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MoS2 Doping Using Potassium Iodide for Reliable Contacts and Efficient FET Operation
No full textIn this paper, we have demonstrated few-layer MoS2 doping using potassium iodide (KI) solution to realize stable/reliable ohmic contacts and achieve efficient electron transport. We have shown that KI doping allows MoS2 doping with a dopant density up to 1 x 10(12) cm(-2) near source/drain edge. The same has been explained using density-functional-theory (DFT)-based band structure calculations. KI doping of MoS2 resulted in contact resistance reduction by 3.5x (0.75 k Omega-mu m). The proposed technique and improved contacts have also resulted in 2x improvement in oN-state current (500 //A// m), transconductance and field-effect mobility (70 cm(2) /Vs) without compromising with oFF-state behavior, while maintaining ON to OFF ratio well above 106. The reproducibility of the transistor characteristics after a longer period (2 months) confirms the stability of proposed doping technique against environmental conditions
A note on electromagnetic and gravitational perturbations of the Bardeen de Sitter black hole: quasinormal modes and greybody factors
No full textBardeen de-Sitter (BdS) black hole is a spherically symmetric solution of Einstein's equation which is coupled to nonlinear electromagnetic field in a way that one gets a regular solution, devoid of any singularity at the origin. We compute the quasinormal (QN) frequencies for BdS black hole due to electromagnetic and gravitational perturbations. We analyse the behaviour of both real and imaginary parts of BdS QN frequencies by varying the black hole parameters and compare frequencies with Reissner-Nordstrom de-Sitter (RN-dS) black hole. Interestingly, we find that the response of BdS and RN-dS black holes under electromagnetic and gravitational perturbations are different when the charge parameter is varied, which can be used to understand nonlinear and linear electromagnetic fields in curved spacetime separately. A study on the dynamics of perturbation as well as the scattering from the BdS black holes using WKB approach is performed. Greybody factors and their variations with black hole parameters are investigated
Effect of CuPc and PEDOT:PSS as hole transport layers in planar heterojunction CdS/CdTe solar cell
No full textThis paper presents the fabrication and photovoltaic performance of new architecture based planar heterojunction CdS/CdTe thin film solar cells which were employed with two hole transport layers (PEDOT:PSS as HTL1 and CuPc as HTL2). The reported solar cells were fabricated through various deposition techniques such as sputtering, thermal evaporation, spin coating and characterized by FESEM, AFM, XPS, UPS and AM 1.5 solar simulator. The interfacial layer growth and chemical state identification of the deposited thin films were studied by cross-sectional FESEM and XPS techniques. The band bending occurs between absorbing and transporting layer helps to inject the excited charge carriers effectively into electrode that was explained using UPS analysis. The present work intends to explain the role of additional window layer (TiO2), buffer layer (CdS) and hole transporting layers (PEDOT:PSS and CuPc) in the novel device architecture. Further, these findings will offer new research directions to address the double hole transport (back contact) layers selection concept in CdS/CdTe heterojunction based solar cells
Coupling Electrochemical Adsorption and Long-range Electron Transfer: Label-free DNA Mismatch Detection with Ultramicroelectrode (UME)
No full textA new electrochemical hybridization transduction pathway, obtained by coupling electrochemical adsorption and long-range electron transfer through double-stranded DNA, was investigated using ultramicroelectrode (UME). The results show that long-range electron transfer does not occurs exclusively throws well-packed and organized self-assembled DNA monolayers. This approach is used to investigate long-range electron transfer properties of both single- and double- stranded short synthetic DNA and DNA plasmids. Single mismatch electrochemical detection protocol of non-labelled short synthetic DNA, without heating or probe labelling, in a 10 minutes protocol, was in fine performed
Are you from North or South India? A hard face-classification task reveals systematic representational differences between humans and machines
