Solution of the incompressible Navier-Stokes equations by the nonlinear Galerkin method

Our aim in this article is to study a new method for the approximation of the Navier-Stokes equations, and to present and discuss numerical results supporting the method. This method, called the nonlinear Galerkin method, uses nonlinear manifolds which are close to the attractor, while in the usual Galerkin method, we look for solutions in a linear space, i.e., whose components are independent. The equation of the manifold corresponds to an interaction law between small and large eddies and it is derived by asymptotic expansion from the exact equation. We consider here the two- and three-dimensional space periodic cases in the context of a pseudo-spectral discretization of the equation. We notice however that the method applies as well to more general flows, in particular nonhomogeneous flows.     

Analysis of signal transduction pathways in human eosinophils activated by chemoattractants and the T-helper 2-derived cytokines interleukin-4 and interleukin-5

Activation and recruitment of eosinophils in allergic inflammation is in part mediated by chemoattractants and T-helper 2 (Th2)-derived cytokines. However, little is known concerning the signal transduction mechanisms by which this activation occurs. We have investigated tyrosine kinase-mediated activation of phosphatidylinositol 3-kinase (PI3K) and compared this with the activation of the p21ras-ERK signaling pathway in human eosinophils. The related cytokines interleukin-3 (IL-3), IL-5, and granulocyte-macrophage colony-stimulating factor (GM-CSF), all induced PI3K activity detected in antiphosphotyrosine immunoprecipitates. Furthermore, the chemoattractants platelet-activating factor (PAF), RANTES, and C5a were also able to induce phosphotyrosine-associated PI3K activity. Protein kinase B (PKB) is a downstream target of PI3K activation by growth factors. Induction of PKB phosphorylation in human eosinophils was transiently induced on activation with the cytokines IL-4 and IL-5, as well as the chemoattractants PAF, C5a, and RANTES showing a broad activation profile. Surprisingly, analysis of the activation of the mitogen-activated protein (MAP) kinases p44(ERK1) and p42(ERK2), showed that ERK2, but not ERK1, was transiently activated in human eosinophils after stimulation with IL-5 or PAF. Activation kinetics correlated with activation of p21ras by both cytokines and chemoattractants as measured by a novel assay for guanosine triphosphate (GTP)-loading. Finally, using specific inhibitors of both the p21ras-ERK and PI3K signaling pathways, a role was demonstrated for PI3K, but not p21ras-ERK, in activation of the serum-treated zymosan (STZ)-mediated respiratory burst in IL-5 and PAF-primed eosinophils. In summary, these data show that in human eosinophils, Th2-derived cytokines differentially activate both PI3K and MAP kinase signal transduction pathways with distinct functional consequences showing complex regulation of eosinophil effector functions.     

Acute scrotum in the child

Although long-term studies report successful results with total knee arthroplasty (TKA), performed with or without posterior cruciate ligament (PCL) retention, controversy exists as to which is preferable in regard to patient outcome and satisfaction. The possible proprioceptive role of the PCL may account for a more normal feeling of the arthroplasty. Although the PCL has been examined using various histological techniques, immunohistochemical techniques are the most sensitive for neural elements. Therefore an immunohistochemical study was designed to determine the patterns of innervation, the morphological types of the proprioceptors, and their immunohistochemical profile. During TKA, samples were obtained from 22 osteoarthritic PCLs and subjected to immunohistochemical analysis with mouse monoclonal antibodies against neurofilament protein (NFP), S100 protein (S100P), epithelial membrane antigen (EMA), and vimentin (all present in neuromechanoreceptors). Three normal PCLs from cadaveric specimens were also obtained and analyzed for comparison. Five types of sensory corpuscles were observed in both the normal and the arthritic PCLs: simple lamellar, Pacini-like, Ruffini, Krause-like, and morphologically unclassified. Their structure included a central axon, inner core, and capsule in lamellar and Pacini corpuscles and variable intracorpuscular axons and periaxonal cells in the Ruffini and Krause-like corpuscles. The immunohistochemical profile showed the central axon to have NFP immunoreactivity, periaxonal cells to have S100P and vimentin immunoreactivity, and the capsule to have EMA and vimentin immunoreactivity. Nerve fibers and free nerve endings displayed NFP and S100P immunoreactivity. The immunohistochemical profile of the PCL sensory corpuscles is almost identical to that of cutaneous sensory corpuscles. Some prior histological studies of the PCL reported Golgi-like mechanoreceptors, and others found encapsulated corpuscles but no Golgi-like structures. This report determined the innervation of the PCL by the more sensitive immunohistochemical means, revealing four major types of encapsulated mechanoreceptors. The plentiful and varied types of encapsulated mechanoreceptors found in even the arthritic PCL suggests a rich proprioceptive role. It is controversial as to whether preservation of the PCL at TKA improves postoperative proprioception. Our findings tend to support those clinical reports of improved proprioception after PCL-retaining versus PCL-substituting TKAs. The presence of many and varied types of mechanoreceptors may account for the improved stair climbing reported in patients with PCL-retaining TKA and may contribute to patient satisfaction and a more normal feeling after TKA.     

