Mumbai, India

The Bhabha Atomic Research Centre is India's premier nuclear research facility based in Trombay, Mumbai. BARC is a multi-disciplinary research centre with extensive infrastructure for advanced research and development covering the entire spectrum of nuclear science, engineering and related areas.BARC's core mandate is to sustain peaceful applications of nuclear energy, primarily for power generation. It manages all facets of nuclear power generation, from theoretical design of reactors, computerised modelling and simulation, risk analysis, development and testing of new reactor fuel materials, etc. It also conducts research in spent fuel processing, and safe disposal of nuclear waste. Its other research focus areas are applications for isotopes in industries, medicine, agriculture, etc. BARC operates a number of research reactors across the country. Wikipedia.

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Singh S.,Bhabha Atomic Research Center | Basu S.,Bhabha Atomic Research Center
Current Applied Physics | Year: 2017

Multilayered structures with artificial oxide hetero-interfaces have recently been dominating the field of new states of matter. The unexpected properties and related functionalities at the interface of complex oxide heterostructures as a consequence of the symmetry breaking, electronic reconstruction etc., make these complex oxide interfaces particularly challenging for understanding the fundamental mechanism and interaction across the interfaces. Magnetic modulation, novel magnetic coupling and emerging interface induced magnetization at the interfaces of complex oxide heterostructures have made the search for their technological applications as an intense field of research in recent time. However to study the structure and magnetism in such interfaces require tools with interface specificity. Polarized neutron reflectivity is a non-destructive technique which has played a decisive role in investigation of interfacial magnetic structures and in understanding the underlying physics in this rapidly developing field. This article presents a review of some recent experimental results on emerging magnetization at the interfaces of complex oxide heterostructures specifically investigated using polarized neutron reflectivity. © 2017 Elsevier B.V.

Sen S.,Bhabha Atomic Research Center | Ghosh H.,Bhabha Atomic Research Center
Computational Materials Science | Year: 2017

A comprehensive study on the evolution of Stoner factor with doping concentration for various doped 122 systems (like BaFe2As2, SrFe2As2) of Fe-based superconductors is presented. Our first principles electronic structure calculations reveal that for Co/Ru (electron or iso-electronic) doping at Fe sites or P doping at As sites result in a reduction of Stoner factor with increasing doping concentration. On the contrary, in case of Na/K (hole) doping at the Ba sites, Stoner factor is enhanced for higher doping concentrations. This may be considered as an indicator of elevation of “magnetic fluctuation” in these systems. We find that the Stoner factor uniquely follows the variation of the pnictide height zAs/Fe[sbnd]As bond length with various kinds of doping. Our calculated Fermi surfaces explicate the diversities in the behaviour of Stoner factors for various doped 122 systems; larger degree of Fermi surface nesting, larger the value of Stoner factor and vice versa. © 2017 Elsevier B.V.

Modak B.,Bhabha Atomic Research Center | Ghosh S.K.,Bhabha Atomic Research Center
Solar Energy Materials and Solar Cells | Year: 2017

Increasing photocatalytic application of KTaO3 motivated us to find efficient strategy to reduce its band gap, so that it can better utilize the solar spectrum. In this study, the effect of (N, Mo/W) pair on the electronic structure of KTaO3 has been investigated using density functional theory. The experimental band gap of KTaO3 (3.6 eV) has been successfully reproduced (3.61 eV) by employing hybrid functional proposed by Heyd, Scuseria, and Ernzerhof. The present study reveals that the dopant elements individually can reduce the band gap either by introducing localized unoccupied states or occupied states in between valence band and conduction band. Unfortunately, these localized states in combination with charge compensating vacancy defects may reduce the photoconversion efficiency. In case of codoping with (N, Mo/W) pair total electrical charge neutrality is maintained. Therefore, vacancy promoted electron-hole recombination can be avoided. Moreover, the feasibility of N doping into crystal structure of KTaO3 increases in presence of (Mo/W) due to reduction in formation energy. Interestingly, in presence of both cationic (Mo/W) and anionic dopant (N) a clean band structure is produced, which is favorable for good photoconversion efficiency. The reduction in band gap due to codoping is quite significant for enhancement of absorption of visible light, and it is more prominent in the case of (Mo, N) pair. The final conclusion has been drawn by checking the relative positions of the band edges of both the codoped systems with respect to water redox potential. Thus present study explores the role of (Mo/W, N) pair in improving the visible light photocatalytic activity of KTaO3. © 2016 Elsevier B.V.

OBJECTIVES: The aims of this study were to perform multiparametric response assessment of metastatic/advanced pulmonary neuroendocrine tumors (NETs) to Lu-DOTATATE peptide receptor radionuclide therapy (PRRT) (clinical, biochemical, molecular/structural imaging, and survival assessment) and to study the relationship between response, mortality, and overall survival with dual-tracer molecular imaging parameters. METHODS: Twenty-two patients (6 women, 16 men; median age, 44 years; range, 16–72 years) of histopathologically proven pulmonary NETs with metastatic/advanced disease were included and analyzed retrospectively. Lu-DOTATATE PRRT was administered using standardized protocol (150 mCi [5.55 GBq] per cycle, cycles repeated at 12–16 weeks’ intervals [range, 1–5 cycles; average, 4 cycles]) with amino acid–based renal protection. Assessment with Tc-HYNIC-TOC (in the initial years of PRRT development, n = 11)/Ga-DOTATATE PET/CT (presently, n = 11) and F-FDG PET/CT (n = 22), symptomatic and biochemical parameters (serum CgA and urinary 5-HIAA levels), and anatomical response using contrast-enhanced CT (after 3 cycles) was part of routine pretreatment and response evaluation. The patients were designated as responders and nonresponders based on predefined response assessment criteria. Kaplan-Meier product-limit method was calculated for overall survival (OS) curve after the first PRRT, and corresponding 95% confidence intervals (95% CIs) were estimated for annual survival at 1, 2, 3, and 4 years. The various prognostic variables were also investigated for association with mortality, OS, and treatment response following PRRT. RESULTS AND CONCLUSIONS: Of 22 patients, 6 had undergone surgical resection of primary tumors. All patients were symptomatic before start of PRRT. Two patients did not qualify for PRRT, and 1 received single cycle with follow-up less than 3 months, hence excluded from the present analysis. Thus, a total 19 patients were analyzed in our study. Symptomatic response following PRRT was observed in 15 (79%) of 19 patients. Based on predefined 3-scale response evaluation criteria, of 19 patients, 12 patients (63%) were finally characterized as responders, and 7 patients (37%) were overall nonresponder to PRRT. All 7 nonresponders had moderate to intense FDG-avid primary lung lesion (SUVmax >5 in 4 of 7 patients), and 5 had FDG-avid metastatic liver disease (SUVmax >5). Peptide receptor radionuclide therapy was well tolerated in all with no major hematologic and renal toxicity (except for 2 patients showing mild grade I renal and hematologic toxicity in the initial cycles and recovery in subsequent follow-up). Seven (37%) of 19 died at the time of analysis. The observed annual OS rates were as follows: 1 year: 94.7% (95% CI, 68.1%–99.2%), 2 years: 66% (95% CI, 35.5%–84.5%), 3 years: 57.7% (95% CI, 28–78.9%), and 4 years: 38.5% (95% CI, 8.1%–69.5%); median OS was 40 months with 39% (95% CI, 13.1%–64.8%). In conclusion, Lu-DOTATATE PRRT was found safe and well tolerated in receptor-positive pulmonary NET. FDG positivity appeared to forecast aggressive tumor behavior. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.

Agarwal R.,Bhabha Atomic Research Center | Sharma M.K.,Bhabha Atomic Research Center
Electrochimica Acta | Year: 2017

A facile hybrid electrochemical-chemical (E-C) methodology is demonstrated to synthesize Prussian blue (PB) on Au electrode from single ferricyanide solution in a two-step process: (i) electrochemical conversion of Au to nanoporous gold (NPAu) and (ii) chemical deposition of PB on NPAu from single ferricyanide solution (neutral pH) in dark, and the role of morphology of Au surface in chemical synthesis of PB is also explored. All the experiments with K3[Fe(CN)6] are performed in dark to exclude the possibility of photochemical/photocatalytic synthesis of PB. Formation of PB is confirmed by cyclic voltammetry (CV), UV-Visible spectroscopy (UV-Vis.), energy dispersive X-ray spectroscopy (EDX), and surface morphology of NPAu film and PB deposited on NPAu is studied by scanning electron microscopy (SEM). The growth of PB film on NPAu shows linear relation with the dipping time and therefore, the amount of the PB deposited on NPAu can be controlled by varying the time. Formation of PB is not observed on Au and AuO electrodes on standing in freshly prepared K3[Fe(CN)6] solution. Open circuit potential (OCP) measurements shows NPAu catalyses the dissociation of ferricyanide to ferric and cyanide ions on standing in freshly prepared 10 mM K3[Fe(CN)6] solution. The ferric ions are reduced to ferrous ions by the water and ferrous ions immediately react with ferricyanide to form PB on NPAu. © 2017 Elsevier Ltd

Jain D.,Bhabha Atomic Research Center | Shrivastava S.,Banasthali Vidhyapith
Advances in Intelligent Systems and Computing | Year: 2017

High-speed VHDL interfaces are used for transmission of huge amount of data. This paper deals with the development of VHDL code for interfacing with high-speed serial data link: Triple-Speed Ethernet (TSE) IP core. It includes the use of high bandwidth structure, Qsys system as System On Programmable Chip (SOPC) builder system for connecting components. Qsys interconnects the components either available in library or the customized components developed by user with VHDL or Verilog code (using Avalon interface interconnect). Modelsim simulator is used to simulate the developed code, and generated Qsys structure is verified and tested with TCL script in system console. Signal Tap II analyzer is used to analyze the behavior of signals used internally in the design. Data packets are generated using data packet module from the processed data and transmitted over communication channel in order to attain the high-speed data transmission. Transfer of these data packets to data archiving server on Ethernet over open core UDP/IP stack at 1 Gbps data rate. © Springer Science+Business Media Singapore 2017.

Rastogi A.,Bhabha Atomic Research Center | Dadheech A.,Banasthali Vidhapth
Advances in Intelligent Systems and Computing | Year: 2017

In industry data acquisition covers the most demanding applications of real-time monitoring. The multi-channel data acquisition is used for the acquisition and monitoring of various industrial sensor signals. The data obtained are processed in real-time execution. For future work, we can access the stored data from an external memory. The proposed design is implementing by combination of EDA tools and nios II Processor. This processor provides an ideal embedded solution that includes the following: flexibility, high performance, low cost, long life for real-time processing. This document entails the design of a network data acquisition system which consists of a number of links RS 422 to communicate with various devices connected to it. The hardware development is to generate VHDL code for implementing the hardware inside the FPGA. Real-time processing and signal processing of data acquisition attains by FPGA. It also involves the development of test routines for simulation and verification of VHDL code. © Springer Science+Business Media Singapore 2017.

Shrivastava R.,Bhabha Atomic Research Center | Oza R.B.,Bhabha Atomic Research Center
Progress in Nuclear Energy | Year: 2017

This paper describes the validation of the Tropical Rainfall Measuring Mission (TRMM) rainfall product 3B42 version 7 over the Pacific Ocean region using rain gauge data from Japan and the Comprehensive Pacific Rainfall Database (PACRAIN) and its application in deriving the scavenging coefficients for 131I (gaseous and particulate forms) and 137Cs (particulate form) over the Pacific Ocean following the Fukushima accident. The validation is carried out for the period of 01st March 2011 - 30th April 2011. For 131I (particulate form), the values of estimated scavenging coefficient ranged from 4.61 × 10-08 (s-1) to 8.18 × 10-05 (s-1) and the same for 137Cs (particulate form) ranged from 5.94 × 10-08 (s-1) to 3.89 × 10-05 (s-1). Since a large quantity of 131I was transported in gaseous form, the scavenging coefficient for gaseous iodine was also computed. The scavenging coefficient for gaseous iodine was found to vary between 6.27 × 10-08 (s-1) to 4.41 × 10-05 (s-1). The scavenging coefficients were also estimated using the parameterization scheme available in Numerical Atmospheric - Dispersion Modeling Environment (NAME) model. They were found to lie between 1.91 × 10-08 (s-1) to 4.91 × 10-05 (s-1) for both 131I and 137Cs. © 2017 Elsevier Ltd.

Mohideen Abdul Razak M.,Bhabha Atomic Research Center | Devan K.,Indira Gandhi Center for Atomic Research
Progress in Nuclear Energy | Year: 2017

A new method of analyzing reactor transients using the modified exponential time differencing method with Improved Quasi Static (IQS) model is developed and presented here. According to this method, the neutron flux is factored into amplitude function and shape function. The amplitude function is solved using the modified exponential time differencing method and the shape function is solved using implicit scheme. Using this method, a large time step can be chosen for solving the amplitude function and the shape function can also be solved by proportionately increasing the time step. This method is applied to estimate the transients in the well known CANDU 3D-PHWR kinetics benchmark, 3D-TWIGL Heterogeneous and 3D Homogeneous Reactors. These reactors contain different kinds of heterogeneities and the reactivity perturbations are also different. The transients in CANDU 3D-PHWR, simulated by LOCA, are estimated by this method for various time steps and the results are compared with other standard methods. From the comparison of results, it is established that this method is capable of estimating the transients using large time steps with good accuracy. A novel scheme to choose the time step for solving the amplitude function under constant and varying reactivity perturbations is also presented and applied here in the estimation of CANDU 3D-PHWR and 3D Homogeneous Reactor transients. It is also shown that by using large time steps, the transient computation time is reduced without affecting the accuracy and the error remains bounded. © 2017 Elsevier Ltd.

Banerjee S.,Bhabha Atomic Research Center | Gupta H.P.,Bhabha Atomic Research Center
Progress in Nuclear Energy | Year: 2017

The strategy for growth of nuclear power in India was planned nearly sixty years ago, noting the rather small uranium and large thorium reserves in the country. This has prompted India to adopt the well-known three stage programme. The first stage is primarily based on the Pressurised Heavy Water Reactors (PHWRs). The evolution of technology of PHWRs is discussed in the first part of this paper. India has constructed eighteen PHWRs, has achieved impressive availability factors and some of these reactors have achieved annual capacity factors of nearly hundred percent in the recent past. Having installed a nuclear power generation capacity of 6780 MWe (4460 MWe from PHWRs, 2000 MWe from PWRs and 320 MWe from BWRs), India is now poised to launch a major expansion programme. This will be based on the increased availability of uranium from import and from the augmented domestic supply. In the immediate future, the nuclear power capacity will grow by installing a series of indigenous PHWRs in addition to light water reactors built under international civil nuclear cooperation agreements. The growth of nuclear capacity in this period is aimed at increasing the share of nuclear power in meeting the base-load demand of non-carbon electricity required for the rapid economic growth in the country.India embarked on its second stage programme with the successful operation of a research reactor named Fast Breeder Test Reactor (FBTR). Based on the experience of FBTR and following the development of all the required enabling technologies in India, the Prototype Fast Breeder Reactor (PFBR) of 500 MWe (gross) capacity has been designed, constructed and is now at an advanced stage of commissioning. A large increase in the nuclear power generation capacity is envisaged through deployment of fast breeder reactors. These reactors will not only help in building up nuclear power capacity but also, in due course, enable conversion of thorium into fissile U233, which will fuel the reactors in the third stage of India's nuclear programme. The adoption of the closed fuel cycle for both thermal and fast reactors has dual objectives: multiplying the fissile inventory by fertile to fissile conversion and reducing the burden of long lived radioactive waste-both being essential for attaining near sustainability of nuclear power.India has designed an Advanced Heavy Water Reactor (AHWR). This reactor can use one of the following fuels:. (i)Low enriched uranium dioxide-thorium dioxide based mixed oxide (MOX) fuel primarily in once through mode.(ii)Plutonium dioxide - thorium dioxide MOX fuel in the closed fuel cycle mode. Eventually when enough of U233 is generated the reactor can operate with the U233- thorium MOX fuel. A large number of passive safety features are incorporated in this design.As a part of the long term objective of the development of Accelerator Driven Sub-critical Systems (ADSS), work on the development of high power linear accelerator has been initiated. © 2017 Elsevier Ltd.

Sarkar A.,Bhabha Atomic Research Center | Singh M.,Bhabha Atomic Research Center
Plasma Science and Technology | Year: 2017

We report spectroscopic studies on plasma electron number density of laser-induced plasma produced by ns-Nd:YAG laser light pulses on an aluminum sample in air at atmospheric pressure. The effect of different laser energy and the effect of different laser wavelengths were compared. The experimentally observed line profiles of neutral aluminum have been used to extract the excitation temperature using the Boltzmann plot method, whereas the electron number density has been determined from the Stark broadened as well as using the Saha-Boltzmann equation (SBE). Each approach was also carried out by using the Al emission line and Mg emission lines. It was observed that the SBE method generated a little higher electron number density value than the Stark broadening method, but within the experimental uncertainty range. Comparisons of N e determined by the two methods show the presence of a linear relation which is independent of laser energy or laser wavelength. These results show the applicability of the SBE method for N e determination, especially when the system does not have any pure emission lines whose electron impact factor is known. Also use of Mg lines gives superior results than Al lines. © 2017 Hefei Institutes of Physical Science, Chinese Academy of Sciences and IOP Publishing.

De S.,Institute of Physics, Bhubaneswar | De S.,Bhabha Atomic Research Center
Journal of Physics G: Nuclear and Particle Physics | Year: 2017

Recent experiments on lead (Pb82 208) nuclei have observed the celebrated phenomenon of the neutron skin thickness of low energy nuclear physics. Skin thickness provides a measure of the extension of the spatial distribution of neutrons inside the atomic nucleus than protons. We have studied the effect of neutron skin thickness on inclusive prompt photon production in Pb + Pb collisions at Large Hadron Collider energies. We have calculated the centralto- peripheral ratio (Rcp) of prompt photon production with and without accounting for the neutron skin effect. The neutron skin causes a characteristic enhancement of the ratio, in particular at forward rapidity, which is distinguishable in our calculation. However, a very precise direct photon measurement up to large transverse momenta would be necessary to constrain the feature in experiment. © 2017 IOP Publishing Ltd Printed in the UK.

Sharma R.K.,Bhabha Atomic Research Center | Sharma A.,Bhabha Atomic Research Center
Review of Scientific Instruments | Year: 2017

This development is concerned with the compact capacitor module for a plasma focus device. Oil-free, non-standard geometry capacitors are designed and developed for high current delivery in sub-microseconds time. Metalized dielectric film based pulse capacitor becomes progressively less viable at currents above 10 kA. It is due to reliability and energy scaling difficulties, based on effects such as vaporization, high resistivity, and end connection. Bipolar electrolytic capacitors are also not preferred due to their limited life and comparatively low peak current delivery. Bi-axially oriented polypropylene (BOPP) film with extended aluminum foil is a combination to deliver moderately high power. But, electrically weak points, relative permittivity, and the edge gap margins have made its adoption difficult. A concept has been developed in lab for implementing the above combination in a less complex and costly manner. This paper concerns the development and testing process techniques for quite different hollow cylindrical, oil-free capacitors (4 μF, 10 kV, 20 nH). Shot life of 1000 has been experimentally performed on the test bed at its rated energy density level. The technological methods and engineering techniques are now available and utilized for manufacturing and testing of BOPP film based oil-free capacitors. © 2017 Author(s).

Namboodiri V.V.,Bhabha Atomic Research Center | Guleria A.,Bhabha Atomic Research Center | Singh A.K.,Bhabha Atomic Research Center
Applied Physics B: Lasers and Optics | Year: 2017

Considering the impending applications of room temperature ionic liquids (RTILs) in various areas involving high optical and radiation fields, it is pertinent to probe the structure–property correlation of these solvents exposed to such conditions. Herein, femtosecond Z-scan technique (at high pulse repetition rate, 80 MHz) was employed to investigate the non-linear optical response of imidazolium RTILs in 3 scenarios: (1) -OH functionalization, (2) C2 methylation, and (3) influence of high radiation fields. Large negative non-linear refractive values (n2) were observed in all the RTIL samples and have been attributed predominantly due to the thermal effects. In order to isolate and determine the contribution of electronic Kerr effect, the Z-scan experiments were also carried out at low pulse repetition rate (i.e. 500 Hz) by means of a mechanical chopper. The closed aperture transmittance profile showed the valley-peak pattern, which signifies positive non-linearity. Nonetheless, the variation in the n2 values of the RTILs follows the same trend in low pulse repetition rate as was observed in case of high pulse repetition rate. The trend in the n2 values clearly showed the decrease in the non-linearity in the first two cases and has been attributed to the weakening of the ion-pair formation, which adversely affects the charge transfer between the ionic moieties via C2 position. However, an increase in the n2 values was observed in case of ILs irradiated to high radiation doses. This enhancement in the non-linearity has been assigned to the formation of double bond order radiolytic products. These results clearly indicate a strong correlation between the non-linearity and the strength of cation–anion interaction amongst them. Therefore, such information about these solvents may significantly contribute to the fundamental understanding of their structure–property relationships. © 2017, Springer-Verlag Berlin Heidelberg.

Ajmi A.,Bhabha Atomic Research Center | Majumder G.,Tata Institute of Fundamental Research
Pramana - Journal of Physics | Year: 2017

The iron calorimeter (ICAL) detector is the proposed underground neutrino-physics experiment in the INO cavern. Its main goal is the determination of sign of 2-3 mass-squared difference, ?m2 32(=m2 3 - m2 2 ) in the presence of matter effects, apart from the precise measurement of other neutrino parameters. Like all other neutrino experiments, the INO Collaboration is going to interface its main software code with a neutrino event generator. The GENIE software is best suited for the ICAL experiment. But, it requires a few modifications before being incorporated in ICAL simulation to have better representation of the neutrino flux and to be more user friendly to the INO user. This paper reports all these modifications.

Dey P.,Bhabha Atomic Research Center | Shukla R.,Bhabha Atomic Research Center | Venkateswarlu D.,Bhabha Atomic Research Center
Applied Optics | Year: 2017

With the commercialization of powerful solid-state lasers as pointer lasers, it is becoming simpler nowadays for the launch and free-space reception of polarized light for polarimetric applications. Additionally, because of the high power of such laser diodes, the alignment of the received light on the small sensor area of a photo-diode with a high bandwidth response is also greatly simplified. A plastic sheet polarizer taken from spectacles of 3D television (commercially available) is simply implemented as an analyzer before the photo-receiver. SF11 glass is used as a magneto-optic modulating medium for the measurement of the magnetic field. A magnetic field of magnitude more than 8 Tesla, generated by a solenoid has been measured using this simple assembly. The measured Verdet constant of 12.46 rad/T-m is obtained at the wavelength of 672 nm for the SF11 glass. The complete measurement system is a cost-effective solution. © 2017 Optical Society of America.

Mehndiratta A.,Indian Institute of Technology Guwahati | Shukla P.,Bhabha Atomic Research Center
Nuclear Physics A | Year: 2017

We revisit the Glauber model to study the heavy ion reaction cross sections and elastic scattering angular distributions at low and intermediate energies. The Glauber model takes nucleon–nucleon cross sections and nuclear densities as inputs and has no free parameter and thus can predict the cross sections for unknown systems. The Glauber model works at low energies down to Coulomb barrier with very simple modifications. We present new parametrization of measured total cross sections as well as ratio of real to imaginary parts of the scattering amplitudes for pp and np collisions as a function of nucleon kinetic energy. The nuclear (charge) densities obtained by electron scattering form factors measured in large momentum transfer range are used in the calculations. The heavy ion reaction cross sections are calculated for light and heavy systems and are compared with available data measured over large energy range. The model gives excellent description of the data. The elastic scattering angular distributions are calculated for various systems at different energies. The model gives good description of the data at small momentum transfer but the calculations deviate from the data at large momentum transfer. © 2017 Elsevier B.V.

Mukherjee A.B.,Bhabha Atomic Research Center | Chakravartty J.K.,Bhabha Atomic Research Center
International Journal of Manufacturing Research | Year: 2016

An improved lap type diffusion-bonded transition joint was developed between titanium (Ti) pipe and stainless steel (SS) pipe with grooves at the interface for use in high pressure-high temperature applications. The groove design was optimised using finite element method (FEM) so as to produce joint strength superior to the strength of the Ti pipe being joined. Elastic-plastic FE analyses were performed simulating large displacement and deformation involved. Further, joints were subjected to a simplified pull-out test to assess its strength. A good matching of joint strength, within 10% of FEM prediction and experimental results has been achieved. Design curves were generated using non dimensional parameters like r/t and a1/t (r-pipe radius, t- pipe thickness and a1-groove depth) to arrive at the groove depth for r/t range of 10, 15 and 20. It was demonstrated experimentally that the joint with groove performs better under thermal cycling loads. [Received 12 March 2016; Accepted 27 October 2016]. Copyright © 2016 Inderscience Enterprises Ltd.

Tailor V.,Bhabha Atomic Research Center | Ballal A.,Bhabha Atomic Research Center
Free Radical Biology and Medicine | Year: 2017

The Peroxiredoxin Q (PrxQ) proteins are thiol-based peroxidases that are important for maintaining redox homeostasis in several organisms. Activity of PrxQs is mediated by two cysteines, peroxidatic (Cp) and resolving (Cr), in association with a reducing partner. A PrxQ, Alr3183, from the cyanobacterium, Anabaena PCC 7120, was characterized in this study. Alr3183, which required thioredoxin A (TrxA) for peroxidase activity, was an intramolecular disulfide bond-containing monomeric protein. However, Alr3183 lacking Cp (Alr3183C46S) or Cr (Alr3183C51S) formed intermolecular disulfide linkages and was dimeric. Alr3183C46S was completely inactive, while Alr3183C51S required higher concentration of TrxA for peroxidase activity. Surface plasmon resonance analysis showed that unlike Alr3183 or Alr3183C46S, Alr3183C51S bound rather poorly to TrxA. Also, compared to the oxidized protein, the DTT-treated (reduced) Alr3183 displayed decreased interaction with TrxA. In vivo, Alr3183 was found to be induced in response to γ-radiation. On exposure to H2O2, Anabaena strain over-expressing Alr3183 showed reduced formation of ROS, intact photosynthetic pigments and consequently better survival than the wild-type, whereas overproduction of Alr3183C46S did not provide any protection. Significantly, this study (1) reveals the importance of Cr for interaction with thioredoxins and (2) demonstrates that over-expression of PrxQs can protect cyanobacteria from oxidative stresses. © 2017 Elsevier Inc.

Tak H.,Bhabha Atomic Research Center | Negi S.,Bhabha Atomic Research Center | Ganapathi T.R.,Bhabha Atomic Research Center
PLoS ONE | Year: 2017

Lignin and polyphenols are important cellular components biosynthesized through phenylpropanoid pathway. Phenylpropanoid pathway in plants is regulated by some important transcription factors including R2R3 MYB transcription factors. In this study, we report the cloning and functional characterization of a banana R2R3-MYB transcription factor (MusaMYB31) by overexpression in transgenic banana plants and evaluated its potential role in regulating biosynthesis of lignin and polyphenols. Sequence analysis of MusaMYB31 indicated its clustering with members of subgroup 4 (Sg4) of R2R3MYB family which are well known for their role as repressors of lignin biosynthesis. Expression analysis indicated higher expression of MusaMYB31 in corm and root tissue, known for presence of highly lignified tissue than other organs of banana. Overexpression of MusaMYB31 in banana cultivar Rasthali was carried out and four transgenic lines were confirmed by GUS histochemical staining, PCR analysis and Southern blot. Histological and biochemical analysis suggested reduction of cell wall lignin in vascular elements of banana. Transgenic lines showed alteration in transcript levels of general phenylpropanoid pathway genes including lignin biosynthesis pathway genes. Reduction of total polyphenols content in transgenic lines was in line with the observation related to repression of general phenylpropanoid pathway genes. This study suggested the potential role of MusaMYB31 as repressor of lignin and polyphenols biosynthesis in banana. © 2017 Tak et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Dey M.K.,Bhabha Atomic Research Center | Satpati A.K.,Bhabha Atomic Research Center
Journal of Electroanalytical Chemistry | Year: 2017

In this paper we report the interaction of functionalised carbon nano spheres (FCNSs) with dopamine (DA), Uric acid (UA) and L-ascorbic acid (AA). FCNSs were characterised using SEM, AFM, spectroscopic and electrochemical measurements. Functionalised carbon nano spheres paste electrode (FCNSPE) has shown excellent preconcentration property of DA over its surface. UA also has also shown good electrochemical activity over the modified electrode. Parameters were optimised for the enhanced oxidation signal of DA in connection with simultaneous determination of DA and UA. An analytical method was developed for the simultaneous determination of DA and UA using the simple method of fabrication of electrode with detection limits (S/N of 3) of 10 nM and 42 nM for DA and UA respectively. Electrochemical oxidation signals of DA and UA were interference free from the oxidation of AA and other commonly occurring interfering agents. The method was applied for the determination of DA in spiked blood serum sample and for UA in real blood serum samples. © 2017 Elsevier B.V.

Kora A.J.,Bhabha Atomic Research Center | Rastogi L.,Bhabha Atomic Research Center
IET Nanobiotechnology | Year: 2017

A biosynthetic method for the production of selenium nanoparticles under ambient temperature and pressure from sodium selenite was developed using Gram-negative bacterial strain Escherichia coli ATCC 35218. Bacteriogenic nanoparticles were methodologically characterized employing UV-vis, XRD, Raman spectroscopy, SEM, TEM, DLS and FTIR techniques. Generation of nanoparticles was visualized from the appearance of red colour in the selenite supplemented culture medium and broad absorption bands in the UV-vis. Biofabricated nanoparticles were spherical, polydisperse, ranged from 100-183 nm and the average particle size was about 155 nm. Based on selected-area electron diffraction, XRD patterns; and Raman spectroscopy the nanospheres were found to be amorphous. IR spectrum revealed the involvement of bacterial proteins in the reduction of selenite and stabilization of nanoparticles. Used bacterial strain demonstrated efficient selenite reduction capability which was evident from 89.2% of selenium removal within 72 h at a concentration of 1 mM. Observation noted in the current study highlight the importance of bacterial reduction in selenium nanoparticle generation which can be scaled up for commercial production. Also, the bacteriogenic, amorphous nanoparticles can also be used as nutritional supplements for humans since selenium nanoparticles of 5-200 nm are bioavailable and known to induce seleno enzymes involved in antioxidant defence. © The Institution of Engineering and Technology 2016.

Bhasikuttan A.C.,Bhabha Atomic Research Center | Mohanty J.,Bhabha Atomic Research Center
Chemical Communications | Year: 2017

Amyloid fibrils are formed by the aberrant aggregation of proteins into highly ordered β-sheet structures and are believed to be the root cause of several neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, Prion diseases, etc. and have been the subject of extensive biochemical, biophysical and clinical studies. Developing methods for the early detection of fibril formation using optical spectroscopic techniques and inhibition/disintegration of amyloid fibrils/plaques by introducing small molecules have been a major challenge to establish a clinically facile therapeutic intervention to combat these neurodegenerative diseases. This feature article provides an account of the recent reports from different research groups, including ours, on the optical detection, and inhibition/disintegration of mature fibrils using fluorescent probes and macrocyclic hosts such as cucurbiturils, calixarenes and cyclodextrins. Site specific or spectrally distinct fluorescence emission from a large number of fluorophores in a broad spectral region has been used to detect the fibrillation of different proteins/peptides, mainly insulin, α-synuclein, transthyretin, barstar, lysozyme, Aβ40 peptide, etc. On the one hand, while macrocyclic receptors modify the inter-protein interactions through molecular recognition of amino acid residues leading to the inhibition of amyloid fibrillation, on the other hand, one of the cavitands, p-sulfonatocalixarenes, has been demonstrated to cause the disintegration of mature fibrils, effectively through surface charge interactions, which destabilize the extended fibrillar structure into soluble or fine particles. Beneficially, the presence of extrinsic p-sulfonatocalix[4/6]arenes did not introduce any additional toxicity to the cell viability, which advocates its potential utility as a therapeutic for amyloidosis. © The Royal Society of Chemistry.

Sengupta A.,Bhabha Atomic Research Center | Kadam R.M.,Bhabha Atomic Research Center
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2017

A systematic photoluminescence based investigation was carried out to understand the complexation of Eu3 + with different ligands (TBP: tri-n-butyl phosphate, DHOA: di-n-hexyl octanamide, Cyanex 923: tri-n-alkyl phosphine oxide and Cyanex 272: Bis (2,4,4 trimethyl) pentyl phosphinic acid) used for preferential separation of lanthanides and actinides in various stages of nuclear fuel cycle. In case of TBP and DHOA complexes, 3 ligand molecules coordinated in monodentate fashion and 3 nitrate ion in bidentate fashion to Eu3 + to satisfy the 9 coordination of Eu. In case of Cyanex 923 and Cyanex 272 complexes, 3 ligand molecules, 3 nitrate ion and 3 water molecules coordinated to Eu3 + in monodentate fashion. The Eu complexes of TBP and DHOA were found to have D3h local symmetry while that for Cyanex 923 and Cyanex 272 were C3h. Judd–Ofelt analysis of these systems revealed that the covalency of Eu[sbnd]O bond followed the trend DHOA > TBP > Cyanex 272 > Cyanex 923. Different photophysical properties like radiative and non-radiative life time, branching ratio for different transitions, magnetic and electric dipole moment transition probabilities and quantum efficiency were also evaluated and compared for these systems. The magnetic dipole transition probability was found to be almost independent of ligand field perturbation while electric dipole transition probability for 5D0-7F2 transition was found to be hypersensitive with ligand field with a trend DHOA > TBP > Cyanex 272 > Cyanex 923. © 2016 Elsevier B.V.

Mishra A.,Bhabha Atomic Research Center | Kumar J.,Bhabha Atomic Research Center | Melo J.S.,Bhabha Atomic Research Center
Biosensors and Bioelectronics | Year: 2017

The previously developed Sphingomonas sp. based optical microplate biosensor for methyl parathion (MP) was good as it detected multiple samples but had poor stability and low sensitivity. The present study aims to overcome these limitations. Silica nanoparticles (Si NP) were thus functionalized with polyethyleneimine (PEI) and the functionalized silica nanoparticles (fSi NP) were then integrated with Sphingomonas sp. cells. The process was optimized for hydrolysis of MP into p-nitrophenol (PNP). Integration of fSi NP with cells was confirmed by FT-IR analysis. Biohybrid of Sphingomonas sp.-fSi NP was immobilized on the wells of microplate and associated directly with the optical transducer of microplate reader. Immobilized biohybrid of Sphingomonas sp.-fSi NP was characterized using SEM. A detection range of 0.1–1 ppm MP was achieved from the linear range of calibration plot. After integration with fSi NP the storage stability of biohybrid was enhanced ten times from 18 to 180 days. This study proves that after interaction of cells with fSi NP, improved the sensitivity and stability of the biosensor. Spiked samples were also analyzed and correlated using this biohybrid based biosensor. © 2016 Elsevier B.V.

Verma A.K.,Bhabha Atomic Research Center | Modak P.,Bhabha Atomic Research Center | Sharma S.M.,Bhabha Atomic Research Center
Journal of Alloys and Compounds | Year: 2017

First-principles crystal structural searches were carried out for Li2S, Na2S and K2S under compression. Below 50 GPa, they follow same sequence of structural phase transitions, namely, anti-fluorite → anti-cotunnite → Ni2In-type phase. At above 50 GPa, they follow different phase transition sequences and in this pressure region several structural phase transitions are proposed. Calculated electronic density of state functions predicts metallization of Li2S and K2S at 225 and 175 GPa, respectively. Surprisingly, Na2S does not metalize even up to 300 GPa. Calculated structural parameters, equation-of-states and Raman data are in good agreement with the experimental results. © 2017 Elsevier B.V.

Rastogi L.,Bhabha Atomic Research Center | Dash K.,Bhabha Atomic Research Center | Ballal A.,Bhabha Atomic Research Center
Sensors and Actuators, B: Chemical | Year: 2017

A method for the selective and sensitive detection of aluminium (Al3+) in aqueous systems has been developed. The detection is achieved by the selective aggregation of ascorbic acid capped gold nanoparticles (AA-AuNPs) in the presence of aluminium which is observed by the change in colour of the colloidal solution from bright red to purple. The change in characteristic absorption peak can also be noticed spectrophotometrically; absorption of AA-AuNPs (λmax–520 nm) decreased and a second peak at 652 nm appeared after the addition of aluminium. The ratio of A652/A520 can be used to quantify the concentration of aluminium in water. The method gave a linear response from 20 ppb − 100 ppb (R2 = 0.996) of Al3+ in drinking water with a detection limit of 6.5 ppb. The proposed method did not suffer any interference from concomitant transition metal ions like: Mn2+, Ni2+, Zn2+, Sn2+, Li+, Co2+, Hg2+, Fe3+, and Pb2+ up to a concentration of 5 ppm and anions (Cl−, F−, SO4 2−, NO3 −, PO4 3−) up to a concentration of 250 ppm. However, a concentration of Ca2+ (≥15 ppm) was found to interfere with the detection of Al3+ in ground water. The interference was eliminated by passing the water through an anion exchange resin converted into oxalate form for the removal of the interferant as calcium oxalate precipitate in the resin phase. After this pre-treatment the linearity range in ground water was found to be 100–350 ppb with R2 = 0.996 and LOD − 12.5 ppb. The simplicity and rapidity of the developed method shows great potential in favour of its application for screening of drinking water samples to check its safety with respect to aluminium toxicity. © 2017 Elsevier B.V.

Sampathirao N.,Bhabha Atomic Research Center | Basu S.,Bhabha Atomic Research Center
Journal of Nuclear Medicine Technology | Year: 2017

Our aim was to comparatively assess dual-tracer PET/CT (68Ga- DOTATATE and 18F-FDG) and multimodality anatomic imaging in studying metastatic neuroendocrine tumors (NETs) of unknown primary (CUP-NETs) scheduled for peptide receptor radionuclide therapy for divergence of tracer uptake on dual-tracer PET/CT, detection of primary, and overall lesion detection vis-a-vis tumor proliferation index (MIB-1/Ki-67). Methods: Fifty-one patients with CUP-NETs (25 men, 26 women; age, 22-74 y), histopathologically proven and thoroughly investigated with conventional imaging modalities (ultrasonography, CT/contrast-enhanced CT, MRI, and endoscopic ultrasound, wherever applicable), were retrospectively analyzed. Patients were primarily referred for deciding on feasibility of peptide receptor radionuclide therapy (except 2 patients), and all had undergone 68Ga-DOTATATE and 18F-FDG PET/CT as part of pretreatment workup. The sites of metastases included liver, lung/mediastinum, skeleton, abdominal nodes, and other soft-tissue sites. Patients were divided into 5 groups on the basis of MIB-1/Ki-67 index on a 5-point scale: group I (1%-5%) (n = 35), group II (6%-10%) (n = 8), group III (11%-15%) (n = 4), group IV (16%-20%) (n = 2), and group V (≥20%) (n = 2). Semiquantitative analysis of tracer uptake was undertaken by SUVmax of metastatic lesions and the primary (when detected). The SUVmax values were studied over increasing MIB-1/Ki-67 index. The detection sensitivity of 68Ga-DOTATATE for primary and metastatic lesions was assessed and compared with other imaging modalities including 18F-FDG PET/CT. Results: Unknown primary was detected on 68Ga-DOTATATE in 31 of 51 patients, resulting in sensitivity of 60.78% whereas overall lesion detection sensitivity was 96.87%. The overall lesion detection sensitivities (individual groupwise from group I to group V) were 97.75%, 87.5%, 100%, 100%, and 66.67%, respectively. As MIB-1/Ki-67 index increased, 68Ga-DOTATATE uptake decreased in metastatic and primary lesions (mean SUVmax, 43.5 and 22.68 g/dL in group I to 22.54 and 16.83 g/dL in group V, respectively), whereas 18F-FDG uptake showed a gradual rise (mean SUVmax, 3.66 and 2.86 g/dL in group I to 7.53 and 9.58 g/dL in group V, respectively). There was a corresponding decrease in the 68Ga-DOTATATE-to-18F-FDG uptake ratio with increasing MIB-1/Ki-67 index (from 11.89 in group I to 2.99 in group V). Conclusion: In CUP-NETs, the pattern of uptake on dual-tracer PET (68Ga-DOTATATE and 18F-FDG) correlates well with tumor proliferation index with a few outliers; combined dual-tracer PET/CT with MIB-1/Ki-67 index would aid in better whole-body assessment of tumor biology in CUP-NETs. © 2017 by the Society of Nuclear Medicine and Molecular Imaging.

Sharma M.P.,Bhabha Atomic Research Center | Nayak A.K.,Bhabha Atomic Research Center
Nuclear Technology | Year: 2017

The Advanced Heavy Water Reactor (AHWR) is a vertical pressure tube-type, heavy watermoderated, and boiling light water-cooled natural-circulation-based reactor. The fuel bundle of AHWR contains 54 fuel rods arranged in three concentric rings of 12, 18, and 24 fuel rods. This fuel bundle is divided into a number of imaginary interacting flow passages called subchannels. Transition from a single-phase-flow condition to a two-phase-flow condition occurs in the reactor rod bundle with increase in power. Prediction of the thermal margin of the reactor has necessitated the determination ofintersubchannel mixing due to void drift. Void drift is due to redistribution of the non-equilibrium void fraction to attain an equilibrium void fraction. This redistribution occurs in the reactor rod bundle until it reaches the state of equilibrium void fraction. Hence, it is vital to evaluate void drift between subchannels of AHWR rod bundles. In this paper, experiments were carried out to investigate the void drift phenomena in simulated subchannels of AHWR. The size of the rod and the pitch in the test section were the same as those of the actual rod bundle in the prototype. Three subchannels are considered in 1/12th of the cross section of the rod bundle. Water and air were used as the working fluid, and the experiments were carried out at atmospheric condition without the addition of heat. The void fraction in the simulated subchannels was varied from 0 to 0.8 under various ranges of superficial liquid velocities. The void drift between the subchannels was measured. The test data were compared with existing models in the literature. It was found that the existing models could predict the measured equilibrium void fraction in the rod bundle of the reactor within the range +8% to -14%. © American Nuclear Society.

Achary S.N.,Bhabha Atomic Research Center | Bevara S.,Bhabha Atomic Research Center | Tyagi A.K.,Bhabha Atomic Research Center
Coordination Chemistry Reviews | Year: 2017

In this article a brief review of recent progress on preparation and crystal chemistry of rare-earth phosphates have been presented. The article begins with a brief note on the rare-earths and then a description on preparation methods of nano and crystalline samples of binary and complex phosphates. The merits and demerits of the typical procedures are explained in brief. Subsequently the crystal chemistry of various rare-earth phosphates is explained. The diversified crystal chemistry of rare-earth phosphates with compositions as well as with external parameters like pressure and temperature are explained. Typical crystal chemistry of hydrated and anhydrous orthophosphates is also covered. A brief note on phosphates of tetravalent cerium is presented. The high temperature behaviors of complex and metastable phosphates are also discussed. Finally the prospects of rare-earth phosphates for optical and nuclear applications are mentioned in brief. © 2017 Elsevier B.V.

