision. Their results were recently published in Scientific Reports. 

Thin film coatings do much more than spruce up walls. For example, they can be used as pharmaceutical devices in edible films, similar to those to deliver drugs used to fight the opioid epidemic. How these coatings dry can change their properties, which is especially important for films used in drug delivery. 

In their paper, “Chemical vs. mechanical microstructure evolution in drying colloid and polymer coatings,” the Lehigh researchers looked at how particles rearrange themselves during drying when their interactions are tuned. These particles behaved as a surrogate for the active pharmaceutical ingredient in a drug delivery film.

Graduate student Titiporn Kaewpetch looks directly inside these films using high speed confocal laser scanning microscopy to take thousands of images that give nanoscale details of how particles flow and assemble during drying. Gigabytes of data for each film are rendered to reveal their 3-D structure, giving simulation-like detail on the otherwise hidden internal processes that happen. 

The researchers found that when particles attract each other, they form a scaffold that buckles and breaks during drying due to the motion of the top interface. “The microstructure for attractive particles at each point during drying is related to the history of the film evolution," says James Gilchrist, a professor in the Department of Chemical and Biomolecular Engineering. Their 3-D analysis of the microstructure evolution reveals clear signatures of this process throughout drying as compared with those where particles are repulsive.

"In real drug delivery systems, there are many ingredients interacting with each other, always changing concentration and their interactions throughout drying," says Gilchrist. "By reducing this process to the essential ingredients, we can see these interactions as they happen. This may allow new insights into manufacturing of these films."

This paper is based upon work supported by the National Science Foundation (grant No. 1936541). Kaewpetch is supported by the Royal Thai Scholars program.

Related Links:

Laboratory for Particle Mixing and Self- Organization (Gilchrist Laboratory)
Scientific Reports: "Chemical vs. mechanical microstructure evolution in drying colloid and polymer coatings"

Rossin College Faculty Profile: James F. Gilchrist

BOZEMAN -- A Montana State University professor's research on plant chemistry in the Northern Great Plains and Northern Rockies has been published in Global Change Biology, a prominent journal that promotes exploration of the connections between biological processes and environmental change.

Jack Brookshire, associate professor in the Department of Land Resources and Environmental Sciences in the MSU College of Agriculture, combined satellite data and plant samples from more than 300 locations around the Northern Great Plains and Northern Rockies to examine trends in greening, a metric which represents plant productivity through photosynthesis. The project began in 2016 and was supported by National Science Foundation EPSCoR funding and a research grant through the Montana Agriculture Experiment Station.

"Studies using remote sensing were showing that much of Earth's land surface has been getting greener over the last several decades mostly due to increased carbon dioxide in the atmosphere," said Brookshire. "However, there was also evidence that plant nitrogen content was declining. No one had yet combined analyses of vegetation greening trends with those changes in plant chemistry."

Brookshire worked with collaborators at the University of Wisconsin-Madison and Idaho State University, as well as graduate and undergraduate students at MSU to examine whether regional climate changes or increased atmospheric carbon dioxide was the cause of the increased greening across Montana and the broader Northern Great Plains. While increased productivity may seem like a benefit, Brookshire said the question is how sustainable those increases are and whether increased greening changes the chemical makeup of the plants themselves.

The work began by sifting through nearly two decades of satellite data from a NASA program called MODIS, which collects data from the entire surface of the Earth every 1-2 days. Brookshire's group analyzed normalized vegetation difference index data, which measures the amount of light reflected by plants. Over 20 years, they noted that the greening across the Northern Great Plains and Northern Rocky Mountains had increased significantly, but the difference was more pronounced in the Northern Great Plains.

"The largest increases in greening were in the places where it was warmest and driest, we think because they have the most marginal gains to be made in response to carbon dioxide and climate change given the changes in plant physiology we observe," said Brookshire. "Also, much of the Northern Great Plains has experienced increases in rainfall over the past few decades, and we find evidence that this has been a major driver of greening trends."

However, while the trends in greening varied by geographic location, Brookshire wanted to see if physiological changes in the plants themselves were uniform across the two regions. If so, the most likely cause would be increased atmospheric carbon dioxide. The increase in carbon dioxide is global in extent, and wouldn't fluctuate regionally, said Brookshire.

To test the physical changes going on inside the plants, Brookshire turned to the MSU Herbarium, which houses thousands of plant samples from across the state, collected over more than 100 years.

"The herbarium is truly a treasure trove of native plant species," said Brookshire. "We selected four representative species for the ecosystems, three grasses and a sagebrush, and then very carefully sampled small sections of their leaves for chemical and isotope analysis."

