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71.
We report the first demonstration of proton-exchanged optical planar waveguides in x-cut and z-cut LiNbO3 doped with 6 mol% ZnO using adipic acid as proton source. These waveguides exhibit a graded index profile which can be modeled by a linear step function with a surface index increase of 0.135 and 0.14 for x-cut and z-cut waveguides, respectively. The diffusion constant Do and the activation energy Q are characterized optically to be 1.64×109 μm2/h and 88.8 KJ/mol for x-cut waveguides, and 1.478×109 μm2/h and 91.25 KJ/mol for z-cut waveguides, respectively. The diffusion rate along the z-axis is slower than that along the x-axis, whereas the surface index increase on z-cut waveguides is larger than that on x-cut waveguides. 相似文献
72.
DT Smoot JH Resau MH Earlington M Simpson TL Cover 《Canadian Metallurgical Quarterly》1996,39(6):795-799
BACKGROUND: Many Helicobacter pylori strains produce a cytotoxin that induces cytoplasmic vacuolation in various types of eukaryotic cells. In contrast with the marked cell vacuolation that occurs in vitro in response to this cytotoxin, comparatively little epithelial vacuolation has been observed in the gastric mucosa of H pylori infected persons. AIMS: Experiments were performed to determine the susceptibility of human gastric epithelial cells in vitro to H pylori vacuolating cytotoxin activity. METHODS: Human gastric epithelial cells, harvested from upper gastrointestinal endoscopic biopsy specimens, were incubated overnight with broth culture supernatants from either a wild type cytotoxin producing (tox+) H pylori strain or an isogenic mutant strain that lacks cytotoxin activity. RESULTS: Prominent cytoplasmic vacuolation occurred in response to tox+ supernatant, but not supernatant from the isogenic mutant strain. Primary human gastric epithelial cells were significantly more sensitive to H pylori vacuolating cytotoxin activity than were either HeLa or AGS cells. Exposure of human gastric epithelial cells to high concentrations of tox+ supernatant for 48 hours caused lethal cell injury. CONCLUSIONS: These studies indicate that primary human gastric epithelial cells are highly sensitive to H pylori vacuolating cytotoxin activity. 相似文献
73.
74.
JH van Bemmel 《Canadian Metallurgical Quarterly》1994,34(1-4):365-371
The development of medical workstations for the support of patient care, the assessment of care, management support, and education is just at its beginning. During the Working Conference on the Health care Professional Workstation held in Washington DC, June 1993, several aspects of such workstations were discussed, but it was also recognized that prototyping or learning by experience could be a rich source to further promote the progress in this field. Eight such prototypes or already operational medical workstations were demonstrated and a preliminary user assessment was done to obtain a first insight in the advantages and the type of criteria of such evaluations. It was concluded that such assessments were of great value to (i) give feedback to the designers of medical workstations, (ii) indicate areas of strength and for further research, and (iii) to offer criteria to potential users of such workstations for making decisions on using such systems. The assessment criteria deal with functionality, architecture, user interfaces, communications and integration, and data and knowledge management. 相似文献
75.
由对硝基苯甲醚制备对氨基苯甲醚的工艺研究 总被引:1,自引:0,他引:1
以硫磺和氢氧化钠为原料,制备多硫化钠,然后用多硫化钠还原对硝基苯甲醚合成对氨基苯甲醚。第一步反应在90℃下回流1h,硫磺的转化率可达100%;第二步反应在110℃下回流8h,对氨基苯甲醚的收率为96%,纯度为99%,副产品硫代硫酸钠的收率为92%,纯度为98%。 相似文献
76.
Despite the wider dissemination of health plan report cards, little is known about whether consumers will use this information in making plan and provider choices. Studies of human judgment and decision making are reviewed, as are their implications for devising strategies to inform consumers. The limitations of human information processing suggest that many consumers will not use performance information in making choices. Strategies are needed to support consumers who prefer to rely on intermediaries as well as those who wish to apply the information for their own use. Many current strategies are based on assumptions not supported by existing decision-making research. Although there is much to learn about assisting consumers in making informed choices, a great deal is known from decision-making research. Our approaches and our research agenda must be based on this existing foundation of knowledge. 相似文献
77.
JM Casasnovas TA Springer JH Liu SC Harrison JH Wang 《Canadian Metallurgical Quarterly》1997,387(6630):312-315
Recognition by integrin proteins on the cell surface regulates the adhesive interactions between cells and their surroundings. The structure of the 'I' domain that is found in some but not all integrins, has been determined. However, the only integrin ligands for which structures are known, namely fibronectin and VCAM-1, are recognized by integrins that lack I domains. The intercellular adhesion molecules ICAM-1, 2 and 3 are, like VCAM-1, members of the immunoglobulin superfamily (IgSF), but they are recognized by an I domain-containing integrin, lymphocyte-function-associated antigen 1 (LFA-1, or CD11a/CD18). Here we present the crystal structure of the extracellular region of ICAM-2. The glutamic acid residue at position 37 is critical for LFA-1 binding and is proposed to coordinate the Mg2+ ion in the I domain; this Glu 37 is surrounded by a relatively flat recognition surface and lies in a beta-strand, whereas the critical aspartic acid residue in VCAM-1 and fibronectin lie in protruding loops. This finding suggests that there are differences in the architecture of recognition sites between integrins that contain or lack I domains. A bend between domains 1 and 2 of ICAM-2 and a tripod-like arrangement of N-linked glycans in the membrane-proximal region of domain 2 may be important for presenting the recognition surface to LFA-1. A model of ICAM-1 based on the ICAM-2 structure provides a framework for understanding its recognition by pathogens. 相似文献
78.
The paper presents a case study of the development of an expert decision support system which uses simple heuristic methods for fast determination of routes for simultaneous signals in a transmission network of limited capacity. It illustrates how heuristic solutions can be embodied in a model-based DSS and how the standard decision support literature, although intuitively appealing, provides little practical assistance in system construction or classification 相似文献
79.
80.