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  • richardmitnick 4:46 pm on January 25, 2021 Permalink | Reply
    Tags: "What’s in a name? A new class of superconductors", , , d+d, In superconductors electrons form pairs and flow without resistance., Multiorbital singlet pairing, Orbital-selective superconductivity, , Rice University   

    From Rice University and From Arizona State University: “What’s in a name? A new class of superconductors” 

    From Rice University

    and


    From Arizona State University

    January 25, 2021

    Jeff Falk
    713-348-6775
    jfalk@rice.edu

    Jade Boyd, writer
    713-348-6778
    jadeboyd@rice.edu

    Commonly mistaken name leads to broader discovery by Rice, Arizona State physicists.

    A new theory that could explain how unconventional superconductivity arises in a diverse set of compounds might never have happened if physicists Qimiao Si and Emilian Nica had chosen a different name for their 2017 model of orbital-selective superconductivity.

    1
    “Levitation of a magnet on top of a superconductor 2” by Jubobroff, Fbouquet, LPS is licensed under CC BY-SA 3.0.

    In a study published this month in npj Quantum Materials, Si of Rice University and Nica of Arizona State University argue that unconventional superconductivity in some iron-based and heavy-fermion materials arises from a general phenomenon called “multiorbital singlet pairing.”

    In superconductors, electrons form pairs and flow without resistance. Physicists cannot fully explain how pairs form in unconventional superconductors, where quantum forces give rise to strange behavior. Heavy fermions, another quantum material, feature electrons that appear to be thousands of times more massive than ordinary electrons.

    Si and Nica proposed the idea [npj Quantum Materials] of selective pairing within atomic orbitals in 2017 to explain unconventional superconductivity in alkaline iron selenides. The following year, they applied the orbital-selective model to the heavy fermion material in which unconventional superconductivity was first demonstrated in 1979.

    They considered naming the model after a related mathematical expression made famous by quantum pioneer Wolfgang Pauli, but opted to call it d+d. The name refers to mathematical wave functions that describe quantum states.

    “It’s like you have a pair of electrons that dance with each other,” said Si, Rice’s Harry C. and Olga K. Wiess Professor of Physics and Astronomy. “You can characterize that dance by s- wave, p-wave and d-wave channels, and d+d refers to two different kinds of d-waves that fuse together into one.”

    In the year after publishing the d+d model, Si gave many lectures about the work and found audience members frequently got the name confused with “d+id,” the name of another pairing state that physicists have discussed for more than a quarter century.

    “People would approach me after a lecture and say, ‘Your theory of d+id is really interesting,’ and they meant it as a compliment, but it happened so often it got annoying,” said Si, who also directs the Rice Center for Quantum Materials (RCQM).

    In mid-2019, Si and Nica met over lunch while visiting Los Alamos National Laboratory, and began sharing stories about the d+d versus d+id confusion.

    “That led to a discussion of whether d+d might be connected with d+id in a meaningful way, and we realized it was not a joke,” Nica said.

    The connection involved d+d pairing states and those made famous by the Nobel Prize-winning discovery of helium-3 superfluidity.

    “There are two types of superfluid pairing states of liquid helium-3, one called the B phase and the other the A phase,” Nica said. “Empirically, the B phase is similar to our d+d, while the A phase is almost like a d+id.”

    The analogy got more intriguing when they discussed mathematics. Physicists use matrix calculations to describe quantum pairing states in helium-3, and that is also the case for the d+d model.

    “You have a number of different ways of organizing that matrix, and we realized our d+d matrix for the orbital space was like a different form of the d+id matrix that describes helium-3 pairing in spin space,” Nica said.

    Si said the associations with superfluid helium-3 pairing states have helped he and Nica advance a more complete description of pairing states in both iron-based and heavy-fermion superconductors.

    “As Emil and I talked more, we realized the periodic table for superconducting pairing was incomplete,” Si said, referring to the chart physicists use to organize superconducting pairing states.

    “We use symmetries — like lattice or spin arrangements, or whether time moving forward versus backward is equivalent, which is time-reversal symmetry — to organize possible pairing states,” he said. “Our revelation was that d+id can be found in the existing list. You can use the periodic table to construct it. But d+d, you cannot. It’s beyond the periodic table, because the table doesn’t include orbitals.”

    Si said orbitals are important for describing the behavior of materials like iron-based superconductors and heavy fermions, where “very strong electron-electron correlations play a crucial role.”

    “Based on our work, the table needs to be expanded to include orbital indices,” Si said.

    The research was supported by a startup grant from Arizona State University, the Department of Energy (DE-SC0018197), the Welch Foundation (C-1411) and the National Science Foundation (PHY-1607611).

    RCQM is a multidisciplinary research effort that leverages the strengths and global partnerships of more than 20 Rice research groups.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings


    Stem Education Coalition

    ASU is the largest public university by enrollment in the United States. Founded in 1885 as the Territorial Normal School at Tempe, the school underwent a series of changes in name and curriculum. In 1945 it was placed under control of the Arizona Board of Regents and was renamed Arizona State College. A 1958 statewide ballot measure gave the university its present name.
    ASU is classified as a research university with very high research activity (RU/VH) by the Carnegie Classification of Institutions of Higher Education, one of 78 U.S. public universities with that designation. Since 2005 ASU has been ranked among the Top 50 research universities, public and private, in the U.S. based on research output, innovation, development, research expenditures, number of awarded patents and awarded research grant proposals. The Center for Measuring University Performance currently ranks ASU 31st among top U.S. public research universities.

    ASU awards bachelor’s, master’s and doctoral degrees in 16 colleges and schools on five locations: the original Tempe campus, the West campus in northwest Phoenix, the Polytechnic campus in eastern Mesa, the Downtown Phoenix campus and the Colleges at Lake Havasu City. ASU’s “Online campus” offers 41 undergraduate degrees, 37 graduate degrees and 14 graduate or undergraduate certificates, earning ASU a Top 10 rating for Best Online Programs. ASU also offers international academic program partnerships in Mexico, Europe and China. ASU is accredited as a single institution by The Higher Learning Commission.

    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

     
  • richardmitnick 5:32 pm on January 19, 2021 Permalink | Reply
    Tags: , , Research finds tiny bubbles tell tales of big volcanic eruptions", Rice University, ,   

    From Rice University and University of Texas at Austin: “Research finds tiny bubbles tell tales of big volcanic eruptions” 


    From Rice University

    and

    U Texas Austin bloc

    From University of Texas at Austin

    January 19, 2021
    Jade Boyd

    Study: Nanocrystals may explain staggering number of bubbles in erupted lava.

    Microscopic bubbles can tell stories about Earth’s biggest volcanic eruptions and geoscientists from Rice University and the University of Texas at Austin have discovered some of those stories are written in nanoparticles.

    In an open-access study published online in Nature Communications, Rice’s Sahand Hajimirza and Helge Gonnermann and UT Austin’s James Gardner answered a longstanding question about explosive volcanic eruptions like the ones at Mount St. Helens in 1980, the Philippines’ Mount Pinatubo in 1991 or Chile’s Mount Chaitén in 2008.

    2
    An aerial view from the southwest of Mount St. Helens, Washington, May 18, 1980. The Plinian eruption was the deadliest and most costly volcanic disaster in U.S. history. Credit: Krimmel, Robert. Public domain.

