[en] The fraction and the distribution of the personal daily solar erythemal UV exposure were assessed for the shade provided by Australian gum trees in each of the four seasons to allow evaluation of the reduction in the personal UV exposure in tree shade over a year. The personal annual erythemal UV exposures in the tree shade ranged from 2510 SED (standard erythemal dose) for the vertical part of the ear to 8016 SED for the vertex of the head compared to 14,834 SED to a horizontal plane in full sun. The erythemal UV seasonal exposures for 15 min intervals on a horizontal plane in full sun in winter are comparable to the UV exposure to the vertex of the head in shade in autumn and spring. The UV exposure in the tree shade for summer, is approximately 20% less than the full sun exposure in autumn. The reduced personal annual erythemal UV exposures due to the tree shade provided reductions by a factor of 2 to 3 and 4 to 6 in the contribution to the risk of basal cell carcinomas and squamous cell carcinomas, respectively, compared to not employing the protection of the tree shade. (author)

[en] Recent experience has shown that certain metal alloys can be put into glass form by rapid melt-quenching or by various condensation processes. Models for the nature and structure of these glasses are surveyed and shown to be quite parallel to those already developed for the more common nonmetallic glasses. The rather unique magnetic, superconducting, and mechanical properties and the technical potential of metallic glasses are also discussed

[en] The mutabilities of normal and xeroderma pigmentosum variant (XP4BE) human fibroblasts by ultraviolet light (UV) were compared under conditions of maximum expression of the 6-thioguanine resistance (TGsup(r)) phenotype. Selection was with 20 μg TG/ml on populations reseeded at various times after irradiation. Approx. 6-12 days (4-8 population doublings), depending on the UV dose, were necessary for complete expression. The induced mutation frequencies were linear functions of the UV dose but the slope of the line for normal cells extrapolated to zero induced mutants at 3 J/m². The postreplication repair-defective XP4BE cells showed a higher frequency of TGsup(r) colonies than normal fibroblasts when compared at equal UV doses or at equitoxic treatments. The induced frequency of TGsup(r) colonies was not a linear function of the logarithm of survival for either cell type. Instead, the initial slope decreased to a constant slope for survivals less than about 50%. The doses and induced mutation frequencies corresponding to 37% survival of cloning abilities were 6.7 J/m² and 6.2 X 10^-5, respectively, for normal cells and 3.75 J/m² and 17.3 X 10^-5 for the XP4BE cells. The lack of an observable increase in the mutant frequency for normal fibroblasts exposed to slightly lethal UV doses suggests that normal postreplication repair of UV-induced lesions is error-free (or nearly so) until a threshold dose is exceeded. (Auth.)

[en] Recent experience has shown that certain metal alloys can be put into glass form by rapid melt-quenching or by various condensation processes. Models for the nature and structure of these glasses are surveyed and shown to be quite parallel to those already developed for the more common nonmetallic glasses. The rather unique magnetic, superconducting, and mechanical properties and the technical potential of metallic glasses are also discussed

[en] Measurements of the pressure dependence of the diffusivity of arsenic in Si are being made. The results are expected to have a direct bearing on whether the primary point defects involved in this process are vacancies or interstitials. Wafers of (100) Si have been implanted with 5 x 10¹⁵ As/cm² at 100 keV and are first annealed by standard rapid thermal annealing techniques to 1100⁰C to restore crystallinity by solid phase epitaxy. Subsequent anneals were done either under pressure in a Boyd-England-type piston-cylinder press or in evacuated ampules in a furnace. The arsenic depth distribution before and after treatment has been examined by RBS techniques. To data the authors have investigated the arsenic diffusivity over the temperature range 850-950⁰C at pressures of 0, 20, and 30 kilobars. Preliminary analyses of the results are discussed

[en] A modified solid-state precipitation process for the formation of stoichiometric A-15 V₃Ga is presented which results in high values of T/sub c/=15.0 K and H/sub c2/(4.2)=22 T, excellent phase homogeneity, and a high critical current J/sub c/(4.2 K)=3 x 10⁵--6 x 10⁴ A/cm² over the field range 0--18 T. We find that grain boundary pinning is dominant, producing a very high specific pinning force Q/sup max/=6.4 x 10⁴ dyn/cm². The nonparamagnetically limited H/sub c2/ is needed to explain our high flux-pinning results

[en] The temperature dependence of lineshape parameters obtained from Doppler profile measurements (from 7 to 350 K) is presented for rolled and unrolled Pb, Pb(Cd), and Pb(Tl) alloys. It is demonstrated that positrons can be used to detect microporosity and dislocations in Pb(Cd) alloys. The porosity is greatly reduced by rolling. Positron trapping by the Pb(Cd) alloys in the as-worked state is attributable to dislocations. (author)

[en] Critical current behavior and intrinsic superconducting properties of liquid quenched Nb₃Al and its pseudobinaries Nb₃ (Al,Si) and Nb₃(Al,Ge) have been studied in fields up to 29 T. Our results show that flux pinning in these materials is dominated by strong precipitate pinning at low temperatures and by grain boundary pinning at high (>10 K) temperatures. The best results were obtained in Nb₇₅Al₁₉Ge₆ samples with T/sub c/ of 20.0 K, estimated H/sub c/2(0) of 43 T and J/sub c/ (4.2 K) in excess of 10⁴ A/cm² at 30 T

[en] We have measured the effects of pressure, temperature, and some variations in impurity content on the growth rate u of quartz into fused silica. Under all conditions the growth rate was interface controlled and increased exponentially with pressure with an activation volume averaging -21.2 cm³/mole. The activation enthalpy for all specimens extrapolated to a zero pressure value of 64 kcal/mole, within the experimental uncertainty. At a given stoichiometry the effect of hydroxyl content on growth rate is described entirely by a linear term C/sub OH/ in the prefactor of the equation for the growth rate. The effect of chlorine impurity can be described similarly. Also u is increased as the ideal stoichiometry is approached from the partially reduced state

[en] Critical current densities of over 1.8 x 10⁶ A/cm² at 4.2 degreeK and 150 kG have been achieved in Nb₃Al tapes rapidly quenched from the liquid state at rates of 10⁵--10⁶ degreeC/sec. The superconducting transition temperature is about 16 degreeK, indicating a relatively high degree of order, and increases to 18.4 degreeK upon annealing at 750 degreeC. The observed microstructure depends sensitively on the quenching rate and consists of small submicron grains surrounded by a thin boundary layer of different composition. The grain size is roughly inversely proportional to the temperature gradient during quenching. The quoted critical current densities, the highest observed to date in any superconductor, should be regarded as a lower limit of the material critical value imposed by the heating problems due to the contact resistance