Science.gov

Sample records for rock mechanics activities

  1. Rock mechanics. Second edition

    SciTech Connect

    Jumikis, A.R.

    1983-01-01

    Rock Mechanics, 2nd Edition deals with rock as an engineering construction material-a material with which, upon which, and within which civil engineers build structures. It thus pertains to hydraulic structures engineering; to highway, railway, canal, foundation, and tunnel engineering; and to all kinds of rock earthworks and to substructures in rock. Major changes in this new edition include: rock classification, rock types and description, rock testing equipment, rock properties, stability effects of discontinuity and gouge, grouting, gunite and shotcrete, and Lugeon's water test. This new edition also covers rock bolting and prestressing, pressure-grouted soil anchors, and rock slope stabilization.

  2. Rock and soil mechanics

    SciTech Connect

    Derski, W.; Izbicki, R.; Kisiel, I.; Mroz, Z.

    1988-01-01

    Although theoretical in character, this book provides a useful source of information for those dealing with practical problems relating to rock and soil mechanics - a discipline which, in the view of the authors, attempts to apply the theory of continuum to the mechanical investigation of rock and soil media. The book is in two separate parts. The first part, embodying the first three chapters, is devoted to a description of the media of interest. Chapter 1 introduces the main argument and discusses the essence of the discipline and its links with other branches of science which are concerned, on the one hand, with technical mechanics and, on the other, with the properties, origins, and formation of rock and soil strata under natural field conditions. Chapter 2 describes mechanical models of bodies useful for the purpose of the discourse and defines the concept of the limit shear resistance of soils and rocks. Chapter 3 gives the actual properties of soils and rocks determined from experiments in laboratories and in situ. Several tests used in geotechnical engineering are described and interconnections between the physical state of rocks and soils and their rheological parameters are considered.

  3. Ultra-fine grinding and mechanical activation of mine waste rock using a high-speed stirred mill for mineral carbonation

    NASA Astrophysics Data System (ADS)

    Li, Jia-jie; Hitch, Michael

    2015-10-01

    CO2 sequestration by mineral carbonation can permanently store CO2 and mitigate climate change. However, the cost and reaction rate of mineral carbonation must be balanced to be viable for industrial applications. In this study, it was attempted to reduce the carbonation costs by using mine waste rock as a feed stock and to enhance the reaction rate using wet mechanical activation as a pre-treatment method. Slurry rheological properties, particle size distribution, specific surface area, crystallinity, and CO2 sequestration reaction efficiency of the initial and mechanically activated mine waste rock and olivine were characterized. The results show that serpentine acts as a catalyst, increasing the slurry yield stress, assisting new surface formation, and hindering the size reduction and structure amorphization. Mechanically activated mine waste rock exhibits a higher carbonation conversion than olivine with equal specific milling energy input. The use of a high-speed stirred mill may render the mineral carbonation suitable for mining industrial practice.

  4. Rock breakage mechanisms with a PDC cutter

    SciTech Connect

    Not Available

    1985-01-01

    Some aspects of chip generation by a polycrystalline diamond compact (PDC) cutter moving through a rock can be understood by examining the shapes of the chips and the fracture patterns in the remaining rock. Data from laboratory experiments have led to general conclusions about the uniformity of chip generation mechanisms in different kinds of rock and about crack nucleation position relative to the cutter tip. 20 refs., 12 figs., 2 tabs.

  5. Rock mechanics contributions from defense programs

    SciTech Connect

    Heuze, F.E.

    1992-02-01

    An attempt is made at illustrating the many contributions to rock mechanics from US defense programs, over the past 30-plus years. Large advances have been achieved in the technology-base area covering instrumentation, material properties, physical modeling, constitutive relations and numerical simulations. In the applications field, much progress has been made in understanding and being able to predict rock mass behavior related to underground explosions, cratering, projectile penetration, and defense nuclear waste storage. All these activities stand on their own merit as benefits to national security. But their impact is even broader, because they have found widespread applications in the non-defense sector; to name a few: the prediction of the response of underground structures to major earthquakes, the physics of the earth`s interior at great depths, instrumentation for monitoring mine blasting, thermo-mechanical instrumentation useful for civilian nuclear waste repositories, dynamic properties of earthquake faults, and transient large-strain numerical modeling of geological processes, such as diapirism. There is not pretense that this summary is exhaustive. It is meant to highlight success stories representative of DOE and DOD geotechnical activities, and to point to remaining challenges.

  6. Mechanisms of large rock avalanche propagation

    NASA Astrophysics Data System (ADS)

    Bowman, Elisabeth

    2014-05-01

    Large rock avalanches present a serious mountain hazard to lifelines, infrastructure and lives. They are one of a class of low frequency, high impact events for which there is a still considerable debate over the transport mechanism. The behaviour of large rock avalanches, sometimes referred to as sturzstrom or "stream flow" after Heim, is characterised by a volumetric dependence, so that very large rock avalanches tend to travel with a greater spreading "efficiency" than smaller ones. In this work we propose a mechanism for the volumetric dependence of rock avalanche spread (or runout) in light of the ubiquitous dynamic fragmentation behaviour of brittle solids, Terzaghi's principle of effective stress as used most commonly in soil mechanics, and concepts of momentum transfer. The proposed conceptual model is based on both observations of field scale events, such as made at Elm in Switzerland, Huascaran in Peru and Falling Mountain in New Zealand, and small scale physical model experiments using analogue rock materials which have been conducted at elevated g-level so as to increase stress levels within the experiments. In particular the model aims to explain how momentum transfer between elements within a fragmenting rock avalanche mass may lead to the greater mobility or spreading efficiency that is observed at large scale and may provide insight as to the conditions needed for rock avalanche propagation and arrest.

  7. Surface Morphology of Active Normal Faults in Hard Rock: Implications for the Mechanics of the Asal Rift, Djibouti

    NASA Astrophysics Data System (ADS)

    Pinzuti, P.; Mignan, A.; King, G. C.

    2009-12-01

    Mechanical stretching models have been previously proposed to explain the process of continental break-up through the example of the Asal Rift, Djibouti, one of the few places where the early stages of seafloor spreading can be observed. In these models, deformation is distributed starting at the base of a shallow seismogenic zone, in which sub-vertical normal faults are responsible for subsidence whereas cracks accommodate extension. Alternative models suggest that extension results from localized magma injection, with normal faults accommodating extension and subsidence above the maximum reach of the magma column. In these magmatic intrusion models, normal faults have dips of 45-55° and root into dikes. Using mechanical and kinematics concepts and vertical profiles of normal fault scarps from an Asal Rift campaign, where normal faults are sub-vertical on surface level, we discuss the creation and evolution of normal faults in massive fractured rocks (basalt). We suggest that the observed fault scarps correspond to sub-vertical en echelon structures and that at greater depth, these scarps combine and give birth to dipping normal faults. Finally, the geometry of faulting between the Fieale volcano and Lake Asal in the Asal Rift can be simply related to the depth of diking, which in turn can be related to magma supply. This new view supports the magmatic intrusion model of early stages of continental breaking.

  8. Surface morphology of active normal faults in hard rock: Implications for the mechanics of the Asal Rift, Djibouti

    NASA Astrophysics Data System (ADS)

    Pinzuti, Paul; Mignan, Arnaud; King, Geoffrey C. P.

    2010-10-01

    Tectonic-stretching models have been previously proposed to explain the process of continental break-up through the example of the Asal Rift, Djibouti, one of the few places where the early stages of seafloor spreading can be observed. In these models, deformation is distributed starting at the base of a shallow seismogenic zone, in which sub-vertical normal faults are responsible for subsidence whereas cracks accommodate extension. Alternative models suggest that extension results from localised magma intrusion, with normal faults accommodating extension and subsidence only above the maximum reach of the magma column. In these magmatic rifting models, or so-called magmatic intrusion models, normal faults have dips of 45-55° and root into dikes. Vertical profiles of normal fault scarps from levelling campaign in the Asal Rift, where normal faults seem sub-vertical at surface level, have been analysed to discuss the creation and evolution of normal faults in massive fractured rocks (basalt lava flows), using mechanical and kinematics concepts. We show that the studied normal fault planes actually have an average dip ranging between 45° and 65° and are characterised by an irregular stepped form. We suggest that these normal fault scarps correspond to sub-vertical en echelon structures, and that, at greater depth, these scarps combine and give birth to dipping normal faults. The results of our analysis are compatible with the magmatic intrusion models instead of tectonic-stretching models. The geometry of faulting between the Fieale volcano and Lake Asal in the Asal Rift can be simply related to the depth of diking, which in turn can be related to magma supply. This new view supports the magmatic intrusion model of early stages of continental breaking.

  9. Mechanism of Rock Burst Occurrence in Specially Thick Coal Seam with Rock Parting

    NASA Astrophysics Data System (ADS)

    Wang, Jian-chao; Jiang, Fu-xing; Meng, Xiang-jun; Wang, Xu-you; Zhu, Si-tao; Feng, Yu

    2016-05-01

    Specially thick coal seam with complex construction, such as rock parting and alternative soft and hard coal, is called specially thick coal seam with rock parting (STCSRP), which easily leads to rock burst during mining. Based on the stress distribution of rock parting zone, this study investigated the mechanism, engineering discriminant conditions, prevention methods, and risk evaluation method of rock burst occurrence in STCSRP through setting up a mechanical model. The main conclusions of this study are as follows. (1) When the mining face moves closer to the rock parting zone, the original non-uniform stress of the rock parting zone and the advancing stress of the mining face are combined to intensify gradually the shearing action of coal near the mining face. When the shearing action reaches a certain degree, rock burst easily occurs near the mining face. (2) Rock burst occurrence in STCSRP is positively associated with mining depth, advancing stress concentration factor of the mining face, thickness of rock parting, bursting liability of coal, thickness ratio of rock parting to coal seam, and difference of elastic modulus between rock parting and coal, whereas negatively associated with shear strength. (3) Technologies of large-diameter drilling, coal seam water injection, and deep hole blasting can reduce advancing stress concentration factor, thickness of rock parting, and difference of elastic modulus between rock parting and coal to lower the risk of rock burst in STCSRP. (4) The research result was applied to evaluate and control the risk of rock burst occurrence in STCSRP.

  10. Laboratory rock mechanics testing manual. Public draft

    SciTech Connect

    Shuri, F S; Cooper, J D; Hamill, M L

    1981-10-01

    Standardized laboratory rock mechanics testing procedures have been prepared for use in the National Terminal Waste Storage Program. The procedures emphasize equipment performance specifications, documentation and reporting, and Quality Assurance acceptance criteria. Sufficient theoretical background is included to allow the user to perform the necessary data reduction. These procedures incorporate existing standards when possible, otherwise they represent the current state-of-the-art. Maximum flexibility in equipment design has been incorporated to allow use of this manual by existing groups and to encourage future improvements.

  11. Panel discussion on rock mechanics issues in repository design

    SciTech Connect

    Bieniawski, Z.T.; Kim, K.S.; Nataraja, M.

    1996-04-01

    The panel discussion was introduced by Mr. Z.T.(Richard) Bieniawski and then continued with five additional speakers. The topics covered in the discussion included rock mechanics pertaining to the design of underground facilities for the disposal of radioactive wastes and the safety of such facilities. The speakers included: Mr. Kun-Soo Kim who is a specialist in the area of rock mechanics testing during the Basalt Waste Isolation Project; Dr. Mysore Nataraja who is the senior project manager with the NRC; Dr. Michael Voegele who is the project manager for Science Applications International Corporation (SAIC) on the Yucca Mountain Project; Dr. Edward Cording who is a member of the Nuclear Waste Technical Review Board; and Dr. Hemendra Kalia who is employed by Los Alamos National Laboratory and coordinates various activities of testing programs at the Yucca Mountain Site.

  12. The Weathering of Rocks: Three Activities.

    ERIC Educational Resources Information Center

    McLure, John W.

    1991-01-01

    Integrates science and social studies in several activities that study weathering caused by the freezing and thawing of rocks, wind erosion, and the effects of weathering on tombstones. Cites the possibility of these activities leading to an interdisciplinary exploration of pollution, customs, and populations. (MCO)

  13. Rock mechanics. Superplastic nanofibrous slip zones control seismogenic fault friction.

    PubMed

    Verberne, Berend A; Plümper, Oliver; de Winter, D A Matthijs; Spiers, Christopher J

    2014-12-12

    Understanding the internal mechanisms controlling fault friction is crucial for understanding seismogenic slip on active faults. Displacement in such fault zones is frequently localized on highly reflective (mirrorlike) slip surfaces, coated with thin films of nanogranular fault rock. We show that mirror-slip surfaces developed in experimentally simulated calcite faults consist of aligned nanogranular chains or fibers that are ductile at room conditions. These microstructures and associated frictional data suggest a fault-slip mechanism resembling classical Ashby-Verrall superplasticity, capable of producing unstable fault slip. Diffusive mass transfer in nanocrystalline calcite gouge is shown to be fast enough for this mechanism to control seismogenesis in limestone terrains. With nanogranular fault surfaces becoming increasingly recognized in crustal faults, the proposed mechanism may be generally relevant to crustal seismogenesis.

  14. Qualitative evaluation of rock weir field performance and failure mechanisms

    USGS Publications Warehouse

    Mooney, David M.; Holmquist-Johnson, Christopher L.; Holburn, Elaina

    2007-01-01

    River spanning loose-rock structures provide sufficient head for irrigation diversion, permit fish passage over barriers, protect banks, stabilize degrading channels, activate side channels, reconnect floodplains, and create in-channel habitat. These structures are called by a variety of names including rock weirs, alphabet (U-, A-, V-, W-) weirs, Jhooks, and rock ramps. These structures share the common characteristics of:Loose rock construction materials (individually placed or dumped rocks with little or no concrete);Extents spanning the width of the river channel; andAn abrupt change in the water surface elevation at low flows.

  15. Significance of grain sliding mechanisms for ductile deformation of rocks

    NASA Astrophysics Data System (ADS)

    Dimanov, A.; Bourcier, M.; Gaye, A.; Héripré, E.; Bornert, M.; Raphanel, J.; Ludwig, W.

    2013-12-01

    Ductile shear zones at depth present polyphase and heterogeneous rocks and multi-scale strain localization patterns. Most strain concentrates in ultramylonitic layers, which exhibit microstructural signatures of several concomitant deformation mechanisms. The latter are either active in volume (dislocation creep), or in the vicinity and along interfaces (grain sliding and solution mass transfer). Because their chronology of appearance and interactions are unclear, inference of the overall rheology seems illusory. We have therefore characterized over a decade the rheology of synthetic lower crustal materials with different compositions and fluid contents, and for various microstructures. Non-Newtonian flow clearly related to dominant dislocation creep. Conversely, Newtonian behavior involved grain sliding mechanisms, but crystal plasticity could be identified as well. In order to clarify the respective roles of these mechanisms we underwent a multi-scale investigation of the ductile deformation of rock analog synthetic halite with controlled microstructures. The mechanical tests were combined with in-situ optical microscopy, scanning electron microscopy and X ray computed tomography, allowing for digital image correlation (DIC) techniques and retrieval of full strain field. Crystal plasticity dominated, as evidenced by physical slip lines and DIC computed slip bands. Crystal orientation mapping allowed to identify strongly active easy glide {110} <110> systems. But, all other slip systems were observed as well, and especially near interfaces, where their activity is necessary to accommodate for the plastic strain incompatibilities between neighboring grains. We also evidenced grain boundary sliding (GBS), which clearly occurred as a secondary, but necessary, accommodation mechanism. The DIC technique allowed the quantification of the relative contribution of each mechanism. The amount of GBS clearly increased with decreasing grain size. Finite element (FE) modeling

  16. Mechanical stimulation of cyclic tensile strain induces reduction of pluripotent related gene expressions via activation of Rho/ROCK and subsequent decreasing of AKT phosphorylation in human induced pluripotent stem cells

    SciTech Connect

    Teramura, Takeshi; Takehara, Toshiyuki; Onodera, Yuta; Nakagawa, Koichi; Hamanishi, Chiaki; Fukuda, Kanji

    2012-01-13

    Highlights: Black-Right-Pointing-Pointer Mechanical stimulation is an important factor for regulation of stem cell fate. Black-Right-Pointing-Pointer Cyclic stretch to human induced pluripotent stem cells activated small GTPase Rho. Black-Right-Pointing-Pointer Rho-kinase activation attenuated pluripotency via inhibition of AKT activation. Black-Right-Pointing-Pointer This reaction could be reproduced only by transfection of dominant active Rho. Black-Right-Pointing-Pointer Rho/ROCK are important molecules in mechanotransduction and control of stemness. -- Abstract: Mechanical stimulation has been shown to regulate the proliferation and differentiation of stem cells. However, the effects of the mechanical stress on the stemness or related molecular mechanisms have not been well determined. Pluripotent stem cells such as embryonic stem (ES) cells and induced pluripotent stem (iPS) cells are used as good materials for cell transplantation therapy and research of mammalian development, since they can self-renew infinitely and differentiate into various cell lineages. Here we demonstrated that the mechanical stimulation to human iPS cells altered alignment of actin fibers and expressions of the pluripotent related genes Nanog, POU5f1 and Sox2. In the mechanically stimulated iPS cells, small GTPase Rho was activated and interestingly, AKT phosphorylation was decreased. Inhibition of Rho-associated kinase ROCK recovered the AKT phosphorylation and the gene expressions. These results clearly suggested that the Rho/ROCK is a potent primary effector of mechanical stress in the pluripotent stem cells and it participates to pluripotency-related signaling cascades as an upper stream regulator.

  17. Mitochondrial fragmentation in excitotoxicity requires ROCK activation.

    PubMed

    Martorell-Riera, Alejandro; Segarra-Mondejar, Marc; Reina, Manuel; Martínez-Estrada, Ofelia M; Soriano, Francesc X

    2015-01-01

    Mitochondria morphology constantly changes through fission and fusion processes that regulate mitochondrial function, and it therefore plays a prominent role in cellular homeostasis. Cell death progression is associated with mitochondrial fission. Fission is mediated by the mainly cytoplasmic Drp1, which is activated by different post-translational modifications and recruited to mitochondria to perform its function. Our research and other studies have shown that in the early moments of excitotoxic insult Drp1 must be nitrosylated to mediate mitochondrial fragmentation in neurons. Nonetheless, mitochondrial fission is a multistep process in which filamentous actin assembly/disassembly and myosin-mediated mitochondrial constriction play prominent roles. Here we establish that in addition to nitric oxide production, excitotoxicity-induced mitochondrial fragmentation also requires activation of the actomyosin regulator ROCK. Although ROCK1 has been shown to phosphorylate and activate Drp1, experiments using phosphor-mutant forms of Drp1 in primary cortical neurons indicate that in excitotoxic conditions, ROCK does not act directly on Drp1 to mediate fission, but may act on the actomyosin complex. Thus, these data indicate that a wider range of signaling pathways than those that target Drp1 are amenable to be inhibited to prevent mitochondrial fragmentation as therapeutic option.

  18. Rock Mechanics Models and Measurements Challenges from Industry. Proceedings

    SciTech Connect

    Laubach, S.E.; Nelson, P.P.

    1994-01-01

    Increased mutual dependence of the economies of Canada, the United States and Mexico has now been recognized formally by agreements between the respective national governments. Noting the basic economic role of rock mechanics in the resource recovery and construction industries, it is appropriate that the First North American Rock Mechanics Symposium should confirm mutual interest in rock mechanics research and engineering practice in the neighboring countries. Different government and industrial emphases in the NAFTA countries lead to complementary strengths in their research and engineering programs. The First NARM Symposium is the first opportunity to explore thoroughly, within the scope of a single meeting, rock mechanics research in progress and engineering achievements in the three countries. Individual papers abstracted separately.

  19. Mechanical Properties of Shock-Damaged Rocks

    NASA Technical Reports Server (NTRS)

    He, Hongliang; Ahrens, T. J.

    1994-01-01

    Stress-strain tests were performed both on shock-damaged gabbro and limestone. The effective Young's modulus decreases with increasing initial damage parameter value, and an apparent work-softening process occurs prior to failure. To further characterize shock-induced microcracks, the longitudinal elastic wave velocity behavior of shock-damaged gabbro in the direction of compression up to failure was measured using an acoustic transmission technique under uniaxial loading. A dramatic increase in velocity was observed for the static compressive stress range of 0-50 MPa. Above that stress range, the velocity behavior of lightly damaged (D(sub 0) less than 0.1) gabbro is almost equal to unshocked gabbro. The failure strength of heavily-damaged (D(sub 0) greater than 0.1) gabbro is approx. 100-150 MPa, much lower than that of lightly damaged and unshocked gabbros (approx. 230-260 MPa). Following Nur's theory, the crack shape distribution was analyzed. The shock-induced cracks in gabbro appear to be largely thin penny-shaped cracks with c/a values below 5 x 10(exp -4). Moreover, the applicability of Ashby and Sammis's theory relating failure strength and damage parameter of shock-damaged rocks was examined and was found to yield a good estimate of the relation of shock-induced deficit in elastic modulus with the deficit in compressive strength.

  20. New Mechanisms of rock-bit wear in geothermal wells

    SciTech Connect

    Macini, Paolo

    1996-01-24

    This paper presents recent results of an investigation on failure mode and wear of rock-bits used to drill geothermal wells located in the area of Larderello (Italy). A new wear mechanism, conceived from drilling records and dull bit evaluation analysis, has been identified and a particular configuration of rock-bit has been developed and tested in order to reduce drilling costs. The role of high Bottom Hole Temperature (BHT) on rock-bit performances seems not yet very well understood: so far, only drillability and formation abrasiveness are generally considered to account for poor drilling performances. In this paper, the detrimental effects of high BHT on sealing and reservoir system of Friction Bearing Rock-bits (FBR) have been investigated, and a new bearing wear pattern for FBR's run in high BHT holes has been identified and further verified via laboratory inspections on dull bits. A novel interpretation of flat worn cutting structure has been derived from the above wear pattern, suggesting the design of a particular bit configuration. Test bits, designed in the light of the above criteria, have been prepared and field tested successfully. The paper reports the results of these tests, which yielded a new rock-bit application, today considered as a standad practice in Italian geothermal fields. This application suggests that the correct evaluation of rock-bit wear can help to improve the overall drilling performances and to minimize drilling problems through a better interpretation of the relationships amongst rock-bits, formation properties and downhole temperature.

  1. Mechanisms for fast flow in unsaturated fractured rock

    SciTech Connect

    Tokunaga, Tetsu K.; Wan, Jiamin

    1998-03-01

    Although fractures in rock are well-recognized as pathways for fast percolation of water, the possibility that fast flow could occur along unsaturated fracture pathways is commonly not considered in vadose zone hydrology. In this study, two mechanisms for fast flow along unsaturated fractures were investigated, film flow and surface zone flow. The importance of fracture surface roughness was demonstrated through experiments conducted on ceramic blocks having simple surface topographies. Those experiments showed that film flow on fracture surfaces is largely due to flow along continuous surface channels which become water-filled at near-zero matric (capillary) potentials. The second mechanism, surface zone flow, is important when the permeability of the rock along fractures (fracture skin) is significantly greater than that of the bulk rock matrix. Surface zone fast flow was demonstrated through water imbibition (sorptivity) experiments. These mechanisms help explain observations of rapid solute transport in unsaturated subsurface environments.

  2. Reconstruction of Sedimentary Rock Based on MechanicalProperties

    SciTech Connect

    Jin, Guodong; Patzek, Tad W.; Silin, Dmitry B.

    2004-05-04

    We describe a general, physics-based approach to numericalreconstruction of the geometrical structure and mechanical properties ofnatural sedimentary rock in 3D. Our procedure consists of three mainsteps: sedimentation, compaction, and diagenesis, followed by theverification of rock mechanical properties. The dynamic geologicprocesses of grain sedimentation and compaction are simulated by solvinga dimensionless form of Newton's equations of motion for an ensemble ofgrains. The diagenetic rock transformation is modeled using a cementationalgorithm, which accounts for the effect of rock grain size on therelative rate of cement overgrowth. Our emphasis is on unconsolidatedsand and sandstone. The main input parameters are the grain sizedistribution, the final rock porosity, the type and amount of cement andclay minerals, and grain mechanical properties: the inter-grain frictioncoefficient, the cement strength, and the grain stiffness moduli. We usea simulated 2D Fontainebleau sandstone to obtain the grain mechanicalproperties. This Fontainebleau sandstone is also used to study theinitiation, growth, and coalescence of micro-cracks under increasingvertical stress. The box fractal dimension of the micro-crackdistribution, and its variation with the applied stress areestimated.

  3. Simulation of Electrical Transport in Rocks under Mechanical Action

    NASA Astrophysics Data System (ADS)

    Salgueiro da Silva, M. A.; Seixas, T. M.

    2015-12-01

    Rock's electrical properties can be changed by mechanical action, especially when deformation is accompanied by micro-fracturing processes. Knowing how electrical charge is generated in inelastically deformed rocks, the nature and properties of the generated charge carriers, and their spatial distribution and propagation is crucial to gain insight into the origin of seismo-electromagnetic signals. In this work, we describe briefly a model for the numerical simulation of electrical transport in rocks under mechanical action, assuming that high and low mobility charge carriers of opposite signs can be simultaneously generated by micro-fracturing processes and recombine, diffuse and drift across the sample rock. The electrical behavior can then be described using an adaptation of the formalism applied to semiconductors. We provide simulation results on a one-dimensional lattice using finite-difference discretization. Our results show that a large mobility contrast among charge carriers allows charge separation inside the deformation region, which leads to the formation of charged layers of alternate signs. Inside these layers, rapid electric field variations are observed which can lead to the emission of electromagnetic radiation. With proper positioning of current electrodes inside the deformation region, it is possible to collect electrical current even without any applied voltage. We discuss our results in the light of available experimental results on the generation of electrical and electromagnetic signals in deformed rocks.

  4. A Preliminary Study of 3D Printing on Rock Mechanics

    NASA Astrophysics Data System (ADS)

    Jiang, Chao; Zhao, Gao-Feng

    2015-05-01

    3D printing is an innovative manufacturing technology that enables the printing of objects through the accumulation of successive layers. This study explores the potential application of this 3D printing technology for rock mechanics. Polylactic acid (PLA) was used as the printing material, and the specimens were constructed with a "3D Touch" printer that employs fused deposition modelling (FDM) technology. Unconfined compressive strength (UCS) tests and direct tensile strength (DTS) tests were performed to determine the Young's modulus ( E) and Poisson's ratio ( υ) for these specimens. The experimental results revealed that the PLA specimens exhibited elastic to brittle behaviour in the DTS tests and exhibited elastic to plastic behaviour in the UCS tests. The influence of structural changes in the mechanical response of the printed specimen was investigated; the results indicated that the mechanical response is highly influenced by the input structures, e.g., granular structure, and lattice structure. Unfortunately, our study has demonstrated that the FDM 3D printing with PLA is unsuitable for the direct simulation of rock. However, the ability for 3D printing on manufactured rock remains appealing for researchers of rock mechanics. Additional studies should focus on the development of an appropriate substitution for the printing material (brittle and stiff) and modification of the printing technology (to print 3D grains with arbitrary shapes).

  5. Preliminary design and definition of field experiments for welded tuff rock mechanics program

    NASA Astrophysics Data System (ADS)

    Zimmerman, R. M.

    1982-06-01

    G-tunnel on the Nevada Test Site intersects the Grouse Canyon Member, Belted Range Tuff, that has similar thermal and mechanical properties to welded tuff strata in nearby Yucca Mountain, which is considered as a site for a nuclear waste repository. A rock mechanics testing program is developed. Field data used for site characterization and repository conceptual design is investigated. This preliminary design is prepared to provide a control document for definition, implementation, operation, and evaluation activities for five rock mechanics experiments that can be placed in this geologic unit.

  6. Mechanical and hydraulic properties of rocks related to induced seismicity

    USGS Publications Warehouse

    Witherspoon, P.A.; Gale, J.E.

    1977-01-01

    Witherspoon, P.A. and Gale, J.E., 1977. Mechanical and hydraulic properties of rocks related to induced seismicity. Eng. Geol., 11(1): 23-55. The mechanical and hydraulic properties of fractured rocks are considered with regard to the role they play in induced seismicity. In many cases, the mechanical properties of fractures determine the stability of a rock mass. The problems of sampling and testing these rock discontinuities and interpreting their non-linear behavior are reviewed. Stick slip has been proposed as the failure mechanism in earthquake events. Because of the complex interactions that are inherent in the mechanical behavior of fractured rocks, there seems to be no simple way to combine the deformation characteristics of several sets of fractures when there are significant perturbations of existing conditions. Thus, the more important fractures must be treated as individual components in the rock mass. In considering the hydraulic properties, it has been customary to treat a fracture as a parallel-plate conduit and a number of mathematical models of fracture systems have adopted this approach. Non-steady flow in fractured systems has usually been based on a two-porosity model, which assumes the primary (intergranular) porosity contributes only to storage and the secondary (fracture) porosity contributes only to the overall conductivity. Using such a model, it has been found that the time required to achieve quasi-steady state flow in a fractured reservoir is one or two orders of magnitude greater than it is in a homogeneous system. In essentially all of this work, the assumption has generally been made that the fractures are rigid. However, it is clear from a review of the mechanical and hydraulic properties that not only are fractures easily deformed but they constitute the main flow paths in many rock masses. This means that one must consider the interaction of mechanical and hydraulic effects. A considerable amount of laboratory and field data is now

  7. A mechanism for high wall-rock velocities in rockbursts

    USGS Publications Warehouse

    McGarr, A.

    1997-01-01

    Considerable evidence has been reported for wall-rock velocities during rockbursts in deep gold mines that are substantially greater than ground velocities associated with the primary seismic events. Whereas varied evidence suggests that slip across a fault at the source of an event generates nearby particle velocities of, at most, several m/s, numerous observations, in nearby damaged tunnels, for instance, imply wall-rock velocities of the order of 10 m/s and greater. The common observation of slab buckling or breakouts in the sidewalls of damaged excavations suggests that slab flexure may be the mechanism for causing high rock ejection velocities. Following its formation, a sidewall slab buckles, causing the flexure to increase until the stress generated by flexure reaches the limit 5 that can be supported by the sidewall rock. I assume here that S is the uniaxial compressive strength. Once the flexural stress exceeds S, presumably due to the additional load imposed by a nearby seismic event, the slab fractures and unflexes violently. The peak wall-rock velocity v thereby generated is given by v=(3 + 1-??2/2)1 2 S/?????E for rock of density ??, Young's modulus E, and Poisson's ratio ??. Typical values of these rock properties for the deep gold mines of South Africa yield v= 26 m/s and for especially strong quartzites encountered in these same mines, v> 50m/s. Even though this slab buckling process leads to remarkably high ejection velocities and violent damage in excavations, the energy released during this failure is only a tiny fraction of that released in the primary seismic event, typically of magnitude 2 or greater.

  8. Increased anticancer activity of the thymidylate synthase inhibitor BGC9331 combined with the topoisomerase I inhibitor SN-38 in human colorectal and breast cancer cells: induction of apoptosis and ROCK cleavage through caspase-3-dependent and -independent mechanisms.

    PubMed

    Coudray, Anne-Marie; Louvet, Christophe; Kornprobst, Michel; Raymond, Eric; André, Thierry; Tournigand, Christophe; Faivre, Sandrine; De Gramont, Aimery; Larsen, Annette K; Gespach, Christian

    2005-08-01

    The folate analogue BGC9331 is a new thymidylate synthase (TS) inhibitor showing a broad spectrum of cyto-toxic activity against several human solid tumors, including colorectal cancer. In this study, we investigated the anticancer activity of BGC9331 either alone or combined with 5-fluorouracil (5-FU), MTA (multi-target antifolate), oxali-platin and SN-38, the active metabolite of the topoisomerase I inhibitor CPT-11. The antiproliferative activity of each drug and BGC9331-based combinations was investigated in the HT-29 human colorectal cancer cell line and its HT-29/5-FU counterparts selected for resistance to 5-FU. BGC9331 combined with MTA or SN-38 induced synergistic responses in HT-29 cells. Treatment of HT-29 cells with either BGC9331 or SN-38 increased caspase-3 activity and the percentage of apoptotic cells from 3 to 13%. Both drugs also augmented the proteolytic cleavage of the Rho-kinase ROCK-1 that was attenuated by the caspase-3 pathway inhibitor z-DEVD-fmk. BGC9331 combined with SN-38 further increased the percentage of apoptotic cells to 25%, and inhibited cell cycle progression and cell proliferation by 65%. This was accompanied by proteolytic activation of ROCK-1, through both caspase-3-dependent and -independent mechanisms, as shown in caspase-3-deficient MCF-7 breast cancer cells. These encouraging results warrant further preclinical investigations and clinical trials on the use of BGC9331 combined with SN-38/CPT-11 in treatment of patients with advanced colorectal or gastric cancers.

  9. Lithophysal Rock Mass Mechanical Properties of the Repository Host Horizon

    SciTech Connect

    D. Rigby

    2004-11-10

    The purpose of this calculation is to develop estimates of key mechanical properties for the lithophysal rock masses of the Topopah Spring Tuff (Tpt) within the repository host horizon, including their uncertainties and spatial variability. The mechanical properties to be characterized include an elastic parameter, Young's modulus, and a strength parameter, uniaxial compressive strength. Since lithophysal porosity is used as a surrogate property to develop the distributions of the mechanical properties, an estimate of the distribution of lithophysal porosity is also developed. The resulting characterizations of rock parameters are important for supporting the subsurface design, developing the preclosure safety analysis, and assessing the postclosure performance of the repository (e.g., drift degradation and modeling of rockfall impacts on engineered barrier system components).

  10. Some observations on the mechanism of aircraft wing rock

    NASA Technical Reports Server (NTRS)

    Hwang, C.; Pi, W. S.

    1978-01-01

    A pressure scale model of Northrop F-5A was tested in NASA Ames Research Center Eleven-Foot Transonic Tunnel to simulate the wing rock oscillations in a transonic maneuver. For this purpose, a flexible model support device was designed and fabricated which allowed the model to oscillate in roll at the scaled wing rock frequency. Two tunnel entries were performed to acquire the pressure (steady state and fluctuating) and response data when the model was held fixed and when it was excited by flow to oscillate in roll. Based on these data, a limit cycle mechanism was identified which supplied energy to the aircraft model and caused the Dutch roll type oscillations, commonly called wing rock. The major origin of the fluctuating pressures which contributed to the limit cycle was traced to the wing surface leading edge stall and the subsequent lift recovery. For typical wing rock oscillations, the energy balance between the pressure work input and the energy consumed by the model aerodynamic and mechanical damping was formulated and numerical data presented.

  11. Some observations on the mechanism of aircraft wing rock

    NASA Technical Reports Server (NTRS)

    Hwang, C.; Pi, W. S.

    1979-01-01

    A scale model of the Northrop F-5A was tested in NASA Ames Research Center Eleven-Foot Transonic Tunnel to simulate the wing rock oscillations in a transonic maneuver. For this purpose, a flexible model support device was designed and fabricated, which allowed the model to oscillate in roll at the scaled wing rock frequency. Two tunnel entries were performed to acquire the pressure (steady state and fluctuating) and response data when the model was held fixed and when it was excited by flow to oscillate in roll. Based on these data, a limit cycle mechanism was identified, which supplied energy to the aircraft model and caused the Dutch roll type oscillations, commonly called wing rock. The major origin of the fluctuating pressures that contributed to the limit cycle was traced to the wing surface leading edge stall and the subsequent lift recovery. For typical wing rock oscillations, the energy balance between the pressure work input and the energy consumed by the model's aerodynamic and mechanical damping was formulated and numerical data presented.

  12. Mechanical changes in thawing permafrost rocks and their influence on rock stability at the Zugspitze summit, Germany - a research concept

    NASA Astrophysics Data System (ADS)

    Mamot, Philipp; Scandroglio, Riccardo; Krautblatter, Michael

    2015-04-01

    During the last century, alpine permafrost warmed up by 0.5 to 0.8 °C in the upper decameters. Its degradation can influence the stability of rock slopes in alpine environments. An increasing number of rockfalls and rockslides of all magnitudes are reported to originate from permafrost-affected rock faces which reveal massive ice at their detachment scarps after failure. Discontinuity patterns and their mechanical properties present a key control of rock slope stability. These fractures are considered to experience considerable mechanical changes during transition from frozen to unfrozen state: the shear resistance of rocks is reduced in terms of decreased critical fracture toughness of intact rock bridges and shear strength; compressive strength and tensile strength of the intact rock are reduced in the same way. The impact of rising rock temperature on rock-mechanical properties which control early stages of destabilization remains poorly understood. In this study we combine rock-mechanical testing in the laboratory with geotechnical, kinematic and geophysical monitoring at the Zugspitze summit, Germany, to investigate the influence of thawing rock on its rock-mechanical properties focusing on mechanisms of destabilization along discontinuities. Our investigations will contribute to a better rock-ice-mechanical process understanding of degrading permafrost rocks. To assess stability conditions at the Zugspitze summit we conduct field work at an unstable area of about 104 m3 of rock at the crest at 2885 m a.s.l. that is affected by degrading permafrost. This is indicated by a persistent ice filled cave with direct contact to the area of instability. Our preliminary work consists of i) continuous and discontinuous fracture displacement measurements since 2009 which reveal deformation rates of 0.06 to 1.7 cm/year, ii) electrical resistivity (ERT) and seismic refraction tomography (SRT) in the August of 2014 and iii) uniaxial compressive strength and tensile

  13. Effect of Rapid Thermal Cooling on Mechanical Rock Properties

    NASA Astrophysics Data System (ADS)

    Kim, Kwangmin; Kemeny, John; Nickerson, Mark

    2014-11-01

    Laboratory tests have been conducted to investigate the effects of rapid thermal cooling on various rock specimens including igneous, sedimentary, and metamorphic rocks. At first, various types of thermal loading were conducted: heating up to 100, 200, and 300 °C, followed by rapid cooling with a fan. In addition, multiple cyclic thermal cooling (10, 15 and 20 cycles) with a maximum temperature of only 100 °C was conducted. Experiments included edge notched disc (END) tests to determine the Mode I fracture toughness, Brazilian disc tests to determine tensile strength, seismic tests to determine P-wave velocity, and porosity tests leading to meaningful results. Even though only small changes of temperature (rapid cooling from 100 °C to room temperature) were applied, the results showed that crack growth occurred in some rock types (granite, diabase with ore veins, and KVS) while crack healing occurred in other rock types (diabase without ore veins, quartzite, and skarn). To better understand the results, 3D transient thermo-mechanical analysis was conducted using the ANSYS program. The results indicated that there was a thin region near the outside of the specimen where large tensile stresses occur and microcracking would be expected, and that there was a large area in the middle of the specimen where lower magnitude compressive stresses occur and crack closure would be expected. It was found that the more heterogeneous and more coarse-grained rock types are more likely to exhibit crack growth, while less heterogeneous and more fine-grained rocks are more likely to exhibit crack healing.

  14. PSYCHOPHYSICAL BENEFITS OF ROCK-CLIMBING ACTIVITY.

    PubMed

    Gallotta, Maria Chiara; Emerenziani, Gian Pietro; Monteiro, Maria Dolores; Iasevoli, Luigi; Iazzoni, Sara; Baldari, Carlo; Guidetti, Laura

    2015-12-01

    The aim of the study was to compare the psychophysical effects of rock climbing with a supervised fitness training in adults. Thirty-three healthy participants (M age=32 yr., SD=7) participated in rock climbing or in fitness training. The participants' functional fitness, anxiety, and mood states were tested before and after 3 mo. of training. There was significant improvement of physical fitness in both groups after the intervention period. Anxiety significantly decreased after each single training session at the end of both courses. Differential effects in the rock-climbing group, as compared to the fitness group, emerged only on Vigor. Specifically, the rock-climbing group showed a decreasing trend in Vigor while the fitness group showed an increasing trend of Vigor after the intervention.

  15. Neutron activation analysis for the demonstration of amphibolite rock-weathering activity of a yeast.

    PubMed

    Rades-Rohkohl, E; Hirsch, P; Fränzle, O

    1979-12-01

    Neutron activation analysis was employed in a survey of weathering abilities of rock surface microorganisms. A yeast isolated from an amphibolite of a megalithic grave was found actively to concentrate, in media and in or on cells, iron and other elements when grown in the presence of ground rock. This was demonstrated by comparing a spectrum of neutron-activated amphibolite powder (particle size, 50 to 100 mum) with the spectra of neutron-activated, lyophilized yeast cells which had grown with or without amphibolite powder added to different media. The most active yeast (IFAM 1171) did not only solubilize Fe from the rock powder, but significant amounts of Co, Eu, Yb, Ca, Ba, Sc, Lu, Cr, Th, and U were also mobilized. The latter two elements occurred as natural radioactive isotopes in this amphibolite. When the yeast cells were grown with neutron-activated amphibolite, the cells contained the same elements. Furthermore, the growth medium contained Fe, Co, and Eu which had been solubilized from the amphibolite. This indicates the presence, in this yeast strain, of active rockweathering abilities as well as of uptake mechanisms for solubilized rock components.

  16. Neutron Activation Analysis for the Demonstration of Amphibolite Rock-Weathering Activity of a Yeast

    PubMed Central

    Rades-Rohkohl, E.; Hirsch, P.; Fränzle, O.

    1979-01-01

    Neutron activation analysis was employed in a survey of weathering abilities of rock surface microorganisms. A yeast isolated from an amphibolite of a megalithic grave was found actively to concentrate, in media and in or on cells, iron and other elements when grown in the presence of ground rock. This was demonstrated by comparing a spectrum of neutron-activated amphibolite powder (particle size, 50 to 100 μm) with the spectra of neutron-activated, lyophilized yeast cells which had grown with or without amphibolite powder added to different media. The most active yeast (IFAM 1171) did not only solubilize Fe from the rock powder, but significant amounts of Co, Eu, Yb, Ca, Ba, Sc, Lu, Cr, Th, and U were also mobilized. The latter two elements occurred as natural radioactive isotopes in this amphibolite. When the yeast cells were grown with neutron-activated amphibolite, the cells contained the same elements. Furthermore, the growth medium contained Fe, Co, and Eu which had been solubilized from the amphibolite. This indicates the presence, in this yeast strain, of active rockweathering abilities as well as of uptake mechanisms for solubilized rock components. PMID:16345472

  17. Integrating rock mechanics issues with repository design through design process principles and methodology

    SciTech Connect

    Bieniawski, Z.T.

    1996-04-01

    A good designer needs not only knowledge for designing (technical know-how that is used to generate alternative design solutions) but also must have knowledge about designing (appropriate principles and systematic methodology to follow). Concepts such as {open_quotes}design for manufacture{close_quotes} or {open_quotes}concurrent engineering{close_quotes} are widely used in the industry. In the field of rock engineering, only limited attention has been paid to the design process because design of structures in rock masses presents unique challenges to the designers as a result of the uncertainties inherent in characterization of geologic media. However, a stage has now been reached where we are be able to sufficiently characterize rock masses for engineering purposes and identify the rock mechanics issues involved but are still lacking engineering design principles and methodology to maximize our design performance. This paper discusses the principles and methodology of the engineering design process directed to integrating site characterization activities with design, construction and performance of an underground repository. Using the latest information from the Yucca Mountain Project on geology, rock mechanics and starter tunnel design, the current lack of integration is pointed out and it is shown how rock mechanics issues can be effectively interwoven with repository design through a systematic design process methodology leading to improved repository performance. In essence, the design process is seen as the use of design principles within an integrating design methodology, leading to innovative problem solving. In particular, a new concept of {open_quotes}Design for Constructibility and Performance{close_quotes} is introduced. This is discussed with respect to ten rock mechanics issues identified for repository design and performance.

  18. The Rho GTPase effector ROCK regulates cyclin A, cyclin D1, and p27Kip1 levels by distinct mechanisms.

    PubMed

    Croft, Daniel R; Olson, Michael F

    2006-06-01

    The members of the Rho GTPase family are well known for their regulation of actin cytoskeletal structures. In addition, they influence progression through the cell cycle. The RhoA and RhoC proteins regulate numerous effector proteins, with a central and vital signaling role mediated by the ROCK I and ROCK II serine/threonine kinases. The requirement for ROCK function in the proliferation of numerous cell types has been revealed by studies utilizing ROCK-selective inhibitors such as Y-27632. However, the mechanisms by which ROCK signaling promotes cell cycle progression have not been thoroughly characterized. Using a conditionally activated ROCK-estrogen receptor fusion protein, we found that ROCK activation is sufficient to stimulate G1/S cell cycle progression in NIH 3T3 mouse fibroblasts. Further analysis revealed that ROCK acts via independent pathways to alter the levels of cell cycle regulatory proteins: cyclin D1 and p21(Cip1) elevation via Ras and the mitogen-activated protein kinase pathway, increased cyclin A via LIM kinase 2, and reduction of p27(Kip1) protein levels. Therefore, the influence of ROCK on cell cycle regulatory proteins occurs by multiple independent mechanisms.

  19. Rocks.

    ERIC Educational Resources Information Center

    Lee, Alice

    This science unit is designed for limited- and non-English speaking students in a Chinese bilingual education program. The unit covers rock material, classification, characteristics of types of rocks, and rock cycles. It is written in Chinese and simple English. At the end of the unit there is a list of main terms in both English and Chinese, and…

  20. ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS

    SciTech Connect

    Thurman E. Scott, Jr.; Younane Abousleiman

    2004-04-01

    The research during this project has concentrated on developing a correlation between rock deformation mechanisms and their acoustic velocity signature. This has included investigating: (1) the acoustic signature of drained and undrained unconsolidated sands, (2) the acoustic emission signature of deforming high porosity rocks (in comparison to their low porosity high strength counterparts), (3) the effects of deformation on anisotropic elastic and poroelastic moduli, and (4) the acoustic tomographic imaging of damage development in rocks. Each of these four areas involve triaxial experimental testing of weak porous rocks or unconsolidated sand and involves measuring acoustic properties. The research is directed at determining the seismic velocity signature of damaged rocks so that 3-D or 4-D seismic imaging can be utilized to image rock damage. These four areas of study are described in the report: (1) Triaxial compression experiments have been conducted on unconsolidated Oil Creek sand at high confining pressures. (2) Initial experiments on measuring the acoustic emission activity from deforming high porosity Danian chalk were accomplished and these indicate that the AE activity was of a very low amplitude. (3) A series of triaxial compression experiments were conducted to investigate the effects of induced stress on the anisotropy developed in dynamic elastic and poroelastic parameters in rocks. (4) Tomographic acoustic imaging was utilized to image the internal damage in a deforming porous limestone sample. Results indicate that the deformation damage in rocks induced during laboratory experimentation can be imaged tomographically in the laboratory. By extension the results also indicate that 4-D seismic imaging of a reservoir may become a powerful tool for imaging reservoir deformation (including imaging compaction and subsidence) and for imaging zones where drilling operation may encounter hazardous shallow water flows.

  1. MECHANICAL DEGRADATION OF EMPLACEMENT DRIFTS AT YUCCA MOUNTAIN - A CASE STUDY IN ROCK MECHANICS, PART 1: NONLITHOPHYSAL ROCK, PART 2: LITHOPHYSAL ROCK

    SciTech Connect

    M. Lin, D. Kicker, B. Damjanac, M. Board, and M. Karakouzian

    2006-02-27

    This paper outlines rock mechanics investigations associated with mechanical degradation of planned emplacement drifts at Yucca Mountain, which is the designated site for a US high-level nuclear waste repository. The factors leading to drift degradation include stresses from the overburden, stresses induced by the heat released from the emplaced waste, stresses due to seismically related ground motions, and time-dependent strength degradation. The welded tuff emplacement horizon consists of two groups of rock with distinct engineering properties: nonlithophysal units and lithophysal units, based on the relative proportion of lithophysal cavities. Part I of the paper concentrates on the generally hard, strong, and fractured nonlithophysal rock. The degradation behavior of the tunnels in the nonlithophysal rock is controlled by the occurrence of keyblocks. A statistically equivalent fracture model was generated based on extensive underground fracture mapping data from the Exploratory Studies Facility at Yucca Mountain. Three-dimensional distinct block analyses, generated with the fracture patterns randomly selected from the fracture model, were developed with the consideration of in situ, thermal, seismic loads. In this study, field data, laboratory data, and numerical analyses are well integrated to provide a solution for the unique problem of modeling drift degradation throughout the regulatory period for repository performance.

  2. Probing Mechanical Properties of Rock with InSAR

    NASA Astrophysics Data System (ADS)

    Jónsson, S.

    2012-04-01

    Interferometric Synthetic Aperture Radar (InSAR) observations from satellites have revolutionized our crustal deformation measurement capabilities with its high spatial resolution, global coverage, and low cost. The high spatial resolution (typically 5-20 m) allows us to map many small-scale surface deformation phenomena in great detail. These include surface faulting, fissuring, fault creep, and other strain localization phenomena. Another advantage of the small-scale deformation mapping is that it can provide information about mechanical properties of near-surface rocks. Several studies have already been published on using InSAR to probe material properties of rock. Strain localizations at fault zones have been observed in co-seismic deformation fields near to large earthquakes and interpreted as expressions of weak fault zone materials that are a factor of two more compliant than the surrounding unbroken rock [Fialko et al., 2002]. Peltzer et al. [1999] argued that asymmetries in coseismic deformation patterns observed by InSAR showed evidence for non-linear elasticity, i.e. that the elastic moduli of shallow crustal material are different for compression and extension, due to small-scale cracks in the medium. This interpretation was later disputed by Funning et al. [2007], who provided an alternative explanation for observed deformation pattern based on along-strike variations in fault geometry and slip. In addition, observations and modeling of poro-elastic rebound after earthquakes have provided information about the difference in undrained and drained Poisson's ratio values of the near-surface rocks [Peltzer et al., 1996; Jónsson et al., 2003]. More recently we have used InSAR observations to put bounds on the tensional bulk strength of surface rocks. A dyke intrusion that took place in western Saudi Arabia in 2009 caused many moderate-sized earthquakes and extensive surface faulting. InSAR data of the area show that large-scale (40 km x 40 km) east

  3. Compaction bands in porous rocks: localization analysis using breakage mechanics

    NASA Astrophysics Data System (ADS)

    Das, Arghya; Nguyen, Giang; Einav, Itai

    2010-05-01

    It has been observed in fields and laboratory studies that compaction bands are formed within porous rocks and crushable granular materials (Mollema and Antonellini, 1996; Wong et al., 2001). These localization zones are oriented at high angles to the compressive maximum principal stress direction. Grain crushing and pore collapse are the integral parts of the compaction band formation; the lower porosity and increased tortuosity within such bands tend to reduce their permeability compared to the outer rock mass. Compaction bands may thereafter act as flow barriers, which can hamper the extraction or injection of fluid into the rocks. The study of compaction bands is therefore not only interesting from a geological viewpoint but has great economic importance to the extraction of oil or natural gas in the industry. In this paper, we study the formation of pure compaction bands (i.e. purely perpendicular to the principal stress direction) or shear-enhanced compaction bands (i.e. with angles close to the perpendicular) in high-porosity rocks using both numerical and analytical methods. A model based on the breakage mechanics theory (Einav, 2007a, b) is employed for the present analysis. The main aspect of this theory is that it enables to take into account the effect that changes in grain size distribution has on the constitutive stress-strain behaviour of granular materials at the microscopic level due to grain crushing. This microscopic phenomenon of grain crushing is explicitly linked with a macroscopic internal variable, called Breakage, so that the evolving grain size distribution can be continuously monitored at macro scale during the process of deformation. Through the inclusion of an appropriate parameter the model is also able to capture the effects of pore collapse on the macroscopic response. Its possession of few physically identifiable parameters is another important feature which minimises the effort of their recalibration, since those become less

  4. Effects of bioleaching on the mechanical and chemical properties of waste rocks

    NASA Astrophysics Data System (ADS)

    Yin, Sheng-Hua; Wu, Ai-Xiang; Wang, Shao-Yong; Ai, Chun-Ming

    2012-01-01

    Bioleaching processes cause dramatic changes in the mechanical and chemical properties of waste rocks, and play an important role in metal recovery and dump stability. This study focused on the characteristics of waste rocks subjected to bioleaching. A series of experiments were conducted to investigate the evolution of rock properties during the bioleaching process. Mechanical behaviors of the leached waste rocks, such as failure patterns, normal stress, shear strength, and cohesion were determined through mechanical tests. The results of SEM imaging show considerable differences in the surface morphology of leached rocks located at different parts of the dump. The mineralogical content of the leached rocks reflects the extent of dissolution and precipitation during bioleaching. The dump porosity and rock size change under the effect of dissolution, precipitation, and clay transportation. The particle size of the leached rocks decreased due to the loss of rock integrity and the conversion of dry precipitation into fine particles.

  5. Towards a mechanical failure model for degrading permafrost rock slopes representing changes in rock toughness and infill

    NASA Astrophysics Data System (ADS)

    Mamot, Philipp; Krautblatter, Michael; Scandroglio, Riccardo

    2016-04-01

    The climate-induced degradation of permafrost in mountain areas can reduce the stability of rock slopes. An increasing number of rockfalls and rockslides originate from permafrost-affected rock faces. Discontinuity patterns and their geometrical and mechanical properties play a decisive role in controlling rock slope stability. Under thawing conditions the shear resistance of rock reduces due to lower friction along rock-rock contacts, decreasing fracture toughness of rock-ice contacts, diminishing fracture toughness of cohesive rock bridges and altered creep or fracture of the ice itself. Compressive strength is reduced by 20 to 50 % and tensile strength decreases by 15 to 70 % when intact saturated rock thaws (KRAUTBLATTER ET AL. 2013). Elevated water pressures in fractures can lead to reduced effective normal stresses and thus to lower shear strengths of fractures. However, the impact of degrading permafrost on the mechanical properties of intact or fractured rock still remains poorly understood. In this study, we develop a new approach for modeling the influence of degrading permafrost on the stability of high mountain rock slopes. Hereby, we focus on the effect of rock- and ice-mechanical changes along striking discontinuities onto the whole rock slope. We aim at contributing to a better rock-ice mechanical process understanding of degrading permafrost rocks. For parametrisation and subsequent calibration of our model, we chose a test site (2885 m a.s.l.) close by the Zugspitze summit in Germany. It reveals i) a potential rockslide at the south face involving 10E4m³ of rock and ii) permafrost occurrence due to ice-filled caves and fractures. Here we combine kinematic, geotechnical and thermal monitoring in the field with rock-mechanical laboratory tests and a 2D numerical failure modeling. Up to date, the following results underline the potential effects of thawing rock and fracture infill on the stability of steep rock slopes in theory and praxis: i. ERT and

  6. Nondestructive Methods to Characterize Rock Mechanical Properties at Low-Temperature: Applications for Asteroid Capture Technologies

    NASA Astrophysics Data System (ADS)

    Savage, Kara A.

    Recent government initiatives and commercial activities have targeted asteroids for in situ material characterization, manipulation, and possible resource extraction. Most of these activities and missions have proposed significant robotic components, given the risks and costs associated with manned missions. To successfully execute these robotic activities, detailed mechanical characteristics of the target space bodies must be known prior to contact, in order to appropriately plan and direct the autonomous robotic protocols. Unfortunately, current estimates of asteroid mechanical properties are based on limited direct information, and significant uncertainty remains specifically concerning internal structures, strengths, and elastic properties of asteroids. One proposed method to elucidate this information is through in situ, nondestructive testing of asteroid material immediately after contact, but prior to any manipulation or resource extraction activities. While numerous nondestructive rock characterization techniques have been widely deployed for terrestrial applications, these methods must be adapted to account for unique properties of asteroid material and environmental conditions of space. For example, asteroid surface temperatures may range from -100°C to 30°C due to diurnal cycling, and these low temperatures are especially noteworthy due to their deleterious influence on non-destructive testing. As a result, this thesis investigates the effect of low temperature on the mechanical characteristics and nondestructive technique responses of rock material. Initially, a novel method to produce low temperature rock samples was developed. Dry ice and methanol cooling baths of specific formulations were used to decrease rock to temperatures ranging from -60°C to 0°C. At these temperatures, shale, chalk, and limestone rock samples were exposed to several nondestructive and conventional mechanical tests, including Schmidt hammer, ultrasonic pulse velocity, point

  7. Site study plan for routine laboratory rock mechanics, Deaf Smith County Site, Texas: Revision 1

    SciTech Connect

    Not Available

    1987-12-01

    This Site Study Plan for Routine Laboratory Rock Mechanics describes routine laboratory testing to be conducted on rock samples collected as part of the characterization of the Deaf Smith County site, Texas. This study plan describes the early laboratory testing. Additional testing may be required and the type and scope of testing will be dependent upon the results of the early testing. This study provides for measurements of index, hydrological, mechanical, and chemical properties with tests which are standardized and used widely in geotechnical investigations. Another Site Study Plan for Nonroutine Laboratory Rock Mechanics describes laboratory testing of samples from the site to determine mechanical, thermomechanical, and thermal properties by less widely used methods, many of which have been developed specifically for characterization of the site. Data from laboratory tests will be used for characterization of rock strata, design of shafts and underground facilities, and modeling of repository behavior in support of resolution of both preclosure and postclosure issues. A tentative testing schedule and milestone log are given. A quality assurance program will be utilized to assure that activities affecting quality are performed correctly and that appropriate documentation is maintained. 18 refs., 8 figs., 3 tabs.

  8. [Synthesis of anabiosis autoinducers in non-spore-forming bacteria as a mechanism regulating their activity in soil and subsoil sedimentary rocks].

    PubMed

    Muliukin, A L; Demkina, E V; Kozlova, A N; Soina, V S; El'-Registan, G I

    2001-01-01

    Non-spore-forming bacteria of the genera Arthrobacter and Micrococcus, isolated from permafrost subsoil, were found to produce greater amounts of the d1 extracellular factor than closely related collection strains isolated from soil. The effect of this factor, responsible for cell transition to anabiosis, was not species-specific. Thus, the d1 crude preparation isolated from the culture liquid of the permafrost isolate Arthrobacter globiformis 245 produced an effect on the collection strain Arthrobacter globiformis B-1112 and also on Micrococcus luteus and Bacillus cereus. The crude d1 preparation from the permafrost isolate of Arthrobacter differed from the chemical analogue of this factor, 4n-hexylresorcinol, in the level of the induced cell response, which may have resulted from different cell sensitivity to various homologs of alkylhydroxybenzenes contained in the d1 preparation. Thus, additional evidence was obtained indicating that autoregulation of bacterial growth and development is implemented at the level of intercellular interactions in microbial communities. Abundant production of the d1 anabiosis-inducing factors by bacteria isolated from permafrost subsoil is probably a result of special antistress mechanisms responsible for the survival of these bacteria under extreme conditions of natural deep cooling.

  9. Microstructure in linear elasticity and scale effects: a reconsideration of basic rock mechanics and rock fracture mechanics

    NASA Astrophysics Data System (ADS)

    Exadaktylos, George E.; Vardoulakis, Ioannis

    2001-06-01

    An account on the role of higher order strain gradients in the mechanical behavior of elastic-perfectly brittle materials, such as rocks, is given that is based on a special grade-2 elasticity theory with surface energy as this was originated by Casal and Mindlin and further elaborated by the authors. The fundamental idea behind the theory is that the effect of the granular and polycrystalline nature of geomaterials (i.e. their microstructural features) on their macroscopic response may be modeled through the concept of volume cohesion forces, as well as surface forces rather than through intractable statistical mechanics concepts of the Boltzmann type. It is shown that the important phenomena of the localization of deformation in macroscopically homogeneous rocks under uniform tractions and of dependence of rock behavior on the specimen's dimensions, commonly known as size or scale effect, can be interpreted by using this 'non-local', higher order theory. These effects are demonstrated for the cases of the unidirectional tension test, and for the small circular hole under uniform internal pressure commonly known as the inflation test. The latter configuration can be taken as a first order approximation of the indentation test that is frequently used for the laboratory or in situ characterization of geomaterials. In addition, it is shown that the solution of the three basic crack deformation modes leads to cusping of the crack tips that is caused by the action of 'cohesive' double forces behind and very close to the tips, that tend to bring the two opposite crack lips in close contact, and further, it is demonstrated that the fracture toughness depends on the size of the crack, and thus it is not a fundamental property of the material. This latter outcome agrees with experimental results which indicate that materials with smaller cracks are more resistant to fracture than those with larger cracks.

  10. Double-Edge Sword of Sustained ROCK Activation in Prion Diseases through Neuritogenesis Defects and Prion Accumulation.

    PubMed

    Alleaume-Butaux, Aurélie; Nicot, Simon; Pietri, Mathéa; Baudry, Anne; Dakowski, Caroline; Tixador, Philippe; Ardila-Osorio, Hector; Haeberlé, Anne-Marie; Bailly, Yannick; Peyrin, Jean-Michel; Launay, Jean-Marie; Kellermann, Odile; Schneider, Benoit

    2015-08-01

    In prion diseases, synapse dysfunction, axon retraction and loss of neuronal polarity precede neuronal death. The mechanisms driving such polarization defects, however, remain unclear. Here, we examined the contribution of RhoA-associated coiled-coil containing kinases (ROCK), key players in neuritogenesis, to prion diseases. We found that overactivation of ROCK signaling occurred in neuronal stem cells infected by pathogenic prions (PrPSc) and impaired the sprouting of neurites. In reconstructed networks of mature neurons, PrPSc-induced ROCK overactivation provoked synapse disconnection and dendrite/axon degeneration. This overactivation of ROCK also disturbed overall neurotransmitter-associated functions. Importantly, we demonstrated that beyond its impact on neuronal polarity ROCK overactivity favored the production of PrPSc through a ROCK-dependent control of 3-phosphoinositide-dependent kinase 1 (PDK1) activity. In non-infectious conditions, ROCK and PDK1 associated within a complex and ROCK phosphorylated PDK1, conferring basal activity to PDK1. In prion-infected neurons, exacerbated ROCK activity increased the pool of PDK1 molecules physically interacting with and phosphorylated by ROCK. ROCK-induced PDK1 overstimulation then canceled the neuroprotective α-cleavage of normal cellular prion protein PrPC by TACE α-secretase, which physiologically precludes PrPSc production. In prion-infected cells, inhibition of ROCK rescued neurite sprouting, preserved neuronal architecture, restored neuronal functions and reduced the amount of PrPSc. In mice challenged with prions, inhibition of ROCK also lowered brain PrPSc accumulation, reduced motor impairment and extended survival. We conclude that ROCK overactivation exerts a double detrimental effect in prion diseases by altering neuronal polarity and triggering PrPSc accumulation. Eventually ROCK emerges as therapeutic target to combat prion diseases.

  11. Double-Edge Sword of Sustained ROCK Activation in Prion Diseases through Neuritogenesis Defects and Prion Accumulation

    PubMed Central

    Alleaume-Butaux, Aurélie; Nicot, Simon; Pietri, Mathéa; Baudry, Anne; Dakowski, Caroline; Tixador, Philippe; Ardila-Osorio, Hector; Haeberlé, Anne-Marie; Bailly, Yannick; Peyrin, Jean-Michel; Launay, Jean-Marie; Kellermann, Odile; Schneider, Benoit

    2015-01-01

    In prion diseases, synapse dysfunction, axon retraction and loss of neuronal polarity precede neuronal death. The mechanisms driving such polarization defects, however, remain unclear. Here, we examined the contribution of RhoA-associated coiled-coil containing kinases (ROCK), key players in neuritogenesis, to prion diseases. We found that overactivation of ROCK signaling occurred in neuronal stem cells infected by pathogenic prions (PrPSc) and impaired the sprouting of neurites. In reconstructed networks of mature neurons, PrPSc-induced ROCK overactivation provoked synapse disconnection and dendrite/axon degeneration. This overactivation of ROCK also disturbed overall neurotransmitter-associated functions. Importantly, we demonstrated that beyond its impact on neuronal polarity ROCK overactivity favored the production of PrPSc through a ROCK-dependent control of 3-phosphoinositide-dependent kinase 1 (PDK1) activity. In non-infectious conditions, ROCK and PDK1 associated within a complex and ROCK phosphorylated PDK1, conferring basal activity to PDK1. In prion-infected neurons, exacerbated ROCK activity increased the pool of PDK1 molecules physically interacting with and phosphorylated by ROCK. ROCK-induced PDK1 overstimulation then canceled the neuroprotective α-cleavage of normal cellular prion protein PrPC by TACE α-secretase, which physiologically precludes PrPSc production. In prion-infected cells, inhibition of ROCK rescued neurite sprouting, preserved neuronal architecture, restored neuronal functions and reduced the amount of PrPSc. In mice challenged with prions, inhibition of ROCK also lowered brain PrPSc accumulation, reduced motor impairment and extended survival. We conclude that ROCK overactivation exerts a double detrimental effect in prion diseases by altering neuronal polarity and triggering PrPSc accumulation. Eventually ROCK emerges as therapeutic target to combat prion diseases. PMID:26241960

  12. Geometric Effect of Asperities on Shear Mechanism of Rock Joints

    NASA Astrophysics Data System (ADS)

    Fathi, Ali; Moradian, Zabihallah; Rivard, Patrice; Ballivy, Gérard; Boyd, Andrew J.

    2016-03-01

    Three-dimensional tracking of changes of asperities is one of the most important ways to illustrate shear mechanism of rock joints during testing. In this paper, the changes of the role of asperities during different stages of shearing are described by using a new methodology for the characterization of the asperities. The basis of the proposed method is the examination of the three-dimensional roughness of joint surfaces scanned before and after shear testing. By defining a concept named `tiny window', the geometric model of the joint surfaces is reconstructed. Tiny windows are expressed as a function of the x and y coordinates, the height (z coordinate), and the angle of a small area of the surface. Constant normal load (CNL) direct shear tests were conducted on replica joints and, by using the proposed method, the distribution and size of contact and damaged areas were identified. Image analysis of the surfaces was used to verify the results of the proposed method. The results indicated that the proposed method is suitable for determining the size and distribution of the contact and damaged areas at any shearing stage. The geometric properties of the tiny windows in the pre-peak, peak, post-peak softening, and residual shearing stages were investigated based on their angle and height. It was found that tiny windows that face the shear direction, especially the steepest ones, have a primary role in shearing. However, due to degradation of asperities at higher normal stresses and shear displacements, some of the tiny windows that do not initially face the shear direction also come in contact. It was also observed that tiny windows with different heights participate in the shearing process, not just the highest ones. Total contact area of the joint surfaces was considered as summation of just-in-contact areas and damaged areas. The results of the proposed method indicated that considering differences between just-in-contact areas and damaged areas provide useful

  13. Workshop on rock mechanics issues in repository design and performance assessment

    SciTech Connect

    1996-04-01

    The Center for Nuclear Waste Regulatory Analyses organized and hosted a workshop on ``Rock Mechanics Issues in Repository Design and Performance Assessment`` on behalf its sponsor the U.S. Nuclear Regulatory Commission (NRC). This workshop was held on September 19- 20, 1994 at the Holiday Inn Crowne Plaza, Rockville, Maryland. The objectives of the workshop were to stimulate exchange of technical information among parties actively investigating rock mechanics issues relevant to the proposed high-level waste repository at Yucca Mountain and identify/confirm rock mechanics issues important to repository design and performance assessment The workshop contained three technical sessions and two panel discussions. The participants included technical and research staffs representing the NRC and the Department of Energy and their contractors, as well as researchers from the academic, commercial, and international technical communities. These proceedings include most of the technical papers presented in the technical sessions and the transcripts for the two panel discussions. Selected papers have been indexed separately for inclusion the Energy Science and Technology Database.

  14. Geophysical analysis of rock glacier internal structure and implications for deformation mechanics

    NASA Astrophysics Data System (ADS)

    Florentine, C. E.; Skidmore, M. L.; Speece, M. A.; Link, C. A.; Locke, W. W.; Carr, C. G.; Shaw, C. A.

    2011-12-01

    An analysis of the internal composition and structure on the active portion of the Lone Peak Rock Glacier (LPRG), Madison range, southwest Montana revealed links between internal structure and surface topography. Seismic refraction surveys performed along transverse and longitudinal profiles corroborate borehole and excavation data by demonstrating a consistent and distinct transition from unconsolidated (unfrozen) surface debris (2-3 m thick) to a consolidated (frozen) subsurface material. Refraction velocities for the seismic survey transects were relatively consistent along their length with 400 m s-1 for the upper layer detected, and 3500 m s-1 for the lower layer detected at a depth of 2-3 m. This second velocity of 3500 m s-1 is consistent with other observed refraction velocities for ice. Ground penetrating radar (GPR) data along similar longitudinal and transverse profiles identified up-slope dipping structures to a depth of ~10 m, consistent with layering of materials with contrasting radar properties within the ice-rock unit. The GPR data is interpreted as a sequence of alternating debris-poor and debris-rich layers which dip upslope toward the rock-glacier headwall along the longitudinal profile, and which show correspondence with transverse ridges at the surface. The presence of fault bounded blocks (i.e. structural horses) detected in the longitudinal GPR data suggests passive roof duplex thrust faulting, in which the roof sequence - unconsolidated (unfrozen) debris - has not been displaced toward the foreland (down glacier), but has been underthrust by the duplex. Transverse ridges commonly characterize rock glacier surfaces in a range of locations worldwide. Approximately one third of 383 rock glaciers inventoried in southwest Montana demonstrate pronounced transverse ridges. It has previously been suggested that transverse ridges are the product of thrusting, which is caused by compressive flow in rock glaciers. Thrusting however has not been

  15. Mechanism of Mesozoic Volcanism in Northeastern China: Evidence from New Distribution Maps of Volcanic Rock and Petrogenesis of Acid Rock in Deep Songliao Basin

    NASA Astrophysics Data System (ADS)

    Meng, Fanchao; Liu, Jiaqi; Rasskazov, Sergei; Gao, Jinliang; Zhang, Yutao

    2014-05-01

    Northeastern China is located in the eastern segment of the Central Asian Orogenic belt, which is characterized by widespread Mesozoic volcanic rocks. At present, there are two different opinions concerning the mechanism of volcanism: one proposal is that volcanism was associated with the closure of Mongolia-Okhotsk (MO) Bay, but another suggestion is that the Mesozoic volcanism is controlled by the subduction of Paleo-Pacific plate. However, most studies have mainly focused on the Mesozoic volcanic rocks in Great Xing'an Range(GXR), lack of evidence from Songliao Basin. In order to exactly reveal the mechanism of volcanic rocks in Northeastern China, five new distribution maps of volcanic rocks in Northeast China are drawn and petrogenesis of Mesozoic volcanic rocks in Songliao Basin are obtained. Based on 1: 50000 geological maps, five distribution maps of volcanic rocks (1:2000000) in Northeastern China are recompiled: Early Jurassic, Middle Jurassic, Late Jurassic, Early Cretaceous, and Late Cretaceous. The Early Jurassic volcanic rocks predominantly occur in the eastern Heilongjiang-Jilin province, with minor in Manzhouli in the western. The Middle Jurassic volcanic rocks are mainly founded in the western Liaoning provinces. The Early-Middle Jurassic volcanic rocks(170-146Ma) belong chemically to sub-alkaline series, implying an active continental margin setting. The Late Jurassic volcanic rocks(146-122Ma) mainly occur in the western GXR area, and the magma derived from enriched lithospheric mantle which is closely associated with the subduction of MO plate. The Early Cretaceous volcanic rocks(122-102Ma), widespread in GXR and Songliao basin, are mainly acid and erupt in extensional setting, probably associated with the lithospheric thinning and asthenospheric mantle upwelling caused by subduction of the Paleo-Pacific plate beneath eastern China. Constraints on the timing of MO Bay closure and the motion direction of Paleo-Pacific plate, we infer that:(1) In

  16. U.S. National Committee for Rock Mechanics; and Conceptual model of fluid infiltration in fractured media. Project summary, July 28, 1997--July 27, 1998

    SciTech Connect

    1998-09-01

    The title describes the two tasks summarized in this report. The remainder of the report contains information on meetings held or to be held on the subjects. The US National Committee for Rock Mechanics (USNC/RM) provides for US participation in international activities in rock mechanics, principally through adherence to the International Society for Rock Mechanics (ISRM). It also keeps the US rock mechanics community informed about new programs directed toward major areas of national concern in which rock mechanics problems represent critical or limiting factors, such as energy resources, excavation, underground storage and waste disposal, and reactor siting. The committee also guides or produces advisory studies and reports on problem areas in rock mechanics. A new panel under the auspices of the US National Committee for Rock Mechanics has been appointed to conduct a study on Conceptual Models of Fluid Infiltration in Fractured Media. The study has health and environmental applications related to the underground flow of pollutants through fractured rock in and around mines and waste repositories. Support of the study has been received from the US Nuclear Regulatory Commission and the Department of Energy`s Yucca Mountain Project Office. The new study builds on the success of a recent USNC/RM report entitled Rock Fractures and Fluid Flow: Contemporary Understanding and Applications (National Academy Press, 1996, 551 pp.). A summary of the new study is provided.

