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Sample records for activated phase slips

  1. Quantum phase slip noise

    NASA Astrophysics Data System (ADS)

    Semenov, Andrew G.; Zaikin, Andrei D.

    2016-07-01

    Quantum phase slips (QPSs) generate voltage fluctuations in superconducting nanowires. Employing the Keldysh technique and making use of the phase-charge duality arguments, we develop a theory of QPS-induced voltage noise in such nanowires. We demonstrate that quantum tunneling of the magnetic flux quanta across the wire yields quantum shot noise which obeys Poisson statistics and is characterized by a power-law dependence of its spectrum SΩ on the external bias. In long wires, SΩ decreases with increasing frequency Ω and vanishes beyond a threshold value of Ω at T →0 . The quantum coherent nature of QPS noise yields nonmonotonous dependence of SΩ on T at small Ω .

  2. Phase Slips in Oscillatory Hair Bundles

    NASA Astrophysics Data System (ADS)

    Roongthumskul, Yuttana; Shlomovitz, Roie; Bruinsma, Robijn; Bozovic, Dolores

    2013-04-01

    Hair cells of the inner ear contain an active amplifier that allows them to detect extremely weak signals. As one of the manifestations of an active process, spontaneous oscillations arise in fluid immersed hair bundles of in vitro preparations of selected auditory and vestibular organs. We measure the phase-locking dynamics of oscillatory bundles exposed to low-amplitude sinusoidal signals, a transition that can be described by a saddle-node bifurcation on an invariant circle. The transition is characterized by the occurrence of phase slips, at a rate that is dependent on the amplitude and detuning of the applied drive. The resultant staircase structure in the phase of the oscillation can be described by the stochastic Adler equation, which reproduces the statistics of phase slip production.

  3. Phase slips in superconducting weak links

    SciTech Connect

    Kimmel, Gregory; Glatz, Andreas; Aranson, Igor S.

    2017-01-01

    Superconducting vortices and phase slips are primary mechanisms of dissipation in superconducting, superfluid, and cold-atom systems. While the dynamics of vortices is fairly well described, phase slips occurring in quasi-one- dimensional superconducting wires still elude understanding. The main reason is that phase slips are strongly nonlinear time-dependent phenomena that cannot be cast in terms of small perturbations of the superconducting state. Here we study phase slips occurring in superconducting weak links. Thanks to partial suppression of superconductivity in weak links, we employ a weakly nonlinear approximation for dynamic phase slips. This approximation is not valid for homogeneous superconducting wires and slabs. Using the numerical solution of the time-dependent Ginzburg-Landau equation and bifurcation analysis of stationary solutions, we show that the onset of phase slips occurs via an infinite period bifurcation, which is manifested in a specific voltage-current dependence. Our analytical results are in good agreement with simulations.

  4. Deterministic phase slips in mesoscopic superconducting rings

    NASA Astrophysics Data System (ADS)

    Petković, I.; Lollo, A.; Glazman, L. I.; Harris, J. G. E.

    2016-11-01

    The properties of one-dimensional superconductors are strongly influenced by topological fluctuations of the order parameter, known as phase slips, which cause the decay of persistent current in superconducting rings and the appearance of resistance in superconducting wires. Despite extensive work, quantitative studies of phase slips have been limited by uncertainty regarding the order parameter's free-energy landscape. Here we show detailed agreement between measurements of the persistent current in isolated flux-biased rings and Ginzburg-Landau theory over a wide range of temperature, magnetic field and ring size; this agreement provides a quantitative picture of the free-energy landscape. We also demonstrate that phase slips occur deterministically as the barrier separating two competing order parameter configurations vanishes. These results will enable studies of quantum and thermal phase slips in a well-characterized system and will provide access to outstanding questions regarding the nature of one-dimensional superconductivity.

  5. Deterministic phase slips in mesoscopic superconducting rings

    PubMed Central

    Petković, I.; Lollo, A.; Glazman, L. I.; Harris, J. G. E.

    2016-01-01

    The properties of one-dimensional superconductors are strongly influenced by topological fluctuations of the order parameter, known as phase slips, which cause the decay of persistent current in superconducting rings and the appearance of resistance in superconducting wires. Despite extensive work, quantitative studies of phase slips have been limited by uncertainty regarding the order parameter's free-energy landscape. Here we show detailed agreement between measurements of the persistent current in isolated flux-biased rings and Ginzburg–Landau theory over a wide range of temperature, magnetic field and ring size; this agreement provides a quantitative picture of the free-energy landscape. We also demonstrate that phase slips occur deterministically as the barrier separating two competing order parameter configurations vanishes. These results will enable studies of quantum and thermal phase slips in a well-characterized system and will provide access to outstanding questions regarding the nature of one-dimensional superconductivity. PMID:27882924

  6. Phase Slips in Topological Superconductor Wire Devices

    NASA Astrophysics Data System (ADS)

    Goldberg, Samuel; Bergman, Doron; Pekker, David; Refael, Gil

    2012-02-01

    We make a detailed study of phase slips in topological superconducting wires and devices based on topological wires. We begin by investigating a device composed of a topological superconducting wire connected to a non-topological wire (T-S). In the T-segment only slips of the phase by multiples of 4π are allowed, while in the S-segment slips by 2π are also allowed. We show that near the interface, 2π phase slips are also allowed and we comment on the consequences of such phase slips for the Aharonov-Casher effect. We also consider an implementation of a q-bit consisting of a T-S-T device, where the quantum information is stored in the parity of the two topological segments via the four Majorana modes. We show that the central S-segment of this type of device can support 2π phase-slips which result in the decoherence of the q-bit.

  7. Macroscopic Quantum Cotunneling of Phase Slips

    NASA Astrophysics Data System (ADS)

    Belkin, Andrey; Belkin, Maxim; Vakaryuk, Victor; Khlebnikov, Sergei; Bezryadin, Alexey

    2014-03-01

    Quantum phenomena that do not have analogues in the classical world include quantum superposition and tunneling. Despite significant efforts invested into demonstration of quantum effects at the macroscopic level, the main principles that govern the transition from classical to quantum are not well understood. Here we report a study of macroscopic quantum tunneling of phase slips that involve both superconducting and normal degrees of freedom in a superconducting nanowire loop. We discover that in addition to single phase slips that unwind the phase difference along the loop by 2 π, there are transitions that change the phase by 4 π. Experimentally we identify the regime in which, surprisingly, 4 π phase slips are more likely than 2 π ones. We interpret our observations in terms of macroscopic cotunneling effect defined as an exact synchronization of two macroscopic phase slip events. The work was supported by grant the DOE Award No. DE-FG0207ER46453, and the NSF No. DMR10-05645

  8. Thermally activated phase slips from metastable states in mesoscopic superconducting rings

    NASA Astrophysics Data System (ADS)

    Petkovic, Ivana; Lollo, Anthony; Harris, Jack

    In equilibrium, a flux-biased superconducting ring at low temperature can occupy any of several metastable states. The particular state that the ring occupies depends on the history of the applied flux, as different states are separated from each other by flux-dependent energy barriers. There is a critical value of the applied flux at which a given barrier goes to zero, the state becomes unstable, and the system transition into another state. In recent experiments performed on arrays of rings we showed that this transition occurs close to the critical flux predicted by Ginzburg-Landau theory. Here, we will describe experiments in which we have extended these measurements to an individual ring in order to study the thermal activation of the ring over a barrier that has been tuned close to zero. We measure the statistics of transitions as function of temperature and ramp rate.

  9. Stochastic phase slips in toroidal Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Snizhko, Kyrylo; Isaieva, Karyna; Kuriatnikov, Yevhenii; Bidasyuk, Yuriy; Vilchinskii, Stanislav; Yakimenko, Alexander

    2016-12-01

    Motivated by recent experiments we study the influence of thermal noise on the phase slips in toroidal Bose-Einstein condensates with a rotating weak link. We derive a generalized Arrhenius-like expression for the rate of stochastic phase slips. We develop a method to estimate the energy barrier separating different superflow states. The parameters at which the energy barrier disappears agree with the critical parameters for deterministic phase slips obtained from dynamics simulations, which confirms the validity of our energetic analysis. We reveal that adding thermal noise lowers the phase-slip threshold. However, the quantitative impact of the stochastic phase slips turns out to be too small to explain the significant discrepancy between theoretical and the experimental results.

  10. Momentum compaction and phase slip factor

    SciTech Connect

    Ng, K.Y.; /Fermilab

    2010-10-01

    Section 2.3.11 of the Handbook of Accelerator Physics and Engineering on Landau damping is updated. The slip factor and its higher orders are given in terms of the various orders of the momentum compaction. With the aid of a simplified FODO lattice, formulas are given for the alteration of the lower orders of the momentum compaction by various higher multipole magnets. The transition to isochronicity is next demonstrated. Formulas are given for the extraction of the first three orders of the slip factor from the measurement of the synchrotron tune while changing the rf frequency. Finally bunch-length compression experiments in semi-isochronous rings are reported.

  11. Phase-slip-induced dissipation in an atomic Bose-Hubbard system.

    PubMed

    McKay, D; White, M; Pasienski, M; DeMarco, B

    2008-05-01

    Phase-slips control dissipation in many bosonic systems, determining the critical velocity of superfluid helium and the generation of resistance in thin superconducting wires. Technological interest has been largely motivated by applications involving nanoscale superconducting circuit elements, such as standards based on quantum phase-slip junctions. Although phase slips caused by thermal fluctuations at high temperatures are well understood, controversy remains over the role of phase slips in small-scale superconductors--in solids, problems such as uncontrolled noise sources and disorder complicate their study and application. Here we show that phase slips can lead to dissipation in a clean and well-characterized Bose-Hubbard system, by experimentally studying the transport of ultracold atoms trapped in an optical lattice. In contrast to previous work, we explore a low-velocity regime described by the three-dimensional Bose-Hubbard model that is unaffected by instabilities, and we measure the effect of temperature on the dissipation strength. The damping rate of atomic motion (the analogue of electrical resistance in a solid) in the confining parabolic potential is well fitted by a model that includes finite damping at zero temperature. The low-temperature behaviour is consistent with the theory of quantum tunnelling of phase slips, whereas at higher temperatures a crossover consistent with a transition to thermal activation of phase slips is evident. Motion-induced features reminiscent of vortices and vortex rings associated with phase slips are also observed in time-of-flight imaging. These results clarify the role of phase slips in superfluid systems. They may also be of relevance in understanding the source of metallic phases observed in thin films, or serve as a test bed for theories of bosonic dissipation based upon variants of the Bose-Hubbard model.

  12. Imaging of early acceleration phase of the 2013-2014 Boso slow slip event

    NASA Astrophysics Data System (ADS)

    Fukuda, J.; Kato, A.; Obara, K.; Miura, S.; Kato, T.

    2014-12-01

    Based on GPS and seismic data, we examine the spatiotemporal evolution of a slow slip event (SSE) and associated seismic activity that occurred off the Boso peninsula, central Japan, from December 2013 to January 2014. We use GPS data from 71 stations of the GEONET and 6 stations operated by Earthquake Research Institute of the University of Tokyo and Tohoku University around the Boso peninsula. We apply a modified version of the Network Inversion Filter to the GPS time series at the 77 stations to estimate the spatiotemporal evolution of daily cumulative slip and slip rate on the subducting Philippine Sea plate. In addition, we create an improved earthquake catalog by applying a matched filter technique to continuous seismograms and examine the spatiotemporal relations between slow slip and seismicity. We find that the SSE started in early December 2013. The spatiotemporal evolution of slow slip and seismicity is divided into two distinct phases, an earlier slow phase from early to 30 December 2013 (Phase I) and a subsequent faster phase from 30 December 2013 to 9 January 2014 (Phase II). During Phase I, slip accelerated slowly up to a maximum rate of 1.6 m/yr with potentially accelerating along-strike propagation at speeds on the order of 1 km/day or less and no accompanying seismicity. On the other hand, during Phase II, slip accelerated rapidly up to a maximum rate of 4.5 m/yr and then rapidly decelerated. The slip front propagated along strike at a constant speed of ~10 km/day. During the Phase II, slow slip was accompanied by seismic swarm activity that was highly correlated in space and time with slip rate, suggesting that the swarm activity was triggered by stress loading due to slow slip. Early slow acceleration of slip has not been identified in the past Boso SSEs in 1996, 2002, 2007, and 2011. It is not clear at this point whether the past Boso SSEs started with slow acceleration similarly to the 2013-2014 SSE. The transition from the slow to the

  13. Measurement of Quantum Phase-Slips in Josephson Junction Chains

    NASA Astrophysics Data System (ADS)

    Guichard, Wiebke

    2011-03-01

    Quantum phase-slip dynamics in Josephson junction chains could provide the basis for the realization of a new type of topologically protected qubit or for the implementation of a new current standard. I will present measurements of the effect of quantum phase-slips on the ground state of a Josephson junction chain. We can tune in situ the strength of the phase-slips. These phase-slips are the result of fluctuations induced by the finite charging energy of each junction in the chain. Our measurements demonstrate that a Josephson junction chain under phase bias constraint behaves in a collective way. I will also show evidence of coherent phase-slip interference, the so called Aharonov-Casher effect. This phenomenon is the dual of the well known Aharonov-Bohm interference. In collaboration with I.M. Pop, Institut Neel, C.N.R.S. and Universite Joseph Fourier, BP 166, 38042 Grenoble, France; I. Protopopov, L. D. Landau Institute for Theoretical Physics, Kosygin str. 2, Moscow 119334, Russia and Institut fuer Nanotechnologie, Karlsruher Institut fuer Technologie, 76021 Karlsruhe, Germany; and F. Lecocq, Z. Peng, B. Pannetier, O. Buisson, Institut Neel, C.N.R.S. and Universite Joseph Fourier. European STREP MIDAS, ANR QUANTJO.

  14. Quantum Nucleation of Phase Slips in 1-d Superfluids

    NASA Astrophysics Data System (ADS)

    Arovas, Daniel

    1998-03-01

    The rate for quantum nucleation of phase slips past an impurity in a one-dimensional superfluid is computed. Real time evolution of the nonlinear Schrödinger equation shows that there is a critical velocity vc below which solutions are time-independent [1,2]; this is the regime of quantum phase slip nucleation. We start with the Gross-Pitaevskii model in the presence of an impurity potential, and derive the Euclidean action for a space-time vortex-antivortex pair, which describes a phase slip event. The action is computed as a function of the superfluid velocity v and the impurity potential width and depth.l [1] V. Hakim, Phys. Rev. E 55, 2835 (1997).l [1] J. A. Freire, D. P. Arovas, and H. Levine, Phys. Rev. Lett (in press, 1997).l

  15. Quantum Phase Slips in Topological Josephson Junction Rings

    NASA Astrophysics Data System (ADS)

    Rodriguez Mota, Rosa; Vishveshwara, Smitha; Pereg-Barnea, Tami

    We study quantum phase slip processes (QPS) in a ring of N topological superconducting islands joined by Josephson junctions and threaded by magnetic flux. In this array, neighboring islands interact through the usual charge 2e Josephson tunneling and the Majorana assisted charge e tunneling. When the charging energy associated with the island's capacitance is zero, the energy vs. flux relation of the system is characterized by parabolas centered around even or odd multiples of the superconducting flux quantum, depending on the parity of the system. For small but non-zero charging energy, quantum fluctuations can lead to tunneling between these classical states. In this work, we calculate the amplitude of these tunneling processes, commonly known as quantum phase slips. We also add gate voltages to our system and study how the amplitude of QPS in these topological Josephson array is modified by Aharanov-Casher interference effects.

  16. Slip sense inversion on active strike-slip faults in southwest Japan and its implications for Cenozoic tectonic evolution

    NASA Astrophysics Data System (ADS)

    Maruyama, Tadashi; Lin, Aiming

    2004-05-01

    Analyses of deflected river channels, offset of basement rocks, and fault rock structures reveal that slip sense inversion occurred on major active strike-slip faults in southwest Japan such as the Yamasaki and Mitoke fault zones and the Median Tectonic Line (MTL). Along the Yamasaki and Mitoke fault zones, small-size rivers cutting shallowly mountain slopes and Quaternary terraces have been deflected sinistrally, whereas large-size rivers which deeply incised into the Mio-Pliocene elevated peneplains show no systematically sinistral offset or complicated hairpin-shaped deflection. When the sinistral offsets accumulated on the small-size rivers are restored, the large-size rivers show residual dextral deflections. This dextral offset sense is consistent with that recorded in the pre-Cenozoic basement rocks. S-C fabrics of fault gouge and breccia zone developed in the active fault zones show sinistral shear sense compatible with earthquake focal mechanisms, whereas those of the foliated cataclasite indicate a dextral shear sense. These observations show that the sinistral strike-slip shear fabrics were overprinted on dextral ones which formed during a previous deformation phase. Similar topographic and geologic features are observed along the MTL in the central-eastern part of the Kii Peninsula. Based on these geomorphological and geological data, we infer that the slip sense inversion occurred in the period between the late Tertiary and mid-Quaternary period. This strike-slip inversion might result from the plate rearrangement consequent to the mid-Miocene Japan Sea opening event. This multidisciplinary study gives insight into how active strike-slip fault might evolves with time.

  17. Topological Effects on Quantum Phase Slips in Superfluid Spin Transport.

    PubMed

    Kim, Se Kwon; Tserkovnyak, Yaroslav

    2016-03-25

    We theoretically investigate effects of quantum fluctuations on superfluid spin transport through easy-plane quantum antiferromagnetic spin chains in the large-spin limit. Quantum fluctuations result in the decaying spin supercurrent by unwinding the magnetic order parameter within the easy plane, which is referred to as phase slips. We show that the topological term in the nonlinear sigma model for the spin chains qualitatively differentiates the decaying rate of the spin supercurrent between the integer versus half-odd-integer spin chains. An experimental setup for a magnetoelectric circuit is proposed, in which the dependence of the decaying rate on constituent spins can be verified by measuring the nonlocal magnetoresistance.

  18. Reachability and Real-Time Actuation Strategies for the Active SLIP Model

    DTIC Science & Technology

    2015-06-01

    reachability space of the actuated SLIP model by acti- vating the series elastic actuator at any possible time during the stance phase. Starting from the...University of California Santa Barbara Reachability and Real- Time Actuation Strategies for the Active SLIP Model A dissertation submitted in partial...Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions

  19. Quantum phase-slip junction under microwave irradiation

    NASA Astrophysics Data System (ADS)

    Di Marco, A.; Hekking, F. W. J.; Rastelli, G.

    2015-05-01

    We consider the dynamics of a quantum phase-slip junction (QPSJ), a dual Josephson junction, connected to a microwave source with frequency ωmw. With respect to an ordinary Josephson junction, a QPSJ can sustain dual Shapiro steps, consisting of well-defined current plateaus at multiple integers of e ωmw/π in the current-voltage (I -V ) characteristic. The experimental observation of these plateaus has been elusive up to now. We argue that thermal as well as quantum fluctuations can smear the I -V characteristic considerably. In order to understand these effects, we study a current-biased QPSJ under microwave irradiation and connected to an inductive and resistive environment. We find that the effect of the fluctuations is governed by the resistance of the environment and by the ratio of the phase-slip energy and the inductive energy. Our results are of interest for experiments aiming at the observation of dual Shapiro steps in QPSJ devices for the definition of a new quantum current standard.

  20. Velocity-dependent quantum phase slips in 1D atomic superfluids

    PubMed Central

    Tanzi, Luca; Scaffidi Abbate, Simona; Cataldini, Federica; Gori, Lorenzo; Lucioni, Eleonora; Inguscio, Massimo; Modugno, Giovanni; D’Errico, Chiara

    2016-01-01

    Quantum phase slips are the primary excitations in one-dimensional superfluids and superconductors at low temperatures but their existence in ultracold quantum gases has not been demonstrated yet. We now study experimentally the nucleation rate of phase slips in one-dimensional superfluids realized with ultracold quantum gases, flowing along a periodic potential. We observe a crossover between a regime of temperature-dependent dissipation at small velocity and interaction and a second regime of velocity-dependent dissipation at larger velocity and interaction. This behavior is consistent with the predicted crossover from thermally-assisted quantum phase slips to purely quantum phase slips. PMID:27188334

  1. Quantum Phase Slips in 6 mm Long Niobium Nanowire.

    PubMed

    Zhao, Weiwei; Liu, Xin; Chan, M H W

    2016-02-10

    Transport measurements were made to study the superconducting transition of four 6 mm long niobium nanowires with different cross-sectional dimensions. A low-temperature residual resistance tail measured with an excitation current of 5 nA is found in the thinnest wire down to 50 mK or 7.7% of Tc of Nb. The functional form of the residual resistance is consistent with quantum phase slip (QPS) processes. Resistance measured at high bias excitation current switches among many discrete values that are well below the normal state resistance. These discrete resistance values as a function of temperature fall into several parallel curves all showing QPS-like decay in the low temperature limit similar to that found at low current. The coexistence of QPS-like resistance tails and resistance jumps found in the same wire unifies results from previous experiments where these two distinct sets of evidence for QPS are exclusive of each other.

  2. Collective Quantum Phase-Slip Dynamics in Superconducting Nanowire Arrays

    NASA Astrophysics Data System (ADS)

    Skacel, Sebastian T.; Voss, Jan N.; Bier, Tobias; Radke, Lucas; Weides, Martin; Rotzinger, Hannes; Mooij, Hans E.; Ustinov, Alexey V.

    2014-03-01

    Superconducting nanowire arrays exhibit quantum phase-slip (QPS) phenomenon if the superconductor has a very high normal-state sheet resistance. We experimentally study QPS effects in arrays of nanowires embedded in a resonant circuit at GHz frequencies. We probe this circuit at ultra-low microwave power, applied flux and mK temperatures. The nanowires are fabricated utilizing aluminium grown in a precisely-controlled oxygen atmosphere. In this way, we aim to control the QPS rate for a given wire width. The wires are defined with conventional electron beam lithography down to a width of 20 nm. We will present the fabrication of the nanowire arrays and first microwave measurements at mK temperatures. Center for Functional Nanostructures, Karlsruhe Institute of Technology, D-76128 Karlsruhe, Germany.

  3. Statistics of localized phase slips in tunable width planar point contacts

    PubMed Central

    Baumans, Xavier D.A.; Zharinov, Vyacheslav S.; Raymenants, Eline; Blanco Alvarez, Sylvain; Scheerder, Jeroen E.; Brisbois, Jérémy; Massarotti, Davide; Caruso, Roberta; Tafuri, Francesco; Janssens, Ewald; Moshchalkov, Victor V.; Van de Vondel, Joris; Silhanek, Alejandro V.

    2017-01-01

    The main dissipation mechanism in superconducting nanowires arises from phase slips. Thus far, most of the studies focus on long nanowires where coexisting events appear randomly along the nanowire. In the present work we investigate highly confined phase slips at the contact point of two superconducting leads. Profiting from the high current crowding at this spot, we are able to shrink in-situ the nanoconstriction. This procedure allows us to investigate, in the very same sample, thermally activated phase slips and the probability density function of the switching current Isw needed to trigger an avalanche of events. Furthermore, for an applied current larger than Isw, we unveil the existence of two distinct thermal regimes. One corresponding to efficient heat removal where the constriction and bath temperatures remain close to each other, and another one in which the constriction temperature can be substantially larger than the bath temperature leading to the formation of a hot spot. Considering that the switching current distribution depends on the exact thermal properties of the sample, the identification of different thermal regimes is of utmost importance for properly interpreting the dissipation mechanisms in narrow point contacts. PMID:28300182

  4. Statistics of localized phase slips in tunable width planar point contacts

    NASA Astrophysics Data System (ADS)

    Baumans, Xavier D. A.; Zharinov, Vyacheslav S.; Raymenants, Eline; Blanco Alvarez, Sylvain; Scheerder, Jeroen E.; Brisbois, Jérémy; Massarotti, Davide; Caruso, Roberta; Tafuri, Francesco; Janssens, Ewald; Moshchalkov, Victor V.; van de Vondel, Joris; Silhanek, Alejandro V.

    2017-03-01

    The main dissipation mechanism in superconducting nanowires arises from phase slips. Thus far, most of the studies focus on long nanowires where coexisting events appear randomly along the nanowire. In the present work we investigate highly confined phase slips at the contact point of two superconducting leads. Profiting from the high current crowding at this spot, we are able to shrink in-situ the nanoconstriction. This procedure allows us to investigate, in the very same sample, thermally activated phase slips and the probability density function of the switching current Isw needed to trigger an avalanche of events. Furthermore, for an applied current larger than Isw, we unveil the existence of two distinct thermal regimes. One corresponding to efficient heat removal where the constriction and bath temperatures remain close to each other, and another one in which the constriction temperature can be substantially larger than the bath temperature leading to the formation of a hot spot. Considering that the switching current distribution depends on the exact thermal properties of the sample, the identification of different thermal regimes is of utmost importance for properly interpreting the dissipation mechanisms in narrow point contacts.

  5. Threshold of Geomorphic Detectability Estimated from Geologic Observations of Active Slow-Slipping Strike-Slip Faults

    NASA Astrophysics Data System (ADS)

    Kaneda, H.

    2002-12-01

    Sources of catastrophic earthquakes include not only major active faults, but also slow-slipping ones. However, geomorphic characteristics and long-term seismic behavior of slow-slipping faults have not been well understood, although intensive paleoseismic studies were carried out after the unexpected 1992 Landers and 1999 Hector Mine earthquakes. Two Japanese surface faulting earthquakes on slow-slipping strike-slip faults (the 1927 Mw=7.0 Kita-Tango and 1943 Mw=7.0 Tottori earthquakes) provided good opportunity to examine these problems. Analysis of coseismic surface slip, cumulative geomorphic expressions, and paleoseismicity for these two events not only supports a characteristic-slip behavior for these faults, but also suggests a concept of threshold of geomorphic detectability for intramontane strike-slip faults, which must be exceeded in order that progressive coseismic surface offsets can be preserved against surface processes as detectable systematic deflections of channels and ridge crests. The determined threshold slip rates for these examples are in the range of 0.06-0.13 mm/yr, which can be a quantitative explanation for an extremely small number of mapped active faults with slip rates of less than 0.1 mm/yr in Japan islands. On the contrary, the threshold of geomorphic detectability is probably negligible in arid regions where denudation rate would be extremely low. To date, the issue of geomorphologically undetectable active faults has been that of blind thrust faults buried beneath thick sediments, but another type of blind active faults or fault segments can exist in humid and mountainous regions. In spite of their low slip rates and long recurrence intervals, their potential presence must be considered, especially in regions under the tectonically undeveloped regime, where regional strain is accommodated by many scattered slow-slipping faults.

  6. Loading and texture bias on the competitive slip activity for basal and prismatic slip systems in HCP alloys

    NASA Astrophysics Data System (ADS)

    Saxena, A. K.; Tewari, A.; Pant, P.

    2015-04-01

    Asymmetry in hexagonal crystal structure makes the occurrence of slip strongly dependent on the texture of sample. In titanium, which has a c/a ratio less than ideal, slip occurs preferentially on prismatic slip system. However other slip systems may get activated depending on the resolved shear stresses. In this paper we present results from plane strain compression experiments where the same area of the sample was imaged before and after deformation to document changes in microstructure. We then compare these results with a simple calculation of plastic strain based on activation of various slip systems depending on their respective critical resolved shear stresses. We show that incorporation of a strain rate dependent hardening parameter provides a reasonable match with the experimentally observed deformation behaviour of various grain orientations.

  7. Tailoring phase slip events through magnetic doping in superconductor-ferromagnet composite films.

    PubMed

    Bawa, Ambika; Jha, Rajveer; Sahoo, Sangeeta

    2015-08-25

    The interplay between superconductivity (SC) and ferromagnetism (FM) when embedded together has attracted unprecedented research interest due to very rare coexistence of these two phenomena. The focus has been mainly put into the proximity induced effects like, coexistence of magnetism and superconductivity, higher critical current, triplet superconductivity etc. However, very little attention has been paid experimentally to the role of magnetic constituent on triggering phase slip processes in the composite films (CFs). We demonstrate that less than 1 at.% of magnetic contribution in the CFs can initiate phase slip events efficiently. Due to advanced state-of-the-art fabrication techniques, phase slip based studies have been concentrated mainly on superconducting nanostructures. Here, we employ wide mesoscopic NbGd based CFs to study the phase slip processes. Low temperature current-voltage characteristics (IVCs) of CFs show stair-like features originated through phase slip events and are absent in pure SC films. Depending on the bias current and temperature, distinct regions, dominated by Abrikosov type vortex-antivortex (v-av) pairs and phase slip events, are observed. The results presented here open a new way to study the phase slip mechanism, its interaction with v-av pairs in two dimensions and hence can be useful for future photonic and metrological applications.

  8. Evidence for coherent quantum phase slips across a Josephson junction array

    NASA Astrophysics Data System (ADS)

    Manucharyan, Vladimir E.; Masluk, Nicholas A.; Kamal, Archana; Koch, Jens; Glazman, Leonid I.; Devoret, Michel H.

    2012-01-01

    Superconducting order in a sufficiently narrow and infinitely long wire is destroyed at zero temperature by quantum fluctuations, which induce 2π slips of the phase of the order parameter. However, in a finite-length wire, coherent quantum phase slips would manifest themselves simply as shifts of energy levels in the excitation spectrum of an electrical circuit incorporating this wire. The higher the phase slips' probability amplitude, the larger are the shifts. Phase slips occurring at different locations along the wire interfere with each other. Due to the Aharonov-Casher effect, the resulting full amplitude of a phase slip depends on the offset charges surrounding the wire. Slow temporal fluctuations of the offset charges make the phase-slip amplitudes random functions of time, and therefore turn energy level shifts into linewidths. We experimentally observed this effect on a long Josephson junction array acting as a “slippery” wire. The slip-induced linewidths, despite being only of order 100kHz, were resolved from the flux-dependent dephasing of the fluxonium qubit.

  9. Spacing and strength of active continental strike-slip faults

    NASA Astrophysics Data System (ADS)

    Zuza, Andrew V.; Yin, An; Lin, Jessica; Sun, Ming

    2017-01-01

    Parallel and evenly-spaced active strike-slip faults occur widely in nature across diverse tectonic settings. Despite their common existence, the fundamental question of what controls fault spacing remains unanswered. Here we present a mechanical model for the generation of parallel strike-slip faults that relates fault spacing to the following parameters: (1) brittle-crust thickness, (2) fault strength, (3) crustal strength, and (4) crustal stress state. Scaled analogue experiments using dry sand, dry crushed walnut shells, and viscous putty were employed to test the key assumptions of our quantitative model. The physical models demonstrate that fault spacing (S) is linearly proportional to brittle-layer thickness (h), both in experiments with only brittle materials and in two-layer trials involving dry sand overlying viscous putty. The S / h slope in the two-layer sand-putty experiments may be controlled by the (1) rheological/geometric properties of the viscous layer, (2) effects of distributed basal loading caused by the viscous shear of the putty layer, and/or (3) frictional interaction at the sand-putty interface (i.e., coupling between the viscous and brittle layers). We tentatively suggest that this third effect exerts the strongest control on fault spacing in the analogue experiments. By applying our quantitative model to crustal-scale strike-slip faults using fault spacing and the seismogenic-zone thickness obtained from high-resolution earthquake-location data, we estimate absolute fault friction of active strike-slip faults in Asia and along the San Andreas fault system in California. We show that the average friction coefficient of strike-slip faults in the India-Asia collisional orogen is lower than that of faults in the San Andreas fault system. Weaker faults explain why deformation penetrates >3500 km into Asia from the Himalaya and why the interior of Asia is prone to large (M > 7.0) devastating earthquakes along major intra-continental strike-slip

  10. Threshold of geomorphic detectability estimated from geologic observations of active low slip-rate strike-slip faults

    NASA Astrophysics Data System (ADS)

    Kaneda, Heitaro

    2003-03-01

    Sources of catastrophic earthquakes include not only major active faults, but also those with low slip rates. Geologic observations of two Japanese surface-rupturing earthquakes on low slip-rate strike-slip faults (the 1927 Kita-Tango and the 1943 Tottori earthquakes) suggests a concept of ``threshold of geomorphic detectability'' for strike-slip faults in humid mountainous regions. This threshold must be exceeded in order that progressive coseismic surface offset can be preserved as detectable faulted topography that may be otherwise erased by surface processes. The determined threshold minimum slip rates for both examples are about 0.1 mm/yr, which can be a quantitative explanation for lack of recognition and mapping of many active faults with slip rates of less than 0.1 mm/yr in Japan islands. Although this threshold is probably negligible in arid regions, it can produce another type of unrecognized active fault in humid mountainous regions, in addition to blind thrusts beneath thick sediments.

  11. Predicting active slip systems in β-Sn from ideal shear resistance

    NASA Astrophysics Data System (ADS)

    Kinoshita, Y.; Matsushima, H.; Ohno, N.

    2012-04-01

    We analyse the ideal shear resistances of 15 nonequivalent slip systems in β-Sn using first-principles density functional theory. From the ideal shear resistance and Schmid's law, the orientation dependence of active slip systems in a β-Sn single crystal subjected to uniaxial tension is investigated. We find that (1\\,0\\,1)[\\bar{1}\\,0\\,1] has the lowest ideal shear resistance among the 15 slip systems. Our calculations indicate that, depending on crystal orientation, uniaxial tension activates seven nonequivalent groups of slip systems. The active slip systems for [1 0 0] and [1 1 0] orientations determined in this study agree with the experimental results.

  12. Phase-locked servo system. [for synchronizing the rotation of slip ring assembly

    NASA Technical Reports Server (NTRS)

    Burdin, C. (Inventor)

    1974-01-01

    A phase lock servo system is described for synchronizing the rotation of a slip ring assembly with the rotation of an air bearing table so that a minimum of torque will be imparted through cables extending from the slip ring assembly to the air bearing table as such is rotated. The system includes two servo loops. The first servo loop includes a rate gyroscope carried on the air bearing table which generates a signal through a summing junction to be compared with a signal coming from a tachometer coupled to the slip ring assembly. The corrective signal is applied to a torque motor for rotating the slip ring assembly. The second servo loop includes a pair of photo detector cells which generate pulses responsive to the rotation of the air bearing table and slip ring assembly which are fed through a phase detector, and a variable gain amplifier to the summing junction circuit to provide a fine adjustment for rotating the slip ring assembly.

  13. Phase-Slip Avalanches in the Superflow of {sup 4}He through Arrays of Nanosize Apertures

    SciTech Connect

    Pekker, David; Barankov, Roman; Goldbart, Paul M.

    2007-04-27

    In response to recent experiments by the Berkeley group, we construct a model of superflow through an array of nanosize apertures that incorporates two basic ingredients: (1) disorder associated with each aperture having its own random critical velocity, and (2) effective interaperture coupling, mediated through the bulk superfluid. As the disorder becomes weak there is a transition from a regime where phase slips are largely independent to a regime where interactions lead to system-wide avalanches of phase slips. We explore the flow dynamics in both regimes, and make connections to the experiments.

  14. Weak-light phase tracking with a low cycle slip rate.

    PubMed

    Francis, Samuel P; Lam, Timothy T-Y; McKenzie, Kirk; Sutton, Andrew J; Ward, Robert L; McClelland, David E; Shaddock, Daniel A

    2014-09-15

    The Gravity Recovery and Climate Experiment Follow-On mission will use a phase-locked loop to track changes in the phase of an optical signal that has been transmitted hundreds of kilometers between two spacecraft. Beam diffraction significantly reduces the received signal power, making it difficult to track, as the phase-locked loop is more susceptible to cycle slips. The lowest reported weak-light phase locking is at 40 fW with a cycle slip rate of 1 cycle per second. By selecting a phase-locked loop bandwidth that minimized the signal variance due to shot noise and laser phase fluctuations, a 30 fW signal has been tracked with a cycle slip rate less than 0.01 cycles per second. This is tracking at a power 25% lower with a 100-fold improvement in the cycle slip rate. This capability will enable a new class of missions, opening up new opportunities for space-based interferometry.

  15. Simplified formula for mean cycle-slip time of phase-locked loops with steady-state phase error.

    NASA Technical Reports Server (NTRS)

    Tausworthe, R. C.

    1972-01-01

    Previous work shows that the mean time from lock to a slipped cycle of a phase-locked loop is given by a certain double integral. Accurate numerical evaluation of this formula for the second-order loop is extremely vexing because the difference between exponentially large quantities is involved. The presented article demonstrates a method in which a much-reduced precision program can be used to obtain the mean first-cycle slip time for a loop of arbitrary degree tracking at a specified SNR and steady-state phase error. It also presents a simple approximate formula that is asymptotically tight at higher loop SNR.

  16. Quantum Nucleation of Phase Slips in a 1D Model of a Superfluid

    SciTech Connect

    Freire, J.A.; Arovas, D.P.; Levine, H.

    1997-12-01

    We use a 1D model of a superfluid based on the Gross-Pitaevskii Lagrangian to illustrate a general numerical method designed to find quantum tunneling rates in extended bosonic systems. Specifically, we study flow past an obstacle and directly solve the imaginary time dynamics to find the {open_quotes}bounce{close_quotes} solution connected with the decay of the metastable laminar state via phase slip nucleation. The action for the tunneling configuration goes to zero at the threshold (in superfluid velocity) for classical production of these slips. Applications to other processes are briefly discussed. {copyright} {ital 1997} {ital The American Physical Society}

  17. Lag, lock, sync, slip: the many 'phases' of coupled flagella.

    PubMed

    Wan, Kirsty Y; Leptos, Kyriacos C; Goldstein, Raymond E

    2014-05-06

    In a multitude of life's processes, cilia and flagella are found indispensable. Recently, the biflagellated chlorophyte alga Chlamydomonas has become a model organism for the study of ciliary motility and synchronization. Here, we use high-speed, high-resolution imaging of single pipette-held cells to quantify the rich dynamics exhibited by their flagella. Underlying this variability in behaviour are biological dissimilarities between the two flagella-termed cis and trans, with respect to a unique eyespot. With emphasis on the wild-type, we derive limit cycles and phase parametrizations for self-sustained flagellar oscillations from digitally tracked flagellar waveforms. Characterizing interflagellar phase synchrony via a simple model of coupled oscillators with noise, we find that during the canonical swimming breaststroke the cis flagellum is consistently phase-lagged relative to, while remaining robustly phase-locked with, the trans flagellum. Transient loss of synchrony, or phase slippage, may be triggered stochastically, in which the trans flagellum transitions to a second mode of beating with attenuated beat envelope and increased frequency. Further, exploiting this alga's ability for flagellar regeneration, we mechanically induced removal of one or the other flagellum of the same cell to reveal a striking disparity between the beatings of the cis and trans flagella, in isolation. These results are evaluated in the context of the dynamic coordination of Chlamydomonas flagella.

  18. Double phase slips and bound defect pairs in parametrically driven waves

    SciTech Connect

    Riecke, H.; Granzow, G.D.

    1997-12-31

    Spatio-temporal chaos in parametrically driven waves is investigated in one and two dimensions using numerical simulations of Ginzburg-Landau equations. A regime is identified in which in one dimension the dynamics are due to double phase slips. In very small systems they are found to arise through a Hopf bifurcation off a mixed mode. In large systems they can lead to a state of localized spatio-temporal chaos, which can be understood within the framework of phase dynamics. In two dimensions the double phase slips are replaced by bound defect pairs. Our simulations indicate the possibility of an unbinding transition of these pairs, which is associated with a transition from ordered to disordered defect chaos.

  19. Quantum phase slip phenomenon in ultra-narrow superconducting nanorings

    PubMed Central

    Arutyunov, Konstantin Yu.; Hongisto, Terhi T.; Lehtinen, Janne S.; Leino, Leena I.; Vasiliev, Alexander L.

    2012-01-01

    The smaller the system, typically - the higher is the impact of fluctuations. In narrow superconducting wires sufficiently close to the critical temperature Tc thermal fluctuations are responsible for the experimentally observable finite resistance. Quite recently it became possible to fabricate sub-10 nm superconducting structures, where the finite resistivity was reported within the whole range of experimentally obtainable temperatures. The observation has been associated with quantum fluctuations capable to quench zero resistivity in superconducting nanowires even at temperatures T→0. Here we demonstrate that in tiny superconducting nanorings the same phenomenon is responsible for suppression of another basic attribute of superconductivity - persistent currents - dramatically affecting their magnitude, the period and the shape of the current-phase relation. The effect is of fundamental importance demonstrating the impact of quantum fluctuations on the ground state of a macroscopically coherent system, and should be taken into consideration in various nanoelectronic applications. PMID:22389762

  20. GNSS Phase Scintillation and Cycle Slips Occurrence at High Latitudes: Climatology and Forecasting

    NASA Astrophysics Data System (ADS)

    Prikryl, Paul; Jayachandran, Periyadan T.; Chadwick, Richard; Kelly, Todd D.

    2014-05-01

    Space weather impacts the operation of modern technology that relies on Global Navigation Satellite Systems (GNSS). Ionospheric scintillation (rapid fluctuation of radio wave amplitude and phase) degrades GPS positional accuracy and causes cycle slips leading to loss of lock that affects performance of radio communication and navigation systems. At high latitudes, GPS scintillation and total electron content has been monitored by the Canadian High Arctic Ionospheric Network (CHAIN). GPS phase scintillation and cycle slips, as a function of magnetic latitude and local time, occur on the dayside in the ionospheric cusp, in the nightside auroral oval, and in the polar cap. Interplanetary coronal mass ejections and corotating interaction regions on the leading edge of high-speed streams are closely correlated with the occurrence of scintillation at high latitudes. Results of a superposed epoch analysis of time series of phase scintillation and cycle slips occurrence keyed by arrival times of high speed solar wind streams and interplanetary coronal mass ejections are presented. Based on these results, a method of probabilistic forecasting of high-latitude phase scintillation occurrence is proposed.

  1. Quantized phase slips with hysteresis in rotating spin-orbit-coupled Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Zhang, Chuanyi

    2017-03-01

    Recently, hysteresis has been observed experimentally in a quantized superfluid circuit [S. Eckel, J. G. Lee, F. Jendrzejewski, N. Murray, C. W. Clark, C. J. Lobb, W. D. Phillips, M. Edwards, and G. K. Campbell, Nature (London) 506, 200 (2014), 10.1038/nature12958], which is a very important step for developing atomtronic devices. Here we find that quantized phase slips occur as the angular velocity rises, and the average angular momenta are quantized at special angular velocities, immune to the nonlinear interactions. When the spin and orbital angular momentum coupling is introduced, we find that two hysteresis loops could arise for each spin, and there exists a phase slip for spin up in one loop and spin down in the other loop. At the special angular velocities, a phase slip emerges for spin down in the lower state of the loop. Especially, multistability appears if the angular velocity is located in the hysteretic region. These results can promote experimental verification and pave the way for atomtronic devices.

  2. Trunk angular kinematics during slip-induced backward falls and activities of daily living.

    PubMed

    Liu, Jian; Lockhart, Thurmon E

    2014-10-01

    Prior to developing any specific fall detection algorithm, it is critical to distinguish the unique motion features associated with fall accidents. The current study aimed to investigate the upper trunk angular kinematics during slip-induced backward falls and activities of daily living (ADLs). Ten healthy older adults (age = 75 ± 6 yr (mean ± SD)) were involved in a laboratory study. Sagittal trunk angular kinematics were measured using optical motion analysis system during normal walking, slip-induced backward falls, lying down, bending over, and various types of sitting down (SN). Trunk angular phase-plane plots were generated to reveal the motion features of falls. It was found that backward falls were characterized by a simultaneous occurrence of a slight trunk extension and an extremely high trunk extension velocity (peak average = 139.7 deg/s), as compared to ADLs (peak average = 84.1 deg/s). It was concluded that the trunk extension angular kinematics of falls were clearly distinguishable from those of ADLs from the perspective of angular phase-plane plot. Such motion features can be utilized in future studies to develop a new prior-to-impact fall detection algorithm.

  3. 400My of Deformation Along Tibet Active Strike Slip Faults

    NASA Astrophysics Data System (ADS)

    Arnaud, N. O.

    2003-12-01

    While it is widely accepted that strike slip faults in Tibet accommodate a significant part of the tertiary convergence between India and Asia, the true Cenozoic magnitude of the offset is still largely debated. Direct dating of Cenozoic piercing points is the most powerful tool to assess the total offset, but their use is not always possible. Therefore one gets to use older markers although this leads to significant results ONLY at the supreme condition that pre-Cenozoic movement of those markers be accurately known. The Kunlun and Altyn Tagh faults for example form a prominent example of Tibetan presently active fault, but they also constitute geological frontiers between blocks of different geological histories accreted at various times since early Paleozoic. One may thus question how much of the visible offset is indeed Cenozoic. Although deformation facies agree with recent kinematics, multi-geochronological approach indicates a series of events from 280-230 Ma to 120+/-10 Ma. The former may be linked either with suturing of the Qiantang and Kunlun blocks farther to the south, or collision further to the north or east in the Qilian Shan and Bei Shan ranges, while the latter range appears to be growing in importance with ongoing work but is still largely unexplained. Oblique subductions of collision to the north of the Qilian Shan are adequate candidates. Argon loss suggests that deformation was associated to a 250-300° C thermal pulse that lasted 5 to 20 Ma after the onset of movement (Arnaud et al., 2003). Unroofing on all faults occurred much later, around 25 Ma ago when sudden cooling suggests a component of normal faulting (Mock et al., 1999). Strong inheritage was also found along the Ghoza active fault, in central western Tibet. Of course the fact that some of the deformation is much older than the Cretaceous and shares compatible deformation criteria with the present-day deformation leads to false appreciation of the pure Cenozoic offset, potentially

  4. Slip rate depth distribution for active faults in Central Italy using numerical models

    NASA Astrophysics Data System (ADS)

    Finocchio, Debora; Barba, Salvatore; Basili, Roberto

    2016-09-01

    Slip rate is a critical parameter for describing geologic and earthquake rates of known active faults. Although faults are inherently three-dimensional surfaces, the paucity of data allows for estimating only the slip rate at the ground surface and often only few values for an entire fault. These values are frequently assumed as proxies or as some average of slip rate at depth. Evidence of geological offset and single earthquake displacement, as well as mechanical requirements, show that fault slip varies significantly with depth. Slip rate should thus vary in a presumably similar way, yet these variations are rarely considered. In this work, we tackle the determination of slip rate depth distributions by applying the finite element method on a 2D vertical section, with stratification and faults, across the central Apennines, Italy. In a first step, we perform a plane-stress analysis assuming visco-elasto-plastic rheology and then search throughout a large range of values to minimize the RMS deviation between the model and the interseismic GPS velocities. Using a parametric analysis, we assess the accuracy of the best model and the sensitivity of its parameters. In a second step, we unlock the faults and let the model simulate 10 kyr of deformation to estimate the fault long-term slip rates. The overall average slip rate at depth is approximately 1.1 mm/yr for normal faults and 0.2 mm/yr for thrust faults. A maximum value of about 2 mm/yr characterizes the Avezzano fault that caused the 1915, Mw 7.0 earthquake. The slip rate depth distribution varies significantly from fault to fault and even between neighbouring faults, with maxima and minima located at different depths. We found uniform distributions only occasionally. We suggest that these findings can strongly influence the forecasting of cumulative earthquake depth distributions based on long-term fault slip rates.

  5. Longitudinal beam dynamics with phase slip in race-track microtrons

    NASA Astrophysics Data System (ADS)

    Kubyshin, Yu. A.; Poseryaev, A. P.; Shvedunov, V. I.

    2008-11-01

    Implementation of low-energy injection schemes in race-track microtron (RTM) designs requires a better understanding of the longitudinal beam dynamics. Unlike the high-energy case a low-energy beam slips in phase with respect to the accelerating field phase so that the standard notion of synchronous particle is not applicable. In the article, we generalize the concept of synchronous particle for the case of non-relativistic energies. An analytic approach for the description of the synchronous phase slip is developed and explicit, though approximate, formulas which allow to determine the equilibrium injection phase and to fix the parameters of the accelerator are derived. The approximation can be improved in a systematic way by calculating higher-order corrections. The precision of the analytic approach is checked by direct numerical computations and is shown to be quite satisfactory. Explicit examples of injection schemes and fixing of RTM global parameters are presented. We also address the issue of stability of synchrotron oscillations around the generalized synchronous trajectory and introduce the notion of critical energy.

  6. Phase slips and vortex dynamics in Josephson oscillations between Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Abad, M.; Guilleumas, M.; Mayol, R.; Piazza, F.; Jezek, D. M.; Smerzi, A.

    2015-02-01

    We study the relation between Josephson dynamics and topological excitations in a dilute Bose-Einstein condensate confined in a double-well trap. We show that the phase slips responsible for the self-trapping regime are created by vortex rings entering and annihilating inside the weak-link region or created at the center of the barrier and expanding outside the system. Large amplitude oscillations just before the onset of self-trapping are also strictly connected with the dynamics of vortex rings at the edges of the inter-well barrier. Our results extend and analyze the dynamics of the vortex-induced phase slippages suggested a few decades ago in relation to the “ac” Josephson effect of superconducting and superfluid helium systems.

  7. Nonvolcanic Tremor Activity is Highly Correlated With Slow Slip Events, Mexico

    NASA Astrophysics Data System (ADS)

    Kostoglodov, V.; Shapiro, N.; Larson, K. M.; Payero, J. S.; Husker, A.; Santiago, L. A.; Clayton, R. W.

    2008-12-01

    Significant activity of nonvolcanic tremor (NVT) has been observed in the central Mexico (Guerrero) subduction zone since 2001 when continuous seismic records became available. Although the quality of these records is poor, it is possible to estimate a temporal variation of energy in the range of 1-2Hz (best signal/noise ratio for the NVT). These clearly indicate a maximum of NVT energy release (En) during the 2001-2002 and 2006 large aseismic slow slip events (SSE) registered by the Guerrero GPS network. In particular En is higher for the 2001-2002 SSE which had larger surface displacements and extension than the 2006 SSE. A more detailed and accurate study of NVT activity was carried out using the data collected during the MASE experiment in Mexico. MASE consisted of 100 broad band seismometers in operation for ~2.5 years (2005-2007) along the profile oriented SSW-NNE from Acapulco, and crossing over the subduction zone for a distance of ~500 km. Epicenters and depths of individual tremor events determined using the envelope cross-correlation technique have rather large uncertainties, partly originated from the essentially 2D geometry of the network. The 'energy' approach is more efficient in this case because it provides an average NVT activity evolution in time and space. The data processing consists of a band pass (1-2Hz) filter of the raw 100 Hz sampled N-S component records, application a 10 min-width median filter to eliminate the effect of local seismic events and noise, and integration of the energy and normalization of daily En using an average coda amplitude from several regional earthquakes of M~5. A time-space distribution of En reveals a strong correlation between NVT energy release and the 2006 SSE, which also replicates the two-phase character of this slow event and a migration of the slow slip maximum from North to South. There are also a few clear episodes of relatively high NVT energy release that do not correspond to any significant geodetic

  8. Insights on activation enthalpy for non-Schmid slip in body-centered cubic metals

    DOE PAGES

    Hale, Lucas M.; Lim, Hojun; Zimmerman, Jonathan A.; ...

    2014-12-18

    We use insights gained from atomistic simulation to develop an activation enthalpy model for dislocation slip in body-centered cubic iron. Furthermore, using a classical potential that predicts dislocation core stabilities consistent with ab initio predictions, we quantify the non-Schmid stress-dependent effects of slip. The kink-pair activation enthalpy is evaluated and a model is identified as a function of the general stress state. Thus, our model enlarges the applicability of the classic Kocks activation enthalpy model to materials with non-Schmid behavior.

  9. Bifurcation Diagram and Pattern Formation of Phase Slip Centers in Superconducting Wires Driven with Electric Currents

    NASA Astrophysics Data System (ADS)

    Rubinstein, J.; Sternberg, P.; Ma, Q.

    2007-10-01

    We provide here new insights into the classical problem of a one-dimensional superconducting wire exposed to an applied electric current using the time-dependent Ginzburg-Landau model. The most striking feature of this system is the well-known appearance of oscillatory solutions exhibiting phase slip centers (PSC’s) where the order parameter vanishes. Retaining temperature and applied current as parameters, we present a simple yet definitive explanation of the mechanism within this nonlinear model that leads to the PSC phenomenon and we establish where in parameter space these oscillatory solutions can be found. One of the most interesting features of the analysis is the evident collision of real eigenvalues of the associated PT-symmetric linearization, leading as it does to the emergence of complex elements of the spectrum.

  10. Quantum phase slips in the presence of finite-range disorder.

    PubMed

    Khlebnikov, Sergei; Pryadko, Leonid P

    2005-09-02

    To study the effect of disorder on quantum phase slips (QPSs) in superconducting wires, we consider the plasmon-only model where disorder can be incorporated into a first-principles instanton calculation. We consider weak but general finite-range disorder and compute the form factor in the QPS rate associated with momentum transfer. We find that the system maps onto dissipative quantum mechanics, with the dissipative coefficient controlled by the wave (plasmon) impedance Z of the wire and with a superconductor-insulator transition at Z = 6.5 k. We speculate that the system will remain in this universality class after resistive effects at the QPS core are taken into account.

  11. Nonlinear current-voltage characteristics due to quantum tunneling of phase slips in superconducting Nb nanowire networks

    NASA Astrophysics Data System (ADS)

    Trezza, M.; Cirillo, C.; Sabatino, P.; Carapella, G.; Prischepa, S. L.; Attanasio, C.

    2013-12-01

    We report on the transport properties of an array of N ˜30 interconnected Nb nanowires, grown by sputtering on robust porous Si substrates. The analyzed system exhibits a broad resistive transition in zero magnetic field, H, and highly nonlinear V(I) characteristics as a function of H, which can be both consistently described by quantum tunneling of phase slips.

  12. Nonlinear current-voltage characteristics due to quantum tunneling of phase slips in superconducting Nb nanowire networks

    SciTech Connect

    Trezza, M.; Cirillo, C.; Sabatino, P.; Carapella, G.; Attanasio, C.; Prischepa, S. L.

    2013-12-16

    We report on the transport properties of an array of N∼30 interconnected Nb nanowires, grown by sputtering on robust porous Si substrates. The analyzed system exhibits a broad resistive transition in zero magnetic field, H, and highly nonlinear V(I) characteristics as a function of H, which can be both consistently described by quantum tunneling of phase slips.

  13. A High-Rate, Single-Crystal Model including Phase Transformations, Plastic Slip, and Twinning

    SciTech Connect

    Addessio, Francis L.; Bronkhorst, Curt Allan; Bolme, Cynthia Anne; Brown, Donald William; Cerreta, Ellen Kathleen; Lebensohn, Ricardo A.; Lookman, Turab; Luscher, Darby Jon; Mayeur, Jason Rhea; Morrow, Benjamin M.; Rigg, Paulo A.

    2016-08-09

    An anisotropic, rate-­dependent, single-­crystal approach for modeling materials under the conditions of high strain rates and pressures is provided. The model includes the effects of large deformations, nonlinear elasticity, phase transformations, and plastic slip and twinning. It is envisioned that the model may be used to examine these coupled effects on the local deformation of materials that are subjected to ballistic impact or explosive loading. The model is formulated using a multiplicative decomposition of the deformation gradient. A plate impact experiment on a multi-­crystal sample of titanium was conducted. The particle velocities at the back surface of three crystal orientations relative to the direction of impact were measured. Molecular dynamics simulations were conducted to investigate the details of the high-­rate deformation and pursue issues related to the phase transformation for titanium. Simulations using the single crystal model were conducted and compared to the high-­rate experimental data for the impact loaded single crystals. The model was found to capture the features of the experiments.

  14. Quantum and thermal phase slips in superconducting niobium nitride (NbN) ultrathin crystalline nanowire: application to single photon detection.