Garg P.,Banaras Hindu University | Mishra D.K.,Bhabha Atomic Research Center | Netrakanti P.K.,Bhabha Atomic Research Center | Mohanty B.,National Institute of Science Education and Research | And 4 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

Net-baryon, net-charge and net-strangeness number fluctuations in high energy heavy-ion collisions are discussed within the framework of a hadron resonance gas (HRG) model. Ratios of the conserved number susceptibilities calculated in HRG are being compared to the corresponding experimental measurements to extract information about the freeze-out condition and the phase structure of systems with strong interactions. We emphasize the importance of considering the actual experimental acceptances in terms of kinematics (pseudorapidity (η) and transverse momentum (pT)), the detected charge state, effect of collective motion of particles in the system and the resonance decay contributions before comparisons are made to the theoretical calculations. In this work, based on HRG model, we report that the net-baryon number fluctuations are least affected by experimental acceptances compared to the net-charge and net-strangeness number fluctuations. © 2013 Elsevier B.V.

de Almeida U.B.,Brazilian Center for Research in Physics (CBPF) | Tavecchio F.,National institute for astrophysics | Mankuzhiyil N.,University of Trieste | Mankuzhiyil N.,Bhabha Atomic Research Center
Monthly Notices of the Royal Astronomical Society | Year: 2014

In this paper, we propose a way of using optical polarization observations to provide independent constraints and to guide the modelling of the spectral energy distribution (SED) of blazars. This is particularly useful when two-zone models are required to fit the observed SED. As an example, we apply the method to the 2008 multiwavelength campaign of PKS 2155- 304, for which the required polarization information was already available. We find that this approach is able to simultaneously describe the SED and the variability of the source, which is otherwise difficult to interpret. More generally, by using polarization data to disentangle different active regions within the source, the method reveals otherwise unseen correlations in the multiwavelength behaviour, which are important for SED modelling. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Singh R.,Jammu University | Kumar L.,Kent State University | Netrakanti P.K.,Bhabha Atomic Research Center | Mohanty B.,National Institute of Science Education and Research
Advances in High Energy Physics | Year: 2013

We review a subset of experimental results from the heavy-ion collisions at the Large Hadron Collider (LHC) facility at CERN. Excellent consistency is observed across all the experiments at the LHC (at center of mass energy sNN=2.76 TeV) for the measurements such as charged particle multiplicity density, azimuthal anisotropy coefficients, and nuclear modification factor of charged hadrons. Comparison to similar measurements from the Relativistic Heavy Ion Collider (RHIC) at lower energy (sNN=200 GeV) suggests that the system formed at LHC has a higher energy density and larger system size and lives for a longer time. These measurements are compared to model calculations to obtain physical insights on the properties of matter created at the RHIC and LHC. © 2013 Ranbir Singh et al.

Fleig T.,CNRS Laboratory for Quantum Chemistry and Physics | Nayak M.K.,CNRS Laboratory for Quantum Chemistry and Physics | Nayak M.K.,Bhabha Atomic Research Center | Kozlov M.G.,RAS Petersburg Nuclear Physics Institute
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2016

All-electron configuration interaction theory in the framework of the Dirac-Coulomb Hamiltonian has been applied to the TaN molecule, a promising candidate in the search for physics beyond the standard model in both the hadron and the lepton sectors of matter. We obtain in the first excited Δ13 state a P,T-odd effective electric field of 36.0 GV/cm, a scalar-pseudoscalar P,T-odd interaction constant of 32.8 kHz, and a nuclear magnetic-quadrupole moment interaction constant of 0.74×1033 Hz/(e cm2). The latter interaction constant has been obtained with an approach which we describe in detail. Using the same highly correlated all-electron wave functions with up to 2.5×109 expansion terms, we obtain a parallel magnetic hyperfine interaction constant of -2954 MHz for the Ta181 nucleus, a very large molecule-frame electric dipole moment of -4.91 D, and spectroscopic constants for the four lowest-lying electronic states of the molecule. © 2016 American Physical Society.

Okram R.,Manipur University | Ningthoujam R.S.,Bhabha Atomic Research Center | Singh N.R.,Manipur University
Inorganic Chemistry | Year: 2014

Crystalline LaVO4:Eu3+ nanophosphors (NPs) codoped with metal ions (Mn+ = Li+, Sr2+, and Bi 3+) are prepared in ethylene glycol (EG) medium at temperature ∼140 °C in 3 h. A mixture of monoclinic and tetragonal phases is observed. The ratio of tetragonal to monoclinic phases increases with increase of Li+ and Sr2+ concentration, but this is opposite in case of Bi3+ concentration. Lattice expansion occurs in the case of Li+ and Sr2+ codoping. Li+ ions occupy the interstitial sites instead of La3+ sites. Lattice contraction occurs in case of Bi3+ codoping indicating substitution of La3+ sites. Luminescence intensity is improved by codoping of Mn+ irrespective of crystal structure. Charges of Li+ and Sr2+ are different from that of La3+ (host lattice), whereas the charge of Bi3+ is same as that of La3+. One interesting observation is in magnetic dipole transition that the intensity of the peak at 594 nm is more than that at 587 nm in the case of charge imbalance, whereas the reverse occurs in the case of charge balance. LaVO4:Eu3+ nanophosphors prepared in water medium have more luminescence intensity when compared to those prepared in ethylene glycol, and this is related to variation of ratio of tetragonal to monoclinic phases. The luminescence intensity is also enhanced as annealing temperature increases from 600 to 800 °C due to the improved crystallinity. Lifetime data are analyzed on the basis of exponential and nonexponential decay equations. Samples are dispersible in polar medium due to capping of particles by EG. Polymer films are prepared by dispersion of NPs in poly(vinyl alcohol), and extra borax is added in order to make cross-link between polymer molecules. Samples of NPs in the forms of powder, dispersion in liquid medium, and film show the red emission. © 2014 American Chemical Society.

Modak B.,Bhabha Atomic Research Center | Srinivasu K.,Bhabha Atomic Research Center | Ghosh S.K.,Bhabha Atomic Research Center
Physical Chemistry Chemical Physics | Year: 2014

In this theoretical study, we employ a codoping strategy to reduce the band gap of NaTaO3 aimed at improving the photocatalytic activity under visible light. The systematic study includes the effects of metal (W) and nonmetal (N) codoping on the electronic structure of NaTaO3 in comparison to the effect of individual dopants. The feasibility of the introduction of N into the NaTaO3 crystal structure is found to be enhanced in the presence of W, as indicated by the calculated formation energy. This codoping leads to formation of a charge compensated system, beneficial for the minimization of vacancy related defect formation. The electronic structure calculations have been carried out using a hybrid density functional for an accurate description of the proposed system. The introduction of W in place of Ta leads to the appearance of donor states below the conduction band, while N doping in place of oxygen introduces isolated acceptor states above the valence band. The codoping of N and W also passivates undesirable discrete midgap states. This feature is not observed in the case of (Cr, N) codoped NaTaO 3 in spite of its charge compensated nature. We have also studied charge non-compensated codoping using several dopant pairs, including anion-anion and cation-anion pairs. However, this non-compensated codoping introduces localized states in between the valence band and the conduction band, and hence may not be effective in enhancing the photocatalytic properties of NaTaO3. The optical spectrum shows that the absorption curve for the (W, N)-codoped NaTaO3 is extended to the visible region due to narrowing of the band gap to 2.67 eV. Moreover, its activity for the photo decomposition of water to produce both H2 and O2 remains intact. Hence, based on the present investigation we can propose (W, N) codoped NaTaO3 as a promising photocatalyst for visible light driven water splitting. © the Partner Organisations 2014.

Ramasamy V.,Annamalai University | Paramasivam K.,Annamalai University | Jose M.T.,Bhabha Atomic Research Center
Journal of Environmental Radioactivity | Year: 2014

The sediment characteristics such as granulometric contents (sand, silt and clay), organic matter, magnetic susceptibility (low and high frequency) and weight percentage of magnetic minerals and the natural radionuclide (238U, 232Th and 40K) contents have been analyzed for the sediment samples of Vaigai river with an aim of evaluating the radiation hazard nature and assessing characterization of sediment. Granulometric analysis confirmed that the sand is major content. The organic matter content is ranged from 0.30 to 8.62% and comparison shows that the present river has high organic content. The magnetic measurement results indicated that the sites S16, S18 and S25 may be affected anthropogenically. Frequency dependence magnetic susceptibility is calculated to know the contribution of grains to magnetic susceptibility. Average of activity concentrations (except 40K) and all calculated radiological parameters are within the recommended level. Multivariate statistical analyses (Pearson correlation, cluster and factor analysis) dictated that the role of sediment characteristics on the level of radioactivity in the river sediments. The content of organic matter and clay, and magnetic parameters are positively correlated with important radioactive variables. The measurement of organic matter and magnetic susceptibility in various granulometric contents show some higher values in silt and clay fractions. Radioactivity level was also measured for the samples (after removing silt and clay fractions from bulk samples) and the results show decrease in radioactive variables. The present study stated that the lower grain sized fractions have the ability to absorb the contents such as organic content and magnetic minerals as cations on their surface and raise the level of radioactivity. Percentage of decrease in the natural radionuclides of 238U, 232Th, 40K and absorbed dose rate of the samples (after removing the silt and clay fractions from bulk samples) to the bulk samples are 13.59, 33.37, 20.52 and 26.13% respectively. Thus, it is concluded that the radiation effect does not pose to the public those who are using these sediments. © 2013 Elsevier Ltd.

Modak B.,Bhabha Atomic Research Center | Srinivasu K.,Bhabha Atomic Research Center | Ghosh S.K.,Bhabha Atomic Research Center
Journal of Physical Chemistry C | Year: 2014

A systematic study using density functional theory has been performed for NaTaO3, codoped with Mo and N, with the objective of improving its photocatalytic activity for water splitting under visible light. The utilization of a more reliable hybrid density functional, as prescribed by Heyd, Scuseria, and Ernzerhof, is found to be effective in predicting the band gap of NaTaO 3 (4.05 eV) in agreement with the experimental result (4.1 eV). The effect of individual dopant elements, Mo and N, has also been discussed. The monodoped systems show reduced band gap, with the presence of discrete midgap states, which have adverse effect on the photocatalytic property. However, those isolated states are passivated in the case of codoping with both Mo and N, leading to the formation of a continuum band structure ensuring improved charge carrier mobility. The band gap is reduced to 2.33 eV due to codoping of Mo and N, resulting in enhancement of visible light activity by an appreciable extent. The band alignments for the codoped NaTaO3 are well positioned for the feasibility of both photo-oxidation and photoreduction of water. Hence the charge-compensated Mo and N codoped NaTaO3 can be a promising photocatalyst for water splitting due to improved visible light activity as well as lower possibility of electron-hole recombination. © 2014 American Chemical Society.

Godwin Wesley S.,Scott Christian College Autonomous | Rajan M.P.,Bhabha Atomic Research Center
Journal of Environmental Radioactivity | Year: 2014

The present study focused on the determination of the alpha-emitter, 210Po, in two species of marine mussels (bivalve molluscs) commonly available in the southern coastal region of India. The brown mussel, Perna indica was collected from the west coast and the green mussel, Perna viridis from the east coast. The concentration of 210Po was related to the allometry (length of shell, wet/dry weight of shell/soft tissue) of the mussels and significant results were found. The study period focused on three seasons namely, pre-monsoon, monsoon and post-monsoon for a 1-year period (2010-2011). The results revealed higher activity levels in smaller-sized mussels compared to larger ones. Marked variation in 210Po activity concentration was noted in the whole-body soft tissues between seasons and sampling site (p<0.05). The dose rate assessment for mussels was performed using the ERICA Assessment tool. The chronic exposure to mussels due to 210Po was found to be lesser than the global benchmark dose rate of 10μGyh-1. The effective ingestion dose to adults who intake mussels was estimated to be in the range 5.1-34.9μSvy-1. The measurement contributes to the furthering of knowledge of 210Po, since no data exist in this region. © 2014 Elsevier Ltd.

Dundas Data Visualization, Inc., a leading, global provider of Business Intelligence and Data Visualization solutions, announced today that they received first place for Visual Design Standards and have been recognized as a leader in several categories in The Business Application Research Center (BARC) BI Survey 16. The BARC BI Survey 16 is the world’s largest survey of business intelligence (BI) software users measuring selection and usage of BI products. The BI Survey 16 is based on findings from the world’s largest and most detailed annual survey of a sample of over 3,100 business intelligence (BI) end-user respondents. Dundas has been recognized as a leader across five different areas, amongst a total group of 37 BI dashboard products that were analyzed in detail. “It’s a fantastic honor to be recognized with a first place ranking for Visual Design Standards in the BI Survey 16 from BARC,” said Troy Marchand, President, CEO and Co-founder, Dundas Data Visualization. “Dundas has a strong history as an innovator in visualization software, so to receive top honors for Visual Design Standards is a wonderful accomplishment and testament to our goal of developing products that help businesses better understand and visualize their data. The fact that this survey uses actual end-users for product feedback of our software makes the recognition a very meaningful achievement for our team.” According to the BI Survey 16, customers of Dundas Data Visualization give Dundas BI consistently high ratings resulting in Dundas being a leader in big data analytics, collaboration, operational BI and overall product satisfaction. About BARC - Business Application Research Center (BARC) is a leading enterprise software industry analyst and consulting firm delivering information to more than 1,000 customers each year. For over twenty years, BARC has specialized in core research areas including Data Management (DM), Business Intelligence (BI), Customer Relationship Management (CRM) and Enterprise Content Management (ECM). Along with CXP and Pierre Audoin Consultants (PAC), BARC forms part of the CXP Group – the leading European IT research and consulting firm with 140 staff in eight countries including the UK, France, Germany, Austria and Switzerland. About Dundas Data Visualization, Inc. – Dundas Data Visualization is a leading, global provider of Business Intelligence (BI) and Data Visualization solutions. Dundas provides organizations with the most flexible, innovative and scalable BI, dashboard and reporting software, through a fully embeddable BI platform, enabling users access to all their data for better decisions and faster insights. For more information, contact: Lynda Phillips, Marketing Communications Manager, Dundas Data Visualization, Inc. 416.467.5100 x 167

News Article | December 7, 2016

A surprising opportunity to explore something new in chemistry and physics has emerged. In March 1989, electrochemists Martin Fleischmann and Stanley Pons, at the University of Utah, announced that they had "established a sustained nuclear fusion reaction" at room temperature. By nearly all accounts, the event was a fiasco. The fundamental reason was that the products of their experiments looked nothing like deuterium-deuterium (D+D) fusion. In the following weeks, Caltech chemist Nathan Lewis sharply criticized Fleischmann and Pons in a symposium, a press release, a one-man press conference at the American Physical Society meeting in Baltimore, Maryland, and during his oral presentation at the APS meeting. Despite Lewis' prominence in the media spotlight, he never published a peer-reviewed critique of the peer-reviewed Fleischmann-Pons papers, and for good reason. Lewis' critique of the Fleischmann-Pons experiment was based on wrong guesses and assumptions. Richard Petrasso, a physicist at MIT, took Fleischmann and Pons to task for their claimed gamma-ray peak. Petrasso and the MIT team, after accusing Fleischmann and Pons of fraud in the Boston Herald, later published a sound and well-deserved peer-reviewed critique of what had become multiple versions of the claimed peak. From this dubious beginning, to the surprise of many people, a new field of nuclear research has emerged: It offers unexplored opportunities for the scientific community. Data show that changes to atomic nuclei, including observed shifts in the abundance of isotopes, can occur without high-energy accelerators or nuclear reactors. For a century, this has been considered impossible. In hindsight, glimpses of the new phenomena were visible 27 years ago. In October 1989, a workshop co-sponsored by the Electric Power Research Institute took place at the National Science Foundation headquarters, in Washington, D.C. Among the 50 scientists in attendance was the preeminent physicist Edward Teller. After hearing from scientists at the Lawrence Livermore National Laboratory and the Naval Research Laboratory who had observed isotopic shifts in room-temperature experiments, Teller concluded that nuclear effects were taking place. He even had a hunch about a possible mechanism, involving some sort of charge-neutral particle. By October, tritium production and low-levels of neutrons in such experiments had been reported from a few reputable laboratories, including Los Alamos National Laboratory and the Bhabha Atomic Research Center in India. Moreover, BARC researchers observed that the tritium production and neutron emissions were temporally correlated. Outside reviewers selected by the Department of Energy and tasked with examining the worldwide claims included this data in a draft of their report. Before the document was finalized, however, they removed the tables containing that data. In the early 1990s, several researchers in the field strongly favored neutron-based explanations for the phenomena. By the mid-1990s, a vocal contingent of scientists attempting to confirm Fleischmann and Pons' claims promoted the room-temperature fusion idea. Other scientists in the field, however, observed evidence—isotopic shifts and heavy-element transmutations—that pointed not to fusion but to some sort of neutron-induced reaction. In 1997, theorist Lewis Larsen looked at some of this data and noticed a similarity to elemental abundances he had learned about while a student in Subrahmanyan Chandrasekhar's astrophysics class at the University of Chicago. Larsen suspected that a neutronization process was occurring in low-energy nuclear reactions (LENR). Physicist Allan Widom joined Larsen's team in 2004, and in 2006 they published a theory in the European Physical Journal C - Particles and Fields. The Widom-Larsen theory has nothing to do with fusion; the key steps are based on weak interactions and are consistent with existing physics. The theory explains how nuclear reactions can occur at or near room temperature through the creation of ultra-low-momentum neutrons and subsequent neutron-capture processes. Such neutrons, according to the theory, have a very large DeBroglie wavelength and therefore have a huge capture cross-section, explaining why so few neutrons are detected. Many-body collective quantum and electromagnetic effects are fundamental to Widom and Larsen's explanation for the energy required to create neutrons in LENR cells. Crucially, such reaction-rate calculations are based not on few-body interactions but on many-body interactions. After 2006, the scientists who remained wedded to their belief in the idea of room-temperature fusion rejected the Widom-Larsen theory. A few of these fusion believers began making unsupported claims of commercially viable energy technologies. Hidden in the confusion are many scientific reports, some of them published in respectable peer-reviewed journals, showing a wide variety of experimental evidence, including transmutations of elements. Reports also show that LENRs can produce local surface temperatures of 4,000-5,000 K and boil metals (palladium, nickel and tungsten) in small numbers of scattered microscopic sites on the surfaces of laboratory devices. For nearly three decades, researchers in the field have not observed the emission of dangerous radiation. Heavy shielding has not been necessary. The Widom-Larsen theory offers a plausible explanation—localized conversion of gamma radiation to infrared radiation. The implication is that immense technological opportunities may exist if a practical source of energy can be developed from these laboratory curiosities. Perhaps most surprising is that, in the formative years of atomic science in the early 20th century, some scientists reported inexplicable experimental evidence of elemental transmutations. In the 1910s and 1920s, this research was reported in popular newspapers and magazines, and papers were published in the top scientific journals of the day, including Physical Review, Science and Nature. The experiments, using relatively simple, low-energy benchtop apparatus, did not use radioactive sources so the results defied prevailing theory. Several researchers independently detected the production of the gases helium-4, neon, argon, and an as-yet-unidentified element of mass-3, which we now identify as tritium. Two of these researchers were Nobel laureates. In 1966, physicist George Gamow wrote, "Let us hope that in a decade or two or, at least, just before the beginning of the 21st century, the present meager years of theoretical physics will come to an end in a burst of entirely new revolutionary ideas similar to those which heralded the beginning of the 20th century." LENR may very well be such an opportunity to explore new science.

Maheshvaran K.,Gandhigram Rural University | Arunkumar S.,Gandhigram Rural University | Sudarsan V.,Bhabha Atomic Research Center | Natarajan V.,Bhabha Atomic Research Center | Marimuthu K.,Gandhigram Rural University
Journal of Alloys and Compounds | Year: 2013

The present work reports structural and optical behaviour of the Er 3+/Yb3+ co-doped boro-tellurite glasses 50TeO2 + 15H3BO3 + (5 - x - y)La2O3 + 15MgCO3 + 15SrCO3 + xEr2O3 + yYb2O3 (where x = 1, y = 0, 0.5, 1 and 2 in wt%) studied through Fourier transform infrared (FTIR), Raman, absorption, luminescence, upconversion luminescence and lifetime measurements for green laser applications. The TeAOATe, O3BAOABO3 bond bending vibrations and the fundamental stretching vibration of OH groups are confirmed through FTIR and Raman spectra. Through the absorption spectra, bonding parameters, oscillator strengths and Judd-Ofelt (JO) parameters were calculated and reported. From the luminescence spectra, radiative parameters have been calculated for the 2H9=2 → 4I15=2; 4S3=2 → 4I15=2 and 4I13=2 → 4I15=2 excited state transitions. Upconversion luminescence spectra of the prepared glasses have been recorded and the excited state absorption (ESA) and Energy transfer (ET) processes are discussed. The luminescence decay curves for the 4I13=2 → 4I15=2 transition of the title glasses under 980 excitation wavelength have also been studied and reported. © 2013 Elsevier B.V. All rights reserved.

Basu M.,Bhabha Atomic Research Center | Samanta T.,Shyamsunder College | Das D.,Bhabha Atomic Research Center
Journal of Chemical Thermodynamics | Year: 2013

Densities (ρ) and speed of sound (u) of the binary mixtures of tributyl phosphate (TBP) and alkanes (n-hexane, cyclohexane, and n-heptane) were measured at temperatures from (298.15 to 323.15) K over the entire composition range and at atmosphere pressure. Using these experimentally determined quantities, the excess molar volume (VE), deviation in isentropic compressibility (Δks), internal pressure (pi), solubility parameter (δ) and excess cohesive energy of mixing (U E) have been calculated. The excess molar volume and deviation in isentropic compressibility data have been fitted to a Redlich-Kister type polynomial equation. The positive or negative deviations shown by these quantities have been interpreted in terms of intermolecular interactions and structure of components. © 2012 Elsevier Ltd. All rights reserved.

Senthilkumar S.T.,Bharathiar University | Selvan R.K.,Bharathiar University | Ponpandian N.,Bharathiar University | Melo J.S.,Bhabha Atomic Research Center | Lee Y.S.,Chonnam National University
Journal of Materials Chemistry A | Year: 2013

Electric double layer capacitors (EDLCs) were fabricated using biomass derived porous activated carbon as electrode material with 1 M H 2SO4 and VOSO4 added 1 M H2SO 4 as electrolytes. Here, VOSO4 was used as redox additive to improve the overall performance of EDLC. As expected, the VOSO4 electrolyte showed ∼43% of improved specific capacitance of 630.6 F g -1 at 1 mA cm-2 compared to pristine 1 M H 2SO4 (440.6 F g-1) due to the contribution of VO2+/VO2 + redox reaction at the electrode-electrolyte interface. Possible redox reaction mechanism of VO 2+/VO2 + pair is also briefly illustrated. The good cycling performance of 97.57% capacitance retention was observed even after 4000 cycles. For comparison, the polymer gel electrolyte (PVA/VOSO 4/H2SO4) was also prepared and then the performance of the fabricated EDLCs was studied. Overall, these findings could open up a simple and cost effective way to improve the performance of EDLCs significantly. © 2013 The Royal Society of Chemistry.

Venkata Nancharaiah Y.,Brookhaven National Laboratory | Venkata Nancharaiah Y.,Bhabha Atomic Research Center | Francis A.J.,Brookhaven National Laboratory
Bioresource Technology | Year: 2011

In this study, the effect of ionic liquids, 1-ethyl-3-methylimidazolium acetate [EMIM][Ac], 1-ethyl-3-methylimidazolium diethylphosphate [EMIM][DEP], and 1-methyl-3-methylimidazolium dimethylphosphate [MMIM][DMP] on the growth and glucose fermentation of Clostridium sp. was investigated. Among the three ionic liquids tested, [MMIM][DMP] was found to be least toxic. Growth of Clostridium sp. was not inhibited up to 2.5, 4 and 4gL-1 of [EMIM][Ac], [EMIM][DEP] and [MMIM][DMP], respectively. [EMIM][Ac] at <2.5gL-1, showed hormetic effect and stimulated the growth and fermentation by modulating medium pH. Total organic acid production increased in the presence of 2.5 and 2gL-1 of [EMIM][Ac] and [MMIM][DMP]. Ionic liquids had no significant influence on alcohol production at <2.5gL-1. Total gas production was affected by ILs at ≥2.5gL-1 and varied with type of methylimidazolium IL. Overall, the results show that the growth and fermentative metabolism of Clostridium sp. is not impacted by ILs at concentrations below 2.5gL-1. © 2011 Elsevier Ltd.

Senthilkumar S.T.,Bharathiar University | Selvan R.K.,Bharathiar University | Lee Y.S.,Chonnam National University | Melo J.S.,Bhabha Atomic Research Center
Journal of Materials Chemistry A | Year: 2013

Halogen (iodide, I-) added aqueous electrolyte facilitates the capacitive behaviour of biomass derived activated carbon based electric double layer capacitors. To produce economically viable electrodes in large scale for supercapacitors (SCs), the activated carbons (ACs) prepared from Eichhornia crassipes (common water hyacinth) by ZnCl2 activation. The prepared ACs were characterized by XRD, Raman, FT-IR and surface area, pore size and pore volume analysis. The electrochemical properties of the SCs were studied using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS) and cycling stability. The 3I-/I 3 -, 2I-/ I2, 2I3 -/3I2 and I2/IO3 - pairs produce redox peaks in CV and a large Faradaic plateau in charge-discharge curves. Similarly, I- ions improves the good ionic conductivity (lower charge transfer resistance) at the electrode/electrolyte interface which was identified through EIS studies. The calculated specific capacitance and energy density was 472 F g-1 and 9.5 W h kg-1 in aqueous solution of 1 M H2SO4. Interestingly, nearly two-fold improved specific capacitance and energy density of 912 F g-1 and 19.04 W h kg-1 were achieved when 0.08 M KI was added in 1 M H 2SO4 electrolyte with excellent cycle stability over 4000 cycles. Subsequently, this improved specific capacitance and energy density was compared with 0.08 M KBr added to 1 M H2SO4 (572 F g -1, 11.6 W h kg-1) and 0.08 M KI added to 1 M Na 2SO4 (604 F g-1, 12.3 W h kg-1) as electrolytes. © The Royal Society of Chemistry 2013.

Pabby A.K.,Bhabha Atomic Research Center | Sastre A.M.,Polytechnic University of Catalonia
Journal of Membrane Science | Year: 2013

This review will examine the most recent research and developments in hollow fibre contactor technology and membrane-based extraction processes, including the latest improvements with regard to stability and flux. The described classification attempts to cover all studies performed by means of non-dispersive contact using hydrophilic/hydrophobic microporous polymeric supports, either by impregnating the membrane or filling its pores with the bulk of the aqueous/organic solution. All membrane processes covered under these categories will be compared with improved versions in terms of performance, mass transfer modelling, stability issues, applications and the state of the art in membrane-based separation techniques. In general, an attempt will be made to review the literature published between 2005 and 2012 (August 2012) in order to focus on the real status of hollow fibre technology and membrane-based extraction processes. In a modern approach, the prospects for the use of ionic liquid (IL) as a membrane carrier for different applications with different membrane morphologies are also presented. In addition, new highly stabilised techniques developed by different researchers, such as hollow fibre renewal liquid membranes (HFRLMs) and pseudo-emulsion-based hollow fibre strip dispersion (PEHFSD), are also discussed. © 2012 Elsevier B.V.

Sonawane J.V.,Bhabha Atomic Research Center | Pabby A.K.,Bhabha Atomic Research Center | Sastre A.M.,Polytechnic University of Catalonia
Journal of Hazardous Materials | Year: 2010

Pseudo-emulsion based hollow fibre strip dispersion (PEHFSD) technique is investigated for the permeation-separation of chromium from hydrochloric acid media. The permeation of Cr(VI) is investigated in relation to various experimental variables: hydrodynamic conditions, the concentration of Cr(VI) and HCl in the feed phase, Cyanex-923 concentration, hydrazine sulphate as the stripping agent in the pseudo-emulsion phase. The performance of the PEHFSD was analyzed and optimum conditions are suggested for chromium separation from simulated industrial waste in a hydrochloric acid media. © 2009.

Coll M.T.,Polytechnic University of Catalonia | Fortuny A.,Polytechnic University of Catalonia | Kedari C.S.,Bhabha Atomic Research Center | Sastre A.M.,Polytechnic University of Catalonia
Hydrometallurgy | Year: 2012

An important problem associated with the development of continuous process for the extraction and separation of Co(II) and Ni(II) is the decrease in the pH of the aqueous phase after its equilibration with organic solvent containing cationic extractants such as Cyanex 272, LIX 860, etc. An improvement in the solvent extraction and separation of Co(II) and Ni(II) from neutral chloride solutions is obtained using ionic liquid extractant tertiary alkyl (C 16-C 22) primary ammonium bis 2,4,4-(trimethylpentyl) phosphinate (HJMT +-Cy272 -) generated by reacting primary amine, Primene®JMT (JMT) and bis(2,4,4-trimethylpentyl)phosphinic acid, Cyanex 272 (Cy272) in the organic phase. The presence of JMT allows to control the pH of the equilibrated aqueous phase during the extractions of Co(II) and Ni(II). This has facilitated the application of continuous counter current liquid-liquid extraction in the given metal extraction system without applying any in-between acid neutralization process. The liquid-liquid extractions were carried out under different experimental conditions such as concentration of JMT and Cy272 in the organic phase, and concentration of metal ions in the aqueous phase. The optimized composition of the organic phase to obtain better recovery and separation of Co(II) and Ni(II) is 10% Cy272 + 10% JMT in D100. The equal percentage of Cy272 and JMT in the organic phase gave minimum change in the pH of the aqueous phase before and after its equilibration. The McCabe-Thiele plot suggested three theoretical stages of counter current operation for obtaining greater than 99% extraction of Co(II) from its 1 g/L solution. For two metal system, four stage counter current extraction was carried out using bench scale mixer-settler equipment which gave > 99% extraction of Co(II) along with 11% of Ni in the organic phase whereas about 89% of Ni(II) with about 0.3% of Co(II) remained in the aqueous phase. The loaded organic phase was treated with 0.02 M EDTA to strip metal ions and the same was used successfully for the second run of the extraction and stripping process. © 2012 Elsevier B.V. All rights reserved.

Rath D.,Uppsala University | Rath D.,Bhabha Atomic Research Center | Amlinger L.,Uppsala University | Hoekzema M.,Uppsala University | And 3 more authors.
Nucleic Acids Research | Year: 2015

Methods that permit controlled changes in the expression of genes are important tools for biological and medical research, and for biotechnological applications. Conventional methods are directed at individually changing each gene, its regulatory elements or its mRNA's translation rate. We demonstrate that the CRISPR-associated DNA-binding Cascade complex can be used for efficient, long-lasting and programmable gene silencing. When Cascade is targeted to a promoter sequence the transcription of the downstream gene is inhibited, resulting in dramatically reduced expression. The specificity of Cascade binding is provided by the integral crRNA component, which is easily designed to target virtually any stretch of DNA. Cascade targeted to the ORF sequence of the gene can also silence expression, albeit at lower efficiency. The system can be used to silence plasmid and chromosome targets, simultaneously target several genes and is active in different bacterial species and strains. The findings described here are an addition to the expanding range of CRISPR-based technologies and may be adapted to additional organisms and cell systems. © 2014 The Author(s).

Nancharaiah Y.V.,UNESCO-IHE Institute for Water Education | Nancharaiah Y.V.,Bhabha Atomic Research Center | Lens P.N.L.,UNESCO-IHE Institute for Water Education
Microbiology and Molecular Biology Reviews | Year: 2015

In nature, selenium is actively cycled between oxic and anoxic habitats, and this cycle plays an important role in carbon and nitrogen mineralization through bacterial anaerobic respiration. Selenium-respiring bacteria (SeRB) are found in geographically diverse, pristine or contaminated environments and play a pivotal role in the selenium cycle. Unlike its structural analogues oxygen and sulfur, the chalcogen selenium and its microbial cycling have received much less attention by the scientific community. This review focuses on microorganisms that use selenate and selenite as terminal electron acceptors, in parallel to the well-studied sulfate-reducing bacteria. It overviews the significant advancements made in recent years on the role of SeRB in the biological selenium cycle and their ecological role, phylogenetic characterization, and metabolism, as well as selenium biomineralization mechanisms and environmental biotechnological applications. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Umare S.S.,Visvesvaraya National Institute of Technology | Shambharkar B.H.,Visvesvaraya National Institute of Technology | Ningthoujam R.S.,Bhabha Atomic Research Center
Synthetic Metals | Year: 2010

Fe3O4 nanoparticles were prepared by hydrolysis reaction of urea in ethylene glycol as solvent at 160 °C. The prepared Fe3O4 nanoparticles were incorporated into polyaniline (PANI) matrix during in situ chemical oxidative polymerization of aniline with different molar ratios of aniline:Fe3O4 (19:1, 16:1, 12:1, 9:1) using (NH4)2S2O8 as oxidant in aqueous solution of sodium dodecylbenzene sulphonic acid under N2 atmosphere. Room temperature conductivities of the synthesized PANI, PANI/Fe3O4 (19:1) and PANI/Fe3O4 (9:1) are 3.2 × 10-4, 1.8 × 10-5 and 1.0 × 10-5 S/cm, respectively, indicating decrease of conductivity with increase of Fe3O4 in PANI. Saturation magnetizations of Fe3O4, PANI/Fe3O4 (19:1), and PANI/Fe3O4 (9:1) are 27.5, 5.5 and 6.3 emu/g, respectively, indicating an increase of ferromagnetic interaction with more incorporation of Fe3O4 in PANI matrix, whereas PANI is diamagnetic. Electrochemical studies shows that Zn-PANI/Fe3O 4 (9:1) battery had delivered maximum discharge capacity (78.6 mAh/g) as compared to Zn-PANI battery (50.1 mAh/g) at constant current of 0.5 mA cm-2. At constant resistance of 1000 Ω, discharge capacities of Zn-PANI/Fe3O4 and Zn-PANI battery are 73.37 and 50.8 mAh/g, respectively. © 2010 Elsevier B.V.

Hussain P.R.,Bhabha Atomic Research Center | Dar M.A.,Bhabha Atomic Research Center | Wani A.M.,Bhabha Atomic Research Center
Radiation Physics and Chemistry | Year: 2013

Gamma irradiation treatment was tested for maintaining storage quality and extending the shelf life of plum fruit. Matured green plums were irradiated in the dose range of 0.2-1.5. kGy and stored under ambient (temperature 25±2 °C, RH 70%) and refrigerated (temperature 3±1 °C, RH 80%) conditions. Studies revealed that irradiation treatment significantly (p≤0.05) maintained the storage quality of plum fruit under ambient as well as refrigerated conditions. Positive correlations (r=0.88) existed between the irradiation doses and firmness retention under both the storage conditions. In samples irradiated at 1.0. kGy, 1.2. kGy and 1.5. kGy, no microbial load was detected up to 8 and 12 days of ambient storage. Dose range of 1.2-1.5. kGy significantly inhibited the decaying of plums up to 16 days of ambient storage. Irradiation in combination with refrigeration prevented the decaying of plums up to 35 days as against the 12.5% decay in un-irradiated control samples. Irradiation dose of 1.2-1.5. kGy also gave an extension of 8 days during additional ambient storage of the plums at 25±2 °C, RH 70% following 35 days of refrigeration. © 2013 Elsevier Ltd.

Chowdhury S.R.,Bhabha Atomic Research Center | Sabharwal S.,Bhabha Atomic Research Center
Journal of Materials Chemistry | Year: 2011

In the age of green chemistry, gamma-radiation-assisted grafting of polar groups onto polymers in aqueous solution is becoming attractive as it is a rapid, scalable, clean physical process with much less chance of contamination. In this case, a methacrylic acid (MAA) polar group was grafted onto LDPE (low density polyethylene) by gamma radiation to increase the compatibility of LDPE with organically modified clay by reducing the hydrophobicity of LDPE. The clay, cloisite 20A was melt-mixed with g-LDPE (grafted LDPE) to synthesize a nanohybrid and the mixes were subsequently compression-molded to make a sheet, which was used for characterization. Many of the drawbacks of polyolefin based nanohybrid synthesis were overcome by this technique. Wide angle X-ray diffraction (WAXS), transmission electron microscopy (TEM), thermogravemetric analysis (TGA), differential scanning calorimetry (DSC) and tensile testing were conducted to characterize the nanohybrids. The interlayer distance (d values) change in WAXS confirmed nanohybrid formation, which was later directly seen by TEM. TGA revealed that nanohybrids were more thermally stable than pure polymer and this went on increasing with clay loading. From DSC it was noticed that melting temperatures (T ms) remained unchanged, but the crystallinity of the polymer was increased by more than 5% at higher clay loading (8 wt%), which was useful for barrier properties as well as mechanical property improvement. Young's modulus of nanohybrid was increased considerably by a small mount of clay incorporation (by 50% and 85% for 2 and 8 wt% clay). Uniquely, with increase in modulus toughness was also found to increase by more than 20%, keeping the elongation-at-break unchanged. Thus by this rapid, clean, user friendly and well controlled technique, pure and high-performance nanohybrids were developed successfully. © 2011 The Royal Society of Chemistry.

Mishra B.B.,Bhabha Atomic Research Center | Gautam S.,Bhabha Atomic Research Center | Sharma A.,Bhabha Atomic Research Center
Food Chemistry | Year: 2012

Eggplant (Solanum melongena) is a very rich source of polyphenol oxidase (PPO), which negatively affects its quality upon cutting and postharvest processing due to enzymatic browning. PPO inhibitors, from natural or synthetic sources, are used to tackle this problem. One isoform of PPO was 259-fold purified using standard chromatographic procedures. The PPO was found to be a 112 kDa homodimer. The enzyme showed very low Km (0.34 mM) and high catalytic efficiency (3.3 × 106) with 4-methyl catechol. The substrate specificity was in the order: 4-methyl catechol > tert-butylcatechol > dihydrocaffeic acid > pyrocatechol. Cysteine hydrochloride, potassium metabilsulphite, ascorbic acid, erythorbic acid, resorcylic acid and kojic acid showed competitive inhibition, whereas, citric acid and sodium azide showed mixed inhibition of PPO activity. Cysteine hydrochloride was found to be an excellent inhibitor with the low inhibitor constant of 1.8 μM. © 2012 Elsevier Ltd. All rights reserved.

Mukadam M.D.,Bhabha Atomic Research Center | Yusuf S.M.,Bhabha Atomic Research Center
Physica B: Condensed Matter | Year: 2010

The magnetocaloric effect (MCE) in the UNiGa compound has been studied using the dc magnetization measurement technique. This system shows normal and inverse MCEs at low field around the paramagnetic to ferrimagnetic transition temperature (38.4 K), and the ferrimagnetic to antiferromagnetic transition temperature (34.5 K), respectively. At higher fields, the inverse MCE becomes very weak, which could be explained due to the presence of a field-induced metamagnetic phase transition. The maximum value of the magnetic entropy change - Δ SM, for Δ μ0 H = 5 T, has been found to be 3.56 J kg- 1 K- 1 at ∼ 37.2 K with a relative cooling power of 22.5 J kg- 1. © 2009 Elsevier B.V. All rights reserved.

Narasimham K.V.N.S.V.P.L.,Bhabha Atomic Research Center
Proceedings of 2015 International Conference on Robotics, Automation, Control and Embedded Systems, RACE 2015 | Year: 2015

Analytical Instrumentation plays a vital role in the production and evaluation of products to be introduced in the market. This instrumentation is used mainly to evaluate the products for the benefit of the people concerned. Quantitative and qualitative analysis of sample matrix is provided by analytical instrumentation. This analysis helps in detecting toxic/essential elements in the field of food, drugs, water and air etc., Inductively coupled plasma mass spectrometer (ICPMS) is a versatile, complex and a very sensitive analytical instrument. ICPMS is used for compositional characterization of materials up to the levels of parts per billion (ppb) and parts per trillion (ppt). For obtaining required high sensitivities, one needs to optimize nearly 30 to 40 process parameters during the analysis/operation of these instruments. Optimization of these parameters has to be carried out in real time environment through a computer and other electronic sub-systems. The use of electronic sub-systems such as Programmable Logic Controllers (PLCs) in ICPMS simplified the design, implementation of interlocks and subsequent optimization of various process parameters. This paper describes the role of PLCs in Mass-spectrometers in general and ICPMS in specific. An Instrument Control Electronics (ICE) module is developed for interfacing vacuum sub-system to ICPMS. The integration aspects of newly developed ICE to the PLC and the advantages of use of PLCs in 'ICPMS' System are discussed, at length, in this paper. © 2015 Hindustan University.

Patra C.N.,Bhabha Atomic Research Center
Journal of Chemical and Engineering Data | Year: 2015

The structure of colloidal solution with size asymmetric electrolytes using a solvent primitive model representation is investigated using density functional theory and Monte Carlo simulation. The solvent is assumed to be an individual component apart from its behavior as a countinuum dielectric medium. The theory is partially perturbative with hard-sphere correlation being treated using a weighted density approach, whereas the residual ionic contribution is calculated through perturbation around the uniform density. A standard canonical ensemble Monte Carlo simulation method is also adopted here, for comparison. The theoretical results are in quantitative agreement with the simulation data for the entire range of parametric conditions. This study points to the importance of including the solvent as an individual component. © 2015 American Chemical Society.

Ramkumar J.,Bhabha Atomic Research Center | Chandramouleeswaran S.,Bhabha Atomic Research Center
Journal of Radioanalytical and Nuclear Chemistry | Year: 2013

Polyaniline (Pani) was synthesized by the chemical oxidation of aniline. The use of persulphate instead of dichromate was desired in order to avoid the incorporation of chromium in the polymer matrix. The presence of chromium in the matrix, when dichromate was used as an oxidant, was confirmed by various techniques. The batch mode experiments showed that Pani could be used for separation of different metal ions. These ions were converted into their anionic complexes using suitable complexing agents. It was found that EDTA was used as a suitable reagent for the separation of Cu2+ from Zn2+ whereas the uranyl ion uptake could be increased to about 95 % when carbonate was used instead of EDTA as complexing agent. A possible application of the above exchange system to preconcentration of uranyl ion from seawater has also been examined. © 2013 Akadémiai Kiadó, Budapest, Hungary.

Karmakar G.,Bhabha Atomic Research Center
2015 IEEE Power and Energy Society Innovative Smart Grid Technologies Conference, ISGT 2015 | Year: 2015

Many energy consuming devices, especially thermostatically controlled electrical devices (TCED) such as air-conditioners, room heaters and refrigerators, have a periodic execution profile, tempting us to draw an analogy between the allocation of electrical power to TCEDs vis-à-vis the allocation of CPU time to computational tasks. The resulting mapping naturally leads us to make use of traditional real-time scheduling policies such as earliest deadline first (EDF) and least slack-time first (LSF) (and the associated schedulability analysis) in managing TCEDs to deal with energy management and peak power constraints. However, the analogy is not without detractors: the execution time (interval when a TCED is ON) and the period of a TCED are dynamic. In this work, we critically examine the similarities and the differences between real-time tasks and TCED activities. The focus of this work is to analyze the ability of scheduling policies from the real-time domain to attain desired thermal comfort within designated spaces, which we term as comfortability. © 2015 IEEE.

A constant pH molecular dynamics (CpHMD) simulation method utilizing generalized Born electrostatics is employed to examine conformational changes of a protein containing a buried ionizable pair in its hydrophobic core, specifically considering a hyperstable variant of staphylococcal nuclease (Δ+PHS). It is observed that the average geometrical parameters obtained from CpHMD simulation at pH 8 and from quantum mechanical calculation nicely match to the reported crystal structure of V23E/L36K variant of Δ+PHS. Strong hydrogen bond formation and salt bridge interactions in the microenvironment around the Glu-23/Lys-36 pair stabilize the core of the V23E/L36K variant. Small rearrangements of the backbone carbonyl oxygen of Gly-20 and the side chain of hydroxyl group of Thr-62 are observed, and these changes in orientation allow for interaction with Lys-36 and Glu-23, respectively, in V23E/L36K variant. We do observe a long hydrogen bond correlation and lifetime (716 ps) in the microenvironment. All these observations suggest that the V23E/L36K variant is stable and CpHMD method can capture small rearrangements of the residues in a protein. © The Royal Society of Chemistry 2015.

