Electron effective mass in InuGa1−uPvAs1−v for 0 ≤ v ≤ 1

The electron effective mass in In_uGa_1−uP_vAs_1−v has been measured on seven samples lattice-matched to InP and evenly spaced in values of v between 0 and 1, using the temperature dependence of the amplitude of the Shubnikov-de Haas oscillations at high magnetic fields. Values of the carrier concentrations, Hall mobilities and Dingle temperatures measured on these samples are also reported. Work sponsored in part by the National Science Foundation, Grant No. ENG 76-09586, and in part by International Telephone and Telegraph Electro-Optical Products Division. Work done in part at the M.I.T. Francis Bitter National Magnet Laboratory. Funded in part by the National Science Foundation under Grant No. DMR-76-80895.     

Carotene cooxidation activity of tomato lipoxygenase-2

The tomato isoenzyme lipoxygenase-2 presented a carotene cooxidation activity; it showed more activity with linoleic acid as substrate than with linolenic acid. The lipoxygenase was inhibited by reagents of the disulphide groups (dithiothreitol and 2-mercaptoethanol) and —SH groups ((4-hydroxymercuri)benzoic acid and iodoacetamide) and some antioxidants.     

Decisions about confidentiality in medical student mental health settings.

Investigated orientations toward confidentiality of 59 mental health practitioners in US medical schools who were requested to respond to 10 case vignettes representing a range of students' problems by indicating the action they would take. Results suggest that Ss were generally unwilling to break confidentiality in response to cluster of presenting problems that involved suicidal tendencies, sexual coercion/seduction, nonviolent social transgressions, and falsifying data. This was most pronounced when risk of suicide was evident. Only a bomb threat scenario clearly elicited responses suggesting a likely breach of confidence. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Synthesis of copolybibenzoates with thioether and ether groups in the flexible spacers

Main‐chain copolybibenzoates with flexible spacers bearing thioether and ether groups were obtained by melt‐transesterification of diethyl 1,1′‐biphenyl‐4,4′‐dicarboxylate and β‐thioether glycols (thiodiethylene glycol or thiotriethylene glycol), using titanium (IV) isopropoxide as catalyst. A side‐reaction of etherification occurred simultaneously with the polycondensation reaction, resulting in the formation of comonomer units with the structure of the dimer of the glycol. This side‐reaction was confirmed by the preparation of model compounds. The most probable mechanism for this etherification reaction is the formation of an intermediate three‐membered cyclic sulfonium ion by neighbouring sulfur participation. The thermal and X‐ray characterization of the synthesised copolymers indicated that a smectic mesophase was rapidly obtained on cooling the copolymers derived from thiodiethylene glycol from the melt and this phase was transformed slowly into a more ordered structure. In contrast, copolymers derived from thiotriethylene glycol did not exhibit liquid‐crystalline phases and their crystallisation from the isotropic melt was very fast. It was found that the copolymerization increased the mesophase stability. Finally, the results obtained were compared with those of corresponding homopolybibenzoates with methylene or oxymethylene spacers. Copyright © 2005 Society of Chemical Industry     

Fractionation of linear saturated (co)polyesters by differential precipitation

Summary Samples of poly(ethylene terephthalate) (PET), poly(ethylene terephthalate-co-naphthalene-2,6-dicarboxylate) (PENT) and poly(ethylene naphthalene-2,6-dicarboxylate) (PEN), materials which find application in textile and packaging industry, have been investigated, with the aim to obtain narrow molecular weight fractions suitable for further characterization. Preliminary results concerning with the fractionation of gram-quantities of the polyesters are reported, using a method based on the fractional precipitation from a phenol/1,2,4-thrichlorobenzene solution of the polymer, using n-heptane as non-solvent. Obtained fractions have been characterized by intrinsic viscosity measurements and Gel Permeation Chromatography analysis.     

Adsorption of Arsenic on Activated Charcoal

This study explores the adsorption behavior of As(III) and As(V) on activated charcoal under the various conditions of solution pH and temperature. The adsorption loading of As(III) remains constant in the pH range from 0.16 to 3.5, while that of As(V) shows a maximum value at pH2.35 when the pH varies from 0.86 to 6.33. The isosteric heat of adsorption for As(III) varies from 4 to 0.75 Kcal/mole and that for As(V), from 4 to 2 Kcal/mole with varying surface loading. The magnitude of these values suggests that the adsorption of arsenic is by physisorption and due to weak forces such as Van der Waals forces. Activated charcoal adsorbs As(V) by 2.5% of its own weight while it absorbs As(III) by 1.2% of its own weight when the equilibrium concentration of each species is 22 × 10^?2 molar. Since arsenic has appreciable adsorbability on activated charcoal, this adsorbent may be a viable candidate to be used for removing arsenic from solution. Further studies to determine more information on the selectivity of arsenic over other valuable metal ions and the ones to determine the effects of other cations such as, ferric, calcium, and magnesium ions are suggested as a next step.     

Théorie de l’information. Structure et modélisation d’un réseau de connexion

The authors study the switching network structures with emphasis on the information theory aspects of the problem (definition of combinatorial power and complexity). Different routing rules and rearranging algorithms are surveyed. Finally, a numerical simulation points out the extensivity concept which is useful in the study of switching networks models of reduced size.     

A quantitative study of air-borne particulate matter collected on membrane filters by means of X-ray photoelectron spectroscopy

The capability of X-ray photoelectron spectroscopy, XPS or ESCA, in analysing oxidation states and measuring the concentration of elements present in air pollution particulates collected on membrane filters is evaluated. Semi-quantitative data are compared with those from XRF and wet chemical analysis. Differences of about a factor of 2.0–2.5 are found which are critically discussed in relation to particle size and the distribution of ionic species. The importance of intrinsic properties of matrix materials and instrumental factors is also discussed.