Studies of heat source driven natural convection

Natural convection energy transport in a horizontal layer of internally heated fluid was measured for Rayleigh numbers from 1890 to 2.17 x 10 to the 12th power. The fluid layer is bounded below by a rigid zero-heat-flux surface and above by a rigid constant-temperature surface. Joule heating by an alternating current passing horizontally through the layer provides the uniform volumetric energy source. The overall steady-state heat transfer coefficient at the upper surface was determined by measuring the temperature difference across the layer and power input to the fluid. The correlation between the Nusselt and Rayleigh numbers for the data of the present study and the data of the Kulacki study is given

Studies of heat-source driven natural convection: A numerical investigation

Thermal convection driven by uniform volumetric energy sources was studied in a horizontal fluid layer bounded from above by a rigid, isothermal surface and from below by a rigid, zero heat-flux surface. The side walls of the fluid domain were assumed to be rigid and perfectly insulating. The computations were formally restricted to two-dimensional laminar convection but were carried out for a range of Rayleigh numbers which spans the regimes of laminar and turbulent flow. The results of the computations consists of streamline and isotherm patterns, horizontally averaged temperature distributions, and horizontally averaged Nusselt numbers at the upper surface. Flow and temperature fields do not exhibit a steady state, but horizontally averaged Nusselt numbers reach limiting, quasi-steady values for all Rayleigh numbers considered. Correlations of the Nusselt number in terms of the Rayleigh and Prandtl numbers were determined

On the Impact of Financial Inclusion on Financial Stability and Inequality: The Role of Macroprudential Policies

Financial Inclusion - access to financial products by households and firms - is one of the main albeit challenging priorities, both for Advanced Economies (AEs) as well as Emerging Markets (EMs), even more so for the latter. Financial inclusion facilitates consumption smoothing, lowers income inequality, enables risk diversification, and tends to positively affect economic growth. Financial stability is another rising priority among policy makers. This is evident in the re-emergence of macroprudential policies after the global financial crisis, minimizing systemic risk, particularly risks associated with rapid credit growth. However, there are significant policy tradeoffs that could exist between both financial inclusion and financial stability, with mixed evidence on the link between the two objectives. Given the importance of macroprudential policies as a toolbox to achieve financial stability, we examine the impact of macroprudential policies on financial inclusion - a potential cause for financial instability if not carefully implemented. Using panel regressions for 67 countries over the period 2000-2014, our results point to mixed effects of macroprudential policies. The usage (and tightening) of some tools, such as the debt-to-income ratio, appear to reduce financial inclusion whereas others, such as the required reserve ratio (RRR), increase it. Specifically, both institutional quality and financial development appear to increase the effectiveness of macroprudential policies on financial inclusion. Institutional quality helps macroprudential policies boost financial inclusion, with mixed effects as a result of financial development, but the results are more significant when we include either institutional quality or financial development. This leads us to believe that macroprudential policies conditional on better institutional quality and financial development improves financial inclusion. This has important policy implications for financial stability

Therapeutic Potential of 25-Hydroxyvitamin D in Promoting Cardiovascular Health

Introduction: The primary focus on vitamin D therapy was to treat metabolic bone disease. Over the past decade, however, researchers have demonstrated that vitamin D may have a role in other disease processes, particularly cardiovascular diseases (CVDs). Review: Serum 25-hydroxyvitamin D (25(OH)D) deficiency is widespread, and is extremely common in kidney transplant recipients. In community surveys, lower levels of 25(OH)D were associated with significantly higher adjusted prevalence of cardiovascular risk factors and CVD. CVD patients have lower 25(OH)D levels than controls, which are associated with more severe disease and worse prognosis. 25(OH)D levels are inversely associated with insulin resistance and future risk of hyperglycemia in non-diabetic subjects. Low levels of 25(OH)D were found to be independent predictors of death and end stage renal disease (ESRD) in chronic kidney disease (CKD) patients. Supplementation with vitamin D was found to lower parathyroid hormone and increase anti-inflammatory cytokines in congestive heart failure patient. It was found to improve flow mediated vasodilatation of the brachial artery in asymptomatic vitamin D deficient subjects and diabetic patients. Vitamin D supplementation was found to reduce proteinuria, mortality and progression to dialysis in CKD patients and to reduce cardiovascular mortality in hemodialysis patients. Vitamin D and calcium supplementation was also found to reduce cancer risk in community dwelling healthy postmenopausal women. Conclusion: Low levels of vitamin D seem to have undesirable effects on health. Based on the results of recent research, the recommended lower value of serum 25(OH)D is likely to be elevated. Key Words: Vitamin D; Cardiovascular disease ; Chronic kidney diseas

