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991.
992.
X-ray diffraction and scanning electron microscope studies of processed rice hull silica 总被引：3，自引：0，他引：3
Andrew Proctor 《Journal of the American Oil Chemists' Society》1990,67(9):576-584
The structure and composition of processed rice hull ash were studied to better understand its adsorption of the soy oil components,
lutein and free fatty acids. The silica-rich ash was composed largely of low order cristobalite and tridymite in the form
of opal CT, with variable particle size. On heating of the ash there was conversion to a more ordered form of opal C, fusing
of particles, and loss of potassium. Acid washing, following heating, also removed potassium and slightly reduced particle
size further. Crystal form, particle size, particle fusion and potassium content may be important factors influencing ash
adsorption of soy oil components. 相似文献
993.
PURPOSE: Abdominal aortic aneurysms (AAAs) rupture when the wall stress exceeds the strength of the vascular tissue. Intraluminal thrombus may absorb tension and reduce AAA wall stress. This study was performed to test the hypothesis that intraluminal thrombus can significantly reduce AAA wall stress. METHODS: AAA wall stresses were determined by axisymmetric finite element analysis. Model AAAs had external diameters ranging from 2.0 to 4.0 cm. Model parameters included: AAA length, 6 cm; wall thickness, 1.5 mm; Poisson's ratio, 0.49; Young's modulus, 1.0 MPa; and luminal pressure, 1.6 x 10(5) dyne/cm2. Stresses were calculated for each model without thrombus, and then were recalculated with thrombus filling 10% of the AAA cavity. Calculations were repeated as thrombus size was increased in 10% increments and as thrombus elastic modulus increased from 0.01 MPa to 1.0 MPa. Maximum wall stresses were compared between models that had intraluminal thrombus and the unmodified models. Stress reduction greater than 25% was considered significant. RESULTS: The maximum stress reduction of 51% occurred when thrombus with elastic modulus of 1.0 MPa filled the entire AAA cavity. Stresses were reduced by only 25% as modulus decreased to 0.2 MPa. Similarly, decreasing thrombus size by 70% resulted in stress reduction of only 28%. Large AAAs experienced greater stress reduction than small AAAs (48% vs 11%). CONCLUSION: Intraluminal thrombus can significantly reduce AAA wall stress. 相似文献
994.
WR Baldwin 《Canadian Metallurgical Quarterly》1993,70(8):634-636
In many of the world's nations, optometry hardly exists because resources are not sufficient to educate optometrists nor to fund their services. In others, tradition and accommodation with other forces have rendered optometry incapable of change that would expand its scope of services. But, in a growing number of countries, there is an accelerating trend toward expansion of education and scope of practice. Optometry is coming to be defined in those parts of the globe as that independent primary health profession whose practitioners are educated in vision and health sciences, and who meet standards that qualify them to diagnose and treat visual problems and ocular disease. Review of this change, wherever it has transpired, leads to the conclusion that the scope of optometric practice expands only after corresponding expansion in optometric education. These goals are being achieved in a group of highly developed countries in which optometry has long been a major eye care provider, and in countries in which socio-economic and political conditions are improving, but where there is no significant source or tradition of primary eye care of any scope. 相似文献
995.
996.
997.
The stability and predictability of orthognathic surgical procedures varies by the direction of surgical movement, the type of fixation, and the surgical technique employed, largely in that order of importance. The most stable orthognathic procedure is superior repositioning of the maxilla, closely followed by mandibular advancement in patients in whom anterior facial height is maintained or increased. (If facial height is decreased by upward rotation of the chin, stability is compromised). The combination of moving the maxilla upward and the mandible forward is significantly more stable when rigid internal fixation is used in the mandible. Forward movement of the maxilla is reasonably stable, with or without rigid internal fixation, but mandibular setback often is not stable, and downward movement of the maxilla that creates downward rotation of the mandible is unstable. For mandibular setback, the inclination of the ramus at surgery appears to be an important influence on stability. It has been suggested that both interpositional synthetic hydroxyapatite grafting and simultaneous ramus osteotomy improve the stability of downward movement of the maxilla, but this has not been well documented. In two-jaw Class III surgery, the stability of each jaw appears to be quite similar to that of isolated maxillary advancement or mandibular setback. The least stable orthognathic procedure is transverse expansion of the maxilla. Although surgically assisted rapid palatal expansion has been suggested as a more stable alternative to segmental Le Fort I osteotomy, the patterns of movement resulting from the two procedures are different, and differences in stability have not been established. 相似文献
998.
GE Cartier D Yoshikami WR Gray S Luo BM Olivera JM McIntosh 《Canadian Metallurgical Quarterly》1996,271(13):7522-7528
We have isolated a 16-amino acid peptide from the venom of the marine snail Conus magus which potently blocks nicotinic acetylcholine receptors (nAChRs) composed of alpha3beta2 subunits. This peptide, named alpha-conotoxin MII, was identified by electrophysiologically screening venom fractions against cloned nicotinic receptors expressed in Xenopus oocytes. The peptide's structure, which has been confirmed by mass spectrometry and total chemical synthesis, differs significantly from those of all previously isolated alpha-conotoxins. Disulfide bridging, however, is conserved. The toxin blocks the response to acetylcholine in oocytes expressing alpha3beta2 nAChRs with an IC50 of 0.5 nM and is 2-4 orders of magnitude less potent on other nAChR subunit combinations. We have recently reported the isolation and characterization of alpha-conotoxin ImI, which selectively targets homomeric alpha7 neuronal nAChRs. Yet other alpha-conotoxins selectively block the muscle subtype of nAChR. Thus, it is increasingly apparent that alpha-conotoxins represent a significant resource for ligands with which to probe structure-function relationships of various nAChR subtypes. 相似文献
999.
BJ Simpson AD Ramage MJ Hulme DJ Burns D Katsaros SP Langdon WR Miller 《Canadian Metallurgical Quarterly》1996,2(1):201-206
The regulatory subunits of protein kinase A, or cyclic AMP-binding proteins, were measured in a series of 107 human ovarian tumors (89 malignant, 7 borderline, and 11 benign tumors) and related to tumor clinicopathological features and patient survival. Total cyclic AMP-binding protein levels were not significantly different between malignant tumors and either borderline or benign tumors. However, serous tumors showed significantly higher levels of total cyclic AMP-binding proteins than other malignant tumors (P = 0.007). Poorly differentiated tumors also possessed significantly higher levels of binding proteins as compared with well/moderately differentiated tumors (P < 0.01). Retrospective analysis of follow-up data also revealed a significant trend for patients with high tumor cyclic AMP-binding proteins to have poorer survival (P = 0.03). Individual binding proteins were identified by photoaffinity labeling, and the RI (Mr 48,000) protein was expressed as a percentage of total cyclic AMP-binding proteins detected. The percentage of the RI protein was not significantly different among malignant, borderline, or benign pathologies and was not associated with tumor stage, differentiation, or debulk status. The percentage of RI was significantly increased in serous tumors compared to other common epithelial malignancies (P = 0.01). In malignant tumors there was a significant positive correlation between the percentage of the RI protein and total cyclic AMP-binding proteins (P = 0.01). These data indicate that high tumor levels of cyclic AMP-binding proteins are associated with serous histology, poor differentiation, and poor patient survival. 相似文献
1000.