113 research outputs found
Properties of the H-alpha-emitting Circumstellar Regions of Be Stars
Long-baseline interferometric observations obtained with the Navy Prototype
Optical Interferometer of the H-alpha-emitting envelopes of the Be stars eta
Tauri and beta Canis Minoris are presented. For compatibility with the
previously published interferometric results in the literature of other Be
stars, circularly symmetric and elliptical Gaussian models were fitted to the
calibrated H-alpha observations. The models are sufficient in characterizing
the angular distribution of the H-alpha-emitting circumstellar material
associated with these Be stars. To study the correlations between the various
model parameters and the stellar properties, the model parameters for eta Tau
and beta CMi were combined with data for other Be stars from the literature.
After accounting for the different distances to the sources and stellar
continuum flux levels, it was possible to study the relationship between the
net H-alpha emission and the physical extent of the H-alpha-emitting
circumstellar region. A clear dependence of the net H-alpha emission on the
linear size of the emitting region is demonstrated and these results are
consistent with an optically thick line emission that is directly proportional
to the effective area of the emitting disk. Within the small sample of stars
considered in this analysis, no clear dependence on the spectral type or
stellar rotation is found, although the results do suggest that hotter stars
might have more extended H-alpha-emitting regions.Comment: 24 pages, 16 figures, accepted for publication in Ap
Consumption patterns and living conditions inside Het Steen, the late medieval prison of Malines (Mechelen, Belgium)
Excavations at the Main Square (Grote Markt) of Malines (Mechelen, Belgium) have unearthed the building remains of a tower, arguably identifiable as the former town prison: Het Steen. When this assumption is followed, the contents of the fills of two cesspits dug out in the cellars of the building illustrate aspects of daily life within the early 14th-century prison. An integrated approach of all find categories, together with the historical context available, illuminates aspects of the material culture of the users of the cesspits, their consumption patterns and the living conditions within the building
Postcolonial manifestations of African spatiality in Europe : the invisible 'public' spaces of Ghent
The focus of this chapter is on everyday spaces of African migration in the mid-sized city of Ghent. One manifestation of African spatiality is discussed in-depth in relation to its (in)visibility and publicity: an African shop located in an ordinary terraced house. With no less than 12 activities taking place in the building, the shop is rather a “public” place than solely a space of commercial transactions, although this is not signaled in very visible ways. By analyzing the modest stylistic appropriations of the façade and the significant re-arrangements of the buildings’ interior spaces that challenge more conventional usages of spaces in Ghent’s ordinary houses, this chapter puts this African shop to the fore as emblematic of how the process of materialization of transnational lifestyles and connections is always a balancing act between the visibility necessary for functioning as a (semi-)pubic place and the invisibility required to circumvent hegemonic regulatory regimes
Ages of A-type Vega-like stars from uvby Photometry
We have estimated the ages of a sample of A-type Vega-like stars by using
Str\"{o}mgren \emph{uvby$\beta} photometric data and theoretical evolutionary
tracks. We find that 13 percent of these A stars have been reported as
Vega-like stars in the literature and that the ages of this subset run the
gamut from very young (50~Myr) to old (1~Gyr), with no obvious age difference
compared to those of field A stars. We clearly show that the fractional IR
luminosity decreases with the ages of Vega-like stars.Comment: 4pages text, 3 tables, 3 figures, Accepted in Ap
Determining the Physical Properties of the B Stars II. Calibration of Synthetic Photometry
We present a new calibration of optical (UBV, Stromgren, uvby-beta, and
Geneva) and near IR (Johnson RIJHK and 2MASS) photometry for B and early A
stars derived from Kurucz (1991) Atlas model atmospheres. Our sample of stars
consists of 45 normal, nearby B and early A stars which have high quality, low
resolution IUE spectra and accurate Hipparcos parallaxes. The calibration is
unique because it relies only on the UV spectral energy distributions, the
absolute flux calibration of the V filter and the Hipparcos distances to
determine the appropriate model atmospheres for the program stars. These models
are then used to calibrate the synthetic photometry. We compare our results
with previous, well accepted results and provide a thorough discussion of the
random errors and systematic effects affecting the calibration. In particular,
we demonstrate the influence of vsini on surface gravities derived from fitting
model atmospheres. Finally, we discuss some of our intended applications of
this new calibration.Comment: 56 pages, 11 Figures, electronic tables not included. To appear in
AJ, March 200
The effective temperature scale of FGK stars. I. Determination of temperatures and angular diameters with the infrared flux method
The infrared flux method (IRFM) has been applied to a sample of 135 dwarf and
36 giant stars covering the following regions of the atmospheric parameters
space: 1) the metal-rich ([Fe/H]>0) end (consisting mostly of planet-hosting
stars), 2) the cool (Teff<5000 K) metal-poor (-1<[Fe/H]<-3) dwarf region, and
3) the very metal-poor ([Fe/H]<-2.5) end. These stars were especially selected
to cover gaps in previous works on Teff vs. color relations, particularly the
IRFM Teff scale of A. Alonso and collaborators. Our IRFM implementation was
largely based on the Alonso et al. study (absolute infrared flux calibration,
bolometric flux calibration, etc.) with the aim of extending the ranges of
applicability of their Teff vs. color calibrations. In addition, in order to
improve the internal accuracy of the IRFM Teff scale, we recomputed the
temperatures of almost all stars from the Alonso et al. work using updated
input data. The updated temperatures do not significantly differ from the
original ones, with few exceptions, leaving the Teff scale of Alonso et al.
