Showing papers by "École Polytechnique published in 1973"
TL;DR: In this paper, the rates relative to the corresponding charged current processes are evaluated for events induced by neutral particles and producing hadrons, but no muon or electron, have been observed in the CERN neutrino experiment.
460 citations
TL;DR: One possible event of the process ν − μ+ e − → v − μ + e − has been observed in this article, and the event is interpreted in terms of the Weinberg theory.
311 citations
01 Jan 1973
TL;DR: In this article, the authors deal with the application of thermodynamics to materials which exhibit plastic deformations (either purely plastic or viscoplastic), focusing on the definition of the thermodynamic state and on the expression of the second law.
Abstract: This study deals with the application of thermodynamics to materials which, besides viscoelastic deformations, exhibit plastic deformations (either purely plastic or viscoplastic). Attention is focussed on the definition of the thermodynamic state and on the expression of the second law. Three different formulations are presented
(1)
With hidden variables and using an intermediate, released, configuration.
(2)
With hidden variables and using a fixed reference configuration.
(3)
In functional representation.
Finally an hypothesis about the dissipativity is investigated.
172 citations
TL;DR: In this paper, the v and v nucleon total cross-sections have been determined as a function of energy using a sample of 2500 v and 950 v event, compared with predictions of scaling and charge symmetry hypotheses.
113 citations
TL;DR: In this paper, conditions for excitation of parametric instabilities in bounded plasmas were obtained for backscatter Brillouin instability, taking into account both damping and inhomogeneity effects.
Abstract: We have obtained conditions for excitation of parametric instabilities in bounded plasmas. Damping and inhomogeneity effects are taken into account. The results are found to be of special importance for backscatter Brillouin instability.
105 citations
103 citations
TL;DR: In this article, the properties of GaSe and GaS are characterized by strong polarization effects reflecting the high anisotropy of the crystal structure, and by a lowest indirect gap whose separation from the next higher direct gap increases linearly with x from Δ E i−d = 0.05 eV in GaSe to Δ E √ n−d in GaS; and by an exciton series associated with the direct gap.
69 citations
TL;DR: Ion Bernstein waves are excited by a long wire in the center of a potassium $Q$-machine plasma column as discussed by the authors, and the wave vector is very nearly perpendicular to the magnetic field, in contrast to neutralized ion Bernstein waves which were previously observed.
Abstract: Ion Bernstein waves are excited by a long wire in the center of a potassium $Q$-machine plasma column. Because the wave vector is very nearly perpendicular to the magnetic field, we observe pure ion Bernstein waves, in contrast to neutralized ion Bernstein waves which were previously observed. The frequency bands for the cyclotron damping are so narrow that we can distinguish the isotopes of potassium.
64 citations
TL;DR: In this article, the authors present and discuss some physical hypotheses on the decrease of truncated correlation functions and show that they imply the analyticity of the thermodynamic limits of the pressure and of all correlation functions with respect to the reciprocal temperature β and the magnetic fieldh (or the chemical potential μ) at all (real) points (β 0,h 0) (or (β0, μ 0)) where they are supposed to hold.
Abstract: We present and discuss some physical hypotheses on the decrease of truncated correlation functions and we show that they imply the analyticity of the thermodynamic limits of the pressure and of all correlation functions with respect to the reciprocal temperature β and the magnetic fieldh (or the chemical potential μ) at all (real) points (β0,h0) (or (β0, μ0)) where they are supposed to hold. A decrease close to our hypotheses is derived in certain particular situations at the end.
64 citations
56 citations
TL;DR: In this paper, the authors present results of measurements of K±p and pp elastic scattering and of the annihilation reactions pp→π+π− and pp→K+K− at an incident laboratory momentum of 5 GeV/c.
TL;DR: Magnetic resonance studies of nucleotide solutions have given evidence of anti conformations, based on the chemical shift of the sugar protons by the diamagnetic current in the base as well as on the shifts of base protONS by the phosphate group; however, this does not exclude the existence, part-time, of other conformations.
