Showing papers by "ETH Zurich published in 1969"
TL;DR: In this article, the Theorie thermisch getriebener Oszillationen fur Helium in Ubereinstimmung with der Erfahrung gebracht.
Abstract: Die Theorie von Kirchhoff fur gedampfte Schwingungen in langen Rohren und die darauf aufgebaute Theorie von Kramers fur thermisch getriebene akustische Oszillationen wird neu hergeleitet, wobei die sogenannte Grenzschichtvereinfachung zunachst nicht benotigt wird. Es zeigt sich, dass fur Helium eine in der Kramersschen Theorie auftretende Konstante fast genau verschwindet; dies hat zur Folge, dass fur thermische Schwingungen in Helium eine Grenzschichttheorie erster Ordnung versagt. Durch Hinzunahme von Gleidern, die vom Grenzschichtstandpunkt als Grossen zweiter Ordnung erscheinen, wird die Theorie thermisch getriebener Oszillationen fur Helium in Ubereinstimmung mit der Erfahrung gebracht.
387 citations
TL;DR: In this paper, the authors demonstrate that saline interstitial waters under an arid coastal plain could be set in hydrodynamic movement to replace the evaporative loss near the surface.
Abstract: SUMMARY
Experiments were performed to demonstrate that saline interstitial waters under an arid coastal plain could be set in hydrodynamic movement to replace the evaporative loss near the surface.
In contrast to movement in a vadose zone, which is related to capillary forces caused by surface tension, the type of movement we observed was induced by a vertical hydraulic gradient under the evaporated area. Fluid flow through porous media was induced by an upward decrease in hydrodynamic potential during evaporation. We propose to call this type of movement evaporative pumping.
Experiments further verified that flow rate induced by evaporative pumping was directly governed by evaporation alone; linear flow rate through coarse sand and that through very fine silt was approximately the same under the same evaporative condition. Yet the movement apparently obeyed Darcy's law. Since the permeability of the medium was fixed, and the flow rate was dictated by evaporation, only the hydraulic gradient could be the dependent variable in the Darcy equation. We observed that the gradient was indeed much greater in relative impermeable silt than in permeable sand, when the water to replace evaporative loss must flow with the same rate through those media.
Our experiments suggested that hydrodynamic movement induced by evaporation could be an effective mechanism to transport magnesium-bearing solutions through relatively impermeable sediments of an arid coastal plain. Computations showed that dolomitization by evaporative pumping could proceed at a rate to account for the origin of Recent dolomite crusts, and for the great thickness of ancient supratidal dolomites. In contrast, we believed that dolomitization by seepage reflux or by groundwaters cannot be extensive, because of the inadequate magnesium-supply rates by such waters.
223 citations
TL;DR: This chapter reviews information on a synaptic fine structure obtained by using iodide compounds of heavy metals for block staining and examining synaptic areas in specimens prepared with the freeze-etching technique, which confirms the true existence and spheric shape of synaptic vesicles.
Abstract: Publisher Summary This chapter reviews information on a synaptic fine structure that is obtained by using iodide compounds of heavy metals for block staining and examining synaptic areas in specimens prepared with the freeze-etching technique. The chapter focuses on synaptic vesicles—internal and external coats of nerve membranes and their specializations at the synaptic junction. The complex interplay of molecular mechanisms at the synapse is discussed in the chapter. Impregnation of synaptic junctions with bismuth iodide and subsequent contrasting with uranyl acetate and lead hydroxide give significant details on the presynaptic membrane and its densities. The methods are useful in monitoring experimental approaches to the problems of excitation, memory, and individuality, which remain great mysteries of living matter and the nervous tissue. Freeze-etching preparations of synapses confirm the true existence and spheric shape of synaptic vesicles. The chapter describes the differences between the outer and inner surfaces of the plasmalemma of presynaptic terminals. The presence of micropinocytosis at the surface of boutons terminaux is demonstrated in a study discussed in the chapter.
144 citations
109 citations
TL;DR: It is concluded that oviposition is very problably stimulated by the seminal fluid within the spermatophore and possibly also by the presence of active spermatozoa in the receptaculum.
80 citations
TL;DR: It is postulated that the exocellular polymers were responsible for the flocculent growth habit of the bacteria, and that the process of bacterial flocculation produced by synthetic polyelectrolytes was essentially the same as that caused by naturally produced exopolymers.
