1,307 research outputs found
A survey of business education in the public high schools of New England
Thesis (Ed.M.)--Boston University
A Multi-Wavelength Infrared Study of NGC 891
We present a multi-wavlength infrared study of the nearby, edge-on, spiral
galaxy NGC 891. We have examined 20 independent, spatially resolved IR images
of this galaxy, 14 of which are newly reduced and/or previously unpublished
images. These images span a wavelength regime from 1.2 microns in which the
emission is dominated by cool stars, through the MIR, in which emission is
dominated by PAHs, to 850 microns, in which emission is dominated by cold dust
in thermal equilibrium with the radiation field. The changing morphology of the
galaxy with wavelength illustrates the changing dominant components. We detect
extra-planar dust emission in this galaxy, consistent with previously published
results, but now show that PAH emission is also in the halo, to a vertical
distance of z >= 2.5 kpc. We compare the vertical extents of various components
and find that the PAHs (from 7.7 and 8 micron data) and warm dust (24 microns)
extend to smaller z heights than the cool dust (450 microns). For six locations
in the galaxy for which the S/N was sufficient, we present SEDs of the IR
emission, including two in the halo - the first time a halo SED in an external
galaxy has been presented. We have modeled these SEDs and find that the PAH
fraction is similar to Galactic values (within a factor of two), with the
lowest value at the galaxy's center, consistent with independent results of
other galaxies. In the halo environment, the fraction of dust exposed to a
colder radiation field, is of order unity, consistent with an environment in
which there is no star formation. The source of excitation is likely from
photons escaping from the disk.Comment: 24 pages, 17 figures, 7 tables, accepted for publication in MNRA
Multi-Element Abundance Measurements from Medium-Resolution Spectra. III. Metallicity Distributions of Milky Way Dwarf Satellite Galaxies
We present metallicity distribution functions (MDFs) for the central regions
of eight dwarf satellite galaxies of the Milky Way: Fornax, Leo I and II,
Sculptor, Sextans, Draco, Canes Venatici I, and Ursa Minor. We use the
published catalog of abundance measurements from the previous paper in this
series. The measurements are based on spectral synthesis of iron absorption
lines. For each MDF, we determine maximum likelihood fits for Leaky Box,
Pre-Enriched, and Extra Gas (wherein the gas supply available for star
formation increases before it decreases to zero) analytic models of chemical
evolution. Although the models are too simplistic to describe any MDF in
detail, a Leaky Box starting from zero metallicity gas fits none of the
galaxies except Canes Venatici I well. The MDFs of some galaxies, particularly
the more luminous ones, strongly prefer the Extra Gas Model to the other
models. Only for Canes Venatici I does the Pre-Enriched Model fit significantly
better than the Extra Gas Model. The best-fit effective yields of the less
luminous half of our galaxy sample do not exceed 0.02 Z_sun, indicating that
gas outflow is important in the chemical evolution of the less luminous
galaxies. We surmise that the ratio of the importance of gas infall to gas
outflow increases with galaxy luminosity. Strong correlations of average [Fe/H]
and metallicity spread with luminosity support this hypothesis.Comment: 17 pages, 5 figures; accepted for publication in ApJ; minor
corrections in v3; corrected typographical errors in Tables 1 and 3 in v
A "superstorm": When moral panic and new risk discourses converge in the media
This is an Author's Accepted Manuscript of an article published in Health, Risk and Society, 15(6), 681-698, 2013, copyright Taylor & Francis, available online at: http://www.tandfonline.com/10.1080/13698575.2013.851180.There has been a proliferation of risk discourses in recent decades but studies of these have been polarised, drawing either on moral panic or new risk frameworks to analyse journalistic discourses. This article opens the theoretical possibility that the two may co-exist and converge in the same scare. I do this by bringing together more recent developments in moral panic thesis, with new risk theory and the concept of media logic. I then apply this theoretical approach to an empirical analysis of how and with what consequences moral panic and new risk type discourses converged in the editorials of four newspaper campaigns against GM food policy in Britain in the