Papers by Sivaprasad Mitra
Physica Status Solidi, 1992
Pramana J Phys, 2008
DSC measurements on p-n-hexyloxybenzylidine-p -n-butylaniline (6O.4) showed that the crystalline ... more DSC measurements on p-n-hexyloxybenzylidine-p -n-butylaniline (6O.4) showed that the crystalline to liquid crystalline (K-S H) transition at 33.7 • C observed in the heating cycle does not revert even when the sample is cooled down to −100 • C. Hence it is inferred that a physically stable supercooled liquid crystalline phase is formed on cooling 6O.4. To investigate the K-SH transition further the techniques of polarized microscopy and X-ray diffraction were used which concurred with the DSC results. Quasielastic neutron scattering measurements carried out to study the re-orientational motions in the ordered phases of 6O.4 (K and SH) show that while in the crystalline phase (at RT) the re-orientational motion is found to involve only the core of the molecule, in the S H phase (at 45 • C) the dynamics involves the whole molecule and this motion is found to persist even when the sample cools back to room temperature corroborating the results of the DSC, microscopy and X-ray diffraction.
Journal of Genetics, 2015
ABSTRACT Linkage map with wide marker coverage is an essential resource for genetic improvement s... more ABSTRACT Linkage map with wide marker coverage is an essential resource for genetic improvement study for any species. Sex-averaged genetic linkage map of Labeo rohita, popularly known as ‘rohu’, widely cultured in the Indian subcontinent, was developed by placing 68 microsatellite markers generated by a simplified method. The parents and their F 1 progeny (92 individuals) were used as segregating populations. The genetic linkage map spans a sex-averaged total length of 1462.2 cM, in 25 linkage groups. The genome length of rohu was estimated to be 3087.9 cM. This genetic linkage map may facilitate systematic searches of the genome to identify genes associated with commercially important characters and marker-assisted selection programmes of this species.
Solid-State Electronics, 2010
A study on the electrostatic discharge (ESD) behaviors of silicide blocked (Sblk) n and p channel... more A study on the electrostatic discharge (ESD) behaviors of silicide blocked (Sblk) n and p channel MOSFETs is presented for a state-of-the-art 65nm SOI technology. It is observed that the charge in the floating body SOI MOSFETs helps to improve their ESD characteristics over the grounded body devices. The ESD behavior of the thin-oxide pMOSFETs shows failure current similar to
Solid-State Electronics, 2003
N-channel FETs fabricated in SiC by ion implantation are studied by using deep level transient sp... more N-channel FETs fabricated in SiC by ion implantation are studied by using deep level transient spectroscopy (DLTS) to detect deep levels, which may influence device performance significantly. Enhancement mode MISFETs, made on 6H-SiC p-type epilayer using nitrogen source/drain implantation and MESFETs, made on semi-insulating bulk 4H-SiC using nitrogen as the channel and source/drain implantations were used for the DLTS characterization. For both of these devices, effective channel mobility is much smaller than the bulk mobility, due to possible residual implant lattice damage or dielectric/SiC interface traps. For MESFETs five different traps were identified and characterized by activation energies of 0.51, 0.6, 0.68, 0.768 and 0.89 eV above the valence band edge E v . Five gate dielectric traps and eight interface hole/electron traps were revealed for MISFETs. Gate dielectric traps were distinguished by different activation energies of 0.109, 0.132, 0.15, 0.4 and 0.6 eV. Two shallow gate dielectric/semiconductor interface traps were identified at E v þ 0:2 eV (hole trap) and E c À 0:362 eV (electron trap). Four deep level traps were found in the activation energy range of 0.6-0.8 eV above the valence band edge with capture cross-section $10 À16 -10 À17 cm 2 . Other traps were detected at DE ¼ 0:437 and 0.47 eV above E v .
