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A Discrete Polymatroidal Framework for Differential Error-Correcting Index Codes
No full textIn the conventional index coding problem, the messages transmitted by the source to satisfy the demands of the receivers are error-free. However, in practice, the messages may be error prone which led to the introduction of error-correcting index codes. An error-correcting index code is an encoding scheme which enables every receiver to decode its demanded message even in the presence of certain number of transmission errors. Formally, an index code capable of correcting at most delta errors at all its receivers is defined as a delta-error-correcting index code. In this paper, we explore the connections between vector linear error-correcting index codes and discrete polymatroids. This is motivated from the connections between linear network error-correcting codes and matroids. It is shown that a vector linear error-correcting index code exists if and only if there exists a representable discrete polymatroid satisfying certain conditions. Differential error-correcting index codes which allow different receivers to have different error-correcting capabilities are also studied. Note that the delta-error-correcting code is a special case of a differential error-correcting index code. Error correction at a subset of receivers is another special case which is discussed
Basal ganglia contributions during the learning of a visuomotor rotation: Effect of dopamine, deep brain stimulation and reinforcement
No full textIt is commonly thought that visuomotor adaptation is mediated by the cerebellum while reinforcement learning is mediated by the basal ganglia. In contrast to this strict dichotomy, we demonstrate a role for the basal ganglia in visuomotor adaptation (error-based motor learning) in patients with Parkinson's disease (PD) by comparing the degree of motor learning in the presence and absence of dopamine medication. We further show similar modulation of learning rates in the presence and absence of subthalamic deep brain stimulation. We also report that reinforcement is an essential component of visuomotor adaptation by demonstrating the lack of motor learning in patients with PD during the ON-dopamine state relative to the OFF-dopamine state in the absence of a reinforcement signal. Taken together, these results raise the possibility that the basal ganglia modulate the gain of visuomotor adaptation based on the reinforcement received at the end of the trial
The Railroad Switch Effect of Seasonally Reversing Currents on the Bay of Bengal High-Salinity Core
No full textThe Southwest Monsoon Current (SMC) flows eastward from the Arabian Sea into the Bay of Bengal (BoB) during summer, advecting a core of high-salinity water. This high-salinity core has been linked with Arabian Sea High-Salinity Water that is presumed to enter the BoB directly from the Arabian Sea via the SMC. Here we show that the high-salinity core originates primarily from the western equatorial Indian Ocean, reaching the BoB via the Somali Current, the Equatorial Undercurrent, and the SMC. Years with anomalously saline high-salinity cores are linked with the East Africa Coastal Current and the Somali Current winter convergence and an anomalously strong Equatorial Undercurrent. Seasonal reversals that occur at the Somali Current and SMC junctions act as railroad switches diverting water masses to different basins in the northern Indian Ocean. Interannual fluctuations of the Equatorial Undercurrent are linked to wind stress and El Nino
An embedding technique to determine tau tau backgrounds in proton-proton collision data
No full textAn embedding technique is presented to estimate standard model tau tau backgrounds from data with minimal simulation input. In the data, the muons are removed from reconstructed mu mu events and replaced with simulated tau leptons with the same kinematic properties. In this way, a set of hybrid events is obtained that does not rely on simulation except for the decay of the tau leptons. The challenges in describing the underlying event or the production of associated jets in the simulation are avoided. The technique described in this paper was developed for CMS. Its validation and the inherent uncertainties are also discussed. The demonstration of the performance of the technique is based on a sample of proton-proton collisions collected by CMS in 2017 at root s = 13 TeV corresponding to an integrated luminosity of 41.5 fb(-1)
Hyperpolarising Pyruvate through Signal Amplification by Reversible Exchange (SABRE)
No full textHyperpolarisation methods that premagnetise agents such as pyruvate are currently receiving significant attention because they produce sensitivity gains that allow disease tracking and interrogation of cellular metabolism by magnetic resonance. Here, we communicate how signal amplification by reversible exchange (SABRE) can provide strong C-13 pyruvate signal enhancements in seconds through the formation of the novel polarisation transfer catalyst Ir(H)(2)(eta(2)-pyruvate)(DMSO)(IMes)]. By harnessing SABRE, strong signals for 1-C-13]- and 2-C-13]pyruvate in addition to a long-lived singlet state in the 1,2-C-13(2)] form are readily created; the latter can be observed five minutes after the initial hyperpolarisation step. We also demonstrate how this development may help with future studies of chemical reactivity
Role of Third Material (Interlayer) on Mechanical Properties of the AA2024-Copper Joints Carried out by Friction Stir Welding (FSW)
