OALib Journal期刊

ISSN: 2333-9721




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匹配条件: “Ramana Murthy K” ,找到相关结果约139458条。
Preparation and evaluation of polyelectrolyte complexes for oral controlled drug delivery
Srinivas L,Ramana Murthy K
Asian Journal of Pharmaceutics , 2010,
Abstract: The electrostatic interaction between oppositely charged polyelectrolytes leads to formation of insoluble polyelectrolyte complexes in aqueous medium. The polyelectrolyte complexes formed between a polyacid and a polybase are little affected by the pH variation of the dissolution medium. In the present study attempts were made to prepare polyelectrolyte complexes of polyvinyl pyrrolidone (polybase) and carbopol (polyacid) into which diclofenac sodium is incorporated and studied for its controlled release. The polyelectrolyte complexation was evaluated by pH, conductivity, Fourier transformed infrared spectroscopy, and X-ray difractometry. The dried polyelectrolyte complexes were also evaluated for micromeritic properties and drug release kinetics. Selected PECs were compressed into tablets and compared with commercial SR product for drug release. The tablets showed comparable results with commercial SR product following zero-order release, and drug release is by erosion as well as the diffusion mechanism. Promising results were obtained suggesting the application of these polyelectrolyte complexes in the design of controlled release systems.
K. Jhansi Rani,Ch. V. Ramana Murthy
International Journal of Engineering Science and Technology , 2012,
Abstract: Analytical solutions for heat transfer in a laminar flow of a Newtonian viscous electrically conducting and heat generating/ absorbing fluid on an inclined permeable surface has been reported in this paper. The dimensionless governing equations are solved the best possible analytical solution. The influence of various participatingparameters are illustrated graphically and explained in detail. It is noticed that, far away from the bounding surface it is seen that a wide dispersion in the velocity profiles is noticed. Such a phenomena could not be observed in boundary layer region. While the Schmidt number (Sc) remains unchanged and as the porosity of the bounding surface decreases, not much of change in the velocity field is noticed. When the bounding is having vertical, as the Schmidt number (Sc) increases the velocity is observed to be increasing. Also, as the pore size of the fluid bed decreases the velocity is seen to be increasing. As Schmidt number (Sc) decreases the fluid velocity is noticed to be decreasing. The Grashoff number (Gr) contributes to the velocity up to some stage and there after a reverse trend is noticed. The modified Grashoff number (Gm) appears to influence the velocity field inversely.
Steady flow of micropolar fluid in a rectangular channel under transverse magnetic field with suction
J. V. Ramana Murthy,K. S. Sai,N. K. Bahali
AIP Advances , 2011, DOI: 10.1063/1.3624837
Abstract: In this paper, the steady flow of an incompressible conducting micropolar fluid through a rectangular channel with uniform cross-section in the presence of a transverse magnetic field with suction and injection at the side walls is considered. Neglecting the induced magnetic and electric fields, velocity and micro-rotation vectors are obtained in terms of a Fourier series. The volumetric flow rate is calculated and the effect of micro-rotation parameter and geometric parameter, Hartmanns number on this are graphically shown and discussed.
Unsteady Flow of Micropolar Fluid through a Circular Pipe under a Transverse Magnetic Field with Suction/Injection
J. V. Ramana Murthy,N. K. Bahali,D. Srinivasacharya
Sel?uk Journal of Applied Mathematics , 2010,
Abstract: In this paper, we consider the unsteady flow of an incompressible electrically conducting micropolar fluid through a circular porous pipe subjected to periodic suction/injection at the walls of the tube and in the presence of a transverse magnetic field. Under the Stokesian assumption and using the similarity transformations, the stream function and microrotation components are obtained in terms of Bessel's functions. The variation of skin friction with respect to micropolar parameters and Hartman's number, suction parameter are studied and depicted through graphs.
Recent sightings of the Hawksbill turtle Eretmochelys imbricata (Linnaeus, 1757) on the coast of Northern Andhra Pradesh, India
K.L.N Murthy,K.V. Ramana Murthy
Asian Journal of Conservation Biology , 2012,
Abstract: The coast of Northern Andhra Pradesh has predominantly rocky and sandy shores with sporadic nesting sites of olive ridley turtles Lepidochelys olivacea. However, there have been rare sightings of hawksbill turtles Eretmochelys imbricata along this coast in the past couple of decades and their nesting is seldom observed. Carcasses of two adult hawksbill turtles were observed on 29/12/2010 and 07/03/2011 along the coast of Visakhapatnam in Northern Andhra Pradesh, India. These sightings of dead hawksbill turtles along this coast come recently after a long gap of several years and emphasize on the need to carry out surveys in the area for devising effective long term conservation management strategies.
