5,421 research outputs found
Binary Population and Spectral Synthesis Version 2.1: construction, observational verification and new results
The Binary Population and Spectral Synthesis (BPASS) suite of binary stellar
evolution models and synthetic stellar populations provides a framework for the
physically motivated analysis of both the integrated light from distant stellar
populations and the detailed properties of those nearby. We present a new
version 2.1 data release of these models, detailing the methodology by which
BPASS incorporates binary mass transfer and its effect on stellar evolution
pathways, as well as the construction of simple stellar populations. We
demonstrate key tests of the latest BPASS model suite demonstrating its ability
to reproduce the colours and derived properties of resolved stellar
populations, including well- constrained eclipsing binaries. We consider
observational constraints on the ratio of massive star types and the
distribution of stellar remnant masses. We describe the identification of
supernova progenitors in our models, and demonstrate a good agreement to the
properties of observed progenitors. We also test our models against photometric
and spectroscopic observations of unresolved stellar populations, both in the
local and distant Universe, finding that binary models provide a
self-consistent explanation for observed galaxy properties across a broad
redshift range. Finally, we carefully describe the limitations of our models,
and areas where we expect to see significant improvement in future versions.Comment: 69 pages, 45 figures. Accepted for publication in PASA. Accompanied
by a full, documented data release at http://bpass.auckland.ac.nz and
http://warwick.ac.uk/bpas
GaAs monolithic frequency doublers with series connected varactor diodes
GaAs monolithic frequency doublers using series connected varactor diodes have been fabricated for the first time. Output powers of 150 mW at 36.9 GHz with 24% efficiency and 300 mW at 24.8 GHz with 18% efficiency have been obtained. Peak efficiencies of 35% at output power levels near 100 mW have been achieved at both frequencies. Both K-band and Ka-band frequency doublers are derived from a lower power, single-diode design by series connection of two diodes and scaling to achieve different power and frequency specifications. Their fabrication was accomplished using the same process sequence
Risk Factors for Long-Term Coronary Artery Calcium Progression in the Multi-Ethnic Study of Atherosclerosis.
BackgroundCoronary artery calcium (CAC) detected by noncontrast cardiac computed tomography scanning is a measure of coronary atherosclerosis burden. Increasing CAC levels have been strongly associated with increased coronary events. Prior studies of cardiovascular disease risk factors and CAC progression have been limited by short follow-up or restricted to patients with advanced disease.Methods and resultsWe examined cardiovascular disease risk factors and CAC progression in a prospective multiethnic cohort study. CAC was measured 1 to 4 times (mean 2.5 scans) over 10 years in 6810 adults without preexisting cardiovascular disease. Mean CAC progression was 23.9 Agatston units/year. An innovative application of mixed-effects models investigated associations between cardiovascular disease risk factors and CAC progression. This approach adjusted for time-varying factors, was flexible with respect to follow-up time and number of observations per participant, and allowed simultaneous control of factors associated with both baseline CAC and CAC progression. Models included age, sex, study site, scanner type, and race/ethnicity. Associations were observed between CAC progression and age (14.2 Agatston units/year per 10 years [95% CI 13.0 to 15.5]), male sex (17.8 Agatston units/year [95% CI 15.3 to 20.3]), hypertension (13.8 Agatston units/year [95% CI 11.2 to 16.5]), diabetes (31.3 Agatston units/year [95% CI 27.4 to 35.3]), and other factors.ConclusionsCAC progression analyzed over 10 years of follow-up, with a novel analytical approach, demonstrated strong relationships with risk factors for incident cardiovascular events. Longitudinal CAC progression analyzed in this framework can be used to evaluate novel cardiovascular risk factors
Narrow-line magneto-optical cooling and trapping of strongly magnetic atoms
Laser cooling on weak transitions is a useful technique for reaching
ultracold temperatures in atoms with multiple valence electrons. However, for
strongly magnetic atoms a conventional narrow-line magneto-optical trap (MOT)
is destabilized by competition between optical and magnetic forces. We overcome
this difficulty in Er by developing an unusual narrow-line MOT that balances
optical and magnetic forces using laser light tuned to the blue side of a
narrow (8 kHz) transition. The trap population is spin-polarized with
temperatures reaching below 2 microkelvin. Our results constitute an
alternative method for laser cooling on weak transitions, applicable to
rare-earth-metal and metastable alkaline earth elements.Comment: To appear in Phys. Rev. Lett. 4 pages, 5 figure
The ACIGA Data Analysis programme
The Data Analysis programme of the Australian Consortium for Interferometric
Gravitational Astronomy (ACIGA) was set up in 1998 by the first author to
complement the then existing ACIGA programmes working on suspension systems,
lasers and optics, and detector configurations. The ACIGA Data Analysis
programme continues to contribute significantly in the field; we present an
overview of our activities.Comment: 10 pages, 0 figures, accepted, Classical and Quantum Gravity,
(Proceedings of the 5th Edoardo Amaldi Conference on Gravitational Waves,
Tirrenia, Pisa, Italy, 6-11 July 2003
Recommended from our members
The relationship of circulating fibroblast growth factor 21 levels with pericardial fat: The Multi-Ethnic Study of Atherosclerosis.
