Microscopic observations of adiabatic shear bands in three different steels

Microscopic observations are made of the shear band material in three different steels: (1) an AISI 1018 cold-rolled steel (CRS), (2) a structural steel (HY-100), and (3) an AISI 4340 vacuum arc remelted (VAR) steel tempered to either of two hardnesses, RHC 44 or 55. To produce the shear bands, specimens were subjected to large shear strains at relatively high strain rates, ≈10³/s, resulting in essentially adiabatic deformation conditions. It was found that whenever the shear band led to fracture of the specimen, the fracture occurred by a process of void nucleation and coalescence; no cleavage was observed on any fracture surface, including the most brittle of the steels tested (RHC = 55). This is presumably due to the softening of the shear band material that results from the local temperature rise occurring during dynamic deformation. Differences in shear band behavior between the various microstructures are also described. Formerly Research Assistant, Brown University     

Birth order and sibling sex ratio in homosexual male adolescents and probably prehomosexual feminine boys.

The purpose of this study was to extend the findings, previously limited to adults, that male homosexuals have a greater than average proportion of male siblings and a later than average birth order. There were 2 matched groups of 156 probands. The homosexual-prehomosexual (HP) group included boys referred to a specialty clinic because of persistent cross-gender behavior plus homosexual adolescents with or without gender identity problems. The controls were male child and adolescent patients referred for reasons other than gender identity disorder, homosexuality, or transvestism. Both predicted results were obtained in comparisons of the HP group with the controls and with expected values for the general population. Psychosocial and biological theories have been advanced to explain why male homosexuals have later births and more brothers; however, none of these is well established. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extending the inelastic thermal spike model for semiconductors and insulators

The inelastic thermal spike framework was extended to incorporate an additional balance equation for the carrier density. Temporal and spatial evolution of carrier density, electronic and lattice temperatures were solved for silicon using a finite difference method. Calculated track radii for a range of electronic stopping powers are presented. The model allows us to fit the electron-phonon coupling to experimental data of amorphised track radii. We compare the methodology of this framework to an earlier inelastic thermal spike model, which is based on the two-temperature model for non-equilibrium processes in metals, and discuss its contribution to the understanding of microscopic processes following a swift ion irradiation event in band gap materials.     

Packaging and integration technologies for future high-frequency power supplies

This paper reviews data from the International Technology Roadmap for Semiconductors to establish where dc-dc converters are headed in the first decade of the new millennium. It focuses on the high performance computing (high current, fast response, high power density) and portable/handheld (low profile) sectors. Magnetics and power device packaging technologies needed to allow power supplies to move to operating frequencies in the 1-10 MHz region are discussed. It introduces the concept of magnetic components fully embedded (windings and core) in PCB and silicon offering low profile and low losses at high frequency. It also reviews developments in wirebond-free power packaging such as flip-chip assembly that offer low profile, reduced parasitics and increased thermal performance. Finally, consideration is given to the changes in the power electronics industry that may need to be addressed to enable these new technologies to play a strategic role.     

In vitro assessment of a collagen sponge for engineering urothelial grafts

OBJECTIVE: To investigate the deposition of urinary crystals and the growth characteristics of urothelial cells on a collagen sponge, as a preliminary step in engineering urothelial autologous grafts. MATERIALS AND METHODS: Collagen sponges were exposed to a continuous flow of urine at pH 5.3 and 6.3 for 1 week. The sponges were examined microscopically for crystal deposition and analysed for their calcium content. Two cell lines, RT112, derived from a well-differentiated transitional cell carcinoma, and UROtsa, an immortalized urothelial cell line, were seeded on the collagen sponges. Cells were cultured for 6, 12 and 21 days. The pattern of growth was analysed by histology and immunostaining with a pan-cytokeratin antibody. Growth was assayed to quantify cell proliferation on the sponges. RESULTS: No crystals were evident on any of the collagen sponges. Calcium deposition was negligible at pH 5.3. Although calcium levels were measurable at pH 6.3, the levels were very low. Both cell lines attached and grew in a stratified manner on the collagen sponge, RT112 forming a layer 6-8 cells thick, and UROtsa a layer 4-6 cells thick; cell proliferation was maximal at 5-10 days. The sponge remained easy to handle after 3 weeks in culture. CONCLUSION: These findings show that collagen sponges support the growth and stratification of urothelial cells, and indicate that the collagen sponge is a suitable substrate for developing urothelial autologous grafts.     

The design and evaluation of online help for Unix EMACS: capturingthe user in menu design

The card-sort technique and cluster analysis were used for determining an effective organization for a help menu in Unix EMACS. Similarity data were gathered for with a card-sorting task using EMACS commands, and a hierarchical cluster analysis of the data was performed. The results indicate that differences among novices, intermediates, and experts appear with computer-based concepts such as windows and buffers, but that the sorts are more similar than they are different. It is argued that cluster analysis may aid designers in determining a functional organization, but that in the domain of this study, this organization may not help users bridge the mapping from real world tasks to computer tasks     

Electrochemical behaviour and glass formation in molten bisulphates

Molten bisulphates form an interesting class of low-temperature fused salts which quench to form glasses; some technical and theoretical applications of these systems are discussed. The NaHSO₄KHSO-₄ eutectic (46.5% KHSO₄, m.p. 125°C,T _g 25°C) is easy to study since at lower temperatures decomposition of the melt is retarded and supercooling readily occurs. The solvent properties of this eutectic towards both inorganic and organic solutes have been investigated. The oxidation states available to transition and post-transition metals were studied spectrophotometrically and voltametrically; the results show a very restricted pattern of redox chemistry. The (abbreviated) electrochemical series is V(V)/V(IV)>Mn(III)/Mn(II)>H(I)/H₂(O)>Ag(I)/Ag(O)>Mo(VI)/Mo(V)> Hg(I)/Hg(O)>Cu(II)/Cu(O)>Zn(II)/Zn(O). The Hammett acidity function,H ₀, was measured as in the range –1 to –2. Various factors influencing redox reactions in the melt are discussed.