Risque professionnel d'hépatite virale A au contact des eaux usées

La disponibilité depuis 1992 d'un premier vaccin contre l'hépatite virale A a soulevé la question de son indication chez le personnel exposé aux eaux usées. Nous avons évalué ce risque professionnel grâce à une étude transversale comparant les taux de prévalence des anticorps totaux (ou des IgG) anti-VHA chez 110 sujets exposés aux eaux usées appariés sur l'âge et le niveau de diplôme à 110 sujets non-exposés de la même entreprise. Chaque personne était interrogée sur ses antécédents d'ictère, la notion de voyages en zone d'endémie et la durée de l'exposition professionnelle. La prévalence des anticorps anti-VHA était globalement de 52,7 %, significativement plus élevée chez les exposés (60,9 %) que chez les non-exposés (44,S %) (p < 0,02). Cette séroprévalence augmentait avec l'âge, et apparaissait liée au niveau de diplôme dans les deux groupes. Ces résultats suggèrent fortement l'existence d'un risque professionnel d'infection par le VHA chez les travailleurs exposés aux eaux usées (risque relatif: 2,4; IC 95 % [1,6 - 3,1]). La vaccination du personnel exposé semble justifiée. La stratégie vaccinale à adopter est liée au coût élevé du vaccin et à la situation épidémiologique du VHA dans le pays.The availability of a first hepatitis A vaccine in 1992 raised the possibility of its use for workers exposed to sewage or sludge. This occupational risk was suspected because of the excretion of hepatitis A virus (HAV) in stools and its resulting presence in sewage, because of the resistance of HAV to environmental stresses, and because of the documented wastewater-mediated transmission of HAV in the general population. On the other hand, the decreased diffusion of HAV in industrialized countries probably results in less contamination of sewage. The aim of this study was to evaluate the possible risk of HAV infection from sewage exposure, which could lead to recommendations of vaccination for exposed workers. MethodsIn a large private company involved in water supply, anti HAV IgG were sought in sera from workers in contact with sewage and from workers not exposed to sewage. Subjects were individually matched for age and education level. Cases included workers involved with the wastewater collection network, workers who monitor drinking water distribution networks in Paris (located in sewer mains in Paris), personnel of a large research laboratory involved with wastewater and sludge, as well as a few workers involved with drinking water production who may be frequently exposed to raw Seine river, Marne river or Oise river water (that could be contaminated with sewage). Histories of jaundice, travels to areas of endemic incidence of hepatitis A, and the duration of occupational exposure were noted. Anti-HAV IgG was measured in serum by an enzyme-linked immunosorbent assay (ELISA) method.ResultsAt this time, 110 exposed workers and 110 non-exposed workers have been studied. Ages ranged from 20 to 58 years, with a mean value of 36.5 year. Cases and controls did not differ with respect to social class or travels in areas of endemic exposure. Duration of exposure ranged from 1 year to 36 years, with a mean value of 10.3, and was correlated to age in this company where workers are usually hired when young. The seroprevalence of anti HAV was globally 52.7 %, significantly higher in exposed workers ( 60.9 %) than in controls ( 44.5 % , p < 0.02 ). This seroprevalence varied widely according to age: for workers in their twenties it was 30.0 % vs. 27.5 %, in their thirties 68.0 % vs. 33.3%, in their forties 80.0 % vs. 54.8% and in their fifties 93.3 % vs. 86.7 %, respectively in exposed and non-exposed workers. The seroprevalence was related to education level in each group, but not to social class. History of jaundice was not correlated with anti HAV status, nor with sewage exposure. The relative risk of HAV infection in this matched range was 2.4, CI 95 % (1.6 - 3.1).These results emphasize the role of occupational exposure to sewage in HAV infection. Exposed workers should be vaccinated because of the frequency of the symptomatic form of hepatitis A in adults with severe and relapsing cases. The strategy of vaccination should take into account the high cost of the vaccine and the epidemiological situation of HAV in the country

Beats of the Magnetocapacitance Oscillations in Lateral Semiconductor Superlattices

