2,045 research outputs found
Ethnicity and the Writing of Medieval Scottish history
Historians have long tended to define medieval Scottish society in terms of interactions between ethnic groups. This approach was developed over the course of the long nineteenth century, a formative period for the study of medieval Scotland. At that time, many scholars based their analysis upon scientific principles, long since debunked, which held that medieval 'peoples' could only be understood in terms of 'full ethnic packages'. This approach was combined with a positivist historical narrative that defined Germanic Anglo-Saxons and Normans as the harbingers of advances of Civilisation. While the prejudices of that era have largely faded away, the modern discipline still relies all too often on a dualistic ethnic framework. This is particularly evident in a structure of periodisation that draws a clear line between the 'Celtic' eleventh century and the 'Norman' twelfth. Furthermore, dualistic oppositions based on ethnicity continue, particularly in discussions of the law, kingship, lordship and religion
Playing Active Video Games may not develop movement skills: an intervention trial
Background: To investigate the impact of playing sports Active Video Games on children\u27s actual and perceived object control skills. Methods: Intervention children played Active Video Games for 6. weeks (1. h/week) in 2012. The Test of Gross Motor Development-2 assessed object control skill. The Pictorial Scale of Perceived Movement Skill Competence assessed perceived object control skill. Repeated measurements of object control and perceived object control were analysed for the whole sample, using linear mixed models, which included fixed effects for group (intervention or control) and time (pre and post) and their interaction. The first model adjusted for sex only and the second model also adjusted for age, and prior ball sports experience (yes/no). Seven mixed-gender focus discussions were conducted with intervention children after programme completion. Results: Ninety-five Australian children (55% girls; 43% intervention group) aged 4 to 8. years (M 6.2, SD 0.95) participated. Object control skill improved over time (p=0.006) but there was no significant difference (p=0.913) between groups in improvement (predicted means: control 31.80 to 33.53, SED=0.748; intervention 30.33 to 31.83, SED=0.835). A similar result held for the second model. Similarly the intervention did not change perceived object control in Model 1 (predicted means: control: 19.08 to 18.68, SED=0.362; intervention 18.67 to 18.88, SED=0.406) or Model 2. Children found the intervention enjoyable, but most did not perceive direct equivalence between Active Video Games and \u27real life\u27 activities. Conclusions: Whilst Active Video Game play may help introduce children to sport, this amount of time playing is unlikely to build skill
Observations of X-rays and Thermal Dust Emission from the Supernova Remnant Kes 75
We present Spitzer Space Telescope and Chandra X-ray Observatory observations
of the composite Galactic supernova remnant Kes 75 (G29.7-0.3). We use the
detected flux at 24 microns and hot gas parameters from fitting spectra from
new, deep X-ray observations to constrain models of dust emission, obtaining a
dust-to-gas mass ratio M_dust/M_gas ~0.001. We find that a two-component
thermal model, nominally representing shocked swept-up interstellar or
circumstellar material and reverse-shocked ejecta, adequately fits the X-ray
spectrum, albeit with somewhat high implied densities for both components. We
surmise that this model implies a Wolf-Rayet progenitor for the remnant. We
also present infrared flux upper limits for the central pulsar wind nebula.Comment: 7 pages, 2 tables, 4 figures, uses emulateapj. Accepted for
publication in Ap
The X-ray Reflectors in the Nucleus of the Seyfert Galaxy NGC 1068
(abridged) Based on observations of the Seyfert nucleus in NGC1068 with ASCA,
RXTE and BeppoSAX, we report the discovery of a flare (increase in flux by a
factor of ~1.6) in the 6.7 keV Fe K line component between observations
obtained 4 months apart, with no significant change in the other (6.21, 6.4,
and 6.97 keV) Fe K_alpha line components. During this time, the continuum flux
decreased by ~20%. The RXTE spectrum requires an Fe K absorption edge near 8.6
keV (Fe XXIII - XXV). The spectral data indicate that the 2-10 keV continuum
emission is dominated (~2/3 of the luminosity) by reflection from a previously
unidentified region of warm, ionized gas located <~ 0.2 pc from the AGN. The
remaining ~1/3 of the observed X-ray emission is reflected from optically
thick, neutral gas. The inferred properties of the warm reflector (WR) are:
size (diameter) ~ 10^{5.5} /cm3, ionization parameter