Chronobiology and Chronotherapy of Hypertension – A Review
K Latha, MU Uhumwangho, SA Sunil, MV Srikanth, KV Ramana Murthy
International Journal of Health Research , 2010,
Abstract: Hypertension occurs in over 90% of all patients with cardiovascular disease (CVD) in the United States and it is a major risk factor for end-organ damage, CVD and death. In the treatment of hypertension, investigation of chronobiology, chronopharmacology and chronotherapy began a few decades ago. Studies over the last decade have revealed that blood pressure (BP) and CVD are influenced by our behaviour such as what we eat and even conditioned by the time of day. Also, the ability of the night: day ratio of systolic BP predicts the risk for cardiovascular events more accurately compared with office BP measured only at once. Evidence clearly points to the fact that nocturnal BP is indeed the BP as it is most consistently correlated with prediction of cardiovascular risk and provides more close surveillance of safety. Circadian rhythm is a significant input into the regulation of BP. Hence, a circadian disorder such as hypertension requires chronopharmacotherapy. However, different medications have been studied for their chronopharmacology and potential chronotherapy. This article reviews the chronobiology of hypertension, and the chronopharmacology and chronotherapy of the various medications used in its management.
Application of Brinkman model to the unsteady flow of Bingham fluid in contact with Newtonian fluid
Y. V. K. Ravi Kumar,M. V. Ramana Murthy,S. Sreenadh,S. Rajender
Journal of Engineering and Applied Sciences , 2009,
Abstract: Unsteady flow of a Bingham fluid in contact with a Newtonian fluid between two permeable beds of different permeabilities is studied. We used the Brinkman model for this problem. Expressions for the interface velocity, velocity distributions in the porous and non-porous regions and mass flow rate are obtained. These expressions are evaluated numerically for different values of the parameters.
Experimental Investigations on the Duel Fueled Diesel Engine
K. Thirupathi Reddy,P. Ram Reddy,P.V. Ramana Murthy
Asian Journal of Scientific Research , 2008,
Abstract: In the present study, a four stroke, five horse power diesel engine was tested with two different fuel blends. In the first case, diesel-kerosene blends and in the second case, air and Liquefied Petroleum Gas (LPG) mixture along with diesel was tested at constant engine speed of 1500 rpm. Different engine exhaust emissions were compared using pure diesel, diesel-kerosene blends and air-LPG mixtures. With diesel-kerosene blends minimum exhaust emissions were observed at 30% kerosene blend, when compared with pure diesel emissions. Slight increase in the NOx exhaust emission was observed. With air-LPG mixtures, minimum exhaust emissions were observed at 11% LPG mixing. However, increase in NOx exhaust emission was observed. Engine performance improved and Specific Fuel Consumption (SFC) was observed to be minimal at 30% kerosene blending and decreased as compared to pure diesel value at the same brake power output. SFC was also observed to be minimum at 11% LPG mix and decreased by about 20% as compared to pure diesel value at the same brake power output. The fuel operating cost also reduced at 30% kerosene blend and further reduced at 23% LPG mixing with air.
