2,007 research outputs found
The Multi-Wavelength Tully-Fisher relation with spatially resolved HI kinematics
In this paper we investigate the statistical properties of the Tully-Fisher
relation for a sample of 32 galaxies with measured distances from the Cepheid
period-luminosity relation and/or TRGB stars.
We take advantage of panchromatic photometry in 12 bands (from FUV to 4.5
m) and of spatially resolved HI kinematics. We use these data together
with three kinematic measures (, and )
extracted from the global HI profiles or HI rotation curves, so as to construct
36 correlations allowing us to select the one with the least scatter. We
introduce a tightness parameter of the TFr, in order to obtain
a slope-independent measure of the goodness of fit. We find that the tightest
correlation occurs when we select the 3.6 m photometric band together with
the parameter extracted from the HI rotation curve.Comment: 16 pages, 16 figures, accepted for publication in MNRAS, minor
changes due to proof correction
Personalizing the Development of Initial Reading Vocabulary at the Campus School Western Michigan University
The Campus School at Western Michigan University recently has been experimenting with the Language-Master Machine as a means of developing initial reading vocabularies with children in the first grade. Realizing that the act of learning to read is unnecessarily complicated when the pupil is asked to deal with printed word symbols whose meaning and sound are foreign or uninteresting to him, the objective here is to identify a personalized reading vocabulary from the actual speaking vocabulary of each individual child. It is hypothesized that such a personalized vocabulary should be an even more effectual device for beginning reading instruction than the basal text which usually offers a controlled vocabulary designed for a specific cultural or socio-economic group
Two Dimensional Velocity Fields of Low Surface Brightness Galaxies
We present high resolution two dimensional velocity fields from integral
field spectroscopy along with derived rotation curves for nine low surface
brightness galaxies. This is a positive step forward in terms of both data
quality and number of objects studied. We fit NFW and pseudo-isothermal halo
models to the observations. We find that the pseudo-isothermal halo better
represents the data in most cases than the NFW halo, as the resulting
concentrations are lower than would be expected for LCDM.Comment: 2 pages, 1 figure, to appear in the XXIst IAP Colloquium "Mass
Profiles and Shapes of Cosmological Structures", Paris 4-9 July 2005, (Eds.)
G. Mamon, F. Combes, C. Deffayet, B. Fort, (EDP Sciences
A quantitative study of the impact of functional classification on competitive anxiety and performance among wheelchair basketball athletes
In adaptive sports (also known as Para sports, disability sports, or Paralympic sports), athletes are assigned to classes that indicate their functional potential, regardless of talent, training, or experience. The aim of the present study among wheelchair basketball athletes (n = 141) was to explore the role of functional classification as a potential stressor. Specifically, we looked into the anecdotal relationship between classification and athletes’ concern about “performing in accordance with one’s class.” Based on a serial mediation research model, we examined the links between functional classification and three outcome variables (i.e., cognitive worry, somatic arousal, and game performance) through the mediator variables of perceived competitive demands and sport-specific self-efficacy. Unexpectedly, we did not find any evidence of a classification effect on either the mediator variables or competitive anxiety. However, we did find positive correlations between functional classification and athletes’ contribution to their team’s score, which align with research supporting the proportionality and the validity of the functional classification system. Moreover, regardless of classification, mediation analyses revealed an indirect link between perceived competitive demands and cognitive worry through sport-specific self-efficacy. These findings suggest that, regardless of classification, athletes’ self-efficacy may be increased by managing their appraisals of competitive demands and that their cognitive worries may be reduced by self-efficacy interventions
Characterization of DTI Indices in the Cervical, Thoracic, and Lumbar Spinal Cord in Healthy Humans
The aim of this study was to characterize in vivo measurements of diffusion along the length of the entire healthy spinal cord and to compare DTI indices, including fractional anisotropy (FA) and mean diffusivity (MD), between cord regions. The objective is to determine whether or not there are significant differences in DTI indices along the cord that must be considered for future applications of characterizing the effects of injury or disease. A cardiac gated, single-shot EPI sequence was used to acquire diffusion-weighted images of the cervical, thoracic, and lumbar regions of the spinal cord in nine neurologically intact subjects (19 to 22 years). For each cord section, FA versus MD values were plotted, and a k-means clustering method was applied to partition the data according to tissue properties. FA and MD values from both white matter (average FA = 0.69, average MD = 0.93 × 10−3 mm2/s) and grey matter (average FA = 0.44, average MD = 1.8 × 10−3 mm2/s) were relatively consistent along the length of the cord
Secants of Lagrangian Grassmannians
We study the dimensions of secant varieties of the Grassmannian of Lagrangian
subspaces in a symplectic vector space. We calculate these dimensions for third
and fourth secant varieties. Our result is obtained by providing a normal form
for four general points on such a Grassmannian and by explicitly calculating
the tangent spaces at these four points
Visualizing elements of Sha[3] in genus 2 jacobians
Mazur proved that any element xi of order three in the Shafarevich-Tate group
of an elliptic curve E over a number field k can be made visible in an abelian
surface A in the sense that xi lies in the kernel of the natural homomorphism
between the cohomology groups H^1(k,E) -> H^1(k,A). However, the abelian
surface in Mazur's construction is almost never a jacobian of a genus 2 curve.
In this paper we show that any element of order three in the Shafarevich-Tate
group of an elliptic curve over a number field can be visualized in the
jacobians of a genus 2 curve. Moreover, we describe how to get explicit models
of the genus 2 curves involved.Comment: 12 page
Circumnuclear Gas in Seyfert 1 Galaxies: Morphology, Kinematics, and Direct Measurement of Black Hole Masses
(Abridged) The two-dimensional distribution and kinematics of the molecular,
ionized, and highly ionized gas in the nuclear regions of Seyfert 1 galaxies
have been measured using high spatial resolution (~0''.09) near-infrared
spectroscopy from NIRSPEC with adaptive optics on the Keck telescope. Molecular
hydrogen, H2, is detected in all nine Seyfert 1 galaxies and, in the majority
of galaxies, has a spatially resolved flux distribution. In contrast, the
narrow component of the BrG emission has a distribution consistent with that of
the K-band continuum. In general, the kinematics of H2 are consistent with thin
disk rotation, with a velocity gradient of over 100 km/s measured across the
central 0''.5 in three galaxies, and across the central 1''.5 in two galaxies.
The kinematics of BrG are in agreement with the H2 rotation, except in all four
cases the central 0''.5 is either blue- or redshifted by more than 75 km/s. The
highly ionized gas, measured with the [Ca VIII] and [Si VII] coronal lines, is
spatially and kinematically consistent with BrG in the central 0''.5. Dynamical
models have been fitted to the two-dimensional H2 kinematics, taking into
account the stellar mass distribution, the emission line flux distribution, and
the point spread function. For NGC 3227 the modeling indicates a black hole
mass of Mbh = 2.0{+1.0/-0.4} x 10^7 Msun, and for NGC 4151 Mbh =
3.0{+0.75/-2.2} x 10^7 Msun. In NGC 7469 the best fit model gives Mbh < 5.0 x
10^7 Msun. In all three galaxies, modeling suggests a near face-on disk
inclination angle, which is consistent with the unification theory of active
galaxies. The direct black hole mass estimates verify that masses determined
from the technique of reverberation mapping are accurate to within a factor of
three with no additional systematic errors.Comment: 43 pages, including 47 figures; Accepted for publication in ApJ. All
2-D maps (in high resolution) are available at
http://www.astro.ucla.edu/~ehicks . Minor changes to the text and updated
reverberation mapped black hole mass estimates; the conclusions are unchange
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