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Showing papers by "Max Planck Society published in 1977"


Journal ArticleDOI
TL;DR: In this article, a detailed study of a special type of functional organization and demonstrates its relevance with respect to the origin and evolution of life is presented, which can be formally represented by the concept of the quasi-species.
Abstract: This paper is the first part of a trilogy, which comprises a detailed study of a special type of functional organization and demonstrates its relevance with respect to the origin and evolution of life. Self-replicative macromolecules, such as RNA or DNA in a suitable environment exhibit a behavior, which we may call Darwinian and which can be formally represented by the concept of the quasi-species. A quasi-species is defined as a given distribution of macromolecular species with closely interrelated sequences, dominated by one or several (degenerate) master copies. External constraints enforce the selection of the best adapted distribution, commonly referred to as the wild-type. Most important for Darwinian behavior are the criteria for internal stability of the quasi-species. If these criteria are violated, the information stored in the nucleotide sequence of the master copy will disintegrate irreversibly leading to an error catastrophy. As a consequence, selection and evolution of RNA or DNA molecules is limited with respect to the amount of information that can be stored in a single replicative unit. An analysis of experimental data regarding RNA and DNA replication at various levels of organization reveals, that a sufficient amount of information for the build up of a translation machinery can be gained only via integration of several different replicative units (or reproductive cycles) through functional linkages. A stable functional integration then will raise the system to a new level of organization and thereby enlarge its information capacity considerably. The hypercycle appears to be such a form of organization.

1,364 citations


Journal ArticleDOI
09 Jun 1977-Nature
TL;DR: It is found that there is no strict correlation between cell morphology and type of collagen synthesised in cartilage colonies kept in monolayer culture at low density.
Abstract: WHEN chondrocytes from sternal or articular cartilage are kept in monolayer culture at low density, they eventually lose their cartilage phenotype1–4. Within four passages or approximately 1 month in culture they change from a polygonal or round to a flattened, amoeboid-like shape5–7, and instead of cartilage collagen (type II collagen8) they synthesise the genetically different type I collagen. It is not known whether there is a strict correlation between the occurrence of cell flattening and the change in collagen synthesis within individual cells. We have reported that preferentially flattened, fibroblast-like cells at the edge of cartilage colonies synthesise type I collagen, whereas round or polygonal chondrocytes generally synthesise type II collagen1–3. The change is nearly complete in a culture at a time when excessive flattening is observed4. Using an immunofluorescence double staining technique9,10, we have now found that there is no strict correlation between cell morphology and type of collagen synthesised.

1,068 citations



Journal ArticleDOI
TL;DR: In this paper, the deformation potential of the phonons at the band edge has been determined for ZnO for photon energies between 1.6 and 3 eV, based on the first and second derivatives of the dielectric constant.
Abstract: The resonance of the Raman scattering by ${E}_{2}, {A}_{1T}, {E}_{1L}$, and ${E}_{1T}$ phonons, and several second-order features, has been studied for ZnO for photon energies between 1.6 and 3 eV. The results are interpreted with a dielectric theory based on the first and second derivatives of the dielectric constant. By combining our results with absolute scattering cross sections previously determined by Arguello et al. at 2.41 eV absolute values of the deformation potentials of the band edge can be determined. The difference in strength between the longitudinal and the transverse modes provides the signs of these deformation potentials. The antiresonance around 1.6 eV suggested by the earlier work of Callender et al. and attributed to a cancellation of the deformation potential and electro-optical contributions to the Raman tensor is confirmed. The deformation potentials of the ${A}_{1}$ phonons at the band edge have been obtained from a pseudopotential calculation. While the sign of these deformation potentials agrees with the experimental determination, their magnitudes do not agree. This fact is attributed to difficulties with the pseudopotential of the ${\mathrm{O}}^{2\ensuremath{-}}$ ion. An estimate of the deformation potentials from the dependence of the band edges on uniaxial stress is also made.

