Showing papers by "University of the Littoral Opal Coast published in 2010"

Plankton in the open Mediterranean Sea: a review

Abstract: . We present an overview of the plankton studies conducted during the last 25 years in the epipelagic offshore waters of the Mediterranean Sea. This quasi-enclosed sea is characterized by a rich and complex physical dynamics with distinctive traits, especially in regard to the thermohaline circulation. Recent investigations have basically confirmed the long-recognised oligotrophic nature of this sea, which increases along both the west-east and the north-south directions. Nutrient availability is low, especially for phosphorous (N:P up to 60), though this limitation may be buffered by inputs from highly populated coasts and from the atmosphere. Phytoplankton biomass, as chl a, generally displays low values (less than 0.2 μg chl a l−1) over large areas, with a modest late winter increase. A large bloom (up to 3 μg l−1) is observed throughout the late winter and spring exclusively in the NW area. Relatively high biomass values are recorded in fronts and cyclonic gyres. A deep chlorophyll maximum is a permanent feature for the whole basin, except during the late winter mixing. It is found at increasingly greater depths ranging from 30 m in the Alboran Sea to 120 m in the easternmost Levantine basin. Primary production reveals a west-east decreasing trend and ranges between 59 and 150 g C m−2 y−1 (in situ measurements). Overall, the basin is largely dominated by small autotrophs, microheterotrophs and egg-carrying copepod species. The microorganisms (phytoplankton, viruses, bacteria, flagellates and ciliates) and zooplankton components reveal a considerable diversity and variability over spatial and temporal scales, although the latter is poorly studied. Examples are the wide diversity of dinoflagellates and coccolithophores, the multifarious role of diatoms or picoeukaryotes, and the distinct seasonal or spatial patterns of the species-rich copepod genera or families which dominate the basin. Major dissimilarities between western and eastern basins have been highlighted in species composition of phytoplankton and mesozooplankton, but also in the heterotrophic microbial components and in their relationships. Superimposed to these longitudinal differences, a pronounced biological heterogeneity is also observed in areas hosting deep convection, fronts, cyclonic and anti-cyclonic gyres or eddies. In such areas, the intermittent nutrient enrichment promotes a switching between a small-sized microbial community and diatom-dominated populations. A classical food web readily substitutes the microbial food web in these cases. These switches, likely occurring within a continuum of trophic pathways, may greatly increase the flux towards higher trophic levels, in spite of the apparent heterotrophy. Basically, the microbial system seems to be both bottom-up and top-down controlled. A "multivorous web" is shown by the great variety of feeding modes and preferences and by the significant and simultaneous grazing impact on phytoplankton and ciliates by mesozooplankton.

Optical, thermal, electrical, damage, and phase-matching properties of lithium selenoindate

Abstract: Lithium selenoindate (LiInSe2) is a new nonlinear chalcogenide biaxial crystal, related to LiInS2 and transparent from 0.54 to 10 μm at the 50% level (10 mm thickness), which has been successfully grown in large sizes and with good optical quality. We report on what we believe to be new physical properties that are relevant for laser and nonlinear optical applications and summarize all relevant characteristics, both from the literature and as measured in the present work. With respect to AgGaS(e)2 ternary chalcopyrite materials, LiInSe2 displays a nearly isotropic thermal expansion behavior with three- to five-times-larger thermal conductivities associated with high optical damage thresholds, and low intensity-dependent absorption, allowing direct high-power downconversion from the near-infrared, especially 1064 nm, to the deep mid-infrared. Continuous-wave difference-frequency generation (5.9–8.1 μm) of Ti:sapphire laser sources is reported for the first time as well as nanosecond optical parametric oscillation with a Nd:YAG laser as the pump source at 100 Hz and idler tuning between 4.7 and 8.7 μm.

