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  • richardmitnick 12:44 pm on June 24, 2019 Permalink | Reply
    Tags: "NASA’s Fermi mission reveals record-setting gamma-ray bursts", , , , , , , Stanford University   

    From Stanford University: “NASA’s Fermi mission reveals record-setting gamma-ray bursts” 

    Stanford University Name
    From Stanford University

    June 13, 2019

    1
    NASA/DOE/FermiLAT Collaboration

    NASA/Fermi Gamma Ray Space Telescope

    NASA/Fermi LAT

    Stanford has played a leading role in compiling Fermi’s gamma-ray bursts catalogs ever since the space observatory launched nearly 11 years ago.

    For 10 years, NASA’s Fermi Gamma-ray Space Telescope has scanned the sky for gamma-ray bursts (GRBs), the universe’s most luminous explosions. A new catalog of the highest-energy blasts provides scientists with fresh insights into how they work.

    “Fermi is an ongoing experiment that keeps producing good science,” said Nicola Omodei, an astrophysicist at Stanford University’s School of Humanities and Sciences. “GRBs are really one of the most spectacular astronomical events that we witness.”

    The catalog was published in the June 13 edition of The Astrophysical Journal. More than 120 authors contributed to the paper, which was led by Omodei and Giacomo Vianello at Stanford, Magnus Axelsson at Stockholm University in Sweden, and Elisabetta Bissaldi at the National Institute of Nuclear Physics and Polytechnic University in Bari, Italy.

    Stanford has played a leading role in compiling Fermi’s GRB catalogs ever since the space observatory launched nearly 11 years ago. “All of the analysis tools and methods that led to the preperation of the catalogs were developed at Stanford and SLAC,” Omodei said. “We’ve continued to refine the analysis techniques and increase the sensitivity of the Fermi Large Area Telescope (LAT) to GRBs. For every GRB, we can characterize its duration, its temporal behavior, and its spectral properties.”

    GRBs emit gamma rays, the highest-energy form of light. Most GRBs occurs when some types of massive stars run out of fuel and collapse to create new black holes. Others happen when two neutron stars, superdense remnants of stellar explosions, merge. Both kinds of cataclysmic events create jetfers of particles that move near the speed of light. The gamma rays are produced in collisions of fast-moving material inside the jets and when the jets interact with the environment around the star.

    Astronomers can distinguish the two GRB classes by the duration of their lower-energy gamma rays. Short bursts from neutron star mergers last less than 2 seconds, while long bursts typically continue for a minute or more. The new catalog, which includes 17 short and 169 long bursts, describes 186 events seen by Fermi’s Large Area Telescope (LAT) LAT over the last 10 years.

    Fermi observes these powerful bursts using two instruments. The LAT sees about one-fifth of the sky at any time and records gamma rays with energies above 30 million electron volts (MeV) — millions of times the energy of visible light. The Gamma-ray Burst Monitor (GBM) sees the entire sky that isn’t blocked by Earth and detects lower-energy emission. All told, the GBM has detected more than 2,300 GRBs so far.

    Included in Fermi’s latest observation set are a number of record-setting and intriguing events, including the shortest burst ever recorded (GRB 081102B, which lasted just one-tenth of a second), the longest burst in the catalog (GRB 160623A, which remained illuminated for 10 hours), and the farthest known burst (GRB 080916C, located 12.2 billion light-years away in the constellation Carina).

    Also included in the new catalog is GRB 170817A, the first burst to have both its light and gravitational waves captured simultaneously. Light from the event — a product of two neutron stars crashing together — was recorded by Fermi’s GBM instrument, while the spacetime ripples it generated were detected by the Laser Interferometer Gravitational Wave Observatory (LIGO), the Virgo interferometer.


    VIRGO Gravitational Wave interferometer, near Pisa, Italy


    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger

    Gravity is talking. Lisa will listen. Dialogos of Eide

    ESA/eLISA the future of gravitational wave research

    Localizations of gravitational-wave signals detected by LIGO in 2015 (GW150914, LVT151012, GW151226, GW170104), more recently, by the LIGO-Virgo network (GW170814, GW170817). After Virgo came online in August 2018


    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    “Now that LIGO and VIRGO have begun another observation period, the astrophysics community will be on the lookout for more joint GRB and gravitational wave events” said Judy Racusin, a co-author and Fermi deputy project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “This catalog was a monumental team effort, and the result helps us learn about the population of these events and prepares us for delving into future groundbreaking finds.”

    The Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Fermi was developed in collaboration with the U.S. Department of Energy, with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

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  • richardmitnick 11:22 am on June 13, 2019 Permalink | Reply
    Tags: "What Stanford researchers have learned from 300 stars", , , , , Gemini South and the Gemini Planet Imager, Stanford University   

    From Stanford University: “What Stanford researchers have learned from 300 stars” 

    Stanford University Name
    From Stanford University

    Analysis from halfway through the Gemini Planet Imager’s planetary survey hints that our solar system may have rare qualities that could possibly be related to the habitability of Earth. See video here.

    Gemini/South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

    NOAO Gemini Planet Imager on Gemini South

    June 12, 2019
    Taylor Kubota

    Over the past four years, an instrument attached to a telescope in the Chilean Andes – known as the Gemini Planet Imager – has set its gaze on 531 stars in search of new planets. The team, led by Stanford University, is now releasing initial findings from the first half of the survey, published June 12 in The Astronomical Journal.

    The survey imaged six planets and three brown dwarfs orbiting these 300 stars and offered new details about Jupiter-like planets, which could influence theories about how Earth formed and became habitable.

    “Over the past twenty years, astronomers have discovered all of these solar systems that are really different from our own,” said Bruce Macintosh, professor of physics at Stanford in the School of Humanities and Sciences. “The question that we want to understand ultimately is: Are there life-bearing, Earth-like planets out there? And one way to answer that is by understanding how other solar systems form.”

    Unlike other planet-hunting techniques, which rely on looking for signs of a planet – like the effect of its gravity on the parent star – rather than the planet itself, the Gemini Planet Imager takes direct images, picking the faint planet out of the glare of a star a million times brighter.

    “The giant planets in our own solar system live between five and 30 times Earth’s orbital distance, and for the first time we’re probing a similar region around other stars,” said Eric Nielsen, a research scientist at the Kavli Institute for Particle Astrophysics and Cosmology and lead author of the paper. “It’s pretty exciting to be able to start to put together a census of the planets larger than Jupiter in the outer solar systems of some of our neighboring stars.”

    Maybe a special system

    Most other techniques probe the inner parts of solar systems. But the Gemini Planet Imager specifically focuses on exoplanets that are large, young and far away from the star they orbit. In our solar system, the outer parts are the home of the giant planets. The Gemini Planet Imager helps the researchers better understand whether other solar systems have planets like Jupiter. However, while the Gemini Planet Imager is one of the most sensitive planet imagers, there are still objects that elude it and the planets this team can currently see are those more than twice the mass of Jupiter.

    In the first half of the survey, the Gemini Planet Imager found fewer exoplanets than the researchers expected. However, the exoplanets they did see contributed to one of their strongest results: every one of the six planets orbited a large, bright star – despite the fact that planets are easier to see near faint stars. This shows conclusively that wide-orbiting giant planets are more common around high mass stars, at least 1.5 times more massive than the sun. Meanwhile, for sun-like stars, Jupiter’s larger cousins are much rarer than the small planets discovered close to their star by missions like NASA’s Kepler.

