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101.
Resistance of acetylated wood to biological degradation 总被引:1,自引:1,他引:0
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Almost all analyses of large structures neglect local effects due to the application of loads and due to the transfer of loads between structural elements. In recent years, however, the use in aircraft structures of highly anisotropic materials, such as graphite/epoxy, has motivated more detailed studies of the applicability of Saint-Venant's principle.
In this paper in graphite/epoxy is analysed using the finite element method (FEM). The influence of anisotropy and transition from a thicker to a thinner laminate cross-section (ply-drop) is investigated. The characteristic decay length which is large for highly anisotropic materials is lessened by a change in thickness. 相似文献
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J H?glund BL Ljungstr?m O Nilsson H Lundquist E Osterman A Uggla 《Canadian Metallurgical Quarterly》1997,38(2):157-165
The biological accuracy of a nonlinear compartmental model describing the in vivo kinetics of L-3,4-dihydroxy-6-[18F]fluorophenylalanine ([18F]FDOPA) metabolism was investigated. Tissue activities for [18F]FDOPA and its labeled metabolites 3-O-methyl-[18F]FDOPA ([18F]OMFD), 6-[18F]fluorodopamine ([18F]FDA), L-3,4-dihydroxy-6-[18F]fluorophenylacetic acid ([18F]FDOPAC), and 6-[18F]fluorohomovanillic acid ([18F]FHVA) were calculated using a plasma [18F]FDOPA input function, and kinetic constants estimated previously by chromatographic fractionation of 18F-labeled compounds in plasma and brain extracts from rat. Present data accurately reflected the measured radiochemical composition in rat brain for tracer circulation times past 10 min. We formulated the hypothesis that the discrepancy between calculated and measured fractions of [18F]FDOPA and the deaminated metabolite [18F]FDOPAC at times earlier than 10 min reflected storage of [18F]FDA in vesicles without monoamine oxidase. This hypothesis explained the initially rapid appearance of [18F]FDOPAC in striatum by delayed transfer of [18F]FDA from cytosol into vesicles. We conclude that the simpler model of [18F]FDOPA compartmentation is accurate when the cytosolic and vesicular fractions of [18F]FDA are at steady-state; the approach to equilibrium has a time constant of 15-30 min. The present model is valid for positron emission tomography studies of [18F]FDOPA metabolism in living brain. 相似文献
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BACKGROUND: Solitary rectal ulcer syndrome (SRUS) is often resistant to medical and surgical treatment. AIM: To determine whether biofeedback retraining is a useful treatment for this condition. PATIENTS: Thirteen consecutive patients with SRUS (three men, median age 34 years, median duration of symptoms three years) underwent treatment. Previous surgical treatment had failed in five. METHODS: Patients were evaluated prospectively. Anorectal physiological studies were performed in 11 patients before treatment. A standardised questionnaire was used before and after treatment, and all but two patients were examined after treatment. RESULTS: Median follow up was nine months (range 3-22 months). After treatment four patients were asymptomatic, and four felt improved. Symptom improvement or elimination occurred in: need to strain (7/13 patients), digitation (7/11), laxative use (5/9). Time in the toilet (median 30 v 10 minutes, before v after treatment) and number of visits to toilet (6 v 3/day) were also improved. Three patients were able to maintain employment before treatment compared with eight after treatment. The solitary ulcer did not heal completely in any of the nine patients examined after treatment, but improved in four. Previous surgery, the macroscopic appearance of the ulcer, the presence of pelvic floor paradox, and other physiological parameters did not predict outcome. CONCLUSION: Biofeedback retraining is a useful treatment for this condition. Long term studies are now required. 相似文献
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A well functioning societal response to crises is benefited by individuals having adequate skills and knowledge. From a municipal perspective this requires the creation of a learning organization. The objective of this study is to determine whether individual municipal employees, who have the responsibility for preparedness planning, reason and act in ways that promote learning about crises and preparedness issues throughout the municipal organization. Analysis of interviews with preparedness planners in six Swedish municipalities on their strategies for preparedness planning, reveal that preparedness planning too often becomes a demarcated activity, restricted to not more than a handful of individuals. This study indicates that one reason for why the preparedness work becomes demarcated is that individuals central to the preparedness planning are not taking on roles for acting in ways that are required in order for a learning organization to be established. 相似文献