Showing papers by "ETH Zurich published in 1973"
Abstract: This article presents evidence that the Mediterranean Sea was a desiccated deep basin some 6 million years ago.
879 citations
TL;DR: In this article, a system of N two-level molecules coupled to finitely many modes of a quantized radiation field via a truncated dipolar interaction is investigated, and the thermodynamic and correlation functions can be exactly computed in the limit N → ∞.
843 citations
TL;DR: In this article, a general effective interaction W(x) describing the interaction of nucleons within a shell, and associated effective operators A (x) were introduced, and the convergence of the expansions for W and A in powers of x was investigated.
239 citations
TL;DR: In this article, the stability limits for thermally driven acoustic oscillations in a helium-filled tube are given in the form of critical temperature ratios versus a parameter representing the ratio between the tube radius and the extent of the viscous flow region.
Abstract: The stability limits for thermally driven acoustic oscillations in a helium-filled tube are given. Calculations are partly based on a step-by-step integration of the differential equation for the acoustic pressure, but most results refer to a model using a discontinuous temperature distribution; in the latter case a transcendental stability-frequency equation has been numerically solved. Results are presented in the form of critical temperature ratios versus a parameter representing the ratio between the tube radius and the extent of the viscous flow region. Several asymptotic limits of the stability curves are analytically treated. Finally, limitations of the theory are discussed which occur when the solid tube wall specific heats become vanishingly small at the cold end.
175 citations
150 citations
TL;DR: The "physiological" substrates of small intestinal phlorizin hydrolase (the activity of which is high at birth and declines at the time of weaning) are most probably glucosylceramides and lactosylaceramides, both of which are components of the fat globules in milk.
113 citations
TL;DR: To determine whether PSTV is a single- or a double-stranded molecule, PSTV in 8 M urea was mixed with native coliphage T7 DNA, or with heat-denatured, formylated carnation mottle virus RNA (CarMV RNA).
108 citations
01 Jan 1973
103 citations
01 Jan 1973
97 citations
TL;DR: In this article, the dielectric, piezoelectric and elastic constants have been measured in single domain KNbO3, and electrooptic r-coefficients are estimated.
Abstract: Dielectric, piezoelectric and elastic constants have been measured in single domain KNbO3, and electrooptic r-coefficients are estimated. Results allow a thorough verification of Devonshire's theory for the orthorhornbic phase. Good agreement is found for the dielectric and piezoelectric properties whereas fitting the elastic behaviour requires inclusion of terms coupling stiffness to spontaneous strain. The temperature dependence of clamped dielectric constants and elastic stiffness points to the importance of piezoelectric coupling for the low temperature phase transitions. Absorption measurements reveal a nearly isotropic polarization-induced band edge shift of 200 meV. Large anisotropy is observed in the polarized UV reflectance spectra measured up to 10 eV. Comparison of reflectivity in ferroelectric KNbO3 with electroreflectance in cubic KTaO3 gives further evidence for the unified nature of electro-optic effects in oxygen-octahedra compounds. Differences in e''-spectra derived from Kramers-Kronig a...
93 citations
01 Jan 1973
TL;DR: In this paper, a class of mean field model Hamiltonians consisting of a small, but macroscopic system S of N components interacting with a large reservoir R is presented, and exact equations of motion are studied, and it is shown that it is possible to eliminate the reservoir variables and, in the limit N → ∞; to derive closed equations for the extensive variables of S.
Abstract: We present a class of mean field model Hamiltonians consisting of a small, but macroscopic system S of N components interacting with a large reservoir R. The Dicke model of a laser is a particular example of S. Both R and S are fully quantum mechanical. The exact equations of motion are studied, and it is shown that it is possible to eliminate the reservoir variables and, in the limit N → ∞; to derive closed equations for the extensive variables of S. These equations are classical, and the effect of the reservoir is to provide damping and driving (or pumping) terms. As the parameters of the system are varied, S can undergo phase transitions in the sense that its equilibrium orbits bifurcate. To the next order, N 1/2, the reservoir drives the fluctuation observables of S linearly with Markovian, Gaussian random forces. Within the context of our class of models our results are rigorous and are obtained without any approximation.
TL;DR: Two distinct amino-acid pools were demonstrated in the food yeast Candida utilis and showed a slow turnover in pulse-labelling experiments and a high proportion of basic, nitrogen-rich amino acids, indicative of a storage function.
