China Science & Technology Forum

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FEBRUARY 21, 2020 REPORT
Adding an adjuvant boosts vaccines ability to fight multiple flu strains
by Bob Yirka , Medical Xpress

Transmission electron micrograph of influenza A virus, late passage. Credit: CDC

A team of researchers from Massachusetts General Hospital, The First Affiliated Hospital of Sun Yat-Sen University and Fudan University has found that adding a certain adjuvant to a vaccine increased its ability to fight multiple strains of influenza. In their paper published in the journal Science, the group describes using lipid components of a pulmonary surfactant to encapsulate the adjuvant to allow lung-resident alveolar macrophages to recognize it. Susanne Herold and Leif-Erik Sander with the Universities of Giessen and Marburg Lung Center and the Berlin Institute of Health, respectively, have published a Perspective piece describing the work by the team in the same journal edition.

In the current strategy for creating flu vaccines, health officials in several countries study outbreak patterns of various strains and then create vaccines against those that seem most likely to develop into an outbreak in a given country. The process is repeated on a seasonal cycle, with new vaccines created every year. What would be better, of course, would be a single vaccine to prevent outbreaks of all of the strains that might pose a threat. Such a vaccine is not yet available, but scientists are working hard to develop one. In this new effort, the researchers have come a step closer with a new approach to using an inactivated virus to trick the immune system into activating a stronger immune response than it normally would when any strain of flu is detected. Thus far, it has worked as planned in mice and ferrets.

The new approach involved combining an inactivated virus with 2′,3′-cyclic guanosine monophosphate–adenosine monophosphate (cGAMP)—a known immune response activator. But to keep the body from overreacting, the researchers covered it in a lipid from a pulmonary surfactant. The two components were then mixed into a nasal spray. Using this approach, the researchers found that the PS-GAMP nanoparticles were pulled into alveolar macrophages, which then transferred them to an innate immune sensor stimulator of interferon genes, activating them. That allowed the immune system to better defend against all five of the flu strains tested.

More information: Ji Wang et al. Pulmonary surfactant–biomimetic nanoparticles potentiate heterosubtypic influenza immunity, Science (2020). DOI: 10.1126/science.aau0810​

Adding an adjuvant boosts vaccines ability to fight multiple flu strains | Medical Xpress

 

[JSCh]

NEWS RELEASE 24-FEB-2020
Going super small to get super strong metals
UNIVERSITY OF UTAH

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A simulation of 3-nm-grain-sized nickel under strain. Colored lines indicate partial or full grain dislocation. CREDIT: Zhou et al

You can't see them, but most of the metals around you--coins, silverware, even the steel beams holding up buildings and overpasses--are made up of tiny metal grains. Under a powerful enough microscope, you can see interlocking crystals that look like a granite countertop.

It's long been known by materials scientists that metals get stronger as the size of the grains making up the metal get smaller - up to a point. If the grains are smaller than 10 nanometers in diameter the materials are weaker because, it was thought, they slide past each other like sand sliding down a dune. The strength of metals had a limit.

But experiments led by former University of Utah postdoctoral scholar Xiaoling Zhou, now at Princeton University, associate professor of geology Lowell Miyagi, and Bin Chen at the Center for High Pressure Science and Technology Advanced Research in Shanghai, China, show that that's not always the case - in samples of nickel with grain diameters as small as 3 nanometers, and under high pressures, the strength of the samples continued to increase with smaller grain sizes.

The result, Zhou and Miyagi say, is a new understanding of how individual atoms of metal grains interact with each other, as well as a way to use those physics to achieve super-strong metals. Their study, carried out with colleagues at the University of California, Berkeley and at universities in China, is published in Nature.

"Our results suggest a possible strategy for making ultrastrong metals," Zhou says. "In the past, researchers believed the strongest grain size was around 10-15 nanometers. But now we found that we could make stronger metals at below 10 nanometers."

Pushing past Hall-Petch

For most metallic objects, Miyagi says, the sizes of the metal grains are on the order of a few to a few hundred micrometers - about the diameter of a human hair. "High end cutlery often will have a finer, and more homogeneous, grain structure which can allow you to get a better edge," he says.

The previously-understood relationship between metal strength and grain size was called the Hall-Petch relationship. Metal strength increased as grain size decreased, according to Hall-Petch, down to a limit of 10-15 nanometers. That's a diameter of only about four to six strands of DNA. Grain sizes below that limit just weren't as strong. So to maximize strength, metallurgists would aim for the smallest effective grain sizes.

"Grain size refinement is a good approach to improve strength," Zhou says. "So it was quite frustrating, in the past, to find this grain size refinement approach no longer works below a critical grain size."

The explanation for the weakening below 10 nanometers had to do with the way grain surfaces interacted. The surfaces of grains have a different atomic structure than the interiors, Miyagi says. As long as the grains are held together by the power of friction, the metal would retain strength. But at small grain sizes, it was thought, the grains would simply slide past each other under strain, leading to a weak metal.

