Synthesis of CuTi-LDH supported on g-C3N4 for electrochemical and photoelectrochemical oxygen evolution reactions

A nanocomposite CuTi layered double hydroxide (LDH) supported on g-C₃N₄ (15 wt% of g-C₃N₄) is facilely synthesized by hydrothermal method. There are electrostatic interactions between positive layers of CuTi-LDH and negatively charged inner g-C₃N₄ sheets. The nanocomposite and its precursors are characterized through various analytical techniques, which affirmed the presence of both g-C₃N₄ and CuTi-LDH characteristic features. The pore-enriched hybrid geometry of CuTi-LDH@g-C₃N₄ with high specific surface area (146 m²/g), and suitable band gap of 2.46 eV enables the nanocomposite to act as both an electrocatalyst and photoelectrocatalyst for oxygen evolution reaction (OER). Both the electrochemical and photoelectrochemical studies are done using 1 M KOH (pH = 13.6) with applied potential of ?0.2 V to 1.5 V vs. Ag/AgCl. The onset potential of CuTi-LDH@g-C₃N₄ for OER appears at η = 0.36 V in dark and η = 0.32 V under visible light illumination of 30 min. Also, Mott-Schottky analysis shows n-type semiconductor behaviour for CuTi-LDH@g-C₃N₄ and its precursors. The photoelectrochemical water oxidation proceeds by charge transfer across a Type II heterojunction formed between the CuTi-LDH and g-C₃N₄ materials.     

A Fast-Response DC Motor Speed Control System

This paper describes the design, construction, and testing of a thyristorized speed control unit for a separately excited dc motor. The motor is fed from a three-phase six-pulse fully controlled thyristor bridge. A speed loop with a proportional plus integral controller maintains the desired speed irrespective of the load variations on the motor. An inner current control loop protects the thyristors from overcurrents. This loop also provides fast response overcoming the effect of disturbances such as variations in supply voltage. The design aspects of the control loops are discussed, and experimental results are given.     

Analysis of Commutation of a Current Inverter Feeding an Induction Motor Load

A method for analyzing the performance of an induction motor fed from a current source inverter and especially for computing the currents during commutation of the inverter is presented. A mathematical model of an inverter-fed induction motor is given in terms of Park's vector. Based on this model a closed form time domain expression is developed for the current during commutation. The stator voltage of a current-controlled inverter-fed induction motor is shown to be almost sinusoidal with superimposed spikes during commutation of current. The computed performance of the machine is verified experimentally, and there is a very close agreement between the computed and test results. The method presented also provides information regarding the voltages across the commutating capacitors and thyristors based on which proper selection of the thyristors and commutating capacitors can be made.     

Overcoming endogenous constraints on neuronal regeneration

One of the grand challenges in neuroengineering is to stimulate regeneration after central nervous system (CNS) or peripheral nervous system (PNS) injury to restore function. The state of the art today is that PNS injuries heal to a limited extent, whereas CNS injuries are largely intractable to regeneration. In this context, we examine the underlying biochemical and cellular constraints on endogenous healing of neural tissues. Identification and characterization of endogenous "rate-limiting" processes that constrain regeneration would allow one to craft solutions to overcome critical impediments for accelerated healing. It is increasingly evident that biochemical pathways triggered by the nature and duration of injury-triggered inflammatory response may determine the endogenous constraints and subsequently determine regenerative fate. In this paper, critical endogenous constraints of PNS and CNS regeneration are identified, and the effects of modulating the phenotypes of immune cells on neuronal regeneration are discussed.     

Construction of ternary hybrid layered reduced graphene oxide supported g-C3N4-TiO2 nanocomposite and its photocatalytic hydrogen production activity

Reduced graphene oxide (rGO) supported g-C₃N₄-TiO₂ ternary hybrid layered photocatalyst was prepared via ultrasound assisted simple wet impregnation method with different mass ratios of g-C₃N₄ to TiO₂. The synthesized composite was investigated by various characterization techniques, such as XRD, FTIR, Raman Spectra, FE-SEM, HR-TEM, UV vis DRS Spectra, XPS Spectra and PL Spectra. The optical band gap of g-C₃N₄-TiO₂/rGO nanocomposite was found to be red shifted to 2.56 eV from 2.70 eV for bare g-C₃N₄. It was found that g-C₃N₄ and TiO₂ in a mass ratio of 70:30 in the g-C₃N₄-TiO₂/rGO nanocomposite, exhibits the highest hydrogen production activity of 23,143 μmol g^?1h^?1 through photocatalytic water splitting. The observed hydrogen production rate from glycerol-water mixture using g-C₃N₄-TiO₂/rGO was found to be 78 and 2.5 times higher than g-C₃N₄ (296 μmol g^?1 h^?1) and TiO₂ (11,954 μmol g^?1 h^?1), respectively. A direct contact between TiO₂ and rGO in the g-C₃N₄-TiO₂/rGO nanocomposite produces an additional 10,500 μmol g^?1h^?1 of hydrogen in 4 h of photocatalytic reaction than the direct contact between g-C₃N₄ and rGO. The enhanced photocatalytic hydrogen production activity of the resultant nanocomposite can be ascribed to the increased visible light absorption and an effective separation of photogenerated electron-hole pairs at the interface of g-C₃N₄-TiO₂/rGO nanocomposite. The effective separation and transportation of photogenerated charge carriers in the presence of rGO sheet was further confirmed by a significant quenching of photoluminescence intensity of the g-C₃N₄-TiO₂/rGO nanocomposite. The photocatalytic hydrogen production rate reported in this work is significantly higher than the previously reported work on g-C₃N₄ and TiO₂ based photocatalysts.     

Tissue Engineering Strategies Designed to Realize the Endogenous Regenerative Potential of Peripheral Nerves

http://doi.wiley.com/10.1002/adma.v21:32/33 Bridging peripheral nerve gaps without the use of autografts has significant clinical importance. But in order to rationally design novel scaffolds, a good understanding of the nerve regeneration process is vital. Appropriate amount of structural and chemical cues are required to stimulate the endogenous mechanisms of repair and functional recovery. Synthetic and natural materials present various opportunities to induce the growth of supporting cells as well as promote axon regeneration. An overview of tissue engineering strategies currently being explored that stimulate the different steps of the regenerative sequence is presented.     

A Novel Three-Phase Reference Sine-Wave Generator for PWM Inverters

A hybrid circuit for producing a three-phase reference sine wave required with PWM inverters is described in this paper. The principle of the circuit is simple and the implementation of the circuit is easy. The circuit has all the features discussed in the literature. The unit built has, apart from the three-phase sine waves, balanced three-phase square and triangular waves. A high-frequency triangular wave already available in the circuit can be used for the PWM control circuitry. The scheme can easily be extended to generate sine waves of any number of phases.     

Bovine serum albumin conformation on methyl and amine functionalized surfaces compared by scanning force microscopy

We investigated the adsorption of albumin on chemically modified gold surfaces by scanning force microscopy operating both in contact and noncontact mode. The surface modification was performed with thiol-based self-assembling molecules carrying amine or methyl groups. The albumin on the aminoethanethiol-coated gold formed a uniform layer and single molecules could be distinguished. On the dodecanethiol-coated surface the protein adsorbed in aggregates or single isolated molecules depending on the incubation time. The width of the albumin molecule on both surface was similar, but the height was much lower on the amine than on the methyl surface. This was interpreted as a difference in the conformation of albumin depending on the substrate, and could explain the promotion of cell adhesion on amine-treated polymers coated with albumin.