620 research outputs found
On the filamentary environment of galaxies
The correlation between the large-scale distribution of galaxies and their
spectroscopic properties at z=1.5 is investigated using the Horizon MareNostrum
cosmological run.
We have extracted a large sample of 10^5 galaxies from this large
hydrodynamical simulation featuring standard galaxy formation physics. Spectral
synthesis is applied to these single stellar populations to generate spectra
and colours for all galaxies. We use the skeleton as a tracer of the cosmic web
and study how our galaxy catalogue depends on the distance to the skeleton. We
show that galaxies closer to the skeleton tend to be redder, but that the
effect is mostly due to the proximity of large haloes at the nodes of the
skeleton, rather than the filaments themselves.
This effects translate into a bimodality in the colour distribution of our
sample. The origin of this bimodality is investigated and seems to follow from
the ram pressure stripping of satellite galaxies within the more massive
clusters of the simulation.
The virtual catalogues (spectroscopical properties of the MareNostrum
galaxies at various redshifts) are available online at
http://www.iap.fr/users/pichon/MareNostrum/cataloguesComment: 18 pages, 27 figures, accepted for publication in MNRA
Enhancing agroecological innovations with a multi-level approach to experimental research needs
Public policies clearly aim at an ecologisation of agriculture. However, few concrete goals or incentives have been established to mobilize the experimental research. Applied to 13-year results of four experimental stations of the South-East of France, the Direct-Indirect-System multi-level analysis grid showed a diversification of their experimental strategies. These three levels of analysis, combined with the identification of different types of agroecosystems, appears as promising for instigating assessment and determining agroecological innovation priorities for an experimental station, a territory or a food chain
Selective Gene Expression by Postnatal Electroporation during Olfactory interneuron Nurogenesis
Neurogenesis persists in the olfactory system throughout life. The mechanisms of how new neurons are generated, how they integrate into circuits, and their role in coding remain mysteries. Here we report a technique that will greatly facilitate research into these questions. We found that electroporation can be used to robustly and selectively label progenitors in the Subventicular Zone. The approach was performed postnatally, without surgery, and with near 100% success rates. Labeling was found in all classes of interneurons in the olfactory bulb, persisted to adulthood and had no adverse effects. The broad utility of electroporation was demonstrated by encoding a calcium sensor and markers of intracellular organelles. The approach was found to be effective in wildtype and transgenic mice as well as rats. Given its versatility, robustness, and both time and cost effectiveness, this method offers a powerful new way to use genetic manipulation to understand adult neurogenesis
Stellar Content from high resolution galactic spectra via Maximum A Posteriori
This paper describes STECMAP (STEllar Content via Maximum A Posteriori), a
flexible, non-parametric inversion method for the interpretation of the
integrated light spectra of galaxies, based on synthetic spectra of single
stellar populations (SSPs). We focus on the recovery of a galaxy's star
formation history and stellar age-metallicity relation. We use the high
resolution SSPs produced by PEGASE-HR to quantify the informational content of
the wavelength range 4000 - 6800 Angstroms.
A detailed investigation of the properties of the corresponding simplified
linear problem is performed using singular value decomposition. It turns out to
be a powerful tool for explaining and predicting the behaviour of the
inversion. We provide means of quantifying the fundamental limitations of the
problem considering the intrinsic properties of the SSPs in the spectral range
of interest, as well as the noise in these models and in the data.
We performed a systematic simulation campaign and found that, when the time
elapsed between two bursts of star formation is larger than 0.8 dex, the
properties of each episode can be constrained with a precision of 0.04 dex in
age and 0.02 dex in metallicity from high quality data (R=10 000,
signal-to-noise ratio SNR=100 per pixel), not taking model errors into account.
The described methods and error estimates will be useful in the design and in
the analysis of extragalactic spectroscopic surveys.Comment: 31 pages, 23 figures, accepted for publication in MNRA
Galaxy merger histories and the role of merging in driving star formation at z>1
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.We use Horizon-AGN, a hydrodynamical cosmological simulation, to explore the role of mergers in the evolution of massive (M > 10^10 MSun) galaxies around the epoch of peak cosmic star formation (1zR(4:1 3 are 'blue' (i.e. have significant associated star formation), the proportion of 'red' mergers increases rapidly at ztodays stellar mass was formed.Peer reviewe
Histidinylated linear PEIs as new DNA carriers for in vitro and in vivo gene transfer with low toxicity
STEllar Content and Kinematics from high resolution galactic spectra via Maximum A Posteriori
We introduce STECKMAP (STEllar Content and Kinematics via Maximum A
Posteriori), a method to recover the kinematical properties of a galaxy
simultaneously with its stellar content from integrated light spectra. It is an
extension of STECMAP (astro-ph/0505209) to the general case where the velocity
distribution of the underlying stars is also unknown.
