Thermal and mechanical structure of the upper mantle: A comparison between continental and oceanic models

Temperature, velocity, and viscosity profiles for coupled thermal and mechanical models of the upper mantle beneath continental shields and old ocean basins show that under the continents, both tectonic plates and the asthenosphere, are thicker than they are beneath the oceans. The minimum value of viscosity in the continental asthenosphere is about an order of magnitude larger than in the shear zone beneath oceans. The shear stress or drag underneath continental plates is also approximately an order of magnitude larger than the drag on oceanic plates. Effects of shear heating may account for flattening of ocean floor topography and heat flux in old ocean basins

Oceanic lithosphere and asthenosphere: The thermal and mechanical structure

A coupled thermal and mechanical solid state model of the oceanic lithosphere and asthenosphere is presented. The model includes vertical conduction of heat with a temperature dependent thermal conductivity, horizontal and vertical advection of heat, viscous dissipation or shear heating, and linear or nonlinear deformation mechanisms with temperature and pressure dependent constitutive relations between shear stress and strain rate. A constant horizontal velocity u sub 0 and temperature t sub 0 at the surface and zero horizontal velocity and constant temperature t sub infinity at great depth are required. In addition to numerical values of the thermal and mechanical properties of the medium, only the values of u sub 0, t sub 0 and t sub infinity are specified. The model determines the depth and age dependent temperature horizontal and vertical velocity, and viscosity structures of the lithosphere and asthenosphere. In particular, ocean floor topography, oceanic heat flow, and lithosphere thickness are deduced as functions of the age of the ocean floor

Protection from lethal Gram-negative bacterial sepsis by targeting Toll-like receptor 4

Rapport de synthèse : L'immunité innée regroupe les mécanismes moléculaires et cellulaires formant la première ligne de défense contre les infections microbiennes. La détection des micro-organismes pathogènes est assurée par des cellules sentinelles (cellules dendritiques et macrophages) qui jouent un rôle fondamental dans l'initiation des mécanismes de défense de l'hôte. Au contact de produits microbiens, ces cellules produisent un large échantillonnage de molécules, dont des cytokines, impliquées dans le développement de la réponse inflammatoire. La régulation de cette réponse relève d'un équilibre délicat, son insuffisance tant que son excès pouvant compromettre le devenir des patients infectés. La sepsis sévère et le choc septique représentent les formes les plus sévères d'infection, et leur mortalité demeure élevée (25 à 30% pour la sepsis sévère et 50 à 60% pour le choc septique). De plus, l'incidence de la sepsis tend à augmenter, atteignant en 2000 plus de 240 cas pour 100'000 personnes en Grande-Bretagne. La sepsis est caractérisée dans sa phase aiguë par une réponse inflammatoire exubérante. La plupart des thérapies visant à la bloquer ont toutefois montré des bénéfices incertains lors de leur application clinique. Il est donc impératif d'identifier de nouvelles cibles thérapeutiques. Les "Toll-like receptors" (TLRs) sont une famille de récepteurs qui jouent un rôle fondamental dans la détection des micro-organismes par les cellules du système immunitaire inné. Parmi eux, TLR4 est indispensable à la reconnaissance du lipopolysaccharide (LPS) des bactéries Gram-négatives. L'interaction entre TLR4 et le LPS représentant un élément précoce de la réponse de l'hôte à l'infection, nous avons émit l'hypothèse que TLR4 pourrait représenter une cible de choix en vue du développement de nouvelles thérapies contre la sepsis. Dans l'objectif de valider ce concept, nous avons, dans un premier temps, démontré que des souris génétiquement déficientes en TLR4 étaient totalement résistantes au choc septique induit par Escherichia coli (E. coli), une bactérie Gram-négative fréquemment responsable de sepsis. Forts de cette observation, nous avons développé une molécule recombinante composée du domaine extracellulaire de TLR4 fusionné à la partie IgGi-Fc. Cette molécule soluble, qui inhibait la réponse des macrophages au LPS in vitro, a été utilisée pour générer des anticorps anti-TLR4 chez le lapin. La spécificité et l'efficacité de ces anticorps ont été prouvées en démontrant que les anti-TLR4 bloquaient les signaux d'activation intracellulaire et la production de TNF et d'IL-6 en réponse au LPS et aux bactéries Gram-négatives in vitro et in vivo. Enfin, l'efficacité des ces anticorps a été testée dans des modèles de sepsis chez la souris. Ainsi, l'injection prophylactique (-lh) ou thérapeutique (+3h) d'anticorps anti-TLR4 réduisait la production de TNF et protégeait les animaux de la mort. De manière spectaculaire, ces anticorps réduisaient également la production de TNF et protégeaient de la sepsis à E. coli lorsqu'ils étaient administrés de manière prophylactique (-4h) et thérapeutique, jusqu'à 13 heures après l'initiation de l'infection. Ces résultats indiquent donc qu'il est possible de bloquer le développement de la réponse inflammatoire et de protéger du choc septique à bactéries Gram-négatives en utilisant des thérapies ciblant TLR4. Par ailleurs, ils suggèrent qu'une fenêtre d'opportunité de plusieurs heures pourrait être mise à profit pour initier un traitement chez les patients septiques. Ces résultats devraient encourager la poursuite des essais cliniques en cours qui visent à tester l'efficacité de thérapies dirigées contre TLR4 comme traitement complémentaire de la sepsis