xi approx 10^{3.5} erg cm/s, and covering fraction 0.003 (L_0/10^{43.5}
erg/s)^{-1} < (Omega/4 pi) < 0.024 (L_0/10^{43.5})^{-1}, where L_0 is the
intrinsic 2-10 keV X-ray luminosity of the AGN. We suggest that the WR gas is
the source of the (variable) 6.7 keV Fe line emission, and the 6.97 keV Fe line
emission. The 6.7 keV line flare is assumed to be due to an increase in the
emissivity of the WR gas from a decrease (by 20-30%) in L_0. The properties of
the WR are most consistent with an intrinsically X-ray weak AGN with L_0 approx
10^{43.0} erg/s. The optical and UV emission that scatters from the WR into our
line of sight is required to suffer strong extinction, which can be reconciled
if the line-of-sight skims the outer surface of the torus. Thermal
bremsstrahlung radio emission from the WR may be detectable in VLBA radio maps
of the NGC 1068 nucleus.Comment: 39 pages (9 postscript figures) AASTEX, ApJ, accepte
Altered Resting-State Functional Connectivity of the Frontal-Striatal Reward System in Social Anxiety Disorder
We investigated differences in the intrinsic functional brain organization (functional connectivity) of the human reward system between healthy control participants and patients with social anxiety disorder. Functional connectivity was measured in the resting-state via functional magnetic resonance imaging (fMRI). 53 patients with social anxiety disorder and 33 healthy control participants underwent a 6-minute resting-state fMRI scan. Functional connectivity of the reward system was analyzed by calculating whole-brain temporal correlations with a bilateral nucleus accumbens seed and a ventromedial prefrontal cortex seed. Patients with social anxiety disorder, relative to the control group, had (1) decreased functional connectivity between the nucleus accumbens seed and other regions associated with reward, including ventromedial prefrontal cortex; (2) decreased functional connectivity between the ventromedial prefrontal cortex seed and lateral prefrontal regions, including the anterior and dorsolateral prefrontal cortices; and (3) increased functional connectivity between both the nucleus accumbens seed and the ventromedial prefrontal cortex seed with more posterior brain regions, including anterior cingulate cortex. Social anxiety disorder appears to be associated with widespread differences in the functional connectivity of the reward system, including markedly decreased functional connectivity between reward regions and between reward regions and lateral prefrontal cortices, and markedly increased functional connectivity between reward regions and posterior brain regions.Massachusetts Institute of Technology (Janet and Sheldon Razin Fellowship
FUSE Observations of a Full Orbit of Hercules X-1: Signatures of Disk, Star, and Wind
We observed an entire 1.7 day orbit of the X-ray binary Hercules X-1 with the
Far Ultraviolet Spectroscopic Explorer (FUSE). Changes in the O VI 1032,1037
line profiles through eclipse ingress and egress indicate a Keplerian accretion
disk spinning prograde with the orbit. These observations may show the first
double-peaked accretion disk line profile to be seen in the Hercules X-1
system. Doppler tomograms of the emission lines show a bright spot offset from
the Roche lobe of the companion star HZ Her, but no obvious signs of the
accretion disk. Simulations show that the bright spot is too far offset from
the Roche lobe to result from uneven X-ray heating of its surface. The absence
of disk signatures in the tomogram can be reproduced in simulations which
include absorption from a stellar wind. We attempt to diagnose the state of the
emitting gas from the C III 977, C III 1175, and N III 991 emission lines. The
latter may be enhanced through Bowen fluorescence.Comment: Accepted for publication in The Astrophysical Journa
Spawning Salmon Density Influences Fruit Production of Salmonberry (Rubus Spectabilis)
Annual spawning migrations by Pacific salmon can provide substantial subsidies to nutrient‐limited freshwater and riparian ecosystems, which can affect the abundance, diversity, and physical characteristics of plant and animal species in these habitats. Here, we provide the first investigation of how salmon subsidies affect reproductive output in plants, focusing on a common riparian shrub, salmonberry (Rubus spectabilis). We studied 14 streams with a range of spawning salmon densities on the central coast of British Columbia, Canada. We determined the effects of chum (Oncorhynchus keta), pink (O. gorbuscha), and total salmon spawning density on the number of fruits per shrub, number of seeds per fruit, fruit weight, and estimated sugar content (° Brix) of salmonberry fruits. We found that the number of fruits per salmonberry shrub increased with increasing salmon density. However, we found no effect of salmon density on the number of seeds per fruit, fruit weight, or sugar content. The effect of salmon density was species‐dependent; the number of fruits per shrub increased with chum salmon density but was not affected by pink salmon density. This could be because chum salmon occur at higher densities and are transferred from water to land at higher rates than pink salmon in our study area. Higher salmonberry fruit production could lead to a larger input of salmonberry fruits to coastal food webs. These results demonstrate how salmon can cross ecological boundaries and influence reproductive output of terrestrial species
