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排序方式: 共有253条查询结果,搜索用时 31 毫秒
1.
The available surgical and non-surgical therapy options for treatment of gallstone disease are presented. Conventional cholecystectomy is regarded as standard therapy of symptomatic cholecystolithiasis. Other modes of therapy may be indicated under certain circumstances, depending on the results of imaging procedures. In this context conventional X-ray examination, oral and intravenous cholecystography, sonography, computed tomography, endoscopic retrograde cholangiography/cholecystography, and magnetic resonance imaging are discussed and their influence on therapeutic decisions is explained. 相似文献
2.
3.
Galal Magdi 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》1996,11(4):381-382
The article reviews the challenges facing cities in the twenty-first century, with particular attention to the role that public transport can play in the healthy development of large cities. The paper addresses the most important applications of the “sustainability” concept to the choice of mass public transportation modes for urban areas. 相似文献
4.
Since the beginning of the twentieth century, different methods to control the quality of analyses have been in use. The advent of modern analytical instruments has prompted the need for such controls. In a modern clinical chemistry laboratory, quality control is an important tool to maintain the high predictive value of the methods in use. In this article the most important aspects of quality control are outlined. For further study, I recommend the references listed at the end of this article. 相似文献
5.
Rasha A. Abdulla 《Journal of Computer-Mediated Communication》2007,12(3):1063-1081
This study analyzed the contents of three of the most popular Arabic-language online message boards regarding the attacks of September 11, 2001 on the United States. Although terrorists claimed that the attacks were committed in the name of Islam, those who posted messages on all three forums rejected this claim. More than 43% of the messages condemned the attacks as a criminal act of terrorism that contradicts the core teachings of Islam. Some 30% saw some justification behind the attacks, even if they felt sorry for the victims and their families. However, those participants viewed the attacks as a political, rather than a religious, issue. 相似文献
6.
Abdulla A. Shaikh S. M. Javaid Zaidi 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1993,56(2):139-145
The absorption and reaction of oxygen in aqueous alkaline solutions of sodium dithionite has been experimentally investigated in a novel gas-liquid contactor. The novel gas-lift bubble column contactor was used to study the kinetics over wide ranges of reactant concentrations, temperature, and pH. The oxygen-sodium dithionite reaction was found to be first-order with respect to dithionite in the range of dithionite concentration < 0.1 M, and second-order in the range of dithionite concentration > 0.1 M. The reaction with respect to oxygen was found to be zero-order for all dithionite concentrations. These results and experimental investigations of the effect of solution alkalinity and temperature on the reaction rate are consistent with previous findings obtained in different gas-liquid contactors. The results thus confirm the feasibility of using the gas-lift bubble column for the kinetics of gas-liquid reactions. 相似文献
7.
A. Galal 《应用聚合物科学杂志》2006,102(3):2416-2425
Poly(3‐methlthiophene) films were prepared under “silent” and “sono‐electrochemical” potentiostatic (SEP) conditions. A three‐electrode one‐compartment sono‐cell was used with a working platinum disc electrode. The sono‐electrochemically formed polymer films were deposited with different working electrode‐to‐horn distances. The composition, electrochemical, spectroscopic, and morphological characteristics of the resulting polymer films were determined. Elemental analysis, FTIR‐spectra, and X‐ray photoelectron spectroscopy (XPS) data proved that the polymer films prepared under SEP conditions have predominant α‐α′‐couplings between the 3MT units, and the aromatic ring integrity is maintained in the film. Scanning electron microscopy showed that those films are more compact and less porous compared to the films prepared under silent conditions. The use of sono‐irradiation during electropolymerization enhanced the diffusion of the monomer units towards the electrode surface and resulted in relatively less doped polymers with less conductivity. Electrochemical impedance spectroscopy (EIS) data for films prepared under silent and SEP conditions were collected in a monomer‐free solution. The results show that the impedance of SEP films is relatively higher than those prepared under silent conditions, and a combination of charge transfer kinetics with diffusion‐controlled conduction mechanism within the films. The diffusion was found to be a function of the porosity of the film. Conductivity measurements are in good agreement with EIS, elemental analysis, and XPS data. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2416–2425, 2006 相似文献
8.
