The dual role of Zn-acid medium for one-step rapid synthesis of M@rGO (M = Au, Pt, Pd and Ag) hybrid nanostructures at room temperature

We report a new protocol for the synthesis of M@rGO (M = Au, Pt, Pd, Ag and rGO = reduced graphene oxide) hybrid nanostructures at room temperature in Zn-acid medium. The roles of Zn-acid are to reduce the GO by generated hydrogen and the deposition of metal nanoparticles on rGO by galvanic replacement reaction between Zn and Mn+.

C-H center dot center dot center dot O-nitrate synthon assisted molecular assembly of hydrogen bonded Ni(II) and Cu(II) complexes

Two Schiff base metal complexes Cu-SPETNNO3 (1) and Ni-SPETNNO3 (2) SPETN=2,2-propane,1,3-diylbis(nitrilomethyldyne)pyridyl,phenolate] ] with hydrogen bonding groups have been synthesized and characterized by single-crystal X-ray diffraction. In both of the compounds nitrates occupy a crystallographic general position. In 1 the lattice nitrates are on the 2(1) screw axis while in 2 they are at the crystallographic inversion center. C-HOnitrate synthons (formed by the nitrate anions and peripheral hydrogen bonding groups of the metal complexes) are non-covalent building blocks in molecular-assembly and packing of the cationic Schiff base metal complexes (M=Ni2+, Cu2+), resulting in 2-D hydrogen bonded networks. The CuCu non-bonding contact in 1 is 3.268 angstrom while the Ni-Ni bonding distance in 2 is 3.437 angstrom.

A Medium-Voltage Inverter-Fed IM Drive Using Multilevel 12-Sided Polygonal Vectors, With Nearly Constant Switching Frequency Current Hysteresis Controller

In this paper, a current error space vector (CESV)-based hysteresis current controller for a multilevel 12-sided voltage space vector-based inverter-fed induction motor (IM) drive is proposed. The proposed controller gives a nearly constant switching frequency operation throughout different speeds in the linear modulation region. It achieves the elimination of 6n +/- 1, n = odd harmonics from the phase voltages and currents in the entire modulation range, with an increase in the linear modulation range. It also exhibits fast dynamic behavior under different transient conditions and has a simple controller implementation. Nearly constant switching frequency is obtained by matching the steady-state CESV boundaries of the proposed controller with that of a constant switching frequency SVPWM-based drive. In the proposed controller, the CESV reference boundaries are computed online, using the switching dwell time and voltage error vector of each applied vector. These quantities are calculated from estimated sampled reference phase voltages. Vector change is decided by projecting the actual current error along the computed hysteresis space vector boundary of the presently applied vector. The estimated reference phase voltages are found from the stator current error ripple and the parameters of the IM.

Early osseointegration of a strontium containing glass ceramic in a rabbit model

The most important property of a bone cement or a bone substitute in load bearing orthopaedic implants is good integration with host bone with reduced bone resorption and increased bone regeneration at the implant interface. Long term implantation of metal-based joint replacements often results in corrosion and particle release, initiating chronic inflammation leading onto osteoporosis of host bone. An alternative solution is the coating of metal implants with hydroxyapatite (HA) or bioglass or the use of bulk bioglass or HA-based composites. In the above perspective, the present study reports the in vivo biocompatibility and bone healing of the strontium (Sr)-stabilized bulk glass ceramics with the nominal composition of 4.5SiO(2)-3Al(2)O(3)-1.5P(2)O(5)-3SrO-2SrF(2) during short term implantation of up to 12 weeks in rabbit animal model. The progression of healing and bone regeneration was qualitatively and quantitatively assessed using fluorescence microscopy, histological analysis and micro-computed tomography. The overall assessment of the present study establishes that the investigated glass ceramic is biocompatible in vivo with regards to local effects after short term implantation in rabbit animal model. Excellent healing was observed, which is comparable to that seen in response to a commercially available implant of HA-based bioglass alone. (C) 2013 Elsevier Ltd. All rights reserved.