Abstract: Nucleotides occur in biological systems as components of DNA and RNA as well as cofactors of numerous enzymatic reactions. There are various derivatives, such as 2’-oxy or 2’-deoxy, among which the relevant enzymes discriminate efficiently. The question has been raised whether the structures of various derivatives in solution could differ, thus contributing to this discrimination. It has also been suggested that the mononucleotide conformation could sometimes be an important factor in the structure of polynucleotides, as contrasted to the role of interactions (stacking, hydrogen-bonding, and so forth) between nucleotides. If such effects are to be significant, it seems necessary for each nucleotide to assume a definite and rigid structure in solution. Although direct observations were lacking until recently, the general view, based on x-ray determinations of the structures in crystals,’ seems to have been that a nucleotide in solution is a rather rigid entity, with the base oriented anti2*3 to the sugar (FIGURE 1) in most but not all cases. Theoretical evaluations of nucleotide configurations usually do not take into account the nucleotide-solvent interactions and are therefore not easily applicable. Magnetic resonance studies of nucleotide solutions have given evidence of anti conformations, based on the chemical shift of the sugar protons by the diamagnetic current in the base as well as on the shifts of base protons by the phosphate group; however, this does not exclude the existence, part-time, of other conformations. The proton shifts and relaxation rates of rare-earth complexes have been interpreted 9 in terms of a rigid anti conformation for adenosine-5’-monophosphate (Ado-5’-P) , although the possibility of other part-time conformations was not ascertained. On the other hand, a number of studies argue against a single, rigid conformation. Circular dichroism measurements show that the conformation of guanosine monophosphates (Guo-Ps) changes according to pH.’O The
TL;DR: In this paper, the energy bands of SnS2 and SnSe2 were calculated using the local empirical pseudopotential method, which was adjusted in such a way that the calculations reproduce the experimental values of the fundamental gaps.
Abstract: The energy bands of SnS2 and SnSe2 are calculated using the local empirical pseudopotential method. The form factors of the pseudopotential were adjusted in such a way that the calculations reproduce the experimental values of the fundamental gaps. The space group D of these compounds is studied in detail and a comparison is made between the recent calculation by Fong and Cohen and the present work. Prom the pseudo wavefunctions the charge distributions of electrons and holes are calculated.
Die Bandstruktur von SnS2und SnSe2wurdemitderempirischen Pseudopotentialmethode berechnet. Die Potential-Formfaktoren wurden an experimentelle Daten angepast. Eine gruppentheoretische Analyse der Raumgruppe D wurde im Detail durchgefuhrt und mit den Ergebnissen von Fong und Cohen verglichen. Die Pseudowellenfunktionen. dienten zur Berechnung der Dichteverteilungen von Lochern und Elektronen.
TL;DR: The total cross-sections for v e (v e ) -nucleon scattering have been measured as discussed by the authors, and a test has been made of the muon number conservation law.
TL;DR: In this article, it was shown that the value of then-shot games is constant inn and is equal to the concavification of the game in which the informed player disregards his extra information.
Abstract: Repeated zero-sum two-person games of incomplete information on one side are considered. If the one-shot game is played sequentially, the informed player moving first, it is proved that the value of then-shot game is constant inn and is equal to the concavification of the game in which the informed player disregards his extra information. This is a strengthening ofAumann andMaschler's results for simultaneous games. Optimal strategies for both players are constructed explicitly.
01 Jan 1973
TL;DR: Theoretically, the position of activated complexes strongly depends on energy, but only weakly on the rotational state as mentioned in this paper, and their position is determined by the minimum density of states criterion.
