Construction of Bending Magnet Beamline at the APS for Environmental

Design and construction of a bending magnet beamline at the Advanced Photon Source (APS) by the Pacific Northwest Consortium-Collaborative Access Team (PNCCAT). The beamline will be optimized for x-ray absorption spectroscopy (XAS) studies with a major focus on environmental issues. The beamline will share the experimental facilities under development at the neighboring undulator based insertion device beamline. It will utilize these facilities for XAS of both bulk and surface samples, with spatial and elemental imaging, on toxic and radioactive samples. It will help meet the rapidly growing need for the application of these techniques to environmental problems

Xafs Study of the Low-Temperature Tetragonal Phase of La₂₋ₓBaₓCuO₄: Disorder, Stripes, and T\u3csub\u3ec\u3c/sub\u3e Suppression at X=0.125

Angular dependent x-ray absorption fine structure (XAFS) measurements of all La, Ba, and Cu sites determined the origin and nature of the intrinsic disorder present in the low temperature tetragonal (LTT) structural ground state of La2-xBaxCuO4 with x=0.125,0.15 at T=10 K. Ba doping induces major local distortions that extend as far as 5 Å from its lattice site. Despite the low Ba content the large distortions significantly affect the XAFS of the majority La and Cu sites. The distribution of the local LTT tilt angle of CuO6 octahedra was directly determined from single and multiple scattering contributions to the XAFS of La and Cu sites. This angle, which regulates the strength of electron-lattice and spin-spin coupling in this material, was found to exhibit large, random fluctuations with rms [〈(θ-〈θ〉)2〉] 1/2≈2〈θ〉, 〈θ〉 being the average tilt angle determined by diffraction techniques. These fluctuations originate in the large, random, static disorder introduced with Ba doping. Their presence has implications for the plausibility of a mobility gap causing Tc suppression at x=0.125 in only the LTT phase, and for the correlation length of the postulated charge and spin stripes

Left ventricular to left atrial communication secondary to a paraaortic abscess: Color flow doppler documentation

Aortic root abscess occurs frequently in aortic prosthetic valve infective endocarditis. The present echocardiography report documents a ruptured abscess that led to a direct communication between the left ventricular outflow tract and the left atrium confirmed by real-time (color flow) Doppler imaging

"Knee" of the cosmic-ray latitude curve

A phenomenon of considerable interest in the study of the distribution of cosmic-ray intensity over the earth has been the apparent absence of low-energy particles in the primary radiation. At sea level the "knee" is probably due to atmospheric absorption and has been placed at 40° to 45° geomagnetic north. At high altitudes a number of divergent results have been obtained by various observers.(1) We wish to point out that some of this seemingly contradictory evidence may be due to the fact that the data were taken at different times