European Journal of Chemistry, 2010
Fluorescence behavior of intramolecular charge transfer probe trans-ethyl-p-(dimethylamino) cinna... more Fluorescence behavior of intramolecular charge transfer probe trans-ethyl-p-(dimethylamino) cinnamate (EDAC) is extremely sensitive to the local environment. This study explores the interaction of EDAC with several Igepal, Brij and Tween series of non-ionic surfactants by steady state and picoseconds time-resolved fluorescence spectroscopy. The physico-chemical properties, like critical micelle concentration and micropolarity of the micellar media surrounding the probe were determined. In most of the cases, the observed values were in good agreement with the data reported in the literature. Results obtained from time-resolved fluorescence experiments show a substantial reduction in total nonradiative decay rate of the probe in micellar medium compared to that in aqueous phase. This indicates preferential association of the probe inside the micellar core. The association constant of the probe-micelle interaction was also evaluated in different cases.
2007 IEEE International Reliability Physics Symposium Proceedings. 45th Annual, 2007
A comprehensive study on the interaction between ESD, NBTI and HCI on silicide blocked (SBLK) PFE... more A comprehensive study on the interaction between ESD, NBTI and HCI on silicide blocked (SBLK) PFET devices is presented for a state-of-the-art 65nm bulk technology. ESD behavior of thin and thick oxide devices are shown to have opposite channel length dependence. ...
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2009
Intramolecular charge transfer (ICT) behavior of trans-ethyl p-(dimethylamino) cinamate (EDAC) an... more Intramolecular charge transfer (ICT) behavior of trans-ethyl p-(dimethylamino) cinamate (EDAC) and 4-(dimethylamino) cinnamic acid (DMACA) were studied by steady state absorption and emission, picosecond time-resolved fluorescence experiments in various pure and mixed solvent systems. The large fluorescence spectral shift in more polar solvents indicates an efficient charge transfer from the donor site to the acceptor moiety in the excited state compared to the ground state. The energy for 0,0 transition (nu(0,0)) for EDAC shows very good linear correlation with static solvent dielectric property; however, fluorescence emission maximum, stokes shift and fluorescence quantum yield show significant deviation from linearity in polar protic solvents, indicating a large contribution of solvent hydrogen bonding on the excited state relaxation mechanism. A quantitative estimation of contribution from different solvatochromic parameters was made using linear free energy relationship based on Kamlet-Taft equation.
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 1958
Downloaded from rspa.royalsocietypublishing.org on January 5, 2011 The behaviour of the paramagne... more Downloaded from rspa.royalsocietypublishing.org on January 5, 2011 The behaviour of the paramagnetic ions in the single crystals of some similar salts of the iron group of elements I. Hydrated cupric salts By A. Bose, S. С Mitra and Stjnil K. Datta Indian Association for the Cultivation of ...
Journal of Physics B: Atomic, Molecular and Optical Physics, 2011
ABSTRACT Atomic coherence resonances such as electromagnetically induced transparency (EIT) and e... more ABSTRACT Atomic coherence resonances such as electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) signals are observed in a Doppler broadened multi-level system for the D2 line of 85Rb atoms in a vapour cell considering different types of atom–laser coupling schemes. Besides the coherence resonances, the nonlinear resonances like velocity selective optical pumping (VSOP) dips and velocity selective resonances (VSR) are also observed for the non-zero velocity selective groups of atoms. In the presence of pump, control and probe laser fields, we observe two EIT signals in a double Λ-type system and two EIA signals in a double V-type system. We are able to see the EIA signal for the non-zero velocity group of atoms when the pump laser is locked with an open transition by a small red detuning. We also report the experimental observation of simultaneous EIT and EIA signals in a (Λ+V)-type system. The effect of frequency tuning of the control laser is also studied in the presence of the frequency locked pump laser. A simple theoretical analysis explains the experimental results.
