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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.

Yugeswaran S.,Osaka University | Kobayashi A.,Osaka University | Ananthapadmanabhan P.V.,Bhabha Atomic Research Center
Journal of the European Ceramic Society | Year: 2012

Gas tunnel type plasma sprayed free-standing La 2Zr 2O 7 coating specimens with a thickness of 300-400μm were prepared under optimized operating conditions and were subjected to hot corrosion test in the presence of corrosive impurities such as V 2O 5, Na 2SO 4, and Na 2SO 4+V 2O 5 mixtures (60:40wt%) at two different temperatures for duration of 5h, i.e. 1000 and 1350K for V 2O 5 and Na 2SO 4+V 2O 5 mixtures, 1200 and 1350K for Na 2SO 4. For temperatures at 1350K, the reaction mechanism of V 2O 5 and the mixture of Na 2SO 4+V 2O 5 are similar and LaVO 4 is formed as the corrosive product, which leads to massive phase transformation from pyrochlore to tetragonal and monoclinic phases. Microstructural observations from planar reaction zone (PRZ) and melt infiltrated reaction zone (MIRZ) reveals that the present La 2Zr 2O 7 coating exhibits good hot corrosion resistance in V 2O 5 environment and moderate for the mixture of Na 2SO 4+V 2O 5, but is worst in Na 2SO 4 environment. © 2011 Elsevier Ltd.

Sengupta P.,Bhabha Atomic Research Center
Journal of Nuclear Materials | Year: 2011

Identification of proper materials for plant scale vitrification furnaces, engaged in immobilization of high level nuclear waste has always been a great challenge. Fast degradation of pour spout materials very often cause problem towards smooth pouring of waste-glass melt in canister and damages bellow kept in between. The present experimental study describes the various reaction products that form due to interaction between waste-glass melt and potential bellow liner materials such as copper, stainless steel and nickel based Superalloys (Alloy 690, 625). The results indicate that copper based material has lesser tendency to form adherent glassy layer. © 2011 Elsevier B.V. All rights reserved.

De S.,Indian Institute of Science | Aswal V.K.,Bhabha Atomic Research Center | Ramakrishnan S.,Indian Institute of Science
Langmuir | Year: 2010

A series of isomeric cationic surfactants (S1-S5) bearing a long alkyl chain that carries a 1,4-phenylene unit and a trimethyl ammonium headgroup was synthesized; the location of the phenyl ring within the alkyl tail was varied in an effort to understand its influence on the amphiphilic properties of the surfactants. The cmcs of the surfactants were estimated using ionic conductivity measurements and isothermal calorimetric titrations (ITC); the values obtained by the two methods were found to be in excellent agreement. The ITC measurements provided additional insight into the various thermodynamic parameters associated with the micellization process. Although all five surfactants have exactly the same molecular formula, their micellar properties were seen to vary dramatically depending on the location of the phenyl ring; the cmc was seen to decrease by almost an order of magnitude when the phenyl ring was moved from the tail end (cmc of S1 is 23 mM) to the headgroup region (cmc of S5 is 3 mM). In all cases, the enthalpy of micellization was negative but the entropy of micellization was positive, suggesting that in all of these systems the formation of micelles is both enthalpically and entropically favored. As expected, the decrease in cmc values upon moving the phenyl ring from the tail end to the headgroup region is accompanied by an increase in the thermodynamic driving force (ΔG) for micellization. To understand further the differences in the micellar structure of these surfactants, small-angle neutron scattering (SANS) measurements were carried out; these measurements reveal that the aggregation number of the micelles increases as the cmc decreases. This increase in the aggregation number is also accompanied by an increase in the asphericity of the micellar aggregate and a decrease in the fractional charge. Geometric packing arguments are presented to account for these changes in aggregation behavior as a function of phenyl ring location. © 2010 American Chemical Society.

Patil B.N.,P.A. College | Naik D.B.,Bhabha Atomic Research Center | Shrivastava V.S.,P.A. College
Desalination | Year: 2011

The present communication deals with the development of a low cost method for the removal of color from textile dyeing and printing wastewater by using nanosized semiconductor Nb 2O 5 as photocatalyst. Photocatalytic degradation studies were carried out for water soluble hazardous Ponceau-S dye in Nb 2O 5 aqueous suspension along with commercial activated carbon (CAC) as co-adsorbent. Different parameters like catalyst concentration, substrate concentration, pH, and contact time have been studied. It was observed that photocatalytic degradation by nanosized Nb 2O 5 along with CAC was a more effective, economic and faster mode of removing Ponceau-S dye from aqueous solutions. The optimum conditions for the degradation of the dye were initial concentration 40ppm, pH 8 and catalyst concentration 5gl -1 with CAC 1gl -1. The adsorption capacity was found to be 41.05mg/g.The SEM and XRD studies were carried for morphological feature characteristics of Nb 2O 5/C semiconductor materials. Besides the above kinetics and isotherm studies have also been carried out. © 2010.

Mitra A.,Bhabha Atomic Research Center
Monthly Notices of the Royal Astronomical Society | Year: 2014

Recently, Melia and his coworkers have proposed the so-called Rh = ct cosmology where the scale factor of the universe is a(t) α t and the spatial part is flat. Here, we look at this proposal from a fundamental angle. First, we note that Melia cosmology looks strikingly similar to the old Milne cosmology where a(t) α t and the spatial part is negatively curved. It is known that though Milne cosmology is a valid Friedmann solution, it actually corresponds to ρ = 0 and can be described by a globally static Minkowski metric. Secondly, we note that for the Melia model, Ricci & Kretschmann scalars assume their perfect static form hinting that it too may tacitly correspond to vacuum. To compare Melia universe with the Milne universe, we express Melia metric too in curvature/Schwarzschild coordinates. Finally, by using the fact for such coordinate transformations dx'4 = J dx4, where J is the appropriate Jacobian, we explicitly show that Melia metric is static, which for k = 0 case implies vacuum. This shows that even apparently meaningful general relativistic solutions could be illusory as far as physical reality is concerned. And since Melia model is the unique solution for the big bang model, eventually, all big bang models could be mathematical illusions. © 2014 The Author. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Mukherjee J.K.,Bhabha Atomic Research Center
Proceedings of the International Conference on Sensing Technology, ICST | Year: 2012

In tele-robotic systems with remote slave robot that mimics human actions on master arm, interactions between remote slave robot with its environment are perceived from reaction that develop when the slave is in physical contact with objects only. A method for enabling early sensing occurring prior to contact has been developed to eliminate 'surprise contact' by taking a synthesised transduction route that uses models of the parts in workspace and sensed velocity of robot tool-tip. Critical factors for making the technique suitable for real-time function of system and automated application have been addressed. © 2012 IEEE.

Kumar R.,Bhabha Atomic Research Center
Journal of applied clinical medical physics / American College of Medical Physics | Year: 2010

A novel IMRT phantom was designed and fabricated using Acrylonitrile Butadiene Styrene (ABS) plastic. Physical properties of ABS plastic related to radiation interaction and dosimetry were compared with commonly available phantom materials for dose measurements in radiotherapy. The ABS IMRT phantom has provisions to hold various types of detectors such as ion chambers, radiographic/radiochromic films, TLDs, MOSFETs, and gel dosimeters. The measurements related to pre-treatment dose verification in IMRT of carcinoma prostate were carried out using ABS and Scanditronics-Wellhoffer RW3 IMRT phantoms for five different cases. Point dose data were acquired using ionization chamber and TLD discs while Gafchromic EBT and radiographic EDR2 films were used for generating 2-D dose distributions. Treatment planning system (TPS) calculated and measured doses in ABS plastic and RW3 IMRT phantom were in agreement within +/-2%. The dose values at a point in a given patient acquired using ABS and RW3 phantoms were found comparable within 1%. Fluence maps and dose distributions of these patients generated by TPS and measured in ABS IMRT phantom were also found comparable both numerically and spatially. This study indicates that ABS plastic IMRT phantom is a tissue equivalent phantom and dosimetrically it is similar to solid/plastic water IMRT phantoms. Though this material is demonstrated for IMRT dose verification but it can be used as a tissue equivalent phantom material for other dosimetry purposes in radiotherapy.

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.

Kumar K.S.A.,Bhabha Atomic Research Center
Bioorganic and Medicinal Chemistry | Year: 2013

A general and efficient route towards the synthesis of three derivatives of structurally and functionally important amino acid, lysine is reported. Chemoselective reduction of aldehydic functionality in C-3-azido conjugated aldehyde 4, under Luche condition, is the key step in the synthetic sequence. The lysine derivative, (2S,3R)-2,6-diazido-3-hydroxy-hex-4-ene-oic acid 9 could be used to prepare switch peptide using Staudinger reaction, while the unprotected (2S,3R)-2,6-diamino-3-hydroxy-hexanoic acid hydrochloride 10 is a proven reaction intermediate towards the synthesis of natural product (-)-Balanol. © 2013 Elsevier Ltd. All rights reserved.

Kakati B.K.,Indian Institute of Technology Guwahati | Sathiyamoorthy D.,Bhabha Atomic Research Center | Verma A.,Indian Institute of Technology Guwahati
International Journal of Hydrogen Energy | Year: 2011

Carbon composite bipolar plates were developed by compression molding of novolac type phenol formaldehyde resin with natural graphite, carbon black, and carbon fiber. The General Effective Media equation was adapted to model the electrical conductivity of the bipolar plate. The experimental values of the electrical conductivity of the composites with different reinforcements were well predicted by the model. For resin-graphite system (2-component), the most effective in-plane and through-plane electrical conductivities for 70% graphite content were found to be 201.26 and 40.91 S cm-1, respectively. Similarly, for optimum resin-graphite-carbon black system (3-component), these values were found as 269.55 and 82.77 S cm-1, respectively. The most effective in-plane and through-plane electrical conductivities were found to be 285.54 and 91.79 S cm-1, respectively, for the composite with resin-graphite-carbon black-carbon fiber system (4-component). The predicted electrical conductivities for all the three systems were found to be in well agreement with the experimental values. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Four 220 MWe pressurised heavy water reactors are under operation at Kaiga in the state of Karnataka in India. Environmental radiological survey of the surrounding areas of the Kaiga site is carried out by Bhabha Atomic Research Centre, Mumbai. The estimated dose to the members of the public due to ingestion of radioactive isotope of potassium, a natural radionuclide, in the surroundings of the Kaiga site is 136 μSv (13.6 mrem) per year. The value indicates that the dose to the public due to operation of the nuclear reactors in Kaiga is insignificant in comparison with the dose due to unavoidable natural radioactivity.

Structures and energetics of CrO4 2-.nH2O (n = 1-8) clusters are studied using second order Moller-Plesset perturbation theory. An analytical expression is also provided which is useful to calculate the size dependent dielectric constant for the entire range of finite size clusters. It is observed that seven thousand water molecules are necessary to mimic the dielectric constant of the bulk water. The calculated conductivity and diffusion constant of chromate dianion in aqueous solution are found to be in good agreement (within 1%) with the reported experimental results. © 2015 Taylor & Francis.

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.

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.

Ramachandran C.S.,Annamalai University | Balasubramanian V.,Annamalai University | Ananthapadmanabhan P.V.,Bhabha Atomic Research Center
Journal of Thermal Spray Technology | Year: 2011

Atmospheric plasma spraying is used extensively to make Thermal Barrier Coatings of 7-8% yttria-stabilized zirconia powders. The main problem faced in the manufacture of yttria-stabilized zirconia coatings by the atmospheric plasma spraying process is the selection of the optimum combination of input variables for achieving the required qualities of coating. This problem can be solved by the development of empirical relationships between the process parameters (input power, primary gas flow rate, stand-off distance, powder feed rate, and carrier gas flow rate) and the coating quality characteristics (deposition efficiency, tensile bond strength, lap shear bond strength, porosity, and hardness) through effective and strategic planning and the execution of experiments by response surface methodology. This article highlights the use of response surface methodology by designing a five-factor five-level central composite rotatable design matrix with full replication for planning, conduction, execution, and development of empirical relationships. Further, response surface methodology was used for the selection of optimum process parameters to achieve desired quality of yttria-stabilized zirconia coating deposits. © 2010 ASM International.

Eapen S.,Bhabha Atomic Research Center
Physiology and Molecular Biology of Plants | Year: 2011

Introduction of foreign genes and development of transgenic plants have become an integral part of crop improvement programmes in the last decade. However, most of the present day plant transformation protocols require long periods for development of transgenic plants and need skilled personnel. Development of alternate, simple and rapid transformation protocols for development of transgenic plants can overcome the constraints of in vitro culture, regeneration and associated problems. Pollen grains, due to their abundance and ease with which they can be handled are ideal targets for introduction of foreign genes into the germ line. However, progress in introduction of transgenes into pollen grains and their subsequent use in fertilization leading to development of transgenic plants are limited. With the recent progress made in understanding of pollen development along with reports of successful pollen-mediated transformation in important crop plants, it should be possible to extend this simple method of transformation to other crop plants. The review deals with development of pollen grains as a target for introduction of genes with special emphasis on recent developments. © 2011 Prof. H.S. Srivastava Foundation for Science and Society.

Mitra A.,Bhabha Atomic Research Center
Astrophysics and Space Science | Year: 2011

By applying Birkhoff's theorem to the problem of the general relativistic collapse of a uniform density dust, we directly show that the density of the dust ρ=0 even when its proper number density n would be assumed to be finite! The physical reason behind this exact result can be traced back to the observation of Arnowitt et al. (Phys. Rev. Lett. 4: 375, 1960) that the gravitational mass of a neutral point particle is zero: m=0. And since, a dust is a mere collection of neutral point particles, unlike a continuous hydrodynamic fluid, its density ρ=mn=0. It is nonetheless found that for k=-1, a homogeneous dust can collapse and expand special relativistically in the fashion of a Milne universe. Thus, in reality, general relativistic homogeneous dust collapse does not lead to the formation of any black hole in conformity of many previous studies (Logunov et al., Phys. Part. Nucl. 37: 317, 2006; Kiselev et al., Theor. Math. Phys. 164: 972, 2010; Mitra, J. Math. Phys. 50: 042502, 2009a; Suggett, J. Phys. A 12: 375 1979b). Interestingly, this result is in agreement with the intuition of Oppenheimer and Snyder (Phys. Rev. 56: 456, 1939) too:"Physically such a singularity would mean that the expressions used for the energy-momentum tensor does not take into account some essential physical fact which would really smooth the singularity out. Further, a star in its early stages of development would not possess a singular density or pressure, it is impossible for a singularity to develop in a finite time." © 2010 Springer Science+Business Media B.V.

Ambashta R.D.,University of Eastern Finland | Ambashta R.D.,Bhabha Atomic Research Center | Sillanpaa M.,University of Eastern Finland | Sillanpaa M.,Lappeenranta University of Technology
Journal of Hazardous Materials | Year: 2010

Water is a major source for survival on this planet. Its conservation is therefore a priority. With the increase in demand, the supply needs to meet specific standards. Several purification techniques have been adopted to meet the standards. Magnetic separation is one purification technique that has been adapted from ore mining industries to anti-scale treatment of pipe lines to seeding magnetic flocculent. No reviews have come up in recent years on the water purification technique using magnetic assistance. The present article brings out a series of information on this water purification technique and explains different aspects of magnetism and magnetic materials for water purification. © 2010 Elsevier B.V.

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.

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.

Ghosh A.,Indian Central Salt and Marine Chemicals Research Institute | Choudhury S.,Bhabha Atomic Research Center | Das A.,Indian Central Salt and Marine Chemicals Research Institute
Chemistry - An Asian Journal | Year: 2010

A tetraphenyl porphyrin derivative with two C16 alkyl chains covalently bound to each of the four peripheral phenyl rings through ether linkages formed multilayer clusters or vesicles at the air-water surface. More interestingly, spherical vesicles were also formed when deposited on appropriate solid surfaces, and these vesicles were stable even in dry conditions. Various microscopic images of the cast film deposited on a mica surface confirmed closed-ended nanotube/nanorod-type formation with necking and bulging. These narrow tubes are proposed to be intermediates for the formation of vesicles by fission at either side of the bulge. Such vesicular formation is not common when either cast or Langmuir-Blodgett films were deposited on a solid surface. © 2010 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim.

Mukherjee J.K.,Bhabha Atomic Research Center
Proceedings of the International Conference on Sensing Technology, ICST | Year: 2012

A technique for virtual transducer formation has been developed to augment remote environment perception by adding proximity feel in tele-robotic systems. It induces proximity feel around approachable and unapproachable parts in distinctly different ways. It uses robot's in built sensors and develops perceivable reaction. The transducer is applicable to tele-robots working in 'man in loop' modality for augmenting perception of remote environment at the master side. © 2012 IEEE.

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.

Thakur J.,Kishanchand Chelaram College | Dutta D.P.,Kishanchand Chelaram College | Bagla H.,Kishanchand Chelaram College | Tyagi A.K.,Bhabha Atomic Research Center
Journal of the American Ceramic Society | Year: 2012

Eu 3+ and Tb 3+ doped in nanocrystalline InBO 3, GdBO 3, and LaBO 3having three different morphs of calcite (CaCO 3) such as Calcite, Vaterite, and Aragonite, respectively, were synthesized by glycine-nitrate combustion method. Luminescence due to Eu 3+ and Tb 3+ doped individually as well as simultaneously in these three different morphs of calcite were investigated and compared. Also the effect of concentration of dopant ions on the luminescence was studied. The highest photoluminescence emission intensity was observed for RE 0.05M 0.95BO 3(RE = Eu 3+, Tb 3+, M = In, Gd, La) samples. Further increase in doping led to concentration quenching of the luminescence. In case of the co-doped borates, the energy transfer between the co-doped rare earth ions was influenced by the host crystal structure. This study reveals that there is remarkable effect of the crystal structure of host and concentration of dopant ions on the luminescence. © 2011 The American Ceramic Society.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Biswas A.,Northwestern University | Biswas A.,Bhabha Atomic Research Center | Siegel D.J.,University of Michigan | Wolverton C.,Northwestern University | Seidman D.N.,Northwestern University
Acta Materialia | Year: 2011

Atom-probe tomography, transmission electron microscopy, X-ray diffraction and first-principles calculations are employed to study: (i) compositional evolution of GPII zones and θ′ precipitates; and (ii) solute segregation at α-Al/θ′ interfaces in Al-1.7 at.% Cu (Al-4 wt.% Cu) alloys. GPII zones are observed after aging at 438 K for 8 h, whereas higher aging temperatures, 463 K for 8 h and 533 K for 4 h, reveal only θ′ precipitates. Most GPII zones and θ′ precipitates are demonstrated to be Cu-deficient at the lower two aging temperatures; only the 533 K treatment resulted in θ′ stoichiometries consistent with the expected Al2Cu equilibrium composition. For alloys containing ∼200 at. ppm Si we find evidence of Si partitioning to GPII zones and θ′ precipitates. Significant Si segregation is observed at the coherent α-Al/θ′ interface for aging at 533 K, resulting in an interfacial Si concentration more than 11 times greater than in the α-Al matrix. Importantly, the Si interfacial concentration undergoes a transition from a non-equilibrium delocalized profile to an equilibrium localized profile as the aging temperature is increased from 463 to 533 K. Consistent with these measurements, first-principles calculations predict a strong thermodynamic driving force favoring Si partitioning to Cu sites in θ′. Silicon segregation at, and partitioning to, θ′ precipitates results in a decrease in interfacial free energy, and concomitantly an increase in the nucleation current. Our results suggest that Si catalyzes the early stages of precipitation in these alloys, consistent with the higher precipitate number densities observed in commercial Al-Cu-Si alloys. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Ghosh S.,Jadavpur University | Mukhopadhyay D.,Bhabha Atomic Research Center | Saha S.K.,Jadavpur University
International Journal of Pressure Vessels and Piping | Year: 2011

The work presented here is an experimental investigation of the critical flashing flow of initially subcooled water through circumferential slits in pipes. The study provides first hand information about the prediction of leak flow rates in piping and pressure vessels retaining high temperature and high pressure. The dedicated experimental facility loop simulates the thermal hydraulic condition of Pressurized Heavy Water Reactors (PHWR). The critical flow characteristics found for varying leakage cross sections at different stagnation pressure and different degree of subcooling has been demonstrated in this paper. A marked decrease in mass flux has been found as subcooling decreases for a fixed stagnation pressure. More observation has revealed that the tighter slits or openings with very short duct as small as 0.8 cm flow length have different flow behavior than greater opening dimensions or with longer flow channels or that for nozzles. The critical flow has been seen to occur at higher pressure differentials along the flaws and prominent changes in the flow rate is reported to occur with varying dimensional parameters of the slit or cracks. © 2011 Elsevier Ltd.