    Geoscientists have long sought to use tiny bubbles in erupted lava and ash to reconstruct some of the conditions, like heat and pressure, that occur in these powerful eruptions. But there’s been a historic disconnect between numerical models that predict how many bubbles will form and the actual amounts of bubbles measured in erupted rocks.

    Hajimirza, Gonnermann and Gardner worked for more than five years to reconcile those differences for Plinian eruptions. Named in honor of Pliny the Younger, the Roman author who described the eruption that destroyed Pompeii in A.D. 79, Plinian eruptions are some of the most intense and destructive volcanic events.

    “Eruption intensity refers to the both the amount of magma that’s erupted and how quickly it comes out,” said Hajimirza, a postdoctoral researcher and former Ph.D. student in Gonnermann’s lab at Rice’s Department of Earth, Environmental and Planetary Sciences. “The typical intensity of Plinian eruptions ranges from about 10 million kilograms per second to 10 billion kilograms per second. That is equivalent to 5,000 to 5 million pickup trucks per second.”

    One way scientists can gauge the speed of rising magma is by studying microscopic bubbles in erupted lava and ash. Like bubbles in uncorked champagne, magma bubbles are created by a rapid decrease in pressure. In magma, this causes dissolved water to escape in the form of gas bubbles.

    “As magma rises, its pressure decreases,” Hajimirza said. “At some point, it reaches a pressure at which water is saturated, and further decompression causes supersaturation and the formation of bubbles.”

    As water escapes in the form of bubbles, the molten rock becomes less saturated. But if the magma continues to rise, decreasing pressure increases saturation.

    “This feedback determines how many bubbles form,” Hajimirza said. “The faster the magma rises, the higher the decompression rate and supersaturation pressure, and the more abundant the nucleated bubbles.”

    In Plinian eruptions, so much magma rises so fast that the number of bubbles is staggering. When Mount St. Helens erupted on May 18, 1980, for example, it spewed more than one cubic kilometer of rock and ash in nine hours, and there were about one million billion bubbles in each cubic meter of that erupted material.

    “The total bubbles would be around a septillion,” Hajimirza said. “That’s a one followed by 24 zeros, or about 1,000 times more than all the grains of sand on all Earth’s beaches.”

    In his Ph.D. studies, Hajimirza developed a predictive model for bubble formation and worked with Gardner to test the model in experiments at UT Austin. The new study builds upon that work by examining how magnetite crystals no larger than a few billionths of a meter could change how bubbles form at various depths.

    “When bubbles nucleate, they can form in liquid, which we call homogeneous nucleation, or they can nucleate on a solid surface, which we call heterogeneous,” Hajimirza said. “A daily life example would be boiling a pot of water. When bubbles form on the bottom of the pot, rather than in the liquid water, that is heterogeneous nucleation.”

    Bubbles from the bottom of the pot are often the first to form, because heterogeneous and homogeneous nucleation typically begin at different temperatures. In rising magma, heterogeneous bubble formation begins earlier, at lower supersaturation levels. And the surfaces where bubbles nucleate are often on tiny crystals.

    “How much they facilitate nucleation depends on the type of crystals,” Hajimirza said. “Magnetites, in particular, are the most effective.”

    In the study, Hajimirza, Gonnermann and Gardner incorporated magnetite-mediated nucleation in numerical models of bubble formation and found the models produced results that agreed with observational data from Plinian eruptions.

    3
    A volcanic plume flows southeast from Chile’s Mount Chaitén in this May 3, 2008 image from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. The Plinian plume rose over the Andes Mountains and drifted across Argentina before dissipating over the Atlantic Ocean. Credit:Jeff Schmaltz/MODIS Rapid Response Team/NASA Goddard Space Flight Center)

    NASA Terra MODIS schematic.


    NASA/Terra satellite.

    Hajimirza said magnetites are likely present in all Plinian magma. And while previous research on hasn’t revealed enough magnetites to account for all observed bubbles, previous studies may have missed small nanocrystals that would only be revealed with transmission electron microscopy, a rarely used technique that is only now becoming more broadly available.

    To find out if that’s the case, Hajimirza, Gonnermann and Gardner called for a “systematic search for magnetite nanolites” in material from Plinian eruptions. That would provide observational data to better define the role of magnetites and heterogeneous nucleation in bubble formation, and could lead to better models and improved volcanic forecasts.

    “Forecasting eruptions is a long-term goal for volcanologists, but it’s challenging because we cannot directly observe subsurface processes,” said Hajimirza. “One of the grand challenges of volcano science, as outlined by the National Academies in 2017, is improving eruption forecasting by better integration of the observational data we have with the quantitative models, like the one we developed for this study.”

    Gonnermann is a professor of Earth, environmental and planetary sciences at Rice. Gardner is a professor of geological sciences in UT’s Jackson School of Geosciences.

    The research was supported by the National Science Foundation.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings


    Stem Education Coalition

    U Texas Austin campus

    In 1839, the Congress of the Republic of Texas ordered that a site be set aside to meet the state’s higher education needs. After a series of delays over the next several decades, the state legislature reinvigorated the project in 1876, calling for the establishment of a “university of the first class.” Austin was selected as the site for the new university in 1881, and construction began on the original Main Building in November 1882. Less than one year later, on Sept. 15, 1883, University of Texas at Austin opened with one building, eight professors, one proctor, and 221 students — and a mission to change the world. Today, UT Austin is a world-renowned higher education, research, and public service institution serving more than 51,000 students annually through 18 top-ranked colleges and schools.

    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

     
  • richardmitnick 2:05 pm on December 15, 2020 Permalink | Reply
    Tags: , , , Nano Engineering, , , Rice University, The hills are alive with the force of van der Walls., Weak force has strong impact on nanosheets"   

    From Rice University: “Weak force has strong impact on nanosheets” 


    From Rice University

    December 15, 2020
    Mike Williams

    1
    A transmission electron microscope image by Rice University scientists shows a silver nanoplate deformed by a particle, forming flower-shaped stress contours in the material that indicate a bump. Changing the shape of the material changes its electromagnetic properties, making it suitable for catalysis or optical applications. Credit: The Jones Lab.

    You have to look closely, but the hills are alive with the force of van der Walls.

    Rice University scientists found that nature’s ubiquitous “weak” force is sufficient to indent rigid nanosheets, extending their potential for use in nanoscale optics or catalytic systems.

    Changing the shape of nanoscale particles changes their electromagnetic properties, said Matt Jones, the Norman and Gene Hackerman Assistant Professor of Chemistry and an assistant professor of materials science and nanoengineering. That makes the phenomenon worth further study.

    “People care about particle shape, because the shape changes its optical properties,” Jones said. “This is a totally novel way of changing the shape of a particle.”

    Jones and graduate student Sarah Rehn led the study in the American Chemical Society’s Nano Letters.

    Van der Waals is a weak force that allows neutral molecules to attract one another through randomly fluctuating dipoles, depending on distance. Though small, its effects can be seen in the macro world, like when geckos walk up walls [Science].

    Van der Waals forces are everywhere and, essentially, at the nanoscale everything is sticky,” Jones said. “When you put a large, flat particle on a large, flat surface, there’s a lot of contact, and it’s enough to permanently deform a particle that’s really thin and flexible.”

    In the new study, the Rice team decided to see if the force could be used to manipulate 8-nanometer-thick sheets of ductile silver. After a mathematical model showed them it was possible, they placed 15-nanometer-wide iron oxide nanospheres on a surface and sprinkled prism-shaped nanosheets over them.

