60 research outputs found
Effective Immersive Analytics for Everyday Use
Data visualization is an important field of work that takes in uncountable amounts of indexes to create an easy-to-read interpretation of what was previously unreadable. Immersive analytics is the new field that brings 3D data visualization to virtual reality, immersing users directly into the data. Focusing on bringing humans and computers closer together through natural function can benefit the world of data science. In order to accurately utilize this field to benefit this world, principles must be laid out and observed to see which techniques and methods are best fit for an everyday immersive analytics platform. Our findings show that, within an immersive 3D environment, users that perform in a static state where no physical or virtual navigation of the environment is present is more beneficial to the interpretation of the data. While reported gender identity does not seem to affect the time to complete the given task, it seems the age of a given participant is one factor which affects the task time
About the nature of Mercer14
We used UKIRT near infrared (NIR) broad band JHK photometry, narrow band
imaging of the 1-0S(1) molecular hydrogen emission line and mid infrared
Spitzer IRAC data to investigate the nature of the young cluster Mercer14.
Foreground star counts in decontaminated NIR photometry and a comparison with
the Besancon Galaxy Model are performed to estimate the cluster distance. This
method yields a distance of 2.5kpc with an uncertainty of about 10% and can be
applied to other young and embedded clusters. Mercer14 shows clear signs of
ongoing star formation with several detected molecular hydrogen outflows, a
high fraction of infrared excess sources and an association to a small gas and
dust cloud. Hence, the cluster is less than 4Myrs old and has a line of sight
extinction of A_K=0.8mag. Based on the most massive cluster members we find
that Mercer14 is an intermediate mass cluster with about 500Mo.Comment: 10pages, 2tables, 5figures, accepted for publication by MNRAS, a
version with higher resolution figures can be found at
http://astro.kent.ac.uk/~df
Modeling the Effects of Star Formation Histories on Halpha and Ultra-Violet Fluxes in Nearby Dwarf Galaxies
We consider the effects of non-constant star formation histories (SFHs) on
Halpha and GALEX far ultra-violet (FUV) star formation rate (SFR) indicators.
Under the assumption of a fully populated Chabrier IMF, we compare the
distribution of Halpha-to-FUV flux ratios from ~ 1500 simple, periodic model
SFHs with observations of 185 galaxies from the Spitzer Local Volume Legacy
survey. We find a set of SFH models that are well matched to the data, such
that more massive galaxies are best characterized by nearly constant SFHs,
while low mass systems experience bursts amplitudes of ~ 30 (i.e., an increase
in the SFR by a factor of 30 over the SFR during the inter-burst period), burst
durations of tens of Myr, and periods of ~ 250 Myr; these SFHs are broadly
consistent with the increased stochastic star formation expected in systems
with lower SFRs. We analyze the predicted temporal evolution of galaxy stellar
mass, R-band surface brightness, Halpha-derived SFR, and blue luminosity, and
find that they provide a reasonable match to observed flux distributions. We
find that our model SFHs are generally able to reproduce both the observed
systematic decline and increased scatter in Halpha-to-FUV ratios toward low
mass systems, without invoking other physical mechanisms. We also compare our
predictions with those from the Integrated Galactic IMF theory with a constant
SFR. We find that while both predict a systematic decline in the observed
ratios, only the time variable SFH models are capable of producing the observed
population of low mass galaxies ( < 10 Msun) with normal
Halpha-to-FUV ratios. These results demonstrate that a variable IMF alone has
difficulty explaining the observed scatter in the Halpha-to-FUV ratios. We
conclude by considering the limitations of the model SFHs, and discuss the use
of additional empirical constraints to improve future SFH modeling efforts.Comment: 15 pages, 11 Figures. Accepted for publication in Ap
A GALEX Ultraviolet Imaging Survey of Galaxies in the Local Volume
We present results from a GALEX ultraviolet (UV) survey of a complete sample
of 390 galaxies within ~11 Mpc of the Milky Way. The UV data are a key
component of the composite Local Volume Legacy (LVL), an
ultraviolet-to-infrared imaging program designed to provide an inventory of
dust and star formation in nearby spiral and irregular galaxies. The ensemble
dataset is an especially valuable resource for studying star formation in dwarf
galaxies, which comprise over 80% of the sample. We describe the GALEX survey
programs which obtained the data and provide a catalog of far-UV (~1500
Angstroms) and near-UV (~2200 Angstroms) integrated photometry. General UV
properties of the sample are briefly discussed. We compute two measures of the
global star formation efficiency, the SFR per unit HI gas mass and the SFR per
unit stellar mass, to illustrate the significant differences that can arise in
our understanding of dwarf galaxies when the FUV is used to measure the SFR
instead of H-alpha. We find that dwarf galaxies may not be as drastically
inefficient in coverting gas into stars as suggested by prior H-alpha studies.
