427 research outputs found
Serum C-reactive protein as a prognostic variable in elective surgery ICU patients: especially valuable following esophagectomy
On the nature of the prototype LBV AG Carinae I. Fundamental parameters during visual minimum phases and changes in the bolometric luminosity during the S-Dor cycle
We present a detailed spectroscopic analysis of the luminous blue variable AG
Carinae during the last two visual minimum phases of its S-Dor cycle (1985-1990
and 2000-2003). The analysis reveals an overabundance of He, N, and Na, and a
depletion of H, C, and O, on the surface of AG Car, indicating the presence of
CNO-processed material. Furthermore, the ratio N/O is higher on the stellar
surface than in the nebula. We found that the minimum phases of AG Car are not
equal to each other, since we derived a noticeable difference between the
maximum effective temperature achieved during 1985-1990 (22,800 K) and
2000-2001 (17,000 K). While the wind terminal velocity was 300 km/s in
1985-1990, it was as low as 105 km/s in 2001. The mass-loss rate, however, was
lower from 1985-1990 (1.5 x 10^(-5) Msun/yr) than from 2000-2001 (3.7 x 10^(-5)
Msun/yr). We found that the wind of AG Car is significantly clumped (f=0.10 -
0.25) and that clumps must be formed deep in the wind. We derived a bolometric
luminosity of 1.5 x 10^6 Lsun during both minimum phases which, contrary to the
common assumption, decreases to 1.0 x 10^6 Lsun as the star moves towards
maximum flux in the V band. Assuming that the decrease in the bolometric
luminosity of AG Car is due to the energy used to expand the outer layers of
the star (Lamers 1995), we found that the expanding layers contain roughly 0.6
- 2 Msun. Such an amount of mass is an order of magnitude lower than the
nebular mass around AG Car, but is comparable to the nebular mass found around
lower-luminosity LBVs and to that of the Little Homunculus of Eta Car. If such
a large amount of mass is indeed involved in the S Dor-type variability, we
speculate that such instability could be a failed Giant Eruption, with several
solar masses never becoming unbound from the star.(abridged)Comment: 22 pages, 13 figures, ApJ in press. A high-resolution PDF version is
also available at http://www.mpifr-bonn.mpg.de/staff/jgroh/agcar.htm
Instability of LBV-stars against radial oscillations
In this study we consider the nonlinear radial oscillations exciting in
LBV--stars with effective temperatures 1.5e4 K <= Teff <= 3e4 K, bolometric
luminosities 1.2e6 L_odot <= L <= 1.9e6 L_odot and masses 35.7 M_odot <= M <=
49.1 M_odot. Hydrodynamic computations were carried out with initial conditions
obtained from evolutionary sequences of population I stars (X=0.7, Z=0.02) with
initial masses from 70M_odot to 90 M_odot. All hydrodynamical models show
instability against radial oscillations with amplitude growth time comparable
with dynamical time scale of the star. Radial oscillations exist in the form of
nonlinear running waves propagating from the boundary of the compact core to
the upper boundary of the hydrodynamical model. The velocity amplitude of outer
layers is of several hundreds of km/s while the bolometric light amplitude does
not exceed 0.2 mag. Stellar oscillations are not driven by the kappa-mechanism
and are due to the instability of the gas with adiabatic exponent close to the
critical value Gamma_1 = 4/3 due to the large contribution of radiation in the
total pressure. The range of the light variation periods (6 day <= P <= 31 day)
of hydrodynamical models agrees with periods of microvariability observed in
LBV--stars.Comment: 14 pages, 5 figures, submitted to Astronomy Letter
The highly polarized open cluster Trumpler 27
We have carried out multicolor linear polarimetry (UBVRI) of the brightest
stars in the area of the open cluster Trumpler 27. Our data show a high level
of polarization in the stellar light with a considerable dispersion, from to . The polarization vectors of the cluster members appear to be
aligned. Foreground polarization was estimated from the data of some non-member
objects, for which two different components were resolved: the first one
associated with a dust cloud close to the Sun producing
and degrees, and a second component, the main source of
polarization for the cluster members, originated in another dust cloud, which
polarizes the light in the direction of degrees. From a detailed
analysis, we found that the two components have associated values for the first one, and for the other. Due the
difference in the orientation of both polarization vectors, almost 90 degrees
(180 degrees at the Stokes representation), the first cloud (
degrees) depolarize the light strongly polarized by the second one ( degrees).Comment: 12 Pages, 6 Figures, 2 tables (9 Pages), accepted for publication in
A
Identification of signaling pathways in early mammary gland development by mouse genetics
The mammary gland develops as an appendage of the ectoderm. The prenatal stage of mammary development is hormone independent and is regulated by sequential and reciprocal signaling between the epithelium and the mesenchyme. A number of recent studies using human and mouse genetics, in particular targeted gene deletion and transgenic expression, have identified some of the signals that control specific steps in development. This process involves cell specification and proliferation, reciprocal tissue interactions and cell migration. Since some of these events are recapitulated during tumorigenesis, an understanding of these signaling pathways may contribute to the development of targeted therapies and novel drugs
