Orbital and whole-atom proton stopping power and shell corrections for atoms with Z ⩽ 36

Stopping cross sections and shell corrections for atoms with 1 ? Z ? 36 have been evaluated using a technique based on Sigmund's kinetic theory of electronic stopping. Results are tabulated for projectile velocities from 1 to 60 atomic units both for the whole atom and for the individual subshells.     

电力转换与管理的数字控制

迄今为止，电力转换——电压与电流的实际处理一直是模拟的而不是数字的，而控制则或者是模拟的，或者是数字的（尽管并非纯数字），这是因为反馈回路中依然需要A／D。     

Survival after a very low (< 5 x 10(6)/l) CD4+ T-cell count in individuals infected with HIV

OBJECTIVE: To describe survival after a CD4+ T-cell count of less than 5 x 10(6)/l and to identify possible baseline factors associated with outcome. DESIGN: A prospective cohort study. SETTING: A large teaching hospital in North London. PATIENTS AND PARTICIPANTS: Patients treated at the Royal Free Hospital, London, who had at least one reported CD4+ T-cell count of less than 5 x 10(6)/l and were being followed up for clinical care prior to the date of this cell count. MAIN OUTCOME MEASURE: Death. METHODS: Proportional hazards models, Kaplan-Meier analysis. RESULTS: One-hundred and sixty-nine patients were included in the study. The median survival after a very low CD4+ T-cell count was 0.95 years (95% confidence interval, 0.78-1.19), although 20% survived for over 2 years. Older age and a previous AIDS diagnosis were related to poorer outcome. A higher CD8+ T-cell count at baseline was also associated with a better prognosis. CONCLUSIONS: A CD4+ T-cell count of less than 5 x 10(6)/l did not necessarily mean imminent death, with a median survival after this count of just under 1 year. These results will enable clinicians to provide appropriate counselling for patients at this late stage and to plan terminal care.     

Quality enhances reliability [power supplies]

As deregulation dawns, electric utilities are awakening to the fact that power quality counts with many a customer-and counts for a lot. Even now, the groundwork is being laid worldwide for a new type of service contract between a utility and its large industrial or commercial clients. In brief, the utility promises to supply its customer's operations with power above a certain level of “quality”, and the customer promises to buy power from no-one else for as long as the contract lasts-a valuable concession now that retail wheeling has clients in those categories picking and choosing among suppliers in the electric power industry     

High accuracy geometric Hermite interpolation

We describe a parametric cubic spline interpolation scheme for planar curves which is based on an idea of Sabin for the construction of C¹ bicubic parametric spline surfaces. The method is a natural generalization of [standard] Hermite interpolation. In addition to position and tangent, the curvature is prescribed at each knot. This ensures that the resulting interpolating piecewise cubic curve is twice continuously differentiable with respect to arclength and can be constructed locally. Moreover, under appropriate assumptions, the interpolant preserves convexity and is 6-th order accurate.     

The opening and closing of a growing crack in a linear viscoelastic body that is subject to alternating tensile and compressive loads

To a degree greater than their elastic counterparts, physically realistic problems for cracked viscoelastic bodies are subject to difficulties arising from the facts that cracks may extend with time and that boundary conditions may not be definitely known until the problem is solved. We have considered a problem for a single Griffith crack in an infinite viscoelastic body that is under the influence of prescribed normal stress acting at infinity normal to the plane of the crack. If, at some instant of time, the crack is not entirely open or entirely closed it is assumed to be open on a symmetric interval of radius b(t) about its center and closed in an annular region surrounding that symmetric interval. Then if the crack is assumed to be strictly extending whenever it is entirely open, it is shown (by using the physical condition that the stresses should be finite except at the crack end) to be always either entirely open or entirely closed. Also, formulae and other information on the stresses and displacements in the body are presented and comparison is made with the case of a crack of constant length.

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Résumé Bien davantage encore que les problèmes élastiques qui sont leur contre-partie, les problèmes associés à la physique réaliste des corps viscoélastiques fissurés sont sujets à des difficultés résultant du fait que les fissures peuvent s'étendre en fonction du temps et que les conditions aux frontières peuvent n'être définitivement connues avant la solution du problème. Nous avons considéré un problème d'une fissure simple de Griffith dans un corps viscoélastique infini sous l'influence de tensions normales prescrites agissant à l'infini, normalement au plan de la fissure. Si à quelque instant, la fissure n'est pas entièrement ouverte ni entièrement fermée, on suppose qu'elle s'ouvre sur un intervalle symétrique de rayon b(t) autour de son centre et qu'elle se ferme sur une région annulaire entourant cet intervalle symétrique. Dès lors, si la fissure est supposée être strictement en cours d'extension chaque fois qu'elle est entièrement ouverte, on montre (en utilisant la condition physique que les contraintes doivent être finies partout à l'exception du sommet de la fissure), que la fissure est toujours soit entièrement ouverte soit entièrement fermée. On présente également les formules et d'autres informations sur les contraintes et les déplacements dans le corps et on effectue une comparaison avec le cas d'une fissure présentant une longueur constante.

     

Portability—some experiences with FORTRAN

During the development of a portable problem-oriented language processor a number of unexpected difficulties and incompatibilities in various FORTRAN compilers were encountered. These are related, and an approach which minimizes the problems suggested.