162 research outputs found
Bioévaluation de la pollution des sédiments de la Seine (région parisienne) par l'emploi d'un bioessai basé sur la croissance à court terme de la micro-algue Selenastrum capricornutum Printz
La bioĂ©valuation de l'Ă©tat de santĂ© des fonds meubles dĂ©pend des conditions expĂ©rimentales du traitement des Ă©chantillons de sĂ©diment conduisant Ă l'obtention de la phase aqueuse sur laquelle sont effectuĂ©es les analyses chimiques et toxicologiques.Au cours de cette Ă©tude prĂ©liminaire nous avons considĂ©rĂ© l'action de ces principales conditions ; nous constatons que l'effet inhibiteur d'un sĂ©diment vis-Ă -vis de la croissance Ă court terme de la micro-algue Selenastrum capricornutum Printz n'est pas aisĂ©ment levĂ©, que ce soit par lessivages successifs du sĂ©diment, par filtration plus fine de l'eau extraite Ă partir de ce dernier ou par autoclavage prĂ©alable de ce mĂȘme sĂ©diment, il peut l'ĂȘtre par contre aprĂšs biodĂ©gradation.Cette Ă©tude expĂ©rimentale a permis de comparer entre eux les pouvoirs inhibiteurs des fonds meubles de la Seine (rĂ©gion parisienne).On note qu'il n'y a pas de corrĂ©lation entre les teneurs en mĂ©taux lourds souvent importantes des eaux issues des sĂ©diments (Pb 70, Cu 100, Cr 150, Cd 9, Ni 280, Zn 400 ”g.L-1) et le dĂ©veloppement des algues : les polluants mĂ©talliques sont masquĂ©s par le pouvoir chĂ©lateur de ces biotopes riches en substances organiques.Une conclusion Ă cette Ă©tude prĂ©liminaire est que l'analyse chimique des sĂ©diments, utilisĂ©e seule, n'a qu'un intĂ©rĂȘt limitĂ©Â : les donnĂ©es les plus fiables correspondent Ă celles fournies par les bioessais.A bioevaluation of the state of health of soft bottoms depends on the experimental conditions in which samples of sediment are treated to obtain the water phase to be subjected to chemical and toxicological analyses.In the course of this preliminary study we have considered the action of these principal conditions. We have noted that the inhibiting effect of a sediment on the short-term growth of a microalga Selenastrum capricornutum is not easy to eliminate, whether by a series of washes of the sediment, by a finer filtration of the water extracted from this sediment or by e previous autoclavage of this sediment.This study quickly revealed which sediments in the River Seine (Paris area) inhibited most the test micro-alga Selenastrum capricornutum (Chlorophyceae); the cause of these inhibitions was then sought.There is no correlation between the often high content of heavy metals in the sediment water (Pb 70, Cu 100, Cr 150, Cd 9, Ni 280, Zn 400 ”g.L-1) and the development of the algae; the metal pollutants are probably masked by the chelating capacity of these biotopes rich in organic substances. The experimental conditions under which the sediment samples are treated to obtain the water phase used for the chemical and toxicological analyses are also important.One conclusion drawn is that a chemical analysis alone of the sediments is of limited interest. The most reliable data from the ecological point of view are those provided by the bio-assays
Convergence towards an asymptotic shape in first-passage percolation on cone-like subgraphs of the integer lattice
In first-passage percolation on the integer lattice, the Shape Theorem
provides precise conditions for convergence of the set of sites reachable
within a given time from the origin, once rescaled, to a compact and convex
limiting shape. Here, we address convergence towards an asymptotic shape for
cone-like subgraphs of the lattice, where . In particular, we
identify the asymptotic shapes associated to these graphs as restrictions of
the asymptotic shape of the lattice. Apart from providing necessary and
sufficient conditions for - and almost sure convergence towards this
shape, we investigate also stronger notions such as complete convergence and
stability with respect to a dynamically evolving environment.Comment: 23 pages. Together with arXiv:1305.6260, this version replaces the
old. The main results have been strengthened and an earlier error in the
statement corrected. To appear in J. Theoret. Proba
MESURE DES GRADIENTS DE DENSITĂ DANS L'INTERACTION LASER-PLASMA
Nous Ă©tudions la densitĂ© Ă©lectronique et son gradient dans l'interaction d'un laser Ă CO2 avec une cible plane de polyĂ©thylĂšne, pour un flux laser de 1012 W/cm2. L'Ă©tude par interfĂ©romĂ©trie Jamin des profils de densitĂ© et la mesure strioscopique de son gradient, couplĂ©es Ă l'Ă©tude de l'image en rayons X du plasma conduisent Ă une valeur de 220 ± 80 ”m de la longueur du gradient de densitĂ©. Ceci est confirmĂ© par des mesures indirectes obtenues Ă partir du bilan optique de l'interaction et du seuil de gĂ©nĂ©ration de l'harmonique 3/2 Ï0 du laser Ă CO2. Les consĂ©quences de ces rĂ©sultats sur les conditions de l'interaction sont discutĂ©es
The near-critical planar FK-Ising model
We study the near-critical FK-Ising model. First, a determination of the
correlation length defined via crossing probabilities is provided. Second, a
phenomenon about the near-critical behavior of FK-Ising is highlighted, which
is completely missing from the case of standard percolation: in any monotone
coupling of FK configurations (e.g., in the one introduced in
[Gri95]), as one raises near , the new edges arrive in a
self-organized way, so that the correlation length is not governed anymore by
the number of pivotal edges at criticality.Comment: 34 pages, 8 figures. This is a streamlined version; the previous one
