Showing papers by "ETH Zurich published in 1983"

An evaluation of criteria to deduce the sense of movement in sheared rocks

Abstract: Some of the most useful criteria for the deduction of the sense of shear are summarized for use in areas where unequivocal field evidence is lacking. Apparently conflicting evidence from rotated pressure-shadow regions around porphyroclasts and porphyroblasts is clarified. The use of quartz-crystallographic fabric asymmetry to deduce the shear sense in the bulk rock should be treated with caution and used only together with detailed microstructural observations.

Characterization of the distribution of internal motions in the basic pancreatic trypsin inhibitor using a large number of internal NMR probes.

Abstract: The experimental observations described in this article indicated that a distribution of many different fluctuations is present in a globular protein. These fluctuations were characterized by observation of many natural internal probes such as the labile peptide protons and the aromatic side chains. The conditions which are necessary to get reactions of the internal probes have been discussed in detail. The structural interpretation of the data was facilitated by the development and the use of new NMR techniques which provided the identification of the resonances of all the labile peptide protons. With NOE measurements a distinction between correlated and uncorrelated exchange events was obtained. This enabled us to elucidate the exchange mechanism over a wide range of p2H and temperature and to classify different subsets of fluctuations with respect to their lifetimes. It was further demonstrated that a change of external conditions such as temperature, p2H or pressure can change the distribution of fluctuations in the protein. The mechanisms responsible for rotation of internal aromatic side chains were also found to change with temperature, and mechanistic aspects of these fluctuations were discussed.

Mixed-valent ground state of Ce O 2

Abstract: The electronic ground state, core-hole states, and valence-hole states of Ce${\mathrm{O}}_{2}$ are studied taking into account strong correlation among the $4f$ electrons. The ground state is considered as a mixture of two configurations, $4{f}^{0}$ and spin-singlet totally symmetric $4{f}^{1}\ensuremath{-}\mathrm{O} 2p$-hole states. By an analysis of the core-level photoemission spectrum, the $4f$ occupancy is obtained to be about 0.6. The possibility of this mixed-valence mechanism in metallic mixed-valent systems and $\ensuremath{\alpha}\ensuremath{-}\mathrm{Ce}$ is also discussed.

VDT Workstation Design: Preferred Settings and Their Effects

Abstract: A field study was conducted to assess the preferences of VDT operators with regard to their body posture and the settings of an adjustable VDT workstation. Subjects came from four different compani...

The regulation of the Na+ -Ca2+ exchanger of heart sarcolemma.

Abstract: The Na+/Ca2+ -exchange of calf-heart sarcolemma is activated by a treatment with ATP, Mg2+, and Ca2+, and deactivated by a treatment with phosphorylase phosphatase. The effect of th e latter can be substituted by a treatment with Mg2+, Ca2+, and calmodulin. the activating treatment does not require added calmodulin, but is inhibited by calmodulin antagonists. Evidently, engdogenous calmodulin is required and sufficient. Activation is half-maximal at about 2μM Ca2+. Added clamodulin, however, decreases the Km (Ca2+) of the activating process to about 0.8 μM. Deactivation is half-maximal, at optimal calmodulin concentrations, at about 1.5 μM Ca2+. Experiments with adenosine 5′-[γ-thio]triphosphate have shown that the activating treatment is mediated by a kinase and the deactivating treatment by a phosphatase. The concerted operation of the two enzymes is made possible by their different Ca2+ affinity. At saturating Ca2+ concentrations, the level of ATP may also influence the balance of the two enzymes.

