Polymerization of styrene with the VOCL3–AlEt2Br catalyst system

The rate of polymerization with the VOCl₃–AlEt₂Br catalyst system at 30°C. in n-hexane reached a maximum at an Al/V molar ratio of 1.5. At this ratio, the rate of polymerization was first-order with respect to catalyst and second-order with respect to monomer concentrations. The apparent activation energy calculated was 6.4 kcal./mole. Diethylzine was found to act as a chain transfer agent. However, the molecular weights of polymers obtained were low. The possibility of bromide-containing catalyst sites acting in the termination reaction has been investigated. The average valence of vanadium is discussed in relation to molecular weights.     

The flow of incompressible immiscible fluids between two plates

Summary The flow of layers of different heights of n incompressible immiscible fluids between two plates has been considered and it has been shown that whatever be the number of fluids and whatever be their heights, a unique velocity maximum always exists and a formula for finding the layer in which this maximum occurs has been given. For the particular case of two layers it has been shown that the curve of total flux against the ratio of the heights of the fluids has always a point of inflexion. Further this ratio has been determined so that the fluxes of the two fluids are equal.     

A comparative study of gamma-ray interaction and absorption in some building materials using Zeff-toolkit

The gamma-ray shielding behaviour of a material can be investigated by determining its various interaction and energy-absorption parameters (such as mass attenuation coefficients, mass energy absorption coefficients, and corresponding effective atomic numbers and electron densities). Literature review indicates that the effective atomic number (Z_eff) has been used as extensive parameters for evaluating the effects and defect in the chosen materials caused by ionising radiations (X-rays and gamma-rays). A computer program (Z_eff-toolkit) has been designed for obtaining the mean value of effective atomic number calculated by three different methods. A good agreement between the results obtained with Z_eff-toolkit, Auto_Z_eff software and experimentally measured values of Z_eff has been observed. Although the Z_eff-toolkit is capable of computing effective atomic numbers for both photon interaction (Z_eff,PI) and energy absorption (Z_eff,En) using three methods in each. No similar computer program is available in the literature which simultaneously computes these parameters simultaneously. The computed parameters have been compared and correlated in the wide energy range (0.001–20?MeV) for 10 commonly used building materials. The prominent variations in these parameters with gamma-ray photon energy have been observed due to the dominance of various absorption and scattering phenomena. The mean values of two effective atomic numbers (Z_eff,PI and Z_eff,En) are equivalent at energies below 0.002?MeV and above 0.3?MeV, indicating the dominance of gamma-ray absorption (photoelectric and pair production) over scattering (Compton) at these energies. Conversely in the energy range 0.002–0.3?MeV, the Compton scattering of gamma-rays dominates the absorption. From the 10 chosen samples of building materials, 2 soils showed better shielding behaviour than did other 8 materials.     

3-O-Methl-6-desoxy-L-talose,Synthese und Identifizierung mit L-Acovenose. Desoxyzucker, 43. Mitteilung

3-O-methly-6-deoxy-L -talose has been synthesized starting from 1, 2–5, 6-di-O-isopropylidene-α-D -allose ( 1 ). Methylation, selective acidic hydrolysis, sodium periodate oxidation and GRIGNARD reaction with CH₃MgBr gave a mixture of the 1, 2-isopropylidene derivatives of 3-O-methyl-6-deoxy-D -allose and 3-O-methyl-6-deoxy-D -allose ( 7 ) and 3-O-methyl-6-deoxy-L -talose ( 8 ) (L -acovenose) could be obtained. Oxidation of the latter gave the corresponding crystalline lactone, which could be indentified with a sample obtained from natural L -acovenose.     

Study of the formation of bimetallic aqueous Tl/Cu sols by gamma and electron irradiation

The spectral characteristics of the bimetallic sols produced by gamma and electron irradiation of mixed solutions of Tl⁺–Cu²⁺ ions in different ratios have been studied in aqueous medium. The intermediate transient species have also been characterized by the technique of pulse radiolysis. The rate constant for the reaction of Cu²⁺ion with the Tl⁺ ion reduction species was founded by 4×10⁹ dm³ mol⁻¹s⁻¹. Developmental absorption spectra in gamma radiolytic reduction of the mixed ions indicated reduction of Tl⁺ ion on the surface of small copper particles, resulting in bimetallic-sol with core of copper. The presence of a small concentration of Cu²⁺ ion was found to restrict the agglomeration process of thallium particles at near neutral pH conditions. The reducing capability of the bimetallic sols was found to be proportional to the thallium content in the sol. The observed UV–Vis spectra of the mixed Tl/Cu sols produced on electron irradiation showed much lower absorption in the higher wavelength region and were more close to that of the pure sol of the ion, present in higher concentration in the feed solution. Thus, the high dose rate-assisted stabilization of smaller thallium particles. Size of all these bimetallic sol particles was much less than 50 nm.     

Characterization of electrode material for electrostatic spray charging: Theoretical and engineering practices

A new electrode material such as Nickel (200/201 forged bar) is used for spray charging. Comparative study has been made using different materials electrode viz. Nickel, Copper, Stainless Steel, Brass, and Aluminum; electrodes were ring shape with same inner diameter 15.0 mm and outer diameter of 22.0 mm of thickness 3.5 mm. The experiments were conducted in air atmosphere at ambient conditions (T = 20 ± 2 °C, RH = 46 ± 3%), with an air feed rate of 24.6 l/min, liquid feed rate 90.0 ml/min and applied voltage ranging from 0 to +3.0 kV. The results of applied induction electrification process were characterized by a charge-to-mass factor as a function of electrode material.     

3-T MR-guided brachytherapy for gynecologic malignancies

Gynecologic malignancies are a leading cause of death in women worldwide. Standard treatment for many primary and recurrent gynecologic cancer cases includes external-beam radiation followed by brachytherapy. Magnetic resonance (MR) imaging is beneficial in diagnostic evaluation, in mapping the tumor location to tailor radiation dose and in monitoring the tumor response to treatment. Initial studies of MR guidance in gynecologic brachytherapy demonstrate the ability to optimize tumor coverage and reduce radiation dose to normal tissues, resulting in improved outcomes for patients.     

Structure-activity relationships in 3-isothiazolones

The biological activity of a series of structurally diverse 3-isothiazolones (1) has been assessed by evaluating the minimum inhibitory concentration required to inhibit the growth of E. Coli. The structure and electronic properties of these derivatives have been calculated using both semi-empirical and ab initio molecular orbital methods. Multi-linear regression analysis shows no correlation between the experimental activity of the 3-isothiazolones and either the calculated geometries, electronic properties, or the frontier orbital energies of these derivatives, but a reasonable relationship is found with other parameters including their calculated solvation energies, suggesting that diffusion may play an important role in their mode of action.