Earth

EUGENE, Ore. -- May 7, 2021 -- Long-running archaeological research, boosted by airborne lidar sensing and machine-learning algorithms, finds that Cambodia's Greater Angkor region was home to 700,000-900,000 people.

The sprawling city, which thrived from the 9th to 15th centuries, has slowly revealed its forest-hidden past to archaeologists, but its total population has been a mystery.

The new estimate, made possible by a study designed at the University of Oregon, is the first for the entire 3,000-square-kilometer mix of urban and rural landscape. The findings published May 7 in the journal Science Advances.

The finding is vital for potentially helping cities under pressure of climate change, said co-author Roland Fletcher of the University of Sydney and director of the Angkor Research Program, a collaboration with Cambodia's Authority for the Protection of the Site and Management of the Region of Angkor.

"We predominantly are living in giant low-density cities around the world that are similar to Angkor, which displayed serious vulnerability to severe climate change," Fletcher said. "We really need to know the mechanics of how Angkor worked and what people were doing to get some idea of how referable those experiences are to the risks that we face in our future."

With the combined data, including that from several decades of research by international and Cambodian researchers, the new study revealed population details of Angkor's ceremonial city center, the metropolis extending outward like modern suburbia and embankments incorporating agricultural areas. Angkor was a low-density city, with its population spread out across a wide area.

An initial population estimate was for 750,000 residents in an area of 1,000-square kilometers around central Angkor, Fletcher said. In this area are stone religious temples, including Angkor Wat that attract tourists.

Beyond the stone temples of central Angkor were homes and locations of supporting structures, all made of organic materials reclaimed by the jungle, said UO archaeologist Alison K. Carter, an expert in fine-grain archaeological research who has conducted fieldwork in Cambodia since 2005.

Carter was co-lead author with Sarah Klassen, formerly a postdoctoral researcher at the University of British Columbia. The two planned and designed the study while Klassen was a visiting scholar at the UO with support from the Office of International Affairs' Global Oregon Faculty Collaboration Fund. In all, 14 long-active Angkor researchers collaborated.

Klassen brought machine-learning to the project, deploying a multilayered statistical analysis that merged data from historical archives and maps with details obtained of lidar scans of the region in a project led by co-author Damian Evans of the French Institute of Asian Studies, in 2012 and 2015.

Lidar, which is short for light detection and ranging, is done by sending laser pulses groundward from aircraft. It captures details of ground by ignoring ground clutter such as forests. The new data, Klassen said, "really transformed our understanding of the landscape."

Lidar documented and mapped 20,000 features not seen before, adding to a previous database of 5,000 locations, said Klassen, now a postdoctoral researcher at the University of Leiden.

"When you are on the ground in the main parts of the city center it is quite forested," Carter said. "As you walk around you can tell there is something in the landscape around you, but you cannot see anything clearly. Lidar gave us a beautiful grid of mounds and depressions, which we think were little ponds."

As initial lidar images were being transmitted, researchers at the Angkor field station stayed up into the early morning hours to watch, Fletcher said.

"It was absolutely fabulous," he said. "We had earlier radar data, but the amount of new information was staggering, especially because the lidar images captured the entire region in great detail."

The new data have been organized into different periods of Angkor's growth, particularly in the lifetimes of kings who were most influential to infrastructure changes, said Carter, who heads the UO's Southeast Asian Archeology Lab.

Lidar showed where houses, which had been built on mounds and elevated on posts, had stood. Researchers estimated that five people lived in each household and extrapolated that data to assess the region's total population.

"We looked at the growth of the city of Angkor over time," Carter said. "We found that different parts of the city grew in different ways. The way we think about population growth in cities and suburbs today is probably the same for Angkor."

The study's findings enhance the "comparative understanding of premodern urbanism," said co-author Miriam T. Stark, director of the Center for Southeast Asian Studies at the University of Hawaii at Manoa.

"Studying Angkor's population is important for envisioning the future's urbanism with respect to global climate change," Stark said. "Angkor was a tropical city that persisted through centuries of political and climatic volatility. Tracking its history and tipping point could help urban planners understand some kinds of constraints that face increasing numbers of the world's cities."

Klassen's machine learning contributions initially were published in a 2018 study in PLOS ONE.

"In this new paper," she said, "we introduced statistical learning paradigms and our archaeological case study and dataset. We then explored four classical mathematical approaches to find statistically significant predictors to date temples built in different locations in the region."

That led to a historical model for temples built between the modern-era years of 821-1149 within an absolute average error of 49-66 years.

"This was critical for our study, because it allowed us to see how the metropolitan area developed in comparison to the civic-ceremonial centers," Klassen said. "It also allowed us to estimate populations connected to the temples and see how those population changed over time."

Population information paves the way for better understanding Angkor's economics and resilience, said co-author Christophe Pottier of the French Institute of Asian Studies, who has researched the site for 30 years.

Periods of growth covered in the new study occurred between 770 and 1300.

Future research, Fletcher said, will more deeply examine the expansion of population clusters.

"What was the population of Angkor prior to this sample period? We have to get below all of the current structures with archaeology to predict and model earlier periods," he said.

Klassen and Carter's contributions are crucial to future research, Fletcher said.

Several of the new study's co-authors, including Carter, Evans and Stark, and other collaborators have questioned the conception that Angkor depopulated quickly due to climate pressures in the 15th century.

"We can tell from our archaeological data that that were still people on the landscape, and there is evidence of modifications being made to temples into the 16th century," Carter said. "Our work isn't really designed to answer the timing question for the shift of population away from this area, but it probably happened much slower than long thought."

Luxembourg, 7 May 2021 - In a new position statement, Alzheimer Europe has issued a call for prioritisation of people with dementia and their carers in national COVID-19 vaccination strategies, urging governments to recognise the disproportionate effect of the pandemic on these groups.

Alzheimer Europe has today issued a call for people with dementia and their carers to be given priority in the ongoing COVID-19 vaccination campaigns across Europe.

In its position statement, Alzheimer Europe notes that people with dementia have almost twice the risk for developing COVID-19 compared to their peers without dementia, with high rates of hospitalisation and a risk of mortality within six months of approximately 20% in certain populations. Those who become infected are also more prone to developing delirium, which can complicate the management of their current and future cognitive health.