Biodegradation of acrylamide and purification of acrylamidase from newly isolated bacterium Moraxella osloensis MSU11

The increasing industrial utilization of polyacrylamide to assist water clarification, sludge conditioning, papermaking, and secondary oil recovery leads to environmental pollution. In this work, an acrylamide degrading bacterium was isolated from paper mill effluent at Charan mahadevi, Tamilnadu, India. The minimal medium containing acrylamide (40 mM) served as a sole source of carbon and nitrogen for acrylamide degrading bacteria. The bacterial strain has grown well in 40 mM acrylamide at pH (6-7) at 30 degrees C. Within 24-48 h acrylamide was converted into acrylic acid and other metabolites. Based on biochemical characteristics and 16S rRNA gene sequence, the bacterial strain was identified as Gram negative, diplobacilli Moraxella osloensis MSU11. The acrylamide hydrolyzing bacterial enzyme acrylamidase was purified by HPLC. The enzyme molecular weight was determined to be approximately 38 kDa by SDS-PAGE using reference enzyme Pectinase. These results show that M. osloensis MSU11 has a potential to degrade the acrylamide present in the environment. (C) 2013 Elsevier Ltd. All rights reserved.

Light transmission through and its complete stoppage in an ultra slow wave optical medium

Light wave transmission - its compression, amplification, and the optical energy storage in an ultra slow wave medium (USWM) is studied analytically. Our phenomenological treatment is based entirely on the continuity equation for the optical energy flux, and the well-known distribution-product property of Dirac delta-function. The results so obtained provide a clear understanding of some recent experiments on light transmission and its complete stoppage in an USWM.

Purifying water containing both anionic and cationic species using a (Zn, Cu)O, ZnO, and Cobalt Ferrite based multiphase adsorbent system

For the purpose of water purification, novel and low-cost adsorbents which are promising replacements for activated carbon are being actively pursued. However, a single-phase material that adsorbs both cationic and anionic species remains elusive. Hence, a low-cost, multiphase adsorbent bed that purifies water containing both anionic and cationic pollutants is a desirable alternative. We choose anionic (Congo red, Orange G) and cationic (methylene blue, malachite green) dyes as model pollutants. These dyes are chosen since they are widely found in effluents from textile, leather, fishery, and pharmaceutical industries, and their carcinogenic, mutagenic, genotoxic, and cytotoxic impact on mammalian cells is well-established. We show that ZnO, (Zn0.24Cu0.76)O and cobalt ferrite based multiphase fixed adsorbent bed efficiently adsorbs model anionic (Congo red, Orange G) and cationic (methylene blue and malachite green) pollutants, and their complex mixtures. All adsorbent phases are synthesized using room-temperature, high-yield (similar to 96-100%), green chemical processes. The nanoadsorbents are characterized by using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, and zeta potential measurements. The constituent nanophases are deliberately chosen to be beyond 50 nm, in order to avoid the nanotoxic size regime of oxides. Adsorption characteristics of each of the phases are examined. Isotherm based analysis shows that adsorption is both spontaneous and highly favorable. zeta potential measurements indicate that electrostatic interactions are the primary driving force for the observed adsorption behavior. The isotherms obtained are best described using a composite Langmuir-Freundlich model. Pseudo-first-order, rapid kinetics is observed (with adsorption rate constants as high as 0.1-0.2 min(-1) in some cases). Film diffusion is shown to be the primary mechanism of adsorption.

Remarkable role of positional isomers in the design of sensors for the ratiometric detection of copper and mercury ions in water

Cation sensing properties of the three positional isomers of rhodamine based sensors (1-3) are studied in water. The sensors differ only in the position of pyridine's nitrogen. The chemosensor 1, with pyridine nitrogen at ortho-position, showed a selective colorimetric detection of Cu(II) ions in water, at physiological pH 7.4 and also in medium containing BSA (bovine serum albumin) and blood serum. Notably the compound 2 and 3, with pyridine end located at meta-and para-positions did not show any color change with Cu(II) ions, although both the compounds showed turn-on change both in color and fluorescence with Hg(II) ions specifically. All the probes showed ratiometric changes with the specific metal ions. The changing position of nitrogen also changed the complexation pattern of the sensors with the metal ions. Probe 1 showed 2 : 1 complexation with Cu(II), whereas 2 and 3 showed 1 : 1 complexation with Hg(II) ions. The mechanism investigation showed that the change in color upon addition of metal ions is due to the ring-opening of the spirolactam ring of the probes. Cu(II) interacted with ligand 1 through a three-point interaction mode comprising carbonyl oxygen, amido nitrogen and pyridine nitrogen end. But in case of 2 and 3, Hg2+ only interacted through pyridine nitrogen ends. Quantitative estimation of Cu2+ and Hg2+ in complex biological media such as bovine albumin protein (BSA) and human blood serum were performed using these sensors. Rapid on-site detection as well as discrimination of these toxic ions was demonstrated using easily prepared portable test-strips.

