Heavens

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical compounds or for biomolecules in solution and is therefore of great industrial importance. In this reaction, charged particles encounter molecules and one molecular group is replaced by another. For a long time, science has been trying to reproduce these processes at the interface of chemistry and physics in the laboratory and to understand them at the atomic level. The team headed by experimental physicist Roland Wester at the Institute of Ion Physics and Applied Physics at the University of Innsbruck is one of the world's leading research groups in this field.

Proton Exchange Reaction Strengthened

In a specially constructed experiment, the physicists from Innsbruck collide the charged particles with molecules in vacuum and examine the reaction products. To determine if targeted vibration excitation has an impact on a chemical reaction, the scientists use a laser beam that excites a vibration in the molecule. In the current experiment, negatively charged fluorine ions (F-) and methyl iodide molecules (CH3I) were used. In the collision, due to the exchange of an iodine bond with a fluorine bond, a methyl fluoride molecule and a negatively charged iodine ion are formed. Before the particles meet, the laser excites carbon-hydrogen stretching vibrations in the molecule. "Our measurements show that the laser excitation does not enhance the exchange reaction," says participating scientist Jennifer Meyer. "The hydrogen atoms just seem to be watching the reaction." The result is substantiated by the observation that a competing reaction strongly increases. In this other proton exchange reaction, a hydrogen atom is torn from the methyl iodide molecule and hydrogen fluoride (HF) is formed. "We let the two species collide 20 times per second, the laser is applied in every second collision, and we repeat the process millions of times," explains Meyer. "Whenever the laser is irradiated, this proton exchange reaction is drastically amplified." Theoretical chemists from the University of Szeged in Hungary and the University of New Mexico in the USA have further supported the experimental results from Innsbruck using computer simulations.

Spectator Role in Focus

In high-precision investigations of chemical processes, only the simplest model, the reaction of an atom with a diatomic molecule, has so far been studied. "Here, all particles are inevitably involved in the reaction. There are no observers", says Roland Wester. The system that we are now studying is so large that observers appear. However it is still small enough to be able to study these observers very precisely." For large molecules, there are many particles that are not directly involved in the reaction. The investigation of their role is one of the long-term goals of the Wester group. The researchers also want to refine the current experiment in order to uncover further possible subtle effects.

Laser Controlled Chemistry

The question of whether certain reactions can be intensified by the targeted excitation of individual molecular groups is also an important consideration. "If you understand something, you can also exercise control," sums up Roland Wester. "Instead of stimulating a reaction through heat, it may make sense to stimulate only individual groups of molecules to achieve a specific reaction," adds Jennifer Meyer. This may avoid competing reaction processes that are a common problem in industrial chemistry or biomedical research. The more precise the control over the chemical reaction, the less waste is produced and the lower the costs.

The current paper has been published in the journal Science Advances. The research was funded by, among others, the Austrian Science Fund FWF and the Austrian Academy of Sciences.

Uranus was hit by a massive object roughly twice the size of Earth that caused the planet to tilt and could explain its freezing temperatures, according to new research.

Astronomers at Durham University, UK, led an international team of experts to investigate how Uranus came to be tilted on its side and what consequences a giant impact would have had on the planet's evolution.

The team ran the first high-resolution computer simulations of different massive collisions with the ice giant to try to work out how the planet evolved.

The research confirms a previous study which said that Uranus' tilted position was caused by a collision with a massive object - most likely a young proto-planet made of rock and ice - during the formation of the solar system about 4 billion years ago.

The simulations also suggested that debris from the impactor could form a thin shell near the edge of the planet's ice layer and trap the heat emanating from Uranus' core. The trapping of this internal heat could in part help explain Uranus' extremely cold temperature of the planet's outer atmosphere (-216 degrees Celsius, -357 degrees Fahrenheit), the researchers said.

The findings are published in The Astrophysical Journal.

Lead author Jacob Kegerreis, PhD researcher in Durham University's Institute for Computational Cosmology, said: "Uranus spins on its side, with its axis pointing almost at right angles to those of all the other planets in the solar system. This was almost certainly caused by a giant impact, but we know very little about how this actually happened and how else such a violent event affected the planet.

"We ran more than 50 different impact scenarios using a high-powered super computer to see if we could recreate the conditions that shaped the planet's evolution.

"Our findings confirm that the most likely outcome was that the young Uranus was involved in a cataclysmic collision with an object twice the mass of Earth, if not larger, knocking it on to its side and setting in process the events that helped create the planet we see today."

There has been a question mark over how Uranus managed to retain its atmosphere when a violent collision might have been expected to send it hurtling into space.

According to the simulations, this can most likely be explained by the impact object striking a grazing blow on the planet. The collision was strong enough to affect Uranus' tilt, but the planet was able to retain the majority of its atmosphere.

The research could also help explain the formation of Uranus' rings and moons, with the simulations suggesting the impact could jettison rock and ice into orbit around the planet. This rock and ice could have then clumped together to form the planet's inner satellites and perhaps altered the rotation of any pre-existing moons already orbiting Uranus.

The simulations show that the impact could have created molten ice and lopsided lumps of rock inside the planet. This could help explain Uranus' tilted and off-centre magnetic field.