We present calculations on the magnetocapacitance of the two-dimensional electron gas in a lateral semiconductor superlattice under two-dimensional weak periodic potential modulation in the presence of a perpendicular magnetic field. Adopting a Gaussian broadening of magnetic-field-dependent width in the density of states, we present explicit and simple expressions for the magnetocapacitance, valid for the relevant weak magnetic fields and modulation strengths. As the modulation strength in both directions increase, beats of the magnetocapacitance oscillations are observed, in the low magnetic field range (Weiss-oscillations regime), which are absent in the one-dimensional weak modulation case.Comment: 11 pages, 7 figures, accepted by Mod. Phys. Lett. B (March 2007

Millau viaduct geotechnical studies and foundations

AbstractThe Millau viaduct over the Tarn River is an exceptional bridge considering the height under the deck and the 2.5km total length. Each of the seven high piers is founded on a thick raft setting on four large piles of 5m in diameter and 10–15m deep. The ground schematically consists of limestone in the north and of marls in the south. As the bridge is very sensitive to foundation settlements, the concessionary company decided to use the observational method for controlling the displacements and if necessary stabilize the foundations. The measurements show that the movements have remained small and admissible, particularly in terms of the rotations. The settlements have not occurred continuously under the load, but by steps

Counting atoms in a deep optical microtrap

We demonstrate a method to count small numbers of atoms held in a deep, microscopic optical dipole trap by collecting fluorescence from atoms exposed to a standing wave of light that is blue detuned from resonance. While scattering photons, the atoms are also cooled by a Sisyphus mechanism that results from the spatial variation in light intensity. The use of a small blue detuning limits the losses due to light assisted collisions, thereby making the method suitable for counting several atoms in a microscopic volume

Automated Correctness Proof of Algorithm Variants in Elliptic Curve Cryptography

The Elliptic Curve Cryptography (ECC) is widely known as secure and reliable cryptographic scheme. In many situations the original cryptographic algorithm is modified to improve its efficiency in terms like power consumption or memory consumption which were not in the focus of the original algorithm. For all this modification it is crucial that the functionality and correctness of the original algorithm is preserved. In particular, various projective coordinate systems are applied in order to reduce the computational complexity of elliptic curve encryption by avoiding division in finite fields. This work investigates the possibilities of automated proofs on the correctness of different algorithmic variants. We introduce the theorems which are required to prove the correctness of a modified algorithm variant and the lemmas and definitions which are necessary to prove these goals. The correctness proof of the projective coordinate system transformation has practically been performed with the help of the an interactive formal verification system XeriFun

Feedback-Optimized Operations with Linear Ion Crystals

We report on transport operations with linear crystals of 40Ca+ ions by applying complex electric time-dependent potentials. For their control we use the information obtained from the ions' fluorescence. We demonstrate that by means of this feedback technique, we can transport a predefined number of ions and also split and unify ion crystals. The feedback control allows for a robust scheme, compensating for experimental errors as it does not rely on a precisely known electrical modeling of the electric potentials in the ion trap beforehand. Our method allows us to generate a self-learning voltage ramp for the required process. With an experimental demonstration of a transport with more than 99.8 % success probability, this technique may facilitate the operation of a future ion based quantum processor

Revealing the Correlation of the Electrochemical Properties and the Hydration of Inkjet-Printed CdSe/CdS Semiconductor Gels

The mobility of charge carriers across a semiconductor nanoparticle based 3D network (i.e. a gel) and the interfacial transfer of the charge carriers across the nanoparticle network/electrolyte boundary are elementary processes for applications in the fields of sensing and energy harvesting. The automated manufacturing of electrodes coated with porous networks can already be realized by inkjet printing. By simultaneous printing of CdSe/CdS dot-in-rod shaped nanorods (NRs) and the destabilization reagent, CdSe/CdS gel network coated electrodes can be obtained. In the presented work, the charge carrier mobility of the electrons and the holes within the porous CdSe/CdS nanorod gel network are investigated via photoelectrochemistry. Under application of linear sweep voltammograms (LSVs) and intensity modulated photocurrent spectra (IMPS) it is shown, that the electron is moving within the tip-to-tip connected CdSe/CdS NR gel structure, while the holes are trapped in the CdSe seed of the semiconductor heterostructures. Furthermore, the preparation process of gel structures is related to the elementary mechanism of hydration, which can be shown via photoelectrochemical long term studies