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Non-Newtonian Power-Law Fluid Flow and Heat Transfer over a Non-Linearly Stretching Surface  [PDF]
Kerehalli Vinayaka Prasad, Seetharaman Rajeswari Santhi, Pampanna Somanna Datti
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.35065
Abstract: The problem of magneto-hydrodynamic flow and heat transfer of an electrically conducting non-Newtonian power-law fluid past a non-linearly stretching surface in the presence of a transverse magnetic field is considered. The stretching velocity, the temperature and the transverse magnetic field are assumed to vary in a power-law with the distance from the origin. The flow is induced due to an infinite elastic sheet which is stretched in its own plane. The governing equations are reduced to non-linear ordinary differential equations by means of similarity transformations. These equations are then solved numerically by an implicit finite-difference scheme known as Keller-Box method. The numerical solution is found to be dependent on several governing parameters, including the magnetic field parameter, power-law index, velocity exponent parameter, temperature exponent parameter, Modified Prandtl number and heat source/sink parameter. A systematic study is carried out to illustrate the effects of these parameters on the fluid velocity and the temperature distribution in the boundary layer. The results for the local skin-friction coefficient and the local Nusselt number are tabulated and discussed. The results obtained reveal many interesting behaviors that warrant further study on the equations related to non-Newtonian fluid phenomena.
Utilization of a Deoxynucleoside Diphosphate Substrate by HIV Reverse Transcriptase
Scott J. Garforth, Michael A. Parniak, Vinayaka R. Prasad
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0002074
Abstract: Background Deoxynucleoside triphosphates (dNTPs) are the normal substrates for DNA synthesis catalyzed by polymerases such as HIV-1 reverse transcriptase (RT). However, substantial amounts of deoxynucleoside diphosphates (dNDPs) are also present in the cell. Use of dNDPs in HIV-1 DNA synthesis could have significant implications for the efficacy of nucleoside RT inhibitors such as AZT which are first line therapeutics for treatment of HIV infection. Our earlier work on HIV-1 reverse transcriptase (RT) suggested that the interaction between the γ-phosphate of the incoming dNTP and RT residue K65 in the active site is not essential for dNTP insertion, implying that this polymerase may be able to insert dNDPs in addition to dNTPs. Methodology/Principal Findings We examined the ability of recombinant wild type (wt) and mutant RTs with substitutions at residue K65 to utilize a dNDP substrate in primer extension reactions. We found that wild type HIV-1 RT indeed catalyzes incorporation of dNDP substrates whereas RT with mutations of residue K65 were unable to catalyze this reaction. Wild type HIV-1 RT also catalyzed the reverse reaction, inorganic phosphate-dependent phosphorolysis. Nucleotide-mediated phosphorolytic removal of chain-terminating 3′-terminal nucleoside inhibitors such as AZT forms the basis for HIV-1 resistance to such drugs, and this removal is enhanced by thymidine analog mutations (TAMs). We found that both wt and TAM-containing RTs were able to catalyze Pi-mediated phosphorolysis of 3′-terminal AZT at physiological levels of Pi with an efficacy similar to that for ATP-dependent AZT-excision. Conclusions We have identified two new catalytic functions of HIV-1 RT, the use of dNDPs as substrates for DNA synthesis, and the use of Pi as substrate for phosphorolytic removal of primer 3′-terminal nucleotides. The ability to insert dNDPs has been documented for only one other DNA polymerase, the RB69 DNA polymerase and the reverse reaction employing inorganic phosphate has not been documented for any DNA polymerase. Importantly, our results show that Pi-mediated phosphorolysis can contribute to AZT resistance and indicates that factors that influence HIV resistance to AZT are more complex than previously appreciated.
