Volumetric and transport properties of <Emphasis Type="Italic">N</Emphasis>-Butyl-<Emphasis Type="Italic">N</Emphasis>-methylpyrrolidinium bis(Trifluoromethanesulfonyl)imide–methanol binary mixtures

Densities, viscosities, and ionic conductivities were measured for the binary mixtures containing the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide and methanol over the entire range of compositions at the temperature varying from 253.15 to 318.15 K. The densities and viscosities decrease monotonously with temperature and the content of ionic liquids (ILs). Furthermore, excess isobaric expansion coefficient has been calculated from the experimental densities. The dependence of temperature on the viscosity has been fitted to the Arrhenius law with high precision. The dependence of temperature on the ionic conductivity has also been gauged by both of the Arrhenius and Vogel–Tamman–Fulcher (VTF) equations. In fact, the shape of the curves shows that the temperature dependence of the conductivity does not follow a simple Arrhenius law, but a better fitting of experimental results is achieved using the VTF model. Additionally, the effects of ILs concentration on the viscosity and the conductivity have been examined using the Walden rule, which shows that the variation of conductivity is inversely proportional to viscosity. Excess molar volumes and viscosity deviations for all mixtures are evaluated and well fitted to the Redlich–Kister polynomial expansions. Physicochemical properties show two clearly distinguished behaviors corresponding to ILs-rich and methanol-rich regions, with distinct transport and volumetric properties. The obtained results are discussed in terms of dipolar interactions and hydrogen bonding establishment between ions of ILs and the methanol molecules.     

Asymmetric synthesis of cyclohexene nucleoside analogues

The asymmetric synthesis of novel cyclohexene nucleoside analogues 12 and 15 is described. An enantiospecific Diels-Alder reaction between (E,E)-diene 2 and (+)-5-(d-mentyloxy)-2(5H)-furanone 3 provided the cycloadduct isomer 4. Three additional steps yielded amine 8 allowing the constructions of the thymine and adenine moieties to afford intermediates 11 and 14, respectively. Amination or cyclization and removal of the protecting groups occurred in one step in the presence of ammonia, giving the target six-membered ring nucleosides.     

Giant magnetoelastic effect at the opening of a spin-gap in Ba3BiIr2O9

As compared to 3d (first-row) transition metals, the 4d and 5d transition metals have much more diffuse valence orbitals. Quantum cooperative phenomena that arise due to changes in the way these orbitals overlap and interact, such as magnetoelasticity, are correspondingly rare in 4d and 5d compounds. Here, we show that the 6H-perovskite Ba(3)BiIr(2)O(9), which contains 5d Ir(4+) (S = 1/2) dimerized into isolated face-sharing Ir(2)O(9) bioctahedra, exhibits a giant magnetoelastic effect, the largest of any known 5d compound, associated with the opening of a spin-gap at T* = 74 K. The resulting first-order transition is characterized by a remarkable 4% increase in Ir-Ir distance and 1% negative thermal volume expansion. The transition is driven by a dramatic change in the interactions among Ir 5d orbitals, and represents a crossover between two very different, competing, ground states: one that optimizes direct Ir-Ir bonding (at high temperature), and one that optimizes Ir-O-Ir magnetic superexchange (at low temperature).     

Phyto-Extract-Mediated Synthesis of Silver Nanoparticles Using Aqueous Extract of Sanvitalia procumbens,and Characterization,Optimization and Photocatalytic Degradation of Azo Dyes Orange G and Direct Blue-15

Green synthesis of silver nanoparticles (AgNPs) employing an aqueous plant extract has emerged as a viable eco-friendly method. The aim of the study was to synthesize AgNPs by using plant extract of Sanvitalia procumbens (creeping zinnia) in which the phytochemicals present in plant extract act as a stabilizing and reducing agent. For the stability of the synthesized AgNPs, different parameters like AgNO₃ concentration, volume ratios of AgNO₃, temperature, pH, and contact time were studied. Further, AgNPs were characterized by UV–visible spectroscopy, FT-IR (Fourier Transform Infrared Spectroscopy), XRD (X-ray Diffraction), SEM (Scanning Electron Microscopy), and EDX (Energy Dispersive X-ray Spectrometer) analysis. FT-IR analysis showed that the plant extract contained essential functional groups like O–H stretching of carboxylic acid, N–H stretching of secondary amides, and C–N stretching of aromatic amines, and C–O indicates the vibration of alcohol, ester, and carboxylic acid that facilitated in the green synthesis of AgNPs. The crystalline nature of synthesized AgNPs was confirmed by XRD, while the elemental composition of AgNPs was detected by energy dispersive X-ray analysis (EDX). SEM studies showed the mean particle diameter of silver nanoparticles. The synthesized AgNPs were used for photocatalytic degradation of Orange G and Direct blue-15 (OG and DB-15), which were analyzed by UV-visible spectroscopy. Maximum degradation percentage of OG and DB-15 azo dyes was observed, without any significant silver leaching, thereby signifying notable photocatalytic properties of AgNPs.     

