Showing papers by "Max Planck Society published in 1995"

Posttraumatic stress disorder in the National Comorbidity Survey.

Abstract: Background: Data were obtained on the general population epidemiology of DSM-III-R posttraumatic stress disorder (PTSD), including information on estimated lifetime prevalence, the kinds of traumas most often associated with PTSD, sociodemographic correlates, the comorbidity of PTSD with other lifetime psychiatric disorders, and the duration of an index episode. Methods: Modified versions of the DSM-III-R PTSD module from the Diagnostic Interview Schedule and of the Composite International Diagnostic Interview were administered to a representative national sample of 5877 persons aged 15 to 54 years in the part II subsample of the National Comorbidity Survey. Results: The estimated lifetime prevalence of PTSD is 7.8%. Prevalence is elevated among women and the previously married. The traumas most commonly associated with PTSD are combat exposure and witnessing among men and rape and sexual molestation among women. Posttraumatic stress disorder is strongly comorbid with other lifetime DSM-III-R disorders. Survival analysis shows that more than one third of people with an index episode of PTSD fail to recover even after many years. Conclusions: Posttraumatic stress disorder is more prevalent than previously believed, and is often persistent. Progress in estimating age-at-onset distributions, cohort effects, and the conditional probabilities of PTSD from different types of trauma will require future epidemiologic studies to assess PTSD for all lifetime traumas rather than for only a small number of retrospectively reported "most serious" traumas. (Arch Gen Psychiatry. 1995;52:1048-1060)

Density-functional theory and strong interactions: Orbital ordering in Mott-Hubbard insulators

Abstract: Evidence is presented that within the density-functional theory orbital polarization has to be treated on an equal footing with spin polarization and charge density for strongly interacting electron systems. Using a basis-set independent generalization of the LDA+U functional, we show that electronic orbital ordering is a necessary condition to obtain the correct crystal structure and parameters of the exchange interaction for the Mott-Hubbard insulator ${\mathrm{KCuF}}_{3}$.

Visual feature integration and the temporal correlation hypothesis

Abstract: The mammalian visual system is endowed with a nearly infinite capacity for the recognition of patterns and objects. To have acquired this capability the visual system must have solved what is a fundamentally combinatorial prob­ lem. Any given image consists of a collection of features, consisting of local contrast borders of luminance and wavelength, distributed across the visual field. For one to detect and recognize an object within a scene, the features comprising the object must be identified and segregated from those comprising other objects. This problem is inherently difficult to solve because of the combinatorial nature of visual images. To appreciate this point, consider a simple local feature such as a small vertically oriented line segment placed within a fixed location of the visual field. When combined with other line segments, this feature can form a nearly infinite number of geometrical objects. Any one of these objects may coexist with an equally large number of other

The Large Angle Spectroscopic Coronagraph (LASCO): Visible light coronal imaging and spectroscopy

Abstract: The Large Angle Spectroscopic Coronagraph (LASCO) is a triple coronagraph being jointly developed for the Solar and Heliospheric Observatory (SOHO) mission LASCO comprises three nested coronagraphs (C1, C2, and C3) that image the solar corona for 11 to 30 solar radii (C1: 11 to 3 solar radii, C2: 15 to 6 solar radii, and C3: 3 to 300 solar radii) The inner coronagraph (C1) is a newly developed mirror version of the classic Lyot coronagraph without an external occultor, while the middle coronagraph (C2) and the outer coronagraph (C3) are externally occulted instruments High resolution coronal spectroscopy from 11 to 3 R solar radii can be performed by using a Fabry-Perot interferometer, which is part of C1 High volume memories and a high speed microprocessor enable extensive onboard image processing Image compression by factors of 10 to 20 will result in the transmission of 10 to 20 full images per hour

Neurotrophins and neuronal plasticity.

Abstract: There is increasing evidence that neurotrophins (NTs) are involved in processes of neuronal plasticity besides their well-established actions in regulating the survival, differentiation, and maintenance of functions of specific populations of neurons. Nerve growth factor, brain-derived neurotrophic factor, NT-4/5, and corresponding antibodies dramatically modify the development of the visual cortex. Although the neuronal elements involved have not yet been identified, complementary studies of other systems have demonstrated that NT synthesis is rapidly regulated by neuronal activity and that NTs are released in an activity-dependent manner from neuronal dendrites. These data, together with the observation that NTs enhance transmitter release from neurons that express the corresponding signal-transducing Trk receptors, suggest a role for NTs as selective retrograde messengers that regulate synaptic efficacy.