Bhattacharya A.,Indian Association for The Cultivation of Science | Bhattacharya S.,Indian Association for The Cultivation of Science | Majumder C.,Bhabha Atomic Research Center | Das G.P.,Indian Association for The Cultivation of Science
Physica Status Solidi - Rapid Research Letters | Year: 2010

We report, using first principles density functional calculations, the relative stabilities, structural and electronic properties of various conformers of hydrogenated BN sheet (BHNH). The already known chair and boat BHNH conformers are structurally similar to those of graphane. We propose a third BHNH conformer called 'stirrup' which turns out to be the most stable one, as also verified by frequency analysis. In this conformer, the B-H and N-H bonds of a hexagon alternate in 3-up and 3-down fashion on either side of the sheet. We also explore that any other alternative hydrogenation of the BN sheet disrupts its periodic puckered geometry and turns out to be energetically less stable. The structural stability, electronic and vibrational properties of a fully hydrogenated BN sheet have been investigated using first-principles density functional calculations. Hydrogen can get attached to B and N atoms in different possible configurations e.g. chair and boat conformers, as observed in graphane. the authors report here a new "stirrup" conformer of puckered BHNH sheet that turns out to be energetically more stable compared to the known chair and boat conformers. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mitra A.,Bhabha Atomic Research Center | Glendenning N.K.,Lawrence Berkeley National Laboratory
Monthly Notices of the Royal Astronomical Society: Letters | Year: 2010

Hoyle & Fowler showed that there could be radiation pressure supported stars (RPSSs) even in Newtonian gravity. Much later, Mitra found that one could also conceive of their general relativistic (GR) version, 'relativistic radiation pressure supported stars' (RRPSSs). While RPSSs have z ≪ l, RRPSSs have z ≫ 1, where z is the surface gravitational redshift. Here, we elaborate on the formation of RRPSSs during continued gravitational collapse by recalling that a contracting massive star must start trapping radiation as it enters its photon sphere. It is found that, irrespective of the details of the contraction process, the trapped radiation flux should attain the corresponding Eddington value at sufficiently large z ≫ 1. This means that continued GR collapse may generate an intermediate RRPSS with z ≫ 1 before a true black hole state with z = ∞ is formed asymptotically. An exciting consequence of this is that the stellar mass black hole candidates, at the present epoch, should be hot balls of quark-gluon plasma, as has been discussed by Royzen in a recent article entitled 'QCD against black holes?'. © 2010 The Authors. Journal compilation © 2010 RAS.

Ramachandan T.V.,Bhabha Atomic Research Center | Sathish L.A.,Government Science College
Journal of Environmental Radioactivity | Year: 2011

Considering the role of radon in epidemiology, an attempt was made to make a nation-wide map of indoor 222Rn and 220Rn for India. More than 5000 measurements have been carried out in 1500 dwellings across the country comprising urban and nonurban locations. The solid state nuclear track detectors based twin cup 222Rn/ 220Rn discrimination dosimeters were deployed for the measurement of indoor 222Rn, 220Rn and their progeny levels. The geometric means of estimated annual inhalation dose rate due to indoor 222Rn, 220Rn and their progeny in the dwellings was 0.94 mSvy -1 (geometric standard deviation 2.5). It was observed that the major contribution to the indoor inhalation dose was due to indoor 222Rn and its progeny. However, the contribution due to indoor 220Rn and its progeny was not trivial as it was found to be about 20% of the total indoor inhalation dose rates. The indoor 222Rn levels in dwellings was significantly different depending on the nature of walls and floorings. © 2011 Elsevier Ltd.

Yakhmi J.V.,Bhabha Atomic Research Center
Journal of Materials Education | Year: 2011

Soft Matter is a term used generally to describe materials that are held together by weak noncovalent interactions - with bond energy of the order of kT. Soft Matter obtains its identity largely from three categories of materials, viz. colloids, polymers and surfactants. It is common to have materials, which may belong to two of these categories simultaneously; in fact, there are some biological systems such as proteins, which have some features characteristic of all these three forms of Soft Matter. On the other hand, there are Soft Materials like liquid crystals, which may not fit strictly into the limits of these three categories, underlining that this classification is only 'broad'. Soft materials sit at the interface of Chemistry, Physics, Biology and Materials Science, thus forming an important focus in the interdisciplinary sciences. Today, traditional materials such as metals, ceramics and wood have partly been replaced by synthetic soft materials, which may be stronger, lighter, cheaper, and which, through scientific research, can be tailored to specific requirements. Hence, we are surrounded by products of daily use made from man-made Soft Matter: toiletries, gels, medicines, plastic containers, soft furnishings, cosmetics, etc. A variety of modern equipment and components in automobiles or in the workplace are often made of, or coated with, soft-composite materials. In spite of these facts, Soft Matter is rarely integrated in traditional instruction in Materials Science and Engineering. The present article is thus an attempt to remedy this situation. Some research done on soft materials recently in the laboratory of the author will also be presented briefly as illustrations. The emerging trends of using Soft Matter in health-related technologies will be highlighted.

Chakraborty S.P.,Bhabha Atomic Research Center
International Journal of Refractory Metals and Hard Materials | Year: 2011

TZM alloy is a potential candidate for high temperature structural applications. However, in the preparation of this alloy by conventional melt-casting route, difficulties are encountered in achieving homogenized alloy composition in view of high melting temperature of the alloy and presence of minor alloying components. Therefore, an alternative technique of aluminothermic co-reduction was adopted to prepare TZM alloy of composition, Mo-0.5Ti-0.1Zr-0.02 °C, wt.% by simultaneous reduction of uniformly premixed oxides of MoO2, TiO2 and ZrO2 by aluminium in presence of requisite amount of carbon. The as-reduced alloy was further arc melted for consolidation. Since, TZM alloy is by nature highly susceptible to oxidation at elevated temperature in air or oxygen, therefore feasibility of development of silicide type of coating over the synthesized alloy by plasma coating technique was also examined. Silicon powder coated on TZM alloy surface by plasma spray technique was finally converted into MoSi2 coating by sintering at 1350 °C for 2-4 h duration under argon. A double layer coating structure was formed with two distinct phases. The inner thin layer was consisted of Mo2Si5 phase (~ 10 μm) followed by thick outer layer of MoSi2 (~ 150 μm). The coating showed good adhesion strength and stable oxidation with negligible mass gain (10 g/m2) at 1000 °C in air. © 2011 Elsevier Ltd.

Biswas A.,Northwestern University | Biswas A.,Bhabha Atomic Research Center | Siegel D.J.,University of Michigan | Seidman D.N.,Northwestern University
Acta Materialia | Year: 2014

Lightweight, age-hardenable aluminum alloys are attracting increasing attention as a means to reduce vehicle mass and improve fuel economy. To accelerate the adoption of these alloys, knowledge of the complex precipitation processes that underlie their primary strengthening mechanism is essential. Here we employ a combination of atom-probe tomography (APT), differential scanning calorimetry (DSC), transmission electron-microscopy, X-ray diffraction and first-principles calculations to reveal the compositional evolution of Q-phase precipitates in a commercial, age-hardenable aluminum alloy, W319. Three different aging conditions are investigated: 438 K/8 h, 463 K/8 h and 533 K/4 h. Co-precipitation of θ′- and Q-phase precipitates is observed for all aging conditions, which, when combined with DSC analysis of the precipitation sequence, suggests that Q-phase precipitates serve as heterogeneous nucleation sites for θ′-platelets. Regarding composition evolution, aging at the lower temperatures yields Q-phase precipitates that are Cu-rich, yet deficient in Mg and Si: 44Al-22Cu-16Mg-16.5Si at.%. The composition evolves to become Mg-rich after aging at 533 K: ∼28Al-9Cu-37Mg-26Si at.%. APT provides evidence for partitioning of Zn to the Q-phase precipitates. The energetics of Zn partitioning was evaluated using first-principles calculations, and suggests that this partitioning is a kinetic effect. Our analyses provide new insights into the complex precipitation processes in commercial Al alloys, and should foster the enhancement of alloy performance through optimization of aging conditions. © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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.

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.

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.

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.

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.

Kundu S.,Institute of Advanced Study in Science and Technology | Das K.,Institute of Advanced Study in Science and Technology | Aswal V.K.,Bhabha Atomic Research Center
Chemical Physics Letters | Year: 2013

Bovine serum albumins, at physiological pH, shows a short-range attraction and in addition a long-range electrostatic repulsion among them. These interactions are modified in presence of different counterions. Small angle neutron scattering study shows that for the equal ionic strength, the interactions are largely modified by the tri-valent (Fe3+) and di-valent (Ni2+) ions and comparatively less by the mono-valent (Na+) ions. The effect is nearly similar for the di- and tri-valent ions in comparison with the mono-valent one. The strength of the attractive and repulsive interactions depends strongly on the type of the dissolved ions and salt concentrations. © 2013 Elsevier B.V. All rights reserved.

Basu S.,Bhabha Atomic Research Center | Alavi A.,University of Pennsylvania
Current Medical Imaging Reviews | Year: 2011

Combined structure-function approach utilizing the fusion of functional and anatomical modalities for more precise localization has been a major innovation of recent times in the arena of medical imaging. This approach is likely to make a major impact on the diagnosis and management of various benign and malignant disorders. The SPECT/CT and the PET/CT imaging systems are the two proof-of-principle examples that clearly depict the power of this approach. The advantages are particularly evident in patients with cancer where fused image obtained by the combination of functional data from PET/SPECT with high-resolution anatomical detail from a multi-slice CT scanner provides useful anatomical and functional information to detect, diagnose, characterize, or monitor tumors before and after therapeutic intervention and guide biopsies or surgical interventions. The approach is likely to be pivotal to optimize individualized treatment planning for several malignancies. Based upon available evidence at this point, the relatively established clinical applications of hybrid SPECT-CT in oncology include (a) lymphoscintigraphy, (b) bone imaging and (c) octreotide scintigraphy for investigating neuroendocrine tumors. The other emerging situations where it holds considerable potential include: patient specific dosimetry and estimation of organ residence time for planning of radionuclide therapy planning, as well as evaluation of malignancies where the role of FDG-PET imaging is limited (e.g. prostate cancer using capromab pendetide and brain tumors). Combined PET/CT imaging, on the other hand, has been integrated into the management of majority of the malignancies because it offers advantages in a large number of decision making steps in oncological practice including staging of the disease, therapy planning and monitoring treatment response and is considered as the 'one stop shop' investigation for the management of these patients. In this mini-review we discuss the impact of SPECT-CT and PET-CT imaging approaches which are becoming increasingly important for therapeutic decision making in the era of personalized medicine. © 2011 Bentham Science Publishers Ltd.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Biju K.,Bhabha Atomic Research Center
Radiation Protection Dosimetry | Year: 2012

Quantifying organ dose to healthy organs during radiotherapy is essential to estimate the radiation risk. Dose factors are generated by simulating radiation transport through an anthropomorphic mathematical phantom representing a reference Indian adult using the Monte Carlo method. The mean organ dose factors (in mGy min -1 GBq -1) are obtained considering the microselectron 192Ir source and BEBIG 60Co sources in the uterus of a reference Indian adult female phantom. The present study provides the factors for mean absorbed dose to organs applicable to the Indian female patient population undergoing brachytherapy treatment of uterus cancer. This study also includes a comparison of the dimension of organs in the phantom model with measured values of organs in the various investigated patients. © The Author 2011. Published by Oxford University Press. All rights reserved.

Rawat K.,Jawaharlal Nehru University | Aswal V.K.,Bhabha Atomic Research Center | Bohidar H.B.,Jawaharlal Nehru University
Journal of Physical Chemistry B | Year: 2012

Study of kinetics of complex coacervation occurring in aqueous 1-octyl-3-methylimidazolium chloride ionic liquid solution of low charge density polypeptide (gelatin A) and 200 base pair DNA, and thermally activated coacervate into anisotropic gel transition, is reported here. Associative interaction between DNA and gelatin A (GA) having charge ratio (DNA:GA = 16:1) and persistence length ratio (5:1) was studied at fixed DNA (0.005% (w/v)) and varying GA concentration (CGA = 0-0.25% (w/v)). The interaction profile was found to be strongly hierarchical and revealed three distinct binding regions: (i) Region I showed DNA-condensation (primary binding) for CGA < 0.10% (w/v), the DNA ζ potential decrease from -80 to -5 mV (95%) (partial charge neutralization), and a size decrease by ≈60%. (ii) Region II (0.10 < CGA < 0.15% (w/v)) indicated secondary binding, a 4-fold turbidity increase, a ζ potential decrease from -5 to 0 mV (complete charge neutralization), which resulted in the appearance of soluble complexes and initiation of coacervation. (iii) Region III (0.15 < C GA < 0.25% (w/v)) revealed growth of insoluble complexes followed by precipitation. The hydration of coacervate was found to be protein concentration specific in Raman studies. The binding profile of DNA-GA complex with IL concentration revealed optimum IL concentration (=0.05% (w/v)) was required to maximize the interactions. Small angle neutron scattering (SANS) data of coacervates gave static structure factor profiles, I(q) versus wave vector q, that were remarkably similar and invariant of protein concentration. This data could be split into two distinct regions: (i) for 0.0173 < q < 0.0353 Å-1, I(q) ∼ q-α with α = 1.35-1.67, and (ii) for 0.0353 < q < 0.35 Å-1, I(q) = I(0)/(1 + q2ξ2). The correlation length found was ξ = 2 ± 0.1 nm independent of protein concentration. The viscoelastic length (≈8 nm) was found to have value close to the persistence length of the protein (≈10 nm). Rheology data indicated that the coacervate phase resided close to the gelation state of the protein. Thus, on a heating-cooling cycle (heating to 50 C followed by cooling to 20 C), the heterogeneous coacervate exhibited an irreversible first-order phase transition to an anisotropic ion gel. This established a coacervate-ion gel phase diagram having a well-defined UCST. © 2012 American Chemical Society.

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.

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.

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.

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.

Fleig T.,CNRS Laboratory for Quantum Chemistry and Physics | Nayak M.K.,Bhabha Atomic Research Center
Journal of Molecular Spectroscopy | Year: 2014

A recently implemented relativistic four-component configuration interaction approach to study ℘- and T-odd interaction constants in atoms and molecules is employed to determine the electron electric dipole moment effective electric field in the Ω=1 first excited state of the ThO molecule. We obtain a value of Eeff=75.2 [GV/cm] with an estimated error bar of 3% and 10% smaller than a previously reported result (Skripnikov et al., 2013). Using the same wavefunction model we obtain an excitation energy of TvΩ=1 =5410 (cm-1), in accord with the experimental value within 2%. In addition, we report the implementation of the magnetic hyperfine interaction constant A|∥ as an expectation value, resulting in A∥=-1339 (MHz) for the Ω=1 state in ThO. The smaller effective electric field increases the previously determined upper bound (Baron et al., 2014) on the electron electric dipole moment to |de|<9.7×10-29e cm and thus mildly mitigates constraints to possible extensions of the Standard Model of particle physics. © 2014 Elsevier Inc. All rights reserved.

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.

Paliya V.S.,Indian Institute of Astrophysics | Paliya V.S.,University of Calicut | Sahayanathan S.,Bhabha Atomic Research Center | Stalin C.S.,Indian Institute of Astrophysics
Astrophysical Journal | Year: 2015

The well-studied blazar 3C 279 underwent a giant γ-ray outburst in 2014 March-April. The measured γ-ray flux (1.21 ± 0.10 × 10-5 in a 0.1-300 GeV energy range) is the highest detected from 3C 279 by the Fermi Large Area Telescope. Hour-scale γ-ray flux variability is observed, with a flux doubling time as short as 1.19 ± 0.36 hr detected during one flare. The γ-ray spectrum is found to be curved at the peak of the flare, suggesting low probability of detecting very high energy (VHE; E 100 GeV) emission, which is further confirmed by the VERITAS observations. The γ-ray flux increased by more than an order in comparison to a low-activity state and the flare consists of multiple sub-structures having a fast rise and slow decay profile. The flux enhancement is seen in all the wavebands, though at a lesser extent compared to γ-rays. During the flare, a considerable amount of the kinetic jet power gets converted to γ-rays and the jet becomes radiatively efficient. A one-zone leptonic emission model is used to reproduce the flare and we find increase in the bulk Lorentz factor as a major cause of the outburst. From the observed fast variability, lack of VHE detection, and the curved γ-ray spectrum, we conclude that the location of the emission region cannot be far out from the broad-line region (BLR) and contributions from both BLR and torus photons are required to explain the observed γ-ray spectrum. © 2015. The American Astronomical Society. All rights reserved.

Ray A.,University of Burdwan | Pal H.,Bhabha Atomic Research Center | Bhattacharya S.,University of Burdwan
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

The photophysical features of non-covalently linked fullerenes C 60 and C70 with a designed free-base phthalocyanine, namely, 2,3,9,10,16,17,23,24-octakis-(octyloxy)-29H,31H-phthalocyanine (1) have been investigated employing various spectroscopic tools like UV-vis absorption spectrophotometry, steady state and time resolved fluorescence along with proton NMR measurements in toluene. The ground state interaction between fullerenes and 1 is nicely demonstrated with the appearance of well defined charge transfer absorption bands in the visible region of the electronic spectra. Steady state fluorescence experiment reveals efficient quenching of the excited singlet state of 1 in presence of both C60 and C70. The average values of binding constants for the non-covalent complexes of C60 and C 70 with 1 are determined to be ∼18,150 and ∼32,000 dm 3 mol-1, respectively. The magnitude of K suggests that 1 preferentially binds C70 in comparison to C60 although average value of selectivity in binding is measured to be low (∼1.75). Time resolved emission measurements establish photoinduced energy transfer from the excited singlet state of 1 to fullerene in toluene. Measurements of free energy of electron transfer and free energy of radical ion-pair formation elicit that C70/1 complex is stabilized more in comparison to C60/1 complex regarding generation of charge-separated state. Proton NMR studies provide very good support in favor of effective ground state complexation between fullerenes and 1. Semi empirical theoretical calculations on fullerene/1 systems in vacuo substantiate the stronger binding between C70 and 1 in comparison to C60/1 system in terms of heat of formation value of the respective complexes, and determine the orientation of bound guest (here C70) towards the plane of 1 during complexation. © 2013 Elsevier B.V. All rights reserved.

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

There have been several endeavors made to investigate the potential role of 2-deoxy-2-[ 18F] fluoro-D-glucose positron emission tomography (FDG-PET) (and tracers) and PET-computed tomography imaging in various benign disorders, particularly those related to thoracic structures. These various conditions can be broadly categorized into three groups: (a) infectious diseases (mycobacterial, fungal, bacterial infection), (b) active granulomatous disease such as sarcoidosis, and (c) other non-infectious/inflammatory conditions or proliferative disorders (e.g., radiation pneumonitis, post-lung transplant lymphoproliferative disorders, occupational pleuropulmonary complications, and post-surgical conditions), all of which can demonstrate varying degrees of FDG uptake on PET scans based upon the degree of inflammatory activity. This article reviews the current state of this very important application of FDG-PET imaging. © Academy of Molecular Imaging and Society for Molecular Imaging, 2010.

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.

Nancharaiah Y.V.,Bhabha Atomic Research Center | Nancharaiah Y.V.,UNESCO-IHE Institute for Water Education | Venkata Mohan S.,Indian Institute of Chemical Technology | Lens P.N.L.,UNESCO-IHE Institute for Water Education | Lens P.N.L.,Tampere University of Technology
Bioresource Technology | Year: 2015

Metal laden wastes and contamination pose a threat to ecosystem well being and human health. Metal containing waste streams are also a valuable resource for recovery of precious and scarce elements. Although biological methods are inexpensive and effective for treating metal wastewaters and in situ bioremediation of metal(loid) contamination, little progress has been made towards metal(loid) recovery. Bioelectrochemical systems are emerging as a new technology platform for removal and recovery of metal ions from metallurgical wastes, process streams and wastewaters. Biodegradation of organic matter by electroactive biofilms at the anode has been successfully coupled to cathodic reduction of metal ions. Until now, leaching of Co(II) from LiCoO2 particles, and removal of metal ions i.e. Co(III/II), Cr(VI), Cu(II), Hg(II), Ag(I), Se(IV), and Cd(II) from aqueous solutions has been demonstrated. This article reviews the state of art research of bioelectrochemical systems for removal and recovery of metal(loid) ions and pertaining removal mechanisms. © 2015 Elsevier Ltd. All rights reserved.

