Assessment of Ge-doped optical fibres as a TSL-mode detector

International audienceThis study analyses the thermally stimulated luminescence or thermoluminescence (TL) glow curve between 300 and 773 K of germanium-doped silica optical fibre. A main glow peak at 530 K with a characteristic spectral emission centred at 400 nm is found. Both features are particularly suitable for dosimetry. Thus, an investigation by the TL technique of some first clinically relevant features of a TL sensor like the dose- and dose rate-responses is examined. The presented studies show that germanium doped silica fibres have potential dosimetric properties and should be excellent TL-mode detectors in instances of radiotherapy (clinical dosimetry) and in-vivo radiation dosimetry as well in the field of nuclear facilities

Étude de l'effet de cycles thermiques sur l'adhérence béton/armature en matériaux composites constituée de polymères renforcés de fibres de carone et de fibres de verre

L'émergence des renforcements composites dans la construction fait suite au problème considérable auquel font face les structures renforcées en acier. Cependant pour être acceptée définitivement par les professionnels de la construction, ces armatures doivent démontrer leur durabilité face aux agents agressifs. Une étude particulière de la durabilité consiste à étudier l'effet des gradients thermiques sur l'adhérence béton/armature PRF. Dans la partie bibliographique, nous avons étudié les matériaux composites polymères renforcées par des fibres. En particulier, nous avons discuté les constituants de base, le comportement et les propriétés thermiques des armatures en matériaux composites, enfin nous avons cité les essais antérieures concernant l'effet de la température sur l'adhérence béton/armature PRF. Dans une deuxième étape, les caractéristiques d'adhérence dans le béton précontraint ainsi que les risques de fissuration ont été analysés, tant sur le plan théorique qu'expérimentale. La partie expérimentale qui a suivi a concerné les étapes suivantes: (1) Étude et mesures des coefficients d'expansion thermique avec la température. (2) Étude microscopique de l'interface béton/armature PRF sous l'effet de gradients thermiques. (3) Étude de l'effet de gradients thermiques sur l'adhérence béton/armature PRF dans des poutres précontraintes, ainsi que sur des poutres simplement armées. La réalisation de ces essais a permis de conclure que: (1) Le coefficient d'expansion thermique transversale a montré une dépendance face à la température. (2) L'étude microscopique a permis de relever que des fissures transversales sur le béton de l'interface ainsi qu'une séparation entre l'armature et le béton pourraient être provoqués par un gradient thermique. (3) Les essais de flexion réalisés sur les poutres précontraintes par des tendons PRFC ont montré une dégradation de la performance structurale. (4) Les essais de flexion effectués sur des poutres en béton armées de PRF n'ont montré aucun effet dû aux cycles thermiques

Antifungal activity of methanolic extracts of four Algerian marine algae species

Since ancient times antimicrobial properties of seaweeds have been recognized. In this study, antifungal activity of four species of marine algae of Bejaia coast (Algeria) was explored. This activity was evaluated by agar diffusion method. The minimum inhibitory concentrations were also determined for all the strains. All the extracts used in this study exhibited antifungal activity. The highest inhibiting effect was noted for Rhodomela confervoides (red algae) and Padina pavonica (brown algae), respectively against Candida albicans (diameter of inhibition zone: 24 mm) and Mucor ramaniannus (diameter of inhibition zone: 26 mm) for the first one and Candida albicans (diameter of inhibition zone: 26 mm) for the second one. Aspergillus niger showed resistance against majority of methanolic extracts. The evaluation of minimum inhibitory concentrations showed that extracts of Padina pavonica, Rhodomela confervoides and Ulva lactuca were very efficient against Mucor ramaniannus and Candida albicans. These results suggest that seaweeds collected from Algerian coast present a significant capacity which makes them interesting for screening for natural products.Key words: Marine algae, antifungal activity, methanolic extracts, natural substances

Effect of swift heavy ion irradiations in polycrystalline aluminum nitride

13International audienceThanks to its high thermal conductivity, aluminum nitride may be a serious candidate as fuel coating for the Gas Fast Reactor. However, its behavior under irradiation is not entirely well understood. In order to catch a glimpse of this behavior, specimens were irradiated with swift heavy ions of different energies then characterised by both thermally stimulated luminescence and optical absorption spectrophotometry. With these techniques, the native defects, as well as those affected by irradiation, were identified: thus, by comparison to the virgin sample, no new defect detectable by these techniques is created by irradiations. Eventually, the fact that these techniques complement each other allowed to understand the effect of irradiation parameters on the defect concentration

A physical model of the photo- and radiation-induced degradation of ytterbium-doped silica optical fibres

International audienceWe propose a model to describe the photo-or/and the radiation-induced darkening of ytterbium-doped silica optical fibers. This model accounts for the well-established experimental features of photo-darkening. Degradation behaviors predicted for fibers pumped in harsh environments are also fully confirmed by experimental data reported in the work by Duchez et al. (this proceeding), which gives a detailed characterization of the interplay between the effects of the pump and those of a superimposed ionizing irradiation (actual operation conditions in space-based applications for instance). In particular, dependences of the darkening build-up on the pump power, the total ionizing dose and the dose rate are all correctly reproduced. The presented model is a 'sufficient' one, including the minimal physical ingredients required to reproduce experimental features. Refinements could be proposed to improve, e.g., quantitative kinetics

Determination of isoquinoline alkaloids contents in two Algerian species of Fumaria (Fumaria capreolata and Fumaria bastardi)

