5,096 research outputs found
A Multiscale Investigation of Habitat Use and Within-river Distribution of Sympatric Sand Darter Species
The western sand darter Ammocrypta clara, and eastern sand darter Ammocrypta pellucida are sand-dwelling fishes of conservation concern. Past research has emphasized the importance of studying individual populations of conservation concern, while recent research has revealed the importance of incorporating landscape scale processes that structure habitat mosaics and local populations. We examined habitat use and distributions of western and eastern sand darters in the lower Elk River of West Virginia. At the sandbar habitat use scale, western sand darters were detected in sandbars with greater area, higher proportions of coarse grain sand and faster bottom current velocity, while the eastern sand darter used a wider range of sandbar habitats. The landscape scale analysis revealed that contributing drainage area was an important predictor for both species, while sinuosity, which presumably represents valley type also contributed to the western sand darter’s habitat suitability. Sandbar quality (area, grain size, and velocity) and fluvial geomorphic variables (drainage area and valley type) are likely key driving factors structuring sand darter distributions in the Elk River. This multiscale study of within-river species distribution and habitat use is unique, given that only a few sympatric populations are known of western and eastern sand darters
Supporting 64-bit global indices in Epetra and other Trilinos packages -- Techniques used and lessons learned
The Trilinos Project is an effort to facilitate the design, development,
integration and ongoing support of mathematical software libraries within an
object-oriented framework. It is intended for large-scale, complex multiphysics
engineering and scientific applications. Epetra is one of its basic packages.
It provides serial and parallel linear algebra capabilities. Before Trilinos
version 11.0, released in 2012, Epetra used the C++ int data-type for storing
global and local indices for degrees of freedom (DOFs). Since int is typically
32-bit, this limited the largest problem size to be smaller than approximately
two billion DOFs. This was true even if a distributed memory machine could
handle larger problems. We have added optional support for C++ long long
data-type, which is at least 64-bit wide, for global indices. To save memory,
maintain the speed of memory-bound operations, and reduce further changes to
the code, the local indices are still 32-bit. We document the changes required
to achieve this feature and how the new functionality can be used. We also
report on the lessons learned in modifying a mature and popular package from
various perspectives -- design goals, backward compatibility, engineering
decisions, C++ language features, effects on existing users and other packages,
and build integration
Risk and safety assessment in child welfare: Instrument comparisons
The assessment of risk is a critical part of child welfare agency practice. This review of the research literature on different instruments for assessing risk and safety in child welfare focuses on instrument reliability, validity, outcomes, and use with children and families of color. The findings suggest that the current actuarial instruments have stronger predictive validity than consensus-based instruments. This review was limited by the variability in definitions and measures across studies, the relatively small number of studies examining risk assessment instruments, and the lack of studies on case decision points other than the initial investigation
Scientific Computing Meets Big Data Technology: An Astronomy Use Case
Scientific analyses commonly compose multiple single-process programs into a
dataflow. An end-to-end dataflow of single-process programs is known as a
many-task application. Typically, tools from the HPC software stack are used to
parallelize these analyses. In this work, we investigate an alternate approach
that uses Apache Spark -- a modern big data platform -- to parallelize
many-task applications. We present Kira, a flexible and distributed astronomy
image processing toolkit using Apache Spark. We then use the Kira toolkit to
implement a Source Extractor application for astronomy images, called Kira SE.
With Kira SE as the use case, we study the programming flexibility, dataflow
richness, scheduling capacity and performance of Apache Spark running on the
EC2 cloud. By exploiting data locality, Kira SE achieves a 2.5x speedup over an
equivalent C program when analyzing a 1TB dataset using 512 cores on the Amazon
EC2 cloud. Furthermore, we show that by leveraging software originally designed
for big data infrastructure, Kira SE achieves competitive performance to the C
implementation running on the NERSC Edison supercomputer. Our experience with
Kira indicates that emerging Big Data platforms such as Apache Spark are a
performant alternative for many-task scientific applications
Homophilic Protocadherin Cell-Cell Interactions Promote Dendrite Complexity
SummaryGrowth of a properly complex dendrite arbor is a key step in neuronal differentiation and a prerequisite for neural circuit formation. Diverse cell surface molecules, such as the clustered protocadherins (Pcdhs), have long been proposed to regulate circuit formation through specific cell-cell interactions. Here, using transgenic and conditional knockout mice to manipulate γ-Pcdh repertoire in the cerebral cortex, we show that the complexity of a neuron’s dendritic arbor is determined by homophilic interactions with other cells. Neurons expressing only one of the 22 γ-Pcdhs can exhibit either exuberant or minimal dendrite complexity, depending only on whether surrounding cells express the same isoform. Furthermore, loss of astrocytic γ-Pcdhs, or disruption of astrocyte-neuron homophilic matching, reduces dendrite complexity cell non-autonomously. Our data indicate that γ-Pcdhs act locally to promote dendrite arborization via homophilic matching, and they confirm that connectivity in vivo depends on molecular interactions between neurons and between neurons and astrocytes
Absorption of Energy at a Metallic Surface due to a Normal Electric Field
The effect of an oscillating electric field normal to a metallic surface may
be described by an effective potential. This induced potential is calculated
using semiclassical variants of the random phase approximation (RPA). Results
are obtained for both ballistic and diffusive electron motion, and for two and
three dimensional systems. The potential induced within the surface causes
absorption of energy. The results are applied to the absorption of radiation by
small metal spheres and discs. They improve upon an earlier treatment which
used the Thomas-Fermi approximation for the effective potential.Comment: 19 pages (Plain TeX), 2 figures, 1 table (Postscript
Nova Sagittarii 1994 #1 (V4332 Sagittarii): The Discovery and Evolution of an Unusual Luminous Red Variable Star
We report photometry and spectroscopy of the evolution of Nova Sagittarii
1994 #1 (V4332 Sagittarii) during outburst. We compare the photometric and
spectral evolution of this outburst to known classes of outbursts -- including
classical novae and outbursts occurring on symbiotic stars -- and find this
object does NOT conform to any known class of outburst. The closest match to
the behavior of this unusual object is M31 RV, an extremely luminous and red
variable object discovered in the bulge of M31 in 1988. However, the temporal
behavior and maximum luminosity of the two events differ by several orders of
magnitude, requiring substantial intrinsic variation if these two events are
members the same type of outburst.