contains more explanations and additional material on exceptional times in FK
models with general . Furthermore, the statement and proof of Theorem 1.2
have slightly change
Explicit formulae in probability and in statistical physics
We consider two aspects of Marc Yor's work that have had an impact in
statistical physics: firstly, his results on the windings of planar Brownian
motion and their implications for the study of polymers; secondly, his theory
of exponential functionals of Levy processes and its connections with
disordered systems. Particular emphasis is placed on techniques leading to
explicit calculations.Comment: 14 pages, 2 figures. To appear in Seminaire de Probabilites, Special
Issue Marc Yo
Noise Sensitivity in Continuum Percolation
We prove that the Poisson Boolean model, also known as the Gilbert disc
model, is noise sensitive at criticality. This is the first such result for a
Continuum Percolation model, and the first for which the critical probability
p_c \ne 1/2. Our proof uses a version of the Benjamini-Kalai-Schramm Theorem
for biased product measures. A quantitative version of this result was recently
proved by Keller and Kindler. We give a simple deduction of the
non-quantitative result from the unbiased version. We also develop a quite
general method of approximating Continuum Percolation models by discrete models
with p_c bounded away from zero; this method is based on an extremal result on
non-uniform hypergraphs.Comment: 42 page
Functionals of the Brownian motion, localization and metric graphs
We review several results related to the problem of a quantum particle in a
random environment.
In an introductory part, we recall how several functionals of the Brownian
motion arise in the study of electronic transport in weakly disordered metals
(weak localization).
Two aspects of the physics of the one-dimensional strong localization are
reviewed : some properties of the scattering by a random potential (time delay
distribution) and a study of the spectrum of a random potential on a bounded
domain (the extreme value statistics of the eigenvalues).
Then we mention several results concerning the diffusion on graphs, and more
generally the spectral properties of the Schr\"odinger operator on graphs. The
interest of spectral determinants as generating functions characterizing the
diffusion on graphs is illustrated.
Finally, we consider a two-dimensional model of a charged particle coupled to
the random magnetic field due to magnetic vortices. We recall the connection
between spectral properties of this model and winding functionals of the planar
Brownian motion.Comment: Review article. 50 pages, 21 eps figures. Version 2: section 5.5 and
conclusion added. Several references adde
Comparison of the Hemostatic Efficacy of Pathogen-Reduced Platelets vs Untreated Platelets in Patients With Thrombocytopenia and Malignant Hematologic Diseases: A Randomized Clinical Trial
Importance: Pathogen reduction of platelet concentrates may reduce transfusion-transmitted infections but is associated with qualitative impairment, which could have clinical significance with regard to platelet hemostatic capacity.
Objective: To compare the effectiveness of platelets in additive solution treated with amotosalen-UV-A vs untreated platelets in plasma or in additive solution in patients with thrombocytopenia and hematologic malignancies.
Design, Setting, and Participants: The Evaluation of the Efficacy of Platelets Treated With Pathogen Reduction Process (EFFIPAP) study was a randomized, noninferiority, 3-arm clinical trial performed from May 16, 2013, through January 21, 2016, at 13 French tertiary university hospitals. Clinical signs of bleeding were assessed daily until the end of aplasia, transfer to another department, need for a specific platelet product, or 30 days after enrollment. Consecutive adult patients with bone marrow aplasia, expected hospital stay of more than 10 days, and expected need of platelet transfusions were included.
Interventions: At least 1 transfusion of platelets in additive solution with amotosalen-UV-A treatment, in plasma, or in additive solution.
Main Outcomes and Measures: The proportion of patients with grade 2 or higher bleeding as defined by World Health Organization criteria.
Results: Among 790 evaluable patients (mean [SD] age, 55 [13.4] years; 458 men [58.0%]), the primary end point was observed in 126 receiving pathogen-reduced platelets in additive solution (47.9%; 95% CI, 41.9%-54.0%), 114 receiving platelets in plasma (43.5%; 95% CI, 37.5%-49.5%), and 120 receiving platelets in additive solution (45.3%; 95% CI, 39.3%-51.3%). With a per-protocol population with a prespecified margin of 12.5%, noninferiority was not achieved when pathogen-reduced platelets in additive solution were compared with platelets in plasma (4.4%; 95% CI, -4.1% to 12.9%) but was achieved when the pathogen-reduced platelets were compared with platelets in additive solution (2.6%; 95% CI, -5.9% to 11.1%). The proportion of patients with grade 3 or 4 bleeding was not different among treatment arms.
Conclusions and Relevance: Although the hemostatic efficacy of pathogen-reduced platelets in thrombopenic patients with hematologic malignancies was noninferior to platelets in additive solution, such noninferiority was not achieved when comparing pathogen-reduced platelets with platelets in plasma.
Trial Registration: clinicaltrials.gov Identifier: NCT01789762
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