Mitra A.,Bhabha Atomic Research Center
International Journal of Modern Physics D | Year: 2015

The Friedmann-Robertson-Walker (FRW) metric expressed, in terms of comoving coordinates (r, t), always looks nonstatic. But by employing the recently derived curvature/Schwarzschild form, (R, T), of FRW metric (A. Mitra, Gravit. Cosmol. 19 (2013) 134), we show here that FRW metric can assume static forms when the net energy density (ρe) is solely due to the vacuum contribution. Earlier this question was explored by Florides (Gen. Relativ. Gravit. 12 (1980) 563) whose approach was complex and of purely mathematical nature. Also, unlike Florides, we do not assume any a priori separability of T(r, t) = F(r)G(t) and thus our treatment is truly general and yet simpler. More interestingly, even if the net energy density involved in a certain FRW model may appear to be nonzero from its algebric appearance, it may still be possible that tacitly ρe = 0 and the model actually corresponds to a vacuum Minkowski metric. For instance, it has been found that FRW universes which appear to be expanding with a fixed speed in comoving coordinates are intrinsically static universes. While such a linearly expanding universe having k = -1 is well-known as the Milne universe, the corresponding k = 0 case has recently been shown to be vacuum in disguise (A. Mitra, Mon. Not. Roy. Astron. Soc. 442 (2014) 382). In addition, here we show that even the k = +1 linearly "expanding" universe (in comoving coordinates) tacitly corresponds to Einstein's static universe. © 2015 World Scientific Publishing Company.

Maurya D.K.,Bhabha Atomic Research Center | Nandakumar N.,Padmashree Dr. D.Y. Patil University | Devasagayam T.P.A.,Bhabha Atomic Research Center
Journal of Clinical Biochemistry and Nutrition | Year: 2011

Gallic acid is widely distributed in plants, fruits and foods with a range of biological activities. In the present study the possible mechanisms of gallic acid anticancer properties were explored in A549, a human lung adenocarcinoma cell line. Our study shows that it inhibited the A549 cell growth and decreased cell viability monitored at 24 h. It also inhibited cell proliferation in dose- and time-dependent manner as measured by 3-[4,5-methylthiazol-2-yl]-2,5- diphenyl-tetrazolium bromide assay at 24 and 48 h. Morphological examination of the cells after gallic acid treatment showed the typical feature of cell death such as cell shrinkage and rounding up of the cells. Clonogenic assay indicated that gallic acid treatments inhibited the colony formation. DNA fragmentation assay indicated the disappearance of the genomic DNA in dose-dependent manner. To find out possible mechanisms, mitochondrial potential and intracellular reactive oxygen species were measured. It was observed that gallic acid treatment decreased mitochondrial membrane potential and increased intracellular reactive oxygen species. Further caspases activity was measured and it was found that gallic acid activated the caspase-3 but not caspase-8 indicating the involvement of intrinsic pathway of cell apoptosis. ©2011 JCBN.

Yadav V.B.,Bhabha Atomic Research Center | Jha S.K.,Bhabha Atomic Research Center
Journal of Radioanalytical and Nuclear Chemistry | Year: 2013

The economic development worldwide has brought in its wake many changes in the environment. Marine ecosystem which forms a part of this environment has been subjected to impact of industrialisation and urbanization. The study has been carried out in the creek ecosystem of Mumbai receiving the effluents from industrial and urban settlements. The trace elements such as P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pb, As, Rb and Sr were analysed in the creek water collected from the side receiving industrial effluent and discharges from the urban settlements using total reflection X-ray fluorescence spectrometry. On comparing the concentration of the trace element from the mid stream water of the creek with the water samples collected from the industrial and city effluent receiving side, it was found that the concentration of P, Ca, Mn, Fe, Co, Cu, Zn, Pb and As were found higher in the industrial side of the creek whereas V, Cr and Ni concentration were found higher in the samples collected from the side receiving city effluent. © 2012 Akadémiai Kiadó, Budapest, Hungary.

Patwardhan R.S.,Bhabha Atomic Research Center | Sharma D.,Bhabha Atomic Research Center | Checker R.,Bhabha Atomic Research Center | Sandur S.K.,Bhabha Atomic Research Center
Free Radical Biology and Medicine | Year: 2014

Here we describe a novel strategy for mitigation of ionizing radiation-induced hematopoietic syndrome by suppressing the activity of MKP3, resulting in ERK activation and enhanced abundance of hematopoietic stem cells, using the antioxidant flavonoid baicalein (5,6,7-trihydroxyflavone). It offered complete protection to mouse splenic lymphocytes against radiation-induced cell death. Inhibitors of ERK and Nrf-2 could significantly abrogate baicalein-mediated radioprotection in lymphocytes. Baicalein inhibited phosphatase MKP3 and thereby enhanced phosphorylation of ERK and its downstream proteins such as Elk and Nrf-2. It also increased the nuclear levels of Nrf-2 and the mRNA levels of its dependent genes. Importantly, baicalein administration to mice before radiation exposure led to significant recovery of loss of bone marrow cellularity and also inhibited cell death. Administration of baicalein increased the hematopoietic stem cell frequency as measured by side-population assay and also by antibody staining. Further, baicalein offered significant protection against whole-body irradiation (WBI; 7.5 Gy)-induced mortality in mice. Interestingly, we found that baicalein works by activating the same target molecules ERK and Nrf-2 both in vitro and in vivo. Finally, administration of all-trans-retinoic acid (inhibitor of Nrf-2) significantly abrogated baicalein-mediated protection against WBI-induced mortality in mice. Thus, in contrast to the generalized conception of antioxidants acting as radioprotectors, we provide a rationale that antioxidants exhibit pleiotropic effects through the activation of multiple cellular signaling pathways. © 2013 Elsevier Inc.

Pandey V.K.,Bhabha Atomic Research Center | Shankar B.S.,Bhabha Atomic Research Center | Sainis K.B.,Bhabha Atomic Research Center
International Immunopharmacology | Year: 2012

The immunogenicity of dendritic cells (DC) is known to increase with their maturation state and both are induced by microbial products like LPS. In this study, we have investigated the effect of G1-4A, a polysaccharide isolated from Indian medicinal plant, Tinospora cordifolia on phenotypic and functional maturation of murine bone marrow derived dendritic cells (BMDC) and its ability to be used as an adjuvant in immunotherapy. G1-4A, enhanced surface expression of CD40, CD80, CD86, MHCII by BMDC in vitro and splenic DC in vivo. T cell allostimulatory activity and secretion of IL-12 and TNFα by BMDC were also increased. Treatment with G1-4A resulted in decreased phagocytosis and increased antigen processing that are characteristic of mature DC. G1-4A treated DC cross presented exogenous antigens on a MHC I background which resulted in the activation of cytotoxic T cells. These cells thus activated could cause lysis of target tumor cells in vitro. Administration of tumor lysate pulsed G1-4A treated DC resulted in decreased tumor burden in preventive as well as therapeutic tumor challenge experiments in a murine lymphoma model. These results thus confirm that G1-4A could be a promising nontoxic maturation agent to be potentially used in DC based immunotherapy of tumor. © 2012 Elsevier B.V. All rights reserved.

AOT-based microemulsions have been studied quite extensively on account of their numerous industrial applications and their existence as simple ternary phases. Properties of these microemulsions with higher alkanes as the oil continuous phase are governed by the presence of a strong inter micellar attractive interaction. In water in oil (w/. o) microemulsions the inter micellar attraction strengthens with increase in temperature and leads to the observation of critical behavior on approaching the lower consolute temperature (LCT). In this manuscript we show that the phase behavior of AOT-based reverse micellar solutions in dodecane transforms dramatically when the polar domain is changed from water to formamide (FA) and even to aqueous solution of urea and NaCl. In all these cases the temperatures dependence of the microemulsion properties undergo complete reversal, which brings about a transition in their phase separation characteristics from lower consolute temperature (LCT) to upper consolute temperature (UCT) regime. Such systematic transformation in the phase behavior as a function of polar domain composition, which has been explained based on the influence of the polar domain on the properties of the interfacial AOT layer, is first of its kind in any reverse micellar system. © 2014 Elsevier Inc.

Kandwal P.,Bhabha Atomic Research Center | Mohapatra P.K.,Bhabha Atomic Research Center
Journal of Membrane Science | Year: 2014

The present paper is a first time report on the pertraction of radio-cesium (137Cs) across a flat sheet supported liquid membrane (FSSLM) containing a solvent system containing chlorinated cobalt dicarbollide (CCD) in a diluent mixture containing 2-nitrophenyloctyl ether (NPOE) and n-dodecane. The feed phase consisted of 1M HNO3 while 8M HNO3 was the receiver phase. The optimized solvent system with 1.0×10-2M CCD in 60% NPOE+40% n-dodecane was found to be highly efficient for the transport of the metal ion in terms of metal ion extraction (87.8%) and stability of the liquid membrane. The transport efficiency decreased with increasing feed phase HNO3 concentration suggesting applicability of the transport system for radioactive wastes at low to moderate acidity (≤1M HNO3). Furthermore, the transport rates of Cs(I) increased with increasing CCD concentration suggesting direct involvement of the carrier molecule in the metal ion transport. The addition of PEG-400 (used for Sr(II) transport) into the solvent system did not result in the expected co-transport of Sr(II) which was attributed to the leaching out of the ligand from the membrane pores due to its high aqueous solubility. The diffusion coefficient was calculated by the lag time method and was found to be 1.7×10-7cm2/s which was somewhat lower than that obtained by Danesi's method. © 2014 Elsevier B.V.

Rao M.S.,Bhabha Atomic Research Center | Chawla S.P.,Bhabha Atomic Research Center | Chander R.,Bhabha Atomic Research Center | Sharma A.,Bhabha Atomic Research Center
Carbohydrate Polymers | Year: 2011

Chitosan-glucose solution was exposed to gamma radiation to doses up to 100 kGy. Formation of Maillard reaction products (MRPs) was monitored by measuring changes in UV absorbance, browning and fluorescence. The amino group and reducing sugar content of the solution decreased with increasing dose of radiation suggesting reaction between carbonyl and amino groups. There was a marked increase in the reducing power of the solution which correlated with high DPPH and superoxide radical scavenging activity. Chitosan-glucose MRPs provided good protection to β-carotene against bleaching indicating its high antioxidant potential. 5-Hydroxymethylfurfural, a known cytotoxic product formed by heat-induced Maillard reaction was not detected in MRPs formed by irradiation of chitosan-glucose solution. These MRPs also showed antibacterial activity against Escherichia coli, Staphylococcus aureus, Pseudomonas fluorescens and Bacillus cereus. © 2010 Elsevier Ltd. All rights reserved.

Parchur A.K.,Banaras Hindu University | Prasad A.I.,Bhabha Atomic Research Center | Rai S.B.,Banaras Hindu University | Ningthoujam R.S.,Bhabha Atomic Research Center
Dalton Transactions | Year: 2012

As-prepared samples of YPO 4:2Dy nanoparticles prepared by polyol route show strong blue luminescence because of strong host contribution, whereas 500 and 900 °C annealed samples show cold and warm white luminescence, respectively because of different energy transfer rates from host to Dy 3+. Li + co-doping improves luminescence intensity as well as crystallinity significantly. Interestingly, Li + ions occupy interstitial sites of lattice. These materials will be potential candidates for white light emitting diodes and near-infrared emitting phosphors. © 2012 The Royal Society of Chemistry.

Sengupta A.,Bhabha Atomic Research Center | Mohapatra P.K.,Bhabha Atomic Research Center | Iqbal M.,MESA Institute for Nanotechnology | Huskens J.,MESA Institute for Nanotechnology | Verboom W.,MESA Institute for Nanotechnology
Dalton Transactions | Year: 2012

Three room temperature ionic liquids (RTILs), viz. C 4mim +·PF 6 -, C 6mim +·PF 6 - and C 8mim +·PF 6 -, were evaluated as diluents for the extraction of Am(iii) by N,N,N′,N′-tetraoctyl diglycolamide (TODGA). At 3 M HNO 3, the D Am-values by 0.01 M TODGA were found to be 102, 34 and 74 for C 4mim +·PF 6 -, C 6mim +·PF 6 - and C 8mim +·PF 6 -, respectively. The extraction of Am(iii) decreased with increasing feed acidity for all three diluents, indicating an ion exchange mechanism for the extraction. The stoichiometry of the extracted species suggested that two TODGA molecules were associated with Am(iii) during the extraction for all three RTILs and the conditional extraction constants have been determined. The D M-values for different metal ions followed the order: 75 (Am(iii)) > 30.7 (Pu(iv)) > 3.9 (Np(iv)) > 1.19 (Pu(vi)) > 0.52 (U(vi)) > 0.12 (Cs(i)) > 0.024 (Sr(ii)). The distribution behaviour of Am(iii) was also studied with a recently synthesized calix[4]arene-4DGA (C4DGA) extractant dissolved in C 8mim +·PF 6 -. Using this extractant diluent combination, the D Am-value was 194 at 3 M HNO 3 using 5 × 10 -5 M C4DGA, suggesting a very high distribution coefficient at very low extractant concentrations. The stoichiometry of the extracted species containing Am was found to be 1:2 (M:L) in C 8mim +· PF 6 -. The thermodynamics of the extraction was also studied for both extractants in C 8mim +·PF 6 -. The use of RTILs gives rise to significantly improved extraction properties than the commonly used n-dodecane and an unusual increase in separation factor values was seen for the first time which can lead to selective separation of Am from wastes containing a mixture of U, Pu and Am. © 2012 The Royal Society of Chemistry.

Chandrasekaran K.,Bhabha Atomic Research Center | Karunasagar D.,Bhabha Atomic Research Center | Arunachalam J.,Bhabha Atomic Research Center
Journal of Analytical Atomic Spectrometry | Year: 2012

This paper reports on the simultaneous extraction and preconcentration of 14 lanthanide (rare earth) elements in groundwater by a dispersive liquid-liquid microextraction (DLLME) method and their determination by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS). A low flow rate (200 μL min -1) SeaSpray™ micro-flow nebulizer was used for the sample introduction. In this method, the rare earth elements are complexed with 2,6-pyridinedicarboxylic acid (2,6-PDCA) in the presence of Aliquat® 336 (tricaprylmethylammonium chloride), which enhanced the hydrophobicity of the ion-association complex, resulting in its improved extraction into chloroform. The extraction was carried out after adjusting the pH of the water sample to 4. The rare earth ions were back extracted from the chloroform layer with nitric acid for determination by ICP-QMS. Some effective parameters for complex formation and extraction, such as volume of extractant/disperser solvent, extraction time, pH and concentration of the chelating agent and surfactant, have been optimized. Under optimum conditions, an average preconcentration factor of 97 was obtained for 50 mL of water sample for determination by ICP-QMS. The calibration graphs were linear in the range of 1-100 ng L -1 for the 14 REEs, with limits of detection ranging from 0.05-0.55 ng L -1. The precision ranged from 1-5% R.S.D. (n = 3), when processing 50 mL aliquots of groundwater. The method has been applied to a few groundwater samples. The recoveries obtained for the rare earth elements in groundwater samples spiked to 10 ng L -1 were 92-109%. © 2012 The Royal Society of Chemistry.

Karve L.,Bhabha Atomic Research Center | Dutt G.B.,Bhabha Atomic Research Center
Journal of Physical Chemistry B | Year: 2011

To assess the influence of the nature of cation on solute reorientation, fluorescence anisotropies of two organic solutes, 2,5-dimethyl-1,4-dioxo-3,6- diphenylpyrrolo[3,4-c]pyrrole (DMDPP) and rhodamine 110 (R110), have been measured in four ionic liquids containing tris(pentafluoroethyl) trifluorophosphate (FAP) anion over the temperature range 308-348 K. The ionic liquids used in the study are 1-butyl-1-methylpyrrolidinium FAP (BMPL FAP), 1-(2-methoxyethyl)-1-methylpyrrolidinium FAP (MOEMPL FAP), 1-(2-methoxyethyl)-1- methylpiperidinium FAP (MOEMPIP FAP), and N-(2-methoxyethyl)-N- methylmorpholinium FAP (MOEMMO FAP). Analysis of the data carried out with the aid of Stokes-Einstein-Debye hydrodynamic theory reveals that the rotation of the neutral solute DMDPP in all the four ionic liquids is essentially governed by the viscosity of the medium and the reorientation times follow slip boundary condition. In contrast, the results obtained for the cationic solute, which experiences specific interactions with the FAP anion, are somewhat different. The reorientation times of R110 are in between stick and slip limits and found to be independent of the nature of the cation of the ionic liquid except in case of highly viscous MOEMMO FAP, wherein it has been observed that the rotation of R110 is faster by a factor of 1.5. The observed behavior has been rationalized on the basis of highly associative nature of the MOEMMO cation, which precludes R110 from experiencing strong specific interactions with the FAP anion. © 2011 American Chemical Society.

Simimol A.,National Aerospace Laboratories, Bangalore | Chowdhury P.,National Aerospace Laboratories, Bangalore | Ghosh S.K.,Bhabha Atomic Research Center | Barshilia H.C.,National Aerospace Laboratories, Bangalore
Electrochimica Acta | Year: 2013

We present the fabrication of highly oriented, well faceted and defect free ZnO nanorods by electrodeposition using ZnCl2 and KCl as the electrolyte. The ZnO nanostructures were prepared on high purity Cu foil, commercial Cu foil, ITO coated glass and Cu (100 nm)/Ti (30 nm)/Si substrates. We have studied in detail the effects of various growth parameters such as bath temperature, deposition time, precursor concentration and applied potential on the morphology, structural and optical properties of ZnO nanorods. A detailed mechanism and the effects of various process parameters on the formation of defect free (with controlled microstructure of) ZnO nanorods are reported. Our studies confirmed that the bath temperature and the deposition time critically influenced the aspect ratio of ZnO nanorods. For instance, the growth of ZnO nanorods along the lateral direction affected marginally, whereas, along the c-axis, the growth affected significantly with bath temperature as well as with the deposition time. At higher deposition time the shape of ZnO nanostructures got distorted because of reduction in the bulk pH value of the solution. Similarly, at bath temperature greater than 80 °C, the ZnO nanorods were misoriented with cauliflower-like microstructure mainly because of reduction in Zn2+ ion concentration. The ZnO nanostructures prepared under the optimized growth conditions showed an intense UV emission without spreading in the visible region as confirmed by photoluminescence spectroscopy, thus demonstrating the formation of defect free structure. © 2012 Elsevier Ltd.

Sengupta A.,Bhabha Atomic Research Center | Mohapatra P.K.,Bhabha Atomic Research Center
Supramolecular Chemistry | Year: 2012

Extraction of radiostrontium from dilute nitric acid solutions was studied using two Sr 2+ selective crown ethers, viz. dicyclohexano-18-crown-6 and 4,4(5)-di-tert-butyl-dicyclohexano-18-crown-6, in several room temperature ionic liquids, viz. 1-butyl-3-methyl-imidazolium hexafluorophosphate (C 4mim +), 1-hexyl-3-methyl-imidazolium hexafluorophosphate (C 6mim +) and 1-octyl-3-methyl-imidazolium hexafluoro phosphate (C 8mim +); 1-butyl-3-methyl-imidazolium bis[(trifluoromethyl)sulphonyl] imide (C4mim +), 1-hexyl-3-methyl- imidazolium bis[(trifluoromethyl)sulphonyl] imide (C6mim +) and 1-octyl-3-methyl-imidazolium bis[(trifluoromethyl)sulphonyl] imide (C 8mim +). The role of time of equilibration, feed acidity and extractant concentration was investigated. The extracted species were found to have the stoichiometry of 1:1 with the metal ion and the crown ethers. Extraction from simulated high-level waste as the feed indicated lowering in the D Sr values, suggesting extraction of other metal ions to a certain extent. The radiolytic stability of the solvent systems was also investigated and compared with those reported in the literature. © 2012 Taylor and Francis Group, LLC.

Kulkarni S.,Bhabha Atomic Research Center | Ballal A.,Bhabha Atomic Research Center | Apte S.K.,Bhabha Atomic Research Center
Journal of Hazardous Materials | Year: 2013

Bioremediation of uranium (U) from alkaline waste solutions remains inadequately explored. We engineered the phoK gene (encoding a novel alkaline phosphatase, PhoK) from Sphingomonas sp. for overexpression in the radioresistant bacterium Deinococcus radiodurans. The recombinant strain thus obtained (Deino-PhoK) exhibited remarkably high alkaline phosphatase activity as evidenced by zymographic and enzyme activity assays. Deino-PhoK cells could efficiently precipitate uranium over a wide range of input U concentrations. At low uranyl concentrations (1. mM), the strain precipitated >90% of uranium within 2. h while a high loading capacity of around 10.7. g. U/g of dry weight of cells was achieved at 10. mM U concentration. Uranium bioprecipitation by Deino-PhoK cells was not affected in the presence of Cs and Sr, commonly present in intermediate and low level liquid radioactive waste, or after exposure to very high doses of ionizing radiation. Transmission electron micrographs revealed the extracellular nature of bioprecipitated U, while X-ray diffraction and fluorescence analysis identified the precipitated uranyl phosphate species as chernikovite. When immobilized into calcium alginate beads, Deino-PhoK cells efficiently removed uranium, which remained trapped in beads, thus accomplishing physical separation of precipitated uranyl phosphate from solutions. The data demonstrate superior ability of Deino-PhoK, over earlier reported strains, in removal of uranium from alkaline solutions and its potential use in bioremediation of nuclear and other waste. © 2013 Elsevier B.V.

Rastogi L.,Bhabha Atomic Research Center | Sashidhar R.B.,Osmania University | Karunasagar D.,Bhabha Atomic Research Center | Arunachalam J.,Bhabha Atomic Research Center
Talanta | Year: 2014

A highly sensitive and selective method is reported for the colorimetric detection of Hg2+ in aqueous system by using label free silver nanoparticles (Ag NPs). Ag NPs used in this method were synthesized by gum kondagogu (GK) which acted as both reducing and stabilizing agent. The average size of the GK-Ag NPs was found to be 5.0±2.8 nm as revealed by transmission electron microscope (TEM) analysis and the nanoparticles were stable at various pH conditions (pH 4-11) and salt concentrations (5-100 mM). The GK reduced/stabilized Ag NPs (GK-Ag NPs) were directly used for the selective colorimetric reaction with Hg2+ without any further modification. The bright yellow colour of Ag NPs was found to fade in a concentration dependent manner with the added Hg+ ions. The fading response was directly correlated with increasing concentration of Hg 2+. More importantly, this response was found to be highly selective for Hg2+ as the absorption spectra were found to be unaffected by the presence of other ions like; Na+, K+, Mg2+, Ca2+, Cu2+, Ni2+, Co2+, As 3+, Fe2+, Cd2+, etc. The metal sensing mechanism is explained based on the turbidometric and X-ray diffraction (XRD) analysis of GK-Ag NPs with Hg2+. The proposed method was successfully applied for the determination of Hg2+ in various ground water samples. The reported method can be effectively used for the quantification of total Hg2+ in samples, wherein the organic mercury is first oxidized to inorganic form by ultraviolet (UV) irradiation. The limit of quantification for Hg2+ using the proposed method was as low as 4.9×10 -8 mol L-1 (50 nM). The proposed method has potential application for on-field qualitative detection of Hg2+ in aqueous environmental samples. © 2013 Published by Elsevier B.V.

Das T.N.,Bhabha Atomic Research Center | Dey G.R.,Bhabha Atomic Research Center
Journal of Hazardous Materials | Year: 2013

A first-time account of direct, on-line, instantaneous and efficient chemical conversion of gas phase benzene to methane in argon Dielectric Barrier Discharge (DBD) is presented. In the absence of another overt hydrogen-donating source, potency of analogous parents toward methane generation is found to follow the order: benzene. >. toluene. >. p-xylene. Simultaneous production of trace amounts of phenolic surface deposits suggest (a) prompt decomposition of the parent molecules, including a large fraction yielding atomic transients (H-atom), (b) continuous and appropriate recombination of such parts, and (c) trace moisture in parent contributing OH radicals and additional H-atoms, which suitably react with the unreacted fraction of the parent, and also other intermediates. Results highlight Ar DBD to be a simple and exploitable technology for transforming undesirable hazardous aromatics to usable/useful low molecular weight open-chain products following the principles of green chemistry and engineering. © 2013 Elsevier B.V.

Aggarwal S.K.,Bhabha Atomic Research Center
Analytical Methods | Year: 2016

The advances which have taken place during the last four decades in the instrumentation and applications of thermal ionisation mass spectrometry (TIMS) particularly of relevance to nuclear science and technology are highlighted. These include the measurements at different stages of the nuclear fuel cycle including nuclear material accounting, nuclear safeguards and nuclear forensics. The present day availability of fully automated TIMS instruments equipped with multi Faraday cup detectors has enhanced the capabilities of providing answers to many of the previous un-solved problems, but at the same time, these instruments are being treated as magic black boxes by operators performing routine analysis. The advances in the instrumentation as well as in the software available with the present TIMS machines allow us to venture into hitherto unexplored areas of R&D including the precise and accurate determination of ultra-trace amounts of different isotopes. TIMS along with isotope dilution will continue to be a gold standard and reference analytical method for various applications in nuclear science. MC-ICP-MS will play a complementary role to the present TIMS measurements, especially for routine analysis of actinides at different stages of nuclear fuel fabrication, burn-up determination and at the reprocessing plants. © The Royal Society of Chemistry 2016.

Panja N.,Bengal Engineering and Science University | Ghanty T.K.,Bhabha Atomic Research Center | Nandi P.K.,Bengal Engineering and Science University
Theoretical Chemistry Accounts | Year: 2010

The static first and second hyperpolarizabilities of a number of spiromolecules with varying degree of polarity have been calculated at the HF and MP2 level using the 6-31+G* basis set and the B3LYP/6-31+G* optimized geometry. The variation of mean second hyperpolarizability in these molecular systems has been explained in terms of the ground state dipole moment, mean linear polarizability and second-order polarizability. A number of relationships among these quantities have been derived in the framework of the sum-over-state scheme and the generalized Thomas-Kuhn sum rule. The spiroconjugation results in the significant increase of the mean polarizability. The appreciable enhancement of first hyperpolarizability due to the spiroconjugation between two dipolar monomer units has been accounted for the rather significant increase of the mean polarizability tensor and the ground state dipole moment. The relatively larger value of the average second hyperpolarizability of the spiroconjugated molecules compared to that of the corresponding monomers arises from the rather significant increase of the nonaxial component γxxyy. The replacement of spirocarbon by spirosilicon results in the enhancement of the cubic polarizability manifold. The donor-acceptor substituted spirocompounds are predicted to be the superior third-order nonlinear optical (NLO) phores. The nature of π-conjugation in the monomer units around the spirocenter shows a strong modulation of the NLO properties of spirocompounds. The influence of electron correlation on the NLO properties at the MP2 level has been found to be rather significant. © 2009 Springer-Verlag.

Sounderajan S.,Bhabha Atomic Research Center | Kumar G.K.,Bhabha Atomic Research Center | Udas A.C.,Bhabha Atomic Research Center
Journal of Hazardous Materials | Year: 2010

This paper presents a method based on the cloud point extraction for the separation and preconcentration of Se (IV) and Se (VI) in environmental water samples as well as total selenium in animal blood and tissue samples. 3,3′-Diaminobenzidine (DAB) is a selective and sensitive reagent and is known to form an intense yellow compound piazselenol with selenium (IV). When a system consisting of sample, DAB and surfactant Triton X-114 is warmed above the cloud point of the surfactant, it was seen that the DAB-Se (IV) complex gets extracted into the surfactant rich phase while the Se (VI) remains in the aqueous phase. Se (VI) in the sample was reduced to Se (IV) by microwave heating of solution in 4 mol L -1 HCl and total Se was estimated by carrying out the CPE. The quantification of selenium was carried out using ETAAS. The analytical parameters for the quantitative cloud point extraction of the Se-DAB complex were investigated and optimized. The proposed procedure was validated by applying it to the determination of the content of Se in Certified Reference Material BND 701-02. (NPL, India). The detection limit of selenium in environmental water samples was 0.0025 μg L -1 with an enrichment factor of 100. The relative standard deviation (RSD) for ten replicate measurements of 5 μg L -1 was 3.6%. The proposed method was successfully applied to the determination of selenium (IV), (VI) in environmental water samples and determination of total selenium in human blood, SRM-IAEA-A-13 animal blood and SRM-IAEA-407 fish tissue. © 2009 Elsevier B.V. All rights reserved.

Verma S.,Bhabha Atomic Research Center | Kar P.,Indian Central Salt and Marine Chemicals Research Institute | Das A.,Indian Central Salt and Marine Chemicals Research Institute | Palit D.K.,Bhabha Atomic Research Center | Ghosh H.N.,Bhabha Atomic Research Center
Chemistry - A European Journal | Year: 2010

We have synthesized ruthenium(II)- and osmium(II)-polypyridyl complexes ([M(bpy)2L]2+, in which M = OsIIor Ru II bpy = 2,2́-bipyridyl, and L = 4-(2,2́-bipyridinyl-4- yl)benzene-l,2-diol) and studied the interfacial electron-transfer process on a TiO2 nanoparticle surface using femtosecond transient-absorption spectroscopy. Ruthenium(II)- and osmium(II)-based dyes have a similar molecular structure; nevertheless, we have observed quite different interfacial electrontransfer dynamics (both forward and backward). In the case of the RuII/TiO2 system, single-exponential electron injection takes place from photoexcited nonthermalized metal-to-ligand charge transfer (MLCT) states. However, in the case of the OsII/TiO2 system, electron injection takes place biexponentially from both nonthermalized and thermalized MLCT states (mainly 3MLCT states). Larger spin-orbit coupling for the heavier transition-metal osmium, relative to that of ruthenium, accounts for the more efficient population of the 3MLCT states in the OsIIbased dye during the electron-injection process that yields biexponential dynamics. Our results tend to suggest that appropriately designed OsII-polypyridyl dye can be a better sensitizer molecule relative to its RuII analogue not only due to much broader absorption in the visible region of the solaremission spectrum, but also on account of slower charge recombination. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

Dutt G.B.,Bhabha Atomic Research Center
Indian Journal of Chemistry - Section A Inorganic, Physical, Theoretical and Analytical Chemistry | Year: 2010

Rotational diffusion of two structurally similar nondipolar solutes, viz., 2,5-dimethyl-1,4-dioxo-3,6-diphenylpyrrolo [3,4-c]pyrrole (DMDPP) and 1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole(DPP) has been examined in two ionic liquids,(l-butyl-3-methylimidazolium octylsulfate([bmim+][OS -]) and 1-butyl-3-methylimidazolium nitrate ([bmim +][NO-3])), to understand the influence of the nature of the anion on solute rotation. It has been observed that the rotation of DPP is slower as compared to that of DMDPP in [bmim+][OS -] as well as in [bmim+][NO-3] by a factor of 2.5 and 1.7, respectively. The slow rotation of DPP is due to the strong hydrogen bonding interactions between the two NH groups of the solute and the respective anions of the ionic liquids. Comparison of the viscosity normalized reorientation times of DMDPP in [bmim+][OS-] and [bmim+][NO-3] indicates that the rotation of the solute is slower by a factor of 2 in nitrate as compared to that in octylsulfate. The faster rotation of DMDPP in [bmim+][OS-] has been rationalized on the basis of size effects. Quasihydrodynamic theories of Gierer-Wirtz and Dote-Kivelson-Schwartz have been invoked to assimilate the results in a qualitative manner. In contrast, the viscosity normalized reorientation times of DPP in [bmim+][NO-3] are longer only by factor of 1.3 as compared to the ones measured in [bmim +][OS-], which is due to the stronger hydrogen bonding interactions between DPP and the nitrate ion.

Density Functional theory (DFT) has been used to optimize the structures of Cyanex925 [bis(2,4,4-trimethylpentyl)octylphosphine oxide], tributyl phosphate (TBP), and their complexes with Hf and Zr oxycations by employing the triple-zeta valence plus polarization (TZVP) basis set. The effect of noncovalent interactions was examined by using the TPSSH and M06-2X density functionals. The free energy of extraction ΔGext from the aqueous to organic phase was calculated by using the standard thermodynamic procedure in conjunction with the conductor-like screening model (COSMO). The calculated ΔGext, either with an implicit or explicit solvation model, fails to capture the experimentally reported preferential selectivity of ZrO2+ ions over HfO2+ ions in the absence of nitrate anions towards Cyanex925 over TBP. The presence of nitrate anions along with the second solvation shell (n = 6 + 1 water molecules) around the oxycation shows consistent results with the calculated ΔGext for the selectivity as reported in solvent extraction experiments [the calculated ΔΔΔGext value (-4.72 kcal/mol) is in qualitative agreement with the experimental ΔΔΔGext (-0.82 kcal/mol) results; separation factor (SF) ≈ exp(-ΔΔΔG ex/RT)]. Different bonding analyses indicate the electrostatic nature of the interactions between the metal oxycations and the organophosphorus ligands. The present study will further assist in the design of new ligand/solvent systems for the preferential extraction of ZrO2+ ions over HfO2+ ions in solvent extraction experiments. Free energy analysis of a thermodynamical cycle and DFT calculations with the conductor-like screening model (COSMO) capture the experimental selectivity of ZrO 2+ ions over HfO2+ ions towards tributyl phosphate (TBP) and Cyanex925 ligands. The selectivity between the two ligands for a particular metal oxycation is independent of the solvation pattern of the oxycation. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Parchur A.K.,Banaras Hindu University | Prasad A.I.,Bhabha Atomic Research Center | Ansari A.A.,King Saud University | Rai S.B.,Banaras Hindu University | Ningthoujam R.S.,Bhabha Atomic Research Center
Dalton Transactions | Year: 2012

Tb 3+-doped CaMoO 4 (Tb 3+ = 1, 3, 5, 7, 10, 15 and 20 atom%) core and core-shell nanoparticles have been prepared by urea hydrolysis in ethylene glycol (EG) as capping agent as well as reaction medium at low temperature ∼150 °C. As-prepared samples were annealed at 500 and 900 °C for 4 h to eliminate unwanted hydrocarbons and/or H 2O present in the sample and to improve crystallinity. The synthesised nanophosphors show tetragonal phase structure. The crystallite size of as-prepared sample is found to be ∼18 nm. The luminescence intensity of the 5D 4 → 7F 5 transition at 547 nm of Tb 3+ is much higher than that of the 5D 4 → 7F 6 transition at 492 nm. 900 °C annealed samples show the highest luminescence intensity. The intensity ratio R (I[ 5D 4 → 7F 6]/I[ 5D 4 → 7F 5]) lies between 0.3-0.6 for as-prepared, 500 and 900 °C annealed samples. The luminescence decay of 5D 4 level under 355 nm excitation shows biexponential behaviour indicating availability of Tb 3+ ions on surface and core regions of particle; whereas, contribution of Mo-O charge transfer to lifetime is obtained under 250 nm excitation. The CIE coordinates of as-prepared, 500 and 900 °C annealed 5 atom% Tb 3+-doped CaMoO 4 samples under 250 nm excitation are (0.28, 0.32), (0.22, 0.28) and (0.25, 0.52), respectively. The dispersed particles in polar medium and its polymer film show green light emission. The luminescence intensity is improved significantly after core-shell formation due to extent of decrease of non-radiative rates arising from surface dangling bonds and capping agent. Quantum yields of as-prepared samples of 1, 5 and 7 atom% Tb 3+-doped CaMoO 4 samples are found to be 10, 3 and 2, respectively. © 2012 The Royal Society of Chemistry.

Koshy P.,Bhabha Atomic Research Center | Aswal V.K.,Bhabha Atomic Research Center | Venkatesh M.,Bhabha Atomic Research Center | Hassan P.A.,Bhabha Atomic Research Center
Journal of Physical Chemistry B | Year: 2011

Natural fatty acids such as sodium oleate form highly viscous supramolecular complexes with long-chain cationic surfactants through cooperative self-assembly. Here we report the rheological behavior of linear and branched wormlike micelles formed in mixtures of cetyltrimethylammonium bromide (CTAB) and sodium oleate (NaOL). Addition of sodium oleate induces an increase in the axial ratio of the mixed micelles. At a constant mole fraction of the mixture, an increase in total surfactant concentration leads to a transition from linear to branched micelles. Both linear and branched micelles impart viscoelastic behavior to the fluid, and the low-frequency data can be approximated to the Maxwell model. Scaling of the rheological parameters of CTAB-NaOL catanionic mixtures, as a function of concentration, employing dynamic rheological measurements has been determined and compared with the predictions of existing scaling laws. The structural transition from linear micelles to the branched micelles in the CTAB-NaOL micellar system greatly influences the scaling behavior of shear modulus. The scaling exponent is lower for the branched micelles compared to linear micelles, analogous to those of linear and branched polymer melts. The structural evolution is probed by light scattering and small-angle neutron scattering measurements as well. © 2011 American Chemical Society.

Tripathi A.,Bhabha Atomic Research Center | Melo J.S.,Bhabha Atomic Research Center | D'Souza S.F.,Bhabha Atomic Research Center
Journal of Hazardous Materials | Year: 2013

This study presents a novel development of a floating polymeric-magnetite cryobead for the recovery of hexavalent uranium from the aqueous sub-surfaces. The alginate-agarose-magnetite cryobeads were synthesized by the process of cryotropic-gelation at subzero-temperature. The physico-chemical properties of cryobeads showed high surface area and high interconnected porosity (∼90%). Low density of these cryobeads explains their floating property in the aqueous medium. The rheological analysis of cryobeads showed its stability and increased stiffness after uranium adsorption. The presence of magnetite nanoparticles in the porous cryobeads facilitates the recovery of these beads by applying an external magnetic field. Maximum uranium adsorption (97 ± 2%) was observed in the pH range of 4.5-5.5. The thermodynamic parameters suggest passive endothermic adsorption behaviour. HCl was found to be an efficient eluent for the uranium desorption. Five repeated cycles for the desorption of uranium from biosorbent showed 69 ± 3% of uranium recovery. These results suggest stability of these novel floating magnetite-cryobeads under environmetal conditions with potential for the recovery of uranium from contaminated aqueous subsurfaces. © 2012 Elsevier B.V.

Mukhopadhyay S.,Bhabha Atomic Research Center | Tiwari A.P.,Bhabha Atomic Research Center
Annals of Nuclear Energy | Year: 2010

A novel technique for estimating system parameters based on consistent output estimate in wavelet domain is proposed as an alternative solution to the classical least squares minimization problem, in this paper. The algorithm is computationally efficient and exhibits excellent performance in cross validation. An iterative algorithm, alternately projecting the solution in time and wavelet domain for penalized minimization of local error in wavelet coefficients, is presented in the paper. As a case study, the paper addresses the problem of modeling a complex process in a large Pressurized Heavy Water Reactor (PHWR) based on the evolution of input and output. Xenon-induced spatial oscillations are kept from growing in large PHWRs, by means of the Liquid Zone Control System (LZCS). In this work, an identification scheme of a single input single output linear time invariant model of the LZCS is studied. Shift invariant orthogonal wavelets are used for consistent output estimate of the LZCS process. The technique is verified on the real experimental data obtained from the LZCS test set-up. It is observed that even a low order wavelet based model gives excellent approximation from fewer numbers of input-output data points. © 2010 Elsevier Ltd.

Naidu B.S.,Bhabha Atomic Research Center | Vishwanadh B.,Bhabha Atomic Research Center | Sudarsan V.,Bhabha Atomic Research Center | Vatsa R.K.,Bhabha Atomic Research Center
Dalton Transactions | Year: 2012

In the present manuscript it is demonstrated that BiPO 4 is a better alternative to lanthanide phosphate host for making lanthanide ion-based luminescent materials. Hexagonal and monoclinic forms of BiPO 4 phase were prepared based on the reaction of Bi 3+ and PO 4 3- ions in ethylene glycol medium at 100 and 185°C, respectively. From the differential thermal analysis (DTA) studies it is confirmed that the difference in the nucleation mechanism rather than the phase transition is responsible for the monoclinic phase formation at low temperatures (125°C). Monoclinic BiPO 4 is quite stable and forms random solid solutions with lanthanide phosphates having both monoclinic (monazite) and tetragonal (xenotime) structures, as confirmed by XRD, FTIR and 31P solid state nuclear magnetic resonance studies. On excitation corresponding to the 1S 0→ 3P 1 transition of Bi 3+ in BiPO 4:Ln samples, energy transfer from host to lanthanide ions takes place. The studies are quite relevant as there is a growing interest all over the world in replacing lanthanide based host used for different applications with easily available, easily purifiable and cheap main group elements (like Sb, Bi etc.) based hosts. © The Royal Society of Chemistry 2012.

Dutta D.P.,Bhabha Atomic Research Center | Roy M.,Bhabha Atomic Research Center | Tyagi A.K.,Bhabha Atomic Research Center
Dalton Transactions | Year: 2012

Undoped Bi 2O 3 and single and double doped Bi 2O 3:M (where M = Tb 3+ and Eu 3+) nanophosphors were synthesized through a simple sonochemical process and characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), EDS, diffuse reflectance (DRS) and photoluminescence (PL) spectrophotometry. The TEM micrographs show that resultant nanoparticles have a rod-like shape. Energy transfer was observed from host to the dopant ions. Characteristic green emissions from Tb 3+ ions and red emissions from Eu 3+ ions were observed. Interestingly, the Commission International de l'Eclairage (CIE) coordinates of the double doped Bi 2O 3:Eu 3+(0.8%):Tb 3+(1.2%) nanorods lie in the white light region of the chromaticity diagram and it has a quantum efficiency of 51%. The undoped Bi 2O 3 showed a band gap of 3.98 eV which is red shifted to 3.81eV in the case of double doped Bi 2O 3:Eu 3+(0.8%):Tb 3+(1.2%) nanorods. The photocatalytic activities of undoped nano Bi 2O 3 and double doped nano Bi 2O 3:Eu 3+(0.8%):Tb 3+(1.2%) were evaluated for the degradation of Rhodamine B under UV irradiation of 310 nm. The results showed that Bi 2O 3:Eu 3+(0.8%):Tb 3+(1.2%) had better photocatalytic activity compared to undoped nano Bi 2O 3. The evolution of CO 2 was realized and these results indicated the continuous mineralization of rhodamine B during the photocatalytic process. Thus double doped Bi 2O 3:Eu 3+(0.8%):Tb 3+(1.2%) nanorods can be termed as a bifunctional material exhibiting both photocatalytic properties and white light emission. © 2012 The Royal Society of Chemistry.

Adya V.C.,Bhabha Atomic Research Center | Sengupta A.,Bhabha Atomic Research Center | Godbole S.V.,Bhabha Atomic Research Center
Atomic Spectroscopy | Year: 2014

The major problem of determining trace analytes in nuclear materials by inductively coupled plasma atomic emission spectrometry (ICP-AES) is the spectral interference of matrix elements such as U, Pu, Zr, Th, etc., originating from their line-rich emission spectra. Chemical or physical separation of the major matrix followed by the determination of trace metallic impurities in the raffinate is a well-accepted protocol in the nuclear industries. However, separation involves handling of the materials which increases the chances of contamination. In this study, the spectral interferences of zirconium on the different analytical lines of 13 analytes (B, Cd, Sm, Dy, Gd, Na, Mg, Cr, Ca, V, Sn, Pb, and Ag) were evaluated to identify the interference-free lines of those elements in the presence of a Zr matrix. A charged coupled detector (CCD) was used because it offers more flexibility in the choice of additional analytical lines. The sensitivity and the detection limits of the analytical channels of the elements in the presence of a zirconium matrix were calculated. An analytical method was also developed for the determination of zirconium by ICP-AES, including identification of suitable analytical lines (343.823nm, 257.139 nm, and 272.262 nm) and their analytical performance such as sensitivity and detection limits.

Sharma A.,Bhabha Atomic Research Center | Eligehausen R.,University of Stuttgart | Reddy G.R.,Bhabha Atomic Research Center
Engineering Structures | Year: 2011

A new model that can simulate the shear behavior of reinforced concrete connections in structures subjected to seismic loads is proposed. The model uses limiting principal tensile stress in the joint as the failure criteria so that due consideration is given to the axial load on the column. The spring characteristics are based on the actual deformations taking place in the sub-assemblage due to joint shear distortion. The model can be easily implemented in any commercial nonlinear analysis package and does not need any special element or subroutine. The model is more rational than the rotational spring models and at the same time being easier to implement in analysis than the multiple spring models. The formulations to obtain the spring characteristics are given in the paper. Currently the model is used to perform nonlinear static analysis for the joints, however, the same can be utilized for the nonlinear dynamic analysis too with an associated hysteretic rule. Highly promising results are obtained using the proposed model for the cases against which the model is validated. This paper focuses on the modeling of exterior joints. An extension to interior joints will be presented later. © 2010 Elsevier Ltd.

