Cross-comparison of convergence algorithms to solve trip-based dynamic traffic assignment problems

Solving a dynamic traffic assignment problem in a transportation network is a computational challenge. This study first reviews the different algorithms in the literature used to numerically calculate the User Equilibrium (UE) related to dynamic network loading. Most of them are based on iterative methods to solve a fixed-point problem. Two elements must be computed: the path set and the optimal path flow distribution between all origin-destination pairs. In a generic framework these two steps are referred to as the outer and the inner loops, respectively. The goal of this study is to assess the computational performance of the inner loop methods that calculate the path flow distribution for different network settings (mainly network size and demand levels). Several improvements are also proposed to speed up convergence: four new swapping algorithms and two new methods for the step size initialization used in each descent iteration. All these extensions significantly reduce the number of iterations to obtain a good convergence rate and drastically speed up the overall simulations. The results show that the performance of different components of the solution algorithm is sensitive to the network size and saturation. Finally, the best algorithms and settings are identified for all network sizes with particular attention being given to the largest scale

Estimation de la durée de vie d'un collecteur en acier P91

National audienceLes aciers ferritiques-martensitiques P91sont réputés pour leur bonnes propriétés de tenue au fluage. Déjà largement présents dans les centrales thermiques classiques, ils sont candidats pour une utilisation dans les futurs réacteurs nucléaires de génération IV. L'intégrité des jonctions soudées est un sujet d'intérêt tant pour les ingénieurs que pour les chercheurs depuis de nombreuses années. Cet intérêt est d'autant plus prononcé, dans le cas des aciers P91, qu'il est connu que le soudage a des conséquences importantes sur leur tenue au fluage. La rupture apparaît dans la Zone Affectée Thermiquement (rupture de type IV dans la zone intercritique) délimitée d'un côté par le métal de base, de l'autre par le métal d'apport. Cette zone ductile présente des propriétés mécaniques affaiblies par rapport au métal de base. La différence de propriétés mécaniques induit des effets de confinement de la déformation de la ZAT de type IV, la soumettant à des chargements multiaxiaux complexes. L'objet du présent papier est double. D'une part on présente les grandes lignes d'un modèle d'approche locale de l'endommagement par fluage du joint soudé de l'acier P91 (9Cr-1Mo-NbV) à 625°C. Ce modèle, basé sur une approche multi-matériaux, met en jeu les propriétés différentes du métal de base, du métal d'apport ainsi que de la ZAT, et en exhibe les conséquences mécaniques sur le développement d'endommagement dans la zone intercritique. D'autre part, ce modèle est appliqué à la prédiction de la durée de vie en fluage d'un collecteur roulé-soudé en acier P91, fonctionnant à 580°C. La particularité de ce collecteur réside dans son défaut de soudage, qui génère un effet de toit, donc des concentrations de contrainte au niveau du joint soudé. L'effet de ces surcontraintes est traduit en termes de réduction de durée de vie estimée

Anti-glomerular basement membrane disease, ulcerative colitis, and primary sclerosing cholangitis: link or co-incidence?

International audienceUlcerative colitis, primary sclerosing cholangitis, and anti-glomerular basement membrane disease (anti-GBM) are three rare immune diseases with incompletely under-stood pathogenic mechanisms. We describe here the case of a 29-year-old man with ulcer-ative colitis and primary sclerosing cholang -itis who, eight years later, developed anti-GBM disease with destruction of all glomeruli leading to end-stage kidney disease. Association of these three immune diseases in the same patient has never been described. Because HLA-mediated susceptibility cannot be incriminated completely in our case, we hypothesize that environmental factors or previous immunosuppressive treatment used might be the link

A murine intestinal intraepithelial NKp46-negative innate lymphoid cell population characterized by group 1 properties

The Ly49E receptor is preferentially expressed on murine innate-like lymphocytes, such as epidermal V gamma 3 T cells, intestinal intraepithelial CD8 alpha alpha(+) T lymphocytes, and CD49a(+) liver natural killer (NK) cells. As the latter have recently been shown to be distinct from conventional NK cells and have innate lymphoid cell type 1 (ILC1) properties, we investigated Ly49E expression on intestinal ILC populations. Here, we show that Ly49E expression is very low on known ILC populations, but it can be used to define a previously unrecognized intraepithelial innate lymphoid population. This Ly49E-positive population is negative for NKp46 and CD8 alpha alpha, expresses CD49a and CD103, and requires T-bet expression and IL-15 signaling for differentiation and/or survival. Transcriptome analysis reveals a group 1 ILC gene profile, different from NK cells, iCD8 alpha cells, and intraepithelial ILC1. Importantly, NKp46(-)CD8 alpha alpha(-)Ly49E(+) cells produce interferon (IFN)-gamma, suggesting that this previously unrecognized population may contribute to Th1-mediated immunity

