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Combinatorial proofs of the Newton�Girard and Chapman�Costas-Santos identities
No full textIn this paper we give combinatorial proofs of some well known identities and obtain some generalizations. We give a visual proof of a result of Chapman and Costas-Santos regarding the determinant of sum of matrices. Also we find a new identity expressing the permanent of sum of matrices. Besides, we give a graph theoretic proof of the Newton�Girard identity in a generalized form. © 2019 Elsevier B.V
Crystal structure of the legume lectin-like domain of an ERGIC-53-like protein from Entamoeba histolytica
No full textERGIC-53-like proteins are type I membrane proteins that belong to the class of intracellular cargo receptors and are known to be indispensable for the intracellular transport of glycoproteins. They are implicated in transporting glycoproteins between the endoplasmic reticulum and the Golgi body. The crystal structure of the legume lectin-like domain of an ERGIC-53-like protein from Entamoeba histolytica has been determined at 2.4à resolution. Although the overall structure of the domain resembles those of its mammalian and yeast orthologs (ERGIC-53 and Emp46, respectively), there are significant changes in the carbohydrate-binding site. A sequence-based search revealed the presence of several homologs of ERGIC-53 in different species of Entamoeba. This is the first report of the structural characterization of a member of this class of proteins from a protozoan and serves to further knowledge and understanding regarding the species-specific differences. © 2019 International Union of Crystallography
Microstructure and corrosion properties of NiCo-graphene oxide composite coatings
No full textMicrostructure-electrochemical behaviour correlation was investigated for electrodeposited Ni rich, NiCo-Graphene oxide composite coatings as a function of the amount of graphene oxide (GO) which was varied by changing the concentration of GO dispersed in the electrolytic bath. Corrosion behaviour of the coatings examined through potentiodynamic polarisation and electrochemical impedance spectroscopy methods revealed that the corrosion rate of the coatings was sensitive to the amount of GO present in the coating. With increasing GO content, the corrosion rate first decreased to a minimum value followed by a sudden increase to values higher than the corrosion rate value exhibited by the pristine coating. Microstructural examination of the coatings conducted using the electron backscatter diffraction method revealed that the �optimum� content of GO which yielded the minimum corrosion rate produced a unique microstructure with highest fraction of low angle grains boundaries and lowest fraction of incoherent twins boundaries when compared to all other composite coatings. Enhancement in the corrosion rate value beyond the optimum GO content was attributed to the galvanic coupling between GO and the metal matrix. © 2019 Elsevier B.V
2D Linear Detector Based on Generalized Belief Propagation Algorithm
No full textVarious ideas have been borrowed from 1D inter symbol interference (ISI) detectors towards approximation of near maximum likelihood (ML) detection over 2D ISI channels. Generalized belief propagation (GBP) algorithm is a graph based algorithm different from these algorithms and is observed to give the best bit error rate (BER) performance by minimizing KL-distance metric. GBP algorithm passes messages between regions instead of messages between nodes in an iterative fashion. However, GBP algorithm has a very high computational complexity and is not suitable for practical deployment. In this paper, we propose a GBP based signal detection algorithm using a quadratic approximation of the KL-distance metric. This allows us to minimize the cost function by solving a set of linear equations i.e., obtain a one shot solution instead of the iterative message passing in the GBP algorithm. We also provide an intuition into the nature of the hard decisions given by the algorithm. The idea opens up various approximations of the GBP algorithm using different convex approximations of the cost function with the desired nature of obtaining the solution. We show the efficacy of the proposed algorithm by detecting 5�5 pages of binary data over a chosen channel with 3�3 ISI span. The quadratic approximation is observed to give 1.5 dB inferior performance in signal-to-noise ratio (SNR) as compared to the GBP algorithm. © 2018 IEEE
Improvements of machinability of aerospace-grade Inconel alloys with ultrasonically assisted hybrid machining
No full textAerospace-grade Ni-based alloys such as Inconel 718 and 625 are widely used in the airspace industry thanks to their excellent mechanical properties at high temperatures. However, these materials are classified as difficult-to-machine' because of their high shear strength, low thermal conductivity, tendency to work-harden and presence of carbide particles in their microstructure, which lead to rapid tool wear. Machining-induced residual stresses in a machined part is an important parameter which is assessed since it can be used to evaluate overall structural resilience of the component and its propensity to fatigue failure in-service. Ultrasonically assisted turning (UAT) is a hybrid machining technique, in which tool-workpiece contact conditions are altered by imposing ultrasonic vibration (typical frequency similar to 20kHz) on a tool's movement in a cutting process. Several studies demonstrated successfully the resulting improvements in cutting forces and surface topography. However, a thorough study of UAT-induced residual stresses is missing. In this study, experimental results are presented for machining Inconel 718 and 625 using both conventional turning (CT) and UAT with different machining parameters to investigate the effect on cutting forces, surface roughness and residual stresses in the machined parts. The study indicates that UAT leads to significant cutting force reductions and improved surface roughness in comparison to CT for cutting speeds below a critical level. The residual stresses in machined workpiece show that UAT generates more compressive stresses when compared to those in CT. Thus, UAT demonstrates an overall improvement in machinability of Inconel alloys
