Analyse de sous-maille par densité présumée en Simulation des Grandes Echelles

On s'intéresse à la modélisation des termes de réaction en Simulation des Grandes Echelles d'écoulements turbulents. La densité de sous-maille est souvent approchée dans ce cadre par une loi beta. Les estimateurs optimaux pour ce problème sont étudiés. Ils montrent que le choix des lois beta est justifié. L'essentiel de l'erreur commise provient en effet du choix des paramètres fondamentaux du modèle. Nous montrons ainsi que les estimateurs optimaux constituent un outil pertinent pour l'exploration des modèles de sous-maille et la recherche de pistes pour des améliorations futures

Tom-based tools to transform EMF models in avionics context

International audienceModel Driven Engineering (MDE) is now widely used in many industrial contexts (such as AeroSpace) which require a high level of system safety. Model-checking is one of the formal techniques which are used to assess a system compliance to its requirements. It relies on verification dedicated languages to model the system under verification and the expected properties. In order to ease the use of these tools, model transformations are provided that translate the end user provided system model to the formal languages than can be verified. In order to rely on these activities for system certification, the correctness of these transformation steps must be assessed (qualification of the development and verification tools). One of the goal of our work is to provide tools to implement the transformation steps between end user source languages used for the system development and target languages used for formal verification. This paper present the {Tom} rule-based approach used in a research project involving industrial partners: Airbus and Ellidiss

Interleukin 2 production by peripheral blood lymphocytes in allograft recipients during acute rejection episodes

Interleukin 2 production by peripheral blood lymphocytes in allograft recipients during acute rejection episodes. Inthis study we investigate the relationship between the Interleukin 2 (IL-2) yield produced by kidney allograft recipient's peripheral blood lymphocytes (PBL) under lectin stimulation and the occurrence of acute rejection episodes. PBL were harvested prospectively before grafting, after grafting in steady-state period, and at the onset of acute rejection episodes. In addition, we tested retrospectively the ability of PBL of recipients engrafted for more than 1yr to produce IL-2. IL-2 levels were assessed on the IL-2-dependent CTL-L2 murine cell line. Our data show: 1) before grafting, hemodialysed patients (N = 14) produced normal IL-2 yield compared with healthy donors (N = 21); 2) the IL-2 secretion of PBL ofrecipients with good graft function (N = 18) is decreased markedly during roughly the first 12 months following transplantation (P < 0.01); 3) when acute rejection crisis occurred during this time period (N = 24), a sharp and highly significant increment (P < 0.01) in lectin-induced IL-2 production of recipient's PBL was seen. After 1 yr, the capacity to secrete IL-2 upon lectin stimulation tends to be restored. Finally, our data correlate rejection and high PBL-IL-2 secretion clearly at a time when recipients with well-functioning grafts have markedly impaired IL-2 secretion

Altered dendritic cell distribution in patients with common variable immunodeficiency

Recent data suggest a critical role for dendritic cells (DCs) in the generation of immunoglobulin-secreting plasma cells. In the work reported herein, we analyzed the frequency of peripheral blood plasmacytoid DCs (pDCs) and myeloid DCs (mDCs) in a cohort of 44 adults with common variable immunodeficiency (CVID) classified according to their CD27 membrane expression status on B cells. A deep alteration in the distribution of DC subsets, especially of pDCs, in the peripheral blood of CVID patients was found. Patients with a reduced number of class-switched CD27(+)IgD(-)IgM(- )memory B cells and patients with granulomatous disease had a dramatic decrease in pDCs (P = 0.00005 and 0.0003 vs controls, respectively) and, to a lesser extent, of mDCs (P = 0.001 and 0.01 vs controls, respectively). In contrast, patients with normal numbers of switched memory B cells had a DC distribution pattern similar to that in controls. Taken together, our results raise the possibility that innate immunity contributes to pathogenesis in CVID

Expression of HLA-G in human cornea, an immune-privileged tissue.

Human leukocyte antigen (HLA)-G retains the capacity to modulate immune responses, favoring the establishment of tolerance in solid-tissue allotransplants. To better understand the mechanisms that promote corneal allograft survival, we investigated whether HLA-G was an immunoregulatory factor involved in corneal immunology. We therefore sought HLA-G expression in corneal tissues. Corneal transplantation consists in replacing the center of a diseased cornea with normal corneal tissue. Two corneal parts are not used in such surgery: diseased central corneal tissue and peripheral normal cornea. For this study, we used healthy corneas obtained from deceased donors and diseased corneas obtained from patients with pseudophakic bullous keratopathy or keratoconus who had undergone corneal transplantation. Immunohistochemical analysis carried out on the cryopreserved corneas showed a positive immunohistochemical staining with anti-HLA-G, anti-HLA-A, -B, and -C, and anti-HLA class I monoclonal antibodies. Staining was obtained for keratocytes, epithelial cells, and endothelial cells from both healthy and pathologic human corneas, revealing the presence of HLA class I proteins, including HLA-G. HLA-G transcripts were detected in normal cornea by reverse transcriptase-polymerase chain reaction with a classical pattern of alternative splicing. The detection of HLA-G protein in adult corneas leads to the conclusion that this protein may contribute to the maintenance of the privileged immune status of cornea

