Buneman instability in a magnetized current-carrying plasma with velocity shear

Buneman instability is often driven in magnetic reconnection. Understanding how velocity shear in the beams driving the Buneman instability affects the growth and saturation of waves is relevant to turbulence, heating, and diffusion in magnetic reconnection. Using a Mathieu-equation analysis for weak cosine velocity shear together with Vlasov simulations, the effects of shear on the kinetic Buneman instability are studied in a plasma consisting of strongly magnetized electrons and cold unmagnetized ions. In the linearly unstable phase, shear enhances the coupling between oblique waves and the sheared electron beam, resulting in a wider range of unstable eigenmodes with common lower growth rates. The wave couplings generate new features of the electric fields in space, which can persist into the nonlinear phase when electron holes form. Lower hybrid instabilities simultaneously occur at $k_{\shortparallel}/k_{\perp} \sim \sqrt{m_e/m_i}$ with a much lower growth rate, and are not affected by the velocity shear.Comment: Accepted by Physics of Plasm

Psychological impact on football players performance

The purpose of this study is to determine the psychological strength among football players. There were a total of (n=90). Psychological strength dimension consists of self-confidence, motivational control, and focus control. The data analyses were conducted using structural equation modeling (SEM) via AMOS (Analysis of Moment Structures) software package Version 20.0. Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) were performed to validate the scales. The results shown that social support from parents, coach, friends and the sports agencies directly contribute towards overall social support which in turn, has significant relationships self-confidence, task orientation and ego orientation. In future research, a longitudinal study would be particularly useful to observe the model changes from one phase of footballers or any other sports performance by applying the model.Keywords: psychological strength; football players; performanc

Social learning approach in designing persuasive e-commerce recommender system model

Intention to purchase in existing online business practice is learned through observation of information display by online seller. The emergent growth of persuasive technologies currently holds a great potential in driving a positive influence towards consumer purchase behavior. But to date, there is still limited research on implementing persuasion concept into the recommender system context. Drawing upon the principle design of persuasive system, the main purpose of this study is to explore social learning advantages in creating persuasive features for E-Commerce recommender system. Based on Social Cognitive Theory, the influence of personal and environmental factors will be examined in measuring consumer purchase intention. In addition, dimensions of social learning environment are represented by observational learning theory and cognitive learning theory. From those reviews, this study assumed that social learning environment can be created based on attentiveness, retentiveness, motivational, knowledge awareness and interest evaluation cues of consumer learning factors. Furthermore, the persuasive environment of recommender system is assumed to have positive influence towards individual characteristics such as self-efficacy behavior, perceived task complexity and confused by over choice. Findings from those reviews have contributed to the development of a research model in visualizing social learning environment that can be used to develop a persuasive recommender system in E-Commerce and hence measures the impact towards consumer purchase intention

Isolation of bioflocculant-producing bacteria from Penaeus vannamei ponds for the production of extracellular polymeric substances

Bioflocculants are essential polymers with their flocculating activity depending on the characteristics of the secreted flocculants by bioflocculant-producing bacteria. However, the characteristics of bioflocculant produced by microorganisms were not investigated profoundly. In order to better understand these characteristics, determination of extracellular polymeric substances (EPS) from bioflocculant-producing bacteria were characterized in terms of protein concentrations. A total of 51 bioflocculant-producing bacteria isolates were screened from Pacific whiteleg shrimp, Penaeus vannamei culture ponds in Setiu, Terengganu, Malaysia. Screening of bioflocculant-producing bacteria were conducted through morphological approaches followed by protein extraction using Lowry assay method. The identified bioflocculant-producing bacteria includes Corynebacterium sp., Klebsiella sp., Lactobacillus sp., Staphylococcus sp., Bacillus sp., Streptococcus sp., Vibrio spp., Neisseria sp., Serratia sp. and Yersinia sp., with the highest protein concentration of 829 mg mL-1 were attained by Staphylococcus sp. The various amounts of EPS concentration produced by different species of bacteria were dependent on their specific population growth and growth rate. Therefore, the establishment of bioflocculant-producing bacteria isolated from biofloc which showed high tendency for EPS production were performed successfully

Analysis of chaotic mixing in plugs moving in meandering microchannels

Droplets moving in meandering microchannels can serve as a passive and robust strategy to produce chaotic mixing of species in droplet-based microfluidics. In this paper, a simplified theoretical model is proposed for plug-shaped droplets moving in meandering microchannels at Stokes flow. With this model to provide the velocity field, particle tracking, which requires a large computation time, is performed directly and easily without interpolation. With this convenience, a broad survey of the parameter space is carried out to investigate chaotic mixing in plugs, including the channel curvature, the Peclet number, the viscosity ratio, and the plug length. The results show that in order to achieve rapid mixing in plugs in meandering microchannels, a large curvature, a small Peclet number, a moderate viscosity ratio, and a moderate plug length are preferred. © 2011 American Physical Society