Caractérisation des sables et morphologie du fond du lac du barrage hydroélectrique de Taabo (Côte d\'Ivoire)

Une analyse sédimentologique et minéralogique réalisée sur un cycle hydrologique entre octobre 2004 et août 2005 a permis d\'évaluer les charges solides en suspension et de caractériser les sédiments du lac du barrage de Taabo. La concentration moyenne en matières en suspension (12 mg.L-1) et la turbidité moyenne (20 NTU) montrent que les eaux du lac sont relativement peu chargées. Ces charges en suspension sont composées d\'une fraction inorganique et d\'une fraction organique. Les sables qui composent les sédiments de ce lac sont majoritairement moyens à grossiers et médiocrement classés avec une moyenne granulométrique de 451,48 μm et un indice de classement moyen de 1,13. Les vases et les sables fins occupent les zones profondes du lac et les zones envahies par les végétaux aquatiques. Les sables moyens sont localisés aux voisinages des berges tandis que les sables grossiers sont situés aux voisinages des îles et de la digue. Le cortège minéralogique des sédiments est caractérisé de minéraux lourds (l\'amphibole, la tourmaline, le diopside et l\'épidote) et de minéraux légers (le quartz et les feldspaths). Par ailleurs, cette étude a permis de réaliser la première carte bathymétrique du lac de Taabo 26 ans après sa mise en eau.A sedimentological and mineralogical study carried out on a hydrological cycle from October 2004 to August 2005 has permitted to assess the solid suspended matters and to characterize the sediments of the Taabo dam lake. The average of suspended matters concentration (12 mg.L -1) and the average of turbidity (20 NTU) reveal that the lake is relatively little loaded with suspended matters. These suspended matters are compound of an inorganic fraction and an organic fraction. Sands size in the sediments of this lake are from middle to coarse and badly classified. The grain size average is 451,48 μm; the standard deviation average is 1,13. Muds and fine sands are found in the deeper zones of the lake and also in the zones invaded by the aquatic plants. Middle sands are located near banks while coarse sands are located aside the islands and the dam. The minerals found in the sediments are characterized by heavy minerals (the amphibole, tourmaline, diopside and epidote) and light minerals (quartz and feldspars). Elsewhere, this study has permitted to carry out the first bathymetric Map of this lake 26 years after its setting in water. Keywords: keywordBarrage, lac, granulométrie, minéralogie, bathymétrie, Taabo./Dam, lake, grain size, mineralogy, bathymetry, Taabo.Sciences & Nature Vol. 4 (1) 2007: pp. 93-10

Feed-back on the development of a small scale Contact Erosion Test in the laboratory (characteristic size ~ 30 cm)

To determine the hydraulic load requested to initiate contact erosion process, tests are performed with an apparatus called the “Contact Erosion Test”. This device originally results from research carried out by Grenoble University, Électricité de France and Compagnie Nationale du Rhône, at the scale of ~60 cm. It has been adapted to a smaller scale in geophyConsult laboratory to conduct tests on samples extracted from core drilling. The instrumentation was improved to enable a better control of the hydraulic loading and avoid biases. The test protocol was modified, especially to better constrain the soil density at the interface. From the first series of test, we drew conclusions on the test repeatability and on the influence of parameters of the soil state. Discrepancies with previous results obtained at the scale of ~60 cm were identified. Therefore, a new erosion test campaign was planned to confirm and determine the reasons for these differences

Cytotoxic polyfunctionality maturation of cytomegalovirus-pp65-specific CD4 + and CD8 + T-cell responses in older adults positively correlates with response size

Cytomegalovirus (CMV) infection is one of the most common persistent viral infections in humans worldwide and is epidemiologically associated with many adverse health consequences during aging. Previous studies yielded conflicting results regarding whether large, CMV-specific T-cell expansions maintain their function during human aging. In the current study, we examined the in vitro CMV-pp65-reactive T-cell response by comprehensively studying five effector functions (i.e., interleukin-2, tumor necrosis factor-α, interferon-γ, perforin, and CD107a expression) in 76 seropositive individuals aged 70 years or older. Two data-driven, polyfunctionality panels (IL-2-associated and cytotoxicity-associated) derived from effector function co-expression patterns were used to analyze the results. We found that, CMV-pp65-reactive CD8 + and CD4 + T cells contained similar polyfunctional subsets, and the level of polyfunctionality was related to the size of antigen-specific response. In both CD8 + and CD4 + cells, polyfunctional cells with high cytotoxic potential accounted for a larger proportion of the total response as the total response size increased. Notably, a higher serum CMV-IgG level was positively associated with a larger T-cell response size and a higher level of cytotoxic polyfunctionality. These findings indicate that CMV-pp65-specific CD4 + and CD8 + T cell undergo simultaneous cytotoxic polyfunctionality maturation during aging

The Functional −765G→C Polymorphism of the COX-2 Gene May Reduce the Risk of Developing Crohn's Disease

