388 research outputs found
Evaluation of Sweet Grain Sorghum Silage for Dairy Cows as an Alternative to Irrigated Maize Silage
Under European dairy cattle rearing conditions, whole plant maize silage is the main part of the dairy cow\u27s diet especially during the winter season. Nevertheless maize production can be limited in some areas because summer rainfall is insufficient and so irrigation is necessary. Grain sorghum hybrids, and especially sweet sorghum types, are potentially of great interest to avoid this water consumption (Lemaire et al., 1996, Legarto, 2000). For this reason we evaluated in 2003 the benefits and limits of a sweet grain sorghum silage for dairy milk production, compared to an irrigated maize silage. We paid particularl attention to forage quality and yield, environmental effects and animal performance
Detecting heterozygosity in shotgun genome assemblies: Lessons from obligately outcrossing nematodes
The majority of nematodes are gonochoristic (dioecious) with distinct male and female sexes, but the best-studied species, Caenorhabditis elegans, is a self-fertile hermaphrodite. The sequencing of the genomes of C. elegans and a second hermaphrodite, C. briggsae, was facilitated in part by the low amount of natural heterozygosity, which typifies selfing species. Ongoing genome projects for gonochoristic Caenorhabditis species seek to approximate this condition by intense inbreeding prior to sequencing. Here we show that despite this inbreeding, the heterozygous fraction of the whole genome shotgun assemblies of three gonochoristic Caenorhabditis species, C. brenneri, C. remanei, and C. japonica, is considerable. We first demonstrate experimentally that independently assembled sequence variants in C. remanei and C. brenneri are allelic. We then present gene-based approaches for recognizing heterozygous regions of WGS assemblies. We also develop a simple method for quantifying heterozygosity that can be applied to assemblies lacking gene annotations. Consistently we find that ∼10% and 30% of the C. remanei and C. brenneri genomes, respectively, are represented by two alleles in the assemblies. Heterozygosity is restricted to autosomes and its retention is accompanied by substantial inbreeding depression, suggesting that it is caused by multiple recessive deleterious alleles and not merely by chance. Both the overall amount and chromosomal distribution of heterozygous DNA is highly variable between assemblies of close relatives produced by identical methodologies, and allele frequencies have continued to change after strains were sequenced. Our results highlight the impact of mating systems on genome sequencing projects
Gap Formation in the Dust Layer of 3D Protoplanetary Disks
We numerically model the evolution of dust in a protoplanetary disk using a
two-phase (gas+dust) Smoothed Particle Hydrodynamics (SPH) code, which is
non-self-gravitating and locally isothermal. The code follows the three
dimensional distribution of dust in a protoplanetary disk as it interacts with
the gas via aerodynamic drag. In this work, we present the evolution of a disk
comprising 1% dust by mass in the presence of an embedded planet for two
different disk configurations: a small, minimum mass solar nebular (MMSN) disk
and a larger, more massive Classical T Tauri star (CTTS) disk. We then vary the
grain size and planetary mass to see how they effect the resulting disk
structure. We find that gap formation is much more rapid and striking in the
dust layer than in the gaseous disk and that a system with a given stellar,
disk and planetary mass will have a different appearance depending on the grain
size and that such differences will be detectable in the millimetre domain with
ALMA. For low mass planets in our MMSN models, a gap can open in the dust disk
while not in the gas disk. We also note that dust accumulates at the external
edge of the planetary gap and speculate that the presence of a planet in the
disk may facilitate the growth of planetesimals in this high density region.Comment: 5 page, 4 figures. Accepted for publication in Astrophysics & Space
Scienc
Foncier et désertification, quelle gestion patrimoniale ? : approche foncière environnementale pour un développement durable au Sahel
Pour une amélioration de l’actuel protocole de lutte contre la tuberculose bovine
Barrière G., Desbrosse H., Germain L., Hugonet R., Ollivet Ch. Pour une amélioration de l’actuel protocole de lutte contre la tuberculose bovine. In: Bulletin de l'Académie Vétérinaire de France tome 113 n°2, 1960. pp. 107-124
R&D progress on second-generation crystals for Laue lens applications
The concept of a gamma-ray telescope based on a Laue lens offers the
possibility to increase the sensitivity by more than an order of magnitude with
respect to existing instruments. Laue lenses have been developed by our
collaboration for several years : the main achievement of this R&D program was
the CLAIRE lens prototype. Since then, the endeavour has been oriented towards
the development of efficient diffracting elements (crystal slabs), the aim
being to step from a technological Laue lens to a scientifically exploitable
lens. The latest mission concept featuring a gamma-ray lens is the European
Gamma-Ray Imager (GRI) which intends to make use of the Laue lens to cover
energies from 200 keV to 1300 keV.