Journal of Physics: Conference Series, 2007
Layered double hydroxides (LDH) are a class of ionic lamellar solids with positively charged laye... more Layered double hydroxides (LDH) are a class of ionic lamellar solids with positively charged layers of two kinds of metallic cations and exchangeable hydrated anions. Quasi-elastic neutron scattering (QENS) measurements are performed in this type of LDH structured hydrated hydrotalcite sample to study the dynamical behaviour of the water in geometric confinement within the layers. Dynamical parameters correspond to the
Journal of Photochemistry and Photobiology B: Biology, 2009
The knowledge of the formation of bile acid micellar aggregates is of great importance because of... more The knowledge of the formation of bile acid micellar aggregates is of great importance because of the biological significance of these compounds and their pharmacological applications. The intramolecular charge transfer (ICT) fluorescence property of trans-ethyl-p-(dimethylamino) cinnamate is used to study the micelles formed by aggregation of three most important bile acids, viz. cholic acid, deoxycholic acid and chenodeoxycholic acid by steady state and picosecond time-resolved fluorescence spectroscopy. The ICT fluorescence band intensity was found to increase with concomitant blue shift with the addition of bile acids. The blue shift in ICT fluorescence maxima as well as decrease in nonradiative decay constants in presence of bile acids indicate the passage of the probe towards the micro domains formed from the aggregated bile acids. Binding constant of the probe with micelles as well as critical micelle concentration and average polarity parameter of the micellar environments were obtained from the variation of fluorescence intensity on increasing concentration of bile acids in the medium.
Journal of Photochemistry and Photobiology B: Biology, 2013
The photophysical behavior of the deprotonated form of lumazine (Lum-anion) was studied in biolog... more The photophysical behavior of the deprotonated form of lumazine (Lum-anion) was studied in biologically relevant surfactant systems like sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB) and TritonX-100 (TX-100) and also model water soluble protein, bovine serum albumin (BSA), using steady-state and time-resolved fluorescence spectroscopy in buffer solution of pH 12.0. The association constant values were calculated from modulated fluorescence intensity of Lum-anion in different medium. The interaction of non-ionic surfactant TX-100 was found to be about 10 times greater than SDS and CTAB. However, while the driving force of binding in SDS and/or TX-100 is mainly hydrophobic in nature, electrostatic interaction with the oppositely charged micellar head group is the predominant factor in CTAB. The thermodynamic parameters like enthalpy (ΔH) and entropy (ΔS) change, etc., corresponding to the binding of Lum-anion with BSA were estimated by performing the fluorescence titration experiment at different temperatures. Thermodynamically favorable and strong binding of Lum-anion (K~10(4) M(-1)) into BSA is due to hydrophobic interaction in the ligand binding domain II. However, the binding mechanism is entirely different in presence of protein denaturing agent like urea and electrostatic interaction plays a major role under this condition.
Journal of Molecular Modeling, 2012
Excited state intramolecular proton transfer (ESIPT) reaction along the O-H[Symbol: see text][Sym... more Excited state intramolecular proton transfer (ESIPT) reaction along the O-H[Symbol: see text][Symbol: see text][Symbol: see text][Symbol: see text]O hydrogen bond of o-hydroxy benzaldehyde (OHBA), methyl salicylate (MS) and salicylic acid (SA) was investigated by ab-initio quantum chemical calculation and theory of atoms and molecules (QTAIM) for the first time. Variation in several geometric as well as QTAIM parameters along the reaction coordinate was monitored in the fully relaxed excited state potential energy curve (PEC) obtained from intrinsic reaction coordinate (IRC) analysis. Although, the excited state barrier height for the forward reaction (∆E (0) (#) ) reduces substantially in all the systems, MS and SA do not show any obvious asymmetry for proton transfer. For MS and SA, the crossover of the bond index as well as the lengths of the participating bonds at the saddle point is assigned due to this symmetry in accordance with bond energy - bond order (BEBO) model, which does not hold true in OHBA both in the ground and excited states. Bond ellipticity, covalent and metallic character were examined for different structures along the reaction path within the QTAIM framework. The QTAIM analysis was found to be able to uniquely distinguish between the ground and excited states of the OHBA molecule as well as both determining the effects on the bonding character of adding different substituent groups and differentiating between the ESIPT reactions in the SA and MS molecules.
