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991.
R Caetano 《Canadian Metallurgical Quarterly》1996,6(5):458-462
This paper reviews past definitions of alcohol dependence as well as that presently adopted in the 4th edition of the Diagnostic and Statistical Manual of the American Psychiatric Association. The role of alcohol consumption in diagnostic criteria and the measurement of various dimensions of drinking (frequency, usual quantity per occasion, overall volume) are also discussed. Reliable criteria for identifying both alcohol abuse and dependence are available. Methodology for assessment of different dimensions of drinking behavior also exists. Epidemiologists examining the role of alcohol in health problems should consider the diagnostic category and the dimensions of drinking behavior that are important to their study. Measurements should be adopted in accordance with this assessment. 相似文献
992.
Awareness of fast transient events in the electrical power environment has increased with the release of related test standards (ANSI C37.90.1 and IEC 801-4) and with increased usage of solid state circuits in utility equipment. Reliable measurement of the fast transient test waveforms and repeatable performance of test setups are persistent problems for equipment manufacturers and users. The construction, characterization, and usage of two high voltage test dividers for measurement of fast transient test waveforms are described. Measurements on a C37.90.1 (SWC) test generator are presented along with tutorial background. Proposals for changes to the ANSI C37.90.1 specification are included 相似文献
993.
A variety of data from different devices has been generated on the smoothness of shield products, but no direct comparison of compound smoothness for the devices themselves has been made. The purpose of this study was to compare four different methods for evaluating the smoothness of power cable compounds. The methods compared include: image analysis, laser scanning, mechanical profilometry and photomicroscopy with visual rating. Extruded tape samples of conductor shields, filled insulations and strippable shields were evaluated 相似文献
994.
Results from applying the model on a sample of contractors, the majority of whom were international and operating in Egypt, reinforces the credibility of the developed methodology, claim the authors. 相似文献
995.
Raman spectroscopic studies on photoreactive retinal proteins are comprehensively described, including the basic physics of Raman scattering and illustrative examples of the types of information on the structure and function of the retinal chromophore and its environment which can be obtained from the vibrational Raman spectra. In addition, practical advice and recipes are given which should enable the reader to plan and eventually perform a Raman experiment in a photolabile retinal protein. A dominant role is played by the resonance Raman (RR) experiment with visible laser excitation which selectively probes the retinal chromophore. Much discussion is devoted to bacteriorhodopsin (bR) and its photocycle as a paradigm for a light-induced reaction of a retinal protein. Various time-resolved techniques are described to study the temporal evolution of the bR chromophore by probing RR spectra of intermediate states. Vibrational Raman spectra are interpreted in terms of structure and structural changes of the chromophore. RR spectroscopic studies on halorhodopsin, sensory rhodopsin, and visual pigments are reported, as well as on modified proteins in which retinal analogues are incorporated, and on site-specific mutants. Results of ultraviolet RR experiments which selectively probe the aromatic side chains in the protein backbone are reported. In addition, a promising new technique of near-infrared Raman excitation is discussed. Finally, application of coherent anti-Stokes Raman spectroscopy (CARS) to retinal proteins is reported. 相似文献
996.
The ElectroScan environmental scanning electron microscope (ESEM) enables wet samples to be observed by eliminating air but allowing water vapour into the sample chamber. However, evaporation from, and condensation on, the sample may occur during the pumpdown sequence used to reach this state, which means that the sample may not be in its natural state when viewed if due care is not taken. In this paper, the pumping system of the ESEM is described mathematically and expressions are derived for the evaporation and condensation. This treatment is then used to calculate the optimum pumpdown sequence. The importance of using the optimized procedure is illustrated by micrographs of fat emulsions. 相似文献
997.
对经固溶处理的二种Al-Li合金(1.94wt.%Li和2.75wt.%Li)的时效过程进行了研究。结果表明:δ’的生长速率遵从Ostward粗化动力学。1.94wt.%Li合金δ’产生于时效过程中,而2.75wt.%Li合金的δ’产生于时效的前期阶段。前者的表现体积分数明显大于根据相图估算的数伍,真实体积分数则与此值接近;后者的体积分数低于根据相图估算的数值,这可能归咎于δ’固相线的位置、统计学误差及Li更易在时效过程中贫化。 相似文献
998.
We propose a new principle for a low temperature semiconductor detector of charged particles with possibly submicron lateral resolution based on point contacts formed in the 2-dimensional electron gas (2DEG) of a GaAs-AlxGa1-xAs heterostructure using split-gates. The detector operates up to liquid nitrogen temperatures. Impinging particles excite locally extra donors in the doping layer of the heterostructure. By measuring simultaneous increase in the conductances of 3 point contacts due to the impacts of charged particles the position of penetration is calculated using the Thomas-Fermi approximation for screening in 2DEG. 相似文献
999.
EPA regulations force owners of PCB (polychlorinated biphenyl) equipment to carefully review regulatory compliance and develop PCB risk management programs. The EPA is currently planning new PCB regulations that may add additional PCB management requirements. The author briefly reviews the EPA regulations, highlighting the more commonly violated requirements. Several risk management techniques are presented and discussed. A method of quantifying PCB equipment owning cost is presented 相似文献
1000.