After testing samples from the herbarium, Brookshire's team returned to some of the locations of the historical plant samples and collected contemporary samples to compare the chemical balances inside the same plant species as many as 100 years later.

Analyzing the chemical and isotope ratios of carbon and nitrogen in the historic and contemporary plant samples, Brookshire found decreased levels of nitrogen and increased levels of carbon in recent samples. They also found that the plants had increased in water use efficiency -- the ratio of how much carbon dioxide they take up per unit of water -- by more than 30% since the 1970s. These measurements confirmed his hypothesis that the plants were adjusting to changes in the Earth's atmosphere over time.

"Fundamentally, plants need carbon dioxide, water, sunlight and nutrients, especially nitrogen, to photosynthesize and grow," he said. "When one of those levers is increased, the others have to adjust. Plants in these ecosystems have adapted to increased carbon dioxide by maintaining a constant ratio between what's inside their leaves and what's outside."

Brookshire said the long-term changes in plant chemistry could have adverse effects on ecosystems. Eventually limitations to greening will emerge, particularly in how little nitrogen plants can survive on.

"Plants cannot increase water or nitrogen use efficiency indefinitely," he said. "These findings are important to the development of the next generation of ecosystem models as plants will likely have to adjust nutrient acquisition strategies."

The changing plant makeup could also impact the creatures that eat those plants. With increased carbon dioxide comes increased plant sugars, and decreasing nitrogen comes decreased protein content, which could lead to dietary impacts for herbivores and even changes in the nutrition of crops grown in the Northern Great Plains and Northern Rocky Mountains for human consumption.

"There is a great amount of uncertainty in how climate change, increases in grassland productivity and declines in plant tissue quality are affecting ecosystems across the Northern Great Plains right now," said Brookshire. "It's difficult yet important to understand how they will continue to change over the next century and beyond."

Researchers from the Center for Diagnostics and Telemedicine together with colleagues from Mayo Clinic College of Medicine and Science, University of Munich and Sechenov University used computed tomography to analyze the individual anatomy of the nasolabial triangle. They identified possible options for the distribution of blood vessels on three-dimensional course. It will help in safety planning of plastic and reconstructive surgeries and procedures. Study results published recently in the Aesthetic Surgery Journal, added to the series of publications about the aesthetic medicine project, which was launched by the Center for Diagnostics and Telemedicine in collaboration with Mayo Clinic.

The anatomy of each person is unique. It is important to know its details in order not to harm a patient during any medical procedure. Special attention always should be paid to the nasolabial triangle.

This part of the face is bounded by the nose on the top, by lips from below, and on the sides by nasolabial folds. In aesthetic medicine, it is one of the most challenging facial regions, since there is a dense network of blood vessels, both arterial and venous. Since with aging, nasolabial sulcus become more pronounced, cosmetic procedures are often performed on this area, such as injections of hyaluronic acid, which fills the subcutaneous space, and evens out the fold. However, ignorance of details of the individual vascular anatomy of this area can result in serious complications, including loss of vision.

In the depth of the nasolabial sulcus, the angular artery is located which is the terminal branch of the facial artery, which supplies blood to the most part of the face. Although its anatomy is well studied, there is a lack of information on how deep the angular artery is located relatively to the skin surface, as well as how its location can vary in three dimensions depending on age, gender and body mass index (BMI). The researchers decided to fill in this gap for people of the Caucasian ethnic group.

"We hope that clearer understanding of the pathway of the artery in this high-risk area will help make surgical procedures safer," said the author Victor Gombolevsky, Head of the Department of Radiology Quality Development at the Center for Diagnostics and Telemedicine.

The research was based on analyses of cranial CT scans from the radiology database of the Center for Diagnostics and Telemedicine. Researchers analyzed CT scans of 150 patients of different age - from 14 to 89 years old, and with various BMI - from 16.7 to 47.8 kg/m2. Their nasolabial sulcus were examined on both sides in three dimensions.

In the entire sample, researchers described three types for angular arteries. In most cases (90%), one arterial trunk was found, the trunk bifurcated in 9%, and three trunks were discovered in 1% of the investigated cases. On average, the angular artery was located at the depth of 21.6 mm in the nasolabial fold, and at a depth of 8.9 mm in the nasal area. In 100% of cases, the angular artery located laterally to the nasolabial sulcus (i.e. closer to the cheek).

