Enhancement of the crystalline perfection of <0 0 1> directed KDP single crystal

<0 0 1> directed good quality potassium dihydrogen phosphate (KDP) single crystal has been grown by Sankaranarayanan–Ramasamy (SR) method with the vision to improve the crystalline perfection and efficiency. A seed crystal of diameter 25 × 15 × 3 mm³ was mounted in the ampoule, where the diameter of the ampoule was much bigger than the seed. The size of the crystal grown was 30 × 20 × 60 mm³. The obtained transparency for the crystal grown by SR method is 93% and by conventional method is 85% in the entire visible region. The HRXRD analysis indicates that the crystalline perfections of the crystals are excellent without having any very internal structural grain boundaries. The obtained FWHM for conventional method grown crystal is 12 arc s and for SR method is 6 arc s. Low dielectric loss indicates that the <0 0 1> directed crystal contains minimum defects. Higher mechanical stability was observed in SR method grown KDP compared to the other. Laser damage threshold value has been determined using Nd:YAG laser operating at 1064 nm. The optical transmission study and the powder SHG measurement show the suitability of the ingot for nonlinear optical applications.     

Modulational instability of dust-ion-acoustic waves in pair-ion plasma having non-thermal non-extensive electrons

The modulational instability (MI) criteria of dust-ion-acoustic (DIA) waves (DIAWs) have been investigated in a four-component pair-ion plasma having inertial pair ions, inertialess non-thermal non-extensive electrons, and immobile negatively charged massive dust grains. A nonlinear Schrödinger equation (NLSE) is derived by using reductive perturbation method. The nonlinear and dispersive coefficients of the NLSE can predict the modulationally stable and unstable parametric regimes of DIAWs and associated first and second-order DIA rogue waves (DIARWs). The MI growth rate and the configuration of the DIARWs are examined, and it is found that the MI growth rate increases (decreases) with increasing the number density of the negatively charged dust grains in the presence (absence) of the negative ions. It is also observed that the amplitude and width of the DIARWs increase (decrease) with the negative (positive) ion mass. The implications of the results to laboratory and space plasmas are briefly discussed.     

Fire reaction properties of polystyrene-based nanocomposites using nanosilica and nanoclay as additives in cone calorimeter test

Using nanofiller additives in the polymer matrix to form nanocomposites is a potential way of reducing the flame spread and enhancing flame retardancy of polymeric materials during fire. To understand the fire reaction properties and the relative performance of flame-retardant additives in polymer during well-developed fire, neat polystyrene, polystyrene–silica and polystyrene–nanoclay (MMT) have been tested in a cone calorimeter. The neat polystyrene and the polystyrene nanocomposites have been prepared via an in situ polymerization method. An external heat flux of 50 kW m^?2 was applied in the test, and parameters such as heat release rate, peak heat release rate, time to ignition, smoke toxicity, CO and CO₂ yield have been investigated. Both neat polystyrene and polystyrene nanocomposites have shown the trend of a thermally thick charring polymer in the heat release rate over time data. The nanocomposites had an overall better flame retardancy than the neat polystyrene in terms of lower peak heat release rate, lower average mass loss rate and enhanced char formation. The nanocomposites had also reduced smoke emission with lower CO and CO₂ yield compared to the neat polystyrene. The overall flame retardancy was enhanced as the nanofiller loading was increased for both the nanosilica and MMT nanocomposites.

     

Quesnoin, a novel pentacyclic ent-diterpene from 55 million years Old Oise Amber

Amber, fossilized tree resin, found at the Oise River area of the Paris basin (France) was dated as being 55 million years old. Quesnoin, a novel unique pure organic compound, was isolated from Oise amber. 1H and 13C NMR spectroscopic analysis indicated an unknown diterpene skeleton, quesnane. The absolute configurations of the eight chiral centers of quesnoin were determined to be 4S, 5S, 8R, 9S, 10S, 13S, 14R, and 16S by chiral auxiliary (R)- and (S)-phenylglycine methyl ester derivatization. Quesnoin allowed us to disclose the tree producer, corresponding to modern Hymenaea oblongifolia, Fabaceae, a subfamily of Caesalpiniaceae, one of the oldest angiosperm. The presence of the Amazon rainforest tree, H. oblongifolia, indicated that the climate of the Paris basin might have been tropical in the early Eocene period, 55 million years ago.     

