solved. Unlike their hole-doped cousins, these crystals do not superconduct when newly grown, but only after a high-temperature treatment in a reducing environment. Using a combination of x-ray diffuse scattering and neutron powder diffraction techniques, their copper-oxide sheets were found to be initially riddled with copper-vacancy defects, which were then reversibly repaired during heat treatments.
Crystal transformations that reduce symmetry are called "distortions". ISODISTORT (iso.byu.edu) is a powerful group-theoretical tool that can generate, parameterize, and interactively visualize virtually any crystal distortion involving atomic displacements, magnetic moments, occupational orderings, or lattice strains. Figure based on La2CoRuO6 (J. Mater. Chem. 15, 715-720, 2005).
The figure shown to the left is from a recent publication in the Astronomical Journal (Oberst, Thomas E., et al., 2017, AJ, 153, 97) that confirms the discovery of a highly irradiated, ultra-short period hot Jupiter in orbit around a distant star. The newly discovered planet has been designated as KELT–16b. The long time series run in the left hand panel that is labeled "Pratt" is from a team of students led by Dr. Denise Stephens using the BYU campus Orson Pratt Observatory. The four multi-color data sets that follow were secured a couple of days later by students under the direction of Dr. Michael Joner at the BYU West Mountain Observatory. These and the other data presented in the paper confirm the sub-stellar mass and other properties of KELT-16b.
The irreducible representations (IRs) of the parent symmetry of a system provide a symmetry-motivated parameter set for describing any periodic or aperiodic distortion. The IRs of complete crystallographic space groups and their extensions to (3+d)-dimensional superspace, including all special and non-special k-vectors, commensurate and incommensurate, have now been exhaustively tabulated for the first time. Photo (Wikipedia): Table Mountain, Capetown, South Africa.
Wave-like modulations with non-lattice periodicities accompany a variety of important physical phenomena (e.g. magnetism and superconductivity). Though such a material is not properly crystalline in three dimensions, it does have a regular crystal lattice in a higher dimensional superspace. The superspace symmetry groups in (3+1), (3+2) and (3+3) dimensions have now been exhaustively tabulated, which will make it easier to solve modulated structure and understand their properties.
25 May, Today
26 May, Friday
29 May, Monday
Joseph Moody et al. recently published an article titled "Multifrequency Photo-polarimetric WEBT Observation Campaign on the Blazar S5 0716+714: Source Microvariability and Search for Characteristic Timescales" in Astrophysical Journal. Click on the image above to read it.
Star Cluster, Spiral Galaxy, Supernova: A cosmic snapshot from May 19, this colorful telescopic field of view spans about 1 degree or 2 full moons on the sky. Spiky in appearance, foreground ...
This photograph and Description come from NASA's Astronomy Picture of the Day web site.