Gravity wave amplification and phase crest re-organization over a shoal

In this experimental work, both wave amplification and phase evolution, due to a submerged mound, are studied. In addition to the classical surface wave measurements, the experimental study takes advantage of photographs that underline crest re-organization above and down-wave the shoal. In particular, together with wave amplification up to more than twice the incident wave, a wave steepening is observed in certain conditions in both the wave direction and in the cross-section. Due to a phase crest separation downstream of the shoal, steepening in the cross-shore direction is enhanced (up to 30% above the steepening along the main direction of propagation). Physical aspects are discussed through the analysis of the diffraction effects on the wave properties

Tapping wave energy through Longuet-Higgins microseism effect

International audienceIt is well-known, since the works of Miche (1944) and Longuet-Higgins (1950), that, under a standing wave system, second-order pressures at twice the wave frequency penetrate the water column down to the sea-°oor, whatever the waterdepth. Recently Gu¶evel proposed that energy could be extracted from the waves with a heaving horizontal plate at the sea bottom, located next to a re°ective cli® or sea-wall, and tuned to oscillate at twice the wave frequency. Encouraging preliminary experiments were conducted in ACRI's wavetank (Lajoie et al. 2007). In this paper we address the theoretical modeling of wave energy extraction with such a device, in the asymptotic case when the waterdepth is very large compared to the wavelength. In section I we assume that the ¯rst-order wave system is little modi¯ed, i.e. the power taken from the waves is a small portion of the power carried by the incoming wave. In section II we relieve this assumption and we show that one hundred percent of the wave power can be extracted, notwithstanding how large the waterdepth

Bt maize: a tool for improving food safety of grains at harvest

A new EU (European Union) regulation came into force in 2007 with Regulation (EC) No. 1126/2007 which established maximum levels for fumonisins B1 and B2 (4000 ppb), deoxynivalenol (1750 ppb) and zearalenone (350 ppb) in maize and maize products. In order to evaluate French maize food safety, studies were carried out by the national Biological Risk Monitoring (BRM) Network. In this study, field trials involving 84 plots were conducted with Bt maize (MON 810) and its isogenic non-Bt counterpart in 2005 and 2006 in South-western France. Mycotoxin levels were determined in grain at harvest. Fumonisins B1 and B2, deoxynivalenol, and zearalenone were analyzed by LC-MS-MS and the results treated statistically using non parametric tests for mycotoxins and analysis of variance test for weather variables. As the climate was homogenous inside the experimental area, the transgenic event introduced into the maize was the only key parameter which differed between Bt and non-Bt maize plots. Our results showed that all mycotoxin families were not impacted in the same way. The efficacy of Bt maize reduced mycotoxins more than 90% for fumonisins and more than 50% for zearalenone although deoxynivalenol was lightly increased. Therefore a competition between the different Fusarium spp. which produced fumonisins or trichothecenes is hypothesized. According to Regulation (EC) No. 1126/2007, 93% of the maize of Bt maize plots were able to be commercialized compared to only 45% for non-Bt maize plots. The results of this work showed that Bt maize improved food safety and constituted an useful tool to reduce significantly mycotoxin levels in harvested and stored grains. Keywords: Bt (MON810) maize, Fumonisins B1 and B2, Deoxynivalenol (DON), Zearalenone, EC regulation 1126/2007 threshold

Evaluation of a Tetracycline-Inducible Promoter in Staphylococcus aureus In Vitro and In Vivo and Its Application in Demonstrating the Role of sigB in Microcolony Formation

An inducible promoter system provides a powerful tool for studying the genetic basis for virulence. A variety of inducible systems have been used in other organisms, including pXyl-xylR-inducible promoter, the pSpac-lacI system, and the arabinose-inducible PBAD promoter, but each of these systems has limitations in its application to Staphylococcus aureus. In this study, we demonstrated the efficacy of a tetracycline-inducible promoter system in inducing gene expression in S. aureus in vitro and inside epithelial cells as well as in an animal model of infection. Using the xyl/tetO promoter::gfpuvr fusion carried on a shuttle plasmid, we demonstrated that dose-dependant tetracycline induction, as measured by bacterial fluorescence, occurred in each of the above environments while basal activation under noninduced conditions remained low. To ascertain how the system can be used to elucidate the genetic basis of a pathogenic phenotype, we cloned the sigB gene downstream of the inducible promoter. Induction of SigB expression led to dose-dependent attachment of the tested strain to polystyrene microtiter wells. Additionally, bacterial microcolony formation, an event preceding mature biofilm formation, also increased with tetracycline induction of SigB

IL-22 mediates goblet cell hyperplasia and worm expulsion in intestinal helminth infection.