HIV-1 reverse transcriptase mutations that confer decreased in vitro susceptibility to anti-RT DNA aptamer RT1t49 confer cross resistance to other anti-RT aptamers but not to standard RT inhibitors
Timothy S Fisher, Pheroze Joshi, Vinayaka R Prasad
AIDS Research and Therapy , 2005, DOI: 10.1186/1742-6405-2-8
Abstract: The reverse transcriptase (RT) of the human immunodeficiency virus type 1 (HIV-1) is a multifunctional enzyme, capable of several discrete activities required for viral replication [1]. These essential activities include DNA- and RNA-dependent DNA polymerase (DDDP and RDDP), ribonuclease H (RNase H), strand transfer and strand displacement activities. Native HIV-1 RT is a heterodimer of p66 and p51 subunits, of which the p66 subunit contains both the polymerase and RNase H domains. The p51 subunit is derived by proteolytic cleavage of the p66 subunit and is thought to play both an architectural role in the context of the p66/p51 heterodimer as well as facilitate template·primer binding [2].Due to its essential role in synthesizing the double-stranded proviral DNA from single-stranded HIV-1 RNA genome, the HIV-1 RT is a major target of current antiviral therapies directed against HIV-1. Current anti-HIV drug regimens, termed highly active antiretroviral therapy (HAART), typically consist of a combination of at least three antiretroviral drugs, with two or more nucleotide reverse transcriptase inhibitors (NRTIs) being a staple of most regimens [3,4]. In addition to NRTIs, which are both competitive inhibitors and chain-terminators, the non-nucleoside reverse transcriptase inhibitors (NNRTIs) consist of structurally dissimilar hydrophobic compounds that bind to a hydrophobic pocket on the RT adjacent to, but distinct from, the active site, which accommodates dNTPs and NRTIs. While HAART regimens have decreased both the mortality and morbidity of HIV-infected individuals, several factors contribute to drug failure. The highly error-prone nature of HIV-1 RT [5,6] combined with a robust rate of viral replication [7,8] provides the virus with an ideal context for the emergence of resistant variants. In addition, the significant toxicity associated with the current crop of anti-HIV drugs often leads to noncompliance, which in turn results in treatment failure [9]. For these
Biorthogonal Wavelet Transform Digital Image Watermarking
B. Rajendra Prasad,k.Vinayaka Kota,B. Mysura Reddy
International Journal of Advanced Computer Research , 2012,
Abstract: With the growing popularity of Digital Mediasthrough the World Wide Web, intellectual propertyneeds copyright protection, prevention of illegalcopying and verification of content integrity. Thenew data hiding techniques need to be developedthat satisfy the requirements of Imperceptibility,Robustness, Capacity, or data hiding rate andSecurity of the hidden data etc. Watermarking hasbeen utilized by researchers for the security ofdigital documents. In this paper we proposed amethod which is an efficient scheme for protectingthe copyrights of digital images with the aid of bothbiometrics and digital watermarking. Newer datahiding techniques that satisfy the requirements ofimperceptibility, robustness, capacities, or datahiding rate and security of the hidden data etc., arebeing developed. Therefore the preference to go fordigital image watermarking, to show resiliencyagainst various unintentional or deliberate attackshas increased. In this paper implementation of twodifferent watermarking algorithms in the frequencydomain will be presented. The first algorithm isbased on the Discrete Wavelet Transform (DWT),the second one is based on the Bi-orthogonalWavelet Transform (BWT). Embedding thewatermark is done by modifying the coefficients ofthe middle frequency band within region of noninterest(RONI) so that the visibility of the imageand diagnosis capability will not be affected and thewatermark will not be removed by attacks. Allschemes are tested using medical images and thesimulation results are compared and thecomparison shows that the best scheme is that basedon using BWT.
