289 research outputs found
Reconstructing the \gamma-ray Photon Optical Depth of the Universe to z~4 from Multiwavelength Galaxy Survey Data
We reconstruct \gamma-ray opacity of the Universe out to z<3-4 using an
extensive library of 342 observed galaxy luminosity function surveys extending
to high redshifts. We cover the whole range from UV to mid-IR (0.15-25mic)
providing for the first time a robust empirical calculation of the
\gamma\gamma-optical depth out to several TeV. Here, we use the same database
as Helgason et al. 2012 where the EBL was reconstructed from luminosity
functions out to 4.5mic and was shown to recover observed galaxy counts to high
accuracy. We extend our earlier library of LFs to 25mic such that it covers the
energy range of pair production with \gamma-rays 1) in the entire Fermi/LAT
energy range, and 2) at higher TeV energies probed by ground-based Cherenkov
telescopes. In the absence of significant contributions to the cosmic diffuse
background from unknown populations, such as the putative Population III era
sources, the Universe appears to be largely transparent to \gamma-rays at all
Fermi/LAT energies out to z~2 whereas becoming opaque to TeV photons already at
z<0.2 and reaching \tau~10 at z=1. Comparing with the currently available
Fermi/LAT GRB and blazar data shows that there is room for significant
emissions originating in the first stars era.Comment: 5 pages, 5 figures. Published in ApJ Letter
Modeling the evolution of infrared galaxies: A Parametric backwards evolution model
We aim at modeling the infrared galaxy evolution in an as simple as possible
way and reproduce statistical properties among which the number counts between
15 microns and 1.1 mm, the luminosity functions, and the redshift
distributions. We then aim at using this model to interpret the recent
observations (Spitzer, Akari, BLAST, LABOCA, AzTEC, SPT and Herschel), and make
predictions for future experiments like CCAT or SPICA.
This model uses an evolution in density and luminosity of the luminosity
function with two breaks at redshift ~0.9 and 2 and contains the two
populations of the Lagache et al. (2004) model: normal and starburst galaxies.
We also take into account the effect of the strong lensing of high-redshift
sub-millimeter galaxies. It has 13 free parameters and 8 additional calibration
parameters. We fit the parameters to the IRAS, Spitzer, Herschel and AzTEC
measurements with a Monte-Carlo Markov chain.
The model ajusted on deep counts at key wavelengths reproduces the counts
from the mid-infrared to the millimeter wavelengths, as well as the
mid-infrared luminosity functions. We discuss the contribution to the cosmic
infrared background (CIB) and to the infrared luminosity density of the
different populations. We also estimate the effect of the lensing on the number
counts, and discuss the recent discovery by the South Pole Telescope (SPT) of a
very bright population lying at high-redshift. We predict confusion level for
future missions using a P(D) formalism, and the Universe opacity to TeV photons
due to the CIB.Comment: 25 pages, 10 tables, 18 figures, accepted for publication in A&
Spitzer IRS 16 micron Observations of the GOODS Fields
We present Spitzer 16 micron imaging of the Great Observatories Origins Deep
Survey (GOODS) fields. We survey 150 square arcminutes in each of the two GOODS
fields (North and South), to an average 3 sigma depth of 40 and 65 micro-Jy
respectively. We detect about 1300 sources in both fields combined. We validate
the photometry using the 3-24 micron spectral energy distribution of stars in
the fields compared to Spitzer spectroscopic templates. Comparison with ISOCAM
and AKARI observations in the same fields show reasonable agreement, though the
uncertainties are large. We provide a catalog of photometry, with sources cross
correlated with available Spitzer, Chandra, and HST data. Galaxy number counts
show good agreement with previous results from ISOCAM and AKARI, with improved
uncertainties. We examine the 16 to 24 micron flux ratio and find that for most
sources it lies within the expected locus for starbursts and infrared luminous
galaxies. A color cut of S_{16}/S_{24}>1.4 selects mostly sources which lie at
1.1<z<1.6, where the 24 micron passband contains both the redshifted 9.7 micron
silicate absorption and the minimum between PAH emission peaks. We measure the
integrated galaxy light of 16 micron sources, and find a lower limit on the
galaxy contribution to the extragalactic background light at this wavelength to
be 2.2\pm 0.2$ nW m^{-2} sr^{-1}.Comment: Accepted for Publication in the AJ. 53 preprint pages, including 15
figures and 8 tables. Table 1-4 are truncated in the ms.tex but are included
in full in the tar file (and will be available in the online version of the
AJ
A far-infrared spectroscopic survey of intermediate redshift (ultra) luminous infrared galaxies
