The role that plastic-frictional energy dissipation in the fracture process zone plays in the workof-fracture method for measuring the fracture energy of concrete or other quasibrittle materials is analyzed, and a possible improvement of this method is proposed. It is shown that by measuring the unloading compliance at a sufficient number of states on the post-peak descending load-deflection cu...

In this paper Cohesive Zone Model (CZM) concepts are applied in order to study mode I fracture in a pre-cracked bonded Double Cantilever Beam (DCB) specimen. A cohesive surface element is implemented in a Finite Element commercial code using intrinsic cohesive zone models: exponential, bilinear and trapezoidal traction-separation laws. The sensitivity of cohesive zone parameters in predicting t...

The complexity and dynamics of microbial metagenomes may be evaluated by genome size, gene duplication and the disruption rate between lineages. In this study, we pyrosequenced the metagenomes of microbes obtained from the brine and sediment of a deep-sea brine pool in the Red Sea to explore the possible genomic adaptations of the microbes in response to environmental changes. The microbes from...

BACKGROUND Nitrilases, which hydrolyze nitriles in a one-step reaction into carboxylic acids and ammonia, gained increasing attention because of the abundance of nitrile compounds in nature and their use in fine chemicals and pharmaceutics. Extreme environments are potential habitats for the isolation and characterization of extremozymes including nitrilases with unique resistant properties. Th...

Results from a combined experimental and numerical investigation into the effects of rate on mode-II fracture of a plastically-deforming, adhesively-bonded joint are presented. It is shown that a cohesive-zone model has to be modified to include coupling between normal and shear modes of deformation when there is extensive shear deformation of the adhesive layer. A suitable cohesive-zone modeli...

A wide array of field observations, in situ testing, and rock and water sampling (and subsequent analyses) within the unsaturated zone (UZ) of Yucca Mountain demonstrate the importance of fractures to flow and transport in the welded tuffs. The abundance of fractures and the spatial variability in their hydraulic properties, along with the heterogeneity within lithologic formations, make evalua...

Acetate plays a key role as electron donor and acceptor and serves as carbon source in oligotrophic deep subsurface environments. It can be produced from inorganic carbon by acetogenic microbes or through breakdown of more complex organic matter. Acetate is an important molecule for sulfate reducers that are substantially present in several deep bedrock environments. Aceticlastic methanogens us...

Exploration and development of the Nordegg in West Central Alberta is challenging because this prolific zone is deep, structured, and has low permeability. The reservoir is quite thick and is charged with gas. We know from core, samples, well log, and drilling data that the Nordegg zone is fractured to some degree. We expect this fracturing will affect the behavior of the Nordegg to our operati...

The seafloor is a unique environment, which allows insights into how geochemical processes affect the diversity of biological life. Among its diverse ecosystems are deep-sea brine pools - water bodies characterized by a unique combination of extreme conditions. The 'polyextremophiles' that constitute the microbial assemblage of these deep hot brines have not been comprehensively studied. We rep...