    “Given what we and other surveys have seen so far, our solar system doesn’t look like other solar systems,” Macintosh said. “We don’t have as many planets packed in as close to the sun as they do to their stars and we now have tentative evidence that another way in which we might be rare is having these kind of Jupiter-and-up planets.”

    Although exact Jupiter-equivalent exoplanets are just beyond the scope of their instruments, not finding even a hint of something Jupiter-like around these 300 stars leaves open the possibility that our Jupiter is special.

    One other result from the first half of the survey is that brown dwarfs – objects larger than planets but smaller than stars – are a very distinct population from planets. This may point to a different formation mechanism for this class of objects, suggesting that brown dwarfs are more similar to failed stars than super-size planets.

    Combined with other techniques, this paper pinpoints a distance from a star at which the number of giant planets goes from increasing to decreasing – at about five to 10 astronomical units (one astronomical unit is the distance from the sun to Earth).

    “The region in the middle could be where you’re most likely to find planets larger than Jupiter around other stars,” Nielsen added, “which is very interesting since this is where we see Jupiter and Saturn in our own solar system.”

    All three of the main findings support the hypothesis that giant planets likely form “bottom up” by accumulation of particles around a solid core, whereas brown dwarfs likely form “top down” as a result of huge gravitational instabilities in the disk of gas and dust from which a solar system develops.

    Working their way to Earth

    The Gemini Planet Imager Exoplanet Survey (GPIES) observed its 531st, and final, new star in January 2019. The Gemini Planet Imager team is now working on making the instrument more sensitive to smaller, cooler exoplanets that orbit closer to their suns. Meanwhile, the surveys capable of indirectly observing those exoplanets are moving their sensitivity outward. In the not-too-distant future, the two should convene at the corners of space where a solar system like our own could still be hiding. Whatever instrument is the first to be capable of directly viewing an Earth-like world, Macintosh imagines it will be, at least in part, a descendant of the Gemini Planet Imager.

    “Right now, we see these planets as fuzzy, red blobs. Someday, it’s going to be a fuzzy blue blob. And that little, tiny, fuzzy, blue blob is going to be an Earth,” Macintosh said. “Getting to Earths will take a space mission that’s probably about 20 years away. But when it flies, it’ll use a spectrograph like the one we built and deformable mirrors like what we have and software with lines of code that we’ve written.”

    More immediately, the GPIES team members plan to publish additional results about the survey, including information they gathered about the atmospheres of exoplanets they saw, and finish analyzing the data obtained during the second half of the survey.

    “I helped take the first GPIES planet search images four and a half years ago,” said Robert De Rosa, a research scientist at the Kavli Institute for Particle Astrophysics and Cosmology and co-author of the paper, who spent many nights observing with the Gemini Planet Imager in Chile and remotely from Stanford. “It’s bittersweet to see it draw to a close.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal

     
  • richardmitnick 10:24 am on June 6, 2019 Permalink | Reply
    Tags: An aquatic highway that lets nutrients from Earth’s belly sweep up to surface waters off the coast of Antarctica and stimulate explosive growth of microscopic ocean algae, , Deep-ocean vents fuel massive phytoplankton blooms, , , Phytoplankton need iron to thrive, Stanford University, When conditions are right phytoplankton can also grow explosively   

    From Stanford University: “Stanford study shows how deep-ocean vents fuel massive phytoplankton blooms – and possible hotspots for carbon storage” 

    Stanford University Name
    From Stanford University

    June 5, 2019
    Josie Garthwaite

    1
    Superheated, iron-rich fluid gushes from a hydrothermal vent more than 2,500 meters deep in the Southern Ocean. The iron spewing from deep water vents like this one may fuel phytoplankton blooms on the surface. (Image credit: NERC/NSF Chesso Consortium)

    Researchers at Stanford University say they have found an aquatic highway that lets nutrients from Earth’s belly sweep up to surface waters off the coast of Antarctica and stimulate explosive growth of microscopic ocean algae.

    Their study, published June 5 in the journal Nature Communications, suggests that hydrothermal vents – openings in the seafloor that gush scorching hot streams of mineral-rich fluid – may affect life near the ocean’s surface and the global carbon cycle more than previously thought.

    Mathieu Ardyna, a postdoctoral scholar and the study’s lead author, said the research provides the first observed evidence of iron from the Southern Ocean’s depths turning normally anemic surface waters into hotspots for phytoplankton – the tiny algae that sustain the marine food web, pull heat-trapping carbon dioxide out of the air and produce a huge amount of the oxygen we breathe. “Our study shows that iron from hydrothermal vents can well up, travel across hundreds of miles of open ocean and allow phytoplankton to thrive in some very unexpected places,” he said.

    Kevin Arrigo, a professor of Earth system science and senior author of the paper, called the findings “important because they show how intimately linked the deep ocean and surface ocean can be.”

    Mysterious blooms

    Phytoplankton need iron to thrive, and that limits their abundance in vast swaths of the ocean where concentrations of the nutrient are low. But when conditions are right, phytoplankton can also grow explosively, blooming across thousands of square miles in a matter of days.

    That’s what Ardyna noticed recently as he looked at data recorded in 2014 and 2015 by a fleet of floating robots outfitted with optical sensors in the Southern Ocean. More than 1,300 miles off the coast of Antarctica and 1,400 miles from the African continent, two unexpectedly large blooms cropped up in an area known for severe iron shortages and low concentrations of chlorophyll, an indicator of phytoplankton populations.

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    A robotic buoy outfitted with sensors as part of the Biogeochemical-Argo network floats in polar waters, taking measurements that help scientists answer questions about the composition of phytoplankton communities and the uptake of carbon dioxide by the ocean. (Image credit: P. Bourgain)

    Massive blooms in this region could only be possible with an influx of iron. Ardyna and Arrigo quickly ruled out the ocean’s most common sources, including continental shelves, melting sea ice and atmospheric dust, which were simply too far away to have much influence.

    That led them to suspect that the nutrient must be welling up from below, possibly from a string of hydrothermal vents that dot a mid-ocean ridge 750 miles from where the massive blooms had inexplicably appeared. To help test their hypothesis, they recruited an international team of collaborators specialized in various aspects of oceanography and modeling.

    “It has long been known that hydrothermal vents create unique and profound oases of life,” Ardyna said. Until recently, scientists generally believed those nourishing effects remained fairly local. But a growing amount of evidence from computer simulations of ocean dynamics has hinted that iron and other life-sustaining elements spewed from hydrothermal vents may in fact fuel planktonic blooms over much wider areas.

    However, direct measurements have been lacking.

    In the Southern Ocean, that’s partly due to the remote location, extreme cold and rough seas, which make it difficult to study up close or collect accurate data. “Your sensors have to be in the right place at the right time to see these blooms,” Ardyna said. “Satellites can underestimate intensity or miss them altogether because of bad coverage or strong mixing of the water column, which pushes phytoplankton down too deep for satellites to see.”

    Clues from space, floating robots

    To track the flow of particles from the vents on the mid-ocean ridge, the scientists analyzed data from satellites measuring chlorophyll and from autonomous, sensor-laden buoys known as Argo floats. As they dive and drift along ocean currents, some of these buoys detect chlorophyll and other proxies for phytoplankton biomass. “The floats give us precious and unique data, covering a large section of the water column down to 1,000 meters deep during an entire annual cycle,” Ardyna said.