No full textWe make a rich variety of judgments on faces, but the underlying features are poorly understood. Here we describe a challenging geographical-origin classification problem that elucidates feature representations in both humans and machine algorithms. In Experiment 1, we collected a diverse set of 1,647 faces from India labeled with their fine-grained geographical origin (North vs. South India), characterized the categorization performance of 129 human subjects on these faces, and compared this with the performance of machine vision algorithms. Our main finding is that while many machine algorithms achieved an overall performance comparable to that of humans (64%), their error patterns across faces were qualitatively different despite training. To elucidate the face parts used by humans for classification, we trained linear classifiers on overcomplete sets of features derived from each face part. This revealed mouth shape to be the most discriminative part compared to eyes, nose, or external contour. In Experiment 2, we confirmed that humans relied the most on mouth shape for classification using an additional experiment in which subjects classified faces with occluded parts. In Experiment 3, we compared human performance for briefly viewed faces and for inverted faces. Interestingly, human performance on inverted faces was predicted better by computational models compared to upright faces, suggesting that humans use relatively more generic features on inverted faces. Taken together, our results show that studying hard classification tasks can lead to useful insights into both machine and human vision
Determining the spacetime structure of bottom-quark couplings to spin-zero particles
No full textWe present a general argument that highlights the difficulty of determining the spacetime structure of the renormalizable bottom-quark Yukawa interactions of the Standard Model Higgs boson, or for that matter of any hypothetical spin-zero particle, at high energy colliders. The essence of the argument is that, it is always possible, by chiral rotations, to transform between scalar and pseudoscalar Yukawa interactions without affecting the interactions of bottom quarks with SM gauge bosons. Since these rotations affect only the b-quark mass terms in the Standard Model Lagrangian, any differences in observables for scalar versus pseudoscalar couplings vanish when m(b) -> 0, and are strongly suppressed in high energy processes involving the heavy spin-zero particle where the b quarks are typically relativistic. We show, however, that the energy dependence of, for instance, e(+) e(-) -> b (b) over barX (here X denotes the spin-zero particle) close to the reaction threshold may serve to provide a distinction between the scalar versus pseudoscalar coupling at electron-positron colliders that are being proposed, provided that the Xb (b) over bar coupling is sizeable. We also note that while various kinematic distributions for t (t) over barh are indeed sensitive to the spacetime structure of the top-Yukawa coupling, for a spin-zero particle X of an arbitrary mass, the said sensitivity is lost if m(X) >> m(t)
Long-term cloud fraction biases in CMIP5 GCMs over India during monsoon season
No full textUsing 24years of cloud fraction (CF) data from the International Satellite Cloud Climatology Project (ISCCP) observations and their corresponding simulators in general circulation models (GCMs) from the Coupled Model Intercomparison Project phase 5 (CMIP5), we have analyzed cloud biases and their role on radiation over the Indian region (65-100 degrees E and 5-40 degrees N) for the monsoon season of June to September. The present study reports the spatial patterns of CFs and their biases in GCMs compared to observations. It is found that the simulated CFs are highly underestimated up to 40%. Mean of total CF from ISCCP observations is 75% with at least 10% difference with simulated CFs. For high-topped clouds, this difference is about 3-4%. Except for high-topped clouds, other cloud types are not simulated realistically by CMIP5 models used in this study. Further, we investigated the individual cloud types classified based on cloud optical depth and cloud top pressure. We found that, in general, individual cloud types are poorly simulated by models, although some (Max Planck Institute Earth System Model, Low Resolution and Hadley Centre Global Environmental Model, version 2, Earth System) models convincingly simulate high-topped thin clouds. To assess the impact of cloud biases on the simulated radiative forcings, we studied shortwave and longwave cloud radiative forcings from CERES (Clouds and the Earth's Radiant Energy System) observations and CMIP5 GCMs. It is noticed that the spatial patterns of biases in radiative forcings are similar to the patterns of biases in CFs for high-topped clouds, specifically over the oceanic regions. We find that the biases in cloud radiative forcings could potentially be caused due to the inefficacy of CMIP5 models in simulating high-topped anvil clouds (high-topped cirrus/stratocirrus clouds). The present study confirms that the uncertainty in simulating cloud fractions over the Indian region is still a prominent issue to be addressed in general circulation models