Abstract: Several gram-negative, polarly flagellated rods were isolated on the basis of their flocculent growth habit. Some of the isolates possessed a capsular matrix which is composed of exocellular fibrils. Other isolates did not appear to have a capsular matrix when examined with a bright-field microscope with or without the aid of stains. However, these latter type isolates did possess exocellular material which can be demonstrated by adsorption of a fluorescent dye under an ultraviolet microscope. Electron microscopic examination demonstrated that the exocellular material around all isolates examined is fibrillar. The fibrils were susceptible to cellulase although all fibrils did not appear to be identical. It is postulated that the exocellular polymers were responsible for the flocculent growth habit of the bacteria, and that the process of bacterial flocculation produced by synthetic polyelectrolytes was essentially the same as that caused by naturally produced exopolymers.
79 citations
TL;DR: In this paper, the transition points to line source or plane source behavior of the sound attenuation with distance are shown to be simply related to the characteristic dimensions of the source, which can be used to make a universal attenuation template.
70 citations
TL;DR: The Mohr-Coulomb criterion for failure, modified in light of the concept of effective stress, is where τ c is the critical shear stress at failure, S the normal pressure, and p the pore pressure across the plane of internal slippage at failure, ϕ i the internal friction angle, and τ 0 an empirical constant, commonly referred to as the cohesive strength.
Abstract: The Mohr-Coulomb criterion for failure, modified in light of the concept of effective stress, is where τ c is the critical shear stress at failure, S the normal pressure, and p the pore pressure across the plane of internal slippage at failure , ϕ i the internal friction angle, and τ 0 an empirical constant, commonly referred to as the cohesive strength. Experiments showed that the τ 0 for sedimentary rocks is about 200 bars. Hubbert and Rubey (1959) assumed that once a fracture is started, TO is eliminated and further movement results when They proceed, however, to use this formula for the frictional sliding of cohesionless block as the criterion of failure of large thrusts, after they assumed that τ 0 could be eliminated through a concentration of stress. This assumption led to their conclusions that very long overthrust blocks are possible and that such blocks may have moved by gravitational sliding along very gentle slopes. I present arguments to show that their assumption of zero τ 0 was based upon a faulty argument and to point out that the τ 0 term should not be omitted unless it could be proved the moving block slid along an already existing fracture plane. The first part of this paper consists mainly of conclusions based on computations. Clearly, an unjustified omission of a 200-bar cohesive strength would lead to erroneous and misleading results; particularly, gravitational sliding cannot be an important mechanism if such a cohesive strength has not been eliminated during overthrust faulting. The second part presents evidence to distinguish between movements of cohesively bound blocks and cohesionless blocks. The Glarus overthrust, characterized by presence of a ductilely deformed limestone layer within the thrust zone, is considered a typical example of thrusting of cohesively bound blocks. The Heart Mountain thrust, characterized by a shattering of the “upper plate” and absence of a weak layer above the thrust contact, is interpreted as an example of thrusting of cohesionless blocks. The former is compared to slowly creeping slides moving at rates of centimeters or less per year, and the latter with catastrophic landslides (such as the Flims, Goldau, and Vaiont slides) moving at speeds of many meters per second. Third, the conclusion of Raleigh and Griggs (1963) that large thrusts can only form when a toe of the thrust is continually eroded is also traced to the assumption of zero cohesive strength along thrust plane. Otherwise, the toe effect would produce a zone of imbrication at the front of overthrust blocks, particularly those sliding downslope under their own weight.
67 citations
64 citations
TL;DR: In this article, photoelectrons from ferromagnetic gadolinium were found to have spin polarization, the preferential direction of the magnetic moment being parallel to the magnetization of the sample.
Abstract: We have found that photoelectrons from ferromagnetic gadolinium show spin polarization, the preferential direction of the magnetic moment being parallel to the magnetization of the sample. Our experiment yields a degree of polarization $P=(5.27\ifmmode\pm\else\textpm\fi{}0.70) %$. $P$ did not vary significantly over the energy range from 2.8 to 5.0 eV of the incident light.
62 citations
TL;DR: The present state of grating spectroscopy is reviewed with special emphasis on the far ir.
Abstract: The present state of grating spectroscopy is reviewed with special emphasis on the far ir. The review includes the discussion of the properties of diffraction gratings, the intensity distribution among different orders of echelette gratings, Wood anomalies, ir and submillimeterwave filters, detectors, grating spectrometers with thermal sources, rules for the construction of far ir and submillimeterwave grating spectrometers, diffraction at the monochromator slits, comparative performance of interferometers and grating spectrometers, and spectroscopy of far ir laser emissions. Extensive references are presented.
TL;DR: The low and high-temperature forms of the isostructural pyrosilicate compounds are described in terms of single crystal-and powder X-ray data as discussed by the authors.
