Simulation of cellular irradiation with the CENBG microbeam line using GEANT4

Light-ion microbeams provide a unique opportunity to irradiate biological samples at the cellular level and to investigate radiobiological effects at low doses of high LET ionising radiation. Since 1998 a single-ion irradiation facility has been developed on the focused horizontal microbeam line of the CENBG 3.5 MV Van de Graaff accelerator. This setup delivers in air single protons and alpha particles of a few MeV onto cultured cells, with a spatial resolution of a few microns, allowing subcellular targeting. In this paper, we present results from the use of the GEANT4 toolkit to simulate cellular irradiation with the CENBG microbeam line, from the entrance to the microprobe up to the cellular medium.Comment: 6 pages, 8 figures, presented at the 2003 IEEE-NSS conference, Portland, OR, USA, October 20-24, 200

Évaluation de l'impact de l'assainissement urbain sur la qualité des eaux du bassin versant de la rivière Chaudière à l'aide du système de modélisation intégrée GIBSI

Le programme d'assainissement des eaux de Québec (PAEQ), mis en place à la fin des années 1970, s'est d'abord attaqué au problème de la pollution ponctuelle d'origine urbaine. Plusieurs stations de traitement des eaux usées municipales ont été construites dans le cadre de ce programme réduisant de façon importante les charges de polluants d'origine urbaine. La question demeure toutefois de savoir dans quelle mesure les charges urbaines rejetées avant et l'après l'instauration de ce programme peuvent entraîner des dépassements de différents critères de l'eau. La présente étude a pour objectif d'examiner cette problématique pour le bassin versant de la rivière Chaudière en utilisant le système de modélisation intégrée GIBSI (Gestion Intégrée par Bassin versant à l'aide d'un Système Informatisé). Deux scénarios d'assainissement urbain ont été examinés, l'un représentatif de la période avant la mise en place du programme, le début des années 1980, et un autre représentatif de la période plus récente. Deux chroniques météorologiques ont été utilisées (années 1983 et 1994). L'estimation des probabilités de dépassement de différents critères de l'eau montre une nette réduction de ces probabilités après mise en place du programme. Pour la DBO5 et l'azote total, les charges urbaines rejetées actuellement n'entraînent pas de dépassement des critères de qualité de l'eau pour les deux années retenues. Toutefois, les résultats montrent que les charges en phosphore total d'origine urbaine peuvent à elles seules entraîner des probabilités de dépassement importantes lors d'étiage.In 1978, the Québec Government put in place a provincial municipal clean water program, referred to as the Programme d'assainissement des eaux du Québec (PAEQ), to restore the province's rivers to their natural state. The program focussed primarily on the problem of municipal waste loads and, hence, a large number of wastewater treatment plants (WWTP) were constructed during the 1980's and the 1990's. At the beginning of the 1980's, only a few percent of the population had their waste water treated, but this figure had increased to over 95% by 1997 (Figure 1). In the Chaudière river watershed, this program resulted in the construction of more than 35 WWTP over an 18-year period. Although an impressive effort was devoted to reduce municipal waste loads, a question remains: how does this reduction translate into terms of overall improvement of water quality at the watershed level?The Chaudière river watershed was considered for this application. This watershed covers an area of 6682 km2 and is located south of Quebec City. Land use is dominated by forest (62%) followed by agricultural land (33%), urban area (3.6 %), and water (1.7 %). The total population in 1996 was 173129 and was mainly located in the northern part (i.e., the downstream region) of the watershed. A total of 44 municipal point loads were identified (see Figure 2 and Table 1), most of them corresponding to WWTP. Characteristic data on municipal WWTP for year 1995 were obtained from the Quebec Department of the Environment (MINISTERE DE L'ENVIRONNEMENT ET DE LA FAUNE DU QUEBEC, 1997) and used to estimate average concentrations of total phosphorus and the biological oxygen demand (BOD). Data included affluent and effluent concentrations at various WWTP. Since no data were available for nitrogen, a concentration of 40 mg-N/l was used (TCHOBANOGLOUS et SCHOEDER, 1985; NOVOTNY et CHESTERS, 1981). Nitrogen removal efficiency for different types of treatment was estimated from available data compiled by the Environment Quebec (Table 2). An average, per capita, daily wastewater volume of 0.73 m3 was derived. This large value indicates a large infiltration capacity in the sewer network and, on average, a poor structural state.Results were analysed at four locations distributed along the river. These points corresponded to the locations of the four major water quality monitoring stations (Figure 3). Total annual loads within the sub-watersheds defined by these points were estimated (Table 3). Affluent characteristics were considered for the simulation of the pre-PAEQ period. Figure 4 represents the evolution of total phosphorus loads at station 2340012 (water intake for the town of Charny, the most downstream point). It shows that an important reduction occurred in 1986. For the same sub-watershed, the overall reduction for the 1982-1999 period was 38% for total phosphorus, 37% for total nitrogen and 83% for BOD.Assessment of the impact of the PAEQ was done using the integrated modelling system GIBSI ("Gestion Intégrée par Bassin versant à l'aide d'un Système Informatisé") (ROUSSEAU et al., 2000; MAILHOT et al., 1997 ; VILLENEUVE et al., 1998). Only pollutant loads originating from sewer networks were considered; pollutant loads from industrial plants not connected to a municipal sewer network were not considered in this study. Similarly, diffuse sources of pollution from urban area or agricultural land were not taken into account. Two scenarios were considered: a first scenario associated with the 1983 year corresponding to the pre-PAEQ period; and a second scenario associated with the 1994 year describing the post-PAEQ period (following load reductions). Two hydrological reference years were also selected, namely, years 1983 and 1994. The former corresponded to a significantly drier year than the latter. At station 2340012 (Charny water intake), this difference was even more pronounced when considering that the cumulative summer flow was 6.9 times larger in 1994 than in 1983. Four simulations corresponding to different combinations of representative municipal waste loads and meteorological conditions were performed (Table 5).Simulation results at the four control points were compared with water quality standards (WQS) for total phosphorus (0.03 mg-P/l, aesthetic WQS for prevention of eutrophication in rivers) and BOD (3 mg-BOD5 /l, sanitary WQS for domestic use of water requiring disinfection treatment only). The probabilities of exceeding these WQS were defined (equation 1) as the number of days (daily computational time step) where simulated values exceeded a given value (complementary cumulative distribution function). Table 8 introduces annual probabilities of exceeding WQS at the four control points and for the different simulations whereas Table 9 introduces those for the summer period. At station 2340012 (Charny water intake), for hydrological year 1994, a comparison of pre- and post-PAEQ conditions for total phosphorus shows that post-PAEQ condition lowered the number of days exceeding WQS by 49. Similar reductions were reached at the other control points. For the 1994 summer period, the reduction was not as pronounced since the probability of exceeding WQS was 0.24 for pre-PAEQ situation and it decreased to 0.21 for the post-PAEQ condition. These probabilities worsened under the 1983 summer conditions as concentrations exceeded the WQS 98% of the time at station 2340014