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.

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.

Roy N.,Jamsetji Tata Center for Disaster Management | Thakkar P.,Bhabha Atomic Research Center | Shah H.,Bhansali Trust
Disaster Medicine and Public Health Preparedness | Year: 2011

Objectives: The technology and resource-rich solutions of the developed world may not be completely applicable to or replicable in disasters occurring in the developing world. With the current looming hazards of pandemics, climatechange, global terrorism and conflicts around the world, policy makers and governments will need high-quality scientific data to make informed decisions for preparedness and mitigation. The evidence on disasters in peerreviewed journals about the developing world was examined for quality and quantity in this systematic review. Methods: PubMed was searched using the Medical Subject Heading (MeSH) terms disasters, disaster medicine, rescue work, relief work, and conflict and then refined using the MeSH term developing country. The final list of selected manuscripts were analyzed by type of article, level of evidence, theme of the manuscript and topic, author affiliation, and region of the study. Results: After searching and refining, <1% of the citations in PubMed addressed disasters in developing countries. The majority was original research articles or reviews, and most of the original research articles were level IV or V evidence. Less than 25% of the authors were from the developing world. The predominant themes were missions, health care provision, and humanitarian aid during the acute phase of disasters in the developing world. Conclusions: Considering that 85% of disasters and 95% of disaster-related deaths occur in the developing world, the overwhelming number of casualties has contributed insignificantly to the world's peer-reviewed literature. Less than 1% of all disaster-related publications are about disasters in the developing world. This may be a publication bias, or it may be a genuine lack of submissions dealing with these disasters. Authors in this part of the world need to contribute to future disaster research through better-quality systematic research and better funding priorities. Aid for sustaining long-term disaster research may be a more useful investment in mitigating future disasters than short-term humanitarian aid missions to the developing world. © 2011 American Medical Association. All rights reserved.

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.

Immobilization of phosphate containing high level nuclear wastes within commonly used silicate glasses is difficult due to restricted solubility of P2O5 within such melts and its tendency to promote crystallization. The situation becomes more adverse when sulfate, chromate, etc. are also present within the waste. To solve this problem waste developers have carried out significant laboratory scale research works in various phosphate based glass systems and successfully identified few formulations which apparently look very promising as they are chemically durable, thermally stable and can be processed at moderate temperatures. However, in the absence of required plant scale manufacturing experiences it is not possible to replace existing silicate based vitrification processes by the phosphate based ones. A review on phosphate glass based wasteforms is presented here. © 2012 Elsevier B.V.

Misra N.L.,Bhabha Atomic Research Center
Spectrochimica Acta - Part B Atomic Spectroscopy | Year: 2014

Advancements in x-ray spectrometric techniques at different stages have made this technique suitable for characterization of nuclear materials with respect to trace/major element determinations and compositional uniformity studies. The two important features of total reflection x-ray fluorescence spectrometry: 1) requirement of very small amount of sample in ng level 2) multielement analytical capability, in addition to other features, make this technique very much suitable to nuclear materials characterization as most of the nuclear materials are radioactive and the radioactive waste generated and radiation hazards to the operator are minimum when such low amount of sample is used. Similarly advanced features of energy dispersive x-ray fluorescence e.g. better geometry for high flux, reduction in background due to application of radiation filters have made the measurements of samples sealed inside thin alkathene/PVC covers possible with good sensitivity. This approach avoids putting the instrument inside a glove box for measuring radioactive samples and makes the operation/maintenance of the instrument and analysis of the samples possible in easy and fast manner. This approach has been used for major element determinations in mixed uranium-plutonium samples. Similarly μ-XRF with brilliant and micro-focused excitation sources can be used for compositional uniformity study of reactor fuel pellets. A μ-XRF study using synchrotron light source has been made to assess the compositional uniformity of mixed uranium-thorium oxide pellets produced by different processes. This approach is simple as it does not involve any sample preparation and is non-destructive. A brief summary of such activities carried out in our laboratory in past as well as ongoing and planned for the future have been discussed in the present manuscript. © 2014 Elsevier B.V.

Chang M.-H.,University of Maryland University College | Das D.,University of Maryland University College | Varde P.V.,University of Maryland University College | Varde P.V.,Bhabha Atomic Research Center | And 2 more authors.
Microelectronics Reliability | Year: 2012

The increasing demand for light emitting diodes (LEDs) has been driven by a number of application categories, including display backlighting, communications, medical services, signage, and general illumination. The construction of LEDs is somewhat similar to microelectronics, but there are functional requirements, materials, and interfaces in LEDs that make their failure modes and mechanisms unique. This paper presents a comprehensive review for industry and academic research on LED failure mechanisms and reliability to help LED developers and end-product manufacturers focus resources in an effective manner. The focus is on the reliability of LEDs at the die and package levels. The reliability information provided by the LED manufacturers is not at a mature enough stage to be useful to most consumers and end-product manufacturers. This paper provides the groundwork for an understanding of the reliability issues of LEDs across the supply chain. We provide an introduction to LEDs and present the key industries that use LEDs and LED applications. The construction details and fabrication steps of LEDs as they relate to failure mechanisms and reliability are discussed next. We then categorize LED failures into thirteen different groups related to semiconductor, interconnect, and package reliability issues. We then identify the relationships between failure causes and their associated mechanisms, issues in thermal standardization, and critical areas of investigation and development in LED technology and reliability. © 2011 Elsevier Ltd. All rights reserved.

Pillai M.R.A.,Bhabha Atomic Research Center | Knapp Jr. F.F.,Isotope Development Group
Quarterly Journal of Nuclear Medicine and Molecular Imaging | Year: 2012

Fission-produced 99Mo (F 99Mo) is traditionally used for fabrication of 99Mo/99mTc alumina-based column generators. In this paper, several emerging strategies are discussed which are being pursued or have been suggested to overcome the continuing shortages of F 99Mo. In addition to the hopeful eventual success of these proposed new 99Mo and 99mTc production technologies, an additional attractive strategy is the alternative production and use of low specific activity (LSA) 99Mo. This strategy avoids fission and is accomplished by direct activation of molybdenum targets in nuclear reactors, which would preclude sole continued reliance on F 99Mo. The principal focus of this paper is a detailed discussion on the advantages and strategies for enhanced production of LSA 99Mo using an international network of research reactors. Several effective strategies are discussed to obtain 99mTc from LSA 99Mo as well as more efficient use of the alumina-based generator system. The delayed time period between 99Mo production and traditional 99Mo/99mTc alumina column generator manufacture and distribution to user sites results in the loss of more than 50% of 99Mo activity. Another strategy is a paradigm shift in the use of 99Mo by recovering clinical-grade 99mTc from 99Mo solution as an alternative to use of 99Mo/ 99mTc column generators, thereby avoiding substantial decreased availability of 99Mo from radioactive decay. Implementation of the suggested strategies would be expected to increase availability of 99mTc to the clinical user community by several fold. Additional important advantages for the use of LSA 99Mo include eliminating the need for fission product waste management and precluding proliferation concerns by phasing out the need for high (HEU)- and low (LEU)-enriched uranium targets required for F 99Mo production.

Das S.,Bhabha Atomic Research Center
Pramana - Journal of Physics | Year: 2010

The cross-section for the π+π-π0 invariant mass distribution in the γp reaction in the GeV region is calculated. This reaction is assumed to proceed through the formation of the ω-meson in the intermediate state, because the production cross-section for this meson in the γp reaction in the GeV region is significant and it has a large branching ratio (88.8%) in the π+π -π0 channel. The cross-sections for this reaction are calculated using the energy-dependent reaction amplitude, fγp→ω p(0), extracted from the latest ω-meson photoproduction data. We use established procedure to calculate other factors, like width and propagator of the ω-meson, so that our calculation can provide reliable cross-section. The calculated results reproduce the measured π+π -π0 invariant mass distribution spectra in the γp reaction. © Indian Academy of Sciences.

Parchur A.K.,Banaras Hindu University | Ningthoujam R.S.,Bhabha Atomic Research Center
Dalton Transactions | Year: 2011

The nanoparticles of CaMoO 4:Eu 3+ (Eu 3+ = 0, 1, 3, 5, 7, 10 at. %) are prepared at low temperature (150 °C for 3 h) using urea hydrolysis in ethylene glycol. These are characterized by X-ray diffraction (XRD), infrared spectroscopy (IR) and transmission electron microscopy (TEM). From XRD study, it was found that the solubility limit of Eu 3+ ions at the Ca 2+ sites is up to 3 at. % and above this, phase segregation occurs. In combination with Rietveld analysis, its crystal structure was found to be tetragonal phase (space group I4 1/a (88) and Z = 4 (number of CaMoO 4 formula units per unit cell). Unit cell parameters and bond distances are calculated. The average crystallite sizes of as-prepared, 500 and 900 °C heated samples are found to be 20, 35 and 70 nm, respectively. The lattice strain is found to be 0.003-0.005. From IR study, the bands at 820 and 441 cm -1 are assigned to asymmetric stretching and bending vibrations of the MoO 4 2- tetrahedron, respectively. From TEM study, the shape of particle was found to be spherical. The high resolution TEM suggests a change in orientation of the crystal on annealing up to 900 °C. © The Royal Society of Chemistry 2011.

Dutta Choudhury S.,University of Maryland Baltimore County | Dutta Choudhury S.,Bhabha Atomic Research Center | Ray K.,University of Maryland Baltimore County | Lakowicz J.R.,University of Maryland Baltimore County
Journal of Physical Chemistry Letters | Year: 2012

Fluorescence correlation spectroscopy (FCS) is a widely used technique to investigate the interactions and dynamics of molecules, below micromolar concentrations. Silver nanostructure (AgNS) substrates can extend the applicability of FCS to higher concentrations, which is useful for many biologically relevant reactions. Additionally, these substrates can improve detection efficiency by increasing fluorescence signal intensities. The ease of preparation of the AgNS substrates in comparison to previously investigated materials prepared by top-down nanofabrication is expected to make them readily available and suitable for various FCS applications. © 2012 American Chemical Society.

Ambashta R.D.,University of Eastern Finland | Ambashta R.D.,Bhabha Atomic Research Center | Sillanpaa M.E.T.,University of Eastern Finland | Sillanpaa M.E.T.,Lappeenranta University of Technology
Journal of Environmental Radioactivity | Year: 2012

Radiation hazards of radionuclides arising from nuclear plant facilities are well known. Separation technologies are used to concentrate the radionuclides and prevent the spread of this hazard to the environment. The present review describes the recent advances made in radioactive waste treatment using membrane separation technology. The first part discusses the membrane methods for collective separation of radionuclides and the second part discusses the membrane methods for selective separation of individual radionuclides. For the collection separation of radionulides, methods include reverse osmosis, precipitation followed by ultrafiltration or microfiltration and membrane distillation. Individual elements have been separated using liquid supported membranes, polymer inclusion membranes, solid polymer based electrolysis, nanofiltration, electrochemical salt-splitting process and other advanced separation methods. © 2011 Elsevier Ltd.

Aggarwal M.,University of Mumbai | Kailas S.,Bhabha Atomic Research Center
Physical Review C - Nuclear Physics | Year: 2010

Dependence of nuclear level density parameter on the angular momentum and temperature is investigated in a theoretical framework using the statistical theory of hot rotating nuclei. The structural effects are incorporated by including shell correction, shape, and deformation. The nuclei around Z≈50 with an excitation energy range of 30 to 40 MeV are considered. The calculations are in good agreement with the experimentally deduced inverse level density parameter values especially for In109, Sb113, Te122, I123, and Cs127 nuclei. © 2010 The American Physical Society.

Mitra A.,Bhabha Atomic Research Center
General Relativity and Gravitation | Year: 2010

Following Einstein's definition of Lagrangian density and gravitational field energy density (Einstein in Ann Phys Lpz 49:806, 1916, Einstein in Phys Z 19:115, 1918, Pauli in Theory of Relativity, B.I. Publications, Mumbai, 1963), Tolman derived a general formula for the total matter plus gravitational field energy (P0) of an arbitrary system (Tolman in Phys Rev 35:875, 1930, Tolman in Relativity, Thermodynamics & Cosmology, Clarendon Press, Oxford, 1962, Xulu in hep-th/0308070, 2003). For a static isolated system, in quasi-Cartesian coordinates, this formula leads to the well known result P0= ∫ √-g(T0 0 - T1 1 - T2 2 - T3 3d3x, where g is the determinant of the metric tensor and Tb a is the energy momentum tensor of the matter. Though in the literature, this is known as "Tolman Mass", it must be realized that this is essentially "Einstein Mass" because the underlying pseudo-tensor here is due to Einstein. In fact, Landau-Lifshitz obtained the same expression for the "inertial mass" of a static isolated system without using any pseudo-tensor at all and which points to physical significance and correctness of Einstein Mass (Landau, Lifshitz in The Classical Theory of Fields, Pergamon Press, Oxford, 1962)! For the first time we apply this general formula to find an expression for P0 for the Friedmann-Robertson-Walker (FRW) metric by using the same quasi-Cartesian basis. As we analyze this new result, it transpires that, physically, a spatially flat model having no cosmological constant is preferred. Eventually, it is seen that conservation of P0 is honoured only in the static limit. © 2009 Springer Science+Business Media, LLC.

Kain V.,Bhabha Atomic Research Center
Procedia Engineering | Year: 2014

Flow accelerated corrosion (FAC) is distinct from erosion and is primarily an electrochemical corrosion process aided by chemical dissolution and mass transfer. The forms of erosion including single and dual phase FAC and liquid droplet impingement are discussed and differentiated. The reasons for a maxima being observed in FAC rates at 150-170 °C has been explained as well as high FAC rates owing to an inversion in solubility occurring with pH occurring at temperatures around 300 °C. Experience from examination of FAC affected components establishing signature patterns of single and two phase FAC is presented. FAC control measures are discussed. The data required from laboratory tests is identified and ongoing lab studies to measure solubility of various oxides is presented. © 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.

Mitra A.,Bhabha Atomic Research Center
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2010

At first sight, for a static fluid sphere, Effective Mass Energy Density (EMD) appears to be (ρ + 3 p / c2), where ρ is the bare mass density, p is the isotropic pressure and c is the speed of light. But it is pointed out that such a direct increase in EMD is valid only for a purely local point of view. And since there is no truly local definition of "gravitational field", such a notion could actually be misleading. On the other hand, by using the Tolman mass formula, we point out that, from a global perspective, the Active Mass Energy Density is sqrt(g00) (ρ + 3 p / c2) and which is obviously smaller than (ρ + 3 p / c2) because g00 < 1. Then we show that the AGMD eventually is (ρ - 3 p / c2), i.e., exactly opposite to what is generally believed. We further identify the AGMD to be proportional to the Ricci Scalar. By using this fundamental and interesting property, we obtain the GR virial theorem in terms of appropriate "proper energies". © 2010 Elsevier B.V. All rights reserved.

Ahmed Z.,Bhabha Atomic Research Center
American Journal of Physics | Year: 2010

Discussions of the scattering length frequently focus on the special case of the deuteron, and sometimes statements that are not true in general are made. To obtain a deeper understanding, we study the scattering length as a function of the depth V0 of a square well and an exponential well and show how the scattering length becomes infinite at values of V0 for which new bound states appear at zero energy. © 2010 American Association of Physics Teachers.

We show from a simulations-based study of the TACTIC telescope that fractal and wavelet analysis of Cerenkov images, recorded in a single imaging Cerenkov telescope, enables almost complete segregation of isotropic gamma-ray initiated events from the overwhelming background of cosmic ray hadron-initiated events. This presents a new method for measuring galactic and extragalactic gamma-ray background above 1 TeV energy. Preliminary results based on this method are reported here. Primary aim is to explore the possibility of using data recorded by a single imaging atmospheric Cerenkov telescope (IACT) for making accurate measurements of diffuse galactic and extragalactic gamma-ray flux above ∼1 TeV energy. Using simulated data of atmospheric Cerenkov images recorded in an IACT, initiated, both, by cosmic ray protons and diffuse gamma-rays with energies above 4 TeV and 2 TeV respectively, we identify the most efficient fractal/wavelet parameters of the recorded images for primary identification. The method is based on the pattern recognition technique and employs fractal and wavelet analysis of the recorded Cerenkov images for gamma-hadron segregation. We show that the value of wavelet dimension parameter B 6 can segregate Cerenkov images of hadronic origin from those of diffuse gamma-ray origin with almost 100% accuracy. We use the results to get a preliminary upper limit estimate of the diffuse galactic gamma-ray flux within galactic range of b ≤ -5° and l ≤ 200° above 2 TeV from a 36 h data set recorded by the TACTIC telescope. © 2010 Elsevier B.V. All rights reserved.

Nasim M.,Variable Energy Cyclotron Center | Kumar L.,Kent State University | Netrakanti P.K.,Bhabha Atomic Research Center | Mohanty B.,Variable Energy Cyclotron Center
Physical Review C - Nuclear Physics | Year: 2010

We have compared the experimental data on charged-particle elliptic flow parameter (v2) in Au+Au collisions at midrapidity for √s NN=9.2, 19.6, 62.4, and 200 GeV with results from various models in heavy-ion collisions such as the ultrarelativistic quantum molecular dynamics (UrQMD) model, a multiphase transport model (AMPT), and heavy-ion jet interaction generator (HIJING). We observe that the average v2 ( 2) from the transport model UrQMD agrees well with the measurements at √sNN=9.2 GeV but increasingly falls short of the experimental 2 values as the beam energy increases. The difference in 2 is of the order of 60% at √sNN=200 GeV. The 2 results from HIJING are consistent with zero, while those from AMPT with default settings, a model based on HIJING with additional initial- and final-state rescattering effects included, give a 2 value of about 4% for all the beam energies studied. This is in contrast to an increase in 2 with beam energy for the experimental data. A different version of the AMPT model, which includes partonic effects and quark coalescence as a mechanism of hadronization, gives higher values of 2 among the models studied and is in agreement with the measured 2 values at √sNN=200 GeV. These studies show that the experimental 2 has substantial contribution from partonic interactions at √sNN=200 GeV, whose magnitude reduces with decrease in beam energy. We also compare the available data on the transverse momentum and pseudorapidity dependence of v2 to those from these models. © 2010 The American Physical Society.

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

Yedukondalu M.,Indian Institute of Technology Bombay | Maity D.K.,Bhabha Atomic Research Center | Ravikanth M.,Indian Institute of Technology Bombay
European Journal of Organic Chemistry | Year: 2010

The first: examples of β,meso-acetylenyl-bridged, asymmetrical, covalently linked, porphyrin, dyads, containing two different subunits, such as ZnN4P-N3OP (1), ZnN4P-N3SP (2), ZnN4P-N2SOP (4) and ZnN4P-N2S 2P (6), were synthesized by the coupling of a β-acetylenyl, ZnN4 porphyrin with a mesobromoheteroporphyrin under mild, Pd°-catalyzed, coupling conditions. The dyads containing different types of metalfree subunits, such as N4P-N3SP (3), N 4P-N2SOP (5) and N4PN2S2P (7), were synthesized by the demetallation of the corresponding dyads. The seven β.meso-acetylenyl dyads 1-7 were characterized, by NMR, MS, absorption, fluorescence and electrochemical techniques. The NMR, absorption and electrochemical studies support an electronic interaction be tween the subunits in all seven dyads. The steady-state fluorescence studies on dyads 1-7 support an efficient energy transfer from the donor (ZnN4 or N4) subunit to the acceptor heteroporphyrin subunit upon excitation of the ZnN 4/N4 subunit. First-principle-based, quantum-chemical studies carried, out on dyads 1, 2, 4 and 6 further support an electronic interaction between the donor and acceptor subunits. The computational studies also predict significant tuning of the electronic energy levels in these dyads with the modification of the porphyrin core of the acceptor groups. The calculations support the experimental results of efficient donor→acceptor energy transfer in these dyads. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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.

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.

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.

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.

Sundararajan M.,Bhabha Atomic Research Center
Separation Science and Technology (Philadelphia) | Year: 2013

We have investigated the possible interaction between functionalized carbon nanotubes (CNT) and uranyl using density functional theory (DFT). Due to the apparent solubility problems of CNT, we have taken the oxidized CNT and we have functionalized it with a supramolcule, curcurbituril (CB). Further, the supramolecule itself has solubility issue and hence, we have taken the hydroxylated CB (OH-CB). The CNT and OH-CB molecule interacts with each other through hydrogen bonding. Our calculations show that functionalized carbon nanotubes and cucurbituril can be used not only for improving the solubilities, but is also much more efficient for binding of uranyl ion as compared to their unfunctionalized counterpart. These findings are new and can open up a new era for actinide speciation and separation chemistry using CNT. © Taylor & Francis Group, LLC.

