779 research outputs found
A study of the relationship between a child's achievement and adjustment in grades one and three.
Thesis (Ed.M.)--Boston Universit
A Survey for HO Megamasers in Active Galactic Nuclei -- II. A Comparison of Detected and Undetected Galaxies
A survey for H2O megamaser emission from 354 active galaxies has resulted in
the detection of 10 new sources, making 16 known altogether. The galaxies
surveyed include a distance-limited sample (covering Seyferts and LINERs with
recession velocities < 7000 km s^{-1}) and a magnitude-limited sample (covering
Seyferts and LINERs with m(B) <= 14.5). In order to determine whether the
H2O-detected galaxies are "typical" AGN or have special properties which
facilitate the production of powerful masers, we have accumulated a database of
physical, morphological, and spectroscopic properties of the observed galaxies.
The most significant finding is that H2O megamasers are detected only in
Seyfert 2 and LINER galaxies, not Seyfert 1s. Implications for this finding are
discussed. LINERs are detected at a similar rate to Seyfert 2s, constituting a
strong argument that at least some nuclear LINERs are AGN rather than
starbursts, since starbursts have not been detected as H2O megamasers. We
preferentially detect H2O emission from the nearer galaxies and from those
which are apparently brighter at mid- and far-infrared and centimeter radio
wavelengths. There is also a possible trend for the H2O-detected galaxies to be
more intrinsically luminous in nuclear 6 cm radio emission than the undetected
ones, though these data are incomplete. We find evidence that Seyfert 2s with
very high (N(H) > 10^{24} cm^{-2}) X-ray absorbing columns of gas are more
often detected as H2O maser emitters than Seyfert 2s with lower columns. It may
be that the probability of detecting H2O maser emission in Seyfert galaxies
increases with increasing column of cool gas to the nucleus, from Seyfert 1s
through NLXGs to Seyfert 2s.Comment: 19 pages, 35 figures, 3 of the tables are contained in separate LaTeX
files: Table 1-a, 1-b, and 3. Also, figure captions are contained in a
separate file which must be compiled with plain TeX, not LaTe
Update on the Surgical Trial in Lobar Intracerebral Haemorrhage (STICH II):Statistical analysis plan
<p>Abstract</p> <p>Background</p> <p>Previous studies had suggested that the outcome for patients with spontaneous lobar intracerebral haemorrhage (ICH) and no intraventricular haemorrhage (IVH) might be improved with early evacuation of the haematoma. The Surgical Trial in Lobar Intracerebral Haemorrhage (STICH II) set out to establish whether a policy of earlier surgical evacuation of the haematoma in selected patients with spontaneous lobar ICH would improve outcome compared to a policy of initial conservative treatment. It is an international, multi-centre, prospective randomised parallel group trial of early surgery in patients with spontaneous lobar ICH. Outcome is measured at six months via a postal questionnaire.</p> <p>Results</p> <p>Recruitment to the study began on 27 November 2006 and closed on 15 August 2012 by which time 601 patients had been recruited. The protocol was published in <it>Trials</it> (<url>http://www.trialsjournal.com/content/12/1/124/</url>). This update presents the analysis plan for the study without reference to the unblinded data. The trial data will not be unblinded until after follow-up is completed in early 2013. The main trial results will be presented in spring 2013 with the aim to publish in a peer-reviewed journal at the same time.</p> <p>Conclusion</p> <p>The data from the trial will provide evidence on the benefits and risks of early surgery in patients with lobar ICH.</p> <p>Trial registration</p> <p>ISRCTN: ISRCTN22153967</p
Expansion of airway basal epithelial cells from primary human non-small cell lung cancer tumors
Pre-clinical non-small cell lung cancer (NSCLC) models are poorly representative of the considerable inter- and intra-tumor heterogeneity of the disease in patients. Primary cell-based in vitro models of NSCLC are therefore desirable for novel therapy development and personalized cancer medicine. Methods have been described to generate rapidly proliferating epithelial cell cultures from multiple human epithelia using 3T3-J2 feeder cell culture in the presence of Y-27632, a RHO-associated protein kinase (ROCK) inhibitor, in what are known as "conditional reprograming conditions" (CRC) or 3T3+Y. In some cancer studies, variations of this methodology have allowed primary tumor cell expansion across a number of cancer types but other studies have demonstrated the preferential expansion of normal epithelial cells from tumors in such conditions. Here, we report our experience regarding the derivation of primary NSCLC cell cultures from 12 lung adenocarcinoma patients enrolled in the Tracking Cancer Evolution through Therapy (TRACERx) clinical study and discuss these in the context of improving the success rate for in vitro cultivation of cells from NSCLC tumors. This article is protected by copyright. All rights reserved
HI Narrow Self-Absorption in Dark Clouds: Correlations with Molecular Gas and Implications for Cloud Evolution and Star Formation
We present the results of a comparative study of HI narrow self-absorption
(HINSA), OH, 13CO, and C18O in five dark clouds. The HINSA follows the
distribution of the emission of the carbon monoxide isotopologues, and has a
characteristic size close to that of 13CO. This confirms that the HINSA is
produced by cold HI which is well mixed with molecular gas in well-shielded
regions. The ratio of the atomic hydrogen density to total proton density for
these sources is 5 to 27 x 10^{-4}. Using cloud temperatures and the density of
HI, we set an upper limit to the cosmic ray ionization rate of 10^{-16} s^{-1}.
