Showing papers by "Max Planck Society published in 1984"

Explicit, First-Principles Tight-Binding Theory

Abstract: The minimal base of muffin-tin orbitals is transformed exactly into a tight-binding base. The linear transformations, the orbitals, and the Hamiltonian, overlap, and Green's function matrices are expressed in terms of one matrix, the canonical structure matrix ${S}_{\mathrm{ij}}$. It vanishes beyond second-nearest neighbors and is tabulated. Tight-binding two-center forms with transfer integrals proportional to ${S}_{\mathrm{ij}}$ are derived.

Vehicles, Experiments in Synthetic Psychology

Abstract: These imaginative thought experiments are the inventions of one of the world's eminent brain researchers. They are "vehicles," a series of hypothetical, self-operating machines that exhibit increasingly intricate if not always successful or civilized "behavior." Each of the vehicles in the series incorporates the essential features of all the earlier models and along the way they come to embody aggression, love, logic, manifestations of foresight, concept formation, creative thinking, personality, and free will. In a section of extensive biological notes, Braitenberg locates many elements of his fantasy in current brain research.

Human tumour necrosis factor: precursor structure, expression and homology to lymphotoxin.

Abstract: Human tumour necrosis factor has about 30% homology in its amino acid sequence with lymphotoxin, a lymphokine that has similar biological properties. Recombinant tumour necrosis factor can be obtained by expression of its complementary DNA in Escherichia coli and induces the haemorrhagic necrosis of transplanted methylcholanthrene-induced sarcomas in syngeneic mice.

Aeronomy of the Middle Atmosphere: Chemistry and Physics of the Stratosphere and Mesosphere

Abstract: Preface. 1: The Middle Atmosphere and its Evolution. 1.1 Introduction. 1.2 Evolution of the Earth's Atmosphere. 1.3 Anthropogenic Perturbations. 2: Chemical Concepts in the Atmosphere. 2.1 Introduction. 2.2 Energy Levels of Molecules. 2.3 Thermodynamic Considerations. 2.4 Elementary Chemical Kinetics. 2.5 Heterogeneous and Multiphase Reactions. 2.6 Photolysis Processes. 2.7 Excited Species in the Middle Atmosphere. 3: Dynamics and Transport. 3.1 Introduction. 3.2 Structure of the Atmosphere and Some Observed Dynamical Characteristics. 3.3 Fundamental Description of Atmospheric Dynamics. 3.4 Atmospheric Waves. 3.5 Effects of Dynamics on Chemical Species: Transport. 3.6 Dynamics and Meridional Transport in Two Dimensions: A Conceptual View. 3.7 The Importance of Wave Transience and Dissipation. 3.8 Vertical Transport above the Mesopause. 3.9 Models of the Middle Atmosphere. 4: Radiation. 4.1 Introduction. 4.2 Definitions. 4.3 Extraterrestrial Solar Radiation. 4.4 The Attenuation of Solar radiation in the Atmosphere. 4.5. Radiative Transfer. 4.6 The Thermal Effects of Radiation. 4.7 Photochemical Effects of Radiation. 5: Composition and Chemistry. 5.1 General. 5.2 Oxygen Compounds. 5.3 Carbon Compounds. 5.4 Hydrogen Compounds. 5.5 Nitrogen Compounds. 5.6 Halogen Compounds. 5.7 Stratospheric Aerosols and Clouds. 5.8 Generalized ozone Balance. 6: Ozone Perturbations. 6.1 Introduction. 6.2 The Photochemically-Controlled Upper Stratosphere and mesosphere: 25-75 km. 6.3 Lower Stratospheric Ozone Depletion: Observations and Explanations. 6.4 Summary and Outlook. 7: The Ions. 7.1 Introduction. 7.2 Formation of Ions in the Middle Atmosphere. 7.3 Positive Ion Chemistry. 7.4 Negative Ion Chemistry. 7.5 Effect of Ionic Processes on Neutral Constituents. 7.6 Radio Waves in the Lower Ionosphere. Appendices. Appendix 1: Physical Constants and Other Data. Appendix 2: Conversion Factors and Multiplying Prefixes. Appendix 3: Rate Coefficients forSecond-Order Gas-Phase Reactions. Appendix 4: Rate Coefficients for Gas-Phase Associating Reactions. Appendix 5: Surface Reaction Probability. Appendix 6: Atmospheric Profiles. Figure acknowledgements. Index.

