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Optical Transparency Enabled by Anomalous Stokes Shift in Visible Light-Emitting CuAlS2-Based Quantum Dots
No full textWe observe and study the anomalous Stokes shift of CuAlS2/CdS quantum dots. While all known I-III-VI2 semiconductor core/shell quantum dots show Stokes shifts in excess of 100 meV, the shift associated with CuAlS2/CdS quantum dots is uniquely large, even exceeding 1.4 eV in some cases. CuAlS2/CdS quantum dots are thus associated with cross sections less than 10(-17) cm(2) under the emission maximum. We investigate this anomaly using spectroscopic techniques and ascribe it to the existence of a strong type-II offset between CuAlS2 and CdS layers. Besides their strong Stokes shift, CuAlS2/CdS quantum dots also exhibit high quantum yields (63%) as well as long emission lifetimes (similar to 1500 ns). Because of the combined existence of these properties, CuAlS2/CdS quantum dots can act as tunable, transparent emitters over the entire visible spectrum. As a demonstration of their potential, we describe the construction of a wide area transparent lighting device with waveguided optical excitation and a clear aperture of 7.5 cm(2)
Direct heating of aqueous droplets using high frequency voltage signals on an EWOD platform
No full textWe demonstrate a new technique of heating aqueous droplets on conventional EWOD electrodes by using high frequency high-voltage AC signals. At high actuation frequencies (10-1000 kHz), the droplet temperature rises due to Joule heating from the ohmic currents inside the drop. Using this direct heating technique, we were able to achieve temperatures of 93-94 degrees C, which is significant for several biochemical applications. The technique is studied extensively using experiments and modelling. Several performance parameters of this heating technique were compared with a standard microheater through experiments and simulation. For the presented technique, the substrate near the droplet was cooler in comparison to the microheater. This will reduce parasitic heating of nearby droplets. A comprehensive study regarding the optimization of the geometrical parameters and the capability to heat solutions to higher temperatures using lower voltage and higher frequency were also performed using simulations. As conventional EWOD electrodes are used for heating the liquid, separate micro heaters are not required. This significantly simplifies design and allows us to heat any droplet at any location on the chip. This on demand reconfigurability of droplet heating is the primary benefit of this technique. To establish the abilities of our suggested method, two biochemical experiments were demonstrated
NiO-CNT composite for high performance supercapacitor electrode and oxygen evolution reaction
No full textNickel-oxide-Carbon nanotube (NiO-CNT) composite has been synthesized and its multifunctional electrochemical properties have been demonstrated by investigating the supercapacitive performance and the oxygen evolution reactivity. The composite exhibits interlinked porous structure and offers high surface area which has been observed by X-ray diffraction, Field emission scanning electron microscopy, Transmission electron microscopy and Brunauer-Emmett-Teller surface area analysis. NiO-CNT composite offers a specific capacitance of 878.19 F g(-1) at a scan rate of 2 mV s(-1) along with high cyclic stability. Asymmetric supercapacitor has been fabricated with the composite material as positive electrode and activated carbon as negative electrode and 1 M Na2SO4 electrolyte medium. The device offers a specific capacitance of 197.7 F g(-1) at a scan rate of 2 mV s(-1). It exhibits specific energy and specific power 85.7 Wh kg(-1) and 11.2 kWkg(-1), respectively. The device is capable of powering LED and DC motor for several minutes. Moreover, NiO-CNT composite shows excellent activity as a catalyst for Oxygen Evolution Reaction. The composite offers an overpotential of 0.301 V. The material shows excellent long term performance. This multifunctional composite material is a promising candidate for future applications in energy storage and conversion. (C) 2018 Elsevier Ltd. All rights reserved
Suppressor of clathrin deficiency (Scd6)An emerging RGG-motif translation repressor