Ramachandran C.S.,Annamalai University | Balasubramanian V.,Annamalai University | Ananthapadmanabhan P.V.,Bhabha Atomic Research Center
Ceramics International | Year: 2013

Thermal barrier coatings (TBCs) used in gas-turbine engines afford higher operating temperatures, resulting in enhanced efficiencies and performance. However, during aero engine operation, environmentally ingested airborne particles, which includes mineral debris, sand dust and volcanic ashes get ingested by the turbine with the intake air. As engine temperatures increase, the finer debris tends to adhere to the coating surface and form calcium magnesium alumino-silicate (CMAS) melts that penetrate the open void spaces in the coating. Upon cooling at the end of an operation cycle, the melt freezes and the infiltrated volume of the coating becomes rigid and starts to spall by losing its ability to accommodate strains arising from the thermal expansion mismatch with the underlying metal. The state-of-the-art ZrO2-7- weight% Y2O3 (YSZ) coatings are susceptible to the aforementioned degradation. Rare-earth zirconates have generated substantial interest as novel thermal barrier coatings (TBC) based primarily on their intrinsically lower thermal conductivity and higher resistance to sintering than YSZ. In addition, the pyrochlore zirconates are stable as single phases at up to their melting point. La2Zr2O7 (LZ) is one among such candidates. Hence, the present study focusses on the comparison of cyclic molten CMAS infiltration behaviour of the base metal Inconel 738 (BM), the bond coat NiCrAlY (BC), the duplex YSZ, the LZ coating and a five layered coated specimen with LZ as top layer. Among those coatings mentioned above, the five layer coated specimen showed excellent CMAS infiltration resistance under thermal cycling conditions. © 2012 Elsevier Ltd and Techna Group S.r.l.

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.

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.

We investigate structural, energetic and spectroscopic aspects of the finite size hydrated NO3- · nH 2O (n = 1-8) clusters based on the first principles electronic structure calculations. It is observed that the geometrical parameters at MP2/6-311++G(d,p) level are almost equal to that of calculated at B3LYP/6-311++G(d,p) level for the higher size of clusters (n > 3). Our results reveal that total interaction energy and its components do vary linearly with the size of the clusters. Two types of scaling factors are implemented in two different regions to account the effect of anharmonic vibrations. The degeneracy of in-plane bending and asymmetric NO stretching mode in nitrate system is lifted due to hydration. An excellent agreement is observed between the present calculated H 2O bending and asymmetric NO stretching frequencies with the experimental results (within 4% w.r.t. experimentally measured values). Understanding the nature of normal modes of vibration at the molecular level provides information of the local hydration environment during stepwise solvation. © 2012 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.

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.

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.

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.

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.

Razdan A.,Bhabha Atomic Research Center
Physica A: Statistical Mechanics and its Applications | Year: 2013

Extensive air showers are produced when high energy cosmic rays or γ-rays enter from the top of the atmosphere. Extensive air showers are multi-fractal in nature and in this paper we explore the topological properties of these showers. We show that the topology of extensive air showers has an exponential distribution which may arise due to the inherent tree structure character of its passage in the atmosphere. © 2012 Elsevier B.V. All rights reserved.

Fleig T.,CNRS Laboratory for Quantum Chemistry and Physics | Nayak M.K.,Bhabha Atomic Research Center
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

We present a rigorous method for accurate ab initio calculations of the electron electric-dipole-moment P,T-odd interaction constant Wd. The approach uses configuration interaction wave functions and Dirac four-component spinors as one-particle basis functions, and the interaction constant W d is obtained as an expectation value over these correlated wave functions. We apply the method to the HfF+ molecular ion and determine spectroscopic constants for four low-lying electronic states. For one of these states (Ω=1) we determine the effective electric field (E eff=WdΩ), which amounts to 23.3 GV/cm, correlating 34 valence and outer atomic core electrons and using wave-function expansions with nearly 5×108 coefficients. © 2013 American Physical Society.

Mhatre M.,Bhabha Atomic Research Center
Methods in Molecular Biology | Year: 2013

Pineapple (Ananas comosus L., Merr.) is a commercially important crop, grown in the tropical and subtropical regions. However, the crop is faced with postharvest damage and poor varietal and nutritional improvement. Being a vegetatively propagated crop, conventional breeding programs take longer time for genetic improvement, which may not necessarily successfully develop an improved cultivar. Hence, the genetic modification of pineapple is an alternative handy approach to improve pineapple. We have established an Agrobacterium-mediated transformation system using leaf bases from in vitro-grown pineapple plants. Being a monocot, acetosyringone is added to the culture medium for overnight growth of Agrobacterium and transformation to transfer a gene of interest MSI99 soybean ferritin. Leaf bases isolated from in vitro shoot cultures are treated with Agrobacterium suspension at two dilutions, 10× and 20×, for 30 min. Explants are subsequently blot dried and cultured on gelrite solidified hormone-free Pin1 medium for 2 days (cocultivation). Periodic transfer is first done to the regeneration medium (Pin1) containing cefotaxime for the suppression of Agrobacterium growth. The transformants are selected by culturing on Pin1 medium containing cefotaxime and kanamycin. Multiple shoots, regenerated in leaf bases, are further multiplied and individually rooted in the liquid RM medium amended with antibiotics to recover plants. Putative transformants are analyzed for transgene integration and expression using standard molecular biological methods of PCR, RT-PCR, and genomic Southern. © 2013 Springer Science+Business Media New York.

Mondal A.,Indian Institute of Technology Bombay | Ghosh S.,Indian Institute of Technology Bombay | Reddy G.R.,Bhabha Atomic Research Center
Engineering Structures | Year: 2013

Most seismic design codes today include the nonlinear response of a structure implicitly through a 'response reduction/modification factor' (R). This factor allows a designer to use a linear elastic force-based design while accounting for nonlinear behaviour and deformation limits. This research focuses on estimating the actual values of this factor for realistic RC moment frame buildings designed and detailed following the Indian standards for seismic and RC designs and for ductile detailing, and comparing these values with the value suggested in the design code. The primary emphases are in a component-wise computation of R, the consideration of performance-based limits at both member and structure levels, a detailed modelling of the RC section behaviour, and the effects of various analysis and design considerations on R. Values of R are obtained for four realistic designs at two performance levels. The results show that the Indian standard recommends a higher than actual value of R, which is potentially dangerous. This paper also provides other significant conclusions and the limitations of this study. © 2013 Elsevier Ltd.

Padma N.,Bhabha Atomic Research Center
Materials Science in Semiconductor Processing | Year: 2015

Effect of channel length on hysteresis and threshold voltage shift in copper phthalocyanine (CuPc) based organic field effect transistors was studied. Contrary to expectation, longer channel length devices exhibited minimum threshold voltage shift. Influence of channel length on the contribution of hole and electron trapping to threshold voltage stability was determined. Shortest channel length devices exhibited highest electron trapping effect while longest channel devices exhibited minimum hole as well as electron trapping. Lower hole trap effect for longer channel length devices was suggested to be due to reduced longitudinal field between source and drain electrodes while minimum electron trapping was attributed to suppression of drain current by increased hole trap centres. © 2015 Elsevier Ltd. All rights reserved.

Mir T.A.,Bhabha Atomic Research Center
Physica A: Statistical Mechanics and its Applications | Year: 2012

Benford's law states that the occurrence of significant digits in many data sets is not uniform but tends to follow a logarithmic distribution such that the smaller digits appear as first significant digits more frequently than the larger ones. We investigate here numerical data on the country-wise adherent distribution of seven major world religions i.e. Christianity, Islam, Buddhism, Hinduism, Sikhism, Judaism and Baha'ism to see if the proportion of the leading digits occurring in the distribution conforms to Benford's law. We find that the adherent data of all the religions, except Christianity, excellently does conform to Benford's law. Furthermore, unlike the adherent data on Christianity, the significant digit distribution of the three major Christian denominations i.e. Catholicism, Protestantism and Orthodoxy obeys the law. Thus in spite of their complexity general laws can be established for the evolution of religious groups. © 2011 Elsevier B.V. All rights reserved.

Pant L.M.,Bhabha Atomic Research Center
Journal of Instrumentation | Year: 2012

It is proposed to install the fourth endcap (RE4) consisting of Resistive Plate Chambers (RPCs) for the Compact Muon Solenoid (CMS) muon endcap system, in order to improve its Level-1 trigger efficiency and thereby completing the full implementation of the Technical Design Report (TDR). This station will be installed in the first long shutdown of the Large Hadron Collider (LHC) during 2013-2014. With lessons learnt from the earlier installation of the RPCs, several modifications in the new construction and test procedures have been recommended for this upgrade. The prototypes for the upgrade were assembled in 2011, thereby giving the green signal for mass production for bakelite and gas gaps. This paper also discusses the standardisation of leak and spacer tests for the bakelite gas-gaps, the new design for the Cu cooling system, the data base and the preparedness at the three assembly sites at CERN, Mumbai and Ghent. © CERN 2012.

Ahmed Z.,Bhabha Atomic Research Center
Journal of Physics A: Mathematical and Theoretical | Year: 2012

For complex one-dimensional potentials, we propose the asymmetry of both reflectivity and transmitivity under time reversal: R(-k) ≠ R(k) and T(-k) ≠ T(k), unless the potentials are real or PT-symmetric. For complex PT-symmetric scattering potentials, we propose that Rleft(-k) = Rright(k) and T(-k) = T(k). So far, the spectral singularities (SS) of a one-dimensional non-Hermitian scattering potential are witnessed/ conjectured to be at most 1. We present a new non-Hermitian parametrization of the Scarf II potential to reveal its four new features. Firstly, it displays the just acclaimed (in)variances. Secondly, it can support two spectral singularities at two pre-assigned real energies (E* = α2, β2) either in T(k) or in T(-k), when αβ > 0. Thirdly, when αβ < 0 it possesses one SS in T(k) and the other in T(-k). Fourthly, when the potential becomes PT-symmetric [(α+β) = 0], we obtain T(k) = T(-k), it possesses a unique SS at E = α2 in both T(-k) and T(k). Lastly, for completeness, when α = iγ and β = iδ there are no SS, instead we get two real energies -γ2 and -δ2 of the complex PT-symmetric Scarf II belonging to the two well-known branches of discrete bound-state eigenvalues. We find them as E+M = -(γ-M)2 and E-N = -(δ - N) 2; M(N) = 0, 1, 2,... with 0≤ M(N) < γ(δ).

Mandal D.,Bhabha Atomic Research Center
Powder Technology | Year: 2015

Hydrodynamic properties of different particles in unary liquid-solid fluidized bed were well studied and are reported in literature. However, till date the same in liquid-solid binary packed fluidized bed has not been studied and no information is available in literature. Presently, it is well known that particles behave differently in a gas-solid packed fluidized bed; than in a unary gas-solid fluidized bed. A series of experiments were conducted to investigate the hydrodynamic characteristics of particles in liquid-solid packed fluidized bed as a function of particle size, fraction of interstitial void volume filled by particles and bed wall temperature. It was found that, like in gas-solid packed fluidized bed; the minimum fluidization velocity of particles in liquid-solid packed fluidized bed is lower than that of particles in conventional unary liquid-solid fluidized bed, but unlike gas-solid system, the minimum fluidization velocity increases with an increase in bed wall temperature. Experimental details and results are discussed in this paper. © 2015 Elsevier B.V.

Misra N.L.,Bhabha Atomic Research Center
Pramana - Journal of Physics | Year: 2011

Nuclear energy is one of the clean options of electricity generation for the betterment of human life. India has an ambitious program for such electricity generation using different types of nuclear reactors. The safe and efficient generation of electricity from these reactors requires quality control of different nuclear materials, e.g. nuclear fuel, structural materials, coolant, moderators etc. These nuclear materials have to undergo strict quality control and should have different specified parameters for their use in nuclear reactors. The concentration of major and trace elements present in these materials should be within specified limits. For such chemical quality control of these materials, major and trace elemental analytical techniques are required. Since some of these materials are radioactive, the ideal chemical characterization techniques should have multielement analytical capability, should require very less sample (micrograms level) for analysis so that the radioactive waste generated, and radiation exposure to the detector and operator are minimum. Total reflection X-ray fluorescence (TXRF) and energy dispersive X-ray fluorescence (EDXRF) with improved features, e.g. application of filters, secondary target and instrumental geometry require very small amount of sample and thus can be suitably used for the characterization of nuclear materials mainly for the determination of elements at trace and major concentration levels. In Fuel Chemistry Division, TXRF analytical methods have been developed for trace element determinations in uranium and thorium oxides, chlorine determination in nuclear fuel and cladding materials, sulphur in uranium, uranium in sea water etc. Similarly, EDXRF analytical methods with radiation filters (to reduce background) and improved sample preapartion techniques, e.g. fusion bead and taking samples in the form of solution on filter papers have been used for developing analytical methods for the determination of U and Th in their mixed matrices, Cd in uranium etc. Some of these studies have been reported in this paper. © Indian Academy of Sciences.

Azam M.,Bhabha Atomic Research Center | Bhatt J.R.,Physical Research Laboratory | Sarkar U.,Physical Research Laboratory
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

Superfluid condensation of neutrinos of cosmological origin at a low enough temperature can provide simple and elegant solution to the problems of neutrino oscillations and the accelerated expansion of the universe. It would give rise to a late time cosmological constant of small magnitude and also generate tiny masses for the neutrinos as observed from their flavor oscillations. We show that carefully prepared beta decay experiments in the laboratory would carry signatures of such a condensation, and thus, it would be possible to either establish or rule out neutrino condensation of cosmological scale in laboratory experiments. © 2011 Elsevier B.V.

Auluck S.K.H.,Bhabha Atomic Research Center
Physics of Plasmas | Year: 2011

Relatively long-lived spheroidal structures coincident with the neutron emission phase have been observed in frozen deuterium fiber Z-pinch and some plasma focus devices. Existence of energetic ion-trapping mechanism in plasma focus has also been inferred from experimental data. It has been conjectured that these are related phenomena. This paper applies Turner's theory [L. Turner, IEEE Trans. Plasma Sci. 14, 849 (1986)] of relaxation of a Hall magnetofluid to construct a model of these structures and ion-trapping mechanism. Turner's solution modified for a finite-length plasma is used to obtain expressions for the magnetic field, velocity, and equilibrium pressure fields and is shown to represent an entity which is simultaneously a fluid vortex, a force-free magnetic field, a confined finite-pressure plasma, a charged object, and a trapped energetic ion beam. Characteristic features expected from diagnostic experiments are evaluated and shown to resemble experimental observations. © 2011 American Institute of Physics.

Basu S.,Bhabha Atomic Research Center
Nature Reviews Clinical Oncology | Year: 2010

In this Perspective the feasibility, scope and impact of integrating PET-based personalized medicine into the evidence-based clinical practice of oncology is discussed. The basic concepts of 'evidence-based medicine' and 'personalized medicine' at times seem contradictory; however, I will discuss, with specific clinical situations as examples, a synergistic and probably incremental link between the two and propose that the result of such integration will ultimately improve patient management. Tailoring therapeutic approaches and regimens by molecular imaging, with PET at its forefront, would enable disease management at the individual level and this modification would hopefully further strengthen the evidence-based approach in oncology. © 2010 Macmillan Publishers Limited. All rights reserved.

Basu B.,Bhabha Atomic Research Center
Molecular & cellular proteomics : MCP | Year: 2012

The extraordinary radioresistance of Deinococcus radiodurans primarily originates from its efficient DNA repair ability. The kinetics of proteomic changes induced by a 6-kGy dose of gamma irradiation was mapped during the post-irradiation growth arrest phase by two-dimensional protein electrophoresis coupled with mass spectrometry. The results revealed that at least 37 proteins displayed either enhanced or de novo expression in the first 1 h of post-irradiation recovery. All of the radiation-responsive proteins were identified, and they belonged to the major functional categories of DNA repair, oxidative stress alleviation, and protein translation/folding. The dynamics of radiation-responsive protein levels throughout the growth arrest phase demonstrated (i) sequential up-regulation and processing of DNA repair proteins such as single-stranded DNA-binding protein (Ssb), DNA damage response protein A (DdrA), DNA damage response protein B (DdrB), pleiotropic protein promoting DNA repair (PprA), and recombinase A (RecA) substantiating stepwise genome restitution by different DNA repair pathways and (ii) concurrent early up-regulation of proteins involved in both DNA repair and oxidative stress alleviation. Among DNA repair proteins, Ssb was found to be the first and most abundant radiation-induced protein only to be followed by alternate Ssb, DdrB, indicating aggressive protection of single strand DNA fragments as the first line of defense by D. radiodurans, thereby preserving genetic information following radiation stress. The implications of both qualitative or quantitative and sequential or co-induction of radiation-responsive proteins for envisaged DNA repair mechanism in D. radiodurans are discussed.

Das S.,Bhabha Atomic Research Center
Physical Review C - Nuclear Physics | Year: 2011

The π0γ invariant mass distribution spectra in the (γ,π0γ) reaction were measured by the TAPS/ELSA Collaboration to look for the hadron parameters of the ω meson in the Nb nucleus. We study the mechanism for this reaction, where we consider that the elementary reaction in the Nb nucleus proceeds as γN→ωN;ω→π0γ. The ω-meson photoproduction amplitude for this reaction is extracted from the measured four-momentum transfer distribution in the γp→ωp reaction. The propagation of the ω meson and the distorted wave function for the π0 meson in the final state are described by the eikonal form. The ω and π0 mesons' nucleus optical potentials, appearing in the ω meson propagator and π0 meson distorted wave function respectively, are estimated using the t approximation. The effects of pair correlation and color transparency are also studied. The calculated results do not show medium modification for the ω meson produced in the nucleus for momentum greater than 200 MeV. It occurs because the ω meson predominantly decays outside the nucleus. The dependence of the cross section on the final-state interaction is also investigated. The broadening of the ω-meson mass distribution spectra is shown to occur due to the large resolution width associated with the detector used in the experiment. © 2011 American Physical Society.

Dikshit B.,Bhabha Atomic Research Center
Physics Essays | Year: 2011

In this paper, a new concept of light is proposed so that two important unsolved problems of light, viz., invariance of speed of light with respect to motion of source/observer and wave-particle duality, are solved. Although the invariance of speed of light is an experimentally verified fact and is incorporated into the second postulate of a special theory of relativity, it is not compatible with our common experience about matter in motion. However, in this new concept, the invariance of speed of light comes as a natural consequence without violating our common sense. Another advantage of this approach is that it solves the problem of wave-particle duality of light by offering a single picture that explains both the results showing particlelike and wavelike behaviors. © 2011 Physics Essays Publication.

Choi S.,Yeungnam University | Tripathi A.,Bhabha Atomic Research Center | Singh D.,Yeungnam University
Journal of Biomedical Nanotechnology | Year: 2014

Nanotechnology has become important in various disciplines of technology and science. It has proven to be a potential candidate for various applications ranging from biosensors to the delivery of genes and therapeutic agents to tissue engineering. Scaffolds for every application can be tailor made to have the appropriate physicochemical properties that will influence the in vivo system in the desired way. For highly sensitive and precise detection of specific signals or pathogenic markers, or for sensing the levels of particular analytes, fabricating target-specific nanomaterials can be very useful. Multi-functional nano-devices can be fabricated using different approaches to achieve multi-directional patterning in a scaffold with the ability to alter topographical cues at scale of less than or equal to 100 nm. Smart nanomaterials are made to understand the surrounding environment and act accordingly by either protecting the drug in hostile conditions or releasing the "payload" at the intended intracellular target site. All of this is achieved by exploiting polymers for their functional groups or incorporating conducting materials into a natural biopolymer to obtain a "smart material" that can be used for detection of circulating tumor cells, detection of differences in the body analytes, or repair of damaged tissue by acting as a cell culture scaffold. Nanotechnology has changed the nature of diagnosis and treatment in the biomedical field, and this review aims to bring together the most recent advances in smart nanomaterials. Copyright © 2014 American Scientific Publishers All rights reserved.