Previous small studies have reported an association between circulating fibroblast growth factor 21 (FGF21) levels and pericardial fat volume in post-menopausal women and high cardiovascular disease (CVD) risk patients. In this study, we investigated the relationship of FGF21 levels with pericardial fat volume in participants free of clinical CVD at baseline. We analysed data from 5765 men and women from the Multi-Ethnic Study of Atherosclerosis (MESA) with both pericardial fat volume and plasma FGF21 levels measured at baseline. 4746 participants had pericardial fat volume measured in at least one follow-up exam. After adjusting for confounding factors, ln-transformed FGF21 levels were positively associated with pericardial fat volume at baseline (β = 0.055, p < 0.001). When assessing change in pericardial fat volume over a mean duration of 3.0 years using a linear mixed-effects model, higher baseline FGF21 levels were associated with higher pericardial fat volume at baseline (2.381 cm3 larger in pericardial fat volume per one SD increase in ln-transformed FGF21 levels), but less pericardial fat accumulation over time (0.191 cm3/year lower per one SD increase in ln-transformed FGF21 levels). Cross-sectionally, higher plasma FGF21 levels were significantly associated with higher pericardial fat volume, independent of traditional CVD risk factors and inflammatory markers. However, higher FGF21 levels tended to be associated with less pericardial fat accumulation over time. Nevertheless, such change in pericardial fat volume is very modest and could be due to measurement error. Further studies are needed to elucidate the longitudinal relationship of baseline FGF21 levels with pericardial fat accumulation
Periorbital edema secondary to imatinib mesylate
Collin M McClelland, George J Harocopos, Philip L CusterSchool of Medicine, Washington University, St. Louis, MO, USAAbstract: Imatinib mesylate (Gleevec&reg;) is a well-established pharmacologic treatment for all phases of chronic myeloid leukemia and for advanced gastrointestinal stromal tumors (GISTs). Edema-related side effects are relatively common in imatinib therapy with the periocular skin representing one of the most common sites for localized edema. While the adverse effect of periorbital edema with imatinib is well documented in the oncology literature, there is limited reference to this common reaction in the ophthalmology literature. We report two patients with upper eyelid edema associated with imatinib therapy who required surgical intervention to ameliorate significant visual field obstruction. We highlight the details of each case including the histopathologic findings of excised redundant skin followed by a thorough review of the literature on imatinib related periorbital edema.Keywords: imatinib mesylate, gleevec, edema, periorbital edema, tyrosine kinase inhibito
Out-of-Distribution Generalization in Algorithmic Reasoning Through Curriculum Learning
Out-of-distribution generalization (OODG) is a longstanding challenge for
neural networks, and is quite apparent in tasks with well-defined variables and
rules, where explicit use of the rules can solve problems independently of the
particular values of the variables. Large transformer-based language models
have pushed the boundaries on how well neural networks can generalize to novel
inputs, but their complexity obfuscates they achieve such robustness. As a step
toward understanding how transformer-based systems generalize, we explore the
question of OODG in smaller scale transformers. Using a reasoning task based on
the puzzle Sudoku, we show that OODG can occur on complex problems if the
training set includes examples sampled from the whole distribution of simpler
component tasks
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