Structure at 2.8 A resolution of cytochrome c oxidase from Paracoccus denitrificans.

Abstract: The crystal structure at 2.8 A resolution of the four protein subunits containing cytochrome c oxidase from the soil bacterium Paracoccus denitrificans, complexed with an antibody Fv fragment, is described. Subunit I contains 12 membrane-spanning, primarily helical segments and binds haem a and the haem a3-copper B binuclear centre where molecular oxygen is reduced to water. Two proton transfer pathways, one for protons consumed in water formation and one for 'proton pumping', could be identified. Mechanisms for proton pumping are discussed.

Domain interaction between NMDA receptor subunits and the postsynaptic density protein PSD-95

Abstract: The N-methyl-D-aspartate (NMDA) receptor subserves synaptic glutamate-induced transmission and plasticity in central neurons. The yeast two-hybrid system was used to show that the cytoplasmic tails of NMDA receptor subunits interact with a prominent postsynaptic density protein PSD-95. The second PDZ domain in PSD-95 binds to the seven-amino acid, COOH-terminal domain containing the terminal tSXV motif (where S is serine, X is any amino acid, and V is valine) common to NR2 subunits and certain NR1 splice forms. Transcripts encoding PSD-95 are expressed in a pattern similar to that of NMDA receptors, and the NR2B subunit co-localizes with PSD-95 in cultured rat hippocampal neurons. The interaction of these proteins may affect the plasticity of excitatory synapses.

How to Improve Bayesian Reasoning Without Instruction: Frequency Formats

Abstract: Is the mind, by design, predisposed against performing Bayesian inference? Previous research on base rate neglect suggests that the mind lacks the appropriate cognitive algorithms. However, any claim against the existence of an algorithm, Bayesian or otherwise, is impossible to evaluate unless one specifies the information format in which it is designed to operate. The authors show that Bayesian algorithms are computationally simpler in frequency formats than in the probability formats used in previous research. Frequency formats correspond to the sequential way information is acquired in natural sampling, from animal foraging to neural networks. By analyzing several thousand solutions to Bayesian problems, the authors found that when information was presented in frequency formats, statistically naive participants derived up to 50% of all inferences by Bayesian algorithms. Non-Bayesian algorithms included simple versions of Fisherian and Neyman-Pearsonian inference. Is the mind, by design, predisposed against performing Bayesian inference? The classical probabilists of the Enlightenment, including Condorcet, Poisson, and Laplace, equated probability theory with the common sense of educated people, who were known then as "hommes eclaires." Laplace (1814/ 1951) declared that "the theory of probability is at bottom nothing more than good sense reduced to a calculus which evaluates that which good minds know by a sort of instinct, without being able to explain how with precision" (p. 196). The available mathematical tools, in particular the theorems of Bayes and Bernoulli, were seen as descriptions of actual human judgment (Daston, 1981,1988). However, the years of political upheaval during the French Revolution prompted Laplace, unlike earlier writers such as Condorcet, to issue repeated disclaimers that probability theory, because of the interference of passion and desire, could not account for all relevant factors in human judgment. The Enlightenment view—that the laws of probability are the laws of the mind—moderated as it was through the French Revolution, had a profound influence on 19th- and 20th-century science. This view became the starting point for seminal contributions to mathematics, as when George Boole

The Large Angle Spectroscopic Coronagraph (LASCO)

Abstract: The Large Angle Spectroscopic Coronagraph (LASCO) is a three coronagraph package which has been jointly developed for the Solar and Heliospheric Observatory (SOHO) mission by the Naval Research Laboratory (USA), the Laboratoire d’Astronomie Spatiale (France), the Max-Planck-Institut fur Aeronomie (Germany), and the University of Birmingham (UK) LASCO comprises three coronagraphs, C1, C2, and C3, that together image the solar corona from 11 to 30 R⊙ (C1: 11–3 R⊙, C2: 15–6 R⊙, and C3: 37 – 30 R⊙) The C1 coronagraph is a newly developed mirror version of the classic internally-occulted Lyot coronagraph, while the C2 and C3 coronagraphs are externally occulted instruments High-resolution imaging spectroscopy of the corona from 11 to 3 R⊙ can be performed with the Fabry-Perot interferometer in C1 High-volume memories and a high-speed microprocessor enable extensive on-board image processing Image compression by a factor of about 10 will result in the transmission of 10 full images per hour

A life-span theory of control.