Ramana A.S.V.,Bhabha Atomic Research Center
Journal of Chemical Physics | Year: 2013

The coupling parameter expansion in thermodynamic perturbation theory of simple fluids is generalized to include the derivatives of bridge function with respect to coupling parameter. We applied seventh order version of the theory to Square-Well (SW) and Lennard-Jones (LJ) fluids using Sarkisov Bridge function. In both cases, the theory reproduced the radial distribution functions obtained from integral equation theory (IET) and simulations with good accuracy. Also, the method worked inside the liquid-vapor coexistence region where the IETs are known to fail. In the case of SW fluids, the use of Carnahan-Starling expression for Helmholtz free energy density of Hard-Sphere reference system has improved the liquid-vapor phase diagram (LVPD) over that obtained from IET with the same bridge function. The derivatives of the bridge function are seen to have significant effect on the liquid part of the LVPD. For extremely narrow SW fluids, we found that the third order theory is more accurate than the higher order versions. However, considering the convergence of the perturbation series, we concluded that the accuracy of the third order version is a spurious result. We also obtained the surface tension for SW fluids of various ranges. Results of present theory and simulations are in good agreement. In the case of LJ fluids, the equation of state obtained from the present method matched with that obtained from IET with negligible deviation. We also obtained LVPD of LJ fluid from virial and energy routes and found that there is slight inconsistency between the two routes. The applications lead to the following conclusions. In cases where reference system properties are known accurately, the present method gives results which are very much improved over those obtained from the IET with the same bridge function. In cases where reference system data is not available, the method serves as an alternative way of solving the Ornstein-Zernike equation with a given closure relation with the advantage that solution can be obtained throughout the phase diagram with a proper choice of the reference system. © 2013 AIP Publishing LLC.

Goswami B.K.,Bhabha Atomic Research Center
Pramana - Journal of Physics | Year: 2011

We study theoretically the effect of truncating the nonlinear restoring force (exp(φ)-1 = σ ∞n =1 φn/n!) in the bistability pattern of the periodically driven, damped one-degree-of-freedom Toda oscillator that originally exhibits soft-spring bistability with counterclockwise hysteresis cycle. We observe that if the truncation is made third order, the harmonic bistability changes to hard-spring type with a clockwise hysteresis cycle. In contrast, for the fourth-order truncation, the bistability again becomes soft-spring type, overriding the effect of third-order nonlinearity. Furthermore, each higher odd-order truncation attempts to introduce hard-spring nature while each even-order truncation turns to soft-spring type of bistability. Overall, the hard-spring effect of every odd-order nonlinear term is weaker in comparison to the soft-spring effect of the next even-order nonlinear term. As a consequence, higher-order approximations ultimately converge to the soft-spring nature. Similar approximate analysis of Toda lattice has in recent past revealed remarkably similar flip-flop pattern between stochasticity (chaotic behaviour) and regularity (integrability). © Indian Academy of Sciences.

Kumar R.,North - Eastern Hill University | Nongkhlaw M.,North - Eastern Hill University | Acharya C.,Bhabha Atomic Research Center | Joshi S.R.,North - Eastern Hill University
Microbes and Environments | Year: 2013

Uranium (U)-tolerant aerobic chemo-heterotrophic bacteria were isolated from the sub-surface soils of U-rich deposits in Domiasiat, North East India. The bacterial community explored at molecular level by amplified ribosomal DNA restriction analysis (ARDRA) resulted in 51 distinct phylotypes. Bacterial community assemblages at the U mining site with the concentration of U ranging from 20 to 100 ppm, were found to be most diverse. Representative bacteria analysed by 16S rRNA gene sequencing were affiliated to Firmicutes (51%), Gammaproteobacteria (26%), Actinobacteria (11%), Bacteroidetes (10%) and Betaproteobacteria (2%). Representative strains removed more than 90% and 53% of U from 100 μM and 2 mM uranyl nitrate solutions, respectively, at pH 3.5 within 10 min of exposure and the activity was retained until 24 h. Overall, 76% of characterized isolates possessed phosphatase enzyme and 53% had PIB-type ATPase genes. This study generated baseline information on the diverse indigenous U-tolerant bacteria which could serve as an indicator to estimate the environmental impact expected to be caused by mining in the future. Also, these natural isolates efficient in uranium binding and harbouring phosphatase enzyme and metal- transporting genes could possibly play a vital role in the bioremediation of metal-/radionuclide-contaminated environments.

OBJECTIVES: To assess the performance of Lu-DOTATATE peptide receptor radionuclide therapy (PRRT) in metastatic gastroenteropancreatic neuroendocrine tumor (GEP-NET) and correlate it with primary tumor site, tumor proliferation index, and dual tracer imaging characteristics. MATERIALS AND METHODS: Fifty patients (M : F 33 : 17, age: 26–71 years) with histopathologically confirmed metastatic/inoperable NETs who had undergone at least three cycles of PRRT with Lu-DOTATATE were included in the analysis. As part of the pretreatment evaluation, they underwent either Tc-HYNIC TOC (n=40)/Ga-DOTATATE PET (n=10) or fluorine-18-fluorodeoxyglucose (F-FDG) PET-computed tomography (CT). Response was assessed after three and five cycles PRRT on the basis of three parameters: (a) symptomatic and subjective scale, (b) biochemical tumor marker level, and (c) objective imaging (F-FDG/Ga DOTATATE PET/CT, Tc-HYNIC TOC, ceCT), and was categorized using predefined criteria (detailed in methods). Stable disease on imaging assessment with response on symptomatic or biochemical tumor marker scales or both were included in the responder group. RESULTS: The study population was broadly classified into (a) metastatic GEP-NET with known primary (n=43 i.e. 86%), which was further subclassified according to the site of primary and (b) those with unknown primary (n=7 i.e. 14%). Symptomatic response: 96% of patients showed a symptomatic response or improvement in health-related quality of life, irrespective of tumor proliferation index, dual tracer imaging characteristics, and response or progression of disease in the scan. Biochemical tumor marker response: 83% of scan responders showed a decrease, 10% showed a stable value, and 7% showed an increase in tumor marker levels. Among the scan nonresponders, 67% patients showed a corresponding increase in the tumor marker level, 22% patient showed a decrease, whereas 11% showed stable values. Scan response: 31 out of total 50 patients (62%) showed a partial scan response with either a decrease in the number of somatostatin receptor (SSTR)-positive lesions or metabolic activity in F-FDG/Ga-DOTATATE PET-CT or both, 10 patients (20%) showed stable disease, and nine patients (18%) showed progressive disease. The higher objective partial scan response documented can be explained by the introduction of the F-FDG-PET/CT parameter as a determinant criterion. Among the responders category (n=41), 32 (78.04%) showed discordance between F-FDG-PET/CT-based and SSTR-based imaging, whereas eight out of nine patients with nonresponse category (88.89%) showed concordance between SSTR-based imaging and F-FDG-PET/CT. Conversely, 32 of 33 patients (96.97%) with SSTR/F-FDG discordance and nine out of 17 (52.94%) with concordance were finally classified as responders, whereas the remaining, that is, 1/33 (3.03%) in the ‘discordant’ category and 8/17 (47.06%) with imaging concordance were classified as nonresponders, respectively. CONCLUSION: Our data show that high pretherapy F-FDG maximum standardized uptake values were associated with increased chances of treatment refractoriness in GEP-NETs. However, symptomatic improvement was observed in most cases irrespective of grade and F-FDG uptake. High pretherapy F-FDG maximum standardized uptake value in both low-grade and high-grade NET predicted a poor outcome and was associated with disease progression. Introduction of F-FDG-PET/CT parameter as a determinant of response classification increases the percentage of objective scan responders among patients with grades I and II GEP-NETs as F-FDG activity was observed to decrease before SSTR-based imaging and more frequently compared with the latter. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.

Parangi T.F.,M. S. University of Baroda | Wani B.N.,Bhabha Atomic Research Center | Chudasama U.V.,M. S. University of Baroda
Industrial and Engineering Chemistry Research | Year: 2013

In the present endeavor, amorphous cerium phosphate (CP) and thorium phosphate (TP) have been synthesized by the sol-gel method. Further, CP and TP also have been synthesized under microwave irradiation to yield CPM and TPM. The materials have been characterized for elemental analysis (inductively coupled plasma-atomic emission spectrometry, ICP-AES), spectral analysis (Fourier transform infrared spectroscopy, FTIR), thermal analysis (TGA), X-ray diffraction studies, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, Brunauer-Emmett-Teller (BET) surface area analysis, and surface acidity (NH3-temperature programmed desorption (TPD)). Chemical stability of the materials in various acids, bases, and organic solvent media has been studied, and their potential use as solid acid catalysts has been explored by studying acetal formation. A simple, efficient, and highly eco-friendly protocol is described for the acetalization of benzaldehyde, cyclohexanone, acetophenone and benzophenone with pentaerythritol by varying parameters such as reaction time, catalyst amount, and mole ratio of the reactants. The catalytic activity of CP, TP, CPM, and TPM has been compared and correlated with surface properties of the materials. © 2013 American Chemical Society.

Paliya V.S.,Indian Institute of Astrophysics | Paliya V.S.,The New School | Stalin C.S.,Indian Institute of Astrophysics | Shukla A.,Indian Institute of Astrophysics | Sahayanathan S.,Bhabha Atomic Research Center
Astrophysical Journal | Year: 2013

Variable γ-ray emission has been discovered in five radio-loud narrow-line Seyfert 1 (NLSy1) galaxies by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. This has clearly demonstrated that these NLSy1 galaxies do have relativistic jets similar to two other cases of γ-ray-emitting active galactic nuclei (AGNs), namely, blazars and radio galaxies. We present here our results on the multi-band analysis of two γ-ray-emitting NLSy1 galaxies, namely, PKS 1502+036 (z = 0.409) and PKS 2004-447 (z = 0.240), using archival data. We generate multi-band long-term light curves of these sources, build their spectral energy distribution (SED), and model them using a one-zone leptonic model. They resemble more the SEDs of the flat spectrum radio quasar (FSRQ) class of AGNs. We then compare the SEDs of these two sources with two other Fermi-detected AGNs along the traditional blazar sequence, namely, the BL Lac Mrk 421 (z = 0.03) and the FSRQ 3C 454.3 (z = 0.86). The SEDs of both PKS 1502+036 and PKS 2004-447 are found to be intermediate to the SEDs of Mrk 421 and 3C 454.3. In the γ-ray spectral index versus γ-ray luminosity plane, both these NLSy1 galaxies occupy a distinct position, wherein they have luminosity between Mrk 421 and 3C 454.3; however, their steep γ-ray spectra are similar to 3C 454.3. Their Compton dominance as well as their X-ray spectral slope also lie between Mrk 421 and 3C 454.3. We argue that the physical properties of both PKS 1502+036 and PKS 2004-447 are generally similar to blazars and intermediate between FSRQs and BL Lac objects and these sources thus could fit into the traditional blazar sequence. © 2013. The American Astronomical Society. All rights reserved.

Singh S.,Indian Institute of Technology Bombay | Barick K.C.,Bhabha Atomic Research Center | Bahadur D.,Indian Institute of Technology Bombay
Powder Technology | Year: 2015

We demonstrate the antibacterial activities of superparamagnetic Fe3O4 embedded porous ZnO nanocomposite (NC) against the Gram-positive, Staphylococcus aureus (S. aureus) and Gram-negative, Escherichia coli (E. coli) bacteria. The chemical interaction between Fe3O4 and ZnO in nanocomposite is evident from X-ray photoelectron spectroscopy (XPS). The NC exhibits stronger antibacterial activity towards S. aureus than E. coli. Further, antibacterial activity is found to be strongly dependent on the concentration of NC and their incubation time. The Fe3O4-ZnO NC shows excellent heat activated killing of bacteria under AC magnetic field (ACMF) than normal heating. This novel method of killing bacterial pathogens can be a new approach towards the treatment of a variety of microbial infectious diseases. Furthermore, it can be used as highly efficient separable and reusable materials for inhibition of bacterial growth under magnetic field. © 2014 Elsevier B.V.

Verma A.K.,Bhabha Atomic Research Center | Karki B.B.,Louisiana State University
American Mineralogist | Year: 2012

We have carried out equilibrium molecular dynamics simulations of CaMgSi 2O 6 (diopside) liquid as a function of pressure (up to 150 GPa) and temperature (2200 to 6000 K) using density functional theory. Self-diffusion of Mg/Ca atoms decouples most from that of framework (Si/O) atoms at 2200 K and zero pressure, and all diffusivities become increasingly similar as temperature and pressure increase. The predicted temperature variations of all transport coefficients at zero pressure closely follow the Arrhenian law with activation energies of 107 to 161 kJ/mol. However, their pressure variations show significant deviations from the Arrhenius behavior. Along the 3000 K isotherm, the Si and O self-diffusivities show non-monotonic variations up to 20 GPa and then rapidly decrease upon further compression. The melt viscosity also shows a weak anomaly in the low-pressure regime before it starts to increase rapidly with pressure. Our results agree favorably with experimental observations of low-pressure non-uniform variations of Si and O self-diffusivities and viscosity. The predicted complex dynamical behavior requires pressure-volume dependent activation volumes and can be associated with structural changes occurring on compression.

Behavioral heterogeneity within a given patient cohort has been a major challenge in clinical practice and is probably most prominently observed in the field of oncology. This has been the prime impetus of the cutting-edge preclinical and clinical research studies over recent times, many of which seek to further stratify patients based on patients' genetic, proteomic, and metabolic profile (the three key components of "-omics" research), in order to select the appropriate therapy according to an individual's best-fit. Data from functional radionuclide imaging particularly that obtained from PET-CT, with regard to characterization of an individual's tumor phenotype, can play a very important role in answering some of the critical decision-making questions on an individual basis. The role of molecular imaging with PET, SPECT, and planar radionuclide technologies is not confined to early response assessment of administered therapeutics (which is its major benefit compared to conventional methods), rather it has a much broader perspective and encompasses multiple steps in decision making steps of patient management. The immense impact of the radionuclide-based molecular imaging techniques on the selection of an appropriate treatment (at initial diagnosis, during therapy, or after therapy) or in defining the tumor biology has been documented and increasingly recognized through both large and small-scale studies. However, there has been relatively less systematic effort towards the development of a successful and definitive clinical model of "personalized cancer medicine" (based on accurate disease triaging on an individual basis) by the medical community that would be suitable for routine adoption. In this paper, an endeavor has been made to explore the potential of this approach and underscore the areas that would require further critical evaluation to make this a reality. © 2013, Discovery Medicine.

Hussain A.A.,Institute of Advanced Study in Science and Technology | Pal A.R.,Institute of Advanced Study in Science and Technology | Patil D.S.,Bhabha Atomic Research Center
Applied Physics Letters | Year: 2014

We report high performance flexible hybrid ultraviolet photodetector with solar-blind sensitivity using nanocomposite film of plasma polymerized aniline-titanium dioxide. A facile solvent-free plasma technique is used to synthesize superior quality hybrid material with high yield. The hybrid photodetector exhibited high photoconductive gain of the order of ∼10 5 and fast speed with response and recovery time of 22.87 ms and 34.23 ms. This is an excellent result towards getting a balance in the response speed and photoconductive gain trade-off of the photodetectors reported so far. In addition, the device has the advantages of enhanced photosensitivity ((I light- Idark)/Idark) of the order of ∼102 and high responsivity of ∼104 AW -1. All the merits substantiates that, to prepare hybrid material, plasma based method holds potential to be an easy way for realizing large scale nanostructured photodetectors for practical applications. © 2014 AIP Publishing LLC.

Sinha S.,Bhabha Atomic Research Center
Ceramics International | Year: 2015

A thermal model based on heat-conduction equation and Hertz-Knudsen equation for vaporization has been employed to simulate nanosecond pulsed laser based ablation of alumina. Heat transfer in the laser irradiated target with allowance for phase transitions, provides estimates for temperature distribution within the target and material ejection rate via ablation. Good agreement between calculated and experimentally measured data on mass ablation rate per pulse and its dependence on incident laser fluence from 5 to 22 J/cm2, validated our theoretical model. Observed deviation between calculated and experimentally measured ablation rates at high average laser fluence levels was explained by ablation induced progressive degradation of target surface. Absence of abrupt increase in ablation rate with increased laser fluence suggested material ejection largely via normal boiling rather than explosive boiling mechanism. Calculated maximum surface temperature of the target was found to lie well below empirically estimated thermodynamic critical temperature for alumina, corroborating our observations on absence of onset of explosive boiling in alumina target on laser irradiation. Our simulation study enables proper selection of laser fluence, successfully minimizing laser induced target damage, as well as, degradation of micro-structural and mechanical properties of alumina films deposited via pulsed laser ablation. © 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Singh S.,Indian Institute of Technology Bombay | Barick K.C.,Bhabha Atomic Research Center | Bahadur D.,Indian Institute of Technology Bombay
CrystEngComm | Year: 2013

A simple soft chemical approach has been successfully adopted for the synthesis of ZnO in spherical assemblies (SA), nanorods assemblies (NRA), cauliflower-like assemblies (CFA) and mushroom-like assemblies (MA). The morphology of self-assembled ZnO nanostructures composed of numerous nanocrystals has been confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray diffraction and optical studies suggest an anisotropic nature of ZnO and presence of structural defects in ZnO nanostructures, respectively. N2 adsorption-desorption isotherm curves of these nanostructures (except MA) indicate predominantly 3D-mesoporous nature. These nanostructures are useful for their potential application in photocatalytic degradation of organic dyes (e.g. methylene blue, Rhodamine B) and inhibition of bacterial growth (S. aureus). Among these ZnO architectures, CFA exhibits excellent photocatalytic and antibacterial activities. In addition, the inhibition of bacterial growth of S. aureus is more effective under UV light than in dark conditions. © 2013 The Royal Society of Chemistry.

Mudsainiyan R.K.,Guru Nanak Dev University | Chawla S.K.,Guru Nanak Dev University | Meena S.S.,Bhabha Atomic Research Center
Journal of Alloys and Compounds | Year: 2014

Herein, we report the synthesis of Co-Zr doped BaCoxZr xFe(12-2x)O19 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) M-type hexagonal ferrites under sol-gel (series 1) and citrate precursor sol-gel (series 2) conditions. These compounds were characterized by TG-DTA, FT-IR, XRD, EDS and BET techniques. XRD patterns and parameters reflect that series 2 yield more symmetrical structures with lower average particle size. Results reveal that magnetization and magnetocrystalline anisotropy are closely related to the distribution of Co-Zr on the five sub lattices. The compounds of series 1 register a steep fall in coercivity [5428 Oe (x = 0) to 630.2 Oe (x = 1.0) than series 2 [2790 Oe (x = 0) to 1210 Oe (x = 1.0)]. MS varies from 63.63 to 56.94 emu/g and 62.79-53.78 emu/g in series 1 and 2, respectively. Mössbauer analysis suggests that site preferences strongly depend upon the nature of dopant, fuel and the preparatory conditions. © 2014 Elsevier B.V. All rights reserved.

Mitra A.,Bhabha Atomic Research Center
Gravitation and Cosmology | Year: 2012

The problem of general-relativistic adiabatic collapse of a uniform-density perfect sphere has been studied since Wyman (Phys. Rev. 70, 396, (1946)) [1]. Apparently, there could be bouncing and oscillating solutions in such a case, as claimed by numerous authors since then. Consequently, various authors invoked such models for explaining pulsations of compact objects. However, here, for this age-old problem, we prove that for an assumed nonstatic adiabatically evolving sphere, density homogeneity implies (isotropic) pressure homogeneity too. This proof is based on the simple fact that in general relativity (GR), given one time coordinate t, one can employ another time coordinate t → t* = f(t) without any loss of generality. Since this proof does not use any exterior boundary condition, it is valid in a cosmological scenario too. However, here we focus on the evolution of an isolated sphere having a boundary. And the proof obtained here shows that a uniform-density perfect fluid collapse can occur only if the (isotropic) pressure is p = 0, i.e., only when the problem is reduced to the one treated by Oppenheimer and Snyder. For such an isolated sphere, we offer a supporting proof. This result is important and nontrivial because in the past 65 years innumerable authors working on this problem failed to see that the collapse of a supposed homogeneous sphere is (actually) synonymous to the old Oppenheimer-Snyder problem. © 2012 Pleiades Publishing, Ltd.

Jain S.R.,Bhabha Atomic Research Center
Pramana - Journal of Physics | Year: 2012

We argue that mass parameters appearing in the treatment of large-amplitude collective motion, be it fission or heavy-ion reactions, originate as a consequence of their relation with Lyapunov exponents coming from the classical dynamics, and, fractal dimension associated with diffusive modes coming from hydrodynamic description. © Indian Academy of Sciences.

Serendipitous observation of multifocal bilobar hepatic metastases on F-fluoride (NaF) PET arising in the setting of infiltrating ductal carcinoma of breast is described in the present report. A 46-year-old female patient with infiltrating ductal carcinoma had an F-fluoride PET which demonstrated uptake in multiple skeletal metastasis and several upper abdominal lesions corresponding to liver metastases on contrast enhanced CT. F-NaF uptake in soft tissue metastases are likely to be more frequently encountered with the increasing use of F-NaF PET/CT in oncology.