It is interesting that in contrast to the prevailing data, we discovered that the depth of the artery varied, and it was located most superficially in the area of the lip junction. In addition, in all cases the artery was located to the side of the nasolabial sulcus at variable distance from it with a greater difference in the nasal area. It turned out that gender and BMI did not have a significant impact on these facts, however, it was a considerable influence of age.

"With aging, both the depth of the angular artery and lateral distances between the nasolabial sulcus and the artery decrease significantly. This emphasizes the need for special caution when injecting soft tissue fillers, such as hyaluronic acid, into the furrow to elderly patients. Loss of fat volume of facial tissues exposes arteries, and it is much easier to damage them during injection procedures, "the authors say.

Coupled quantum dots can be an important building block in the development of scalable quantum devices by controlling the quantum states of two adjacent quantum dots (QDs) electrically and optically. Recently, remarkable progress has been made in controlling the coupled states of CQDs, but individual control of vertically stacked quantum dots is still challenging. Unless each dot can provide a logical bit operation, this becomes a limit in progress towards scalable qubit arrays. Laterally-coupled QDs can be an alternative system if the charge state and the lateral coupling of two dots are controlled separately. For example, tunable vector electric fields with arbitrary magnitude and angles can be generated in laterally-coupled QDs when four electrodes are implemented in a mesa structure.

In a new paper published in Light Science & Applications, an international team of scientists from China, South Korea, and the UK has found that emission from laterally coupled quantum dots is strongly polarized along the coupling direction (90°), and its polarization anisotropy can be shaped by changing the orientation of the polarized excitation. When the linear polarization of non-resonant excitation is perpendicular to the coupled direction (0°), excitons and local biexcitons from the two separate quantum dots still show an emission anisotropy with a small degree of polarization (10%). On the other hand, when the excitation polarization becomes parallel to the coupled direction, the polarization anisotropy of excitons, local biexcitons, and coupled biexcitons becomes enhanced with a degree of polarization of 74%. They also observed a consistent anisotropy in time-resolved photoluminescence. Therefore, the coupling of laterally-coupled QDs can be controlled by excitation polarization. Specifically, they revealed the optically-controlled anisotropic wavefunctions in terms of the anisotropy of the emission intensity and decay rate. These results confirm that optical shaping of the polarization anisotropy is possible in laterally coupled QDs, where the spatial arrangement of excitons and biexcitons can be controlled by excitation polarization.

"New information storage technologies could use this polarized light to control the optical properties of coupled quantum dots. The idea of combining quantum dots - nanoscale semiconductor crystals - into coupled pairs has attracted great attention due to the increased number of exotic quantum states that can be realized for storing data. This 'optical shaping' reflects different arrangements of excitons - bound states of electrons and holes - in the coupled dots, and could open new avenues for data storage and thermoelectric energy harvesting."

MIR spectra have been widely used for thermal imaging, molecule characterizations, and communications. MIR light source is the key component of MIR technologies. Among them, MIR light-emitting diodes (LED) show advantages of narrow linewidth, low power consumption and portability. Since the rediscovery of thin-film BP in 2014, it has received much attention due to its unique properties, such as in-plane anisotropy, high carrier mobility, and tunable band gap, etc., making BP a promising material for applications in electronics and optoelectronics.

BP has a thickness-dependent (0.3-2 eV) bandgap, and the bandgap size can be further tuned through introducing external electric field or chemical doping. Because of these reasons, thin-film BP has been regarded as a star MIR material. Previous research mainly focused on the luminescence properties of monolayer and few-layer BP flakes (with layer number 7 layers) shows remarkable photoluminescence properties in MIR region.

In this report, we proposed a novel vdW heterostructure for MIR light-emission applications, built from BP and TMDC (such as WSe2 and MoS2). According to the DFT calculation, the BP-WSe2 heterostructure forms a type-I band alignment. Hence, the electron and hole pairs in the monolayer WSe2 can be efficiently transported into the narrow-bandgap BP, thereby enhancing the MIR photoluminescence of thin-film BP. An enhancement factor ~200% was achieved in the 5nm-thick BP-WSe2 heterostructure.

On the other hand, the BP-MoS2 heterostructure forms a type-II band alignment. A natural PN junction is formed at the interface between p-type BP and n-type MoS2. When a positive voltage bias is applied between BP and MoS2 (Vds > 0), electrons in the conduction band of MoS2 can cross the barrier and enter into the conduction band of BP. At the same time, the majority of holes are blocked at the interface inside BP due to the large Schottky barrier of the valence band. As a result, an efficient MIR electroluminescence is achieved in the BP-MoS2 heterostructure.

