1,538 research outputs found

    Topological Defects in the Left-Right Symmetric Model and their Relevance to Cosmology

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    It is shown that the minimal left-right symmetric model admits cosmic string and domain wall solutions. The cosmic strings arise when the SU(2)_R is broken and can either be destabilized at the electroweak scale or remain stable through the subsequent breakdown to U(1)_{EM}. The strings carry zero modes of the neutrino fields. Two distinct domain wall configurations exist above the electroweak phase transition and disappear after that. Thier destablization provides new sources of non-equilibrium effects below the electroweak scale which is relevant to baryogenesis.Comment: 29 pages, LaTex file with 6 postscript figure

    DISSOLUTION ENHANCEMENT OF POORLY WATER-SOLUBLE DRUG BY CYCLODEXTRINS INCLUSION COMPLEXATION

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    Objective: Solubility of a drug is an important property that mainly influences the extent of oral bioavailability. Enhancement of oral bioavailability of poorly water-soluble drugs is the most challenging aspects of drug development. It is very important to find appropriate formulation approaches to improve the aqueous solubility and bioavailability of poorly aqueous soluble drugs. Ezetimibe is a new lipid lowering agent in the management of hypercholesterolemia. The drug is water-insoluble, lipophilic, and highly permeable according to the pharmaceutical classification system. Therefore, the bioavailability of ezetimibe may be improved by increasing its solubility. Methods: In present work solubility of ezetimibe was increased with inclusion complexes by a different technique like physical mixture, co-grinding and modified kneading method. The physical properties of the prepared inclusion complex of ezetimibe were characterised by Differential scanning calorimetry (DSC), X-ray diffraction spectroscopy (XRD), Fourier transform infra-red spectroscopy (FTIR) and in vitro dissolution studies. Results: From the dissolution studies of ezetimibe with HP-β-cyclodextrin(1:1 and 1:2), we conclude that the prepared complexes of ezetimibe with HP-β-cyclodextrin (1:2) by modified kneading method showed higher release i.e. 88.35% in 60 min. than in (1:1) 76.75% in 60 min. So, ezetimibe with HP-β-cyclodextrin (1:2) inclusion complex was used to formulate tablet by direct compression method. Conclusion: From the dissolution data of formulated tablets was observed that drug release was more in tablet dosage form as compared to plain ezetimibe and especially formulation in a ratio of 1:2 was found the promising result. Also from one-month stability data shows no significant change compared to the initial result

    Formulation Development and Evaluation of Aqueous Injection of Poorly Soluble Drug Made by Novel Application of Mixed Solvency Concept

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    It is commonly recognized in the pharmaceutical industry that on average more than 40% of newly discovered drug candidates are poorly water-soluble. The objective of present research is to explore the application of mixed solvency technique in the injection formulation of poorly soluble drugs and to reduce concentration of individual solubilizers (used for solubility enhancement) to minimize the toxic effects of solubilizers. In the present work poorly soluble drugs Ofloxacin are selected as model drugs. Ofloxacin is an antibiotic drug tried to formulate the aqueous injection by the use of various physiologically compatible solubilizing agent like Lignocaine Hydrochloride, Niacinamide, Sodium benzoate, Sodium citrate, PEG 400, PEG 4000, PVP 40000, Ethanol, and Propylene Glycol. For expected synergistic enhancement effect on solubility of these poorly soluble drugs various blends of solubilizers shall be tried to decrease the amounts of Solubilizer employed for a desired solubility enhancement ratio. The study further opens the chances of preparing dry powders for injection of drug which are not stable in aqueous solution, ready to use injection. Key word- Mixed solvency solubilization, Ofloxacin, solubility enhancement, synergistic enhancement effect

    Using Nanocavity Plasmons to Improve Solar Cell Efficiency

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    Although in principle very promising, photovoltaic technology has so far failed to deliver robust high efficiency modules at affordable prices. Despite considerable research, high efficiency silicon based cells remain expensive, while the more recent organic photovoltaics are still struggling with low efficiencies and short lifetimes. Meanwhile, over the last few years, the study of localized plasmons [1,2] has also received great attention due to the high field enhancements associated with confined fields , with a wide range of applications possible, from optical switches to substrates for surface enhanced Raman spectroscopy (SERS). Here we discuss how combining the structures normally used in photovoltaic devices with metallic cavities supporting localized plasmons can lead to considerable improvements in the performance of solar cells. In particular we show how by changing the shape and size of spherical voids on a metallic surface, one can tune the plasmon modes to obtain significant absorptions across the solar spectrum [3]. By coating one such nanocavity surface with a sub 100 nm-layer of semiconductor, we can create a nanostructured solar cell, where the localised Mie modes efficiently couple light into the semiconductor layer. As the plasmons electric field enhancement is largest very close to the surface, significant absorption can be maintained even when the semiconductor thickness is reduced to below the typical exciton diffusion length. In addition minority carrier transport is improved. That means we can beat the usual balance between light absorption and exciton recombination loses, and so significantly increase the overall efficiency of the photovoltaic devices. Keywords: plasmons, solar cells, nanostructured surfaces

    Collapse Dynamics of a Star of Dark Matter and Dark Energy

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    In this work, we study the collapse dynamics of an inhomogeneous spherically symmetric star made of dark matter (DM) and dark energy (DE). The dark matter is taken in the form of a dust cloud while anisotropic fluid is chosen as the candidate for dark energy. It is investigated how dark energy modifies the collapsing process and is examined whether dark energy has any effect on the Cosmic Censorship Conjecture. The collapsing star is assumed to be of finite radius and the space time is divided into three distinct regions Σ\Sigma and V±V^{\pm}, where Σ\Sigma represents the boundary of the star and V(V+)V^{-}(V^{+}) denotes the interior (exterior) of the star. The junction conditions for matching V±V^{\pm} over Σ\Sigma are specified. Role of Dark energy in the formation of apparent horizon is studied and central singularity is analyzed.Comment: 13 page

    Unitarity constraints on the stabilized Randall-Sundrum scenario

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    Recently proposed stabilization mechanism of the Randall-Sundrum metric gives rise to a scalar radion, which couples universally to matter with a weak interaction (1\simeq 1 TeV) scale. Demanding that gauge boson scattering as described by the effective low enerrgy theory be unitary upto a given scale leads to significant constraints on the mass of such a radion.Comment: 10 page Latex 2e file including 4 postscript figures. Accepted in Journal of Physics
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