On the evolution of flow topology in turbulent Rayleigh-Bénard convection

Copyright 2016 AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.Small-scale dynamics is the spirit of turbulence physics. It implicates many attributes of flow topology evolution, coherent structures, hairpin vorticity dynamics, and mechanism of the kinetic energy cascade. In this work, several dynamical aspects of the small-scale motions have been numerically studied in a framework of Rayleigh-Benard convection (RBC). To do so, direct numerical simulations have been carried out at two Rayleigh numbers Ra = 10(8) and 10(10), inside an air-filled rectangular cell of aspect ratio unity and pi span-wise open-ended distance. As a main feature, the average rate of the invariants of the velocity gradient tensor (Q(G), R-G) has displayed the so-calledPeer ReviewedPostprint (author's final draft

New subgrid-scale models for large-eddy simulation of Rayleigh-Bénard convection

Published under licence in Journal of Physics: Conference Series by IOP Publishing Ltd. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.At the crossroad between flow topology analysis and the theory of turbulence, a new eddy-viscosity model for Large-eddy simulation has been recently proposed by Trias et al.[PoF, 27, 065103 (2015)]. The S3PQR-model has the proper cubic near-wall behaviour and no intrinsic limitations for statistically inhomogeneous flows. In this work, the new model has been tested for an air turbulent Rayleigh-Benard convection in a rectangular cell of aspect ratio unity and n span-wise open-ended distance. To do so, direct numerical simulation has been carried out at two Rayleigh numbers Ra = 108 and 1010, to assess the model performance and investigate a priori the effect of the turbulent Prandtl number. Using an approximate formula based on the Taylor series expansion, the turbulent Prandtl number has been calculated and revealed a constant and Ra-independent value across the bulk region equals to 0.55. It is found that the turbulent components of eddy-viscosity and eddy-diffusivity are positively prevalent to maintain a turbulent wind essentially driven by the mean buoyant force at the sidewalls. On the other hand, the new eddy-viscosity model is preliminary tested for the case of Ra = 108 and showed overestimation of heat flux within the boundary layer but fairly good prediction of turbulent kinetics at this moderate turbulent flow.Peer ReviewedPostprint (published version

AXIAL Crushing Of Thin-Walled Tube With Hole Under Quasi-Static Loading

Thin-walled tube is one of the energy absorbing structure utilized to dissipate energy and increase the efficiency of crashworthiness. During the accident, thin-walled tube dissipates the kinetic energy of the structure and converts it into other form of energy. Thus, this gives enough energy dissipation before hitting the human. This study examines the circular and square thin-walled tubes of mild steel subjected to axial crushing test by using Instron machine. These tubes include imperfection (round holes) located at three different locations. The theoretical results obtained from mathematical equations for the circular and square tubes crushing have been compared to the experimental results and a good agreement has been achieved between the theoretical and experimental results. The analysis of load-displacement characteristics includes the peak load, energy absorption capacity, mean crushing load, crush force efficiency (CFE), and specific energy absorption(SEA) results. The diameter, location and number of the holes were varied to investigate the effect of these parameters to the load-displacement characteristics. The location of round hole is located in 3 different level in the tube. As a result, the circular tube is capable of providing better decrease peak load and higher absorbed energy compared to the square tube.It was found that the better specimen is the circular tube with multi-hole, due to it has the excellent result in decrease the peak load reached to 16 %, it was concluded that value of the peak load is optimum in circular thin-walled tube. While the value of energy absorption slightly decreases in all specimens with holes compared with tube without hole. The location of holes in circular tube has the effect on the type of deformation. However, it does not affect the deformation in the square tube the location unaffected on the deformation. At the end, the modifications performed on the original tube shows an improvement in the load-displacement characteristics. The information obtained in this study will serve as a guide to better design the thin-walled tube in the future

“Thinking Out of the Box” from Out of the Box! Increasing the Dimension of “Starting Point” Case Study: Architecture Students

To start a design process with plan and section in 2D environment (pen and paper) will exclude thousands of possibilities, which the designer will never be able to consider them. The 2D designer will never touch upon the rich world of complexity. Starting the design from higher dimension is the solution to get rid of old conventional designing methods. Adding extra dimension to the “starting point” is applying CAD (computer aided architectural design) software not to extrude the 2D lines, but thinking from a higher dimension. Now thinking out of the box from out of the box becomes possible. To prove the hypothesis, authors decided to conduct an experiment and asked a group of architecture students to design a same architectural task with different dimensions. First the conventional pen and paper in 2D and the second time applying 3D environment interface of their own choice for the same task. The jury of experts concluded that students were more creative when they chose a 3D interface (higher dimension)

A study of the efficacy of furosemide as a prophylaxis of acute renal failure in coronary artery bypass grafting patients: A clinical trial

BACKGROUND: Renal failure is a frequent event after coronary artery bypass grafting (CABG). Hemodynamic alterations during surgery as well as the underlying disease are the predisposing factors. We aimed to study intermittent furosemide therapy in the prevention of renal failure in patients undergoing CABG. METHODS: In a single-blind randomized controlled trial, 123 elective CABG patients, 18-75 years, entered the study. Clearance of creatinine, urea and water were measured. Patients were randomly assigned into three groups: furosemide in prime (0.3-0.4 mg/kg); intermittent furosemide during CABG (0.2 mg/kg, if there was a decrease in urinary excretion) and control (no furosemide). RESULTS: There was a significant change in serum urea, sodium and fluid balance in �intermittent furosemide� group; other variables did not change significantly before or after the operation. Post-operative fluid balance was significantly higher in �intermittent furosemide� group (2573 ± 205 ml) compared to control (1574 ± 155 ml) (P < 0.010); also, fluid balance was higher in �intermittent furosemide� group (2573 ± 205 ml) compared to �furosemide in prime� group (1935 ± 169 ml) (P < 0.010). CONCLUSION: The study demonstrated no benefit from intermittent furosemide in elective CABG compared to furosemide in prime volume or even placebo. © 2015, Isfahan University of Medical Sciences(IUMS). All rights reserved

