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Search Results: 1 - 10 of 1492 matches for " Meenakshi Tiwari "
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RECENT DEVELOPMENTS IN FLUORINATION CHEMISTRY OF DAST WITH SPECIAL REFERENCE TO ALCOHOLS AKTUELLE ENTWICKLUNGEN IN DER CHEMIE FLUORIERUNG DAST MIT SPECIAL VERWEIS AUF ALCOHOLS
Meenakshi Jain1 and Anjali Tiwari
Heterocyclic Letters , 2012, DOI: february 10, 2012
Abstract: Fluorine containing organic compounds have influenced both medicinal and agrochemical fields.The presence of fluorine or a fluorine containing group causes notable changes in the physical and chemical properties of ordinary organic compounds.The most significant method to introduce fluorine into organic compounds is the nucleophilic replacement of oxygen with fluorine. Diethylaminosulfur trifluoride (DAST), Bis(2-methoxyethyl)aminosulfur trifluoride (BAST) or deoxofluor are the popular fluorinating reagents. By the use of these reagents, organic compounds that contain oxygen in hydroxyl and carbonyl groups are readily converted into their corresponding fluorinated analogues by the introduction of one or two fluorine atoms respectively. Our interest in applying various synthetic methods to incorporate fluorine or a fluorinated group into a large variety of organic compounds encouraged us to summarize the recent chemistry of DAST
Clomiphene Citrate Induces ROS-Mediated Apoptosis in Mammalian Oocytes  [PDF]
Shail K. Chaube, Tulsidas G. Shrivastav, Shilpa Prasad, Meenakshi Tiwari, Anima Tripathi, Ashutosh N. Pandey, Karuppanan V. Premkumar
Open Journal of Apoptosis (OJApo) , 2014, DOI: 10.4236/ojapo.2014.33006
Abstract: The clomiphene citrate (CC), a nonsteroidal triphenylethylene compound, is a first line of medicine used for the induction of ovulation in anovulatory women worldwide. In spite of high ovulation induction with the use of CC, the pregnancy rate is much lower. Such a discrepancy could be due to the peripheral anti-estrogenic effect of CC, particularly at the level of ovary, endometrium and cervical mucus. CC induces ovulation by binding to the estrogen receptors and generates hypoestrogrnic state in hypothalamus leading to release of pituitary gonadotropins. CC may have a direct effect at the level of ovary but the molecular mechanism remains unclear. Animal studies suggest that the CC induces apoptosis in granulosa cells and results hypoestrogenic state in the ovary. Reduced estradiol 17β level in the ovary affects development and maturation of oocyte leading to oocyte apoptosis. Further, CC increases hydrogen peroxide (H2O2) level and thereby bax protein expression and DNA fragmentation in cumulus-granulosa cells as well as in oocytes. The exogenous supplementation of either estradiol 17β or melatonin reduces H2O2 level in ovary, delays meiotic cell cycle progression in oocyte and protects oocyte apoptosis. Hence, supplementation of estradiol 17β or melatonin along with CC could be beneficial to protect granulosa cell as well as oocyte apoptosis and inhibit deterioration of oocyte quality. Thus, maintenance of oocyte quality may overcome the adverse effect caused due to CC treatment during infertility management.
Investigation of Surface Tryptophan of Protein by Selective Excitation at 305 nm  [PDF]
Vishvanath Tiwari, Monalisa Tiwari
Journal of Biophysical Chemistry (JBPC) , 2015, DOI: 10.4236/jbpc.2015.63009
Abstract: Intrinsic fluorescence of tryptophan is a powerful tool that is used to investigate structure, dynamics, and folding-unfolding of proteins. Here, we have signified the importance of selective monitoring of “surface” tryptophans from the “buried” tryptophans in a protein via selective excitation of surface tryptophan using light of 305 nm wavelength. We have also enlightened the effect of pH and temperature on the conformation of protein by selective excitation of surface tryptophan of protein using 305 nm light. The result concludes that this novel approach could be used to investigate surface tryptophan of protein selectively at diverse conditions.
Selective Recognition and Detection of L-Aspartic Acid by Molecularly Imprinted Polymer in Aqueous Solution  [PDF]
Nazia Tarannum, Meenakshi Singh
American Journal of Analytical Chemistry (AJAC) , 2011, DOI: 10.4236/ajac.2011.28105
Abstract: Molecularly imprinted polymers selective for L-aspartic acid (LAA) have been prepared using the carboxy-betaine polymer bearing zwitterionic centres along the backbone. LAA is well known to promote good me-tabolism, treat fatigue and depression along with its significance in accurate age estimation in the field of forensic science and is an important constituent of ‘aspartame’, the low calorie sweetener. In order to study the intermolecular interactions in the prepolymerization mixture between the monomer and the template (LAA)/non-template (DAA), a computational approach was developed. It was based on the binding energy of the complex between the template and functional monomer. The results demonstrate that electrostatic in-teractions primarily guide the imprinting protocol. The MIP was able to selectively and specifically take up LAA from aqueous solution, human blood serum and certain pharmaceutical samples quantitatively. Hence, a facile, specific and selective technique to detect the amino acid, LAA in the presence of various interfer-rants, in different kinds of matrices is presented.
