MHD free convection-radiation interaction in a porous medium - part I : numerical investigation

A numerical investigation of two dimensional steady magnetohydrodynamics heat and mass transfer by laminar free convection from a radiative horizontal circular cylinder in a non-Darcy porous medium is presented by taking into account the Soret/Dufour effects. The boundary layer conservation equations, which are parabolic in nature, are normalized into non-similar form and then solved numerically with the well-tested, efficient, implicit, stable Keller–Box finite-difference scheme. We use simple central difference derivatives and averages at the mid points of net rectangles to get finite difference equations with a second order truncation error. We have conducted a grid sensitivity and time calculation of the solution execution. Numerical results are obtained for the velocity, temperature and concentration distributions, as well as the local skin friction, Nusselt number and Sherwood number for several values of the parameters. The dependency of the thermophysical properties has been discussed on the parameters and shown graphically. The Darcy number accelerates the flow due to a corresponding rise in permeability of the regime and concomitant decrease in Darcian impedance. A comparative study between the previously published and present results in a limiting sense is found in an excellent agreement

Singularity in Gravitational Collapse of Plane Symmetric Charged Vaidya Spacetime

We study the final outcome of gravitational collapse resulting from the plane symmetric charged Vaidya spacetime. Using the field equations, we show that the weak energy condition is always satisfied by collapsing fluid. It is found that the singularity formed is naked. The strength of singularity is also investigated by using Nolan's method. This turns out to be a strong curvature singularity in Tipler's sense and hence provides a counter example to the cosmic censorship hypothesis.Comment: 8 pages, accepted for publication in Mod. Phys. Lett

Assessment Of Pond Water Quality Of Thakurgaon Sadar Upazila For Fish Production

During dry season, physico-chemical properties of waters from 30 ponds of Thakugaon Sadar Upazila, Thakurgaon, Bangladesh were analyzed for its quality and suitability for aquaculture. The variation in the physico-chemical parameters of the aquaculture ponds above or below standard values has potential effects on the health and productivity of aquaculture. Overall, we found that the pond water were acidic to neutral in nature (pH varied from 6.0 to 7.2) and could be suitable for aquaculture. The dissolved oxygen (DO) concentration was suitable for fish production but more DO level should be present for all aquatic life especially for fish production. Chemical oxygen demands (COD) of all pond waters were within the permissible limits for fish production. The temperature values were remained within the standard values in all the aquaculture ponds. Pond water samples contained Ca2+, Mg2+ and Na+ as the dominant cations and HCO3- and Cl- were the dominant anions. All samples were within soft class regarding hardness. Based on Zn2+, Mn2+, Fe3+, SO42-, NO3- and Cl- all pond water samples were within the safe limit for fish production during dry period. Int. J. Agril. Res. Innov. & Tech. 3 (1): 29-34, June, 2013 DOI: http://dx.doi.org/10.3329/ijarit.v3i1.1605

Synthesis and antibacterial evaluation of 2-(1,3- Benzodioxol-5-ylcarbonyl)arylsulfonohydrazide derivatives

Purpose: To study the antibacterial activity of various sulfonamides derived from 1,3-benzodioxol-5- carbohydrazide.Methods: The synthesis involved the conversion of 1,3-benzodioxol-5-carboxylic acid (1) to ethyl 1,3- benzodioxol-5-carboxylate (2) and then to 1,3-benzodioxol-5-carbohydrazide (3). The target molecules, 2-(1,3-benzodioxol-5-ylcarbonyl)arylsulfonohydrazide derivatives (5a-l) were synthesized through a benignant method from aqueous medium by the reaction of 3 and arylsulfonyl chlorides (4a-l). The structural formulae of the synthesized compounds were characterized by infra red spectroscopy (IR), proton nuclear magnetic resonance (1H-NMR) and electron impact mass spectrometry (EI-MS). The compounds were screened for in vitro antibacterial activity by determining their minimum inhibitory concentration (MIC).Results: The molecule, 5k, bearing 2-hydroxy-3,5-dichlorophenyl group exhibited the highest activity with MIC of 11.92 ± 3.40 (S. typhi), 8.37 ± 2.22 (E. coli), 9.28 ± 2.31 (P. aeroginosa), 11.76 ± 1.30 (B. subtilis) and 10.30 ± 1.63 (S. aureus) μmoles/L relative to that of ciprofloxacin with 9.42 ± 1.09, 8.02 ± 2.17, 8.11 ± 1.32, 8.88 ± 2.00 and 9.23 ± 1.87 μmoles/L respectively.Conclusion: The most potent of the synthesized compounds (5k) posesses moderate activity against all the bacterial strains, while 5g remained completely inactive.Keywords: 1,3-Benzodioxol-5-carboxylic acid, Antibacterial activity, Sulfonohydrazide, Synthesi

