The initiation of crack growth in linear polyethylene

The initiation of crack growth was observed in single edge notched tensile specimens under plane strain conditions. The shape of the deformation zone varied from being balloon-like above 12 MPa and nearly planar below but neither shape conformed to that predicted by the conventional shear type yield criteria. The initial damaged zone grew at a constant velocity with a stress dependence ofV=V ₀ ⁿ . The spectrum of damage morphologies that preceed crack growth consists of a leading edge of crack-like pores followed by a region of increasing fibrillation which is terminated by a region of increasing fibril fracture.     

The thermal reactions of montmorillonite studied by high-resolution solid-state29Si and27Al NMR

Only very slight changes are observed in the²⁹Si and²⁷Al solid-sate magic-angle spinning NMR spectra of a montmorillonite containing almost equal numbers of octahedral aluminium and magnesium ions when its interlayer water is driven off by heating. The²⁹Si NMR spectra are unaffected by dehydroxylation which begins at 450° C, but the²⁷Al spectra show a decrease in total intensity, possibly due to the formation of 5-coordinated aluminium, with a slight increase in the intensity of the tetrahedral aluminium resonance. On the basis of these results, a structural model is proposed for the dehydroxylate phase and its formation mechanism is discussed. The destruction of the dehydroxylate X-ray pattern at 850° C and the subsequent recrystallization of the high-temperature products (-quartz, enstatite and high-cordierite at 1100° C;-cristobalite, enstatite and sapphirine at 1200° C) is accompanied by changes in the silicon and aluminium NMR spectra and in the⁵⁷Fe Mbssbauer spectra which are fully consistent with the known structural features of these phases.     

Nanogoldpharmaceutics (i) The use of colloidal gold to treat experimentally-induced arthritis in rat models; (ii) Characterization of the gold in Swarna bhasma, a microparticulate used in traditional Indian medicine

Nanosized gold particles (27 +/− 3 nm) have been proven to be effective in ameliorating the symptoms of mycobacterial-, collagen- and pristane-induced arthritis in rat models. This contrasts with the drug sodium aurothiomalate that was only effective against mycobacterial-induced arthritis but not to the same extent as Au⁰. Gold in the traditional Indian Ayurvedic medicine,Swarna bhasma (gold ash), has been characterized as globular particles of gold with an average size of 56–57 nm.     

Association of seed size with genotypic variation in the chemical constituents of soybeans

Ten soybean genotypes grown in 1992 with seed size ranging from 7.6 to 30.3 g/100 seeds and maturity group V or VI were selected and tested for oil and protein content and for fatty acid composition. In these germplasm, protein varied from 39.5 to 50.2%, oil, 16.3 to 21.6%, and protein plus oil, 59.7 to 67.5%. Percentages of individual fatty acids relative to total fatty acids varied as follows: palmitic, 11.0 to 12.8; stearic, 3.2 to 4.7; oleic, 17.6 to 24.2; linoleic, 51.1 to 56.3 and linolenic, 6.9 to 10.0. Seed size showed no significant correlations with individual saturated fatty acids, protein or oil content. However, significant correlations were found between seed size and individual unsaturated fatty acids: positive with oleic, and negative with linoleic and linolenic. Oil and protein content were negatively correlated with each other. Among the major fatty acids, only the unsaturated were significantly correlated with each other: negative between oleic and linoleic or linolenic, and positive between linoleic and linolenic. A subsequent study with soybeans grown in 1993 generally confirmed these findings. Variation in relative percentages of unsaturated fatty acids andr values for most pairs of relationships were even higher than those obtained from the 1992 crop. Presented at the 85th AOCS Annual Meeting and Expo, Atlanta, Georgia, May 8–12, 1994.     

High resolution XPS characterization of chemical functionalised MWCNTs and SWCNTs

High resolution XPS analysis of chemical functionalised multi-wall carbon nanotubes (MWCNTs) and single wall carbon nanotubes (SWCNT) was done with ESCA300 (overall instrument resolution of 0.35 eV). Information to the degree of functionalisation was ascertained by argon ion bombardment of the samples followed by XPS analysis to detect the functional groups, the percentage atomic concentration of various elements present and whether or not the detected functional groups imposed a chemical shift on the CNT atoms. The results show that true chemical functionalisation was achieved and by argon ion bombardment these functional groups can be altered relative to the C 1s carbon atoms of the CNT. The choice of chemicals used for functionalisation, the techniques employed and the types of nanotubes treated are important factors in chemical characterisation. The carbon atom on the nanotube ring to which the functional group (atom) is bonded, the chirality of the CNT, the electronegativity of the functional group, the bond type and whether the CNT is single-wall or multi-wall, or cut (short) could play a role in determining the chemical shift on the CNTs atoms. These investigations are relevant to chemical functionalisation of carbon nanotubes for various applications for example DNA sensors and other biomedical sensors.