Excited-state OH Mainline Masers in AU Geminorum and NML Cygni
Excited-state OH maser emission has previously been reported in the
circumstellar envelopes of only two evolved stars: the Mira star AU Geminorum
and the hypergiant NML Cygni. We present Very Large Array (VLA) observations of
the 1665, 1667, and excited-state 4750 MHz mainline OH transitions in AU Gem
and Expanded Very Large Array (EVLA) observations of the excited-state 6030 and
6035 MHz OH mainline transitions in NML Cyg. We detect masers in both mainline
transitions in AU Gem but no excited-state emission in either star. We conclude
that the excited-state OH emission in AU Gem is either a transient phenomenon
(such as for NML Cyg outlined below), or possibly an artifact in the data, and
that the excited state OH emission in NML Cyg was generated by an episode of
enhanced shock between the stellar mass-loss and an outflow of the Cyg OB2
association. With these single exceptions, it therefore appears that
excited-state OH emission indeed should not be predicted nor observable in
evolved stars as part of their normal structure or evolution.Comment: ApJ Letter, accepted, 4 pages, 2 figure
The spectral variability and magnetic field characteristics of the Of?p star HD 148937
We report magnetic and spectroscopic observations and modeling of the Of?p
star HD 148937 within the context of the MiMeS LP at the CFHT. Thirty-two high
signal-to-noise ratio circularly polarised (Stokes V) spectra and 13
unpolarised (Stokes I) spectra of HD 148937 were acquired in 2009 and 2010. A
definite detection of a Stokes V Zeeman signature is obtained in the grand mean
of all observations (in both LSD mean profiles and individual spectral lines).
The longitudinal magnetic field inferred from the Stokes V LSD profiles is
consistently negative, in contrast to the essentially zero field strength
measured from the diagnostic null profiles. A period search of equivalent width
measurements confirms the previously-reported 7.03 d variability period. The
variation of equivalent widths is not strictly periodic: we present evidence
for evolution of the amount or distribution of circumstellar plasma.
Interpreting the 7.03 d period as the stellar rotational period within the
context of the ORM, we have phased the equivalent widths and longitudinal field
measurements. The longitudinal field measurements show a weak sinusoidal
variation of constant sign, with extrema out of phase with the H{\alpha}
variation by about 0.25 cycles. The inferred magnetic configuration confirms
the suggestion of Naz\'e et al (2010), who proposed that the weaker variability
of HD 148937 as compared to other members of this class is a consequence of the
stellar geometry. Based on the derived magnetic properties and published wind
characteristics, we find a wind magnetic confinement parameter \eta\ast \simeq
20 and rotation parameter W = 0.12, supporting a picture in which the Halpha
emission and other line variability have their origin in an oblique, rigidly
rotating magnetospheric structure resulting from a magnetically channeled wind.
(Abridged.)Comment: 13 pages, MNRAS. Version 2, small change to Fig. 1
Patients suffering from psychological impairments following critical illness are in need of information
Background: Because critical illness survivors frequently experience several long-term psychological impairments altering quality of life after ICU, there is a trend towards increasing follow-up care, mainly via ICU follow-up clinics. Despite these and other initiatives, understanding of patient's post-ICU needs to help them cope with their problems and subsequently improve quality of life is largely lacking. Our aim was therefore to assess the needs, expectations and wishes in ICU survivors to receive information with the purpose to help them better grasp ICU treatment. In addition, we assessed the perceived burden of psychological trauma after ICU treatment and the health-related quality of life (HRQoL) up to 2.5 years after ICU discharge. Methods: In a multicentre, retrospective cross-sectional cohort study, the needs and preferred intervention methods were assessed using a self-composed inventory in adult mechanically ventilated ICU survivors (n = 43). Additionally, the Impact of Event Scale Revised, the Beck Depression Inventory, the EuroQol-5D-5L, and the Short-Form 12 were used to assess psychological burden and HRQoL. Results: A substantial proportion of all ICU survivors (59%, 95% CI 44% to 74%) suffered from psychological impairments after ICU treatment. Seventy-five percent of these patients expressed a wish to receive information, but only 36% desired to receive this information using a commonly used information brochure. In contrast, 71% of these patients had a wish to receive information using a video film/VR. Furthermore, only 33% of these patients was satisfied with the information provided by their treating hospital. Patients with psychological PICS reported a worse HRQoL as compared to a normative Dutch sample (P < 0.001) and as compared to patients without psychological PICS (P < 0.01). Conclusions: In a Dutch cohort of critical illness survivors, a substantial part of ICU survivors suffer from psychological impairments, such as PTSD and depression, which was associated with a worse HRQoL. These patients are in need of information, have no desire using an information brochure, but are willing to receive information using a video film/virtual reality module. These results support the exploration of such an intervention
- …