Biodegradable polyol-based polymers for biomedical applications
No full textPolyols are multifunctional alcohols, with branched structures, where each arm terminates with an -OH group. These free -OH groups have been utilised to make a variety of polymer structures ranging from cross-linked to linear to starshaped. This review presents a comprehensive account of polyol-based polymers in biomedical applications. The advantages afforded by polyolbased biodegradable polymers are detailed in this review, alongside a general historical perspective on the development of biodegradable polymers. The major advantage of these polyols is that they are endogenous to the human body. Synthesis strategies and fabrication techniques to mould these materials into three-dimensional (3D) scaffolds are discussed. Modifications to the conventionally used polyol-based polyesters have been achieved by chemically incorporating drugs/ bioactives or by preparing nanocomposites. This review discusses the physicochemical properties and biological responses of these polymers relevant in biomedical applications and further outlines the need for improving their processability and performance
Continuous transition from weakly localized regime to strong localization regime in Nd0.7La0.3NiO3 films
No full textWe report an investigation of metal-insulator transition (MIT) using conductivity and magnetoconductance (MC) measurements down to 0.3 K in Nd0.7La0.3NiO3 films grown on crystalline substrates of LaAlO3 (LAO), SrTiO3 (STO), and NdGaO3 (NGO) by pulsed laser deposition. The film grown on LAO experiences a compressive strain and shows metallic behavior with the onset of a weak resistivity upturn below 2 K which is linked to the onset of weak localization contribution. Films grown on STO and NGO show a cross-over from a positive temperature coefficient (PTC) resistance regime to negative temperature coefficient (NTC) resistance regime at definite temperatures. We establish that a cross-over from PTC to NTC on cooling does not necessarily constitute a MIT because the extrapolated conductivity at zero temperature (lim(T -> 0) sigma - sigma(0)) though small (< 10 S cm(-1)) is finite, signaling the existence of a bad metallic state and absence of an activated transport. The value of sigma(0) for films grown on NGO is reduced by a factor of 40 compared to that for films grown on STO. We show that a combination of certain physical factors makes substituted nickelate (that are known to exhibit first-order Mott type transition), undergo a continuous transition as seen in systems undergoing disorder/composition driven Anderson transition. The MC measurement also supports the above observation and shows that at low temperatures, there exists a positive MC that arises from the quantum interference which co-exists with a spin-related negative MC that becomes progressively stronger as the electrons approach a strongly localized state in the film grown on NGO
Why the angular distribution of the top decay lepton is unchanged by anomalous tbW couplings
No full textWe give a simple physical argument to understand the observation that the angular distribution of the top decay lepton depends only on the polarisation of the top and is independent of any anomalous tbW coupling to linear order. (C) 2019 The Author(s). Published by Elsevier B.V
Uplift capacity of horizontal anchor plate in geocell reinforced sand
No full textThe paper investigates the uplift performance of horizontal anchor plate in geocell reinforced sand through a series of model tests. It is noted that the unreinforced anchor plate undergoes a clear failure at a displacement of about 3% of its width, whereas with the provision of geocell and a layer of geotextile right below the geocell mattress significantly increases the uplift capacity by about 4.5 times higher than that of unreinforced sand and could sustain anchor displacement of more than 60%. Results indicates that the geocell mattress by virtue of its rigidity distributes the uplift load in the lateral directions to a larger area, thereby reducing the stress in the overlying soil mass and hence increases the performance of anchor plate system. The provision of the additional geotextile layer right below the geocell mattress is found to be very effective in increasing the stiffness as well as load carrying capacity of anchor plate system. The optimum size (i.e., width and length) of geocell mattress giving adequate load carrying capacity of anchor plate is found to be 5.4 times of anchor width (5.4B). The comparison of model tests results with 3D numerical analysis shows good agreement, indicating that the proposed model is able to capture the uplift load-displacement behaviour of geocell reinforced anchor plate system
Influence of Molecular Beam Epitaxy (MBE) Parameters on Catalyst-Free Growth of InAs Nanowires on Silicon (111) Substrate
No full textThe effect of molecular beam epitaxy parameters on catalyst-free growth of InAs nanowires using oxide templates on Si (111) substrate has been studied. Two different approaches, i.e., thermal and plasma-enhanced chemical vapor deposition, were used to prepare the oxide templates. The length, diameter, density, and quality of the nanowires depended strongly on the substrate temperature, As/In beam equivalent pressure ratio, and growth rate, whereas the type, thickness, and uniformity of the oxide were found to affect only the density of the nanowires. Nanowires could be grown effectively in only a very narrow range of these growth parameters. The surface morphological, structural, and optical properties of the nanowires were assessed using various techniques including field-emission scanning electron microscopy, high-resolution x-ray diffraction analysis, transmission electron microscopy, and Raman spectroscopy