Instability of retroviral vectors with HIV-1-specific RT aptamers due to cryptic splice sites in the U6 promoter
Stephen E Braun, Xuanling Shi, Gang Qiu, Fay Wong, Pheroze J Joshi, Vinayaka R Prasad, R Paul Johnson
AIDS Research and Therapy , 2007, DOI: 10.1186/1742-6405-4-24
Abstract: A series of retroviral vectors was generated carrying the U6+1 promoter with 3 different HIV-1 RT-specific RNA aptamers and one control aptamer, all in the reverse orientation. After shuttle packaging, the CD4+ cell line CEMx174 was transduced with each vector, selected for expression of GFP, and challenged with HIV-1. We did not observe inhibition of HIV-1 replication in these transduced populations. PCR amplification of the U6+1 promoter-RNA aptamer inhibitor cassette from transduced CEMx174 cells and RT-PCR amplification from transfected Phoenix (amphotropic) packaging cells showed two distinct products: a full-length product of the expected size as well as a truncated product. The sequence of the full-length PCR product was identical to the predicted amplicon sequence. However, sequencing of the truncated product revealed a 139 bp deletion in the U6 promoter. This deletion decreased transcriptional activity of the U6 promoter. Analysis of the deleted sequences from the U6 promoter in the antisense direction indicated consensus splice donor, splice acceptor and branch point sequences.The existence of a cryptic splice site in the U6 promoter when expressed in a retroviral vector in the reverse orientation generates deletions during packaging and may limit the utility of this promoter for expression of small RNA inhibitors.The tRNAs, U6 small nuclear (sn) RNA and adenovirus-virus-associated RNAs are normally expressed in cells at high levels by RNA polymerase III. These polymerase III promoters have been used in gene therapy applications to express a variety of inhibitory RNAs, including RNAi, aptamers, ribozymes, antisense RNAs, and decoy RNAs [1-5]. Retroviral and lentiviral vectors have been the primary method of gene delivery to carry these inhibitor cassettes [1,4]. Importantly, high levels of expression and inhibitory activity have been demonstrated in several studies targeting HIV-1 sequences with RNA polymerase III-driven inhibitory RNAs [4,5].While stable
Exceptional molecular and coreceptor-requirement properties of molecular clones isolated from an Human Immunodeficiency Virus Type-1 subtype C infection
Prasanta K Dash, Nagadenahalli B Siddappa, Asokan Mangaiarkarasi, Aruna V Mahendarkar, Padmanabhan Roshan, Krishnamurthy Anand, Anita Mahadevan, Parthasarathy Satishchandra, Susarla K Shankar, Vinayaka R Prasad, Udaykumar Ranga
Retrovirology , 2008, DOI: 10.1186/1742-4690-5-25
Abstract: Using this strategy, we isolated 8 full-length molecular clones from the donor. Two of the eight molecular clones, 03In94_D17 and 03In94_D24, (D17 and D24) generated replication-competent viruses. Phylogenetic analysis of the full-length viral sequences revealed that both clones were non-recombinant subtype C viruses. They contain intact open reading frames in all the viral proteins. Both the viral clones are endowed with several unique molecular and biological properties. The viral promoter of the clones is characterized by the presence of four NF-kB binding elements, a feature rarely seen in the subtype C HIV-1 LTR. Interestingly, we identified the coexistence of two different forms of Rev, a truncated form common to subtype C and a full-length form less common for this subtype, in both proviral and plasma virus compartments. An exceptional property of the viruses, atypical of subtype C, is their ability to use a wide range of coreceptors including CCR5, CXCR4, and several others tested. Sequence analysis of Env of D17 and D24 clones identified differences within the variable loops providing important clues for the expanded coreceptor use. The V1, V2 and V4 loops in both of the molecular clones are longer due to the insertion of several amino acid residues that generated potential N-linked glycosylation sites.The exceptional biological and molecular properties of these clones make them invaluable tools to understand the unique pathogenic characteristics of subtype C.Of the various subtypes of Human Immunodeficiency Type I (HIV-1) and their recombinant forms, the subtype C strains are responsible for the rapidly expanding epidemics in the most populous nations such as India, China, Sub-Saharan African countries and southern Brazil. [1]. More than half the new HIV-1 infections in the world [2] and nearly 99% of the infections of India [3] are due to subtype C. During the past decade, the infection incidence of subtype C in southern Brazil reportedly increased from 3
A bi-convex optimization problem to compute Nash equilibrium in n-player games and an algorithm
Vinayaka Yaji,Shalabh Bhatnagar
Computer Science , 2015,
Abstract: In this paper we present optimization problems with biconvex objective function and linear constraints such that the set of global minima of the optimization problems is the same as the set of Nash equilibria of a n-player general-sum normal form game. We further show that the objective function is an invex function and consider a projected gradient descent algorithm. We prove that the projected gradient descent scheme converges to a partial optimum of the objective function. We also present simulation results on certain test cases showing convergence to a Nash equilibrium strategy.