  17. Classification of mechanical heterogeneity of petroleum reservoir rocks optimal for radial drilling technology

    NASA Astrophysics Data System (ADS)

    Ivakhnenko, Aleksandr; Seitova, Nargiza; Dzhafarov, Tarlan

    2013-04-01

    The radial drilling technology involves drilling lateral horizontal boreholes of small diameter and up to one hundred meters long with the possibility of placing several wells within productive petroleum reservoirs. The usage of the radial drilling involves making small diameter horizontal perforations in the rock formation by using water jet and the jet propulsion which facilitate the penetration along the rock formation. In this study was reviewed the effectiveness of water jet propulsion for different mechanical heterogeneity of rocks. Experiments were carried out to investigate the variation in water jet penetration in different rock types, such as sandstones, carbonates, conglomerates, dolomites, limestone, etc., and their mechanical variations including unconsolidated and cemented members. There were also addressed cases when the pores of the rocks were filled with different minerals including clays and quartz. It was found that the method of penetration differ for mechanical heterogeneity of rocks. The results are shown for the different types of rocks and degree of their porosity variations. The efficiency of the rock penetration obtained by dividing the energy of the jet by the volume of hole created is discussed in relation to rock types and the method of rock failure.

  18. Mechanical heterogeneities along carbonate-bearing faults constrained from field and rock deformation experiments

    NASA Astrophysics Data System (ADS)

    Collettini, Cristiano; Carpenter, Brett; Tesei, Telemaco; Viti, Cecilia; Di Stefano, Giuseppe; Mollo, Silvio; Scarlato, Piergiorgio; Chiaraluce, Lauro

    2014-05-01

    Recent high-resolution GPS and seismological data have revealed that tectonic faults exhibit complex, multi-mode slip behavior. One way to improve our understanding of processes controlling the mode of slip is to study fault rock microstructures, collected from ancient faults exposed at Earth's surface or in deep boreholes and to characterize friction of the collected fault rocks. In several seismically active regions, like Italy, Greece, Iran, and China, a significant number of earthquakes nucleate and/or propagate through carbonates. For these reasons, we have been working to improve the characterization of carbonate bearing faults by integrating field and microstructural studies with mechanical data. Along some portions of carbonate fault zones: 1) the localization of deformation along sharp principal slipping zones (0.1-1 mm) made of fine-grained (0.1-10 μm) ultracataclasite and 2) the velocity weakening behavior of this material suggest a fast and seismic mechanism. Microstructural evidence indicates that seismic mechanisms are associated with thermally activated processes (i.e. dehydration and decarbonation). In other portions of these fault zones: 1) the distribution of deformation over thick (< 200 m) shear zones affected by pressure solution of carbonates and frictional sliding along foliated and clay-rich (illite-smectite) horizons, and 2) the velocity strengthening behavior of these foliated rocks indicate a slow and aseismic slip behavior. Sharp principal slipping zones that show high friction and significant re-strengthening during hold periods, indicate a fault patch capable of unstable slip with the ability to regain elastic strain energy. Conversely, phyllosilicate-rich shear zones showing low friction with no frictional healing suggest fault patches that can slip slowly and continuously with time. We are currently using a new biaxial apparatus with a pressure vessel to work on a large, 20x20 cm, experimental fault. In this fault we are reproducing

  19. Rock Degradation by Alkali Metals: A Possible Lunar Erosion Mechanism.

    PubMed

    Naughton, J J; Barnes, I L; Hammond, D A

    1965-08-06

    When rocks melt under ultrahigh-vacuum conditions, their alkali components volatilize as metals. These metal vapors act to comminute polycrystalline rocks to their component minerals. The resultant powder is porous and loosely packed and its characteristics may be compatible with the lunar surface as revealed by the Ranger photographs. If meteorite impact or lunar volcanism has produced vaporization or areas of molten lava, alkali erosion may have given dust of this character in adjacent solid areas.

  20. Chemically- and mechanically-mediated influences on the transport and mechanical characteristics of rock fractures

    SciTech Connect

    Min, K.-B.; Rutqvist, J.; Elsworth, D.

    2009-02-01

    A model is presented to represent changes in the mechanical and transport characteristics of fractured rock that result from coupled mechanical and chemical effects. The specific influence is the elevation of dissolution rates on contacting asperities, which results in a stress- and temperature-dependent permanent closure. A model representing this pressure-dissolution-like behavior is adapted to define the threshold and resulting response in terms of fundamental thermodynamic properties of a contacting fracture. These relations are incorporated in a stress-stiffening model of fracture closure to define the stress- and temperature-dependency of aperture loss and behavior during stress and temperature cycling. These models compare well with laboratory and field experiments, representing both decoupled isobaric and isothermal responses. The model was applied to explore the impact of these responses on heated structures in rock. The result showed a reduction in ultimate induced stresses over the case where chemical effects were not incorporated, with permanent reduction in final stresses after cooling to ambient conditions. Similarly, permeabilities may be lower than they were in the case where chemical effects were not considered, with a net reduction apparent even after cooling to ambient temperature. These heretofore-neglected effects may have a correspondingly significant impact on the performance of heated structures in rock, such as repositories for the containment of radioactive wastes.

  1. Is rock slope instability in high-mountain systems driven by topo-climatic, paraglacial or rock mechanical factors? - A question of scale!

    NASA Astrophysics Data System (ADS)

    Messenzehl, Karoline; Dikau, Richard

    2016-04-01

    Due to the emergent and (often non-linear) complex nature of mountain systems the key small-scale system properties responsible for rock slope instability contrast to those being dominant at larger spatial scales. This geomorphic system behaviour has major epistemological consequences for the study of rockfalls and associated form-process-relationships. As each scale requires its own scientific explanation, we cannot simply upscale bedrock-scale findings and, in turn, we cannot downscale the valley-scale knowledge to smaller phenomena. Here, we present a multi-scale study from the Turtmann Valley (Swiss Alps), that addresses rock slope properties at three different geomorphic levels: (i) regional valley scale, (ii) the hillslope scale and (iii) the bedrock scale. Using this hierarchical approach, we aim to understand the key properties of high-mountain systems responsible for rockfall initiation with respect to the resulting form-process-relationship at each scale. (i) At the valley scale (110 km2) rock slope instability was evaluated using a GIS-based modelling approach. Topo-climatic parameters, i.e. the permafrost distribution and the time since deglaciation after LGM were found to be the key variables causative for the regional-scale bedrock erosion and the storage of 62.3 - 65.3 x 106 m3 rockfall sediments in the hanging valleys (Messenzehl et al. 2015). (ii) At the hillslope scale (0.03 km2) geotechnical scanline surveys of 16 rock slopes and one-year rock temperature data of 25 ibuttons reveal that the local rockfall activity and the resulting deposition of individual talus slope landforms is mainly controlled by the specific rock mass strength with respect to the slope aspect, than being a paraglacial reaction. Permafrost might be only of secondary importance for the present-day rock mechanical state as geophysical surveys disprove the existence of frozen bedrock below 2600 m asl. (Messenzehl & Draebing 2015). (iii) At the bedrock scale (0.01 mm - 10 m) the

  2. Mechanical Behavior of the Near-field Host Rock Surrounding Excavations

    SciTech Connect

    Kelkar, Sharad M.; Stauffer, Philip H.; Robinson, Bruce Alan

    2015-01-09

    This report is being prepared under the FY14 activity FT-14LA0818069, Mechanical and Hydrological Behavior of the Near-Field Host Rock Surrounding Excavations, and fulfills the Los Alamos National Laboratory deliverable M4FT-14LA08180610, which in PICS:NE is titled “Draft report, Test Plan for Mechanical and Hydrological Behavior of the Near-field Host Rock Surrounding Excavations.” Since the report is an intermediate deliverable intended as input to the eventual test plan for this test, rather than being an actual test plan, the activity title is used as the title of this document to avoid confusion as to the contents in the report. This report summarizes efforts to simulate mechanical processes occurring within a hypothetical high-level waste (HLW) repository in bedded salt. The report summarizes work completed since the last project deliverable, “Coupled model for heat and water transport in a high level waste repository in salt “, a Level 2 milestone submitted to DOE in September 2013 (Stauffer et al., 2013).

  3. Determination of indium in standard rocks by neutron activation analysis.

    PubMed

    Johansen, O; Steinnes, E

    1966-08-01

    A rapid neutron activation method for the determination of indium in rocks, based on 54 min (116m)In, is described. The method has been applied to a series of geochemical standards including granite G-1 and diabase W-1. The precision is better than +/- 5% for samples containing more than 5 x 10(-10)g indium. Good agreement with previously published values for G-1 and W-1 has been obtained.

  4. [Inflammasome: activation mechanisms].

    PubMed

    Suárez, Raibel; Buelvas, Neudo

    2015-03-01

    Inflammation is a rapid biologic response of the immune system in vascular tissues, directed to eliminate stimuli capable of causing damage and begin the process of repair. The macromolecular complexes known as "inflammasomes" are formed by a receptor, either NOD (NLR) or ALR, the receptor absent in melanoma 2 (AIM2). In addition, the inflammasome is formed by the speck-like protein associated to apoptosis (ASC) and procaspase-1, that may be activated by variations in the ionic and intracellular and extracellular ATP concentrations; and the loss of stabilization of the fagolisosomme by internalization of insoluble crystals and redox mechanisms. As a result, there is activation of the molecular platform and the processing of inflammatory prointerleukins to their active forms. There are two modalities of activation of the inflammasome: canonical and non-canonical, both capable of generating effector responses. Recent data associate NLRP 3, IL-1β and IL-18 in the pathogenesis of a variety of diseases, including atherosclerosis, type II diabetes, hyperhomocysteinemia, gout, malaria and hypertension. The inflammasome cascade is emerging as a new chemotherapeutic target in these diseases. In this review we shall discuss the mechanisms of activation and regulation of the inflammasome that stimulate, modulate and resolve inflammation.

  5. Water and abrasive jetting, and mechanical techniques expedite hard rock drilling

    SciTech Connect

    Kolle, J.J.

    1998-04-20

    Construction activities that require the placement of gas, electrical, or communication utilities in hard rock will benefit from lightweight systems capable of precisely drilling short, constant-radius arcs. Existing mechanical drilling systems are capable of drilling shallow directional holes, but the equipment is heavy, drilling rates are low, and costs are high. A comparison of approaches for rapidly drilling small-diameter (25--50 mm) and near-surface holes along a short-radius (30 m) arc, in a variety of hard rock types, is describes. Four approaches are considered: (1) rotary diamond drilling with a downhole motor; (2) ultra-high pressure (UHP) water jet drilling; (3) mechanically assisted UHP water jet drilling; and (4) abrasive jet drilling -- abrasive water jet and abrasive slurry jet. Data relating mechanical and hydraulic drilling parameters for each approach were compiled from literature and drilling tests for all four techniques. The drilling data are summarized in a common format to provide direct drilling efficiency comparisons for: jet pressure and hydraulic power, and thrust and torque requirements and abrasive feed.

  6. The three-dimension model for the rock-breaking mechanism of disc cutter and analysis of rock-breaking forces

    NASA Astrophysics Data System (ADS)

    Zhang, Zhao-Huang; Sun, Fei

    2012-06-01

    To study the rock deformation with three-dimensional model under rolling forces of disc cutter, by carrying out the circular-grooving test with disc cutter rolling around on the rock, the rock mechanical behavior under rolling disc cutter is studied, the mechanical model of disc cutter rolling around the groove is established, and the theory of single-point and double-angle variables is proposed. Based on this theory, the physics equations and geometric equations of rock mechanical behavior under disc cutters of tunnel boring machine (TBM) are studied, and then the balance equations of interactive forces between disc cutter and rock are established. Accordingly, formulas about normal force, rolling force and side force of a disc cutter are derived, and their validity is studied by tests. Therefore, a new method and theory is proposed to study rock-breaking mechanism of disc cutters.

  7. Heterogeneities of mechanical properties in potential geothermal reservoir rocks of the North German Basin

    NASA Astrophysics Data System (ADS)

    Reyer, D.; Philipp, S. L.

    2012-04-01

    Heterogeneous rock properties in terms of layering and complex infrastructure of fault zones are typical phenomena in sedimentary basins such as the North German Basin. To be able to model reservoir stimulation in layered stratifications and to better adapt the drilling strategy to the rock mechanical conditions it is important to have knowledge about the effects of heterogeneous rock properties on fracture propagation and fault zone infrastructure for typical sedimentary reservoir rocks in the North German Basin. Therefore we aim at quantifying these properties by performing structural geological field studies in outcrop analogues combined with laboratory analyses. The field studies in Rotliegend sandstones (Lower Permian), the sandstones of the Middle Bunter (Lower Triassic) and the sandstones of the Upper Keuper (Upper Triassic) focus on 1) host rock fracture systems and 2) fault zone infrastructure. We analyse quantitatively the dimension, geometry, persistence and connectivity of fracture systems separately for host rocks and fault damage zones. The results show that in rocks with distinctive layering (sandstones and shales) natural fractures are often restricted to individual layers, that is, they are stratabound. The probability of fracture arrest seems to depend on the stiffness contrast between the two layers and on the thickness of the softer layer. The field studies are complemented by systematic sampling to obtain mechanical property variations caused by the layering. For the samples we measure the parameters Young's modulus, compressive and tensile strengths, elastic strain energy, density and porosity. The results show that the mechanical properties vary considerably and many samples are clearly anisotropic. That is, samples taken perpendicular to layering commonly have higher strengths but lower stiffnesses than those taken parallel to layering. We combine the results of laboratory analyses and field measurements to specify the mechanical

  8. Event triggered data acquisition in the Rock Mechanics Laboratory upgrades and revisions

    SciTech Connect

    Hardy, R.D.

    1997-06-01

    This paper describes updates and revisions to the data acquisition computer program DATAVG which has served as the basic data collection system for the Sandia National Laboratories Geomechanics Department, Rock Mechanics Laboratory since late 1992. DATAVG was first described in Event Triggered Data Acquisition in the Rock Mechanics Laboratory, [Hardy, 1993]. DATAVG has been modified to incorporate numerous user-requested enhancements and a few bug fixes. In this paper these changes to DATAVG are described.

  9. Correlating P-wave Velocity with the Physico-Mechanical Properties of Different Rocks

    NASA Astrophysics Data System (ADS)

    Khandelwal, Manoj

    2013-04-01

    In mining and civil engineering projects, physico-mechanical properties of the rock affect both the project design and the construction operation. Determination of various physico-mechanical properties of rocks is expensive and time consuming, and sometimes it is very difficult to get cores to perform direct tests to evaluate the rock mass. The purpose of this work is to investigate the relationships between the different physico-mechanical properties of the various rock types with the P-wave velocity. Measurement of P-wave velocity is relatively cheap, non-destructive and easy to carry out. In this study, representative rock mass samples of igneous, sedimentary, and metamorphic rocks were collected from the different locations of India to obtain an empirical relation between P-wave velocity and uniaxial compressive strength, tensile strength, punch shear, density, slake durability index, Young's modulus, Poisson's ratio, impact strength index and Schmidt hammer rebound number. A very strong correlation was found between the P-wave velocity and different physico-mechanical properties of various rock types with very high coefficients of determination. To check the sensitivity of the empirical equations, Students t test was also performed, which confirmed the validity of the proposed correlations.

  10. Mechanically Activated Ion Channels

    PubMed Central

    Ranade, Sanjeev S.; Syeda, Ruhma; Patapoutian, Ardem

    2015-01-01

    Mechanotransduction, the conversion of physical forces into biochemical signals, is an essential component of numerous physiological processes including not only conscious senses of touch and hearing, but also unconscious senses such as blood pressure regulation. Mechanically activated (MA) ion channels have been proposed as sensors of physical force, but the identity of these channels and an understanding of how mechanical force is transduced has remained elusive. A number of recent studies on previously known ion channels along with the identification of novel MA ion channels have greatly transformed our understanding of touch and hearing in both vertebrates and invertebrates. Here, we present an updated review of eukaryotic ion channel families that have been implicated in mechanotransduction processes and evaluate the qualifications of the candidate genes according to specified criteria. We then discuss the proposed gating models for MA ion channels and highlight recent structural studies of mechanosensitive potassium channels. PMID:26402601

  11. Mechanically Activated Ion Channels.

    PubMed

    Ranade, Sanjeev S; Syeda, Ruhma; Patapoutian, Ardem

    2015-09-23

    Mechanotransduction, the conversion of physical forces into biochemical signals, is essential for various physiological processes such as the conscious sensations of touch and hearing, and the unconscious sensation of blood flow. Mechanically activated (MA) ion channels have been proposed as sensors of physical force, but the identity of these channels and an understanding of how mechanical force is transduced has remained elusive. A number of recent studies on previously known ion channels along with the identification of novel MA ion channels have greatly transformed our understanding of touch and hearing in both vertebrates and invertebrates. Here, we present an updated review of eukaryotic ion channel families that have been implicated in mechanotransduction processes and evaluate the qualifications of the candidate genes according to specified criteria. We then discuss the proposed gating models for MA ion channels and highlight recent structural studies of mechanosensitive potassium channels.

  12. RhoA/ROCK downregulates FPR2-mediated NADPH oxidase activation in mouse bone marrow granulocytes.

    PubMed

    Filina, Julia V; Gabdoulkhakova, Aida G; Safronova, Valentina G

    2014-10-01

    Polymorphonuclear neutrophils (PMNs) express the high and low affinity receptors to formylated peptides (mFPR1 and mFPR2 in mice, accordingly). RhoA/ROCK (Rho activated kinase) pathway is crucial for cell motility and oxidase activity regulated via FPRs. There are contradictory data on RhoA-mediated regulation of NADPH oxidase activity in phagocytes. We have shown divergent Rho GTPases signaling via mFPR1 and mFPR2 to NADPH oxidase in PMNs from inflammatory site. The present study was aimed to find out the role of RhoA/ROCK in the respiratory burst activated via mFPR1 and mFPR2 in the bone marrow PMNs. Different kinetics of RhoA activation were detected with 0.1μM fMLF and 1μM WKYMVM operating via mFPR1 and mFPR2, accordingly. RhoA was translocated in fMLF-activated cells towards the cell center and juxtamembrane space versus uniform allocation in the resting cells. Specific inhibition of RhoA by CT04, Rho inhibitor I, weakly depressed the respiratory burst induced via mFPR1, but significantly increased the one induced via mFPR2. Inhibition of ROCK, the main effector of RhoA, by Y27632 led to the same effect on the respiratory burst. Regulation of mFPR2-induced respiratory response by ROCK was impossible under the cytoskeleton disruption by cytochalasin D, whereas it persisted in the case of mFPR1 activation. Thus we suggest RhoA to be one of the regulatory and signal transduction components in the respiratory burst through FPRs in the mouse bone marrow PMNs. Both mFPR1 and mFPR2 binding with a ligand trigger the activation of RhoA. FPR1 signaling through RhoA/ROCK increases NADPH-oxidase activity. But in FPR2 action RhoA/ROCK together with cytoskeleton-linked systems down-regulates NADPH-oxidase. This mechanism could restrain the reactive oxygen species dependent damage of own tissues during the chemotaxis of PMNs and in the resting cells.

  13. Hydro-mechanically coupled modelling of deep-seated rock slides in the surroundings of reservoirs

    NASA Astrophysics Data System (ADS)

    Lechner, Heidrun; Preh, Alexander; Zangerl, Christian

    2016-04-01

    In order to enhance the understanding of the behaviour of deep-seated rock slides in the surroundings of large dam reservoirs, this study concentrates on failure mechanisms, deformation processes and the ability of self-stabilisation of rock slides influenced by reservoirs. Particular focus is put on internal rock mass deformations, progressive topographical slope changes due to reservoir impoundment and shear displacements along the basal shear zone in relation to its shear strength properties. In this study, a two-dimensional numerical rock slide model is designed by means of the Universal Distinct Element Code UDEC and investigated concerning different groundwater flow scenarios. These include: (i) a completely drained rock slide model, (ii) a model with fully saturated rock mass below an inclined groundwater table and (iii) a saturated groundwater model with a reservoir at the slope toe. Slope displacements initiate when the shear strength properties of the basal shear zone are at or below the critical parameters for the limit-equilibrium state and continue until a numerical equilibrium is reached due to deformation- and displacement-based geometrical changes. The study focuses on the influence of a reservoir at the toe of a rock slide and tries to evaluate the degree of displacement which is needed for a re-stabilisation in relation to the geometrical characteristics of the rock slide. Besides, challenges and limitations of applied distinct element methods to simulate large strain and displacements of deep-seated rock slides are discussed. The ongoing study will help to understand the deformation behaviour of deep-seated pre-existing rock slides in fractured rock mass during initial impounding and will be part of a hazard assessment for large reservoirs.

  14. Experimental Studies on the Mechanical Behaviour of Rock Joints with Various Openings

    NASA Astrophysics Data System (ADS)

    Li, Y.; Oh, J.; Mitra, R.; Hebblewhite, B.

    2016-03-01

    The mechanical behaviour of rough joints is markedly affected by the degree of joint opening. A systematic experimental study was conducted to investigate the effect of the initial opening on both normal and shear deformations of rock joints. Two types of joints with triangular asperities were produced in the laboratory and subjected to compression tests and direct shear tests with different initial opening values. The results showed that opened rock joints allow much greater normal closure and result in much lower normal stiffness. A semi-logarithmic law incorporating the degree of interlocking is proposed to describe the normal deformation of opened rock joints. The proposed equation agrees well with the experimental results. Additionally, the results of direct shear tests demonstrated that shear strength and dilation are reduced because of reduced involvement of and increased damage to asperities in the process of shearing. The results indicate that constitutive models of rock joints that consider the true asperity contact area can be used to predict shear resistance along opened rock joints. Because rock masses are loosened and rock joints become open after excavation, the model suggested in this study can be incorporated into numerical procedures such as finite-element or discrete-element methods. Use of the model could then increase the accuracy and reliability of stability predictions for rock masses under excavation.

  15. Assessment of rock wool as support material for on-site sanitation: hydrodynamic and mechanical characterization.

    PubMed

    Wanko, Adrien; Laurent, Julien; Bois, Paul; Mosé, Robert; Wagner-Kocher, Christiane; Bahlouli, Nadia; Tiffay, Serge; Braun, Bouke; Provo kluit, Pieter-Willem

    2016-01-01

    This study proposes mechanical and hydrodynamic characterization of rock wool used as support material in compact filter. A double-pronged approach, based on experimental simulation of various physical states of this material was done. First of all a scanning electron microscopy observation allows to highlight the fibrous network structure, the fibres sizing distribution and the atomic absorption spectrum. The material was essentially lacunar with 97 ± 2% of void space. Static compression tests on variably saturated rock wool samples provide the fact that the strain/stress behaviours depend on both the sample conditioning and the saturation level. Results showed that water exerts plastifying effect on mechanical behaviour of rock wool. The load-displacement curves and drainage evolution under different water saturation levels allowed exhibiting hydraulic retention capacities under stress. Finally, several tracer experiments on rock wool column considering continuous and batch feeding flow regime allowed: (i) to determine the flow model for each test case and the implications for water dynamic in rock wool medium, (ii) to assess the rock wool double porosity and discuss its advantages for wastewater treatment, (iii) to analyse the benefits effect for water treatment when the high level of rock wool hydric retention was associated with the plug-flow effect, and (iv) to discuss the practical contributions for compact filter conception and management.

  16. Deformation mechanisms in a coal mine roadway in extremely swelling soft rock.

    PubMed

    Li, Qinghai; Shi, Weiping; Yang, Renshu

    2016-01-01

    The problem of roadway support in swelling soft rock was one of the challenging problems during mining. For most geological conditions, combinations of two or more supporting approaches could meet the requirements of most roadways; however, in extremely swelling soft rock, combined approaches even could not control large deformations. The purpose of this work was to probe the roadway deformation mechanisms in extremely swelling soft rock. Based on the main return air-way in a coal mine, deformation monitoring and geomechanical analysis were conducted, as well as plastic zone mechanical model was analysed. Results indicated that this soft rock was potentially very swelling. When the ground stress acted alone, the support strength needed in situ was not too large and combined supporting approaches could meet this requirement; however, when this potential released, the roadway would undergo permanent deformation. When the loose zone reached 3 m within surrounding rock, remote stress p ∞ and supporting stress P presented a linear relationship. Namely, the greater the swelling stress, the more difficult it would be in roadway supporting. So in this extremely swelling soft rock, a better way to control roadway deformation was to control the releasing of surrounding rock's swelling potential.

  17. Mapping the mechanical properties of rocks using automated microindentation tests

    NASA Astrophysics Data System (ADS)

    Masson, Yder; Pride, Steven R.

    2015-10-01

    A microindentation scanner is constructed that measures the spatial fluctuation in the elastic properties of natural rocks. This novel instrument performs automated indentation tests on the surface of a rock slab and outputs 2-D maps of the indentation modulus at submillimeter resolution. Maps obtained for clean, well-consolidated, sandstone are presented and demonstrate the capabilities of the instrument. We observe that the elastic structure of sandstones correlates well with their visual appearance. Further, we show that the probability distribution of the indentation modulus fluctuations across the slab surfaces can be modeled using a lognormal probability density function. To illustrate possible use of the data obtained with the microindentation scanner, we use roughly 10 cm × 10 cm scans with millimeter resolution over four sandstone planar slabs to numerically compute the overall drained elastic moduli for each sandstone sample. We show that such numerically computed moduli are well modeled using the multicomponent form of the Hashin-Shtrikman lower bound that employs the observed lognormal probability distribution for the mesoscopic-scale moduli (the geometric mean works almost the same). We also compute the seismic attenuation versus frequency associated with wave-induced fluid flow between the heterogeneities in the scanned sandstones and observe relatively small values for the inverse quality factor (Q-1<10-2) in the seismic frequency band 102 Hz

  18. Plant- and microbial-based mechanisms to improve the agronomic effectiveness of phosphate rock: a review.

    PubMed

    Arcand, Melissa M; Schneider, Kim D

    2006-12-01

    Deficiency in plant-available phosphorus is considered to be a major limiting factor to food production in many agricultural soils. Mineral resources are necessary to restore soil phosphorus content. In regions where conventional fertilizers are not used due to cost limitations or to mitigate adverse environmental effects, local sources of phosphate rock are being increasingly recognized for potential use as alternative phosphorus fertilizers. The main obstacle associated with using directly applied ground phosphate rock is that the phosphate released is often unable to supply sufficient plant-available phosphorus for crop uptake. Plantand microbial-based mechanisms are low-cost, appropriate technologies to enhance the solubilization and increase the agronomic effectiveness of phosphate rock. Common mechanisms of phosphate rock dissolution including proton and organic acid production will be reviewed for both plants and microorganisms. This review will also address possibilities for future research directions and applications to agriculture, as well as highlight ongoing research at the University of Guelph, Guelph, Canada.

  19. ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS

    SciTech Connect

    Thurman E. Scott, Jr., Ph.D.; Younane Abousleiman, Ph.D.; Musharraf Zaman, Ph.D., P.E.

    2001-01-31

    During this phase of the project the research team concentrated on acquisition of acoustic emission data from the high porosity rock samples. The initial experiments indicated that the acoustic emission activity from high porosity Danian chalk were of a very low amplitude. Even though the sample underwent yielding and significant plastic deformation the sample did not generate significant AE activity. This was somewhat surprising. These initial results call into question the validity of attempting to locate AE activity in this weak rock type. As a result the testing program was slightly altered to include measuring the acoustic emission activity from many of the rock types listed in the research program. The preliminary experimental results indicate that AE activity in the sandstones is much higher than in the carbonate rocks (i.e., the chalks and limestones). This observation may be particularly important for planning microseismic imaging of reservoir rocks in the field environment. The preliminary results suggest that microseismic imaging of reservoir rock from acoustic emission activity generated from matrix deformation (during compaction and subsidence) would be extremely difficult to accomplish.

  20. Berberine ameliorates experimental diabetes-induced renal inflammation and fibronectin by inhibiting the activation of RhoA/ROCK signaling.

    PubMed

    Xie, Xi; Chang, Xiuting; Chen, Lei; Huang, Kaipeng; Huang, Juan; Wang, Shaogui; Shen, Xiaoyan; Liu, Peiqing; Huang, Heqing

    2013-12-05

    The accumulation of glomerular extracellular matrix proteins, especially fibronectin (FN), is a critical pathological characteristic of diabetic renal fibrosis. Inflammation mediated by nuclear factor-κB (NF-κB) plays a critical role in the pathogenesis of diabetic nephropathy (DN). RhoA/ROCK signaling is responsible for FN accumulation and NF-κB activation. Berberine (BBR) treatment significantly inhibited renal inflammation and thus improved renal damage in diabetes. Here, we study whether BBR inhibits FN accumulation and NF-κB activation by inhibiting RhoA/ROCK signaling and the underlying mechanisms involved. Results showed that BBR effectively inhibited RhoA/ROCK signaling activation in diabetic rat kidneys and high glucose-induced glomerular mesangial cells (GMCs) and simultaneously down-regulated NF-κB activity, which was accompanied by reduced intercellular adhesionmolecule-1, transforming growth factor-beta 1 and FN overproduction. Furthermore, we observed that BBR abrogated high glucose-mediated reactive oxygen species generation in GMCs. BBR and N-acetylcysteine inhibited RhoA/ROCK signaling activation in high glucose-exposed GMCs. Collectively, our data suggest that the renoprotective effect of BBR on DN partly depends on RhoA/ROCK inhibition. The anti-oxidative stress effect of BBR is responsible for RhoA/ROCK inhibition in DN.

  1. The migration law of overlay rock and coal in deeply inclined coal seam with fully mechanized top coal caving.

    PubMed

    Liu, Jian; Chen, Shan-Le; Wang, Hua-Jun; Li, Yu-Cheng; Geng, Xiaowei

    2015-07-01

    In a mine area, some environment geotechnics problems always occure, induced by mined-out region such as the subsidence and cracks at ground level, deformation and destruction of buildings, landslides destruction of water resources and the ecological environment. In order to research the migration of surrounding rock and coal in steeply inclined super high seams which used fully mechanized top coal caving, a working face of a certain mine was made as an example, analyzed the migration law of the overlay rock and coal under different caving ratio of fully mechanized top coal caving with numerical simulation analysis. The results suggest that the laws of overlay rock deformation caused by deeply inclined coal seam were different from horizontal coal seam. On the inclined direction, with an increase of dip angle and caving ratio, the vertical displacement of overlay rock and coal became greater, the asymmetric phenomenon of vertical displacement became obvious. On the trend direction, active region and transition region in goaf became smaller along with the increase of mining and caving ratio. On the contrary, the stable region area became greater. Therefore, there was an essential difference between the mechanism of surface movement deformation with deeply inclined coal seam and that with horizontal coal seam.

  2. Sulfate-dependent Anaerobic Oxidation of Methane as a Generation Mechanism for Calcite Cap Rock in Gulf Coast Salt Domes

    NASA Astrophysics Data System (ADS)

    Caesar, K. H.; Kyle, R.; Lyons, T. W.; Loyd, S. J.

    2015-12-01

    Gulf Coast salt domes, specifically their calcite cap rocks, have been widely recognized for their association with significant reserves of crude oil and natural gas. However, the specific microbial reactions that facilitate the precipitation of these cap rocks are still largely unknown. Insight into the mineralization mechanism(s) can be obtained from the specific geochemical signatures recorded in these structures. Gulf Coast cap rocks contain carbonate and sulfur minerals that exhibit variable carbon (d13C) and sulfur isotope (δ34S) signatures. Calcite d13C values are isotopically depleted and show a large range of values from -1 to -52‰, reflecting a mixture of various carbon sources including a substantial methane component. These depleted carbon isotope compositions combined with the presence of abundant sulfide minerals in cap rocks have led to interpretations that invoke microbial sulfate reduction as an important carbonate mineral-yielding process in salt dome environments. Sulfur isotope data from carbonate-associated sulfate (CAS: trace sulfate incorporated within the carbonate mineral crystal lattice) provide a more direct proxy for aqueous sulfate in salt dome systems and may provide a means to directly fingerprint ancient sulfate reduction. We find CAS sulfur isotope compositions (δ34SCAS) significantly greater than those of the precursor Jurassic sulfate-salt deposits (which exhibit δ34S values of ~ +15‰). This implies that cap rock carbonate generation occurred via microbial sulfate reduction under closed-system conditions. The co-occurrence of depleted carbonate d13C values (< ~30‰) and the enriched δ34SCAS values are evidence for sulfate-dependent anaerobic oxidation of methane (AOM). AOM, which has been shown to yield extensive seafloor carbonate authigenesis, is also potentially partly responsible for the carbonate minerals of the Gulf Coast calcite cap rocks through concomitant production of alkalinity. Collectively, these data shed

  3. Interactive evolution concept for analyzing a rock salt cavern under cyclic thermo-mechanical loading

    NASA Astrophysics Data System (ADS)

    König, Diethard; Mahmoudi, Elham; Khaledi, Kavan; von Blumenthal, Achim; Schanz, Tom

    2016-04-01

    The excess electricity produced by renewable energy sources available during off-peak periods of consumption can be used e.g. to produce and compress hydrogen or to compress air. Afterwards the pressurized gas is stored in the rock salt cavities. During this process, thermo-mechanical cyclic loading is applied to the rock salt surrounding the cavern. Compared to the operation of conventional storage caverns in rock salt the frequencies of filling and discharging cycles and therefore the thermo-mechanical loading cycles are much higher, e.g. daily or weekly compared to seasonally or yearly. The stress strain behavior of rock salt as well as the deformation behavior and the stability of caverns in rock salt under such loading conditions are unknown. To overcome this, existing experimental studies have to be supplemented by exploring the behavior of rock salt under combined thermo-mechanical cyclic loading. Existing constitutive relations have to be extended to cover degradation of rock salt under thermo-mechanical cyclic loading. At least the complex system of a cavern in rock salt under these loading conditions has to be analyzed by numerical modeling taking into account the uncertainties due to limited access in large depth to investigate material composition and properties. An interactive evolution concept is presented to link the different components of such a study - experimental modeling, constitutive modeling and numerical modeling. A triaxial experimental setup is designed to characterize the cyclic thermo-mechanical behavior of rock salt. The imposed boundary conditions in the experimental setup are assumed to be similar to the stress state obtained from a full-scale numerical simulation. The computational model relies primarily on the governing constitutive model for predicting the behavior of rock salt cavity. Hence, a sophisticated elasto-viscoplastic creep constitutive model is developed to take into account the dilatancy and damage progress, as well as

  4. Earthquake-induced collapse mechanism of two types of dangerous rock masses

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Yuan, Wei; Wang, Qizhi; Xue, Kang

    2016-06-01

    As the economy of China develops, an increasing number of key traffic projects have been undertaken in the west of China, where there are high, steep rock slopes. The collapse of dangerous rock masses, especially following a strong earthquake, is one of common geological disasters known in rock slope engineering. Therefore, it is important to study the collapse mechanism of dangerous rock masses induced by an earthquake and the analysis approach of its stability. This study provides a simple and convenient method to determine the collapse mechanisms of two types of dangerous rock masses (i.e. cantilever and upright) associated with the definition and calculation of the safety factor, which is based on the flexure theory of a constant-section beam by combining with the maximum tensile-stress criterion to depict the process of crack propagation caused by seismic waves. The calculation results show that there are critical crack depths in each form of the dangerous rock masses. Once the accumulated depth of the crack growth during an earthquake exceeds the critical depth, the collapse will occur. It is also demonstrated that the crack extension amount of each step is not a constant value, and is closely associated with the current accumulated crack depth. The greater the cumulative crack depth, the more easily the crack propagates. Finally, the validity and applicability of the proposed method are verified through two actual engineering examples.

  5. The Effect of Scale on the Mechanical Properties of Jointed Rock Masses

    SciTech Connect

    Heuze, F E

    2004-05-24

    These notes were prepared for presentation at the Defense Threat Reduction Agency's (DTRA) Hard Target Research and Analysis Center (HTRAC), at the occasion of a short course held on June 14-15, 2004. The material is intended for analysts who must evaluate the geo-mechanical characteristics of sites of interest, in order to provide appropriate input to calculations of ground shock effects on underground facilities in rock masses. These analysts are associated with the Interagency Geotechnical Assessment Team (IGAT). Because geological discontinuities introduce scale effects on the mechanical properties of rock formations, these large-scale properties cannot be estimated on the basis of tests on small cores.

  6. ROCK activity affects IL-1-induced signaling possibly through MKK4 and p38 MAPK in Caco-2 cells.

    PubMed

    Banerjee, Sayantan; McGee, Dennis W

    2016-09-01

    Elevated levels of interleukin-1 (IL-1) accompany inflammatory bowel disease. IL-1-stimulated intestinal epithelial cells can secrete potent chemokines like CXCL8 to exacerbate inflammation. Previously, we found that inhibiting the Rho-associated kinase (ROCK) could inhibit IL-1- or TNF-α-induced CXCL8 secretion by the Caco-2 colonic epithelial cell line. This ROCK inhibition did not affect IκBα phosphorylation and degradation, but suppressed the phosphorylation of c-Jun N-terminal kinase (JNK). Therefore, ROCK must play an important role in epithelial cell CXCL8 responses through an effect on the JNK signaling pathway. Here, we extend these studies by showing that inhibiting ROCK suppressed the IL-1-induced phosphorylation of MKK4, a known activator of JNK, but not MKK7. Yet, ROCK inhibition had no significant effect on the IL-1-induced phosphorylation of extracellular-signal-regulated kinase (ERK) 1/2. Inhibiting ROCK also suppressed the phosphorylation of p38 MAPK after IL-1 stimulation, but this inhibition had no significant effect on the stability of CXCL8 messenger RNA (mRNA) after IL-1 stimulation. These results suggest that ROCK may be important in IL-1-induced signaling through MKK4 to JNK and the activation of p38 MAPK. Finally, inhibiting ROCK in IL-1 and TNF-α co-stimulated Caco-2 cells also resulted in a significant suppression of CXCL8 secretion and mRNA levels suggesting that inhibiting ROCK may be a mechanism to inhibit the overall response of epithelial cells to both cytokines. These studies indicate a novel signaling event, which could provide a target for suppressing intestinal epithelial cells (IEC) chemokine responses involved in mucosal inflammation.

  7. Influence of Water Content on Mechanical Properties of Rock in Both Saturation and Drying Processes

    NASA Astrophysics Data System (ADS)

    Zhou, Zilong; Cai, Xin; Cao, Wenzhuo; Li, Xibing; Xiong, Cheng

    2016-08-01

    Water content has a pronounced influence on the properties of rock materials, which is responsible for many rock engineering hazards, such as landslides and karst collapse. Meanwhile, water injection is also used for the prevention of some engineering disasters like rock-bursts. To comprehensively investigate the effect of water content on mechanical properties of rocks, laboratory tests were carried out on sandstone specimens with different water contents in both saturation and drying processes. The Nuclear Magnetic Resonance technique was applied to study the water distribution in specimens with variation of water contents. The servo-controlled rock mechanics testing machine and Split Hopkinson Pressure Bar technique were used to conduct both compressive and tensile tests on sandstone specimens with different water contents. From the laboratory tests, reductions of the compressive and tensile strength of sandstone under static and dynamic states in different saturation processes were observed. In the drying process, all of the saturated specimens could basically regain their mechanical properties and recover its strength as in the dry state. However, for partially saturated specimens in the saturation and drying processes, the tensile strength of specimens with the same water content was different, which could be related to different water distributions in specimens.

  8. Discrete element modeling of indentation tests to investigate mechanisms of CO2-related chemomechanical rock alteration

    NASA Astrophysics Data System (ADS)

    Sun, Zhuang; Espinoza, D. Nicolas; Balhoff, Matthew T.

    2016-11-01

    During CO2 injection into geological formations, petrophysical and geomechanical properties of host formations can be altered due to mineral dissolution and precipitation. Field and laboratory results have shown that sandstone and siltstone can be altered by CO2-water mixtures, but few quantitative studies have been performed to fully investigate underlying mechanisms. Based on the hypothesis that CO2-water mixtures alter the integrity of rock structure by attacking cements rather than grains, we attempt to explain the degradation of cementation due to long-term contact with CO2 and water and mechanisms for changes in rock mechanical properties. Many sandstones, including calcite-cemented quartzitic sandstone, chlorite-cemented quartzitic sandstone, and hematite-cemented quartzitic sandstone, contain interparticle cements that are more readily affected by CO2-water mixtures than grains. A model that couples the discrete element method and the bonded-particle model is used to perform simulations of indentation tests on synthetic rocks with crystal and random packings. The model is verified against the analytical cavity expansion model and validated against laboratory indentation tests on Entrada sandstone with and without CO2 alteration. Sensitivity analysis is performed for cementation microscopic parameters including stiffness, size, axial, and shear strength. The simulation results indicate that the CO2-related degradation of mechanical properties in bleached Entrada sandstone can be attributed to the reduction of cement size rather than cement strength. Our study indicates that it is possible to describe the CO2-related rock alteration through particle-scale mechanisms.

  9. A probabilistic approach to rock mechanical property characterization for nuclear waste repository design

    SciTech Connect

    Kim, Kunsoo; Gao, Hang

    1996-04-01

    A probabilistic approach is proposed for the characterization of host rock mechanical properties at the Yucca Mountain site. This approach helps define the probability distribution of rock properties by utilizing extreme value statistics and Monte Carlo simulation. We analyze mechanical property data of tuff obtained by the NNWSI Project to assess the utility of the methodology. The analysis indicates that laboratory measured strength and deformation data of Calico Hills and Bullfrog tuffs follow an extremal. probability distribution (the third type asymptotic distribution of the smallest values). Monte Carlo simulation is carried out to estimate rock mass deformation moduli using a one-dimensional tuff model proposed by Zimmermann and Finley. We suggest that the results of these analyses be incorporated into the repository design.

  10. Effect of Particle Shape on Mechanical Behaviors of Rocks: A Numerical Study Using Clumped Particle Model

    PubMed Central

    Rong, Guan; Liu, Guang; Zhou, Chuang-bing

    2013-01-01

    Since rocks are aggregates of mineral particles, the effect of mineral microstructure on macroscopic mechanical behaviors of rocks is inneglectable. Rock samples of four different particle shapes are established in this study based on clumped particle model, and a sphericity index is used to quantify particle shape. Model parameters for simulation in PFC are obtained by triaxial compression test of quartz sandstone, and simulation of triaxial compression test is then conducted on four rock samples with different particle shapes. It is seen from the results that stress thresholds of rock samples such as crack initiation stress, crack damage stress, and peak stress decrease with the increasing of the sphericity index. The increase of sphericity leads to a drop of elastic modulus and a rise in Poisson ratio, while the decreasing sphericity usually results in the increase of cohesion and internal friction angle. Based on volume change of rock samples during simulation of triaxial compression test, variation of dilation angle with plastic strain is also studied. PMID:23997677

  11. Experimental Investigation of the Mechanical Behavior of Bedded Rocks and Its Implication for High Sidewall Caverns

    NASA Astrophysics Data System (ADS)

    Zhou, Yang-Yi; Feng, Xia-Ting; Xu, Ding-Ping; Fan, Qi-Xiang

    2016-09-01

    The stability of high sidewalls of large-span underground powerhouses will be a major issue when the cavern axis forms a small angle to the steeply inclined rock strata. A synthetic test scheme composed of four experiments was performed on two rocks with clear bedding features, aiming at better understanding the otherwise confusing deformation behavior and failure patterns of bedded rocks. Bedding orientations with respect to stress direction impose significant effect on the mechanical behavior of bedded rocks. Excessive tensile strain is observed in the direction perpendicular to bedding or across material interface in uniaxial test. Under low confinement in true triaxial test, the σ 2 angle mainly influences the deformation and fracture propagation but not strength. Deformation dependence of bedded rocks on two stress paths is thoroughly investigated. Confining pressure unloading leads to pronounced volumetric dilation accompanied by moduli drop. Samples with large bedding angle exhibit more obvious lateral dilation. Post-peak degradation of deformation parameters is confirmed by cyclic test. Fractures entirely or partly along bedding occurred under different stress states depend not only on the bonding strength between beds but on the anisotropic deformation field. Based on these observations, it is deduced that the possible reasons for the failure of steeply dipping rock mass after excavation are a combination of (1) the pervasive bedding planes, (2) the more pronounced deformation normal to bedding, and (3) the excavation-induced unloading of confinement.

  12. Modeling the Progressive Failure of Jointed Rock Slope Using Fracture Mechanics and the Strength Reduction Method

    NASA Astrophysics Data System (ADS)

    Zhang, Ke; Cao, Ping; Meng, Jingjing; Li, Kaihui; Fan, Wenchen

    2015-03-01

    The fracturing process during the progressive failure of a jointed rock slope is numerically investigated by using fracture mechanics and the strength reduction method (SRM). A displacement discontinuity method containing frictional elements is developed for the calculation of the stress intensity factor (SIF). The failure initiation of the jointed rock slope is analyzed by evaluating the SIF. A new joint model is proposed by combining solid elements with interface elements in the commercial software FLAC3D. These represent the discontinuous planes in a rock mass on which sliding or separation can occur. The progressive failure process is simulated by reducing the shear strength of the rock mass, which includes the process of stress concentration, crack initiation, crack propagation, slip weakening, and coalescence of failure surfaces. The factor of safety (FS) and location of the critical failure surface are determined by the SRM. The influence of the joint inclination is investigated using the FS and the SIF. Laboratory experiments on specimens containing an inclined flaw under compression-shear stress are also conducted to investigate the effect of the angle between the shear direction and the flaw inclination, which provides an experimental explanation for the shear behavior of jointed rock. The results show that the joint inclination dominates the failure behavior of jointed rock slope, and two failure patterns have been classified.

  13. Subcritical crack growth and mechanical weathering: a new consideration of how moisture influences rock erosion rates.

    NASA Astrophysics Data System (ADS)

    Eppes, Martha-Cary; Keanini, Russell; Hancock, Gregory S.

    2016-04-01

    The contributions of moisture to the mechanical aspects of rock weathering and regolith production are poorly quantified. In particular, geomorphologists have largely overlooked the role of subcritical crack growth processes in physical weathering and the fact that moisture strongly influences the rates of those processes. This influence is irrespective of the function that moisture plays in stress loading mechanisms like freezing or hydration. Here we present a simple numerical model that explores the efficacy of subcritical crack growth in granite rock subaerially exposed under a range of moisture conditions. Because most weathering-related stress loading for rocks found at, or near, Earth's surface (hereafter surface rocks) is cyclic, we modeled crack growth using a novel combination of Paris' Law and Charles' Law. This combination allowed us to apply existing empirically-derived data for the stress corrosion index of Charles' Law to fatigue cracking. For stress, we focused on the relatively straightforward case of intergranular stresses that arise during solar-induced thermal cycling by conductive heat transfer, making the assumption that such stresses represent a universal minimum weathering stress experienced by all surface rocks. Because all other tensile weathering-related stresses would be additive in the context of crack growth, however, our model can be adapted to include other stress loading mechanisms. We validated our calculations using recently published thermal-stress-induced cracking rates. Our results demonstrate that 1) weathering-induced stresses as modeled herein, and as published by others, are sufficient to propagate fractures subcritically over long timescales with or without the presence of water 2) fracture propagation rates increase exponentially with respect to moisture, specifically relative humidity 3) fracture propagation rates driven by thermal cycling are strongly dependent on the magnitude of diurnal temperature ranges and the

  14. Mechanical defradation of Emplacement Drifts at Yucca Mountain- A Modeling Case Study. Part I: Nonlithophysal Rock

    SciTech Connect

    M. Lin; D. Kicker; B. Damjanac; M. Board; M. Karakouzian

    2006-07-05

    This paper outlines rock mechanics investigations associated with mechanical degradation of planned emplacement drifts at Yucca Mountain, which is the designated site for the proposed U.S. high-level nuclear waste repository. The factors leading to drift degradation include stresses from the overburden, stresses induced by the heat released from the emplaced waste, stresses due to seismically related ground motions, and time-dependent strength degradation. The welded tuff emplacement horizon consists of two groups of rock with distinct engineering properties: nonlithophysal units and lithophysal units, based on the relative proportion of lithophysal cavities. The term 'lithophysal' refers to hollow, bubble like cavities in volcanic rock that are surrounded by a porous rim formed by fine-grained alkali feldspar, quartz, and other minerals. Lithophysae are typically a few centimeters to a few decimeters in diameter. Part I of the paper concentrates on the generally hard, strong, and fractured nonlithophysal rock. The degradation behavior of the tunnels in the nonlithophysal rock is controlled by the occurrence of keyblocks. A statistically equivalent fracture model was generated based on extensive underground fracture mapping data from the Exploratory Studies Facility at Yucca Mountain. Three-dimensional distinct block analyses, generated with the fracture patterns randomly selected from the fracture model, were developed with the consideration of in situ, thermal, and seismic loads. In this study, field data, laboratory data, and numerical analyses are well integrated to provide a solution for the unique problem of modeling drift degradation.

  15. Rho-associated kinase ROCK activates LIM-kinase 1 by phosphorylation at threonine 508 within the activation loop.

    PubMed

    Ohashi, K; Nagata, K; Maekawa, M; Ishizaki, T; Narumiya, S; Mizuno, K

    2000-02-04

    LIM-kinase 1 (LIMK1) phosphorylates cofilin, an actin-depolymerizing factor, and regulates actin cytoskeletal reorganization. LIMK1 is activated by the small GTPase Rho and its downstream protein kinase ROCK. We now report the site of phosphorylation of LIMK1 by ROCK. In vitro kinase reaction revealed that the active forms of ROCK phosphorylated LIMK1 on the threonine residue and markedly increased its cofilin-phosphorylating activity. A LIMK1 mutant (T508A) with replacement of Thr-508 within the activation loop of the kinase domain by alanine was neither phosphorylated nor activated by ROCK. Replacement of Thr-508 by serine changed the ROCK-catalyzed phosphorylation residue from threonine to serine. A LIMK1 mutant with replacement of Thr-508 by two glutamates increased the kinase activity about 2-fold but was not further activated by ROCK. In addition, wild-type LIMK1, but not its T508A mutant, was activated by co-expression with ROCK in cultured cells. These results suggest that ROCK activates LIMK1 in vitro and in vivo by phosphorylation at Thr-508. Together with the recent finding that PAK1, a downstream effector of Rac, also activates LIMK1 by phosphorylation at Thr-508, these results suggest that activation of LIMK1 is one of the common targets for Rho and Rac to reorganize the actin cytoskeleton.

  16. REDBACK: an Open-Source Highly Scalable Simulation Tool for Rock Mechanics with Dissipative Feedbacks

    NASA Astrophysics Data System (ADS)

    Poulet, T.; Veveakis, M.; Paesold, M.; Regenauer-Lieb, K.

    2014-12-01

    Multiphysics modelling has become an indispensable tool for geoscientists to simulate the complex behaviours observed in their various fields of study where multiple processes are involved, including thermal, hydraulic, mechanical and chemical (THMC) laws. This modelling activity involves simulations that are computationally expensive and its soaring uptake is tightly linked to the increasing availability of supercomputing power and easy access to powerful nonlinear solvers such as PETSc (http://www.mcs.anl.gov/petsc/). The Multiphysics Object-Oriented Simulation Environment (MOOSE) is a finite-element, multiphysics framework (http://mooseframework.org) that can harness such computational power and allow scientists to develop easily some tightly-coupled fully implicit multiphysics simulations that run automatically in parallel on large clusters. This open-source framework provides a powerful tool to collaborate on numerical modelling activities and we are contributing to its development with REDBACK (https://github.com/pou036/redback), a module for Rock mEchanics with Dissipative feedBACKs. REDBACK builds on the tensor mechanics finite strain implementation available in MOOSE to provide a THMC simulator where the energetic formulation highlights the importance of all dissipative terms in the coupled system of equations. We show first applications of fully coupled dehydration reactions triggering episodic fluid transfer through shear zones (Alevizos et al, 2014). The dimensionless approach used allows focusing on the critical underlying variables which are driving the resulting behaviours observed and this tool is specifically designed to study material instabilities underpinning geological features like faulting, folding, boudinage, shearing, fracturing, etc. REDBACK provides a collaborative and educational tool which captures the physical and mathematical understanding of such material instabilities and provides an easy way to apply this knowledge to realistic

  17. Quantifying the impact of lithology upon the mechanical properties of rock

    NASA Astrophysics Data System (ADS)

    Weatherley, Dion

    2013-04-01

    The physical characteristics of rock, its lithology, undoubtedly influences its deformation under natural or engineering loads. Mineral texture, micro-damage, joints, bedding planes, inclusions, unconformities and faults are all postulated to alter the mechanical response of rock on different scales and under different stressing conditions. Whilst laboratory studies have elucidated some aspects of the relationship between lithology and mechanical properties, these small-scale results are difficult to extrapolate to lithospheric scales. To augment laboratory-derived knowledge, physics-based numerical modelling is a promising avenue [3]. Bonded particle models implemented using the Discrete Element Method (DEM [1]) are a practical numerical laboratory to investigate the interplay between lithology and the mechanical response of rock specimens [4]. Numerical rock specimens are represented as an assembly of indivisible spherical particles connected to nearest neighbours via brittle-elastic beams which impart forces and moments upon one-another as particles move relative to each other. By applying boundary forces and solving Newton's Laws for each particle, elastic deformation and brittle failure may be simulated [2]. Each beam interaction is defined by four model parameters: Young's modulus, Poisson's ratio, cohesive strength and internal friction angle. Beam interactions in different subvolumes of the specimen are assigned different parameters to model different rock types or mineral assemblages. Micro-cracks, joints, unconformities and faults are geometrically incorporated by fitting particles to either side of triangulated surfaces [5]. The utility of this modelling approach is verified by reproducing analytical results from fracture mechanics (Griffith crack propagation and wing-crack formation) and results of controlled laboratory investigations. To quantify the impact of particular lithologic structures on mechanical response, a range of control experiments are

  18. Hydromechanical coupling in fractured rock masses: mechanisms and processes of selected case studies

    NASA Astrophysics Data System (ADS)

    Zangerl, Christian

    2015-04-01

    in the range of millimetres to a very few centimetres and can be linked to annual groundwater fluctuations. Due to pore pressure variations HM coupling can influence seepage forces and effective stresses in the rock mass. Effective stress changes can adversely affect the stability and deformation behaviour of deep-seated rock slides by influencing the shear strength or the time dependent (viscous) material behaviour of the basal shear zone. The shear strength of active shear zones is often reasonably well described by Coulomb's law. In Coulomb's law the operative normal stresses to the shear surface/zone are effective stresses and hence pore pressures which should be taken into account reduces the shear strength. According to the time dependent material behaviour a few effective stress based viscous models exists which are able to consider pore pressures. For slowly moving rock slides HM coupling could be highly relevant when low-permeability clayey-silty shear zones (fault gouges) are existing. An important parameters therefore is the hydraulic diffusivity, which is controlled by the permeability and fluid-pore compressibility of the shear zone, and by fluid viscosity. Thus time dependent pore pressure diffusion in the shear zone can either control the stability condition or the viscous behaviour (creep) of the rock slide. Numerous cases studies show that HM coupling can effect deformability, shear strength and time dependent behaviour of fractured rock masses. A process-based consideration can be important to avoid unexpected impacts on infrastructures and to understand complex rock mass as well rock slide behaviour.

  19. Expectations of Rock Music Consumption for Entertainment and Information Relative to the Active Involvement of the User.

    ERIC Educational Resources Information Center

    Rouner, Donna; Noyes, Amy

    Before examining potentially negative effects of rock music on adolescents, it is necessary to demonstrate links between adolescent motivations for consuming rock music and active involvement relative to that use and also to consider how much rock listeners rely on rock music as a source for information about values, beliefs, and social…

  20. Sensitivity Analysis of Mechanical Parameters of Different Rock Layers to the Stability of Coal Roadway in Soft Rock Strata

    PubMed Central

    Zhao, Zeng-hui; Wang, Wei-ming; Gao, Xin; Yan, Ji-xing

    2013-01-01

    According to the geological characteristics of Xinjiang Ili mine in western area of China, a physical model of interstratified strata composed of soft rock and hard coal seam was established. Selecting the tunnel position, deformation modulus, and strength parameters of each layer as influencing factors, the sensitivity coefficient of roadway deformation to each parameter was firstly analyzed based on a Mohr-Columb strain softening model and nonlinear elastic-plastic finite element analysis. Then the effect laws of influencing factors which showed high sensitivity were further discussed. Finally, a regression model for the relationship between roadway displacements and multifactors was obtained by equivalent linear regression under multiple factors. The results show that the roadway deformation is highly sensitive to the depth of coal seam under the floor which should be considered in the layout of coal roadway; deformation modulus and strength of coal seam and floor have a great influence on the global stability of tunnel; on the contrary, roadway deformation is not sensitive to the mechanical parameters of soft roof; roadway deformation under random combinations of multi-factors can be deduced by the regression model. These conclusions provide theoretical significance to the arrangement and stability maintenance of coal roadway. PMID:24459447

  1. Mechanically Active Electrospun Materials

    NASA Astrophysics Data System (ADS)

    Robertson, Jaimee M.

    Electrospinning, a technique used to fabricate small diameter polymer fibers, has been employed to develop unique, active materials falling under two categories: (1) shape memory elastomeric composites (SMECs) and (2) water responsive fiber mats. (1) Previous work has characterized in detail the properties and behavior of traditional SMECs with isotropic fibers embedded in an elastomer matrix. The current work has two goals: (i) characterize laminated anisotropic SMECs and (ii) develop a fabrication process that is scalable for commercial SMEC manufacturing. The former ((i)) requires electrospinning aligned polymer fibers. The aligned fibers are similarly embedded in an elastomer matrix and stacked at various fiber orientations. The resulting laminated composite has a unique response to tensile deformation: after stretching and releasing, the composite curls. This curling response was characterized based on fiber orientation. The latter goal ((ii)) required use of a dual-electrospinning process to simultaneously electrospin two polymers. This fabrication approach incorporated only industrially relevant processing techniques, enabling the possibility of commercial application of a shape memory rubber. Furthermore, the approach had the added benefit of increased control over composition and material properties. (2) The strong elongational forces experienced by polymer chains during the electrospinning process induce molecular alignment along the length of electrospun fibers. Such orientation is maintained in the fibers as the polymer vitrifies. Consequently, residual stress is stored in electrospun fiber mats and can be recovered by heating through the polymer's glass transition temperature. Alternatively, the glass transition temperature can be depressed by introducing a plasticizing agent. Poly(vinyl acetate) (PVAc) is plasticized by water, and its glass transition temperature is lowered below room temperature. Therefore, the residual stress can be relaxed at room

  2. Rock Mechanics and Enhanced Geothermal Systems: A DOE-sponsored Workshop to Explore Research Needs

    SciTech Connect

    Francois Heuze; Peter Smeallie; Derek Elsworth; Joel L. Renner

    2003-10-01

    This workshop on rock mechanics and enhanced geothermal systems (EGS) was held in Cambridge, Mass., on June 20-21 2003, before the Soil and Rock America 2003 International Conference at MIT. Its purpose was to bring together experts in the field of rock mechanics and geothermal systems to encourage innovative thinking, explore new ideas, and identify research needs in the areas of rock mechanics and rock engineering applied to enhanced geothermal systems. The agenda is shown in Appendix A. The workshop included experts in the fields of rock mechanics and engineering, geological engineering, geophysics, drilling, the geothermal energy production from industry, universities and government agencies, and laboratories. The list of participants is shown is Appendix B. The first day consisted of formal presentations. These are summarized in Chapter 1 of the report. By the end of the first day, two broad topic areas were defined: reservoir characterization and reservoir performance. Working groups were formed for each topic. They met and reported in plenary on the second day. The working group summaries are described in Chapter 2. The final session of the workshop was devoted to reaching consensus recommendations. These recommendations are given in Chapter 3. That objective was achieved. All the working group recommendations were considered and, in order to arrive at a practical research agenda usable by the workshop sponsors, workshop recommendations were reduced to a total of seven topics. These topics were divided in three priority groups, as follows. First-priority research topics (2): {sm_bullet} Define the pre-existing and time-dependent geometry and physical characteristics of the reservoir and its fracture network. That includes the identification of hydraulically controlling fractures. {sm_bullet} Characterize the physical and chemical processes affecting the reservoir geophysical parameters and influencing the transport properties of fractures. Incorporate those

  3. The Effect of Water on the Flow of Stress-Activated Electric Currents through Rocks

    NASA Astrophysics Data System (ADS)

    Jahoda, A. M.; Cyr, G. G.; Dahlgren, R.; Freund, F. T.

    2011-12-01

    When igneous or high-grade metamorphic rocks are subjected to deviatoric stresses, dormant defects in the matrix of common rock-forming minerals become activated. These defects consist of pairs of oxygen anions in the 1- valence state, e.g. peroxy links such as O3Si-OO-SiO3. When a peroxy bond breaks, O3Si-O:O-SiO3, an electron is transferred from a neighboring O2- causing the donor oxygen, now O-, to turn into a defect electron, also known as a positive hole, that can propagate as a highly mobile positive charge through the rocks1. The current outflow is driven by the battery potential that builds up during this process. The question is how this electric current through rocks is affected by water. When positive holes flow into bulk water, they oxidize H2O to H2O2 and are thereby consumed2. This electrochemical reaction is driven by the potential drop across the rock-water interface. However, no such potential drop occurs across water that fills pores inside the rocks along the path of the electronic charge carriers. We present evidence that the presence of water in the pore space does indeed not "kill" the current flow. This observation leads to the conclusion that stress-activated positive hole currents should be able to flow through water-saturated rocks maybe as well as, possibly even better than through dry rocks. 1 Freund, F. T., et al.: Electric currents streaming out of stressed igneous rocks - A step towards understanding pre-earthquake low frequency EM emissions, Phys. Chem. Earth, 2006, 31, 389-396. 2 Balk, M., et al.: Oxidation of water to hydrogen peroxide at the rock-water interface due to stress-activated electric currents in rocks, Earth Planet. Sci. Lett. 2009, 283, 87-92

  4. Active auditory mechanics in mosquitoes.

    PubMed Central

    Göpfert, M. C.; Robert, D.

    2001-01-01

    In humans and other vertebrates, hearing is improved by active contractile properties of hair cells. Comparable active auditory mechanics is now demonstrated in insects. In mosquitoes, Johnston's organ transduces sound-induced vibrations of the antennal flagellum. A non-muscular 'motor' activity enhances the sensitivity and tuning of the flagellar mechanical response in physiologically intact animals. This motor is capable of driving the flagellum autonomously, amplifying sound-induced vibrations at specific frequencies and intensities. Motor-related electrical activity of Johnston's organ strongly suggests that mosquito hearing is improved by mechanoreceptor motility. PMID:11270428

  5. Mechanical properties of carboniferous rocks in the Upper Silesian Coal Basin under uniaxial and triaxial compression tests

    SciTech Connect

    Bukowska, M.

    2005-04-01

    Many years' studies of geological properties of rocks from the Upper Silesian Coal Basin have resulted in acquisition of a substantial data base of mechanical parameters of rocks over the total strain range. It is found that the post-peak rock properties are closely related with the peak strength and the pre-peak properties. The relationship between the uniaxial ultimate strength, elastic modulus, and drop modulus are determined.

  6. ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS

    SciTech Connect

    Thurman E. Scott, Jr., Ph.D.; Younane Abousleiman, Ph.D.; Musharraf Zaman, Ph.D., P.E.

    2001-07-01

    Mechanically weak formations, such as chalks, high porosity sandstones, and marine sediments, pose significant problems for oil and gas operators. Problems such as compaction, subsidence, and loss of permeability can affect reservoir production operations. For example, the unexpected subsidence of the Ekofisk chalk in the North Sea required over one billion dollars to re-engineer production facilities to account for losses created during that compaction (Sulak 1991). Another problem in weak formations is that of shallow water flows (SWF). Deep water drilling operations sometimes encounter cases where the marine sediments, at shallow depths just below the seafloor, begin to uncontrollably flow up and around the drill pipe. SWF problems created a loss of $150 million for the Ursa development project in the U.S. Gulf Coast SWF (Furlow 1998a,b; 1999a,b). The goal of this project is to provide a database on both the rock mechanical properties and the geophysical properties of weak rocks and sediments. These could be used by oil and gas companies to detect, evaluate, and alleviate potential production and drilling problems. The results will be useful in, for example, pre-drill detection of events such as SWF's by allowing a correlation of seismic data (such as hazard surveys) to rock mechanical properties. The data sets could also be useful for 4-D monitoring of the compaction and subsidence of an existing reservoir and imaging the zones of damage. During the second quarter of the project the research team has: (1) completed acoustic sensor construction, (2) conducted reconnaissance tests to map the deformational behaviors of the various rocks, (3) developed a sample assembly for the measurement of dynamic elastic and poroelastic parameters during triaxial testing, and (4) conducted a detailed review of the scientific literature and compiled a bibliography of that review. During the first quarter of the project the research team acquired several rock types for testing

  7. The microstructural character and evolution of fault rocks from SAFOD and potential weakening mechanisms along the San Andreas Fault

    NASA Astrophysics Data System (ADS)

    van Diggelen, E.; Holdsworth, R. E.; de Bresser, J. H.; Spiers, C.; Smith, S. A.; Walker, R. J.; Bowen, L.

    2010-12-01

    The San Andreas Fault (SAF) forms the boundary between two geological terranes; the Salinian block (SB, Pacific plate) and the Great Valley block (GVB, North American plate). The SB contains arkosic sandstones, the GVB consists mostly of claystones and siltstones. The SAFOD borehole provides an extensive set of samples across the SAF and permits direct study of fault zone processes at 2-3 km depth. In order to determine the fault rock properties and deformation mechanisms in the SAF, in particular in two actively creeping fault segments, we have visually assessed the SAFOD phase 3 core material and we have performed detailed optical and electron microscopy, including chemical analyses using EDX. We compared the natural microstructures with microstructures developed in simulated fault gouges deformed in laboratory experiments. The rocks in Core interval 1 (SB) are mildly deformed and show evidence of cataclasis, pressure solution and reaction of feldspar to form phyllosilicates. Most of Core interval 3 (GVB) is also only mildly deformed, similar to Core interval 1. Sedimentary features are still visible, together with limited evidence for cataclasis, pressure solution and reaction of feldspar to phyllosilicates. The rocks in Core interval 2 (GVB) show ample evidence for micro-folding, foliation development, development of anastomosing shear bands, gouge formation, veining, and reworking of earlier microstructures. In addition, evidence is widespread for cataclasis, pressure solution and reaction of feldspar to form phyllosilicates. The SB and GVB host rocks are cut by numerous minor faults and small calcite-filled veins. Thin foliated gouges contain fine-grained, Fe-rich smectitic phyllosilicates. The development of interconnected networks of these phyllosilicates following cataclasis is prevalent in the inactive gouges. The actively creeping zones in Core intervals 2 and 3 consist mostly of Mg-rich smectitic phyllosilicates and show a strong, wavy foliation, lens

  8. Analysis on the Rock-Cutter Interaction Mechanism During the TBM Tunneling Process

    NASA Astrophysics Data System (ADS)

    Yang, Haiqing; Wang, He; Zhou, Xiaoping

    2016-03-01

    The accurate prediction of rock cutting forces of disc cutters is crucial for tunnel boring machine (TBM) design and construction. Disc cutter wear, which affects TBM penetration performance, has frequently been found at TBM sites. By considering the operating path and wear of the disc cutter, a new model is proposed for evaluating the cutting force and wear of the disc cutter in the tunneling process. The circular path adopted herein, which is the actual running path of the TBM disc cutter, shows that the lateral force of the disc cutter is asymmetric. The lateral forces on the sides of the disc cutter are clearly different. However, traditional solutions are obtained by assuming a linear path, where the later forces are viewed as equal. To simulate the interaction between the rock and disc cutter, a simple brittle damage model for rock mass is introduced here. Based on the explicit dynamic finite element method, the cutting force acting on the rock generated by a single disc cutter is simulated. It is shown that the lateral cutting force of the disc cutter strongly affects the wear extent of disc cutter. The wear mechanism is thus underestimated by the classical model, which was obtained by linear cutting tests. The simulation results are discussed and compared with other models, and these simulation results agree well with the results of present ones.

  9. A Negative Regulatory Mechanism Involving 14-3-3ζ Limits Signaling Downstream of ROCK to Regulate Tissue Stiffness in Epidermal Homeostasis.

    PubMed

    Kular, Jasreen; Scheer, Kaitlin G; Pyne, Natasha T; Allam, Amr H; Pollard, Anthony N; Magenau, Astrid; Wright, Rebecca L; Kolesnikoff, Natasha; Moretti, Paul A; Wullkopf, Lena; Stomski, Frank C; Cowin, Allison J; Woodcock, Joanna M; Grimbaldeston, Michele A; Pitson, Stuart M; Timpson, Paul; Ramshaw, Hayley S; Lopez, Angel F; Samuel, Michael S

    2015-12-21

    ROCK signaling causes epidermal hyper-proliferation by increasing ECM production, elevating dermal stiffness, and enhancing Fak-mediated mechano-transduction signaling. Elevated dermal stiffness in turn causes ROCK activation, establishing mechano-reciprocity, a positive feedback loop that can promote tumors. We have identified a negative feedback mechanism that limits excessive ROCK signaling during wound healing and is lost in squamous cell carcinomas (SCCs). Signal flux through ROCK was selectively tuned down by increased levels of 14-3-3ζ, which interacted with Mypt1, a ROCK signaling antagonist. In 14-3-3ζ(-/-) mice, unrestrained ROCK signaling at wound margins elevated ECM production and reduced ECM remodeling, increasing dermal stiffness and causing rapid wound healing. Conversely, 14-3-3ζ deficiency enhanced cutaneous SCC size. Significantly, inhibiting 14-3-3ζ with a novel pharmacological agent accelerated wound healing 2-fold. Patient samples of chronic non-healing wounds overexpressed 14-3-3ζ, while cutaneous SCCs had reduced 14-3-3ζ. These results reveal a novel 14-3-3ζ-dependent mechanism that negatively regulates mechano-reciprocity, suggesting new therapeutic opportunities.

  10. A novel FOXM1 isoform, FOXM1D, promotes epithelial-mesenchymal transition and metastasis through ROCKs activation in colorectal cancer.

    PubMed

    Zhang, X; Zhang, L; Du, Y; Zheng, H; Zhang, P; Sun, Y; Wang, Y; Chen, J; Ding, P; Wang, N; Yang, C; Huang, T; Yao, X; Qiao, Q; Gu, H; Cai, G; Cai, S; Zhou, X; Hu, W

    2017-02-09

    Epithelial-mesenchymal transition (EMT) is a critical event in metastasis of colorectal cancer (CRC). Rho/ROCKs signaling has a pivotal role in orchestrating actin cytoskeleton, leading to EMT and cancer invasion. However, the underlying mechanisms for ROCKs activation are not fully understood. Here, we identified FOXM1D, a novel isoform of Forkhead box M1 (FOXM1) that has a pivotal role in ROCKs activation by directly interacting with coiled-coil region of ROCK2. FOXM1D overexpression significantly polymerizes actin assembly and impairs E-cadherin expression, resulting in EMT and metastasis in xenograft mouse model and knockdown of FOXM1D has the opposite effect. Moreover, a high FOXM1D level correlates closely with clinical CRC metastasis. FOXM1D-induced ROCKs activation could be abrogated by the ROCKs inhibitors Y-27632 and fasudil. These observations indicate that the FOXM1D-ROCK2 interaction is crucial for Rho/ROCKs signaling and provide novel insight into actin cytoskeleton regulation and therapeutic potential for CRC metastasis.

  11. A novel FOXM1 isoform, FOXM1D, promotes epithelial–mesenchymal transition and metastasis through ROCKs activation in colorectal cancer

    PubMed Central

    Zhang, X; Zhang, L; Du, Y; Zheng, H; Zhang, P; Sun, Y; Wang, Y; Chen, J; Ding, P; Wang, N; Yang, C; Huang, T; Yao, X; Qiao, Q; Gu, H; Cai, G; Cai, S; Zhou, X; Hu, W

    2017-01-01

    Epithelial–mesenchymal transition (EMT) is a critical event in metastasis of colorectal cancer (CRC). Rho/ROCKs signaling has a pivotal role in orchestrating actin cytoskeleton, leading to EMT and cancer invasion. However, the underlying mechanisms for ROCKs activation are not fully understood. Here, we identified FOXM1D, a novel isoform of Forkhead box M1 (FOXM1) that has a pivotal role in ROCKs activation by directly interacting with coiled-coil region of ROCK2. FOXM1D overexpression significantly polymerizes actin assembly and impairs E-cadherin expression, resulting in EMT and metastasis in xenograft mouse model and knockdown of FOXM1D has the opposite effect. Moreover, a high FOXM1D level correlates closely with clinical CRC metastasis. FOXM1D-induced ROCKs activation could be abrogated by the ROCKs inhibitors Y-27632 and fasudil. These observations indicate that the FOXM1D–ROCK2 interaction is crucial for Rho/ROCKs signaling and provide novel insight into actin cytoskeleton regulation and therapeutic potential for CRC metastasis. PMID:27399334

  12. ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS

    SciTech Connect

    Thurman E. Scott, Jr., Ph.D.; Younane Abousleiman, Ph.D.; Musharraf Zaman, Ph.D., P.E.

    2002-11-18

    During the seven quarter of the project the research team analyzed some of the acoustic velocity data and rock deformation data. The goal is to create a series of ''deformation-velocity maps'' which can outline the types of rock deformational mechanisms which can occur at high pressures and then associate those with specific compressional or shear wave velocity signatures. During this quarter, we began to analyze both the acoustical and deformational properties of the various rock types. Some of the preliminary velocity data from the Danian chalk will be presented in this report. This rock type was selected for the initial efforts as it will be used in the tomographic imaging study outlined in Task 10. This is one of the more important rock types in the study as the Danian chalk is thought to represent an excellent analog to the Ekofisk chalk that has caused so many problems in the North Sea. Some of the preliminary acoustic velocity data obtained during this phase of the project indicates that during pore collapse and compaction of this chalk, the acoustic velocities can change by as much as 200 m/s. Theoretically, this significant velocity change should be detectable during repeated successive 3-D seismic images. In addition, research continues with an analysis of the unconsolidated sand samples at high confining pressures obtained in Task 9. The analysis of the results indicate that sands with 10% volume of fines can undergo liquefaction at lower stress conditions than sand samples which do not have fines added. This liquefaction and/or sand flow is similar to ''shallow water'' flows observed during drilling in the offshore Gulf of Mexico.

