19672 research outputs found
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Effect of polar aprotic solvents on hydroxyethyl cellulose-based gel polymer electrolyte
No full textQuasi-solid bioelectrolytes based on hydroxyethyl cellulose (HEC) and sodium iodide (NaI) in three different polar aprotic solvent systems, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and dimethylacetamide (DMA), were fabricated and characterized. FTIR studies revealed active solvent-ion interactions in DMF-based electrolytes in comparison to DMA and DMSO. The effect of the solvent system on the crystallinity of HEC gel electrolytes was more significant at low NaI concentration. In each solvent system, the highest ionic conductivity was achieved at 70 wt% NaI and generally DMF-based electrolytes showed higher conductivity than the other solvents. The availability of multiple complexation sites present in DMF is ascribed to improvement in ion mobility and hence conductivity. Rheological analysis was carried out to elucidate the mechanical properties of the gels. Generally, the mechanical strength of the polymer gels was unaffected by the type of solvent
Cytotoxic Effects and Anti-Angiogenesis Potential of Pistachio (Pistacia vera L.) Hulls against MCF-7 Human Breast Cancer Cells
No full textPistachio (Pistacia vera L.) hulls (PVLH) represents a significant by-product of industrial pistachio processing that contains high amounta of phenolic and flavonoid compounds known to act as antioxidants. The current study was designed to evaluate the anti-tumor and anti-angiogenic potentials of PVLH extracts. The cytotoxic effects of hexane, ethyl acetate, methanol, and water PVLH extracts toward human colon cancer (HT-29 and HCT-116), breast adenocarcinoma (MCF-7), lung adenocarcinoma (H23), liver hepatocellular carcinoma (HepG2), cervical cancer (Ca Ski), and normal fibroblast (BJ-5ta) cells were assessed using a MTT cell viability assay. Apoptosis induction was evaluated through the different nuclear staining assays and confirmed by flow cytometry analysis. Anti-angiogenic activities were also determined using chorioallantoic membrane (CAM) assay. PVLH ethyl acetate extracts (PVLH-EAE) demonstrated a suppressive effect with an IC50 value of 21.20 ± 1.35, 23.00 ± 1.2 and 25.15 ± 1.85 µg/mL against MCF-7, HT-29 and HCT-116, respectively, after 72 h of treatment. Morphological assessment and flow cytometry analysis showed the potential of PVLH-EAE to induce apoptosis. PVLH-EAE at the highest concentration demonstrated significant inhibition of angiogenesis as comparing with control group. Also the expression of Bax increased and the expression of Bcl-2 decreased in treated MCF-7 cells. Thus, the apoptosis induction and angiogenesis potential of PVLH-EAE make it to be the most suitable for further cancer research study to deal with selective antitumor active substances to human cancers especially breast cancer
Graphene Oxide-Gold Nanosheets Containing Chitosan Scaffold Improves Ventricular Contractility and Function After Implantation into Infarcted Heart
No full textAbnormal conduction and improper electrical impulse propagation are common in heart after myocardial infarction (MI). The scar tissue is non-conductive therefore the electrical communication between adjacent cardiomyocytes is disrupted. In the current study, we synthesized and characterized a conductive biodegradable scaffold by incorporating graphene oxide gold nanosheets (GO-Au) into a clinically approved natural polymer chitosan (CS). Inclusion of GO-Au nanosheets in CS scaffold displayed two fold increase in electrical conductivity. The scaffold exhibited excellent porous architecture with desired swelling and controlled degradation properties. It also supported cell attachment and growth with no signs of discrete cytotoxicity. In a rat model of MI, in vivo as well as in isolated heart, the scaffold after 5 weeks of implantation showed a significant improvement in QRS interval which was associated with enhanced conduction velocity and contractility in the infarct zone by increasing connexin 43 levels. These results corroborate that implantation of novel conductive polymeric scaffold in the infarcted heart improved the cardiac contractility and restored ventricular function. Therefore, our approach may be useful in planning future strategies to construct clinically relevant conductive polymer patches for cardiac patients with conduction defects
A high gain 10 watts wideband distributed power amplifier for two way radio system
No full textPurpose – This paper aims to propose a practical design methodology of high-power wideband power amplifier. Design/methodology/approach – The distributed power amplification method is used for a Gallium Nitride device to achieve wideband operation. To achieve the high power without trading-off the bandwidth and gain, a methodology to extract the package-loading effect is proposed and verified. Findings – A maximum output power of 10 W is achieved from 100 MHz to 2 GHz with a wideband power gain of 32 dB in measurement. This performance is achieved through a single section matching network. Research limitations/implications – Measurement accuracy is dependable to the thermal behaviour of the high-power device. Practical implications – The proposed technique is an excellent solution to be used in the two way radio power amplifier that minimizes the fundamental trade-off issue between power, gain, bandwidth and efficiency. Originality/value – In this work, a practical distributed power amplifier (DPA) design methodology is proposed that reduces the development cycle time for industrial engineers working on high-power circuit design application
Performance of the WRF Model for Surface Wind Prediction around Qatar
