Wear-quantification of textured geomembranes using digital imaging analysis

During the past decades there has been an increase in the use of geosynthetics in construction due to their versatility in providing a wide array of functions such as reinforcement, containment, separation, filtration and drainage. Often, geosynthetics are used in conjunction with other geosynthetics to accomplish these functions. However, geosynthetics create possible planes of weakness which can lead to failures. Textured geomembranes are widely used within landfill and mining industries due to their containment and shear strength properties, however, there are subjected to a wide array of loads and environments which are potentially hazardous, as such is of utmost importance to retain their integrity in order to avoid ecological disasters. The challenge is to understand how geomembranes resist damage, wear and which of these factors control the development of wear on textured geomembranes. Digital imaging techniques have been used in order to develop a protocol that describes the quantification of wear on textured structured geomembranes. Direct shear tests were performed to induce wear on the geomembrane textures (asperities) to analyse the wear mechanisms and study the factors that induce wear on the asperities. The research showed that normal stress and shear displacement have a major role in the development of wear on interfaces. However, the geometrical characteristics of the geomembrane asperities control the amount of wear the geomembrane can sustain without significant shear strength loss. These outcomes help to better understand the behaviour of interfaces which have as component geomembranes, leading to more robust designs. This study also proposed new asperity texture shapes by using Rapid Prototyping (RP) techniques, such as Selective Laser Sintering and Fused Filament Fabrication. Using RP techniques to create new textures for the geomembrane, could allow the creation of textures which have increased shear strength thresholds and better withstand wear, allowing for more advanced and economical designs

On the Distribution of Small Powers of a Primitive Root

AbstractLet Ng={gn:1⩽n⩽N}, where g is a primitive root modulo an odd prime p, and let fg(m, H) denote the number of elements of Ng that lie in the interval (m, m+H], where 1⩽m⩽p. H. Montgomery calculated the asymptotic size of the second moment of fg(m, H) about its mean for a certain range of the parameters N and H and asked to what extent this range could be increased if one were to average over all the primitive roots (modp). We address this question as well as the related one of averaging over the prime p

Tin dioxide sol-gel derived thin films deposited on porous silicon

Undoped and Sb-doped SnO2 sol¿gel derived thin films have been prepared for the first time from tin (IV) ethoxide precursor and SbCl3 in order to be utilised for gas sensing applications where porous silicon is used as a substrate. Transparent, crack-free and adherent layers were obtained on different types of substrates (Si, SiO2/Si). The evolution of the Sn¿O chemical bonds in the SnO2 during film consolidation treatments was monitored by infrared spectroscopy. By energy dispersive X-ray spectroscopy performed on the cross section of the porosified silicon coupled with transmission electron microscopy, the penetration of the SnO2 sol¿gel derived films in the nanometric pores of the porous silicon has been experimentally proved

A coupled microscopy approach to assess the nano-landscape of weathering

Mineral weathering is a balanced interplay among physical, chemical, and biological processes. Fundamental knowledge gaps exist in characterizing the biogeochemical mechanisms that transform microbe-mineral interfaces at submicron scales, particularly in complex field systems. Our objective was to develop methods targeting the nanoscale by using high-resolution microscopy to assess biological and geochemical drivers of weathering in natural settings. Basalt, granite, and quartz (53-250 mu m) were deployed in surface soils (10 cm) of three ecosystems (semiarid, subhumid, humid) for one year. We successfully developed a reference grid method to analyze individual grains using: (1) helium ion microscopy to capture micron to sub-nanometer imagery of mineral-organic interactions; and (2) scanning electron microscopy to quantify elemental distribution on the same surfaces via element mapping and point analyses. We detected locations of biomechanical weathering, secondary mineral precipitation, biofilm formation, and grain coatings across the three contrasting climates. To our knowledge, this is the first time these coupled microscopy techniques were applied in the earth and ecosystem sciences to assess microbe-mineral interfaces and in situ biological contributors to incipient weathering.Oregon State University faculty startup fund; Office of Biological and Environmental Research; NSF [EAR-GEO-1331846, EAR-0724958, IOS-1354219]; [EAR-1023215]Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Ecosystem-bedrock interaction changes nutrient compartmentalization during early oxidative weathering

Ecosystem-bedrock interactions power the biogeochemical cycles of Earth's shallow crust, supporting life, stimulating substrate transformation, and spurring evolutionary innovation. While oxidative processes have dominated half of terrestrial history, the relative contribution of the biosphere and its chemical fingerprints on Earth's developing regolith are still poorly constrained. Here, we report results from a two-year incipient weathering experiment. We found that the mass release and compartmentalization of major elements during weathering of granite, rhyolite, schist and basalt was rock-specific and regulated by ecosystem components. A tight interplay between physiological needs of different biota, mineral dissolution rates, and substrate nutrient availability resulted in intricate elemental distribution patterns. Biota accelerated CO2 mineralization over abiotic controls as ecosystem complexity increased, and significantly modified stoichiometry of mobilized elements. Microbial and fungal components inhibited element leaching (23.4% and 7%), while plants increased leaching and biomass retention by 63.4%. All biota left comparable biosignatures in the dissolved weathering products. Nevertheless, the magnitude and allocation of weathered fractions under abiotic and biotic treatments provide quantitative evidence for the role of major biosphere components in the evolution of upper continental crust, presenting critical information for large-scale biogeochemical models and for the search for stable in situ biosignatures beyond Earth.Comment: 41 pages (MS, SI and Data), 16 figures (MS and SI), 6 tables (SI and Data). Journal article manuscrip