Effects of a magnetic field on the free convective flow through a porous medium bounded by an infinite vertical porous plate with constant heat flux

This paper investigates the effects of a magnetic field on the free convective flow of a viscous, incompressible, dissipative fluid through a porous medium, occupying a semi-infinite region of the space bounded by an infinite vertical and porous plate. The plate is subjected to a normal suction velocity and the heat flux at the plate is constant. The magnetic field is of uniform strength and is applied perpendicular to the plate. An analytical solution to the problem is obtained. The influence of the magnetic parameter (M) and permeability parameter (K) is discussed for the case of air (P = 0.71) when the plate is subjected to a constant suction velocity and is being cooled by free convection currents.     

Effect of wall permittivity on electroviscous flow through a contraction

The electroviscous flow at low Reynolds number through a two-dimensional slit contraction with electric double-layer overlap is investigated numerically for cases where the permittivity of the wall material is significant in comparison with the permittivity of the liquid. The liquid-solid interface is assumed to have uniform surface-charge density. It is demonstrated that a finite wall permittivity has a marked effect on the distribution of ions in and around the contraction, with a significant build-up of counter-ions observed at the back-step. The development length of the flow increases substantially as the wall permittivity becomes significant, meaning that the electric double-layers require a longer distance to develop within the contraction. Consequently, there is a corresponding decrease in the hydrodynamic and electro-potential resistance caused by the contraction. The effect of wall-region width on the flow characteristics is also quantified, demonstrating that the development length increases with increasing wall-region width for widths up to 5 channel widths.     

End effects on the flow of heat,mass or electrical energy through a cylindrical rod

End effects on the flow of heat, mass or electrical energy through a cylindrical rod were investigated analytically. Three of the eight analytical solutions were evaluated on a $\text{360}\text{91}$ computer and compared with the results of a numerical analysis package dubbed “Heating III” to show that both compared favorably.Platinum and Hastelloy X rods were subjected to an electrical current applied via two electrodes, one covering one end and the application of the other being thesubject of this investigation. End effects based on voltage deviations of one part in a thousand or more were found to extend for a length to diameter ratio ranging from 0·6 to 1·9 depending upon whether the small electrode position being investigated was at the center of the end or on the periphery of the end. Calculated results from Heating III showed excellent agreement with the experimental results.In addition to their reported applications, the analytical solutions represent a contribution to a neglected area of applied mathematical physics and as such should prove equally useful in other areas that are dynamically analogous. Also the discontinuous infinite integral technique of solution has proven to be a very powerful one.     

Adiabatic flow of hydrogen gas through a rocket nozzle with and without composition change

A procedure is described for determining the characteristics of adiabatic flow through a rocket nozzle with and without composition change. The method of calculation is illustrated for the expansion of pure hydrogen gas from a chamber temperature of 306° K. and a pressure of 20.42 atm. to atmospheric pressure.The study indicates that the exhaust velocity and temperature are highest for flow where complete equilibrium is reached at each temperature with respect to the reaction

$\text{H}{}_2\text{?2H}$

Flow with composition change requires a nozzle exit to nozzle throat area ratio somewhat greater than that determined for adiabatic flow without composition change for the same ratio of chamber pressure to exit pressure.The residence time in a given temperature range is computed as a function of gas temperature for the two types of flow. The results of this calculation may be used to determine the minimum required reaction rates which allow composition changes during flow through the nozzle.     

流式细胞术分析五味子乙素促进阿霉素内化的实验研究

[目的]建立流式细胞术分析肿瘤细胞内阿霉素分布的方法,并研究低浓度五味子乙素对K562细胞内化阿霉素的影响。[方法]体外培养猪内皮细胞(pEC),以20μmol/L阿霉素处理2、4和6小时;或加入不同浓度阿霉素(0、10、20、40、80和100μmol/L)处理4小时。培养K562细胞,以5μmol/L阿霉素处理2、4和6小时;或加入不同浓度阿霉素(0、2.5、5、10和20μmol/L)处理4小时。采用不同浓度(0、25、50和100μmol/L)五味子乙素(Sch B)与阿霉素联合处理K562细胞4小时。收集细胞,采用流式细胞术分析阿霉素的特异荧光。[结果]固定浓度处理pEC(20μmol/L)和K562(5μmol/L)后检测,发现细胞内荧光强度随时间延长而增加,两种细胞4小时组荧光强度分别达到6小时组的96.93%和95.23%/。在直方图上,阴性和阳性细胞群界限分明。阿霉素(2.5、5和10μmol/L)单独处理细胞的荧光强度分别为26.78±3.34、64.70±6.24和118.35±9.67;添加25μmol/L Sch B实验后荧光强度增加到43.45±4.25、103.74±7.36和146.69±8.32,Sch B显著增加了K562细胞内阿霉素的分布(p<0.05)。[结论]建立的方案可快速测定细胞内的阿霉素分布;低浓度Sch B促进肿瘤细胞内化阿霉素。     

Growing through copying: The negative consequences of innovation on franchise network growth

We explore how more exactly copying a blueprint for establishing a franchise network in a new country influences franchising network growth. We test opposing hypotheses using panel data involving the transfer of franchising knowledge to 23 different countries, measuring the degree to which master licensees ‘copy exactly’ knowledge concerning how to grow a network in their country and the effect that their approach has on subsequent network growth. We conclude that a strategy of copying more exactly seems to enhance growth and that the benefits of more exactly replicating knowledge in the 1st year of a local network’s existence persist for several years. Thus, innovation, in this specific context, seems to hinder firm growth.     

