High-efficiency fused-silica transmission gratings

We describe the design, fabrication, and performance of high-efficiency transmission gratings fabricated in bulk fused silica for use in high-power ultraviolet laser systems. The gratings exhibit a diffraction efficiency of 94% in order m=-1 and a damage threshold greater than 13>J/cm( 2) for 3-ns pulses at 351 nm. Model calculations and experimental measurements are in good agreement.     

Spectral measurements of the emission from highly scattering gain media

The spectral properties of the emission of a colloidal suspension of titanium dioxide particles in Rhodamine 640 perchlorate were studied systematically. The particle density rho, the dye concentration c, and the energy of the pump pulse were varied over several orders of magnitude; the dependence of the spectra on these three parameters is discussed. We discovered a strong correlation between the particle density and the dye concentration. The amplification by stimulated emission was found to be strongest when the absorption length l(a) and the mean-free-path length l(*) had approximately the same magnitude. The respective l(*) values were determined by a pulsed transmission experiment.     

The Effect of Diet Quality on δ(13)C and δ(15)N in the Tissues of Locusts, Locusta migratoria L

Abstract Locust nymphs were raised from hatching to adult locusts on either seedling wheat (C(3)) or maize (C(4)), to determine whether relative enrichments/depletions of (15)N and (13)C within body tissues are influenced by diet. The maize contained less hexose sugars and protein per gram than wheat. The isotopic spacing between the food and the whole insect was found to differ between the two diets. The lower quality maize diet showed an overall +5.1‰ enrichment in δ(15)N compared to + 2.8‰ for wheat, possibly due to increased fractionation due to protein recycling. The maize diet resulted in increased depletion in lipid and trehalose and depletion in chitin relative to diet. The results for both δ(15)N and δ(13)C suggest that substrate recycling was occurring on the low quality maize diet. Therefore diet quality determines the enrichment/depletion in δ(15)N and δ(13)C within organisms.     

Bis(ligand) Rhenium(V) and Technetium(V) Complexes of Two Naturally Occurring Binding Moieties (Oxazoline and Thiazoline)

Attempts to prepare tris(ligand) metal complexes of technetium in intermediate oxidation states with potentially bidentate oxazoline- and thiazoline-containing ligands were unsuccessful; when pertechnetate was reduced in the presence of excess ligand, TcO(2).xH(2)O was produced. Instead, by reaction with preformed M.O cores, a series of oxotechnetium(V) and oxorhenium(V) complexes of the formula MOXL(2) (M = Re, X = Br; M = Tc, X = Cl) and HL = 2-(2'-hydroxyphenyl)-2-oxazoline (Hoz), 2-(2'-hydroxy-3'-methylphenyl)-2-oxazoline (Hmoz), 2-(2'-hydroxyphenyl)-2-thiazoline (Hthoz), and 2-(2'-hydroxyphenyl)-2-benzoxazoline (Hhbo) have been prepared. These compounds have been characterized by a variety of techniques including single-crystal X-ray diffraction. Crystals of Hthoz (C(9)H(9)NOS) are monoclinic, with space group P2(1)/n, a = 7.5342(6) ?, b = 12.2187(6) ?, c = 9.3942(8) ?, beta = 94.233(7) degrees, and Z = 4; those of TcOCl(thoz)(2) (C(18)H(16)ClN(2)O(3)S(2)Tc) are monoclinic, with space group P2(1)/n, a = 16.506(1) ?, b = 7.664(1) ?, c = 16.3216(6) ?, beta = 111.154(4) degrees, and Z = 4; those of ReOBr(oz)(2) (C(18)H(16)BrN(2)O(5)Re) are orthorhombic, with space group Pbca, a = 12.864(2) ?, b = 25.369(2) ?, c = 11.025(2) ?, and Z = 8. The structures were solved by direct (Hthoz) or Patterson (metal complexes) methods and were refined by full-matrix least-squares procedures to R = 0.033, 0.032, and 0.028 for 1600, 3152, and 2651 reflections with I >/= 3sigma(I), respectively. In the two complexes, the geometry around the metals is distorted octahedral with the halide ligands in each bound cis, and one phenolate oxygen from one ligand in each bound trans to the metal-oxo linkage. In ReOBr(oz)(2), the two oxazoline nitrogens are coordinated trans to one another; in TcOCl(thoz)(2), the two thiazoline nitrogens are found cis to one another.