Mesure de l'intensité et de la sélectivité du bronzage zooplanctonique diurne et nocturne sur le peuplement physoplanctonique de la retenue Al Massira (Maroc)

La retenue de barrage Al Massira (Maroc) constitue une pièce maîtresse dans le plan d'aménagement du bassin versant de l'Oum Er Rbia. Elle se situe dans la province de Settat, à 120 km au sud-est de Casablanca. La mesure de l'intensité du broutage zooplanctonique sur le peuplement phytoplanctonique a été réalisée à trois périodes différentes; le 20 mars 1992 d'une part et les 27 et 28 mai 1992 d'autre part, avec respectivement des mesures de jour et de nuit . Pour cela, une analyse de l'évolution des densités phytoplanctoniques au sein d'enceintes immergées in situ à 5 et 15 m pendant 8 heures, en absence (enceintes témoins) et en présence (enceintes expérimentales) de zooplancton, a été réalisée. Les résultats obtenus montrent que:- La technique adoptée est performante dans la mesure où les différences entre les densités algales entre les temps initial et final sont en général significatives dans les deux enceintes. - Conformément aux données de la littérature, le broutage apparaît bien comme sélectif; de nombreuses espèces n'apparaissant pas être consommées. - La sélection effectuée par le zooplancton est principalement basée sur la taille des cellules. Toutefois, à tailles égales, certaines espèces phytoplanctoniques semblent être consommées préférentiellement par les copépodes. - Seules les espèces algales présentant un développement important dans les enceintes témoins sont soumises à la prédation.The Al Massira reservoir, located in the district of Settat 120 km south-east of Casablanca, is of great importance notably at the level of the management of the Oum Er Rbia River-catchment basin.Several grazing experiments were performed to assess the intensity of phytoplankton predation by zooplankton species, on 20 March l992, 27 and 28 May 1992, respectively, over the day and the night. Two enclosures were used and incubated in situ at 5 and 15 m over 8 hours, The first enclosure consisted of a mixture of several phytoplankton and zooplankton species. The second was free of zooplancton.The results clearly demonstrated that the technique used in this work seemed to be effective in that a signifïcant difference between the initial and final numbers of phytoplankton species incubated in the enclosure was detected. In addition, we confirmed several literature reports relative to the selective characteristics of herbivore predation on algae: large phytoplankton (e.g., Peridinium cinctum, Ceratium hirundinellaand Staurastrum pingue) were not affected. The grazing pressure depended on the size of preys and on the exudates released by the physiofogically active small phytoplankton species (e.g., Oocystis crassa, Cyclotella sp.) evolving in the enclosures. Among small preys, only species with high growth rate (estimed in the control flask, e.g., Cosmarium sp. and Tetraedron sp.) were subjected to the zooplankton predation. The copepod nightgrazing was lower than that recorder during the day, probably due to a decrease in their ability to detect preys in the dark.Our result contradict several results obtained by the method of NANEY (1971) according to which grazing increases during the night.Two assumptions may be proposed to explain such a discrepancy:- The zooplankton community of the Al Massira Reservoir was quantitatively dominated by the Calanoid Neolovenula alluaudi.Yet, according to HANEY and HALL (1975), these Copepods showed a slight diel grazing change compared to that of Cladocera. It seemed likely that these temporal variabilities were not statistically significant but rather inherent to the overall internal fluctuation oftlte cell metabolism.- The HANEY (1971) method allows estimation of the water volume per unit time, which transits along the digestive tract of zooplankters. Nevertheless, this technique was mostly performed in markedly stratified natural lakes. From a strictly physiological point of view, and as demonstrated by MC LAREN (1963), organisms which evolved in deep layers (low temperature) became metabolically more active when they reached superficial layers (increased temperature). Clearly, this increase in the cell metabolism abilities is translated into a higher volume of water passing through the digestive tract but not necessarily into an increase in ingested phytoplankton preys. Our results went along with the aforementioned interpretation since we clearly demonstrated an optimal Copepoda-grazing selectivity. However, the selection of preys would not imply a direct relationship between the ingested volume of water and energetic inputs

MAT-717: MECHANICAL PERFORMANCE OF HYBRID FIBRE-REINFORCED ENGINEERED CEMENTITIOUS COMPOSITE INCORPORATING NITISMA SHORT FIBRES

A new high-strength, high-tensile ductility hybrid fibre-reinforced engineered cementitious composite (HECCSMAF) incorporating randomly dispersed nickel-titanium shape memory alloy short fibres (NiTi-SMA) has been pioneered in this study. The mechanical properties of the HECC-SMAF produced with a combination of 2% polyvinyl-alcohol (PVA) and 0.5%, 1%, and 1.5% NiTi-SMA fibres by volume fraction have been explored. The experimental results indicate that utilizing a combination of those fibres can enhance the tensile capacity of ECC by up to 39% with a slight to no increase in compressive strength. An overall reduction in workability was observed compared to that of ECC made with only 2% PVA by volume fraction, which is typical of metallic fibre-reinforced cementitious systems. Among the tested ECC mixtures, HECC-SMAF made with 2% PVA and 1% NiTi-SMA presents the best mechanical performance

Exploring Spoken Named Entity Recognition: A Cross-Lingual Perspective

Recent advancements in Named Entity Recognition (NER) have significantly improved the identification of entities in textual data. However, spoken NER, a specialized field of spoken document retrieval, lags behind due to its limited research and scarce datasets. Moreover, cross-lingual transfer learning in spoken NER has remained unexplored. This paper utilizes transfer learning across Dutch, English, and German using pipeline and End-to-End (E2E) schemes. We employ Wav2Vec2-XLS-R models on custom pseudo-annotated datasets and investigate several architectures for the adaptability of cross-lingual systems. Our results demonstrate that End-to-End spoken NER outperforms pipeline-based alternatives over our limited annotations. Notably, transfer learning from German to Dutch surpasses the Dutch E2E system by 7% and the Dutch pipeline system by 4%. This study not only underscores the feasibility of transfer learning in spoken NER but also sets promising outcomes for future evaluations, hinting at the need for comprehensive data collection to augment the results

