2,024 research outputs found
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
Perceptions about quality of life in a school-based population of adolescents with menorrhagia: implications for adolescents with bleeding disorders
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73106/1/j.1365-2516.2008.01652.x.pd
Social Studies Content Reading about the American Revolution Enhanced with Graphic Novels
Graphic novels can contribute to effective content area reading on social studies topics such as the American Revolution. This action research studyâs purpose was to examine student recall of facts, enjoyment of reading, and interest in the topic when using graphic novels as compared to illustrated nonfiction prose in social studies content area reading. Twenty-two fifth grade students (13 females, 9 males) in a public school in a Midwestern state participated in the study. Half of the students read about the Boston Massacre and Patrick Henry through graphic novels and read about Paul Revere and the Boston Tea Party with illustrated nonfiction texts, with the other half doing the opposite. The mean number of correct ideas recalled by students two weeks after reading two books in the graphic novel condition was 8.6 compared to 7.1 for the nonfiction prose condition with a medium effect size. Students rated their reading enjoyment significantly higher in the graphic novel condition indicating that graphic novels should be employed more often into the school curriculum. Suggestions for integrating graphic novels into the curriculum are provided along with other ways to take action
The SKA view of the Neutral Interstellar Medium in Galaxies
Two major questions in galaxy evolution are how star-formation on small
scales leads to global scaling laws and how galaxies acquire sufficient gas to
sustain their star formation rates. HI observations with high angular
resolution and with sensitivity to very low column densities are some of the
important observational ingredients that are currently still missing. Answers
to these questions are necessary for a correct interpretation of observations
of galaxy evolution in the high-redshift universe and will provide crucial
input for the sub-grid physics in hydrodynamical simulations of galaxy
evolutions. In this chapter we discuss the progress that will be made with the
SKA using targeted observations of nearby individual disk and dwarf galaxies.Comment: 22 pages, 4 figures, to appear as part of 'Neutral Hydrogen' in
Proceedings 'Advancing Astrophysics with the SKA (AASKA14)', PoS(AASKA14)12
âVictimsâ participation rights in the post-sentencing phase:The Netherlands in comparative perspectiveâ
Victimsâ rights have proliferated rapidly over the past decades. However, the development of rights in the post-sentencing phase has lagged behind. In this article, we argue that victimsâ rights may contribute to the acknowledgement of victims, something that victimological research suggests is important for victimsâ well-being at every stage of criminal proceedings. We review a new Dutch law and a legislative proposal aiming to improve victimsâ rights in the post-sentencing phase in relation to conditional release from prison and conditional discharge from forensic psychiatric hospital. More specifically, we compare these (proposed) victimsâ participatory rights with those existing in the Canadian, Belgian and German framework. We argue for a strengthened position of the victim in the post-sentencing phase. We close by showing that the practical effectiveness of these proposed rights is put at risk by COVID-19 and statesâ response to the same
Setting the normalcy level of HI properties in isolated galaxies
Studying the atomic gas (HI) properties of the most isolated galaxies is
essential to quantify the effect that the environment exerts on this sensitive
component of the interstellar medium. We observed and compiled HI data for a
well defined sample of ~ 800 galaxies in the Catalog of Isolated Galaxies, as
part of the AMIGA project (Analysis of the ISM in Isolated GAlaxies,
http://amiga.iaa.es), which enlarges considerably previous samples used to
quantify the HI deficiency in galaxies located in denser environments. By
studying the shape of 182 HI profiles, we revisited the usually accepted result
that, independently of the environment, more than half of the galaxies present
a perturbed HI disk. In isolated galaxies this would certainly be a striking
result if these are supposed to be the most relaxed systems, and has
implications in the relaxation time scales of HI disks and the nature of the