789 citations


Journal ArticleDOI
01 Aug 1977-Tellus A
TL;DR: In this paper, it is shown that large-scale, long-time sea surface temperature (SST) anomalies may be explained naturally as the response of the oceanic surface layers to short-time-scale atmospheric forcing.
Abstract: The concept of stochastic climate models developed in Part I of this series (Hasselmann, 1976) is applied to the investigation of the low frequency variability of the upper ocean. It is shown that large-scale, long-time sea surface temperature (SST) anomalies may be explained naturally as the response of the oceanic surface layers to short-time-scale atmospheric forcing. The white-noise spectrum of the atmospheric input produces a red response spectrum, with most of the variance concentrated in very long periods. Without stabilizing negative feedback, the oceanic response would be nonstationary, the total SST variance growing indefinitely with time. With negative feedback, the response is asymptotically stationary. These effects are illustrated through numerical experiments with a very simple ocean-atmosphere model. The model reproduces the principal features and orders of magnitude of the observed SST anomalies in mid-latitudes. Independent support of the stochastic forcing model is provided by direct comparisons of observed sensible and latent heat flux spectra with SST anomaly spectra, and also by the structure of the cross correlation functions of atmospheric surface pressure and SST anomaly patterns. The numerical model is further used to simulate anomalies in the near-surface thermocline through Ekman pumping driven by the curl of the wind stress. The results suggest that short-time-scale atmospheric forcing should be regarded as a possible candidate for the origin of large-scale, low-period variability in the seasonal thermocline. DOI: 10.1111/j.2153-3490.1977.tb00740.x

762 citations


Journal ArticleDOI
TL;DR: In this paper, the renormalization of the action principle is defined in such a way that renormalized action principle holds, and the derivation of Ward-Takahashi indentities and Callan-Symanzik equations is exemplified.
Abstract: Dimensional renormalization is defined in such a way that the renormalized action principle holds. It is shown that this leads to a minimal, additive renormalization. The derivation of Ward-Takahashi indentities and Callan-Symanzik equations from the action principle is exemplified.

667 citations


Journal ArticleDOI
TL;DR: It is concluded that alterations of Ca++ dependent mechanisms participate in the generation of epileptic activity.
Abstract: Extracellular calcium and potassium activities (aCa and aK) as well as neuronal activity were simultaneously recorded with ion-sensitive electrodes in the somatosensory cortex of cats. Baseline aCa was 1.2–1.5 mM/1, baseline a k 2.7–3.2 mM/1. Transient decreases in aCa and simultaneous increases in aK were evoked by repetitive stimulation of the contralateral forepaw, the nucleus ventroposterolateralis thalami and the cortical surface. Considerable decreases in aCa (by up to 0.7 mM/1) were found during seizure activity. A fall in aCa preceded the onset of paroxysmal discharges and the rise in aK after injection of pentylene tetrazol. The decrease in aCa led also the rise in aK during cyclical spike driving in a penicillin focus. It is concluded that alterations of Ca++ dependent mechanisms participate in the generation of epileptic activity.

612 citations


Journal ArticleDOI
TL;DR: In this article, the structure parameters of AlN and GaN using X-ray intensities from single crystals collected with an automatic single crystal diffractometer were refined using a single crystal detector.

555 citations


Journal ArticleDOI
TL;DR: In this article, an adiabatic bond charge model (BCM) for the lattice dynamics of diamond-type crystals is developed, which unifies elements of earlier models by Phillips and Martin, Keating, and Cochran.
Abstract: An adiabatic bond charge model (BCM) for the lattice dynamics of diamond-type crystals is developed. Our BCM unites elements of earlier models by Phillips and Martin, Keating, and Cochran. Four types of interactions are used: (a) central ion-ion forces, (b) Coulomb interactions of the ions and bond charges (BC's), (c) central ion-BC forces, and (d) bond-bending forces. These interactions represent the metal-like (a) and covalent (b)-(d) part of the crystal bonding. The phonon dispersion curves for Si, Ge, and $\ensuremath{\alpha}\ensuremath{-}\mathrm{Sn}$ are calculated using only four disposable parameters; for diamond, five parameters are employed. For all crystals, very good agreement with experiment is obtained. In particular, the typical flattening of the transverse acoustic phonons in the semiconducting materials is understood as a consequence of the adiabatic motion of the BC's, when the effective ion-BC coupling (b)+(c) is weak compared to the bond-bending forces (d). In an alternative representation of the BCM, the interactions (b) and (c) are replaced by central and noncentral ion-BC-ion potentials along one bond. The remaining long-range part of the Coulomb forces is unimportant; therefore, all essential interactions of the BCM are of very short range. Furthermore, the interaction parameters follow clear trends from diamond to $\ensuremath{\alpha}\ensuremath{-}\mathrm{Sn}$: type (a) increases, whereas types (b)-(d) decrease, especially the ion-BC coupling tends to vanish toward $\ensuremath{\alpha}\ensuremath{-}\mathrm{Sn}$.

