Bimetallic nanoparticles: a single step synthesis, stabilization, and characterization of Au-Ag, Au-Pd, and Au-Pt in sol-gel derived silicates

Nanobimetallic particles consisting of Au-Pd, Au-Ag, and Au-Pt have been synthesized in a single step by a sol-gel process and stabilized in liquid and solid matrices. Organically modified silicates (Ormosils) that play a dual role of a matrix and of a stabilizer have been used to obtain very stable dispersions in the form of sols, gels, and monoliths. The simultaneous reduction of metal ions leads to either a surface enriched with one component or an alloy type of structure depending on the bimetal combination. The nanometallic dispersions are characterized by absorbance, TEM, XRD, IR, XPS, and CO adsorption studies. The stabilized nanoparticles are found to be good electrocatalysts and the preliminary results on the electrochemical reduction of oxygen are reported.     

Tosic Acid-on-Silica Gel: A Cheap and Eco-friendly Catalyst for a Convenient One-pot Synthesis of Substituted Benzimidazoles

Summary. 2-Substituted and 1,2-disubstited benzimidazoles were prepared efficiently from o-phenylenediamines and aryl aldehydes using p-toluenesulphonic acid (5 mol%)-on-silica gel as a cheap and environmentally benign catalyst.     

Unsupervised image thresholding: hardware architecture and its usage for FPGA-SoC platform

ABSTRACT

Otsu’s global automatic image thresholding operation is used in various image processing applications. It needs computation of normalized cumulative histogram, mean and cumulative moments that are compute-intensive operations. In this paper, a custom architecture is presented for an efficient computation of Otsu’s algorithm along with its utilization as an intellectual property (IP) core in a field programmable gate array (FPGA) based system-on-chip (SoC) environment for the application of connected component analysis (CCA). A self-normalization technique is employed, where single-cycle, read–modify–write operations are performed with block random access memories (BRAMs) and digital signal processing (DSP)slices. The architecture is designed for 640 × 480 size of images that are captured by a high-resolution analouge camera and buffered in a DDR2 SDRAM of Xilinx ML-507 platform at 25.175 MHz clock frequency. The embedded PowerPC processor core is used to control the frame acquisition process. Experimental results on Virtex-5 xc5vfx70t FPGA device show that the architecture utilizes 1.4% slices, 2.7% BRAMs and 3.9% DSP48E slices. The total power consumption of the design is 1440.59 mW. The proposed architecture as an IP core is able to work in real-time with standard VGA resolution video and requires low computational resources.     

Generalized solution to symbol error probability integral containing over different fading models

This paper presents a generalized solution to the symbol error probability (SEP) integral containing the product of two Gaussian Q‐functions . Numerical integration technique is first used to approximate the polar form of as a sum of exponentials. This approximation is then used to derive a closed‐form solution to the related SEP integral. Due to the exponential nature of the approximation, solution to the integral is expressed in terms of moment generating function (MGF) of a fading distribution. Therefore, the solution to integral exists for all fading distributions which have well‐defined MGF. The mathematical complexity of the proposed solution is directly proportional to the complexity of MGF expression. For most of the fading models, the corresponding MGF involves power or exponential functions, which guarantees algebraic simplicity of the proposed solution. Further, this generalized solution is used to evaluate the SEP of various modulation schemes over different fading channels. Various computer simulations run in MATLAB for wide range of scenarios confirm the accuracy of the proposed approximation and solution.     

Non-uniform distributions of photonic bandgap microstripline structures

With the advent of planar photonic bandgap (PBG) materials different topologies of PBG structures have been proposed to improve the bandpass and band rejection performances of microwave signals. Conventional circular patterned PBGs have constraints in the broadband performance due to the high ripple heights in S-parameters. In this paper, we suggest two novel configurations with non-uniform dimensions of circular patterned PBG to improve the stopband bandwidth and the ripples. The dimensions of the circles are varied proportionally to the Binomial and Shebyshev polynomial distributions. The S-parameter performances with respect to frequencies have been presented. It is seen that Shebyshev distribution produce excellent performances by suppressing ripples and generating sharp cut-offs.     