    PubMed

    Delacour, Cécile; Pannetier, Bernard; Villegier, Jean-Claude; Bouchiat, Vincent

    2012-07-11

    We present low-temperature electronic transport properties of superconducting nanowires obtained by nanolithography of 4-nm-thick niobium nitride (NbN) films epitaxially grown on sapphire substrate. Below 6 K, clear evidence of phase slippages is observed in the transport measurements. Upon lowering the temperature, we observe the signatures of a crossover between a thermal and a quantum behavior in the phase slip regimes. We find that phase slips are stable even at the lowest temperatures and that no hotspot is formed. The photoresponse of these nanowires is measured as a function of the light irradiation wavelength and temperature and exhibits a behavior comparable with previous results obtained on thicker films.

  15. Bond slip detection of concrete-encased composite structure using shear wave based active sensing approach

    NASA Astrophysics Data System (ADS)

    Zeng, Lei; Parvasi, Seyed Mohammad; Kong, Qingzhao; Huo, Linsheng; Lim, Ing; Li, Mo; Song, Gangbing

    2015-12-01

    Concrete-encased composite structure exhibits improved strength, ductility and fire resistance compared to traditional reinforced concrete, by incorporating the advantages of both steel and concrete materials. A major drawback of this type of structure is the bond slip introduced between steel and concrete, which directly reduces the load capacity of the structure. In this paper, an active sensing approach using shear waves to provide monitoring and early warning of the development of bond slip in the concrete-encased composite structure is proposed. A specimen of concrete-encased composite structure was investigated. In this active sensing approach, shear mode smart aggregates (SAs) embedded in the concrete act as actuators and generate desired shear stress waves. Distributed piezoceramic transducers installed in the cavities of steel plates act as sensors and detect the wave response from shear mode SAs. Bond slip acts as a form of stress relief and attenuates the wave propagation energy. Experimental results from the time domain analysis clearly indicate that the amplitudes of received signal by lead zirconate titanate sensors decreased when bond slip occurred. In addition, a wavelet packet-based analysis was developed to compute the received signal energy values, which can be used to determine the initiation and development of bond slip in concrete-encased composite structure. In order to establish the validity of the proposed method, a 3D finite element analysis of the concrete-steel bond model is further performed with the aid of the commercial finite element package, Abaqus, and the numerical results are compared with the results obtained in experimental study.

  16. Active aperture phased arrays

    NASA Astrophysics Data System (ADS)

    Shenoy, R. P.

    1989-04-01

    Developments towards the realization of active aperture phased arrays are reviewed. The technology and cost aspects of the power amplifier and phase shifter subsystems are discussed. Consideration is given to research concerning T/R modules, MESFETs, side lobe control, beam steering, optical control techniques, and printed circuit antennas. Methods for configuring the array are examined, focusing on the tile and brick configurations. It is found that there is no technological impediment for introducing active aperture phased arrays.

  17. Distinct Nucleation and Propagation Phases of Northern Cascadia Episodic Tremor and Slip Events

    NASA Astrophysics Data System (ADS)

    Ulberg, C.; Creager, K. C.

    2013-12-01

    Northern Cascadia episodic tremor and slip (ETS) events appear to have distinct nucleation and propagation phases. We find that there is a roughly linear increase in tremor amplitude over the first ~5 days of each ETS event. We observe a corresponding linear increase in the areal distribution of tremor. These episodes typically initiate down dip, and after approximately 5 days have organized and migrated to fill the up-dip/down-dip width of the tremorgenic zone. After this time, tremor amplitudes vary wildly, modulated by tidal stresses, as the tremor propagates along strike in one or both directions at roughly 8 km/day, continuing for 4-5 weeks. Inter-ETS tremor swarms can begin similarly to ETS events, but do not reach the maximum area and amplitude of ETS events, and instead die away in less than 5-10 days. Since the increase in tremor amplitude during the nucleation phase is proportional to the increase in tremoring area, the source amplitude per unit area is approximately constant, indicating a constant radiated energy rate per unit area associated with tremor. In order to estimate tremor amplitude we use three-component seismograms from temporary deployments and permanent stations (Array of Arrays, CAFE, PNSN, TA) to estimate the amplitude of tremor bursts at the source location, using a method similar to Maeda and Obara (JGR, 2009). Source amplitude, or radiated energy rate, is proportional to the root-mean square of band limited (1.5-5.5 Hz) ground velocity for each 5-minute window. Station ground velocities and tremor locations, determined by a waveform envelope cross-correlation method (Wech and Creager, GRL, 2008), are inverted to obtain source amplitude and station statics, taking into account geometrical spreading and attenuation. The result is a catalog of source amplitudes for each of 40,000 tremor locations in northern Cascadia from 2006 to 2011.

  18. Calculation of the Slip System Activity in Deformed Zinc Single Crystals Using Digital 3-D Image Correlation Data

    SciTech Connect

    Florando, J; Rhee, M; Arsenlis, A; LeBlanc, M; Lassila, D

    2006-02-21

    A 3-D image correlation system, which measures the full-field displacements in 3 dimensions, has been used to experimentally determine the full deformation gradient matrix for two zinc single crystals. Based on the image correlation data, the slip system activity for the two crystals has been calculated. The results of the calculation show that for one crystal, only the primary slip system is active, which is consistent with traditional theory. The other crystal however, shows appreciable deformation on slip systems other than the primary. An analysis has been conducted which confirms the experimental observation that these other slip system deform in such a manner that the net result is slip which is approximately one third the magnitude and directly orthogonal to the primary system.

  19. Slip Rates of Main Active Fault Zones Through Turkey Inferred From GPS Observations

    NASA Astrophysics Data System (ADS)

    Ozener, H.; Aktug, B.; Dogru, A.; Tasci, L.; Acar, M.; Emre, O.; Yilmaz, O.; Turgut, B.; Halicioglu, K.; Sabuncu, A.; Bal, O.; Eraslan, A.

    2015-12-01

    Active Fault Map of Turkey was revised and published by General Directorate of Mineral Research and Exploration in 2012. This map reveals that there are about 500 faults can generate earthquakes.In order to understand the earthquake potential of these faults, it is needed to determine the slip rates. Although many regional and local studies were performed in the past, the slip rates of the active faults in Turkey have not been determined. In this study, the block modelling, which is the most common method to produce slip rates, will be done. GPS velocities required for block modeling is being compiled from the published studies and the raw data provided then velocity field is combined. To form a homogeneous velocity field, different stochastic models will be used and the optimal velocity field will be achieved. In literature, GPS site velocities, which are computed for different purposes and published, are combined globally and this combined velocity field are used in the analysis of strain accumulation. It is also aimed to develop optimal stochastic models to combine the velocity data. Real time, survey mode and published GPS observations is being combined in this study. We also perform new GPS observations. Furthermore, micro blocks and main fault zones from Active Fault Map Turkey will be determined and homogeneous velocity field will be used to infer slip rates of these active faults. Here, we present the result of first year of the study. This study is being supported by THE SCIENTIFIC AND TECHNOLOGICAL RESEARCH COUNCIL OF TURKEY (TUBITAK)-CAYDAG with grant no. 113Y430.

  20. Vortex-induced phase slip dissipation in a torioidal Bose-Einstein condensate flowing through a barrier

    SciTech Connect

    Collins, Lee A

    2009-01-01

    We study the phase slips superfluid dissipation mechanism with a BEC flowing through a repulsive barrier inside a torus. The barrier is adiabatically raised across the annulus while the condensate is flowing with a finite quantized angular momentum. We found that, at a critical height, a vortex reaches the barrier moving radially from the inner region to eventually circulate along the annulus. At a slightly higher barrier, an anti-vortex also enters into the annulus from the outward region. The vortex and anti-vortex decrease the total angular momentum by leaving behind their respective paths a 2{pi} phase slip. When they collide or orbit along the same loop, the condensate suffers a global 2{pi} phase slip and the total angular momentum decreases by one quantum. The analysis is based on numerical simulations of the dynamical Gross-Pitaevskii equation both in two- and three-dimensions, the latter with the experimental parameters of the torus trap recently created at the NIST institute.

  1. a case of casing deformation and fault slip for the active fault drilling

    NASA Astrophysics Data System (ADS)

    Ge, H.; Song, L.; Yuan, S.; Yang, W.

    2010-12-01

    Active fault is normally defined as a fault with displacement or seismic activity during the geologically recent period (in the last 10,000 years, USGS). Here, we refer the active fault to the fault that is under the post-seismic stress modification or recovery. Micro-seismic, fault slip would happen during the recovery of the active faults. It is possible that the drilling through this active fault, such as the Wenchuan Fault Scientific Drilling(WFSD), will be accompanied with some possible wellbore instability and casing deformation, which is noteworthy for the fault scientific drilling. This presentation gives a field case of the Wenchuan earthquake. The great Wenchuan earthquake happened on May 12, 2008. An oilfield is 400km apart from the epicenter and 260km from the main fault. Many wells were drilled or are under drilling. Some are drilled through the active fault and a few tectonic active phenomenons were observed. For instance, a drill pipe was cut off in the well which was just drilled through the fault. We concluded that this is due to the fault slip,if not, so thick wall pipe cannot be cut off. At the same time, a mass of well casings of the oilfield deformed during the great Wenchuan Earthquake. The analysis of the casing deformation characteristic, formation structure, seismicity, tectonic stress variation suggest that the casing deformation is closely related to the Wenchuan Earthquake. It is the tectonic stress variation that induces seismic activities, fault slip, salt/gypsum creep speedup, and deformation inconsistent between stratums. Additional earthquake dynamic loads were exerted on the casing and caused its deformation. Active fault scientific drilling has become an important tool to understand earthquake mechanism and physics. The casing deformation and wellbore instability is not only a consequence of the earthquake but also an indicator of stress modification and fault activity. It is noteworthy that tectonic stress variation and fault

  2. Structural Control on the Megathrust Slip: the Example of the Ecuador-Colombia Active Margin.

    NASA Astrophysics Data System (ADS)

    Collot, J.; Marcaillou, B.; Agudelo, W.; Sage, F.; Ribodetti, A.

    2007-12-01

    large events. On a ~50 km-scale, a crustal splay fault and the underlying updip segment of the plate interface may have respectively controlled the updip coseismic and postseismic slips of the M7.7 1958 earthquake. The splay fault is interpreted as an inverted, landward dipping normal listric fault that developed initially in the oceanic plateau that makes up the margin. Reactivation and inversion of the fault occurred when subduction erosion put the fault into contact with the megathrust. The splay fault separates inner and outer margin wedges. The wedges behave differently during the earthquake cycle, according to their differing velocity structures, and the slip weakening and slip hardening nature of their respective underlying interplate fault segments. It is suggested that during co-seismic slip along the splay fault, the elastic rebound of the inner wedge load the outer wedge with elastic stress. The resulting accumulated strain is likely to be released during the post-seismic phase, by creeping along the upper segment of the megathrust. Combination of the three scales of margin segmentation generates a complex pattern of stress distribution at the plate interface, and shows the importance of geologic structures on the megathrust slip.

  3. Structural Control on the Megathrust Slip: the Example of the Ecuador-Colombia Active Margin.

    NASA Astrophysics Data System (ADS)

    Collot, J.; Marcaillou, B.; Agudelo, W.; Sage, F.; Ribodetti, A.

    2004-12-01

    large events. On a ~50 km-scale, a crustal splay fault and the underlying updip segment of the plate interface may have respectively controlled the updip coseismic and postseismic slips of the M7.7 1958 earthquake. The splay fault is interpreted as an inverted, landward dipping normal listric fault that developed initially in the oceanic plateau that makes up the margin. Reactivation and inversion of the fault occurred when subduction erosion put the fault into contact with the megathrust. The splay fault separates inner and outer margin wedges. The wedges behave differently during the earthquake cycle, according to their differing velocity structures, and the slip weakening and slip hardening nature of their respective underlying interplate fault segments. It is suggested that during co-seismic slip along the splay fault, the elastic rebound of the inner wedge load the outer wedge with elastic stress. The resulting accumulated strain is likely to be released during the post-seismic phase, by creeping along the upper segment of the megathrust. Combination of the three scales of margin segmentation generates a complex pattern of stress distribution at the plate interface, and shows the importance of geologic structures on the megathrust slip.

  4. GPS-derived slip rates of active faults in eastern Venezuela, along the southeastern Caribbean PBZ

    NASA Astrophysics Data System (ADS)

    Audemard, F. A.; Beck, C.; Jouanne, F.; Reinoza, C. E.; Fegag

    2013-05-01

    For over 20 years, GPS campaign measurements have been performed in eastern Venezuela, as well as in other areas of the country, by different scientific groups and in the frame of different either national or international efforts and/or projects, essentially aiming at the estimation of the rate of motion along the major Quaternary faults (i.e., Boconó, San Sebastián and El Pilar faults) composing the plate boundary zone (PBZ) between the Caribbean and South America, along onshore northern and western Venezuela. The slip rates and sense of slip of those major faults derived from the comparison of several GPS campaigns carried out through the years have confirmed the slip data (fault kinematics) previously derived from geologic data, through comprehensive neotectonic and paleoseismic studies mainly made by the FUNVISIS' Earth Sciences Dpt. staff. In a rough way, we could conclude that those faults are dextrally moving at a rate in the order of 10-12 mm/a. More recently, it has been shown that the El Pilar fault has a locking depth close to 10 km deep and that about half of the PBZ dextral motion is accommodated as creep, reducing the seismic hazard for northeastern Venezuela almost by half. On the contrary, in the near past, very little attention has been paid to the secondary active faulting in eastern Venezuela. In that sense, FUNVISIS, in collaboration with the Université de Savoie, started the monitoring of these secondary features by installing 36 brass benchmarks on bedrock in that region in 2003, which have been occupied 3 times, in late 2003 and 2005 and in early 2013. The comparison between the 2003 and 2005 occupations shows promising results, such as: a) The Charagato fault on Cubagua island is left-lateral with a slip rate of about 2 mm/a; b) slip vectors across the El Pilar fault tend to head to the ESE, suggesting that the tectonic regime is compressive transcurrent to transcurrent compressional (transpressional); c) The NW-SE-trending San Francisco

  5. Atomistically determined phase-field modeling of dislocation dissociation, stacking fault formation, dislocation slip, and reactions in fcc systems

    NASA Astrophysics Data System (ADS)

    Rezaei Mianroodi, Jaber; Svendsen, Bob

    2015-04-01

    The purpose of the current work is the development of a phase field model for dislocation dissociation, slip and stacking fault formation in single crystals amenable to determination via atomistic or ab initio methods in the spirit of computational material design. The current approach is based in particular on periodic microelasticity (Wang and Jin, 2001; Bulatov and Cai, 2006; Wang and Li, 2010) to model the strongly non-local elastic interaction of dislocation lines via their (residual) strain fields. These strain fields depend in turn on phase fields which are used to parameterize the energy stored in dislocation lines and stacking faults. This energy storage is modeled here with the help of the "interface" energy concept and model of Cahn and Hilliard (1958) (see also Allen and Cahn, 1979; Wang and Li, 2010). In particular, the "homogeneous" part of this energy is related to the "rigid" (i.e., purely translational) part of the displacement of atoms across the slip plane, while the "gradient" part accounts for energy storage in those regions near the slip plane where atomic displacements deviate from being rigid, e.g., in the dislocation core. Via the attendant global energy scaling, the interface energy model facilitates an atomistic determination of the entire phase field energy as an optimal approximation of the (exact) atomistic energy; no adjustable parameters remain. For simplicity, an interatomic potential and molecular statics are employed for this purpose here; alternatively, ab initio (i.e., DFT-based) methods can be used. To illustrate the current approach, it is applied to determine the phase field free energy for fcc aluminum and copper. The identified models are then applied to modeling of dislocation dissociation, stacking fault formation, glide and dislocation reactions in these materials. As well, the tensile loading of a dislocation loop is considered. In the process, the current thermodynamic picture is compared with the classical mechanical

  6. Relative tectonic activity assessment along the East Anatolian strike-slip fault, Eastern Turkey

    NASA Astrophysics Data System (ADS)

    Khalifa, Abdelrahman

    2016-04-01

    The East Anatolian transform fault is a morphologically distinct and seismically active left-lateral strike-slip fault that extends for ~ 500 km from Karlıova to the Maraş defining the boundary between the Anatolian Block and Syrian Foreland. Deformed landforms along the East Anatolian fault provide important insights into the nature of landscape development within an intra-continental strike-slip fault system. Geomorphic analysis of the East Anatolian fault using geomorphic indices including mountain front sinuosity, stream length-gradient index, drainage density, hypsometric integral, and the valley-width to valley height ratio helped differentiate the faulting into segments of differing degrees of the tectonic and geomorphic activity. Watershed maps for the East Anatolian fault showing the relative relief, incision, and maturity of basins along the fault zone help define segments of the higher seismic risk and help evaluate the regional seismic hazard. The results of the geomorphic indices show a high degree of activity, reveal each segment along the fault is active and represent a higher seismic hazard along the entire fault.

  7. Slip Activity in Single Grains Extracted from Polycrystalline Specimen by X-Ray Line Broadening (Preprint)

    DTIC Science & Technology

    2010-01-01

    4 6 8 0.005 0.010 -101-3 -110-2 1-10-2F W H M [ 1 /n m ] K [ 1/nm ] Gr #44 Gr #50 Gr #72 -101-1 1-101 (a...0 2 4 6 0.000 0.005 0.010 (b) K2Ccalc [ 1/nm ] FW H M [ 1 /n m ] Gr #44 Gr #50 Gr #72 17 Figure 5. The FWHM (in 1/nm scales) in...Preprint 01 January 2010 – 01 January 2010 4 . TITLE AND SUBTITLE SLIP ACTIVITY IN SINGLE GRAINS EXTRACTED FROM POLYCRYSTALLINE SPECIMEN BY X-RAY

  8. Preservation of amorphous ultrafine material: A proposed proxy for slip during recent earthquakes on active faults

    NASA Astrophysics Data System (ADS)

    Hirono, Tetsuro; Asayama, Satoru; Kaneki, Shunya; Ito, Akihiro

    2016-11-01

    The criteria for designating an “Active Fault” not only are important for understanding regional tectonics, but also are a paramount issue for assessing the earthquake risk of faults that are near important structures such as nuclear power plants. Here we propose a proxy, based on the preservation of amorphous ultrafine particles, to assess fault activity within the last millennium. X-ray diffraction data and electron microscope observations of samples from an active fault demonstrated the preservation of large amounts of amorphous ultrafine particles in two slip zones that last ruptured in 1596 and 1999, respectively. A chemical kinetic evaluation of the dissolution process indicated that such particles could survive for centuries, which is consistent with the observations. Thus, preservation of amorphous ultrafine particles in a fault may be valuable for assessing the fault’s latest activity, aiding efforts to evaluate faults that may damage critical facilities in tectonically active zones.

  9. Preservation of amorphous ultrafine material: A proposed proxy for slip during recent earthquakes on active faults

    PubMed Central

    Hirono, Tetsuro; Asayama, Satoru; Kaneki, Shunya; Ito, Akihiro

    2016-01-01

    The criteria for designating an “Active Fault” not only are important for understanding regional tectonics, but also are a paramount issue for assessing the earthquake risk of faults that are near important structures such as nuclear power plants. Here we propose a proxy, based on the preservation of amorphous ultrafine particles, to assess fault activity within the last millennium. X-ray diffraction data and electron microscope observations of samples from an active fault demonstrated the preservation of large amounts of amorphous ultrafine particles in two slip zones that last ruptured in 1596 and 1999, respectively. A chemical kinetic evaluation of the dissolution process indicated that such particles could survive for centuries, which is consistent with the observations. Thus, preservation of amorphous ultrafine particles in a fault may be valuable for assessing the fault’s latest activity, aiding efforts to evaluate faults that may damage critical facilities in tectonically active zones. PMID:27827413

  10. Role of futC slipped strand mispairing in Helicobacter pylori Lewisy phase variation

    PubMed Central

    Sanabria-Valentín, Edgardo; Colbert, Marie-Teresa C.; Blaser, Martin J.

    2008-01-01

    Summary The O antigen of the Helicobacter pylori lipopolysaccharide is composed of repeating units of fucosylated Lewis (Le) antigens. The α(1,2)-fucosyltransferase (futC) of H. pylori, which catalyzes the conversion of Lex to Ley by addition of fucose, is subject to slipped-strand mispairing involving a homonucleotide (poly-C) tract. To explore the distribution of Le phenotypes within H. pylori cells grown in vitro, 379 single colonies of strain J166 were examined for Le expression. Two major populations with reciprocal Lex/Ley phenotypes were identified. Phenotypes correlated with futC frame status, suggesting that strain J166 represents a mixed population with respect to futC poly-C tract length, which was confirmed by a translational reporter. After hundreds of generations in vitro, phenotypes did not change significantly, indicating that the observed J166 Le diversity reflects the founding population. Since slipped-strand mispairing in the futC poly-C tract was postulated to explain the Ley phenotypic change observed in J166 derivative strain 98-169 isolated 10 months after rhesus monkey challenge, in trans complementation with in-frame futC was performed. Ley synthesis was restored and Lex expression was reciprocally lowered. From these studies, we confirmed the principal role of futC slipped-strand mispairing in Le antigenic variation in vitro and in vivo. PMID:18024122

  11. Precursory Seismic Activity Surrounding the High-Slip Patches of the 2011 Mw9.0 Tohoku-Oki Earthquake

    NASA Astrophysics Data System (ADS)

    Sato, T.; Hiratsuka, S.; Mori, J. J.

    2013-12-01

    The 11 March 2011 Tohoku-Oki earthquake (Mw9.0) occurred on the megathrust along the western margin of the Pacific Ocean where the Pacific plate is being subducted beneath the island of Honshu, Japan. The slip near the Japan Trench was estimated to be enormous; it averaged about 40 m over the upper 100 km of the megathrust and peaked at 60-80 m close to the trench (Lay et al., 2011; Ozawa et al., 2012; Iinuma et al., 2012). Nearly a thousand years are required to accumulate such a large slip for the convergence rate of 8-9 cm/yr along this plate boundary zone. Two days before the Tohoku-Oki earthquake, foreshock activity (largest event M7.3) occurred north of the main-shock epicenter. The epicentral area of the foreshock activity is similar to a M7.0 earthquake in 1981 (Shao et al., 2011). The question arises, why did the 1981 event not trigger a great earthquake? A time difference of 30 years is negligible in comparison with the long time required for the slip deficit of more than 40 m. In order to address this question, we investigated the seismic activity prior to the Tohoku-Oki earthquake using the earthquake catalogue compiled by the Japan Meteorological Agency (JMA) since 1923. For the purpose of the present study, we independently determined the slip distribution of the Tohoku-Oki earthquake, using the coseismic displacements derived from the GEONET GPS stations on land (Ozawa et al., 2011) and those from the offshore GPS stations and ocean-bottom water pressure gauges (Sato et al., 2011; Iinuma et al., 2012). The slip distribution is characterized by two high-slip ( 20m) patches separated by a zone of relatively low slip. The peak of the northern high-slip patch is located near the trench while the peak of the southern high-slip patches are situated about 40 km southeast of the main-shock epicenter, about 70 km away from the trench. Combined with the analyses of main-shock rupture process by Ide et al. (2011) and Shao et al. (2011), it is estimated that the

  12. Three Temperature Regimes in Superconducting Photon Detectors: Quantum, Thermal and Multiple Phase-Slips as Generators of Dark Counts

    PubMed Central

    Murphy, Andrew; Semenov, Alexander; Korneev, Alexander; Korneeva, Yulia; Gol’tsman, Gregory; Bezryadin, Alexey

    2015-01-01

    We perform measurements of the switching current distributions of three w ≈ 120 nm wide, 4 nm thick NbN superconducting strips which are used for single-photon detectors. These strips are much wider than the diameter of the vortex cores, so they are classified as quasi-two-dimensional (quasi-2D). We discover evidence of macroscopic quantum tunneling by observing the saturation of the standard deviation of the switching distributions at temperatures around 2 K. We analyze our results using the Kurkijärvi-Garg model and find that the escape temperature also saturates at low temperatures, confirming that at sufficiently low temperatures, macroscopic quantum tunneling is possible in quasi-2D strips and can contribute to dark counts observed in single photon detectors. At the highest temperatures the system enters a multiple phase-slip regime. In this range single phase-slips are unable to produce dark counts and the fluctuations in the switching current are reduced. PMID:25988591

  13. Three temperature regimes in superconducting photon detectors: quantum, thermal and multiple phase-slips as generators of dark counts.

    PubMed

    Murphy, Andrew; Semenov, Alexander; Korneev, Alexander; Korneeva, Yulia; Gol'tsman, Gregory; Bezryadin, Alexey

    2015-05-19

    We perform measurements of the switching current distributions of three w ≈ 120 nm wide, 4 nm thick NbN superconducting strips which are used for single-photon detectors. These strips are much wider than the diameter of the vortex cores, so they are classified as quasi-two-dimensional (quasi-2D). We discover evidence of macroscopic quantum tunneling by observing the saturation of the standard deviation of the switching distributions at temperatures around 2 K. We analyze our results using the Kurkijärvi-Garg model and find that the escape temperature also saturates at low temperatures, confirming that at sufficiently low temperatures, macroscopic quantum tunneling is possible in quasi-2D strips and can contribute to dark counts observed in single photon detectors. At the highest temperatures the system enters a multiple phase-slip regime. In this range single phase-slips are unable to produce dark counts and the fluctuations in the switching current are reduced.

  14. Earthquake cycle associated with active strike slip faults in central Panamá

    NASA Astrophysics Data System (ADS)

    Rick, Bennett; Spinler, Joshua C.; Compton, Kathleen; Rockwell, Thomas K.; Gath, Eldon

    2013-04-01

    The rigidity of the Panamá Isthmus is currently under debate, with important implications for seismic hazards to the Panamá Canal and Panamá City. Whereas Panamá has traditionally been described as a non-deforming microplate caught between a number of larger tectonic plates, new paleoseismic data collected at a limited number of trench sites in association with the ongoing expansion of the Panamá Canal may challenge the validity of the rigid microplate hypothesis. Crustal velocities from a new, ~100 km aperture, 5-station continuous GPS network constructed across the Rio Gatún, Limón, and Pedro Miguel fault zones confirm that these fault zones are active, forming a system of faults that traverse central Panamá in close proximity to the Panamá Canal and Panamá City. However, the slip rates inferred from these new geodetic data are lower than the geologic rates when using an elastic halfspace model. Differences among previous geodetic investigations, which concluded that Panamá is rigid, and the geological slip rate estimates are explained by earthquake cycle effects associated with long recurrence intervals relative to lower crust and upper mantle Maxwell relaxation times. Late in the earthquake cycle the geodetic strain field is broadly distributed, giving the false appearance of low seismic hazards.

  15. Reducing employee slips, trips, and falls during employee-assisted patient activities.

    PubMed

    Staal, Collette; White, Barbra; Brasser, Bruce; LeForge, Larry; Dlouhy, Amie; Gabier, Jeff

    2004-01-01

    Following a remodeling of patient care rooms at Mary Free Bed Rehabilitation Hospital, the nursing staff reported frequent slipping in patient care areas. Data were analyzed and revealed that most slips were occurring during transfer of patients from shower chairs. An extensive literature review was done, and solutions to slipping were sought from areas outside of the healthcare industry. Specifically, ideas were borrowed from the commercial fishing industry and the restaurant industry. Both industries rely heavily on footwear to reduce slipping in the workplace. A trial was initiated with nursing staff members wearing positive-grip shoe covers that can be worn over regular footwear. No slips occurred during the trial. The purpose of this article is to motivate nurses who are involved in transferring patients from shower chairs (often used in rehabilitation settings) to consider the role their footwear has in reducing slips and potential injury.

  16. Athena: Assessment Phase Activities

    NASA Astrophysics Data System (ADS)

    Lumb, David; Ayre, Mark

    2015-09-01

    The Athena mission concept has been proposed by the community in response to science themes of the Hot and Energetic Universe. Unlike other, competitive, mission selection exercises this "Large" class observatory mission has essentially been pre-selected. Nevertheless it has to be demonstrated that Athena meets the programmatic constraints of 1Bn euro cost cap, and a readiness level appropriate for formal mission adoption by the end 2019. This should be confirmed through a Phase A study conducted with two parallel industry activities. We describe the technical and programmatic content of these and latest progress in space and ground segment definition.

  17. Anthropogenically-Induced Superficial Seismic Activity Modulated By Slow-Slip Events in Guerrero, Mexico

    NASA Astrophysics Data System (ADS)

    Frank, W.; Shapiro, N.; Husker, A. L.; Kostoglodov, V.; Campillo, M.

    2014-12-01

    We use the data of the MASE seismic experiment operated during 2.5 years in Guerrero, Mexico to create a large catalog of seismic multiplets. This catalog is dominated by families of Low-Frequency Earthquakes (LFE) occurring in vicinity of the main subduction interface. In addition to more than one thousand LFE families, we detected nine repeating seismic event families that are located in the upper crust and are anthropogenically induced (AI) by mining blasts. Analysis of the recurrence of these AI events in time shows that their activity significantly increases during the strong Slow-Slip Event (SSE) in 2006. Modeled static stress perturbations induced by the SSE at the surface are ~5 kPa that is on the same order of magnitude as dynamic stress perturbations observed to trigger other low stress drop phenomena, such as tectonic tremor. We propose therefore that strong SSEs in Guerrero impose an extensional regime throughout the continental crust, modifying the stress field near the surface and increasing AI activity. This modulation of the recurrence of the crustal seismic events by the SSE-induced stress might be related to another recent observation: the SSE-induced reduction of seismic velocities linked to nonlinear elastic effects caused by opening of cracks (Rivet et al., 2011, 2014).

  18. Active faulting induced by the slip partitioning in the Lesser Antilles arc

    NASA Astrophysics Data System (ADS)

    Leclerc, Frédérique; Feuillet, Nathalie

    2010-05-01

    AGUADOMAR marine cruise data acquired 11 years ago allowed us to identified and map two main sets of active faults within the Lesser Antilles arc (Feuillet et al., 2002; 2004). The faults belonging to the first set, such as Morne-Piton in Guadeloupe, bound up to 100km-long and 50km-wide arc-perpendicular graben or half graben that disrupt the fore-arc reef platforms. The faults of the second set form right-stepping en echelon arrays, accommodating left-lateral slip along the inner, volcanic islands. The two fault systems form a sinistral horsetail east of the tip of the left-lateral Puerto Rico fault zone that takes up the trench-parallel component of convergence between the North-American and Caribbean plates west of the Anegada passage. In other words, they together accommodate large-scale slip partitioning along the northeastern arc, consistent with recent GPS measurements (Lopez et al., 2006). These intraplate faults are responsible for a part of the shallow seismicity in the arc and have produce damaging historical earthquakes. Two magnitude 6.3 events occurred in the last 25 years along the inner en echelon faults, the last one on November 21 2004 in Les Saintes in the Guadeloupe archipelago. To better constrain the seismic hazard related to the inner arc faults and image the ruptures and effects on the seafloor of Les Saintes 2004 earthquake, we acquired new marine data between 23 February and 25 March 2009 aboard the French R/V le Suroît during the GWADASEIS cruise. We present here the data (high-resolution 72 channel and very high-resolution chirp 3.5 khz seismic reflection profiles, EM300 multibeam bathymetry, Küllenberg coring and SAR imagery) and the first results. We identified, mapped and characterized in detail several normal to oblique fault systems between Martinique and Saba. They offset the seafloor by several hundred meters and crosscut all active volcanoes, among them Nevis Peak, Soufriere Hills, Soufriere de Guadeloupe and Montagne Pel

  19. First evidence of anisotropy of GPS phase slips caused by the mid-latitude field-aligned ionospheric irregularities

    NASA Astrophysics Data System (ADS)

    Afraimovich, E. L.; Ishin, A. B.; Tinin, M. V.; Yasyukevich, Yu. V.; Jin, S. G.

    2011-05-01

    The mid-latitude field-aligned irregularity (FAI) along the magnetic field line is a common phenomenon in the ionosphere. However, few data reveal the field-aligned ionospheric irregularities. They are insufficient to identify FAIs effects so far, particularly effect on global positioning system (GPS) signals. In this paper, the mid-latitude FAIs by line-of-sight angular scanning relative to the local magnetic field vector are investigated using the denser GPS network observations in Japan. It has been the first found that total GPS L2 phase slips over Japan, during the recovery phase of the 12 Feb 2000 geomagnetic storm were caused by GPS signal scattering on FAIs both for the lines-of-sight aligned to the magnetic field line (the field of aligned scattering, FALS) and across the magnetic field line (the field of across scattering, FACS). The FALS results are also in a good agreement with the data of the magnetic field orientation control of GPS occultation observations of equatorial scintillation during thorough low earth orbit (LEO) satellites measurements, e.g. Challenging Minisatellite Payload (CHAMP) and Satellite de Aplicaciones Cientificas-C (SAC-C). The role of large-angle scattering almost along the normal to the magnetic field line in GPS scintillation is determined by attenuation of the irregularity anisotropy factor as compared with the other factors.

  20. Holocene activity and paleoseismicity of the Selaha Fault, southeastern segment of the strike-slip Xianshuihe Fault Zone, Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Yan, Bing; Lin, Aiming

    2017-01-01

    In this study we examine the Holocene activity, including slip rate and paleoseismicity, of the Selaha Fault, a branch of the left-lateral strike-slip Xianshuihe Fault Zone located along the southeastern segment of the Ganzhi-Yushu-Xianshuihe Fault System (GYXFS) of the Tibetan Plateau. Interpretation of high-resolution images and field investigations reveal that the Selaha Fault is characterized by left-lateral strike-slip faulting with an average horizontal slip-rate of 9.0 mm/year during the Holocene. Trench excavations and 14C dating results show that at least three morphogenic earthquakes occurred during the past millennium; the most recent event occurred in the past 450 years and corresponds to the 1786 M 7.75 earthquake. The penultimate seismic event (E2) occurred in the period between 560 and 820 year BP (i.e., 1166-1428 CE) and is probably associated with the 1327 M 7.5 earthquake. The antepenultimate event (E3) is inferred to have occurred in the period between 820 ± 30 and 950 ± 30 year BP. Our results confirm that the Selaha Fault, as a portion of the GYXFS, plays an important role as a tectonic boundary in releasing the strain energy accumulated during the northeastward motion of the Tibetan Plateau in response to the ongoing northward penetration of the Indian Plate into the Eurasian Plate. The strain energy is released in the form of repeated large earthquakes that are recorded by strike-slip displacements of stream channels and alluvial fans.

  1. Active normal faulting during the 1997 seismic sequence in Colfiorito, Umbria: Did slip propagate to the surface?

    NASA Astrophysics Data System (ADS)

    Mildon, Zoë K.; Roberts, Gerald P.; Faure Walker, Joanna P.; Wedmore, Luke N. J.; McCaffrey, Ken J. W.

    2016-10-01

    In order to determine whether slip during an earthquake on the 26th September 1997 propagated to the surface, structural data have been collected along a bedrock fault scarp in Umbria, Italy. These collected data are used to investigate the relationship between the throw associated with a debated surface rupture (observed as a pale unweathered stripe at the base of the bedrock fault scarp) and the strike, dip and slip-vector. Previous studies have suggested that the surface rupture was produced either by primary surface slip or secondary compaction of hangingwall sediments. Some authors favour the latter because sparse surface fault dip measurements do not match nodal plane dips at depth. It is demonstrated herein that the strike, dip and height of the surface rupture, represented by a pale unweathered stripe at the base of the bedrock scarp, shows a systematic relationship with respect to the geometry and kinematics of faulting in the bedrock. The strike and dip co-vary and the throw is greatest where the strike is oblique to the slip-vector azimuth where the highest dip values are recorded. This implies that the throw values vary to accommodate spatial variation in the strike and dip of the fault across fault plane corrugations, a feature that is predicted by theory describing conservation of strain along faults, but not by compaction. Furthermore, published earthquake locations and reported fault dips are consistent with the analysed surface scarps when natural variation for surface dips and uncertainty for nodal plane dips at depth are taken into account. This implies that the fresh stripe is indeed a primary coseismic surface rupture whose slip is connected to the seismogenic fault at depth. We discuss how this knowledge of the locations and geometry of the active faults can be used as an input for seismic hazard assessment.

  2. Quantum phase slips in superconducting Nb nanowire networks deposited on self-assembled Si templates

    NASA Astrophysics Data System (ADS)

    Cirillo, C.; Trezza, M.; Chiarella, F.; Vecchione, A.; Bondarenko, V. P.; Prischepa, S. L.; Attanasio, C.

    2012-10-01

    Robust porous silicon substrates were employed for generating interconnected networks of superconducting ultrathin Nb nanowires. Scanning electron microscopy analysis was performed to investigate the morphology of the samples, which constitute of polycrystalline single wires with grain size of about 10 nm. The samples exhibit nonzero resistance over a broad temperature range below the critical temperature, fingerprint of phase slippage processes. The transport data are satisfactory reproduced by models describing both thermal and quantum fluctuations of the superconducting order parameter in thin homogeneous superconducting wires.

  3. Fabrication of Activated Rice Husk Charcoal by Slip Casting as a Hybrid Material for Water Filter Aid

    NASA Astrophysics Data System (ADS)

    Tuaprakone, T.; Wongphaet, N.; Wasanapiarnpong, T.

    2011-04-01

    Activated charcoal has been widely used as an odor absorbent in household and water purification industry. Filtration equipment for drinking water generally consists of four parts, which are microporous membrane (porous alumina ceramic or diatomite, or porous polymer), odor absorbent (activated carbon), hard water treatment (ion exchange resin), and UV irradiation. Ceramic filter aid is usually prepared by slip casting of alumina or diatomite. The membrane offers high flux, high porosity and maximum pore size does not exceed 0.3 μm. This study investigated the fabrication of hybrid activated charcoal tube for water filtration and odor absorption by slip casting. The suitable rice husk charcoal and water ratio was 48 to 52 wt% by weight with 1.5wt% (by dry basis) of CMC binder. The green rice husk charcoal bodies were dried and fired between 700-900 °C in reduction atmosphere. The resulting prepared slip in high speed porcelain pot for 60 min and sintered at 700 °C for 1 h showed the highest specific surface area as 174.95 m2/g. The characterizations of microstructure and pore size distribution as a function of particle size were investigated.

  4. Are non-slip socks really 'non-slip'? An analysis of slip resistance

    PubMed Central

    Chari, Satyan; Haines, Terrence; Varghese, Paul; Economidis, Alyssia

    2009-01-01

    Background Non-slip socks have been suggested as a means of preventing accidental falls due to slips. This study compared the relative slip resistance of commercially available non-slip socks with other foot conditions, namely bare feet, compression stockings and conventional socks, in order to determine any traction benefit. Methods Phase one involved slip resistance testing of two commercially available non-slip socks and one compression-stocking sample through an independent blinded materials testing laboratory using a Wet Pendulum Test. Phase two of the study involved in-situ testing among healthy adult subjects (n = 3). Subjects stood unsupported on a variable angle, inclined platform topped with hospital grade vinyl, in a range of foot conditions (bare feet, non-slip socks, conventional socks and compression stockings). Inclination was increased incrementally for each condition until slippage of any magnitude was detected. The platform angle was monitored using a spatial orientation tracking sensor and slippage point was recorded on video. Results Phase one results generated through Wet Pendulum Test suggested that non-slip socks did not offer better traction than compression stockings. However, in phase two, slippage in compression stockings was detected at the lowest angles across all participants. Amongst the foot conditions tested, barefoot conditions produced the highest slip angles for all participants indicating that this foot condition provided the highest slip resistance. Conclusion It is evident that bare feet provide better slip resistance than non-slip socks and therefore might represent a safer foot condition. This study did not explore whether traction provided by bare feet was comparable to 'optimal' footwear such as shoes. However, previous studies have associated barefoot mobilisation with increased falls. Therefore, it is suggested that all patients continue to be encouraged to mobilise in appropriate, well-fitting shoes whilst in hospital

  5. A multi-chain polymer slip-spring model with fluctuating number of entanglements: Density fluctuations, confinement, and phase separation.

    PubMed

    Ramírez-Hernández, Abelardo; Peters, Brandon L; Schneider, Ludwig; Andreev, Marat; Schieber, Jay D; Müller, Marcus; de Pablo, Juan J

    2017-01-07

    Coarse grained simulation approaches provide powerful tools for the prediction of the equilibrium properties of polymeric systems. Recent efforts have sought to develop coarse-graining strategies capable of predicting the non-equilibrium behavior of entangled polymeric materials. Slip-link and slip-spring models, in particular, have been shown to be capable of reproducing several key aspects of the linear response and rheology of polymer melts. In this work, we extend a previously proposed multi-chain slip-spring model in a way that correctly incorporates the effects of the fluctuating environment in which polymer segments are immersed. The model is used to obtain the equation of state associated with the slip-springs, and the results are compared to those of related numerical approaches and an approximate analytical expression. The model is also used to examine a polymer melt confined into a thin film, where an inhomogeneous distribution of polymer segments is observed, and the corresponding inhomogeneities associated with density fluctuations are reflected on the spatial slip-spring distribution.

  6. Refining the shallow slip deficit

    NASA Astrophysics Data System (ADS)

    Xu, Xiaohua; Tong, Xiaopeng; Sandwell, David T.; Milliner, Christopher W. D.; Dolan, James F.; Hollingsworth, James; Leprince, Sebastien; Ayoub, Francois

    2016-03-01

    Geodetic slip inversions for three major (Mw > 7) strike-slip earthquakes (1992 Landers, 1999 Hector Mine and 2010 El Mayor-Cucapah) show a 15-60 per cent reduction in slip near the surface (depth < 2 km) relative to the slip at deeper depths (4-6 km). This significant difference between surface coseismic slip and slip at depth has been termed the shallow slip deficit (SSD). The large magnitude of this deficit has been an enigma since it cannot be explained by shallow creep during the interseismic period or by triggered slip from nearby earthquakes. One potential explanation for the SSD is that the previous geodetic inversions lack data coverage close to surface rupture such that the shallow portions of the slip models are poorly resolved and generally underestimated. In this study, we improve the static coseismic slip inversion for these three earthquakes, especially at shallow depths, by: (1) including data capturing the near-fault deformation from optical imagery and SAR azimuth offsets; (2) refining the interferometric synthetic aperture radar processing with non-boxcar phase filtering, model-dependent range corrections, more complete phase unwrapping by SNAPHU (Statistical Non-linear Approach for Phase Unwrapping) assuming a maximum discontinuity and an on-fault correlation mask; (3) using more detailed, geologically constrained fault geometries and (4) incorporating additional campaign global positioning system (GPS) data. The refined slip models result in much smaller SSDs of 3-19 per cent. We suspect that the remaining minor SSD for these earthquakes likely reflects a combination of our elastic model's inability to fully account for near-surface deformation, which will render our estimates of shallow slip minima, and potentially small amounts of interseismic fault creep or triggered slip, which could `make up' a small percentages of the coseismic SSD during the interseismic period. Our results indicate that it is imperative that slip inversions include

  7. Sag-ponding and its Significance in determining Paleo-seismic events along the active strike- slip fault

    NASA Astrophysics Data System (ADS)

    Li, C.; Zhang, P.; Yuan, D.

    2007-12-01

    During the development of one active fault, we really want to know how it behaves and what it will do next. This mostly depends on the record and preservation of the information showing the action of the fault. Sparse young sediments or sediments with coarse grain along most of big strike-slip faults make it hard record and preserve the vestige of the paleo-seismic events. This extremely restricts the development of the Paleo-seismic research. Sag-ponding as well as the deposits in ponds, which are formed by the movement of the fault, can help settling the difficulty. Periodic sag-ponding is a feature to which should be paid more attention along the strike-slip fault, it can develop a pond to capture plenty fine sediments which well record the action of the faults. Sag-ponding can easily be found on the main active strike-slip faults in northern and eastern Tibet. By disclosing the sag-ponding depositions with 3-D excavations, sediment distribution and characters of relevant sag-ponds, and the relation between the sag-ponding and faulting were discussed. 1. Mechanism of the formation of the sag-pond When the valleys and ridges intersecting with the fault are displaced, the fault scarps will block the flow of the streams cut by the fault, or make the gullies develop ancon-like bend. This would form a space for water-storage, and thus a sag-pond comes into being. If the fault behaves like this many times, multi-sag-ponding will occur. 2. Rhythmic sag-ponding deposition features and stratigraphic sequence (1) Vertical characteristics. Observed from the stratigraphic profiles disclosed by the excavation, stratigraphic sequence shows good rhythms. There are several rhythms in each pond, and one rhythm is composed of the lower coarse layers and the upper fine layers. That is, the grains are coarser below and finer upward. (2) Transverse variation. In the direction parallel to the fault, the deposition center of each sag-pond appears regular movement, or migration

  8. A Geometry-Based Cycle Slip Detection and Repair Method with Time-Differenced Carrier Phase (TDCP) for a Single Frequency Global Position System (GPS) + BeiDou Navigation Satellite System (BDS) Receiver

    PubMed Central

    Qian, Chuang; Liu, Hui; Zhang, Ming; Shu, Bao; Xu, Longwei; Zhang, Rufei

    2016-01-01

    As the field of high-precision applications based on carriers continues to expand, the development of low-cost, small, modular receivers and their application in diverse scenarios and situations with complex data quality has increased the requirements of carrier-phase data preprocessing. A new geometry-based cycle slip detection and repair method based on Global Position System (GPS) + BeiDou Navigation Satellite System (BDS) is proposed. The method uses a Time-differenced Carrier Phase (TDCP) model, which eliminates the Inner-System Bias (ISB) between GPS and BDS, and it is conducive to the effective combination of GPS and BDS. It avoids the interference of the noise of the pseudo-range with cycle slip detection, while the cycle slips are preserved as integers. This method does not limit the receiver frequency number, and it is applicable to single-frequency data. The process is divided into two steps to detect and repair cycle slip. The first step is cycle slip detection, using the Improved Local Analysis Method (ILAM) to find satellites that have cycle slips; The second step is to repair the cycle slips, including estimating the float solution of changes in ambiguities at the satellites that have cycle slips with the least squares method and the integer solution of the cycle slips by rounding. In the process of rounding, in addition to the success probability, a decimal test is carried out to validate the result. Finally, experiments with filed test data are carried out to prove the effectiveness of this method. The results show that the detectable cycle slips number with GPS + BDS is much greater than that with GPS. The method can also detect the non-integer outliers while fixing the cycle slip. The maximum decimal bias in repair is less than that with GPS. It implies that this method takes full advantages of multi-system. PMID:27929390

  9. A Geometry-Based Cycle Slip Detection and Repair Method with Time-Differenced Carrier Phase (TDCP) for a Single Frequency Global Position System (GPS) + BeiDou Navigation Satellite System (BDS) Receiver.

    PubMed

    Qian, Chuang; Liu, Hui; Zhang, Ming; Shu, Bao; Xu, Longwei; Zhang, Rufei

    2016-12-05

    As the field of high-precision applications based on carriers continues to expand, the development of low-cost, small, modular receivers and their application in diverse scenarios and situations with complex data quality has increased the requirements of carrier-phase data preprocessing. A new geometry-based cycle slip detection and repair method based on Global Position System (GPS) + BeiDou Navigation Satellite System (BDS) is proposed. The method uses a Time-differenced Carrier Phase (TDCP) model, which eliminates the Inner-System Bias (ISB) between GPS and BDS, and it is conducive to the effective combination of GPS and BDS. It avoids the interference of the noise of the pseudo-range with cycle slip detection, while the cycle slips are preserved as integers. This method does not limit the receiver frequency number, and it is applicable to single-frequency data. The process is divided into two steps to detect and repair cycle slip. The first step is cycle slip detection, using the Improved Local Analysis Method (ILAM) to find satellites that have cycle slips; The second step is to repair the cycle slips, including estimating the float solution of changes in ambiguities at the satellites that have cycle slips with the least squares method and the integer solution of the cycle slips by rounding. In the process of rounding, in addition to the success probability, a decimal test is carried out to validate the result. Finally, experiments with filed test data are carried out to prove the effectiveness of this method. The results show that the detectable cycle slips number with GPS + BDS is much greater than that with GPS. The method can also detect the non-integer outliers while fixing the cycle slip. The maximum decimal bias in repair is less than that with GPS. It implies that this method takes full advantages of multi-system.

  10. Global distribution of GPS losses of phase lock and total electron content slips during the 2005 May 15 and the 2003 November 20 magnetic storms

    NASA Astrophysics Data System (ADS)

    Yasyukevich, Yuriy; Astafeva, Elvira; Givetev, Ilya; Maksikov, Aleksey

    2015-12-01

    Using data of worldwide network of GPS receivers we investigated losses of GPS phase lock (LoL) during two strong magnetic storms. At fundamental L1 frequency, LoL density is found to increase up to 0.25 % and at L2 frequency the increase is up to 3 %. This is several times as much compared with the background level. During the 2003 November 20 magnetic storm, the number of total electron content (TEC) slips exceeded the background level ~50 times. During superstorms, the most number of GPS LoL is observed at low and high latitudes. At the same time, the area of numerous TEC slips correspond to auroral oval boundaries.

  11. Active membrane phased array radar

    NASA Technical Reports Server (NTRS)

    Moussessian, Alina; Del Castillo, Linda; Huang, John; Sadowy, Greg; Hoffman, James; Smith, Phil; Hatake, Toshiro; Derksen, Chuck; Lopez, Bernardo; Caro, Ed

    2005-01-01

    We have developed the first membrane-based active phased array in L-band (1.26GHz). The array uses membrane compatible Transmit/Receive (T/R) modules (membrane T/R) for each antenna element. We use phase shifters within each T/R module for electronic beam steering. We will discuss the T/R module design and integration with the membrane, We will also present transmit and receive beam-steering results for the array.

  12. Thermally Activated Motion of a Screw Dislocation Overcoming the Peierls Potential for Prismatic Slip in an hcp Lattice

    NASA Astrophysics Data System (ADS)

    Edagawa, Keiichi; Suzuki, Takayoshi; Takeuchi, Shin

    1998-07-01

    The prismatic slip in hcp metals has been studied by calculating the thermally activated motion of a 1/3[11\\bar{2}0] screw dislocation in a two-dimensional Peierls potential assumed in the (11\\bar{2}0) plane. The kink pair formation process for the transition of the dislocation from a stable position to another under applied stress has been investigated and the activation energies for the two types of transitions constituting the prismatic slip have been calculated. Using the activation energies, the critical flow stress τc has been deduced as a function of the direction of the applied stress χ and temperature. The calculated τc χ relations deviate significantly from the Schmid law and well reproduce the deviation relation observed in the experimental data of Ti. The deviation from the Schmid law originates in a structural feature of the hcp lattice itself, i.e., a zigzag arrangement along the prismatic plane of atomic rows.

  13. Analysis of the different slip systems activated by tension in a {alpha}/{beta} titanium alloy in relation with local crystallographic orientation

    SciTech Connect

    Bridier, F.; Villechaise, P. . E-mail: p.villechaise@lmpm.ensma.fr; Mendez, J.

    2005-02-01

    The gliding modes of a duplex Ti-6Al-4V titanium alloy were investigated through in situ (scanning electron microscopy) tensile tests. A method based on electron back-scattering diffraction (EBSD) measurements was used to identify activated slip systems. The approach applied to a large number of grains allowed a statistical analysis of the nature (basal, prismatic, pyramidal) and distribution of the slip systems according to the crystallographic texture. A discussion concerning the pertinence of Schmid's law to explain the occurrence and succession of slip events is then proposed. The domain in favor of each type of slip system is finally presented by using inverse pole figures mapped with Schmid's factor iso-curves.

  14. Slip-rate Estimation of Active Fault by Luminescence Dating on Deformed River Terraces at Tsaotun, Central Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Chen, W.; Lee, C.

    2003-12-01

    This study carried out luminescence ages of the deformed terraces located at Tsaotun in central Taiwan. These terraces are considered as a result of crustal deformation caused by recent activity of the Chelungpu fault, 1999 surface rupture. Since this active fault runs through urban area, it is urgently needed to figure out its neotectonic behavior, including slip-rate and recurrence interval. Based on new ages, we also discuss the terrace correlation and its related structures. The study terraces are all strath terraces with only a few meters of veneered fluvial deposits on top. Due to the strong stream-power, nearly all the outcrops are dominated by fluvial cobbles, which is worst condition to preserve the syndepositional carbonaceous materials. Alternatively, optical stimulated luminescence (OSL) dating uses sandy quartz as the material and even has longer dating upper limit (up to several hundreds of years). Fortunately, sandy layer are found intercalated within the fluvial cobbles in studying terraces. We adopted the Single-Aliquot Regenerative (SAR) dose protocol on large aliquots of 90-150μ m quartz, which were cleaned using HCL, H2O2 and HF in the usual way. In case of incomplete bleaching during quick deposition, the OSL/TL ratio was adopted to approach the true De. Dosimetry is derived by ICP-MS and XRF analyses. For ascertainment of the initial bleaching of fluvial sediment, the modern samples collected in river bed of Wuhsi were also measured. Based on the results of modern samples, we believe that the residuals are inevitable in younger sediments, especially along the upper stream. On the contrary, the samples older than 10 kyr are little influenced due to the larger age error than the younger ones. The OSL age of the terrace samples in the hanging wall is dated ca. 13 kyr, which has been corrected for poorly-bleaching problem. Comparing to the ages collected down hole in the footwalls, we found out vertical displacements of ca. 67 and 37 m, has been

  15. Quaternary strike-slip crustal deformation around an active fault based on paleomagnetic analysis: a case study of the Enako fault in central Japan

    NASA Astrophysics Data System (ADS)

    Kimura, Haruo; Itoh, Yasuto; Tsutsumi, Hiroyuki

    2004-10-01

    To evaluate cumulative strike-slip deformation around an active fault, we carried out tectonic geomorphic investigations of the active right-lateral strike-slip Enako fault in central Japan and paleomagnetic investigations of the Kamitakara pyroclastic flow deposit (KPFD; 0.6 Ma welded tuff) distributed around the fault. Tectonic geomorphic study revealed that the strike-slip displacement on the fault is ca. 150 m during the past 600 ka. We carried out measurements of paleomagnetic directions and anisotropy of magnetic susceptibility (AMS) within the pyroclastic flow deposit. Stable primary magnetic directions at each sampling site are well clustered and the AMS fabric is very oblate. We then applied tilt correction of paleomagnetic directions at 15 sites using tilting data obtained by the AMS property and orientations of eutaxitic structures. Within a distance of about 500 m from the fault trace, differential clockwise rotations were detected; the rotation angle is larger for zones closer to the fault. Because of this relation and absence of block boundary faults, a continuous deformation model explains the crustal deformation in the study area. The calculated minimum value of strike-slip displacement associated with this deformation detected within the shear zone is 210 m. The sum of this and offset on the Enako fault is 360 m and the slip rate is estimated at 0.6 mm/year.

  16. Slip initiation in alternative and slip-resistant footwear.

    PubMed

    Chander, Harish; Wade, Chip; Garner, John C; Knight, Adam C

    2016-12-21

    Slips occur as a result of failure of normal locomotion. The purpose of this study is to analyze the impact of alternative footwear (Crocs™, flip-flops) and an industry standard low-top slip-resistant shoe (SRS) under multiple gait trials (normal dry, unexpected slip, alert slip and expected slip) on lower extremity joint kinematics, kinetics and muscle activity. Eighteen healthy male participants (age: 22.28 ± 2.2 years; height: 177.66 ± 6.9 cm; mass: 79.27 ± 7.6 kg) completed the study. Kinematic, kinetic and muscle activity variables were analyzed using a 3(footwear) × 4(gait trials) repeated-measures analysis of variance at p = 0.05. Greater plantar flexion angles, lower ground reaction forces and greater muscle activity were seen on slip trials with the alternative footwear. During slip events, SRS closely resembled normal dry biomechanics, suggesting it to be a safer footwear choice compared with alternative footwear.