Un colloque sur la pluridisciplinariaté dans les problèmes d'environnement : quelques enseignements et orientations pour l'avenir

International audienceAn experiment has been carried out in Rennes (Brittany, West of France) in June 2000 to estimate atrazine and alachlor volatilisation fluxes after application over a maize crop. Fluxes were calculated using the classical aerodynamic micrometeorological method from vertical gradients of pesticide concentrations, temperature and wind speed. Volatilisation fluxes showed a diurnal pattern of the order of few ng/m2/s for atrazine and the order of a few 10 ng/m2/s for alachlor, leading to cumulated losses of approximately 0.1% of the theoretical application dose for atrazine and several-fold of that in the case of alachlor

Infrared spectroscopy of diatomic molecules - a fractional calculus approach

The eigenvalue spectrum of the fractional quantum harmonic oscillator is calculated numerically solving the fractional Schr\"odinger equation based on the Riemann and Caputo definition of a fractional derivative. The fractional approach allows a smooth transition between vibrational and rotational type spectra, which is shown to be an appropriate tool to analyze IR spectra of diatomic molecules.Comment: revised + extended version, 9 pages, 6 figure

Critical temperature and superfluid density suppression in disordered high-TcT_c cuprate superconductors

We argue that the standard Abrikosov-Gorkov (AG) type theory of $T_c$ in disordered $d$-wave superconductors breaks down in short coherence length high-$T_c$ cuprates. Numerical calculations within the Bogoliubov-de Gennes formalism demonstrate that the correct description of such systems must allow for the spatial variation of the order parameter, which is strongly suppressed in the vicinity of impurities but mostly unaffected elsewhere. Suppression of $T_c$ as measured with respect to the attendant decrease in the superfluid density is found to be significantly weaker than that predicted by the AG theory, in good agreement with experiment.Comment: REVTeX, 4 pages, 3 ps figures included [The version to appear in PRB Sept. 1. Conclusions of the paper unchanged; several changes in text and figures for added clarity, discussion of phase fluctuations added.

Non-magnetic impurity scattering in a dx2−y2d_{x^2 - y^2} superconductor near a van Hove point: Zn versus Ni in the cuprates

We consider the effect of non-magnetic impurities in a $d_{x^2 - y^2}$ superconductor with \ef close to a van Hove singularity. It is shown that the non-trivial density of states (DOS) allows for resonant scattering already at intermediate potential strengths $|u| \approx 1-2$eV. The residual DOS at \ef, and the \tc suppression rate are found to strongly depend on the carrier concentration. Quantitative agreement with experiments on Zn and Ni doped cuprates is obtained by adjusting a single parameter, $u$.Comment: 4 pages uuencoded compressed Postscript (Minor changes

Unusual consequences of status epilepticus in Dravet syndrome

AbstractAlthough status epilepticus (SE) affects the course of Dravet syndrome (DS), it rarely alters dramatically psychomotor outcome. We report an unusual pattern in 3 patients who following refractory SE lasting respectively 2, 7 and 12h experienced persistent and severe cognitive and motor deterioration. We compared these patients to published data and to personal experience in Necker hospital, to find links between severe outcome and clinical features such as treatment or duration of refractory SE. The key point was that anoxoischemic-like lesions appeared on MRI although cardiovascular function had remained stable. Therefore, neither hemodynamic failure, nor abnormalities of cardiac rhythm could explain the lesions and neurological worsening. For theoretical reasons the responsibility of therapy common for the 3 patients, e.g., barbiturates was suspected