Optimization of thermal management and power density of small-scale wind turbine applications using SiC-MOSFETs

This paper presents an optimized design of 12kW 2L-FB inverter for small-scale wind turbine, taking into account some specific behavioral features of SiC power MOSFETs. Power converters used in renewable energy conversion have to deal with intermittent and variable power availability from the source, which implies that they actually work at their maximum rated power for only a small fraction of their operational time. Still, traditional thermal management design of power modules has to refer to maximum load conditions. SiC-MOSFETs exhibit a very stable performance over a broad temperature range [1-3]; this feature enables to design the cooling device for nominal operational conditions, typically corresponding to a much lower than maximum power rating. When this capability is added to the decrease in the size of passive filter elements, which can be gained by the higher switching frequency capability of SiC MOSFETs, the result is a significant increase of the converter powe, density

ANTIFUNGAL ACTIVITY OF CHITOSAN AGAINST Rhizopus stolonifer

These days instead of chemical pesticides, various natural alternatives have been used for the management of post-harvest diseases. This research was carried out to evaluate the antifungal potential of different chitosan concentrations viz., 5, 10, and 15 mg/µl against Rhizopus stolonifer by the agar dilution and well diffusion methods. The evaluation was carried out after seven days of incubation by measuring the inhibition of R. stolonifer mycelial growth. Results of the study revealed that the chitosan had a significant inhibitory effect on mycelial growth and maximum mycelial growth inhibition was reported at the 10 and 15 mg/µl concentrations and these two treatments are not significantly different. Based on these results, the best concentration (15 mg/µl) was further evaluated by the well diffusion technique. The average inhibition zones formed by the higher concentration was 25mm. Results of the study suggested that chitosan can be used for the management of post-harvesting diseases of tomatoes

Dynamic performance analysis of a 3.3 kV SiC MOSFET half-bridge module with parallel chips and body-diode freewheeling

Recently, 3.3 and 6.5 kV power MOSFETs have been introduced. Based on the 3.3 kV device, a 100 A half-bridge power module has been developed, using parallel chips for current scaling and relying exclusively on the use of the transistors body-diode for current free-wheeling (i.e., no antiparallel external diode chips are used). This paper presents a thorough parametric characterization of the module switching performance. Single-chip and parallel-chip operation are investigated in both double-pulsea type tests and realistic singlephase inverter operation

Evaluating the Quality of Services Provided by the Saudi Institute of Internal Auditors from Internal Auditors Perspective Using the SERVPERF Scale

This study aimed to measure the quality of services provided by the Saudi Institute of Internal Auditors using the actual performance model (SERVPERF), which compares the services that internal auditors wish to obtain with those that were actually obtained for the dimensions of this service. The study's data was collected using a questionnaire that includes five dimensions, i.e., tangibility, responsiveness, empathy, reliability, and assurance. The questionnaire helped obtain primary data from the study population, which consists of internal auditors in various sectors, whether governmental or private. A Paired Samples T Test was used to determine if there was a significant difference between the level of service desired by the recipient, and what is actually obtained. The results showed that the general evaluation of the services of the Saudi Institute for Internal Auditors was very good. The results also showed that there are significant differences in the level of service desired by the recipient and what was actually obtained in the dimensions of tangibility, responsiveness, empathy, and assurance. On the other hand, the study showed no significant differences in the level of reliability. The study also showed that the reliability dimension is the dimension that was in accordance with the aspirations of the internal auditors and received a very high evaluation, unlike the rest of the dimensions that were below aspirations, as they were close in their values and obtained an average evaluation. Keywords: Evaluation of service quality, Service quality dimensions, SERVPERF scale, Saudi Institute of Internal Auditors, Internal auditors DOI: 10.7176/RJFA/14-10-03 Publication date:May 31st 202

Biological Control and Plant Growth Promotion Properties of Volatile Organic Compound-Producing Antagonistic Trichoderma spp.

Trichoderma is environmentally vital due to their plant growth-promoting effects (such as enhancement of nutrients supply, suppression of plant pathogens, and promotion of plant defense). Biogenic volatile organic compounds (VOCs) are diverse chemical substances emitted by Trichoderma spp. The potential role of VOCs in biological control and plant growth promotion has recently been recognized. Here, the Trichoderma-VOCs' performance for plant growth promotion and suppression of plant pathogens are evaluated. We further investigated VOC emission profiles of T. harzianum using GC–MS. The Trichoderma-VOCs exhibited significant (p < 0.05) antifungal properties against all tested pathogenic fungi. T. atroviride-VOCs showed a decisive inhibition of Alternaria panax, Botrytis cinerea, Cylindrocarpon destructans, and Sclerotinia nivalis. The germinating seeds demonstrated growth enhancement in the presence of Trichoderma-VOCs emitted by different strains. Low levels of cyclopentasiloxane, decamethyl, cyclotetrasiloxane, and octamethyl were found in T. harzianum KNU1 strain whereas cyclopentasiloxane, decamethyl, cyclotetrasiloxane, and octamethyl showed higher emission levels as Si-containing compounds. The results reveal the potentiality of VOCs as a biocontrol resource against deleterious rhizosphere microorganisms and underline the importance of Trichoderma-VOCs emissions in regulating plant growth and development