mostly unchanged. Including the stars with updated temperatures, a large sample
of 580 dwarf and 470 giant stars (in the field and in clusters), which cover
the ranges: 3600 K<Teff<8000 K, -4.0<[Fe/H]<+0.5, have Teff homogeneously
determined with the IRFM. (Abridged)Comment: To appear in ApJ. For online tables and figures, see
http://webspace.utexas.edu/ir68/tef
Effects of binary particle size distribution on the fluid dynamic behavior of fluidized, vibrated and vibrofluidized beds
Depth of reading vocabulary in hearing and hearing-impaired children
The main point of our study was to examine the vocabulary knowledge of pupils in grades 3–6, and in particular the relative reading vocabulary disadvantage of hearing-impaired pupils. The achievements of 394 pupils with normal hearing and 106 pupils with a hearing impairment were examined on two vocabulary assessment tasks: a lexical decision task and a use decision task. The target words in both tasks represent the vocabulary children should have at the end of primary school. The results showed that most hearing pupils reached this norm, whereas most hearing-impaired pupils did not. In addition, results showed that hearing-impaired pupils not only knew fewer words, but that they also knew them less well. This lack of deeper knowledge remained even when matching hearing and hearing-impaired children on minimal word knowledge. Additionally, comparison of the two tasks demonstrated the efficacy of the lexical decision task as a measure of lexical semantic knowledge
Global Self-Organization of the Cellular Metabolic Structure
Background: Over many years, it has been assumed that enzymes work either in an isolated way, or organized in small catalytic groups. Several studies performed using "metabolic networks models'' are helping to understand the degree of functional complexity that characterizes enzymatic dynamic systems. In a previous work, we used "dissipative metabolic networks'' (DMNs) to show that enzymes can present a self-organized global functional structure, in which several sets of enzymes are always in an active state, whereas the rest of molecular catalytic sets exhibit dynamics of on-off changing states. We suggested that this kind of global metabolic dynamics might be a genuine and universal functional configuration of the cellular metabolic structure, common to all living cells. Later, a different group has shown experimentally that this kind of functional structure does, indeed, exist in several microorganisms.
Methodology/Principal Findings: Here we have analyzed around 2.500.000 different DMNs in order to investigate the underlying mechanism of this dynamic global configuration. The numerical analyses that we have performed show that this global configuration is an emergent property inherent to the cellular metabolic dynamics. Concretely, we have found that the existence of a high number of enzymatic subsystems belonging to the DMNs is the fundamental element for the spontaneous emergence of a functional reactive structure characterized by a metabolic core formed by several sets of enzymes always in an active state.
Conclusions/Significance: This self-organized dynamic structure seems to be an intrinsic characteristic of metabolism, common to all living cellular organisms. To better understand cellular functionality, it will be crucial to structurally characterize these enzymatic self-organized global structures.Supported by the Spanish Ministry of Science and Education Grants MTM2005-01504, MTM2004-04665, partly with FEDER funds, and by the Basque Government, Grant IT252-07
Allogeneic Hematopoietic Stem Cell Transplantation After Prior Lung Transplantation for Hereditary Pulmonary Alveolar Proteinosis: A Case Report
Pulmonary alveolar proteinosis (PAP) is a rare, diffuse lung disorder characterized by surfactant accumulation in the small airways due to defective clearance by alveolar macrophages, resulting in impaired gas exchange. Whole lung lavage is the current standard of care treatment for PAP. Lung transplantation is an accepted treatment option when whole lung lavage or other experimental treatment options are ineffective, or in case of extensive pulmonary fibrosis secondary to PAP. A disadvantage of lung transplantation is recurrence of PAP in the transplanted lungs, especially in hereditary PAP. The hereditary form of PAP is an ultra-rare condition caused by genetic mutations in genes encoding for the granulocyte macrophage-colony stimulating factor (GM-CSF) receptor, and intrinsically affects bone marrow derived-monocytes, which differentiate into macrophages in the lung. Consequently, these macrophages typically display disrupted GM-CSF receptor-signaling, causing defective surfactant clearance. Bone marrow/hematopoietic stem cell transplantation may potentially reverse the lung disease in hereditary PAP. In patients with hereditary PAP undergoing lung transplantation, post-lung transplant recurrence of PAP may theoretically be averted by subsequent hematopoietic stem cell transplantation, which results in a graft-versus-disease (PAP) effect, and thus could improve long-term outcome. We describe the successful long-term post-transplant outcome of a unique case of end-stage respiratory failure due to hereditary PAP-induced pulmonary fibrosis, successfully treated by bilateral lung transplantation and subsequent allogeneic hematopoietic stem cell transplantation. Our report supports treatment with serial lung and hematopoietic stem cell transplantation to improve quality of life and prolong survival, without PAP recurrence, in selected patients with end-stage hereditary PAP
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