  17. Spatiotemporal evolution of slow slip events in a nonplanar fault model for northern Cascadia subduction zone

    NASA Astrophysics Data System (ADS)

    Li, Duo; Liu, Yajing

    2016-09-01

    Slow slip events (SSEs) are identified as the quasi-stable fault deformation in the deep transition zone from locked to continuous sliding in many subduction zones. In the well-instrumented Cascadia margin, a class of Mw6.0 slow slip events arise beneath Port Angeles every ˜14 months, as inferred from two decades of continuous geodetic monitoring. The along-strike bending of the incoming oceanic plate beneath north Washington is a unique geometric feature whose influence on slow slip processes is still unknown. Here we incorporate a realistic fault geometry of northern Cascadia in the framework of rate- and state-dependent friction law, to simulate the spatiotemporal evolution of slow slip events on a nonplanar subduction fault. The modeled SSEs capture the major characteristics revealed by GPS observations. The central 150 km long fault segment beneath Port Angeles acts as a repetitive slip patch, where SSEs appear every ˜1.5 years with a maximum slip of ˜2.5 cm. Two minor slip patches with smaller areas and cumulative slips straddle this central slip patch. The along-strike segmentation of slow slip is inversely related to the local fault dip and strike angles of the slow slip zone, suggesting strong geometrical control on the slow slip process. This correlation holds even after removing the effect of W/h∗, ratio between velocity-weakening SSE fault width and characteristic nucleation size. Besides the GPS-detectable fast-spreading phase, we find that each SSE cycle consists of deep pre-SSE preparation and post-SSE relaxation phases, which may be the driving mechanism for the deep tremor activity between major SSE episodes discovered in Cascadia.

  18. Active faulting within a megacity: the geometry and slip rate of the Pardisan thrust in central Tehran, Iran

    NASA Astrophysics Data System (ADS)

    Talebian, M.; Copley, A. C.; Fattahi, M.; Ghorashi, M.; Jackson, J. A.; Nazari, H.; Sloan, R. A.; Walker, R. T.

    2016-12-01

    Tehran, the capital city of Iran with a population of over 12 million, is one of the largest urban centres within the seismically active Alpine-Himalayan orogenic belt. Although several historic earthquakes have affected Tehran, their relation to individual faults is ambiguous for most. This ambiguity is partly due to a lack of knowledge about the locations, geometries and seismic potential of structures that have been obscured by dramatic urban growth over the past three decades, and which have covered most of the young geomorphic markers and natural exposures. Here we use aerial photographs from 1956, combined with an ˜1 m DEM derived from stereo Pleiades satellite imagery to investigate the geomorphology of a growing anticline above a thrust fault-the Pardisan thrust-within central Tehran. The topography across the ridge is consistent with a steep ramp extending from close to the surface to a depth of ˜2 km, where it presumably connects with a shallow-dipping detachment. No primary fault is visible at the surface, and it is possible that the faulting dissipates in the near surface as distributed shearing. We use optically stimulated luminescence to date remnants of uplifted and warped alluvial deposits that are offset vertically across the Pardisan fault, providing minimum uplift and slip-rates of at least 1 mm yr-1. Our study shows that the faults within the Tehran urban region have relatively rapid rates of slip, are important in the regional tectonics, and have a great impact on earthquake hazard assessment of the city and surrounding region.

  19. Olivine Slip-system Activity at High Pressure: Implications for Upper-Mantle Rheology and Seismic Anisotropy (Invited)

    NASA Astrophysics Data System (ADS)

    Raterron, P.; Castelnau, O.; Geenen, T.; Merkel, S.

    2013-12-01

    The past decade abounded in technical developments allowing the investigation of materials rheology at high pressure (P > 3 GPa) [1]. This had a significant impact on our understanding of olivine rheology in the Earth asthenosphere, where P is in the range 3 - 13 GPa. A dislocation slip-system transition induced by pressure has been documented in dry Fe-bearing olivine [2]; it induces changes in olivine aggregate lattice preferred orientation (LPO) [3,4], which may explain the seismic velocity anisotropy attenuation observed at depths > 200 km in the upper mantle [5]. Deformation experiments carried out on olivine single crystals at high pressure allowed quantifying the effect of P on individual slip system activities [6]. Integration of these data, together with data on lattice friction arising from computational models (e.g., [7]), into analytical or mean-field numerical models for aggregate plasticity gave insight on the viscosity and LPO of olivine aggregates deformed at geological conditions in the dislocation creep regime [8,9]. We will review these recent findings and their implications for upper mantle rheology and seismic anisotropy. [1] Raterron & Merkel, 2009, J. Sync. Rad., 16, 748 ; [2] Raterron et al., 2009, PEPI, 172, 74 ; [3] Jung et al., 2009, Nature Geoscience, 2, 73 ; [4] Ohuchi et al., 2011, EPSL, 304, 55 ; [5] Mainprice et al., 2005, Nature, 433, 731 ; [6] Raterron et al., 2012, PEPI, 200-201, 105 ; [7] Durinck et al., 2007, EJM, 19, 631 ; [8] Castelnau et al., 2010, C.R. Physique, 11, 304 ; [9] Raterron et al., 2011, PEPI, 188, 26

  20. Small repeating earthquakes activity and interplate quasi-static slips in the Hyuga-nada, SW Japan

    NASA Astrophysics Data System (ADS)

    Yamashita, Y.; Shimizu, H.; Goto, K.

    2009-12-01

    The Hyuga-nada region, a high-angle subduction zone belong the Kyushu-Ryukyu arc, is one of the most seismically active area in Japan and earthquakes with magnitude from 6.5 to 7.5 usually occur at dozens of years interval. In this region, the Philippine Sea Plate (PHS) subducts northwestward beneath the Eurasian Plate (EU) at a rate of about 5cm/year [Seno et al. (1993)]. We detected small repeating earthquakes in and around the Hyuga-nada using waveform similarity based on Igarashi et al. (2003). We used about 20,000 earthquakes which occurred in and around the Hyuga-nada and magnitude range is more than 2.0 detected by SEVO, Kyushu University from 1994 to 2008. We identified about 1,000 small repeating earthquakes, and they were compiled 390 groups. Most of small repeating earthquakes occur near the plate boundary between the PHS and the EU. They do not distribute in large moment-release areas of large earthquakes, but they distribute in those areas surrounding them; these characteristics are also found in NE Japan [e.g. Igarashi et al. (2003); Uchida et al. (2003)]. We selected 145 groups of small repeating earthquakes occurring in the plate boundary based on focal mechanism analysis. Almost all of them distribute the southern side from 32.5N, which suggests that an interplate coupling is probably changing near 32.5N. This result is consistent with present study of interplate coupling in and around Hyuga-nada using a geodetic data by GPS observation [e.g., Nishimura et al. (1999)]. We also estimated interplate quasi-static slip rate distribution in the Hyuga-nada using small repeating earthquakes. The result shows that the slip rate of shallow side of plate boundary is relatively larger than deep side of that in the area of 31.3~32N. In the deep side, the Hyuga-nada earthquakes (Mw6.7) occurred in Dec. 1996. It suggests that the interplate coupling of deep side is stronger than that of shallow side. Acknowledgments: In this study, we have used the data of

  1. Faults paragenesis and paleostress state in the zone of actively propagating continental strike-slip on the example of North Khangai fault (Northern Mongolia)

    NASA Astrophysics Data System (ADS)

    Sankov, Vladimir; Parfeevets, Anna

    2014-05-01

    Sublatitudinal North Khangai fault extends from Ubsunuur basin to the eastern part of the Selenga corridor trough 800 km. It is the northern boundary of the massive Mongolian block and limits of the Baikal rift system structures propagation in the south (Logatchev, 2003). Late Cenozoic and present-day fault activity are expressed in the left-lateral displacements of a different order of river valleys and high seismicity. We have carried out studies of the kinematics of active faults and palaeostresses reconstruction in the zone of the dynamic influence of North Khangai fault, the width of which varies along the strike and can exceeds 100 km. The result shows that the fault zone has a longitudinal and a transverse zoning. Longitudinal zonation presented gradual change from west to east regions of compression and transpression regimes (Khan-Khukhey ridge) to strike-slip regime (Bolnay ridge) and strike-slip and transtensive regimes (west of Selenga corridor). Strike-slip zones are represented by linearly concentrated rupture deformations. In contrast, near the termination of the fault the cluster fault deformation formed. Here, from north to south, there are radical changes in the palaeostress state. In the north-western sector (east of Selenga corridor) strike-slip faults, strike-slip faults with normal components and normal faults are dominated. For this sector the stress tensors of extensive, transtension and strike-slip regimes are typical. South-western sector is separated from the north-eastern one by massive Buren Nuruu ridge within which the active faults are not identified. In the south-western sector between the Orkhon and Tola rivers the cluster of NW thrusts and N-S strike-slip faults with reverse component are discovered. The faults are perfectly expressed by NW and N-S scarps in the relief. The most structures dip to the east and north-east. Holocene fault activity is demonstrated by the hanging river valleys and horizontal displacements with amplitudes

  2. Walker Lake, Nevada: sedimentation in an active, strike-slip related basin

    SciTech Connect

    Link, M.H.; Roberts, M.T.

    1984-04-01

    Walker Lake, Nevada, is in an active fault-controlled basin related to the right-lateral, northwest-trending Walker Lane Shear Zone on the western side of the Basin and Range province. The lake occurs in a half graben bounded on its west side by a high-angle normal fault zone along the Wassuk Range front. This fault zone may merge to the north into the Walker Lane fault system, which forms the northeast boundary of the basin. To the south of Walker Lake, the Wassuk front fault merges with an east-northeast trending left-lateral fault. The Walker Lake basin is interpreted to be a pull-apart basin formed within the triangular zone bounded by the Wassuk front, the Walker Lane, and left-lateral faults. The Walker River drainage basin occupies about 10,000 km/sup 2/ (3800 mi/sup 2/) in western Nevada and parts of California and is essentially a closed hydrologic system that drains from the crest of the Sierra Nevada in California and terminates in Walker Lake. Walker Lake trends north-northwest and is 27.4 km (17 mi) long and 8 km (5 mi) wide with water depths exceeding 30 m (100 ft). Lake Lahontan (Wisconsinian) shorelines ring Walker Lake and suggest water depths of 150 m (500 ft) above the present lake level. The lake is situated in an asymmetric basin with steep alluvial fans flanking the western shoreline (Wassuk Range) and gentle, areally more extensive fans flanking the eastern shoreline (Gillis Range). The Walker River delta enters the lake from the north and is a major sediment point source for the basin. Older dissected shoreline, alluvial fan, Gilbert delta, and beach ridge deposits were built largely of coarse-grained, locally derived materials. Stromatolites, oncolites, and tufas formed along the shorelines, whereas mud and organic sediments accumulated in the lake on the west side of the basin. Extensive submerged sand flats and local sand dunes occur on the east side of the basin.

  3. Active strike-slip faulting history inferred from offsets of topographic features and basement rocks: a case study of the Arima Takatsuki Tectonic Line, southwest Japan

    NASA Astrophysics Data System (ADS)

    Maruyama, Tadashi; Lin, Aiming

    2002-01-01

    Geological, geomorphological and geophysical data have been used to determine the total displacement, slip rates and age of formation of the Arima-Takatsuki Tectonic Line (ATTL) in southwest Japan. The ATTL is an ENE-WSW-trending dextral strike-slip fault zone that extends for about 60 km from northwest of the Rokko Mountains to southwest of the Kyoto Basin. The ATTL marks a distinct topographic boundary between mountainous regions and basin regions. Tectonic landforms typically associated with active strike-slip faults, such as systematically-deflected stream channels, offset ridges and fault scarps, are recognized along the ATTL. The Quaternary drainage system shows progressive displacement along the fault traces: the greater the magnitude of stream channel, the larger the amount of offset. The maximum dextral deflection of stream channels is 600-700 m. The field data and detailed topographic analyses, however, show that pre-Neogene basement rocks on both sides of the ATTL are displaced by about 16-18 km dextrally and pre-Mio-Pliocene elevated peneplains are also offset 16-17 km in dextral along the ATTL. This suggests that the ATTL formed in the period between the development of the pre-Mio-Pliocene peneplains and deflection of the Quaternary stream channels. The geological, geomorphological and geophysical evidence presented in this study indicates that (1) the ATTL formed after the mid-Miocene, (2) the ATTL has moved as a dextral strike-slip fault with minor vertical component since its formation to late Holocene and (3) the ATTL is presently active with dextral slip rates of 1-3 mm/year and a vertical component of >0.3 mm/year. The formation of the ATTL was probably related to the opening of the Japan Sea, which is the dominant tectonic event around Japan since mid-Miocene. The case study of the ATTL provides insight into understanding the tectonic history and relationship between tectonic landforms and structures in active strike-slip faults.

  4. Late Quaternary Activity and Seismogenic Potential of the Gonave Microplate: Plantain Garden Strike-Slip Fault Zone of Eastern Jamaica

    NASA Astrophysics Data System (ADS)

    Mann, P.; Prentice, C.; King, W.; Demets, C.; Wiggins-Grandison, M.; Benford, B.

    2008-12-01

    At the longitude of Jamaica, Caribbean (Carib)-North America (Noam) plate motion of 19 ± 2 mm/a is carried by two parallel, left-lateral strike-slip faults, the Oriente fault zone, immediately south of Cuba, and the Enriquillo-Plantain Garden fault zone (EPGFZ), which lies 100-150 km further south. It has been postulated that the lithosphere between these faults constitutes an independent Gonave microplate that has formed in response to the ongoing collision between the leading edge of Carib in Hispaniola and the Bahama carbonate platform. GPS measurements in Jamaica and Hispanola is supportive of the microplate hypothesis and indicates that roughly half of Carib-Noam plate motion (8-14 mm/a) is carried by the EPGFZ of southern Hispaniola and eastern Jamaica. This study applies geomorphic and paleoseismic methods as a direct test of the activity and amount of microplate motion carried on the Plantain Garden fault segment of eastern Hispaniola and how this motion is distributed across a large restraining bend that has formed the island of Jamaica since the late Miocene. The EPFZ curves gently to the northeast and forming a steep mountain front to the Blue Mountains restraining bend with elevations up to 2200 m. Geomorphic fault-related features along the mountain front fault zone include left-laterally deflected rivers and streams, but no small scale features indicative of Holocene activity. River and stream deflections range from 0.1 to 0.5 km. We identified and trenched the most active trace of the mountain front fault at the Morant River where the fault is characterized by a 1.5-m-wide sub-vertical fault zone juxtaposing sheared alluvium and fault Cretaceous basement rocks This section is overlain by a 6-m-thick fluvial terrace. Trenching in the unfaulted terrace immediately overlying the fault trace revealed radiocarbon and OSL ages ranging from 20 to 21 ka that are consistent with a prominent unfaulted alluvial fan along the projection of this fault 1.5 km to

  5. Slipped capital femoral epiphysis

    MedlinePlus

    ... page: //medlineplus.gov/ency/article/000972.htm Slipped capital femoral epiphysis To use the sharing features on this page, please enable JavaScript. A slipped capital femoral epiphysis is a separation of the ball ...

  6. Precursory Processes during Stick-Slip Experiments on Crustal Rocks

    NASA Astrophysics Data System (ADS)

    Passelègue, F. X.; Latour, S.; Schubnel, A.; Nielsen, S. B.; Bhat Suresh, H.; Madariaga, R. I.

    2014-12-01

    Recent seismological observations have highlighted increasing foreshock activity preceding the failure of large earthquakes. Foreshock sequences are the signature of a precursory slip during the nucleation of earthquakes, as observed both prior the Tohoku-Oki Mw 9.0 and the recent Iquique 2014 Mw 8.1 earthquakes. However, foreshocks are not systematic and the reason why they occur remains poorly understood. Recent advances in laboratory experiments allow to mimic seismic ruptures and to study the earthquake nucleation phase. Here, we track the occurrence of foreshocks prior to stick-slip instabilities in crustal rocks. Here we present the results of 6 experiments on saw cut granite samples submitted to triaxial loading under in-situ upper crustal condition that provide additional clues to understand the physical processes of foreshock dynamics. We obtained a catalog of more than 200 stick-slip cycles, composed of loading period and mainshock. Thirty STick-slip Events (STE) are preceded by a foreshock sequence. The moment and location of the 900 measured foreshocks are obtained using acoustic emission (AE) monitoring. We systematically observed that (i) the static friction coefficient, (ii) the stress drop and, consequently, (3) the moment magnitude (and total seismic slip) of the mainshock increases with increasing σn. In our experiments, an exponential acceleration of the precursory slip is systematically observed, but foreshocks are only observed when the normal stress becomes greater than 55MPa. This threshold corresponds to the normal stress above which the nucleation length becomes comparable to the size of typical fault asperities. In these conditions, the total cumulative moment of the foreshock sequence also increases exponentially up to failure, and the fault surface evolves like a cascading asperity model. This exponential growth implies that the nucleation phase has a characteristic time, i.e. that the foreshock sequence duration and moment release

  7. [Slipped capital femoral epiphysis].

    PubMed

    Klein, C; Haraux, E; Leroux, J; Gouron, R

    2017-03-01

    Slipped capital femoral epiphysis (SFCE) is a disorder of the hip, characterized by a displacement of the capital femoral epiphysis from the metaphysic through the femoral growth plate. The epiphysis slips posteriorly and inferiorly. SCFE occurs during puberty and metabolic and epidemiologic risk factors, such as obesity are frequently found. Most chronic slips are diagnosed late. Sagittal hip X-rays show epiphysis slip. In case of untreated SCFE, a slip progression arises with an acute slip risk. Treatment is indicated to prevent slip worsening. The clinical and radiological classification is useful to guide treatment and it is predictive of the prognosis. In situ fixation of stable and moderately displaced SCFE with cannulated screws gives excellent results. Major complications are chondrolysis and osteonecrosis and the major sequelae are femoroacetabular impingement and early arthritis.

  8. Transition from Slow to Fast Slip with Temperature, Forcing Velocity and Normal Stress: Experimental Evidence

    NASA Astrophysics Data System (ADS)

    Mitchell, E. K.; Brown, K. M.; Fialko, Y.

    2009-12-01

    temperatures. Our observations are consistent with the concept that thermally activated flattening and associated increases in asperity contact area dominate over any decrease in shear strength with temperature to produce a net strengthening effect. We plan to model individual asperities as Hertzian contacts to define the temperature dependent rheology that controls the evolution of frictional strength as a function of temperature, slip rate and stress. We will use a finite element Abaqus code to run our numerical simulations. We also plan to compare model predictions with data from laboratory experiments. Interestingly, we observe stick-slip behavior at temperatures as high as 500 °C in our dry tests. This may highlight the importance of water in the stick-slip/creep transition at the bottom of the seismogenic zone as well as the presence of the refractory feldspar phase. We also observe other interesting frictional phenomena, such as the growth or decay of oscillations in friction coefficient, slow slip events, and “double period” slip events. These phenomena may be due to a complex transition between stick-slip and creep frictional behavior and are in many ways similar to observations in natural slow-slip systems.

  9. Active accommodation of plate convergence in Southern Iran: Earthquake locations, triggered aseismic slip, and regional strain rates

    NASA Astrophysics Data System (ADS)

    Barnhart, William D.; Lohman, Rowena B.; Mellors, Robert J.

    2013-10-01

    We present a catalog of interferometric synthetic aperture radar (InSAR) constraints on deformation that occurred during earthquake sequences in southern Iran between 1992 and 2011, and explore the implications on the accommodation of large-scale continental convergence between Saudi Arabia and Eurasia within the Zagros Mountains. The Zagros Mountains, a salt-laden fold-and-thrust belt involving ~10 km of sedimentary rocks overlying Precambrian basement rocks, have formed as a result of ongoing continental collision since 10-20 Ma that is currently occurring at a rate of ~3 cm/yr. We first demonstrate that there is a biased misfit in earthquake locations in global catalogs that likely results from neglect of 3-D velocity structure. Previous work involving two M ~ 6 earthquakes with well-recorded aftershocks has shown that the deformation observed with InSAR may represent triggered slip on faults much shallower than the primary earthquake, which likely occurred within the basement rocks (>10 km depth). We explore the hypothesis that most of the deformation observed with InSAR spanning earthquake sequences is also due to shallow, triggered slip above a deeper earthquake, effectively doubling the moment release for each event. We quantify the effects that this extra moment release would have on the discrepancy between seismically and geodetically constrained moment rates in the region, finding that even with the extra triggered fault slip, significant aseismic deformation during the interseismic period is necessary to fully explain the convergence between Eurasia and Saudi Arabia.

  10. Millennial Slip Rate of the Longitudinal Valley Fault From River Terraces: Implications for Convergence Across the Active Suture of Eastern Taiwan

    NASA Astrophysics Data System (ADS)

    Shyu, J. H.; Sieh, K.; Avouac, J.; Chen, W.; Chen, Y.

    2005-12-01

    Interpreting a geomorphic analysis of fluvial terraces in the hanging-wall block of a major active fault in Taiwan by means of a structural model, we have created a model for the creation of a lithospheric suture that may have broader application. The Longitudinal Valley fault is a key element in the active tectonics of Taiwan. It is the principal structure accommodating convergence across the eastern of the two active sutures of the Taiwan orogeny. To understand more precisely its role in the suturing process, we analyzed fluvial terraces along the Hsiukuluan River, which is the only river that cuts across the Coastal Range of eastern Taiwan, in the hanging-wall block of the Longitudinal Valley fault. This allowed us to determine both the subsurface geometry and the millennial slip rate of the fault. The uplift pattern of the Hsiukuluan River terraces is consistent with a fault-bend fold model. Our analysis yields a listric geometry for the Longitudinal Valley fault in its uppermost 2.5 km, with dips decreasing downdip from about 50° to about 30°. The maximum dip-slip component of the Holocene slip rate of the fault is about 23 mm/yr, which yields a maximum horizontal shortening rate of about 25.6 mm/yr in the direction of plate convergence. This rate is far less than the 40 mm/yr rate of shortening across the Longitudinal Valley derived from GPS measurements. The discrepancy may reflect an actual difference in millennial and decadal rates of convergence. An alternative explanation, however, is that the discrepancy is accommodated by a combination of subsidence of the Longitudinal Valley and slip on the Central Range fault, the other active fault of the suture. The shallow listric geometry of the Longitudinal Valley fault at the Hsiukuluan River valley differs markedly from the deep listric geometry illuminated by earthquake hypocenters near Chihshang, about 45 km to the south. We propose a model whereby this fundamental along-strike difference in geometry of

  11. Phase Transitions in Model Active Systems

    NASA Astrophysics Data System (ADS)

    Redner, Gabriel S.

    The amazing collective behaviors of active systems such as bird flocks, schools of fish, and colonies of microorganisms have long amazed scientists and laypeople alike. Understanding the physics of such systems is challenging due to their far-from-equilibrium dynamics, as well as the extreme diversity in their ingredients, relevant time- and length-scales, and emergent phenomenology. To make progress, one can categorize active systems by the symmetries of their constituent particles, as well as how activity is expressed. In this work, we examine two categories of active systems, and explore their phase behavior in detail. First, we study systems of self-propelled spherical particles moving in two dimensions. Despite the absence of an aligning interaction, this system displays complex emergent dynamics, including phase separation into a dense active solid and dilute gas. Using simulations and analytic modeling, we quantify the phase diagram and separation kinetics. We show that this nonequilibrium phase transition is analogous to an equilibrium vapor-liquid system, with binodal and spinodal curves and a critical point. We also characterize the dense active solid phase, a unique material which exhibits the structural signatures of a crystalline solid near the crystal-hexatic transition point, as well as anomalous dynamics including superdiffusive motion on intermediate timescales. We also explore the role of interparticle attraction in this system. We demonstrate that attraction drastically changes the phase diagram, which contains two distinct phase-separated regions and is reentrant as a function of propulsion speed. We interpret this complex situation with a simple kinetic model, which builds from the observed microdynamics of individual particles to a full description of the macroscopic phase behavior. We also study active nematics, liquid crystals driven out of equilibrium by energy-dissipating active stresses. The equilibrium nematic state is unstable in these

  12. Superplastic flow lubricates carbonate faults during earthquake slip

    NASA Astrophysics Data System (ADS)

    De Paola, Nicola; Holdsworth, Robert; Viti, Cecilia; Collettini, Cristiano; Faoro, Igor; Bullock, Rachael

    2014-05-01

    is controlled by cataclastic frictional sliding rather than by dislocation creep or nanopowder lubrication mechanisms. When T ≥ 800 °C are attained, micro-textures diagnostic of diffusion-dominated grain boundary sliding are widespread within the slip zone, and suggest bulk superplastic flow. Flow stresses predicted by superplasticity constitutive laws at the slip zone temperatures, grain sizes and strain rates attained during the experiments match those we measured in the laboratory (μ = 0.16). We propose therefore that the activation of diffusion creep at high temperatures (T ≥ 800 °C) leads to slip zone-localised superplastic flow and that this causes the dynamic weakening of carbonate faults at seismic slip rates. Note, however, that both cataclasis and dislocation creep operating at lower temperatures, during the earlier stages of slip, are critical, precursory processes needed to produce the nanoscale grain sizes required to activate grainsize sensitive mechanisms during superplastic flow. Finally, the re-strengthening observed during the decelerating phase of deformation can be explained by the falling temperature "switching off" slip zone-localized superplasticity, leading to a return to frictional sliding. These results indicate that superplastic flow can effectively weaken faults, and facilitate earthquake propagation in the upper crust.

  13. Reconsidering Fault Slip Scaling

    NASA Astrophysics Data System (ADS)

    Gomberg, J. S.; Wech, A.; Creager, K. C.; Obara, K.; Agnew, D. C.

    2015-12-01

    The scaling of fault slip events given by the relationship between the scalar moment M0, and duration T, potentially provides key constraints on the underlying physics controlling slip. Many studies have suggested that measurements of M0 and T are related as M0=KfT3 for 'fast' slip events (earthquakes) and M0=KsT for 'slow' slip events, in which Kf and Ks are proportionality constants, although some studies have inferred intermediate relations. Here 'slow' and 'fast' refer to slip front propagation velocities, either so slow that seismic radiation is too small or long period to be measurable or fast enough that dynamic processes may be important for the slip process and measurable seismic waves radiate. Numerous models have been proposed to explain the differing M0-T scaling relations. We show that a single, simple dislocation model of slip events within a bounded slip zone may explain nearly all M0-T observations. Rather than different scaling for fast and slow populations, we suggest that within each population the scaling changes from M0 proportional to T3 to T when the slipping area reaches the slip zone boundaries and transitions from unbounded, 2-dimensional to bounded, 1-dimensional growth. This transition has not been apparent previously for slow events because data have sampled only the bounded regime and may be obscured for earthquakes when observations from multiple tectonic regions are combined. We have attempted to sample the expected transition between bounded and unbounded regimes for the slow slip population, measuring tremor cluster parameters from catalogs for Japan and Cascadia and using them as proxies for small slow slip event characteristics. For fast events we employed published earthquake slip models. Observations corroborate our hypothesis, but highlight observational difficulties. We find that M0-T observations for both slow and fast slip events, spanning 12 orders of magnitude in M0, are consistent with a single model based on dislocation

  14. The Distribution of Fault Slip Rates and Oblique Slip Patterns in the Greater Los Angeles, CA Region

    NASA Astrophysics Data System (ADS)

    Harper, H.; Marshall, S. T.

    2014-12-01

    The Los Angeles basin is host to a complex network of active strike-slip, reverse, and oblique slip faults. Because of the large metropolitan region occupying the basin, even moderately large earthquakes (M6+) pose a significant natural hazard. Since geologic estimates have not fully characterized the distribution of active fault slip rates in the region, we use a mechanical model driven by geodetically-measured shortening rates to calculate the full three-dimensional fault slip rate distributions in the region. The modeled nonplanar fault geometries are relatively well-constrained, and use data from the SCEC community fault model. Area-weighted average fault slip rates predicted by the model match previously measured geologic slip rates in most cases; however, some geologic measurements were made in locations where the slip rate is non-characteristic of the fault (e.g. near a fault tip) and the geologic slip rate estimate disagrees with the model-predicted average slip rate. The largest discrepancy between the model predictions and geologic estimates occurs on the Sierra Madre fault, which has a model-predicted slip rate approximately 2 mm/yr greater than the geologic estimates. An advantage of the model is that it can predict the full three-dimensional mechanically compatible slip distribution along all modeled faults. The fault surface slip distribution maps show complex oblique slip patterns that arise due to the nonplanar geometries and mechanical interactions between intersecting and neighboring faults. For example, the Hollywood fault exhibits a net slip of 0.7 mm/yr at depth which increases to 1.6 mm/yr where it is intersected by the Santa Monica fault in the near-surface. Model results suggest that nearly all faults in the region have an oblique component of slip at depth, so slip rate estimates of only dip or strike-slip may underestimate the total net slip rates and seismic hazards in the region.

  15. Dynamical stability of slip-stacking particles

    SciTech Connect

    Eldred, Jeffrey; Zwaska, Robert

    2014-09-01

    We study the stability of particles in slip-stacking configuration, used to nearly double proton beam intensity at Fermilab. We introduce universal area factors to calculate the available phase space area for any set of beam parameters without individual simulation. We find perturbative solutions for stable particle trajectories. We establish Booster beam quality requirements to achieve 97% slip-stacking efficiency. We show that slip-stacking dynamics directly correspond to the driven pendulum and to the system of two standing-wave traps moving with respect to each other.

  16. Water generation and transport below Europa's strike-slip faults

    NASA Astrophysics Data System (ADS)

    Kalousová, Klára; Souček, Ondřej; Tobie, Gabriel; Choblet, Gaël.; Čadek, Ondřej

    2016-12-01

    Jupiter's moon Europa has a very young surface with the abundance of unique terrains that indicate recent endogenic activity. Morphological models as well as spectral observations suggest that it might possess shallow lenses of liquid water within its outer ice shell. Here we investigate the generation and possible accumulation of liquid water below the tidally activated strike-slip faults using a numerical model of two-phase ice-water mixture in two-dimensional Cartesian geometry. Our results suggest that generation of shallow partially molten regions underneath Europa's active strike-slip faults is possible, but their lifetime is constrained by the formation of Rayleigh-Taylor instabilities due to the negative buoyancy of the melt. Once formed, typically within a few million years, these instabilities efficiently transport the meltwater through the shell. Consequently, the maximum water content in the partially molten regions never exceeds 10% which challenges their possible detection by future exploration mission.

  17. Contactless Magnetic Slip Ring

    NASA Technical Reports Server (NTRS)

    Kumagai, Hiroyuki (Inventor); Deardon, Joe D. (Inventor)

    1997-01-01

    A contactless magnetic slip ring is disclosed having a primary coil and a secondary coil. The primary and secondary coils are preferably magnetically coupled together, in a highly reliable efficient manner, by a magnetic layered core. One of the secondary and primary coils is rotatable and the contactless magnetic slip ring provides a substantially constant output.

  18. SLIPPING MAGNETIC RECONNECTION TRIGGERING A SOLAR ERUPTION OF A TRIANGLE-SHAPED FLAG FLUX ROPE

    SciTech Connect

    Li, Ting; Zhang, Jun E-mail: zjun@nao.cas.cn

    2014-08-10

    We report the first simultaneous activities of the slipping motion of flare loops and a slipping eruption of a flux rope in 131 Å and 94 Å channels on 2014 February 2. The east hook-like flare ribbon propagated with a slipping motion at a speed of about 50 km s{sup –1}, which lasted about 40 minutes and extended by more than 100 Mm, but the west flare ribbon moved in the opposite direction with a speed of 30 km s{sup –1}. At the later phase of flare activity, there was a well developed ''bi-fan'' system of flare loops. The east footpoints of the flux rope showed an apparent slipping motion along the hook of the ribbon. Simultaneously, the fine structures of the flux rope rose up rapidly at a speed of 130 km s{sup –1}, much faster than that of the whole flux rope. We infer that the east footpoints of the flux rope are successively heated by a slipping magnetic reconnection during the flare, which results in the apparent slippage of the flux rope. The slipping motion delineates a ''triangle-shaped flag surface'' of the flux rope, implying that the topology of a flux rope is more complex than anticipated.

  19. Slip-mediated dewetting of polymer microdroplets

    PubMed Central

    McGraw, Joshua D.; Chan, Tak Shing; Maurer, Simon; Salez, Thomas; Benzaquen, Michael; Raphaël, Elie; Brinkmann, Martin; Jacobs, Karin

    2016-01-01

    Classical hydrodynamic models predict that infinite work is required to move a three-phase contact line, defined here as the line where a liquid/vapor interface intersects a solid surface. Assuming a slip boundary condition, in which the liquid slides against the solid, such an unphysical prediction is avoided. In this article, we present the results of experiments in which a contact line moves and where slip is a dominating and controllable factor. Spherical cap-shaped polystyrene microdroplets, with nonequilibrium contact angle, are placed on solid self-assembled monolayer coatings from which they dewet. The relaxation is monitored using in situ atomic force microscopy. We find that slip has a strong influence on the droplet evolutions, both on the transient nonspherical shapes and contact line dynamics. The observations are in agreement with scaling analysis and boundary element numerical integration of the governing Stokes equations, including a Navier slip boundary condition. PMID:26787903

  20. Slow slip event at Kilauea Volcano

    USGS Publications Warehouse

    Poland, Michael P.; Miklius, Asta; Wilson, J. David; Okubo, Paul G.; Montgomery-Brown, Emily; Segall, Paul; Brooks, Benjamin; Foster, James; Wolfe, Cecily; Syracuse, Ellen; Thurbe, Clifford

    2010-01-01

    Early in the morning of 1 February 2010 (UTC; early afternoon 31 January 2010 local time), continuous Global Positioning System (GPS) and tilt instruments detected a slow slip event (SSE) on the south flank of Kilauea volcano, Hawaii. The SSE lasted at least 36 hours and resulted in a maximum of about 3 centimeters of seaward displacement. About 10 hours after the start of the slip, a flurry of small earthquakes began (Figure 1) in an area of the south flank recognized as having been seismically active during past SSEs [Wolfe et al., 2007], suggesting that the February earthquakes were triggered by stress associated with slip [Segall et al., 2006].

  1. Geomorphic features of surface ruptures associated with the 2016 Kumamoto earthquake in and around the downtown of Kumamoto City, and implications on triggered slip along active faults

    NASA Astrophysics Data System (ADS)

    Goto, Hideaki; Tsutsumi, Hiroyuki; Toda, Shinji; Kumahara, Yasuhiro

    2017-02-01

    The 30-km-long surface ruptures associated with the M w 7.0 ( M j 7.3) earthquake at 01:25 JST on April 16 in Kumamoto Prefecture appeared along the previously mapped 100-km-long active fault called the Futagawa-Hinagu fault zone (FHFZ). The surface ruptures appeared to have extended further west out of the main FHFZ into the Kumamoto Plain. Although InSAR analysis by Geospatial Information Authority of Japan (GSI) indicated coseismic surface deformation in and around the downtown of Kumamoto City, the surface ruptures have not been clearly mapped in the central part of the Kumamoto Plain, and whether there are other active faults other than the Futagawa fault in the Kumamoto Plain remained unclear. We produced topographical stereo images (anaglyph) from 5-m-mesh digital elevation model of GSI, which was generated from light detection and ranging data. We interpreted them and identified that several SW-sloping river terraces formed after the deposition of the pyroclastic flow deposits related to the latest large eruption of the Aso caldera (86.8-87.3 ka) are cut and deformed by several NW-trending flexure scarps down to the southwest. These 5.4-km-long scarps that cut across downtown Kumamoto were identified for the first time, and we name them as the Suizenji fault zone. Surface deformation such as continuous cracks, tilts, and monoclinal folding associated with the main shock of the 2016 Kumamoto earthquake was observed in the field along the fault zone. The amount of vertical deformation ( 0.1 m) along this fault associated with the 2016 Kumamoto earthquake was quite small compared to the empirically calculated coseismic slip (0.5 m) based on the fault length. We thus suggest that the slip on this fault zone was triggered by the Kumamoto earthquake, but the fault zone has potential to generate an earthquake with larger slip that poses a high seismic risk in downtown Kumamoto area.[Figure not available: see fulltext.

  2. SLIP CASTING METHOD

    DOEpatents

    Allison, A.G.

    1959-09-01

    S>A process is described for preparing a magnesium oxide slip casting slurry which when used in conjunction with standard casting techniques results in a very strong "green" slip casting and a fired piece of very close dimensional tolerance. The process involves aging an aqueous magnestum oxide slurry, having a basic pH value, until it attains a specified critical viscosity at which time a deflocculating agent is added without upsetting the basic pH value.

  3. Biomechanics of slips.

    PubMed

    Redfern, M S; Cham, R; Gielo-Perczak, K; Grönqvist, R; Hirvonen, M; Lanshammar, H; Marpet, M; Pai, C Y; Powers, C

    2001-10-20

    The biomechanics of slips are an important component in the prevention of fall-related injuries. The purpose of this paper is to review the available literature on the biomechanics of gait relevant to slips. This knowledge can be used to develop slip resistance testing methodologies and to determine critical differences in human behaviour between slips leading to recovery and those resulting in falls. Ground reaction forces at the shoe-floor interface have been extensively studied and are probably the most critical biomechanical factor in slips. The ratio of the shear to normal foot forces generated during gait, known as the required coefficient of friction (RCOF) during normal locomotion on dry surfaces or 'friction used/achievable' during slips, has been one biomechanical variable most closely associated with the measured frictional properties of the shoe/floor interface (usually the coefficient of friction or COF). Other biomechanical factors that also play an important role are the kinematics of the foot at heel contact and human responses to slipping perturbations, often evident in the moments generated at the lower extremity joints and postural adaptations. In addition, it must be realized that the biomechanics are dependent upon the capabilities of the postural control system, the mental set of the individual, and the perception of the environment, particularly, the danger of slipping. The focus of this paper is to review what is known regarding the kinematics and kinetics of walking on surfaces under a variety of environmental conditions. Finally, we discuss future biomechanical research needs to help to improve walkway-friction measurements and safety.

  4. Hairpin river loops and slip-sense inversion on southeast Asian strike-slip faults

    NASA Astrophysics Data System (ADS)

    Lacassin, Robin; Replumaz, Anne; Hervé Leloup, P.

    1998-08-01

    In the Golden Triangle region of southeast Asia (northern Thailand, Laos and Burma, southern Yunnan), the Mekong, Salween, and neighboring rivers show hairpin geometries where they cross active strike-slip faults. Restoration of young, left-lateral offsets of these rivers leaves residual right-lateral bends of many kilometers. We interpret these hairpins as evidence of late Cenozoic slip-sense inversion on these faults, about 5 to 20 Ma. Near the Red River fault, stress field and slip-sense inversion occurred ca. 5 Ma. This implies that the present course of these large rivers has existed for at least several million years. Pliocene Quaternary slip rates, possibly on the order of 1 mm/yr, are inferred on each of the strike-slip faults of the Golden Triangle.

  5. Falls study: Proprioception, postural stability, and slips.

    PubMed

    Sohn, Jeehoon; Kim, Sukwon

    2015-01-01

    The present study evaluated effects of exercise training on the proprioception sensitivity, postural stability, and the likelihood of slip-induced falls. Eighteen older adults (6 in balance, 6 in weight, and 6 in control groups) participated in this study. Three groups met three times per week over the course of eight weeks. Ankle and knee proprioception sensitivities and postural stability were measured. Slip-induced events were introduced for all participants before and after training. The results indicated that, overall, strength and postural stability were improved only in the training group, although proprioception sensitivity was improved in all groups. Training for older adults resulted in decreased likelihood of slip-induced falls. The study suggested that proprioception can be improved by simply being active, however, the results suggested that training would aid older adults in reducing the likelihood of slip-induced falls.

  6. Frictional evolution, acoustic emissions activity, and off-fault damage in simulated faults sheared at seismic slip rates

    NASA Astrophysics Data System (ADS)

    Passelègue, François. X.; Spagnuolo, Elena; Violay, Marie; Nielsen, Stefan; Di Toro, Giulio; Schubnel, Alexandre

    2016-10-01

    We present a series of high-velocity friction tests conducted on Westerly granite, using the Slow to HIgh Velocity Apparatus (SHIVA) installed at Istituto Nazionale di Geofisica e Vulcanologia Roma with acoustic emissions (AEs) monitored at high frequency (4 MHz). Both atmospheric humidity and pore fluid (water) pressure conditions were tested, under effective normal stress σneff in the range 5-20 MPa and at target sliding velocities Vs in the range 0.003-3 m/s. Under atmospheric humidity two consecutive friction drops were observed. The first one is related to flash weakening, and the second one to the formation and growth of a continuous layer of melt in the slip zone. In the presence of fluid, a single drop in friction was observed. Average values of fracture energy are independent of effective normal stress and sliding velocity. However, measurements of elastic wave velocities on the sheared samples suggested that larger damage was induced for 0.1 < Vs<0.3 m/s. This observation is supported by AEs recorded during the test, most of which were detected after the initiation of the second friction drop, once the fault surface temperature was high. Some AEs were detected up to a few seconds after the end of the experiments, indicating thermal rather than mechanical cracking. In addition, the presence of pore water delayed the onset of AEs by cooling effects and by reducing of the heat produced, supporting the link between AEs and the production and diffusion of heat during sliding. Using a thermoelastic crack model developed by Fredrich and Wong (1986), we confirm that damage may be induced by heat diffusion. Indeed, our theoretical results predict accurately the amount of shortening and shortening rate, supporting the idea that gouge production and gouge comminution are in fact largely controlled by thermal cracking. Finally, we discuss the contribution of thermal cracking in the seismic energy balance. In fact, while a dichotomy exists in the literature regarding

  7. Some properties of unstable slip on rough surfaces

    NASA Astrophysics Data System (ADS)

    Spetzler, Hartmut; Sobolev, Guennadi; Koltsov, Anatoli; Zang, Arno; Getting, Ivan C.

    1991-03-01

    In this paper we report results obtained from various friction experiments under direct and oblique shear loading conditions. We used four rock types of varying brittleness (quartzite, anhydrite, limestone, pyrophyllite) with different surface roughness. The observations concentrate on the time span several milliseconds before dynamic failure occurs. During this period a premonitory, unstable phase of slip (slip 2) occurs. This differs importantly from a premonitory, stable process (slip 1) with durations of hundreds of seconds. On smooth surfaces slip 2 is usually observed with ductile rocks and less reliably with brittle rocks. Slip 2 is mostly accompanied by acoustic emissions, which increase in rate of occurrence and in magnitude until the stick-slip event. Foreshocks are observed during approximately 50% of the slip 2 events on rough surfaces. Foreshocks far exceed the “acoustic noise level”, which is also prevalent before stick-slip events on rough surfaces. In the direct shear experiment, where two faults are being loaded simultaneously, in about 20% of the cases precursory slip 2 was observed on the opposite side on which the final stick-slip event occurred.

  8. Strain Wave during the Transient Process of Fault Unstable Slip

    NASA Astrophysics Data System (ADS)

    Guo, L.; Liu, L.

    2011-12-01

    The "stick-slip" model was proposed as an important mechanism for shallow-focus earthquakes. The study on the transient process of fault unstable slip failure is helpful for understanding the earthquake preparatory process, the mechanism of energy released, the precursor and after shake effect. Double shear frictional experiments are conducted for simulating "stick-slip" phenomenon, and a specially designed multi-channel super dynamic strain field observation system is employed to acquire dada continuously with the sample rate of 3,400 samples/second. The rock deformation process can be recorded in detail, especially in the moment of unstable slip (The unstable slip duration is less than two second in experiments). The strain results from super dynamic strain field observation system show that multi-frequency components and tremendous amplitude fluctuation are included in strain signals along the fault. There are three clear phases during the unstable slip progress: pre-slip (phase I), high-frequency strain vibration (phase II) and strain regulating to stop (phase III). Each phase has its own characteristics on duration, strain rate, frequency, amplitude and energy release. There are strong fluctuations in duration of approximately 70ms in phase II. The frequency and maximum amplitude are 300-400Hz and 150~300μɛ respectively. Main strain energy release takes place at phase II, less than one-tenth of the total slip time, so that the whole course of dislocation or stress drop would not be taken as earthquake simply at least in laboratory. The phase characteristic of the strain wave is probably its inherent attribute of unstable slip process and independent of dynamical loading conditions. The elastic rebound phenomena, considered as one classic earthquake generation model, can be observed clearly by analyzing the rotation of the principal strain axis with strain variation. The rotated angle ranges from 5° to 15° typically. The value and location of precursor slip

  9. {110} Slip with {112} slip traces in bcc Tungsten.

    PubMed

    Marichal, Cecile; Van Swygenhoven, Helena; Van Petegem, Steven; Borca, Camelia

    2013-01-01

    While propagation of dislocations in body centered cubic metals at low temperature is understood in terms of elementary steps on {110} planes, slip traces correspond often with other crystallographic or non-crystallographic planes. In the past, characterization of slip was limited to post-mortem electron microscopy and slip trace analysis on the sample surface. Here with in-situ Laue diffraction experiments during micro-compression we demonstrate that when two {110} planes containing the same slip direction experience the same resolved shear stress, sharp slip traces are observed on a {112} plane. When however the {110} planes are slightly differently stressed, macroscopic strain is measured on the individual planes and collective cross-slip is used to fulfill mechanical boundary conditions, resulting in a zig-zag or broad slip trace on the sample surface. We anticipate that such dynamics can occur in polycrystalline metals due to local inhomogeneous stress distributions and can cause unusual slip transfer among grains.

  10. Slip on normal faults induced by surface processes after the cessation of regional extension-Insights from three-dimensional numerical modelling

    NASA Astrophysics Data System (ADS)

    Turpeinen, Heidi; Maniatis, Georgios; Hampel, Andrea

    2015-05-01

    In regions of active extension, normal faulting generates topography that is continuously modified by erosion, sediment transport and deposition. As shown by previous numerical models with full coupling between tectonics and surface processes, the redistribution of mass at the Earth's surface accelerates the rate of faulting by affecting the stress state of the crust. It remains unknown, however, how fault slip evolves as a result of ongoing surface processes if regional extension as the main driver of faulting ceases. Here we use three-dimensional finite-element modelling to show that surface processes acting on normal-fault bounded mountain ranges may sustain fault slip for millions of years even after regional extension has stopped. The models consist of two successive phases. During the first phase, the normal fault accumulates displacement owing to an extensional boundary condition, while erosion and sediment deposition are active on the model surface. At the beginning of the second phase, extension of the model is stopped while the surface processes remain active. The results show that in most models normal faulting continues during the second phase at rates of ~ 20 to ~ 70 m/Ma for more than 1 Ma. In some experiments, normal slip is maintained for ~ 3 Ma, whereas in other models, a short phase of normal faulting is followed by slow reverse slip. The maximum amount of normal slip in different experiments reaches up to 90 m during the second model phase. If erosion is intensified by increasing the diffusion constant by a factor of 5, the fault accumulates the additional normal slip at a faster rate, i.e. during a shorter time period. In contrast, a five-fold variation of the fluvial erosion constant does not significantly affect the fault slip evolution. Variations of the fault dip and length have a similar effect on the duration of the phase with additional normal slip as variations of the diffusion constant. The fault slip evolution is correlated with the

  11. Production of nanoparticles during experimental deformation of smectite and implications for seismic slip

    NASA Astrophysics Data System (ADS)

    Aretusini, S.; Mittempergher, S.; Plümper, O.; Spagnuolo, E.; Gualtieri, A. F.; Di Toro, G.

    2017-04-01

    Nanoparticles and amorphous materials are common constituents of the shallow sections of active faults. Understanding the conditions at which nanoparticles are produced and their effects on friction can further improve our understanding of fault mechanics and earthquake energy budgets. Here we present the results of 59 rotary shear experiments conducted at room humidity conditions on gouge consisting of mixtures of smectite (Ca-montmorillonite) and quartz. Experiments with 60, 50, 25, 0 wt.% Ca-montmorillonite, were performed to investigate the influence of variable clay content on nanoparticle production and their influence on frictional processes. All experiments were performed at a normal stress of 5 MPa, slip rate of 0.0003 ≤ V ≤ 1.5 ms-1, and at a displacement of 3 m. To monitor the development of fabric and the mineralogical changes during the experiments, we investigated the deformed gouges using scanning and transmission electron microscopy combined with X-ray powder diffraction quantitative phase analysis. This integrated analytical approach reveals that, at all slip rates and compositions, the nanoparticles (grain size of 10-50 nm) are partly amorphous and result from cataclasis, wear and mechanical solid-state amorphization of smectite. The maximum production of amorphous nanoparticle occurs in the intermediate slip rate range (0.0003 ≤ V ≤ 0.1 ms-1), at the highest frictional work, and is associated to diffuse deformation and slip strengthening behavior. Instead, the lowest production of amorphous nanoparticles occurs at co-seismic slip rates (V ≥ 1.3 ms-1), at the highest frictional power and is associated with strain and heat localization and slip weakening behavior. Our findings suggest that, independently of the amount of smectite nanoparticles, they produce fault weakening only when typical co-seismic slip rates (>0.1 ms-1) are achieved. This implies that estimates of the fracture surface energy dissipated during earthquakes in natural

  12. Inorganic glass ceramic slip rings

    NASA Technical Reports Server (NTRS)

    Glossbrenner, E. W.; Cole, S. R.

    1972-01-01

    Prototypes of slip rings have been fabricated from ceramic glass, a material which is highly resistant to deterioration due to high temperature. Slip ring assemblies were not structurally damaged by mechanical tests and performed statisfactorily for 200 hours.

  13. Enhanced dynamical stability with harmonic slip stacking

    NASA Astrophysics Data System (ADS)

    Eldred, Jeffrey; Zwaska, Robert

    2016-10-01

    We develop a configuration of radio-frequency (rf) cavities to dramatically improve the performance of slip stacking. Slip stacking is an accumulation technique used at Fermilab to nearly double proton intensity by maintaining two beams of different momenta in the same storage ring. The two particle beams are longitudinally focused in the Recycler by two 53 MHz 100 kV rf cavities with a small frequency difference between them. We propose an additional 106 MHz 20 kV rf cavity with a frequency at the double the average of the upper and lower main rf frequencies. We show the harmonic rf cavity cancels out the resonances generated between the two main rf cavities and we derive the relationship between the harmonic rf voltage and the main rf voltage. We find the area factors that can be used to calculate the available phase space area for any set of beam parameters without individual simulation. We establish Booster beam quality requirements to achieve 99% slip stacking efficiency. We measure the longitudinal distribution of the Booster beam and use it to generate a realistic beam model for slip stacking simulation. We demonstrate that the harmonic rf cavity can not only reduce particle loss during slip stacking, but also reduce the final longitudinal emittance.

  14. Actively evolving microplate formation by oblique collision and sideways motion along strike-slip faults: An example from the northeastern Caribbean plate margin

    NASA Astrophysics Data System (ADS)

    Mann, Paul; Taylor, F. W.; Edwards, R. Lawrence; Ku, Teh-Lung

    1995-06-01

    The pattern of folding, faulting, and late Quaternary coral-reef uplift rates in western and central Hispaniola (Haiti and Dominican Republic) suggest that the elongate Gonave microplate, a 190,000-km 2 area of the northeastern Caribbean plate, is in the process of shearing off the Caribbean plate and accreting to the North American plate. Late Cenozoic transpression between the southeastern Bahama Platform and the Caribbean plate in Hispaniola has inhibited the eastward motion of the northeastern corner of the plate. Transpression is manifested in western and central Hispaniola by the formation of regional scale folds that correspond to present-day, anticlinal topographic mountain chains continuous with offshore anticlinal ridges. Areas of most rapid Quaternary uplift determined from onland coral reefs 125 ka and younger, coincide with the axial traces of these folds. Offshore data suggest recent folding and faulting of the seafloor. Onshore reef data do not conclusively require late Quaternary folding, but demonstrate that tectonic uplift rates of the axial areas of the anticlines decrease from the Northwest Peninsula of Haiti (0.37 mm/yr) to to the central part of the coast of western Haiti (0.19 mm/yr) to the south-central part of western Haiti (0 mm/yr). Formation of the 1200-km-long Enriquillo-Plantain Garden-Walton fault zone as a 'bypass' strike-slip fault has isolated the southern edge of the Gonave microplate and is allowing continued, unimpeded eastward motion of a smaller Caribbean plate past the zone of late Neogene convergence and Quaternary uplift of coral reefs in Hispaniola. Offshore seismic reflection data from the Jamaica Passage, the marine strait separating Jamaica and Haiti, show that the Enriquillo-Plantain Garden fault zone forms a narrow but deep, active fault-bounded trough beneath the passage. The active fault is continuous with active faults mapped onshore in western Haiti and eastern Jamaica; the bathymetric deep is present because the

  15. Active limited-angle tomographic phase microscope.

    PubMed

    Kus, Arkadiusz; Krauze, Wojciech; Kujawinska, Malgorzata

    2015-01-01

    We demonstrate an active, holographic tomography system, working with limited angle of projections, realized by optical-only, diffraction-based beam steering. The system created for this purpose is a Mach–Zehnder interferometer modified to serve as a digital holographic microscope with a high numerical aperture illumination module and a spatial light modulator (SLM). Such a solution is fast and robust. Apart from providing an elegant solution to viewing angle shifting, it also adds new capabilities of the holographic microscope system. SLM, being an active optical element, allows wavefront correction in order to improve measurement accuracy. Integrated phase data captured with different illumination scenarios within a highly limited angular range are processed by a new tomographic reconstruction algorithm based on the compressed sensing technique: total variation minimization, which is applied here to reconstruct nonpiecewise constant samples. Finally, the accuracy of full measurement and the proposed processing path is tested for a calibrated three-dimensional micro-object as well as a biological object--C2C12 myoblast cell.

  16. Active limited-angle tomographic phase microscope

    NASA Astrophysics Data System (ADS)

    Kuś, Arkadiusz; Krauze, Wojciech; Kujawińska, Małgorzata

    2015-11-01

    We demonstrate an active, holographic tomography system, working with limited angle of projections, realized by optical-only, diffraction-based beam steering. The system created for this purpose is a Mach-Zehnder interferometer modified to serve as a digital holographic microscope with a high numerical aperture illumination module and a spatial light modulator (SLM). Such a solution is fast and robust. Apart from providing an elegant solution to viewing angle shifting, it also adds new capabilities of the holographic microscope system. SLM, being an active optical element, allows wavefront correction in order to improve measurement accuracy. Integrated phase data captured with different illumination scenarios within a highly limited angular range are processed by a new tomographic reconstruction algorithm based on the compressed sensing technique: total variation minimization, which is applied here to reconstruct nonpiecewise constant samples. Finally, the accuracy of full measurement and the proposed processing path is tested for a calibrated three-dimensional micro-object as well as a biological object-C2C12 myoblast cell.

  17. Detection of precursory slips on a fault by the quiescence and activation of seismicity relative to the ETAS model and by the anomalous trend of the geodetic time series of distances between GPS stations around the fault

    NASA Astrophysics Data System (ADS)

    Ogata, Y.

    2006-12-01

    This paper is concerned with the detection of precursory slip on a rupturing fault, supported by both seismic and geodetic records. Basically, the detection relies on the principle that, assuming precursory slip on the rupturing fault, the seismic activity around the fault should be enhanced or reduced in the zones where increment of the Coulomb failure stress (CFS) is positive or negative, respectively. However, any occurring event also affects the stress changes in neighboring regions, which can trigger further aftershock clusters. Whereas such stress transfers are too difficult to be computed precisely, due to the unknown complex fault system, the ordinary short-term occurrence rate of earthquakes in a region is easily predicted using the ETAS model of triggering seismicity; and any anomalous seismic activity, such as quiescence and activation, can be quantified by identifying a significant deviation from the predicted rate. Such anomalies are revealed to have occurred during several years leading up to the 2004 Chuetsu Earthquake of M6.8, central Honshu, and also the 2005 Western Fukuoka-Ken-Oki Earthquake of M7.0, Kyushu, Japan. Quiescence and activation in the regions coincided with negative and positive increments of the CFS, respectively, and were probably transferred from possible aseismic slips on the focal fault plane. Such slips are further supported by transient crustal movement around the source preceding the rupture. Time series records of the baseline distances between the permanent GPS stations deviated from the predicted trends, with the deviations consistent with the coseismic horizontal displacements of the stations due to these earthquakes. References Ogata, Y. (2006) Report of the Coordinating Committee for Earthquake Prediction, 76 (to appear, in Japanese).