This paper describes a fast and efficient procedure to separate and identify isoquinoline alkaloids from methalonic extract of two Algerian Fumaria (Fumariacea) species (Fumaria capreolata L. and Fumariabastardi L.) used in traditional medicine in cases of hepatobiliary disfunction and diarrhoea. Total quinolizidine alkaloid contents were 426 mg/100 g (F. capreolata) and 521 mg/100 g (F. bastardi). Theisoquinoline alkaloids, stylopine, protopine, fumaritine, fumaricine, fumarophycine, fumariline and fumarofine were determined by gas chromatography – mass spectrometry (GC-MS) in aerial parts ofboth Fumaria capreolata and Fumaria bastardi. In the first species, an ester of phtalic acid was identified, and in the second species a peak seems to be a benzophenanthridine, probably a dehydro derivative and three other peaks which were identified as phtalidisoquinoline, one of them seems to bedihydrofumariline. The chemotaxonomic significance of the results is discussed

APPROCHE REGIONALE POUR L’ESTIMATION DES PRECIPITATIONS JOURNALIERES EXTREMES DU NORD EST ALGERIEN

L’information sur les valeurs des précipitations extrêmes et leurs fréquences est nécessaire pour les différents projets liés à l’eau. Dans cette étude, l’analyse fréquentielle régionale basée sur les L-moments a été utilisée pour améliorer la qualité d’estimation des quantiles des précipitations journalières maximales annuelles de la région située au Nord Est de l’Algérie représentée par 50 stations de mesure. La région d’étude a été divisée en deux régions statistiquement homogènes en termes des rapports des L-moments. Parmi les différentes distributions testées, (i) la distribution GEV (Generalized Extreme Value) a été identifiée comme distribution régionale la plus adéquate pour la modélisation des précipitations de la région 1 caractérisée par un climat méditerranéen et (ii) la distribution lognormale à trois paramètres (LN3) pour la région 2, sujette à un climat semi-aride. Les courbes de croissance ont été établies pour chaque région homogène. Ainsi, les quantiles des précipitations dans un site sont déterminés en multipliant la moyenne des précipitations par les quantiles régionaux correspondants. La comparaison des quantiles estimés à partir de l’approche régionale et locale a montré que pour 50,4 % des stations de la région d’étude, le modèle local sous estime les quantiles de fortes périodes de retour  Information on precipitation magnitudes and their frequencies is needed in various projects related to water. In this study, the regional frequency analysis based on L-moments was used to improve the quality of estimating of the annual maximum daily precipitations of the north eastern area of Algeria represented by 50 measuring stations. The investigated area was divided into two regions statistically homogeneous in terms of L-moments ratios. Among the different tested distributions, (i) the Generalized Extreme Value (GEV) distribution has been identified as the most appropriate regional distribution for modeling precipitation in the northern region (region 1) characterized by a Mediterranean climate and (ii) the generalized lognormal distribution (LN3) for region 2 of southern part subject to semi-arid climate. Growth curves, derived from the regional distributions, were established for each homogeneous region. The growth curves shapes difference reflects the difference between the two homogeneous regions precipitation patterns. Therefore, to estimate the different return period’s precipitation quantiles in a given site of the region, the mean precipitation of the site has to be multiplied by the corresponding regional quantile. Comparison of estimated quantiles given by the regional and local approach showed that for 50.4 % of stations, at-site model underestimates the quantiles having high return periods

The interplay between photo-and radiation-induced darkening in ytterbium-doped fibres

International audienceThis letter demonstrates a remarkable interplay between photo-and radiation-induced darkening of ytterbium-doped alumino-silica optical fibres operated in amplifying conditions and harsh environments (as e.g. in space-based applications). Influences of the pump power, ionizing dose and dose rate on this interaction are characterized. The pump is capable of accelerating or slowing-down the radiation-induced darkening build-up depending on the ionizing dose. The steady state photo-radio-darkening level is independent of the dose and at least equal to the equilibrium level of pure photo-darkening. This lower limit is notably reached at low dose rates, including those encountered in space. We therefore argue that photo-resistant ytterbium-doped fibres will resist against a space mission, whatever the dose

Characterization of aluminum nitride material under swift heavy ion irradiations

International audienceFor Generation IV reactors, and more particularly the Gas Fast Reactor, aluminum nitride is an interesting candidate for the application as fuel coating; actually, its great thermal conductivity should allow efficient thermal transfer between the fuel pellets and the coolant. Unfortunately, few data are available on its behavior under irradiation. In this study, we attempted to understand the effect of irradiation parameters on the defect creation thanks to thermally-stimulated luminescence and optical absorption spectrophotometry. Thus, we didn't note any new defect created by the irradiation and the fact that these techniques complement each other allowed to know the influence of each irradiation parameter on the defects concentration

Detection of tetragonal zirconia in alumina–zirconia powders by thermoluminescence

International audienceThe thermoluminescence (TL) after excitation by UV or X-rays radiation of alumina-zirconia powders is investigated. The composites present five of the characteristic peaks of zirconia at −170, −145, −90, 0 and 95 °C. After a thermal treatment of mixed oxides, a new peak is observed at −35 °C in TL. This peak reveals the presence of stabilized tetragonal zirconia in the material. Moreover by comparing this analysis with those realised by X-ray diffraction (XRD), it can by shown that the TL has one better limit of detection than the XRD