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Identification of a specific biomolecular target appropriately sensitive to a wide array of anesthetics has been elusive. At concentrations close to their respective ED50's for anesthesia in man or other species, 18 compounds, differing in potencies up to 66,000 fold, inhibited cytochrome P450 mediated metabolism of aminopyrine, a synthetic substrate, and arachidonic acid (AA), an endogenous substrate, in isolated liver microsomes. There was a highly significant correlation for both substrates between the absolute concentrations required for anesthesia (EC50) and for inhibition of P450 activity (Ki or IC50). The mean Ki/EC50 ratio was 0.97 for inhibition of aminopyrine demethylase. The mean IC50/EC50 ratios were 0.42 and 0.64 for inhibition of two AA-derived products and 2.8 for a third; a mean ratio of 1.4 for inhibition of overall AA metabolism suggests interaction of general anesthetics with a composite of P450 isozymes. The universal cytochrome P450 monooxygenases, in conjunction with other lipid oxygenases (cyclooxygenases and lipoxygenases) participate in the second messenger AA cascade. In nerve cells the sensitivity of these enzymes to hydrophobic neurodepressant drugs may underlie the state of general anesthesia: reversible disruption of intracellular and intercellular signalling without impairment of enzymes vital to cell respiration.  相似文献   
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Leo Egghe 《Scientometrics》2005,63(2):277-296
Summary We study new and existing data sets which show that growth rates of sources usually are different from growth rates of items. Examples: references in publications grow with a rate that is different (usually higher) from the growth rate of the publications themselves; article growth rates are different from journal growth rates and so on. In this paper we interpret this phenomenon of “disproportionate growth' in terms of Naranan's growth model and in terms of the self-similar fractal dimension of such an information system, which follows from Naranan's growth model. The main part of the paper is devoted to explain disproportionate growth. We show that the “simple' 2-dimensional informetrics models of source-item relations are not able to explain this but we also show that linear 3-dimensional informetrics (i.e. adding a new source set) is capable to model disproportionate growth. Formulae of such different growth rates are presented using Lotkaian informetrics and new and existing data sets are presented and interpreted in terms of the used linear 3-dimensional model.  相似文献   
126.
In connection with the specific features of high velocity aerated flow generated by hydraulic engineering structures, the mathematical model is developed for high turbulence air-water two-phase flow with the use of twin flow theoretical model in this paper. Furthermore the numerical method is proposed to treat bubbled flows. In addition, on the basis of air-water stratified twin flow model, the new calculation methods and free surface tracking technique are proposed to describe complicated movements of the free surface. Finally, the proposed model is used to calculate artificial aerated flows. The computed results coincide quite well with experimental results. This means that the proposed method can provide solid basis for practical engineering design.  相似文献   
127.
Although the dams produce remarkable social and economic benefits, the threat made by unsafe dams to the life and property of people who live in the lower river area is un-negligible. Based on the monitoring data which reflect the safety condition of dams, the risk degree concept is proposed and the analysis system and model for evaluating risk degree (rate) are established in this paper by combining the reliability theory and field monitoring data. The analysis method for risk degree is presented based on Bayesian approach. A five-grade risk degree system for dam operation risk and corresponding risk degree is put forward according to the safety condition of dams. The operation risks of four cascade dams on some river are analyzed by the model and approach presented here and the result is adopted by the owner.  相似文献   
128.
DC resistivity, dielectric constant, dielectric loss and positron annihilation spectra of (Ba1−x Ho x )TiO3 ceramics have been measured as a function of holmium concentration x. It has been found that the DC resistivity of (Ba1−x Ho x )TiO3 is strongly dependent on the Ho content: it decreases three orders of magnitude and reaches a minimum at x = 0.4%. Doping with 0.6% holmium increases the permittivity of BaTiO3 by approximately three times (from ∼1,300 to ∼4,000), with only a slight increase in the corresponding dielectric loss. The local electron density and defect concentration estimated using positron annihilation technique conforms well to the features found in the dielectric and resistivity measurements. The results have been discussed in terms of a mixed compensation model.  相似文献   
129.
Document caching and connection caching are extensively studied problems. In document caching, one has to maintain caches containing documents accessible in a network. In connection caching, one has to maintain a set of open network connections that handle data transfer. Previous work investigated these two problems separately while in practice the problems occur together: In order to load a document, one has to establish a connection between network nodes if the required connection is not already open. In this paper we present the first study that integrates document and connection caching. We first consider a very basic model in which all documents have the same size and the cost of loading a document or establishing a connection is equal to 1. We present deterministic and randomized online algorithms that achieve nearly optimal competitive ratios unless the size of the connection cache is extremely small. We then consider general settings where documents have varying sizes. We investigate a FAULT model in which the loading cost of a document is 1 as well as a BIT model in which the loading cost is equal to the size of the document.  相似文献   
130.
Non-redundant data clustering   总被引:6,自引:6,他引:0  
Data clustering is a popular approach for automatically finding classes, concepts, or groups of patterns. In practice, this discovery process should avoid redundancies with existing knowledge about class structures or groupings, and reveal novel, previously unknown aspects of the data. In order to deal with this problem, we present an extension of the information bottleneck framework, called coordinated conditional information bottleneck, which takes negative relevance information into account by maximizing a conditional mutual information score subject to constraints. Algorithmically, one can apply an alternating optimization scheme that can be used in conjunction with different types of numeric and non-numeric attributes. We discuss extensions of the technique to the tasks of semi-supervised classification and enumeration of successive non-redundant clusterings. We present experimental results for applications in text mining and computer vision.  相似文献   
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