1,713 research outputs found
Neutrino mass bounds from confronting an effective model with BOSS Lyman-alpha data
We present an effective model for the one-dimensional Lyman- flux
power spectrum far above the baryonic Jeans scale. The main new ingredient is
constituted by a set of two parameters that encode the impact of small, highly
non-linear scales on the one-dimensional power spectrum on large scales, where
it is measured by BOSS. We show that, by marginalizing over the model
parameters that capture the impact of the intergalactic medium, the flux power
spectrum from both simulations and observations can be described with high
precision. The model displays a degeneracy between the neutrino masses and the
(unknown, in our formalism) normalization of the flux power spectrum. This
degeneracy can be lifted by calibrating one of the model parameters with
simulation data, and using input from Planck CMB data. We demonstrate that this
approach can be used to extract bounds on the sum of neutrino masses with
comparably low numerical effort, while allowing for a conservative treatment of
uncertainties from the dynamics of the intergalactic medium. An explorative
analysis yields an upper bound of eV at C.L. when applied to
BOSS data at . We also forecast that if the systematic and
statistical errors will be reduced by a factor two the upper bound will become
eV at C.L.Comment: 27 pages, 11 figure
Expansion and Collapse in the Cosmic Web
We study the kinematics of the gaseous cosmic web at high redshift with Lyman
alpha forest absorption in multiple QSO sightlines. Using a simple analytic
model and a cosmological hydrodynamic simulation we constrain the underlying
three-dimensional distribution of velocities from the observed line-of-sight
distribution of velocity shear across the plane of the sky. The distribution is
found to be in good agreement with the intergalactic medium (IGM) undergoing
large scale motions dominated by the Hubble flow. Modeling the Lyman alpha
clouds analytically and with a hydrodynamics simulation, the average expansion
velocity of the gaseous structures causing the Lyman alpha forest in the lower
redshift (z = 2) sample appears about 20 percent lower than the local Hubble
expansion velocity. We interpret this as tentative evidence for some clouds
undergoing gravitational collapse. However, the distribution of velocities is
highly skewed, and the majority of clouds at redshifts from 2 to 3.8 expand
typically about 5 - 20 percent faster than the Hubble flow. This behavior is
explained if most absorbers in the column density range typically detectable
are expanding filaments that stretch and drain into more massive nodes. We find
no evidence for the observed distribution of velocity shear being significantly
influenced by processes other than Hubble expansion and gravitational
instability, like galactic winds. To avoid overly disturbing the IGM, winds may
be old and/or limp by the time we observe them in the Lyman alpha forest, or
they may occupy only an insignificant volume fraction of the IGM. (abridged)Comment: 63 pages, 26 figures, AAS Latex; ApJ, in pres
The effect of neutrinos on the matter distribution as probed by the Intergalactic Medium
We present a suite of full hydrodynamical cosmological simulations that
quantitatively address the impact of neutrinos on the (mildly non-linear)
spatial distribution of matter and in particular on the neutral hydrogen
distribution in the Intergalactic Medium (IGM), which is responsible for the
intervening Lyman-alpha absorption in quasar spectra. The free-streaming of
neutrinos results in a (non-linear) scale-dependent suppression of power
spectrum of the total matter distribution at scales probed by Lyman-alpha
forest data which is larger than the linear theory prediction by about 25% and
strongly redshift dependent. By extracting a set of realistic mock quasar
spectra, we quantify the effect of neutrinos on the flux probability
distribution function and flux power spectrum. The differences in the matter
power spectra translate into a ~2.5% (5%) difference in the flux power spectrum
for neutrino masses with Sigma m_{\nu} = 0.3 eV (0.6 eV). This rather small
effect is difficult to detect from present Lyman-alpha forest data and nearly
perfectly degenerate with the overall amplitude of the matter power spectrum as
characterised by sigma_8. If the results of the numerical simulations are
normalized to have the same sigma_8 in the initial conditions, then neutrinos
produce a smaller suppression in the flux power of about 3% (5%) for Sigma
m_{\nu} = 0.6 eV (2
sigma C.L.), comparable to constraints obtained from the cosmic microwave
background data or other large scale structure probes.Comment: 38 pages, 21 figures. One section and references added. JCAP in pres
Massive Neutrinos and the Non-linear Matter Power Spectrum
We perform an extensive suite of N-body simulations of the matter power
spectrum, incorporating massive neutrinos in the range M = 0.15-0.6 eV, probing