Surface-enhanced resonance Raman spectroscopy of Rhodamine 6G adsorbed on colloidal silver

Abstract: Resultats d'etudes par diffusion Raman augmentee en surface et par des mesures fluorescentes. Mise en evidence de l'existence de 2 types de sites d'adsorption

Flow by mean curvature of convex surfaces into spheres

Abstract: The motion of surfaces by their mean curvature has been studied by Brakke [1] from the viewpoint of geometric measure theory. Other authors investigated the corresponding nonparametric problem [2], [5], [9]. A reason for this interest is that evolutionary surfaces of prescribed mean curvature model the behavior of grain boundaries in annealing pure metal. In this paper we take a more classical point of view: Consider a compact, uniformly convex w-dimensional surface M = Mo without boundary, which is smoothly imbedded in R. Let Mo be represented locally by a diffeomorphism

On the existence of a fully developed wind-sea spectrum

Abstract: We consider the energy transfer equation for well-developed ocean waves under the influence of wind, and study the conditions for the existence of an equilibrium solution in which wind input, wave-wave interaction and dissipation balance each other. For the wind input we take the parameterization proposed by Snyder and others, which was based on their measurements in the Bight of Abaco and which agrees with Miles's theory. The wave-wave interaction is computed with an algorithm given recently by S. Hasselmann and others. The dissipation is less well-known, but we will make the general assumption that it is quasi-linear in the wave spectrum with a factor coefficient depending only on frequency and integral spectral parameters. In the first part of this paper we investigate whether the assumption that the equilibrium spectrum exits and is given by the Pierson-Moskowitz spectrum with a standard type of angular distribution leads to a reasonable dissipation function. We find that this is not the case...

Functional Syntax and Universal Grammar

Abstract: List of tables List of figures Preface Abbreviations 1. Theoretical preliminaries 2. The semantic structure of the clause 3. Case marking 4. Intraclausal syntax 5. Juncture and operators 6. Nexus 7. Systems of discourse cohesion: reference-tracking mechanisms List of tables List of figures.

A low voltage-activated, fully inactivating Ca channel in vertebrate sensory neurones

Abstract: Calcium channels in excitable membranes are essential for many cellular functions. Recent analyses of the burst-firing mode of some vertebrate neurones suggest that changes in their functional state are controlled by a Ca conductance that is largely inactivated at resting membrane potentials (-50 to -60 mV), but becomes activated following a conditioning hyperpolarization of the cell membrane. Here, using chick and rat sensory neurones, we present evidence for a new type of Ca channel with time- and voltage-dependent properties which is probably responsible for the inactivation behaviour of the Ca conductance. At membrane potentials between -50 and +10 mV, openings of this channel last 3-6 ms and tend to occur in rapid succession. Inactivation of this channel is indicated by prolonged and eventually complete closures brought about by long-lasting depolarizing voltage steps. This channel coexists in isolated membrane patches with the more common Ca channel which is less sensitive to changes in holding potential and shows a considerably shorter average life time and smaller currents.

Expression of active human factor VIII from recombinant DNA clones

Abstract: DNA clones encoding the complete 2,351 amino acid sequence for human factor VIII have been isolated and used to produce biologically active factor VIII in cultured mammalian cells. The recombinant protein corrects the clotting time of plasma from haemophiliacs and has many of the biochemical and immunological characteristics of serum-derived factor VIII.

The gapped duplex DNA approach to oligonucleotide-directed mutation construction

Abstract: A simple and efficient method is described to introduce structurally pre-determined mutations into recombinant genomes of filamentous phage M13. The method rests on gapped duplex DNA (gdDNA) molecules of the phage M13 genome as the key intermediate. In this gdDNA, the (+) and the (shorter) (-) strand carry different genetic markers in such a way, that a rigorous selection can be applied for phage carrying the markers of the (-) strand. For introduction of the mutation, a synthetic oligonucleotide with partial homology to a target site within the single stranded DNA region is annealed to the gdDNA. The oligonucleotide subsequently becomes part of the (-) strand by enzymatic DNA gap filling and sealing. This physical linkage is preserved at the genetic level after transfection of a recipient E.coli strain deficient in DNA mismatch correction, so that the synthetic marker can be selected from the phage progeny independent from its potential phenotype. It is demonstrated that by this method mutants can be constructed with marker yields in excess of 70%.