Abstract: A life-span theory of development is presented that is based on the concepts of primary and secondary control. Primary control refers to behaviors directed at the external environment and involves attempts to change the world to fit the needs and desires of the individual. Secondary control is targeted at internal processes and serves to minimize losses in, maintain, and expand existing levels of primary control. Secondary control helps the individual to cope with failure and fosters primary control by channeling motivational resources toward selected action goals throughout the life course. Primary control has functional primacy over secondary control. An analysis of extensive and diverse literatures spanning infancy through old age shows that trade-offs between primary and secondary control undergo systematic shifts across the life course in response to the opportunities and constraints encountered. In this article, we present a life-span theory of development based on the concept of control. Research on life-span development has become an increasingly active area of inquiry in the last two decades and has the potential of yielding fundamental theories about the emergence and transformation of human behavior over the life course (e.g., P. B. Baltes, 1987). However, as noted by Birren and Bengtson (1988), the field of life-course development and aging is at present best characterized as data rich but theory poor. Most existing developmental theories embrace limited temporal and functioning domains. With the exception of personality theorists such as Erikson, Loevinger, Gould, and Levinson (see Cavanaugh, 1990; Schulz & Ewen, 1993), psychologists have made few attempts to develop lifespan theories of development, in part because such efforts require the integration of information from multiple domains, including the behavioral, social, and biological sciences. A second formidable challenge posed by such an undertaking is the problem of level of analysis. Ideally, such a theory should explain both macro-level behaviors such as major life-course decisions

Calculation of thermal noise in atomic force microscopy

Abstract: Thermal fluctuations of the cantilever are a fundamental source of noise in atomic force microscopy. We calculated thermal noise using the equipartition theorem and considering all possible vibration modes of the cantilever. The measurable amplitude of thermal noise depends on the temperature, the spring constant K of the cantilever and on the method by which the cantilever deflection is detected. If the deflection is measured directly, e.g. with an interferometer or a scanning tunneling microscope, the thermal noise of a cantilever with a free end can be calculated from square root kT/K. If the end of the cantilever is supported by a hard surface no thermal fluctuations of the deflection are possible. If the optical lever technique is applied to measure the deflection, the thermal noise of a cantilever with a free end is square root 4kT/3K. When the cantilever is supported thermal noise decreases to square root kT/3K, but it does not vanish.

Crystal structure of the 20S proteasome from the archaeon T. acidophilum at 3.4 A resolution.

Abstract: The three-dimensional structure of the proteasome from the archaebacterium Thermoplasma acidophilum has been elucidated by x-ray crystallographic analysis by means of isomorphous replacement and cyclic averaging. The atomic model was built and refined to a crystallographic R factor of 22.1 percent. The 673-kilodalton protease complex consists of 14 copies of two different subunits, alpha and beta, forming a barrel-shaped structure of four stacked rings. The two inner rings consist of seven beta subunits each, and the two outer rings consist of seven alpha subunits each. A narrow channel controls access to the three inner compartments. The alpha 7 beta 7 beta 7 alpha 7 subunit assembly has 72-point group symmetry. The structures of the alpha and beta subunits are similar, consisting of a core of two antiparallel beta sheets that is flanked by alpha helices on both sides. The binding of a peptide aldehyde inhibitor marks the active site in the central cavity at the amino termini of the beta subunits and suggests a novel proteolytic mechanism.

Homological Algebra of Mirror Symmetry

Abstract: Mirror symmetry (MS) was discovered several years ago in string theory as a duality between families of 3-dimensional Calabi-Yau manifolds (more precisely, complex algebraic manifolds possessing holomorphic volume elements without zeros). The name comes from the symmetry among Hodge numbers. For dual Calabi-Yau manifolds V, W of dimension n (not necessarily equal to 3) one has $$\dim {H^p}(V,{\Omega ^q}) = \dim {H^{n - p}}(W,{\Omega ^q}).$$ .