Investigations of two promising materials, low mosaicity copper and gradient
concentration silicon-germanium are presented in this paper. The measurements
have been performed during three runs on beamline ID15A of the European
Synchrotron Radiation Facility, and on the GAMS 4 instrument of the Institute
Laue-Langevin (both in Grenoble, France) using highly monochromatic beam of
energy close to 500 keV. Despite it was not perfectly homogeneous, the
presented copper crystal exhibits peak reflectivity of 25% in accordance with
theoretical predictions, and a mosaicity around 26 arcsec, the ideal range for
the realization of a Laue lens such as GRI. Silicon-germanium featuring a
constant gradient have been measured for the very first time at 500 keV. Two
samples showed a quite homogeneous reflectivity reaching 26%, which is far from
the 48% already observed in experimental crystals but a very encouraging
beginning. This results have been used to estimate the performance of the GRI
Laue lens design
Pelizaeus-Merzbacher-Like disease presentation of MCT8 mutated male subjects.
Pelizaeus-Merzbacher Disease is an X-linked hypomyelinatiing leukodystrophy. We
report mutations in the thyroid hormone transporter gene MCT8 in 11% of 53
families affected by hypomyelinating leukodystrophies of unknown aetiology. The
12 MCT8 mutated patients express initially a Pelizaeus-Merzbacher-Like disease
phenotype with a latter unusual improvement of magnetic resonance imaging white
matter signal despite absence of clinical progression. This observation
underlines the interest of determining both free T3 and free T4 serum
concentrations to screen for MCT8 mutations in young patients (<3 y) with a
severe Pelizaeus-Merzbacher-Like disease presentation or older severe mentally
retarded male patients with "hypomyelinated" regions
Gathering in Dynamic Rings
The gathering problem requires a set of mobile agents, arbitrarily positioned
at different nodes of a network to group within finite time at the same
location, not fixed in advanced.
The extensive existing literature on this problem shares the same fundamental
assumption: the topological structure does not change during the rendezvous or
the gathering; this is true also for those investigations that consider faulty
nodes. In other words, they only consider static graphs. In this paper we start
the investigation of gathering in dynamic graphs, that is networks where the
topology changes continuously and at unpredictable locations.
We study the feasibility of gathering mobile agents, identical and without
explicit communication capabilities, in a dynamic ring of anonymous nodes; the
class of dynamics we consider is the classic 1-interval-connectivity.
We focus on the impact that factors such as chirality (i.e., a common sense
of orientation) and cross detection (i.e., the ability to detect, when
traversing an edge, whether some agent is traversing it in the other
direction), have on the solvability of the problem. We provide a complete
characterization of the classes of initial configurations from which the
gathering problem is solvable in presence and in absence of cross detection and
of chirality. The feasibility results of the characterization are all
constructive: we provide distributed algorithms that allow the agents to
gather. In particular, the protocols for gathering with cross detection are
time optimal. We also show that cross detection is a powerful computational
element.
We prove that, without chirality, knowledge of the ring size is strictly more
powerful than knowledge of the number of agents; on the other hand, with
chirality, knowledge of n can be substituted by knowledge of k, yielding the
same classes of feasible initial configurations
The X-ray Flux Distribution of Sagittarius A* as Seen by Chandra
We present a statistical analysis of the X-ray flux distribution of Sgr A*
from the Chandra X-ray Observatory's 3 Ms Sgr A* X-ray Visionary Project (XVP)
in 2012. Our analysis indicates that the observed X-ray flux distribution can
be decomposed into a steady quiescent component, represented by a Poisson
process with rate cts s and a variable
component, represented by a power law process (
). This slope matches our recently-reported
distribution of flare luminosities. The variability may also be described by a
log-normal process with a median unabsorbed 2-8 keV flux of
erg s cm and a shape parameter
but the power law provides a superior description of the
data. In this decomposition of the flux distribution, all of the intrinsic
X-ray variability of Sgr A* (spanning at least three orders of magnitude in
flux) can be attributed to flaring activity, likely in the inner accretion
flow. We confirm that at the faint end, the variable component contributes ~10%
of the apparent quiescent flux, as previously indicated by our statistical
analysis of X-ray flares in these Chandra observations. Our flux distribution
provides a new and important observational constraint on theoretical models of
Sgr A*, and we use simple radiation models to explore the extent to which a
statistical comparison of the X-ray and infrared can provide insights into the
physics of the X-ray emission mechanism.Comment: 13 pages, 7 figures, accepted for publication in ApJ. Comments
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