50175 research outputs found
Sort by
Fracture of pre-cracked thin metallic conductors due to electric current induced electromagnetic force
No full textWe investigated propagation of a sharp crack in a thin metallic conductor with an edge crack due to electric current induced electromagnetic forces. Finite element method (FEM) simulations showed mode I crack opening in the edge-cracked conductor due to the aforementioned (i.e., self-induced) electromagnetic forces. Mode I stress intensity factor due to the self-induced electromagnetic forces, was evaluated numerically as , where is the magnetic permeability, l is the length of the conductor, a is the crack length, j is the current density, w is the width of the sample and f(a / w) is a geometric factor. Effect of dynamic electric current loading on edge-cracked conductor, incorporating the effects of induced currents, was also studied numerically, and dynamic stress intensity factor, , was observed to vary as . Consistent with the FEM simulation, experiments conducted using thick Al foil with an edge crack showed propagation of sharp crack due to the self-induced electromagnetic forces at pulsed current densities of for . Further, effects of current density, pulse-width and ambient temperature on the fracture behavior of the Al foil were observed experimentally and corroborated with FEM simulations
Mobile nanotweezers for active colloidal manipulation
No full textAn important goal in nanotechnology is to control and manipulate submicrometer objects in fluidic environments, for which optical traps based on strongly localized electromagnetic fields around plasmonic nanostructures can provide a promising solution. Conventional plasmonics based trapping occurs at predefined spots on the surface of a nanopatterned substrate and is severely speed-limited by the diffusion of colloidal objects into the trapping volume. As we demonstrate, these limitations can be overcome by integrating plasmonic nanostructures with magnetically driven helical microrobots and maneuvering the resultant mobile nanotweezers (MNTs) under optical illumination. These nanotweezers can be remotely maneuvered within the bulk fluid and temporarily stamped onto the microfluidic chamber surface. The working range of these MNTs matches that of state-of-the-art plasmonic tweezers and allows selective pickup, transport, release, and positioning of submicrometer objects with great speed and accuracy. The MNTs can be used in standard microfluidic chambers to manipulate one or many nano-objects in three dimensions and are applicable to a variety of materials, including bacteria and fluorescent nanodiamonds. MNTs may allow previously unknown capabilities in optical nanomanipulation by combining the strengths of two recent advances in nanotechnology
Photothermal trap utilizing solar illumination for ice mitigation
No full textIce buildup is an operational and safety hazard in wind turbines, power lines, and airplanes. Traditional deicing methods, including mechanical and chemical means, are energy-intensive or environmentally unfriendly. Super hydrophobic anti-icing surfaces, while promising, can become ineffective due to frost formation within textures. We report on a ``photothermal trap'' a laminate applied to a base substrate that can efficiently deice by converting solar illumination to heat at the ice-substrate interface. It relies on the complementing properties of three layers: a selective absorber for solar radiation, a thermal spreader for lateral dispersal of heat, and insulation to minimize transverse heat loss. Upon illumination, thermal confinement at the heat spreader leads to rapid increase of the surface temperature, thereby forming a thin lubricating melt layer that facilitates ice removal. Lateral heat spreading overcomes the unavoidable shadowing of certain areas from direct illumination. We provide a design map that captures the key physics guiding illumination-induced ice removal. We demonstrate the deicing performance of the photothermal trap at very low temperatures, and under frost and snow coverage, via laboratory-scale and outdoor experiments
Insights into protein structure, stability and function from saturation mutagenesis
No full textWhere convenient phenotypic readouts are available, saturation mutagenesis coupled to deep sequencing provides a rapid and facile method to infer sequence determinants of protein structure, stability and function. We provide brief descriptions and currently available options for the various steps involved, and mention limitations of current implementations. We also highlight recent applications such as estimating relative stabilities and affinities of protein variants, mapping epitopes, protein model discrimination and prediction of mutant phenotypes. Most mutational scans have so far been applied to single genes and proteins. Additional methodological improvements are required to expand the scope to study intergenic epistasis and intermolecular interactions in macromolecular complexes