    Without applying any other force, they saw through a transmission electron microscope that the nanosheets acquired permanent bumps where none existed before, right on top of the spheres. As measured, the distortions were about 10 times larger than the width of the spheres.

    The hills weren’t very high, but simulations confirmed that van der Waals attraction between the sheet and the substrate surrounding the spheres was sufficient to influence the plasticity of the silver’s crystalline atomic lattice. They also showed that the same effect would occur in silicon dioxide and cadmium selenide nanosheets, and perhaps other compounds.

    “We were trying to make really thin, large silver nanoplates and when we started taking images, we saw these strange, six-fold strain patterns, like flowers,” said Jones, who earned a multiyear Packard Fellowship in 2018 to develop advanced microscopy techniques.

    “It didn’t make any sense, but we eventually figured out that it was a little ball of gunk that the plate was draped over, creating the strain,” he said. “We didn’t think anyone had investigated that, so we decided to have a look.

    “What it comes down to is that when you make a particle really thin, it becomes really flexible, even if it’s a rigid metal,” Jones said.

    In further experiments, the researchers saw nanospheres could be used to control the shape of the deformation, from single ridges when two spheres are close, to saddle shapes or isolated bumps when the spheres are farther apart.

    They determined that sheets less than about 10 nanometers thick and with aspect ratios of about 100 are most amenable to deformation.

    2
    Rice University scientists found the ubiquitous, “weak” van der Waals force was sufficient to indent a rigid silver nanosheet. The phenomenon suggests possible applications in nanoscale optics or catalytic systems. Credit: The Jones Lab.

    The researchers noted their technique creates “a new class of curvilinear structures based on substrate topography” that “would be difficult to generate lithographically.” That opens new possibilities for electromagnetic devices that are especially relevant to nanophotonic research.

    Straining the silver lattice also turns the inert metal into a possible catalyst by creating defects where chemical reactions can happen.

    “This gets exciting because now, most people make these kinds of metamaterials through lithography,” Jones said. “That’s a really powerful tool, but once you’ve used that to pattern your metal, you can never change it.

    “Now we have the option, perhaps someday, to build a material that has one set of properties and then change it by deforming it,” he said. “Because the forces required to do so are so small, we hope to find a way to toggle between the two.”

    Co-authors of the paper are graduate student Theodor Gerrard-Anderson, postdoctoral researchers Liang Qiao and Qing Zhu, and Geoff Wehmeyer, an assistant professor of mechanical engineering.

    The Robert A. Welch Foundation, the David and Lucile Packard Foundation and the National Science Foundation supported the research.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings


    Stem Education Coalition

    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

     
  • richardmitnick 2:12 pm on December 7, 2020 Permalink | Reply
    Tags: "Scientists get the lowdown on sun’s super-hot atmosphere", Rice University,   

    From Rice University: “Scientists get the lowdown on sun’s super-hot atmosphere” 


    From Rice University

    December 7, 2020

    Jeff Falk
    713-348-6775
    jfalk@rice.edu

    Mike Williams
    713-348-6728
    mikewilliams@rice.edu

    Orbiting instrument hints at how stored magnetic energy heats solar atmosphere.

    A phenomenon first detected in the solar wind may help solve a long-standing mystery about the sun: why the solar atmosphere is millions of degrees hotter than the surface.

    Images from the Earth-orbiting Interface Region Imaging Spectrograph, aka IRIS, and the Atmospheric Imaging Assembly, aka AIA, show evidence that low-lying magnetic loops are heated to millions of degrees Kelvin.

    NASA IRIS Interface Region Imaging Spectrograph


    Scientists get the low down on sun’s super hot atmosphere.

    Researchers at Rice University, the University of Colorado Boulder and NASA’s Marshall Space Flight Center make the case that heavier ions, such as silicon, are preferentially heated in both the solar wind and in the transition region between the sun’s chromosphere and corona.

    There, loops of magnetized plasma arc continuously, not unlike their cousins in the corona above. They’re much smaller and hard to analyze, but have long been thought to harbor the magnetically driven mechanism that releases bursts of energy in the form of nanoflares.

    Rice solar physicist Stephen Bradshaw and his colleagues were among those who suspected as much, but none had sufficient evidence before IRIS.

    The high-flying spectrometer was built specifically to observe the transition region. In the NASA-funded study, which appears in Nature Astronomy, the researchers describe “brightenings” in the reconnecting loops that contain strong spectral signatures of oxygen and, especially, heavier silicon ions.

    The team of Bradshaw, his former student and lead author Shah Mohammad Bahauddin, now a research faculty member at the Laboratory for Atmospheric and Space Physics at Colorado, and NASA astrophysicist Amy Winebarger studied IRIS images able to resolve details of these transition region loops and detect pockets of super-hot plasma. The images allow them to analyze the movements and temperatures of ions within the loops via the light they emit, read as spectral lines that serve as chemical “fingerprints.”

    “It’s in the emission lines where all the physics is imprinted,” said Bradshaw, an associate professor of physics and astronomy. “The idea was to learn how these tiny structures are heated and hope to say something about how the corona itself is heated. This might be a ubiquitous mechanism that operates throughout the solar atmosphere.”

    The images revealed hot-spot spectra where the lines were broadened by thermal and Doppler effects, indicating not only the elements involved in nanoflares but also their temperatures and velocities.

    At the hot spots, they found reconnecting jets containing silicon ions moved toward (blue-shifted) and away from (red-shifted) the observer (IRIS) at speeds up to 100 kilometers per second. No Doppler shift was detected for the lighter oxygen ions.

    The researchers studied two components of the mechanism: how the energy gets out of the magnetic field, and then how it actually heats the plasma.

    The transition region is only about 10,000 degrees Fahrenheit, but convection on the sun’s surface affects the loops, twisting and braiding the thin magnetic strands that comprise them, and adds energy to the magnetic fields that ultimately heat the plasma, Bradshaw said. “The IRIS observations showed that process taking place and we’re reasonably sure at least one answer to the first part is through magnetic reconnection, of which the jets are a key signature,” he said.

    In that process, the magnetic fields of the plasma strands break and reconnect at braiding sites into lower energy states, releasing stored magnetic energy. Where this takes place, the plasma becomes superheated.

    But how plasma is heated by the released magnetic energy has remained a puzzle until now. “We looked at the regions in these little loop structures where reconnection was taking place and measured the emission lines from the ions, chiefly silicon and oxygen,” he said. “We found the spectral lines of the silicon ions were much broader than the oxygen.”

    That indicated preferential heating of the silicon ions. “We needed to explain it,” Bradshaw said. “We had a look and a think and it turns out there’s a kinetic process called ion cyclotron heating that favors heating heavy ions over lighter ones.”

    He said ion cyclotron waves are generated at the reconnection sites. The waves carried by the heavier ions are more susceptible to an instability that causes the waves to “break” and generate turbulence, which scatters and energizes the ions. This broadens their spectral lines beyond what would be expected from the local temperature of the plasma alone. In the case of the lighter ions, there might be insufficient energy left over to heat them. “Otherwise, they don’t exceed the critical velocity needed to trigger the instability, which is faster for lighter ions,” he said.