Effect of TiN particulate reinforcement on corrosive behaviour of aluminium 6061 composites in chloride medium

In the present investigation, the corrosive behaviour of Al 6061-TiN particulate composites prepared by liquid metallurgy has been studied in chloride medium using electroanalytical techniques such as Tafel, cyclic polarization and electrochemical impedance spectroscopy (EIS). Surface morphology of the sample electrodes was examined using scanning electron micrography and energy dispersive X-ray methods. X-ray diffraction technique was used to confirm inclusion of TiN particulates in the matrix alloy and identify the alloying elements and intermetallic compounds in the Al 6061 composites. Polarization studies indicate an increase in the corrosion resistance in composites compared to the matrix alloy. EIS study reveals that the polarization resistance (R (p)) increases with increase in TiN content in composites, thus confirming improved corrosion resistance in composites. The observed decrease in corrosion rate in the case of composites is due to decoupling between TiN particles and Al 6061 alloy. It is understood that after the initiation of corrosion, interfacial corrosion products may have decoupled the conducting ceramic TiN from Al 6061 matrix alloy thus eliminating the galvanic effect between them.

Anthracene-Containing Conjugated Polymer Showing Four Optical Transitions Upon Doping: A Spectroscopic Study

An anthracene-containing poly(arylene-ethynylene)-alt-poly(arylene-vinylene) (PAE-PAV) of general constitutional unit (PhCCAnthrCCPhCHCHAnthrCHCH)(n) bearing two 2-ethylhexyloxy solubilizing side chains on each phenylene (Ph) unit has been synthesized and characterized. The basic electrochemical characterization was done, showing the existence of two non-reversible oxidation and one reversible reduction peaks. The optical properties, the real and imaginary part of the dielectric function, were probed using spectroscopic ellipsometry (SE). The vibrational structure of the undoped/doped polymer was investigated using Fourier transformed infrared spectroscopy. A strong change in the polaronic absorption was observed during the doping, which after modeling revealed the existence of two separated transitions. The optical changes upon doping were additionally recorded using the SE technique. Similar to the results from FT-IR spectroscopy, two new in-the-gap absorptions were found. Moreover, the electrical conductivity as well as the mobility of positive carriers were measured. In the undoped state, the conductivity of the polymer was found to be below the detection limit (

A promising ketone containing alternating copolymer for organic photovoltaics

An alternating copolymer containing dithienylcyclopentadienone, thiophene and benzothiadiazole was synthesized by palladium (0) catalyzed Stille coupling reaction. Structural characterization of the synthesized alternating copolymer was carried out by NMR and FTIR spectroscopy. This solution processable copolymer shows an excellent thermal stability and has a broad absorption range from 300-800 nm. High LUMO energy level and low band gap of the synthesized copolymers suggest that, this copolymer will be a better donor material for application in organic photovoltaics. Particle size analysis and molecular weight determination of the synthesized copolymer through dynamic light scattering experiment indicates that, high molecular weight copolymer was obtained by this polymerization route. Photovoltaic devices were fabricated from the blend of copolymer and phenyl-C61- butyric acid methyl ester as the active material. Fabricated photovoltaic device results show that this alternating copolymer is a promising candidate for use in organic photovoltaics.

