236 research outputs found
Anomalous RR Lyrae stars(?). III. CM Leonis
Time series of B,V,I CCD photometry and radial velocity measurements from
high resolution spectroscopy (R=30,000) covering the full pulsation cycle are
presented for the field RR Lyrae star CM Leonis. The photometric data span a 6
year interval from 1994 to 1999, and allow us to firmly establish the pulsation
mode and periodicity of the variable. The derived period P=0.361699 days (+/-
0.000001) is very close to the value published in the Fourth Edition of the
General Catalogue of Variable Stars (P=0.361732 days). However, contrary to
what was previously found, the amplitude and shape of the light curve qualify
CM Leo as a very regular first overtone pulsator with a prominent hump on the
rising branch of its multicolour light curves. According to an abundace
analysis performed on three spectra taken near minimum light (0.42 < phase <
0.61), CM Leo is a metal-poor star with metal abundance [Fe/H]=-1.93 +/- 0.20.
The photometric and radial velocity curves of CM Leo have been compared with
the predictions of suitable pulsational models to infer tight constraints on
the stellar mass, effective temperature, and distance modulus of the star. We
derive a true distance modulus of CM Leo of (m-M)0=13.11 +/- 0.02 mag and a
corresponding absolute magnitude of Mv=0.47 +/- 0.04. This absolute magnitude,
once corrected for evolutionary and metallicity effects, leads to a true
distance modulus of the Large Magellanic Cloud of (m-M)0=18.43 +/- 0.06 mag, in
better agreement with the long astronomical distance scale.Comment: 14 pages, 10 figures, accepted for publication in MNRA
BibliografĂa
 Denna uppsats undersöker två läroböcker avsedda för gymnasiets A-kurs i engelskämnet, Progress Gold A (2003) och Solid Ground (2003), i syfte att se vad de kan kommunicera ur ett genusperspektiv. De frågeställningar som behandlas är följande: Hur konstrueras genus i texterna i dessa båda läroböcker? Då läsaren inkluderas exempelvis i ett "vi" eller "du", förutsätts läsaren då vara antingen man eller kvinna, eller har detta inte någon betydelse? Hur förhåller sig resultaten till läroplanens mål om jämställdhet? Den teori och metod som ligger till grund för analysen har hämtats från det fält som kallas diskursanalys. Såsom den utformats i detta arbete kan metoden närmast beskrivas som en kvalitativ närläsning av materialet. Resultatet visar på att båda läroböckerna till stor del tycks reproducera genuskontraktets grundpelare, dikotomiseringen av manligt och kvinnligt samt hierarkin dem emellan som ger det manliga högre statuts än det kvinnliga. Huruvida texterna förutsätter att läsaren är man, kvinna eller om detta inte har någon betydelse skiljer sig mellan läroböckerna. Solid Ground påvisar genusneutralitet i det avseendet, medan det i Progress finns tillfällen där det allmängiltiga underförstått riktar sig till antingen män eller kvinnor. I förhållande till läroplanen framgår av resultatet att dessa båda läroböcker stämmer illa överens med läroplanens grundläggande värderingar om jämlikhet mellan män och kvinnor, samt läroplanens krav på att undervisningen ska återspegla både manliga och kvinnliga perspektiv.
In vivo manipulation of the extracellular matrix induces vascular regression in a basal chordate.
We investigated the physical role of the extracellular matrix (ECM) in vascular homeostasis in the basal chordate Botryllus schlosseri, which has a large, transparent, extracorporeal vascular network encompassing an area >100 cm2 We found that the collagen cross-linking enzyme lysyl oxidase is expressed in all vascular cells and that in vivo inhibition using β-aminopropionitrile (BAPN) caused a rapid, global regression of the entire network, with some vessels regressing >10 mm within 16 h. BAPN treatment changed the ultrastructure of collagen fibers in the vessel basement membrane, and the kinetics of regression were dose dependent. Pharmacological inhibition of both focal adhesion kinase (FAK) and Raf also induced regression, and levels of phosphorylated FAK in vascular cells decreased during BAPN treatment and FAK inhibition but not Raf inhibition, suggesting that physical changes in the vessel ECM are detected via canonical integrin signaling pathways. Regression is driven by apoptosis and extrusion of cells through the basal lamina, which are then engulfed by blood-borne phagocytes. Extrusion and regression occurred in a coordinated manner that maintained vessel integrity, with no loss of barrier function. This suggests the presence of regulatory mechanisms linking physical changes to a homeostatic, tissue-level response
Metagenomic monitoring of soil bacterial community after the construction of a crude oil flowline
CU Comae: a new field double-mode RR Lyrae, the most metal poor discovered to date
We report the discovery of a new double-mode RR Lyrae variable (RRd) in the
field of our Galaxy: CU Comae. CU Comae is the sixth such RRd identified to
date and is the most metal-poor RRd ever detected. Based on BVI CCD photometry
spanning eleven years of observations, we find that CU Comae has periods
P0=0.5441641 +/-0.0000049d and P1=0.4057605 +/-0.0000018d. The amplitude of the
primary (first-overtone) period of CU Comae is about twice the amplitude of the
secondary (fundamental) period. The combination of the fundamental period of
pulsation P0 and the period ratio of P1/P0=0.7457 places the variable on the
metal-poor side of the Petersen diagram, in the region occupied by M68 and M15
RRd's. A mass of 0.83 solar masses is estimated for CU Comae using an updated
theoretical calibration of the Petersen diagram. High resolution spectroscopy