  18. Variable phase sine wave generator for active phased arrays

    NASA Astrophysics Data System (ADS)

    Waters, W. M.

    1992-09-01

    A waveform generator is provided for generating a high frequency waveform. A pulse generator provides a pulse train at a low frequency. A pulse converter converts the pulse train into an alternatingly positive and negative groups of pulses. A bandpass filter passes the alternatingly positive and negative groups of pulses in a frequency band centered at the high frequency to output the generated waveform at the high frequency. When the groups of pulses are a pair of pulses, a sine wave is output from the bandpass filter. A pulse delay circuit can be used to variably delay the pulse train and thereby cause a phase change in the generated waveform.

  19. Electrophysiological characterization of texture information slip-resistance dependent in the rat vibrissal nerve

    PubMed Central

    2011-01-01

    Background Studies in tactile discrimination agree that rats are able to learn a rough-smooth discrimination task by actively touching (whisking) objects with their vibrissae. In particular, we focus on recent evidence of how neurons at different levels of the sensory pathway carry information about tactile stimuli. Here, we analyzed the multifiber afferent discharge of one vibrissal nerve during active whisking. Vibrissae movements were induced by electrical stimulation of motor branches of the facial nerve. We used sandpapers of different grain size as roughness discrimination surfaces and we also consider the change of vibrissal slip-resistance as a way to improve tactile information acquisition. The amplitude of afferent activity was analyzed according to its Root Mean Square value (RMS). The comparisons among experimental situation were quantified by using the information theory. Results We found that the change of the vibrissal slip-resistance is a way to improve the roughness discrimination of surfaces. As roughness increased, the RMS values also increased in almost all cases. In addition, we observed a better discrimination performance in the retraction phase (maximum amount of information). Conclusions The evidence of amplitude changes due to roughness surfaces and slip-resistance levels allows to speculate that texture information is slip-resistance dependent at peripheral level. PMID:21496307

  20. Volcanism and aseismic slip in subduction zones

    SciTech Connect

    Acharya, H.

    1981-01-10

    The spatial and temporal relationship of volcanism to the occurrence of large earthquakes and convergent plate motion is examined. The number of volcanic eruptions per year in a convergent zone is found to be linearly related to the aseismic slip component of plate motion. If the aseismic slip rate is low (coupling between converging plates is strong), then the primary manifestation of tectonic activity is the occurrence of large earthquakes with only infrequent volcanic activity. If, however, the aseismic slip rate is high (coupling is weak), then there are few large earthquakes, and volcanism is the principal manifestation of tectonic activity. This model is consistent with the spatial distribution of large earthquakes and active volcanoes in the circum-Pacific area. It is tested by examining the extent of volcanic activity in the rupture zones of the 1952--1973 sequence of earthquakes in the Japan--Kurile Islands area. The number of volcanic euptions along these zones during the interval between large earthquakes is used to compute the aseismic slip rates for these segments, based on the relationship developed in this study. The aseismic slip rates so computed agree with those determined from the earthquake history of the area and rates of plate motion. The agreement suggests that in the interval between large earthquakes, the aseismic plate motion is manifested in a specific number of volcanic eruptions. Therefore in areas with adequate historial data it should be possible to use the model developed in this study to monitor volcanic eruptions for long-term prediction of large earthquakes.

  1. Two cases of lichen striatus with prolonged active phase.

    PubMed

    Feely, Meghan A; Silverberg, Nanette B

    2014-01-01

    Lichen striatus is a localized, eczematous disorder distributed along the lines of Blaschko, primarily affecting children. In the literature, lesions have been described as having an active phase of inflamed lesions for 6 to 12 months followed by flattening and persistent pigmentary alteration. We describe two girls who had prolonged active-phase lesions for 2.5 and 3.5 years, respectively. Practitioners should be aware that lesions of lichen striatus may have a prolonged active phase.

  2. Active impedance metasurface with full 360° reflection phase tuning

    PubMed Central

    Zhu, Bo O.; Zhao, Junming; Feng, Yijun

    2013-01-01

    Impedance metasurface is composed of electrical small scatters in two dimensional plane, of which the surface impedance can be designed to produce desired reflection phase. Tunable reflection phase can be achieved by incorporating active element into the scatters, but the tuning range of the reflection phase is limited. In this paper, an active impedance metasurface with full 360° reflection phase control is presented to remove the phase tuning deficiency in conventional approach. The unit cell of the metasurface is a multiple resonance structure with two resonance poles and one resonance zero, capable of providing 360° reflection phase variation and active tuning within a finite frequency band. Linear reflection phase tuning can also be obtained. Theoretical analysis and simulation are presented and validated by experiment at microwave frequency. The proposed approach can be applied to many cases where fine and full phase tuning is needed, such as beam steering in reflectarray antennas. PMID:24162366

  3. Effect of interfacial slip on the deformation of a viscoelastic drop in uniaxial extensional flow field

    NASA Astrophysics Data System (ADS)

    Das, Sayan; Mandal, Shubhadeep; Som, S. K.; Chakraborty, Suman

    2017-03-01

    The effect of interfacial slip on the deformation of a viscoelastic droplet, suspended in another viscoelastic medium, in the presence of a uniaxial extensional flow, is studied analytically. Using the Oldroyd-B constitutive relation, the Stokes flow problem is solved in the limit of a small capillary number and small Deborah number. Experimentally observed interfacial velocity slip is incorporated using a Navier slip boundary condition. The interfacial slip significantly reduces the magnitude of droplet deformation when the droplet has larger viscosity as compared with the suspending phase. The droplet shape becomes less ellipsoidal in the presence of slip. The effect of slip diminishes for low viscosity droplets. Slip effectively weakens the dependence of the droplet deformation on the droplet to medium viscosity ratio. The viscoelasticity of the suspending phase plays a dominant role on the droplet deformation as compared with the viscoelasticity of the droplet phase when there is velocity slip at the droplet surface. The interfacial slip aids the viscoelasticity of the suspending phase in deforming the droplet, while the effect of viscoelasticity of the droplet phase is suppressed by the interfacial slip.

  4. Mechanism of slip and twinning

    NASA Technical Reports Server (NTRS)

    Rastani, Mansur

    1992-01-01

    The objectives are to: (1) demonstrate the mechanisms of deformation in body centered cubic (BCC), face centered cubic (FCC), and hexagonal close-packed (HCP)-structure metals and alloys and in some ceramics as well; (2) examine the deformed microstructures (slip lines and twin boundaries) in different grains of metallic and ceramic specimens; and (3) study visually the deformed macrostructure (slip and twin bands) of metals and alloys. Some of the topics covered include: deformation behavior of materials, mechanisms of plastic deformation, slip bands, twin bands, ductile failure, intergranular fracture, shear failure, slip planes, crystal deformation, and dislocations in ceramics.

  5. Slip flow in graphene nanochannels.

    PubMed

    Kannam, Sridhar Kumar; Todd, B D; Hansen, J S; Daivis, Peter J

    2011-10-14

    We investigate the hydrodynamic boundary condition for simple nanofluidic systems such as argon and methane flowing in graphene nanochannels using equilibrium molecular dynamics simulations (EMD) in conjunction with our recently proposed method [J. S. Hansen, B. D. Todd, and P. J. Daivis, Phys. Rev. E 84, 016313 (2011)]. We first calculate the fluid-graphene interfacial friction coefficient, from which we can predict the slip length and the average velocity of the first fluid layer close to the wall (referred to as the slip velocity). Using direct nonequilibrium molecular dynamics simulations (NEMD) we then calculate the slip length and slip velocity from the streaming velocity profiles in Poiseuille and Couette flows. The slip lengths and slip velocities from the NEMD simulations are found to be in excellent agreement with our EMD predictions. Our EMD method therefore enables one to directly calculate this intrinsic friction coefficient between fluid and solid and the slip length for a given fluid and solid, which is otherwise tedious to calculate using direct NEMD simulations at low pressure gradients or shear rates. The advantages of the EMD method over the NEMD method to calculate the slip lengths/flow rates for nanofluidic systems are discussed, and we finally examine the dynamic behaviour of slip due to an externally applied field and shear rate.

  6. Single slip dynamics

    NASA Astrophysics Data System (ADS)

    Bizzarri, Andrea; Petri, Alberto

    2016-12-01

    In the present paper we consider a 1-D, single spring-slider analog model of fault and we solve the equation of motion within the coseismic time window. We incorporate in the dynamic problem different rheologic behavior, starting from the Coulomb friction (which postulates a constant value of the dynamic resistance), then the viscous rheology (where the friction resistance linearly depends on the sliding speed), and finally a version of the more refined rate-and state-dependent friction law. We present analytical solutions of the equation of motion for the different cases and we are able to find the common features of the solutions, in terms of the most important physical observables characterizing the solutions of a 1-D dynamic fault problem; the peak slip velocity, the time at which it is attained (or, in other words, the so-called rise time), the total cumulative slip developed at the end of the process (assumed to occur when the sliding speed vanishes or become comparable to its initial value). We also extract some useful dependences of these quantities on the parameters of the models. Finally, we compare the spectral behavior of the resulting sliding velocity and its fall-off at high frequencies.

  7. Frequency translating phase conjugation circuit for active retrodirective antenna array

    NASA Astrophysics Data System (ADS)

    Chernoff, R.

    1980-11-01

    An active retrodirective antenna array which has central phasing from a reference antenna element through a "tree" structured network of transmission lines utilizes a number of phase conjugate circuits (PCCs) at each node and a phase reference regeneration circuit (PRR) at each node except the initial node. Each node virtually coincides with an element of the array. A PCC generates the exact conjugate phase of an incident signal using a phase locked loop which combines the phases in an up converter, divides the sum by 2 and mixes the result with the phase in a down converter for phase detection. The PRR extracts the phase from the conjugate phase. Both the PCC and the PRR are not only exact but also free from mixer degeneracy.

  8. The Slip Hypothesis: Tactile Perception and its Neuronal Bases.

    PubMed

    Schwarz, Cornelius

    2016-07-01

    The slip hypothesis of epicritic tactile perception interprets actively moving sensor and touched objects as a frictional system, known to lead to jerky relative movements called 'slips'. These slips depend on object geometry, forces, material properties, and environmental factors, and, thus, have the power to incorporate coding of the perceptual target, as well as perceptual strategies (sensor movement). Tactile information as transferred by slips will be encoded discontinuously in space and time, because slips sometimes engage only parts of the touching surfaces and appear as discrete and rare events in time. This discontinuity may have forced tactile systems of vibrissae and fingertips to evolve special ways to convert touch signals to a tactile percept.

  9. 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.

  10. Superplastic nanofibrous slip zones control seismogenic fault friction

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  11. Handling a slip | Smokefree 60+

    Cancer.gov

    Plan how you will recover from a slip—before it happens. You can recover from a slip If you do go back to smoking, you are not a failure. Don't toss aside your attempt as worthless. Use it to try and succeed. Think of your quit attempt as a learning experience, and if you do slip, try again.

  12. Centrifugal slip casting of components

    SciTech Connect

    Steinlage, G.A.; Roeder, R.K.; Trumble, K.P.; Bowman, K.J.

    1996-05-01

    Research in layered and functionally gradient materials has emerged because of the increasing demand for high-performance engineering materials. Many techniques have been used to produce layered and functionally gradient components. Common examples include thermal spray processing, powder processing, chemical and physical vapor deposition, high-temperature or combustion synthesis, diffusion treatments, microwave processing and infiltration. Of these techniques, powder processing routes offer excellent microstructural control and product quality, and they are capable of producing large components. Centrifugal slip casting is a powder-processing technique combining the effects of slip casting and centrifugation. In slip casting, consolidation takes place as fluid is removed by the porous mold. Particles within the slip move with the suspending fluid until reaching the mold wall, at which point they are consolidated. In centrifugation, particles within the slip move through the fluid at a rate dependent upon the gravitational force and particle drag.

  13. Competing dynamic phases of active polymer networks

    NASA Astrophysics Data System (ADS)

    Freedman, Simon; Banerjee, Shiladitya; Dinner, Aaron R.

    Recent experiments on in-vitro reconstituted assemblies of F-actin, myosin-II motors, and cross-linking proteins show that tuning local network properties can changes the fundamental biomechanical behavior of the system. For example, by varying cross-linker density and actin bundle rigidity, one can switch between contractile networks useful for reshaping cells, polarity sorted networks ideal for directed molecular transport, and frustrated networks with robust structural properties. To efficiently investigate the dynamic phases of actomyosin networks, we developed a coarse grained non-equilibrium molecular dynamics simulation of model semiflexible filaments, molecular motors, and cross-linkers with phenomenologically defined interactions. The simulation's accuracy was verified by benchmarking the mechanical properties of its individual components and collective behavior against experimental results at the molecular and network scales. By adjusting the model's parameters, we can reproduce the qualitative phases observed in experiment and predict the protein characteristics where phase crossovers could occur in collective network dynamics. Our model provides a framework for understanding cells' multiple uses of actomyosin networks and their applicability in materials research. Supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program.

  14. Consequences of abnormal CDK activity in S phase.

    PubMed

    Anda, Silje; Rothe, Christiane; Boye, Erik; Grallert, Beáta

    2016-01-01

    Cyclin Dependent Kinases (CDKs) are important regulators of DNA replication. In this work we have investigated the consequences of increasing or decreasing the CDK activity in S phase. To this end we identified S-phase regulators of the fission yeast CDK, Cdc2, and used appropriate mutants to modulate Cdc2 activity. In fission yeast Mik1 has been thought to be the main regulator of Cdc2 activity in S phase. However, we find that Wee1 has a major function in S phase and thus we used wee1 mutants to investigate the consequences of increased Cdc2 activity. These wee1 mutants display increased replication stress and, particularly in the absence of the S-phase checkpoint, accumulate DNA damage. Notably, more cells incorporate EdU in a wee1(-) strain as compared to wildtype, suggesting altered regulation of DNA replication. In addition, a higher number of cells contain chromatin-bound Cdc45, an indicator of active replication forks. In addition, we found that Cdc25 is required to activate Cdc2 in S phase and used a cdc25 mutant to explore a situation where Cdc2 activity is reduced. Interestingly, a cdc25 mutant has a higher tolerance for replication stress than wild-type cells, suggesting that reduced CDK activity in S phase confers resistance to at least some forms of replication stress.

  15. Basic Chad Arabic: The Active Phase.

    ERIC Educational Resources Information Center

    Absi, Samir Abu; Sinaud, Andre

    This third volume in the course on Chad Arabic emphasizes the active development of speaking skills in the target language. The active participation of the student requires imitation and induction of linguistic structures to a large extent. Some 45 units present grammatical material on gender, parts of speech, and verbs. Each unit contains a…

  16. A phase field dislocation dynamics model for a bicrystal interface system: An investigation into dislocation slip transmission across cube-on-cube interfaces

    SciTech Connect

    Zeng, Y.; Hunter, A.; Beyerlein, I. J.; Koslowski, M.

    2015-09-14

    In this study, we present a phase field dislocation dynamics formulation designed to treat a system comprised of two materials differing in moduli and lattice parameters that meet at a common interface. We apply the model to calculate the critical stress τcrit required to transmit a perfect dislocation across the bimaterial interface with a cube-on-cube orientation relationship. The calculation of τcrit accounts for the effects of: 1) the lattice mismatch (misfit or coherency stresses), 2) the elastic moduli mismatch (Koehler forces or image stresses), and 3) the formation of the residual dislocation in the interface. Our results show that the value of τcrit associated with the transmission of a dislocation from material 1 to material 2 is not the same as that from material 2 to material 1. Dislocation transmission from the material with the lower shear modulus and larger lattice parameter tends to be easier than the reverse and this apparent asymmetry in τcrit generally increases with increases in either lattice or moduli mismatch or both. In efforts to clarify the roles of lattice and moduli mismatch, we construct an analytical model for τcrit based on the formation energy of the residual dislocation. We show that path dependence in this energetic barrier can explain the asymmetry seen in the calculated τcrit values.

  17. A phase field dislocation dynamics model for a bicrystal interface system: An investigation into dislocation slip transmission across cube-on-cube interfaces

    DOE PAGES

    Zeng, Y.; Hunter, A.; Beyerlein, I. J.; ...

    2015-09-14

    In this study, we present a phase field dislocation dynamics formulation designed to treat a system comprised of two materials differing in moduli and lattice parameters that meet at a common interface. We apply the model to calculate the critical stress τcrit required to transmit a perfect dislocation across the bimaterial interface with a cube-on-cube orientation relationship. The calculation of τcrit accounts for the effects of: 1) the lattice mismatch (misfit or coherency stresses), 2) the elastic moduli mismatch (Koehler forces or image stresses), and 3) the formation of the residual dislocation in the interface. Our results show that themore » value of τcrit associated with the transmission of a dislocation from material 1 to material 2 is not the same as that from material 2 to material 1. Dislocation transmission from the material with the lower shear modulus and larger lattice parameter tends to be easier than the reverse and this apparent asymmetry in τcrit generally increases with increases in either lattice or moduli mismatch or both. In efforts to clarify the roles of lattice and moduli mismatch, we construct an analytical model for τcrit based on the formation energy of the residual dislocation. We show that path dependence in this energetic barrier can explain the asymmetry seen in the calculated τcrit values.« less

  18. Active Nematics Are Intrinsically Phase Separated

    NASA Astrophysics Data System (ADS)

    Mishra, Shradha; Ramaswamy, Sriram

    2006-09-01

    Two-dimensional nonequilibrium nematic steady states, as found in agitated granular-rod monolayers or films of orientable amoeboid cells, were predicted [Europhys. Lett. 62, 196 (2003)EULEEJ0295-507510.1209/epl/i2003-00346-7] to have giant number fluctuations, with the standard deviation proportional to the mean. We show numerically that the steady state of such systems is macroscopically phase separated, yet dominated by fluctuations, as in the Das-Barma model [Phys. Rev. Lett. 85, 1602 (2000)PRLTAO0031-900710.1103/PhysRevLett.85.1602]. We suggest experimental tests of our findings in granular and living-cell systems.

  19. Origins of oblique-slip faulting during caldera subsidence

    NASA Astrophysics Data System (ADS)

    Holohan, Eoghan P.; Walter, Thomas R.; SchöPfer, Martin P. J.; Walsh, John J.; Wyk de Vries, Benjamin; Troll, Valentin R.

    2013-04-01

    Although conventionally described as purely dip-slip, faults at caldera volcanoes may have a strike-slip displacement component. Examples occur in the calderas of Olympus Mons (Mars), Miyakejima (Japan), and Dolomieu (La Reunion). To investigate this phenomenon, we use numerical and analog simulations of caldera subsidence caused by magma reservoir deflation. The numerical models constrain mechanical causes of oblique-slip faulting from the three-dimensional stress field in the initial elastic phase of subsidence. The analog experiments directly characterize the development of oblique-slip faulting, especially in the later, non-elastic phases of subsidence. The combined results of both approaches can account for the orientation, mode, and location of oblique-slip faulting at natural calderas. Kinematically, oblique-slip faulting originates to resolve the following: (1) horizontal components of displacement that are directed radially toward the caldera center and (2) horizontal translation arising from off-centered or "asymmetric" subsidence. We informally call these two origins the "camera iris" and "sliding trapdoor" effects, respectively. Our findings emphasize the fundamentally three-dimensional nature of deformation during caldera subsidence. They hence provide an improved basis for analyzing structural, geodetic, and geophysical data from calderas, as well as analogous systems, such as mines and producing hydrocarbon reservoirs.

  20. Defect-Stabilized Phases in Extensile Active Nematics

    NASA Astrophysics Data System (ADS)

    Redner, Gabriel; Decamp, Stephen; Dogic, Zvonimir; Hagan, Michael

    2015-03-01

    Active nematics are liquid crystals which are driven out of equilibrium by energy-dissipating active stresses. The equilibrium nematic state is unstable in these materials, leading to beautiful and surprising behaviors including the spontaneous generation of topological defect pairs which stream through the system and later annihilate, yielding a complex, seemingly chaotic dynamical steady-state. In this talk, I will describe the emergence of order from this chaos in the form of previously unknown broken-symmetry phases in which the topological defects themselves undergo orientational ordering. We have identified these defect-ordered phases in two realizations of an active nematic: first, a suspension of extensile bundles of microtubules and molecular motor proteins, and second, a computational model of extending hard rods. I will describe the defect-stabilized phases that manifest in these systems, our current understanding of their origins, and discuss whether such phases may be a general feature of extensile active nematics.

  1. MMIC devices for active phased array antennas

    NASA Technical Reports Server (NTRS)

    Mittra, R.

    1984-01-01

    The study of printed circuit discontinuities is necessary in order to design, for example, transitions between rectangular waveguides and printed circuits. New developments with respect to the analytical approaches to this problem are discussed. A summary of the progress in the experimental approach is presented. The accurate solution for the modes in various millimeter-wave waveguides is essential in the analysis of many integrated circuit components, such as filters and impedance transformers. Problems associated with the numerical computation of these modes in two frequently used waveguide forms, namely, the finline and microstrip, are presented. The spectral domain method of formulation, with a moment method solution, is considered. This approach can be readily extended to analyze an arbitrary configuration of dielectric and metallized regions in a shielded enclosure. Galerkin's method is used, where the testing and basic functions are the same. It is shown that the mode functions, or eigenfunctions, are more sensitive to errors than the phase constants, or eigenvalues. The approximate mode functions do not satisfy the orthogonality relationship well, resulting in difficulties when these modal solutions are used to form an approximate Green's function or are used in a mode matching analysis.

  2. Interfacial slip on a transverse-shear mode acoustic wave device

    NASA Astrophysics Data System (ADS)

    Ellis, Jonathan S.; Hayward, Gordon L.

    2003-12-01

    This article describes a mathematical relationship between the slip parameter α and the slip length b for a slip boundary condition applied to the transverse-shear model for a quartz-crystal acoustic wave device. The theory presented here reduces empirical determination of slip to a one-parameter fit. It shows that the magnitude and phase of the slip parameter, which describes the relative motion of the surface and liquid in the transverse-shear model, can be linked to the slip length. Furthermore, the magnitude and phase of the slip parameter are shown to depend on one another. An experiment is described to compare the effects of liquid-surface affinity on the resonant properties of a transverse-shear mode wave device by applying different polar and nonpolar liquids to surfaces of different polarity. The theory is validated with slip values determined from the transverse-shear model and compared to slip length values from literature. Agreement with literature values of slip length is within one order of magnitude.

  3. Continuum Theory of Phase Separation Kinetics for Active Brownian Particles

    NASA Astrophysics Data System (ADS)

    Stenhammar, Joakim; Tiribocchi, Adriano; Allen, Rosalind J.; Marenduzzo, Davide; Cates, Michael E.

    2013-10-01

    Active Brownian particles (ABPs), when subject to purely repulsive interactions, are known to undergo activity-induced phase separation broadly resembling an equilibrium (attraction-induced) gas-liquid coexistence. Here we present an accurate continuum theory for the dynamics of phase-separating ABPs, derived by direct coarse graining, capturing leading-order density gradient terms alongside an effective bulk free energy. Such gradient terms do not obey detailed balance; yet we find coarsening dynamics closely resembling that of equilibrium phase separation. Our continuum theory is numerically compared to large-scale direct simulations of ABPs and accurately accounts for domain growth kinetics, domain topologies, and coexistence densities.

  4. ACTIVATION OF HAGEMAN FACTOR IN SOLID AND FLUID PHASES

    PubMed Central

    Cochrane, C. G.; Revak, S. D.; Wuepper, K. D.

    1973-01-01

    The activation of Hageman factor in solid and fluid phase has been analyzed. Activation of highly purified Hageman factor occurred after it interacted with and became bound to a negatively charged surface. Activation was observed in the absence of enzymes that are inhibitable with diisopropylfluorophosphate, phenyl methyl sulfonyl fluoride and ε-amino-n-caproic acid. The binding of [125I]Hageman factor to the negatively charged surface was markedly inhibited by plasma or purified plasma proteins. Activation of Hageman factor in solution (fluid phase) was obtained with kallikrein, plasmin, and Factor XI (plasma thromboplastin antecedent). Kallikrein was greater than 10 times more active in its ability to activate Hageman factor than plasmin and Factor XI. The data offer a plausible explanation for the finding that highly purified kallikrein promotes clotting of normal plasma. In addition, the combined results of this and previously reported data from this laboratory indicate that the reciprocal activation of Hageman factor by kallikrein in fluid phase is essential for normal rate of activation of the intrinsic-clotting, kinin-forming, and fibrinolytic systems. Activation of Hageman factor was associated with three different structural changes in the molecule: (a) Purified Hageman factor, activated on negatively charged surfaces retained its native mol wt of 80–90,000. Presumably a conformational change accompanied activation. (b) In fluid phase, activation with kallikrein and plasmin did not result in cleavage of large fragments of rabbit Hageman factor, although the activation required hydrolytic capacity of the enzymes. (c) Activation of human Hageman factor with kallikrein or plasmin was associated with cleavage of the molecule to 52,000, 40,000, and 28,000 mol wt fragments. Activation of rabbit Hageman factor with trypsin resulted in cleavage of the molecule into three fragments, each of 30,000 mol wt as noted previously. This major cleavage occurred

  5. Middeck Active Control Experiment (MACE), phase A

    NASA Technical Reports Server (NTRS)

    Crawley, Edward F.; Deluis, Javier; Miller, David W.

    1989-01-01

    A rationale to determine which structural experiments are sufficient to verify the design of structures employing Controlled Structures Technology was derived. A survey of proposed NASA missions was undertaken to identify candidate test articles for use in the Middeck Active Control Experiment (MACE). The survey revealed that potential test articles could be classified into one of three roles: development, demonstration, and qualification, depending on the maturity of the technology and the mission the structure must fulfill. A set of criteria was derived that allowed determination of which role a potential test article must fulfill. A review of the capabilities and limitations of the STS middeck was conducted. A reference design for the MACE test article was presented. Computing requirements for running typical closed-loop controllers was determined, and various computer configurations were studied. The various components required to manufacture the structure were identified. A management plan was established for the remainder of the program experiment development, flight and ground systems development, and integration to the carrier. Procedures for configuration control, fiscal control, and safety, reliabilty, and quality assurance were developed.

  6. Foreshocks during the nucleation of stick-slip instability

    USGS Publications Warehouse

    McLaskey, Gregory C.; Kilgore, Brian D.

    2013-01-01

    We report on laboratory experiments which investigate interactions between aseismic slip, stress changes, and seismicity on a critically stressed fault during the nucleation of stick-slip instability. We monitor quasi-static and dynamic changes in local shear stress and fault slip with arrays of gages deployed along a simulated strike-slip fault (2 m long and 0.4 m deep) in a saw cut sample of Sierra White granite. With 14 piezoelectric sensors, we simultaneously monitor seismic signals produced during the nucleation phase and subsequent dynamic rupture. We observe localized aseismic fault slip in an approximately meter-sized zone in the center of the fault, while the ends of the fault remain locked. Clusters of high-frequency foreshocks (Mw ~ −6.5 to −5.0) can occur in this slowly slipping zone 5–50 ms prior to the initiation of dynamic rupture; their occurrence appears to be dependent on the rate at which local shear stress is applied to the fault. The meter-sized nucleation zone is generally consistent with theoretical estimates, but source radii of the foreshocks (2 to 70 mm) are 1 to 2 orders of magnitude smaller than the theoretical minimum length scale over which earthquake nucleation can occur. We propose that frictional stability and the transition between seismic and aseismic slip are modulated by local stressing rate and that fault sections, which would typically slip aseismically, may radiate seismic waves if they are rapidly stressed. Fault behavior of this type may provide physical insight into the mechanics of foreshocks, tremor, repeating earthquake sequences, and a minimum earthquake source dimension.

  7. Variations in strength and slip rate along the san andreas fault system.

    PubMed

    Jones, C H; Wesnousky, S G

    1992-04-03

    Convergence across the San Andreas fault (SAF) system is partitioned between strike-slip motion on the vertical SAF and oblique-slip motion on parallel dip-slip faults, as illustrated by the recent magnitude M(s) = 6.0 Palm Springs, M(s) = 6.7 Coalinga, and M(s) = 7.1 Loma Prieta earthquakes. If the partitioning of slip minimizes the work done against friction, the direction of slip during these recent earthquakes depends primarily on fault dip and indicates that the normal stress coefficient and frictional coefficient (micro) vary among the faults. Additionally, accounting for the active dip-slip faults reduces estimates of fault slip rates along the vertical trace of the SAF by about 50 percent in the Loma Prieta and 100 percent in the North Palm Springs segments.

  8. Phase response curves in the characterization of epileptiform activity

    NASA Astrophysics Data System (ADS)

    Perez Velazquez, J. L.; Galán, R. F.; Dominguez, L. Garcia; Leshchenko, Y.; Lo, S.; Belkas, J.; Erra, R. Guevara

    2007-12-01

    Coordinated cellular activity is a major characteristic of nervous system function. Coupled oscillator theory offers unique avenues to address cellular coordination phenomena. In this study, we focus on the characterization of the dynamics of epileptiform activity, based on some seizures that manifest themselves with very periodic rhythmic activity, termed absence seizures. Our approach consists in obtaining experimentally the phase response curves (PRCs) in the neocortex and thalamus, and incorporating these PRCs into a model of coupled oscillators. Phase preferences of the stationary states and their stability are determined, and these results from the model are compared with the experimental recordings, and interpreted in physiological terms.

  9. Smectite-illite transition during coseismic slip

    NASA Astrophysics Data System (ADS)

    Takahashi, M.; Kitajima, H.

    2013-12-01

    Few evidences for coseismic slip events are preserved in natural fault rocks except pseudotachylytes showing a clear evidence of melting caused by frictional shear at high slip rates [e.g., Spray, 1987; Tsutsumi and Shimamoto, 1997; Hirose and Shimamoto, 2005]. Higher maturity of vitrinite of coal fragments is observed in the fault cores recovered from the Nankai accretionary prism [Sakaguchi eta al., 2011], and also in the friction experiments sheared at seismic slip rates [Kitamura et al., 2012], implying that local heating is caused by frictional shear during earthquakes. Another possible evidence for coseismic slip is illitization of smectite clay along faults observed in the present and ancient accretionary prisms [Yamaguchi et al., 2011; Kameda et al., 2013]. Kameda et al. [2013] have estimated the fault activity using the kinetics of smectite-illite transition, which is determined in the studies on long-term diagenetic processes of smectite-illite transition and may not be appropriate for the short-tem reaction caused by frictional heating associated with coseismic slip. Here we report on high-speed friction experiments on synthetic smectite-quartz mixtures. The goals of our experiments are: (1) to reproduce the illitization of smectite clay (Na-montmorillonite) during coseismic shear and (2) to obtain better kinetic parameters to estimate the fault activity of coseismic slip. The friction experiments were conducted on the rotary-shear apparatus at AIST. One gram of the synthetic gouge of smectite-quartz (70:30 wt.%) mixture was sheared at slip velocity of 1.3 m/s, normal stress of 1 MPa, and up to displacement of 55 m. Because cation exchange between sodium ion in smectite and potassium ion in fluid is required for the illitization, we used gouge samples dampened with two different pore fluid media: (1) 1 mol/L aqueous solution of potassium chloride (KCl) and (2) pure water. Friction coefficient of the gouge sheared with potassium rich fluid is 0.45 at peak

  10. Semi-active tuned mass dampers with phase control

    NASA Astrophysics Data System (ADS)

    Chung, Lap-Loi; Lai, Yong-An; Walter Yang, Chuang-Sheng; Lien, Kuan-Hua; Wu, Lai-Yun

    2013-07-01

    The present study aims at proposing an innovative phase control methodology for semi-active tuned mass dampers (SA-TMDs) that intend to minimize the off-tuned problems associated with passive tuned mass dampers (P-TMDs). The phase control algorithm is first developed, the essential of which is to apply the variable friction force to slow down the mass block at specific moments when the phase lag of the SA-TMD with respect to the structure is different from 90°, resulting in the SA-TMD back to the desired phase lag, i.e., -90° phase deviation, so that the SA-TMD has the maximum power flow to reduce the structural vibration. The feasibility of the application of the phase control in SA-TMDs is verified by performing numerical analyses of a simplified Taipei 101 structure model with a SA-TMD subjected to sinusoidal loads and design level wind loads. The numerical simulation results show that the SA-TMD implemented with phase control can enable the mass block to vibrate in a manner with a phase lag close to the -90° when the structure model is under sinusoidal excitations with frequencies different from the structural fundamental mode. The SA-TMD with phase control not only exhibits better performance than the optimal P-TMD in terms of suppressing the structural vibration, but also enhances its robustness, particularly when the SA-TMD is off-tuned to the structure.

  11. Field measurements of fault slow slip and associated seismicity

    NASA Astrophysics Data System (ADS)

    Guglielmi, Y.; Cappa, F.; Avouac, J. P.; Henry, P.; Elsworth, D.

    2015-12-01

    We show results of slow slip (1-to-10 micrometers/seconds) activations along faults in carbonates and in shales using a hydromechanical in situ testing method. A controlled step-rate injection of a given water volume is conducted between two inflatable packers in an uncased borehole, to produce elastic and inelastic deformations of the surrounding fractured rock mass, with synchronously monitoring of borehole fluid pressure and wall deformation with a specially designed probe. The transition between elastic/inelastic slip occurs at the fault extension pressure (FEP) at the onset of injection flowrate increase. In a typical test, the FEP transition associated with the characterization of the activated slip (strike and dip) on the faults may be used for calibration in a slip sensitivity study related to the ambient stress field. The potential use of the post FEP's response to estimate the variation of the friction coefficient as a function of slip, slip rate and other static controls is discussed taking different in situ test examples. We show that permeability increase may be a predominant control on fault stability and induced seismicity.

  12. EMG and Kinematic Responses to Unexpected Slips After Slip Training in Virtual Reality

    PubMed Central

    Parijat, Prakriti; Lockhart, Thurmon E.

    2015-01-01

    The objective of the study was to design a virtual reality (VR) training to induce perturbation in older adults similar to a slip and examine the effect of the training on kinematic and muscular responses in older adults. Twenty-four older adults were involved in a laboratory study and randomly assigned to two groups (virtual reality training and control). Both groups went through three sessions including baseline slip, training, and transfer of training on slippery surface. The training group experienced twelve simulated slips using a visual perturbation induced by tilting a virtual reality scene while walking on the treadmill and the control group completed normal walking during the training session. Kinematic, kinetic, and EMG data were collected during all the sessions. Results demonstrated the proactive adjustments such as increased trunk flexion at heel contact after training. Reactive adjustments included reduced time to peak activations of knee flexors, reduced knee coactivation, reduced time to trunk flexion, and reduced trunk angular velocity after training. In conclusion, the study findings indicate that the VR training was able to generate a perturbation in older adults that evoked recovery reactions and such motor skill can be transferred to the actual slip trials. PMID:25296401

  13. GPS Cycle Slip Detection Considering Satellite Geometry Based on TDCP/INS Integrated Navigation

    PubMed Central

    Kim, Younsil; Song, Junesol; Kee, Changdon; Park, Byungwoon

    2015-01-01

    This paper presents a means of carrier phase cycle slip detection for an inertial-aided global positioning system (GPS), which is based on consideration of the satellite geometry. An integrated navigation solution incorporating a tightly coupled time differenced carrier phase (TDCP) and inertial navigation system (INS) is used to detect cycle slips. Cycle-slips are detected by comparing the satellite-difference (SD) and time-difference (TD) carrier phase measurements obtained from the GPS satellites with the range estimated by the integrated navigation solution. Additionally the satellite geometry information effectively improves the range estimation performance without a hardware upgrade. And the covariance obtained from the TDCP/INS filter is used to compute the threshold for determining cycle slip occurrence. A simulation and the results of a vehicle-based experiment verify the cycle slip detection performance of the proposed algorithm. PMID:26437412

  14. Recovery Efficiency Test Project: Phase 1, Activity report

    SciTech Connect

    Overbey, W.K. Jr.; Wilkins, D.W.; Keltch, B.; Saradji, B.; Salamy, S.P.

    1988-04-01

    This report is the second volume of the Recovery Efficiency Test Phase I Report of Activities. Volume 1 covered selection, well planning, drilling, coring, logging and completion operations. This volume reports on well testing activities, reclamation activities on the drilling site and access roads, and the results of physical and mechanical properties tests on the oriented core material obtained from a horizontal section of the well. 3 refs., 21 figs., 10 tabs.

  15. Modeling stick-slip-separation dynamics in a bimodal standing wave ultrasonic motor

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Yao, Zhiyuan; Lv, Qibao; Liu, Zhen

    2016-11-01

    Ultrasonic motor (USM) is an electromechanical coupling system with ultrasonic vibration, which is driven by the frictional contact force between the stator (vibrating body) and the rotor/slider (driven body). Stick-slip motion can occur at the contact interface when USM is operating, which may affect the performance of the motor. This paper develops a physically-based model to investigate the complex stick-slip-separation dynamics in a bimodal standing wave ultrasonic motor. The model includes both friction nonlinearity and intermittent separation nonlinearity of the system. Utilizing Hamilton's principle and assumed mode method, the dynamic equations of the stator are deduced. Based on the dynamics of the stator and the slider, sticking force during the stick phase is derived, which is used to examine the stick-to-slip transition. Furthermore, the stick-slip-separation kinematics is analyzed by establishing analytical criteria that predict the transition between stick, slip and separation of the interface. Stick-slip-separation motion is observed in the resulting model, and numerical simulations are performed to study the influence of parameters on the range of possible motions. Results show that stick-slip motion can occur with greater preload and smaller voltage amplitude. Furthermore, a dimensionless parameter is proposed to predict the occurrence of stick-slip versus slip-separation motions, and its role in designing ultrasonic motors is discussed. It is shown that slip-separation motion is favorable for the slider velocity.

  16. Personality and Situational Influences upon Verbal Slips: A Laboratory Test of Freudian and Prearticulatory Editing Hypotheses.

    ERIC Educational Resources Information Center

    Motley, Michael T.; And Others

    1979-01-01

    Demonstrates that a more direct cause of verbal slips is occasional noise or interference in the phonological encoding processes, with the associations provided by cognitive states (and verbal context) serving merely as reference information for the semantic phase of prearticulatory editing. Relates this to "Freudian slips." (JMF)

  17. Megathrust Earthquake Swarms Contemporaneous to Slow Slip and Non-Volcanic Tremor in Southern Mexico, Detected and Analyzed through a Template Matching Approach

    NASA Astrophysics Data System (ADS)

    Holtkamp, S.; Brudzinski, M. R.; Cabral-Cano, E.; Arciniega-Ceballos, A.

    2012-12-01

    An outstanding question in geophysics is the degree to which the newly discovered types of slow fault slip are related to their destructive cousin - the earthquake. Here, we utilize a local network along the Oaxacan segment of the Middle American subduction zone to investigate the potential relationship between slow slip, non-volcanic tremor (NVT), and earthquakes along the subduction megathrust. We have developed a multi-station "template matching" waveform cross correlation technique which is able to detect and locate events several orders of magnitude smaller than would be possible using more traditional techniques. Also, our template matching procedure is capable of consistently locate events which occur during periods of increased background activity (e.g., during productive NVT, loud cultural noise, or after larger earthquakes) because the multi-station detector is finely tuned to events with similar hypocentral location and focal mechanism. The local network in the Oaxaca region allows us to focus on documented megathrust earthquake swarms, which we focus on because slow slip is hypothesized to be the cause for earthquake swarms in some tectonic environments. We identify a productive earthquake swarm in July 2006 (~600 similar earthquakes detected), which occurred during a week-long episode of productive tremor and slow slip. Families of events in this sequence were also active during larger and longer slow slip events, which provides a potential link between slow slip in the transition zone and earthquakes at the downdip end of the seismogenic portion of the megathrust. Because template matching techniques only detect similar signals, detected waveforms can be stacked together to produce higher signal to noise ratios or cross correlated against each other to produce precise relative phase arrival times. We are using the refined signals to look for evidence of expansion or propagation of hypocenters during these earthquake swarms, which could be used as a

  18. Comments on the slip factor and the relation Delta phi = -h Delta theta

    SciTech Connect

    Ng, K.Y.; /Fermilab

    2009-09-01

    The definition of the slip factor can be obtained from the phase equation. However, a derivation using the relation {Delta}{phi} = -h{Delta}{theta} leads to a different slip-factor definition. This apparent paradox is examined in detail and resolved. Here {Delta}{phi} is the rf phase difference and {Delta}{theta} is the azimuthal phase difference around the accelerator ring between an off-momentum particle and the synchronous particle, while h is the rf harmonic.

  19. Toward probabilistic answers to key scientific questions in source modeling: Bayesian explorations of fault slip and coupling over the earthquake cycle

    NASA Astrophysics Data System (ADS)

    Jolivet, Romain; Duputel, Zacharie; Simons, Mark

    2016-04-01

    The ever-increasing amount of data sampling ground displacements over tectonically deforming regions continuously opens new perspectives on fundamental questions on the seismogenic behavior of active faults. How much overlap is inferred between seismic and aseismic slip from geodetic and seismological data? Can we quantify the robustness of potential relationships between fault locking, aseismic slip and coseismic slip? However, knowing how much information we have gained compared to our preconceptions and which parameters of our models still need inputs from additional data is difficult to assess and very rarely quantified because of the size of the problems we are dealing with. We have developed AlTar, a massively parallel Monte Carlo Markov Chain algorithm exploiting cutting-edge computing capabilities of Graphic Processing Units, to sample Probability Density Functions (PDFs) in large-dimensional spaces. We use this solver to derive the PDFs of fault coupling and fault slip, seismic or aseismic, along active faults, focusing on the creeping section of the San Andreas fault, California, and on the northern Chilean subduction zone. We derive the gain of information from our coseismic and interseismic data sets and interrogate these probabilities to derive quantified answers to questions pertaining to the behavior of these faults during the earthquake cycle. Large amounts of data are an opportunity and we need to assess how much we still don't know about distributions of slip during the inter-, co- and post-seismic phases in order to assess where progress has to be made for future data developments.

  20. Slip-localization within confined gouge powder sheared at moderate to high slip-velocity

    NASA Astrophysics Data System (ADS)

    Reches, Zeev; Chen, Xiaofeng; Morgan, Chance; Madden, Andrew

    2015-04-01

    conditions. The ultra-fine grains and extreme slip localization in these experiments are generally similar to ultra-cataclasites found in exhumed faults-zones, and the intensely pulverized gouge found in drilling across active faults.

  1. Modelling Paleoearthquake Slip Distributions using a Gentic Algorithm

    NASA Astrophysics Data System (ADS)

    Lindsay, Anthony; Simão, Nuno; McCloskey, John; Nalbant, Suleyman; Murphy, Shane; Bhloscaidh, Mairead Nic

    2013-04-01

    Along the Sunda trench, the annual growth rings of coral microatolls store long term records of tectonic deformation. Spread over large areas of an active megathrust fault, they offer the possibility of high resolution reconstructions of slip for a number of paleo-earthquakes. These data are complex with spatial and temporal variations in uncertainty. Rather than assuming that any one model will uniquely fit the data, Monte Carlo Slip Estimation (MCSE) modelling produces a catalogue of possible models for each event. From each earthquake's catalogue, a model is selected and a possible history of slip along the fault reconstructed. By generating multiple histories, then finding the average slip during each earthquake, a probabilistic history of slip along the fault can be generated and areas that may have a large slip deficit identified. However, the MCSE technique requires the production of many hundreds of billions of models to yield the few models that fit the observed coral data. In an attempt to accelerate this process, we have designed a Genetic Algorithm (GA). The GA uses evolutionary operators to recombine the information held by a population of possible slip models to produce a set of new models, based on how well they reproduce a set of coral deformation data. Repeated iterations of the algorithm produce populations of improved models, each generation better satisfying the coral data. Preliminary results have shown the GA to be capable of recovering synthetically generated slip distributions based their displacements of sets of corals faster than the MCSE technique. The results of the systematic testing of the GA technique and its performance using both synthetic and observed coral displacement data will be presented.

  2. Slip-stacking Dynamics for High-Power Proton Beams at Fermilab

    SciTech Connect

    Eldred, Jeffrey Scott

    2015-12-01

    Slip-stacking is a particle accelerator configuration used to store two particle beams with different momenta in the same ring. The two beams are longitudinally focused by two radiofrequency (RF) cavities with a small frequency difference between them. Each beam is synchronized to one RF cavity and perturbed by the other RF cavity. Fermilab uses slip-stacking in the Recycler so as to double the power of the 120 GeV proton beam in the Main Injector. This dissertation investigates the dynamics of slip-stacking beams analytically, numerically and experimentally. In the analytic analysis, I find the general trajectory of stable slip-stacking particles and identify the slip-stacking parametric resonances. In the numerical analysis, I characterize the stable phase-space area and model the particle losses. In particular, I evaluate the impact of upgrading the Fermilab Booster cycle-rate from 15 Hz to 20 Hz as part of the Proton Improvement Plan II (PIP-II). The experimental analysis is used to verify my approach to simulating slip-stacking loss. I design a study for measuring losses from the longitudinal single-particle dynamics of slip-stacking as a function of RF cavity voltage and RF frequency separation. I further propose the installation of a harmonic RF cavity and study the dynamics of this novel slip-stacking configuration. I show the harmonic RF cavity cancels out parametric resonances in slip-stacking, reduces emittance growth during slip-stacking, and dramatically enhances the stable phase-space area. The harmonic cavity is expected to reduce slip-stacking losses to far exceed PIP-II requirements. These results raise the possibility of extending slip-stacking beyond the PIP-II era.

  3. Slip-stacking dynamics for high-power proton beams at Fermilab

    NASA Astrophysics Data System (ADS)

    Eldred, Jeffrey

    Slip-stacking is a particle accelerator configuration used to store two particle beams with different momenta in the same ring. The two beams are longitudinally focused by two radiofrequency (RF) cavities with a small frequency difference between them. Each beam is synchronized to one RF cavity and perturbed by the other RF cavity. Fermilab uses slip-stacking in the Recycler as to double the power of the 120 GeV proton beam in the Main Injector. This dissertation investigates the dynamics of slip-stacking beams analytically, numerically and experimentally. In the analytic analysis, I find the general trajectory of stable slip-stacking particles and identify the slip-stacking parametric resonances. In the numerical analysis, I characterize the stable phase-space area and model the particle losses. In particular, I evaluate the impact of upgrading the Fermilab Booster cycle-rate from 15 Hz to 20 Hz as part of the Proton Improvement Plan II (PIP-II). The experimental analysis is used to verify my approach to simulating slip-stacking loss. I design a study for measuring losses from the longitudinal single-particle dynamics of slip-stacking as a function of RF cavity voltage and RF frequency separation. I further propose the installation of a harmonic RF cavity and study the dynamics of this novel slip-stacking configuration. I show the harmonic RF cavity cancels out parametric resonances in slip-stacking, reduces emittance growth during slip-stacking, and dramatically enhances the stable phase-space area. The harmonic cavity is expected to reduce slip-stacking losses to far exceed PIP-II requirements. These results raise the possibility of extending slip-stacking beyond the PIP-II era.

  4. Slip-Cast Superconductive Parts

    NASA Technical Reports Server (NTRS)

    Wise, Stephanie A.; Buckley, John D.; Vasquez, Peter; Buck, Gregory M.; Hicks, Lana P.; Hooker, Matthew W.; Taylor, Theodore D.

    1993-01-01

    Complex shapes fabricated without machining. Nonaqueous slip-casting technique used to form complexly shaped parts from high-temperature superconductive materials like YBa(2)Cu(3)O(7-delta). Such parts useful in motors, vibration dampers, and bearings. In process, organic solvent used as liquid medium. Ceramic molds made by lost-wax process used instead of plaster-of-paris molds, used in aqueous slip-casting but impervious to organic solvents and cannot drain away liquid medium. Organic-solvent-based castings do not stick to ceramic molds as they do to plaster molds.

  5. Whillans Ice Plain Stick Slip

    NASA Astrophysics Data System (ADS)

    Lipovsky, B.; Dunham, E. M.

    2015-12-01

    Concern about future sea level rise motivates the study of fast flowing ice. The Whillans Ice Plain (WIP) region of the West Antarctic Ice Sheet is notable for decelerating from previously fast motion during the instrumental record. Since most ice flux in Antarctica occurs through ice streams, understanding the conditions that cause ice stream stagnation is of basic importance in understanding the continent's contribution to future sea level rise. Although recent progress has been made in understanding the relationship between basal conditions and ice stream motion, direct observation of the temporal variation in subglacial conditions during ice stream stagnation has remained elusive. The Whillans Ice Plain flows to the sea mostly by way of stick-slip motion. We present numerical simulations of this stick-slip motion that capture the inertial dynamics, seismic waves, and the evolution of sliding with rate- and state-dependent basal friction. Large scale stick-slip behavior is tidally modulated and encompasses the entire WIP. Sliding initiates within one of several locked regions and then propagates outward with low average rupture velocity (~ 200 m/s). Sliding accelerates over a period of 200 s attain values as large as 65 m/d. From Newton's second law, this acceleration is ~ T / (rho H) for average shear stress drop T, ice thickness H, and ice density rho. This implies a 3 Pa stress drop that must be reconciled with the final stress drop of 300 Pa inferred from the total slip and fault dimensions. A possible explanation of this apparent discrepancy is that deceleration of the ice is associated with a substantial decrease in traction within rate-strengthening regions of the bed. During these large-scale sliding events, m-scale patches at the bed produce rapid (20 Hz) stick-slip motion. Each small event occurs over ~ 1/100 s, produces ~ 40 microns of slip, and gives rise to a spectacular form of seismic tremor. Variation between successive tremor episodes allows us

  6. On the transient behavior of frictional melt during seismic slip

    NASA Astrophysics Data System (ADS)

    Nielsen, S.; Mosca, P.; Giberti, G.; di Toro, G.; Hirose, T.; Shimamoto, T.

    2010-10-01

    In a recent work on the problem of sliding surfaces under the presence of frictional melt (applying in particular to earthquake fault dynamics), we derived from first principles an expression for the steady state friction compatible with experimental observations. Building on the expressions of heat and mass balance obtained in the above study for this particular case of Stefan problem (phase transition with a migrating boundary), we propose here an extension providing a full time-dependent solution (including the weakening transient after pervasive melting has started, the effect of eventual steps in velocity, and the final decelerating phase). A system of coupled equations is derived and solved numerically. The resulting transient friction and wear evolution yield a satisfactory fit (1) with experiments performed under variable sliding velocities (0.9-2 m s-1) and different normal stresses (0.5-20 MPa) for various rock types and (2) with estimates of slip weakening obtained from observations on ancient seismogenic faults that host pseudotachylite (solidified melt). The model allows us to extrapolate the experimentally observed frictional behavior to large normal stresses representative of the seismogenic Earth crust (up to 200 MPa), high slip rates (up to 9 m s-1), and cases where melt extrusion is negligible. Though weakening distance and peak stress vary widely, the net breakdown energy appears to be essentially independent of either slip velocity or normal stress. In addition, the response to earthquakelike slip can be simulated, showing a rapid friction recovery when slip rate drops. We discuss the properties of energy dissipation, transient duration, velocity weakening, restrengthening in the decelerating final slip phase, and the implications for earthquake source dynamics.

  7. Slip zone structure and processes in seismogenic carbonate faults

    NASA Astrophysics Data System (ADS)

    Bullock, R. J.; De Paola, N.

    2011-12-01

    High velocity rotary shear experiments performed at seismic slip velocities (>1 m/s) have shown that experimental faults are weak; with increasing displacement, friction coefficient values decrease from Byerlee's values (μ = 0.6-0.85) to values of ~0.1. In carbonate rocks, experimental studies have shown that fault lubrication is due to the operation of multiple dynamic weakening mechanisms (e.g., flash heating, thermal pressurization, nanoparticle lubrication), which are thermally activated due to the frictional heat generated along localized slip surfaces during rapid slip. This study has set out to investigate whether evidence for the operation of these weakening mechanisms can be found in naturally occurring carbonate fault zones. Field studies were carried out on the active Gubbio fault zone (1984, Mw = 5.6) in the northern Apennines of Italy. Jurassic-Oligocene carbonates in the footwall are heavily deformed within a fault core of ~15 m thickness, which contains a number of very well exposed, highly localized principal slip surfaces (PSSs). Fault rocks are predominantly breccias and foliated cataclasites. Microstructural analyses of the PSSs reveal that slip is localized within very narrow principal slip zones (PSZs), ranging from 10-85 μm in thickness, with sub-millimetre scale asperities. PSZs are composed of very fine-grained, orange-brown ultracataclasite gouge containing a high proportion of nano-sized particles. The ultracataclasite commonly displays a foliated texture and sub-micron scale zones of extreme shear localization. A broader slip zone, up to 1.5 mm wide and containing multiple slip surfaces, is associated with the most evolved PSSs; it is located on the opposite side of the PSS to the PSZ. Here, the host rock material is heavily fractured, abraded and altered, sometimes with an ultracataclasite matrix. The surrounding wall rock often appears to have a porous texture, and calcite crystals within the slip zone have altered rims with lobate

  8. A latchable thermally activated phase change actuator for microfluidic systems

    NASA Astrophysics Data System (ADS)

    Richter, Christiane; Sachsenheimer, Kai; Rapp, Bastian E.

    2016-03-01

    Complex microfluidic systems often require a high number of individually controllable active components like valves and pumps. In this paper we present the development and optimization of a latchable thermally controlled phase change actuator which uses a solid/liquid phase transition of a phase change medium and the displacement of the liquid phase change medium to change and stabilize the two states of the actuator. Because the phase change is triggered by heat produced with ohmic resistors the used control signal is an electrical signal. In contrast to pneumatically activated membrane valves this concept allows the individual control of several dozen actuators with only two external pressure lines. Within this paper we show the general working principle of the actuator and demonstrate its general function and the scalability of the concept at an example of four actuators. Additionally we present the complete results of our studies to optimize the response behavior of the actuator - the influence of the heating power as well as the used phase change medium on melting and solidifying times.

  9. Dynamic phases of active matter systems with quenched disorder

    NASA Astrophysics Data System (ADS)

    Sándor, Cs.; Libál, A.; Reichhardt, C.; Olson Reichhardt, C. J.

    2017-03-01

    Depinning and nonequilibrium transitions within sliding states in systems driven over quenched disorder arise across a wide spectrum of size scales ranging from atomic friction at the nanoscale, flux motion in type II superconductors at the mesoscale, colloidal motion in disordered media at the microscale, and plate tectonics at geological length scales. Here we show that active matter or self-propelled particles interacting with quenched disorder under an external drive represents a class of system that can also exhibit pinning-depinning phenomena, plastic flow phases, and nonequilibrium sliding transitions that are correlated with distinct morphologies and velocity-force curve signatures. When interactions with the substrate are strong, a homogeneous pinned liquid phase forms that depins plastically into a uniform disordered phase and then dynamically transitions first into a moving stripe coexisting with a pinned liquid and then into a moving phase-separated state at higher drives. We numerically map the resulting dynamical phase diagrams as a function of external drive, substrate interaction strength, and self-propulsion correlation length. These phases can be observed for active matter moving through random disorder. Our results indicate that intrinsically nonequilibrium systems can exhibit additional nonequilibrium transitions when subjected to an external drive.

