Showing papers by "Indian Institute of Science published in 1997"
TL;DR: In this paper, the asymptotic behavior of a two-time scale stochastic approximation algorithm is analyzed in terms of a related singular ordinary differential equation (SDE), and the authors show that the SDE is a non-asymptotic function.
442 citations
TL;DR: In this article, the authors present a theory of dielectric relaxation of biological water, which is described in terms of a dynamic equilibrium between the free and bound water molecules, and then determined by the equilibrium constant between the two species and the rate of conversion from bound to free state and vice versa.
Abstract: Dielectric relaxation and NMR spectrum of water in biological systems such as proteins, DNA, and reverse micelles can often be described by two widely different time constants, one of which is in the picosecond while the other is in the nanosecond regime. Although it is widely believed that the bimodal relaxation arises from water at the hydration shell, a quantitative understanding of this important phenomenon is lacking. In this article we present a theory of dielectric relaxation of biological water. The time dependent relaxation of biological water is described in terms of a dynamic equilibrium between the free and bound water molecules. It is assumed that only the free water molecules undergo orientational motion; the bound water contribution enters only through the rotation of the biomolecule, which is also considered. The dielectric relaxation is then determined by the equilibrium constant between the two species and the rate of conversion from bound to free state and vice versa. However, the diele...
427 citations
28 Feb 1997
TL;DR: In the new edition of this widely praised textbook, all the chapters have been revised and the authors have brought the work completely up to date by the addition of new material on numerous topics as mentioned in this paper.
Abstract: In the new edition of this widely praised textbook, all the chapters have been revised and the authors have brought the work completely up to date by the addition of new material on numerous topics. In recent years, solid state chemistry has emerged as a very important element of mainstream chemistry and materials science. Students, teachers and researchers need to understand the chemistry of solids because of the crucial role this plays in determining the properties of materials. An understanding of solid state chemistry is also essential in materials design, and many fascinating relationships between the structure and properties of solids have been discovered by chemists. This text requires only an understanding of basic physics, chemistry and crystallography, and is enhanced with the most recent examples, case studies and references. It will be of value to advanced students and researchers studying solid state chemistry and materials science as a text and reference work.
375 citations
324 citations
TL;DR: In this article, it was shown that pyrolysis of metallocenes such as ferrocene, cobaltocene and nickelocene yields carbon nanotubes and metal-filled onion-like structures.
320 citations
TL;DR: These studies with aromatase inhibitors in the monkey suggest that these compounds have a potential for use as fertility regulating agents in both the male and female primate.
311 citations
TL;DR: In this paper, hollow nanotubes of SiO2, Al2O3, V2O5, and MoO3 have been prepared using carbon as templates using tetraethylorthosilicate, aluminum isopropoxide, or vanadium pentoxide gel.
Abstract: Hollow nanotubes of SiO2, Al2O3, V2O5, and MoO3 have been prepared using carbon nanotubes as templates. The procedure involves coating the carbon nanotubes with tetraethylorthosilicate, aluminum isopropoxide, or vanadium pentoxide gel, followed by calcination and heating at higher temperatures in air to oxidize the carbon. SiO2 nanotubes containing transition metal ions have been prepared by this procedure since such materials may be of use in catalysis.
265 citations
TL;DR: In this paper, the authors study the ergodic control problem of switching diffusions representing a typical hybrid system that arises in numerous applications such as fault-tolerant control systems, flexible manufacturing systems, etc.
Abstract: We study the ergodic control problem of switching diffusions representing a typical hybrid system that arises in numerous applications such as fault-tolerant control systems, flexible manufacturing systems, etc. Under fairly general conditions, we establish the existence of a stable, nonrandomized Markov policy which almost surely minimizes the pathwise long-run average cost. We then study the corresponding Hamilton--Jacobi--Bellman (HJB) equation and establish the existence of a unique solution in a certain class. Using this, we characterize the optimal policy as a minimizing selector of the Hamiltonian associated with the HJB equations. As an example we apply the results to a failure-prone manufacturing system and obtain closed form solutions for the optimal policy.
233 citations
TL;DR: In this article, the reduction of their salts by ethyl alcohol under refluxing conditions in the presence of polyvinylpyrrolidone (PVP) is described.