Abstract: Nach der Theorie des aktivierten Komplexes werden spezifische Geschwindigkeitskonstanten k(E) fur Zerfallsreaktionen bei verschiedenen Anregungsenergien E berechnet. Zur Lokalisierung der Lage aktivierter Komplexe wird das Prinzip des Minimums der Zustandsdichte systematisch angewandt. Wegen der starken Kopplung zwischen Reaktionskoordinate und Molekulrest liegen die aktivierten Komplexe weit vor den Zentrifugalmaxima. Ihre Lage hangt stark von der Anregungsenergie, jedoch nur schwach vom Rotationszustand ab. Bei zu hohen Anregungsenergien existieren aktivierte Komplexe im definierten Sinne nicht mehr. Die Berechnungen von k(E) stehen in guter Ubereinstimmung mit Experimenten zur Photolyse von NO2 sowie zur thermischen Dissoziation und Rekombination O + NO NO2 im Hochdruckbereich.
Specific rate constants k(E) for dissociation processes at different excitation energies E have been calculated by the use of transitionstate theory. Activated complexes have systematically been localized by the minimum density of states criterion. Because of strong coupling between the reaction coordinate and the rest of the molecule, activated complexes are found at interfragment distances much smaller than those of the centrifugal maxima. Their position strongly depends on energy, but only weakly on the rotational state. At too high excitation energies, activated complexes in the defined sense do not exist. The calculated values of k(E) agree well with experimental data from the photolysis of NO2 and the thermal dissociation and the recombination O + NONO2 in the high pressure limit.
TL;DR: In this paper, a measurement of the I = 3/2 Kπ elastic scattering cross section by applying the Chew-Low extrapolation method in the reaction K−p → K−π−Δ++ at 14.3GeV/c was presented.
TL;DR: In this paper, the electric dipole moments of substituted benzene- and thiophene-chromium tricarbonyl compounds were examined and it was shown that the arene-Cr(CO)3 group moment depends upon the nature of the substituent in a precise manner.
TL;DR: In this paper, the diffusion coefficients of silver on singular and vicinal surfaces of copper have been measured using an oxidation method to determine the concentration profiles, and the differences between this model and the diffusion observed on the singular surfaces are explained by the presence of separated ledge loops on these surfaces.
TL;DR: In this article, the authors have made a theoretical and an experimental study of these phenomena and the results allow them to derive some simple rules which make the choice of parameters of the system of data acquisition easy.
Abstract: It is not possible in practice to carry out measurements in quantitative or qualitative analysis at a precision level better than 0.5% if conventional equipment such as recorders and electronic integrators are used to obtain the data. Only numerical techniques of on-line or off-line measurements associated with data handling by computer can be used. From their very nature numerical techniques are discontinuous and the number of experimental points is limited. According to information theory this discontinuous character does not imply a loss of accuracy provided that some simple relationship derived from the theory of sampled systems is fulfilled. These conditions deal with the choice of the sampling frequency, the frequency band-width of the amplifier and measurement system, and the upper limit of the signal frequency. We have made a theoretical and an experimental study of these phenomena and the results allow us to derive some simple rules which make the choice of parameters of the system of data acquisition easy. We have also determined the main sources of error in data acquisition systems and calculated their contribution.
TL;DR: In this paper, the authors investigate experimentally electron (ne), negative ion (n-) and positive ion(n+) densities characterizing laboratory negative ion-rich plasmas, produced by electron attachment in N2O3, O2 and I2.
Abstract: The scope of this research is to investigate experimentally electron (ne), negative ion (n-) and positive ion (n+) densities characterizing laboratory negative ion-rich plasmas, produced by electron attachment in N2O3, O2 and I2, and to find out the factors limiting the achievement of very low s (relative electron density s = ne/n+). These plasmas may be of great interest for the production of negative ion beams. It is shown experimentally that it is possible to produce plasmas with a high proportion of negative ions (n-/n+ ? 90 %) and a low proportion of electrons, at densities n+ up to 1011 cm-3. The comparison of mass spectrometric data with kinetic calculations leads to the conclusion that the loss of negative ions by diffusion limits the lowest s achieved at low ion density (n+ < 109 cm-3). At higher ion density, mutual neutralization seems to control the s values. A general limitation seems to exist for the lowest s attainable in small plasmas produced by electron attachment : the confinement of negative ions in a plasma is due to the presence of electrons and therefore this confinement becomes inefficient when s drops to values as low as 10-3.
TL;DR: In this article, the authors propose an extension of Loxydation d'alcools primaires deuteries, RCD 2 OH and trities RCHTOH par le carbonate dargent conduit aux aldehydes avec un rendementeleve.
TL;DR: In this paper, a detailed experimental and theoretical investigation of the large Knight shifts of PbSe and PbTe at low temperature was performed on bulk single crystals using the technique of helicon-spin interaction.
Abstract: We report a detailed experimental and theoretical investigation of the large Knight shifts of ${\mathrm{Pb}}^{207}$ in $N$- and $P$-type PbSe and PbTe at low temperature. The nuclear-resonance experiments are performed on bulk single crystals using the technique of helicon-spin interaction. We give the first quantitative account of the Knight shift of ${\mathrm{Pb}}^{207}$ due to $s$-like holes, and we determine a value of the hyperfine coupling constant that confirms the validity of augmented-plane-wave calculations for the lead salts. The large shift created by the $p$-like conduction electrons is shown to be due to the large orbital and dipolar hyperfine fields arising from ${p}_{\frac{1}{2}}$ states. In presence of spin-orbit interaction, the dipolar field (which previous studies, invoking cubic symmetry, ignored) cannot be neglected: It is in fact responsible for half of the shift. This study shows that a large Knight shift must not be interpreted as an experimental evidence of an $s$-like symmetry of the wave function.
TL;DR: In this paper, the authors studied the Kππ system in the 14.3 GeV/c reactions and found that the first two final states are dominated by Q-production.
TL;DR: In this paper, a double cavity laser pumped dye laser using the same amplifying cell was used to obtain short pulses fully adjustable between 2 and 20 nsec, where the duration of the pulse (short cavity) was controlled using a lower threshold cavity with adjustable length.
TL;DR: In this article, it was shown that if particle or antiparticle total cross-sections are unbounded, then the ratio of the ratio between particle and antiparticle's total crosssections is at most 0.0.
Abstract: If particle or antiparticle total cross sections ${\ensuremath{\sigma}}_{P}$, ${\ensuremath{\sigma}}_{A}$ are unbounded as $E\ensuremath{\rightarrow}\ensuremath{\infty}$, using unitarity it is shown that on the average the ratio $\frac{〈{\ensuremath{\sigma}}_{P}\ensuremath{-}{\ensuremath{\sigma}}_{A}〉}{〈{\ensuremath{\sigma}}_{P}+{\ensuremath{\sigma}}_{A}〉}\ensuremath{\rightarrow}0$.
TL;DR: In this paper, a theoretical amplification gain equation was derived in the case of an abscissa-dependent steady-state concentration of excited molecules, including triplet-triplet absorption effect.
01 Sep 1973
TL;DR: A variable sensitivity technique using the projection of a fringe pattern is demonstrated for mapping deformations, vibrations, contour lines and differences between two objects.
Abstract: A variable sensitivity technique using the projection of a fringe pattern is demonstrated for mapping deformations, vibrations, contour lines and differences between two objects. The method does not require laser illumination and gives an opportunity for studying large objects with incoherent light, and is compared with other techniques such as holography or speckle. The limitations likely to be encountered in industrial environments are discussed. The realization and incoherent projection of gratings is also discussed.
01 Dec 1973
TL;DR: In this paper, the surface activity coefficients are independent of the bulk properties for polar systems leading to a small solubility of the solute in the stationary phase, and the method appears to be sensitive and quite reliable in the range of infinite dilution.
Abstract: Equations allowing the calculation of gas-liquid interface and bulk liquid activity coefficients from gas-liquid chromatography data have been derived. The method appears to be sensitive and quite reliable in the range of infinite dilution. Practical results seem to show that the surface activity coefficients are independent of the bulk properties for polar systems leading to a small solubility of the solute in the stationary phase.