Normal forms for real surfaces in C2 near complex tangents and hyperbolic surface transformations

Abstract: It is well known that the complex analytical properties of a real submanifold M in the complex space C n are most accessible through consideration of the complex tangents to M. The properties we have in mind are related to the behavior of holomorphic functions on or near M and to the behavior of M under biholomorphic transformation. The case in which M is a real hypersurface is most familiar, while much less is known for higher codimension. In this paper we consider the critical case of a real ndimensional manifold M in C n, which we also assume to be real analytic. At a generic point M is locally equivalent to the standard R n in C n. However, near a complex tangent M may aquire a non-trivial local hull of holomorphy and other biholomorphic invariants. We begin with the simplest non-trivial case, which is a surface M2cC 2 with an isolated, suitably non-degenerate complex tangent. Here one already encounters a rich structure and non-trivial problems. In coordinates zj=xi+iy i, j= 1,2, M may be written locally as

Stability analysis of single loop control systems with saturation and antireset-windup circuits

Abstract: "Reset-windup" appears when regulators with integral action are used with saturating actuators. Antireset-windup (ARW) circuits are in practice used in most standard control equipment today. Their design is based on intuition and simulation. This paper presents analysis of systems with ARW circuits based on nonlinear stability theory. The analysis gives possibilities to compare the performance of different ARW circuits. It predicts the system response adequately without need for extensive simulations.

Diagenetic magnetite carries ancient yet secondary remanence in some Paleozoic sedimentary carbonates

Abstract: Many sedimentary carbonate rocks carry stable magnetizations that can be shown to reside in magnetite. When such magnetizations are observed, it is often argued or demonstrated that the magnetite was incorporated into the sediment during deposition. However, paleomagnetic and rock magnetic studies in conjunction with analyses of magnetic extracts from the Helderberg and Bonneterre carbonates (United States) indicate that the magnetite present in these rocks is most likely of diagenetic (i.e., postdepositional) origin.

Fast pulsations in the solar corona

Abstract: Pulsations in radio emission from the solar coronal plasma have been detected for over a decade1–9. The oscillations are quasiperiodic, with periods of typically a second or so. Recently, sub-second time structures have been found in hard X rays10, and simultaneously in hard X rays and microwaves11. Here we examine whether magnetohydrodynamical oscillations in a density enhancement, treated for simplicity as a straight magnetic slab, can explain the observed short periods. A dense region in the corona (for example, a loop) can act as a wave trap, and symmetrical oscillations within that trap must be of short wavelength with correspondingly short period. An impulsive source (such as a flare) naturally gives rise to a quasiperiodic disturbance. Such oscillations are closely akin to the Pekeris modes of oceanography, the Love waves of seismology and the dielectric waves of fibre optics.

The activation of FeTi for hydrogen absorption

Abstract: FeTi is an interesting hydrogen storage material which has to be activated at ≈670 K for the absorption of hydrogen. We review critically the great number of previously published results and models on this activation process and emphasize the controversial points. To eliminate the controversy we analysed the variation of the surface composition of FeTi upon activation in the high-pressure cell of a photoelectron spectrometer. The initially passivating surface oxide is shown to be converted into a mixture of TiO2 and Fe by surface segregation and chemical reduction. No evidence for the formation of Fe2Ti4O x , FeTiO x , and TiH x is found. H2/D2 exchange reactions show that H2 dissociates rapidly on Fe and FeTi, but not on TiO2. The surface of FeTi is activated easily at 670 K. Difficulties encountered with the initial hydrogen absorption by virgin high purity FeTi are probably related to bulk (H diffusion, fracture toughness) rather than surface properties.

Interference of aromatic sulfo groups in the microbial degradation of the azo dyes Orange I and Orange II

Abstract: Pseudomonas strains K22 and KF46 had previously been isolated from chemostat cultures that were adapted to growth on 1-(4′-carboxyphenylazo)-4-naphthol (carboxy-Orange I) and 1-(4′-carboxyphenylazo)-2-naphthol (carboxy-Orange II), respectively. They were tested for their ability to degrade the sulfonated analogs 1-(4′-sulfophenylazo)-4-naphthol (Orange I) and 1-(4′-sulfophenylazo)-4-naphthol (Orange I) and 1-(4′-sulfophenylazo)-2-naphthol (Orange II). The sulfonated dyes served as models for commercially used textile dyes, which are known to be recalcitrant in aerobic waste water treatment plants. Substitution of sulfo for carboxy groups led to disturbance of the degradative pathways. The enzymes initiating degradation, the Orange I azoreductase and the Orange II azoreductase, accepted both, carboxylated and sulfonated dyes. Experiments with specifically 14C-labelled dyes indicated that sulfanilic acid, one of the products of the initial fission of the dyes, was channeled into a dead-end pathway. In the case of Orange I degradation, reactive metabolites of sulfanilic acid, presumably catechols, coupled with aminonaphthol, the other product of the azoreductase reaction. Orange II was degraded by strain KF46 when another suitable carbon source (e.g. 4-hydroxybenzoate) was supplied. Most but not all of the internally generated sulfanilic acid was excreted and intermolecular coupling of aromatic metabolites was not observed. However, the presence of sulfanilic acid and/or its metabolities still interfered with the degradation of the aminonaphthol part of the dye molecule and complete mineralization was not achieved.