Abstract: Two distinct amino-acid pools were demonstrated in the food yeast Candida utilis. Treatment of the cells with basic protein (cytochrome c) under isotonic conditions permeabilized the plasmalemma but left the tonoplast intact. The selective effect on these membranes was indicated by the observation of intact vacuoles but changed contrast of the cytoplasm in the phase-contrast microscope and by the free access of a chromogenic substrate to a cytoplasmic enzyme (α-glucosidase). However, only 10–20% of the soluble amino acids were released from the cells and these had a rapid turnover as demonstrated by pulse labelling experiments using 14C(U)-arginine, 14C(U)-glucose, and 15N-ammonia. This indicates a rapidly metabolized amino-acid pool located within the cytoplasm. Osmotic shock with water following the treatment with basic protein disrupted the tonoplast, an event which could be followed by phase-contrast microscopy. Most of the remaining amino acids were then released. These showed a slow turnover in pulse-labelling experiments and a high proportion of basic, nitrogen-rich amino acids, indicative of a storage function. The significance of such vacuolar and cytoplasmic pools in the regulation of cellular metabolism is discussed.
TL;DR: Ergonomic measurements of noise, lighting and room climate were made in 15 large-space offices in Switzerland as discussed by the authors, and 519 employees were given a questionnaire about working in such offic...
Abstract: Ergonomic measurements of noise, lighting and room climate were made in 15 large-space offices in Switzerland. At the same time, 519 employees were given a questionnaire about working in such offic...
TL;DR: In this paper, the orientation of observed domain walls is consistent with the principles of mechanical compatibility and electrical neutrality, and experimental evidence for the existence of a new type of ferroelectric domain wall (S-wall) is presented.
Abstract: Domain configurations in large KNbO3 single crystals grown by a top seeded flux growth technique are studied by optical methods and etching techniques. The orientation of observed domain walls is consistent with the principles of mechanical compatibility and electrical neutrality. Experimental evidence for the existence of a new type of ferroelectric domain wall (S-wall) is presented. Miller indices of such walls are irrational and depend on spontaneous strain tensor coefficients. The preparation of large single domain crystals (up to 1/3 cm3) is described. Assessment of crystal perfection by x-ray topographic and interference methods reveals a very small mosaic spread (one minute of arc) and a good optical homogeneity.
TL;DR: In this paper, a wide range of Ba/Si and Ra/Si values is noted in siliceous plankton collected from different oceans. But although the Ba distribution in the ocean correlates linearly with that of 226Ra, reflecting little fractionation of the two elements in their uptake by marine organisms.
TL;DR: In this article, the ion selectivity exhibited by different types of membrane electrodes is rationalized by a theoretical treatment of the membrane potential, which is admirably suited for the interpolation of e.m.f.
Abstract: The ion selectivity exhibited by different types of membrane electrodes is rationalized by a theoretical treatment of the membrane potential. An equation, which is admirably suited for the interpolation of e.m.f.-values, is derived for the electrode response of membrane electrodes of the electrically neutral ligand type (antibiotics, model compounds) to mixed solutions of monovalent and divalent cations. In contrast to the classical Nicolsky equation it describes the contribution of interfering ions to the e.m.f. by an activity-independent selectivity term. Electrically neutral ligands selective for calcium ions to be used as components for liquid membrane electrodes were designed and prepared. The corresponding electrodes are in all respects superior to the calcium ion liquid membrane electrodes described so far.
TL;DR: Circular dichroic, fluorescence emission and excitation spectra of O tyr -NBD-lysozyme show changes from those of the native protein which suggest some limited structural alterations in the helical segment of the protein.
TL;DR: In this article, the lattice dynamics, the transition mechanisms, their influence on physical properties and their dependence on the various possibilities of molecular engineering offered in these quasi two-dimensional perovskites was started.
TL;DR: In this article, the alignment of the trigonal axes of the ilmenohematite trigonal axis with the directions of minimum low field susceptibility anisotropy was investigated.
TL;DR: In this paper, an x-ray photoemission spectroscopy study of the rare earths La, Ce, Pr, and Nd was performed and it was shown that the spectra of these metals in the vicinity of the Fermi energy account for the $4f$ levels as well as for the valence states.
Abstract: We present an x-ray photoemission spectroscopy study of the rare earths La, Ce, Pr, and Nd. We show that the spectra of these metals in the vicinity of the Fermi energy account for the $4f$ levels as well as for the valence states. The energy location of the $4f$ electrons is in fairly good agreement with an existing computation performed in the framework of the renormalized-atom method.
TL;DR: An isolation procedure involving a sedimentation velocity cut in Urografin gradients has been worked out for isolating vacuolar membrane fragments directly from whole cells which were mechanically disintegrated.