Currently, countries vary significantly in their prioritisation of different groups for COVID-19 vaccination. The vast majority of European countries have prioritised frontline healthcare workers, long-term care facility residents and the oldest old in the first phases of vaccination, with a smaller number also prioritising social care personnel and professional carers. A small number of European countries, recognising dementia per se as a risk category for severe COVID-19, have prioritised people with dementia for COVID-19 vaccination. However, in the majority of countries, neither people with dementia, nor informal carers have been specifically identified as priority groups for the COVID-19 vaccination, despite their increased risk.

Alzheimer Europe notes the disproportionate impact of the pandemic already experienced by people with dementia and their carers, as a result of service cancellations, care home restrictions etc., and accordingly, makes the following three demands of European governments:

Include dementia as a risk category for severe COVID-19, prioritising people with dementia for the COVID-19 vaccine, independent of age, place of residence or other risk factors for severe COVID-19.

Prioritise informal carers for the COVID-19 vaccine, acknowledging their important contribution during the pandemic to the care, support and even survival of people with dementia, as well as the indirect protection vaccination can confer for the people for whom they care.

Ensure that reasonable accommodations are made and that support mechanisms are in place when organising and rolling out the vaccine to people with dementia, such as the possibility to be vaccinated at home and to have decision-making support, if required.

Commenting further, Alzheimer Europe's Executive Director, Jean Georges, stated:

"People with dementia and their carers have often been overlooked and forgotten during this pandemic. Particularly during the early stages of the outbreak, public health measures designed to control the spread of the virus have had profound and often tragic consequences for people with dementia, their families and carers.

Governments must recognise that people with dementia, their families and carers have already been disproportionately affected by the pandemic and ensure that people with dementia and their carers will not be overlooked again in the development and implementation of vaccination strategies.

We urge governments across Europe to revise their approaches to vaccination campaigns and prioritise people with dementia and their carers, allowing a return to some semblance of normality for this vulnerable group."

They may be tiny weapons, but Brigham Young University's holography research group has figured out how to create lightsabers -- green for Yoda and red for Darth Vader, naturally -- with actual luminous beams rising from them.

Inspired by the displays of science fiction, the researchers have also engineered battles between equally small versions of the Starship Enterprise and a Klingon Battle Cruiser that incorporate photon torpedoes launching and striking the enemy vessel that you can see with the naked eye.

"What you're seeing in the scenes we create is real; there is nothing computer generated about them," said lead researcher Dan Smalley, a professor of electrical engineering at BYU. "This is not like the movies, where the lightsabers or the photon torpedoes never really existed in physical space. These are real, and if you look at them from any angle, you will see them existing in that space."

It's the latest work from Smalley and his team of researchers who garnered national and international attention three years ago when they figured out how to draw screenless, free-floating objects in space. Called optical trap displays, they're created by trapping a single particle in the air with a laser beam and then moving that particle around, leaving behind a laser-illuminated path that floats in midair; like a "a 3D printer for light."

The research group's new project, funded by a National Science Foundation CAREER grant, goes to the next level and produces simple animations in thin air. The development paves the way for an immersive experience where people can interact with holographic-like virtual objects that co-exist in their immediate space.

"Most 3D displays require you to look at a screen, but our technology allows us to create images floating in space -- and they're physical; not some mirage," Smalley said. "This technology can make it possible to create vibrant animated content that orbits around or crawls on or explodes out of every day physical objects."

To demonstrate that principle, the team has created virtual stick figures that walk in thin air. They were able to demonstrate the interaction between their virtual images and humans by having a student place a finger in the middle of the volumetric display and then film the same stick finger walking along and jumping off that finger.

Smalley and Rogers detail these and other recent breakthroughs in a new paper published in Nature Scientific Reports this month. The work overcomes a limiting factor to optical trap displays: wherein this technology lacks the ability to show virtual images, Smalley and Rogers show it is possible to simulate virtual images by employing a time-varying perspective projection backdrop.

"We can play some fancy tricks with motion parallax and we can make the display look a lot bigger than it physically is," Rogers said. "This methodology would allow us to create the illusion of a much deeper display up to theoretically an infinite size display."

Observing how cells stick to surfaces and their motility is vitally important in the study of tissue maintenance, wound healing and even understanding how cancers progress. A new paper published in EPJ Plus, by Raj Kumar Sadhu, Weizmann Institute of Science, Rehovot, Israel, takes a step towards a deeper understanding of these processes.

"Cell adhesion is the ability of a cell to stick to another cell or an extracellular matrix. This process is important in order to understand how cells interact and coordinate their behaviour in multicellular organisms," says sadhu. "We theoretically model the adhesion of a cell-like vesicle by describing the cell as a three-dimensional vesicle adhering on a flat substrate with a constant adhesion interaction."

Alongside his co-authors, Sadhu set about exploring the role of membrane-bound curvature sensitive proteins and the forces that act on the cytoskeleton?--?the network of interlinking protein filaments found in the cytoplasm of all cells?--?during the adhesion process. The team discovered that curved proteins enhance the adhesion process considerably, especially when coupled with active cytoskeleton forces.

"Our work shows that the curved membrane proteins, coupled with the pushing force due to the cytoskeleton, can play a key role in the cell adhesion process," adds Sadhu. "In addition, we showed that these minimal ingredients are sufficient to produce a motile shape that closely resembles migrating cells. Our present work will motivate more research in this direction."

One aspect of the research that pleasantly surprised the team was the fact that the relatively simple model they created could not just describe cell adhesion, but also allowed them to capture cell movement as well. The resultant paper belongs to the Topical Collection 'Focus Point on Mechanobiology across Scales,' edited by M. Ben Amar, A. Boudaoud and M. Lenz.

"Physical principles of shape, curvature and forces, combine to give living cells their shapes," concludes Sadhu. "We show that the cells can have a variety of dynamic shapes, which spontaneously arise due to physical principles, and control the function of the cells in our bodies."

The team will seek to improve on this current study by examining the adhesion of cells on more complex surfaces. This will include curved surfaces, those with adhesion gradients, and others upon which adhesive elements are temporary.