the non-linear regime at scales k < 10 hMpc-1 at z < 3. We extend the widely
used HALOFIT approximation to account for the effect of massive neutrinos on
the power spectrum. In the strongly non-linear regime HALOFIT systematically
over-predicts the suppression due to the free-streaming of the neutrinos. The
maximal discrepancy occurs at k ~ 1 hMpc-1, and is at the level of 10% of the
total suppression. Most published constraints on neutrino masses based on
HALOFIT are not affected, as they rely on data probing the matter power
spectrum in the linear or mildly non-linear regime. However, predictions for
future galaxy, Lyman-alpha forest and weak lensing surveys extending to more
non-linear scales will benefit from the improved approximation to the
non-linear matter power spectrum we provide. Our approximation reproduces the
induced neutrino suppression over the targeted scales and redshifts
significantly better. We test its robustness with regard to changing
cosmological parameters and a variety of modelling effects.Comment: 12 pages, 6 figures, version accepted by MNRAS. v2: Minor
clarifications and corrections, citations added. Code available in CAMB and
from http://www.sns.ias.edu/~spb v3: Correct typo in equation A
Effects of biodegradable-based microplastics in Paracentrotus lividus Lmk embryos: Morphological and gene expression analysis
: Plastic pollution is a remarkable environmental issue. In fact, plastic is widespread in the lifetime and serious environmental problems are caused by the improper management of plastic end of life, being plastic litter detected in any environment. Efforts are put to implement the development of sustainable and circular materials. In this scenario, biodegradable polymers, BPs, are promising materials if correctly applied and managed at the end of life to minimize environmental problems. However, a lack of data on BPs fate and toxicity on marine organisms, limits their applicability. In this research, the impact of microplastics obtained from BPs, BMPs, were analyzed on Paracentrotus lividus. Microplastics were produced from five biodegradable polyesters at laboratory scale by milling the pristine polymers, under cryogenic conditions. Morphological analysis of P. lividus embryos exposed to polycaprolactone (PCL), polyhydroxy butyrate (PHB) and polylactic acid (PLA) showed their delay and malformations, which at molecular level are due to variation in expression levels of eighty-seven genes involved in various cellular processes, such as skeletogenesis, differentiation and development, stress, and detoxification response. Exposure to poly(butylene succinate) (PBS) and poly(butylene succinate-co-adipate) (PBSA) microplastics showed no detectable effects on P. lividus embryos. These findings contribute with important data on the effect of BPs on the physiology of marine invertebrates
A comparison of discrete versus continuous environment in a variance components-based linkage analysis of the COGA data
BACKGROUND: The information content of a continuous variable exceeds that of its categorical counterpart. The parameterization of a model may diminish the benefit of using a continuous variable. We explored the use of continuous versus discrete environment in variance components based analyses examining gene × environment interaction in the electrophysiological phenotypes from the Collaborative Study on the Genetics of Alcoholism. RESULTS: The parameterization using the continuous environment produced a greater number of significant gene × environment interactions and lower AICs (Akaike's information criterion). In these cases, the genetic variance increased with increasing cigarette pack-years, the continuous environment of interest. This did not, however, result in enhanced LOD scores when linkage analyses incorporated the gene × continuous environment interaction. CONCLUSION: Alternative parameterizations may better represent the functional relationship between the continuous environment and the genetic variance
PkANN - I. Non-linear matter power spectrum interpolation through artificial neural networks
We investigate the interpolation of power spectra of matter fluctuations
using Artificial Neural Network (PkANN). We present a new approach to confront
small-scale non-linearities in the power spectrum of matter fluctuations. This
ever-present and pernicious uncertainty is often the Achilles' heel in
cosmological studies and must be reduced if we are to see the advent of
precision cosmology in the late-time Universe. We show that an optimally
trained artificial neural network (ANN), when presented with a set of
cosmological parameters (Omega_m h^2, Omega_b h^2, n_s, w_0, sigma_8, m_nu and
redshift z), can provide a worst-case error <=1 per cent (for z<=2) fit to the
non-linear matter power spectrum deduced through N-body simulations, for modes
up to k<=0.7 h/Mpc. Our power spectrum interpolator is accurate over the entire
parameter space. This is a significant improvement over some of the current