MHD free convection-radiation interaction in a porous medium - part II : Soret/Dufour effects

This paper is focused on the study of two dimensional steady magnetohydrodynamics heat and mass transfer by laminar free convection from a radiative horizontal circular cylinder in a nonDarcy porous medium by taking account the Soret/Dufour effects. The boundary layer equations, which are parabolic in nature, are normalized into non-similar form and then solved numerically with the well-tested, efficient, implicit, stable Keller–Box finite-difference scheme. Numerical results obtained for the velocity, temperature and concentration distributions, as well as the local skin friction, Nusselt number and Sherwood number for several values of the parameters, namely the buoyancy ratio parameter, Prandtl number, Forchheimer number, magnetohydrodynamic body force parameter, Soret and Dufour numbers. The dependency of the thermophysical properties has been discussed on the parameters and showed graphically. Increasing Forchheimer inertial drag parameter reduces velocity but elevates temperature and concentration. Increasing Soret number and simultaneously reducing Dufour number greatly boosts the local heat transfer rate at the cylinder surface. A comparative study between the previous published and present results in a limiting sense is found in an excellent agreement

Thermal Marangoni Convection of Two-phase Dusty Fluid Flow along a Vertical Wavy Surface

The paper considers the influence of thermal Marangoni convection on boundary layer flow of two-phase dusty fluid along a vertical wavy surface. The dimensionless boundary layer equations for two-phase problem are reduced to a convenient form by primitive variable transformations (PVF) and then integrated numerically by employing the implicit finite difference method along with the Thomas Algorithm. The effect of thermal Marangoni convection, dusty water and sinusoidal waveform are discussed in detail in terms of local heat transfer rate, skin friction coefficient, velocity and temperature distributions. This investigation reveals the fact that the water-particle mixture reduces the rate of heat transfer, significantly

Dynamics of Charged Plane Symmetric Gravitational Collapse

In this paper, we study dynamics of the charged plane symmetric gravitational collapse. For this purpose, we discuss non-adiabatic flow of a viscous fluid and deduce the results for adiabatic case. The Einstein and Maxwell field equations are formulated for general plane symmetric spacetime in the interior. Junction conditions between the interior and exterior regions are derived. For the non-adiabatic case, the exterior is taken as plane symmetric charged Vaidya spacetime while for the adiabatic case, it is described by plane Reissner-Nordstr$\ddot{o}$m spacetime. Using Misner and Sharp formalism, we obtain dynamical equations to investigate the effects of different forces over the rate of collapse. In non-adiabatic case, a dynamical equation is joined with transport equation of heat flux. Finally, a relation between the Weyl tensor and energy density is found.Comment: 21 pages, accepted for publication Gen. Relativ. Gra

Simulation of natural convective boundary layer flow of a nanofluid past a convectively heated inclined plate in the presence of magnetic field