Neuroblastoma is a childhood cancer, most commonly affecting children aged between 2 -3 and can be fatal. Since the tumour cells resemble certain cells in the adrenal glands, a joint research group from MedUni Vienna's Center for Brain Research and the Swedish Karolinska Institute investigated the cellular origin of these cells and sympathetic neurons during the embryonic development of human adrenal glands. During the course of their investigations, they discovered a previously unknown cell type that might potentially be the origin of the tumour cells.

Treatments for this disease are extremely aggressive and challenging and relapses are not uncommon. So far, little is known about the origins of this cancer or the causes of relapse. However, it is assumed that neuroblastomas are due to abnormalities in the neural crest cells, which form the peripheral nervous system during embryogenesis.

The cells of neuroblastoma resemble sympathetic neurons. Although these neurons occur in sympathetic ganglia and are therefore found in many different sites in the human body, neuroblastomas often occur in the adrenal medulla. The reason for this is not yet clear. However, recent studies found that the chromaffin cells of the adrenal medulla, which have long been thought to be related to sympathetic neurons and to derive from neural crest cells, are derived from a completely new cell type, namely from nerve-associated Schwann cell precursors. Based on these observations, the researchers led by Igor Adameyko from MedUni Vienna's Center for Brain Research and the Swedish Karolinska Institute looked for another new cell type in the human adrenal glands that might play a major role in the development of neuroblastoma.

Cells develop in different directions

In order to investigate the cellular origin of chromaffin cells and sympathetic neurons during embryonic development of the human adrenal glands, they analysed the RNA expression profiles of individual cells and found a population of intra-medullary sympathoblasts that derive from Schwann cell precursors. These cells divide and, in humans, organise themselves into large ganglia-like structures in the medulla of the developing adrenals. Such structures are primarily found during embryogenesis. After birth, only isolated cells or small groups of sympathetic nerves are observed. Based on these bioinformatic investigations, the researchers are now able to predict that these intra-adrenal sympathoblasts can develop into chromaffin cells under certain conditions.

Further investigations will now be conducted to find out what happens if the cells are unable to turn into chromaffin cells. It is assumed that the nerve-associated Schwann cell precursors, which continue to divide for a long time and can differentiate to form various cell types, lead to the formation of neuroblastoma. The researchers therefore want to conduct a detailed study into the role of these cells in the development of neuroblastoma, in the hope that this will provide a basis for effective treatments.

Important findings about adrenal gland development

During the course of the investigations conducted so far, an atlas has been produced of the transcription profiles of individual cells in early stages of human adrenal development and this is a valuable and freely available resource for the scientific community and might be of particular interest to developmental biologists and endocrinologists studying congenital diseases of the adrenal glands.

Australia, the driest inhabited continent, is prone to natural disasters and wild swings in weather conditions - from floods to droughts, heatwaves and bushfires.

Now two new Flinders University studies of long-term hydro-climatic patterns provide fresh insights into the causes of the island continent's strong climate variability which affect extreme wet or dry weather and other conditions vital to water supply, agriculture, the environment and the nation's future.

For the first time, researchers from the National Centre for Groundwater Research and Training (NCGRT) at Flinders have revealed a vegetation-mediated seesaw wetting-drying phenomenon between eastern and western Australia.

The seesaw phenomenon covered in a new paper in Earth's Future is characterised by eastern Australia gaining water, while western Australia is losing water, and vice-versa being reset by strong La Niña induced continent?wide wetting.

"The seesaw phase seems to depend on vegetation cover anomaly prior to the strong La Niña event, and can be explained by subsequent vegetation and soil moisture interactions," says lead researcher Dr Huade Guan, Associate Professor in Hydrology.

"This finding provides society with valuable reference for managing forest, water, and disaster risks in the wake of a next strong La Niña induced continent?wide wetting in Australia," says co-author Flinders University Professor Okke Batalaan.

Rainfall on land has its moisture source mostly from evaporation in oceans. Sea surface temperature variation - in tropical Pacific in rhythm with the El Nino-Southern Oscillation, and in northern Indian Ocean represented by Indian Ocean Dipole - provides a lead up of several months for predicting overall drought or wet condition in Australia.

In another lengthy NCGRT study over more than a decade, Flinders researchers evaluated the impacts of sea surface temperature variations in Southern Hemisphere oceans on rainfall in South Australia. They found a seven-year lead ocean-atmosphere oscillation for precipitation patterns - which may help prepare South Australia for future extreme weather conditions, the Frontiers in Earth Science paper says.

"This long-running study, beginning with a postgraduate project (by Dr CP Rofe in 2009), revealed a seven-year lag precipitation teleconnection with a large-scale ocean-atmosphere oscillation index known as Southern Annular Mode, or Antarctic Oscillation," Associate Professor Guan says.

"We filled the teleconnection with a 27-season lag correlation between sea surface temperature off the coast of South Australia and the Southern Annual Mode, and a two-season lag correlation between rainfall in SA and sea surface temperature."

Other co-authors Dr Wenju Cai (CSIRO and Flinders alumnus) and previous visiting scholars Dr Lingli Fan and Dr Jianjun Xu (Guangdong Ocean University) confirmed this oceanic teleconnection dominant between 1979-1998.

"Focusing on this period, we were able to delineate an oceanic pathway showing how sea water temperature anomaly associated with the South Annual Mode propagated from the southern Pacific Ocean to South Australian seas in about 27 seasons.

"This sea temperature anomaly propagation only existed in 1979-1998 when the Pacific Ocean was in a certain stage, known as the positive phase of Interdecadal Pacific Oscillation (IPO)."

With this teleconnection, the team successfully "hindcasted" the 1988 and 1999 droughts in SA without ambiguity with seven-year lead time, Associate Professor Guan says, adding that the next positive phase of IPO will further test this theory to support water resource and agricultural planning in South Australia.