  13. ZYZ-168 alleviates cardiac fibrosis after myocardial infarction through inhibition of ERK1/2-dependent ROCK1 activation

    PubMed Central

    Luo, Shanshan; Hieu, Tran Ba; Ma, Fenfen; Yu, Ying; Cao, Zhonglian; Wang, Minjun; Wu, Weijun; Mao, Yicheng; Rose, Peter; Law, Betty Yuen-Kwan; Zhu, Yi Zhun

    2017-01-01

    Selective treatments for myocardial infarction (MI) induced cardiac fibrosis are lacking. In this study, we focus on the therapeutic potential of a synthetic cardio-protective agent named ZYZ-168 towards MI-induced cardiac fibrosis and try to reveal the underlying mechanism. ZYZ-168 was administered to rats with coronary artery ligation over a period of six weeks. Ecocardiography and Masson staining showed that ZYZ-168 substantially improved cardiac function and reduced interstitial fibrosis. The expression of α–smooth muscle actin (α-SMA) and Collagen I were reduced as was the activity of matrix metalloproteinase 9 (MMP-9). These were related with decreased phosphorylation of ERK1/2 and expression of Rho-associated coiled-coil containing protein kinase 1 (ROCK1). In cardiac fibroblasts stimulated with TGF-β1, phenotypic switches of cardiac fibroblasts to myofibroblasts were observed. Inhibition of ERK1/2 phosphorylation or knockdown of ROCK1 expectedly reduced TGF-β1 induced fibrotic responses. ZYZ-168 appeared to inhibit the fibrotic responses in a concentration dependent manner, in part via a decrease in ROCK 1 expression through inhibition of the phosphorylation status of ERK1/2. For inhibition of ERK1/2 phosphorylation with a specific inhibitor reduced the activation of ROCK1. Considering its anti-apoptosis activity in MI, ZYZ-168 may be a potential drug candidate for treatment of MI-induced cardiac fibrosis. PMID:28266583

  14. Determination of basic physical and mechanical properties of basaltic rocks from P-wave velocity

    NASA Astrophysics Data System (ADS)

    Karakuş, Askeri; Akatay, Mahmut

    2013-12-01

    Physical and mechanical properties of basaltic rocks used as main building material in historical buildings in Diyarbakir show great diversity depending on the place of origin. Especially, earthquake studies as well as restoration jobs and civil engineers and architects who work on building dynamics need to know basic material properties of basaltic rocks that are the main building material. In this study, the basalt samples obtained from 18 different locations of the Diyarbakir area were tested in order to estimate the main material properties of basalts used in historical buildings without collecting samples from them. Subsequently, statistical relationships between the nondestructive P-wave velocity and other properties of basalts were investigated. Consequently, highly correlated models (R2 = 0.717-0.890) were obtained between P-wave velocity and density, porosity, uniaxial compressive strength, Brazilian tensile strength, modulus of elasticity and Poisson's ratio.

  15. ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS

    SciTech Connect

    Thurman E. Scott, Jr., Ph.D.; Younane Abousleiman, Ph.D.; Musharraf Zaman, Ph.D., P.E.

    2002-11-18

    During the sixth quarter of this research project the research team developed a method and the experimental procedures for acquiring the data needed for ultrasonic tomography of rock core samples under triaxial stress conditions as outlined in Task 10. Traditional triaxial compression experiments, where compressional and shear wave velocities are measured, provide little or no information about the internal spatial distribution of mechanical damage within the sample. The velocities measured between platen-to-platen or sensor-to-sensor reflects an averaging of all the velocities occurring along that particular raypath across the boundaries of the rock. The research team is attempting to develop and refine a laboratory equivalent of seismic tomography for use on rock samples deformed under triaxial stress conditions. Seismic tomography, utilized for example in crosswell tomography, allows an imaging of the velocities within a discrete zone within the rock. Ultrasonic or acoustic tomography is essentially the extension of that field technology applied to rock samples deforming in the laboratory at high pressures. This report outlines the technical steps and procedures for developing this technology for use on weak, soft chalk samples. Laboratory tests indicate that the chalk samples exhibit major changes in compressional and shear wave velocities during compaction. Since chalk is the rock type responsible for the severe subsidence and compaction in the North Sea it was selected for the first efforts at tomographic imaging of soft rocks. Field evidence from the North Sea suggests that compaction, which has resulted in over 30 feet of subsidence to date, is heterogeneously distributed within the reservoir. The research team will attempt to image this very process in chalk samples. The initial tomographic studies (Scott et al., 1994a,b; 1998) were accomplished on well cemented, competent rocks such as Berea sandstone. The extension of the technology to weaker samples is

  16. Airborne particulate matter in vitro exposure induces cytoskeleton remodeling through activation of the ROCK-MYPT1-MLC pathway in A549 epithelial lung cells.

    PubMed

    Chirino, Yolanda I; García-Cuellar, Claudia María; García-García, Carlos; Soto-Reyes, Ernesto; Osornio-Vargas, Álvaro Román; Herrera, Luis A; López-Saavedra, Alejandro; Miranda, Javier; Quintana-Belmares, Raúl; Pérez, Irma Rosas; Sánchez-Pérez, Yesennia

    2017-03-06

    Airborne particulate matter with an aerodynamic diameter ≤10μm (PM10) is considered a risk factor for the development of lung cancer. Little is known about the cellular mechanisms by which PM10 is associated with cancer, but there is evidence that its exposure can lead to an acquired invasive phenotype, apoptosis evasion, inflammasome activation, and cytoskeleton remodeling in lung epithelial cells. Cytoskeleton remodeling occurs through actin stress fiber formation, which is partially regulated through ROCK kinase activation, we aimed to investigate if this protein was activated in response to PM10 exposure in A549 lung epithelial cells. Results showed that 10μg/cm(2) of PM10 had no influence on cell viability but increased actin stress fibers, cytoplasmic ROCK expression, and phosphorylation of myosin phosphatase-targeting 1 (MYPT1) and myosin light chain (MLC) proteins, which are targeted by ROCK. The inhibition of ROCK prevented actin stress fiber formation and the phosphorylation of MYPT1 and MLC, suggesting that PM10 activated the ROCK-MYPT1-MLC pathway in lung epithelial cells. The activation of ROCK1 has been involved in the acquisition of malignant phenotypes, and its induction by PM10 exposure could contribute to the understanding of PM10 as a risk factor for cancer development through the mechanisms associated with invasive phenotype.

  17. ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS

    SciTech Connect

    Thurman E. Scott, Jr., Ph.D.; Musharraf Zaman, Ph.D.; Younane Abousleiman, Ph.D.

    2001-04-01

    The oil and gas industry has encountered significant problems in the production of oil and gas from weak rocks (such as chalks and limestones) and from unconsolidated sand formations. Problems include subsidence, compaction, sand production, and catastrophic shallow water sand flows during deep water drilling. Together these cost the petroleum industry hundreds of millions of dollars annually. The goals of this first quarterly report is to document the progress on the project to provide data on the acoustic imaging and mechanical properties of soft rock and marine sediments. The project is intended to determine the geophysical (acoustic velocities) rock properties of weak, poorly cemented rocks and unconsolidated sands. In some cases these weak formations can create problems for reservoir engineers. For example, it cost Phillips Petroleum 1 billion dollars to repair of offshore production facilities damaged during the unexpected subsidence and compaction of the Ekofisk Field in the North Sea (Sulak 1991). Another example is the problem of shallow water flows (SWF) occurring in sands just below the seafloor encountered during deep water drilling operations. In these cases the unconsolidated sands uncontrollably flow up around the annulus of the borehole resulting in loss of the drill casing. The $150 million dollar loss of the Ursa development project in the U.S. Gulf Coast resulted from an uncontrolled SWF (Furlow 1998a,b; 1999a,b). The first three tasks outlined in the work plan are: (1) obtain rock samples, (2) construct new acoustic platens, (3) calibrate and test the equipment. These have been completed as scheduled. Rock Mechanics Institute researchers at the University of Oklahoma have obtained eight different types of samples for the experimental program. These include: (a) Danian Chalk, (b) Cordoba Cream Limestone, (c) Indiana Limestone, (d) Ekofisk Chalk, (e) Oil Creek Sandstone, (f) unconsolidated Oil Creek sand, and (g) unconsolidated Brazos river sand

  18. Experimental investigations for the modeling of chemo-mechanical processes of anhydritic rock

    NASA Astrophysics Data System (ADS)

    Huber, Tara; Pimentel, Erich; Anagnostou, Georg

    2015-04-01

    When anhydritic rock comes into contact with water, the anhydrite dissolves and gypsum precipitates as a result of an oversaturation of the sulphate and calcium ions in the water. This anhydrite to gypsum transformation (AGT) leads to an increase in the solid volume by roughly 61% and possibly also of the pore volume, thus resulting in macroscopic swelling. In tunneling, swelling rock can cause massive damage, since it can exhibit high pressures on the lining or result in large deformations of the lining. Even though this phenomenon has already been observed more than a century ago, AGT in sulphatic rock still raises many open questions. One question we focus on is the mechanical (i.e. stress, strain) behavior of anhydritic rock during swelling. The coupled chemo-mechanical processes, i.e. the development of stresses and strains during AGT, has not been fully understood so far. A chemo-mechanical model must be considered which take anhydrite dissolution, gypsum precipitation as well as stresses and strains into account. In this contribution we present some fundamental research which was done in order to establish a relationship between AGT and the resulting or applied strains and stresses. The research contains experiments on samples consisting of anhydrite and kaolin under oedometric conditions. In order to reduce uncertainties due to swelling of clay as well as inhomogeneous compositions and structures of the natural rock samples, the experiments at the present stage of this research are performed on artificially created, reproducible samples. The samples contain 40% industrial anhydritic powder and 60% Polwhite E Chinaclay (of which the main component is kaolinite). The powders are mixed and compacted in a steel ring under high axial pressure, thus creating intact discs with a dry density of roughly 1.9 g/cm3. In a first series of Oedometer tests the swelling strain under various constant axial stress is measured until the maximal strain is reached. At the

  19. Multi-element analysis of emeralds and associated rocks by k(o) neutron activation analysis

    PubMed

    Acharya; Mondal; Burte; Nair; Reddy; Reddy; Reddy; Manohar

    2000-12-01

    Multi-element analysis was carried out in natural emeralds, their associated rocks and one sample of beryl obtained from Rajasthan, India. The concentrations of 21 elements were assayed by Instrumental Neutron Activation Analysis using the k0 method (k0 INAA method) and high-resolution gamma ray spectrometry. The data reveal the segregation of some elements from associated (trapped and host) rocks to the mineral beryl forming the gemstones. A reference rock standard of the US Geological Survey (USGS BCR-1) was also analysed as a control of the method.

  20. Cigarette Smoke inhibits ROCK2 activation in T cells and modulates IL-22 production

    PubMed Central

    Weng, Chien-Huan; Gupta, Sanjay; Geraghty, Patrick; Foronjy, Robert

    2016-01-01

    Gene-environment interactions are known to play a key role in the development of rheumatoid arthritis (RA). Exposure to cigarette smoke (CS) is one of the strongest environmental risk factors associated with RA and has been shown to mediate a range of complex immunomodulatory effects from decreased T and B cell activation to depressed phagocytic function. The effects of CS on the function of TH17 cells, one of the key TH effector subsets implicated in RA pathogenesis, are not fully understood. IRF4 is one of the crucial transcription factors involved in TH-17 differentiation and is absolutely required for the production of IL-17 and IL-21 but, interestingly, inhibits the synthesis of IL-22. The production of IL-17 and IL-21 by IRF4 can be augmented by its phosphorylation by the serine-threonine kinase ROCK2. Given that CS has been reported to increase ROCK activity in endothelial cells, here we investigated the effects of CS on the ROCK2-IRF4 axis in T cells. Surprisingly, we found that CS leads to decreased ROCK2 activation and IRF4 phosphorylation in T cells. This effect was associated with increased IL-22 production. Using a GEF pull-down assay we furthermore identify ARHGEF1 as a key upstream regulator of ROCK2 whose activity in T cells is inhibited by CS. Thus CS can inhibit the ROCK2-IRF4 axis and modulate T cell production of IL-22. PMID:26882474

  1. E. coli RS2GFP Retention Mechanisms in Laboratory-Scale Fractured Rocks: A Statistical Model

    NASA Astrophysics Data System (ADS)

    Rodrigues, S. N.; Qu, J.; Dickson, S. E.

    2011-12-01

    With billions of gallons of groundwater being withdrawn every day in the US and Canada, it is imperative to understand the mechanisms which jeopardize this resource and the health of those who rely on it. Porous media aquifers have typically been considered to provide significant filtration of particulate matter (e.g. microorganisms), while the fractures in fractured rock aquifers and aquitards are considered to act as contaminant highways allowing a large fraction of pathogens to travel deep into an aquifer relatively quickly. Recent research results indicate that fractured rocks filter out more particulates than typically believed. The goal of the research presented here is to quantify the number of E. coli RS2GFP retained in a single, saturated, laboratory-scale fracture, and to relate the retention of E. coli RS2GFP to the aperture field characteristics and groundwater flow rate. To achieve this goal, physical experiments were conducted at the laboratory-scale to quantify the retention of E. coli RS2GFP through several single, saturated, dolomitic limestone fractures under a range of flow rates. These fractures were also cast with a transparent epoxy in order to visualize the transport mechanisms in the various different aperture fields. The E. coli RS2GFP is tagged with a green-fluorescent protein (GFP) that is used to obtain visualization data when excited by ultraviolet light. A series of experiments was conducted, each of which involved the release of a known number of E. coli RS2GFP at the upstream end of the fracture and measuring the effluent concentration profile. These experiments were conducted using both the natural rock and transparent cast of several different aperture fields, under a range of flow rates. The effects of different aperture field characteristics and flow rates on the retention of E. coli RS2GFP will be determined by conducting a statistical analysis of the retention data under different experimental conditions. The images captured

  2. Ancient microbial activity recorded in fracture fillings from granitic rocks (Äspö Hard Rock Laboratory, Sweden).

    PubMed

    Heim, C; Lausmaa, J; Sjövall, P; Toporski, J; Dieing, T; Simon, K; Hansen, B T; Kronz, A; Arp, G; Reitner, J; Thiel, V

    2012-07-01

    Fracture minerals within the 1.8-Ga-old Äspö Diorite (Sweden) were investigated for fossil traces of subterranean microbial activity. To track the potential organic and inorganic biosignatures, an approach combining complementary analytical techniques of high lateral resolution was applied to drill core material obtained at -450 m depth in the Äspö Hard Rock Laboratory. This approach included polarization microscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS), confocal Raman microscopy, electron microprobe (EMP) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The fracture mineral succession, consisting of fluorite and low-temperature calcite, showed a thin (20-100 μm), dark amorphous layer lining the boundary between the two phases. Microscopic investigations of the amorphous layer revealed corrosion marks and, in places, branched tubular structures within the fluorite. Geochemical analysis showed significant accumulations of Si, Al, Mg, Fe and the light rare earth elements (REE) in the amorphous layer. In the same area, ToF-SIMS imaging revealed abundant, partly functionalized organic moieties, for example, C(x)H(y)⁺, C(x)H(y)N⁺, C(x)H(y)O⁺. The presence of such functionalized organic compounds was corroborated by Raman imaging showing bands characteristic of C-C, C-N and C-O bonds. According to its organic nature and the abundance of relatively unstable N- and O- heterocompounds, the organic-rich amorphous layer is interpreted to represent the remains of a microbial biofilm that established much later than the initial cooling of the Precambrian host rock. Indeed, δ¹³C, δ¹⁸O and ⁸⁷Sr/⁸⁶Sr isotope data of the fracture minerals and the host rock point to an association with a fracture reactivation event in the most recent geological past.

  3. Digital Rock Physics: Mechanical Properties of Carbonate Core Plug at Different Resolutions

    NASA Astrophysics Data System (ADS)

    Faisal, T. F.; Jouini, M. S.; Islam, A.; Chevalier, S.; Jouiad, M.; Sassi, M.

    2014-12-01

    Digital Rock Physics (DRP) is a novel technology that could be used to generate accurate, fast and cost effective special core analysis (SCAL) properties to support reservoir characterization and simulation tools. For this work, Micro-CT images at different resolutions have been used to run simulations to determine elastic properties like bulk, shear, Young's Modulus and Poisson's ratio of a dry carbonate core plug from Abu Dhabi reservoirs. Pre processing and segmentation of raw images is performed in FEI 3D visualization and analysis tool Avizo. Carbonates are characterized by a very complex pore-space structure and so a high degree of heterogeneity. Abaqus that is based on Finite Element Method is used to run 2D and 3D elastic simulations. Results will be compared by simulating the same core-plug in an alternative segmentation and FEM modeling environment used previously by Jouini & Vega et al. 2012 [1]. Acoustic wave propagation experiments at different confining pressures are performed in the laboratory Triaxial machine to determine the dynamic Young's modulus and Poisson's ratio for the same core plug. Expeirmental results are compared with numerical results. [1] Jouini, M.S. and Vega, S. 2012. Simulation of carbonate rocks elastic properties using 3D X-Ray computed tomography images based on Discrete Element Method and Finite Element Method. 46th US Rock Mechanics / Geomechanics Symposium, Chicago, Il, USA, 24-27 June 2012.

  4. Rock Finding

    ERIC Educational Resources Information Center

    Rommel-Esham, Katie; Constable, Susan D.

    2006-01-01

    In this article, the authors discuss a literature-based activity that helps students discover the importance of making detailed observations. In an inspiring children's classic book, "Everybody Needs a Rock" by Byrd Baylor (1974), the author invites readers to go "rock finding," laying out 10 rules for finding a "perfect" rock. In this way, the…

  5. Young Scientists Explore Rocks & Minerals. Book 11--Intermediate Level. A Good Apple Activity Book.

    ERIC Educational Resources Information Center

    DeBruin, Jerry

    Designed to develop creativity in young learners, this book contains interdisciplinary activities which focus on the theme of rocks and minerals. Activity pages are provided that can serve as front and back covers of a student booklet and the suggested activities can be duplicated for insertion between the covers resulting in a booklet for each…

  6. Whisking mechanics and active sensing.

    PubMed

    Bush, Nicholas E; Solla, Sara A; Hartmann, Mitra Jz

    2016-10-01

    We describe recent advances in quantifying the three-dimensional (3D) geometry and mechanics of whisking. Careful delineation of relevant 3D reference frames reveals important geometric and mechanical distinctions between the localization problem ('where' is an object) and the feature extraction problem ('what' is an object). Head-centered and resting-whisker reference frames lend themselves to quantifying temporal and kinematic cues used for object localization. The whisking-centered reference frame lends itself to quantifying the contact mechanics likely associated with feature extraction. We offer the 'windowed sampling' hypothesis for active sensing: that rats can estimate an object's spatial features by integrating mechanical information across whiskers during brief (25-60ms) windows of 'haptic enclosure' with the whiskers, a motion that resembles a hand grasp.

  7. Numerical Investigation of Seismically Induced Rock Mass Fatigue as a Mechanism Contributing to the Progressive Failure of Deep-Seated Landslides

    NASA Astrophysics Data System (ADS)

    Gischig, Valentin; Preisig, Giona; Eberhardt, Erik

    2016-06-01

    The importance of earthquakes in triggering catastrophic failure of deep-seated landslides has long been recognized and is well documented in the literature. However, seismic waves do not only act as a trigger mechanism. They also contribute to the progressive failure of large rock slopes as a fatigue process that is highly efficient in deforming and damaging rock slopes. Given the typically long recurrence time and unpredictability of earthquakes, field-based investigations of co-seismic rock slope deformations are difficult. We present here a conceptual numerical study that demonstrates how repeated earthquake activity over time can destabilize a relatively strong rock slope by creating and propagating new fractures until the rock mass is sufficiently weakened to initiate catastrophic failure. Our results further show that the damage and displacement induced by a certain earthquake strongly depends on pre-existing damage. In fact, the damage history of the slope influences the earthquake-induced displacement as much as earthquake ground motion characteristics such as the peak ground acceleration. Because seismically induced fatigue is: (1) characterized by low repeat frequency, (2) represents a large amplitude damage event, and (3) weakens the entire rock mass, it differs from other fatigue processes. Hydro-mechanical cycles, for instance, occur at higher repeat frequencies (i.e., annual cycles), lower amplitude, and only affect limited parts of the rock mass. Thus, we also compare seismically induced fatigue to seasonal hydro-mechanical fatigue. While earthquakes can progressively weaken even a strong, competent rock mass, hydro-mechanical fatigue requires a higher degree of pre-existing damage to be effective. We conclude that displacement rates induced by hydro-mechanical cycling are indicative of the degree of pre-existing damage in the rock mass. Another indicator of pre-existing damage is the seismic amplification pattern of a slope; frequency

  8. A New Rock Strength Criterion from Microcracking Mechanisms Which Provides Theoretical Evidence of Hybrid Failure

    NASA Astrophysics Data System (ADS)

    Zhu, Qi-Zhi

    2017-02-01

    A proper criterion describing when material fails is essential for deep understanding and constitutive modeling of rock damage and failure by microcracking. Physically, such a criterion should be the global effect of local mechanical response and microstructure evolution inside the material. This paper aims at deriving a new mechanisms-based failure criterion for brittle rocks, based on micromechanical unilateral damage-friction coupling analyses rather than on the basic results from the classical linear elastic fracture mechanics. The failure functions respectively describing three failure modes (purely tensile mode, tensile-shear mode as well as compressive-shear mode) are achieved in a unified upscaling framework and illustrated in the Mohr plane and also in the plane of principal stresses. The strength envelope is proved to be continuous and smooth with a compressive to tensile strength ratio dependent on material properties. Comparisons with experimental data are finally carried out. By this work, we also provide a theoretical evidence on the hybrid failure and the smooth transition from tensile failure to compressive-shear failure.

  9. Field and in-situ rock-mechanics testing manual. Technical report

    SciTech Connect

    Shuri, F S; Feves, M L; Peterson, G L; Foster, K M; Kienle, Jr, C F

    1981-10-01

    Standardized field and in situ rock mechanics testing procedures have been prepared for use in the National Terminal Waste Storage Program. The procedures emphasize equipment performance specifications, documentation and reporting, and Quality Assurance acceptance criteria. Sufficient theoretical background is included to allow the user to perform the necessary data reduction. These procedures incorporate existing standards when possible, otherwise they represent the current state of the art. Maximum flexibility in equipment design has been incorporated to allow use of this manual by existing groups and to encourage future improvements.

  10. Abnormal Activation of RhoA/ROCK-I Signaling in Junctional Zone Smooth Muscle Cells of Patients With Adenomyosis.

    PubMed

    Wang, S; Duan, H; Zhang, Y; Sun, F Q

    2016-03-01

    Adenomyosis (ADS) is a common estrogen-dependent gynecological disease with unknown etiology. The RhoA/Rho-kinase (ROCK) signaling pathway is involved in various cellular functions, including migration, proliferation, and smooth muscle contraction. Here we examined the potential role of this pathway in junctional zone (JZ) contraction in women with and without ADS. We demonstrated that in the normal JZ, RhoA and ROCK-I messenger RNA (mRNA) and protein expression was significantly higher in the proliferative phase of the menstrual cycle than in the secretory phase. Expression of RhoA and ROCK-I in the JZ from women with ADS was significantly higher than in the control women and showed no significant differences across the menstrual cycle. Treatment of JZ smooth muscle cells (JZSMCs) with estrogen at 0, 1, 10, or 100 nmol/L for 24 hours resulted in increased expression of RhoA, ROCK-I, and myosin light-chain (MLC) phosphorylation (p-MLC) in a dose-dependent manner. In parallel to its effects on p-MLC, estrogen-mediated, dose-dependent contraction responses in JZSMCs. Estrogen-mediated contraction in the ADS group was significantly higher than in the controls and also showed no significant differences across the menstrual cycle. These effects were suppressed in the presence of ICI 182780 or Y27632, supporting an estrogen receptor-dependent and RhoA activation-dependent mechanism. Our results indicate that the level of RhoA and ROCK-I increases in patients with ADS and the cyclic change is lost. Estrogen may affect uterine JZ contraction of ADS by enhancing RhoA/ ROCK-I signaling.

  11. Stress Activation and Propagation of Electronic Charge Carriers in Igneous Rocks

    NASA Astrophysics Data System (ADS)

    Ling, J.; Freund, F. T.

    2007-12-01

    Igneous and high-grade metamorphic rocks in the Earth's crust generate electric currents when subjected to deviatoric stresses. The reason is that these rocks contain dormant electronic charge carriers in the form of peroxy links. Peroxy links are sites in the crystal structures of the constituent minerals where oxygen anions have converted from their common 2- valence state to the 1- valence state, O3X-OO-XO3 with X=Si4+, Al3+ etc. As rocks are stressed and dislocations sweep through the mineral grains, the peroxy links break up, activating electrons and pholes ("phole" is an abbreviation for "positive hole", a defect electron on the oxygen sublattice, chemically O- in a matrix of O2-). The pholes are mobile electronic charge carriers that can spread out of the stressed rock into the surrounding unstressed rock. They travel via energy levels at the upper edge of the valence bands, cross grain boundaries and achieve a phase velocity on the order of 200±50 m/sec, consistent with phonon-assisted electron hopping. Due to mutual repulsion inside the rock volume the pholes spread to the surface, where they build up a positive surface charge. The surface charge can be measured with a non-contact capacitive sensor. If a Cu contact is applied to the surface of the rock, electrons are injected from ground into the rock in response to the evolving positive charge on the rock surface. We modeled surface potentials and burst-like electron injections following low and medium velocity impact experiments, 100 m/sec and 1.5 km/sec respectively.

  12. Fundamental Research on Percussion Drilling: Improved rock mechanics analysis, advanced simulation technology, and full-scale laboratory investigations

    SciTech Connect

    Michael S. Bruno

    2005-12-31

    This report summarizes the research efforts on the DOE supported research project Percussion Drilling (DE-FC26-03NT41999), which is to significantly advance the fundamental understandings of the physical mechanisms involved in combined percussion and rotary drilling, and thereby facilitate more efficient and lower cost drilling and exploration of hard-rock reservoirs. The project has been divided into multiple tasks: literature reviews, analytical and numerical modeling, full scale laboratory testing and model validation, and final report delivery. Literature reviews document the history, pros and cons, and rock failure physics of percussion drilling in oil and gas industries. Based on the current understandings, a conceptual drilling model is proposed for modeling efforts. Both analytical and numerical approaches are deployed to investigate drilling processes such as drillbit penetration with compression, rotation and percussion, rock response with stress propagation, damage accumulation and failure, and debris transportation inside the annulus after disintegrated from rock. For rock mechanics modeling, a dynamic numerical tool has been developed to describe rock damage and failure, including rock crushing by compressive bit load, rock fracturing by both shearing and tensile forces, and rock weakening by repetitive compression-tension loading. Besides multiple failure criteria, the tool also includes a damping algorithm to dissipate oscillation energy and a fatigue/damage algorithm to update rock properties during each impact. From the model, Rate of Penetration (ROP) and rock failure history can be estimated. For cuttings transport in annulus, a 3D numerical particle flowing model has been developed with aid of analytical approaches. The tool can simulate cuttings movement at particle scale under laminar or turbulent fluid flow conditions and evaluate the efficiency of cutting removal. To calibrate the modeling efforts, a series of full-scale fluid hammer

  13. New mechanism of lenalidomide activity.

    PubMed

    Keevan, Jacob; Figg, William D

    2014-08-01

    Lenalidomide is an immunomodulatory agent (IMiD) that has activity in hematologic cancer (e.g., multiple myeloma). The immunomodulatory and apoptotic properties are readily apparent in therapy. However, the exact mechanism of action has been difficult to quantify until recently when it was shown that another IMiD, thalidomide, binds to an E3 ubiquitin ligase complex constituent, CRBN. The article by Kronke et al. demonstrates that, by binding to CRBN and altering its selectivity, lenalidomide potentiates the ubiquitination and proteolysis of 2 specific proteins, IKZF1 and IKZF3. An article in the same issue, by Lu et al., supports these observations. IKZF1 and IKZF3 are transcription factors that are necessary for multiple myeloma, and repression of these transcription factors is a likely mechanism for lenalidomide activity in this disease.

  14. Reading the Rocks. A Fall Activity Packet for Fifth Grade.

    ERIC Educational Resources Information Center

    Jackson Community Coll., MI. Dahlem Environmental Education Center.

    This instructional packet is one of 14 school environmental education programs developed for use in the classroom and at the Dahlem Environmental Education Center (DEEC) of the Jackson Community College (Michigan). Provided in the packet are pre-trip activities, field trip activities, and post-trip activities which focus on various geological…

  15. A Dynamic Damage Mechanics Source Model for Explosions in Crystalline Rock

    NASA Astrophysics Data System (ADS)

    Mihaly, J. M.; Bhat, H. S.; Sammis, C. G.; Rosakis, A.

    2011-12-01

    The micromechanical damage mechanics formulated by Ashby and Sammis [PAGEOPH, 1990] and generalized by Deshpande and Evans [J. Mech. Phys. Solids, 2008] has been extended to allow for a more generalized stress state and to incorporate an experimentally motivated crack growth (damage evolution) law that is valid over a wide range of loading rates. This law is sensitive to both the crack tip stress field and its time derivative, and thus produces strain-rate sensitivity in the constitutive response. The model is experimentally verified by predicting the failure strength of Dionysus-Pentelicon marble over strain rates ranging from to . This rate-dependent damage mechanics has been implemented in the ABAQUS dynamic finite element code and used to explore the effects of burn rate (loading rate) and lithostatic stress on the spatial extent of fracture damage and S waves generated by explosions in crystalline rock. Slower rise times and longer pressure pulses produce more damage and stronger S waves.

  16. Active and passive seismic methods for characterization and monitoring of unstable rock masses: field surveys, laboratory tests and modeling.

    NASA Astrophysics Data System (ADS)

    Colombero, Chiara; Baillet, Laurent; Comina, Cesare; Jongmans, Denis; Vinciguerra, Sergio

    2016-04-01

    Appropriate characterization and monitoring of potentially unstable rock masses may provide a better knowledge of the active processes and help to forecast the evolution to failure. Among the available geophysical methods, active seismic surveys are often suitable to infer the internal structure and the fracturing conditions of the unstable body. For monitoring purposes, although remote-sensing techniques and in-situ geotechnical measurements are successfully tested on landslides, they may not be suitable to early forecast sudden rapid rockslides. Passive seismic monitoring can help for this purpose. Detection, classification and localization of microseismic events within the prone-to-fall rock mass can provide information about the incipient failure of internal rock bridges. Acceleration to failure can be detected from an increasing microseismic event rate. The latter can be compared with meteorological data to understand the external factors controlling stability. On the other hand, seismic noise recorded on prone-to-fall rock slopes shows that the temporal variations in spectral content and correlation of ambient vibrations can be related to both reversible and irreversible changes within the rock mass. We present the results of the active and passive seismic data acquired at the potentially unstable granitic cliff of Madonna del Sasso (NW Italy). Down-hole tests, surface refraction and cross-hole tomography were carried out for the characterization of the fracturing state of the site. Field surveys were implemented with laboratory determination of physico-mechanical properties on rock samples and measurements of the ultrasonic pulse velocity. This multi-scale approach led to a lithological interpretation of the seismic velocity field obtained at the site and to a systematic correlation of the measured velocities with physical properties (density and porosity) and macroscopic features of the granitic cliff (fracturing, weathering and anisotropy). Continuous

  17. Assessment of rock mechanical properties and seismic slope stability in variably weathered layered basalts

    NASA Astrophysics Data System (ADS)

    Greenwood, William; Clark, Marin; Zekkos, Dimitrios; Von Voigtlander, Jennifer; Bateman, Julie; Lowe, Katherine; Hirose, Mitsuhito; Anderson, Suzanne; Anderson, Robert; Lynch, Jerome

    2016-04-01

    A field and laboratory experimental study was conducted to assess the influence of weathering on the mechanical properties of basalts in the region of the Kohala volcano on the island of Hawaii. Through the systematic characterization of the weathering profiles developed in different precipitation regimes, we aim to explain the regional pattern of stability of slopes in layered basalts that were observed during the 2006 Mw 6.7 Kiholo Bay earthquake. While deeper weathering profiles on the wet side of the island might be expected to promote more and larger landslides, the distribution of landslides during the Kiholo Bay earthquake did not follow this anticipated trend. Landslide frequency (defined as number of landslides divided by total area) was similar on the steepest slopes (> 50-60) for both the dry and the wet side of the study area suggesting relatively strong ground materials irrespective of weathering. The study location is ideally suited to investigate the role of precipitation, and more broadly of climate, on the mechanical properties of the local rock units because the presence of the Kohala volcano produces a significant precipitation gradient on what are essentially identical basaltic flows. Mean annual precipitation (MAP) varies by more than an order of magnitude, from 200 mm/year on the western side of the volcano to 4000 mm/year in the eastern side. We will present results of measured shear wave velocities using a seismic surface wave methodology. These results were paired with laboratory testing on selected basalt specimens that document the sample-scale shear wave velocity and unconfined compressive strength of the basaltic rocks. Shear wave velocity and unconfined strength of the rocks are correlated and are both significantly lower in weathered rocks near the ground surface than at depth. This weathering-related reduction in shear wave velocity extends to greater depths in areas of high precipitation compared to areas of lower precipitation

  18. Shrinkage Cracking: A mechanism for self-sustaining carbon mineralization reactions in olivine rocks

    NASA Astrophysics Data System (ADS)

    Zhu, W.; Fusseis, F.; Lisabeth, H. P.; Xing, T.; Xiao, X.; De Andrade, V. J. D.; Karato, S. I.

    2015-12-01

    The hydration and carbonation of olivine results in an up to ~44% increase in solid molar volume, which may choke off of fluid supply and passivate reactive surfaces, thus preventing further carbonation reactions. The carbonation of olivine has ben studied extensively in the laboratory. To date, observations from these experimental studies indicate that carbonation reaction rates generally decrease with time and the extent of carbonation is limited in olivine rocks. Field studies, however, show that 100% hydration and carbonation occur naturally in ultramafic rocks. The disagreement between the laboratory results under controlled conditions and the field observations underlines the lack of understanding of the mechanisms responsible for the self-sustaining carbonation interaction in nature. We developed a state-of-the-art pressurized hydrothermal cell that is transparent to X-rays to characterize the real-time evolution of pore geometry during fluid-rock interaction using in-situ synchrotron-based X-ray microtomography. Through a time series of high-resolution 3-dimensional images, we document the microstructural evolution of a porous olivine aggregate reacting with a sodium bicarbonate solution at elevated pressure and temperature conditions. We observed porosity increases, near constant rate of crystal growth, and pervasive reaction-induced fractures. Based on the nanometer scale tomography data, we propose that shrinkage cracking is the mechanism responsible for producing new reactive surface and keep the carbonation reaction self-sustaining in our experiment. Shrinkage cracks are commonly observed in drying mud ponds, cooling lava flows and ice wedge fields. Stretching of a contracting surface bonded to a substrate of nearly constant dimensions leads to a stress buildup in the surface layer. When the stress exceeds the tensile strength, polygonal cracks develop in the surface layer. In our experiments, the stretching mismatch between the surface and interior of

  19. Numerical investigation of the hydro-mechanical contribution to seismic attenuation in damaged rocks

    NASA Astrophysics Data System (ADS)

    Pollmann, Nele; Jänicke, Ralf; Renner, Jörg; Steeb, Holger

    2016-04-01

    The investigation of hydro-mechanical processes, in particular the modeling of seismic waves in fractured porous media, is essential for the physical interpretation of data obtained from seismic exploration. Here, we specifically investigate attenuation processes in fluid-saturated porous rock containing fracture networks to identify effective hydro-mechanical properties by numerical simulation. The main purpose of this work is the characterization of the overall hydro-mechanical properties by computational homogenization. We determine an effective Skempton coefficient by investigating the fluid pressure and the solid displacement of the skeleton saturated by compressible fluids. Fracture networks are stochastically generated to mimic geological in-situ situations. The fractures are approximated as ellipses with aspect ratios up to 1/100, i.e. they constitute thin and long hydraulic conduits with high permeabilities. Simulations are designed on the material scale with and without conservation of fluid mass in the control volume. Using computational homogenization approaches, we define an effective Skempton coefficient. A range of fracture networks with different characteristic properties is studied for different varieties of fractures. On the material scale we find strongly heterogeneous pressure propagation in the fracture network and the surrounding rock, respectively. The pressure diffusion is much faster in the fracture network than in the matrix, rendering the macroscopic hydro-mechanical behavior strongly time dependent. The effective Skempton coefficient converges to an ensemble-specific instantaneous value and to 1 for long-time studies. The ultimate objective of our study is to evaluate whether constraints on the structure of fracture networks can be deduced from observations of attenuation and its frequency dependence.

  20. Mechanical Behavior of Low Porosity Carbonate Rock: From Brittle Creep to Ductile Creep.

    NASA Astrophysics Data System (ADS)

    Nicolas, A.; Fortin, J.; Gueguen, Y.

    2014-12-01

    Mechanical compaction and associated porosity reduction play an important role in the diagenesis of porous rocks. They may also affect reservoir rocks during hydrocarbon production, as the pore pressure field is modified. This inelastic compaction can lead to subsidence, cause casing failure, trigger earthquake, or change the fluid transport properties. In addition, inelastic deformation can be time - dependent. In particular, brittle creep phenomena have been deeply investigated since the 90s, especially in sandstones. However knowledge of carbonates behavior is still insufficient. In this study, we focus on the mechanical behavior of a 14.7% porosity white Tavel (France) carbonate rock (>98% calcite). The samples were deformed in a triaxial cell at effective confining pressures ranging from 0 MPa to 85 MPa at room temperature and 70°C. Experiments were carried under dry and water saturated conditions in order to explore the role played by the pore fluids. Two types of experiments have been carried out: (1) a first series in order to investigate the rupture envelopes, and (2) a second series with creep experiments. During the experiments, elastic wave velocities (P and S) were measured to infer crack density evolution. Permeability was also measured during creep experiments. Our results show two different mechanical behaviors: (1) brittle behavior is observed at low confining pressures, whereas (2) ductile behavior is observed at higher confining pressures. During creep experiments, these two behaviors have a different signature in term of elastic wave velocities and permeability changes, due to two different mechanisms: development of micro-cracks at low confining pressures and competition between cracks and microplasticity at high confining pressure. The attached figure is a summary of 20 triaxial experiments performed on Tavel limestone under different conditions. Stress states C',C* and C*' and brittle strength are shown in the P-Q space: (a) 20°C and dry

  1. Discoidin domain receptor 1 promotes Th17 cell migration by activating the RhoA/ROCK/MAPK/ERK signaling pathway

    PubMed Central

    Azreq, Mohammed-Amine El; Kadiri, Maleck; Boisvert, Marc; Pagé, Nathalie; Tessier, Philippe A.; Aoudjit, Fawzi

    2016-01-01

    Effector T cell migration through the tissue extracellular matrix (ECM) is an important step of the adaptive immune response and in the development of inflammatory diseases. However, the mechanisms involved in this process are still poorly understood. In this study, we addressed the role of a collagen receptor, the discoidin domain receptor 1 (DDR1), in the migration of Th17 cells. We showed that the vast majority of human Th17 cells express DDR1 and that silencing DDR1 or using the blocking recombinant receptor DDR1:Fc significantly reduced their motility and invasion in three-dimensional (3D) collagen. DDR1 promoted Th17 migration by activating RhoA/ROCK and MAPK/ERK signaling pathways. Interestingly, the RhoA/ROCK signaling module was required for MAPK/ERK activation. Finally, we showed that DDR1 is important for the recruitment of Th17 cells into the mouse dorsal air pouch containing the chemoattractant CCL20. Collectively, our results indicate that DDR1, via the activation of RhoA/ROCK/MAPK/ERK signaling axis, is a key pathway of effector T cell migration through collagen of perivascular tissues. As such, DDR1 can contribute to the development of Th17-dependent inflammatory diseases. PMID:27391444

  2. Biological energy from the igneous rock enhances cell growth and enzyme activity.

    PubMed

    Lin, Y; Kuo, H; Chen, C; Kuo, S

    2000-08-01

    Some effects from natural resources might be ignored and unused by humans. Environmental hormesis could be a phenomena necessary to bio-organism existence on earth. Since 1919, radiation and some heavy metal hormesis from the environment were proved in various reports. In this study, igneous rock with very low radioactivity and high ferrous activity was measured by multichannel analyzer and inductively coupled plasma analyzer. The water treated by igneous rock, both directly soaked or indirectly in contact, induced increased activities of glucose oxidase, catalase, peroxidase, and superoxide dismutase. It also increased cell growth of SC-M1, HCT-15, Raji, and fibroblast cell lines. The water after treatment of igneous rock had no change in pH values, but displayed decreased conductivity values. We assume that the igneous rock could transfer energy to water to change the molecular structure or conformation of water cluster, or by radiation hormesis effect could then induce increased enzyme activity and cell growth. It is also possible that the energy from rock may combine radiation hormesis with other transferable biological energy forms to change water cluster conformation.

  3. Rock squirrel (Spermophilus variegatus) blood sera affects proteolytic and hemolytic activities of rattlesnake venoms.

    PubMed

    Biardi, James E; Coss, Richard G

    2011-02-01

    Rock squirrels (Spermophilus variegatus) from two sites in south central New Mexico, where prairie (Crotalus viridis viridis) and western diamondback (Crotalus atrox) rattlesnakes are common predators, were assayed for inhibition of rattlesnake venom digestive and hemostatic activities. At statistically significant levels rock squirrel blood sera reduced the metalloprotease and hemolytic activity of venoms from C. v. viridis and C. atrox more than venom from an allopatric snake species, the northern Pacific rattlesnake (Crotalus oreganus). In contrast, general proteolytic activity of venom from C. oreganus was inhibited more by S. variegatus serum defenses than activity of venom from sympatric snakes. For all three venoms, incubation with squirrel sera increased the level of fibrinolysis over venom-only treatments. These results suggest that rock squirrels (S. variegatus) can defend against metalloproteases and other proteases after envenomation from at least two of five rattlesnake predators they might encounter. However, there were statistically significant differences between general proteolytic activity and fibrinolytic activity of C. v. viridis and C. atrox venom, suggesting that rock squirrels might be differentially vulnerable to these two predators. The hypothesis that prey resistance influences snake venom evolution in a predator-prey arms race is given further support by the previously cryptic variation in venoms detected when assayed against prey defenses.

  4. Mechanical Assessment of the Drep Shield Subject to Vibratory Motion and Dynamic and Static Rock Loading

    SciTech Connect

    R.C. Quittmeyer

    2005-11-16

    The purpose of the drip shield (DS) is to divert water that may seep into emplacement drifts from contacting the waste packages, and to protect the waste packages from impact or static loading from rockfall. The objective of this document is to summarize, into one location, the results of a series of supporting engineering calculations that were developed to study the effect of static and dynamic loads on the mechanical performance of the DS. The potential DS loads are a result of: (1) Potential earthquake vibratory ground motion, and resulting interaction of the DS, waste package and pallet, and drift invert; (2) Dynamic impacts of rockfall resulting from emplacement drift damage as a result of earthquake vibratory motion; and (3) Static load of the caved rock rubble that may come to rest on the DS as a result of vibratory motion or from time-dependent yielding of the rock mass surrounding the emplacement drift. The potential mechanical failure mechanisms that may result from these loads include: (1) Overturning and/or separation of the interlocking DS segments; (2) Loss of structural integrity and stability of the DS, including excessive deformation or buckling; and (3) Localized damage to the top and side-wall plates of the DS. The scope of this document is limited to summarizing results presented in the supporting calculations in the areas of analysis of the potential for DS collapse, and determination of the damaged surface area of the DS plates. New calculations are presented to determine whether or not separation of DSs occur under vibratory motion.

  5. Mechanical behavior of low porosity carbonate rock: from brittle creep to ductile creep

    NASA Astrophysics Data System (ADS)

    Nicolas, A.; Fortin, J.; Gueguen, Y.

    2013-12-01

    Mechanical compaction and associated porosity reduction play an important role in the diagenesis of porous rocks. They may also affect reservoir rocks during hydrocarbon production, as the pore pressure field is modified. This inelastic compaction can lead to subsidence, cause casing failure, trigger earthquake, or change the fluid transport properties. In addition, inelastic deformation can be time - dependent. In particular, brittle creep phenomena have been deeply investigated since the 90s, especially in sandstones. However knowledge of carbonates behavior is still insufficient. In this experimental study, we focus on the mechanical behavior of a low porosity (9%) white Tavel (France) carbonate rock (>98% calcite) at P-Q conditions beyond the elastic domain. It has been shown that in sandstones composed of quartz, cracks are developing under these conditions. However, in carbonates, calcite minerals can meanwhile also exhibit microplasticity. The samples were deformed in the triaxial cell of the Ecole Normale Superieure de Paris at effective confining pressures ranging from 35 MPa to 85 MPa and room temperature. Experiments were carried on dry and water saturated samples to explore the role played by the pore fluids. Time dependency was investigated by a creep steps methodology: at each step, differential stress was increased rapidly and kept constant for at least 24h. During these steps elastic wave velocities (P and S) and permeability were measured continuously. Our results show two different creep behaviors: (1) brittle creep is observed at low confining pressures, whereas (2) ductile creep is observed at higher confining pressures. These two creep behaviors have a different signature in term of elastic wave velocities and permeability changes. Indeed, in the brittle domain, the primary creep is associated with a decrease of elastic wave velocities and an increase of permeability, and no secondary creep is observed. In the ductile domain, the primary creep

  6. Analysis of propagation mechanisms of stimulation-induced fractures in rocks

    NASA Astrophysics Data System (ADS)

    Krause, Michael; Renner, Joerg

    2016-04-01

    Effectivity of geothermal energy production depends crucially on the heat exchange between the penetrated hot rock and the circulating water. Hydraulic stimulation of rocks at depth intends to create a network of fractures that constitutes a large area for exchange. Two endmembers of stimulation products are typically considered, tensile hydro-fractures that propagate in direction of the largest principal stress and pre-existing faults that are sheared when fluid pressure reduces the effective normal stress acting on them. The understanding of the propagation mechanisms of fractures under in-situ conditions is still incomplete despite intensive research over the last decades. Wing-cracking has been suggested as a mechanism of fracture extension from pre-existent faults with finite length that are induced to shear. The initiation and extension of the wings is believed to be in tensile mode. Open questions concern the variability of the nominal material property controlling tensile fracture initiation and extension, the mode I facture toughness KIC, with in-situ conditions, e.g., its mean-stress dependence. We investigated the fracture-propagation mechanism in different rocks (sandstones and granites) under varying conditions mimicking those representative for geothermal systems. To determine KIC-values we performed 3-point bending experiments. We varied the confining pressure, the piston velocity, and the position of the chevron notch relative to the loading configuration. Additional triaxial experiments at a range of confining pressures were performed to study wing crack propagation from artificial flaws whose geometrical characteristics, i.e., length, width, and orientation relative to the axial load are varied. We monitored acoustic emissions to constrain the spacio-temporal evolution of the fracturing. We found a significant effect of the length of the artificial flaw and the confining pressure on wing-crack initiation but did not observe a systematic dependence

  7. Dyke propagation and tensile fracturing at high temperature and pressure, insights from experimental rock mechanics.

    NASA Astrophysics Data System (ADS)

    Bakker, Richard; Benson, Philip; Vinciguerra, Sergio

    2014-05-01

    It is well known that magma ascends trough the crust by the process of dyking. To enable dyke emplacement, basement rocks typically fail in a mode 1 fracture, which acts as conduits for magma transport. An overpressure of the ascending magma will further open/widen the fracture and permit the fracture to propagate. In order to further understand the emplacement and arrest of dykes in the subsurface, analogue and numerical studies have been conducted. However, a number of assumptions regarding rock mechanical behaviour frequently has to be made as such data are very hard to directly measure at the pressure/temperature conditions of interest: high temperatures at relatively shallow depths. Such data are key to simulating the magma intrusion dynamics through the lithologies that underlie the volcanic edifice. Here we present a new laboratory setup, which allows us to investigate the tensile fracturing properties under both temperature and confining pressure, and the emplacement of molten material within the newly formed fracture. We have modified a traditional tri-axial test assembly setup to be able to use a Paterson type High Pressure, High Temperature deformation apparatus. Sample setup consists of cylindrical rock samples with a 22 mm diameter and a 8 mm bore at their centre, filled with a material chosen as such that it's in a liquid state at the experimental temperature and solid at room temperature to enable post-experiment analysis. The top and lower parts of the rock sample are fitted with plugs, sealing in the melt. The assembly is then placed between ceramic pistons to ensure there are no thermal gradients across the sample. The assembly is jacketed to ensure the confining medium (Ar) cannot enter the assembly. A piston is driven into the sample such that the inner conduit materials pressure is slowly increased. At some point a sufficient pressure difference between the inner and outer surfaces causes the sample to deform and fail in the tensile regime

  8. The geology and mechanics of formation of the Fort Rock Dome, Yavapai County, Arizona

    USGS Publications Warehouse

    Fuis, Gary S.

    1996-01-01

    The Fort Rock Dome, a craterlike structure in northern Arizona, is the erosional product of a circular domal uplift associated with a Precambrian shear zone exposed within the crater and with Tertiary volcanism. A section of Precambrian to Quaternary rocks is described, and two Tertiary units, the Crater Pasture Formation and the Fort Rock Creek Rhyodacite, are named. A mathematical model of the doming process is developed that is consistent with the history of the Fort Rock Dome.

  9. Predicting Folding Sequences Based on the Maximum Rock Strength and Mechanical Equilibrium

    NASA Astrophysics Data System (ADS)

    Cubas, N.; Souloumiac, P.; Maillot, B.; Leroy, Y. M.

    2007-12-01

    The objective is to propose and validate simple procedures, compared to the finite-element method, to select and optimize the dominant mode of folding in fold-and-thrust belts and accretionary wedges, and to determine its stress distribution. Mechanical equilibrium as well as the constraints due to the limited rock strength of the bulk material and of major discontinuities, such as décollements, are accounted for. The first part of the proposed procedure, which is at the core of the external approach of classical limit analysis, consists in estimating the least upper bound on the tectonic force by minimisation of the internal dissipation and part of the external work. The new twist to the method is that the optimization is also done with respect to the geometry of the evolving fold. If several folding events are possible, the dominant mode is the one leading to the least upper bound. The second part of the procedure is based on the Equilibrium Element Method, which is an application of the internal approach of limit analysis. The optimum stress field, obtained by spatial discretisation of the fold, provides the best lower bound on the tectonic force. The difference between the two bounds defines an error estimate of the exact unknown tectonic force. To show the merits of the proposed procedure, its first part is applied to predict the life span of a thrust within an accretionary prism, from its onset, its development with a relief build up and its arrest because of the onset of a more favorable new thrust (Cubas et al., 2007). This life span is sensitive to the friction angles over the ramp and the décollement. It is shown how the normal sequence of thrusting in a supercritical wedge is ended with the first out-of sequence event. The second part of the procedure provides the stress state over each thrust showing that the active back thrust is a narrow fan which dip is sensitive to the friction angle over the ramp and the amount of relief build up (Souloumiac et

  10. Substrate Stiffness Influences Doxorubicin-Induced p53 Activation via ROCK2 Expression

    PubMed Central

    Ebata, Takahiro; Mitsui, Yasumasa; Sugimoto, Wataru; Maeda, Miho; Machiyama, Hiroaki; Harada, Ichiro; Sawada, Yasuhiro; Fujita, Hideaki; Hirata, Hiroaki

    2017-01-01

    The physical properties of the extracellular matrix (ECM), such as stiffness, are involved in the determination of the characteristics of cancer cells, including chemotherapy sensitivity. Resistance to chemotherapy is often linked to dysfunction of tumor suppressor p53; however, it remains elusive whether the ECM microenvironment interferes with p53 activation in cancer cells. Here, we show that, in MCF-7 breast cancer cells, extracellular stiffness influences p53 activation induced by the antitumor drug doxorubicin. Cell growth inhibition by doxorubicin was increased in response to ECM rigidity in a p53-dependent manner. The expression of Rho-associated coiled coil-containing protein kinase (ROCK) 2, which induces the activation of myosin II, was significantly higher when cells were cultured on stiffer ECM substrates. Knockdown of ROCK2 expression or pharmacological inhibition of ROCK decreased doxorubicin-induced p53 activation. Our results suggest that a soft ECM causes downregulation of ROCK2 expression, which drives resistance to chemotherapy by repressing p53 activation. PMID:28191463

  11. (Relative mobilities and transport mechanisms of trace elements during contact metamorphism of carbonate rocks). Progress report

    SciTech Connect

    1980-01-01

    The main objective of this study is to investigate the relative mobilities and transport mechanisms of major, minor, and trace elements during the contact metamorphism of carbonate rocks. The large contrasts in chemical potentials of SiO/sub 2/, Al/sub 2/O/sub 3/, and CaO across a granitic pluton-limestone contact may induce metasomatism. In addition, rare earth and transition metal elements may act as tracers, and their redistribution during metamorphism may record convective cooling processes. The results of this study may have an application toward the problem of radioactive waste disposal and the degree to which radioactive nuclides may be expected to migrate during geologically significant periods of time.

  12. An experimental study of the mechanism of failure of rocks under borehole jack loading

    NASA Technical Reports Server (NTRS)

    Van, T. K.; Goodman, R. E.

    1971-01-01

    Laboratory and field tests with an experimental jack and an NX-borehole jack are reported. The following conclusions were made: Under borehole jack loading, a circular opening in a brittle solid fails by tensile fracturing when the bearing plate width is not too small. Two proposed contact stress distributions can explain the mechanism of tensile fracturing. The contact stress distribution factor is a material property which can be determined experimentally. The borehole tensile strength is larger than the rupture flexural strength. Knowing the magnitude and orientation of the in situ stress field, borehole jack test results can be used to determine the borehole tensile strength. Knowing the orientation of the in situ stress field and the flexural strength of the rock substance, the magnitude of the in situ stress components can be calculated. The detection of very small cracks is essential for the accurate determination of the failure loads which are used in the calculation of strengths and stress components.

  13. Hydraulic and mechanical properties of natural fractures in low-permeability rock

    SciTech Connect

    Pyrack-Nolte, L.J.; Myer, L.R.; Cook, N.G.W.; Witherspoon, P.A.

    1987-01-01

    The results of a comprehensive laboratory study of the mechanical displacement, permeability, and void geometry of single rock fractures in a quartz monzonite are summarized and analyzed. A metal-injection technique was developed that provided quantitative data on the precise geometry of the void spaces between the fracture surfaces and the areas of contact at different stresses. At effective stresses of less than 20 MPa fluid flow was proportional to the mean fracture aperture raised to a power greater than 3. As stress was increased, contact area was increased and void spaces become interconnected by small tortuous channels that constitute the principal impediment to fluid flow. At effective stresses higher than 20 MPa, the mean fracture aperture continued to diminish with increasing stress, but this had little effect on flow because the small tortuous flow channels deformed little with increasing stress.

  14. Fundamental Study on Applicability of Powder-Based 3D Printer for Physical Modeling in Rock Mechanics

    NASA Astrophysics Data System (ADS)

    Fereshtenejad, Sayedalireza; Song, Jae-Joon

    2016-06-01

    Applications of 3D printing technology become more widespread in many research fields because of its rapid development and valuable capabilities. In rock mechanics and mining engineering, this technology has the potential to become a useful tool that might help implement a number of research studies previously considered impractical. Most commercial 3D printers cannot print prototypes with mechanical properties that match precisely those of natural rock samples. Therefore, some additional enhancements are required for 3D printers to be effectively utilized for rock mechanics applications. In this study, we printed and studied specimens using a powder-based commercial ZPrinter® 450 with ZP® 150 powder and Zb® 63 binder used as raw materials. The specimens printed by this 3D printer exhibited relatively low strength and ductile behavior, implying that it needs further improvements. Hence, we focused on several ways to determine the best combination of printing options and post-processing including the effects of the printing direction, printing layer thickness, binder saturation level, and heating process on the uniaxial compressive strength (UCS) and stress-strain behavior of the printed samples. The suggested procedures have demonstrated their effectiveness by obtaining the printed samples that behave similarly to the natural rocks with low UCS. Although our optimization methods were particularly successful, further improvements are required to expand 3D printer application in the area of rock mechanics.

  15. Deformation mechanism of basic rock during long-term compression: Area of HLW repository design, Chelyabinsk District, Russia

    SciTech Connect

    Petrov, V.A.; Zviagintsev, L.I.; Poluektov, V.V.

    1996-08-01

    A combination of ultrasound, mechanical and petrographic results for long-term experimental compression of greenschist facies porphyritic andesite tuffs indicate a deformation mechanism that depends upon the mineral composition, textural-structural features of the rocks and the orientation of compression relative to the rock textures. Three dry samples of rock were investigated. Coaxial compression of a massive sample for 816 hours and a foliated sample for 1,176 hours (pressure orthogonal to foliation) is characterized by solidification when the rocks are temporarily metastable. Compressive strength of the first sample is 850 kg/cm{sup 2} and of the second one, 800 kg/cm{sup 2}. Experimentally, the rock behavior changes from a plastic to a brittle regime of deformation. In contrast, compression of the foliated sample parallel to foliation causes disintegration along the foliation within 480 hours without solidification. The rock is liable to brittle deformation and its compressive strength is 500 kg/cm{sup 2}. These results may have implications for characterization of near-field processes in connection with numerous subhorizontal zones of schistosity within the strata that are targeted for underground disposal of high-level wastes (HLW) in the Mayak radiochemical complex area.

  16. Mechanical study of the Chartreuse Fold-and-Thrust Belt: relationships between fluids overpressure and decollement within the Toarcian source-rock

    NASA Astrophysics Data System (ADS)

    Berthelon, Josselin; Sassi, William; Burov, Evgueni

    2016-04-01

    the decollement layer. In turn, with the FLAMAR geo-mechanical models it is shown that for key mechanical parameters within the Chartreuse mechanical stratigraphy (such as friction coefficient, cohesion and viscosity properties), the mechanical boundary conditions to activate, localize and propagate shear thrust in the toarcian source-rock can be found to discuss on the hydro-mechanics of the structural evolution: the very weak mechanical properties that must be attributed to the source-rock to promote the formation of a decollement tend to justify the hypothesis of high fluids pressures in it. In FLAMAR, the evolution of the toarcian source-rock mechanical properties, calibrated on the temperature of kerogen-to-gas transformation, can be introduced to allow its activation as a decollement at a burial threshold. However, without hydro-mechanical coupling, it is not possible to predict where the overpressured regions that localised these changes are positioned. As such, this work also highlights the need for a fully-coupled hydro-mechanical model to further investigate the relationship between fluids and deformations in FTB and accretionary prisms. Burov, E., Francois, T., Yamato, P., & Wolf, S. (2014). Mechanisms of continental subduction and exhumation of HP and UHP rocks. Gondwana Research, 25(2), 464-493. Faille, I., Thibaut, M., Cacas, M.-C., Havé, P., Willien, F., Wolf, S., Agelas, L., Pegaz-Fiornet, S., 2014. Modeling Fluid Flow in Faulted Basins. Oil Gas Sci. Technol. - Rev. d'IFP Energies Nouv. 69, 529-553.

  17. Earthquake lights and the stress-activation of positive hole charge carriers in rocks

    USGS Publications Warehouse

    St-Laurent, F.; Derr, J.S.; Freund, F.T.

    2006-01-01

    Earthquake-related luminous phenomena (also known as earthquake lights) may arise from (1) the stress-activation of positive hole (p-hole) charge carriers in igneous rocks and (2) the accumulation of high charge carrier concentrations at asperities in the crust where the stress rates increase very rapidly as an earthquake approaches. It is proposed that, when a critical charge carrier concentration is reached, the p-holes form a degenerated solid state plasma that can break out of the confined rock volume and propagate as a rapidly expanding charge cloud. Upon reaching the surface the charge cloud causes dielectric breakdown at the air-rock interface, i.e. corona discharges, accompanied by the emission of light and high frequency electromagnetic radiation. ?? 2006 Elsevier Ltd. All rights reserved.

  18. THERMO-HYDRO-MECHANICAL MODELING OF WORKING FLUID INJECTION AND THERMAL ENERGY EXTRACTION IN EGS FRACTURES AND ROCK MATRIX

    SciTech Connect

    Robert Podgorney; Chuan Lu; Hai Huang

    2012-01-01

    Development of enhanced geothermal systems (EGS) will require creation of a reservoir of sufficient volume to enable commercial-scale heat transfer from the reservoir rocks to the working fluid. A key assumption associated with reservoir creation/stimulation is that sufficient rock volumes can be hydraulically fractured via both tensile and shear failure, and more importantly by reactivation of naturally existing fractures (by shearing), to create the reservoir. The advancement of EGS greatly depends on our understanding of the dynamics of the intimately coupled rock-fracture-fluid-heat system and our ability to reliably predict how reservoirs behave under stimulation and production. Reliable performance predictions of EGS reservoirs require accurate and robust modeling for strongly coupled thermal-hydrological-mechanical (THM) processes. Conventionally, these types of problems have been solved using operator-splitting methods, usually by coupling a subsurface flow and heat transport simulators with a solid mechanics simulator via input files. An alternative approach is to solve the system of nonlinear partial differential equations that govern multiphase fluid flow, heat transport, and rock mechanics simultaneously, using a fully coupled, fully implicit solution procedure, in which all solution variables (pressure, enthalpy, and rock displacement fields) are solved simultaneously. This paper describes numerical simulations used to investigate the poro- and thermal- elastic effects of working fluid injection and thermal energy extraction on the properties of the fractures and rock matrix of a hypothetical EGS reservoir, using a novel simulation software FALCON (Podgorney et al., 2011), a finite element based simulator solving fully coupled multiphase fluid flow, heat transport, rock deformation, and fracturing using a global implicit approach. Investigations are also conducted on how these poro- and thermal-elastic effects are related to fracture permeability

  19. HDR (Hot Dry Rock) technology transfer activities in the Clear Lake Area, California

    SciTech Connect

    Burns, K.; Potter, R.

    1990-01-01

    A large Hot Dry Rock resource has been recognized in northern California. It underlies the region extending NE of The Geysers to N of the City of Clearlake. The long-range productive potential is thousands of megawatts. The geothermal resource is heterogeneous. There are two mechanisms of heat flow occurring together. One is fluid transport, up natural zones of permeability, to outflows as surface springs. The other is conductive heat flow through impermeable rock. The temperature isotherms are thought to be nearly level surfaces, for example, the 300{degree}C isotherm is at about 8000 ft depth, with spikes'' or ridges'' occurring around narrow zones of fluid flow. While there is accessible heat at shallow depth in the naturally permeable rocks, the really substantial resource is in the impermeable rock. This is the HDR resource. The potential reservoir rocks are Franciscan greywackes and greenstones. Recorded drilling problems appear to be mainly due to intersection with serpentinites or to the effects of stimulation, so are potentially avoidable. Greywacke is favoured as a reservoir rock, and is expected to fail by brittle fracture. The water shortages in Northern California appear to be surmountable. Leakoff rates are expected to be low. Sewerage water may be available for fill and makeup. There is a possibility of combining HDR heat power production with sewerage disposal. To establish the first HDR producer in Northern California offers challenges in technology transfer. Two significant challenges will be creation of dispersed permeability in a greywacke reservoir, and pressure management in the vicinity of naturally permeable zones. A successful demonstration of HDR production technology will improve the long-term prospects for the geothermal power industry in California. 29 refs., 20 figs., 4 tabs.

  20. Dielectric relaxation behavior of Callovo-Oxfordian clay rock: A hydraulic-mechanical-electromagnetic coupling approach

    NASA Astrophysics Data System (ADS)

    Wagner, Norman; Bore, Thierry; Robinet, Jean-Charles; Coelho, Daniel; Taillade, Frederic; Delepine-Lesoille, Sylvie

    2013-09-01

    Water content is a key parameter to monitor in nuclear waste repositories such as the planed underground repository in Bure, France, in the Callovo-Oxfordian (COx) clay formation. High-frequency electromagnetic (HF-EM) measurement techniques, i.e., time or frequency domain reflectometry, offer useful tools for quantitative estimation of water content in porous media. However, despite the efficiency of HF-EM methods, the relationship between water content and dielectric material properties needs to be characterized. Moreover, the high amount of swelling clay in the COx clay leads to dielectric relaxation effects which induce strong dispersion coupled with high absorption of EM waves. Against this background, the dielectric relaxation behavior of the clay rock was studied at frequencies from 1 MHz to 10 GHz with network analyzer technique in combination with coaxial transmission line cells. For this purpose, undisturbed and disturbed clay rock samples were conditioned to achieve a water saturation range from 0.16 to nearly saturation. The relaxation behavior was quantified based on a generalized fractional relaxation model under consideration of an apparent direct current conductivity assuming three relaxation processes: a high-frequency water process and two interface processes which are related to interactions between the aqueous pore solution and mineral particles (adsorbed/hydrated water relaxation, counter ion relaxation and Maxwell-Wagner effects). The frequency-dependent HF-EM properties were further modeled based on a novel hydraulic-mechanical-electromagnetic coupling approach developed for soils. The results show the potential of HF-EM techniques for quantitative monitoring of the hydraulic state in underground repositories in clay formations.

  1. A damage mechanics approach for quantifying stress changes due to brittle failure of porous rocks

    NASA Astrophysics Data System (ADS)

    Jacquey, Antoine B.; Cacace, Mauro; Blöcher, Guido; Milsch, Harald; Scheck-Wenderoth, Magdalena

    2016-04-01

    Natural fault zones or man-made injection or production of fluid impact the regional stress distribution in Earth's crust and can be responsible for localized stress discontinuities. Understanding the processes controlling fracturing of the porous rocks and mechanical behaviour of fault zones is therefore of interest for several applications including geothermal energy production. In this contribution, we will present a thermodynamically consistent visco-poroelastic damage model which can deal with the multi-scale and multi-physics nature of the physical processes controlling the deformation of porous rocks during and after brittle failure. Deformation of a porous medium is crucially influenced by the changes in the effective stress. Considering a strain-formulated yield cap and the compaction-dilation transition, three different regimes can be identified: quasi-elastic deformation, cataclastic compaction with microcracking (damage accumulation) and macroscopic brittle failure with dilation. The governing equations for deformation, damage accumulation/healing and fluid flow have been implemented in a fully-coupled finite-element-method based framework (MOOSE). The MOOSE framework provides a powerful and flexible platform to solve multiphysics problems implicitly and in a tightly coupled manner on unstructured meshes which is of interest for such non-linear context. To illustrate the model, simulation of a compaction experiment of a sandstone leading to shear failure will be presented which allows to quantify the stress drop accompanying the failure. Finally, we will demonstrate that this approach can also be used at the field scale to simulate hydraulic fracturing and assess the resulting changes in the stress field.

  2. The mechanisms and characteristics of a complex rock-debris avalanche at the Nigeria-Cameroon border, West Africa

    NASA Astrophysics Data System (ADS)

    Igwe, Ogbonnaya; Mode, Ayonma Wilfred; Nnebedum, Okechukwu; Okonkwo, Ikenna; Oha, Ifeanyi

    2015-04-01

    We describe a rock-debris avalanche which occurred on steep, symmetrical ridges resulting from fracture-controlled erosion in the valley. The fractures were partially filled with clayey materials, probably derived from the weathering of feldspar. Major fault lines trending N-S were located less than 7 km from the landslide location. Exposed sections revealed that the basal rock units were migmatites and gneisses, while the upper section consisted of porphyritic granites. A failure of the residual clay-rich soil, composed of visible crystals of feldspar and mica, is thought to have triggered a long chain of events that led to the development of a rock-debris avalanche, which diverted the course of the rivers in the valley. The area was characterised by a shallow water table in the dry season (2 to 3 m) and this might have facilitated the formation of a slip surface at the regolith-rock interface. Field observations and laboratory analysis showed that the regolith probably failed first because of high pore pressure build-up and rapid reduction in shear resistance; this then triggered the failure of the fractured rock units. The slope movement was perpendicular to the foliation of the gneissic rocks, which probably contributed to landslide mobility. Of interest was that changing saturation level at constant relative density of about 32% resulted in either complete or limited liquefaction, indicating that the mechanism of failure depended on the moisture content of the regolith.

  3. Stress-dependent voltage offsets from polymer insulators used in rock mechanics and material testing

    NASA Astrophysics Data System (ADS)

    Carlson, G. G.; Dahlgren, R.; Vanderbilt, V. C.; Johnston, M. J.; Dunson, C.; Gray, A.; Freund, F.

    2013-12-01

    Dielectric insulators are used in a variety of laboratory settings when performing experiments in rock mechanics, petrology, and electromagnetic studies of rocks in the fields of geophysics, material science, and civil engineering. These components may be used to electrically isolate geological samples from the experimental equipment, to perform a mechanical compliance function between brittle samples and the loading equipment, to match ultrasonic transducers, or perform other functions. In many experimental configurations the insulators bear the full brunt of force applied to the sample but do not need to withstand high voltages, therefore the insulators are often thin sheets of mechanically tough polymers. From an instrument perspective, transduction from various types of mechanical perturbation has been qualitatively compared for a number of polymers [1, 2] and these error sources are readily apparent during high-impedance measurements if not mitigated. However even when following best practices, a force-dependent voltage signal still remains and its behavior is explored in this presentation. In this experiment two thin sheets (0.25 mm) of high-density polyethylene (HDPE) were set up in a stack, held alternately between three aluminum bars; this stack was placed on the platen of a 60T capacity hydraulic testing machine. The surface area, A, over which the force is applied to the PE sheets in this sandwich is roughly 40 square cm, each sheet forming a parallel-plate capacitor having roughly 320 pF [3], assuming the relative dielectric permittivity of PE is ~2.3. The outer two aluminum bars were connected to the LO input of the electrometer and the central aluminum bar was connected to the HI input of a Keithley model 617 electrometer. Once the stack is mechanically well-seated with no air gaps, the voltage offset is observed to be a linear function of the baseline voltage for a given change in applied force. For a periodically applied force of 66.7 kN the voltage

  4. Alteration of Fractured Rocks Due to Coupled Chemical and Mechanical Processes: High-Resolution Simulations and Experimental Observations

    NASA Astrophysics Data System (ADS)

    Ameli, Pasha

    Engineering activities such as enhanced geothermal energy production and improved oil recovery techniques are heavily dependent on the permeability of the subsurface, while others such as CO2 sequestration and nuclear waste disposal rely on the efficiency of rock formations as transport barriers. In either case fractures provide the main pathways for fluid flow and transport, especially in rocks with lower matrix porosity. Laboratory experiments aimed at quantifying the chemo-mechanical responses of fractures have shown a range of results, some of which contradict simple conceptual models. For example, under conditions favoring mineral dissolution, where one would expect an overall increase in permeability, experiments show that permeability increases under some conditions and decreases under others. Recent experiments have attempted to link these core-scale observations to the relevant small-scale processes occurring within fractures. Results suggest that the loss of mechanical strength in asperities due to chemical alteration may cause non-uniform deformation and alteration of fracture apertures. However, due to the lack of direct micro-scale measurements of the coupled chemical and mechanical processes that lead to alteration of contacting fracture surfaces, our ability to predict the long-term evolution of fractures is still limited. To explore the processes that control permeability evolution, I developed a computational model that uses micro-scale surface roughness and explicitly couples dissolution and elastic deformation to calculate local alterations in fracture aperture under chemical and mechanical stresses. A depth-averaged algorithm of fracture flow is used to model reactive transport and chemical alteration of the fracture surfaces. Then, I deform the resulting altered fracture-surfaces using an algorithm that calculates the elastic deformation. The results of the model are compared with flow-through experiments conducted on fractured limestone. The

  5. Biologically-initiated rock crust on sandstone: Mechanical and hydraulic properties and resistance to erosion

    NASA Astrophysics Data System (ADS)

    Slavík, Martin; Bruthans, Jiří; Filippi, Michal; Schweigstillová, Jana; Falteisek, Lukáš; Řihošek, Jaroslav

    2017-02-01

    Biocolonization on sandstone surfaces is known to play an important role in rock disintegration, yet it sometimes also aids in the protection of the underlying materials from rapid erosion. There have been few studies comparing the mechanical and/or hydraulic properties of the BIRC (Biologically-Initiated Rock Crust) with its subsurface. As a result, the overall effects of the BIRC are not yet well understood. The objective of the present study was to briefly characterize the BIRC from both the mineralogical and biological points of view, and especially to quantify the effect of the BIRC upon the mechanical and hydraulic properties of friable sandstone. The mineralogical investigation of a well-developed BIRC showed that its surface is enriched in kaolinite and clay- to silt-sized quartz particles. Total organic carbon increases with the age of the BIRC. Based on DNA sequencing and microscopy, the BIRC is formed by various fungi, including components of lichens and green algae. Using the method of drilling resistance, by measuring tensile strength, and based on water jet testing, it was determined that a BIRC is up to 12 times less erodible and has 3-35 times higher tensile strength than the subsurface friable sandstone. Saturated hydraulic conductivity of the studied BIRC is 15-300 times lower than the subsurface, and was measured to also decrease in capillary water absorption (2-33 times). Water-vapor diffusion is not significantly influenced by the presence of the BIRC. The BIRC thus forms a hardened surface which protects the underlying material from rain and flowing water erosion, and considerably modifies the sandstone's hydraulic properties. Exposing the material to calcination (550 °C), and experiments with the enzyme zymolyase indicated that a major contribution to the surface hardening is provided by organic matter. In firmer sandstones, the BIRC may still considerably decrease the rate of weathering, as it is capable of providing cohesion to strongly

  6. Modeling naturally fractured reservoirs: From experimental rock mechanics to flow simulation

    NASA Astrophysics Data System (ADS)

    Rijken, Margaretha Catharina Maria

    Fractures have a big impact on reservoir production but are inherently difficult to quantify. This study gives a robust and practical workflow to obtain a mechanically consistent naturally fractured reservoir model without direct sampling of the fracture network. The three tiers of the workflow are: (1) subcritical testing, (2) geomechanical modeling, and (3) flow modeling. Subcritical fracture index, a rock property, has been shown to influence fracture attributes such as length, spacing and connectivity. Subcritical tests show that the average subcritical index for sandstones in ambient air is around 62, whereas the average value for microstructurally comparable carbonates samples is 120. Thin-section analysis shows that an increase in cement content increases the subcritical index. Furthermore, sandstone samples containing more than 15% carbonate cement, sandstone samples containing more than 40% clay, and pure carbonate samples exhibit a large drop in subcritical index when the environment is changed from ambient air or oil to fresh water or brine. Geomechanical modeling has shown that the mechanical bed thickness has a large influence on fracture pattern characteristics and has the potential to overshadow fracture pattern changes due to strain level, strain anisotropy and subcritical index. Furthermore, an increase in strain anisotropy reduces the number of dominant through-going fracture sets and decreases the fracture spacing between the through-going fractures. This spacing variation not only influences the preferential drainage direction, it can also enhance the drainage efficiency, because more rock is exposed to the through-going fractures which are more likely to be intersected by a borehole. The level of detail provided by the geomechanical model greatly exceeds the level of detail normally used in reservoir simulation. Therefore, upscaling of the geomechanically generated fracture patterns is necessary for practical flow modeling. This study shows

  7. Mechanics of soft active materials

    NASA Astrophysics Data System (ADS)

    Zhao, Xuanhe

    Soft active materials, mostly elastomers and polymeric gels, are being developed to mimic a salient feature of life: movement in response to stimuli. For example, when an electric voltage is applied across a layer of a dielectric elastomer, the layer reduces in thickness and expands in area, giving a strain greater than 100%. As another example, in response to a small change of pH or temperature, a hydrogel may absorb a large amount of water and increase its volume over 100 times. The mechanics involved in these processes is important, interesting, and not well understood. This thesis studies large deformations and instabilities in dielectric elastomers and polymeric gels. The thesis first presents a nonlinear field theory for deformable dielectrics. The theory uses measurable quantities to define field variables. The definitions lead to decoupled field equations, and electromechanical coupling enters the theory through material laws. We use the theory to study electromechanical instability and coexistent states in dielectric elastomers. A computational method is also developed to analyze inhomogeneous deformations in complicated structures of dielectric elastomers. The second part of the thesis discusses large deformation and mass transportation in polymeric gels. A gel can undergo large deformation of two modes: local rearrangement and long-range migration. We assume that the local rearrangement is instantaneous, and model the long-range migration by assuming that the solvent molecules diffuse inside the gel. We further study inhomogeneous and anisotropic deformations and instabilities in gels constrained by rigid materials.

