114,322 research outputs found
Comparison of mass limiting two-phase flow in a straight tube and in a nozzle
Mass-limiting and near mass-limiting two-phase flow in straight tube and nozzle of refrigerant flow loop syste
Stuffed MO layer as a diffusion barrier in metallizations for high temperature electronics
Auger electron spectroscopy was employed to characterize the diffusion barrier properties of molybdenum in the CrSi2/Mo/Au metallization system. The barrier action of Mo was demonstrated to persist even after 2000 hours annealing time at 300 C in a nitrogen ambient. At 340 C annealing temperature, however, rapid interdiffusion was observed to have occurred between the various metal layers after only 261 hours. The presence of controlled amounts of oxygen in the Mo layer is believed to be responsible for suppressing the short circuit interdiffusion between the thin film layers. Above 340 C, its is believed that the increase in the oxygen mobility led to deterioration of its stuffing action, resulting in the rapid interdiffusion of the thin film layers along grain boundaries
Fluorine in a Carbon-Enhanced Metal-Poor Star
The fluorine abundance of the Carbon-Enhanced Metal-Poor (CEMP) star HE
1305+0132 has been derived by analysis of the molecular HF (1-0) R9 line at
2.3357 microns in a high-resolution (R = 50,000) spectrum obtained with the
Phoenix spectrometer and Gemini-South telescope. Our abundance analysis makes
use of a CNO-enhanced ATLAS12 model atmosphere characterized by a metallicity
and CNO enhancements determined utilizing medium-resolution (R = 3,000) optical
and near-IR spectra. The effective iron abundance is found to be [Fe/H] = -2.5,
making HE 1305+0132 the most Fe-deficient star, by more than an order of
magnitude, for which the abundance of fluorine has been measured. Using
spectral synthesis, we derive a super-solar fluorine abundance of A(19F) = 4.96
+/- 0.21, corresponding to a relative abundance of [F/Fe] = 2.90. A single line
of the Phillips C_2 system is identified in our Phoenix spectrum, and along
with multiple lines of the first-overtone vibration-rotation CO (3-1) band
head, C and O abundances of A(12C) = 8.57 +/- 0.11 and A(16O) = 7.04 +/- 0.14
are derived. We consider the striking fluorine overabundance in the framework
of the nucleosynthetic processes thought to be responsible for the
C-enhancement of CEMP stars and conclude that the atmosphere of HE 1305+0132
was polluted via mass transfer by a primary companion during its asymptotic
giant branch phase. This is the first study of fluorine in a CEMP star, and it
demonstrates that this rare nuclide can be a key diagnostic of nucleosynthetic
processes in the early Galaxy.Comment: 13 pages, 3 figures; Accepted for publication in ApJ Letter
Abundance Patterns in Stars in the Bulge and Galactic Center
We discuss oxygen and iron abundance patterns in K and M red-giant members of
the Galactic bulge and in the young and massive M-type stars inhabiting the
very center of the Milky Way. The abundance results from the different bulge
studies in the literature, both in the optical and the infrared, indicate that
the [O/Fe]-[Fe/H] relation in the bulge does not follow the disk relation, with
[O/Fe] values falling above those of the disk. Based on these elevated values
of [O/Fe] extending to large Fe abundances, it is suggested that the bulge
underwent a rapid chemical enrichment with perhaps a top-heavy initial mass
function. The Galactic Center stars reveal a nearly uniform and slightly
elevated (relative to solar) iron abundance for a studied sample which is
composed of 10 red giants and supergiants. Perhaps of more significance is the
fact that the young Galactic Center M-type stars show abundance patterns that
are reminiscent of those observed for the bulge population and contain enhanced
abundance ratios of alpha-elements relative to either the Sun or Milky Way disk
at near-solar metallicities.Comment: requires iaus.cls; to appear in Formation and Evolution of Galaxy
Bulges, Proceedings IAU Symposium No. 245, 2007, M. Bureau et al. eds., in
pres
Feeling good about being hungry: food-related thoughts in eating disorder
Objectives: This study explores the relationships to food and hunger in women living with anorexic type eating difficulties and asks how imagery-based elaborations of food and eating thoughts are involved in their eating restraint, and recovery. Design: The qualitative idiographic approach of Interpretative Phenomenological Analysis (IPA) was used. Four in-depth semi-structured interviews were conducted with women self-selected as having experienced anorexia or anorexic like behaviour. Methods: The data was analysed using IPA and an audit of the analysis was conducted to ensure that the process followed had been systematic and rigorous and appropriately considered reflexivity. Results: Hunger was perceived positively by participants as confirmation that they were achieving their goal of losing weight, or avoiding weight gain. Hunger conferred a sense of being in control for the participants. Intrusive thoughts about food were reported as being quickly followed by elaborative mental imagery of the positive aspects of weight loss, and the negative consequences of eating. Imagery appeared to serve to maintain anorexic behaviours rather than to motivate food seeking. However, negative imagery of the consequences of anorexia were also described as supporting recovery. Conclusions: The finding that physiological sensations of hunger were experienced as positive confirmation of maintaining control has potentially important clinical and theoretical implications. It suggests further attention needs to be focused upon how changes in cognitive elaboration, involving mental imagery, are components of the psychological changes in the development of, maintenance of, and recovery from, anorexia
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