Read the article online, A 7-Year Lag Precipitation Teleconnection in South Australia and Its Possible Mechanism (2021) by L Fan, H Guan, W Cai, CP Rofe and J Xu has been published in Frontiers in Earth Science DOI: 10.3389/feart.2020.553506

The Earth's Future study confirmed four consecutive periods of seesaw wetting and drying between eastern and western Australia in the past five decades, based on analyses of GRACE satellite-derived terrestrial water storage and extended datasets by co-author and Flinders PhD student Ms Ajiao Chen.

"These findings support the idea of better stormwater harvesting and other environmental measures to prepare for a drying phase - and more disaster risk and adaptive land management in the wake of a strong La Niña induced continent-wide wetting in Australia.

"Reducing vegetation cover right after the wetting episode might reduce the risk of heatwaves and bushfires in the later dry stage," researchers say.

7 May 2021/Kiel. Corals are the backbone of marine ecosystems in the tropics. They are threatened by rising water temperatures caused by global warming and they are among the first ecosystems worldwide that are on the verge of ecological collapse. Coral bleaching, which is becoming stronger and more frequent due to heat stress, has already wiped out corals at many locations globally. With the help of a microbiome-targeting strategy developed by an international team led by GEOMAR Helmholtz Centre for Ocean Research Kiel, it could become feasible to help protect corals from heat stress. The work has now been published in the international journal Microbiome.

Corals are the backbone of marine ecosystems in the tropics. They are threatened by rising water temperatures caused by global warming and they are among the first ecosystems worldwide that are on the verge of ecological collapse. Coral bleaching, which is becoming stronger and more frequent due to heat stress, has already wiped out corals at many locations globally. With the help of a microbiome-targeting strategy developed by an international team led by GEOMAR Helmholtz Centre for Ocean Research Kiel, it could become feasible to help protect corals from heat stress. The work has now been published in the international journal Microbiome.

Images of bare, naked white coral reefs have been increasingly circulating around the world. The typically colourful reefs of tropical oceans, which are home to many species of the marine ecosystem, are suffering from rising water temperatures due to global warming. There is no heat relieve for the corals in sight. Scientists are desperately seeking out ways to make the temperature-sensitive organisms more resistant to heat stress. A group of scientists led by GEOMAR Helmholtz Centre for Ocean Research Kiel are developing a promising approach, which is based on a therapeutic treatment known from human medicine. The study was published in the international journal Microbiome.

"The idea is that probiotic bacteria with beneficial functions could help a coral to better withstand heat stress," explains Dr Anna Roik from GEOMAR, lead author of the study, which was funded as part of a Future Ocean Network project at Kiel University. "In the current study, we tested the approach of a 'microbiome transplantation', inspired by microbiome-based applications we know for example from clinical treatments", Roik continues.

The research group conducted coral microbiome transplantation experiments with the reef-building corals Pocillopora and Porites in the Andaman Sea in Thailand. They investigated whether this technique can improve the heat resistance of corals by modifying the bacterial microbiome. The scientists first looked for more heat-tolerant "donor" corals. "We then used material from the coral tissue of the donor corals to inoculate conspecific, heat-sensitive recipients and then documented their bleaching responses and microbiome changes using a genetic analysis method called 16S rRNA gene metabarcoding", explains Dr Roik.

The recipient corals of both species bleached more mildly compared to the control group during a short-term heat stress test (34 °C). "The results show that the inoculated corals were able to resist the heat stress response for a short time", explains Prof. Dr Ute Hentschel Humeida, head of the Marine Symbioses Research Unit at GEOMAR and co-author of the study. "In addition, the microbiome data suggest that the 'inoculated' corals may favour the uptake of putative bacterial symbionts", Dr Anna Roik continues. "However, further experimental studies are required to unravel the exact mechanism of action, as well as long-term field-based studies to test the durability of the effect", says the marine biologist, looking ahead.

The functions of water-dominated ecosystems can be considerably influenced and changed by hydrological fluctuation. The varying states of redox-active substances are of crucial importance here. Researchers at the University of Bayreuth have discovered this, in cooperation with partners from the Universities of Tübingen and Bristol and the Helmholtz Centre for Environmental Research, Halle-Leipzig. They present their discovery in the journal Nature Geoscience. The new study enables a more precise understanding of the biogeochemical processes that contribute to the degradation of pollutants and the reduction of greenhouse gas emissions.

Reducing the generation of greenhouse gases, storing carbon, removing environmental pollutants such as nitrate, and providing high-quality drinking water - these are important services provided by aquatic ecosystems, such as lakes, streams, marshes, and bogs. The functions of such aquatic ecosystems are closely linked to the cycles of oxygen, nitrogen, carbon, and other elements in nature. It has long been known that elemental cycles are interconnected biogeochemical processes that can be significantly influenced by hydrological fluctuation. Examples of this are fluctuations in the water level of wetlands, peatlands, and groundwater, or even changing flow directions in groundwater.

The research team led by Prof. Dr. Stefan Peiffer at the University of Bayreuth has now succeeded in understanding the dependence of element cycles on hydrological fluctuation more precisely. As numerous laboratory studies have shown, redox-active substances have a key function in this. "Anyone who has ever trudged through a swamp or rummaged in the sand of a swimming lake will have noticed these substances because of their variety of colour. In a very confined space, colour shades alternate from deep black to grey and brown to light red. What is behind this, is an interplay of microbiological and chemical processes in which electrons are being transferred. In research, we call them redox reactions," says Peiffer.

A comparatively simple form of redox reaction is respiration in humans and animals. Carbon is oxidised by oxygen to form carbon dioxide. In the microbially driven redox reactions that take place in a swamp, for example, the role of oxygen is taken over by a variety of redox-active substances - iron, sulphur, and manganese compounds or humic substances. The life span of these substances is very short, but they show a very strong tendency to engage in redox reactions. They are therefore called "redox-active metastable phases" (RAMPs). Due to their high reactivity, RAMPs play a major role in elemental cycles in ecosystems. For example, they are able to degrade pollutants such as nitrates or various other organic chemicals.