Technical limitations previously prevented direct experiments on nanograins, though, limiting understanding of how nanoscale grains behaved and whether there may yet be untapped strength below the Hall-Petch limit. "So we designed our study to measure the strength of nanometals," Zhou says.

Under pressure

The researchers tested samples of nickel, a material that's available in a wide range of nanograin sizes, down to three nanometers. Their experiments involved placing samples of various grain sizes under intense pressures in a diamond anvil cell and using x-ray diffraction to watch what was happening at the nanoscale in each sample.

"If you've ever played around with a spring, you've probably pulled on it hard enough to ruin it so that it doesn't do what it's supposed to do," Miyagi says. "That's basically what we're measuring here; how hard we can push on this nickel until we would deform it past the point of it being able to recover."

Strength continued to increase all the way down to the smallest grain size available. The 3 nm sample withstood a force of 4.2 gigapascals (about the same force as ten 10,000 lbs. elephants balanced on a single high heel) before deforming irreversibly. That's ten times stronger than nickel with a commercial-grade grain size.

It's not that the Hall-Petch relationship broke down, Miyagi says, but that the way the grains interacted was different under the experimental conditions. The high pressure likely overcame the grain sliding effects.

"If you push two grains together really hard," he says, "it's hard for them to slide past each other because the friction between grains becomes large, and you can suppress these grain boundary sliding mechanisms that turns out are responsible for this weakening."

When grain boundary sliding was suppressed at grain sizes below 20nm, the researchers observed a new atomic-scale deformation mechanism which resulted in extreme strengthening in the finest grained samples.

Ultrastrong possibilities

Zhou says that one of the advances of this study is in their method to measure the strength of materials at the nanoscale in a way that hasn't been done before.

Miyagi says another advance is a new way to think about strengthening metals--by engineering their grain surfaces to suppress grain sliding.

"We don't have many applications, industrially, of things where the pressures are as high as in these experiments, but by showing pressure is one way of suppressing grain boundary deformation we can think about other strategies to suppress it, maybe using complicated microstructures where you have grain shapes that inhibit sliding of grains past each other."


Going super small to get super strong metals | EurekAlert! Science News

Xiaoling Zhou, Zongqiang Feng, Linli Zhu, Jianing Xu, Lowell Miyagi, Hongliang Dong, Hongwei Sheng, Yanju Wang, Quan Li, Yanming Ma, Hengzhong Zhang, Jinyuan Yan, Nobumichi Tamura, Martin Kunz, Katie Lutker, Tianlin Huang, Darcy A. Hughes, Xiaoxu Huang & Bin Chen . High-pressure strengthening in ultrafine-grained metals. Nature (2020). DOI: 10.1038/s41586-020-2036-z​

 

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Scientists Develop Ionogel-based Sodium Ion Micro-batteries with 3D Na-ion Diffusion Mechanism
By LI Yuan | Feb 24, 2020

A research team led by Prof. WU Zhongshuai and Prof. BAO Xinhe from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences, in collaboration with Prof. YU Yan from University of Science and Technology of China (USTC), developed high-performance ionogel-based sodium ion micro-batteries with 3D Na-ion diffusion mechanism.

The newly developed batteries, featured with ultrahigh rate capability, high areal energy density, remarkable mechanical flexibility and high-temperature stability, are promising in the development of microelectronics and microsystems.

Planar lithium ion micro-batteries (LIMBs) with interdigital microelectrodes can be seamlessly integrated into microelectronic devices mounted on a planar integrated circuit, facilitating the miniaturization of the entire microelectronic system. However, its development is limited by the scarcity, uneven distribution and increasing cost of metal lithium.

Since sodium is naturally abundant, low cost, and shows similarly low potential (-2.7 V vs SHE) as lithium, sodium ion micro-batteries (NIMBs) have been exploited after LIMBs. However, it faces challenges of lacking of effective electron-ion diffusion network and suitable electrolyte.

Schematic diagram of sodium ion micro-batteries. (Image by ZHENG Shuanghao)

To address this issue, the researchers reported one prototype quasi-solid-state planar ionogel-based NIMBs constructed by separator-free interdigital microelectrodes of sodium titanate anode and sodium vanadate phosphate cathode, both of which were embedded into three-dimensional interconnected graphene scaffold.
Meanwhile, a novel NaBF4-based ionogel electrolyte with robust ionic conductivity of 8.1 mS/cm was developed. The fabricated NIMBs revealed 3D multi-directional pathways for sodium ion diffusions, which can provide universal guidance to improve the performance of other planar micro-batteries.

Benefiting from the synergetic merits of the planar architecture, dominated pseudocapacitance contribution, and 3D multi-directional Na-ion diffusion mechanism, the assembled NIMBs exhibited high volumetric capacity of 30.7 mAh/cm3 at 1 C, and high rate performance with 15.7 mAh/cm3 at 30 C at room temperature and 13.5 mAh/cm3 at 100 C at high temperature of 100 oC.