Influence of buoyancy-driven flow on mass transfer in a two-stream microfluidic channel: Introduction of cryoprotective agents into cell suspensions

A variety of methods have been used to introduce chemicals into a stream or to mix two or more streams of different compositions using microfluidic devices. In the following paper, the introduction of cryoprotective agents (CPAs) used during cryopreservation of cells in order to protect them from freezing injuries and increase viability post thaw is described. Dimethylsulphoxide (DMSO) is the most commonly used CPA. We aim to optimize the operating conditions of a two-stream microfluidic device to introduce a 10% vol/vol solution of DMSO into a cell suspension. Transport behavior of DMSO between two streams in the device has been experimentally characterized for a spectrum of flow conditions (0.7 < Re < 10), varying initial donor stream concentrations, (1% vol/vol < C_o < 15% vol/vol) and different flow rate fractions (0.23 < f_q < 0.77). The outlet cell stream concentration is analyzed for two different flow configurations: one with the cell stream flowing on top of the DMSO-rich donor stream, and the other with the cell stream flowing beneath the heavy DMSO-laden stream. We establish a transition from a diffusive mode of mass transfer to gravity-influenced convective currents for Atwood numbers (A_t) in the range of (1.7 × 10⁻³ < A_t < 3.1 × 10⁻³) for the latter configuration. Flow visualization with cells further our understanding of the effect of A_t on the nature of mass transport. Cell motion studies performed with Jurkat cells confirm a high cell recovery from the device while underscoring the need to collect both the streams at the outlet of the device and suggesting flow conditions that will help us achieve the target DMSO outlet concentration for clinical scale flow rates of the cell suspension.     

三维创新空间下的银行创新成长模式探讨——以五大股份制商业银行为例

企业的创新空间由技术创新、制度创新和管理创新三个维度构成.在三维创新空间下,处于某一生命周期阶段的银行创新成长模式可分为:基于技术创新的成长模式、基于制度创新的成长模式、基于管理创新的成长模式和混合创新的成长模式四种.在成长过程中,我国五大股份制商业银行由于经营理念、市场定位和战略规划不同,其创新成长模式也有所差异.     

煤层气产出水中高浓度Cl-和HC03-对活性氧化铝吸附F-的动力学影响

通过静态试验研究了高质量浓度Cl-(1000mg·L-1)和HCO3-(2000 mg·L-1)对活性氧化铝吸附F-(10 mg·L-1)的动力学特性影响.结果表明:高质量浓度Cl-使活性氧化铝吸附F-速率加快,吸附量增加;高质量浓度HCO3-有相反趋势.建议采用活性氧化铝吸附除氟法作为煤层气产出水F-净化工艺时,考虑高质量浓度Cl-和HCO3-效应.     

Electrotaxis of oral squamous cell carcinoma cells in a multiple-electric-field chip with uniform flow field

We report a new design of microfluidic chip (Multiple electric Field with Uniform Flow chip, MFUF chip) to create multiple electric field strengths (EFSs) while providing a uniform flow field simultaneously. MFUF chip was fabricated from poly-methyl methacrylates (PMMA) substrates by using CO₂ laser micromachining. A microfluidic network with interconnecting segments was utilized to de-couple the flow field and the electric field (EF). Using our special design, different EFSs were obtained in channel segments that had an identical cross-section and therefore a uniform flow field. Four electric fields with EFS ratio of 7.9:2.8:1:0 were obtained with flow velocity variation of only 7.8% CV (coefficient of variation). Possible biological effect of shear force can therefore be avoided. Cell behavior under three EFSs and the control condition, where there is no EF, was observed in a single experiment. We validated MFUF chip performance using lung adenocarcinoma cell lines and then used the chip to study the electrotaxis of HSC-3, an oral squamous cell carcinoma cell line. The MFUF chip has high throughput capability for studying the EF-induced cell behavior under various EFSs, including the control condition (EFS = 0).     

一株以原油为碳源的Pseudomonas sp.菌化学趋向性研究

从某油田产出水中分离得到一株以原油为碳源的Pseudomonassp .菌 (假单孢菌 ) ,其化学趋向性运动能力中等 ,趋向性机理在本文中得以详细描述 .在可视化模型实验中可看到微生物向油水界面处的有序运动 ,而在有效的营养物浓度梯度范围内 ,化学趋向性运移速度与距油水界面的距离无关 ,受温度的影响很大 .并且在微观仿真模型实验中 ,可观察到细菌在孔隙壁和油、水三相交界处聚集 ,并讨论了该现象的形成原因及其对微生物采油的有利作用 .     

Defining the determinants of online impulse buying through a shopping process of integrating perceived risk,expectation-confirmation model,and flow theory issues

Since much online shopping is attributed to online impulse buying, it is important to define this particular shopping process. This process has three important issues, perceived risk for virtual stores as well as e-store design and psychological state for online shopping. This is because consumers are both system users and impulse buyers when shopping on e-stores. E-store design is based on the interaction of customers with e-stores and the expectation-confirmation model supports examination of this issue with a wide familiarity in IT use. Psychological state is emotional responses to the stimulus of products in e-stores and flow theory, with task skill and task challenge as precursors, is suitable for exploring this issue. Grounding on the three issues, this study proposes a new research model with these considerations to thoroughly examine the determinants of online impulse buying. Flow state and customer satisfaction also interact with each other. Empirical research shows an important link for the three defined issues of online impulse buying.