Uranus is similar to the most common type of exoplanets - planets found outside of our solar system - and the researchers hope their findings will help explain how these planets evolved and understand more about their chemical composition.

Co-author Dr Luis Teodoro, of the BAER/NASA Ames Research Center, said: "All the evidence points to giant impacts being frequent during planet formation, and with this kind of research we are now gaining more insight into their effect on potentially habitable exoplanets."

Among the most studied protein machines in history, mTORC1 has long been known to sense whether a cell has enough energy to build the proteins it needs to multiply as part of growth. Because faulty versions of mTORC1 contribute to the abnormal growth seen in cancer, drugs targeting the complex have been the subject of 1,300 clinical trials since 1970.

Now a new study finds that mTORC1 has a second function of profound importance: controlling how "crowded" human cells become.

Led by researchers at NYU School of Medicine and published online in the journal Cell on June 21, the finding explains for the first time the workings of a physical quality that cells use to regulate their actions, and more closely links malfunctions in mTORC1-related genes to several diseases of aging.

"Our results begin to clarify how mTORC1-driven changes in crowding could cause the insides of human cells to solidify as a person ages, packing more proteins into the same space and interfering with functions that require them to move around," says senior study author Liam Holt, PhD, assistant professor in the Institute for Systems Genetics at NYU Langone Health. "This work may also help explain the origin of the solid protein clumps that appear in the cells of patients with cardiovascular diseases, diabetes and Alzheimer's."

Freedom to Move

Based on past studies, biologists have long concluded that cells require for survival a limit on the number of proteins in their fluid-filled inner spaces, the cytoplasm where many cellular functions occur.

Specifically, the current study found that the mTORC1 complex controls crowding by determining the number of ribosomes, multi-protein machines that build other proteins there.

By engineering cells to make their own glowing tracers to measure crowding, the researchers showed that, by adjusting levels of mTORC1 action, they could cause a two-fold swing in the ability of multi-protein cellular machines to move around (diffuse) in the cytoplasm of human kidney cells.

Experiments further confirmed ribosomes as the main "crowding agent" regulated by mTORC1, influencing the physical environment of large molecules - like those particularly important to cell growth and death - but leaving alone reactions depending on single proteins.

Many proteins are barely dissolved in the cell, with as much chance of glomming onto each other as to interact with the liquid surrounding them. Crowding increases the chances that these like-structured molecules will together undergo a shift from one state of matter to another (e.g. liquid to a solid), say the authors. In one such "phase transition," similar proteins spread out in the cytoplasmic fluid come together to form dense liquid droplets, the way oil forms its own globs in vinegar.

"The biological consequences of phase changes are an area of intense inquiry right now, with emerging theories suggesting that genetic material, for instance, forms droplets that help to turn genes on and off," says Holt, also faculty in the Department of Biochemistry and Molecular Pharmacology at NYU Langone Health.

By separating protein complexes into phase-separated droplets, or into even denser gels, the cell forms semi-compartments that do not mix as freely with their surroundings, spaces in which more distinct, faster biological reactions can proceed.

The current study suggests that malfunctioning mTORC1 may increase crowding, and therefore cause droplets and gels to become the solids found in cells with diseases of aging - like the tau fibers that build up in the brain tissue of Alzheimer's patients.

Furthermore, the decades of limited success by mTORC1-based cancer drugs could proceed in part from the crowding effect, says Holt. For example, mTORC1 activation may be important to initiate cancer in some cases, but could hinder aggressive growth later as cancer cells become crowded with ribosomes. Thus, the current line of work may help to set new guidelines about when to use mTORC1 inhibitors based on the stage of a patient's cancer.

Moving forward, the team also is studying how crowding affects phase change in different cell types, with the long-term goal of designing anti-crowding therapies for neurodegeneration and cancer.

RIVERSIDE, Calif. (http://www.ucr.edu) -- Earth's first complex animals were an eclectic bunch that lived in the shallow oceans between 580-540 million years ago.

The iconic Dickinsonia -- large flat animals with a quilt-like appearance -- were joined by tube-shaped organisms, frond-like creatures that looked more like plants, and several dozen other varieties already characterized by scientists.

Add to that list two new animals discovered by a UC Riverside-led team of researchers:

Obamus coronatus, a name that honors President Barack Obama's passion for science. This disc-shaped creature was between 0.5-2 cm across with raised spiral grooves on its surface. Obamus coronatus did not seem to move around, rather it was embedded to the ocean mat, a thick layer of organic matter that covered the early ocean floor.

Attenborites janeae, named after the English naturalist and broadcaster Sir David Attenborough for his science advocacy and support of paleontology. This tiny ovoid, less than a centimeter across, was adorned with internal grooves and ridges giving it a raisin-like appearance.

The discovery of Obamus coronatus was published online June 14 in the Australian Journal of Earth Sciences, or AJES, and the Attenborites janeae paper is forthcoming in the same journal. The studies were led by Mary Droser, a professor of paleontology in UCR's Department of Earth Sciences. Both papers will be included in print in a 2019 thematic AJES issue focusing on South Australia's Flinders Ranges region, where the discoveries were made.