  8. Stress-Dependent Voltage Offsets From Polymer Insulators Used in Rock Mechanics and Material Testing

    NASA Technical Reports Server (NTRS)

    Carlson, G. G.; Dahlgren, Robert; Gray, Amber; Vanderbilt, V. C.; Freund, F.; Johnston, M. J.; Dunson, C.

    2013-01-01

    Dielectric insulators are used in a variety of laboratory settings when performing experiments in rock mechanics, petrology, and electromagnetic studies of rocks in the fields of geophysics,material science, and civil engineering. These components may be used to electrically isolate geological samples from the experimental equipment, to perform a mechanical compliance function between brittle samples and the loading equipment, to match ultrasonic transducers, or perform other functions. In manyexperimental configurations the insulators bear the full brunt of force applied to the sample but do not need to withstand high voltages, therefore the insulators are often thin sheets of mechanically tough polymers. From an instrument perspective, transduction from various types of mechanical perturbation has beenqualitatively compared for a number of polymers [1, 2] and these error sources are readily apparent duringhigh-impedance measurements if not mitigated. However even when following best practices, a force dependent voltage signal still remains and its behavior is explored in this presentation. In this experimenttwo thin sheets (0.25 mm) of high-density polyethylene (HDPE) were set up in a stack, held alternatelybetween three aluminum bars; this stack was placed on the platen of a 60T capacity hydraulic testingmachine. The surface area, A, over which the force is applied to the PE sheets in this sandwich is roughly 40 square cm, each sheet forming a parallel-plate capacitor having roughly 320 pF [3], assuming therelative dielectric permittivity of PE is approximately 2.3. The outer two aluminum bars were connected to the LO input ofthe electrometer and the central aluminum bar was connected to the HI input of a Keithley model 617 electrometer. Once the stack is mechanically well-seated with no air gaps, the voltage offset is observed tobe a linear function of the baseline voltage for a given change in applied force. For a periodically appliedforce of 66.7 kN the

  9. Site exploration for rock-mechanics field tests in the Grouse Canyon Member, Belted Range Tuff, U12g Tunnel Complex, Nevada Test Site

    SciTech Connect

    Langkopf, B.S.; Eshom, E.

    1982-02-01

    This report describes site exploration work completed in support of planned rock-mechanics field tests in the Grouse Canyon Member of the Belted Range Ruff at Nevada Test Site`s, G-Tunnel. As part of this work, the Rock Mechanics Drift (RMD) and the Rock Mass Property Alcove (RMPA) were mined and three coreholes drilled. The results of mapping and corehole logging are displayed, described, and analyzed.

  10. How ocean waves rock the Earth: Two mechanisms explain microseisms with periods 3 to 300 s

    NASA Astrophysics Data System (ADS)

    Ardhuin, Fabrice; Gualtieri, Lucia; Stutzmann, Eléonore

    2015-02-01

    Microseismic activity, recorded everywhere on Earth, is largely due to ocean waves. Recent progress has clearly identified sources of microseisms in the most energetic band, with periods from 3 to 10 s. In contrast, the generation of longer-period microseisms has been strongly debated. Two mechanisms have been proposed to explain seismic wave generation: a primary mechanism, by which ocean waves propagating over bottom slopes generate seismic waves, and a secondary mechanism which relies on the nonlinear interaction of ocean waves. Here we show that the primary mechanism explains the average power, frequency distribution, and most of the variability in signals recorded by vertical seismometers, for seismic periods ranging from 13 to 300 s. The secondary mechanism only explains seismic motions with periods shorter than 13 s. Our results build on a quantitative numerical model that gives access to time-varying maps of seismic noise sources.

  11. Dating previously balanced rocks in seismically active parts of California and Nevada

    USGS Publications Warehouse

    Bell, J.W.; Brune, J.N.; Liu, T.; Zreda, M.; Yount, J.C.

    1998-01-01

    Precariously balanced boulders that could be knocked down by strong earthquake ground motion are found in some seismically active areas of southern California and Nevada. In this study we used two independent surface-exposure dating techniques - rock-varnish microlamination and cosmogenic 36Cl dating methodologies - to estimate minimum- and maximum-limiting ages, respectively, of the precarious boulders and by inference the elapsed time since the sites were shaken down. The results of the exposure dating indicate that all of the precarious rocks are >10.5 ka and that some may be significantly older. At Victorville and Jacumba, California, these results show that the precarious rocks have not been knocked down for at least 10.5 k.y., a conclusion in apparent conflict with some commonly used probabilistic seismic hazard maps. At Yucca Mountain, Nevada, the ages of the precarious rocks are >10.5 to >27.0 ka, providing an independent measure of the minimum time elapsed since faulting occurred on the Solitario Canyon fault.

  12. Active cell mechanics: Measurement and theory.

    PubMed

    Ahmed, Wylie W; Fodor, Étienne; Betz, Timo

    2015-11-01

    Living cells are active mechanical systems that are able to generate forces. Their structure and shape are primarily determined by biopolymer filaments and molecular motors that form the cytoskeleton. Active force generation requires constant consumption of energy to maintain the nonequilibrium activity to drive organization and transport processes necessary for their function. To understand this activity it is necessary to develop new approaches to probe the underlying physical processes. Active cell mechanics incorporates active molecular-scale force generation into the traditional framework of mechanics of materials. This review highlights recent experimental and theoretical developments towards understanding active cell mechanics. We focus primarily on intracellular mechanical measurements and theoretical advances utilizing the Langevin framework. These developing approaches allow a quantitative understanding of nonequilibrium mechanical activity in living cells. This article is part of a Special Issue entitled: Mechanobiology.

  13. The Alpha-Proton-X-ray Spectrometer deployment mechanism: An anthropomorphic approach to sensor placement on Martian rocks and soil

    NASA Technical Reports Server (NTRS)

    Blomquist, Richard S.

    1995-01-01

    On July 4,1997, the Mars Pathfinder spacecraft lands on Mars and starts conducting technological and scientific experiments. One experiment, the Alpha-Proton-X-ray Spectrometer, uses a sensor head placed against rocks and soil to determine their composition. To guarantee proper placement, a deployment mechanism mounted on the Mars Rover aligns the sensor head to within 20 deg of the rock and soil surfaces. In carrying out its task, the mechanism mimics the action of a human hand and arm. Consisting of a flexible wrist, a parallel link arm, a brush dc motor actuator, and a revolutionary non-pyrotechnic fail-safe release device, the mechanism correctly positions the sensor head on rocks as high as 0.29 m and on targets whose surfaces are tilted as much as 45 deg from the nominal orientation of the sensor head face. The mechanism weighs less than 0.5 kg, can withstand 100 g's, and requires less than 2.8 N x m of actuation torque. The fail-safe coupler utilizes Cerrobend, a metal alloy that melts at 60 C, to fuse the actuator and the rest of the mechanism together. A film heater wrapped around the coupler melts the metal, and Negator springs drive the mechanism into its stowed position. The fail-safe actuates using 6.75 Watts for 5 minutes in the event of an actuator failure.

  14. The Alpha-Proton-X-ray Spectrometer deployment mechanism: an anthropomorphic approach to sensor placement on Martian rocks and soil

    NASA Astrophysics Data System (ADS)

    Blomquist, Richard S.

    1995-05-01

    On July 4,1997, the Mars Pathfinder spacecraft lands on Mars and starts conducting technological and scientific experiments. One experiment, the Alpha-Proton-X-ray Spectrometer, uses a sensor head placed against rocks and soil to determine their composition. To guarantee proper placement, a deployment mechanism mounted on the Mars Rover aligns the sensor head to within 20 deg of the rock and soil surfaces. In carrying out its task, the mechanism mimics the action of a human hand and arm. Consisting of a flexible wrist, a parallel link arm, a brush dc motor actuator, and a revolutionary non-pyrotechnic fail-safe release device, the mechanism correctly positions the sensor head on rocks as high as 0.29 m and on targets whose surfaces are tilted as much as 45 deg from the nominal orientation of the sensor head face. The mechanism weighs less than 0.5 kg, can withstand 100 g's, and requires less than 2.8 N x m of actuation torque. The fail-safe coupler utilizes Cerrobend, a metal alloy that melts at 60 C, to fuse the actuator and the rest of the mechanism together. A film heater wrapped around the coupler melts the metal, and Negator springs drive the mechanism into its stowed position. The fail-safe actuates using 6.75 Watts for 5 minutes in the event of an actuator failure.

  15. Statistical Characterization of the Mechanical Parameters of Intact Rock Under Triaxial Compression: An Experimental Proof of the Jinping Marble

    NASA Astrophysics Data System (ADS)

    Jiang, Quan; Zhong, Shan; Cui, Jie; Feng, Xia-Ting; Song, Leibo

    2016-12-01

    We investigated the statistical characteristics and probability distribution of the mechanical parameters of natural rock using triaxial compression tests. Twenty cores of Jinping marble were tested under each different levels of confining stress (i.e., 5, 10, 20, 30, and 40 MPa). From these full stress-strain data, we summarized the numerical characteristics and determined the probability distribution form of several important mechanical parameters, including deformational parameters, characteristic strength, characteristic strains, and failure angle. The statistical proofs relating to the mechanical parameters of rock presented new information about the marble's probabilistic distribution characteristics. The normal and log-normal distributions were appropriate for describing random strengths of rock; the coefficients of variation of the peak strengths had no relationship to the confining stress; the only acceptable random distribution for both Young's elastic modulus and Poisson's ratio was the log-normal function; and the cohesive strength had a different probability distribution pattern than the frictional angle. The triaxial tests and statistical analysis also provided experimental evidence for deciding the minimum reliable number of experimental sample and for picking appropriate parameter distributions to use in reliability calculations for rock engineering.

  16. A numerical model of hydro-thermo-mechanical coupling in a fractured rock mass

    SciTech Connect

    Bower, Kathleen Marie

    1996-06-01

    Coupled hydro-thermo-mechanical codes with the ability to model fractured materials are used for predicting groundwater flow behavior in fractured aquifers containing thermal sources. The potential applications of such a code include the analysis of groundwater behavior within a geothermal reservoir. The capability of modeling hydro-thermo systems with a dual porosity, fracture flow model has been previously developed in the finite element code, FEHM. FEHM has been modified to include stress coupling with the dual porosity feature. FEHM has been further developed to implicitly couple the dependence of fracture hydraulic conductivity on effective stress within two dimensional, saturated aquifers containing fracture systems. The cubic law for flow between parallel plates was used to model fracture permeability. The Bartin-Bandis relationship was used to determine the fracture aperture within the cubic law. The code used a Newton Raphson iteration to implicitly solve for six unknowns at each node. Results from a model of heat flow from a reservoir to the moving fluid in a single fracture compared well with analytic results. Results of a model showing the increase in fracture flow due to a single fracture opening under fluid pressure compared well with analytic results. A hot dry rock, geothermal reservoir was modeled with realistic time steps indicating that the modified FEHM code does successfully model coupled flow problems with no convergence problems.

  17. Clostridium perfringens TpeL Induces Formation of Stress Fibers via Activation of RhoA-ROCK Signaling Pathway.

    PubMed

    Nagahama, Masahiro; Ohkubo, Akiko; Kinouchi, Yoshihito; Kobayashi, Keiko; Miyamoto, Kazuaki; Takehara, Masaya; Sakurai, Jun

    2015-01-01

    Clostridium perfringens TpeL belongs to a family of large clostridial glucosylating cytotoxins. TpeL modifies Rac1 and Ras subfamily proteins. Herein we report TpeL-induced formation of stress fibers via RhoA-Rho kinase (ROCK) signaling. A recombinant protein (TpeL1-525) derived from the TpeL N-terminal catalytic domain in the presence of streptolysin O (SLO) induced the formation of actin stress fibers in Madin-Darby canine kidney (MDCK) cells in a dose-dependent manner. The RhoA/ROCK pathway is known to control the formation of stress fibers. We examined the role of the RhoA/ROCK pathway in TpeL-induced formation of stress fibers. TpeL1-525-induced formation of stress fibers was inhibited by the ROCK inhibitor, Y27632 and Rho protein inhibitor, C3 transferase. TpeL1-525 activated RhoA and ROCK in a dose-dependent manner. C3 transferase blocked TpeL1-525-induced activation of RhoA and ROCK whereas Y27632 inhibited TpeL-induced activation of ROCK. These results demonstrate for the first time that TpeL induces the formation of stress fibers by activating the RhoA/ROCK signaling pathway.

  18. Effect of chemical environment and rock composition on fracture mechanics properties of reservoir lithologies in context of CO2 sequestration

    NASA Astrophysics Data System (ADS)

    Major, J. R.; Eichhubl, P.; Callahan, O. A.

    2015-12-01

    The coupled chemical and mechanical response of reservoir and seal rocks to injection of CO2 have major implications on the short and long term security of sequestered carbon. Many current numerical models evaluating behavior of reservoirs and seals during and after CO2 injection in the subsurface consider chemistry and mechanics separately and use only simple mechanical stability criteria while ignoring time-dependent failure parameters. CO2 injection irreversibly alters the subsurface chemical environment which can then affect geomechanical properties on a range of time scales by altering rock mineralogy and cements through dissolution, remobilization, and precipitation. It has also been documented that geomechanical parameters such as fracture toughness (KIC) and subcritical index (SCI) are sensitive to chemical environment. Double torsion fracture mechanics testing of reservoir lithologies under controlled environmental conditions relevant to CO2 sequestration show that chemical environment can measurably affect KIC and SCI. This coupled chemical-mechanical behavior is also influenced by rock composition, grains, amount and types of cement, and fabric. Fracture mechanics testing of the Aztec Sandstone, a largely silica-cemented, subarkose sandstone demonstrate it is less sensitive to chemical environment than Entrada Sandstone, a silty, clay-rich sandstone. The presence of de-ionized water lowers KIC by approximately 20% and SCI 30% in the Aztec Sandstone relative to tests performed in air, whereas the Entrada Sandstone shows reductions on the order of 70% and 90%, respectively. These results indicate that rock composition influences the chemical-mechanical response to deformation, and that the relative chemical reactivity of target reservoirs should be recognized in context of CO2 sequestration. In general, inert grains and cements such as quartz will be less sensitive to the changing subsurface environment than carbonates and clays.

  19. Rock mechanics observations pertinent to the rheology of the continental lithosphere and the localization of strain along shear zones

    USGS Publications Warehouse

    Kirby, S.H.

    1985-01-01

    Emphasized in this paper are the deformation processes and rheologies of rocks at high temperatures and high effective pressures, conditions that are presumably appropriate to the lower crust and upper mantle in continental collision zones. Much recent progress has been made in understanding the flexure of the oceanic lithosphere using rock-mechanics-based yield criteria for the inelastic deformations at the top and base. At mid-plate depths, stresses are likely to be supported elastically because bending strains and elastic stresses are low. The collisional tectonic regime, however, is far more complex because very large permanent strains are sustained at mid-plate depths and this requires us to include the broad transition between brittle and ductile flow. Moreover, important changes in the ductile flow mechanisms occur at the intermediate temperatures found at mid-plate depths. Two specific contributions of laboratory rock rheology research are considered in this paper. First, the high-temperature steady-state flow mechanisms and rheology of mafic and ultramafic rocks are reviewed with special emphasis on olivine and crystalline rocks. Rock strength decreases very markedly with increases in temperature and it is the onset of flow by high temperature ductile mechanisms that defines the base of the lithosphere. The thickness of the continental lithosphere can therefore be defined by the depth to a particular isotherm Tc above which (at geologic strain rates) the high-temperature ductile strength falls below some arbitrary strength isobar (e.g., 100 MPa). For olivine Tc is about 700??-800??C but for other crustal silicates, Tc may be as low as 400??-600??C, suggesting that substantial decoupling may take place within thick continental crust and that strength may increase with depth at the Moho, as suggested by a number of workers on independent grounds. Put another way, the Moho is a rheological discontinuity. A second class of laboratory observations pertains to

  20. Computational method for thermoviscoelasticity with application to rock mechanics. [Ph. D. Thesis

    SciTech Connect

    Lee, S.C.

    1984-01-01

    Large-scale numerical computations associated with rock mechanics problems have required efficient and economical models for predicting temperature, stress, failure, and deformed structural configuration under various loading conditions. To meet this requirement, the complex dependence of the properties of geological materials on the time and temperature is modified to yield a reduced time scale as a function of time and temperature under the thermorheologically simple material (TSM) postulate. The thermorheologically linear concept is adopted in the finite element formulation by uncoupling thermal and mechanical responses. The thermal responses, based on transient heat conduction or convective-diffusion, are formulated by using the two-point recurrence scheme and the upwinding scheme, respectively. An incremental solution procedure with the implicit time stepping scheme is proposed for the solution of the thermoviscoelastic response. The proposed thermoviscoelastic solution algorithm is based on the uniaxial creep experimental data and the corresponding temperature shift functions, and is intended to minimize computational efforts by allowing large time step size with stable solutions. A thermoelastic fracture formulation is also presented by introducing the degenerate quadratic isoparametric singular element for the thermally-induced line crack problems. The stress intensity factors are computed by use of the displacement method. Efficiency of the presented formulation and solution algorithm is initially demonstrated by comparison with other available solutions for a variety of problems. Subsequent field applications are made to simulate the post-burn and post-repose phases of an underground coal conversion (UCC) experiment and in-situ nuclear waste disposal management problems. 137 references, 48 figures, 6 tables.

  1. How stress and temperature conditions affect rock-fluid chemistry and mechanical deformation

    NASA Astrophysics Data System (ADS)

    Nermoen, Anders; Korsnes, Reidar; Aursjø, Olav; Madland, Merete; Kjørslevik, Trygve Alexander; Østensen, Geir

    2016-02-01

    We report the results from a series of chalk flow-through-compaction experiments performed at three effective stresses (0.5 MPa, 3.5 MPa and 12.3 MPa) and two temperatures (92° and and 130°). The results show that both stress and temperature are important to both chemical alteration and mechanical deformation. The experiments were conducted on cores drilled from the same block of outcrop chalks from the Obourg quarry within the Saint Vast formation (Mons, Belgium). The pore pressure was kept at 0.7 MPa for all experiments with a continuous flow of 0.219 M MgCl2 brine at a constant flow rate; 1 original pore volume (PV) per day. The experiments have been performed in tri-axial cells with independent control of the external stress (hydraulic pressure in the confining oil), pore pressure, temperature, and the injected flow rate. Each experiment consists of two phases; a loading phase where stress-strain dependencies are investigated (approx. 2 days), and a creep phase that lasts for more than 150-160 days. During creep, the axial deformation was logged, and the effluent samples were collected for ion chromatography analyses. Any difference between the injected and produced water chemistry gives insight into the rock-fluid interactions that occur during flow through of the core. The observed effluent concentration shows a reduction in Mg2+, while the Ca2+ concentration is increased. This, together with SEM-EDS analysis, indicates that magnesium-bearing mineral phases are precipitated leading to dissolution of calcite, an observation . This is in-line with other flow-through experiments reported earlier. The observed dissolution and precipitation are sensitive to the effective stress and test temperature. Typically. H, higher stress and temperature lead to increased concentration differences of Mg2+ and Ca2+ concentration changes.. The observed strain can be partitioned additively into a mechanical and chemical driven component.

  2. ROCK activity regulates functional tight junction assembly during blastocyst formation in porcine parthenogenetic embryos

    PubMed Central

    Kwon, Jeongwoo

    2016-01-01

    The Rho-associated coiled-coil-containing protein serine/threonine kinases 1 and 2 (ROCK1 and ROCK2) are Rho subfamily GTPase downstream effectors that regulate cell migration, intercellular adhesion, cell polarity, and cell proliferation by stimulating actin cytoskeleton reorganization. Inhibition of ROCK proteins affects specification of the trophectoderm (TE) and inner cell mass (ICM) lineages, compaction, and blastocyst cavitation. However, the molecules involved in blastocyst formation are not known. Here, we examined developmental competence and levels of adherens/tight junction (AJ/TJ) constituent proteins, such as CXADR, OCLN, TJP1, and CDH1, as well as expression of their respective mRNAs, after treating porcine parthenogenetic four-cell embryos with Y-27632, a specific inhibitor of ROCK, at concentrations of 0, 10, 20, 100 µM for 24 h. Following this treatment, the blastocyst development rates were 39.1, 20.7, 10.0, and 0% respectively. In embryos treated with 20 µM treatment, expression levels of CXADR, OCLN, TJP1, and CDH1 mRNA and protein molecules were significantly reduced (P < 0.05). FITC-dextran uptake assay revealed that the treatment caused an increase in TE TJ permeability. Interestingly, the majority of the four-cell and morula embryos treated with 20 µM Y-27643 for 24 h showed defective compaction and cavitation. Taken together, our results indicate that ROCK activity may differentially affect assembly of AJ/TJs as well as regulate expression of genes encoding junctional proteins. PMID:27077008

  3. Systematic study of the effects of mass and time scaling techniques applied in numerical rock mechanics simulations

    NASA Astrophysics Data System (ADS)

    Heinze, Thomas; Jansen, Gunnar; Galvan, Boris; Miller, Stephen A.

    2016-08-01

    Numerical modeling is a well established tool in rock mechanics studies investigating a wide range of problems. Implicit methods for solving linear equations have the advantage of being unconditionally stable, while explicit methods, although limited by the time step, are often used because of their limited memory demand, their scalability in parallel computing, and simple implementation of complex boundary conditions. In numerical modeling of explicit elastoplastic dynamics where the time step is limited by the material density, mass scaling techniques can be used to overcome this limit and significantly reduce computation time. While often used, the effect of mass and time scaling and how it may influence the numerical results is rarely-mentioned in publications, and choosing the right scaling technique is typically performed by trial and error. To our knowledge, no systematic studies have addressed how mass scaling might affect the numerical results. In this paper, we present results from an extensive and systematic study of the influence of mass and time scaling on the behavior of a variety of rock-mechanical models. We employ a finite difference scheme to model uniaxial and biaxial compression experiments using different mass and time scaling factors, and with physical models of increasing complexity up to a cohesion-weakening frictional-strengthening model (CWFS). We also introduce a normalized energy ratio to assist analyzing mass scaling effects. We find the tested models to be less sensitive to time scaling than to mass scaling, so mass scaling has higher potential for decreasing computational costs. However, we also demonstrate that mass scaling may lead to quantitatively wrong results, so care must be taken in interpreting stress values when mass scaling is used in complicated rock mechanics simulations. Mass scaling significantly influences the stress-strain response of numerical rocks because mass scaling acts as an artificial hardening agent on rock

  4. Coupled hydro-mechanical processes in crytalline rock and ininduratedand plastic clays: A comparative discussion

    SciTech Connect

    Tsang, Chin-Fu; Blumling, Peter; Bernier, Frederic

    2006-02-15

    This paper provides a comparative discussion of coupledhydromechanical processes in three different geological formations:crystalline rock, plastic clay, and indurated clay. First, the importantprocesses and associated property characteristics in the three rock typesare discussed. Then, one particular hydromechanical coupling is broughtup for detailed consideration, that of pore pressure changes in nearbyrock during tunnel excavation. Three field experiments in the three rocktypes are presented and their results are discussed. It is shown that themain physical processes are common to all three rock types, but with verydifferent time constants. The different issues raised by these cases arepointed out, and the transferable lessons learned are identified. Suchcross fertilization and simultaneous understanding of coupled processesin three very different rock types help to greatly enhance confidence inthe state of science in this field.

  5. Oxygen uptake and energy expenditure for children during rock climbing activity.

    PubMed

    Watts, Phillip Baxter; Ostrowski, Megan L

    2014-02-01

    The purpose of this study was to measure oxygen uptake and energy expenditure in children during rock climbing activity. 29 children (age = 10.9 ± 1.7 yr) participated in the study. A commercially available rock climbing structure with ample features for submaximal effort climbing provided continuous terrain. Participants were instructed to climb at a comfortable pace. Following an initial 5-min rest, each child climbed one sustained 5-min bout followed by 5-min sitting recovery for a total of 10 min (SUS). This was immediately followed by five 1-min climbing + 1-min recovery intervals for a second total of 10 min (INT). Expired air was analyzed continuously. Energy expenditure (EE) was determined via the Weir method for 10-s intervals throughout the full protocol. The total energy expenditure in kilocalories during the 10-min SUS period was 34.3 ± 11.3 kcal. Energy expenditure during the 10-min INT period averaged 39.3 ± 13.1 kcal and was significantly higher than during SUS (p < .05). The mean total EE for SUS + INT was 73.7 ± 24.2 kcal. EE was correlated with body mass; r = .86. The rock climbing tasks employed in this study produced EE levels similar to what have been reported in children for stair climbing, sports/games activities, and easy jogging.

  6. Coseismic landslides reveal near-surface rock strength in a high-relief tectonically active setting

    USGS Publications Warehouse

    Gallen, Sean F; Clark, Marin K; Godt, Jonathan W.

    2014-01-01

    We present quantitative estimates of near-surface rock strength relevant to landscape evolution and landslide hazard assessment for 15 geologic map units of the Longmen Shan, China. Strength estimates are derived from a novel method that inverts earthquake peak ground acceleration models and coseismic landslide inventories to obtain material proper- ties and landslide thickness. Aggregate rock strength is determined by prescribing a friction angle of 30° and solving for effective cohesion. Effective cohesion ranges are from 70 kPa to 107 kPa for 15 geologic map units, and are approximately an order of magnitude less than typical laboratory measurements, probably because laboratory tests on hand-sized specimens do not incorporate the effects of heterogeneity and fracturing that likely control near-surface strength at the hillslope scale. We find that strength among the geologic map units studied varies by less than a factor of two. However, increased weakening of units with proximity to the range front, where precipitation and active fault density are the greatest, suggests that cli- matic and tectonic factors overwhelm lithologic differences in rock strength in this high-relief tectonically active setting.

  7. Origin and accumulation mechanisms of petroleum in the Carboniferous volcanic rocks of the Kebai Fault zone, Western Junggar Basin, China

    NASA Astrophysics Data System (ADS)

    Chen, Zhonghong; Zha, Ming; Liu, Keyu; Zhang, Yueqian; Yang, Disheng; Tang, Yong; Wu, Kongyou; Chen, Yong

    2016-09-01

    The Kebai Fault zone of the West Junggar Basin in northwestern China is a unique region to gain insights on the formation of large-scale petroleum reservoirs in volcanic rocks of the western Central Asian Orogenic Belt. Carboniferous volcanic rocks are widespread in the Kebai Fault zone and consist of basalt, basaltic andesite, andesite, tuff, volcanic breccia, sandy conglomerate and metamorphic rocks. The volcanic oil reservoirs are characterized by multiple sources and multi-stage charge and filling history, characteristic of a complex petroleum system. Geochemical analysis of the reservoir oil, hydrocarbon inclusions and source rocks associated with these volcanic rocks was conducted to better constrain the oil source, the petroleum filling history, and the dominant mechanisms controlling the petroleum accumulation. Reservoir oil geochemistry indicates that the oil contained in the Carboniferous volcanic rocks of the Kebai Fault zone is a mixture. The oil is primarily derived from the source rock of the Permian Fengcheng Formation (P1f), and secondarily from the Permian Lower Wuerhe Formation (P2w). Compared with the P2w source rock, P1f exhibits lower values of C19 TT/C23 TT, C19+20TT/ΣTT, Ts/(Ts + Tm) and ααα-20R sterane C27/C28 ratios but higher values of TT C23/C21, HHI, gammacerane/αβ C30 hopane, hopane (20S) C34/C33, C29ββ/(ββ + αα), and C29 20S/(20S + 20R) ratios. Three major stages of oil charge occurred in the Carboniferous, in the Middle Triassic, Late Triassic to Early Jurassic, and in the Middle Jurassic to Late Jurassic periods, respectively. Most of the oil charged during the first stage was lost, while moderately and highly mature oils were generated and accumulated during the second and third stages. Oil migration and accumulation in the large-scale stratigraphic reservoir was primarily controlled by the top Carboniferous unconformity with better porosity and high oil enrichment developed near the unconformity. Secondary dissolution

  8. Recent rock fall activity in the Wetterstein Mountains revealed by a time series of terrestrial laser scans

    NASA Astrophysics Data System (ADS)

    Schöpa, Anne; Baewert, Henning; Cook, Kristen; Morche, David

    2015-04-01

    The north face of the Hochwanner in the Reintal valley, Wetterstein Mountains, southern Germany, has been a site of frequent rock fall activity for the past several hundred years. The so-called 'Steingerümpel' rock fall included an estimated volume of 2.3-2.7 x 106 m3 and led to damming of the Partnach river. This event was dated to 1400-1600 AD. The rock fall left a prominent scar in the rock face where subsequent rock fall activity was concentrated, postulated to be a 'delayed consequence' of the Steingerümpel event. Previous workers used airborne and terrestrial laser scan data to evaluate the volume of the detached material and the deposits on the talus cone at the foot of the slope from the 'delayed consequence' activity between 2006 and 2008 (Heckmann et al., 2012). The largest event during this period was a 5 x 104 m3 rock fall in August 2007. We compared the data of six terrestrial laser scans, which were acquired in June and September 2008, September 2010, June 2011, August 2013, October and November 2014, in order to assess the volumes of detached material after the large rock fall event of 2007. The aim is to investigate the post-event activity at a site of a large rock fall in order to give estimates about the timing when the activity is back to normal conditions in relation to the magnitude of the large event. Although no large rock fall occurred in the observation period, the comparison of the laser scan data indicate that the average rock wall retreat at this site is still higher compared to the mean annual rock wall retreat rate of 0.54 mm/yr for the last millennium in the Reintal valley (Krautblatter et al., 2012). This shows that sites of large rock falls remain active even years after the event. Heckmann, T.; Bimböse, M.; Krautblatter, M.; Haas, F.; Becht, M.; Morche, D. (2012): From geotechnical analysis to quantification and modelling using LiDAR data: a study on rockfall in the Reintal catchment, Bavarian Alps, Germany; Earth Surface

  9. Dissolution of bedded rock salt: A seismic profile across the active eastern margin of the Hutchinson Salt Member, central Kansas

    USGS Publications Warehouse

    Anderson, N.L.; Hopkins, J.; Martinez, A.; Knapp, R.W.; Macfarlane, P.A.; Watney, W.L.; Black, R.

    1994-01-01

    Since late Tertiary, bedded rock salt of the Permian Hutchinson Salt Member has been dissolved more-or-less continuously along its active eastern margin in central Kansas as a result of sustained contact with unconfined, undersaturated groundwater. The associated westward migration of the eastern margin has resulted in surface subsidence and the contemporaneous sedimentation of predominantly valley-filling Quarternary alluvium. In places, these alluvium deposits extend more than 25 km to the east of the present-day edge of the main body of contiguous rock salt. The margin could have receded this distance during the past several million years. From an environmental perspective, the continued leaching of the Hutchinson Salt is a major concern. This predominantly natural dissolution occurs in a broad zone across the central part of the State and adversely affects groundwater and surface-water quality as nonpoint source pollution. Significant surface subsidence occurs as well. Most of these subsidence features have formed gradually; others developed in a more catastrophic manner. The latter in particular pose real threats to roadways, railways, and buried oil and gas pipelines. In an effort to further clarify the process of natural salt dissolution in central Kansas and with the long-term goal of mitigating the adverse environmental affects of such leaching, the Kansas Geological Survey acquired a 4-km seismic profile across the eastern margin of the Hutchinson Salt in the Punkin Center area of central Kansas. The interpretation of these seismic data (and supporting surficial and borehole geologic control) is consistent with several hypotheses regarding the process and mechanisms of dissolution. More specifically these data support the theses that: 1. (1) Dissolution along the active eastern margin of the Hutchinson Salt Member was initiated during late Tertiary. Leaching has resulted in the steady westward migration of the eastern margin, surface subsidence, and the

  10. Leaching of boron, arsenic and selenium from sedimentary rocks: II. pH dependence, speciation and mechanisms of release.

    PubMed

    Tabelin, Carlito Baltazar; Hashimoto, Ayaka; Igarashi, Toshifumi; Yoneda, Tetsuro

    2014-03-01

    Sedimentary rocks excavated in Japan from road- and railway-tunnel projects contain relatively low concentrations of hazardous trace elements like boron (B), arsenic (As) and selenium (Se). However, these seemingly harmless waste rocks often produced leachates with concentrations of hazardous trace elements that exceeded the environmental standards. In this study, the leaching behaviors and release mechanisms of B, As and Se were evaluated using batch leaching experiments, sequential extraction and geochemical modeling calculations. The results showed that B was mostly partitioned with the residual/crystalline phase that is relatively stable under normal environmental conditions. In contrast, the majority of As and Se were associated with the exchangeable and organics/sulfides phases that are unstable under oxidizing conditions. Dissolution of water-soluble phases controlled the leaching of B, As and Se from these rocks in the short term, but pyrite oxidation, calcite dissolution and adsorption/desorption reactions became more important in the long term. The mobilities of these trace elements were also strongly influenced by the pH of the rock-water system. Although the leaching of Se only increased in the acidic region, those of B and As were enhanced under both acidic and alkaline conditions. Under strongly acidic conditions, the primarily release mechanism of B, As and Se was the dissolution of mineral phases that incorporated and/or adsorbed these elements. Lower concentrations of these trace elements in the circumneutral pH range could be attributed to their strong adsorption onto minerals like Al-/Fe-oxyhydroxides and clays, which are inherently present and/or precipitated in the rock-water system. The leaching of As and B increased under strongly alkaline conditions because of enhanced desorption and pyrite oxidation while that of Se remained minimal due to its adsorption onto Fe-oxyhydroxides and co-precipitation with calcite.

  11. A numerical manifold method model for analyzing fully coupled hydro-mechanical processes in porous rock masses with discrete fractures

    NASA Astrophysics Data System (ADS)

    Hu, Mengsu; Rutqvist, Jonny; Wang, Yuan

    2017-04-01

    In this study, a numerical manifold method (NMM) model was developed for fully coupled analysis of hydro-mechanical (HM) processes in porous rock masses with discrete fractures. Using an NMM two-cover-mesh system of mathematical and physical covers, fractures are conveniently discretized by dividing the mathematical cover along fracture traces to physical cover, resulting in a discontinuous model on a non-conforming mesh. In this model, discrete fracture deformation (e.g. open and slip) and fracture fluid flow within a permeable and deformable porous rock matrix are rigorously considered. For porous rock, direct pore-volume coupling was modeled based on an energy-work scheme. For mechanical analysis of fractures, a fracture constitutive model for mechanically open states was introduced. For fluid flow in fractures, both along-fracture and normal-to-fracture fluid flow are modeled without introducing additional degrees of freedom. When the mechanical aperture of a fracture is changing, its hydraulic aperture and hydraulic conductivity is updated. At the same time, under the effect of coupled deformation and fluid flow, the contact state may dynamically change, and the corresponding contact constraint is updated each time step. Therefore, indirect coupling is realized under stringent considerations of coupled HM effects and fracture constitutive behavior transfer dynamically. To verify the new model, examples involving deformable porous media containing a single and two sets of fractures were designed, showing good accuracy. Last, the model was applied to analyze coupled HM behavior of fractured porous rock domains with complex fracture networks under effects of loading and injection.

  12. From Sand to Rock: a teaching activity to introduce beach dynamics.

    NASA Astrophysics Data System (ADS)

    Gravina, Teresita

    2015-04-01

    The Italian coastline is about 7,500 km long; approximately 53% of the coastlines are low or deltaic coastlines, while 3,240 km were mainly composed of sand or gravel beaches. Most of the Italian coastal environment suffers from intense and growing urbanization, tourism and industry pressure, which could partly explain that 42% of Italian beaches experience erosion. Terracina is situated Lazio (Central Italy), a region strongly impacted by coastal erosion, and for this reason we organized a teaching activity, carried out with fourth year high school classes, in order to help students to understand sand beach dynamics, acquisition of geology issues and land conservation and preservation skills. We decided to focus our activity on the mineralogical composition of beach sand in order to relate beach formations with the geological evolution of the territory. Sand beach minerals were used as tracers in order to support students to understand dynamics that influence beach formations. In addition to mineral characteristic recognition, this activity allows us to introduce the beach balance concept and the phenomena that regulate sediment balance, in order to allow students to consider beaches as a resource which needs to be preserved. Sand mineralogical composition data is treated in a worksheet to elaborate simple statistical analysis in order to recognize the mineral composition of Terracina beach sand's rock sources. This exercise allows students to find relationships between regional geology and beach sand's composition. Finally, statistical evidence could be compared with geological maps of the area in order to find the probable provenance of sand's rock source and rocks recognition thanks to related morphologies. Our main purpose was to help students to understand that beaches are dynamic systems subject to anthropogenic pressure and for this reason they needed to be preserved. Proposed teaching activities involve topics related to students' living territory and to

  13. Bibliography for acid-rock drainage and selected acid-mine drainage issues related to acid-rock drainage from transportation activities

    USGS Publications Warehouse

    Bradley, Michael W.; Worland, Scott C.

    2015-01-01

    Acid-rock drainage occurs through the interaction of rainfall on pyrite-bearing formations. When pyrite (FeS2) is exposed to oxygen and water in mine workings or roadcuts, the mineral decomposes and sulfur may react to form sulfuric acid, which often results in environmental problems and potential damage to the transportation infrastructure. The accelerated oxidation of pyrite and other sulfidic minerals generates low pH water with potentially high concentrations of trace metals. Much attention has been given to contamination arising from acid mine drainage, but studies related to acid-rock drainage from road construction are relatively limited. The U.S. Geological Survey, in cooperation with the Tennessee Department of Transportation, is conducting an investigation to evaluate the occurrence and processes controlling acid-rock drainage and contaminant transport from roadcuts in Tennessee. The basic components of acid-rock drainage resulting from transportation activities are described and a bibliography, organized by relevant categories (remediation, geochemical, microbial, biological impact, and secondary mineralization) is presented.

  14. Oxidation of water to hydrogen peroxide at the rock-water interface due to stress-activated electric currents in rocks

    NASA Astrophysics Data System (ADS)

    Balk, Melike; Bose, Milton; Ertem, Gözen; Rogoff, Dana A.; Rothschild, Lynn J.; Freund, Friedemann T.

    2009-06-01

    Common igneous and high-grade metamorphic rocks contain dormant defects, which release electronic charge carriers when stressed. Rocks thereby behave like a battery. The charge carriers of interest are defect electrons h •, e.g. electronic states associated with O - in a matrix of O 2-. Known as "positive holes" or pholes for short, the h • travel along stress gradients over distances on the order of meters in the laboratory and kilometers in the field. At rock-water interfaces the h • turn into •O radicals, e.g. highly reactive oxygen species, which oxidize H 2O to H 2O 2. For every two h • charge carriers one H 2O 2 molecule is formed. In the laboratory the battery circuit is closed by running a Cu wire from the stressed to the unstressed rock. In the field closure of the circuit may be provided through the electrolytical conductivity of water. The discovery of h • charge carriers, their stress-activation, and their effect on Earth's surface environment may help better understand the oxidation of the early Earth and the evolution of early life.

  15. Molecular Mechanisms of Anthracycline Activity

    NASA Astrophysics Data System (ADS)

    Beretta, Giovanni Luca; Zunino, Franco

    On the basis of evidence that anthracyclines are DNA intercalating agents and DNA is the primary target, a large number of analogs and related intercalators have been developed. However, doxorubicin and closely related anthracyclines still remain among the most effective antitumor agents. Multiple mechanisms have been proposed to explain their efficacy. They include inhibition of DNA-dependent functions, free radical formation, and membrane interactions. The primary mechanism of action is now ascribed to drug interference with the function of DNA topoisomerase II. The stabilization of the topoisomerase-mediated cleavable complex results in a specific type of DNA damage (i.e., double-strand protein-associated DNA breaks). The drug-stabilized cleavable complex is a potentially reversible molecular event and its persistence, as a consequence of strong DNA binding, may be recognized as an apoptotic stimulus. Indirect evidence supports the notion that the bioreductive processes of the quinone moiety generating the semiquinone radical with concomitant production of reactive oxygen species may contribute to the drug effects. The cellular defense mechanisms and response to genotoxic/cytotoxic stress appear to be critical determinants of the tumor sensitivity to anthracyclines.

  16. Applicability of failure criteria and empirical relations of mechanical rock properties from outcrop analogue samples for wellbore stability analyses

    NASA Astrophysics Data System (ADS)

    Reyer, D.; Philipp, S. L.

    2013-12-01

    Knowledge of failure criteria, Young's modulus and uniaxial and tensile strengths, are important to avoid borehole instabilities and adapt the drilling plan on rock mechanical conditions. By this means, a considerable reduction of the total drilling costs can be achieved. This is desirable to enlarge the profit margin of geothermal projects which is rather small compared with hydrocarbon projects. Because core material is rare we aim at predicting in situ rock properties from outcrop analogue samples which are easy and cheap to provide. The comparability of properties determined from analogue samples with samples from depths is analysed by performing conventional triaxial tests, uniaxial compressive strength tests and Brazilian tests of both quarry and equivalent core samples. Equivalent means that the quarry sample is of the same stratigraphic age and of comparable sedimentary facies and composition as the associated core sample. We determined the parameters uniaxial compressive strength (UCS), Young's modulus, and tensile strength for 35 rock samples from quarries and 14 equivalent core samples from the North German Basin. A subgroup of these samples, consisting of one volcanic rock sample, three sandstone and three carbonate samples, was used for triaxial tests. In all cases, comparability of core samples with quarry samples is evaluated using thin section analyses. For UCS versus Young's modulus and tensile strengths, linear- and non-linear regression analyses were performed. We repeat regression separately for clastic rock samples or carbonate rock samples only as well as for quarry samples or core samples only. Empirical relations have high statistical significance and properties of core samples lie within 90% prediction bands of developed regression functions of quarry samples. With triaxial tests we determined linearized Mohr-Coulomb failure criteria, expressed in both principal stresses and shear and normal stresses, for quarry samples. Comparison with

  17. Possible mechanism for seismic attenuation in rocks containing small amounts of volatiles

    NASA Astrophysics Data System (ADS)

    Tittmann, B. R.; Clark, V. A.; Richardson, J. M.; Spencer, T. W.

    1980-10-01

    Measurements were made of the specific dissipation factor of rocks with small contents of volatiles. The factor was measured for shear waves as a function of relative partial pressure for benzene, hexane, ethanol, methanol and water at 10 kHz with the vibrating bar method in a chamber with relative partial pressures between zero and 0.9. The one- or two-monolayer coverage of absorbed volatiles increased the shear wave dissipation factor with exposure to alcohols and water, but only slightly when exposed to hexane and benzene. Direct ellipsometry data and absorption isotherm results are given for thin films or adsorbed volatiles at low partial pressures; the measurements are analyzed in terms of a model relating the dissipation factor to the relative mass of the adsorbed volatiles, the surface area of the rock, and the rock temperature.

  18. Anti-cancer effect of ursolic acid activates apoptosis through ROCK/PTEN mediated mitochondrial translocation of cofilin-1 in prostate cancer

    PubMed Central

    Gai, Wen-Tao; Yu, Da-Peng; Wang, Xin-Sheng; Wang, Pei-Tao

    2016-01-01

    Ursolic acid is a type of pentacyclic triterpene compound with multiple pharmacological activities including cancer resistance, protection from liver injury, antisepsis, anti-inflammation and antiviral activity. The present study aimed to investigate the anticancer effect of ursolic acid. Ursolic acid activates cell apoptosis and its pro-apoptotic mechanism remains to be fully elucidated. Cell Counting kit-8 assays, flow cytometric analysis and analysis of caspase-3 and caspase-9 activity were used to estimate the anticancer effect of ursolic acid on DU145 prostate cancer cells. The protein expression of cytochrome c, rho-associated protein kinase (ROCK), phosphatase and tensin homolog (PTEN) and cofilin-1 were examined using western blot analysis. In the present study, ursolic acid significantly suppressed cell growth and induced apoptosis, as well as increasing caspase-3 and caspase-9 activities of DU145 cells. Furthermore, cytoplasmic and mitochondrial cytochrome c protein expression was significantly activated and suppressed, respectively, by ursolic acid. Ursolic acid significantly suppressed the ROCK/PTEN signaling pathway and inhibited cofilin-1 protein expression in DU145 cells. The results of the present study indicate that the anticancer effect of ursolic acid activates cell apoptosis through ROCK/PTEN mediated mitochondrial translocation of cofilin-1 in prostate cancer. PMID:27698874

  19. Variability of the groundwater sulfate concentration in fractured rock slopes: a tool to identify active unstable areas

    NASA Astrophysics Data System (ADS)

    Binet, S.; Spadini, L.; Bertrand, C.; Guglielmi, Y.; Mudry, J.; Scavia, C.

    2009-12-01

    Water chemical analysis of 100 springs from the Orco and the Tinée valleys (Western Italy and Southern France) and a 7 year groundwater chemistry monitoring of the 5 main springs were performed. All these springs drain from crystalline rock slopes. Some of these drain from currently active gravitational slope deformations. All groundwaters flowing through presently unstable slopes show anomalies in the sulfate concentrations compared to stable aquifers. Particularly, an increase of sulfate concentrations was observed repeatedly after each of five consecutive landslides on the La Clapière slope, thus attesting to the mechanical deformations are at the origin of this concentration change. Significant changes in the water chemistry are produced even from slow (mm/year) and low magnitude deformations of the geological settings. Pyrite nuclei in open fractures were found to be coated by iron oxides. This suggests that the increase of dissolved sulfate relates to oxidative dissolution of Pyrite. Speciation calculations of Pyrite versus Gypsum confirmed that observed changes in the sulfate concentrations is predominantly provided from Pyrite. Calculated amounts of dissolved minerals in the springs water was obtained through inverse modelling of the major ion water analysis data. It is shown that the concentration ratio of calculated dissolved Pyrite versus calculated dissolved gneiss rock allows us to unambiguously distinguish water from stable and unstable areas. This result opens an interesting perspective for the follow-up of sliding or friction dynamic in landslides or in (a) seismic faults.

  20. Heterogeneity in friction strength of an active fault by incorporation of fragments of the surrounding host rock

    NASA Astrophysics Data System (ADS)

    Kato, Naoki; Hirono, Tetsuro

    2016-07-01

    To understand the correlation between the mesoscale structure and the frictional strength of an active fault, we performed a field investigation of the Atera fault at Tase, central Japan, and made laboratory-based determinations of its mineral assemblages and friction coefficients. The fault zone contains a light gray fault gouge, a brown fault gouge, and a black fault breccia. Samples of the two gouges contained large amounts of clay minerals such as smectite and had low friction coefficients of approximately 0.2-0.4 under the condition of 0.01 m s-1 slip velocity and 0.5-2.5 MP confining pressure, whereas the breccia contained large amounts of angular quartz and feldspar and had a friction coefficient of 0.7 under the same condition. Because the fault breccia closely resembles the granitic rock of the hangingwall in composition, texture, and friction coefficient, we interpret the breccia as having originated from this protolith. If the mechanical incorporation of wall rocks of high friction coefficient into fault zones is widespread at the mesoscale, it causes the heterogeneity in friction strength of fault zones and might contribute to the evolution of fault-zone architectures.

  1. Conical Euler simulation and active suppression of delta wing rocking motion

    NASA Technical Reports Server (NTRS)

    Lee, Elizabeth M.; Batina, John T.

    1990-01-01

    A conical Euler code was developed to study unsteady vortex-dominated flows about rolling highly-swept delta wings, undergoing either forced or free-to-roll motions including active roll suppression. The flow solver of the code involves a multistage Runge-Kutta time-stepping scheme which uses a finite volume spatial discretization of the Euler equations on an unstructured grid of triangles. The code allows for the additional analysis of the free-to-roll case, by including the rigid-body equation of motion for its simultaneous time integration with the governing flow equations. Results are presented for a 75 deg swept sharp leading edge delta wing at a freestream Mach number of 1.2 and at alpha equal to 10 and 30 deg angle of attack. A forced harmonic analysis indicates that the rolling moment coefficient provides: (1) a positive damping at the lower angle of attack equal to 10 deg, which is verified in a free-to-roll calculation; (2) a negative damping at the higher angle of attack equal to 30 deg at the small roll amplitudes. A free-to-roll calculation for the latter case produces an initially divergent response, but as the amplitude of motion grows with time, the response transitions to a wing-rock type of limit cycle oscillation. The wing rocking motion may be actively suppressed, however, through the use of a rate-feedback control law and antisymmetrically deflected leading edge flaps. The descriptions of the conical Euler flow solver and the free-to-roll analysis are presented. Results are also presented which give insight into the flow physics associated with unsteady vortical flows about forced and free-to-roll delta wings, including the active roll suppression of this wing-rock phenomenon.

  2. Reaction-transport-mechanical (RTM) simulator Sym.CS: Putting together water-rock interaction, multi-phase and heat flow, composite petrophysics model, and fracture mechanics

    NASA Astrophysics Data System (ADS)

    Paolini, C.; Park, A. J.; Mellors, R. J.; Castillo, J.

    2009-12-01

    A typical CO2 sequestration scenario involves the use of multiple simulators for addressing multiphase fluid and heat flow, water-rock interaction and mass-transfer, rock mechanics, and other chemical and physical processes. The benefit of such workflow is that each model can be constrained rigorously; however, the drawback is final modeling results may achieve only a limited extent of the theoretically possible capabilities of each model. Furthermore, such an approach in modeling carbon sequestration cannot capture the nonlinearity of the various chemical and physical processes. Hence, the models can only provide guidelines for carbon sequestration processes with large margins of error. As an alternative, a simulator is being constructed by a multi-disciplinary team with the aim of implementing a large array of fundamental phenomenologies, including, but not limited to: water-rock interaction using elemental mass-balance and explicit mass-transfer and reaction coupling methods; multi-phase and heat flow, including super-critical CO2 and oil; fracture mechanics with anisotropic permeabilities; rheological rock mechanics based on incremental stress theory; and a composite petrophysics model capable of describing changing rock composition and properties. The modules representing the processes will be solved using a layered iteration method, with the goal of capturing the nonlinear feedback among all of the processes. The simulator will be constructed using proven optimization and modular, object-oriented, and service-oriented programming methods. Finally, a novel AJAX (asynchronous JavaScript and XML) user interface is being tested to host the simulator that will allow usage through an Internet browser. Currently, the water-rock interaction, composite petrophysics, and multi-phase fluid and heat flow modules are available for integration. Results of the water-rock interaction and petrophysics coupling has been used to model interaction between a CO2-charged water and

  3. Nanoscale Properties of Rocks and Subduction Zone Rheology: Inferences for the Mechanisms of Deep Earthquakes

    NASA Astrophysics Data System (ADS)

    Riedel, M. R.

    2007-12-01

    Grain boundaries are the key for the understanding of mineral reaction kinetics. More generally, nanometer scale processes involved in breaking and establishing bonds at reaction sites determine how and at which rate bulk rock properties change in response to external tectonic forcing and possibly feed back into various geodynamic processes. A particular problem is the effects of grain-boundary energy on the kinetics of the olivine-spinel phase transformation in subducting slabs. Slab rheology is affected in many ways by this (metastable) mineral phase change. Sluggish kinetics due to metastable hindrance is likely to cause particular difficulties, because of possible strong non-linear feedback loops between strain-rate and change of creep properties during transformation. In order to get these nanoscale properties included into thermo-mechanical models, reliable kinetic data is required. The measurement of grain-boundary energies is, however, a rather difficult problem. Conventional methods of grain boundary surface tension measurement include (a) equilibrium angles at triple junction (b) rotating ball method (c) thermal groove method, and others (Gottstein & Shvindlerman, 1999). Here I suggest a new method that allows for the derivation of grain-boundary energies for an isochemical phase transformation based on experimental (in-situ) kinetic data in combination with a corresponding dynamic scaling law (Riedel and Karato, 1997). The application of this method to the olivine-spinel phase transformation in subducting slabs provides a solution to the extrapolation problem of measured kinetic data: Any kinetic phase boundary measured at the laboratory time scale can be "scaled" to the correct critical isotherm at subduction zones, under experimentelly "forbidden" conditions (Liou et al., 2000). Consequences for the metastability hypothesis that relates deep seismicity with olivine metastability are derived and discussed. References: Gottstein G, Shvindlerman LS (1999

  4. ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS

    SciTech Connect

    Thurman E. Scott, Jr., Ph.D.; Younane Abousleiman, Ph.D.; Musharraf Zaman, Ph.D., P.E.

    2002-04-30

    } and {alpha}{sub h}, using the equations of Abousleiman et al. (1996). A series of experiments have been conducted, on an initially inherently isotropic Berea sandstone rock sample, to dynamically determine these anisotropic Biot's parameters during deformational pathway experiments. Data acquired during hydrostatic, triaxial, and uniaxial strain pathway experiments indicates that Biot's effective stress parameter changes significantly if the applied stresses are not hydrostatic. Variations, as large as 20% between the axial (vertical) and lateral (horizontal) Biot's effective stress parameters, were observed in some experiments. A series of triaxial compression experiments have been conducted on unconsolidated sand (Oil Creek sand) to determine the pressure/stress conditions which would be favorable for liquefaction. Liquefaction of geopressured sands is thought to be one of the major causative mechanisms of damaging shallow water flows. The experiments were developed to determine if: (1) liquefaction could be made to occur in this particular sand at high confining pressures, and (2) the state of liquefication had the same nature at high pressure conditions typical of shallow water flows as it does in low confining pressure soil mechanics tests. A series of undrained triaxial experiments were successfully used to document that the Oil Creek sand could undergo liquefaction. The nature (i.e., the shape of the deformational pathway in mean pressure/shear stress space) was very similar to those observed in soil mechanics experiments. The undrained triaxial experiments also indicated that this sand would strain soften at relatively high confining pressures--a necessary precursor to liquefaction. These experiments serve as a starting point for a series of acoustic experiments to determine the signature of compressional and shear wave properties as the sand packs approach the state of liquefaction (and shallow water flows).

  5. Rho-associated kinase (ROCK) inhibition reverses low cell activity on hydrophobic surfaces.

    PubMed

    Tian, Yu Shun; Kim, Hyun Jung; Kim, Hyun-Man

    2009-08-28

    Hydrophobic polymers do not offer an adequate scaffold surface for cells to attach, migrate, proliferate, and differentiate. Thus, hydrophobic scaffolds for tissue engineering have traditionally been physicochemically modified to enhance cellular activity. However, modifying the surface by chemical or physical treatment requires supplementary engineering procedures. In the present study, regulation of a cell signal transduction pathway reversed the low cellular activity on a hydrophobic surface without surface modification. Inhibition of Rho-associated kinase (ROCK) by Y-27632 markedly enhanced adhesion, migration, and proliferation of osteoblastic cells cultured on a hydrophobic polystyrene surface. ROCK inhibition regulated cell-cycle-related molecules on the hydrophobic surface. This inhibition also decreased expression of the inhibitors of cyclin-dependent kinases such as p21(cip1) and p27(kip1) and increased expression of cyclin A and D. These results indicate that defective cellular activity on the hydrophobic surface can be reversed by the control of a cell signal transduction pathway without physicochemical surface modification.

  6. Observations, models, and mechanisms of failure of surface rocks surrounding planetary surface loads

    NASA Technical Reports Server (NTRS)

    Schultz, R. A.; Zuber, M. T.

    1994-01-01

    Geophysical models of flexural stresses in an elastic lithosphere due to an axisymmetric surface load typically predict a transition with increased distance from the center of the load of radial thrust faults to strike-slip faults to concentric normal faults. These model predictions are in conflict with the absence of annular zones of strike-slip faults around prominent loads such as lunar maria, Martian volcanoes, and the Martian Tharsis rise. We suggest that this paradox arises from difficulties in relating failure criteria for brittle rocks to the stress models. Indications that model stresses are inappropriate for use in fault-type prediction include (1) tensile principal stresses larger than realistic values of rock tensile strength, and/or (2) stress differences significantly larger than those allowed by rock-strength criteria. Predictions of surface faulting that are consistent with observations can be obtained instead by using tensile and shear failure criteria, along with calculated stress differences and trajectories, with model stress states not greatly in excess of the maximum allowed by rock fracture criteria.

  7. Benidipine protects kidney through inhibiting ROCK1 activity and reducing the epithelium-mesenchymal transdifferentiation in type 1 diabetic rats.

    PubMed

    Wu, Ganlin; Xu, Meirong; Xu, Kui; Hu, Yilan

    2013-01-01

    We investigated the protective effect of benidipine, by testing the changes of the activity of Rho kinase and transdifferentiation of renal tubular epithelium cells in vivo. Wistar rats were randomly divided into two groups: normal (N) and diabetes. STZ were used to make the rats type 1 diabetic and were randomly assigned as diabetes without treatment (D), diabetes treated with benidipine (B), and diabetes treated with fasudil (F) and treated for 3 months. Immunohistochemistry and western blotting were for protein expressions of ROCK1, α-SMA, and E-cadherin and real-time PCR for the mRNA quantification of ROCK1. Compared with N group, D group had significant proliferation of glomerular mesangial matrix, increased cell number, thickened basement membrane, widely infiltrated by inflammatory cells and fibrosis in the renal interstitial, and dilated tubular. Those presentations in F and B groups were milder. Compared with N group, D group showed elevated MYPT1 phosphorylation, increased expression of ROCK1, α-SMA protein, and ROCK1 mRNA and decreased expression of E-cadherin protein. B group showed attenuated MYPT1 phosphorylation, decreased ROCK1, α-SMA protein, and ROCK1 mRNA expression and increased expression of E-cadherin protein. In conclusion, benidipine reduces the epithelium-mesenchymal transdifferentiation and renal interstitial fibrosis in diabetic kidney by inhibiting ROCK1 activity.

  8. Discrete Element Modelling of the Influence of Reinforcement in Structurally Controlled Squeezing Mechanisms in a Hard Rock Mine

    NASA Astrophysics Data System (ADS)

    Karampinos, Efstratios; Hadjigeorgiou, John; Turcotte, Pascal

    2016-12-01

    Structurally defined squeezing mechanisms in hard rock mining often result in buckling failures and large deformations. In mining drives, the primary objective is to mitigate and manage, in a cost-effective way, as opposed to arrest the deformation. This paper is a contribution to an improved understanding of the impact of several reinforcement scenarios in structurally controlled deformations in hard rock mines. The influence of reinforcement in the 3D discrete element method is explored, extending previous numerical work that has captured the squeezing buckling mechanism driven by foliation and high stresses in the selected mine site. A comprehensive strategy for explicitly modelling rock reinforcement using the DEM was developed and implemented in a series of 3D numerical models. The models were calibrated based on field testing of reinforcement and observations at the LaRonde Mine. They were used to investigate the influence of different reinforcement strategies at different deformation stages. The numerical results were in agreement with the field observations and demonstrated the practical implications of using yielding reinforcement elements. This was supported by field data where the use of yielding bolts reduced the drift convergence and rehabilitation. The methodology is applicable to other mine sites facing structurally controlled large deformations.

  9. Rocks and Minerals.

    ERIC Educational Resources Information Center

    Naturescope, 1987

    1987-01-01

    Provides background information on rocks and minerals, including the unique characteristics of each. Teaching activities on rock-hunting and identification, mineral configurations, mystery minerals, and growing crystals are provided. Reproducible worksheets are included for two of the activities. (TW)

  10. Mechanical Aqueous Alteration Dominates Textures of Gale Crater Rocks: Mars Hand Lens Imager (MAHLI) Results

    NASA Astrophysics Data System (ADS)

    Aileen Yingst, R.; Minitti, Michelle; Edgett, Kenneth; McBride, Marie; Stack, Kathryn

    2015-04-01

    The Mars Hand Lens Imager (MAHLI) acquired sub-mm/pixel scale color images of over 70 individual rocks and outcrops during Curiosity's first year on Mars, permitting the study of textures down to the distinction between silt and very fine sand. We group imaged rock textures into classes based on their grain size, sorting, matrix characteristics, and abundance of pores. Because the recent campaign at Pahrump Hills acquired many more MAHLI images than elsewhere along the rover traverse [6], textural analysis there is more detailed and thus types observed there are sub-divided. Mudstones: These rocks contain framework grains smaller than the highest resolution MAHLI images (16 μm/pixel), and thus are interpreted to consist of grains that are silt-sized or smaller. Some rocks contain nodules, sulfate veins, and Mg-enriched erosionally-resistant ridges. The Pahrump Hills region contains mudstones of at least four different sub-textures: recessive massive, recessive parallel-laminated, resistant laminated-to-massive, and resistant cross-stratified. Recessive mudstones are slope-forming; parallel-laminated recessive mudstones display mm-scale parallel (and in some cases rhythmic) lamination that extends laterally for many meters, and are interbedded with recessive massive mudstones. Coarse cm- to mm-scale laminae appear within resistant mudstones though some portions are more massive; laminae tend to be traceable for cm to meters. Well-sorted sandstones: Rocks in this class are made of gray, fine-to-medium sand and exhibit little to no porosity. Two examples of this class show fine lineations with sub-mm spacing. Aillik, a target in the Shaler outcrop, shows abundant cross-lamination. The Pahrump Hills region contains a sub-texture of well-sorted, very fine to fine-grained cross-stratified sandstone at the dune and ripple-scale. Poorly-sorted sandstones. This class is subdivided into two sub-classes: rounded, coarse-to-very coarse sand grains of variable colors and

  11. On Discrimination of Thermal Versus Mechanical Effects of Shock on Rock Magnetic Properties of Spherically Shocked up to ˜10-140 GPa Basalt and Diabase

    NASA Astrophysics Data System (ADS)

    Bezaeva, N. S.; Swanson-Hysell, N. L.; Tikoo, S. M.; Kars, M.; Egli, R.

    2016-08-01

    We present a new experimental method of discrimination in shock-recovery experiments between thermal and mechanical effects of shock on rock magnetic properties of spherically shocked (Ti) magnetite-bearing basalt and diabase.

  12. Dielectric Properties of Volcanic Material and Their Role for Assessing Rock Hardness in the Martian Subsurface

    NASA Astrophysics Data System (ADS)

    Elshafie, A.; Heggy, E.

    2012-03-01

    We perform dielectric permittivity and hardness measurements for martian analog rocks in an attempt to correlate between the physical and mechanical properties of volcanic rocks and its implication for optimizing ExoMars drilling and sampling activities.

  13. The Cretaceous-Tertiary extinction: A lethal mechanism involving anhydrite target rocks

    USGS Publications Warehouse

    Brett, R.

    1992-01-01

    The Chicxulub Crater, Yucatan, Mexico, is a leading contender as the site for the impact event that caused the Cretaceous-Tertiary (K-T) extinctions. A considerable thickness of anhydrite (CaSO4) forms part of the target rock. High temperatures resulting from impact would drive SO2 off from the anhydrite. Hundreds of billions of tonnes of sulfuric acid aerosol would thus enter the stratosphere and cause considerable cooling of the Earth's surface, decrease photosynthesis by orders of magnitude, deplete the ozone layer, and permit increased UV radiation to reach the Earth's surface. Finally, the aerosol would fall back to Earth as acid rain and devastate land and some lacustrine biota and near-surface marine creatures. The presence of anhydrite in the Chicxulub target rock may thus help explain the many extinctions observed at the K-T boundary. ?? 1992.

  14. Mechanism for the activation of glutamate receptors

    Cancer.gov

    Scientists at the NIH have used a technique called cryo-electron microscopy to determine a molecular mechanism for the activation and desensitization of ionotropic glutamate receptors, a prominent class of neurotransmitter receptors in the brain and spina

  15. Dissecting Oceanic Detachment Faults: Fault Zone Geometry, Deformation Mechanisms, and Nature of Fluid-Rock Interactions

    NASA Astrophysics Data System (ADS)

    Bonnemains, D.; Escartin, J.; Verlaguet, A.; Andreani, M.; Mevel, C.

    2015-12-01

    To understand the extreme strain localization at long-lived oceanic detachment faults rooting deeply below the axis, we present results of geological investigations at the 13°19'N detachment along the Mid-Atlantic Ridge, conducted during the ODEMAR cruise (Nov-Dec13, NO Pourquoi Pas?) with ROV Victor6000 (IFREMER). During this cruise we investigated and sampled the corrugated fault to understand its geometry, nature of deformation, and links to fluid flow. We identified and explored 7 fault outcrops on the flanks of microbathymetric striations subparallel to extension. These outcrops expose extensive fault planes, with the most prominent ones extending 40-90m laterally, and up to 10 m vertically. These fault surfaces systematically show subhorizontal striations subparallel to extension, and define slabs of fault-rock that are flat and also striated at sample scale. Visual observations show a complex detachment fault zone, with anastomosing fault planes at outcrop scale (1-10 m), with a highly heterogeneous distribution of deformation. We observe heterogeneity in fault-rock nature at outcrop scale. In situ samples from striated faults are primarily basalt breccias with prior green-schist facies alteration, and a few ultramafic fault-rocks that show a complex deformation history, with early schistose textures, brittlely reworked as clasts within the fault. The basalt breccias show variable silicification and associated sulfides, recording important fluid-rock interactions during exhumation. To understand the link between fluid and deformation during exhumation, we will present microstructural observation of deformation textures, composition, and distribution and origin of quartz and sulfides, as well as constraints on the temperature of silicifying fluids from fluid inclusions in quartz. These results allow us to characterize in detail the detachment fault zone geometry, and investigate the timing of silicification relative to deformation.

  16. Influence of mechanical rock properties and fracture healing rate on crustal fluid flow dynamics

    NASA Astrophysics Data System (ADS)

    Sachau, Till; Bons, Paul; Gomez-Rivas, Enrique; Koehn, Daniel; de Riese, Tamara

    2016-04-01

    Fluid flow in the Earth's crust is very slow over extended periods of time, during which it occurs within the connected pore space of rocks. If the fluid production rate exceeds a certain threshold, matrix permeability alone is insufficient to drain the fluid volume and fluid pressure builds up, thereby reducing the effective stress supported by the rock matrix. Hydraulic fractures form once the effective pressure exceeds the tensile strength of the rock matrix and act subsequently as highly effective fluid conduits. Once local fluid pressure is sufficiently low again, flow ceases and fractures begin to heal. Since fluid flow is controlled by the alternation of fracture permeability and matrix permeability, the flow rate in the system is strongly discontinuous and occurs in intermittent pulses. Resulting hydraulic fracture networks are largely self-organized: opening and subsequent healing of hydraulic fractures depends on the local fluid pressure and on the time-span between fluid pulses. We simulate this process with a computer model and describe the resulting dynamics statistically. Special interest is given to a) the spatially and temporally discontinuous formation and closure of fractures and fracture networks and b) the total flow rate over time. The computer model consists of a crustal-scale dual-porosity setup. Control parameters are the pressure- and time-dependent fracture healing rate, and the strength and the permeability of the intact rock. Statistical analysis involves determination of the multifractal properties and of the power spectral density of the temporal development of the total drainage rate and hydraulic fractures. References Bons, P. D. (2001). The formation of large quartz veins by rapid ascent of fluids in mobile hydrofractures. Tectonophysics, 336, 1-17. Miller, S. a., & Nur, A. (2000). Permeability as a toggle switch in fluid-controlled crustal processes. Earth and Planetary Science Letters, 183(1-2), 133-146. Sachau, T., Bons, P. D

  17. Glassy fragmental rocks of Macquarie Island (Southern Ocean): Mechanism of formation and deposition

    NASA Astrophysics Data System (ADS)

    Dickinson, J. A.; Harb, N.; Portner, R. A.; Daczko, N. R.

    2009-04-01

    Glassy fragmental rocks are interlayered with pillow basalt and tabular basalt on Macquarie Island (54°30' S, 158°54' E). These facies formed along the Proto-Macquarie Spreading Ridge between 6 and 12 Ma and have since been uplifted and exposed on the apex of the Macquarie Ridge Complex. Through a combination of field and microscopic analyses, we investigate the submarine production, transportation, deposition and lithification of basalt and sideromelane clasts within a spreading-ridge environment. The findings of this study indicate that these glassy grains form predominantly by cooling-contraction granulation of pillow lava rinds while crystalline basalt clasts are derived from the fragmentation of pillows along concentric and radial cooling joints. Hyaloclastite breccias consist of crystalline volcanic clasts in a matrix of glassy fragments, and are termed pillow-fragment breccias when clasts identifiable as pillows account for > 25% of the cobble-sized fraction. This glassy fragmental sediment was transported predominantly by short-lived grain flows and deposited as a result of syn-eruptive talus accumulation. The above interpretations culminate in the production of a depositional model: these glassy fragmental rocks formed on the slopes of pillow cones following gravitational collapse of a destabilised cone flank along the Proto-Macquarie Spreading Ridge. Scanning electron microscopy reveals that palagonite alteration rims on glassy grains lithify the sediment. The findings may be used as an analogue for the formation of glassy fragmental rocks along past and present mid-oceanic ridges.

  18. Feldspathic Rock Spectral Detections on Mars: Geologic Context, Possible Formation Mechanisms, and the TES/Themis Perspective

    NASA Astrophysics Data System (ADS)

    Rogers, D.; Nekvasil, H.

