The Bergman-Fridman invariant on some classes of pseudoconvex domains

We study the boundary behaviour of a variant of the Fridman's invariant function (defined in terms of the Bergman metric) on Levi corank one domains, strongly pseudoconvex domains, smoothly bounded convex domains in $\mathbb{C}^n$ and polyhedral domains in $\mathbb{C}^2$

Interfaces in Discontinuously Reinforced Metal Matrix Composites

The paper overviews the fundamental and engineering aspects of the interfaces in discontinuously reinforced metal-matrix composites. The major findings of studies undertaken at the Defence Metallurgical Research Laboratory, India, and Northwestern University, USA, are highlighted in addition to a detailed survey of the literature. The various issues such as the nature of interfacial bond, chemical reaction at the interfaces, effect of alloying and processing on structure of the interfaces and the properties of the composites are examined in this paper. Strategies are suggested to exploit the full potential of reinforcing the metallic matrix

Quantum many body physics in single and bilayer graphene

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.Cataloged from PDF version of thesis.Includes bibliographical references.Two dimensional electron systems (2DES) provide a uniquely promising avenue for investigation of many body physics. Graphene constitutes a new and unusual 2DES, which may give rise to unexpected collective phenomena. However, the vanishing density of states in charge neutral single layer graphene suppresses many body effects, and one has to alter the system to observe strongly ordered states. We consider three ways of accessing quantum many body physics using graphene. First, we consider doping single layer graphene to a Van Hove singularity in the density of states. We show that there are strong instabilities to several strongly ordered states, with the leading instability being to a d-wave superconducting state. The superconducting state realizes chiral superconductivity, an exotic form of superconductivity wherein the phase of the order parameter winds by 4[pi] as we go around the Fermi surface. We also discuss the nature of the spin density wave state which is the principal competitor to superconductivity in doped graphene. Next, we study bilayer graphene (BLG), which has a non-vanishing density of states even at charge neutrality. We show that Coulomb interactions give rise to a zero bias anomaly in the tunneling density of states for BLG, which manifests itself at high energy scales. We also show that the quadratic band crossing in BLG is unstable to arbitrarily weak interactions, and estimate the energy scale for formation of strongly ordered states. We show that gapped states in BLG have topological properties, and we classify the various possible gapped and gapless states in terms of symmetries. We study the competition between various ordered states, and discuss how the nature of the ground state may be deduced experimentally. We also discuss recent experimental observations of strongly ordered states in bilayer graphene. Finally, we study bilayer graphene in a transverse magnetic field, focusing on the properties of the quantum Hall ferromagnet (QHF) state. We resolve an apparent discrepancy between the experimentally observed energetics and theory. We close with a discussion of the exotic topological defects that form above the QHF state.by Rahul Nandkishore.Ph.D

Implementation of Multidomain Unified Forward Operators (UFO) Within the Joint Effort for Data Assimilation Integration (JEDI): Ocean Applications

The Joint Effort for Data assimilation Integration (JEDI) is a collaborative development led by the Joint Center for Satellite Data Assimilation (JCSDA) in conjunction with NASA, NOAA and the Department of Defense (NAVY and Air Force). The (Sea-Ice Ocean and Coupled Assimilation) SOCA as one of the JCSDA projects, focuses on the application of JEDI to marine data assimilation. One of the goals of SOCA is to make use of surface-sensitive radiances to constrain sea-ice and upper ocean fields (e.g., salinity, temperature, sea-ice fraction, sea-ice temperature, etc.). The first elements toward an ocean/atmosphere coupled data assimilation capability within JEDI, with a focus on supporting and developing the assimilation of radiance observations sensitive to the ocean and atmosphere has been implemented. The direct radiance assimilation of surface sensitive microwave radiances focusing on Global Precipitation Measurement (GPM) Imager (GMI) for the SST Constraint and Soil Moisture Active Passive (SMAP) for the Sea Surface Salinity (SSS) has been the main focus. Also, in UFO the capability to calculate the cool skin layer depth and skin temperature has been implemented similar to the GEOS-5. It has been tested with GMI sea surface temperature retrievals. This is important because Satellite and in-situ observations of the Sea-Surface Temperature (SST) show high variability, including a diurnal cycle and very thin, cool skin layer in contact with the atmosphere, and Incorporating a realistic skin SST is essential for atmosphere-ocean coupled data assimilation

