A Hybrid Virtual Cloud Learning Model during the COVID-19 Pandemic

The COVID-19 pandemic has affected the educational systems worldwide, leading to the near-total closures of schools, universities, and colleges. Universities need to adapt to changes to face this crisis without negatively affecting students’ performance. Accordingly, the purpose of this study is to identify and help solve to critical challenges and factors that influence the e-learning system for Computer Maintenance courses during the COVID-19 pandemic. The paper examines the effect of a hybrid modeling approach that uses Cloud Computing Services (CCS) and Virtual Reality (VR) in a Virtual Cloud Learning Environment (VCLE) system. The VCLE system provides students with various utilities and educational services such as presentation slides/text, data sharing, assignments, quizzes/tests, and chatrooms. In addition, learning through VR enables the students to simulate physical presence, and they respond well to VR environments that are closer to reality as they feel that they are an integral part of the environment. Also, the research presents a rubric assessment that the students can use to reflect on the skills they used during the course. The research findings offer useful suggestions for enabling students to become acquainted with the proposed system’s usage, especially during the COVID-19 pandemic, and for improving student achievement more than the traditional methods of learning.     

Dynamic storage and access load balancing for answering range queries in peer-to-peer networks

Recently, many applications have used Peer-to-Peer (P2P) systems to overcome the current problems with client/server systems such as non-scalability, high bandwidth requirement and single point of failure. In this paper, we propose an efficient scheme to support efficient range query processing over structured P2P systems, while balancing both the storage load and access load. The paper proposes a rotating token scheme to balance the storage load by placing joining nodes in appropriate locations in the identifier space to share loads with already overloaded nodes. Then, to support range queries, we utilize an order-preserving mapping function to map keys to nodes in order preserving way and without hashing. This may result in an access load imbalance due to non-uniform distribution of keys in the identifier space. Thus, we propose an adaptive replication scheme to relieve overloaded nodes by shedding some load on other nodes to balance the access load. We derive a formula for estimating the overhead of the proposed adaptive replication scheme. In this study, we carry simulation experiments with synthetic data to measure the performance of the proposed schemes. Our simulation experiments show significant gains in both storage load balancing and access load balancing.     

Assignment and Scheduling in Flexible Job-Shops by Hierarchical Optimization

In this paper, we propose a new hierarchical method for the flexible job-shop scheduling problem (FJSP). This approach is mainly adapted to a job-shop problem (JSP) with high flexibility and is based on the decomposition of the problem in an assignment subproblem and a sequencing subproblem. For the first subproblem, we propose two methods: the first one is based successively on a heuristic approach and a local search; the second one, however, is based on a branch-and-bound algorithm. The quality of the assignment is evaluated by a lower bound. For the second subproblem we apply a hybrid genetic algorithm to deal with the sequencing problem. Computational tests are finally presented.     

Diffusing the Internet in the Arab world: the role of social norms and technological culturation

Drawing on the theoretical work of Hill et al. and Straub et al., this study examines culture-specific inducements and impediments to using the Internet in the Arab world. Research questions were: (1) to what extent does the process of technology culturation affect the acceptance of the Internet? and (2) to what extent do social norms (SNs) affect the acceptance of the Internet? Of the two research methods employed, the first was a quantitative field study of knowledge workers. The instrument measured the extent to which respondents and their organizations are influenced by advanced technology cultures. Using partial least squares (PLS), the first of two models tested links between SNs; technological culturation and Internet usage for each respondent. The second model investigated links between technological culturation and Internet utilization for the respondent's organization. Findings show strong support for both models, explaining, respectively, 47% and 37% of the variance. The second method was a qualitative analysis of respondents' free-format comments. These findings reinforce the quantitative findings, on the one hand, and reveal additional cultural barriers that still need to be studied, on the other. Findings identify how culture can both inhibit and encourage technological innovation and how Arab cultures can move their economies more quickly into the digital age.     