Effects of Spawning Pacific Salmon on Terrestrial Invertebrates: Insects near Spawning Habitat Are Isotopically Enriched with Nitrogen-15 but Display No Differences in Body Size
When Pacific salmon (Oncorhynchus spp.) spawn and die, they deliver marine-derived nutrient subsidies to freshwater and riparian ecosystems. These subsidies can alter the behavior, productivity, and abundance of recipient species and their habitats. Isotopes, such as nitrogen-15 (15N), are often used to trace the destination of marine-derived nutrients in riparian habitats. However, few studies have tested for correlations between stable isotopes and physiological responses of riparian organisms. We examined whether increases in δ15N in terrestrial insect bodies adjacent to salmon spawning habitat translate to changes in percent nitrogen content and body size. This involved comparisons between distance from a salmon-bearing river, marine-derived nutrients in soils and insects, soil moisture content, and body size and nitrogen content in two common beetle families (Coleoptera: Curculionidae, Carabidae). As predicted, δ15N in riparian soils attenuated with distance from the river but was unaffected by soil moisture. This gradient was mirrored by δ15N in the herbivorous curculionid beetles, whereas carabid beetles, which feed at a higher trophic level and are more mobile, did not show discernable patterns in their δ15N content. Additionally, neither distance from the river nor body δ15N content was related to beetle body size. We also found that nitrogen-15 was not correlated with total percent nitrogen in insect bodies, meaning that the presence of spawning salmon did not increase the percent nitrogen content of these insects. We conclude that while salmon-derived nutrients had entered terrestrial food webs, the presence of δ15N alone did not indicate meaningful physiological changes in these insects in terms of percent nitrogen nor body size. While stable isotopes may be useful tracers of marine-derived nutrients, they cannot necessarily be used as a proxy for physiologically important response variables
AGN Feedback and Cooling Flows: Problems with Simple Hydrodynamical Models
In recent years it has become increasingly clear that Active Galactic Nuclei,
and radio-galaxies in particular, have an impact on large scale structure and
galaxy formation. In principle, radio-galaxies are energetic enough to halt the
cooling of the virialized intracluster medium (ICM) in the inner regions of
galaxy clusters, solving the cooling flow problem and explaining the high-mass
truncation of the galaxy luminosity function. We explore this process through a
series of high resolution, three dimensional hydrodynamic simulations of jetted
active galaxies that act in response to cooling-mediated accretion of an ICM
atmosphere. We find that our models are incapable of producing a long term
balance of heating and cooling; catastrophic cooling can be delayed by the jet
action but inevitably takes hold. At the heart of the failure of these models
is the formation of a low density channel through which the jet can freely
flow, carrying its energy out of the cooling core. It is possible that this
failure is due to an over-simplified treatment of the fast jet (which may
underestimate the ``dentist drill'' effect). However, it seems likely that
additional complexity (large-angle jet precession or ICM turbulence) or
additional physics (magnetohydrodynamic effects and plasma transport processes)
is required to produce a spatial distribution of jet heating that can prevent
catastrophic cooling. This work also underscores the importance of including
jet dynamics in any feedback model as opposed to the isotropically inflated
bubble approach taken in some previous works.Comment: 15 pages, Replaced with version accepted for publication in ApJ. PDF
version with high-resolution figures and animations available at
http://www.astro.umd.edu/~vernaleo/publications/AGNfeedback-simple-hydro.html
Our modified version of the ZEUS-MP code is available at
http://www.astro.umd.edu/~vernaleo/zeusmp.htm
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