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Stochastic recursive inclusions with non-additive iterate-dependent Markov noise
No full textIn this paper we study the asymptotic behaviour of stochastic approximation schemes with set-valued drift function and non-additive iterate-dependent Markov noise. We show that a linearly interpolated trajectory of such a recursion is an asymptotic pseudotrajectory for the flow of a limiting differential inclusion obtained by averaging the set-valued drift function of the recursion w.r.t. the stationary distributions of the Markov noise. The limit set theorem by Benaim is then used to characterize the limit sets of the recursion in terms of the dynamics of the limiting differential inclusion. We then state two variants of the Markov noise assumption under which the analysis of the recursion is similar to the one presented in this paper. Scenarios where our recursion naturally appears are presented as applications. These include controlled stochastic approximation, subgradient descent, approximate drift problem and analysis of discontinuous dynamics all in the presence of non-additive iterate-dependent Markov noise
Effect of different solute diffusivities on precipitate coarsening in ternary alloys
No full textAccording to Gibbs phase rule, ternary two phase alloys have a single degree of freedom at equilibrium at a given temperature. Thus, multiple precipitate-matrix equilibrium compositions are possible at the interface. From Philippe-Voorhees' (PV) theory (Philippe and Voorhees, 2013), it is known that during coarsening in multicomponent alloys, precipitate-matrix compositions at the interface during coarsening are not just dependent on the Gibbs-Thomson effect but also on the relative mobilities of the solute elements. Our computer simulations, based on a phase field model, show that this effect of different solute diffusivities on size-dependent particle composition is more pronounced in alloys richer in the slower diffusing solute. (C) 2018 Elsevier B.V. All rights reserved
Temperature-dependent electrical characteristics and carrier transport mechanism of p-Cu2ZnSnS4/n-GaN heterojunctions
No full textThis work explores the temperature-dependent electrical characteristics and carrier transport mechanism of Au/p-Cu2ZnSnS4/n-type GaN heterojunction (HJ) diodes with a CZTS interlayer. The electrical characteristics were examined by current-voltage-temperature, turn-on voltage-temperature and series resistance-temperature in the high-temperature range of 300-420 K. It is observed that an exponential decrease in the series resistance (R-S) and increase in the ideality factor (n) and barrier height (phi(b)) with increase in temperature. The thermal coefficient (K-j) is determined to be -1.3 mV K-1 at >= 300 K. The effective phi(b) is determined to be 1.21 eV. This obtained barrier height is consistent with the theoretical one. The characteristic temperature (T-0) resulting from the Cheung's functions dV/d(lnI) vs. I and H(I) vs. I], is seen that there is good agreement between the T-0 values from both Cheung's functions. The relevant carrier transport mechanisms of Au/p-CZTS/n-type GaN HJ are explained based on the thermally decreased energy band gap of n-type GaN layers, thermally activated deep donors and increased further activated shallow donors
(Fe/Sr) Codoped Biphasic Calcium Phosphate with Tailored Osteoblast Cell Functionality
No full textAlthough doped bioceramics have been widely investigated for biomedical applications, the codoped bioceramics remain mostly unexplored for bone regeneration applications. For example, the impact of codoping of Sr2+ and Fe3+ ions on the phase stability and cytocompatibility is not explored so far. In this perspective, the objective of the present study is to quantitatively understand this aspect in case of Fe/Sr codoped biphasic calcium phosphate (BCP). Following sol gel synthesis, codoped BCP samples with Sr/Fe dopant concentrations of 2, 10, 20, 30, and 40 mol % as well as doped BCPs with single dopant (Sr or Fe) with similar compositions were calcined at 800 degrees C in air. Using extensive Rietveld analysis, the dopant content dependent crystallographic properties (e.g lattice parameters) and phase stability of HA/TCP are quantitatively assessed. In vitro cytocompatibility of codoped samples has been assessed using mouse osteoblast cells. An important observation is that, while singular dopant of Sr/Fe at 20 mol % or higher amount reduces cell viability significantly, osteoblast viability is not compromised to any significant extent on Sr/Fe codoped BCP, compared to undoped BCP. Our results indicate that one can tailor osteoblast functionality by controlling the codopant content. More importantly, all the codoped BCPs support cell proliferation, when single doped BCP exhibits significant reductionin cell viability, at dopant content of 10 mol % or higher. Cell morphological analysis supports extensive cell spreading on codoped BCPs. An attempt has been made to correlate the variation in cellular response with HA/TCP ratio and ion dissolution behavior. Taken together, the present work establishes unique advantage of Sr/Fe codoping approach toward realizing their bone replacement application
Evolution of Neutralization Response in HIV-1 Subtype C-Infected Individuals Exhibiting Broad Cross-Clade Neutralization of HIV-1 Strains
No full textStrain-specific neutralizing antibodies develop in all human immunodeficiency virus type 1 (HIV-1)-infected individuals. However, only 10-30% of infected individuals produce broadly neutralizing antibodies (bNAbs). Identification and characterization of these bNAbs and understanding their evolution dynamics are critical for obtaining useful clues for the development of an effective HIV vaccine. Very recently, we published a study in which we identified 12 HIV-1 subtype C-infected individuals from India whose plasma showed potent and broad cross-clade neutralization (BCN) ability (1). In the present study, we report our findings on the evolution of host bNAb response over a period of 4 years in a subset of these individuals. Three of the five individuals (NAB033, NAB059, and NAB065) demonstrated a significant increase (p < 0.05) in potency. Interestingly, two of the three samples also showed a significant increase in CD4 binding site-specific antibody response, maintained stable CD4+ T cell counts (> 350 cells/mm(3)) and continued to remain ART-naive for more than 10 years after initial diagnosis, implying a strong clinical correlation with the development and evolution of broadly neutralizing antibody response against HIV-1
