Air permeability of electrospun polyacrylonitrile nanoweb

Ultrafine fibers were spun from polyacrylonitrile (PAN) solution in N,N‐dimethylformamide using a homemade electrospinning setup. Fibers with diameter ranging from 80 to 340 nm were obtained. Fiber size and fiber size distribution were investigated for various concentration, applied voltage, and tip‐to‐collector distance using image analysis. The diameters of the electrospun fibers increase when increasing the solution concentration and decrease slightly when increasing the voltage and needle tip‐to‐collector distance. Porosity and air permeability are vital properties in applications of electrospun nanofibrous structures. In this study, effects of process parameters on the porosity and air permeability of electrospun nanoweb were investigated as well. Results of statistical analysis showed that solution concentration and applied voltage have significant influences on pore diameters. It was concluded that nanofiber diameter played an important role on the diameter of pores formed by the intersections of nanofibers. A more realistic understanding of porosity was obtained and a quantitative relationship between nanoweb parameters and its air permeability was established by regression analysis. Two separate models were constructed for predicting air permeability in relation to process parameters. Optimization of electrospinning process for producing nanoweb with desirable air permeability is well achieved by these models. The models presented in this study are of high importance for their ability to predict the air permeability of PAN nanoweb both by process or structure parameters. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Characterization of Staphylococcus aureus isolates from white-brined Urfa cheese

The aim of this study was to investigate the presence of Staphylococcus aureus and staphylococcal enterotoxin (SE) genes in Urfa cheese samples and to characterize the enterotoxigenic potential of these isolates. From a total of 127 Urfa cheese samples, 53 isolates (from 41.7% of the samples) were identified by a species-specific PCR assay as S. aureus. Of these isolates, 40 (75.5%) gave positive PCR results for the 3' end of the coa gene. The coa-positive S. aureus strains were characterized for their population levels and enterotoxigenic properties, including slime factor, β-lactamase, antibiotic susceptibilities, production of the classical SEs (SEA through SEE), in both cheese and liquid cultures by enzyme-linked immunosorbent assay (ELISA) and for the presence of specific genes, including classical SE genes (sea through see), mecA, femA, and spa, by PCR. The genetic relatedness among the coa-positive S. aureus isolates was investigated by PCR-based restriction fragment length polymorphism (RFLP) analysis and the 23S rRNA gene spacer. The 23S rRNA gene spacer and coa RFLP analysis using AluI and Hin6I revealed 14 different patterns. SEB, SEC, and SEA and SEE were detected by ELISA in three cheese samples. Fourteen S. aureus strains harbored enterotoxin genes sea through see, and three strains carried multiple toxin genes. The most commonly detected toxin gene was sec (25% of tested strains). Of the 40 analyzed S. aureus strains, 3 (7.5%) were mecA positive. Based on tandem repeats, four coa and spa types were identified. The results of this study indicate that S. aureus and SEs are present at significant levels in Urfa cheese. These toxins can cause staphylococcal food poisoning, creating a serious hazard for public health.     

Studies on the antioxidant potential of flavones of Allium vineale isolated from its water-soluble fraction

The aim of this work was to examine the chemical constituents and antioxidant potential of water-soluble fractions from the commonly consumed vegetable, Allium vineale. The water-soluble fraction, containing phenolic compounds, was extracted with ethyl acetate to obtain flavonoids which were separated and purified by repeated column chromatography over Sephadex LH-20, RP C18 and silica gel. The isolated compounds were identified according to their physicochemical properties and spectral data (UV, HPLC–TOF/MS, ¹H NMR, ¹³C NMR and 2D NMR). Three flavonoids were isolated and identified as chrysoeriol-7-O-[2″-O-E-feruloyl]-β-d-glucoside (1), chrysoeriol (2), and isorhamnetin-3-β-d-glucoside (3). Antioxidant studies of the aqueous extract and three isolated compounds, 1, 2, 3, were undertaken and they were found to have significant antioxidant activity. Antioxidant activities were evaluated for total antioxidant activity by the ferric thiocyanate method, ferric ion (Fe³⁺) reducing antioxidant power assay (FRAP), ferrous ion (Fe²⁺) metal chelating activity, and DPPH free radical-scavenging activity. The water-soluble ethyl acetate and methanol extraction methods were also compared using HPLC–TOF/MS.     

<Emphasis Type="Italic">I-Quest</Emphasis>: an <Emphasis Type="Italic">i</Emphasis>ntelligent <Emphasis Type="Italic">que</Emphasis>ry <Emphasis Type="Italic">st</Emphasis>ructuring based on user browsing feedback for semantic retrieval of video data

In spite of significant improvements in video data retrieval, a system has not yet been developed that can adequately respond to a user’s query. Typically, the user has to refine the query many times and view query results until eventually the expected videos are retrieved from the database. The complexity of video data and questionable query structuring by the user aggravates the retrieval process. Most previous research in this area has focused on retrieval based on low-level features. Managing imprecise queries using semantic (high-level) content is no easier than queries based on low-level features due to the absence of a proper continuous distance function. We provide a method to help users search for clips and videos of interest in video databases. The video clips are classified as interesting and uninteresting based on user browsing. The attribute values of clips are classified by commonality, presence, and frequency within each of the two groups to be used in computing the relevance of each clip to the user’s query. In this paper, we provide an intelligent query structuring system, called I-Quest, to rank clips based on user browsing feedback, where a template generation from the set of interesting and uninteresting sets is impossible or yields poor results.

Educational UTAUT-based virtual reality acceptance scale: a validity and reliability study

Virtual Reality - This study aims to fill a gap in current research on virtual reality (VR) by developing a valid and reliable educational VR acceptance scale based on the unified theory of...     

Development of educational virtual reality attitude scale: A validity and reliability study

Virtual Reality - The aim of the study is to address a gap in the literature by developing an educational virtual reality (edVR) attitude measurement instrument, which determines college...     

Modal analysis and improvement of lightweight wings for micro air vehicle (MAV) applications

Journal of Mechanical Science and Technology - Micro air vehicles (MAVs) are small portable flying machines designed to perform some specific tasks. Presently, the MAVs are being highly considered...     

The effect of learning analytics-based interventions in mobile learning on students' academic achievements,self-regulated learning skills,and motivations

Universal Access in the Information Society - This study examines the effects of using learning analytics (LA) in a mobile-based learning setting on students' self-regulated learning (SRL)...