    “In the solar wind, heavier ions are significantly hotter than lighter ions,” Bradshaw said. “That’s been definitively measured. Our study shows for the first time that this is also a property of the transition region, and might therefore persist throughout the entire atmosphere due to the mechanism we have identified, including heating the solar corona, particularly since the solar wind is a manifestation of the corona expanding into interplanetary space.”

    The next question, Bahauddin said, is whether such phenomena are happening at the same rate all over the sun. “Most probably the answer is no,” he said. “Then the question is, how much do they contribute to the coronal heating problem? Can they supply sufficient energy to the upper atmosphere so that it can maintain a multimillion-degree corona?

    “What we’ve shown for the transition region was a solution to an important piece of the puzzle, but the big picture requires more pieces to fall in the right place,” Bahauddin said. “I believe IRIS will be able to tell us about the chromospheric pieces in the near future. That will help us build a unified and global theory of the sun’s atmosphere.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings


    Stem Education Coalition

    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

     
  • richardmitnick 4:54 pm on November 23, 2020 Permalink | Reply
    Tags: "Understanding frustration could lead to better drugs", , , Rice University, The atom-scale models zero in on the interactions within possible binding sites rather than the vast majority of the interactions in proteins that guide their folding.   

    From Rice University: “Understanding frustration could lead to better drugs” 


    From Rice University

    November 23, 2020
    Mike Williams

    1
    Atom-scale models by Rice University scientists based on those used to predict how proteins fold show a strong correlation between minimally frustrated binding sites and drug specificity. The funnel, a visual representation of the protein’s energy landscape as it folds, helps locate those frustrated sites. Such models could lead to better-designed drugs with fewer side effects. Credit: Mingchen Chen/Rice University.

    Knowing precisely where proteins are frustrated could go a long way toward making better drugs.

    That’s one result of a new study by Rice University scientists looking for the mechanisms that stabilize or destabilize key sections of biomolecules.

    Atom-scale models by Rice theorist Peter Wolynes, lead author and alumnus Mingchen Chen and their colleagues at the Center for Theoretical Biological Physics show that not only are some specific frustrated sequences in proteins necessary to allow them to function, locating them also offers clues to achieve better specificity for drugs.

    That knowledge could also help design drugs with fewer side effects, Wolynes said.

    The team’s open-access study appears in Nature Communications.

    The atom-scale models zero in on the interactions within possible binding sites rather than the vast majority of the interactions in proteins that guide their folding. The finer resolution models allow the incorporation of co-factors like chemically active ligands, including drug molecules. The researchers say this ability gives new insight into why ligands are best captured only by specific proteins and not by others.

    “Unnatural ligands,” aka drugs, tend to bind best with those frustrated pockets in proteins that become minimally frustrated once the drugs bind, Wolynes said. Having a way to find and then learn the details of these minimally frustrated sites would help pharmaceutical companies eliminate a lot of trial and error.

    “The standard way of doing drug design is to try out 10,000 binding sites on a protein to find ones that fit,” Wolynes said. “We’re saying you don’t have to sample all possible binding sites, just a reasonably fair number to understand the statistics of what could work in local environments.

    “It’s the difference between taking a poll and actually having an election,” he said. “The poll is cheaper, but you still will need to check things out.”

    The Rice researchers are known for their energy landscape theory of how proteins fold. It usually employs coarse-grained models in which amino acids are represented by just a few sites.

    That strategy takes less computing power than trying to determine the positions over time of every atom in every residue, and yet it has proven highly accurate in predicting how proteins fold based on their sequences. But for this study, the researchers modeled proteins and protein-ligand complexes at the atomic level to see if they could find how frustration gives some parts of a protein the flexibility required to bind to other molecules.

    “One of the great things about modeling at all-atom resolution is that it allows us to evaluate whether drug molecules fit well into binding sites or not,” Wolynes said. “This method is able to quickly show whether a binding site for a certain drug will be minimally frustrated or will remain a frustrated region. If after the molecule binds the site remains frustrated, the protein could rearrange or the drug could change its orientation in such a way that it could give rise to side effects.”

    Modeling the frustrated sites — and sometimes altering them to see what would happen — lets the researchers see how drug specificity correlates with binding pockets. Frustration analysis, they wrote, provides “a route for screening for more specific compounds for drug discovery.”

    “This concept of frustration was there at the very beginning of our work on protein folding,” Wolynes said. “When we applied it to real protein molecules, we found some examples where the mechanism of folding violated what we would predict from a perfect funnel. Then we discovered these deviations from the funnel picture occurred where the protein was, in fact, somewhat frustrated.

    “It was like the exception that proves the rule,” he said. “Something that’s true all the time might be trivial. But if it’s not true 1% of the time, it’s a problem to be solved, and we’ve been able to do that with AWSEM, our structure-prediction software.”

    Extending the software to analyze frustration on the atomic level is possible, as described by the group in another recent paper. But the computational cost of tracking every atom in a protein is so high that the researchers needed a way to sample the motions of specific regions where frustration might confuse the folding route.

    “Mingchen realized there was an efficient algorithm to sample the local environments in binding sites but keep the atomistic resolution,” said Wolynes, who noted he and Chen, now in private industry, are using the models to investigate possible therapeutics, including COVID-19-related drugs.

    Co-authors of the paper are Rice graduate student Xun Chen, alumnus Nicholas Schafer and Cecilia Clementi, a former Rice professor and now the Einstein Professor of Physics at the Free University of Berlin (DE); Elizabeth Komives, a professor of chemistry and biochemistry at the University of California, San Diego; and Diego Ferreiro, a biological chemist at the University of Buenos Aires (AR) . Wolynes is the D.R. Bullard-Welch Foundation Professor of Science, Professor of Chemistry, BioSciences, and Physics and Astronomy at Rice and co-director of the CTBP.

    The National Science Foundation supported the research.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings


    Stem Education Coalition

    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

     
  • richardmitnick 12:08 pm on November 16, 2020 Permalink | Reply
    Tags: "Former piece of Pacific Ocean floor imaged deep beneath China", , , , , Rice University   

    From Rice University: “Former piece of Pacific Ocean floor imaged deep beneath China” 

    From Rice University

    November 16, 2020

    Jeff Falk
    713-348-6775
    jfalk@rice.edu

    Jade Boyd
    713-348-6778
    jadeboyd@rice.edu

    1
    A graphic showing the convective heat cycle (red arrows) that drives plate tectonic motion (black arrows) on Earth. Heat flows toward subduction zones through the uppermost mantle layer, the asthenosphere. A computer model from Rice University finds that the asthenosphere can locally drag plates along with it rather than acting exclusively as a brake on plate movements as had been widely believed. Credit: Surachit/Wikimedia Commons.

    Study offers clues about the fate of tectonic plates that sink deep in Earth’s mantle.

    In a study that gives new meaning to the term “rock bottom,” seismic researchers have discovered the underside of a rocky slab of Earth’s surface layer, or lithosphere, that has been pulled more than 400 miles beneath northeastern China by the process of tectonic subduction.

    The study, published by a team of Chinese and U.S. researchers in Nature Geoscience, offers new evidence about what happens to water-rich oceanic tectonic plates as they are drawn through Earth’s mantle beneath continents.

    Rice University seismologist Fenglin Niu, a co-corresponding author, said the study provides the first high-resolution seismic images of the top and bottom boundaries of a rocky, or lithospheric, tectonic plate within a key region known as the mantle transition zone, which starts about 254 miles (410 kilometers) below Earth’s surface and extends to about 410 miles (660 kilometers).