One reason for the short lifespan of RAMPs is the constant change between electron-donating and electron-accepting conditions. The study, published in Nature Geoscience, comes to a conclusion decisive for ecological and environmental research. The dynamics of the redox reactivity of RAMPs is triggered by hydrological fluctuations that occur in shore zones, in wetlands, in waterlogged soils, in rice-growing soils or at the surface of sediments in lakes and rivers. These small-scale biogeochemical reactions, in turn, influence the large-scale reactions of the ecosystem, for example, the amount of greenhouse gases released into the atmosphere. This makes it understandable for the first time how hydrological fluctuations, for example fluctuating water levels, affect elemental cycles in nature, and thus the functioning of ecosystems.

"Our study shows that biogeochemical reactions on a scale of only a few micrometres form an important crux between two large-scale processes: between hydrological fluctuations on the one hand, and ecosystem functions on the other. Our new findings will therefore help to better predict pollutant degradation in aquatic ecosystems in future. The consequences of climate change for carbon and nitrogen conversion in these ecosystems may also be more accurately assessed in future," says Peiffer.

Recently, laser scientists at the Center for Relativistic Laser Science (CoReLS) within the Institute for Basic Science (IBS) in South Korea realized the unprecedented laser intensity of 1023 W/cm2. This has been a milestone that has been pursued for almost two decades by many laser institutes around the world.

An ultrahigh intensity laser is an important research tool in several fields of science, including those which explore novel physical phenomena occurring under extreme physical conditions. Since the demonstration of the 1022 W/cm2 intensity laser by a team at the University of Michigan in 2004, the realization of laser intensity over 1023 W/cm2 has been pursued for nearly 20 years.

In general, achieving such a level of ultra-high laser intensity requires two things: laser with extremely high power output, and focusing that laser to the smallest spot as possible. While continuous-wave lasers are limited to megawatt-scale intensity, far higher peak power output (on the order of petawatt) is possible in pulsed laser systems by delivering the energy in the time scale as short as femtoseconds. In order to reach the goal of developing the world's most powerful laser, several ultrahigh power laser facilities with outputs of 10 PW and beyond, such as ELI (EU), Apollon (France), EP-OPAL (USA), and SEL (China), have been built or are being planned. A recent study from Osaka University even proposed a concept prototype for an exawatt class laser.

Meanwhile, the CoReLS laser team has been operating a 4-PW laser system since 2016. This year in April 2021, they have finally achieved the record-breaking milestone of 1023 W/cm2 by tightly focusing the multi-PW laser beam.

Several special techniques have been employed to achieve this feat. The power intensity was maximized by using a focusing optics called an off-axis parabolic mirror, which was used to focus a 28 cm laser beam down to a spot only 1.1 micrometers wide. Such a diffraction-limited tight focusing can be obtained only with a clean laser beam without wavefront distortion. The CoReLS laser team, thus, made its PW laser beam as clean as possible using a set of deformable mirrors to correct the wavefront distortion of the PW laser.

The CoReLS 4-PW laser is a femtosecond, ultrahigh power Ti:sapphire laser, based on the chirped pulse amplification (CPA) technique. The layout of the CoReLS 4-PW laser, including the experimental setup to control the wavefront and to measure the intensity, is given in Fig. 1. A low-energy femtosecond laser pulse from the front-end was stretched to a nanosecond pulse by the pulse stretcher. The initial laser pulse was then amplified to 4.5 J by the two power amplifiers and then up to 112 J by the two booster amplifiers. The size of the laser beam increased along the beam path by a series of beam expanders; 25 mm right after the power amplifiers, 65 mm at the entrance of the 1st booster amplifier, 85 mm at the entrance of the 2nd booster amplifier, and 280 mm at the entrance of the pulse compressor. In the pulse compressor, the laser pulse was recompressed to 20 fs (FWHM), which caused its peak power to become 4 PW after the compression.

In order to compensate for the wavefront distortion of the PW laser beam, two deformable mirrors were employed in the PW laser beamline. The first deformable mirror (DM1) with a diameter of 100 mm was installed after the final booster amplifier, with its role being to correct the wavefront distortion accumulated from the front end to the final beam expander. The second deformable mirror (DM2) with a diameter of 310 mm was installed after the pulse compressor, which corrects the additional aberrations induced from large aperture optics in the pulse compressor, the beam delivery line, and the target area. In the target chamber, the PW laser beam was tightly focused with an f /1.1 off-axis parabolic mirror, which possessed an effective focal length of 300 mm. For imaging and characterization of the focused spot, the focused beam was collimated by an objective lens. It was then divided into two beams with a beam splitter for the focal spot and wavefront characterization. A camera was used for the focal spot monitoring of the transmitted laser beam, and a wavefront sensor was used to measure the wavefront of the reflected laser beam. Figure 3 shows the 3-D focal spot image measured by the camera in the target chamber.

Prof. NAM Chang Hee, the Director of CoReLS, notes, "This work has shown that the CoReLS PW laser is the most powerful laser in the world. With the highest laser intensity achieved ever, we can tackle new challenging areas of experimental science, especially strong field quantum electrodynamics (QED) that has been dealt with mainly by theoreticians. We can explore new physical problems of electron-photon scattering (Compton scattering) and photon-photon scattering (Breit-Wheeler process) in the nonlinear regime. This kind of research is directly related to various astrophysical phenomena occurring in the universe and can help us to further expand our knowledge horizon."

Moderate alcohol intake--defined as no more than one alcoholic drink for women and two for men per day--has been associated with a lower risk of dying from cardiovascular disease when compared with individuals who abstain from drinking or partake in excessive drinking, according to a new study being presented at the American College of Cardiology's 70th Annual Scientific Session. It's also the first study to show that drinking moderate amounts of alcohol may be heart protective, in part, by reducing stress-related brain signals based on a subset of patients who underwent brain imaging.

"We found that stress-related activity in the brain was higher in non-drinkers when compared with people who drank moderately, while people who drank excessively (more than 14 drinks per week) had the highest level of stress-related brain activity," said Kenechukwu Mezue, MD, a fellow in nuclear cardiology at Massachusetts General Hospital and the study's lead author. "The thought is that moderate amounts of alcohol may have effects on the brain that can help you relax, reduce stress levels and, perhaps through these mechanisms, lower the incidence of cardiovascular disease."

