Showing papers by "University of Paris published in 1969"

Statistical analysis as a tool to make patterns emerge from data

Abstract: Publisher Summary This chapter focuses on statistical analysis as a tool to make patterns emerge from data. When faced with intricate sets of data, human scientist or biologist calls for help from the statistician, the former generally has some hypothesis, or even an accepted theory, while the latter has none. Besides, only in the past decade has statistical science received from electronic devices because of help to cope with the huge mass of digits that has to be handled to submit the flesh of data to the soul of formulae. Alternating the study of the numerical data and of the concepts of the field is sound and unavoidable. The results of computational analysis have suggested extending the measurements or rebuilding the experimental framework. Usually a classification algorithm consists of two fairly independent parts: (1) the computation of a similarity index and (2) the formation of clusters. The chapter presents a few mathematical principles illustrated by examples.

Quantum-Mechanical Investigations of the Electronic Structure of Nucleic Acids and Their Constituents

Abstract: Publisher Summary Quantum-Mechanical Investigations of the Electronic Structure of Nucleic Acids and Their Constituents11The work was supported by Grant No. 67-00-532 of the Delegation Generale a la Recherche Scientifique et Technique (Comite de Biologie Moleculaire), Grant No. CR-66-236 of the Institut National des Sciences et de Recherche Medicale (Intergroupe Cancer Leucemie), and Grant No. GM 12289 of the U.S. Public Health Service (National Institute of General Medical Sciences) This chapter explains quantum-mechanical investigations of the electronic structure of nucleic acids and their constituents. The quantum-mechanical calculations so far performed on purines and pyrimidines or on the nucleic acids may be considered in two ways: first, they may be classified with respect to the method of calculation used; second, they may be classified in connection with the problems that they have dealt with. The chapter discusses the methodology of the calculations, which are carried out by a large variety of methods. For a number of years, marly of these properties, such as dipole moments, ionization potentials, electron affinities, and spin densities in free radicals originating from the bases-are known only theoretically. The recent evolution of the theoretical procedures, together with the rapid development of the computational techniques and of the capacities of the computers themselves, has opened up the possibilities for an effective direct investigation of the macromolecules themselves and of their essential properties. Such an enlargement is essential for the transformation of quantum biochemistry into a quantum biology.

Fluctuations and the superconducting phase transition: II. Onset of Josephson tunneling and paraconductivity of a junction

Abstract: When one metallic film of a tunneling junction is in the superconducting state but the other is above its transition temperature, fluctuations in the pair field of the second film cause instantaneous Josephson currents to flow. Application of the Kubo formula to these current fluctuations yields a conductivity with a strong temperature dependence, tending to infinity at the transition. The numerical magnitude of this "paraconductivity" is sufficiently large to be observable for junctions of very low normal resistance (and may possibly be compared with some recent measurements of Lipsonet al.). High-frequency studies would determine directly the pair relaxation rate. An experimental advantage of tunneling paraconductivity is that it is not sensitive to the electron mean free path and therefore does not require amorphous films.

