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Kumar A.A.,Yogivemana University | Reddy V.R.,Sri Venkateswara University | Janardhanam V.,Chonbuk National University | Seo M.-W.,Chonbuk National University | And 3 more authors.
Journal of the Electrochemical Society

We investigated the electrical properties and reverse leakage mechanisms of Pt/n-Ge Schottky contacts with copper phthalocyanine (CuPc) as an interlayer. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the Schottky contacts were used to evaluate Schottky barrier parameters such as ideality factor, barrier height, and series resistance. The barrier heights and ideality factors measured from the forward bias I-V characteristics were found to be 0.50 eV and 1.06 for Pt/n-Ge Schottky contact, and 0.58 eV and 1.31 for Pt/CuPc/n-Ge Schottky contact, respectively. Cheung method was used to measure the series resistances of the Schottky contacts, and the consistency was checked using the Norde method. The reverse leakage conduction mechanism of the Schottky contacts was investigated. Pt/CuPc/n-Ge Schottky contacts showed a transition from Schottky emission to Poole-Frenkel emission at a higher bias range. This could be associated with the high density of structural defects or traps associated with the organic material. © 2011 The Electrochemical Society. Source

Chandra Sekhar E.,Acharya Nagarjuna University | Krishna Rao K.S.V.,Yogivemana University | Ramesh Raju R.,Acharya Nagarjuna University
Journal of Applied Pharmaceutical Science

Chitosan and guargum-gt-acrylamide (CH-GG-g-AAm) semi interpenetrating microspheres (semi IPNMs) were prepared by water-in-oil (w/o) emulsion cross linking method using glutaraldehyde as a crosslinker. 5-fluorouracil (5-FU) is an anticancer drug was successfully loaded in these semi IPNMs. X-ray diffraction (XRD) and differential scanning calorimetric (DSC) examined the crystalline nature of drug after encapsulation into semi IPNMs. Scanning electron microscopy (SEM) shows the formation of semi IPNMs is spherical with size around 200 ??m. The encapsulation efficiency of 5-FU was achieved 58%. In-vitro release studies were performed basic (pH 7.4) buffer medium. The release patterns depend on graft polymer composition, effect of cross linker and drug content in the polymer matrices. In vitro release studies indicated the release of 5- FU more than 12 hours. Source

Reddy V.R.,Sri Venkateswara University | Reddy M.S.P.,Sri Venkateswara University | Lakshmi B.P.,Sri Venkateswara University | Kumar A.A.,Yogivemana University
Journal of Alloys and Compounds

In the present work, we have investigated the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of Au/SiO2/n-GaN metal-insulator-semiconductor (MIS) Schottky diode and compared with Au/n-GaN metal-semiconductor (MS) Schottky diode. Calculations showed that the Schottky barrier height and ideality factor of the MS Schottky diode is 0.79 eV (I-V), 0.87 eV (C-V) and 1.45, respectively. It is observed that the Schottky barrier height increases to 0.86 eV (I-V), 0.99 eV (C-V) and ideality factor deceases to 1.3 for MIS diode. For the MS diode, the calculated doping concentration is 4.17 × 1017 cm-3. However, in the case of the MIS Schottky diode, the decrease in doping concentration is observed and the respective value is 2.08 × 1017 cm-3. The obtained carrier concentration of the MIS diode is reduced about 50% when compared to the MS diode. The interface state density as determined by Terman's method is found to be 3.79 × 1012 and 3.41 × 1010 cm -2 eV-1 for the MS and MIS Schottky diodes, respectively. The calculated interface densities are 2.47 × 1011 cm -2 eV-1, 3.35 × 1011 cm-2 eV-1 and 3.5 × 1011 cm-2 eV-1 for the sweep rates of 300, 450 and 600 mV/s from MOS C-V measurements for the MIS Schottky diode. The interface state density calculated from Terman's method is found to be increased with sweep rate. From the C-V measurement, it is noted that the decrease in the carrier concentration in MIS diodes as compared to MS diode may be due to the presence of oxide interfacial layer. DLTS measurements have also been performed on MIS Schottky diode and discussed. © 2011 Elsevier B.V. All rights reserved. Source

Reddy N.B.P.,Minor Irrigation | Reddy M.R.,Yogivemana University
ISH Journal of Hydraulic Engineering

The effect of convergent angle on the non-uniform flow through porous media was studied in a converging permeameter. The scope of the present paper is to present the relationship between Hydraulic Gradient (I) and Froude Number (FK 2) for flow through porous media with converging boundaries, using intrinsic permeability (K) as characteristic length, and to also show pictorically the relation between linear parameter, a, and non-linear parameter, b, in terms of Media Constant (CW). In the present case, McCorquodale data of size 1.66 cm was used as media, to develop theoretical curves using friction factor (FK) and Reynolds number (RK) relationship, and verified with the help of existing experimental data of different convergent angles. © 2014 Indian Society for Hydraulics. Source

Madhusudana Rao K.,Sri Krishnadevaraya University | Krishna Rao K.S.V.,Yogivemana University | Sudhakar P.,Sri Krishnadevaraya University | Chowdoji Rao K.,Sri Krishnadevaraya University | Subha M.C.S.,Sri Krishnadevaraya University
Journal of Applied Pharmaceutical Science

Biodegradable sodium alginate-g-poly (vinyl caprolactam) synthesized by graft copolymerization of N-vinyl caprolactam (VCL) on to sodium alginate (NaAlg) via free radical initiation mechanism using a redox initiation system. Grafting (%), efficiency (%), and conversion (%) were all found to depend on the content of potassium persulfate (KPS), VCL reaction temperature and time. The maximum % of grafting was ascertained to be 251 at the optimum conditions of 65 oC reaction temperature, 180 min of reaction time, 1.1098X10-3 mol of KPS and 7.1844X10-3 mol of VCL. Evidence of graft copolymerization was obtained by fouriertransform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Further, graft copolymer was used for preparation of microgels (MGs) using Ca+2 as a crosslinking agent. SEM results showed that the MGs are spherical in structure with smooth surface. The effects of pH and temperature on the swelling behaviour of MGs were studied and ascertained that they were sensitive to both pH and temperature. 5-FU drug was successfully loaded in to these MGs and encapsulation efficiency was found 84%. The release of 5-FU was systematically investigated as a function of temperature, pH, amount of crosslinker and % of drug loading concentration. The results indicate that the responsive MGs have the potential to be used as an effective pH and temperature controlled delivery of 5-FU for more than 12 h. © 2013 K. Madhusudana Rao et al. Source

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