Type 2 immune responses are essential in protection against intestinal helminth infections. In this study we show that IL-22, a cytokine important in defence against bacterial infections in the intestinal tract, is also a critical mediator of anti-helminth immunity. After infection with Nippostrongylus brasiliensis, a rodent hookworm, IL-22-deficient mice showed impaired worm expulsion despite normal levels of type 2 cytokine production. The impaired worm expulsion correlated with reduced goblet cell hyperplasia and reduced expression of goblet cell markers. We further confirmed our findings in a second nematode model, the murine whipworm Trichuris muris. T.muris infected IL-22-deficient mice had a similar phenotype to that seen in N.brasiliensis infection, with impaired worm expulsion and reduced goblet cell hyperplasia. Ex vivo and in vitro analysis demonstrated that IL-22 is able to directly induce the expression of several goblet cell markers, including mucins. Taken together, our findings reveal that IL-22 plays an important role in goblet cell activation, and thus, a key role in anti-helminth immunity

Radiation hardness qualification of PbWO4 scintillation crystals for the CMS Electromagnetic Calorimeter

This is the Pre-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2010 IOPEnsuring the radiation hardness of PbWO4 crystals was one of the main priorities during the construction of the electromagnetic calorimeter of the CMS experiment at CERN. The production on an industrial scale of radiation hard crystals and their certification over a period of several years represented a difficult challenge both for CMS and for the crystal suppliers. The present article reviews the related scientific and technological problems encountered

Intercalibration of the barrel electromagnetic calorimeter of the CMS experiment at start-up

Calibration of the relative response of the individual channels of the barrel electromagnetic calorimeter of the CMS detector was accomplished, before installation, with cosmic ray muons and test beams. One fourth of the calorimeter was exposed to a beam of high energy electrons and the relative calibration of the channels, the intercalibration, was found to be reproducible to a precision of about 0.3%. Additionally, data were collected with cosmic rays for the entire ECAL barrel during the commissioning phase. By comparing the intercalibration constants obtained with the electron beam data with those from the cosmic ray data, it is demonstrated that the latter provide an intercalibration precision of 1.5% over most of the barrel ECAL. The best intercalibration precision is expected to come from the analysis of events collected in situ during the LHC operation. Using data collected with both electrons and pion beams, several aspects of the intercalibration procedures based on electrons or neutral pions were investigated

Study of Leading Hadrons in Gluon and Quark Fragmentation

The study of quark jets in e+e- reactions at LEP has demonstrated that the hadronisation process is reproduced well by the Lund string model. However, our understanding of gluon fragmentation is less complete. In this study enriched quark and gluon jet samples of different purities are selected in three-jet events from hadronic decays of the Z collected by the DELPHI experiment in the LEP runs during 1994 and 1995. The leading systems of the two kinds of jets are defined by requiring a rapidity gap and their sum of charges is studied. An excess of leading systems with total charge zero is found for gluon jets in all cases, when compared to Monte Carlo Simulations with JETSET (with and without Bose-Einstein correlations included) and ARIADNE. The corresponding leading systems of quark jets do not exhibit such an excess. The influence of the gap size and of the gluon purity on the effect is studied and a concentration of the excess of neutral leading systems at low invariant masses (<~ 2 GeV/c^2) is observed, indicating that gluon jets might have an additional hitherto undetected fragmentation mode via a two-gluon system. This could be an indication of a possible production of gluonic states as predicted by QCD.Comment: 19 pages, 6 figures, Accepted by Phys. Lett.

Determination of the b quark mass at the M_Z scale with the DELPHI detector at LEP

An experimental study of the normalized three-jet rate of b quark events with respect to light quarks events (light= \ell \equiv u,d,s) has been performed using the CAMBRIDGE and DURHAM jet algorithms. The data used were collected by the DELPHI experiment at LEP on the Z peak from 1994 to 2000. The results are found to agree with theoretical predictions treating mass corrections at next-to-leading order. Measurements of the b quark mass have also been performed for both the b pole mass: M_b and the b running mass: m_b(M_Z). Data are found to be better described when using the running mass. The measurement yields: m_b(M_Z) = 2.85 +/- 0.18 (stat) +/- 0.13 (exp) +/- 0.19 (had) +/- 0.12 (theo) GeV/c^2 for the CAMBRIDGE algorithm. This result is the most precise measurement of the b mass derived from a high energy process. When compared to other b mass determinations by experiments at lower energy scales, this value agrees with the prediction of Quantum Chromodynamics for the energy evolution of the running mass. The mass measurement is equivalent to a test of the flavour independence of the strong coupling constant with an accuracy of 7 permil.Comment: 24 pages, 10 figures, Accepted by Eur. Phys. J.

Measurement and Interpretation of Fermion-Pair Production at LEP energies above the Z Resonance

This paper presents DELPHI measurements and interpretations of cross-sections, forward-backward asymmetries, and angular distributions, for the e+e- -> ffbar process for centre-of-mass energies above the Z resonance, from sqrt(s) ~ 130 - 207 GeV at the LEP collider. The measurements are consistent with the predictions of the Standard Model and are used to study a variety of models including the S-Matrix ansatz for e+e- -> ffbar scattering and several models which include physics beyond the Standard Model: the exchange of Z' bosons, contact interactions between fermions, the exchange of gravitons in large extra dimensions and the exchange of sneutrino in R-parity violating supersymmetry.Comment: 79 pages, 16 figures, Accepted by Eur. Phys. J.