Influence de divers facteurs écologiques sur la bioaccumulation d'éléments métalliques (Cd, Cu, Pb, Zn) chez de jeunes palourdes (Ruditapes philippinarum) au cours du prégrossissement en nourricerie

La bioaccumulation des métaux chez les mollusques peut être une conséquence de la désorption des éléments métalliques fixés sur les particules inertes ou vivantes en suspension dans l'eau qui leur servent de nourriture. Les meilleures expériences réalisées jusqu'ici semblent indiquer que les matières en suspension ont un rôle mineur dans la contamination des mollusques. Mais quelles que soient les précautions prises, les expériences ne simulent jamais parfaitement les phénomènes naturels. Aussi, nous avons choisi de reprendre cette question à l'aide d'une expérience en grand volume où le nombre de paramètres contrôlés est restreint mais où les organismes sont dans des conditions aussi proches que possible de la réalité.Au cours d'un prégrossissement expérimental, les jeunes palourdes reçoivent des quantités variables contrôlées de nourriture phytoplanctonique. La fourniture d'une nourriture plus abondante a pour conséquence d'augmenter les quantités de cuivre et de zinc et au contraire de diminuer celles de plomb contenues dans chaque individu. Elle entraîne également une diminution des concentrations en cadmium et plomb traduisant une « dilution biologique » de ces métaux. L'augmentation de la densité de la population expérimentale a un effet négatif sur les quantités de cuivre et de zinc contenues dans les individus. A âge identique, les individus les plus grands présentent des concentrations plus faibles en cuivre et zinc et plus élevées en cadmium et plomb.L'utilisation des eaux marines souterraines présente deux avantages: une production algale intense à un coût économique négligeable et la possibilité par échange thermique de réchauffer en hiver les eaux marines naturelles et ainsi de maintenir une croissance des mollusques toute l'année. L'emploi des eaux de forage n'entraîne aucun effet néfaste dans les phénomènes de bioaccumulation des métaux, du moins pour ceux étudiés ici : cadmium, cuivre, plomb et zinc.Metal bioaccumulation in bivalves may occur as a consequence of the ingestion of inert or living particles with fixed trace elements. The best experiments like those carried out by BORCHARDT (1983, 1985) concerning Cd in mussels have shown that the role suspended matter plays in the contamination of molluscs is insignificant. But, however reliable the experimental methodologies, laboratory conditions never reproduce perfectly natural phenomena. We planned therefore to restudy the problem by using a largescale experiment where the procedure was characterized by a restricted number of controlled parameters and the organisms as close as possible to the real conditions.During an experimental nursing of young carpet shells, we assessed the influence of various controlled quantifies of phytoplankton and of experimental population density on the transfer of metal from their environment to molluscs.Carpet-shell brood (Ruditapes philippinarum) was distributed in several cylindrical containers the bottom of which consisted in a sieve. Food and seawater were renewed continuously by means of an ascending current (BAUD et BACHER, 1990). Nursing assays were carried out during summer over a period of 74 days. Eight groups of carpet shells were constituted according to food supplies (0, lx, 2x and 4x of Skeletonema costatum grown upon underground seawater plus natural phytoplankton) and population density (25 000 or 50 000 individuals per experimental container). Young molluscs were fed according to a cycle of 3 h-feeding periods and 2 h-periods with no food alternately. The average concentrations of algal cells in mollusc breeding seawater were 17.5, 35 and 70.103 cells/L. This seawater was renewed at a flow rate of 3 m3/h.At the end of the nursing period, molluscs exposed to different experimental conditions were separated by using sieves of different mesh-size (6, 8 and 10 mm). Young carpet shells were purged for 36 h in order to limit the overvaluation of bioaccumulated metal levels due to ingested matter (AMIARD-TRIQUET et al., 1984; KENNEDY, 1986). In each experimental and size-related categories, 90 individuals were sampled and divided into 3 groups of 30 specimens.In these groups, soft tissues were separated from the shells and oven-dried at 80 °C for 48 h. The dry samples were powdered and three aliquot parts of about 100 mg each were digested with 1 ml of concentrated nitric acid (HNO3, Suprapur) at 95 °C for 1 h. Then the trace element analyses were performed in this solution diluted with deionized water by dame (Zn) or by flameless (Cd, Cu, Pb) atomic absorption spectrophotometry using the Zeeman effect (AMIARD et al., 1987).The influence of both food supplies and experimental population density on the dry weight of soil tissues of young carpet shells, their metal concentration and body burdens were examined by means of multi-linear regression analysis.Increasing body burdens of Cu (4) and Zn (5) and decreasing body burden of Pb (3), corresponded to more abundant food supplies. The increase of phytoplankton supplies induced a decrease of Cd (6) and Pb (7) concentrations as a consequence of a « biological dilution » of these metals. Increasing density induced a depletion of Cu (4) and Zn (5) body burdens. Among individuals of the same age, the biggest ones exhibited the lowest concentrations of Cu and Zn (8 and 9) and the highest concentrations of Cd and Pb (6 and 7).Increased food supplies induce a biological dilution of Cd and Pb in young carpet-shells. These results are in agreement with previous data concerning Cd, Cu, Pb and Zn in different species (MACKAY et al., 1975; BOYDEN, 1971; PHELPS et al., 1985; BERTHET, 1986). Thus front a sanitary point of view, the use of ground seawater for algal culture is not a risk since metal concentrations in molluscs are not enhanced

