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21.
The photoconductive properties of a carotenoid polyene,β-Apo-8′ carotenal in polycrystalline form has been studied. The growth of the photocurrent shows an overshoot in the growth-time
curve before steady state value is attained. This behaviour of photocurrent is proposed to be due to higher value of recombination
coefficient than trapping coefficient. From the temperature dependence study it is observed that the steady state photocurrent,
at first increases with increase of temperature, attains a maximum at a particular temperatureT
max and then decreases with temperature. TheT
max value agrees with the temperature above and below which steady state photocurrent is attained differently. Monomolecular
and bimolecular recombination processes at two temperature regimes are proposed to account for the observed behaviour. The
dependence of photocurrent with excitation light intensity and wavelength study provide information on the carrier generation
processes. The fast decay of photocurrent have been observed at different temperatures and from this study the decay constant
is calculated and it is found to be temperature independent. 相似文献
22.
MS Harbuz Z Perveen-Gill SL Lightman DS Jessop 《Canadian Metallurgical Quarterly》1995,34(12):1117-1122
We have investigated the role of the gonadal steroids testosterone (T) and progesterone in modulating: (1) the onset and severity of adjuvant-induced arthritis (AA), (2) the response of the hypothalamo-pituitary-adrenal (HPA) axis, and (3) the levels of plasma prolactin and anterior pituitary prolactin messenger ribonucleic acid (mRNA) in the rat. Male rats were castrated (CSX) and received either no T, low T or high T delivered using silastic implants. In a second study experimental groups comprised CSX/AA, CSX/AA + progesterone or CSX/AA + progesterone + T. The time of onset was sooner and the severity of AA was greater in CSX rats. Inflammation was prevented by T replacement. Endogenous plasma T levels were decreased in AA rats. In control animals with AA there was an increase in pro-opiomelanocortin (POMC) mRNA in the anterior pituitary and of plasma corticosterone, and a decrease in corticotrophin-releasing factor (CRF) mRNA. These changes in the HPA axis of AA and CSX/AA rats were reversed by T replacement. These data suggest that T has an important protective effect on the progress and severity of AA. This was reflected by a reversal of the neuroendocrine changes of the HPA axis. Progesterone treatment alone had no effect on the severity of the disease. Prolactin mRNA in the anterior pituitary was decreased in the CSX and in the CSX/AA group but was not altered by AA. Plasma prolactin was raised in AA but T replacement did not reduce these elevated levels despite the absence of disease. Thus, prolactin provides a poor indicator of inflammation, suggesting that it may not be a potent pro-inflammatory compound in AA. 相似文献
23.
OBJECTIVE: This study investigated hypotheses concerning the importance of symptoms of numbing in posttraumatic stress disorder (PTSD). METHODS: Symptoms of PTSD were assessed in 72 female rape victims and 86 female victims of nonsexual assault approximately 3 months after the crimes occurred. A principal-components factor analysis of subjects' symptoms was then undertaken. RESULTS: The analysis yielded three factors: arousal/avoidance, numbing, and intrusion. These were somewhat different from the symptom clusters in DSM-III-R, since effortful avoidance and numbing symptoms did not load on the same factor. Numbing symptoms appeared to be particularly important in identifying individuals with PTSD. CONCLUSIONS: The results imply that there are two patterns of posttrauma symptoms, one characterizing PTSD and the second characterizing a phobic reaction. 相似文献
24.
Oxidized low density lipoprotein (LDL) may play a significant role in atherosclerosis. We have investigated the effect of pH on the oxidation of LDL by iron or copper. When LDL was oxidized by iron in the presence of cysteine in either Hanks' balanced salt solution (HBSS) or Ham's F-10 medium, an acidic pH greatly decreased the lag period and increased the rate of formation of hydroperoxides and thiobarbituric acid-reactive substances (TBARS), and increased its uptake by macrophages. There was a dose-dependent increase of LDL oxidation at acidic pH in the presence of increasing concentrations of cysteine. When LDL was oxidized by copper in HBSS, an acidic pH increased the lag phase before the rapid formation of conjugated dienes, hydroperoxides, and TBARS, but increased its uptake by macrophages. Similar results were obtained using Ham's F-10 medium. Cysteine (100 microM) inhibited the modification of LDL by copper in HBSS at both pH 7.4 and 5.5 As atherosclerotic lesions may be acidic, these observations may help to explain why LDL oxidation occurs locally at these sites. 相似文献
25.
26.
DS Levine 《Canadian Metallurgical Quarterly》1994,344(8917):212-213
27.
A methodology for evaluating the reactivity of titanium with mould materials during casting has been developed. Microhardness
profiles and analysis of oxygen contamination have provided an index for evaluation of the reactivity of titanium. Microhardness
profile delineates two distinct regions, one of which is characterised by a low value of hardness which is invariant with
distance. The reaction products are uniformly distributed in the metal in this region. The second is characterised by a sharp
decrease in microhardness with distance from the metal-mould interface. It represents a diffusion zone for solutes that dissolve
into titanium from the mould. The qualitative profiles for contaminants determined by scanning electron probe microanalyser
and secondary ion mass spectroscopy in the as-cast titanium were found to be similar to that of microhardness, implying that
microhardness can be considered as an index of the contamination resulting from metal-mould reaction. 相似文献
28.
29.
30.
DS Cunningham 《Canadian Metallurgical Quarterly》1993,36(4):193-197
We did a statistical study of 294 strains of Staphylococcus aureus (S. aureus) isolated from skin infections during the period from January of 1989 to December of 1991 in the Department of Dermatology, Kansai Medical University Hospital. We especially examined methicillin-resistant S. aureus (MRSA) from the point of view of incidence, variety of skin infections with MRSA, coagulase type, phase type, and resistance against antimicrobial agents. The frequency of isolation of MRSA has been increasing. In 1991, the proportion of MRSA isolates among all S. aureus strains isolated from skin infections was 41.5%. MRSA was isolated most often from infectious decubitus. Coagulase type II and phage group NT (not typable) MRSA were most frequently isolated. The resistance of MRSA to OFLX and IMP/CS had remarkably increased. Notably, the resistance to MINO was low before 1991. 相似文献