Tunnelling Characteristics of Stone-Wales Defects in Monolayers of Sn and Group-V Elements

Topological defects in ultrathin layers are often formed during synthesis and processing, thereby, strongly influencing their electronic properties . In this paper, we investigate the role of Stone-Wales (SW) defects in modifying the electronic properties of the monolayers of Sn and group-V elements. The calculated results find the electronic properties of stanene (monolayer of Sn atoms) to be strongly dependent on the concentration of SW-defects e.g., defective stanene has nearly zero band gap (~ 0.03 eV) for the defect concentration of 2.2 x 10^13 cm^-2 which opens up to 0.2 eV for the defect concentration of 3.7 x 10^13 cm^-2. In contrast, SW-defects appear to induce conduction states in the semiconducting monolayers of group-V elements. These conduction states act as channels for electron tunnelling, and the calculated tunnelling characteristics show the highest differential conductance for the negative bias with the asymmetric current-voltage characteristics. On the other hand, the highest differential conductance was found for the positive bias in stanene. Simulated STM topographical images of stanene and group-V monolayers show distinctly different features in terms of their cross-sectional views and distance-height profiles which can serve as fingerprints to identify the topological defects in the monolayers of group-IV and group-V elements in experiments.Comment: 18 pages, 5 figures, 1 tabl

Monitoring Changes in Vegetation Cover of Bhitarkanika Marine National Park Region, Odisha, India Using Vegetation Indices of Multidate Satellite Data

1916-1924The coast of Odisha extends from Balasore in the north to Ganjam in the south spreading 480 km. It exhibits a depositional terrain formed by the action of fluvio-marine, lacustrine, estuarine and aeolian agents. The river system coupled with marine action help in generating diversified physiographic and dynamic coastal features. Over the period, the coastal tract also witnesses the vagary of nature. Vast alluvial plain, meandering pattern of rivers, low lying swamps and swamp forests, sand dunes, beach ridges, beaches and swales are typical landforms associated with the coastal tract. The Bhitarkanika Marine National Park region, the study area is situated on the northern part of the coast which mostly exhibit swampy habitat due to large fine clastic deposits by riverine action. Mangroves on the swampy region occupy around 18,348 ha and regarded as the second largest mangrove formation in the subcontinent. Besides, the coastal tract also exhibits a congenial place for mass nesting of sea turtles coming from Pacific Ocean. The study area is now under stress due to various natural as well as anthropogenic pressure. The degradation of mangroves is mainly due to human encroachment and reclamation of land for aquaculture practices. It is observed that the occurrence of vegetation cover decreases continuously from 1973 to 2017. Dense vegetation cover is recorded as 35.23 % ( 1973) which decreased to 22.43 % ( 2017). On the southern end of the study area lies an all-weather port named Paradeep and on the northern side one emerging new port called Dhamra port. Their activities and impact as well as blooming aquaculture practices have bearing on the ecosystem of the mangroves. The assessment of vegetation vigor of the region portrays the condition of the environment shaped after years of degradation activities due to natural as well as anthropogenic activities induced from 595 villages having 50,6930 population. The objective of the study is to analyze the changes of vegetation vigor using NDVI from multi date satellite data and record the changes for better monitoring of the area. It may be inferred that the existing conservation measures and protection plans are inadequate to hold the coastal natural resources intact. The community participation and public awareness are not sufficient to abate the brittle coastal environment. Public participation, education programme, awareness initiatives are the foundation of success of any sustainable development in the sensitive coastal region

COPid: composition based protein identification

In the past, a large number of methods have been developed for predicting various characteristics of a protein from its composition. In order to exploit the full potential of protein composition, we developed the web-server COPid to assist the researchers in annotating the function of a protein from its composition using whole or part of the protein. COPid has three modules called search, composition and analysis. The search module allows searching of protein sequences in six different databases. Search results list database proteins in ascending order of Euclidian distance or descending order of compositional similarity with the query sequence. The composition module allows calculation of the composition of a sequence and average composition of a group of sequences. The composition module also allows computing composition of various types of amino acids (e.g. charge, polar, hydrophobic residues). The analysis module provides the following options; i) comparing composition of two classes of proteins, ii) creating a phylogenetic tree based on the composition and iii) generating input patterns for machine learning techniques. We have evaluated the performance of composition-based (or alignment-free) similarity search in the subcellular localization of proteins. It was found that the alignment free method performs reasonably well in predicting certain classes of proteins. The COPid web-server is available at http://www.imtech.res.in/raghava/copid/

