193 research outputs found
Pratiques phytosanitaires en agriculture et environnement : des tensions irréductibles ?
La vulnérabilité croissante des ressources en eau et des milieux aquatiques aux pollutions a conduit au développement de dispositifs agri-environnementaux chargés en particulier de réduire et d’encadrer l’utilisation des pesticides (le plus récent étant le plan Ecophyto 2018 issu du Grenelle de l’environnement). Cette contribution analyse la tension entre les contraintes agricoles qui conditionnent les changements de pratiques phytosanitaires et les exigences environnementales désormais posées en termes d’obtention de résultats. L’observation d’un dispositif expérimental de diffusion de " pratiques améliorées " de traitement phytosanitaire, inscrit dans le Groupe d’action phytosanitaire de Midi-Pyrénées (Gramip), est mobilisée pour interroger, à partir d’une approche interdisciplinaire (économie, sociologie, agronomie), la permanence de logiques agricoles technico-économiques et l’émergence d’arguments sanitaires et commerciaux comme facteurs potentiels de diffusion de pratiques alternatives à l’utilisation des pesticides en agriculture. / The increasing vulnerability of water resources and aquatic pollution has led to the development of agrienvironmental tools in particular to reduce and control the use of pesticides. This paper explores the tension between the constraints that affect changes of phytosanitary practices and environmental requirements now posed in terms of environmental results. The observation of an experimental policy instrument of "better practices" in Midi-Pyrenees (Gramip), is mobilized to examine, from an interdisciplinary approach (economics, sociology, agronomy), the permanence of agricultural techno-economic logic and the emergence of health and commercial factors as potential diffusion of alternative practices to the use of pesticides in agriculture
Energy analysis of organic crop systems. Impact of intensification level.
This study reveals a wide variability in the major parameters of the energy analysis applied to 44 four-year-long organic crop sequences. The intensification level of the systems in terms of the use or nonuse of organic fertilisation on cereals and of irrigation on summer crops (mainly pulses) is largely responsible for this variability. Average energy consumption ranges from 5 000 to 12 270 MJ/ha/year depending on the intensification level. Energy production varies from 35 500 to 43 950 MJ/ha/year. Since energy consumption and production both vary in the same direction with the degree of intensification, the energy gain is stable at an average value of 29300 MJ/ha/year. Energy efficiency decreases from 7.1 MJ/MJ for unfertilised and unirrigated crop sequences, to 3.5 MJ/MJ for fertilised and irrigated sequences, where soy and faba bean are among the major crops
Both TLR2 and TRIF Contribute to Interferon-β Production during Listeria Infection
Synthesis of interferon-β (IFN-β) is an innate response to cytoplasmic infection with bacterial pathogens. Our recent studies showed that Listeria monocytogenes limits immune detection and IFN-β synthesis via deacetylation of its peptidoglycan, which renders the bacterium resistant to lysozyme degradation. Here, we examined signaling requirements for the massive IFN-β production resulting from the infection of murine macrophages with a mutant strain of L. monocytogenes, ΔpgdA, which is unable to modify its peptidoglycan. We report the identification of unconventional signaling pathways to the IFN-β gene, requiring TLR2 and bacterial internalization. Induction of IFN-β was independent of the Mal/TIRAP adaptor protein but required TRIF and the transcription factors IRF3 and IRF7. These pathways were stimulated to a lesser degree by wild-type L. monocytogenes. They operated in both resident and inflammatory macrophages derived from the peritoneal cavity, but not in bone marrow-derived macrophages. The novelty of our findings thus lies in the first description of TLR2 and TRIF as two critical components leading to the induction of the IFN-β gene and in uncovering that individual macrophage populations adopt different strategies to link pathogen recognition signals to IFN-β gene expression
Preclinical modeling of myelodysplastic syndromes
Myelodysplastic syndromes (MDS) represent a heterogeneous group of hematological clonal disorders. Here, we have tested the bone marrow (BM) cells from 38 MDS patients covering all risk groups in two immunodeficient mouse models: NSG and NSG-S. Our data show comparable level of engraftment in both models. The level of engraftment was patient specific with no correlation to any specific MDS risk group. Furthermore, the co-injection of mesenchymal stromal cells (MSCs) did not improve the level of engraftment. Finally, we have developed an in vitro two-dimensional co-culture system as an alternative tool to in vivo. Using our in vitro system, we have been able to co-culture CD34+cells from MDS patient BM on auto- and/or allogeneic MSCs over 4 weeks with a fold expansion of up to 600 times. More importantly, these expanded cells conserved their MDS clonal architecture as well as genomic integrity
Muon capture by 3He nuclei followed by proton and deuteron production
The paper describes an experiment aimed at studying muon capture by
