A gas transport system for fast chemistry

The gas transport system (GTS) brings short-lived radioactive nuclides to low back-ground areas for chemical separation and/or on-line α-, γ- and X-ray analysis. A pressure difference of a few Torr (3–5) is enough to maintain the transport, thus eliminating the need for costly pumping systems and making it possible to perform chemistry at atmospheric pressure. This technique was applied to a variety of radioactive sources. There is some Z-dependence on the transportation efficiency for the various transported nuclides as a function of the transporting gas and extracting solvent.     

Chemical and environmental implications of visible and near-infrared spectral features of salt crusts formed from different brines

This work describes a laboratory experiment intended to study the formation and spectral reflectance properties of stratified salt crusts that cause severe environmental degradations to soil and water resources in arid regions. Salt crusts were prepared by evaporating three types of saline solutions consisting of i) NaCl - Na2SO4, ii) Na2SO4 - MgSO4, and iii) NaCl - MgSO4 at an initial concentrations of 50 mmol L(-1). They were examined for evaporite mineralogy using X-ray diffraction, optical and reflected microscopes, and for spectral reflectance with a high-resolution spectroradiometer (GER 3700) in the visible and near-infrared regions (400-2500 nm). The study documented chemical and environmental implications of the spectral properties of salt formed from the studied saline-systems. The reported results can be used to understand remotely sensed signatures of salt crusts and their implications.     

A novel framework of N—H...Br hydrogen bonds forming Br(4,4′‐bipyridinium)4 supramolecular synthons: bis(4,4′‐bipyridinium) tris[tetrabromidoferrate(III)] bromide

In the asymmetric unit of the title compound, (C₁₀H₁₀N₂)₂[FeBr₄]₃Br, the Fe atoms are in a distorted tetrahedral environment. The crystal structure contains a novel arrangement of Br(4,4′‐bipyridinium)₄ supramolecular synthons assembled via short N—H...Br hydrogen bonds (H...Br = 2.55, 2.40, 2.38 and 2.55 Å), where four cations surround one nonbonded bromide ion in a tetrahedral arrangement. These synthons are further connected by hydrogen bonds using the remaining terminal NH hydrogens in each cation and the Br⁻ ions to form an adamantoid‐like network and thus produce a three‐dimensional supramolecular architecture with the [FeBr₄]⁻ ions located in the cavities. The structure shows no significant intermolecular Br...Br, Br...aryl or aryl–aryl interactions.     

Bis(enaminones) as Versatile Precursors for Novel Bis([1,2,4]triazolo[1,5‐a]pyrimidines) and Bis(2‐thioxo‐2,3‐dihydropyrido[2,3‐d]pyrimidin‐4(1H)‐ones)

Novel bis([1,2,4]triazolo[1,5‐a]pyrimidines) and bis(2‐thioxo‐2,3‐dihydropyrido[2,3‐d]pyrimidin‐4(1H)‐ones) were prepared utilizing bis(enaminones) as precursors. The structures of the prepared compounds were elucidated by several spectral tools as well as elemental analyses.     

Microwave-assisted three component synthesis of novel bis-fused quinazolin-8(4H)-ones linked to aliphatic or aromatic spacer via amide linkages

Abstract

A novel series of bis(tetrahydro[1,2,4]triazolo[5,1-b]quinazolin-8-ones) and bis(tetrahydrobenzo[4,5]imidazo[2,1-b]quinazolinones) containing amide linkages were regionselectively prepared via a three-component reaction of bis(aldehydes) with dimedone and 3-amino-1,2,4-triazole (or 2-aminobenzimidazole) under conventional heating as well as under microwave irradiation.     

Adiabatic self-focusing in media with spatially variable nonlinearity

An optical medium whose nonlinearity can be spatially adjusted is considered to study beam reshaping. The concept is applied to perform adiabatic self-focusing of broad beams. Experimental results are obtained in a photorefractive lithium niobate crystal where the self-focusing nonlinearity is controlled over propagation by a temperature gradient. As a demonstration, gradual self-focusing is shown to transform an incoming beam into an output circular spot 10 times smaller over a 2 cm long crystal submitted to a 30 °C temperature gradient. Once formed, the adiabatic self-focused beam has inscribed a funnel waveguide in the crystal.     

Versatile Pectin Grafted Poly (N-isopropylacrylamide); Modulated Targeted Drug Release

This study describes synthesis and optimization of pectin grafted poly(N-isopropylacrylamide) hydrogels as vehicles for colon-targeted theophylline model drug release. The gels were prepared in the presence of N, N′–methylenebisacrylamide (MBAA) crosslinker and ceric ammonium nitrate (CAN) initiator under N₂ atmosphere. Optimum conditions, in terms of percent of grafting (%G), were determined as follows: pectin = 1.0 g, [NIPAAm] = 26.51 mM, [MBAA] = 0.65 mM, [CAN] = 0.073 mM, polymerization temperature = 30°C and time = 4.0 h. Hydrogels were characterized by FTIR, TGA, DSC, XRD and SEM. The formed hydrogel did not have a thermo-sensitivity behavior. The in vitro percent drug release was studied in terms of different percent of grafting and different polymerization temperatures under two pH values namely 5.5 and 7.4. Conclusively, the optimum colon-targeted vehicle properties that provide the least drug release at pH5.5 and the most drug release at pH7.4 were as follows: [NIPAAm] = 26.51 mM and [MBAA] = 0.56 mM, polymerization temperature = 30°C and %G = 55.5.