Facile Synthesis of Concave Cuboid Au NCs with Precisely Tunable Dimensions and Mechanistic Insight
No full textConcave cuboid (CCB) nanostructure is a member of the high-index facet (HIF) nanocrystals (NCs) family, geometrically derived from regular cuboid-excavation of each face. CCB NCs hold some additional characteristics such as surface cavity and sharp edges and corners as compared to its convex counterpart that makes it relatively more active in applications like electrochemical catalysis, surface enhanced Raman spectroscopy (SERS), and plasmonics. To date, there are only few reports available on the synthesis of CCB Au NCs where Br- containing surfactants have been used as a shape directing and stabilizing agent. However, none of them led to decent yield and size tunability. Herein, we report a robust seed mediated growth strategy where cetyltrimethylammonium chloride (CTAC) and tannic acid (TA) have been used as shape-directing/stabilizing and mild reducing agents, respectively. Our method not only allows the high yield fabrication of CCB Au NCs with uniform shape and size but also precise control over dimensions and degree of surface concavity. Moreover, the investigation of growth mechanism revealed that the evolution of CCB Au NCs from cylindrical nanorods (NRs) take place via arrow-headed nanorods and truncated CCB nanostructures. Furthermore, it has been observed that the presence of excess of Cl- is indeed playing a decisive role despite the headgroup of counter cationic part of surfactant. We anticipate that our findings may pave the path to design new synthetic strategies and understand the evolution of new nanostructures
Diplatinum(II) Catecholate of Photoactive Boron-Dipyrromethene for Lysosome-Targeted Photodynamic Therapy in Red Light
No full textThe binuclear platinum(II) boron-dipyrromethene (BODIPY) complex {Pt(dach)}(2)(mu-Dcrb)] (DP), where dach is 1,2-diaminocyclohexane and H(4)Dcrb is a morpholine-conjugated BODIPY-linked dicatechol bridging ligand, was prepared for lysosome organelle targeting and near-IR (NIR) light (600-720 nm) induced photocytotoxic activity. The platinum complex Pt(dach)(cat)] (CP), where H(2)cat is catechol, was synthesized and used as a control complex without bearing the BODIPY unit. The complex DP displayed a band at 660 nm (epsilon = 2.1 X 10(4) M-1 cm(-1)) in the red region of the UV visible spectrum recorded in 10% dimethyl sulfoxide/Dulbecco's Modified Eagle's Medium (DMSO/DMEM, pH 7.2). The complex DP and the BODIPY ligand displayed emission in 10% DMSO DMEM (pH 7.2) giving an lambda(em) value of 668 nm (lambda(ex) = 650 nm) with a Phi(F) value of 0.02 for DP and 0.16 for H(4)Dcrb (Phi(F), fluorescence quantum yield). Titration experiments using 1,3-diphenylisobenzofuran (DPBF) indicated that the complex DP and H(4)Dcrb on irradiation with near-IR light of 600-720 nm generated singlet oxygen (O-1(2)) as the ROS (reactive oxygen species). The complex DP showed significant lysosomal localization and remarkable apoptotic photodynamic therapy (PDT) effects, giving half-maximal inhibitory concentration values (IC50) within 0.6-3.4 mu M in HeLa cervical cancer, A549 lung cancer, and MDA-MB231 multidrug resistant cancer cells, while being essentially nontoxic in the dark and in the HPL1D immortalized lung epithelial normal cells. The acridine orange assay using A549 cells showed lysosomal membrane permeabilization by the complex DP under near-IR light (600-720 nm). This complex on near-IR light (600-720 nm) activation in A549 cells induced apoptotic cell death, as observed from an Annexin-V FITC assay
The journey of self-healing and shape memory polyurethanes from bench to translational research
No full textResearch on self-healing materials has been a topic of interest for almost one decade now and it represents a wide interdisciplinary area, exhibiting a large variety of different approaches. Although different types of polymers have been researched upon for this application, synthesizing them and using them for large-scale applications still remain a challenge. Polyurethanes (PU) have emerged as a promising class of polymeric materials in this context due to their ease of synthesis, shape memory properties and the ability to be fabricated on the basis of desired end properties. In this critical review, we have enlisted a comprehensive summary of different approaches that have been used over the past decade to synthesize self-healing PUs. In addition, we have also discussed in detail the ``close then heal'' and ``shape memory assisted self-healing'' concept whereby the shape memory properties of PUs can be utilised to bring the damaged parts together to achieve autonomous healing. Such a review will help guide researchers working in this field both from academia and industry