  10. Slip characteristics of San Andreas Fault transition zone segments

    NASA Astrophysics Data System (ADS)

    Johanson, Ingrid Anne

    Transition zones are areas of mixed behavior that divide areas of velocity strengthening and velocity weakening frictional parameters. Their slip characteristics have implications for the underlying mechanism for interseismic creep, the relationship between aseismic slip and earthquakes, and the seismic potential of the transition zones. Two transition zones on the San Andreas fault in California, USA are included in this work; the San Juan Bautista and the Parkfield segments. They are analyzed in three phases of the earthquake cycle; the interseismic, coseismic and postseismic. The San Juan Bautista segment currently undergoes only moderate seismicity. However, six M≥6 earthquakes occurred near the SJB segment between 1840 and 1899. A joint inversion of Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) measurements was performed to determine its current rate and distribution of interseismic creep. The model resolves two low-slip asperities surrounded by creep, indicating that its behavior arises from the heterogeneous distribution of fault frictional properties. InSAR and GPS data were also used to constrain models of coseismic and post-seismic slip in the 2004 Parkfield earthquake. The models indicate that coseismic and postseismic slip occurred in separate regions of the fault, suggesting that the distribution of frictional parameters on the fault exerted some control over the size of the earthquake. The postseismic model included nearly equal amounts of slip as the coseismic, suggesting that this is an important method of relieving stress along areas of the fault that slip aseismically and that these areas may not participate in earthquakes. The sensitivity of the Parkfield segment to outside stresses was also explored. Static stress changes from the 2003 San Simeon earthquake encouraged right-lateral strike slip on the Parkfield segment. While there is no clear correlation between the distribution of slip in the 2004

  11. Phase diagram for assembly of biologically-active peptide amphiphiles.

    PubMed

    Tsonchev, Stefan; Niece, Krista L; Schatz, George C; Ratner, Mark A; Stupp, Samuel I

    2008-01-17

    We construct a phase diagram for self-assembling biologically active peptide amphiphiles. The structure and stability of the assemblies are studied as a function of pH and salinity of the solution. The general features of the phase diagram are predicted based on theoretical modeling of the self-assembly process, as well as experimental data, and further experiments are performed to verify and ascertain the boundary locations of the diagram. Depending on solution conditions, the amphiphiles can form cylindrical or spherical micelles, intermediate structures between these, or may not assemble at all. We also demonstrate that changing conditions may result in phase transitions among these structures. This type of phase diagram could be useful in the design of certain supramolecular nanostructures by providing information on the necessary conditions to form them.

  12. Assessing the Updip Spatial Offset of Tremor and Slip during ETS Events in Cascadia

    NASA Astrophysics Data System (ADS)

    Krogstad, R. D.; Schmidt, D. A.

    2015-12-01

    We investigate the updip spatial overlap of tremor and slip during recent episodic tremor and slip (ETS) events in Cascadia using a combination of forward and inverse models constrained by GPS, strainmeter, and tremor observations. Results from major ETS events in northern Cascadia suggest that, although there is significant spatial overlap, slow slip tends to extend further updip than tremor. ETS activity is thought to be dependent on a range of parameters, such as variable fluid pressures, temperature dependent physical properties, and facies changes. A spatial offset would indicant that tremor and slip are reflective of different physical conditions. While a clear offset of tremor and slip has been observed in multiple other subduction zones, a similar offset in Cascadia has remained difficult to constrain. Here we seek to establish whether the updip spatial offset is real in Cascadia and to quantify its extent. To complement GPS observations in Cascadia, we incorporate high fidelity strainmeter observations into inversions and sensitivity tests of iterative forward models. Tremor distributions are used as a proxy for slip and incorporated into slip models where parameters affecting the distribution and magnitude of slip are allowed to vary. These slip models are used to forward predict surface displacements and strains, which are then compared to the geodetic observations and inferred slip based on geodetic inversions. Results indicate that, while the tremor-derived slip distributions do a good job predicting the broad-scale surface deformation, the best-fit models have slip updip of the peak tremor activity. The fine-scale relationship of tremor and slip appears to vary on an event-by-event basis, where areas of high tremor density do not always correlate with increased surface displacements and vice-versa.

  13. Pressure and phase equilibria in interacting active brownian spheres.

    PubMed

    Solon, Alexandre P; Stenhammar, Joakim; Wittkowski, Raphael; Kardar, Mehran; Kafri, Yariv; Cates, Michael E; Tailleur, Julien

    2015-05-15

    We derive a microscopic expression for the mechanical pressure P in a system of spherical active Brownian particles at density ρ. Our exact result relates P, defined as the force per unit area on a bounding wall, to bulk correlation functions evaluated far away from the wall. It shows that (i) P(ρ) is a state function, independent of the particle-wall interaction; (ii) interactions contribute two terms to P, one encoding the slow-down that drives motility-induced phase separation, and the other a direct contribution well known for passive systems; and (iii) P is equal in coexisting phases. We discuss the consequences of these results for the motility-induced phase separation of active Brownian particles and show that the densities at coexistence do not satisfy a Maxwell construction on P.

  14. Shaker slip-plate adapter

    NASA Technical Reports Server (NTRS)

    Holm, O. S.

    1969-01-01

    Magnesium adapter ties in all of the attachment bosses on a horizontal slip table and makes a rigid coupling which terminates in a single row of attachment bosses at the edge of the horizontal plate. This eliminates ineffective dissipation of the driving force in vibration tests.

  15. Hydrodynamic slip in silicon nanochannels

    NASA Astrophysics Data System (ADS)

    Ramos-Alvarado, Bladimir; Kumar, Satish; Peterson, G. P.

    2016-03-01

    Equilibrium and nonequilibrium molecular dynamics simulations were performed to better understand the hydrodynamic behavior of water flowing through silicon nanochannels. The water-silicon interaction potential was calibrated by means of size-independent molecular dynamics simulations of silicon wettability. The wettability of silicon was found to be dependent on the strength of the water-silicon interaction and the structure of the underlying surface. As a result, the anisotropy was found to be an important factor in the wettability of these types of crystalline solids. Using this premise as a fundamental starting point, the hydrodynamic slip in nanoconfined water was characterized using both equilibrium and nonequilibrium calculations of the slip length under low shear rate operating conditions. As was the case for the wettability analysis, the hydrodynamic slip was found to be dependent on the wetted solid surface atomic structure. Additionally, the interfacial water liquid structure was the most significant parameter to describe the hydrodynamic boundary condition. The calibration of the water-silicon interaction potential performed by matching the experimental contact angle of silicon led to the verification of the no-slip condition, experimentally reported for silicon nanochannels at low shear rates.

  16. Slip-System-Related Dislocation Study from In-Situ Neutron Measurements

    SciTech Connect

    Huang, E-Wen; Barabash, Rozaliya; Jia, Nan; Wang, Yandong; Ice, Gene E; Clausen, Bjorn; Horton Jr, Joe A; Liaw, Peter K

    2008-01-01

    A combined experimental/computational approach is employed to study slip-system-related dislocation-substructure formation during uniaxial tension of a single-phase, face-centered-cubic (fcc), nickel-based alloy. In-situ neutron-diffraction measurements were conducted to monitor the peak-intensity, peak-position, and peak-broadening evolution during a displacement-controlled, monotonic-tension experiment at room temperature. The measured lattice-strain evolution and the macrostress/macrostrain curves were used to obtain the material parameters required for simulating the texture development by a visco-plastic self-consistent (VPSC) model. The simulated texture compared favorably with experimentally-determined texture results over a range of 0 to 30 pct engineering strain. The grain-orientation-dependent input into the Debye-intensity ring was considered. Grains favorably oriented relative to the two detector banks in the geometry of the neutron experiment were indicated. For the favorably oriented grains, the simulated slip-system activity was used to calculate the slip-system-dependent, dislocation-contrast factor. The combination of the calculated contrast factor with the experimentally-measured peak broadening allows the assessment of the parameters of the dislocation arrangement within the specifically oriented grains, which has a quantitative agreement with the transmission-electron-microscopy results.

  17. Contact stresses calculated for miniature slip rings

    NASA Technical Reports Server (NTRS)

    Albright, F. G.; Domerest, K. E.; Horton, J. C.

    1965-01-01

    Using mathematical formulations to plot the graphs of the contact preload versus the Hertzian load, calculations of unit loading of the preloaded brushes on slip rings can be made. This optimizes the design of contact brushes and miniature slip rings.

  18. Slip rate and tremor genesis in Cascadia

    USGS Publications Warehouse

    Wech, Aaron G.; Bartlow, Noel M.

    2014-01-01

    At many plate boundaries, conditions in the transition zone between seismogenic and stable slip produce slow earthquakes. In the Cascadia subduction zone, these events are consistently observed as slow, aseismic slip on the plate interface accompanied by persistent tectonic tremor. However, not all slow slip at other plate boundaries coincides spatially and temporally with tremor, leaving the physics of tremor genesis poorly understood. Here we analyze seismic, geodetic, and strainmeter data in Cascadia to observe for the first time a large, tremor-generating slow earthquake change from tremor-genic to silent and back again. The tremor falls silent at reduced slip speeds when the migrating slip front pauses as it loads the stronger adjacent fault segment to failure. The finding suggests that rheology and slip-speed-regulated stressing rate control tremor genesis, and the same section of fault can slip both with and without detectable tremor, limiting tremor's use as a proxy for slip.

  19. How Orogen-scale Exhumed Strike-slip Faults Initiate

    NASA Astrophysics Data System (ADS)

    Cao, S.; Neubauer, F.

    2015-12-01

    Orogen-scale strike-slip faults present one the most important geodynamic processes affecting the lithosphere-asthenosphere system. In specific subtypes, faulting is virtually initiated along hot-to-cool boundaries, e.g. at such of hot granite intrusions or metamorphic core complexes to cool country rocks. Such fault zones are often subparallel to mountain ranges and expose a wide variety of mylonitic, cataclastic and non-cohesive fault rocks, which were formed at different structural levels of the crust and are stacked within each other ("telescoping"). Exhumation of rocks is, therefore, a common feature of such strike-slip faults implying major transtensive and/or transpressive processes accompanying pure strike-slip motion. The hot-to-cool thermal structure across the fault zone significantly influences the physical fault rock properties. One major question is how and where a major strike-slip initiates and further development. Here, we propose a model in which major continental exhumed strike-slip faults potentially evolve along rheologically weak zones such as plutons or margins of metamorphic complexes. As an example, we propose a model for the Ailao Shan-Red River (ASRR) fault, SE Asia, which initiated along the edge of a plutonic belt and evolved in response to India-Asia collision with four tectonic phases.

  20. Characterizing the Relationship of Tremor and Slip during Recent ETS Events in Northern Cascadia using Strainmeters, GPS, and Tremor Observations

    NASA Astrophysics Data System (ADS)

    Krogstad, R. D.; Schmidt, D. A.

    2014-12-01

    We investigate the relationship between slip and tremor during multiple recent slow slip events in northern Cascadia. While the relationship of geodetically detectable slow slip and nonvolcanic tremor appears to be broadly coincident, the exact spatial and temporal characteristics remain unclear at a finer scale. Typical GPS derived slip distributions tend to be spatially and temporally smoothed and offset slightly updip of tremor distributions. These discrepancies may be real, or they may be a consequence of the resolution of GPS data or an artifact of the inversion methodology. Borehole strainmeters provide additional independent geodetic constraints for characterizing slip, provide greater temporal resolution, and greater precision than GPS. However, various non-tectonic artifacts and other sources of error have limited the number of usable stations and made deriving reliable information from strainmeters during slip events difficult. We utilize strainmeters with low levels of noise and minimal observable artifacts to constrain forward models and to provide additional independent observations in joint geodetic inversions with GPS data. A series of slip distributions are derived by inverting strainmeter and GPS data using the Kalman-filter-based Extended Network Inversion Filter. To compare the tremor distributions to the geodetically derived slip we also construct slip distributions using tremor occurrences as a proxy for localized slip on the plate interface. The magnitude of slip per tremor occurrence is then scaled to best match the observed surface displacements. Separate slip distributions informed by GPS and tremor are then used to predict strain time series. The comparisons between strain predictions and observations produce mixed results. This may indicate that that tremor and slip are not always coincident. This is particularly evident during the Aug. 2010 event, where the peak GPS-derived slip is located in a region with decreased tremor activity

  1. Pontine respiratory activity involved in inspiratory/expiratory phase transition

    PubMed Central

    Mörschel, Michael; Dutschmann, Mathias

    2009-01-01

    Control of the timing of the inspiratory/expiratory (IE) phase transition is a hallmark of respiratory pattern formation. In principle, sensory feedback from pulmonary stretch receptors (Breuer–Hering reflex, BHR) is seen as the major controller for the IE phase transition, while pontine-based control of IE phase transition by both the pontine Kölliker–Fuse nucleus (KF) and parabrachial complex is seen as a secondary or backup mechanism. However, previous studies have shown that the BHR can habituate in vivo. Thus, habituation reduces sensory feedback, so the role of the pons, and specifically the KF, for IE phase transition may increase dramatically. Pontine-mediated control of the IE phase transition is not completely understood. In the present review, we discuss existing models for ponto-medullary interaction that may be involved in the control of inspiratory duration and IE transition. We also present intracellular recordings of pontine respiratory units derived from an in situ intra-arterially perfused brainstem preparation of rats. With the absence of lung inflation, this preparation generates a normal respiratory pattern and many of the recorded pontine units demonstrated phasic respiratory-related activity. The analysis of changes in membrane potentials of pontine respiratory neurons has allowed us to propose a number of pontine-medullary interactions not considered before. The involvement of these putative interactions in pontine-mediated control of IE phase transitions is discussed. PMID:19651653

  2. A reality check on the timing of initiation, geological offsets, slip rates and geodetic rates on the Karakoram strike-slip fault.

    NASA Astrophysics Data System (ADS)

    Searle, M. P.; Phillips, R. J.

    2003-12-01

    Total geological offset of 1000 km along the dextral Karakoram fault (Peltzer & Tapponnier 1989) were based on incorrect correlation of granite belts from the Pamir to S. Tibet and active slip rates of 30mm/yr-1 were based on an assumption of the age of offset post-glacial features (10 +/- 2 ka; Liu et al. 1992). Detailed mapping and U-Pb and 40Ar/39Ar geochronology has confirmed that total dextral offsets are less than 120 km, the timing of initiation of the fault must have been younger than 15 Ma and that exhumation of sheared leucogranites and migmatites occurred between 15-11 Ma (Searle et al., 1997; Dunlap et al., 1998). We stress that: 1. All Tibetan fault slip rates published prior to 1996 are invalid as no precise timing constraints on the post-glacial Quaternary features were used. The common assumption was that all glacial features were formed 10 +/- 2 ka, without any absolute dating. The glacial and fluvial features used to constrain offsets could have been awry by a factor of 3 or 4 (from 3.5 Ma - 20,000 ka). 2. Recent slip rates derived from cosmogenic isotope dating of offset Quaternary features should be treated with immense caution because during the continual recycling process of glacial moraine or alluvial fan burial, exposure and re-deposition, it cannot be known precisely which phase of exhumation is being dated. 3. Long-term geological slip rates on offset granites, precisely constrained by U-Pb geochronology remain the best estimates of timing of initiation, total finite offset and slip rates on Tibetan strike-slip faults. 4. The Karakoram fault is unlikely to be a lithospheric scale fault, because (a) temperatures beneath the southern part of the Tibetan plateau and beneath the faults are high enough to induce melting (>700° C at only 20 km depth), and (b) the lower crust beneath these faults must be underplated cold, old granulite facies crust of the Indian shield. 5. There appears to be a distinct lack of seismicity located along the

  3. Quantitative phase imaging technologies to assess neuronal activity (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Thouvenin, Olivier; Fink, Mathias; Boccara, Claude

    2016-03-01

    Active neurons tends to have a different dynamical behavior compared to resting ones. Non-exhaustively, vesicular transport towards the synapses is increased, since axonal growth becomes slower. Previous studies also reported small phase variations occurring simultaneously with the action potential. Such changes exhibit times scales ranging from milliseconds to several seconds on spatial scales smaller than the optical diffraction limit. Therefore, QPI systems are of particular interest to measure neuronal activity without labels. Here, we report the development of two new QPI systems that should enable the detection of such activity. Both systems can acquire full field phase images with a sub nanometer sensitivity at a few hundreds of frames per second. The first setup is a synchronous combination of Full Field Optical Coherence Tomography (FF-OCT) and Fluorescence wide field imaging. The latter modality enables the measurement of neurons electrical activity using calcium indicators. In cultures, FF-OCT exhibits similar features to Digital Holographic Microscopy (DHM), except from complex computational reconstruction. However, FF-OCT is of particular interest in order to measure phase variations in tissues. The second setup is based on a Quantitative Differential Interference Contrast setup mounted in an epi-illumination configuration with a spectrally incoherent illumination. Such a common path interferometer exhibits a very good mechanical stability, and thus enables the measurement of phase images during hours. Additionally, such setup can not only measure a height change, but also an optical index change for both polarization. Hence, one can measure simultaneously a phase change and a birefringence change.

  4. Offset of latest pleistocene shoreface reveals slip rate on the Hosgri strike-slip fault, offshore central California

    USGS Publications Warehouse

    Johnson, Samuel Y.; Hartwell, Stephen R.; Dartnell, Peter

    2014-01-01

    The Hosgri fault is the southern part of the regional Hosgri–San Gregorio dextral strike‐slip fault system, which extends primarily in the offshore for about 400 km in central California. Between Morro Bay and San Simeon, high‐resolution multibeam bathymetry reveals that the eastern strand of the Hosgri fault is crossed by an ∼265  m wide slope interpreted as the shoreface of a latest Pleistocene sand spit. This sand spit crossed an embayment and connected a western fault‐bounded bedrock peninsula and an eastern bedrock highland, a paleogeography resembling modern coastal geomorphology along the San Andreas fault. Detailed analysis of the relict shoreface with slope profiles and slope maps indicates a lateral slip rate of 2.6±0.9  mm/yr, considered a minimum rate for the Hosgri given the presence of an active western strand. This slip rate indicates that the Hosgri system takes up the largest share of the strike‐slip fault budget and is the most active strike‐slip fault west of the San Andreas fault in central California. This result further demonstrates the value and potential of high‐resolution bathymetry in characterization of active offshore faults.

  5. Slipping properties of ceramic tiles / Quantification of slip resistance

    NASA Astrophysics Data System (ADS)

    Terjek, Anita

    2013-12-01

    Regarding the research and application of ceramic tiles there is a great importance of defining precisely the interaction and friction between surfaces. Measuring slip resistance of floor coverings is a complex problem; slipperiness is always interpreted relatively. In the lack of a consistent and clear EU standard, it is practical to use more method in combination. It is necessary to examine the structure of materials in order to get adequate correlation. That is why measuring techniques of surface roughness, an important contributor to slip resistance and cleaning, is fundamental in the research. By comparing the obtained test results, relationship between individual methods of analysis and values may be determined and based on these information recommendations shall be prepared concerning the selection and application of tiles.

  6. Slow slip hidden in the noise: The intermittence of tectonic release

    NASA Astrophysics Data System (ADS)

    Frank, William B.

    2016-10-01

    Referred to as slow slip events, the transient aseismic slip that occurs along plate boundaries can be indirectly characterized through colocated seismicity, such as tectonic tremor and low-frequency earthquakes (LFEs). Using the timing of cataloged LFE and tremor activity in Guerrero, Mexico, and northern Cascadia, I decompose the interaseismic GPS displacement, defined as the surface deformation between previously detected slow slip events, into separate regimes of tectonic loading and release. In such a way, previously undetected slow slip events that produce less than a millimeter of surface deformation are extracted from the geodetic noise. These new observations demonstrate that the interaseismic period is not quiescent and that slow slip occurs much more often than previously thought. This suggests that the plate interface where slow slip and tremor occur is in fact strongly coupled and that slow aseismic release occurs over a wide spectrum of time scales.

  7. Neogene-Quaternary strike-slip tectonics in the central Calabrian Arc (southern Italy)

    NASA Astrophysics Data System (ADS)

    Tansi, Carlo; Muto, Francesco; Critelli, Salvatore; Iovine, Giulio

    2007-04-01

    A Middle Miocene-Middle Pleistocene regional NW-SE left-lateral strike-slip fault system profoundly conditioned the evolution of central Calabria, during the late tectonic phases which involved the Apulian block and the Calabrian Arc. This system dissected an Oligocene-Early Miocene orogenic belt, made of Alpine nappes overthrusted the Apennine Chain. In the present study, three major faults, arranged in a right-hand en échelon pattern, have been identified within the mentioned strike-slip system: the Falconara-Carpanzano Fault, the Amantea-Gimigliano Fault, and the Lamezia-Catanzaro Fault. A wide active transtensional area (N-S-trending Crati Graben), developed since Late Pliocene, is located at the SE termination of the Falconara-Carpanzano Fault. In the sectors of overlapping of the faults, the transpressional regime induced tectonic extrusions of the deep-seated units of the Chain, producing push-ups within the overlying complexes. In particular, push-ups are either made of Mesozoic carbonate rocks at Mt. Cocuzzo-Mt. Guono and Mt. S. Lucerna, or of ophiolite rocks at Mt. Reventino and Gimigliano. In these sectors, the primary geometric relationships among the units of the orogenic belt were locally altered. The en échelon arrangement of the above-mentioned NW-SE major strike-slip faults indicates the existence of a left-lateral crustal shear zone, striking on average N160. The age of the regional NW-SE left-lateral strike-slip system deserves thorough investigation. Besides evidence from historical and instrumental earthquakes, and from paleoseismological investigations, the kinematic data suggests that the "cause" of the transtensional sector (Crati Graben) could be found in the regional Falconara-Carpanzano Fault.

  8. Effects of multi-joint muscular fatigue on biomechanics of slips.

    PubMed

    Lew, Fui Ling; Qu, Xingda

    2014-01-03

    The objective of the present study was to investigate the effects of multi-joint muscular fatigue on biomechanics of slips. Both lower-limb fatigue and upper-limb fatigue were examined, and the fatiguing exercises involved multi-joint movements to replicate muscular fatigue in realistic scenarios. Sixty healthy young adults participated in the study, and were evenly categorized into three groups: no fatigue, lower-limb fatigue, and upper-limb fatigue. These participants were instructed to walk on a linear walkway, and slips were induced unexpectedly during walking. The results showed that multi-joint muscular fatigue affects biomechanics of slips in all three phases of slips (i.e. initiation, detection, and recovery). In particular, adaptive safer postural control strategies were adopted with the application of both lower-limb fatigue and upper-limb fatigue to maintain the likelihood of slip initiation as in the no fatigue condition. In the phases of detection and recovery, lower-limb fatigue was found to compromise biomechanics of slips while upper-limb fatigue did not show any effects. Based on these findings, minimizing exposures to lower-limb fatigue should be given higher priority compared to upper-limb fatigue when developing interventions to prevent slip-induced falls. In addition, these findings also suggest that interventions aimed at enhancing proprioceptive acuity and increasing muscular strength in the lower limb could also be effective in slip-induced fall prevention.

  9. Effective heterogeneity controlling premonitory slip on laboratory faults

    NASA Astrophysics Data System (ADS)

    Selvadurai, P. A.; Glaser, S.; Parker, J.

    2015-12-01

    solitary wave', Phys. Rev. E 85, 026111. Fukuda, J., A. Kato, K. Obara, S. Miura & T. Kato (2014), 'Imaging of the early acceleration phase of the 2013-2014 Boso slow slip event', Geophysical Research Letters 41(21), 7493-7500.

  10. Rotating single cycle two-phase thermally activated heat pump

    SciTech Connect

    Fabris, G.

    1993-06-08

    A thermally activated heat pump is described which utilizes single working fluid which as a whole passes consecutively through all parts of the apparatus in a closed loop series; the working fluid in low temperature saturated liquid state at condensation is pumped to higher pressure with a pump; subsequently heat is added to the liquid of increased pressure, the liquid via the heating is brought to a high temperature saturated liquid state; the high temperature liquid passes and flashes subsequently in form of two-phase flow through a rotating two-phase flow turbine; in such a way the working fluid performs work on the two-phase turbine which in turn powers the liquid pump and a lower compressor; two-phase flow exiting the two-phase turbine separated by impinging tangentially on housing of the turbine; low temperature heat is added to the housing in such a way evaporating the separated liquid on the housing; in such a way the liquid is fully vaporized the vapor then enters a compressor, the compressor compresses the vapor to a higher condensation pressure and corresponding increased temperature, the vapor at the condensation pressure enters a condenser whereby heat is rejected and the vapor is fully condensed into state of saturated liquid, mid saturated liquid enters the pump and repeats the cycle.

  11. Phase Segregation of Passive Advective Particles in an Active Medium

    NASA Astrophysics Data System (ADS)

    Das, Amit; Polley, Anirban; Rao, Madan

    2016-02-01

    Localized contractile configurations or asters spontaneously appear and disappear as emergent structures in the collective stochastic dynamics of active polar actomyosin filaments. Passive particles which (un)bind to the active filaments get advected into the asters, forming transient clusters. We study the phase segregation of such passive advective scalars in a medium of dynamic asters, as a function of the aster density and the ratio of the rates of aster remodeling to particle diffusion. The dynamics of coarsening shows a violation of Porod behavior; the growing domains have diffuse interfaces and low interfacial tension. The phase-segregated steady state shows strong macroscopic fluctuations characterized by multiscaling and intermittency, signifying rapid reorganization of macroscopic structures. We expect these unique nonequilibrium features to manifest in the actin-dependent molecular clustering at the cell surface.

  12. Accessory slips of the extensor digiti minimi.

    PubMed

    Li, Jing; Mao, Qing Hua

    2014-01-01

    During the educational dissection of a 69-year-old Chinese male cadaver, an extensor digiti minimi (EDM) with five slips on the right hand was discovered. Except for the two slips of the little finger, the two radial slips were inserted into the dorsal aponeurosis of the middle finger and the ring finger, respectively. The middle slip was connected to the junctura tendinum in the fourth intermetacarpal spaces. Variations in this region are of paramount importance for the reconstructive surgeons, who may utilize the accessory slips to restore functional capacity of the fingers.

  13. Oxytocin discontinuation after the active phase of labor is established.

    PubMed

    Vlachos, Dimitrios-Efthymios G; Pergialiotis, Vasilios; Papantoniou, Nikolaos; Trompoukis, Stamoulis; Vlachos, Georgios D

    2015-08-01

    Despite the widespread usage of oxytocin, there is still no consensus on its mode of administration. The scope of the present meta-analysis was to assess the effect of oxytocin discontinuation after the active phase of labor is established on maternal fetal and neonatal outcomes. We searched Medline, Scopus, Popline, ClinicalTrials.gov and Google Scholar databases. Eight studies were finally retrieved, which involved 1232 parturient. We observed significantly decreased rates of cesarean sections among parturient that discontinued oxytocin (OR 0.51, 95% CI 0.35, 0.74) as well as decreased rates of uterine hyperstimulation (OR 0.33, 95% CI 0.19, 0.58). Similarly, cases of non-reassuring fetal heart rates were fewer among women that did not receive oxytocin after the establishment of the active phase of labor (OR 0.63, 95% CI 0.41, 0.97). Keeping in mind the aforementioned maternal and neonatal adverse effects that seem to result from infusion of oxytocin until delivery, future practice should aim towards its discontinuation after the establishment of the active phase of labor, as it does not seem to influence the total duration of labor. Future studies should aim towards specific populations of parturient in order to clarify whether different approaches are needed.

  14. Small Activity Differences Drive Phase Separation in Active-Passive Polymer Mixtures

    NASA Astrophysics Data System (ADS)

    Smrek, Jan; Kremer, Kurt

    2017-03-01

    Recent theoretical studies found that mixtures of active and passive colloidal particles phase separate but only at very high activity ratio. The high value poses serious obstacles for experimental exploration of this phenomenon. Here we show using simulations that when the active and passive particles are polymers, the critical activity ratio decreases with the polymer length. This not only facilitates the experiments but also has implications on the DNA organization in living cell nuclei. Entropy production can be used as an accurate indicator of this nonequilibrium phase transition.

  15. Back analysis of fault-slip in burst prone environment

    NASA Astrophysics Data System (ADS)

    Sainoki, Atsushi; Mitri, Hani S.

    2016-11-01

    In deep underground mines, stress re-distribution induced by mining activities could cause fault-slip. Seismic waves arising from fault-slip occasionally induce rock ejection when hitting the boundary of mine openings, and as a result, severe damage could be inflicted. In general, it is difficult to estimate fault-slip-induced ground motion in the vicinity of mine openings because of the complexity of the dynamic response of faults and the presence of geological structures. In this paper, a case study is conducted for a Canadian underground mine, herein called "Mine-A", which is known for its seismic activities. Using a microseismic database collected from the mine, a back analysis of fault-slip is carried out with mine-wide 3-dimensional numerical modeling. A back analysis is conducted to estimate the physical and mechanical properties of the causative fracture or shear zones. One large seismic event has been selected for the back analysis to detect a fault-slip related seismic event. In the back analysis, the shear zone properties are estimated with respect to moment magnitude of the seismic event and peak particle velocity (PPV) recorded by a strong ground motion sensor. The estimated properties are then validated through comparison with peak ground acceleration recorded by accelerometers. Lastly, ground motion in active mining areas is estimated by conducting dynamic analysis with the estimated values. The present study implies that it would be possible to estimate the magnitude of seismic events that might occur in the near future by applying the estimated properties to the numerical model. Although the case study is conducted for a specific mine, the developed methodology can be equally applied to other mines suffering from fault-slip related seismic events.

  16. A series of transient slip events on Kilauea volcano, Hawaii.

    NASA Astrophysics Data System (ADS)

    Desmarais, E. K.; Segall, P.; Miklius, A.; Cervelli, P.

    2005-12-01

    Deformation on Kilauea volcano, Hawaii is monitored by a network of continuously recording GPS stations, among other methds. Since its installation in 1996, the GPS network has detected four spatially coherent accelerations on Kilauea's south flank that are not caused by either intrusions or earthquakes. These events, each lasting several hours to two days, occurred in September 1998, November 2000, July 2003, and January 2005. Previously, Cervelli et al., (Nature, 2002) interpreted the 2000 event as a silent earthquake due to slip on a sub-horizontal fault beneath Kilauea's south flank. We inverted the cumulative displacements ( less than 2 cm) using a simulated annealing algorithm for each event and found similarly sized, near horizontal, uniform slip source locations for all four events at depths of ~6 km. The estimated slip magnitudes are between 9 and 15 cm, with the upper block moving seaward. The 2005 event is the largest detected to date. Volcano-tectonic (VT) earthquakes on the south flank of Kilauea are typically restricted to the volume between the East Rift Zone and the Hilina and Poliokeawe Palis. Seismicity in this volume increased significantly during the silent events at depths of 5-10 km. However, all of the VT earthquakes were small ( less than M3) and their cumulative moment does not account for the moment released during the silent slip events. We are currently examining seismic waveform data for evidence of other signals, such as non-volcanic tremor, that might be associated with the slip events. To determine the exact onset and duration of the silent earthquakes, we invert for slip as a function of time directly from raw GPS phase and pseudorange observations. The November 2000 silent earthquake was preceded 9 days earlier by nearly 1 m of rainfall, which was speculated in Cervelli et al., (Nature, 2002) to have reduced fault stability through surface loading or pore pressure increase. In contrast, both the 2003 and 2005 events occurred

  17. Multi-asperity models of slow slip and tremor

    NASA Astrophysics Data System (ADS)

    Ampuero, Jean Paul; Luo, Yingdi; Lengline, Olivier; Inbal, Asaf

    2016-04-01

    Field observations of exhumed faults indicate that fault zones can comprise mixtures of materials with different dominant deformation mechanisms, including contrasts in strength, frictional stability and hydrothermal transport properties. Computational modeling helps quantify the potential effects of fault zone heterogeneity on fault slip styles from seismic to aseismic slip, including slow slip and tremor phenomena, foreshocks sequences and swarms, high- and low-frequency radiation during large earthquakes. We will summarize results of ongoing modeling studies of slow slip and tremor in which fault zone structure comprises a collection of frictionally unstable patches capable of seismic slip (tremorgenic asperities) embedded in a frictionally stable matrix hosting aseismic transient slips. Such models are consistent with the current view that tremors result from repeated shear failure of multiple asperities as Low Frequency Earthquakes (LFEs). The collective behavior of asperities embedded in creeping faults generate a rich spectrum of tremor migration patterns, as observed in natural faults, whose seismicity rate, recurrence time and migration speed can be mechanically related to the underlying transient slow slip rate. Tremor activity and slow slip also responds to periodic loadings induced by tides or surface waves, and models relate tremor tidal sensitivity to frictional properties, fluid pressure and creep rate. The overall behavior of a heterogeneous fault is affected by structural parameters, such as the ratio of stable to unstable materials, but also by time-dependent variables, such as pore pressure and loading rate. Some behaviors are well predicted by homogenization theory based on spatially-averaged frictional properties, but others are somewhat unexpected, such as seismic slip behavior found in asperities that are much smaller than their nucleation size. Two end-member regimes are obtained in rate-and-state models with velocity-weakening asperities

  18. 33 CFR 165.751 - Security Zone: LNG mooring slip, Savannah River, Savannah, Georgia.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Security Zone: LNG mooring slip... § 165.751 Security Zone: LNG mooring slip, Savannah River, Savannah, Georgia. (a) Security zone. The... security zone; or (4) Actively engaged in escort, maneuvering, or support duties for an LNG tankship....

  19. Mirror-like slip surfaces in dolostone: natural and experimental constraints on a potential seismic marker

    NASA Astrophysics Data System (ADS)

    Fondriest, M.; Smith, S. A.; Di Toro, G.; Nielsen, S. B.

    2012-12-01

    transient phase of strengthening. During the tests the instantaneous power density (shear stress*slip rate) dissipated on the sample reaches values of 6-10 MW/m2 over distances of 0.02-1 m, comparable to those of natural earthquakes. At 26 MPa normal stress a mirror-like slip surface is formed after only 0.03 m of slip. At intermediate slip rates (0.113 m/s) only moderate reductions in μ are observed. Instantaneous power density is ~1 MW/m2 and the mirror-like slip surface starts to develop after 0.1 m of slip. At sub-seismic slip rates (0.0001-0.0013 m/s) μ remains ~0.7, instantaneous power density is ~0.02 MW/m2, and no mirror-like slip surface develops. Microstructural observations suggest that the natural and experimental slip zones are comparable: both have a compacted layer up to 20 μm thick immediately below the mirror-like slip surface in which deformation is strongly localized. The layer consists of partially-welded dolomite clasts 0.1-10 μm in size. In the experimental samples, chemical analyses recognized small (<100 μm long), discontinuous patches of periclase and Mg-calcite nanoparticles formed by dolomite decomposition. Field, experimental and microstructural data suggest that mirror-like slip surfaces in dolostone develop at seismic conditions, when instantaneous power density is of the order of 1-10 MW/m2.

  20. Boundary slip study on hydrophilic, hydrophobic, and superhydrophobic surfaces with dynamic atomic force microscopy.

    PubMed

    Bhushan, Bharat; Wang, Yuliang; Maali, Abdelhamid

    2009-07-21

    Slip length has been measured using the dynamic atomic force microscopy (AFM) method. Unlike the contact AFM method, the sample surface approaches an oscillating sphere with a very low velocity in the dynamic AFM method. During this process, the amplitude and phase shift data are recorded to calculate the hydrodynamic damping coefficient, which is then used to obtain slip length. In this study, a glass sphere with a large radius was glued to the end of an AFM cantilever to measure the slip length on rough surfaces. Experimental results for hydrophilic, hydrophobic, and superhydrophobic surfaces show that the hydrodynamic damping coefficient decreases from the hydrophilic surface to the hydrophobic surface and from the hydrophobic one to the superhydrophobic one. The slip lengths obtained on the hydrophobic and superhydrophobic surfaces are 43 and 236 nm, respectively, which indicates increasing boundary slip from the hydrophobic surface to the superhydrophobic one.

  1. Slip length measurement of confined air flow on three smooth surfaces.

    PubMed

    Pan, Yunlu; Bhushan, Bharat; Maali, Abdelhamid

    2013-04-02

    An experimental measurement of the slip length of air flow close to three different solid surfaces is presented. The substrate was driven by a nanopositioner moving toward an oscillating glass sphere glued to an atomic force microscopy (AFM) cantilever. A large separation distance was used to get more effective data. The slip length value was obtained by analyzing the amplitude and phase data of the cantilever. The measurements show that the slip length does not depend on the oscillation amplitude of the cantilever. Because of the small difference among the slip lengths of the three surfaces, a simplified analysis method was used. The results show that on glass, graphite, and mica surfaces the slip lengths are 98, 234, and 110 nm, respectively.

  2. A complex systems analysis of stick-slip dynamics of a laboratory fault

    SciTech Connect

    Walker, David M.; Tordesillas, Antoinette; Small, Michael; Behringer, Robert P.; Tse, Chi K.

    2014-03-15

    We study the stick-slip behavior of a granular bed of photoelastic disks sheared by a rough slider pulled along the surface. Time series of a proxy for granular friction are examined using complex systems methods to characterize the observed stick-slip dynamics of this laboratory fault. Nonlinear surrogate time series methods show that the stick-slip behavior appears more complex than a periodic dynamics description. Phase space embedding methods show that the dynamics can be locally captured within a four to six dimensional subspace. These slider time series also provide an experimental test for recent complex network methods. Phase space networks, constructed by connecting nearby phase space points, proved useful in capturing the key features of the dynamics. In particular, network communities could be associated to slip events and the ranking of small network subgraphs exhibited a heretofore unreported ordering.

  3. Using a genetic algorithm to estimate the details of earthquake slip distributions from point surface displacements

    NASA Astrophysics Data System (ADS)

    Lindsay, A.; McCloskey, J.; Nic Bhloscaidh, M.

    2016-03-01

    Examining fault activity over several earthquake cycles is necessary for long-term modeling of the fault strain budget and stress state. While this requires knowledge of coseismic slip distributions for successive earthquakes along the fault, these exist only for the most recent events. However, overlying the Sunda Trench, sparsely distributed coral microatolls are sensitive to tectonically induced changes in relative sea levels and provide a century-spanning paleogeodetic and paleoseismic record. Here we present a new technique called the Genetic Algorithm Slip Estimator to constrain slip distributions from observed surface deformations of corals. We identify a suite of models consistent with the observations, and from them we compute an ensemble estimate of the causative slip. We systematically test our technique using synthetic data. Applying the technique to observed coral displacements for the 2005 Nias-Simeulue earthquake and 2007 Mentawai sequence, we reproduce key features of slip present in previously published inversions such as the magnitude and location of slip asperities. From the displacement data available for the 1797 and 1833 Mentawai earthquakes, we present slip estimates reproducing observed displacements. The areas of highest modeled slip in the paleoearthquake are nonoverlapping, and our solutions appear to tile the plate interface, complementing one another. This observation is supported by the complex rupture pattern of the 2007 Mentawai sequence, underlining the need to examine earthquake occurrence through long-term strain budget and stress modeling. Although developed to estimate earthquake slip, the technique is readily adaptable for a wider range of applications.

  4. Fault Slip Embedded in Creep: Insight into Tectonic Tremors and Slow Slip Events from Acoustic and Optical Monitoring of Fractures

    NASA Astrophysics Data System (ADS)

    Elkhoury, J. E.; Lengline, O.; Ampuero, J. P.; Schmittbuhl, J.

    2010-12-01

    Observations of temporal and spatial correlations between slow slip earthquakes and tectonic tremor activity suggest a physical relation between them. Early descriptions of mechanisms relating these phenomena simply attributed the relation between seismic and aseismic events to fluid mediated processes. More recent hypotheses suggest that tectonic tremors are bursts of seismic energy due to the rupturing of small asperities within slow slipping regions. Here we present laboratory results of a unique experimental setting aimed at understanding the response to transient loads of a system of small asperities embedded in creep as a model of tectonic tremor activity triggered by slow slip and modulated by tides. We performed mode I crack propagation experiments on glass bead blasted and annealed 2D interfaces of transparent material (Polymethylmethacrylate) where fracture fronts were confined to the 2D weakness plane of the heterogeneous interface. We monitored acoustic emissions (AE) with piezo-electric sensors surrounding the crack front line. We also optically monitored the rupture front line with up to 1000 frames per second. The experimental loading conditions produce quasi-static front propagation at slow average speeds. Image processing reveals de-pinning along the front that we characterize as intermittent opening during slow front propagation. AE locations strongly correlate to the spatiotemporal clustering of the de-penning events along the front. Moreover, this correlation is preserved at the time of imposed transient fluctuations in loading during front propagation. Using the analogy between mode I and modes II and III fractures, our results translate into intermittent slip on faults linked to clustering of seismic activity produced by the breakage of asperities embedded in creeping regions with no need of invoking fluid mediated processes. Thus our experiments help reveal the interplay between aseismic and seismic slip on faults. We also observe qualitative

  5. Offset of Latest Pleistocene Shoreface Reveals Slip Rate on the Hosgri Strike-Slip Fault, Offshore Central California

    NASA Astrophysics Data System (ADS)

    Johnson, S. Y.; Hartwell, S. R.; Dartnell, P.

    2014-12-01

    The Hosgri fault is the southern part of the regional Hosgri-San Gregorio dextral strike-slip fault system, which extends primarily in the offshore region for about 400 km in central California. Between Morro Bay and San Simeon, high-resolution multibeam bathymetry reveals that the eastern strand of the Hosgri fault is crossed by a ~265-m-wide slope interpreted as the shoreface of a relict sand spit that formed during a period of relatively slower sea-level rise (Younger Dryas stadial) in the latest Pleistocene. This sand spit crossed an embayment and connected a western fault-bounded bedrock peninsula and an eastern bedrock highland, a paleogeography similar to modern geomorphology along coastal segments of the San Andreas fault. Detailed analysis of the relict shoreface with slope profiles and slope maps indicates a lateral slip rate of 2.6 ± 0.9 mm/yr. Because the Hosgri fault locally includes an active western strand, and regionally converges with several other faults, this slip rate should be considered a minimum for the Hosgri fault in central California and should not be applied for the entire Hosgri-San Gregorio fault system. This slip rate indicates that the Hosgri system takes up the largest share of the strike-slip fault budget and is the most active strike-slip fault west of the San Andreas fault in central California. This result further demonstrates the value and potential of high-resolution bathymetry in earthquake-hazard characterization of active offshore faults.

  6. Wear studies made of slip rings and gas bearing components

    NASA Technical Reports Server (NTRS)

    Furr, A. K.

    1967-01-01

    Neutron activation analysis techniques were employed for the study of the wear and performance characteristics of slip ring and rotor assemblies and of the problems arising from environmental conditions with special reference to surface contamination. Results showed that the techniques could be successfully applied to measurement of wear parameters.

  7. Post-Cretaceous Sinistral Transpression in Southwest Alxa: Structural and Paleomagnetic Insights into the Long-Term Slip History of the Altyn Tagh Fault

    NASA Astrophysics Data System (ADS)

    Shumaker, L.; Lippert, P. C.; Darby, B. J.; Ritts, B. D.; Coe, R. S.

    2010-12-01

    Piercing point studies demonstrate two distinct phases of slip on the Altyn Tagh Fault (ATF) following its initiation ~30 Ma. An initial rapid, large magnitude slip phase transitioned to the present slower, smaller slip phase during the Middle Miocene. Piercing point studies near the Modern NE tip of the ATF, the Neogene shortening and cooling record of the Qilian Shan, and the slip history of faults within the Qilian Shan suggest that the >310 km of pre-Middle Miocene ATF displacement was transferred northeast into the Alxa block. Indeed, recent field mapping revealed numerous NE-SW trending sinistral strike-slip faults showing large Cretaceous and minimal Neogene offsets. These structures may have been kinematically linked to the ATF. We test this proposed linkage with new structural and paleomagnetic data from the Hei Shan, the Alxa range closest to the Modern terminus of the ATF. An ENE-WSW trending sub-vertical fault, which we call the Hei Shan Fault (HSF), can be traced WSW toward the ATF and ESE toward sinistral structures in the Heli and Beida Shan. Paleozoic and Mesozoic strata show left-lateral offset along the HSF, supported by slickenlines and S-C fabrics in the ~30m-thick gouge zone. At least nine fault-bound blocks of Paleozoic basement define a strike-slip duplex along the eastern HSF. Several NW-SE trending thrusts and folds that involve basement and Cretaceous strata occur north and south of the HSF. In the western Hei Shan, minor NE-SW trending strike-slip faults display small (tens of meters) dextral displacements. All of these structures appear to be kinematically linked to the HSF. Upper Neogene alluvial gravels show only minor offset and tilting by the HSF and these secondary structures. Paleomagnetic directions from more than 230 samples from 36 new Hei Shan sampling sites demonstrate that significant vertical axis rotations (relative to a stable Eurasia reference frame) occur only within the fault zones and that block rotations adjacent to

  8. Texture development and slip systems in bridgmanite and bridgmanite + ferropericlase aggregates

    NASA Astrophysics Data System (ADS)

    Miyagi, L.; Wenk, H.-R.

    2016-09-01

    Bridgmanite (Mg,Fe)SiO3 and ferropericlase (Mg,Fe)O are the most abundant phases in the lower mantle and localized regions of the D″ layer just above the core mantle boundary. Seismic anisotropy is observed near subduction zones at the top of the lower mantle and in the D″ region. One source of anisotropy is dislocation glide and associated texture (crystallographic preferred orientation) development. Thus, in order to interpret seismic anisotropy, it is important to understand texture development and slip system activities in bridgmanite and bridgmanite + ferropericlase aggregates. Here we report on in situ texture development in bridgmanite and bridgmanite + ferropericlase aggregates deformed in the diamond anvil cell up to 61 GPa. When bridgmanite is synthesized from enstatite, it exhibits a strong (4.2 m.r.d.) 001 transformation texture due to a structural relationship with the precursor enstatite phase. When bridgmanite + ferropericlase are synthesized from olivine or ringwoodite, bridgmanite exhibits a relatively weak 100 transformation texture (1.2 and 1.6 m.r.d., respectively). This is likely due to minimization of elastic strain energy as a result of Young's modulus anisotropy. In bridgmanite, 001 deformation textures are observed at pressures <55 GPa. The 001 texture is likely due to slip on (001) planes in the [100], [010] and < {110} rangle directions. Stress relaxation by laser annealing to 1500-1600 K does not result in a change in this texture type. However, at pressures >55 GPa a change in texture to a 100 maximum is observed, consistent with slip on the (100) plane. Ferropericlase, when deformed with bridgmanite, does not develop a coherent texture. This is likely due to strain heterogeneity within the softer ferropericlase grains. Thus, it is plausible that ferropericlase is not a significant source of anisotropy in the lower mantle.

  9. Process for slip casting textured tubular structures

    SciTech Connect

    Steinlage, Greg A.; Trumble, Kevin P.; Bowman, Keith J.

    2002-01-01

    A process for centrifugal slip casting a textured hollow tube. A slip made up of a carrier fluid and a suspended powder is introduced into a porous mold which is rotated at a speed sufficient to create a centrifugal force that forces the slip radially outward toward the inner surface of the mold. The suspended powder, which is formed of particles having large dimensional aspect ratios such as particles of superconductive BSCCO, settles in a textured fashion radially outward toward the mold surface. The carrier fluid of the slip passes by capillary action radially outward around the settled particles and into the absorbent mold. A layer of mold release material is preferably centrifugally slip cast to cover the mold inner surface prior to the introduction of the BSCCO slip, and the mold release layer facilitates removal of the BSCCO greenbody from the mold without fracturing.

  10. Estimating Fault Slip Rates and Deformation at Complex Strike-Slip Plate Boundaries

    NASA Astrophysics Data System (ADS)

    Thatcher, Wayne; Murray-Moraleda, Jessica

    2010-05-01

    Modeling GPS velocity fields in seismically active regions worldwide indicates deformation can be efficiently and usefully described as relative motions among elastic, fault-bounded crustal blocks. These models are providing hundreds of new decadal fault slip rate estimates that can be compared with the (much smaller) independent Holocene (<10 ka) to late Quaternary (<125 ka) rates obtained by geological methods. Updated comparisons show general agreement but a subset of apparently significant outliers. Some of these outliers have been discussed previously and attributed either to a temporal change in slip rate or systematic error in one of the estimates. Here we focus particularly on recent GPS and geologic results from southern California and discuss criteria for assessing the differing rates. In southern California (and elsewhere), subjective choices of block geometry are unavoidable and introduce significant uncertainties in model formulation and in the resultant GPS fault slip rate estimates. To facilitate comparison between GPS and geologic results in southern California we use the SCEC Community Fault Model (CFM) and geologic slip rates tabulated in the 2008 Uniform California Earthquake Rupture Forecast (UCERF2) report as starting points for identifying the most important faults and specifying the block geometry. We then apply this geometry in an inversion of the SCEC Crustal Motion Model (CMM4) GPS velocity field to estimate block motions and intra-block fault slip rates and compare our results with previous work. Here we use 4 criteria to evaluate GPS/geologic slip rate differences. First: Is there even-handed evaluation of random and systematic errors? ‘Random error' is sometimes subjectively estimated and its statistical properties are unknown or idealized. Differences between ~equally likely block models introduces a systematic error into GPS rate estimates that is difficult to assess and seldom discussed. Difficulties in constraining the true

  11. Reduced Aftershock Productivity in Regions with Known Slow Slip Events

    NASA Astrophysics Data System (ADS)

    Collins, G.; Mina, A.; Richardson, E.; McGuire, J. J.

    2013-12-01

    Reduced aftershock activity has been observed in areas with high rates of aseismic slip, such as transform fault zones and some subduction zones. Fault conditions that could explain both of these observations include a low effective normal stress regime and/or a high temperature, semi-brittle/plastic rheology. To further investigate the possible connection between areas of aseismic slip and reduced aftershock productivity, we compared the mainshock-aftershock sequences in subduction zones where aseismic slip transients have been observed to those of adjacent (along-strike) regions where no slow slip events have been detected. Using the Advanced National Seismic System (ANSS) catalog, we counted aftershocks that occurred within 100 km and 14 days of 112 M>=5.0 slab earthquake mainshocks from January 1980 - July 2013, including 90 since January 2000, inside observed regions of detected slow slip: south central Alaska, Cascadia, the Nicoya Peninsula (Costa Rica), Guerrero (Mexico), and the North Island of New Zealand. We also compiled aftershock counts from 97 mainshocks from areas adjacent to each of these regions using the same criteria and over the same time interval. Preliminary analysis of these two datasets shows an aftershock triggering exponent (alpha in the ETAS model) of approximately 0.8, consistent with previous studies of aftershocks in a variety of tectonic settings. Aftershock productivity for both datasets is less than that of continental earthquakes. Contrasting the two datasets, aftershock productivity inside slow slip regions is lower than in adjacent areas along the same subduction zone and is comparable to that of mid-ocean ridge transform faults.

  12. Shared and Task-Specific Muscle Synergies during Normal Walking and Slipping

    PubMed Central

    Nazifi, Mohammad Moein; Yoon, Han Ul; Beschorner, Kurt; Hur, Pilwon

    2017-01-01

    Falling accidents are costly due to their prevalence in the workplace. Slipping has been known to be the main cause of falling. Understanding the motor response used to regain balance after slipping is crucial to developing intervention strategies for effective recovery. Interestingly, studies on spinalized animals and studies on animals subjected to electrical microstimulation have provided major evidence that the Central Nervous System (CNS) uses motor primitives, such as muscle synergies, to control motor tasks. Muscle synergies are thought to be a critical mechanism used by the CNS to control complex motor tasks by reducing the dimensional complexity of the system. Even though synergies have demonstrated potential for indicating how the body responds to balance perturbations by accounting for majority of the data set's variability, this concept has not been applied to slipping. To address this gap, data from 11 healthy young adults were collected and analyzed during both unperturbed walking and slipping. Applying an iterative non-negative matrix decomposition technique, four muscle synergies and the corresponding time-series activation coefficients were extracted. The synergies and the activation coefficients were then compared between baseline walking and slipping to determine shared vs. task-specific synergies. Correlation analyses found that among four synergies, two synergies were shared between normal walking and slipping. However, the other two synergies were task-specific. Both limbs were contributing to each of the four synergies, suggesting substantial inter-limb coordination during gait and slip. These findings stay consistent with previous unilateral studies that reported similar synergies between unperturbed and perturbed walking. Activation coefficients corresponding to the two shared synergies were similar between normal walking and slipping for the first 200 ms after heel contact and differed later in stance, suggesting the activation of muscle

  13. Pressure-Induced Slip-System Transition in Forsterite: Single-Crystal Rheological Properties at Mantle Pressure and Temperature

    SciTech Connect

    Raterron,P.; Chen, J.; Li, L.; Weidner, D.; Cordier, P.

    2007-01-01

    Deformation experiments were carried out in a Deformation-DIA high-pressure apparatus (D-DIA) on oriented Mg2SiO4 olivine (Fo100) single crystals, at pressure (P) ranging from 2.1 to 7.5 GPa, in the temperature (T) range 1373-1677 K, and in dry conditions. These experiments were designed to investigate the effect of pressure on olivine dislocation slip-system activities, responsible for the lattice-preferred orientations observed in the upper mantle. Two compression directions were tested, promoting either [100] slip alone or [001] slip alone in (010) crystallographic plane. Constant applied stress ({sigma}) and specimen strain rates (Formula) were monitored in situ using time-resolved X-ray synchrotron diffraction and radiography, respectively. Transmission electron microscopy (TEM) investigation of the run products reveals that dislocation creep assisted by dislocation climb and cross slip was responsible for sample deformation. A slip transition with increasing pressure, from a dominant [100]-slip to a dominant [001]-slip, is documented. Extrapolation of the obtained rheological laws to upper-mantle P, T, and {sigma} conditions, suggests that [001]-slip activity becomes comparable to [100]-slip activity in the deep upper mantle, while [001] slip is mostly dominant in subduction zones. These results provide alternative explanations for the seismic anisotropy attenuation observed in the upper mantle, and for the 'puzzling' seismic-anisotropy anomalies commonly observed in subduction zones.

  14. Active Phase and Amplitude Fluctuations of Flagellar Beating

    NASA Astrophysics Data System (ADS)

    Ma, Rui; Klindt, Gary S.; Riedel-Kruse, Ingmar H.; Jülicher, Frank; Friedrich, Benjamin M.

    2014-07-01

    The eukaryotic flagellum beats periodically, driven by the oscillatory dynamics of molecular motors, to propel cells and pump fluids. Small but perceivable fluctuations in the beat of individual flagella have physiological implications for synchronization in collections of flagella as well as for hydrodynamic interactions between flagellated swimmers. Here, we characterize phase and amplitude fluctuations of flagellar bending waves using shape mode analysis and limit-cycle reconstruction. We report a quality factor of flagellar oscillations Q =38.0±16.7 (mean±s.e.). Our analysis shows that flagellar fluctuations are dominantly of active origin. Using a minimal model of collective motor oscillations, we demonstrate how the stochastic dynamics of individual motors can give rise to active small-number fluctuations in motor-cytoskeleton systems.

  15. Development of a liquid metal slip ring

    NASA Technical Reports Server (NTRS)

    Weinberger, S. M.

    1972-01-01

    A liquid metal slip ring/solar orientation mechanism was designed and a model tested. This was a follow-up of previous efforts for the development of a gallium liquid metal slip ring in which the major problem was the formation and ejection of debris. A number of slip ring design approaches were studied. The probe design concept was fully implemented with detail drawings and a model was successfully tested for dielectric strength, shock vibration, acceleration and operation. The conclusions are that a gallium liquid metal slip ring/solar orientation mechanism is feasible and that the problem of debris formation and ejection has been successfully solved.