    “A lot of studies suggest that the slab actually deforms a lot in the mantle transition zone, that it becomes soft, so it’s easily deformed,” Niu said. How much the slab deforms or retains its shape is important for explaining whether and how it mixes with the mantle and what kind of cooling effect it has.

    Earth’s mantle convects like heat in an oven. Heat from Earth’s core rises through the mantle at the center of oceans, where tectonic plates form. From there, heat flows through the mantle, cooling as it moves toward continents, where it drops back toward the core to collect more heat, rise and complete the convective circle.

    Previous studies have probed the boundaries of subducting slabs in the mantle, but few have looked deeper than 125 miles (200 kilometers) and none with the resolution of the current study, which used more than 67,000 measurements collected from 313 regional seismic stations in northeastern China. That work, which was done in collaboration with the China Earthquake Administration, was led by co-corresponding author Qi-Fu Chen from the Chinese Academy of Sciences.

    The research probes fundamental questions about the processes that shaped Earth’s surface over billions of years. Mantle convection drives the movements of Earth’s tectonic plates, rigid interlocked pieces of Earth’s surface that are in constant motion as they float atop the asthenosphere, the topmost mantle layer and the most fluid part of the inner planet.

    Where tectonic plates meet, they jostle and grind together, releasing seismic energy. In extreme cases, this can cause destructive earthquakes and tsunamis, but most seismic motion is too faint for humans to feel without instruments. Using seismometers, scientists can measure the magnitude and location of seismic disturbances. And because seismic waves speed up in some kinds of rock and slow in others, scientists can use them to create images of Earth’s interior, in much the same way a doctor might use ultrasound to image what’s inside a patient.

    2
    Illustration of the subduction of an oceanic lithospheric plate sliding beneath a continental plate. Credit:Booyabazooka/Wikimedia Commons.

    Niu, a professor of Earth, environmental and planetary sciences at Rice, has been at the forefront of seismic imaging for more than two decades. When he did his Ph.D. training in Japan more than 20 years ago, researchers were using dense networks of seismic stations to gather some of the first detailed images of the submerged slab boundaries of the Pacific plate, the same plate that was imaged in study published this week.

    “Japan is located about where the Pacific plate reaches around 100-kilometer depths,” Niu said. “There is a lot of water in this slab, and it produces a lot of partial melt. That produces arc volcanoes that helped create Japan. But, we are still debating whether this water is totally released in that depth. There is increasing evidence that a portion of the water stays inside the plate to go much, much deeper.”

    Northeastern China offers one of the best vantage points to investigate whether this is true. The region is about 1,000 kilometers from the Japan trench where the Pacific plate begins its plunge back into the planet’s interior. In 2009, with funding from the National Science Foundation and others, Niu and scientists from the University of Texas at Austin, the China Earthquake Administration, the Earthquake Research Institute of Tokyo University and the Research Center for Prediction of Earthquakes and Volcanic Eruptions at Japan’s Tohoku University began installing broadband seismometers in the region.

    “We put 140 stations there, and of course the more stations the better for resolution,” Niu said. “The Chinese Academy of Sciences put additional stations so they can get a finer, more detailed image.”

    3
    Seismic imaging in northeastern China revealed both the top (X1) and bottom (X2) boundaries of a tectonic plate (blue) that formerly sat at bottom of the Pacific Ocean and is being pulled into Earth’s mantle transition zone, which lies about 254-410 miles (410-660 kilometers) beneath Earth’s surface. Credit: F. Niu/Rice University.

    n the new study, data from the stations revealed both the upper and lower boundaries of the Pacific plate, dipping down at a 25-degree angle within the mantle transition zone. The placement within this zone is important for the study of mantle convection because the transition zone lies below the asthenosphere, at depths where increased pressure causes specific mantle minerals to undergo dramatic phase changes. These phases of the minerals behave very differently in seismic profiles, just as liquid water and solid ice behave very different even though they are made of identical molecules. Because phase changes in the mantle transition zone happen at specific pressures and temperatures, geoscientists can use them like a thermometer to measure the temperature in the mantle.

    Niu said the fact that both the top and bottom of the slab are visible is evidence that the slab hasn’t completely mixed with the surrounding mantle. He said heat signatures of partially melted portions of the mantle beneath the slab also provide indirect evidence that the slab transported some of its water into the transition zone.

    “The problem is explaining how these hot materials can be dropped into the deeper part of the mantle,” Niu said. “It’s still a question. Because they are hot, they are buoyant.”

    4
    Illustration of a process where holes in the subducting Pacific plate would allow heat to escape, driving volcanic activity in the Changbaishan region at the border of China and North Korea, even as the plate continues to sink into the mantle.
    Credit: F. Niu/Rice University.

    That buoyancy should act like a life preserver, pushing upward on the underside of the sinking slab. Niu said the answer to this question could be that holes have appeared in the deforming slab, allowing the hot melt to rise while the slab sinks.

    “If you have a hole, the melt will come out,” he said. “That’s why we think the slab can go deeper.”

    Holes could also explain the appearance of volcanos like the Changbaishan on the border between China and North Korea.

    “It’s 1,000 kilometers away from the plate boundary,” Niu said. “We don’t really understand the mechanism of this kind of volcano. But melt rising from holes in the slab could be a possible explanation.”

    Study co-authors include Xin Wang and Juan Li, both of the Chinese Academy of Sciences (CN), Shengji Wei of Singapore’s Nanyang Technological University (SG), Weijun Wang of the China Earthquake Administration (CN), Johannes Buchen of the California Institute of Technology and Lijun Liu of the University of Illinois at Urbana-Champaign. The research was funded by the Chinese Academy of Sciences (XDB18000000) and the National Natural Science Foundation of China (CN) (91958209, 41974057, 41130316).

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings


    Stem Education Coalition

    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

     
  • richardmitnick 1:43 pm on October 5, 2020 Permalink | Reply
    Tags: "Gemini South’s high-def version of ‘A Star is Born’", , , , , , Rice University   

    From Rice University: “Gemini South’s high-def version of ‘A Star is Born’” 

    From Rice University

    Sharpness of star-forming image matches expected resolution of Webb Space Telescope.

    NASA’s James Webb Space Telescope is still more than a year from launching, but the Gemini South telescope in Chile has provided astronomers a glimpse of what the orbiting observatory should deliver.

    NASA/ESA/CSA Webb Telescope annotated


    NOIRLab NOAO Gemini/South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet on the summit of Cerro Pachon.


    Gemini South’s high def version of ‘A Star is Born

    Hartigan, Isella and Downes describe their work in a study published online this week in The Astrophysical Journal Letters. Their images, gathered over 10 hours in January 2018 at the international Gemini Observatory, a program of the National Science Foundation’s NOIRLab, show part of a molecular cloud about 7,500 light years from Earth. All stars, including Earth’s sun, are thought to form within molecular clouds.

    NOIRLab.

    “The results are stunning,” Hartigan said. “We see a wealth of detail never observed before along the edge of the cloud, including a long series of parallel ridges that may be produced by a magnetic field, a remarkable almost perfectly smooth sine wave and fragments at the top that appear to be in the process of being sheared off the cloud by a strong wind.”