Moreover, the quasi-solid-state NIMBs presented outstanding flexibility, tunable voltage and capacity output, and remarkable areal energy density of 145 μWh/cm2 (55.6 mWh/cm3).

The results were published in Energy & Environmental Science.



Scientists Develop Ionogel-based Sodium Ion Micro-batteries with 3D Na-ion Diffusion Mechanism----Chinese Academy of Sciences

 

[JSCh]

NEWS RELEASE 25-FEB-2020
From China to the South Pole: Joining forces to solve the neutrino mass puzzle
Study by Mainz physicists indicates that the next generation of neutrino experiments may well find the answer to one of the most pressing issues in neutrino physics

JOHANNES GUTENBERG UNIVERSITAET MAINZ

Among the most exciting challenges in modern physics is the identification of the neutrino mass ordering. Physicists from the Cluster of Excellence PRISMA+ at Johannes Gutenberg University Mainz (JGU) play a leading role in a new study that indicates that the puzzle of neutrino mass ordering may finally be solved in the next few years. This will be thanks to the combined performance of two new neutrino experiments that are in the pipeline - the Upgrade of the IceCube experiment at the South Pole and the Jiangmen Underground Neutrino Observatory (JUNO) in China. They will soon give the physicists access to much more sensitive and complementary data on the neutrino mass ordering.

Neutrinos are the chameleons among elementary particles
Neutrinos are produced by natural sources - in the interior of the sun or other astronomical objects, for example - but also in vast quantities by nuclear power plants. However, they can pass through normal matter - such as the human body - practically unhindered without leaving a trace of their presence. This means that extremely complex methods requiring the use of massive detectors are needed to observe the occasional rare reactions in which these 'ghost particles' are involved.

Neutrinos come in three different types: electron, muon and tau neutrinos. They can change from one type to another, a phenomenon that scientists call 'neutrino oscillation'. It is possible to determine the mass of the particles from observations of the oscillation patterns. For years now, physicists have been trying to establish which of the three neutrinos is the lightest and which is the heaviest. Prof. Michael Wurm, a physicist at the PRISMA+ Cluster of Excellence and the Institute of Physics at JGU, who is playing an instrumental role in setting up the JUNO experiment in China, explains: "We believe that answering this question will contribute significantly towards enabling us to gather long-term data on the violation of matter-antimatter symmetry in the neutrino sector. Then, using this data, we hope to find out once and for all why matter and anti-matter did not completely annihilate each other after the Big Bang."

Global cooperation pays off
Both large-scale experiments use very different and complementary methods in order to solve the puzzle of the neutrino mass ordering. "An obvious approach is to combine the expected results of both experiments," points out Prof. Sebastian Böser, also from the PRISMA+ Cluster of Excellence and the Institute of Physics at JGU, who researches neutrinos and is a major contributor to the IceCube experiment.

No sooner said than done. In the current issue of the journal Physical Review D, researchers from the IceCube and the JUNO collaboration have published a combined analysis of their experiments. For this, the authors simulated the predicted experimental data as a function of the measuring time for each experiment. The results vary depending on whether the neutrino masses are in their normal or reversed (inverted) order. Next, the physicists carried out a statistical test, in which they applied a combined analysis to the simulated results of both experiments. This revealed the degree of sensitivity with which both experiments combined could predict the correct order, or rather rule out the wrong order. As the observed oscillation patterns in JUNO and IceCube depend on the actual neutrino mass ordering in a way specific to each experiment, the combined test has a discriminating power significantly higher than the individual experimental results. The combination will thus permit to definitively rule out the incorrect neutrino mass ordering within a measuring period of three to seven years.

"In this case, the whole really is more than the sum of its parts," concludes Sebastian Böser. "Here we have clear evidence of the effectiveness of a complementary experimental approach when it comes to solving the remaining neutrino puzzles." "No experiment could achieve this by itself, whether it's the IceCube Upgrade, JUNO or any of the others currently running," adds Michael Wurm. "Moreover it just shows what neutrino physicists here in Mainz can achieve by working together."



From China to the South Pole: Joining forces to solve the neutrino mass puzzle | EurekAlert! Science News

 

[JSCh]

China develops first AI earthquake monitoring system
2020-02-26 16:09:53 Ecns.cn

This combo photo shows the artificial intelligence earthquake monitoring system, with the red triangles in the right representing the seismic stations in Yunnan Province, the blue triangles the seismic stations in Sichuan Province, and circles being the earthquake location automatically announced by the system. (Photo provided to China News Service)

(ECNS) -- The University of Science and Technology of China (USTC) has invented the world's first artificial intelligence earthquake monitoring system after six years of research.

It can report all seismic source parameters within two seconds.

The fruit of USTC professors and a team led by Zhao Cuiping at the Earthquake Prediction Institute of China Seismological Administration, the system underwent testing at earthquake test sites in Sichuan and Yunnan provinces for a year.

