Pressure effects on flow and fracture of Be-Al alloys

The flow and fracture behavior of Be-Al alloys were determined in tension with different levels of superimposed pressure. The Be-Al alloys were prepared by Brush Wellman, Inc. (Cleveland, OH) from prealloyed powders processed to either a hot isostatically pressed (“hipped”) or cold isostatically pressed and extruded condition. Significant effects of pressure on both the flow and ductility have been observed at room temperature, with implications on the formability of these materials. The effects of changes in processing conditions and stress state on the flow and fracture behavior are summarized in addition to both optical and scanning electron microscopy (SEM) examination of the fracture surfaces. Separate other studies on the alloy constituents (e.g., Al and Be) are also reported. The results are also compared to previous works on monolithic materials and composites tested with high pressure.     

Survival of Yersinia enterocolitica and Escherichia coli in spring water

Survival of pure and mixed cultures of Yersinia enterocolitica and Escherichia coli in sterile spring water stored at 4 degrees C was evaluated. Y. enterocolitica increased two or three logs during the first 3 weeks of incubation, and at the end of 64 weeks viable cells in numbers corresponding to the initial inoculum level were still detectable. However, after 1 week of incubation, the number of E. coli in water started to decrease and in 13 weeks time no E. coli was detected. More rapid decrease of E. coli was observed in mixed cultures.     

A note on computing environments and network reliability

Interest has increased during recent years in using microcomputers for implementation of network reliability algorithms. There are indications that some implementations suffer severe restrictions imposed by such a computing environment, whereas some other results indicate otherwise. This brief note attempts to clarify the apparently contradictory conclusions that would be naturally drawn from recent papers that treat this subject.     

Prebiotic synthesis of sequential peptides on the Hadean beach by a molecular engine working with nitrogen oxides as energy sources

Addressing the still open question of the prebiotic origin of sequential macromolecules (peptides, nucleic acids) on the primitive Earth, we describe a molecular engine (the primary pump), which works at ambient temperature and continuously generates, elongates and complexifies sequential peptides. This new scenario is based on a cyclic reaction sequence, whose keystep is the activation of amino acids into their N‐carboxyanhydrides (NCA) through nitrosation by NOx. This process could have taken place on tidal beaches; it requires a buffered ocean, emerged land and a nitrosating atmosphere. With the help of geochemical studies and computer simulations of atmosphere photochemistry, we show that the primitive Earth during the Hadean may have satisfied all these requirements. © 2001 Society of Chemical Industry.     

Lack of de-epoxidation of type B trichothecenes in incubates with human faeces

The ability of human gastrointestinal organisms to transform the trichothecenes 3-acetyldeoxynivalenol and nivalenol was investigated. Samples of human faeces were incubated under anaerobic conditions for 48 h with the toxins. They were then extracted and analysed for trichothecenes and metabolites. 3-Acetyldeoxynivalenol was metabolized to deoxynivalenol during the incubation period. In contrast to what has been reported for other species such as rats, mice and pigs, no de-epoxidated metabolites were detected in the faecal incubates. The toxicological significance of the difference in the intestinal ability to transform trichothecenes between species is unknown.     

Structural properties of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 relaxor ferroelectric thin films on SrRuO3 conducting oxides

Coating of 0.65Pb(Mg_1/3Nb_2/3)O₃–0.35PbTiO₃ (PMN–PT) relaxor ferroelectrics by a sol–gel method is followed by growth of epitaxial SrRuO₃ (SRO) metallic oxide electrodes on SrTiO₃ (STO) single-crystal substrate by pulsed laser deposition. High-quality PMN–PT films on SRO with preferred growth orientation were successfully fabricated by controlling the operation parameters. Structural properties of relaxor ferroelectric PMN–PT thin films on SRO/STO substrates have been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). In-plane and out-of-plane alignments of the heterostructure are confirmed and the structural twinning of the materials are also revealed.     

Dissolution kinetics of ulexite in acetic acid solutions

Ulexite is an important boron mineral used for the production of boron compounds. The aims of this study are to examine the dissolution kinetics of ulexite in acetic acid solutions, and to present an alternative process to produce boric acid. In order to investigate the dissolution kinetics of ulexite in acetic acid solutions, the concentration of solution, reaction temperature, solid-to-liquid ratio, and particle size were selected as experimental parameters. It was determined that the dissolution rate of ulexite increased with increasing solution concentration and temperature and decreasing particle size and solid-to-liquid ratio. The activation energy of the process was found to be 55.8 kJ/mol.     

Oil yield and compressibility modeling during microscale expression: Criteria for linseed breeding

Seven linseed varieties were harvested at seven times before complete maturity. Microscale oilseed expressions were subsequently carried out on it. A pressure of 10 MPa was applied for 1 h under uniaxial stress. The results were characterized in terms of oil, water and mucilage content, harvest date and oil yield. The piston displacement versus time (creep curves) was described by a four‐Kelvin‐Voigt elements viscoelastic model. Parameters were derived from the model, such as the mechanical properties of seeds (compressibility moduli), showing that the viscoelastic model fits well the experimental data (R² ≈ 0.999). The modeling parameters were combined with some biochemical data in order to predict the kinetics of oil extraction.     

On the crystal structure and magnetic properties of the ternary rare earth compounds RETSb2 with RE rare earth and T Ni, Pd, Cu and Au

Novel compounds RETSb₂ have been prepared and characterized for T Cu (RE rare earth from La to Lu), Ni (RE La to Ho), Pd (RE La to Tb) and Au (RE La to Sm). From X-ray powder diffraction analyses all compounds were found to crystallize as the ZrCuSi₂ type. Magnetic susceptibilities were generally measured in the temperature range from 4 to 100 K. YCuSb₂ and LaTSb_z are temperature-independent paramagnets. RETSb₂ compounds are found to order antiferromagnetically below T = 20 K. PrPdSb₂ and TbPdSb₂ undergo metamagnetic transitions, whereas PrCuSb₂ and ErCuSb₂ are simple ferromagnets. The Sm-containing compounds are typical Van Vleck paramagnets owing to the closely spaced multiplets.