Koul D.K.,Bhabha Atomic Research Center
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2012

Studies involving the pre-dosed OSL emission suggested it to be, broadly, similar to its TL counterpart, the 110 °C pre-dosed TL emission [1-3]. However, in order to have a better understanding of the relationship between the two emissions their comparative analysis based on their response to various stimuli, incorporated in these reported studies, was undertaken. Though the two signals demonstrated a definite co-relation yet some degree of disparity in their relative sensitization was observed, which seems to occur due to competition prevailing during recombination at L-centre and traps creation/destruction at high annealing temperatures of >700°C. Also, the conventional and pre-dosed OSL emissions were seen to be similar in composition. © 2012 Elsevier B.V. All rights reserved.

Guo P.,University of Michigan | Dutta D.,University of Michigan | Dutta D.,Bhabha Atomic Research Center | Wong-Foy A.G.,University of Michigan | And 2 more authors.
Journal of the American Chemical Society | Year: 2015

Moisture can cause irreversible structural collapse in metal-organic frameworks (MOFs) resulting in decreased internal surface areas and pore volumes. The details of such structural collapse with regard to pore size evolution during degradation are currently unknown due to a lack of suitable in situ probes of porosity. Here we acquire MOF porosity data under dynamic conditions by incorporating a flow-through system in tandem with positronium annihilation lifetime spectroscopy (PALS). From the decrease in porosity, we have observed an induction period for water degradation of some Zn4O-based MOFs that signals much greater stability than commonly believed to be possible. The sigmoidal trend in the degradation curve of unfunctionalized MOFs caused by water vapor has been established from the temporal component of pore size evolution as characterized by in situ PALS. IRMOF-3 is found to degrade at a lower relative humidity than MOF-5, a likely consequence of the amine groups in the structure, although, in contrast to MOF-5, residual porosity remains. The presence of an induction period, which itself depends on previous water exposure of the sample (history dependence), and sigmoidal temporal behavior of the moisture-induced degradation mechanism of MOFs was also verified using powder X-ray diffraction analysis and ex situ gas adsorption measurements. Our work provides insight into porosity evolution under application-relevant conditions as well as identifying chemical and structural characteristics influencing stability. © 2015 American Chemical Society.

Betty C.A.,Bhabha Atomic Research Center
Materials Science and Technology (United Kingdom) | Year: 2016

Nanostructured materials possess better tunability of their properties compared to their bulk counterparts. These properties have opened up new avenues for fabricating highly sensitive, miniaturised and cost effective sensing devices. For the realisation of a rapid and easy to use immunosensor, nanostructured porous silicon/polyaniline heterostructure has been prepared electrochemically which provides label free, real time electrical detection with high sensitivity for biomolecules (mouse IgG/goat antimouse IgG) from whole serum. Nanostructured thin film SnO2 sensors prepared by Langmuir Blodgett technique has been investigated for room temperature gas sensing under various chemically polluting ambiances (NH3, H2S, SO2, CO, H2, NO2 and CH4) using electrochemical methods which were able to detect specific gases at room temperature in the presence of other residual gases. © 2016 Institute of Materials, Minerals and Mining.

Anand S.,Bhabha Atomic Research Center | Mayya Y.S.,Indian Institute of Technology Bombay
Atmospheric Chemistry and Physics | Year: 2015

We examine the parameterized model of Stuart et al. (2013) vis-à-vis a diffusion-based model proposed by us earlier (Anand and Mayya, 2011) to estimate the fraction of aerosol particles surviving coagulation in a dispersing plume. While the Stuart et al. approach is based on the solutions to the coagulation problem in an expanding plume model, the diffusion-based approach solves the diffusion-coagulation equation for a steady-state standing plume to arrive at the survival fraction correlations. We discuss the differences in the functional forms of the survival fraction expressions obtained in the two approaches and compare the results for the case studies presented in Stuart et al. (2013) involving different particle emission rates and atmospheric stability categories. There appears to be a better agreement between the two models at higher survival fractions as compared to lower survival fractions; on the whole, the two models agree with each other within a difference of 10%. The diffusion-based expression involves a single exponent fit to a theoretically generated similarity variable combining the parameters of the problem with inbuilt exponents and hence avoids the multi-exponent parameterization exercise. It also possesses a wider range of applicability in respect of the source and atmospheric parameters as compared to that based on parameterization. However, in the diffusion model, the choice of a representative value for the coagulation coefficient is more prescriptive than rigorous, which has been addressed in a more satisfactory manner by the parameterization method. The present comparative exercise, although limited in scope, confirms the importance of aerosol microphysical processes envisaged by Stuart et al. for cloud brightening applications. In a larger context, it seems to suggest that either of the two forms of expressions might be suitable for incorporation into global-/regional-scale air pollution models for predicting the contribution of localized sources to the particle number loading in the atmosphere. © 2015 Author(s).

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.

Sharma N.K.,Bhabha Atomic Research Center
Journal of Radiation Research | Year: 2013

Apigenin (APG), a flavone, is known to exhibit antioxidant, antimutagenic and antitumorigenic activity, both in vivo and in vitro. The aim of this study is to investigate the modulatory effects of APG on human lymphocytes after irradiation with gamma rays (3 Gy) or treatment with the antineoplastic agent, mitomycin C (MMC), in vitro. Cytogenetic biomarkers such as chromosome aberrations (CAs), sister chromatid exchanges (SCEs) and cytochalasin-B blocked micronuclei (CBMN), were studied in blood lymphocytes treated with radiation, or antineoplastic agent (MMC), and APG. Whole blood lymphocytes were cultured in vitro using a standard protocol. No significant differences were found in the frequency of CAs or micronuclei (MN) in human peripheral blood lymphocytes irradiated with gamma rays (3 Gy) and then posttreated with APG. There was an increase in the frequency of SCEs per cell in APG-treated samples compared with the controls. Lymphocytes treated with MMC in the presence of APG exhibited a significant decrease (P < 0.01) in the frequency of SCEs compared with MMC treatment alone. The data for the MN test indicated that APG treatment significantly reduced (P < 0.01) the frequency of MMC-induced MN. © The Author 2013. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Therapeutic Radiology and Oncology.

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

The unidirectional growth and dissolution at the opposite and hemihedral faces of the polar crystals from vapour phase is an important and unresolved problem till date. Here, we report periodic density functional total energy calculations to elucidate the mechanism of growth and dissolution at the opposite and hemihedral faces of two polar crystals, namely α-resorcinol and urea crystals from vapour phase. We employed a molecular-scale modelling based on the surface docking approach to determine the molecular attachment and detachment energies. The approach is based on the fact that polarization along the polar axis is different and hence the molecular attachment and detachment energies of molecules at these faces are different. Our results show that the phenomena of asymmetric growth and dissolution along the polar axis of α-resorcinol and urea crystals are intrinsic to the acentric crystals on which surface relaxation further enhances the asymmetry which is in agreement with the experimental observations. © 2013 The Royal Society of Chemistry.

Seidenfuss M.,University of Stuttgart | Samal M.K.,Bhabha Atomic Research Center | Roos E.,University of Stuttgart
International Journal of Solids and Structures | Year: 2011

In this work, we have assessed the results of the local and nonlocal versions of Rousselier's damage model, which have been used here for simulation of ductile crack growth. There are several issues regarding the accuracy of the results which has been addressed in this paper, e.g.; accuracy in simulation of crack path, extent and width of the damaged region, fracture resistance behaviour in situations such as symmetric vs. non-symmetric boundary-value problems, mixed-mode loading vs. mode-I loading of the crack-tip, etc. It was also observed that the shape and orientation of the elements at the crack-tip, in addition to their size, influence the results of the local damage model. In this work, it was shown that the above issues can be resolved through the use of nonlocal damage models. The predictions of the nonlocal model are also consistent with the experimental observations unlike its local counterpart. Several examples were presented, where the results as obtained by both the local and nonlocal models were compared. From this experience, it is recommended that the local damage models should not be used blindly by the analysts for all kinds of mesh design, loading, boundary conditions, etc. © 2011 Elsevier Ltd. All rights reserved.

Modak A.,Indian Association for The Cultivation of Science | Mondal J.,Indian Association for The Cultivation of Science | Aswal V.K.,Bhabha Atomic Research Center | Bhaumik A.,Indian Association for The Cultivation of Science
Journal of Materials Chemistry | Year: 2010

A new organosilane precursor has been designed via Vilsmeier-Haack formylation of phloroglucinol followed by its Schiff base condensation with 3-aminopropyl-triethoxysilane (APTES). A novel organic-inorganic hybrid periodic mesoporous organosilica (PMO) LHMS-3 containing the highly coordinating bis(propyliminomethyl)-phloroglucinol moiety inside the pore wall has been synthesized by using this precursor organosilane molecule. Phenolic-OH and imine-N donor sites present in this PMO material have been utilized to anchor Pd(ii) species at the surface of the mesopores. Small angle neutron scattering, XRD, HR TEM, SEM, 13C and 29Si solid state MAS NMR, UV-vis and FT IR spectroscopic tools are utilized to characterize the 2D-hexagonal mesophase and the presence of the bis(propyliminomethyl)-phloroglucinol moiety inside the pore wall. This Pd-anchored material Pd-LHMS-3 showed excellent catalytic activity and trans-selectivity in Heck C-C bond formation reactions for the synthesis of a series of value-added aromatic and aliphatic olefins. © 2010 The Royal Society of Chemistry.

Kiran V.,Indian Institute of Science | Srinivasu K.,Bhabha Atomic Research Center | Sampath S.,Indian Institute of Science
Physical Chemistry Chemical Physics | Year: 2013

Titanium carbide (TiC) possesses fascinating properties like high electrical conductivity and high mechanical strength coupled with high corrosion resistance and stability in acidic and alkaline environments. The present study demonstrates the tunability of mechanistic aspects of oxygen reduction reaction (ORR) using TiC nanostructures. One dimensional TiC nanostructures (TiC-NW) have been synthesized using a simple, hydrothermal method and used as a catalyst for ORR. Shape dependent electroactivity is demonstrated by comparing the activity of TiC-NW with its bulk counterparts. Comparative studies reveal higher ORR activities in the case of 1D TiC-NW involving ∼4 electrons showing efficient reduction of molecular oxygen. Excellent stability and high methanol tolerance with good selectivity for ORR is reported. © 2013 The Owner Societies.

Mukherjee J.K.,Bhabha Atomic Research Center
Pramana - Journal of Physics | Year: 2015

A workspace modelling technique, that achieves real-time detection of closeness of robot to workspace object, has been developed by additional physics attribute attachment to workspace. Physics phenomena suiting the realistic work conditions have been identified and a computational model for emulating the phenomenon has been developed. Need for building sensitivity to dynamics in the model has also been addressed. Model building and algorithms for embedding the model in workspace comprising complex object shapes have been studied in detail. Applications like fast execution in real-time scenarios, design of data structure for realistic implementation and the problem of attaining functionality without new sensor addition to telerobots working in radioactive environment are addressed. © Indian Academy of Sciences.

Ozbolt J.,University of Stuttgart | Sharma A.,Bhabha Atomic Research Center | Reinhardt H.-W.,University of Stuttgart
International Journal of Solids and Structures | Year: 2011

The behavior of concrete structures is strongly influenced by the loading rate. Compared to quasi-static loading concrete loaded by impact loading acts in a different way. First, there is a strain-rate influence on strength, stiffness, and ductility, and, second, there are inertia forces activated. Both influences are clearly demonstrated in experiments. Moreover, for concrete structures, which exhibit damage and fracture phenomena, the failure mode and cracking pattern depend 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 the crack propagation of the concrete compact tension specimen. The rate sensitive microplane model is used as a constitutive law for concrete. The strain-rate influence is captured by the activation energy theory. Inertia forces are implicitly accounted for through dynamic finite element analysis. The results of the study show that the fracture of the specimen strongly depends on the loading rate. For relatively low loading rates there is a single crack due to the mode-I fracture. However, with the increase of loading rate crack branching is observed. Up to certain threshold (critical) loading rate the maximal crack velocity increases with increase of loading rate, however, for higher loading rates maximal velocity of the crack propagation becomes independent of the loading rate. The critical crack velocity at the onset of crack branching is found to be approximately 500 m/s. © 2011 Elsevier Ltd. All rights reserved.

Phaomei G.,Manipur University | Rameshwor Singh W.,Manipur University | Shanta Singh N.,Manipur University | Ningthoujam R.S.,Bhabha Atomic Research Center
Journal of Luminescence | Year: 2013

The nanorods of Ce3+ sensitized LaPO4:Dy3+ with and without co-activation of Eu3+ have been synthesized by simple chemical route at relatively low temperature (150 °C). Effect of solvents on photoluminescence properties of Ce3+ sensitized LaPO 4:Dy3+ is studied by taking different solvents such as water, ethylene glycol (EG), dimethyl sulfoxide (DMSO) and their mixture. The samples prepared in EG and DMSO show monoclinic phase, whereas the samples prepared in water and mixed solvents show hexagonal phase. This hexagonal phase is transformed to monoclinic phase when the sample is heated at or above 600 °C and exhibits less luminescence intensity than that in monoclinic phase. The luminescence intensity of Dy3+ is enhanced when co-doped with Ce3+ because of energy transfer process. The luminescence color can be tuned from blue to white when Eu3+ is co-doped into LaPO 4:Dy3+, Ce3+. The prepared nanoparticles are dispersible and their polymer films are prepared after incorporation in to the polymer matrix. © 2012 Elsevier B.V. All rights reserved.

Gundra K.,Indian Institute of Technology Bombay | Gundra K.,Bhabha Atomic Research Center | Shukla A.,Indian Institute of Technology Bombay
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We present calculations of the optical absorption and electroabsorption spectra of graphene nanoribbons (GNRs) using a π-electron approach, incorporating long-range Coulomb interactions within the Pariser-Parr-Pople- model Hamiltonian. The approach is carefully benchmarked by computing quantities, such as the band structure, electric-field-driven half-metallicity, and linear optical absorption spectra of GNRs of various types, and the results are in good agreement with those obtained using ab initio calculations. Our predictions on the linear absorption spectra for the transversely polarized photons provide a means to characterize GNRs by optical probes. We also compute the electroabsorption spectra of the zigzag GNRs and argue that it can be used to determine whether or not they have a magnetic ground state, thereby allowing the edge magnetism to be probed through nonmagnetic experiments. © 2011 American Physical Society.

Bhattacharya A.,Indian Association for The Cultivation of Science | Bhattacharya S.,Indian Association for The Cultivation of Science | Majumder C.,Bhabha Atomic Research Center | Das G.P.,Indian Association for The Cultivation of Science
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We propose, on the basis of our first-principles density functional based calculations, an interesting isomer of graphane in which the C-H bonds of a hexagon alternate in three-up-three-down fashion on either side of the sheet. This two-dimensional puckered structure, called "stirrup," has an intermediate stability between the previously reported chair and boat conformers of graphane. The physicochemical properties of this conformer are found to be similar to the other two conformers of graphane with an insulating direct band gap of 3.1eV at the Γ point. Any other alternative hydrogenation of the graphene sheet disrupts its symmetrically puckered geometry and turns out to be energetically less favorable than these three conformers. © 2011 The American Physical Society.

The equation-of-motion coupled cluster (EOMCC) method based on the excited state Hartree-Fock (ESHF) solutions is shown to be appropriate for computing the entire ground state potential energy curves of strongly correlated higher-order bonds. The new approach is best illustrated for the homolytic dissociation of higher-order bonds in molecules. The required multireference character of the true ground state wavefunction is introduced through the linear excitation operator of the EOMCC method. Even at the singles and doubles level of cluster excitation truncation, the nonparallelity error of the ground state potential energy curve from the ESHF based EOMCC method is small. © 2015 Author(s).

Dikshit B.,Bhabha Atomic Research Center
European Journal of Physics | Year: 2015

The expression for relativistic variation of mass with speed has been derived in the literature in the following ways: by considering the principles of electrodynamics; by considering elastic collision between two identical particles in which momentum and energy are conserved; or by more advanced methods such as the Lagrangian approach. However, in this paper, the same expression is derived simply by applying the law of conservation of momentum to the motion of a single particle that is subjected to a force (which may be non-electromagnetic) at some point in its trajectory. The advantage of this method is that, in addition to being simple, we can observe how the mass is increased from rest mass to relativistic mass when the speed is changed from 0 to a value of v, as only a single particle is involved in the analysis. This is in contrast to the two particles considered in most text books, in which one represents rest mass and the other represents relativistic mass. © 2015 IOP Publishing Ltd.

Thomas R.G.,Bhabha Atomic Research Center
Pramana - Journal of Physics | Year: 2015

Synthesis of heavy and superheavy elements is severely hindered by fission and fissionlike processes. The probability of these fission-like, non-equilibrium processes strongly depends on the entrance channel parameters. This article attempts to summarize the recent experimental findings and classify the signatures of these non-equilibrium processes based on macroscopic variables. The importance of the sticking time of the dinuclear complex with respect to the equilibration times of various degrees of freedom is emphasized. © Indian Academy of Sciences.

John B.,Bhabha Atomic Research Center
Pramana - Journal of Physics | Year: 2015

In the final phases of fission process, there are fast collective rotational degrees of freedom, which can exert a force on the slower tilting rotational degree. Experimental observations that lead to this realization and theoretical studies that account for dynamics of the processes are discussed briefly. Supported by these studies, and by assuming a conditional equilibrium of the collective rotational modes at a pre-scission point, a new statistical model for fission fragment angular and spin distributions has been developed. This model gives a consistent description of the fragment angular and spin distributions for a wide variety of heavy-and light-ion-induced fission reactions. © Indian Academy of Sciences.

Ganesan S.,Bhabha Atomic Research Center
Nuclear Data Sheets | Year: 2015

We present a brief overview of progress, challenges, excitement and perspectives in developing nuclear data covariances in the Indian context in relation to target accuracies and sensitivity studies that are of great importance to Bhabha's 3-stage nuclear programme for energy and non-energy applications. © 2014 Elsevier Inc.

Choudhury R.K.,Bhabha Atomic Research Center
Pramana - Journal of Physics | Year: 2015

Nuclear fission studies in Trombay began nearly six decades ago, with the commissioning of the APSARA research reactor. Early experimental work was based on mass, kinetic energy distributions, neutron and X-ray emission in thermal neutron fission of 235U, which were carried out with indigenously developed detectors and electronics instrumentation. With the commissioning of CIRUS reactor and the availability of higher neutron flux, advanced experiments were carried out on ternary fission, pre-scission neutron emission, fragment charge distributions, quarternary fission, etc. In the late eighties, heavy-ion beams from the pelletron-based medium energy heavy-ion accelerator were available, which provided a rich variety of possibilities in nuclear fission studies. Pioneering work on fragment angular distributions, fission time-scales, transfer-induced fission, ã-ray multiplicities and mass-energy correlations were carried out, providing important information on the dynamics of the fission process. More recently, work on fission fragment ã-ray spectroscopy has been initiated, to understand the nuclear structure aspects of the neutron-rich fission fragment nuclei. There have also been parallel efforts to carry out theoretical studies in the areas of shell effects, superheavy nuclei, fusion-fission dynamics, fragment angular distributions, etc. to complement the experimental studies. This paper will provide a glimpse of the work carried out by the fission group at Trombay in the above-mentioned topics. © Indian Academy of Sciences.

Mahata K.,Bhabha Atomic Research Center
Pramana - Journal of Physics | Year: 2015

Statistical model analysis is carried out for p-and α-induced fission reactions using a consistent description for fission barrier and level density in A ∼ 200 mass region. A continuous damping of shell correction with excitation energy is considered. Extracted fission barriers agree well with the recent microscopic-macroscopic model. The shell corrections at the saddle point were found to be insignificant. © Indian Academy of Sciences.