Right mini-thoracotomy versus median sternotomy for mitral valve replacement

Background: The advantages of minimally invasive mitral valve surgery over the conventional approach is still debated. This study aimed to evaluate early outcomes after mitral valve replacement (MVR) using the right mini-thoracotomy (RMT) versus median sternotomy (MS). Methods: We prospectively included 60 patients who had MVR from May 2015 to June 2017. We classified patients into two groups; Group A (n= 30) had RMT, and Group B (n= 30) had MS. Postoperative pain score, wound satisfaction, and clinical and echocardiographic outcomes were compared between both groups. Results: The mean age was 39.90 ± 12.34 years in Group A and 45.75 ± 13.10 years in Group B (p= 0.08). Preoperative and echocardiographic data showed no statistical significance difference between the groups. Group A had longer aortic cross-clamp (118.85 ± 40.56 vs. 70.75 ± 24.81 minutes, p<0.001) and cardiopulmonary bypass times (186.70 ± 67.44 vs. 104.65 ± 42.60 minutes, p<0.001).  Group B had more blood loss (565 ± 344.3 vs. 241.5 ±89.16 ml/24 hours, p<0.001). The median pain score was 1 (range: 1- 3) in Group A and 4 (2- 8) in Group B (p<0.001), and the median wound satisfaction was 1.5 (1- 4) in Group A and 4 (1- 7) in Group B (p<0.001).  Wound infection occurred in 1 (3.3%) patient in Group A and 6 (20%) patients in Group B (p=0.04). Conclusion: Mitral valve replacement through the right mini-thoracotomy could be a safe alternative to median sternotomy. The right mini-thoracotomy was associated with longer operative times but better pain and wound satisfaction scores and lower wound infection

Hypoxic regulation of cytoglobin and neuroglobin expression in human normal and tumor tissues

<p>Abstract</p> <p>Background</p> <p>Cytoglobin (Cygb) and neuroglobin (Ngb) are recently identified globin molecules that are expressed in vertebrate tissues. Upregulation of Cygb and Ngb under hypoxic and/or ischemic conditions <it>in vitro </it>and <it>in vivo </it>increases cell survival, suggesting possible protective roles through prevention of oxidative damage. We have previously shown that Ngb is expressed in human glioblastoma multiforme (GBM) cell lines, and that expression of its transcript and protein can be significantly increased after exposure to physiologically relevant levels of hypoxia. In this study, we extended this work to determine whether Cygb is also expressed in GBM cells, and whether its expression is enhanced under hypoxic conditions. We also compared Cygb and Ngb expression in human primary tumor specimens, including brain tumors, as well as in human normal tissues. Immunoreactivity of carbonic anhydrase IX (CA IX), a hypoxia-inducible metalloenzyme that catalyzes the hydration of CO₂to bicarbonate, was used as an endogenous marker of hypoxia.</p> <p>Results</p> <p>Cygb transcript and protein were expressed in human GBM cells, and this expression was significantly increased in most cells following 48 h incubation under hypoxia. We also showed that Cygb and Ngb are expressed in both normal tissues and human primary cancers, including GBM. Among normal tissues, Cygb and Ngb expression was restricted to distinct cell types and was especially prominent in ductal cells. Additionally, certain normal organs (<it>e.g. </it>stomach fundus, small bowel) showed distinct regional co-localization of Ngb, Cygb and CA IX. In most tumors, Ngb immunoreactivity was significantly greater than that of Cygb. In keeping with previous <it>in vitro </it>results, tumor regions that were positively stained for CA IX were also positive for Ngb and Cygb, suggesting that hypoxic upregulation of Ngb and Cygb also occurs <it>in vivo</it>.</p> <p>Conclusions</p> <p>Our finding of hypoxic up-regulation of Cygb/Ngb in GBM cell lines and human tumor tissues suggests that these globin molecules may be part of the repertoire of defense mechanisms that allow cancer cells to survive in hypoxic microenvironments.</p

Improvement of Gas Turbine Performance Using Multi-Stage Inlet Air Cooling System

Gas turbines play a significant role as an energy source if it has been designed according to the ISO operating conditions taking into consideration the operating conditions varied with the variation of the ambient conditions. This work aims to determine the effect of many parameters like the temperature at the compressor inlet, relative humidity, pressure ratios, and polytropic efficiency on each component of gas turbine performance (compressor, combustion chamber, and turbine). In this work, the Engineering Equation Solver (EES) software is used to calculate exergy destruction, net power, and all efficiencies (1st law and 2nd efficiency). After that, the validation of the code generated through EES software is performed using the actual performance data from the Heliopolis gas turbine power plant 25 MW. model, (GE GT-TM) made by GE. The results show the performance of the overall gas turbine behaves with and without a multi-stage cooling system. &nbsp;In addition, the effect of using the new inlet air cooling system on the gas turbine performance improvement under different conditions is determined. It is worth mentioning that the maximum power output increase is about 14.3% at the maximum ambient temperature (313oK). While the change of the 1st low efficiency and the 2nd low efficiency are so small it could be neglected. Also, the results illustrate that first and second law efficiencies provide quantitative and qualitative compressor performance assessments. The present multi-stage cooling system reduces the back-period cost if it uses a chiller system. Adding a chilling system before the fogging cooling system reflects the downsizing of the chilling system. This means low initial capital investment costs and low total annual costs. In addition, the multi-stage cooling system capital cost will be cashback during the first year regarding recovered power pric