While Mezue was quick to caution that these findings should not encourage alcohol use, he said they could open doors to new therapeutics or prescribing stress-relieving activities like exercise or yoga to help minimize stress signals in the brain.

"The current study suggests that moderate alcohol intake beneficially impacts the brain-heart connection. However, alcohol has several important side effects, including an increased risk of cancer, liver damage and dependence, so other interventions with better side effect profiles that beneficially impact brain-heart pathways are needed," Mezue said.

In a related study by the same research team (which is also being presented at ACC.21), exercise was found to have a similar effect on brain activity as well as on the incidence of cardiovascular disease and events. The authors said exercise is associated with decreased stress-associated brain activity in a dose-dependent manner. While the connection between stress and heart disease is widely accepted, the authors said relatively little research has been done on how modifying stress may help protect heart health.

Data were obtained from the Mass General Brigham Biobank health care survey of 53,064 participants, of which 59.9% were women and the average age was 57.2 years. Alcohol intake was based on self-report and was classified as low (14 drinks/week). Major adverse cardiovascular events, including heart attack, stroke or related hospitalizations, were determined using diagnostic (ICD) codes.

Of the patients included, 752 underwent 18F-fluorodeoxyglucose positron emission tomography, or PET imaging, which is often used as part of cancer screening but can also show areas in the brain that have increased activity. The scans allowed researchers to objectively measure activity in regions of the brain known to be associated with stress. Researchers assessed stress-related brain activity by measuring the activity of the amygdala (the part of the brain associated with fear and stress) and dividing it by activity in the frontal cortex (the part of the brain involved in executive functions). They then grouped patients based on the extent of brain stress activity.

Of the 53,064 participants, 7,905 (15%) experienced a major adverse cardiovascular event: 17% in the low alcohol intake group and 13% in the moderate alcohol intake group. People who reported moderate alcohol intake were found to have a 20% lower chance of having a major event compared to low alcohol intake (in adjusted analysis), and also had lower stress-related brain activity. This remained significant even after controlling for demographic variables, cardiovascular risk factors, socioeconomic variables and psychological factors.

"Previous studies by our group and others have shown a robust association between heightened amygdalar activity and a higher risk of major adverse cardiovascular outcomes, such as heart attack, stroke or death. In the current study, path analyses showed that the link between moderate alcohol intake and lowered cardiovascular event risk is significantly mediated though reductions in amygdalar activity," Mezue said.

The study is limited due to the self-reporting of alcohol intake based on the average consumption of drinks per week. The data is also from a single center, and each participant in the imaging sub-study only received a single brain scan. Further study would be needed to show that the observed reductions in brain activity are the direct result of moderate alcohol intake through repeated brain scans and more detailed alcohol intake assessments over time.

A premature start in life can cause problems even into teenage years. A study by the University of Basel and the University Children's Hospital Basel (UKBB) indicates that training motor skills in these children helps even when they are older.

Children that are born before the 37th week of pregnancy remain under close medical supervision while they are young. Any cognitive limitations often disappear after a few years. However, children who come into the world even before the 32nd week of gestation still exhibit differences even into their teenage years. In a new study, researchers led by Dr. Sebastian Ludyga and Professor Uwe Pühse have demonstrated that these children have weaker impulse control compared with children born at term (after the 37th week of pregnancy). This can, for example, have disadvantages in school performance and is linked to behavioral problems and a higher susceptibility to addiction.

As the research team reports in the journal Developmental Cognitive Neuroscience, these differences in impulse control can be fully explained by the children's motor skills. "In other words, premature children who had very well-developed motor skills were practically equal to children born at term when it came to impulse control," explains Ludyga.

In their study, the researchers compared a group of 54 very preterm children aged 9 to 13 years with a control group of children of the same age who had been born at term. To test impulse control, the sports scientists conducted a "go/no go" test with the children. When given a signal, the young study participants had to push a button as quickly as possible. When given a different signal, they were not allowed to push the button - in other words, they had to suppress their impulse to move.

During the experiment, the researchers monitored certain brain activity parameters using an EEG (electroencephalogram) to determine how the children processed the stimulus. A comparison of the two groups showed that on average, the premature children found it more difficult to suppress the impulse to move due to impaired attention processes.

In further experiments, the researchers tested gross and fine motor skills, as well as ball handling. They found that the greater the deficit in motor skills, the more limited the impulse control in the children born very preterm.

"We conclude from these findings that targeted motor skills training could also reduce cognitive limitations," explains Ludyga. The researchers now want to test this in a follow-up study.

Ludyga says that there are few support options for very premature children as they grow into teenagers unless they come under scrutiny for a different reason, such as ADHD or another illness: "Limited impulse control at this age, even if it sorts itself out later, can have negative consequences and restrict these children's educational opportunities."

In younger children in particular, the development of motor and cognitive skills are closely linked. The time window from 9 to 13 years is therefore a promising period in which to reduce cognitive deficits in children born very preterm.

The published data provide additional detail of an initial analysis conducted in January, while more robust data from a complete analysis of the study was subsequently shared in March 2021.

Publication of initial primary analysis highlights cross-protection by the Novavax Covid-19 vaccine against the B.1.351 variant prevalent in South Africa during the study.

This is the first published study to show protection against mild Covid-19 caused by the B.1.351 variant circulating in South Africa.

An updated analysis of the study indicated 100% protection against severe Covid-19 due to the B.1.351 variant.

"An efficacy of 50% is sufficient to meet the World Health Organization criteria for regulatory approval of the vaccine," says Madhi.

The Novavax Covid-19 vaccine, known as NVX-CoV2373, is made by Novavax, Inc., a US-based biotechnology company developing next-generation vaccines for serious infectious diseases.

Gregory M. Glenn, M.D., President of Research and Development, Novavax, says: "This data publication reinforces the encouraging safety profile and cross-protective effect across variants seen in studies of our vaccine to-date."

ABOUT THE STUDY

The Phase 2b randomised, observer-blinded, placebo-controlled trial conducted in South Africa evaluated efficacy, safety and immunogenicity in healthy adults, and in a small cohort of medically stable adults living with human immunodeficiency virus (HIV).

