481 research outputs found
Freezing Unbound Images
This statement is concerned with examining my development as an artist in the media of drawing and printmaking while in attendance at the University of North Dakota
Double Bars, Inner Disks, and Nuclear Rings in Early-Type Disk Galaxies
We present results from an imaging survey of an unbiased sample of
thirty-eight early-type (S0--Sa), low-inclination, optically barred galaxies in
the field. Our goal was to find and characterize central stellar and gaseous
structures: secondary bars, inner disks, and nuclear rings. Bars inside bars
are surprisingly common: at least one quarter of the sample galaxies (possibly
as many as 40%) are double-barred, with no preference for Hubble type or the
strength of the primary bar. A typical secondary bar is ~12% of the size of its
primary bar and 240--750 pc in radius. We see no significant effect of
secondary bars on nuclear activity. We also find kiloparsec-scale inner disks
in at least 20% of our sample, almost exclusively in S0 galaxies. These disks
are on average 20% the size of their host bar, and show a wider range of
relative sizes than do secondary bars. Nuclear rings are present in about a
third of our sample. Most are dusty, sites of current or recent star formation,
or both; such rings are preferentially found in Sa galaxies. Three S0 galaxies
(15% of the S0's) appear to have purely stellar nuclear rings, with no evidence
for dust or recent star formation. The fact that these central stellar
structures are so common indicates that the inner regions of early-type barred
galaxies typically contain dynamically cool and disklike structures. This is
especially true for S0 galaxies, where secondary bars, inner disks, and/or
stellar nuclear rings are present at least two thirds of the time. (abridged)Comment: LaTeX, 15 pages, 7 EPS figures; to appear in The Astronomical Journal
(July 2002
Twenty-five-year outcomes after multiple internal thoracic artery bypass
ObjectiveCoronary artery bypass grafting with multiple internal thoracic artery grafts is currently controversial. This study assessed single institutional outcomes with multiple internal thoracic artery grafting for guidance with future clinical decisions.MethodsIn 19,482 patients undergoing multivessel coronary artery bypass grafting (1984-2009), baseline characteristics were recorded in a prospective databank, and follow-up was obtained by questionnaires, phone contact, or National Death Index. Outcomes examined were subsequent myocardial infarction, percutaneous coronary intervention, reoperative coronary artery bypass grafting, all-cause death, and a composite of the 4. Three groups were defined: (1) no internal thoracic artery graft (1874/19,482 or 9%); (2) single internal thoracic artery grafts and adjunctive venous conduits (single internal thoracic artery; 16,881/19,482 or 87%); and (3) multiple internal thoracic artery grafts (728/19,482 or 4%). Multivariable Cox modeling adjusted for differences in baseline characteristics, and comparisons were performed using area under the curve analysis.ResultsDifferences in baseline characteristics for the no internal thoracic artery graft, single internal thoracic artery, and multiple internal thoracic artery groups were as follows: median age 66, 64, and 59 years, respectively; congestive heart failure 22%, 18%, and 13%, respectively; ejection fraction 0.50, 0.52, and 0.51, respectively; reoperation 10%, 3%, and 7%, respectively; diabetes 27%, 30%, and 15%, respectively; and female gender 33%, 28%, and 20%, respectively. No differences existed in the median number of diseased vessels (3, 3, and 3, respectively) or number of grafts per patient (3, 3, and 3, respectively). Composite outcome improved with increasing internal thoracic artery grafts, whether assessing unadjusted or risk-adjusted data. Compared with no internal thoracic artery graft, the adjusted hazard ratio was 0.79 (confidence interval, 0.74-0.83) for single internal thoracic artery grafting and 0.70 (confidence interval, 0.62-0.80) for multiple internal thoracic artery grafting (both PÂ <Â .001), reducing risk by 21% and 30%, respectively.ConclusionsThis study confirms improved patient outcomes with multiple internal thoracic artery grafting, achieving half again as much benefit as single internal thoracic artery grafting alone. The data suggest that increasing application of multiple internal thoracic artery grafting should be encouraged to mitigate the inherent risks and costs of long-term cardiac events
Regular Orbits and Periodic Loops in Multiply-Barred Galactic Potentials
We show that non-chaotic multiply-periodic particle orbits can exist in a
galaxy-like potential where a small fast-tumbling nuclear bar is nested inside
a main bar which has a slower pattern speed. We introduce the concept of a
loop: a one-dimensional curve such that particles distributed along it at some
initial instant return to the same curve (as viewed in the rotating frame of
one of the bars) after the bars return to the same relative position. Just as
particles following regular orbits in a simply-barred potential are trapped
around closed periodic orbits, so regular orbits in a doubly-barred potential
oscillate about stable loops. We find both loops which remain aligned with the