Journal of Materials Science, 1986
The effects of annealing in vacuum on the electrical and optical properties of GaAs thin films de... more The effects of annealing in vacuum on the electrical and optical properties of GaAs thin films deposited by the flash evaporation method were studied. Thin films of compound GaAs deposited upon glass substrates at room temperature were annealed in a vacuum of 2 • 10-6torr at different temperatures up to 350 ~ C. The properties of the films depended strongly on annealing temperature. The lowest resistivity measured was about 1.6 x 104 ~cm at an annealing temperature of about 240 ~ C. The activation energy of as-deposited and annealed films were measured and compared. Optical absorption measurements of the asdeposited samples and the samples annealed at a temperature of 240~ were made as a function of photon energy.
Dalton Transactions, 2013
Ten neutral monomeric, dimeric and polymeric mercury(II) complexes of compositions HgX(2)L (3, 8)... more Ten neutral monomeric, dimeric and polymeric mercury(II) complexes of compositions HgX(2)L (3, 8), [HgX(2)L](2) (1, 2, 4-6 and 7), [Hg(NO(3))(2)L](n) (9) and {[Hg(N(3))(2)L](2)}(n) (10) where X = chloride, bromide, iodide, nitrate and azide, and L = (E)-N-(pyridin-2-ylmethylidene)arylamine, are described. Compounds 1-10 were characterized by elemental analyses, and IR and (1)H NMR spectroscopic studies. The solution-state photophysical properties of the complexes are highly dependent on the anions as seen in the fluorescence emission features. Single-crystal X-ray crystallography showed that the molecular complexes can aggregate into larger entities depending upon the anion coordinated to the metal centre. Iodide gives discrete monomeric complexes, chloride and bromide generate binuclear complexes formed through Hg-X-Hg bridges, while nitrate and azide lead to 1D coordination polymers. The significant differences in the observed aggregation patterns of the compounds indicate that the anions exert a substantial influence on the formation of the compounds. A further influence upon supramolecular aggregation is the presence of methyl substituents in L(3) and L(4), which generally enhances the probability of forming supramolecular ππ interactions involving the five-membered C(2)N(2)Hg chelate rings in their crystal structures.
Chemical Physics, 2013
ABSTRACT The photophysical properties and tautomerization behavior of neutral lumazine were studi... more ABSTRACT The photophysical properties and tautomerization behavior of neutral lumazine were studied by fluorescence spectroscopy and density functional theory calculation. A quantitative estimation of the contributions from different solvatochromic parameters, like solvent polarizibility (π∗), hydrogen bond donation (α) and hydrogen bond accepting (β) ability of the solvent, was made using linear free energy relationships based on the Kamlet–Taft equation. The analysis reveals that the hydrogen bond acceptance ability of the solvent is the most important parameter characterizing the excited state behavior of lumazine. Theoretical calculations result predict an extensive charge redistribution of lumazine upon excitation corresponding to the N3 and N1 proton dissociation sites by solvents in the ground and excited states, respectively. Comparison of S0 and S1 state potential energy curves constructed for several water mediated tautomerization processes by intrinsic reaction coordinate analysis of lumazine-H2O cluster shows that (3,2) and (1,8) hydrogen migrations are the most favorable processes upon excitation.
Biophysical Chemistry, 2008
A systematic study on the spectroscopy and photophysical properties of widely used analgesic and ... more A systematic study on the spectroscopy and photophysical properties of widely used analgesic and anti-pyretic drug acetaminophen (NAPAP) was presented using steady state and time-resolved fluorescence spectroscopy. The results in homogeneous solvents were compared with those in bio-mimicking environments of cyclodextrin and micellar cavities. Extensive theoretical calculations using time dependent density functional theory (TDDFT) were also done to substantiate the spectral assignment as well as to compare the structure and stability of possible hydrogen bonded conformations of NAPAP in aqueous medium. Facile proton dissociation occurs due to extensive charge redistribution in the excited state. The variation in fluorescence yield and the life time of excited state species in cyclodextrin cavities and micellar medium is due to shift in acid-base dissociation equilibrium in these environments.
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Papers by Sivaprasad Mitra