    2014-12-01

    Spectral detections from VNIR imaging spectrometers OMEGA and CRISM suggest feldspar-bearing rocks with <5% mafic minerals in restricted locations on Mars. The detections have been interpreted as anorthositic, or alternatively, felsic lithologies such as granite. The detections occur in a variety of contexts, including crater central peaks, walls, and floors, intercrater plains of Noachis Terra, and the Nili patera caldera floor. Here we focus on the Noachis Terra feldspathic rock detections, and present constraints from geologic context and complementary thermal infrared measurements. We also examine mechanisms for forming feldspar-rich lavas from crystal fractionation at the base of thick Martian crust. Noachis Terra exposures exhibit high thermal inertias and deep spectral contrast, consistent with competent, non-porous rock. They commonly overlie olivine basaltic bedrock and are ~20-25 m thick. THEMIS spectra from these units are inconsistent with quartz abundances > 5%, ruling out felsic compositions. THEMIS spectra are consistent with both anorthositic and basaltic lithologies; laboratory spectra of these lithologies are indistinguishable at THEMIS resolution. TES spectra do not match library anorthosites, with ~20-30% modeled pyroxene and ~5-10% olivine. Strong contribution from basaltic sediment to the TES spectra is unlikely given the deeper spectral contrast associated with the feldspathic units than underlying olivine basaltic bedrock. Future work will include spectral comparison with other low silica, feldspathic rocks to determine if there is an analog material that is consistent with both the VNIR and TIR observations. The geologic context of the Noachis units suggests volcanic, rather than plutonic origins, although shallow sills or subglacial eruptive units are possible. Previous experimental and modeling work by Nekvasil showed that feldspar-rich (up to 75 wt%), low-silica lavas may be produced from known Martian basalt by shallow crystallization

  19. Potential fluid mechanic pathways of platelet activation.

    PubMed

    Shadden, Shawn C; Hendabadi, Sahar

    2013-06-01

    Platelet activation is a precursor for blood clotting, which plays leading roles in many vascular complications and causes of death. Platelets can be activated by chemical or mechanical stimuli. Mechanically, platelet activation has been shown to be a function of elevated shear stress and exposure time. These contributions can be combined by considering the cumulative stress or strain on a platelet as it is transported. Here, we develop a framework for computing a hemodynamic-based activation potential that is derived from a Lagrangian integral of strain rate magnitude. We demonstrate that such a measure is generally maximized along, and near to, distinguished material surfaces in the flow. The connections between activation potential and these structures are illustrated through stenotic flow computations. We uncover two distinct structures that may explain observed thrombus formation at the apex and downstream of stenoses. More broadly, these findings suggest fundamental relationships may exist between potential fluid mechanic pathways for mechanical platelet activation and the mechanisms governing their transport.

  20. Crack initiation around prestressed rock bolts

    NASA Astrophysics Data System (ADS)

    Wijk, G.

    1982-07-01

    The stress fields in the rock in the immediate vicinities of the ends of prestressed rock bolts are considered. In particular, the tensile stresses that are likely to initiate cracks are studies. A fracture mechanics analysis shows that if cracks are initiated they will normally not be extended more than a few bore hole diameters and cause negligable reduction of the tensile force in the rock bolts. It is suggested that the initiated cracks can be considerably extended by blasting activities in the neighborhood and accordingly cause loss of bolt tension. If so retensioning of the rock bolts is quite meaningless.

  1. Studies on deformation/pore pressure coupling processes at Japanese URLs and the development of ultra-high resolution FBG strain sensors for rock mechanics (Invited)

    NASA Astrophysics Data System (ADS)

    Tokunaga, T.; Matsui, H.; Zuyuan, H.; Kashiwai, Y.

    2009-12-01

    Generic, purpose-build underground research laboratories have been under construction in Japan. The objective for the construction is to conduct integrated studies on geology, geophysics, hydrogeology, rock mechanics, hydro-geochemistry, etc., to better understand the behavior and long-term stability of subsurface environments and subsurface openings. The Japan Atomic Energy Agency is responsible for the construction and selected two sites, i.e., Mizunami in central Japan and Horonobe in northern tip of Hokkaido, each representing granitic/crystalline rock environment and sedimentary formations, respectively. The construction of the Mizunami URL site began in July 2003, and the shafts reached to 400 m below ground level as of August 2009. The URL is situated in granitic rock masses including highly altered, fractured and faulted zones which are typical in Japan. The Main Shaft is situated at the fault which strikes to NNW while the Ventilation Shaft at the intact granitic rock. Sub-stages, which connect two shafts were constructed every 100 m depth interval, and several boreholes were drilled and are planned to be drilled from the shafts and the galleries for sampling rocks, groundwater, and for continuous monitoring of pore pressures. During the construction, we observed transient pore pressure responses caused by the excavation and dewatering/flooding of the shafts and boreholes. Here, we present one example of the spatio-temporal pore pressure responses caused by the rapid discharge of groundwater of which amount was 0.5 tons per minute from one pilot borehole. Pore pressure responses showed two distinct patterns, one continuous decline and the other transient increase and subsequent decline. The former pattern was observed at the locations where pore pressure transducers were set in the granitic rocks and were situated in the same block with discharge points with respect to the fault with NNW strike, while the latter in sedimentary formations and in the granite

  2. Importance of neutron energy distribution in borehole activation analysis in relatively dry, low-porosity rocks

    USGS Publications Warehouse

    Senftle, F.E.; Moxham, R.M.; Tanner, A.B.; Philbin, P.W.; Boynton, G.R.; Wager, R.E.

    1977-01-01

    To evaluate the importance of variations in the neutron energy distribution in borehole activation analysis, capture gamma-ray measurements were made in relatively dry, low-porosity gabbro of the Duluth Complex. Although sections of over a meter of solid rock were encountered in the borehole, there was significant fracturing with interstitial water leading to a substantial variation of water with depth in the borehole. The linear-correlation coefficients calculated for the peak intensities of several elements compared to the chemical core analyses were generally poor throughout the depth investigated. The data suggest and arguments are given which indicate that the variation of the thermal-to-intermediate-to-fast neutron flux density as a function of borehole depth is a serious source of error and is a major cause of the changes observed in the capture gamma-ray peak intensities. These variations in neutron energy may also cause a shift in the observed capture gamma-ray energy.

  3. A study of the depth of weathering and its relationship to the mechanical properties of near-surface rocks in the Mojave Desert

    USGS Publications Warehouse

    Stierman, D.J.; Healy, J.H.

    1985-01-01

    Weathered granite extends 70 m deep at Hi Vista in the arid central Mojave Desert of southern California. The low strength of this granite is due to the alteration of biotite and chlorite montmorillonite. Deep weathering probably occurs in most granites, although we cannot rule out some anomalous mechanisms at Hi Vista. Geophysical instruments set in these slightly altered rocks are limited by the unstable behavior of the rocks. Thus, tectonic signals from instruments placed in shallow boreholes give vague results. Geophysical measurements of these weathered rocks resemble measurements of granitic rocks near major faults. The rheology of the rocks in which instruments are placed limits the useful sensitivity of the instruments. ?? 1985 Birkha??user Verlag.

  4. Hydrocarbon-water-rock interaction: Redox reaction as a mechanism for sandstone reservoir porosity enhancement

    SciTech Connect

    Shebl, M.A.; Surdam, R.C.

    1995-06-01

    Experiments evaluated the potential for and extent of oil-water-rock reactions in hydrocarbon reservoirs. Results indicate not only that significant potential exists for redox reactions between oxidized mineral phases and crude oil, but that such reactions can significantly alter porosity and permeability characteristics of an elastic hydrocarbon reservoir. The red (oxidized) sandstones used in the redox experiment initially contained 10 to 25% carbonate, anhydrite, and intergranular clay cements. Porosity ranged from 6 to 15%. The sandstones were gray or white after experimentation, and porosity increased 12 to 20% over original values, primarily due to carbonate dissolution. It is suggested that during the redox experiments, the iron oxides ({+-} sulphate) were reduced and hydrocarbon was oxidized to produce oxygenated organic compounds (e.g., organic acid anions, CO{sub 2}). These redox reaction products destabilized the carbonate cements and enhanced sandstone porosity. It is concluded that redox reactions involving crude oil and the mineral matrix of these reservoir rocks in the presence of H{sub 2}O do occur and may result in significantly enhanced porosity. Hydrocarbon emplacement and the resultant redox reactions can cause bleaching and changes in porosity and permeability. This relationship is well documented in the Wingate, White Rim, and Tensleep sandstones. The hydrocarbon reservoir units are white to gray and have good porosity and permeability. The adjacent non-reservoir units are red (due to hematite staining), and have good carbonate cementation and poor porosity and permeability, confining hydrocarbon flow to the nearby reservoir units or associated fractures.

  5. Caspase-3 dependent nitrergic neuronal apoptosis following cavernous nerve injury is mediated via RhoA and ROCK activation in major pelvic ganglion.

    PubMed

    Hannan, Johanna L; Matsui, Hotaka; Sopko, Nikolai A; Liu, Xiaopu; Weyne, Emmanuel; Albersen, Maarten; Watson, Joseph W; Hoke, Ahmet; Burnett, Arthur L; Bivalacqua, Trinity J

    2016-07-08

    Axonal injury due to prostatectomy leads to Wallerian degeneration of the cavernous nerve (CN) and erectile dysfunction (ED). Return of potency is dependent on axonal regeneration and reinnervation of the penis. Following CN injury (CNI), RhoA and Rho-associated protein kinase (ROCK) increase in penile endothelial and smooth muscle cells. Previous studies indicate that nerve regeneration is hampered by activation of RhoA/ROCK pathway. We evaluated the role of RhoA/ROCK pathway in CN regulation following CNI using a validated rat model. CNI upregulated gene and protein expression of RhoA/ROCK and caspase-3 mediated apoptosis in the major pelvic ganglion (MPG). ROCK inhibitor (ROCK-I) prevented upregulation of RhoA/ROCK pathway as well as activation of caspase-3 in the MPG. Following CNI, there was decrease in the dimer to monomer ratio of neuronal nitric oxide synthase (nNOS) protein and lowered NOS activity in the MPG, which were prevented by ROCK-I. CNI lowered intracavernous pressure and impaired non-adrenergic non-cholinergic-mediated relaxation in the penis, consistent with ED. ROCK-I maintained the intracavernous pressure and non-adrenergic non-cholinergic-mediated relaxation in the penis following CNI. These results suggest that activation of RhoA/ROCK pathway mediates caspase-3 dependent apoptosis of nitrergic neurons in the MPG following CNI and that ROCK-I can prevent post-prostatectomy ED.

  6. Caspase-3 dependent nitrergic neuronal apoptosis following cavernous nerve injury is mediated via RhoA and ROCK activation in major pelvic ganglion

    PubMed Central

    Hannan, Johanna L.; Matsui, Hotaka; Sopko, Nikolai A.; Liu, Xiaopu; Weyne, Emmanuel; Albersen, Maarten; Watson, Joseph W.; Hoke, Ahmet; Burnett, Arthur L.; Bivalacqua, Trinity J.

    2016-01-01

    Axonal injury due to prostatectomy leads to Wallerian degeneration of the cavernous nerve (CN) and erectile dysfunction (ED). Return of potency is dependent on axonal regeneration and reinnervation of the penis. Following CN injury (CNI), RhoA and Rho-associated protein kinase (ROCK) increase in penile endothelial and smooth muscle cells. Previous studies indicate that nerve regeneration is hampered by activation of RhoA/ROCK pathway. We evaluated the role of RhoA/ROCK pathway in CN regulation following CNI using a validated rat model. CNI upregulated gene and protein expression of RhoA/ROCK and caspase-3 mediated apoptosis in the major pelvic ganglion (MPG). ROCK inhibitor (ROCK-I) prevented upregulation of RhoA/ROCK pathway as well as activation of caspase-3 in the MPG. Following CNI, there was decrease in the dimer to monomer ratio of neuronal nitric oxide synthase (nNOS) protein and lowered NOS activity in the MPG, which were prevented by ROCK-I. CNI lowered intracavernous pressure and impaired non-adrenergic non-cholinergic-mediated relaxation in the penis, consistent with ED. ROCK-I maintained the intracavernous pressure and non-adrenergic non-cholinergic-mediated relaxation in the penis following CNI. These results suggest that activation of RhoA/ROCK pathway mediates caspase-3 dependent apoptosis of nitrergic neurons in the MPG following CNI and that ROCK-I can prevent post-prostatectomy ED. PMID:27388816

  7. Rocks in Our Pockets

    ERIC Educational Resources Information Center

    Plummer, Donna; Kuhlman, Wilma

    2005-01-01

    To introduce students to rocks and their characteristics, teacher can begin rock units with the activities described in this article. Students need the ability to make simple observations using their senses and simple tools.

  8. Effects of fluid-rock interactions on faulting within active fault zones - evidence from fault rock samples retrieved from international drilling projects

    NASA Astrophysics Data System (ADS)

    Janssen, C.; Wirth, R.; Kienast, M.; Yabe, Y.; Sulem, J.; Dresen, G. H.

    2015-12-01

    Chemical and mechanical effects of fluids influence the fault mechanical behavior. We analyzed fresh fault rocks from several scientific drilling projects to study the effects of fluids on fault strength. For example, in drill core samples on a rupture plane of an Mw 2.2 earthquake in a deep gold mine in South Africa the main shock occurred on a preexisting plane of weakness that was formed by fluid-rock interaction (magnesiohornblende was intensively altered to chlinochlore). The plane acted as conduit for hydrothermal fluids at some time in the past. The chemical influence of fluids on mineralogical alteration and geomechanical processes in fault core samples from SAFOD (San Andreas Fault Observatory at Depth) is visible in pronounced dissolution-precipitation processes (stylolites, solution seams) as well as in the formation of new phases. Detrital quartz and feldspar grains are partially dissolved and replaced by authigenic illite-smectite (I-S) mixed-layer clay minerals. Transmission Electron Microscopy (TEM) imaging of these grains reveals that the alteration processes and healing were initiated within pores and small intra-grain fissures. Newly formed phyllosilicates growing into open pore spaces likely reduced the fluid permeability. The mechanical influence of fluids is indicated by TEM observations, which document open pores that formed in-situ in the gouge material during or after deformation. Pores were possibly filled with formation water and/or hydrothermal fluids suggesting elevated fluid pressure preventing pore collapse. Fluid-driven healing of fractures in samples from SAFOD and the DGLab Gulf of Corinth project is visible in cementation. Cathodoluminescence microscopy (CL) reveals different generations of calcite veins. Differences in CL-colors suggest repeated infiltration of fluids with different chemical composition from varying sources (formation and meteoric water).

  9. [Activation and inhibitory mechanisms of blood platelets].

    PubMed

    Suzuki-Inoue, Katsue

    2014-07-01

    Exposure of platelets to subendothelial matrices initiates physiological hemostasis and pathological thrombosis. Under high shear stress, von Willebrand factor bridges newly exposed collagen to glycoprotein (GP) Ib on platelets. This initial tethering facilitates association between the collagen receptor GPVI and collagen, which generates tyrosine kinase-dependent activation signals, followed by release of secondary mediators and integrin activation. Activated integrin can bind to their ligands including fibrinogen. The released secondary mediators, ADP and thromboxane A2, activate integrin of flowing platelets, which enables formation of platelet thrombi by binding of activated flowing platelets and adhered platelets to collagen via binding between activated aIIbbeta3 integrin and fibrinogen. Platelets also have inhibitory mechanisms, which help to prevent unwanted platelet activation in vivo.

  10. Spontaneous mechanical activity in depolarized frog ventricle

    PubMed Central

    1976-01-01

    Spontaneous mechanical activity can be produced in depolarized frog ventricle by bathing the tissue in a solution with low Na, Iow Ca, and high K+. The contractions can be inhibited by depleting the tissue of Ca first, but they are relatively insensitive to changes in either extracellular [Ca++] or [Ca++]/[Na+]2. They are terminated very rapidly by raising [Na+] to 40 mM. Local anesthetics enhance the spontaneous activity in proportion to the concentration of their free base form. These contractions occur relatively rhythmically for several hours. Since the preparation is multicellular, this suggests a mechanism for intercellular communication without change in membrane potential. PMID:822122

  11. Feldspathic rocks on Mars: Compositional constraints from infrared spectroscopy and possible formation mechanisms

    NASA Astrophysics Data System (ADS)

    Rogers, A. Deanne; Nekvasil, Hanna

    2015-04-01

    Rare feldspar-dominated surfaces on Mars were previously reported based on near-infrared (NIR) spectral data and were interpreted to consist of anorthosite or felsic rocks. Using thermal infrared (TIR) data over the feldspar detections with the largest areal extent in Nili Patera and Noachis Terra, we rule out felsic interpretations. Basaltic or anorthositic compositions are consistent with TIR measurements, but the geologic contexts for these regions do not support a plutonic origin. Laboratory NIR spectral measurements demonstrate that large plagioclase crystals (>~840 µm) can be detected in mixtures with as much as 50 vol % mafics, which is higher than the previously stated requirement of no more than 15% mafics. Thus, anorthositic or felsic interpretations need not be invoked for all NIR-based feldspar detections. Plagioclase-enriched basaltic eruptive products can be formed from Martian basalts through partial crystallization at the base of a thick crust, followed by low-pressure crystallization of the residual liquids.

  12. Quasistatic Shock Waves: A Mechanism for Nonuniform Compaction in Porous Rock

    SciTech Connect

    OLSSON,WILLIAM A.

    2000-09-08

    Recent studies have observed compaction zones pass through porous rock under axisymmetric compression. An initially thin, compacted layer appears at the yield point of the stress-strain curve and then grows by thickening in the direction of maximum compression at constant stress. Strain localization theory has been applied to compaction to explain the formation of these features. This paper describes the growth of the compaction zones, that is, the propagation of their boundaries, in terms of shock wave analysis. The ratio of the applied shortening rate to the velocity of the boundary is related to the porosity change across the boundary. Certain features of the stress-strain curve are explained by the model.

  13. Subcritical fracture propagation in rocks: An examination using the methods of fracture mechanics and non-destructive testing. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Swanson, P. L.

    1984-01-01

    An experimental investigation of tensile rock fracture is presented with an emphasis on characterizing time dependent crack growth using the methods of fracture mechanics. Subcritical fracture experiments were performed in moist air on glass and five different rock types at crack velocities using the double torsion technique. The experimental results suggest that subcritical fracture resistance in polycrystals is dominated by microstructural effects. Evidence for gross violations of the assumptions of linear elastic fracture mechanics and double torsion theory was found in the tests on rocks. In an effort to obtain a better understanding of the physical breakdown processes associated with rock fracture, a series of nondestructive evaluation tests were performed during subcritical fracture experiments on glass and granite. Comparison of the observed process zone shape with that expected on the basis of a critical normal principal tensile stress criterion shows that the zone is much more elongated in the crack propagation direction than predicted by the continuum based microcracking model alone.

  14. Specific activities of natural rocks and soils at quaternary intraplate volcanism north of Sana’a, Yemen

    PubMed Central

    Harb, Shaban; El-Kamel, Abd El-Hadi; Abbady, Abd El-Bast; Saleh, Imran Issa; El-Mageed, Abdallah Ibrahim Abd

    2012-01-01

    The level of natural radioactivity in rocks and soil of 32 samples collected from locations at North Sana′a in Yemen was measured. Concentrations of radionuclides in rocks and soils samples were determined by gamma-ray spectrometer using high purity germanium (HPGe) detector with specially designed shield. The average radioactivity concentrations of 226Ra, 232Th, 40K were determined and expressed in Bq/kg. The results showed that these radionuclides were present in concentrations of 21.79 ± 3.1, 19.5 ± 2.6 and 399.3 ± 16 Bq/kg, respectively, for rocks. For soil, the corresponding values were 48.2 ± 4.4, 41.7 ± 4.5 and 939.1 ± 36 Bq/kg, respectively. Also, the radiological hazard of the natural radionuclide content, radium equivalent activity, total dose rates, external hazard index and gamma activity concentration index of the (rocks/soils) samples in the area under consideration were calculated. The dose rates at 1 m above the ground from terrestrial sources were 38.39 and 86.89 nGy/h for rocks and surface soil, respectively, which present no significant health hazards to humans. PMID:22363113

  15. Specific activities of natural rocks and soils at quaternary intraplate volcanism north of Sana'a, Yemen.

    PubMed

    Harb, Shaban; El-Kamel, Abd El-Hadi; Abbady, Abd El-Bast; Saleh, Imran Issa; El-Mageed, Abdallah Ibrahim Abd

    2012-01-01

    The level of natural radioactivity in rocks and soil of 32 samples collected from locations at North Sana'a in Yemen was measured. Concentrations of radionuclides in rocks and soils samples were determined by gamma-ray spectrometer using high purity germanium (HPGe) detector with specially designed shield. The average radioactivity concentrations of (226)Ra, (232)Th, (40)K were determined and expressed in Bq/kg. The results showed that these radionuclides were present in concentrations of 21.79 ± 3.1, 19.5 ± 2.6 and 399.3 ± 16 Bq/kg, respectively, for rocks. For soil, the corresponding values were 48.2 ± 4.4, 41.7 ± 4.5 and 939.1 ± 36 Bq/kg, respectively. Also, the radiological hazard of the natural radionuclide content, radium equivalent activity, total dose rates, external hazard index and gamma activity concentration index of the (rocks/soils) samples in the area under consideration were calculated. The dose rates at 1 m above the ground from terrestrial sources were 38.39 and 86.89 nGy/h for rocks and surface soil, respectively, which present no significant health hazards to humans.

  16. Reaction zone between pre-UHP titanite and host rock: insights into fluid-rock interaction and deformation mechanisms during exhumation of deeply subducted continental crust (Dabie Shan UHP unit, China)

    NASA Astrophysics Data System (ADS)

    Wawrzenitz, N.; Romer, R. L.; Grasemann, B.; Morales, L. F. G.

    2012-04-01

    Exhumed crustal UHP rocks may occur as relict blocks in strongly metasomatized matrix rocks. Due to variations in competence between the mm to km sized blocks and their ductile matrix, the largely undeformed blocks may preserve the pre-subduction and the prograde history, whereas the matrix rocks have been ductilely deformed to high magnitudes and record successive stages of deformation. The reaction zones between blocks and matrix, however, provide insights into the fluid-rock interaction, deformation and the deformation mechanisms active during the exhumation of deeply subducted continental crust in the subduction channel. We investigate a titanite megacryst (3 cm in diameter) in a calc-silicate marble from the UHP unit in the Dabie Shan, China. The core of the titanite megacryst grew prograde during subduction. Its U-Pb system remained closed and yields a maximum age for UHP metamorphism. Sr and Nd isotope compositions in the core demonstrate that the titanite megacryst precipitated from a homogeneous fluid source. During metamorphism in the subduction zone, infiltration of external fluids resulted first in Sr-loss from the marbles and then introduction of Sr with unusually low 87Sr/86S values (Romer et al., 2003), leading to the contrasting 87Sr/86Sr values in the titanite megacryst and the hosting UHP marbles (Wawrzenitz et al., 2006). Related to deformation in the calc-silicate marble matrix, the rim of the titanite megacryst has been replaced during the following dissolution-precipitation reactions: (i) Pseudomorphic replacement of the old titanite megacryst by coupled dissolution-reprecipitation. Fluid migrated into the old grain producing a sharp boundary of the replacement front. (ii) New small titanite grains grew with their long axes parallel to the foliation of the marble matrix, reflecting the activation of dissolution precipitation creep. In the matrix, the foliation is defined by the orientation of the basal planes of phengitic white mica. The new

  17. A coupled thermo-poro-mechanical finite element analysis of fractured porous rocks using a cohesive interface element

    NASA Astrophysics Data System (ADS)

    Wang, W.; Regueiro, R. A.

    2014-12-01

    The coupling between multiphase flow, heat transfer, and poromechanics in fractured geomaterials has aroused great interest in the areas of geomechanics, geoenvironmental engineering, and petroleum engineering. Relevant applications include nuclear waste repositories, geological sequestration of CO2, geothermal systems, and exploitation of shale gas reservoirs. The paper presents a fully coupled thermo-poro-mechanical (TPM) cohesive interface element (CIE) model, which can represent fluid and heat flow along and across the fracture, and shear/normal deformation of the fracture surfaces. The proposed model is then applied to analyze two popular geological engineering problems using the finite element method (FEM) with a small strain formulation. The first application is the fracturing process in organic-rich shale due to heating. In the finite element analysis, multiple horizontal microcracks parallel to the bedding plane are assumed to preexist in the porous source rock, and are represented by coupled TPM cohesive interface elements. The porous bulk rock is assumed to be homogeneous, isotropic (for the time being, with transverse isotropy a natural extension), and linearly elastic. The excess pore fluid pressure, which mainly causes the development of the fractures, is actually induced by the rapid decomposition of organic matter during heating according to the literature. However, the involved complex chemical reaction process is beyond the scope of the paper, and is therefore substituted by a fluid injection process within the cracks under room temperature (25C) and high temperature (400C) in the paper. We investigate the fracture propagation due to pore fluid pressure increase and the development of fracture-induced permeability. The second application is a nuclear waste repository in a partially saturated fractured rock. Multiphase transport of moisture and heat, thermally-induced stress, as well as the change of fracture apertures are investigated due to short

  18. Seismic response of rock joints and jointed rock mass

    SciTech Connect

    Ghosh, A.; Hsiung, S.M.; Chowdhury, A.H.

    1996-06-01

    Long-term stability of emplacement drifts and potential near-field fluid flow resulting from coupled effects are among the concerns for safe disposal of high-level nuclear waste (HLW). A number of factors can induce drift instability or change the near-field flow patterns. Repetitive seismic loads from earthquakes and thermal loads generated by the decay of emplaced waste are two significant factors. One of two key technical uncertainties (KTU) that can potentially pose a high risk of noncompliance with the performance objectives of 10 CFR Part 60 is the prediction of thermal-mechanical (including repetitive seismic load) effects on stability of emplacement drifts and the engineered barrier system. The second KTU of concern is the prediction of thermal-mechanical-hydrological (including repetitive seismic load) effects on the host rock surrounding the engineered barrier system. The Rock Mechanics research project being conducted at the Center for Nuclear Waste Regulatory Analyses (CNWRA) is intended to address certain specific technical issues associated with these two KTUs. This research project has two major components: (i) seismic response of rock joints and a jointed rock mass and (ii) coupled thermal-mechanical-hydrological (TMH) response of a jointed rock mass surrounding the engineered barrier system (EBS). This final report summarizes the research activities concerned with the repetitive seismic load aspect of both these KTUs.

  19. Deformation mechanisms and petrophysical properties of chert and limestone fault rocks within slope-to-basin succession (Gargano Promontory, Southern Italy)

    NASA Astrophysics Data System (ADS)

    Korneva, Irina; Tondi, Emanuele; Balsamo, Fabrizio; Agosta, Fabrizio

    2016-10-01

    In this work, we examine faults that crosscut limestone and chert rocks pertaining to a slope-to-basin succession of the eastern Gargano Promontory (southern Italy). Based on field data, microstructural observations, and quantitative analysis of cataclastic fabric, two stages of faulting are recognized. The first one, the pre-lithification faulting stage, took place within partially lithified sediments prior to their complete lithification. Differently, the second one, the post-lithification faulting stage, occurred within cohesive, well-lithified rocks. The structural properties of pre-lithification faults were likely controlled by the competence contrast between limestone and chert sediments. In fact, due to their different lithification stages, faulting occurred when chert was still not completely lithified, and hence was dragged along the fault planes. As a consequence, the pre-lithification fault cores are mainly composed of chert clasts. On the contrary, post-lithification fault cores are mostly made up of limestone clasts. The results of both microstructural and image analyses show that the carbonate fault rock includes a higher percentage of bigger clasts with lower values of angularity than the chert fault rock. Mercury-intrusion porosimetry indicates that the chert fault rock is characterized by larger pore throats and a lower amount of total porosity with respect to the limestone fault rock. The permeability values obtained for the limestone fault rock are lower than those for the chert fault rock, probably because of the lower amount of pore connectivity within the former fault rock. Results of this multidisciplinary work highlight the role played by cherty layers present within well-layered, slope-to-basin carbonate successions on both microtextural and petrophysical fault rock properties. Furthermore, these results increase our ability to predict how lithological heterogeneities and amount of lithification influence the deformation mechanisms, hence

  20. Partial reactivation of a huge deep-seated ancient rock slide: recognition, formation mechanism, and stability

    NASA Astrophysics Data System (ADS)

    Tang, Minggao; Xu, Qiang; Li, Yusheng; Huang, Runqiu; Rengers, Niek; Zhu, Xing

    2016-08-01

    About 18 years ago, a large-scale discontinuous layer in properties and colour was found in the new Fengjie town at the shore of the Three Gorges Reservoir area in China. There are many resettled residents and buildings on the sloping area, the safety of which is potentially affected by this layer, so it has become the focus of attention. Before this study started there were two viewpoints regarding the origin of this layer. One was that is was from a huge ancient slide and the other was that is was from a fault graben. In order to find out how it was formed and to be able to carry out a stability analysis of the slope the authors have carried out a research program, including geological field investigations and mapping, a deep drilling hole, a geotechnical centrifuge model test, and a simulation analysis. The results of the research led to the conclusion that the layer is the sliding plane of a huge deep-seated ancient rock slide, which we called the Sanmashan landslide. An important argument for the conclusion is the recognition of a regional compressive tectonic stress field in this area, which cannot lead to the formation of a fault graben because it needs a tensional tectonic stress field. Moreover, numerous unique geological features, sliding marks, and other relics of the ancient slide have been discovered in the field. The formation process of the ancient slide could be repeated in a large geotechnical centrifuge model test. The test shows that a deformation and failure process of "creep-crack-cut" has occurred. The type of the ancient slide can be classified as a "successive rotational rock slide". Finally, the role of seepage in the stability of the Sanmashan landslide has been analysed. Our final conclusions are that, during rainfall and filling-drawdown cycles in the Three Gorges Reservoir, the Sanmashan landslide as a whole is dormant and stable and the secondary landslides in the toe area of the slope are presently stable but can be reactivated. This

  1. Low-activity spectrometric gamma-ray logging technique for delineation of coal/rock interfaces in dry blast holes.

    PubMed

    Asfahani, J; Borsaru, M

    2007-06-01

    A low-activity spectrometric gamma-ray logging technique is proposed in this paper as a sensitive tool for the delineation of coal/rock interfaces in dry blast holes. The advantages and superiority of this technique over traditional micro-density non-spectrometric gamma-ray tools are demonstrated.

  2. Real-time Observations of Rock Cracking and Weather Provide Insights into Thermal Stress-Related Processes of Mechanical Weathering.

    NASA Astrophysics Data System (ADS)

    Eppes, M. C.; Magi, B. I.; Keanini, R.

    2015-12-01

    The environmental conditions (weather and/or climate) that limit or drive mechanical weathering via thermal stress are poorly understood. Here we examine acoustic emission (AE) records of rock cracking in boulders sitting on the ground in humid-temperate (~1 year of data) and semi-arid (~3 years) locations. We compare on-site average ambient daily temperature for days in which cracking occurs to the average temperatures for those dates derived from local climate records. The temperatures characterizing days on which cracking occurs is similar for both stations (range = -10 C to +30 C); where 21% and 73% of cracking occurs on hot days (> 20C) in the humid and semi-arid climates respectively while 17% and 0.1% occurs on very cold days (-8C to -3C). When days during which cracking occurs are compared to climate averages, 81% (NC) and 51% (NM) of all cracking occurs on days with absolute temperature anomalies >1, regardless of the temperature. The proportion of cracking that occurs on anomalously hot or cold days rises to 92% and 77% when the data is normalized to account for uneven sampling of the days with extreme temperatures. In order to determine to what extent this trend holds true in a more complex setting, we examined an existing 100+ year record of rock falls from Yosemite Valley. Preliminary results, although more equivocal, are consistent with the boulder cracking AE data. We examine the AE datasets in the context of our previous numerical modeling of insolation-driven thermal stress in rock and hypothesize that there is an increased potential for fracture on days with extreme temperatures because 1) thermal-stress is dependent on temperature variance from far-field and/or average rock temperatures and 2) that days with climatologically extreme air temperatures result in maximums in such variance. An implication of our results is that environments with extreme weather variability may have higher thermal breakdown rates, including certain locations today and

  3. Molecular mechanisms regulating NLRP3 inflammasome activation

    PubMed Central

    Jo, Eun-Kyeong; Kim, Jin Kyung; Shin, Dong-Min; Sasakawa, Chihiro

    2016-01-01

    Inflammasomes are multi-protein signaling complexes that trigger the activation of inflammatory caspases and the maturation of interleukin-1β. Among various inflammasome complexes, the NLRP3 inflammasome is best characterized and has been linked with various human autoinflammatory and autoimmune diseases. Thus, the NLRP3 inflammasome may be a promising target for anti-inflammatory therapies. In this review, we summarize the current understanding of the mechanisms by which the NLRP3 inflammasome is activated in the cytosol. We also describe the binding partners of NLRP3 inflammasome complexes activating or inhibiting the inflammasome assembly. Our knowledge of the mechanisms regulating NLRP3 inflammasome signaling and how these influence inflammatory responses offers further insight into potential therapeutic strategies to treat inflammatory diseases associated with dysregulation of the NLRP3 inflammasome. PMID:26549800

  4. Warm Eocene climate enhanced petroleum generation from Cretaceous source rocks: A potential climate feedback mechanism?

    NASA Astrophysics Data System (ADS)

    Kroeger, K. F.; Funnell, R. H.

    2012-02-01

    Earth surface temperatures, including in the deep sea increased by 5-10°C from the late Paleocene ca. 58 Myr ago to the Early Eocene Climatic Optimum (EECO) centered at about 51 Myr ago. A large (˜2.5‰) drop in δ13C of carbonate spans much of this interval. This suggests a long-term increase in the net flux of 13C-depleted carbon to the ocean and atmosphere that is difficult to explain by changes in surficial carbon cycling alone. We reveal a relationship between surface temperature increase and increased petroleum generation in sedimentary basins operating on 100 kyr to Myr time scales. We propose that early Eocene warming has led to a synchronization of periods of maximum petroleum generation and enhanced generation in otherwise unproductive basins through extension of the volume of source rock within the oil and gas window across hundreds of sedimentary basins globally. Modelling the thermal evolution of four sedimentary basins in the southwest Pacific predicted an up to 50% increase in petroleum generation that would have significantly increased leakage of light hydrocarbons and oil degeneration products into the atmosphere. Extrapolating our modelling results to hundreds of sedimentary basins worldwide suggests that globally increased leakage could have caused a climate feedback effect, driving or enhancing early Eocene climate warming.

  5. Preliminary assessment of active rock slope instabilities in the high Himalaya of Bhutan

    NASA Astrophysics Data System (ADS)

    Dini, Benedetta; Manconi, Andrea; Leith, Kerry; Loew, Simon

    2016-04-01

    The small kingdom of Bhutan, nested between India and Tibet (between 88° and 92° east and 26° and 28° north), is characterised by markedly different landscapes and climatic zones. V-shaped, forest-covered valleys in the south, affected by the monsoonal rains, give gradually way to steep, barren slopes of U-shaped valleys in the drier north, host of the highest peaks, a large number of glaciers and glacial lakes. A transition zone of vegetated, elevated plateaus collects the towns in which most of the population lives. Landslides in the high Himalaya of Bhutan have not been extensively studied despite the primary and secondary hazards related to them. The regulations and restrictions to travel to and within Bhutan imposed by the government, as well as the extremely rugged terrain hinder the accessibility to remote slopes and valleys, both of which have resulted in lack of data and investigations. In this work, we aim at producing an inventory of large rock slope instabilities (> 1 million m3) across the high Himalaya of Bhutan, identifying types of failure, assessing the activity and analysing the distribution of landslides in combination with predisposing and preparatory factors, such as lithology, tectonic structures, hypsometry, deglaciation, fluvial erosive power and climate. At this stage, we rely on the information retrieved through satellite remote sensing data, i.e. medium and high resolution DEMs, optical images and space borne Synthetic Aperture Radar (SAR) data. An initial inventory was compiled based on the identification of geomorphological features associated with slope instabilities using the available Google Earth images. Moreover, we assessed the SAR data coverage and the expected geometrical distortions by assuming different sensors (ERS, Envisat, and ALOS Palsar-1). As we are mainly interested in detecting the surface deformation related to large unstable slopes by applying Differential SAR, we also computed the percentage of potentially

  6. North-south compression, active uplift, and abyssal mantle exhumation of the Saint Peter and Saint Paul Rock, Equatorial Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Motoki, A.; Sichel, S. E.; Campos, T. F.; Motoki, K. F.; Szatmari, P.; Poseidon-Colmeia

    2013-05-01

    This article presents near N-S compression, active uplift tectonism, and the consequent abyssal mantle exhumation of the Saint Peter and Saint Paul Rock, Equatorial Atlantic Ocean. The mantle peridotite ridge is about 80 km long, 25 km wide, 3800 m high, and of near E-W direction. The ridge flanks are extremely steep with sub-vertical scarps of about 2000 m of relative height. The Flandrian wave-cut and the 14C datings for the carbonaceous algae of the Saint Peter and Saint Paul Rock indicate active uplift of 1.5 mm/year. The tectonic factures shows conjugated system of N-S compression tending slightly to NW-ES. Close to the peridotite ridge, the earthquakes with near N-S compression focal mechanism take place. The southern half of the peridotite ridge is constituted by undeformed peridotite. The existence of corrugation morphology indicates that the mantle rocks are originated from old megamullion. On the other hand, the northern half is composed of strongly deformed mylonitic peridotite suggesting that the ultramafic rocks are possibly originated from sub-crustal abyssal mantle of old transform fault. The mylonite structure is intensely perturbed indicating the tectonic events which disturbed the original parallel structure. The Saint Paul transform fault zone is characterized by E-W trend right lateral movement and the near N-S compression is unlikely. Therefore, an unusual local geotectonic process is expected. This tectonism was originated from the plate boundary jump at about 8 Ma, caused by the emergence of a new ridge segment, and the new transform fault is oblique to the relative plate movement. This angular discrepancy causes the compression perpendicular to the oblique transform fault, of near N-S direction, which squeeze out the sub-crustal abyssal mantle up to sea level. Therefore, the peridotite Ridge is considered to be a pressure ridge of the strike-slip movement of the Saint Paul transform fault.

  7. Microfabrics and 3D grain shape of Gorleben rock salt: Constraints on deformation mechanisms and paleodifferential stress

    NASA Astrophysics Data System (ADS)

    Thiemeyer, Nicolas; Zulauf, Gernold; Mertineit, Michael; Linckens, Jolien; Pusch, Maximilian; Hammer, Jörg

    2016-04-01

    The Permian Knäuel- and Streifensalz formations (z2HS1 and z2HS2) are main constituents of the Gorleben salt dome (Northern Germany) and show different amounts and distributions of anhydrite. The reconstruction of 3D halite grain shape ellipsoids reveals small grain size (3.4 ± 0.6 mm) and heterogeneous grain shapes in both formations, the latter attributed to the polyphase deformation of the rock salt during diapirism. The halite microfabrics of both formations indicate that strain-induced grain boundary migration was active during deformation. Crystal plastic deformation of halite is further documented by lattice bending, subgrain formation and minor subgrain rotation. Evidence for pressure solution of halite has not been found, but cannot be excluded because of the small grain size, the lack of LPO and the low differential stress (1.1-1.3 MPa) as deduced from subgrain-size piezometry. Anhydrite has been deformed in the brittle-ductile regime by solution precipitation creep, minor dislocation creep and brittle boudinage. No continuous anhydrite layers are preserved, and halite has acted as a sealing matrix embedding the disrupted anhydrite fragments prohibiting any potential migration pathways for fluids. Thus, anhydrite should not have a negative effect on the barrier properties of the Gorleben rock salts investigated in this study.

  8. Failure of cap-rock seals as determined from mechanical stratigraphy, stress history, and tensile-failure analysis of exhumed analogs

    DOE PAGES

    Petrie, E. S.; Evans, J. P.; Bauer, S. J.

    2014-11-01

    In this study, the sedimentologic and tectonic histories of clastic cap rocks and their inherent mechanical properties control the nature of permeable fractures within them. The migration of fluid through mm- to cm-scale fracture networks can result in focused fluid flow allowing hydrocarbon production from unconventional reservoirs or compromising the seal integrity of fluid traps. To understand the nature and distribution of subsurface fluid-flow pathways through fracture networks in cap-rock seals we examine four exhumed Paleozoic and Mesozoic seal analogs in Utah. We combine these outcrop analyses with subsidence analysis, paleoloading histories, and rock-strength testing data in modified Mohr–Coulomb–Griffith analysesmore » to evaluate the effects of differential stress and rock type on fracture mode.« less

  9. Failure of cap-rock seals as determined from mechanical stratigraphy, stress history, and tensile-failure analysis of exhumed analogs

    SciTech Connect

    Petrie, E. S.; Evans, J. P.; Bauer, S. J.

    2014-11-01

    In this study, the sedimentologic and tectonic histories of clastic cap rocks and their inherent mechanical properties control the nature of permeable fractures within them. The migration of fluid through mm- to cm-scale fracture networks can result in focused fluid flow allowing hydrocarbon production from unconventional reservoirs or compromising the seal integrity of fluid traps. To understand the nature and distribution of subsurface fluid-flow pathways through fracture networks in cap-rock seals we examine four exhumed Paleozoic and Mesozoic seal analogs in Utah. We combine these outcrop analyses with subsidence analysis, paleoloading histories, and rock-strength testing data in modified Mohr–Coulomb–Griffith analyses to evaluate the effects of differential stress and rock type on fracture mode.

  10. An insight to the eruption mechanism of volcanic rocks in North Tibet: Project TITAN

    NASA Astrophysics Data System (ADS)

    He, R.; Gao, R.; Li, Q.

    2013-12-01

    Since Cenozoic continent-continental collision between India and Asia [Yin and Harrison, 2000], many surface features happened within the plateau were prominent. As one of them, high-to-ultra potassic lavas of Neogene, even younger, are widely distributed in NW Tibet, as shown in Figure1. Obvious petrological and geochemical characteristics of those lavas [Turner et al., 1993; Deng et al., 1996; Hacker et al., 2000; Ding et al., 2003; Williams et al., 2004; Chung et al., 2005; Luo et al., 2006; Guo et al., 2006] were presumably associated with extensional collapse of the lithospheric mantle [Deng et al., 1998; Li et al., 2000; Ding et al., 2003; Williams et al., 2004; Chung et al., 2005; Luo et al., 2006; Guo et al., 2006], which started at about 4Ma [Yin et al., 1999] and still goes on [Lin et al., 2002]. (1) What kinetics happened within the lithosphere beneath the lava region since Late Neogene? (2) What kind of mechanism leads to the lava eruption, it is only the result of far-long effect of northward subduction of the India plate, or directly related to the south margin of the Asian lithosphere, or bilaterally affected by India and Asia plate, or other factors? (3) Why did the strong volcanic activities only wrecked the North Qiangtang terrane, Jinshajiang suture and Hoh Xil terrane, instead of going northward across Altyn Tagh Fault and East Kunlun? As is known, to reveal the scientific secret concealed in lavas within NW Tibet geophysical observations are very necessary and urgent. NW Tibet including North Qiangtang and Hoh Xil is a very tough region for human beings. The project for geophysical observatory in the region is named as TITAN. TITAN has currently made some great progress, such as 103 broadband Seismic observation stations were deployed along longitude 88.5E in recent 5 years, as shown in Figure 1. Some primary results were got, such as (1) P-velocity structure from teleseismic tomography around Shuanghu in central Qiangtang (Figure 2) showed

  11. Electrical Conductivity of Rocks and Dominant Charge Carriers. Part 1; Thermally Activated Positive Holes

    NASA Technical Reports Server (NTRS)

    Freund, Friedemann T.; Freund, Minoru M.

    2012-01-01

    The prevailing view in the geophysics community is that the electrical conductivity structure of the Earth's continental crust over the 5-35 km depth range can best be understood by assuming the presence of intergranular fluids and/or of intragranular carbon films. Based on single crystal studies of melt-grown MgO, magma-derived sanidine and anorthosite feldspars and upper mantle olivine, we present evidence for the presence of electronic charge carriers, which derive from peroxy defects that are introduced during cooling, under non-equilibrium conditions, through a redox conversion of pairs of solute hydroxyl arising from dissolution of H2O.The peroxy defects become thermally activated in a 2-step process, leading to the release of defect electrons in the oxygen anion sublattice. Known as positive holes and symbolized by h(dot), these electronic charge carriers are highly mobile. Chemically equivalent to O(-) in a matrix of O(2-) they are highly oxidizing. Being metastable they can exist in the matrix of minerals, which crystallized in highly reduced environments. The h(dot) are highly mobile. They appear to control the electrical conductivity of crustal rocks in much of the 5-35 km depth range.

  12. Mechanobiocatalysis: Modulating Enzymatic Activity with Mechanical Force

    DTIC Science & Technology

    2015-09-28

    displayed by enzymes and other materials. It was demonstrated that the application of forces to enzymes properly outfitted with polymers resulted in...intrinsic activities displayed by enzymes and other materials. It was demonstrated that the application of forces to enzymes properly outfitted with polymers ...of eYFP-containing polymer composites via the application of mechanical force, as well as showing that the photophysical properties displayed by

  13. Topological mechanics: from metamaterials to active matter

    NASA Astrophysics Data System (ADS)

    Vitelli, Vincenzo

    2015-03-01

    Mechanical metamaterials are artificial structures with unusual properties, such as negative Poisson ratio, bistability or tunable acoustic response, which originate in the geometry of their unit cell. At the heart of such unusual behavior is often a mechanism: a motion that does not significantly stretch or compress the links between constituent elements. When activated by motors or external fields, these soft motions become the building blocks of robots and smart materials. In this talk, we discuss topological mechanisms that possess two key properties: (i) their existence cannot be traced to a local imbalance between degrees of freedom and constraints (ii) they are robust against a wide range of structural deformations or changes in material parameters. The continuum elasticity of these mechanical structures is captured by non-linear field theories with a topological boundary term similar to topological insulators and quantum Hall systems. We present several applications of these concepts to the design and experimental realization of 2D and 3D topological structures based on linkages, origami, buckling meta-materials and lastly active media that break time-reversal symmetry.

  14. Seismic Faulting of Dolomite Rocks: Textures and Possible Slip Weakening Mechanisms

    NASA Astrophysics Data System (ADS)

    Togo, T.; de Paola, N.; di Toro, G.; Hirose, T.; Mitchell, T.; Shimamoto, T.

    2008-12-01

    We performed high velocity friction experiments on dolomite gouge material for normal stress sn=0.4-2 MPa and slip rates v=1.3 m/s. During the experiments, the CO2 emission rate was monitored, since dolomite decomposes to Mg-calcite+MgO+CO2 for temperatures T>550 C. For sn>0.8 MPa, CO2 emissions have been recorded. XRD analyses of the deformed gouge layer confirmed the presence of small amount (3%) of Mg-calcite and MgO. The shear strength (t)displays an exponential decay trend, over a slip weakening distance Dc, from a peak to a steady state value. For displacement values >Dc, t sharply increases resulting in the attainment of a second steady state. The observed strengthening always occurs at about the same time of a dramatic increase in the rate of the CO2 emissions. We interpret the increase of t, after the first steady state, as due to the increase of the effective normal stress when pressurized CO2 escapes from the slip zone and fluid pressure is reduced. Micro-structural observations show the development of a thin slip zone (50-150 microns) of very to ultra fine-grained material. Thick bands (100-500 microns) of decomposed dolomite gouge developed adjacent to the slip zone. The thermally decomposed dolomite is characterized by rounded and vesiculated clasts (different from clasts of initially intact material which have angular shape) displaying reaction rims and patches of ultra fine-grained decomposed material, enriched in Ca (Mg-Calcite) and Mg (MgO). A thin layer (10-20 microns) of ultra fine-grained decomposed material, made of Mg-Calcite and MgO, has been observed to develop within the slip zone. It displays a sharp contact with the band of decomposed material developed outside the slip zone. The microstructures observed in the areas adjacent/within the slip zone can be used in future studies as new diagnostic features to aid in the recognition of seismic faulting within carbonatic rocks and, potentially, of thermal pressurization slip weakening

  15. Mechanically activated artificial cell by using microfluidics

    PubMed Central

    Ho, Kenneth K. Y.; Lee, Lap Man; Liu, Allen P.

    2016-01-01

    All living organisms sense mechanical forces. Engineering mechanosensitive artificial cell through bottom-up in vitro reconstitution offers a way to understand how mixtures of macromolecules assemble and organize into a complex system that responds to forces. We use stable double emulsion droplets (aqueous/oil/aqueous) to prototype mechanosensitive artificial cells. In order to demonstrate mechanosensation in artificial cells, we develop a novel microfluidic device that is capable of trapping double emulsions into designated chambers, followed by compression and aspiration in a parallel manner. The microfluidic device is fabricated using multilayer soft lithography technology, and consists of a control layer and a deformable flow channel. Deflections of the PDMS membrane above the main microfluidic flow channels and trapping chamber array are independently regulated pneumatically by two sets of integrated microfluidic valves. We successfully compress and aspirate the double emulsions, which result in transient increase and permanent decrease in oil thickness, respectively. Finally, we demonstrate the influx of calcium ions as a response of our mechanically activated artificial cell through thinning of oil. The development of a microfluidic device to mechanically activate artificial cells creates new opportunities in force-activated synthetic biology. PMID:27610921

  16. Mechanically activated artificial cell by using microfluidics

    NASA Astrophysics Data System (ADS)

    Ho, Kenneth K. Y.; Lee, Lap Man; Liu, Allen P.

    2016-09-01

    All living organisms sense mechanical forces. Engineering mechanosensitive artificial cell through bottom-up in vitro reconstitution offers a way to understand how mixtures of macromolecules assemble and organize into a complex system that responds to forces. We use stable double emulsion droplets (aqueous/oil/aqueous) to prototype mechanosensitive artificial cells. In order to demonstrate mechanosensation in artificial cells, we develop a novel microfluidic device that is capable of trapping double emulsions into designated chambers, followed by compression and aspiration in a parallel manner. The microfluidic device is fabricated using multilayer soft lithography technology, and consists of a control layer and a deformable flow channel. Deflections of the PDMS membrane above the main microfluidic flow channels and trapping chamber array are independently regulated pneumatically by two sets of integrated microfluidic valves. We successfully compress and aspirate the double emulsions, which result in transient increase and permanent decrease in oil thickness, respectively. Finally, we demonstrate the influx of calcium ions as a response of our mechanically activated artificial cell through thinning of oil. The development of a microfluidic device to mechanically activate artificial cells creates new opportunities in force-activated synthetic biology.

  17. 10Be dating of the end of low-altitude rock glacier activity in the Alps - evidence for cold conditions during the early Preboreal.

    NASA Astrophysics Data System (ADS)

    Kerschner, Hanns; Ivy-Ochs, Susan

    2010-05-01

    Large relict rock glacier complexes are conspicious features in the Alps. Their occurence can roughly be subdivided into a "lower rock glacier belt", which reaches down to about 1900 m a.s.l., an "intermediate rock glacier belt" with rock glacier snouts at around present-day timberline (approx. 2200 m a.s.l) in the central Alps and an "upper rock glacier belt" at similar altitudes as presently active rock glaciers. All these rock glaciers indicate the former presence of discontinuous permafrost at their respective altitudes and are good indicators for the mean annual air temperature during their active period. The end of rock glacier activity at a given altitude marks also the end of the existence of permafrost conditions. Experience from the Alps shows that it may take about a century until the surface of a rock glacier is stabilized, Hence, if it is possible to date the surface of a relict rock glacier with 10Be, we get a close date for the end of permafrost activity at the altitude of the rock glacier. From the difference between the altitude of the relict rock glacier and presently active rock glaciers, the rise of mean annual air temperature can be calculated. Relict rock glaciers at present-day timberline at Julierpass (Swiss Alps) and at Larstigtal (Austrian Alps) gave ages in the order of 10.5 ka BP for surface stabilization. Both rock glaciers, which belong to the "intermediate rock glacier belt", developed from lateral moraines and scree slopes. They started to move into former glacier beds after ice recession from the Younger Dryas "Egesen" advance. Their age indicates that climatic conditions favouring permafrost existence about 300 - 400 m below 20th century permafrost occurence prevailed during most of the Preboreal. Taken together with the Kartell glacier advance (10.8 ka) they show that rapid climatic warming at the Younger Dryas / Holocene boundary was followed by more unstable climatic conditions and and somewhat slower warming until full Holocene

  18. Microbial Community Structure of Activated Sludge for Biosolubilization of Two Different Rock Phosphates.

    PubMed

    Xiao, Chunqiao; Wu, Xiaoyan; Liu, Tingting; Xu, Guang; Chi, Ruan

    2016-12-16

    A microbial consortium was directly taken from activated sludge and was used to solubilize rock phosphates (RPs) in a lab-scale bioreactor in this study. Results showed that the microbial consortium could efficiently release soluble phosphorus (P) from the RPs, and during 30-day incubation, it grew well in the bioreactor and reduced the pH of the solutions. The biosolubilization process was also illustrated by the observation of scanning electron microscopy combined with an energy dispersive X-ray spectroscopy (SEM-EDX), which showed an obvious corrosion on the ore surfaces, and most elements were removed from the ore samples. The analysis of microbial community structure by Illumina 16S ribosomal RNA (rRNA) gene and 18S rRNA gene MiSeq sequencing reflected different microbial diversity and richness in the solutions added with different ore samples. A lower richness and diversity of bacteria but a higher richness and diversity of fungi occurred in the solution added with ore sample 1 compared to that of in the solution added with ore sample 2. Alphaproteobacteria and Saccharomycetes were the dominating bacterial and fungal group, respectively, both in the solutions added with ore samples 1 and 2 at the class level. However, their abundances in the solution added with ore sample 1 were obviously lower than that in the solution added with ore sample 2. This study provides new insights into our understanding of the microbial community structure in the biosolubilization of RPs by a microbial consortium directly taken from activated sludge.

  19. Critical Chemical-Mechanical Couplings that Define Permeability Modifications in Pressure-Sensitive Rock Fractures

    SciTech Connect

    Derek Elsworth; Abraham Grader; Susan Brantley

    2007-04-25

    This work examined and quantified processes controlling changes in the transport characteristics of natural fractures, subjected to coupled thermal-mechanical-chemical (TMC) effects. Specifically, it examined the effects of mineral dissolution and precipitation mediated by mechanical effects, using laboratory through-flow experiments concurrently imaged by X-ray CT. These were conducted on natural and artificial fractures in cores using water as the permeant. Fluid and mineral mass balances are recorded and are correlated with in-sample saturation, porosity and fracture aperture maps, acquired in real-time by X-ray CT-imaging at a maximum spatial resolution of 15-50 microns per pixel. Post-test, the samples were resin-impregnated, thin-sectioned, and examined by microscopy to define the characteristics of dissolution and precipitation. The test-concurrent X-ray imaging, mass balances, and measurements of permeability, together with the post-test microscopy, were used to define dissolution/precipitation processes, and to constrain process-based models. These models define and quantify key processes of pressure solution, free-face dissolution, and shear-dilation, and the influence of temperature, stress level, and chemistry on the rate of dissolution, its distribution in space and time, and its influence on the mechanical and transport properties of the fracture.

  20. Rock expansion caused by ultrasound

    NASA Astrophysics Data System (ADS)

    Hedberg, C.; Gray, A.

    2013-12-01

    It has during many years been reported that materials' elastic modulus decrease when exposed to influences like mechanical impacts, ultrasound, magnetic fields, electricity and even humidity. Non-perfect atomic structures like rocks, concrete, or damaged metals exhibit a larger effect. This softening has most often been recorded by wave resonance measurements. The motion towards equilibrium is slow - often taking hours or days, which is why the effect is called Slow Dynamics [1]. The question had been raised, if a material expansion also occurs. 'The most fundamental parameter to consider is the volume expansion predicted to occur when positive hole charge carriers become activated, causing a decrease of the electron density in the O2- sublattice of the rock-forming minerals. This decrease of electron density should affect essentially all physical parameters, including the volume.' [2]. A new type of configuration has measured expansion of a rock subjected to ultrasound. A PZT was used as a pressure sensor while the combined thickness of the rock sample and the PZT sensor was held fixed. The expansion increased the stress in both the rock and the PZT, which gave an out-put voltage from the PZT. Knowing its material properties then made it possible to calculate the rock expansion. The equivalent strain caused by the ultrasound was approximately 3 x 10-5. The temperature was monitored and accounted for during the tests and for the maximum expansion the increase was 0.7 C, which means the expansion is at least to some degree caused by heating of the material by the ultrasound. The fraction of bonds activated by ultrasound was estimated to be around 10-5. References: [1] Guyer, R.A., Johnson, P.A.: Nonlinear Mesoscopic Elasticity: The Complex Behaviour of Rocks, Soils, Concrete. Wiley-VCH 2009 [2] M.M. Freund, F.F. Freund, Manipulating the Toughness of Rocks through Electric Potentials, Final Report CIF 2011 Award NNX11AJ84A, NAS Ames 2012.

  1. Mechanism of FGF receptor dimerization and activation

    NASA Astrophysics Data System (ADS)

    Sarabipour, Sarvenaz; Hristova, Kalina

    2016-01-01

    Fibroblast growth factors (fgfs) are widely believed to activate their receptors by mediating receptor dimerization. Here we show, however, that the FGF receptors form dimers in the absence of ligand, and that these unliganded dimers are phosphorylated. We further show that ligand binding triggers structural changes in the FGFR dimers, which increase FGFR phosphorylation. The observed effects due to the ligands fgf1 and fgf2 are very different. The fgf2-bound dimer structure ensures the smallest separation between the transmembrane (TM) domains and the highest possible phosphorylation, a conclusion that is supported by a strong correlation between TM helix separation in the dimer and kinase phosphorylation. The pathogenic A391E mutation in FGFR3 TM domain emulates the action of fgf2, trapping the FGFR3 dimer in its most active state. This study establishes the existence of multiple active ligand-bound states, and uncovers a novel molecular mechanism through which FGFR-linked pathologies can arise.

  2. From rock to magma and back again: The evolution of temperature and deformation mechanism in conduit margin zones

    NASA Astrophysics Data System (ADS)

    Heap, Michael J.; Violay, Marie; Wadsworth, Fabian B.; Vasseur, Jérémie

    2017-04-01

    Explosive silicic volcanism is driven by gas overpressure in systems that are inefficient at outgassing. The zone at the margin of a volcanic conduit-thought to play an important role in the outgassing of magma and therefore pore pressure changes and explosivity-is the boundary through which heat is exchanged from the hot magma to the colder country rock. Using a simple heat transfer model, we first show that the isotherm for the glass transition temperature (whereat the glass within the groundmass transitions from a glass to an undercooled liquid) moves into the country rock when the magma within the conduit can stay hot, or into the conduit when the magma is quasi-stagnant and cools (on the centimetric scale over days to months). We then explore the influence of a migrating viscous boundary on compactive deformation micromechanisms in the conduit margin zone using high-pressure (effective pressure of 40 MPa), high-temperature (up to 800 °C) triaxial deformation experiments on porous andesite. Our experiments show that the micromechanism facilitating compaction in andesite is localised cataclastic pore collapse at all temperatures below the glass transition of the amorphous groundmass glass Tg (i.e., rock). In this regime, porosity is only reduced within the bands of crushed pores; the porosity outside the bands remains unchanged. Further, the strength of andesite is a positive function of temperature below the threshold Tg due to thermal expansion driven microcrack closure. The micromechanism driving compaction above Tg (i.e., magma) is the distributed viscous flow of the melt phase. In this regime, porosity loss is distributed and is accommodated by the widespread flattening and closure of pores. We find that viscous flow is much more efficient at reducing porosity than cataclastic pore collapse, and that it requires stresses much lower than those required to form bands of crushed pores. Our study therefore highlights that temperature excursions can result in a

  3. Site study plan for non-routine laboratory rock mechanics, Deaf Smith County Site, Texas: Revision 1

    SciTech Connect

    Not Available

    1987-12-01

    This Site Study Plan describes the non-routine rock mechanics and thermal properties laboratory testing program planned for the characterization of site-specific geologic materials for the Deaf Smith County site, Texas. The study design provides for measurements of index, mechanical, thermomechanical, thermal and special properties for the host salt, and where appropriate, for nonhost lithologies. The types of tests which will be conducted are constant stress (creep) tests, constant strain (stress relaxation) tests, constant strain-rate tests, constant stress-rate tests, cyclic loading tests, hollow cylinder tests, uniaxial and triaxial compression tests, direct tension tests, indirect (triaxial) shear tests, thermal property determinations (conductivity, specific heat, expansivity, and diffusivity), fracture healing tests, thermal decrepitation tests, moisture content determinations, and petrographic and micromechanics analyses. Tests will be conducted at confining pressures up to 30 MPa and temperatures up to 300/degree/C. These data are used to construct mathematical models for the phenomenology of salt deformation. The models are then used in finite-element codes to predict repository response. A tentative testing schedule and milestone log are given. The duration of the testing program is expected to be approximately 5 years. 44 refs., 13 figs., 13 tabs.

  4. Activities of the Institute for Mechanical Engineering

    NASA Astrophysics Data System (ADS)

    The Institute of Mechanical Engineering (IME) is part of Canada's National Research Council. Its mission is to undertake, support, promote, and disseminate research and development in the mechanical engineering aspects of three vital sectors of the Canadian economy: transportation, resource industries, and manufacturing. The IME achieves its mission by performing research and development in its own facilities; by developing, providing, and transferring expertise and knowledge; by making its research facilities available to collaborators and clients; and by participating in international liaison and collaborative research activities. Six research programs are conducted in the IME: Advanced Manufacturing Technology; Coastal Zone Engineering; Cold Regions Engineering; Combustion and Fluids Engineering; Ground Transportation Technology; and Machinery and Engine Technology. The rationale and major research thrusts of each program are described, and specific achievements in 1991-92 are reviewed. Lists of technical reports and papers presented by IME personnel are also included.

  5. Optimizations of particle size and pulp density for solubilization of rock phosphate by a microbial consortium from activated sludge.

    PubMed

    Xiao, Chunqiao; Wu, Xiaoyan; Liu, Tingting; Xu, Guang; Chi, Ruan

    2016-12-29

    Microbial solubilization of rock phosphate is getting more and more attention recently. However, the microorganisms used in previous studies were mostly single or known species, and seldom studies focused on the mixed microorganisms or microbial consortia from natural environments. In this study, a microbial consortium taken from activated sludge was used to solubilize two different mid-low-grade rock phosphates. The results showed that the microbial consortium could effectively solubilize the rock phosphates in National Botanical Research Institute's phosphate growth medium and released soluble phosphorus in the broth. The biomass increased gradually, whereas the pH decreased sharply during the solubilizing process. The maximum phosphorus solubilization was recorded at particle size of 150 µm. Higher or lower than this optimal particle size, the phosphorus solubilization decreased. The phosphorus solubilization gradually decreased with a larger pulp density from 1 to 5%, and the optimal pulp density was 1%. The solubilization level of microbial consortium varied with different rock phosphates. The results revealed that the soluble phosphorus released from high-silicon ore was higher than which from high-magnesium ore. A strong positive correlation between biomass and phosphorus solubilization in the broth was observed from regression analysis results, and the phosphorus solubilization also had a significant negative correlation with pH in the broth.

  6. Talking Rocks.

    ERIC Educational Resources Information Center

    Rice, Dale; Corley, Brenda

    1987-01-01

    Discusses some of the ways that rocks can be used to enhance children's creativity and their interest in science. Suggests the creation of a dramatic production involving rocks. Includes basic information on sedimentary, igneous, and metamorphic rocks. (TW)

  7. Mechanical properties and processes of deformation in shallow sedimentary rocks from subduction zones: An experimental study

    NASA Astrophysics Data System (ADS)

    Gadenne, Leslie; Raimbourg, Hugues; Champallier, Rémi; Yamamoto, Yuzuru

    2014-12-01

    better constrain the mechanical behavior of sediments accreted to accretionary prism, we conducted triaxial mechanical tests on natural samples from the Miura-Boso paleo-accretionary prism (Japan) in drained conditions with confining pressures up to 200 MPa as well as postexperiments P-wave velocity (Vp) measurements. During experiments, deformation is principally noncoaxial and accommodated by two successive modes of deformation, both associated with strain-hardening and velocity-strengthening behavior: (1) compaction-assisted shearing, distributed in a several mm-wide shear zone and (2) faulting, localized within a few tens of μm-wide, dilatant fault zone. Deformation is also associated with (1) a decrease in Young's modulus all over the tests, (2) anomalously low Vp in the deformed samples compared to their porosity and (3) an increase in sensitivity of Vp to effective pressure. We interpret this evolution of the poroelastic properties of the material as reflecting the progressive breakage of intergrain cement and the formation of microcracks along with macroscopic deformation. When applied to natural conditions, these results suggest that the deformation style (localized versus distributed) of shallow (z < a few km) sediments is mainly controlled by the variations in stress/strain rate during the seismic cycle and is therefore independent of the porosity of sediments. Finally, we show that the effect of strain, through cement breakage and microcracks formation, may lower Vp for effective pressure up to 40 MPa. As a consequence, the low Vp anomalies observed in Nankai accretionary prisms by seismic imaging between 2 and 4 km depth could reflect sediment deformation rather than porosity anomalies.

  8. Deformation mechanisms of antigorite serpentinite at subduction zone conditions determined from experimentally and naturally deformed rocks

    NASA Astrophysics Data System (ADS)

    Auzende, Anne-Line; Escartin, Javier; Walte, Nicolas P.; Guillot, Stéphane; Hirth, Greg; Frost, Daniel J.

    2015-02-01

    We performed deformation-DIA experiments on antigorite serpentinite at pressures of 1-3.5 GPa and temperatures of between 400 and 650 °C, bracketing the stability of antigorite under subduction zone conditions. For each set of pressure-temperature (P-T) conditions, we conducted two runs at strain rates of 5 ×10-5 and 1 ×10-4 s-1. We complemented our study with a sample deformed in a Griggs-type apparatus at 1 GPa and 400 °C (Chernak and Hirth, 2010), and with natural samples from Cuba and the Alps deformed under blueschist/eclogitic conditions. Optical and transmission electron microscopies were used for microstructural characterization and determination of deformation mechanisms. Our observations on experimentally deformed antigorite prior to breakdown show that deformation is dominated by cataclastic flow with observable but minor contribution of plastic deformation (microkinking and (001) gliding mainly expressed by stacking disorder mainly). In contrast, in naturally deformed samples, plastic deformation structures are dominant (stacking disorder, kinking, pressure solution), with minor but also perceptible contribution of brittle deformation. When dehydration occurs in experiments, plasticity increases and is coupled to local embrittlement that we attribute to antigorite dehydration. In dehydrating samples collected in the Alps, embrittlement is also observed suggesting that dehydration may contribute to intermediate-depth seismicity. Our results thus show that semibrittle deformation operates within and above the stability field of antigorite. However, the plastic deformation recorded by naturally deformed samples was likely acquired at low strain rates. We also document that the corrugated structure of antigorite controls the strain accommodation mechanisms under subduction conditions, with preferred inter- and intra-grain cracking along (001) and gliding along both a and b. We also show that antigorite rheology in subduction zones is partly controlled

  9. Fault-related clay authigenesis along the Moab Fault: Implications for calculations of fault rock composition and mechanical and hydrologic fault zone properties

    USGS Publications Warehouse

    Solum, J.G.; Davatzes, N.C.; Lockner, D.A.

    2010-01-01

    The presence of clays in fault rocks influences both the mechanical and hydrologic properties of clay-bearing faults, and therefore it is critical to understand the origin of clays in fault rocks and their distributions is of great importance for defining fundamental properties of faults in the shallow crust. Field mapping shows that layers of clay gouge and shale smear are common along the Moab Fault, from exposures with throws ranging from 10 to ???1000 m. Elemental analyses of four locations along the Moab Fault show that fault rocks are enriched in clays at R191 and Bartlett Wash, but that this clay enrichment occurred at different times and was associated with different fluids. Fault rocks at Corral and Courthouse Canyons show little difference in elemental composition from adjacent protolith, suggesting that formation of fault rocks at those locations is governed by mechanical processes. Friction tests show that these authigenic clays result in fault zone weakening, and potentially influence the style of failure along the fault (seismogenic vs. aseismic) and potentially influence the amount of fluid loss associated with coseismic dilation. Scanning electron microscopy shows that authigenesis promotes that continuity of slip surfaces, thereby enhancing seal capacity. The occurrence of the authigenesis, and its influence on the sealing properties of faults, highlights the importance of determining the processes that control this phenomenon. ?? 2010 Elsevier Ltd.

  10. Mechanism of the Two-Phase Flow Model for Water and Gas Based on Adsorption and Desorption in Fractured Coal and Rock

    NASA Astrophysics Data System (ADS)

    Chen, Shikuo; Yang, Tianhong; Ranjith, P. G.; Wei, Chenhui

    2017-03-01

    Coalbed methane (CBM) is an important high-efficiency, clean-energy raw material with immense potential for application; however, its occurrence in low-permeability reservoirs limits its application. Hydraulic fracturing has been used in low-permeability CBM exploration and as a new technique for preventing gas hazards in coal mines. Fractures are the main pathways of fluid accumulation and migration, and they exert some control over the stability of rock mass. However, the differences in progression between the original fractures of the coal mass and the new discrete fractures caused by hydraulic fracturing remain unclear, and the unsaturated seepage flows require further study. Therefore, a cross-scale hydraulic fractured rock mass numerical model was developed by using the 3D fractured extrusion coupling variables reconstruction technique. This paper uses fracture surface parameters combined with the fractal dimension and multi-medium theory to provide a high-precision characterization and interpretation of the fracture mechanics. The mechanism of the permeability evolution of fractured coal and rock under stress-releasing mining combined with water injection was studied by considering gas adsorption and desorption as well as the coupling characteristic of seepage-stress in fractured rock masses. Aperture, contact area ratio, and stress in permeability and fracture development have a strong influence on the permeability and seepage path, which in turn control the effective radius by absolute water injection. All of these factors should be considered when studying the structural characteristics of rock masses.

  11. Molecular Mechanisms of DNA Replication Checkpoint Activation

    PubMed Central

    Recolin, Bénédicte; van der Laan, Siem; Tsanov, Nikolay; Maiorano, Domenico

    2014-01-01

    The major challenge of the cell cycle is to deliver an intact, and fully duplicated, genetic material to the daughter cells. To this end, progression of DNA synthesis is monitored by a feedback mechanism known as replication checkpoint that is untimely linked to DNA replication. This signaling pathway ensures coordination of DNA synthesis with cell cycle progression. Failure to activate this checkpoint in response to perturbation of DNA synthesis (replication stress) results in forced cell division leading to chromosome fragmentation, aneuploidy, and genomic instability. In this review, we will describe current knowledge of the molecular determinants of the DNA replication checkpoint in eukaryotic cells and discuss a model of activation of this signaling pathway crucial for maintenance of genomic stability. PMID:24705291

  12. Mechanism and active variety of allelochemicals

    USGS Publications Warehouse

    Peng, S.-L.; Wen, J.; Guo, Q.-F.

    2004-01-01

    This article summarizes allelochemicals' active variety, its potential causes and function mechanisms. Allelochemicals' activity varies with temperature, photoperiod, water and soils during natural processes, with its initial concentration, compound structure and mixed degree during functional processes, with plant accessions, tissues and maturity within-species, and with research techniques and operation processes. The prospective developmental aspects of allelopathy studies in the future are discussed. Future research should focus on: (1) to identify and purify allelochemicals more effectively, especially for agriculture, (2) the functions of allelopathy at the molecular structure level, (3) using allelopathy to explain plant species interactions, (4) allelopathy as a driving force of succession, and (5) the significance of allelopathy in the evolutionary processes.

  13. Using earthquake-triggered landslides as a hillslope-scale shear strength test: Insights into rock strength properties at geomorphically relevant spatial scales in high-relief, tectonically active settings

    NASA Astrophysics Data System (ADS)

    Gallen, Sean; Clark, Marin; Godt, Jonathan; Lowe, Katherine

    2016-04-01

    obtained using typical laboratory shear strength measurements on intact rock samples. Furthermore, the near-surface material strength is similar between the study areas despite differences in tectonic, climatic, and lithologic conditions. Variations in near-surface strength within each setting appear to be more strongly associated with factors contributing to the weakening rock through chemical or physical weathering, such as mean annual precipitation and distance to active faults (a proxy for rock shattering intensity), rather than intrinsic lithologic properties. We hypothesize that the shattering of rock through long-term permanent strain accumulation and by repeated earthquakes is an important mechanism that can explain low rock strength values among the different study sites and the spatial pattern of rock strength within each location. These findings emphasize the potential role of factors other than lithology in controlling the spatial distribution of near-surface rock strength in high-relief, tectonically active settings, which has important implications for understanding the evolution of landscapes, interpreting tectonic and climatic signals from topography, critical zone processes, and natural hazard assessment.