Mixing state of aerosols and direct observation of carbonaceous and marine coatings on African dust by individual particle analysis

Abstract: [1] The mixing state of aerosols collected at M'Bour, Senegal, during the Special Observing Period conducted in January–February 2006 (SOP-0) of the African Monsoon Multidisciplinary Analysis project (AMMA), was studied by individual particle analysis. The sampling location on the Atlantic coast is particularly adapted for studying the mixing state of tropospheric aerosols since it is (1) located on the path of Saharan dust plumes transported westward over the northern tropical Atlantic, (2) influenced by biomass burning events particularly frequent from December to March, and (3) strongly influenced by anthropogenic emissions from polluted African cities. Particle size, morphology, and chemical composition were determined for 12,672 particles using scanning electron microscopy (automated SEM-EDX). Complementary analyses were performed using transmission electron microscopy combined with electron energy loss spectrometry (TEM-EELS) and Raman microspectrometry. Mineral dust and carbonaceous and marine compounds were predominantly found externally mixed, i.e., not present together in the same particles. Binary internally mixed particles, i.e., dust/carbonaceous, carbonaceous/marine, and dust/marine mixtures, accounted for a significant fraction of analyzed particles (from 10.5% to 46.5%). Western Sahara was identified as the main source of mineral dust. Two major types of carbonaceous particles were identified: “tar balls” probably coming from biomass burning emissions and soot from anthropogenic emissions. Regarding binary internally mixed particles, marine and carbonaceous compounds generally formed a coating on mineral dust particles. The carbonaceous coating observed at the particle scale on African dust was evidenced by the combined use of elemental and molecular microanalysis techniques, with the identification of an amorphous rather than crystallized carbon structure.

Characteristics of the biofilm matrix and its role as a possible target for the detection and eradication of Staphylococcus epidermidis associated with medical implant infections.

Abstract: The virulence of Staphylococcus epidermidis is related to its capacity to form biofilms. Such biofilm-related infections are extremely difficult to treat and to detect in early stages by the traditional microbiological analyses. The determination of the chemical composition of the extracellular polymeric substances (EPS) of the biofilm matrix, as well as the elucidation of the sensitivity of biofilms to enzymatic degradation should facilitate the development of new therapies against biofilm-related infections. The chemical analyses of EPS had shown qualitative and quantitative variations of their nature, depending on the strains and culture conditions. The poly-N-acetylglucosamine (PNAG) is considered the main component of staphylococcal biofilms. However, certain strains form biofilms without PNAG. In addition to PNAG and proteins, extracellular teichoic acid was identified as a new component of the staphylococcal biofilms. The sensitivity of staphylococcal biofilms to enzymatic treatments depended on their relative chemical composition, and a PNAG-degrading enzyme, in conjunction with proteases, could be an efficient solution to eliminate the staphylococcal biofilms. A detection of specific 'antibiofilm' antibodies in the blood serum of patients could serve as a convenient noninvasive and inexpensive diagnostic tool for the detection of foreign body-associated staphylococcal infections. Used as a coating antigen in the enzyme-linked immunosorbent assay test, PNAG did not sufficiently discriminate healthy individuals from the infected patients.

Rate Coefficients for the Gas-Phase Reaction of Hydroxyl Radicals with 2-Methoxyphenol (Guaiacol) and Related Compounds

Abstract: 2-Methoxyphenol (guaiacol) and its derivatives are potential marker compounds for wood smoke emissions in the atmosphere. To investigate the atmospheric reactivity of this type of compounds, rate coefficients for their reactions with hydroxyl (OH) radicals have been determined at 294 ± 2 K and 1 atm using the relative rate method with gas chromatography for chemical analysis. The rate coefficients (in units of cm3 molecule−1 s−1) are: 2-methoxyphenol, (7.53 ± 0.41) × 10−11; 3-methoxyphenol, (9.80 ± 0.46) × 10−11; 4-methoxyphenol, (9.50 ± 0.55) × 10−11; 2-methoxy-4-methylphenol, (9.45 ± 0.59) × 10−11; and methoxybenzene, (2.20 ± 0.15) × 10−11. The estimated atmospheric lifetime for 2-methoxyphenol is ∼2 h, indicating that it is too reactive to be used as a tracer for wood smoke emissions. The reactivity of the methoxyphenols is compared with other substituted aromatics and interpreted in relation to the type, number, and positions of the different substituents on the aromatic ring. The atmospheric implicat...