In the past two to three decades, great progress has been achieved in the field of plant genetic manipulation. This progress is based on fine-tuning gene transfer methods, selection of transformed cells and regulation of transgene expression. Transgenic plant production requires selectable marker genes that enable the selection of transformed cells, tissue and plants. The most used are those that exhibit resistance to antibiotics or herbicides. Although this type of selection is routinely practiced, there are perceived risks in the deployment of transgenic plants containing these markers. A number of strategies have emerged on the development of alternate selection systems referred to as positive selection and marker-free systems. Transgenes that permit plant cells to utilize new carbon sources are being employed in transformation research. Current research on development of novel selection methods in transgenics is growing rapidly and its application is being tested in different plant species. © 2010 Landes Bioscience

Ozbolt J.,University of Stuttgart | Sharma A.,University of Stuttgart | Sharma A.,Bhabha Atomic Research Center
International Journal of Impact Engineering | Year: 2011

The behavior of concrete/reinforced concrete structures is strongly influenced by the loading rate. Reinforced concrete structural members subjected to impact loads behave quite differently as compared to the same subjected to quasi-static loading. This difference is attributed to the strain-rate influence on strength, stiffness, and ductility as well as to the activation of inertia forces. These influences are clearly demonstrated in experiments. Moreover, for concrete structures, which exhibit damage and fracture phenomena, the failure mode and cracking pattern depend significantly on loading rate. In general, there is a tendency that with the increase of loading rate the failure mode changes from mode-I to mixed mode. Furthermore, theoretical and experimental investigations indicate that after the crack reaches critical speed of propagation there is crack branching. The present paper focuses on 3D finite-element study of reinforced concrete beams with different amount of shear reinforcement under impact. The experiments reported in literature are numerically simulated using the rate sensitive microplane model as constitutive law for concrete, while the strain-rate influence is captured by the activation energy theory. Inertia forces are implicitly accounted for through dynamic finite element analysis. However, the impact was modeled not by explicit modeling of two bodies but by incrementing the load point displacement till the maximum value and at the rate reported from the test. The results of the numerical study show that the numerical analysis using the procedure followed in this work can very well simulate the impact behavior of reinforced concrete beams. The static and dynamic reactions, crack patterns and failure modes as predicted in analysis are in close agreement with their experimentally observed counterparts. It was concluded that under impact loads, of the order as simulated in this work (blunt impact with velocity of around 1 m/s), the shear reinforcement does not get activated and therefore the dynamic reactions, unlike static reactions, are almost independent of the amount of shear reinforcement in the beams. However, the presence of shear reinforcement significantly affects the crack pattern and the cracks are well distributed in the presence of shear reinforcement, thus avoiding the formation of shear plugs. © 2011 Elsevier Ltd. All rights reserved.

Jha N.,Bhabha Atomic Research Center
AIP Conference Proceedings | Year: 2014

In this paper we study rectangular quantum wire based IR detector with magnetic field applied along the wires. The energy spectrum of a particle in rectangular box shows level repulsions & crossings when external magnetic field is applied. Due to this complex level dynamics, we can tune the spacing between any two levels by varying the magnetic field. This method allows user to change the detector parameters according to his/her requirements. In this paper, we numerically calculate the energy sub-band levels of the square quantum wire in constant magnetic field along the wire and quantify the possible operating wavelength range that can be obtained by varying the magnetic field. We also calculate the photon absorption probability at different magnetic fields and give the efficiency for different wavelengths if the transition is assumed between two lowest levels. © 2014 AIP Publishing LLC.

Gupta S.K.,Bhabha Atomic Research Center | Joshi A.,University of Pune | Manmeet K.,Bhabha Atomic Research Center
Journal of Chemical Sciences | Year: 2010

Different ZnO nanostructures such as nanowires, nanobelts and tetrapods have been grown and used for preparation of thick film (with random grain boundaries) as well as isolated nanowire/ nanobelt gas sensors. Sensitivity of different type of sensors has been studied to H2S and NO gases. The results show that the response of ZnO sensors to H2S arises from grain boundary only whereas both grain boundaries and intragrain resistances contribute towards response to NO. In addition, oxygen vacancies in the lattice were also seen to help in improvement of sensor response. Room temperature operating H2S and NO sensors based on ZnO nanowires have been demonstrated. Further, sensors based on isolated nanobelts were found to be highly selective in their response to NO. © Indian Academy of Sciences.

Chandrasekaran K.,Bhabha Atomic Research Center | Balaramakrishna M.V.,Bhabha Atomic Research Center | Karunasagar D.,Bhabha Atomic Research Center
Journal of Analytical Atomic Spectrometry | Year: 2010

A home made PTFE micro-column loaded with polyaniline (50mg), prepared freshly by a chemical method was used for the on-line separation of arsenite [As(iii)] and arsenate [As(v)] followed by determination at ultra trace levels in natural waters by flow injection-hydride generation-inductively coupled plasma mass spectrometry (FI-HG-ICPMS). The species were determined using time resolved mode of data acquisition, by monitoring 75As. The volume of sample injected was 100μl. Both the species eluted within 3min. The effects of variation in sample pH, eluent concentration and the hydride generation conditions were investigated. The calibration in the range of 0.5-50μg L -1 was found to be linear with a regression coefficient, R 2 ≥ 0.997. The detection limits (3σ) were calculated to be 0.05 and 0.09μg L-1 for As(iii) and As(v) respectively and the precision (%RSD) at 1μg L-1 level was found to be 2.0% for As(iii) and 2.5% As(v). The method validation was carried out by analyzing two BCR groundwater certified reference materials, BCR609 and BCR610, certified for total arsenic. The developed speciation method has been applied to groundwater samples collected from West Bengal, India, where there have been many instances of arsenic contamination. © The Royal Society of Chemistry 2010.

Gupta J.,Indian Institute of Technology Bombay | Barick K.C.,Indian Institute of Technology Bombay | Barick K.C.,Bhabha Atomic Research Center | Bahadur D.,Indian Institute of Technology Bombay
Journal of Alloys and Compounds | Year: 2011

Shape-controlled ZnO nanostructures were synthesized through a facile soft-chemical approach by varying the concentration of OH - ions. X-ray diffraction and Raman spectra reveal the formation of highly crystalline single-phase hexagonal wurtzite nanostructure. It has been observed that the concentration of OH - ions plays an important role in controlling the shape of ZnO nanostructures. TEM micrographs indicate that well-spherical particles of size about 8 nm were formed at lower concentration of OH - ions whereas the higher concentration of OH - ions favor the formation of nanorods of length 30-40 nm. The optical studies confirmed that the band gap and near band edge emission of ZnO nanostructures are strongly dependent on the shape of particles. Furthermore, the decrease in the intensity of green emission as shape of particles changes from sphere to rod indicates the suppressing of defect density, which in turn influences the photocatalytic activity and ferromagnetic-like behavior of ZnO nanostructures. © 2011 Elsevier B.V. All rights reserved.

Vasundhara K.,Bhabha Atomic Research Center | Achary S.N.,Bhabha Atomic Research Center | Tyagi A.K.,Bhabha Atomic Research Center
International Journal of Hydrogen Energy | Year: 2015

Herein we report the structure, thermal and electrical properties of pyrochlore type Pr2-xCaxZr2O7 (x = 0.00, 0.10 and 0.20) compositions. These compounds have been prepared by gel combustion method followed by heating in reducing (Argon/Hydrogen) atmosphere and characterized by powder X-ray diffraction, Raman spectroscopy and ac-impedance studies. The powder XRD and Raman spectroscopic studies revealed the retention of the parent cubic pyrochlore type structure up to the compositions with x = 0.10. The thermal stabilities of the compositions have been investigated by in situ high temperature powder XRD and thermogravimetric studies. A maximum of about 1.25% weight gain due to oxidation of Pr3+ is observed in all the samples. The typical axial thermal expansion coefficients (αa) for the compositions with x = 0.00, 0.10 and 0.20 are 8.40 × 10-6, 11.29 × 10-6 and 11.67 × 10-6 K-1, respectively. The analyses of impedance and admittance spectra revealed maximum conductivity at x = 0.10, while the activation energy increases with Ca2+ content. At around 770 K, the conductivities of the compositions with x = 0.00, 0.10 and 0.20 are 2.26 × 10-5 S/cm, 1.88 × 10-4 S/cm and 1.23 × 10-4 S/cm, respectively. The activation energy for electronic conductivity for the composition with x = 0.00 and 0.10 are 0.42 and 0.63 eV, respectively. The temperature dependent conductivity of the composition with x = 0.20 composition revealed a deviation around 700 K where the aviation energy decreased from 0.97 eV to 0.38 eV. The electrical properties Pr2-xCaxZr2O7 have been correlated with structural parameters and explained by the coexisting electronic and ionic conductivities. © 2015 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Cardiovascular disease (CVD) is associated with dietary practices, along with other factors. Metabolism of choline containing diets (e.g., red meat, egg, and various over-the-counter dietary supplements) increases the level of trimethylamine N-oxide (TMAO) in blood, which in turn speeds up the deposition of fat on the inner wall of arteries, making them prone to CVD. Hence, a molecular-level understanding of the TMAO-effect on the fat depositing receptor-ligand interaction at the artery wall-blood interface is essential for the elucidation of the pathogenesis of CVD. Interface-selective and phase-sensitive vibrational spectroscopic study (heterodyne-detected vibrational sum frequency generation, HD-VSFG) of suitable model systems, mimicking the artery wall-blood interface, reveals a surprising charge specific "TMAO-effect" on interfacial electrostatics. The interfacial electric field due to cationic ammonium group embedded in lipid monolayer (mimic of the positively charged domains of lipid-bound receptor/ligand) is strongly screened by TMAO, whereas the interfacial field due to anionic carboxylate in the lipid monolayer (mimic of the negatively charged domains of the lipid-bound receptor/ligand) remains almost unaffected in the presence of TMAO. Altogether, these observations suggest that TMAO (in blood) weakens the receptor-ligand electrostatic interaction at the artery wall-blood interface. As a result, the receptor-mediated removal of fatty deposits (from the artery wall) becomes ineffective, leading to the increased risk of CVD. © 2016 American Chemical Society.

Desai S.,Bhabha Atomic Research Center | Laskar S.,Tata Memorial Hospital | Pandey B.N.,Bhabha Atomic Research Center
Cellular Signalling | Year: 2013

Soluble factors in tumour microenvironment play a major role in modulating the metastatic potential of cancer cells. Herein, we investigated the effect of autocrine cytokines and growth factors in the form of self-conditioned medium (CM) on A549 lung carcinoma cells. We demonstrated that CM induced morphological and molecular changes associated with epithelial-mesenchymal transition viz change in shape from cuboidal to spindle, actin cytoskeleton remodelling, upregulation of vimentin and downregulation of E-cadherin etc. These changes were accompanied with enhanced motility, invasion, anchorage-independent growth and anoikis-resistance. Amongst the different factors of CM, IL-8 and VEGF were found to play a major role in the CM-induced motility and invasion. In the intracellular signalling cascade, CM triggered phosphorylation of JNK and p38 which was associated with the CM-enhanced invasiveness. In CM-treated cells, activated p38 and JNK further activated ATF-2 (Activating Transcription Factor-2) and knock-down of ATF-2 abrogated the CM-induced invasiveness, suggesting the signal transduction along the p38/JNK-ATF-2 axis. Furthermore, neutralising IL-8 and VEGF in CM, significantly abrogated CM-induced phosphorylation of ATF-2. Conversely, exogenous addition of these individual cytokines in plain medium, increased the activation of ATF-2 and invasiveness marginally. However, when added in combination these cytokines (IL-8 and VEGF) resulted in drastic increase in ATF-2 phosphorylation and subsequent invasiveness suggesting their synergetic interplay in the observed phenomenon. Taken together, our results identify IL-8/VEGF induced JNK/p38-ATF-2 as a novel pro-invasive pathway, which may be explored as potential therapeutic target to circumvent the invasiveness of lung malignancies. © 2013 Elsevier Inc.

Murli C.,University of Western Ontario | Song Y.,Bhabha Atomic Research Center
Journal of Physical Chemistry B | Year: 2010

We report here the first in-situ Raman spectroscopic study of pressure-induced structural and polymeric transformations of acrylic acid. Two crystalline phases (I and II) were observed upon compression to ∼0.3 and ∼2.7 GPa. Phase I can be characterized with a single s-cis molecular conformation with possibly a similar structure to the low-temperature phase, while phase II suggests significantly enhanced molecular interactions toward polymerization and structural disordering. Beyond ∼8 GPa, spectroscopic features indicate the onset of polymerization. The high-pressure polymeric phase together with the pressure-quenched materials was examined and compared with two commercial acrylic acid polymers using Raman spectroscopy. The characteristics of polymeric acrylic acid and their transformation mechanisms as well as the implications of hydrogen-bonding interactions are discussed. © 2010 American Chemical Society.

Mandal B.P.,Bhabha Atomic Research Center | Shukla R.,Bhabha Atomic Research Center | Achary S.N.,Bhabha Atomic Research Center | Tyagi A.K.,Bhabha Atomic Research Center
Inorganic Chemistry | Year: 2010

A series of samples with composition Gd2-yCeyZr 2O7(0.0 ≤ y ≤ 2.0) were prepared by the gel combustion method followed by high-temperature reduction. The details of the structural variations as a function of the composition, temperature, and oxygen stoichiometry have been investigated by X-ray diffraction (XRD), high-temperature XRD (HT-XRD), and thermogravimetry. A complete solubility of Gd3+in Ce2Zr2O7and Ce 2Zr2O8could be achieved by this adaptive preparative method. Analysis of the XRD data revealed a sequential variation of the structural features with oxygen stoichiometry as well as Gd 3+contents in these compositions. The variation in the unit cell parameter along the compositions has a strong influence on the oxygen uptake behavior in the Gd2-yCeyZr2O7system, as observed from the thermogravimetric and HT-XRD studies. The preparation and stability of various metastable phases in Gd-Ce-Zr-O have been addressed in detail. The details of the study will be useful for the design and application of a potential redox catalyst and an oxygen storage capacitor. © 2010 American Chemical Society.

Manna P.K.,Bhabha Atomic Research Center | Yusuf S.M.,Bhabha Atomic Research Center | Shukla R.,Bhabha Atomic Research Center | Tyagi A.K.,Bhabha Atomic Research Center
Applied Physics Letters | Year: 2010

We report an extraordinary coexistence of sign reversal of both magnetization and exchange bias field in the La0.2 Ce0.8 CrO3 nanoparticles. From the high resolution transmission electron microscopy image, and field dependence of thermoremanent and isothermoremanent magnetization measurements, the nanoparticles are found to be of core-shell nature. The core-shell configuration with an antiferromagnetic core of the Cr3+ and Ce3+ spins and a disordered shell with the uncompensated spins, explains the sign reversal of both magnetization and exchange bias field. The present study shows an excellent way of tuning the sign of both magnetization and exchange bias field in a single magnetic system. © 2010 American Institute of Physics.

Sahoo N.K.,Bhabha Atomic Research Center
AIP Conference Proceedings | Year: 2010

Optical nanometric multilayer interference coatings, the crucial components in lasers, synchrotron beamlines, optical communication, spectroscopic experiments, analytical instruments, and remote sensing applications have strongly influenced the progress in these associated frontier fields of science and technology. With demanding and more complex requirements, various aspects of material selections, numerical multilayer designs, and their practical realizations have posed serious challenges. The newer concepts, viz, intelligent numerical design methodologies, rugate and quasi-rugate formulations, resonant sub-wavelength structured grating waveguide geometries; high energetic physical vapour deposition processes are drawing more attraction to fulfill the requirements. © 2010 American Institute of Physics.

Nigam S.,Bhabha Atomic Research Center | Majumder C.,Bhabha Atomic Research Center
Journal of Physics Condensed Matter | Year: 2010

Using state-of-the-art first-principles calculations we report the interaction of M atoms (M = Cu, Ag and Au) with small Agn, Au n clusters (n = 3 and 6) and periodic Ag(111) and Au(111) surfaces. All calculations were performed using the plane wave pseudo-potential approach under the spin polarized version of the generalized gradient approximation scheme. The result shows that the equilibrium geometry of all MAg3 and MAu3 clusters favor a planar rhombus structure. From the charge distribution analysis of MAgn/MAun clusters it is found that, while Cu and Ag donates electronic charge towards the host clusters, the Au atom acts as an acceptor, thus creating charge polarization in the system. The difference in orbital decomposed charges before and after the M interaction reveals that enhanced s-d hybridization is responsible for keeping the MAu6 cluster planar, and increased p-orbital participation induces three-dimensional configurations in MAg6 clusters. The optimization of M atom deposition on the Ag(111) and Au(111) surfaces shows that M atoms prefer to adsorb on the threefold fcc site over other well-defined sites. From the orbital decomposed charge analysis it is inferred that, although there is significant difference in the absolute magnitude of the interaction energy between M atoms and the Ag or Au substrates, the nature of chemical bonding is similar for the finite size clusters as well as in slab models. © 2010 IOP Publishing Ltd.

Gurao N.P.,Indian Institute of Science | Kapoor R.,Bhabha Atomic Research Center | Suwas S.,Indian Institute of Science
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2010

The evolution of crystallographic texture in polycrystalline copper and nickel has been studied. The deformation texture evolution in these two materials over seven orders of magnitude of strain rate from 3 × 10 -4 to ∼2.0 × 10+3 s-1 show little dependence on the stacking fault energy (SFE) and the amount of deformation. Higher strain rate deformation in nickel leads to weaker 〈{101}〉 texture because of extensive microband formation and grain fragmentation. This behavior, in turn, causes less plastic spin and hence retards texture evolution. Copper maintains the stable end 〈{101}〉 component over large strain rates (from 3 × 10-4 to 10+2 s-1) because of its higher strain-hardening rate that resists formation of deformation heterogeneities. At higher strain rates of the order of 2 × 10 +3 s-1, the adiabatic temperature rise assists in continuous dynamic recrystallization that leads to an increase in the volume fraction of the 〈{101}〉 component. Thus, strain-hardening behavior plays a significant role in the texture evolution of face-centered cubic materials. In addition, factors governing the onset of restoration mechanisms like purity and melting point govern texture evolution at high strain rates. SFE may play a secondary role by governing the propensity of cross slip that in turn helps in the activation of restoration processes. © 2010 The Minerals, Metals & Materials Society and ASM International.

Halder M.,Bhabha Atomic Research Center | Yusuf S.M.,Bhabha Atomic Research Center | Mukadam M.D.,Bhabha Atomic Research Center | Shashikala K.,Bhabha Atomic Research Center
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

Magnetocaloric effect (MCE) in TbCo2-xFex has been studied by dc magnetization measurements. On substituting Fe in TbCo 2, not only the magnetic transition temperature is tuned to room temperature but also the operating temperature range for MCE is increased from 50 K for TbCo2 to 95 K for TbCo1.9Fe0.1. The maximum magnetic entropy change (-Δ SM) for TbCo1.9 Fe 0.1 is found to be 3.7J kg-1 K-1 for a 5 T field change, making it a promising candidate for magnetic refrigeration near room temperature. The temperature-dependent neutron-diffraction study shows a structural phase transition (from cubic to rhombohedral phase with lowering of temperature) which is associated with the magnetic phase transition and these transitions broaden on Fe substitution. To investigate the nature of the paramagnetic to ferrimagnetic phase transition, we performed a critical exponent study. From the derived values of critical exponents, we conclude that TbCo2 belongs to the three-dimensional Heisenberg class with short-range interaction, while on Fe substitution it tends towards mean field with long-range interaction. The derived values of critical exponents represent the phenomenological universal curve for the field dependence of Δ SM, indicating that TbCo2 and TbCo1.9Fe0.1 belong to two different universality classes. © 2010 The American Physical Society.

Modak B.,Bhabha Atomic Research Center | Ghosh S.K.,Bhabha Atomic Research Center
Journal of Physical Chemistry C | Year: 2016

In this theoretical study, a systematic investigation has been carried out to explore the effect of several anionic dopants (individually as well as in combination) on the electronic structure of KTaO3. According to the defect formation energy calculation, the formation of a codoped system is more favored in comparison to the monodoped KTaO3. All the electronic structure calculations have been performed using the Heyd, Scuseria, and Ernzerhof hybrid functional, which reproduces the band gap of KTaO3 (3.61 eV) in very close agreement with the experimental value of 3.60 eV. Although doping with N reduces the effective band gap of KTaO3, introduction of localized acceptor states may adversely affect the photoconversion efficiency. However, the band gap remains almost unchanged due to doping with F and decreases by only a small extent for Cl, Br, and I doping. The scenario, however, changes on codoping with N and any of the halogen elements, which results in the formation of charge-compensated systems. In all the cases, a clear band structure is produced, ensuring good photoconversion efficiency. The present study reveals that the extent of band gap narrowing in the case of codoping with N and F is quite significant (almost 1 eV) to improve the visible light activity of KTaO3 effectively. More interestingly, this does not involve any considerable shifting of the conduction band minimum (CBM) in the downward direction. This is very crucial for KTaO3 because its CBM potential is quite close to the hydrogen reduction potential. The CBM level is found to be shifted in the upward direction for codoping with (N, Cl/Br/I). Therefore, all the codoped systems are suitable for overall water splitting, which has also been confirmed though band edge alignment with respect to water redox levels. Thus, the present study through electronic structure calculation finds suitable dopant pairs for the controlled band gap engineering of KTaO3. (Graph Presented). © 2016 American Chemical Society.

Senthilkumar S.T.,Bharathiar University | Kalai Selvan R.,Bharathiar University | Ulaganathan M.,Nanyang Technological University | Melo J.S.,Bhabha Atomic Research Center
Electrochimica Acta | Year: 2014

A new asymmetric supercapacitor (ASC) was fabricated using flower like α-Bi2O3as negative and bio-waste derived activated carbon (AC) as positive electrodes with Li2SO4as electrolyte. Here, the fabricated ASC was operated over the potential range of 0-1.6 V and evaluated by cyclic voltammetry (CV), galvano static charge-discharge (GCD), electrochemical impedance spectroscopy (EIS) and cycle life. Further to improve the performance of ASC, KI was used as electrolyte redox additive with pristine (Li2SO4) electrolyte due to their possible redox reactions of iodine ions. Remarkably, a nearly threefold improved specific capacitance and energy density of 99.5 F g-1and 35.4 Wh kg-1respectively was achieved by adding of KI into Li 2SO4 electrolyte, while it was only 29 F g-1and 10.2 Wh kg-1for pristine (Li2SO4) electrolyte used ASC at 1.5 mA cm-2. © 2013 Elsevier Ltd. All rights reserved.

Modak B.,Bhabha Atomic Research Center | Ghosh S.K.,Bhabha Atomic Research Center
Journal of Physical Chemistry C | Year: 2015

In this study, the effect of F doping on the electronic structure and photocatalytic activity of Rh doped SrTiO3 has been investigated using hybrid density functional theory as a tool. Although doping with only Rh significantly enhances the visible light activity, the photoconversion efficiency has been found to be poor. This is due to the Rh4+ state, which introduces localized unoccupied states above the valence band and promotes the electron hole recombination process. Upon codoping with F, the localized states are found to be completely passivated. Analysis of Bader charge indicates the existence of the lower oxidation state of Rh in the (Rh, F) codoped SrTiO3. The valence band maxima are elevated significantly due to strong hybridization of the O 2p orbital and Rh 4d orbital, resulting in band gap narrowing to 2.50 eV. The nature of the band structure of (Rh, F) codoped SrTiO3 is found to be strongly dependent on the relative proportion of the dopant elements. 1:2 (Rh, F) codoping not only results in a clean band structure but also reduces the band gap by a larger extent (0.88 eV). In the case of 2:1 (Rh, F) codoping, localized unoccupied states in the forbidden region are still present. Calculation of the defect formation energy indicates that the doping of Rh becomes more feasible in the presence of F. The relative locations of the band edge for both 1:1 and 1:2 (Rh, F) codoped SrTiO3 are found to be suitable for the overall water splitting process. Hence, introduction of F is expected to enhance the photocatalytic activity of Rh doped SrTiO3 under visible light due to narrowing of the band gap as well as lowering of the electron hole recombination rate. © 2015 American Chemical Society.

Joshi J.B.,Bhabha Atomic Research Center | Nandakumar K.,Louisiana State University
Annual Review of Chemical and Biomolecular Engineering | Year: 2015

Multiphase reactors are very common in chemical industry, and numerous review articles exist that are focused on types of reactors, such as bubble columns, trickle beds, fluid catalytic beds, etc. Currently, there is a high degree of empiricism in the design process of such reactors owing to the complexity of coupled flow and reaction mechanisms. Hence, we focus on synthesizing recent advances in computational and experimental techniques that will enable future designs of such reactors in a more rational manner by exploring a large design space with high-fidelity models (computational fluid dynamics and computational chemistry models) that are validated with high-fidelity measurements (tomography and other detailed spatial measurements) to provide a high degree of rigor. Understanding the spatial distributions of dispersed phases and their interaction during scale up are key challenges that were traditionally addressed through pilot scale experiments, but now can be addressed through advanced modeling. © 2015 by Annual Reviews. All rights reserved.

Prudhvi Raju P.V.S.N.,Nuclear Fuel Complex | Mandal D.,Bhabha Atomic Research Center
Journal of Nuclear Materials | Year: 2015

The mean particle size and size distribution of Ammonium Di-Uranate (ADU) particles, precipitated during the precipitation reaction of Uranyl Nitrate Pure Solution (UNPS) with ammonia play an important role on the sintered density of UO2 pellets. The quality of precipitated ADU depends on number of process parameters viz., pH of UNPS, concentration of uranium in UNPS, flow rate of ammonium hydroxide, temperature etc. However, the effects of the presence of free acid and entrained Tri-Butyl-Phosphate (TBP) in UNPS on the quality of ADU powder were not studied till date. Experiments were conducted to study the effect of free acidity and the presence of entrained TBP on the quality of precipitated ADU particles. It was found that as the concentration of free acid as well as the concentration of entrained TBP in UNPS increases, the particle size of precipitated ADU decreases. Based on the experimental results two correlations were developed to determine the mean particle size of ADU; one is based on the free acid content of UNPS and the other is based on the content of entrained TBP in UNPS, which is used for the precipitation. It was found that the correlated values are well fitted with the experimental data within ±3% errors for both the cases. Both these correlations are applicable when other process parameters remain constant. The experimental details and results are discussed in this paper. © 2015 Published by Elsevier B.V.

Malavi P.S.,Bhabha Atomic Research Center
Journal of physics. Condensed matter : an Institute of Physics journal | Year: 2014

Optimally doped iron-chalcogenide superconductor Fe1.03Se0.5Te0.5 has been investigated under high pressures using synchrotron-based x-ray diffraction and mid-infrared reflectance measurements at room temperature. The superconducting transition temperature (Tc) of the same sample has been determined by temperature-dependent resistance measurements up to 10 GPa. The tetragonal phase (P4/nmm) is found to exist in phase-separated states where both the phases have remarkably high compressibility. A first-order structural transition to the orthorhombic phase (Pbnm) is reported above 10 GPa. For the tetragonal phase, a strong correlation is observed between the Fe(Se,Te)4 tetrahedral deformation and the sharp rise of Tc up to ∼ 4 GPa, above which Tc shows marginal pressure dependence at least up to 10 GPa. The evolution with pressure of the optical conductivity shows that with increasing pressure the tetragonal phase approaches towards a conventional metallic state. Above ∼ 6 GPa, the Drude term reduces drastically, indicating poor metallic character of the high-pressure orthorhombic phase.

Nagar V.,Bhabha Atomic Research Center | Bandekar J.R.,Bhabha Atomic Research Center
Radiation Physics and Chemistry | Year: 2011

Genus Aeromonas has emerged as an important human pathogen because it causes a variety of diseases including gastroenteritis and extra-intestinal infections. Contaminated water, sprouts, vegetables, seafood and food of animal origin have been considered to be the important sources of Aeromonas infection. In the present study, radiation sensitivity of indigenous strains of Aeromonas spp. from different food samples was evaluated. The decimal reduction dose (D 10) values of different Aeromonas isolates in saline at 0-4°C were in the range of 0.031-0.046kGy. The mixed sprouts, chicken and fish samples were inoculated with a cocktail of five most resistant isolates (A. salmonicida Y567, A. caviae A85, A. jandaei A514A, A. hydrophila CECT 839 T and A. veronii Y47) and exposed to γ radiation to study the effectiveness of radiation treatment in elimination of Aeromonas. D 10 values of Aeromonas cocktail in mixed sprouts, chicken and fish samples were found to be 0.081±0.001, 0.089±0.003 and 0.091±0.003kGy, respectively. Radiation treatment with a 1.5kGy dose resulted in complete elimination of 10 5CFU/g of Aeromonas spp. from mixed sprouts, chicken and fish samples. No recovery of Aeromonas was observed in the 1.5kGy treated samples stored at 4°C up to 12 (mixed sprouts) and 7 days (chicken and fish samples), even after enrichment and selective plating. This study demonstrates that a 1.5kGy dose of irradiation treatment could result in complete elimination of 10 5CFU/g of Aeromonas spp. from mixed sprouts, chicken and fish samples. © 2011 Elsevier Ltd.

Khan N.M.,Bhabha Atomic Research Center | Poduval T.B.,Bhabha Atomic Research Center
Journal of Leukocyte Biology | Year: 2011

The immunomodulatory and immunotoxic effects of purified UCB have not been evaluated previously at clinically relevant UCB concentrations and UCB:BSA ratios. To delineate the molecular mechanism of UCB-induced immunomodulation, immune cells were exposed to clinically relevant concentrations of UCB. It inhibited LPSinduced B cell proliferation and cytokine production from splenic macrophages. UCB (≥25 μM) was toxic to unfractionated splenocytes, splenic T cells, B cells, macrophages, LPS-stimulated CD19+ B cells, human PBMCs, and RBCs. Purified UCB also was found to be toxic to splenocytes and human PBMCs. UCB induced necrosis and apoptosis in splenocytes. UCB activated the extrinsic and intrinsic pathways of apoptosis, as reflected by the markers, such as CD95, caspase-8, Bax, MMP, cytoplasmic Ca +2, caspase-3, and DNA fragmentation. UCB depleted GSH and activated p38MAPK. NAC, caspase inhibitors, and p38MAPK inhibitor attenuated the UCB-induced apoptosis. In vivo administration of ≥25 mg/kbw UCB induced atrophy of spleen, depletion of bone marrow cells, and leukopenia and decreased lymphocyte count and the T and B cell response to mitogens. UCB administration to mice led to induction of oxidative stress, activation of p38MAPK, and cell death in splenocytes. These parameters were attenuated by the injection of NAC and the p38MAPK inhibitor. Our results demonstrate for the first time that clinically relevant concentrations of UCB induce apoptosis and necrosis in immune cells by depleting cellular GSH. These findings should prove useful in understanding the immunosuppression associated with hyperbilirubinemia. © Society for Leukocyte Biology.

Basu S.,Bhabha Atomic Research Center | Saboury B.,University of Pennsylvania | Torigian D.A.,University of Pennsylvania | Alavi A.,University of Pennsylvania
Molecular Imaging and Biology | Year: 2011

Increasingly, integrated positron emission tomography-computed tomography (PET/CT) imaging is playing a crucial role in the assessment of patients with known or suspected malignant pleural mesothelioma (MPM). Based on the data reported in the literature, this combined modality is likely to become the instrument of choice for examining patients of MPM. The research on this subject has focused on the following five domains: (1) differentiation of MPM from other benign pleural diseases, (2) preoperative staging for the selection of appropriate candidates for surgery, (3) evaluation for therapy response and post-treatment surveillance for recurrence, (4) prognostication based upon the intensity of 2-deoxy-2-[ 18F]fluoro-D-glucose (FDG) uptake, and (5) planning of radiotherapy. These represent the bases for critical decision making in the management of mesothelioma, and FDG-PET/CT offers potential advantages over conventional CT imaging and thus can play a pivotal role in this regard. Optimal characterization of this potentially fatal disease with a high negative predictive value for MPM, superior capability for cancer staging initially and at the later course of disease, and ability for measuring therapeutic response and the precise determination of the target volume for radiotherapy planning represent distinct advantages of this promising molecular imaging tool. In this communication, we have explored the promising role of integrated FDG-PET/CT in the overall management of this serious malignancy. From the available data, the major role of PET-CT at present appears to be in the preoperative disease staging, response to treatment assessment, and post-treatment disease surveillance of MPM. In all these three areas, PET-CT convincingly shows better results than conventional anatomical imaging alone and thereby can aid in exploring novel therapeutic approaches. Disease prognosis and radiotherapy planning are evolving areas where this modality has demonstrated significant promise, but this has to be investigated further. The differentiating ofMPM from benign pleural disease is a challenging issue; though in limited studies, it has shown promising results, single standardized uptake value (SUV) cutoff technique cannot be the optimal way for this purpose. Dual time point and delayed imaging helps further in this setting; however, more data require to be accrued in this area. We, in this review, have also discussed the feasibility of a new method of image segmentation based on an iterative thresholding algorithm, which permits definition of the boundaries of lesions based on PET images alone to provide lesional metabolically active tumor volumes, lesional partial volume corrected SUV (PVC-SUV) measurements, lesional PVC metabolic burden (PVC-MB) (calculated as the product of lesional MVP and lesional PVC-SUV), and whole body metabolic burden (WBMB) (calculated as the sum of lesional PVC-MB of all lesions). This global disease assessment, we believe, will be the way forward for assessing this malignancy with a non-invasive imaging modality. © Academy of Molecular Imaging and Society for Molecular Imaging, 2010.

Priyadarsini K.I.,Bhabha Atomic Research Center
Molecules | Year: 2014

Curcumin, a pigment from turmeric, is one of the very few promising natural products that has been extensively investigated by researchers from both the biological and chemical point of view. While there are several reviews on the biological and pharmacological effects of curcumin, chemistry reviews are comparatively scarcer. In this article, an overview of different aspects of the unique chemistry research on curcumin will be discussed. These include methods for the extraction from turmeric, laboratory synthesis methods, chemical and photochemical degradation and the chemistry behind its metabolism. Additionally other chemical reactions that have biological relevance like nucleophilic addition reactions, and metal chelation will be discussed. Recent advances in the preparation of new curcumin nanoconjugates with metal and metal oxide nanoparticles will also be mentioned. Directions for future investigations to be undertaken in the chemistry of curcumin have also been suggested. © 2014 by the authors; licensee MDPI, Basel, Switzerland.

We describe an efficient ab initio L2-stabilization method for computing the real part of the complex potential energy surface of electronic resonance state. Unlike most other commonly used stabilization methods, without repeating the eigenvalue calculation for stabilizing or extrapolating the eigenvalues, the new method offers basis set limit calculations. The non-interaction region of the metastable system is perturbed by an artificial potential which avoids the variational collapse of resonance wavefunction to its free-electron descriptions. This makes possible the use of all available bound-state methods for electronic resonance states. The method is best illustrated with Feshbach- and shape-type electronic resonance states.© 2013 Elsevier B.V. All rights reserved.

Nalawade P.,Bhabha Atomic Research Center | Kapoor S.,Bhabha Atomic Research Center
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

(Graph Presented) An optical detection method based on the interaction of gold nanoflowers with Hg2+ and Pb2+ has been described. After interaction, gold nanoflowers change the color from violet to wine red. The nanoflowers are capable of determining Hg2+ and Pb2+ over a dynamic range of 1.0 × 10-6 and 1.0 × 10 -5 M, respectively. The response time of nanoflowers depends on the concentration of ions. The presence of both Hg2+ and Pb2+ ions in the mixture having Au nanoflowers induced color changes of the solution within several seconds even at 1.0 × 10-6 M. Common metal ions were chosen to investigate their interference in Hg2+ and Pb 2+ detection, and the concentration of each metal ion studied was 1.0 × 10-5 M. Other metallic ions could not induce color change even at 1.0 × 10-5 M. The feasibility of our method to detect Hg2+ and Pb2+ ions at high concentration in real water samples was verified. Water samples were from our own laboratory and no pretreatment was made. As the particles are stable they can be used for more than 3 months without observing any major deviation. © 2013 Elsevier B.V. All rights reserved.

Chadha S.,Bhabha Atomic Research Center | Sharma M.,Bhabha Atomic Research Center
PLoS ONE | Year: 2014

A fundamental problem in fungal pathogenesis is to elucidate the evolutionary forces responsible for genomic rearrangements leading to races with fitter genotypes. Understanding the adaptive evolutionary mechanisms requires identification of genomic components and environmental factors reshaping the genome of fungal pathogens to adapt. Herein, Magnaporthe oryzae, a model fungal plant pathogen is used to demonstrate the impact of environmental cues on transposable elements (TE) based genome dynamics. For heat shock and copper stress exposed samples, eight TEs belonging to class I and II family were employed to obtain DNA profiles. Stress induced mutant bands showed a positive correlation with dose/duration of stress and provided evidences of TEs role in stress adaptiveness. Further, we demonstrate that genome dynamics differ for the type/family of TEs upon stress exposition and previous reports of stress induced MAGGY transposition has underestimated the role of TEs in M. oryzae. Here, we identified Pyret, MAGGY, Pot3, MINE, Mg-SINE, Grasshopper and MGLR3 as contributors of high genomic instability in M. oryzae in respective order. Sequencing of mutated bands led to the identification of LTR-retrotransposon sequences within regulatory regions of psuedogenes. DNA transposon Pot3 was identified in the coding regions of chromatin remodelling protein containing tyrosinase copperbinding and PWWP domains. LTR-retrotransposons Pyret and MAGGY are identified as key components responsible for the high genomic instability and perhaps these TEs are utilized by M. oryzae for its acclimatization to adverse environmental conditions. Our results demonstrate how common field stresses change genome dynamics of pathogen and provide perspective to explore the role of TEs in genome adaptability, signalling network and its impact on the virulence of fungal pathogens. © 2014 Chadha, Sharma.

Senthilkumar S.T.,Bharathiar University | Selvan R.K.,Bharathiar University | Ponpandian N.,Bharathiar University | Melo J.S.,Bhabha Atomic Research Center
RSC Advances | Year: 2012

A hydroquinone mediated PVA-H2SO4 gel electrolyte (PHHQ) and activated carbon from bio-waste were prepared for supercapacitor fabrication. PHHQ delivered a higher capacitance (941 F g-1 at 1 mA cm-2) and energy density (20 Wh kg-1 at 0.33 W g -1) than the PVA-H2SO4 gel electrolyte (425 F g-1 at 1 mA cm-2, 9 Wh kg-1 at 0.33 W g -1). © 2012 The Royal Society of Chemistry.

Parchur A.K.,Banaras Hindu University | Ningthoujam R.S.,Bhabha Atomic Research Center
RSC Advances | Year: 2012

The effect of Li+ co-doping on the photoluminescence properties of YPO4:Eu is discussed. Interesting behaviours, such as the presence of intermediate bands, shifting of the Eu-O charge transfer band (Eu-O CTB) to a lower wavelength, variation in intensities of magnetic (5D 0 → 7F1) and electric dipole ( 5D0 → 7F2) transitions of Eu3+ and shift of 5D0 → 7F 0 to higher energy with increasing excitation wavelengths are observed. The Eu3+ ion does not have an absorption band in the range 340-350 nm, but after excitation at these wavelengths, a broad emission band (370-570 nm), as well as sharp peaks of Eu3+, could be observed. This is due to strong energy transfer from the intermediate band of the host to the Eu3+ ion. X-ray photoelectron spectroscopy (XPS) study also confirms that intermediate band emission is not due to Eu2+ ion emission. The blue shifting of Eu-O CTB is because of the increase in the optical electronegativity of the Eu3+ ion on Li+ co-doping. The variation in intensities of the 5D0 → 7F2 and 5D0 → 7F1 dipole transitions is related to (i) overlapping interaction parameters within the ground and excited states, (ii) exchange interaction among atoms/ions and (iii) density of the incoming photons. Shift of 5D0 → 7F0 to a higher energy with increasing excitation wavelengths is because of change in the second order crystal field parameter B20 with excitation wavelength. The significant enhancement of luminescence intensity is found with Li+ co-doping due to the increase in crystallinity. © 2012 The Royal Society of Chemistry.

Mondal J.A.,RIKEN | Mondal J.A.,Bhabha Atomic Research Center | Nihonyanagi S.,RIKEN | Yamaguchi S.,RIKEN | Tahara T.,RIKEN
Journal of the American Chemical Society | Year: 2012

Lipid/water interfaces and associated interfacial water are vital for various biochemical reactions, but the molecular-level understanding of their property is very limited. We investigated the water structure at a zwitterionic lipid, phosphatidylcholine, monolayer/water interface using heterodyne-detected vibrational sum frequency generation spectroscopy. Isotopically diluted water was utilized in the experiments to minimize the effect of intra/intermolecular couplings. It was found that the OH stretch band in the Imχ (2) spectrum of the phosphatidylcholine/water interface exhibits a characteristic double-peaked feature. To interpret this peculiar spectrum of the zwitterionic lipid/water interface, Imχ (2) spectra of a zwitterionic surfactant/water interface and mixed lipid/water interfaces were measured. The Imχ (2) spectrum of the zwitterionic surfactant/water interface clearly shows both positive and negative bands in the OH stretch region, revealing that multiple water structures exist at the interface. At the mixed lipid/water interfaces, while gradually varying the fraction of the anionic and cationic lipids, we observed a drastic change in the Imχ (2) spectra in which spectral features similar to those of the anionic, zwitterionic, and cationic lipid/water interfaces appeared successively. These observations demonstrate that, when the positive and negative charges coexist at the interface, the H-down-oriented water structure and H-up-oriented water structure appear in the vicinity of the respective charged sites. In addition, it was found that a positive Imχ (2) appears around 3600 cm -1 for all the monolayer interfaces examined, indicating weakly interacting water species existing in the hydrophobic region of the monolayer at the interface. On the basis of these results, we concluded that the characteristic Imχ (2) spectrum of the zwitterionic lipid/water interface arises from three different types of water existing at the interface: (1) the water associated with the negatively charged phosphate, which is strongly H-bonded and has a net H-up orientation, (2) the water around the positively charged choline, which forms weaker H-bonds and has a net H-down orientation, and (3) the water weakly interacting with the hydrophobic region of the lipid, which has a net H-up orientation. © 2012 American Chemical Society.

Jena N.K.,Bhabha Atomic Research Center | Sundararajan M.,Bhabha Atomic Research Center | Ghosh S.K.,Bhabha Atomic Research Center
RSC Advances | Year: 2012

Understanding the interaction between uranyl and C 60 can be useful for nuclear waste management processes. In this paper, we have investigated the binding of uranyl with bare C 60 as well as functionalized C 60 using density functional theory. It is observed that, the uranyl is only weakly bound to bare C 60. On the contrary, functionalization of C 60 with malonate ligand is shown to increase its binding ability to uranyl species. Further, we notice that pH could play an important role in the binding of uranyl at the malonate site. Our calculated geometries are in close agreement with the experimental data of the malonate uranyl complex. Further, based on the calculated binding energies, we show that a chelate type binding is more favorable in comparison to bidentate carboxylate binding. © 2012 The Royal Society of Chemistry.

Dhole V.J.,Bhabha Atomic Research Center | Reddy K.S.,Bhabha Atomic Research Center
Plant Breeding | Year: 2013

Yellow mosaic disease (YMD) caused by mungbean yellow mosaic virus (MYMV) is the most important disease of mungbean, causing great yield loss. The present investigation was carried out to study the inheritance and identify molecular markers linked with MYMV resistance gene by using F1, F2 and 167 F2 : 8 recombinant inbred lines (RILs) developed from the cross 'TM-99-37' (resistant) × Mulmarada (susceptible). The F1 was susceptible, F2 segregated in 3S:1R phenotypic ratio and RILs segregated in 1S:1R ratio in the field screening indicating that the MYMV resistance gene is governed by a single recessive gene. Of the 140 RAPD primers, 45 primers showing polymorphism in parents were screened using bulked segregant analysis. Three primers amplified specific polymorphic fragments viz. OPB-07600, OPC-061750 and OPB-12820. The marker OPB-07600 was more closely linked (6.8 cM) with a MYMV resistance gene as compared to OPC-061750 (22.8 cM) and OPB-12820 (25.2 cM). The resistance-specific fragment OPB-07600 was cloned, sequenced and converted into a sequence-characterized amplified region (SCAR) marker and validated in twenty genotypes with different genetic backgrounds. © 2012 Blackwell Verlag GmbH.