The study met its primary endpoint - i.e., the Novavax vaccine demonstrated an overall efficacy of 49% in the initial analysis (published in NEJM), and 49% in the subsequent complete analysis (unpublished).

Among healthy adults without HIV, the Novavax vaccine demonstrated efficacy of 60% in the initial analysis, and 55% in the subsequent complete analysis.

In the initial analysis, cases were predominantly mild-to-moderate and due to the B.1.351 variant that dominates in South Africa, and increasingly in southern Africa.

In the subsequent complete analysis, circulation of the B.1.351 variant continued to dominate, and all five cases of severe disease observed in the trial occurred in the placebo group.

The initial analysis, now being published in NEJM, suggested that prior infection with the original Covid-19 strain did not protect against subsequent infection by the variant predominantly circulating in South Africa through 60 days of follow-up.

However, with additional follow-up, the complete analysis of the South Africa trial indicates that there may be a modest protective effect of prior exposure with the original Covid-19 strain.

Among placebo recipients, at 90 days of follow-up, the illness rate was 8.0% in baseline seronegative participants and 5.9% in baseline seropositive participants.

"The data make a compelling case for use of the Novavax Covid-19 vaccine in settings where the B.1.351 variant dominates - which is most of southern Africa - to reduce the risk of mild disease and also to maximise the opportunity for protection against severe Covid," says Madhi. "Further work is required for Novavax and all other Covid-19 vaccines, particularly in people living with HIV."

The Novavax Covid-19 vaccine trial is one of two Covid-19 vaccine trials in South Africa led by Madhi and Wits VIDA, with the other being the Oxford/AstraZeneca Covid-19 vaccine trial.

In addition to directing Wits VIDA, Madhi is Dean of the Faculty of Health Sciences at the University of the Witwatersrand, Johannesburg (Wits), and co-Director of African Leadership in Vaccinology Expertise (ALIVE).

ABOUT THE WITS VACCINES & INFECTIOUS DISEASES ANALYTICS (VIDA) RESEARCH UNIT

Formerly known as the Respiratory and Meningeal Pathogens Research Unit (RMPRU) and founded in 1995, the Vaccines and Infectious Diseases Analytics (VIDA) Research Unit of the University of the Witwatersrand (Wits) is an internationally recognised, African-led research unit in the field of epidemiology of vaccine preventable diseases, and clinical development of life-saving vaccines.

Under the guidance of Professor Shabir Madhi, a global leader in the field of paediatric infectious diseases and the Dean of the Faculty of Health Sciences at Wits University, Wits VIDA is conducting translational research on vaccine preventable diseases and training the next generation of clinician scientists.

Combining clinical, microbiological and epidemiological expertise in an African setting, Wits VIDA's cutting-edge scientific research informs local and global policy recommendations on the use of next-generation and novel vaccines today.

In addition to various other studies on Covid-19, Wits VIDA championed and led the first two Covid-19 vaccine trials in Africa in 2020, for the Oxford and Novavax vaccine candidates.

A recent study analyses data collect4d at 44 of the darkest places in the world, including the Canary Island Observatories, to develop the first complete reference method to measure the natural brightness of the night sky using low-cost photometers.

Of the 44 photometers in the survey, the Roque de los Muchachos Observatory (Garafía, La Palma, Canary Islands) stands out at the darkest of all the skies analysed.

The night sky is not completely dark; even in the remotest places there is a glow in the sky produced by natural components, both terrestrial and extraterrestrial, and by artificial lighting of human origin. Even though the main bright sources such as the Moon, the Milky Way, and the Zodiacal light are easily recognisable, there is a glow which dominates the sky brightness on the darkest nights, produced in the upper layers of the atmosphere, and whose strength depends on a set of complex factors such as the time of year, the geographical location, and the solar cycle.

Solar Cycles are ordered in periods of activity lasting 11 years. We refer to solar maximum when the activity of the Sun has grown, sunspots appear on its surface, and its radiative emission has grown, which affects the molecules in the Earth's atmosphere, causing an increase in the brightness of the night sky. When these events are much reduced we call this solar minimum.

In 2018 Solar Cycle 24 entered into this phase and since then a series of photometers, TESS, situated around the world, have collected 11 million measurements which have been used to define a method of reference for the study of natural darkness with equipment of this kind. Among the results in the article, which will soon be published in The Astronomical Journal, there are outstanding "systematic observations of short period variations (of the order of tens of minutes, or of hours) in the brightness of the sky, independently of the site, the season, the time of night, or of solar activity, and which have been shown, for the first time, with low cost photometers, to be associated with events produced in the upper layers of the mesosphere, that is to say to the "airglow", explains Miguel R. Alarcón, a researcher at the Instituto de Astrofísica de Canarias (IAC) and first author of the article.

"This work has demonstrated the high sensitivity of low-cost photometers if they are linked in a network. The final analysis of the full set of TESS photometers shows the Gegenschein, a faint glow in the night sky, visible around the ecliptic, the same plane on which we see the zodiacal light and the planets" explains Miquel Serra-Ricart, an astronomer at the IAC and a co-author of the article. "The network of photometers has shown, yet again, that the Canary Observatories are in the First Division" he adds.

From the 44 photometers which took data from such places as Namibia, Australia, Mexico, Argentina and the United States, among others, it was possible to determine that the Roque de los Muchachos Observatory (ORM, Garafía, La Palma, Canary Islands) is the darkest of all of them". As can be read in the article, the darkness at the ORM is very close to natural darkness, artificial light adds only 2% to the sky background. From the network of photometers installed in the Spanish Peninsula, we should pick out the excellent sky darkness in the Community of Extremadura, the region of Montsec (Lleida), Javalambre (Teruel) the Sierra Nevada and the Pyrenees in Navarre.

Studying light pollution

The glow produced by the scattering of artificial light at night (ALAN) by the components of the atmosphere (gas molecules, aerosols, clouds...) is known as artificial skyglow. Estimates suggest that more than 10% of the Earth's surface receives ALAN and that this figure increases to 23% if we include the atmospheric skyglow. Some 80% of the human population lives in places with light pollution, and around a third of them cannot see the Milky Way. There are few places left in the world where one can appreciate, observe, and measure the natural darkness.