Chemical Analysis of Cellular and Extracellular Carbohydrates of a Biofilm-Forming Strain Pseudomonas aeruginosa PA14

Abstract: Background: Pseudomonas aeruginosa is a Gram-negative bacterium and an opportunistic pathogen, which causes persisting life-threatening infections in cystic fibrosis (CF) patients. Biofilm mode of growth facilitates its survival in a variety of environments. Most P. aeruginosa isolates, including the non-mucoid laboratory strain PA14, are able to form a thick pellicle, which results in a surface-associated biofilm at the air-liquid (A–L) interface in standing liquid cultures. Exopolysaccharides (EPS) are considered as key components in the formation of this biofilm pellicle. In the non-mucoid P. aeruginosa strain PA14, the ‘‘scaffolding’’ polysaccharides of the biofilm matrix, and the molecules responsible for the structural integrity of rigid A–L biofilm have not been identified. Moreover, the role of LPS in this process is unclear, and the chemical structure of the LPS O-antigen of PA14 has not yet been elucidated. Principal Findings: In the present work we carried out a systematic analysis of cellular and extracellular (EC) carbohydrates of P. aeruginosa PA14. We also elucidated the chemical structure of the LPS O-antigen by chemical methods and 2-D NMR spectroscopy. Our results showed that it is composed of linear trisaccharide repeating units, identical to those described for

Mutagenicity and genotoxicity of PM2.5 issued from an urbano-industrialized area of Dunkerque (France).

Abstract: Epidemiological studies have demonstrated the link between chronic exposure to particulate matter (PM), especially particles with an aerodynamic diameter lesser than 2.5 µm (PM(2.5) ), and lung cancer. Mechanistic investigations focus on the contribution of the various genotoxicants adsorbed onto the particles, and more particularly on polycyclic aromatic hydrocarbons or nitroaromatics. Most of the previous studies dealing with genotoxic and/or mutagenic measurements were performed on organic extracts obtained from PM(2.5) collected in polluted areas. In contrast, we have evaluated genotoxic and mutagenic properties of urbano-industrial PM(2.5) (PM) collected in Dunkerque (France). Thermally desorbed PM(2.5) (dPM) was also comparatively studied. Suspensions of PM and dPM (5-50 µg per plate) were tested in Salmonella tester strains TA98, TA102 and YG1041 ± S9mix. Significant mutagenicity was observed for PM in YG1041 ± S9 mix. In strain TA102 - S9mix, a slight, but not significant dose-response increase was observed, for both PM and dPM. Genotoxic properties of PM and dPM were evaluated by the measurement of (1) 8-OHdG in A549 cells and (2) bulky DNA adducts on A549 cells and on human alveolar macrophages (AMs) in primary culture. A dose-dependant formation of 8-OHdG adducts was observed on A549 cells for PM and dPM, probably mainly attributed to the core of the particles. Bulky DNA adducts were observed only in AMs after exposure to PM and dPM. In conclusion, using relevant exposure models, suspension of PM(2.5) induces a combination of DNA-interaction mechanisms, which could contribute to the induction of lung cancer in exposed populations.

Distinct defenses induced in wheat against powdery mildew by acetylated and nonacetylated oligogalacturonides.

Abstract: In wheat, little is known about disease resistance inducers and, more specifically, about the biological activities from those derived from endogenous elicitors, such as oligogalacturonides (OGAs). Therefore, we tested the ability of two fractions of OGAs, with polymerization degrees (DPs) of 2–25, to induce resistance to Blumeria graminis f. sp. tritici and defense responses in wheat. One fraction was unacetylated (OGAs–Ac) whereas the second one was 30% chemically acetylated (OGAs+Ac). Infection level was reduced to 57 and 58% relative to controls when OGAs–Ac and OGAs+Ac, respectively, were sprayed 48 h before inoculation. Activities of various defense-related enzymes were then assayed in noninoculated wheat leaves infiltrated with OGAs. Oxalate oxidase, peroxidase, and lipoxygenase were responsive to both OGAs–Ac and OGAs+Ac, which suggests involvement of reactive oxygen species and oxilipins in OGAs-mediated responses in wheat. In inoculated leaves, both fractions induced a similar increase ...

