Some electrical properties of wood pulp treated with sodium hydroxide

The effect of the degree of crystallinity and degree of polymerization on the electrical properties of soda-treated wood pulp has been investigated. The dielectric constant (E′) and the dielectric loss (E″) were measured for the treated samples over a frequency band 0.2–10 MHz at 20°C. Also, the electrical conductivity (σ) was calculated from the measured data of the dielectric constant. From the results obtained we found that the degree of crystallinity and the degree of polymerization decrease with time of oxidation while the number of carboxylic groups increased. E″,E′, and σ were found to increase with the decrease in the degree of crystallinity.     

Synthesis and Crystal Structure of <Emphasis Type="Italic">Tris</Emphasis>-(<Emphasis Type="Italic">N</Emphasis>–<Emphasis Type="Italic">N</Emphasis> dimethyl benzylammonium)-hexachlorobismuthate(III)

Abstract  The salt tris-(N–N dimethyl benzylammonium)-hexachlorobismuthate(III) crystallizes in the triclinic system P1 with unit cell parameters: a = 9.0300(12), b = 9.9220(3), c = 19.575(2) ?, α = 79.955(5), β = 89.952(2), γ = 88.108(6)°, V = 1726.0(3) ?³, Z = 2. The examination of the structure shows an alternate stacking of inorganic layers of hexachlorobismuthate(III) anions and organic layers of [C₆H₅CH₂NH(CH₃)₂]⁺ cations parallel to the a-axis. The cohesion forces of the packing of N–N dimethyl benzylammonium units in the layer and between two adjacent layers are provided by hydrogen bonds (N–H⋯Cl) and van der Waals contacts. Index Abstract  The examination of the structure shows a layer arrangement parallel to the a-axis: planes of octahedral anions [BiCl₆]³⁻ alternate with planes of [C₆H₅CH₂NH(CH₃)₂]⁺ cations (Fig. 3). The cohesion forces of the packing of the N–N dimethyl benzylammonium units in the layer and between two adjacent layers are provided by hydrogen bonds (N–H⋯Cl) and van der Waals contacts. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synthesis and QSAR Study of Some Novel Heterocyclic Derivatives as In Vitro Cytotoxic Agents

2,3‐Diaryloxirane‐2,3‐dicarbonitriles have employed in heterocyclic synthesis in many organic reactions. Authors highlight its use as intermediate in the synthesis of various organic compounds through the reaction with different nitrogen nucleophiles as methyl hydrazine, thiourea, thiosemicarbazide, methylglycinate, and others to furnish new heterocyclic derivatives. They are also used as key starting materials to construct some important heterocycles. Structures of all newly synthesized products are substantiated by studying their micro analytical and spectral data. Some of newly synthesized compounds were evaluated for their in vitro cytotoxic effects against a panel of three human tumor cell lines, namely, Hep‐G2, Hela, and MCF‐7. Most of the newly synthesized compounds ( 1a , 2a , 2d , 3 , 4 , 5 , 6a , 6c , 6d , 7a , and 7b ) inhibited cell proliferation with IC₅₀ values in range of 0.52–5.21 μΜ. For activity against HepG2 cell line, compounds 5 , 6a , 6d , and 7b emerged as the most active members. The Hela cell line showed highest sensitivity toward compounds 2a , 2d , and 6c whereas compounds 2d and 6c showed the highest inhibitory activity against MCF‐7 cell line.     

Synthesis and Anticancer Evaluation of Some Novel Quinazolin‐4(3H)‐one Derivatives

A new series of quinazolinone derivatives bearing pyridine, pyrimidine, pyrazole, or pyran moieties were synthesized for the purpose of anticancer cell line evaluation. Synthesis of these derivatives was achieved by the reaction of the ketone 2 with the appropriate aldehydes in the presence of either ethylcyanoacetate or malononitrile and ammonium acetate in one‐pot reaction. Chalcones 6 reacted also with hydrazine hydrate to give the corresponding pyrazolines 7 and reacted with urea or thiourea to give the 2‐oxopyrimidines or the 2‐thioxopyrimidines 8 , respectively. Evaluation of some representative examples of the newly synthesized compounds against cancer cell lines showed promising activity as anticancer agents.     