A Diode Bridge Rectifier With Improved Power Quality Using the Capacitive Network
No full textWidely distributed single-phase power electronic rectifier loads are an increasing source of harmonics in the power distribution system. These harmonics have many well-known adverse impacts on the power system, so it is necessary to improve the power quality of the rectifiers. This paper presents a novel single-phase rectifier in which capacitors are used in parallel with diodes in one leg of the rectifier. Ageneral analyticalmodel of the proposed topology is obtained. The closed-form expressions for the rectifier waveforms are utilized in parameter selection that leads to optimal performance in terms of input current total harmonic distortion (THD). Different topologies of rectifiers are compared in terms of the input voltage, current waveform distortion, output dc voltage ripple, and desired target for the dc output voltage. The proposed topology reduces the THD from 145% in a normal rectifier to 63% while maintaining voltage ripple less than 0.3%. The proposed topology keeps dc bus ripple small while simultaneously providing better THD. The passive components considered for improving harmonic injection are two small capacitors. The additional cost required for the proposed rectifier is low, and the proposed rectifier also has a higher efficiency than the other commonly used diode rectifier topologies
Logic of two antagonizing intra-species quorum sensing systems in bacteria
No full textBacteria release signaling molecules into the surrounding environment and sense them when present in their proximity. Using this strategy, a cell estimates the number of neighbors in its surrounding. Upon sensing a critical number of individuals, bacteria coordinate a number of cellular processes. This density-dependent control of gene expression and physiology is called quorum sensing (QS). Quorum sensing controls a wide variety of functions in bacteria, including those related to motility, growth, virulence etc. Quorum sensing has been widely observed in bacteria while the individuals of the same species or different species compete and cooperate each other. Interestingly, many species possess more than one QS system (intra-species) and these QS systems interact each other to perform quorum sensing. Thus, several logical arrangements can be possible based on the interaction among intra-species QS systems - parallel, series, antagonizing, and agonizing. In this work, we perform simulations to understand the logic of interaction between two antagonizing intra-species QS systems. In such an interaction, one QS system gets fully expressed and the other only gets partially expressed. This is found to be dictated by the interplay between autoinducer's diffusivity and antagonizing strength. In addition, we speculate an important role of the intracellular regulators (eg. LuxR) in maintaining the uniform response among the individual cells from the different localities. We also expect the interplay between the autoinducer's diffusivity and distribution of cells in fine tuning the collective response. Interestingly, in a localized niche with a heterogeneous cell distribution, the cells are expected to perform a global quorum sensing via fully expressed QS system and a local quorum sensing via partially expressed QS system. (C) 2018 Elsevier B.V. All rights reserved
A Critical Appraisal of Some Recent Views on the Evolution of the Archaean Dharwar Craton, Southern India
No full textPlaying it safe? Behavioural responses of mosquito larvae encountering a fish predator
No full textPredation is a strong selective force that affects prey population and ecosystem dynamics. Detecting predators and associated levels of threat is crucial to prey responses. Once a predator is detected, anti-predatory responses improve the chances of survival of prey. We used Aedes aegypti larvae to study behavioural responses to predation threat from guppies (Poecilia reticulata). Specifically, we tested the relative importance of chemical cues, both in isolation and in combination with physical cues, in eliciting anti-predatory behaviours. Larvae responded more strongly, by reducing the lengths of their wriggle bursts, when presented with a combination of chemical and physical cues than with chemical cues alone. Anti-predatory responses often come with an associated cost, and we expect that the ability to pay these costs should influence responses to predation risk. To test this, we compared wriggling patterns of satiated vs starved larvae in the same experiment. We found that, under predation risk, starved larvae were willing to take more risks than satiated larvae were. We sought to experimentally test the assumption that anti-predator behaviours increase the survival of prey. To do this, starved guppies were made to choose between displays of simulated larvae, moving in short and long wriggle bursts as observed in the previous experiment. The fish preferentially attacked larvae moving in long bursts, demonstrating the survival value of the larval anti-predatory response of shifting to a preponderance of short wriggle bursts. Our study identifies specific ways in which trade-offs between predation risk and energetic costs could affect anti-predator behaviour
Synthesis and electrochemical performance of Li2VxMn1-xO3 positive electrode for lithium batteries
No full textLithium excess manganese oxide, namely, Li2MnO3 is under investigations to improve its electrochemical performance as the next generation high capacity electrode material. Partial substitution of Mn by another metal is one of the ways to influence the properties of Li2MnO3. In the present study, vanadium is used to partially substitute Mn in various ratios. Li2VxMn1-xO3 (x = 0.1, 0.2, 0.3 and 0.4) samples are prepared by sol-gel method using stoichiometric ratios weights of Mn(CH3COO)(2)center dot 4H(2)O, Li2CO3 and NH4VO3. The crystalline phases are identified by X-ray diffraction. The particles morphology is studied with a scanning electron microscope. Furthermore, impedance measurements (EIS) are applied using frequency range between 10(6) and 10(-2) Hz. The optimum EIS is obtained with for the Li2V0.3Mn0.7O3 cell. Cyclic voltammetric measurements are carried out for the lithium manganate materials between 0.01 and 4.5 V versus Li+ with scan rate 0.1 mV s(-1). Also, galvanostatic charging and discharging cycling of the cells are achieved with the same potentials windows using charging and discharging current intensity of 10 mA g(-1) between 1.5 and 4.5 V versus Li+. It is observed that Li/Li2V0.3Mn0.7O3 cell has higher specific discharge capacity, 227 mAh g(-1) rather than the other cells