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61.
PL Smith 《Canadian Metallurgical Quarterly》1996,11(3):196-199
The acquired immune deficiency syndrome (AIDS) is a lethal multisystem disease. Its ocular manifestations have received relatively little attention in the literature. Between 73% and 100% of AIDS patients develop ocular lesions. The commonest lesions seen are retinal--either infectious or noninfectious retinopathy. Involvement of the conjunctiva with Kaposi's sarcoma, infected tears and infected cornea as well as the vitreous are less common. Infections with cytomegalovirus and varicella zoster virus are common causes of visual loss and can be treated with antiviral agents such as ganciclovir and foscarnet. This greatly increases the quality of life in these patients by preventing visual loss. 相似文献
62.
To investigate the pathogenicity of Aspergillus fumigatus mutants lacking putative virulence factors, we have developed a new murine model of invasive pulmonary aspergillosis based on neutropenia, the major factor predisposing patients to this infection. Mice were treated with cyclophosphamide and inoculated by the intranasal route with 5 x 10(3) conidia, a significant reduction from inoculum levels used in previous models. Evidence for the production of the extracellular alkaline protease (Alp) in lung tissue was obtained by using a fungal transformant harboring an alp::lacZ reporter gene fusion. The pathogenicities of single mutant strains lacking either Alp or the ribotoxin restrictocin and of a double mutant strain lacking both proteins were assessed in this infection model. There were no significant differences between the mutant and the wild-type strains in terms of mortality or histological-features. Inoculations with mixtures of conidia showed that the double mutant strain is slightly less virulent than the wild-type strain. We conclude that Alp and restrictocin are not important virulence determinants in pulmonary infection. 相似文献
63.
We present the results of an evaluation of the performance characteristics of a composite multivariate quality control (CMQC) system that incorporates quality control rules for univariate, multivariate, and correlation conditions. The CMQC system evaluated is designed to help analysts detect unacceptable trends and systematic error in one or more variables, unacceptable random error in one or more variables, and unacceptable changes in the correlation structure of any pair of variables. It is also designed to be tolerant of missing data, to allow analysts to reject as few as one or as many as all variables in a run, and to provide analysts with control statistics and graphics that logically relate to sources of analytical error. We show that the various components of the CMQC system have adequate statistical power to detect systematic errors, random errors, and correlation changes under the conditions likely to be encountered with multivariate analytical measurement systems: (1) a single variable with increased systematic or random error; (2) all variables or a subgroup of variables affected by a common problem that increases systematic or random error; and (3) missing data for one or more variables in a run. We also show that the power of the multivariate component of the CMQC system to detect systematic and random errors is higher than the power of an alternative multivariate test criterion. 相似文献
64.
An improved accelerated cable life test is described. Through the use of programmable logic controllers (PLCs), very precise and consistent control of the accelerated aging process has been achieved. A computer has been utilized to make continuous real-time acquisition and storage of key operating parameters possible. This precise control and monitoring methodology has permitted the study of the synergistic effects of voltage and temperature on the accelerated aging of full-sized cables in the laboratory 相似文献
65.
J. C. W. Davenport D. J. Smith 《Fatigue & Fracture of Engineering Materials & Structures》1993,16(10):1125-1133
A test apparatus has been developed to study the fracture behaviour of engineering materials subjected to superimposed tensile and shear (Mode I and II) loads using a single edge notch specimen. Stress intensity factors were calculated using finite element analysis. Test results for PMMA are reported. Results from circumferentially notched round bar specimens, subjected to combined tension and torsion (Mode I and III) loading are also reported. The Mode I/II results are consistent with the mixed mode fracture response of a wide range of brittle materials, although there is some evidence of non-linear behaviour. The fracture behaviour for superimposed Modes I and III indicates the strong influence of non-linear deformation which causes the mixed mode toughness to be dependent on the sequence and type of loading. 相似文献
66.
67.
Summary An initiator for living free radical polymerization may be prepared by trapping the benzylic ethylbenzene radical with the stable 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) radical. The adduct, 2,2,6,6-tetramethyl-1-(1-phenethyloxy)piperidine (TMPEP), smoothly undergoes thermal fragmentation at temperatures approaching 140° C to afford an active carbon radical capable of initiating polymerization and a passive mediating nitroxyl radical to reversibly cap and preserve the propagating polymer chain. 相似文献
68.
Mulcahy Nicholas J.; Call Josep; Dunbar Robin I. M. 《Canadian Metallurgical Quarterly》2005,119(1):23
Two important elements in problem solving are the abilities to encode relevant task features and to combine multiple actions to achieve the goal. The authors investigated these 2 elements in a task in which gorillas (Gorilla gorilla) and orangutans (Pongo pygmaeus) had to use a tool to retrieve an out-of-reach reward. Subjects were able to select tools of an appropriate length to reach the reward even when the position of the reward and tools were not simultaneously visible. When presented with tools that were too short to retrieve the reward, subjects were more likely to refuse to use them than when tools were the appropriate length. Subjects were proficient at using tools in sequence to retrieve the reward. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
69.
70.
The effect of the degree of crosslinking of glassy polymers on the transport mechanism of penetrants was investigated using a series of divinyl benzene (DVB)-crosslinked polystyrenes of nominal crosslinking ratio X from 0.001 38 to 0.060 mol DVB/mol styrene. The number average molecular weight between crosslinks, , was determined from equilibrium swelling experiments in cyclohexane. Dynamic swelling experiments with cyclohexane at 30°C showed that the mechanism of penetrant transport was anomalous. An overshoot in the penetrant uptake was observed, characteristic of macromolecular relaxations and of changing solubility of the cyclohexane in the continuously swelling polystyrene. Photographs of various samples during the swelling process showed that solvent crazing occurred predominantly in loosely crosslinked samples. 相似文献