Cross-coupling reactions of alkenylsilanols with fluoroalkylsulfonates

[reaction: see text] The design and development of an effective protocol for the palladium-catalyzed cross-coupling of (E)- and (Z)-heptenyldimethylsilanols with organo-triflates and nonaflates is described. Optimization of this coupling focused on the issues of both reactivity and stability of the psuedohalides in the presence of the nucleophilic fluoride promoter for the coupling. The crucial role of varying amounts of water to modulate the reactivity of the fluoride ion is highlighted.     

Synthesis of nanosized TiO2 powder by sol gel method at low temperature

ABSTRACT

Nanotechnology is all about making products from very small constituents, components or subsystems to gain greatly enhanced material properties and functionality. Nanocrystalline anatase TiO₂ was prepared by a facile sol–gel route at a temperature of 50°C under mild conditions. Titanium tetraisopropoxide (TTIP) was used as a titanium precursor, and 2-propanol was used as a solvent. XRD, TEM, SEM, FT-IR and BET were applied to characterize the crystal phase. The Crystalline size of TiO₂ powder has been obtained with diameter < 30 nm for anatase at 500°C using an acid.     

Core-shell structure of degradable, thermosensitive polymeric micelles studied by small-angle neutron scattering

The structure of assemblies of block copolymers composed of thermosensitive, biodegradable poly(N-(2-hydroxypropyl) methacrylamide-dilactate) and poly(ethylene glycol) (pHPMAmDL-b-PEG) has been studied by small-angle neutron scattering (SANS). Three amphiphilic copolymers with a fixed PEG of 5 kDa and a partially deuterated pHPMAmDL(d) block of 6700, 10400, or 21200 Da were used to form micelles in aqueous media by heating the polymeric solution from below to above the cloud point temperature (around 10 degrees C) of the thermosensitive block. Simultaneous and quantitative analysis of the scattering cross sections obtained at three different solvent contrasts is expedited using core-shell model, which assumed a homogeneous core of uniform scattering length density. The mean core radius increased from 13 to 18.5 nm with the molecular weight of the pHPMAmDL(d) block, while the thickness of the stabilizing PEG layer was around 8 nm for the three investigated assemblies. In addition, the volume fraction values of the stabilizing PEG chains in the shell are low and decreased from 31% to 14% with increasing the size of pHPMAmDL(d) block which shows that the shell layer of the assemblies is highly hydrated. The corresponding PEG chain grafting densities decreased from 0.22 to 0.11 nm-2 and the distance between PEG chains on the nanoparticles surface increased from 2.4 to 3.4 nm. The pHPMAmDL-b-PEG micelles showed a controlled instability due to hydrolysis of the lactic acid side groups in the thermosensitive block; that is, an increase of the degradation time leads to an increase of the size of the core which becomes less hydrophobic and consequently more hydrated. Neutron experiments supplied accurate information on how the size of the core and the micelle's aggregation number changed with the incubation time. This feature and the initially small size and dense structure in aqueous solution make the polymeric micelles suitable as carriers for hydrophobic drugs.     

Isometries of a generalized numerical radius

For 0<q<1, the q-numerical range is defined on the algebra M_n of all n×n complex matrices by

W_q(A)={x^∗Ay:x,y∈Cⁿ,∥x∥=∥y∥=1,〈y,x〉=q}.     

Single Step Fabrication of Chitosan Nanocrystals Using <Emphasis Type="Italic">Penaeus semisulcatus</Emphasis>: Potential as New Insecticides,Antimicrobials and Plant Growth Promoters

In this study, chitosan nanoparticles (CH-NPs) were synthesized using Penaeus semisulcatus shrimp shells and characterized using UV–Vis and FT-IR spectroscopy, as well as XRD and HR-TEM analyses. CH-NPs were investigated for growth inhibition properties against selected species of bacterial and fungal pathogens, showing performances higher or comparable over positive controls, respectively. Furthermore, CH-NPs were tested on three important mosquito vectors, achieving LC₅₀ from 12.27 to 14.62 µg/ml. In addition, CH-NPs were evaluated using in vitro plant tissue culture by rooting gel method, to enhance the vegetative growth of the medicinal plant species Sphaeranthus indicus. With the simple technique presented here, large-scale industrial production of CH-NPs is possible. They can be used to develop pesticides highly effective against mosquito vectors of high medical and veterinary importance, as well as for plant tissue culture and food packaging applications.     

Estimation of the Scale Deposits Near Wellbore via Software in the Presence of Inhibitors

In this study, computer software was used in order to estimate the scaling tendency of the commingling of two incompatible waters existed in Egyptian oil reservoirs of Gulf of Suez area. The chemical analyses of the two incompatible waters (injection and formation waters) have been used as input data to the computer simulator. The reservoirs characterized by a temperature of 90–127°C, and salinity of 100,000–230,000 ppm. The scaling results for the commingling of both injection and formation water at reservoir temperatures and pressures are recorded. The results of theoretical software and laboratory jar-testing were compared. It was found that mixing of the injection water and formation water may lead to calcium carbonate and barium sulphate scaling at 40% formation water in absence of scale inhibitor. Two types of commercial scale inhibitors (AII and SII) were evaluated using both jar test method and National Association of Corrosion engineers standard test methods. The results showed the mastery of AII over the commercial inhibitor SII in preventing of both scales.