Mechanistic aspects of ligand substitution on <Emphasis Type="Italic">cis</Emphasis>-diaqua(<Emphasis Type="Italic">cis</Emphasis>-1,2-diaminocyclohexane)platinum(II) by Glycine-<Emphasis Type="SmallCaps">l</Emphasis>-Leucine

The kinetics of the interaction of glycine-l-leucine (Glyleu) with cis-[Pt(cis-dach)(OH₂)₂]²⁺ (dach = 1,2-diaminocyclohexane) has been studied spectrophotometrically as a function of [cis-[Pt(cis-dach)(OH₂)₂]²⁺], [Glyleu] and temperature at pH 4.0, where the complex exists predominantly as the diaqua species and Glyleu as a zwitterion. The substitution reaction shows two consecutive steps: the first is the ligand-assisted anation and the second is the chelation step. The activation parameters for both the steps were evaluated using Eyring’s equation. The low ∆H₁^≠ (51.9 ± 2.8 kJmol⁻¹) and large negative value of ∆S₁^≠ (−152 ± 8 JK⁻¹mol⁻¹) as well as ∆H₂^≠ (54.4 ± 1.7 kJmol⁻¹) and ∆S₂^≠ (−162 ± 5 JK⁻¹mol⁻¹) indicate an associative mode of activation for both the aqua ligand substitution processes.     

One-pot three-component reaction for the synthesis of biologically important spiro[benzo[f]quinoline-3,3′-indoline] derivatives

A previously unknown class of highly substituted benzoquinoline–spirooxindole are easily prepared by a novel application of a mild and efficient catalyst SbCl₃ for carbon–carbon and carbon–nitrogen bond formation reaction involving isatin, alkyne (dialkyl but-2-ynedioate) with aromatic amine (2-naphthylamine) in a one-pot three-component reaction. This protocol of one-pot synthesis afforded a library of dialkyl 2′-oxo-4H-spiro[benzo[f]quinoline-3,3′-indoline]-1,2-dicarboxylate derivatives, a potential bioactive compound in very good to excellent yields.     

Numerical modelling of a direct current non-transferred thermal plasma torch for optimal performance

A laminar steady-state 2D axisymmetric model of a direct current (DC) thermal plasma torch using a magneto-hydrodynamic approach has been developed. The model takes into account the entire torch system comprising the plasma gas injection, the inner region of the torch, and the jet exiting into the ambient environment. Numerical results are obtained for two different power inputs chosen from published experimental data. The temperature predictions at the torch exit are found in good agreement with experimental results. Velocity analysis of the plasma jet has been presented and the impact of electromagnetic force on jet velocity is analysed. The Lorentz force arising due to the coupling of fluid motion and electromagnetic forces shoots up the jet velocity to significantly high values near the cathode tip. Temperature and velocity profiles are in good agreement with the characteristics of a long laminar plasma jet. An operating value of heat transfer coefficient (h) has been suggested for optimal torch operation, thus ensuring a low anode erosion rate and acceptable thermal efficiency. The argon torch has the maximum temperature and longest jet length among the plasma gases considered.     

Kinetics and mechanism of the reaction of hydroxopentaaquarhodium(III) ion with <Emphasis Type="SmallCaps">l</Emphasis>-Arginine in aqueous solution

The kinetics of the aqua ligand substitution from hydroxopentaaquarhodium(III) ion, [Rh(H₂O)₅(OH)]²⁺, by l-Arginine has been studied spectrophotometrically as a function of Arginine concentration, and temperature, at pH 4.3. The reaction proceeds via a rapid outer sphere association complex formation step followed by two consecutive steps. The first of these involves ligand-assisted anation, while the second involves chelation as the second aqua ligand is displaced. The association equilibrium constant for the outer sphere complex formation has been evaluated together with the rate constants for the two subsequent steps. The activation parameters for both steps have been evaluated using Eyring’s equation. Thermodynamic parameters calculated from the temperature dependence of the outer sphere association equilibrium constants are also consistent with an associative mode of activation. The product of the reaction has been characterized by conductivity measurement and IR spectroscopic analysis.