70,052 research outputs found
Neutron star properties in the Thomas-Fermi model
The modern nucleon-nucleon interaction of Myers and Swiatecki, adjusted to
the properties of finite nuclei, the parameters of the mass formula, and the
behavior of the optical potential is used to calculate the properties of
--equilibrated neutron star matter, and to study the impact of this
equation of state on the properties of (rapidly rotating) neutron stars and
their cooling behavior. The results are in excellent agreement with the outcome
of calculations performed for a broad collection of sophisticated
nonrelativistic as well as relativistic models for the equation of state.Comment: 23 pages, LaTeX, 15 ps-figure
Mini erythema migrans - A sign of early Lyme borreliosis
Background: An erythema migrans (EM) remaining smaller than 5 cm in diameter, called mini EM by us, has not been addressed in detail. Objective: To study the significance of the mini EM as a sign of Lyme borreliosis. Methods: Patients with suspected mini EM were retrospectively selected out of 257 consecutive patients with EM. The diagnosis of mini EM rested on the cultivation of Borrelia burgdorferi. Species and subtype analysis of culture isolates was performed using outer surface protein A (OspA) polymerase chain reaction followed by restriction fragment length polymorphism and sequencing of the OspA gene. Results: There was one patient with definite (0.4%) and another patient with a questionable mini EM. Borrelia garinii OspA type 6 was identified in the patient with the definite and B. burgdorferi sensu lato in the patient with the questionable mini EM. Conclusion: The mini EM represents an important and apparently uncommon sign of early Lyme borreliosis
Baryon Spin and Magnetic Moments in Relativistic Chiral Quark Models
Spin-flavor fractions of quarks in the proton and several hyperons are
obtained from their lowest order chiral fluctuations involving Goldstone
bosons. SU(3) flavor breaking, relativistic effects and the axial anomaly are
included. The validity of the Karl-Sehgal formulas for magnetic moments is
studied as well.Comment: 24 pages, 7 tables, no figure
Spin Clustering of Accreting X-ray Neutron Stars as Possible Evidence of Quark Matter
A neutron star in binary orbit with a low-mass non-degenerate companion
becomes a source of x-rays with millisecond variability when mass accretion
spins it up. Centrifugally driven changes in density profile may initiate a
phase transition in a growing region of the core parallel to what may take
place in an isolated millisecond pulsar, but in reverse. Such a star will spend
a longer time in the spin frequency range over which the transition occurs than
elsewhere because the change of phase, paced by the spinup rate, is accompanied
by a growth in the moment of inertia. The population of accreters will exhibit
a clustering in the critical frequency range. A phase change triggered by
changing spin and the accompanying adjustment of moment of inertia has its
analogue in rotating nuclei.Comment: 5 pages (AIPproc latex) 6 figures. To be presented at the
International Conference on Nuclear Physics, 30 July - 3 August 2001,
Berkeley, Californi
Maturation of nuclear lamin A involves a specific carboxy-terminal trimming, which removes the polyisoprenylation site from the precursor; implications for the structure of the nuclear lamina.
Lamin A, a nuclear lamina protein of differentiated cells, is synthesized as a precursor of the mature molecule. Protein sequencing of the carboxyterminal 14 kDa fragment shows a lack of the last 18 residues predicted by cDNA sequencing. The carboxy-terminal proteolytic maturation explains previous biochemical results including the loss of the polyisoprenylation site now located to the CXXM motif at the end of the chain. This view and earlier results on lamin B predict multiple post-translational modifications shared by lamins A and B. While retained by lamin B, which is present in all cells, they are lost by maturation from lamin
Modeling the Rise of Fibril Magnetic Fields in Fully Convective Stars
Many fully convective stars exhibit a wide variety of surface magnetism,
including starspots and chromospheric activity. The manner by which bundles of
magnetic field traverse portions of the convection zone to emerge at the
stellar surface is not especially well understood. In the Solar context, some
insight into this process has been gleaned by regarding the magnetism as
consisting partly of idealized thin flux tubes (TFT). Here, we present the
results of a large set of TFT simulations in a rotating spherical domain of
convective flows representative of a 0.3 solar-mass, main-sequence star. This
is the first study to investigate how individual flux tubes in such a star
might rise under the combined influence of buoyancy, convection, and
differential rotation. A time-dependent hydrodynamic convective flow field,
taken from separate 3D simulations calculated with the anelastic equations,
impacts the flux tube as it rises. Convective motions modulate the shape of the
initially buoyant flux ring, promoting localized rising loops. Flux tubes in
fully convective stars have a tendency to rise nearly parallel to the rotation
axis. However, the presence of strong differential rotation allows some
initially low latitude flux tubes of moderate strength to develop rising loops
that emerge in the near-equatorial region. Magnetic pumping suppresses the
global rise of the flux tube most efficiently in the deeper interior and at
lower latitudes. The results of these simulations aim to provide a link between
dynamo-generated magnetic fields, fluid motions, and observations of starspots
for fully convective stars.Comment: 20 pages, 15 figures, accepted to Astrophysical Journa
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