%and can be used as is for the analysis of large sets of data. The
reconstructions of the stellar age distribution, the age-metallicity relation,
and the Line-Of-Sight Velocity Distribution (LOSVD) are all non-parametric,
i.e. no specific shape is assumed. The only a propri we use are positivity and
the requirement that the solution is smooth enough. The smoothness parameter
can be set by GCV according to the level of noise in the data in order to avoid
overinterpretation. We use single stellar populations (SSP) from PEGASE-HR
(R=10000, lambda lambda = 4000-6800 Angstrom, Le Borgne et al. 2004) to test
the method through realistic simulations. Non-Gaussianities in LOSVDs are
reliably recovered with SNR as low as 20 per 0.2 Angstrom pixel. It turns out
that the recovery of the stellar content is not degraded by the simultaneous
recovery of the kinematic distribution, so that the resolution in age and error
estimates given in Ocvirk et al. 2005 remain appropriate when used with
STECKMAP. We also explore the case of age-dependent kinematics (i.e. when each
stellar component has its own LOSVD). We separate the bulge and disk components
of an idealized simplified spiral galaxy in integrated light from high quality
pseudo data (SNR=100 per pixel, R=10000), and constrain the kinematics (mean
projected velocity, projected velocity dispersion) and age of both components.Comment: 12 pages, 6 figures, accepted for publication in MNRA
Hyperactivity in the Gunn rat model of neonatal jaundice: age-related attenuation and emergence of gait deficits
Background
Neonatal jaundice resulting from elevated unconjugated bilirubin (UCB) occurs in 60â80% of newborn infants. Although mild jaundice is generally considered harmless, little is known about its long-term consequences. Recent studies have linked mild bilirubin-induced neurological dysfunction (BIND) with a range of neurological syndromes, including attention deficit-hyperactivity disorder. The goal of this study was to measure BIND across the lifespan in the Gunn rat model of BIND.
Methods
Using a sensitive force plate actometer, we measured locomotor activity and gait in jaundiced (jj) Gunn rats versus their non-jaundiced (Nj) littermates. Data were analyzed for young adult (3â4 months), early middle-aged (9â10 months), and late middle-aged (17â20 months) male rats.
Results
jj rats exhibited lower body weights at all ages and a hyperactivity that resolved at 17â20 months of age. Increased propulsive force and gait velocity accompanied hyperactivity during locomotor bouts at 9â10 months in jj rats. Stride length did not differ between the two groups at this age. Hyperactivity normalized and gait deficits, including decreased stride length, propulsive force, and gait velocity, emerged in the 17â20-month-old jj rats.
Conclusions
These results demonstrate that, in aging, hyperactivity decreases with the onset of gait deficits in the Gunn rat model of BIND
Yield scaling, size hierarchy and fluctuations of observables in fragmentation of excited heavy nuclei
Multifragmentation properties measured with INDRA are studied for single
sources produced in Xe+Sn reactions in the incident energy range 32-50 A MeV
and quasiprojectiles from Au+Au collisions at 80 A MeV. A comparison for both
types of sources is presented concerning Fisher scaling, Zipf law, fragment
size and fluctuation observables. A Fisher scaling is observed for all the
data. The pseudo-critical energies extracted from the Fisher scaling are
consistent between Xe+Sn central collisions and Au quasi-projectiles. In the
latter case it also corresponds to the energy region at which fluctuations are
maximal. The critical energies deduced from the Zipf analysis are higher than
those from the Fisher analysis.Comment: 30 pages, accepted for publication in Nuclear Physics A, references
correcte
Using dense seismo-acoustic network to provide timely warning of the 2019 paroxysmal Stromboli eruptions
Stromboli Volcano is well known for its persistent explosive activity. On July 3rd and August 28th 2019, two paroxysmal explosions occurred, generating an eruptive column that quickly rose up to 5Â km above sea level. Both events were detected by advanced local monitoring networks operated by Istituto Nazionale di Geofisica e Vulcanologia (INGV) and Laboratorio di Geofisica Sperimentale of the University of Firenze (LGS-UNIFI). Signals were also recorded by the Italian national seismic network at a range of hundreds of kilometres and by infrasonic arrays up to distances of 3700Â km. Using state-of-the-art propagation modeling, we identify the various seismic and infrasound phases that are used for precise timing of the eruptions. We highlight the advantage of dense regional seismo-acoustic networks to enhance volcanic signal detection in poorly monitored regions, to provide timely warning of eruptions and reliable source amplitude estimate to Volcanic Ash Advisory Centres (VAAC)
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