3,797 research outputs found
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Warm dark matter as a solution to the small scale crisis: New constraints from high redshift Lyman-α forest data
We present updated constraints on the free-streaming of warm dark matter
(WDM) particles derived from an analysis of the Lya flux power spectrum
measured from high-resolution spectra of 25 z > 4 quasars obtained with the
Keck High Resolution Echelle Spectrometer (HIRES) and the Magellan Inamori
Kyocera Echelle (MIKE) spectrograph. We utilize a new suite of high-resolution
hydrodynamical simulations that explore WDM masses of 1, 2 and 4 keV (assuming
the WDM consists of thermal relics), along with different physically motivated
thermal histories. We carefully address different sources of systematic error
that may affect our final results and perform an analysis of the Lya flux power
with conservative error estimates. By using a method that samples the
multi-dimensional astrophysical and cosmological parameter space, we obtain a
lower limit mwdm > 3.3 keV (2sigma) for warm dark matter particles in the form
of early decoupled thermal relics. Adding the Sloan Digital Sky Survey (SDSS)
Lya flux power spectrum does not improve this limit. Thermal relics of masses 1
keV, 2 keV and 2.5 keV are disfavoured by the data at about the 9sigma, 4sigma
and 3sigma C.L., respectively. Our analysis disfavours WDM models where there
is a suppression in the linear matter power spectrum at (non-linear) scales
corresponding to k=10h/Mpc which deviates more than 10% from a LCDM model.
Given this limit, the corresponding "free-streaming mass" below which the mass
function may be suppressed is 2x10^8 Msun/h. There is thus very little room for
a contribution of the free-streaming of WDM to the solution of what has been
termed the small scale crisis of cold dark matter
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A consistent determination of the temperature of the intergalactic medium at redshift (z) = 2.4
We present new measurements of the thermal state of the intergalactic medium
(IGM) at derived from absorption line profiles in the Ly
forest. We use a large set of high-resolution hydrodynamical simulations to
calibrate the relationship between the temperature-density (--)
relation in the IGM and the distribution of HI column densities, ,
and velocity widths, , of discrete Ly forest absorbers.
This calibration is then applied to the measurement of the lower cut-off of the
-- distribution recently presented by Rudie et al.
(2012). We infer a power-law -- relation,
, with a temperature at mean density,
and slope
. The slope is fully consistent with that advocated by
the analysis of Rudie et al (2012); however, the temperature at mean density is
lower by almost a factor of two, primarily due to an adjustment in the
relationship between column density and physical density assumed by these
authors. These new results are in excellent agreement with the recent
temperature measurements of Becker et al. (2011), based on the curvature of the
transmitted flux in the Ly forest. This suggests that the thermal state
of the IGM at this redshift is reasonably well characterised over the range of
densities probed by these methods
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A z = 3.045 Lyα emitting halo hosting a QSO and a possible candidate for AGN-triggered star formation
In this third paper in a series on the nature of extended, asymmetric Lyman
alpha emitters at z ~ 3 we report the discovery, in an ultra-deep, blind,
spectroscopic long-slit survey, of a Lyman alpha emitting halo around a QSO at
redshift 3.045. The QSO is a previously known, obscured AGN. The halo appears
extended along the direction of the slit and exhibits two faint patches
separated by 17 proper kpc in projection from the QSO. Comparison of the
2-dimensional spectrum with archival HST ACS images shows that these patches
coincide spatially with emission from a peculiar, dumbbell-shaped, faint
galaxy. The assumptions that the Lyman alpha emission patches are originating
in the galaxy and that the galaxy is physically related to the QSO are at
variance with photometric estimates of the galaxy redshift. We show, however,
that a population of very young stars at the redshift of the QSO may fit the
existing rest frame broad band UV photometry of the galaxy. If this scenario is
correct then the symmetry of the galaxy in continuum and Lyman alpha emission,
the extension of the QSO's Lyman alpha emission in its direction, and the
likely presence of a young stellar population in close proximity to a
(short-lived) AGN suggest that this may be an example of AGN feedback
triggering external star formation in high redshift galaxies
The photoheating of the intergalactic medium in synthesis models of the UV background
We compare cosmological hydrodynamical simulations combined with the
homogeneous metagalactic UV background (UVB) of Haardt & Madau (2012) (HM2012)
to observations of the Lyman-alpha forest that are sensitive to the thermal and
ionization state of the intergalactic medium (IGM). The transition from
optically thick to thin photoheating predicted by the simple one-zone,
radiative transfer model implemented by HM2012 predicts a thermal history that
is in remarkably good agreement with the observed rise of the IGM temperature
at z~3 if we account for the expected evolution of the volume filling factor of
HeIII. Our simulations indicate that there may be, however, some tension
between the observed peak in the temperature evolution and the rather slow
evolution of the HeII opacities suggested by recent Hubble Space Telescope/COS
measurements. The HM2012 UVB also underpredicts the metagalactic hydrogen
photoionization rate required by our simulations to match the observed opacity
of the forest at z>4 and z<2
Clinicopathological factors influencing outcome in metastatic colorectal cancer patients treated with fluoropyrimidine and bevacizumab maintenance treatment vs observation: an individual patient data meta-analysis of two phase 3 trials
BACKGROUND:
The CAIRO3 and AIO 0207 trials demonstrated the efficacy of fluoropyrimidine plus bevacizumab (FP+Bev) maintenance treatment in metastatic colorectal cancer (mCRC) patients. In this individual patient data meta-analysis with updated follow-up, we aim to provide more precise estimates of treatment effects and to identify subgroups that benefit most from maintenance treatment or observation.