Abstract: α-Mannosidase was found associated with the vacuolar membranes of yeast. The vacuoles were isolated by flotation from osmotically disrupted spheroplasts of Saccharomyces cerevisiae. The enzyme was used as marker for isolating vacuolar membrane fragments directly from whole cells which were mechanically disintegrated. Over 90% of the total α-mannosidase was recovered in the particulate fraction. The enzyme was present in all of the fractions obtained upon differential centrifugation. Density gradient centrifugation in Urografin (5 - 20% w/v) of preparations obtained by differential centrifugation between 20 000 and 50 000 × g did not result in density equilibrium of the membrane. An isolation procedure involving a sedimentation velocity cut in Urografin gradients has, therefore, been worked out.
TL;DR: In this article, the change ΔE of the zero-point energy of the electromagnetic field in vacuum caused by the presence of a perfectly conducting surface is calculated for the infinite wedge of arbitrary wedge angle and for the rectangular cavity with the Green's function method derived earlier.
Abstract: The change ΔE of the zero-point energy of the electromagnetic field in vacuum caused by the presence of a perfectly conducting surface is calculated for the infinite wedge of arbitrary wedge angle and for the rectangular cavity with the Green's function method derived earlier (Z. Physik 258, 99 (1973)). The required Green's functions pertaining to the scalar wave equation for imaginary time which obey homogeneous boundary conditions on the conducting surface following from the scalar description of theE- andH-modes are obtained by the method of images.
TL;DR: In this paper, well known features of the geology of Western Europe are reinterpreted in the light of the deep-sea drilling results and other recent data, and the authors propose a new geology model for Western Europe.
Abstract: Well known features of the geology of Western Europe are reinterpreted in the light of the deep-sea drilling results and other recent data.
TL;DR: The insect pathogen Bacillus thuringiensis was cultured at different glucose concentrations and size, protein content, and insecticidal activity of the parasporal inclusions, which are formed during the sporulation process, were measured.
Abstract: The insect pathogen Bacillus thuringiensis was cultured at different glucose concentrations. Size, protein content, and insecticidal activity of the parasporal inclusions, which are formed during the sporulation process, were measured. Increased glucose concentrations led to bigger crystalline inclusions with a higher content of protein and insecticidal activity. Maximum yields of protein and endotoxin were obtained in a semisynthetic medium that contained glucose concentrations of 6 to 8 g/liter.
TL;DR: The general properties and structures of a family of several glycoproteins with this characteristic have recently been described in Antarctic fishes, and the apparent molecular weight in the blood sera of some polar fishes is only 20 g mol−1, a value equivalent to >500 times the depression calculated from the molecular weights.
Abstract: SCHOLANDER and colleagues1–3 observed that the blood sera of some polar fishes contain a substance of high molecular weight which lowers the freezing point. The general properties and structures of a family of several glycoproteins with this characteristic have recently been described in Antarctic fishes4–14. These “antifreeze” glycoproteins (AFGP) consist of repeating units of the triglycopeptide Ala-Ala-Thr-o-disaccharide. Three active glycoproteins have been characterized; these differ only in polymer length, with molecular weights ranging from 10,500 to 21,000 g mol−1 as determined by ultracentrifugation, light scattering, or osmotic pressure6,11. According to the freezing point depression, however, the apparent molecular weight is only 20 g mol−1, a value equivalent to >500 times the depression calculated from the molecular weights.
TL;DR: Noise and its disturbing effect - of an extensive study carried out in 15 landscaped offices in Switzerland and the results of a questionnaire which examined annoyance, sources of noise, ability to concentrate, and causes of distractions are considered.
TL;DR: Transformation formulas for the four noise parameters are given as a function of the four scattering parameters in this paper, where the influence of the lead inductances of a microwave bipolar transistor is examined, showing new significant results.
Abstract: Transformation formulas for the four noise parameters are given as a function of the four scattering parameters. For example, the influence of the lead inductances of a microwave bipolar transistor is examined, showing new significant results. The described procedure is applicable to other semiconductor devices. Most of the general formulas in Section II are believed to be new.
TL;DR: The proton NMR spectra at 220 MHz of oxidised and reduced cytochrome b2 core are presented and compared with the previously published NMR data on cy tochrome b5 infer that quite striking structural similarities exist between the two proteins.
TL;DR: In this paper the proton NMR features of cytochrome c-557 from Crithidia oncopelti are reported and compared with those of other cytochromes c.