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排序方式: 共有90条查询结果,搜索用时 15 毫秒
1.
In this study, we describe the tracheal-relaxant and tocolytic activities of the methanol (ME) and aqueous (AQ) crude extracts of ginger (rhizome of Zingiber officinale) in an attempt to rationalize its traditional use in disorders of airways and uterine hyperactivity. Both of the ginger extracts dose-dependently relaxed K+ (80 mM) and carbachol (CCh, 1 μM)-induced contractions with more potency against K+, similar to that elicited by verapamil, a Ca2+ channel blocker. In isolated uterine preparations, the extracts suppressed the K+-induced contractions with respective EC50 values of 0.03 mg/ml (0.02–0.05, 95% CI) and 0.05 mg/ml (0.04–0.06). Activity-directed fractionation of AQ yielded an organic and an aqueous fraction with the activities concentrated in the former. Both the crude extracts were found safe in mice up to the oral dose of 5 g/kg when tested for acute toxicity for 24 h. The study shows that ginger possesses tracheal and uterine smooth muscle relaxant activity, possibility mediated via Ca2+ channel blockade, justifying its use in disorders such as asthma, cough as well as in dysmenorrhoea and uterine and menstrual spasms and congestion.  相似文献   
2.
Neural Computing and Applications - In order to provide benchmark performance for Urdu text document classification, the contribution of this paper is manifold. First, it provides a publicly...  相似文献   
3.
The quantity of information placed on the web has been greater than before and is increasing rapidly day by day. Searching through the huge amount of data and finding the most relevant and useful result set involves searching, ranking, and presenting the results. Most of the users probe into the top few results and neglect the rest. In order to increase user’s satisfaction, the presented result set should not only be relevant to the search topic, but should also present a variety of perspectives, that is, the results should be different from one another. The effectiveness of web search and the satisfaction of users can be enhanced through providing various results of a search query in a certain order of relevance and concern. The technique used to avoid presenting similar, though relevant, results to the user is known as a diversification of search results. This article presents a survey of the approaches used for search result diversification. To this end, this article not only provides a technical survey of existing diversification techniques, but also presents a taxonomy of diversification algorithms with respect to the types of search queries.  相似文献   
4.
Te-doped ZnO nanostructures were synthesized by an annealing (vapor–solid) process under ambient conditions, and characterized in terms of their morphological, structural, compositional and optical properties. The structural and morphological characterizations revealed that the synthesized nanostructures were well-defined multipods, needles and spherical particles, and possessed well-crystalline ZnO wurtzite hexagonal phase. Also, in the X-ray diffraction studies, the presence of a shift in the peak positions towards a lower angle, and a decrease in the intensity, with an increase in the Te concentration, as compared to the undoped ZnO, were observed. The chemical composition confirmed the presence of Te, in the case of multipod and needle morphologies. The effect of doping on the crystalline quality and optical properties was also investigated, by using photoluminescence (PL) and Raman spectrometers. The Raman results demonstrated that the doped ZnO nanostructures had a lower crystalline quality than the undoped ZnO. Moreover, the PL results showed a decrease in the band gap for the doped ZnO nanostructures, in comparison to the undoped ZnO. A possible growth mechanism was also proposed.  相似文献   
5.
This paper presents a technical approach for electronic multilateral trade of electricity in competitive power industries. The trade involves strategic sharing of data among agents in an attempt to provide the opportunity to intelligently discover competitive behavior of peer suppliers. A trading logic is implemented as a specialized software module within the agent. The logic mimics intelligence of the human strategic trade. A time-bounded trade protocol has been introduced as a trading basis among rivalry trade agents in the market. The protocol limits the trade rounds in order to bind the trading process to specific deadlines. The protocol is coded as part of the automated trade server. The results of a generic 3-bus test system show that the electronic multilateral trade logic presented in this paper better distributes market sales, lowers prices and consequently provides higher social welfare compared to the standard Cournot economic model that may be used by the human decision-maker for market trading. Based on a set of test cases with different load profiles, it is noted that the electronic multilateral trade drives the market price closer to the marginal cost of generation supply and far away from the estimated Cournot price.  相似文献   
6.
