Adhesives: Liquid Fasteners for Modern Manufacturing

Adhesives are currently used in many industries worldwide, but are sometimes overlooked by engineers as a high-performance method of joining parts in an assembly. In fact, adhesives can often provide strong advantages over other methods of assembly such as riveting, bolting and even welding, in a variety of applications. An Engineer from ITW Performance Polymers, a regional manufacturer of high-performance structural adhesives, will discuss some typical adhesive chemistries, the mechanisms of adhesion, general comparisons with other assembly methods, and a few current market applications with industry leading brands of Plexus, Devcon, and Insulcast

3D Visualization of biofilms in porous media without using a contrast agent

International audienceIn this study, the challenge is to characterize biofilm growth in a natural aquifer, identified as a potential future location for storing biogas. More precisely, we want to evaluate the impact of biofilm growth on the porosity by means of high-resolution X-ray computed tomography without using artificial contrast agents as these substances could affect the phenomenon of interest

Local Complexity of Delone Sets and Crystallinity

This paper characterizes when a Delone set X is an ideal crystal in terms of restrictions on the number of its local patches of a given size or on the hetereogeneity of their distribution. Let N(T) count the number of translation-inequivalent patches of radius T in X and let M(T) be the minimum radius such that every closed ball of radius M(T) contains the center of a patch of every one of these kinds. We show that for each of these functions there is a `gap in the spectrum' of possible growth rates between being bounded and having linear growth, and that having linear growth is equivalent to X being an ideal crystal. Explicitly, for N(T), if R is the covering radius of X then either N(T) is bounded or N(T) >= T/2R for all T>0. The constant 1/2R in this bound is best possible in all dimensions. For M(T), either M(T) is bounded or M(T) >= T/3 for all T>0. Examples show that the constant 1/3 in this bound cannot be replaced by any number exceeding 1/2. We also show that every aperiodic Delone set X has M(T) >= c(n)T for all T>0, for a certain constant c(n) which depends on the dimension n of X and is greater than 1/3 when n > 1.Comment: 26 pages. Uses latexsym and amsfonts package

Etude du potentiel des écorces de tournesol et de maïs comme granulats végétaux dans la formulation de bétons légers

International audienceABSTRACT. Bio-aggregate based building materials offer promising perspectives thanks to their low environmental impact and interesting hygrothermal behaviour. As one of the high-potential agricultural resources, hemp has been extensively investigated for the last 15 years. This article aims to evaluate the potential of two other vegetal aggregates as a raw material to design bio-aggregate based concrete. Being locally available, the use of sunflower and maize bark particles could reduce transport and the associated carbon dioxide emissions. This study focuses on assessing the porous structure of bio-aggregates by X-ray tomography, their hygric sorption capacities (vapour and liquid water) as well as their chemical interactions with mineral binder and their effects on setting. The results underline the high transfer and storage capacities of these materials. Hence, the findings demonstrate that sunflower and maize bark particles are high-potential plant aggregates to design bio-aggregates based concrete.L'association de particules biosourcées à un liant minéral permet de formuler des bétons végétaux légers à faible impact environnemental et aux propriétés hygrothermiques intéressantes. Ces dernières années, les travaux de recherche se sont principalement focalisés sur l'utilisation du chanvre comme granulat végétal. L'étude présentée s'intéresse au potentiel d'autres agroressources disponibles localement afin de réduire le coût environnemental lié au transport des matières premières. Les travaux menés ont visé à caractériser l'arrangement granulaire des particules (granulométrie et densité), leur structure poreuse par tomographie à rayons X, leur comportement hydrique (vis-à-vis de l'eau liquide comme de la vapeur d'eau) et les interactions chimiques entre les hydrosolubles des agroressources et une matrice minérale. L'analyse de ces résultats met en évidence des capacités de transfert et de stockage de l'humidité élevée pour les particules de tournesol et de maïs. Les travaux menés révèlent les perspectives prometteuses des écorces de maïs et de tournesol comme granulats végétaux

Characterization Study of CO2, CH4, and CO2/CH4 Hydroquinone Clathrates Formed by Gas–Solid Reaction

Hydroquinone (HQ) is known to form organic clathrates with some gaseous species such as CO2 and CH4. This work presents spectroscopic data, surface and internal morphologies, gas storage capacities, guest release temperatures, and structural transition temperatures for HQ clathrates obtained from pure CO2, pure CH4, and an equimolar CO2/CH4 mixture. All analyses are performed on clathrates formed by direct gas–solid reaction after 1 month’s reaction at ambient temperature conditions and under a pressure of 3.0 MPa. A collection of spectroscopic data (Raman, FT-IR, and 13C NMR) is presented, and the results confirm total conversion of the native HQ (α-HQ) into HQ clathrates (β-HQ) at the end of the reaction. Optical microscopy and SEM analyses reveal morphology changes after the enclathration reaction, such as the presence of surface asperities. Gas porosimetry measurements show that HQ clathrates and native HQ are neither micro- nor mesoporous materials. However, as highlighted by TEM analyses and X-ray tomography, α- and β-HQ contain unsuspected macroscopic voids and channels, which create a macroporosity inside the crystals that decreases due to the enclathration reaction. TGA and in situ Raman spectroscopy give the guest release temperatures as well as the structural transition temperatures from β-HQ to α-HQ. The gas storage capacity of the clathrates is also quantified by means of different types of gravimetric analyses (mass balance and TGA). After having been formed under pressure, the characterized clathrates exhibit exceptional metastability: the gases remain in the clathrate structure at ambient conditions over time scales of more than 1 month. Consequently, HQ gas clathrates display very interesting properties for gas storage and sequestration applications

Amyloid precursor protein knockout mice show age-dependent deficits in passive avoidance learning.