    1
    Two near-infrared images of the star-forming region in the Carina Nebula known as the Western Wall illustrate the capabilities of a wide-field adaptive optics camera at the Gemini South 8.1-meter telescope on Cerro Pachón mountain in Chile. Both images were captured by captured by Rice University astronomer Patrick Hartigan and colleagues from telescopes at the National Science Foundation’s NOIRLab observatory near near Vicuña, Chile. The lefthand image was taken with the four-meter Blanco telescope’s Extremely Wide-Field Infrared Imager in 2015. The righthand image, taken in January 2018, has about 10 times finer resolution thanks to a mirror in the Gemini South Adaptive Optics Imager that changes shape to correct for atmospheric distortion caused by Earth’s atmosphere. (Images courtesy of P. Hartigan/Rice University)

    Carina Nebula. 1.5-m Danish telescope at ESO’s La Silla Observatory.

    ESO Danish 1.54 meter telescope at La Silla, 600 km north of Santiago de Chile at an altitude of 2400 metres.


    NOIRLab NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet.

    NOIRLab NOAO CTIO Gemini Planet Imager on Gemini South

    The images show a cloud of dust and gas in the Carina Nebula known as the Western Wall. The cloud’s surface is slowly evaporating in the intense glow of radiation from a nearby cluster of massive young stars. The radiation causes hydrogen to glow with near-infrared light, and specially designed filters allowed the astronomers to capture separate images of hydrogen at the cloud’s surface and hydrogen that was evaporating.

    An additional filter captured starlight reflected from dust, and combining the images allowed Hartigan, Isella and Downes to visualize how the cloud and cluster are interacting. Hartigan has previously observed the Western Wall with other NOIRLab telescopes and said it was a prime choice to follow up with Gemini’s adaptive optics system.

    “This region is probably the best example in the sky of an irradiated interface,” he said. “The new images of it are so much sharper than anything we’ve previously seen. They provide the clearest view to date of how massive young stars affect their surroundings and influence star and planet formation.”

    Images of star-forming regions taken from Earth are usually blurred by turbulence in the atmosphere. Placing telescopes in orbit eliminates that problem. And one of the Hubble Space Telescope’s most iconic photographs, 1995’s “Pillars of Creation,” captured the grandeur of dust columns in a star-forming region.

    NASA’s Hubble Space Telescope has revisited the famous Pillars of Creation, revealing a sharper and wider view of the structures in this visible-light image.
    Astronomers combined several Hubble exposures to assemble the wider view. The towering pillars are about 5 light-years tall. The dark, finger-like feature at bottom right may be a smaller version of the giant pillars. The new image was taken with Hubble’s versatile and sharp-eyed Wide Field Camera 3.
    The pillars are bathed in the blistering ultraviolet light from a grouping of young, massive stars located off the top of the image. Streamers of gas can be seen bleeding off the pillars as the intense radiation heats and evaporates it into space. Denser regions of the pillars are shadowing material beneath them from the powerful radiation. Stars are being born deep inside the pillars, which are made of cold hydrogen gas laced with dust. The pillars are part of a small region of the Eagle Nebula, a vast star-forming region 6,500 light-years from Earth.
    The colors in the image highlight emission from several chemical elements. Oxygen emission is blue, sulfur is orange, and hydrogen and nitrogen are green.
    Object Names: M16, Eagle Nebula, NGC 6611
    Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

    But the beauty of the image belied Hubble’s weakness for studying molecular clouds.

    “Hubble operates at optical and ultraviolet wavelengths that are blocked by dust in star-forming regions like these,” Hartigan said.

    Because near-infrared light penetrates the outer layers of dust in molecular clouds, near-infrared cameras like the Gemini South Adaptive Optics Imager can see what lies beneath. Unlike traditional infrared cameras, Gemini South’s imager uses “a mirror that changes its shape to correct for shimmering in our atmosphere,” Hartigan said. The result: photos with roughly 10 times the resolution of images taken from ground-based telescopes that don’t use adaptive optics.

    But the atmosphere causes more than blur. Water vapor, carbon dioxide and other atmospheric gases absorb some parts of the near-infrared spectrum before it reaches the ground.

    “Many near-infrared wavelengths will only be visible from a space telescope like the Webb,” Hartigan said. “But for near-infrared wavelengths that reach Earth’s surface, adaptive optics can produce images as sharp as those acquired from space.”

    The advantages of each technique bode well for the study of star formation, he said.

    “Structures like the Western Wall are going to be rich hunting grounds for both Webb and ground-based telescopes with adaptive optics like Gemini South,” Hartigan said. “Each will pierce the dust shrouds and reveal new information about the birth of stars.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings


    Stem Education Coalition

    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

     
  • richardmitnick 9:09 am on September 5, 2020 Permalink | Reply
    Tags: "Quantum leap for speed limit bounds", , Nature’s ultimate speed limit is the speed of light but in nearly all matter around us the speed of energy and information is much slower., , Rice University, Theoretical quantum physics   

    From Rice University: “Quantum leap for speed limit bounds” 

    Rice U bloc

    From Rice University

    September 2, 2020
    Jade Boyd

    Rice physicists set far-more-accurate limits on speed of quantum information.

    1
    A Wang-Hazzard commutativity graph captures the microscopic detail of the mathematical functions physicists typically use to describe energy in quantum systems, reducing the calculation of quantum speed limits to an equation with just two inputs. (Image courtesy of Zhiyuan Wang/Rice University)

    Nature’s speed limits aren’t posted on road signs, but Rice University physicists have discovered a new way to deduce them that is better — infinitely better, in some cases — than previous methods.

    “The big question is, ‘How fast can anything — information, mass, energy — move in nature?’” said Kaden Hazzard, a theoretical quantum physicist at Rice. “It turns out that if somebody hands you a material, it is incredibly difficult, in general, to answer the question.”

    In a study published today in the American Physical Society journal PRX Quantum, Hazzard and Rice graduate student Zhiyuan Wang describe a new method for calculating the upper bound of speed limits in quantum matter.

    “At a fundamental level, these bounds are much better than what was previously available,” said Hazzard, an assistant professor of physics and astronomy and member of the Rice Center for Quantum Materials. “This method frequently produces bounds that are 10 times more accurate, and it’s not unusual for them to be 100 times more accurate. In some cases, the improvement is so dramatic that we find finite speed limits where previous approaches predicted infinite ones.”

    Nature’s ultimate speed limit is the speed of light, but in nearly all matter around us, the speed of energy and information is much slower. Frequently, it is impossible to describe this speed without accounting for the large role of quantum effects.

    In the 1970s, physicists proved that information must move much slower than the speed of light in quantum materials, and though they could not compute an exact solution for the speeds, physicists Elliott Lieb and Derek Robinson pioneered mathematical methods for calculating the upper bounds of those speeds.

    “The idea is that even if I can’t tell you the exact top speed, can I tell you that the top speed must be less than a particular value,” Hazzard said. “If I can give a 100% guarantee that the real value is less than that upper bound, that can be extremely useful.”

    Hazzard said physicists have long known that some of the bounds produced by the Lieb-Robinson method are “ridiculously imprecise.”

    “It might say that information must move less than 100 miles per hour in a material when the real speed was measured at 0.01 miles per hour,” he said. “It’s not wrong, but it’s not very helpful.”

    The more accurate bounds described in the PRX Quantum paper were calculated by a method Wang created.

    “We invented a new graphical tool that lets us account for the microscopic interactions in the material instead of relying only on cruder properties such as its lattice structure,” Wang said.