The Adrenergic and Cholinergic Control of Food and Water Intake

Abstract: It is still difficult to discover by precisely what means of specialized communication processes the central nervous system is aroused for the performance of hunger and thirst behavior. A very large number of experiments has given rise to a great diversity,of theories, from which it would appear that there is agreement on the following general pattern: the various organic requirements arising from the exploitation of nutritive reserves produce modifications in the biological equilibria which are probably transmitted in message form to more or less specialized nervous structures, the duty of which must be to co-ordinate this multiplicity of information into patterns capable of being transmitted in their entirety to higherranking nervous structures, the process being repeated until the behavior mechanisms themselves are brought into play. It is probable that this arousal of the nervous system for the purposes of initiating a specific activity allows the various external stimuli (smell, sight, touch, etc.) to become significant at a given moment and hence effective in inducing behavior (open drive). An important problem, therefore, is to ascertain under what conditions the nervous structures are able to receive the essential information and, above all, the state of receptivity that is required for the correct use of the messages involved. It is clearly evident that the same piece of information will produce its effects, or not, according to the nervous condition of the animal concerned. Hence it would appear essential in this pattern for the vigilance-regulating mechanisms to interact, if not directly, at least in such a manner as to allow the messages to be used and the required behavior to be put into effect. If an outline of the principal mechanisms guaranteeing the animal’s vigilance is required, two main types may be described at the present time: 1) A fundamental vigilance level that assures the general arousal of the animal and keeps i t awake. The nervous structures responsible are situated for the most part in the mesencephalon and constitute the classical reticular activator system of the midbrain (Moruzzi & Magoun, 1949). The blocking of this system (or its experimental or pathological injury) induces a persistent sleep with slow, high amplitude cortical waves of generalized sleep, while its activation by any sensory (or experimental) stimulation causes the systemic arousal of the cortex with the appearance of characteristic rapid waves of low amplitude. The administration of adrenalin, noradrenalin or any other adrenergic drug (amphetamine, for example) gives results similar to those produced by sensory or electrical stimuli, and it is considered that the activation of this system is preferentially, therefore, probably adrenergic. On the other hand, the administration of adrenolytic drugs (dibenamine, chlorpromazine, etc.) results in the blocking of the mesencephalic activator system and the manifestation of sleep behavior. It has been established that at the behavioral level this generalized cortical arousal allows global reception of various types of information, but not their specific utilization. In fact, if this form of vigilance is experimentally maintained by strong doses of adrenergic drugs, or by intense nociceptive stimuli, a diffuse, nonorientated, hyperactive behavior is provoked which never becomes properly coordinated and adjusted. For purposes of simplification I shall refer to this vigilance level as the mesencephalic reticular level, or level of adrenoceptive vigilance.

Some aspects of the method of the hypercircle applied to elliptic variational problems.

Abstract: : The hypercircle method is studied from the point of view of the recently developing theory of Galerkin-type approximations in Sobolev spaces using spline functions. Given an elliptic boundary value problem it is shown how to obtain a conjugate problem - thereby interchanging the roles of 'forced' and 'natural boundary conditions. Given approximate solutions for both problems their errors can be estimated 'a posteriori'. The approximate solution of the primal problem being well-known, the authors consider the approximation of the solution of the conjugate problem, obtaining theorems of convergence and estimates of the rate of convergence. (Author)

Permeability to Water of the Shell of the Egg of Locusta Migratoria Migratorioides, with Observations on the Egg of Teleogryllus Commodus

Abstract: 1. Eggs of Locusta migratoria migratorioides were cut open at one end, the tissues were removed, and the empty egg shells were filled with water or with an osmotic solution. The open end was tied off to form a balloon. Balloons containing water were placed in osmotic solutions, and those containing a solution were immersed water. 2. Balloons were made from eggs 1 or 2 days old before water absorption had begun, from eggs during the course of rapid water absorption and from eggs which water absorption was complete. Diapausing and non-diapausing eggs were used. The hydropylar end of the egg was included in the balloons in half the observations. 3. All balloons containing solution gained water and all those containing water lost it. Shells from diapausing eggs were much less permeable than all other categories Little difference was observed between balloons whether the hydropylar end was present or not. 4. Eggs exposed to unsaturated air lost water rapidly, except those in diapause. 5. Balloons made with the shells of young eggs of Teleogryllus commodus were also permeable to water in both directions. 6. The results are discussed in the light of their contribution to an understanding of the control of the absorption of water in insect eggs.

Amine-imine tautomerism in adenines

Abstract: CNDO/2 calculations predict that while the amine form of adenine should be the most stable one for the N(9)H, N(7)H and N(3)H tautomers of this substance, the inline form should on the contrary be the most stable for the N(1)H tautomer. The prediction is verified by experiment.

Fossil Tracks in Meteorites and the Chemical Abundance and Energy Spectrum of Extremely Heavy Cosmic Rays

Abstract: It has been previously shown that certain meteorites contain fossil tracks that are produced by slowing down heavy nuclei in the primary cosmic radiation In this paper we give calculations of the angular distributions and densities of such tracks as a function of the depth and orientation of test samples Comparison of the theoretical results with previous experimental work in the meteorite Saint-Severin shows that the cosmic-ray energy spectrum has not changed appreciably in the last 107 years We also report an experimental study of cosmic-ray tracks in the meteorite Johnstown Using a new ‘coincidence’ technique we have found a much higher proportion of longer tracks among the group of tracks attributed to particles with Z>30, than heretofore reported Evidence is presented for the existence of particles in the range 40–70 One track that can be attributed to a particle with Z≥80 was found These results tend to remove the differences that have heretofore existed between measurements of ancient and modern cosmic rays, and thus support the long time constancy of the cosmic radiation