Part of the Ediacara Biota, the soft-bodied animals are visible as fossils cast in fine-grained sandstone that have been preserved for hundreds of millions of years. These Precambrian lifeforms represent the dawn of animal life and are named after the Ediacara Hills in the Flinders Ranges, the first of several areas in the world where they have been found.

In the hierarchical taxonomic classification system, the Ediacara Biota are not yet organized into families, and little is known about how they relate to modern animals. About 50 genera have been described, which often have only one species.

"The two genera that we identified are a new body plan, unlike anything else that has been described," Droser said. "We have been seeing evidence for these animals for quite a long time, but it took us a while to verify that they are animals within their own rights and not part of another animal."

The animals were glimpsed in a particularly well-preserved fossil bed described in another paper published by Droser's group that will be included in the Flinders Ranges issue of AJES. The researchers dubbed this fossil bed "Alice's Restaurant Bed," a tribute to the Arlo Guthrie song and its lyric, "You can get anything you want at Alice's Restaurant."

"I've been working in this region for 30 years, and I've never seen such a beautifully preserved bed with so many high quality and rare specimens, including Obamus and Attenborites," Droser said. "The AJES issue on the Flinders Ranges will support South Australia's effort to obtain World Heritage Site status for this area, and this new bed demonstrates the importance of protecting it."

Halocynthia roretzi is a solitary ascidian, whose body is entirely covered with the tissue called the 'tunic'. While the tunic has cellulose Iβ, chitin sulfate-like polysaccharide, blood vessels, nerve cells and hemocytes, it also has the components contributing to mechanical properties, including α-smooth muscle actin. The previous reports indicated that the tunic of Halocynthia roretzi responded to mechanical stimuli and deformed itself. In this study, the mechanism of responding the mechanical stimuli in the tunic was investigated. When the tunic was just put into the artificial seawater without the mechanical stimuli at 5 °C, an increment in the mass of the tunic, corresponding to that in the water content of the tunic, was observed. Also, the increment per day became higher at the position closer to the siphon, where the seawater flows in and out. When the mechanical stimuli were given to the tunic at the temperature less than 10°C, the mass was decreased for all the positions. In addition, the increment of the mass per day at the siphon was reduced after the mechanical stimuli were given while those at other positions were not. The distribution of the layer at the outermost surface of the tunic, positive for the Hematoxylin-Eosin stain, was varied in each position. The tunic position with larger distribution size and thickness of the layer showed smaller increment in the mass of the tunic. The tunic discharged nitrate and dissolved organic matter, the ratio of which was kept constant whether the mechanical stimuli were given to the tunic or not. The concentrations of nitrate and dissolved organic matter increased not just after giving the mechanical stimuli to the tunic, but 5 days later.

For more information, please visit: https://benthamopen.com/ABSTRACT/CHEM-5-1

A team of scientists led by University of Hawai'i at Manoa (UH Mānoa) School of Ocean and Earth Science and Technology (SOEST) researcher Hope Ishii, discovered that certain interplanetary dust particles (IDPs) contain dust leftover from the initial formation of the solar system.

The initial solids from which the solar system formed consisted almost entirely of amorphous silicate, carbon and ices. This dust was mostly destroyed and reworked by processes that led to the formation of planets. Surviving samples of pre-solar dust are most likely to be preserved in comets--small, cold bodies that formed in the outer solar nebula.

In a relatively obscure class of IDPs believed to originate from comets, there are tiny glassy grains called GEMS, or glass embedded with metal and sulfides--typically only tens to hundreds of nanometers in diameter, less than 1/100th the thickness of human hair.

Using transmission electron microscopy, Ishii and colleagues made maps of the element distributions and discovered that these glassy grains are made up of subgrains that aggregated together in a different environment and prior to the formation of the comet parent body. This aggregate is encapsulated by carbon of a different type than the carbon that forms a matrix gluing together GEMS and other components of cometary dust.

The types of carbon that rims the subgrains and that forms the matrix in these particles decomposes with even weak heating, suggesting that the GEMS could not have formed in the hot inner solar nebula, and instead formed in a cold, radiation-rich environment, such as the outer solar nebula or pre-solar molecular cloud.

"Our observations suggest that these exotic grains represent surviving pre-solar interstellar dust that formed the very building blocks of planets and stars," said Ishii, who is based at the UH Manoa Hawai'i Institute of Geophysics and Planetology. "If we have at our fingertips the starting materials of planet formation from 4.6 billion years ago, that is thrilling and makes possible a deeper understanding of the processes that formed and have since altered them."

The University of Hawai'i has a strong footprint in space science and state-of-the-art instrumentation and is recognized as world-class in this field.

"This is an example of research that seeks to satisfy the human urge to understand our world's origins and serves the people of Hawai'i by boosting our reputation for excellence in space science and as a training ground for our students to be engaged in exciting science," said Ishii. In the future, the team plans to search the interiors of additional comet dust particles, especially those that were well-protected during their passage through the Earth's atmosphere, to increase understanding of the distribution of carbon within GEMS and the size distributions of GEMS subgrains.