A Dynamical Model for the Low Efficiency of Induced Pluripotent Stem Cell Reprogramming (Extended Version)

This is an extended version of a paper of the same title accepted to the 2016 American Control Conference (ACC)In the past decade, researchers have been able to obtain pluripotent stem cells directly from an organism’s differentiated cells through a process called cell reprogramming. This opens the way to potentially groundbreaking applications in regenerative and personalized medicine, in which ill patients could use self-derived induced pluripotent stem (iPS) cells where needed. While the process of reprogramming has been shown to be possible, its efficiency remains so low after almost ten years since its conception as to render its applicability limited to laboratory research. In this paper, we study a mathematical model of the core transcriptional circuitry among a set of key transcription factors, which is thought to determine the switch among pluripotent and blue early differentiated cell types. By employing standard tools from dynamical systems theory, we analyze the effects on the system’s dynamics of overexpressing the core factors, which is what is performed during the reprogramming process. We demonstrate that the structure of the system is such that it can render the switch from an initial stable steady state (differentiated cell type) to the desired stable steady state (pluripotent cell type) highly unlikely. This finding provides insights into a possible reason for the low efficiency of current reprogramming approaches. We also suggest a strategy for improving the reprogramming process that employs simultaneous overexpression of one transcription factor along with enhanced degradation of another

Effect of Thyme aqueous and alcoholic extract on the Beef Mincemeat shelf life extension

Antioxidant and antimicrobial activity of thyme has been well established against various microorganisms. This study was carried out to investigate the effect of aqueous and alcoholic extract of thyme on beef mincemeat quality. Three differential concentrations (0.4, 0.8, and 1.2 mg/ml) of both thyme extracts were used for the beef mincemeat preservation. Untreated meat samples were considered as the control group while the extracts treated beef mincemeat are stored at 4°C for 7 to 14 days. To validate the extract's ability to prolong the storage period at 4 °C, various bacteriological indicators like total plate count, presence of total coliform, Salmonella, Shigella, and Staphylococcus aureus count were assessed. The results of the antimicrobial assay of aqueous and alcoholic extracts of thyme at different concentrations showed that the aqueous extract had significant inhibitory action on the growth of a wide range of bacteria compared to the alcoholic extract. Thus, the thyme aqueous extracts can be efficient and promising as preservatives for meat and its products, especially at high concentrations to inhibit bacterial growth

Influence of Okra Extract Supplementation on Some Haematological Parameters of Male Mice Exposed to Aflatoxin

This research was directed to determine the influence of an alcoholic extract of okra on the lessening of the destructive impact of the aflatoxin produced by Aspergillus fumigatus in white mice and its influence on some physiological blood parameters. Different food samples, (grains and fruits) such as  (wheat, barley, corn, rice, citrus, strawberries, and apples) were selected for the isolation of a variety of fungi. The results showed  that Aspergillus flavus 15(18.7%), Aspergillus niger12(15%), Penicillium spp 7(8.7%), Aspergillus terreus 7 (8.7%), Aspergillus fumigatus7(8.7%), Alternaria spp. 10 (12.5%), Aspergillus parasiticus 6 (7.5%) Fusarium 6 (7.5%), Penicillium chrysogenum5(6.3), Mucor spp.2(2.5%),and Rhizopus stoloinfier 3(5.5%).The identified fungi were tested for aflatoxin production, and the results revealed  that Aspergillus fumigatus produced the most aflatoxin. Okra alcoholic extract was tested in vivo against  the negative impact of aflatoxins using different concentrations. The findings revealed that alcoholic extracts showed reasonable influence on some blood parameters, and the results are promising. &nbsp

The Frequency of Type 2 Diabetes Mellitus among Diabetic Children in El Minia Governorate, Egypt

Objectives: Type 2 diabetes mellitus (T2DM) in children and adolescents is becoming an increasingly important public health concern throughout the world. This study aimed to estimate the frequency of T2DM among diabetic young people in El-Minia Governorate, Egypt, and to detect its risk factors. Methods: A total of 210 diabetic patients under 18 years old in Minia Governorate were included in the study and underwent a thorough history-taking, a physical examination and laboratory investigations. Results: T2DM was present in 28 patients (13.3%); it was significantly present in 18 females (64.3%) and 20 (71.4%) of them had a positive family history of DM. T2DM patients had significantly higher BMI and waist circumference centiles for age and sex than those with T1DM. Also, haemoglobin A1c %, serum C-peptide and cholesterol levels were significantly higher in T2DM than T1DM patients. Finally, there were weak significant positive correlations between C-peptide level and both BMI and waist circumference. Conclusion: T2DM is no longer a disease of adults but can also occur in children and adolescents. The results suggested that obesity, female gender and a positive family history of DM are risk factors for T2DM. Also, patients with T2DM had poorer glycaemic control and hypercholesterolemia than those with other types of diabetes