    Hazzard said Wang, a third-year graduate student, has an incredible talent for synthesizing mathematical relationships and recasting them in new terms.

    “When I check his calculations, I can go step by step, churn through the calculations and see that they’re valid,” Hazzard said. “But to actually figure out how to get from point A to point B, what set of steps to take when there’s an infinite variety of things you could try at each step, the creativity is just amazing to me.”

    The Wang-Hazzard method can be applied to any material made of particles moving in a discrete lattice. That includes oft-studied quantum materials like high-temperature superconductors, topological materials, heavy fermions and others. In each of these, the behavior of the materials arises from interactions of billions upon billions of particles, whose complexity is beyond direct calculation.

    Hazzard said he expects the new method to be used in several ways.

    “Besides the fundamental nature of this, it could be useful for understanding the performance of quantum computers, in particular in understanding how long they take to solve important problems in materials and chemistry,” he said.

    Hazzard said he is certain the method will also be used to develop numerical algorithms because Wang has shown it can put rigorous bounds on the errors produced by oft-used numerical techniques that approximate the behavior of large systems.

    A popular technique physicists have used for more than 60 years is to approximate a large system by a small one that can be simulated by a computer.

    “We draw a small box around a finite chunk, simulate that and hope that’s enough to approximate the gigantic system,” Hazzard said. “But there has not been a rigorous way of bounding the errors in these approximations.”

    The Wang-Hazzard method of calculating bounds could lead to just that.

    “There is an intrinsic relationship between the error of a numerical algorithm and the speed of information propagation,” Wang explained, using the sound of his voice and the walls in his room to illustrate the link.

    “The finite chunk has edges, just as my room has walls. When I speak, the sound will get reflected by the wall and echo back to me. In an infinite system, there is no edge, so there is no echo.”

    In numerical algorithms, errors are the mathematical equivalent of echoes. They reverberate from the edges of the finite box, and the reflection undermines the algorithms’ ability to simulate the infinite case. The faster information moves through the finite system, the shorter the time the algorithm faithfully represents the infinite.

    Hazzard said he, Wang and others in his research group are using their method to craft numerical algorithms with guaranteed error bars.

    “We don’t even have to change the existing algorithms to put strict, guaranteed error bars on the calculations,” he said. “But you can also flip it around and use this to make better numerical algorithms. We’re exploring that, and other people are interested in using these as well.”

    The research was supported by the Welch Foundation and the National Science Foundation.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings


    Stem Education Coalition

    Rice U campus

    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

     
  • richardmitnick 3:43 pm on August 25, 2020 Permalink | Reply
    Tags: "Small quake clusters can’t hide from AI", Constant monitoring in real time will save lives., Deep learning may someday help predict seismic events like earthquakes and volcanic eruptions., , Nuugaatsiaq landslide released up to 51 million cubic meters of material., Rice researchers use deep learning to find signs were present before deadly Greenland landslide., Rice University, The approach represents a new research direction for machine learning as applied to geophysics   

    From Rice University: “Small quake clusters can’t hide from AI” 

    Rice U bloc

    From Rice University

    August 24, 2020
    Mike Williams

    Rice researchers use deep learning to find signs were present before deadly Greenland landslide.

    Researchers at Rice University’s Brown School of Engineering are using data gathered before a deadly 2017 landslide in Greenland to show how deep learning may someday help predict seismic events like earthquakes and volcanic eruptions.

    Seismic data collected before the massive landslide at a Greenland fjord shows the subtle signals of the impending event were there, but no human analyst could possibly have put the clues together in time to make a prediction. The resulting tsunami that devastated the village of Nuugaatsiaq killed four people and injured nine and washed 11 buildings into the sea.

    1
    An overview by the U.S. Geological Survey shows the location of the Nuugaatsiaq landslide (yellow star) relative to five broadband seismic stations (pink triangles) within 500 km of the landslide. Nuugaatsiaq (NUUG) was impacted by the resulting tsunami the reached a height of 300 feet at sea, though it was much lower before it reached the village. The inset shows the geometry of the fjords relative to the landslide and Nuugaatsiaq. Courtesy of USGS.

    A study lead by former Rice visiting scholar Léonard Seydoux, now an assistant professor at the University of Grenoble-Alpes, employs techniques developed by Rice engineers and co-authors Maarten de Hoop, Richard Baraniuk and graduate student Randall Balestriero. Their open-access report in Nature Communications shows how deep learning methods can process the overwhelming amount of data provided by seismic tools fast enough to predict events.

    De Hoop, who specializes in mathematical analysis of inverse problems and deep learning in connection with Rice’s Department of Earth, Environmental and Planetary Sciences, said advances in artificial intelligence (AI) are well-suited to independently monitor large and growing amounts of seismic data. AI has the ability to identify clusters of events and detect background noise to make connections that human experts might not recognize due to biases in their models, not to mention sheer volume, he said.

    Hours before the Nuugaatsiaq event, those small signals began to appear in data collected by a nearby seismic station. The researchers analyzed data from midnight on June 17, 2017, until one minute before the slide at 11:39 p.m. that released up to 51 million cubic meters of material.

    The Rice algorithm revealed weak but repetitive rumblings — undetectable in raw seismic records — that began about nine hours before the event and accelerated over time, leading to the landslide.

    “There was a precursor paper [Geophysical Research Letters] to this one by our co-author, Piero Poli at Grenoble, that studied the event without AI,” de Hoop said. “They discovered something in the data they thought we should look at, and because the area is isolated from a lot of other noise and tectonic activity, it was the purest data we could work with to try our ideas.”

    De Hoop is continuing to test the algorithm to analyze volcanic activity in Costa Rica and is also involved with NASA’s InSight lander, which delivered a seismic detector to the surface of Mars nearly two years ago.

    Constant monitoring that delivers such warnings in real time will save lives, de Hoop said.

    “People ask me if this study is significant — and yes, it is a major step forward — and then if we can predict earthquakes. We’re not quite ready to do that, but this direction is, I think, one of the most promising at the moment.”

    When de Hoop joined Rice five years ago, he brought expertise in solving inverse problems that involve working backwards from data to find a cause. Baraniuk is a leading expert in machine learning and compressive sensing, which help extract useful data from sparse samples. Together, they’re a formidable team.

    “The most exciting thing about this work is not the current result, but the fact that the approach represents a new research direction for machine learning as applied to geophysics,” Baraniuk said.

    “I come from the mathematics of deep learning and Rich comes from signal processing, which are at opposite ends of the discipline,” de Hoop said. “But here we meet in the middle. And now we have a tremendous opportunity for Rice to build upon its expertise as a hub for seismologists to gather and put these pieces together. There’s just so much data now that it’s becoming impossible to handle any other way.”

    De Hoop is helping to grow Rice’s reputation for seismic expertise with the Simons Foundation Math+X Symposia, which have already featured events on space exploration and mitigating natural hazards like volcanoes and earthquakes. A third event, dates to be announced, will study deep learning applications for solar giants and exoplanets.

