10,007 research outputs found
The Perceived Advantage of Agile Development Methodologies By Software Professionals: Testing an Innovation-Theoretic Model
Proponents of agile processes claim that agile practices result in higher quality software while allowing the flexibility to respond to evolving user requirements. Yet, to the best of our knowledge, no empirical study has really confirmed that benefits accrue to those who use agile processes. Grounded in the agility and diffusion of innovations literature, this research introduces a measure of process agility within the software development domain and relates it to constructs previously employed in the innovation literature. For agile methods, our study has provided empirical support for the proposal that agile development methods lead to developers’ beliefs that they are less complex, more compatible and provide increased benefits. Since developers believe that agility leads to increased benefits, they will be more likely to accept agile methods. For practitioners, this study provides valuable insights into the underlying factors that influence a developer’s beliefs about agile methods
Exploring the Dust Content of Galactic Winds with Herschel. I. NGC 4631
We present a detailed analysis of deep far-infrared observations of the
nearby edge-on star-forming galaxy NGC 4631 obtained with the Herschel Space
Observatory. Our PACS images at 70 and 160 um show a rich complex of filaments
and chimney-like features that extends up to a projected distance of 6 kpc
above the plane of the galaxy. The PACS features often match extraplanar
Halpha, radio-continuum, and soft X-ray features observed in this galaxy,
pointing to a tight disk-halo connection regulated by star formation. On the
other hand, the morphology of the colder dust component detected on larger
scale in the SPIRE 250, 350, and 500 um data matches the extraplanar H~I
streams previously reported in NGC 4631 and suggests a tidal origin. The PACS
70/160 ratios are elevated in the central ~3.0 kpc region above the nucleus of
this galaxy (the "superbubble"). A pixel-by-pixel analysis shows that dust in
this region has a higher temperature and/or an emissivity with a steeper
spectral index (beta > 2) than the dust in the disk, possibly the result of the
harsher environment in the superbubble. Star formation in the disk seems
energetically insufficient to lift the material out of the disk, unless it was
more active in the past or the dust-to-gas ratio in the superbubble region is
higher than the Galactic value. Some of the dust in the halo may also have been
tidally stripped from nearby companions or lifted from the disk by galaxy
interactions.Comment: Accepted for publication in The Astrophysical Journa
Stock comovement and financial flexibility
We develop a dynamic model of corporate investment and financing, in which shocks to the value of collateralizable assets generate variation in firms’ debt capacity. We show that the degree of similarity among firms’ financial flexibility forecasts cross-sectional variation in return correlation. We test the implications of the model with firm-level data in two empirical analyses using i) an instrumental variable approach based on shocks to the value of collateralizable corporate assets and ii) the outbreak of the COVID-19 crisis as an event study. We find that firms in the same percentile of the cross-sectional distribution of financial flexibility have 62% higher correlation in stock-return residuals than firms 50 percentiles apart
A cohort study: temporal trends in prevalence of antecedents, comorbidities and mortality in Aboriginal and non-Aboriginal Australians with first heart failure hospitalization, 2000-2009
Abstract Background/objectives: Little is known about trends in risk factors and mortality for Aboriginal Australians with heart failure (HF). This population-based study evaluated trends in prevalence of risk factors, 30-day and 1-year all-cause mortality following first HF hospitalization among Aboriginal and non-Aboriginal Western Australians in the decade 2000-2009. Methods: Linked-health data were used to identify patients (20-84 years), with a first-ever HF hospitalization. Trends in demographics, comorbidities, interventions and risk factors were evaluated. Logistic and Cox regression models were fitted to test and compare trends over time in 30-day and 1-year mortality. Results: Of 17,379 HF patients, 1,013 (5.8 %) were Aboriginal. Compared with 2000-2002, the prevalence (as history) of myocardial infarction and hypertension increased more markedly in 2006-2009 in Aboriginal (versus non-Aboriginal) patients, while diabetes and chronic kidney disease remained disproportionately higher in Aboriginal patients. Risk factor trends, including the Charlson comorbidity index, increased over time in younger Aboriginal patients. Risk-adjusted 30-day mortality did not change over the decade in either group. Risk-adjusted 1-year mortality (in 30-day survivors) was non-significantly higher in Aboriginal patients in 2006-2008 compared with 2000-2002 (hazard ratio (HR) 1.44; 95 % CI 0.85-2.41; p-trend = 0.47) whereas it decreased in non-Aboriginal patients (HR 0.87; 95 % CI 0.78-0.97; p-trend = 0.01). Conclusions: Between 2000 and 2009, the prevalence of HF antecedents increased and remained disproportionately higher in Aboriginal (versus non-Aboriginal) HF patients. Risk-adjusted 1-year mortality did not improve in Aboriginal patients over the period in contrast with non-Aboriginal patients. These findings highlight the need for better prevention and post-HF care in Aboriginal Australians
Data production models for the CDF experiment
The data production for the CDF experiment is conducted on a large Linux PC
farm designed to meet the needs of data collection at a maximum rate of 40
MByte/sec. We present two data production models that exploits advances in
computing and communication technology. The first production farm is a
centralized system that has achieved a stable data processing rate of
approximately 2 TByte per day. The recently upgraded farm is migrated to the
SAM (Sequential Access to data via Metadata) data handling system. The software
and hardware of the CDF production farms has been successful in providing large
computing and data throughput capacity to the experiment.Comment: 8 pages, 9 figures; presented at HPC Asia2005, Beijing, China, Nov 30
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Reactivity of Gold Hydrides: O2 Insertion into the Au–H Bond
Dioxygen reacts with the gold(I) hydride (IPr)AuH under insertion to give the hydroperoxide, (IPr)AuOOH, a long-postulated reaction in gold catalysis and the first demonstration of O2 activation by Au-H in a well-defined system. Subsequent condensation gave the peroxide (IPr)Au-OO-Au(IPr) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene). The reaction kinetics are reported, as well as the reactivity of Au(I) hydrides with radical scavengers
Quasiclassical double photoionization from the 2^{1,3}S excited states of helium including shakeoff
We account for the different symmetries of the 2^{1,3}S helium excited states
in a quasiclassical description of the knockout mechanism augmented by a
quantum shakeoff contribution. We are thus able to formulate the separate
contribution of the knockout and shakeoff mechanisms for double photoionization
for any excess energy from the 2^{1,3}S states. Photoionization ratios and
singly differential cross sections calculated for the 2^{1,3}S excited states
of helium are found to be in very good agreement with recent theoretical
results.Comment: 9 pages, 5 figure
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