The BP-TMDC vdW heterostructures show many merits, such as simple fabrication process, high efficiency, and good compatibility with silicon technology. Hence, it provides a promising platform for investigating silicon-2D hybrid optoelectronic systems.

Deep ultraviolet (DUV) optoelectronic devices (

To understand the underlying mechanism of orbital intercoupling based on the quantum con?nement direction, high-Al-content AlGaN QW models were constructed and studied by first-principle simulations. The band structure analysis shows that valence band is consist of p orbitals. p orbitals overlapping in a head-over-head fashion tend to form ppσ coupling with positive energy gain, while p orbital overlapping with one another in a side-by-side fashion tend to bring about ppπ coupling with negative energy variation. In the c-plane polar AlGaN QW, the compensation of CH band potential barrier at VBM is dominantly contributed from the ppσ coupling. In the case of the HH/LH band, the barrier is enhanced by the ppπ coupling. The carrier distribution and the orbital projected density of states at VBM along the confinement direction in figure 2 exhibit that the dominant ppσ coupling of pz state lower the potential barrier, resulting in the delocalization of the pz orbital. The situation is reversed upon the the ppπ coupling that px orbital have higher barrier for quantum confinement to confine carriers in the quantum well.

In the light of the relationship between the orbital coupling and the confinement direction, orbital engineering was proposed by incline quantum well plane to modify the energy variations in duced by the orbital coupling. Al0.75Ga0.25N/AlN quantum well models were constructed with the well plane inclined from 0° to 90° at a step of 30° referred to the c plane. The inclination angle of 30° and 60° correspond to the (10¯13) and (10¯11), two 90° models of (10¯10) and (11¯20) plane nonpolar quantum well. As increasing the inclination angles, the ppσ component decreases while the ppπ component increases. The distribution of p states at VBM further confirm the enhancement of quantum confinement with the increase in radiative transition rate at the band edge. Experimentally, the quantum well were grown on different facets of the hexagonal microrods with pyramid-shaped tops , as shown in figure 3. According to scanning electron microscope and cathodoluminescence (CL) spectra, even the characterization are taken from the top of the pyramid, the emission from the quantum well on the nonpolar plane is stronger than that on the semipolar and polar plane, which demonstrates the feasibility of the orbital engineering.

The research effort in the present work has led to the evidence that the orbital intercoupling plays a pivotal role especially in the materials with strong polarization. The valence p orbitals in the quantum structure are sensitive to the confinement direction, which distorts the symmetric the rectangular well potential. Awareness of the orbital intercoupling and its influence on the well potential provides a new perspective on the construction of heterostructures and superlattices. It has been reported in the literature that high-temperature superconductivity is observed in charge-transfer compounds characterized by strong hybridization between oxygen 2p and transition metal 3d states and with complex electronic configurations, which gives hints for the active presence of the orbital coupling. It is natural to expect that the orbital engineering is not just limited to AlGaN but also to extending the applications in novel semiconductor material and structure with unique functional properties.

NASA used satellite data to create an animation of Fay's development and progression over the past few days, showing how the storm organized into a tropical storm. Additionally, NASA's Aqua satellite used infrared light to find the location of the strongest storms in Tropical Storm Fay occurring in the northeastern quadrant of the storm, mostly over the Atlantic Ocean.

Tropical Storm Fay was officially named as the sixth tropical storm the Atlantic Ocean Hurricane Season by 5 p.m. EDT on July 9. The storm formed just off the North Carolina coast. For several days before that, forecasters were using satellite data to track the storm as it developed.

Animating the Development of Fay

Previously designated as System 98L, the low-pressure area formed off the Georgia coast and moved north. At NASA's Goddard Space Flight Center in Greenbelt, Md. NASA Worldview was used to create an animation of visible imagery of the storm using data from NASA-NOAA Suomi NPP satellite. The animation showed the development and progression of System 98L into Tropical Storm Fay from July 6 to July 9.

NASA's Earth Observing System Data and Information System (EOSDIS) Worldview application provides the capability to interactively browse over 700 global, full-resolution satellite imagery layers and then download the underlying data. Many of the available imagery layers are updated within three hours of observation, essentially showing the entire Earth as it looks "right now." Worldview is a tool that can be used to generate satellite imagery and animations.

NASA Analyzing Fay in Infrared Light

On July 10 at 2:55 a.m. EDT (0655 UTC), the Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA's Aqua satellite gathered temperature information about Tropical Storm Fay's cloud tops. MODIS found powerful thunderstorms where temperatures were as cold as or colder than minus 63 degrees Fahrenheit (minus 53 Celsius) mostly over the western Atlantic Ocean and along coastal areas of Delaware and southern New Jersey. Cloud top temperatures that cold indicate strong storms with the potential to generate heavy rainfall.