Panja S.,Bhabha Atomic Research Center | Mohapatra P.K.,Bhabha Atomic Research Center | Tripathi S.C.,Bhabha Atomic Research Center | Gandhi P.M.,Bhabha Atomic Research Center | Janardan P.,Bhabha Atomic Research Center
Separation and Purification Technology | Year: 2012

Extraction behavior of several actinide ions viz. Am 3+, Pu 4+ and UO22+ was investigated using N,N,N',N'-tetra-n-octyl diglycolamide (TODGA) as extractant in three different room temperature ionic liquids (RTIL), viz. C4mim+·NTf2- C6mim+·NTf2- and C8mim+·NTf2- as the diluents. The solvent systems containing TODGA in the RTILs were found to result in higher distribution ratios for all the actinides (trivalent, hexavalent, tetravalent) as compared to that containing n-dodecane as the diluent. Moreover, the distribution ratio values of the metal ions at lower acidities were found to decrease with increasing feed nitric acid concentration. Extraction was found to be independent of the anion of the aqueous phase. Mechanism of extraction of the actinides was found to be different compared to n-dodecane, molecular diluent. Cation-exchange was found to be the mechanism of extraction followed in RTILs. Effect of carbon chain length of alkyl groups of the RTILs conclusively proved the mechanism of extraction of the actinides by TODGA. Nature of extracted species was also found to differ from n-dodecane. Stripping studies were carried out using complexing agents such as EDTA, DTPA in guanidine carbonate or a buffer mixture. © 2012 Elsevier B.V.

Debnath T.,Bhabha Atomic Research Center | Maity P.,Bhabha Atomic Research Center | Maiti S.,Bhabha Atomic Research Center | Ghosh H.N.,Bhabha Atomic Research Center
Journal of Physical Chemistry Letters | Year: 2014

Specially aligned surface-accumulated Mn-doped CdSe (MnCdSe) quantum dots (QDs) have been synthesized to study the effect of dopant atom on charge-carrier dynamics in QD materials. EPR studies suggest that the 4T 1 state of Mn2+ lies above the conduction band of CdSe, and as a result no Mn-luminescence was observed from MnCdSe. Femtosecond transient absorption studies suggest that Mn atom introduces structural defects in surface-doped CdSe, which acts as electron trap center in doped QD for the photoexcited electron. Bromo-pyrogallol red (Br-PGR) were found to form strong charge-trasfer complex with both CdSe and MnCdSe QDs. Charge separation in both the CdSe/Br-PGR and MnCdSe/Br-PGR composites was found to take place in three different pathways by transferring the photoexcited hole of CdSe/MnCdSe QDs to Br-PGR, electron injection from photoexcited Br-PGR to the QDs, and direct electron transfer from the HOMO of Br-PGR to the conduction band of both the QDs. Hole-transfer dynamics are found to be quite similar (∼1.1 to 1.3 ps) for both of the systems and found to be independent of Mn doping. However, charge recombination dynamics was found to be much slower in the MnCdSe/Br-PGR system as compared with that in the CdSe/Br-PGR system, which confirms that the Mn dopant act as the electron storage center. As a consequence, the MnCdSe/Br-PGR system can be used as a better super sensitizer in quantum-dot-sensitized solar cell to increase efficiency further. © 2014 American Chemical Society.

Kushwaha P.,Tata Institute of Fundamental Research | Sahayanathan S.,Bhabha Atomic Research Center | Singh K.P.,Tata Institute of Fundamental Research
Monthly Notices of the Royal Astronomical Society | Year: 2013

The broad-band spectrum of a BL Lac object. OJ 287. from radio to γ-rays obtained during a major γ-ray flare detected by Fermi in 2009 is studied to understand the high energy emission mechanism during this episode. Using a simple one-zone leptonic model, incorporating synchrotron and inverse Compton emission processes, we show that the explanation of high energy emission from X-rays to γ-rays, by considering a single emission mechanism, namely, synchrotron self-Compton (SSC) or external Compton (EC), requires unlikely physical conditions. However, a combination of both SSC and EC mechanisms can reproduce the observed high energy spectrum satisfactorily. Using these emission mechanisms we extract the physical parameters governing the source and its environment. Our study suggests that the emission region of OJ 287 is surrounded by a warm infrared emitting region of ∼250 K. Assuming this region as a spherical cloud illuminated by an accretion disc, we obtain the location of the emission region to be ∼9pc. This supports the claim that the γ-ray emission from OJ 287 during the 2009 flare arises from a location far away from the central engine as deduced from millimetre-γ-ray correlation study and very long baseline array images. © 2013 The Authors.

Nayak B.,Bhabha Atomic Research Center | Menon S.V.G.,Bhabha Atomic Research Center
Laser and Particle Beams | Year: 2012

Conditions for thermonuclear ignition are determined by three parameters: fuel density, temperature and hot-spot size. A simple three temperature model is developed to calculate the critical burn-up parameter or the minimum ρR product. Extensive results obtained are compared with earlier one temperature model for DT and DD fuels. While the two approaches are found to provide similar results for DT fuel except at low temperature regime (∼10 keV), three temperature modeling is found to be necessary for DD fuel. This is argued to be due to the lower fusion reactivity and energy production in DD reactions. Copyright © 2012 Cambridge University Press.

Naik S.R.,Goa University | Salker A.V.,Goa University | Yusuf S.M.,Bhabha Atomic Research Center | Meena S.S.,Bhabha Atomic Research Center
Journal of Alloys and Compounds | Year: 2013

Superparamagnetic properties of the cobalt ferrite nanocrystals have been demonstrated. The significance of the solgel autocombustion method in preparation of cobalt ferrite oxide in the nano range (30-40 nm) has been very well complimented with the structural, dimensional and morphological techniques, such as X-ray diffraction technique, Transmission Electron Microscopy and Scanning Electron Microscopy. The valence states of the metal ions and single phase formation of the polycrystalline oxide have been confirmed with the help of X-ray photoelectron spectroscopy and Raman spectroscopy. The distribution of the Fe3+ ions in the tetrahedral and octahedral lattice sites has been illustrated with the help of the Mössbauer spectroscopy that shows five sextets, indicating occupancies of one tetrahedral and four octahedral sites by Fe3+ ions. Hyperfine fields of 51.29, 48.74, 46.78, 43.58 and 48.59 Tesla, respectively in CoFe2O4 have been found for four octahedral and one tetrahedral site respectively, at ambient temperature. The magnetic measurements M-H and M-T demonstrate a change in the magnetic moment and a superparamagnetic-ferrimagnetic transition at 235 K in the ferrite system. © 2013 Elsevier B.V. All rights reserved.

Momin T.,Bhabha Atomic Research Center | Bhowmick A.,Bhabha Atomic Research Center
Journal of Alloys and Compounds | Year: 2013

Abundance measurements of bimetallic clusters synthesized in gas phase could address the issues of alloying between two metals at nanometer scale. In fact, these studies might be able to answer why some metals do not form good alloy in bulk phase, from an atomic point of view. We report one such investigation between Cu and Ag atoms. Formation of free bimetallic clusters between these two coin metals is investigated up to 7100 amu by synthesizing them in gas phase under completely unperturbed conditions. The results produce evidence of magic combination as proposed in several theoretical calculations. A total of 1465 binary CumAgn nanoclusters could be identified in which many magic compositions appear with higher abundances. Overall, it is observed that Cu and Ag atoms do not mix randomly but preferably surface segregate. The findings validate the structure motif reported in theoretical studies and thereby, depict a natural selectivity in the formation of these nanoscale alloys. Thus, the study contributes in the understanding of fundamental issues involved in alloying between two noble metals. © 2013 Elsevier B.V. All rights reserved.

Saha D.,Central Ground Water Board | Sinha U.K.,Bhabha Atomic Research Center | Dwivedi S.N.,Central Ground Water Board
Applied Geochemistry | Year: 2011

Arsenic concentrations in groundwater extracted from shallow aquifers in some areas of the Ganga Plain in the states of Bihar and Uttar Pradesh, exceed 50μgL -1 and locally reach levels in the 400μgL -1 range. The study covered 535km 2 of active flood plain of the River Ganga, in Bihar where a two-tier aquifer system has been delineated in a multi-cyclic sequence of Quaternary sand, clay, sandy clay and silty clay all ≤∼250m below ground surface. The research used isotopic signatures (δ 18O, δ 2, 3H, 14C) and major chemical constituents HCO3-,SO42-,NO3-,Cl-,Ca2+,Mg2+,Na+,K+,Astotal of groundwater to understand the recharge processes and groundwater circulation in the aquifers. Values of δ 18O and δ 2 combined with 3H data indicate that the recharge to the As-enriched top 40m of the deposits is modern (<50a), predominantly meteoric, with some evaporation during infiltration, and partly from tanks and other surface water bodies. The lower part of the upper aquifer is vulnerable to mobilization of As with increasing groundwater extraction. The low As lower aquifer (max. 5μgL -1) is hydrologically isolated from the upper aquifer and is characterized by lower 14C concentration and lower (more negative) δ 18O values. Groundwater in the lower aquifer is ∼3ka old, occurs under semi-confined to confined conditions, with hydrostatic head at 1.10m above the head of the upper aquifer during the pre-monsoon. The recharge areas of the lower aquifer lies in Pleistocene deposits in basin margin areas with the exposed Vindhyan System, at about 55km south of the area. © 2011 Elsevier Ltd.

Sinha A.,Bhabha Atomic Research Center | Nair S.R.,Bhabha Atomic Research Center | Sinha P.K.,Bhabha Atomic Research Center
Journal of Nuclear Materials | Year: 2010

A novel process method based on solid-liquid combustion synthesis has been developed to produce high purity monoclinic Li2TiO3 directly after combustion. The process does not call for any additional heat treatment for phase formation. The lattice parameters of Li2TiO3 were determined through Rietveld refinement of XRD pattern. Systematic studies were carried out to optimize the sintering temperature to obtain the desired microstructure and density in the sintered specimens. The morphology of Li2TiO3 powder and microstructures of sintered specimens were studied by scanning electron microscopy. The powder produced through this route could be sintered to 90% of theoretical density at relatively low temperatures (<1150 °C). The process developed in the present investigation is simple and convenient for mass production. © 2010 Elsevier B.V. All rights reserved.

Mufti S.,Bhabha Atomic Research Center | Shah G.N.,Bhabha Atomic Research Center
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2011

A long uninterrupted homogeneous data set on the annual mean Sea Surface Temperature (SST) anomaly records as a representative of the Earth's climatic parameter has been analyzed in conjunction with 158 year long time series on the annual sunspot indices, Rz and geomagnetic activity indices, aa for the period 1850-2007. The 11-year and 23-year overlapping means of global (δtg) as well as northern (δtn) and southern (δts) hemispheric SST anomalies reveal significant positive correlation with both Rz and aa indices. Rz, aa and δtg depict a similar trend in their long-term variation and both seem to be on increase after attaining a minimum in the early 20th century (~1905). Whereas the results on the power spectrum analysis by the Multi-Taper Method (MTM) on δtg, Rz and aa reveal periodicities of ~79-80 years (Gleissberg's cycle) and ~9-11 years (Schwabe solar cycle) consistent with earlier findings, MTM spectrum analysis also reveals fast cycles of 3-5 years. A period of ~4.2 years in aa at 99% confidence level appears recorded in δtg at ~4.3 years at 90% confidence level. A period of ~3.6-3.7 years at 99% confidence level found in δtg is correlating with a similar periodic variation in sector structure of Interplanetary Magnetic Field (IMF). This fast cycle parallelism is new and is supportive of a possible link between the solar-modulated geomagnetic activity and Earth's climatic parameter i.e. SST. © 2011 Elsevier Ltd.

Mukherjee P.K.,Bhabha Atomic Research Center | Horwitz B.A.,Technion - Israel Institute of Technology | Herrera-Estrella A.,CINVESTAV | Schmoll M.,University and Research Center | Kenerley C.M.,Texas A&M University
Annual Review of Phytopathology | Year: 2013

Trichoderma species are widely used in agriculture and industry as biopesticides and sources of enzymes, respectively. These fungi reproduce asexually by production of conidia and chlamydospores and in wild habitats by ascospores. Trichoderma species are efficient mycoparasites and prolific producers of secondary metabolites, some of which have clinical importance. However, the ecological or biological significance of this metabolite diversity is sorely lagging behind the chemical significance. Many strains produce elicitors and induce resistance in plants through colonization of roots. Seven species have now been sequenced. Comparison of a primarily saprophytic species with two mycoparasitic species has provided striking contrasts and has established that mycoparasitism is an ancestral trait of this genus. Among the interesting outcomes of genome comparison is the discovery of a vast repertoire of secondary metabolism pathways and of numerous small cysteine-rich secreted proteins. Genomics has also facilitated investigation of sexual crossing in Trichoderma reesei, suggesting the possibility of strain improvement through hybridization. © Copyright © 2013 by Annual Reviews. All rights reserved.

Anu Prathap M.U.,Bhabha Atomic Research Center | Chaurasia A.K.,Bhabha Atomic Research Center | Sawant S.N.,Bhabha Atomic Research Center | Apte S.K.,Bhabha Atomic Research Center
Analytical Chemistry | Year: 2012

A highly sensitive, selective, and rapid, whole-cell-based electrochemical biosensor was developed for detection of the persistent organochlorine pesticide γ-hexachlorocyclohexane (γ-HCH), commonly known as lindane. The gene linA2 encoding the enzyme γ-hexachlorocyclohexane (HCH) dehydrochlorinase (LinA2), involved in the initial steps of lindane (γ-HCH) biotransformation, was cloned and overexpressed in Escherichia coli. The lindane-biodegrading E. coli cells were immobilized on polyaniline film. The rapid and selective degradation of lindane and concomitant generation of hydrochloric acid by the recombinant E. coli cells in the microenvironment of polyaniline led to a change in its conductivity, which was monitored by pulsed amperometry. The biosensor could detect lindane in the part-per-trillion concentration range with a linear response from 2 to 45 ppt. The sensor was found to be selective to all the isomers of hexachlorocyclohexane (HCH) and to pentachlorocyclohexane (PCCH) but did not respond to other aliphatic and aromatic chlorides or to the end product of lindane degradation, i.e., trichlorobenzene (TCB). The sensor also did not respond to other commonly used organochlorine pesticides like DDT and DDE. On the basis of experimental results, a rationale has been proposed for the excellent sensitivity of polyaniline as a pH sensor for detection of H+ ions released in its microenvironment. © 2012 American Chemical Society.

Das G.P.,Indian Association for The Cultivation of Science | Bhattacharya A.,Indian Association for The Cultivation of Science | Bhattacharya S.,Indian Association for The Cultivation of Science | Majumder C.,Bhabha Atomic Research Center
Journal of Physical Chemistry C | Year: 2010

Using first-principles density functional calculations, we show that a transition-metal (TM)-doped defected graphene sheet with periodic repetition of a C atom vacancy (Vc) can be used as a promising system for hydrogen storage. The TM atoms adsorbed above and below the defected site are found to have a strong bonding to the graphene sheet, thereby circumventing the problem of TM clustering, which is the main impediment for efficient hydrogen storage in nanostructure systems. The results reveal that, when the vacancy-modulated graphene sheet is decorated on both sides by a combination of less than half-filled (TM1) and more than half-filled (TM2) elements, it results in the adsorption of molecular hydrogen with a binding energy lying in the desirable energy window. Among all the different TM 1-TM2 combinations at a C vacancy site, Fe-Ti turns out to be the best choice where five H2 molecules get attached on each pair. To underscore the stability of these hydrogenated systems, we have performed an ab initio molecular dynamics simulation for a fully decorated defected graphene structure. The results show that, at room temperature, the system is stable with a gravimetric efficiency of 5.1 wt % of hydrogen, whereas desorption starts only at ∼400 K. © 2010 American Chemical Society.

Brindha K.,Anna University | Elango L.,Anna University | Nair R.N.,Bhabha Atomic Research Center
Journal of Earth System Science | Year: 2011

Uranium occurs naturally in groundwater and surface water. The objective of this study is to understand the causes for the occurrence of uranium and its spatio-temporal variation in groundwater in a part of Nalgonda district, Andhra Pradesh, south India. Uranium deposits occur in the southeastern part of this area. Groundwater samples were collected from 44 wells every two months from March 2008 to January 2009. The samples were analyzed for pH, ORP and uranium concentration. The uranium concentration in groundwater varies from 0.2 ppb to a maximum of 68 ppb with a mean of 18.5 ppb. About 21.6% of the samples were above the drinking water limit of 30 ppb set by USEPA. The uranium concentration varied with fluctuation in groundwater level, pH and ORP. Uranium concentration in groundwater changes depending on lithology, degree of weathering and rainfall recharge. © Indian Academy of Sciences.

Mollick P.K.,Bhabha Atomic Research Center | Sathiyamoorthy D.,Bhabha Atomic Research Center
Industrial and Engineering Chemistry Research | Year: 2012

Spouted beds are widely used in many industrial applications for achieving good gas-solid contact/mixing especially for a bed of coarse/nonspherical particles. The stability of the spouted bed is important and critical for certain sensitive applications like coating, blending, catalytic conversion, etc. This paper presents the results of experimental investigations carried out using both two-dimensional and three-dimensional spouted beds to identify various transition velocities and condition to arrive at a stable spouted bed. Standard deviation and power spectral density (PSD) of pressure fluctuation were used to determine the stable operating fluidization/spouting velocity. Zirconia microspheres were used as the spouted bed material and argon, nitrogen, and methane were used as spouting gases. Standard deviation of pressure fluctuation was calculated at minimum spouting velocity and at a velocity corresponding to transition from stable spouting to unstable spouting condition. It is shown that standard deviation of pressure fluctuation and PSD varies with various spouting gases and seen to follow a trend with Archemedes number of a given gas-solid system. © 2012 American Chemical Society.

Bhowmick S.,Bhabha Atomic Research Center | Sathiyamoorthy D.,Bhabha Atomic Research Center
Industrial and Engineering Chemistry Research | Year: 2012

Ammonium diuranate (ADU) filtrate, which contains mainly ammonium nitrate (80-100 g/L), is generated during hydrometallurgical processing of uranium. This filtrate stream poses a disposal problem because of its high nitrate content and residual radioactivity. Fluidized-bed thermal denitration is considered as a suitable chemical-free disposal option for the aqueous waste nitrate stream. Hence, investigations to explore the decomposition of ammonium nitrate in a fluidized bed have been carried out. To enable theoretical analysis and performance evaluation of the process, a mathematical model was developed. The model is based on two-phase theory of a bubbling fluidized bed. Model calculations were used to predict the axial concentration profile of ammonium nitrate in the emulsion and bubble phases and the axial temperature profiles of gas bubbles, emulsion gas, and emulsion particles. The mechanism of decomposition of ammonium nitrate in a fluidized bed was explored, and the conversion of ammonium nitrate was estimated. Model predictions were compared with experimental data available from a bench-scale plant. Good agreement was obtained between the model predictions and the experimental measurements. A steady-state parametric study indicated that conversion is enhanced with an increase in bed temperature and feed concentration. It was found that operation at higher feed concentration leads to local hot spots. The required reaction-zone length for complete conversion of ammonium nitrate vapor in the emulsion phase was found to decrease significantly with increased bed temperature. No marked effect of u/u mf on conversion was observed. Optimum values of process parameters to maximize the conversion were derived. © 2012 American Chemical Society.

Nayak S.K.,Bhabha Atomic Research Center | Choudhary M.K.,Bhabha Atomic Research Center
Tetrahedron Letters | Year: 2012

Partial etherification of phenolic-OH groups of calix[4]arenes with various alkyl halides/tosylates and K 2CO 3 under microwave irradiation afforded 1,3-dialkoxycalix[4]arenes in their cone conformation only as predominant/sole product in good yields (71-85%). The protocol was found to be much superior to conventional heating both in terms of yield and reaction time. Some of the 1,3-dialkoxycalix[4]arenes were elaborated further to the syntheses of cesium selective calix[4]crown-6 ionophores. © 2011 Published by Elsevier Ltd.

Jha D.K.,Bhabha Atomic Research Center | Kant T.,Indian Institute of Technology Bombay | Singh R.K.,Bhabha Atomic Research Center
Composite Structures | Year: 2013

Free vibration response of functionally graded (FG) elastic, rectangular, and simply (diaphragm) supported plates is presented based on higher order shear/shear-normal deformations theories (HOSTs/HOSNTs). The theoretical models are based on Taylor's series expansion of in-plane and transverse displacements in thickness coordinate defining the plate deformations. Some of these advanced models account for the effects of transverse shear deformations, transverse normal deformation and non-linear variation of in-plane displacements through plate's thickness. Functionally graded materials (FGMs) are idealized as continua with mechanical properties changing smoothly with respect to spatial coordinates. The material properties of FG plates are assumed here to be varying through thickness of plate in a continuous manner. Poisson's ratios of FG plates are assumed constant, but their Young's modulii and material densities vary continuously in thickness direction according to the volume fraction of constituents which is modeled as exponential and power law functions. The equations of motion are derived using Hamilton's principle on the basis of HOSTs/HOSNTs. Numerical solutions are obtained using Navier solution method. The accuracy of numerical solutions is first established through comparison with the exact three dimensional (3D) elasticity solutions and then compared with available other models' solutions. New solutions are then provided for future use. © 2012 Elsevier Ltd.

Thomas J.J.,Mahatma Gandhi University | Shinde A.B.,Bhabha Atomic Research Center | Krishna P.S.R.,Bhabha Atomic Research Center | Kalarikkal N.,Mahatma Gandhi University
Journal of Alloys and Compounds | Year: 2013

Ni0.5Zn0.5Fe2O4 nanoparticles were synthesized through sol-gel synthesis method. Sintering at elevated temperatures was employed to obtain samples with higher particle sizes. The structural characterization using X-ray diffraction suggests that the three samples possess uniformal cation distribution. The variation of magnetization as a function of applied magnetic field at room temperature is studied using a vibrating sample magnetometer and all the samples found to exhibit nearly zero remanence and zero coercivity suggesting a superparamagnetic behaviour. The variation of magnetizations of the three different samples with temperature was studied by ZFC-FC technique at two different applied fields of 10 Oe and 1000 Oe. In order to study the possibility of structural changes, chemical and coordination differences of iron in the nanocrystalline Ni-Zn ferrite particles, room temperature 57Fe Mössbauer spectroscopy study was used. The application of 5 T magnetic field at 5 K temperature resolves the two sub spectra and canting angle of 27o and 12o were observed which clearly indicates the noncollinear magnetic alignment in nano crystallites of Ni0.5Zn0.5Fe2O4. The neutron diffraction study was performed at seven different temperatures 20, 50, 100, 150, 200, 250 and 300 K. Rietveld refinement of the neutron diffraction data was performed to deduce the basic structural parameters, cation distribution and micro level magnetic alignments in the nanosized nickel zinc ferrite. © 2012 Elsevier B.V. All rights reserved.

Chopra M.,Bhabha Atomic Research Center | Choudhury N.,Bhabha Atomic Research Center
AIP Conference Proceedings | Year: 2014

The present work describes a molecular dynamics simulation study of structure and dynamics of aqueous solution of uranyl ions in water. Structural properties of the system in terms of radial distribution functions and dynamical characteristics as obtained through velocity autocorrelation function and mean square displacements have been analyzed. The results for radial distribution functions show the oxygen of water to form the first solvation shell at 2.4 Å around the uranium atom, whereas the hydrogen atoms of water are distributed around the uranium atom with the major peak at around 3.0 Å. Analyses of transport behaviors of ions and water through MSD indicates that the diffusion of the uranyl ion is much less as compared to that of the water molecules. It is also observed that the dynamical behavior of water molecules gets modified due to the presence of uranyl ion. The effect of increase in concentration of uranyl ions on the structure and dynamics of water molecules is also studied. © 2014 AIP Publishing LLC.

Desai S.S.,Bhabha Atomic Research Center
AIP Conference Proceedings | Year: 2014

Neutron detectors used for cosmic neutron monitoring and various other applications are mounted in hostile environment. It is essential for detectors to sustain extreme climatic conditions, such as extreme temperature and humidity. Effort is made to evaluate the performance of detectors in extreme temperature in terms of pulse height distribution and avalanche formation. Neutron detectors filled with 3He incorporate an additive gas with quantity optimized for a particular application. Measurements are performed on neutron detectors filled with 3He and stopping gases Kr and CF4. Detector performance for these fill gas combinations in terms of pulse height distribution is evaluated. Gas gain and Diethorn gas constants measured and analyzed for the microscopic effect on pulse formation. Results from these investigations are presented. © 2014 AIP Publishing LLC.

Nagaraj R.,Bhabha Atomic Research Center
India International Conference on Power Electronics, IICPE | Year: 2012

Water, energy and environment are essential inputs for sustainable development of society. It is a common phenomenon that certain packets of the country that are water stressed are also power stressed at the same time. There is a huge potential for utilizing renewable energy sources, for example solar energy, wind energy, or micro hydropower to provide a quality power supply to remote areas. The abundant energy available in nature can be harnessed and converted to electricity in a sustainable way to supply the necessary power to elevate the living standards of the people without access to the electricity grid. The advantages of using renewable energy sources for generating power in remote areas are obvious such as the cost of transported fuel are often prohibitive fossil fuel and that there is increasing concern on the issues of climate change and global warming. The disadvantage of standalone power systems using renewable energy is that the availability of renewable energy sources has daily and seasonal patterns which results in difficulties in regulating the output power to cope with the load demand. Combining more than one form of the renewable energy generation and also conventional diesel power generation will enable the power generated from a renewable energy sources to be more reliable and affordable. This kind of electric power generation system, which consists of renewable energy and fossil fuel generators together with an energy storage system and power conditioning system, is known as a hybrid power system. This paper elaborates on the analysis of small capacity hybrid power system for supplying electricity and clean water demand in rural and remote areas by using mini-grid hybrid power system consisting of renewable energy (Solar Photovoltaic cells & Windmill) and battery with a reverse osmosis desalination plant as a primary / deferrable load. © 2012 IEEE.

Raut D.R.,Bhabha Atomic Research Center | Mohapatra P.K.,Bhabha Atomic Research Center
Separation Science and Technology (Philadelphia) | Year: 2013

A series of novel polyvinylchloride (PVC) based polymer inclusion membrane (PIM) containing N,N,N',N'-tetraoctyl diglycolamide (TODGA) were prepared and applied for recovery of americium from acidic feed solutions. Transport properties of developed PIM for 241Am; were studied in flat sheet supported liquid membrane mode. Quantitative transport (>99.99%) was achieved at four hours with the optimized membrane composition. Optimum PVC PIM was further used for preconcentration of Am from acidic feed solutions. PIM was dipped in required solution with constant stirring. Kinetics of extraction was found to be rapid and about 80% extraction was achieved within two hours. Out of the four strippants used 0.1M α-HIBA was found to be most suitable and took two hours for complete stripping. Four times volume reduction factors were achieved from acidic waste solutions. Using 24 PVC PIMs, 6.01 mg was successfully trapped from 1.75L waste solution containing 6.2 mg of Am (2.79M HNO3). The method was quite simple and can be applied for the recovery of Am from laboratory waste. © Taylor & Francis Group, LLC.

Kedari C.S.,Bhabha Atomic Research Center | Pandit S.S.,Bhabha Atomic Research Center | Gandhi P.M.,Bhabha Atomic Research Center
Journal of Membrane Science | Year: 2013

Supported renewable liquid membrane (SRLM) technique is investigated for the selective separation of uranium from thorium solutions. Trioctylphosphine oxide (TOPO) dissolved in dodecane is used as the metal carrier in the liquid membrane (LM) phase. The renewable LM configuration used is highly stable for consistent long run operations. Systematic investigations were carried out to investigate the transport of U(VI) across the SRLM under different experimental conditions such as, concentration of TOPO in the LM phase, concentration of U(VI), Th(IV) and nitric acid in the feed, receiving phase composition and hydrodynamic conditions across the polymeric membrane support. By combining the process of in situ precipitation of thorium carbonate in the receiving phase, an excellent separation of uranium from thorium with decontamination factor of the order of 350 could be achieved. The solid precipitate of thorium carbonate generated in the receiving phase did not create any hindrance to the transport of U(VI) across the SRLM. The parameters defining the transport mechanism of U(VI) across the SRLM are experimentally evaluated as; maximum permeability coefficient, PU=9.66×10-5cm/min, diffusion coefficient for U(VI) in the aqueous feed solution, Da=2.35×10-4cm2/min with length of the concentration depletion layer from membrane interface, da=4.17×10-2cm and membrane diffusion coefficient for UO2(NO3)2·2TOPO in the LM phase, Do=5.36×10-6cm2/min. The numerical model obtained with these parameters gives satisfactory concordance with the experimental results under given constraint of the concentrations of nitric acid, TOPO and U(VI). Selectivity of this separation process is tested by determining permeability of different metal ions across the SRLM under optimized conditions. © 2012 Elsevier B.V.

Chandra K.,Bhabha Atomic Research Center | Kain V.,Bhabha Atomic Research Center | Tewari R.,Bhabha Atomic Research Center
Corrosion Science | Year: 2013

Type 347 stainless steel was solution annealed at three different temperatures (1100, 1250 and 1300. °C) followed by ageing at 650 and 750. °C. This was done to study the phase transformations that may occur in stainless steel 347 during welding and/or subsequent ageing. The microstructural examination showed chromium carbide and σ phase formation at the grain boundaries after ageing. The electrochemical behaviour was evaluated by double-loop electrochemical potentiokinetic reactivation test and anodic polarisation in HCl solution. Chromium carbide precipitation caused large increase in the degree of sensitisation, while σ phase had the major effect in decreasing the pitting resistance. © 2012 Elsevier Ltd.

Banerjee T.,CSIR - National Chemical Laboratory | Das A.,CSIR - National Chemical Laboratory | Ghosh H.N.,Bhabha Atomic Research Center
New Journal of Chemistry | Year: 2013

Femtosecond transient absorption spectroscopic studies of an osmium(ii)-polypyridyl-resorcinol complex, 1, on oleic acid capped TiO 2 have been carried out and the results have been compared with our previous studies on poly(vinyl)alcohol capped TiO2. While on both these surfaces the complex exhibits a single exponential <120 fs injection, the back electron transfer reaction is slower on the oleic acid capped TiO 2 surface early on while it is faster on the same surface at longer times than on poly(vinyl)alcohol capped TiO2. The probable origin of these disparate observations has been analyzed. © 2013 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

Shekhawat U.K.S.,Bhabha Atomic Research Center | Ganapathi T.R.,Bhabha Atomic Research Center
PLoS ONE | Year: 2013

WRKY transcription factors are specifically involved in the transcriptional reprogramming following incidence of abiotic or biotic stress on plants. We have previously documented a novel WRKY gene from banana, MusaWRKY71, which was inducible in response to a wide array of abiotic or biotic stress stimuli. The present work details the effects of MusaWRKY71 overexpression in transgenic banana plants. Stable integration and overexpression of MusaWRKY71 in transgenic banana plants was proved by Southern blot analysis and quantitative real time PCR. Transgenic banana plants overexpressing MusaWRKY71 displayed enhanced tolerance towards oxidative and salt stress as indicated by better photosynthesis efficiency (Fv/Fm) and lower membrane damage of the assayed leaves. Further, differential regulation of putative downstream genes of MusaWRKY71 was investigated using real-time RT-PCR expression analysis. Out of a total of 122 genes belonging to WRKY, pathogenesis-related (PR) protein genes, non-expressor of pathogenesis-related genes 1 (NPR1) and chitinase families analyzed, 10 genes (six belonging to WRKY family, three belonging to PR proteins family and one belonging to chitinase family) showed significant differential regulation in MusaWRKY71 overexpressing lines. These results indicate that MusaWRKY71 is an important constituent in the transcriptional reprogramming involved in diverse stress responses in banana. © 2013 Shekhawat, Ganapathi.

Rajaram H.,Bhabha Atomic Research Center | Apte S.K.,Bhabha Atomic Research Center
Archives of Microbiology | Year: 2010

The HrcA protein is known to bind the cis-element CIRCE and repress expression of hsp60 in certain bacteria. However, recent data from cyanobacteria have seriously questioned the HrcA/CIRCE interaction paradigm. A hrcA null mutant showed constitutive expression of Hsp60 proteins [GroEL/Cpn60(GroEL2)], and an unexpected further increase in GroEL during temperature upshift, suggesting involvement of regulatory mechanisms other than HrcA in groESL expression in Anabaena. The negative regulation of both hsp60 genes [groEL and cpn60 (groEL2)] at CIRCE element was established by: (1) constitutive expression of Green Fluorescent Protein gene, tagged to Anabaena hsp60 promoters, in E. coli, and its repression upon co-expression of Anabaena HrcA and (2) specific binding of Anabaena HrcA to the CIRCE element. Deletion analysis of other cis-elements further distinguished (a) a photo-regulation by the K-box and (b) thermoregulation from a novel H-box, over and above the negative regulation by HrcA at CIRCE. © 2010 Springer-Verlag.

Guin J.P.,Bhabha Atomic Research Center | Naik D.B.,Bhabha Atomic Research Center | Bhardwaj Y.K.,Bhabha Atomic Research Center | Varshney L.,Bhabha Atomic Research Center
RSC Advances | Year: 2014

The efficiencies of the advanced oxidation processes (AOP) viz. photocatalysis, ozonolysis and gamma radiolysis in the absence and presence of potassium persulfate (K2S2O8) were systematically investigated for the treatment of simulated textile dye waste water (STDWW) containing Reactive Red 120. The oxygen-equivalent chemical-oxidation capacities of photocatalysis, ozonolysis and gamma radiolysis in the absence and presence of K2S2O8for 16% mineralization of STDWW were calculated as 4.02, 16.19, 0.13, 0.05 kg equiv. O2m-3, respectively. The gamma radiolysis in the presence of K2S2O8showed the maximum extent of mineralization among these three AOPs. The pulse radiolysis studies revealed that the favourable reaction of SO4 -with SDBS (the most robust organic component of STDWW) producing benzyl and hydroxycyclohexadienyl type of radicals caused the enhancement in the extent of mineralization of STDWW during gamma radiolysis in the presence of K2S2O8. The COD of the STDWW was brought down to 1558 ppm from 3128 ppm by gamma radiolysis at 50 kGy dose in the presence of K2S2O8; though that index could not meet the allowed discharge limit (COD ≤ 250 ppm) of industrial effluent in the main water stream. Conversely, on replacing organic acid (CH3COOH) by inorganic acid (H2SO4) in the pH adjustment step, COD of STDWW was brought down to 245 ppm by gamma radiolysis at 60 kGy in the presence of K2S2O8. This paper recommends using H2SO4in place of CH3COOH in the pH adjustment step followed by the gamma radiolysis of STDWW in the presence of K2S2O8for an effective effluent treatment. © 2014 the Partner Organisations.

Mukherjee P.K.,Texas A&M University | Mukherjee P.K.,Bhabha Atomic Research Center | Kenerley C.M.,Texas A&M University
Applied and Environmental Microbiology | Year: 2010

Mycoparasitic strains of Trichoderma are applied as commercial biofungicides for control of soilborne plant pathogens. Although the majority of commercial biofungicides are Trichoderma based, chemical pesticides, which are ecological and environmental hazards, still dominate the market. This is because biofungicides are not as effective or consistent as chemical fungicides. Efforts to improve these products have been limited by a lack of understanding of the genetic regulation of biocontrol activities. In this study, using gene knockout and complementation, we identified the VELVET protein Veil as a key regulator of biocontrol, as well as morphogenetic traits, in Trichoderma virens, a commercial biocontrol agent. Mutants with mutations in veil were defective in secondary metabolism (antibiosis), mycoparasitism, and biocontrol efficacy. In nutrient-rich media they also lacked two types of spores important for survival and development of formulation products: conidia (on agar) and chlamydospores (in liquid shake cultures). These findings provide an opportunity for genetic enhancement of biocontrol and industrial strains of Trichoderma, since Vei1 is very highly conserved across three Trichoderma species. Copyright © 2010, American Society for Microbiology. All Rights Reserved.

Singh P.K.,Bhabha Atomic Research Center | Kumbhakar M.,Bhabha Atomic Research Center | Pal H.,Bhabha Atomic Research Center | Nath S.,Bhabha Atomic Research Center
Physical Chemistry Chemical Physics | Year: 2011

The influence of confinement in the supramolecular β-cyclodextrin nanocavity on the excited state torsional dynamics of the amyloid fibril sensor, Thioflavin-T, is explored using subpicosecond fluorescence up-conversion spectroscopy. In the presence of β-cyclodextrin, the emission intensity and the fluorescence lifetime of Thioflavin-T significantly increases, indicating the confinement effect of the nanocage on the photophysical behaviour of the dye. Detailed time-resolved fluorescence studies show an appreciable dynamic Stokes' shift for the dye in the β-cyclodextrin nanocavity. Analysis of the time-resolved area normalized emission spectra (TRANES) indicates the formation of an emissive TICT state. The rate of formation of the TICT state, as calculated from the time dependent changes in the peak frequency and the width of the emission spectra, is found to be substantially slower in the β-cyclodextrin nanocavity compared to that in bulk water. Present results indicate that ultrafast torsional motion in Thioflavin-T is significantly retarded due to confinement by the β-cyclodextrin nanocavity. © 2011 the Owner Societies.

Ghosh K.,Bhabha Atomic Research Center | Menon S.V.G.,Bhabha Atomic Research Center
Journal of Computational Physics | Year: 2010

A fully implicit finite difference scheme has been developed to solve the hydrodynamic equations coupled with radiation transport. Solution of the time-dependent radiation transport equation is obtained using the discrete ordinates method and the energy flow into the Lagrangian meshes as a result of radiation interaction is fully accounted for. A tridiagonal matrix system is solved at each time step to determine the hydrodynamic variables implicitly. The results obtained from this fully implicit radiation hydrodynamics code in the planar geometry agrees well with the scaling law for radiation driven strong shock propagation in aluminium. For the point explosion problem the self similar solutions are compared with results for pure hydrodynamic case in spherical geometry. Results obtained when radiation interaction is also accounted agree with those of point explosion with heat conduction for lower input energies. Having, thus, benchmarked the code, self convergence of the method w.r.t. time step is studied in detail for both the planar and spherical problems. Spatial as well as temporal convergence rates are ≃1 as expected from the difference forms of mass, momentum and energy conservation equations. This shows that the asymptotic convergence rate of the code is realized properly. © 2010 Elsevier Inc.

Sijoy C.D.,Bhabha Atomic Research Center | Chaturvedi S.,Bhabha Atomic Research Center
Journal of Computational Physics | Year: 2010

Volume-of-fluid (VOF) interface reconstruction methods are used to define material interfaces to separate different materials in a mixed cell. These material interfaces are then used to evaluate transport flux at each cell edges in multi-material hydrodynamic calculations. Most of the VOF interface reconstruction methods and volume transport schemes rely on an accurate material order unique to each computational cell. Similarly, to achieve over-shoot-free volume fractions, a non-intersecting interface reconstruction procedure has to be performed with the help of a 'material-order list' determined prior to interface reconstruction. It is, however, the least explored area of VOF technique especially for 'onion-skin' or 'layered' model. Also, important technical details how to prevent intersection among different material interfaces are missing in many literature. Here, we present an efficient VOF interface tracking algorithm along with modified 'material order' methods and different interface reconstruction methods. The relative accuracy of different methods are evaluated for sample problems. Finally, a convergence study with respect to mesh-size is performed. © 2010 Elsevier Inc. All rights reserved.

Charanpahari A.,Visvesvaraya National Institute of Technology | Umare S.S.,Visvesvaraya National Institute of Technology | Sasikala R.,Bhabha Atomic Research Center
Catalysis Communications | Year: 2013

We report the photocatalytic activity of a visible light active N doped GeO2 (NG), which can degrade Rhodamine B (cationic) and Acid violet 7 (anionic) dyes efficiently from aqueous solutions. A considerable red-shift in the absorption edge is seen for NG compared to pure GeO2 due to N doping. Presence of bonded nitrogen in the doped sample is clearly seen from X-ray photoelectron spectroscopy. NG exhibits higher degradation rate for cationic, Rhodamine B as compared to anionic, Acid violet 7 dyes. Studies with quenchers indicate that superoxide radical is the main active species involved in photocatalytic degradation of Rhodamine B. © 2013 Elsevier B.V. All rights reserved.

Pathak A.K.,Bhabha Atomic Research Center | Pathak A.K.,University of California at San Diego | Bandyopadhyay T.,Bhabha Atomic Research Center
Proteins: Structure, Function and Bioinformatics | Year: 2014

Because of the pivotal role that the nerve enzyme, acetylcholinesterase plays in terminating nerve impulses at cholinergic synapses. Its active site, located deep inside a 20 Å gorge, is a vulnerable target of the lethal organophosphorus compounds. Potent reactivators of the intoxicated enzyme are nucleophiles, such as bispyridinium oxime that binds to the peripheral anionic site and the active site of the enzyme through suitable cation-π interactions. Atomic scale molecular dynamics and free energy calculations in explicit water are used to study unbinding pathways of two oxime drugs (Ortho-7 and Obidoxime) from the gorge of the enzyme. The role of enzyme-drug cation-π interactions are explored with the metadynamics simulation. The metadynamics discovered potential of mean force (PMF) of the unbinding events is refined by the umbrella sampling (US) corrections. The bidimensional free energy landscape of the metadynamics runs are further subjected to finite temperature string analysis to obtain the transition tube connecting the minima and bottlenecks of the unbinding pathway. The PMF is also obtained from US simulations using the biasing potential constructed from the transition tube and are found to be consistent with the metadynamics-US corrected results. Although experimental structural data clearly shows analogous coordination of the two drugs inside the gorge in the bound state, the PMF of the drug trafficking along the gorge pathway point, within an equilibrium free energy context, to a multistep process that differs from one another. Routes, milestones and subtlety toward the unbinding pathway of the two oximes at finite temperature are identified. © 2014 Wiley Periodicals, Inc.

Ghanty T.K.,Bhabha Atomic Research Center | Banerjee A.,Raja Ramanna Center for Advanced Technology | Chakrabarti A.,Raja Ramanna Center for Advanced Technology
Journal of Physical Chemistry C | Year: 2010

We employ an ab initio scalar relativistic density functional theory based method to calculate the ground state structures and the electronic properties for Au19X clusters, X being the alkali metal atoms, Li, Na, K, Rb, and Cs as well as the coinage metal atoms, Ag and Cu. The tetrahedral Au 20 clusters have been doped exohedrally with these atoms at three different types of unique sites where the dopant atom substitutes one gold atom from (i) the vertex, (ii) the surface, and (iii) the edge sites. In addition to the structures based on tetrahedral Au20, we also consider cage-like structures for Au19X clusters with the dopant atom located at an endohedral position. We first optimize the geometries of these clusters and then we carry out vibrational analysis on these optimized structures of the substituted Au20 clusters in order to check the stability of the final optimized structures. Further, using the optimized geometries of these doped clusters, we calculate the binding energy, interaction energy of the dopant atom with the Au19 cluster, vertical ionization potential, vertical electron affinity, and HOMO-LUMO gaps of these doped clusters. For these systems, we also carry out the charge population analysis. We compare these properties of the doped clusters with those of the pure Au20 cluster to characterize the stability and chemical inertness of the doped clusters. Few cage like endohedrally doped Au19X clusters (X = Li, Na, and Cu) are found to have binding energies comparable to those of the corresponding exohedrally doped clusters. For the larger atoms (X = K, Rb, Cs, and Ag), all of the endohedrally doped cage-like structures have been found to be less stable than the corresponding exohedral structures. Nevertheless, exohedrally doped Au19X clusters with X located at one of the surfaces of tetrahedral structure correspond to the most stable isomer for all the dopants. We observe that the Li and Cu doped gold clusters, where the dopant atom is located at one of the surface sites of the Au20 cluster are more stable than the pure Au20 cluster. This leads to the possibility of finding highly reactive anions of these doped clusters. Geometric as well as energetic considerations indicate that it may be possible to characterize these species experimentally using photoelectron spectroscopy. © 2010 American Chemical Society.

