The Effect of Subfilter-Scale Physics on Regularization Models

The subfilter-scale (SFS) physics of regularization models are investigated to understand the regularizations’ performance as SFS models. Suppression of spectrally local SFS interactions and conservation of small-scale circulation in the Lagrangian-averaged Navier-Stokes α-model (LANS-α) is found to lead to the formation of rigid bodies. These contaminate the superfilter-scale energy spectrum with a scaling that approaches k ⁺¹ as the SFS spectra is resolved. The Clark-α and Leray-α models, truncations of LANS-α, do not conserve small-scale circulation and do not develop rigid bodies. LANS-α, however, is closest to Navier-Stokes in intermittency properties. All three models are found to be stable at high Reynolds number. Differences between L ² and H ¹ norm models are clarified. For magnetohydrodynamics (MHD), the presence of the Lorentz force as a source (or sink) for circulation and as a facilitator of both spectrally nonlocal large to small scale interactions as well as local SFS interactions prevents the formation of rigid bodies in Lagrangian-averaged MHD (LAMHD-α). LAMHD-α performs well as a predictor of superfilter-scale energy spectra and of intermittent current sheets at high Reynolds numbers. It may prove generally applicable as a MHD-LES.     

Gröbner basis of the alternating galoisian ideal

This article proposes an efficient and simple algebraic method of computation of a Gröbner basis generating the alternating galoisian ideal of a univariate separable polynomial. We named this method “the descent of the Vandermonde determinants”.     

An intercomparison of bio-optical techniques for detecting dominant phytoplankton size class from satellite remote sensing

Satellite remote sensing of ocean colour is the only method currently available for synoptically measuring wide-area properties of ocean ecosystems, such as phytoplankton chlorophyll biomass. Recently, a variety of bio-optical and ecological methods have been established that use satellite data to identify and differentiate between either phytoplankton functional types (PFTs) or phytoplankton size classes (PSCs). In this study, several of these techniques were evaluated against in situ observations to determine their ability to detect dominant phytoplankton size classes (micro-, nano- and picoplankton). The techniques are applied to a 10-year ocean-colour data series from the SeaWiFS satellite sensor and compared with in situ data (6504 samples) from a variety of locations in the global ocean. Results show that spectral-response, ecological and abundance-based approaches can all perform with similar accuracy. Detection of microplankton and picoplankton were generally better than detection of nanoplankton. Abundance-based approaches were shown to provide better spatial retrieval of PSCs. Individual model performance varied according to PSC, input satellite data sources and in situ validation data types. Uncertainty in the comparison procedure and data sources was considered. Improved availability of in situ observations would aid ongoing research in this field.     

MERIS potential for ocean colour studies in the open ocean

The interest of space observations of ocean colour for determining variations in phytoplankton distribution and for deriving primary production (via models) has been largely demonstrated by the Coastal Zone Color Scanner (CZCS) which operated from 1978 to 1986. The capabilities of this pioneer sensor, however, were limited both in spectral resolution and radiometric accuracy. The next generation of ocean colour sensors will benefit from major improvements. The Medium Resolution Imaging Spectrometer (MERIS), planned by the European Space Agency (ESA) for the Envisat platform, has been designed to measure radiances in 15 visible and infrared channels. Three infrared channels will allow aerosol characterization, and therefore accurate atmospheric corrections, to be performed for each pixel. For the retrieval of marine parameters, nine channels between 410 and 705nm will be available (as opposed to only four with the CZCS). In coastal waters this should, in principle, allow a separate quantification of different substances (phytoplankton, mineral particles, yellow substance) to be performed. In open ocean waters optically dominated by phytoplankton and their associate detrital matter, the basic information (i.e. the concentration of phytoplanktonic pigments) will be retrieved with improved accuracy due to the increased radiometric performances of MERIS. The adoption of multi-wavelength algorithms could also lead to additional information concerning auxiliary pigments and taxonomic groups. Finally, MERIS will be one of the first sensors to allow measurements of Sun-induced chlorophyll a in vivo fluorescence, which could provide a complementary approach for the assessment of phytoplankton abundance. The development of these next-generation algorithms, however, requires a number of fundamental studies.     

Utilisation of attenuated total reflectance MIR and front-face fluorescence spectroscopies for the identification of Saint-Nectaire cheeses varying by manufacturing conditions

Twelve samples of cheeses (three types of Saint-Nectaire PDO cheeses and Savaron cheeses) differing by manufacturing and ripening conditions, from 12 different producers, were characterised by attenuated total reflectance mid-infrared (MIR) and front-face fluorescence spectroscopies, dynamic testing rheology and physico-chemical analysis. Fluorescence spectra (tryptophan residues, vitamin A and riboflavin) and MIR (3,000–2,800 (fat region), 1,700–1,500 (protein region) and 1,500–900 cm⁻¹ (fingerprint region)) spectra were recorded on cheese samples. The potential of the data tables was investigated for discriminating the four different groups of cheeses. The results of factorial discriminant analysis (FDA) performed on the fluorescence and mid-infrared spectra showed a good discrimination of the four cheese groups. Considering cross-validation results, the best classifications (100%) were achieved from mid-infrared and fluorescence spectra, while only 91.7 and 72.2% of correct classification were obtained by applying FDA to rheology and physico-chemical data, respectively. Spectroscopic techniques could provide useful fingerprints and allow the identification of investigated cheeses according to manufacturing conditions. Simple and rapid spectroscopic methods offer a promising approach to the authentication of cheeses.     