Warnings and Watches on July 9

At 8 a.m. EDT (1200 UTC), the National Hurricane Center (NHC) noted a Tropical Storm Warning is in effect for Fenwick Island, Delaware to Watch Hill, Rhode Island including Long Island and Long Island Sound, as well as Southern Delaware Bay. A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area.

What to Expect from Fay

The National Hurricane Center noted that in addition to tropical-storm force winds, storm surge and a possibility for isolated tornadoes, Fay is expected to produce heavy rainfall. "Fay is forecast to generate 2 to 4 inches of rain with isolated maxima of 7 inches along and near the track from the lower Maryland Eastern Shore and Delaware northward into New Jersey, eastern Pennsylvania, southeast New York, and southern New England. These rains may result in flash flooding where the heaviest amounts occur."

Fay's Status on July 9

At that time the NHC reported the center of Tropical Storm Fay was located by an Air Force Reserve Hurricane Hunter aircraft near latitude 37.6 degrees north and longitude 74.7 degrees west. Fay was centered about 55 miles (85 km) south-southeast of Ocean City, Md. Fay is moving toward the north near 10 mph (17 kph). A northward to north-northeastward motion at a faster forward speed is expected over the next couple of days.

Maximum sustained winds are near 50 mph (85 kph) with higher gusts. Little change in strength is forecast today and tonight while the center remains over water. Weakening should begin after the center moves inland. The estimated minimum central pressure based on aircraft data is 999 millibars.

A Weatherflow station at Lewes, Delaware recently reported a sustained wind of 33 mph (54 kph) and a wind gust of 39 mph (63 kph).

Fay's Forecast Track

NHC forecasters expect the center of Fay to move near the mid-Atlantic coast today and move inland over the mid-Atlantic or the northeast United States late tonight or on Saturday.

Typhoons/hurricanes are the most powerful weather events on Earth. NASA's expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.

NASA's Aqua satellite revealed better organization and colder cloud top temperatures in Tropical Storm Cristina, indications that the storm was strengthening.

On July 10 at 4:35 a.m. EDT (0835 UTC), the MODIS instrument aboard NASA's Aqua satellite analyzed Tropical Storm Cristina's cloud tops in infrared light. Infrared data provides temperature information, and the strongest thunderstorms that reach high into the atmosphere have the coldest cloud top temperatures.

The Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA's Aqua satellite found that the most powerful thunderstorms were east and south of the center of circulation, where temperatures were as cold as or colder than minus 70 degrees Fahrenheit (minus 56.6 Celsius). These cloud top temperatures had become colder than they were over the previous day. Cloud top temperatures that cold indicate strong storms with the potential to generate heavy rainfall.

The National Hurricane Center noted, "Cristina has become better organized during the past several hours. A curved band wraps almost completely around the center, and a ragged eye has occasionally been apparent in satellite images."

At 5 a.m. EDT (0900 UTC) on July 10, the center of Tropical Storm Cristina was located near latitude 18.8 degrees north and longitude 113.0 degrees west. Cristina is far from land and about 345 miles (560 km) southwest of the southern tip of Baja California. Cristina was moving toward the west-northwest near 12 mph (19 kph) and this general motion with a gradual bend to the west is expected during the next few days. The estimated minimum central pressure was 993 millibars.

Maximum sustained winds are near 70 mph (110 kph) with higher gusts. The National Hurricane Center indicated that Cristina could become a hurricane later today; however, a weakening trend should begin by tonight.

Typhoons/hurricanes are the most powerful weather events on Earth. NASA's expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.

RMIT-UNSW collaboration applies liquid-metal synthesis to piezoelectrics, advancing future flexible, wearable electronics, and biosensors drawing their power from the body's movements.

Materials such as atomically-thin tin-monosulfide (SnS) are predicted to exhibit strong piezoelectric properties, converting mechanical forces or movement into electrical energy.

This property, along with their inherent flexibility, makes them likely candidates for developing flexible nanogenerators that could be used in wearable electronics or internal, self-powered biosensors.

However to date, this potential has been held back by limitations in synthesising large, highly crystalline monolayer tin-monosulfide (and other group IV monochalcogenides), with difficulties caused by strong interlayer coupling.

The new study resolves this issue by applying a new liquid-metal technique, developed at RMIT, to synthesise the materials.

Subsequent measurements confirm that tin-monosulfide synthesised using the new method displays excellent electronic and piezoelectric properties.