  16. Longitudinal wheel slip during ABS braking

    NASA Astrophysics Data System (ADS)

    Hartikainen, Lassi; Petry, Frank; Westermann, Stephan

    2015-02-01

    Anti-lock braking system (ABS) braking tests with two subcompact passenger cars were performed on dry and wet asphalt, as well as on snow and ice surfaces. The operating conditions of the tyres in terms of wheel slip were evaluated using histograms of the wheel slip data. The results showed different average slip levels for different road surfaces. It was also found that changes in the tyre tread stiffness affected the slip operating range through a modification of the slip value at which the maximum longitudinal force is achieved. Variation of the tyre footprint length through modifications in the inflation pressure affected the slip operating range as well. Differences in the slip distribution between vehicles with different brake controllers were also observed. The changes in slip operating range in turn modified the relative local sliding speeds between the tyre and the road. The results highlight the importance of the ABS controller's ability to adapt to changing slip-force characteristics of tyres and provide estimates of the magnitude of the effects of different tyre and road operating conditions.

  17. Bulk metallic glasses deform via slip avalanches.

    PubMed

    Antonaglia, James; Wright, Wendelin J; Gu, Xiaojun; Byer, Rachel R; Hufnagel, Todd C; LeBlanc, Michael; Uhl, Jonathan T; Dahmen, Karin A

    2014-04-18

    For the first time in metallic glasses, we extract both the exponents and scaling functions that describe the nature, statistics, and dynamics of slip events during slow deformation, according to a simple mean field model. We model the slips as avalanches of rearrangements of atoms in coupled shear transformation zones (STZs). Using high temporal resolution measurements, we find the predicted, different statistics and dynamics for small and large slips thereby excluding self-organized criticality. The agreement between model and data across numerous independent measures provides evidence for slip avalanches of STZs as the elementary mechanism of inhomogeneous deformation in metallic glasses.

  18. Bulk Metallic Glasses Deform via Slip Avalanches

    NASA Astrophysics Data System (ADS)

    Antonaglia, James; Wright, Wendelin J.; Gu, Xiaojun; Byer, Rachel R.; Hufnagel, Todd C.; LeBlanc, Michael; Uhl, Jonathan T.; Dahmen, Karin A.

    2014-04-01

    For the first time in metallic glasses, we extract both the exponents and scaling functions that describe the nature, statistics, and dynamics of slip events during slow deformation, according to a simple mean field model. We model the slips as avalanches of rearrangements of atoms in coupled shear transformation zones (STZs). Using high temporal resolution measurements, we find the predicted, different statistics and dynamics for small and large slips thereby excluding self-organized criticality. The agreement between model and data across numerous independent measures provides evidence for slip avalanches of STZs as the elementary mechanism of inhomogeneous deformation in metallic glasses.

  19. Observation of slip flow in thermophoresis.

    PubMed

    Weinert, Franz M; Braun, Dieter

    2008-10-17

    Two differing theories aim to describe fluidic thermophoresis, the movement of particles along a temperature gradient. While thermodynamic approaches rely on local equilibrium, hydrodynamic descriptions assume a quasi-slip-flow boundary condition at the particle's surface. Evidence for slip flow is presented for the case of thermal gradients exceeding (aS_(T)(-1) with particle radius a and Soret coefficient S_(T). Thermophoretic slip flow at spheres near a surface attracts or repels tracer particles perpendicular to the thermal gradient. Moreover, particles mutually attract and form colloidal crystals. Fluid dynamic slip explains the latter quantitatively.

  20. Feedback-induced phase transitions in active heterogeneous conductors.

    PubMed

    Ocko, Samuel A; Mahadevan, L

    2015-04-03

    An active conducting medium is one where the resistance (conductance) of the medium is modified by the current (flow) and in turn modifies the flow, so that the classical linear laws relating current and resistance, e.g., Ohm's law or Darcy's law, are modified over time as the system itself evolves. We consider a minimal model for this feedback coupling in terms of two parameters that characterize the way in which addition or removal of matter follows a simple local (or nonlocal) feedback rule corresponding to either flow-seeking or flow-avoiding behavior. Using numerical simulations and a continuum mean field theory, we show that flow-avoiding feedback causes an initially uniform system to become strongly heterogeneous via a tunneling (channel-building) phase separation; flow-seeking feedback leads to an immuring (wall-building) phase separation. Our results provide a qualitative explanation for the patterning of active conducting media in natural systems, while suggesting ways to realize complex architectures using simple rules in engineered systems.

  1. Slip resistance of non-slip socks--an accelerometer-based approach.

    PubMed

    Hübscher, Markus; Thiel, Christian; Schmidt, Jens; Bach, Matthias; Banzer, Winfried; Vogt, Lutz

    2011-04-01

    The present study investigated the relative slip resistance of commercially available non-slip socks during gait. Twenty-four healthy subjects (29.3±10.4 years) participated in the study. Each subject completed 4 different test conditions (barefoot, non-slip socks, conventional socks, backless slippers) in a randomized, balanced order. The slip resistance was estimated by measuring the heel deceleration time using a heel-mounted accelerometer. Repeated measures ANOVA and post hoc paired-sample t-test with Bonferroni correction were used for statistical analysis. Compared to barefoot walking absolute deceleration times [ms] were significantly increased when wearing conventional socks or slippers. No significant differences were observed between the barefoot and non-slip socks conditions. The present study shows that non-slip socks improved slip-resistance during gait when compared to conventional socks and slippers. Future investigations should verify the present findings in hospital populations prone to slip-related falls.

  2. Comparison of GPS and Quaternary slip rates: Insights from a new Quaternary fault database for Central Asia

    NASA Astrophysics Data System (ADS)

    Mohadjer, Solmaz; Ehlers, Todd; Bendick, Rebecca; Mutz, Sebastian

    2016-04-01

    Previous studies related to the kinematics of deformation within the India-Asia collision zone have relied on slip rate data for major active faults to test kinematic models that explain the deformation of the region. The slip rate data, however, are generally disputed for many of the first-order faults in the region (e.g., Altyn Tagh and Karakorum faults). Several studies have also challenged the common assumption that geodetic slip rates are representative of Quaternary slip rates. What has received little attention is the degree to which geodetic slip rates relate to Quaternary slip rates for active faults in the India-Asia collision zone. In this study, we utilize slip rate data from a new Quaternary fault database for Central Asia to determine the overall relationship between Quaternary and GPS-derived slip rates for 18 faults. The preliminary analysis investigating this relationship uses weighted least squares and a re-sampling analysis to test the sensitivity of this relationship to different data point attributes (e.g., faults associated with data points and dating methods used for estimating Quaternary slip rates). The resulting sample subsets of data points yield a maximum possible Pearson correlation coefficient of ~0.6, suggesting moderate correlation between Quaternary and GPS-derived slip rates for some faults (e.g., Kunlun and Longmen Shan faults). Faults with poorly correlated Quaternary and GPS-derived slip rates were identified and dating methods used for the Quaternary slip rates were examined. Results indicate that a poor correlation between Quaternary and GPS-derived slip rates exist for the Karakorum and Chaman faults. Large differences between Quaternary and GPS slip rates for these faults appear to be connected to qualitative dating of landforms used in the estimation of the Quaternary slip rates and errors in the geomorphic and structural reconstruction of offset landforms (e.g., offset terrace riser reconstructions for Altyn Tagh fault

  3. Predicting the probability of slip in gait: methodology and distribution study.

    PubMed

    Gragg, Jared; Yang, James

    2016-01-01

    The likelihood of a slip is related to the available and required friction for a certain activity, here gait. Classical slip and fall analysis presumed that a walking surface was safe if the difference between the mean available and required friction coefficients exceeded a certain threshold. Previous research was dedicated to reformulating the classical slip and fall theory to include the stochastic variation of the available and required friction when predicting the probability of slip in gait. However, when predicting the probability of a slip, previous researchers have either ignored the variation in the required friction or assumed the available and required friction to be normally distributed. Also, there are no published results that actually give the probability of slip for various combinations of required and available frictions. This study proposes a modification to the equation for predicting the probability of slip, reducing the previous equation from a double-integral to a more convenient single-integral form. Also, a simple numerical integration technique is provided to predict the probability of slip in gait: the trapezoidal method. The effect of the random variable distributions on the probability of slip is also studied. It is shown that both the required and available friction distributions cannot automatically be assumed as being normally distributed. The proposed methods allow for any combination of distributions for the available and required friction, and numerical results are compared to analytical solutions for an error analysis. The trapezoidal method is shown to be highly accurate and efficient. The probability of slip is also shown to be sensitive to the input distributions of the required and available friction. Lastly, a critical value for the probability of slip is proposed based on the number of steps taken by an average person in a single day.

  4. Airborne Antenna System for Minimum-Cycle-Slip GPS Reception

    NASA Technical Reports Server (NTRS)

    Wright, C. Wayne

    2009-01-01

    A system that includes a Global Positioning System (GPS) antenna and associated apparatus for keeping the antenna aimed upward has been developed for use aboard a remote-sensing-survey airplane. The purpose served by the system is to enable minimum- cycle-slip reception of GPS signals used in precise computation of the trajectory of the airplane, without having to restrict the airplane to maneuvers that increase the flight time needed to perform a survey. Cycle slip signifies loss of continuous track of the phase of a signal. Minimum-cycle-slip reception is desirable because maintaining constant track of the phase of the carrier signal from each available GPS satellite is necessary for surveying to centimeter or subcentimeter precision. Even a loss of signal for as short a time as a nanosecond can cause cycle slip. Cycle slips degrade the quality and precision of survey data acquired during a flight. The two principal causes of cycle slip are weakness of signals and multipath propagation. Heretofore, it has been standard practice to mount a GPS antenna rigidly on top of an airplane, and the radiation pattern of the antenna is typically hemispherical, so that all GPS satellites above the horizon are viewed by the antenna during level flight. When the airplane must be banked for a turn or other maneuver, the reception hemisphere becomes correspondingly tilted; hence, the antenna no longer views satellites that may still be above the Earth horizon but are now below the equatorial plane of the tilted reception hemisphere. Moreover, part of the reception hemisphere (typically, on the inside of a turn) becomes pointed toward ground, with a consequent increase in received noise and, therefore, degradation of GPS measurements. To minimize the likelihood of loss of signal and cycle slip, bank angles of remote-sensing survey airplanes have generally been limited to 10 or less, resulting in skidding or slipping uncoordinated turns. An airplane must be banked in order to make

  5. Multiple slip in copper single crystals deformed in compression under uniaxial stress

    SciTech Connect

    Florando, J N; LeBlanc, M M; Lassila, D H

    2006-11-30

    Uniaxial compression experiments on copper single crystals, oriented to maximize the shear for one slip system, show some unexpected results. In addition to the expected activity on the primary slip system, the results show appreciable activity perpendicular to the primary system. The magnitude of the activity orthogonal to the primary varies from being equal to the primary for the as-fabricated samples to 1/5 of the primary in the samples annealed after fabrication.

  6. Slipping on pedestrian surfaces: methods for measuring and evaluating the slip resistance.

    PubMed

    Wetzel, Christoph; Windhövel, Ulrich; Mewes, Detlef; Ceylan, Orhan

    2015-01-01

    Tripping, slipping and falling accidents are among the types of accident with a high incidence. This article describes the requirements concerning slip resistance, as well as the state of the art of slip resistance measurement standards in the European Community and the USA. The article also describes how risk assessment can be performed in the field.

  7. Study of seismic activity during the ascending and descending phases of solar activity

    NASA Astrophysics Data System (ADS)

    Sukma, Indriani; Abidin, Zamri Zainal

    2016-12-01

    The study of the solar cycle and geomagnetic index associated with the seismic activity from the year 1901 to the end of 2015 has been done for an area that covers the majority of China and its bordering countries. Data of sunspot number, solar wind speed, daily storm time index and earthquake number are collected from NOAA, NASA, WDC, OMNI and USGS databases and websites. The earthquakes are classified into small (M < 5) and large (M ≥ 5) magnitudes (in Richter scale). We investigated the variation of earthquake activities with the geomagnetic storm index due to the solar wind. We focused on their variation in the ascending and descending phases of solar cycle. From our study, we conclude that there is a correlation between the phases' geomagnetic index and solar wind speed. We have also suggested that there is a certain degree of correlation between solar activity and seismicity in these phases. For every solar cycle, we find that there is a trend for earthquakes to occur in greater numbers during the descending phase. This can be explained by the increment in the solar wind speed and geomagnetic storm index during this phase.

  8. Seafloor observations indicate spatial separation of coseismic and postseismic slips in the 2011 Tohoku earthquake

    NASA Astrophysics Data System (ADS)

    Iinuma, Takeshi; Hino, Ryota; Uchida, Naoki; Nakamura, Wataru; Kido, Motoyuki; Osada, Yukihito; Miura, Satoshi

    2016-11-01

    Large interplate earthquakes are often followed by postseismic slip that is considered to occur in areas surrounding the coseismic ruptures. Such spatial separation is expected from the difference in frictional and material properties in and around the faults. However, even though the 2011 Tohoku Earthquake ruptured a vast area on the plate interface, the estimation of high-resolution slip is usually difficult because of the lack of seafloor geodetic data. Here using the seafloor and terrestrial geodetic data, we investigated the postseismic slip to examine whether it was spatially separated with the coseismic slip by applying a comprehensive finite-element method model to subtract the viscoelastic components from the observed postseismic displacements. The high-resolution co- and postseismic slip distributions clarified the spatial separation, which also agreed with the activities of interplate and repeating earthquakes. These findings suggest that the conventional frictional property model is valid for the source region of gigantic earthquakes.

  9. Seafloor observations indicate spatial separation of coseismic and postseismic slips in the 2011 Tohoku earthquake

    PubMed Central

    Iinuma, Takeshi; Hino, Ryota; Uchida, Naoki; Nakamura, Wataru; Kido, Motoyuki; Osada, Yukihito; Miura, Satoshi

    2016-01-01

    Large interplate earthquakes are often followed by postseismic slip that is considered to occur in areas surrounding the coseismic ruptures. Such spatial separation is expected from the difference in frictional and material properties in and around the faults. However, even though the 2011 Tohoku Earthquake ruptured a vast area on the plate interface, the estimation of high-resolution slip is usually difficult because of the lack of seafloor geodetic data. Here using the seafloor and terrestrial geodetic data, we investigated the postseismic slip to examine whether it was spatially separated with the coseismic slip by applying a comprehensive finite-element method model to subtract the viscoelastic components from the observed postseismic displacements. The high-resolution co- and postseismic slip distributions clarified the spatial separation, which also agreed with the activities of interplate and repeating earthquakes. These findings suggest that the conventional frictional property model is valid for the source region of gigantic earthquakes. PMID:27853138

  10. Seafloor observations indicate spatial separation of coseismic and postseismic slips in the 2011 Tohoku earthquake.

    PubMed

    Iinuma, Takeshi; Hino, Ryota; Uchida, Naoki; Nakamura, Wataru; Kido, Motoyuki; Osada, Yukihito; Miura, Satoshi

    2016-11-17

    Large interplate earthquakes are often followed by postseismic slip that is considered to occur in areas surrounding the coseismic ruptures. Such spatial separation is expected from the difference in frictional and material properties in and around the faults. However, even though the 2011 Tohoku Earthquake ruptured a vast area on the plate interface, the estimation of high-resolution slip is usually difficult because of the lack of seafloor geodetic data. Here using the seafloor and terrestrial geodetic data, we investigated the postseismic slip to examine whether it was spatially separated with the coseismic slip by applying a comprehensive finite-element method model to subtract the viscoelastic components from the observed postseismic displacements. The high-resolution co- and postseismic slip distributions clarified the spatial separation, which also agreed with the activities of interplate and repeating earthquakes. These findings suggest that the conventional frictional property model is valid for the source region of gigantic earthquakes.

  11. Mechanical properties and determination of slip systems of the B2 YZn intermetallic compound

    SciTech Connect

    Cao, G. H.; Becker, A. T.; Wu, D.; Chumbley, L. S.; Lograsso, T. A.; Russell, A. M.; Gschneidner Jr., K. A.

    2010-04-30

    Single crystal specimens of YZn (B2) were tested in tension at room temperature. Specimens with a [1 0 1] tensile axis orientation exhibited {r_brace}0 1 1{l_brace} <100> primary slip and an ultimate tensile strength of 365MPa at 3.7% elongation. Specimens with [0 0 1] and [1 1 1] tensile axis orientations showed no slip lines and fractured at a stress of 180MPa at 3.3% and 130MPa at 2.9% elongation, respectively. Transmission electron microscopy (TEM) examination of the Burger's vector of dislocations in tensile tested specimens revealed <1 0 0>-type dislocations. TEM analysis suggested that a secondary slip system, {l_brace}0 0 1{r_brace}<1 0 0>, may be active. Banded features with a {l_brace}0 2 1{r_brace} orientation were observed in deformed YZn; these may be slip traces produced by the cross-slip of <1 0 0> dislocations. Acting together, {l_brace}0 1 1{r_brace} <1 0 0> and {l_brace}0 0 1{r_brace} <1 0 0> slip provide only three independent slip systems, and no extra independent systems are provided by the cross-slip. This finding is consistent with the low ductility of YZn.

  12. Vertical-axis rotations and deformation along the active strike-slip El Tigre Fault (Precordillera of San Juan, Argentina) assessed through palaeomagnetism and anisotropy of magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Fazzito, Sabrina Y.; Rapalini, Augusto E.; Cortés, José M.; Terrizzano, Carla M.

    2017-03-01

    Palaeomagnetic data from poorly consolidated to non-consolidated late Cenozoic sediments along the central segment of the active El Tigre Fault (Central-Western Precordillera of the San Juan Province, Argentina) demonstrate broad cumulative deformation up to 450 m from the fault trace and reveal clockwise and anticlockwise vertical-axis rotations of variable magnitude. This deformation has affected in different amounts Miocene to late Pleistocene samples and indicates a complex kinematic pattern. Several inherited linear structures in the shear zone that are oblique to the El Tigre Fault may have acted as block boundary faults. Displacement along these faults may have resulted in a complex pattern of rotations. The maximum magnitude of rotation is a function of the age of the sediments sampled, with largest values corresponding to middle Miocene-lower Pliocene deposits and minimum values obtained from late Pleistocene deposits. The kinematic study is complemented by low-field anisotropy of magnetic susceptibility data to show that the local strain regime suggests a N-S stretching direction, subparallel to the strike of the main fault.

  13. Vertical-axis rotations and deformation along the active strike-slip El Tigre Fault (Precordillera of San Juan, Argentina) assessed through palaeomagnetism and anisotropy of magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Fazzito, Sabrina Y.; Rapalini, Augusto E.; Cortés, José M.; Terrizzano, Carla M.

    2016-05-01

    Palaeomagnetic data from poorly consolidated to non-consolidated late Cenozoic sediments along the central segment of the active El Tigre Fault (Central-Western Precordillera of the San Juan Province, Argentina) demonstrate broad cumulative deformation up to ~450 m from the fault trace and reveal clockwise and anticlockwise vertical-axis rotations of variable magnitude. This deformation has affected in different amounts Miocene to late Pleistocene samples and indicates a complex kinematic pattern. Several inherited linear structures in the shear zone that are oblique to the El Tigre Fault may have acted as block boundary faults. Displacement along these faults may have resulted in a complex pattern of rotations. The maximum magnitude of rotation is a function of the age of the sediments sampled, with largest values corresponding to middle Miocene-lower Pliocene deposits and minimum values obtained from late Pleistocene deposits. The kinematic study is complemented by low-field anisotropy of magnetic susceptibility data to show that the local strain regime suggests a N-S stretching direction, subparallel to the strike of the main fault.

  14. Lessons learned with the Active Phasing Experiment: comparison of four optical phasing sensors on a segmented Very Large Telescope

    NASA Astrophysics Data System (ADS)

    Gonte, F.; Surdej, I.

    The adaptive optics capabilities are strongly limited by the quality of the phasing of the primary mirror of the extremely large telescope. Up to date, the Keck telescopes are the only segmented telescope phased with a quality enabling the application of adaptive optics. The Active Phasing Experiment has been installed at the Namyth focus of the Very Large Telescope Melipal during the last 6 months. Its purpose is to understand and compare different technological concepts for an optical phasing sensor dedicated to the European Extremely Large Telescope. The pupil of the telescope is segmented in 61 hexagonal segments by projecting it on an Active Segmented Mirror. The ASM is controlled by a dual wavenlength interferometer made by Fogale Nanotech with a nanometric precision. The segmented pupil is distributed in parallel to four optical phasing sensors. They are a pyramid sensor, a curvature sensor, a phase filtering sensor and a ShackHartmann sensor. They have been developed respectively by Istituto Nazionale di Astrofisica in Florenze, Instituto Astrofisica Canarias in Tenerife, Laboratoire d'Astrophysique de Marseille and ESO. The global behaviour of the optical phasing sensors will be described and preliminary results of the Active Phasing Experiments obtained on sky will be explained. The extrapolation of the results to the EELT and the potential consequences for the adaptive optics will be given. The Active Phasing Experiment has been financed by the European Union and the European Southern Observatory via the Sixth European Union Framework Program for Research and Technological Development under the contract number 011863.

  15. Inverse Slip Accompanying Twinning and Detwinning during Cyclic Loading of Magnesium Single Crystal

    DOE PAGES

    Yu, Qin; Wang, Jian; Jiang, Yanyao

    2013-01-01

    In situ , observation of twinning and detwinning in magnesium single crystals during tension-compression cyclic loading was made using optical microscopy. A quantitative analysis of plastic strain indicates that twinning and detwinning experience two stages, low and high work hardening de-twinning, and pure re-twinning and fresh twinning combined with retwinning. Slip is always activated. For the first time, inverse slip accompanying with pure retwinning and high work hardening detwinning was experimentally identified, which provides insights in better understanding of the activity of twining, detwinning, and slips.

  16. Slip versus Friction : Modifying the Navier condition

    NASA Astrophysics Data System (ADS)

    Kotsalis, Evangelos; Walther, Jens; Koumoutsakos, Petros

    2006-03-01

    The modeling of fluid-solid interfaces remains one of the key challenges in fluid mechanics. The prevailing model, attributed to Navier, defines the fluid ``slip'' velocity as proportional to the wall shear and a parameter defined as the slip length. Several works have in turn proposed models for this slip length but no universal model for the slip velocity has been accepted. We present results from large scale molecular dynamics simulations of canonical flow problems, indicating, that the inadequacy of this classic model, stems from not properly accounting for the pressure field. We propose and validate a new model, based on the fundamental observation that the finite ``slip'' velocity is a result of an imbalance between fluid and solid intermolecular forces. An excess force on the fluid elements will lead to their acceleration which in turn may result in a slip velocity at the interface. We formulate the slip velocity in terms of fluid-solid friction Ff and propose a generalized boundary condition: Ff= Fs+ Fp= λuus+ λpp where p denotes the pressure, and λuand λp the viscous and static friction coefficients, for which universal constants are presented. We demonstrate that the present model can overcome difficulties encountered by the classical slip model in canonical flow configurations.

  17. Environmental study of miniature slip rings

    NASA Technical Reports Server (NTRS)

    Radnik, J. L.

    1967-01-01

    Investigation studied the long term operation of miniature slip ring assembles in high vacuum of space and included the influence of ring, brush, and insulator materials on electrical noise and mechanical wear. Results show that soft metal vapor plating and niobium diselenide miniature slip rings are beneficial.

  18. Jelly Quakes - Characteristics of periodic slip events in an analog model of strike slip seismotectonics using ballistic gelatin.

    NASA Astrophysics Data System (ADS)

    Rudolf, Michael; Rosenau, Matthias; Oncken, Onno

    2016-04-01

    Large lithospheric strike-slip faults, such as the San-Andreas Fault, North-Anatolian Fault, or the Tancheng-Lujiang Faultzone, are major sources of seismic hazard. The interplay of complex 3D-geometry and displacement style along the fault, coupled with a varying rheological layering makes it very difficult to model these faults on all relevant timescales. Here we present a novel experimental approach to model intra- and interplate strike-slip faults using a physical/ analog model. We model earthquakes as a stick-slip process, following a rate-and-state frictional law, with glass beads as granular material within a molded fault zone. Crustal elasticity is introduced by using ballistic gelatin (30 w%, pig skin) as analog material. Furthermore, the low-strength and viscous deep crust below 15 km depth, is modeled using a viscoelastic silicone oil (PDMS-G30M). The layered model crust floats on sugar syrup and is compressed in pure shear vice configuration. We monitor the compressive force along with surface kinematics from optical image correlation. The fault is oriented at 45° to the compression direction imposing ideal strike-slip kinematics onto it. After an initial loading phase the model shows periodic slip events occurring alongside with creep on the fault. Using digital image correlation, surface displacement maps are obtained which are similar to those of natural earthquakes. Coseismic displacement along strike is showing a similar bell-shaped distribution as for natural faults. Furthermore, the recurrence intervals and stress drops are scalable to the natural prototype. The modeling results are combined with numerical rate-and-state models using physical parameters from the experiment. This enables us to explore a wide range of parameters and to draw connections between the parameters that control the behavior of seismic and aseismic fault systems.

  19. APE: the Active Phasing Experiment to test new control system and phasing technology for a European Extremely Large Optical Telescope

    NASA Astrophysics Data System (ADS)

    Gonte, F.; Yaitskova, N.; Derie, F.; Constanza, A.; Brast, R.; Buzzoni, B.; Delabre, B.; Dierickx, P.; Dupuy, C.; Esteves, R.; Frank, C.; Guisard, S.; Karban, R.; Koenig, E.; Kolb, J.; Nylund, M.; Noethe, L.; Surdej, I.; Courteville, A.; Wilhelm, R.; Montoya, L.; Reyes, M.; Esposito, S.; Pinna, E.; Dohlen, K.; Ferrari, M.; Langlois, M.

    2005-08-01

    The future European Extremely Large Telescope will be composed of one or two giant segmented mirrors (up to 100 m of diameter) and of several large monolithic mirrors (up to 8 m in diameter). To limit the aberrations due to misalignments and defective surface quality it is necessary to have a proper active optics system. This active optics system must include a phasing system to limit the degradation of the PSF due to misphasing of the segmented mirrors. We will present the lastest design and development of the Active Phasing Experiment that will be tested in laboratory and on-sky connected to a VLT at Paranal in Chile. It includes an active segmented mirror, a static piston plate to simulate a secondary segmented mirror and of four phasing wavefront sensors to measure the piston, tip and tilt of the segments and the aberrations of the VLT. The four phasing sensors are the Diffraction Image Phase Sensing Instrument developed by Instituto de Astrofisica de Canarias, the Pyramid Phasing Sensor developed by Arcetri Astrophysical Observatory, the Shack-Hartmann Phasing Sensor developed by the European Southern Observatory and the Zernike Unit for Segment phasing developed by Laboratoire d'Astrophysique de Marseille. A reference measurement of the segmented mirror is made by an internal metrology developed by Fogale Nanotech. The control system of Active Phasing Experiment will perform the phasing of the segments, the guiding of the VLT and the active optics of the VLT. These activities are included in the Framework Programme 6 of the European Union.

  20. The role of water in slip casting

    NASA Technical Reports Server (NTRS)

    Mccauley, R. A.; Phelps, G. W.

    1984-01-01

    Slips and casting are considered in terms of physical and colloidal chemistry. Casting slips are polydisperse suspensions of lyophobic particles in water, whose degree of coagulation is controlled by interaction of flocculating and deflocculating agents. Slip casting rate and viscosity are functions of temperature. Slip rheology and response to deflocculating agents varies significantly as the kinds and amounts of colloid modifiers change. Water is considered as a raw material. Various concepts of water/clay interactions and structures are discussed. Casting is a de-watering operation in which water moves from slip to cast to mold in response to a potential energy termed moisture stress. Drying is an evaporative process from a free water surface.

  1. [Evaporating Droplet and Imaging Slip Flows

    NASA Technical Reports Server (NTRS)

    Larson, R. G.

    2002-01-01

    In this report, we summarize work on Evaporating Droplet and Imaging Slip Flows. The work was primarily performed by post-doc Hue Hu, and partially by grad students Lei Li and Danish Chopra. The work includes studies on droplet evaporation and its effects on temperature and velocity fields in an evaporating droplet, new 3-D microscopic particle image velocimetry and direct visualization on wall slip in a surfactant solution. With the exception of the slip measurements, these projects were those proposed in the grant application. Instead of slip flow, the original grant proposed imaging electro-osmotic flows. However, shortly after the grant was issued, the PI became aware of work on electro-osmotic flows by the group of Saville in Princeton that was similar to that proposed, and we therefore elected to carry out work on imaging slip flows rather than electro-osmotic flows.

  2. Large-Aperture Membrane Active Phased-Array Antennas

    NASA Technical Reports Server (NTRS)

    Karasik, Boris; McGrath, William; Leduc, Henry

    2009-01-01

    Large-aperture phased-array microwave antennas supported by membranes are being developed for use in spaceborne interferometric synthetic aperture radar systems. There may also be terrestrial uses for such antennas supported on stationary membranes, large balloons, and blimps. These antennas are expected to have areal mass densities of about 2 kg/sq m, satisfying a need for lightweight alternatives to conventional rigid phased-array antennas, which have typical areal mass densities between 8 and 15 kg/sq m. The differences in areal mass densities translate to substantial differences in total mass in contemplated applications involving aperture areas as large as 400 sq m. A membrane phased-array antenna includes patch antenna elements in a repeating pattern. All previously reported membrane antennas were passive antennas; this is the first active membrane antenna that includes transmitting/receiving (T/R) electronic circuits as integral parts. Other integral parts of the antenna include a network of radio-frequency (RF) feed lines (more specifically, a corporate feed network) and of bias and control lines, all in the form of flexible copper strip conductors on flexible polymeric membranes. Each unit cell of a prototype antenna (see Figure 1) contains a patch antenna element and a compact T/R module that is compatible with flexible membrane circuitry. There are two membrane layers separated by a 12.7-mm air gap. Each membrane layer is made from a commercially available flexible circuit material that, as supplied, comprises a 127-micron-thick polyimide dielectric layer clad on both sides with 17.5-micron-thick copper layers. The copper layers are patterned into RF, bias, and control conductors. The T/R module is located on the back side of the ground plane and is RF-coupled to the patch element via a slot. The T/R module is a hybrid multilayer module assembled and packaged independently and attached to the membrane array. At the time of reporting the information for

  3. Multi-phase inversion tectonics related to the Hendijan-Nowrooz-Khafji Fault activity, Zagros Mountains, SW Iran

    NASA Astrophysics Data System (ADS)

    Kazem Shiroodi, Sadjad; Ghafoori, Mohammad; Faghih, Ali; Ghanadian, Mostafa; Lashkaripour, Gholamreza; Hafezi Moghadas, Naser

    2015-11-01

    Distinctive characteristics of inverted structures make them important criteria for the identification of certain structural styles of folded belts. The interpretation of 3D seismic reflection and well data sheds new light on the structural evolution and age of inverted structures associated to the Hendijan-Nowrooz-Khafji Fault within the Persian Gulf Basin and northeastern margin of Afro-Arabian plate. Analysis of thickness variations of growth strata using "T-Z plot" (thickness versus throw plot) method revealed the kinematics of the fault. Obtained results show that the fault has experienced a multi-phase evolutionary history over six different extension and compression deformation events (i.e. positive and negative inversion) between 252.2 and 11.62 Ma. This cyclic activity of the growth fault was resulted from alteration of sedimentary processes during continuous fault slip. The structural development of the study area both during positive and negative inversion geometry styles was ultimately controlled by the relative motion between the Afro-Arabian and Central-Iranian plates.

  4. Frictional slip of a rigid punch on an elastic half-plane

    NASA Astrophysics Data System (ADS)

    Adams, George G.

    2016-07-01

    If a rigid punch is perfectly bonded to an elastic half-plane, the stress state possesses a well-known oscillating singularity. Because the shear and normal stresses are out of phase with each other, the application of a frictional slip model is expected to result in a slip zone at each of the corners. A solution exists in the literature if the punch is subjected to a normal load. It was shown that the extent of the slip zone is an eigenvalue which depends upon Poisson's ratio and the coefficient of friction, but is independent of the magnitude of the applied load. In this investigation, the extent of the slip zone as well as the slip displacement is determined from the perfect bond solution. The analysis is valid if the length of the slip zone is small compared with the punch width. However, the results are shown to be in excellent agreement with the solution in the literature even when the total length of the slip zones is equal to half of the punch width. A solution is then obtained for combined normal and tangential loading. This work, and its extensions, is expected to be applicable in the study of the mechanics of fretting.

  5. Electro-optical hybrid slip ring

    NASA Astrophysics Data System (ADS)

    Hong, En

    2005-11-01

    The slip ring is a rotary electrical interface, collector, swivel or rotary joint. It is a physical system that can perform continuous data transfer and data exchange between a stationary and a rotating structure. A slip ring is generally used to transfer data or power from an unrestrained, continuously rotating electro-mechanical system in real-time, thereby simplifying operations and eliminating damage-prone wires dangling from moving joints. Slip rings are widely used for testing, evaluating, developing and improving various technical equipment and facilities with rotating parts. They are widely used in industry, especially in manufacturing industries employing turbo machinery, as in aviation, shipbuilding, aerospace, defense, and in precise facilities having rotating parts such as medical Computerized Tomography (CT) and MRI scanners and so forth. Therefore, any improvement in slip ring technology can impact large markets. Research and development in this field will have broad prospects long into the future. The goal in developing the current slip ring technology is to improve and increase the reliability, stability, anti-interference, and high data fidelity between rotating and stationary structures. Up to now, there have been numerous approaches used for signal and data transfer utilizing a slip ring such as metal contacts, wires, radio transmission, and even liquid media. However, all suffer from drawbacks such as data transfer speed limitations, reliability, stability, electro-magnetic interference and durability. The purpose of the current research is to break through these basic limitations using an optical solution, thereby improving performance in current slip ring applications. This dissertation introduces a novel Electro-Optical Hybrid Slip Ring technology, which makes "through the air" digital-optical communication between stationary and rotating systems a reality with high data transfer speed, better reliability and low interference susceptibility

  6. Introduction to special section on phenomenology, underlying processes, and hazard implications of aseismic slip and nonvolcanic tremor

    USGS Publications Warehouse

    Gomberg, Joan

    2010-01-01

    This paper introduces the special section on the "phenomenology, underlying processes, and hazard implications of aseismic slip and nonvolcanic tremor" by highlighting key results of the studies published in it. Many of the results indicate that seismic and aseismic manifestations of slow slip reflect transient shear displacements on the plate interface, with the outstanding exception of northern Cascadia where tremor sources have been located on and above the plate interface (differing models of the plate interface there also need to be reconciled). Slow slip phenomena appear to result from propagating deformation that may develop with persistent gaps and segment boundaries. Results add to evidence that when tectonic deformation is relaxed via slow slip, most relaxation occurs aseismically but with seismic signals providing higher-resolution proxies for the aseismic slip. Instead of two distinct slip modes as suggested previously, lines between "fast" and "slow" slip more appropriately may be described as blurry zones. Results reported also show that slow slip sources do not coincide with a specific temperature or metamorphic reaction. Their associations with zones of high conductivity and low shear to compressional wave velocity ratios corroborate source models involving pore fluid pressure buildup and release. These models and spatial anticorrelations between earthquake and tremor activity also corroborate a linkage between slow slip and frictional properties transitional between steady state and stick-slip. Finally, this special section highlights the benefits of global and multidisciplinary studies, which demonstrate that slow phenomena are not confined to beneath the locked zone but exist in many settings.

  7. Slow slip generated by dehydration reaction coupled with slip-induced dilatancy and thermal pressurization

    NASA Astrophysics Data System (ADS)

    Yamashita, Teruo; Schubnel, Alexandre

    2016-10-01

    Sustained slow slip, which is a distinctive feature of slow slip events (SSEs), is investigated theoretically, assuming a fault embedded within a fluid-saturated 1D thermo-poro-elastic medium. The object of study is specifically SSEs occurring at the down-dip edge of seismogenic zone in hot subduction zones, where mineral dehydrations (antigorite, lawsonite, chlorite, and glaucophane) are expected to occur near locations where deep slow slip events are observed. In the modeling, we introduce dehydration reactions, coupled with slip-induced dilatancy and thermal pressurization, and slip evolution is assumed to interact with fluid pressure change through Coulomb's frictional stress. Our calculations show that sustained slow slip events occur when the dehydration reaction is coupled with slip-induced dilatancy. Specifically, slow slip is favored by a low initial stress drop, an initial temperature of the medium close to that of the dehydration reaction equilibrium temperature, a low permeability, and overall negative volume change associated with the reaction (i.e., void space created by the reaction larger than the space occupied by the fluid released). Importantly, if we do not assume slip-induced dilatancy, slip is accelerated with time soon after the slip onset even if the dehydration reaction is assumed. This suggests that slow slip is sustained for a long time at hot subduction zones because dehydration reaction is coupled with slip-induced dilatancy. Such slip-induced dilatancy may occur at the down-dip edge of seismogenic zone at hot subduction zones because of repetitive occurrence of dehydration reaction there.

  8. Using a hybrid Monte Carlo/Genetic Algorithm Slip Estimator to produce high resolution models of paleoearthquakes from geodetic data

    NASA Astrophysics Data System (ADS)

    Lindsay, A.; McCloskey, J.; Nalbant, S. S.; Simao, N.; Murphy, S.; NicBhloscaidh, M.; Steacy, S.

    2013-12-01

    Identifying fault sections where slip deficits have accumulated may provide a means for understanding sequences of large megathrust earthquakes. Stress accumulated during the interseismic period on locked sections of an active fault is stored as potential slip. Where this potential slip remains unreleased during earthquakes, a slip deficit can be said to have accrued. Analysis of the spatial distribution of slip during antecedent events along the fault will show where the locked plate has spent its stored slip and indicate where the potential for large events remains. The location of recent earthquakes and their distribution of slip can be estimated instrumentally. To develop the idea of long-term slip-deficit modelling it is necessary to constrain the size and distribution of slip for pre-instrumental events dating back hundreds of years covering more than one ';seismic cycle'. This requires the exploitation of proxy sources of data. Coral microatolls, growing in the intertidal zone of the outer island arc of the Sunda trench, present the possibility of producing high resolution reconstructions of slip for a number of pre-instrumental earthquakes. Their growth is influenced by tectonic flexing of the continental plate beneath them allows them to act as long term geodetic recorders. However, the sparse distribution of data available using coral geodesy results in a under determined problem with non-unique solutions. Instead of producing one definite model satisfying the observed corals displacements, a Monte Carlo Slip Estimator based on a Genetic Algorithm (MCSE-GA) accelerating the rate of convergence is used to identify a suite of models consistent with the data. Successive iterations of the MCSE-GA sample different displacements at each coral location, from within the spread of associated uncertainties, producing a catalog of models from the full range of possibilities. The suite of best slip distributions are weighted according to their fitness and stacked to

  9. A reconnaissance technique for estimating the slip rates of normal-slip faults in the Great Basin, and application to faults in Nevada, United States of America

    NASA Astrophysics Data System (ADS)

    Depolo, Craig Michael

    The slip rates of 270 normal-slip faults in Nevada are estimated using a new procedure that uses geomorphic features. The slip rate estimation scheme is based on the existence and non-existence of alluvial fault scarps and fault facets, and the height of the maximum basal fault facet. Faults that lack alluvial fault scarps and fault facets are assigned a vertical slip rate of 0.001 m/kyr and a range of 0.0005 to 0.009 m/kyr. Fault with alluvial fault scarps that lack active fault facets are assigned a vertical slip rate of 0.01 m/kyr and a range of 0.003 to 0.07 m/kyr. Faults that have relict facets, that is facets left over from a prior, more active period of the fault, are included in the 0.01 m/kyr group. Faults with active facets have vertical slip rates of ≥0.1 m/kyr. Slip rates for these higher activity faults are estimated using the height of the largest basal fault facet and the relationship,$log\\ S = 0.00267 H - 0.963where S is vertical slip rate in m/kyr and H is maxiμm basal facet height in meters. One standard deviation in this relationship is equivalent to a multiplicative factor of 1.8 in vertical slip rate. In Nevada, the fastest normal-slip faults (geq0.5 m/kyr) are located along the province-boundary with the Sierra Nevada and in Western Nevada, in the Walker Lane belt. In regions that are relatively active within the Great Basin, faults have vertical slip rates of up to 0.5 m/kyr. Less active parts of Nevada are characterized by faults with vertical slip rates of 0.001 and 0.01 m/kyr. Strain rates calculated for subregions indicate the state is deforming at rates comparable to the overall strain rate of the Great Basin or less, and support the division of the state into different subprovinces. An east-west strain-rate transect was made at the Latitude of 40spcirc\\ 30spprimeN, from the Wasatch front in Utah to the western Nevada border. A cumulative horizontal slip vector of 3.9 mm/yr in a N79spcircW direction is estimated if the preferred

  10. Phase-field dithering for active catheter tracking.

    PubMed

    Dumoulin, Charles L; Mallozzi, Richard P; Darrow, Robert D; Schmidt, Ehud J

    2010-05-01

    A strategy to increase the robustness of active MR tracking of microcoils in low signal-to-noise ratio conditions was developed and tested. The method employs dephasing magnetic field gradient pulses that are applied orthogonal to the frequency-encoding gradient pulse used in conventional point-source MR tracking. In subsequent acquisitions, the orthogonal dephasing gradient pulse is rotated while maintaining a perpendicular orientation with respect to the frequency-encoding gradient. The effect of the dephasing gradient is to apply a spatially dependent phase shift in directions perpendicular to the frequency-encoding gradient. Since the desired MR signal for robust MR tracking comes from the small volume of nuclear spins near the small detection coil, the desired signal is not dramatically altered by the dephasing gradient. Undesired MR signals arising from larger volumes (e.g., due to coupling with the body coil or surface coils), on the other hand, are dephased and reduced in signal intensity. Since the approach requires no a priori knowledge of the microcoil orientation with respect to the main magnetic field, data from several orthogonal dephasing gradients are acquired and analyzed in real time. One of several selection algorithms is employed to identify the "best" data for use in the coil localization algorithm. This approach was tested in flow phantoms and animal models, with several multiplexing schemes, including the Hadamard and zero-phase reference approaches. It was found to provide improved MR tracking of untuned microcoils. It also dramatically improved MR tracking robustness in low signal-to-noise-ratio conditions and permitted tracking of microcoils that were inductively coupled to the body coil.

  11. Thenature of marbled Terra Sigillata slips: a combined mu XRF and mu XRD investigation

    SciTech Connect

    Leon, Yoanna; Sciau, Philippe; Goudeau, Philippe; Tamura, Nobumichi; Webb, Sam; Mehta, Apurva

    2009-01-31

    In addition to the red terra sigillata production, the largest Gallic workshop (La Graufesenque) made a special type of terra sigillata, called 'marbled' by the archaeologists. Produced exclusively on this site, this pottery is characterized by a surface finish made of a mixture of yellow and red slips. Because the two slips are intimately mixed, it is difficult to obtain the precise composition of one of the two constituents without contamination by the other. In order to obtain very precise correlation at the appropriate scale between the color aspect and the element and mineralogical phase distributions in the slip, combined electron microprobe, x-ray micro spectroscopies and micro diffraction on cross sectional samples were performed. The aim is to discover how potters were able to produce this unique type of terra sigillata and especially this slip showing an intense yellow color. Results show that the yellow component of marbled sigillata was made from a titanium-rich clay preparation. The color is related to the formation of a pseudobrookite (TiFe2O5) phase in the yellow part of the slip, the main characteristics of that structure being considered nowadays as essential for the fabrication of stable yellow ceramic pigments. Its physical properties such as high refractive indices and a melting point higher than that of most silicates widely used as ceramic colorants are indeed determinant for this kind of applications. Finally, the red parts have a similar composition (elementary and mineralogical) to the one of standard red slip.

  12. Determination of a Holocene Slip Rate on the Puente Hills Blind-Thrust Fault, Los Angeles Basin, California

    NASA Astrophysics Data System (ADS)

    Christofferson, S. A.; Dolan, J. F.; Shaw, J. H.; Pratt, T. L.

    2001-12-01

    Paleoseismologic observations of slip histories and slip rates of faults that break the surface are available at an ever-increasing rate, but the nature of blind-thrust faults has kept paleoearthquake information on these faults out of reach. The complex network of blind thrust faults beneath the Los Angeles metropolitan region includes the Puente Hills thrust fault (PHT), which extends southeastward for >35 km from beneath downtown Los Angeles into northern Orange County. This thrust is active, as demonstrated by the occurrence of the 1987 Mw 6.0 Whittier Narrows earthquake (Shaw and Shearer 1999). Despite our awareness of the hazard posed by this fault, we do not know its current slip rate or its earthquake history prior to the 1987 event. To determine these critical data, we have begun a two-phase project in which we will acquire high-resolution seismic reflection data and excavate paleoseismologic boreholes and trenches across the zone of active folding associated with major earthquakes on the PHT. We have acquired high-resolution seismic reflection profiles along two transects across the zone of active folding. In our eastern most profile, along Trojan Way in La Mirada, the seismic reflection data show that the locus of active folding extends to < 30 m below the surface as a discrete zone < 30-m-wide. Our first borehole at this site, excavated at the top of the prominent fold scarp, revealed a soil with a >1.5- 2-m-thick reddish-brown argillic horizon. This soil indicates that the geomorphic surface atop the scarp is late Pleistocene in age. The 9 m height of the scarp provides a minimum estimate of total structural relief since stabilization of the ground surface. These observations yield an approximate uplift rate on the order of a few tenths of a mm/yr. Assuming simple hangingwall block translation and given the 19° -22° N dip of the PHT beneath the site, we calculate a minimum average late Pleistocene-Recent dip-slip rate of \\sim 0.2 to 1.1 mm/yr. This

  13. Electrophoresis of particles with Navier velocity slip.

    PubMed

    Park, Hung Mok

    2013-03-01

    In the present investigation, it is found that the electrophoretic mobility of hydrophobic particles is affected not only by the zeta potential but also by the velocity slip at the particle surface. From a physicochemical viewpoint, zeta potential represents the surface charge properties and the slip coefficient indicates the hydrophobicity of the particle surface. Thus, it is necessary to separate the contribution of zeta potential from that of slip coefficient to the particle mobility, since zeta potential can be changed by varying the bulk ionic concentration while the slip coefficient can be modified by adjusting surfactant concentration. In the present investigation, a method is devised that allows a simultaneous estimation of zeta potential and slip coefficient of micro and nanoparticles using measurements of electrophoretic mobility at various bulk ionic concentrations. Employing a nonlinear curve-fitting technique and an analytic solution of electrophoresis for a particle with velocity slip, the present technique predicts both zeta potential and slip coefficient simultaneously with reasonable accuracy using the measured values of electrophoretic mobility at various bulk ionic concentrations.

  14. Frictional Melting can Terminate Seismic Slips: Experimental Results of Stick-slips

    NASA Astrophysics Data System (ADS)

    Koizumi, Y.; Otsuki, K.

    2004-12-01

    Whether frictionally melted layers are weak or strong is a question in issue. We conducted stick-slip experiments for granite samples at 150 MPa confining pressure using a tri-axial apparatus. The pre-cut surfaces were mirror finished. In order to detect the exact time of melting, we set sensors inside the pressure vessel; two strain gauges for measurement of axial stress and fault slip, two electrodes on a pre-cut surface to measure tribo-electromotive force, and a troidal coil for monitoring the current which flows along the slip zone. From the electrode potential and the potential induced in the coil we calculate the resistance of the slip zone which is expected to decrease by several orders of magnitude once the slip zone is melted. The signals from these sensors were recorded synchronously at 2 MHz sampling rate. A moderately large stick-slip event was analyzed in detail. The fault slip, stress drop, rise time and maximum slip velocity were 0.32 mm, 230 MPa, 23 μ s and 40 m/s. The sensors detected precisely the time point when the slip zone melted. This occurred only 2 μ s after the slip velocity reached the maximum, and at the same time the friction coefficient reached a minimum (0.3). Immediately thereafter, it recovered promptly and remarkably, and the slip stopped eventually. Our SEM and EPMA observations ascertained the melting of the slip zone that was evidenced by a glass layer a few μ m thick in the experimented sample. The early half of the slip event is assumed to have been governed by solid interface friction, because carrot-shaped grooved and blobs of scratched debris were well developed in other experimented samples which experienced small events with ca. 0.1 mm slip. Our numerical simulations for frictional melting using observed time-shear stress and/or time-slip velocity data successfully reproduced the temperature and thickness of the melt layer, validating our experimental result at least phenomenologically. Therefore, we conclude that

  15. Slip preference on pre-existing faults: a guide tool for the separation of heterogeneous fault-slip data in extensional stress regimes

    NASA Astrophysics Data System (ADS)

    Tranos, Markos D.

    2012-05-01

    Synthetic fault-slip data have been considered in the present paper, in order to examine through a simple graphical manner the validity and use of the widely mentioned and applied criteria such as the slip preference, slip tendency, kinematic (P and T) axes, transport orientation and strain compatibility. The examination and description concern extensional stress regimes whose greatest principal stress axis (σ1) always remains in vertical position as in Andersonian stress states. In particular, radial extension (RE), radial-pure extension (RE-PE), pure extension (PE), pure extension-transtension (PE-TRN) and transtension (TRN) are examined with the aid of the Win-Tensor stress inversion software. In all of these extensional stress regimes only extensional faults can be activated. The lower dip angle of the reactivated faults is about 40° assuming that the coefficient of friction is no smaller than 0.6. The increase of the stress ratio and/or the fault dip angle up to 70° results in the increase of the slip deviation from the normal activation. Based on the present examination of the slip preference and slip tendency in different extensional stress regimes, a new simple and practical method is proposed herein in order to separate originally heterogeneous fault-slip data into homogeneous fault groups, by which different extensional stress regimes could be determined. The application of the method on the already published fault-slip data of Lemnos Island supports its validity since over 90% the resulted fault groups and stress regimes coincide to the already published ones.

  16. Episodic slow slip process in a non-planar fault model constrained by non-volcanic tremor locations along Cascadia subduction zone

    NASA Astrophysics Data System (ADS)

    Li, D.; Liu, Y.

    2015-12-01

    Slow slip events (SSEs) are observed in the circum-Pacific subduction zones and exhibit a wide diversity of source parameters (including equivalent moment, duration and recurrence interval). Gao et al [2012] compiled source parameters of SSEs around the world and revealed their empirical scaling relations distinct from those of regular earthquakes. However, the nature of this diversity is unclear. Previous 3-D numerical simulations in a simplified plate model have reproduced the along-strike segmentation of episodic SSEs in Cascadia margin and their source scaling relations in the framework of rate- and state- friction law [Liu, 2014]. But the planar fault model is inefficient to investigate the effect of the fault geometry on the source characteristics of SSEs in a specific subduction zone. In this study, we adopt a non-planar Cascadia subduction fault geometry constrained by relocated seismicity [McCrory et al. 2012] in the rate-state friction model. We have reproduced episodic SSEs beneath Vancouver Island and Washington arising every ~1.5 year with a maximum cumulative slip of ~2.5 cm. We find three phases characteristic in cumulative moment rate and slip rate in each episode. These three phases, defined as nucleation, fast-spreading and healing, lasting for ~160, ~60 and ~140 days, respectively. Both the nucleation and healing phases are beneath GPS detection threshold but the nucleation phase is spatially correlated with the small tremor activities arising deeper than episodic tremor and slip (ETS). To further investigate the diversity of SSEs in Cascadia, we introduce the recent 6-year tremor locations in Cascadia (http://pnsn.org/tremor) to constrain the near-lithostatic pore pressure distribution at the SSE depths in an 800km-long Cascadia fault model. Additionally, we set a step change of effective normal stress in SSE region from 1.5 MPa in Vancouver Island and Washington to 2.0 MPa in Oregon. The results show that the modeled SSEs exhibit distinct slip

  17. 29 CFR 510.23 - Agricultural activities eligible for minimum wage phase-in.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 3 2011-07-01 2011-07-01 false Agricultural activities eligible for minimum wage phase-in..., DEPARTMENT OF LABOR REGULATIONS IMPLEMENTATION OF THE MINIMUM WAGE PROVISIONS OF THE 1989 AMENDMENTS TO THE... eligible for minimum wage phase-in. Agriculture activities eligible for an extended phase-in of the...

  18. 29 CFR 510.23 - Agricultural activities eligible for minimum wage phase-in.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 29 Labor 3 2014-07-01 2014-07-01 false Agricultural activities eligible for minimum wage phase-in..., DEPARTMENT OF LABOR REGULATIONS IMPLEMENTATION OF THE MINIMUM WAGE PROVISIONS OF THE 1989 AMENDMENTS TO THE... eligible for minimum wage phase-in. Agriculture activities eligible for an extended phase-in of the...

  19. 29 CFR 510.23 - Agricultural activities eligible for minimum wage phase-in.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 29 Labor 3 2013-07-01 2013-07-01 false Agricultural activities eligible for minimum wage phase-in..., DEPARTMENT OF LABOR REGULATIONS IMPLEMENTATION OF THE MINIMUM WAGE PROVISIONS OF THE 1989 AMENDMENTS TO THE... eligible for minimum wage phase-in. Agriculture activities eligible for an extended phase-in of the...

  20. 29 CFR 510.23 - Agricultural activities eligible for minimum wage phase-in.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 3 2012-07-01 2012-07-01 false Agricultural activities eligible for minimum wage phase-in..., DEPARTMENT OF LABOR REGULATIONS IMPLEMENTATION OF THE MINIMUM WAGE PROVISIONS OF THE 1989 AMENDMENTS TO THE... eligible for minimum wage phase-in. Agriculture activities eligible for an extended phase-in of the...

  1. 29 CFR 510.23 - Agricultural activities eligible for minimum wage phase-in.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 3 2010-07-01 2010-07-01 false Agricultural activities eligible for minimum wage phase-in..., DEPARTMENT OF LABOR REGULATIONS IMPLEMENTATION OF THE MINIMUM WAGE PROVISIONS OF THE 1989 AMENDMENTS TO THE... eligible for minimum wage phase-in. Agriculture activities eligible for an extended phase-in of the...

  2. Maximum slip in earthquake fault zones, apparent stress, and stick-slip friction

    USGS Publications Warehouse

    McGarr, A.; Fletcher, Joe B.

    2003-01-01

    The maximum slip, observed or inferred, for a small patch within the larger fault zone of an earthquake is a remarkably well-constrained function of the seismic moment. A large set of maximum slips, mostly derived from slip models of major earthquakes, indicate that this parameter increases according to the cube root of the seismic moment. Consistent with this finding, neither the average slip rate for the patches of maximum slip nor the apparent stresses of earthquakes show any systematic dependence on seismic moment. Maximum average slip rates are several meters per second independent of moment and, for earthquakes in continental crustal settings, the apparent stress is limited to about 10 MPa. Results from stick-slip friction experiments in the laboratory, combined with information about the state of stress in the crust, can be used to predict, quite closely, the maximum slips and maximum average slip rates within the fault zones of major earthquakes as well as their apparent stresses. These findings suggest that stick-slip friction events observed in the laboratory and earthquakes in continental settings, even with large magnitudes, have similar rupture mechanisms.

  3. Slip mechanisms in complex fluid flows.

    PubMed

    Hatzikiriakos, Savvas G

    2015-10-28

    The classical no-slip boundary condition of fluid mechanics is not always a valid assumption for the flow of several classes of complex fluids including polymer melts, their blends, polymer solutions, microgels, glasses, suspensions and pastes. In fact, it appears that slip effect in these systems is the rule and not the exemption. The occurrence of slip complicates the analysis of rheological data, although it provides new opportunities to understand their behavior in restricted environments delineating additional molecular mechanisms i.e. entropic restrictions due to limitations in the number of molecular conformations. This article discusses these complexities and provides future research opportunities.

  4. Improved Slip Casting Of Ceramic Models

    NASA Technical Reports Server (NTRS)

    Buck, Gregory M.; Vasquez, Peter; Hicks, Lana P.

    1994-01-01

    Improved technique of investment slip casting developed for making precise ceramic wind-tunnel models. Needed in wind-tunnel experiments to verify predictions of aerothermodynamical computer codes. Ceramic materials used because of their low heat conductivities and ability to survive high temperatures. Present improved slip-casting technique enables casting of highly detailed models from aqueous or nonaqueous solutions. Wet shell molds peeled off models to ensure precise and undamaged details. Used at NASA Langley Research Center to form superconducting ceramic components from nonaqueous slip solutions. Technique has many more applications when ceramic materials developed further for such high-strength/ temperature components as engine parts.