Abstract: The low- and high-temperature forms of the isostructural pyrosilicate compounds are described in terms of single crystal- and powder X-ray data. The low-temperature form is tetragonal, space group P41, or P4122. Crystals of the high-temperature form show orthorhombic symmetry, possible space group Pna21, or Pnma. Cell dimensions and indexed d-spacings of all compounds are given. The polymorphs are isostructural with the α-and β-form of the pyrophosphates M2P2O7, [M = Ca, Sr, (Ba)].
TL;DR: In this paper, the interaction of an electron with the photon field was studied for all finite time and the asymptotic states of the system were constructed explicitly for all the states.
Abstract: In this model we study the interaction of an quantized non relativistic electron with the photon field. We discuss the system for all finite time and we are in the position to construct explicitly the asymptotic states.
TL;DR: In this paper, the operation of a metastable ion selector is described, which by variation of the electric sector voltage of a double focusing mass spectrometer allows a more detailed observation of metastable transitions.
TL;DR: A carrier relay mechanism accounting for all experimental results is proposed since exchange of ligands is shown to occur during the transport of potassium ions in a potential gradient across a bulk membrane containing macrotetrolide antibiotics.
TL;DR: In this paper, the EuIIIEDTA complex exhibits a strong temperature dependence of its absorption band at 395 nm in dilute aqueous solution, whereas EDTA complexes of the other lanthanide ions as well as the aquo ions of the whole series show no significant change of their absorption spectra in nation number along the series.
Abstract: The EuIIIEDTA complex exhibits a strong temperature dependence of its absorption band at 395 nm in dilute aqueous solution. Similar but much weaker effects can be observed in solutions of SmEDTA and GdEDTA, whereas EDTA complexes of the other lanthanide ions as well as the aquo ions of the whole series show no significant change of their absorption spectra in nation number along the series of the lanthanide EDTA complexes that takes place from Sm to Tb at room temperature. It can be concluded from the nephelauxetic effect that the coordination number decreases with increasing atomic number. The coordination numbers of the aquo ions are the same for all trivalent lanthanide ions in dilute solutions.
TL;DR: In this article, the room temperature pressure dependence of the absorption edge of EuO, EuS and EuTe single crystals was found to be −4.4, −7.9, −8.4 and −12 meV/kbar respectively.
01 Oct 1969
TL;DR: The mesure des parametres des reseaux cristallins des semi-conducteurs ferromagnetiques EuO et EuS, a basse temperature, revele que le volume de ces cristaux est reduit de 3, respectivement de 1,2, lorsqu'ils sont refroidis au-dessous de leur temperature de Curie as mentioned in this paper.
Abstract: La mesure des parametres des reseaux cristallins des semi-conducteurs ferromagnetiques EuO et EuS, a basse temperature, revele que le volume de ces cristaux est reduit de 3, respectivement de 1,2‰, lorsqu'ils sont refroidis au-dessous de leur temperature de Curie. Cette contraction est attribuee a la magnetostriction d'echange et la variation relative de volume est proportionnelle a la fonction de correlation des spins. Dans l'approximation du champ moleculaire, cette interaction magnetoelastique peut etre representee par la relationTC=T0[1+β(V−V0/V0]. Pour EuO et EuS, les valeurs du parametre d'interaction magnetoelastiqueβ sont respectivement −3,5 et −6,4, en accord avec les valeurs derivees des mesures du point de Curie en fonction de la pression. Aucune anomalie d'expansion thermique n'a ete decelee dans les combinaisons EuSe et EuTe.
TL;DR: Based on a new method which allows the determination of the chain-arrangement in the elementary fibrils it was found that the structural carbohydrate must be aggregated into continuous, extended-chain filaments of nearly perfect crystallinity.
Abstract: The ultrastructure of cellulose in higher plant cell walls is discussed. The primary and secondary wall is built up of a framework of microfibrils composed of smaller strands which are termed elementary fibrils. In recent years a number of models for the chain-arrangement of the cellulose molecules have been proposed. According to one view the cellulose chains are in a folded conformation. Based on a new method which allows the determination of the chain-arrangement in the elementary fibrils it was found that the structural carbohydrate must be aggregated into continuous, extended-chain filaments of nearly perfect crystallinity. Freezeeten profiles suggest that the mechanism of fibrillar formation is characterized by enzyme particles attached to the plasma membrane and involved in cellulose synthesis.
TL;DR: Freeze-etched neuropil of the cat subfornical organ was examined with the electron microscope for synaptic vesicles; round stomata were found at the outer surface of the plasmalemma of nerve terminials and are interpreted as pinocytotic vesicle.