Sputtering Studies with the Monte Carlo Program TRIM.SP

Abstract: The Monte Carlo Program TRIM.SP (sputtering version of TRIM) was used to determine sputtering yields and energy and angular distributions of sputtered particles in physical (collisional) sputtering processes. The output is set up to distinguish between the contributions of primary and secondary knock-on atoms as caused by in- and outgoing incident ions, in order to get a better understanding of the sputtering mechanisms and to check on previous theoretical models. The influence of the interatomic potential and the inelastic energy loss model as well as the surface binding energy on the sputtering yield is investigated. Further results are sputtering yields versus incident energy and angle as well as total angular distributions of sputtered particles and energy distributions in specific solid angles for non-normal incidence. The calculated data are compared with experimental results as far as possible. From this comparison it turns out that the TRIM.SP is able to reproduce experimental results even in very special details of angular and energy distributions.

Patch clamp techniques for studying ionic channels in excitable membranes.

Abstract: Availability of techniques largely influences the choice of preparations in electrophysiological research. To study basic mechanisms of electrical excita­ bility, usually the squid axon or giant snail neurons are used for technical reasons, or more simply, because they are large. For other reasons one would very often prefer to use mammalian cells, but they are much smaller and more difficult to handle. Recently, more freedom of choice was introduced by the so-called patch clamp techniques, which resulted from the technical challenge that the measurement of single-channel currents presented. It is evident that the smallness of these quantities required that the measurement be restricted to very small structures-small patches of membrane or very small cells. This led to the development of new techniques well suited for studying membrane currents from cells of any size and particularly suited to study small cells in culture. This review aims to describe the uses of the technique and to emphasize those results that use features specific to the various configurations of the patch clamp. We do not intend to present technical details, which can be found in the original literature (32, 74).

Temperature dependence of the first-order Raman scattering by phonons in Si, Ge, and α − S n : Anharmonic effects

Abstract: We have measured the temperature dependence of the first-order Raman scattering by phonons in Si, Ge, and $\ensuremath{\alpha}\ensuremath{-}\mathrm{S}\mathrm{n}$. The full widths at half maximum of the Raman lines, extrapolated to zero temperature, are 1.24\ifmmode\pm\else\textpm\fi{}0.07, 0.75\ifmmode\pm\else\textpm\fi{}0.03, and 0.81\ifmmode\pm\else\textpm\fi{}0.15 ${\mathrm{cm}}^{\ensuremath{-}1}$ for Si, Ge, and $\ensuremath{\alpha}\ensuremath{-}\mathrm{S}\mathrm{n}$, respectively. The reliability of the data obtained allows a critical examination of the theoretical calculations published so far. We show that the model assuming the decay of the Raman phonon into two acoustical phonons belonging to the same branch, first proposed by Klemens, does not represent adequately the temperature dependence of the Raman linewidth. The most important decay channels are shown to be combinations of optical and acoustical phonons. However, the more complete calculation by Cowley, which involves all possible decay channels, gives very large zero-temperature linewidths. We show that this arises mainly from the poor description of the phonon dispersion curves by the shell model used by Cowley, and that a better agreement between theory and experiment is to be expected by repeating the calculation with Weber's adiabatic bond-charge model.

Temperature dependence of the dielectric function of germanium

Abstract: Ellipsometric measurements of the dielectric constant of undoped Ge were performed between 1.25 and 5.6 eV in the temperature range of 100 to 850 K. The dependence of the ${E}_{1}$, ${E}_{1}+{\ensuremath{\Delta}}_{1}$, ${E}_{0}^{\ensuremath{'}}$, and ${E}_{2}$ critical energies on temperature was obtained. It can be represented either with Varshni's empirical formula or with an expression proportional to the Bose-Einstein statistical factor of an average phonon. Broadening parameters, amplitudes, and phase angles for the corresponding critical points were also obtained. A decrease of the excitonic interaction with increasing temperature was found. The results are discussed in the light of recent calculations of the effect of temperature on the band structure of Ge containing Debye-Waller and self-energy contributions.