METHODS:
In 871 patients, randomised to FP+Bev maintenance treatment or observation, we investigated whether treatment effect was modified by sex, age, performance status, response to induction treatment, primary tumour location, number of metastatic sites, disease stage and primary tumour resection, serum LDH, platelet count, CEA, and RAS/BRAF mutation status. Primary end point was time to second progression after reintroduction of the induction regimen (PFS2). Secondary end points were first progression-free survival (PFS1) and overall survival (OS).
RESULTS:
At a median follow-up of 68.5 months (IQR 54.6-87.0 months), maintenance treatment was more effective compared with observation in PFS1 (HR 0.40(95% CI 0.34-0.47)) and PFS2 (HR 0.70(0.60-0.81)). No subgroups were identified that did not benefit from maintenance treatment in PFS1 and PFS2; no clinically relevant subgroup effects were observed. Regarding OS, pooled results were not significant (HR 0.91(0.78-1.05)), and the trials showed marked heterogeneity in overall treatment effect and subgroup effects.
CONCLUSIONS:
FP+Bev maintenance treatment is effective in all patients, regardless of the investigated subgroups.info:eu-repo/semantics/publishedVersio
Microalgae production in fresh market wastewater and its utilization as a protein substitute in formulated fish feed for oreochromis spp.
Rapid growing of human population has led to increasing demand of aquaculture production. Oreochromis niloticus or known as tilapia is one of the most globally cultured freshwater fish due to its great adaptation towards extreme environment. Besides, farming of tilapia not only involves small scales farming for local consumption but also larger scales for international market which contributes to a foreign currency earning. Extensive use of fishmeal as feed for fish and for other animals indirectly caused an increasing depletion of the natural resource and may consequently cause economic and environmental unstable. Microalgae biomass seems to be a promising feedstock in aquaculture industry. It can be used for many purposes such as live food for fish larvae and dried microalgae to substitute protein material in fish feed. The microalgae replacement in fish feed formulation as protein alternative seem potentially beneficial for long term aqua-business sustainability. The present chapter discussed the potential of microalgae as an alternative nutrition in fish feed formulations, specifically Tilapia
Natalizumab in acute ischemic stroke (ACTION II): a randomized, placebo-controlled trial
OBJECTIVE: We evaluated the effect of two doses of natalizumab on functional outcomes in acute ischemic stroke (AIS) patients. METHODS: In this double-blind phase 2b trial, AIS patients aged 18-80 years with National Institutes of Health Stroke Scale scores of 5-23 from 53 US and European sites were randomized 1:1:1 to receive a single dose of 300 or 600 mg intravenous natalizumab or placebo, with randomization stratified by treatment window (≤9 or >9 to ≤24 hours from patient's last known normal state). The primary endpoint was a composite measure of excellent outcome (modified Rankin Scale score ≤1 and Barthel Index score ≥95) at day 90 assessed in all patients receiving a full dose. Sample size was estimated from a Bayesian model; p values were not used for hypothesis testing. RESULTS: An excellent outcome was less likely with natalizumab than with placebo (natalizumab 300 mg or 600 mg odds ratio 0.60; 95% confidence interval 0.39-0.93). There was no effect modification by time to treatment or use of thrombolysis/thrombectomy. For natalizumab 300 mg, 600 mg, or placebo, there were no differences in incidence of adverse events (90%, 92%, and 92%, respectively), serious adverse events (26%, 33%, and 21%, respectively), or deaths (7%, 5%, and 6%, respectively). CONCLUSIONS: Natalizumab administered ≤24 hours after AIS did not improve patient outcomes. CLINICALTRIALSGOV IDENTIFIER: NCT02730455 CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that for patients with AIS, an excellent outcome was less likely in patients treated with natalizumab than with placebo
DNA looping: the consequences and its control
The formation of DNA loops by proteins and protein complexes is ubiquitous to
many fundamental cellular processes, including transcription, recombination,
and replication. Here we review recent advances in understanding the properties
of DNA looping in its natural context and how they propagate to the cellular
behavior through gene regulation. The results of connecting the molecular
properties with cellular physiology indicate that looping of DNA in vivo is
much more complex and easier than predicted from current models and reveals a
wealth of previously unappreciated details
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