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101.
The carrier lifetime is the most important electronic property of semiconductor materials for solar cells. In this paper we discuss traditional and novel methods for its experimental determination. Among the latter, the Quasi-steady-state photoconductance is particularly powerful since it permits measuring the injection level dependence of the lifetime. The analysis and interpretation of this dependence yields a wealth of information on the physical mechanisms that limit the performance of silicon solar cells. The effect of the surfaces of the silicon wafers, the emitter saturation current density and the Shockley–Read–Hall and Auger recombination mechanisms are explained and their possible determination from lifetime measurements discussed. 相似文献
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IM Kapetanovic CD Torchin CD Thompson TA Miller PJ McNeilly TL Macdonald HJ Kupferberg JL Perhach RD Sofia JM Strong 《Canadian Metallurgical Quarterly》1998,26(11):1089-1095
To gain insights into the different forms of modified amyloid beta peptides (A beta) in the Alzheimer disease (AD) and Down syndrome (DS) brain, we used two-site ELISAs with antibodies specific for isomerized (i.e. A beta with L-isoaspartate at positions 1 and 7) and pyroglutamate-modified (i.e. A beta beginning with pyroglutamate at position 3) forms of A beta to quantitate the levels of these different A beta peptides in formic acid extracts of AD and DS frontal cortex. Despite variations in the proportions of distinct forms of A beta in AD and DS frontal cortex, the major species of A beta in these samples were A betaN3(pyroGlu)-42 as well as A beta x-42 (where x is a residue at position 2 or less in A beta), whereas isomerized A beta was a minor species. Further, the levels of isomerized and pyroglutamate-modified forms of A beta terminating at amino acid 42 were higher than those ending at amino acid 40. The abundance of the distinct forms of A beta reported here in formic acid extracts of AD and DS frontal cortex suggests that these A beta species could play important roles in the deposition of A beta in AD and DS brains. 相似文献
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MD Phillips RI Grossman Y Miki L Wei DL Kolson MA van Buchem M Polansky JC McGowan JK Udupa 《Canadian Metallurgical Quarterly》1998,19(6):1055-1060
A kinetic analysis of degradation of saturated oligoguluronates by poly(alpha-L-guluronate)lyase from Corynebacterium sp. ALY-1 strain was done. The saturated oligoguluronates were prepared by hydrolyzing poly alpha-1,4-L-guluronate from alginate with HCl, and then by gel filtration on a Bio-Gel P-6 column. The saturated pentaguluronate or above were rapidly degraded by the enzyme, while tetraguluronate was slowly degraded. From the dependency of the catalytic rate constant (kcat) on the degree of polymerization of substrates, the enzyme was found to have a subsite size corresponding to hexaguluronate units. The action pattern of the enzyme on hexaguluronate suggested that the catalytic site of the enzyme was matched to the linkage between the second and third uronic residue from the non-reducing end, since the substrate was mainly split into a unsaturated tetramer and a saturated dimer from a HPLC analysis. 相似文献
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AJ Macdonald 《Canadian Metallurgical Quarterly》1997,315(7105):413-417
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We report a patient with biopsy-proven progressive multifocal leukoencephalopathy (PML) who was serially imaged with MRI and magnetization transfer imaging. The magnetization transfer ratio (MTR) was profoundly and significantly diminished when compared with normal control subjects. The pattern of MTR was distinct from that of MS and periventricular ischemic white matter disease. Magnetization transfer imaging techniques may aid in the differential diagnosis of PML. 相似文献
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