    The scientists couldn’t directly measure iron in the water, but instead analyzed measurements of helium collected by scientific cruises in the 1990s. The presence of helium signals waters influenced by hydrothermal vents, which funnel large amounts of primordial helium from beneath Earth’s crust.

    The chlorophyll, phytoplankton and helium data suggest that a powerful current circling Antarctica grabs nutrients rising up from vents. Two turbulent, fast-moving branches of the current then shuttle the nutrients eastward for a month or two before serving them like a banquet to undernourished phytoplankton. Together with the arrival of spring sunshine that phytoplankton need for photosynthesis, the delivery triggers a massive bloom that can likely absorb and store significant amounts of carbon from the atmosphere, said Arrigo, who is also the Donald and Donald M. Steel Professor in Earth Sciences.

    Over time, the blooms drift eastward toward the current racing around Antarctica and fade as sea creatures devour them. “We suspect these hotspots are either consumed or exported to deep waters,” Ardyna said.

    Each bloom lasts little more than a month, but the mechanisms that trigger them are likely to be more common in the global ocean than scientists previously suspected.

    “Hydrothermal vents are scattered all over the ocean floor,” Ardyna said. Knowing about the pathways that bring their nutrients up to surface waters will help researchers make more accurate calculations about the flow of carbon in the world’s oceans. “Much remains to be done to reveal other potential hotspots and quantify how this mechanism is altering the carbon cycle.”

    Arrigo is also a member of Stanford Bio-X and an affiliate of the Stanford Woods Institute for the Environment. Ardyna is also affiliated with Sorbonne Université in France and the French National Centre for Scientific Research (CNRS). Co-authors are affiliated with Sorbonne Université, CNRS, Laval University in Canada, University of Liverpool in the United Kingdom, the Alfred Wegener Institute in Germany and the Université de Toulouse in France.

    The research was supported by the Centre National d’Etudes Spatiales, the European Union’s Horizon 2020 program, the European Research Council, BNP Paribas, the French Polar Institute (IPEV), Sorbonne Université and the National Science Foundation.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal

     
  • richardmitnick 8:41 am on June 5, 2019 Permalink | Reply
    Tags: "Stanford joins collaboration to explore 'ultra-quantum matter'", , , , Stanford University, The Simons Collaboration on Ultra-Quantum Matter   

    From Stanford University: “Stanford joins collaboration to explore ‘ultra-quantum matter'” 

    Stanford University Name
    From Stanford University

    June 3, 2019
    Ker Than

    1

    The Simons Collaboration on Ultra-Quantum Matter brings together physicists from 12 institutions to “understand, classify and realize” new forms of ultra-quantum matter in the lab.

    Stanford physicist Shamit Kachru is a member of a new collaboration that aims to unravel the mystery of entangled quantum matter — macroscopic assemblages of atoms and electrons that seem to share the same seemingly telepathic link as entangled subatomic particles.

    The Simons Collaboration on Ultra-Quantum Matter is funded by the Simons Foundation and led by Harvard physics Professor Ashvin Vishwanath. It is part of the Simons Collaborations in Mathematics and Physical Sciences program, which aims to “stimulate progress on fundamental scientific questions of major importance in mathematics, theoretical physics and theoretical computer science.” The Simons Collaboration on Ultra-Quantum Matter will be one of 12 such collaborations ranging across these fields.

    Ultra-quantum matter, or UQM, exhibit non-intuitive quantum properties that were once thought to arise only in very small systems. One key property is “non-local entanglement,” in which two physically separated groups of atoms can share joint properties, so that measuring one affects the measurement outcome of the other. UQM should exhibit entirely new physical properties, a better understanding of which could lead to new types of quantum information storage systems and quantum materials.

    The Simons Collaboration on Ultra-Quantum Matter brings together physicists from 12 institutions to “understand, classify and realize” new forms of ultra-quantum matter in the lab. To achieve this, the collaboration includes physicists working in different domains, including condensed matter and high energy theorists, as well as atomic and quantum information experts. Kachru’s own background is in string theory, theoretical cosmology, and condensed matter physics.

    A confluence of factors makes this a particularly exciting time to study UQM, said Kachru, who is the Wells Family Director of the Stanford Institute for Theoretical Physics (SITP) and the chair of the physics department.

    “Many of the cutting-edge questions in quantum field theory now seem to involve highly quantum condensed matter systems,” Kachru said. “These systems are often best studied using elegant and clean mathematical techniques, and there is a promise of genuine contact between high level theory and experiment. I can’t imagine better people to teach me about issues and opportunities here than the collaboration members, who are leading experts in all aspects of UQM.”

    Kachru also looks forward to working again with former Stanford graduate student and collaboration member, John McGreevy, who was Kachru’s first PhD advisee and is now a professor of physics at the University of California, San Diego.

    Ultra-Quantum Matter is an $8M four-year award funded by the Simons Foundation and renewable for three additional years. It will support researchers from the following institutions: Caltech, Harvard, the Institute for Advanced Study, MIT, Stanford, University of California Santa Barbara, University of California San Diego, the University of Chicago, the University of Colorado Boulder, the University of Innsbruck, University of Maryland and University of Washington.

    A UQM meeting of the new collaboration is scheduled to take place at Stanford in May of 2020.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal

     
  • richardmitnick 12:56 pm on May 24, 2019 Permalink | Reply
    Tags: , , , Geothermal energy’s earthquake problem, Stanford University   

    From Stanford University-“Lessons from Pohang: A Stanford geophysicist discusses geothermal energy’s earthquake problem – and possible solutions” 

    Stanford University Name
    From Stanford University

    May 23, 2019
    Josie Garthwaite

    A geothermal energy project triggered a damaging earthquake in 2017 in South Korea. A new analysis suggests flaws in some of the most common ways of trying to minimize the risk of such quakes when harnessing Earth’s heat for energy.

    1
    Conventional geothermal resources have been generating commercial power for decades in places where heat and water from burble up through naturally permeable rock. (Image credit: Shutterstock)

    On a November afternoon in 2017, a magnitude 5.5 earthquake shook Pohang, South Korea, injuring dozens and forcing more than 1,700 of the city’s residents into emergency housing. Research now shows that development of a geothermal energy project shoulders the blame.

    “There is no doubt,” said Stanford geophysicist William Ellsworth. “Usually we don’t say that in science, but in this case, the evidence is overwhelming.” Ellsworth is among a group of scientists, including Kang-Kun Lee of Seoul National University, who published a perspective piece May 24 in Science outlining lessons from Pohang’s failure.

    The Pohang earthquake stands out as by far the largest ever linked directly to development of what’s known as an enhanced geothermal system, which typically involves forcing open new underground pathways for Earth’s heat to reach the surface and generate power [read “fracking].

    3
    NAPA Valley College

    And it comes at a time when the technology could provide a stable, ever-present complement to more finicky wind and solar power as a growing number of nations and U.S. states push to develop low-carbon energy sources. By some estimates, it could amount to as much as 10 percent of current U.S. electric capacity. Understanding what went wrong in Pohang could allow other regions to more safely develop this promising energy source.

    Conventional geothermal resources have been generating power for decades in places where heat and water from deep underground can burble up through naturally permeable rock. In Pohang, as in other enhanced geothermal projects, injections cracked open impermeable rocks to create conduits for heat from the Earth that would otherwise remain inaccessible for making electricity.