  14. Training and Research on Probabilistic Hydro-Thermo-Mechanical Modeling of Carbon Dioxide Geological Sequestration in Fractured Porous Rocks

    SciTech Connect

    Gutierrez, Marte

    2013-05-31

    Colorado School of Mines conducted research and training in the development and validation of an advanced CO{sub 2} GS (Geological Sequestration) probabilistic simulation and risk assessment model. CO{sub 2} GS simulation and risk assessment is used to develop advanced numerical simulation models of the subsurface to forecast CO2 behavior and transport; optimize site operational practices; ensure site safety; and refine site monitoring, verification, and accounting efforts. As simulation models are refined with new data, the uncertainty surrounding the identified risks decrease, thereby providing more accurate risk assessment. The models considered the full coupling of multiple physical processes (geomechanical and fluid flow) and describe the effects of stochastic hydro-mechanical (H-M) parameters on the modeling of CO{sub 2} flow and transport in fractured porous rocks. Graduate students were involved in the development and validation of the model that can be used to predict the fate, movement, and storage of CO{sub 2} in subsurface formations, and to evaluate the risk of potential leakage to the atmosphere and underground aquifers. The main major contributions from the project include the development of: 1) an improved procedure to rigorously couple the simulations of hydro-thermomechanical (H-M) processes involved in CO{sub 2} GS; 2) models for the hydro-mechanical behavior of fractured porous rocks with random fracture patterns; and 3) probabilistic methods to account for the effects of stochastic fluid flow and geomechanical properties on flow, transport, storage and leakage associated with CO{sub 2} GS. The research project provided the means to educate and train graduate students in the science and technology of CO{sub 2} GS, with a focus on geologic storage. Specifically, the training included the investigation of an advanced CO{sub 2} GS simulation and risk assessment model that can be used to predict the fate, movement, and storage of CO{sub 2} in

  15. Study on the deterioration mechanism of layered rock-salt electrodes using epitaxial thin films - Li(Ni, Co, Mn)O2 and their Zr-O surface modified electrodes

    NASA Astrophysics Data System (ADS)

    Abe, Machiko; Iba, Hideaki; Suzuki, Kota; Minamishima, Hiroaki; Hirayama, Masaaki; Tamura, Kazuhisa; Mizuki, Jun'ichiro; Saito, Tomohiro; Ikuhara, Yuichi; Kanno, Ryoji

    2017-03-01

    Deterioration mechanism of Li(Ni, Co, Mn)O2 and Zr-O surface modified electrodes has been elucidated using epitaxial thin films synthesized by pulsed laser deposition. The electrodes comprise a mixture of layered rock-salt and spinel phases. The deterioration mechanism is analyzed using cyclic voltammetry, in situ X-ray diffraction measurements, and in situ neutron reflectometry. The spinel phase in the electrodes has low electrochemical activity and is not involved in Li insertion/extraction. The amount of Li participating in the charge-discharge reactions in the layered rock-salt phase increases with cycling, inducing a phase change at the electrode surface, lowering the reversibility. In contrast, in the Zr-O surface modified electrode, the spinel phase does not increase on charging/discharging. Thus, the Zr-O modification stabilizes the surface of layered rock-salt structure, thereby improving the cycling characteristics. Also, after the Zr-O modification, the Li concentration in the liquid electrolyte near the electrode/electrolyte interface increases during charging/discharging. The Zr-O surface modification not only stabilizes the electrode surface but also causes changes on the electrolyte side. Using the mixed model electrodes, we elucidate the mechanism of electrode deterioration and the origin of the improvement in cycling characteristics occurring on surface modification.

  16. Microbial populations and activities in the rhizoplane of rock-weathering desert plants. I. Root colonization and weathering of igneous rocks.

    PubMed

    Puente, M E; Bashan, Y; Li, C Y; Lebsky, V K

    2004-09-01

    Dense layers of bacteria and fungi in the rhizoplane of three species of cactus (Pachycereus pringlei, Stenocereus thurberi, Opuntia cholla) and a wild fig tree (Ficus palmeri) growing in rocks devoid of soil were revealed by bright-field and fluorescence microscopy and field emission scanning electron microscopy. These desert plants are responsible for rock weathering in an ancient lava flow at La Purisima-San Isidro and in sedimentary rock in the Sierra de La Paz, both in Baja California Sur, Mexico. The dominant bacterial groups colonizing the rhizoplane were fluorescent pseudomonads and bacilli. Seven of these bacterial species were identified by the 16S rRNA molecular method. Unidentified fungal and actimomycete species were also present. Some of the root-colonizing microorganisms fixed in vitro N(2), produced volatile and non-volatile organic acids that subsequently reduced the pH of the rock medium in which the bacteria grew, and significantly dissolved insoluble phosphates, extrusive igneous rock, marble, and limestone. The bacteria were able to release significant amounts of useful minerals, such as P, K, Mg, Mn, Fe, Cu, and Zn from the rocks and were thermo-tolerant, halo-tolerant, and drought-tolerant. The microbial community survived in the rhizoplane of cacti during the annual 10-month dry season. This study indicates that rhizoplane bacteria on cacti roots in rock may be involved in chemical weathering in hot, subtropical deserts.

  17. 76 FR 28460 - Agency Information Collection Activities; Submission for OMB Review; Comment Request; Rock Burst...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-17

    ...; Rock Burst Control Plan--Pertains to Underground Metal and Nonmetal Mines ACTION: Notice. SUMMARY: The... information collection request (ICR) titled, ``Burst Control Plan--Pertains to Underground Metal and Nonmetal... INFORMATION: Regulations 30 CFR 57.3461 requires underground metal and nonmetal mine operators to develop...

  18. Mechanism of Highly Synchronized Bilateral Hippocampal Activity

    PubMed Central

    Wang, Y.; Toprani, S.; Tang, Y.; Vrabec, T.; Durand, D.M.

    2014-01-01

    In vivo studies of epileptiform discharges in the hippocampi of rodents have shown that bilateral seizure activity can sometimes be synchronized with very small delays (< 2 ms). This observed small time delay of epileptiform activity between the left and right CA3 regions is unexpected given the physiological propagation time across the hemispheres (> 6 ms). The goal of this study is to determine the mechanisms of this tight synchronization with in-vitro electrophysiology techniques and computer simulations. The hypothesis of a common source was first eliminated by using an in-vitro preparation containing both hippocampi with a functional ventral hippocampal commissure (VHC) and no other tissue. Next, the hypothesis that a noisy baseline could mask the underlying synchronous activity between the two hemispheres was ruled out by low noise in-vivo recordings and computer simulation of the noisy environment. Then we built a novel bilateral CA3 model to test the hypothesis that the phenomenon of very small left-to-right propagation delay of seizure activity is a product of epileptic cell network dynamics. We found that the commissural tract connectivity could decrease the delay between seizure events recorded from two sides while the activity propagated longitudinally along the CA3 layer thereby yielding delays much smaller than the propagation time between the two sides. The modeling results indicate that both recurrent and feedforward inhibition were required for shortening the bilateral propagation delay and depended critically on the length of the commissural fiber tract as well as the number of cells involved in seizure generation. These combined modeling/experimental studies indicate that it is possible to explain near perfect synchronization between the two hemispheres by taking into account the structure of the hippocampal network. PMID:24262205

  19. Thermal-chemical-mechanical feedback during fluid-rock interactions: Implications for chemical transport and scales of equilibria in the crust

    SciTech Connect

    Dutrow, Barbara

    2008-08-13

    Our research evaluates the hypothesis that feedback amongst thermal-chemical-mechanical processes operative in fluid-rock systems alters the fluid flow dynamics of the system which, in turn, affects chemical transport and temporal and spatial scales of equilibria, thus impacting the resultant mineral textural development of rocks. Our methods include computational experimentation and detailed analyses of fluid-infiltrated rocks from well-characterized terranes. This work focuses on metamorphic rocks and hydrothermal systems where minerals and their textures are utilized to evaluate pressure (P), temperature (T), and time (t) paths in the evolution of mountain belts and ore deposits, and to interpret tectonic events and the timing of these events. Our work on coupled processes also extends to other areas where subsurface flow and transport in porous media have consequences such as oil and gas movement, geothermal system development, transport of contaminants, nuclear waste disposal, and other systems rich in fluid-rock reactions. Fluid-rock systems are widespread in the geologic record. Correctly deciphering the products resulting from such systems is important to interpreting a number of geologic phenomena. These systems are characterized by complex interactions involving time-dependent, non-linear processes in heterogeneous materials. While many of these interactions have been studied in isolation, they are more appropriately analyzed in the context of a system with feedback. When one process impacts another process, time and space scales as well as the overall outcome of the interaction can be dramatically altered. Our goals to test this hypothesis are: to develop and incorporate algorithms into our 3D heat and mass transport code to allow the effects of feedback to be investigated numerically, to analyze fluid infiltrated rocks from a variety of terranes at differing P-T conditions, to identify subtle features of the infiltration of fluids and/or feedback, and

  20. Assessment of Hydro-Mechanical Behavior of a Granite Rock Mass for a Pilot Underground Crude Oil Storage Facility in China

    NASA Astrophysics Data System (ADS)

    Wang, Zhechao; Li, Shucai; Qiao, Liping

    2015-11-01

    The hydro-mechanical behavior of a pilot underground crude oil storage facility in a granite host rock in China was analyzed using the finite element method (FEM). Characterization of hydro-mechanical behavior of the rock mass was performed using laboratory test, field monitoring, back analysis of field measurements and permeability tests. FEM numerical analyses were used to assess the hydro-mechanical behavior of the granite to study several design and construction issues. The containment properties of the storage facility were investigated without and with the water curtain system. Results showed that the stored oil would leak into rock mass if a water curtain system is not provided, whereas the containment property of the facility will be maintained when a water curtain system is in place. On the influence of cavern excavation sequence, it was indicated that the excavation of the caverns from left to right is a better choice than right to left for the containment property of the facility. On the influence of permeable condition, it was found that the extent of plastic zones, horizontal convergence and crown settlement under permeable condition are lower than those under impermeable condition due to the different stress paths in the rock mass experienced during excavation.

  1. Mechanism of base activation of persulfate.

    PubMed

    Furman, Olha S; Teel, Amy L; Watts, Richard J

    2010-08-15

    Base is the most commonly used activator of persulfate for the treatment of contaminated groundwater by in situ chemical oxidation (ISCO). A mechanism for the base activation of persulfate is proposed involving the base-catalyzed hydrolysis of persulfate to hydroperoxide anion and sulfate followed by the reduction of another persulfate molecule by hydroperoxide. Reduction by hydroperoxide decomposes persulfate into sulfate radical and sulfate anion, and hydroperoxide is oxidized to superoxide. The base-catalyzed hydrolysis of persulfate was supported by kinetic analyses of persulfate decomposition at various base:persulfate molar ratios and an increased rate of persulfate decomposition in D(2)O vs H(2)O. Stoichiometric analyses confirmed that hydroperoxide reacts with persulfate in a 1:1 molar ratio. Addition of hydroperoxide to basic persulfate systems resulted in rapid decomposition of the hydroperoxide and persulfate and decomposition of the superoxide probe hexachloroethane. The presence of superoxide was confirmed with scavenging by Cu(II). Electron spin resonance spectroscopy confirmed the generation of sulfate radical, hydroxyl radical, and superoxide. The results of this research are consistent with the widespread reactivity reported for base-activated persulfate when it is used for ISCO.

  2. Inhibition of RHO-ROCK signaling enhances ICM and suppresses TE characteristics through activation of Hippo signaling in the mouse blastocyst

    PubMed Central

    Kono, Kanako; Tamashiro, Dana Ann A.; Alarcon, Vernadeth B.

    2014-01-01

    Specification of the trophectoderm (TE) and inner cell mass (ICM) lineages in the mouse blastocyst correlates with cell position, as TE derives from outer cells whereas ICM from inner cells. Differences in position are reflected by cell polarization and Hippo signaling. Only in outer cells, the apical-basal cell polarity is established, and Hippo signaling is inhibited in such a manner that LATS1 and 2 (LATS1/2) kinases are prevented from phosphorylating YAP, a key transcriptional co-activator of the TE-specifying gene Cdx2. However, the molecular mechanisms that regulate these events are not fully understood. Here, we showed that inhibition of RHO-ROCK signaling enhances ICM and suppresses TE characteristics through activation of Hippo signaling and disruption of apical-basal polarity. Embryos treated with ROCK inhibitor Y-27632 exhibited elevated expression of ICM marker NANOG and reduced expression of CDX2 at the blastocyst stage. Y-27632-treated embryos failed to accumulate YAP in the nucleus, although it was rescued by concomitant inhibition of LATS1/2. Segregation between apical and basal polarity regulators, namely PARD6B, PRKCZ, SCRIB, and LLGL1, was dampened by Y-27632 treatment, whereas some of the polarization events at the late 8-cell stage such as compaction and apical localization of p-ERM and tyrosinated tubulin occurred normally. Similar abnormalities of Hippo signaling and apical-basal polarization were also observed in embryos that were treated with RHO GTPases inhibitor. These results suggest that RHO-ROCK signaling plays an essential role in regulating Hippo signaling and cell polarization to enable proper specification of the ICM and TE lineages. PMID:24997360

  3. L-F001, a novel multifunctional ROCK inhibitor, suppresses neuroinflammation in vitro and in vivo: Involvement of NF-κB inhibition and Nrf2 pathway activation.

    PubMed

    Chen, Jingkao; Yin, Wei; Tu, Yalin; Wang, Shengnan; Yang, Xiaohong; Chen, Qiuhe; Zhang, Xiao; Han, Yifan; Pi, Rongbiao

    2017-03-16

    Microglia and astrocytes are largely responsible for inflammatory injury in the brain of Alzheimer's disease (AD). Increasing evidence has indicated that Rho kinase (ROCK) plays an important role in the regulation of neuroinflammation. Previously, we synthesized a new chemical entity L-F001 and proved its potential inhibitory effects on ROCK and oxidative stress. Here, we investigated the anti-inflammatory effects and the molecular mechanisms of L-F001 in vitro and in vivo. L-F001 remarkably suppressed lipopolysaccharides (LPS)-elevated expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) as well as LPS-induced production of nitric oxide (NO), reactive oxygen species, interleukin-6 (IL-6) and tumor necreactive oxygen speciesis factor-α (TNF-α) in microglial BV-2 cells and in cultured astrocytes. Furthermore, L-F001 inhibited the degradation of IκB and nuclear translocation of nuclear factor kappa B (NF-κB) p65 subunit. Moreover, L-F001 induced the upregulation of heme-oxygenase-1 (HO-1) and glutamate cysteine ligase modifier subunit (GCLM) expression, two downstream effectors of nuclear factor (erythroid-derived 2)-like 2 (Nrf2). It was interesting that L-F001 also activated phosphatidylinositol 3-kinase (PI3K) pathway and induced M1 (CD16/32, M1 marker)/ M2 (CD206, M2 maker) transition in BV-2 cells which was significantly blocked by a PI3K inhibitor, wortmannin. Finally, L-F001 markedly attenuated the level of pro-inflammatory mediators in a murine model of systemic acute brain inflammation induced by LPS. Taken together, these results indicate that the novel multifunctional ROCK inhibitor L-F001 suppresses neuroinflammation in vitro and in vivo via NF-κB inhibition and Nrf2 activation, suggesting that L-F001 may be a promising drug candidate for treating neuroinflammation-associated CNS diseases, including AD.

  4. Determination of trace halogens in rock samples by radiochemical neutron activation analysis coupled with the k0-standardization method.

    PubMed

    Ozaki, Hiromasa; Ebihara, Mitsuru

    2007-02-05

    Radiochemical neutron activation analysis coupled with the k0-standardization method (k0-RNAA method) was applied to silicate rock samples for the simultaneous determination of trace halogens (Cl, Br and I). Analytical results obtained by the k0-RNAA method for geological standard rocks and meteorite samples agreed with those determined by the conventional comparison method conducted in the same set of experiments, suggesting that the k0-RNAA method is as reliable as the conventional method. Our data for these samples are in good agreement with their literature values except for rare cases. Detection limits calculated under the present experimental condition are sufficiently low for Cl and Br but not for I for typical geologic and meteoritic samples. The k0-RNAA method coupled with longer neutron-irradiation is expected to yield satisfactorily low detection limits for halogens including I in these samples.

  5. Geochronology of igneous rocks and formation of the Late Paleozoic south Mongolian active margin of the Siberian continent

    NASA Astrophysics Data System (ADS)

    Yarmolyuk, V. V.; Kovalenko, V. I.; Sal'Nikova, E. B.; Kovach, V. P.; Kozlovsky, A. M.; Kotov, A. B.; Lebedev, V. I.

    2008-04-01

    The succession of magmatic events associated with development of the Early Carboniferous-Early Permian marginal continental magmatic belt of southern Mongolia is studied. In the belt structure there are defined the successive rock complexes: the older one represented by differentiated basalt-andesite-rhyodacite series and younger bimodal complex of basalt-comendite-trachyrhyolite composition. The granodiorite-plagiogranite and banatite (diorite-monzonite-granodiorite) plutonic massifs are associated with the former, while peralkaline granite massifs are characteristic of the latter. First systematic geochronological study of igneous rock associations is performed to establish time succession and structural position of both complexes. Geochronological results and geological relations between rocks of the bimodal and differentiated complexes showed first that rocks of the differentiated complex originated 350 to 330 Ma ago at the initial stage of development of the marginal continental belt. This is evident from geochronological dates obtained for the Adzh-Bogd and Edrengiyn-Nuruu massifs and for volcanic associations of the complex. The dates are consistent with paleontological data. The bimodal association was formed later, 320 to 290 Ma ago. The time span separating formation of two igneous complexes ranges from several to 20 30 m.y. in different areas of the marginal belt. The bimodal magmatism was interrelated with rifting responsible for development of the Gobi-Tien Shan rift zone in the belt axial part and the Main Mongolian lineament along the belt northern boundary. Loci of bimodal rift magmatism likely migrated with time: the respective magmatic activity first initiated on the west of the rift system and then advanced gradually eastward with development of rift structures. Normal granitoids untypical but occurring nevertheless among the products of rift magmatism in addition to peralkaline massifs are assumed to have been formed, when the basic magmatism

  6. Displaced rocks, strong motion, and the mechanics of shallow faulting associated with the 1999 Hector Mine, California, earthquake

    USGS Publications Warehouse

    Michael, A.J.; Ross, S.L.; Stenner, Heidi D.

    2002-01-01

    The paucity of strong-motion stations near the 1999 Hector Mine earthquake makes it impossible to make instrumental studies of key questions about near-fault strong-motion patterns associated with this event. However, observations of displaced rocks allow a qualitative investigation of these problems. By observing the slope of the desert surface and the frictional coefficient between these rocks and the desert surface, we estimate the minimum horizontal acceleration needed to displace the rocks. Combining this information with observations of how many rocks were displaced in different areas near the fault, we infer the level of shaking. Given current empirical shaking attenuation relationships, the number of rocks that moved is slightly lower than expected; this implies that slightly lower than expected shaking occurred during the Hector Mine earthquake. Perhaps more importantly, stretches of the fault with 4 m of total displacement at the surface displaced few nearby rocks on 15?? slopes, suggesting that the horizontal accelerations were below 0.2g within meters of the fault scarp. This low level of shaking suggests that the shallow parts of this rupture did not produce strong accelerations. Finally, we did not observe an increased incidence of displaced rocks along the fault zone itself. This suggests that, despite observations of fault-zone-trapped waves generated by aftershocks of the Hector Mine earthquake, such waves were not an important factor in controlling peak ground acceleration during the mainshock.

  7. Acid-fog deposition at Kilauea volcano: A possible mechanism for the formation of siliceous-sulfate rock coatings on Mars

    NASA Astrophysics Data System (ADS)

    Schiffman, Peter; Zierenberg, Robert; Marks, Naomi; Bishop, Janice L.; Darby Dyar, M.

    2006-11-01

    On the summit of Kilauea volcano, sulfur dioxide, which is continuously emitted from Halemaumau crater and rapidly sequestered into sulfuric-acid rich aerosol entrained in the prevailing trade winds, is subsequently precipitated as acid fog immediately downwind from Kilauea caldera in the Kau Desert. The characteristic pH of surface tephra deposits is <4.0 in Sand Wash, a region of nearly continuous, acidic aerosol fallout immediately southwest of the caldera. Vertical exposures of unconsolidated tephras of the Keanakakoi Ash found within fissures and small, dry gullies are coated with thin rock coatings of amorphous silica and jarosite. These rock coatings are formed via an evaporative mechanism whereby acidic pore fluids, circulating in the upper few meters within the highly porous tephra, are wicked toward the walls of the gullies. Geochemical modeling of the rock coating formation process implies that the sulfate formation via evaporation occurs subsequent to minimal interaction of acidic pore fluids with the basaltic tephra. This also suggests that the cycle from acid-fog fallout to precipitation of the siliceous-sulfate rock coatings must occur quite rapidly. Acid-fog deposition of sulfate and silica at Kilauea may provide one mechanism for the origin of jarosite-bearing outcrops on Mars.

  8. Prolonged magmatic activity on Mars inferred from the detection of felsic rocks

    USGS Publications Warehouse

    Wray, James J.; Hansen, Sarah T.; Dufek, Josef; Swayze, Scott L.; Murchie, Scott L.; Seelos, Frank P.; Skok, John R.; Irwin, Rossman P.; Ghiorso, Mark S.

    2013-01-01

    Rocks dominated by the silicate minerals quartz and feldspar are abundant in Earth’s upper continental crust. Yet felsic rocks have not been widely identified on Mars, a planet that seems to lack plate tectonics and the associated magmatic processes that can produce evolved siliceous melts on Earth. If Mars once had a feldspar-rich crust that crystallized from an early magma ocean such as that on the Moon, erosion, sedimentation and volcanism have erased any clear surface evidence for widespread felsic materials. Here we report near-infrared spectral evidence from the Compact Reconnaissance Imaging Spectrometer for Mars onboard the Mars Reconnaissance Orbiter for felsic rocks in three geographically disparate locations on Mars. Spectral characteristics resemble those of feldspar-rich lunar anorthosites, but are accompanied by secondary alteration products (clay minerals). Thermodynamic phase equilibrium calculations demonstrate that fractional crystallization of magma compositionally similar to volcanic flows near one of the detection sites can yield residual melts with compositions consistent with our observations. In addition to an origin by significant magma evolution, the presence of felsic materials could also be explained by feldspar enrichment by fluvial weathering processes. Our finding of felsic materials in several locations on Mars suggests that similar observations by the Curiosity rover in Gale crater may be more widely applicable across the planet.

  9. The transition from hydrostatic to greater than hydrostatic fluid pressure in presently active continental hydrothermal systems in crystalline rock

    SciTech Connect

    Fournier, R.O. )

    1991-05-01

    Fluid flow at hydrostatic pressure (P{sub h}) is relatively common through fractures in silicic and in mafic crystalline rocks where temperatures are less than about 350-370C. In contrast, pore-fluid pressure (P{sub f}) > P{sub h} has been encountered at the bottom of 3 geothermal exploration wells that attained temperatures >370C (at Larderello, Italy, at Nesjavellir, Iceland, and at The Geysers, California). Chemical sealing by deposition of minerals in veins appears to have allowed the development of the high P{sub f} encountered in the above wells. The upper limit for the magnitude of P{sub f} that can be attained is controlled by either the onset of shear fracturing (where differential stress is relatively high) that reopens clogged veins, or the hydraulic opening of new or old fractures (at relatively low values of differential stress). The brittle-plastic transition for silicic rocks can occur at temperatures as high as 370-400C in tectonically active regions. In regions where high-temperature geothermal systems develop and persist, it appears that either strain rates commonly are in the range 10{sup {minus}12} to 10{sup {minus}13}, or that silicic rocks in the shallow crust generally behave rheologically more like wet quartz diorite than wet Westerly granite.

  10. Basal sliding in ice streams as seen through the lens of rock mechanics: an experimental study of ice-on-rock friction

    NASA Astrophysics Data System (ADS)

    McCarthy, C.; Savage, H. M.; Nettles, M.

    2015-12-01

    An understanding of the controls on ice stream flow is critical for improved predictions of sea level rise and glacier response to climate change. Basal sliding is one aspect of ice stream motion that has received relatively little attention. Although it is difficult and costly to measure direct motion at the base of a glacier, laboratory experiments can be used to recreate the physics of ice sliding over bedrock. Using a new, custom-built, servo-controlled biaxial loading apparatus, we are measuring the friction of polycrystalline ice samples sliding on rock in a double direct shear configuration. Temperature is maintained with an insulated cryostat that uses liquid cooling blocks and a programmable circulating bath. We will share results from a series of velocity stepping and slide-hold-slide experiments designed to measure key properties of rate- and state-dependent frictional behavior. The experimental conditions for the study are as follows: temperatures ranging from -20ºC to the pressure melting point; normal stresses of 20 - 200 kPa, velocities from 10-6 to 10-3 m s-1; and ambient pressure. Ice sample microstructure (grain size, porosity, purity) and surface roughness are carefully controlled and characterized before and after experiments to identify microstructural sources for macroscopic behavior. Careful monitoring of temperature at the sliding interface will elucidate the role of frictional heating/melting on both sliding behavior and microstructure evolution. By measuring rate-state friction parameters, we will explore the transition between stable sliding and stick-slip motion of glaciers and ice streams. These results can be directly compared to the differing sliding styles observed for ice streams feeding into the Ross Ice Shelf to infer characteristics of the bed interface and the bulk glacier. The values obtained from this study will provide better constraints for next generation modeling of glacier and ice-stream response to external forcing.

  11. Mechanism of ascaridole activation in Leishmania.

    PubMed

    Geroldinger, Gerald; Tonner, Matthias; Hettegger, Hubert; Bacher, Markus; Monzote, Lianet; Walter, Martin; Staniek, Katrin; Rosenau, Thomas; Gille, Lars

    2017-03-02

    values for Art. In a heme association assay Asc demonstrated a lower binding affinity to heme than Art. ICP-OES measurements revealed that in LtP the total iron concentrations were twice as high as values in J774 macrophages. Since low molecular iron was important in Asc activation we studied the influence of Asc on the labile iron pool (LIP) in LtP. Low temperature EPR experiments demonstrated that Asc shifts the redox balance of iron in the LIP to its oxidized state. These data demonstrate that univalent cleavage of Asc/Art in LtP is an essential part of their pharmacological mechanism. The structure of the EP determines whether activation by low molecular iron or heme is favored and the availability of these intracellular activators modulates their cytotoxicity. These findings may be helpful for synthesis of new Asc derivatives and understanding the action of EP in other cell types.

  12. Dynamics of Fragmentation: Developing a non-Equilibrium Mechanism for Impact-loading tests on Rock Materials

    NASA Astrophysics Data System (ADS)

    Ghaffari, H.; Griffith, W. A.; Barber, T. J.

    2015-12-01

    Formation of fragments as the result of dynamic processes associated with impulsive loads has been the subject of numerous studies ranging from shaped-charge jet break up and rock blasting to bolide impacts, and, more recently, earthquake rupture. The dynamic strength of solids is varies as a strong function of loading rate, and, in completely failed solids, the characteristic size of fragments is related to the loading dynamics. In this study, we present some novel results using fragmentation of an "order" parameter in an isotropic body, while we use a non-equilibrium thermodynamic formulation to infer characteristics of the fragments. The order parameter is related to general rigidity of the system and is investigated in 3D space including amplitude and phase modes. To this end, we use the idea of the formation of topological defects in the course of rapid pressure changes and show that a power-law scaling describes transient strength versus inverse of the stress-ramp time. Furthermore, we illustrate that the coefficient of this power-law is deeply connected to relaxation (healing) time of the body. In addition, we show that dynamic polarization patterns of the dynamic cracks are analogous to the transition from ferrimagnets to paramagnets, providing insight to the dynamics of microscopic-scale catastrophic failure. This connection helps us to use the Kibble-Zurek mechanism (KZM) to infer the size of fragments from loading rate when considering a linear loading ramp. The idea behind the KZM is to compare the relaxation time (or healing time of the system in equilibrium) with the timescale of change of the control parameter (ɛ). In addition, we discuss a case where inherent defects are present prior to the impulse load and discuss the effect of impurities on the scaling coefficients. To support our approach, we use the results of fast-loading experiments on Westerly Granite supported by recording multiple acoustic emissions.

  13. Disclinations and grain boundary migration: evidence for a new deformation mechanism in olivine-rich rocks (Invited)

    NASA Astrophysics Data System (ADS)

    Cordier, P.; Demouchy, S. A.; Beausir, B.; Taupin, V.; Fressengeas, C.

    2013-12-01

    The rheology of olivine-rich rocks remains poorly understood. In particular, the ability of orthorhombic olivine to bear large strains represents an apparent violation of the von Mises criterion due to a lack of slip systems. In this study we show that a more general description of the deformation process including the motion of rotational defects referred to as disclinations can solve the olivine deformation paradox. Disclinations were proposed together with dislocations by Volterra (1907) to account for elastic distorsions (distorzione) in solids. They have recently been experimentally evidenced from orientation maps in several polycrystalline metallic alloys (Beausir & Fressengeas, 2013). Using high-resolution EBSD orientation maps we show that disclinations decorate grain boundaries in olivine samples deformed experimentally and in nature. We present a disclination-based model of a high-angle tilt boundary in olivine, which demonstrates that an applied shear induces grain boundary migration through disclination motion. This new approach allows further understanding of grain boundary-mediated plasticity in polycrystalline aggregates. By providing the missing mechanism for describing plastic flow in olivine, the present work allows multiscale modeling of the rheology of the upper mantle, from the atomic scale to the scale of the flow. Beausir, B. & Fressengeas, C., Disclination densities from EBSD orientation mapping. International Journal of Solids and Structures 50 (1), 137-146 (2013). Volterra, V., Sur l'équilibre des corps élastiques multiplement connexes. Annales scientifiques de l'École Normale Supérieure 24, 401-517 (1907). Acknowledgement for support: ERC grant RheoMan, Marie Curie fellowship PoEM and ANR NanoMec.

  14. Thermal, Mechanical and Thermo-Mechanical Assessment of the Rock Mass Surrounding SKB's Prototype Repository at Äspö HRL

    NASA Astrophysics Data System (ADS)

    Lönnqvist, Margareta; Hökmark, Harald

    2016-04-01

    The Prototype Repository (PR) was a field test of six, electrically heated, full-scale waste containers resembling the key component of a KBS-3 nuclear waste repository. The design and heat load was similar to the proposed repository at Forsmark, Sweden. In this paper, the thermal, mechanical and thermo-mechanical response of the PR host rock to excavation and to the subsequent heating is assessed. The assessment is carried out using three-dimensional models (numerical and analytical) in combination with monitoring data and visual observations from the excavations. Certain measurements and observations agree well with results from the models. These include temperature measurements during the heating phase. Additional measurements include patterns of low-magnitude acoustic emission events around the deposition holes tracked during the excavation. The spatial distribution of these events coincide with regions of modelled high compressive stresses. Models with a simple fracture network, consisting of planar disks with laboratory-scale properties, appear to give upper bound estimates of the stress disturbances caused by a real fracture network. The magnitude of the modelled stresses around the deposition hole is typically below the spalling strength. The lack of any significant or systematic occurrence of spalling in the deposition hole walls supports the modelling results. Several instruments installed at different positions to monitor stress change, strain and deformation malfunctioned during the nearly 8-year-long monitoring period. Despite this, there is ample evidence to support the overall conclusion that the modelling results and observations are in sufficient agreement to strengthen the confidence in the modelling approach.

  15. Influence of mechanical activation of steel powder on its properties

    NASA Astrophysics Data System (ADS)

    Vaulina, O. Yu; Darenskaia, E. A.; Myachin, Y. V.; Vasilyeva, I. E.; Kulkov, S. N.

    2017-02-01

    It has been studied properties of stainless steel based powders after mechanical activation using planetary ball milling technique. It have been shown that after one minute mechanical activation porosity of sintered steel is less than 5%, which is less than the porosity of the sintered steel powder without mechanical activation. The sample without activation has austenite state, which changes after activation toaustenite and ferrite mixtures. X-ray analysis confirmed that the mechanical activation leads to a change in the phase state of the samples: the samples without activation of the FCC structure (γ-Fe), after activation - FCC (γ-Fe) and BCC (α-Fe). The hardness increases at increasing activation time from 800 MPa for the sample without mechanical activation to 1250 MPa for the sample with the activation time of 10 minutes.

  16. The RhoE/ROCK/ARHGAP25 signaling pathway controls cell invasion by inhibition of Rac activity

    PubMed Central

    Thuault, Sylvie; Comunale, Franck; Hasna, Jessy; Fortier, Mathieu; Planchon, Damien; Elarouci, Nabila; De Reynies, Aurélien; Bodin, Stéphane; Blangy, Anne; Gauthier-Rouvière, Cécile

    2016-01-01

    Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma of skeletal muscle origin in children and adolescents. Among RMS subtypes, alveolar rhabdomyosarcoma (ARMS), which is characterized by the presence of the PAX3-FOXO1A or PAX7-FOXO1A chimeric oncogenic transcription factor, is associated with poor prognosis and a strong risk of metastasis compared with the embryonal subtype (ERMS). To identify molecular pathways involved in ARMS aggressiveness, we first characterized the migratory behavior of cell lines derived from ARMS and ERMS biopsies using a three-dimensional spheroid cell invasion assay. ARMS cells were more invasive than ERMS cells and adopted an ellipsoidal morphology to efficiently invade the extracellular matrix. Moreover, the invasive potential of ARMS cells depended on ROCK activity, which is regulated by the GTPase RhoE. Specifically, RhoE expression was low in ARMS biopsies, and its overexpression in ARMS cells reduced their invasion potential. Conversely, ARHGAP25, a GTPase-activating protein for Rac, was up-regulated in ARMS biopsies. Moreover, we found that ARHGAP25 inhibits Rac activity downstream of ROCKII and is required for ARMS cell invasion. Our results indicate that the RhoE/ROCK/ARHGAP25 signaling pathway promotes ARMS invasive potential and identify these proteins as potential therapeutic targets for ARMS treatment. PMID:27413008

  17. Geochemical and geochronological constraints on the origin and evolution of rocks in the active Woodlark Rift of Papua New Guinea

    NASA Astrophysics Data System (ADS)

    Zirakparvar, Nasser Alexander

    Tectonically active regions provide important natural laboratories to glean information that is applicable to developing a better understanding of the geologic record. One such area of the World is Papua New Guinea, much of which is situated in an active and transient plate boundary zone. The focus of this PhD research is to develop a better understanding of rocks in the active Woodlark Rift, situated in Papua New Guinea's southernmost reaches. In this region, rifting and lithospheric rupture is occurring within a former subduction complex where there is a history of continental subduction and (U)HP metamorphism. The lithostratigraphic units exposed in the Woodlark Rift provide an opportunity to better understand the records of plate boundary processes at many scales from micron-sized domains within individual minerals to regional geological relationships. This thesis is composed of three chapters that are independent of one another but are all related to the overall goal of developing a better understanding of the record of plate boundary processes in the rocks currently exposed in the Woodlark Rift. The first chapter, published in its entirety in Earth and Planetary Science Letters (2011 v. 309, p. 56 - 66), is entitled 'Lu-Hf garnet geochronology applied to plate boundary zones: Insights from the (U)HP terrane exhumed within the Woodlark Rift'. This chapter focuses on the use of the Lu-Hf isotopic system to date garnets in the Woodlark Rift. Major findings of this study are that some of the rocks in the Woodlark Rift preserve a Lu-Hf garnet isotopic record of initial metamorphism and continental subduction occurring in the Late Mesozoic, whereas others only preserve a record of tectonic processes related to lithospheric rupture during the initiation of rifting in the Late Cenozoic. The second chapter is entitled 'Geochemical and geochronological constraints on the origin of rocks in the active Woodlark Rift of Papua New Guinea: Recognizing the dispersed

  18. Active recovery of the finger flexors enhances intermittent handgrip performance in rock climbers.

    PubMed

    Baláš, Jiří; Michailov, Michail; Giles, David; Kodejška, Jan; Panáčková, Michaela; Fryer, Simon

    2016-10-01

    This study aimed to (1) evaluate the effect of hand shaking during recovery phases of intermittent testing on the time-force characteristics of performance and muscle oxygenation, and (2) assess inter-individual variability in the time to achieve the target force during intermittent testing in rock climbers. Twenty-two participants undertook three finger flexor endurance tests at 60% of their maximal voluntary contraction until failure. Performances of a sustained contraction and two intermittent contractions, each with different recovery strategies, were analysed by time-force parameters and near-infrared spectroscopy. Recovery with shaking of the forearm beside the body led to a significantly greater intermittent test time (↑ 22%, P < .05), force-time integral (↑ 28%, P < .05) and faster muscle re-oxygenation (↑ 32%, P < .05), when compared to the hand over hold condition. Further, the ratio of intermittent to continuous test time distinguished specific aerobic muscular adaptations among sport climbers (2.02), boulderers (1.74) and lower grade climbers (1.25). Lower grade climbers and boulderers produced shorter duration contractions due to the slower development of target force during the intermittent test, indicating worse kinaesthetic differentiation. Both the type of recovery and climbing discipline determined muscle re-oxygenation and intermittent performance in rock climbers.

  19. Rock Cycle Roulette.

    ERIC Educational Resources Information Center

    Schmidt, Stan M.; Palmer, Courtney

    2000-01-01

    Introduces an activity on the rock cycle. Sets 11 stages representing the transitions of an earth material in the rock cycle. Builds six-sided die for each station, and students move to the stations depending on the rolling side of the die. Evaluates students by discussing several questions in the classroom. Provides instructional information for…

  20. Rock Art

    ERIC Educational Resources Information Center

    Henn, Cynthia A.

    2004-01-01

    There are many interpretations for the symbols that are seen in rock art, but no decoding key has ever been discovered. This article describes one classroom's experiences with a lesson on rock art--making their rock art and developing their own personal symbols. This lesson allowed for creativity, while giving an opportunity for integration…

  1. Collecting Rocks.

    ERIC Educational Resources Information Center

    Barker, Rachel M.

    One of a series of general interest publications on science topics, the booklet provides those interested in rock collecting with a nontechnical introduction to the subject. Following a section examining the nature and formation of igneous, sedimentary, and metamorphic rocks, the booklet gives suggestions for starting a rock collection and using…

  2. Science Rocks!

    ERIC Educational Resources Information Center

    Prestwich, Dorothy; Sumrall, Joseph; Chessin, Debby A.

    2010-01-01

    It all began one Monday morning. Raymond could not wait to come to large group. In his hand, he held a chunk of white granite he had found. "Look at my beautiful rock!" he cried. The rock was passed around and examined by each student. "I wonder how rocks are made?" wondered one student. "Where do they come from?"…

  3. Dynamic Assessment of Fibroblast Mechanical Activity during Rac-induced Cell Spreading in 3-D Culture

    PubMed Central

    Petroll, W. Matthew; Ma, Lisha; Kim, Areum; Ly, Linda; Vishwanath, Mridula

    2009-01-01

    The goal of this study was to determine the morphological and sub-cellular mechanical effects of Rac activation on fibroblasts within 3-D collagen matrices. Corneal fibroblasts were plated at low density inside 100 μm thick fibrillar collagen matrices and cultured for 1 to 2 days in serum-free media. Time-lapse imaging was then performed using Nomarski DIC. After an acclimation period, perfusion was switched to media containing PDGF. In some experiments, Y-27632 or blebbistatin were used to inhibit Rho-kinase (ROCK) or myosin II, respectively. PDGF activated Rac and induced cell spreading, which resulted in an increase in cell length, cell area, and the number of pseudopodial processes. Tractional forces were generated by extending pseudopodia, as indicated by centripetal displacement and realignment of collagen fibrils. Interestingly, the pattern of pseudopodial extension and local collagen fibril realignment was highly dependent upon the initial orientation of fibrils at the leading edge. Following ROCK or myosin II inhibition, significant ECM relaxation was observed, but small displacements of collagen fibrils continued to be detected at the tips of pseudopodia. Taken together, the data suggests that during Rac-induced cell spreading within 3-D matrices, there is a shift in the distribution of forces from the center to the periphery of corneal fibroblasts. ROCK mediates the generation of large myosin II-based tractional forces during cell spreading within 3-D collagen matrices, however residual forces can be generated at the tips of extending pseudopodia that are both ROCK and myosin II-independent. PMID:18452153

  4. Platelet Activation: The Mechanisms and Potential Biomarkers

    PubMed Central

    Yun, Seong-Hoon; Sim, Eun-Hye; Goh, Ri-Young; Park, Joo-In

    2016-01-01

    Beyond hemostasis and thrombosis, an increasing number of studies indicate that platelets play an integral role in intercellular communication, mediating inflammatory and immunomodulatory activities. Our knowledge about how platelets modulate inflammatory and immunity has greatly improved in recent years. In this review, we discuss recent advances in the pathways of platelet activation and potential application of platelet activation biomarkers to diagnosis and prediction of disease states. PMID:27403440

  5. 'Escher' Rock

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site] Chemical Changes in 'Endurance' Rocks

    [figure removed for brevity, see original site] Figure 1

    This false-color image taken by NASA's Mars Exploration Rover Opportunity shows a rock dubbed 'Escher' on the southwestern slopes of 'Endurance Crater.' Scientists believe the rock's fractures, which divide the surface into polygons, may have been formed by one of several processes. They may have been caused by the impact that created Endurance Crater, or they might have arisen when water leftover from the rock's formation dried up. A third possibility is that much later, after the rock was formed, and after the crater was created, the rock became wet once again, then dried up and developed cracks. Opportunity has spent the last 14 sols investigating Escher, specifically the target dubbed 'Kirchner,' and other similar rocks with its scientific instruments. This image was taken on sol 208 (Aug. 24, 2004) by the rover's panoramic camera, using the 750-, 530- and 430-nanometer filters.

    The graph above shows that rocks located deeper into 'Endurance Crater' are chemically altered to a greater degree than rocks located higher up. This chemical alteration is believed to result from exposure to water.

    Specifically, the graph compares ratios of chemicals between the deep rock dubbed 'Escher,' and the more shallow rock called 'Virginia,' before (red and blue lines) and after (green line) the Mars Exploration Rover Opportunity drilled into the rocks. As the red and blue lines indicate, Escher's levels of chlorine relative to Virginia's went up, and sulfur down, before the rover dug a hole into the rocks. This implies that the surface of Escher has been chemically altered to a greater extent than the surface of Virginia. Scientists are still investigating the role water played in influencing this trend.

    These data were taken by the rover's alpha particle X-ray spectrometer.

  6. Indentation as an extrusion mechanism of lower crustal rocks: Insight from analogue and numerical modelling, application to the Eastern Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Duretz, T.; Kaus, B. J. P.; Schulmann, K.; Gapais, D.; Kermarrec, J.-J.

    2011-05-01

    Recent petrological, structural and geochronological studies of the eastern margin of the Bohemian Massif (Czech Republic) suggest a conceptual geodynamical model to explain exhumation of lower crustal (20 kbar, 800 °C) felsic rocks. The model involves indentation of a weak orogenic lower crust by an adjacent rigid mantle lithosphere, resulting in crustal-scale buckling of the weak orogenic lower/middle crust interface followed by extrusion of a ductile nappe over the rigid promontory. The hypothesis has been investigated using both analogue and numerical models. Analogue experiments using a three layer sand-silicone setup were carried out in Rennes laboratory (France). Results show that the most important features of the conceptual model can be reproduced: extrusion of lowermost silicone over the indenter and flow of horizontal viscous channel underneath a rigid lid above the actively progressing promontory. Furthermore, experimental results show that a plateau develops above the channelling lower crust. Two sets of sandbox-scale numerical simulations were performed. The first set of experiments is designed to study the influence of viscosity stratification within the crust on the extrusion process. A second set of experiments were performed in order to quantify the influence of the viscosity and the geometry of the indentor. Non-dimensional scaling laws were derived to predict the maximum extrusion rates associated with the indentation mechanism. Such laws enable the computation vertical extrusion rates that are in good agreement with natural exhumation rates inferred from petrological data. Finally, we discuss the potential positive feedback of Rayleigh-Taylor instability on vertical extrusion for the case of Eastern Bohemian Massif.

  7. Focus on the Rock.

    ERIC Educational Resources Information Center

    Shewell, John

    1994-01-01

    Describes historical accounts of the manipulation and importance of the Earth and its mineral resources. A foldout, "Out of the Rock," provides a collection of activities and information that helps make integration of the aforementioned concepts easy. (ZWH)

  8. Rock Bites into 'Bounce'

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This panoramic camera image from the Mars Exploration Rover Opportunity features the 6.44 millimeter (0.25 inch) deep hole ground into the rock dubbed 'Bounce' by the rover's rock abrasion tool. The tool took 2 hours and 15 minutes to grind the hole on sol 66 of the rover's journey. A combination of limited solar power and the rock's jagged texture led the rock abrasion tool team to set very aggressive grinding parameters to ensure that the end result was a full circle, suitable for a thorough read from the rover's spectrometers.

    Bounce's markedly different appearance (when compared to the rocks that were previously examined in the Eagle Crater outcrop) made it a natural target for rover research. In order to achieve an ideal position from which to grind into the rock, Opportunity moved in very close with its right wheel next to Bounce. In this image, the panoramic camera on the rover's mast is looking down, catching the tip of the solar panel which partially blocks the full circle ground by the rock abrasion tool.

    The outer ring consists of the cuttings from the rock, pushed out by the brushes on the grinding instrument. The dark impression at the top of the outer circle was caused by the instrument's contact mechanism which serves to stabilize it while grinding.

  9. Laboratory evaluation of mechanical properties of rock using an automated triaxial compression test with a constant mean stress criterion

    SciTech Connect

    Mellegard, K.D.; Pfeifle, T.W.

    1999-07-01

    A computerized, servohydraulic test system has been used in the laboratory to perform axisymmetric, triaxial compression tests on natural rock salt using a load path that maintains constant mean stress. The constant mean stress test protocol illustrates that modern test systems allow a nonstandard load path which can focus on a particular aspect of rock characterization; namely, the onset of dilation. Included are discussions of how the constant mean stress test could be used to investigate material anisotropy and determine elastic moduli. The results from the constant mean stress tests are compared to test results from a traditional test method. The paper also addresses system calibration concerns and the effects of pressure changes on the direct-contact extensometers used to measure strain.

  10. Investigations of Near-Field Thermal-Hydrologic-Mechanical-Chemical Models for Radioactive Waste Disposal in Clay/Shale Rock

    SciTech Connect

    Liu, H.H.; Li, L.; Zheng, L.; Houseworth, J.E.; Rutqvist, J.

    2011-06-20

    Clay/shale has been considered as potential host rock for geological disposal of high-level radioactive waste throughout the world, because of its low permeability, low diffusion coefficient, high retention capacity for radionuclides, and capability to self-seal fractures. For example, Callovo-Oxfordian argillites at the Bure site, France (Fouche et al., 2004), Toarcian argillites at the Tournemire site, France (Patriarche et al., 2004), Opalinus Clay at the Mont Terri site, Switzerland (Meier et al., 2000), and Boom clay at the Mol site, Belgium (Barnichon and Volckaert, 2003) have all been under intensive scientific investigation (at both field and laboratory scales) for understanding a variety of rock properties and their relationships to flow and transport processes associated with geological disposal of radioactive waste. Figure 1-1 presents the distribution of clay/shale formations within the USA.

  11. Fault Rock Variation as a Function of Host Rock Lithology

    NASA Astrophysics Data System (ADS)

    Fagereng, A.; Diener, J.

    2013-12-01

    Fault rocks contain an integrated record of the slip history of a fault, and thereby reflect the deformation processes associated with fault slip. Within the Aus Granulite Terrane, Namibia, a number of Jurassic to Cretaceous age strike-slip faults cross-cut Precambrian high grade metamorphic rocks. These strike-slip faults were active at subgreenschist conditions and occur in a variety of host rock lithologies. Where the host rock contains significant amounts of hydrous minerals, representing granulites that have undergone retrogressive metamorphism, the fault rock is dominated by hydrothermal breccias. In anhydrous, foliated rocks interlayered with minor layers containing hydrous phyllosilicates, the fault rock is a cataclasite partially cemented by jasper and quartz. Where the host rock is an isotropic granitic rock the fault rock is predominantly a fine grained black fault rock. Cataclasites and breccias show evidence for multiple deformation events, whereas the fine grained black fault rocks appear to only record a single slip increment. The strike-slip faults observed all formed in the same general orientation and at a similar time, and it is unlikely that regional stress, strain rate, pressure and temperature varied between the different faults. We therefore conclude that the type of fault rock here depended on the host rock lithology, and that lithology alone accounts for why some faults developed a hydrothermal breccia, some cataclasite, and some a fine grained black fault rock. Consequently, based on the assumption that fault rocks reflect specific slip styles, lithology was also the main control on different fault slip styles in this area at the time of strike-slip fault activity. Whereas fine grained black fault rock is inferred to represent high stress events, hydrothermal breccia is rather related to events involving fluid pressure in excess of the least stress. Jasper-bearing cataclasites may represent faults that experienced dynamic weakening as seen

  12. Analysis of mechanical and thermal response of rock due to laser drilling using optical fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Quintero, Sully M. M.; Patusco, Guilherme B.; da Silva, Hugo G.; Furtado, Felipe O.; Valente, Luiz C. G.; Braga, Arthur M. B.

    2015-09-01

    Optical fiber Bragg grating sensors (FBGs) were used to measure strain and the temperature field that develop during laser drilling of carbonate rock samples. The shear deformation and high temperature gradient measured are clearly correlated with traces of fractures observed. Beyond the volume directly evaporated by laser exposure, a greater volume around the drilling area was fractured. From the perforation process point of view, it results in an increase of efficiency.

  13. 'Earhart' Rock

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This false-color image taken by NASA's Mars Exploration Rover Opportunity shows a rock informally named 'Earhart' on the lower slopes of 'Endurance Crater.' The rock was named after the pilot Amelia Earhart. Like 'Escher' and other rocks dotting the bottom of Endurance, scientists believe fractures in Earhart could have been formed by one of several processes. They may have been caused by the impact that created Endurance Crater, or they might have arisen when water leftover from the rock's formation dried up. A third possibility is that much later, after the rock was formed, and after the crater was created, the rock became wet once again, then dried up and developed cracks. Rover team members do not have plans to investigate Earhart in detail because it is located across potentially hazardous sandy terrain. This image was taken on sol 219 (Sept. 4) by the rover's panoramic camera, using its 750-, 530- and 430-nanometer filters.

  14. Final Report “Electrical and mechanical characterization of rocks at the sub-millimeter scale” DE-SC0000757

    SciTech Connect

    Scales, John

    2016-06-01

    The broad purpose of CSM's 6-year (3 years plus renewal) DOE project was to develop and apply new experimental physics technology to the material characterization of rocks at the grain scale or smaller. This is motivated by a knowledge that the bulk chemistry and physics of rocks are strongly influenced by processes occurring at the grain scale: the flow of fluids, cation exchange, the state of cementation of grains, and many more. It may also be possible in some cases to ``upscale'' or homogenize the mesoscopic properties of rocks in order to directly infer the large-scale properties of formations, but that is not our central goal. Understanding the physics and chemistry at the small scale is. During the first 3 years, most effort was devoted to developing and validating the near-field scanning technology. During the 3 year renewal phase, most effort was focused on applying the technology in the labs Professors Batzle (now deceased) in Geophysics and Prasad in Petroleum engineering.

  15. Three-Dimensional Numerical Simulation on Triaxial Failure Mechanical Behavior of Rock-Like Specimen Containing Two Unparallel Fissures

    NASA Astrophysics Data System (ADS)

    Huang, Yan-Hua; Yang, Sheng-Qi; Zhao, Jian

    2016-12-01

    A three-dimensional particle flow code (PFC3D) was used for a systematic numerical simulation of the strength failure and cracking behavior of rock-like material specimens containing two unparallel fissures under conventional triaxial compression. The micro-parameters of the parallel bond model were first calibrated using the laboratory results of intact specimens and then validated from the experimental results of pre-fissured specimens under triaxial compression. Numerically simulated stress-strain curves, strength and deformation parameters and macro-failure modes of pre-fissured specimens were all in good agreement with the experimental results. The relationship between stress and the micro-crack numbers was summarized. Crack initiation, propagation and coalescence process of pre-fissured specimens were analyzed in detail. Finally, horizontal and vertical cross sections of numerical specimens were derived from PFC3D. A detailed analysis to reveal the internal damage behavior of rock under triaxial compression was carried out. The experimental and simulated results are expected to improve the understanding of the strength failure and cracking behavior of fractured rock under triaxial compression.

  16. Crustal Seismic Anisotropy Produced by Rock Fabric Terranes in the Taiwan Central Range Deformational Orogen: Integrative Study Combining Rock Physics, Structural Geology, and Passive/Active-Source Seismology

    NASA Astrophysics Data System (ADS)

    Okaya, D. A.; Ross, Z.; Christensen, N. I.; Wu, F. T.; Byrne, T. B.

    2014-12-01

    The island of Taiwan is currently under construction due to the collision of the northwestern corner of the Philippine Sea plate and the embedded Luzon island arc with the larger continental Eurasian plate. This collision is responsible for the current growth of the Central Range that dominates the eastern half of the island. An international collaboration involving several USA and Taiwan universities and academic institutions was formed to study how the orogen evolves through time and to understand the role of a colliding island arc in mountain building. The project, Taiwan Integrated Geodynamics Research (TAIGER), was funded by NSF-Continental Dynamics and Taiwan National Science Council. The Central Range grows at one of the most rapid rates of uplift in the world, exposing metamorphic rocks that were once at least 10 km deep. The range offers unique opportunities for studies of crustal seismic anisotropy for two major reasons: (1) its geological makeup is conducive for producing crustal seismic anisotropy; that is, the rocks are highly foliated; and (2) a seismological data volume of significant breadth offers extensive coverage of sources and recording stations throughout the region. We carried out a crustal shear wave splitting study by data mining 3300 local earthquakes collected in the TAIGER 2009 sea-land experiment. We used an automated P and S wave arrival time picking method (Ross and Ben-Zion, 2014) applied to over 100,000 event-station pairs. These data were analyzed for shear-wave splitting using the MFAST automated package (Savage et al., 2010), producing 3300 quality shear wave split measurements. The splitting results were then station-averaged. The results show NNE to NE orientation trends that are consistent with regional cleavage strikes. Average crustal shear wave split time is 0.244 sec. These measurements are consistent with rock physics measurements of Central Range slate and metamorphic acoustic velocities. The splits exhibit orientations

  17. Rock flows

    NASA Technical Reports Server (NTRS)

    Matveyev, S. N.

    1986-01-01

    Rock flows are defined as forms of spontaneous mass movements, commonly found in mountainous countries, which have been studied very little. The article considers formations known as rock rivers, rock flows, boulder flows, boulder stria, gravel flows, rock seas, and rubble seas. It describes their genesis as seen from their morphological characteristics and presents a classification of these forms. This classification is based on the difference in the genesis of the rubbly matter and characterizes these forms of mass movement according to their source, drainage, and deposit areas.

  18. Transient fluvial incision and spatial distribution of active rock uplift in the Uspallata-Calingasta-Iglesia Valley, Central Argentina.

    NASA Astrophysics Data System (ADS)

    Val, P.; Hoke, G. D.

    2014-12-01

    In the southern portion of the Pampean flat-slab subduction zone, a narrow, elongate intermontane depression separates the Precordillera fold-and-thrust belt from the Frontal and Principal Cordilleras of the high Andes. This depression, the Uspallata-Callingasta-Iglesia Valley, is divided into three catchments based on drainage divides between three large, transverse rivers. These catchments have their headwaters in the western Precordillera, Frontal Cordillera and Principal Cordillera ranges. Deformation is thought to have ceased near the core of the range (Frontal and Principal Cordilleras) and propagated to the east during the Miocene to present. In this study, river profiles and knickpoint topographic data are assessed to determine the distribution of active rock uplift and amount of fluvial incision in the Calingasta and Iglesia valleys. Slope-area data extracted from a digital elevation model consistently show slope-break knickpoints separating distinct sections of river profiles, which suggests relative bedrock uplift. Catchment-wide, normalized steepness indices (ksn) - using a concavity index of 0.45 (common in steady state profiles in the study area) - for both basins revealed consistently high ksn signals (>300) in the main stems and tributaries draining the Frontal Cordillera and the western Precordillera. The highest ksn values are situated in an elevation range of 2500 to 4000 m, west of the fold and thrust belt in the Principal and Frontal Cordilleras. Slope-break knickpoints are not clustered in elevation and there is no obvious correlation between upstream drainage area at knickpoints and respective distance from the tributaries' mouths, which suggests that they are not part of an upstream migrating wave of knickpoints. The data presented here indicate active rock uplift in the eastern edge of the Frontal Cordillera, which was previously considered inactive.

  19. Short and long term release mechanisms of arsenic, selenium and boron from a tunnel-excavated sedimentary rock under in situ conditions.

    PubMed

    Tamoto, Shuichi; Tabelin, Carlito Baltazar; Igarashi, Toshifumi; Ito, Mayumi; Hiroyoshi, Naoki

    2015-01-01

    Sedimentary rocks of marine origin excavated from tunnel construction projects usually contain background levels of hazardous trace elements, but when exposed to the environment, they generate leachates with concentrations of arsenic (As), selenium (Se) and boron (B) exceeding the WHO guideline for drinking water. In this study, the leaching of As, Se and B was evaluated under in situ conditions at various flow patterns, particle size distributions and column thicknesses. The results showed that these trace elements were leached out of the rock via short and long term mechanisms. In the short term, all three elements were rapidly and simultaneously released due to the dissolution of soluble evaporite salts formed from entrapped sea water of the Cretaceous. After their rapid release, however, these trace elements behaved differently as a result of their contrasting adsorption affinities onto minerals like clays and Fe-oxyhydroxides, which were further influenced by the pH, presence of coexisting ions and speciation of the trace elements. Selenium was quickly and easily transported out of the columns because it was mostly present as the very mobile selenate ion (Se[VI]). In comparison, the migration of As and B was hindered by adsorption reactions onto mineral phases of the rock. Boron was initially the least mobile among the three because of its preferential adsorption onto clay minerals that was further enhanced by the slightly alkaline pH and high concentrations of Ca(2+) and Na(+). However, it was gradually re-mobilized in the latter part of the experiments because it was only weakly adsorbed via outer sphere complexation reactions. In the long term, the rock continued to release substantial amounts of As, Se and B via pyrite oxidation and adsorption/desorption reactions, which were regulated by the temperature and rainfall intensity/frequency on site.

  20. Hydrogeologic controls imposed by mechanical stratigraphy in layered rocks of the Chateauguay River Basin, a U.S.-Canada transborder aquifer

    USGS Publications Warehouse

    Morin, Roger H.; Godin, Rejean; Nastev, Miroslav; Rouleau, Alain

    2007-01-01

    [1] The Châteauguay River Basin delineates a transborder watershed with roughly half of its surface area located in northern New York State and half in southern Québec Province, Canada. As part of a multidisciplinary study designed to characterize the hydrogeologic properties of this basin, geophysical logs were obtained in 12 wells strategically located to penetrate the four major sedimentary rock formations that constitute the regional aquifers. The layered rocks were classified according to their elastic properties into three primary units: soft sandstone, hard sandstone, and dolostone. Downhole measurements were analyzed to identify fracture patterns associated with each unit and to evaluate their role in controlling groundwater flow. Fracture networks are composed of orthogonal sets of laterally extensive, subhorizontal bedding plane partings and bed-delimited, subvertical joints with spacings that are consistent with rock mechanics principles and stress models. The vertical distribution of transmissive zones is confined to a few select bedding plane fractures, with soft sandstone having the fewest (one per 70-m depth) and hard sandstone the most (five per 70-m depth). Bed-normal permeability is examined using a probabilistic model that considers the lengths of flow paths winding along joints and bedding plane fractures. Soft sandstone has the smallest bed-normal permeability primarily because of its wide, geomechanically undersaturated joint spacing. Results indicate that the three formations have similar values of bulk transmissivity, within roughly an order of magnitude, but that each rock unit has its own unique system of groundwater flow paths that constitute that transmissivity.

  1. Physiologic mechanism of the ultrasonically activated scalpel.

    PubMed

    McCarus, S D

    1996-08-01

    An ultrasonically activated scalpel was developed and used clinically to provide hemostatic cutting in laparoscopic surgery. Results of experimental work with the ultrasonic scalpel blades were compared with those of electrosurgery and lasers. Some features that distinguish this energy form may confer specific advantages in various surgical procedures.

  2. The novel mechanism of lenalidomide activity.

    PubMed

    Fink, Emma C; Ebert, Benjamin L

    2015-11-19

    Lenalidomide acts by a novel drug mechanism-modulation of the substrate specificity of the CRL4(CRBN) E3 ubiquitin ligase. In multiple myeloma, lenalidomide induces the ubiquitination of IKZF1 and IKZF3 by CRL4(CRBN). Subsequent proteasomal degradation of these transcription factors kills multiple myeloma cells. In del(5q) myelodysplastic syndrome, lenalidomide induces the degradation of CK1α, which preferentially affects del(5q) cells because they express this gene at haploinsufficient levels. In the future, modulation of ubiquitin ligase function may enable us to target previously "undruggable" proteins.

  3. Optimal Control of Active Recoil Mechanisms

    DTIC Science & Technology

    1977-02-01

    forces from 25 to 2.5% for lower zones and cavitation was avoided for zone 8. Tachometer feedback was shown to be effective for low zones. The...concept of feedback control system coupled with optimization procedure to design recoil mechanisms was demonstrated to be an efficient and very effective ...122o •nl260 .01300 .01340 .01380 • ouzo #01460 •01500 •01540 •01580 •0162" .0166 i 309o,6 504P.6 9964.5 10075,9 39121.5 75397.3

  4. AMPK activators: mechanisms of action and physiological activities

    PubMed Central

    Kim, Joungmok; Yang, Goowon; Kim, Yeji; Kim, Jin; Ha, Joohun

    2016-01-01

    AMP-activated protein kinase (AMPK) is a central regulator of energy homeostasis, which coordinates metabolic pathways and thus balances nutrient supply with energy demand. Because of the favorable physiological outcomes of AMPK activation on metabolism, AMPK has been considered to be an important therapeutic target for controlling human diseases including metabolic syndrome and cancer. Thus, activators of AMPK may have potential as novel therapeutics for these diseases. In this review, we provide a comprehensive summary of both indirect and direct AMPK activators and their modes of action in relation to the structure of AMPK. We discuss the functional differences among isoform-specific AMPK complexes and their significance regarding the development of novel AMPK activators and the potential for combining different AMPK activators in the treatment of human disease. PMID:27034026

  5. Rocks of the Columbia Hills

    USGS Publications Warehouse

    Squyres, S. W.; Arvidson, R. E.; Blaney, D.L.; Clark, B. C.; Crumpler, L.; Farrand, W. H.; Gorevan, S.; Herkenhoff, K. E.; Hurowitz, J.; Kusack, A.; McSween, H.Y.; Ming, D. W.; Morris, R.V.; Ruff, S.W.; Wang, A.; Yen, A.

    2006-01-01

    The Mars Exploration Rover Spirit has identified five distinct rock types in the Columbia Hills of Gusev crater. Clovis Class rock is a poorly sorted clastic rock that has undergone substantial aqueous alteration. We interpret it to be aqueously altered ejecta deposits formed by impacts into basaltic materials. Wishstone Class rock is also a poorly sorted clastic rock that has a distinctive chemical composition that is high in Ti and P and low in Cr. Wishstone Class rock may be pyroclastic or impact in origin. Peace Class rock is a sedimentary material composed of ultramafic sand grains cemented by significant quantities of Mg- and Ca-sulfates. Peace Class rock may have formed when water briefly saturated the ultramafic sands and evaporated to allow precipitation of the sulfates. Watchtower Class rocks are similar chemically to Wishstone Class rocks and have undergone widely varying degrees of near-isochemical aqueous alteration. They may also be ejecta deposits, formed by impacts into Wishstone-rich materials and altered by small amounts of water. Backstay Class rocks are basalt/trachybasalt lavas that were emplaced in the Columbia Hills after the other rock classes were, either as impact ejecta or by localized volcanic activity. The geologic record preserved in the rocks of the Columbia Hills reveals a period very early in Martian history in which volcanic materials were widespread, impact was a dominant process, and water was commonly present. Copyright 2006 by the American Geophysical Union.

  6. Rocks of the Columbia Hills

    NASA Astrophysics Data System (ADS)

    Squyres, Steven W.; Arvidson, Raymond E.; Blaney, Diana L.; Clark, Benton C.; Crumpler, Larry; Farrand, William H.; Gorevan, Stephen; Herkenhoff, Kenneth E.; Hurowitz, Joel; Kusack, Alastair; McSween, Harry Y.; Ming, Douglas W.; Morris, Richard V.; Ruff, Steven W.; Wang, Alian; Yen, Albert

    2006-02-01

    The Mars Exploration Rover Spirit has identified five distinct rock types in the Columbia Hills of Gusev crater. Clovis Class rock is a poorly sorted clastic rock that has undergone substantial aqueous alteration. We interpret it to be aqueously altered ejecta deposits formed by impacts into basaltic materials. Wishstone Class rock is also a poorly sorted clastic rock that has a distinctive chemical composition that is high in Ti and P and low in Cr. Wishstone Class rock may be pyroclastic or impact in origin. Peace Class rock is a sedimentary material composed of ultramafic sand grains cemented by significant quantities of Mg- and Ca-sulfates. Peace Class rock may have formed when water briefly saturated the ultramafic sands and evaporated to allow precipitation of the sulfates. Watchtower Class rocks are similar chemically to Wishstone Class rocks and have undergone widely varying degrees of near-isochemical aqueous alteration. They may also be ejecta deposits, formed by impacts into Wishstone-rich materials and altered by small amounts of water. Backstay Class rocks are basalt/trachybasalt lavas that were emplaced in the Columbia Hills after the other rock classes were, either as impact ejecta or by localized volcanic activity. The geologic record preserved in the rocks of the Columbia Hills reveals a period very early in Martian history in which volcanic materials were widespread, impact was a dominant process, and water was commonly present.

  7. Elastic Rock Heterogeneity Controls Brittle Rock Failure during Hydraulic Fracturing

    NASA Astrophysics Data System (ADS)

    Langenbruch, C.; Shapiro, S. A.

    2014-12-01

    For interpretation and inversion of microseismic data it is important to understand, which properties of the reservoir rock control the occurrence probability of brittle rock failure and associated seismicity during hydraulic stimulation. This is especially important, when inverting for key properties like permeability and fracture conductivity. Although it became accepted that seismic events are triggered by fluid flow and the resulting perturbation of the stress field in the reservoir rock, the magnitude of stress perturbations, capable of triggering failure in rocks, can be highly variable. The controlling physical mechanism of this variability is still under discussion. We compare the occurrence of microseismic events at the Cotton Valley gas field to elastic rock heterogeneity, obtained from measurements along the treatment wells. The heterogeneity is characterized by scale invariant fluctuations of elastic properties. We observe that the elastic heterogeneity of the rock formation controls the occurrence of brittle failure. In particular, we find that the density of events is increasing with the Brittleness Index (BI) of the rock, which is defined as a combination of Young's modulus and Poisson's ratio. We evaluate the physical meaning of the BI. By applying geomechanical investigations we characterize the influence of fluctuating elastic properties in rocks on the probability of brittle rock failure. Our analysis is based on the computation of stress fluctuations caused by elastic heterogeneity of rocks. We find that elastic rock heterogeneity causes stress fluctuations of significant magnitude. Moreover, the stress changes necessary to open and reactivate fractures in rocks are strongly related to fluctuations of elastic moduli. Our analysis gives a physical explanation to the observed relation between elastic heterogeneity of the rock formation and the occurrence of brittle failure during hydraulic reservoir stimulations. A crucial factor for understanding

  8. Lipid Dependent Mechanisms of Protein Pump Activity

    DTIC Science & Technology

    1989-05-23

    properties which result form the colligative interactions of many lipid molecules. Important materials properties include . . . i I I II II I i I 1 the...d identify by olock number) *This project is aime at investigating if a lipid elastic property , known as the spontaneous radius of curvature Ro’, is...a regulated membrane property and if its value modulates membrane protein activity. Specific aims reported on here include: 1) Correlation of ion pump

  9. Integrated Experimental and Modeling Studies of Mineral Carbonation as a Mechanism for Permanent Carbon Sequestration in Mafic/Ultramafic Rocks

    SciTech Connect

    Wang, Zhengrong; Qiu, Lin; Zhang, Shuang; Bolton, Edward; Bercovici, David; Ague, Jay; Karato, Shun-Ichiro; Oristaglio, Michael; Zhu, Wen-Iu; Lisabeth, Harry; Johnson, Kevin

    2014-09-30

    A program of laboratory experiments, modeling and fieldwork was carried out at Yale University, University of Maryland, and University of Hawai‘i, under a DOE Award (DE-FE0004375) to study mineral carbonation as a practical method of geologic carbon sequestration. Mineral carbonation, also called carbon mineralization, is the conversion of (fluid) carbon dioxide into (solid) carbonate minerals in rocks, by way of naturally occurring chemical reactions. Mafic and ultramafic rocks, such as volcanic basalt, are natural candidates for carbonation, because the magnesium and iron silicate minerals in these rocks react with brines of dissolved carbon dioxide to form carbonate minerals. By trapping carbon dioxide (CO2) underground as a constituent of solid rock, carbonation of natural basalt formations would be a secure method of sequestering CO2 captured at power plants in efforts to mitigate climate change. Geochemical laboratory experiments at Yale, carried out in a batch reactor at 200°C and 150 bar (15 MPa), studied carbonation of the olivine mineral forsterite (Mg2SiO4) reacting with CO2 brines in the form of sodium bicarbonate (NaHCO3) solutions. The main carbonation product in these reactions is the carbonate mineral magnesite (MgCO3). A series of 32 runs varied the reaction time, the reactive surface area of olivine grains and powders, the concentration of the reacting fluid, and the starting ratio of fluid to olivine mass. These experiments were the first to study the rate of olivine carbonation under passive conditions approaching equilibrium. The results show that, in a simple batch reaction, olivine carbonation is fastest during the first 24 hours and then slows significantly and even reverses. A natural measure of the extent of carbonation is a quantity called the carbonation fraction, which compares the amount of carbon removed from solution, during a run, to the maximum amount

  10. Activity concentration of natural radionuclides and radon and thoron exhalation rates in rocks used as decorative wall coverings in Japan.

    PubMed

    Iwaoka, Kazuki; Hosoda, Masahiro; Tabe, Hiroyuki; Ishikawa, Tetsuo; Tokonami, Shinji; Yonehara, Hidenori

    2013-01-01

    In Japan, many dwellings have decorative wall coverings made from granite, andesite, tuff, gabbro, and marble. However, information regarding activity concentrations and radon (Rn) and thoron (Rn) exhalation rates for such rocks is very scarce. Therefore, samples of the granite, andesite, tuff, and marble that are used as wall coverings in Japan were collected from mining companies, and their activity concentrations and Rn and Rn exhalation rates were measured. Dose estimations for inhabitants living in houses built with these materials were also carried out. The activity concentration of natural radionuclides in all the materials was lower than the critical values described by the International Atomic Energy Agency (IAEA) (10,000 Bq kg for K and 1,000 Bq kg for all other radionuclides of natural origin). The maximum values of Rn and Rn mass exhalation rates for the granite samples were 0.12 and 430 mBq kg s, and those for the area exhalation rates were 1.8 and 6300 mBq m s, respectively; these values are higher than those for other samples. The maximum value of effective doses to inhabitants was 0.68 mSv y, which is lower than the intervention exemption level (1 mSv y) given in the International Commission on Radiological Protection (ICRP) Publication 82.

  11. Mechanism for Clastogenic Activity of Naphthalene

    SciTech Connect

    Buchholz, Bruce A.

    2015-09-29

    Naphthalene incubations form DNA adducts in vitro in a dose dependent manner in both mouse and rat tissues. Rodent tissue incubations with naphthalene indicate that naphthalene forms as many DNA adducts as Benzo(a)pyrene, a known DNA binding carcinogen. The mouse airway has the greatest number of DNA adducts, corresponding to the higher metabolic activation of naphthalene in this location. Both rat tissues, the rat olfactory (tumor target) and the airways (non-tumor target), have similar levels of NA-DNA adducts, indicating that short term measures of initial adduct formation do not directly correlate with sites of tumor formation in the NTP bioassays.

  12. Mechanism for Clastogenic Activity of Naphthalene

    SciTech Connect

    Buchholz, Bruce A.

    2016-06-24

    Naphthalene incubations form DNA adducts in vitro in a dose dependent manner in both mouse and rat tissues. Rodent tissue incubations with naphthalene indicate that naphthalene forms as many DNA adducts as Benzo(a)pyrene, a known DNA binding carcinogen. The mouse airway has the greatest number of DNA adducts, corresponding to the higher metabolic activation of naphthalene in this location. Both rat tissues, the rat olfactory (tumor target) and the airways (non-tumor target), have similar levels of NA-DNA adducts, indicating that short term measures of initial adduct formation do not directly correlate with sites of tumor formation in the NTP bioassays.

  13. {delta}-ALAD activity variations in red blood cells in response to lead accumulation in rock doves (Columba livia)

    SciTech Connect

    Gonzalez, M.; Tejedor, M.C.

    1992-10-01

    The enzyme {delta}-aminolevulinic acid dehydratase ({delta}-ALAD, E.C. 4.2.1.24), catalyses the second step of the haeme biosynthetic pathway and is required to maintain the haemoglobin and cytochrome content in red cells. {delta}-ALAD is not only found in bone marrow cells, the major site of haeme synthesis, but also in circulating erythrocytes and other tissues. An inverse correlation was found between {delta}-ALAD activity in red blood cells and lead concentration in the blood. The degree of {delta}-ALAD inhibition in erythrocytes has been widely accepted as a standard bioassay to detect acute and chronic lead exposure in humans and in avians. The value of this parameter as an indicator for environmental lead has been often reported in doves and Scanlon. In lead-treated rats, an increase in {delta}-ALAD activity in bone marrow cells and in blood samples was shown by radioimmunoassay at 5 and 9 days after the treatment. Similarly, the amount of {delta}-ALAD seems to be more sensitive to lead in avian species than in mammals, the usefulness of blood {delta}-ALAD activity as an index of lead exposure has already been questioned by Hutton in the pigeon and by Jaffe et al. in humans. The present investigation studied the toxic effects of lead on rock dove red blood cell {delta}-ALAD activity in two situations: in doves treated with lead acetate in the laboratory and in doves exposed to the environment of Alcala de Henares. The final lead blood concentrations were lower in the environmental than in the laboratory doves. {delta}-ALAD activity in bone marrow cells and the relationships between lead accumulation and enzyme activity in red cells, are examined. 20 refs., 5 figs., 1 tab.