510 citations


Journal ArticleDOI
08 Dec 1977-Nature
TL;DR: The primary structure of DNA containing the sequence for rat pituitary growth hormone mRNA has been determined and the amino acid sequences for rat growth hormone and its precursor form have been deduced from the determined nucleotide sequences.
Abstract: The primary structure of DNA containing the sequence for rat pituitary growth hormone mRNA has been determined. DNA was obtained by reverse transcription of polyadenylated RNA from cultured pituitary cells and from recombinant bacterial plasmids. The amino acid sequences for rat growth hormone and its precursor form have been deduced from the determined nucleotide sequences.

509 citations


Journal ArticleDOI
TL;DR: In this article, the results of Raman scattering and infrared reflectivity measurements on the IV-VI layer-type semiconductors SnS and SnSe are presented and the infrared-active TO, the associated LO-phonon frequencies, and the dielectric constants for all three principal polarizations are determined from a Kramers-Kronig analysis of the reflectivity data.
Abstract: The results of Raman scattering and infrared reflectivity measurements on the IV-VI layer-type semiconductors SnS and SnSe are presented. The infrared-active TO, the associated LO-phonon frequencies, and the dielectric constants for all three principal polarizations have been determined from a Kramers-Kronig analysis of the reflectivity data. The symmetries of the zone-center phonons observed in the different polarization configurations are in agreement with the group-theoretical analysis of the ${D}_{2h}^{16}$ space group of these compounds. Despite the center of inversion symmetry in this structure, some infrared- and Raman-active modes are found to be nearly degenerate, suggesting the importance of the layerlike character in these compounds as in the isomorphic GeS and GeSe. A comparison of the phonon frequencies of the corresponding modes in the spectra of SnS and SnSe, or GeS and GeSe, indicates that the frequencies vary as a power (-2.2) of the lattice constant.

Journal ArticleDOI
TL;DR: In this paper, a least square method for simultaneously optimizing simultaneously thermodynamic functions and phase diagrams from experimental data of both types of functions is described. But the success of the method depends mainly on the appropriate construction and weighting of the equations of error associated with each measurement.
Abstract: A least squares method for optimizing simultaneously thermodynamic functions and phase diagrams from experimental data of both is described. The success of the method depends mainly on the appropriate construction and weighting of the equations of error associated with each measurement.

Book ChapterDOI
B. Hamprecht1
TL;DR: This chapter discusses the structural, electrophysiological, biochemical and pharmacological properties of neuroblastoma-glioma cell hybrids in cell culture and the rescue of latent viruses and the genetic analysis of malignancy and of viral gene expression.
Abstract: Publisher Summary This chapter discusses the structural, electrophysiological, biochemical and pharmacological properties of neuroblastoma-glioma cell hybrids in cell culture. Hybrid cells are formed by the fusion of two different cell types. The cells fused may be as different as those of humans and of mosquitos, as similar as cells from two strains of mice, or only clearly different in one gene or in the kind of tissue of the same animal they were derived from. Hybrids are prepared by fusion, e.g., of a mutant hamster cell line and a wild-type human cell line. If one selects for wild-type cells, the segregation of human chromosomes will provide hybrid cells that retain a single human chromosome, or part of one, carrying the gene that complements the hamster cell to a wild-type cell. This and similar methods are also used for the analysis of gene linkage. Other important applications of cell hybrids are the rescue of latent viruses and the genetic analysis of malignancy and of viral gene expression.

01 Nov 1977
TL;DR: This proposal provides a theoretical framework for most existing phychophysical and neurophysiological data about stereopsis, and several critical experimental predictions are made, for instance, about the wsize of Panum?s area under various conditions.
Abstract: An Algorithm is proposed for solving the stereoscopic matching problem. The algorithm consists of five steps: (1) Each image is filtered with bar masks of four sizes that vary with eccentricity; the equivalent filters are about one octave wide. (2) Zero-crossings of the mask values are localized, and positions that correspond to terminations are found; (3) For each mask size, matching takes place between pairs of zero- crossings or terminations of the same sign in the two images, for a range of disparities up to about the vergence movements, thus causing small masks to come into correspondence; (5) When a correspondence is achieved, it is written into a dynamic buffer, called the 2 1/2 D sketch. It is shown that this proposal provides a theoretical framework for most existing phychophysical and neurophysiological data about stereopsis. Several critical experimental predictions are also made, for instance, about the wsize of Panum?s area under various conditions. The results of such experiments would tell us whether, for example, cooperativity is necessary for the fusion process.

Journal ArticleDOI
TL;DR: It is suggested that the ceiling in its steady state is maintained by an active K+ uptake mechanism which balances extra releases of K+.

