Ray stability is investigated in environments consisting of a range-independent background sound-speed profile on which a range-dependent perturbation is superimposed. Theoretical arguments suggest and numerical results confirm that ray stability is strongly influenced by the background sound speed profile. Ray instability is shown to increase with increasing magnitude of alpha(I)=(I/omega)d om...

The Small Magellanic Cloud is increasingly an invaluable laboratory for studying accreting and isolated X-ray pulsars. We add to the class of compact SMC objects by reporting the discovery of three new long period X-ray pulsars detected with the Chandra X-ray Observatory. The pulsars, with periods of 152, 304 and 565 seconds, all show hard X-ray spectra over the range from 0.6 7.5 keV. The sour...

The CR-39 nuclear track detector is used in many nuclear diagnostics fielded at inertial confinement fusion (ICF) facilities. Large x-ray fluences generated by ICF experiments may impact the CR-39 response to incident charged particles. To determine the impact of x-ray exposure on the CR-39 response to alpha particles, a thick-target bremsstrahlung x-ray generator was used to expose CR-39 to va...

It is well established experimentally that cosmic ray neutrons are a source of soft errors in silicon based microelectronics. The mechanism which produces the errors appears to be the detection of the high density of charge associated with the production of alpha particles in the semiconductor by the neutrons. In vitro experiments using alpha particles, and an end point of chromosomal rearrange...

This article reports development of a practical laboratory hard X-ray photoelectron spectroscopy (HXPS) system by combining a focused monochromatic Cr K(alpha) X-ray source, a wide angle acceptance objective lens and a high kinetic energy electron analyzer. The Cr K(alpha) source consists of a Cr target, a 15 kV focused electron gun, and a compact bent crystal monochromator. The X-ray spot size...

Crystal structures of all five crystalline methyl D-pentofuranosides, methyl alpha-D-arabinofuranoside (1), methyl beta-D-arabinofuranoside (2), methyl alpha-D-lyxofuranoside (3), methyl beta-D-ribofuranoside (4) and methyl alpha-D-xylofuranoside (5) have been determined by means of cryogenic X-ray and neutron crystallography. The neutron diffraction experiments provide accurate, unbiased H-ato...

The structure of PFE, an aryl esterase from Pseudomonas fluorescens, has been solved to a resolution of 1.8 A by X-ray diffraction and shows a characteristic alpha/beta-hydrolase fold. In addition to catalyzing the hydrolysis of esters in vitro, PFE also shows low bromoperoxidase activity. PFE shows highest structural similarity, including the active-site environment, to a family of non-heme ba...

3,3-(Biphenyl-2,2'-diyl)-1-alpha,alpha,alpha-trifluoro-p-tolyl-allene, 9, sequentially forms head-to-tail, 12, cis-tail-to-tail, 13, and trans tail-to-tail, 14, 1,2-dialkylidene-cyclobutane dimers, each of which has been characterised by X-ray crystallography. Thermolysis at 180 degrees C yields the dispirotetracene, 15, and di-indenotetracene, 16; the latter compound forms an air-stable Diels-...