    “We have understood for half a century that this process of pumping up the Earth with high pressure can cause earthquakes,” said Ellsworth, who co-directs the Stanford Center for Induced and Triggered Seismicity and is a professor in the School of Earth, Energy & Environmental Sciences (Stanford Earth).

    Here, Ellsworth explains what failed in Pohang and how their analysis could help lower risks for not only the next generation of geothermal plants, but also fracking projects that rely on similar technology. He also discusses why, despite these risks, he still believes enhanced geothermal can play a role in providing renewable energy.

    How does enhanced geothermal technology work?

    The goal of an enhanced geothermal system is to create a network of fractures in hot rock that is otherwise too impermeable for water to flow through. If you can create that network of fractures, then you can use two wells to create a heat exchanger. You pump cold water down one, the Earth warms it up, and you extract hot water at the other end.

    Operators drilling a geothermal well line it with a steel tube using the same process and technology used to construct an oil well. A section of bare rock is left open at the bottom of the well. They pump water into the well at high pressure, forcing open existing fractures or creating new ones.

    Sometimes these tiny fractures make tiny little earthquakes. The problem is when the earthquakes get too big.

    What led to the big earthquake in Pohang, South Korea?

    When they began injecting fluids at high pressure, one well produced a network of fractures as planned. But water injected in the other well began to activate a previously unknown fault that crossed right through the well.

    Pressure migrating into the fault zone reduced the forces that would normally make it difficult for the fault to move. Small earthquakes lingered for weeks after the operators turned the pumps off or backed off the pressure. And the earthquakes kept getting bigger as time went by.

    That should have been recognized as a sign that it wouldn’t take a very big kick to trigger a strong earthquake. This was a particularly dangerous place. Pressure from the fluid injections ended up providing the kick.

    What are the current methods for monitoring and minimizing the threat of earthquakes related to fluid injection for geothermal or other types of energy projects?

    Civil authorities worldwide generally don’t want drilling and injection to cause earthquakes big enough to disturb people. In practice, authorities and drillers tend to focus more on preventing small earthquakes that can be felt rather than on avoiding the much less likely event of an earthquake strong enough to do serious harm.

    With this in mind, many projects are managed by using a so-called traffic light system. As long as the earthquakes are small, then you have a green light and you go ahead. If earthquakes begin to get larger, then you adjust operations. And if they get too big then you stop, at least temporarily. That’s the red light.

    Many geothermal, oil and gas projects have also been guided by a hypothesis that as long as you don’t put more than a certain volume of fluid into a well, you won’t get earthquakes beyond a certain size. There may be some truth to that in some places, but the experience in Pohang tells us it’s not the whole story.

    What would a better approach look like?

    The potential for a runaway or triggered earthquake always has to be considered. And it’s important to consider it through the lens of evolving risk rather than hazard. Hazard is a potential source of harm or danger. Risk is the possibility of loss caused by harm or danger. Think of it this way: An earthquake as large as Pohang poses the same hazard whether it strikes in a densely populated city or an uninhabited desert. But the risk is very much higher in the city.

    The probability of a serious event may be small, but it needs to be acknowledged and factored into decisions. Maybe you would decide that this is not such a good idea at all.

    For example, if there’s a possibility of a magnitude 5.0 earthquake before the project starts, then you can estimate the damages and injuries that might be expected. If we can assign a probability to earthquakes of different magnitudes, then civil authorities can decide whether or not they want to accept the risk and under what terms.

    As the project proceeds, those conversations need to continue. If a fault ends up being activated and the chance of a damaging earthquake increases, civil authorities and project managers might say, “we’re done.”

    From everything you’ve learned about what happened at Pohang, do you think enhanced geothermal development should slow down?

    Natural geothermal systems are an important source of clean energy. But they are rare and pretty much tapped out. If we can figure out how to safely develop power plants based on enhanced geothermal systems technology, it’s going to have huge benefits for all of us as a low-carbon option for electricity and space heating.

    Additional Stanford co-authors include postdoctoral research fellow Cornelius Langenbruch. Other co-authors are affiliated with ETH, Zurich in Switzerland, Victoria University of Wellington in New Zealand, University of Colorado, Boulder, the China Earthquake Administration, and Seoul National University, Chonnam National University and Chungnam National University in the Republic of Korea.

    The work was supported by the Korea Institute of Energy Technology.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal

     
  • richardmitnick 10:40 am on May 11, 2019 Permalink | Reply
    Tags: An array of artificial synapses designed by researchers at Stanford and Sandia National Laboratories can mimic how the brain processes and stores information., , , , , Stanford University   

    From Stanford University: “Stanford researchers’ artificial synapse is fast, efficient and durable” 

    Stanford University Name
    From Stanford University

    April 25, 2019
    Taylor Kubota

    1
    An array of artificial synapses designed by researchers at Stanford and Sandia National Laboratories can mimic how the brain processes and stores information. (Image credit: Armantas Melianas and Scott Keene)

    The brain’s capacity for simultaneously learning and memorizing large amounts of information while requiring little energy has inspired an entire field to pursue brain-like – or neuromorphic – computers. Researchers at Stanford University and Sandia National Laboratories previously developed [Nature Materials] one portion of such a computer: a device that acts as an artificial synapse, mimicking the way neurons communicate in the brain.

    In a paper published online by the journal Science on April 25, the team reports that a prototype array of nine of these devices performed even better than expected in processing speed, energy efficiency, reproducibility and durability.

    Looking forward, the team members want to combine their artificial synapse with traditional electronics, which they hope could be a step toward supporting artificially intelligent learning on small devices.

    “If you have a memory system that can learn with the energy efficiency and speed that we’ve presented, then you can put that in a smartphone or laptop,” said Scott Keene, co-author of the paper and a graduate student in the lab of Alberto Salleo, professor of materials science and engineering at Stanford who is co-senior author. “That would open up access to the ability to train our own networks and solve problems locally on our own devices without relying on data transfer to do so.”

    A bad battery, a good synapse

    The team’s artificial synapse is similar to a battery, modified so that the researchers can dial up or down the flow of electricity between the two terminals. That flow of electricity emulates how learning is wired in the brain. This is an especially efficient design because data processing and memory storage happen in one action, rather than a more traditional computer system where the data is processed first and then later moved to storage.

    Seeing how these devices perform in an array is a crucial step because it allows the researchers to program several artificial synapses simultaneously. This is far less time consuming than having to program each synapse one-by-one and is comparable to how the brain actually works.

    In previous tests of an earlier version of this device, the researchers found their processing and memory action requires about one-tenth as much energy as a state-of-the-art computing system needs in order to carry out specific tasks. Still, the researchers worried that the sum of all these devices working together in larger arrays could risk drawing too much power. So, they retooled each device to conduct less electrical current – making them much worse batteries but making the array even more energy efficient.

    The 3-by-3 array relied on a second type of device – developed by Joshua Yang at the University of Massachusetts, Amherst, who is co-author of the paper – that acts as a switch for programming synapses within the array.

    “Wiring everything up took a lot of troubleshooting and a lot of wires. We had to ensure all of the array components were working in concert,” said Armantas Melianas, a postdoctoral scholar in the Salleo lab. “But when we saw everything light up, it was like a Christmas tree. That was the most exciting moment.”