Calibration of the RT3 accelerometer for various patterns of physical activity in children and adolescents

Abstract: The aim of this study was to determine thresholds for various intensities of physical activity in children and adolescents using the RT3 accelerometer. Forty healthy participants aged 10–16 years were recruited to the study. To validate the RT3 accelerometer data, an independent sample of 20 children and adolescents aged 10–16 years performed the same activities. Accelerometer data, heart rate, and oxygen consumption were measured at nine levels of physical activity, which varied in intensity: sedentary, light, moderate, and vigorous. Age and sex did not affect thresholds. The activity categories and accelerometer counts were: sedentary activity, 0–40 counts · min−1; light activity, 41–950 counts · min−1; moderate activity, 951–3410 counts · min−1; and vigorous activity, >3410 counts · min−1, respectively. These thresholds were considered valid as the difference between threshold values obtained using two independent groups of children was not significant. This study has established threshold val...

Correlation of in planta endo‐beta‐1,4‐xylanase activity with the necrotrophic phase of the hemibiotrophic fungus Mycosphaerella graminicola

Abstract: The association of the cell wall degrading enzyme endo-beta-1,4-xylanase (EC 3.2.1.8) with pathogenicity of Mycosphaerella graminicola was examined in planta. The enzyme production of two M. graminicola isolates (T0372 and T0491), as well as their ability to infect seedlings of susceptible wheat cv. Scorpion, was first compared. No significant difference was found between the two isolates regarding spore germination rates, mycelial growth on the leaf surface or direct and stomatal penetrations. However, restricted hyphal growth was observed inside leaves inoculated with T0372, whereas successful mesophyll colonization with a strong intercellular fungal growth was found in leaves infected with T0491. Likewise, T0372 was unable to induce lesions bearing pycnidia and to produce endo-beta-1,4-xylanase activity until 22 days post-inoculation (d.p.i.). On the other hand, significant high increases of both diseased leaf area bearing pycnidia and endo-beta-1,4-xylanase activity were observed between 16 and 22 d.p.i. for T0491 (r = 0·98). The investigation of 24 additional isolates, including the IPO323 and IPO94269 reference isolates, highlighted a strong correlation between endo-beta-1,4-xylanase activity and disease development levels (r = 0·94). This study demonstrates that differences in pathogenicity in M. graminicola are not linked to events on the leaf surface or to frequency of leaf penetration, but to the ability of the fungus to colonize the mesophyll and to produce the cell wall degrading enzyme endo-1,4-beta-xylanase during the necrotrophic phase.

Cultural Districts, A New Strategy for Regional Development? The South-East Cultural District in Sicily

Abstract: Le Blanc A. Cultural districts, a new strategy for regional development? The South-East Cultural District in Sicily, Regional Studies. The industrialization of cultural production and a strong trend for the development of regional networks have recently led to the creation of new spatial and economic forms called ‘cultural districts’. However, these new economic systems rely on very different geographical bases, types of products, and developmental processes. In Italy, the first cultural district was created in 2004 to foster the preservation of cultural heritage and boost tourist development in the late Baroque cities of the so-called Val di Noto in south-east Sicily. The main objective of the district is to support local socio-economic development through the promotion of the region's architectural cultural heritage and the local craft industry. The new structure aims at creating a real network between these towns so that they can compete globally. A specific form of spatial organization, the newly crea...

Kalman filtering real-time measurements of H2O isotopologue ratios by laser absorption spectroscopy at 2.73 mu m

Abstract: Kalman adaptive filtering was applied for the first time, to our knowledge, to the real-time simultaneous determination of water isotopic ratios using laser absorption spectroscopy at 2.73 μm. Measurements of the oxygen and hydrogen isotopologue ratios δ O18, δ O17, and δ H2 in water showed a 1−σ precision of 0.72‰ for δ O18, 0.48‰ for δ O17, and 0.84‰ for δ H2, while sampling the output of the tuned Kalman filter at 1 s time intervals. Using a standard running average technique, averaging over ~30 s is required to obtain the same level of precision.