Hippocampal long-term potentiation is impaired in mice lacking brain-derived neurotrophic factor.

Abstract: Brain-derived neurotrophic factor (BDNF), a member of the nerve growth factor (NGF) gene family, has been shown to influence the survival and differentiation of specific classes of neurons in vitro and in vivo. The possibility that neurotrophins are also involved in processes of neuronal plasticity has only recently begun to receive attention. To determine whether BDNF has a function in processes such as long-term potentiation (LTP), we produced a strain of mice with a deletion in the coding sequence of the BDNF gene. We then used hippocampal slices from these mice to investigate whether LTP was affected by this mutation. Homo- and heterozygous mutant mice showed significantly reduced LTP in the CA1 region of the hippocampus. The magnitude of the potentiation, as well as the percentage of cases in which LTP could be induced successfully, was clearly affected. According to the criteria tested, important pharmacological, anatomical, and morphological parameters in the hippocampus of these animals appear to be normal. These results suggest that BDNF might have a functional role in the expression of LTP in the hippocampus.

Frame of analysis

Abstract: In this chapter, we shall explain the way in which the data were analysed. A frame of analysis, such as the one used here, is not a theory which is meant to excel by the depth of its insights or by its explanatory power. Rather, it is an instrument designed for a specific purpose, and to serve this purpose, it should be simple, clear and handy. Moreover, it is allowed to ignore many of the subtleties and complications which a satisfactory theory of temporality and its expression in natural language eventually has to account for. On the other hand, it must not be at variance with such a theory. A frame of analysis, if it is to be more than a temporary crutch, should also be flexible in the sense that it can easily be enlarged, refined and made more precise, whenever there is need to. The frame of analysis presented here is the outcome of several earlier attempts and considerable practical experience. In many respects, it is an elaboration of ideas sketched in Perdue (1984, chapter 7.4), which in turn are based on a number of previous empirical studies of temporality in second language acquisition, notably Klein (1981) and von Stutterheim (1986). During subsequent work, empirical findings have led to many changes, even compared to the project's final report (Bhardwaj, Dietrich and Noyau 1988), although most of these changes do not so very much concern our basic assumptions as terminology and presentation.

Phylogenetic relationships of Thiomicrospira species and their identification in deep-sea hydrothermal vent samples by denaturing gradient gel electrophoresis of 16S rDNA fragments

Abstract: Denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rDNA fragments was used to explore the genetic diversity of hydrothermal vent microbial communities, specifically to determine the importance of sulfur-oxidizing bacteria therein. DGGE analysis of two different hydrothermal vent samples revealed one PCR band for one sample and three PCR bands for the other sample, which probably correspond to the dominant bacterial populations in these communities. Three of the four 16S rDNA fragments were sequenced. By comparison with 16S rRNA sequences of the Ribosomal Database Project, two of the DGGE-separated fragments were assigned to the genus Thiomicrospira. To identify these 'phylotypes' in more detail, a phylogenetic framework was created by determining the nearly complete 16S rRNA gene sequence (approx. 1500 nucleotides) from three described Thiomicrospira species, viz., Tms. crunogena, Tms. pelophila, Tms. denitrificans, and from a new isolate, Thiomicrospira sp. strain MA2-6. All Thiomicrospira species except Tms. denitrificans formed a monophyletic group within the gamma subdivision of the Proteobacteria. Tms. denitrificans was assigned as a member of the epsilon subdivision and was distantly affiliated with Thiovulum, another sulfur-oxidizing bacterium. Sequences of two dominant 16S rDNA fragments obtained by DGGE analysis fell into the gamma subdivision Thiomicrospira. The sequence of one fragment was in all comparable positions identical to the 16S rRNA sequence of Tms. crunogena. Identifying a dominant molecular isolate as Tms. crunogena indicates that this species is a dominant community member of hydrothermal vent sites. Another 'phylotype' represented a new Thiomicrospira species, phylogenetically in an intermediate position between Tms. crunogena and Tms. pelophila. The third 'phylotype' was identified as a Desulfovibrio, indicating that sulfate-reducing bacteria, as sources of sulfide, may complement sulfur- and sulfide-oxidizing bacteria ecologically in these sulfide-producing hydrothermal vents.

