2,415 research outputs found
Near-Infrared Spectroscopy of Low Mass X-ray Binaries : Accretion Disk Contamination and Compact Object Mass Determination in V404 Cyg and Cen X-4
We present near-infrared (NIR) broadband (0.80--2.42 m) spectroscopy of
two low mass X-ray binaries: V404 Cyg and Cen X-4. One important parameter
required in the determination of the mass of the compact objects in these
systems is the binary inclination. We can determine the inclination by modeling
the ellipsoidal modulations of the Roche-lobe filling donor star, but the
contamination of the donor star light from other components of the binary,
particularly the accretion disk, must be taken into account. To this end, we
determined the donor star contribution to the infrared flux by comparing the
spectra of V404 Cyg and Cen X-4 to those of various field K-stars of known
spectral type. For V404 Cyg, we determined that the donor star has a spectral
type of K3 III. We determined the fractional donor contribution to the NIR flux
in the H- and K-bands as and , respectively. We
remodeled the H-band light curve from \citet{sanwal1996} after correcting for
the donor star contribution to obtain a new value for the binary inclination.
From this, we determined the mass of the black hole in V404 Cyg to be . We performed the same spectral analysis for Cen X-4
and found the spectral type of the donor star to be in the range K5 -- M1V. The
donor star contribution in Cen X-4 is in the H-band while in the
K-band, the accretion disk can contribute up to 10% of the infrared flux. We
remodeled the H-band light curve from \citet{shahbaz1993}, again correcting for
the fractional contribution of the donor star to obtain the inclination. From
this, we determined the mass of the neutron star as . However, the masses obtained for both systems should
be viewed with some caution since contemporaneous light curve and spectral data
are required to obtain definitive masses
Toxicity of unsaturated fatty acids to the biohydrogenating ruminal bacterium, Butyrivibrio fibrisolvens
Peer reviewedPublisher PD
California Extremely Large Telescope: Conceptual Design for a Thirty-Meter Telescope
Following great success in the creation of the Keck Observatory, scientists at the California Institute of
Technology and the University of California have begun to explore the scientific and technical prospects
for a much larger telescope. The Keck telescopes will remain the largest telescopes in the world for a
number of years, with many decades of forefront research ahead after that. Though these telescopes
have produced dramatic discoveries, it is already clear that even larger telescopes must be built if we
are to address some of the most profound questions about our universe. The time required to build a
larger telescope is approximately ten years, and the California community is presently well-positioned
to begin its design and construction. The same scientists who conceived, led the design, and guided
the construction of the Keck Observatory have been intensely engaged in a study of the prospects for
an extremely large telescope. Building on our experience with the Keck Observatory, we have concluded
that the large telescope is feasible and is within the bounds set by present-day technology. Our reference
telescope has a diameter of 30 meters, the largest size we believe can be built with acceptable risk. The
project is currently designated the California Extremely Large Telescope (CELT)
1951: Abilene Christian College Bible Lectures - Full Text
Delivered in the Auditorium of Abilene Christian College
Abilene, Texas
February 18-22, 1951
Price, $3.00
FIRM FOUNDATION PUBLISHING HOUSE
Austin, Texa
A comparative evaluation of PDQ-Evidence
BACKGROUND: A strategy for minimising the time and obstacles to accessing systematic reviews of health system
evidence is to collect them in a freely available database and make them easy to find through a simple ‘Google-style’
search interface. PDQ-Evidence was developed in this way. The objective of this study was to compare PDQ-Evidence
to six other databases, namely Cochrane Library, EVIPNet VHL, Google Scholar, Health Systems Evidence, PubMed
and Trip.
METHODS: We recruited healthcare policy-makers, managers and health researchers in low-, middle- and highincome
countries. Participants selected one of six pre-determined questions. They searched for a systematic
review that addressed the chosen question and one question of their own in PDQ-Evidence and in two of the
other six databases which they would normally have searched. We randomly allocated participants to search
PDQ-Evidence first or to search the two other databases first. The primary outcomes were whether a systematic
review was found and the time taken to find it. Secondary outcomes were perceived ease of use and perceived
time spent searching. We asked open-ended questions about PDQ-Evidence, including likes, dislikes, challenges
and suggestions for improvements.
RESULTS: A total of 89 people from 21 countries completed the study; 83 were included in the primary analyses
and 6 were excluded because of data errors that could not be corrected. Most participants chose PubMed and
Cochrane Library as the other two databases. Participants were more likely to find a systematic review using
PDQ-Evidence than using Cochrane Library or PubMed for the pre-defined questions. For their own questions, this
difference was not found. Overall, it took slightly less time to find a systematic review using PDQ-Evidence. Participants
perceived that it took less time, and most participants perceived PDQ-Evidence to be slightly easier to use than the
two other databases. However, there were conflicting views about the design of PDQ-Evidence.
