Use of High Strength Steel for Hydrogen Containment

The research involves experiments on model lab heats of an ultra-high-strength steel (high C, low Ni ) and a high-toughness, high-strength steel (high Ni, low C) to determine the limits of toughness as a function of yield strength, grain-boundary purity, and hydrogen fugacity. In addition, the existence and mechanism of brittle intergranular cracking in ideally pure steels is being investigated

IODP Expedition 334: An Investigation of the Sedimentary Record, Fluid Flow and State of Stress on Top of the Seismogenic Zone of an Erosive Subduction Margin

The Costa Rica Seismogenesis Project (CRISP) is an experiment to understand the processes that control nucleation and seismic rupture of large earthquakes at erosional subduction zones. Integrated Ocean Drililng Program (IODP) Expedition 334 by R/V JOIDES Resolution is the first step toward deep drilling through the aseismic and seismic plate boundary at the Costa Rica subduction zone offshore the Osa Peninsula where the Cocos Ridge is subducting beneath the Caribbean plate. Drilling operations included logging while drilling (LWD) at two slope sites (Sites U1378 and U1379) and coring at three slope sites (Sites U1378–1380) and at one site on the Cocos plate (Site U1381). For the first time the lithology, stratigraphy, and age of the slope and incoming sediments as well as the petrology of the subducting Cocos Ridge have been characterized at this margin. The slope sites recorded a high sediment accumulation rate of 160–1035m m.y.-1 possibly caused by on-land uplift triggered by the subduction of the Cocos Ridge. The geochemical data as well as the in situ temperature data obtained at the slope sites suggest that fluids are transported from greater depths. The geochemical profiles at Site U1381 reflect diffusional communication of a fluid with seawater-like chemistry and the igneous basement of the Cocos plate (Solomon et al., 2011; Vannucchi et al., 2012a). The present-day in situ stress orientation determined by borehole breakouts at Site U1378 in the middle slope and Site U1379 in the upper slope shows a marked change in stress state within ~12 km along the CRISP transect; that may correspond to a change from compression (middle slope) to extension (upper slope)

Assignment of PolyProline II Conformation and Analysis of Sequence – Structure Relationship

International audienceBACKGROUND: Secondary structures are elements of great importance in structural biology, biochemistry and bioinformatics. They are broadly composed of two repetitive structures namely α-helices and β-sheets, apart from turns, and the rest is associated to coil. These repetitive secondary structures have specific and conserved biophysical and geometric properties. PolyProline II (PPII) helix is yet another interesting repetitive structure which is less frequent and not usually associated with stabilizing interactions. Recent studies have shown that PPII frequency is higher than expected, and they could have an important role in protein - protein interactions. METHODOLOGY/PRINCIPAL FINDINGS: A major factor that limits the study of PPII is that its assignment cannot be carried out with the most commonly used secondary structure assignment methods (SSAMs). The purpose of this work is to propose a PPII assignment methodology that can be defined in the frame of DSSP secondary structure assignment. Considering the ambiguity in PPII assignments by different methods, a consensus assignment strategy was utilized. To define the most consensual rule of PPII assignment, three SSAMs that can assign PPII, were compared and analyzed. The assignment rule was defined to have a maximum coverage of all assignments made by these SSAMs. Not many constraints were added to the assignment and only PPII helices of at least 2 residues length are defined. CONCLUSIONS/SIGNIFICANCE: The simple rules designed in this study for characterizing PPII conformation, lead to the assignment of 5% of all amino as PPII. Sequence - structure relationships associated with PPII, defined by the different SSAMs, underline few striking differences. A specific study of amino acid preferences in their N and C-cap regions was carried out as their solvent accessibility and contact patterns. Thus the assignment of PPII can be coupled with DSSP and thus opens a simple way for further analysis in this field

IODP expedition 334: An investigation of the sedimentary record, fluid flow and state of stress on top of the seismogenic zone of an erosive subduction margin

金沢大学理工研究域地球社会基盤学

Stacking faults with 180° layer rotation in celadonite, an fe- and mg-rich dioctahedral mica

Stacking disorder in celadonite, a dioctahedral mica with Fe and Mg as major octahedral cations and which generally adopts the 1M stacking sequence, was investigated mainly by using transmission electron microscopy (TEM). The selected-area electron diffraction patterns with 0kl reflections along the [100] beam direction correspond to the 1M stacking but those along the [110], [11-0], [010], [310], and [31-0] directions are frequently streaked along the [001]* direction or contain extra spots from twinned domains. Three-dimensional stacking analyses using sets of two high-resolution TEM images along different directions of the same area of one crystal indicate that all stacking faults involve only 180° layer rotations. These stacking faults produce greater peaks of 0kl reflections than expected in powder X-ray diffraction (XRD) patterns. Simulation of the XRD patterns indicated that 180° layer rotations occur at >10% of total interlayer regions in one celadonite specimen. The interlayer region of celadonite is characterized by a near-zero ditrigonal rotation angle, a small surface corrugation of the basal oxygen plane, and a small amount of Al substitution in the tetrahedral sheets. These features suggest that there is no preference for any of the six stacking angles around the interlayer region. The abundance of 180° layer rotation rather than G60° and G120° in the present specimens may be related to their ribbon-like morphologies elongated along the a axis

Polytype and morphological analyses of Gümbelite a fibrous Mg-rich illite

Polytypism in gümbelite and its relationship to the fibrous or ribbon-like morphology exhibited by this Mg-rich illite were investigated by powder X-ray diffraction (XRD), electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). Comparison between the XRD pattern from oriented fibers using a conventional powder diffractometer and a randomly oriented pattern using a Gandolfi camera suggested that 2M is dominant but other polytypes belonging to subfamily A also exist, and that the fiber axis of gümbelite is parallel to in 2M, in 2M, and in 1M. The EBSD analyses confirmed these crystallographic directions directly from individual crystals. Electron diffraction and high-resolution TEM showed that twinning and intergrowths of various polytypes including both subfamilies are common in a single crystal and that the two types of rotations [2n60° and (2n+1)60°] between adjacent layers are often randomly mixed at the monolayer level. The data suggest that high densities of twinning and intergrowths account for the origin of the fibrous morphology along for 2M and 2M polytypes. Volume restriction in a confined vein space may also play a role

Opal-CT in chert beneath the toe of the Tohoku margin and its influence on the seismic aseismic transition in subduction zones

Thick accumulation of chert is a ubiquitous feature of old oceanic plates at convergent margins. In this study, we investigate chert fragments recovered by the Integrated Ocean Drilling Program expedition 343 at the Japan Trench where the 2011 Tohoku-Oki earthquake (M-w 9.0) occurred. This sample provides a unique opportunity to investigate in situ chert diagenesis at an active subduction margin and its influence on the kinematics of megathrust faulting. Our mineralogical analyses revealed that the chert is characterized by hydrous opal-CT and may therefore be highly deformable via pressure solution creep and readily accommodate shear strain between the converging plates at driving stresses of kilopascal order. As chert diagenesis advances, any further deformation requires stresses of >100MPa, given the increasing transport distances for solutes as represented in cherts on land. The chert diagenesis is thus related to the mechanical transition from a weakly to strongly coupled plate interface at this margin