Tridyn — A TRIM simulation code including dynamic composition changes

Abstract: Based on the sputtering version of the TRIM program for multicomponent targets, a Monte Carlo code has been developed which computes range profiles of implanted ions, composition profiles of the target and sputtering rates for a dynamically varying target composition. It takes into account compositional changes both due to the spatial distribution of target atoms deposited in collision cascades, and due to the presence of the implanted ions. The local density of the target is allowed to relax according to a given function of the densities of the individual components. The applications of the program cover a wide range of problems like the collisional atomic mixing of multilayered targets, dynamic implantation profiles at large fluences, and the fluence-dependent preferential sputtering of multicomponent materials. The present paper provides a description of the program and a critical comparison to similar Monte Carlo codes. As an application, the behaviour of the Ta-C system under He bombardment is studied with respect to sputtering yields, surface composition and composition profiles. Satisfactory agreement is obtained with experimental results given in the literature.

Volitional aspects of achievement motivation and learned helplessness: toward a comprehensive theory of action control.

Abstract: Publisher Summary This chapter provides an overview on the development of a theoretical framework for research on action control. It discusses that a person may have all the cognitive abilities that are necessary to solve a given anagram task and he or she may be sufficiently motivated to find the solution, and he or she may still fail to perform the necessary cognitive activities because he or she is unable to shield the task-oriented intention against competing action tendencies, for example, thinking about the self-evaluative implications of past failures to solve some other task. Likewise, persistence has been regarded as a pure motivational phenomenon. The duration of the time period a person persists on a task is not only a function of the strength of his or her motivation to solve the task as compared to the motivation to engage in some alternative activity, but also a function of the ability to protect the task-oriented action tendency against the interfering effect of competing action tendencies. The chapter discusses several historical reasons for the neglect of volitional processes in theories of action and it also presents several approaches in various subfields of psychology that are related to the problem of action control.

Biological properties of human c-Ha-ras1 genes mutated at codon 12

Abstract: Vertebrate genomes contain proto-oncogenes whose enhanced expression or alteration by mutation seems to be involved in the development of naturally occurring tumours. These activated genes, usually assayed by their ability to induce the malignant transformation of NIH 3T3 cells, are frequently related to the ras oncogene of Harvey (Ha-ras) or Kirsten (Ki-ras) murine sarcoma viruses, or a third member of this family (N-ras). Activation involves point mutation which often affect codon 12 (refs 16-26) of the encoded 21,000-molecular weight polypeptide (p21). To provide insight into structural requirements involved in p21 activation, we have now constructed 20 mutant c-Ha-ras1 genes by in vitro mutagenesis, each encoding a different amino acid at codon 12. Analysis of rat fibroblasts transfected with these altered genes demonstrates that all amino acids except glycine (which is encoded by normal cellular ras genes) and proline at position 12 activate p21, suggesting a requirement for an alpha-helical structure in this region of the polypeptide. The morphological phenotype of cells transformed by the activated genes can, however, depend on the particular amino acid at this position.

Identity of p36K phosphorylated upon Rous sarcoma virus transformation with a protein purified from brush borders; calcium-dependent binding to non-erythroid spectrin and F-actin.

Abstract: Membrane vesicles derived from the apical side of procine intestinal epithelial cells retain, after demembranation in the presence of calcium, two major proteins (I, II) which are released by the addition of calcium chelators. We have purified and characterized these two calcium-binding proteins. Protein I has a mol. wt. of 85 000 and contains two copies of a 36-K subunit and an additional 10-K subunit. It binds in a calcium-dependent manner to F-actin as well as to non-erythroid spectrin. Immunofluorescence microscopy reveals protein I-related antigens in the terminal web of the intestinal cell and in a submembraneous cortical layer in various tissue culture cells. Biochemical and immunological results document that the 36-K subunit of protein I is identical with the cellular p36K recognized as a major substrate for tyrosine phosphorylation by the sarc gene kinase in Rous sarcoma virus-transformed cells. The biochemical properties of protein I agree with its location seen in immunofluorescence microscopy and cell fractionation and suggest that the actin-spectrin network in the cortical layer may be affected by virus transformation.

Conductance properties of single inwardly rectifying potassium channels in ventricular cells from guinea-pig heart.