Pelagic food web patterns: do they modulate virus and nanoflagellate effects on picoplankton during the phytoplankton spring bloom?

Abstract: Summary As agents of mortality, viruses and nanoflagellates impact on picoplankton populations. We examined the differences in interactions between these compartments in two French Atlantic bays. Microbes, considered here as central actors of the planktonic food web, were first monitored seasonally in Arcachon (2005) and Marennes-Oleron (2006) bays. Their dynamics were evaluated to categorize trophic periods using the models of Legendre and Rassoulzadegan as a reference framework. Microbial interactions were then compared through 48 h batch culture experiments performed during the phytoplankton spring bloom, identified as herbivorous in Marennes and multivorous in Arcachon. Marennes was spatially homogeneous compared with Arcachon. The former was potentially more productive, featuring a large number of heterotrophic pathways, while autotrophic mechanisms dominated in Arcachon. A link was found between viruses and phytoplankton in Marennes, suggesting a role of virus in the regulation of autotroph biomass. Moreover, the virus–bacteria relation was weaker in Marennes, with a bacterial lysis potential of 2.6% compared with 39% in Arcachon. The batch experiments (based on size-fractionation and viral enrichment) revealed different microbial interactions that corresponded to the spring-bloom trophic interactions in each bay. In Arcachon, where there is a multivorous web, flagellate predation and viral lysis acted in an opposite way on picophytoplankton. When together they both reduced viral production. Conversely, in Marennes (herbivorous web), flagellates and viruses together increased viral production. Differences in the composition of the bacterial community composition explained the combined flagellate-virus effects on viral production in the two bays.

Reliability of the RT3 accelerometer for measurement of physical activity in adolescents

Abstract: The aim of this study was to assess the reliability of the RT3 accelerometer under conditions of normal physical activity. Sixty healthy individuals (30 boys, 30 girls) aged 10-16 years wore two accelerometers while performing different structured physical activities. The accelerometers were synchronized and data were recorded every minute during nine 15-min sessions of physical activity that varied in intensity from sedentary (watching television, playing video games) to vigorous (running on a treadmill at different speeds). Intra-instrument coefficients of variation (CV) were assessed using the formula CV = standard deviation of the measure x 100/mean of the measure. The intra-instrument coefficient of variation was higher for sedentary (17%) and light activity (16.2%) than moderate (9.3%) and vigorous activity (6.6%). These results confirmed the poor reliability of the RT3 for activity of low magnitude and frequency that was demonstrated in studies using a shaker.

Microwave dielectric properties of the system Ba1−xSrxTiO3

Abstract: Barium–strontium titanate, Ba1−xSrxTiO3 (BST), is a continuous solid solution between barium titanate, BaTiO3, and strontium titanate, SrTiO3, over the whole composition range. The Curie temperature (TC) of this system increases with the concentration of Sr in the BaTiO3 lattice, and hence can be tailored through different Ba/Sr molar ratios to obtain a desired TC. In this work we present dielectric permittivity for the system Ba1−xSrxTiO3, with 0≤x≤1, at 2.7 GHz. The measurements were made using the small perturbation method, where resonance frequency and the quality factor of a cavity, with and without the sample, were used to calculate the complex dielectric permittivity, e * = e ′ − i e ″ , of the material.

Synthesis and Properties of Tetrathiafulvalene End-Functionalized Polymers Prepared via RAFT Polymerization

Abstract: The reversible addition−fragmentation chain transfer (RAFT) polymerization technique has been employed to synthesize various linear tetrathiafulvalene end-functionalized polymers. n-Butyl acrylate,...