CONCLUSIONS: PDQ-Evidence is at least as efficient as other databases for finding health system evidence. However,
using PDQ-Evidence is not intuitive for some people
Recent Studies in Andean Prehistory and Protohistory: Papers from the Second Annual Northeast Conference on Andean Archaeology and Ethnohistory
The contributions in this volume represent nine of the twenty-three papers presented at the Second Annual Northeast Conference on Andean Archaeology and Ethnohistory (NCAAE) held at the American Museum of Natural History on November 19-20, 1983. Papers include The Preceramic and Formative Period Occupations in the Cordillera Negra: Preliminary Report by Michael A. Malpass, The Early Horizon--Early Intermediate Period Transition: A View from the Nepena and Viru Valleys by Richard E. Daggett, Paracas in Chincha and Pisco: A Reappraisal of the Ocucaje Sequence by Dwight T. Wallace, Impressions in Metal: Reconstructing Burial Context at Loma Negra, Peru by Anne-Louise Schaeffer, The Moche Moon by Elizabeth P. Benson, Archaeological Investigation in the Andean Piedmont and High Llanos of Western Venezuela: A Preliminary Report by Charles S. Spencer and Elsa M. Redmond, Pachacamac--An Andean Oracle Under Inca Rule by Thomas C. Patterson, The Spanish League and Inca Sites: A Reassessment of the Itinerary of Juan de Matienzo through N.W. Argentina by Gordon C. Pollard, and Written Sources on Andean Cosmogony by George Kubler.https://digitalcommons.library.umaine.edu/andean_past_special/1001/thumbnail.jp
Interleukin-1 polymorphisms associated with increased risk of gastric cancer
Helicobacter pylori infection is associated with a variety of clinical outcomes including gastric cancer and duodenal ulcer disease. The reasons for this variation are not clear, but the gastric physiological response is influenced by the severity and anatomical distribution of gastritis induced by H. pylori. Thus, individuals with gastritis predominantly localized to the antrum retain normal (or even high) acid secretion, whereas individuals with extensive corpus gastritis develop hypochlorhydria and gastric atrophy, which are presumptive precursors of gastric cancer. Here we report that interleukin-1 gene cluster polymorphisms suspected of enhancing production of interleukin-1-beta are associated with an increased risk of both hypochlorhydria induced by H. pylori and gastric cancer. Two of these polymorphism are in near-complete linkage disequilibrium and one is a TATA-box polymorphism that markedly affects DNA-protein interactions in vitro. The association with disease may be explained by the biological properties of interleukin-1-beta, which is an important pro-inflammatory cytokine and a powerful inhibitor of gastric acid secretion. Host genetic factors that affect interleukin-1-beta may determine why some individuals infected with H. pylori develop gastric cancer while others do no
High-field side scrape-off layer investigation: Plasma profiles and impurity screening behavior in near-double-null configurations
New experiments on Alcator C-Mod reveal that the favorable impurity screening characteristics of the high-field side (HFS) scrape-off layer (SOL), previously reported for single null geometries, is retained in double null configurations, despite the formation of an extremely thin SOL. In balanced double-null, nitrogen injected locally into the HFS SOL is better screened by a factor of 2.5 compared to the same injection into the low field side (LFS) SOL. This result is insensitive to plasma current and Greenwald fraction. Nitrogen injected into the HFS SOL is not as well screened (only a factor of 1.5 improvement over LFS) in unbalanced double-null discharges, when the primary divertor is in the direction of B×∇B. In this configuration, impurity ‘plume’ emission patterns indicate that an opposing E × B drift competes with the parallel impurity flow to the divertor. In balanced double-null plasmas, the dispersal pattern exhibits a dominant E × B motion. Unbalanced discharges with the primary divertor opposite the direction of B×∇B exhibit excellent HFS screening characteristics – a factor of 5 enhancement compared to LFS. These data support the idea that future tokamaks should locate all RF actuators and close-fitting wall structures on the HFS and employ near-double-null magnetic topologies, both to precisely control plasma conditions at the antenna/plasma interface and to maximally mitigate the impact of local impurity sources arising from plasma-material interactions. Keywords:
Alcator C-Mod; Impurity screening; Double null; High field side scrape-off layerUnited States. Department of Energy (Contract DE-FC02-99ER54512
History of Periodontitis Diagnosis and Edentulism as Predictors of Cardiovascular Disease, Stroke, and Mortality in Postmenopausal Women
BACKGROUND: Few studies have reported associations between periodontitis and cardiovascular disease (CVD) risk in older women, which is the objective of the present investigation.
METHODS AND RESULTS: Participants were 57 001 postmenopausal women ages 55 to 89 years (mean 68 years; \u3e 85% 60 and older) who were enrolled (1993-1998) in the Women\u27s Health Initiative Observational Study, and were without known CVD when history of periodontitis and edentulism was assessed by questionnaire at study Year-5 (1998-2003). There were 3589 incident CVD events and 3816 total deaths during a mean follow-up of 6.7 years. In multivariable analysis, periodontitis was not associated with CVD events, but was associated with higher total mortality (hazard ratio (HR)=1.12, 95% CI: 1.05-1.21). Edentulism was associated with higher age- and smoking-adjusted risks of CVD (HR=1.42, 95% CI: 1.27-1.59) and mortality (HR=1.47, 95% CI: 1.32-1.63). Further adjustment eliminated the association with CVD, but mortality remained significantly increased (HR=1.17, 95% CI: 1.02-1.33). Stratification on age, race-ethnicity, smoking, and diabetes mellitus yielded comparable results; however, edentulism was more strongly associated with CVD in women reporting \u3e /=1 dental visit (HR=1.57) compared with (HR 1.03, interaction P=0.004) annually.
CONCLUSIONS: In community-dwelling older women, edentulism was associated with increased risks of CVD and total mortality, and presence of periodontitis, which is more prevalent than edentulism, was associated with 17% higher mortality rate. These findings suggest that improving periodontal condition of the general population could reduce overall mortality
- …