Showing papers by "École Polytechnique Fédérale de Lausanne published in 1980"
TL;DR: In this article, five electrostastic models for the oxide surface/eletrolyte solution interface, and the adjustable parameters associated with each model, are discussed, and a mathematical procedure for parameter adjustment to obtain optimal fit of the model to experimental data is introduced.
741 citations
TL;DR: In the present work, an ATP-dependent Ca2+ transport system which can be conclusively ascribed to heart sarcolemma is described and it is shown that a heart vesicular preparation particularly enriched in sar colemma markers accumulates Ca2- in the presence of ATP.
Abstract: Since the pioneering studies of Ringer of almost a century ago1,2, it has been known that the contraction of heart cells requires the presence of calcium in the extracellular medium. Ca2+ penetrates into the sarcoplasm where it either directly activates troponin C (ref. 3), or indirectly conveys the contraction signal to the myofibrils, possibly by inducing Ca2+ release from intracellular stores (sarcoplasmic reticulum, SR)4–6. After contraction Ca2+ must obviously leave the heart cell again to prevent its progressive accumulation. As the electrochemical potential of Ca2+ across the sarcolemma would prevent its passive outflow, the efflux of Ca2+ is an energy requiring process. Most of the Ca2+ is apparently ejected from heart cells in exchange for Na+ (refs 7, 8), on an electrophoretic antiporter which exchanges three Na+ ions for one Ca2+ (ref. 9). However, there is some evidence10–14 of a specific ATPase in cardiac sarcolemma, which could also have a role in the energy-dependent ejection of Ca2+. One important difficulty in trying to establish the existence of a specific Ca2+-ATPase in cardiac sarcolemma lies in the fact that most of the preparations used in such studies have been heavily contaminated by other sub-cellular fractions (mitochondria, SR) which also possess ATP-dependent Ca2+ transporting systems. In the present work we describe an ATP-dependent Ca2+ transport system which can be conclusively ascribed to heart sarcolemma. We show that a heart vesicular preparation particularly enriched in sarcolemma markers accumulates Ca2+ in the presence of ATP. That the process takes place in sarcolemmal vesicles is demonstrated by the fact that the accumulated Ca2+ is promptly and completely released in exchange for Na+.
287 citations
TL;DR: In this paper, a first attempt is made to incorporate the various disparate facts concerning their growth into a coherent growth model in particular, the usual minimum undercooling criterion is abandoned in favour of one based on the morphological instability and branching of the phases Despite numerous approximations, the correct order of magnitude of spacing and under cooling is predicted, as is the effect of the imposed temperature gradient.
189 citations
TL;DR: In this paper, the authors show that n-heptadecane is most abundant in the surface sediments (8-24 μg/g dry sediment) due to the extensive phytoplankton production in the highly eutrophic lake.
166 citations
TL;DR: Investigation in the yeasts Hansenula polymorpha and Kloeckera sp.
Abstract: The regulation of the synthesis of four dissimilatory enzymes involved in methanol metabolism, namely alcohol oxidase, formaldehyde dehydrogenase, formate dehydrogenase and catalase was investigated in the yeasts Hansenula polymorpha and Kloeckera sp. 2201. Enzyme profiles in cell-free extracts of the two organisms grown under glucose limitation at various dilution rates, suggested that the synthesis of these enzymes is controlled by derepression — represion rather than by induction — repression. Except for alcohol oxidase, the extent to which catabolite repression of the catabolic enzymes was relieved at low dilution rates was similar in both organisms. In Hansenula polymorpha the level of alcohol oxidase in the cells gradually increased with decreasing dilution rate, whilst in Kloeckera sp. 2201 derepression of alcohol oxidase synthesis was only observed at dilution rates below 0.10 h−1 and occurred to a much smaller extent than in Hansenula polymorpha.
144 citations
TL;DR: In this paper, the spontaneous emission rates of emitters embedded in a thin layer 0 of a loss-free dielectric depend on their optical environment, i.e., on the optical properties of the two media 1 and 2 adjoining layer 0.
Abstract: The spontaneous-emission rates of emitters embedded in a thin layer 0 of a loss-free dielectric depend on their optical environment, i.e., on the optical properties of the two media 1 and 2 adjoining layer 0. For electric- and magnetic-dipole transitions the spontaneous-emission rates, normalized with respect to those in an infinite medium 0, are expressed in terms of the Fresnel reflection coefficients for plane and evanescent waves incident from medium 0 on the interfaces to the planar-stratified or homogeneous media 1 and 2, respectively. From this result which is valid for arbitrary layer thicknesses ${d}_{0}$ we derive an approximation for extremely thin layers of optical thickness ${n}_{0}{d}_{0}\ensuremath{\ll}\frac{\ensuremath{\lambda}}{8}$ (where $\ensuremath{\lambda}$ is the emission wavelength) between two homogeneous loss-free dielectric media 1 and 2. For the normalized spontaneous-emission rates as functions of the refractive indices ${n}_{j}$ of media $j=0, 1, \mathrm{and} 2$ analytical expressions are obtained. We have used these expressions previously without proof [Phys. Rev. B 21, 4814 (1980)] to analyze experimentally observed changes in the fluorescence lifetime of ${\mathrm{Eu}}^{3+}$ ions in varying optical environments, which yielded the quantum efficiency of the emitting state.