    During testing, the array outperformed the researchers’ expectations. It performed with such speed that the team predicts the next version of these devices will need to be tested with special high-speed electronics. After measuring high energy efficiency in the 3-by-3 array, the researchers ran computer simulations of a larger 1024-by-1024 synapse array and estimated that it could be powered by the same batteries currently used in smartphones or small drones. The researchers were also able to switch the devices over a billion times – another testament to its speed – without seeing any degradation in its behavior.

    “It turns out that polymer devices, if you treat them well, can be as resilient as traditional counterparts made of silicon. That was maybe the most surprising aspect from my point of view,” Salleo said. “For me, it changes how I think about these polymer devices in terms of reliability and how we might be able to use them.”

    Room for creativity

    The researchers haven’t yet submitted their array to tests that determine how well it learns but that is something they plan to study. The team also wants to see how their device weathers different conditions – such as high temperatures – and to work on integrating it with electronics. There are also many fundamental questions left to answer that could help the researchers understand exactly why their device performs so well.

    “We hope that more people will start working on this type of device because there are not many groups focusing on this particular architecture, but we think it’s very promising,” Melianas said. “There’s still a lot of room for improvement and creativity. We only barely touched the surface.”

    To read all stories about Stanford science, subscribe to the biweekly Stanford Science Digest.

    This work was funded by Sandia National Laboratories, the U.S. Department of Energy, the National Science Foundation, the Semiconductor Research Corporation, the Stanford Graduate Fellowship fund, and the Knut and Alice Wallenberg Foundation for Postdoctoral Research at Stanford University.

    See the full article here .


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    Please help promote STEM in your local schools.

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    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

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  • richardmitnick 2:47 pm on May 7, 2019 Permalink | Reply
    Tags: "What it’s like to be a theoretical physicist", Read Brandon Rayhaun's interview, Read Natalie Paquette's Interview, Read Richard Nally's interview, Read Shamit Kachru’s interview, Shamit Kachru and three of his graduate students talk about what life is like as a theoretical physicist today, Stanford University   

    From Stanford University: “What it’s like to be a theoretical physicist” 

    Stanford University Name
    From Stanford University

    May 3, 2019
    Nathan Collins

    1
    Shamit Kachru and three of his graduate students talk about what life is like as a theoretical physicist today – how they got into the field, what keeps them motivated and what their work means to them.

    Kachru has been studying physics in one form or another for three decades. He spoke about his newfound interest in theoretical biology, why he likes being an administrator and what motivates him to continue on in science.

    Walk into Shamit Kachru’s office, and the first things you’ll notice are the couch and the coffee table that sits in front of it, both situated across from a chalkboard that takes up most of one wall. Intentionally or not, it is a social space. Kachru is a professor of physics and director of the Stanford Institute for Theoretical Physics, and what that means in practical terms is that when he’s not reading books or printouts of academic papers, he’s usually talking to other people and sharing ideas.

    Of late, Kachru’s ideas include thoughts on how to better understand black holes through the lens of number theory, a branch of pure mathematics concerned with questions such as “What is the distribution of prime numbers?” And as a new member of Stanford Bio-X, more and more of the ideas Kachru thinks about concern biology and the theory of evolution, a field Kachru got into simply by talking to a fellow physicist.

    Here, in a glimpse into the lives of theoretical physicists, Kachru, his former graduate student Natalie Paquette and two current graduate students, Brandon Rayhaun and Richard Nally, talk about what it’s like to be a theoretical physicist today – how they got into the field, what keeps them motivated and what their work means to them.

    “We’re not all marveling at the universe all the time. But occasionally in my work, and these are the moments that keep one going, you do encounter something that really inspires awe in a serious way.”

    Read Shamit Kachru’s interview

    Shamit Kachru’s work is abstract and mathematical, and as a result, his days are spent reading academic journals, working out his thoughts on a pad of paper or a chalkboard and sharing ideas with other physicists. In the big picture, he is on a kind of search for Platonic forms – eternal, unchangeable truths that exist outside of our experience of them. Kachru talks about why he likes administrative positions (it’s not the paperwork), why he recently decided to branch out into theoretical biology and the sense of awe that keeps him going.

    “Right now I’m department chair, and I’m also director of the Stanford Institute for Theoretical Physics, and so you might look at this and say, ‘OK, this is somebody who is going to turn 50 soon and has decided to be an administrator.’ And this is a total misreading. The thing that interested me about both of those roles is they give you the ability and even force you to interact with even more people who tell you more interesting things that you otherwise wouldn’t hear.

    “I personally get a lot of joy out of interacting with students. I’ve had graduate students who were wonderful and who play, as I get older, a really important role in my research. I’ve just started taking biology students. It’s a different cohort. They’ll teach me different things. A lot of research is two different people explaining things to each other, then you put those two things together and at that moment you get something new.

    “I have spent some time in the past couple of years hanging out in the group meetings of Dmitri Petrov’s group and Daniel Fisher’s group in biology and Bio-X, and have heard absolutely fascinating things there about evolutionary experiment and theory. I finally decided that the time was right for me to start trying to contribute my own research to ongoing attempts to understand evolutionary dynamics.

    “Biology was the place I entered science as a kid. I used to get these cards from the World Wildlife Federation with pictures of pandas and belugas and raccoons – you know, whatever they put on these cards. And so you grow up already with a natural affinity for living things. Only much later when I was on leave from Stanford at the University of California, Santa Barbara, did I meet a prominent physicist, Boris Shraiman, who transitioned to studying theoretical questions in biology. Without any preconception, I spent a lot of my time there listening to the things he works on and going to a workshop. What struck me was what an exciting time it was in their field. What’s happened is people started to do experiments in evolution, and this together with the ability to rapidly sequence genomes opens up a host of questions to scientific inquiry.

    “Now if you ask, ‘What are motivations to understand how evolution works?’ here I can be practical. The 1918 flu killed millions and millions of people, and sometime there will be another such flu strain and millions and millions of people will die. If you ask, ‘How are we going to combat the flu,’ some of the best ideas involve studying the way that different flu strains’ genetic lines of descent are splitting and branching, to figure out which flu is the most successful, to figure out what the vaccine should be that we use to combat what next year’s flu is likely to be. And that work came out of theoretical physicists working with biologists.

    “I’m not a religious person, but when you read accounts of religious people about how they feel, there is a feeling of awe people can have. Now, daily life as a scientist, just like daily life as anything, is mostly, you know, you get up and you’re tired and you have to feed the rabbits or whatever you happen to have, and so on and so forth. So we’re not all marveling at the universe all the time. But occasionally in my work, and these are the moments that keep one going, you do encounter something that really inspires awe in a serious way.

    “For many people, the way it comes about is some fact about nature that’s discovered in an experiment, and that can happen for me too. But as a theorist, another way it really comes about is when some fact about nature, or at least a toy model of something that could be seen in nature, turns out to also have a really deep and fundamental origin in pure mathematics, which as far as I can tell is the closest thing to pure Platonic thought that we have as humans.”

    2
    Natalie Paquette

    Paquette graduated from Stanford in 2017 and is now a Sherman Fairchild Postdoctoral Fellow at Caltech. She talked about discovering physics in college, why physics never gets old and how, in a way, she has a superpower.

    “String theory feels like a little superpower that I have, this physical intuition that enables me to make connections and have insights into things that by rights I should not be able to say anything interesting about.”

    Read Natalie Paquette’s Interview

    Natalie Paquette works on the mathematics underlying string theory and quantum field theory. Until 2017, she was a graduate student in Kachru’s group. She is now a Sherman Fairchild Postdoctoral Fellow at Caltech. Here, she talks about how she first fell in love with physics in college, why string theory is a kind of mathematical superpower and why, for her, physics never gets boring.

