4,023 research outputs found
Assessing the Effectiveness of a Computerized Pharmacy System
Conference PaperBiomedical Informatic
Forest canopy affects stream macroinvertebrate assemblage structure but not trophic stability
Understanding the determinates of community structure and function is a central theme in community ecology. The form in which energy is supplied to foodwebs can strongly influence community structure and function. Trophic stability is also thought to be affected by the nature of food web energy pathways and whether they are external (allochthonous) or internal (autochthonous) to the ecosystem. In this study, we assessed whether stream invertebrate assemblages differ in taxonomic composition, energetic network structure, trophic network stability, and assemblage temporal variability based on whether the streams they occupy occur under forested canopies or in open grasslands. We assumed that forested sites would receive more allochthonous inputs, whereas grassland sites would rely more on autochthonous resources. We also tested whether food web stability (robustness, the conservation of energy flow) changed after simulated species extinctions. We found that the forest stream assemblages were dominated by filter feeders and shredders, whereas the grassland assemblages were dominated by grazers. In spite of these differences in assemblage composition, we found no significant differences in trophic network structure, stability, or temporal variability among different site types. Many stream systems, particularly in mountainous areas, such as New Zealand, are exposed to regular and large physical disturbance from flooding, which may result in assemblages with similarly generic diets irrespective of the energy source
UVUDF: Ultraviolet Imaging of the Hubble Ultradeep Field with Wide-field Camera 3
We present an overview of a 90-orbit Hubble Space Telescope treasury program
to obtain near ultraviolet imaging of the Hubble Ultra Deep Field using the
Wide Field Camera 3 UVIS detector with the F225W, F275W, and F336W filters.
This survey is designed to: (i) Investigate the episode of peak star formation
activity in galaxies at 1<z<2.5; (ii) Probe the evolution of massive galaxies
by resolving sub-galactic units (clumps); (iii) Examine the escape fraction of
ionizing radiation from galaxies at z~2-3; (iv) Greatly improve the reliability
of photometric redshift estimates; and (v) Measure the star formation rate
efficiency of neutral atomic-dominated hydrogen gas at z~1-3. In this overview
paper, we describe the survey details and data reduction challenges, including
both the necessity of specialized calibrations and the effects of charge
transfer inefficiency. We provide a stark demonstration of the effects of
charge transfer inefficiency on resultant data products, which when
uncorrected, result in uncertain photometry, elongation of morphology in the
readout direction, and loss of faint sources far from the readout. We agree
with the STScI recommendation that future UVIS observations that require very
sensitive measurements use the instrument's capability to add background light
through a "post-flash". Preliminary results on number counts of UV-selected
galaxies and morphology of galaxies at z~1 are presented. We find that the
number density of UV dropouts at redshifts 1.7, 2.1, and 2.7 is largely
consistent with the number predicted by published luminosity functions. We also
confirm that the image mosaics have sufficient sensitivity and resolution to
support the analysis of the evolution of star-forming clumps, reaching 28-29th
magnitude depth at 5 sigma in a 0.2 arcsecond radius aperture depending on
filter and observing epoch.Comment: Accepted A
Microscopic Theory of Heterogeneity and Non-Exponential Relaxations in Supercooled Liquids
Recent experiments and computer simulations show that supercooled liquids
around the glass transition temperature are "dynamically heterogeneous" [1].
Such heterogeneity is expected from the random first order transition theory of
the glass transition. Using a microscopic approach based on this theory, we
derive a relation between the departure from Debye relaxation as characterized
by the value of a stretched exponential response function , and the fragility of the liquid. The
value is also predicted to depend on temperature and to vanish as the ideal
glass transition is approached at the Kauzmann temperature.Comment: 4 pages including 3 eps figure
The Hubble Deep Field South Flanking Fields
As part of the Hubble Deep Field South program, a set of shorter 2-orbit
observations were obtained of the area adjacent to the deep fields. The WFPC2
flanking fields cover a contiguous solid angle of 48 square arcminutes.