  14. Determination of thorium concentrations and activity ratios in silicate rocks by alpha spectrometry.

    PubMed

    dos Santos, R N; Marques, L S; Nicolai, S H A; Ribeiro, F B

    2004-01-01

    A detailed radiochemical procedure for alpha spectrometry measurements of thorium concentrations and of 230Th/232Th activity ratios in silicates is presented. The Th behaviour, during each step of the chemical process, was investigated by using a 234Th tracer, which is a gamma-ray emitter. The described chemical processing provides relatively high thorium yields, which varied between 56% and 88%, in the analysis of GB-1 (granite) and BB-1 (basalt) Brazilian geological standards. Also, the application of the established radiochemical method allowed a determination of both Th concentrations and activity ratios with high reproducibility, on the order of 2%. The estimation of the concentration result accuracy is also about 2%, which was calculated by using published data obtained from neutron activation analysis as reference values.

  15. Mechanism of antibacterial activity of copper nanoparticles

    NASA Astrophysics Data System (ADS)

    Chatterjee, Arijit Kumar; Chakraborty, Ruchira; Basu, Tarakdas

    2014-04-01

    In a previous communication, we reported a new method of synthesis of stable metallic copper nanoparticles (Cu-NPs), which had high potency for bacterial cell filamentation and cell killing. The present study deals with the mechanism of filament formation and antibacterial roles of Cu-NPs in E. coli cells. Our results demonstrate that NP-mediated dissipation of cell membrane potential was the probable reason for the formation of cell filaments. On the other hand, Cu-NPs were found to cause multiple toxic effects such as generation of reactive oxygen species, lipid peroxidation, protein oxidation and DNA degradation in E. coli cells. In vitro interaction between plasmid pUC19 DNA and Cu-NPs showed that the degradation of DNA was highly inhibited in the presence of the divalent metal ion chelator EDTA, which indicated a positive role of Cu2+ ions in the degradation process. Moreover, the fast destabilization, i.e. the reduction in size, of NPs in the presence of EDTA led us to propose that the nascent Cu ions liberated from the NP surface were responsible for higher reactivity of the Cu-NPs than the equivalent amount of its precursor CuCl2; the nascent ions were generated from the oxidation of metallic NPs when they were in the vicinity of agents, namely cells, biomolecules or medium components, to be reduced simultaneously.

  16. Mechanism of antibacterial activity of copper nanoparticles.

    PubMed

    Chatterjee, Arijit Kumar; Chakraborty, Ruchira; Basu, Tarakdas

    2014-04-04

    In a previous communication, we reported a new method of synthesis of stable metallic copper nanoparticles (Cu-NPs), which had high potency for bacterial cell filamentation and cell killing. The present study deals with the mechanism of filament formation and antibacterial roles of Cu-NPs in E. coli cells. Our results demonstrate that NP-mediated dissipation of cell membrane potential was the probable reason for the formation of cell filaments. On the other hand, Cu-NPs were found to cause multiple toxic effects such as generation of reactive oxygen species, lipid peroxidation, protein oxidation and DNA degradation in E. coli cells. In vitro interaction between plasmid pUC19 DNA and Cu-NPs showed that the degradation of DNA was highly inhibited in the presence of the divalent metal ion chelator EDTA, which indicated a positive role of Cu(2+) ions in the degradation process. Moreover, the fast destabilization, i.e. the reduction in size, of NPs in the presence of EDTA led us to propose that the nascent Cu ions liberated from the NP surface were responsible for higher reactivity of the Cu-NPs than the equivalent amount of its precursor CuCl2; the nascent ions were generated from the oxidation of metallic NPs when they were in the vicinity of agents, namely cells, biomolecules or medium components, to be reduced simultaneously.

  17. Mechanism of photodynamic activity of pheophorbides.

    PubMed

    Tanielian, C; Kobayashi, M; Wolff, C

    2001-04-01

    Plasmid DNA is efficiently photocleaved by sodium pheophorbides (Na-Phdes) a and b in the absence of oxygen as well as in the presence of oxygen. Fluorescence microscopic observation shows a rapid incorporation of Na-Phde a into nuclei, mitochondria, and lysosome of human oral mucosa cells. In contrast Na-Phde b is incorporated only into the plasma membrane. The photodynamic activity of these pigments in living tissues is probably determined by the monomeric pigment molecules formed in hydrophobic cellular structures and involves two types of reactions: (i) direct electron transfer between DNA bases (especially guanine) and pheophorbide singlet excited state, and (ii) indirect reactions mediated by reactive oxygen species, including singlet oxygen whose production from molecular oxygen is sensitized by the Na-Phdes triplet state. A preliminary report has appeared in "Photodynamic Therapy of Cancer II," Proc. SPIE 2325, 416-424 (1994).

  18. Art Rocks with Rock Art!

    ERIC Educational Resources Information Center

    Bickett, Marianne

    2011-01-01

    This article discusses rock art which was the very first "art." Rock art, such as the images created on the stone surfaces of the caves of Lascaux and Altimira, is the true origin of the canvas, paintbrush, and painting media. For there, within caverns deep in the earth, the first artists mixed animal fat, urine, and saliva with powdered minerals…

  19. Genesis of Syntectonic Hydrothermal Veins in the Igneous Rock of Teschenite Association (Outer Western Carpathians, Czech Republic): Growth Mechanism and Origin of Fluids

    NASA Astrophysics Data System (ADS)

    Urubek, Tomáš; Dolníček, Zdeněk; Kropáč, Kamil

    2015-01-01

    Hydrothermal mineralization hosted by the Lower Cretaceous igneous rock of the teschenite association at Jasenice (Silesian Unit, Flysch Belt, Outer Western Carpathians) occurs in two morphological types - irregular vein filled by granular calcite and regular composite vein formed by both fibrous and granular calcite and minor chlorite, quartz, and pyrite. Crosscutting evidence indicates that the granular veins are younger than the composite vein. The composite vein was formed by two mechanisms at different times. The arrangement of solid inclusions in the marginal fibrous zone suggests an episodic growth by the crack-seal mechanism during syntectonic deformation which was at least partially driven by tectonic suction pump during some stages of the Alpine Orogeny. Both the central part of the composite vein and monomineral veins developed in a brittle regime. In these cases, the textures of vein suggest the flow of fluids along an open fracture. The parent fluids of both types of vein are characterized by low temperatures (Th=66-163 °C), low salinities (0.4 to 3.4 wt. % NaCl eq.), low content of strong REE-complexing ligands, and δ18O and δ13C ranges of + 0.2/+12.5 %. SMOW and -11.8/-14.1 %. PDB, respectively. The parent fluids are interpreted as the results of mixing of residual seawater and diagenetic waters produced by dewatering of clay minerals in the associ-ated flysch sediments. The flow of fluids was controlled by tectonic deformation of the host rock.

  20. Long Live Rock! Exploring Active Microbial Populations in North Pond Subsurface Basalt

    NASA Astrophysics Data System (ADS)

    Mills, H. J.; Lehne, J.

    2014-12-01

    Microbial life should be considered as an active source for subsurface alterations of crustal material. Over the past several decades, microbial populations have been qualitatively and quantitatively characterized in marine sediments from the near shore to gyre centers, from the surface to two kilometers below the surface. Recent exploration of the underlying basement has revealed bacterial populations within the basalt. Initial cultivation-based and in situ analysis of subsurface basalt has produced some structural identification of populations that have the potential to alter the crust. Within this study, we have advanced this understanding by characterizing the metabolically active fraction of these populations. A 16S rRNA gene transcript approach was conducted using high throughput sequencing on RNA extracted from breccia, glass basalts and ultramafic basalts of the western flank of the Mid-Atlantic Ridge. Previous research has shown that the fluid within the basement is oxic. As expected, populations associated with aerobic metabolism were detected. In addition, iron-utilizing populations were observed to be metabolically active within the basalt samples characterized. Future characterization will reveal overlap between previous studies to determine the total versus metabolically active populations.

  1. Opportunity Rocks!

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This high-resolution image captured by the Mars Exploration Rover Opportunity's panoramic camera shows in superb detail a portion of the puzzling rock outcropping that scientists are eagerly planning to investigate. Presently, Opportunity is on its lander facing northeast; the outcropping lies to the northwest. These layered rocks measure only 10 centimeters (4 inches) tall and are thought to be either volcanic ash deposits or sediments carried by water or wind. The small rock in the center is about the size of a golf ball.

  2. Terby's Rocks

    NASA Technical Reports Server (NTRS)

    2006-01-01

    27 January 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows some of the light-toned, layered, sedimentary rock outcrops in northern Terby Crater. Terby is located along the north edge of Hellas Planitia. The sedimentary rocks might have been deposited in a greater, Hellas-filling sea -- or not. Today, the rocks are partly covered by dark-toned sediment and debris.

    Location near: 27.2oS, 285.3oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  3. Changes in14c activity over time during vacuum distillation of carbon from rock pore water

    USGS Publications Warehouse

    Davidson, G.R.; Yang, I.C.

    1999-01-01

    The radiocarbon activity of carbon collected by vacuum distillation from a single partially saturated tuff began to decline after approximately 60% of the water and carbon had been extracted. Disproportionate changes in 14C activity and ??13C during distillation rule out simple isotopic fractionation as a causative explanation. Additional phenomena such as matrix diffusion and ion exclusion in micropores may play a role in altering the isotopic value of extracted carbon, but neither can fully account for the observed changes. The most plausible explanation is that distillation recovers carbon from an adsorbed phase that is depleted in 14C relative to DIC in the bulk pore water. ?? 1999 by the Arizona Board of Regents on behalf of the University of Arizona.

  4. The Trofobiose Theory and organic agriculture: the active mobilization of nutrients and the use of rock powder as a tool for sustainability.

    PubMed

    Polito, Wagner L

    2006-12-01

    The primary objective of the present paper is to link some relevant concepts on the use of ecological agricultural practices to the production of food crops. In a special topic the Trofobiose Theory, as well as the principle of Active Dissolution of Rocks are considered as important tools in improving the sustainability of Organic, Biodynamic and Process Agricultures.

  5. Lunar Rocks

    NASA Technical Reports Server (NTRS)

    1969-01-01

    The second manned lunar landing mission, Apollo 12 launched from launch pad 39-A at Kennedy Space Center in Florida on November 14, 1969 via a Saturn V launch vehicle. The Saturn V vehicle was developed by the Marshall Space Flight Center (MSFC) under the direction of Dr. Wernher von Braun. Aboard Apollo 12 was a crew of three astronauts: Alan L. Bean, pilot of the Lunar Module (LM), Intrepid; Richard Gordon, pilot of the Command Module (CM), Yankee Clipper; and Spacecraft Commander Charles Conrad. The LM, Intrepid, landed astronauts Conrad and Bean on the lunar surface in what's known as the Ocean of Storms while astronaut Richard Gordon piloted the CM, Yankee Clipper, in a parking orbit around the Moon. Lunar soil activities included the deployment of the Apollo Lunar Surface Experiments Package (ALSEP), finding the unmanned Surveyor 3 that landed on the Moon on April 19, 1967, and collecting 75 pounds (34 kilograms) of rock samples, some of which can be seen in this photograph. Apollo 12 safely returned to Earth on November 24, 1969.

  6. Alkali-aggregate reactivity of typical siliceious glass and carbonate rocks in alkali-activated fly ash based geopolymers

    NASA Astrophysics Data System (ADS)

    Lu, Duyou; Liu, Yongdao; Zheng, Yanzeng; Xu, Zhongzi; Shen, Xiaodong

    2013-08-01

    For exploring the behaviour of alkali-aggregate reactivity (AAR) in alkali-activated geopolymeric materials and assessing the procedures for testing AAR in geopolymers, the expansion behaviour of fly ash based geopolymer mortars with pure silica glass and typical carbonate rocks were studied respectively by curing at various conditions, i.e. 23°C and 38°C with relative humidity over 95%, immersed in 1M NaOH solution at 80°C. Results show that, at various curing conditions, neither harmful ASR nor harmful ACR was observed in geopolymers with the criteria specified for OPC system. However, with the change of curing conditions, the geopolymer binder and reactive aggregates may experience different reaction processes leading to quite different dimensional changes, especially with additional alkalis and elevated temperatures. It suggests that high temperature with additional alkali for accelerating AAR in traditional OPC system may not appropriate for assessing the alkali-aggregate reactivity behaviour in geopolymers designed for normal conditions. On the other hand, it is hopeful to control the dimensional change of geopolymer mortar or concrete by selecting the type of aggregates and the appropriate curing conditions, thus changing the harmful AAR in OPC into beneficial AAR in geopolymers and other alkali-activated cementitious systems.

  7. ROCK has a crucial role in regulating prostate tumor growth through interaction with c-Myc.

    PubMed

    Zhang, C; Zhang, S; Zhang, Z; He, J; Xu, Y; Liu, S

    2014-12-04

    Rho-associated kinase (ROCK) has an essential role in governing cell morphology and motility, and increased ROCK activity contributes to cancer cell invasion and metastasis. Burgeoning data suggest that ROCK is also involved in the growth regulation of tumor cells. However, thus far, the molecular mechanisms responsible for ROCK-governed tumor cell growth have not been clearly elucidated. Here we showed that inhibition of ROCK kinase activity, either by a selective ROCK inhibitor Y27632 or by specific ROCK small interfering RNA (siRNA) molecules, attenuated not only motility but also the proliferation of PC3 prostate cancer cells in vitro and in vivo. Importantly, mechanistic investigation revealed that ROCK endowed cancer cells with tumorigenic capability, mainly by targeting c-Myc. ROCK could increase the transcriptional activity of c-Myc by promoting c-Myc protein stability, and ROCK inhibition reduced c-Myc-mediated expression of mRNA targets (such as HSPC111) and microRNA targets (such as miR-17-92 cluster). We provided evidence demonstrating that ROCK1 directly interacted with and phosphorylated c-Myc, resulting in stabilization of the protein and activation of its transcriptional activity. Suppression of ROCK-c-Myc downstream molecules, such as c-Myc-regulated miR-17, also impaired tumor cell growth in vitro and in vivo. In addition, c-Myc was shown to exert a positive feedback regulation on ROCK by increasing RhoA mRNA expression. Therefore, inhibition of ROCK and its stimulated signaling might prove to be a promising strategy for restraining tumor progression in prostate cancer.

  8. Improved concept of lithospheric strength and earthquake activity at shallow depths based upon the fan-head dynamic shear rupture mechanism

    NASA Astrophysics Data System (ADS)

    Tarasov, Boris G.; Randolph, Mark F.

    2016-01-01

    The typical depth-frequency distribution of earthquake hypocentres (DFDE) demonstrates that, below an upper cutoff, the earthquake frequency increases with depth up to a maximum value and then decreases and ceases at a lower cutoff. Such regular behaviour of earthquakes implies the existence of some fundamental mechanisms responsible for the distribution. Conventional models of lithospheric strength based upon the assumption that the frictional strength along pre-existing faults represents a lower limit on the rock shear strength do not provide any intrinsic logic for the observed DFDE. The paper shows that these models ignore the specific properties of intact hard rocks which can exhibit extremely low transient strength (significantly lower than the frictional strength) during failure under the high confining stresses corresponding to seismogenic depths. The low transient strength is provided by a recently identified fan-head shear rupture mechanism which can be initiated in intact rocks in the proximity of pre-existing faults. The low transient shear strength of intact rock determines the correspondingly low transient strength of the lithosphere, which favours generation of new earthquake faults in the intact rock mass adjoining pre-existing faults in preference to frictional stick-slip instability along these faults. The efficiency of the fan-mechanism within the seismogenic layer is variable, with maximum efficiency at the middle range between the upper and lower cutoffs, thus providing minimum transient strength of the lithosphere and maximum earthquake frequency at that depth. We believe that this intrinsic property of hard rocks is responsible for the observed DFDE. Importantly, the formation of new faults in intact rock generated by the fan-mechanism can be accompanied by very small stress-drops (similar to, or lower than, stress-drops for frictional stick-slip instability) combined with abnormally high energy release. The paper proposes an improved concept

  9. Gamma Band Activity in the RAS-intracellular mechanisms

    PubMed Central

    Garcia-Rill, E.; Kezunovic, N.; D’Onofrio, S.; Luster, B.; Hyde, J.; Bisagno, V.; Urbano, F.J.

    2014-01-01

    Gamma band activity participates in sensory perception, problem solving, and memory. This review considers recent evidence showing that cells in the reticular activating system (RAS) exhibit gamma band activity, and describes the intrinsic membrane properties behind such manifestation. Specifically, we discuss how cells in the mesopontine pedunculopontine nucleus (PPN), intralaminar parafascicular nucleus (Pf), and pontine Subcoeruleus nucleus dorsalis (SubCD) all fire in the gamma band range when maximally activated, but no higher. The mechanisms involve high threshold, voltage-dependent P/Q-type calcium channels or sodium-dependent subthreshold oscillations. Rather than participating in the temporal binding of sensory events as in the cortex, gamma band activity in the RAS may participate in the processes of preconscious awareness, and provide the essential stream of information for the formulation of many of our actions. We address three necessary next steps resulting from these discoveries, an intracellular mechanism responsible for maintaining gamma band activity based on persistent G-protein activation, separate intracellular pathways that differentiate between gamma band activity during waking vs during REM sleep, and an intracellular mechanism responsible for the dysregulation in gamma band activity in schizophrenia. These findings open several promising research avenues that have not been thoroughly explored. What are the effects of sleep or REM sleep deprivation on these RAS mechanisms? Are these mechanisms involved in memory processing during waking and/or during REM sleep? Does gamma band processing differ during waking vs REM sleep after sleep or REM sleep deprivation? PMID:24309750

  10. Rock Garden

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This false color composite image of the Rock Garden shows the rocks 'Shark' and 'Half Dome' at upper left and middle, respectively. Between these two large rocks is a smaller rock (about 0.20 m wide, 0.10 m high, and 6.33 m from the Lander) that was observed close-up with the Sojourner rover (see PIA00989).

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

  11. Mechanical Activation of Construction Binder Materials by Various Mills

    NASA Astrophysics Data System (ADS)

    Fediuk, R. S.

    2016-04-01

    The paper deals with the mechanical grinding down to the nano powder of construction materials. During mechanical activation a composite binder active molecules cement minerals occur in the destruction of the molecular defects in the areas of packaging and breaking metastable phase decompensation intermolecular forces. The process is accompanied by a change in the kinetics of hardening of portland cement. Mechanical processes during grinding mineral materials cause, along with the increase in their surface energy, increase the Gibbs energy of powders and, respectively, their chemical activity, which also contributes to the high adhesion strength when contacting them with binders. Thus, the set of measures for mechanical activation makes better use of the weight of components filled with cement systems and adjust their properties. At relatively low cost is possible to provide a spectacular and, importantly, easily repeatable results in a production environment.

  12. Investigation of oxidation process of mechanically activated ultrafine iron powders

    NASA Astrophysics Data System (ADS)

    Lysenko, E. N.; Nikolaev, E. V.; Vlasov, V. A.; Zhuravkov, S. P.

    2016-02-01

    The oxidation of mechanically activated ultrafine iron powders was studied using X- ray powder diffraction and thermogravimetric analyzes. The powders with average particles size of 100 nm were made by the electric explosion of wire, and were subjected to mechanical activation in planetary ball mill for 15 and 40 minutes. It was shown that a certain amount of FeO phase is formed during mechanical activation of ultrafine iron powders. According to thermogravimetric analysis, the oxidation process of non-milled ultrafine iron powders is a complex process and occurs in three stages. The preliminary mechanical activation of powders considerably changes the nature of the iron powders oxidation, leads to increasing in the temperature of oxidation onset and shifts the reaction to higher temperatures. For the milled powders, the oxidation is more simple process and occurs in a single step.

  13. Calcineurin/NFAT Activation-Dependence of Leptin Synthesis and Vascular Growth in Response to Mechanical Stretch

    PubMed Central

    Soudani, Nadia; Ghantous, Crystal M.; Farhat, Zein; Shebaby, Wassim N.; Zibara, Kazem; Zeidan, Asad

    2016-01-01

    Background and Aims: Hypertension and obesity are important risk factors of cardiovascular disease. They are both associated with high leptin levels and have been shown to promote vascular hypertrophy, through the RhoA/ROCK and ERK1/2 phosphorylation. Calcineurin/NFAT activation also induces vascular hypertrophy by upregulating various genes. This study aimed to decipher whether a crosstalk exists between the RhoA/ROCK pathway, Ca2+/calcineurin/NFAT pathway, and ERK1/2 phosphorylation in the process of mechanical stretch-induced vascular smooth muscle cell (VSMC) hypertrophy and leptin synthesis. Methods and Results: Rat portal vein (RPV) organ culture was used to investigate the effect of mechanical stretch and exogenous leptin (3.1 nM) on VSMC hypertrophy and leptin synthesis. Results showed that stretching the RPV significantly upregulated leptin secretion, mRNA, and protein expression, which were inhibited by the calcium channel blocker nifedipine (10 μM), the selective calcineurin inhibitor FK506 (1 nM), and the ERK1/2 inhibitor PD98059 (1 μM). The transcription inhibitor actinomycin D (0.1 μM) and the translation inhibitor cycloheximide (1 mM) significantly decreased stretch-induced leptin protein expression. Mechanical stretch or leptin caused an increase in wet weight changes and protein synthesis, considered as hypertrophic markers, while they were inhibited by FK506 (0.1 nM; 1 nM). In addition, stretch or exogenous leptin significantly increased calcineurin activity and MCIP1 expression whereas leptin induced NFAT nuclear translocation in VSMCs. Moreover, in response to stretch or exogenous leptin, the Rho inhibitor C3 exoenzyme (30 ng/mL), the ROCK inhibitor Y-27632 (10 μM), and the actin depolymerization agents Latrunculin B (50 nM) and cytochalasin D (1 μM) reduced calcineurin activation and NFAT nuclear translocation. ERK1/2 phosphorylation was inhibited by FK506 and C3. Conclusions: Mechanical stretch-induced VSMC hypertrophy and leptin

  14. FTY720 Phosphate Activates Sphingosine-1-Phosphate Receptor 2 and Selectively Couples to Gα12/13/Rho/ROCK to Induce Myofibroblast Contraction.

    PubMed

    Sobel, Katrin; Monnier, Lucile; Menyhart, Katalin; Bolinger, Matthias; Studer, Rolf; Nayler, Oliver; Gatfield, John

    2015-06-01

    FTY720 phosphate (FTY720-P; 2-amino-2-[2-(4-octylphenyl)ethyl]-1,3-propanediol, monodihydrogen phosphate ester) is a nonselective sphingosine-1-phosphate (S1P) receptor agonist thought to be devoid of activity at the S1P2 receptor subtype. However, we have recently shown that FTY720-P displays significant S1P2 receptor agonist activity in recombinant cells and fibroblasts expressing endogenous S1P2 receptors. To elucidate the S1P2-dependent signaling pathways that were activated by FTY720-P, we employed second messenger assays and impedance-based assays in combination with pharmacological and small interfering RNA-based pathway inhibition in recombinant Chinese hamster ovary (CHO)-S1P2 cells as well as human lung myofibroblasts generated in vitro. In CHO-S1P2 cells, FTY720-P did not modulate cAMP or calcium levels. However, reporter-gene assays, impedance-based assays with a selective Rho-associated kinase (ROCK) inhibitor, Gα12/13 knockdown and activated Rho-pull-down assays demonstrated that FTY720-P potently activated Gα12/13/Rho/ROCK signaling. S1P similarly activated Gα12/13/Rho/ROCK signaling via S1P2 receptors, whereas the two selective S1P1 receptor agonists (Z,Z)-5-(3-chloro-4-[(2R)-2,3-dihydroxy-propoxy]-benzylidene)-2-propylimino-3-o-tolyl-thiazolidin-4-one (ponesimond) and 5-[4-phenyl-5-(trifluoromethyl)thiophen-2-yl]-3-[3-(trifluoromethyl)phenyl]1,2,4-oxadiazole (SEW2871) were inactive. In lung myofibroblasts, which mainly expressed the S1P2 receptor subtype, we showed that FTY720-P selectively activated the Gα12/13/Rho/ROCK pathway via the S1P2 receptor. Moreover, the activation of the Gα12/13/Rho/ROCK pathway in myofibroblasts by FTY720-P caused potent myofibroblast contraction similar to that induced by the natural ligand S1P. Thus, complementing second messenger assays with unbiased label-free assays or phenotypic assays in native expression systems can uncover activation of additional pathways, such as Gα12/13/Rho/ROCK signaling.

  15. Microhabitat resource use, activity patterns, and episodic catastrophe: Conus on tropical intertidal reef rock benches

    SciTech Connect

    Leviten, P.J.; Kohn, A.J.

    1980-03-01

    Low species richness (five to nine species) and high population density (means of 0.2-8.6 individuals per square metre) characterize Conus assemblages on intertidal benches throughout the tropical Indo-West Pacific region. Data from 16 such habitats in Hawaii, Marshall Islands, Australia, Maldives, and Seychelles indicate that similarity of microhabitats between species is equal to or greater than random expectation. Significant between-species differences in zonation pattern occur across benches at a given time and place. The peak of C. ebraeus abundance typically occurs closest to shore; C. chaldaeus and C. sponsalis are usually most distant from shore. However, we found about as many significant within-species differences between censuses made at different times on the same bench as between-species differences within censuses. Co-occurring species thus tend not to use microhabitat resources differentially. Physical environmental variables including tide level, strength of water flow and time of day determine refuging and foraging activity patterns, and all species apear to respond similarly to these factors. The data thus do not support the hypothesis of temporal resource partitioning. We found evidence neither for homing, as mark-recapture results suggested that individuals occupy any convenient refuge after foraging, nor for interference competition for protected sites among Conus. Conus species diversity is significantly correlated with (1) substrate topographic diversity measured either independently or as the diversity of microhabitats utilized by all species together, and (2) the proportion of individuals occupying protected sites.

  16. Prolonged rock climbing activity induces structural changes in cerebellum and parietal lobe.

    PubMed

    Di Paola, Margherita; Caltagirone, Carlo; Petrosini, Laura

    2013-10-01

    This article analyzes whether climbing, a motor activity featured by upward movements by using both feet and hands, generation of new strategies of motor control, maintenance of not stable equilibrium and adoption of long-lasting quadrupedal posture, is able to modify specific brain areas. MRI data of 10 word-class mountain climbers (MC) and 10 age-matched controls, with no climbing experience were acquired. Combining region-of-interest analyses and voxel-based morphometry we investigated cerebellar volumes and correlation between cerebellum and whole cerebral gray matter. In comparison to controls, world-class MC showed significantly larger vermian lobules I-V volumes, with no significant difference in other cerebellar vermian lobules or hemispheres. The cerebellar enlargement was associated with an enlargement of right medial posterior parietal area. The specific features of the motor climbing skills perfectly fit with the plastic anatomical changes we found. The enlargement of the vermian lobules I-V seems to be related to highly dexterous hand movements and to eye-hand coordination in the detection of and correction of visuomotor errors. The concomitant enlargement of the parietal area is related to parallel work in predicting sensory consequences of action to make movement corrections. Motor control and sensory-motor prediction of actions make the difference between survive or not at extreme altitude.

  17. Neutron activation and other analytical data for plutonic rocks from North America and Africa. National Uranium Resource Evaluation

    SciTech Connect

    Price, V.; Fay, W.M.; Cook, J.R.

    1982-09-01

    The objective of this report is to retrieve the elements of an analytical study of granites and associated other plutonic rocks which was begun as a part of the U.S. Department of Energy's National Uranium Resource Evaluation (NURE) program. A discussion of the Savannah River Laboratory (SRL) neutron activation analysis system is given so that a user will understand the linmitations of the data. Enough information is given so that an experienced geochemist can clean up the data set to the extent required by any project. The data are generally good as they are presented. It is intended that the data be read from a magnetic tape written to accompany this report. Microfiche tables of the data follow the text. These tables were prepared from data on the tape, and programs which will read the tape are presented in the section THE DATA TAPE. It is our intent to write a later paper which will include a thoroughly scrubbed data set and a technical discussion of results of the study. 1 figure.

  18. Geomorphological activity at a rock glacier front detected with a 3D density-based clustering algorithm

    NASA Astrophysics Data System (ADS)

    Micheletti, Natan; Tonini, Marj; Lane, Stuart N.

    2017-02-01

    Acquisition of high density point clouds using terrestrial laser scanners (TLSs) has become commonplace in geomorphic science. The derived point clouds are often interpolated onto regular grids and the grids compared to detect change (i.e. erosion and deposition/advancement movements). This procedure is necessary for some applications (e.g. digital terrain analysis), but it inevitably leads to a certain loss of potentially valuable information contained within the point clouds. In the present study, an alternative methodology for geomorphological analysis and feature detection from point clouds is proposed. It rests on the use of the Density-Based Spatial Clustering of Applications with Noise (DBSCAN), applied to TLS data for a rock glacier front slope in the Swiss Alps. The proposed methods allowed the detection and isolation of movements directly from point clouds which yield to accuracies in the following computation of volumes that depend only on the actual registered distance between points. We demonstrated that these values are more conservative than volumes computed with the traditional DEM comparison. The results are illustrated for the summer of 2015, a season of enhanced geomorphic activity associated with exceptionally high temperatures.

  19. Processes, mechanisms, parameters, and modeling approaches for partially saturated flow in soil and rock media; Yucca Mountain Site Characterization Project

    SciTech Connect

    Wang, J.S.Y.; Narasimhan, T.N.

    1993-06-01

    This report discusses conceptual models and mathematical equations, analyzes distributions and correlations among hydrological parameters of soils and tuff, introduces new path integration approaches, and outlines scaling procedures to model potential-driven fluid flow in heterogeneous media. To properly model the transition from fracture-dominated flow under saturated conditions to matrix-dominated flow under partially saturated conditions, characteristic curves and permeability functions for fractures and matrix need to be improved and validated. Couplings from two-phase flow, heat transfer, solute transport, and rock deformation to liquid flow are also important. For stochastic modeling of alternating units of welded and nonwelded tuff or formations bounded by fault zones, correlations and constraints on average values of saturated permeability and air entry scaling factor between different units need to be imposed to avoid unlikely combinations of parameters and predictions. Large-scale simulations require efficient and verifiable numerical algorithms. New path integration approaches based on postulates of minimum work and mass conservation to solve flow geometry and potential distribution simultaneously are introduced. This verifiable integral approach, together with fractal scaling procedures to generate statistical realizations with parameter distribution, correlation, and scaling taken into account, can be used to quantify uncertainties and generate the cumulative distribution function for groundwater travel times.

  20. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Synchronization of Local Oscillations in a Spatial Rock-Scissors-Paper Game Model

    NASA Astrophysics Data System (ADS)

    Sun, Rong-Sheng; Hua, Da-Yin

    2009-08-01

    We study a spatial rock-scissors-paper model in a square lattice and a quenched small-world network. The system exhibits a global oscillation in the quenched small-world network, but the oscillation disappears in the square lattice. We find that there is a local oscillation in the square lattice the same as in the quenched small-world network. We define (where di is the density of a kind of species and langledirangle is the average value) as the variance of the oscillation amplitude in a certain local patch. It is found that s decays in a power law with an increase of the local patch size R in the square lattice σ propto R-δ, but it remains constant with an increase of the patch size in the quenched small-world network. We can speculate that in the square lattice, superposition between the local oscillations in different patches leads to global stabilization, while in the quenched small-world network, long-range interactions can synchronize the local oscillations, and their coherence results in the global oscillation.

  1. Rock `N' Rho in Outer Hair Cell Motility

    NASA Astrophysics Data System (ADS)

    Zhang, M.; Kalinec, G.; Kalinec, F.; Billadeau, D. D.; Urrutia, R.

    2003-02-01

    RhoA, Cdc42 and Rac1, small GTPases of the Rho family, are crucial regulators of the actin cytoskeleton and mediate different types of cell motility. They also help to maintain cellular homeostasis, actively regulating the structure and mechanical properties of the cells. We investigated the expression in the guinea-pig cochlea of the serine/threonine kinase ROCK, a well-known effector of RhoA, and measured electromotile amplitude in outer hair cells (OHCs) internally perfused with C3 and Y-27632, pharmacological inhibitors of RhoA and ROCK respectively, and dominant-negative mutants of Rac1 and Cdc42. We found that a RhoA/ROCK-mediated signaling pathway is important for mechanical homeostasis of cochlear OHCs, and identified ROCK as a potential target to selectively modulate outer hair cell electromotility.

  2. Tractor Mechanics: Learning Activity Packages 1-19.

    ERIC Educational Resources Information Center

    Clemson Univ., SC. Vocational Education Media Center.

    Learning activity packages are presented for teaching tractor mechanics. The first of two sections deals with miscellaneous tasks and contains learning activity packages on cleaning the tractor and receiving new tractor parts. Section 2 is concerned with maintaining and servicing the electrical system, and it includes the following learning…

  3. Calc-alkaline mafic rocks of the Black Dyke Formation: Remnants of the final activity of a submerged Permian volcano

    SciTech Connect

    Blein, O.; Lapierre, H.; Pecher, A. ); Schweickert, R.A. . Dept. of Geological Science)

    1993-04-01

    The Permian Black Dyke Fm., which occurs as large tectonic slices within the Luning allochthon in the Excelsior Mountains, NV, forms an E-W trending anticline at Black Dyke Mountain. The 800-m thick stratigraphic succession consists of volcanic and pyroclastic rocks overlain conformably by volcaniclastic sediments. Along the northern limb of the anticline, the rocks consist of mafic porphyritic lavas, breccias, and graded and ungraded pyroclastic beds. The sedimentary unit consists of thick volcaniclastic turbidites overlain by conglomerates, sandstones, and mudstones. Along the southern limb of the anticline, the sequence is replaced by reworked breccia, tuffs, and sandstones. Mafic plutonic rocks occur as xenoliths in the lavas and breccias, and as coeval plugs intruding the section. Gabbros show cumulate or porphyritic textures and are composed of amph, cpx, and zoned plag. Their Ti/V (14.5--15) and Nb/Y (0.25--0.3) ratios fall in the range commonly found in calc-alkaline rocks. Diorite porphyry shows high Al[sub 2]O[sub 3], ZrO[sub 2], and REE abundances indicating that this rock is more fractionated. Basalts and andesites are plag-cpx-opx phyric. They often include glomeroporphyritic clots of cpx with amph coronas. Some rocks exhibit fluidal textures. Both volcanic and plutonic rocks show homogeneous geochemical features and similar crystallization sequences: Fe-Ti oxides---->plag---->opx + cpx----> brown zoned hbl, suggesting that they are cogenetic. Thus, the lower part of the Black Dyke Fm. likely represents the final products formed in a calc-alkaline magma chamber because pyroclastic rocks prevail over lava flows and abundant early crystal cumulates occur as plugs or as inclusions in the lavas and breccias.

  4. Active control of wing rock of a delta wing at post-stall using tangential leading edge blowing

    NASA Technical Reports Server (NTRS)

    Wong, G. S.; Rock, S. M.; Wood, N. J.; Roberts, L.

    1993-01-01

    Post-stall roll control utilizing tangential leading edge blowing is demonstrated in a wind tunnel on a delta wing model that exhibited wing rock. The dampening effect of symmetric blowing alone on wing rock is found to be effective up to a certain maximum amount of blowing. A moderate amount of symmetric blowing was shown to be effective in linearizing the asymmetric blowing static rolling moment responses.

  5. RhoB/ROCK mediates oxygen-glucose deprivation-stimulated syncytiotrophoblast microparticle shedding in preeclampsia.

    PubMed

    Han, Jian; Yang, Bo-Ping; Li, Yi-Lin; Li, Hong-Mei; Zheng, Xiu-Hui; Yu, Li-Li; Zhang, Qiong; Zheng, Ying-Ru; Yi, Ping; Li, Li; Guo, Jian-Xin; Zhou, Yuan-Guo

    2016-11-01

    Increased circulating syncytiotrophoblast microparticles (STBMs) are often associated with preeclampsia (PE) but the molecular mechanisms regulating STBM shedding remain elusive. Experimental evidence has shown that actin plays a key role in STBM shedding and that Rho/ROCK is important in regulating actin rearrangement. To investigate the role of RhoB/ROCK-regulated actin arrangement in STBM shedding in PE, chorionic villous explants were prepared from placenta of patients with normotensive or PE pregnancies and BeWo cells were fused to imitate syncytiotrophoblasts. The oxygen-glucose deprivation (OGD) conditions were applied to imitate the pathophysiology of PE in vitro. The results showed that RhoB and ROCK were activated in the preeclamptic placenta, accompanied by increased actin polymerization and decreased outgrowing microvilli. In villous tissue cultures or BeWo cells, OGD activated RhoB, ROCK1 and ROCK2 and promoted STBM shedding and actin stress fibers formation. In BeWo cells, RhoB overexpression activated ROCK1 and ROCK2, leading to F-actin redistribution and STBM shedding and the OGD-induced actin polymerization and STBM shedding could be reversed by RhoB or ROCK knockdown. These results reveal that RhoB and ROCK play a key role in PE by targeting STBM shedding through actin rearrangement and that RhoB/ROCK intervention may be a potential therapeutic strategy for PE.

  6. Deriving mechanisms and thresholds for cliff retreat in soft-rock cliffs under changing climates: Rapidly retreating cliffs of the Suffolk coast, UK

    NASA Astrophysics Data System (ADS)

    Brooks, S. M.; Spencer, T.; Boreham, S.

    2012-06-01

    Understanding changing thresholds and mechanisms for retreat in soft rock cliffs is important under changing climates. This can be achieved through combining detailed field observation, long-term process and morphological monitoring and numerical modelling. The cliffs of the Suffolk coast, southern North Sea have exhibited long-term (1883-2010) recession rates of 3.5 m a- 1, rising to 4.7 m a- 1 in the period 1993-2010. Annual to biannual ground survey data, and the application of GIS techniques to digitised records of changing shoreline position from historic maps and aerial photography, reveal considerable decadal-scale variations in cliff recession, within which are nested inter-annual fluctuations in rates of retreat. Archival datasets on significant periods of onshore winds and their interaction with high water levels (including the incidence of storm surges) and rainstorm events are used to determine thresholds for cliff base erosion and its propagation upwards through the cliff profile. In addition, the ‘GEO-Slope' dynamic coupled hydrology-stability model is used to establish thresholds for cliff face failures driven by variations in rainfall inputs. Retreat mechanisms are complex, governed by cliff geology, both as a primary control on suction loss and through its interaction with basal marine conditions. The study allows a general model of cliff retreat for soft rock cliffs to be put forward, whereby a resistant basal platform is overlain by more erodible, weakly and moderately cemented sands and gravels. In this model, the varying balance between marine and terrestrial forcing factors are reflected in low (< 4 m a- 1), intermediate (4-7 m a- 1) and high (> 7 m a- 1) modes of cliff retreat.

  7. 'Wopmay' Rock

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This approximate true-color image taken by NASA's Mars Exploration Rover Opportunity shows an unusual, lumpy rock informally named 'Wopmay' on the lower slopes of 'Endurance Crater.' The rock was named after the Canadian bush pilot Wilfrid Reid 'Wop' May. Like 'Escher' and other rocks dotting the bottom of Endurance, scientists believe the lumps in Wopmay may be related to cracking and alteration processes, possibly caused by exposure to water. The area between intersecting sets of cracks eroded in a way that created the lumpy appearance. Rover team members plan to drive Opportunity over to Wopmay for a closer look in coming sols. This image was taken by the rover's panoramic camera on sol 248 (Oct. 4, 2004), using its 750-, 530- and 480-nanometer filters.

  8. Effect of Weathering Processes on Mineralogical and Mechanical Properties of Volcanic Rocks Used as Ballast Material for Railway Between Sabuncupinar and Kütahya in Western Turkey

    NASA Astrophysics Data System (ADS)

    Abiddin Erguler, Zeynal; Adıgüzel, Ömer; Derman, Mustafa

    2015-04-01

    Geomaterials used in engineering projects and man-made structures such as railway ballasts, buildings, historical structures, monuments and tombstones naturally weather as a result of various physico-chemical factors. Due to being long-term exposure to the anthroposphere, geomaterials used for these purposes provides important information to the researchers for understanding the effect of weathering processes on their time dependent physical, mineralogical and mechanical changes. Thus, researchers frequently can take advantage of available engineering time of man-made structures to assess weathering properties of the geomaterials used in their construction in terms of time dependent durability and stability of these structures. Considering the fact that railway ballasts produced from natural deposits of limestone, dolomite, granite, basalt etc., supply an important contribution for evaluation weathering processes, a research was carried out to determine the effect of weathering as a function of time on physical, mineralogical and mechanical properties of ballasts used for railway between Kütahya and Sabuncupınar in western Turkey. For this purpose, fresh and weathered rock samples exposed to physical and chemical weathering processes at different times were collected from quarry located in Sabuncupınar and nearby railway. This volcanic rock was previously classified as basalt based on the detailed mineralogical and geochemical analyses performed at the laboratories of the Mineral Research & Exploration General Directorate located in Ankara (Turkey). In-situ characteristics of sampling site were also investigated at different locations of quarry site by line surveying technique to describe the influence of discontinuity conditions on the weathering rate of selected rocks. Several techniques were utilized to determine time dependent deterioration in mineralogical and chemical composition of these samples for understanding their weathering rate. The porosity, water

  9. Predicting the Sources and Formation Mechanisms of Evolved Lunar Crust by Linking K/Ca Ratios of Lunar Granites to Analogous Terrestrial Igneous Rocks

    NASA Technical Reports Server (NTRS)

    Mills, R. D.; Simon, J. I.

    2012-01-01

    Although silicic rocks (i.e. granites and rhyolites) comprise a minor component of the sampled portion of the lunar crust, recent remote sensing studies [e.g., 1-4] indicate that several un-sampled regions of the Moon have significantly higher concentrations of silicic material (also high in [K], [U], and [Th]) than sampled regions. Within these areas are morphological features that are best explained by the existence of chemically evolved volcanic rocks. Observations of silicic domes [e.g., 1-5] suggest that sizable networks of silicic melt were present during crust formation. Isotopic data indicate that silicic melts were generated over a prolonged timespan from 4.3 to 3.9 Ga [e.g., 6-8]. The protracted age range and broad distribution of silicic rocks on the Moon indicate that their petrogenesis was an important mechanism for secondary crust formation. Understanding the origin and evolution of such silicic magmas is critical to determining the composition of the lunar crustal highlands and will help to distinguish between opposing ideas for the Moon's bulk composition and differentiation. The two main hypotheses for generating silicic melts on Earth are fractional crystallization or partial melting. On the Moon silicic melts are thought to have been generated during extreme fractional crystallization involving end-stage silicate liquid immiscibility (SLI) [e.g. 9, 10]. However, SLI cannot account for the production of significant volumes of silicic melt and its wide distribution, as reported by the remote global surveys [1, 2, 3]. In addition, experimental and natural products of SLI show that U and Th, which are abundant in the lunar granites and seen in the remote sensing data of the domes, are preferentially partitioned into the depolymerized ferrobasaltic magma and not the silicic portion [11, 12]. If SLI is not the mechanism that generated silicic magmas on the Moon then alternative processes such as fractional crystallization (only crystal

  10. Mechanical properties that influence antimicrobial peptide activity in lipid membranes.

    PubMed

    Marín-Medina, Nathaly; Ramírez, Diego Alejandro; Trier, Steve; Leidy, Chad

    2016-12-01

    Antimicrobial peptides are small amphiphilic proteins found in animals and plants as essential components of the innate immune system and whose function is to control bacterial infectious activity. In order to accomplish their function, antimicrobial peptides use different mechanisms of action which have been deeply studied in view of their potential exploitation to treat antibiotic-resistant bacterial infections. One of the main mechanisms of action of these peptides is the disruption of the bacterial membrane through pore formation, which, in some cases, takes place via a monomer to oligomer cooperative transition. Previous studies have shown that lipid composition, and the presence of exogenous components, such as cholesterol in model membranes or carotenoids in bacteria, can affect the potency of distinct antimicrobial peptides. At the same time, considering the membrane as a two-dimensional material, it has been shown that membrane composition defines its mechanical properties which might be relevant in many membrane-related processes. Nevertheless, the correlation between the mechanical properties of the membrane and antimicrobial peptide potency has not been considered according to the importance it deserves. The relevance of these mechanical properties in membrane deformation due to peptide insertion is reviewed here for different types of pores in order to elucidate if indeed membrane composition affects antimicrobial peptide activity by modulation of the mechanical properties of the membrane. This would also provide a better understanding of the mechanisms used by bacteria to overcome antimicrobial peptide activity.

  11. Evolution of Stiffness and Permeability in Fractures Subject to - and Mechanically-Activated Dissolution

    NASA Astrophysics Data System (ADS)

    Faoro, I.; Elsworth, D.; Candela, T.

    2013-12-01

    Strong feedbacks link thermal gradients (T), hydrologic flow (H), chemical alteration (C) and mechanical deformation (M) in fractured rock. These processes are strongly interconnected since one process effects the initiation and progress of another. Dissolution and precipitation of minerals are affected by temperature and stress, and can result in significant changes in permeability and solute transport characteristics. Understanding these couplings is important for oil, gas, and geothermal reservoir engineering and for waste disposal in underground repositories and reservoirs. In order to experimentally investigate the interactions between THCM processes in a natural stressed fracture, we report on heated ( up to 150C) flow-through experiments on fractured core samples of Westerly granite. These experiments are performed to examine the influence of thermally and mechanically activated dissolution on the mechanical (stress/strain) and transport (permeability) characteristics of fractures. The evolutions of both the permeability and stiffness of the sample are recorded as the experimental thermal conditions change and chemical alteration progresses. Furthermore efflux of dissolved mineral mass is measured periodically to provide a record of the net mass removal, to correlate this with observed changes in fracture aperture, defined by the flow test. During the experiments the fracture shows high hydraulic sensitivity to the changing conditions of stress and temperature. Significant variation of the effluent fluid chemistry is observed. We argue that the formation of clay (Kaolinite) is the main mechanism responsible for the permanent change in permeability recorded at higher confining stresses (40 MPa).

  12. Application of flexure structures to active and adaptive opto-mechanical mechanisms

    NASA Astrophysics Data System (ADS)

    Zago, Lorenzo; Genequand, Pierre M.; Kjelberg, Ivar; Morschel, Joseph

    1997-03-01

    Active and adaptive structures, also commonly called 'smart' structures, combine in one integrated system various functions such as load carrying and structural function, mechanical (cinematic) functions, sensing, control and actuating. Originally developed for high accuracy opto-mechanical applications, CSEM's technology of flexure structures and flexible mechanisms is particularly suited to solve many structural and mechanical issues found in such active/adaptive mechanisms. The paper illustrates some recent flexure structures developments at CSEM and outlines the comprehensive know-how involved in this technology. This comprises in particular the elaboration of optimal design guidelines, related to the geometry, kinematics and dynamics issues (for instance, the minimization of spurious high frequency effects), the evaluation and predictability of all performance quantities relevant to the utilization of flexure structures in space (reliability, fatigue, static and dynamic modeling, etc.). material issues and manufacturing procedures.

  13. Cellular and Molecular Mechanisms Underpinning Macrophage Activation during Remyelination

    PubMed Central

    Lloyd, Amy F.; Miron, Veronique E.

    2016-01-01

    Remyelination is an example of central nervous system (CNS) regeneration, whereby myelin is restored around demyelinated axons, re-establishing saltatory conduction and trophic/metabolic support. In progressive multiple sclerosis, remyelination is limited or fails altogether which is considered to contribute to axonal damage/loss and consequent disability. Macrophages have critical roles in both CNS damage and regeneration, such as remyelination. This diverse range in functions reflects the ability of macrophages to acquire tissue microenvironment-specific activation states. This activation is dynamically regulated during efficient regeneration, with a switch from pro-inflammatory to inflammation-resolution/pro-regenerative phenotypes. Although, some molecules and pathways have been implicated in the dynamic activation of macrophages, such as NFκB, the cellular and molecular mechanisms underpinning plasticity of macrophage activation are unclear. Identifying mechanisms regulating macrophage activation to pro-regenerative phenotypes may lead to novel therapeutic strategies to promote remyelination in multiple sclerosis. PMID:27446913

  14. Active vibration control using mechanical and electrical analogies

    NASA Astrophysics Data System (ADS)

    Torres-Perez, A.; Hassan, A.; Kaczmarczyk, S.; Picton, P.

    2016-05-01

    Mechanical-electrical analogous circuit models are widely used in electromechanical system design as they represent the function of a coupled electrical and mechanical system using an equivalent electrical system. This research uses electrical circuits to establish a discussion of simple active vibration control principles using two scenarios: an active vibration isolation system and an active dynamic vibration absorber (DVA) using a voice coil motor (VCM) actuator. Active control laws such as gain scheduling are intuitively explained using circuit analysis techniques. Active vibration control approaches are typically constraint by electrical power requirements. The electrical analogous is a fast approach for specifying power requirements on the experimental test platform which is based on a vibration shaker that provides the based excitation required for the single Degree- of-Freedom (1DoF) vibration model under study.

  15. Modeling Transport of Viruses in Fractured Rock

    NASA Astrophysics Data System (ADS)

    Sleep, B. E.; Mondal, P. K.

    2011-12-01

    Fractured rock aquifers are frequently used for water supply for human consumption. In many instances the fractured rock aquifers are vulnerable to contamination by pathogens, including viruses, due to co-location of on-site septic systems, wastewater discharges, biosolids and agricultural activities. Approximately half of the illnesses associated with groundwater consumption in the Unites States have been attributed to viral contamination. A number of these cases have been related to transport of viruses from septic systems to drinking water wells. Despite the potential for rapid transport of viruses through rock fractures to drinking water wells, the understanding of virus transport in fractured rock is limited. In particular, the impacts of virus size, fracture aperture variability and roughness, matrix porosity, groundwater velocity, and geochemical conditions have not been well studied. In this study, a multidimensional model for virus transport in variable aperture fractures is presented. The model is applied to laboratory experiments on transport of virus-sized latex microspheres (0.02 and 0.2 microns) and bacteriophages (MS2 and PR772) in artificially fractured dolomite rocks. In these experiments significant impacts of particle size, fracture characteristics, groundwater velocity, and geochemistry were observed. Given the variability in aperture distribution and associated spatial variation in groundwater flow field, one-dimensional models were not suitable for a comprehensive evaluation of the mechanisms governing the microsphere and bacteriophage transport. Various relationships for virus retention (attachment and detachment) are evaluated to provide insight into the governing processes in virus transport in fractured rock. In addition, the role of virus size, fracture aperture variability, fracture roughness, fracture surface charge, matrix porosity, groundwater velocity, and ionic strength in virus transport are evaluated. Scale-up to the field is

  16. Influence of F(OH)-1 substitution on the relative mechanical strength of rock-forming micas

    NASA Astrophysics Data System (ADS)

    Dahl, Peter S.; Dorais, Michael J.

    1996-05-01

    Microtextural and experimental studies have yielded conflicting data on the relative mechanical strengths of muscovite and biotite [Wilson and Bell, 1979; Kronenberg et al., 1990; Mares and Kronenberg, 1993]. We propose a crystal-chemical resolution to this conflict, namely, that (001) dislocation glide in biotite is rate-limited by its fluorine content. Significant F(OH)-1 substitution, and concomitant removal of hydroxyl H+ directed into the interlayer cavity, potentially increases mechanical strength of biotite in two ways: (1) it eliminates K+-H+ repulsion, thereby strengthening the interlayer bonds, and (2) it allows K+ to "sink" deeper into the interlayer cavity, the resultant geometry being less favorable to basal slip. In testing this hypothesis we analyzed the naturally deformed biotite studied by Wilson and Bell [1979] and documented its very low F content (XF ≤ 0.02) compared to that of the biotite experimentally deformed by Kronenberg et al. [1990]. Our model and the comparative XF data explain why the biotite of Wilson and Bell [1979] deformed more easily in nature than its coexisting muscovite, whereas the biotite of Kronenberg et al. [1990] was mechanically stronger than muscovite similarly deformed by Mares and Kronenberg [1993]. Our reconciliation of these otherwise conflicting results provides a framework for predicting mechanical strength of natural micas based upon the extent of their F(OH)-1 substitution. Our synthesis highlights the potential role of crystal chemistry in determining mechanical behavior in multicomponent mineral families. Further testing of crystal-chemical effects on rheology will require mineral specimens of both appropriate composition and sufficient size.

  17. Mechanisms of Activation of Voltage-Gated Potassium Channels

    PubMed Central

    Grizel, A. V.; Glukhov, G. S.; Sokolova, O. S.

    2014-01-01

    Voltage-gated potassium ion channels (Kv) play an important role in a variety of cellular processes, including the functioning of excitable cells, regulation of apoptosis, cell growth and differentiation, the release of neurotransmitters and hormones, maintenance of cardiac activity, etc. Failure in the functioning of Kv channels leads to severe genetic disorders and the development of tumors, including malignant ones. Understanding the mechanisms underlying Kv channels functioning is a key factor in determining the cause of the diseases associated with mutations in the channels, and in the search for new drugs. The mechanism of activation of the channels is a topic of ongoing debate, and a consensus on the issue has not yet been reached. This review discusses the key stages in studying the mechanisms of functioning of Kv channels and describes the basic models of their activation known to date. PMID:25558391

  18. Innovative Application of Mechanical Activation for Rare Earth Elements Recovering: Process Optimization and Mechanism Exploration

    PubMed Central

    Tan, Quanyin; Deng, Chao; Li, Jinhui

    2016-01-01

    With the rapidly expanding use of fluorescent lamps (FLs) and increasing interest in conservation and sustainable utilization of critical metals such as rare earth elements (REEs), the recovering of REEs from phosphors in waste FLs is becoming a critical environmental and economic issue. To effectively recycle REEs with metallurgical methods, mechanical activation by ball milling was introduced to pretreat the waste phosphors. This current study put the emphasis on the mechanical activation and leaching processes for REEs, and explored the feasibility of the method from both theoretical and practical standpoints. Results showed physicochemical changes of structural destruction and particle size reduction after mechanical activation, leading to the easy dissolution of REEs in the activated samples. Under optimal conditions, dissolution yields of 89.4%, 93.1% and 94.6% for Tb, Eu and Y, respectively, were achieved from activated waste phosphors using hydrochloric acid as the dissolution agent. The shrinking core model proved to be the most applicable for the leaching procedure, with an apparent activation energy of 10.96 ± 2.79 kJ/mol. This novel process indicates that mechanical activation is an efficient method for recovering REEs from waste phosphors, and it has promising potential for REE recovery with low cost and high efficiency. PMID:26819083

  19. Innovative Application of Mechanical Activation for Rare Earth Elements Recovering: Process Optimization and Mechanism Exploration

    NASA Astrophysics Data System (ADS)

    Tan, Quanyin; Deng, Chao; Li, Jinhui

    2016-01-01

    With the rapidly expanding use of fluorescent lamps (FLs) and increasing interest in conservation and sustainable utilization of critical metals such as rare earth elements (REEs), the recovering of REEs from phosphors in waste FLs is becoming a critical environmental and economic issue. To effectively recycle REEs with metallurgical methods, mechanical activation by ball milling was introduced to pretreat the waste phosphors. This current study put the emphasis on the mechanical activation and leaching processes for REEs, and explored the feasibility of the method from both theoretical and practical standpoints. Results showed physicochemical changes of structural destruction and particle size reduction after mechanical activation, leading to the easy dissolution of REEs in the activated samples. Under optimal conditions, dissolution yields of 89.4%, 93.1% and 94.6% for Tb, Eu and Y, respectively, were achieved from activated waste phosphors using hydrochloric acid as the dissolution agent. The shrinking core model proved to be the most applicable for the leaching procedure, with an apparent activation energy of 10.96 ± 2.79 kJ/mol. This novel process indicates that mechanical activation is an efficient method for recovering REEs from waste phosphors, and it has promising potential for REE recovery with low cost and high efficiency.

  20. Innovative Application of Mechanical Activation for Rare Earth Elements Recovering: Process Optimization and Mechanism Exploration.

    PubMed

    Tan, Quanyin; Deng, Chao; Li, Jinhui

    2016-01-28

    With the rapidly expanding use of fluorescent lamps (FLs) and increasing interest in conservation and sustainable utilization of critical metals such as rare earth elements (REEs), the recovering of REEs from phosphors in waste FLs is becoming a critical environmental and economic issue. To effectively recycle REEs with metallurgical methods, mechanical activation by ball milling was introduced to pretreat the waste phosphors. This current study put the emphasis on the mechanical activation and leaching processes for REEs, and explored the feasibility of the method from both theoretical and practical standpoints. Results showed physicochemical changes of structural destruction and particle size reduction after mechanical activation, leading to the easy dissolution of REEs in the activated samples. Under optimal conditions, dissolution yields of 89.4%, 93.1% and 94.6% for Tb, Eu and Y, respectively, were achieved from activated waste phosphors using hydrochloric acid as the dissolution agent. The shrinking core model proved to be the most applicable for the leaching procedure, with an apparent activation energy of 10.96 ± 2.79 kJ/mol. This novel process indicates that mechanical activation is an efficient method for recovering REEs from waste phosphors, and it has promising potential for REE recovery with low cost and high efficiency.

  1. RhoA/ROCK pathway activity is essential for the correct localization of the germ plasm mRNAs in zebrafish embryos.

    PubMed

    Miranda-Rodríguez, Jerónimo Roberto; Salas-Vidal, Enrique; Lomelí, Hilda; Zurita, Mario; Schnabel, Denhi

    2017-01-01

    Zebrafish germ plasm is composed of mRNAs such as vasa and nanos and of proteins such as Bucky ball, all of which localize symmetrically in four aggregates at the distal region of the first two cleavage furrows. The coordination of actin microfilaments, microtubules and kinesin is essential for the correct localization of the germ plasm. Rho-GTPases, through their effectors, coordinate cytoskeletal dynamics. We address the participation of RhoA and its effector ROCK in germ plasm localization during the transition from two- to eight-cell embryos. We found that active RhoA is enriched along the cleavage furrow during the first two division cycles, whereas ROCK localizes at the distal region of the cleavage furrows in a similar pattern as the germ plasm mRNAs. Specific inhibition of RhoA and ROCK affected microtubules organization at the cleavage furrow; these caused the incorrect localization of the germ plasm mRNAs. The incorrect localization of the germ plasm led to a dramatic change in the number of germ cells during the blastula and 24hpf embryo stages without affecting any other developmental processes. We demonstrate that the Rho/ROCK pathway is intimately related to the determination of germ cells in zebrafish embryos.

  2. Modulation of bone remodeling via mechanically activated ion channels

    NASA Technical Reports Server (NTRS)

    Duncan, Randall L. (Principal Investigator)

    1996-01-01

    A critical factor in the maintenance of bone mass is the physical forces imposed upon the skeleton. Removal of these forces, such as in a weightless environment, results in a rapid loss of bone, whereas application of exogenous mechanical strain has been shown to increase bone formation. Numerous flight and ground-based experiments indicate that the osteoblast is the key bone cell influenced by mechanical stimulation. Aside from early transient fluctuations in response to unloading, osteoclast number and activity seem unaffected by removal of strain. However, bone formation is drastically reduced in weightlessness and osteoblasts respond to mechanical strain with an increase in the activity of a number of second messenger pathways resulting in increased anabolic activity. Unfortunately, the mechanism by which the osteoblast converts physical stimuli into a biochemical message, a process we have termed biochemical coupling, remains elusive. Prior to the application of this grant, we had characterized a mechanosensitive, cation nonselective channel (SA-cat) in osteoblast-like osteosarcoma cells that we proposed is the initial signalling mechanism for mechanotransduction. During the execution of this grant, we have made considerable progress to further characterize this channel as well as to determine its role in the osteoblastic response to mechanical strain. To achieve these goals, we combined electrophysiologic techniques with cellular and molecular biology methods to examine the role of these channels in the normal function of the osteoblast in vitro.

  3. Classic Rock

    ERIC Educational Resources Information Center

    Beem, Edgar Allen

    2004-01-01

    While "early college" programs designed for high-school-age students are beginning to proliferate nationwide, a small New England school has been successfully educating teens for nearly four decades. In this article, the author features Simon's Rock, a small liberal arts college located in the Great Barrington, Massachusetts, that has…

  4. Risk Analysis and Prediction of Floor Failure Mechanisms at Longwall Face in Parvadeh-I Coal Mine using Rock Engineering System (RES)

    NASA Astrophysics Data System (ADS)

    Aghababaei, Sajjad; Saeedi, Gholamreza; Jalalifar, Hossein

    2016-05-01

    The floor failure at longwall face decreases productivity and safety, increases operation costs, and causes other serious problems. In Parvadeh-I coal mine, the timber is used to prevent the puncture of powered support base into the floor. In this paper, a rock engineering system (RES)-based model is presented to evaluate the risk of floor failure mechanisms at the longwall face of E 2 and W 1 panels. The presented model is used to determine the most probable floor failure mechanism, effective factors, damaged regions and remedial actions. From the analyzed results, it is found that soft floor failure is dominant in the floor failure mechanism at Parvadeh-I coal mine. The average of vulnerability index (VI) for soft, buckling and compressive floor failure mechanisms was estimated equal to 52, 43 and 30 for both panels, respectively. By determining the critical VI for soft floor failure mechanism equal to 54, the percentage of regions with VIs beyond the critical VI in E 2 and W 1 panels is equal to 65.5 and 30, respectively. The percentage of damaged regions showed that the excess amount of used timber to prevent the puncture of weak floor below the powered support base is equal to 4,180,739 kg. RES outputs and analyzed results showed that setting and yielding load of powered supports, length of face, existent water at face, geometry of powered supports, changing the cutting pattern at longwall face and limiting the panels to damaged regions with supercritical VIs could be considered to control the soft floor failure in this mine. The results of this research could be used as a useful tool to identify the damaged regions prior to mining operation at longwall panel for the same conditions.

  5. Small molecules reveal an alternative mechanism of Bax activation

    PubMed Central

    Brahmbhatt, Hetal; Uehling, David; Al-awar, Rima; Leber, Brian; Andrews, David

    2016-01-01

    The pro-apoptotic protein Bax commits a cell to death by permeabilizing the mitochondrial outer membrane (MOM). To obtain small-molecule probes for elucidating the molecular mechanism(s) of Bax activation, we screened for compounds that induced Bax-mediated liposome permeabilization. We identified five structurally different small molecules that promoted both Bax targeting to and oligomerization at membranes. All five compounds initiated Bax oligomerization in the absence of membranes by a mechanism unlike Bax activation by Bcl-2 homology 3 domain (BH3) proteins. Some of the compounds induced Bax/Bak-dependent apoptosis in cells. Activation of Bax by the most active compound was poorly inhibited by the anti-apoptotic protein Bcl-XL and requires a cysteine residue at position 126 of Bax that is not required for activation by BH3 proteins. Our results reveal a novel pathway for Bax activation independent of pro-apoptotic BH3 proteins that may have important implications for the regulation of Bax activity in cells. PMID:26916338

  6. Application of epithermal neutron activation in multielement analysis of silicate rocks employing both coaxial Ge(Li) and low energy photon detector systems

    USGS Publications Warehouse

    Baedecker, P.A.; Rowe, J.J.; Steinnes, E.

    1977-01-01

    The instrumental activation analysis of silicate rocks using epithermal neutrons has been studied using both high resolution coaxial Ge(Li) detectors and low energy photon detectors, and applied to the determination of 23 elements in eight new U.S.G.S. standard rocks. The analytical use X-ray peaks associated with electron capture or internal conversion processes has been evaluated. Of 28 elements which can be considered to be determinable by instrumental means, the epithermal activation approach is capable of giving improved sensitivity and precision in 16 cases, over the normal INAA procedure. In eleven cases the use of the low energy photon detector is thought to show advantages over convertional coaxial Ge(Li) spectroscopy. ?? 1977 Akade??miai Kiado??.

  7. The mechanical and tribological properties of UHMWPE loaded ALN after mechanical activation for joint replacements.

    PubMed

    Gong, Kemeng; Qu, Shuxin; Liu, Yumei; Wang, Jing; Zhang, Yongchao; Jiang, Chongxi; Shen, Ru

    2016-08-01

    Ultra-high molecular weight polyethylene (UHMWPE) loaded with alendronate sodium (ALN) has tremendous potential as an orthopeadic biomaterial for joint replacements. However, poor mechanical and tribological properties of UHMWPE-ALN are still obstacle for further application. The purpose of this study was to investigate the effect and mechanism of mechanical activation on mechanical and tribological properties of 1wt% ALN-loaded UHMWPE (UHMWPE-ALN-ma). In this study, tensile test, small punch test and reciprocating sliding wear test were applied to characterize the mechanical and tribological properties of UHMWPE-ALN-ma. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) were employed to characterize UHMWPE-ALN-ma. Tensile test and small punch test showed that Young׳s modulus, tensile strength and work-to-failure (WTF) of UHMWPE-ALN-ma increased significantly compared to those of UHMWPE-ALN. The friction coefficients and wear factors of UHMWPE-ALN-ma both decreased significantly compared to those of UHMWPE-ALN. Mechanical activation obviously reduced type 1 (void) and type 2 (the disconnected and dislocated machining marks) fusion defects of UHMWPE-ALN-ma, which were revealed by SEM images of freeze fracture surfaces after etching and lateral surfaces of specimens after extension to fracture, respectively. It was attributed to peeled-off layers and chain scission of molecular chains of UHMWPE particles after mechanical activation, which were revealed by SEM images and FTIR spectra of UHMWPE-ALN-ma and UHMWPE-ALN, respectively. Moreover, EDS spectra revealed the more homogeneous distribution of ALN in UHMWPE-ALN-ma compared to that of UHMWPE-ALN. The present results showed that mechanical activation was a potential strategy to improve mechanical and tribological properties of UHMWPE-ALN-ma as an orthopeadic biomaterial for joint replacements.

  8. Epithermal neutron activation, radiometric, correlation and principal component analysis applied to the distribution of major and trace elements in some igneous and metamorphic rocks from Romania.

    PubMed

    Cristache, C I; Duliu, O G; Culicov, O A; Frontasyeva, M V; Ricman, C; Toma, M

    2009-05-01

    Six major (Na, Al, K, Ca, Ti, Fe) and 28 trace (Sc, Cr, V, Mn, Co, Zn, Cu, As, Br, Sr, Rb, Zr, Mo, Sn, Sb, Ba, Cs, La, Ce, Nd, Eu, Sm, Tb, Hf, Ta, W, Th and U) elements were determined by epithermal neutron activation analysis (ENAA) in nine Meridional Carpathian and Macin Mountains samples of igneous and metamorphic rocks. Correlation and principal factor analysis were used to interpret data while natural radionuclides radiometry shows a good correlation with ENAA results.

  9. The microstructural character and evolution of fault rocks from the SAFOD core and potential weakening mechanisms along the San Andreas Fault (Invited)

    NASA Astrophysics Data System (ADS)

    Holdsworth, R. E.; van Diggelen, E.; Spiers, C.; de Bresser, J. H.; Smith, S. A.

    2009-12-01

    In the region of the SAFOD borehole, the San Andreas Fault (SAF) separates two very different geological terranes referred to here as the Salinian and Great Valley blocks (SB, GVB). The three sections of core preserve a diverse range of fault rocks and pass through the two currently active, highly localised slipping sections, the so-called ‘10480’ and ‘10830’ fault zones . These coincide with a broader region - perhaps as much as 100m wide - of high strain fault rocks formed at some time in the geological past, but now currently inactive. Both the slipping segments and older high strain zone(s) are developed in the GVB located NE of the terrane boundary. This is likely influenced by the phyllosilicate-rich protolith of the GVB and the large volume of trapped fluid known to exist NE and below the SAF in this region. Microstructurally, lower strain domains (most of Core 1 cutting the SB, significant parts of Core 3 cutting the GVB) preserve clear evidence for classic upper crustal cataclastic brittle faulting processes and associated fluid flow. The GVB in particular shows clear geological evidence for both fluid pressure and differential stress cycling (variable modes of hydrofacture associated with faults) during seismicity. There is also some evidence in all minor faults for the operation of limited amounts of solution-precipitation creep. High strain domains (much of Core 2 cutting the GVB, parts of Core 3 adjacent to the 10830 fault) are characterised by the development of foliated cataclasites and gouge largely due to the new growth of fine-grained phyllosilicate networks (predominantly smectite-bearing mixed layer clays, locally serpentinite, but not talc). The most deformed sections are characterised by the development of shear band fabrics and asymmetric folds. Reworking and reactivation is widespread manifested by: i) the preservation of one or more earlier generations of gouge preserved as clasts; and ii) by the development of later interconnected

  10. ROCK1 via LIM kinase regulates growth, maturation and actin based functions in mast cells

    PubMed Central

    Kapur, Reuben; Shi, Jianjian; Ghosh, Joydeep; Munugalavadla, Veerendra; Sims, Emily; Martin, Holly; Wei, Lei; Mali, Raghuveer Singh

    2016-01-01

    Understanding mast cell development is essential due to their critical role in regulating immunity and autoimmune diseases. Here, we show how Rho kinases (ROCK) regulate mast cell development and can function as therapeutic targets for treating allergic diseases. Rock1 deficiency results in delayed maturation of bone marrow derived mast cells (BMMCs) in response to IL-3 stimulation and reduced growth in response to stem cell factor (SCF) stimulation. Further, integrin-mediated adhesion and migration, and IgE-mediated degranulation are all impaired in Rock1-deficient BMMCs. To understand the mechanism behind altered mast cell development in Rock1−/− BMMCs, we analyzed the activation of ROCK and its downstream targets including LIM kinase (LIMK). We observed reduced activation of ROCK, LIMK, AKT and ERK1/2 in Rock1-deficient BMMCs in response to SCF stimulation. Further, loss of either Limk1 or Limk2 also demonstrated altered BMMC maturation and growth; combined deletion of both Limk1 and Limk2 resulted in further reduction in BMMC maturation and growth. In passive cutaneous anaphylaxis model, deficiency of Rock1 or treatment with ROCK inhibitor Fasudil protected mice against IgE-mediated challenge. Our results identify ROCK/LIMK pathway as a novel therapeutic target for treating allergic diseases involving mast cells. PMID:26943578

  11. Mechanisms of active control for noise inside a vibrating cylinder

    NASA Technical Reports Server (NTRS)

    Lester, Harold C.; Fuller, Chris R.

    1987-01-01

    The active control of propeller-induced noise fields inside a flexible cylinder is studied with attention given to the noise reduction mechanisms inherent in the present coupled acoustic shell model. The active noise control model consists of an infinitely long aluminum cylinder with a radius of 0.4 m and a thickness of 0.001 m. Pressure maps are shown when the two external sources are driven in-phase at a frequency corresponding to Omega = 0.22.

  12. Rock Pore Structure as Main Reason of Rock Deterioration

    NASA Astrophysics Data System (ADS)

    Ondrášik, Martin; Kopecký, Miloslav

    2014-03-01

    Crashed or dimensional rocks have been used as natural construction material, decoration stone or as material for artistic sculptures. Especially old historical towns not only in Slovakia have had experiences with use of stones for construction purposes for centuries. The whole buildings were made from dimensional stone, like sandstone, limestone or rhyolite. Pavements were made especially from basalt, andesite, rhyolite or granite. Also the most common modern construction material - concrete includes large amounts of crashed rock, especially limestone, dolostone and andesite. However, rock as any other material if exposed to exogenous processes starts to deteriorate. Especially mechanical weathering can be very intensive if rock with unsuitable rock properties is used. For long it had been believed that repeated freezing and thawing in relation to high absorption is the main reason of the rock deterioration. In Slovakia for many years the high water absorption was set as exclusion criterion for use of rocks and stones in building industry. Only after 1989 the absorption was accepted as merely informational rock property and not exclusion. The reason of the change was not the understanding of the relationship between the porosity and rock deterioration, but more or less good experiences with some high porous rocks used in constructions exposed to severe weather conditions and proving a lack of relationship between rock freeze-thaw resistivity and water absorption. Results of the recent worldwide research suggest that understanding a resistivity of rocks against deterioration is hidden not in the absorption but in the structure of rock pores in relation to thermodynamic properties of pore water and tensile strength of rocks and rock minerals. Also this article presents some results of research on rock deterioration and pore structure performed on 88 rock samples. The results divide the rocks tested into two groups - group N in which the pore water does not freeze

  13. Multivariable Dynamic Ankle Mechanical Impedance With Active Muscles

    PubMed Central

    Lee, Hyunglae; Krebs, Hermano Igo; Hogan, Neville

    2015-01-01

    Multivariable dynamic ankle mechanical impedance in two coupled degrees-of-freedom (DOFs) was quantified when muscles were active. Measurements were performed at five different target activation levels of tibialis anterior and soleus, from 10% to 30% of maximum voluntary contraction (MVC) with increments of 5% MVC. Interestingly, several ankle behaviors characterized in our previous study of the relaxed ankle were observed with muscles active: ankle mechanical impedance in joint coordinates showed responses largely consistent with a second-order system consisting of inertia, viscosity, and stiffness; stiffness was greater in the sagittal plane than in the frontal plane at all activation conditions for all subjects; and the coupling between dorsiflexion–plantarflexion and inversion–eversion was small—the two DOF measurements were well explained by a strictly diagonal impedance matrix. In general, ankle stiffness increased linearly with muscle activation in all directions in the 2-D space formed by the sagittal and frontal planes, but more in the sagittal than in the frontal plane, resulting in an accentuated “peanut shape.” This characterization of young healthy subjects’ ankle mechanical impedance with active muscles will serve as a baseline to investigate pathophysiological ankle behaviors of biomechanically and/or neurologically impaired patients. PMID:25203497

  14. Differential MSC activation leads to distinct mononuclear leukocyte binding mechanisms

    NASA Astrophysics Data System (ADS)

    Kota, Daniel J.; Dicarlo, Bryan; Hetz, Robert A.; Smith, Philippa; Cox, Charles S.; Olson, Scott D.

