Disparity in the natural cycles of Borrelia burgdorferi and the agent of human granulocytic ehrlichiosis.

We studied the prevalence of Borrelia burgdorferi and the agent of human granulocytic ehrlichiosis (HGE) among questing nymphal and adult Ixodes scapularis ticks of the same generation and the infectivity of wild white-footed mice for ticks feeding on them. The prevalence of B. burgdorferi infection in host-seeking ticks increased less than twofold from nymphal (31% to 33%) to adult (52% to 56%) stage, and 52% of white-footed mice were infected. Prevalence of the agent of HGE increased 4.5- to 10.6-fold from nymphal (1.5% to 1.8%) to adult stage (7.6% to 19.0%), while only 18% of mice were infectious to ticks. B. burgdorferi infection was more common in mouse-fed ticks than in ticks collected from vegetation, whereas the agent of HGE was half as common in mouse-fed ticks as in ticks collected from vegetation. The different prevalence in nature of these pathogens in ticks suggests that their maintenance cycles are also different

Bipartite partial duals and circuits in medial graphs

It is well known that a plane graph is Eulerian if and only if its geometric dual is bipartite. We extend this result to partial duals of plane graphs. We then characterize all bipartite partial duals of a plane graph in terms of oriented circuits in its medial graph.Comment: v2: minor changes. To appear in Combinatoric

Longitudinal study of the effect of sporidesmin toxicity on lamb production and serum biochemistry in a flock of 46 Romney ewes using a standardised measure of liver damage

CAUL Read and Publish Agreement.Publishe

The relationship between red blood cell deformability metrics and perfusion of an artificial microvascular network

The ability of red blood cells (RBC) to undergo a wide range of deformations while traversing the microvasculature is crucial for adequate perfusion. Interpretation of RBC deformability measurements performed in vitro in the context of microvascular perfusion has been notoriously difficult. This study compares the measurements of RBC deformability performed using micropore filtration and ektacytometry with the RBC ability to perfuse an artificial microvascular network (AMVN). Human RBCs were collected from healthy consenting volunteers, leukoreduced, washed and exposed to graded concentrations (0% – 0.08%) of glutaraldehyde (a non-specific protein cross-linker) and diamide (a spectrin-specific protein cross-linker) to impair the deformability of RBCs. Samples comprising cells with two different levels of deformability were created by adding non-deformable RBCs (hardened by exposure to 0.08% glutaraldehyde) to the sample of normal healthy RBCs. Ektacytometry indicated a nearly linear decline in RBC deformability with increasing glutaraldehyde concentration. Micropore filtration showed a significant reduction only for concentrations of glutaraldehyde higher than 0.04%. Neither micropore filtration nor ektacytometry measurements could accurately predict the AMVN perfusion. Treatment with diamide reduced RBC deformability as indicated by ektacytometry, but had no significant effect on either micropore filtration or the AMVN perfusion. Both micropore filtration and ektacytometry showed a linear decline in effective RBC deformability with increasing fraction of non-deformable RBCs in the sample. The corresponding decline in the AMVN perfusion plateaued above 50%, reflecting the innate ability of blood flow in the microvasculature to bypass occluded capillaries. Our results suggest that in vitro measurements of RBC deformability performed using either micropore filtration or ektacytometry may not represent the ability of same RBCs to perfuse microvascular networks. Further development of biomimetic tools for measuring RBC deformability (e.g. the AMVN) could enable a more functionally relevant testing of RBC mechanical properties

Rigorous Multicomponent Reactive Separations Modelling : Complete Consideration of Reaction-Diffusion Phenomena