The AI earthquake monitoring system can operate in real-time to timely process massive seismic network big data, greatly alleviating labor pressure while reducing false and missed alarms.

Research and development teams are seeking cooperation oppurtunities with international earthquake monitoring agencies in Japan, Turkey, Mexico and other countries where earthquakes occur frequently.

 

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Researchers Identify Novel Anti-aging Targets
By LIU Jia | Feb 27, 2020

A recent study published in Nature has reported two conserved epigenetic regulators as novel anti-aging targets. The research, by scientists from Dr. CAI Shiqing’s Lab at the Center for Excellence in Brain Science and Intelligence Technology, Institute of Neuroscience of the Chinese Academy of Sciences (CAS), and Dr. JIANG Lubing’s team at Institut Pasteur of Shanghai of CAS, identified conserved negative regulators of healthy aging by using multiple modalities and systems, thus providing insights into how to achieve healthy aging.

Aging is associated with progressive decline in physiological functions over time and is a major risk factor for a number of chronic diseases, such as Alzheimer's disease, cancer, and diabetes. Over the past decades, the understanding of longevity regulation has progressed greatly, and a number of longevity pathways conserved from yeast to mammals have been delineated.

However, increasing longevity is not often accompanied by an extended healthspan, despite global increases in life expectancy. Thus, how to achieve healthy aging (i.e., an extension of healthspan) is one of the most important and challenging heath issues nowadays. Despite its extreme importance, the biological mechanisms underlying healthy aging, as defined by the preservation of normal behavioral capabilities, remains to be elucidated.

Previous studies from Dr. CAI’s lab have revealed that behavioral performance in aged animals can be improved by increasing neurotransmitters. They also showed that variation in levels of neurotransmitters may contribute to different rates of age-related decline among individuals.

In the current study, the researchers used the animal models C. elegans and mouse, along with human datasets to identify novel anti-aging targets and unravel a mechanism for regulating cognitive aging. C. elegans is a tiny free-living nematode, about 1 mm in length. Due to its short lifespan and clear genetic background, C. elegans has been widely used in aging research.

To identify aging modulators, the researchers performed a genome-wide RNAi screen for genes that regulate behavioral deterioration in aging C. elegans. They identified 59 genes that potentially regulate the rate of age-related behavioral deterioration. By constructing a co-expression network of these screening hits, they found that a neuronal epigenetic reader BAZ-2 and a neuronal histone 3 lysine 9 (H3K9) methyltransferase SET-6 appeared as a key node in the network. Deletion of baz-2 and set-6 prevented age-related deterioration in the worm’s food-induced behavior, food intake, and male virility.

By analyzing published databases, the researchers found that the expression levels of their human homologues BAZ2B and EHMT1 increase with age in human brains, and positively correlate with Alzheimer's disease (AD) progression. Strikingly, ablation of Baz2b, the mouse ortholog of baz-2, attenuated age-dependent body weight gain and prevented cognitive decline in aging mice. Their findings suggest that BAZ2B and EHMT1 are key aging modulators and appear to be novel anti-aging targets.

In addition, the researchers demonstrated that these epigenetic modulators repressed the expression of nuclear genes encoding mitochondrial proteins by occupying the promoter regions and hence reduced mitochondrial function, a mechanism conserved in mouse brain tissues. Deletion of baz-2/BAZ2B and set-6/EHMT1 delayed the aging process by improving mitochondrial function.

Mitochondrial dysfunction has been implicated in the pathogenesis of Alzheimer’s disease (AD). By analyzing gene expression in the brains of AD patients, they found that the expression levels of BAZ2B and EHMT1 negatively correlate with the expression of key mitochondrial function-related genes, suggesting that BAZ2B and EHMT1 can regulate mitochondrial function in aging human brains.

The researchers in this study performed a genome-wide RNAi screen and provided the first view of genes that modulate behavioral aging. They showed that two conserved epigenetic factors modulate the aging of the nervous system by regulating mitochondrial function. This newly discovered epigenetic regulation of mitochondrial function is critical for achieving healthy aging of the brain. Given the reversible nature of epigenetic regulation, BAZ2B and EHMT1 emerge as promising drug targets for combating behavioral and cognitive aging.



Researchers Identify Novel Anti-aging Targets----Chinese Academy of Sciences

 

[JSCh]

NEWS AND VIEWS * 26 FEBRUARY 2020
Metallic glasses rejuvenated to harden under strain
Metallic glasses are much stronger than conventional metals, but form certain instabilities under stress that lead to fracture. A process known as rejuvenation has been shown to solve this problem.

Frans Spaepen

Metallic glasses are formed by cooling melted alloys under conditions that prevent the melt from crystallizing1. They have remarkable mechanical properties — in particular, they can be subjected to high forces and undergo a large amount of deformation before they stop behaving elastically and start to deform permanently (plastically). However, they have one key weakness: they are prone to catastrophic failure under stress because they soften during plastic deformation, rather than hardening, as crystalline metals do. Writing in Nature, Pan et al.2 report a method for preparing metallic glasses that causes them to harden during plastic deformation, thereby avoiding the instabilities that lead to failure.

