Department of Physics

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IIT Jodhpur

We present results from molecular dynamics simulations for the non-equilibrium evolution of a binary fluid in the presence of a wetting surface. We study the pattern dynamics which results when a homogeneous fluid mixture is quenched to temperatures both above and below the critical temperature. Our extensive computer simulation results are in agreement with arguments based on Ginzburg-Landau theory. © 2013 EDP Sciences and Springer.

World University root node

European Physical Journal: Special Topics

Surface-directed spinodal decomposition and enrichment in fluid mixtures: Molecular dynamics simulations: Kinetics of fluid mixtures at surfaces

In the X-Band PASOTRON under development in CSIR-CEERI, a rippled wall waveguide is designed and developed as the slow wave structure. The dispersion characteristic of a slow wave structure is a very crucial parameter in deciding the operating point in a microwave tube. The resonant method technique is used here to measure the dispersion relation and axial modes of dominant transverse magnetic modes (TM01) in a slow wave structure with sinusoidal varying radius. The resonant method is simple to use as compared to non-resonant methods where we have to move a bead through the structure which makes process complicated. In the technique we use, an advantage of our structure being a resonant structure has been taken. The purpose of this work is to compare the simulation results of dispersion characteristics using CST simulation code with experimental results, which comes out to be in close agreement. © 2013 IEEE.

Digest of Technical Papers-IEEE International Pulsed Power Conference

Design and characterization of rippled wall slow wave structure for X-band PASOTRON

Co doped nanocrystalline ZnO powders (Zn1-xCoxO; 0.03≤x ≤ 0.1) were synthesized by autocombustion technique. The average particle sizes reduce to 40 nm in comparison to the particle sizes of ZnO synthesized by the same technique. The XRD pattern reveals the absence of any secondary phases like Co or oxides of Co. This investigation suggests the possibility of solid solution of Co in ZnO. The 3% Co doped ZnO shows the diamagnetic behavior whereas other percentage of Co doped ZnO upto 10% shows the room temperature ferromagnetic signature with broadening of M∼H loop. The decrease in band gap suggests the Co substitution in ZnO matrix. © 2013 American Scientific Publishers. All rights reserved.

Nanoscience and Nanotechnology Letters

Synthesis of nanocrystalline Co doped ZnO by chemical route and its magnetic properties

The influence of melt spinning and heat treatment on the structure, phase transformation and magnetic field induced strain (MFIS) properties have been investigated for Ni55Mn22Ga22Al1 (at%) alloy. The microstructure showed distinct improvement in morphology of as spun ribbon as compared to ingot. Annealing further enhanced martensite state and displayed systematic arrangement of dislocations. It contributed to increase MFIS to 482 ppm in annealed ribbon as compared to 190 ppm and 28 ppm for as-spun ribbon and ingot, respectively. © 2013 Elsevier B.V. All rights reserved.

Journal of Magnetism and Magnetic Materials

Modification in martensite morphology and magneto-strain through rapid solidification and heat treatment of NiMnGaAl alloy

Design of a mid-wave IR (MWIR) broad-band fiber-based light source exploiting degenerate four-wave mixing (D-FWM) in a meter long suitably designed highly nonlinear (NL) chalcogenide microstructured optical fiber (MOF) is reported. This superior FWM bandwidth (BW) was obtained through precise tailoring of the fiber's dispersion profile so as to realize positive quartic dispersion at the pump wavelength. We consider an Erbium (Er3+) -doped continuous wave (CW) ZBLAN fiber laser emitting at 2.8 μm as the pump source with an average power of 5 W. Amplification factor as high as 25 dB is achievable in the 3 -3.9 μm spectral range with average power conversion efficiency &gt;32%. © 2013 Optical Society of America.

Fulltext

Optics Express

An efficient broad-band mid-wave IR fiber optic light source: Design and performance simulation

Single-qubit dissipative and non-dissipative channels, set in the general scenario of a system's interaction with a squeezed thermal bath, are compared in the Choi isomorphism framework, to bring out their contrasting rank and geometric properties. The equivalence of commutativity between the signal states and the Kraus operators to that between the system and interaction Hamiltonian, and thus to non-dissipativeness, is pointed out. Two distinct unitarily equivalent Kraus representations of the dissipative channel, one based on the Choi isomorphism, and the other based on an ansatz, are used to illustrate that the orthogonality of Kraus operators under the Hilbert-Schmidt inner product is not a unitary invariant. Unlike the non-dissipative (Pauli) channels, the dissipative (squeezed generalized amplitude damping) channels do not form a convex set. Further, whereas the rank of Pauli channels can be any positive integer up to 4, that of the amplitude damping ones is either 2 or 4. In the latter case, a noise range is identified where environmental squeezing counteracts the effect of thermal decoherence. © 2013 Springer Science+Business Media New York.