Incorporating Surface Convection into a 3D Babcock-Leighton Solar Dynamo Model
No full textThe convective flows observed on the photosphere (e.g., supergranulation, granulation) play a key role in the Babcock-Leighton (BL) process to generate large-scale polar fields from sunspot fields. In most surface flux transport (SFT) and BL dynamo models, the dispersal and migration of surface fields are modeled as an effective turbulent diffusion. Recent SFT models have incorporated explicit, realistic convective flows in order to improve the fidelity of convective transport but, to our knowledge, this has not yet been implemented in previous BL models. We present the first kinematic 3D Flux-Transport/BL model to explicitly incorporate realistic convective flows based on solar observations. Though we describe a means to generalize these flows to 3D, we find that the kinematic small-scale dynamo action they produce disrupts the operation of the cyclic dynamo. The cyclic solution is found by limiting the convective flow to act only on the vertical radial component of the magnetic field. The results obtained are generally in good agreement with the observed surface flux evolution and with non-convective models that have a turbulent diffusivity of the order of 3 x 10(12) cm(2) s(-1) (300 km(2) s(-1)). However, we find that the use of a turbulent diffusivity underestimates the dynamo efficiency, producing weaker mean fields and a shorter cycle than in the convective models. Also, the convective models exhibit bands of mixed polarity in the polar regions that have no counterpart in solar observations, and the poleward migration speed of poloidal flux is determined mainly by the meridional flow and the vertical diffusion
Comparison of Force Required for Lumbar Puncture With Different Gauges of Spinal Needle Using Fiber Bragg Grating Force Device
No full textThe deployment of the spinal needle of an appropriate gauge is highly essential in order to significantly reduce the side effects of lumbar puncture procedures performed for spinal anaesthesia and spinal surgeries. The gauge of the spinal needle used for the procedure plays a significant role in determining the force required for its insertion into the tissue and is chosen by the medical practitioner performing the procedure based on the expertise. The selection of the optimum gauge of the needle is subjective to the level of discretion exercised by the surgeon. This paper shows a comparative analysis of the force required for lumbar puncture with various tissue layers traversal by four different gauges of the spinal needle, making use of a real time dynamic force monitoring device which employs a fiber Bragg grating sensor. The fiber Bragg grating (FBG) force device (FBGFD) is used to measure the force variations on different gauges of spinal needle during the lumbar puncture procedure performed first on a simulator model and subsequently on a human cadaver specimen. The FBGFD facilitates dynamic measurement of force variation on the spinal needle during the penetration by the sensing bar mechanism which is acquired by the FBG sensor bonded over it with a resolution of 0.021 N. This comparative study of force may serve as a guideline for selection of proper gauge spinal needle during tissue puncture procedures minimizing post puncture effects on patients
Polyanionic Insertion Materials for Sodium-Ion Batteries
No full textEfficient energy storage is a driving factor propelling myriads of mobile electronics, electric vehicles and stationary electric grid storage. Li-ion batteries have realized these goals in a commercially viable manner with ever increasing penetration to different technology sectors across the globe. While these electronic devices are more evident and appealing to consumers, there has been a growing concern for micro-to-mega grid storage systems. Overall, the modern world demands energy in terawatt' scale. It needs a multipronged approach with alternate technologies complementing the Li-ion batteries. One such viable approach is to design and implement Na-ion batteries. With the uniform geographical distribution, abundance and materials economy of Na resources as well as a striking operational similarity to Li-ion batteries, Na-ion batteries have commercial potential, particularly for applications unrestricted by volumetric/gravimetric energy density. In pursuit of the development of Na-ion batteries, suites of oxides, sulfides, fluorides, and polyanionic materials have been reported in addition to several organic complexes. This article gives an overview of recent progress in polyanionic framework compounds, with emphasis on high-voltage candidates consisting of earth abundant elements. Guided by ternary phase diagrams, recently discovered and potential cathode candidates will be discussed gauging their performance, current status, and future perspectives