No full textThe performance of the Weather Research and Forecasting (WRF) Model is examined for the region around Qatar in the context of surface winds. The wind fields around this peninsula can be complicated owing to its small size, to a complex pattern of land and sea breezes influenced by the prevailing shamal winds, and to its dry and arid nature. Modeled winds are verified with data from 19 land stations and two offshore buoys. A comparison with these data shows that nonlocal planetary boundary layer (PBL) schemes generally perform better than local schemes over land stations during the daytime, when convective conditions prevail; at nighttime, over land and over water, both schemes yield similar results. Among other parameters, modifications to standard USGS land-use descriptors were necessary to reduce model errors. The RMSE values are comparable to those reported elsewhere. Simulated winds, when used with a wave model, result in wave heights comparable to buoy measurements. Furthermore, WRF results, confirmed by data, show that at times sea breezes develop from both coasts, leading to convergence in the middle of the country; at other times, the large-scale wind impedes the formation of sea breezes on one or both coasts. Simulations also indicate greater land/sea-breeze activity in the summer than in the winter. Differences in the diurnal evolution of surface winds over land and water are found to be related to differences in the boundary layer stability. Overall, the results indicate that the WRF Model as configured here yields reliable simulations and can be used for various practical applications
Platelet rich concentrate enhances mesenchymal stem cells capacity to repair focal cartilage injury in rabbits
No full textBackground: It has been previously suggested that the use of regenerative promoters, which include bone marrow-derived mesenchymal stem cells (MSCs) or natural growth factors supplement such as platelet-rich concentrate (PRC) could promote cartilage regeneration. However, the notion that the concurrent use of both promoters may provide a synergistic effect that improves the repair outcome of focal cartilage injury has not been previously demonstrated. This study was thus conducted to determine whether the concomitant use of PRC could further enhance the reparative potential of MSCs encapsulated in alginate transplanted into focal cartilage injury in rabbits. Methods: Artifically created full thickness cartilage defects were made on the weight-bearing region of medial femoral condyles in bilateral knees of New Zealand White rabbits (N = 30). After one month, the right knee was treated with either i) PRC (n = 10), ii) MSCs (n = 10), or, iii) a combination of PRC and MSCs (PRC + MSC) (n = 10), all encapsulated in alginate. The left knee remained untreated (control). Rabbits were sacrificed at 3 and 6 months after treatment. Cartilage tissue regeneration was accessed using ICRS morphologic scoring, histologic grading by O'Driscoll scoring, immunohistochemical staining and quantitative analysis of glycosaminoglycans (GAG) per total protein content. Results: At 3 months, transplantation using PRC alone was equally effective as MSCs in inducing the repair of cartilage defects. However, PRC + MSC resulted in significantly higher ICRS and O'Driscoll scores (p < 0.05) as compared to other groups. The regenerated tissues from the PRC + MSC group also had stronger staining for Safranin-O and collagen type II. By 6 months, in addition to superior ICRS and O'Driscoll scores as well as stronger staining, glycosaminoglycan per total protein content was also significantly higher (p < 0.05) in the PRC + MSC group (3.4 ± 0.3 μg/mg) as compared to the MSC (2.6 ± 0.2 μg/mg) or PRC (2.1 ± 0.2 μg/mg) groups. Conclusion: PRC enhances the reparative effects of MSC in treating focal articular cartilage injuries
The conductivity and dielectric studies of solid polymer electrolytes based on poly (acrylamide-co-acrylic acid) doped with sodium iodide
No full textSolid polymer electrolyte thin films based on polyacrylamide-co-acrylic acid (PAAC) doped with sodium iodide (NaI) with different ratios of polymer and salt added with fixed amount of additive of propylene carbonate (PC) were prepared by using solution casting method. The PC was added to the mixture of the solution to provide more flexibility to the polymer film by increasing the plasticity of the thin film membrane. The conductivity and dielectric studies were carried out on these thin films to understand the ion transport properties of the polymer electrolytes. The highest conductivity obtained was 1.88 × 10−5 S cm−1 for the 30% NaI salt-doped polymer electrolyte system at room temperature. The temperature-dependent conductivity agrees with Arrhenius relationship which shows that hopping mechanism of ions in the polymer matrix. The dielectric properties especially the loss tangent used to analyze the segmental relaxation of the polymer chain as more concentration of salt was incorporated. The electric modulus was studied to understand the electrical relaxation processes to overcome electrode polarization effect
The Asia-Pacific origins of the current outbreaks of Zika virus
No full textZika virus (ZIKV) is a mosquito-borne arbovirus from the Flaviviridae family, first isolated in 1947 from a monkey in Uganda. In the ensuing decades up to the 2000s, there have been sporadic reports of infections and seropositivity in humans in Africa and Asia1,2. The first isolation of ZIKV outside Africa was from Aedes aegypti mosquitoes in Malaysia in 19663. Seropositivity has also been reported in wild monkeys in Malaysia3, although the relevance of this in sylvatic transmission of ZIKV is unknown. These studies suggest that there was endemic and mostly undetected transmission in Asia during this period. Re-emergence from Asia has now brought this relatively neglected virus into the focus of global attention
Engaging EFL Learners in Online Peer Feedback on Writing: What Does It Tell Us?