140 citations
TL;DR: In this article, evidence is presented indicating that the extinction of large terrestrial animals was caused by atmospheric heating during a cometary impact and that the mass extinction of marine plankton was a consequence of poisoning by cyanide released by the fallen comet and of a catastrophic rise in calcite-compensation depth in the oceans after the detoxification of the cyanide.
Abstract: Evidence is presented indicating that the extinction, at the end of the Cretaceous, of large terrestrial animals was caused by atmospheric heating during a cometary impact and that the extinction of calcareous marine plankton was a consequence of poisoning by cyanide released by the fallen comet and of a catastrophic rise in calcite-compensation depth in the oceans after the detoxification of the cyanide.
128 citations
127 citations
TL;DR: In this paper, a network of seismic refraction profiles across the Betic Cordillera was established with shotpoints at sea off the Spanish coast, and the longest profile with a length of 440 km runs parallel to the general strike through the centre of the Biclòs.
Abstract: Summary. In 1974 and 1975 a network of crustal seismic refraction profiles across the Betic Cordillera was established with shotpoints at sea off the Spanish coast. The longest profile with a length of 440 km runs parallel to the general strike through the centre of the Betic Cordillera. Two other profiles lie south of the main profile closer to the coast and perpendicular to the east-west strike, respectively. The interpretation of P waves indicates pronounced lateral variations of the structure and thckness of the crust and upper mantle. Two different crustal blocks seem to exist on either side of the north-east trending Palomares and Alhama de Murcia fault system in the eastern Betic Cordillera. East of this fault system the crust is only 23 km thick with a shallow high velocity layer of 6.9 km s-'. West of this line in the central and southern part of the Betic Cordillera the crust-mantle boundary lies at depths of 39 km and 24 km, respectively. In this area a velocity of 6 km s-l is reached at about 3 km depth. A layer of reduced P-wave velocity follows between 7 and 12 km depth with a velocity of 5.4 km s-'. At its lower boundary the velocity increases to 6.2 km s-l and reaches values between 6.6 and 6.7 km s-l at a depth of 18 km under the south coast and 24 km under the centre of the Betic Coddlera east of Granada. A thin lid of about 6 km thickness and a P, velocity of 8.1 km s-' lies on top of a rather thick layer with the reduced velocity of 7.8 km s-'. At a depth of 63 km the velocity increases again to 8.3 km s-'. Deep-reaching structural differences mark the east-west trending boundary between the internal and external zones of the central Betic Cordillera.
126 citations
TL;DR: This paper defines a heuristic method as a procedure for solving a well-defined mathematical problem by an intuitive approach in which the structure of the problem can be interpreted and exploited intelligently to obtain a reasonable solution.
107 citations
TL;DR: Graph theoretical models are proposed for dealing with so called geographical constraints: these are due to the fact that the teams of the league are located in different cities which may be at various distances from each other.
TL;DR: In this article, a field study was carried out with a group of 119 female accounting machine operators, where the keyboard was operated with the right hand only, while the left hand was turning over coupons.
TL;DR: Automatic generation control is discussed from the point of view of the steady-state loadflow between areas, the control algorithm, noninteractive control, optimum control and its impact on security enhancement, as well as the various interfaces to upper and lower level control functions.
TL;DR: In this paper, two classes of phase transitions have been observed; order-disorder transitions of the rigid hydrocarbon chains and conformational transition of the chains, and typical examples of both classes are presented and their chain dynamics are discussed.
Abstract: Perovskite type layer-structure compounds of the formulas (Cn H2n+1 NH3)2·MCl4 and NH3 (CH2)n NH3MCl4 (M = Cd, Mn, Cu, Fe, n = 1–18) exhibit a variety of structural phase transitions which are connected with the dynamics of the alkyl-ammonium or alkylenediammonium chains respectively. Two classes of phase transitions have been observed; Order-disorder transitions of the rigid hydrocarbon chains and conformational transitions of the chains. Typical examples of both classes are presented and their chain dynamics are discussed.
TL;DR: It is demonstrated that the modulation transfer function of the coherent four-wave process mixing can be controlled by the amplitude of externally applied field E0.