Nanocrystalline Pb(Zr0.52Ti0.48)O3 Ferroelectric Ceramics: Mechanical and Electrical Properties
M. Venkata Ramana,M. Penchal Reddy,N. Ramamanohar Reddy,K. V. Siva Kumar,V. R. K. Murthy,B. S. Murty
Journal of Nanomaterials , 2010, DOI: 10.1155/2010/783043
Abstract: Nanocrystalline powders of the composition were obtained by Mechanical alloying (high-energy ball milling). X-ray diffraction studies show that these compounds are completely into the perovskite phase. Detailed studies of electrical and mechanical properties of PZT as a function of temperature (and frequency) showed the high permittivity of 20653 at Curie transition temperature. Temperature variation of longitudinal modulus and internal friction of these ceramics at 104?kHz frequency were studied in the wide temperature range of C– C. The internal friction measurements showed sharp stress induced relaxation peaks in the present composition corresponding to those temperatures where the minima were noticed in temperature variation of longitudinal modulus behavior. This dielectric and internal friction behaviour was explained in the light of polaron hopping mechanism and structural phase transitions in the present piezoelectric compositions. 1. Introduction In the preparation of nonvolatile memory devices, lead zirconate titanate (PZT) ceramics are very attractive for application as capacitor of dynamic random access memory (DRAM) and gate materials of ferroelectric RAM (FRAM). PZT materials are well known for their good piezoelectric properties and are ideal candidates for making sensors and actuators. The mechanical properties of PZT ceramics have received much less attention from researchers as compared to their electrical properties. Thus understanding of the mechanical properties of PZT has become important since these properties must be considered in the design of piezoelectric devices [1]. The solid solution of ferroelectric lead titanate and antiferroelectric lead zirconate abbreviated as PZT with varying Zr/Ti ration is of great interest for many piezoelectric, pyroelectric, and ferroelectric devices. PZT with close to 0.48, near the morphotropic phase boundary between rhombohedral and tetragonal phases, has been considered very promising for piezoelectric devices [2]. Nanocrystalline ceramics can be synthesized by a various physical, chemical, and mechanical methods [3]. Recently, a mechanical alloying technique (i.e., high energy ball milling) has successfully been used to synthesize the nanocrystalline ferroelectric materials. Indeed, mechanical alloying was found to be superior to the high-temperature solid state reaction method/wet chemical process because it lowers the calcination and sintering temperature due to the nanocrystalline nature of the resultant powder. The properties of nanocrystalline materials are found superior to those of
Ferromagnetic-Dielectric Ni0.5Zn0.5Fe1.9O4?δ/PbZr0.52Ti0.48O3 Particulate Composites: Electric, Magnetic, Mechanical, and Electromagnetic Properties
M. Venkata Ramana,N. Ramamanohar Reddy,B. S. Murty,V. R. K. Murthy,K. V. Siva Kumar
Advances in Condensed Matter Physics , 2010, DOI: 10.1155/2010/763406
Abstract: Novel ferromagnetic-dielectric particulate composites of Ni0.5Zn0.5Fe1.95O4?δ (NZF) and PbZr0.52Ti0.48O3 (PZT) were prepared by conventional ceramic method. The presence of two phases in composites was confirmed by XRD technique. The variations of dielectric constant ( ) with frequency in the range of 100?kHz–1?MHz at room temperature and also with temperature at three different frequencies (50?kHz, 100?kHz, and 500?kHz) were studied. Detailed studies on the dielectric properties were done confirming that the magnetoelectric interaction between the constituent phases may result in various anomalies in the dielectric behaviour of the composites. It is proposed that interfaces play an important role in the dielectric properties, causing space charge effects and Maxwell-Wagner relaxation, particularly at low frequencies and high temperatures. The piezoelectric d33 constant was studied at room temperature, and the d33 constant value decreased with ferrite content. Magnetic properties like B-H loops traces were studied to understand the saturation magnetic (Ms) and magnetic moment ( ) of the present particulate composites. The magnetoelectric (ME) output was measured by varying dc bias magnetic field. A large ME output signal of 2780?mV/cm Oe was observed in the composite having 50% ferrite. The temperature variation of longitudinal modulus (L) and internal friction (Q?1) of these particulate composites at 104?kHz was studied in the temperature range 30°C–420°C by the composite oscillator technique. Longitudinal modulus showed a sharp minimum, and internal friction exhibits a sharp peak at ferroelectric-paraelectric phase transition. These ferroelectric-dielectric particulate composites were prepared with a view to using them as ME sensors and transducers. 1. Introduction Multifunctional or smart materials combining several properties in the same structure in order to produce new or enhanced phenomena have stimulated much scientific and technological interest within the scientific community in the last years. One of the most interesting categories of multifunctional system is the magnetoelectric, that is, materials showing magnetoelectric effects. Having simultaneous magnetic and ferroelectric activity, possible attractive functionalities caused by the interactions between electric polarization and spontaneous magnetization can be envisaged. The primary magnetoelectric (ME) effect is defined as the appearance of an electric polarization under a magnetic field P(H): ME output or a magnetization at the application of an electric field. The ME of second order

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