Toward a better definition of the restless legs syndrome

Abstract: A large International Restless Legs Syndrome (RLS) Study Group has been formed. As its first task, the group has taken upon itself the role of definig the clinical features of the RLS. As minimal criteria for diagnosis, the group proposes the following four features: (a) desire to move the extremities, often associated with paresthesias/dysesthesias; (b) motor restlessness; (c) worsening of symptoms at rest with at least temporary relief by activity, and (d) worsening of symptoms in the evening or night. Other features commonly seen in RLS include sleep disturbance, periodic limb movements in sleep and similar involuntary movements while awake, a normal neurological examination in the idiopathic from, a tendency for the symptoms to be worse in middle to older age, and, in some cases, a family history suggestive of an autosomal dominant mode of inheritance.

DARN/SUPERDARN : A global view of the dynamics of high-latitude convection

Abstract: The Dual Auroral Radar Network (DARN) is a global-scale network of HF and VHF radars capable of sensing backscatter from ionospheric irregularities in the E and F-regions of the high-latitude ionosphere. Currently, the network consists of the STARE VHF radar system in northern Scandinavia, a northern-hemisphere, longitudinal chain of HF radars that is funded to extend from Saskatoon, Canada to central Finland, and a southern-hemisphere chain that is funded to include Halley Station, SANAE and Syowa Station in Antarctica. When all of the HF radars have been completed they will operate in pairs with common viewing areas so that the Doppler information contained in the backscattered signals may be combined to yield maps of high-latitude plasma convection and the convection electric field. In this paper, the evolution of DARN and particularly the development of its SuperDARN HF radar element is discussed. The DARN/SupperDARN network is particularly suited to studies of large-scale dynamical processes in the magnetosphere-ionosphere system, such as the evolution of the global configuration of the convection electric field under changing IMF conditions and the development and global extent of large-scale MHD waves in the magnetosphere-ionosphere cavity. A description of the HF radars within SuperDARN is given along with an overview of their existing and intended locations, intended start of operations, Principal Investigators, and sponsoring agencies. Finally, the operation of the DARN experiment within ISTP/GGS, the availability of data, and the form and availability of the Key Parameter files is discussed.

Gravitationally redshifted emission implying an accretion disk and massive black hole in the active galaxy MCG-6-30-15

Abstract: ACTIVE galactic nuclei and quasars are probably powered by the accretion of gas onto a supermassive black hole at the centre of the host galaxy1, but direct confirmation of the presence of a black hole is hard to obtain. As the gas nears the event horizon, its velocity should approach the speed of light; the resulting relativistic effects, and a gravitational redshift arising from the proximity to the black hole, should be observable, allowing us to test specific predictions of the models with the observations. Here we report the detection of these relativistic effects in an X-ray emission line (the Kα line) from ionized iron in the galaxy MCG–6–30–15. The line is extremely broad, corresponding to a velocity of ∼100,000 km s−1, and asymmetric, with most of the line flux being redshifted. These features indicate that the line most probably arises in a region between three and ten Schwarzschild radii from the centre, so that we are observing the innermost region of the accretion disk.

A gene (PEX) with homologies to endopeptidases is mutated in patients with X–linked hypophosphatemic rickets

Abstract: X–linked hypophosphatemic rickets (HYP) is a dominant disorder characterised by impaired phosphate uptake in the kidney, which is likely to be caused by abnormal regulation of sodium phosphate cotransport in the proximal tubules. By positional cloning, we have isolated a candidate gene from the HYP region in Xp22.1. This gene exhibits homology to a family of endopeptidase genes, members of which are involved in the degradation or activation of a variety of peptide hormones. This gene (which we have called PEX) is composed of multiple exons which span at least five cosmids. Intragenic non–overlapping deletions from four different families and three mutations (two splice sites and one frameshift) have been detected in HYP patients, which suggest that the PEX gene is involved in the HYP disorder.