We present Herschel far-IR photometry and spectroscopy as well as ground-based CO observations of an intermediate redshift (0.21 _ z _ 0.88) sample of Herschel-selected (ultra)-luminous infrared galaxies (LIR >1011.5 L_). With these measurements, we trace the dust continuum, far-IR atomic line emission, in particular [C ii] 157.7μm, as well as the molecular gas of z ∼ 0.3 luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) and perform a detailed investigation of the interstellar medium of the population. We find that the majority of Herschel-selected intermediate redshift (U)LIRGs have LCii/LFIR ratios that are a factor of about 10 higher than that of local ULIRGs and comparable to that of local normal and high-z star-forming galaxies. Using our sample to bridge local and high-z [C ii] observations, we find that the majority of galaxies at all redshifts and all luminosities follow an LCii−LFIR relation with a slope of unity, from which local ULIRGs and high-z active-galactic-nucleus-dominated sources are clear outliers.We also confirm that the strong anti-correlation between the LCii/LFIR ratio and the far-IR color L60/L100 observed in the local universe holds over a broad range of redshifts and luminosities, in the sense that warmer sources exhibit lower LC ii/LFIR at any epoch. Intermediate redshift ULIRGs are also characterized by large molecular gas reservoirs and by lower star formation efficiencies compared to that of local ULIRGs. The high LC ii/LFIR ratios, the moderate star formation efficiencies (LIR/L _COor LIR/MH2 ), and the relatively low dust temperatures of our sample (which are also common characteristics of high-z star-forming galaxies with ULIRG-like luminosities) indicate that the evolution of the physical properties of (U)LIRGs between the present day and z > 1 is already significant by z ∼ 0.3
Defining and analysing symptom palliation in cancer clinical trials: a deceptively difficult exercise
The assessment of symptom palliation is an essential component of many treatment comparisons in clinical trials, yet an extensive literature search revealed no consensus as to its precise definition, which could embrace relief of symptoms, time to their onset, duration, degree, as well as symptom control and prevention. In an attempt to assess the importance of these aspects and to compare different methods of analysis, we used one symptom (cough) from a patient self-assessment questionnaire (the Rotterdam Symptom Checklist) in a large (>300 patient) multicentre randomized clinical trial (conducted by the Medical Research Council Lung Cancer Working Party) of palliative chemotherapy in small-cell lung cancer. The regimens compared were a two-drug regimen (2D) and a four-drug regimen (4D). No differences were seen between the regimens in time of onset of palliation or its duration. The degree of palliation was strongly related to the initial severity: 90% of the patients with moderate or severe cough at baseline reported improvement, compared with only 53% of those with mild cough. Analyses using different landmark time points gave conflicting results: the 4D regimen was superior at 1 month and at 3 months, whereas at 2 months the 2D regimen appeared superior. When improvement at any time up to 3 months was considered, the 4D regimen showed a significant benefit (4D 79%, 2D 60%, P = 0.02). These findings emphasize the need for caution in interpreting results, and the importance of working towards a standard definition of symptom palliation. The current lack of specified criteria makes analysis and interpretation of trial results difficult, and comparison across trials impossible. A standard definition of palliation for use in the analysis of clinical trials data is proposed, which takes into account aspects of onset, duration and degree of palliation, and symptom improvement, control and prevention. © 1999 Cancer Research Campaig
Semi-analytic modeling of the EBL and consequences for extragalactic gamma-ray spectra
Attenuation of high-energy gamma rays by pair-production with UV, optical and
IR extragalactic background light (EBL) photons provides a link between the
history of galaxy formation and high-energy astrophysics. We present results
from our latest semi-analytic models (SAMs), which employ the main ingredients
thought to be important to galaxy formation and evolution, as well as an
improved model for reprocessing of starlight by dust to mid- and far-IR
wavelengths. These SAMs are based upon a Lambda-CDM hierarchical structural
formation scenario, and are successful in reproducing a large variety of
observational constraints such as number counts, luminosity and mass functions,
and color bimodality. Our fiducial model is based upon a WMAP5 cosmology, and
treats dust emission using empirical templates. This model predicts a
background flux considerably lower than optical and near-IR measurements that
rely on subtraction of zodiacal and galactic foregrounds, and near the lower
bounds set by number counts of resolvable sources at a large number of
wavelengths. We also show the results of varying cosmological parameters and
dust attenuation model used in our SAM. For each EBL prediction, we show how
the optical depth due to electron-positron pair-production is affected by
redshift and gamma-ray energy, and the effect of gamma-ray absorption on the
spectra of a variety of extragalactic sources. We conclude with a discussion of
the implications of our work, comparisons to other models and key measurements
of the EBL and a discussion of how the burgeoning science of gamma-ray
astronomy will continue to help constrain cosmology. The low EBL flux predicted
by our fiducial model suggests an optimistic future for further studies of
distant gamma-ray sources.Comment: 23 pages, 11 figures, 3 tables, accepted by MNRAS; this preprint
matches accepted versio
Galaxy Properties from the Ultra-violet to the Far-Infrared: Lambda-CDM models confront observations
We combine a semi-analytic model of galaxy formation with simple analytic
recipes describing the absorption and re-emission of starlight by dust in the
interstellar medium of galaxies. We use the resulting models to predict galaxy
counts and luminosity functions from the far-ultraviolet to the sub-mm, from
redshift five to the present, and compare with an extensive compilation of
observations. We find that in order to reproduce the rest-UV and optical