Abstract: Nanoparticles of Ag, Au, Pd, and Cu have been prepared by the reduction of their salts by ethyl alcohol under refluxing conditions in the presence of polyvinylpyrrolidone (PVP). In the case of Au and Cu, it was necessary to use magnesium metal as a catalyst during the reduction. The nanoparticles are in the 5–35 nm range in the case of Ag, Au, and Pd, but there is considerable agglomeration in the case of Cu even in the presence of PVP.
218 citations
TL;DR: In this article, the results of an extensive investigation of the $La 0.7}Ca 0.3}MnO_3$ system were reported and it was shown that even a small amount of Co substitution can destroy the FM order, the metallic state, and the CMR.
Abstract: In this paper we report the results of an extensive investigation of the $La_{0.7}Ca_{0.3}Mn_{1-x}Co_xO_3$ system. Substitution of Mn by Co dilutes the double-exchange (DE) mechanism and changes the long range ferromagnetic order of $La_{0.7}Ca_{0.3}MnO_3$ to a cluster glass-type ferromagnetic (FM) order similar to that observed in $La_{0.7}Ca_{0.3}CoO_3$. This happens even for the lowest Co substitution of x50.05 and persists over the entire composition range studied $(0.05\leqx\leq0.5)$. The Co substitution also destroys the metallic state and the resistivity increases by orders of magnitude even with a very small extent of Co substitution. The charge localization due to Co substitution is likely to have its origin in polaronic lattice distortion. The Co substitution also suppresses the colossal magnetoresistance (CMR) of the pure manganate (x = 0) over the entire temperature and composition range and it becomes very small for $x\geq0.2$. We conclude that the DE interaction and the resulting metallic state is very ‘‘fragile’’ and hence even a small amount of Co substitution can destroy the FM order, the metallic state, and the CMR.
204 citations
TL;DR: An extensive analysis of sequences and structures of several legume lectins shows that despite the hypervariability of their combining regions they exhibit within a significant pattern of uniformity, providing a framework for understanding the molecular basis of carbohydrate recognition by legumes lectins and a rationale for redesign of their ligand binding propensities.
TL;DR: In this paper, the authors estimate the net emission of carbon from the forest sector in India and show that under a business as usual scenario at current rates of afforestation, projected carbon emissions would continue to be balanced by carbon sequestration.
Abstract: The present study estimates the net emission of carbon from the forest sector in India. For the reference year (1986), the gross emission from deforestation in that year, plus committed emissions from deforestation in the preceding years, is estimated to be 64 × 106 t of C. The carbon sequestration (or net woody biomass accumulation in trees for long-term storage) from the area brought under tree plantations and the existing forest area under forest succession is estimated to offset the gross carbon emission in India, leading to no net emissions of carbon from the forest sector. Medium-term projections for India (for the year 2011) show that under a ‘business as usual’ scenario at current rates of afforestation, projected carbon emissions would continue to be balanced by sequestration.
TL;DR: The results presented in this study provide inputs for the de novo design of consensus loop segments in synthetic hairpins by estimation of the specific amino acid preferences for loop positions in two, three and four residue loops.
Abstract: Beta-Hairpins with short connecting loops (1-5 residues) have been identified from a data set of 250 non-homologous, high resolution (< or =2.0 A) protein crystal structures. The conformational preferences of the loop segments have been analyzed with the specific aim of identifying frequently occurring motifs. Type I' and II' beta-turns were found to have a high propensity for occurrence in two residue loops. For three and four residue loops, the major conformational motif in the linking segments is alphaR-alphaR-alphaL (type I beta-turn followed by a residue in a left-handed helical conformation) and alphaR- alphaR-alphaR-alphaL (a pi-turn motif), respectively. The present larger data set confirms the high occurrences of these motifs which have been identified in earlier analyses. In addition to type I' and type II' beta-turns, several examples of type I beta-turn nucleated two residue loop hairpins, in spite of having an opposing sense of twist to that of type I' beta-turn, have also been observed. Examination of these frequently occurring motifs (flanked by extended conformation [beta]) in the data set reveals that the motifs beta-alphaR-alphaR- alphaL-beta and beta-type I'-beta have equal propensity and type II' indeed having highest propensity to nucleate beta-hairpins. The larger number of examples in this study allows the estimation of the specific amino acid preferences for loop positions in two, three and four residue loops. Small polar residues Asn, Asp, Ser, Thr, Gly and Pro in general have a high propensity for the loop positions but they reveal specific positional preferences in these frequently occurring motifs. There are no strong compositional preferences in the strand segments. Amino acid pair correlations across strands also do not show any significant pattern, with the exception of Cys-Cys pairs. Several Cys- Cys pairs have been identified at the non-hydrogen bonded positions of beta-hairpins; as many as six are disulfide bonded pairs. An examination of longer loop length hairpins reveals that the distortions of hairpins nucleated by tight turns (two residues) are much less frequently observed. The results presented in this study provide inputs for the de novo design of consensus loop segments in synthetic hairpins.