No full textTranslation control plays a key role in variety of cellular processes. Translation initiation factors augment translation, whereas translation repressor proteins inhibit translation. Different repressors act by distinct mechanisms to accomplish the repression process. Although messenger RNAs (mRNAs) can be repressed at various steps of translation, most repressors have been reported to target the initiation step. We focus on one such translation repressor, an Arginine-Glycine-Glycine (RGG)-motif containing protein Scd6. Using this protein as a model, we present a discourse on the known and possible functions of this repressor, its mechanism of action and its recently reported regulation. We suggest a case for conservation of the mechanism employed by Scd6 along with its regulation in orthologs, and propose that Scd6 family of proteins will be an ideal tool to understand translation control and mRNA fate decision mechanisms across biological systems. This article is categorized under: Translation > Translation Regulation RNA Turnover and Surveillance > Turnover/Surveillance Mechanisms RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexe
Fracture of pre-cracked metallic conductors under combined electric current and mechanical loading
No full textRecently, we reported fracture of edge cracked thin metallic conductors upon passing only electric current, i.e., due to the self-induced electromagnetic forces. In this study, effect of simultaneous application of an electric current and a mechanical load on fracture of a thin edge-cracked conductor is investigated. Firstly, finite element method (FEM) simulation was performed to analyze the interaction between stress fields due to the electric current and the far-field mechanical loading. FEM simulations showed that stress fields as well as stress intensity factors due to each stimulus can be linearly superimposed to calculate their respective values under the combined loading. To corroborate the FEM results, experiments were conducted where a mechanical load was applied along with the electric pulse current. The critical current density required to propagate the sharp crack under combined loading decreased and the rate of crack propagation per electric current pulse drastically increased. Effect of mode-mixity on the fracture behavior of thin metallic foil under the combined loading was also studied by applying the mechanical load at different angles relative to the crack, and it was observed that the crack could be deflected at a desired, pre-determined angle by changing the mode mixity
An Extrinsic Approach Toward Achieving Fast Response and Self-Powered Photodetector
No full textAn extrinsic approach toward achieving fast response and self-powered photodetector is reported. It is shown that an organic-inorganic hybrid device (SnSe2/PEDOT:PSS) not only operates in self-powered mode for infra-red photodetection but also improves the response time with respect to inorganic (SnSe2) linear devices. Fast response and recovery time constants of approximate to 1.33 and 1.22 s, respectively, are obtained. Furthermore, the sensitivity is highest at zero bias and the device is stable for over 6 months stored in open air condition. The observed photo-current, faster response and recovery time constants are ascribed to the formation of a strong built-in electric field at the interface between SnSe2 and PEDOT:PSS. In a broader view of these findings, the device proves its potential as a self-powered photo-detector and the results reported here can pave the way to design self-powered and fast response for other wavelengths
Synthetic Control on Structure/Dimensionality and Photophysical Properties of Low Dimensional Organic Lead Bromide Perovskite
No full textLow dimensional lead halide perovskites have attracted huge research interest due to their structural diversity and remarkable photophysical properties. The ability to controllably change dimensionality/structure of perovskites remains highly challenging. Here, we report synthetic control on structure/dimensionality of ethylenediammonium (ED) lead bromide perovskite from a two dimensionally networked (2DN) sheet to a one dimensionally networked (1DN) chain structure. Intercalation of solvent molecules into the perovskite plays a crucial role in directing the final dimensionality/structure. This change in dimensionality reflects strongly in the observed differences in photophysical properties. Upon UV excitation, the 1DN structure emits white light due to easily formed ``self-trapped'' excitons. 2DN perovskites show band edge blue emission (similar to 410 nm). Interestingly, Mn2+ incorporated 2DN perovskites show a highly red-shifted Mn2+ emission peak at similar to 670 nm. Such a long wavelength Mn2+ emission peak is unprecedented in the perovskite family. This report highlights the synthetic ability to control the dimensionality/structure of perovskite and consequently its photophysical properties
