Using LES to Study Reacting Flows and Instabilities in Annular Combustion Chambers

Great prominence is put on the design of aeronautical gas turbines due to increasingly stringent regulations and the need to tackle rising fuel prices. This drive towards innovation has resulted sometimes in new concepts being prone to combustion instabilities. In the particular field of annular combustion chambers, these instabilities often take the form of azimuthal modes. To predict these modes, one must compute the full combustion chamber, which remained out of reach until very recently and the development of massively parallel computers. Since one of the most limiting factors in performing Large Eddy Simulation (LES) of real combustors is estimating the adequate grid, the effects of mesh resolution are investigated by computing full annular LES of a realistic helicopter combustion chamber on three grids, respectively made of 38, 93 and 336 million elements. Results are compared in terms of mean and fluctuating fields. LES captures self-established azimuthal modes. The presence and structure of the modes is discussed. This study therefore highlights the potential of LES for studying combustion instabilities in annular gas turbine combustors

Heritability and intrafamilial aggregation of arterial characteristics

BACKGROUND: We investigated the heritability and familial aggregation of various indexes of arterial stiffness and wave reflection and we partitioned the phenotypic correlation between these traits into shared genetic and environmental components. METHODS: Using a family-based population sample, we recruited 204 parents (mean age, 51.7 years) and 290 offspring (29.4 years) from the population in Cracow, Poland (62 families), Hechtel-Eksel, Belgium (36), and Pilsen, the Czech Republic (50). We measured peripheral pulse pressure (PPp) sphygmomanometrically at the brachial artery; central pulse pressure (PPc), the peripheral augmentation indexes (PAIxs) and central augmentation indexes (CAIxs) by applanation tonometry at the radial artery; and aortic pulse wave velocity (PWV) by tonometry or ultrasound. In multivariate-adjusted analyses, we used the ASSOC and PROC GENMOD procedures as implemented in SAGE and SAS, respectively. RESULTS: We found significant heritability for PAIx, CAIx, PPc and mean arterial pressure ranging from 0.37 to 0.41; P </= 0.0001. The method of intrafamilial concordance confirmed these results; intrafamilial correlation coefficients were significant for all arterial indexes (r >/= 0.12; P </= 0.02) with the exception of PPc (r = -0.007; P = 0.90) in parent-offspring pairs. The sib-sib correlations were also significant for CAIx (r = 0.22; P = 0.001). The genetic correlation between PWV and the other arterial indexes were significant (rhoG >/= 0.29; P < 0.0001). The corresponding environmental correlations were only significantly positive for PPp (rhoE = 0.10, P = 0.03). CONCLUSION: The observation of significant intrafamilial concordance and heritability of various indexes of arterial stiffness as well as the genetic correlations among arterial phenotypes strongly support the search for shared genetic determinants underlying these traits

Organising multi-dimensional biological image information: The BioImage Database

Nowadays it is possible to unravel complex information at all levels of cellular organization by obtaining multi-dimensional image information. at the macromolecular level, three-dimensional (3D) electron microscopy, together with other techniques, is able to reach resolutions at the nanometer or subnanometer level. The information is delivered in the form of 3D volumes containing samples of a given function, for example, the electron density distribution within a given macromolecule. The same situation happens at the cellular level with the new forms of light microscopy, particularly confocal microscopy, all of which produce biological 3D volume information. Furthermore, it is possible to record sequences of images over time (videos), as well as sequences of volumes, bringing key information on the dynamics of living biological systems. It is in this context that work on bioimage started two years ago, and that its first version is now presented here. In essence, Bioimage is a database specifically designed to contain multi-dimensional images, perform queries and interactively work with the resulting multi-dimensional information on the World Wide Web, as well as accomplish the required cross-database links. Two sister home pages of bioimage can be accessed at http://www.bioimage.org and http://www-embl.bioimage.or

Nucleic Acids Res

The HIV-1 transactivator of transcription (Tat) protein is thought to stimulate reverse transcription (RTion). The Tat protein and, more specifically, its (44-61) domain were recently shown to promote the annealing of complementary DNA sequences representing the HIV-1 transactivation response element TAR, named dTAR and cTAR, that plays a key role in RTion. Moreover, the kinetic mechanism of the basic Tat(44-61) peptide in this annealing further revealed that this peptide constitutes a representative nucleic acid annealer. To further understand the structure-activity relationships of this highly conserved domain, we investigated by electrophoresis and fluorescence approaches the binding and annealing properties of various Tat(44-61) mutants. Our data showed that the Tyr47 and basic residues of the Tat(44-61) domain were instrumental for binding to cTAR through stacking and electrostatic interactions, respectively, and promoting its annealing with dTAR. Furthermore, the annealing efficiency of the mutants clearly correlates with their ability to rapidly associate and dissociate the complementary oligonucleotides and to promote RTion. Thus, transient and dynamic nucleic acid interactions likely constitute a key mechanistic component of annealers and the role of Tat in the late steps of RTion. Finally, our data suggest that Lys50 and Lys51 acetylation regulates Tat activity in RTion