AbstractThis paper deals with the numerical simulation of transient magnetohydrodynamics natural convective boundary layer flow of a nanofluid over an inclined plate. In the modeling of nanofluids, dynamic effects including the Brownian motion and thermophoresis are taken into account. Numerical solutions have been computed via the Galerkin-finite element method. The effects of angle of inclination, buoyancy-ratio parameter, Brownian motion, thermophoresis and magnetic field are taken into account and controlled by non-dimensional parameters. To compute the rate of convergence and error of the computed numerical solution, the double mesh principle is used. Similarity solutions are calculated and presented graphically for non-dimensional velocity, temperature, local rate of heat and mass transfer with pertinent parameters. The modified Nusselt number decreases with increasing inclination angle, buoyancy-ratio parameter, Brownian motion and thermophoresis parameter, whereas it increases with increasing Prandtl number. Validation of the results is achieved with earlier results for forced convective flow and non-magnetic studies. Such problems have several applications in engineering and petroleum industries such as electroplating, chemical processing of heavy metals and solar water heaters. External magnetic fields play an important role in electrical power generation, inclination/acceleration sensors, fine-tuning of the final materials to industrial specification because of their controlling behaviour on the flow characteristics of nanofluids

Deregulated expression of CD40 ligand in HTLV-I infection: Distinct mechanisms of downregulation in HTLV-I-transformed cell lines and ATL patients

AbstractHTLV-I infection is associated with the development of adult T cell leukemia (ATL) and the neuroinflammatory disease HAM/TSP. There are quantitative and qualitative differences in the antiviral cytotoxic T cell (CTL) response in ATL and HAM/TSP although the underlying mechanisms are unclear. Here, we demonstrate that the HTLV-I Tax trans-activating protein is a transcriptional activator of CD40 ligand (CD40L), a critical regulator of dendritic cell maturation and adaptive immunity. Tax activates CD40L expression via a cyclosporin A insensitive pathway that is also independent of NF-κB. Although Tax upregulates CD40L gene expression, CD40L expression is absent in Tax-expressing HTLV-I-transformed cell lines via an epigenetic mechanism involving methylation. T lymphocytes cultured ex vivo from ATL patients, but not HAM/TSP or normal controls, exhibit a potent block in the induction of CD40L, but not CD69. However, the CD40L gene is not silenced by methylation in ATL patients, thus CD40L is downregulated by distinct mechanisms in HTLV-I-transformed cell lines and ATL patients

Polymorphisms in MTHFR, MS and CBS Genes and Homocysteine Levels in a Pakistani Population

Background: Hyperhomocysteinemia (\u3e15 mol/L) is highly prevalent in South Asian populations including Pakistan. In order to investigate the genetic determinants of this condition, we studied 6 polymorphisms in genes of 3 enzymes--methylenetetrahydrofolate reductase (MTHFR, C677T, A1298C), methionine synthase (MS, A2756G), cystathionine-beta-synthase (CBS, T833C/844ins68, G919A) involved in homocysteine metabolism and investigated their interactions with nutritional and environmental factors in a Pakistani population. Methodology/Principal Findings: In a cross-sectional survey, 872 healthy adults (355 males and 517 females, age 18-60 years) were recruited from a low-income urban population in Karachi. Fasting venous blood was obtained and assessed for plasma/serum homocysteine, folate, vitamin B12, pyridoxal phosphate and blood lead. DNA was isolated and genotyping was performed by PCR-RFLP (restriction-fragment-length-polymorphism) based assays. The average changes in homocysteine levels for MTHFR 677CT and TT genotypes were positive [beta(SE beta), 2.01(0.63) and 16.19(1.8) mol/L, respectively]. Contrary to MTHFR C677T polymorphism, the average changes in plasma homocysteine levels for MS 2756AG and GG variants were negative [beta(SE beta), -0.56(0.58) and -0.83(0.99) mol/L, respectively]. The average change occurring for CBS 844ins68 heterozygous genotype (ancestral/insertion) was -1.88(0.81) mol/L. The combined effect of MTHFR C677T, MS A2756G and CBS 844ins68 genotypes for plasma homocysteine levels was additive (p valu