Contains fulltext : 87827.pdf (publisher's version ) (Open Access)BACKGROUND: Cyclooxygenase-2 (COX-2) is a key enzyme involved in the conversion of arachidonic acid into prostaglandins. COX-2 is mainly induced at sites of inflammation in response to proinflammatory cytokines such as interleukin-1alpha/beta, interferon-gamma and tumor necrosis factor-alpha produced by inflammatory cells. AIM: The aim of this study was to investigate the possible modulating effect of the functional COX-2 polymorphisms -1195 A-->G and -765G-->C on the risk for development of inflammatory bowel disease (IBD) in a Dutch population. METHODS: Genomic DNA of 525 patients with Crohn's disease (CD), 211 patients with ulcerative colitis (UC) and 973 healthy controls was genotyped for the -1195 A-->G (rs689466) and -765G-->C (rs20417) polymorphisms. Distribution of genotypes in patients and controls were compared and genotype-phenotype interactions were investigated. RESULTS: The genotype distribution of the -1195A-->G polymorphism was not different between the patients with CD or UC and the control group. The -765GG genotype was more prevalent in CD patients compared to controls with an OR of 1.33 (95%CI 1.04-1.69, pC polymorphism was associated with a reduced risk for developing Crohn's disease in a Dutch population

Evaluation de l’apport d’un sondeur de sédiment pour l’estimation des épaisseurs de sédiments dans les retenues de barrage

La carte des épaisseurs de sédiments et le volume total de sédiments déposés dans les réservoirs sont des données essentielles pour traiter les problèmes liés à la gestion quantitative et qualitative des dépôts de sédiments dans les retenues. Lorsque la topographie de la retenue avant la mise en eau n’est pas connue, il est nécessaire de recourir à des techniques de mesure spécifiques pour évaluer l’épaisseur de sédiment et le volume total du dépôt. EDF a réalisé un projet de recherche dont le but était d’évaluer les technologies les plus prometteuses dans ce domaine, dans l’état de l’art actuel. Dans le cadre de ce projet, un sondeur acoustique de sédiment utilisant la technologie « chirp » a été évalué. Une méthodologie pour la production et la validation des résultats a été définie. Une étude expérimentale de la sensibilité des paramètres célérité du son dans les sédiments et atténuation a été menée. Une première évaluation de la capacité de ce sondeur à déterminer la carte des épaisseurs de sédiments a été conduite dans le bassin de délimonage de Cadarache, ce qui a permis de préciser les limites d’utilisation de cette technique

Industry research into dam and levee breach erosion through coarser grained materials

Predicting breach erosion processes is essential for the effective risk management of both dams and levees. In recent years, a variety of research efforts have improved our knowledge of erosion processes, and in particular validation of the work on headcut erosion through cohesive soils performed at USDA-HERU. A similar level of analysis and validation is required for coarser grained and mixed materials to provide a clearer overview of when breach erosion processes change from headcut through surface erosion to slumping of rockfill. Since the release of flood water through a breached dam or levee depends both upon the rate of soil particle erosion and the macro erosion process (i.e. whether headcut or surface erosion or some other process occurs) it is important to ensure that conditions for these macro and micro erosion processes are understood in relation to different soil types and conditions, and that any breach prediction models correctly reflect these processes. This paper presents an update on progress with a programme of research being implemented by EDF which investigates (i) how macro erosion processes change in relation to soil type and state, (ii) the validity of soil erosion relationships used for coarser and mixed grained erosion and (iii) the performance of breach models in predicting the breaching processes. This research combines laboratory testing at UPM (~1m scale tests), and potentially also at CNR (~2m scale tests), with large scale field tests (2-4m high) to be undertaken at a new test facility being constructed in the River Ebro catchment in Spain near Zaragoza. The work also combines breach model performance validation through a programme of international collaboration and aligns with research into soil erosion currently underway in the USA by the Army Corps of Engineers (ERDC, Vicksburg) and the Bureau of Reclamation (Denver)

Innovative minimally invasive options to treat drug-resistant epilepsies

International audienceDespite the regular discovery of new molecules, one-third of epileptic patients are resistant to antiepileptic drugs. Only a few can benefit from resective surgery, the current gold standard. Although effective in 50–70% of cases, this therapy remains risky, costly, and can be associated with long-term cognitive or neurological side effects. In addition, patients are increasingly reluctant to have a craniotomy, emphasizing the need for new less invasive therapies for focal drug-resistant epilepsies. Here, we review different minimally invasive approaches already in use in the clinic or under preclinical development to treat drug-resistant epilepsies. Localized thermolesion of the epileptogenic zone has been developed in the clinic using high-frequency thermo-coagulations or magnetic resonance imaging-guided laser or ultrasounds. Although less invasive, they have not yet significantly improved the outcomes when compared with resective surgery. Radiosurgery techniques have been used in the clinic for the last 20 years and have proven efficiency. However, their efficacy is not better than resective surgery, and various side effects have been reported as well as the potential risk of sudden unexpected death associated with epilepsy. Recently, a new strategy of radiosurgery has emerged using synchrotron-generated X-ray microbeams: microbeam radiation therapy (MRT). The low divergence and high-flux of the synchrotron beams and the unique tolerance to MRT by healthy brain tissues, allows a precise targeting of specific brain regions with minimal invasiveness and limited behavioral or functional consequences in animals. Antiepileptic effects over several months have been recorded in animal models, and histological and synaptic tracing analysis suggest a reduction of neuronal connectivity as a mechanism of action. The possibility of transferring this approach to epileptic patients is discussed in this review