nuclei in pure and mixtures at various densities. Energy distributions of
protons and deuterons produced via and are measured for the
energy intervals MeV and MeV, respectively. Muon capture
rates, and are obtained using two different analysis methods. The
least--squares methods gives , . The Bayes theorem
gives ,
. The experimental
differential capture rates, and , are compared with theoretical
calculations performed using the plane--wave impulse approximation (PWIA) with
the realistic NN interaction Bonn B potential. Extrapolation to the full energy
range yields total proton and deuteron capture rates in good agreement with
former results.Comment: 17 pages, 13 figures, accepted for publication in PR
Induced pseudoscalar coupling of the proton weak interaction
The induced pseudoscalar coupling is the least well known of the weak
coupling constants of the proton's charged--current interaction. Its size is
dictated by chiral symmetry arguments, and its measurement represents an
important test of quantum chromodynamics at low energies. During the past
decade a large body of new data relevant to the coupling has been
accumulated. This data includes measurements of radiative and non radiative
muon capture on targets ranging from hydrogen and few--nucleon systems to
complex nuclei. Herein the authors review the theoretical underpinnings of
, the experimental studies of , and the procedures and uncertainties
in extracting the coupling from data. Current puzzles are highlighted and
future opportunities are discussed.Comment: 58 pages, Latex, Revtex4, prepared for Reviews of Modern Physic
The (muon^-,muon^+) conversion in nuclei as a probe of new physics
A detailed study of the muonic analogue of neutrinoless double beta decay,
(muon^-,muon^+) conversion, has been carried out for the A=44 nuclear system.
We studied several lepton number violating (LNV) mechanisms potentially
triggering this process: exchange by light and heavy Majorana neutrinos as well
as exchange by supersymmetric particles participating in R-parity violating
interactions. The nuclear structure has been taken into account within the
renormalized Quasiparticle Random Phase Approximation method. To our knowledge,
this is the first realistic treatment of nuclear structure aspects of the
(muon^-,muon^+) conversion. We estimated the rate of this process utilizing the
existing experimental constraints on the parameters of the underlying LNV
interactions and conclude that the (muon^-,muon^+) conversion is hardly
detectable in the near future experiments.Comment: 23 pages, RevTex, 3 Postscript figure
Modeling visual-based pitch, lift and speed control strategies in hoverflies
<div><p>To avoid crashing onto the floor, a free falling fly needs to trigger its wingbeats quickly and control the orientation of its thrust accurately and swiftly to stabilize its pitch and hence its speed. Behavioural data have suggested that the vertical optic flow produced by the fall and crossing the visual field plays a key role in this anti-crash response. Free fall behavior analyses have also suggested that flying insect may not rely on graviception to stabilize their flight. Based on these two assumptions, we have developed a model which accounts for hoverflies´ position and pitch orientation recorded in 3D with a fast stereo camera during experimental free falls. Our dynamic model shows that optic flow-based control combined with closed-loop control of the pitch suffice to stabilize the flight properly. In addition, our model sheds a new light on the visual-based feedback control of fly´s pitch, lift and thrust. Since graviceptive cues are possibly not used by flying insects, the use of a vertical reference to control the pitch is discussed, based on the results obtained on a complete dynamic model of a virtual fly falling in a textured corridor. This model would provide a useful tool for understanding more clearly how insects may or not estimate their absolute attitude.</p></div
A copula model for marked point processes
The final publication (Diao, Liqun, Richard J. Cook, and Ker-Ai Lee. (2013) A copula model for marked point processes. Lifetime Data Analysis, 19(4): 463-489) is available at Springer via http://dx.doi.org/10.1007/s10985-013-9259-3Many chronic diseases feature recurring clinically important events. In addition, however, there
often exists a random variable which is realized upon the occurrence of each event reflecting the
severity of the event, a cost associated with it, or possibly a short term response indicating the
effect of a therapeutic intervention. We describe a novel model for a marked point process which
incorporates a dependence between continuous marks and the event process through the use of a
copula function. The copula formulation ensures that event times can be modeled by any intensity
function for point processes, and any multivariate model can be specified for the continuous
marks. The relative efficiency of joint versus separate analyses of the event times and the marks is
examined through simulation under random censoring. An application to data from a recent trial
in transfusion medicine is given for illustration.Natural Sciences and Engineering Research Council of Canada (RGPIN 155849); Canadian Institutes for Health Research (FRN 13887); Canada Research Chair (Tier 1) – CIHR funded (950-226626
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