Structural analysis of xCsCl(1−x)Ga2S3 glasses by means of DFT calculations and Raman spectroscopy

Abstract: The alkali metal halide doping of gallium-sulfide glasses yields improvements in the optical, thermal and glass forming properties. To understand these improvements, the short-range order of xCsCl(1 − x)Ga2S3 glasses was probed by Raman spectroscopy. Raman spectra have been interpreted using density functional theory (DFT) harmonic frequency calculations on specific clusters of GaS4H4 and/or GaS3H3Cl tetrahedral subunits. The assignment of the observed vibrational bands confirms the main structural conclusions obtained with X-ray and neutron diffraction experiments and gives some new insights into the gallium-network present in the xCsCl(1 − x)Ga2S3 glasses. At the lowest concentration, the observed spectrum may be interpreted with small clusters such as dimers and trimers connected by corner-sharing (CS) GaS4H4 tetrahedral subunits. The vibrational fingerprints of tri-clusters with three-fold coordinated sulfur atoms have also been identified; however, no Raman signature of chlorine-doped subunits has been found to be caused by their insufficient intensity. For higher CsCl concentrations, distinct spectral features corresponding to chlorine-doped clusters appear and are increasing in intensity with x. In other words, undoped and Cl-doped tetrahedra coexist in the xCsCl(1 − x)Ga2S3 glasses. The added chlorine atoms induce a fragmentation of the glass network and replace the sulfur atoms in the CS tetrahedral environment. The comparison of the observed spectra with theoretical predictions and diffraction data favoured one-fold coordinated chlorine atoms in the glass network. Copyright © 2009 John Wiley & Sons, Ltd.

Parameterization of volume scattering function of coastal waters based on the statistical approach.

Abstract: A parameterization of the volume scattering function (VSF) specific to coastal waters is proposed. We have found that the standard VSF parameterizations proposed by Fournier-Forand and Petzold do not fit our measurements obtained with a high angular resolution VSF-meter for water samples taken in the Black Sea coastal zone. We propose modeling VSF as a linear function of scattering, backscattering and particulate absorption. The statistical techniques employed allow us to retrieve the variability of VSF and to demonstrate the significance of the estimates obtained. The results of independent validation and the comparison with other commonly used parameterizations are provided.

Using constraint programming to schedule an operating theatre

Abstract: The daily operating rooms scheduling is a highly constrained problem. It is also hard to find an optimal solution or at least high quality solutions. To solve this scheduling problem, we use the “expressive power” of the constraint programming paradigm to include as many as possible real-life constraints in our model, such as the availability and the preferences of the staff. We develop a “generic” adaptive model which embeds most of the characteristics of the problem encountered in the literature as well as real-life constraints coming from practical problems in hospitals.

Mapping Legal Semiotics

Abstract: The essay seeks to harness the diverse and innovative work to date of legal semiotics. It seeks to bring together the cumulative research traditions of these related areas as a preclusion to identifying fertile avenues for research.

Benzene-induced mutational pattern in the tumour suppressor gene TP53 analysed by use of a functional assay, the functional analysis of separated alleles in yeast, in human lung cells

Abstract: Recent concern has centred on the effects of continuous exposure to low concentrations of benzene, both occupationally and environmentally. Although benzene has for a long time been recognised as a carcinogen for humans, its mechanistic pathway remains unclear. Since mutations in the tumour suppressor gene TP53 are the most common genetic alterations involved in human cancer, our objective was to establish the first mutational pattern induced by benzene on the TP53 gene in human type II-like alveolar epithelial A549 cells by using the Functional Analysis of Separated Alleles in Yeast (FASAY). Seventeen mutations linked to benzene exposure were found: 3 one- or two-base deletions, and 14 single nucleotide substitutions (1 nonsense and 13 missense mutations). A>G and G>A transitions were the most prevalent (23.5% for both). Other mutations included A>C transversions and deletions (3/17, 17.6% for both), G>T transversions (2/17, 11.8%) and A>T transversions (1/17, 5.9%). Data arising from this benzene-induced mutational pattern affecting TP53, a critical target gene in human carcinogenesis, have been compared with those reported in human acute myeloid leukaemia, the aetiology of which is clearly linked to benzene exposure, and in experimental benzene-induced carcinoma. This comparison suggests that A>G transition could be a fingerprint of benzene exposure in tumours. Furthermore, our results demonstrate that FASAY is a promising tool for the study of the carcinogenic potency of benzene in the human lung.