late 1990s. The article analyses 112 editorials published between January 1998 and December 2000, supplemented with news stories where these were needed for contextual clarity. This analysis shows that not only did this novel food generate intense media and public reactions; these developed in the absence of the type of concrete details journalists usually look for in risk stories. Media logic is important in understanding how journalists were able to engage and hence how a major scare could be constructed around convergent moral panic and new risk type discourses. The result was a media âsuperstormâ of sustained coverage in which both types of discourse converged in highly emotive mutually reinforcing ways that resonated in a highly sensitised context. The consequence was acute anxiety, social volatility and the potential for the disruption of policy and social change
Extremely metal-poor stars in classical dwarf spheroidal galaxies: Fornax, Sculptor and Sextans
We present the results of a dedicated search for extremely metal-poor stars
in the Fornax, Sculptor and Sextans dSphs. Five stars were selected from two
earlier VLT/Giraffe and HET/HRS surveys and subsequently followed up at high
spectroscopic resolution with VLT/UVES. All of them turned out to have [Fe/H]
<= -3 and three stars are below [Fe/H] -3.5. This constitutes the first
evidence that the classical dSphs Fornax and Sextans join Sculptor in
containing extremely metal-poor stars and suggests that all of the classical
dSphs contain extremely metal-poor stars. One giant in Sculptor at [Fe/H]=-3.96
+- 0.10 is the most metal-poor star ever observed in an external galaxy. We
carried out a detailed analysis of the chemical abundances of the alpha, iron
peak, and the heavy elements, and we performed a comparison with the Milky Way
halo and the ultra faint dwarf stellar populations. Carbon, barium and
strontium show distinct features characterized by the early stages of galaxy
formation and can constrain the origin of their nucleosynthesis.Comment: In A&A. This version corrects a few typographical errors in the
coordinates of some of our stars (Table 1
Surprising dissimilarities in a newly formed pair of 'identical twin' stars
The mass and chemical composition of a star are the primary determinants of
its basic physical properties--radius, temperature, luminosity--and how those
properties evolve with time. Thus, two stars born at the same time, from the
same natal material, and with the same mass are 'identical twins,' and as such
might be expected to possess identical physical attributes. We have discovered
in the Orion Nebula a pair of stellar twins in a newborn binary star system.
Each star in the binary has a mass of 0.41 +/- 0.01 solar masses, identical to
within 2 percent. Here we report that these twin stars have surface
temperatures that differ by ~300K (~10%), and luminosities that differ by ~50%,
both at high confidence level. Preliminary results indicate that the stars'
radii also differ, by 5-10%. These surprising dissimilarities suggest that one
of the twins may have been delayed by several hundred thousand years in its
formation relative to its sibling. Such a delay could only have been detected
in a very young, definitively equal-mass binary system3 such as that reported
here. Our findings reveal cosmic limits on the age synchronisation of young
binary stars, often used as tests for the age calibrations of star-formation
models.Comment: Published in Nature, 19 June 200
X-ray observations of three young, early-type galaxies
Massive haloes of hot plasma exist around some, but not all elliptical galaxies. There is evidence that this is related to the age of the galaxy. In this paper, new X-ray observations are presented for three early-type galaxies that show evidence of youth, in order to investigate their X-ray components and properties. NGC 5363 and NGC 2865 were found to have X-ray emission dominated by purely discrete stellar sources. Limits are set on the mass distribution in one of the galaxies observed with XMMâNewton, NGC 4382, which contains significant hot gas. We detect the X-ray emission in NGC 4382 out to 4re. The mass-to-light ratio is consistent with a stellar origin in the inner regions but rises steadily to values indicative of some dark matter by 4re. These results are set in context with other data drawn from the literature, for galaxies with ages estimated from dynamical or spectroscopic indicators. Ages obtained from optical spectroscopy represent central luminosity-weighted stellar ages. We examine the X-ray evolution with age, normalized by B- and K-band luminosities. Low values of Log(LX/LB) and Log(LX/LK) are found for all galaxies with ages between 1 and 4 Gyr. Luminous X-ray emission only appears in older galaxies. This suggests that the interstellar medium is removed and then it takes several gigayears for hot gas haloes to build up, following a merger. A possible mechanism for gas expulsion might be associated with feedback from an active nucleus triggered during a merger