Note: This press release was adapted from an original release by the University of Hawaii at Manoa in Honolulu.

Experiments conducted at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) helped to confirm that samples of interplanetary particles - collected from Earth's upper atmosphere and believed to originate from comets - contain dust leftover from the initial formation of the solar system.

An international team, led by Hope Ishii, a researcher at the University of Hawaii at Manoa (UH Manoa), studied the particles' chemical composition using infrared light at Berkeley Lab's Advanced Light Source (ALS). Scientists also explored their nanoscale chemical makeup using electron microscopes at the Lab's Molecular Foundry, which specializes in nanoscale R&D, and at the University of Hawaii's Advanced Electron Microscopy Center.

The study was published online June 11 in the journal Proceedings of the National Academy of Sciences.

The initial solids from which the solar system formed consisted almost entirely of carbon, ices, and disordered (amorphous) silicate, the team concluded. This dust was mostly destroyed and reworked by processes that led to the formation of planets. Surviving samples of pre-solar dust are most likely to be preserved in comets - small, cold bodies that formed in the outer solar nebula.

(See a related article - From Moon Rocks to Space Dust: Berkeley Lab's Extraterrestrial Research)

In a relatively obscure class of these interplanetary dust particles believed to originate from comets, there are tiny glassy grains called GEMS (glass embedded with metal and sulfides) that are typically only tens to hundreds of nanometers in diameter, or less than a hundredth of the thickness of a human hair. Researchers embedded the sample grains in an epoxy that was cut into thin slices for the various experiments.

Using transmission electron microscopy at the Molecular Foundry, the research team made maps of the element distributions and discovered that these glassy grains are made up of subgrains that aggregated together in a different environment prior to the formation of the comet.

The nanoscale GEMS subgrains are bound together by dense organic carbon in clusters comprising the GEMS grains. These GEMS grains were later glued together with other components of the cometary dust by a distinct, lower-density organic carbon matrix.

The types of carbon that rim the subgrains and that form the matrix in these particles decompose with even weak heating, suggesting that the GEMS could not have formed in the hot inner solar nebula, and instead formed in a cold, radiation-rich environment, such as the outer solar nebula or pre-solar molecular cloud.

Jim Ciston, a staff scientist at the Molecular Foundry, said the particle-mapping process of the microscopy techniques provided key clues to their origins. “The presence of specific types of organic carbon in both the inner and outer regions of the particles suggests the formation process occurred entirely at low temperatures,” he said.

"Therefore, these interplanetary dust particles survived from the time before formation of the planetary bodies in the solar system, and provide insight into the chemistry of those ancient building blocks."

He also noted that the "sticky" organics that covered the particles may be a clue to how these nanoscale particles could gather into larger bodies without the need for extreme heat and melting.

Ishii, who is based at the UH Manoa's Hawaii Institute of Geophysics and Planetology, said, "Our observations suggest that these exotic grains represent surviving pre-solar interstellar dust that formed the very building blocks of planets and stars. If we have at our fingertips the starting materials of planet formation from 4.6 billion years ago, that is thrilling and makes possible a deeper understanding of the processes that formed and have since altered them."

Hans Bechtel, a research scientist in the Scientific Support Group at Berkeley Lab's ALS, said that the research team also employed infrared spectroscopy at the ALS to confirm the presence of organic carbon and identify the coupling of carbon with nitrogen and oxygen, which corroborated the electron microscopy measurements.

The ALS measurements provided micron-scale (millionths of a meter) resolution that gave an average of measurements for entire samples, while the Molecular Foundry's measurements provided nanometer-scale (billionths of a meter) resolution that allowed scientists to explore tiny portions of individual grains.

In the future, the team plans to search the interiors of additional comet dust particles, especially those that were well-protected during their passage through the Earth's atmosphere, to increase understanding of the distribution of carbon within GEMS and the size distributions of GEMS subgrains.

A new study by the University of Liverpool, in collaboration with the Universities of Lancaster and Oslo, sheds light on a longstanding question that has puzzled earth scientists.

Using previously unavailable data, researchers confirm a correlation between the movement of plate tectonics on the Earth's surface, the flow of mantle above the Earth's core and the rate of reversal of the Earth's magnetic field which has long been hypothesised.

In a paper published in the journal Tectonophysics, they suggest that it takes around 120-130 million years for slabs of ancient ocean floor to sink (subduct) from the Earth's surface to a sufficient depth in the mantle where they can cool the core, which in turn causes the liquid iron in the Earth's outer core to flow more vigorously and produce more reversals of the Earth's magnetic field.

This study is the first to demonstrate this correlation using records and proxies of global rates of subduction from various sources including a continuous global plate reconstruction model developed at the University of Sydney. These records were compared with a new compilation of magnetic field reversals whose occurrence is locked into volcanic and sedimentary rocks.

Liverpool palaeomagnetist, Professor Andy Biggin, said: "Until recently we did not have good enough records of how much global rates of subduction had changed over the last few hundreds of millions of years and so we had nothing to compare with the magnetic records.

