Grain boundaries are the interfaces between the small crystals that make up nearly every material in our physical world. Understanding grain boundaries is essential because they dictate the most important characteristics of a material. Want to make steel corrosion resistant? The key is in the grain boundaries because they are the pathways for corrosive elements. Scientists at BYU, in collaboration with a scientist at Cambridge (UK), recently developed a machine learning approach predicting grain boundary properties. Not only can it make predictions, but the design of the machine learning model also makes it explanatory---It can identify the "physics reason" why some grain boundaries are good, and some are bad.
The small, northern constellation Triangulum harbors this magnificent face-on spiral galaxy, M33. Its popular names include the Pinwheel Galaxy or just the Triangulum Galaxy. M33 is over 50,000 light-years in diameter, third largest in the Local Group of galaxies after the Andromeda Galaxy (M31), and our own Milky Way. About 3 million light-years from the Milky Way, M33 is itself thought to be a satellite of the Andromeda Galaxy and astronomers in these two galaxies would likely have spectacular views of each other's grand spiral star systems. As for the view from planet Earth, this sharp composite image, a 25 panel mosaic, nicely shows off M33's blue star clusters and pinkish star forming regions that trace the galaxy's loosely wound spiral arms. In fact, the cavernous NGC 604 is the brightest star forming region, seen here at about the 1 o'clock position from the galaxy center. Like M31, M33's population of well-measured variable stars have helped make this nearby spiral a cosmic yardstick for establishing the distance scale of the Universe. This image using data from the BYU West Mountain Observatory and the Subaru telescope on Mauna Kea was featured as the NASA Astronomy Picture of the Day for December 20, 2012. Image Credit & Copyright: Robert Gendler, Subaru Telescope (NAOJ) Image data: Subaru Telescope, Robert Gendler, Michael Joner and David Laney; Brigham Young University West Mountain Observatory, and Johannes Schedler
Every technology is intimately related to a particular materials set. The steam engines that powered the industrial revolution in the eighteenth century were made of steel and, information and communication technologies are underpinned by silicon. Once a material is chosen for a given technology, it gets locked with it because of the investments associated with establishing large-scale production lines. This means that changing the materials set in an established technology is a rare event and must be considered as a revolution. Computational materials discovery can play an important role in fueling such revolutions
A recent article that appeared in the Astronomical Journal (Joner and Hintz, 2015, AJ, 150, 204), established a new photometric system based on a pair of filter functions used to measure the strength of the H-alpha line in stars. The paper presented H-alpha and H-beta indices for 136 field and cluster stars that were observed with the 1.2-meter telescope at the Dominion Astrophysical Observatory during an 11 year period. The indices were determined from spectro-photometry of the thousands of spectra exposures. The figure to the left shows a relation for normal main sequence stars between the new H-alpha index and the more than 60 year old H-beta index. Color-color plots like this one are useful in surveys to detect objects of astrophysical interest that display emission features of various strengths. These extreme objects are easily seen in a color-color plot. One High Mass X-ray Binary recently observed for a followup study was located at (0.87,1.87) in the color-color plot.
The figure shows two different integration "grids," a standard rectangular grid versus an contour-by-contour grid. The Materials Simulation Group (msg.byu.edu) is exploring competing schemes for speeding up the integration of electron bands in materials. An important part of "first-principles" materials calculations involves integrating over the occupied electron states, the so-called "band energy integration." This is the primary source of error in first-principles calculations of solids. Improving this integration would have a dramatic impact on computational simulations of metallic systems.
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Kent Gee, Paul Russavage, Traci Neilsen, Hales Swift, and Aaron Vaughn recently published an article titled "Subjective rating of the jet noise crackle percept" in Journal of The Acoustical Society of America. Click on the image above to read it.
M86 in the Central Virgo Cluster : Is there a bridge of gas connecting these two great galaxies? Quite possibly, but it is hard to be sure. M86 on the upper left is a giant elliptical galaxy near the center of the nearby Virgo Cluster of galaxies....
This photograph and Description come from NASA's Astronomy Picture of the Day web site.