Abstract: Dependence of phase-conjugate wave-front reflectivity on the spatial frequency of the dynamic hologram recorded in Bi12SiO20 crystals is analyzed. Depending on the respective values of applied field E0 and fringe spacing Λ, drift or diffusion of the photocarriers dominates the space-charge buildup and affects the phase-conjugate wave-front intensity differently. It is demonstrated that the modulation transfer function of the coherent four-wave process mixing can be controlled by the amplitude of externally applied field E0. Experimental results are interpreted on the basis of the dynamic theory of Kukhtarev et al.
TL;DR: In this article, the Caledonian Jotun nappe in the Tyin area of southern Norway has been investigated using U-Pb analysis of zircon and sphene and Rb-Sr measurements of minerals and whole rocks, with special reference to the reaction of the isotope systems to various kinds of metamorphic event.
TL;DR: In this article, the authors investigated the influence of current density and electrolyte flow rate on anode potential, current efficiency for metal dissolution and surface texture resulting from dissolution in a flow channel cell under controlled hydrodynamic conditions.
TL;DR: In this article, the Coulomb forces on particles in an infinite configuration of charges in one dimension were computed and a structural proof of the translation symmetry breaking in jellium, at all temperatures, and a related phenomenon of phase nonuniqueness in the two component system were discussed.
Abstract: We present a method of computing the Coulomb forces on particles in an infinite configuration of charges in one dimension. The resolution of the apparent nonuniqueness in this problem leads to a structural proof of the translation symmetry breaking in jellium, at all temperatures, and to a related phenomenon of phase nonuniqueness in the two component system. The appropriate generalizations of the DLR and KMS conditions for these states are discussed.
TL;DR: In this paper, the ordering of random-site electric dipoles in a nonpolar lattice was shown for nuclear magnetic resonance and dielectric susceptibility data in KTa${\mathrm{O}}_{3}$: Li.
Abstract: Nuclear magnetic resonance and dielectric susceptibility data are reported in KTa${\mathrm{O}}_{3}$: Li which show, for the first time, ordering of random-site electric dipoles in a nonpolar lattice.
TL;DR: The surface-bound aminopeptidase had broad substrate specificity and hydrolyzed many amino acid arylamides and many peptides with unsubstituted NH(2)-terminal amino acids.
Abstract: A surface-bound aminopeptidase of Lactobacillus lactis cells was solubilized with lysozyme, and the extract was subjected to streptomycin sulfate precipitation, ammonium sulfate fractionation, chromatography on Sephadex G-100 and diethylaminoethyl-Sephadex A-50, and preparative polyacrylamide gel electrophoresis. The purified enzyme was homogeneous in disc electrophoretic analysis and consisted of a single polypeptide chain with a molecular weight of 78,000 to 81,000. The optimal pH and optimal temperature for enzyme activity were 6.2 to 7.2 and 47.5°C, respectively, for l-lysine-4-nitroanilide as the substrate. The enzyme was activated by Co2+ and Zn2+ ions and inhibited by Cu2+, Hg2+, and Fe3+ ions and by the metal-complexing reagents ethylenediaminetetraacetic acid, 1,10-phenanthroline, and α,α′-dipyridyl. Higher concentrations of substrate and hydrolysis products also inhibited the activity of the enzyme. The aminopeptidase had broad substrate specificity and hydrolyzed many amino acid arylamides and many peptides with unsubstituted NH2-terminal amino acids.
TL;DR: In this paper, the authors defined a transferable valence force field for a series of molecules containing C�O groups, including pyruvic acid, acetone, acetic acid, methyl acetate, formic acid and methyl formate.
01 Jul 1980
TL;DR: This paper gives a review of block coding for picture data compression with a slight increase in complexity, block coding can be made adaptive in a number of ways, leading to much higher compressions.
Abstract: This paper gives a review of block coding for picture data compression. Block coding has been devised primarily for coding of graphics, but it has subsequently been extended to multilevel pictures. All the proposed codes are simple suboptimum prefix codes. Their simplicity make them suitable for real-time applications. Although blocks can be of any shape, higher efficiencies are obtained with two-dimensional blocks, thus exploiting the inherent two-dimensional correlation of pictures. According to the value of a preset parameter, block coding can be either information lossless or information lossy. In the former case, the original digitized picture can be exactly reconstructed from its coded version. In the latter case, where the compression is much higher, distortions possess easily identified features. An appropriate filtering can restore the decoded picture satisfactorily. With a slight increase in complexity, block coding can be made adaptive in a number of ways, leading to much higher compressions. For each case, comprehensive theoretical models are developed to predict the performances and to optimize the parameters. The dependence of the compression ratio on image resolution for each specific code is also examined.
TL;DR: In this paper, the incompressible flow in a labyrinth seal is computed using the ''κ−e'' turbulence model with a pressure-velocity computer code in order to explain leakage phenomena against the mean pressure gradient.