Vancomycin dimerization and chiral recognition studied by high-performance liquid chromatography

The retention and separation of D,L-dansylvaline enantiomers (used as test solutes) were investigated using silica gel as stationary phase and vancomycin as chiral mobile-phase additive. A retention model was developed to describe the mechanistic aspects of the interaction between solute and vancomycin in the chromatographic system. It considered the formation of vancomycin dimers both "free" in the mobile phase and adsorbed on silica. By fitting the model equation to experimental data, it appeared clearly that the approach taking into account the vancomycin dimerization described accurately the retention behavior of the compounds. The examination of the model equation parameters showed that the glycopeptide dimerization increased the enantioselectivity by a factor of approximately 3.7. This study demonstrated the preponderant role of the vancomycin dimerization on the chiral recognition process of D,L-dansylvaline. Also, an additional analysis on a vancomycin chiral stationary phase indicated that the addition of vancomycin in the mobile phase promoted a greater enantioselectivity mediated by the formation of dimers in the stationary phase.     

Immobilized DNA aptamers as target-specific chiral stationary phases for resolution of nucleoside and amino acid derivative enantiomers

Recently, we described the use of a DNA aptamer as a new target-specific chiral stationary phase (CSP) for the separation of oligopeptide enantiomers (Michaud, M.; Jourdan, E.; Villet, A.; Ravel, A.; Grosset, C.; Peyrin, E. J. Am. Chem. Soc. 2003, 125, 8672). However, from a practical point of view, it was fundamental to extend the applicability of such target-specific aptamer CSP to the resolution of small (bioactive) molecule enantiomers. In this paper, immobilized DNA aptamers specifically selected against D-adenosine and L-tyrosinamide were used to resolve the enantiomers by HPLC, using microbore columns. At 20 degrees C, the adenosine enantioseparation was similar to that classically reported with imprinted CSPs (approximately 3.5) while a very high enantioselectivity was observed for the tyrosinamide enantiomers (the nontarget enantiomer was essentially nonretained on the CSP). The influence of temperature on solute binding and chiral discrimination was analyzed. The binding enthalpic contributions were determined from linear van't Hoff plots. Very large DeltaH values were obtained for the target enantiomers (-71.4 +/- 0.7 kJ/mol for D-adenosine and -139.4 +/- 2.0 kJ/mol for L-tyrosinamide). Such values were consistent with the formation of a tight complex between these analytes and the aptamer CSPs. This work demonstrates that target-specific aptamer CSPs constitute a powerful tool for the resolution of small (bioactive) molecule enantiomers.     

Estimation of the exposure of the French population to the BSE agent: comparison of the 1980-95 consumption of beef products containing mechanically recovered meat in France and the UK,by birth cohort and gender

Assuming that human exposure to BSE was through beef mechanically recovered meat (MRM) consumed as burgers and other meat products, we estimated the French consumption of different food items containing beef MRM, and compared these consumptions for French and British populations. To estimate consumption of meat products containing bovine MRM, we used dietary data from national individual and household food surveys conducted between 1980 and 1995. After reconciliation of consumption data between the available surveys and calendar year adjustments, we simulated consumption of one-thousandth of the French population. Consumption was estimated by birth cohort and gender, and for the periods 1980-89 and 1990-95 separately. Data showed that burgers (including manufactured minced meat) represented around 75-80% of the individual consumption of meat products containing MRM, and that consumption of burgers increased by 40% over the 1980-95 period. In all age groups, consumption was higher in males than in females. In both genders, the 1940-69 birth cohort had the highest mean consumption of burgers and other beef products containing MRM. Similar findings have been reported for the UK population. Estimated consumption of bovine MRM per calendar year increased markedly over the study period, concomitantly with an increase of bovine carcasses imported from the UK. Comparison of the 1980-1995 pattern of bovine MRM consumption in the UK and France indicated thatthis consumption peaked later in France than in the UK. This difference might result in different temporal pattern of vCJD incidence.     

Potential of diffuse scatterer interferometry for monitoring CO2 storage sites in European contexts (land cover types)

This article proposes to test the feasibility of long-term surface deformation monitoring based on synthetic aperture radar (SAR) interferometry on carbon dioxide (CO₂) storage sites with land cover representative of potential European injection sites (agricultural or forests with minimum built-up land cover). Because no operational injection site is currently active in Europe, a SAR data set (based on EnviSAT–ASAR spaceborne data) is simulated by combining SAR scenes acquired over a potential future European injection site with deformation measurements from SAR analysis carried out on the In-Salah (Algeria) CO₂ injection demonstrator site. The study shows that under such conditions, both persistent scatterer interferometry (PSI) and diffuse scatterer (DS) interferometry appear insufficient to provide a sufficiently dense measurement network to characterize surface deformation correctly. Alternative solutions, to be investigated in further studies, include the use of data archives with shorter acquisition time spans (e.g. Sentinel-1 data when available) or installation of corner reflectors. The cost of the latter mixed space/ground solution must be evaluated with respect to conventional ground-based measurement methods in the proposed context.