    2014-04-01

    Advances in the field of Multipotent Mesenchymal Stromal cell (MSC) biology have demonstrated that MSCs can improve disease outcome when `activated' to exert immunomodulatory effects. However, the precise mechanisms modulating MSC-immune cells interactions remain largely elusive. In here, we activated MSC based on a recent polarization paradigm, in which MSCs can be polarized towards a pro- or anti-inflammatory phenotype depending on the Toll-like receptor stimulated, to dissect the mechanisms through which MSCs physically interact with and modulate leukocytes in this context. Our data show that MSCs activated through the Toll-like receptor (TLR) 4 pathway increased VCAM-1 and ICAM-1 dependent binding of leukocytes. On the other hand, TLR3 stimulation strongly increases leukocytes affinity to MSC comparatively, through the formation of cable-like hyaluronic acid structures. In addition, TLR4 activation elicited secretion of pro-inflammatory mediators by MSCs, whereas TLR3-activated MSCs displayed a milder pro-inflammatory phenotype, similar to inactivated MSCs. However, the differently activated MSCs maintained their ability to suppress leukocyte activation at similar levels in our in vitro model, and this immunomodulatory property was shown here to be partially mediated by prostaglandin. These results reinforce the concept that alternate activation profiles control MSC responses and may impact the therapeutic use of MSCs.

  15. Rockin' around the Rock Cycle

    ERIC Educational Resources Information Center

    Frack, Susan; Blanchard, Scott Alan

    2005-01-01

    In this activity students will simulate how sedimentary rocks can be changed into metamorphic rocks by intense pressure. The materials needed are two small pieces of white bread, one piece of wheat bread, and one piece of a dark bread (such as pumpernickel or dark rye) per student, two pieces of waxed paper, scissors, a ruler, and heavy books.…

  16. The River Rock School.

    ERIC Educational Resources Information Center

    Gereaux, Teresa Thomas

    1999-01-01

    In the early 1920s, the small Appalachian community of Damascus, Virginia, used private subscriptions and volunteer labor to build a 15-classroom school made of rocks from a nearby river and chestnut wood from nearby forests. The school building's history, uses for various community activities, and current condition are described. (SV)

  17. Turning Bread into Rocks: A Multisensory Unit Opener.

    ERIC Educational Resources Information Center

    Smith, Shaw

    2000-01-01

    Presents an earth science activity on rocks to demonstrate the vital links between minerals and rocks. Uses different kinds of breads to demonstrate that rocks, like breads, are composed of various ingredients in different proportions. (ASK)

  18. Limit state for gas pressurized homogenous and inhomogenous media and rock. [Mechanical effects of high gas pressure applied to a porous, but only slightly permeable surface of a rock

    SciTech Connect

    Protosenya, A.G.; Chernikov, A.K.; Shirkes, O.A.; Stavrogin, A.N.

    1982-11-01

    The limiting strength state of gas-pressurized rock is examined in this paper. In experiments, pores of rock specimens were filled with gas. Tests of the influence of pore pressure on the magitude of the limiting strength of coal were made. The structure of a gas-pressurized porous medium is defined. The strain process is seen to exert influence on the magnitude of the porosity of the limiting state of the rock. The limiting state for plastic fracture is derived. The system of equations for the theory of the limiting strength state under plastic deformation follows. The Coulomb plasticity condition is introduced. The system of equations in inhomogenous media is also studied. Finally, a few simple solutions--stress distribution around circular holes, the elastic plastic problem--are given, to be used as component parts of more complex solutions.

  19. Poohbear Rock

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This image, taken by Sojourner's front right camera, was taken when the rover was next to Poohbear (rock at left) and Piglet (not seen) as it looked out toward Mermaid Dune. The textures differ from the foreground soil containing a sorted mix of small rocks, fines and clods, from the area a bit ahead of the rover where the surface is covered with a bright drift material. Soil experiments where the rover wheels dug in the soil revealed that the cloudy material exists underneath the drift.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

  20. White Rock

    NASA Technical Reports Server (NTRS)

    2002-01-01

    (Released 19 April 2002) The Science 'White Rock' is the unofficial name for this unusual landform which was first observed during the Mariner 9 mission in the early 1970's. As later analysis of additional data sets would show, White Rock is neither white nor dense rock. Its apparent brightness arises from the fact that the material surrounding it is so dark. Images from the Mars Global Surveyor MOC camera revealed dark sand dunes surrounding White Rock and on the floor of the troughs within it. Some of these dunes are just apparent in the THEMIS image. Although there was speculation that the material composing White Rock could be salts from an ancient dry lakebed, spectral data from the MGS TES instrument did not support this claim. Instead, the White Rock deposit may be the erosional remnant of a previously more continuous occurrence of air fall sediments, either volcanic ash or windblown dust. The THEMIS image offers new evidence for the idea that the original deposit covered a larger area. Approximately 10 kilometers to the southeast of the main deposit are some tiny knobs of similarly bright material preserved on the floor of a small crater. Given that the eolian erosion of the main White Rock deposit has produced isolated knobs at its edges, it is reasonable to suspect that the more distant outliers are the remnants of a once continuous deposit that stretched at least to this location. The fact that so little remains of the larger deposit suggests that the material is very easily eroded and simply blows away. The Story Fingers of hard, white rock seem to jut out like icy daggers across a moody Martian surface, but appearances can be deceiving. These bright, jagged features are neither white, nor icy, nor even hard and rocky! So what are they, and why are they so different from the surrounding terrain? Scientists know that you can't always trust what your eyes see alone. You have to use other kinds of science instruments to measure things that our eyes can

  1. Inter-seasonal surface deformations of an active rock glacier imaged with radar and lidar remote sensing; Turtmann valley, Switzerland

    NASA Astrophysics Data System (ADS)

    Kos, Andrew; Buchli, Thomas; Strozzi, Tazio; Springman, Sarah

    2013-04-01

    Inter-seasonal changes in surface deformation were imaged using a portable radar interferometer and terrestrial laser scanner during a series of three campaigns that took place in autumn 2011, summer 2012 and autumn 2012 on a rock glacier located in the Turtmann valley, Switzerland. Satellite radar interferometry (ERS 1 & 2, CosmoSkymed) indicate that accelerated downslope movement of the rock glacier commenced during the 1990s. Due to signal decorrelation associated with the satellite repeat pass time interval, continuous ground-based radar interferometry measurements were undertaken. Results show that the rock glacier accelerated significantly in Summer (Vmax = 6.0cm/25hrs), probably in response to the condition of the subsurface hydrology (e.g. post-peak spring snow melt and/or infiltration of rainfall). In autumn, the displacement velocity was reduced (Vmax = 2.0cm/25hrs). A one year surface difference of the glacier topography, derived from terrestrial laser scanning, provided insight into the rock glacier kinematics. Ongoing research is aimed at integrating surface displacement results with an extensive borehole monitoring system consisting of inclinometers and temperature sensors.

  2. Snow control on active layer and permafrost in steep alpine rock walls (Aiguille du Midi, 3842 m a.s.l, Mont Blanc massif)

    NASA Astrophysics Data System (ADS)

    Magnin, Florence; Westermann, Sebastian; Pogliotti, Paolo; Ravanel, Ludovic; Deline, Philip

    2016-04-01

    Permafrost degradation through the thickening of the active layer and the rising temperature at depth is a crucial process of rock wall stability. The ongoing increase in rock falls observed during hot periods in mid-latitude mountain ranges is regarded as a result of permafrost degradation. However, the short-term thermal dynamics of alpine rock walls are misunderstood since they result of complex processes related to the interaction of local climate variables, heterogeneous snow cover and heat transfers. As a consequence steady-state and long-term changes that can be approached with simpler process mainly related to air temperature, solar radiations and heat conduction were the most common dynamics to be studied so far. The effect of snow on the bedrock surface temperature is increasingly investigated and has already been demonstrated to be an essential factor of permafrost distribution. Nevertheless, its effect on the year-to-year changes of the active layer thickness and of the permafrost temperature in steep alpine bedrock has not been investigated yet, partly due to the lack of appropriate data. We explore the role of snow accumulations on the active layer and permafrost thermal regime of steep rock walls of a high-elevated site, the Aiguille du Midi (AdM, 3842 m a.s.l, Mont Blanc massif, Western European Alps) by mean of a multi-methods approach. We first analyse six years of temperature records in three 10-m-deep boreholes. Then we describe the snow accumulation patterns on two rock faces by means of automatically processed camera records. Finally, sensitivity analyses of the active layer thickness and permafrost temperature towards timing and magnitude of snow accumulations are performed using the numerical permafrost model CryoGrid 3. The energy balance module is forced with local meteorological measurements on the AdM S face and validated with surface temperature measurements at the weather station location. The heat conduction scheme is calibrated with

  3. Platelet activation through a Bi-leaflet mechanical heart valve

    NASA Astrophysics Data System (ADS)

    Hedayat, Mohammadali; Borazjani, Iman

    2016-11-01

    Platelet activation is one of the major drawbacks of the Mechanical Heart Valves (MHVs) which can increase the risk of thrombus formation in patients. The platelet activation in MHVs can be due to the abnormal shear stress during the systole, the backward leakage flow during the diastole, and the flow through the hinge region. We investigate the contribution of each of the above mechanism to the activation of platelets in MHVs by performing simulations of the flow through the MHV and in the hinge region. The large scale heart valve simulations are performed in a straight aorta using a sharp interface curvilinear immersed boundary method along with a strong-coupling algorithm under physiological flow conditions. In addition, in order to perform the simulation of hinge region the flow field boundary conditions are obtained from the largescale simulations during a whole cardiac cycle. In order to investigate the role of hinge flow on platelet activation in MHVs, a 23mm St. Jude Medical Regent valve hinge with three different gap sizes is tested along with different platelet activation models to ensure the consistency of our results with different activation models. We compare the platelet activation of the hinge region against the bulk of the flow during one cardiac cycle. This work is supported by the American Heart Association Grant 13SDG17220022, and the computational resources were partly provided by Center for Computational Research (CCR) at University at Buffalo.

  4. Platelet activation of mechanical versus bioprosthetic heart valves during systole.

    PubMed

    Hedayat, Mohammadali; Asgharzadeh, Hafez; Borazjani, Iman

    2017-03-11

    Thrombus formation is a major concern for recipients of mechanical heart valves (MHVs), which requires them to take anticoagulant drugs for the rest of their lives. Bioprosthetic heart valves (BHVs) do not require life-long anticoagulant therapy but deteriorate after 10-15years. The thrombus formation is initiated by the platelet activation which is thought to be mainly generated in MHVs by the flow through the hinge and the leakage flow during the diastole. However, our results show that the activation in the bulk flow during the systole phase might play an essential role as well. This is based on our results obtained by comparing the thrombogenic performance of a MHV and a BHV (as control) in terms of shear induced platelet activation under exactly the same conditions. Three different mathematical activation models including linear level of activation, damage accumulation, and Soares model are tested to quantify the platelet activation during systole using the previous simulations of the flow through MHV and BHV in a straight aorta under the same physiologic flow conditions. Results indicate that the platelet activation in the MHV at the beginning of the systole phase is slightly less than the BHV. However, at the end of the systole phase the platelet activation by the bulk flow for the MHV is several folds (1.41, 5.12, and 2.81 for linear level of activation, damage accumulation, and Soares model, respectively) higher than the BHV for all tested platelet activation models.

  5. Universal Hydrodynamic Mechanisms for Crystallization in Active Colloidal Suspensions

    NASA Astrophysics Data System (ADS)

    Singh, Rajesh; Adhikari, R.

    2016-11-01

    The lack of detailed balance in active colloidal suspensions allows dissipation to determine stationary states. Here we show that slow viscous flow produced by polar or apolar active colloids near plane walls mediates attractive hydrodynamic forces that drive crystallization. Hydrodynamically mediated torques tend to destabilize the crystal but stability can be regained through critical amounts of bottom heaviness or chiral activity. Numerical simulations show that crystallization is not nucleational, as in equilibrium, but is preceded by a spinodal-like instability. Harmonic excitations of the active crystal relax diffusively but the normal modes are distinct from an equilibrium colloidal crystal. The hydrodynamic mechanisms presented here are universal and rationalize recent experiments on the crystallization of active colloids.

  6. Structure and Mechanism of the Phosphotyrosyl Phosphatase Activator

    SciTech Connect

    Chao,Y.; Xing, Y.; Chen, Y.; Xu, Y.; Lin, Z.; Li, Z.; Jeffrey, P.; Stock, J.; Shi, Y.

    2006-01-01

    Phosphotyrosyl phosphatase activator (PTPA), also known as PP2A phosphatase activator, is a conserved protein from yeast to human. Here we report the 1.9 {angstrom} crystal structure of human PTPA, which reveals a previously unreported fold consisting of three subdomains: core, lid, and linker. Structural analysis uncovers a highly conserved surface patch, which borders the three subdomains, and an associated deep pocket located between the core and the linker subdomains. The conserved surface patch and the deep pocket are responsible for binding to PP2A and ATP, respectively. PTPA and PP2A A-C dimer together constitute a composite ATPase. PTPA binding to PP2A results in a dramatic alteration of substrate specificity, with enhanced phosphotyrosine phosphatase activity and decreased phosphoserine phosphatase activity. This function of PTPA strictly depends on the composite ATPase activity. These observations reveal significant insights into the function and mechanism of PTPA and have important ramifications for understanding PP2A function.

  7. Mechanisms underlying spontaneous patterned activity in developing neural circuits

    PubMed Central

    Blankenship, Aaron G.; Feller, Marla B.

    2010-01-01

    Patterned, spontaneous activity occurs in many developing neural circuits, including the retina, the cochlea, the spinal cord, the cerebellum and the hippocampus, where it provides signals that are important for the development of neurons and their connections. Despite differences in adult architecture and output across these various circuits, the patterns of spontaneous network activity and the mechanisms that generate it are remarkably similar and can include a depolarizing action of GABA, transient synaptic connections, extrasynaptic transmission, gap junction coupling and the presence of pacemaker-like neurons. Interestingly, spontaneous activity is robust; if one element of a circuit is disrupted another will generate similar activity. This research suggests that developing neural circuits exhibit transient and tunable features that maintain a source of correlated activity during critical stages of development. PMID:19953103

  8. A quantized mechanism for activation of pannexin channels

    PubMed Central

    Chiu, Yu-Hsin; Jin, Xueyao; Medina, Christopher B.; Leonhardt, Susan A.; Kiessling, Volker; Bennett, Brad C.; Shu, Shaofang; Tamm, Lukas K.; Yeager, Mark; Ravichandran, Kodi S.; Bayliss, Douglas A.

    2017-01-01

    Pannexin 1 (PANX1) subunits form oligomeric plasma membrane channels that mediate nucleotide release for purinergic signalling, which is involved in diverse physiological processes such as apoptosis, inflammation, blood pressure regulation, and cancer progression and metastasis. Here we explore the mechanistic basis for PANX1 activation by using wild type and engineered concatemeric channels. We find that PANX1 activation involves sequential stepwise sojourns through multiple discrete open states, each with unique channel gating and conductance properties that reflect contributions of the individual subunits of the hexamer. Progressive PANX1 channel opening is directly linked to permeation of ions and large molecules (ATP and fluorescent dyes) and occurs during both irreversible (caspase cleavage-mediated) and reversible (α1 adrenoceptor-mediated) forms of channel activation. This unique, quantized activation process enables fine tuning of PANX1 channel activity and may be a generalized regulatory mechanism for other related multimeric channels. PMID:28134257

  9. Insights into the Thiamine Diphosphate Enzyme Activation Mechanism: Computational Model for Transketolase Using a Quantum Mechanical/Molecular Mechanical Method.

    PubMed

    Nauton, Lionel; Hélaine, Virgil; Théry, Vincent; Hecquet, Laurence

    2016-04-12

    We propose the first computational model for transketolase (TK), a thiamine diphosphate (ThDP)-dependent enzyme, using a quantum mechanical/molecular mechanical method on the basis of crystallographic TK structures from yeast and Escherichia coli, together with experimental kinetic data reported in the literature with wild-type and mutant TK. This model allowed us to define a new route for ThDP activation in the enzyme environment. We evidenced a strong interaction between ThDP and Glu418B of the TK active site, itself stabilized by Glu162A. The crucial point highlighted here is that deprotonation of ThDP C2 is not performed by ThDP N4' as reported in the literature, but by His481B, involving a HOH688A molecule bridge. Thus, ThDP N4' is converted from an amino form to an iminium form, ensuring the stabilization of the C2 carbanion or carbene. Finally, ThDP activation proceeds via an intermolecular process and not by an intramolecular one as reported in the literature. More generally, this proposed ThDP activation mechanism can be applied to some other ThDP-dependent enzymes and used to define the entire TK mechanism with donor and acceptor substrates more accurately.

  10. GTPase regulation: getting aRnd Rock and Rho inhibition.

    PubMed

    Chardin, Pierre

    2003-09-16

    Rnd proteins are atypical members of the Rho small G protein family that inhibit the formation of actomyosin contractile fibers via activation of RhoGAPs and inhibition of a Rho effector, the Ser/Thr kinase Rock. These mechanisms might be used to fine-tune Rho GTPase inhibition locally at sites where particular actin structures need to be made.

  11. Diacylglycerol kinase ζ regulates RhoA activation via a kinase-independent scaffolding mechanism.

    PubMed

    Ard, Ryan; Mulatz, Kirk; Abramovici, Hanan; Maillet, Jean-Christian; Fottinger, Alexandra; Foley, Tanya; Byham, Michèle-Renée; Iqbal, Tasfia Ahmed; Yoneda, Atsuko; Couchman, John R; Parks, Robin J; Gee, Stephen H

    2012-10-01

    Rho GTPases share a common inhibitor, Rho guanine nucleotide dissociation inhibitor (RhoGDI), which regulates their expression levels, membrane localization, and activation state. The selective dissociation of individual Rho GTPases from RhoGDI ensures appropriate responses to cellular signals, but the underlying mechanisms are unclear. Diacylglycerol kinase ζ (DGKζ), which phosphorylates diacylglycerol to yield phosphatidic acid, selectively dissociates Rac1 by stimulating PAK1-mediated phosphorylation of RhoGDI on Ser-101/174. Similarly, phosphorylation of RhoGDI on Ser-34 by protein kinase Cα (PKCα) selectively releases RhoA. Here we show DGKζ is required for RhoA activation and Ser-34 phosphorylation, which were decreased in DGKζ-deficient fibroblasts and rescued by wild-type DGKζ or a catalytically inactive mutant. DGKζ bound directly to the C-terminus of RhoA and the regulatory arm of RhoGDI and was required for efficient interaction of PKCα and RhoA. DGKζ-null fibroblasts had condensed F-actin bundles and altered focal adhesion distribution, indicative of aberrant RhoA signaling. Two targets of the RhoA effector ROCK showed reduced phosphorylation in DGKζ-null cells. Collectively our findings suggest DGKζ functions as a scaffold to assemble a signaling complex that functions as a RhoA-selective, GDI dissociation factor. As a regulator of Rac1 and RhoA activity, DGKζ is a critical factor linking changes in lipid signaling to actin reorganization.

  12. Critically Stressed Fractures as Conduits: Mechanically-Chemically-Mediated Anisotropy of the Effective Permeability of Fractured Rock

    NASA Astrophysics Data System (ADS)

    Lang, P. S.; Nejati, M.; Paluszny, A.; Zimmerman, R. W.

    2015-12-01

    It has long been suggested that fractures that are critically oriented with respect to the in situ stress field are the most likely to be hydraulically conductive. This observation is revisited from the point of view of chemically mediated compaction processes, using numerical multi-physics, multi-scale simulations. Fracture contact is computed explicitly for discrete fracture networks, to find local displacements and contact tractions, which govern the initial permeability of the fractures. Subsequent flow simulations compute the full permeability tensor of the network. Local normal tractions then inform a series of transient reactive-transport, elastic-contact simulations at the grain scale that model the compaction of the fracture void space due to pressure-solution and free-face precipitation, assuming the pore-fluid in equilibrium concentration. The ensuing change of fracture transmissivity feeds back to the discrete fracture network model, wherein changes in the permeability tensor are evaluated. The eigenvectors of the initial permeability tensor reflect the higher permeability of fractures having shear/normal stress ratios near 0.6, which are characterized by relatively high permeability due to their combination of shear displacement and normal compression. The resulting preferred flow direction of the network becomes more pronounced over time as fractures that are subject to larger normal stresses experience stronger compaction, for two reasons. Firstly, larger normal traction over the surfaces provides a stronger drive for pressure solution at the contacting asperities. Secondly, these fractures are subject to smaller shear displacement. Their void space has less pronounced channels and is more sensitive to hydraulic sealing due to contact-zone percolation during the compaction process. It is concluded that mechanically-chemically mediated closure processes contribute to critically stressed fractures being likely hydraulic conduits.

  13. Mechanism of activity and toxicity of Nystatin-Intralipid.

    PubMed

    Semis, Rita; Kagan, Sarah; Berdicevsky, Israela; Polacheck, Itzhack; Segal, Esther

    2013-05-01

    A novel lipid formulation of Nystatin (NYT), Nystatin-Intralipid (NYT-IL), which was found to be more active and less toxic in vitro and in vivo, was developed in our laboratory. The aim of the present study was to explore the possible mechanisms underlying its biological activity. To assess mechanisms affecting fungal cells we conducted the following experiments: killing kinetics, scanning and transmission electron microscopy (EM), measurements of potassium ion leakage and susceptibility in the presence of ergosterol. To study mechanisms affecting mammalian cells, we evaluated the effect of NYT-IL on a kidney cell line, with respect to viability, metabolic activity, potassium leakage and internalization of FITC-labeled human transferrin. NYT-IL exhibited killing kinetics patterns against Candida albicans similar to those of NYT and caused disruption of fungal cells and potassium ion leakage. Susceptibility tests showed that NYT-IL had lower antifungal activity in the presence of ergosterol. Thus, NYT-IL acts apparently by damaging fungal membrane, possibly through interaction with ergosterol, and maybe by additional modes of action. NYT-IL did not cause potassium leakage from mammalian kidney cells at any tested concentration and was not cytotoxic, whereas NYT, at high concentrations, led to K(+) leakage and was cytotoxic. Furthermore, the high NYT concentration interfered in the internalization process of human transferrin receptor (hTfnR) while NYT-IL did not. In summary, the Intralipid formulation of NYT diminishes the mechanisms responsible for toxicity to mammalian cells but preserves mechanisms of action against fungi, thereby suggesting superiority of NYT-IL as compared to NYT as an antifungal agent.

  14. Rock fall triggering from cyclic thermal forcing of exfoliation fractures

    NASA Astrophysics Data System (ADS)

    Collins, B. D.; Stock, G. M.

    2013-12-01

    Exfoliation of rocks cause cliffs to deteriorate through the formation and subsequent opening of fractures. Where human activities are exposed to this process, rock fall hazard is potentially high. A number of mechanisms (e.g., freeze-thaw, precipitation-induced seepage) are capable of triggering rock fall in steep rock masses, however, some rock falls occur in the absence of any identified trigger. Among the suggested causes for these unexplained rock falls is thermal heating which can lead to outward expansion of rock surfaces. Here we use data from three years of displacement transducer field monitoring and corroborated by lidar measurements to test this hypothesis by assessing the magnitude and temporal pattern of thermally-induced rock deformation in an exfoliating granitic landscape. We show that daily, seasonal, and annual temperature effects are sufficient to cause cyclic and cumulative deformation of fractures, and that fracture tip propagation with consequent detachment of rock masses likely results. We use thermodynamic and structural engineering principals to show that thermally-forced exfoliation surfaces (i.e., partially detached 'flakes' of rock) follow Carnot-cycle-type hysteresis loops (i.e., the cyclical conversion of thermal energy to work that occurs in a heat engine) and can be modeled by Euler-type buckling criteria (i.e., the resultant lateral deformation that occurs upon an increase in axial compressive loading, here, caused by thermal expansion along the axis of partially detached exfoliation flakes). Our data from a 19-m-tall, 4-m-wide, 10-cm-thick, instrumented granodiorite exfoliation flake indicate that cumulative annual outward deformation of up to 1 mm/yr occurs under fatigue crack growth conditions. These conditions are related to both cyclic thermal and mechanical forcing and gravitational loads acting along the surfaces that attach the flake to the rock mass. Based on these observations and our analyses, we suggest that the warmest

  15. Physical activity and cancer prevention: etiologic evidence and biological mechanisms.

    PubMed

    Friedenreich, Christine M; Orenstein, Marla R

    2002-11-01

    Scientific evidence is accumulating on physical activity as a means for the primary prevention of cancer. Nearly 170 observational epidemiologic studies of physical activity and cancer risk at a number of specific cancer sites have been conducted. The evidence for decreased risk with increased physical activity is classified as convincing for breast and colon cancers, probable for prostate cancer, possible for lung and endometrial cancers and insufficient for cancers at all other sites. Despite the large number of studies conducted on physical activity and cancer, most have been hampered by incomplete assessment of physical activity and a lack of full examination of effect modification and confounding. Several plausible hypothesized biological mechanisms exist for the association between physical activity and cancer, including changes in endogenous sexual and metabolic hormone levels and growth factors, decreased obesity and central adiposity and possibly changes in immune function. Weight control may play a particularly important role because links between excess weight and increased cancer risk have been established for several sites, and central adiposity has been particularly implicated in promoting metabolic conditions amenable to carcinogenesis. Based on existing evidence, some public health organizations have issued physical activity guidelines for cancer prevention, generally recommending at least 30 min of moderate-to-vigorous intensity physical activity on > or =5 d/wk. Although most research has focused on the efficacy of physical activity in cancer prevention, evidence is increasing that exercise also influences other aspects of the cancer experience, including cancer detection, coping, rehabilitation and survival after diagnosis.

  16. Mechanisms of spontaneous activity in developing spinal networks.

    PubMed

    O'Donovan, M J; Chub, N; Wenner, P

    1998-10-01

    Developing networks of the chick spinal cord become spontaneously active early in development and remain so until hatching. Experiments using an isolated preparation of the spinal cord have begun to reveal the mechanisms responsible for this activity. Whole-cell and optical recordings have shown that spinal neurons receive a rhythmic, depolarizing synaptic drive and experience rhythmic elevations of intracellular calcium during spontaneous episodes. Activity is expressed throughout the neuraxis and can be produced by different parts of the cord and by the isolated brain stem, suggesting that it does not depend upon the details of network architecture. Two factors appear to be particularly important for the production of endogenous activity. The first is the predominantly excitatory nature of developing synaptic connections, and the second is the presence of prolonged activity-dependent depression of network excitability. The interaction between high excitability and depression results in an equilibrium in which episodes are expressed periodically by the network. The mechanism of the rhythmic bursting within an episode is not understood, but it may be due to a "fast" form of network depression. Spontaneous embryonic activity has been shown to play a role in neuron and muscle development, but is probably not involved in the initial formation of connections between spinal neurons. It may be important in refining the initial connections, but this possibility remains to be explored.

  17. Class I Microcins: Their Structures, Activities, and Mechanisms of Resistance

    NASA Astrophysics Data System (ADS)

    Severinov, Konstantin; Semenova, Ekaterina; Kazakov, Teymur

    Microcin J25, microcin B17, and microcin C7-C51 are the three known members of class I posttranslationally modified microcins (heavily posttranslationally modified antibacterial peptides produced by Enterobacteriaceae with molecular weights of less than 5 kDa). The three microcins are unrelated to each other; they have structures that are highly atypical for ribosomally synthesized peptides and target essential molecular machines that are validated drug targets. In this chapter, available data on mechanisms of action, structure-activity relationships, and immunity mechanisms for class I microcins and related compounds are discussed.

  18. The Importance of Geochemical Parameters and Shale Composition on Rock Mechanical Properties of Gas Shale Reservoirs: a Case Study From the Kockatea Shale and Carynginia Formation From the Perth Basin, Western Australia

    NASA Astrophysics Data System (ADS)

    Labani, Mohammad Mahdi; Rezaee, Reza

    2015-05-01

    Evaluation of the gas shale mechanical properties is very important screening criteria for determining the potential intervals for hydraulic fracturing and as a result in gas shale sweet spot mapping. Young's modulus and Poisson's ratio are two controlling mechanical properties that dictate the brittleness of the gas shale layers. These parameters can be determined in the laboratory by testing the rock sample under different conditions (static method) or can be calculated using the well-logging data including sonic and density log data (dynamic method). This study investigates the importance of the shale composition and geochemical parameters on the Young's modulus and Poisson's ratio using log data. The data set of this study is coming from five different wells targeting the Kockatea Shale and Carynginia formation, two potential gas shale formations in the Perth Basin, Western Australia. The results show that converse to the common idea the effect of organic matter quantity and maturity on the rock mechanical properties of the gas shale reservoirs is not so much prominent, while the composition of the rock has an important effect on these properties. Considering the weight percentage of shale composition and organic matter quantity it could be concluded that effect of these parameters on rock mechanical properties is dependent on their weight contribution on the shale matrix. As well as effect of thermal maturity on the shale matrix and consequently on the rock mechanical properties of the shales is dependent on the organic matter content itself; therefore, obviously with a low organic matter content thermal maturity has no prominent effect on the brittleness as well.

  19. Snow-cover dynamics monitored by automatic digital photography at the rooting zone of an active rock glacier in the Hinteres Lantal Cirque, Austria

    NASA Astrophysics Data System (ADS)

    Kellerer-Pirklbauer, Andreas; Rieckh, Matthias; Avian, Michael

    2010-05-01

    Knowledge regarding snow-cover dynamics and climatic conditions in the rooting zone of active rock glaciers is still limited. The number of meteorological stations on the surface of or close to active rock glaciers is increasing. However, areal information on snow-cover distribution and its spatial dynamics caused by different processes on rock glaciers surfaces with a high temporal resolution from such remote alpine areas are mostly difficult to obtain. To face this problem an automatic remote digital camera (RDC) system was proprietary developed. The core parts of the RDC system are a standard hand-held digital camera, a remote control, a water proof casing with a transparent opening, a 12V/25Ah battery and solar panels with a charge controller. Three such devices were constructed and installed at different sites in the Central Alps of Austria. One RDC system is used to monitor the rooting zone of the highly active rock glacier in the Hinteres Langtal Cirque (46°59'N, 12°47'E), Central Schober Mountains, Austria. The 0.15 km² large NW-facing rock glaciers is tongue-shaped with a fast moving lower part (>1m/a) and a substantially slower upper part, ranging in elevation between 2455-2700 m a.s.l. The RDC system was set up in September 2006 and is located since than at 2770 m a.s.l. on a pronounced ridge crest that confines the Hinteres Langtal Cirque to the SW. The water proof casing was attached to a 1.5 m high metal pole which itself was fixed to the bedrock by screws and concrete glue. The viewing direction of the camera is NE. Hence, the image section of the RDC focuses on the rooting zone of the rock glacier and its headwalls up to c. 3000 m a.s.l. Photographs were taken daily at 3 pm providing the optimal lighting conditions in the relevant part of the cirque. 720 photographs were taken continuously in the period 12.09.2006 to 31.08.2008. These optical data were analysed by applying GIS and remote sensing techniques regarding snow-cover distribution

  20. Analysis of Inflatable Rock Bolts

    NASA Astrophysics Data System (ADS)

    Li, Charlie C.

    2016-01-01

    An inflatable bolt is integrated in the rock mass through the friction and mechanical interlock at the bolt-rock interface. The pullout resistance of the inflatable bolt is determined by the contact stress at the interface. The contact stress is composed of two parts, termed the primary and secondary contact stresses. The former refers to the stress established during bolt installation and the latter is mobilized when the bolt tends to slip in the borehole owing to the roughness of the borehole surface. The existing analysis of the inflatable rock bolt does not appropriately describe the interaction between the bolt and the rock since the influence of the folded tongue of the bolt on the stiffness of the bolt and the elastic rebound of the bolt tube in the end of bolt installation are ignored. The interaction of the inflatable bolt with the rock is thoroughly analysed by taking into account the elastic displacements of the rock mass and the bolt tube during and after bolt installation in this article. The study aims to reveal the influence of the bolt tongue on the contact stress and the different anchoring mechanisms of the bolt in hard and soft rocks. A new solution to the primary contact stress is derived, which is more realistic than the existing one in describing the interaction between the bolt and the rock. The mechanism of the secondary contact stress is also discussed from the point of view of the mechanical behaviour of the asperities on the borehole surface. The analytical solutions are in agreement with both the laboratory and field pullout test results. The analysis reveals that the primary contact stress decreases with the Young's modulus of the rock mass and increases with the borehole diameter and installation pump pressure. The primary contact stress can be easily established in soft and weak rock but is low or zero in hard and strong rock. In soft and weak rock, the primary contact stress is crucially important for the anchorage of the bolt, while

  1. Microalloying of transition metal silicides by mechanical activation and field-activated reaction

    DOEpatents

    Munir, Zuhair A.; Woolman, Joseph N.; Petrovic, John J.

    2003-09-02

    Alloys of transition metal suicides that contain one or more alloying elements are fabricated by a two-stage process involving mechanical activation as the first stage and densification and field-activated reaction as the second stage. Mechanical activation, preferably performed by high-energy planetary milling, results in the incorporation of atoms of the alloying element(s) into the crystal lattice of the transition metal, while the densification and field-activated reaction, preferably performed by spark plasma sintering, result in the formation of the alloyed transition metal silicide. Among the many advantages of the process are its ability to accommodate materials that are incompatible in other alloying methods.

  2. Low temperature elastic behavior of rocks

    NASA Astrophysics Data System (ADS)

    Ulrich, T. J.; Darling, T. W.; McCall, K. R.; Fenn, J.

    2002-12-01

    The resonant frequencies of a material sample are directly related to the elastic constants characterizing the sample. Thus, by studying trends in resonant frequencies as a function of temperature, the elastic behavior of the sample may be inferred, and changes in the physical properties of the material may be tracked (for example, phase changes). Historically, tracking the resonant frequencies of a crystalline sample as a function of temperature is one of the most sensitive methods for identifying phase changes in the sample. We are using Resonant Ultrasound Spectroscopy (RUS) to track the resonant frequencies of rock samples at low temperatures. Our initial measurements showed unexpected behavior in a millimeter-sized sample of Berea sandstone in the temperature range from 77 K to 300 K [Ulrich and Darling, 2001], including hysteresis in the temperature dependence of the resonant frequencies, and softening rather than hardening as the temperature decreases. A second experimental apparatus has been developed to make RUS measurements on samples up to 2 cm by 3 cm by 8 cm in size, and over the temperature range 77 K - 400 K. RUS measurements using the new experimental system have been made on several rock samples, as well as several standards, and will be described in this talk. In general, the rock samples exhibit anomalous elastic behavior, consistent with the initial measurements on much smaller samples. Similar elastic phenomena, with similar activation energies, are seen in these rocks in room temperature measurements of resonant frequency versus strain [Tencate and Shankland, 1996]. Thus, low temperature measurements could provide insight into the mechanisms for the nonlinear elastic behavior of rocks and other materials. Ulrich T.J., Darling T.W., Observation of anomalous elastic behavior in rock at low temperatures. Geophys. Res. Let., Vol. 28, No. 11, pgs. 2293-2296, June 1, 2001. Tencate J.A., Shankland, T.J., Slow dynamics in the nonlinear response of

  3. Physical activity, stress reduction, and mood: insight into immunological mechanisms.

    PubMed

    Hamer, Mark; Endrighi, Romano; Poole, Lydia

    2012-01-01

    Psychosocial factors, such as chronic mental stress and mood, are recognized as an important predictor of longevity and wellbeing. In particular, depression is independently associated with cardiovascular disease and all-cause mortality, and is often comorbid with chronic diseases that can worsen their associated health outcomes. Regular exercise is thought to be associated with stress reduction and better mood, which may partly mediate associations between depression, stress, and health outcomes. The underlying mechanisms for the positive effects of exercise on wellbeing remain poorly understood. In this overview we examine epidemiological evidence for an association between physical activity and mental health. We then describe the exercise withdrawal paradigm as an experimental protocol to study mechanisms linking exercise, mood, and stress. In particular we will discuss the potential role of the inflammatory response as a central mechanism.

  4. Mechanical stress-controlled tunable active frequency-selective surface

    NASA Astrophysics Data System (ADS)

    Huang, Bo-Cin; Hong, Jian-Wei; Lo, Cheng-Yao

    2017-01-01

    This study proposes a tunable active frequency-selective surface (AFSS) realized by mechanically expanding or contracting a split-ring resonator (SRR) array. The proposed AFSS transfers mechanical stress from its elastic substrate to the top of the SRR, thereby achieving electromagnetic (EM) modulation without the need for an additional external power supply, meeting the requirements for the target application: the invisibility cloak. The operating mechanism of the proposed AFSS differs from those of other AFSSs, supporting modulations in arbitrary frequencies in the target range. The proposed stress-controlled or strain-induced EM modulation proves the existence of an identical and linear relationship between the strain gradient and the frequency shift, implying its suitability for other EM modulation ranges and applications.

  5. Active Cellular Mechanics and Information Processing in the Living Cell

    NASA Astrophysics Data System (ADS)

    Rao, M.

    2014-07-01

    I will present our recent work on the organization of signaling molecules on the surface of living cells. Using novel experimental and theoretical approaches we have found that many cell surface receptors are organized as dynamic clusters driven by active currents and stresses generated by the cortical cytoskeleton adjoining the cell surface. We have shown that this organization is optimal for both information processing and computation. In connecting active mechanics in the cell with information processing and computation, we bring together two of the seminal works of Alan Turing.

  6. About mechanisms of tetonic activity of the satellites

    NASA Astrophysics Data System (ADS)

    Barkin, Yu. V.

    2003-04-01

    ABOUT MECHANISMS OF TECTONIC ACTIVITY OF THE SATELLITES Yu.V. Barkin Sternberg Astronomical Institute, Moscow, Russia, barkin@sai.msu.ru Due to attraction of the central planet and others external bodies satellite is subjected by tidal and non-tidal deformations. Elastic energy is changed in dependence from mutual position and motion of celestial bodies and as result the tensional state of satellite and its tectonic (endogenous) activity also is changed. Satellites of the planets have the definite shell’s structure and due to own rotation these shells are characterized by different oblatenesses. Gravitational interaction of the satellite and its mother planet generates big additional mechanical forces (and moments) between the neighboring non-spherical shells of the satellite (mantle, core and crust). These forces and moments are cyclic functions of time, which are changed in the different time-scales. They generate corresponding cyclic perturbations of the tensional state of the shells, their deformations, small relative transnational displacements and slow rotation of the shells and others. In geological period of time it leads to a fundamental tectonic reconstruction of the body. Definite contribution to discussed phenomena are caused by classical tidal mechanism. of planet-satellite interaction. But in this report we discuss in first the new mechanisms of endogenous activity of celestial bodies. They are connected with differential gravitational attraction of non-spherical satellite shells by the external celestial bodies which leads: 1) to small relative rotation (nutations) of the shells; 2) to small relative translational motions of the shells (displacements of their center of mass); 3) to relative displacements and rotations of the shells due to eccentricity of their center of mass positions; 4) to viscous elastic deformations of the shells and oth. (Barkin, 2001). For higher evaluations of the power of satellite endogenous activities were obtained

  7. Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2005-01-01

    6 November 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows outcrops of sedimentary rocks in a crater located just north of the Sinus Meridiani region. Perhaps the crater was once the site of a martian lake.

    Location near: 2.9oN, 359.0oW Image width: width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Autumn

  8. Mechanics of post-cam engagement during simulated dynamic activity.

    PubMed

    Fitzpatrick, Clare K; Clary, Chadd W; Cyr, Adam J; Maletsky, Lorin P; Rullkoetter, Paul J

    2013-09-01

    Posterior-stabilized (PS) total knee arthroplasty (TKA) components employ a tibial post and femoral cam mechanism to guide anteroposterior knee motion in lieu of the posterior cruciate ligament. Some PS TKA patients report a clicking sensation when the post and cam engage, while severe wear and fracture of the post; we hypothesize that these complications are associated with excessive impact velocity at engagement. We evaluated the effect of implant design on engagement dynamics of the post-cam mechanism and resulting polyethylene stresses during dynamic activity. In vitro simulation of a knee bend activity was performed for four cadaveric specimens implanted with PS TKA components. Post-cam engagement velocity and flexion angle at initial contact were determined. The experimental data were used to validate computational predictions of PS mechanics using the same loading conditions. A lower limb model was subsequently utilized to compare engagement mechanics of eight TKA designs, relating differences between implants to geometric design features. Flexion angle and post-cam velocity at engagement demonstrated considerable ranges among designs (23°-89°, and 0.05-0.22 mm/°, respectively). Post-cam velocity was correlated (r = 0.89) with tibiofemoral condylar design features. Condylar geometry, in addition to post-cam geometry, played a significant role in minimizing engagement velocity and forces and stresses in the post. This analysis guides selection and design of PS implants that facilitate smooth post-cam engagement and reduce edge loading of the post.

  9. Microglia mechanics: immune activation alters traction forces and durotaxis

    PubMed Central

    Bollmann, Lars; Koser, David E.; Shahapure, Rajesh; Gautier, Hélène O. B.; Holzapfel, Gerhard A.; Scarcelli, Giuliano; Gather, Malte C.; Ulbricht, Elke; Franze, Kristian

    2015-01-01

    Microglial cells are key players in the primary immune response of the central nervous system. They are highly active and motile cells that chemically and mechanically interact with their environment. While the impact of chemical signaling on microglia function has been studied in much detail, the current understanding of mechanical signaling is very limited. When cultured on compliant substrates, primary microglial cells adapted their spread area, morphology, and actin cytoskeleton to the stiffness of their environment. Traction force microscopy revealed that forces exerted by microglia increase with substrate stiffness until reaching a plateau at a shear modulus of ~5 kPa. When cultured on substrates incorporating stiffness gradients, microglia preferentially migrated toward stiffer regions, a process termed durotaxis. Lipopolysaccharide-induced immune-activation of microglia led to changes in traction forces, increased migration velocities and an amplification of durotaxis. We finally developed a mathematical model connecting traction forces with the durotactic behavior of migrating microglial cells. Our results demonstrate that microglia are susceptible to mechanical signals, which could be important during central nervous system development and pathologies. Stiffness gradients in tissue surrounding neural implants such as electrodes, for example, could mechanically attract microglial cells, thus facilitating foreign body reactions detrimental to electrode functioning. PMID:26441534

  10. Active Control of Mixing and Combustion, from Mechanisms to Implementation

    NASA Astrophysics Data System (ADS)

    Ghoniem, Ahmed F.

    2001-11-01

    Implementation of active control in complex processes, of the type encountered in high Reynolds number mixing and combustion, is predicated upon the identification of the underlying mechanisms and the construction of reduced order models that capture their essential characteristics. The mechanisms of interest must be shown to be amenable to external actuations, allowing optimal control strategies to exploit the delicate interactions that lead to the desired outcome. Reduced order models are utilized in defining the form and requisite attributes of actuation, its relationship to the monitoring system and the relevant control algorithms embedded in a feedforward or a feedback loop. The talk will review recent work on active control of mixing in combustion devices in which strong shear zones concur with mixing, combustion stabilization and flame anchoring. The underlying mechanisms, e.g., stability of shear flows, formation/evolution of large vortical structures in separating and swirling flows, their mutual interactions with acoustic fields, flame fronts and chemical kinetics, etc., are discussed in light of their key roles in mixing, burning enhancement/suppression, and combustion instability. Subtle attributes of combustion mechanisms are used to suggest the requisite control strategies.

  11. The Mechanical Environment Modulates Intracellular Calcium Oscillation Activities of Myofibroblasts

    PubMed Central

    Godbout, Charles; Follonier Castella, Lysianne; Smith, Eric A.; Talele, Nilesh; Chow, Melissa L.; Garonna, Adriano; Hinz, Boris

    2013-01-01

    Myofibroblast contraction is fundamental in the excessive tissue remodeling that is characteristic of fibrotic tissue contractures. Tissue remodeling during development of fibrosis leads to gradually increasing stiffness of the extracellular matrix. We propose that this increased stiffness positively feeds back on the contractile activities of myofibroblasts. We have previously shown that cycles of contraction directly correlate with periodic intracellular calcium oscillations in cultured myofibroblasts. We analyze cytosolic calcium dynamics using fluorescent calcium indicators to evaluate the possible impact of mechanical stress on myofibroblast contractile activity. To modulate extracellular mechanics, we seeded primary rat subcutaneous myofibroblasts on silicone substrates and into collagen gels of different elastic modulus. We modulated cell stress by cell growth on differently adhesive culture substrates, by restricting cell spreading area on micro-printed adhesive islands, and depolymerizing actin with Cytochalasin D. In general, calcium oscillation frequencies in myofibroblasts increased with increasing mechanical challenge. These results provide new insight on how changing mechanical conditions for myofibroblasts are encoded in calcium oscillations and possibly explain how reparative cells adapt their contractile behavior to the stresses occurring in normal and pathological tissue repair. PMID:23691248

  12. KMUP-1 Attenuates Endothelin-1-Induced Cardiomyocyte Hypertrophy through Activation of Heme Oxygenase-1 and Suppression of the Akt/GSK-3β, Calcineurin/NFATc4 and RhoA/ROCK Pathways.

    PubMed

    Liou, Shu-Fen; Hsu, Jong-Hau; Chen, You-Ting; Chen, Ing-Jun; Yeh, Jwu-Lai

    2015-06-05

    The signaling cascades of the mitogen activated protein kinase (MAPK) family, calcineurin/NFATc4, and PI3K/Akt/GSK3, are believed to participate in endothelin-1 (ET-1)-induced cardiac hypertrophy. The aim of this study was to investigate whether KMUP-1, a synthetic xanthine-based derivative, prevents cardiomyocyte hypertrophy induced by ET-1 and to elucidate the underlying mechanisms. We found that in H9c2 cardiomyocytes, stimulation with ET-1 (100 nM) for 4 days induced cell hypertrophy and enhanced expressions of hypertrophic markers, including atrial natriuretic peptide and brain natriuretic peptide, which were all inhibited by KMUP-1 in a dose-dependent manner. In addition, KMUP-1 prevented ET-1-induced intracellular reactive oxygen species generation determined by the DCFH-DA assay in cardiomyocytes. KMUP-1 also attenuated phosphorylation of ERK1/2 and Akt/GSK-3β, and activation of calcineurin/NFATc4 and RhoA/ROCK pathways induced by ET-1. Furthermore, we found that the expression of heme oxygenase-1 (HO-1), a stress-response enzyme implicated in cardio-protection, was up-regulated by KMUP-1. Finally, KMUP-1 attenuated ET-1-stimulated activator protein-1 DNA binding activity. In conclusion, KMUP-1 attenuates cardiomyocyte hypertrophy induced by ET-1 through inhibiting ERK1/2, calcineurin/NFATc4 and RhoA/ROCK pathways, with associated cardioprotective effects via HO-1 activation. Therefore, KMUP-1 may have a role in pharmacological therapy of cardiac hypertrophy.

  13. TRPA1 contributes to specific mechanically activated currents and sensory neuron mechanical hypersensitivity.

    PubMed

    Brierley, Stuart M; Castro, Joel; Harrington, Andrea M; Hughes, Patrick A; Page, Amanda J; Rychkov, Grigori Y; Blackshaw, L Ashley

    2011-07-15

    The mechanosensory role of TRPA1 and its contribution to mechanical hypersensitivity in sensory neurons remains enigmatic. We elucidated this role by recording mechanically activated currents in conjunction with TRPA1 over- and under-expression and selective pharmacology. First, we established that TRPA1 transcript, protein and functional expression are more abundant in smaller-diameter neurons than larger-diameter neurons, allowing comparison of two different neuronal populations. Utilising whole cell patch clamping, we applied calibrated displacements to neurites of dorsal root ganglion (DRG) neurons in short-term culture and recorded mechanically activated currents termed intermediately (IAMCs), rapidly (RAMCs) or slowly adapting (SAMCs). Trpa1 deletion (–/–) significantly reduced maximum IAMC amplitude by 43% in small-diameter neurons compared with wild-type (+/+) neurons. All other mechanically activated currents in small- and large-diameter Trpa1−/− neurons were unaltered. Seventy-three per cent of Trpa1+/+ small-diameter neurons responding to the TRPA1 agonist allyl-isothiocyanate (AITC) displayed IAMCs to neurite displacement, which were significantly enhanced after AITC addition. The TRPA1 antagonist HC-030031 significantly decreased Trpa1+/+ IAMC amplitudes, but only in AITC responsive neurons. Using a transfection system we also showed TRPA1 over-expression in Trpa1+/+ small-diameter neurons increases IAMC amplitude, an effect reversed by HC-030031. Furthermore, TRPA1 introduction into Trpa1−/− small-diameter neurons restored IAMC amplitudes to Trpa1+/+ levels, which was subsequently reversed by HC-030031. In summary our data demonstrate TRPA1 makes a contribution to normal mechanosensation in a specific subset of DRG neurons. Furthermore, they also provide new evidence illustrating mechanisms by which sensitisation or over-expression of TRPA1 enhances nociceptor mechanosensitivity. Overall, these findings suggest TRPA1 has the capacity to

  14. TRPA1 contributes to specific mechanically activated currents and sensory neuron mechanical hypersensitivity

    PubMed Central

    Brierley, Stuart M; Castro, Joel; Harrington, Andrea M; Hughes, Patrick A; Page, Amanda J; Rychkov, Grigori Y; Blackshaw, L Ashley

    2011-01-01

    Abstract The mechanosensory role of TRPA1 and its contribution to mechanical hypersensitivity in sensory neurons remains enigmatic. We elucidated this role by recording mechanically activated currents in conjunction with TRPA1 over- and under-expression and selective pharmacology. First, we established that TRPA1 transcript, protein and functional expression are more abundant in smaller-diameter neurons than larger-diameter neurons, allowing comparison of two different neuronal populations. Utilising whole cell patch clamping, we applied calibrated displacements to neurites of dorsal root ganglion (DRG) neurons in short-term culture and recorded mechanically activated currents termed intermediately (IAMCs), rapidly (RAMCs) or slowly adapting (SAMCs). Trpa1 deletion (–/–) significantly reduced maximum IAMC amplitude by 43% in small-diameter neurons compared with wild-type (+/+) neurons. All other mechanically activated currents in small- and large-diameter Trpa1−/− neurons were unaltered. Seventy-three per cent of Trpa1+/+ small-diameter neurons responding to the TRPA1 agonist allyl-isothiocyanate (AITC) displayed IAMCs to neurite displacement, which were significantly enhanced after AITC addition. The TRPA1 antagonist HC-030031 significantly decreased Trpa1+/+ IAMC amplitudes, but only in AITC responsive neurons. Using a transfection system we also showed TRPA1 over-expression in Trpa1+/+ small-diameter neurons increases IAMC amplitude, an effect reversed by HC-030031. Furthermore, TRPA1 introduction into Trpa1−/− small-diameter neurons restored IAMC amplitudes to Trpa1+/+ levels, which was subsequently reversed by HC-030031. In summary our data demonstrate TRPA1 makes a contribution to normal mechanosensation in a specific subset of DRG neurons. Furthermore, they also provide new evidence illustrating mechanisms by which sensitisation or over-expression of TRPA1 enhances nociceptor mechanosensitivity. Overall, these findings suggest TRPA1 has the

  15. Mechanical research and development activities at the European space agency

    NASA Astrophysics Data System (ADS)

    Stavrinidis, C.

    1996-02-01

    The research and development activities of satellite mechanical systems at ESA are driven by the requirements of future European space programmes, evolution of technologies resulting in new technical capabilities, and the need to reduce the cost, to increase the reliability of the European space effort and to improve the competitiveness of the European space industry. Technology developments require in many cases several years from initial concept to technological readiness, and this needs to be taken into account when considering satellite mission requirements. On the other hand difficulties encountered with the performance of existing mechanical system need to be resolved in a shorter timescale. Agency research and development activities of mechanical systems include: - new materials applications - design and manufacture techniques - structural dynamics and low disturbance environment - high precision reflectors - vibroacoustics - meteoroid and debris protection - tribology - pyrotechnics The activities take into account requirements of future space missions for science, earth observation, telecommunications, launchers, and microgravity applications. There are efforts to improve the competitive edge of space industry for example through the European Coordination for Space Standardization (ECSS).

  16. Astronomy and Rock Art Studies

    NASA Astrophysics Data System (ADS)

    Murray, William Breen

    Rock art is often used as evidence for the earliest phases of prehistoric celestial knowledge and sky observation. Like the sky, rock art is a global phenomenon and it is also one of the earliest manifestations of human cognitive awareness. Similarities in iconography and visual context may provide evidence of sky-watching activity, and in some cases, ethnographic analogies, ethnohistoric documentation, and surviving archaeological evidence may confirm that these activities were related to rock art production. Nevertheless, the problem of random matches makes proofs of intentional relation more complicated. Probabilities are measured differently in archaeology and astronomy and can sometimes lead to ambiguous or contradictory conclusions.

  17. Rock softening due to ultrasonic acoustical energy

    NASA Astrophysics Data System (ADS)

    Freund, F. T.; Freund, M. M.; Hedberg, C. M.; Haller, K. C.; Dahlgren, R.; Williams, C.; Agrawal, P.

    2011-12-01

    When igneous or high-grade metamorphic rocks are subjected to deviatoric stresses, dormant defects existing in the matrix of common rock-forming minerals become activated releasing mobile positive hole charge carriers. These defects consist of pairs of oxygen anions in the 1- valence state, e.g. peroxy links such as O3Si-OO-SiO3. When the peroxy bond breaks, O3Si-O:O-SiO3, an electron is transferred from a neighboring O2- creating a trapped electron defect, O3Si-O.O-SiO3, while the donor oxygen, now O-, turns into a defect electron or hole that can propagate as a highly mobile positive charge traveling along the upper edge of the valence band. There is evidence that the wave function associated with these positive hole charge carriers is highly delocalized. The delocalization lowers the electron density at the surrounding O2-, hence the bond energy, thereby affecting fundamental properties including the mechanical strength. To demonstrate the rock softening effect we mounted a rectangular bar of fine-grained gabbro about 30 cm long in a horizontal position clamping it at one end. A piezoelectric transducer (PZT) was epoxied to the fixed end of the rock bar to send ultrasonic energy at 57 KHz toward the cantilevered end. The downward deflection of the free end of the beam was measured with an interferometer to a high degree of precision. With ultrasonic energy present, the free end of the beam sagged near-instantaneously by about 0.2 μm and continued to sag slowly by about 0.4 μm over 120 sec. Upon turning off the PZT the rock bar returned slowly to the baseline deflection value. The ultrasound waves generated by the PZT activate positive holes, changing the apparent stiffness of the beam and causing its cantilevered end to bend downward. We also conducted experiments using an Instron 5569 Dual Column Testing System to subject rectangular plates (15.2 x 3.8 x 0.5 cm) of the same gabbro to dynamic three-point flexural tests. Using electrostatic fields of different

  18. Cooperative autoinhibition and multi-level activation mechanisms of calcineurin

    PubMed Central

    Li, Sheng-Jie; Wang, Jue; Ma, Lei; Lu, Chang; Wang, Jie; Wu, Jia-Wei; Wang, Zhi-Xin

    2016-01-01

    The Ca2+/calmodulin-dependent protein phosphatase calcineurin (CN), a heterodimer composed of a catalytic subunit A and an essential regulatory subunit B, plays critical functions in various cellular processes such as cardiac hypertrophy and T cell activation. It is the target of the most widely used immunosuppressants for transplantation, tacrolimus (FK506) and cyclosporin A. However, the structure of a large part of the CNA regulatory region remains to be determined, and there has been considerable debate concerning the regulation of CN activity. Here, we report the crystal structure of full-length CN (β isoform), which revealed a novel autoinhibitory segment (AIS) in addition to the well-known autoinhibitory domain (AID). The AIS nestles in a hydrophobic intersubunit groove, which overlaps the recognition site for substrates and immunosuppressant-immunophilin complexes. Indeed, disruption of this AIS interaction results in partial stimulation of CN activity. More importantly, our biochemical studies demonstrate that calmodulin does not remove AID from the active site, but only regulates the orientation of AID with respect to the catalytic core, causing incomplete activation of CN. Our findings challenge the current model for CN activation, and provide a better understanding of molecular mechanisms of CN activity regulation. PMID:26794871

  19. Rock Driller

    NASA Technical Reports Server (NTRS)

    Peterson, Thomas M.

    2001-01-01

    The next series of planetary exploration missions require a method of extracting rock and soil core samples. Therefore a prototype ultrasonic core driller (UTCD) was developed to meet the constraints of Small Bodies Exploration and Mars Sample Return Missions. The constraints in the design are size, weight, power, and axial loading. The ultrasonic transducer requires a relatively low axial load, which is one of the reasons this technology was chosen. The ultrasonic generator breadboard section can be contained within the 5x5x3 limits and weighs less than two pounds. Based on results attained the objectives for the first phase were achieved. A number of transducer probes were made and tested. One version only drills, and the other will actually provide a small core from a rock. Because of a more efficient transducer/probe, it will run at very low power (less than 5 Watts) and still drill/core. The prototype generator was built to allow for variation of all the performance-effecting elements of the transducer/probe/end effector, i.e., pulse, duty cycle, frequency, etc. The heart of the circuitry is what will be converted to a surface mounted board for the next phase, after all the parameters have been optimized and the microprocessor feedback can be installed.

  20. A molecular mechanism for direct sirtuin activation by resveratrol.

    PubMed

    Gertz, Melanie; Nguyen, Giang Thi Tuyet; Fischer, Frank; Suenkel, Benjamin; Schlicker, Christine; Fränzel, Benjamin; Tomaschewski, Jana; Aladini, Firouzeh; Becker, Christian; Wolters, Dirk; Steegborn, Clemens

    2012-01-01

    Sirtuins are protein deacetylases regulating metabolism, stress responses, and aging processes, and they were suggested to mediate the lifespan extending effect of a low calorie diet. Sirtuin activation by the polyphenol resveratrol can mimic such lifespan extending effects and alleviate metabolic diseases. The mechanism of Sirtuin stimulation is unknown, hindering the development of improved activators. Here we show that resveratrol inhibits human Sirt3 and stimulates Sirt5, in addition to Sirt1, against fluorophore-labeled peptide substrates but also against peptides and proteins lacking the non-physiological fluorophore modification. We further present crystal structures of Sirt3 and Sirt5 in complex with fluorogenic substrate peptide and modulator. The compound acts as a top cover, closing the Sirtuin's polypeptide binding pocket and influencing details of peptide binding by directly interacting with this substrate. Our results provide a mechanism for the direct activation of Sirtuins by small molecules and suggest that activators have to be tailored to a specific Sirtuin/substrate pair.

  1. NNWSI unit evaluation at Yucca Mountain, Nevada Test Site: Near field mechanical calculations using a continuum jointed rock moel in the JAC code

    SciTech Connect

    Thomas, R.K.

    1987-05-01

    The Nevada Nuclear Waste Storage Investigations (NNWSI) Project, managed by the Nevada Operations Office of the US Department of Energy, is examining the feasibility of siting a repository for high level nuclear wastes at Yucca Mountain on and adjacent to the Nevada Test Site (NTS). The work reported herein was done to support the selection, on a technical basis, of a single target repository horizon upon which to concentrate future activities. Presented in this report are the results of a comparative study between two candidate horizons: the devitrified Topopah Spring member of the Paintbrush Tuff and the nonwelded, zeolitized Tuffaceous Beds of Calico Hills. Performance of a repository sited in each candidate horizon was assessed by conducting structural calculations using a two-dimensional room-and-pillar geometry and average and limit material properties. The computer code JAC, with a constitutive model for jointed rock masses, was used to make the calculations. Based on analyses of the confining pressures in the pillar and the joint movement near the room, it is concluded that the Topopah Spring unit is more suitable than the Calico Hills unit for the placement of a nuclear waste repository. Finally, a comparison is made with a similar mine geometry sited in the Grouse Canyon Tuff, a horizon of known performance characteristics, using properties from G-Tunnel at NTS.

  2. Activation mechanism of Gi and Go by reactive oxygen species.

    PubMed

    Nishida, Motohiro; Schey, Kevin L; Takagahara, Shuichi; Kontani, Kenji; Katada, Toshiaki; Urano, Yasuteru; Nagano, Tetsuo; Nagao, Taku; Kurose, Hitoshi

    2002-03-15

    Reactive oxygen species are proposed to work as intracellular mediators. One of their target proteins is the alpha subunit of heterotrimeric GTP-binding proteins (Galpha(i) and Galpha(o)), leading to activation. H(2)O(2) is one of the reactive oxygen species and activates purified Galpha(i2). However, the activation requires the presence of Fe(2+), suggesting that H(2)O(2) is converted to more reactive species such as c*OH. The analysis with mass spectrometry shows that seven cysteine residues (Cys(66), Cys(112), Cys(140), Cys(255), Cys(287), Cys(326), and Cys(352)) of Galpha(i2) are modified by the treatment with *OH. Among these cysteine residues, Cys(66), Cys(112), Cys(140), Cys(255), and Cys(352) are not involved in *OH-induced activation of Galpha(i2). Although the modification of Cys(287) but not Cys(326) is required for subunit dissociation, the modification of both Cys(287) and Cys(326) is necessary for the activation of Galpha(i2) as determined by pertussis toxin-catalyzed ADP-ribosylation, conformation-dependent change of trypsin digestion pattern or guanosine 5'-3-O-(thio)triphosphate binding. Wild type Galpha(i2) but not Cys(287)- or Cys(326)-substituted mutants are activated by UV light, singlet oxygen, superoxide anion, and nitric oxide, indicating that these oxidative stresses activate Galpha(i2) by the mechanism similar to *OH-induced activation. Because Cys(287) exists only in G(i) family, this study explains the selective activation of G(i)/G(o) by oxidative stresses.

  3. Dual allosteric activation mechanisms in monomeric human glucokinase.

    PubMed

    Whittington, A Carl; Larion, Mioara; Bowler, Joseph M; Ramsey, Kristen M; Brüschweiler, Rafael; Miller, Brian G

    2015-09-15

    Cooperativity in human glucokinase (GCK), the body's primary glucose sensor and a major determinant of glucose homeostatic diseases, is fundamentally different from textbook models of allostery because GCK is monomeric and contains only one glucose-binding site. Prior work has demonstrated that millisecond timescale order-disorder transitions within the enzyme's small domain govern cooperativity. Here, using limited proteolysis, we map the site of disorder in unliganded GCK to a 30-residue active-site loop that closes upon glucose binding. Positional randomization of the loop, coupled with genetic selection in a glucokinase-deficient bacterium, uncovers a hyperactive GCK variant with substantially reduced cooperativity. Biochemical and structural analysis of this loop variant and GCK variants associated with hyperinsulinemic hypoglycemia reveal two distinct mechanisms of enzyme activation. In α-type activation, glucose affinity is increased, the proteolytic susceptibility of the active site loop is suppressed and the (1)H-(13)C heteronuclear multiple quantum coherence (HMQC) spectrum of (13)C-Ile-labeled enzyme resembles the glucose-bound state. In β-type activation, glucose affinity is largely unchanged, proteolytic susceptibility of the loop is enhanced, and the (1)H-(13)C HMQC spectrum reveals no perturbation in ensemble structure. Leveraging both activation mechanisms, we engineer a fully noncooperative GCK variant, whose functional properties are indistinguishable from other hexokinase isozymes, and which displays a 100-fold increase in catalytic efficiency over wild-type GCK. This work elucidates specific structural features responsible for generating allostery in a monomeric enzyme and suggests a general strategy for engineering cooperativity into proteins that lack the structural framework typical of traditional allosteric systems.

  4. Mechanism of human natural killer cell activation by Haemophilus ducreyi.

    PubMed

    Li, Wei; Janowicz, Diane M; Fortney, Kate R; Katz, Barry P; Spinola, Stanley M

    2009-08-15

    The role of natural killer (NK) cells in the host response to Haemophilus ducreyi infection is unclear. In pustules obtained from infected human volunteers, there was an enrichment of CD56bright NK cells bearing the activation markers CD69 and HLA-DR, compared with peripheral blood. To study the mechanism by which H. ducreyi activated NK cells, we used peripheral blood mononuclear cells from uninfected volunteers. H. ducreyi activated NK cells only in the presence of antigen-presenting cells. H. ducreyi-infected monocytes and monocyte-derived macrophages activated NK cells in a contact- and interleukin-18 (IL-18)-dependent manner, whereas monocyte-derived dendritic cells induced NK activation through soluble IL-12. More lesional NK cells than peripheral blood NK cells produced IFN-gamma in response to IL-12 and IL-18. We conclude that NK cells are recruited to experimental lesions and likely are activated by infected macrophages and dendritic cells. IFN-gamma produced by lesional NK cells may facilitate phagocytosis of H. ducreyi.

  5. Mechanisms Underlying Desynchronization of Cholinergic-Evoked Thalamic Network Activity

    PubMed Central

    Pita-Almenar, Juan Diego; Yu, Dinghui; Lu, Hui-Chen

    2014-01-01

    Synchronous neuronal activity in the thalamocortical system is critical for a number of behaviorally relevant computations, but hypersynchrony can limit information coding and lead to epileptiform responses. In the somatosensory thalamus, afferent inputs are transformed by networks of reciprocally connected thalamocortical neurons in the ventrobasal nucleus (VB) and GABAergic neurons in the thalamic reticular nucleus (TRN). These networks can generate oscillatory activity, and studies in vivo and in vitro have suggested that thalamic oscillations are often accompanied by synchronous neuronal activity, in part mediated by widespread divergence and convergence of both reticulothalamic and thalamoreticular pathways, as well as by electrical synapses interconnecting TRN neurons. However, the functional organization of thalamic circuits and its role in shaping input-evoked activity patterns remain poorly understood. Here we show that optogenetic activation of cholinergic synaptic afferents evokes near-synchronous firing in mouse TRN neurons that is rapidly desynchronized in thalamic networks. We identify several mechanisms responsible for desynchronization: (1) shared inhibitory inputs in local VB neurons leading to asynchronous and imprecise rebound bursting; (2) TRN-mediated lateral inhibition that further desynchronizes firing in the VB; and (3) powerful yet sparse thalamoreticular connectivity that mediates re-excitation of the TRN but preserves asynchronous firing. Our findings reveal how distinct local circuit features interact to desynchronize thalamic network activity. PMID:25339757

  6. Regarding "Semi-active control of the rocking motion of monolithic art objects" [Journal of Sound and Vibration, 374 (2016) 1-16

    NASA Astrophysics Data System (ADS)

    Cartmell, Matthew P.

    2016-09-01

    The Editor wishes to make the reader aware that the paper "Semi-active control of the rocking motion of monolithic art objects" by R. Ceravolo, M.L. Pecorelli, and L.Z. Fragonara, did not contain a direct citation of the fundamental and original work by D. Konstantinidis and N. Makris entitled "Experimental and analytical studies on the seismic response of free-standing and anchored laboratory equipment", Report No. PEER 2005/07. Pacific Earthquake Engineering Research (PEER) Center, University of California, Berkeley, 2005. The Editor regrets that this omission was not noted at the time that the above paper was accepted and published.

  7. Mechanical stress activates NMDA receptors in the absence of agonists.

    PubMed

    Maneshi, Mohammad Mehdi; Maki, Bruce; Gnanasambandam, Radhakrishnan; Belin, Sophie; Popescu, Gabriela K; Sachs, Frederick; Hua, Susan Z

    2017-01-03

    While studying the physiological response of primary rat astrocytes to fluid shear stress in a model of traumatic brain injury (TBI), we found that shear stress induced Ca(2+) entry. The influx was inhibited by MK-801, a specific pore blocker of N-Methyl-D-aspartic acid receptor (NMDAR) channels, and this occurred in the absence of agonists. Other NMDA open channel blockers ketamine and memantine showed a similar effect. The competitive glutamate antagonists AP5 and GluN2B-selective inhibitor ifenprodil reduced NMDA-activated currents, but had no effect on the mechanically induced Ca(2+) influx. Extracellular Mg(2+) at 2 mM did not significantly affect the shear induced Ca(2+) influx, but at 10 mM it produced significant inhibition. Patch clamp experiments showed mechanical activation of NMDAR and inhibition by MK-801. The mechanical sensitivity of NMDARs may play a role in the normal physiology of fluid flow in the glymphatic system and it has obvious relevance to TBI.

  8. Mechanical stress activates NMDA receptors in the absence of agonists

    PubMed Central

    Maneshi, Mohammad Mehdi; Maki, Bruce; Gnanasambandam, Radhakrishnan; Belin, Sophie; Popescu, Gabriela K.; Sachs, Frederick; Hua, Susan Z.

    2017-01-01

    While studying the physiological response of primary rat astrocytes to fluid shear stress in a model of traumatic brain injury (TBI), we found that shear stress induced Ca2+ entry. The influx was inhibited by MK-801, a specific pore blocker of N-Methyl-D-aspartic acid receptor (NMDAR) channels, and this occurred in the absence of agonists. Other NMDA open channel blockers ketamine and memantine showed a similar effect. The competitive glutamate antagonists AP5 and GluN2B-selective inhibitor ifenprodil reduced NMDA-activated currents, but had no effect on the mechanically induced Ca2+ influx. Extracellular Mg2+ at 2 mM did not significantly affect the shear induced Ca2+ influx, but at 10 mM it produced significant inhibition. Patch clamp experiments showed mechanical activation of NMDAR and inhibition by MK-801. The mechanical sensitivity of NMDARs may play a role in the normal physiology of fluid flow in the glymphatic system and it has obvious relevance to TBI. PMID:28045032

  9. A Numerical Hydro-Chemo-Mechanical Model for Fault Activation under Reactive Fluid Flow

    NASA Astrophysics Data System (ADS)

    Pouya, A.; Tounsi, H.; Rohmer, J.

    2015-12-01

    The migration of CO2-rich fluid in fractured rock masses can cause processes such as mineral dissolution and precipitation, chemically induced weakening, which can affect the long-term mechanical and transport properties of the rock mass as well as the stability of fault systems. Some numerical approaches are already available in the literature for modelling the dissolution/precipitation phenomena in fractures (e.g. Yasuhara & Elsworth 2007) as well as subcritical crack propagation (e.g. Park et al. 2007). Generally, the dissolution is supposed to increase the rock porosity and, in this way, decrease the rock strength. Some experimental data are available for the variation of rock strength and stiffness parameters with the porosity and so as a consequence of dissolution process (Bemer et al. 2004). Also the effect of chemical processes on the mechanical stability has been studied and modelled numerically in the framework of continuum materials and the context, in particular, of weathering in underground galleries (Ghabezloo & Pouya 2006). In the context of fault systems, a complete numerical modelling of the stability evolution with the flow of a reactive fluid has not yet been done. In this paper we present a simplified, but complete, set of equations for a whole system of coupled hydro-chemo-mechanical process of reactive fluid flow inside a fault. These equations have been implemented in Porofis, a FEM numerical code specially conceived for HCM processes in porous fractured media. We show how this numerical method allows to model the coupled HCM processes in the fault and the evolution of the mechanical stability in presence of in situ stresses and reactive fluid flow.

  10. Infiltration flux distributions in unsaturated rock deposits andtheir potential implications for fractured rock formations

    SciTech Connect

    Tokunaga, Tetsu K.; Olson, Keith R.; Wan, Jiamin

    2004-11-01

    Although water infiltration through unconsolidated rocks and fractured rock formations control flow and transport to groundwater, spatial distributions of flow paths are poorly understood. Infiltration experiments conducted on packs of rocks showed that a well-constrained distribution of fluxes develops despite differences in rock type (angular diabase and sandstone, and subangular serpentinite), rock size (30 to 200mm), and packing (up to 42 rock layers). Fluxes stabilize into a geometric (exponential) distribution that keeps about half of the system depleted of flow, retains a small fraction of high flow regions, and has a characteristic scale determined by the rock size. Modification of a statistical mechanical model shows that gravity-directed, random flowpaths evolve to the observed flux distribution, and that it represents the most probable distribution. Key similarities between infiltration in rock deposits and fractured rock formations indicate that the geometric flow distribution may also apply in the latter systems.

  11. Hair Growth Promotion Activity and Its Mechanism of Polygonum multiflorum

    PubMed Central

    Li, Yunfei; Han, Mingnuan; Lin, Pei; He, Yanran; Yu, Jie; Zhao, Ronghua

    2015-01-01

    Polygonum multiflorum Radix (PMR) has long history in hair growth promotion and hair coloring in clinical applications. However, several crucial problems in its clinic usage and mechanisms are still unsolved or lack scientific evidences. In this research, C57BL/6J mice were used to investigate hair growth promotion activity and possible mechanism of PMR and Polygonum multiflorum Radix Preparata (PMRP). Hair growth promotion activities were investigated by hair length, hair covered skin ratio, the number of follicles, and hair color. Regulation effects of several cytokines invo