用毛细管焦点法精确测量微量液体的折射率

介绍了用毛细管焦点法精确测最微量液体折射率的一种新技术.该技术基于共轴球面光学系统的成像原理,用LED(λ=580 nm,FWHM为32nm)为测量光源,用CCD为像接收装置.一次测量样品需要量小于0.002 mL.待测样品封闭在毛细管内测量,有利于对毒性、挥发性和吸湿性强的液体介质折射率的测量.用此技术对纯水、乙醇、乙二醇和丙三醇样品的折射率做了测量,测量精度分别为0.0001,0.0002,0.0003和0.0003.论文在分析实验装置的测量灵敏度和成像景深基础上,提出了进一步提高测最精度的方法.     

Thermodynamic analysis of fly ash nanofluid for automobile (heavy vehicle) radiators

Journal of Thermal Analysis and Calorimetry - On the basis of symmetry group analysis applied to fluid flow, heat and mass transfer equations for nanofluids in parabolic approximation, their...     

Electrochemical Sensing of Chemical Warfare Agent Based on Hybrid Material Silver‐aminosilane Graphene Oxide

The threat from chemical warfare agents (CWAs) imparts an alarming call for the global community not limited to human being but also extends as unprecedented environmental threat, hence, timely detection and degradation in the event of CWAs attack is very crucial. Herein, we describe a hybrid material of 3‐aminopropyltriethoxysilane (APTES) modified graphene oxide (GO) on glassy carbon (GC) electrode along with electrodeposited silver nanodendrimers (AgNDs) for the electrochemical detection and degradation of CWA sulphur mustard (HD). The AgNDs/APTES‐GO hybrid material was characterized by SEM, EDX, BET, TGA, Raman, UV‐Vis, XPS and XRD techniques. The AgNDs/APTES‐GO modified GC electrode was also characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Electrochemical studies indicated presence of electrocatalysis owing to the synergistic effect of AgNDs and GO for sensing CWA HD via reductive dehalogenation. The AgNDs/APTES‐GO modified GC electrode exhibited linearity for CWA HD from 5.3 μM to 42.4 μM. Constant potential electrolysis was performed with modified electrode and degradation products were analysed using GC‐MS, highlighting the great potential of graphene based hybrid material. This new strategy provides an opportunity for the development of “detect and destroy” system for the CWAs and other environmental toxic pollutant, which could help in mitigation of on‐ site events for first responders.     

Evaluation of resazurin microtiter plate assay and HPLC- photodiode array analysis of the roots of Asparagus adscendens

Asparagus adscendens Roxb. (Asparagaceae), is native to the Himalayas. The present study, for the first time, was undertaken to explore the antimicrobial potential, to determine the minimum inhibitory concentration (MIC) values of the methanol extract of the roots of A. adscendens and its solid-phase extraction (SPE) fractions using resazurin microtitre assay against Gram-positive and negative bacterial-registered strains and to carry out HPLC-photodiode array analysis of the SPE fractions. The methanol extract and all SPE exhibited considerable level of antibacterial potential against Gram-positive bacteria (MIC: 2.5–0.009 mg/mL) than against Gram-negative bacteria (MIC: 1.25–2.5 mg/mL). The use of microtitre plates has the advantage of lower cost, fast and quantitative results. Like other Asparagus species, the presence of phenolic compounds in all SPE fractions was evident in the HPLC-PDA data.     

A sensor for acetaminophen in a blood medium using a Cu(II)-conducting polymer complex modified electrode

Complexation of Cu ions in a terthiophene carboxylic acid (TTCA) polymer film resulted an enhanced anodic current for acetaminophen oxidation when compared to polymer coated and bare glassy carbon electrodes in human blood and buffer media. Scanning electron microscopy (SEM) and ESCA experiments indicate the involvement of copper in the electrocatalytic oxidation of acetaminophen. No interference was observed from other biologically important and phenolic compounds used with this modified electrode. Especially, the non-interference from N-acetylcysteine, an antidote for the treatment of acetaminophen poisoning, reveals the proposed method’s superiority in medicinal applications. In addition, the present modified electrode avoids surface fouling at higher concentrations of acetaminophen. The calibration range obtained with CV was based between 2.0×10⁻⁵ and 5.0×10⁻³ M [r²=0.997 (n=5, R.S.D.=2.5%); DL=5.0×10⁻⁶ M (S/N=3)]. The analytical utility of the modified electrode was achieved by analyzing the content of acetaminophen in different drugs without pretreatment using CV and amperometric techniques.