Étude d'une nouvelle technique de mesure des températures dans le sol

The measure of soil temperatures is generally achieved by implanting thermocouples at different depths. For the setting up of these thermocouples, and in order to resist the constraints of shearing, some rigid pegs were employed as supports. The utilization of these pegs, which are generally in metal, introduces some soil thermal perturbations. In order to minimize this kind of perturbation, a new technique of temperature measurements in soil is presented. The principle of this technique consists of replacing the peg by a removable stem which could be removed after setting up thermocouples in the soil. Apart from the thermal aspect, some mechanical tests of the new technical device are achieved. In order to notice the effects of the pegs, a qualitative study is carried out. It concerns, in particular, depths of 20, 30 and 50 cm and shows gaps in temperatures between the two techniques.     

Étude des phénomènes de transferts thermiques dans les stérilisateurs à vapeur

Study of heat transfer phenomena in a vapor sterilizer. Steam sterilization occupies a preferential place in the hospital hygiene. Hospital infection designates any sickness contracted in a hospital, allocated to microorganisms which affected sick people or hospital staff. The research work aims at studying heat transfer phenomena in a vapor sterilizer. The interactions between the different modes of heat transfer confer great complexity to this problem. The development of calculation method, zonal method, allowed to predict the field of temperature and heat transfer to optimise vapor sterilizers. This work presents the results of experiments carried out on a cycle of instrument sterilization. The main motivations of this study are the droplets of water which remain pasted to the load at the end of the drying process.     

Étude analytique des instabilités induites à la transition ébullition nucléée — ébullition en film

After a reminder of the static stability criterion of a system with non-linear characteristics, the thermal stability of a single-dimensional system was studied with the help of simple analytical methods. The influence of axial conduction, connected in particular with limit conditions, was highlighted and it was demonstrated that even if the static stability criterion is verified, the system can present second order instability over part of its intrinsic character. Multiple stationary states can also be superimposed on the instability. A more sophisticated analytical method allowed the existence of several temperature profiles to be verified on a heated conductor wire, dependent on the value of the amperage of the electric current. An experimental visualization confirms the existence of three temperature profiles, corresponding to three different heat exchange regimes.     

Études RMN haute résolution et RPE des composés Ba3C60 et Ba6C60

We report the results of ¹³C MAS NMR and EPR measurements on Ba₃C₆₀ and Ba₆C₆₀ fullerides. Using high resolution NMR, we were able to identify an isotropic line around 156 ppm for Ba₃C₆₀ and a broad isotropic one with three components at 132, 134.6, 139.9 ppm for Ba₆C₆₀ compound. The latter line is consistent with orientationally ordered C₆₀ molecules leading to three unequivalent carbon sites in agreement with X-ray studies. A strong diamagnetic shift was observed for the NMR line of Ba₆C₆₀ that is interpreted in terms of transition moment in an indirect gap system. EPR results confirm the insulating nature of both studied compounds. To cite this article: A. Rezzouk et al., C. R. Physique 4 (2003).     

Étude tridimensionnelle du transfert radiatif dans un milieu semi-transparent diffusant anisotrope par la méthode des transferts discrets modifiée

The development of the modified discrete transfer method (MDT) in a three-dimensional rectangular configuration allowed us to simulate the thermal behaviour of a semi-transparent, grey, absorbing emitting and anisotropically scattering medium at the radiative equilibrium. An internal source distributes heat uniformly in the medium while the walls of the enclosure that surround it, opaque, grey, diffuse for emission and reflection, are submitted to prescribed temperatures. A linear variation law of the temperature, as well as the scattered radiation intensity, within a grid cell associated with the direction set of the discrete ordinates method has been adopted. A grid close enough to each inner wall was necessary for a better estimation of the incident flux near the singularities of the considered system. These global improvements led to a new version of the stable MDT method, as accurate as the zonal method and as flexible as the discrete ordinates one.     

