Wave-like modulations with non-lattice periodicities accompany a variety of important physical phenomena (e.g. magnetism and superconductivity) and dramatically complicate any quantitative crystal-structure analysis. An exhaustive group-theoretical enumeration of the order parameters that can arise from 1D incommensurate modulations now make it much easier to characterize crystals that behave this way. Figure: Short-range modulation in La1.8Sr2.2Mn2O7.
In this image of from BYU's x-ray diffraction facility, x-rays arriving from the left scatter in all directions from a tiny crystal at the center, and are then imaged by a 16-megapixel x-ray camera. The often beautiful scattering patterns that result contain a wealth of information about the atomic structure of the sample. The speed and sensitivity of state-of-the-art instruments like this have revolutionized the study of crystalline materials.
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
This demonstration illustrates the power of a wave focusing technique called time reversal acoustics. A vibration speaker and a laser Doppler vibrometer are used to knock over one targeted Lego figure among many placed on an aluminum plate. BYU researchers (Brian Anderson and students) use this technique to locate and characterize cracks in structures, to deliver private communications, and many other potential applications. Click the title link and watch a video of the demo.
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Brent Reichman, Kent Gee, and Traci Neilsen et al. recently published an article titled "Acoustic shock formation in noise propagation during ground run-up operations of military aircraft" in 23rd AIAA/CEAS Aeroacoustics Conference (Denver, CO, June 2017), AIAA AVIATION Forum, (AIAA 2017-4043). Click on the image above to read it.
Blue Comet in the Hyades: Stars of the Hyades cluster are scattered through this mosaic spanning over 5 degrees on the sky toward the constellation Taurus. Presently cruising through the Solar System, the remarkably blue comet C/2016 R2 PanSTARRS is placed in the wide field of view using image data from January 12....
This photograph and Description come from NASA's Astronomy Picture of the Day web site.