Effect of Initial Annealing Temperature on Microstructural Development and Microhardness in High‐Purity Copper Processed by High‐Pressure Torsion 下载免费PDF全文
Saleh N. Alhajeri Abdulla I. Almazrouee Khaled J. Al‐Fadhalah Terence G. Langdon 《Advanced Engineering Materials》2018,20(1)
The effect of the initial annealing temperature on the evolution of microstructure and microhardness in high purity OFHC Cu is investigated after processing by HPT. Disks of Cu are annealed for 1 h at two different annealing temperatures, 400 and 800 °C, and then processed by HPT at room temperature under a pressure of 6.0 GPa for 1/4, 1/2, 1, 5, and 10 turns. Samples are stored for 6 months after HPT processing to examine the self‐annealing effects. Electron backscattered diffraction (EBSD) measurements are recorded for each disk at three positions: center, mid‐radius, and near edge. Microhardness measurements are also recorded along the diameters of each disk. Both alloys show rapid hardening and then strain softening in the very early stages of straining due to self‐annealing with a clear delay in the onset of softening in the alloy initially annealed at 800 °C. This delay is due to the relatively larger initial grain size compared to the alloy initially annealed at 400 °C. The final microstructures consist of homogeneous fine grains having average sizes of ≈0.28 and ≈0.34 µm for the alloys initially annealed at 400 and 800 °C, respectively. A new model is proposed to describe the behavior of the hardness evolution by HPT in high purity OFHC Cu. 相似文献
9.
Jiahui Sun Wenjia Liu Yulong Li Azarmidokht Gholamipour-Shirazi Aynur Abdulla Xianting Ding 《Microfluidics and nanofluidics》2017,21(7):125
A low-cost, convenient and precise drug combination screening microfluidic platform is developed, in which cell culture chambers designed with micropillars integrate with three laminar flow diffusion channels. This platform has several distinct features, including minimum shear stress on cells, biocompatibility, optimum concentration distribution and automatic combinatorial gradient generation, which can potentially speed up the discovery of an effective drug combination for cancer ablations. The presented device can generate two-drug combination gradients at the optimum flow rate of 90 μL/h and can be applied to identify the optimal combination of two clinically relevant chemotherapy drugs. For demonstration, paclitaxel at 0.77 × 10?3 mg/mL and cisplatin at 0.23 × 10?4 mg/mL were studied against lung cancer cells (A549). This microfluidic device has the potential to provide a precise and robust screening for anticancer combinational drugs practiced in clinics. 相似文献
10.
This article proposes several two-timescale simulation-based actor-critic algorithms for solution of infinite horizon Markov
Decision Processes with finite state-space under the average cost criterion. Two of the algorithms are for the compact (non-discrete)
action setting while the rest are for finite-action spaces. On the slower timescale, all the algorithms perform a gradient
search over corresponding policy spaces using two different Simultaneous Perturbation Stochastic Approximation (SPSA) gradient
estimates. On the faster timescale, the differential cost function corresponding to a given stationary policy is updated and
an additional averaging is performed for enhanced performance. A proof of convergence to a locally optimal policy is presented.
Next, we discuss a memory efficient implementation that uses a feature-based representation of the state-space and performs
TD(0) learning along the faster timescale. The TD(0) algorithm does not follow an on-line sampling of states but is observed
to do well on our setting. Numerical experiments on a problem of rate based flow control are presented using the proposed
algorithms. We consider here the model of a single bottleneck node in the continuous time queueing framework. We show performance
comparisons of our algorithms with the two-timescale actor-critic algorithms of Konda and Borkar (1999) and Bhatnagar and Kumar (2004). Our algorithms exhibit more than an order of magnitude better performance over those of Konda and Borkar (1999).
相似文献
Shalabh Bhatnagar (Corresponding author)Email: |