Defect annealing in phosphorus implanted silicon: A D.L.T.S. study

Deep-level transient spectroscopy (D.L.T.S.) has been applied to the determination of defects in ion implanted silicon. Preliminary results concerning defects introduced by 130 KeV phosphorous ion implantation are described. Four electron traps are found: atE _c -0.21 eV,E _c -0.39 eV,E _c -0.52 eV andE _c -0.58 eV and their cross-sections estimated. The annealing behaviour in the range 450–800°C of these traps is described. Work supported in part by the Institute of Physics, Polish Academy of Science, Warsaw. Laboratoire associé au C.N.R.S.     

Contribution of intercellular links to ultrasonic absorption of liver tissue

The method discussed aims to characterize the ultrasonic absorption of liver tissues between 3 and 8.75 MHz by the slope of its linear variation with frequency. A transmission measuring device has been used and a data processing system has directly calculated this slope, which is reduced when the strength of intercellular links are lessened by mild treatment with trypsin, although the cells are left intact. This was performed on three batches of Wistar rats and the effect is explained mainly by reduction of the amplitude of relaxation processes dissipating energy in the cells.     

Turbulent transport of material particles: an experimental study of finite size effects

We present experimental Lagrangian statistics of finite sized, neutrally bouyant, particles transported in an isotropic turbulent flow. The particle's diameter is varied over turbulent inertial scales. Finite size effects are shown not to be trivially related to velocity intermittency. The global shape of the particle's acceleration probability density functions is not found to depend significantly on its size while the particle's acceleration variance decreases as it becomes larger in quantitative agreement with the classical k(-7/3) scaling for the spectrum of Eulerian pressure fluctuations in the carrier flow.     

A cryostat design for radiation damage experiments at low temperature

Abstract

A cryostat for electron irradiations at liquid hydrogen or helium temperatures is described. The cryostat uses two concentric liquid coolant containers, of which the inner reservoir is sealed and acts as a heat exchanger through ebullition and recondensation of the coolant gas. This allows irradiations with a power input from the beam of up to a few watts, and when the sample is thermally isolated allows it to be annealed up to room temperature.     

Acceleration statistics of inertial particles in turbulent flow

Turbulent transport of material inclusions plays an important role in many natural and industrial situations. Being able to accurately model and predict the dynamics of dispersed particles transported by a turbulent carrier flow, remains a challenge. One critical and difficult point is to develop models which correctly describe the dynamics of particles over a wide range of sizes and densities. Our measurements show that acceleration statistics of particles dispersed in a turbulent flow do exhibit specific, and so far unpredicted, size and density effects and that they preserve an extremely robust turbulent signature with lognormal fluctuations, regardless of particles size and density. This has important consequences in terms of modeling for the turbulent transport of dispersed inclusions.     

Dehalogenation of α -haloketones and vic-dibromides with nickel boride

α-Haloketones and $\text{vic}$-dibromides are converted to the corresponding ketones and alkenes respectively with nickel boride generated $\text{in situ}$ from sodium borohydride and nickel chloride.     

Instrumental comparison for the determination of cadmium and lead in calcium supplements and other calcium-rich matrices.

Three brands of Ca supplement, a laboratory-reagent grade CaCO3 and a certified reference material (International Atomic Energy Agency H-5 Animal Bone) wee analysed for Cd and Pb by four different analytical techniques, viz., anodic stripping voltammetry inductively coupled plasma mass spectrometry, flame atomic absorption spectrometry and electrothermal atomic absorption spectrometry. The Pb levels measured by the four techniques in the bone powder were within the certified Pb level in this certified reference material. Similarly, no significant differences [p less than 0.05; analysis of variance (ANOVA)] were observed in samples with Pb concentrations greater than 1 microgram g-1. However, the Pb levels in the laboratory-reagent grade CaCO3 obtained by flame atomic absorption spectrometry (0.79 micrograms g-1) averaged about three times higher than those measured by the other three techniques (i.e., 0.25 micrograms g-1). Although no significant differences (p less than 0.05; ANOVA) in Cd levels were observed within any of the samples (intra-sample variability), the Cd concentration measured in the different Ca supplements (inter-sample variability) varied by three orders of magnitude (ranging from 0.07 to 3.59 micrograms g-1).     

Nouvelles Recherches sur le Mécanisme de Gélification

Résumé On a étudié, par la biréfringence d'écoulement, la transformation sol-gel de la solution de gélatine et précisé les modifications apportées au comportement de ces solutions par la variation des facteurs température, concentration et masse moléculaire de la gélatine, pression, p_H, concentration en sels (chlorures, iodure, nitrate, sulfates, fluorure, alun de chrome, phosphate), en gomme arabique, en non-électrolytes (alcool, glycérine, urée, formol). Les renseignements ainsi obtenus sont comparés avec ceux relatifs à d'autres substances capable de donner des gels. En général, on distingue deux phases au cours de la transformation sol-gel (organisation de la solution, puis prise en masse). La température, la concentration mais non la masse moléculaire de la gélatine, le p_H, la nature du sel mais non la force ionique ont une influence importante sur le comportement de ces systèmes et, en particulier, agissent sur la vitesse de la transformation. L'étude de ces solutions où entrent des substances tannantes (alun, formol) montre que non seulement l'intensité mais le sens de leur action dépend de la concentration en gélatine. Les mélanges contenant de la gomme arabique manifestent une grande diversité de comportements suivant la concentration de cette dernière.

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Zusammenfassung Mit Hilfe der Strömungsdoppelbrechung wurde die Sol-Gel-Umwandlung von Gelatinelösung untersucht und die Abhängigkeiten des Verhaltens der Lösungen durch Variation aller maßgebenden Faktoren festgestellt: Temperatur, Konzentration, Molekulargewicht der Gelatine, Druck, p_H, Salzkonzentration (Chloride, Jodide, Nitrate, Sulfate, Fluoride, Aluminium usw.), Konzentration von Gummi arabicum und Nichtelektrolyten (Alkohol, Glycerin, Harnstoff, Formaldehyd). Die Ergebnisse werden mit denen an anderen gelbildenden Substanzen verglichen. Im allgemeinen unterscheidet man zwei Phasen der Sol-Gel-Umwandlung (Ausbildung von Ordnungszuständen in der Lösung, dann Verfestigung in der Masse). Temperatur, Konzentration, nicht aber das Molekulargewicht der Gelatine, p_H, die Natur des Salzes, nicht aber die Ionenkräfte haben wesentlichen Einfluß auf das Verhalten dieser Systeme, insbesondere hinsichtlich der Geschwindigkeit der Umwandlung. Die Untersuchung solcher Lösungen, denen gerbende Substanzen zugegeben sind (Alaun, Formaldehyd), zeigt, daß nicht nur die Stärke, sondern auch der Sinn ihrer Wirkung von der Gelatinekonzentration abhängt. Gummi arabicum enthaltende Gemische weisen eine große Verschiedenheit im Verhalten der Substanzen auf, stark abhängig von der Konzentration des Gummi arabicums.