If you take a paper clip and bend it, you’ll find that more force is needed as you bend it to an increasingly sharp angle. This is an example of work, or strain, hardening — the strengthening of a material through plastic deformation. At the atomic scale, the plastic deformation of metallic crystals in the wire is caused by the motion of ‘dislocations’. These linear defects in the crystal structure multiply, intersect and entangle as deformation proceeds, thereby getting in each other’s way and strengthening the material3. This makes work hardening one of the most complex problems in science: it needs to be understood at many length scales, from the atomic-scale lengths of the dislocation cores, through the nano- and micrometre scales involved in dislocation interactions and structures, to the macroscale lengths associated with crack propagation and the structural stability of bulk materials.


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Metallic glasses rejuvenated to harden under strain | Nature

 

[JSCh]

FEBRUARY 28, 2020
Innovative switching mechanism improves ultrafast control of microlasers
by Harbin Institute of Technology

Ultrafast control of the quasi-BIC microlasers. (A) Schematic of two-beam pumping experiments. Two beams are spatially detuned with a distance d < 2R, being shifted temporally with a delay time τ. The insets show the far-field emission patterns from the perovskite metasurface under both symmetric and asymmetric excitations. (B) Transition from a BIC microlaser to a linearly-polarized laser. I1,2 are the intensities at the marked regions in the insert to (A). Insets show the corresponding beam profiles. (C) Reverse process of (B). (D) Transition from a donut beam to two-lobe beam and back within a few picoseconds. Red curves are guiding lines for the calculation of the transition time. Credit: Science (2020). DOI: 10.1126/science.aba4597

The all-optical switch is a kind of device that controls light with light, which is the fundamental building block of modern optical communications and information processing. Creating an efficient, ultrafast, and compact all-optical switch has been recognized as the key step for the developments of next-generation optical and quantum computing. In principle, photons don't interact with one another directly in the low power linear regime, and a cavity is usually needed to resonantly enhance the field of control light and increase the interaction. In early work, the performance of all-optical switches has been improved rapidly by optimizing resonators such as microrings or photonic crystals. For further improvements, the research area reaches the limit—the trade-off between ultralow energy consumption and ultrashort switching time.

"Low energy consumption usually requires a high Q factor of the resonator, whereas the longer lifetime high-Q mode imposes an obstacle for improving switching speed," said Qinghai Song from Harbin Institute of Technology, China. "An alternative approach with plasmonic nanostructure has been recently exploited to break the trade-off. The inserting and propagating loss is as large as 19 dB and additional power consumption is required to amplify the signals."

The lasing actions at the topologically protected bounded states in the continuum has the potential to eventually solve this long-standing challenge. In Science, researchers from Harbin Institute of Technology, Australian National University and City University of New York detail their innovation of the switching mechanism at the topologically protected bounded states in the continuum (BICs), which offers an ultrafast transition of microlaser emission from a radially polarized donut beam to linearly polarized lobes and vice versa. The extremely high Q factor of the BICs can dramatically reduce the laser threshold and eventually break the above trade-off in conventional all-optical switches.

The next step of this research is to integrate cascade-wise several such switchable microlasers with an integrated photonic chip and to perform optical logic operations. This is the prerequisite for the ultimate goal—optical or quantum computing.


...

https://phys.org/news/2020-02-mechanism-ultrafast-microlasers.html

More information: Can Huang et al. Ultrafast control of vortex microlasers, Science (2020). DOI: 10.1126/science.aba4597

 

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Novel Pulse Duration Achieved by 1 PW/0.1 Hz Laser Beamline in SULF Facility----Chinese Academy of Sciences
By ZHANG Nannan | Mar 04, 2020

Significant advances on ultra-intense and ultra-short laser technology have led numerous laboratories to develop table-top PW-class laser systems as a means of investigating laser-matter interactions in relativistic regime. The repetition rate of PW-class femtosecond lasers is an important issue for their practical applications. And the development of repetitive PW-class lasers has attracted a great attention in recent years.

Shanghai superintense ultrafast laser facility (SULF) is a large-scale scientific project located in Shanghai, China. The project was formally launched and funded in 2016. The SULF facility mainly consists of two laser beamlines, SULF-10PW beamline operating at one shot per minute and SULF-1PW beamline operating at 0.1Hz repetition rate. This facility can provide repetitive PW-level and 10PW-level laser pulses for scientific researches on dynamic of materials under extreme conditions (DMEC), ultrafast sub-atomic physics (USAP), and big molecule dynamics and extreme-fast chemistry (MODEC).

The recent progress on the 1PW/0.1Hz laser beamline of SULF was reported on High Power Laser Science and Engineering. The SULF-1PW beamline is a typical double-CPA system equipped with a novel temporal filter combining the techniques of cross-polarized wave generation (XPWG) and femtosecond optical parametric amplication (OPA).

