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排序方式: 共有151条查询结果,搜索用时 31 毫秒
1.
Jarrett Robin B.; Basco Monica R.; Risser Richard; Ramanan Janaki; Marwill Maria; Kraft Dolores; Rush A. John 《Canadian Metallurgical Quarterly》1998,66(6):1036
Two pilot studies evaluated the rate of relapse or recurrence (i.e., major depressive disorder) after cognitive therapy (CT). Two sequential cohorts included outpatients who responded to acute phase CT (A-CT) and who agreed to monthly, treatment-free follow-up. In Study 1, the Kaplan-Meier technique estimated relapse and recurrence rates of 40% at 6 months, 45% at 8 months, 50% at 12 months, 67% at 18 months, and 74% at 24 months. In Study 2, responders to A-CT received 8 months (10 sessions) of continuation phase CT (C-CT). In Study 2, relapse or recurrence was 20% at 6 and 8 months, 27% at 12 months, and 36% at 18 and 24 months after A-CT. An exploratory log-rank test showed that relapse or recurrence-free survival was greater in Study 2 than in Study 1. If replicated, this result suggests that C-CT can reduce depressive relapse or recurrence. Alternative explanations are presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
2.
A series of Nafion®/ORMOSIL hybrids, generated by in situ sol-gel co-polymerizations of tetraethylorthosilicate (TEOS) and semi-organic R′nSi(OR)4−n co-monomers (SOC), were developed to generate a spectrum of nanoscale chemical environments within the Nafion® morphological template. The molecular structures of the ORMOSIL phases were analyzed by means of 29Si solid-state NMR (SSNMR) spectroscopy. A high average degree of Si atom coordination about SiO4 molecular sub-units can be achieved, but a significant number of unreacted SiOH groups on reacted Q=Si(O1/2)4 units is always present. The shifting, with relative ORMOSIL composition, of D=RR′Si(O1/2)2 or T=R″Si(O1/2)3 (R, R′ and R″ are organic moeities) peak envelopes for difunctional or trifunctional SOCs is suggested to reflect random co-condensation rather than distinct Q and D (or T) block formation. The numbers of membrane-incorporated Q and D (or T) units per fixed sulfonate group were calculated from the 29Si SSNMR spectra for those particular hybrids that had a reasonably low noise/signal aspect. Spectra for hybrids based on in situ sol-gel reactions for TEOS (no SOC present) suggest that inserted hydroquinone molecules interfere with condensation reactions between (RO)4−xSi(OH)x molecules and silanol oligomers to yield silicate structures with lower average coordination. While earlier small angle X-ray scattering studies indicated that ORMOSIL structures can be grown within the polar regions of Nafion®, the results reported here address the specific compositions of these nanoscale structures. 相似文献
3.
Antibacterial silver 总被引:5,自引:0,他引:5
The antibacterial activity of silver has long been known and has found a variety of applications because its toxicity to human cells is considerably lower than to bacteria. The most widely documented uses are prophylactic treatment of burns and water disinfection. However, the mechanisms by which silver kills cells are not known. Information on resistance mechanisms is apparently contradictory and even the chemistry of Ag(+) in such systems is poorly understood.Silver binds to many cellular components, with membrane components probably being more important than nucleic acids. It is difficult to know whether strong binding reflects toxicity or detoxification: some sensitive bacterial strains have been reported as accumulating more silver than the corresponding resistant strain, in others the reverse apparently occurs. In several cases resistance has been shown to be plasmid mediated. The plasmids are reported as difficult to transfer, and can also be difficult to maintain, as we too have found. Attempts to find biochemical differences between resistant and sensitive strains have met with limited success: differences are subtle, such as increased cell surface hydrophobicity in a resistant Escherichia coli.Some of the problems are due to defining conditions in which resistance can be observed. Silver(I) has been shown to bind to components of cell culture media, and the presence of chloride is necessary to demonstrate resistance. The form of silver used must also be considered. This is usually water soluble AgNO(3), which readily precipitates as AgCl. The clinically preferred compound is the highly insoluble silver sulfadiazine, which does not cause hypochloraemia in burns. It has been suggested that resistant bacteria are those unable to bind Ag(+) more tightly than does chloride. It may be that certain forms of insoluble silver are taken up by cells, as has been found for nickel. Under our experimental conditions, silver complexed by certain ligands is more cytotoxic than AgNO(3), yet with related ligands is considerably less toxic. There is evidently a subtle interplay of solubility and stability which should reward further investigation. 相似文献
4.