most frequent perturbing mechanisms in galaxies. Our sample likely exhibits the
lowest HI asymmetry level in the local Universe. We found that other field
samples present an excess of ~ 20% more asymmetric HI profiles than that in
CIG. Still a small percentage of galaxies in our sample present large
asymmetries. Follow-up high resolution VLA maps give insight into the origin of
such asymmetries.Comment: 4 pages, 2 figures, Conference 'Galaxies in Isolation: Exploring
Nature vs. Nurture', Granada, 12-15 May 2009. To be published in the ASP
Conference Serie
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
CD1d-dependent immune suppression mediated by regulatory B cells through modulations of iNKT cells
Regulatory B cells (Breg) express high levels of CD1d that presents lipid antigens to invariant natural killer T (iNKT) cells. The function of CD1d in Breg biology and iNKT cell activity during inflammation remains unclear. Here we show, using chimeric mice, cell depletion and adoptive cell transfer, that CD1dâlipid presentation by Bregs induces iNKT cells to secrete interferon (IFN)-Îł to contribute, partially, to the downregulation of T helper (Th)1 and Th17-adaptive immune responses and ameliorate experimental arthritis. Mice lacking CD1d-expressing B cells develop exacerbated disease compared to wild-type mice, and fail to respond to treatment with the prototypical iNKT cell agonist α-galactosylceramide. The absence of lipid presentation by B cells alters iNKT cell activation with disruption of metabolism regulation and cytokine responses. Thus, we identify a mechanism by which Bregs restrain excessive inflammation via lipid presentation
A Search for Kinematic Evidence of Radial Gas Flows in Spiral Galaxies
CO and HI velocity fields of seven nearby spiral galaxies, derived from
radio-interferometric observations, are decomposed into Fourier components
whose radial variation is used to search for evidence of radial gas flows.
Additional information provided by optical or near-infrared isophotes is also
considered, including the relationship between the morphological and kinematic
position angles. To assist in interpreting the data, we present detailed
modeling that demonstrates the effects of bar streaming, inflow, and a warp on
the observed Fourier components. We find in all of the galaxies evidence for
either elliptical streaming or a warped disk over some range in radius, with
deviations from pure circular rotation at the level of ~20-60 km/s. Evidence
for kinematic warps is observed in several cases well inside R_{25}. No
unambiguous evidence for radial inflows is seen in any of the seven galaxies,
and we are able to place an upper limit of ~5-10 km/s (3-5% of the circular
speed) on the magnitude of any radial inflow in the inner regions of NGC 4414,
5033 and 5055. We conclude that the inherent non-axisymmetry of spiral galaxies
is the greatest limitation to the direct detection of radial inflows.Comment: 22 emulateapj pages with bitmapped colour figures, to appear in ApJ
(April 2004). For full resolution figures go to
http://www.atnf.csiro.au/people/twong/preprints
Is dark matter present in NGC4736? An iterative spectral method for finding mass distribution in spiral galaxies
An iterative method for reconstructing mass distribution in spiral galaxies
using a thin disk approximation is developed. As an example, the method is
applied to galaxy NGC 4736; its rotation curve does not allow one to employ a
model with a massive spherical halo. We find a global mass distribution in this
galaxy (without non-baryonic dark matter) that agrees perfectly with the high
resolution rotation curve of the galaxy. This mass distribution is consistent
with the -band luminosity profile with the mean mass-to-light ratio
, and also agrees with the amount of hydrogen observed in the
outermost regions of the galaxy. We predict the total mass of the galaxy to be
only 3.43\times10^{10}M_{\sun}. It is very close to the value predicted by
the modified gravity models and much less than the currently accepted value of
5.0\times10^{10}M_{\sun} (with of the mass in a dark matter
halo).Comment: in v2 version: 1) changed the reference luminosities of the Sun in
different bands - this affects mass-to-light ratio, giving more reliable 1.2
in the I-band, 2) found typos corrected, 3) corrected references to
literature, figures and equations 4) text permutations + language
corrections, accepted for publication in ApJ, May 200
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