2,732 research outputs found
Narrative language competence in children and adolescents with Down syndrome
This study was designed to examine the narrative language abilities of children and adolescents with Down syndrome in comparison to same-age peers with fragile X syndrome and younger typically developing children matched by nonverbal cognitive ability levels. Participants produced narrative retells from a wordless picture book. Narratives were analyzed at the macrostructural (i.e., their internal episodic structure) and the microstructural (i.e., rate of use of specific word categories) levels. Mean length of utterance, a microstructural metric of syntactic complexity, was used as a control variable. Participants with Down syndrome produced fewer episodic elements in their narratives (i.e., their narratives were less fully realized) than the typically developing participants, although mean length of utterance differences accounted for the macrostructural differences between participant groups. At the microstructural level, participants with Down syndrome displayed a lower rate of verb use than the groups with fragile X syndrome and typical development, even after accounting for mean length of utterance. These findings reflect both similarities and differences between individuals with Down syndrome or fragile X syndrome and contribute to our understanding of the language phenotype of Down syndrome. Implications for interventions to promote language development and academic achievement are discussed
Peroxisome Proliferator-Activated Receptor (PPAR): Balance for Survival in Parasitic Infections
Parasitic infections induce a magnitude of host responses. At the opposite ends of the spectrum are those that ensure the host's needs to eliminate the invaders and to minimize damage to its own tissues. This review analyzes how parasites would manipulate immunity by activating the immunosuppressive nuclear factor, peroxisome proliferator-activated receptors (PPARs) with type 2 cytokines and free fatty acids from arachidonic acid metabolism. PPARs limit the action of type 1 immunity, in which classically activated macrophages act through the production of proinflammatory signals, to spare the parasites. They also favor the development of alternately activated macrophages which control inflammation so the host would not be destroyed. Possibly, the nuclear factors hold a pivotal role in the establishment of chronic infection by delicately balancing the pro- and anti-inflammatory signaling mechanisms and their ligands may be used as combination therapeutics to limit host pathology
Modeling the Daily Activities of Breeding Colonial Seabirds: Dynamic Occupancy Patterns in Multiple Habitat Patches
We constructed differential equation models for the diurnal abundance and distribution of breeding glaucous-winged gulls (Larus glaucescens) as they moved among nesting and non-nesting habitat patches. We used time scale techniques to reduce the differential equations to algebraic equations and connected the models to field data. The models explained the data as a function of abiotic environmental variables with R2=0.57. A primary goal of this study is to demonstrate the utility of a methodology that can be used by ecologists and wildlife managers to understand and predict daily activity patterns in breeding seabirds
Dependence of the local reionization history on halo mass and environment: did Virgo reionize the Local Group?
The reionization of the Universe has profound effects on the way galaxies form and on their observed properties at later times. Of particular importance is the relative timing of the reionization history of a region and its halo assembly history, which can affect the nature of the first stars formed in that region, the properties and radial distribution of its stellar halo, globular cluster population and its satellite galaxies. We distinguish two basic cases for the reionization of a halo - internal reionization, whereby the stars forming in situ reionize their host galaxy, and external reionization, whereby the progenitor of a galaxy is reionized by external radiation before its own stars are able to form in sufficient numbers. We use a set of large-scale radiative transfer and structure formation simulations, based on cosmologies derived from both Wilkinson Microwave Anisotropy Probe (WMAP) one-year and WMAP three-year data, to evaluate the mean reionization redshifts and the probability of internal/external reionization for Local Group-like systems, galaxies in the field and central cD galaxies in clusters. We find that these probabilities are strongly dependent on the underlying cosmology and the efficiency of photon production, but also on the halo mass. There is a rapid transition between predominantly external and predominantly internal reionization at a mass scale of ∼1012 M⊙ (corresponding roughly to L* galaxies), with haloes less massive than this being reionized preferentially from distant sources. We provide a fit for the reionization redshift as a function of halo mass, which could be helpful to parametrize reionization in semi-analytical models of galaxy formation on cosmological scales. We find no statistical correlation between the reionization history of field galaxies and their environmen
The origin of polar ring galaxies: evidence for galaxy formation by cold accretion
Polar ring galaxies are flattened stellar systems with an extended ring of
gas and stars rotating in a plane almost perpendicular to the central galaxy.
We show that their formation can occur naturally in a hierarchical universe
where most low mass galaxies are assembled through the accretion of cold gas
infalling along megaparsec scale filamentary structures. Within a large
cosmological hydrodynamical simulation we find a system that closely resembles
the classic polar ring galaxy NGC 4650A. How galaxies acquire their gas is a
major uncertainty in models of galaxy formation and recent theoretical work has
argued that cold accretion plays a major role. This idea is supported by our
numerical simulations and the fact that polar ring galaxies are typically low
mass systems.Comment: 4 pages, 5 figures, stability of the ring discussed, minor changes to
match the accepted version by ApJL. A preprint with high-resolution figures
is available at http://krone.physik.unizh.ch/~andrea/PolarRing/PolarRing.p
The formation of ultra-compact dwarf galaxies and nucleated dwarf galaxies
Ultra compact dwarf galaxies (UCDs) have similar properties as massive
globular clusters or the nuclei of nucleated galaxies. Recent observations
suggesting a high dark matter content and a steep spatial distribution within
groups and clusters provide new clues as to their origins. We perform
high-resolution N-body / smoothed particle hydrodynamics simulations designed
to elucidate two possible formation mechanisms for these systems: the merging
of globular clusters in the centre of a dark matter halo, or the massively
stripped remnant of a nucleated galaxy. Both models produce density profiles as
well as the half light radii that can fit the observational constraints.