TL;DR: In this article, a model of target motion in three-dimensional space that includes position derivatives up to the third order is developed, called the jerk model, which can more accurately describe agile target maneuvers which are likely to contain significant higher order derivatives.
Abstract: A model of target motion in three-dimensional space that includes position derivatives up to the third order is developed. Compared with available models, which include terms at the most up to the second derivative, the model introduced in this work, called the jerk model, can more accurately describe agile target maneuvers which are likely to contain significant higher order derivatives. A compatible 4-state Kalman filter to perform tracking in conjunction with the jerk model is also presented, and an initialization procedure for the filter is provided. The improved performance of the jerk model over a lower order model is illustrated through numerical simulation.
TL;DR: In this article, an approach has been suggested to design chalcogenide-based amorphous materials for threshold or memory switching characteristics, using this guideline, glasses have been formed in a new CHG Al-Ge-As-Te system.
Abstract: Chalcogenide-based switching materials have potential applications in power control and information storage. In this work, an approach has been suggested to design chalcogenide-based amorphous materials for threshold or memory switching characteristics. Using this guideline, glasses have been formed in a new chalcogenide Al-Ge-As-Te system. All the samples studied have been found to exhibit threshold switching characteristics, which proves the validity of the suggested guideline.
TL;DR: In this article, the ground and low-lying excited states of uniform and dimerized alternating spin chains were analyzed using spin wave and density-matrix renormalization group (DMRG) studies.
Abstract: We report spin wave and density-matrix renormalization-group (DMRG) studies of the ground and low-lying excited states of uniform and dimerized alternating spin chains. The DMRG procedure is also employed to obtain low-temperature thermodynamic properties of the system. The ground state of a 2N spin system with spin-1 and spin- alternating from site to site and interacting via an antiferromagnetic exchange is found to be ferrimagnetic with total spin ${\mathrm{s}}_{\mathrm{G}}$=N/2 from both DMRG and spin wave analysis. Both the studies also show that there is a gapless excitation to a state with spin ${\mathrm{s}}_{\mathrm{G}}$-1 and a gapped excitation to a state with spin ${\mathrm{s}}_{\mathrm{G}}$+1. Surprisingly, the correlation length in the ground state is found to be very small from both the studies for this gapless system. For this very reason, we show that the ground state can be described by a variational ansatz of the product type. DMRG analysis shows that the chain is susceptible to a conditional spin-Peierls' instability. The DMRG studies of magnetization, magnetic susceptibility (\ensuremath{\chi}), and specific heat show strong magnetic-field dependence. The product \ensuremath{\chi}T shows a minimum as a function of temperature (T) at low-magnetic fields and the minimum vanishes at high-magnetic fields. This low-field behavior is in agreement with earlier experimental observations. The specific heat shows a maximum as a function of temperature and the height of the maximum increases sharply at high-magnetic fields. It is hoped that these studies will motivate experimental studies at high-magnetic fields.
TL;DR: The fine particle nature of combustion derived phosphors has been studied by powder density (55-82% of theoretical value), particle size (5.7-9.5 μm) and surface area (5-22 m2 g−1) measurements as mentioned in this paper.
01 Jan 1997
TL;DR: The average cost control problem for linear stochastic systems with Gaussian noise and quadratic cost is considered in the presence of communication constraints, and if instead of the state observations an associated “innovations process” is encoded and transmitted, then the separation principle holds, leading to an optimal control linear in state estimate.