A high resolution VLT/FLAMES study of individual stars in the centre of the Fornax dwarf spheroidal galaxy
For the first time we show the detailed late-stage chemical evolution history
of small nearby dwarf spheroidal galaxy in the Local Group. We present the
results of a high resolution (R20000) FLAMES/GIRAFFE abundance study at
ESO/VLT of 81 photometrically selected red giant branch stars in the central
25 of the Fornax dwarf spheroidal galaxy. We present abundances of \alfe\
(Mg, Si, Ca and Ti), iron-peak elements (Fe, Ni and Cr) and heavy elements (Y,
Ba, La, Nd and Eu). Our sample was randomly selected, and is clearly dominated
by the younger and more metal rich component of Fornax which represents the
major fraction of stars in the central region. This means that the majority of
our stars are 14 Gyr old, and thus represent the end phase of chemical
evolution in this system. Our sample of stars has unusually low [/Fe],
[Ni/Fe] and [Na/Fe] compared to the Milky Way stellar populations at the same
[Fe/H]. The particularly important role of stellar winds from low metallicity
AGB stars in the creation of s-process elements is clearly seen from the high
[Ba/Y]. Furthermore, we present evidence for an s-process contribution to Eu.Comment: 40 pages, 20 figures, accepted for publication in A&
Effects of gluteal kinesio-taping on performance with respect to fatigue in rugby players
Kinesio-tapeÂŽ has been suggested to increase blood circulation and lymph flow and might influence the muscle's ability to maintain strength during fatigue. Therefore, the aim of this study was to investigate the influence of gluteal Kinesio-tapeÂŽ on lower limb muscle strength in non-fatigued and fatigued conditions. A total of 10 male rugby union players performed 20-m sprint and vertical jump tests before and after a rugby-specific fatigue protocol. The 20-m sprint time was collected using light gates (SMARTSPEED). A 9-camera motion analysis system (VICON, 100 Hz) and a force plate (Kistler, 1000 Hz) measured the kinematics and kinetics during a counter movement jump and drop-jump. The effect of tape and fatigue on jump height, maximal vertical ground reaction force, reactivity strength index as well as lower limb joint work were analysed via a two-way analysis of variance. The fatigue protocol resulted in significantly decreased performance of sprint time, jump heights and alterations in joint work. No statistical differences were found between the taped and un-taped conditions in non-fatigued and fatigued situation as well as in the interaction with fatigue. Therefore, taping the gluteal muscle does not influence the leg explosive strength after fatiguing in healthy rugby players
Autism as a disorder of neural information processing: directions for research and targets for therapy
The broad variation in phenotypes and severities within autism spectrum disorders suggests the involvement of multiple predisposing factors, interacting in complex ways with normal developmental courses and gradients. Identification of these factors, and the common developmental path into which theyfeed, is hampered bythe large degrees of convergence from causal factors to altered brain development, and divergence from abnormal brain development into altered cognition and behaviour. Genetic, neurochemical, neuroimaging and behavioural findings on autism, as well as studies of normal development and of genetic syndromes that share symptoms with autism, offer hypotheses as to the nature of causal factors and their possible effects on the structure and dynamics of neural systems. Such alterations in neural properties may in turn perturb activity-dependent development, giving rise to a complex behavioural syndrome many steps removed from the root causes. Animal models based on genetic, neurochemical, neurophysiological, and behavioural manipulations offer the possibility of exploring these developmental processes in detail, as do human studies addressing endophenotypes beyond the diagnosis itself
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