luminosity functions at high redshift, we must assume an evolving normalization
in the dust-to-metal ratio, implying that galaxies of a given bolometric
luminosity (or metal column density) must be less extinguished than their local
counterparts. In our best-fit model, we find remarkably good agreement with
observations from rest-frame 1500 Angstroms to 250 microns. At longer
wavelengths, most dramatically in the sub-mm, our models underpredict the
number of bright galaxies by a large factor. The models reproduce the observed
total IR luminosity function fairly well. We show the results of varying
several ingredients of the models, including various aspects of the dust
attenuation recipe, the dust emission templates, and the cosmology. We use our
models to predict the integrated Extragalactic Background Light (EBL), and
compare with an observationally-motivated EBL model and with other available
observational constraints.Comment: 27 pages, 17 figures, 1 table, accepted to MNRAS, this version
matches accepted manuscrip
Risk perception after genetic counseling in patients with increased risk of cancer
<p>Abstract</p> <p>Background</p> <p>Counselees are more aware of genetics and seek information, reassurance, screening and genetic testing. Risk counseling is a key component of genetic counseling process helping patients to achieve a realistic view for their own personal risk and therefore adapt to the medical, psychological and familial implications of disease and to encourage the patient to make informed choices <abbrgrp><abbr bid="B1">1</abbr><abbr bid="B2">2</abbr></abbrgrp>.</p> <p>The aim of this study was to conceptualize risk perception and anxiety about cancer in individuals attending to genetic counseling.</p> <p>Methods</p> <p>The questionnaire study measured risk perception and anxiety about cancer at three time points: before and one week after initial genetic counseling and one year after completed genetic investigations. Eligibility criteria were designed to include only index patients without a previous genetic consultation in the family. A total of 215 individuals were included. Data was collected during three years period.</p> <p>Results</p> <p>Before genetic counseling all of the unaffected participants subjectively estimated their risk as higher than their objective risk. Participants with a similar risk as the population overestimated their risk most. All risk groups estimated the risk for children's/siblings to be lower than their own. The benefits of preventive surveillance program were well understood among unaffected participants.</p> <p>The difference in subjective risk perception before and directly after genetic counseling was statistically significantly lower in all risk groups. Difference in risk perception for children as well as for population was also statistically significant. Experienced anxiety about developing cancer in the unaffected subjects was lower after genetic counseling compared to baseline in all groups. Anxiety about cancer had clear correlation to perceived risk of cancer before and one year after genetic investigations.</p> <p>The affected participants overestimated their children's risk as well as risk for anyone in population. Difference in risk perception for children/siblings as for the general population was significant between the first and second measurement time points. Anxiety about developing cancer again among affected participants continued to be high throughout this investigation.</p> <p>Conclusion</p> <p>The participant's accuracy in risk perception was poor, especially in low risk individuals before genetic counseling. There was a general trend towards more accurate estimation in all risk groups after genetic counseling. The importance of preventive programs was well understood. Cancer anxiety was prevalent and associated with risk perception, but decreased after genetic counseling.</p> <p><abbrgrp><abbr bid="B1">1</abbr></abbrgrp> National Society of Genetic Counselors (2005), Genetic Counseling as a Profession. Available at <url>http://www.nsgc.org/about/definition.cfm</url> (accessed November 25th 2007)</p> <p><abbrgrp><abbr bid="B2">2</abbr></abbrgrp> Julian-Reynier C., Welkenhuysen M-, Hagoel L., Decruyenaere M., Hopwood P. (2003) Risk communication strategies: state of the art and effectiveness in the context of cancer genetic services. Eur J of Human Genetics 11, 725736.</p
Highly variable iron content modulates iceberg-ocean fertilisation and potential carbon export
Marine phytoplankton growth at high latitudes is extensively limited by iron availability. Icebergs are a vector transporting the bioessential micronutrient iron into polar oceans. Therefore, increasing iceberg fluxes due to global warming have the potential to increase marine productivity and carbon export, creating a negative climate feedback. However, the magnitude of the iceberg iron flux, the subsequent fertilization effect and the resultant carbon export have not been quantified. Using a global analysis of iceberg samples, we reveal that iceberg iron concentrations vary over 6 orders of magnitude. Our results demonstrate that, whilst icebergs are the largest source of iron to the polar oceans, the heterogeneous iron distribution within ice moderates iron delivery to offshore waters and likely also affects the subsequent ocean iron enrichment. Future marine productivity may therefore be not only sensitive to increasing total iceberg fluxes, but also to changing iceberg properties, internal sediment distribution and melt dynamics
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