Effects of MHD free convection and mass transfer on the flow past a vibrating infinite vertical circular cylinder

The effects of MHD free convection and mass transfer are taken into account on the flow past a vibrating infinite isothermal and constant heat flux vertical circular cylinder. The expressions for velocity, temperature, concentration and skin-friction of the fluid are obtained in closed form by using Laplace transform technique. The effects ofPr (Prandtl number),Sc (Schmidt number),Gr (Grashof number,Gr>0 implies cooling andGr<0 heating of the cylinder),Gm (modified Grashof number),M (magnetic field parameter) and variation of time on velocity distribution have been studied graphically. The results presented in this paper agree with the results of Lien and Chen when magnetic parameter approaches zero.

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Effekte der freien MHD Konvektion und der Stoffübertragung auf die Strömung längs eines vibrierenden unendlich langen vertikalen Kreiszylinders

Zusammenfassung Es werden die Effekte der freien MHD Konvektion und der Stoffübertragung auf die Strömung längs eines vibrierenden unendlich langen vertikalen isothermen Kreiszylinders mit konstanter Wärmestromdichte untersucht. Es werden geschlossene Ausdrücke für die Geschwindigkeit, Temperatur, Konzentration und Wandreibung des Fluides mittels der Laplace-Transformation erhalten. Die Effekte der Prandtl-ZahlPr, Schmidt-ZahlSc, Grashof-ZahlGr (Gr>0 bedeutet kühlen,Gr<0 heizen), der modifizierten Grashof-ZahlGm, des ParametersM für das magnetische Feld und das zeitliche Verhalten der Geschwindigkeitsverteilung wurden graphisch untersucht. Die Ergebnisse dieser Untersuchung stimmen mit denen von Lien und Chen überein, wenn der Parameter für das magnetische Feld nahe bei 0 liegt.

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Nomenclature C _p Specific heat at constant temperature - C the species concentration near the circular cylinder - C _w the species concentration of the circular cylinder - C the species concentration of the fluid at infinite - * dimensionless species concentration - D chemical molecular diffusivity - g acceleration due to gravity - Gr Grashof number - Gm modified Grashof number - K thermal conductivity - Pr Prandtl number - r ₀ radius of the circular cylinder - r ₀ dimensionless radius - r, r coordinate and dimensionless coordinate normal to the circular cylinder - Sc Schmidt number - t time - t dimensionless time - T temperature of the fluid near the circular cylinder - T _w temperature of the circular cylinder - T temperature of the fluid at infinite - u velocity of the fluid - u dimensionless velocity of the fluid - U ₀ reference velocity - z, z coordinate and dimensionless coordinate along the circular cylinder - coefficient of volume expansion - * coefficient of thermal expansion with concentration - dimensionless temperature - H ₀ magnetic field intensity - coefficient of viscosity - _e permeability (magnetic) - kinematic viscosity - electric conductivity - density - M Hartmann number - dimensionless skin-friction - frequency - dimensionless frequency     

Different Heterocycles Functionalized s‐Triazine Analogues: Design,Synthesis and In Vitro Antimicrobial,Antituberculosis, and Anti‐HIV Assessment

Some new quinolone condensed s‐triazine derivatives endowed with different heterocycles and 4‐aminobenzonitrile moiety has been synthesized and examined for their bioactivities against eight bacteria (Staphylococcus aureus, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella typhi, Proteus vulgaris, and Shigella flexneri), two fungi (Aspergillus niger, Candida albicans) by using agar streak dilution method, and Mycobacterium tuberculosis H37Rv by using Lowenstein and Jensen MIC method. Upon preliminary biological screening, it was observed that the majority of the compounds were found to possess a significant broad spectrum antimicrobial (MICs: 6.25–25 µg/mL) and antitubercular (MIC: 12.5 µg/mL) potential. Hence, anti‐HIV activity against two types of HIV viral strains [HIV‐1 (III_B) and HIV‐2 (ROD)] has been carried out using the MTT assay. From this bioassay, we have identified some potent inhibitors acting as anti‐HIV‐1 agents (IC₅₀: 4.45 µg/mL) with promising therapeutic index of 16 for analogue 7 h. The structural assignments of the new products were carried out on the basis of IR, ¹H NMR, ¹³C NMR spectroscopy, and elemental analysis.     