"When we were able to compare them, we found that the two records of subduction and magnetic reversal rate do appear to be correlated after allowing for a time delay of 120-130 million years for the slabs of ocean floor to go from the surface to a sufficient depth in the mantle where they can cool the core.

"We do not know for sure that the correlation is causal but it does seem to fit with our understanding of how the crust, mantle and core should all be interacting and this value of 120-130 million could provide a really useful observational constraint on how quickly slabs of ancient sea floor can fall through the mantle and affect flow currents within it and in the underlying core."

The magnetic field is generated deep within the Earth in a fluid outer core of iron and other elements that creates electric currents, which in turn produces magnetic fields.

The core is surrounded by a nearly 3,000 km thick mantle which although made of solid rock, flows very slowly (mm per year). The mantle produces convection currents which are strongly linked to movement of the tectonic plates but also affect the core by varying the amount of heat that is transferred across the core-mantle boundary.

The Earth's magnetic field occasionally flips its polarity and the average length of time between such flips has changed dramatically through Earth's history. For example, today such magnetic reversals occur on average four times per million years but one hundred million years ago, the field essentially stayed in the same polarity for nearly 40 million years.

Professor Biggin heads up the University's Determining Earth Evolution from Palaeomagnetism (DEEP) research group which brings together research expertise across geophysics and geology to develop palaeomagnetism as a tool for understanding deep Earth processes occurring across timescales of millions to billions of years.

Using the Titan supercomputer at the Oak Ridge Leadership Computing Facility (OLCF), a team of researchers has calculated a fundamental property of protons and neutrons, known as the nucleon axial coupling, with groundbreaking precision.

Led by Andre Walker-Loud of the US Department of Energy's (DOE's) Lawrence Berkeley National Laboratory, the project also used computing resources at DOE's Lawrence Livermore National Laboratory. The OLCF is a DOE Office of Science User Facility located at DOE's Oak Ridge National Laboratory (ORNL).

By applying lattice quantum chromodynamics (QCD)--a numerical method for calculating the underlying physics of the subatomic particles that make up protons and neutrons known as quarks and gluons--the team calculated the nucleon axial coupling with an unprecedented 1 percent precision, meaning all their computational results were in close agreement, or reside within a narrow distribution. The results also accurately matched long-standing experimental results.

"Lattice QCD is the only way we know how to compute properties of strongly interacting matter directly from fundamental theory," Walker-Loud said. "For about a decade it has been an important predictive tool for high-energy physics."

Although lattice QCD is often applied in the atom-smashing world of high-energy physics where scientists model particles interacting within very short distances, it has been a less manageable approach at the size of protons and neutrons (known as nucleons for their essential role in forming nuclei). Instead low-energy, or nuclear, physics problems are often modeled using data-driven, approximate methods.

The new nucleon axial coupling calculation, published in the journal Nature, provides the research community with a critical benchmark for applying lattice QCD to nuclear physics problems. Ultimately, this and other calculations enabled by the team's computational technique could aid in the search for dark matter and help answer other outstanding questions about the nature of the universe.

Fundamental forces

Of the four fundamental forces by which matter interacts, the "strong" force gets its name for being stronger than the other three forces: the weak force, electromagnetism, and gravity.

Because the strong force is exerted at short distances--the space between particles in the nucleus of an atom--it is perhaps not as well known as gravity or electromagnetism, which can affect matter at visible scales. The strong force shapes an atom by bringing together, first, the quarks that make up nucleons and, second, the nucleons that make up the nucleus.

When scientists refer to the "underlying" or "fundamental" physics of nuclei, they are talking about the strong force interactions of quarks and gluons, including the property of color charge that influences how quarks are bound together and from which the study of quantum "chromo"-dynamics gets its name. Lattice QCD formulates these strong force interactions on a 4D grid, or lattice, representing space-time. The weak force is also a lesser known but fundamentally important force in nuclear physics because it drives the decay and transformation of an unstable particle into other particles, contributing to the rich diversity of elements and their many properties.

By changing a down quark to an up quark, a weak force interaction known as the weak axial current drives the decay of a neutron into a proton. The nucleon axial coupling, or gA, is the strength by which the weak axial current couples to nucleons, which are held together by the strong force. Influenced by both of these fundamental forces, the nucleon axial coupling is an important value for making predictions about neutron decay and exploring new physics beyond the current Standard Model of Particle Physics.

"When we talk about the possibility of using lattice QCD for nuclear physics models, members of the experimental community often say 'Come back when you have gA' because it is such an important benchmark quantity," Walker-Loud said.

Neutron decay is a current topic in dark matter searches, among other questions related to the nature of matter. If dark matter particles are released in neutron decay, as some theories suggest, then it might explain the presence of dark matter in the universe and offer a means of detection.

"There is a giant experimental effort to look for new physics in nuclear physics backgrounds," Walker-Loud said. "Dark matter detection is one example. Other examples include looking for slight deviations from the predicted decay pattern of neutrons for which you have to be able to compute the contributions very precisely."

The main reason it is difficult to apply lattice QCD problems to low-energy nuclear physics and get such precise computations, even as computing power increases, is known as the "signal-to-noise" problem. Just as large error bars clutter a graph, uncertainty or noise in computational results complicates researchers' efforts to extract the signal they are seeking.