    3
    A graph extracted by a novel Rice University algorithm shows waveforms from the cluster associated with precursors and aligned with respect to a reference waveform within the cluster. The data was from three seismograms collected over the course of the day before the Nuugaatsiaq landslide. Courtesy of Nature Communications.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings


    Stem Education Coalition

    Rice U campus

    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

     
  • richardmitnick 7:01 pm on March 4, 2020 Permalink | Reply
    Tags: "A small step for atoms a giant leap for microelectronics", , Gordon Moore's prediction is getting "long in the tooth"., In 1975 Intel’s Gordon Moore predicted that the number of transistors in an integrated circuit would double every two years., , Rice University, Step by step scientists are figuring out new ways to extend Moore’s Law. The latest reveals a path toward integrated circuits with two-dimensional transistors., The ability to stack 2D layers each with millions of transistors may overcome such limitations if they can be isolated from one other., The main discovery in this work is that a monocrystal across a wafer can be achieved and then they can move it.   

    From Rice University: “A small step for atoms, a giant leap for microelectronics” 

    Rice U bloc

    From Rice University

    March 4, 2020
    Jeff Falk
    713-348-6775
    jfalk@rice.edu

    Mike Williams
    713-348-6728
    mikewilliams@rice.edu

    1
    Atoms of boron and nitride align on a copper substrate to create a large-scale, ordered crystal of hexagonal boron nitride. The wafer-sized material could become a key insulator in future two-dimensional electronics. Illustration by Tse-An Chen/TSMC

    Step by step, scientists are figuring out new ways to extend Moore’s Law. The latest reveals a path toward integrated circuits with two-dimensional transistors.

    A Rice University scientist and his collaborators in Taiwan and China reported in Nature today that they have successfully grown atom-thick sheets of hexagonal boron nitride (hBN) as two-inch diameter crystals across a wafer.

    Surprisingly, they achieved the long-sought goal of making perfectly ordered crystals of hBN, a wide band gap semiconductor, by taking advantage of disorder among the meandering steps on a copper substrate. The random steps keep the hBN in line.

    Set into chips as a dielectric between layers of nanoscale transistors, wafer-scale hBN would excel in damping electron scattering and trapping that limit the efficiency of an integrated circuit. But until now, nobody has been able to make perfectly ordered hBN crystals that are large enough — in this case, on a wafer — to be useful.

    Brown School of Engineering materials theorist Boris Yakobson is co-lead scientist on the study with Lain-Jong (Lance) Li of the Taiwan Semiconductor Manufacturing Co. (TSMC) and his team. Yakobson and Chih-Piao Chuu of TSMC performed theoretical analysis and first principles calculations to unravel the mechanisms of what their co-authors saw in experiments.

    As a proof of concept for manufacturing, experimentalists at TSMC and Taiwan’s National Chiao Tung University grew a two-inch, 2D hBN film, transferred it to silicon and then placed a layer of field-effect transistors patterned onto 2D molybdenum disulfide atop the hBN.

    “The main discovery in this work is that a monocrystal across a wafer can be achieved, and then they can move it,” Yakobson said. “Then they can make devices.”

    “There is no existing method that can produce hBN monolayer dielectrics with extremely high reproducibility on a wafer, which is necessary for the electronics industry,” Li added. “This paper reveals the scientific reasons why we can achieve this.”

    Yakobson hopes the technique may also apply broadly to other 2D materials, with some trial and error. “I think the underlying physics is pretty general,” he said. “Boron nitride is a big-deal material for dielectrics, but many desirable 2D materials, like the 50 or so transition metal dichalcogenides, have the same issues with growth and transfer, and may benefit from what we discovered.”

    In 1975, Intel’s Gordon Moore predicted that the number of transistors in an integrated circuit would double every two years. But as integrated circuit architectures get smaller, with circuit lines down to a few nanometers, the pace of progress has been hard to maintain.

    The ability to stack 2D layers, each with millions of transistors, may overcome such limitations if they can be isolated from one other. Insulating hBN is a prime candidate for that purpose because of its wide band gap.

    Despite having “hexagonal” in its name, monolayers of hBN as seen from above appear as a superposition of two distinct triangular lattices of boron and nitrogen atoms. For the material to perform up to spec, hBN crystals must be perfect; that is, the triangles have to be connected and all point in the same direction. Non-perfect crystals have grain boundaries that degrade the material’s electronic properties.

    For hBN to become perfect, its atoms have to precisely align with those on the substrate below. The researchers found that copper in a (111) arrangement — the number refers to how the crystal surface is oriented — does the job, but only after the copper is annealed at high temperature on a sapphire substrate and in the presence of hydrogen.

    Annealing eliminates grain boundaries in the copper, leaving a single crystal. Such a perfect surface would, however, be “way too smooth” to enforce the hBN orientation, Yakobson said.

    Yakobson reported on research last year to grow pristine borophene on silver (111), and also a theoretical prediction that copper can align hBN by virtue of the complementary steps on its surface. The copper surface was vicinal — that is, slightly miscut to expose atomic steps between the expansive terraces. That paper caught the attention of industrial researchers in Taiwan, who approached the professor after a talk there last year.

    “They said, ‘We read your paper,’” Yakobson recalled. “‘We see something strange in our experiments. Can we talk?’ That’s how it started.”

    Informed by his earlier experience, Yakobson suggested that thermal fluctuations allow copper (111) to retain step-like terraces across its surface, even when its own grain boundaries are eliminated. The atoms in these meandering “steps” present just the right interfacial energies to bind and constrain hBN, which then grows in one direction while it attaches to the copper plane via the very weak van der Waals force.

    2
    Researchers in Taiwan, China and at Rice made wafer-sized, two-dimensional sheets of hexagonal boron nitride, as reported in Nature. The material may be removed from its copper substrate and used as a dielectric for two-dimensional electronics.

    “Every surface has steps, but in the prior work, the steps were on a hard-engineered vicinal surface, which means they all go down, or all up,” he said. “But on copper (111), the steps are up and down, by just an atom or two randomly, offered by the fundamental thermodynamics.”

    Because of the copper’s orientation, the horizontal atomic planes are offset by a fraction to the lattice underneath. “The surface step-edges look the same, but they’re not exact mirror-twins,” Yakobson explained. “There’s a larger overlap with the layer below on one side than on the opposite.”

    That makes the binding energies on each side of the copper plateau different by a minute 0.23 electron volts (per every quarter-nanometer of contact), which is enough to force docking hBN nuclei to grow in the same direction, he said.

    The experimental team found the optimal copper thickness was 500 nanometers, enough to prevent its evaporation during hBN growth via chemical vapor deposition of ammonia borane on a copper (111)/sapphire substrate.

    Tse-An Chen of TSMC is co-lead author of the paper. Co-authors are Chien-Chih Tseng, Chao-Kai Wen, Wei-Chen Chueh and Wen-Hao Chang of Chiao Tung; H.-S. Philip Wong and Tsu-Ang Chao of TSMC; Shuangyuan Pan and Yanfeng Zhang of Peking University, China; Qiang Fu of the Chinese Academy of Sciences, Dalian, China; and Rongtan Li of the Chinese Academy of Sciences and the University of Chinese Academy of Sciences, Beijing.

    Yakobson is the Karl F. Hasselmann Professor of Materials Science and NanoEngineering and a professor of chemistry at Rice. Chang is a professor at Chiao Tung and director of the university’s Center for Emergent Functional Matter Science. Li is Director, Corporate Research, Taiwan Semiconductor Manufacturing Co.

    The research was supported by TSMC, the Ministry of Science and Technology of Taiwan, the Ministry of Education of Taiwan, the National Natural Science Foundation of China, the Chinese Academy of Sciences and the U.S. Department of Energy.

    See the full article here .


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    Stem Education Coalition

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    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

     
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