Where Fail-Safe Default Logics Fail

Reiter's original definition of default logic allows for the application of a default that contradicts a previously applied one. We call failure this condition. The possibility of generating failures has been in the past considered as a semantical problem, and variants have been proposed to solve it. We show that it is instead a computational feature that is needed to encode some domains into default logic

The UARS microwave limb sounder version 5 data set: Theory, characterization, and validation

Nitric acid (HNO3) is a major player in processes controlling the springtime depletion of polar ozone. It is the main constituent of the Polar Stratospheric Clouds (PSCs) and a primary reservoir for reactive nitrogen. Potential variations in the stratospheric circulation and temperature may alter the extent and duration of PSCs activity, influencing the future ozone levels significantly. Monitoring HNO3 and its long-term variability, especially in polar region, is then crucial for better understanding issues related to ozone decline and expected recovery. In this study we present an intercomparison between ground based HNO3 measurements, carried out by means of the Ground-Based Millimeter-wave Spectrometer (GBMS), and two satellite data sets produced by the two NASA/JPL Microwave Limb Sounder (MLS) experiments. In particular, we compare UARS MLS measurements (1991-1999) with those carried out by the GBMS at South Pole, Antarctica (90°S), Fall of 1993 and 1995. A similar intercomparison is made between Aura MLS HNO3 observations (2004 - to date) and GBMS measurements obtained during the period February 2004 - March 2007, at the mid-latitudes/high altitudes station of Testa Grigia (45.9° N, 7.7° E, elev. 3500 m), and during polar winters 2008/09 and 2009/2010 at Thule Air Base (76.5°N 68.8°W), Greenland. We assess systematic differences between GBMS and both UARS and Aura HNO3 data sets at seven potential temperature levels (θ) spanning the range 465 – 960 K. The UARS data set advected to the South Pole shows a low bias, within 20% for all θ levels but the 960 K, with respect to GBMS measurements. A very good agreement, within 5%, is obtained between Aura and GBMS observations at Testa Grigia, while larger differences, possibly due to latitude dependent effects, are observed over Thule. These differences are under further investigations but a preliminary comparison over Thule among MLS v3, GBMS, and ACE-FTS measurements suggests that GBMS measurements carried out during winter 2009 might not be reliable. These comparisons have been performed in the framework of the NASA JPL GOZCARDS project, which is aimed at developing a long-term, global data record of the relevant stratospheric constituents in the context of ozone decline. GBMS has been selected in GOZCARDS since its HNO3 dataset, although sampling different latitudes in different years, is the only one spanning a sufficiently long time interval for cross-calibrating HNO3 measurements by the UARS and Aura MLS experiments

Use of dipicolinate-based complexes for producing ion-imprinted polystyrene resins for the extraction of yttrium-90 and heavy lanthanide cations

Highly selective separation of yttrium (and lanthanides) is of interest for the design of radiopharmaceuticals, and an efficient method based on the ion-imprinting concept is proposed here. The synthesis and structural, thermodynamic and photophysical characterization of complexes of trivalent yttrium and lanthanides with two new vinyl derivatives of dipicolinic acid, HL1 and L2, are described. The feasibility of using ion-imprinted resins for yttrium and lanthanide separation is demonstrated. The resins were obtained by copolymerization with styrene and divinylbenzene and subsequent acid treatment to remove the metal ion. High-resolution Eu luminescence experiments revealed that the geometry of the complexation sites is well preserved in the imprinted polymers. The ion-imprinted polymer based on HL1 proved to be particularly well adapted for yttrium extraction, having a sizeable capacity (8.9 +- 0.2 g/mg resin) and a fast rate of extraction (t1/2 = 1.7 min). In addition, lighter and heavier lanthanide ions are separated. Finally, the resin displays high selectivity for yttrium and lanthanide cations against alkali and alkaline earth metals. For instance, in a typical experiment, 10 mg of yttrium was extracted from 5 g of milk ash sample by 2 g of the resin. The good separation properties displayed by the resin based on HL1 open interesting perspectives for the production of highly pure 90Y and radiolanthanides for medical applications, and for trace analysis of these radiochemicals in food and in the environment

A Global Climatology of Tropospheric and Stratospheric Ozone Derived from Aura OMI and MLS Measurements

A global climatology of tropospheric and stratospheric column ozone is derived by combining six years of Aura Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) ozone measurements for the period October 2004 through December 2010. The OMI/MLS tropospheric ozone climatology exhibits large temporal and spatial variability which includes ozone accumulation zones in the tropical south Atlantic year-round and in the subtropical Mediterranean! Asia region in summer months. High levels of tropospheric ozone in the northern hemisphere also persist in mid-latitudes over the eastern North American and Asian continents extending eastward over the Pacific Ocean. For stratospheric ozone climatology from MLS, largest ozone abundance lies in the northern hemisphere in the latitude range 70degN-80degN in February-April and in the southern hemisphere around 40degS-50degS during months August-October. The largest stratospheric ozone abundances in the northern hemisphere lie over North America and eastern Asia extending eastward across the Pacific Ocean and in the southern hemisphere south of Australia extending eastward across the dateline. With the advent of many newly developing 3D chemistry and transport models it is advantageous to have such a dataset for evaluating the performance of the models in relation to dynamical and photochemical processes controlling the ozone distributions in the troposphere and stratosphere