However, we show that the first scenario results to UCDs that are underluminous
and contain no dark matter. This is because the sinking process ejects most of
the dark matter particles from the halo centre. Stripped nuclei give a more
promising explanation, especially if the nuclei form via the sinking of gas,
funneled down inner galactic bars, since this process enhances the central dark
matter content. Even when the entire disk is tidally stripped away, the nucleus
stays intact and can remain dark matter dominated even after severe stripping.
Total galaxy disruption beyond the nuclei only occurs on certain orbits and
depends on the amount of dissipation during nuclei formation. By comparing the
total disruption of CDM subhaloes in a cluster potential we demonstrate that
this model also leads to the observed spatial distribution of UCDs which can be
tested in more detail with larger data sets.Comment: 8 pages, 8 figures, final version accepted for publication in MNRA
The infrared imaging spectrograph (IRIS) for TMT: the science case
The InfraRed Imaging Spectrograph (IRIS) is a first-light instrument being
designed for the Thirty Meter Telescope (TMT). IRIS is a combination of an
imager that will cover a 16.4" field of view at the diffraction limit of TMT (4
mas sampling), and an integral field unit spectrograph that will sample objects
at 4-50 mas scales. IRIS will open up new areas of observational parameter
space, allowing major progress in diverse fields of astronomy. We present the
science case and resulting requirements for the performance of IRIS.
Ultimately, the spectrograph will enable very well-resolved and sensitive
studies of the kinematics and internal chemical abundances of high-redshift
galaxies, shedding light on many scenarios for the evolution of galaxies at
early times. With unprecedented imaging and spectroscopy of exoplanets, IRIS
will allow detailed exploration of a range of planetary systems that are
inaccessible with current technology. By revealing details about resolved
stellar populations in nearby galaxies, it will directly probe the formation of
systems like our own Milky Way. Because it will be possible to directly
characterize the stellar initial mass function in many environments and in
galaxies outside of the the Milky Way, IRIS will enable a greater understanding
of whether stars form differently in diverse conditions. IRIS will reveal
detailed kinematics in the centers of low-mass galaxies, allowing a test of
black hole formation scenarios. Finally, it will revolutionize the
characterization of reionization and the first galaxies to form in the
universe.Comment: to appear in Proc. SPIE 773
Marine mammal necropsy : an introductory guide for stranding responders and field biologists
This necropsy manual is designed to establish a base level of profiency in marine mammal necropsy techniques.
It is written for stranding network members who do not have a formal pathobiological training and have
limited knowledge of anatomy. Anatomical and pathological jargon has been kept to a minimum. This manual is
divided into six sections: preliminary data, sample management, pinniped, small ceetacean, large whale (at sea
and on the beach), and multiple appendices (A-H). A well-illustrated, carefully written gross necropsy report
is essential to an adequate diagnostic investigation. Gross reports with significant detail and description tend to
engender useful histopathological findings. A sample blank gross necropsy report and guidelines in writing a
report can be found in Appendices A & B. Overall, this guide aims to lead the enquiring mind through the
necessary steps to produce such reports. While this manual focuses on process and interpretation, it is
important to understand that the gross necropsy is primarily about making detailed, descriptive observations
without bias as to possible etiology. The necropsy should establish a list of differential diagnoses and the
sampling be directed by an attempt to discriminate between them.Funding was provided by the National Oceanic and Atmospheric Administration
under Cooperative Grant No. NA05NMF4391165
Emerging zoonoses in marine mammals and seabirds of the Northeast U.S.
Author Posting. © IEEE, 2006. Author Posting. © IEEE, 2006. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in Proceedings Oceans 2006, Boston, MA, USA, 5 pp, doi:10.1109/OCEANS.2006.306826.In the Northeast United States, marine vertebrates come into contact with each other and with humans through a variety of mechanisms which allow for the transfer of pathogens from one taxa to another. Though there are many ways in which humans come into contact with infectious agents, there is an inadequate understanding of the prevalence of clinical and sub-clinical zoonotic agents in the marine vertebrates of the Northeast United States. We are strengthening our understanding of the issue by targeting marine mammals and seabirds of New England and screening normal and diseased individuals of this ecosystem to establish a baseline prevalence of zoonotic agents in this ecosystem. Samples from stranded, bycaught and wild marine mammals and seabirds have been found to be positive for our screened pathogens. Most notable are the diseases found in bycaught marine mammals as well as wild caught individuals. Our current focus is specifically on influenza A and B, brucellosis, leptospirosis, Giardia and Cryptosporidium. Samples for virology, bacterial screening and molecular screening are being archived and analyzed as practical. Our goal is to create an optimized PCR-based molecular detection protocol for the above agents.This research is supported by NOAA Ocean and Human Health Initiative Grant Number NA05NOS4781247 and NOAA
Prescott Grant NA05NMF4391165
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