1,417 research outputs found
Die Pflanzenareale : [Welt] : Sammlung kartographischer Darstellungen von Verbreitungsbezirken der lebenden und fossilen Pflanzen-Familien, -Gattungen und -Arten / 3/8 Die Gattung Verbascum L : (Karte 71) ; Die Gattung Staurophragma Fisch. et Mey : (Karte 72)
No full textvon Sv. Murbeck. Alisma L. : (Karte 73-75) / von Gunnar Samuelsson. Die Verbreitung einiger Isoteiden II : (Karte 76-78) / von A. Donat. Erica arborea L. : (Karte 79-80) / von M. Rikl
Gravitational waves from color-magnetic “mountains” in neutron stars
No full textNeutron stars may harbor the true ground state of matter in the form of strange quark matter. If present, this type of matter is expected to be a color superconductor, a consequence of quark pairing with respect to the color and flavor degrees of freedom. The stellar magnetic field threading the quark core becomes a color-magnetic admixture and, in the event that superconductivity is of type II, leads to the formation of color-magnetic vortices. In this Letter, we show that the volume-averaged color-magnetic vortex tension force should naturally lead to a significant degree of nonaxisymmetry in systems such as radio pulsars. We show that gravitational radiation from such color-magnetic “mountains” in young pulsars, such as the Crab and Vela, could be observable by the future Einstein Telescope, thus, becoming a probe of paired quark matter in neutron stars. The detectability threshold can be pushed up toward the sensitivity level of Advanced LIGO if we invoke an interior magnetic field about a factor ten stronger than the surface polar field
Superfluid signatures in magnetar seismology
No full textWe investigate the role of neutron star superfluidity for magnetar oscillations. Using a plane-wave analysis, we estimate the effects of a neutron superfluid in the elastic crust region. We demonstrate that the superfluid imprint is likely to be more significant than the effects of the crustal magnetic field. We also consider the region immediately beneath the crust, where superfluid neutrons are thought to coexist with a type II proton superconductor. Since the magnetic field in the latter is carried by an array of fluxtubes, the dynamics of this region differ from standard magnetohydrodynamics. We show that the presence of the neutron superfluid (again) leaves a clear imprint on the oscillations of the system. Taken together, our estimates show that the superfluid components cannot be ignored in efforts to carry out 'magnetar seismology'. This increases the level of complexity of the modelling problem, but also points to the possibility of using observations to probe the superfluid nature of supranuclear matter
Opinie
No full textItem does not contain fulltextIngezonden brief 'Literaire kritiek: man niet overal aan de macht', samen met Lina Samuelsson (Mälardalen Universiteit, Zweden)20 april 201
Cognition in myotonic dystrophy type 1: a 5-year follow-up study
No full textBackground and purpose: Studies on cognitive decline in myotonic dystrophy type 1 (DM1) are characterized by conflicting results. The purpose of the present study was to analyse possible decline in classical/adult onset DM1 at a 5-year follow-up and to explore the correlation with disease-related and demographic factors. Methods: Patients with DM1 (n = 37) were examined with a comprehensive neuropsychological test battery yielding measures on memory, attention, verbal, visuospatial and executive functions. Assessment of muscle impairment and CTG repeat expansion size was performed. Results: A majority of the participants (65%) performed worse at follow-up. Compared to normative data, patients scored significantly worse on tests measuring memory, attention, visuospatial construction and verbal ability. Neither CTG repeat size nor muscle impairment related to cognitive decline. However, age at onset and disease duration were correlated with the number of tests in which performance was below 1 SD at both baseline and follow-up examination. Conclusions: Measurements show that classical/adult onset DM1 is characterized by cognitive decline. Both earlier onset and longer duration of the disease are indicative of more cognitive deficits.
The dynamics of neutron star crusts: Lagrangian perturbation theory for a relativistic superfluid-elastic system
No full textThe inner crust of a mature neutron star is composed of an elastic lattice of neutron-rich nuclei penetrated by free neutrons. These neutrons can flow relative to the crust once the star cools below the superfluid transition temperature. In order to model the dynamics of this system, which is relevant for a range of problems from pulsar glitches to magnetar seismology and continuous gravitational-wave emission from rotating deformed neutron stars, we need to understand general relativistic Lagrangian perturbation theory for elastic matter coupled to a superfluid component. This paper develops the relevant formalism to the level required for astrophysical applications
Are neutron stars with crystalline color-superconducting cores relevant for the LIGO experiment?
No full textWe estimate the maximal deformation that can be sustained by a rotating neutron star with a crystalline
color-superconducting quark core. Our results suggest that current gravitational-wave data from the Laser
Interferometer Gravitational-Wave Observatory have already reached the level where a detection would
have been possible over a wide range of the poorly constrained QCD parameters. This leads to the
nontrivial conclusion that compact objects do not contain maximally strained color crystalline cores
drawn from this range of parameter space. We discuss the uncertainties associated with our simple model
and how it can be improved in the future
Modelling magnetically deformed neutron stars
No full textRotating deformed neutron stars are important potential sources for ground-based gravitational wave interferometers such as LIGO, GEO600 and VIRGO. One mechanism that may lead to significant non-asymmetries is the internal magnetic field. It is well known that a magnetic star will not be spherical and, if the magnetic axis is not aligned with the spin axis, the deformation will lead to the emission of gravitational waves. The aim of this paper is to develop a formalism that would allow us to model magnetically deformed stars, using both realistic equations of state and field configurations. As a first step, we consider a set of simplified model problems. Focusing on dipolar fields, we determine the internal magnetic field which is consistent with a given neutron star model and calculate the associated deformation. We discuss the relevance of our results for current gravitational wave detectors and future prospects
Cognitive decline in Myotonic dystrophy type 1 (DM1)
No full textBackground: Myotonic dystrophy type 1 (DM1) is a disorder associated with deficits in facial emotion recognition ability and social interaction skills 1, 2, 3. This study aimed to explore an important function associated with facial analysis and social interplay - the ability to remember and to recognize faces.
Methods: Thirty-three persons with adult onset DM1 and thirty healthy controls performed a facial memory task included in the Rivermead Behavioral Memory Test-Extended (RBMT-E) 4. Scores in this task were correlated with duration of the disease, CTG repeat expansion size as measured in blood and results on neuropsychological tests.
Results: Deficits in facial memory ability were significantly (P 475 repeats, failure in facial memory ability was associated with larger repeats and longer duration of the disease. Furthermore, a significant association between general visuoconstructive ability and facial memory in the DM1 group (but not in healthy controls) indicated the use of compensatory visual analytic strategies. These strategies involved a focus on details in favor of holistic analyses.
Conclusions: In summary, this study is the first to show facial memory deficits and prosopagnosia in adult onset DM1. Thus, the ability to recognize faces is a basic prerequisite in social interplay, this finding adds an important clue on understanding social interaction associated with the disease
Tidal deformations of neutron stars: the role of stratification and elasticity
No full textWe discuss the response of neutron stars to the tidal interaction in a compact binary system, as encoded in the Love number associated with the induced deformation. This problem is of interest for gravitational-wave astronomy as there may be a detectable imprint on the signal from the late stages of binary coalescence. Previous work has focused on simple barotropic neutron star models, providing an understanding of the role of the stellar compactness and overall density profile. We add realism to the discussion by developing the framework required to model stars with varying composition and an elastic crust. These effects are not expected to be significant for the next generation of detectors, but it is nevertheless useful to be able to quantify them. Our results show that (perhaps surprisingly) internal stratification has no impact whatsoever on the Love number. We also show that crust elasticity provides a (predictably) small correction to existing models.<br/
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