Tag Archives: particle

NASA Observations Point to ‘Dry Ice’ Snowfall on Mars

PASADENA, Calif. — NASA’s Mars Reconnaissance Orbiter data have given scientists the clearest evidence yet of carbon-dioxide snowfalls on Mars. This reveals the only known example of carbon-dioxide snow falling anywhere in our solar system.

Frozen carbon dioxide, better known as “dry ice,” requires temperatures of about minus 193 degrees Fahrenheit (minus 125 Celsius), which is much colder than needed for freezing water. Carbon-dioxide snow reminds scientists that although some parts of Mars may look quite Earth-like, the Red Planet is very different. The report is being published in the Journal of Geophysical Research. (more…)

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Experiment Would Test Cloud Geoengineering as Way to Slow Warming

Even though it sounds like science fiction, researchers are taking a second look at a controversial idea that uses futuristic ships to shoot salt water high into the sky over the oceans, creating clouds that reflect sunlight and thus counter global warming.

University of Washington atmospheric physicist Rob Wood describes a possible way to run an experiment to test the concept on a small scale in a comprehensive paper published this month in the journal Philosophical Transactions of the Royal Society.

The point of the paper — which includes updates on the latest study into what kind of ship would be best to spray the salt water into the sky, how large the water droplets should be and the potential climatological impacts — is to encourage more scientists to consider the idea of marine cloud brightening and even poke holes in it. In the paper, he and a colleague detail an experiment to test the concept. (more…)

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Entropy Can Lead to Order, Paving The Route to Nanostructures

ANN ARBOR, Mich.— Researchers trying to herd tiny particles into useful ordered formations have found an unlikely ally: entropy, a tendency generally described as “disorder.”

Computer simulations by University of Michigan scientists and engineers show that the property can nudge particles to form organized structures. By analyzing the shapes of the particles beforehand, they can even predict what kinds of structures will form.

The findings, published in this week’s edition of Science, help lay the ground rules for making designer materials with wild capabilities such as shape-shifting skins to camouflage a vehicle or optimize its aerodynamics. (more…)

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Greg Landsberg: Seeking the Higgs boson

Greg Landsberg, professor of physics at Brown, is the physics coordinator for the Compact Muon Solenoid (CMS) at CERN in Switzerland, part of a Brown team that includes professors David Cutts, Ultich Heintz, and Meenakshi Narain. The giant instrument’s primary mission is finding the Higgs boson, a particle whose existence would confirm the best guess physicists have made about why things have mass.

On July 4, Landsberg and his colleagues will reveal the latest results of their search. Anything could happen when Greg Landsberg and, including an announcement that the Higgs has been found or that it has been ruled out, sending theorists back to the whiteboard. Landsberg spoke by Skype with science news officer David Orenstein on June 26 as CERN physicists were preparing for their press conference. (more…)

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Images Capture Split Personality of Dense Suspensions

Stir lots of small particles into water, and the resulting thick mixture appears highly viscous. When this dense suspension slips through a nozzle and forms a droplet, however, its behavior momentarily reveals a decidedly non-viscous side. University of Chicago physicists recorded this surprising behavior in laboratory experiments using high-speed photography, which can capture action taking place in one hundred-thousandths of a second or less.

UChicago graduate student Marc Miskin and Heinrich Jaeger, the William J. Friedman and Alicia Townsend Friedman Professor in Physics, expected that the dense suspensions in their experiments would behave strictly like viscous liquids, which tend to flow less freely than non-viscous liquids. Viscosity certainly does matter as the particle-laden liquid begins to exit the nozzle, but not at the moment where the drop’s thinning neck breaks in two. (more…)

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Under the Electron Microscope – A 3-D Image of an Individual Protein

*The high resolution of Lawrence Berkeley National Laboratory’s Gang Ren*

When Gang Ren whirls the controls of his cryo-electron microscope, he compares it to fine-tuning the gearshift and brakes of a racing bicycle. But this machine at the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) is a bit more complex. It costs nearly $1.5 million, operates at the frigid temperature of liquid nitrogen, and it is allowing scientists to see what no one has seen before.

At the Molecular Foundry, Berkeley Lab’s acclaimed nanotechnology research center, Ren has pushed his Zeiss Libra 120 Cryo-Tem microscope to resolutions never envisioned by its German manufacturers, producing detailed snapshots of individual molecules. Today, he and his colleague Lei Zhang are reporting the first 3-D images of an individual protein ever obtained with enough clarity to determine its structure. (more…)

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Anti-Helium Discovered in the Heart of STAR

*Berkeley Lab nuclear scientists join with their international colleagues in the latest record-breaking discovery at RHIC*

Eighteen examples of the heaviest antiparticle ever found, the nucleus of antihelium-4, have been made in the STAR experiment at RHIC, the Relativistic Heavy Ion Collider at the U.S. Department of Energy’s Brookhaven National Laboratory.

“The STAR experiment is uniquely capable of finding antihelium‑4,” says the STAR experiment’s spokesperson, Nu Xu, of the Nuclear Science Division (NSD) at Lawrence Berkeley National Laboratory (Berkeley Lab). “STAR already holds the record for massive antiparticles, last year having identified the anti-hypertriton, which contains three constituent antiparticles. With four antinucleons, antihelium-4 is produced at a rate a thousand times lower yet. To identify the 18 examples required sifting through the debris of a billion gold-gold collisions.” (more…)

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