    “I didn’t really know that I wanted to do physics until I was in college. I remember when I was young I liked to read and write a lot. I thought about being an author. I briefly contemplated being a doctor. I thought about being an engineer, a marine biologist – I really wasn’t sure. I was interested in all sorts of things, and so it wasn’t really until I came to college that I got a better sense of who I was interest-wise and what my academic aptitudes were. I went to Cornell University as an undergrad, and originally I matriculated in biological engineering, and then eventually I ended up taking a physics class. I just knew after that class that physics was the thing that I liked the best.

    “String theory feels like a little superpower that I have, this physical intuition, this extremely powerful framework that enables me to make connections and have insights into things that by rights I should not be able to say anything interesting about. I’m not trained as a geometer, I’m not trained as a number theorist, but somehow by thinking really hard about aspects of string theory, I’m able to get insight into all of these far-reaching mathematical fields. I find that sort of really amazing and powerful. Of course, compared to mathematicians in any of these areas, I’m still a dilettante, but hopefully an insightful one. It’s just been really fun for me to learn mathematics through this unconventional physical lens.

    “Does physics ever get boring? No, it never gets boring. If I’m really frustrated by the particular things I’m working on or if I feel really stuck, I’ll try to learn some subject in condensed matter physics or I’ll try to learn something in cosmology or just some other area of physics, and that’s all it takes for me to be re-inspired with this subject. I need to take breaks from time to time and study other things and think about other things, but the subject as a whole definitely never gets boring for me.

    “I am a lot more regimented now than I was when I was a grad student. I wasn’t a morning person. I was one of those sleep-late-and-work-late, very night-shifted grad students. Right now I’m trying to wake up around 7 or 7:30. I made a choice to start training in mixed martial arts recently, and I do my training in the morning and that forced me to rotate my whole schedule. There is something about doing really, really intense physical activity that sort of balances how intense your day can be mentally.

    “I don’t think physics is the only interesting thing in the world. That would be very shortsighted of me. I do have other things I’m interested in, things I learned about as a hobby, things related to economics or biology or other things. There’s all kinds of cool stuff going on in all kinds of other places. And so if nothing worked out with physics, then I’m sure I could find something else interesting to do and be happy about it. But as long as I have a chance of getting to do my favorite thing indefinitely, if I’m lucky enough to get a tenure-track job, then I’ll try to do that as long as I can.”

    3
    Brandon Rayhaun

    Rayhaun is a third-year graduate student and works on string theory with Kachru. He spoke about what science means to him, how no day is particularly typical and the other Stanford professor who inspired him to pursue a career in physics.

    Read Brandon Rayhaun’s interview

    Graduate student Brandon Rayhaun works with Kachru probing the mathematical connections between string theory, black holes and number theory. Of his choice to pursue a career in physics, he says “it was sort of serendipitous.” Here, he talks about the late-night epiphany that solidified his desire to pursue physics, a typical day in the life of a theoretical physics graduate student and why it’s worth developing theories that, for the time being at least, can’t be tested.

    “I had various romantic notions about theoretical physics because I grew up watching various documentaries about string theory. But I think if I had to pinpoint the exact moment where I really knew that I wanted to study physics, I was in high school studying for a French exam, and I was procrastinating, looking up random videos on YouTube, and I stumbled upon Leonard Susskind’s quantum mechanics lectures. It was 5 a.m. and I had watched maybe four or five hours of Lenny Susskind lectures and I forgot to study for the French exam. That’s when I got more interested in actually pursuing physics as a possibility.

    “No day’s terribly typical. I wake up anytime between 6 a.m. and 3 p.m. It’s truly that variable. Part of that is because there are times where I’m in a place where I can be working and there are other times where I’m just not feeling it. I’ve learned over time to not force myself to do creative type work when I’m not in the zone or I’m not feeling it. But when I’m really feeling it, I’ll be too excited to stay asleep for too long, so I’ll force myself to wake up at 6 a.m. or 5 a.m. or whatever and get up, and I’m really eager and excited to think about the problem I was thinking about the night before.

    “Why should we do it? This is a question I still grapple with. The fact is that the theories we’re working with offer predictions that are currently inaccessible to experiments. I think there is this amnesia about things. We look at things like quantum mechanics, and in retrospect it’s clear that we should have done it because it led to all kinds of interesting technological advancements, like MRI machines, your computer, everything uses quantum mechanics. But at the time that people were thinking about it, when it first arrived on the scene, it was an incredibly abstract, really removed thing.

    “Here’s another way to answer the question. I mean, why do we do art? You can make sort of similar arguments that art doesn’t impact humans in the same way that antibiotics do or something like that. But I would argue that it really does. Art adds beauty to our lives.

    “I tend to think about string theory in a similar way. Science is a collection of stories, really beautiful stories, about how the universe works. We need to do a better job of communicating these stories to people, but say we were communicating these stories to people – that I think would be a totally worthwhile endeavor. I think scientists would then be like a combination of artists and adventurers. There are these adventurers who go out into these abstract universes, kind of find patterns, interesting gems, interesting rocks and bring them back and then show them to people and add some beauty to their lives.”

    4
    Richard Nally is a fourth-year graduate student in Kachru’s group studying black holes and number theory. He spoke about the experiences that led him to physics, the excitement of seeing math come alive and the inherently social nature of his work.

    “One of the things I like so much about this field is that it’s very social. People tend to be confused about a lot of the same things, so you go talk to somebody else and find out their perspective on it.”

    Read Richard Nally’s interview

    Graduate student Richard Nally is unabashed about his reasons for studying an abstract corner of theoretical physics, and it has nothing to do with the possibility his work might someday have practical value. Instead, he studies theoretical physics “because it’s cool.” Like many physicists, his interest in the subject grew from reading popular books written by leaders in the field, but Nally also cites a curiosity that grew out of a childhood conundrum.

    “I was very clumsy. I dropped basically everything I got my hands on, and I could never quite understand why that happened. And so I asked. I wanted to understand why things fall basically. That’s still more or less what I think about.

    “So I kept on asking my science teachers, and they all just said it’s this thing called gravity. So I kept on asking and asking and heckling, and eventually sometime in middle school one of them threw at me a copy of Hawking’s A Brief History of Time. I read it and I’m like, ‘OK, this is the coolest thing ever. I need to do this.’

    “The big problem in theoretical physics very broadly is, there’s four forces in the universe, and one of them is very different than the others, and that one is gravity, and so we’re trying to understand how it works. There’s a framework for trying to understand it, string theory, and so that’s always what I wanted to work on.

    “There are a couple different archetypical days. One is I lock myself in my office and read papers until I get confused, and then I go talk to someone about them. Another is you go to a seminar. Sometimes it’s on a topic very close to you and you understand it quite well. Sometimes it’s on a topic completely orthogonal to your research and you get confused very quickly. But you want to get the big picture and come up with an interesting question to ask.

    “The third type of day is when you’re trying to find a good question to ask. You could ask, ‘Where did the universe come from?’ And that’s a question that people have been trying to answer forever, but that’s a problem that takes an infinite amount of work. You need to find a question that’s concrete enough that you can handle, interesting enough to keep on motivating yourself to do it and important enough that somebody else will care. That’s a struggle, and that’s sort of why you go to all of these seminars and read so many papers, just to understand what other people have been thinking about and do you have something to say.

