2,302 research outputs found
Relative "-Numerical Ranges for Applications in Quantum Control and Quantum Information
Motivated by applications in quantum information and quantum control, a new
type of "-numerical range, the relative "-numerical range denoted
, is introduced. It arises upon replacing the unitary group U(N) in
the definition of the classical "-numerical range by any of its compact and
connected subgroups .
The geometric properties of the relative "-numerical range are analysed in
detail. Counterexamples prove its geometry is more intricate than in the
classical case: e.g. is neither star-shaped nor simply-connected.
Yet, a well-known result on the rotational symmetry of the classical
"-numerical range extends to , as shown by a new approach based on
Lie theory. Furthermore, we concentrate on the subgroup , i.e. the -fold tensor product of SU(2),
which is of particular interest in applications. In this case, sufficient
conditions are derived for being a circular disc centered at
origin of the complex plane. Finally, the previous results are illustrated in
detail for .Comment: accompanying paper to math-ph/070103
Hepatic effects of Cimicifuga racemosa extract in vivo and in vitro
Abstract.: Extracts of Cimicifuga racemosa are used frequently for menopausal complaints. Cimicifuga is well tolerated but can occasionally cause liver injury. To assess hepatotoxicity of cimicifuga in more detail, ethanolic C. racemosa extract was administered orally to rats, and liver sections were analyzed by electron microscopy. Tests for cytotoxicity, mitochondrial toxicity and apoptosis/necrosis were performed using HepG2 cells. Mitochondrial toxicity was studied using isolated rat liver mitochondria. Microvesicular steatosis was found in rats treated with > 500 μg/kg body weight cimicifuga extract. In vitro, cytotoxicity was apparent at concentrations ≥ 75 μg/mL, and mitochondrial β-oxidation was impaired at concentrations ≥ 10 μg/mL. The mitochondrial membrane potential was decreased at concentrations ≥ 100 μg/mL, and oxidative phosphorylation was impaired at concentrations ≥ 300 μg/mL. The mechanism of cell death was predominantly apoptosis. C. racemosa exerts toxicity in vivo and in vitro, eventually resulting in apoptotic cell death. The results are compatible with idiosyncratic hepatotoxicity as observed in patients treated with cimicifuga extract
Additional Ultracool White Dwarfs Found in the Sloan Digital Sky Survey
We identify seven new ultracool white dwarfs discovered in the Sloan Digital
Sky Survey (SDSS). The SDSS photometry, spectra, and proper motions are
presented, and additional BVRI data are given for these and other previously
discovered ultracool white dwarfs. The observed colors span a remarkably wide
range, qualitatively similar to colors predicted by models for very cool white
dwarfs. One of the new stars (SDSS J1251+44) exhibits strong collision-induced
absorption (CIA) in its spectra, while the spectra and colors of the other six
are consistent with mild CIA. Another of the new discoveries (SDSS J2239+00A)
is part of a binary system -- its companion is also a cool white dwarf, and
other data indicate that the companion exhibits an infrared flux deficiency,
making this the first binary system composed of two CIA white dwarfs. A third
discovery (SDSS J0310-00) has weak Balmer emission lines. The proper motions of
all seven stars are consistent with membership in the disk or thick disk.Comment: Accepted for Astrophysical Journal. 16 pages (includes 3 figures
The new carbon symbiotic star IPHAS J205836.43+503307.2
We are performing a search for symbiotic stars using IPHAS, the INT Halpha
survey of the northern Galactic plane, and follow-up observations. Candidate
symbiotic stars are selected on the basis of their IPHAS and near-IR colours,
and spectroscopy and photometry are obtained to determine their nature. We
present here observations of the symbiotic star candidate IPHAS
J205836.43+503307.2. The optical spectrum shows the combination of a number of
emission lines, among which are the high-excitation species of [OIII], HeII,
[Ca V], and [Fe VII], and a red continuum with the features of a star at the
cool end of the carbon star sequence. The nebular component is spatially
resolved: the analysis of the spatial profile of the [NII]6583 line in the
spectrum indicates a linear size of ~2.5 arcsec along the east-west direction.
Its velocity structure suggests an aspherical morphology. The near-infrared
excess of the source, which was especially strong in 1999, indicated that a
thick circumstellar dust shell was also present in the system. The carbon star
has brightened in the last decade by two to four magnitudes at red and
near-infrared wavelengths. Photometric monitoring during a period of 60 days
from November 2010 to January 2011 reveals a slow luminosity decrease of 0.2
magnitudes. From the observed spectrophotometric properties and variability, we
conclude that the source is a new Galactic symbiotic star of the D-type, of the
rare kind that contains a carbon star, likely a carbon Mira. Only two other
systems of this type are known in the Galaxy.Comment: 6 pages, 4 figure
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