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Search Results: 1 - 10 of 20965 matches for " Kumar Mukerjee "
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Homology Curve Complex  [PDF]
Ningthoujam Jiban Singh, Himadri Kumar Mukerjee
Advances in Pure Mathematics (APM) , 2012, DOI: 10.4236/apm.2012.22017
Abstract: A homological analogue of curve complex of a closed connected orientable surface is developed and studied. The dis-tance in this complex is shown to be quite computable and an algorithm given (Theorem 3.5). As an application of this complex it is shown that for a closed orientable 3-manifold, and any of its Heegaard splittings, one can give an algorithm to decide whether the manifold contains a 2-sided, non-separating, closed incompressible surface (Theorem 1.1).
Inferior Distraction of the Kidney to Aid Upper Pole and Supracostal Punctures During Supine Percutaneous Renal Access
Anuj Goyal,Kumar Mukerjee,Theocharis Karaolides,Christian Bach
Urology Journal , 2012,
Abstract: No Abstract
Thermopower of the Hubbard model: Effects of multiple orbitals and magnetic fields in the atomic limit
Subroto Mukerjee
Physics , 2004, DOI: 10.1103/PhysRevB.72.195109
Abstract: We consider strongly-correlated systems described by the multi-orbital Hubbard model in the atomic limit and obtain exact expressions for the chemical potential and thermopower. We show that these expressions reduce to the Heikes formula in the appropriate limits ($k_BT \gg U$) and ($k_BT \ll U$) and obtain the full temperature dependence in between these regimes. We also investigate the effect of a magnetic field introduced through a Zeeman term and observe that the thermopower of the multi-orbital Hubbard model displays spikes as a function of magnetic field at certain special values of the field. This effect might be observable in experiments for materials with a large magnetic coupling.
Data-dependent probability matching priors for empirical and related likelihoods
Rahul Mukerjee
Mathematics , 2008, DOI: 10.1214/074921708000000057
Abstract: We consider a general class of empirical-type likelihoods and develop higher order asymptotics with a view to characterizing members thereof that allow the existence of possibly data-dependent probability matching priors ensuring approximate frequentist validity of posterior quantiles. In particular, for the usual empirical likelihood, positive results are obtained. This is in contrast with what happens if only data-free priors are entertained.
Fundamental Mechanistic Understanding of Electrocatalysis of Oxygen Reduction on Pt and Non-Pt Surfaces: Acid versus Alkaline Media
Nagappan Ramaswamy,Sanjeev Mukerjee
Advances in Physical Chemistry , 2012, DOI: 10.1155/2012/491604
Abstract: Complex electrochemical reactions such as Oxygen Reduction Reaction (ORR) involving multi-electron transfer is an electrocatalytic inner-sphere electron transfer process that exhibit strong dependence on the nature of the electrode surface. This criterion (along with required stability in acidic electrolytes) has largely limited ORR catalysts to the platinum-based surfaces. New evidence in alkaline media, discussed here, throws light on the involvement of surface-independent outer-sphere electron transfer component in the overall electrocatalytic process. This surface non-specificity gives rise to the possibility of using a wide-range of non-noble metal surfaces as electrode materials for ORR in alkaline media. However, this outer-sphere process predominantly leads only to peroxide intermediate as the final product. The importance of promoting the electrocatalytic inner-sphere electron transfer by facilitation of direct adsorption of molecular oxygen on the active site is emphasized by using pyrolyzed metal porphyrins as electrocatalysts. A comparison of ORR reaction mechanisms between acidic and alkaline conditions is elucidated here. The primary advantage of performing ORR in alkaline media is found to be the enhanced activation of the peroxide intermediate on the active site that enables the complete four-electron transfer. ORR reaction schemes involving both outer- and inner-sphere electron transfer mechanisms are proposed. 