Polyisoprene-Polystyrene Diblock Copolymer Phase Diagram near the Order-Disorder Transition

Abstract: The phase behavior of ten polyisoprene-polystyrene (PI-PS) diblock copolymers, spanning the composition range from 0.24 to 0.82 polyisoprene volume fraction (f PI ), has been studied near the order-disorder transition (ODT). Dynamic mechanical spectroscopy, transmission electron microscopy, and neutron and X-ray scattering have been used to characterize phase transition temperatures and ordered state symmetries. Five distinct microstructures were observed for this chemical system : spheres, hexagonally packed cylinders (HEX), lamellae (LAM), hexagonally perforated layers (HPL), and a bicontinuous cubic phase having an Ia3d space group symmetry. The bicontinuous Ia3d phase only occurs in the vicinity of the ODT between the HEX and LAM states at compositions of 0.65 ≤ f pI ≤ 0.68 and 0.36 ≤ f pI ≤ 0.39 (prior report). Farther from the ODT, within these composition ranges, the HPL phase occurs. We did not find the ordered bicontinuous double diamond (OBDD) morphology at any composition or temperature studied, and the overall phase diagram is qualitatively different from those reported previously for PI-PS block copolymers.

LEDA: A Platform for Combinatorial and Geometric Computing

Abstract: Combinatorial and geometric computing is a core area of computer science (CS). In fact, most CS curricula contain a course in data structures and algorithms. The area deals with objects such as graphs, sequences, dictionaries, trees, shortest paths, flows, matchings, points, segments, lines, convex hulls, and Voronoi diagrams and forms the basis for application areas such as discrete optimization, scheduling, traffic control, CAD, and graphics. There is no standard library of the data structures and algorithms of combinatorial and geometric computing. This is in sharp contrast to many other areas of computing. There are, for example, packages in statistics (SPSS), numerical analysis (LINPACK, EISPACK), symbolic computation (MAPLE, MATHEMATICA), and linear programming (CPLEX).

Structure of the Arabidopsis RPM1 gene enabling dual specificity disease resistance

Abstract: Plants can recognize pathogens through the action of disease resistance (R) genes, which confer resistance to pathogens expressing unique corresponding avirulence (avr) genes. The molecular basis of this gene-for-gene specificity is unknown. The Arabidopsis thaliana RPM1 gene enables dual specificity to pathogens expressing either of two unrelated Pseudomonas syringae avr genes. Despite this function, RPM1 encodes a protein sharing molecular features with recently described single-specificity R genes. Surprisingly, RPM1 is lacking from naturally occurring, disease-susceptible Arabidopsis accessions.

Recombination line intensities for hydrogenic ions-IV. Total recombination coefficients and machine-readable tables for Z=1 to 8

Abstract: Line emissivities, effective recombination coefficients, opacity factors, departure coefficients and total recombination coefficients are calculated for hydrogenic ions with Z less-than-or-equal-to 8. Results are obtained for Cases A and B for n less-than-or-equal-to 50. Collisional transitions among individual n and l states are fully treated. Calculations were made for log N(e) = 2(1)14 for Case B and log N(e) = 2(1)10 for Case A. The electron temperature takes between nine and 12 values, lying within the range 500 to 100 000 K, depending on the ion. All results are available in the form of machine-readable files.Secondary files containing only effective emissivities for transitions for n less-than-or-equal-to 25 and total recombination coefficients are also available for use with an interactive data server. The server produces tables of relative intensities of any two specified transitions or emissivities for any transition at all temperatures and densities in the data set. Extensive facilities for two-dimensional interpolation of relative intensities, emissivities and total recombination coefficients are provided.

MHD structures, waves and turbulence in the solar wind : observations and theories

Abstract: A comprehensive overview is presented of recent observational and theoretical results on solar wind structures and fluctuations and magnetohydrodynamic waves and turbulence, with preference given to phenomena in the inner heliosphere. Emphasis is placed on the progress made in the past decade in the understanding of the nature and origin of especially small-scale, compressible and incompressible fluctuations. Turbulence models to describe the spatial transport and spectral transfer of the fluctuations in the inner heliosphere are discussed, and results from direct numerical simulations are dealt with. Intermittency of solar wind fluctuations and their statistical distributions are briefly investigated. Studies of the heating and acceleration effects of the turbulence on the background wind are critically surveyed. Finally, open questions concerning the origin, nature and evolution of the fluctuations are listed, and possible avenues and perspectives for future research are outlined.