Department of Physics

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Physics

It is well known that the hydrodynamics of a zero-temperature superfluid can be formulated in field-theoretic terms, relating for example the superfluid four-velocity to the gradient of the phase of a Bose-condensed scalar field. At nonzero temperatures, where the phenomenology of a superfluid is usually described within a two-fluid picture, this relationship is less obvious. For the case of a uniform, dissipationless superfluid at small temperatures and weak coupling we discuss this relationship within a j4 model. For instance, we compute the entrainment coefficient, which describes the interaction between the superfluid and the normal-fluid components, and the velocities of first and second sound in the presence of a superflow. Our study is very general, but can also be seen as a step towards understanding the superfluid properties of various phases of dense nuclear and quark matter in the interior of compact stars. © Copyright owned by the author(s).

World University root node

School of Advanced Sciences

Chennai Campus

Proceedings of Science

Relativistic superfluid hydrodynamics from field theory

Polyurethane nanofibers containing calcium chloride (CaCl 2) were prepared via an electrospinning technique for the biomedical applications. Polyurethane nanofibers with different concentration of CaCl 2 were electrospun, and their bioactivity evaluation was conducted by incubating in biomimetic simulated body fluid (SBF) solution. The morphology, structure and thermal properties of the polyurethane/CaCl 2 composite nanofibers were characterized by means of scanning electron microscopy (SEM), field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetry. SEM images revealed that the CaCl 2 salt incorporated homogeneously to form well-oriented nanofibers with smooth surface and uniform diameters along their lengths. The SBF incubation test confirmed the formation of apatite-like materials, exhibiting enhanced bioactive behavior of the polyurethane/CaCl 2 composite nanofibers. This study demonstrated that the electrospun polyurethane containing CaCl 2 composite nanofibers enhanced the in vitro bioactivity and supports the growth of apatite-like materials. © 2010 Nirmala et al.

Fulltext

Nanoscale Research Letters

Hydroxyapatite mineralization on the calcium chloride blended polyurethane nanofiber via biomimetic method

We present a theoretical analysis of the mode-coupling dynamics of heterogeneous 6- and 7-core multicore fibers (MCFs). Simple analytical expressions for the mode amplitudes are derived, which highlight the effects of dissimilar cores on the coupling characteristics. Although power transfer is confined among the group of identical cores, the coupling within each group is significantly affected by the presence of neighboring dissimilar cores and is dependent on the propagation constants of the eigenmodes of the composite multicore structure. The dissimilar cores can enhance or mitigate the coupling effects by choosing appropriate design parameters. The formulas can serve as a basis for understanding the cross-talk of MCFs for more complicated cases involving longitudinal perturbations. © 2012 IEEE.

IEEE Photonics Technology Letters

Influence of dissimilar cores on the mode-coupling dynamics of multicore fibers

Low-dielectric constant SiOC(H) films were deposited on p-type Si(100) substrates using plasma enhanced chemical vapor deposition (PECVD) at different radio frequency (rf) powers. The structural characteristics of the SiOC(H) films were characterized using Fourier transform infrared spectroscopy (FTIR) in the absorbance mode. The bonding configurations of the SiOC(H) films remained unchanged upon annealing, showing their good thermal stability. Electrical characteristics of the SiOC(H) thin films with Al/SiOC(H)/p-Si(100)/Al metal-insulator-semiconductor (MIS) structures were analyzed using capacitancevoltage (CV) and conductancevoltage (G/ωV) at different frequencies. The conductance and the capacitance measurements were used to extract the interface state density in the MIS structures. From the experimental data and the subsequent quasi-static CV analysis, the energy distribution of interface state density was obtained. The interface state density of the as-deposited and 400°C annealed MIS structures increased with increasing rf powers, whereas the fixed charge density decreased with increasing rf powers. The interface state densities and their electrical properties of the SiOC(H) films strongly affected by the radio frequency power. © 2012 Elsevier Ltd. All rights reserved.

Journal of Physics and Chemistry of Solids

A study on structural and electrical properties of low dielectric constant SiOC(H) thin films deposited via PECVD

The in vitro cytocompatibility response of bioresourced hydroxyapatite (HA) containing silver nanoparticles was investigated. The morphology, structure and thermal properties of the HA containing Ag nanoparticles were characterised using scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis. Scanning electron microscopy observations showed that the HA powder has nearly uniform shape with spherical morphology and highly dispersed with diameter in the range of 800-2000 nm. X-ray diffraction patterns revealed that the Ag nanoparticles were incorporated into the HA powder very well. The adhesion, viability and proliferation properties of HA containing Ag nanoparticles and the differentiation of osteoblast were performed to evaluate the in vitro cell compatibility of the HA containing Ag nanoparticles. Our results showed that HA containing Ag nanoparticles were cytotoxic to human osteoblastic cells. © W. S. Maney & Son Ltd. 2012.

