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51.
Xu C. Ou Y. Dalessio J. Schuster E. Luce T. C. Ferron J. R. Walker M. L. Humphreys D. A. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2010,38(2):163-173
52.
Anas F. Jarjour Alex M. Green Tim J. Parker Robert A. Taylor Rachel A. Oliver G. Andrew D. Briggs Menno J. Kappers Colin J. Humphreys Robert W. Martin Ian M. Watson 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):119
We present a study of the time-integrated and time-resolved photoluminescence properties of single-InGaN/GaN quantum dots (QDs) using two-photon spectroscopy. Two samples containing QDs produced by different growth techniques are examined. We find that two-photon excitation results in the suppression of the emission from the underlying quantum well to which the QDs are coupled and yet relatively strong QD emission is observed. This effect is explained in terms of the enhancement of two-photon absorption in QDs due to the full confinement of carriers. Furthermore, evidence of the presence of excited states is revealed from the two-photon photoluminescence excitation spectra presented in the study. 相似文献
53.
Yang Y Grubb MF Luk CE Humphreys WG Josephs JL 《Rapid communications in mass spectrometry : RCM》2011,25(21):3245-3251
An early assessment of metabolite exposure in preclinical species can provide quantitative estimation on possible active or toxic metabolites. Frequently, synthetic metabolite standards are not available at the preclinical stage, precluding the quantitation of metabolites by means of calibration curves and quality control (QC) samples. We present here an approach to determine the extent of circulating metabolites using 'metabolite standards' generated by in vitro incubations in combination with the correction for mass spectrometry response based on UV response. The study was done by coupling ultra-high-performance liquid chromatography (UHPLC) to LTQ-Orbitrap high-resolution mass spectrometry, and the quantitation was based on full scan high-resolution accurate mass analysis in combination with retention time. First, we investigated the separation capacity of a 10.5 min UHPLC method and the quantitative capability of an LTQ-Orbitrap for full scan accurate mass quantitation by spiking chemical standards of buspirone and its six metabolites in blank plasma. Then we demonstrated the use of a UV correction approach to quantitatively estimate buspirone and its metabolites in plasma samples from a rat pharmacokinetics study. We compared the concentration versus time profiles of buspirone and its six metabolites in rat plasma samples obtained using three different approaches, including using UV correction, using individual standard curves for each metabolite prepared from the synthetic standard, and using a calibration curve of the parent compound buspirone. We demonstrated the estimated metabolite exposure of buspirone using this UV correction approach resulted in rank ordering of metabolite exposure within three-fold of the value obtained with metabolite standards, in contrast to eight-fold without UV correction. The approach presented in this paper provides a practical solution to an unmet bioanalytical need for quantitative information on metabolites without standards in preclinical in vivo studies. 相似文献
54.
M.A. Moram C.F. Johnston M.J. Kappers C.J. Humphreys 《Physica B: Condensed Matter》2009,404(16):2189-2191
Nonpolar (11-20) GaN films with different basal-plane stacking fault (BSF) densities (determined using transmission electron microscopy) were investigated using X-ray diffraction. Diffuse streaking from I1 and I2 BSFs was observed in reciprocal space maps of the 10-10 and 20-20 reflections. X-ray calibration curves for BSF density determination can be plotted using the diffusely scattered intensity of open detector 10-10 or 20-20 ω-scans measured at a fixed, large separation from the peak maximum. However, ab initio determination of stacking fault densities is not possible due to additional broadening from other defects. Similarly, ω-scan peak widths are poor indicators of BSF densities. 相似文献
55.
56.
An aeroacoustic model test has been conducted to investigate the mechanisms of sound generation on high-lift wing configurations. This paper presents an analysis of flap side-edge noise, which is often the most dominant source. A model of a main element wing section with a half-span flap was tested at low speeds of up to a Mach number of 0.17, corresponding to a wing chord Reynolds number of approximately 1.7 million. Results are presented for flat (or blunt), flanged, and round flap-edge geometries, with and without boundary-layer tripping, deployed at both moderate and high flap angles. The acoustic database is obtained from a small aperture directional array (SADA) of microphones, which was constructed to electronically steer to different regions of the model and to obtain farfield noise spectra and directivity from these regions. The basic flap-edge aerodynamics is established by static surface pressure data, as well as by computational fluid dynamics (CFD) calculations and simplified edge flow analyses. Distributions of unsteady pressure sensors over the flap allow the noise source regions to be defined and quantified via cross-spectral diagnostics using the SADA output. It is found that shear layer instability and related pressure scatter is the primary noise mechanism. For the flat edge flap, two noise prediction methods based on unsteady-surface-pressure measurements are evaluated and compared to measured noise. One is a new causality spectral approach developed here. The other is a new application of an edge-noise scatter prediction method. The good comparisons for both approaches suggest that the prediction models capture much of the physics. Areas of disagreement appear to reveal when the assumed edge noise mechanism does not fully define the noise production. For the different edge conditions, extensive spectra and directivity are presented. The complexity of the directivity results demonstrate the strong role of edge source geometry and frequency in the noise radiation. Significantly, for each edge configuration, the spectra for different flow speeds, flap angles, and surface roughness were successfully scaled by utilizing aerodynamic performance and boundary-layer scaling methods developed herein. 相似文献
57.
Jane L. Humphreys 《Tetrahedron letters》2004,45(17):3429-3432
The synthesis of 6,6-difluoroshikimic acid (4) has been achieved in nine steps from the enantiopure diol 9, which is derived from microbial dihydroxylation of iodobenzene. The synthetic strategy has also been demonstrated to be applicable to the preparation of other 6-substituted analogues of shikimic acid. 相似文献
58.
G. Moldovan M. J. Roe I. Harrison M. Kappers C. J. Humphreys P. D. Brown 《哲学杂志》2013,93(16):2315-2327
The effects of a KOH treatment on the properties of n-type GaN surfaces and associated Au/n-GaN contacts have been investigated by X-ray photoelectron spectroscopy, atomic force microscopy, reflection high-energy-electron diffraction, current–voltage and electron-beam-induced current characterization. Ga-polar surfaces grown by molecular beam epitaxy and metal–organic chemical vapour deposition were compared. A decrease in electron barrier height and an increase in non-radiative recombination properties of Au/n-GaN contacts were found with KOH treatment, correlated with an increase of surface Ga vacancies, an increase in surface N–H2 content and a decrease in surface C contamination. A 0.3-eV shift in the Ga3d peak position towards the valence band and a reduction in the dislocation contrast were observed for the case of molecular-beam-epitaxy-grown GaN only, demonstrating that surface Ga vacancies and threading dislocations play only a limited role in defining the resultant metal/GaN contact properties. Accordingly, the surface atomic content and the resulting surface states, following KOH treatment, should be taken into consideration when appraising the electrical properties of n-GaN surfaces and the performance of associated metallic contacts. 相似文献
59.
J. E. Humphreys 《代数通讯》2013,41(6):475-490
With a Weyl group W and a positive integer p are associated p-linkage classes of weights [4,13]. Small deformations of such classes by elements of W are introduced here. These lead in turn to certain polynomials in p with highest term pm, m = number of positive roots (one polynomial for each conjugacy class of W), which are written down explicitly for types A1, A2, B2. These polynomials give (for each prime p) the degrees of the various large series of irreducible characters of the corresponding Chevalley group over the field of p elements. Indeed, the formal behavior of weights appears to reflect the actual behavior of the characters under reduction modulo p. 相似文献
60.
J.E. Humphreys 《代数通讯》2013,41(12):4773-4779