The worrying consequences of light pollution due to human activity, for nature, our health, and for astronomy, have motivated scientific interest in this type of atmospheric pollution. Over the last decades, various increasingly accurate devices have been developed and marketed to measure the darkness at night. The TESS photometers of the STARS4ALL project, which made this study possible, are based on the same sensor as the Sky Quality Meter (SQM) photometer.

EELabs: The sustainable use of artificial lighting

But now there are new projects under way using new technologies, to continue to investigate this threat. This article proposes that to measure the reach of light pollution it is necessary to combine measurements of the scattered light from urban nuclei made from space (mainly from satellites) with maps of darkness in remote natural areas taken by installing networks of self-running photometers with high time resolution and a mean separation of several kilometres. This is one of the main aims of the EELabs project. EELabs (Energy Efficiency Laboratories) is coordinated by the Instituto de Astrofísica de Canarias, with participation by the Portuguese Society for the study of Birds (SPEA), the University of Las Palmas de Gran Canaria (ULPGC) and the Technological Institute for Renewable Energies (ITER).

They are 50,000 times thinner than a human hair, and just a few atoms thick: two-dimensional materials are the thinnest substances it is possible to make today. They have completely new properties and are regarded as the next major step in modern semiconductor technology. In the future they could be used instead of silicon in computer chips, light-emitting diodes and solar cells. Until now, the development of new two-dimensional materials has been limited to structures with layers of rigid chemical bonds in two spatial directions - like a sheet of paper in a stack. Now for the first time, a research team from the universities of Marburg, Giessen and Paderborn, led by Dr. Johanna Heine (Inorganic Chemistry, Philipps University of Marburg) has overcome this limitation by using an innovative concept. The researchers developed an organic-inorganic hybrid crystal which consists of chains in a single direction, yet still forms two-dimensional layers in spite of this. This makes it possible to combine different material components, like pieces in a construction set, to create tailored materials with innovative properties.

In this project, the research team combined the advantages of two-dimensional materials and hybrid perovskites - the eponymous mineral perovskite is well-known for its optoelectronic properties, and can be combined with other materials to improve these characteristics. "What is special about this is that it offers completely new options for targeted design of future functional materials," says Dr. Johanna Heine, a chemist and junior research group leader at the University of Marburg, describing this highly topical research area which has great application potential. "This physical effect - first discovered here - could make it possible to tune the colour of future lighting and display technologies in a simple and targeted way," says physicist Philip Klement, lead author and doctoral student in the research group led by Professor Sangam Chatterjee at the Justus Liebig University of Giessen (JLU).

The work was carried out in an interdisciplinary collaboration: Dr. Johanna Heine's team at the University of Marburg first developed the chemical synthesis and created the material as a single bulk crystal. Philip Klement and Professor Chatterjee's team at JLU then used these crystals to produce individual atomically thin layers and investigated them using optical laser spectroscopy. They found a spectrally broadband ("white") light emission, whose colour temperature can be tuned by changing the thickness of the layer. Working closely with Professor Stefan Schumacher and his team of theoretical physicists at Paderborn University the researchers made a microscopic study of the effect and were able to improve the properties of the material.

In this way the researchers were able to cover the entire process from synthesis of the material and understanding its properties, to modelling the properties. Their findings have been published in the specialist journal "Advanced Materials".

Through a unique combination of computer simulations and laboratory experiments, researchers at the Paul Scherrer Institute PSI have discovered new binding sites for active agents - against cancer, for example - on a vital protein of the cell cytoskeleton. Eleven of the sites hadn't been known before. The study appears today in the journal Angewandte Chemie International Edition.

The protein tubulin is an essential building block of the so-called cell cytoskeleton. In cells, tubulin molecules arrange themselves into tube-like structures, the microtubule filaments. These give cells their shape, aid in transporting proteins and larger cellular components, and play a crucial role in cell division.

Thus tubulin performs diverse functions in the cell and in doing so interacts with numerous other substances. "Tubulin can bind an astonishing number of different proteins and small molecules, several hundred for sure," says Tobias Mühlethaler, a doctoral candidate in the PSI Laboratory of Biomolecular Research and first author of the study. The functions of the protein are guided by means of such bonds. Also, many drugs dock on tubulin and take effect, for example, by preventing cell division in tumours.

"In this project, we addressed the fundamental question of how many binding sites in total exist on this vital protein," Mühlethaler explains. "If we discover new ones, these could possibly be used therapeutically."

From the virtual to the laboratory

In computer simulations conducted in collaboration with the Italian Institute of Technology in Genoa, the researchers combed through the structure of the protein: They identified places where other molecules could dock particularly well to tubulin. These are the so-called binding pockets.
Subsequently, in an actual laboratory experiment, the researchers sought to verify such sites. For this, they used a method called fragment screening: Starting with hundreds of crystals of tubulin, the researchers added individual solutions containing fragments of molecules that are typical precursors for promising active agents. Within an hour, the tubulin crystals were able to soak up as much of the fragment solution as they could hold. Finally the crystals were fished out of the liquid and exposed to synchrotron X-ray radiation. On the basis of the resulting diffraction pattern, the researchers are able to infer the structure of the crystal. Thus it could be determined if and where the molecule fragments have bound to the protein.

"Both methods, computer simulations and fragment screening, have their respective strengths and weaknesses," says Michel Steinmetz, head of the Laboratory of Biomolecular Research. "By combining them, we ensure that no binding site on the protein escapes our search."

Eleven new ones

Overall, the researchers found 27 binding sites on tubulin where molecules or other proteins can dock. "Eleven of them had never been described before," says Mühlethaler. In addition, the researchers identified 56 fragments that bind to tubulin and might be suitable for developing new active agents.

As the researchers stress, their approach is also transferable to other proteins. "Here we have developed a method for early discovery of so-called lead molecules and, with that, new starting points for the development of active agents," says Michel Steinmetz. It should be possible to apply this method successfully to all proteins for which high quality crystals can be obtained.

"The search for potential new lead molecules is a focus of the Swiss Light Source SLS," Steinmetz adds. "This will gain increasing significance after the upgrade to SLS 2.0, planned for the coming years, has taken place."