Neuromorphic In-Memory Computing Framework using Memtransistor Cross-bar based Support Vector Machines

This paper presents a novel framework for designing support vector machines (SVMs), which does not impose restriction on the SVM kernel to be positive-definite and allows the user to define memory constraint in terms of fixed template vectors. This makes the framework scalable and enables its implementation for low-power, high-density and memory constrained embedded application. An efficient hardware implementation of the same is also discussed, which utilizes novel low power memtransistor based cross-bar architecture, and is robust to device mismatch and randomness. We used memtransistor measurement data, and showed that the designed SVMs can achieve classification accuracy comparable to traditional SVMs on both synthetic and real-world benchmark datasets. This framework would be beneficial for design of SVM based wake-up systems for internet of things (IoTs) and edge devices where memtransistors can be used to optimize system's energy-efficiency and perform in-memory matrix-vector multiplication (MVM).Comment: 4 pages, 5 figures, MWSCAS 201

In-situ integrated processing and characterization of thin films of high temperature superconductors, dielectrics and semiconductors by MOCVD

In this strategy of depositing the basic building blocks of superconductors, semiconductors, and dielectric having common elements, researchers deposited superconducting films of Y-Ba-Cu-O, semiconductor films of Cu2O, and dielectric films of BaF2 and Y2O3 by metal oxide chemical vapor deposition (MOCVD). By switching source materials entering the chamber, and by using direct writting capability, complex device structures like three-terminal hybrid semiconductors/superconductors transistors can be fabricated. The Y-Ba-Cu-O superconducting thin films on BaF2/YSZ substrates show a T(sub c) of 80 K and are textured with most of the grains having their c-axis or a-axis perpendicular to the substrate. Electrical characteristics as well as structural characteristics of superconductors and related materials obtained by x-ray defraction, electron microscopy, and energy dispersive x-ray analysis are discussed

In-situ integrated processing and characterization of thin films of high temperature superconductors, dielectrics and semiconductors by MOCVD

In this strategy of depositing the basic building blocks of superconductors, semiconductors, and dielectrics having common elements, researchers deposited superconducting films of Y-Ba-Cu-O, semiconductor films of Cu2O, and dielectric films of BaF2 and Y2O3 by metal oxide chemical vapor deposition (MOCVD). By switching source materials entering the chamber, and by using direct writing capability, complex device structures like three terminal hybrid semiconductor/superconductor transistors can be fabricated. The Y-Ba-Cu-O superconducting thin films on BaF2/YSZ substrates show a T(sub c) of 80 K and are textured with most of the grains having their c-axis or a-axis perpendicular to the substrate. Electrical characteristics as well as structural characteristics of superconductors and related materials obtained by x-ray deffraction, electron microscopy, and energy dispersive x-ray analysis are discussed

Giant pressure sensitivity in piezo/ferro-electric ceramics

We report the fabrication of single-phase polycrystalline Pb0.85Bi0.10(Zr0.52Ti0.48)O-3 (PBiZT) ceramic which shows large polarization, i.e., similar to 40 mu C cm(-2) and piezoelectric coefficients similar to 130 pC N-1 and giant linear change in capacitive reactance and dielectric properties with increasing and decreasing pressure in the range of 1 kHz to 5 MHz. Nearly 70% change in dielectric constant and 56% change in capacitive reactance were obtained in the pressure range of 20-200 MPa, which makes it suitable for applications as a capacitive pressure sensor/gauge. The sensitivity of the device is calculated as 0.66 MPa-1 and 18.2 MPa-1 at 1 MHz and 5 MHz, respectively, which is the highest ever reported value so far for any bulk polycrystalline ceramic. The compressive stress of the device was tested according to the standard test method as a function of linear and volumetric strain, which yields the Young's modulus, Bulk modulus, and Poisson's ratio of the device. These values were further utilized to calculate actual stress in the sample and energy density using ANSYS software, which indicates at least four orders smaller pressure in the sample compared to the applied pressure