Sai Venkata Ramana A.,Bhabha Atomic Research Center
Contributions to Plasma Physics | Year: 2015

We present in this work, a thermodynamic perturbation theory for equation of state of hydrogen and helium in the warm dense regime. The system is modeled as a mixture of classical point ions and quantum electrons. A perturbation series for Helmholtz free energy and correlation functions of the ions and electrons as a function of density and temperature is proposed. Combining the classical thermodynamic perturbation theory and the orbitial-free quantum hyper-netted chain theory, a systematic procedure to obtain the terms of the perturbation series is developed. The ion-ion correlations are treated within the hyper-netted chain approximation and the ion-electron correlations are treated within the Thomas-Fermi-Dirac-Weizsäcker approximation. The method has been applied to obtain isotherms of hydrogen and helium in the warm dense regime. The isotherms are compared with available ab-initio data and the results are analyzed. A good agreement with ab-initio data has been observed for pressures greater than one Mbar. Advantages and limitations of the present method are discussed along with possible future improvements. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chakravarty R.,University of Wisconsin - Madison | Chakravarty R.,Bhabha Atomic Research Center | Goel S.,University of Wisconsin - Madison | Cai W.,University of Wisconsin - Madison
Theranostics | Year: 2014

Molecular imaging involves the non-invasive investigation of biological processes in vivo at the cellular and molecular level, which can play diverse roles in better understanding and treatment of various diseases. Recently, single domain antigen-binding fragments known as 'nanobodies' were bioengineered and tested for molecular imaging applications. Small molecular size (~15 kDa) and suitable configuration of the complementarity determining regions (CDRs) of nanobodies offer many desirable features suitable for imaging applications, such as rapid targeting and fast blood clearance, high solubility, high stability, easy cloning, modular nature, and the capability of binding to cavities and difficult-to-access antigens. Using nanobody-based probes, several imaging techniques such as radionuclide-based, optical and ultrasound have been employed for visualization of target expression in various disease models. This review summarizes the recent developments in the use of nanobody-based probes for molecular imaging applications. The preclinical data reported to date are quite promising, and it is expected that nanobody-based molecular imaging agents will play an important role in the diagnosis and management of various diseases. © Ivyspring International Publisher.

Goswami A.,Bhabha Atomic Research Center
Pramana - Journal of Physics | Year: 2015

Since the discovery of nuclear fission in the year 1939, both physical and radiochemical techniques have been adopted for the study of various aspects of the phenomenon. Due to the ability to separate individual elements from a complex reaction mixture with a high degree of sensitivity and selectivity, a chemist plays a significant role in the measurements of mass, charge, kinetic energy, angular momentum and angular distribution of fission products in various fissioning systems. At Trombay, a small group of radiochemists initiated the work on radiochemical studies of mass distribution in the early sixties. Since then, radiochemical investigations on various fission observables have been carried out at Trombay in n, p, α and heavy-ion-induced fissions. An attempt has been made to highlight the important findings of such studies in this paper, with an emphasis on medium energy and heavy-ion-induced fission. © Indian Academy of Sciences.

Das A.,Indian National Metallurgical Laboratory | Das A.,Bhabha Atomic Research Center
Philosophical Magazine | Year: 2015

Metastable austenitic stainless steels are prone to form deformation-induced martensite under the influence of externally applied stress. Crystallographic variant selection during martensitic transformation of metastable austenite has been investigated thoroughly with respect to the interaction between the applied uniaxial cyclic stress and the resulting accumulated plastic strain during cyclic plastic deformation. The orientation of all the Kurdjomov-Sachs (K-S) variants has been evaluated extensively and compared with the measured orientation of martensite with their corresponding interaction energies by applying the elegant transformation texture model recently developed by Kundu and Bhadeshia. Encouraging correlation between model prediction and experimental data generation for martensite pole figures at many deformed austenite grains has been observed. It has been found that both the applied uniaxial cyclic stress and the accumulated plastic strain are having strong influence on crystallographic variant selection during cyclic plastic deformation. Patel and Cohen's classical theory can be utilized to predict the crystallographic variant selection, if it is correctly used along with the phenomenological theory of martensite crystallography. © 2015 Taylor & Francis.

Das S.,Bhabha Atomic Research Center
Physics of Atomic Nuclei | Year: 2015

There exist model calculations showing the modification of the hadronic parameters of ρ meson in the nuclear environment. From these parameters, we extract the ρ-meson-nucleus optical potential and show the medium effect due to this potential on the ρ-meson mass distribution spectra in the photonuclear reactions. The calculated results reproduced reasonably the measured e+e− invariant mass, i.e., ρ-meson mass, distribution spectra in γ, ρ0 → e+e− reactions on nuclei. © 2015, Pleiades Publishing, Ltd.

Venugopal E.,CSIR - National Chemical Laboratory | Aswal V.K.,Bhabha Atomic Research Center | Kumaraswamy G.,CSIR - National Chemical Laboratory
Langmuir | Year: 2013

We show that the size of silica nanoparticles influences the nature of their aggregation in an aqueous solution of a relatively hydrophobic nonionic surfactant, C12E4. We present results for dispersions of silica nanoparticles with sizes varying from 8 to 26 nm, in a 75: 25 C 12E4/water system, that forms a lamellar phase, L α, at room temperature. Addition of silica particles does not affect the formation of the Lα phase. Nanoparticles smaller than about 11 nm aggregate irreversibly in the C12E4/water system. However, nanoparticles larger than about 15 nm aggregate in the L α phase, but are dispersed at temperatures above the L α order-disorder temperature. Thus, in contrast to the smaller particles, aggregation of silica nanoparticles larger than about 15 nm is reversible with temperature. We use small-angle neutron scattering (SANS) to demonstrate that these results can be explained by the size-dependent wrapping of nanoparticles by surfactant bilayers. Larger particles, above 15 nm in size, are sterically stabilized by the formation of an adsorbed surfactant bilayer. The cost of bilayer bending inhibits adsorption onto the highly curved surfaces of smaller particles, and these "bare" particles aggregate irreversibly. © 2013 American Chemical Society.

Kondayya G.,Indian Institute of Technology Bombay | Kondayya G.,Bhabha Atomic Research Center | Shukla A.,Indian Institute of Technology Bombay
Computer Physics Communications | Year: 2012

Pariser-Parr-Pople (P-P-P) model Hamiltonian is employed frequently to study the electronic structure and optical properties of π-conjugated systems. In this paper we describe a Fortran 90 computer program which uses the P-P-P model Hamiltonian to solve the Hartree-Fock (HF) equation for infinitely long, one-dimensional, periodic, π-electron systems. The code is capable of computing the band structure, as also the linear optical absorption spectrum, by using the tight-binding and the HF methods. Furthermore, using our program the user can solve the HF equation in the presence of a finite external electric field, thereby, allowing the simulation of gated systems. We apply our code to compute various properties of polymers such as trans-polyacetylene, poly-para-phenylene, and armchair and zigzag graphene nanoribbons, in the infinite length limit. © 2011 Elsevier B.V.

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.

Banerjee S.,Bhabha Atomic Research Center | Pillai M.R.A.,Molecular Group of Companies | Knapp F.F.,Oak Ridge National Laboratory
Chemical Reviews | Year: 2015

Interest in the use of radionuclides for treatment of various diseases has a long history and parallels the isolation of radium by Marie and Pierre Curie in the early part of the 20th Century. The availability of radium generated widespread enthusiasm and was considered as a potential medicine for many incurable diseases. Radiopharmaceuticals are radio-labeled molecules designed to target tissues and processes in vivo and are used in either diagnostic or therapeutic applications. Unlike the well-established applications of nonradioactive drugs, diagnostic radiopharmaceuticals contain very small doses of the active ingredients and are not pharmacologically active. On the other hand, therapeutic radiopharmaceuticals generally possess a significant concentration of active ingredient which can induce pharmacological changes.

Dey G.R.,Bhabha Atomic Research Center
Research on Chemical Intermediates | Year: 2015

Studies on the radical cations and radicals of thioacetamide [(CH3)(NH2)C=S] and thiobenzamide [(C6H5)(NH2)C=S], in aqueous sulfuric acid media of various strengths were carried out using pulse radiolysis technique. In this system, the formation time of thioacetamide/thiobenzamide radical cation was observed to be different at different acid strengths. At acid system of pH/H 0 = -3.5, the slow growth kinetics signifies a dominating reaction of SO4 •- radical with these solutes (reaction rate constants found in the range of 1-4 × 108 M-1 s-1). Two different reactions (solute molecule with •OH and SO4 •-) lead to the formation of lone intermediate species (radical cation) following immediate (fast) and delayed (slow) kinetics. By this process, the transient yield increased by 65 % (as the transients' absorbance at 400 nm increased to 0.090 from 0.055) in the case of thiobenzamide, whereas in the case of thioacetamide, this figure was higher. The general mechanism for the formation of radical cations of these solutes during radiation chemical studies has been revisited wherein the electron transfer reactions are more favorable. © 2013 Springer Science+Business Media Dordrecht.

Dutta Choudhury S.,Bhabha Atomic Research Center | Badugu R.,University of Maryland, Baltimore | Lakowicz J.R.,University of Maryland, Baltimore
Accounts of Chemical Research | Year: 2015

Conspectus Fluorescence technology pervades all areas of chemical and biological sciences. In recent years, it is being realized that traditional fluorescence can be enriched in many ways by harnessing the power of plasmonic or photonic structures that have remarkable abilities to mold the flow of optical energy. Conventional fluorescence is omnidirectional in nature, which makes it difficult to capture the entire emission. Suitably designed emission directivity can improve collection efficiency and is desirable for many fluorescence-based applications like sensing, imaging, single molecule spectroscopy, and optical communication.By incorporating fluorophores in plasmonic or photonic substrates, it is possible to tailor the optical environment surrounding the fluorophores and to modify the spatial distribution of emission. This promising approach works on the principle of near-field interaction of fluorescence with spectrally overlapping optical modes present in the substrates.In this Account, we present our studies on directional emission with different kinds of planar metallic, dielectric, and hybrid structures. In metal-dielectric substrates, the coupling of fluorescence with surface plasmons leads to directional surface-plasmon-coupled emission with characteristic dispersion and polarization properties. In one-dimensional photonic crystals (1DPC), fluorophores can interact with Bloch surface waves, giving rise to sharply directional Bloch surface wave-coupled emission. The interaction of fluorescence with Fabry-Pérot-like modes in metal-dielectric-metal substrates and with Tamm states in plasmonic-photonic hybrid substrates provides beaming emission normal to the substrate surface. These interesting features are explained in the context of reflectivity dispersion diagrams, which provide a complete picture of the mode profiles and the corresponding coupled emission patterns. Other than planar substrates, specially fabricated plasmonic nanoantennas also have tremendous potential in controlling and steering fluorescence beams. Some representative studies by other research groups with various nanoantenna structures are described.While there are complexities to near-field interactions of fluorescence with plasmonic and photonic structures, there are also many exciting possibilities. The routing of each emission wavelength along a specific direction with a given angular width and polarization will allow spatial and spectral multiplexing. Directional emission close to surface normal will be particularly useful for microscopy and array-based studies. Application-specific angular emission patterns can be obtained by varying the design parameters of the plasmonic/photonic substrates in a flexible manner. We anticipate that the ability to control the flow of emitted light in the nanoscale will lead to the development of a new generation of fluorescence-based assays, instrumentation, portable diagnostics, and emissive devices. © 2015 American Chemical Society.

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.

Reddy D.H.K.,Sri Venkateswara University | Harinath Y.,Sri Venkateswara University | Seshaiah K.,Sri Venkateswara University | Reddy A.V.R.,Bhabha Atomic Research Center
Chemical Engineering Journal | Year: 2010

Moringa oleifera leaves (MOL); an agro-waste material has been used as a precursor to prepare a new biosorbent. The leaves were washed with base and citric acid, and obtained new chemically modified MOL biosorbent (CAMOL) for sequestration of Pb(II) from aqueous solution. The biosorbent was characterized by SEM, FTIR spectral and elemental analyses. The effect of experimental parameters such as pH, dose, initial concentration, contact time and temperature on the biosorption was studied. The kinetic data were analyzed using three adsorption kinetic models: the pseudo-first and second-order kinetics and intraparticle diffusion. The equilibrium data were analyzed using Langmuir, Freundlich, Dubinin-Radushkevick and Temkin isotherm models. Langmuir model provided the best correlation with biosorption capacity of 209.54mgg-1 at 313K. The thermodynamic properties, ΔG°, ΔH° and ΔS° showed that biosorption of Pb(II) onto CAMOL was spontaneous, endothermic and feasible in the temperature range of 293-313K. Desorption experiments showed feasibility of regeneration of the biosorbent for further use after treating with dilute HCl. The presence of other common metal ions like Na+, K+, Ca2+ and Mg2+ did not affect the biosorption of lead. Investigations carried out proved that CAMOL is a biosorbent with good potential for removal of lead from the aqueous media. © 2010.

Sastry N.V.,Sardar Patel University | Vaghela N.M.,Sardar Patel University | Aswal V.K.,Bhabha Atomic Research Center
Fluid Phase Equilibria | Year: 2012

A series of surfactant-like ionic liquids (ILs), typically consisting of a long hydrocarbon tail and an ionic head group have been synthesized by a direct reaction of 1-methylimidazole and 1-choloroalkane, RCl, R=C 10, C 12, C 14, C 16 and C 18, 1-methylpipridine or 1-methylpyrrolidine and 1-chlorooctadecane respectively. Surface activity and aggregation of these surfactants have been explored by surface tension and solution conductivity measurements. New results (critical aggregation concentrations (cac), and surface active parameters (at 298.15K), thermodynamic parameters of aggregation (at 298.15, 303.15 and 313.15K)) are reported. The increase in length of R decreased cac, minimum area/surfactant molecule at air/water interface and while the adsorption efficiency, surface excess concentrations, standard entropy of aggregation were increased indicating that the aggregation with in the temperature limits of present study is an entropy driven process. The analysis of the small angle neutron scattering (SANS) curves revealed that the aggregates are of oblate ellipsoidal shape and the aggregation numbers increased with the increase in the chain length (C 10-C 18) of alkyl branch and therefore it is suggested that the longer the alkyl chains, parallel would be their alignment in the core part of the aggregates. Comparison of surface active parameters for the three ILs with a common octadecyl chain but different cationic head groups revealed that the methylimidazolium moiety is more effective than methylpiperidine and methylpyrrolidine at air/water interface. Similarly, the number of molecules in an aggregate was found to be more, when the cationic head group is made up of π electron ring systems as compared to the one with point charge. © 2012 Elsevier B.V.

Patil A.B.,Institute of Chemical Technology | Patil D.S.,Bhabha Atomic Research Center | Bhanage B.M.,Institute of Chemical Technology
Journal of Molecular Catalysis A: Chemical | Year: 2012

A convenient, mild and cost-effective synthesis of decahedral palladium nanoparticles by exposing aqueous PdCl 2 solution to the sunlight in the presence of citric acid as a reducing agent and PVP as a capping agent was reported. Natural solar energy which acts as a driving force for the generation of palladium nanoparticles makes the process attractive and economical. The obtained nanoparticles were thoroughly characterized by using techniques like TEM, SAED, FEG-SEM, XRD and EDAX. It was observed that up to 70% of the palladium nanoparticles have decahedron shape, while remaining 30% consists of all other different shapes. The citric acid helps in shapes selective synthesis, whereas concentrated solar energy supplies dual energy which helps to speed up the reduction process. The aqueous reaction mixture of palladium nanoparticles was directly employed for the Suzuki coupling reaction and hence centrifuging efforts and cost of reagents required for the isolation of nanoparticles were avoided. The synthesized nanoparticles demonstrated excellent catalytic activity in Suzuki coupling reaction of aryl halides with phenyl boronic acid under mild reaction conditions. The methodology is applicable to diverse substrates providing good to excellent yields of desired products. Notably, the obtained yields with lowest catalytic loading resulting in highest TOF (0.05 mol% catalyst loading and TOF of 1960 h -1) were among the best ever reported for the Suzuki coupling reaction. In addition, the catalyst could be reused for three more consecutive recycles. The effectiveness of present new protocol for the PdNPs synthesis was also compared with PdNPs prepared using conventional heating method. © 2012 Elsevier B.V.

An explicit analytical expression has been obtained for vertical detachment energy (VDE) that can be used to calculate the same over a wide range (both stable and unstable regions) of cluster sizes including the bulk from the knowledge of VDE for a finite number of stable clusters (n = 16-23). The calculated VDE for the bulk is found to be very good in agreement (within 1%) with the available experimental result and the domain of instability lies between n = 0 and n = 15 for the hydrated clusters, PO3 - 4 · nH2O. The minimum number (n0) of water molecules needed to stabilise the phosphate anion is 16. We are able to explain the origin of solvent-berg model and anomalous conductivity from the knowledge of first stable cluster. We have also provided a scheme to calculate the radius of the solvent-berg for phosphate anion. The calculated conductivity using Stokes-Einstein relation and the radius of solvent-berg is found to be very good in agreement (within 4%) with the available experimental results. © 2014 © 2014 Taylor & Francis.

Pathak A.K.,University of California at San Diego | Pathak A.K.,Bhabha Atomic Research Center
Molecular Physics | Year: 2014

Analytical expressions have been derived for the vertical detachment energy (VDE) for hydrated sulphate (SO2- 4) and oxalate (C 2O2- 4) dianions that can be used to calculate the same over a wide range of cluster sizes including the bulk from the knowledge of VDE for a finite number of stable clusters. The calculated bulk detachment energies are found to be very good in agreement (within 5%) with the available experimental results for both the systems. It is observed that two or more water molecules will be essential for the stability of sulphate and oxalate dianions against spontaneous electron loss and this is consistent with the experiment. We have, for the first time, provided a scheme to calculate the radius of the solvent berg for sulphate and oxalate dianions. The calculated conductivity values for the sulphate and oxalate dianions using Stokes-Einstein relation and the radius of solvent berg are found to be very good in agreement (within 4%) with the available experimental results. © 2013 Taylor & Francis.

Sharma K.,Bhabha Atomic Research Center
Journal of Solid Mechanics | Year: 2014

In this paper, edge crack problems under mechanical loads have been analysed using extended finite element method (XFEM) as it has proved to be a competent method for handling problems with discontinuities. The XFEM provides a versatile technique to model discontinuities in the solution domain without re-meshing or conformal mesh. The stress intensity factors (SIF) have been calculated by domain based interaction integral method. The effect of crack orientation and interaction under mechanical loading has been studied. Analytical solutions, which are available for two dimensional displacement fields in linear elastic fracture mechanics, have been used for crack tip enrichment. From the present analysis, it has been observed that there is monotonous decrease in the SIF-1 value with the increase in inclination, while SIF-II values first increases then it also decreases. Next study was performed for first edge crack in the presence of second crack on opposite edge. The results were obtained by changing the distance between the crack tips as well as by changing the orientation of second crack. SIFs values decrease with increase in distances between the crack tips for collinear cracks. In next study, for the first crack in presence of inclined second edge crack and it was found that SIFs increase initially with the increase in inclination and decrease after that. It emphasizes the fact that cracks at larger distances act more or less independently. In next study, with the use of level set method crack growth path is evaluated without remeshing for plate with hole, soft inclusion & hard inclusion under mode-I loading and compare with available published results. © 2014 IAU, Arak Branch.

Pathak A.K.,Bhabha Atomic Research Center
Chemical Physics | Year: 2011

We report theoretical results on the structure, static, and dynamic polarizability of hydrated nitrate anion in finite size cluster, NO3-·nH2O (n = 1-8) based on the first principles electronic structure methods. The interesting observation is that for 3 ≤ n ≤ 8, the surface structures are more stable than the corresponding interior structures. It is observed that the polarizability (both static and dynamic) varies linearly with the size (n) of the hydrated cluster. It is found that the dynamic polarizability becomes infinite at a frequency of 6.12 eV. This observation is in very good agreement with the previously measured electronic transition energy corresponding to 6.13 eV for nitrate anion in aqueous solution. © 2011 Elsevier B.V. All rights reserved.

Gundra K.,Indian Institute of Technology Bombay | Gundra K.,Bhabha Atomic Research Center | Shukla A.,Indian Institute of Technology Bombay
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

Using the tight-binding and Pariser-Parr-Pople model Hamiltonians, we study the electronic structure and optical response of multilayer armchair graphene nanoribbons (AGNRs), both with and without a gate bias. In particular, the influence of the number of layers (n), and the strength of the electric field applied perpendicularly to layers, for different types of edge alignments is explored via their electro-optical properties. As a function of increasing n, the energy gap initially decreases, eventually saturating for large n. The intensity of the linear optical absorption in these systems also increases with increasing n and depends crucially on the polarization direction of the incident light and the type of the edge alignment. This provides an efficient way of determining the nature of the edge alignment, and n, in the experiments. In the presence of a gate bias, the intensity of optical absorption behaves in a nontrivial way. The absorption becomes more intense for the large fields in narrow ribbons exhibiting a redshift of the band gap with the increasing field strength, while in broad ribbons exhibiting a blueshift, the absorption becomes weaker. However, for smaller electric fields, the absorption intensity exhibits more complicated behavior with respect to the field strength. Thus, the effect of the gate bias on optical absorption intensity in multilayer AGNRs is in sharp contrast to bilayer graphene, which exhibits only enhancement of the absorption intensity with the increasing electric field. © 2011 American Physical Society.