Quantum Information Processing

Dissipative and non-dissipative single-qubit channels: Dynamics and geometry

Negatively charged DNA can be compacted by positively charged dendrimers and the degree of compaction is a delicate balance between the strength of the electrostatic interaction and the elasticity of DNA. We report various elastic properties of short double-stranded DNA (dsDNA) and the effect of dendrimer binding using fully atomistic molecular dynamics and numerical simulations. In equilibrium at room temperature, the contour length distribution P(L) and the end-to-end distance distribution P(R) are nearly Gaussian, the former gives an estimate of the stretch modulus $\gamma-{1}$ of dsDNA in quantitative agreement with the literature value. The bend angle distribution $P(\theta)$ of the dsDNA also has a Gaussian form and allows to extract a persistence length, Lp of 43nm. When the dsDNA is compacted by positively charged dendrimer, the stretch modulus stays invariant but the effective bending rigidity estimated from the end-to-end distance distribution decreases dramatically due to backbone charge neutralization of dsDNA by dendrimer. We support our observations with numerical solutions of the worm-like-chain (WLC) model as well as using non-equilibrium dsDNA stretching simulations. These results are helpful in understanding the dsDNA elasticity at short length scales as well as how the elasticity is modulated when dsDNA binds to a charged object such as a dendrimer or protein. © 2013 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.

European Physical Journal E

Elasticity of DNA and the effect of dendrimer binding

We assessed groundwater quality for irrigation purpose in intensively wheat cultivated semi-arid regions of Haryana during 2008. Eight to ten water samples from each representing village of Bawani Khera and Bhiwani blocks of Bhiwani district of Haryana were collected from running tube-wells and analyzed for pH, electrical conductivity (EC), soluble cations (Ca+2, Mg+2, Na+ and K+) and anions (CO32, HCO3-, SO4-2, Cl", NO 3- and F-) as well as categorized on the basis of water quality classification of Manchanda (1976) and All India Co-ordinated Research Project (1989). Results revealed that pH, EC, SAR and RSC in ground waters of Bawani Khera block varied from 7.56-9.23,0.26-18.49 (d/Sm), 0.11-39.82 (mmol/l)1/2 and nil-6.60 (me/1), respectively. Likewise, corresponding values of groundwater samples for Bhiwani block varied from 7.43-9.67, 0.25-18.26 (dS/m), 0.32-65.41 (mmol/1)1/2 and nil-7.20 (me/1), respectively. Cations were in the order Na+&gt;Mg+2&gt; Ca+2&gt;K+, while anions were C1-&gt;SO 4-2&gt;HCO3-&gt;CO3 -2 in both the blocks. As per Manchanda (1976) classification in Bawani Khera block 19.0, 19.0, 21.0, 6.0 and 35% water samples were found to be good, marginal, saline, sodic and saline-sodic, respectively. Likewise according to AICRP (1989) criteria 19.0% water samples were found in good category, 19.0% marginally saline and 21.0% saline. Of the remaining 41.0% waters, 6.0% were highly alkali and 35.0% were high SAR saline waters. Similarly, in Bhiwani block 20.0% water samples were good, whereas 17.0, 20.0, 5.0 and 38.0% waters were categorized as marginal, saline, sodic and saline-sodic as per Manchanda (1976) classification. As per AICRP (1989) classification, 19.0% water samples were found under good category, 17.0% marginally saline, 21.0% saline, 2.0% marginally alkali, 4.0% highly alkali, and 37.0% water samples were classified as high SAR saline waters. Spatial distribution of ground water quality did not follow any definite pattern in any direction but it showed that good quality waters frequency was more in grid blocks where canal supply was more assured and vice versa.

Annals of Biology

Assessment of quality of groundwater under intensively wheat cultivated semi-arid regions of Haryana, India

Plasma assisted microwave devices are unique source for microwave radiation. This paper presents the status for development of X-band Plasma Assisted Slow Wave Oscillator (PASOTRON) of peak power 0.5MW. © 2013 IEEE.

14th IEEE International Vacuum Electronics Conference, IVEC 2013 - Proceedings

Technological development for X-band Plasma Assisted Slow Wave Oscillator (PASOTRON)

Room-temperature tunable excitonic photoluminescence is demonstrated in alloy-tuned layered Inorganic-Organic (IO) hybrids, (C12H 25NH3)2PbI4(1-y)Br4y (y = 0 to 1). These perovskite IO hybrids adopt structures with alternating stacks of low-dimensional inorganic and organic layers, considered to be naturally self-assembled multiple quantum wells. These systems resemble stacked monolayer 2D semiconductors since no interlayer coupling exists. Thin films of IO hybrids exhibit sharp and strong photoluminescence (PL) at room-temperature due to stable excitons formed within the low-dimensional inorganic layers. Systematic variation in the observed exciton PL from 510 nm to 350 nm as the alloy composition is changed, is attributed to the structural readjustment of crystal packing upon increase of the Br content in the Pb-I inorganic network. The energy separation between exciton absorption and PL is attributed to the modified exciton density of states and diffusion of excitons from relatively higher energy states corresponding to bromine rich sites towards the lower energy iodine sites. Apart from compositional fluctuations, these excitons show remarkable reversible flips at temperature-induced phase transitions. All the results are successfully correlated with thermal and structural studies. Such structural engineering flexibility in these hybrids allows selective tuning of desirable exciton properties within suitable operating temperature ranges. Such wide-range PL tunability and reversible exciton switching in these novel IO hybrids paves the way to potential applications in new generation of optoelectronic devices. © 2013 AIP Publishing LLC.