In the case of nuclear physics applications, a small subatomic particle known as the pion, which mediates nucleon interactions, introduces a lot of uncertainty in lattice QCD calculations.

"The tiny mass of the pion particles generates a lot of unwanted, statistical noise in the results," Walker-Loud said. Reducing the pion mass toward its physical value, which is tiny compared with the neutron mass, is important to accurate calculations but exacerbates the signal-to-noise problem.

Because QCD is a strongly interacting theory, creating an isolated neutron from the vacuum in lattice QCD calculations is nearly impossible. Instead, the neutron is simultaneously created with many other "excited" energy states, such as "breathing" or "resonating" modes of the neutron. As time progresses, these excited states decay away, leaving only the lowest energy state or "ground state" neutron. To calculate properties of the neutron, such as the nucleon axial coupling, these excited state contributions must be filtered out. Ironically, as the excited states decay away later, the signal-to-noise problem increases.

Using traditional lattice QCD methods, calculating the nucleon axial coupling can be a no-win situation. Because of these and other computational challenges, the research community predicted that computing the nucleon axial coupling with a total uncertainty of 2 percent would take a couple more years and require next-generation supercomputers.

"For us to do it with 1 percent uncertainty required us to develop new ideas," Walker-Loud said. "We have to continue to develop new strategies for computing that can accelerate the entire application of lattice QCD to nuclear physics."

Turning down the noise

The team's improved computational strategy reduced the amount of statistical sampling needed for an accurate answer, and GPUs accelerated the subsequent computations.

"We used about a factor of 10 fewer samples than previous projects," Walker-Loud said. "The most computationally expensive calculations could only be performed on Titan, which enabled us to do our calculations about 100 times faster than we would have been able to do so otherwise."

To reduce the signal-to-noise problem, the team's improved method first averaged the interaction of the weak axial current across many points in time as a neutron decays to a proton, as opposed to selecting one interaction time as in previous methods. Second, the method filtered out excited state data, providing the team more control over uncertainty and enabling access to the signal earlier in the simulation time when the data is most precise.

"This was an intense two-and-a-half-year project that only came together because of the great team of people working on it," Walker-Loud said.

The success of the project also relied on publicly available QCD configurations (which allow researchers to model how particles move on the lattice) from the MIMD Lattice Computation Collaboration; the lattice QCD code Chroma developed by USQCD; and QUDA, the lattice QCD library for NVIDIA GPU-accelerated compute nodes.

Walker-Loud said the data from Titan will allow the team to solve other physics problems by reducing the supercomputing cost of these additional results. The team also plans to pursue an even more precise calculation of the nucleon axial coupling on next-generation supercomputers, which could help resolve fine-grained discrepancies in existing experimental results and provide experimentalists looking for corrections to the Standard Model with more narrow search parameters.

Researchers at the University of Colorado Boulder have discovered microbes living in a toxic volcanic lake that may rank as one of the harshest environments on Earth. Their findings, published recently online, could guide scientists looking for signs of ancient life on Mars.

The team, led by CU Boulder Associate Professor Brian Hynek, braved second-degree burns, sulfuric acid fumes and the threat of eruptions to collect samples of water from the aptly-named Laguna Caliente. Nestled in Costa Rica's Poás Volcano, this body of water is 10 million times more acidic than tap water and can reach near boiling temperatures. It also resembles the ancient hot springs that dotted the surface of early Mars, Hynek said.

The Costa Rican lake can support life--but only barely. Hynek and his colleagues found microbes belonging to just a single species of bacteria in the lake water, a rock-bottom level of diversity.

"Even in an extremely harsh environment, there can still be life," said Hynek of the Laboratory for Atmospheric and Space Physics and the Department of Geological Sciences. "But then there's very little life. Mars was just as extreme in its early history, so we should probably not expect to find evidence of large-scale biodiversity there."

Laguna Caliente is chaotic, with water temperatures that can swing wildly in the span of hours and magma channels running under the lake that kick off frequent, geyser-like eruptions.

"We're at the limits of what life on Earth can tolerate," Hynek said. "It's not somewhere you want to spend a lot of time because you'd probably get covered in boiling mud and sulfur from the eruptions."

To search for living organisms in this "fringe" environment, the researchers scanned samples of lake water for DNA. In research published this month in Astrobiology, they found the signature of one species of bacteria belonging to the genus Acidiphilium--a group of microbes that scientists have previously seen in toxic drainage from coal mines and other harsh locations.

"It's not uncommon to find an environment with no life, say in a volcano that's self-sterilizing," Hynek said. "But to find a single type of organism and not a whole community of organisms is very, very rare in nature."

If life did evolve on Mars, Hynek said, it would likely have survived in ways similar to the lake's bacterium--by processing the energy from iron- or sulfur-bearing minerals. Hynek has spent much of his career searching for places on Earth today that look like Mars did nearly four billion years ago, when liquid water was plentiful on the surface.

It's a hard task: Rampant volcanism during that period created volatile and mineral-rich pools of water, giving rise to "Yellowstones all over Mars," Hynek said.