Etude théorique du pK des états excités

Abstract: On montre a partir de considerations theoriques qu'une molecule conjugee dont un substituant donneur d'electrons est le centre d'acidite doit devenir plus acide quand eile passe de l'etat fondamental au premier etat electronique excite. Le contraire doit se produire lorsque le substituant est accepteur d'electrons. Enfin une molecule conjugee contenant un heteroatome centre de basicite doit devenir plus basique au cours de la mEme transition. On suggere, par ailleurs, une interpretation du fait que dans cette serie de molecules le premier etat excite triplet possede une force acido-basique tres differente de celle du premier etat excite singlet.

Lysozyme: Ein Kapitel Molekularbiologie

Abstract: Huhnereiweis-Lysozym war das erste Enzym, dessen Tertiarstruktur aufgeklart werden konnte. Seine Peptidkette ist in zwei etwa gleich grosen Teilen angeordnet, zwischen denen ein tiefer Spalt klafft. Die Substrate (und Inhibitoren) werden in diesem Spalt durch Wasserstoffbrucken gebunden und unter Mitwirkung von Glu 35 und Asp 52 — die das aktive Zentrum bilden — hydrolysiert. — Die Lysozyme, die in vielen Tier- und Pflanzenarten vorkommen, sind zwar chemisch verschieden, haben jedoch qualitativ die gleiche biologische Aktivitat; quantitativ lassen sich grose Unterschiede nachweisen, die auch die Spezifitat betreffen. Nach Infektion mit Bakteriophagen entsteht in E. coli ein Lysozym, dessen Bildung von der Phagen-DNS kontrolliert wird. Da mutierte Phagen abgeanderte Lysozyme erzeugen, eroffnet sich ein weites Feld fur die molekularbiologische Forschung.

Une démonstration simplifiée et une extension de la formule d'Abramov sur l'entropie des transformations induites

Abstract: Abramov's formula on the entropy of induced automorphisms is simplified and extended to random powers of automorphisms.

Temps d'arrÊt d'un système dynamique

Abstract: The most general positive integer-valued random variable v such that for a given bijective measure preserving transformation θ, the transformation θ v is still bijective and measure preserving is shown to be a (generally infinite) superposition of return times.

Van der Waals Onteractions in molecular complexes of tetracyanoethylene

Abstract: The interaction energy of complexes formed between methylbenzenes and tetracyanoethylene is calculated by two procedures. The first one is the “monopoles-bond polarizabilities” procedure previously described, while the second is derived from the semi-empirical treatment proposed by Kitaygorodsky. A satisfactory agreement is obtained between the calculated energies and the observed energies of formation in the gas phase. The dipole moment induced by mutual electronic polarization of the components is calculated for the Durene-Tetracyanoethylene complex, and is found to account for the major part of the observed dipole.

Studies on the calculation of stacking energies in DNA.

Abstract: It is perhaps unnecessary to emphasize here the importance of understanding, both qualitatively and quantitatively, the detailed nature of the intermolecular forces between adjacent conjugated molecules, which frequently occur in the biological macromolecules and between molecular complexes often referred t o as 7r-complexes. A large amount of work in theoretical chemistry and biochemistry in the last fifteen years or so has been devoted to promoting such an understanding. Special interest was aroused in an attempt to understand these forces between pyrimidines and purines occurring in DNA, following the experiments on the denaturation of the double helical structure into two single-stranded coils by Doty’” and his collaborators. Thus, these purine and pyrimidine pairs are perhaps the best studied among the various adjacent conjugated molecules. These forces are reflected in the stacking and bond-free energies between various purines and pyrimidine base pairs in DNA; and the amount of stacking and bond-free energies determine, in part, the detailed melting behavior of DNA.3’4 Thus the obvious, though indirect, approach to an understanding of these forces is to calculate these energies-assuming that there are certain forces between the base pairs-and t o evaluate the worth of the values in explaining the observed melting behavior of DNA. The pioneering calculations for these energies, using quantum mechanical methods and making certain approximations, were made by DeVoe and Tinoco5 in 1962. Since then, there have been several attempts by various groups of w0rkers6-l~ to refine these calculations by gradually replacing some of

4-Allyloxy-3-chlorophenylacetic acid, a new type of analgesic, antipyretic and antiphlogistic drug.