Abstract: The average cost control problem for linear stochastic systems with Gaussian noise and quadratic cost is considered in the presence of communication constraints. The latter take the form of finite alphabet codewords, being transmitted to the controller with ensuing delay and distortion. It is shown that if instead of the state observations an associated “innovations process” is encoded and transmitted, then the separation principle holds, leading to an optimal control linear in state estimate. An associated “off-line” optimization problem for code length selection is formulated. Some possible extensions are also pointed out.
TL;DR: In this article, the authors suggest that α-hydroxides acquire a positive charge by partial protonation of the hydroxyl ions according to the equationM(OH)2+xH+→[M( OH)2−x(H2O)x]x+.
TL;DR: In this article, the equilibrium structures, harmonic frequencies, and mode assignments for TAB and CAB and their isotopic analogues, using restricted Hartree-Fock (RHF), hybrid Hartree Fock/density functional (HF/DF), and pure density functional theoretical (DFT) methods utilizing the 6-31G* basis set.
Abstract: The vibrational structures of trans- (TAB) and cis-azobenzene (CAB) are of interest due to their importance in optoelectronic applications as well as due to the unique isomerization mechanism involving the inversion process (at the nitrogen site). In this paper, we report the equilibrium structures, harmonic frequencies, and mode assignments for TAB and CAB and their isotopic analogues, using restricted Hartree-Fock (RHF), hybrid Hartree-Fock/density functional (HF/DF), and pure density functional theoretical (DFT) methods utilizing the 6-31G* basis set. The results of the optimized molecular structure obtained on the basis of RHF and all the DFT calculations are presented and then critically compared with the experimental electron diffraction results. It is observed that best structural parameters are predicted by the hybrid HF/DF method, viz. B3LYP and B3P86 followed by the pure DFT method BP86. In the case of harmonic vibrational frequencies (unsealed) and the normal modes, it is found that the BP86/6-31G* is the most accurate. The data obtained here has been used to reassign (in contrast to the previously reported MP2 results) some of the vibrational frequencies, particularly, for the main N=N and C-N vibrations of TAB. On the basis of BP86/6-31G* force field, the infrared intensities for both TAB and CAB and their isotopomers have also been calculated. Moreover, the main differences in the vibrational spectra of the two isomers of azobenzene have been discussed from normal mode analysis.
TL;DR: In this paper, single crystals of bis(thiourea) cadmium chloride (BTCC) were grown from aqueous solutions and characterized by recording the powder X-ray diffraction pattern and by identifying the diffracting planes.
TL;DR: The data indicate that C. decidua may have potential use as an antidiabetic agent and in lowering oxidative stress in diabetes and the changes such as the increase in kidney and heart SOD may be an adaptive response in order to neutralize superoxide anions.
TL;DR: In this paper, the authors address the concept of a particle distribution map which can help in predicting particle distribution under different solidification conditions, and present a method to obtain composites with tailored microstructures.
TL;DR: The significant feature of the proposed technique is that, while the error is nearly uniform throughout the cycle, the diagnostically crucial QRS region is kept free of maximal reconstruction error.
Abstract: Presents a novel coding scheme for the electrocardiogram (ECG). Following beat delineation, the periods of the beats are normalized by multirate processing. After amplitude normalization, a discrete wavelet transform is applied to each beat. Due to the period and amplitude normalization, the wavelet transform coefficients bear a high correlation across beats at identical locations. To increase the compression ratio, the residual sequence obtained after linear prediction of the significant wavelet coefficients is transmitted to the decoder. The difference between the actual period and the mean beat period, and that between the actual scale factor and the average amplitude scale factor are also transmitted for each beat. At the decoder, the inverse wavelet transform is computed from the reconstructed wavelet transform coefficients. The original amplitude and period of each beat are then recovered. The approximation achieved, at an average rate of 180 b/s, is of high quality. The authors have evaluated the normalized maximum amplitude error and its position in each cycle, in addition to the normalized root mean square error. The significant feature of the proposed technique is that, while the error is nearly uniform throughout the cycle, the diagnostically crucial QRS region is kept free of maximal reconstruction error.
