@article { ISI:000264899000012, title = {Effect of organic solvents on cell-bound penicillin V acylase activity of erwinia aroideae (DSMZ 30186): a permeabilization effect}, journal = {Journal of Molecular Catalysis B-Enzymatic}, volume = {57}, number = {1-4}, year = {2009}, month = {MAY}, pages = {67-71}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Erwinia aroideae (DSMZ 30186) is a potential microbial culture to produce intracellular penicillin V acylase (PVA). The whole cell PVA activity was improved by permeabilization with various organic solvents. The cell-bound PVA activity showed an eightfold increase upon treatment with chloroform (5 mu L/mg(dry) (biomass)) for 10 min and diethyl ether (10 mu L/mg(dry) (biomass)) for 45 min. Hexane, toluene, ethyl acetate and dichloromethane enhanced the enzyme activity up to two-, six-, four- and two-fold, respectively; whereas, PVA activity declined drastically on permeabilization with acetone, pyridine and alcohols. The physicochemical properties of the organic solvents used for permeabilization were correlated with the change in activity. It was found that solvents with high hydrophobicity (log P \> 0.68) and lower dielectric constant (\< 9) were relatively effective in increasing PVA activity. These results allow systematic selection of suitable solvent for best performance. (c) 2008 Elsevier B.V. All rights reserved.

}, keywords = {dielectric constant, Erwinia aroideae, Hydrophobicity, Organic solvents, Penicillin V acylase, Permeabilization}, issn = {1381-1177}, doi = {10.1016/j.molcatb.2008.06.018}, author = {Kumar, Atul and Pundle, Archana} } @article { ISI:000268022700058, title = {Magnetic and dielectric properties of nanophase manganese-substituted lithium ferrite}, journal = {Journal of Magnetism and Magnetic Materials}, volume = {321}, number = {19}, year = {2009}, month = {OCT}, pages = {3270-3273}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Nanocrystalline manganese-substituted lithium ferrites viz. Li0.5Fe2.5-xMnxO4 (2.5 \<= x \>= 0) were prepared by sol-gel autocombustion method. X-ray diffraction analysis confirmed that as the concentration of manganese increases the cubic phase changes to the tetragonal phase. The variation of saturation magnetization was studied as a function of manganese content. All the compositions indicate that they are ferrimagnetic in nature. The dielectric constant, dielectric loss tangent and ac conductivity of all samples were measured at room temperature as a function of frequency. These parameters decrease with increase in frequency for all of the samples. The substitution of manganese plays an important role in changing the structural and magnetic properties of these ferrites. The compositional variation of dielectric constant and d.c. resistivity shows an inverse trend of variation with each other. (C) 2009 Elsevier B.V. All rights reserved.

}, keywords = {dielectric constant, Ferrite, Magnetization, X-ray diffraction}, issn = {0304-8853}, doi = {10.1016/j.jmmm.2009.05.074}, author = {Hankare, P. P. and Patil, R. P. and Sankpal, U. B. and Jadhav, S. D. and Mulla, Imtiaz S. and Jadhav, K. M. and Chougule, B. K.} } @article { ISI:000272591100003, title = {Multiferroic behavior of gd based manganite}, journal = {Ferroelectrics}, volume = {392}, year = {2009}, month = {OCT}, pages = {PII 917324971}, publisher = {TAYLOR \& FRANCIS LTD}, address = {4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND}, abstract = {

Here we report the multiferroic nature of charge ordered manganite Gd0.5Sr0.5MnO3 for the first time. The temperature variation of dielectric constant shows broad relaxor type ferroelectric transition at around 210K and magnetization measurements shows weak ferromagnetism at 50K. The dielectric peak is very close to charge ordering temperature which is an evidence of the link between electronic state and increase of dielectric response. Butterfly variation of capacitance with voltage confirms ferroelectric nature of the sample at room temperature.