Autocyclized and oxidized forms of SCR7 induce cancer cell death by inhibiting nonhomologous DNA end joining in a Ligase IV dependent manner
No full textNonhomologous DNA end joining (NHEJ) is the major DNA double-strand break (DSB) repair pathway in mammals. Previously, we have described a small molecule inhibitor, SCR7, which can inhibit NHEJ in a Ligase IV-dependent manner. Administration of SCR7 within the cells resulted in the accumulation of DNA breaks, cell death, and inhibition of tumor growth in mice. In the present study, we report that parental SCR7, which is unstable, can be autocyclized into a stable form. Both parental SCR7 and cyclized SCR7 possess the same molecular weight (334.09) and molecular formula (C18H14N4OS), whereas its oxidized form, SCR7-pyrazine, possesses a different molecular formula (C18H12N4OS), molecular weight (332.07), and structure. While cyclized form of SCR7 showed robust inhibition of NHEJ in vitro, both forms exhibited efficient cytotoxicity. Cyclized and oxidized forms of SCR7 inhibited DNA end joining catalyzed by Ligase IV, whereas their impact was minimal on Ligase III, Ligase I, and T4 DNA Ligase-mediated joining. Importantly, both forms inhibited V(D)J recombination, although the effect was more pronounced for SCR7-cyclized. Both forms blocked NHEJ in a Ligase IV-dependent manner leading to the accumulation of DSBs within the cells. Although cytotoxicity due to SCR7-cyclized was Ligase IV specific, the pyrazine form exhibited nonspecific cytotoxicity at higher concentrations in Ligase IV-null cells. Finally, we demonstrate that both forms can potentiate the effect of radiation. Thus, we report that cyclized and oxidized forms of SCR7 can inhibit NHEJ in a Ligase IV-dependent manner, although SCR7-pyrazine is less specific to Ligase IV inside the cell
Knee Angle Measurement Device Using Fiber Bragg Grating Sensor
No full textHuman joint kinematics has established its capacity as a vital tool for joint pathology and gait analysis. Range of motion (ROM) of a knee joint performed by flexion and extension is an essential tool to assess the efficacy of surgical interventions or therapeutic assessment. This paper proposes a novel wearable device for dynamic measurement of knee joint angle using fiber Bragg grating (FRG) sensor. The proposed knee angle measurement device (KAMD) can transduce the angular movement between the shin and the thigh into strain variations on a cantilever, which is acquired by the FRG sensor over it. The KAMD is also facilitated with tuneable sensitivity with three modes of high sensitivity mode, medium sensitivity mode, and low sensitivity mode, which can be opted based on application specific resolution and range of measurement. The ROM data obtained from the KAMD are validated against ROM obtained from commercially available Polhemus Sensors. Furthermore, the synchronization of the knee joint movement of both legs during walking along with stance and swing phase is illustrated, which shows the ability of KAMD to perform gait analysis. Employment of KAMDs on both legs eliminating the time synchronization complexity makes the proposed FBG-hased KAMD an efficient means to evaluate the knee angle from both legs simultaneously
Facile synthesis of BSCF perovskite oxide as an efficient bifunctional oxygen electrocatalyst
No full textWe present a facile way to synthesize BSCF by using glycine-nitrate auto-combustion followed by annealing at different conditions, which work as high-performance bifunctional electrocatalyst for oxygen evolution (OER) as well as oxygen reduction (ORR) reactions in alkaline solution with comparatively better efficiency for OER. Annealing condition plays an important role towards catalytic performance due to morphological control and surface composition. Although, there is no significant change in onset potentials but these catalysts afford a current density >10 mA cm(-2) at the potential of 1.65 V for oxygen evolution reaction and a current density >2.5 mA cm(-2) at the potential of 0.009 V for oxygen reduction reaction with respect to RHE in 0.1 M KOH. The underlying mechanism for ORR and OER as well as catalytic activity differences were understood with the help of different analytical characterization techniques. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved