Showing papers by "École Normale Supérieure published in 1973"
428 citations
TL;DR: In this article, the formulation of international marketing strategies is requiring more sophisticated management approaches due to the increasing importance of international business operations, and the authors examine the impact of such approaches on international marketing.
Abstract: The formulation of international marketing strategies is requiring more sophisticated management approaches due to the increasing importance of international business operations. The authors examin...
206 citations
TL;DR: Upon conversion to product, flavin mononucleotide-like absorption and fluorescence appear, supporting the postulate that flavin turns over in the reaction, which is equal to that of pure luciferase.
Abstract: Bacterial luciferase catalyzes the oxidation of reduced flavin mononucleotide by molecular oxygen; long-chain aldehyde is required for light emission. At 20° the bioluminescence has a lifetime of tens of seconds, while excess reduced flavin is removed by way of nonenzymatic autoxidation in less than a second. This observation indicates the existence of a long-lived enzyme intermediate, which has been postulated to be a peroxide of the enzyme-bound reduced flavin. This intermediate was isolated and studied at low temperature (-20°), where it has a lifetime measured in days. It has an absorption with a single band peaking at 372 nm, and fluorescence emission centered at about 485 nm, which might be expected for the postulated flavin peroxide. Upon conversion to product, flavin mononucleotide-like absorption and fluorescence appear, supporting the postulate that flavin turns over in the reaction. Upon injection into buffer at 20° with added aldehyde, bioluminescence occurs. Based on a stoichiometry of one flavin per luciferase molecule, the specific activity of the intermediate is equal to that of pure luciferase.
163 citations
TL;DR: In this paper, the authors attributed changes in an East African Game Reserve may be attributed to changes in climatic conditions and soil salinity, and tree damage from elephants and overgrazing by livestock.
Abstract: Ecological changes in an East African Game Reserve may be attributed to changes in climatic conditions and soil salinity. Tree damage from elephants and overgrazing by livestock are probably secondary factors.
161 citations
TL;DR: In the study of the enzyme produced by a strain of Escherichia coli resistant to ampicillin, penicillin G and V, the pHmetric technique was able to increase the sensitivity and computer analysis of the curve obtained from a single titration gave values of Km and Vm.
136 citations
TL;DR: In mice, yohimbine antagonized very effectively the prolongation of chloral-induced sleep by clonidine; 883F was effective at high dosage but the other α-adrenoceptor blocking agents were ineffective; these results support the hypothesis that sedation induced byClonidine is mediated by the activation of α- adrenoceptors different from the peripheral adrenoceptor.
83 citations
TL;DR: In this article, the surface potential of jellium is determined exactly in terms of the bulk properties of the uniform electron gas, independent of any assumption concerning the electron energy density functional in an inhomogeneous system and dependent only on the energy density in the homogeneous solid.
Abstract: Analytic results are derived for the surface properties of jellium. The surface potential relative to its bulk value is determined exactly in terms of the bulk properties of the uniform electron gas. This result is independent of any assumption concerning the electron energy density functional in an inhomogeneous system and depends only on the energy density in the homogeneous solid. We discuss the basic inapplicability of dispersiontype calculations of the surface energy.
81 citations
TL;DR: In this paper, the Luttinger model was used to explain interband and intraband magnetoabsorption in pure HgTe thin crystals in the spectral region 300-400 meV.
Abstract: Magnetoabsorption associated with ${\ensuremath{\Gamma}}_{6}\ensuremath{\rightarrow}{\ensuremath{\Gamma}}_{8}$ transitions was investigated at 4.4 \ifmmode^\circ\else\textdegree\fi{}K, on pure $n$-type HgTe thin crystals in the spectral region 300-400 meV for $\ensuremath{\sigma}$ and $\ensuremath{\pi}$ polarizations. Analysis of experimental spectra is performed using both the three-band model (including the nonparabolicity), and the theory of Luttinger. Band parameters are determined by fitting transition energies: ${E}_{{\ensuremath{\Gamma}}_{8}}\ensuremath{-}{E}_{{\ensuremath{\Gamma}}_{6}}=302.5$ meV, $\frac{{m}_{{\ensuremath{\Gamma}}_{6}}}{{m}_{0}}=0.028\ifmmode\pm\else\textpm\fi{}0.001$, and ${g}_{{\ensuremath{\Gamma}}_{6}}=\ensuremath{-}41\ifmmode\pm\else\textpm\fi{}4$ at $\ensuremath{\Gamma}$. ${\ensuremath{\Gamma}}_{8}$ Luttinger parameters (${\ensuremath{\gamma}}_{1}=\ensuremath{-}12.8,\overline{\ensuremath{\gamma}}=\ensuremath{-}8.4,\ensuremath{\kappa}=\ensuremath{-}10.5$) satisfactorily explain interband and intraband ${\ensuremath{\Gamma}}_{8}$ magnetoabsorption. The structure of ${\ensuremath{\Gamma}}_{8}$ magnetic levels near $\ensuremath{\Gamma}$ is quantitatively described by calculating the ${k}_{H}$ dependence of the energies in the [111] direction. A complex structure is found for a set of heavy holes.
72 citations
TL;DR: In this paper, light reflectivity measurements show that the molecules of MBBA lie parallel to the nematic-isotropic interface, that their orientations in the absence of any external field are correlated in the plane of the interface over distances greater than the optical wavelength and allow a study of the dynamics of the effect of a magnetic field on these molecules.
Abstract: Light reflectivity measurements show that the molecules of MBBA lie parallel to the nematic-isotropic interface, that their orientations in the absence of any external field are correlated in the plane of the interface over distances greater than the optical wavelength and allow a study of the dynamics of the effect of a magnetic field on these molecules. The spectrum analysis of the light scattered by the interface yields the value of the surface tension. This experimental value is used to estimate the correlation length in the isotropic phase.
71 citations
TL;DR: This model is examined for its consistency with a low resistance pathway between cardiac muscle cells, thought to be equivalent to intercellular channels in a recently proposed model.
Abstract: A morphometric study of the nexus of rat cardiac muscle was carried out. The nexus surface of one intercalated disk of one 15 µm thick fiber is found to range between 47 µm2 and 94 µm2, the latter value taking into account the maximal underestimation caused by tangential sectioning. Dividing the lower, minimal value by the surface of the observed subunits (90 A periodicity), one obtains for one intercalated disk 6.7 x 105 subunits, each of them assumed to be permeated by a central pore. These pores are thought to be equivalent to intercellular channels in a recently proposed model. Taking our morphometric and recently reported physiological values, this model is examined for its consistency with a low resistance pathway between cardiac muscle cells.
64 citations
TL;DR: Clonidine and l-dopa reduced pressor responses evoked by submaximal high frequency stimulation of the sciatic nerve, and medullary and hypotahalamic pressor areas and low frequency stimulation at these sites and in the cervical spinal cord evoked responses in the splanchnic nerve consiting of early and late components which were inhibited by clonidine.
TL;DR: In this paper, the authors re-alise'la ce´talisation se´lective de la fonction oxo-1 du me´thyl-8a dioxo- 1,6 octahydro-1,2,3,4,6,7,8, 8,8a naphtale`ne 1,2.
TL;DR: In this article, the positions and relative magnitudes of peaks appearing in some of these spectra are analyzed and quantitatively explained in terms of indirect creation of free excitons, which leads to important discriminations between direct and indirect optical absorption and between volume and surface radiative recombination.
Abstract: Excitation spectra of the excitonic luminescence in CdS are presented for three types of samples: doped, pure, and surface contaminated samples. The positions and relative magnitudes of peaks appearing in some of these spectra are analyzed and quantitatively explained in terms of indirect creation of free excitons. The different behaviour of the three types of samples investigated allows a more general discussion which leads to important discriminations between direct and indirect optical absorption and between volume and surface radiative recombination.
Nous presentons des spectres d'excitation de la luminescence excitonique du CdS pour trois types d'echantillons: dopes, purs et pollues en surface. Les positions et les tailles relatives des pics apparaissant dans certains de ces spectres sont analysees et expliquees quantitativement en terme de creation indirecte d'excitons libres. Les comportements diffetrents de nos trois types d'echantillons nous autorisent une discussion plus genetrale, qui conduit e, des distinctions importantes entre l'absorption optique directe et indirecte et entre la recombinaison radiative de surface et de volume.
TL;DR: The methode des fonctions modulatrices permet d'analyser une courbe experimentale resultant de la convolution d'une somme d'exponentielles avec une excitation as discussed by the authors.
Abstract: La methode des fonctions modulatrices permet d’analyser une courbe experimentale resultant de la convolution d’une somme d'exponentielles avec une excitation La troncature des enregistrements n’a pas d’influence directe sur la determination des parametres Les donnees experimentales peuvent etre depouillees automatiquement sans iterations
TL;DR: In this article, the binding energy of electron-hole drops in pure Ge and Si at low temperature has been investigated and it has been shown that their emission line shape is subject to a Gaussian broadening due to the phonon lifetime.
TL;DR: The zero-field splitting of the high spin ferric ion in a frozen solution of acid methemoglobin is determined from the frequency dependence of the g- value from the number of different wavelengths available in a wide range.
TL;DR: The same preparations used to investigate the different forms of acetylcholinesterase from electric eel to investigate their subunit composition by SDS acrylamide gel electrophoresis are used, coupled with those from electron microscopy, to lead to specific proposals about the molecular structure of the various forms.
TL;DR: In this article, a theoretical and experimental analysis of the optical pumping of neon atoms by the 6328 A laser line (transition 3s 2 -2p 4 ; J = 1-J = 2) shows clear evidence for fourth-order and sixth-order nonlinear effects in gas lasers.
TL;DR: Study by scanning electron microscopy of heads of Ascaris lumbricoides Linne 1758 and Asaris suum Goeze 1782 showed typical distinctive characteristics between these two species.
TL;DR: It is shown that the overall quantum yield of photoreduction is governed by the second step and can be calculated from the ratio of the rate constants of the two elementary processes involved in this step.
Abstract: — The photoreduction of thiazine dyes by ethylene diamine tetraacetic acid (EDTA) was investigated by Rash photolysis. This reaction was found to occur according to a three-step mechanism. the first being the formation of the dye triplet state followed, in weakly acid solutions, by protonation. During the second step, the triplet state of the dye disappears through two competing processes: spontaneous deactivation and reaction with EDTA, which leads to the semireduced dye. The third step leads to the leucodye. It is shown that the overall quantum yield of photoreduction is governed by the second step and can be calculated from the ratio of the rate constants of the two elementary processes involved in this step. This ratio was measured over a wide pH range.
TL;DR: In this article, the problem of an electron in crossed and parallel fields is solved in the one-level effective mass approximation (EMA), and the results are used to interpret the experimental interband transitions in Ge, with due account of the degenerate character of the valence band in this material.
TL;DR: In this paper, a methode du trace des diagrammes d'admittance complexe a ete appliquee a l’etude des electrodes O2, Ag/zircone stabilisee and O2, Pt/ZrO2 stabilizee.
Abstract: La methode du trace des diagrammes d’admittance complexe a ete appliquee a l’etude des cellules O2 , metal/(ZrO2 )0,91 — (Y2 O3 )0,09 /metaI, O2 . Trois domaines de frequence distincts ont ete mis en evidence. Les resultats obtenus dans le domaine des basses frequences sont plus particulierement caracteristiques des reactions d’electrodes. Les mesures effectuees dans ce domaine permettent de determiner les parametres de la reaction d’electrode a oxygene en s’affranchissant des effets dielectriques dus a l’electrolyte. La methode a ete appliquee a l’etude des electrodes O2 , Ag/zircone stabilisee et O2 , Pt/zircone stabilisee.La surtension de l'electrode en argent est negligeable pour les pressions d’oxygene voisines de l’atmosphere, pour les pressions plus faibles la composante reelle de l’impedance d’electrode est proportionnelle a [math] et son energie d’activation voisine de 2 eV. Dans le cas de l’electrode de platine les surtensions sont notables meme sous pression d’oxygene elevee, leurs variations sont beaucoup plus complexes que dans le cas de l’argent et semblent resulter de la formation d’un oxyde superficiel de platine.Les effets capacitifs observes resulteraient principalement d’une surtension de concentration en oxygene neutre. La capacite de double couche des electrodes est petite par rapport aux capacites mesurees el est donc inferieure a 10 µ.F/cm2 .
TL;DR: In this article, the authors presented very detailed ac measurements of the convection heat flux and induction electric field associated with the moving vortex lines in a low-$\ensuremath{\kappa}$ type-II superconductor (Pb-4.56-at.% In).
Abstract: We present here very detailed ac measurements of the convection heat flux ${\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}}_{2}^{h}$ and the induction electric field $\stackrel{\ensuremath{\rightarrow}}{E}$ associated with the moving vortex lines in a low-$\ensuremath{\kappa}$ type-II superconductor (Pb-4.56-at.% In). The measurements were made using an original low-frequency current-modulation method based on a second-sound technique. ${\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}}_{2}^{h}$ and $\stackrel{\ensuremath{\rightarrow}}{E}$ have been measured as functions of the applied magnetic field ${H}_{e}$ and the applied electric current density and frequency $\ensuremath{
u}$ ($300l\ensuremath{
u}l1200$Hz) in the temperature range between 1.3 and 2.1 \ifmmode^\circ\else\textdegree\fi{}K. The great accuracy of this ac method allows us to observe some interesting details in the ${\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}}_{2}^{h}({H}_{e})$ and $\stackrel{\ensuremath{\rightarrow}}{E}({H}_{e})$ curves. In particular, ${\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}}_{2}^{h}({H}_{e})$ reverses its direction at low fields (${H}_{e}\ensuremath{\gtrsim}{H}_{c1}$), while $\stackrel{\ensuremath{\rightarrow}}{E}({H}_{e})$ remains in the same direction in the whole of the mixed state. This reversal effect suggests that, due to the presence of nonlocal effects in our low-$\ensuremath{\kappa}$ alloy ($\ensuremath{\kappa}\ensuremath{\approx}1.25$), there are vortex lines of opposite sign in the superconductor. Furthermore, we have observed that ${\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}}_{2}^{h}({H}_{e})$ vanishes only for fields larger than the upper critical field ${H}_{c2}(T)$. The transported entropy ${S}_{D}$ per unit lenght of flux line per flux quantum computed from these measurements was found to be independent of the applied current density and frequency. In the high-field region (${H}_{e}\ensuremath{\lesssim}{H}_{c2}$) experimental values of ${S}_{D}$ are in good agreement with the theoretical predictions of Caroli and Maki in the dirty limit. The calorimetric entropy per vortex line was obtained theoretically from the free-energy forms in the mixed state and compared with ${S}_{D}$.
TL;DR: In this article, the inverse scattering method is applied to a perfectly conducting sphere and the results of a simulated experiment are compared to those given by this method in real-world experiments.
Abstract: Lewis' inverse scattering method is applied to a perfectly conducting sphere. The results of a simulated experiment are compared to those given by this method.
TL;DR: La diphénylhydantoïne agit sur la face externe de la peau de grenouille en provoquant une augmentation de la différence de potentiel et du courant de court circuit.
Abstract: La diphenylhydantoine agit sur la face externe de la peau de grenouille en provoquant une augmentation de la difference de potentiel et du courant de court circuit L'effet est rapide, soutenu et reversible Des interactions entre DPH, ocytocine, amiloride et amphotericine B ont ete etudiees
01 Jan 1973
TL;DR: In this paper, a nouvelle interpretation des proprietes dielectriques des electrolytes solides a base de zircone stabilisee a l'oxyde d'yttrium was proposed.
Abstract: Des mesures d’admittance ont ete effectuees sur des cellules symetriques du typeO2 , Metal/(ZrO2 )0,91 (Y2 O3 )0,09 /Metal, O2 .Les resultats experimentaux ont permis de proposer une nouvelle interpretation des proprietes dielectriques des electrolytes solides a base de zircone stabilisee a l’oxyde d'yttrium. Des echantillons frittes de differentes puretes et des monocristaux ont ete etudies dans le cadre de cette interpretation. Les resultats obtenus montrent que : —une partie des impuretes dissoutes dans l’electrolyte est segregee aux joints de grains lorsque la temperature s’abaisse; ce phenomene est reversible; —le « vieillissement » des zircones stabilisees resulte habituellement de deux phenomenes distincts et depend iortcment du degre de purete de l’electrolyte; —les impuretes jouent un role notable dans la conductivite des zircones stabilisees a basse temperature.
TL;DR: In this paper, the combined use of Hanle effect and optical pumping was shown to allow one to measure magnetic fields as small as 10−9 G. The Hanle Effect can be used to create alignment of states.
TL;DR: In this paper, a general treatment of the relationship between internal and external parameters for a charged dielectric in a plane-parallel geometry is given, where the charges induced on the electrodes by surface charges, volume charges, oriented dipoles in the dielectrics, and an applied voltage are calculated for contacting or non-contacting electrodes.
Abstract: A general treatment is given of the relationship between internal and external parameters for a charged dielectric in a plane-parallel geometry. The charges induced on the electrodes by surface charges, volume charges, oriented dipoles in the dielectric, and an applied voltage are calculated for contacting or noncontacting electrodes. The fields outside and inside the sample are also calculated. Similarly, the external current is related to the internal conduction and depolarization currents. An analogy is developed between the current flowing through the system in short-circuit conditions and the time derivative of the applied voltage that cancels the external current. Because of its relation to the motion of carriers in the dielectric, the motion of the zero-field plane is investigated under very general conditions.