    “One of the things I like so much about this field is that it’s very social. People tend to be confused about a lot of the same things, or sometimes you find something very confusing that nobody else does, so you go talk to somebody else and find out their perspective on it. If you don’t talk to people, you’re never really going to understand all of what’s going on. Really, you’re always confused about something. That’s the natural state of doing research, and for me, a lot of the time being confused is part of the fun.

    “The fun parts aren’t necessarily doing long calculations with twos and minus signs and all that other stuff that you’re going to screw up a million times, and you have to keep on redoing until you get it completely right and then you check and double-check and triple-check. I don’t think many people find that very exciting. What really excites me is when you can see the math come alive and give you some sort of picture of the reality that lives behind it.

    “I want to continue in academia. It’s hard, you know. There are not enough jobs to go around. And it becomes very competitive very quickly. But I love it. I really can’t imagine doing anything else at this point in my life. For me what matters is being passionate about what I do every day, and that means doing physics.”

    See the full article here .


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    Please help promote STEM in your local schools.

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    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

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  • richardmitnick 4:57 pm on April 2, 2019 Permalink | Reply
    Tags: , , , Semiconductor research, Stanford University   

    From Stanford University: “Stanford researchers measure near-perfect performance in low-cost semiconductors” 

    Stanford University Name
    From Stanford University

    March 15, 2019
    Taylor Kubota

    Stanford researchers redefine what it means for low-cost semiconductors, called quantum dots, to be near-perfect and find that quantum dots meet quality standards set by more expensive alternatives.

    1
    A close-up artist’s rendering of quantum dots emitting light they’ve absorbed. (Image credit: Ella Marushchenko)

    Tiny, easy-to-produce particles, called quantum dots, may soon take the place of more expensive single crystal semiconductors in advanced electronics found in solar panels, camera sensors and medical imaging tools. Although quantum dots have begun to break into the consumer market – in the form of quantum dot TVs – they have been hampered by long-standing uncertainties about their quality. Now, a new measurement technique developed by researchers at Stanford University may finally dissolve those doubts.

    “Traditional semiconductors are single crystals, grown in vacuum under special conditions. These we can make in large numbers, in flask, in a lab and we’ve shown they are as good as the best single crystals,” said David Hanifi, graduate student in chemistry at Stanford and co-lead author of the paper written about this work, published March 15 in Science.

    The researchers focused on how efficiently quantum dots reemit the light they absorb, one telltale measure of semiconductor quality. While previous attempts to figure out quantum dot efficiency hinted at high performance, this is the first measurement method to confidently show they could compete with single crystals.

    This work is the result of a collaboration between the labs of Alberto Salleo, professor of materials science and engineering at Stanford, and Paul Alivisatos, the Samsung Distinguished Professor of Nanoscience and Nanotechnology at the University of California, Berkeley, who is a pioneer in quantum dot research and co-senior author of the paper. Alivisatos emphasized how the measurement technique could lead to the development of new technologies and materials that require knowing the efficiency of our semiconductors to a painstaking degree.

    “These materials are so efficient that existing measurements were not capable of quantifying just how good they are. This is a giant leap forward,” said Alivisatos. “It may someday enable applications that require materials with luminescence efficiency well above 99 percent, most of which haven’t been invented yet.”

    Between 99 and 100

    Being able to forego the need for pricey fabrication equipment isn’t the only advantage of quantum dots. Even prior to this work, there were signs that quantum dots could approach or surpass the performance of some of the best crystals. They are also highly customizable. Changing their size changes the wavelength of light they emit, a useful feature for color-based applications such as tagging biological samples, TVs or computer monitors.

    Despite these positive qualities, the small size of quantum dots means that it may take billions of them to do the work of one large, perfect single crystal. Making so many of these quantum dots means more chances for something to grow incorrectly, more chances for a defect that can hamper performance. Techniques that measure the quality of other semiconductors previously suggested quantum dots emit over 99 percent of the light they absorb but that was not enough to answer questions about their potential for defects. To do this, the researchers needed a measurement technique better suited to precisely evaluating these particles.

    “We want to measure emission efficiencies in the realm of 99.9 to 99.999 percent because, if semiconductors are able to reemit as light every photon they absorb, you can do really fun science and make devices that haven’t existed before,” said Hanifi.

    The researchers’ technique involved checking for excess heat produced by energized quantum dots, rather than only assessing light emission because excess heat is a signature of inefficient emission. This technique, commonly used for other materials, had never been applied to measure quantum dots in this way and it was 100 times more precise than what others have used in the past. They found that groups of quantum dots reliably emitted about 99.6 percent of the light they absorbed (with a potential error of 0.2 percent in either direction), which is comparable to the best single-crystal emissions.

    “It was surprising that a film with many potential defects is as good as the most perfect semiconductor you can make,” said Salleo, who is co-senior author of the paper.

    Contrary to concerns, the results suggest that the quantum dots are strikingly defect-tolerant. The measurement technique is also the first to firmly resolve how different quantum dot structures compare to each other – quantum dots with precisely eight atomic layers of a special coating material emitted light the fastest, an indicator of superior quality. The shape of those dots should guide the design for new light-emitting materials, said Alivisatos.

    Entirely new technologies

    This research is part of a collection of projects within a Department of Energy-funded Energy Frontier Research Center, called Photonics at Thermodynamic Limits. Led by Jennifer Dionne, associate professor of materials science and engineering at Stanford, the center’s goal is to create optical materials – materials that affect the flow of light – with the highest possible efficiencies.

    A next step in this project is developing even more precise measurements. If the researchers can determine that these materials reach efficiencies at or above 99.999 percent, that opens up the possibility for technologies we’ve never seen before. These could include new glowing dyes to enhance our ability to look at biology at the atomic scale, luminescent cooling and luminescent solar concentrators, which allow a relatively small set of solar cells to take in energy from a large area of solar radiation. All this being said, the measurements they’ve already established are a milestone of their own, likely to encourage a more immediate boost in quantum dot research and applications.

    “People working on these quantum dot materials have thought for more than a decade that dots could be as efficient as single crystal materials,” said Hanifi,” and now we finally have proof.”

    See the full article here .


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    Please help promote STEM in your local schools.

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    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

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  • richardmitnick 12:51 pm on March 27, 2019 Permalink | Reply
    Tags: BioAIMS, ChemAIMS, Natalie Geise and Jen Marrero, Stanford University, The group gives women, The group gives women LGBTQ+ and underrepresented minority students a place to find support and organizes opportunities to interact with visiting faculty,   

    From Stanford University: Women in STEM-“Chemistry students provide space for underrepresented groups in science” Natalie Geise and Jen Marrero 

    Stanford University Name
    From Stanford University

    March 21, 2019
    Erin I. Garcia de Jesus

    Two Stanford graduate students are helping underrepresented students in the Chemistry Department chat with faculty they relate to over breakfast. Their group aims to establish a community and facilitate conversations about diversity in science.

    1
    Chemistry graduate students Natalie Geise, left, and Jen Marrero Hope founded ChemAIM as a way of creating a community for women and minorities in chemistry. (Image credit: Binhong Lin)

    Breakfast conversations have taken a new shape in Stanford’s Chemistry Department, thanks to the efforts of two graduate students: Jen Marrero Hope and Natalie Geise, now fourth-year students in the department’s PhD program.