1. Introduction Oxygen reduction reaction (ORR) on noble and nonnoble metal surfaces remains as one of the well-investigated electrochemical processes. While under acidic conditions Pt-based systems remain the mainstay as catalyst materials for ORR, in alkaline electrolyte a wide range of nonnoble metals and their oxides are stable enough for practical applications [1, 2]. ORR pathway rather than ORR mechanism has typically been addressed in the literature due to the easy accessibility of the former from rotating ring-disk electrode (RRDE) studies, and the complexity in understanding the latter [3]. ORR pathway is found to be similar in both acid and alkaline media on Pt-based materials [3, 4]. Based on the initial propositions by Damjanovic et al. [4–6], rate determining step (rds) on Pt electrodes is widely agreed to be the first electron transfer step to the adsorbed molecular O2 with or without rapid proton transfer [4–6]. A major alternative viewpoint to rds in ORR was proposed by Yeager et al. [7], wherein it was proposed that ORR on Pt surfaces is likely to involve dissociative chemisorption of molecular O2 with the
Review: Bilirubin pKa studies; new models and theories indicate high pKa values in water, dimethylformamide and DMSO
Pasupati Mukerjee, J Ostrow
BMC Biochemistry , 2010, DOI: 10.1186/1471-2091-11-15
Abstract: These re-assessments identified major deficiencies that invalidate the results of all but our partition studies. New theoretical modeling of UCB titrations shows remarkable, unexpected effects of self-association, yielding falsely low pKa estimates, and provides some rationalization of the titration anomalies. The titration behavior reported for a soluble thioether conjugate of UCB at high aqueous concentrations is shown to be highly anomalous. Theoretical re-interpretations of data in DMSO and dimethylformamide show that those indirectly-derived aqueous pKa values are unacceptable, and indicate new, high average pKa values for UCB in non-aqueous media (>11 in DMSO and, probably, >10 in dimethylformamide).No reliable aqueous pKa values of UCB are available for comparison with our partition-derived results. A companion paper shows that only the high pKa values can explain the pH-dependence of UCB binding to phospholipids, cyclodextrins, and alkyl-glycoside and bile salt micelles.Unconjugated bilirubin (UCB) in aqueous solution exists as an equilibrium among three species, the diacid (H2B), the monoanions (HB-) and the dianion (B=) [1]. Each species differs as to ionization states, properties and functions [1]. The fully protonated, uncharged, UCB diacid diffuses freely across lipid membranes [2,3]. The monoanion, with one ionized carboxylic group, is the main substrate for active cellular export of UCB by ABC-transporters [3]. The dianion, with two ionized -COO- groups, is reported to be bound preferentially with high affinity to serum albumin [4,5], apolipoprotein-D [6], and ligandin and other GSH-transferases [7], as well as to bile salts [8].Since the relative proportion of the three species depends on the pH of the solution and the pKa values of UCB [1], the true pKa values of UCB are of great physiological and basic relevance. There are, however, tremendous variations among the reported pKa values for bilirubin in aqueous solutions, as determined by a wide varie
Accessory hepatic artery: incidence and distribution
Dutta, Sukhendu;Mukerjee, Bimalendu;
Jornal Vascular Brasileiro , 2010, DOI: 10.1590/S1677-54492010005000006
Abstract: background: anatomic variations of the hepatic arteries are common. preoperative identification of these variations is important to prevent inadvertent injury and potentially lethal complications during open and endovascular procedures. objective: to evaluate the incidence, extra-hepatic course, and presence of side branches of accessory hepatic arteries, defined as an additional arterial supply to the liver in the presence of normal hepatic artery. methods: eighty-four human male cadavers were dissected using a transperitoneal midline laparotomy. the supra-celiac aorta, celiac axis, and hepatic arteries were dissected, and their trajectories were identified to describe arterial branching patterns. results: normal hepatic arterial anatomy was identified in 95% of the cadavers and six (5%) had accessory hepatic arteries. in five cadavers the accessory hepatic artery followed its course through the fissure for ligamentum venosum, and in one it coursed adjacent to the hepatic artery through the margin of the lesser omentum. one cadaver had a single side branch, which provided arterial blood supply to the left adrenal gland in the absence of any left inferior phrenic artery. conclusion: accessory hepatic artery most often follows the course of the hepatic fissure for ligamentum venosum. albeit uncommonly found in 5% of cases, this finding should be identified during open and endovascular procedures to prevent inadvertent injury.