Journal ArticleDOI
TL;DR: In this article, the adsorption of N2 on clean Fe(100) and Fe(111) single-crystal surfaces was studied in the temperature range 140-1000 K by means of Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), ultraviolet photoelectron spectroscopic (UPS), thermal-desorption (TDS) and work-function measurements (Δφ).

Journal ArticleDOI
TL;DR: In this article, the first direct measurements of charged particle multiplicity distributions for pp collisions at ISR energies were performed by means of a streamer chamber detector with large solid-angle coverage and excellent multitrack efficiency.

Journal ArticleDOI
TL;DR: In this article, a classification scheme for boundary points of incomplete space-times is described and explicit examples of the geometry near those boundary points are presented to illustrate the different behaviour of the geometrical geometry near the boundary points.
Abstract: A classification scheme for boundary points of incomplete space-times is described. For all classes explicit examples are presented to illustrate the different behaviour of the geometry near those boundary points.


Journal ArticleDOI
TL;DR: This two-dimensional system can be used as the floor of a tissue culture chamber and should be suitable for simultaneous long-term monitoring of single unit extracellular electrical activity from more than 30 neurons in culture.

Journal ArticleDOI
TL;DR: At least in well spread cells containing a strongly developed system of microfilamentous bundles, the detergent-resistant cytoskeleton includes the nucleus, large amounts of the 58 000 molecular weight protein and the microfilmous bundles.

Journal ArticleDOI
TL;DR: The results suggest that the known conformations of adenylate kinase reflect an induced-fit of the enzyme: conformation Bbeing related to the free enzyme E and conformation A being related to E∗, the enzyme species after a substrate-induced conformational change.

Journal ArticleDOI
TL;DR: Evidence is presented which indicates that inDrosophila melanogaster the optomotor response to both horizontal and vertical movement is mediated predominantly by the 6 large retinula cells (R1–6) in each facet of the compound eye.
Abstract: We propose that inDrosophila melanogaster the optomotor response to both horizontal and vertical movement is mediated predominantly by the 6 large retinula cells (R1–6) in each facet of the compound eye. Evidence is presented which indicates that this may also be true for most of the other visual responses which at present can be quantitatively studied. These responses include visually controlled landing, pattern-induced orientation of flying and walking animals, the abnormal jump reflex of the mutant Hk1 (Kaplan, 1976) and probably also phototaxis. The only function for which the small retinula cells R7 and/or R8 seem to be required so far is spectral wavelength discrimination in phototaxis at high light intensity. Our hypothesis is based on studies of the receptor deficient mutantssevenless, outer rhabdomeres absent andreceptor degeneration B as well as on results of bleaching experiments by which the retinula cells R1–6 of the eye color mutantwhite can be reversibly blocked. Visual performance of wild typeDrosophila in the optomotor response reflects receptor properties (visual acuity, spectral sensitivity and polarization sensitivity) expected for the R1–6 receptor subsystem. The notion of a ‘high sensitivity’ and a ‘high acuity’ state which was proposed earlier on the basis of experiments on various visual mutants is in agreement with the present results but their interpretation as reflecting properties of different receptor subsystems must be abandoned. Experimental data on wild type also suggest the existence of such an adaptational mechanism; this, however, remains to be demonstrated more conclusively.

Journal ArticleDOI
TL;DR: The Earth-Pointing Faraday Cup (OPEF) was used on the 1977 Voyager mission to study the properties and radial evolution of the solar wind, the interaction of solar wind with Jupiter, and the sources, properties and morphology of the Jovian magnetospheric plasma, with particular emphasis on plasma properties in the vicinity of Io, and ion of interstellar origin this paper.
Abstract: This paper contains a brief description of the plasma experiment to be flown on the 1977 Voyager Mission, its principal scientific objectives, and the expected results. The instrument consists of two Faraday cup plasma detectors: one pointed along and one at right angles to the Earth-spacecraft line. The Earth-pointing detector uses a novel geometrical arrangement: it consists of three Faraday cups, each of which views a different direction in velocity space. With this detector, accurate values of plasma parameters (velocity, density, and pressure) can be obtained for plasma conditions expected between 1 and 20 AU. The energy range for protons and for electrons is from 10 to 5950 eV. Two sequential energy per charge scans are employed with nominal values of ΔE/E equal to 29%, and 3.6%. The two scans allow the instrument to cover a broad range between subsonic (M < 1) and highly supersonic (M-100) flows; thus, significant measurements can be made in a hot planetary magnetosheath as well as in a cold solar wind. In addition, the use of two energy resolutions during the cruise phase of the mission allows simultaneously the measurement of solar wind properties and a search for interstellar ions. The Earth-pointing detector cluster has an approximately conical field of view with a half angle of 90°. The exceptionally large field of view makes this detector especially suited for use on a three-axis stabilized spacecraft. Both the solar wind direction during the cruise phase of the mission, and the deviated magnetosheath flow directions expected at Jupiter and Saturn fall within the field of view of the main detector; thus, no mechanical or electrical scanning is required. An additional sensor with a field of view perpendicular to that of the main cluster, is included to improve the spatial coverage for the drifting or corotating positive ions expected at planetary encounter. This detector is also used to make measurements of electrons in the energy range 10 to 5950 eV. The scientific goals include studies of (a) the properties and radial evolution of the solar wind, (b) the interaction of the solar wind with Jupiter, (c) the sources, properties and morphology of the Jovian magnetospheric plasma, (d) the interaction of magnetospheric plasma with the Galilean satellites with particular emphasis on plasma properties in the vicinity of Io, (e) the interaction of the solar wind with Saturn and the Saturnian satellites with particular emphasis on Titan, and (f) ions of interstellar origin.