Amyloid precursor protein (APP) is involved in the pathogenesis of Alzheimer's disease (AD), but its role in cognition has been relatively little studied. APP knockout (KO) animals have been described previously and show deficits in grip strength, reduced locomotor activity and impaired learning and memory in a conditioned avoidance test and the Morris water-maze. In order to further investigate the in vivo function of APP and its proteolytic derivatives, we tested APP KO mice and age-matched wild type controls at two different ages, 3 and 8 months, in a range of behavioural tests measuring neuromuscular, locomotor and cognitive functions. These tests included the acquisition of a passive avoidance response as a measure of long-term memory of an aversive experience, and spontaneous alternation in a Y-maze, regarded as a measure of spatial short-term memory. The absence of APP expression in APP KO mice was confirmed at the protein level using hippocampal tissue in Western blotting. APP KO mice displayed deficits in forelimb grip strength and locomotor activity in agreement with previous studies. In the Y-maze test used for spontaneous alternation behaviour, APP KO animals did not exhibit reduced alternation rates. On the other hand, in the passive avoidance test, APP KO mice showed an age-related deficit in retention of memory for an aversive experience. The results suggest that APP and/or its proteolytic derivatives may play a role in long-term memory in adult brain and/or may be required during the development and maintenance of neuronal networks involved in this type of memory

Etude du potentiel des écorces de tournesol et de maïs comme granulats végétaux dans la formulation de bétons légers

International audienceABSTRACT. Bio-aggregate based building materials offer promising perspectives thanks to their low environmental impact and interesting hygrothermal behaviour. As one of the high-potential agricultural resources, hemp has been extensively investigated for the last 15 years. This article aims to evaluate the potential of two other vegetal aggregates as a raw material to design bio-aggregate based concrete. Being locally available, the use of sunflower and maize bark particles could reduce transport and the associated carbon dioxide emissions. This study focuses on assessing the porous structure of bio-aggregates by X-ray tomography, their hygric sorption capacities (vapour and liquid water) as well as their chemical interactions with mineral binder and their effects on setting. The results underline the high transfer and storage capacities of these materials. Hence, the findings demonstrate that sunflower and maize bark particles are high-potential plant aggregates to design bio-aggregates based concrete.L'association de particules biosourcées à un liant minéral permet de formuler des bétons végétaux légers à faible impact environnemental et aux propriétés hygrothermiques intéressantes. Ces dernières années, les travaux de recherche se sont principalement focalisés sur l'utilisation du chanvre comme granulat végétal. L'étude présentée s'intéresse au potentiel d'autres agroressources disponibles localement afin de réduire le coût environnemental lié au transport des matières premières. Les travaux menés ont visé à caractériser l'arrangement granulaire des particules (granulométrie et densité), leur structure poreuse par tomographie à rayons X, leur comportement hydrique (vis-à-vis de l'eau liquide comme de la vapeur d'eau) et les interactions chimiques entre les hydrosolubles des agroressources et une matrice minérale. L'analyse de ces résultats met en évidence des capacités de transfert et de stockage de l'humidité élevée pour les particules de tournesol et de maïs. Les travaux menés révèlent les perspectives prometteuses des écorces de maïs et de tournesol comme granulats végétaux

Influence of types of binder and plant aggregates on hygrothermal and mechanical properties of vegetal concretes

International audienceBio-aggregate based building materials offer promising perspectives thanks to their low environmental impact and interesting hygrothermal behaviour. In this paper, different formulations of bio-aggregate concrete are proposed and analysed. We focus on two types of locally available bio-aggregates, namely maize and sunflower bark chips, and two types of binder matrices, based on respectively metakaolin and lime. The study specifically focuses on the pore structure of the composite material, as this quantity has a decisive impact on the insulating properties (thermal conductivity), the hygric behaviour (sorption isotherms, water vapour permeability and moisture buffer value) as well as on the mechanical performance (compressive strength). The results underline the impact of the constituents' porosity on the complex porous structure of the bio-concrete and the influence of porosity on its performance. The findings demonstrate that metakaolin and sunflower are high-potential raw materials for the design of a bio-aggregate based concrete

Installation d'une plate-forme d'imagerie à l'Université de Pau et des Pays de l'Adour

International audienceUne plate-forme Imagerie est en cours d'installation sur le site de l'Université de Pau et des Pays de l'Adour. Elle comprend deux tomographes à rayons X permettant des acquisitions en micro et nano tomographie. Cette plate-forme sera également équipée de périphériques permettant d'effectuer des acquisitions in situ (dans des cellules d'essai) sous pression et sous température avec circulation de fluides, ainsi que d'équipements informatiques pour le traitement et l'analyse des images obtenues (post-traitement, segmentation, quantification, etc.). Ces équipements permettront d'obtenir des images présentant une résolution comprise entre quelques dizaines de microns et environ 0,7 microns et ce dans des conditions statiques ou dynamiques (si les contraintes liées à l'échantillon l'autorisent). Outre les applications de caractérisation de géomatériaux, ces équipements ont pour objet de fournir des données expérimentales permettant en particulier de faire progresser la compréhension des écoulements complexes en milieux poreux, la caractérisation des microstructures et de leur évolution liées aux divers processus de vieillissement. Nous ferons ici une présentation de cette nouvelle plate-forme