Parallel observations with the STIS and NICMOS instruments produce a patchwork
of additional fields with optical and near-infrared (1.6 micron) response.
Deeper parallel exposures with WFPC2 and NICMOS were obtained when STIS
observed the NICMOS deep field. These deeper fields are offset from the rest,
and an extended low surface brightness object is visible in the deeper WFPC2
flanking field. In this data paper, which serves as an archival record of the
project, we discuss the observations and data reduction, and present SExtractor
source catalogs and number counts derived from the data. Number counts are
broadly consistent with previous surveys from both ground and space. Among
other things, these flanking field observations are useful for defining slit
masks for spectroscopic follow-up over a wider area around the deep fields, for
studying large-scale structure that extends beyond the deep fields, for future
supernova searches, and for number counts and morphological studies, but their
ultimate utility will be defined by the astronomical community.Comment: 46 pages, 15 figures. Images and full catalogs available via the
HDF-S at http://www.stsci.edu/ftp/science/hdfsouth/hdfs.html at present. The
paper is accepted for the February 2003 Astronomical Journal. Full versions
of the catalogs will also be available on-line from AJ after publicatio
Hand Preference for Coordinated Bimanual Actions in 777 Great Apes: Implications for the Evolution of Handedness in Hominins
Whether or not nonhuman primates exhibit population-level handedness remains a topic of considerable scientific debate. Here, we examined handedness for coordinated bimanual actions in a sample of 777 great apes including chimpanzees, bonobos, gorillas, and orangutans. We found population-level right-handedness in chimpanzees, bonobos and gorillas, but left-handedness in orangutans. Directional biases in handedness were consistent across independent samples of apes within each genus. We suggest that, contrary to previous claims, population-level handedness is evident in great apes but differs among species as a result of ecological adaptations associated with posture and locomotion. We further suggest that historical views of nonhuman primate handedness have been too anthropocentric, and we advocate for a larger evolutionary framework for the consideration of handedness and other aspects of hemispheric specialization among primates
Experimental analysis of gas-sensitive Braitenberg vehicles
This article addresses the problem of localizing a static gas source in an indoor environment by a mobile robot. In contrast to previous works, the environment is not artificially ventilated to produce a strong unidirectional airflow. Here, the dominant transport mechanisms of gas molecules are turbulence and convection flow rather than diffusion, which results in a patchy, chaotically fluctuating gas distribution. Two Braitenberg-type strategies (positive and negative tropotaxis) based on the instantaneously measured spatial concentration gradient were investigated. Both strategies were shown to be of potential use for gas source localization. As a possible solution to the problem of gas source declaration (the task of determining with certainty that the gas source has been found), an indirect localization strategy based on exploration and concentration peak avoidance is suggested. Here, a gas source is located by exploiting the fact that local concentration maxima occur more frequently near the gas source compared to distant regions
Are chimpanzees really so poor at understanding imperative pointing? Some new data and an alternative view of canine and ape social cognition
There is considerable interest in comparative research on different species’ abilities to respond to human communicative cues such as gaze and pointing. It has been reported that some canines perform significantly better than monkeys and apes on tasks requiring the comprehension of either declarative or imperative pointing and these differences have been attributed to domestication in dogs. Here we tested a sample of chimpanzees on a task requiring comprehension of an imperative request and show that, though there are considerable individual differences, the performance by the apes rival those reported in pet dogs. We suggest that small differences in methodology can have a pronounced influence on performance on these types of tasks. We further suggest that basic differences in subject sampling, subject recruitment and rearing experiences have resulted in a skewed representation of canine abilities compared to those of monkeys and apes
Could Public Restrooms Be an Environment for Bacterial Resistomes?
PMCID: PMC3547874This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Computerized ICU Data Management Pitfalls and Promises
journal articleBiomedical Informatic
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