Our model of the spectroscopic evolution of this outburst shows that the
effective temperature cooled from 4400 K to 2300 K over the three month span of
our observations. In combination with line diagnostics in our later spectra,
including [OI] lambda 5577 and the dramatic increase in the Halpha to Hbeta
ratio, we infer the existence of a cool, dense (N_e ~ 10^{8-9} cm^{-3})
envelope that is optically thick in the Hydrogen Balmer recombination lines
(case C). We suggest that a nuclear event in a single star, in which a slow
shock drove the photosphere outwards, can power the observed luminosity
evolution and the emission spectrum.Comment: Accepted for publication in AJ. 24 pages including 8 embedded
postscript figures. Also available at
http://www.astronomy.ohio-state.edu/~martini/pub
Crossover from self-defocusing to discrete trapping in nonlinear waveguide arrays
We predict a sharp crossover from nonlinear self-defocusing to discrete
self-trapping of a narrow Gaussian beam with the increase of the refractive
index contrast in a periodic photonic lattice. We demonstrate experimentally
nonlinear discrete localization of light with defocusing nonlinearity by single
site excitation in LiNbO waveguide arrays.Comment: 6 pages, 4 figure
Implementing Welfare-to-Work Services: A Study of Staff Decision-Making
Copyright 2006 Alliance for Children and FamiliesIn the post-welfare reform era, increased discretion has been given to frontline staff for day-today
welfare policy implementation. To determine how frontline staff address the complex needs
of welfare program participants in this new policy environment, the decision-making processes
of welfare staff (N = 52) in 11 San Francisco Bay Area county social service agencies were assessed
through a case vignette using a Web-based survey design. We examined staff decision making in
four areas: problem recognition, goal formulation, information search processes, and evaluation.
The results suggest that the high level o f staff discretion apparent in the day-to-day implementation
of welfare policy may have important implications for participants. Several recommendations
for policy, practice, and future research are presented
The Challenges of Multimorbidity from the Patient Perspective
BACKGROUND
Although multiple co-occurring chronic illnesses within the same individual are increasingly common, few studies have examined the challenges of multimorbidity from the patient perspective.
OBJECTIVE
The aim of this study is to examine the self-management learning needs and willingness to see non-physician providers of patients with multimorbidity compared to patients with single chronic illnesses. DESIGN. This research is designed as a cross-sectional survey.
PARTICIPANTS
Based upon ICD-9 codes, patients from a single VHA healthcare system were stratified into multimorbidity clusters or groups with a single chronic illness from the corresponding cluster. Nonproportional sampling was used to randomly select 720 patients.
MEASUREMENTS
Demographic characteristics, functional status, number of contacts with healthcare providers, components of primary care, self-management learning needs, and willingness to see nonphysician providers.
RESULTS
Four hundred twenty-two patients returned surveys. A higher percentage of multimorbidity patients compared to single morbidity patients were "definitely" willing to learn all 22 self-management skills, of these only 2 were not significant. Compared to patients with single morbidity, a significantly higher percentage of patients with multimorbidity also reported that they were "definitely" willing to see 6 of 11 non-physician healthcare providers.
CONCLUSIONS
Self-management learning needs of multimorbidity patients are extensive, and their preferences are consistent with team-based primary care. Alternative methods of providing support and chronic illness care may be needed to meet the needs of these complex patients.US Department of Veterans Affairs (01-110, 02-197); Agency for Healthcare Research and Quality (K08 HS013008-02
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