Abstract: Bei s t rahlenbiologischen Un te r suchungen [1, 2] am Deutschen E lek t ronen-Synchro t ron wurde der yon den Megavol t s t rahlungen her be ka nn t e Dosisanst ieg mi t der durchs t rah l t en Mater ieschicht (build-up-effect) in e inem ex te rnen Bremss t rah lenbfmdel bei verschiedenen Pr im~renergien der Elekt ronen im GeV-Bereich gemessen. Die Dosis wurde s t rahlenchemisch mi t der F e I I / F e I I I R e a k t i o n bes i immt . Fiir die Berechnung der Dosis wurde ein G-~Wert yon 15,6 zugrunde gelegt. Die S t rah len in tens i t~ t wurde fiber ein Q u a n t a m e t e r gemessen [3]. Als Moni tor d iente eine d fmnwandige Ionisat i onskammer in Verb indung mi t e inem Duplexdos imete r (PTW). Die d i rekte Proport ional i t&t zwischen d e r m i t dem Ferrosul fa t -Dos imeter in e inem 2-GeV-Bremsst rahlenbf indel b e s t i m m t e n Energiedosis und der Zahl der im Q u a n t a m e t e r gemessenen effekt iven Quan ten pro cm ~ sowie der Ionisat ionskammer-Anze ige zeigt Fig. I a. Der durch die hochenerget i sche Bremss t rah lung erzeugte Aufbaueffek% in der Tiefe wurde in e inem W a s s e r p h a n t o m (20 • 20 • 150 cm s) gemessen. Die Fer rosul fa t -Dosimeter wurden in verschiedenen Schicht t iefen in der L&ngsaehse des P h a n t o m s just ier t . Fig. t b zeigt die Tiefendosis-Vertei lung bei 4 , t5und 6 ,15-GeV-Bremsst rahlnng. Die Dosiswerte s ind auf die Energiedosis des e rs ten Fer rosul fa t -Dosimeters nor15 o

Lúdico e educação: novas perspectivas

Abstract: In this article the ideas developed in the book Jogo e educacao (Brougere, 1998) will be reviewed in the sense of expanding its analysis. The relationship between games and teaching are analyzed within the context of informal education and ieisure time, and associateci to activities of adult and children. Not only is it important to support game specificity, which we have tried to point out in various aspects, but to relate it to familiar activities as well. Such proposal aims to promote the introduction of new anaiyses features and to re-address the issue in a less mythical context.

Constellations et propriétés algébriques des graphes topologiques

Abstract: Dans un premier chapitre, nous faisons l'etude des proprietes algebriques d'un objet du a GUSTIN que nous appelons constellation : cet objet permet, grâce au theoreme de J. EDMONDS, de traduire les proprietes des graphes topologiques en termes purement algebriques et combinatoires. Dans un deuxieme chapitre, nous developpons l'etude des representations topologiques des graphes de CAYLEY (graphes associes a des groupes) : nous donnons une nouvelle caracterisation des graphes de CAYLEY (differente de celle donnee dans MAGNUS-KARRAS$ & SOLITAR), puis grâce au concept de constellation, nous reprenons dans un cadre plus general la theorie developpee par GUSTIN et YOUNGS Ce chapitre se termine par la determination du genre de plusieurs familles de graphes de CAYLEY du groupe symetrique.

Sur les suites de Toeplitz

Abstract: The spectral properties and strict ergodicity property of the Toeplitz sequences which have been introduced in [1] are also consequences of an isomorphism of the dynamical systems associated to these sequences with translations on certain abelian compact groups.

Response of an isolated magnetic grain suspended in a liquid to a rotating field

Abstract: We have studied the response of an isolated uniaxial magnetic grain suspended in a liquid to an applied fieldh rotating with frequencyω. In the presence of an applied static field (H≫h), at low frequencies (i.e. for fast relaxation), the easy axis followsh, while at high frequencies the behavior is similar to that of a bulk sample. In zero static field, the response of a ferromagnetic grain is more complicated; there exists a critical frequencyωe below which a steady state is reached, with the easy axis followingh. Forω>ωe the mechanical behavior depends crucially on the initial conditions. Finally, a superparamagnetic grain has a (different) critical frequencyωe, below which it reacts similarly to the ferromagnetic particle, while forω>ωe it does not follow steadily the rotating field, but can only oscillate about its initial position.