Vertical uplift resistance of two closely spaced horizontal strip anchors embedded in cohesive-frictional weightless medium

The vertical uplift resistance of two closely spaced horizontal strip plate anchors has been investigated by using lower and upper bound theorems of the limit analysis in combination with finite elements and linear optimization. The interference effect on uplift resistance of the two anchors is evaluated in terms of a nondimensional efficiency factor (eta(c)). The variation of eta(c) with changes in the clear spacing (S) between the two anchors has been established for different combinations of embedment ratio (H/B) and angle of internal friction of the soil (phi). An interference of the anchors leads to a continuous reduction in uplift resistance with a decrease in spacing between the anchors. The uplift resistance becomes a minimum when the two anchors are placed next to each other without any gap. The critical spacing (S-cr) between the two anchors required to eliminate the interference effect increases with an increase in the values of both H/B and phi. The value of S-cr was found to lie approximately in the range 0.65B-1.5B with H/B = 1 and 11B-14B with H/B = 7 for phi varying from 0 degrees to 30 degrees.

Microstructural evolution and mechanical properties of Mg composites containing nano-B4C hybridized micro-Ti particulates

In this work, the microstructural evolution and mechanical properties of extruded Mg composites containing micro-Ti particulates hybridized with varying contents of nano-B4C are investigated, and compared with Mg-5.6Ti. Microstructural characterization showed the presence of uniformly distributed micro-Ti particles embedded with nano-B4C particulates that resulted in significant grain refinement. Electron back scattered diffraction (EBSD) analyses of Mg-(5.6Ti + x-B4C)(BM) hybrid composites showed that the addition of hybridized particle resulted in relatively more recrystallized grains, realignment of basal planes and extension of weak basal fibre texture when compared to Mg-5.6Ti. The evaluation of mechanical properties indicated improved strength with ductility retention in Mg-(5.6Ti + x-B4C)(BM) hybrid composites. When compared to Mg-5.6Ti, the superior strength properties of the Mg-(5.6Ti + xB(4)C)(BM) hybrid composites are attributed to the presence of nano-reinforcements, the uniform distribution of the hybridized particles, better interfacial bonding between the matrix and the reinforcement particles and the matrix grain refinement achieved by nano-B4C addition. The ductility enhancement obtained in hybrid composites can be attributed to the fibre texture spread and favourable basal plane orientation achieved due to nano B4C addition. (C) 2013 Elsevier B.V. All rights reserved.

The N-terminal region containing the zinc finger domain of tobacco streak virus coat protein is essential for the formation of virus-like particles

Tobacco streak virus (TSV), a member of the genus Ilarvirus (family Bromoviridae), has a tripartite genome and forms quasi-isometric virions. All three viral capsids, encapsidating RNA 1, RNA 2 or RNA 3 and subgenomic RNA 4, are constituted of a single species of coat protein (CP). Formation of virus-like particles (VLPs) could be observed when the TSV CP gene was cloned and the recombinant CP (rCP) was expressed in E. coli. TSV VLPs were found to be stabilized by Zn2+ ions and could be disassembled in the presence of 500 mM CaCl2. Mutational analysis corroborated previous studies that showed that an N-terminal arginine-rich motif was crucial for RNA binding; however, the results presented here demonstrate that the presence of RNA is not a prerequisite for assembly of TSV VLPs. Instead, the N-terminal region containing the zinc finger domain preceding the arginine-rich motif is essential for assembly of these VLPs.

An oxygen evolution Co-Ac catalyst - the synergistic effect of phosphate ions

Formation of an amorphous cobalt based oxygen evolution catalyst called Co-Pi has been recently reported from a neutral phosphate buffer solution containing Co2+. But the concentration of Co2+ is as low as 0.5 mM due to poor solubility of a cobalt salt in phosphate medium. In the present study, a cobalt acetate based oxygen evolution catalyst (Co-Ac) is prepared from a neutral acetate buffer solution, where the solubility of Co2+ is very high (>100 times in comparison with phosphate buffer solution). The Co-Ac possesses better catalytic activity than the Co-Pi with an additional advantage of easy bulk scale preparation. The comparative studies on the oxygen evolution reaction (OER) activity of Co-Ac and Co-Pi in phosphate and acetate buffer electrolytes reveal that the Co-Ac exhibits enhanced synergistic catalytic activity in phosphate solution, probably due to partial substitution of acetate in the catalyst layer by phosphate, resulting in the formation of a Co-Ac-Pi catalyst.