Retour d'expérience sur 10 années de réalisation d'essais d'érosion sur des sols provenant d'ouvrages hydrauliques

Le projet national ERINOH (ERosion INterne dans les Ouvrages Hydrauliques) a permis le développement en France de dispositifs destinés à tester en laboratoire et/ou in-situ la résistance à l’érosion des sols. Pour chaque typologie d’érosion, un dispositif spécifique a été développé : le HET (Hole Erosion Test) pour la caractérisation de la résistance à l’érosion de conduit [1][2]; le JET (Jet Erosion Test) adapté notamment pour l’estimation de la résistance à la surverse [3]; le CET (Contact Erosion Test) dédié à la résistance à l’érosion d’une interface entre deux couches de sols [4], ainsi que d’autres appareillages, pour la suffusion notamment. Ces essais se sont diffusés dans la profession et commencent à être régulièrement utilisés. geophyConsult commercialise des essais JET (depuis 2009), HET et CET ainsi que, ponctuellement, des essais de suffusion sur-mesure et de dispersivité. Durant ces 10 années, plus de 450 essais d’érosion ont ainsi été réalisés sur des sols constitutifs d’ouvrages hydrauliques, principalement français. Cette base de données a été confrontée avec les classifications reconnues internationalement et des décalages systématiques ont été constatés. La gamme de résistance obtenue a été illustrée par des applications numériques (temps de rupture, conditions d’initiation…). L’analyse de la qualité des essais réalisés en fonction du type de sol testé permet de définir des gammes de sol compatibles avec chacun des dispositifs. Un bilan est aussi tiré du retour d’expérience des opérateurs sur la réalisation de ces essais : sélection d’échantillons au sein des carottes, facilité de mise en œuvre, difficultés généralement rencontrées, complémentarité entre les dispositifs... Enfin, les évolutions des bancs d’essai durant cette période sont présentées, avec notamment le développement d’un Large JET pour s’affranchir des limites de l’essai JET original

Radionuclides concentrations in the Loire river system resulting from routine discharges of five nuclear power plants: assessment of dose to man

Low level radioactive liquid discharges have been carried out in the Loire river since 1963. Since then, the number of power plants located on the Loire river and its tributaries has been steadily increasing to reach, in the year 2000, 14 reactors operating on 5 different sites. The question arose to evaluate to what extent the addition of several nuclear power plants on the same river system could increase the concentrations in radionuclides in the environment and affect the dose to the public. To address this issue, EDF initiated in 1998 the “Loire river and estuary radioecology” program with the focus on assessing possible accumulation of radionuclide in river bottom sediments or on river shores. The following radionuclides were considered because of their importance in power plant liquid discharges: tritium, 14C, 58Co, 60Co, $^{110{\rm m}}$Ag, 134Cs, 137Cs, 54Mn, 124Sb, and 131I. Radionuclide concentrations in the dissolved, particulate and sedimentary forms were evaluated using the CRESCENDO model. The development and validation of this model required a multi-step process. The first step was to design a 350-km long 1D hydraulic and water transport based on currently available tools and data. Next, daily tritium concentrations measured in Angers, at the downstream limit of the river, were compared with computed values. The following step was to calibrate the sediment transport model. Areas where fine particles settled (dams and river shores) were monitored to improve our understanding of sediment dynamics. Then equations representing radionuclide exchange between water and particles were derived from laboratory experiments and included in the model. After each step the computed values were compared to measure data sets to ensure the model adequately described the processes involved. In the final step, the CALVADOS model was used to calculate dose to the public at different locations along the Loire river

An overview of current knowledge and challenges in predicting breach through dams and levees

Predicting breach erosion processes is essential for the effective risk management of both dams and levees. This has been recognised for decades, with efforts to develop breach prediction models dating back to the 1960s and 70s. Over the past decades, numerical methods and computing have advanced, but since breach processes depend upon a combination of hydraulics, soil mechanics and structure response, the challenge to accurately predict breach formation for all scenarios has yet to be met. Research into different aspects of breach, and in particular into the soil erosion processes of different soils in different states, is starting to show how different erosion behaviour can arise for different hydraulic load and soil conditions. This new knowledge and understanding then needs to feed through into predictive and probabilistic models that industry can use in analysing and determining flood risk from breach. This paper provides an overview of current knowledge and practice in predicting the different types and phases of breach showing how research efforts around the world are progressively piecing together the jigsaw puzzle of processes that affect and dictate how breach initiates, forms and grows through dams and levees. This includes reference to recent and ongoing work in the France, Spain, the UK, the Netherlands and the USA, and shows how these research efforts are feeding into models and solutions suitable for industry application