}, keywords = {dielectric constant, manganite, Multiferroic}, issn = {0015-0193}, doi = {10.1080/00150190903412408}, author = {Sagar, S. and Joy, Pattayil Alias and Anantharaman, Maliemadom R.} } @article { ISI:000286305100010, title = {Effect of leakage current and dielectric constant on single and double layer oxides in MOS structure}, journal = {Thin Solid Films}, volume = {519}, number = {5, SI}, year = {2010}, note = {37th International Conference on Metallurgical Coatings and Thin Films, San Diego, CA, APR 26-30, 2010}, month = {DEC}, pages = {1530-1535}, publisher = {Amer Vacuum Soc, Adv Surface Engn Div}, address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND}, abstract = {

MOS structure of Al/Al2O3/n-Si, Al/TiO2/n-Si and Al/Al2O3/TiO2/n-Si was obtained by deposition of Al2O3 and TiO2 on silicon substrate by RF Magnetron Sputtering system. The total thickness of the oxide layer similar to 40 +/- 5 nm in the MOS structure was kept constant. Samples were characterized by X-Ray diffraction (XRD). X-Ray photoelectron spectroscopy (XPS), Impedance analyzer and Current-voltage (J-V) characteristics. The variations in the dielectric constant and tan 8 of the MOS capacitor in the frequency range of 1000Hz-1MHz were measured by impedance analyzer. The variation in dielectric constant of the Al/Al2O3/TiO2/n-Si multilayer compared to single layer of Al/Al2O3/n-Si and Al/TiO2/n-Si is due to high probability of defects, lattice mismatch and interface interactions. The steep rise of Tan 6 values in the Al/Al2O3/TiO2/n-Si structure is due to the resonance effect of both Al2O3 and TiO2 layers. The leakage current mechanisms of MOS structures were extracted from Schottky coefficient and Poole-Frenkel coefficient. Theoretical values of Schottky coefficients (beta(SC)) and Poole-Frenkel coefficients (beta(PF)) for each sample were estimated using the real part of the dielectric constant. The experimental values were calculated from J-V characteristics and compared with theoretical values. The appropriate model has been proposed. It was found that Schottky and Poole-Frenkel mechanisms are applicable at low and high field respectively for all MOS structures. The combination of Al/Al2O3/TiO2/n-Si is found to be a promising structure with high dielectric constant and low leakage current suitable for MOS devices. (C) 2010 Elsevier B.V. All rights reserved.

}, keywords = {Al2O3, dielectric constant, Leakage current, MOS device, Poole-Frenkel emission, Schottky emission, TiO2}, issn = {0040-6090}, doi = {10.1016/j.tsf.2010.08.089}, author = {Laha, Pinaki and Panda, A. B. and Dahiwale, S. and Date, Kalyani S. and Patil, K. R. and Barhai, P. K. and Das, A. K. and Banerjee, Indrani and Mahapatra, S. K.} } @article { ISI:000278112200007, title = {Effect of solvents having different dielectric constants on reactivity: a conceptual DFT approach}, journal = {International Journal of Quantum Chemistry}, volume = {110}, number = {9}, year = {2010}, month = {AUG}, pages = {1642-1647}, publisher = {WILEY-BLACKWELL}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {

Conceptual density functional theory is exploited to understand the reactivity in a medium of solvents with increasing dielectric constants. Aprotic as well as protic solvents are used for this study. It is found that the global parameters, such as chemical potential and hardness, decrease from gas phase to solvent phase with increasing dielectric constant. However, it is observed that the Fukui functions of the reactive atoms increase significantly with the dielectric constants of the aprotic solvents while for the protic solvents the variation of the reactivity indices is insignificant. (C) 2009 Wiley Periodicals, Inc. Int J Quantum Chem 110: 1642-1647, 2010

