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Optical reflectivity spectra are useful in assessing the structure of vertical-cavity surface-emitting lasers (VCSELs) but show little of the nature of the active quantum well (QW). Here we use photomodulated reflectance to identify a region of an epitaxial wafer with optimal cavity-QW alignment. AlInGaP-AlGaAs visible VCSEL devices fabricated from this region lased well, compared with devices from a nearby control piece of the wafer which failed to lase at all. 相似文献
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A Akhmanova FG Voncken H Harhangi KM Hosea GD Vogels JH Hackstein 《Canadian Metallurgical Quarterly》1998,30(5):1017-1027
The anaerobic chytrid Piromyces sp. E2 lacks mitochondria, but contains hydrogen-producing organelles, the hydrogenosomes. We are interested in how the adaptation to anaerobiosis influenced enzyme compartmentalization in this organism. Random sequencing of a cDNA library from Piromyces sp. E2 resulted in the isolation of cDNAs encoding malate dehydrogenase, aconitase and acetohydroxyacid reductoisomerase. Phylogenetic analysis of the deduced amino acid sequences revealed that they are closely related to their mitochondrial homologues from aerobic eukaryotes. However, the deduced sequences lack N-terminal extensions, which function as mitochondrial leader sequences in the corresponding mitochondrial enzymes from aerobic eukaryotes. Subcellular fractionation and enzyme assays confirmed that the corresponding enzymes are located in the cytosol. As anaerobic chytrids evolved from aerobic, mitochondria-bearing ancestors, we suggest that, in the course of the adaptation from an aerobic to an anaerobic lifestyle, mitochondrial enzymes were retargeted to the cytosol with the concomitant loss of their N-terminal leader sequences. 相似文献
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Efthimion PC Arunasalam V Bitzer R Campbell L Hosea JC 《The Review of scientific instruments》1979,50(8):949-951
We have developed a fast-scanning heterodyne receiver into a plasma diagnostic that measures the fundamental cyclotron emission from the PLT plasma and thus ascertains the time evolution of the electron temperature profile. The receiver scans 60-90 GHz every 10 ms and is interfaced to a computer for completely automated calibrated temperature measurements. 相似文献
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M. Ono M.G. Bell R. Kaita H.W. Kugel J.-W. Ahn J.P. Allain D. Battaglia R.E. Bell J.M. Canik S. Ding S. Gerhardt T.K. Gray W. Guttenfelder J. Hosea M.A. Jaworski J. Kallman S. Kaye B.P. LeBlanc L.E. Zakharov 《Fusion Engineering and Design》2012,87(10):1770-1776
Lithium wall coating techniques have been experimentally explored on National Spherical Torus Experiment (NSTX) for the last six years. The lithium experimentation on NSTX started with a few milligrams of lithium injected into the plasma as pellets and it has evolved to a dual lithium evaporation system which can evaporate up to ~160 g of lithium onto the lower divertor plates between re-loadings. The unique feature of the NSTX lithium research program is that it can investigate the effects of lithium coated plasma-facing components in H-mode divertor plasmas. This lithium evaporation system has produced many intriguing and potentially important results. In 2010, the NSTX lithium program has focused on the effects of liquid lithium divertor (LLD) surfaces including the divertor heat load, deuterium pumping, impurity control, electron thermal confinement, H-mode pedestal physics, and enhanced plasma performance. To fill the LLD with lithium, 1300 g of lithium was evaporated into the NSTX vacuum vessel during the 2010 operations. The routine use of lithium in 2010 has significantly improved the plasma shot availability resulting in a record number of plasma shots in any given year. In this paper, as a follow-on paper from the 1st lithium symposium [1], we review the recent progress toward developing fundamental understanding of the NSTX lithium experimental observations as well as the opportunities and associated R&D required for use of lithium in future magnetic fusion facilities including ITER. 相似文献
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FP Guengerich NA Hosea A Parikh LC Bell-Parikh WW Johnson EM Gillam T Shimada 《Canadian Metallurgical Quarterly》1998,26(12):1175-1178
Today cytochrome P450 (P450) research is accepted as an integral part of drug development and discovery. Work leading to this point included biochemical studies on P450 in experimental animal models and application to human systems. The development of recombinant expression systems has been an important part of the progress, and in this article we describe some recently developed bacterial systems that can be used for the production of metabolites, genotoxicity testing, and screening in random mutagenesis work. Rate-limiting aspects of P450 reactions vary with particular systems, and further investigations are in order. Non-ionic detergents have been utilized widely in P450 purification work; these compounds are now shown to be substrates for P450s. These oxidations are not only of fundamental interest in expanding the repertoire of P450 substrates but have significance in light of human exposure to these compounds. 相似文献
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Summary The Brillouin spectrum of polyethylene has been measured as a function of temperature through the crystalline melting range, using a five-pass Fabry-Perot interferometer. Discontinuities have been observed in the Brillouin shift and width and the Landau-Placzek ratio near the melting temperature. The results are discussed in terms of phenomena associated with the process of melting. 相似文献
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Tomic S. O'Reilly E.P. Fehse R. Sweeney S.J. Adams A.R. Andreev A.D. Choulis S.A. Hosea T.J.C. Riechert H. 《IEEE journal of selected topics in quantum electronics》2003,9(5):1228-1238
We present a comprehensive theoretical and experimental analysis of 1.3-/spl mu/m InGaAsN/GaAs lasers. After introducing the 10-band k /spl middot/ p Hamiltonian which predicts transition energies observed experimentally, we employ it to investigate laser properties of ideal and real InGaAsN/GaAs laser devices. Our calculations show that the addition of N reduces the peak gain and differential gain at fixed carrier density, although the gain saturation value and the peak gain as a function of radiative current density are largely unchanged due to the incorporation of N. The gain characteristics are optimized by including the minimum amount of nitrogen necessary to prevent strain relaxation at the given well thickness. The measured spontaneous emission and gain characteristics of real devices are well described by the theoretical model. Our analysis shows that the threshold current is dominated by nonradiative, defect-related recombination. Elimination of these losses would enable laser characteristics comparable with the best InGaAsP/InP-based lasers with the added advantages provided by the GaAs system that are important for vertical integration. 相似文献