Optimirana i validirana protočna injekcijska spektrofotometrijska analiza topiramata, piracetama i levetiracetama u farmaceutskim pripravcima

Application of a sensitive and rapid flow injection analysis (FIA) method for determination of topiramate, piracetam, and levetiracetam in pharmaceutical formulations has been investigated. The method is based on the reaction with ortho-phtalaldehyde and 2-mercaptoethanol in a basic buffer and measurement of absorbance at 295 nm under flow conditions. Variables affecting the determination such as sample injection volume, pH, ionic strength, reagent concentrations, flow rate of reagent and other FIA parameters were optimized to produce the most sensitive and reproducible results using a quarter-fraction factorial design, for five factors at two levels. Also, the method has been optimized and fully validated in terms of linearity and range, limit of detection and quantitation, precision, selectivity and accuracy. The method was successfully applied to the analysis of pharmaceutical preparations.Opisana je osjetljiva i brza protočna injekcijska analiza (FIA) za određivanje topiramata, piracetama i levetiracetama u farmaceutskim pripravcima. Metoda se temelji na reakciji ortho-ftalaldehida i 2-merkaptoetanola u bazičnom puferu i mjerenju apsorbancije na 295 nm u protočnim uvjetima. U svrhu povećanja osjetljivosti i dobivanja reproducibilnih rezultata optimirane su varijable koje utječu na određivanje kao što su volumen injektiranog uzorka, pH, ionska jakost, koncentracija reagensa, brzina protoka reagensa i drugi FIA parametri koristeći četvrt-frakcijski faktorijalni dizajn, za pet faktora na dva nivoa. Metoda je optimirana i potpuno validirana (linearnost, područje određivanja, granica detekcije i kvantifikacije, preciznost, selektivnost i točnost). Metoda je uspješno primijenjena za analizu farmaceutskih pripravaka

The Effectiveness of Interspersal Strategy in the Improving Accuracy Level to Solve Mathematics Problems and Task Engagement among Grade 4 Students with Learning Disabilities at the Sultanate of Oman

This study aimed to identify the effectiveness of interspersal strategy in improving accuracy level to solve mathematics problems and facilitating task engagement among grade 4 students with learning disabilities. The study sample included 20 students. They were divided randomly into two equal groups each consisting of 10 students; experimental group and controll group. The researchers used the semi-experimental method. The researchers designed mathematical problems tests, a task engagement scale and a manual for the implementation of the interspersal strategy. The findings of the study revealed statistically significant differences between the result of the pre and post-test of the experimental group in favor of the post-test. Additionally, there were statistically significant differences between the average achieved by the experimental group and the controlled group in relation to the mathematics problems. Furthermore, the study found out that there were statistically significant differences between the average resulting from the pre and post-tests relative to the level of task engagement. However, there were no statistically significant differences between the average achieved by the experimental group and the controlled group in the engagement on task

Utility of diffusion weighted imaging (DWI) in assessment of liver fibrosis

Objectives: hepatic fibrosis occurs due to chronic liver injury. Early fibrosis can be reversed by treatment with specific antifibrotic therapy in addition to removal of the cause if possible, that is why, identification of the early liver fibrosis is important. MRI DWI is a non-invasive non-contrast imaging technique which help in diagnosis of different stages of hepatic fibrosis.Aim of the work: was to study the predictive value of diffusion weighted MRI for assessing liver fibrosis in comparison to liver biopsy in chronic hepatitis C virus patients.Methods: all the studied cases were subjected to the followings: (1) History and laboratory examination (PCR for HCV and liver function tests). (2) MRI DWI and post processing ADC map. (3) Percutaneous liver biopsy in cases with HCV for histopathological examination to assess the stage of fibrosis.Results: this study was carried out on 75 subjects, divided into two group, 50 cases and 25 controls, the mean age in the two studied groups was 36.5 ± 9.32 and 35.8 ± 6.75 respectively in patients and control. ADC of both liver and spleen showed a highly significant increase in the control than in the cases with mean liver ADC in the control group = 2.3 ± 0.25. There was a significant negative correlation between the mean ADC of the liver, spleen and the stage of liver fibrosis