Sreenivas T.,Bhabha Atomic Research Center | Rajan K.C.,Bhabha Atomic Research Center
Separation and Purification Technology | Year: 2013

The increasing demand for uranium fuel for energy generation has triggered interest in the exploitation of various resources including lean tenor ores and tailing dumps which are otherwise considered uneconomical till recently. The process-schemes of new plants are incorporating several new technologies such that the process is economically attractive and eco-friendly. One such development catching the lime-light in uranium ore processing industry everywhere is the resin-in-pulp (RIP) technology. This paper describes the results of laboratory studies on the recovery of dissolved uranium values from an alkaline leach slurry of a medium-grade uranium ore from Gogi (Karnataka, India) using the resin-in-pulp (RIP) process. Besides anionic carbonate complex of uranium - [UO2(CO3)3]4-, the other major anionic constituents of the leach solution are CO32-, HCO3-, SO42-, Cl-, PO43- and MoO42-. The total dissolved solutes (TDSs) are about 45 g/l. Various commercially available strong base anionic type resin-in-pulp (RIP) grade resins - both macro-porous and gel type, were studied with respect to their loading capacity. The gel type polystyrene based resins grafted with quaternary ammonium ion gave superior loading capacity in comparison to macro-porous resins. Parametric variation studies for optimizing the other process conditions, including adsorption kinetics, were then carried out on the short-listed resin. Results of the semi-continuous counter-current extraction and elution tests indicated that about 98% of the dissolved uranium values can be recovered during the loading process and practically the entire loaded uranium can be eluted using NaCl eluant. © 2013 Elsevier Ltd. All rights reserved.

Shaikh M.,Bhabha Atomic Research Center | Swamy Y.M.,Bhabha Atomic Research Center | Pal H.,Bhabha Atomic Research Center
Journal of Photochemistry and Photobiology A: Chemistry | Year: 2013

Supramolecular host-guest interaction of acridine dye, a biologically important molecule, with β and γ cyclodextrin (βCD and γCD, respectively) macrocycles has been investigated in aqueous solution using photophysical methods. Neutral form (Ac) of the dye undergoes significant interaction with βCD and γCD hosts, forming mainly the 1:1 stoichiometric host-guest complex. Fluorescence intensity and lifetime of Ac reduces drastically on binding with CD hosts, ascribed to H-bonding interaction of the portal OH groups of the hosts with bound excited dye. The fraction of the free dye in these systems also shows significant reduction in fluorescence lifetime that displays liner Stern-Volmer correlation, suggesting dynamic quenching of the free dye through similar H-bonding interaction with the portal OH groups of the hosts. Present contention is support by the fluorescence intensity and lifetime reduction of the dye on using d-glucose as the quencher. Ac interacts relatively strongly with βCD than γCD, attributed to tighter binding of the dye with smaller βCD cavity than larger γCD cavity. The inclusion complex formation in the present Ac-CD systems is suitably supported by time-resolved fluorescence anisotropy results. Unlike neutral Ac form, the protonated AcH+ form of the dye does not show any significant interaction with either βCD or γCD hosts. The differential interaction of Ac and AcH+ forms with the CDs results in the downward pKa shifts for the dye by ∼0.43 and ∼0.32 units, respectively, in the presence of 16 mM βCD and 40 mM γCD (4) hosts. Since CD concentrations much higher than these could not be used due to their solubility limitations and hence the condition of complete complexation for both Ac and AcH+ forms with CD hosts could not be achieved in these solutions, the above pKa shifts are certainly the apparent ones, and the true pKa shifts for the complexed dye would have been significantly higher than the above values. In any case, the observed pK a shifts in the present study is the first report on the macrocyclic host induced changes in the prototropic properties of acridine dye. Observed modulations in the photophysics and acid-base properties of acridine dye reported here can have a bearing to the host assisted drug stabilization and supramolecular fluorescence probes and sensors. © 2013 Elsevier B.V.

Tak H.,Bhabha Atomic Research Center | Mhatre M.,Bhabha Atomic Research Center
Protoplasma | Year: 2013

The proteins harboring bZIP domains comprise a large family and play key roles in many cellular processes, one of them being tolerance to biotic and abiotic stresses in plants. In the present study, we characterize a putative bZIP transcription factor from Vitis vinifera namely VvbZIP23. Our studies revealed that a GFP fusion of VvbZIP23 is localized in the nucleus showing VvbZIP23 codes for a nuclear localized protein. VvbZIP23 identified by in silico approaches from grapevine DNA databases available in the public domain NCBI is present in a single copy in the grapevine genome as shown by Southern blot analysis. Expression of VvbZIP23 is induced by a wide spectrum of abiotic stresses, including drought, salt, and cold. Exogenous application of signaling chemicals like abscisic acid, methyl viologen, salicylic acid, jasmonic acid, and ethephon also induced expression of VvbZIP23. This shows that VvbZIP23 is involved in regulating a number of stress responses in V. vinifera. The 5′ proximal region of VvbZIP23 contains many cis-acting elements, which show induction of VvbZIP23 expression in multiple stress responses. Transcripts of VvbZIP23 were found in many parts of the grapevine plant with the highest expression detected in leaves. Further in silico analysis shows that the open reading frame of VvbZIP23 is 822 bp long and codes for a 273 amino acid long protein having a characteristic bZIP domain in its N-terminal end. Overexpression of VvbZIP23-GFP fusion protein in grapevine callus leads to enhanced transcript levels of genes, homologues of which are reported to be important in regulating many stress conditions. © 2012 Springer-Verlag.

Shukla R.,Bhabha Atomic Research Center | Shyam A.,Bhabha Atomic Research Center
Review of Scientific Instruments | Year: 2013

We have already reported the low-voltage operation of a plasma focus describing the operation of plasma focus at 4.2 kV which proposes possibility of making a repetitive system using compact driving source. Another recent article describes that the same capacitor-bank can drive the plasma focus for a measured ∼5 × 104 neutrons per shot at 5 kV and 59 kA current. In the present work, repetitive operation of the capacitor-bank of plasma focus is done and that too is being reported at a very high repetition rate of 50 Hz using very simple scheme of charging and triggering the bank. The bank is continuously discharged to burst duration of 20 s in this configuration admeasuring a thousand shots. © 2013 AIP Publishing LLC.

Banerjee S.,Bhabha Atomic Research Center | Majumder C.,Bhabha Atomic Research Center
AIP Advances | Year: 2013

The structural and electronic properties of fully hydrogenated SiC graphane-like nano-structures have been investigated. The objective of this study is to underscore the relative stability of different conformers of hydrogenated SiC sheet. All calculations are carried out using plane wave based pseudo-potential approach under the density functional theory. The results reveal that the fully hydrogenated SiC sheet forms five stable isomers, and the chair conformer is most stable. Further study through molecular dynamic simulation strategy demonstrates that even at room temperature the chair conformer remains stable. © 2013 © 2013 Author(s).

Various neutron scattering instruments at Dhruva reactor, BARC, are equipped with indigenously developed neutron detectors. Range of detectors includes proportional counters, beam monitors and linear position sensitive detectors (PSD). One of the instruments is recently upgraded with multi-PSD system of high efficiency and high resolution PSDs arranged in stacking geometry. These efforts have resulted in improving the throughput of the instrument and reducing experiment time. Global scarcity of 3He has made essential to explore other options like BF3 gas and 10B coatings. PSDs with coaxial geometry using BF3 gas and 10B coating (90% enriched) are fabricated and characterized successfully. These PSDs are used as the alternative to 3He PSD in equivalent geometry. Though efficiency of PSDs in similar dimensions is lower than that with 3He, these large numbers of PSDs can be arranged in multi-PSD system. The PSD design is optimized for reasonable efficiency. An array of 60 BF3 filled PSDs (1 m long) is under development for the Time of Flight Instrument at Dhruva. Further improvement in efficiency can be obtained with novel designs with complex anode-cathode geometry. Various challenges arise for long term operation of PSDs with BF3 gas, in addition to complexity of data acquisition electronics. Study of gas aging with detector fabrication materials has been carried out. PSDs with 10B coating show advantage of non toxic nature but have low efficiency. Multiple 10B layers intercepting neutron beam are used to increase the efficiency. PSD designed with small anode- cathode spacing and array of multiwire grids placed between double sided 10B coated plates are being fabricated. Assembly is arranged in curvilinear geometry with zero parallax. Overview of these developments is presented. © Published under licence by IOP Publishing Ltd.

Dutta S.,Bhabha Atomic Research Center | Mohapatra P.K.,Bhabha Atomic Research Center | Manchanda V.K.,Bhabha Atomic Research Center
Applied Radiation and Isotopes | Year: 2011

The relative extraction efficiency of N,N,N′,N′-tetraoctyldiglycolamide (TODGA) towards Y3+ and Sr2+ was investigated from HNO3 as well as HCl medium. The separation factor (S.F.) values were found to be much higher in HCl medium as compared to those obtained from HNO3 medium. Based on the high separation factor values obtained in the HCl media, a separation method for 90Y from 90Sr (containing 90Y in secular equilibrium) has been developed in the present work. The purity of the separated 90Y was ascertained from its decay profile and half-life measurements. The extracted species was determined to be Y(X)3̇3TODGA where X- is the nitrate or the chloride anion. The thermodynamic parameters were also determined and the two phase extraction constants (logKex) were calculated. The extraction of Y(III) was highly exothermic and entropy destabilized and was equally favourable from both HNO3 medium as well as HCl medium. © 2010 Elsevier Ltd.

Recently the possibility of achieving quasi-isentropic compression using functionally graded materials, in both gas gun and explosive driven systems was explored by hydro-dynamic simulations. In the current paper, we show that multi-layered composite flyer with progressively increasing shock impedances, referred to as graded density impactor (GDI), has the potential to enable increased flexibility in suitably tailoring the applied-pressure profiles, further relaxing constraints on the thermodynamic path of compressed material. Present simulation study pertaining to constant velocity impact of GDI reveals that linear ramp pulses of different pressure rise times, with comparable peak values can be realized only by changing the layer thicknesses of a particular GDI. We report generation of three different slope ramp pulses by five layer GDI made of PMMA, Al, Ti, Cu and Ta with different set of thicknesses obtained by genetic algorithm based optimization technique. Generation of long duration (μs) isentropic pressures using discrete GDI is a significant step, since it is devoid of fabrication difficulties of ultra-thin lamellae of FGM. Signatures of isentropic compression of a thin Cu target under different slope ramp loadings are identified from basic thermodynamic aspects in terms of temperature rise and entropy production. It is shown that that extent of entropy increase is closely related to the slope of ramping pulse. Further, a physical model has been constructed to determine approximate time profile of pressure pulse generated by equal layer-width GDI. © Published under licence by IOP Publishing Ltd.

Kiran Kumar P.V.,Bhabha Atomic Research Center | Suryanarayana M.V.,Bhabha Atomic Research Center
Pramana - Journal of Physics | Year: 2014

In this paper, we have briefly reviewed the work on two-photon spectroscopy of alkali elements and its applications. The technique of Doppler-free two-photon spectroscopy is briefly summarized. A review of various techniques adopted for measuring absolute frequencies of the atomic transitions and precision measurements of isotope shifts and hyperfine structures (HFS) is presented. Some of the recent works on precision measurements of HFS constants of 6s 2S1/2 level of 39K and 41K, 9s 2S1/2 level and 7d 2D3/2 level of 133Cs are also discussed. © 2014 Indian Academy of Sciences.

Anand S.,Bhabha Atomic Research Center | Mayya Y.S.,Indian Institute of Technology Bombay
Journal of Aerosol Science | Year: 2015

Aerosol systems are more often spatially heterogeneous than homogeneous due to various factors such as turbulence in the atmosphere, flow field in a pipe, and varying generation rates at the source. As a general result, we demonstrate that an initially monodisperse and spatially heterogeneous aerosol system evolves into a bimodal size distribution purely by coagulation. The spatial inhomogeneity in the particle number concentration initiates differential coagulation rates which lead to a distribution with larger size modes in regions with higher concentration. When averaged over space. , this would appear as a bimodal size distribution. We show this effect through a free-molecular coagulation model for a spatially heterogeneous system combined with the scaling theory of self-preserving distributions. It is found that sharper the occurrence of spatial heterogeneity, more pronounced is the bimodal effect. The study clearly demonstrates spatial heterogeneity as an additional factor for the origin of bimodality in aerosols. © 2015 Elsevier Ltd.

Dash A.,Bhabha Atomic Research Center | Chakravarty R.,Bhabha Atomic Research Center
RSC Advances | Year: 2014

While the application of radionuclide generators in nuclear medicine constitutes a successful example of the availing of short lived radionuclides on demand, the success and growth of generator technology largely depend on the progress in separation science. Separation science plays a pivotal role in the development of radionuclide generators, with this branch of science being in a process of continuous evolution. Any breakthrough, technology innovation, or improvement over existing paradigms in separation science represent not only an important driving force but also lay the cornerstone for further accomplishments in radionuclide generator technology. With the emergence of professionally run central radiopharmacies, radionuclide generator technology is poised to undergo a game change in terms of design and user profiles. It is of utmost importance to assure the access to appropriate radionuclide generator systems that are adaptable to the existing and foreseeable demands of the nuclear medicine community. The purpose of this review is to assess the recent advances in separation science which can act as a springboard to spur further development in radionuclide generator technology. Such advances are expected to unfold a wide spectrum of radionuclide generators to accelerate further development in this field. In light of this, a variety of separation technologies that have traditionally been used and emerging techniques that have the potential to promote rapid growth in generator technology have been selected, highlighted, and critically evaluated to illustrate their impact on the development of clinically useful radionuclide generators. The advantages, limitations, and potential applications of the separation methods, along with their current status and future prospective in radionuclide generator development, are discussed. This journal is © the Partner Organisations 2014.

Jadhav S.G.,Institute of Chemical Technology | Vaidya P.D.,Institute of Chemical Technology | Bhanage B.M.,Institute of Chemical Technology | Joshi J.B.,Institute of Chemical Technology | Joshi J.B.,Bhabha Atomic Research Center
Chemical Engineering Research and Design | Year: 2014

Methanol demand is continuously increasing in the chemical and energy industries. It is commercially produced from synthesis gas (CO+CO2+H2) using CuO/ZnO/Al2O3 catalysts. Today, much effort is being put on the development of technologies for its production from carbon dioxide (CO2). In this way, the Greenhouse effect may be mitigated. Over the years, several useful works on CO2 hydrogenation to methanol have been reported in the literature. In this article, we present a comprehensive overview of all the recent studies published during the past decade. Various aspects on this reaction system (such as thermodynamic considerations, innovations in catalysts, influences of reaction variables, overall catalyst performance, reaction mechanism and kinetics, and recent technological advances) are described in detail. The major challenges confronting methanol production from CO2 are considered. By now, such a discussion is still missing, and we intend to close this gap in this paper. © 2014 The Institution of Chemical Engineers.

Chakraborty B.,Bhabha Atomic Research Center | Modak P.,Bhabha Atomic Research Center | Banerjee S.,Indian Department of Atomic Energy
Journal of Physical Chemistry C | Year: 2012

Applying first principles electronic structure calculations and molecular dynamics (MD) simulations we have studied the structural stability, hydrogen adsorption capability and hydrogen desorption kinetics of Y-decorated single walled carbon nanotube (SWCNT). We have predicted that a single Y atom attached on SWCNT can physisorb up to six hydrogen molecules which is not reported so far. Our MD simulations with four Y atoms placed at the alternate hexagons of SWCNT showed no clustering effect of Y atoms at room temperature and also we found that the system is stable even at higher temperature (700 K). For the first time we showed that 100% desorption at comparatively lower temperature can be achieved in a transition metal-decorated SWCNT system. Therefore the Y-decorated SWCNT has the potential to become a promising hydrogen storage device. © 2012 American Chemical Society.

Rao T.S.,Bhabha Atomic Research Center
Aquatic Ecology | Year: 2010

Progression of biofilm formation was monitored at two stations near a nuclear power plant, Kalpakkam, located near coastal waters of Bay of Bengal. These stations are natural marine environment, station 1; and the condenser outfall area of the power plant the modified marine environment station 2. The biofilm formed on plexiglas panels was analysed in triplicates at 24 h intervals for various physical, chemical and biological parameters for 120 h (5 days). The biofilm formation showed both temporal and spatial variation in various parameters assayed. Among the water-quality parameters analysed, seawater temperature showed significant increase (~5°C) at station 2. The increase in water temperature enhanced the metabolism and influenced most of the biofilm parameters assayed at station 2. Biofilm formed at station 2 was very thick (113 μm) than that of at station 1 (22 μm). The distribution of parameters like biofilm thickness, biomass, chlorophyll a, particulate organic carbon, hexose sugar and diatom counts showed similar trend (i.e., a sharp increase after 96 h of biofilm growth) in the biofilm formed at station 2. Moderately high ammonia levels (44 μg l-1) were detected in the biofilm formed at station 2. The biofilm microbiota was diverse at both the stations: it constituted bacteria [nitrate reducers (NRB), ammonia oxidizers (AOB) and culturable aerobic heterotrophic bacteria (CAHB)], algae and macrofoulants. The various bacterial types assayed showed a population range from 102 to 106 cfu cm-2. The final community after 120 h at station 1 comprised CAHB, NRB, diatoms, barnacle cyprids and juvenile bryozoans. At station 2, the biofilm initially consisted of CAHB, NRB and diatoms but after 120 h, AOB, cyanobacteria and filamentous algae were dominant. The plausible factors that influenced biofilm formation were temperature, nutrients and organic matter. The biofilm phenomenon in natural and modified marine environment was hypothesized and discussed. © Springer Science+Business Media B.V. 2009.

Selvakumar N.,National Aerospace Laboratories, Bangalore | Manikandanath N.T.,National Aerospace Laboratories, Bangalore | Biswas A.,Bhabha Atomic Research Center | Barshilia H.C.,National Aerospace Laboratories, Bangalore
Solar Energy Materials and Solar Cells | Year: 2012

A new HfMoN(H)/HfMoN(L)/HfON/Al 2O 3 tandem absorber is designed and developed for high temperature solar thermal applications. The first absorber layer, HfMoN(H) is designed to have higher metallic content than the second HfMoN(L) layer. By varying the nitrogen flow rate, two different HfMoN layers with different refractive indices were deposited on SS substrates. The optical constants (n and k) measured using spectroscopic ellipsometry showed that HfMoN(H) and HfMoN(L) are the main absorber layers and HfON/Al 2O 3 acts as a double layer antireflection coating. The gradual decrease in the refractive indices from the substrate to the top resulted in increase in the absorptance, which was confirmed by the ellipsometric measurements. The optimized four layer tandem absorber exhibited high absorptance (α=0.94-0.95) and low thermal emittance (ε 82 °C=0.13-0.14). The four layer tandem absorber was thermally stable up to 600 °C for 450 h and 650 °C for 100 h in vacuum. Whereas, coatings heat-treated in air were thermally stable up to 475 °C for 34 h. © 2012 Elsevier B.V. All rights reserved.

Dash A.,Bhabha Atomic Research Center | Pillai M.R.A.,Molecular Group of Companies | Knapp F.F.,Oak Ridge National Laboratory
Nuclear Medicine and Molecular Imaging | Year: 2015

Background: This review provides a comprehensive summary of the production of 177Lu to meet expected future research and clinical demands. Availability of options represents the cornerstone for sustainable growth for the routine production of adequate activity levels of 177Lu having the required quality for preparation of a variety of 177Lu-labeled radiopharmaceuticals. The tremendous prospects associated with production of 177Lu for use in targeted radionuclide therapy (TRT) dictate that a holistic consideration should evaluate all governing factors that determine its success. Methods: While both “direct” and “indirect” reactor production routes offer the possibility for sustainable 177Lu availability, there are several issues and challenges that must be considered to realize the full potential of these production strategies. Results: This article presents a mini review on the latest developments, current status, key challenges and possibilities for the near future. Conclusion: A broad understanding and discussion of the issues associated with 177Lu production and processing approaches would not only ensure sustained growth and future expansion for the availability and use of 177Lu-labeled radiopharmaceuticals, but also help future developments. © 2015, Korean Society of Nuclear Medicine.

Mangal A.,Bhabha Atomic Research Center | Jain V.,Bhabha Atomic Research Center | Nayak A.K.,Bhabha Atomic Research Center
Progress in Nuclear Energy | Year: 2012

Many advanced reactor designs incorporate passive systems mainly to enhance the operational safety and possible elimination of severe accident condition. Some reactors are even designed to remove the nominal fission heat passively by natural circulation without using mechanical pumps e.g. ESBWR, AHWR, CHTR, CAREM, etc. while in most other new reactor concepts, the decay heat is removed passively by natural circulation following the pump trip conditions. The design and safety analysis of these reactors are carried out using the best estimate codes such as RELAP5, TRAC and CATHARE, etc. These best estimate codes have been developed for pumped circulation systems and it is not proven about their adequacy or applicability for natural circulation systems wherein the driving mechanism is completely different. Some of the key phenomena which are difficult to model but are significantly important to assess the natural circulation system performances are - low flow natural circulation mainly because the flow is not fully developed and can be multi-dimensional in nature; flow instabilities; critical heat flux under oscillatory condition; flow stratification particularly in large diameter vessel; thermal stratification in large pools; effect of non-condensable gases on condensation, etc. Though, these best estimate codes use a six equation two-fluid model formulation for the thermal-hydraulic calculation which is considered to be the best representative of two-phase flows, but their accuracies depend on the accuracies of the models for interfacial relationships for mass, energy and momentum transfer which are semi-empirical in nature. The other problem with two-fluid models is the effect of ill-posedness which may cause numerical instability. Besides, the numerical diffusion associated due to truncation of higher order terms can affect the prediction of flow instabilities. All these effects may lead to inability to capture the important physical instability in natural circulation systems and instability characteristics i.e. amplitude and frequency of flow oscillation. In view of this, it is essential to test the capability of these codes to simulate natural circulation behavior under single and two-phase flow conditions before applying them to the future reactor concepts. In the present study, one of the extensively used best estimate code RELAP5 has been used for simulation of steady state, transient and stability behavior of natural circulation based experimental facilities, such as the High-Pressure Natural Circulation Loop (HPNCL) and the Parallel Channel Loop (PCL) installed and operating at BARC. The test data have been generated for a range of pressure, power and subcooling conditions. The computer code RELAP5/MOD3.2 was applied to predict the transient natural circulation characteristics under single-phase and two-phase conditions, thresholds of flow instability, amplitude and frequency of flow oscillations for different operating conditions of the loops. This paper presents the effect of nodalisation in prediction of natural circulation behavior in test facilities and a comparison of experimental data in with that of code predictions. The errors associated with the predictions are also characterized. © 2012 Elsevier Ltd. All rights reserved.

Mathuriya A.S.,Anand Engineering College | Yakhmi J.V.,Bhabha Atomic Research Center
Environmental Chemistry Letters | Year: 2014

Heavy metals play a major role in several industrial, medical, and household applications. However, as constituents of effluents from many industries, heavy metals also pose a serious problem to the environment and public health due to their toxicity, bioaccumulation, and non-biodegradability. Conventional physical, chemical, and biological methodologies to treat wastewater containing heavy metals are energy-intensive and become ineffective if metals concentrations are below 1–100 mg L−1. Microbial fuel cells appear promising for wastewater treatment and metal recovery by bioelectrocatalysis because metal ions can be reduced and deposited by bacteria, algae, yeasts, and fungi. Interestingly, treatment of heavy metal-containing wastewater can be attempted in both anode and cathode chambers of microbial fuel cells. Here, we review the treatment of metal-containing effluents using microbial fuel cells. © 2014, Springer International Publishing Switzerland.

Chakravarty R.,Bhabha Atomic Research Center | Dash A.,Bhabha Atomic Research Center
Journal of Radioanalytical and Nuclear Chemistry | Year: 2014

Nanostructured materials by virtue of huge surface to volume ratios, altered physical properties, tailored surface chemistry, favorable adsorption characteristics, and enhanced surface reactivity resulting from the nanoscale dimensions, have attracted considerable attention as a new class of adsorbent material in column chromatographic separation. This emerging class of adsorbent represents an innovative paradigm and is expected to play an important role in the development of radionuclide generators for nuclear medicine. The optimal combination of suitable nanomaterial and appropriate parent/daughter radionuclide pair forms the basis of such generators. Development of such generators is currently under intensive investigations and the utility of such systems is expected to pave the way for broad panoply of diagnostic and therapeutic applications in nuclear medicine. While nanomaterial-based radionuclide generator is still in its infancy, the use of such novel class of adsorbents is expected to have potential impact on shaping the radionuclide generator technology of future generation. This review provides a comprehensive summary on the utility of nanomaterials as effective adsorbents in the development column chromatographic radionuclide generators for medical applications. This overview outlines a critical assessment of role of the nanosorbents, recent developments, the contemporary status, and key challenges and apertures to the near future. © 2013 Akadémiai Kiadó, Budapest, Hungary.

Kumar S.,Bhabha Atomic Research Center | Krishnamurthy N.,Bhabha Atomic Research Center
International Journal of Hydrogen Energy | Year: 2012

Hydrogen absorption kinetics of vanadium-aluminum alloys in the temperature range of 624-924 K have been studied. These alloys were prepared by the aluminothermy process and refined by electron beam melting. The data of instantaneous reacted fractions at four different temperatures were obtained using the pressure drop method and these data were linearly fitted to a suitable reaction mechanism function. Three-dimensional diffusion appears to be the intrinsic rate limiting step of the hydrogen absorption. The rate constants were obtained from the slope of the linearly fitted curves. Apparent activation energies were calculated using the Arrhenius equation. The activation energies were increased linearly with aluminum content resulting in a decrease in the hydrogen absorption rate. The variation in standard entropies and enthalpies of vanadium-hydrogen solid solution has been studied as a function of aluminum content. Highlights: Activation energy of H absorption of vanadium increased with aluminum content. Standard entropies of vanadium-hydrogen solid solution decreased with aluminum. Standard enthalpies of vanadium-hydrogen solid solution increased with aluminum. Hydrogen absorption of vanadium controlled by three dimensional diffusion. Hydrogen absorption kinetics was controlled by Fermi energy level of vanadium. © 2012 Hydrogen Energy Publications, LLC.

Banerjee A.,Raja Ramanna Center for Advanced Technology | Ghanty T.K.,Bhabha Atomic Research Center | Chakrabarti A.,Raja Ramanna Center for Advanced Technology | Kamal C.,Raja Ramanna Center for Advanced Technology
Journal of Physical Chemistry C | Year: 2012

We study the effect of doping on the linear and nonlinear optical properties of Au 19M clusters, M being the alkali metal atoms, Li, Na, K, Rb, and Cs, as well as the coinage metal atoms, Ag and Cu, by employing response theory within time-dependent density functional theory. We consider doping at both exohedral and endohedral locations and use several optimized geometries already reported in our earlier work on the ground-state structures and electronic properties of these clusters. Using these structures, we calculate the dipole polarizability and first-order hyperpolarizability characterizing linear and nonlinear optical properties, respectively, of these doped gold clusters. We find that the nonlinear optical response property depends crucially on the nature and the location of the dopant atom. The alkali atom doped gold clusters with the dopant atom sitting at the vertex of the tetrahedral structure are found to yield the highest value of the first-order hyperpolarizability. On the other hand, the endohedrally doped clusters are found to be significantly less hyperpolarizable. We rationalize the nonlinear optical properties by studying the low-energy UV-vis optical absorption band obtained by employing time-dependent density functional theory. © 2011 American Chemical Society.

Sijoy C.D.,Bhabha Atomic Research Center | Chaturvedi S.,Bhabha Atomic Research Center
Fusion Engineering and Design | Year: 2012

The process of magnetic flux compression (MFC) inside a solenoid by expanding diamagnetic plasma sphere produced by an inertial fusion micro-explosions and its application as a direct energy conversion scheme to convert a part of plasma kinetic energy into pulsed electrical energy has been recently reported [1]. For a detailed analysis of this concept, an Eulerian multi-material MHD model is developed using magnetic vector potential formulation for electro-magnetic field calculations and classical volume-of-fluid method for material interface tracking. The diffusion term in the magnetic induction equation is solved implicitly while the advection terms are computed using a second-order MUSCL scheme. An iteration procedure using ADI scheme is used for the free space field calculation. In this paper, we describe the details of the new MHD model, its validation against the semi-analytical solutions (for magnetic Reynolds number ≫1) of magnetic convective-diffusion equations and application to explore the concept of MFC by expanding plasma sphere. The simulation results show that the algorithm is capable of handling complex plasma dynamics inside the MFC system. Also, the results indicate the development and the evolution of MRT like instability near the stagnation point. The magnetic field diffusion into the plasma during the expansion phase is found to be negligible. © 2011 Elsevier B.V. All rights reserved.

Kumar S.,Bhabha Atomic Research Center | Taxak M.,Bhabha Atomic Research Center | Krishnamurthy N.,Bhabha Atomic Research Center
International Journal of Hydrogen Energy | Year: 2012

The hydrogen absorption kinetics of V4Cr4Ti alloy, synthesized by aluminothermy process has been investigated in the temperature range of 373-773 K. The obtained hydrogen absorption kinetic curves were linearly fitted using a series of mechanism function to reveal the kinetics parameter and reaction mechanism. Nucleation and growth, one dimensional diffusion and three-dimensional diffusion processes are the intrinsic rate limiting steps of hydrogen absorption at 373 K. It was found that nucleation and growth processes disappear between 413 K-473 K. However at higher temperatures (>473 K), nucleation and growth as well as one dimensional diffusion process disappear. In the temperature ranges investigated (473 K-773 K), three-dimensional diffusion process was the intrinsic rate limiting step. The apparent activation energy was calculated using Arrhenius equation and found to be 6.1 kJ/mol. This value appears to be relatively higher which can be attributed to the presence of aluminium, which has blocked the absorption sites and increased the activation energy. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Gupta S.K.,Bhabha Atomic Research Center | Kumar M.,Bhabha Atomic Research Center | Natarajan V.,Bhabha Atomic Research Center | Godbole S.V.,Bhabha Atomic Research Center
Optical Materials | Year: 2013

Trivalent dysprosium-doped strontium silicate (Sr2SiO 4) phosphors were prepared by sol-gel synthesis using tetra ethyl orthosilicate (TEOS) as precursor. The synthesis temperature could be brought down to 600 C for formation of a single phase sample. The material was characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), photoluminescence (PL), and thermally stimulated luminescence (TSL). The luminescence study revealed strong 4F9/2 → 6H13/2 transition at 577 nm (yellow), strong 4F9/2 → 6H15/2 transition at 482 nm (blue) and weak 4F9/2 → 6H 11/2 transition at 677 nm (red), when excited by 250 nm (Charge transfer band, CTB) or 352 nm (f-f band). The concentration of the dopant ion and the temperature of annealing were optimized for maximum PL intensity. The critical energy-transfer distance for the Dy3+ ions was evaluated based on which, the quenching mechanism was verified to be a multipole-multipole interaction. The thermally stimulated luminescence studies of Sr 2SiO4:Dy3+ sample showed main TSL glow peak at 413 K. The trap parameters namely activation energy (E), order of kinetics (b), and frequency factor (s) for this peak were determined using glow curve shape method. © 2013 Elsevier B.V. All rights reserved.

Seshadri H.,AERB Safety Research Institute | Sinha P.K.,Bhabha Atomic Research Center
Journal of Radioanalytical and Nuclear Chemistry | Year: 2012

Nanostructures of β-Ga 2O 3 were prepared by solution combustion route using urea as the fuel. Transmission electron microscopic measurements and powder X-ray diffraction measurements confirmed the crystalline nature of β-Ga 2O 3 with particle size in the range of 10-15 nm. Surface area measurements indicated that the synthesized semiconductor catalyst had a specific surface area of 30 m 2/g. In this work, photocatalytic degradation studies of tri-n-butyl phosphate using nano sized β-Ga is presented. A cylindrical photoreactor was used for the degradation studies and gas chromatographic estimation was adopted to follow the extent of degradation. Complete degradation of tributyl phosphate could be achieved in less than 40 min using 10 mg of photocatalyst and 0.5 mL of H 2O 2 for 1000 mL of 400 ppm TBP. Degradation of TBP was found to follow pseudo first order kinetics and the rate of TBP degradation was found to be superior for β-Ga 2O 3 photocatalyst compared to P-25 TiO 2. © 2012 Akadémiai Kiadó, Budapest, Hungary.

Dhanasekaran P.,CSIR - National Chemical Laboratory | Salunke H.G.,Bhabha Atomic Research Center | Gupta N.M.,CSIR - National Chemical Laboratory
Journal of Physical Chemistry C | Year: 2012

The application of γ′-Fe 4N, a noble-metal-free, low-cost catalyst, in the photosplitting of neat water into stoichiometric amounts of H 2 and O 2 under visible-light irradiation is reported for the first time. The catalyst showed optical absorption and photoluminescence emission bands in the entire visible region. The photocatalytic water-splitting activity was wavelength-dependent, the quantum efficiency for H 2 evolution being ca. 1.7 and 0.7% at excitation wavelengths of 450 and 500 nm, respectively. Addition of electron donor/acceptor sacrificial reagents considerably affected the yield and stoichiometry of H 2 and O 2. At the same time, the product yield increased in a composition-dependent manner for (γ′-Fe 4N) x + (α-Fe 2O 3) 1-x nanocomposites. This activity augmentation is ascribed to the better dispersion of the active component γ′-Fe 4N and also to the availability of more active surface sites at Fe 4N/Fe 2O 3 contacts. Moreover, the proximity of the valence band potential of the component photosystems promotes the preferential transfer/entrapment of photoexcited hole carriers. We envisage that the defect/impurity-induced interband-gap energy states may play a vital role in these charge-transfer processes, leading thereby to more effective e --h + separation and the enhanced rate of the water-splitting reaction. First-principles electronic structure analysis suggests that the extraordinary photocatalytic and optical properties of intermetallic γ′-Fe 4N may arise from the particle-size-dependent changes in electronic structure. © 2012 American Chemical Society.

Srinivasu K.,Bhabha Atomic Research Center | Ghosh S.K.,Bhabha Atomic Research Center
Journal of Physical Chemistry C | Year: 2012

Ab initio first-principles calculations were carried out to investigate lithium-dispersed two-dimensional carbon allotropes, viz. graphyne and graphdiyne, for their applications as lithium storage and hydrogen storage materials. The lithiation potentials (vs Li/Li +) and specific capacities in these materials are found to be enhanced considerably as compared to the conventional graphite-based electrode materials. Lithium metal binding to these carbon materials is found to be enhanced considerably and is more than the cohesive energy of lithium. Each lithium atom in these metal-dispersed materials is found to carry nearly one unit positive charge and bind molecular hydrogen with considerably improved adsorption energies. Our calculated hydrogen adsorption enthalpies (-3.5 to -2.8 kcal/mol) are very close to the optimum adsorption enthalpy proposed for ambient temperature hydrogen storage (-3.6 kcal/mol). We have also shown that the band gaps in these planar carbon allotropes can be tuned by varying the number of acetylenic bridging units which will have versatile applications in nanoelectronics. © 2012 American Chemical Society.

Rajesh T.,CSIR - National Chemical Laboratory | Rajarajan A.K.,Bhabha Atomic Research Center | Rajarajan A.K.,CSIR - National Chemical Laboratory | Gopinath C.S.,CSIR - National Chemical Laboratory | Devi R.N.,CSIR - National Chemical Laboratory
Journal of Physical Chemistry C | Year: 2012

Precious metal incorporated into stable lattices like perovskites can be envisaged as an alternative catalysts to address deactivation problems. Here we report the barium cerate perovskite doped with varying amounts of Pt as catalysts for the water-gas shift reaction whereby ionic Pt is evidenced to be active. It is found that maximum CO conversion occurs above 325 °C and increases more than 2-fold after the first cycle. XPS analysis shows that after the first cycle, more ionic Pt species are present on the surface of the catalyst. X-ray and neutron diffraction studies also indicate the presence of oxygen vacancies that increases with increasing Pt substitution. © 2012 American Chemical Society.

Jena N.K.,Bhabha Atomic Research Center | Chandrakumar K.R.S.,Bhabha Atomic Research Center | Ghosh S.K.,Bhabha Atomic Research Center
Journal of Physical Chemistry C | Year: 2012

The important contribution of DNA to modern day nanobiotechnology is sometimes ascribed to its potential role as a programmable building block for the assembly of nanomaterials. In this work, our density functional theory (DFT) based study explores the possibilities of using complexes of DNA bases (viz., adenine (A), thymine (T), guanine (G), and cytosine (C)) as well as DNA base pairs (such as A-T, C-G, and G4-quadruplex) with the gold cluster Au 3 as a model catalyst system for oxidation of CO to CO 2. The complexes are energetically stable, and our calculated binding energies of the gold cluster-DNA base complexes are found to match closely with the experimentally obtained heat of desorption of DNA bases on Au films. Our results also reveal that the oxidation of CO on these complexes takes place exclusively via an Eley-Rideal (E-R) type of mechanism whereas both E-R and Langmuir-Hinshelwood (L-H) mechanisms for this reaction are observed for a bare Au 3 cluster. More interestingly, the CO oxidation reaction on the gold cluster (in the complexes) is found to be more facile, with a lesser activation barrier and higher heat of formation of the products, as compared to that of a pristine Au 3 cluster. Our results suggest that DNA base-gold cluster complexes can be an attractive and efficient catalytic model system that can have wider ramifications. Since the nanoscale gold is already known as a potential catalyst for variety of chemical reactions, our approach will richly supplement to the expanding horizons of catalysis involving gold. © 2012 American Chemical Society.

Kakade S.,Bhabha Atomic Research Center | Ghosh R.,Bhabha Atomic Research Center | Palit D.K.,Bhabha Atomic Research Center
Journal of Physical Chemistry C | Year: 2012

{Zinc 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine} (ZnPC) exists as monomeric species in DMSO and is reasonably strong fluorescent. But ZnPC forms H-aggregates in water and hexafluoroisopropanol, which are strong hydrogen bonding solvents. Nanoaggregates are nearly nonemissive. Transient absorption spectroscopic technique has been used to investigate the excited state relaxation processes in both monomeric and aggregated forms of ZnPC. The lifetime of the S 1 state of the monomoric form in DMSO is long (τ = 3.4 ns) but the excited states of ZnPC nanoaggregates show much faster ground state recovery (within 100 ps). The longest lifetime component, τ 3, which is independent of excitation density, has been assigned to the unimolecular decay of the S 1-exciton in the absence of annihilation reaction, while τ 1 and τ 2 are the lifetimes obtained by the two-component fit of the nonexponential decay arising due to the time-dependent decay rates of the S 1-excitons because of diffusive migration controlled exciton - exciton annihilation reaction. Rates of the annihilation reaction (2.0 × 10 -6 cm 3s -1) and exciton migration (4.3 × 10 -5 m 2/s) as well as diffusion length (about 85 nm) of the S 1-exciton created in the ZnPC nanoaggregates in HFIP have been determined. © 2012 American Chemical Society.

Manna D.,Bhabha Atomic Research Center | Ghanty T.K.,Bhabha Atomic Research Center
Journal of Physical Chemistry C | Year: 2012

The electronic structures, bonding, stability, aromaticity, and spectroscopic properties of the endohedral metallofullerenes, M@C 20 (M = Pr -, Pa -, Nd, U, Pm +, Np +, Sm 2+, Pu 2+, Eu 3+, Am 3+, Gd 4+, and Cm 4+), have been investigated in a unified and systematic way using relativistic density functional theory (DFT) within the framework of zeroth-order regular approximation. The bare C 20 cage with D 3d point group transforms to highly symmetrical I h structure through encapsulation of an f-block metal atom/ion with 6 valence electrons. The calculated values of HOMO-LUMO gap lie in the range of 2.5-4.9 eV (8.8-11.5 eV) at the B3LYP (HF) level. The stability of these metal encapsulated clusters can be attributed to the fulfillment of 26 valence electrons criteria corresponding to the fully occupied 2s2p1d atomic shells, where strong participation of the central metal atom orbitals in the a g, t 1u, g u, and h g valence molecular orbitals have been observed. © 2012 American Chemical Society.

Kaniyankandy S.,Bhabha Atomic Research Center | Rawalekar S.,Bhabha Atomic Research Center | Ghosh H.N.,Bhabha Atomic Research Center
Journal of Physical Chemistry C | Year: 2012

We report synthesis and ultrafast charge transfer dynamics of photoexcited CdTe quantum dots (QDs) decorated on graphene. We have synthesized CdTe QD particles of 2.2 nm sizes with first exciton (1S 3/2-1S e) band ∼450 nm and then decorated the QD particles on graphene which has been confirmed by HRTEM studies. The CdTe QD decorated graphene has been named as G-CdTe. Steady state emission studies revealed that on the graphene surface CdTe emission gets quenched drastically which indicates the charge transfer from photoexcited CdTe to graphene. To unravel the charge transfer dynamics in ultrafast time scale we have carried out femtosecond transient absorption studies by exciting the CdTe QD particles and monitoring the transients in the visible to near-IR region. Transient absorption studies indicate that exciton recombination time (as monitored the exciton bleach) of pure CdTe QD takes place within 50 ps; however, on graphene the surface exciton recombination time was found to be much longer (>1 ns). Our studies clearly indicate that charge separation of G-CdTe composite materials drastically improves as compared to that CdTe QD. © 2012 American Chemical Society.

Jha D.K.,Bhabha Atomic Research Center | Kant T.,Indian Institute of Technology Bombay | Singh R.K.,Bhabha Atomic Research Center
Nuclear Engineering and Design | Year: 2012

A higher order shear and normal deformation theory (HOSNT) is presented for free vibration analysis of functionally graded (FG) elastic, rectangular, and simply supported (diaphragm) plates. Functionally graded materials (FGMs), although heterogeneous are idealized as continua with their mechanical properties changing smoothly with respect to the spatial coordinates. The material properties of FG plates are assumed to be varying through thickness of the plate in a continuous manner. Poisson's ratio is assumed to be constant, but their Young's moduli and densities vary continuously in the thickness direction according to the volume fraction of constituents, which is mathematically modelled as power law function. The equations of motion are obtained using Hamilton's principle employing HOSNT. Navier solution method is used to solve the equations of motion. The effect of variation of material properties in terms of gradation index on the natural frequencies of FG plates is studied in this article. In this study, the effects of aspect ratios, thickness ratio, material variations of FG plates on their natural frequencies are examined. It is thought that the tabulated results would be a reference for other researchers to compare their results. © 2012 Elsevier B.V.

The reactions between dimethylsulfonium methylide and 1,3-diene- or 1,3,5-triene-1,1-dioates under specific conditions enable the highly regioselective tandem ylide addition-eliminative olefination to provide 1,3-butadien-2-yl- or 1,3,5-hexatriene-2-yl-malonates. Alkylation at malonate methine carbon of 1,3-butadien-2-ylmalonates with a suitable alkyl halide having in-built functionalities for a dienophile generation led to quick assembly of precursors for type 2 intramolecular Diels-Alder reaction. Syntheses of functionalized bicyclo[n.3.1] alkenes (n=5 or 6) with the double bond at the bridgehead position have been achieved via the IMDA. An asymmetric version of this reaction has been developed using a MacMillan's imidazolidinone catalyst, which provided a bicyclo[5.3.1] alkene with very high enantioselectivity. In situ methylation at malonate methine carbon of 1,3,5-hexatriene-2-yl-malonates followed by intermolecular Diels-Alder reaction with N-methylmaleimide provided the cycloadduct with complete regiocontrol and high diastereoselectivity. © 2010 Elsevier Ltd. All rights reserved.