An Intelligent Fuzzy Based Energy Detection Approach for Cooperative Spectrum Sensing  [PDF]
Sitadevi Bharatula, Meenakshi Murugappan
Circuits and Systems (CS) , 2016, DOI: 10.4236/cs.2016.76088
Abstract: Cognitive radio systems are helpful to access the unused spectrum using the popular technique, referred to as spectrum sensing. Spectrum sensing involves the detection of primary user (PU) signal using dynamic spectrum access. Cooperative spectrum sensing takes advantage of the spatial diversity in multiple cognitive radio user networks to improve the sensing accuracy. Though the cooperative spectrum sensing schemes significantly improve the sensing accuracy, it requires the noise variance and channel state information which may lead to transmission overhead. To overcome the drawbacks in conventional cooperative spectrum sensing, this paper proposes a fuzzy system based cooperative spectrum sensing. Selection combining (SC) and maximum ratio combining (MRC) are used at fuzzy based fusion center to obtain the value of the sensing energy. These energy values are utilized in finding the presence of PU, results in improved sensing accuracy. In addition, an intelligent fuzzy fusion algorithm determines the PU presence without the channel state information based on multiple threshold values. Simulation results show that the proposed scheme outperforms the existing schemes in terms of sensing accuracy.
Nanomechanical Analysis of Hybrid Silicones and Hybrid Epoxy Coatings—A Brief Review  [PDF]
Atul Tiwari
Advances in Chemical Engineering and Science (ACES) , 2012, DOI: 10.4236/aces.2012.21005
Abstract: This review article is written on the investigations of nanomechanical properties of coatings by using nanoindentation techniques. The focus is on the studies that were conducted on epoxy polymer, silicones and their hybrid materials. The article describes a large number of developmental studies that are conducted on coatings. Materials properties such as nanoindentation hardness, modulus, scratch, wear and viscoelastic behavior have been described. Moreover, the article summarizes various studies that mention the use of different nanoparticles in coating formulations that could improve the mechanical strength and service life span of the coatings. The mode and mechanism of material’s failure has been outlined and discussed.
Imperfection of Domain Knowledge and Its Formalization in Context of Design of Robust Software Systems  [PDF]
Meenakshi Sridhar, Naseeb Singh Gill
Journal of Software Engineering and Applications (JSEA) , 2015, DOI: 10.4236/jsea.2015.89047
Abstract: In this paper, it is emphasized that taking into consideration of imperfection of knowledge, of the team of the designers/developers, about the problem domains and environments is essential in order to develop robust software metrics and systems. In this respect, first various possible types of imperfections in knowledge are discussed and then various available formal/mathematical models for representing and handling these imperfections are discussed. The discussion of knowledge classification & representation is from computational perspective and that also within the context of software development enterprise, and not necessarily from organizational management, from library & information science, or from psychological perspectives.
Comprehensive Mitigation Mechanism Against DdoS Attack-A Comparative Study
S. Meenakshi
Asian Journal of Information Technology , 2012,
Abstract: Distributed Denial of Service (DDoS) attacks are a relatively new type of attack on the availability of Internet services and resources. A Denial of service attack is with the purpose of preventing legitimate users from using victim system resources. DDoS is a large scale coordinated attack on the availability of services of a victim system (or) network resource. Large-scale distributed nature of Internet makes DDoS attack stealthy and difficult to counter. As attack traffic is indistinguishable from normal traffic, it would be desirable to develop comprehensive DDoS solution. As various attack tools become widely available, automated anti-DdoS systems become increasingly important. This study proposes taxonomy of various mitigation mechanisms against DDoS attack. We studied the different mitigation mechanisms like IP-Traceback,Change point monitoring method and perimeter based defense. Finally we drafted a taxonomy which helps to understand the advantages and drawbacks of various mitigation mechanisms and scope of the DDoS problem.
A Survey of Routing Protocols for Ad Hoc Wireless Home Networks
Meenakshi Chaturvedi
International Journal of Electronics and Computer Science Engineering , 2012,
Abstract: Ad hoc networks are wireless mobile networks that do not rely on preexisting infrastructure and these networks allow a more flexible model of communication than traditional networks since the user is not limited to a fixed physical location. In order to facilitate communication within the network, a routing protocol is used to discover routes between nodes. The primary goal of such an ad hoc network routing protocol is correct and efficient route establishment between a pair of nodes so that messages may be delivered in a timely manner. Route construction should be done with a minimum of overhead and bandwidth consumption. In this paper, we present routing protocols designed for these ad hoc networks by describing the operation of each of the protocols. The remainder of the paper is organized as follows. The next section presents a discussion of two subdivisions of ad hoc routing protocols. Another section discusses current table driven protocols, while a later section describes those protocols which are classified as ondemand. The paper then presents qualitative comparisons of table-driven protocols, followed by demand-driven and on-demand protocols; and finally, the last section concludes the paper.
Antitumor activity of ethanol extract of Gracilaria edulis (Gmelin) Silva on Ehrlich ascites carcinoma-bearing mice
Meenakshi Sundaram
Zhong Xi Yi Jie He Xue Bao , 2012,
Abstract:
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