Abstract: Freeze-etched neuropil of the cat subfornical organ was examined with the electron microscope for synaptic vesicles. Round vesicles were found exclusively in both unfixed and aldehyde-fixed specimens. Range of diameters and histograms failed to differ significantly between freeze-etched and conventionally prepared material. The mnode of distribution of diameters was approximately 500 angstroms. Round stomata (approximately 350 angstromns in diameter) were found at the outer surface of the plasmalemma of nerve terminials; they are interpreted as pinocytotic vesicles.
TL;DR: In this article, the far infrared spectra of dimethyl sulfoxide and several aliphatic nitriles have been studied with a view towards elucidating the mechanism responsible for the intense absorption bands which have been observed in this region.
Abstract: The far infrared spectra of dimethyl sulfoxide and several aliphatic nitriles have been studied with a view towards elucidating the mechanism responsible for the intense absorption bands which have been observed in this region. Spectra of pure liquids, solid DMSO, DMSO-d6, CD3CN, and dilute solutions in non-polar solvents are presented. The results are discussed in terms of the possible mechanisms proposed for these absorptions.
TL;DR: In this article, the energy distribution of photoemission from europium-oxide and Europiumselenide has been investigated and it has been shown that the electronic density of states shows a peak at the top of the valence band.
TL;DR: In this article, an arbitrary Feynman integral is considered for external momenta in the Euclidean region, the usual rotation of energy contours having been used to write the integral as an integral over internal momenta.
Abstract: An arbitrary Feynman integral is considered for external momenta in the Euclidean region, the usual rotation of energy contours having been used to write the integral as an integral over Euclidean internal momenta. A compactification of the space of internal momenta is defined, and the Feynman integral is written as the integral of a current on this compact manifold. This presentation of the integral is used to give a proof of the convergence criterion for Feynman integrals, and to show that a well-defined renormalized integral may be obtained by a subtraction operation or by analytic renormalization.
TL;DR: In this article, the 13C NMR spectra of seventeen m- and p- subsituted benzonitriles were examined and partially anlayzed, and the C-1 carbon shieldings can be expressed in terms of a linear correlation with the LCAO-MO-π-electron density at C 1.
Abstract: The 13C NMR. spectra of seventeen m- and p- subsituted benzonitriles were examined and partially anlayzed. The C-1 carbon shieldings can be expressed in terms of a linear correlation with the LCAO-MO-π-electron density at C-1. No such correlation was found for the cyanocarbon, whose electron density shows only slight varriations for the different substitutents. This fact is consistent with the relatively small range of the chemical shifts at this center.
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TL;DR: In this article, the anomeric methyl 4-deoxy-L -threo -hex-4-enopyranosid (LD-ENOPRANSID) was derived by base-catalyzed elimination reaction.
TL;DR: A selective transport of potassium ions in the presence of an equal amount of sodium ions is obtained by applying a potential difference across a synthetic membrane impregnated with a macrotetrolide antibiotic.
TL;DR: In this article, a finite element procedure based on the minimum of complementary energy principle is developed for the problem of elastic plate bending, a strain energy bound is found and compared with known solutions.
Abstract: For the problem of elastic plate bending, a finite element procedure based on the minimum of complementary energy principle is developed. Primary variable of the problem is the distribution of the bending moments m x , m y and m xy . These vary parabolically inside each triangular element and have continuous values throughout the plate. In order to satisfy the equilibrium conditions, Lagrangean multipliers are introduced as secondary variables. It is then shown that these multipliers are generalized displacement parameters. The final solution will therefore provide direct information about both the stress distribution and the displaced shape of the plate. Equilibrium conditions are satisfied exactly. A strain energy bound is found. For several cases numerical results are given and compared with known solutions.
TL;DR: The reflectivity of europium chalcogenide single crystals and the optical constants of EuSe have been determined at room temperature in the fundamental absorption region from 1.0 to 6.0 eV.
TL;DR: In this paper, the existence of excessively degenerate eigenvalues occuring often in the Huckel approach is discussed from the point of the topological matrix, and conditions for removal of excessive degeneracy are discussed.
Abstract: The existence of excessively degenerate eigenvalues occuring often in the Huckel approach is discussed from the point of the topological matrix. First the full symmetry group of the Huckel problem of three typical examples is discussed and its relation to the commonly used geometrical symmetry group is established. Excessive degeneracy of eigenvalues of Huckel spectra may now be interpreted in terms of the irreducible representation of the full Huckel graph group. The results then are generalized to give more extended though no fully general conditions for excessive degeneracies in Huckel eigenvalues spectra. Furthermore conditions for removal of excessive degeneracy are discussed.