In 2020, NASA is planning to send the Mars 2020 Rover to the Red Planet to hunt for fossil evidence of life. Hynek said that they should look first at these "Yellowstones."

The SPHERE instrument on ESO's Very Large Telescope (VLT) in Chile allows astronomers to suppress the brilliant light of nearby stars in order to obtain a better view of the regions surrounding them. This collection of new SPHERE images is just a sample of the wide variety of dusty discs being found around young stars.

These discs are wildly different in size and shape -- some contain bright rings, some dark rings, and some even resemble hamburgers. They also differ dramatically in appearance depending on their orientation in the sky -- from circular face-on discs to narrow discs seen almost edge-on.

SPHERE's primary task is to discover and study giant exoplanets orbiting nearby stars using direct imaging . But the instrument is also one of the best tools in existence to obtain images of the discs around young stars -- regions where planets may be forming. Studying such discs is critical to investigating the link between disc properties and the formation and presence of planets.

Many of the young stars shown here come from a new study of T Tauri stars, a class of stars that are very young (less than 10 million years old) and vary in brightness. The discs around these stars contain gas, dust, and planetesimals -- the building blocks of planets and the progenitors of planetary systems.

These images also show what our own Solar System may have looked like in the early stages of its formation, more than four billion years ago.

Most of the images presented were obtained as part of the DARTTS-S (Discs ARound T Tauri Stars with SPHERE) survey. The distances of the targets ranged from 230 to 550 light-years away from Earth. For comparison, the Milky Way is roughly 100 000 light-years across, so these stars are, relatively speaking, very close to Earth. But even at this distance, it is very challenging to obtain good images of the faint reflected light from discs, since they are outshone by the dazzling light of their parent stars.

Another new SPHERE observation is the discovery of an edge-on disc around the star GSC 07396-00759, found by the SHINE (SpHere INfrared survey for Exoplanets) survey. This red star is a member of a multiple star system also included in the DARTTS-S sample but, oddly, this new disc appears to be more evolved than the gas-rich disc around the T Tauri star in the same system, although they are the same age. This puzzling difference in the evolutionary timescales of discs around two stars of the same age is another reason why astronomers are keen to find out more about discs and their characteristics.

Astronomers have used SPHERE to obtain many other impressive images , as well as for other studies including the interaction of a planet with a disc , the orbital motions within a system, and the time evolution of a disc.

The new results from SPHERE, along with data from other telescopes such as ALMA, are revolutionising astronomers' understanding of the environments around young stars and the complex mechanisms of planetary formation.

In 2016, University of California, Berkeley, engineers demonstrated the first implanted, ultrasonic neural dust sensors, bringing closer the day when a Fitbit-like device could monitor internal nerves, muscles or organs in real time. Now, Berkeley engineers have taken neural dust a step forward by building the smallest volume, most efficient wireless nerve stimulator to date.

The device, called StimDust, short for stimulating neural dust, adds more sophisticated electronics to neural dust without sacrificing the technology's tiny size or safety, greatly expanding the range of neural dust applications. The researchers' goal is to have StimDust implanted in the body through minimally invasive procedures to monitor and treat disease in a real-time, patient-specific approach. StimDust is just 6.5 cubic millimeters in volume and is powered wirelessly by ultrasound, which the device then uses to power nerve stimulation at an efficiency of 82 percent.

"StimDust is the smallest deep-tissue stimulator that we are aware of that's capable of stimulating almost all of the major therapeutic targets in the peripheral nervous system," said Rikky Muller, co-lead of the work and assistant professor of electrical engineering and computer sciences at Berkeley. "This device represents our vision of having tiny devices that can be implanted in minimally invasive ways to modulate or stimulate the peripheral nervous system, which has been shown to be efficacious in treating a number of diseases."

The research will be presented April 10 at the IEEE Custom Integrated Circuits Conference in San Diego. The research team was co-led by one of neural dust's inventors, Michel Maharbiz, a professor of electrical engineering and computer sciences at Berkeley.

The creation of neural dust at Berkeley, led by Maharbiz and Jose Carmena, a Berkeley professor of electrical engineering and computer sciences and a member of the Helen Wills Neuroscience Institute, has opened the door for wireless communication to the brain and peripheral nervous system through tiny implantable devices inside the body that are powered by ultrasound. Engineering teams around the world are now using the neural dust platform to build devices that can be charged wirelessly by ultrasound.

Maharbiz came up with the idea to use ultrasound for powering and communicating with very small implants. Together with Berkeley professors Elad Alon and Jan Rabaey, the group then developed the technical framework to demonstrate the scaling power of ultrasound for implantable devices.

Early engineering work by D.J. Seo, a Berkeley Ph.D. student who was co-advised by Alon and Maharbiz, followed by experimental validations by Ryan Neely, another Berkeley Ph.D. student, advised by Carmena, set the foundations of the neural dust vision. In the years since neural dust's invention, ultrasound has proven to be among the most promising technologies for powering and communicating implantable devices.