The role of secretory leukocyte proteinase inhibitor and elafin (elastase-specific inhibitor/skin-derived antileukoprotease) as alarm antiproteinases in inflammatory lung disease

Secretory leukocyte proteinase inhibitor and elafin are two low-molecular-mass elastase inhibitors that are mainly synthesized locally at mucosal sites. It is thought that their physicochemical properties allow them to efficiently inhibit target enzymes, such as neutrophil elastase, released into the interstitium. Historically, in the lung, these inhibitors were first purified from secretions of patients with chronic obstructive pulmonary disease and cystic fibrosis. This suggested that they might be important in controlling excessive neutrophil elastase release in these pathologies. They are upregulated by 'alarm signals' such as bacterial lipopolysaccharides, and cytokines such as interleukin-1 and tumor necrosis factor and have been shown to be active against Gram-positive and Gram-negative bacteria, so that they have joined the growing list of antimicrobial 'defensin-like' peptides produced by the lung. Their site of synthesis and presumed functions make them very attractive candidates as potential therapeutic agents under conditions in which the excessive release of elastase by neutrophils might be detrimental. Because of its natural tropism for the lung, the use of adenovirus-mediated gene transfer is extremely promising in such applications

Microvascular function is preserved in newly diagnosed rheumatoid arthritis and low systemic inflammatory activity

Rheumatoid arthritis (RA) is associated with increased cardiovascular morbidity and mortality. Microvascular function has been linked to several risk factors for cardiovascular disease and may be affected in RA. It is, however, presently unknown at what point in the disease course the abnormalities in microvascular function occur. We determined whether microvascular function is already disturbed in early disease-modifying antirheumatic drugs (DMARD)-naive RA patients with low systemic inflammation. Fifteen consecutive RA patients with a median symptom duration of 5 months, a C-reactive protein level of ≤20 mg/l and without a history of cardiovascular disease, and age 15 and sex-matched healthy controls were recruited. Endothelium-dependent and endothelium-independent vasodilatation in skin was evaluated with laser Doppler fluxmetry after iontophoresis of acetylcholine and sodium nitroprusside, respectively. Videomicroscopy was used to measure recruitment of skin capillaries after arterial occlusion. CRP and ESR levels were mildly, but significantly elevated in patients compared to controls. No differences in both endothelium-dependent vasodilatation and capillary recruitment were observed between groups [709% (95% CI, 457–961%) vs 797% (95% CI, 556–1,037%), P = 0.59 and 37% (95% CI, 26–47%) vs 41% (95% CI, 31–50%), P = 0.59, respectively]. Skin microvascular function is preserved in early, DMARD-naive RA patients with moderately active RA but low systemic inflammatory activity. Both the extent of the systemic inflammation and disease duration, therefore, may be important determinants of microvascular dysfunction and subsequent increased risk for cardiovascular disease

2007 Guidelines for the management of arterial hypertension: The Task Force for the Management of Arterial Hypertension of the European Society of Hypertension (ESH) and of the European Society of Cardiology (ESC)

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Magmatic processes in developing oceanic crust revealed in a cumulate xenolith collected at the East Pacific Rise, 9°50′N

Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 7 (2006): Q12O04, doi:10.1029/2006GC001316.The petrology and geochemistry of a xenolith, a fragment of a melt-bearing cumulate, within a recently erupted mid-ocean ridge (MOR) lava flow provide information on petrogenetic processes occurring within the newly forming oceanic crust beneath the northern East Pacific Rise (NEPR). The xenolith reveals important petrologic information about MOR magmatic systems concerning (1) melt distribution in a crystal-dominated mush; (2) melt-crystal reactions within the mush; (3) the chemistry of melts that have contributed to the cumulate lithology; and (4) the chemistry of axial melts that enter the axial magma system. The xenolith was enclosed within a moderately primitive, normal mid-ocean ridge basalt (NMORB) erupted in 1991 within the neovolcanic zone of the NEPR, at approximately 9°50′N. The sample is a matrix-dominated, cumulate olivine anorthosite, composed of anorthite (An94-90) and bytownite (An89-70), intergranular olivine (Fo86±0.3), minor sulfide and spinel, and intergranular glass. Marginal corrosion of plagioclase, and possibly olivine, and internal remelting of plagioclase indicate syntexis. It is surmised that the pore volume was eviscerated several times with moderately primitive basaltic melts and reduced by intergranular crystallization of forsteritic olivine. The presence of anorthite as a cumulate phase in the xenolith and the observation of anorthite xenocrysts in NMORB lavas, and as a cumulate phase in ophiolite gabbros, indicate that Ca-rich melts that are not a part of the NMORB lineage play an important role in the construction of the oceanic crust.The Mineral Resources Program, USGS, provided support to W.I.R. for this research. Field and laboratory research was supported by NSF grants OCE-9402360, 9403773, and 0138088 to M.R.P. and NSF grants OCE-9819261 and OCE-0525863 to D.J.F