Experimental and theoretical electronic absorption spectra of 2,4‐diphenyl‐1,5‐benzothiazepine and its derivatives: Solvatochromic effect and time dependent density functional theory approach

Electronic spectra of 2,4‐diphenyl‐1,5‐benzothiazepine and some of its derivatives in 1,2‐dichloromethane and ethanol are investigated experimentally and theoretically using the time dependent density functional theory (TD‐DFT) method at the B3LYP/6‐311G** level of the theory. The origin of the spectrum of the parent compound is found to be an additive one. The observed ultra violet (UV) spectra in both solvents show two bands S1 in the range between 312–334 nm and S2 in the range between 248–272 nm. The solvent effect is investigated experimentally and theoretically and a blue shift is observed, which is explained in terms of a hydrogen bond model between the solvent and the most negative site of the solute (N atom). This theoretical model is robust in reproducing the experimental blue shift and calculating the hydrogen bond energy and hydrogen bond length. The extent of delocalization and charge transfer processes of the studied compounds is estimated and discussed in terms of natural bond orbital (NBO) analysis and second order perturbation interactions (E²) between donors and acceptors. The effect of substituents of the studied compounds in both solvents shows a noticeable red shift attributed to hyperconjugation effects of the π electron systems of the different moieties.     

Synthesis and reactions of thiosemicarbazides,triazoles, and <Emphasis Type="Italic">Schiff</Emphasis> bases as antihypertensive α-blocking agents

Methyl 2-(thiazol-2-ylcarbamoyl)acetate was synthesized and used as starting material. It was treated with hydrazine hydrate to afford the hydrazide, which was reacted with nitromethane and formaldehyde to give the saturated nitropyrimidine. The hydrazide was reacted with phenyl isothiocyanate to afford the thiosemicarbazide, which was cyclized with ethyl bromoacetate, sodium hydroxide, or sulfuric acid to afford N-phenylthiazolidinone, N-phenyltriazole, and thiadiazolyl derivatives. The methyl 2-(thiazol-2-ylcarbamoyl)acetate was coupled with diazonium salts of aniline, 4-chloroaniline, 4-bromoaniline, or 4-aminobenzenesulfonamide to afford the carbamoyl acetates, which were reacted with 2-aminobenzimidazole, 1,2,4,5-tetrachlorophthalic anhydride, and hydrazine hydrate to afford the corresponding thiazolylmalonamide, tetrachloroisoindolylimide, and tri-azole derivatives. Schiff bases and imides are newly synthesized candidates obtained via simple condensation of the hydrazide with aldehydes, 2,3-pyridinedicarboxylic anhydride, or 1,8-naphthalenedicarboxylic anhydride. The pharmacological screening showed that many of these compounds have good antihypertensive α-blocking activity and low toxicity. Correspondence: Abd El-Galil E. Amr, National Research Center, Applied Organic Chemistry, Dokki, Cairo, Egypt.     

Algorithms for the CMRH method for dense linear systems

The CMRH (Changing Minimal Residual method based on the Hessenberg process) method is a Krylov subspace method for solving large linear systems with non-symmetric coefficient matrices. CMRH generates a (non orthogonal) basis of the Krylov subspace through the Hessenberg process, and minimizes a quasi-residual norm. On dense matrices, the CMRH method is less expensive and requires less storage than other Krylov methods. In this work, we describe Matlab codes for the best of these implementations. Fortran codes for sequential and parallel implementations are also presented.     

Multisyringe Flow Injection Analysis of Tropomyosin Allergens in Shellfish Samples

This paper presents the development and the application of a multisyringe flow injection analysis system for the fluorimetric determination of the major heat-stable known allergen in shrimp, rPen a 1 (tropomyosin). This muscle protein, made up of 284 amino acids, is the main allergen in crustaceans and can be hydrolyzed by microwave in hydrochloric acid medium to produce glutamic acid, the major amino acid in the protein. Glutamic acid can then be quantified specifically by thermal conversion into pyroglutamic acid followed by chemical derivatization of the pyroglutamic acid formed by an analytical protocol based on an OPA-NAC reagent. Pyroglutamic acid can thus be quantified between 1 and 100 µM in less than 15 min with a detection limit of 1.3 µM. The method has been validated by measurements on real samples demonstrating that the response increases with the increase in the tropomyosin content or with the increase in the mass of the shrimp sample.     

Foundations of retention in partition chromatography

The connection between the observable output in column chromatography (retention time, retention volume, retention factor, separation factor, etc.) and system properties (hold-up volume, pressure, temperature, isotherm behavior, etc.) is discussed from a practical and mechanistic perspective for gas–liquid chromatography, reversed-phase liquid chromatography, supercritical fluid chromatography, micellar electrokinetic chromatography, and capillary electrochromatography. The unifying feature of these techniques is that retention can be described by a partition model, although not always exclusively. When over simplistic system models are used to explain variation in retention parameters they frequently mask the true reasons for poor repeatability and difficulties in transfer between system. Methods employing relative retention afford higher precision but may contain residual uncorrected errors. For those systems with several separate mechanisms contributing to retention the effective retention parameters can no longer be interpreted by simple partition models. The broadly based and practically focused material in this article affords an illustration of the often complicated relationship between system properties and retention, and the dangers that lurk in simplified retention models if the validity of their underlining approximations is not appropriate for the system under study.