inner bar and loops aligned with the outer bar: particles trapped around these
loops could form the building blocks for a long-lived, self-consistent,
doubly-barred galaxy. In a realistic doubly-barred galaxy potential, we
demonstrate the existence of stable loops which support the structure of the
inner bar. We use the epicyclic approximation to preview the pattern of gas
flow in a doubly-barred potential.Comment: 6 pages, 1 figure, submitted to ApJ Letter
It’s not what you do, it’s the way that you do it: An experimental task delineates among passive, reactive and interactive styles of behaviour on social networking sites
Studies have produced vastly disparate findings when exploring relationships between social networking site (SNS) usage and psychosocial well-being. These inconsistencies might reflect a lack of consideration for how people use SNS; specifically, while meaningful interactions are suggested to foster positive feelings, the passive consumption of others’ feeds is proposed to have negative effects on users’ well-being. To facilitate the empirical evaluation of these claims, the present study developed a computerised task to measure styles of usage on a mock SNS platform. Administering this Social Network Site Behaviour Task (SNSBT) online to 526 individuals, we identified three dissociable usage styles that extend the active-passive dichotomy employed frequently in the literature: passive use (consuming content posted by others), reactive use (reacting to others’ content), and interactive use (interacting with others through content sharing). Furthermore, our data reveal that these usage styles differ on several measures of psychosocial variables employed frequently in the disparate literature: more interactive users reported greater feelings of social connectedness and social capital than passive or reactive users. Importantly, however, our results also reveal the multi-dimensional nature of usage styles, with online network size and time spent on SNS platforms serving as potentially confounding influences on some psychosocial measures. These findings not only advance our understanding of SNS behaviour by providing empirical support for theoretic propositions, but also demonstrate the utility of the SNSBT for experimental investigations into the psychosocial outcomes of different SNS usage styles
Race and Sex Differences in QRS Interval and Associated Outcome Among Patients with Left Ventricular Systolic Dysfunction
BACKGROUND: Prolonged QRS duration is associated with increased mortality among heart failure patients, but race or sex differences in QRS duration and associated effect on outcomes are unknown.
METHODS AND RESULTS: We investigated QRS duration and morphology among 2463 black and white patients with heart failure and left ventricular ejection fraction ≤35% who underwent coronary angiography and 12-lead electrocardiography at Duke University Hospital from 1995 through 2011. We used multivariable Cox regression models to assess the relationship between QRS duration and all-cause mortality and investigate race-QRS and sex-QRS duration interaction. Median QRS duration was 105 ms (interquartile range [IQR], 92-132) with variation by race and sex (P<0.001). QRS duration was longest in white men (111 ms; IQR, 98-139) followed by white women (108 ms; IQR, 92-140), black men (100 ms; IQR, 91-120), and black women (94 ms; IQR, 86-118). Left bundle branch block was more common in women than men (24% vs 14%) and in white (21%) versus black individuals (12%). In black patients, there was a 16% increase in risk of mortality for every 10 ms increase in QRS duration up to 112 ms (hazard ratio, 1.16; 95% CI, 1.07, 1.25) that was not present among white patients (interaction, P=0.06).
CONCLUSIONS: Black individuals with heart failure had a shorter QRS duration and more often had non-left bundle branch block morphology than white patients. Women had left bundle branch block more commonly than men. Among black patients, modest QRS prolongation was associated with increased mortality
An Imaging Survey of Early-Type Barred Galaxies
This paper presents the results of a high-resolution imaging survey, using
both ground-based and Hubble Space Telescope images, of a complete sample of
nearby barred S0--Sa galaxies in the field, with a particular emphasis on
identifying and measuring central structures within the bars: secondary bars,
inner disks, nuclear rings and spirals, and off-plane dust. A discussion of the
frequency and statistical properties of the various types of inner structures
has already been published. Here, we present the data for the individual
galaxies and measurements of their bars and inner structures. We set out the
methods we use to find and measure these structures, and how we discriminate
between them. In particular, we discuss some of the deficiencies of ellipse
fitting of the isophotes, which by itself cannot always distinguish between
bars, rings, spirals, and dust, and which can produce erroneous measurements of
bar sizes and orientations.Comment: LaTeX, 66 pages (including 42 figures, 36 in color). To appear in The
Astrophysical Journal Supplement. Full-resolution and text-only versions
available at http://www.iac.es/galeria/erwin/research
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