74,379 research outputs found
Variation in Lepidopteran Occurrence in Hemlock-Dominated and Deciduous-Dominated Forests of Central Appalachia
Eastern hemlock, (Tsuga canadensis Carrière, Pinaceae), is threatened with extirpation by an exotic invasive herbivore, the hemlock woolly adelgid, (Adelges tsugae Annand, Homoptera: Adelgidae). Given this threat, a broader and more detailed knowledge of the community associated with eastern hem- lock is merited. As Lepidoptera are important members of forest communities, this study was initiated to determine the relative occurrence of Lepidoptera in hemlock-dominated and deciduous-dominated habitats by evaluating abundance, species richness, temporal variation, and composition overlap. Lepidoptera were surveyed using blacklight traps from May – August 2010 at two collection sites in the Appalachian region of eastern Kentucky. The first collection site was within a forest stand dominated by mixed deciduous species, the second site possessed an overstory of eastern hemlock. Lepidoptera ≥ 20 mm in wingspan were identified and enumerated, yielding a total of 1,020 individuals of ≥ 137 species and 18 families. The total number of Lepidoptera captured in May and June was fewer than in July and August (P ≤ 0.05). The composition of the assemblage varied between collection sites as well as seasonally; 85 species were identified at the deciduous site and 107 species were identified at the hemlock site. While 27 species were recorded only at the deciduous site, 49 species were unique to the hemlock site. Of those unique to the hemlock site, five species were either detritivores or conifer specialists. These data demonstrate the importance of both deciduous and hemlock-dominated forest habitats for many species of Lepidoptera in Appalachia. Our study forms a foundation for understanding species richness patterns of Lepidoptera in hemlock forests in North America and is a useful baseline for comparisons of richness and diversity post invasion by the hemlock woolly adelgid
Compression properties of polymeric syntactic foam composites under cyclic loading
Syntactic foams are composite materials frequently used in applications
requiring the properties of low density and high damage tolerance. In the
present work, polymer-based syntactic foams were studied under cyclic
compression in order to investigate their compressibility, recoverability,
energy dissipation and damage tolerance. These syntactic foams were
manufactured by adding hollow polymer microspheres of various sizes and wall
thicknesses into a polyurethane matrix. The associated loading and unloading
curves during cyclic testing were recorded, revealing the viscoelastic nature
of the materials. SEM images of the samples were obtained in order to study
potential damage mechanisms during compression. It was observed that these
syntactic foams exhibit high elastic recovery and energy dissipation over a
wide range of compressional strains and the addition of polymer microspheres
mitigate the damage under compressional loading.Comment: 25 pages, 13 figure
CMB Isotropy Anomalies and the Local Kinetic Sunyaev-Zel'dovich Effect
Several anomalies have been identified which may imply a breakdown of the
statistical isotropy of the cosmic microwave background (CMB). In particular,
an anomalous alignment of the quadrupole and octopole and a hemispherical power
asymmetry have increased in significance as the data have improved. There have
been several attempts to explain these observations which explore isotropy
breaking mechanisms within the early universe, but little attention has been
given to the possibility that these anomalies have their origin within the
local universe. We explore such a mechanism by considering the kinetic
Sunyaev-Zel'dovich effect due to a gaseous halo associated with the Milky Way.
Considering several physical models of an anisotropic free electron optical
depth contributed by such a halo, we find that the associated screening maps of
the primordial anisotropies have the necessary orientations to affect the
anomaly statistics very significantly, but only if the column density of free
electrons in the halo is at least an order of magnitude higher than indicated
by current observations.Comment: 10 pages, 4 figure
Feeling good about being hungry: food-related thoughts in eating disorder
Objectives: This study explores the relationships to food and hunger in women living with anorexic type eating difficulties and asks how imagery-based elaborations of food and eating thoughts are involved in their eating restraint, and recovery. Design: The qualitative idiographic approach of Interpretative Phenomenological Analysis (IPA) was used. Four in-depth semi-structured interviews were conducted with women self-selected as having experienced anorexia or anorexic like behaviour. Methods: The data was analysed using IPA and an audit of the analysis was conducted to ensure that the process followed had been systematic and rigorous and appropriately considered reflexivity. Results: Hunger was perceived positively by participants as confirmation that they were achieving their goal of losing weight, or avoiding weight gain. Hunger conferred a sense of being in control for the participants. Intrusive thoughts about food were reported as being quickly followed by elaborative mental imagery of the positive aspects of weight loss, and the negative consequences of eating. Imagery appeared to serve to maintain anorexic behaviours rather than to motivate food seeking. However, negative imagery of the consequences of anorexia were also described as supporting recovery. Conclusions: The finding that physiological sensations of hunger were experienced as positive confirmation of maintaining control has potentially important clinical and theoretical implications. It suggests further attention needs to be focused upon how changes in cognitive elaboration, involving mental imagery, are components of the psychological changes in the development of, maintenance of, and recovery from, anorexia
Setting UBVRI Photometric Zero-Points Using Sloan Digital Sky Survey ugriz Magnitudes
We discuss the use of Sloan Digital Sky Survey (SDSS) ugriz point-spread
function (PSF) photometry for setting the zero points of UBVRI CCD images. From
a comparison with the Landolt (1992) standards and our own photometry we find
that there is a fairly abrupt change in B, V, R, & I zero points around g, r, i
~ 14.5, and in the U zero point at u ~ 16. These changes correspond to where
there is significant interpolation due to saturation in the SDSS PSF fluxes.