Abstract: Single ventricular cells were enzymatically isolated from adult guinea-pig hearts (Isenberg & Klockner, 1982). The patch-clamp technique (Hamill, Marty, Neher, Sakmann & Sigworth, 1981) was used to examine the conductance properties of an inward-rectifying K+ channel present in their sarcolemmal membrane. When the K+ concentration on the extracellular side of the patch was between 10.8 and 300 mM, inward current steps were observed at potentials more negative than the K+ equilibrium potential (EK). At more positive potentials no current steps were detectable, demonstrating the strong rectification of the channel. The zero-current potential extrapolated from the voltage dependence of the inward currents depends on the external K4 concentration [K+]o in a fashion expected for a predominantly K+-selective ion channel. It is shifted by 49 mV for a tenfold change in [K+]o. The conductance of the channel depends on the square root of [K+]o. In approximately symmetrical transmembrane K+ concentrations (145 mM-external K+), the single-channel conductance is 27 pS (at 19-23 degrees C). In normal Tyrode solution (5.4 mM-external K+) we calculate a single-channel conductance of 3.6 pS. The size of inward current steps at a fixed negative membrane potential V increases with [K+]o. The relation between step size and [K+]o shows saturation. Assuming a Michaelis-Menten scheme for binding of permeating K+ to the channel, an apparent binding constant of 210 mM is calculated for a membrane potential of -100 mV. For this potential the current at saturating [K+]o is estimated as 6.5 pA. The rectification of the single-channel conductance at membrane potentials positive to EK occurs within 1.5 ms of stepping the membrane potential from a potential of high conductance to one of low conductance. In addition to the main conductance state, the channel can adopt several substates of conductance. The main state could be the result of the simultaneous opening of four conducting subunits, each of which has a conductance of about 7 pS in 145 mM-external K+. The density of the inward-rectifying K+ channels in the ventricular sarcolemma is 0-10 channel/10 micron2 of surface membrane; the average of twenty-eight patches was 1 channel/1.8 micron2. It is concluded that the inward-rectifying K+ channels mediate the resting K+ conductance of ventricular heart muscle and the current termed IK1 in conventional voltage-clamp experiments.

Normal He 3 : an almost localized Fermi liquid

Abstract: The Hubbard model is used to calculate static properties of normal-liquid $^{3}\mathrm{He}$ at $T=0$. For this, Gutzwiller's variational approach to that model is employed. The work is based on an observation by Anderson and Brinkman that the results of this method, obtained by Brinkman and Rice for the metal-insulator transition in the case of one particle per site, appear to be in qualitative agreement with the experimentally measured properties of that liquid. In this sense normal $^{3}\mathrm{He}$ can be understood to be close to a localization transition of the particles where their effective mass diverges. The incipient localization is found to determine the properties of that liquid. Hence $^{3}\mathrm{He}$ is "almost localized" rather than "almost ferromagnetic," as often claimed by paramagnon theory. The author further investigates this motion. Discussing Gutzwiller's approach to the Hubbard model, he shows that it is well suited for a description of a liquid system like $^{3}\mathrm{He}$. The approach and its physical implications are investigated by means of the reformulation of the solution due to Ogawa et al. It is shown explicitly that Gutzwiller's results can be placed into the concepts of Landau-Fermi-liquid theory and that within this model the Landau parameters ${F}_{0}^{s}$ and ${F}_{0}^{a}$ are related. Furthermore, the author identifies two different kinds of spin-fluctuation processes inherent to the model, one of which is shown to be responsible for the largeness of ${F}_{0}^{s}$. Going beyond these qualitative aspects, the author evaluates ${F}_{0}^{a}$ and ${F}_{0}^{s}$ quantitatively, finding that ${F}_{0}^{a}$ agrees very well with the experimentally determined values at all pressures, with ${F}_{0}^{a}\ensuremath{\rightarrow}\ensuremath{-}\frac{3}{4}p$ at high pressures, where $p$ is always close to unity. Hence the system is never close to a ferromagnetic transition. By means of the forward scattering sum rule for $ll2$ an analytic expression for ${F}_{1}^{a}$ is obtained. Finally, the author extends the analysis to large magnetic fields, finding that in the case of normal $^{3}\mathrm{He}$ the magnetization increases very rapidly with the magnetic field. This is due to the large zero-field effective mass. There is a line of critical values for the interaction and the magnetic field where a fully magnetized state is formed via a first-order transition. Calculating the drop in melting pressure due to the magnetic field, the author finds that it essentially removes the minimum in the melting curve. Thus the melting pressure even of fully polarized $^{3}\mathrm{He}$ is larger than zero, in agreement with arguments by Castaing and Nozi\`eres.

The Amazon and its main affluents: Hydrography, morphology of the river courses, and river types

Abstract: The geological history of Amazonia (Putzer, Chapter 2) resulted in the formation of the greatest river system on earth. 7050000 km2 of land drain toward the Amazon and are interlaced by an uncountable number of large and small rivers and streams.