TL;DR: Vegetatively dividing cells of Saccharomyces cerevisiae carrying a mutation in RAD50 grow significantly more slowly in rich medium and are sensitive to DNA damage inflicted by X‐ray or chemical mutagens.
Abstract: Background: Vegetatively dividing cells of Saccharomyces cerevisiae carrying a mutation in RAD50 grow significantly more slowly in rich medium and are sensitive to DNA damage inflicted by X-ray or chemical mutagens. RAD50 function is essential for the formation and repair of meiosis-specific double-strand breaks and chromosome stability,
Results: We present evidence for two new phenotypes associated with the rad50 Delta mutant; shortened telomeres and cell senescence. Comparison of TG(1-3) telomeric sequences in an isogenic pair of RAD50 and rad50 Delta haploid strains showed that they were considerably shortened in the latter. Although rad50 Delta mutation conferred cell enlargement and slow growth, cell doubling was faster but caused an increase in the frequency of cell death, Telomeres were restored to the wild-type size in hemizygous RAD50/rad50 Delta and ran50S/rad50 Delta strains; however, they showed a significant increase in rad50S/rad50S diploid with a concomitant rise in cell viability. Telomeres were stabilized in hemizygous RAD50/ rad50 Delta and rad50S/rad50 Delta diploids during prolonged growth, suggesting that even a half-dosage of RAD50 is sufficient to conserve the telomere size during successive cell divisions. Furthermore, cells bearing the rad50 Delta mutation revealed abnormalities in nuclear segregation and, in the presence of hydroxyurea, displayed phenotypes consistent with defects in S-phase checkpoint control,
Conclusion: This report presents evidence of the involvement of a gene relevant to recombinational repair in the maintenance of telomeres. We conclude that the phenotypes displayed by yeast rad50 Delta cells have intriguing similarities among the human cell lines representing DNA repair-deficient chromosome instability syndromes.
TL;DR: In this article, the melting of small particles and in particular, embedded small particles which have been studied less extensively is discussed. And the observed asymmetry in the solidification and melting behavior of metals and alloys is investigated.
TL;DR: A region which may be responsible for binding PfTIM to cytoskeletal elements or the band 3 protein of erythrocytes may subsequently lead to the extracellular exposure of parts of the protein and provide a framework for new therapeutic leads.
TL;DR: Inclusion of surfactants and other additives into the DNA generally enhanced the DNA melting temperatures by a few degrees C and at high [surfactant], the corresponding melting profiles got broadened.
TL;DR: In this paper, a new route to synthesize pure TiN, VN, and CrN from the ammonolysis of TiS 2, VS 2, and Cr 2 S 3 is described.
01 May 1997
TL;DR: A dynamic loop vectorization mechanism that builds on top of the above mechanisms is briefly outlined, showing that the mechanism vectorizes up to 60% of the dynamic instructions for some programs, albeit the average number of iterations per loop is quite small.
Abstract: Superscalar processors currently have the potential to fetch multiple basic blocks per cycle by employing one of several recently proposed instruction fetch mechanisms. However, this increased fetch bandwidth cannot be exploited unless pipeline stages further downstream correspondingly improve. In particular, register renaming a large number of instructions per cycle is difficult. A large instruction window, needed to receive multiple basic blocks per cycle, will slow down dependence resolution and instruction issue. This paper addresses these and related issues by proposing (i) partitioning of the instruction window into multiple blocks, each holding a dynamic code sequence; (ii) logical partitioning of the register file into a global file and several local files, the latter holding registers local to a dynamic code sequence; (iii) the dynamic recording and reuse of register renaming information for registers local to a dynamic code sequence. Performance studies show these mechanisms improve performance over traditional superscalar processors by factors ranging from 1.5 to a little over 3 for the SPEC Integer programs. Next, it is observed that several of the loops in the benchmarks display vector-like behavior during execution, even if the static loop bodies are likely complex for compile-time vectorization. A dynamic loop vectorization mechanism that builds on top of the above mechanisms is briefly outlined. The mechanism vectorizes up to 60% of the dynamic instructions for some programs, albeit the average number of iterations per loop is quite small.