Permo-Triassic Deposits: from shallow water to base of slope

Conference on the Geology of Oman, Muscat, Oman, Field Guidebook A0

The ALICE Data Challenges

Since 1998, the ALICE experiment and the CERN/IT division have jointly executed several large-scale high throughput distributed computing exercises: the ALICE data challenges. The goals of these regular exercises are to test hardware and software components of the data acquisition and computing systems in realistic conditions and to execute an early integration of the overall ALICE computing infrastructure. This paper reports on the third ALICE Data Challenge (ADC III) that has been performed at CERN from January to March 2001. The data used during the ADC III are simulated physics raw data of the ALICE TPC, produced with the ALICE simulation program AliRoot. The data acquisition was based on the ALICE online framework called the ALICE Data Acquisition Test Environment (DATE) system. The data after event building were then formatted with the ROOT I/O package and a data catalogue based on MySQL was established. The Mass Storage System used during ADC III is CASTOR. Different software tools have been used to monitor the performances. DATE has demonstrated performances of more than 500 MByte/s. An aggregate data throughput of 85 MByte/s was sustained in CASTOR over several days. The total collected data amounts to 100 TBytes in 100,000 files

Anomalous electric conductions in KSbO3-type metallic rhenium oxides

Single crystals of KSbO3-type rhenium oxides, La4Re6O$19, Pb6Re6O19, Sr2Re3O9 and Bi3Re3O11, were synthesized by a hydrothermal method. Their crystal structures can be regarded as a network of three-dimensional orthogonal-dimer lattice of edge-shared ReO6 octahedra. All of them exhibit small magnitude of Pauli paramagnetism, indicating metallic electronic states without strong electron correlations. The resistivity of these rhenates, except Bi3Re3O11, have a temperature dependence of$rho(T)=\rho_{0}+AT^{n}$$(n \approx 1.6)$ in a wide temperature range between 5 K and 300 K, which is extraordinary for three-dimensional metals without strong electron correlations. The resistivity of Bi3Re3O11 shows an anomaly around at 50 K, where the magnetic susceptibility also detects a deviation from ordinary Pauli paramagnetism.Comment: 13 pages, 7 figures. J. Phys. Soc. Japan, in pres

Challenging the challenge: handling data in the Gigabit/s range

The ALICE experiment at CERN will propose unprecedented requirements for event building and data recording. New technologies will be adopted as well as ad-hoc frameworks, from the acquisition of experimental data up to the transfer onto permanent media and its later access. These issues justify a careful, in-depth planning and preparation. The ALICE Data Challenge is a very important step of this development process where simulated detector data is moved from dummy data sources up to the recording media using processing elements and data-paths as realistic as possible. We will review herein the current status of past, present and future ALICE Data Challenges, with particular reference to the sessions held in 2002 when - for the first time - streams worth one week of ALICE data were recorded onto tape media at sustained rates exceeding 300 MB/s.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics (CHEP03), La Jolla, Ca, USA, March 2003, 9 pages, PDF. PSN MOGT00