Abstract: The incompressible flow in a labyrinth seal is computed using the ‘κ−e’ turbulence model with a pressure-velocity computer code in order to explain leakage phenomena against the mean pressure gradient. The flow is axisymmetric between a rotating shaft and an enclosing cylinder at rest. The main stream in circumferential direction induces a secondary mean flow vortex pattern inside annular cavities on the surface of the shaft. The domain of interest is one such cavity of an enlarged model of a labyrinth seal, where the finite difference result of a computer program is compared with measurements obtained by a back-scattering laser-Doppler anemometer at a cavity Reynolds number of ∼ 3 × 104 and a Taylor number of ∼ 1·2 × 104. The turbulent kinetic energy and the turbulence dissipation rate are verified experimentally for a comparison with the result of the turbulence model.
TL;DR: Lipophilic, steric, electronic, and enzyme resistance characteristics of carboranylalanine, adamantylalanines, neopentylglycine and tert-butyl glycine are described.
Abstract: Lipophilic, steric, electronic, and enzyme resistance characteristics of carboranylalanine, adamantylalanine, neopentylglycine and tert-butylglycine are described. The first 2 amino-acids display lipophilicities 2 orders of magnitude higher than tryptophan.
TL;DR: In this article, an efficient and flexible method for the preparation of silyl nitronates is described, and NMR spectral investigations indicate a rapid 1,3-silyl migration process, with an activation energy of about 10 kcal mol−1.
Abstract: An efficient and flexible method for the preparation of silyl nitronates is described (see 1–10). NMR. spectral investigations indicate a rapid 1,3-silyl migration process, with an activation energy of about 10 kcal mol−1. X-ray crystallographic studies on the silyl nitronates 3 and 8 show structures that lean towards an SN2 retention pathway at silicon.
TL;DR: In this article, the Coulomb force at the boundary between different properties of one-component systems is defined and its properties are discussed in relation to the asymptotic behavior of the force at infinity.
Abstract: Several definitions of the “pressure” are introduced for one-component systems and shown to be nonequivalent in the presence of a rigid neutralizing background. Relations between these pressures are derived for finite and infinite systems; these relations depend on the asymptotic behavior of the force at infinity, with the Coulomb force at the borderline between different properties. It is argued that only one of those definitions is physically acceptable and its properties are discussed in relation to the asymptotic behavior of the force. It is seen in particular that a knowledge of the state of the infinite system is not sufficient to determine its thermodynamic properties. The results are illustrated by some typical examples.
TL;DR: Growth temperature has been measured as a function of applied growth velocity for grey (austenite-flake graphite) eutectic, austenite dendrites and white eutectoric in Fe-428 wt pct C at a temperature gradientG of ∼7 K/mm, showing that the growth form with the highest growth temperature at a particularV should prevail as discussed by the authors.
Abstract: Growth temperature has been measured as a function of applied growth velocityV for grey (austenite-flake graphite) eutectic, austenite dendrites and white (austenite-cementite) eutectic in Fe-428 wt pct C at a temperature gradientG of ∼7 K/mm Grey eutectic (04 to 65 µm/s) required an undercoolingΔTfor growth equal toK1V1/2 withK1 as 34 ± 01 Ks1/2/µm1/2, giving values ofΔT nearly an order of magnitude larger than predicted for growth at the extremum, as shown previously by Toloui and Hellawell for the related Al-Si eutectic Austenite dendrites growing together with the grey eutectic atV between 11 and 65 µ m/s exhibited a range of tip temperatures giving rise to average undercoolings of magnitude [GD/V +K2Vn] withD as diffusion coefficient of carbon in the melt andK2 as 073 Ksn µm−n withn as 046 predicted by Ivantsov’s theory for growth of an austenite needle White eutectic displaced both grey eutectic and austenite dendrites atV of 100 µm/s Except for the persistence of grey eutectic rather than white eutectic in the presence of austenite dendrites (11
01 Dec 1980
TL;DR: The influence of temperature on the growth of the theromophilic Bacillus caldotenax was investigated using chemostat techniques and a chemically defined minimal medium and all determined growth constants, that is maximal specific growth rate, yield and maintenance, were temperature dependent.
Abstract: The influence of temperature on the growth of the theromophilic Bacillus caldotenax was investigated using chemostat techniques and a chemically defined minimal medium. All determined growth constants, that is maximal specific growth rate, yield and maintenance, were temperature dependent. It was striking that the very large maintenance requirement was about 10 times higher than for mesophilic cells under equivalent conditions. A death rate, which was very substantial at optimal and supraoptimal growth temperatures, was estimated by comparing the maintenance for substrate and oxygen. There was no indication for a thermoadaptation as postulated by Haberstich and Zuber (1974).