01 Jan 1977
TL;DR: In this paper, the first part of the Helios-1 mission was used to study the solar corona and the solar wind during the period between 0.3 and 1 AU and the separation of proton double streams and alpha-particles.
Abstract: The reported results are mainly based on data obtained during the first part of the Helios-1 mission. The sun was very quiet during the considered period. The data are, therefore, representative for comparatively stationary conditions in the solar corona. Data obtained concerning the protons were evaluated by means of a special computer routine. The significance of the data is discussed, taking into account the status of the corona and the interplanetary plasma during the considered part of the Helios-1 mission, fast stream structures in the region between 0.3 and 1 AU, radial gradients of fast and slow solar wind, and the separation of proton double streams and alpha-particles. Attention is also given to the 'strahl' in the electron distribution, differences between fast streams and slow plasma on the basis of the observed electron distributions, and radial gradients in the case of solar wind electron parameters.

Journal ArticleDOI
TL;DR: The adsorption of hydrogen on Fe(110, (100) and (111) single crystal planes has been studied by means of low energy diffraction (LEED), thermal desorption spectroscopy (TDS), work function measurements and ultraviolet photoelectron spectroscopic (UPS).

Journal ArticleDOI
TL;DR: It is now generally recognized that the cerebellum has a computer-like function in regard to a wide range of performances generated in the central nervous system.

Journal ArticleDOI
TL;DR: Haplochromis burtoni observed in their natural habitat behave differently from those observed in aquaria in several respects, with the majority of the territorial males observed in Lake Tanganyika living in a colony not having the characteristic black eye bar as a part of their bright coloration.

Journal ArticleDOI
TL;DR: Following joint tests in the Netherlands, Germany and the United Kingdom a new scheme is proposed for naming pathotypes of potato cyst-nematodes, with several of the pathotypes recognised in the British, Dutch and German National Schemes are the same.
Abstract: Following joint tests in the Netherlands, Germany and the United Kingdom a new scheme is proposed for naming pathotypes of potato cyst-nematodes. Pathotypes of Globodera ( = Heterodera) rostochiensis and G. pallida are designated separately using a simple nomenclature Ro1 to Ron for G. rostochiensis and Pa1 to Pan for G. pallida. Currently seven clones are used to differentiate five pathotypes of G. rostochiensis and three of G. pallida. Several of the pathotypes recognised in the British, Dutch and German National Schemes are the same. Results of pathotyping tests may show considerable variation; adequate replication and standardisation of method are essential. With an internationally used scheme it is highly desirable that new pathotypes or differential clones are added only after testing at Institutes in several countries.

Journal ArticleDOI
01 May 1977
TL;DR: This paper describes the feature extraction stage of a proposed pattern recognition system aimed at automatic EEG analysis, which involves splitting the basic pattern into "elementary patterns" called segments and transients by a method relying on linear predictive filtering.
Abstract: This paper describes the feature extraction stage of a proposed pattern recognition system aimed at automatic EEG analysis. The basic pattern-the EEG record-is split into "elementary patterns" called segments and transients, by means of a method relying on linear predictive filtering. Appropriate features, representing power spectra and the time structure of the signal, are then extracted and finally combined into a feature set representing the EEG as a whole. The quality of this representation may be assessed by comparing the original signal with its simulation from the stored features.