No full textAim/Purpose The current case study aimed to investigate the engagement of nine English as foreign language (EFL) learners in online peer feedback on writing in a Facebook group. Specifically, the study focused on the issues of writing addressed in peer feedback and the learners' perception of peer feedback in the Facebook group. Background Peer feedback on writing has attracted the attention of many researchers and in-structors of writing in English as second/foreign language (ESL/EFL) contexts. More recently, the application of synchronous and asynchronous technologies, including Facebook, has been reported to foster ESL/EFL learners' engagement in peer feedback. Yet, in the EFL university context, the teacher/instructor still represents the sole resource of feedback, while learners are only passive receivers of feedback. Therefore, it is necessary to encourage EFL learners to be providers of feedback by engaging them in peer work in writing. Methodology The study was conducted among nine EFL Arab learners beyond the university writing course. As an extension to enhance their writing in the Facebook group, the activities of peer feedback reported in this study were monitored by the course instructor for three months. The learners' interactional feedback exchang-es, text revisions, and written reflections were qualitatively analyzed and the pat-terns of interaction were quantified. Contribution The findings contribute to the previous body of knowledge about the role of peer feedback, as well as the application of how asynchronous technological tools such as Facebook facilitate learners' interactional feedback exchanges in writing. Findings The learners engaged in interactional feedback exchanges in the revision-oriented discourse (n=1100 (64%)). These comments triggered global text revisions focus-ing on content, organization, and argumentative genre (n=533 (31%)) and local text revisions focusing on language and mechanics/conventions (n=567 (33%)). The learners also engaged in the non-revision-oriented discourse (n=620 (36%)) that focused on establishing group cohesion in terms of a friendly social context, social support, socialization, social ties, and attachment among them. The learners also perceived the Facebook group as an interactive learning environment that facilitates their peer feedback on writing beyond the university context. Recommendations for Practitioners The findings of the current study underlie useful pedagogical implications for EFL instructors and lecturers as well university students, specifically how peer feedback can be used by instructors as a way to enhance learners' writing skills. Moreover, with the increasing access to social networks such as Facebook groups, EFL learners can engage themselves in peer feedback activities beyond the uni-versity writing courses for further development in writing. Recommendation for Researchers Significant insights on EFL learning may be gleaned from analysing peer feedback on learning activities, which are easily facilitated by commonly available social networks such as Facebook. Hence, researchers who are interested in this domain are encouraged to look beyond the traditional teaching medium. Impact on Society The use of social networks (including Facebook groups) for educational purposes has received much attention from university learners worldwide. This research can facilitate people's awareness of the value of such networks in creating learning opportunities outside the university context. Future Research Future research could combine both synchronous and asynchronous technologies in peer feedback and focus on the effect of peer feedback on each learner's writing
CFD modeling of turbulent convection heat transfer of nanofluids containing green functionalized graphene nanoplatelets flowing in a horizontal tube: Comparison with experimental data
No full textIn this research, a series of numerical simulations were conducted utilizing computational fluid dynamics (CFD) software in order to predict the heat transfer performance of queues nanofluids containing clove-treated graphene nanoplatelets (CGNPs) flowing in a horizontal stainless steel heated pipe. The GNPs were covalently functionalized with clove buds using free radical grafting reaction using an eco-friendly process. The advantage of this synthesis method was that it did not use hazardous acids, which are typically used in traditional treatment methods of carbon nanostructures. The thermo-physical properties of the aqueous nanofluids obtained experimentally were used as inputs for the CFD simulations for solving the governing equations of heat transfer and fluid motion. The shear stress transport (SST) k-ω turbulence model was also used in these simulations. The corresponding convective heat transfer coefficient and friction factor of aqueous nanofluids for nanoparticle weight concentrations of 0.025, 0.075, and 0.1% were evaluated. The simulation results for both heat transfer coefficient and friction factor were shown to be in agreement with the experimental data with an average relative deviation of about ±10%. The presented results confirmed the applicability of the numerical model for simulating the heat transfer performance of CGNPs aqueous nanofluids in turbulent flow regimes