Accessory hepatic artery: incidence and distribution Artéria hepática acessória: incidência e distribui o
Sukhendu Dutta,Bimalendu Mukerjee
Jornal Vascular Brasileiro , 2010,
Abstract: Background: Anatomic variations of the hepatic arteries are common. Preoperative identification of these variations is important to prevent inadvertent injury and potentially lethal complications during open and endovascular procedures. Objective: To evaluate the incidence, extra-hepatic course, and presence of side branches of accessory hepatic arteries, defined as an additional arterial supply to the liver in the presence of normal hepatic artery. Methods: Eighty-four human male cadavers were dissected using a transperitoneal midline laparotomy. The supra-celiac aorta, celiac axis, and hepatic arteries were dissected, and their trajectories were identified to describe arterial branching patterns. Results: Normal hepatic arterial anatomy was identified in 95% of the cadavers and six (5%) had accessory hepatic arteries. In five cadavers the accessory hepatic artery followed its course through the fissure for ligamentum venosum, and in one it coursed adjacent to the hepatic artery through the margin of the lesser omentum. One cadaver had a single side branch, which provided arterial blood supply to the left adrenal gland in the absence of any left inferior phrenic artery. Conclusion: Accessory hepatic artery most often follows the course of the hepatic fissure for ligamentum venosum. Albeit uncommonly found in 5% of cases, this finding should be identified during open and endovascular procedures to prevent inadvertent injury. Contexto: As varia es anat micas das artérias hepáticas s o comuns. A identifica o pré-operatória dessas varia es é importante para prevenir les o inadvertida e complica es potencialmente letais durante procedimentos abertos e endovasculares. Objetivo: Avaliar a incidência, o trajeto extra-hepático e a presen a de ramos laterais das artérias hepáticas acessórias definidas como um suprimento arterial adicional para o fígado na presen a de artéria hepática normal. Métodos: Oitenta e quatro cadáveres humanos masculinos foram dissecados através de laparotomia mediana transperitoneal. A aorta supracelíaca, o eixo celíaco e as artérias hepáticas foram dissecados, e suas trajetórias foram identificadas para descrever os padr es dos ramos arteriais. Resultados: Anatomia arterial hepática normal foi identificada em 95% dos cadáveres, e seis (5%) tinha artérias hepáticas acessórias. Em cinco cadáveres, a artéria hepática acessória seguia seu trajeto através da fissura para o ligamento venoso, e em um caso a artéria corria adjacente à artéria hepática através da margem do pequeno omento. Um cadáver tinha um ramo unilateral que fornecia san
Finite size scaling in crossover among different random matrix ensembles in microscopic lattice models
Ranjan Modak,Subroto Mukerjee
Physics , 2013, DOI: 10.1088/1367-2630/16/9/093016
Abstract: Using numerical diagonalization we study the crossover among different random matrix ensembles [Poissonian, Gaussian Orthogonal Ensemble (GOE), Gaussian Unitary Ensemble (GUE) and Gaussian Symplectic Ensemble (GSE)] realized in two different microscopic models. The specific diagnostic tool used to study the crossovers is the level spacing distribution. The first model is a one dimensional lattice model of interacting hard core bosons (or equivalently spin 1/2 objects) and the other a higher dimensional model of non-interacting particles with disorder and spin orbit coupling. We find that the perturbation causing the crossover among the different ensembles scales to zero with system size as a power law with an exponent that depends on the ensembles between which the crossover takes place. This exponent is independent of microscopic details of the perturbation. We also find that the crossover from the Poissonian ensemble to the other three is dominated by the Poissonian to GOE crossover which introduces level repulsion while the crossover from GOE to GUE or GOE to GSE associated with symmetry breaking introduces a subdominant contribution. We also conjecture that the exponent is dependent on whether the system contains interactions among the elementary degrees of freedom or not and is independent of the dimensionality of the system.
Many body localization in the presence of a single particle mobility edge
Ranjan Modak,Subroto Mukerjee
Physics , 2015, DOI: 10.1103/PhysRevLett.115.230401
Abstract: In one dimension, noninteracting particles can undergo a localization-delocalization transition in a quasiperiodic potential. Recent studies have suggested that this transition transforms into a many-body localization (MBL) transition upon the introduction of interactions. It has also been shown that mobility edges can appear in the single particle spectrum for certain types of quasiperiodic potentials. Here, we investigate the effect of interactions in two models with such mobility edges. Employing the technique of exact diagonalization for finite-sized systems, we calculate the level spacing distribution, time evolution of entanglement entropy, optical conductivity, and return probability to detect MBL. We find that MBL does indeed occur in one of the two models we study, but the entanglement appears to grow faster than logarithmically with time unlike in other MBL systems.
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