In the study, the SULF-1PW beamline could generate laser pulses of 50.8J at 0.1Hz after the final amplifier, and the shot-to-shot energy fluctuation of the amplified pulse was as low as 1.2% (std). After compression, pulse duration of 29.6fs was achieved, which could support a maximal peak power of 1PW.

Benefited from the large-energy and high-contrast seed pulses generated by the novel temporal filter, the contrast ratio at -80ps before the main pulse was measured to be 2.5×10-11 in the SULF-1PW beamline. After optimization of the angular dispersion in the grating compressor, the maximal focused peak intensity might reach 2.7×1019W/cm2 even with an f/26.5 off-axis parabolic mirror.

Moreover, the horizontal and vertical angular pointing fluctuations in one hour were measured to be 1.89 μrad (std) and 2.45 μrad (std) respectively. The moderate repetition rate, the good stability and the high temporal contrast make the SULF-1PW beamline a desirable driving laser for laser-matter interactions in relativistic regime.

The SULF-1PW laser beamline is now in the phase of commissioning, while preliminary experiments of particle acceleration and secondary radiation have been implemented. 300MeV quasi-monoenergetic electrons was repetitively produced under ~300 TW/0.1Hz laser condition. Moreover, the maximum proton energy of 14 MeV was also obtained under ~ 400 TW/0.1Hz laser condition.

The SULF research group from Shanghai Institute of Optics and Fine mechanics of the Chinese Academy of Sciences, comments that the progress on the preliminary experiments and the stable daily operation of the laser have demonstrated the availability of SULF-1PW beamline. The following works would be focused on the further improvement of pulse spatial-temporal quality. By utilization of acousto-optic programmable dispersive filter and deformable mirror, a higher focused peak intensity can be expected in the near future.

The layout of SULF facility. (Image by SIOM)

 

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How a Magnet Could Help Boost Understanding of Superconductivity
March 4, 2020

Todd Bates
848-932-0550
todd.bates@rutgers.edu

Entangled electrons in quantum mechanics can be visualized as connected by an invisible thread, so an "up-spin" on the left electron (red) forces the other electron to be "spin-down" (red) & vice-versa (green). Image: Yashar Komijani

Physicists have unraveled a mystery behind the strange behavior of electrons in a ferromagnet, a finding that could eventually help develop high temperature superconductivity.

A Rutgers co-authored study of the unusual ferromagnetic material appears in the journal Nature.

The Rutgers Center for Materials Theory, a world leader in the field, studies “quantum phase transitions.” Phase transitions, such as when ice melts, usually require heat to jiggle atoms and melt ice crystals. Quantum phase transitions are driven by the jiggling of atoms and electrons that result from fluctuations that never cease even at low temperatures.

A quantum phase transition can be achieved by tuning a material to enhance quantum fluctuations, either by applying a magnetic field or exposing it to intense pressure when the temperature is near absolute zero. In certain quantum phase transitions, the quantum fluctuations become infinitely intense, forming a “quantum critical point.” These unusual states of matter are of great interest because of their propensity to form superconductors. Think of it as like an electronic stem cell, a form of matter that can transform itself in many ways.

Meanwhile, in the weird world of quantum mechanics, “entanglement” allows something to be in two different states or places at the same time. The Austrian physicist Erwin Schrödinger’s famous thought experiment, which features a cat that is simultaneously dead and alive, is an example of entanglement.

Inside materials with electrons moving through them, entanglement often involves the spin of electrons, which can be simultaneously up and down. Typically, only electrons near each other are entangled in quantum materials, but at a quantum critical point, the entanglement patterns can change abruptly, spreading out across the material and transforming it. Electrons, even distant ones, become entangled.

Ferromagnets are an unlikely setting for studying quantum entanglement because the electrons moving through them align in one direction instead of spinning up and down. But physicists found that the ferromagnetism in “Cerge,” (CeRh6Ge4) a ferromagnet, must have a large amount of entanglement with electrons that spin up and down and are connected with each other. That had never been seen in ferromagnets.

“We believe our work, connecting entanglement with the strange metal and ferromagnets, provides important clues for our efforts to understand superconductors that work at room temperature,” said co-author Piers Coleman, a professor in the Department of Physics and Astronomy in the School of Arts and Sciences at Rutgers University–New Brunswick. “As we learn to understand how nature controls entanglement in matter, we hope we’ll develop the skills to control quantum entanglement inside quantum computers and to design and develop new kinds of quantum matter useful for technology.”

Rutgers scientists have used some of their findings to propose a new theory for a family of iron-based superconductors that were discovered about 10 years ago. “If we are right, these systems, like ferromagnets, are driven by forces that like to align electrons,” Coleman said.