Chavan N.L.,University of Pune | Nayak S.K.,Bhabha Atomic Research Center | Kusurkar R.S.,University of Pune
Tetrahedron | Year: 2010

A rapid and efficient method for stereoselective synthesis of new substituted tetrahydro-α-carbolines using Diels-Alder reaction under microwave irradiation has been developed. Further, dehydrogenation of these adducts resulted in synthesis of new substituted α-carbolines. © 2010 Elsevier Ltd. All rights reserved.

Senthilkumar S.T.,Bharathiar University | Selvan R.K.,Bharathiar University | Melo J.S.,Bhabha Atomic Research Center | Sanjeeviraja C.,Alagappa Chettiar College of Engineering And Technology
ACS Applied Materials and Interfaces | Year: 2013

The activated carbon was derived from tamarind fruit shell and utilized as electrodes in a solid state electrochemical double layer capacitor (SSEDLC). The fabricated SSEDLC with PVA (polyvinyl alcohol)/H2SO4 gel electrolyte delivered high specific capacitance and energy density of 412 F g-1 and 9.166 W h kg-1, respectively, at 1.56 A g -1. Subsequently, Na2MoO4 (sodium molybdate) added PVA/H2SO4 gel electrolyte was also prepared and applied for SSEDLC, to improve the performance. Surprisingly, 57.2% of specific capacitance (648 F g-1) and of energy density (14.4 Wh kg -1) was increased while introducing Na2MoO4 as the redox mediator in PVA/H2SO4 gel electrolyte. This improved performance is owed to the redox reaction between Mo(VI)/Mo(V) and Mo(VI)/Mo(IV) redox couples in Na2MoO4/PVA/H 2SO4 gel electrolyte. Similarly, the fabricated device shows the excellent capacitance retention of 93% for over 3000 cycles. The present work suggests that the Na2MoO4 added PVA/H 2SO4 gel is a potential electrolyte to improve the performance instead of pristine PVA/H2SO4 gel electrolyte. Based on the overall performance, it is strongly believed that the combination of tamarind fruit shell derived activated carbon and Na2MoO 4/PVA/H2SO4 gel electrolyte is more attractive in the near future for high performance SSEDLCs. © 2013 American Chemical Society.

Kumar S.,Bhabha Atomic Research Center | Aswal V.K.,Bhabha Atomic Research Center | Kohlbrecher J.,Paul Scherrer Institute
Langmuir | Year: 2012

The size-dependent interaction of anionic silica nanoparticles with ionic (anionic and cationic) and nonionic surfactants has been studied using small-angle neutron scattering (SANS). The surfactants used are anionic sodium dodecyl sulfate (SDS), cationic dodecyltrimethyl ammonium bromide (DTAB), and nonionic decaoxyethylene n-dodecylether (C 12E 10). The measurements have been carried out for three different sizes of silica nanoparticles (8, 16, and 26 nm) at fixed concentrations (1 wt % each) of nanoparticles and surfactants. It is found that irrespective of the size of the nanoparticles there is no significant interaction evolved between like-charged nanoparticles and the SDS micelles leading to any structural changes. However, the strong attraction of oppositely charged DTAB micelles with silica nanoparticles results in the aggregation of nanoparticles. The number of micelles mediating the nanoparticle aggregation increases with the size of the nanoparticle. The aggregates are characterized by fractal structure where the fractal dimension is found to be constant (D ≈ 2.3) independent of the size of the nanoparticles and consistent with diffusion-limited-aggregation-type fractal morphology in these systems. In the case of nonionic surfactant C 12E 10, micelles interact with the individual silica nanoparticles. The number of adsorbed micelles per nanoparticle increases drastically whereas the percentage of adsorbed micelles on nanoparticles decreases with the increase in the size of the nanoparticles. © 2012 American Chemical Society.

Ghosh S.,Bhabha Atomic Research Center | Kumar M.K.,Bhabha Atomic Research Center | Kain V.,Bhabha Atomic Research Center
Applied Surface Science | Year: 2013

The oxidation behavior of grade 304L stainless steel (SS) subjected to different surface finishing (machining and grinding) operations was followed in situ by contact electric resistance (CER) and electrochemical impedance spectroscopy (EIS) measurements using controlled distance electrochemistry (CDE) technique in high purity water (conductivity < 0.1 μS cm-1) at 300 °C and 10 MPa in an autoclave connected to a recirculation loop system. The results highlight the distinct differences in the oxidation behavior of surface worked material as compared to solution annealed material in terms of specific resistivity and low frequency Warburg impedance. The resultant oxide layer was characterized for (a) elemental analyses by glow discharge optical emission spectroscopy (GDOES) and (b) morphology by scanning electron microscopy (SEM). Oxide layers with higher specific resistivity and chromium content were formed in case of machined and ground conditions. Presence of an additional ionic transport process has also been identified for the ground condition at the metal/oxide interface. These differences in electrochemical properties and distinct morphological features of the oxide layer as a result of surface working were attributed to the prevalence of heavily fragmented grain structure and presence of martensite. © 2012 Elsevier B.V. All rights reserved.

Laik A.,Bhabha Atomic Research Center | Mishra P.,Bhabha Atomic Research Center | Bhanumurthy K.,Bhabha Atomic Research Center | Kale G.B.,Bhabha Atomic Research Center | Kashyap B.P.,Indian Institute of Technology Bombay
Acta Materialia | Year: 2013

A metal-ceramic bonding process was developed to produce vacuum tight alumina-Inconel 600 joints using an Ag-based active metal brazing alloy that can withstand continuous operating temperature up to 560 °C. The microstructure and microchemistry of the braze zone was examined using extensive microanalysis of the constituent phases and a mechanism for the interfacial reactions responsible for the bonding is proposed. Prolonged heat treatment at 400 and 560 °C under simulated in-service conditions revealed that the microstructure of braze zone of the joints was stable and maintained leak-tightness and strength. The bond strength of the interface was high enough to cause failure in the alumina side of the joints. Failure of the joints was caused by initiation of crack on the surface of alumina as a result of high tensile residual stress adjacent to the metal-ceramic interface. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Manna D.,Bhabha Atomic Research Center | Ghanty T.K.,Bhabha Atomic Research Center
Journal of Physical Chemistry C | Year: 2012

Density functional theory (DFT) within the framework of zeroth order regular approximation has been used to predict a new class of stable clusters through encapsulation of an actinide or lanthanide atom/ion into the C 26 cage. The electronic structures, bonding, stability, aromaticity and spectroscopic properties of these endohedral metallofullerenes, M@C 26 (M = Pr-, Pa-, Nd, U, Pm+, Np+, Sm2+, Pu2+, Eu3+, Am 3+, Gd4+, and Cm4+) have been investigated systematically using DFT and its time-dependent variant. On encapsulation of an f-block metal atom/ion with 6 valence electrons, the classical bare open shell C26 cage with D3h symmetry and ellipsoid shape is transformed to a more spherical closed shell D3h structures with high HOMO-LUMO gap (in the range of 2.44-3.99 eV for M@C26 clusters as compared to 1.62 eV for the bare C26 cage). Calculated binding energy values imply that all of the M@C26 clusters are stable with respect to dissociation into atomic fragments. Moreover, thermodynamic parameters indicate that the encapsulation process is highly favorable for all of the actinides and some of the lanthanides considered here. A higher stability and nearly spherical shape of M@C26 system is rationalized through the fulfillment of 32-electron principle corresponding to the fully occupied spdf atomic shells for the encapsulated central atom, where considerable amount of overlap between the metal and cage orbitals has been found. Thus, the calculated structural and energetic parameters strongly suggest the possible formation of M@C26 species under appropriate experimental conditions. Furthermore, the present work implies that the 32-electron principle might be important in designing of new materials involving lanthanides and actinides. © 2012 American Chemical Society.

Srinivasu K.,Bhabha Atomic Research Center | Ghosh S.K.,Bhabha Atomic Research Center
Journal of Physical Chemistry C | Year: 2012

Transition metal decorated carbon materials like fullerenes and nanotubes have been studied extensively for hydrogen adsorption applications. However, the weaker metal binding energy makes these materials unsuitable for making a stable hydrogen storage material. Here, using ab initio based density functional theory (DFT) calculations, we have studied the hydrogen adsorption in transition metal doped porphyrin-like porous fullerene, C24N 24. This porous fullerene is generated through truncated doping of 24 carbon atoms by 24 nitrogen atoms, and the resulting fullerene contains six N4 cavities with a cavity diameter of 3.708 Å These N 4 cavities are found to bind with transition metal atoms (Sc, Ti, and V) very strongly, and the binding energies are found to be considerably larger than (nearly double) the corresponding metal cohesive energies. These transition metal sites are found to adsorb molecular hydrogen through well-known Kubas-type interactions. The calculated adsorption energies of molecular hydrogen around the different metal sites are found to be in the range of -9.0 to -3.0 kcal/mol, which is considered to be the enthalpy range required for ambient condition hydrogen storage. In the case of C24N 24Sc6, the maximum hydrogen adsorption capacity is found to be ∼5.1 wt % with a total of 24 H2 molecules adsorbed around the metal doped fullerene. © 2012 American Chemical Society.

Nigam S.,Bhabha Atomic Research Center | Majumder C.,Bhabha Atomic Research Center
Journal of Physical Chemistry C | Year: 2012

The decomposition of SO3 is energetically the most demanding step for producing hydrogen through the sulfur-iodine thermochemical cycle. Using first principles density functional theory, we report a comparative study of the SO3 interaction with three tetramer clusters (Ag4, Pd4, and Ag2Pd2) deposited on the alumina surface. All calculations are performed using the plane wave based pseudopotential approach under the spin-polarized density functional theory. The results reveal that the supported Ag-Pd bimetallic clusters are more efficient to weaken the S-O bond in the SO3 molecule. A comparison of the SO3 interaction with Ag4, Pd4, and Ag 2Pd2 tetramers showed that while Ag4 elongates the S-O bond by 7%, Ag2Pd2@Al2O3 can stretch the S-O bond up to 14%. The higher efficiency of the Ag 2Pd2@Al2O3 system is attributed to both excess charge transfers from the oxide surface and the combination of acceptor-donor properties of Pd and Ag, respectively, which makes a better catalyst for weakening the S-O bond in the SO3 molecule. © 2012 American Chemical Society.

Dash A.,Bhabha Atomic Research Center | Chakravarty R.,Bhabha Atomic Research Center
Industrial and Engineering Chemistry Research | Year: 2014

This review provides a comprehensive summary of the role of the electrochemical separation process to develop next-generation radionuclide generators to meet future research and clinical demands. This innovative technology paradigm, straddling the disciplines of electrochemistry and separation science, is poised to serve as a springboard to spur new breakthroughs and bring evolutionary progress in radionuclide generator technology. Without doubt, the major impetus for the advancement in radionuclide generator technology stems from nuclear medicine requirements, as a means of obtaining short-lived radionuclides on demand for the formulation of a gamut of diagnostic and therapeutic radiopharmaceuticals. The tremendous prospects associated with the use of electrochemical radionuclide generators in nuclear medicine dictate that a holistic consideration should given to all governing factors that determine their success. The purpose of this paper is to present a concise and comprehensive review of the latest research and development activities in the utility of electrochemical separation process in development of radionuclide generators that have already established footholds of acceptance in nuclear medicine and are expected to change the future landscape of radionuclide generator technology. This review provides a summary of the principle, factors that govern the electrochemical separation, desirable characteristics of the generator systems developed with typical examples, critical assessment of recent developments, contemporary status, key challenges, and apertures to the near future. © 2014 American Chemical Society.

Rastogi L.,Bhabha Atomic Research Center | Arunachalam J.,Bhabha Atomic Research Center
Advanced Materials Letters | Year: 2013

A green synthetic approach for the highly stable, size controlled synthesis of gold nanoparticles is being described. The study explores the use of aqueous extract of garlic cloves as reducing/stabilizing agent for the synthesis of gold nanoparticles. The synthesis is achieved by heating the mixture of aqueous garlic extract and HAuCl4 at 95°C in water bath at pH-10 for 2 hrs. The formation of gold nanoparticles was confirmed from the appearance of pink color and an absorption maximum at 530 nm. Further, extract concentration and type of alkali (NH4OH/NaOH) has been varied to tune the size of nanoparticles. The size of the synthesized gold nanoparticles was found to decrease (56.5 ± 13.6 to 24.7 ± 8.2) with increasing extract concentration (0.5%-1.0%) in the presence of NH4OH. In the presence of NaOH, the synthesis time was reduced to 20 min, with an average particle size of 5.5 ± 2.7. Transmission electron microscopy analysis indicated that non-aggregated gold nanoparticles of various sizes could be synthesized by simple change in reaction conditions. The synthesized gold nanoparticles were found to be pure face centered cubic crystals as suggested by selected area electron diffraction and X-ray diffraction patterns. Fourier transform infrared spectroscopy revealed possible role of S-allyl-cysteine as the major component responsible for reduction of Au3+ to Au0 and protein/amino acids as stabilizing agents. The gold nanoparticles were found to have remarkable in vitro stability: showed no sign of aggregation at room temperature storage for a long time (more than 6 months), could resist aggregation in aqueous media with high concentrations of NaCl, in various buffers including: cysteine, histidine, bovine serum albumin and at host of pH ranges. Further, cytotoxicity evaluations on S. cerevisiae have shown non-toxic nature of the synthesized gold nanoparticles up to 100 μM of concentration as assessed by well diffusion and inhibition of colony forming efficiency assay. Ease in size control, high stability and biocompatible nature of garlic extract reduced, stabilized gold nanoparticles suggests that they could be potential candidates for drug delivery applications. ©2013 VBRI press.

Khot V.M.,The Interdisciplinary Center | Salunkhe A.B.,The Interdisciplinary Center | Thorat N.D.,The Interdisciplinary Center | Ningthoujam R.S.,Bhabha Atomic Research Center | Pawar S.H.,The Interdisciplinary Center
Dalton Transactions | Year: 2013

MgFe2O4 nanoparticles with sizes around 20 nm have been prepared by a combustion method and functionalized with dextran for their possible applications in magnetic particle hyperthermia. The induction heating study of these nanoparticles at different magnetic field amplitudes, from 6.7 kA m-1 to 26.7 kA m-1, showed self-heating temperature rise up to 50.25 °C and 73.32 °C (at 5 mg mL-1 and 10 mg mL -1 concentrations in water respectively) which was primarily thought to be due to hysteresis losses activated by an AC magnetic field. The dextran coated nanoparticles showed a maximum specific absorption rate (SAR) of about 85.57 W g-1 at 26.7 kA m-1 (265 kHz). Dextran coated nanoparticles at concentrations below 1.8 mg mL-1 exhibit good viability above 86% on mice fibroblast L929 cells. The results suggest that combustion synthesized MgFe2O4 nanoparticles coated with dextran can be used as potential heating agents in magnetic particle hyperthermia. Uncoated and dextran coated samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric-differential thermal analysis (TG-DTA) and zeta potential-DLS studies. © The Royal Society of Chemistry 2013.

Pal A.,Indian Institute of Science | Datta S.,Indian Institute of Science | Aswal V.K.,Bhabha Atomic Research Center | Bhattacharya S.,Indian Institute of Science | Bhattacharya S.,Chemical Biology Unit
Journal of Physical Chemistry B | Year: 2012

Planar imidazolium cation based gemini surfactants [16-Im-n-Im-16], 2Br- (where n = 2, 3, 4, 5, 6, 8, 10, and 12), exhibit different morphologies and internal packing arrangements by adopting different supramolecular assemblies in aqueous media depending on their number of spacer methylene units (CH2)n. Detailed measurements of the small-angle neutron-scattering (SANS) cross sections from different imidazolium-based surfactant micelles in aqueous media (D2O) are reported. The SANS data, containing the information of aggregation behavior of such surfactants in the molecular level, have been analyzed on the basis of the Hayter and Penfold model for the macro ion solution to compute the interparticle structure factor S(Q) taking into account the screened Coulomb interactions between the dimeric surfactant micelles. The characteristic changes in the SANS spectra of the dimeric surfactant with n = 4 due to variation of temperature have also been investigated. These data are then compared with the SANS characterization data of the corresponding gemini micelles containing tetrahedral ammonium ion based polar headgroups. The critical micellar concentration of each surfactant micelle (cmc) has been determined using pyrene as an extrinsic fluorescence probe. The variation of cmc as a function of spacer chain length has been explained in terms of conformational variation and progressive looping of the spacer into the micellar interior upon increasing the n values. Small-angle neutron-scattering (SANS) cross sections from different mixed micelles composed of surfactants with ammonium headgroups, 16-A 0, [16-Am-n-Am-16], 2Br- (where n = 4), 16-I0, and [16-Im-n-Im-16], 2Br- (where n = 4), in aqueous media (D 2O) have also been analyzed. The aggregate composition matches with that predicted from the ideal mixing model. © 2012 American Chemical Society.

Sharma G.,Bhabha Atomic Research Center | Mukherjee P.,Variable Energy Cyclotron Center | Chatterjee A.,Bhabha Atomic Research Center | Gayathri N.,Variable Energy Cyclotron Center | And 2 more authors.
Acta Materialia | Year: 2013

The effect of irradiation damage on the microstructure evolution and mechanical properties in nanocrystalline (nc) Ni with an average grain size of ∼60 nm was studied. Samples were irradiated at doses of 1.6 × 10 15, 2.3 × 1015, 5 × 1015 and 2.3 × 1016 He2+ cm-2 by 12 MeV He ions at room temperature. Microstructural parameters like domain size and microstrain were studied in detail using the X-ray diffraction (XRD) technique with the simplified breadth method and Williamson-Hall analysis. The average domain size was found to decrease systematically with the increase in irradiation dose. Microscopic observations made with transmission electron microscopy showed dislocation loops and dislocation networks within the grain interior of the irradiated sample. In addition, irradiation at a higher dose showed small amounts of the sand-like black dots inside some grains, which could be due to the accumulation of point defects. Tensile tests performed on the irradiated sample were compared with unirradiated samples. The irradiated sample showed higher ultimate tensile strength and average work-hardening rate as compared to the unirradiated sample. Nanoindentation studies were performed to study the effect of irradiation on deformation parameters like strain rate sensitivity (m) and activation volume (V-). The value of m was found to increase whereas V- was found to decrease with increase in irradiation dose. Fracture surfaces of the tensile sample were investigated by SEM. The fracture morphology of the unirradiated sample showed dimpled rupture with much large dimple diameter and depth. The irradiated sample also showed dimple rupture but with much finer dimple diameter with wide size distribution and shallow depths. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Ganguly R.,Bhabha Atomic Research Center | Sharma J.N.,Bhabha Atomic Research Center | Choudhury N.,Bhabha Atomic Research Center
Journal of Colloid and Interface Science | Year: 2011

N,N,N′,N′-tetraoctyl diglycolamide abbreviated as TODGA, is one of the most promising extractant for actinide partitioning from high level nuclear waste. It forms reverse micelles in non polar solvents on equilibration with aqueous HNO 3 solutions. This reverse micellar system undergoes phase separation into dilute and concentrated reverse micellar solutions at high aqueous acid concentration. Small angle neutron scattering (SANS) studies reported in the literature explained this phenomenon based on gas-liquid type phase transition in the framework of Baxter adhesive hard sphere theory in the presence of a strong inter-micellar attractive interaction. The present investigation attempts to throw further light on this system by carrying out systematic dynamic light scattering (DLS) and viscometry studies, and their modeling on the TODGA reverse micellar solutions in the dodecane medium. The variation of the diffusion coefficient with the micellar volume fraction observed from the DLS studies is suggestive of the presence of an attractive interaction between the TODGA reverse micelles, which weakens at the high micellar volume fraction due to the increased dominance of the excluded volume effect. It is suggested that this weakened interaction is responsible for the absence of phase separation in this system at high TODGA concentration. The results thus highlight the importance of the presence of an attractive interaction between the TODGA micelles in determining the observed phase separation in the TODGA reverse micellar systems. The modeling of the DLS and viscosity data, however, suggest that the characteristic stickiness parameter of this system could be smaller than the critical value required for inducing a gas-liquid type phase transition. © 2010 Elsevier Inc.

Vaghela N.M.,Sardar Patel University | Sastry N.V.,Sardar Patel University | Aswal V.K.,Bhabha Atomic Research Center
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2011

The influence of two salts as additives namely sodium chloride and sodium sulphate and a nonelectrolyte, 2-butoxyethanol on surface chemical and aggregation characteristics of ionic liquids (IL) of 1-octyl-3-methylimidazolium chloride, [C8mim][Cl], 1-octyl-3-methylimidazolium bromide, [C8mim][Br], and 1-octyl-3-methylimidazolium iodide, [C8mim][I] in aqueous media were monitored through surface tension and small angle neutron scattering measurements. The addition of salts drastically decreased the critical aggregation concentration (CAC) and increased the area per adsorbed IL molecule. The co-ions of salts modify the surface of IL molecules and aggregates through various interactions such as charge neutralization, specific interactions and dehydration The results obtained by analyzing the SANS curves in the whole Q range showed that the oblate ellipsoidal shape of the aggregates of ionic liquids is un-altered upon the addition of additives. However the additives facilitate the growth of the aggregates in to microstructures with cubic packing at high salt concentrations. © 2010 Elsevier B.V.

Pandit S.,Indian Institute of Technology Kharagpur | Sengupta A.,Indian Institute of Technology Kharagpur | Kale S.,Bhabha Atomic Research Center | Das D.,Indian Institute of Technology Kharagpur
Bioresource Technology | Year: 2011

The performance of the cathodic electron acceptors (CEA) used in the two-chambered microbial fuel cell (MFC) was in the following order: potassium permanganate (1.11V; 116.2mW/m2)>potassium persulfate (1.10V; 101.7mW/m2)>potassium dichromate, K2Cr2O7 (0.76V; 45.9mW/m2)>potassium ferricyanide (0.78V; 40.6mW/m2). Different operational parameters were considered to find out the performance of the MFC like initial pH in aqueous solutions, concentrations of the electron acceptors, phosphate buffer and aeration. Potassium persulfate was found to be more suitable out of the four electron acceptors which had a higher open circuit potential (OCP) but sustained the voltage for a much longer period than permanganate. Chemical oxygen demand (COD) reduction of 59% was achieved using 10mM persulfate in a batch process. RALEX™ AEM-PES, an anion exchange membrane (AEM), performed better in terms of power density and OCP in comparison to Nafion®117 Cation Exchange Membrane (CEM). © 2010 Elsevier Ltd.

Maity P.,Bhabha Atomic Research Center | Debnath T.,Bhabha Atomic Research Center | Ghosh H.N.,Bhabha Atomic Research Center
Journal of Physical Chemistry Letters | Year: 2013

Ultrafast charge-transfer (CT) dynamics has been demonstrated in CdS quantum dot (QD)-4′,5′-dibromofluorescein (DBF) composite materials, which form a strong CT complex in the ground state. Charge separation in the CdS-DBF composite was found to take place in three different pathways, by transferring the photoexcited hole of CdS to DBF, electron injection from photoexcited DBF to the CdS QD, and direct electron transfer from the HOMO of DBF to the conduction band of the CdS QD. CT dynamics was monitored by direct detection of the DBF cation radical and electron in the QD in the transient absorption spectra. Electron injection and the electron-transfer process are found to be pulse-width-limited (<100 fs); however, the hole-transfer time was measured to be 800 fs. Charge recombination dynamics has been found to be very slow, confirming spatial charge separation in the CdS-DBF supersensitized quantum dot system. Grand charge separation process suggests that the CdS-DBF supersensitized quantum dot system can be used as superior materials for quantum dot solar cells (QDSCs). © 2013 American Chemical Society.

Mudliar N.H.,Bhabha Atomic Research Center | Singh P.K.,Bhabha Atomic Research Center
Chemistry - A European Journal | Year: 2016

Most macrocyclic host molecules, including cyclodextrins, usually prevent self-aggregation of the guest organic molecules, by exploiting inclusion complexation of the guest with the host. In this work, it was found that a negatively charged β-cylcodextrin derivative induces aggregation of a well-known amyloid sensing dye, Thioflavin-T, and leads to an unprecedented formation of the rarely observed emissive H-type aggregates of the dye. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Patil A.B.,Bhabha Atomic Research Center | Patil A.B.,University of Pune | Pathak P.,Bhabha Atomic Research Center | Shinde V.S.,University of Pune | And 2 more authors.
Dalton Transactions | Year: 2013

Solvent extraction studies of actinide metal ions such as Am(iii), U(vi), Np(iv), Np(vi), Pu(iv) were carried out in a nitric acid medium using two diamides (L) viz. (DMDBTDMA (N,N′-dimethyl-N,N′-dibutyl-2- tetradecylmalonamide) and DMDOHEMA (N,N′-dimethyl-N,N′-dioctyl-2- (2′-(hexyloxy)ethyl)-malonamide) dissolved in different room temperature ionic liquids (RTILs). The use of RTILs as the diluent significantly enhanced metal ion extraction as compared to that observed in non polar diluent such as n-dodecane. The effects of parameters such as kinetics, aqueous phase acidity (0.01-3 M HNO3), metal ion oxidation states, diamide concentration on the extraction of metal ions were studied. The stoichiometry of the extracted Am(iii) species using these diamides varied with ligand concentration viz. (Am.3L)3+ ([L] = 0.005-0.02 M) and (Am.2-2.5L)3+ ([L] = 0.05-0.1 M). Time resolved laser induced fluorescence spectroscopy (TRLFS) studies showed that the extracted species of Eu(iii) in an ionic liquid medium had no coordinated water molecules, in contrast to the presence of 1-2 water molecules in the extracted species in a n-dodecane medium. The radiolytic degradation behavior of the diamides/RTIL system has been studied using IR spectroscopy and gas chromatography-mass spectrometry (GC-MS). The data revealed that a significantly lower ligand concentration is required for actinide extraction in ionic liquids as the extraction media as compared to nonpolar diluents. © The Royal Society of Chemistry 2013.

Nandy S.K.,Bhabha Atomic Research Center | Rajan M.G.R.,Bhabha Atomic Research Center
Applied Radiation and Isotopes | Year: 2010

A novel fully automated radiosynthesis procedure for the fluorine-18 analog of 1-α-D-(5'-deoxy-5'-fluoro-(1S,2R,3S,4S) arabinofuranosyl)-2-nitroimidazole ([ 18F]FAZA) using a commercially available combination column - Chromabond ® Set V (FDG-base-hydrolysis) - for purification was developed. [ 18F]FAZA was prepared via a one-pot, two-step synthesis using a nuclear interface nucleophilic synthesis module. Nucleophilic fluorination of the precursor molecule, 1-(2,3-di-O-acetyl-5-O-tosyl-α-D-arabinofuranosyl)-2-nitroimidazole, with no-carrier added [ 18F]fluoride followed by hydrolysis of the protecting groups with 0.3M NaOH was performed. Purification was carried out using the Chromabond ® Set V column without any modifications. The overall radiochemical yield obtained was 21.98±1.40% (n=5, without decay correction) within a total synthesis period of 51±1min. The radiochemical purity was greater than 95% and devoid of any other chemical impurities. The reported method can easily be adapted in any commercial FDG synthesis module. © 2010 Elsevier Ltd.

Charanpahari A.,Visvesvaraya National Institute of Technology | Umare S.S.,Visvesvaraya National Institute of Technology | Sasikala R.,Bhabha Atomic Research Center
Applied Surface Science | Year: 2013

A visible light active photocatalyst was synthesized by multiple doping of TiO2 with Ce, N and S. The multidoped catalyst showed higher photocatalytic activity for methyl orange degradation from aqueous solution compared to P25 and undoped TiO2. The photocatalytic activity decreased in the order Ce0.6NS-TiO2 > P25 > NS-TiO2 > Ce0.6-TiO2 > TiO2. TiO2 and doped TiO2 existed as anatase phase with average particle size of 10 nm. In the multidoped TiO2, N substituted for O whereas S substituted for Ti. UV-vis absorption spectra showed an increased visible light absorption for doped TiO2 compared to the undoped one. An increased fluorescence lifetime for the charge carriers was observed for the doped samples as compared to undoped TiO2. The enhanced photocatalytic activity of Ce0.6NS-TiO2 is attributed to a synergistic effect of the dopants in increasing the visible light absorption and lifetime of the photogenerated charge carriers. © 2013 Elsevier B.V. All rights reserved.

Srivastava S.C.L.,Variable Energy Cyclotron Center | Jain S.R.,Bhabha Atomic Research Center
Fortschritte der Physik | Year: 2013

Complex extension of quantum mechanics and the discovery of pseudo-unitarily invariant random matrix theory has set the stage for a number of applications of these concepts in physics. We briefly review the basic ideas and present applications to problems in statistical mechanics where new results have become possible. We have found it important to mention the precise directions where advances could be made if further results become available. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mitra A.,Bhabha Atomic Research Center
Gravitation and Cosmology | Year: 2013

For the first time, we express the general Friedmann-Robertson-Walker (FRW) metric (k = +1, 0,-1) into explicit "Schwarzschild" or "Curvature" form, which is important from the viewpoint of cosmology. With this form of the FRW metric, we reconsider the old problem of embedding a Schwarzschild mass (SM) in a pre-existing FRW background from the viewpoints of both (1) the enigmatic McVittie metric, obtained in 1933 and (2) the Einstein-Straus approach (1945) of scooping out a spherical cavity in the same background. Since the exterior of the SM is, by definition, described in the Schwarzschild coordinates, for a definitive study of the Einstein-Straus approach we employ this form of the FRW metric. We find that a necessary condition for a SM to participate in the cosmic expansion is that the background fluid is dust. © 2013 Pleiades Publishing, Ltd.

Auluck S.K.H.,Bhabha Atomic Research Center
IEEE Transactions on Plasma Science | Year: 2013

Some features of neutron emission from dense plasma focus suggest that the participating deuterons have energy in the range of 105eV and have a directionality of toroidal motion. Theoretical models of these devices assume that the plasma evolves through a purely irrotational flow and thus fail to predict such solenoidal flow on the scale of the plasma dimensions. Predictions of a relaxation theory are consistent with experimental data [S K H Auluck, Physics of Plasmas, 18, 032508 (2011)], but the assumptions upon which it is based are not compatible with known features of these devices. There is thus no satisfactory theoretical construct which provides the necessity for solenoidal flow in these devices. This paper proposes such theoretical construct, namely, the principle of constrained dynamics, and describes an experiment which provides support for this idea. The experiment consisted of low-inductance self-breaking spark discharge in helium at a pressure ∼ 100 hPa between two pointed electrodes separated by 30-50-mm distance kept inside a vacuum chamber mounted on a low-inductance high-voltage capacitor. The current derivative signal showed reproducible sharp dips at all of the extrema of the damped sinusoidal discharge. A planar diamagnetic loop centered with and perpendicular to the discharge axis consistently showed a signal representing rate of change of axial magnetic flux. The discharge plasma was very weakly ionized. Its acceleration was constrained by viscous drag of the neutrals, pressure gradient was constrained by heat conduction by neutrals, and at the same time, the axial current density and azimuthal magnetic field were constrained to follow an oscillatory temporal profile. Under these conditions, radial momentum balance equation cannot be satisfied unless the plasma possesses a degree of freedom, which supplies the shortfall in momentum balance. Azimuthal symmetry of the plasma allows azimuthal current density to provide such degree of freedom. A qualitative explanation of observed phenomena is obtained using a simple model. © 1973-2012 IEEE.

Mitra A.,Bhabha Atomic Research Center
Journal of Cosmology and Astroparticle Physics | Year: 2013

The total Einstein energy (P0) of a homogeneous and isotropic universe can be computed by using an appropriate superpotential (Rosen 1994) and also by a direct method (Mitra 2010). Irrespective of the physical significance of P0, its eventual numerical value must be same in both the cases because both are derived from the same Einstein pseudo tensor and by employing the same coordinates. It follows then that the static isotropic and homogeneous universe, i.e., Einstein's static universe (ESU), must have an infinite radius and which tantamounts to a spatially flat case. The physical significance of this result is that the cosmological constant, Λ, is actually zero and ESU is the vacuous Minkowski spacetime. It is the same result which has recently been obtained in a completely independent manner (Mitra, Bhattacharyya & Bhatt 2013). Thus even though, mathematically, one can conceive of a static 3-sphere for the foundation of relativistic cosmology, physically, no such 3-sphere exists. On the other hand, the spatial section of the universe could essentially be an Euclidean space with local curvature spikes due to presence of lumpy matter. Since the ''Dark Energy'' is associated with Λ in the ΛCDM model, the result obtained here suggests that it is an artifact of departure of the lumpy and fractal universe from the ideal Friedmann Robertson Walker model (Jackson et al. 2012, Cowley et al. 2013).© 2013 IOP Publishing Ltd and Sissa Medialab srl.

Singh A.K.,Bhabha Atomic Research Center | Kutty T.R.G.,Bhabha Atomic Research Center | Sinha S.,Bhabha Atomic Research Center
Journal of Nuclear Materials | Year: 2012

Among ceramics and oxides, Yttria (Y 2O 3) films have been widely investigated as potential corrosion protective coatings largely on account of their wear resistant and non-wettable properties. Results presented here describe successful use of pulsed laser deposition (PLD) technique for deposition of thin film Yttria coating on stainless steel substrates. Deposited Yttria coatings have been characterized in terms of their microstructure, crystalline phase and hardness using Scanning Electron Microscope (SEM), X-ray diffraction (XRD) and scratch test techniques, respectively. Characterization tests of these coatings of thickness up to 50 μm have shown strong bonding with substrate surface and a high degree of homogeneity and compaction. Resistance of these PLD based Yttria coatings to molten uranium have also been studied via Differential Thermal Analysis (DTA). Our results on DTA tests evaluating compatibility of the Yttria coatings with molten uranium have established the excellent corrosion resistance property of such Y 2O 3 coatings when exposed to molten uranium. © 2011 Elsevier B.V. All rights reserved.

1H MAS NMR spectra of Bi0.05Eu0.05Y 0.90PO4·xH2O show chemical shift from -0.56 ppm at 300 K to -3.8 ppm at 215 K and another one at 5-6 ppm, which are related to the confined or interstitial water in the hexagonal structure and water molecules on the surface of the particles, respectively. Negative value of the chemical shift indicates that H of H2O is closer to metal ions (Y3+ or Eu3+ ), which is a source of luminescence quencher. H coupling and decoupling 31P MAS NMR spectra at 300 and 250 K show the same chemical shift (-0.4 ppm) indicating that there is no direct bond between P and H. It is concluded that the confined water is not frozen even at 215 K because of the less number of H-bonding.

Mishra G.,Bhabha Atomic Research Center | Gupta N.K.,Bhabha Atomic Research Center
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2013

A three-dimensional molecular dynamic approach is employed to investigate the ionization dynamics of small Xe400 clusters irradiated by intense lasers (I = 1016W cm-2) in the near infrared wavelength region (λ = 800 nm). The pulse duration of the incident laser is varied from a few cycles (τ = 2T0 with T0 as one laser time cycle) to many cycles (τ = 8T0). In the case of pulse durations of a few cycles, the carrier-envelope (CE) phase of the incident laser electric field is found to be an important parameter that affects the ionization dynamics of Xe clusters. The fractions of various ionized Xe species are observed to be different for the two values of the CE phases (φ = 0 and φ = π/2) in the case of the shorter laser pulse duration of τ = 2T0. The nature of the instantaneous electric field (the rising or falling edge of the field) at the time of birth of the electron due to ionization decides the extent of ionization. The difference in time-evolution of the electric field for the two values of the CE phase leads to an observable disparity in the yield of various ionic species. For the case of a pulse duration of many cycles (τ = 8T0), these differences average out and we do not observe any change in the yield of various ionic species for the two values of the CE phase. © 2013 IOP Publishing Ltd.

Karmakar S.,Bhabha Atomic Research Center
High Pressure Research | Year: 2013

We describe a technique for making electrical transport measurements in a diamond anvil cell at liquid helium temperature having in situ pressure measurement option, permitting accurate pressure determination at any low temperature during the resistance measurement scan. In general, for four-probe resistivity measurements on a polycrystalline sample, four fine gold wires are kept in contact with the sample with the help of the compression from the soft solid (usually alkali halides such as NaCl, KCl, etc.) acting as a pressure-transmitting medium. The actual pressure on the sample is underestimated if not measured from a ruby sphere placed adjacent to the sample and at that very low temperature. Here, we demonstrate the technique with a quasi-four-probe resistance measurement on an Fe-based superconductor in the temperature range 1.2-300 K and pressures up to 8 GPa to find an improved pressure dependence of the superconducting transition temperature. © 2013 Copyright Taylor and Francis Group, LLC.

Ahmed Z.,Bhabha Atomic Research Center
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2013

In quantum scattering, Hermiticity is necessary for both reciprocity and unitarity. Reciprocity means that both reflectivity (R) and transmitivity (T) are insensitive to the direction of incidence of a wave (particle) at a scatterer from left/right. Unitarity means that R+T=1. In scattering from non-Hermitian PT-symmetric structures the (left/right) handedness (non-reciprocity) of reflectivity is known to be essential and unitarity remains elusive so far. Here we present a surprising occurrence of both reciprocity and unitarity in some parametric regimes of scattering from a complex PT-symmetric potential. In special cases, we show that this potential can even become invisible (R=0, T=1) remarkably this time from both left and right sides. We also find that this potential in a parametric regime enjoys a pseudo-unitarity of the type: T+RleftRright=1. © 2013 Elsevier B.V.

The PHENIX experiment provides excellent capabilities to measure particles containing s/sbar quarks in a wide transverse momentum (p T) range using a combination of different analysis techniques. In this article, we present latest PHENIX result on production of K ±, Ks, K * and φ at intermediate and high p T in p + p, d+Au, Cu + Cu and Au + Au collisions at √sNN=200 GeV. The nuclear modification factors are obtained for d+Au and heavy ion collisions at different centralities covering a wide range of transverse momenta. The systematic study of these mesons improve the understanding of the strange meson production and their difference from light hadrons. © 2013 Elsevier B.V.

Recent resurgence of interest in applications of dense plasma focus and doubts about the conventional view of dense plasma focus as a purely irrotational compressive flow have re-opened questions concerning device optimization. In this context, this paper re-appraises and extends the analytical snowplow model of plasma focus sheath evolution developed by F. Gratton and J. M. Vargas [Energy Storage, Compression and Switching, edited by V. Nardi, H. Sahlin, and W. H. Bostick (Plenum, New York, 1983), Vol. 2, p. 353)] and shows its relevance to contemporary research. The Gratton-Vargas (GV) model enables construction of a special orthogonal coordinate system in which the plasma flow problem can be simplified and a model of sheath structure can be formulated. The Lawrenceville Plasma Physics (LPP) plasma focus facility, which reports neutron yield better than global scaling law, is shown to be operating closer to an optimum operating point of the GV model as compared with PF-1000. © 2013 AIP Publishing LLC.

Abdulsalam A.,Bhabha Atomic Research Center | Shukla P.,Bhabha Atomic Research Center
International Journal of Modern Physics A | Year: 2013

The bottomonium states due to their varying binding energies dissolve at different temperatures and thus their nuclear modification factors and relative yields have potential to map the properties of Quark-Gluon Plasma (QGP). We estimate the suppression of bottomonia states due to color screening in an expanding QGP of finite lifetime and size with the conditions relevant for PbPb collisions at Large Hadron Collider. The properties of Υ states and recent results on their dissociation temperatures have been used as ingredients in the study. The nuclear modification factors and the ratios of yields of Υ states are then obtained as a function of transverse momentum and centrality. We compare our theoretical calculations with the bottomonia yields measured with CMS in PbPb collisions at sNN = 2.76 TeV. The model calculations explain the data very well. © 2013 World Scientific Publishing Company.

Ghorui S.,Bhabha Atomic Research Center | Das A.K.,Bhabha Atomic Research Center
Physics of Plasmas | Year: 2013

Choice of an appropriate form of shielding distance in the estimation of collision integrals under screened coulomb potential for two-temperature non-equilibrium plasma is addressed. Simple expressions for collision integrals for charged-charged interactions are derived. It is shown that while some of the formalisms used earlier completely ignore the presence of ions, the others incorporating it may result in negative collision integrals for the interactions involving particles at higher charged states. The parametric regimes of concern and impact of different formalisms on the computed transport properties are investigated with specific reference to nitrogen plasma. A revised definition of the shielding distance is proposed, which incorporates both electrons and ions, avoids the problem of negative collision integrals in all practical regimes of interest and results in calculated property values in close agreement with experimentally observed results. © 2013 AIP Publishing LLC.

Constant pH molecular dynamics (CpHMD) is a commonly used sampling method, which incorporates the coupling of conformational flexibility and protonation state of a protein during the simulation by using pH as an external parameter. The effects on the structure and stability of a hyperstable variant of staphylococcal nuclease (Δ+PHS) protein of an artificial charge pair buried in its hydrophobic core are investigated by applying both CpHMD and accelerated molecular dynamics coupled with constant pH (CpHaMD) methods. Generalized Born electrostatics is used to model the solvent water. Two sets of starting coordinates of V23E/L36K variant of Δ+PHS, namely, Maestro generated coordinates from Δ+PHS and crystal structure coordinates of the same are considered for detail investigations. On the basis of root mean square displacement (RMSD) and root mean square fluctuations (RMSF) calculations, it is observed that this variant is stable over a wide range of pH. The calculated pKa values for aspartate and glutamate residues based on both CpHMD and CpHaMD simulations are consistent with the reported experimental values (within ± 0.5 to ± 1.5 pH unit), which clearly indicates that the local chemical environment of the carboxylic acids in V23E/L36K variant are comparable to the parent form. The strong salt bridge interaction between the mutated pair, E23/K36 and additional hydrogen bonds formed in the V23E/L36K variant, may help to compensate for the unfavorable self-energy experienced by the burial of these residues in the hydrophobic core. However, from RMSD, RMSF, and pKa analysis, no significant change in the global conformation of V23E/L36K variant with respect to the parent form, Δ+PHS is noticed. © 2014 Wiley Periodicals, Inc.

Shah S.,Bhabha Atomic Research Center | Sensarma P.S.,Indian Institute of Technology Kanpur
IEEE Transactions on Power Electronics | Year: 2010

Voltage controlled voltage source inverters (VCVSI) are predominantly used as an interface between source and grid in distributed generation. Modularity of system is achieved by parallel operation of several VCVSI of reduced rating. In this paper, a 3-DOF control scheme is proposed for parallel operation of three phase inverters to enable equal load sharing even during transients while tracking a common sinusoidal voltage reference. The voltage reference is either free running or derived from grid voltage and can be used to synchronize a parallel inverter module with any utility grid. The control algorithm for each inverter is identical, and it is independent of terminal parameters of other inverters, granting N+1 modularity to the system. The proposed fast inner voltage loop with second-order controller and lead compensators enable stable operation at low switching frequencies. A voltage correction is added to the reference to ensure sharing of higher order load current harmonics among inverters. A method to estimate the system tolerance to parametric uncertainties and delays is developed using μ-analysis and a method is presented to improve it. The analysis is validated with simulation and experimental results on two 110 Vac/2.5 kVA three-phase inverters, paralleled to form a stand-alone grid and feeding a nonlinear load. © 2010 IEEE.

