Cultural Dimensions’ Effects on Perceptions of Learning Using Social Media: A Comparative Study between the University of Sharjah and the University of Arkansas Students

This research examines the impact of cultural dimensions on perceptions of social media as an educational tool in two different contexts. The study included 815 students volunteered to answer the survey questions from the University of Sharjah (UoS) in the United Arab Emirates and the University of Arkansas (UoA) in the United States of America. The results were analyzed via SPSS, and then counteracted with a Push-pull-mooring model to check for differences in terms of cultural contexts that would be reflected in perceptions of the value of social media in learning. The results reveal a number of differences. Students from the University of Sharjah are more immersed in social media for learning, and more interested in forming strong, long-term, and reliable collaborative friendships based on the exchange of ideas and academic assistance. By contrast, students from the University of Arkansas seem to be short-term oriented because their use of social media is related to discussion and instant chat. The authors conclude that UoS students’ perceptions reflect a culture of collectivism that invests in social networks to enhance the already deeply rooted offline social activities, while those from UoA reveal a culture of individualism in which social media use is restricted to self-information

Delays in Biological Regulatory Networks

International audienceIn this article, we propose a refinement of the modeling of genetic regulatory networks based on the approach of René Thomas. The notion of delays of activation/inhibition are added in order to specify which variable is faster affected by a change of its regulators. The formalism of linear hybrid automata is well suited to allow such refinement. We then use HyTech for two purposes: (1) to find automatically all paths from a specified initial state to another one and (2) to synthesize co nstraints on the delay parameters in order to follow any specific path

Antagonistic, biofilm-forming rhizospheric Pseudomonas spp. isolated from Hail province

Background: The objectives of this study were to characterize Pseudomonas rhizospheric strains, that have a biocontrol activity, in rhizosphere soil in Hail province and study their ability to form biofilm.Methods: Rhizosphere soil samples were collected from rhizosphere of soil plantation areas, to be used for bacteria isolation. The identified bacteria were qualitatively tested for their ability to produce slime and subsequently develop biofilm.Results: The cultural and biochemical identification techniques, including morphological, biochemical and molecular methods revealed that the antagonistic bacteria- from the distinctive rhizosphere soil samples belong to Pseudomonas genus in particular, P. aeruginosa (PF1a, pf2a, PF-8) and P. putida (PF-7). These identified isolates inhibited Aspergillus niger development with percentage of parasitic growth inhibition greater than (48.095 ± 2.182)% for P. aeruginosa (pf-8). In addition, these identified isolates were significantly shown to be able to produce exopolysaccharide and subsequently develop biofilm on polystyrene and glass surfaces.Conclusion: Superior strains of these bio-control and plant growth promoting rhizobacteria will enable for better biological control of fungal and bacterial plant diseases and may reduce chemical pesticide usage. The indigenous strains isolated could potentially have a great impact on controlling plant diseases, in particular, those caused by microorganisms, and could be used as an alternative bio control agents instead of harmful chemical pesticides. Most of the tried microbes produced exopolysaccharides as well as formed biofilm on polystyrene and glass surfaces.Keywords: Biological control, Rhizosphere; Biofilm; Pseudomonas; Antimicrobial

Virulence properties and random amplification of polymorphic DNA (RAPD) fingerprinting of Candida albicans isolates obtained from Monastir dental hospital, Tunisia

Genotypic and phenotypic characterization as well as studies on the virulence factors of Candida albicans isolates obtained from oral cavity of patients was carried out using random amplified polymorphic DNA (RAPD) fingerprinting and epithelial cells adherence assay, respectively. RAPD patterns revealed the presence of 13 C. albicans genotypes separated into two clusters at 75% ofsimilarity when they were combined. Results also showed the presence of haemolytic protease activity as virulence factors with 88% of the C. albicans strains been able to adhere to Caco-2 cells and only 64% to Hep-2. RAPD-polymerase chain reaction (PCR) is a molecular tool used to differentiate the isolates into various genotypes based on their virulence properties.Key words: Candida albicans, stomatitis, random amplified polymorphic DNA, Hep-2, Caco-2 cells

Separation of instrumental and astrophysical foregrounds for mapping CMB anisotropies

We address the extended problem of component separation for CMB applications when a mixture of both astrophysical and instrumental components are present in the observations, and show how standard methods can be adapted to handle this more complex inversion problem.Comment: 12 pages, 5 figures, submitted to MNRA

Indeterminacy of Reverse Engineering of Gene Regulatory Networks: The Curse of Gene Elasticity

Gene Regulatory Networks (GRNs) have become a major focus of interest in recent years. A number of reverse engineering approaches have been developed to help uncover the regulatory networks giving rise to the observed gene expression profiles. However, this is an overspecified problem due to the fact that more than one genotype (network wiring) can give rise to the same phenotype. We refer to this phenomenon as “gene elasticity.” In this work, we study the effect of this particular problem on the pure, data-driven inference of gene regulatory networks.We simulated a four-gene network in order to produce “data” (protein levels) that we use in lieu of real experimental data. We then optimized the network connections between the four genes with a view to obtain the original network that gave rise to the data. We did this for two different cases: one in which only the network connections were optimized and the other in which both the network connections as well as the kinetic parameters (given as reaction probabilities in our case) were estimated. We observed that multiple genotypes gave rise to very similar protein levels. Statistical experimentation indicates that it is impossible to differentiate between the different networks on the basis of both equilibrium as well as dynamic data.We show explicitly that reverse engineering of GRNs from pure expression data is an indeterminate problem. Our results suggest the unsuitability of an inferential, purely data-driven approach for the reverse engineering transcriptional networks in the case of gene regulatory networks displaying a certain level of complexity

A Theoretical Exploration of Birhythmicity in the p53-Mdm2 Network

Experimental observations performed in the p53-Mdm2 network, one of the key protein modules involved in the control of proliferation of abnormal cells in mammals, revealed the existence of two frequencies of oscillations of p53 and Mdm2 in irradiated cells depending on the irradiation dose. These observations raised the question of the existence of birhythmicity, i.e. the coexistence of two oscillatory regimes for the same external conditions, in the p53-Mdm2 network which would be at the origin of these two distinct frequencies. A theoretical answer has been recently suggested by Ouattara, Abou-Jaoudé and Kaufman who proposed a 3-dimensional differential model showing birhythmicity to reproduce the two frequencies experimentally observed. The aim of this work is to analyze the mechanisms at the origin of the birhythmic behavior through a theoretical analysis of this differential model. To do so, we reduced this model, in a first step, into a 3-dimensional piecewise linear differential model where the Hill functions have been approximated by step functions, and, in a second step, into a 2-dimensional piecewise linear differential model by setting one autonomous variable as a constant in each domain of the phase space. We find that two features related to the phase space structure of the system are at the origin of the birhythmic behavior: the existence of two embedded cycles in the transition graph of the reduced models; the presence of a bypass in the orbit of the large amplitude oscillatory regime of low frequency. Based on this analysis, an experimental strategy is proposed to test the existence of birhythmicity in the p53-Mdm2 network. From a methodological point of view, this approach greatly facilitates the computational analysis of complex oscillatory behavior and could represent a valuable tool to explore mathematical models of biological rhythms showing sufficiently steep nonlinearities