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

Internal erosion breach model review and validation

Predicting breach erosion processes is essential for the effective risk management of both dams and levees. Following the success of an earlier initiative to assess the performance of breach models for predicting overflow erosion of dams and levees (i.e. the CEATI Dam Safety Interest Group Breach Modelling Project), a new project has been launched to investigate the performance of industry models predicting breach formation initiated through internal erosion. The project was initiated by Electricité de France (EDF) and started mid-2019, with a planned duration of ~2 ½ years. The approach being taken is to: review existing IE models with the most promising few (with potential for industry application) selected for closer analysis; review available laboratory, field and case study data in order to identify a number of data sets that can be used for model performance assessment and validation; invite international organisations to participate in programme of model review, testing and validation; implement a programme of both ‘blind’ and ‘aware’ model testing, with results shared and assessed transparently by the international team; review and conclude as to the capabilities and potential of existing internal erosion models. The overall conclusions from this work will be guidance for industry practitioners regarding the types, availability and likely performance of industry applicable internal erosion breach prediction models. This paper will present details of the programme in April 2020, almost one year into the 2 ½ year overall programme. At this stage, the initial model and data reviews will have been completed, the working group established and the first phase (of three) of modelling and performance review underway

Overflowing erosion modelling of embankment and concrete dams: state of the art and research needs

Overflowing erosion of embankment dams and levees and overflowing erosion of bedrock downstream of concrete dams (through crest overflowing or spillway flow impact) are of major concern for dam and levee owners. Despite extensive research efforts performed in North America and Europe since the late 1990s, many gaps in knowledge still need to be answered in order to provide engineers with validated numerical tools able to predict the erosion mechanisms to an acceptable level of certainty. As addressing these gaps in knowledge will likely require a substantial and expensive research effort, international research collaboration in this field seems the most efficient way to reach these objectives. In order to structure and launch such international collaboration, an international workshop was organized in Aussois, France, from 11th to 14th December 2017, on behalf of the European Group of ICOLD and the French Committee on Dams and Reservoirs. This paper presents the outcomes of this workshop and includes a presentation of the state of the art in overflowing erosion of embankment dams and levees, overflowing erosion of bedrock downstream of concrete dams, the main knowledge gaps which need to be addressed and the outlines of a future international research project to solve these issues

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

International audienceMapping of sediment thickness and the total volume of sediment deposited in the reservoirs are essential data to deal with both quantitative and qualitative problems caused by siltation. When the topography of the initial ground level of the reservoir is unknown, it is necessary to use specific measurement technologies to value sediment thickness and total volume of sediment. EDF has carried out a research project which aim was to evaluate the most promising technologies in that field in the present state of the art. In the frame of this project, a chirp sonar has been evaluated. A methodology to produce and validate the results has been defined. An experimental study of sound celerity in sediments and attenuation sensitivity has been carried out. A first evaluation of the capability of this sonar to determine sediment thickness maps was carried out in Cadarache desilting basin which permitted to have a first view of the limitations of this technology.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

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)