GASKAP -- The Galactic ASKAP Survey

A survey of the Milky Way disk and the Magellanic System at the wavelengths of the 21-cm atomic hydrogen (HI) line and three 18-cm lines of the OH molecule will be carried out with the Australian Square Kilometre Array Pathfinder telescope. The survey will study the distribution of HI emission and absorption with unprecedented angular and velocity resolution, as well as molecular line thermal emission, absorption, and maser lines. The area to be covered includes the Galactic plane (|b|< 10deg) at all declinations south of delta = +40deg, spanning longitudes 167deg through 360deg to 79deg at b=0deg, plus the entire area of the Magellanic Stream and Clouds, a total of 13,020 square degrees. The brightness temperature sensitivity will be very good, typically sigma_T ~ 1 K at resolution 30arcsec and 1 km/s. The survey has a wide spectrum of scientific goals, from studies of galaxy evolution to star formation, with particular contributions to understanding stellar wind kinematics, the thermal phases of the interstellar medium, the interaction between gas in the disk and halo, and the dynamical and thermal states of gas at various positions along the Magellanic Stream.Comment: 45 pages, 8 figures, Pub. Astron. Soc. Australia (in press

Computational exploration of molecular receptive fields in the olfactory bulb reveals a glomerulus-centric chemical map

© The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.Progress in olfactory research is currently hampered by incomplete knowledge about chemical receptive ranges of primary receptors. Moreover, the chemical logic underlying the arrangement of computational units in the olfactory bulb has still not been resolved. We undertook a large-scale approach at characterising molecular receptive ranges (MRRs) of glomeruli in the dorsal olfactory bulb (dOB) innervated by the MOR18-2 olfactory receptor, also known as Olfr78, with human ortholog OR51E2. Guided by an iterative approach that combined biological screening and machine learning, we selected 214 odorants to characterise the response of MOR18-2 and its neighbouring glomeruli. We found that a combination of conventional physico-chemical and vibrational molecular descriptors performed best in predicting glomerular responses using nonlinear Support-Vector Regression. We also discovered several previously unknown odorants activating MOR18-2 glomeruli, and obtained detailed MRRs of MOR18-2 glomeruli and their neighbours. Our results confirm earlier findings that demonstrated tunotopy, that is, glomeruli with similar tuning curves tend to be located in spatial proximity in the dOB. In addition, our results indicate chemotopy, that is, a preference for glomeruli with similar physico-chemical MRR descriptions being located in spatial proximity. Together, these findings suggest the existence of a partial chemical map underlying glomerular arrangement in the dOB. Our methodology that combines machine learning and physiological measurements lights the way towards future high-throughput studies to deorphanise and characterise structure-activity relationships in olfaction.Peer reviewe

Summary of the BDS and MDI CLIC08 Working Group

This note summarizes the presentations held within the Beam Delivery System and Machine Detector Interface working group of the CLIC08 workshop. The written contributions have been provided by the presenters on a voluntary basis

The analysis of 2-amino-2-thiazoline-4-carboxylic acid in the plasma of smokers and non-smokers

ATCA (2-amino-2-thiazoline-4-carboxylic acid) is a promising marker to assess cyanide exposure because of several advantages of ATCA analysis over direct determination of cyanide and alternative cyanide biomarkers (i.e. stability in biological matrices, consistent recovery, and relatively small endogenous concentrations). Concentrations of ATCA in the plasma of smoking and non-smoking human volunteers were analyzed using gas-chromatography mass-spectrometry to establish the feasibility of using ATCA as a marker for cyanide exposure. The levels of ATCA in plasma of smoking volunteers, 17.2 ng/ml, were found to be significantly (p < 0.001) higher than that of non-smoking volunteers, 11.8 ng/ml. Comparison of ATCA concentrations of smokers relative to non-smokers in both urine and plasma yielded relatively similar results. The concentration ratio of ATCA for smokers versus non-smokers in plasma and urine was compared to similar literature studies of cyanide and thiocyanate, and correlations are discussed. This study supports previous evidence that ATCA can be used to determine past cyanide exposure and indicates that further studies should be pursued to validate the use of ATCA as a marker of cyanide exposure