Search

The influence of high temperature annealing and heavy current treatments of porous Pt electrodes is investigated with scanning electron microscopy. The results are discussed on the basis of the kinetic behaviour of these electrodes, known from the literature or deduced from our still unpublished results. It is demonstrated that both the structure and the catalytic activity are influenced by the treatments.

Col metodo delle anticoincidenze si studiano i fotoni degli sciami estesi al livello del mare e a 2000 metri. Si trova che il rapporto fra fotoni ed elettroni e praticamente indipendente dalla quota e cresce con la densita dello sciame. Si mette in evidenza la componente fotonica presente sotto forti spessori di piombo.

Highly multiple interacting systems can be formally treated by means of classical tistical mechanics or by means of stochastic methods. Within the framework of a recently developed general relational systems formalism, it is here shown how the two approaches are related: the method for constructing the prior probability distribution needed in the stochastic approach is shown to imply Gibbs statistical mechanics. This generalization of statistical mechanics has a wider applicability since it does not require the postulation of the existence of a Liouville equation, nor of a conserved quantity, nor of an ergodic hypothesis. These results are here applied to the classical problem of a Volterra-Lotka system of interacting biological species, and it is shown how the statistical mechanical treatment of such a system, as developed by Kerner, can meaningfully be carried on in terms of observable variables only.

SummaryThe survival of spermatogonia of type B in mice after exposure to negative and positive pions is presented. It is found that the survival curve in the case of negative pions has an inverse shoulder and in the case of positive pions the best fit seems to be a straight line. The observed survival curves have been compared to provide information about the radiobiological significance of the negative pion nuclear interactions. Discussions of the results obtained show that one cannot exclude the possibility that the biological system used might behave as a mixed population in the case of negative pions as compared with x-rays.

The chemical behavior of 4-keto-1H-4,5-dihydro-1,2,5-benzotriazepines towards basic reagents has been investigated. Evidence is given that 4-keto-1H-4,5-dihydro-1,2,5-benzotriazepines unsubstituted at position 3 are cleaved by sodium hydroxide and alkoxides furnishing sodium cyanide and 2-amino-3-keto-quinoxalines. The same benzotriazepines substituted by a carbamidoximo- or a carbohydrazino-group at position 3 undergo, when treated with the same reagents, isomerization reactions yielding 3-amino-4-arylazo-isoxazolin-5-ones and 4-arylazo-pyrazolidin-3,5-diones respectively. The structure of these products is demonstrated and a mechanism for their formation is proposed.

1. L'etude de 95 echantillons preleves sur 16 carottes effectuees en Mediterranee Orientale a des profondeurs comprises entre 283 et 4350 m, a montre que, dans les sediments superficiels, les populations bacteriennes superieures a 105 germes/cm3 de sediment sont exceptionnelles, au moins dans la zone oceanique etudiee. Au-dela de 1000 m les populations bacteriennes ne sont que tres rarement superieures a 104 germes/cm3. 2. Etant rappele que la population bacterienne moyenne des sediments littoraux est comprise entre 5.105 et 6.106 germes/cm3, il apparait que la portion du sol des oceans favorable a la proliferation bacterienne est particulierement limitee. 3. De meme, ce n'est que dans les sediments superficiels que la microflore est relativement abondante. Au-dela de 50 cm d'epaisseur sedimentaire, les populations bacteriennes superieures a 103 germes/cm3 de sediment sont rares. 4. L'etude des divers groupements physiologiques bacteriens montre la rarete des germes chitinolytiques et agarolytiques et l'absence de germes cellulolytiques et sulfato-reducteurs. Par contre, amylolytiques, gelatinolytiques, lipolytiques et reducteurs de nitrate sont bien representes. Les germes auxotrophes ne representent qu'une part peu importante de ces populations bacteriennes.

1. Les numerations de population bacterienne effectuees bi-mensuellement pendant deux annees consecutives a 5 stations de prelevement situees sur le littoral provencal, montrent que les populations bacteriennes des eaux du fond ne sont pas liees aux caracteristiques chimiques et biologiques des sediments qu'elles recouvrent. Elles sont, par contre, fortement influencees par les apports d'eau douce qui favorisent les concentrations bacteriennes elevees. 2. Dans les sediments, la concentration bacterienne est liee a la teneur de la reserve organique. Il n'apparait pas de relation avec la microflore des aux ou le peuplement macrobenthique. 3. En raison de la rapide diminution de la concentration bacterienne dans l'epaisseur sedimentaire, ainsi qu'en fonction de l'eloignement du rivage, on peut estimer que la zone d'activite intense des germes heterotrophes est extremement limitee par rapport a la surface oceanique. C'est done probablement dans les masses d'eau et non dans les sediments que doit se derouler la plus grande part des phenomenes de transformation du materiel organique. 4. L'amplitude des variations observees en cours d'annee est nettement superieure a celle resultant de l'imprecision des numerations bacteriennes ou de l'echantillonnage. Certaines poussees, apparaissant simultanement aux differents niveaux sedimentaires et a differentes stations, semblent liees a l'evolution generale de facteurs ecologiques. 5. Dans les sediments on ne peut pas relier les variations annuelles a l'evolution des populations macrobenthiques, non plus qu'a celles de la reserve organique globale. Dans les aux, les poussees bacteriennes paraissent succeder aux poussees phytoplanctoniques. La periode de production bacterienne la plus intense se situe pendant la saison chaude, a l'inverse de ce qu'on observe pour les populations phytoplanctoniques.

Si descrive una misura della distribuzione zenitale delle particelle degli sciami estesi dell'aria, eseguita con contatori. Assumendo una dipendenza dall'angolo zenitale della forma cosn ϑ si trova un valore din fra 3 e 4. Se ne studia la dipendenza dalla quota, dalla densita dello sciame e dall'angolo zenitale.

The principal thesis of this paper is that it is possible to construct a hierarchical system, via the prescription for hierarchical continuation, which exhibits the necessary conditions for the emergence of life. The sufficiency of these conditions is shown to be highly plausible on the basis of the deducibility of certain formal considerations in biological control theory from the formal decision process whereby a life-dynamics is generated.

Si descrive una misura sulla dipendenza dall'indice di rifrazione dell'energia emessa per effetto Cerenkov. E posta in evidenza una fluorescenza in plexiglas e acqua confrontabile con l'effetto Cerenkov.

SummaryA number of compounds more or less related to iodoacetic acid (IAA) have been tested for their radiosensitizing effect on rabbit erythrocytes.As reported previously, red cells irradiated in vitro with x-rays lose the intracellular potassium and haemolyse as a function of radiation dose and, when they have been treated previously with IAA, their radiosensitivity increases up to four times.Bromoacetic acid, iodoacetamide, iodopropionic acid, N-ethylmaleimide, alcaline iodides and molecular iodine all exhibit radiosensitizing ability.The sensitization occurs to the same extent, whether the samples are irradiated under atmospheric oxygen-tension or after flushing with oxygen or nitrogen. For all the halogenated compounds it occurs only if the substance is present in the system at the moment of irradiation.The sensitizing effect appears to be independent of the alkylating ability of tested compounds, and of the inhibition of glycolysis and lowering of ATP-level in red cells.Experiments with iodoacetic a...