  5. Variability of fault slip behavior along the San Andreas Fault in the San Juan Bautista Region

    NASA Astrophysics Data System (ADS)

    Taira, Taka'aki; Bürgmann, Roland; Nadeau, Robert M.; Dreger, Douglas S.

    2014-12-01

    An improved understanding of the time history of fault slip at depth is an essential step toward understanding the underlying mechanics of the faulting process. Using a waveform cross-correlation approach, we document spatially and temporally varying fault slip along the northernmost creeping section of the San Andreas Fault near San Juan Bautista (SJB), California, by systematically examining spatiotemporal behaviors of characteristically repeating earthquakes (CREs). The spatial distribution of pre-1998 SJB earthquake (1984-1998) fault slip rate inferred from the CREs reveals a ~15 km long low creep or partially locked section located near the 1998 Mw 5.1 SJB earthquake rupture. A finite-fault slip inversion reveals that the rupture of the 1998 SJB earthquake is characterized by the failure of a compact ~4 km2 asperity with a maximum slip of about 90 cm and corresponding peak stress drop of up to 50 MPa, whereas the mean stress drop is about 15 MPa. Following the 1998 earthquake, the CRE activity was significantly increased in a 5-10 km deep zone extending 2-7 km northwest of the main shock, which indicates triggering of substantial aseismic slip. The postseismic slip inferred from the CRE activity primarily propagated to the northwest and released a maximum slip of 9 cm. In this 5-10 km depth range, the estimated postseismic moment release is 8.6 × 1016 N m, which is equivalent to Mw 5.22. The aseismic slip distribution following the 1998 earthquake is not consistent with coseismic stress-driven afterslip but represents a triggered, long-lasting slow earthquake.

  6. Slip distribution, strain accumulation and aseismic slip on the Chaman Fault system

    NASA Astrophysics Data System (ADS)

    Amelug, F.

    2015-12-01

    The Chaman fault system is a transcurrent fault system developed due to the oblique convergence of the India and Eurasia plates in the western boundary of the India plate. To evaluate the contemporary rates of strain accumulation along and across the Chaman Fault system, we use 2003-2011 Envisat SAR imagery and InSAR time-series methods to obtain a ground velocity field in radar line-of-sight (LOS) direction. We correct the InSAR data for different sources of systematic biases including the phase unwrapping errors, local oscillator drift, topographic residuals and stratified tropospheric delay and evaluate the uncertainty due to the residual delay using time-series of MODIS observations of precipitable water vapor. The InSAR velocity field and modeling demonstrates the distribution of deformation across the Chaman fault system. In the central Chaman fault system, the InSAR velocity shows clear strain localization on the Chaman and Ghazaband faults and modeling suggests a total slip rate of ~24 mm/yr distributed on the two faults with rates of 8 and 16 mm/yr, respectively corresponding to the 80% of the total ~3 cm/yr plate motion between India and Eurasia at these latitudes and consistent with the kinematic models which have predicted a slip rate of ~17-24 mm/yr for the Chaman Fault. In the northern Chaman fault system (north of 30.5N), ~6 mm/yr of the relative plate motion is accommodated across Chaman fault. North of 30.5 N where the topographic expression of the Ghazaband fault vanishes, its slip does not transfer to the Chaman fault but rather distributes among different faults in the Kirthar range and Sulaiman lobe. Observed surface creep on the southern Chaman fault between Nushki and north of City of Chaman, indicates that the fault is partially locked, consistent with the recorded M<7 earthquakes in last century on this segment. The Chaman fault between north of the City of Chaman to North of Kabul, does not show an increase in the rate of strain

  7. Slip-stacking Dynamics and the 20 Hz Booster

    SciTech Connect

    Eldred, Jeffery; Zwaska, Robert

    2015-03-01

    Slip-stacking is an accumulation technique used at Fermilab since 2004 which nearly doubles the proton intensity. The Proton Improvement Plan II intensity upgrades require a reduction in slip-stacking losses by approximately a factor of 2. We study the single-particle dynamics that determine the stability of slip-stacking particles. We introduce universal area factors to calculate the available phase space area for any set of beam parameters without individual simulation. We show the particle loss as a function of time. We calculate the injection efficiency as a function of longitudinal emittance and aspect-ratio. We demonstrate that the losses from RF single particle dynamics can be reduced by a factor of 4-10 (depending on beam parameters) by upgrading the Fermilab Booster from a 15-Hz cycle-rate to a 20-Hz cycle-rate. We recommend a change in injection scheme to eliminate the need for a greater momentum aperture in the Fermilab Recycler.

  8. Distribution of strike-slip faults on Europa

    NASA Astrophysics Data System (ADS)

    Hoppa, Gregory; Greenberg, Richard; Tufts, B. Randall; Geissler, Paul; Phillips, Cynthia; Milazzo, Moses

    2000-09-01

    Study of four different regions on Europa imaged by the Galileo spacecraft during its first 15 orbits has revealed 117 strike-slip faults. Europa appears to form preferentially right-lateral faults in the southern hemisphere and left-lateral faults in the northern hemisphere. This observation is consistent with a model where diurnal tides due to orbital eccentricity drive strike-slip motion through a process of ``walking,'' in which faults open and close out of phase with alternating right-and left-lateral shear. Lineaments that record both left-and right-lateral motion (e.g., Agave Linea) may record the accommodation of compression in nearby chaotic zones. Nearly all identified strike-slip faults were associated with double ridges or bands, and few were detected along ridgeless cracks. Thus the depth of cracks without ridges does not appear to have penetrated to the low-viscosity decoupling layer, required for diurnal displacement, but cracks that have developed ridges do extend down to such a level. This result supports a model for ridge formation that requires cracks to penetrate to a decoupling layer, such as a liquid water ocean.

  9. Plans for the next phase of CORDEX activities

    NASA Astrophysics Data System (ADS)

    Giorgi, Filippo; Gutowski, William

    2016-04-01

    Ensembles of Regional Climate Model (RCM) projections have been completed under the protocol of the first phase of the COordinated Regional Downscaling EXperiment (CORDEX, Giorgi et al. 2009) over most CORDEX domains. As a result of these activities a number of scientific issues have emerged, which provide the basis for discussion of the next phase of the CORDEX program. Among such issues are a clearer identification and quantification of the added value of the use of RCMs, the development and use of a new generation of very high resolution (<10 km), convection permitting RCMs, the coordination across development efforts of coupled Regional Earth System Models (RESMs), a more detailed and process-based analysis of RCM simulations, the effects of regional forcings (e.g. land use change and aerosols) and a better integration of empirical/statistical downscaling within the CORDEX framework. A large inhomogeneity was also noted across different CORDEX regional efforts, with some domains (e.g. EURO-CORDEX, AFRICA-CORDEX and MED-CORDEX) being covered by large ensembles and others by much more sparse experiment matrices. This has limited the use of CORDEX results in international programs such as the Intergovernmental Panel on Climate Change (IPCC). Two avenues are being discussed in order to address these issues. The first is to produce a homogeneous set of higher resolution projections (10-20 km) across all or most CORDEX domains using a core set of RCMs downscaling a core set of GCMs. The second is to develop and implement a set of "Flagship Pilot Studies (FPSs)" over sub-regions of interest aimed at addressing specific scientific questions (e.g. added value and convection-permitting simulations, intercomparison of different downscaling approaches, land-use and aerosol effects). In this presentation we will describe the status of the discussion and plans for these new CORDEX initiatives, which will be likely finalized at the upcoming third Pan-CORDEX conference (ICRC

  10. Microstructural and phase evolution in metakaolin geopolymers with different activators and added aluminosilicate fillers

    NASA Astrophysics Data System (ADS)

    Sarkar, Madhuchhanda; Dana, Kausik; Das, Sukhen

    2015-10-01

    This work aims to investigate the microstructural and phase evolution of alkali activated metakaolin products with different activators and added aluminosilicate filler phases. The added filler phases have different reactivity to the alkali activated metakaolin system. Microstructural evolution in the alkali activated products has been investigated by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Field Emission Scanning Electron Microscope (FESEM). Variation in strength development in alkali activated metakaolin products was followed by compressive strength measurement test. Microstructural study shows that in case of metakaolin with NaOH activator crystalline sodalite formed in all the product samples irrespective of the added filler phases. The microstructure of these NaOH activated products investigated by FESEM showed crystalline and inhomogeneous morphology. Mixed activator containing both NaOH and sodium silicate in a fixed mass ratio formed predominantly amorphous phase. Microstructure of these samples showed more homogeneity than that of NaOH activated metakaolin products. The study further shows that addition of α-Al2O3 powder, non reactive phase to the alkali activated metakaolin system when used in larger amount increased crystalline phase in the matrix. α-Al2O3 powder addition increased the compressive strength of the product samples for both the activator compositions. Added phase of colloidal silica, reactive to the alkali activated metakaolin system when used in larger amount was found to increase amorphous nature of the matrix. Addition of colloidal silica influenced the compressive strength property differently with different activator compositions.

  11. Basal slip and texture development in calcite: new results from torsion experiments

    SciTech Connect

    Barber, D. J.; Wenk, H.-R.; Gomez-Barreiro, J.; Rybacki, E.; Dresen, G.

    2008-06-09

    The deformation behavior of calcite has been of longstanding interest. Through experiments on single crystals, deformation mechanisms were established such as mechanical twinning on e = {l_brace}{bar 1}018{r_brace} <40{bar 4}1> in the positive sense and slip on r = {l_brace}10{bar 1}4{r_brace} <20{bar 2}{bar 1}> and f = {l_brace}{bar 1}012{r_brace} <0{bar 2}2{bar 1}> both in the negative sense. More recently it was observed that at higher temperatures f{l_brace}{bar 1}012{r_brace} <10{bar 1}1> slip in both senses becomes active and, based on slip line analysis, it was suggested that e(0001) <11{bar 2}0> slip may occur. So far there had been no direct evidence for basal slip, which is the dominant system in dolomite. With new torsion experiments on calcite single crystals at 900 K and transmission electron microscopy, this study identifies (0001) <11{bar 2}0> slip unambiguously by direct imaging of dislocations and diffraction contrast analysis. Including this slip system in polycrystal plasticity simulations, enigmatic texture patterns observed in compression and torsion of calcite rocks at high temperature can now be explained, resolving a long-standing puzzle.

  12. Slip boundary conditions over curved surfaces

    NASA Astrophysics Data System (ADS)

    Guo, Lin; Chen, Shiyi; Robbins, Mark O.

    2016-01-01

    Molecular dynamics simulations are used to investigate the influence of surface curvature on the slip boundary condition for a simple fluid. The slip length is measured for flows in planar and cylindrical geometries with a range of wall-fluid interactions. As wall curvature increases, the slip length decreases dramatically for closely packed surfaces and increases for sparse ones. The magnitude of the changes depends on the crystallographic orientation and differs for flow along and perpendicular to the direction of curvature. These different patterns of behavior are related to the curvature-induced variation in the ratio of the spacing between fluid atoms to the spacing between minima in the potential from the solid surface. The results are consistent with a microscopic theory for the viscous friction between fluid and wall that expresses the slip length in terms of the lateral response of the fluid to the wall potential and the characteristic decay time of this response.

  13. Tightness of slip-linked polymer chains.

    PubMed

    Metzler, Ralf; Hanke, Andreas; Dommersnes, Paul G; Kantor, Yacov; Kardar, Mehran

    2002-06-01

    We study the interplay between entropy and topological constraints for a polymer chain in which sliding rings (slip links) enforce pair contacts between monomers. These slip links divide a closed ring polymer into a number of subloops which can exchange length among each other. In the ideal chain limit, we find the joint probability density function for the sizes of segments within such a slip-linked polymer chain (paraknot). A particular segment is tight (small in size) or loose (of the order of the overall size of the paraknot) depending on both the number of slip links it incorporates and its competition with other segments. When self-avoiding interactions are included, scaling arguments can be used to predict the statistics of segment sizes for certain paraknot configurations.

  14. Action slips during whole-body vibration.

    PubMed

    Ishimatsu, Kazuma; Meland, Anders; Hansen, Tor Are S; Kåsin, Jan Ivar; Wagstaff, Anthony S

    2016-07-01

    Helicopter aircrew members engage in highly demanding cognitive tasks in an environment subject to whole-body vibration (WBV). Sometimes their actions may not be according to plan (e.g. action slips and lapses). This study used a Sustained Attention to Response Task (SART) to examine whether action slips were more frequent during exposure to WBV. Nineteen participants performed the SART in two blocks. In the WBV block participants were exposed to 17 Hz vertical WBV, which is typical of larger helicopter working environments. In the No-WBV block there was no WBV. There were more responses to the rare no-go digit 3 (i.e. action slips) in the WBV block, and participants responded faster in the WBV block. These results suggest that WBV influences response inhibition, and can induce impulsive responding. WBV may increase the likelihood of action slips, mainly due to failure of response inhibition.

  15. The Hills are Alive: Dynamic Ridges and Valleys in a Strike-Slip Environment

    NASA Astrophysics Data System (ADS)

    Duvall, A. R.; Tucker, G. E.

    2014-12-01

    Strike-slip fault zones have long been known for characteristic landforms such as offset and deflected rivers, linear strike-parallel valleys, and shutter ridges. Despite their common presence, questions remain about the mechanics of how these landforms arise or how their form varies as a function of slip rate, geomorphic process, or material properties. We know even less about what happens far from the fault, in drainage basin headwaters, as a result of strike-slip motion. Here we explore the effects of horizontal fault slip rate, bedrock erodibility, and hillslope diffusivity on river catchments that drain across an active strike-slip fault using the CHILD landscape evolution model. Model calculations demonstrate that lateral fault motion induces a permanent state of landscape disequilibrium brought about by fault offset-generated river lengthening alternating with abrupt shortening due to stream capture. This cycle of shifting drainage patterns and base level change continues until fault motion ceases thus creating a perpetual state of transience unique to strike-slip systems. Our models also make the surprising prediction that, in some cases, hillslope ridges oriented perpendicular to the fault migrate laterally in conjunction with fault motion. Ridge migration happens when slip rate is slow enough and/or diffusion and river incision are fast enough that the hillslopes can respond to the disequilibrium brought about by strike-slip motion. In models with faster slip rates, stronger rocks or less-diffusive hillslopes, ridge mobility is limited or arrested despite the fact that the process of river lengthening and capture continues. Fast-slip cases also develop prominent steep fault-facing hillslope facets proximal to the fault valley and along-strike topographic profiles with reduced local relief between ridges and valleys. Our results demonstrate the dynamic nature of strike-slip landscapes that vary systematically with a ratio of bedrock erodibility (K) and

  16. A search in strainmeter data for slow slip associated with triggered and ambient tremor near Parkfield, California

    USGS Publications Warehouse

    Smith, E.F.; Gomberg, J.

    2009-01-01

    We test the hypothesis that, as in subduction zones, slow slip facilitates triggered and ambient tremor in the transform boundary setting of California. Our study builds on the study of Peng et al. (2009) of triggered and ambient tremor near Parkfield, California during time intervals surrounding 31, potentially triggering, M ≥ 7.5 teleseismic earthquakes; waves from 10 of these triggered tremor and 29 occurred in periods of ambient tremor activity. We look for transient slow slip during 3-month windows that include 11 of these triggering and nontriggering teleseisms, using continuous strain data recorded on two borehole Gladwin tensor strainmeters (GTSM) located within the distribution of tremor epicenters. We model the GTSM data assuming only tidal and “drift” signals are present and find no detectable slow slip, either ongoing when the teleseismic waves passed or triggered by them. We infer a conservative detection threshold of about 5 nanostrain for abrupt changes and about twice this for slowly evolving signals. This could be lowered slightly by adding analyses of other data types, modeled slow slip signals, and GTSM data calibration. Detection of slow slip also depends on the slipping fault's location and size, which we describe in terms of equivalent earthquake moment magnitude, M. In the best case of the GTSM above a very shallow slipping fault, detectable slip events must exceed M~2, and if the slow slip is beneath the seismogenic zone (below ~15 km depth), even M~5 events are likely to remain hidden.

  17. Stalled slip during the 2011 Cascadia ETS event

    NASA Astrophysics Data System (ADS)

    Bartlow, N. M.; Wech, A.; Segall, P.

    2013-12-01

    In regions with Episodic Tremor and Slip (ETS), such as Cascadia and southwest Japan, behavior can range from large events where both phenomena migrate together for 100s of kilometers along strike, to smaller tremor swarms without geodetically detected slip. Slip without tremor, while observed elsewhere, has not been seen large ETS in Cascadia. However, recent observations have identified slip during the 2011 Cascadia ETS event that did not generate tremor (see the 'Episodic silence and slip' presentation by Wech & Bartlow). Here we expand on that analysis to present details of the inversion of GPS data from this event using the Network Inversion Filter (Segall and Matthews, 1997). We find that in the middle of the 2011 ETS event there are about 20 days of tremor-less slip, with slip occurring at a much lower slip-rate than typical ETS slip in Cascadia. During this time slip is also 'stalled' in place, with little to no migration along strike. Slip-rate and propagation rate are theoretically proportional (Rubin, G3, 2011), consistent with the low slip-rate and 'stalled' nature of the observed tremorless slip. This finding demonstrates that Cascadia may exhibit a wider range of slow slip behavior than previously recognized, and may imply a minimum slip-rate for tremor generation. In this presentation we will discuss details of the slip inversion, including resolution, the range of models that fit the data, and a comparison of time-dependent vs. static inversions.

  18. Micromechanics of sea ice frictional slip from test basin scale experiments

    NASA Astrophysics Data System (ADS)

    Sammonds, Peter R.; Hatton, Daniel C.; Feltham, Daniel L.

    2017-02-01

    We have conducted a series of high-resolution friction experiments on large floating saline ice floes in an environmental test basin. In these experiments, a central ice floe was pushed between two other floes, sliding along two interfacial faults. The frictional motion was predominantly stick-slip. Shear stresses, normal stresses, local strains and slip displacement were measured along the sliding faults, and acoustic emissions were monitored. High-resolution measurements during a single stick-slip cycle at several positions along the fault allowed us to identify two phases of frictional slip: a nucleation phase, where a nucleation zone begins to slip before the rest of the fault, and a propagation phase when the entire fault is slipping. This is slip-weakening behaviour. We have therefore characterized what we consider to be a key deformation mechanism in Arctic Ocean dynamics. In order to understand the micromechanics of sea ice friction, we have employed a theoretical constitutive relation (i.e. an equation for shear stress in terms of temperature, normal load, acceleration, velocity and slip displacement) derived from the physics of asperity-asperity contact and sliding (Hatton et al. 2009 Phil. Mag. 89, 2771-2799 (doi:10.1080/14786430903113769)). We find that our experimental data conform reasonably with this frictional law once slip weakening is introduced. We find that the constitutive relation follows Archard's law rather than Amontons' law, with ? (where τ is the shear stress and σn is the normal stress) and n = 26/27, with a fractal asperity distribution, where the frictional shear stress, τ = ffractal Tmlws, where ffractal is the fractal asperity height distribution, Tml is the shear strength for frictional melting and lubrication and ws is the slip weakening. We can therefore deduce that the interfacial faults failed in shear for these experimental conditions through processes of brittle failure of asperities in shear, and, at higher velocities

  19. Late Quaternary Range-Front Fault Scarps in the Western Sierra El Mayor, Baja California, Mexico: A Geomorphologic Expression of Slip Across an Active Low-Angle Normal Fault

    NASA Astrophysics Data System (ADS)

    Spelz, R. M.; Fletcher, J.; Owen, L.

    2006-12-01

    The western margin of the Sierra El Mayor (SEM), in northeastern Baja California, is controlled by an active, top-to-the-west, low-angle normal fault named the Canada David detachment (CDD) that accommodates part of the extensional component of shearing between the Pacific and North American plates. The CDD has a length of 60 km and shows a curvilinear trace with two major antiformal and synformal megamullion pairs. Late Quaternary slip has produced a broad array of Quaternary scarps cutting alluvial fans along nearly the entire length of the CDD. Detailed mapping reveals eight regional strath terraces distinguished by surface weathering characteristics, soil profile development and relative elevation. Relative height between terraces increases in domains where the CDD and basin deposits are being uplifted due to either the basinward migration of faulting (e.g., rolling hinge) or flexural uplift in antiformal megamullion domains. Linear diffusion analysis of 46 synthetic fault scarps, with a calculated angle of repose Θo = 28.75°, reveal fault scarp domains exhibiting both multi-modal and unimodal distribution of diffusion ages (kt). Uni-modal domains are typically younger, but there is no systematic variation in scarp age with distance along the CDD. Scarps yielding negative kt ages (i.e. scarps steeper than Θo) are common in the north, near inferred locations of important historic seismic events. Microseismicity drops off significantly adjacent to these very young scarp arrays, which likely reflects a recent post-seismic stress drop. Domains of high seismic risk are identified by high microseismicity and lack of young scarps. Minimum estimates of the diffusivity constant (k) are calculated by coupling scarp diffusion ages and 10Be surface exposure ages of the faulted deposits. In the southernmost SEM a Q6 terrace with a minimum surface exposure age t = 233±6.6 ky (weighted mean of six rock samples) is cut by scarps with an average kt = 11.25±9.31 m2, which

  20. Fault structure, frictional properties and mixed-mode fault slip behavior

    NASA Astrophysics Data System (ADS)

    Collettini, Cristiano; Niemeijer, André; Viti, Cecilia; Smith, Steven A. F.; Marone, Chris

    2011-11-01

    Recent high-resolution GPS and seismological data reveal that tectonic faults exhibit complex, multi-mode slip behavior including earthquakes, creep events, slow and silent earthquakes, low-frequency events and earthquake afterslip. The physical processes responsible for this range of behavior and the mechanisms that dictate fault slip rate or rupture propagation velocity are poorly understood. One avenue for improving knowledge of these mechanisms involves coupling direct observations of ancient faults exhumed at the Earth's surface with laboratory experiments on the frictional properties of the fault rocks. Here, we show that fault zone structure has an important influence on mixed-mode fault slip behavior. Our field studies depict a complex fault zone structure where foliated horizons surround meter- to decameter-sized lenses of competent material. The foliated rocks are composed of weak mineral phases, possess low frictional strength, and exhibit inherently stable, velocity-strengthening frictional behavior. In contrast, the competent lenses are made of strong minerals, possess high frictional strength, and exhibit potentially unstable, velocity-weakening frictional behavior. Tectonic loading of this heterogeneous fault zone may initially result in fault creep along the weak and frictionally stable foliated horizons. With continued deformation, fault creep will concentrate stress within and around the strong and potentially unstable competent lenses, which may lead to earthquake nucleation. Our studies provide field and mechanical constraints for complex, mixed-mode fault slip behavior ranging from repeating earthquakes to transient slip, episodic slow-slip and creep events.

  1. Slip effects associated with Knudsen transport phenomena in porous media

    NASA Technical Reports Server (NTRS)

    Frederking, T. H. K.; Hepler, W. A.; Khandhar, P. K.

    1988-01-01

    Porous media used in phase separators and thermomechanical pumps have been the subject of characterization efforts based on the Darcy permeability of laminar continuum flow. The latter is not always observed at low speed, in particular at permeabilities below 10 to the -9th/squared cm. The present experimental and theoretical studies address questions of slip effects associated with long mean free paths of gas flow at room temperature. Data obtained are in good agreement, within data uncertainty, with a simplified asymptotic Knudsen equation proposed for porous plugs on the basis of Knudsen's classical flow equation for long mean free paths.

  2. Resolving slip evolution of deep tremor in western Japan

    NASA Astrophysics Data System (ADS)

    Ohta, K.; Ide, S.

    2011-12-01

    Recent studies have shown that deep tectonic tremors in many subduction zones consist of numerous low-frequency earthquakes (LFEs) that occur as shear slips on the plate interface. LFE hypocenters are determined relatively accurately, and in western Japan, they are concentrated in a narrow zone around the anticipated plate interface [Ohta and Ide, 2011]. Therefore, the location of LFEs may constrain the instantaneous location of tremor sources and illustrate its migration behavior, as demonstrated by a matched filter analysis with template LFEs [Shelly et al., 2007]. Nevertheless, it is yet unclear whether tremor occurs at exactly the same location as LFEs. Since tremor behavior on the plate interface are various and spatially characteristic [Ide, 2010], there might be some tremor activity undetectable using template LFEs. Moreover, while the previous method using matched templates has achieved to draw the discrete picture of the slip behavior of potential tremor, it is not sufficient to explain the entire rupture process. To understand the underlying physics of tremor and other slow earthquakes, it is essential to highly resolve the spatial and temporal behavior of the rupture of these events. This study determines spatiotemporal slip distribution associated with deep tremor in western Japan, without the spatial limitation of template LFEs. We first estimate the location of the plate interface based on the precise hypocenter locations of LFEs in a target region and prepare "synthetic template waveforms" by stacking the seismograms of these LFEs at every grid point arranged on this interface. These synthetic template waveforms can be used in a matched filter analysis to continuous waveforms, to grasp a crude image of tremor source. Furthermore, we use the synthetic waveforms as substitute of Green's functions, and invert continuous tremor waveforms by a non-linear slip inversion method. We apply the method to 3600 s continuous velocity seismograms recorded at Hi

  3. Nonlinear Dynamical Triggering of Slow-Slip

    NASA Astrophysics Data System (ADS)

    Johnson, P. A.; Knuth, M. W.; Kaproth, B. M.; Carpenter, B. M.; Guyer, R. A.; Le Bas, P.; Daub, E. G.; Marone, C.

    2010-12-01

    Among the most fascinating, recent discoveries in seismology have been the phenomena of triggered slip, including triggered earthquakes and triggered-tremor, as well as triggered slow, silent-slip during which no seismic energy is radiated. Because fault nucleation depths cannot be probed directly, the physical regimes in which these phenomena occur are poorly understood. Thus determining physical properties that control diverse types of triggered fault sliding and what frictional constitutive laws govern triggered faulting variability is challenging. We are characterizing the physical controls of triggered faulting with the goal of developing constitutive relations by conducting laboratory and numerical modeling experiments in sheared granular media at varying load conditions. In order to simulate granular fault zone gouge in the laboratory, glass beads are sheared in a double-direct configuration under constant normal stress, while subject to transient perturbation by acoustic waves. We find that triggered, slow, silent-slip occurs at very small confining loads (~1-3 MPa) that are smaller than those where dynamic earthquake triggering takes place (4-7 MPa), and that triggered slow-slip is associated with bursts of LFE-like acoustic emission. Experimental evidence suggests that the nonlinear dynamical response of the gouge material induced by dynamic waves may be responsible for the triggered slip behavior: the slip-duration, stress-drop and along-strike slip displacement are proportional to the triggering wave amplitude. Further, we observe a shear-modulus decrease corresponding to dynamic-wave triggering relative to the shear modulus of stick-slips. Modulus decrease in response to dynamical wave amplitudes of roughly a microstrain and above is a hallmark of elastic nonlinear behavior. We believe that the dynamical waves increase the material non-affine elastic deformation during shearing, simultaneously leading to instability and slow-slip. The inferred

  4. Nonlinear dynamical triggering of slow slip

    SciTech Connect

    Johnson, Paul A; Knuth, Matthew W; Kaproth, Bryan M; Carpenter, Brett; Guyer, Robert A; Le Bas, Pierre - Yves; Daub, Eric G; Marone, Chris

    2010-12-10

    Among the most fascinating, recent discoveries in seismology have been the phenomena of triggered slip, including triggered earthquakes and triggered-tremor, as well as triggered slow, silent-slip during which no seismic energy is radiated. Because fault nucleation depths cannot be probed directly, the physical regimes in which these phenomena occur are poorly understood. Thus determining physical properties that control diverse types of triggered fault sliding and what frictional constitutive laws govern triggered faulting variability is challenging. We are characterizing the physical controls of triggered faulting with the goal of developing constitutive relations by conducting laboratory and numerical modeling experiments in sheared granular media at varying load conditions. In order to simulate granular fault zone gouge in the laboratory, glass beads are sheared in a double-direct configuration under constant normal stress, while subject to transient perturbation by acoustic waves. We find that triggered, slow, silent-slip occurs at very small confining loads ({approx}1-3 MPa) that are smaller than those where dynamic earthquake triggering takes place (4-7 MPa), and that triggered slow-slip is associated with bursts of LFE-like acoustic emission. Experimental evidence suggests that the nonlinear dynamical response of the gouge material induced by dynamic waves may be responsible for the triggered slip behavior: the slip-duration, stress-drop and along-strike slip displacement are proportional to the triggering wave amplitude. Further, we observe a shear-modulus decrease corresponding to dynamic-wave triggering relative to the shear modulus of stick-slips. Modulus decrease in response to dynamical wave amplitudes of roughly a microstrain and above is a hallmark of elastic nonlinear behavior. We believe that the dynamical waves increase the material non-affine elastic deformation during shearing, simultaneously leading to instability and slow-slip. The inferred

  5. Slip-Related Changes in Plantar Pressure Distribution, and Parameters for Early Detection of Slip Events

    PubMed Central

    Choi, Seungyoung; Cho, Hyungpil; Kang, Boram; Lee, Dong Hun; Kim, Mi Jung

    2015-01-01

    Objective To investigate differences in plantar pressure distribution between a normal gait and unpredictable slip events to predict the initiation of the slipping process. Methods Eleven male participants were enrolled. Subjects walked onto a wooden tile, and two layers of oily vinyl sheet were placed on the expected spot of the 4th step to induce a slip. An insole pressure-measuring system was used to monitor plantar pressure distribution. This system measured plantar pressure in four regions (the toes, metatarsal head, arch, and heel) for three events: the step during normal gait; the recovered step, when the subject recovered from a slip; and the uncorrected, harmful slipped step. Four variables were analyzed: peak pressure (PP), contact time (CT), the pressure-time integral (PTI), and the instant of peak pressure (IPP). Results The plantar pressure pattern in the heel was unique, as compared with other parts of the sole. In the heel, PP, CT, and PTI values were high in slipped and recovered steps compared with normal steps. The IPP differed markedly among the three steps. The IPPs in the heel for the three events were, in descending order (from latest to earliest), slipped, recovered, and normal steps, whereas in the other regions the order was normal, recovered, and slipped steps. Finally, the metatarsal head-to-heel IPP ratios for the normal, recovered, and slipped steps were 6.1±2.9, 3.1±3.0, and 2.2±2.5, respectively. Conclusion A distinctive plantar pressure pattern in the heel might be useful for early detection of a slip event to prevent slip-related injuries. PMID:26798603

  6. A comparison of slow slip events at Etna and Kilauea volcanoes

    NASA Astrophysics Data System (ADS)

    Mattia, Mario; Montgomery-Brown, Emily K.; Bruno, Valentina; Scandura, Danila

    2016-04-01

    Mt. Etna and Kilauea Volcano are both large basaltic volcanoes with unstable flanks, on which slow slip events have been observed by continuous GPS networks. The slow slip events (SSEs) last about two days at both volcanoes, although there are some differences in the depths and frequencies. While recurrence intervals were initially somewhat irregular at Kilauea, the most recent 5 events have become more regular with an inter-event time of about 2.4 years. At Mt. Etna, these events seem to be more frequent (about 2 per year) and are often related to the main recharge phases of the volcano. Ground deformation data have been used on both volcanoes for determining the source of the anomalous displacements and, from this point of view, the two volcanoes seem very different. Although slow slip events at Mt. Etna and Kilauea are much shallower than many subduction zone slow slip events, slip at Kilauea occurs on a discrete decollement at about 8 km deep. At Mt. Etna, a variety of data suggest that the sliding could be much shallower and more diffuse. In this work, we show some preliminary results of a "block-like" model of Mt. Etna's slow slip events that is able to explain the source of the flank displacements with slip on the Giarre Wedge near the coast. This work will allow a possible classification of different types of slip events affecting the flanks of large basaltic volcanoes, often densely populated, with a significant impact on the evaluation of seismic and volcanic hazard.

  7. Frequency translating phase conjugation circuit for active retrodirective antenna array. [microwave transmission

    NASA Technical Reports Server (NTRS)

    Chernoff, R. (Inventor)

    1980-01-01

    An active retrodirective antenna array which has central phasing from a reference antenna element through a "tree" structured network of transmission lines utilizes a number of phase conjugate circuits (PCCs) at each node and a phase reference regeneration circuit (PRR) at each node except the initial node. Each node virtually coincides with an element of the array. A PCC generates the exact conjugate phase of an incident signal using a phase locked loop which combines the phases in an up converter, divides the sum by 2 and mixes the result with the phase in a down converter for phase detection. The PRR extracts the phase from the conjugate phase. Both the PCC and the PRR are not only exact but also free from mixer degeneracy.

  8. Pyrometamorphism of Fault Zone Rocks Induced by Frictional Heating in High-velocity Friction Tests: Reliable Records of Seismic Slip?

    NASA Astrophysics Data System (ADS)

    Ree, J.; Ando, J.; Kim, J.; Han, R.; Shimamoto, T.

    2008-12-01

    Recognition of seismic slip zone is important for a better understanding of earthquake generation processes in fault zones and paleoseismology. However, there has been no reliable record of ancient seismic slip except pseudotachylyte. Recently, it has been suggested that decomposition (dehydration or decarbonation) products due to frictional heating can be used as a seismic slip record. The decomposition products, however, can be easily rehydrated or recarbonated with pervasive fluid migration in the fault zone after seismic slip, raising some question about their stability as a seismic slip record. Here, we review microstructural and mineralogical changes of the simulated fault zones induced by frictional heating (pyrometamorphism) from high-velocity friction tests (HVFT) on siltstone, sandstone and carbonates at seismic slip rates, and discuss on their stability after seismic slip. HVFT on siltstone generates pseuodotachylyte in the principal slip zone (0.30-0.75 mm thick) with 'damage' layer (0.1-0.2 mm thick) along its margins. Chlorite in the damage layer suffers an incipient dehydration with many voids (0.2-1.0 μm in diameter) in transmission electron microscopy (TEM), appearing as dark tiny spots both in plane-polarized light and back-scattered electron (BSE) photomicrographs. HVFT on brown sandstone induces a color change of wall rocks adjacent to the principal slip zone (brown to red) due to the dehydration of iron hydroxides with frictional heating. These dehydration products in siltstone and sandstone due to frictional heating may be unstable since they would be easily rehydrated with fluid infiltration after a seismic slip. HVFT on carbonates including Carrara marble and siderite-bearing gouges produces decarbonation products of nano-scale lime (CaO) and magnetite (Fe3O4), respectively. Lime is a very unstable phase whereas magnetite is a stable and thus may be used as an indicator of seismic slip. The simulated fault zones of Carrara marble contain

  9. Viscoelastic Drag Forces and Crossover from No-Slip to Slip Boundary Conditions for Flow near Air-Water Interfaces

    NASA Astrophysics Data System (ADS)

    Maali, A.; Boisgard, R.; Chraibi, H.; Zhang, Z.; Kellay, H.; Würger, A.

    2017-02-01

    The "free" water surface is generally prone to contamination with surface impurities, be they surfactants, particles, or other surface active agents. The presence of such impurities can modify flow near such interfaces in a drastic manner. Here we show that vibrating a small sphere mounted on an atomic force microscope cantilever near a gas bubble immersed in water is an excellent probe of surface contamination. Both viscous and elastic forces are exerted by an air-water interface on the vibrating sphere even when very low doses of contaminants are present. The viscous drag forces show a crossover from no-slip to slip boundary conditions while the elastic forces show a nontrivial variation as the vibration frequency changes. We provide a simple model to rationalize these results and propose a simple way of evaluating the concentration of such surface impurities.

  10. Triggered surface slips in the Coachella Valley area associated with the 1992 Joshua Tree and Landers, California, Earthquakes

    USGS Publications Warehouse

    Rymer, M.J.

    2000-01-01

    The Coachella Valley area was strongly shaken by the 1992 Joshua Tree (23 April) and Landers (28 June) earthquakes, and both events caused triggered slip on active faults within the area. Triggered slip associated with the Joshua Tree earthquake was on a newly recognized fault, the East Wide Canyon fault, near the southwestern edge of the Little San Bernardino Mountains. Slip associated with the Landers earthquake formed along the San Andreas fault in the southeastern Coachella Valley. Surface fractures formed along the East Wide Canyon fault in association with the Joshua Tree earthquake. The fractures extended discontinuously over a 1.5-km stretch of the fault, near its southern end. Sense of slip was consistently right-oblique, west side down, similar to the long-term style of faulting. Measured offset values were small, with right-lateral and vertical components of slip ranging from 1 to 6 mm and 1 to 4 mm, respectively. This is the first documented historic slip on the East Wide Canyon fault, which was first mapped only months before the Joshua Tree earthquake. Surface slip associated with the Joshua Tree earthquake most likely developed as triggered slip given its 5 km distance from the Joshua Tree epicenter and aftershocks. As revealed in a trench investigation, slip formed in an area with only a thin (<3 m thick) veneer of alluvium in contrast to earlier documented triggered slip events in this region, all in the deep basins of the Salton Trough. A paleoseismic trench study in an area of 1992 surface slip revealed evidence of two and possibly three surface faulting events on the East Wide Canyon fault during the late Quaternary, probably latest Pleistocene (first event) and mid- to late Holocene (second two events). About two months after the Joshua Tree earthquake, the Landers earthquake then triggered slip on many faults, including the San Andreas fault in the southeastern Coachella Valley. Surface fractures associated with this event formed discontinuous

  11. Support for the slip hypothesis from whisker-related tactile perception of rats in a noisy environment.

    PubMed

    Waiblinger, Christian; Brugger, Dominik; Whitmire, Clarissa J; Stanley, Garrett B; Schwarz, Cornelius

    2015-01-01

    Rodents use active whisker movements to explore their environment. The "slip hypothesis" of whisker-related tactile perception entails that short-lived kinematic events (abrupt whisker movements, called "slips", due to bioelastic whisker properties that occur during active touch of textures) carry the decisive texture information. Supporting this hypothesis, previous studies have shown that slip amplitude and frequency occur in a texture-dependent way. Further, experiments employing passive pulsatile whisker deflections revealed that perceptual performance based on pulse kinematics (i.e., signatures that resemble slips) is far superior to the one based on time-integrated variables like frequency and intensity. So far, pulsatile stimuli were employed in a noise free environment. However, the realistic scenario involves background noise (e.g., evoked by rubbing across the texture). Therefore, if slips are used for tactile perception, the tactile neuronal system would need to differentiate slip-evoked spikes from those evoked by noise. To test the animals under these more realistic conditions, we presented passive whisker-deflections to head-fixed trained rats, consisting of "slip-like" events (waveforms mimicking slips occurring with touch of real textures) embedded into background noise. Varying the (i) shapes (ramp or pulse); (ii) kinematics (amplitude, velocity, etc.); and (iii) the probabilities of occurrence of slip-like events, we observed that rats could readily detect slip-like events of different shapes against noisy background. Psychophysical curves revealed that the difference of slip event and noise amplitude determined perception, while increased probability of occurrence (frequency) had barely any effect. These results strongly support the notion that encoding of kinematics dominantly determines whisker-related tactile perception while the computation of frequency or intensity plays a minor role.

  12. Origin and structure of major orogen-scale exhumed strike-slip

    NASA Astrophysics Data System (ADS)

    Cao, Shuyun; Neubauer, Franz

    2016-04-01

    The formation of major exhumed strike-slip faults represents one of the most important dynamic processes affecting the evolution of the Earth's lithosphere and surface. Detailed models of the potential initiation and properties and architecture of orogen-scale exhumed strike-slip faults and how these relate to exhumation are rare. In this study, we deal with key properties controlling the development of major exhumed strike-slip fault systems, which are equivalent to the deep crustal sections of active across fault zones. We also propose two dominant processes for the initiation of orogen-scale exhumed strike-slip faults: (1) pluton-controlled and (2) metamorphic core complex-controlled strike-slip faults. In these tectonic settings, the initiation of faults occurs by rheological weakening along hot-to-cool contacts and guides the overall displacement and ultimate exhumation. These processes result in a specific thermal and structural architecture of such faults. These types of strike-slip dominated fault zones are often subparallel to mountain ranges and expose a wide variety of mylonitic, cataclastic and non-cohesive fault rocks, which were formed at different structural levels of the crust during various stages of faulting. The high variety of distinctive fault rocks is a potential evidence for recognition of these types of strike-slip faults. Exhumation of mylonitic rocks is, therefore, a common feature of such reverse oblique-slip strike-slip faults, implying major transtensive and/or transpressive processes accompanying pure strike-slip motion during exhumation. Some orogen-scale strike-slip faults nucleate and initiate along rheologically weak zones, e.g. at granite intrusions, zones of low-strength minerals, thermally weakened crust due to ascending fluids, and lateral borders of hot metamorphic core complexes. A further mechanism is the juxtaposition of mechanically strong mantle lithosphere to hot asthenosphere in continental transform faults (e.g., San

  13. Prismatic Slip in PVT-Grown 4H-SiC Crystals

    NASA Astrophysics Data System (ADS)

    Guo, Jianqiu; Yang, Yu; Raghothamachar, Balaji; Kim, Jungyu; Dudley, Michael; Chung, Gilyong; Sanchez, Edward; Quast, Jeffrey; Manning, Ian

    2017-04-01

    Basal plane slip is the most frequently observed deformation mechanism in 4H-type silicon carbon (4H-SiC) single crystals grown by the physical vapor transport (PVT) method. However, it was recently reported that dislocations in such crystals can also glide in prismatic slip systems. In this study, we observed nonuniform distributions of three sets of prismatic dislocations in a commercial 4H-SiC substrate wafer. The nonuniformity is a result of the distribution of resolved shear stress on each prismatic slip system caused by radial thermal gradients in the growing crystal boule. A radial thermal model has been developed to estimate the thermal stress across the entire area of the crystal boule during PVT growth. The model results show excellent agreement with the observations, confirming that radial thermal gradients play a key role in activating prismatic slip in 4H-SiC during bulk growth.

  14. Prismatic Slip in PVT-Grown 4H-SiC Crystals

    NASA Astrophysics Data System (ADS)

    Guo, Jianqiu; Yang, Yu; Raghothamachar, Balaji; Kim, Jungyu; Dudley, Michael; Chung, Gilyong; Sanchez, Edward; Quast, Jeffrey; Manning, Ian

    2016-11-01

    Basal plane slip is the most frequently observed deformation mechanism in 4H-type silicon carbon (4H-SiC) single crystals grown by the physical vapor transport (PVT) method. However, it was recently reported that dislocations in such crystals can also glide in prismatic slip systems. In this study, we observed nonuniform distributions of three sets of prismatic dislocations in a commercial 4H-SiC substrate wafer. The nonuniformity is a result of the distribution of resolved shear stress on each prismatic slip system caused by radial thermal gradients in the growing crystal boule. A radial thermal model has been developed to estimate the thermal stress across the entire area of the crystal boule during PVT growth. The model results show excellent agreement with the observations, confirming that radial thermal gradients play a key role in activating prismatic slip in 4H-SiC during bulk growth.

  15. Slow earthquakes, preseismic velocity changes, and the origin of slow frictional stick-slip.

    PubMed

    Kaproth, Bryan M; Marone, C

    2013-09-13

    Earthquakes normally occur as frictional stick-slip instabilities, resulting in catastrophic failure and seismic rupture. Tectonic faults also fail in slow earthquakes with rupture durations of months or more, yet their origin is poorly understood. Here, we present laboratory observations of repetitive, slow stick-slip in serpentinite fault zones and mechanical evidence for their origin. We document a transition from unstable to stable frictional behavior with increasing slip velocity, providing a mechanism to limit the speed of slow earthquakes. We also document reduction of P-wave speed within the active shear zone before stick-slip events. If similar mechanisms operate in nature, our results suggest that higher-resolution studies of elastic properties in tectonic fault zones may aid in the search for reliable earthquake precursors.

  16. Scale effect of slip boundary condition at solid–liquid interface

    NASA Astrophysics Data System (ADS)

    Nagayama, Gyoko; Matsumoto, Takenori; Fukushima, Kohei; Tsuruta, Takaharu

    2017-03-01

    Rapid advances in microelectromechanical systems have stimulated the development of compact devices, which require effective cooling technologies (e.g., microchannel cooling). However, the inconsistencies between experimental and classical theoretical predictions for the liquid flow in microchannel remain unclarified. Given the larger surface/volume ratio of microchannel, the surface effects increase as channel scale decreases. Here we show the scale effect of the boundary condition at the solid–liquid interface on single-phase convective heat transfer characteristics in microchannels. We demonstrate that the deviation from classical theory with a reduction in hydraulic diameters is due to the breakdown of the continuum solid–liquid boundary condition. The forced convective heat transfer characteristics of single-phase laminar flow in a parallel-plate microchannel are investigated. Using the theoretical Poiseuille and Nusselt numbers derived under the slip boundary condition at the solid–liquid interface, we estimate the slip length and thermal slip length at the interface.

  17. Scale effect of slip boundary condition at solid–liquid interface

    PubMed Central

    Nagayama, Gyoko; Matsumoto, Takenori; Fukushima, Kohei; Tsuruta, Takaharu

    2017-01-01

    Rapid advances in microelectromechanical systems have stimulated the development of compact devices, which require effective cooling technologies (e.g., microchannel cooling). However, the inconsistencies between experimental and classical theoretical predictions for the liquid flow in microchannel remain unclarified. Given the larger surface/volume ratio of microchannel, the surface effects increase as channel scale decreases. Here we show the scale effect of the boundary condition at the solid–liquid interface on single-phase convective heat transfer characteristics in microchannels. We demonstrate that the deviation from classical theory with a reduction in hydraulic diameters is due to the breakdown of the continuum solid–liquid boundary condition. The forced convective heat transfer characteristics of single-phase laminar flow in a parallel-plate microchannel are investigated. Using the theoretical Poiseuille and Nusselt numbers derived under the slip boundary condition at the solid–liquid interface, we estimate the slip length and thermal slip length at the interface. PMID:28256536

  18. Scale effect of slip boundary condition at solid-liquid interface.

    PubMed

    Nagayama, Gyoko; Matsumoto, Takenori; Fukushima, Kohei; Tsuruta, Takaharu

    2017-03-03

    Rapid advances in microelectromechanical systems have stimulated the development of compact devices, which require effective cooling technologies (e.g., microchannel cooling). However, the inconsistencies between experimental and classical theoretical predictions for the liquid flow in microchannel remain unclarified. Given the larger surface/volume ratio of microchannel, the surface effects increase as channel scale decreases. Here we show the scale effect of the boundary condition at the solid-liquid interface on single-phase convective heat transfer characteristics in microchannels. We demonstrate that the deviation from classical theory with a reduction in hydraulic diameters is due to the breakdown of the continuum solid-liquid boundary condition. The forced convective heat transfer characteristics of single-phase laminar flow in a parallel-plate microchannel are investigated. Using the theoretical Poiseuille and Nusselt numbers derived under the slip boundary condition at the solid-liquid interface, we estimate the slip length and thermal slip length at the interface.

  19. Modeling yarn slip in woven fabric at the continuum level: Simulations of ballistic impact

    NASA Astrophysics Data System (ADS)

    Parsons, Ethan M.; King, Michael J.; Socrate, Simona

    2013-01-01

    Woven fabric is used in a wide variety of military and commercial products—both in neat form and as the reinforcement phase of composites. In many applications, yarn slip, the relative sliding of the yarns composing the weave, is an important mode of deformation or failure. Yarn slip can significantly change the energy absorption capacity and yarn density of the fabric and also cause yarns to unravel from the weave. Virtually all existing models for woven fabric that allow yarn slip are discrete in nature. They simulate every yarn in the weave and are therefore computationally expensive and difficult to integrate with other material models. A promising alternative to discrete models is the mesostructure-based continuum technique. With this technique, homogenized continuum properties are determined from a deforming analytic model of the fabric mesostructure at each material point. Yarn-level mechanisms of deformation are thus captured without the computational cost of simulating every yarn in the fabric. However, existing mesostructure-based continuum models treat the yarns as pinned together at the cross-over points of the weave, and an operative model that allows yarn slip has not been published. Here, we introduce a mesostructure-based continuum model that permits yarn slip and use the model to simulate the ballistic impact of woven fabric. In our approach, the weave is the continuum substrate on which the model is anchored, and slip of the yarns occurs relative to the weave continuum. The cross-over points of the weave act as the material points of the continuum, and the evolution of the local weave mesostructure at each point of the continuum is represented by state variables. At the same time, slip velocity fields simulate the slip of each yarn family relative to the weave continuum and therefore control the evolution of the yarn pitch. We found that simulating yarn slip significantly improves finite element predictions of the ballistic impact of a Kevlar

  20. The influence of footwear sole hardness on slip characteristics and slip-induced falls in young adults.

    PubMed

    Tsai, Yi-Ju; Powers, Christopher M

    2013-01-01

    Theoretically, a shoe that provides less friction could result in a greater slip distance and foot slipping velocity, thereby increasing the likelihood of falling. The purpose of this study was to investigate the effects of sole hardness on the probability of slip-induced falls. Forty young adults were randomized into a hard or a soft sole shoe group, and tested under both nonslippery and slippery floor conditions using a motion analysis system. The proportions of fall events in the hard- and soft-soled shoe groups were not statistically different. No differences were observed between shoe groups for average slip distance, peak and average heel velocity, and center of mass slipping velocity. A strong association was found between slip distance and the fall probability. Our results demonstrate that the probability of a slip-induced fall was not influenced by shoe hardness. Once a slip is induced, slip distance was the primary predictor of a slip-induced fall.

  1. Digital slip frequency generator and method for determining the desired slip frequency

    DOEpatents

    Klein, Frederick F.

    1989-01-01

    The output frequency of an electric power generator is kept constant with variable rotor speed by automatic adjustment of the excitation slip frequency. The invention features a digital slip frequency generator which provides sine and cosine waveforms from a look-up table, which are combined with real and reactive power output of the power generator.

  2. Rapid slip of the Gyaring Co fault in Central Tibet

    NASA Astrophysics Data System (ADS)

    Chung, Lingho; Chen, Yue-Gau; Cao, Zhongquan; Yin, Gongming; Kunz, Alexander; Fan, Anchuan; Wu, Tzu-Shuan; Xu, XiWei

    2015-04-01

    The Gyaring Co fault (GCF) is one of a series of active en echelon faults of the Karakoram-Jiali fault zone (KJFZ) in the Central Tibetan Plateau. It has been reported as a dextral fault, striking N50°-60°W at a rate of ca. 10 to 20 mm/yr (Armijo et al. 1989). Another en echelon fault, Beng Co fault (BCF), was located on the 1951 M8 event also implies the possibility of earthquake hazard at GCF. By interpreting high resolution satellite imageries, we are able to remap ~140 fault traces along the GCF. Combining optically stimulated luminescence (OSL) ages with the offset obtained from satellite imagery analysis and field survey, the slip rate along the GCF can be estimated as 12-17 mm/yr since ca. 80 ka. This study also focuses on a section of the western segment of the GCF, where the slip has been recognized to have occurred at 3.0 ± 1.6 m more than 7 times. This ~3 m slip implies MW 7.2-7.4 earthquakes recurring to the western segment in every 200 yrs, while reaching about MW 7.7 if both segments could break at the same time.

  3. Rapidly Activated Dynamic Phase Transitions in Nonlinear Solids

    DTIC Science & Technology

    1993-02-15

    I Form Approv# edAD -A263 601 AiENTA11ON PAGE- f____________18 1. AGENCY USE ONLY (Lea"e blaWk 12. REPORT DATE 13. REPORT TYPE AND OATES COVEREO Feb...phase transforming media during high energy impact. Conversion of mechanical energy to thermal ener- gy has been studied by means of an extended theory...and Phase Structures in General Media , R. Fosdick, E. Dunn & M. Slemrod eds., IMA volume series, Springer- Verlag. Song, J. and T. L. Pence (1992

  4. General Electric ATS Program technical review Phase 2 activities

    SciTech Connect

    Chance, T.; Smith, D.

    1995-12-31

    The Advanced Turbine Systems (ATS) Program Phase 2 objectives are to select a cycle, and to identify and resolve technical issues required to realize the ATS Program goals of 60% net combined cycle efficiency, single digit NOx, and a 10% electric power cost reduction, compared to current technology. The Phase 2 efforts have showns that the ATS Program goals are achievable. The GE Power Generation advanced gas turbine will use closed-loop steam cooling in the first two turbine stages and advanced coatings, seals and cooling designs to meet ATS performance and cost of electricity goals.

  5. Slip rate and slip magnitudes of past earthquakes along the Bogd left-lateral strike-slip fault (Mongolia)

    USGS Publications Warehouse

    Rizza, M.; Ritz, J.-F.; Braucher, R.; Vassallo, R.; Prentice, C.; Mahan, S.; McGill, S.; Chauvet, A.; Marco, S.; Todbileg, M.; Demberel, S.; Bourles, D.

    2011-01-01

    We carried out morphotectonic studies along the left-lateral strike-slip Bogd Fault, the principal structure involved in the Gobi-Altay earthquake of 1957 December 4 (published magnitudes range from 7.8 to 8.3). The Bogd Fault is 260 km long and can be subdivided into five main geometric segments, based on variation in strike direction. West to East these segments are, respectively: the West Ih Bogd (WIB), The North Ih Bogd (NIB), the West Ih Bogd (WIB), the West Baga Bogd (WBB) and the East Baga Bogd (EBB) segments. Morphological analysis of offset streams, ridges and alluvial fans-particularly well preserved in the arid environment of the Gobi region-allows evaluation of late Quaternary slip rates along the different faults segments. In this paper, we measure slip rates over the past 200 ka at four sites distributed across the three western segments of the Bogd Fault. Our results show that the left-lateral slip rate is ~1 mm yr-1 along the WIB and EIB segments and ~0.5 mm yr-1 along the NIB segment. These variations are consistent with the restraining bend geometry of the Bogd Fault. Our study also provides additional estimates of the horizontal offset associated with the 1957 earthquake along the western part of the Bogd rupture, complementing previously published studies. We show that the mean horizontal offset associated with the 1957 earthquake decreases progressively from 5.2 m in the west to 2.0 m in the east, reflecting the progressive change of kinematic style from pure left-lateral strike-slip faulting to left-lateral-reverse faulting. Along the three western segments, we measure cumulative displacements that are multiples of the 1957 coseismic offset, which may be consistent with a characteristic slip. Moreover, using these data, we re-estimate the moment magnitude of the Gobi-Altay earthquake at Mw 7.78-7.95. Combining our slip rate estimates and the slip distribution per event we also determined a mean recurrence interval of ~2500-5200 yr for past

  6. Slip rate and slip magnitudes of past earthquakes along the Bogd left-lateral strike-slip fault (Mongolia)

    USGS Publications Warehouse

    Prentice, Carol S.; Rizza, M.; Ritz, J.F.; Baucher, R.; Vassallo, R.; Mahan, S.