Paediatric lateral humeral condyle fractures managed by k-wire fixation, should the wires be buried or left exposed: a dilemma

Background: Fractures of the lateral condyle of the humerus in children are common injuries. If displaced or unstable they may require surgical reduction and fixation with Kirschner wires (K-wires). These may be passed through the skin and left exposed or buried subcutaneously.Methods: A prospective study was carried out in department of orthopaedics at my college from January 2019 to March 2020.  A total number of 37 subjects were included in the study.Results: Patients were followed for a period of 3 months and results were drawn on basis of union, infection, carrying angle at the elbow, and range of motion (ROM) which was assessed by clinico-radiological means.Conclusions: Buried wire group has shown better union rate than exposed group, wires could be removed under local anaesthesia thereby avoiding any major procedure and also the risk of infection is low making this a better option than the exposed cohort

Gβγ acts at an inter-subunit cleft to activate GIRK1 channels

Heterotrimeric guanine nucleotide-binding proteins (G-proteins) consist of an alpha subunit (Gα) and the dimeric beta-gamma subunit (Gβγ). The first example of direct cell signaling by Gβγ was the discovery of its role in activating G-protein regulated inwardly rectifying K+ (GIRK) channels which underlie the acetylcholine-induced K+ current responsible for vagal inhibition of heart rate. Published crystal structures have provided important insights into the structures of the G-protein subunits and GIRK channels separately, but co-crystals of the channel and Gβγ together remain elusive and no specific reciprocal residue interactions between the two proteins are currently known. Given the absence of direct structural evidence, we attempted to identify these functionally important channel-Gβγ interactions using a computational approach. We developed a multistage computational docking algorithm that combines several known methods in protein-protein docking. Application of the docking protocol to previously published structures of Gβγ and GIRK1 homomeric channels produced a clear signal of a favored binding mode. Analysis of this binding mode suggested a mechanism by which Gβγ promotes the open state of the channel. The channel-Gβγ interactions predicted by the model in silico could be disrupted in vitro by mutation of one protein and rescued by additional mutation of reciprocal residues in the other protein. These interactions were found to extend to agonist induced activation of the channels as well as to activation of the native heteromeric channels. Currently, the structural mechanism by which Gβγ regulates the functional conformations of GIRK channels or of any of its membrane-associated effector proteins is not known. This work shows the first evidence for specific reciprocal interactions between Gβγ and a GIRK channel and places these interactions in the context of a general model of intracellular regulation of GIRK gating

Disorder-tuned selection of order in bilayer graphene

The nature of the interaction-driven spontaneously broken-symmetry state in charge-neutral bilayer graphene (BLG) has attracted a lot of interest. Theoretical studies predict various ordered states as the candidates for the ground state of BLG in the absence of external fields. Several experiments have been performed by different groups to identify the nature of the collective ground state in BLG. However, so far, there is no consensus: some experiments show evidence that suggests the establishment of a nematic gapless state, while others present results that are more consistent with the establishment of a fully gapped state. Moreover, even among the experiments that appear to see a bulk gap, some of the samples are found to be conducting (suggesting the existence of gapless edge states), while others are insulating. Here we explore the hypothesis that disorder might explain the discrepancy between experiments. We find that the pair-breaking effect due to nonmagnetic short-range disorder varies among the candidate ground states, giving rise to different amounts of suppression of their mean-field transition temperatures. Our results indicate that BLG can undergo a transition between different ordered states as a function of the disorder strength, providing a possible scenario to resolve the discrepancy between experimental observations.Princeton University (Princeton Center for Theoretical Science Fellowship

Functional results of AO 13C fractures managed with bicolumnar plating in a tertiary care centre of North India

Background: Distal humerus fractures are associated with many problems like fracture comminution and complex fracture anatomy. Achieving a good functional range of motion at the elbow with stability are the primary objectives in managing a comminuted distal humerus fracture.Methods: 25 consecutive patients were operated with bicolumnar plating for fracture distal humerus AO type 13C. The patients were kept in follow up for at least six months. Mayo elbow performance (MEP) score and flexion extension arc was calculated to study the outcome.Results: All patients achieved fracture union with mean MEP score of 73.2 and mean flexion extension arc of 93º. This was within the functional range of elbow. Stiffness was observed to be most common complication.Conclusions: Our study concluded that internal fixation with bicolumnar plating offers good functional results in comminuted intra-articular fractures even in osteoporotic bone with negligible complications