PhI(OAc)2 and BF3–OEt2 mediated heterocyclization: metal-free synthesis of pyrimidine-annulated oxazolines

A simple high yielding and highly efficient synthesis of oxazoline ring fused with uracil moiety is reported. Hypervalent iodine (PIDA) in the presence of BF₃–OEt₂ generates an effective electrophile to activate uracil C5–C6 double bond leading to heterocyclization.     

Designing of Optical Fiber Sensing Probe

Evanescent wave configuration has been extensively used in the development of fiber-optic sensor for different biomedical applications. In the present investigation we have theoretically proposed the designing of single-mode and multimode optical fiber sensing probes, which can be prepared by removing a few centimeters of cladding near the distal end of the step index optical fiber. In this theoretical study, we found that the removal of cladding causes V-number mismatching and this has led to the loss of signal acquisition from the sensing region. Therefore, to minimize these losses we have proposed to reduce the radius by step etch and tapering technique. It was found that step etching and tapering enhances the strength and penetration depth of the evanescent wave significantly.     

Bianchi type-II universe with linear equation of state

We have studied anisotropic and homogeneous Bianchi type-II cosmological model with linear equation of state (EoS) p = αρ?β, where α and β are constants, in General Relativity. In order to obtain the solutions of the field equations we have assumed the geometrical restriction that expansion scalar θ is proportional to shear scalar σ. The geometrical and physical aspects of the model are also studied.     

Stochastic petri net analysis of finite-population vacation queueing systems

We consider queueing systems in which the server occasionally takes a vacation of random duration. The vacation can be used to do additional work; it can also be a rest period. Several models of this problem have been analyzed in the past assuming that the population of the system is infinite. Similarly, it is generally assumed that the capacity of the system is infinite. In this paper we show how the finite-population system can be modeled by the stochastic Petri net. We also extend the model to the finite-capacity system. This research was sponsored by the SDIO Innovative Science and Technology Office and was managed by the Office of Naval Research under grant N3014-88-K-0623.     

Exploring dried blood spot sampling technique for simultaneous quantification of antiretrovirals: lamivudine, stavudine and nevirapine in a rodent pharmacokinetic study

A high‐performance liquid chromatography/positive ion electrospray tandem mass spectrometry method for the simultaneous quantification of lamivudine, stavudine and nevirapine was developed and validated in dried blood spot (DBS) cards. The analytes were separated using an isocratic mobile phase on a reverse phase column and analyzed by MS/MS in the MRM mode using the respective [M + H]⁺ ions, m/z 230–112 for lamivudine, m/z 225–127 for stavudine, m/z 267–226 for nevirapine, m/z 383–337 for zidovudine (IS). The lower limit of quantification was 1 ng/mL for both lamivudine and stavudine and 10 ng/mL for nevirapine. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The method was successfully applied to quantify them in a rat pharmacokinetic study in whole blood, plasma and DBS cards after a single oral co‐administration at the dose of 10, 2 and 13 mg/kg for lamivudine, stavudine and nevirapine, respectively, to male Wistar rats. Following oral administration the pharmacokinetic results in all the matrices are in close agreement. Thus accomplishment of this method would facilitate the ease of collection of clinical samples on DBS cards for lamivudine, stavudine and nevirapine during human clinical trials and therapeutic drug monitoring. Copyright © 2012 John Wiley & Sons, Ltd.     

Highly regio- and stereoselective ruthenium(II)-catalyzed direct ortho-alkenylation of aromatic and heteroaromatic aldehydes with activated alkenes under open atmosphere

Various aromatic and heteroaromatic aldehydes reacted with activated alkenes in the presence of a catalytic amount of [{RuCl(2)(p-cymene)}(2)], AgSbF(6), and Cu(OAc)(2)·H(2)O to give substituted alkene derivatives in a highly regio- and stereoselective manner. The corresponding alkene derivatives were further converted into unusual four-membered cyclic ketones or a polycyclic isochromanone derivative via a photochemical rearrangement. Notably, the catalytic reaction was conducted under an open atmosphere.