Defective CD4(+)CD25(+ )regulatory T cell functioning in collagen-induced arthritis: an important factor in pathogenesis, counter-regulated by endogenous IFN-γ

Mice with a deficiency in IFN-γ or IFN-γ receptor (IFN-γR) are more susceptible to collagen-induced arthritis (CIA), an experimental autoimmune disease that relies on the use of complete Freund's adjuvant (CFA). Here we report that the heightened susceptibility of IFN-γR knock-out (KO) mice is associated with a functional impairment of CD4(+)CD25(+ )T(reg )cells. Treatment of wild-type mice with depleting anti-CD25 antibody after CFA-assisted immunisation with collagen type II (CII) significantly accelerated the onset of arthritis and increased the severity of CIA. This is an indication of a role of T(reg )cells in the effector phase of CIA. IFN-γR deficiency did not affect the number of CD4(+)CD25(+ )T cells in the central and peripheral lymphoid tissues. In addition, CD4(+)CD25(+ )T cells isolated from naive IFN-γR KO mice had a normal potential to suppress T cell proliferation in vitro. However, after immunisation with CII in CFA, the suppressive activity of CD4(+)CD25(+ )T cells became significantly more impaired in IFN-γR-deficient mice. Moreover, expression of the mRNA for Foxp3, a highly specific marker for T(reg )cells, was lower. We further demonstrated that the effect of endogenous IFN-γ, which accounts for more suppressive activity in wild-type mice, concerns both T(reg )cells and accessory cells. Our results demonstrate that the decrease in T(reg )cell activity in CIA is counter-regulated by endogenous IFN-γ

Human Listeriosis Caused by Listeria ivanovii

Two species of Listeria are pathogenic; L. monocytogenes infects humans and animals, and L. ivanovii has been considered to infect ruminants only. We report L. ivanovii–associated gastroenteritis and bacteremia in a man. This isolate was indistinguishable from prototypic ruminant strains. L. ivanovii is thus an enteric opportunistic human pathogen

Aircraft-Engine Particulate Matter Emissions from Conventional and Sustainable Aviation Fuel Combustion: Comparison of Measurement Techniques for Mass, Number, and Size

Sustainable aviation fuels (SAFs) have different compositions compared to conventional petroleum jet fuels, particularly in terms of fuel sulfur and hydrocarbon content. These differences may change the amount and physicochemical properties of volatile and non-volatile particulate matter (nvPM) emitted by aircraft engines. In this study, we evaluate whether comparable nvPM measurement techniques respond similarly to nvPM produced by three blends of SAFs compared to three conventional fuels. Multiple SAF blends and conventional (Jet A-1) jet fuels were combusted in a V2527-A5 engine, while an additional conventional fuel (JP-8) was combusted in a CFM56-2C1 engine. We evaluated nvPM mass concentration measured by three real-Time measurement techniques: photoacoustic spectroscopy, laser-induced incandescence, and the extinction-minus-scattering technique. Various commercial instruments were tested, including three laser-induced incandescence (LII) 300s, one photoacoustic extinctiometer (PAX), one micro soot sensor (MSS+), and two cavity-Attenuated phase shift PMSSA (CAPS PMSSA) instruments. Mass-based emission indices (EIm) reported by these techniques were similar, falling within 30ĝ€¯% of their geometric mean for EIm above 100ĝ€¯mg per kg fuel (approximately 10ĝ€¯μgĝ€¯PMĝ€¯m-3 at the instrument); this geometric mean was therefore used as a reference value. Additionally, two integrative measurement techniques were evaluated: filter photometry and particle size distribution (PSD) integration. The commercial instruments used were one tricolor absorption photometer (TAP), one particle soot absorption photometer (PSAP), and two scanning mobility particle sizers (SMPSs). The TAP and PSAP were operated at 5ĝ€¯% and 10ĝ€¯% of their nominal flow rates, respectively, to extend the life of their filters. These techniques are used in specific applications, such as on board research aircraft to determine particulate matter (PM) emissions at cruise. EIm reported by the alternative techniques fell within approximately 50ĝ€¯% of the mean aerosol-phase EIm. In addition, we measured PM-number-based emission indices using PSDs and condensation particle counters (CPCs). The commercial instruments used included TSI SMPSs, a Cambustion differential mobility spectrometer (DMS500), and an AVL particle counter (APC), and the data also fell within approximately 50ĝ€¯% of their geometric mean. The number-based emission indices were highly sensitive to the accuracy of the sampling-line penetration functions applied as corrections. In contrast, the EIm data were less sensitive to those corrections since a smaller volume fraction fell within the size range where corrections were substantial. A separate, dedicated experiment also showed that the operating laser fluence used in the LII 300 laser-induced incandescence instrument for aircraft-engine nvPM measurement is adequate for a range of SAF blends investigated in this study. Overall, we conclude that all tested instruments are suitable for the measurement of nvPM emissions from the combustion of SAF blends in aircraft engines