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81.
A linear programming problem subject to uncertainty in the requirements vector is solved deterministically, then sensitivity analysis is performed to determine the effect of the random variation on this solution. Since there could be an appreciable cost of modifying a solution once implemented, the probability of the random components perturbing a solution is considered. Unlike existing methods of linear programming under uncertainty, this article assumes no knowledge of the distributions of the random variables. Rather, the notion of non-parametric tolerance limits is employed to establish a criterion for changing basic solutions. 相似文献
82.
When the thickness of a film is of the order of the de Broglie wavelength of the electron, size effects appear in the electrical properties of the material. In this paper we derive the current in the presence of a magnetic field perpendicular to the plane of the film. We use the quantum mechanical density-matrix formalism. Unlike previous works we obtain an exact expression for the current. It is found that the current has a non-linear behavior with the electric field. The current also oscillates with the thickness of the film. 相似文献
83.
Lee R Beatty ME Bogard AK Esko MP Angulo FJ Selman C;EHS-NET Working Group 《Journal of food protection》2004,67(7):1444-1450
Salmonella enterica serotype Enteritidis (SE) is a common cause of foodborne illness in the United States. Foods prepared with raw shell eggs have often been associated with SE outbreaks. The federal government published the Egg Safety Action Plan in December 1999 that called for reduction of egg-preparation practices that may contribute to the survival and proliferation of SE. In seven states, an interview and brief site evaluation of 153 restaurants that prepare eggs during all hours of operation was conducted by the Environmental Health Specialists Network to determine the prevalence of such practices. Fifty-four percent (83 of 153) of restaurants pooled raw shell eggs not intended for immediate service. These pooled eggs were held a median of 4 h for scrambled eggs, 5.5 h for omelets, and 6 h for pancakes and French toast. Nearly 26% (39 of 152) of restaurants reported storing eggs at room temperature, and 5% (7 of 152) stored eggs on ice or in cold-water baths before cooking. Generally, eggs were cooked to 72 to 83 degrees C, which is above the recommended final cook temperature of 63 to 68 degrees C. Employees reported sanitizing utensils used to prepare eggs less than once every 4 h in 42% (57 of 136) of restaurants. Several areas were identified in which further emphasis might reduce egg-associated SE infections in accordance with Healthy People 2010 goals. 相似文献
84.
Buch JS Kimball C Rosenberger F Highsmith WE DeVoe DL Lee CS 《Analytical chemistry》2004,76(4):874-881
A miniaturized system for DNA mutation analysis, utilizing temperature gradient gel electrophoresis (TGGE) in a polycarbonate (PC) microfluidic device, is reported. TGGE reveals the presence of sequence heterogeneity in a given heteroduplex sample by introducing a thermal denaturing gradient that results in differences between the average electrophoretic mobilities of DNA sequence variants. Bulk heater assemblies are designed and employed to externally generate temperature gradients in spatial and temporal formats along the separation channels. TGGE analyses of model mutant DNA fragments, each containing a single base substitution, are achieved using both single- and 10-channel parallel measurements in a microfluidic platform. Additionally, a comprehensive polymer microfluidic device containing an integrated microheater and sensor array is developed and demonstrated for performing spatial TGGE for DNA mutation analysis. The device consists of two PC modular substrates mechanically bonded together. One substrate is embossed with microchannels, and the other contains a tapered microheater, lithographically patterned along with an array of temperature sensors. Compared with the external heating approaches, the integrated platform provides significant reduction in power requirement and thermal response time while establishing more accurate and highly effective control of the temperature gradient for achieving improved separation resolution. 相似文献
85.
Barnes RA Eplee RE Patt FS Kieffer HH Stone TC Meister G Butler JJ McClain CR 《Applied optics》2004,43(31):5838-5854
The Sea-Viewing Wide-Field-of-View Sensor (SeaWiFS) has made monthly observations of the Moon since 1997. Using 66 monthly measurements, the SeaWiFS calibration team has developed a correction for the instrument's on-orbit response changes. Concurrently, a lunar irradiance model has been developed by the U.S. Geological Survey (USGS) from extensive Earth-based observations of the Moon. The lunar irradiances measured by SeaWiFS are compared with the USGS model. The comparison shows essentially identical response histories for SeaWiFS, with differences from the model of less than 0.05% per thousand days in the long-term trends. From the SeaWiFS experience we have learned that it is important to view the entire lunar image at a constant phase angle from measurement to measurement and to understand, as best as possible, the size of each lunar image. However, a constant phase angle is not required for using the USGS model. With a long-term satellite lunar data set it is possible to determine instrument changes at a quality level approximating that from the USGS lunar model. However, early in a mission, when the dependence on factors such as phase and libration cannot be adequately determined from satellite measurements alone, the USGS model is critical to an understanding of trends in instruments that use the Moon for calibration. This is the case for SeaWiFS. 相似文献
86.