Materials Research Innovations

Characterisation of bioresourced hydroxyapatite containing silver nanoparticles

We investigate various aspects of a geometric flow defined using the Bach tensor. First, using a well-known split of the Bach tensor components for (2, 2) unwarped product manifolds, we solve the Bach flow equations for typical examples of product manifolds like S 2 × S 2, R 2 × S 2. In addition, we obtain the fixed-point condition for general (2, 2) manifolds and solve it for a restricted case. Next, we consider warped manifolds. For Bach flows on a special class of asymmetrically warped 4-manifolds, we reduce the flow equations to a first-order dynamical system, which is solved exactly to find the flow characteristics. We compare our results for Bach flow with those for Ricci flow and discuss the differences qualitatively. Finally, we conclude by mentioning possible directions for future work. © 2012 World Scientific Publishing Company.

International Journal of Geometric Methods in Modern Physics

Bach flows of product manifolds

We report on the preparation and characterization of core-shell structure of bovine serum albumin (BSA) blended poly(vinyl alcohol) (PVA) composite nanofibers by using electrospinning process. The core-shell structure nanofibers have been electrospun from the homogeneous solution of BSA (as shell) and PVA (as core). The morphology, chemical compositions, structure and thermal properties of the resultant products were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDX), high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry, thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) techniques. The blending ratio of PVA and BSA, molecular weight of BSA and the applied voltage of electrospinning process were observed to be the key influence factors on the formation of core-shell nanofibers structure. Based on the experimental findings, we proposed a possible physical mechanism for the formation of core-shell nanofibers structure of PVA blended BSA composite. © 2012 Elsevier B.V.

International Journal of Biological Macromolecules

Electrospun core-shell nanofibers from homogeneous solution of poly(vinyl alcohol)/bovine serum albumin

The electrical characteristics of nylon-6 nanofibers incorporated with TiO 2 and Fe 3O 4 nanoparticles were investigated. The resultant nanofibers exhibited good incorporation of nanoparticles. The impregnated TiO 2 and Fe 3O 4 nanoparticles into the nylon-6 nanofibers were confirmed by high resolution transmission electron microscopy (HR-TEM) and energy dispersive X-ray (EDX) spectroscopy studies. The electrical conductivity of the nylon-6 incorporated with TiO 2 and Fe 3O 4 composite nanofibers were higher than that of the pristine nylon-6 nanofibers. The impregnation of TiO 2 and Fe 3O 4 nanoparticles significantly enhanced the electrical property of the composite nanofibers. These polymeric/nanoparticles composite nanofibers structure may open a new direction for future organic electronics. © 2012 Elsevier Ltd. All rights reserved.

Electrical characterization of nylon-6 composite nanofibers

We report on the growth behavior of high-quality GaN epilayers via GaN nanowires (NWs) assisted epitaxial lateral overgrowth (NWELOG) by using metalorganic chemical vapor deposition (MOCVD). Initially, an array of well-aligned GaN NWs were grown on Si(111) substrates via vapor-liquid-solid (VLS) method and then the successive lateral overgrowth of GaN epilayers using 4 step NWELOG at the upper part of the NWs. A thickness of GaN epilayer of about 5 to 6 μm was achieved. Transmission electron microscopy (TEM) study revealed a significant reduction of the dislocation density at the laterally coalesced GaN epilayers. A comparative analysis of atomic force microscopy (AFM), photoluminescence (PL) and X-ray diffraction (XRD) data of the GaN epilayer between NWELOG and lateral epitaxy on patterned substrates (LEPS) revealed that the NWELOG grown GaN epilayers were superior. From the AFM analysis, there were no surface pits on the GaN epilayers grown by the NWELOG process. The strong PL emission peak was observed at 365 nm for the GaN epilayer on Si(111). These results demonstrate that the NWELOG technique can improve the quality of GaN epilayers on Si substrates without surface crack generation or any related defects. © 2012 The Royal Society of Chemistry.

CrystEngComm

Growth behavior of GaN epilayers on Si(111) grown by GaN nanowires assisted epitaxial lateral overgrowth

In this study, Ni-doped titanium dioxide (TiO 2) electrospun nanofibers are introduced as novel material for dehydrogenation of ammonia borane (AB) complex. Hydrolysis experiments with introduced catalytic nanofibers are prevailed to rapidly release hydrogen from AB complex. Typically, Ni nanoparticles (NPs) behave as a catalyst, meanwhile the incorporation of nickel NPs lead to decrease in the electrons/holes recombination rate in TiO 2 which resulted in the increase of active ions in the solution to a rapid evolution of hydrogen gas at room temperature. The utilized physiochemical analyses indicate that the introduced Ni-doped TiO 2 nanofibers have a smooth surface and uniform diameters along their lengths. Under sunlight irradiation, the hydrogen production rate in case of utilizing Ni-doped TiO 2 nanofibers is rapidly increased compared to the pristine TiO 2 nanofibers, the maximum hydrogen equivalent in case of the doped nanofibers is 2.6 while the pristine one is 1.4. Both formulations exhibit almost equal low activity in daylight as the observed hydrogen equivalent is 0.4. Overall, this study proposes cheap, stable and effective material for AB dehydrogenation at room temperature. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.