In this context, we also examine the UV properties of late-type dwarf galaxies
that appear to be devoid of star formation because they were not detected in
previous H-alpha narrowband observations. Nearly all such galaxies in our
sample are detected in the FUV, and have FUV SFRs that fall below the limit
where the H-alpha flux is robust to Poisson fluctuations in the formation of
massive stars. The UV colors and star formation efficiencies of
H-alpha-undetected, UV-bright dwarf irregulars appear to be relatively
unremarkable with respect to those exhibited by the general population of
star-forming galaxies.Comment: submitted to ApJS, revised per referee's comments; accepted Oct. 30
w/o further revision; 37 pages; figure 6 omitted due to size; figure
available from http://users.obs.carnegiescience.edu/jlee/paper
Upper limits on the strength of periodic gravitational waves from PSR J1939+2134
The first science run of the LIGO and GEO gravitational wave detectors
presented the opportunity to test methods of searching for gravitational waves
from known pulsars. Here we present new direct upper limits on the strength of
waves from the pulsar PSR J1939+2134 using two independent analysis methods,
one in the frequency domain using frequentist statistics and one in the time
domain using Bayesian inference. Both methods show that the strain amplitude at
Earth from this pulsar is less than a few times .Comment: 7 pages, 1 figure, to appear in the Proceedings of the 5th Edoardo
Amaldi Conference on Gravitational Waves, Tirrenia, Pisa, Italy, 6-11 July
200
Improving the sensitivity to gravitational-wave sources by modifying the input-output optics of advanced interferometers
We study frequency dependent (FD) input-output schemes for signal-recycling
interferometers, the baseline design of Advanced LIGO and the current
configuration of GEO 600. Complementary to a recent proposal by Harms et al. to
use FD input squeezing and ordinary homodyne detection, we explore a scheme
which uses ordinary squeezed vacuum, but FD readout. Both schemes, which are
sub-optimal among all possible input-output schemes, provide a global noise
suppression by the power squeeze factor, while being realizable by using
detuned Fabry-Perot cavities as input/output filters. At high frequencies, the
two schemes are shown to be equivalent, while at low frequencies our scheme
gives better performance than that of Harms et al., and is nearly fully
optimal. We then study the sensitivity improvement achievable by these schemes
in Advanced LIGO era (with 30-m filter cavities and current estimates of
filter-mirror losses and thermal noise), for neutron star binary inspirals, and
for narrowband GW sources such as low-mass X-ray binaries and known radio
pulsars. Optical losses are shown to be a major obstacle for the actual
implementation of these techniques in Advanced LIGO. On time scales of
third-generation interferometers, like EURO/LIGO-III (~2012), with
kilometer-scale filter cavities, a signal-recycling interferometer with the FD
readout scheme explored in this paper can have performances comparable to
existing proposals. [abridged]Comment: Figs. 9 and 12 corrected; Appendix added for narrowband data analysi
The ACS Nearby Galaxy Survey Treasury II. Young Stars and their Relation to Halpha and UV Emission Timescales in the M81 Outer Disk
We have obtained resolved stellar photometry from Hubble Space Telescope
(HST) Advanced Camera for Surveys (ACS) observations of a field in the outer
disk of M81 as part of the ACS Nearby Galaxy Survey Treasury (ANGST). Motivated
by the recent discovery of extended UV (XUV) disks around many nearby spiral
galaxies, we use the observed stellar population to derive the recent star
formation histories of five ~0.5 kpc-sized regions within this field. These
regions were selected on the basis of their UV luminosity from GALEX and
include two HII regions, two regions which are UV-bright but Halpha-faint, and
one "control" region faint in both UV and Halpha. We estimate our effective SFR
detection limit at ~2 x 10^-4 Msun/yr, which is lower than that of GALEX for
regions of this size. As expected, the HII regions contain massive main
sequence stars (in the mass range 18-27 Msun, based on our best extinction
estimates), while similar massive main sequence stars are lacking in the
UV-bright/Halpha-faint regions. The observations are consistent with stellar
ages 16 Myr in the UV-bright/Halpha-faint
regions. All regions but the control have formed ~10^4 Msun of stars over the
past ~65 Myr. Thus, our results, for at least one small area in the outer disk
of M81, are consistent with an age difference being sufficient to explain the
observed discrepancy between star-forming regions detected in Halpha and those
detected exclusively in UV. However, our data cannot conclusively rule out
other explanations, such as a strongly truncated initial mass function (IMF).Comment: 18 pages, 12 figures, accepted for publication in ApJ, paper with