The resulting stable, flexible monolayer tin-monosulfide can be incorporated in a variety of devices for efficient energy harvesting.

The work started over two and a half years ago and strong collaborative work between RMIT and UNSW allowed its fruition. Ms Hareem Khan, the first author of the paper, showed remarkable perseverance to surmount many technical challenges to demonstrate the viability of the concept, with Prof Yongxiang Li.

LIQUID METAL SYNTHESIS

The unprecedented technique of synthesis used involves the van der Waals exfoliation of a tin sulphide (SnS), that is formed on the surface of tin when it is melted, while being exposed to the ambient of hydrogen sulfide (H2S) gas. H2S breaks down on the interface and sulfurises the surface of the melt to form SnS.

The technique is equally applicable to other monolayer group IV monochalcogenide, which are predicted to exhibit the same strong piezoelectricity.

This liquid metal based method allows us to extract homogenous and large scale monolayers of SnS with minimal grain boundaries.

Measurements confirm the material has high carrier mobility and piezoelectric coefficient, which translates into exceptional peak values of generated voltage and loading power for a particular applied strain, impressively higher than that any previously reported 2D nanogenerator.

High durability and flexibility of the devices are also demonstrated.

This is evidence that the very stable as-synthesised monolayer SnS can be commercially implemented into power-generating nanodevices.

They can also be used for developing transducers for harvesting mechanical human movements, in accordance to the current technological inclinations towards smart, portable and flexible electronics.

The results are a step towards piezoelectric-based, flexible, wearable energy-scavenging devices.

It also presents an unprecedented synthesis technique for large (wafer) scale tin-monosulfide monolayers.

PIEZOELECTRIC MATERIALS

Piezoelectric materials can convert applied mechanical force or strain into electrical energy.

Best known by name in the simple 'piezo' lighter used for gas BBQs and stovetops, piezo-electric devices sensing sudden changes in acceleration are used to trigger vehicle air bags, and more-sensitive devices recognise orientation changes in mobile phones, or form the basis of sound and pressure sensors.

Even more sensitive piezoelectric materials can take advantage of the small voltages generated by extremely small mechanical displacement, vibration, bending or stretching to power miniaturised devices, for example biosensors embedded in the human body, removing the need for an external power source.

THE STUDY

Liquid metal-based synthesis of high performance monolayer SnS piezoelectric nanogenerators was published in Nature Communications in July 2020 (DOI 10.1038/s41467-020-17296-0).

The study represents a collaboration between two Australian Research Council Centres of Excellence: the Centre for Exciton Science, and the Centre for Future Low-Energy Electronics Technologies (FLEET). ARC funding also comes from the Discovery Project, DECRA and ARC Laureate programs, and from the RMIT Vice-Chancellor Fellowship.

Facilities and advice from the Australian Microscopy & Microanalysis Research Facility (RMMF), RMIT Micro Nano Research Facility (MNRF) and the Centre for Advanced Solid and Liquid based Electronics and Optics (CASLEO) was critical to the success of the study, as was assistance from the CSIRO for PESA measurements.

Research has shown that the tumor microenvironment (TME) can help cancers grow and evade the immune response. The TME has even been shown to inhibit cellular immunotherapy, a novel form of treatment in which the cells of a patient's immune system are re-engineered in the lab to attack cancer cells. Therefore, scientists are now developing cellular immunotherapies that attempt not only to promote the anti-cancer activity of the immune system, but also combat the inhibitory effect of the tumor microenvironment. While it is straightforward to assess the effect of new therapies on the cancer cells, assessing the effectiveness on the TME is challenging.

A research team led by scientists at Baylor College of Medicine and Texas Children's Hospital developed a new approach called nano-radiomics that utilizes complex analyses of imaging data to assess changes in the tumor microenvironment that cannot be detected with conventional imaging methods. This approach, published in the journal Science Advances, provides the promise of a new noninvasive means to enhance current imaging methods in measuring and monitoring the effectiveness of cellular immunotherapies designed to specifically target the TME.

"Understanding the response of the tumor microenvironment to anti-cancer therapy is becoming increasingly important," said co-corresponding author Dr. Robin Parihar, assistant professor of pediatric hematology-oncology at Baylor and Texas Children's and a member of Baylor's Center for Cell and Gene Therapy, "particularly when the tumor microenvironment is inhibiting the anti-tumor effectiveness of cellular immunotherapies that are engineered to attack the cancer."