Pettinati Helen M.; Evans Frederick J.; Orne Emily C.; Orne Martin T. 《Canadian Metallurgical Quarterly》1981,90(4):345
Evaluated memory for successful and unsuccessful responses to hypnotic suggestions in partially amnesic Ss and in those Ss with normal forgetting. Two analyses (278 undergraduates) demonstrated that highly hypnotizable Ss experiencing partial posthypnotic amnesia tended to show no selective recall for their successes or failures during amnesia, whereas the remainder of the Ss showed definite selective recall of hypnotic success posthypnotically. These findings support F. J. Evans and J. F. Kihlstrom's (see record 1974-06307-001) hypothesis that posthypnotic amnesia involves a disruption of memory organization and suggest that the phenomenon may be mediated by a restriction in the use of normally employed retrieval cues. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
Examined the effect on the 2-yr driving record of drinking drivers referred by the courts to 6 programs for individual treatment. 2,723 drivers treated were classified as light or heavy drinkers, and compared with a no-treatment group similarly classified (n?=?2,127). Outcome criteria were (1) alcohol-related violations, (2) total moving violations, (3) alcohol-related accidents, and (4) total number of accidents. For light drinkers, 5 of the 6 countermeasures were significantly successful on at least 2 of the outcome measures, whereas 1 of them produced a significant decrease on all 4 criteria. Heavy drinkers apparently did not respond to treatment or had significantly worse records than those not treated. It is concluded that a variety of programs successfully treat the light drinker, but many existing programs result in worse records for the heavy drinker. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
88.
Neuman JA Ryerson TB Huey LG Jakoubek R Nowak JB Simons C Fehsenfeld FC 《Environmental science & technology》2003,37(13):2975-2981
An ultraviolet (UV) optical absorption system has been developed for absolute calibrations of nitric acid (HNO3) and ammonia (NH3) permeation tube emission rates. Using this technique, dilute mixtures containing NH3 or HNO3, both of which interact strongly with many surfaces, are accurately measured at levels below a part per million by volume. This compact and portable instrument operates continuously and autonomously to rapidly (<1 h) quantify the emission of trace gases from permeation devices that are commonly used to calibrate air-monitoring instruments. The output from several HNO3 and NH3 permeation tubes, with emission rates that ranged between 13 and 150 ng/min, was examined as a function of temperature, pressure, and carrier gas flow. Absorptions of 0.015% can be detected which allows a precision (3sigma) of +/-1 ng/min for the HNO3 and NH3 permeation tubes studied here. The accuracy of the measurements, which relies on published UV absorption cross sections, is estimated to be +/-10%. Measurements of permeation tube emission rates using ion chromatography analysis are made to further assess measurement accuracy. The output from the HNO3 and NH3 permeation tubes examined here was stable over the study period, which ranged between 3 months and 1 year for each permeation tube. 相似文献
89.
Pharmacological analysis of the contractile role of M2 and M3 muscarinic receptors in smooth muscle 总被引:3,自引:0,他引:3
Ehlert FJ 《Receptors & channels》2003,9(4):261-277
Muscarinic receptors expressed on smooth muscle cells are primarily of the M(2) and M(3) subtypes. The M(3) subtype triggers contraction through an interaction with G(q) proteins to stimulate phosphoinositide hydrolysis and mobilize Ca(2+). In contrast, activation of M(2) receptors modulates contraction by preventing relaxation or by potentiating M(3) receptor-mediated contractions, which enhances heterologous desensitization. These effects can be explained by the coupling of M(2) receptors to G(i) proteins that mediate an inhibition of adenylyl cyclase and calcium-activated potassium channels. The pharmacological antagonism of a response mediated through an interaction between M(2) and M(3) receptors has been shown to resemble the profile of the directly acting receptor (M(3)), primarily, and not that of the conditional receptor (M(2)). Evidence for a contractile role of the M(2) receptor has been obtained by inactivating its signaling pathway with pertussis toxin or by measuring contractile effects of muscarinic agonists after M(3) receptors have been covalently inactivated. Under these conditions, M(2) receptors have been shown to mediate an inhibition of the relaxant effects of agents, like isoproterenol, on the contractile effects of nonmuscarinic spasmogens. Muscarinic M(2) and M(3) receptor knockout mice are useful tools for exploring interactions between these receptors in smooth muscle. 相似文献
90.
An automated method for producing multivariate optical element (MOE) interference filters that are robust to errors in the reactive magnetron sputtering process is described. Reactive magnetron sputtering produces films of excellent thickness and uniformity. However, small changes in the thickness of individual layers can have severe adverse effects on the predictive ability of the MOE. Adaptive reoptimization of the filter design during the deposition process can maintain the predictive ability of the final filter by changing the thickness of the undeposited layers to compensate for the errors in deposition. The merit function used, the standard error of calibration, is fundamentally different from the standard spectrum matching. This new merit function allows large changes in the transmission spectrum of the filter to maintain performance. 相似文献