This paper gives the first step of the development of a rigorous multicomponent reactive separation model. Such a model is highly essential to further the optimization of acid gases removal plants (CO2 capture, gas treating, etc.) in terms of size and energy consumption, since chemical solvents are conventionally used.Firstly, two main modelling approaches are presented: the equilibrium-based and the rate-based approaches. Secondly, an extended rate-based model with rigorous modelling methodology for diffusion-reaction phenomena is proposed. The film theory and the generalized Maxwell-Stefan equations are used in order to characterize multicomponent interactions. The complete chain of chemical reactions is taken into account. The reactions can be kinetically controlled or at chemical equilibrium, and they are considered for both liquid film and liquid bulk. Thirdly, the method of numerical resolution is described. Coupling the generalized Maxwell-Stefan equations with chemical equilibrium equations leads to a highly non-linear Differential-Algebraic Equations system known as DAE index 3. The set of equations is discretized with finite-differences as its integration by Gear method is complex. The resulting algebraic system is resolved by the Newton- Raphson method. Finally, the present model and the associated methods of numerical resolution are validated for the example of esterification of methanol. This archetype non-electrolytic system permits an interesting analysis of reaction impact on mass transfer, especially near the phase interface. The numerical resolution of the model by Newton-Raphson method gives good results in terms of calculation time and convergence. The simulations show that the impact of reactions at chemical equilibrium and that of kinetically controlled reactions with high kinetics on mass transfer is relatively similar. Moreover, the Fick’s law is less adapted for multicomponent mixtures where some abnormalities such as counter-diffusion take place

Quizz en Infectiologie

National audienc

On the Effective Action of Noncommutative Yang-Mills Theory

We compute here the Yang-Mills effective action on Moyal space by integrating over the scalar fields in a noncommutative scalar field theory with harmonic term, minimally coupled to an external gauge potential. We also explain the special regularisation scheme chosen here and give some links to the Schwinger parametric representation. Finally, we discuss the results obtained: a noncommutative possibly renormalisable Yang-Mills theory.Comment: 19 pages, 6 figures. At the occasion of the "International Conference on Noncommutative Geometry and Physics", April 2007, Orsay (France). To appear in J. Phys. Conf. Se

Resistance and resilience of ecosystem descriptors and properties to dystrophic events: a study case in a Mediterranean lagoon

Mediterranean lagoons are naturally exposed, during the dry season, to dystrophic and hypoxic events determining dis-equilibrium conditions along temporal and spatial scales, which are linked to metabolism and life cycle of the biotic components. In summer 2008, Lesina lagoon (SE Italian coastline) was interested by a geographically localized dystrophic crisis which affected up to 8% of the total lagoon surface. Temporal dynamics of principal descriptors of abiotic (water, sediment) and biotic (phytoplankton, benthic macroinvertebrate) compartments have been followed during the 2008 by collecting data inside stressed and control lagoon areas before a dystrophic event and in the six months after the dystrophic event. The aim of the study was to analyse the pathways of ecosystem responses to dystrophic stress, searching for the characteristic scales of ecosystem compartment resistance and resilience. The characteristic time-scale of abiotic and biotic component time responses varied from days, for the selected markers of the water column, to year, for the benthic ones. Short-term biotic and abiotic responses in the water column were strongly coupled while biotic and abiotic responses at the sediment level were remarkably un-coupled. Dynamics and recovery time of water column and benthic components do not match in Lesina following the dystrophic crisis, highlighting an intrinsic individualistic behavior within the lagoon community driving ecosystem processes and ecosystem level responses. Taxonomic and non-taxonomic descriptors of both phytoplankton and benthic macroinvertebrates showed different response patterns as early warning signals and overall resilience. The emphasized differences in the stability components, i.e., resistance and resilience, of water column and sediment abiotic and biotic characteristics as well as of taxonomic and non-taxonomic descriptors has key implication in planning monitoring strategies and programs for transitional waters in the Mediterranean and Black Sea EcoRegions

Overview of the parametric representation of renormalizable non-commutative field theory

We review here the parametric representation of Feynman amplitudes of renormalizable non-commutative quantum field models.Comment: 10 pages, 3 figures, to be published in "Journal of Physics: Conference Series

Degenerate noncommutativity

We study a renormalizable four dimensional model with two deformed quantized space directions. A one-loop renormalization is performed explicitly. The Euclidean model is connected to the Minkowski version via an analytic continuation. At a special value of the parameters a nontrivial fixed point of the renormalization group occurs.Comment: 16 page