Yashar Komijani, a Rutgers post-doctoral associate, is one of three co-lead authors. Scientists at Zhejiang University in China, Max Planck Institute for Chemical Physics of Solids in Germany and Nanjing University in China contributed to the study.


https://www.rutgers.edu/news/how-magnet-could-help-boost-understanding-superconductivity

 

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"The CSNS is expected to reach its design beam power of 100 KW in three years or less after it passed the national acceptance because we have taken fewer detours thanks to the experience of our foreign peers. Moreover, we Chinese always work hard," Xu explained.

To Xu and his colleagues, working overtime is quite normal. Xu once worked for about 37 hours straight without a break. "I didn't feel sleepy at all. I used to work on the computer, but when I saw the devices running as expected step by step, I was really excited and couldn't wait to carry out the next test," Xu said.

Scientists hope to eventually increase the beam power of the CSNS from 100 KW to 500 KW. To meet the goal, they have reserved room for further modifications and upgrading in the initial design. Now the researchers have started to work on the plan to upgrade the accelerators for the CSNS phase II project.

"One of the great joys of studying physics is being able to explore and get closer to the essence of the world, and the spallation neutron source is helping us to realize it," Xu said.

CSNS Beam Power Reaches Design Goal Ahead of Schedule----Chinese Academy of Sciences
By LIU Jia | Mar 05, 2020

The China Spallation Neutron Source (CSNS) conducted on-schedule beam commissioning from Feb. 3 to Feb. 28, thus achieving its design goal of 100kW 18 months ahead of schedule. Since then it has conducted stable operations at 100 kW.

CSNS project passed the national acceptance and was officially opened to users on Aug. 23, 2018. Based on the commissioning and operating experience of other facilities around the world, scientists had planned for CSNS beam power to reach its design goal three years after acceptance. Since then, plans were made to gradually increasing the beam power and much efforts were paid by the CSNS team to achieve its design goal faster. In September 2018, the operating beam power was 20kW. In January 2019, the beam power was increased to 50kW. In October 2019, the beam power was increased to 80kW, and now it has achieved the design goal of 100kW.

The hardest part of high power accelerator beam commissioning is to control the beam loss. CSNS has performed well, since the uncontrollable beam loss at 100kW is even less than when operated at 80kW.

Besides the machine development, CSNS has also achieved a successful operation for user experiments in 2019. CSNS originally planned to provide 3600 hours of beam time to users. In fact, it provided a total of 4576 hours, for an beam availability of accelerator operation of 92.6%.

The efficiency of CSNS's recent beam commissioning offers valuable design-related experience for the upcoming CSNS Phase II project.

 

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NEWS AND VIEWS * 11 MARCH 2020
Tiny bird fossil might be the world’s smallest dinosaur
A tiny skull trapped in 99-million-year-old amber suggests that some of the earliest birds evolved to become miniature. The fossil illustrates how ancient amber can act as a window into the distant past.

Roger B. J. Benson

Dinosaurs were big, whereas birds — which evolved from dinosaurs — are small. This variation is of great importance, because body size affects lifespan, food requirements, sensory capabilities and many other fundamental aspects of biology. The smallest dinosaurs1 weighed hundreds of grams, but the smallest living bird, the bee hummingbird (Mellisuga helenae)2, weighs only 2 grams. How did this difference come about, and why? In a paper in Nature, Xing et al.3 describe the tiny, fossilized, bird-like skull of a previously unknown species, which they name Oculudentavis khaungraae. The discovery suggests that miniature body sizes in birds evolved earlier than previously recognized, and might provide insights into the evolutionary process of miniaturization.


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Tiny bird fossil might be the world’s smallest dinosaur | Nature

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The bird in amber: A tiny skull from the age of dinosaurs
Mar 11, 2020
nature video

A tiny new species of bird-like dinosaur has been discovered, preserved in a lump of 99-million-year-old amber. The tooth-filled skull is only 7.1mm long, suggesting that this ancient creature would have been the size of a hummingbird - far smaller than other dinosaurs known from that time. Unusual features include large, side-facing eyes and a large number of sharp teeth suggesting a predatory lifestyle. The species has been named Oculudentavis khaungraae and is evidence of previously unimagined biodiversity in the Mesozoic era.

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https://twitter.com/x/status/1239838887750422528

 

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NEWS RELEASE 19-MAR-2020
Glucagon receptor structures reveal G protein specificity mechanism
CHINESE ACADEMY OF SCIENCES HEADQUARTERS

G protein-coupled receptors (GPCRs) play essential roles in cell signal transduction and serve as important therapeutic targets for a large number of diseases. Upon binding to extracellular agonists, GPCRs stimulate various signaling pathways by recruiting different G proteins (Gs, Gi, Gq, etc.) to mediate a wide variety of physiological functions. The selective coupling between a GPCR and specific G proteins is critical for the biological action of the receptor.

However, the molecular details that define how an individual GPCR recognizes different G protein subtypes remain elusive, thus limiting the understanding of mechanisms of GPCR signal transduction.