(R=30,000) covering the full pulsation cycle of CU Comae was obtained with the
2.7 m telescope of the Mc Donald Observatory, and has been used to build up the
radial velocity curve of the variable. Abundance analysis done on the four
spectra taken near minimum light (phase: 0.54 -- 0.71) confirms the metal poor
nature of CU Comae, for which we derive [Fe/H]=-2.38 +/-0.20. This value places
this new RRd at the extreme metal-poor edge of the metallicity distribution of
the RR Lyrae variables in our Galaxy.Comment: 21 pages including 8 Tables, Latex, 11 Figures. Accepted for
publication in The Astronomical Journal, October 2000 issu
A multi-Lorentzian timing study of the atoll sources 4U 0614+09 and 4U 1728-34
We present the results of a multi-Lorentzian fit to the power spectra of two
kilohertz QPO sources; 4U 0614+09 and 4U 1728-34. This work was triggered by
recent results of a similar fit to the black-hole candidates (BHCs) GX 339-4
and Cyg X-1 by Nowak in 2000. We find that one to six Lorentzians are needed to
fit the power spectra of our two sources. The use of exactly the same fit
function reveals that the timing behaviour of 4U 0614+09 and 4U 1728-34 is
almost identical at luminosities which are about a factor 5 different. As the
characteristic frequency of the Lorentzians we use the frequency, nu_max, at
which each component contributes most of its variance per log frequency as
proposed by Belloni, Psaltis & van der Klis in 2001. When using nu_max instead
of the centroid frequency of the Lorentzian, the recently discovered hectohertz
Lorentzian is practically constant in frequency. We use our results to test the
suggestions by, respectively, Psaltis Belloni and van der Klis in 1999 and
Nowak in 2000 that the two Lorentzians describing the high-frequency end of the
broad-band noise in BHCs in the low state can be identified with the kilohertz
QPOs in the neutron star low mass X-ray binaries. We find, that when the two
kilohertz QPOs are clearly present, the low-frequency part of the power
spectrum is too complicated to draw immediate conclusions from the nature of
the components detected in any one power spectrum. However, the relations we
observe between the characteristic frequencies of the kilohertz QPOs and the
band-limited noise, when compared to the corresponding relations in BHCs, hint
towards the identification of the second-highest frequency Lorentzian in the
BHCs with the lower kilohertz QPO. They do not confirm the identification of
the highest-frequency Lorentzian with the upper kilohertz QPO.Comment: 30 pages, 35 figures, ApJ accepted; changed name of BLN QPO into very
low-frequency Lorentzian, removed table 4 and figure 8 from previous versio
Cancer-Initiating Cells from Colorectal cancer Patients Escape from T Cell-Mediated Immunosurveillance In Vitro through Membrane-Bound IL-4
Cancer-initiating cells (CICs) that are responsible for tumor initiation, propagation, and resistance to standard therapies have been isolated from human solid tumors, including colorectal cancer (CRC). The aim of this study was to obtain an immunological profile of CRC-derived CICs and to identify CIC-associated target molecules for T cell immunotherapy. We have isolated cells with CIC properties along with their putative non-CIC autologous counterparts from human primary CRC tissues. These CICs have been shown to display “tumor-initiating/stemness” properties, including the expression of CIC-associated markers (e.g., CD44, CD24, ALDH-1, EpCAM, Lgr5), multipotency, and tumorigenicity following injection in immunodeficient mice. The immune profile of these cells was assessed by phenotype analysis and by in vitro stimulation of PBMCs with CICs as a source of Ags. CICs, compared with non-CIC counterparts, showed weak immunogenicity. This feature correlated with the expression of high levels of immu- nomodulatory molecules, such as IL-4, and with CIC-mediated inhibitory activity for anti-tumor T cell responses. CIC-associated IL-4 was found to be responsible for this negative function, which requires cell-to-cell contact with T lymphocytes and which is impaired by blocking IL-4 signaling. In addition, the CRC-associated Ag COA-1 was found to be expressed by CICs and to represent, in an autologous setting, a target molecule for anti-tumor T cells. Our study provides relevant information that may contribute to designing new immunotherapy protocols to target CICs in CRC patient
Hierarchical information clustering by means of topologically embedded graphs
We introduce a graph-theoretic approach to extract clusters and hierarchies
in complex data-sets in an unsupervised and deterministic manner, without the
use of any prior information. This is achieved by building topologically
embedded networks containing the subset of most significant links and analyzing
the network structure. For a planar embedding, this method provides both the
intra-cluster hierarchy, which describes the way clusters are composed, and the
inter-cluster hierarchy which describes how clusters gather together. We
discuss performance, robustness and reliability of this method by first
investigating several artificial data-sets, finding that it can outperform
significantly other established approaches. Then we show that our method can
successfully differentiate meaningful clusters and hierarchies in a variety of
real data-sets. In particular, we find that the application to gene expression
patterns of lymphoma samples uncovers biologically significant groups of genes
which play key-roles in diagnosis, prognosis and treatment of some of the most
relevant human lymphoid malignancies.Comment: 33 Pages, 18 Figures, 5 Table
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