Riza NA  Arain MA 《Applied optics》2003,42(13):2341-2345
A highly accurate method of optical path-length measurement is introduced by use of a scanning heterodyne optical interferometer with no moving parts. The instrument has demonstrated the potential to measure optical path length at angstrom resolution over continuous thickness in the micrometer range. This optical path length can be used to calculate the thickness of any material if the refractive index is known or to measure the refractive index of the material if the thickness is known. The instrument uses a single acousto-optic device in an in-line ultra-stable reflective geometry to implement rapid scanning in the microsecond domain for thickness measurements of the test medium.  相似文献   
7.
A dynamic model for simulation of the transient interaction between radially oriented permanent magnet-type synchronous machines and their corresponding transistorized current source power conditioners is presented. Some key machine parameters used in this dynamic model were obtained from finite element field solutions. This dynamic model was used to obtain the transient interaction between a 15-hp samarium cobalt radially oriented permanent magnet electronically operated synchronous machine and its corresponding power conditioner. This machine was constructed for electric vehicle propulsion. Excellent correlation between various digitally simulated and actual test current and voltage waveforms, in various branches of the machine-conditioner network, has been achieved. These results are given. This modeling approach is applied to machines during the design stage, where the finite element modeling is the only way to obtain the necessary machine parameters for dynamic simulation. It is shown how such a combination of the computer-aided design tools can help in prevention of design mis-judgements that can prove costly to remedy once the hardware is in place. This is done through an actual design example of an additional machine being manufactured for electric propulsion applications.  相似文献   
8.
This study presents new experimental results on the direct conversion of crude oil to chemicals via steam-enhanced catalytic cracking. We have organized the experimental results with a kinetics model using crude oil and steam co-feed in a fixed-bed flow reactor at reaction temperatures of 625, 650, and 675°C over the Ce-Fe/ZSM-5 catalyst. The model let us find optimum conditions for crude oil conversion, and the order of the steam cracking reaction was 2.0 for heavy oil fractions and 1.0 for light oil fractions. The estimated activation energies for the steam cracking reactions ranged between 20 and 200 kJ/mol. Interestingly, the results from kinetic modelling helped in identifying a maximum yield of light olefins at an optimized residence time in the reactor at each temperature level. An equal propylene and ethylene yield was observed between 650 and 670°C, indicating a transition from dominating catalytic cracking at a lower temperature to a dominating thermal cracking at a higher temperature. The results illustrate that steam-enhanced catalytic cracking can be utilized to effectively convert crude oil into basic chemicals (52.1% C2-C4 light olefins and naphtha) at a moderate severity (650°C) as compared to the conventional high-temperature steam cracking process.  相似文献   
9.
The effect of interconnection and bypass diodes on the reliability of photovoltaic modules and arrays have been evaluated. Analysis of different cell or panel interconnections for the determination of the optimum item configuration and circuit design strategies to achieve reliable modules and arrays has been carried out. A computer program for finding the optimum configuration which produce maximum module and array reliability is presented. The roll of bypass diodes for module and array reliability improvements have been studied theoretically and experimentally. It is found that module and array reliability depends on the item's (cells or panels) probability of failure, arrangement of the items, and failure mode. Discussion and suggestions for optimum design are presented.  相似文献   
10.

Conductive polymeric blends (CPBs) of polystyrene and polyaniline (PS/PANI) were prepared by solution casting method in various compositions. Film thickness of CPBs was achieved?~?250 micron. PS/PANI blend films were analyzed for electromagnetic interference (EMI) shielding characteristics in microwave and near-infrared (NIR) regions. PS/PANI blends showed remarkable features. Most mobile telecommunications use GHz frequency range and shielding effectiveness was observed in 9 GHz to 18 GHz. In 9 GHz to 18 GHz frequency range, 45 dB shielding effectiveness was measured. CPBs were also analyzed in the NIR region and showed transmittance of <1%. Microwaves and NIR radiation are the most abundant in the environment and cause damage to human health. Both types of radiation causes serious damage to electronic devices as well.

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