n/a

n/a

n/a

n/a

n/a

We describe a detailed study of scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) analysis to study composition and structure of 500nm thick polycrystalline GaN samples. The films have been deposited by cyclic-pulsed laser deposition (cyclic-PLD) with a Nd:YAG nanosecond pulsed laser at 1064nm. SEM pictures of the GaN layers revealed a structure composed of grains with typical dimensions of 200nm. Coalescence of the grains was more evident for a 1 mu m thick sample. EDS mapping of the GaN layer was performed for Ga, N, O, and Al and could be related with the corresponding SEM scan. Both EDS and XPS composition analyses pointed to a Ga rich (or N deficient) GaN layer. (c) 2007 Elsevier Ltd. All rights reserved.

We extend a result of Bottcher and Silbermann on higher order asymptotics of determinants of block Toeplitz matrices with symbols in Wiener algebras with power weights to the case of Wiener algebras with general weights satisfying natural submultiplicativity, monotonicity, and regularity conditions.

Sauropod dinosaurs were the largest animals ever to inhabit the land, with truly gigantic forms in at least three lineages1, 2, 3. Small species with an adult body mass less than five tonnes are very rare4, 5, and small sauropod bones generally represent juveniles. Here we describe a new diminutive species of basal macronarian sauropod, Europasaurus holgeri gen. et sp. nov., and on the basis of bone histology we show it to have been a dwarf species. The fossils, including excellent skull material, come from Kimmeridgian marine beds of northern Germany6, 7, and record more than 11 individuals of sauropods 1.7 to 6.2 m in total body length. Morphological overlap between partial skeletons and isolated bones links all material to the same new taxon. Cortical histology of femora and tibiae indicates that size differences within the specimens are due to different ontogenetic stages, from juveniles to fully grown individuals. The little dinosaurs must have lived on one of the large islands around the Lower Saxony basin8. Comparison with the long-bone histology of large-bodied sauropods suggests that the island dwarf species evolved through a decrease in growth rate from its larger ancestor.

n/a

n/a

n/a

n/a

n/a

n/a

n/a

n/a

n/a

n/a

This paper describes some theoretical and experimental results obtained in an effort to optimize the Series Resonant Converter (SRC) when used with a loosely coupled transformer for Inductive Coupling Power Transfer (ICPT). The main goal of this work is to define precisely which mode of operation of the power stage is the most efficient. The results also suggest a way to choose the design criteria for the physical parameters (operation frequency, characteristic impedance, transformer ratio, etc.) to achieve that mode of operation. The analysis involves also the investigation of the separated in two halves pot core ferrite transformer, especially the way it changes its magnetizing and leakage fluxes and hence, inductances. It is shown that for the practical values of the separation distance, the leakage inductance remains almost unchanged. Nevertheless the current distribution between the primary and the secondary windings changes drastically due to the large variation of the magnetizing inductance. The analysis has lead to a set of equations with solutions that show graphically the way to an optimized operation of the converter, i.e. higher primary currents and higher transformer ratios to fit in the desired mode.

We establish a Fredholm criterion for an arbitrary operator in the Banach algebra of singular integral operators
with piecewise continuous coefficients on Nakano spaces (generalized Lebesgue spaces with variable exponent) with Khvedelidze weights over Carleson curves with logarithmic whirl points.

A classical theorem of Coifman, Rochberg, and Weiss on commutators of singular integrals is extended to the case of generalized Lp spaces with variable exponent.

n/a