A priori study of subgrid-scale features in turbulent Rayleigh-Bénard convection

At the crossroad between flow topology analysis and turbulence modeling, a priori studies are a reliable tool to understand the underlying physics of the subgrid-scale (SGS) motions in turbulent flows. In this paper, properties of the SGS features in the framework of a large-eddy simulation are studied for a turbulent Rayleigh-Bénard convection (RBC). To do so, data from direct numerical simulation (DNS) of a turbulent air-filled RBC in a rectangular cavity of aspect ratio unity and p spanwise open-ended distance are used at two Rayleigh numbers Ra € (108, 1010) [Dabbagh et al.,Peer ReviewedPostprint (author's final draft

Use of microarray technology for the detection of a range of RNA viruses in clinical samples

There are many RNA virus pathogens of humans including influenza, parainfluenza, enteroviruses, parechoviruses, coronaviruses, pneumoviruses, and metapneumoviruses. These commonly invade and infect the respiratory and gastrointestinal tracts, giving rise to acute and chronic respiratory tract infections, and some may also reach the central nervous system (CNS) either via haematogenous or neural routes resulting in a variety of clinical presentations, (e.g. meningitis, encephalitis) which may lead to severe irreparable damage such as poliomyelitis especially in young children. Early correct diagnosis of viral infections is indispensable in order to prevent potential outbreaks which threaten the public health worldwide and might lead to high morbidity and some with significant mortality. Several laboratory techniques such as virus isolation, direct visualization of viral particles, detection of viral antigens and/or nucleic acids, and detection of host immune response (e.g. anti-viral antibodies) to infection, are available for diagnosis, but may have significant drawbacks such as time-inefficiency, cost and certain individual limitations. Microarray technology offers one way to overcome some of these limitations. In this study, a microarray chip containing 7967 oligonucleotides (probes) covering the whole genomes of human enteroviruses, rhinoviruses, respiratory syncytial viruses, metapneumoviruses and influenza viruses was designed and constructed using both OligoArray and Agilent eArray software, to allow simultaneous detection of any of the above viruses present in any clinical specimen. This virochip was tested against positive controls and clinical samples known to contain RNA nucleic acids of these viruses. Viral RNA was reverse transcribed, and amplified. Considerable effort was expended in trying to optimise a multiple displacement amplification (MDA) protocol for whole genome amplification, and in addition, long-range PCR was also utilised. Amplification products were fragmented, labelled and loaded into a hybridization reaction with the designed viral probes printed on the virochip. The results revealed (i) a number of technical problems associated with MDA; (ii) that some probes either failed to recognise their intended targets, or produced cross-reactive signals with non-intended targets; (iii) that many of the designed probes hybridized to their relevant viral nucleic acids and generated hybridization signals of high fluorescent intensity offering an opportunity to develop this probe array in order to be used for the identification of a wide variety of virus species up to the serogroup level or beyond (if required) specifically those causing CNS and respiratory tract infections

Detection of Toxoplasma gondii IgM and Cytomegalovirus IgM antibodies among blood donors in Mosul

Background: Toxoplasmosis is an infection caused by the protozoan parasite Toxoplasma gondii. This parasite can be transmitted via blood transfusion. Cytomegalovirus (CMV) is a herpes virus that can cause many complications and mostly transfer via blood transfusion. The aim of this study was to evaluate the percentage of risk of infections that could occur due to blood transfusion. Subjects and methods: Ninety blood donor samples were randomly obtained from central blood bank of Mosul city and investigated for IgM of toxoplasmosis and CMV by the serological method ELISA, IgM. Results: ELISA test for Toxoplasma gondii IgM test showed 3% seropositive and for CMV showed 10% seropositive. Conclusion: The results indicate a risk of infection with toxoplasmosis and CMV via blood transfusion

The effect of different bleaching protocols, used with and without sodium ascorbate, on bond strength between composite and enamel

This in vitro study aims to evaluate whether a solution of 10% sodium ascorbate (SA) may exert a beneficial effect on the bonding of composite to enamel after using different bleaching agents and protocols. Microtensile bond strength (μTBS) was evaluated on 72 freshly extracted human central incisors, divided into eight experimental groups and one control group (total n = 9): Group 1 serves as control (nonbleached). Group 2 was bleached with 5% carbamide peroxide. Group 3 was bleached with 5% carbamide peroxide and then treated with 10% SA. Group 4 was bleached with 10% carbamide peroxide. Group 5 was bleached with 10% carbamide peroxide, then treated with 10% SA. Group 6 was bleached with 16% carbamide peroxide. Group 7 was bleached with 16% carbamide peroxide, then treated with 10% SA. Group 8 was bleached with 6% hydrogen peroxide. Group 9 was bleached with 6% hydrogen peroxide, then treated with 10% SA. All groups were restored immediately after the different treatments using a resin composite. The μTBS values were measured using a universal testing machine and statistical analysis was performed by means of normality and variance analyses, SIDAK test for univariate test and multiple comparisons, and Student test to compare μTBS values of each group with the control. The mean μTBS values in groups 2, 4, 6, 8 were significantly lower than controls. For groups 3, 5, 7, 9, subjected to antioxidant (10% SA) application, all μTBS values increased significantly. However, only for Groups 3 and 5 there was no significant difference with the control. Applying 10% SA for 10 min may improve the bond strength composite/bleached enamel just when whitening is performed with 5% and 10% carbamide peroxide