Muller came to Berkeley in 2016 and has been a key driver of neural dust innovation. Her research group specializes in bidirectional electronic interfaces with human body, specifically in the brain and peripheral nervous system. Her team has been working on ways to use the power that can be transmitted to neural dust. In StimDust, her lab has taken the neural dust platform and built a more effective stimulator that can wrap around a nerve cuff and can also record, transmit and receive data. They did this by designing a custom integrated circuit to transfer ultrasound charge to the nerve in a well-controlled, safe and efficient way.

StimDust is about an order of magnitude smaller than any active device with similar capabilities that the research team is aware of. The components of StimDust include a single piezocrystal, which is the antenna of the system, a 1-millimeter integrated circuit and one charge storage capacitor. StimDust has electrodes on the bottom, which make contact with a nerve through a cuff that wraps around the nerve. In addition to the device, Muller's team designed a custom wireless protocol that gives them a large range of programmability while maintaining efficiency. The entire device is powered by just 4 microwatts and has a mass of 10 milligrams.

After testing StimDust on the benchtop, the research team implanted it in a live rodent to test it in a realistic environment. Through a cuff around the sciatic nerve, the research team was able to control hind leg motion, record the stimulation activity and measure how much force was exerted on the hind leg muscle as it was stimulated. The researchers then gradually increased stimulation and mapped the response of the hind leg muscle so they could know exactly how much stimulation was needed for a desired muscle recruitment, a kind of sophisticated analysis required of medical devices.

Muller hopes that her work can lead to applications of StimDust to treat diseases such as heart irregularities, chronic pain, asthma or epilepsy.

"One of the big visions of my group is to create these very efficient bidirectional interfaces with the nervous system and couple that with intelligence to really understand the signals of disease and then to be able to treat disease in an intelligent, methodical way," Muller said. There's an incredible opportunity for healthcare applications that can really be transformative."

BOSTON -- Researchers from Hebrew SeniorLife's Institute for Aging Research (IFAR), Wageningen University, Tilburg University, University of Reading, and Beth Israel Deaconess Medical Center (BIDMC) have discovered that higher intake of dairy foods, such as milk, yogurt, and cheese, is associated with higher volumetric bone mineral density and vertebral strength at the spine in men. Dairy intake seems to be most beneficial for men over age 50, and continued to have positive associations irrespective of serum vitamin D status.

In women, researchers found no significant results except for a positive association of cream intake in the cross sectional area of the bone.

Study participants included 1,522 men and 1,104 women from the Framingham Study, aged 32-81 years. Researchers examined quantitative computed tomography (QCT) measures of bone to determine associations with dairy intake.

Shivani Sahni, Ph.D., Director Nutrition Program and Associate Scientist at IFAR and senior author of the study said, "This study related dairy intake with QCT- derived bone measures, which are unique because they provide information on bone geometry and compartment-specific bone density that are key determinants of bone strength. The results of this study highlight the beneficial role of a combination of dairy foods upon bone health and these beneficial associations remain irrespective of serum vitamin D status in a person."

The results of this study were published recently in the Journal of Bone and Mineral Density.

NASA's Project Mercury was the United States' first human-in-space program. Between 1961 and 1963, six astronauts carried out successful one-person spaceflights that offered physicians and scientists the first opportunity to observe the effects of living in space on the human body.

"Spaceflight data is hard to come by; we should remember what's already been done, so we can make the most of new opportunities to do human research in space," said corresponding author Dr. Virginia Wotring, associate professor of the Center for Space Medicine and pharmacology and chemical biology at Baylor College of Medicine.

The Project Mercury astronauts were military test pilots on active duty who volunteered for these missions. They were between 35 and 40 years of age at the time of the flight, and, because room was limited inside the space capsule, they had to be no taller than 5 feet 11 inches.

Depending on the mission, the flights were either in a suborbital or in a low-orbit path and lasted between 15 minutes and 34 hours. During the flights, the astronauts wore a 20-pound spacesuit designed to back up the capsule's support system and remained restrained by a harness in a semi-supine position while performing their tasks. Common clinical measures, such as heart rate, body temperature and breathing rate, were taken to monitor their medical condition. At the time, scientists and physicians knew little about the human tolerance to a sustained weightless environment, only what ground simulations - 'dress rehearsals' - would predict. These first flights provided some answers to what to expect during short-term space flights.

"The Mercury missions taught us that human beings could function in the space environments for more than a day. Other findings were that heart rate and the weight loss on early space flight missions related more to time spent in a space suit, as opposed to time spent in weightlessness," said Wotring, who also is chief scientist and deputy director of the Translational Research Institute for Space Health. "Also, that the 'dress rehearsals' were excellent predictors of what would be seen later in space."

We hope that these and other findings will influence the design of space suits and that ground simulations and 'rehearsals' will be given the attention they deserve," she said.

The Project Mercury astronaut data can be of interest to operators of future commercial space flights as the short duration of the Mercury missions is similar to that of planned future tourist spaceflight opportunities.

"When Dr. William R. Carpentier at NASA Johnson Space Center offered the National Space Biomedical Research Institute and the Center for Space Medicine at Baylor the opportunity to collaborate on this publication, we felt privileged to work with him," Wotring said. "This paper is our effort to make available all the medical data collected in those early days of crewed space flight so that future researchers can find it and benefit from it."