full resolution figures available:
http://www.nearbygalaxies.org/papers/M81_Halpha_uv.pd
Source clustering in the Hi-GAL survey determined using a minimum spanning tree method
The aims are to investigate the clustering of the far-infrared sources from the Herschel infrared Galactic Plane Survey (Hi-GAL) in the Galactic longitude range of 71 to 67 deg. These clumps, and their spatial distribution, are an imprint of the original conditions within a molecular cloud. This will produce a catalogue of over-densities. Methods. The minimum spanning tree (MST) method was used to identify the over-densities in two dimensions. The catalogue was further refined by folding in heliocentric distances, resulting in more reliable over-densities, which are cluster candidates. Results. We found 1633 over-densities with more than ten members. Of these, 496 are defined as cluster candidates because of the reliability of the distances, with a further 1137 potential cluster candidates. The spatial distributions of the cluster candidates are different in the first and fourth quadrants, with all clusters following the spiral structure of the Milky Way. The cluster candidates are fractal. The clump mass functions of the clustered and isolated are statistically indistinguishable from each other and are consistent with Kroupa’s initial mass function
Primary Xenografts of Human Prostate Tissue as a Model to Study Angiogenesis Induced by Reactive Stroma
Characterization of the mechanism(s) of androgen-driven human angiogenesis could have significant implications for modeling new forms of anti-angiogenic therapies for CaP and for developing targeted adjuvant therapies to improve efficacy of androgen-deprivation therapy. However, models of angiogenesis by human endothelial cells localized within an intact human prostate tissue architecture are until now extremely limited. This report characterizes the burst of angiogenesis by endogenous human blood vessels in primary xenografts of fresh surgical specimens of benign prostate or prostate cancer (CaP) tissue that occurs between Days 6–14 after transplantation into SCID mice pre-implanted with testosterone pellets. The wave of human angiogenesis was preceded by androgen-mediated up-regulation of VEGF-A expression in the stromal compartment. The neo-vessel network anastomosed to the host mouse vascular system between Days 6–10 post-transplantation, the angiogenic response ceased by Day 15, and by Day 30 the vasculature had matured and stabilized, as indicated by a lack of leakage of serum components into the interstitial tissue space and by association of nascent endothelial cells with mural cells/pericytes. The angiogenic wave was concurrent with the appearance of a reactive stroma phenotype, as determined by staining for α-SMA, Vimentin, Tenascin, Calponin, Desmin and Masson's trichrome, but the reactive stroma phenotype appeared to be largely independent of androgen availability. Transplantation-induced angiogenesis by endogenous human endothelial cells present in primary xenografts of benign and malignant human prostate tissue was preceded by induction of androgen-driven expression of VEGF by the prostate stroma, and was concurrent with and the appearance of a reactive stroma phenotype. Androgen-modulated expression of VEGF-A appeared to be a causal regulator of angiogenesis, and possibly of stromal activation, in human prostate xenografts
Antimetastatic activity of a cyclooxygenase-2 inhibitor
Cyclooxygenase-2 (COX-2) expression is increased in breast cancer and surgery has been shown to increase the growth of metastatic tumours. We investigated the effect of selective COX-2 inhibition on the growth of metastases in either an experimental metastasis model or following excision of a murine primary breast tumour. 50,000 4T1 mammary carcinoma cells were injected into the mammary fat pad of female BALB/c mice. When the mean TD reached 8+/-0.4 mm, tumours were excised and the mice were randomised into two groups (n=12 per group) to receive daily intraperitoneal injections of the selective COX-2 inhibitor, SC-236 or drug vehicle for 14 days. Alternatively, experimental metastases were established by tail-vein injection of 50,000 4T1 cells. Mice received either the selective COX-2 inhibitor, SC-236 or drug vehicle for 14 days (n=12 per group). SC-236 treatment significantly reduced tumour burden, the number and size of spontaneous metastases following primary tumour excision. SC-236 treatment also reduced tumour burden, the number and size of experimental metastases. Immunohistochemical staining demonstrated that COX-2 inhibition reduced microvessel density and increased apoptosis within both spontaneous and experimental metastases. These data clearly demonstrate that the selective COX-2 inhibitor, SC-236, has potent antimetastatic activity against both spontaneous metastases arising following primary tumour excision and experimental metastases.</p
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