There also seems to be another, much smaller systematic effect for stars with
g, r > 19.5. The latter effect is consistent with a small Malmquist bias.
Because of the difficulties with PSF fluxes of brighter stars, we recommend
that comparisons of ugriz and UBVRI photometry should only be made for
unsaturated stars with g, r and i in the range 14.5 - 19.5, and u in the range
16 - 19.5. We give a prescription for setting the UBVRI zero points for CCD
images, and general equations for transforming from ugriz to UBVRI.Comment: 13 pages. 6 figures. Accepted for publication in the Astronomical
Journa
Dependence of X-Ray Burst Models on Nuclear Reaction Rates
X-ray bursts are thermonuclear flashes on the surface of accreting neutron
stars and reliable burst models are needed to interpret observations in terms
of properties of the neutron star and the binary system. We investigate the
dependence of X-ray burst models on uncertainties in (p,),
(,), and (,p) nuclear reaction rates using fully
self-consistent burst models that account for the feedbacks between changes in
nuclear energy generation and changes in astrophysical conditions. A two-step
approach first identified sensitive nuclear reaction rates in a single-zone
model with ignition conditions chosen to match calculations with a
state-of-the-art 1D multi-zone model based on the {\Kepler} stellar evolution
code. All relevant reaction rates on neutron deficient isotopes up to mass 106
were individually varied by a factor of 100 up and down. Calculations of the 84
highest impact reaction rate changes were then repeated in the 1D multi-zone
model. We find a number of uncertain reaction rates that affect predictions of
light curves and burst ashes significantly. The results provide insights into
the nuclear processes that shape X-ray burst observables and guidance for
future nuclear physics work to reduce nuclear uncertainties in X-ray burst
models.Comment: 24 pages, 13 figures, 4 tables, submitte
Spitzer Mid-Infrared Imaging of Nearby Ultraluminous Infrared Galaxies
We have observed 14 nearby (z<0.16) Ultraluminous Infrared Galaxies (ULIRGs)
with Spitzer at 3.6-24 microns. The underlying host galaxies are well-detected,
in addition to the luminous nuclear cores. While the spatial resolution of
Spitzer is poor, the great sensitivity of the data reveals the underlying
galaxy merger remnant, and provides the first look at off-nuclear mid-infrared
activity.Comment: To appear in the conference proceedings for Spitzer New Views of the
Universe, held Nov. 2004 in Pasadena, C
A high resolution coupled hydrologic–hydraulic model (HiResFlood-UCI) for flash flood modeling
HiResFlood-UCI was developed by coupling the NWS's hydrologic model (HL-RDHM) with the hydraulic model (BreZo) for flash flood modeling at decameter resolutions. The coupled model uses HL-RDHM as a rainfall-runoff generator and replaces the routing scheme of HL-RDHM with the 2D hydraulic model (BreZo) in order to predict localized flood depths and velocities. A semi-automated technique of unstructured mesh generation was developed to cluster an adequate density of computational cells along river channels such that numerical errors are negligible compared with other sources of error, while ensuring that computational costs of the hydraulic model are kept to a bare minimum. HiResFlood-UCI was implemented for a watershed (ELDO2) in the DMIP2 experiment domain in Oklahoma. Using synthetic precipitation input, the model was tested for various components including HL-RDHM parameters (a priori versus calibrated), channel and floodplain Manning n values, DEM resolution (10 m versus 30 m) and computation mesh resolution (10 m+ versus 30 m+). Simulations with calibrated versus a priori parameters of HL-RDHM show that HiResFlood-UCI produces reasonable results with the a priori parameters from NWS. Sensitivities to hydraulic model resistance parameters, mesh resolution and DEM resolution are also identified, pointing to the importance of model calibration and validation for accurate prediction of localized flood intensities. HiResFlood-UCI performance was examined using 6 measured precipitation events as model input for model calibration and validation of the streamflow at the outlet. The Nash–Sutcliffe Efficiency (NSE) obtained ranges from 0.588 to 0.905. The model was also validated for the flooded map using USGS observed water level at an interior point. The predicted flood stage error is 0.82 m or less, based on a comparison to measured stage. Validation of stage and discharge predictions builds confidence in model predictions of flood extent and localized velocities, which are fundamental to reliable flash flood warning
Individual differences in infant fixation duration relate to attention and behavioral control in childhood
Individual differences in fixation duration are considered a reliable measure of attentional control in adults. However, the degree to which individual differences in fixation duration in infancy (0–12 months) relate to temperament and behavior in childhood is largely unknown. In the present study, data were examined from 120 infants (mean age = 7.69 months, SD = 1.90) who previously participated in an eye-tracking study. At follow-up, parents completed age-appropriate questionnaires about their child’s temperament and behavior (mean age of children = 41.59 months, SD = 9.83). Mean fixation duration in infancy was positively associated with effortful control (β = 0.20, R2 = .02, p = .04) and negatively with surgency (β = −0.37, R2 = .07, p = .003) and hyperactivity-inattention (β = −0.35, R2 = .06, p = .005) in childhood. These findings suggest that individual differences in mean fixation duration in infancy are linked to attentional and behavioral control in childhood
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