}, keywords = {COSMO, DFT, dielectric constant, Reactivity descriptors, solvent effect}, issn = {0020-7608}, doi = {10.1002/qua.22333}, author = {Kar, Rahul and Pal, Sourav} } @article { ISI:000278307300007, title = {Influence of filler size and morphology in controlling the thermal emissivity of aluminium/polymer composites for space applications}, journal = {Materials Science and Engineering B-Advanced Functional Solid-State Materials}, volume = {168}, number = {1-3, SI}, year = {2010}, note = {Conference on Specialty Advanced Materials and Polymers for Aerospace and Defense and Applications (SAMPADA-2008), Mat Res Soc Singapore, Singapore, SINGAPORE, JUL 03-08, 2005}, month = {APR}, pages = {40-44}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The paper has addressed the problem of controlling the thermal emissivities from metal/polymer composites prepared by solution method. Aluminium is used as a filler and polystyrene as a polymer-matrix. Aluminium particles, with micrometer and nanometer dimensions having different morphologies, were employed. The values of emissivities were reduced when the coarse grains and flakes of aluminium were used as fillers, whereas, no significant change was observed when nano-aluminium was used in the composite. Dielectric dispersion for the composites was measured and the results are analysed in view of Fresnel relation. The differences in the values of dielectric constants, between the experimentally measured and those which can be predicted theoretically, are thought to arise from the interfacial polarization. (C) 2009 Elsevier B.V. All rights reserved.

}, keywords = {Camouflaging, Composite, dielectric constant, Infra-red, Thermal emissivity}, issn = {0921-5107}, doi = {10.1016/j.mseb.2009.11.009}, author = {Babrekar, Harshada A. and Kulkarni, Naveen V. and Jog, Jyoti Prakash and Mathe, Vikas L. and Bhoraskar, S. V.} } @article { ISI:000309024900024, title = {Swift heavy ion induced formation of Al/polymer composite layer for low thermal emissivity in the IR range}, journal = {Nuclear Instruments \& Methods in Physics Research Section B-Beam Interactions with Materials and Atoms}, volume = {287}, year = {2012}, month = {SEP}, pages = {135-140}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Composites of polymers with aluminium were formed by swift high energy ions of 150 MeV, which are used as low thermal emissivity materials for infrared wavelengths between 8-14 mu m. Emissivity and dielectric constants were studied for these structures. A semi-empirical model has been established to obtain the relation between emissivity and dielectric constant. (C) 2012 Elsevier B.V. All rights reserved.

}, keywords = {composites, dielectric constant, Swift heavy ion, Thermal emissivity}, issn = {0168-583X}, doi = {10.1016/j.nimb.2012.06.005}, author = {Babrekar, Harshada A. and Jog, Jyoti Prakash and Mathe, Vikas L. and Avasthi, D. K. and Ojha, S. and Bhoraskar, S. V.} } @article { ISI:000355656000013, title = {Low-temperature sintering and microwave dielectric properties of Zn2SiO4 ceramic added with crystalline zinc borate}, journal = {Journal of Electronic Materials}, volume = {44}, number = {7}, year = {2015}, month = {JUL}, pages = {2312-2320}, publisher = {SPRINGER}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

The physical and dielectric properties of composites of known microwave materials, Zn2SiO4 and Zn3B2O6, prepared by solid-state reaction, were investigated with the purpose of developing a low-loss dielectric material for low-temperature co-fired ceramic applications. An off-stoichiometric phase of Zn2SiO4 with extra SiO2 was used to avoid the occurrence of unreacted ZnO. During sintering, zinc borate was found to partially react with residual SiO2 to form Zn2SiO4. The residual zinc borate was converted to a boron-rich glassy phase which helped to reduce the sintering temperature of the composite. Good relative sintering density (\> 90\%) at temperatures below the melting temperature of zinc borate is indicative of a sintering mechanism of diffusion-based mass transfer. Composites containing 15 wt.\% zinc borate, 2.5 wt.\% lithium carbonate and 20 wt.\% zinc borate in zinc silicate had dielectric constants of 6.8 and 6.1, quality factors (Qxf) of 48,800 and 94,300 GHz when sintered at 900A degrees C and 950A degrees C, respectively. These quality factor results are close to the best values reported for zinc silicate at these sintering temperatures.

}, keywords = {dielectric constant, LTCC, quality factor, sintering density, zinc borate, zinc silicate}, issn = {0361-5235}, doi = {10.1007/s11664-015-3762-0}, author = {Chaware, Varsha and Deshmukh, Ravindra and Sarode, Chetan and Gokhale, Suresh and Phatak, Girish} }