Model Transformations with Tom

International audienceModel Driven Engineering (MDE) advocates the use of Model Transformations (MT) in order to automate repetitive development tasks. Many different model transformation languages have been proposed with a significant tool development cost as common language elements like expressions, statements, ... must be built from scratch for each new language development tools. The Tom language is a shallow extension of Java tailored to describe and implement transformations of tree based data-structures. A key feature of Tom allows to map any Java data-structure to tree based data abstractions that can then be accessed by powerful non-linear, associative, commutative pattern matching. In this paper, we present how this approach can be used in order to develop model transformations, in particular relying on Eclipse Modeling Framework (EMF) based metamodeling facilities. This allows to provide a transformation language at a low cost both for the development of its tools and the training of its users

Tom-based tools to transform EMF models in avionics context

International audienceModel Driven Engineering (MDE) is now widely used in many industrial contexts (such as AeroSpace) which require a high level of system safety. Model-checking is one of the formal techniques which are used to assess a system compliance to its requirements. It relies on verification dedicated languages to model the system under verification and the expected properties. In order to ease the use of these tools, model transformations are provided that translate the end user provided system model to the formal languages than can be verified. In order to rely on these activities for system certification, the correctness of these transformation steps must be assessed (qualification of the development and verification tools). One of the goal of our work is to provide tools to implement the transformation steps between end user source languages used for the system development and target languages used for formal verification. This paper present the {Tom} rule-based approach used in a research project involving industrial partners: Airbus and Ellidiss

Early calcium increase triggers the formation of olfactory long-term memory in honeybees

<p>Abstract</p> <p>Background</p> <p>Synaptic plasticity associated with an important wave of gene transcription and protein synthesis underlies long-term memory processes. Calcium (Ca²⁺) plays an important role in a variety of neuronal functions and indirect evidence suggests that it may be involved in synaptic plasticity and in the regulation of gene expression correlated to long-term memory formation. The aim of this study was to determine whether Ca²⁺is necessary and sufficient for inducing long-term memory formation. A suitable model to address this question is the Pavlovian appetitive conditioning of the proboscis extension reflex in the honeybee <it>Apis mellifera, </it>in which animals learn to associate an odor with a sucrose reward.</p> <p>Results</p> <p>By modulating the intracellular Ca²⁺concentration ([Ca²⁺]i) in the brain, we show that: (i) blocking [Ca²⁺]i increase during multiple-trial conditioning selectively impairs long-term memory performance; (ii) conversely, increasing [Ca²⁺]i during single-trial conditioning triggers long-term memory formation; and finally, (iii) as was the case for long-term memory produced by multiple-trial conditioning, enhancement of long-term memory performance induced by a [Ca²⁺]i increase depends on <it>de novo </it>protein synthesis.</p> <p>Conclusion</p> <p>Altogether our data suggest that during olfactory conditioning Ca²⁺is both a necessary and a sufficient signal for the formation of protein-dependent long-term memory. Ca²⁺therefore appears to act as a switch between short- and long-term storage of learned information.</p

Long term expression of bicistronic vector driven by the FGF-1 IRES in mouse muscle

<p>Abstract</p> <p>Background</p> <p>Electrotransfer of plasmid DNA into skeletal muscle is a promising strategy for the delivery of therapeutic molecules targeting various muscular diseases, cancer and lower-limb ischemia. Internal Ribosome Entry Sites (IRESs) allow co-expression of proteins of interest from a single transcriptional unit. IRESs are RNA elements that have been found in viral RNAs as well as a variety of cellular mRNAs with long 5' untranslated regions. While the encephalomyocarditis virus (EMCV) IRES is often used in expression vectors, we have shown that the FGF-1 IRES is equally active to drive short term transgene expression in mouse muscle. To compare the ability of the FGF-1 IRES to drive long term expression against the EMCV and FGF-2 IRESs, we performed analyses of expression kinetics using bicistronic vectors that express the bioluminescent <it>renilla </it>and firefly luciferase reporter genes. Long term expression of bicistronic vectors was also compared to that of monocistronic vectors. Bioluminescence was quantified <it>ex vivo </it>using a luminometer and <it>in vivo </it>using a CCD camera that monitors luminescence within live animals.</p> <p>Results</p> <p>Our data demonstrate that the efficiency of the FGF-1 IRES is comparable to that of the EMCV IRES for long term expression of bicistronic transgenes in mouse muscle, whereas the FGF-2 IRES has a very poor activity. Interestingly, we show that despite the global decrease of vector expression over time, the ratio of firefly to <it>renilla </it>luciferase remains stable with bicistronic vectors containing the FGF-1 or FGF-2 IRES and is slightly affected with the EMCV IRES, whereas it is clearly unstable for mixed monocistronic vectors. In addition, long term expression more drastically decreases with monocistronic vectors, and is different for single or mixed vector injection.</p> <p>Conclusion</p> <p>These data validate the use of bicistronic vectors rather than mixed monocistronic vectors for long term expression, and support the use of the FGF-1 IRES. The use of a cellular IRES over one of viral origin is of particular interest in the goal of eliminating viral sequences from transgenic vectors. In addition, the FGF-1 IRES, compared to the EMCV IRES, has a more stable activity, is shorter in length and more flexible in terms of downstream cloning of second cistrons. Finally, the FGF-1 IRES is very attractive to develop multicistronic expression cassettes for gene transfer in mouse muscle.</p