Hankare P.P.,Shivaji University | Patil R.P.,Shivaji University | Jadhav A.V.,Shivaji University | Garadkar K.M.,Shivaji University | Sasikala R.,Bhabha Atomic Research Center
Applied Catalysis B: Environmental | Year: 2011

Nanocomposite of magnetically separable, TiO2-ZnFe2O4 with an intermediate layer of alumina has been synthesized by a multistep wet chemical process. UV-vis absorption spectra show a red shift of the absorption edges for the composite systems compared to single phase TiO2. Magnetic measurements indicate that the ZnFe2O4 is ferromagnetic at room temperature with low coercivity when the applied field is low, typical of soft magnetic materials. After TiO2 and alumina coatings, the samples show similar magnetic behaviour. Photocatalytic activity studies for methyl red and thymol blue degradation indicate an enhanced activity for the composites when the alumina interlayer is present between TiO2 and ZnFe2O4. When Pd is used as a co-catalyst in TiO2-ZnFe2O4, an enhanced activity is observed, which is comparable to that of TiO2-Al2O3-ZnFe2O4. The present study leads to a new result that an insulating interlayer like alumina can enhance the photocatalytic activity of TiO2 coated ferrites as much as that of a noble metal co-catalyst like Pd. The enhanced photocatalytic activity of TiO2-Al2O3-ZnFe2O4 is attributed to the decrease in the migration of photogenerated charge carriers to zinc ferrite layer and due to the increased adsorption of the reactants on the surface of TiO2-Al2O3-ZnFe2O4. © 2011 Elsevier B.V.

Karimpil J.J.,Bhabha Atomic Research Center | Melo J.S.,Bhabha Atomic Research Center | D'Souza S.F.,Bhabha Atomic Research Center
Journal of Molecular Catalysis B: Enzymatic | Year: 2011

Enzyme stabilization via immobilization is one of the preferred processes as it provides the advantages of recovery and reusability. In this study, Thermomyces lanuginosus lipase has been immobilized through crosslinking using 2% glutaraldehyde and hen egg white, as an approach towards CLEA preparation. The immobilization efficiency and the properties of the immobilized enzyme in terms of stability to pH, temperature, and denaturants was studied and compared with the free enzyme. Immobilization efficiency of 56% was achieved with hen egg white. The immobilized enzyme displayed a shift in optimum pH towards the acidic side with an optimum at pH 4.0 whereas the pH optimum for free enzyme was at pH 6.0. The immobilized enzyme was stable at higher temperature retaining about 83% of its maximum activity as compared to the free enzyme retaining only 41% activity at 70 °C. The denaturation of lipase in free form was rapid with a half-life of 2 h at 60 °C and 58 min at 70 °C as compared to 12 h at 60 °C and 2 h at 70 °C for the immobilized enzyme. The effect of denaturants, urea and guanidine hydrochloride on the free and immobilized enzyme was studied and the immobilized enzyme was found to be more stable towards denaturants retaining 74% activity in 8 M urea and 98% in 6 M GndHCl as compared to 42% and 33% respectively in the case of free enzyme. The apparent K m (2.08 mM) and apparent V max (0.95 μmol/min) of immobilized enzyme was lower as compared to free enzyme; K m (8.0 mM) and V max (2.857 μmol/min). The immobilized enzyme was reused several times for the hydrolysis of olive oil. © 2011 Elsevier B.V. All Rights Reserved.

Swapnalee B.T.,Bhabha Atomic Research Center | Vijayan P.K.,Bhabha Atomic Research Center
International Journal of Heat and Mass Transfer | Year: 2011

The heat transport capability of natural circulation loops is directly proportional to the flow rate it can generate. Therefore, reliable prediction of flow rate is essential for design and performance evaluation of natural circulation loops. The reported generalized flow equation applicable for single-phase natural circulation is only valid for cases where the entire loop follows a single friction law. Such a situation arises when the natural circulation loop is either fully laminar or fully turbulent. It is possible that a natural circulation loop can be partly laminar and partly in transition or turbulent flow. In such cases, a single friction law is not applicable throughout the loop. In the present study, a generalized flow equation is proposed for cases where a single friction law is not applicable for the entire loop. The proposed equation is tested with experimental data generated in a uniform diameter rectangular loop and is found to be in good agreement. Subsequently the equation is tested with data reported in the literature. Stability analysis reported in literature for single-phase loops are either for laminar or turbulent flows. In practice, in natural circulation loops, all the flow regimes like laminar, transition and turbulent are observed. Therefore, it is required to develop a stability map, which is valid for all the three regions. In the present paper, such a stability map is presented. © 2011 Elsevier Ltd. All rights reserved.

Srinivasu K.,Bhabha Atomic Research Center | Ghosh S.K.,Bhabha Atomic Research Center
Journal of Physical Chemistry C | Year: 2012

Three-dimensional porous carbon materials based on supercubane structure are modeled through first principles based density functional theory calculations. The basic supercubane structure is expanded through the insertion of acetylinic and diacetylinic units between both inter- and intracubane C-C bonds leading to more variety of porous carbon materials. The supercubane is found to be an insulator with an indirect band gap of 5.26 eV and the gap is found to decrease on introducing the acetylinic linking groups between the intercubane C-C bonds. The completely carbomerized supercubane structures are also found to be insulators. We have also calculated the phonon dispersion and the variation in free energy with increasing temperature to verify the stability of the materials considered. The calculated free energy profiles are compared with some of the previously studied carbon allotropes to show the possible thermodynamic stability of these 3D carbon systems. The complex frequency-dependent dielectric constant has been calculated for all the designed structures to study the optical properties such as absorption spectra and energy-loss spectra. As these designed structures are associated with high porosity and reactive carbon sites, we have investigated their hydrogen adsorption properties and it is observed that the expanded supercubanes can adsorb hydrogen with a gravimetric density of ∼2.0 wt %. © 2012 American Chemical Society.

Dash K.,Bhabha Atomic Research Center | Rastogi L.,Bhabha Atomic Research Center | Arunachalam J.,Bhabha Atomic Research Center
Analyst | Year: 2012

Accurate quantification of deoxyribonucleic acid (DNA) is critical for many analyses in molecular biology and genetic tests. We present a method in which the stoichiometrically existing phosphorus content in purified genomic DNA is quantitatively converted into orthophosphate ions by microwave assisted-UV digestion in the presence of microlitre quantities of dilute reagents (HCl, HNO 3, H 2O 2). The tandem use of microwave energy and ultraviolet photons for DNA digestion in pressurized quartz vessels enables a maximum reaction temperature of 240 °C resulting in efficient and fast mineralization of high molecular weight DNA within 30 minutes. Compared to hotplate digestion, the digestion time is reduced by a factor of 32. The MW-UV sample preparation approach coupled with the ion chromatographic measurement of phosphate using a high performance (HP) methodology provides an accurate quantitation of phosphorus mass fractions as low as 0.3 μg g -1, corresponding to a DNA mass of 25 μg. The relative expanded uncertainties (% U) expressed at 95% confidence for these analyses range from 0.2 to 0.6%. Critically, the matrix of the calibrant solution is also matched with respect to the digested matrix anions (chloride, nitrate), without which significant bias in IC performance is observed. The phosphorus content of the calf thymus DNA was also measured using high-performance inductively coupled plasma optical emission spectroscopy (HP-ICP-OES), which provided independent data for comparison with the MW-UV digestion-IC based approach. Ion chromatography requires smaller volume of materials to perform the analysis and could be useful for characterizing primary calibration standards and certified reference materials with low uncertainties. © 2012 The Royal Society of Chemistry.

Tyagi A.K.,Bhabha Atomic Research Center | Ramkumar J.,Bhabha Atomic Research Center | Jayakumar O.D.,Bhabha Atomic Research Center
Analyst | Year: 2012

Lead metal ions are of great concern and the monitoring of their concentration in the environment has become extremely important. In the present study, a new inorganic-organic hybrid assay of Ag nanorods (AgNR)-Rhodamine 6G (R6G) was developed for the sensitive and selective determination of Pb 2+ ions in aqueous solutions. To the best of our knowledge there is almost no literature on the use of silver nanorod sensors for determination of lead ions in aqueous solutions. The sensor is developed by the coating of R6G on the surface of AgNRs. The sensing is based on the photoluminescence of R6G. The sensor was rapid as the measurements were carried out within 3 min of addition of the test solution to the AgNR-R6G hybrid. Moreover, the system showed excellent stability at tested concentration levels of Pb 2+ ions. The naked eye detection of the colour was possible with 1 mg L -1 of Pb 2+ ions. The present method has a detection limit of 50 μg L -1 of Pb 2+ (for a signal/noise (S/N) ratio > 3). The selectivity toward Pb 2+ ions against other metal ions was improved using chelating agents. The proposed method was validated by analysis using different techniques. © 2012 The Royal Society of Chemistry.

Jayasekharan T.,Bhabha Atomic Research Center | Sahoo N.K.,Bhabha Atomic Research Center
Rapid Communications in Mass Spectrometry | Year: 2010

Silver ion complexes of peptides [M + (Ag)n]+, M = angiotensin I or substance P where n = 1-8 and 17-23 for angiotensin I and n = 1-5 for substance P, are identified and characterized using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The Ag+ coordination number exceeds the number of available amino acid residues in angiotensin I whereas the number of observed complexes in substance P is less than the number of amino acid residues in it. The larger coordination number of angiotensin I with Ag+ indicates the simultaneous binding of several Ag+ ions to the amino acid residue present in it. The lower number of observed complexes in substance P suggests the binding of two or more residues to one Ag+ ion. The presence of trifluoroacetic acid in the peptide samples reduces the Ag+ coordination ability in both the peptides which indicates that the basic residues in it are already protonated and do not participate in the Ag+-binding process. The Ag+ ion also forms a complex with the α-cyano-4-hydroxycinnamic acid (CHCA) matrix and is observed in the MALDI mass spectra and the formation of [CHCA + Ag]+, [CHCA + AgNO3]+ and [(CHCA)2 + Ag]+ ions is due to the high binding affinity of Ag+ to the CN group of CHCA. Copyright © 2010 John Wiley & Sons, Ltd.

Kuroda D.G.,University of Pennsylvania | Singh P.K.,University of Pennsylvania | Singh P.K.,Bhabha Atomic Research Center | Hochstrasser R.M.,University of Pennsylvania
Journal of Physical Chemistry B | Year: 2013

The degenerate transition corresponding to asymmetric stretches of the D3h tricyanomethanide anion, C(CN)3-, in aqueous solution was investigated by linear FTIR spectroscopy, femtosecond pump-probe spectroscopy, and 2D IR spectroscopy. Time resolved vibrational spectroscopy shows that water induces vibrational energy transfer between the degenerate asymmetric stretch modes of tricyanomethanide. The frequency-frequency correlation function and the vibrational energy transfer show two significantly different ultrafast time scales. The system is modeled with molecular dynamics simulations and ab initio calculations. A new model for theoretically describing the vibrational dynamics of a degenerate transition is presented. Microscopic models, where water interacts axially and radially with the ion, are suggested for the transition dipole reorientation mechanism. © 2012 American Chemical Society.

Kaniyankandy S.,Bhabha Atomic Research Center | Rawalekar S.,Bhabha Atomic Research Center | Ghosh H.N.,Bhabha Atomic Research Center
Journal of Materials Chemistry C | Year: 2013

We report the synthesis, structural characterisation and charge separation behaviour in an interface graded Type II CdSe-CdTe core-shell nanostructure. The gradation was accomplished by the use of two layers consisting of an alloyed composition with increasing Te composition between the CdSe core and finally a CdTe shell grown by the successive ionic layer adsorption and reaction (SILAR) method. The effect of gradation was analysed by steady state UV-Vis absorption, photoluminescence (PL) spectroscopy, time-resolved luminescence and femtosecond transient absorption spectroscopy and was found to be immensely beneficial in improving the quantum yield as compared to an ungraded core-shell. Improvement in charge separation was further ascertained by temperature dependent luminescence studies and time correlated single photon counting studies. Better charge separation behaviour accompanied by a more robust PL yield is indicative of better surface passivation and band alignment for charge carrier funnelling. The reduction in stress was further verified by Raman studies where the Raman peak position was used as an index for stress in the film. This journal is © 2013 The Royal Society of Chemistry.

Sharma B.B.,Bhabha Atomic Research Center | Murli C.,Bhabha Atomic Research Center | Sharma S.M.,Bhabha Atomic Research Center
Journal of Raman Spectroscopy | Year: 2013

Acrylamide (C3H5NO), a hydrogen-bonded amide, is an important compound from the point of view of basic and material research. It can be used as a model system for studying hydrogen bonding interactions in amides under pressure. As it is a monomer of polyacrylamide, an important polymer, high pressure investigation of polymerization in this material is also of interest. Our in-situ high pressure Raman spectroscopic investigations of acrylamide carried out up to 17 GPa under quasi-hydrostatic conditions indicate possible structural variations through the reconstruction of the N-H - -O hydrogen bonds at pressures above 2.6 GPa. Emergence of several new spectral features at higher pressures indicate onset of polymerization. The characteristic polymer band becomes discernible at ~17 GPa. The increase in the relative intensity of the polymer peaks with respect to the monomer peaks on release to ambient conditions suggests that higher fraction of polymer is obtained on decompression. Copyright © 2013 John Wiley & Sons, Ltd.

Banerjee M.,Bhabha Atomic Research Center | Ballal A.,Bhabha Atomic Research Center | Apte S.K.,Bhabha Atomic Research Center
Biochemical Journal | Year: 2012

Prxs (peroxiredoxins) are ubiquitous thiol-based peroxidases that detoxify toxic peroxides. The Anabaena PCC 7120 genome harbours seven genes/ORFs (open reading frames) which have homology with Prxs. One of these (all1541) was identified to encode a novel Grx (glutaredoxin) domain-containing Prx by bioinformatic analysis. A recombinant N-terminal histidine-tagged All1541 protein was overexpressed in Escherichia coli and purified. Analysis with the protein alkylating agent AMS (4-acetamido-4′-maleimidyl-stilbene-2, 2′-disulfonate) showed All1541 to form an intra-molecular disulfide bond. The All1541 protein used glutathione (GSH) more efficiently than Trx (thioredoxin) to detoxify H 2O 2. Deletion of the Grx domain from All1541 resulted in loss of GSH-dependent peroxidase activity. Employing site-directed mutagenesis, the cysteine residues at positions 50 and 75 were identified as peroxidatic and resolving cysteine residues respectively, whereas both the cysteine residues within the Grx domain (positions 181 and 184) were shown to be essential for GSH-dependent peroxidase activity. On the basis of these data, a reaction mechanism has been proposed for All1541. In vitro All1541 protein protected plasmid DNA from oxidative damage. In Anabaena PCC 7120, all1541 was transcriptionally activated under oxidative stress. Recombinant Anabaena PCC 7120 strain overexpressing All1541 protein showed superior oxidative stress tolerance to H 2O 2 as compared with the wild-type strain. The results suggest that the glutathione-dependent peroxidase All1541 plays an important role in protecting Anabaena from oxidative stress. © The Authors Journal compilation © 2012 Biochemical Society.

The objective of this study was to examine the effect of 60Co-gamma (γ) radiation on modulation of genomic DNA methylation, if any, of mice maintained (6weeks) on normal control diet (NCD) and l-methionine supplemented diet (MSD). To elucidate the possible underlying mechanism(s), we exposed the animals to γ-radiation (2, 3 and 4Gy) and investigated the profile of downstream metabolites and enzymes involved in S-adenosyl-l-methionine (SAM) generation. Liver samples were also subjected to histopathological examinations. Compared to NCD fed and irradiated animals, hepatic folate, choline and l-methionine levels decreased moderately, while hepatic SAM levels increased in MSD fed and irradiated animals. Under these conditions, a marked modulation of methionine adenosyltransferase (MAT) and l-methionine synthase (MSase) activities was observed. Concomitant with increase in liver SAM pool, increased DNA methyltransferase (dnmt) activity in MSD fed mice indicated enhanced metabolic flux towards DNA methylation. Further results showed that genomic DNA methylation and 5-methyl-2'-deoxy cytidine residues were maintained at normal levels in MSD fed and irradiated mice compared to NCD fed and irradiated animals. In conclusion, our results suggest that increasing supply of preformed methyl groups, via dietary l-methionine supplementation might significantly increase methylation potential of radiation stress compromised DNA methylation cycle. © 2014 Elsevier Ltd.

The Gibbs free energy of formation of Er2Ru2O 7(s) has been determined using solid-state electrochemical technique employing oxide ion conducting electrolyte. The reversible electromotive force (e.m.f.) of the following solid-state electrochemical cell has been measured:(-)Pt/{Er2O3(s) + Er2Ru 2O7(s) + Ru(s)}//CSZ//O2(p(O2) = 21.21 kPa)/Pt(+). The Gibbs free energy of formation of Er2Ru 2O7(s) from elements in their standard state, calculated by the least squares regression analysis of the data obtained in the present study, can be given by:{ΔfG° (Er2Ru 2O7,s) / (kJ·mol-1) ± 2.2} = - 2517.3 + 0.6099 · (T/K); (934.6 ≤ T/K ≤ 1236.3). Standard molar heat capacity C°p,m(T) of Er2Ru2O 7(s) was measured using a heat flux type differential scanning calorimeter (DSC) in two different temperature ranges, from 129 K to 296 K and 307 K to 845 K. The heat capacity in the higher temperature range was fitted into a polynomial expression and can be represented by: C° p,m(Er2Ru2O7,s,T)(J·K -1·mol-1) = 293.88 + 2.397 10-2 T(K) - 54.74717 105/T2(K); (307 ≤ T(K) ≤ 845). The heat capacity of Er2Ru2O7(s), was used along with the data obtained from the oxide electrochemical cell to calculate the standard enthalpy and entropy of formation of the compound at 298.15 K. © 2013 Elsevier B.V. All rights reserved.

Bhadwal M.,Bhabha Atomic Research Center
The quarterly journal of nuclear medicine and molecular imaging : official publication of the Italian Association of Nuclear Medicine (AIMN) [and] the International Association of Radiopharmacology (IAR), [and] Section of the Society of Radiopharmaceutical Chemistry and Biology | Year: 2014

A novel unsymmetrically substituted water soluble porphyrin derivative namely, 5-(p-amino-propylene--oxyphenyl)-10,15,20-tris-(p-carboxy-methyl-ene-oxyphenyl)porphyrin was synthesized and coupled with a bifunctional chelating agent, viz. p-NCS-benzyl-DOTA (p-isothiocyanatobenzyl-1,4,7,10-tetra-aza-cyclodo-decane-1,4,7,10-tetra-acetic acid) for developing a suitable conjugate for use in targeted tumor therapy. The porphyrin-p-NCS-benzyl-DOTA conjugate was radiolabeled with 177Lu in good radiolabeling yield. Biodistribution studies performed in Swiss mice bearing fibrosarcoma tumors revealed high tumor uptake (5.33±1.11% injected activity per gm of tumor) within 30 min post-injection. The complex exhibited favorable tumor to blood and tumor to muscle ratios at various post-administration time points. Fast clearance of the non-accumulated activity was observed mostly through the renal pathway. Scintigraphic imaging studies performed in Swiss mice bearing fibrosarcoma tumors also exhibited selective accumulation of activity in the tumor.

Jayakumar O.D.,Bhabha Atomic Research Center | Mandal B.P.,Bhabha Atomic Research Center | Majeed J.,Bhabha Atomic Research Center | Lawes G.,Wayne State University | And 2 more authors.
Journal of Materials Chemistry C | Year: 2013

Flexible and self-standing inorganic-organic hybrid films of silica coated Fe3O4 nanoparticles and polyvinylidene fluoride (PVDF) polymer with significant magneto-dielectric coupling have been prepared at low temperature by a simple solvent casting method. PVDF films with two different concentrations of silica coated Fe3O4 (4.76 and 9.09 wt%) have been developed and well characterized using different techniques like XRD, TEM and IR. The thin film coating of silica on Fe3O4 could be detected by IR and TEM. The ferroelectric, magnetic and magneto-capacitive measurements at room temperature confirm the multiferroic nature of the composite films with significant magneto-electric coupling between Fe 3O4 and PVDF. © 2013 The Royal Society of Chemistry.

Singh M.K.,Raja Ramanna Center for Advanced Technology | Banerjee A.,Raja Ramanna Center for Advanced Technology | Banerjee A.,Bhabha Atomic Research Center
Crystal Growth and Design | Year: 2013

We report a computational method to investigate the mechanism through which the solvent interacts with the crystal surfaces during the crystal growth process. We have considered the role of the internal, crystal-solution interfacial structure and external growth environments affecting crystal growth to predict the growth morphology by calculating relative growth rate of different crystal faces. The interfacial structure and bonding energies of solute and solvent molecules of faces having different crystallographic orientations are obtained using periodic first-principles density functional method. The effects of molecular orientation of growth units and surface relaxation of the habit faces have also been considered in order to identify the adsorption of rate-determining molecules to different faces of crystals for their growth. On the basis of the analysis of interfacial structure and external growth environment, the expression for growth rates relating the level of supersaturation, temperature, solubility, bonding energies of solute-surface, solvent-surface, and the rate of growth has been derived. The method is applied to study growth morphology of two molecular crystals, namely, urea and β-succinic acid crystals from vapor and different solvents. The results obtained from calculations match well with the corresponding available experimental data. The remarkable agreement between the predicted growth shapes and the corresponding experimental results allow us to understand the role played by solvents and external growth factors on growth morphologies of molecular crystals. © 2013 American Chemical Society.

Gangamallaiah V.,Bhabha Atomic Research Center | Dutt G.B.,Bhabha Atomic Research Center
Journal of Physical Chemistry B | Year: 2013

Temperature-dependent fluorescence anisotropies of a nonpolar solute 9-phenylanthracene (9-PA) have been measured in 1-alkyl-3-methylimidazolium- based ionic liquids with anions such as bis(trifluoromethylsulfonyl)imide ([Tf2N-]), tris(pentafluoroethyl)trifluorophosphate ([FAP]), tetrafluoroborate ([BF4), and hexafluorophosphate ([PF6) to find out if the organized structure of the ionic liquid has a bearing on solute rotation. Analysis of the experimental data using the Stokes-Einstein-Debye hydrodynamic theory indicates that there is no significant variation in the solute-solvent coupling constants (Cobs) with an increase in the length of the alkyl chain on the imidazolium cation for the ionic liquids with [Tf2N] and [FAP] anions. However, in the case of ionic liquids with [BF4] and [PF6] anions, the rotation of 9-PA for a given viscosity at constant temperature becomes progressively faster and Cobs decreases by a factor of 2.4 from ethyl to octyl derivatives. Quasihydrodynamic theories of Gierer-Wirtz and Dote-Kivelson-Schwartz could not account for the significant decrease in the Cobs values. The observed behavior has been rationalized in terms of the organized structure of the ionic liquids having [BF4] and [PF6] anions, which results as a consequence of the high charge-to-size ratio of these anions compared to [Tf2N] and [FAP]. © 2013 American Chemical Society.

Prabhu S.R.,Bhabha Atomic Research Center | Dutt G.B.,Bhabha Atomic Research Center
Journal of Physical Chemistry B | Year: 2013

Rotational diffusion of two ionic probes, cationic rhodamine 110 (R110) and anionic fluorescein (FL), has been examined in reverse micelles formed with the triblock copolymer (EO)13-(PO)30-(EO)13 (L64), where EO and PO represent ethylene oxide and propylene oxide units, respectively, with small amounts of water in p-xylene. This study has essentially been undertaken to explore the influence of mole ratio of water to copolymer (W) as well as copolymer concentration on probe rotation. On the basis of fluorescence lifetimes and reorientation times, it has been established that both R110 and FL are located in the interfacial region of L64/water/p-xylene reverse micellar system. The average reorientation time decreases by 10-35% with an increase in W for both the probes at a given copolymer concentration. However, for a particular W, the average reorientation time increases by 10-30% as the concentration of the copolymer is enhanced. From the micellar structural parameters available in the literature, critical packing parameters have been calculated for the L64/water/p-xylene reverse micellar system, and it has been noticed that the average reorientation times of both the probes scale linearly with the critical packing parameter. In essence, the results of this study indicate that the probe mobility in the interfacial region of block copolymer reverse micelles is governed by the micellar packing. © 2013 American Chemical Society.

Sundararajan M.,Bhabha Atomic Research Center
Journal of Physical Chemistry B | Year: 2013

Binding of hydrocarbon guests to supramolecular hosts can lead to unusual geometric changes such as bending or coiling of guests upon encapsulation. Cucurbiturils (CBs) are classic cation binders that were recently used for the selective binding of small-membered hydrocarbons with a very high association constant (Ka ≈ 106 M-1). In this study, we have systematically investigated the binding of some alkanes to CB-[6] using a series of quantum chemical methods. The calculated binding free energies are very strong and are largely influenced by guest orientations inside the host and reorganization of host and guests. The computed 1H NMR chemical shifts of the encapsulated alkanes agree with the experimental estimates thus confirming guest encapsulation. Further, we have shown that although binding of both cyclopentane and neopentane have very strong binding affinities (>20 kcal mol-1), the selectivity of cyclopentane to neopentane at CB-[6] is a kinetically driven process through the computation of approximate transition state structures of both alkanes to CB-[6]. The calculated binding affinities with dispersion corrected density functionals (DFs) are very close to the experimental estimates, whereas DFs that lack dispersion correction predict that alkane binding to CB-[6] is largely unfavorable. Finally, we have investigated the binding of some long chain alkanes to several supramolecular hosts using dispersion corrected semiempirical methods which cannot be routinely studied through density functional theory methods due to the larger size of the system. © 2013 American Chemical Society.

Kand P.,Bhabha Atomic Research Center | Basu S.,Bhabha Atomic Research Center
Journal of Laryngology and Otology | Year: 2014

Abstract Background: Renal metastasis is relatively unusual in patients with differentiated thyroid carcinoma. Methods: The clinicoradiological parameters of a series of patients with differentiated thyroid carcinoma and renal metastasis were assessed, together with follow-up data. Results and conclusion: The series comprised 4 male patients over the age of 45 years with extensive disease at the primary site. Retro-sternal extension of a large goitre was observed in three patients. The primary tumour was 4 cm or larger in all patients (range, 4-14 cm), and three patients had associated lymph node metastasis. None had any genito-urinary symptoms at presentation. Two patients had isolated renal metastases with no other distant metastases, while the others had extensive multi-organ involvement. The bilateral occurrence of lesions was a hallmark, being observed in all cases. Ultrasound-guided fine needle aspiration cytology and 131I scintigraphy were pivotal in confirming the diagnosis. Evidence of 'flip-flop' between 131I study and fluoro-deoxyglucose positron emission tomography was noted in one patient, while the other three demonstrated concordant lesions in both modalities. At a minimum follow-up period of four years after diagnosis, three patients demonstrated stable disease with radioiodine therapy, and one had expired due to a poorly differentiated lung carcinoma which developed subsequently. © JLO (1984) Limited 2014.

Subramanian S.,Bhabha Atomic Research Center
The quarterly journal of nuclear medicine and molecular imaging : official publication of the Italian Association of Nuclear Medicine (AIMN) [and] the International Association of Radiopharmacology (IAR), [and] Section of the Society of Radiopharmaceutical Chemistry and Biology | Year: 2014

This work aims to develop receptor based alternatives to the conventional colloidal tracers in sentinel lymph node (SLN) detection. In this study, we report the detailed biological evaluation of two dextran pyrazolyl mannose derivatives towards this purpose. The dextran pyrazolyl mannose derivatives (DAPM4 and DAPM8) were labeled with the [99mTc(CO)3(H2O)3]+ core. In vitro saturation binding studies for the ligands were performed in mannose receptor-bearing RAW 264.7 macrophage precursor cells. Localization and pharmacokinetics studies of the tracers were conducted in normal Wistar rats with different ligand concentrations using in vivo activity distribution and scintigraphic imaging techniques. The ligands were labeled with the [99mTc(CO)3)]+ core in high yield and radiochemical purity (>90%). DAPM4 and DAPM8 showed specific uptake in RAW 264.7 cells. In vivo localization studies showed concentration-dependent uptake and selective retention of the [99mTc]-labeled complexes of DAPM4 and DAPM8 in the sentinel node with highly favorable values of popliteal extraction [PE] (%PEDAPM4=92.94%,%PEDAPM8=91.80% at 180 min p.i.) and rapid clearance from the site of injection when administered at 50 μg/mL ligand concentration. [99mTc(CO)3]-complexes of DAPM4 and DAPM8 show good in vivo potential to undergo further testing as agents for SLN detection in the clinic and their biological efficacy varies depending upon the concentration of ligands used for the procedure.

Sinha S.,Bhabha Atomic Research Center
Applied Physics A: Materials Science and Processing | Year: 2013

A thermal model to describe high-power nanosecond pulsed laser ablation of yttria (Y2O3) has been developed. This model simulates ablation of material occurring primarily through vaporization and also accounts for attenuation of the incident laser beam in the evolving vapor plume. Theoretical estimates of process features such as time evolution of target temperature distribution, melt depth and ablation rate and their dependence on laser parameters particularly for laser fluences in the range of 6 to 30 J/cm2 are investigated. Calculated maximum surface temperatures when compared with the estimated critical temperature for yttria indicate absence of explosive boiling at typical laser fluxes of 10 to 30 J/cm2. Material ejection in large fragments associated with explosive boiling of the target needs to be avoided when depositing thin films via the pulsed laser deposition (PLD) technique as it leads to coatings with high residual porosity and poor compaction restricting the protective quality of such corrosion-resistant yttria coatings. Our model calculations facilitate proper selection of laser parameters to be employed for deposition of PLD yttria corrosion-resistive coatings. Such coatings have been found to be highly effective in handling and containment of liquid uranium. © 2013 Springer-Verlag Berlin Heidelberg.

Sonone R.L.,University of Pune | Jain S.R.,Bhabha Atomic Research Center
European Physical Journal: Special Topics | Year: 2013

We enumerate simple periodic orbits for the well-known Fermi-Pasta-Ulam (FPU) problem. Using these solutions as simple modes for the problem, we construct quantum solutions of the corresponding problem. These studies present a natural generalization of the concept of phonon in the nonlinear realm. © 2013 EDP Sciences and Springer.

Gangamallaiah V.,Bhabha Atomic Research Center | Dutt G.B.,Bhabha Atomic Research Center
Journal of Physical Chemistry B | Year: 2013

To understand the influence of organized structure of the ionic liquids on the rotational diffusion of a hydrogen bond donating ionic solute, reorientation times (τr) of rhodamine 110 (R110) have been measured in 1-alkyl-3-methylimidazolium ([Rmim+]) based ionic liquids with anions tetrafluoroborate ([BF4 -]) and hexafluorophosphate ([PF6-]). The viscosity (η) was varied by changing the temperature (T) and also the alkyl chain length on the imidazolium cation (ethyl, butyl, hexyl, and octyl). It has been noticed that τr versus η/T plots contain two slopes corresponding to lower and higher values of η/T for ionic liquids with [BF4 -] as well as [PF6 -] anions. For lower values of η/T (<0.2 and <0.3 mPa s K-1, respectively, for [Rmim+][BF 4 -] and [Rmim+][PF6 -]), rotational diffusion of R110 follows Stokes-Einstein-Debye hydrodynamic theory with stick boundary condition due to specific interactions between the solute and the anions of the ionic liquids. In contrast, at higher η/T, the rotational diffusion of the solute is faster than the stick predictions and this trend could not be explained by the quasihydrodynamic theories of Gierer-Wirtz and Dote-Kivelson-Schwartz as well. Diminishing hydrogen bonding interactions between the solute and the anions, which transpire as a consequence of the organized structure of the ionic liquids, are responsible for the observed behavior. © 2013 American Chemical Society.

Dey G.R.,Bhabha Atomic Research Center
Radiation Physics and Chemistry | Year: 2014

The reduction of Au3+ with free radicals such as esolv - and {bullet operator}CH2OH in methanol is reported. The rate constant values for esolv - and {bullet operator}CH2OH reactions with Au3+ were determined to be 6.5±1.0×109M-1s-1 and 1.6×109M-1s-1, respectively. In esolv --Au3+ reduction process, the time resolved spectra recorded exhibit three absorption bands with peaks maxima at 270, 370 and 470nm along with a strong bleaching around 320nm. Similarly, in presence of I-, the transient absorption spectrum obtained exhibits four well-defined bands with peaks maxima at 290, 355, 505 and 720nm, which were significantly different from those observed in the absence of I- under identical conditions. The difference in spectral and kinetics parameter in I- systems reveals the significance of I-, which helps in stabilization of various time-dependent transients formed in Au3+ reduction in methanol. The gold nanoparticles generated in γ-radiolysis were inert to oxygen. © 2014 Elsevier Ltd.

Verma A.K.,Bhabha Atomic Research Center | Karki B.B.,Louisiana State University
American Mineralogist | Year: 2010

Three {n10}/[001] tilt grain boundaries (n = 2, 3, and 4) of MgO were studied as a function of pressure from first principles within density functional theory. Our results show that the physical properties of the grain boundary are very distinct from the bulk properties. The predicted symmetric boundary containing well-defined dislocation pipes at zero pressure transforms to asymmetric boundaries with denser structures at higher pressures. The asymmetric boundary structure stable at 50 GPa can be associated with a shear in the boundary plane, whereas the asymmetric boundary structure stable at 100 GPa can be associated with an additional shear in the direction perpendicular to the boundary plane. Unlike in the bulk, several nonequivalent sites exist for vacancy formation in the boundary regions, and the calculated Schottky defect formation enthalpy varies among different boundaries with the {310} and {410} boundary values at zero pressure being similar to the bulk value. Pressure increasingly stabilizes the boundary vacancies relative to the bulk thereby causing an enhancement in the vacancy concentration, which is further enhanced due to high-binding energy for cation-anion vacancy pairs in the interfacial regions. Also, the grain boundary was shown to induce electronic states in the band gap below the conduction band, which can trap the electrons inside the free space at the interface. Additional states with strong electron localization character appear at the boundary in the presence of the vacancies. Our results are expected to be useful to understand how grain boundaries can serve as primary storage sites for defects and high-diffusion pathways.

Bera A.K.,Bhabha Atomic Research Center | Yusuf S.M.,Bhabha Atomic Research Center | Banerjee S.,Indian Department of Atomic Energy
Solid State Sciences | Year: 2013

Structural and magnetic properties of the geometrically frustrated layered compound YBaCo4O7 have been studied by magnetization and neutron diffraction. A layered type crystal structure, with alternating tetrahedral layers of Kagomé and triangular types, along the c axis (hexagonal symmetry, space group P63mc) has been found. The oxygen content of the present compound was determined by iodometric titration to be 7.00 ± 0.01. Presence of a short-range antiferromagnetic ordering (below TN ∼ 110 K) has been concluded from the appearance of an addition broad magnetic peak (at Q ∼ 1.35 Å-1) in the neutron diffraction pattern. A staggered chiral type (3×3) spin structure in the Kagomé layers has been found. Presence of a significant magneto-structural coupling is concluded from the changes in lattice parameters across the magnetic ordering temperature TN ∼ 110 K.© 2012 Elsevier Masson SAS. All rights reserved.

Rath D.,Bhabha Atomic Research Center | Amlinger L.,Uppsala University | Rath A.,University of Mumbai | Lundgren M.,Uppsala University
Biochimie | Year: 2015

Viruses are a common threat to cellular life, not the least to bacteria and archaea who constitute the majority of life on Earth. Consequently, a variety of mechanisms to resist virus infection has evolved. A recent discovery is the adaptive immune system in prokaryotes, a type of system previously thought to be present only in vertebrates. The system, called CRISPR-Cas, provide sequence-specific adaptive immunity and fundamentally affect our understanding of virus-host interaction. CRISPR-based immunity acts by integrating short virus sequences in the cell's CRISPR locus, allowing the cell to remember, recognize and clear infections. There has been rapid advancement in our understanding of this immune system and its applications, but there are many aspects that await elucidation making the field an exciting area of research. This review provides an overview of the field and highlights unresolved issues. © 2015 The Authors. Published by Elsevier B.V.

Yadav S.K.,Dr Bc Roy Post Graduate Institute Of Basic Medical Science | Adhikary B.,Dr Bc Roy Post Graduate Institute Of Basic Medical Science | Chand S.,Bhabha Atomic Research Center | Maity B.,Dr Bc Roy Post Graduate Institute Of Basic Medical Science | And 2 more authors.
Free Radical Biology and Medicine | Year: 2012

The probable cross talk among large numbers of inflammatory and angiogenic parameters in indomethacin (IND)-induced gastropathy and the associated signaling mechanism were studied in a mouse model. A single dose of IND (18 mg/kg, po) produced robust gastric ulceration in mice without any mortality, which peaked on the third day, but started healing from the fifth day onward. The ulceration was associated with increased myeloperoxidase activity and expression of proinflammatory (TNF-α, adhesion molecules, COX-2) and antiangiogenic (endostatin) parameters. The levels of proangiogenic factors such as COX-1, prostaglandin E, VEGF, and von Willebrand factor VIII were downregulated by IND. Our results revealed that although the maximal and minimal levels of these parameters were attained sequentially at different time points, TNF-α upregulation was the primary event to initiate and induce gastric ulceration. IND also activated NF-κB and all the MAP kinases, but only the inhibitors of TNF-α, NF-κB, and JNK MAP kinase could abrogate the IND-induced damages. Further TNF-α inhibition also reduced the IND-mediated activation of NF-κB and JNK MAP kinase. All this evidence strongly suggests that mitigation of TNF-α may offer a potential solution to IND-mediated gastropathy. © 2012 Elsevier Inc.

Jain R.,Institute of Chemical Technology | Nabar S.,Bhabha Atomic Research Center | Dandekar P.,Institute of Chemical Technology | Vandana P.,Institute of Chemical Technology
Pharmaceutical Research | Year: 2010

Purpose. The investigation was aimed at developing micellar nanocarriers for nose-to-brain delivery of zolmitriptan with the objective to investigate the pathway involved in the drug transport. Methods. The micellar nanocarrier was successfully formulated and characterized for particle size and shape by multi-angle dynamic light scattering, small angle neutron scattering and cryo-transmission electron microscopy. Toxicity and biodistribution studies were carried, out in rat. The distribution of the nasally administered labeled micellar nanocarrier in various regions of the rat brain was determined using the brain localization and autoradiography studies. Results. Micellar nanocarrier of zolmitriptan, with size of around 23 nm, was successfully formulated. The spherical nature of the nanocarrier was confirmed using DLS, SANS and cryo-TEM. Toxicity studies indicated the safety for administration in the nasal cavity. In vivo biodistribution studies indicated, the superiority of the developed nanocarrier for brain targeting when compared with the intravenous and nasal solutions of the drug. Brain localization and autoradiography studies illustrated the distribution of the drug in various regions of the brain and revealed a possible nose-to-brain transport pathway for the labeled drug. Conclusion. The investigation indicated the potential of the developed nanocarrier as an effective newgeneration vehicle for brain targeting of zolmitriptan. © 2010 Springer Science+Business Media, LLC.

Mishra V.,Bhabha Atomic Research Center | Chaturvedi S.,Bhabha Atomic Research Center
Journal of Physics and Chemistry of Solids | Year: 2013

Tungsten carbide is used in high pressure devices therefore knowledge of its elastic properties and their pressure dependence is of utmost practical importance. In this paper we present first principles results of equation of state and elastic properties of α and β phases of tungsten carbide and compare our results with the available reported experimental results. These calculations have been performed using the FPLAPW method within the framework of density functional theory. Enthalpies of α and β phases of WC have been compared up to 350 GPa to investigate possibility of structural transformation. Density-dependent Grüneisen parameter has been deduced from P-V isotherm using the well-known Slater's formula. High pressure elastic constants of α and β phases of WC have been calculated by applying various distortions to the original crystal structure. The elastic properties such as bulk, shear and Young's moduli have been derived from the calculated elastic constants. Pressure-dependent longitudinal velocity, shear velocity, Debye temperature and melting temperature have been deduced from the elastic properties. These calculated properties are in good agreement with the available experimental results. © 2012 Elsevier Ltd.

Gyanchandani J.,Bhabha Atomic Research Center | Sikka S.K.,Bhabha Atomic Research Center
Solid State Communications | Year: 2013

Using the first principles DFT calculations, we have elucidated the electronic basis of the α→ω and the ω→β transitions in group IVB elements. After considering several possible factors that could give rise to the structural stability of a particular crystal structure, the changes in the band structure energy due to Peierls-Jahn-Teller distortion and crystal-field effects on sub orbital of d bands coupled with Ewald energy differences have been identified as the causes for these transitions. The role of van Hove singularities and consequent electronic topological transitions has also been examined. © 2012 Elsevier Ltd.

Vasundhara K.,Bhabha Atomic Research Center | Mandal B.P.,Bhabha Atomic Research Center | Tyagi A.K.,Bhabha Atomic Research Center
RSC Advances | Year: 2015

Dielectric permittivity and loss of percolative composites of cobalt nanoparticle loaded polyvinylidene fluoride (PVDF) have been investigated. The films have been characterized by X-ray diffraction, infrared spectroscopy, dielectric relaxation spectroscopy and electrical polarization measurements. A remarkable increase in the amount of polar β phase of PVDF has been observed upon dispersion of cobalt nanoparticles in the PVDF matrix. The dielectric constant of the composite increases significantly near the percolation threshold (19 vol%) of filler cobalt nanoparticles in the PVDF matrix. The results have been explained by the space charge polarization at the interfaces between the two phases of the composite and the development of several micro capacitor structures. The electrical field dependent polarization also increases upon addition of cobalt nanoparticles. This could be due to formation of a higher amount of the β phase of PVDF. © The Royal Society of Chemistry 2015.

Banerji A.,Bhabha Atomic Research Center
2015 International Conference on Industrial Instrumentation and Control, ICIC 2015 | Year: 2015

The parallel jaw grippers have been in use in industrial manipulators as standard end-effectors for a long time. A simple ON-OFF controller is adequate for these grippers. They typically use pneumatic cylinders as actuators for opening and closing of its jaws. However, a gripper of this type is incapable of handling convex objects; and dexterous manipulations like unscrewing a flask is almost impossible. It is obvious that fingers instead of jaws are required to perform complex tasks. However, the control of such fingers is not simple ON-OFF events. This paper presents a computational frame work on the basis of constraints of a closed kinematic chain, in order to grasp and manipulate unknown objects. This approach does not depend on grasped objects geometry for articulating the fingers. © 2015 IEEE.

Murli C.,Bhabha Atomic Research Center | Mishra A.K.,Bhabha Atomic Research Center | Thomas S.,Bhabha Atomic Research Center | Sharma S.M.,Bhabha Atomic Research Center
Journal of Physical Chemistry B | Year: 2012

Our high pressure Raman scattering experiments on carnosine, a dipeptide of l-histidine and β-alanine, show pressure induced ring-opening polymerization involving the imidazole ring. While the onset of polymeric transformation is found to be at ∼2.8 GPa, a substantial fraction of the monomeric solid becomes polymerized by 12 GPa. On release to ambient conditions, the observed Raman spectra do not contain any of the Raman modes of the ambient phase. © 2012 American Chemical Society.

Karve L.,Bhabha Atomic Research Center | Dutt G.B.,Bhabha Atomic Research Center
Journal of Physical Chemistry B | Year: 2012

Temperature-dependent fluorescence anisotropies of two organic solutes, 2,5-dimethyl-1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DMDPP) and rhodamine 110 (R110), have been measured in 1-butyl-3-methylimidazolium ([bmim +])-based ionic liquids containing the anions hexafluorophosphate ([PF6 -]), bis(trifluoromethylsulfonyl)imide ([Tf 2N-]), tetrafluoroborate ([BF4 -]), trifluoromethanesulfonate ([TfO-]), and nitrate ([NO3 -]). This data has been used in conjunction with the recently published results (Dutt, G. B. J. Phys. Chem. B2010, 114, 8971) for the same solutes in [bmim+] tris(pentafluoroethyl)trifluorophosphate ([FAP-]) to understand the influence of various anions on solute rotation. The boundary condition parameter Cobs, which has been obtained from the analysis of the data using Stokes-Einstein-Debye hydrodynamic theory, for the neutral solute DMDPP is more or less the same in all the ionic liquids. Moreover, Cobs values are close to the predictions of slip boundary condition, which indicates that solvent viscosity alone governs the rotation of DMDPP. In contrast, for R110, which experiences specific interactions with the anions of the ionic liquids, the Cobs values are close to stick hydrodynamics. It has also been noticed that the C obs values vary with the nature of the anion and this variation correlates with the hydrogen bond basicities of the anions of the ionic liquids. © 2012 American Chemical Society.

Charaka V.K.,Bhabha Atomic Research Center | Misra H.S.,Bhabha Atomic Research Center