Drilling Optimization: A Review
Abhilash M Bharadwaj,Vinayaka S
International Journal on Theoretical and Applied Research in Mechanical Engineering , 2012,
Abstract: With rapidly growing global demand for energy resources, oil and gas exploration & production companies face mounting pressure to maximize supply and increase the rate of discovery for new energy sources. Increasingly operating in more remote locations and investing heavily in equipment and facilities, companies face greater financial and operational risks than ever before. Optimization of drilling parameters during drilling operations aims to optimize weight on bit, bit rotation speed for obtaining maximum drilling rate as well as minimizing the drilling cost. Communication and computer technologies are among the most important disciplines which can contribute to drilling optimization. Large amount of data could be piped through different locations on the planet in reliable and time efficient manners.
Drilling Optimization: A Review
Abhilash M Bharadwaj,Vinayaka S
International Journal on Theoretical and Applied Research in Mechanical Engineering , 2013,
Abstract: With rapidly growing global demand for energy resources, oil and gas exploration & production companies face mounting pressure to maximize supply and increase the rate of discovery for new energy sources. Increasingly operating in more remote locations and investing heavily in equipment and facilities, companies face greater financial and operational risks than ever before. Optimization of drilling parameters during drilling operations aims to optimize weight on bit, bit rotation speed for obtaining maximum drilling rate as well as minimizing the drilling cost. Communication and computer technologies are among the most important disciplines which can contribute to drilling optimization. Large amount of data could be piped through different locations on the planet in reliable and time efficient manners.
Antenatal Bartter Syndrome: A Review
Y. Ramesh Bhat,G. Vinayaka,K. Sreelakshmi
International Journal of Pediatrics , 2012, DOI: 10.1155/2012/857136
Abstract: Antenatal Bartter syndrome (ABS) is a rare autosomal recessive renal tubular disorder. The defective chloride transport in the loop of Henle leads to fetal polyuria resulting in severe hydramnios and premature delivery. Early onset, unexplained maternal polyhydramnios often challenges the treating obstetrician. Increasing polyhydramnios without apparent fetal or placental abnormalities should lead to the suspicion of this entity. Biochemical analysis of amniotic fluid is suggested as elevated chloride level is usually diagnostic. Awareness, early recognition, maternal treatment with indomethacin, and amniocentesis allow the pregnancy to continue. Affected neonates are usually born premature, have postnatal polyuria, vomiting, failure to thrive, hypercalciuria, and subsequently nephrocalcinosis. Hypokalemia, metabolic alkalosis, secondary hyperaldosteronism and hyperreninaemia are other characteristic features. Volume depletion due to excessive salt and water loss on long term stimulates renin-angiotensin-aldosterone system resulting in juxtaglomerular hyperplasia. Clinical features and electrolyte abnormalities may also depend on the subtype of the syndrome. Prenatal diagnosis and timely indomethacin administration prevent electrolyte imbalance, restitute normal growth, and improve activity. In this paper, authors present classification, pathophysiology, clinical manifestations, laboratory findings, complications, and prognosis of ABS.
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