HYPERGEOMETRIC SOLUTIONS TO AN ULTRADISCRETE PAINLEVÉ EQUATION

We show that an ultradiscrete analogue of the third Painlevé equation admits discrete Riccati type solutions. We derive these solutions by considering a framework in which the ultradiscretization process arises as a restriction of a non-archimedean valuation over a field. Using this framework we may relax the conditions one requires to apply the ultradiscretization process. We derive a family of transcendental solutions that appear as the non-archimedean field valuation of hypergeometric functions.     

Comparaison des fonctions de corrélation mono- et multimoléculaires des liquides et des solutions

Le théorème de corrélation microscopique-macroscopique correspondante est redérivé à l'aide de la théorie des groupes. La démonstration est fondée sur l'invariance de l'hamiltonien d'un échantillon de liquide sous l'effet des permutations des molécules identiques. Les conséquences et les limitations du théorème sont examinées en détail.     

Die Bestimmung des Kern-Quadrupolmomentes des 247 keV-Niveaus des Cadmium-111 durch Messung der zirkularen Polarisation der γ-Strahlung

The interaction of the nuclear electric quadrupolemoment with an electric field gradient at the position of the nucleus changes the angular correlation of two successiveγ-rays and should also produce a circular polarization of theγ-rays. By measuring this polarization it should be possible to distinguish between electric and magnetic attenuation of theγ-cascade. In the electric case this measurement leads to determine not only the absolute value of the interaction product\(Q \cdot \frac{{\partial E}}{{\partial z}}\) but also the sign of it and therefore the sign of the nuclear quadrupolemoment. In the following paper the measurement of the circular polarization of the 247 kevγ-ray of Cadmium-111 is described. A polarization ofP=(0.8±0.2)% leads to the determination of the quadrupolemoment of the first excited state toQ=+0·9·10^?24cm².     

Statistics of the journal “Kvantovaya Élektronika”

Summary statistical data on the journal Kvantovaya Élektronika (English translation — Soviet Journal of Quantum Electronics) for the first 15 years of its publication from 1974 through 1988. They include the number of articles published, their distribution by subject, statistics on the authors of the papers, questions dealing with the size of the journal and with the effective utilization of the paper. Relative estimates are made of the contributions of different journals to the common flow of information. The shares of different topics in the sum total of the articles are given.Translated from Preprint No. 166 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1990.     

On the Algebraic Index for Riemannian Étale Groupoids

In this paper, we construct an explicit quasi-isomorphism to study the cyclic cohomology of a deformation quantization over a Riemannian étale groupoid. Such a quasi-isomorphism allows us to propose a general algebraic index problem for Riemannian étale groupoids. We discuss solutions to that index problem when the groupoid is proper or defined by a constant Dirac structure on a 3-dimensional torus.     

Der Einfluss des Gradienten des äusseren elektrischen Feldes auf die Chemoemission

Zusammenfassung Es wurde der Einfluss des Gradienten des äusseren elektrischen Feldes auf eine der besonderen Elektronenemissionen, die als Begleiterscheinung der Interaktion der festen Phase — Kupfer — mit einem gasförmigen Medium — Sauerstoff — eintritt, studiert. Es wurde ein abnormal grosser Schottky-Effekt festgestellt.     

Zur Isotopenanalyse des Bors an Bandenköpfen des BO-Moleküs

Es wurde ein emissionsspektroskopisches Verfahren zur Bestimmung des Borisotopenverhältnisses ¹⁰B/¹¹B im Bortrifluorid-Diāthylāther-Komplex [BF₃(C₂H₅)₂O] studiert. Dazu wurde das Bortifluoridätherat durch ein probenchemisches Umarbeitungsverfahren in BF₃-Gas umgewandlet und dieses mit einer Hochfrequenzentladung angeregt. Das emittierle Licht wurde mit Hilfe eines Spektrographen oder Monochromators spektral zerlegt und mit Fotoplatte oder Schreiber registriert. Es ergab sich ein ausgegrägtes Emissionsspektrum des α-Systems der BO-Banden, wobei für die Bestimmung des Borisotopenverhāltnisses die Isotopieverschiebung an der 2-0 Bande bei 384,7 nm und an der 2–0 Bande bei 382,99 nm in Frage kam.