MAT-715: SUSTAINABLE HIGH-VOLUME FLY ASH GROUTS FOR TWO-STAGE CONCRETE

Two-stage concrete (TSC) is a special type of concrete in which coarse aggregates are pre-placed in the formwork and subsequently injected with a grout. Beneficiating fly ash in TSC grouts increases TSC sustainability through the ecological use of large quantities of fly ash, reduced carbon-dioxide emissions associated with cement production, and enhancement of resource productivity of the concrete industry. Limited research has explored the effects of using high volume of fly ash as partial replacement for cement in TSC grout mixtures. Therefore, the flowability of grout mixtures incorporating various fly ash addition rates (i.e. 0%, 30%, 50% and 70%) was evaluated using the flow cone method and spread flow test. Correlations between the efflux time and spread flow for the grout mixtures were developed. Results show that increasing the fly ash addition reduced the grouts efflux time while increasing its spread flow. The optimum high-volume fly ash dosage for achieving high flowability and acceptable TSC compressive strength was identified

Perceptual Quality Assessment Based on Visual Attention Analysis

Most existing quality metrics do not take the human attention analysis into account. Attention to particular objects or regions is an important attribute of human vision and perception system in measuring perceived image and video qualities. This paper presents an approach for extracting visual attention regions based on a combination of a bottom-up saliency model and semantic image analysis. The use of PSNR (Peak Signal-to-Noise Ratio) and SSIM (Structural SIMilarity) in extracted attention regions is analyzed for image/video quality assessment, and a novel quality metric is proposed which can exploit the attributes of visual attention information adequately. The experimental results with respect to the subjective measurement demonstrate that the proposed metric outperforms the current methods

MAT-741: IMPACT BEHAVIOUR OF SHAPE MEMORY ALLOY HYBRID FIBRE-REINFORCED ENGINEERED CEMENTITIOUS COMPOSITE

An experimental study was conducted to evaluate the impact behaviour of an innovative hybrid-fibre engineered cementitious composite (ECC) incorporating randomly dispersed short shape memory alloy fibres (SMA). A modified drop weight test was conducted on specimens from various ECC mixtures with and without SMA fibres. The impact behaviour was evaluated and compared based on the ability to dissipate energy and sustain impact load without damage. Results show that the addition of SMA to ECC mixtures significantly enhanced their performance under impact loading. The amount of dissipated energy by ECC increased by about 51% as a result of SMA fibre addition. This highlights the potential benefits of incorporating SMA in composite materials exposed to impact loads, paving the way for a wider implementation in the field of fortified structures

MAT-716: GREEN SIDEWALKS USING SUSTAINABLE TWO-STAGE CONCRETE

Two-stage concrete (TSC) is a special type of concrete, which has a high potential for use in sidewalk construction owing to its high volume stability. TSC is characterized by its high coarse aggregate content. Hence, using recycled solid waste materials as a coarse aggregate will increase TSC sustainability, while providing a cost-effective alternative to natural aggregates. Aggregates are pre-placed in TSC. Hence, water absorption by recycled concrete aggregates and the associated rheology problems do not exist in TSC. This study explores the performance of green TSC sidewalks incorporating recycled concrete aggregates (RCA) and crumb rubber from scrap tires. Mechanical properties of the proposed green TSC including compressive strength, modulus of elasticity, flexural strength and toughness, as well as durability to freeze-thaw cycles were investigated. Results show a slight reduction in TSC mechanical properties due to the use of RCA. Moreover, incorporating tire particles reduced TSC mechanical properties significantly, while improving its toughness and freeze-thaw resistance. Addition of recycled tire steel wires allowed to overcome the negative effects on the mechanical properties induced by crumb tire rubber. Therefore, recycling solid waste materials in TSC sidewalks can be an effective strategy to beneficiate such waste materials

Anthropogenic radionuclides in the water column and a sediment core from the Alboran Sea: application to radiometric dating and reconstruction of historical water column radionuclide concentrations

Global fallout is the main source of anthropogenic radionuclides in the Mediterranean Sea. This work presents 137Cs, 239+240Pu and 241Am concentrations in the water column in the southwest Alboran Sea, which was sampled in December 1999. A sediment core was taken at 800 m depth in the area (35°47′ N, 04°48′ W). 210Pb, 226Ra, 137Cs and 239+240Pu specific activities were measured at multiple depths in the core for dating purposes. 137Cs and 239+240Pu profiles did not show defined peaks that could be used as time markers, and they extended up to depths for which the 210Pb-based constant rate of supply (CRS) dating model provided inconsistent dates. These profiles can be useful to test dating models, understood as particular solutions of a general advection–diffusion problem, if the time series of radionuclide inputs into the sediment is provided. Thus, historical records of depth-averaged 137Cs and 239+240Pu concentrations in water, and their corresponding fluxes into the sediment, were reconstructed. A simple water-column model was used for this purpose, involving atmospheric fallout, measured distribution coefficient (k d) values, and a first-estimate of sedimentation rates. A dating model of constant mixing with constant sedimentation rate was applied successfully to three independent records (unsupported 210Pb, 137Cs and 239+240Pu), and provided the objective determination of mixing parameters and mass sedimentation rate. These results provide some insight into the fate of atmospheric inputs to this marine environment and, particularly, into the contribution from the Chernobyl accident.International Atomic Energy Agency Research Project RAF/7/00