Using a technique for CCD polarimetry, we have obtained stellar polarization data with the 0.9-m telescope on Kitt Peak and with the Tek 2048 CCD camera. Measurements of stars viewed through holes in polarizing filters serve to correct for variations in atmospheric transparency. For the brightest stars the uncertainties in the measured polarization during a single, hour-long, polarimetric sequence are 0.3-0.5%, because of the residual effects of the variations in transparency. For fainter stars we are Poisson noise limited. Our technique provides some advantages over other techniques for CCD polarimetry, primarily because it can be easily integrated into existing photometric systems. 相似文献
5.
The serum of some patients with insulin-resistant "diabetes" contains antibodies that bind to and block the cell membrane receptors for insulin. In this report, we have characterized the effects of the antireceptor antibodies on the interaction of (125)I-insulin with its receptor on the human lymphoblastoid cell line IM-9. Up to 95% of specific insulin binding can be inhibited by pretreatment of the cells with these immunoglobulins. The onset of the inhibitory effect is time- and temperature-dependent, and the effect is reversed extremely slowly if the cells are suspended in a large excess of antibody-free buffer. These features of antibody binding can be easily distinguished from those for insulin binding to its receptor. The inhibitory effect of the antibodies can be reversed by exposure of the cells to conditions known to elute surface immunoglobulins. The three antireceptor sera studied appear to alter the insulin-receptor interaction in different ways. Two antisera markedly reduce receptor affinity through combined effects on the insulin association and dissociation rates, and, additionally, have smaller effects on available receptor number. A third antiserum primarily affects available receptor number and has little effect on receptor affinity. All three antisera inhibit the capacity of insulin to promote negatively cooperative site-site interactions among insulin receptors. The data suggest that these autoantibodies to the insulin receptor bind to different determinants on the receptor and may therefore be useful as unique probes of insulin receptor structure and function. 相似文献
6.
Amol Nalawade Mohammad K. Hassan William A. Jarrett Kenneth A. Mauritz Morton H. Litt 《Polymer International》2012,61(1):55-64
A broadband dielectric spectroscopic (BDS) study of poly(2,5‐benzimidazole) revealed three sub‐glass relaxations and the manner in which the time scales of these local molecular motions shift with annealing temperature and time. Also issuing from the BDS studies was a trend in the degree of connectivity of charge migration pathways and conductivity with annealing temperature and time. These studies were complemented with dynamic mechanical analysis, which showed the same relaxations, and solid state 1H and 13C NMR studies that showed hydrogen bonding group mobility versus temperature. Wide angle X‐ray diffraction investigations indicated an increase in chain‐packing efficiency that was used to rationalize the BDS and NMR results. Copyright © 2011 Society of Chemical Industry 相似文献
7.
Kai Xu Pavel Hrma Jarrett A. Rice Michael J. Schweiger Brian J. Riley Nicole R. Overman Albert A. Kruger 《Journal of the American Ceramic Society》2016,99(9):2964-2970
The feed‐to‐glass conversion, which comprises complex chemical reactions and phase transitions, occurs in the cold cap during nuclear waste vitrification. To investigate the conversion process, we analyzed heat‐treated samples of a simulated high‐level waste feed using X‐ray diffraction, electron probe microanalysis, leaching tests, and residual anion analysis. Feed dehydration, gas evolution, and borate phase formation occurred at temperatures below 700°C before the emerging glass‐forming melt was completely connected. Above 700°C, intermediate aluminosilicate phases and quartz particles gradually dissolved in the continuous borosilicate melt, which expanded with transient foam. Knowledge of the chemistry and physics of feed‐to‐glass conversion will help us control the conversion path by changing the melter feed makeup to maximize the glass production rate. 相似文献
8.
JA Beatty JJ Callanan A Terry O Jarrett JC Neil 《Canadian Metallurgical Quarterly》1998,72(1):767-771
We describe the histopathological, immunohistochemical, and molecular characterization of a lymphoma arising in a 7-year-old cat following experimental infection with feline immunodeficiency virus (FIV). The tumor was high grade and of B-cell lineage. The transformed cell had an immature phenotype (CD79a+, CD79b-, CD21-, immunoglobulin heavy and light chain negative), confirmed by antigen receptor gene analysis, which showed germ line configuration. Single-copy, clonally integrated FIV provirus was detected in tumor genomic DNA. FIV p24 antigen was not detected in tumor cells by immunostaining. This study provides the first evidence that the feline lentivirus may play a direct role in cell transformation under certain circumstances. 相似文献
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