Currently, imaging technologies such as computed tomography (CT) or magnetic resonance imaging (MRI) generate three-dimensional images that provide information about the overall tumor response to therapy, for instance, whether it is growing or shrinking, but provide very little, if any, information about the TME.

Parihar approached Dr. Ketan Ghaghada, assistant professor of radiology at Baylor and a member of the Translational Imaging Group (TIGr) at Texas Children's, and their laboratories began a collaboration to develop a noninvasive method to assess the effect of a cellular immunotherapy treatment specifically directed at the TME.

Nano-radiomics unveils treatment effect on the tumor microenvironment

Parihar, Ghaghada and their colleagues developed nano-radiomics, a novel method that combines imaging technology using a nanoparticle contrast agent, with radiomics for computational mining of 3-D imaging data.

"Radiomics is an emerging area in the field of radiology wherein images are analyzed to extract information that may reveal patterns or textures in the tumor that are not visible to the naked eye. To enhance the quality of the images, we used a nanoparticle contrast agent developed in our lab that has a different pattern of distribution within the tumor than traditional contrast agents, one that is indicative of changes in the TME," said Ghaghada, co-corresponding author of this work and a member of Baylor's Dan L Duncan Comprehensive Cancer Center.

Using mouse models of cancer, the researchers treated one group of animals with a cellular immunotherapy that effectively eliminated the TME and another group with a placebo. Both groups received the nanoparticle contrast agent followed by a CT scan. Radiomics analysis of the imaging data of both groups showed that nano-radiomics revealed texture-based features that distinguished the two groups while traditional CT scans did not, suggesting that this new approach has the potential to enhance the ability of clinicians to noninvasively assess the effect of treatments directed at the TME, ultimately enhancing the impact of cancer treatment and management.

A genetic analysis of the American crocodile (Crocodylus acutus) has re-established our understanding of its population structure, aiding its conservation. The collaborative study spanning seven countries and led by the Wildlife Conservation Society and University of Bristol researchers is published in PLOS ONE.

The American crocodile is widespread across the American continent (from South Florida to Venezuela, across the Greater Antilles, and from Mexico to Ecuador). Successful due to its ability to thrive within brackish and saltwater environments. Efforts to conserve the crocodile species have existed since 1975 when their status was set to vulnerable on the IUCN (International Union for Conservation of Nature) red list. However, although conservation efforts have been put in place, the American crocodile faces further threats including habitat degradation due to coastal development.

Replenishing these populations requires understanding of population structures through genetic analysis, which can elaborate on the evolution of the species' distribution. Gaining more understanding on how a species has come to be distributed so widely and how populations can differentiate genetically, can inform regions how best to manage their populations.

The study reflected a regional collaborative effort, where DNA sampling occurred across seven countries including Venezuela, Jamaica and Cuba. There has been ongoing discussion on how these regional populations of C.acutus are similar. However, the study's results found that populations in Northern, Central and Southern America's and Great Antilles differed genetically. There were similarities found between Costa Rica and Jamaican populations. In Venezuela, they identified three new haplotypes, which are closely related genes that help scientists identify an origin of distribution.

Researchers believe that the mating with different species could have contributed to this distribution, also known as hybridisation. Crocodiles hybridise easily, contributing to their ability to survive since the prehistoric era. Additionally, in Florida genetic analysis showed there had been a case of unintentional translocation, where the species had been moved from a different location over time. This had been flagged by previous research, where crocodiles with haplotypes from Central and South America had been transported to Florida, most likely for the pet trade, and later escaped or released into the wild by owners.

By identifying these differences between regional populations of C. acutus, conservation efforts can establish population clusters which consider the populations as independent management units that may have different needs and focuses.

Natalia Rossi, Country Manager of the Cuba Program at the Wildlife Conservation Society and the study's co-author explains some of the challenges around taking samples from large crocodiles: "Our study involved several research teams across multiple sites and countries and often in difficult field conditions. For four years between May to July the team would record, mark and sample crocodile hatchings, and juvenile and adult crocodiles in Cuba's Birama Swamp, one of the study sites. It was not unusual for us to have to spend hours in the mangrove lakes waiting for one to appear, and when a crocodile was spotted the whole team would have to enter the water to help net it. While both exciting and rewarding work, it is also dangerous as the crocodiles are powerful and it involves lots of team co-ordination and trust to secure the crocodile to enable us to take samples."

The study was ambitious and could not have been achieved without its global collaboration and efforts from its long list of authors. In particular, the late John Thorbjarnarson and Rafael Crespo, who dedicated their lives to this research.

