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Category: materials

A pair of researchers with Indiana University and Illinois University, respectively, has developed a theory that suggests crystalizing uranium “snowflakes” deep inside white dwarfs could instigate an explosion large enough to destroy the star. In their paper published in the journal Physical Review Letters, C. J. Horowitz and M. E. Caplan describe their theory and what it could mean to astrophysical theories about white dwarfs and supernovas.

White dwarfs are small stars that have burned up most of their nuclear fuel—they are typically much cooler than they once were and are very dense. In this new effort, Horowitz and Caplan used data from the Gaia space observatory to theorize that sometimes small grains of uranium could begin to crystalize (due to enriched actinides), forming what they describe as snowflakes. They suggest this could happen because of the differing melting points of the material involved. They further suggest that if this were to occur, it could lead to splitting of atomic nuclei, resulting in a series of fission reactions as the solids become enriched in actinides. And if such reactions were to raise the temperature of the interior of the star by igniting carbon, the result would likely be merging of atomic nuclei and eventually a very large fusion reaction that would result in a large explosion—likely large enough to destroy the star.

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“Whooshes of creation” may be producing multiverses at this moment, says astronomer.

The cosmic inflation credited with creating the homogeneous universe which we now enjoy was likely not a one-off event, University of California, Berkeley astronomer Alexei Filippenko, told me. In fact, these ‘whooshes of creation’ may be producing multiverses even at this moment, says Filippenko.

The idea of an exponential, faster-than-light expansion of the early universe, was first put forth by MIT astrophysicist Alan Guth in 1981. And today, Inflation theory is used to explain the Cosmos’ current size, expansion, homogeneity and the fact that it appears to be geometrically flat, I noted in a 2011 issue of Astronomy magazine.

“Inflation happened within the first trillionth of a trillionth of a trillionth of a second of the universe’s existence,” said Filippenko. “It disappeared and then transformed itself into the material that eventually formed us.”

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Radio observations of a cold, dense cloud of molecular gas reveal more than a dozen unexpected molecules.

Scientists have discovered a vast, previously unknown reservoir of new aromatic material in a cold, dark molecular cloud by detecting individual polycyclic aromatic hydrocarbon molecules in the interstellar medium for the first time, and in doing so are beginning to answer a three-decades-old scientific mystery: how and where are these molecules formed in space?

“We had always thought polycyclic aromatic hydrocarbons were primarily formed in the atmospheres of dying stars,” said Brett McGuire, Assistant Professor of Chemistry at the Massachusetts Institute of Technology, and the Project Principal Investigator for GOTHAM, or Green Bank Telescope (GBT) Observations of TMC-1: Hunting Aromatic Molecules. “In this study, we found them in cold, dark clouds where stars haven’t even started forming yet.”

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The recent synthesis of one-dimensional van der Waals heterostructures, a type of heterostructure made by layering two-dimensional materials that are one atom thick, may lead to new, miniaturized electronics that are currently not possible, according to a team of Penn State and University of Tokyo researchers.

Engineers commonly produce heterostructures to achieve new device properties that are not available in a . A van der Waals is one made of 2D materials that are stacked directly on top of each other like Lego-blocks or a sandwich. The van der Waals force, which is an attractive force between uncharged molecules or atoms, holds the materials together.

According to Slava V. Rotkin, Penn State Frontier Professor of Engineering Science and Mechanics, the one-dimensional van der Waals heterostructure produced by the researchers is different from the van der Waals heterostructures engineers have produced thus far.

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For decades, there has been a trend in microelectronics towards ever smaller and more compact transistors. 2D materials such as graphene are seen as a beacon of hope here: they are the thinnest material layers that can possibly exist, consisting of only one or a few atomic layers. Nevertheless, they can conduct electrical currents—conventional silicon technology, on the other hand, no longer works properly if the layers become too thin.

However, such materials are not used in a vacuum; they have to be combined with suitable insulators—in order to seal them off from unwanted environmental influences, and also in order to control the flow of current via the so-called field effect. Until now, hexagonal boron nitride (hBN) has frequently been used for this purpose as it forms an excellent environment for 2D materials. However, studies conducted by TU Wien, in cooperation with ETH Zurich, the Russian Ioffe Institute and researchers from Saudi Arabia and Japan, now show that, contrary to previous assumptions, thin hBN layers are not suitable as insulators for future miniaturized field-effect transistors, as exorbitant leakage currents occur. So if 2D materials are really to revolutionize the , one has to start looking for other insulator materials. The study has now been published in the scientific journal Nature Electronics.

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‘A class of subluminal, spherically symmetric warp drive spacetimes, at least in principle, can be constructed based on the physical principles known to humanity today,’ the scientists say.

“Conceptually, we demonstrate that any warp drive, including the Alcubierre drive, is a shell of regular or exotic material moving inertially with a certain velocity. Therefore, any warp drive requires propulsion. We show that a class of subluminal, spherically symmetric warp drive spacetimes, at least in principle, can be constructed based on the physical principles known to humanity today.”

The scientists’ theories are based on the Alcubierre warp drive, named after theoretical physicist Miguel Alcubierre. In his paper’s abstract, published in 2000, he wrote that the drive world work by modifying spacetime.

“By a purely local expansion of spacetime behind the spaceship and an opposite contraction in front of it, motion faster than the speed of light as seen by observers outside the disturbed region is possible,” Alcubierre wrote.

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Study describes passive cooling system that aims to help impoverished communities, reduce cooling and heating costs, lower CO2 emissions.

Passive cooling, like the shade a tree provides, has been around forever.

Recently, researchers have been exploring how to turbo charge a passive cooling technique — known as radiative or sky cooling — with sun-blocking, nanomaterials that emit heat away from building rooftops. While progress has been made, this eco-friendly technology isn’t commonplace because researchers have struggled to maximize the materials’ cooling capabilities.

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Advertisement The device for sweeping mines is built using low-cost material available in abundance, hence easily replaceable too. The new mine killer device known as Mine Kafon, developed by an Afghan designer, is an expertly designed device that uses cheap materials that are easily replaceable, hence giving tremendous results.

The device is wind-powered and seems like a Hoberman sphere. The device’s weight and height match that of an average-sized man, hence replicating the effect of a man stepping on a mine.

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