matter power spectrum calculators. In this paper, we detail how an accurate
interpolation of the matter power spectrum is achievable with only a sparsely
sampled grid of cosmological parameters. Unlike large-scale N-body simulations
which are computationally expensive and/or infeasible, a well-trained ANN can
be an extremely quick and reliable tool in interpreting cosmological
observations and parameter estimation. This paper is the first in a series. In
this method paper, we generate the non-linear matter power spectra using
HaloFit and use them as mock observations to train the ANN. This work sets the
foundation for Paper II, where a suite of N-body simulations will be used to
compute the non-linear matter power spectra at sub-per cent accuracy, in the
quasi-non-linear regime 0.1 h/Mpc <= k <= 0.9 h/Mpc. A trained ANN based on
this N-body suite will be released for the scientific community.Comment: 12 pages, 9 figures, 2 tables, updated to match version accepted by
MNRA
Cardiac metabolic deregulation induced by the tyrosine kinase receptor inhibitor sunitinib is rescued by endothelin receptor antagonism
International audienceThe growing field of cardio-oncology addresses the side effects of cancer treatment on the cardiovascular system. Here, we explored the cardiotoxicity of the antiangiogenic therapy, sunitinib, in the mouse heart from a diagnostic and therapeutic perspective. We showed that sunitinib induces an anaerobic switch of cellular metabolism within the myocardium which is associated with the development of myocardial fibrosis and reduced left ventricular ejection fraction as demonstrated by echocardiography. The capacity of positron emission tomography with [ 18 F]fluorodeoxyglucose to detect the changes in cardiac metabolism caused by sunitinib was dependent on fasting status and duration of treatment. Pan proteomic analysis in the myocardium showed that sunitinib induced (i) an early metabolic switch with enhanced glycolysis and reduced oxidative phosphorylation, and (ii) a metabolic failure to use glucose as energy substrate, similar to the insulin resistance found in type 2 diabetes. Co-administration of the endothelin receptor antagonist, macitentan, to sunitinib-treated animals prevented both metabolic defects, restored glucose uptake and cardiac function, and prevented myocardial fibrosis. These results support the endothelin system in mediating the cardiotoxic effects of sunitinib and endothelin receptor antagonism as a potential therapeutic approach to prevent cardiotoxicity. Furthermore, metabolic and functional imaging can monitor the cardiotoxic effects and the benefits of endothelin antagonism in a theranostic approach
Dark matter as a heavy thermal hot relic
If, during the early Universe epoch, the dark matter particle thermalizes in
a hidden sector which does not thermalize with the Standard Model thermal bath,
its relativistic thermal decoupling can easily lead to the observed relic
density, even if the dark matter particle mass is many orders of magnitude
heavier than the usual eV hot relic mass scale. This straightforward
scenario simply requires that the temperature of the hidden sector thermal bath
is one to five orders of magnitude cooler than the temperature of the Standard
Model thermal bath. In this way the resulting relic density turns out to be
determined only by the dark matter mass scale and the ratio of the temperatures
of both sectors. In a model independent way we determine that this can work for
a dark matter mass all the way from keV to PeV. We also show
how this scenario works explicitly in the framework of two illustrative models.
One of them can lead to a PeV neutrino flux from dark matter decay of the order
of the one needed to account for the high energy neutrinos observed by IceCube.Comment: 6 pages with 2 figures, published versio
Photoactivated surface grafting from PVDF surfaces
International audienceEconomic and easy methods to tune surface properties of polymers as Poly(vinylidene fluoride) (PVDF) without altering bulk properties are of major interest for different applications as biotechnological devices, medical implant device. . . UV irradiation appears as one of the simplest, easy and safe method to modify surface properties. In the case of self-initiated grafting, it is generally assumed that the pretreatment of the PVDF surface with UV irradiation can yield alkyl and per-oxy radicals originating from breaking bonds and capable of initiating the subsequent surface grafting polymerizations. Surprisingly, the present work shows that it is possible to obtain polymer grafting using low energetic UV-A irradiation (3.1-3.9 eV) without breaking PVDF bonds. An EPR study has been performed in order to investigate the nature of involved species. The ability of the activated PVDF surface to graft different kinds of hydrophilic monomers using the initiated surface polymerization method has been tested and discussed on the basis of ATR FT-IR, XPS and NMR HRMAS results
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