LOS ALAMOS, N.M., July 9, 2020--New research revealed that tiny, sunlight-absorbing particles in wildfire smoke may have less impact on climate than widely hypothesized because reactions as the plume mixes with clean air reduce its absorbing power and climate-warming effect. In a unique megafire study, a Los Alamos National Laboratory-led research team studied the properties of smoke from Arizona's massive Woodbury Fire last summer using a powerful set of observing techniques.

"These observations may be useful for those trying to represent organic light absorbing aerosols, or brown carbon, in climate models by identifying how they age, as well as understanding processes affecting how strongly they absorb light and cause warming," said James Lee, lead author on a paper released in JGR: Atmospheres this week and a Los Alamos postdoctoral researcher.

The Woodbury Fire burned nearly 124,000 acres for more than a month before it was contained. With powerful instruments including an aerosol mass spectrometer at Los Alamos' Center for Aerosol Forensic Experiments (CAFÉ), researchers from Los Alamos and New Mexico Tech measured the chemical, physical, and optical properties of ambient aerosol and trace gas concentrations in four large plumes in real time. The team found that the composition of the plumes as well as aerosol properties within the plumes are more varied than expected. More oxidation of smoke lowers its sunlight absorbing potential and lessens its climatic impact.

"Wildfire plumes are complex and change quickly," said Allison Aiken, an atmospheric chemist at Los Alamos and coauthor of the study. "Particles at the plume's center have different shapes and chemistries than at its edge."

The team was able to observe intact and more-disperse plumes that aged more than half a day while traveling 300 miles across New Mexico, retaining relatively unchanged aerosols at the plume's core but providing valuable insight to how the smoke transforms as it mixes with cleaner air.

"This is important as we need to capture the physicochemical changes that occur as plumes are transported long distances to model the climate impacts correctly and to understand the human health impacts at different locations and distances from the source," Aiken said.

While the team observed that the Woodbury fire emissions contained brown carbon that absorbed light at a potency that validated previous observations, this was only the case in the core of the plumes. At the edges, organic aerosols absorbed far less light.

Fine-scale results revealed that mixing and oxidation lightened the brown carbon, reducing its ability to absorb light and cause warming. This implies that the warming effects of wildfire brown carbon is likely smaller than published model assessments.

An ancient European volcanic region may pose both a greater long-term volcanic risk and seismic risk to northwestern Europe than scientists had realized, geophysicists report in a study in the Geophysical Journal International.

The scientists are not predicting that a volcanic eruption or earthquake is imminent in the densely populated area, which is centered in the Eifel region of Germany, and covers parts of Belgium, the Netherlands, France and Luxembourg. But the study revealed activity that is uncommon for the region.

"Our findings suggest this region is an active volcanic system, and much more seismically active than many of the faults in Europe between the Eifel volcanic region and the Alps," said Paul Davis, a UCLA research professor of geophysics and a senior author of the study.

Davis and his co-authors report subtle, unusual movements in the surface of the Earth, from which they conclude the Eifel volcanic region remains seismically active. The region has a long history of volcanic activity, but it has been dormant for a long time; scientists think the last volcanic eruption there was some 11,000 years ago.

The geophysicists report that the land surface in that region is lifting up and stretching apart, both of which are unusual in Europe. Although the uplift is only a fraction of an inch per year, it is significant in geological terms, Davis said.

The geophysicists analyzed global positioning system data from across Western Europe that showed subtle movements in the Earth's surface. That enabled them to map out how the ground is moving vertically and horizontally as the Earth's crust is pushed, stretched and sheared.

The dome-like uplift they observed suggests those movements are generated by a rising subsurface mantle plume, which occurs when extremely hot rock in the Earth's mantle becomes buoyant and rises up, sending extremely hot material to the Earth's surface, causing the deformation and volcanic activity. The mantle is the geological layer of rock between the Earth's crust and its outer core.

Corné Kreemer, the study's lead author, is a research professor at the University of Nevada, Reno's Nevada Bureau of Mines and Geology. He said many scientists had assumed that volcanic activity in the Eifel was a thing of the past, but the study indicates that no longer seems to be the case.

"It seems clear that something is brewing underneath the heart of northwest Europe," he said.

The Eifel volcanic region houses many ancient volcanic features, including circular lakes known as maars -- which are remnants of violent volcanic eruptions, such as the one that created Laacher See, the largest lake in the area. The explosion that created Laacher See is believed to have occurred approximately 13,000 years ago, with an explosive power similar to that of the spectacular 1991 Mount Pinatubo eruption in the Philippines.

The researchers plan to continue monitoring the area using a variety of geophysical and geochemical techniques to better understand potential risks.