Aluminium and rhodium co-doped ceria for water gas shift reaction and CO oxidation
No full textThis study presents the synthesis and application of aluminium and rhodium co-doped ceria for water gas shift (WGS) reaction and CO oxidation. The catalyst was synthesized using single step solution combustion method to obtain porous catalyst of relatively high surface area. The catalyst was characterized by various techniques. All the characterization results revealed successful substitution of the constituent dopants in ceria. The catalyst obtained was tested for its activity for WGS and CO oxidation. The catalyst exhibited higher catalytic activity in comparison to the other noble metal counterparts. A plausible dual site microkinetic model has been proposed in this study for WGS and CO oxidation over Rhiceria based catalyst and a robust rate expression has been obtained. This rate expression in conjunction with the kinetic parameters and isothermal plug flow reactor model was used to predict the experimental CO conversion. As evident from the simulation results, the kinetic model developed in this study was able to predict the experimental trend with reasonable accuracy for both WGS and CO oxidation. (C) 2017 Elsevier B.V. All rights reserved
A systematic revision of Calotes Cuvier, 1817 (Squamata: Agamidae) from the Western Ghats adds two genera and reveals two new species
No full textLizards of the genus Calotes are geographically restricted to South Asia, Indo-China and parts of Southeast Asia. The greatest diversity of the genus is from the biodiversity hotspots in South Asia: Western Ghats (Peninsular India), Sri Lanka and Indo-Burma. Here, we present a systematic revision of members of the genus Calotes from Peninsular India using a combination of molecular phylogeny, geographical distribution and morphological characters. We show that Calotes from the Western Ghats is paraphyletic and consists of three major clades, one of which is widely distributed in South and Southeast (SE) Asia, while the others are restricted to Peninsular India. The Peninsular Indian Glade is composed of two sister clades: Psammophilus, with a wider distribution and a second Glade, composed of two extant species, Calotes rouxii and Calotes ellioti and two new species, all restricted to the Western Ghats region. Based on morphological differences, we retain the generic status of Psammophilus and assign its sister Glade to a new genus Monilesaurus gen. nov. and transfer the following species, C. rouxii and C. ellioti, to this new genus. We also provide diagnoses and descriptions for two new species recognized within Monilesaurus gen. nov. In addition, Calotes aurantolabium from the Western Ghats was observed to be deeply divergent and to share a sister-relationship with the Glade composed of Calotes, Monilesaurus gen. nov., and Psammophilus. Based on its phylogenetic position and morphological attributes, we assign this species to a new genus Microauris gen. nov. These new discoveries highlight the evolutionary significance of the Western Ghats in housing novel lizard diversity
Printed Electronics Based on Inorganic Semiconductors: From Processes and Materials to Devices
No full textFollowing the ever-expanding technological demands, printed electronics has shown palpable potential to create new and commercially viable technologies that will benefit from its unique characteristics, such as, large-area and wide range of substrate compatibility, conformability and low-cost. Through the last few decades, printed/solution-processed field-effect transistors (FETs) and circuits have witnessed immense research efforts, technological growth and increased commercial interests. Although printing of functional inks comprising organic semiconductors has already been initiated in early 1990s, gradually the attention, at least partially, has been shifted to various forms of inorganic semiconductors, starting from metal chalcogenides, oxides, carbon nanotubes and very recently to graphene and other 2D semiconductors. In this review, the entire domain of printable inorganic semiconductors is considered. In fact, thanks to the continuous development of materials/functional inks and novel design/printing strategies, the inorganic printed semiconductor-based circuits today have reached an operation frequency up to several hundreds of kilohertz with only a few nanosecond time delays at the individual FET/inverter levels; in this regard, often circuits based on hybrid material systems have been found to be advantageous. At the end, a comparison of relative successes of various printable inorganic semiconductor materials, the remaining challenges and the available future opportunities are summarized