    The duo began the Chemistry Association for the Interests of Minority Students, ChemAIMS for short, when they saw a gap in support for underrepresented groups in chemistry and decided to set up a group on their own. The group gives women, LGBTQ+ and underrepresented minority students a place to find support and organizes opportunities to interact with visiting faculty.

    The founders said chemistry graduate students typically bond with their cohort as they take classes and teach in their first year. But then they withdraw to their respective labs – which may be less diverse – for the next few years to do experiments and complete their degrees.

    “It’s much more likely that you would be the only woman or only Latinx in your lab or that you see in your day-to-day life,” Geise said. “That can be really hard and graduate school is already pretty isolating, so it’s important to have a community.”

    A friend of Hope’s at Caltech coordinated student breakfasts with women invited to give department seminars. Based on the success of that program, Hope started a similar group at Stanford, boosted by department funding for food. “Since then it has expanded with the goal of hosting speakers from a broader range of underrepresented backgrounds,” Hope said.

    With the breakfasts, Hope and Geise sought to create a space for students to interact with speakers they have something in common with. Students have the chance to ask questions they might not feel comfortable asking in front of the entire department or to discuss the struggles of being an underrepresented person in science.

    “When the department invites speakers who look like us, getting a piece of their time to talk with them and say ‘Hey, I don’t see you guys very often. How did you do it?’ felt really important,” Hope said.

    Promoting inclusion

    Hope and Geise learned the ins and outs of planning department events when they joined the Chemistry Department’s Graduate Student Affairs Committee in their first year at Stanford. They discovered how to find funds and get people on board for new events. So, when Hope and Geise launched ChemAIMS in 2017, they had at least some idea of what to do.

    The name, they said, was “shamelessly stolen” from the biomedical diversity group on campus (with permission), called BioAIMS. While BioAIMS supports students in the biosciences and medical school, which encompasses a large portion of Stanford’s campus, ChemAIMS focuses on helping students whose work might not be related to biology. To date, 91 trainees – which includes graduate students and some post-doctoral researchers – are on their mailing list.

    “It’s cool to try and spread the love so that people in other sciences also have somewhere to go,” Hope said.

    Though ChemAIMS started with breakfasts, it has expanded to include a research discussion group spearheaded by Geise and a community-driven book club, which just finished reading Bad Blood by John Carreyou. And this spring, ChemAIMS will host their first student-invited seminar speaker, Miriam Bowring from Reed College in Portland, Oregon. Bowring will give a talk on her research but will also focus on diversity in science.

    “It’s important to have the smaller groups where we are the focus,” Hope said. “It’s also important to have a larger, inviting community and say, ‘Hey, you also need to be thinking about this.’”

    This year Hope and Geise were invited to speak about ChemAIMS at student orientation in the fall. And they will present a poster at the department’s recruiting events.

    “We’d like to see more students who feel that they’d be welcome and that this is an environment where we do care about these issues,” Geise said.

    Balancing act

    Despite their success, Hope and Geise are not primarily focused on advocacy – they are graduate students striving to earn their doctorates. That can make it hard to find time for ChemAIMS, but both see it as an important part of their Stanford experience.

    “I know logically that being at the bench and working all the time is not efficient,” Geise said. She added that her research is structured in a way that keeps her busy during some periods and more relaxed in others, which makes it easier for her take time away to organize ChemAIMS events.

    “This kind of work is what keeps me sane in graduate school,” Hope said. “Because experiments don’t work all the time and it’s good to remember that there are other ways that I’m making an impact on my community and the department.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

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  • richardmitnick 11:10 am on March 20, 2019 Permalink | Reply
    Tags: "Computer science college seniors in U.S. outperform peers in China, , , , India and Russia, new research says", Stanford University   

    From Stanford University: “Computer science college seniors in U.S. outperform peers in China, India and Russia, new research says” 

    Stanford University Name
    From Stanford University

    March 19, 2019
    Alex Shashkevich, Stanford News Service
    (650) 497-4419
    ashashkevich@stanford.edu

    1
    New Stanford-led research found that undergraduate seniors studying computer science in the United States outperformed their peers in China, India and Russia on a standardized exam measuring their skills. (Image credit: Sidekick / Getty Images)

    An international group of scholars led by the Graduate School of Education’s Prashant Loyalka found that undergraduate seniors studying computer science in the United States outperformed final-year students in China, India and Russia on a standardized exam measuring their skills. The research results were published on March 18 in a new paper in Proceedings of the National Academy of Sciences.

    International comparison of universities usually falls in the domain of popular news rankings and general public perception, which rely on limited information and do not consider the skills students acquire, Loyalka said. That’s why he and his team wanted to collect and analyze data on what students learn in colleges and universities in different countries.

    “There is this narrative that higher education in the United States is much stronger than in other countries, and we wanted to test whether that’s true,” said Loyalka, who is also a center research fellow at the Rural Education Action Program in the Freeman Spogli Institute for International Studies. “Our results suggest that the U.S. is doing a great job at least in terms of computer science education compared to these three other major countries.”

    The findings

    As part of the study, the researchers selected nationally representative samples of seniors from undergraduate computer science programs in the U.S., China, India and Russia. Students were given a two-hour standardized computer science test developed by the nonprofit testing and assessment organization Educational Testing Service. In total, 678 students in China, 364 students in India and 551 students in Russia were tested. In the United States, the researchers used assessment data on 6,847 seniors.

    The test, which aligns with national and international guidelines on what should be taught, probed how well students understand different concepts and knowledge about programming, algorithms, software engineering and other computer science principles.

    Researchers found that the average computer science student in the U.S. ranked higher than about 80 percent of students tested in China, India and Russia, Loyalka said. In contrast, the difference in scores among students in China, India and Russia was small and not statistically significant.

    Researchers also compared a smaller pool of students from top-ranking institutions in each country. They found that the average student in a top computer science program in the U.S. also ranked higher than about 80 percent of students from top programs in China, India and Russia. But the top Chinese, Indian and Russian students scored comparably with the U.S. students from regular institutions, according to the research.

    The researchers also found that the success of the American students wasn’t due to the sample having a large number of high-scoring international students. The researchers distinguished international students by their language skills. Of all sampled U.S. students, 89.1 percent reported that their best language is only English, which the researchers considered to be domestic U.S. students.

    “There is this sense in the public that the high quality of STEM programs in the United States is driven by its international students,” Loyalka said. “Our data show that’s not the case. The results hold if we only consider domestic students in the U.S.”

    The researchers also found that male students scored moderately higher than female students in each of the four countries.

    “The difference between men and women is there in every country, but the gaps are modest compared to the gaps we see between countries and elite and non-elite institutions,” Loyalka said.

    Further research

    The new research is a part of a larger effort led by Loyalka to examine the skills of students in science, technology, engineering and math fields in different countries. In another forthcoming paper, he and his collaborators examine other skills among students in the same four countries. Further research will also look at the relationship between skills developed in college and labor market outcomes, he said.

    Another major goal of the research team is to look more deeply at what might be driving the difference in the performance among countries.

    “We’re looking at different aspects of the college experience including faculty behavior, instruction and student interactions,” Loyalka said. “One of our major goals is to see what types of college experiences could contribute to better student performance.”

    Other Stanford co-authors on the paper included doctoral students Angela Sun Johnson and Saurabh Khanna as well as Ashutosh Bhuradia, a project manager for the research.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal

     
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