Chakraborty B.,Bhabha Atomic Research Center
Journal of Physical Chemistry B | Year: 2015

Applying Green-Kubo formalism and equilibrium molecular dynamics (MD) simulations, we have studied for the first time the dynamic correlation, Onsager coefficients, and Maxwell-Stefan (MS) diffusivities of molten salt LiF-BeF2, which is a potential candidate for a coolant in a high temperature reactor. We observe an unusual composition dependence and strikingly a crossover in sign for all the MS diffusivities at a composition of around 7% of LiF where the MS diffusivity between cation-anion pair (BeF and DLiF) jumps from positive to negative value while the MS diffusivity between cation-cation pair (DLiBe) becomes positive from a negative value. Even though the negative MS diffusivities have been observed for electrolyte solutions between cation-cation pair, here we report negative MS diffusivity between cation-anion pair where DBeF shows a sharp rise around 66% of BeF2, reaches maximum value at 70% of BeF2, and then decreases almost exponentially with a sign change for BeF2 around 93%. For low mole fraction of LiF, DBeF follows the Debye-Huckel theory and rises with the square root of LiF mole fraction similar to the MS diffusivity between cation-anion pair in aqueous solution of electrolyte salt. Negative MS diffusivities while unusual are, however, shown to satisfy the non-negative entropy constraints at all thermodynamic states as required by the second law of thermodynamics. We have established a strong correlation between the structure and dynamics and predict that the formation of flouride polyanion network between Be and F ions and coulomb interaction is responsible for sharp variation of the MS diffusivities which controls the multicomponent diffusion phenomenon in LiF-BeF2 which has a strong impact on the performance of the reactor. © 2015 American Chemical Society.

Garg A.B.,Bhabha Atomic Research Center | Errandonea D.,University of Valencia
Journal of Solid State Chemistry | Year: 2015

The high-pressure structural behavior of europium orthovanadate has been studied using in-situ, synchrotron based, high-pressure x-ray powder diffraction technique. Angle-dispersive x-ray diffraction measurements were carried out at room temperature up to 34.7 GPa using a diamond-anvil cell, extending the pressure range reported in previous experiments. We confirmed the occurrence of zircon-scheelite phase transition at 6.8 GPa and the coexistence of low- and high-pressure phases up to 10.1 GPa. In addition, clear evidence of a scheelite-fregusonite transition is found at 23.4 GPa. The fergusonite structure remains stable up to 34.7 GPa, the highest pressure reached in the present measurements. A partial decomposition of EuVO4 was also observed from 8.1 to 12.8 GPa; however, this fact did not preclude the identification of the different crystal structures of EuVO4. The crystal structures of the different phases have been Rietveld refined and their equations of state (EOS) have been determined. The results are compared with the previous experimental data and theoretical calculations. © 2015 Elsevier Inc.

Abdulla S.,University of Pennsylvania | Salavati A.,University of Pennsylvania | Saboury B.,University of Pennsylvania | Basu S.,Bhabha Atomic Research Center | And 2 more authors.
European Journal of Nuclear Medicine and Molecular Imaging | Year: 2014

Purpose: Radiation pneumonitis is the most severe doselimiting complication in patients receiving thoracic radiation therapy. The aim of this study was to quantify global lung inflammation following radiation therapy using FDG PET/CT. Methods: We studied 20 subjects with stage III non-small-cell lung carcinoma who had undergone FDG PET/CT imaging before and after radiation therapy. On all PET/CT studies, the sectional lung volume (sLV) of each lung was calculated from each slice by multiplying the lung area by slice thickness. The sectional lung glycolysis (sLG) was calculated by multiplying the sLVand the lung sectional mean standardized uptake value (sSUVmean) on each slice passing through the lung. The lung volume (LV) was calculated by adding all sLVs from the lung, and the global lung glycolysis (GLG) was calculated by adding all sLGs from the lung. Finally, the lung SUVmean was calculated by dividing the GLG by the LV. The amount of inflammation in the lung parenchyma directly receiving radiation therapy was calculated by subtracting tumor measurements from GLG. Results: In the lung directly receiving radiation therapy, the lung parenchyma SUVmean and global lung parenchymal glycolysis were significantly increased following therapy. In the contralateral lung (internal control), no significant changes were observed in lung SUVmean or GLG following radiation therapy. Conclusion: Global lung parenchymal glycolysis and lung parenchymal SUVmean may serve as potentially useful biomarkers to quantify lung inflammation on FDG PET/CT following thoracic radiation therapy. © Springer-Verlag Berlin Heidelberg 2013.

Rao A.,RC and IG | Kumar P.,Bhabha Atomic Research Center | Tomar B.S.,RC and IG
Separation and Purification Technology | Year: 2014

N,N-dialkyl aliphatic amides with varying alkyl groups viz. N,N-dibutyl-2-ethyl hexanamide (DBEHA), N,N-dibutyl-3,3-dimethyl butanamide (DBDMBA), N,N-dihexyl octanamide (DHOA), N,N-di-sec-butyl pentanamide (DBPA), N,N-dibutyl octanamide (DBOA), have been evaluated for supercritical fluid extraction (SFE) of uranium and thorium from nitric acid medium as well as from tissue paper matrix. The trend in extraction efficiency could be correlated to the structure of the amides and the amide complex of uranium/thorium. Straight chain amide DBOA was found suitable for SFE of both uranium and thorium. Under optimised conditions (200 atm. pressure, 323 K temperature, 30 min static time followed by 30 min dynamic time, 0.5 M amide in methanol), (94 ± 3)% uranium and (85 ± 4)% thorium could be extracted from 4 M nitric acid medium. For tissue paper matrix, under optimised conditions (200 atm pressure, 323 K temperature, 45 min static time followed by 30 min dynamic time, 0.2 M amide in methanol) (87 ± 7)% uranium and (88 ± 7)% thorium were extractable. For the amide having branching at Cα, DBEHA, extraction efficiency of thorium was as low as 7% for 2 M HNO3 medium while extraction efficiency of uranium was still 95%. For tissue paper matrix, extraction efficiency for uranium with 0.2 M DBEHA (in methanol) was 86% while only 11% thorium was extractable under same conditions. This fact could be exploited for separation of thorium and uranium. © 2014 Elsevier B.V. All rights reserved.

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.

Garg A.B.,Bhabha Atomic Research Center
Physica Status Solidi (B) Basic Research | Year: 2014

High-pressure behavior of tetragonal rutile structured, nanocrystalline SnO2, with an average grain size of 5nm is investigated by in situ synchrotron based angle dispersive powder X-ray diffraction technique up to 34GPa at ambient temperature. Results indicate that the tetragonal structure remains stable up to 18GPa. Beyond 18GPa a first order phase transformation to a cubic phase with large volume discontinuity is observed. Co-existence of both ambient and high pressure phases is observed till the highest pressure investigated. On pressure release, the high pressure daughter phase is retained. The bulk modulus for ambient rutile phase and high pressure daughter phase is 217 (±10) and 202 (±5) GPa respectively with the value of pressure derivative of bulk modulus fixed at 4. The observed phase transition sequence in nanomaterial is different from the bulk compound. It is concluded that the anomaly in the pressure-volume data in present studies and electrical transport data seen near 3GPa in previous work is of electronic in nature since material is structurally stable in this pressure region. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sarkar P.K.,Bhabha Atomic Research Center
Radiation Measurements | Year: 2010

Radiological safety aspects in general and neutron dosimetry in particular, around medium and high-energy particle accelerators pose some unique challenges to the practitioners of radiation protection. This is mainly because the source of radiations are directional, dynamic, pulsed and a mixture of different types. In conventional dosimetry, measurements are done in the units of the quantities in which the radiological protection limits are expressed. In the accelerator environment, measurement of energy and angular distribution of radiations is preferred instead. Research activities being carried out (particularly in India) in the field of neutron dosimetry are discussed. Measurements of neutron ambient dose equivalent directly using conventional rem-meters as well as neutron energy distributions using the time-of-flight technique employing proton recoil scintillators have been done at different directions with respect to light and heavy ion projectiles incident on various thick elemental targets. The observations and conclusions are summarized. Finally, a discussion on the concept of dose and radiological protection and operational quantities is done along with the recommendation of using Evidence theory instead of Bayesian probability in assessing radiological risk. © 2010 Published by Elsevier Ltd. All rights reserved.

Puri R.R.,Bhabha Atomic Research Center
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

A sufficient condition for a quantum state of a system of spin-1/2 particles to admit a local hidden variable description, i.e., to be classical, is the separability of the density matrix characterizing its state, but not all classical states are separable. This leads one to infer that separability and classicality are two different concepts. These concepts are examined here in the framework of a criterion for identifying the classicality of a system of spin-1/2 particles based on the concept of joint quasiprobability (JQP) for the eigenvalues of spin components [Puri, J. Phys. A1361-644710.1088/0305-4470/29/ 17/041 29, 5719 (1996)]. The said criterion identifies a state as classical if a suitably defined JQP of the eigenvalues of spin components in three suitably chosen orthogonal directions is non-negative. In agreement with other approaches, the JQP-based criterion also leads to the result that all nonfactorizable pure states of two spin-1/2 particles are nonclassical. In this paper it is shown that the application of the said criterion to mixed states suggests that the states it identifies as classical are also separable and that there exist states which, identified as classical by other methods, may not be identified as classical by the criterion as it stands. However, results in agreement with the known ones are obtained if the criterion is modified to identify as classical also those states for which the JQP of the eigenvalues of the spin components in two of the three prescribed orthogonal directions is non-negative. The validity of the modified criterion is confirmed by comparing its predictions with those arrived at by other methods when applied to several mixed states of two spin-1/2 particles and the Werner-like state of three spin-1/2 particles [Tòth and Acìn, Phys. Rev. APLRAAN1050-294710. 1103/PhysRevA.74.030306 74, 030306(R) (2006)]. The JQP-based approach, formulated as it is along the lines of the P-function approach for identifying classical states of the electromagnetic field, offers a unified approach for systems of an arbitrary number of spin-1/2 particles and the possibility of linking classicality with the nature of the measurement process. © 2012 American Physical Society.

Patra C.N.,Bhabha Atomic Research Center
Molecular Physics | Year: 2016

A three-component model on the structure of colloidal solution with size asymmetric electrolytes is attempted here using density functional theory and Monte Carlo simulation. The solvent is represented as an individual component along with that as a dielectric continuum. The theory uses a weighted density approximation for the hard-sphere contribution to the free energy, whereas the ionic contribution is evaluated through a perturbation expansion around the bulk density. The theory is found to reproduce the simulation data quite well for a wide range of parametric conditions. The present study reflects the importance of the presence of the solvent in determining the structural behaviour of spherical double layers. © 2016 Taylor & Francis

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.

Dalvi V.H.,Institute of Chemical Technology | Panse S.V.,Institute of Chemical Technology | Joshi J.B.,Institute of Chemical Technology | Joshi J.B.,Bhabha Atomic Research Center
Nature Climate Change | Year: 2015

Integrating solar thermal systems into Rankine-cycle power plants can be done with minimal modification to the existing infrastructure. This presents an opportunity to introduce these technologies into the commercial space incrementally, to allow engineers to build familiarity with the systems before phasing out fossil-fuel energy with solar electricity. This paper shows that there is no thermodynamic barrier to injecting solar thermal heat into Rankine-cycle plants to offset even up to 50% fossil-fuel combustion with existing technology: with better solar-to-electricity efficiencies than conventionally deployed solar-thermal power plants. This strategy is economically preferable to installing carbon-capture and compression equipment for mitigating an equivalent amount of greenhouse-gas emissions. We suggest that such projects be encouraged by extending the same subsidy/incentives to the solar-thermal fraction of a 'solar-aided' plant that would be offered to a conventionally deployed solar-thermal power plant of similar capacity. Such a policy would prepare the ground for an incremental solar-thermal takeover of fossil-fuel power plants. © 2015 Macmillan Publishers Limited.

Reddy D.H.K.,Sri Venkateswara University | Reddy D.H.K.,Catholic Kwandong University | Seshaiah K.,Sri Venkateswara University | Reddy A.V.R.,Bhabha Atomic Research Center | Lee S.M.,Catholic Kwandong University
Carbohydrate Polymers | Year: 2012

A cation exchange biosorbent was developed by chemically modifying the Moringa oleifera leaves powder by esterifying with NaOH followed by citric acid treatment. The modified biosorbent was characterized by FTIR, SEM and XRD techniques and was used for the removal of Cd(II), Cu(II) and Ni(II) from aqueous solution. Different operational parameters such as the effect of pH, biomass dose, equilibrium time and temperature and initial metal ion concentrations were studied. Experimental data were analyzed by kinetic parameters and found that biosorption of three metal ions followed pseudo-second-order. Equilibrium data were analyzed using the Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. The thermodynamic properties, ΔG°, ΔH°and ΔS°showed that biosorption of Cd(II), Cu(II) and Ni(II) onto CAMOL were spontaneous, endothermic and feasible in the temperature range of 293-313 K. Furthermore, the CAMOL can be regenerated and reused for the metal removal. © 2012 Elsevier Ltd. All rights reserved.

Patel P.K.,Indian Institute of Technology Roorkee | Yadav K.L.,Indian Institute of Technology Roorkee | Singh H.,Raja Ramanna Center for Advanced Technology | Yadav A.K.,Bhabha Atomic Research Center
Journal of Alloys and Compounds | Year: 2014

Lead free Ba(Fe0.5Nb0.5)O3 (BFN) ceramics were synthesized by sol-gel method. X-ray diffraction pattern of the samples at room temperature shows a monoclinic structure. The influence of sintering temperature on microstructure and dielectric properties of BFN ceramics were analysed. Microstructure analysis shows well-grown and dense microstructure in 1200 C sintered sample exhibiting enhanced dielectric and magnetodielectric properties. We report a very high dielectric constant (∼33,000) with low dielectric loss (∼0.45) at room temperature for 1200 C sintered sample at 100 Hz frequency. Cole-Cole plot shows that the grain boundary effect (barrier layer formation) is responsible for such a high value of dielectric constant. The sample was also analyzed by Fe K-edge X-ray absorption near-edge structure spectroscopy to obtain the Fe oxidation state. This analysis confirms that Fe ions in BFN ceramics are in mixed valance state (Fe2+/Fe 3+). Another interesting feature of BFN ceramics is the appearance of room temperature high magnetodielectric response (3.8%) at 7 kOe magnetic field and 100 Hz frequency. © 2013 Elsevier B.V. All rights reserved.

Barick K.C.,Bhabha Atomic Research Center | Aslam M.,Indian Institute of Technology Bombay | Bahadur D.,Indian Institute of Technology Bombay
Journal of Alloys and Compounds | Year: 2014

Spherical assemblies of Co doped ZnO comprised of numerous nanocrystals of size 10-15 nm were prepared by refluxing their acetate precursors in diethylene glycol medium. The detailed structural analysis by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) reveal that Co ions are successfully incorporated into the hexagonal wurtzite ZnO nanostructure and do not appear as precipitates or secondary phases. These Co ions are uniformly distributed in the ZnO host lattice and exist in +2 oxidation state. Further, HRTEM analysis also confirmed the oriented attachment of nanocrystals as well as their defects structure. Raman spectra clearly indicate the incorporation of Co2+ ions into ZnO nanostructures at Zn2+ site (appearance of an additional Raman mode at 527 cm-1) and the resulted defects and lattice disorder in host lattice (shifting, broadening and weakening of 2E2 (low) and E2 (high) phonon modes). These Co doped ZnO samples exhibit ferromagnetic like behavior at room temperature, presumably due to the presence of defects in host ZnO lattice. © 2013 Elsevier B.V. All rights reserved.

Das M.,Indian Institute of Technology Bombay | Das M.,Bhabha Atomic Research Center
Physics of Plasmas | Year: 2012

Effect of plasma screening on various properties like transition energy, polarizability (dipole and quadrupole), etc. of hydrogen like ions is studied. The bound and free state wave functions and transition matrix elements are obtained by numerically integrating the radial Schrodinger equation for appropriate plasma potential. We have used adaptive step size controlled Runge-Kutta method to perform the numerical integration. Debye-Huckel potential is used to investigate the variation in transition lines and polarizabilities (dipole and quadrupole) with increasing plasma screening. For a strongly coupled plasma, ion sphere potential is used to show the variation in excitation energy with decreasing ion sphere radius. It is observed that plasma screening sets in phenomena like continuum lowering and pressure ionization, which are unique to ions in plasma. Of particular interest is the blue (red) shift in transitions conserving (non-conserving) principal quantum number. The plasma environment also affects the dipole and quadrupole polarizability of ions in a significant manner. The bound state contribution to polarizabilities decreases with increase in plasma density whereas the continuum contribution is significantly enhanced. This is a result of variation in the behavior of bound and continuum state wave functions in the presence of plasma. We have compared the results with existing theoretical and experimental data wherever present. © 2012 American Institute of Physics.

Bhat C.K.,Bhabha Atomic Research Center
Astroparticle Physics | Year: 2012

A preliminary flux estimate of various cosmic-ray constituents based on the atmospheric Cerenkov light flux of extensive air showers using fractal and wavelet analysis approach is proposed. Using a Monte-Carlo simulated database of Cerenkov images recorded by the TACTIC telescope, we show that one of the wavelet parameters (wavelet dimension B 6) provides ≥90% segregation of the simulated events in terms of the primary mass. We use these results to get a preliminary estimate of primary flux for various cosmic-ray primaries above 5 TeV energy. The simulation based flux estimates of the primary mass as recorded by the TACTIC telescope are in good agreement with the experimentally determined values. © 2012 Elsevier B.V. All rights reserved.

Sahu N.K.,Indian Institute of Technology Bombay | Ningthoujam R.S.,Bhabha Atomic Research Center | Bahadur D.,Indian Institute of Technology Bombay
Journal of Applied Physics | Year: 2012

Luminescence intensity of rare-earth doped materials can be varied depending on shape of particles, capping agent, and heat-treatment. This is related to the non-radiative rate possessed by the material. Here, we observed the high quenching of the luminescence intensity of Eu 3 doped GdPO 4 prepared in water (H 2O) medium. On the contrary, in ethylene glycol (EG) medium, it shows high luminescence. Luminescence intensity is recovered when Eu 3+ doped GdPO 4 nanorods prepared in H 2O medium is heated above 700 °C. This transforms hexagonal to monoclinic structure following the removal of water. Luminescence intensity is enhanced by changing the medium from H 2O to D 2O and also if core-shell formation occurs. Also, we found significant variation in bending and stretching vibrations of O-H and microstructure in this material prepared in H 2O and EG. Two types of O-H stretching frequencies are observed at 3450 and 3520 cm -1 in H 2O medium prepared sample which are assigned to the O-H having the hydrogen bonding (surface water) and the confined water, respectively. The formation of nanorods is due to the presence of water on the surface of particles or/and inside the pores of compound. The available water in the nanoparticles pores can be utilized for the efficient killing of mass cells tumor by generating reactive free radicals (H · and OH ·) through the application of laser near infrared (NIR) source and the subsequent irradiation of gamma ray. This proposed mechanism is quite different from the conventional treatment of mass cell/malignant tumor using gamma ray radiation. Sample is highly paramagnetic and it will be useful for magnetic resonance imaging contrast agent. © 2012 American Institute of Physics.

Mitra A.,Bhabha Atomic Research Center
Results in Physics | Year: 2012

In general relativity, one is supposed to derive the metric by solving the relevant Einstein equations. However, the metric for the Friedmann-Lemaitre-Robertson-Walker (FLRW) metric has so far been obtained by starting from Weyl's postulate and eventually by geometric considerations alone. But here, instead, we rigorously derive the same by solving the Einstein equations appropriate for gravitational collapse/expansion of a perfect fluid. The fact that FLRW metric can indeed be obtained by solving a Einstein equations shows the physical correctness of the Weyl postulate. This exercise thus complements rather than rivals the traditional derivation of the FLRW metric. During this exercise, we derive rather than merely obtain the Hubble's law. This exercise also confirms that the total energy of the FLRW universe, including matter and gravitation, is indeed given by the well known " Misner-Sharp mass" With this firm identification, we confirm the intuitive idea that while the " closed model" is gravitationally bound, the " open model" is gravitationally unbound.Video. For a video summary of this paper, please click here or visit http://www.youtube.com/watch?v=wdUI2l_Gj6U. © 2012 Elsevier B.V.