Patterns of substrate utilization by some fungal endophytes from coniferous foliage

Abstract: Fifty-six strains of endophytic fungi isolated from coniferous foliage in Europe and in Oregon, U.S.A., were tested for their ability to utilize various complex substrates including cellulose, xylan, mannan, several other hemicelluloses, pectin, and two lignin derivatives. Cultures were also assayed for lipolytic activity, laccase production, growth on gallic acid, and production of darkly pigmented reaction products on gallic acid. A majority of isolates utilized xylan and pectin, showed lipolytic activity, and grew on gallic acid. Fewer isolates (54%) utilized cellulose, and only a small proportion utilized hemicelluloses other than xylan. Among isolates from conifers with distinct needles, fungi occurring only in the petioles showed a broad range of substrate utilization capabilities, while those from the needle blades were more restricted in their abilities. Isolates from cuppressaceous foliage utilized xylan but varied greatly with respect to other capabilities. Different isolates of the same fungus often varied in their substrate utilization capacities. Substrate utilization patterns of all the common endophytes from a single host suggested that several endophytes may co-exist within a single leaf by biochemical partitioning of resources.

Spatio-temporal recoding of rapid eye movement signals in the monkey paramedian pontine reticular formation (PPRF)

Abstract: The integrity of the paramedian pontine reticular formation (PPRF) is necessary for the generation of rapid eye movements. The main saccade-related population is of the burst type with latencies between 0 and 40 ms preceding a saccade, and they can be divided into medium- and long-lead burst neurons. Burst neurons have predominantly spatially coded movement fields in the rostral PPRF, while in the caudal PPRF they increase their burst strength in temporal coding approximately in the pulling directions of extraocular eye muscles (i.e. almost horizontal or vertical). Both neuronal populations have ipsilateral on-directions and contain long-lead burst neurons. In a quantitative analysis the firing patterns of long-lead burst neurons are compared to those of medium-lead burst neurons, which form the predominant output of the saccadic pulse generator to the motoneurons. The firing patterns of temporally coded long-lead bursters are similar to those of medium-lead bursters, except for earlier on-latencies, larger statistical fluctuations, and specializations for small or large saccades in oblique directions. The spatially coded burst neurons form a motor map of saccadic vectors. The diameter of their movement field is often about the size of the saccade vector, and they encode saccadic onset and duration. These results are consistent with a model for visual saccades in eye displacement coordinates, where the spatio-temporal recording of horizontal eye movements is effected by long-lead burst neurons in the PPRF.

Pathways of Propionate Degradation by Enriched Methanogenic Cultures

Abstract: A mixed methanogenic culture was highly enriched in a growth medium containing propionate as the sole organic carbon and energy source. With this culture, the pathways of propionate degradation were studied by use of 14C-radiotracers. Propionate was first metabolized to acetate, carbon dioxide, and hydrogen by nonmethanogenic organisms. Formate was not excreted. The carbon dioxide originated exclusively from the carboxyl group of propionate, whereas both [2-14C]- and [3-14C]propionate lead to the production of radioactive acetate. The methyl and carboxyl groups of the acetate produced were equally labeled, regardless of whether [2-14C]- or [3-14C]propionate was used. These observations suggest that in the culture, propionate was degraded through a randomizing pathway.