Comparison of observed and modeled fractional HI abundances indicates ages for
these clouds to be 10^{6.5} to 10^{7} yr. The low values of the HI density we
have determined make it certain that the time scale for evolution from an
atomic to an almost entirely molecular phase, must be a minimum of several
million years. This clearly sets a lower limit to the overall time scale for
star formation and the lifetime of molecular clouds
AzTEC millimeter survey of the COSMOS field - III. Source catalog over 0.72 sq. deg. and plausible boosting by large-scale structure
We present a 0.72 sq. deg. contiguous 1.1mm survey in the central area of the
COSMOS field carried out to a 1sigma ~ 1.26 mJy/beam depth with the AzTEC
camera mounted on the 10m Atacama Submillimeter Telescope Experiment (ASTE). We
have uncovered 189 candidate sources at a signal-to-noise ratio S/N >= 3.5, out
of which 129, with S/N >= 4, can be considered to have little chance of being
spurious (< 2 per cent). We present the number counts derived with this survey,
which show a significant excess of sources when compared to the number counts
derived from the ~0.5 sq. deg. area sampled at similar depths in the Scuba HAlf
Degree Extragalactic Survey (SHADES, Austermann et al. 2010). They are,
however, consistent with those derived from fields that were considered too
small to characterize the overall blank-field population. We identify
differences to be more significant in the S > 5 mJy regime, and demonstrate
that these excesses in number counts are related to the areas where galaxies at
redshifts z < 1.1 are more densely clustered. The positions of optical-IR
galaxies in the redshift interval 0.6 < z < 0.75 are the ones that show the
strongest correlation with the positions of the 1.1mm bright population (S > 5
mJy), a result which does not depend exclusively on the presence of rich
clusters within the survey sampled area. The most likely explanation for the
observed excess in number counts at 1.1mm is galaxy-galaxy and galaxy-group
lensing at moderate amplification levels, that increases in amplitude as one
samples larger and larger flux densities. This effect should also be detectable
in other high redshift populations.Comment: 21 pages, 17 figures, accepted for publication in MNRA
Are CO lines good indicators of the star formation rate in galaxies?
In this paper, we investigate the relevance of using the CO line
emissions as indicators of star formation rates (SFR). For the first time, we
present this study for a relatively large number of CO transitions (12)
as well as over a large interval in redshift (from z0 to z6). For
the nearby sources (D10 Mpc), we have used homogeneous sample of
CO data provided by Bayet et al. (2004, 2006), mixing observational and
modelled line intensities. For higher-z sources (z 1), we have collected
CO observations from various papers and have completed the data set of
line intensities with model predictions which we also present in this paper.