No full textThe work focused on improving the mechanical properties of AA2024-Cu joints by introducing a third material in the form of interlayer. The interlayer chosen for this purpose was Zn based on the resultant intermetallic phases that could have formed with matrix. Experiment was carried between AA2024 and copper plates with Zn strip. It included the optimization of tool-offset positions. The welds were characterized by scanning electron microscope (SEM) equipped with electron probe micro-analyser (EPMA) and X-ray diffraction (XRD) techniques. The results showed that the Zn strip diffused well into the AA2024 matrix at the optimum tool-offset position and it had formed more than two intermetallic phases in the processed region, which had improved the strength and ductility of the welds significantly. It concluded that it was possible to enhance the properties by altering the composition and kind of intermetallics by using an appropriate filler metal in the form of interlayer
Smoothed finite element approach for kinematic limit analysis of cohesive frictional materials
No full textBy employing different smoothed finite element (S-FE) methods, the kinematic limit analysis approach has been presented by using three noded triangular elements to solve plane strain and plane stress stability problems on basis of the Mohr-Coulomb yield criterion. By using the concept of duality in conic programming, the expressions for the power dissipation function and the associated constraints have been written entirely in terms of kinematic variables. The optimization formulation is framed as a second order cone programming problem. Based on the absolute maximum magnitude of the shear strain rate, an algorithm to update the mesh has been provided. Amongst the different approaches, the node-based S-FE formulation has been found to be very accurate as well as efficient to solve large scale stability problems. The selective edge-based and the edge-based with a bubble node approaches also generate quite accurate solutions though require a little more computational time
Enhancement of microwave absorption bandwidth of polymer blend using ferromagnetic gadolinium silicide nanoparticles
No full textFerromagnetic gadolinium silicide (Gd5Si4) nanoparticles significantly enhance the microwave absorption bandwidth of a polymer blend (PVB-PEDOT:PSS). These materials are critically needed for various military and civilian applications such as X-band (8.2-12.4 GHz) and Ku-band (12.4-18 GHz) absorption. A single 1.2 mm thick layer of PVB-PEDOT: PSS-Gd5Si4 (PPGS) nanocomposite film shows the most promising bandwidth (8.2-18 GHz) with a minimum reflection loss of -14 dB. Mechanistically, dielectric loss (tan delta(e) approximate to 2.4) and magnetic loss (tan delta(m) approximate to 1.1) contributes more efficiently, and standard microwave simulation confirms the stored energy is predominant in PPGS nanocomposite which enhances the bandwidth
Cloud fraction retrieval and its variability during daytime from ground-based sky imagery over a tropical station in India
No full textTotal Sky Imager (TSI) is operated at a high altitude station in the Western Ghats of the Indian sub-continent from June 2012 to June 2013. The TSI image content is classified as clear, thin and thick clouds using red blue ratio (RBR) threshold technique and then cloud fraction (CF) is retrieved. An algorithm is proposed to improve the accuracy of CF retrieval, by adapting the methodologies used in earlier studies and new developments are suggested in sections of the validation of clear sky image and the aerosol correction factor. Time series of thin, thick and total CF are constructed for each day at 5 min interval. These measurements at high temporal resolution are first of their kind over a tropical station in India. Both thick and thin CFs showed high temporal variability. The transition from one season to another season also showed distinct CF variability. Monthly mean CF showed a mono model distribution in the winter months (December and January) and a bimodal distribution in the pre-monsoon months (March, April, May) including February. During the monsoon season (JJAS) about 90% CF is observed throughout the day. The post-monsoon months (October, November) show a bimodal distribution with one peak in the morning hours and another peak in the afternoon hours. Unlike thin CF, total and thick CFs showed almost similar variability. The comparison of CF retrieved from MODIS (Terra and Aqua) and TSI showed a good correlation for overcast sky conditions, while partial cloudy skies showed less correlation due to the effect of satellite viewing angles. Such continuous measurements of CF at high temporal resolution are essential for cloud radiative forcing studies
Chemoselective Reduction of Imines Catalyzed by Ruthenium(II) Half-Sandwich Complexes: A Mechanistic Study
No full textRuthenium half-sandwich complexes ligated to chiral 2-oxazolidinethiones or 2-thiozolidinethiones in the reduction of N-benzylideneaniline using silyl hydrides as reductants has been examined. The chemoselective reduction of imines takes place under mild conditions to afford the corresponding amines in nearly quantitative yield. Mechanistic studies indicate that dissociation of the ancillary ligands generate the active catalyst in all the complexes studied, which is the same species generated by Ru(p-cymene)(Cl)(2)](2) under the reaction conditions. This results in the formation of a single catalytic species irrespective of the starting half-sandwich complex. Detailed mechanistic studies involving trapping of intermediates, in situ studies using mass spectrometry and NMR spectroscopy were carried out using the active catalyst generated by Ru(p-cymene)(Cl)(2)](2). The mechanism of the reaction is dependent on the number of the hydrogen atoms in the reducing silane. The reaction proceeds via Gade-Hoffman pathway or Zheng-Chan pathway when a dihydro or trihydrosilane is the reductant. However, the use of a monohydrosilane, leads to longer reaction times presumably due to a change in the reaction pathway