Analysis of metal- ceramic bonding by frettage

Metal-ceramic bonds have been produced by sintering a metallic hollow cold-pressed cylinder (iron-based powder) around a ceramic insert (silicon nitride). Pushout tests were carried out to characterize the bond strength. An analytical model considering a strain-hardening plastic matrix was developed and used to analyze the pushout tests in terms of residual stresses. Dilatometry and tensile tests were also carried out on the matrix materials in order to characterize phase transformations and mechanical behavior. These data are then used in the model to calculate a friction coefficient between the steel and the ceramic at different temperatures. The validity of the model is checked by comparing measured and calculated hoop deformations of the metal ring during pushout. formerly Undergraduate Student, Ecole des Mines de Paris. formerly Research Engineer with the Metafram Company.     

Electrical properties of electrochemically prepared thin polytetrahydrofuran films II: Characterization under D.C. conditions

The electrical characteristics of electrochemically prepared polytetrahydrofuran (poly-THF) films were studied under d.c. conditions. At low fields (?10⁵ V cm^?1) a phonon-assisted hopping conduction occurs in poly-THF films 2000 Å thick. The low temperature dependence of the conductivity (T< 243 K) is related to interchain hopping, whereas the high temperature dependence of the conductivity (>320 K) is ascribed to trap hopping. At high fields (E>10⁵ V cm^?1) and high temperatures (T>320 K) Schottky conduction is observed and the Schottky barrier height depends both on the electrode metal and on the field direction. At temperatures below 320 K, Poole-Frenkel conduction occurs and the current intensity is independent of the nature of the electrodes and of the field direction. At very low temperatures (T<100 K) and high fields (E>10⁶ V cm^?1), thermally assisted tunnel effect conduction (δj∞T²) is observed. These changes in conduction with the temperature and the field are ascribed to changes in the polymer structure.     

Un schema regional des gravieres selon l'article 109.1 du code minier français

The extraction of aggregates in the alluvial Plain of Alsace has grown rapidly since 1962. The production of these aggregates, half of which are exported, has certainly had positive effects on the local economy, but the untidy sprawl of extraction sites had had a damaging impact on the local environment (effects on water table, rural landscape and land prices). To deal with this situation, the regional authorities have decided to define a regional policy on gravel pits, with three objectives: maximum economic return on deposits, protection of the environment and recovering of worked-out pits. Under Article 109-1 of the French Mining Code, the Region of Alsace has embarked on the operational phase of this new policy on gravel pits by commissioning studies of 7 “Zones.... Gravières” or “Coordinated Gravel Extraction and Site Revovering Zones” (ZERC). Within these zones, 16 potential gravel extraction areas have been defined. Detailed studies will make it possible to establish the economic, geological, geotechnical, hydrogeological and agricultural criteria which will determine the siting of future gravel pits to meet production requirements for the next 30 years. Apart from these studies, consultation between the industry, elected representatives and local government bodies is necessary in working out such a scheme, whose purpose is to ensure that gravel extraction can exist in harmony side by side with agriculture or any other industrial or leisure activity in the region.     