In a study published in Science on Mar. 20, a group led by WU Beili and ZHAO Qiang at the Shanghai Institute of Materia Medica (SIMM) of the Chinese Academy of Sciences (CAS), a group led by SUN Fei at the Institute of Biophysics of CAS, and a group led by Denise Wootten from Monash University, determined two cryo-electron microscopy (cryo-EM) structures of the human glucagon receptor (GCGR) in complex with its cognate agonist glucagon and distinct classes of G proteins, Gs or Gi.

These structures, for the first time, provide a detailed molecular map of interaction patterns between a GPCR and different G protein subtypes, and unexpectedly disclose many molecular features that govern G protein specificity, thereby greatly deepening the understanding of GPCR signaling mechanisms.

GCGR, a member of the class B GPCR family, is critical to glucose homeostasis by triggering the release of glucose from the liver, making it a potential drug target for type 2 diabetes and obesity.

Although GCGR canonically exerts its physiological action through Gs signaling, it can also couple to other G proteins such as Gi and Gq, leading to diverse cellular responses. In 2017 and 2018, the scientists at SIMM determined the crystal structures of the full-length GCGR bound to a negative allosteric modulator or a partial peptide agonist, providing insights into signal recognition and modulation of class B GPCRs.

This time, the scientists made further progress by solving the complex structures of GCGR bound to two transducer proteins with opposing biological activities. This study offers valuable insights into pleiotropic GPCR-G protein coupling and G protein specificity. Notably, it revealed that the sixth transmembrane helix (helix VI) of GCGR adopts a similar outward shift in the two G protein-bound GCGR structures, forming a common binding cavity to accommodate Gs and Gi. This is contrary to the hypothesis based on the previously determined GPCR-G protein complex structures, which proposed that the positional difference of helix VI is a major discriminator in the coupling specificity of Gs and Gi.

The common G protein binding pocket observed in the GCGR-G protein complex structures is consistent with the signaling pleiotropy of GCGR and allows for maximal efficiency in activating various pathways. Although GCGR couples to both G proteins through the common pocket, it does so with different interaction patterns, which account for G protein specificity. The measured interaction interface between GCGR and Gs is much larger than for Gi, resulting in higher binding affinity of Gs to the receptor. This offers a structural basis for the preferential coupling of GCGR to Gs.

Based on the structures of GCGR-Gs and GCGR-Gi complexes, the scientists performed extensive functional studies using techniques such as mutagenesis, G protein activation and cell signaling to investigate the roles of key residues in the receptor-G protein binding interface in Gs and Gi activation.

The results show that conformational differences of intracellular loops and residue side chains in the receptor are sufficient to guide G protein selectivity. The interactions contributed by the second intracellular loop (ICL2) and helix VII/VIII junction of the receptor play a crucial role in Gs coupling, while the other two intracellular loops, ICL1 and ICL3, and the receptor hydrophobic intracellular binding cavity are more important for Gi recognition.

These findings extend knowledge about GPCR activation, pleiotropic coupling, and G protein specificity. They also present new opportunities for drug discovery by designing biased ligands to selectively block one specific signaling pathway, thus resulting in reduced side effects.


Glucagon receptor structures reveal G protein specificity mechanism | EurekAlert! Science News

 

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China Focus: Chinese researchers grow organoids from mouse stem cells
Xinhua, March 23, 2020

SHANGHAI, March 23 (Xinhua) -- Using stem cells from mice, Chinese researchers have grown tiny functioning segments of insulin-producing organs, called islet organoids, in a laboratory, in a bid to find ways to treat diabetes.

In a recent study published in the scientific journal Cell, a research team, led by the Shanghai Institute of Biochemistry and Cell Biology under the Chinese Academy of Sciences, identified the stem cells in adult mouse pancreatic islets and established an in vitro culture system for the long-term growth of the islet organoids.

According to the study, with the help of single-cell sequencing technologies, the researchers found a new group of cell types called "Procr+cells" in mice. Experiments then showed that the Procr+cells are stem cells in mouse islets that can differentiate all islet cell types.

They cultured the Procr+cells in vitro and established an in vitro system that can derive functional islet organoids for the long term.

The artificial islet organoids are very similar to the mouse islets in function and morphology. When the researchers transplanted these organoids into diabetic mice, the blood sugar levels of these mice became normal and their symptoms of diabetes went away.

Diabetes is one of the major chronic diseases that threaten human health. Many patients need to use insulin for lifelong treatment due to insufficient insulin secretion caused by abnormal functions of islet cells.

Islet transplantation has been considered an approach for diabetic patients, but it is limited due to the shortage of donors. Scientists have been investigating better ways to treat diabetes.

Zeng Yi, the lead researcher, said the study is a major breakthrough in basic stem cell research. It has for the first time identified stem cells in mouse islets, answering a long-standing controversial question of whether there are stem cells in islets.

But Zeng also emphasized that the current research results have only been proved in mice.

"Answering questions such as can stem cells also exist in human islets and can they also be cultured into islets in vitro still needs further exploration and study," Zeng said.