Mother''s milk protein profile, a possible biomarker for human exposure to persistent insecticides

In earlier studies we found that E. coli is sensitive to anticalmodulin drugs such as W7. Mutants that are resistant to this drug were isolated, including wseA1. In an attempt to clone the wseA gene, we isolated a clone that restored sensitivity to the drug in the mutant. We found that this clone in fact suppresses W7 resistance through expression of djlA, which encodes a novel DnaJ-like protein. It was found previously that overproduction of DjlA could induce capsule synthesis via activation of the two-component regulatory pathway RcsC/B. In addition to suppression of wseA1, djlA overexpression increases the sensitivity of cells to EDTA and novobiocin, but not to other drugs tested. Although overexpression of a form of the protein carrying a mutation in, or lacking, the J-region of DjlA also led to increased sensitivity, indicating that the chaperone activity of this protein was not strictly required. the full-length, wild-type protein had a more pronounced effect. In contrast, a point mutation which affects the function of the transmembrane domain but not the localisation or stability of DjlA abolished the effects of DjlA overproduction.     

Imaging of abdominal manifestations of melanoma

Despite an increasing incidence of melanoma in this country, innovative new therapies are allowing patients to receive aggressive experimental treatments. Diagnostic imaging remains crucial for tumor staging and for follow-up of patients being treated with these protocols. Because metastases occur in the abdomen and pelvis in approximately 60% of patients, it is important to accurately identify all sites of tumor spread. A variety of imaging techniques are used to image these patients, with CT currently being used for staging purposes and to guide diagnostic biopsies. Other imaging techniques, such as MR, ultrasound, and fluoroscopy, are currently reserved for investigating specific complications of melanoma, such as vascular invasion, hemorrhage from a tumor, and small bowel involvement, including intussusception. Recently, whole body positron emission tomography (PET) imaging using 2-deoxy-2-fluoro-D-glucose (FDG) has been shown to be highly accurate in assessing patients with metastatic malignant melanoma. This review illustrates the spectrum of manifestations of metastatic melanoma throughout the abdomen and pelvis, including solid organ, hollow lumen, and retroperitoneal involvement, and demonstrates some of the typical and atypical manifestations that may be identified.     

Concentration polarisation in tubular membranes —a numerical approach

A theoretical investigation ofparticle deposition onto a permeable surface of a tubular membrane is presented. Themass transport mechanisms are mathematically expressed using the two-dimensional convective diffusion equation. A numerical scheme is presented to solve the two-dimensional convective diffusion equation at the steady state for the case of nonuniform permeation velocity. This equation is solved numerically using a finite difference method. The numerical prediction of mass transfer in the mass boundary requires the use of a very dense grid. The concentration profiles along the membrane surface and the mass boundary layer are predicted. The effect of the Reynolds number, the wall Reynolds number and the Schmidt number were investigated. Correlations for the concentration boundary layer thickness δ_c/D=2(z/D)^0.33(ReSc)^{− 0.33} Re_w^−0.3 (1-0.4377 Sc^−0.0018 Re_w^−0.1551), and for the Sherwood number Sh =1.230 [(D/z) ReSc] ^0.33 (1 + 0.010 Re^−0.125Sc^1.055 Re_w.^1.132) based on the predicted values of the solute concentration profiles, are proposed, in the operating condition ranges 300 < Re < 1000, 0.02 < Re_w < 0.3 and 600 < Sc < 3200.     

Argon plasma treatment of glass surfaces

The effect of argon plasma treatment of glass surfaces is studied by FTIR and SEM. The argon plasma on cleaned glass surfaces resulted in increased surface area due to microetching and surface rearrangement of the silicate network as indicated by the observed changes in the Si-O stretching infrared absorption. The result was a relative increase in surface hydrophilicity which could be optimized by the plasma reaction conditions. The etching action of the argon plasma on the substrate surfaces facilitated the removal of the micrometre thick sizing from the commercial fibres accompanied by little loss in tensile strength. Plasma was also used to graft selected monomers to the surface of glass fibres for enhancement of bond compatibility in a composite system. This grafting treatment was followed by an argon etching step. The argon plasma action on the coated surfaces improved the wettability further and increased the sur face area. Changes in surface chemistry that accompanied the argon etching treatment were very subtle in the case of the plasma polymer of allylamine, but proved significant in the case of the plasma polymer of hexamethyldisiloxane. On the latter surfaces, rearrangement of the siloxane (Si-O-Si) bonds to silylmethylene (Si-(CH₂) _n -Si) groups is suggested.