Allergen-avoidance measures in homes of house-dust-mite-allergic asthmatic patients: effects of acaricides and mattress encasings

This double-blind, placebo-controlled study investigated whether the application of an acaricide (Acarosan) on mattresses and on textile floor coverings in living rooms and bedrooms can contribute to improvement in lung function and airway hyperresponsiveness in 40 adult asthmatic patients sensitized to house-dust mite. In a second group of 19 patients who refused chemical intervention, the clinical effects of application of allergen-impermeable mattress encasings were studied. In all three treatment groups, Der p 1 levels in mattress dust were statistically significantly decreased after 12 months. However, this decrease was much greater in the group who received mattress encasings (final mean level 430 ng/g) than in groups with acaricide- or placebo-treated mattresses (final mean levels 1730 and 2100 ng/g, respectively). Treatment of textile floors with either Acarosan or placebo chemical caused a statistically significant decrease in the level of the house-dust-mite allergen Der p1 in floor dust. In the group with mattress encasings, no significant changes of floor dust Der p 1 were found. Airway hyperresponsiveness (as measured by the PC20 histamine) improved significantly in the mattress cover group after 6 months. The Acarosan group also showed a small but statistically significant improvement after 12 months.     

SPIC: a training simulator for coelioscopic interventions with gynecologic purpose

In order to assess the diagnostic accuracy of stress/rest myocardial perfusion scintigraphy in the follow-up of patients undergoing percutaneous transluminal coronary angioplasty (PTCA) we studied 50 patients (pts) before and 6 months after PTCA. All patients underwent control coronary angiography and then were divided in 2 groups, according to angiographic evidence of restenosis (25 pts) or no restenosis (25 pts). Myocardial perfusion imaging was performed with 99mTc-methoxy-isobutyl-isonitrile (MIBI). For MIBI scans, both qualitative and semi-quantitative analysis were performed. SPECT images were displayed on a color monitor in random order and graded blindly by 2 experienced observers. Rest and stress MIBI uptake was scored using a 4-point scale (ranging from 0 = normal, to 3 = absence of uptake). Individual subjects' perfusion scores were calculated by adding the individual segments' scores. History of relapsing angina showed a sensitivity and specificity of 76 and 96%, respectively. Exercise testing and MIBI tomoscintigraphy exhibited sensitivity and specificity of 80 and 56%, and 92 and 44%, respectively. However, when considering semiquantitative data and comparing them with pre-PTCA studies, specificity of MIBI scan increased to 96%, while sensitivity decreased to 72%. The results of the present study confirm high sensitivity and low specificity for both exercise ECG and myocardial perfusion scintigraphy, in the detection of restenosis following PTCA. However, when performing semiquantitative analysis of perfusion scanning and comparison with pre-PTCA images, the specificity of MIBI tomoscintigraphy increases significantly. Therefore, when adopting myocardial perfusion scintigraphy for the follow-up of patients undergoing PTCA, a pre-revascularization scan should be obtained as often as possible. This approach, in the context of a positive test, makes feasible the assessment of often partial improvements in perfusion of the myocardium relative to the treated vessel, consequently avoiding many false positive results which invariably lead to coronary angiography.     

The Influence of C60 Powders On Cultured Human Leukocytes

In order to check its possible acute toxicity, C₆₀ was incorporated into living human phagocytes. It was observed that C₆₀ has no influence on the survival of human leukocytes.     

Macromolecular engineering of polylactones and polylactides

Summary Aluminum alkoxides carrying functional alkoxy groups are effective initiators for the-caprolactone polymerization in toluene and tetrahydrofuran. The coordination-insertion type of polymerization is living and yields exclusively linear polyesters of a predictable molecular weight with a narrow molecular weight distribution within the period of time required for the total monomer conversion. The functional group associated to the active alkoxy group of the initiator is selectively attached to one chain-end, and the second end-group is systematically a hydroxyl function resulting from the hydrolysis of the living growing site. Asymmetric telechelic polyesters are thus obtained in a perfectly controlled way, including macromonomers. Beside (meth)acrylic double bond, the functional end-group derived from the initiator can be, for instance, an unsaturation, a halogen and a tert-amine. Coupling the asymmetric telechelic polymer via the OH end-group (or the precursor Al alkoxide end-group) is a direct way to the related symmetric telechelic of a twofold increased molecular weight.The authors are indebted to IRSIA for a fellowship to one of them (Ph. Dubois) and to the Services de la Programmation de la Politique Scientifique for financial support. NMR spectra were recorded at the CREMAN facility of the University of Liège which has been funded by a grant from the Fonds National de la Recherche Scientifique. The helpful assistance of Dr. Warin has been very much appreciated. They are very greatful to G. Broze (Colgate Palmolive) who initiated this research.