Finally, for increasing the statistics, we have included recent CO(1-0)
and CO(3-2) observations of intermediate-z sources. Linear regressions
have been calculated for identifying the tightest SFR-CO line luminosity
relationships. We show that the \emph{total} CO, the CO(5-4), the
CO(6-5) and the CO(7-6) luminosities are the best indicators of
SFR (as measured by the far-infrared luminosity). Comparisons with theoretical
approaches from Krumholz and Thompson (2007) and Narayanan et al. (2008) are
also performed in this paper. Although in general agreement, the predictions
made by these authors and the observational results we present here show small
and interesting discrepancies. In particular, the slope of the linear
regressions, for J 4 CO lines are not similar between
theoretical studies and observations. On one hand, a larger high-J CO
data set of observations might help to better agree with models, increasing the
statistics. On the other hand, theoretical studies extended to high redshift
sources might also reduce such discrepancies.Comment: 10 pages, 3 figures and 4 tables, Accepted in MNRA
An ultraviolet-selected galaxy redshift survey - III: Multicolour imaging and non-uniform star formation histories
(abridged) We present panoramic u' and optical ground-based imaging
observations of a complete sample of low-redshift (0<z<0.4) galaxies selected
in the ultraviolet (UV) at 2000A using the balloon-borne FOCA instrument of
Milliard et al. This survey is highly sensitive to newly-formed massive stars,
and hence to actively star-forming galaxies. We use the new data to further
investigate the stellar population and star formation properties of this
sample. When combined with our earlier spectroscopic surveys, these new data
allow us to compare star-formation measures derived from aperture-corrected Ha
line fluxes, UV(2000A) and u'(3600A) continuum fluxes on a galaxy-by-galaxy
basis. As expected from our earlier studies, we find broad correlations between
the dust-corrected star-formation diagnostics, though the scatter is larger
than that from observational errors, with significant offsets from trends
expected according to simple star-formation history (SFH) models. Varying
metallicities and/or initial mass functions seem unable to explain the observed
discrepancies. We investigate the star-formation properties further by
modelling the observed spectroscopic and photometric properties of the galaxies
in our survey. Nearly half of the galaxies surveyed possess features that
appear incompatible with simple constant or smoothly declining SFHs, favouring
instead irregular or temporally-varying SFHs. We demonstrate how this can
reconcile the majority of our observations, and determine empirical corrections
to calculate intrinsic star formation rates from measures based on UV (or u')
observations alone. We discuss the broader implications of our finding that a
significant fraction of star-forming galaxies have complex SFHs, particularly
in the context of recent determinations of the cosmic SFH.Comment: MNRAS; post-referee report version. 16 pages, 10 figure
Linking radio to infrared: a radio source count model
We investigate the populations and evolution of normal and active galaxies by
extending the infrared source count model of Rowan-Robinson (2001) into the
radio. The FIR-radio correlation is used to extend the SEDs to the radio region
and it is assumed that there are two distinct populations of quasar: radio loud
and radio quiet. It is found that the radio luminosity function and source
count data are best fit when the fraction of quasars that are radio loud is
allowed to increase with optical luminosity. This implications for this are
discussed, as are the possible causes for the variation in radio loud fraction.Comment: 9 pages (TeX file), 9 figures (eps format), submitted to MNRAS and
corrected for referee's comment
Mapping the cold dust temperatures and masses of nearby Kingfish galaxies with Herschel
Taking advantage of the sensitivity and angular resolution of the Herschel
Space Observatory at far-infrared and submm wavelengths, we aim to characterize
the physical properties of cold dust within nearby galaxies and study the
robustness of the parameters we derive using different modified blackbody
models. For a pilot subsample of the KINGFISH program, we perform 2 temperature
fits of the Spitzer and Herschel photometric data (24 to 500um), with a warm
and a cold component, globally and in each resolution element.At global scales,
we observe ranges of values for beta_c(0.8 to 2.5) and Tc(19.1 to 25.1K).We
compute maps of our parameters with beta fixed or free to test the robustness
of the temperature and dust surface density maps we deduce. When the emissivity
is fixed, we observe temperature gradients as a function of radius.When the
emissivity is fitted as a free parameter, barred galaxies tend to have uniform
fitted emissivities.Gathering resolved elements in a Tc-beta_c diagram
underlines an anti-correlation between the two parameters.It remains difficult
to assess whether the dominant effect is the physics of dust grains, noise, or
mixing along the line of sight and in the beam. We finally observe in both
cases that the dust column density peaks in central regions of galaxies and bar
ends (coinciding with molecular gas density enhancements usually found in these
locations).We also quantify how the total dust mass varies with our assumptions
about the emissivity index as well as the influence of the wavelength coverage
used in the fits. We show that modified blackbody fits using a shallow
emissivity (beta_c < 2.0) lead to significantly lower dust masses compared to
the beta_c < 2.0 case, with dust masses lower by up to 50% if beta_c=1.5 for
instance.The working resolution affects our total dust mass estimates: masses
increase from global fits to spatially-resolved fits.Comment: 26 pages, 12 figures, 4 tables, accepted for publication in MNRAS,
2012 June 2
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