    2011-01-01

    We carried out morphotectonic studies along the left-lateral strike-slip Bogd Fault, the principal structure involved in the Gobi-Altay earthquake of 1957 December 4 (published magnitudes range from 7.8 to 8.3). The Bogd Fault is 260 km long and can be subdivided into five main geometric segments, based on variation in strike direction. West to East these segments are, respectively: the West Ih Bogd (WIB), The North Ih Bogd (NIB), the West Ih Bogd (WIB), the West Baga Bogd (WBB) and the East Baga Bogd (EBB) segments. Morphological analysis of offset streams, ridges and alluvial fans—particularly well preserved in the arid environment of the Gobi region—allows evaluation of late Quaternary slip rates along the different faults segments. In this paper, we measure slip rates over the past 200 ka at four sites distributed across the three western segments of the Bogd Fault. Our results show that the left-lateral slip rate is∼1 mm yr–1 along the WIB and EIB segments and∼0.5 mm yr–1 along the NIB segment. These variations are consistent with the restraining bend geometry of the Bogd Fault. Our study also provides additional estimates of the horizontal offset associated with the 1957 earthquake along the western part of the Bogd rupture, complementing previously published studies. We show that the mean horizontal offset associated with the 1957 earthquake decreases progressively from 5.2 m in the west to 2.0 m in the east, reflecting the progressive change of kinematic style from pure left-lateral strike-slip faulting to left-lateral-reverse faulting. Along the three western segments, we measure cumulative displacements that are multiples of the 1957 coseismic offset, which may be consistent with a characteristic slip. Moreover, using these data, we re-estimate the moment magnitude of the Gobi-Altay earthquake at Mw 7.78–7.95. Combining our slip rate estimates and the slip distribution per event we also determined a mean recurrence interval of∼2500

  7. Nonvolcanic tremors and their correlation with slow slip events in Mexico

    NASA Astrophysics Data System (ADS)

    Kolstoglodov, V.; Shapiro, N. M.; Larson, K.; Payero, J.; Husker, A.; Santiago, L. A.; Clayton, R.; Peyrat, S.

    2009-04-01

    Significant activity of nonvolcanic tremor (NVT) has been observed in the central Mexico (Guerrero) subduction zone since 2001 when continuous seismic records became available. Albeit the quality of these records is poor, it is possible to estimate a temporal variation of energy in the range of 1-2Hz (best signal/noise ratio for the NVT), which clearly indicate the maximum of NVT energy release (En) during the 2001-2002 and 2006 large aseismic slow slip events (SSE) registered by a GPS network. In particular the En is higher for the 2001-2002 SSE which had larger surface displacements and extension than the 2006 SSE. A more detailed and accurate study of NVT activity was carried out using the data collected during the MASE experiment in Mexico. MASE consisted of 100 broad band seismometers in operation for ~2.5 years (2005-2007) along the profile oriented SSW-NNE from Acapulco, and crossing over the subduction zone for a distance of ~500 km. Epicenters and depths of individual tremor events determined using the envelope cross-correlation technique have rather large uncertainties partly originated from the essentially 2D geometry of the network. The "energy" approach is more efficient in this case because it provides an average NVT activity evolution in time and space. The data processing consists of a band pass (1-2Hz) filter of the raw 100 Hz sampled N-S component records, application a 10 min-width median filter to eliminate an effect of local seismic events and noise, and integration of the energy and normalization of daily En using an average coda amplitude from several regional earthquakes of M~5. A time-space distribution of En reveals a strong correlation between NVT energy release and 2006 SSE, which also replicates the two-phase character of this slow event and a migration of the slow slip maximum from North to South. There are also a few clear episodes of relatively high NVT energy release that do not correspond to any significant geodetic signal in GPS

  8. Effects of cobalt concentration on the relative resistance to octahedral and cube slip in nickel-base superalloys

    NASA Astrophysics Data System (ADS)

    Bobeck, Gene E.; Miner, R. V.

    1988-11-01

    Compression yielding tests at 760 °C were performed on near [001]- and [lll]-oriented crystals of the Ni-base superalloys René 150 and a modified MAR-M247, both having two different Co concentrations. Octahedral and cube slip occurred for the near [001]- and [lll]-oriented crystals, respectively, for all compositions. For both alloy bases, increasing Co concentration was found to decrease the critical resolved shear stress for octahedral slip but to have little effect on that for cube slip. In the present work, phase analyses and variations in heat treatment indicated that the effects of Co concentration observed were not due simply to changes in the volume fraction or size of the γ' phase. It is suggested that decreasing complex stacking fault energy in the γ' with increasing Co would lead to the observed effects based on current interpretations of the dislocation locking mechanism by cube cross slip in the γ'.

  9. Aseismic Slip Events along the Southern San Andreas Fault System Captured by Radar Interferometry

    SciTech Connect

    Vincent, P

    2001-10-01

    A seismic slip is observed along several faults in the Salton Sea and southernmost Landers rupture zone regions using interferometric synthetic aperture radar (InSAR) data spanning different time periods between 1992 and 1997. In the southernmost Landers rupture zone, projecting south from the Pinto Mountain Fault, sharp discontinuities in the interferometric phase are observed along the sub-parallel Burnt Mountain and Eureka Peak Faults beginning three months after the Landers earthquake and is interpreted to be post-Landers after-slip. Abrupt phase offsets are also seen along the two southernmost contiguous 11 km Durmid Hill and North Shore segments of the San Andreas Fault with an abrupt termination of slip near the northern end of the North Shore Segment. A sharp phase offset is seen across 20 km of the 30 km-long Superstition Hills Fault before phase decorrelation in the Imperial Valley along the southern 10 km of the fault prevents coherent imaging by InSAR. A time series of deformation interferograms suggest most of this slip occurred between 1993 and 1995 and none of it occurred between 1992 and 1993. A phase offset is also seen along a 5 km central segment of the Coyote Creek fault that forms a wedge with an adjoining northeast-southwest trending conjugate fault. Most of the slip observed on the southern San Andreas and Superstition Hills Faults occurred between 1993 and 1995--no slip is observed in the 92-93 interferograms. These slip events, especially the Burnt Mountain and Eureka Peak events, are inferred to be related to stress redistribution from the June, 1992 M{sub w} = 7.3 Landers earthquake. Best-fit elastic models of the San Andreas and Superstition Hills slip events suggest source mechanisms with seismic moments over three orders of magnitude larger than a maximum possible summation of seismic moments from all seismicity along each fault segment during the entire 4.8-year time interval spanned by the InSAR data. Aseismic moment releases of this

  10. The effect of shoe material on the kinetics and kinematics of foot slip at impact on concrete.

    PubMed

    Pardoe, C H; McGuigan, M P; Rogers, K M; Rowe, L L; Wilson, A M

    2001-04-01

    Previous studies on shoeing have demonstrated that shoe material alters the time taken from foot impact to the foot stopping sliding (slip time) and the distance slid. These are assumed to reflect differences in the craniocaudal ground reaction force (GRF) between the shoe and the ground during foot slip. This study tested the hypothesis that the slip time and distance are reflected in the resistance to slippage of the foot after impact. The forefeet of 8 horses were shod in horseshoes constructed of steel, plastic and rubber. Each horse was trotted for 8 placements per forefoot in each shoe type over a concrete topped forceplate and simultaneous kinematic data recorded at 240 Hz. Slip distance and slip time were calculated from the kinematic data and craniocaudal (Fy), and vertical (Fz) GRFs determined during slip the averaged for each shoe type. The slip time and distance were variable between runs in all 3 shoe types, and there was no significant difference between the mean values for the 3 shoe types. Fy reached a value of 0.98 +/- 0.17 N/kg during slip in the plastic shoes which was significantly lower than the rubber shoes, at 1.13 +/- 0.17 N/kg, P = 0.02. The Fy/Fz ratio (a measure of dynamic friction) was significantly lower in the plastic shoes, 0.34 +/- 0.08, compared to the steel shoes, 0.46 +/- 0.04, P = 0.003. This study is being extended to investigate effects of shoe slippage at the end of the stance phase and the energy dissipation during foot slip in the different shoe types. Future investigations should aim to identify the optimum slip characteristics to modulate loading (magnitude and rate) during impact, with the aim of reducing the risk of injury.

  11. Phenomenological model of propagation of the elastic waves in a fluid-saturated porous solid with nonzero boundary slip velocity.

    PubMed

    Tsiklauri, David

    2002-09-01

    It is known that a boundary slip velocity starts to play an important role when the length scale over which the fluid velocity changes approaches the slip length, i.e., when the fluid is highly confined, for example, fluid flow through porous rock or blood vessel capillaries. Zhu and Granick [Phys. Rev. Lett. 87, 096105 (2001)] have recently experimentally established the existence of a boundary slip in a Newtonian liquid. They reported typical values of the slip length of the order of few micrometers. In this light, the effect of introduction of the boundary slip into the theory of propagation of elastic waves in a fluid-saturated porous medium formulated by Biot [J. Acoust. Soc. Am. 28, 179-191 (1956)] is investigated. Namely, the effect of introduction of boundary slip upon the function F(kappa) that measures the deviation from Poiseuille flow friction as a function of frequency parameter kappa is studied. By postulating phenomenological dependence of the slip velocity upon frequency, notable deviations in the domain of intermediate frequencies in the behavior of F(kappa) are introduced with the incorporation of the boundary slip into the model. It is known that F(kappa) crucially enters Biot's equations, which describe dynamics of fluid-saturated porous solid. Thus, consequences of the nonzero boundary slip by calculating the phase velocities and attenuation coefficients of both rotational and dilatational waves with the variation of frequency are investigated. The new model should allow one to fit the experimental seismic data in circumstances when Biot's theory fails, as the introduction of phenomenological dependence of the slip velocity upon frequency, which is based on robust physical arguments, adds an additional degree of freedom to the model. In fact, it predicts higher than the Biot's theory values of attenuation coefficients of the both rotational and dilatational waves in the intermediate frequency domain, which is in qualitative agreement with the

  12. Frictional Evolution of Schists during Seismic Slip

    NASA Astrophysics Data System (ADS)

    Chae, S.; Ree, J.; Hirose, T.; Lee, S.

    2012-12-01

    Pseudotachylytes (PT) of pelitic rocks are relatively rare, although there have been some reports on natural and experimental PT of argillites and siltstones. Thus our knowledge on earthquake mechanics in pelitic rocks is limited. The conventional wisdom for the rare occurrence of pelitic PT is that dehydration of phyllosilicate minerals due to frictional heating during seismic slip increases the pore pressure and facilitates thermal pressurization to work as a main slip weakening mechanism. We performed high-velocity-rotary-shear experiments on mica schists at seismic slip rates (up to 1.3 ms-1) and at normal stress of 2-16 MPa to understand the earthquake faulting mechanics and microstructural evolution of metapelites. The simulated fault zones show two transient peak frictions followed by a final slip weakening to reach a steady-state friction with friction coefficient of 0.16 to 0.5. The steady-state friction decreases with an increase in slip velocity, indicating a velocity-weakening behavior. Also, steady-state friction decreases with an increase in normal stress. The fault zone consists of a principal slip zone (PSZ) mantled by damage zone (DZ). The fracture density and grain size in DZ increases and decreases toward PSZ, respectively. The quartz grains of DZ tend to exhibit patchy undulose extinction and deformation bands, while those of the wall rock are mostly strain-free. Biotite grains of DZ become darker toward the PSZ in plane-polarized light and the darker color is presumably due to tiny holes produced by incipient dehydration of biotite. The PSZ is a molten layer laden with clasts of quartz and plagioclase. The melt composition of the central PSZ is felsic, whereas that of the marginal PSZ is mafic. To figure out the reason for the compositionally layered configuration of the melt in PSZ, microstructural analyses using electron microscopies and correlation of microstructural evolution with mechanical evolution are underway.

  13. Up-dip partitioning of displacement components on the oblique-slip Clarence Fault, New Zealand

    NASA Astrophysics Data System (ADS)

    Nicol, Andrew; Van Dissen, Russell

    2002-09-01

    Active strike-slip faults in New Zealand occur within an obliquely-convergent plate boundary zone. Although the traces of these faults commonly delineate the base of mountain ranges, they do not always accommodate significant shortening at the free surface. Along the active trace of Clarence Fault in northeastern South Island, New Zealand, displaced landforms and slickenside striations indicate predominantly horizontal displacements at the ground surface, and a right-lateral slip rate of ca. 3.5-5 mm/year during the Holocene. The Inland Kaikoura mountain range occupies the hanging wall of the fault and rises steeply from the active trace to altitudes of ca. 3 km. The geomorphology of the range indicates active uplift and mountain building, which is interpreted to result, in part, from a vertical component of fault slip at depth. These data are consistent with the fault accommodating oblique-slip at depth aligned parallel to the plate-motion vector and compatible with regional geodetic data and earthquake focal-mechanisms. Oblique-slip on the Clarence Fault at depth is partitioned at the free surface into: (1) right-lateral displacement on the fault, and (2) hanging wall uplift produced by distributed displacement on small-scale faults parallel to the main fault. Decoupling of slip components reflects an up-dip transfer of fault throw to an off-fault zone of distributed uplift. Such zones are common in the hanging walls of thrusts and reverse faults, and support the idea that the dip of the oblique-slip Clarence Fault steepens towards the free surface.

  14. Approach to In- Situ Producing Reinforcing Phase Within an Active-Transient Liquid Phase Bond Seam for Aluminum Matrix Composite

    NASA Astrophysics Data System (ADS)

    Zhang, Guifeng; Liao, Xianjin; Chen, Bo; Zhang, Linjie; Zhang, Jianxun

    2015-06-01

    To optimize the braze composition design route for aluminum matrix composite, the feasibility of in situ producing reinforcing phase within the transient liquid phase bond seam matrix, by adding active melting point increaser (MPI, e.g., Ti) together with general melting point depressant (MPD, e.g., Cu) into the interlayer, was demonstrated. For SiC p /A356 composite, by comparing the wettability, joint microstructure, joint shear strength, and fracture path for the developed Al-19Cu-1Ti, Al-19Cu, Al-33Cu-1Ti, Al-33Cu (wt pct), and commercial Cu foils as interlayer, the feasibility of in situ producing reinforcing phase within the bond seam by adding Ti was demonstrated. Especially for Al-19Cu-1Ti active braze, small and dispersed ternary aluminide of Al-Si-Ti phase was obtained within the bond seam as in situ reinforcement, leading to a favorable fracture path within SiC p /A356, not along the initial interface or within the bond seam. For the formation mechanism of the in situ reinforcing phase of MPI-containing intermetallic compound within the bond seam, a model of repeating concentration-precipitation-termination-engulfment during isothermal solidification is proposed.

  15. Dynamical Transitions between Stick-Slip and Steady Motions of Bistable Units with Global and Asymmetric Local Interactions

    NASA Astrophysics Data System (ADS)

    Yamazaki, Yoshihiro

    2017-04-01

    For a system consisting of bistable units with global and asymmetric local interactions, there exist two different types of dynamical transition between stick-slip and steady motions: continuous and discontinuous in the amplitude of stick-slip motion. These two types are consistent with the experimental findings in a dry friction system. The dynamical phase diagram and other types of transition are also discussed.

  16. Slip length measurement of gas flow

    NASA Astrophysics Data System (ADS)

    Maali, Abdelhamid; Colin, Stéphane; Bhushan, Bharat

    2016-09-01

    In this paper, we present a review of the most important techniques used to measure the slip length of gas flow on isothermal surfaces. First, we present the famous Millikan experiment and then the rotating cylinder and spinning rotor gauge methods. Then, we describe the gas flow rate experiment, which is the most widely used technique to probe a confined gas and measure the slip. Finally, we present a promising technique using an atomic force microscope introduced recently to study the behavior of nanoscale confined gas.

  17. Slipping processes in residual badlands reliefs

    NASA Astrophysics Data System (ADS)

    Díaz-Hernández, Jose Luis; Yepes, Jorge

    2010-05-01

    We define slips as structures developed by more or less saturated colloidal suspension that slide down the walls of residual reliefs found in badlands. These suspensions seem to originate in the soils crowning gully reliefs and also from rainwater dripping onto the walls of poorly cemented sediments such as siltstone. We call this process slipping and the resulting morphologies represent a group of minor badlands forms, often linked to piping and fluting. Slipping occurs according to the following sequence of forms: 1. Mud droplets. These are irregular linear structures caused by mud droplets sliding down sub-vertical walls. The droplet is usually found at the end of a small channel. These morphologies represent the course of the sliding droplets that become fossilized and not the impact of the droplets on the sediment. 2. Slips sensu stricto. These are uninterrupted surface structures covering sub-vertical walls to a greater or lesser extent. The thickness of this type of covering varies from a few millimetres to 5cm. The inner structure of the slips consists of small laminas (» 100mm) and on the exterior they often present drip channels. A special case of these forms is butterfly structures, which appear in isolation, with repetitive patterns and the appearance of a winged insect stuck to the wall. 3. Pseudo-stalactites. These are free-standing conical regrowths with some similarity to stalactites in a karst cave. They occur when slips grow to over 5cm thick. The growth of these forms is similar to that of slips, with external superposition of fine, concentric layers with no central pore. A variety of these pseudo-stalactites are nodulous stalactites whose genesis is unknown. In this context, we should mention the existence of occasional stalagmites. In other cases, curtains of pseudo-stalactites can be found where these patterns are repeated finely. A more evolved stage of this form is the coalescence of pseudo-stalactites, representing a massive advance of

  18. Structural and stress analysis based on fault-slip data in the Amman area, Jordan

    NASA Astrophysics Data System (ADS)

    Diabat, Abdullah A.

    2009-08-01

    This study presents a structural analysis based on hundreds of striated small faults (fault-slip data) in the Amman area east of the Dead Sea Transform System. Stress inversion of the fault-slip data was performed using an improved Right-Dihedral method, followed by rotational optimization (TENSOR Program, Delvaux, 1993). Fault-slip data (totaling 212) include fault planes, striations and sense of movements, are obtained from the Turonian Wadi As Sir Formation, distributed mainly along the southern side of the Amman - Hallabat structure in Jordan the study area. Results show that σ1 (SHmax) and σ3 (SHmin) are generally sub-horizontal and σ2 is sub-vertical in 8 of 11 paleostress tensors, which are belonging to a major strike-slip system with σ1 swinging around N to NW direction. The other three stress tensors show σ2 (SHmax), σ1 vertical and σ3 is NE oriented. This situation explained as permutation of stress axes σ1 and σ2 that occur during tectonic events and partitioned strike slip deformation. NW compressional stresses affected the area and produced the major Amman - Hallabat strike-slip fault and its related structures, e.g., NW trending normal faults and NE trending folds in the study area. The new paleostress results related with the active major stress field of the region the Dead Sea Stress Field (DSS) during the Miocene to Recent.

  19. Novel Cross-Slip Mechanism of Pyramidal Screw Dislocations in Magnesium

    NASA Astrophysics Data System (ADS)

    Itakura, Mitsuhiro; Kaburaki, Hideo; Yamaguchi, Masatake; Tsuru, Tomohito

    2016-06-01

    Compared to cubic metals, whose primary slip mode includes twelve equivalent systems, the lower crystalline symmetry of hexagonal close-packed metals results in a reduced number of equivalent primary slips and anisotropy in plasticity, leading to brittleness at the ambient temperature. At higher temperatures, the ductility of hexagonal close-packed metals improves owing to the activation of secondary ⟨c +a ⟩ pyramidal slip systems. Thus, understanding the fundamental properties of corresponding dislocations is essential for the improvement of ductility at the ambient temperature. Here, we present the results of large-scale ab initio calculations for ⟨c +a ⟩ pyramidal screw dislocations in magnesium and show that their slip behavior is a stark counterexample to the conventional wisdom that a slip plane is determined by the stacking fault plane of dislocations. A stacking fault between dissociated partial dislocations can assume a nonplanar shape with a negligible energy cost and can migrate normal to its plane by a local shuffling of atoms. Partial dislocations dissociated on a {2 1 ¯ 1 ¯ 2 } plane "slither" in the {01 1 ¯1 } plane, dragging the stacking fault with them in response to an applied shear stress. This finding resolves the apparent discrepancy that both {2 1 ¯1 ¯2 } and {01 1 ¯1 } slip traces are observed in experiments while ab initio calculations indicate that dislocations preferably dissociate in the {2 1 ¯1 ¯2 } planes.

  20. Bond slip detection of steel plate and concrete beams using smart aggregates

    NASA Astrophysics Data System (ADS)

    Qin, Feng; Kong, Qingzhao; Li, Mo; Mo, Y. L.; Song, Gangbing; Fan, Feng

    2015-11-01

    The newly emerged steel plate concrete (SC), benefited from a composite effect of steel and concrete materials, has been applied to shield building and internal structures of AP1000 nuclear power plants. The detection of bond-slip between steel plate and concrete is of great importance to provide early warnings of steel plate and concrete debonding and to ensure the safety of SC structures. In this paper, an active sensing approach using smart aggregates (SAs) is developed to detect the initiation and to monitor the development of bond-slip. A SA, designed by sandwiching a fragile piezoceramic patch between protection materials, can be utilized as both actuator and sensor by taking advantage of the piezoelectricity of piezoceramic material. Two SC beams with distinct shear reinforcement ratios ≤ft({ρ }t\\right) were experimentally investigated. Based on the wavelet packet decomposition of the received signals from SAs, the initiation of bond-slip is detected, and the development of bond-slip is quantitatively monitored to better understand the structural performance of SC beams, including the stiffness and capacity. The bond-slip severities of the two SC beams are compared to study the improvement of bond-slip condition rendered by providing more shear reinforcement.

  1. Neotectonics of a subduction/strike-slip transition: the northeastern Dominican Republic

    SciTech Connect

    Winslow, M.A.; McCann, W.R.

    1985-01-01

    The Septentrional fault system in the northeastern Dominican Republic marks the zone where the North American-Carribean plate boundary is evolving from subduction to strike-slip motion, and where terranes appear to be forming and migrating laterally in a subduction complex/forearc region. On the Island of Hispaniola, slip vectors are oblique to the strike of the Puerto Rico trench, and oblique subduction thrusts the upper plate over normal seafloor. The offshore geology and seismicity of the northern Caribbean suggest that uplift, broad crustal warping, thrusting, and strike-slip faulting (ie. collisional tectonics) should be present in the northern part of the Dominican Republic. The high topography (>1000m), high levels of seismicity, and large earthquakes support the hypothesis of contemporary deformation in Hispaniola. In this region, the subduction regime dies out toward the west, and deformation is transferred to onshore, oblique-slip faults. As this change in tectonic style has occurred in Neogene to Recent times, we are investigating the modern evolution of a plate boundary. We have already documented: (1) the presence of a strike-slip faulting in the northeastern Dominican Republic; (2) an anomalous push-up structure; and (3) a region of numerous splay faults. In conclusion, recent seismicity suggest a wide zone of deformation and variations in interplate motions near Hispaniola. This island lies at the western limit of active underthrusting and at the eastern limit of onshore faulting, i.e., at an important transition from a subduction to strike-slip regime.

  2. Oscillatory activity, phase differences, and phase resetting in the inferior olivary nucleus.

    PubMed

    Lefler, Yaara; Torben-Nielsen, Benjamin; Yarom, Yosef

    2013-01-01

    The generation of temporal patterns is one of the most fascinating functions of the brain. Unlike the response to external stimuli temporal patterns are generated within the system and recalled for a specific use. To generate temporal patterns one needs a timing machine, a "master clock" that determines the temporal framework within which temporal patterns can be generated and implemented. Here we present the concept that in this putative "master clock" phase and frequency interact to generate temporal patterns. We define the requirements for a neuronal "master clock" to be both reliable and versatile. We introduce this concept within the inferior olive nucleus which at least by some scientists is regarded as the source of timing for cerebellar function. We review the basic properties of the subthreshold oscillation recorded from olivary neurons, analyze the phase relationships between neurons and demonstrate that the phase and onset of oscillation is tightly controlled by synaptic input. These properties endowed the olivary nucleus with the ability to act as a "master clock."

  3. Recent Findings on the Nature of Episodic Tremor and Slip Along the Northern Cascadia Margin

    NASA Astrophysics Data System (ADS)

    Dragert, H.; Wang, K.; Kao, H.

    2008-12-01

    Episodic Tremor and Slip (ETS), as observed along the northern Cascadia margin, has been defined empirically as repeated, transient ground motions at a plate margin, roughly opposite to longer-term interseismic deformation, occurring synchronously with low-frequency, emergent seismic signals. Although the exact causal processes are still a matter of debate, recent improvements in the monitoring of these transient events provide clearer constraints for the location and the migration of both tremor and slip. In areal distribution, the tremors continue to occur in a band overlying the 25 to 55 km depth contours of the nominal subducting plate interface. The previously reported extended depth distribution of tremor is also observed for the most recent tremor episodes, as is the coincidence of peak tremor activity with a band of seismic reflectors that is commonly interpreted to be positioned above the plate interface. In these episodes, tremors migrate along strike of the subduction zone from the southeast to the northwest at speeds ranging from 5 to 13 km/day. Tremor data also show changes in migration speed during the course of a single episode. No systematic migration in depth has yet been resolved. Denser GPS monitoring and the introduction of borehole strainmeters have also led to a better definition of the ETS surface deformations patterns, including those derived from the vertical GPS component. Inversion of the GPS data, constrained by limiting slip to the currently accepted plate interface, results in an area of slip that parallels the strike of the subduction zone, overlapping with but narrower than the band of tremor distribution and displaced slightly seaward. Inversion constrained by a shallower occurrence of slip, on or near the reflector band, results in a broader distribution of slip with reduced magnitudes. This would be more commensurate with the wider distribution of tremor. The current GPS deformation data are unable to tell whether the slip could

  4. A new perspective on the Guerrero gap: Slow slip events and tremors

    NASA Astrophysics Data System (ADS)

    Radiguet, Mathilde; Campillo, Michel

    2010-05-01

    The slow slip events (SSE) that have been detected in several subduction zones are characterized by an important variability (in terms of duration, migration, recurrence time). The physical mechanisms responsible for their occurrence and their role in the mechanical evolution leading to large thrust classic earthquakes are still unclear. Two of the largest events recorded occurred in 2002 and 2006 in the Guerrero segment of the Mexican subduction zone. These events where recorded by 8 and 15 continuous GPS stations respectively, and give us a good opportunity to constrain the characteristics of large SSEs. The total slip during the 2006 SSE has been also measured with InSAR. Combining GPS and InSAR allows a detailed study of the spatial and temporal evolution of slip at depth. We inverted the cumulative GPS displacements to find the distribution of total slip on the fault plane during the 2002 and 2006 SSEs. The two events show significantly different slip distributions, both extending in the deeper part of the seismogenic zone and in the transition zone. For the 2006 SSE, we modeled the spatial and temporal evolution of slip on the subduction interface by inverting the GPS time series. We assumed a functional form for the slip function, and we inverted for the slip amplitude, the initiation time and the duration, using a linearized least-square inversion procedure. The rupture initiated at a depth of 40 km (transition zone), in the western part of the Guerrero gap, and propagated with an average velocity of 1.2 km/day (with regional variations). The rise time (duration of slip in each cell) is about 170 days and the total duration of the event is 11-12 months. We also analyzed the energy of seismic records to detect non-volcanic tremors (NVT). We found that NVT are not synchronous with SSE slip and are separated spatially with the zones of large slip of the SSE. It is nevertheless observed that the NVT activity increased during the 2006 SSE. G-GAP team (LGIT

  5. Vaginal cone use in passive and active phases in patients with stress urinary incontinence

    PubMed Central

    Haddad, Jorge Milhem; Ribeiro, Ricardo Muniz; Bernardo, Wanderley Marques; Abrão, Maurício Simões; Baracat, Edmund Chada

    2011-01-01

    OBJECTIVE: To evaluate vaginal cone therapy in two phases, passive and active, in women with stress urinary incontinence. METHODS: A prospective study was conducted at the Department of Obstetrics and Gynecology, São Paulo University, Brazil. Twenty-four women with a clinical and urodynamic diagnosis of stress urinary incontinence were treated with vaginal cones in a passive phase (without voluntary contractions of the pelvic floor) and an active phase (with voluntary contractions), each of which lasted three months. Clinical complaints, a functional evaluation of the pelvic floor, a pad test, and bladder neck mobility were analyzed before and after each phase. RESULTS: Twenty-one patients completed the treatment. The reduction in absolute risk with the pad test was 0.38 (p<0.034) at the end of the passive phase and 0.67 (p<0.0001) at the end of the active phase. The reduction in absolute risk with the pelvic floor evaluation was 0.62 (p<0.0001) at the end of the passive phase and 0.77 (p<0.0001) at the end of the active phase. The reduction in absolute risk of bladder neck mobility was 0.38 (p<0.0089) at the end of the passive phase and 0.52 (p<0.0005) at the end of the active phase. Complete reversal of symptomatology was observed in 12 (57.1%) patients, and satisfaction was expressed by 19 (90.4%). CONCLUSION: Using vaginal cones in the passive phase, as other researchers did, was effective. Inclusion of the active phase led to additional improvement in all of the study parameters evaluated in women with stress urinary incontinence. Randomized studies are needed, however, to confirm these results. PMID:21789381

  6. Analysis of the Seismic Activity During the Preparatory Phase of the Mw 8.2 Iquique Earthquake, Chile 2014

    NASA Astrophysics Data System (ADS)

    Aden-Antoniow, F.; Satriano, C.; Poiata, N.; Bernard, P.; Vilotte, J. P.; Aissaoui, E. M.; Ruiz, S.; Schurr, B.; Sobiesiak, M.

    2015-12-01

    The 2014 Iquique seismic crisis, culminating with the main Mw 8.2 Iquique earthquake (Chile), 1st of April 2014, and the largest Mw 7.7 aftershock, 3rd of April, highlighted a complex unlocking of the North Chile subduction interface. Indeed, during many months preceding this event, at least three large seismic clusters have been observed, in July 2013, in January and in March 2014. Their location and final migration towards the mainshock rupture area represents the main motivation of this work.We built a new, more complete catalogue for the period over December 2013 to March 2014 in Northern Chile, using a new automated array method for earthquake detection and location [Poiata et al. 2015]. With the data-set provided by the IPOC and ILN networks, we detected an average of 8000 events per month, forty times more than the catalogue produced by Centro Sismologico National del Chile. The new catalogue decreases the magnitude of completeness by more than two units, from 3.3 to 1.2. We observe two shallow clusters offshore of the cities of Iquique and Pisagua in January 2014, and a strong one covering the rupture zone of Mw 8.2 mainshock in March. A spatial-temporal statistical analysis of these three clusters allows us to better characterize the whole preparatory phase. We interpret our results in light of the location, timing and energy of several aseismic slip events, evidenced by Boudin et al. [AGU 2014], which coincide with the seismic clusters. We propose that the preparatory phase of the Iquique earthquake consists of a complex interplay of seismic and aseismic slip along the subduction surface. Furthermore, our analysis raises new questions regarding the complex slip during the Mw 7.7 aftershock, and the spatial variation of the effective coupling along the subduction interface, imaged by GPS studies, suggesting new research direction that will be outlined.

  7. Along strike-slip faults, do fault segments exist and how long are they ? (Invited)

    NASA Astrophysics Data System (ADS)

    Klinger, Y.; Rockwell, T. K.; Cubas, N.; Souloumiac, P.

    2013-12-01

    The existence of relay zones and bends along strike-slip faults has long been recognized. The control of such geometrical asperities in initiation and arrest of seismic ruptures has been documented in many cases, suggesting they have a key role in the structure along strike of strike-slip faults. We produced dense slip distribution for two large strike-slip earthquakes, the 2001 Kunlun earthquake and the 1940 Imperial fault earthquake. In the Kunlun case we correlated satellite images acquired before and after the event to obtain a slip distribution of 1 point/km over 300 km. For the Imperial fault earthquake, we used a set of low altitude aerial photos that were flown just after the earthquake. The resolution of the photos is good enough to allow us to measure offsets of hundreds of plow lines along the trace of the rupture. In both cases the amplitude of the slip varies at a scale of several kilometers. In the case of Kunlun, the correlation between slip variations and jogs or side faults branching off the main rupture is straightforward. In the case of the Imperial fault, where long-term morphology is not preserved because of anthropic activities, still the slip distribution corresponds well with the slip patches determined independently by seismologists. These two examples strongly suggest that the segmentation of the fault controls the way seismic ruptures propagate along strike-slip faults. A more systematic exploration of slip maps derived from kinematic inversions of geophysical data shows that beyond variation due to different methodology and data, the lateral size of slip patches derived from such geophysical studies saturates around 20 km, independently of the earthquake magnitude. In parallel, using the available dataset of well documented ground ruptures maps for strike slip earthquakes, we designed an automatic procedure to quantify the minimum number of connected strait lines, approximating fault segment, needed to fit the rupture trace. The

  8. GENERALIZATION OF TREADMILL-SLIP TRAINING TO PREVENT A FALL FOLLLOWING A SUDDEN (NOVEL) SLIP IN OVER-GROUND WALKING

    PubMed Central

    Yang, Feng; Bhatt, Tanvi; Pai, Yi-Chung

    2012-01-01

    The purposes of the study were to determine 1) whether treadmill-slip training could reduce the likelihood of falls during a novel slip in over-ground walking, and 2) to what extent such (indirect) training would be comparable to (direct) over-ground-slip training. A treadmill-slip training group (Group A, n=17) initially experienced repeated perturbations on treadmill intended to simulate forward-slip in over-ground walking. Perturbation continued and its intensity reduced when necessary to ensure subjects’ successful adaptation (i.e., when they could land their trailing foot ahead of the slipping foot in at least 3 of 5 consecutive trials). They then experienced a novel slip during over-ground walking. Another 17 young adults in Group B experienced an identical novel slip that served as the controls. They then underwent more slip trials during over-ground walking. Their 16th slip trial was analyzed to represent the over-ground-slip training effect. Eight subjects (47%) in Group A fell upon their first treadmill slip, while all adapted successfully after a minimum of 15 slip trials. Upon the novel slip during over-ground walking, none of them fell in comparison to four subjects (23.5%) fell in Group B upon the same trial (p<0.05). Group A’s control of stability, both proactive and reactive, was significantly better than that of Group B’s on their first over-ground slip, while the level of improvement derived from indirect treadmill training was not as strong as that from direct over-ground-slip training, as demonstrated in Group B’s 16th slip trial (p<0.001). These results clearly demonstrated the feasibility of fall reduction through treadmill-slip training. PMID:23141636

  9. Support for the slip hypothesis from whisker-related tactile perception of rats in a noisy environment

    PubMed Central

    Waiblinger, Christian; Brugger, Dominik; Whitmire, Clarissa J.; Stanley, Garrett B.; Schwarz, Cornelius

    2015-01-01

    Rodents use active whisker movements to explore their environment. The “slip hypothesis” of whisker-related tactile perception entails that short-lived kinematic events (abrupt whisker movements, called “slips”, due to bioelastic whisker properties that occur during active touch of textures) carry the decisive texture information. Supporting this hypothesis, previous studies have shown that slip amplitude and frequency occur in a texture-dependent way. Further, experiments employing passive pulsatile whisker deflections revealed that perceptual performance based on pulse kinematics (i.e., signatures that resemble slips) is far superior to the one based on time-integrated variables like frequency and intensity. So far, pulsatile stimuli were employed in a noise free environment. However, the realistic scenario involves background noise (e.g., evoked by rubbing across the texture). Therefore, if slips are used for tactile perception, the tactile neuronal system would need to differentiate slip-evoked spikes from those evoked by noise. To test the animals under these more realistic conditions, we presented passive whisker-deflections to head-fixed trained rats, consisting of “slip-like” events (waveforms mimicking slips occurring with touch of real textures) embedded into background noise. Varying the (i) shapes (ramp or pulse); (ii) kinematics (amplitude, velocity, etc.); and (iii) the probabilities of occurrence of slip-like events, we observed that rats could readily detect slip-like events of different shapes against noisy background. Psychophysical curves revealed that the difference of slip event and noise amplitude determined perception, while increased probability of occurrence (frequency) had barely any effect. These results strongly support the notion that encoding of kinematics dominantly determines whisker-related tactile perception while the computation of frequency or intensity plays a minor role. PMID:26528148

  10. Recovery Efficiency Test Project Phase 2 activity report, Volume 1

    SciTech Connect

    Overbey, W.K. Jr.; Salamy, S.P.; Locke, C.D.

    1989-02-01

    The purpose of Phase II operations of the Recovery Efficiency Test Project is to enhance the natural production of the well and evaluate the relative improvement as a function of the type of stimulation conducted. Another purpose is to compare the stimulated production performance of the horizontal well with vertical wells in the field. The objectives considered for Phase II operations and plans were: (1) Develop a rationale for a systematic approach to designing stimulations for the well. (2) Conduct a series of stimulations designed to optimize the fluids, injection rates, proppant volumes and general approach to stimulating a horizontal well with similar geologic conditions. (3) Develop and test a method or methods for determining the geometry of stimulation-induced fractures. (4) Conduct tests and analyze the results to determine the efficiency of stimulation operations. The technical approach pursued in developing plans to accomplish three objectives was to: (1) Review the data needs for all objectives and obtain that data first. (2) Identify the operating geologic, geomechanical, and reservoir parameters that need additional clarification or definition. (3) Investigate existing models which could be used to plan or evaluate stimulation on the well and the reservoir. (4) Plan for analysis and verification of models and approaches.

  11. Influence of perturbative phase noise on active coherent polarization beam combining system.

    PubMed

    Ma, Pengfei; Zhou, Pu; Wang, Xiaolin; Ma, Yanxing; Su, Rongtao; Liu, Zejin

    2013-12-02

    In this manuscript, the influence of perturbative phase noise on active coherent polarization beam combining (CPBC) system is studied theoretically and experimentally. By employing a photo-detector to obtain phase error signal for feedback loop, actively coherent polarization beam combining of two 20 W-level single mode polarization-maintained (PM) fiber amplifiers are demonstrated with more than 94% combining efficiency. Then the influence of perturbative phase noise on active CPBC system is illustrated by incorporating a simulated phase noise signal in one of the two amplifiers. Experimental results show that the combining efficiency of the CPBC system is susceptible to the frequency or amplitude of the perturbative phase noise. In order to ensure the combining efficiency of the unit of CPBC system higher than 90%, the competence of our active phase control module for high power operation is discussed, which suggests that it could be worked at 100s W power level. The relationship between residual phase noise of the active controller and the normalized voltage signal of the photo-detector is developed and validated experimentally. Experimental results correspond exactly with the theoretically analyzed combining efficiency. Our method offers a useful approach to estimate the influence of phase noise on CPBC system.

  12. Stick-Slip and Granular Force Networks

    NASA Astrophysics Data System (ADS)

    Behringer, Robert; Yu, Peidong

    2008-03-01

    We describe friction/failure experiments for a granular system consisting of photoelastic particles. The goal of the experiments is to provide a microscopic understanding of stick-slip friction for an object that is pulled across a granular material. The granular material consists of a photoelastic disks (bidisperse distribution) that are confined to a vertically oriented channel. A slider that is rough at the grain scale is pulled across the upper surface of the material. The pulling is accomplished by a screw-driven platform that is connected to the slider by a spring. Photoelastic image data are acquired by a camera and light source that move with the platform. Non-periodic stick-slip occurs for the regime of parameters studied here. During a stick event, force builds up in a strong network of force chains in the granular material. When one or more of the chains break, a slip event occurs. Energy changes from these events are power-law distributed. Analysis of failure points and slip events yields the effective friction coefficients, which are broadly scattered. An alternative description involves modeling the force chain network as a collection of springs. Failure of one spring can lead to a cascade and hence the broad distribution of energy losses.

  13. Oblique slip in Laramide foreland arches

    SciTech Connect

    Erslev, E.A.; Selvig, B.; Molzer, P. . Dept. of Earth Resources)

    1993-03-01

    Don Wise was one of the first structural geologists to recognize the complex, four-dimensional (space and time) nature of basement-involved faulting in the Rocky Mountain foreland. His focus on both small scale kinematic indicators and regional tectonic hypotheses has provided a launching point for many Rocky Mountain geologists. The implications of the anastomosing patterns of Laramide foreland arches on models of regional stress and strain have provoked considerable debate. Hypotheses range from those invoking multiple stages of lateral compression from different directions to single-stage models necessitating a component of strike-slip motion in east-west and north-south arches. These hypotheses were tested using slickenline analysis of minor faulting in structures with different orientations. In Wyoming, structures paralleling the dominant northwest structural trend have slickenlines in the NE-SW vertical plane, consistent with shortening and compression in this direction. The east-west Owl Creek and Casper Mountain structures also have NE-SW trending slickenlines, indicating slip oblique to these arches. In Colorado, minor faults in the north-south margin of the northeastern Front Range also indicate oblique slip, with shortening in the NE-SW quadrant. The actual trend of the slickenlines is more easterly, however, suggesting a change of slip trajectory with latitude, not time, possibly in response to identation by the Colorado Plateau.

  14. Kinematics of Slip Partitioning in Sumatra

    NASA Astrophysics Data System (ADS)

    Bradley, K. E.; Feng, L.; Hill, E.; Natawidjaja, D. H.; Sieh, K.; Daryono, M. R.

    2015-12-01

    Published geological slip rates of the Sumatran Fault, slip vectors of Sunda megathrust earthquakes, and the geodetic velocity field of Sumatra and the forearc islands appear the require distributed and rapid stretching of the Sumatran forearc parallel to the Sunda Trench. We show that revised Sumatran Fault slip rates, earthquake slip vector azimuths, and the long-term geodetic velocity field are consistent instead with a non-deforming, rigid forearc block that overlies a heterogeneously coupled Sunda megathrust and is separated from the Sunda Block by the Sumatran Fault. Like previous studies, we conclude that rigid plate tectonics fails to describe the Sumatran subduction system; however, we attribute this failure to the well documented internal strain within the Eastern Indian Ocean lithosphere. We further constrain the along-strike variation in the rate of underthrusting of oceanic lithosphere beneath the Sumatran forearc, an important boundary condition for paleogeodetic studies of elastic strain accumulation within the forearc and the cycle of great Sunda megathrust earthquakes.

  15. Slip casting and nitridation of silicon powder

    NASA Astrophysics Data System (ADS)

    Seiko, Y.

    1985-03-01

    Powdered Silicon was slip-cast with a CaSO4 x 0.5H2O mold and nitrided in a N atm. containing 0 or 5 vol. % H at 1000 to 1420 deg. To remove the castings, the modeling faces were coated successively with an aq. salt soap and powdered cellulose containing Na alginate, and thus prevented the sticking problem.

  16. Hydrodynamic slip length as a surface property

    NASA Astrophysics Data System (ADS)

    Ramos-Alvarado, Bladimir; Kumar, Satish; Peterson, G. P.

    2016-02-01

    Equilibrium and nonequilibrium molecular dynamics simulations were conducted in order to evaluate the hypothesis that the hydrodynamic slip length is a surface property. The system under investigation was water confined between two graphite layers to form nanochannels of different sizes (3-8 nm). The water-carbon interaction potential was calibrated by matching wettability experiments of graphitic-carbon surfaces free of airborne hydrocarbon contamination. Three equilibrium theories were used to calculate the hydrodynamic slip length. It was found that one of the recently reported equilibrium theories for the calculation of the slip length featured confinement effects, while the others resulted in calculations significantly hindered by the large margin of error observed between independent simulations. The hydrodynamic slip length was found to be channel-size independent using equilibrium calculations, i.e., suggesting a consistency with the definition of a surface property, for 5-nm channels and larger. The analysis of the individual trajectories of liquid particles revealed that the reason for observing confinement effects in 3-nm nanochannels is the high mobility of the bulk particles. Nonequilibrium calculations were not consistently affected by size but by noisiness in the smallest systems.

  17. Intermolecular Slip Mechanism in Tropocollagen Nanofibrils

    DTIC Science & Technology

    2009-01-01

    Imperfecta or Ehlers - Danlos Syndrome. REPORT DOCUMENTATION PAGE (SF298) (Continuation Sheet) Continuation for Block 13 ARO Report Number Intermolecular slip...our studies could advance our knowledge of mechan- isms underlying important collagen-related diseases like Osteogenesis Imperfecta or Ehlers - Danlos

  18. Slip casting and nitridation of silicon powder

    NASA Technical Reports Server (NTRS)

    Seiko, Y.

    1985-01-01

    Powdered Silicon was slip-cast with a CaSO4 x 0.5H2O mold and nitrided in a N atm. containing 0 or 5 vol. % H at 1000 to 1420 deg. To remove the castings, the modeling faces were coated successively with an aq. salt soap and powdered cellulose containing Na alginate, and thus prevented the sticking problem.

  19. Slip complexity in earthquake fault models.

    PubMed

    Rice, J R; Ben-Zion, Y

    1996-04-30

    We summarize studies of earthquake fault models that give rise to slip complexities like those in natural earthquakes. For models of smooth faults between elastically deformable continua, it is critical that the friction laws involve a characteristic distance for slip weakening or evolution of surface state. That results in a finite nucleation size, or coherent slip patch size, h*. Models of smooth faults, using numerical cell size properly small compared to h*, show periodic response or complex and apparently chaotic histories of large events but have not been found to show small event complexity like the self-similar (power law) Gutenberg-Richter frequency-size statistics. This conclusion is supported in the present paper by fully inertial elastodynamic modeling of earthquake sequences. In contrast, some models of locally heterogeneous faults with quasi-independent fault segments, represented approximately by simulations with cell size larger than h* so that the model becomes "inherently discrete," do show small event complexity of the Gutenberg-Richter type. Models based on classical friction laws without a weakening length scale or for which the numerical procedure imposes an abrupt strength drop at the onset of slip have h* = 0 and hence always fall into the inherently discrete class. We suggest that the small-event complexity that some such models show will not survive regularization of the constitutive description, by inclusion of an appropriate length scale leading to a finite h*, and a corresponding reduction of numerical grid size.

  20. PRODUCTION OF SLIP CAST CALCIA HOLLOWWARE

    DOEpatents

    Stoddard, S.D.; Nuckolls, D.E.; Cowan, R.E.

    1963-12-31

    A method for producing slip cast calcia hollow ware in which a dense calcia grain is suspended in isobutyl acetate or a mixture of tertiary amyl alcohol and o-xylene is presented. A minor amount of triethanolamine and oleic acid is added to the suspension vehicle as viscosity adjusting agents and the suspension is cast in a plaster mold, dried, and fired. (AEC)

  1. A spectroscopic and catalytic investigation of active phase-support interactions

    SciTech Connect

    Haller, G.L.

    1991-01-01

    Active catalytic phases (metal, mixed metals, oxide or mixed oxides) interacting with oxide support on which the active phase is dispersed can affect the percentage exposed, the morphology of supported particles, the degree of reducibility of cations, etc., in a variety of ways. Our objective is to characterize the physical chemistry of the active phase-oxide support by spectroscopic methods and to correlate this structure with catalytic function. The three systems discussed in this progress report are Ag/TiO{sub 2}, Ru-Cu/SiO{sub 2} and SiO{sub 2}/Al{sub 2}O{sub 3}. 24 refs., 3 figs., 2 tabs.

  2. Effects of intracerebroventricular histamine injection on circadian activity phase entrainment during rapid illumination changes.

    PubMed

    Itowi, N; Yamatodani, A; Mochizuki, T; Wada, H

    1991-02-11

    Histamine is reported to have different effects on shifting the circadian activity phase depending on its circadian administration time (CT). The delay-sensitive period is CT 12-15, and the advance-sensitive period is CT 0-3. The activity phase of rats was entrained by a new light-dark cycle within a week in groups treated with either saline or i.c.v. histamine at CT 12-15. However, on treatment at CT 0-3 the activity phase of the group treated with histamine was entrained by the new light-dark cycle in half the period required for entrainment in the control group.

  3. Evolution of activity signatures during the main sequence phase

    NASA Astrophysics Data System (ADS)

    Skumanich, A.; MacGregor, K.

    Recent work on the decay of magnetic activity signatures, such as chromospheric/transition region/coronal emission as well as mean flare emission, with age for solar and later type stars is reviewed. In terms of magnetic flux, as measured by excess chromospheric Ca II luminosity, it is shown that a simple dynamo-rotation relation that incorporates both a saturated state with its characteristic critical rotation as well as an asymptotic linear power law, i.e., a scale free relation, fits the extant data that includes the dMe stars. Introducing the saturated dynamo state, as exemplified by the dMe stars, into activity power-power diagrams, allows for not only specification of the saturated state, but for definition of evolutionary tracks that represent the decay from the saturated state. Using the quiescent coronal X-ray power (luminosity) as a basic measure of magnetic activity, simple monomial relations for both the saturated state (linear) and for the evolutionary tracks governing both quiescent activity and mean flare activity are found. In particular, the coronal power loss is found to vary quadratically with the chromospheric power loss, hence with magnetic flux.

  4. Brazing of the Tore Supra actively cooled Phase III Limiter

    SciTech Connect

    Nygren, R.E.; Walker, C.A.; Lutz, T.J.; Hosking, F.M.; McGrath, R.T.

    1993-12-31

    The head of the water-cooled Tore Supra Phase 3 Limiter is a bank of 14 round OFHC copper tubes, curved to fit the plasma radius, onto which several hundred pyrolytic graphite (PG) tiles and a lesser number of carbon fiber composite tiles are brazed. The small allowable tolerances for fitting the tiles to the tubes and mating of compound curvatures made the brazing and fabrication extremely challenging. The paper describes the fabrication process with emphasis on the procedure for brazing. In the fixturing for vacuum furnace brazing, the tiles were each independently clamped to the tube with an elaborate set of window frame clamps. Braze quality was evaluated with transient heating tests. Some rebrazing was necessary.

  5. The structure of slip-pulses and supershear ruptures driving slip in bimaterial friction

    PubMed Central

    Shlomai, Hadar; Fineberg, Jay

    2016-01-01

    The most general frictional motion in nature involves bimaterial interfaces, when contacting bodies possess different elastic properties. Frictional motion occurs when the contacts composing the interface separating these bodies detach via propagating rupture fronts. Coupling between slip and normal stress variations is unique to bimaterial interfaces. Here we use high speed simultaneous measurements of slip velocities, real contact area and stresses to explicitly reveal this bimaterial coupling and its role in determining different classes of rupture modes and their structures. We directly observe slip-pulses, highly localized slip accompanied by large local reduction of the normal stress near the rupture tip. These pulses propagate in the direction of motion of the softer material at a selected (maximal) velocity and continuously evolve while propagating. In the opposite direction bimaterial coupling favors crack-like ‘supershear' fronts. The robustness of these structures shows the importance of bimaterial coupling to frictional motion and modes of frictional dissipation. PMID:27278687

  6. Experimental Slip Events as Possible Proxies for Fault Patch Slip During Earthquakes

    NASA Astrophysics Data System (ADS)

    Chang, J. C.; Lockner, D. A.; Reches, Z.

    2011-12-01

    The slip and strength histories of a fault patch during an earthquake are experimentally simulated with a high-speed rotary apparatus. The experimental fault comprises two solid cylindrical blocks with a raised-ring contact of 7 cm diameter and 1 cm width. Our conceptual model assumes that slip on a fault patch is initiated by the stress increase associated with the passage of an earthquake front, and that this slip is facilitated by dissipation of potential energy stored in the surrounding crust. To simulate this process in the laboratory, we first store kinetic energy by spinning up a 225 kg flywheel that is adjacent to, but not connected to, the locked fault. Then, the flywheel is engaged to the lower fault block via a fast-acting (<0.03 s) clutch, and the drive motor is turned off. This loading procedure produces slip behavior that has many similarities to the slip envisioned to occur along an earthquake patch. (1) In both cases, a finite energy is available to drive slip. (2) The initial dynamic stress rise leading to fault slip is rapid (<< 1 s). (3) Slip history is controlled by spontaneous interaction between fault strength and the stored energy. (4) Radiated seismic energy is probably a small fraction of the energy budget. We refer to our experiments as 'Earthquake-Like-Slip-Event' or ELSE. Direct measurements of slip-velocity, normal and shear stresses, fault-normal displacement, and temperature are recorded at 5 kHz sampling. We present synthesis of 43 ELSE runs with Sierra White granite, and 15 with Kasota dolomite. Samples were axially loaded up to 7 MPa, potential energy up to 25 MJ/m^2, and slip-velocity up to ~1.0 m/s; they produced slip-distances up to 5.55 m, and fault-normal displacement from -300 microns (closure) to 160 microns (dilation). The main ELSE observations and inferences are: (1) In most experiments, the strength drops significantly (~50-70%) during the early slip stage, and this weakening is associated with intense fault wear and

  7. 1. Ferry slip, view looking north. On the right, west ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. Ferry slip, view looking north. On the right, west side of the main dock: on the left, east side of the Sand and Gravel Wharf. - Curtis Wharf, Ferry Slip & Sand & Gravel Wharf, O & Second Streets, Anacortes, Skagit County, WA

  8. Ultrasonographic Diagnosis of Slipped Capital Femoral Epiphysis

    PubMed Central

    Palaniappan, Manikandan; Indiran, Venkatraman; Maduraimuthu, Prabakaran

    2017-01-01

    Summary Background Slipped capital femoral epiphysis (SCFE), a fracture through the physis with resultant slip of the epiphysis, is the most common hip abnormality in adolescents and is a major cause of early osteoarthritis. Plain radiograph is the initial modality used to evaluate patients with painful hip joints. Ultrasonography and magnetic resonance imaging (MRI), which do not involve radiation exposure, have also been used. This case report supports the view that ultrasound can be used as an initial, cost-effective and radiation-free modality for the evaluation of suspected SCFE. Case Report A 15-year-old male patient presented with pain in the right hip for 5 days, following a slip and fall accident while playing soccer. The patient was referred to the Department of Radio-diagnosis for ultrasound. A posterior displacement of the femoral head epiphysis with a physeal step was seen on the longitudinal section obtained over the right hip joint region. The anterior physeal step (APS) measured ~3.8 mm on the right side. The distance between the anterior rim of the acetabulum and the metaphysis measured ~20.4 mm on the affected right side and ~23.6 mm on the left side. A plain radiograph in frog leg position showed a widening of the right proximal physis below the right femoral head, with a medial and posterior slip of the right femoral head. A frontal radiograph of the pelvis taken six months before showed a widening of the proximal right femoral physis. Conclusions Although MRI appears to be the most sensitive modality for identifying slips early, ultrasound may be used as a cost-effective and radiation-free alternative before proceeding with further evaluation of suspected SCFE, especially considering the demographics of the affected population. PMID:28382187

  9. Distributed Slip Model for Simulating Virtual Earthquakes

    NASA Astrophysics Data System (ADS)

    Shani-Kadmiel, S.; Tsesarsky, M.; Gvirtzman, Z.

    2014-12-01

    We develop a physics based, generic finite fault source, which we call the Distributed Slip Model (DSM) for simulating large virtual earthquakes. This task is a necessary step towards ground motion prediction in earthquake-prone areas with limited instrumental coverage. A reliable ground motion prediction based on virtual earthquakes must account for site, path, and source effects. Assessment of site effect mainly depends on near-surface material properties which are relatively well constrained, using geotechnical site data and borehole measurements. Assessment of path effect depends on the deeper geological structure, which is also typically known to an acceptable resolution. Contrarily to these two effects, which remain constant for a given area of interest, the earthquake rupture process and geometry varies from one earthquake to the other. In this study we focus on a finite fault source representation which is both generic and physics-based, for simulating large earthquakes where limited knowledge is available. Thirteen geometric and kinematic parameters are used to describe the smooth "pseudo-Gaussian" slip distribution, such that slip decays from a point of peak slip within an elliptical rupture patch to zero at the borders of the patch. Radiation pattern and spectral charectaristics of our DSM are compared to those of commonly used finite fault models, i.e., the classical Haskell's Model (HM) and the modified HM with Radial Rupture Propagation (HM-RRP) and the Point Source Model (PSM). Ground motion prediction based on our DSM benefits from the symmetry of the PSM and the directivity of the HM while overcoming inadequacy for modeling large earthquakes of the former and the non-physical uniform slip of the latter.

  10. Digital active material processing platform effort (DAMPER), SBIR phase 2

    NASA Technical Reports Server (NTRS)

    Blackburn, John; Smith, Dennis

    1992-01-01

    Applied Technology Associates, Inc., (ATA) has demonstrated that inertial actuation can be employed effectively in digital, active vibration isolation systems. Inertial actuation involves the use of momentum exchange to produce corrective forces which act directly on the payload being actively isolated. In a typical active vibration isolation system, accelerometers are used to measure the inertial motion of the payload. The signals from the accelerometers are then used to calculate the corrective forces required to counteract, or 'cancel out' the payload motion. Active vibration isolation is common technology, but the use of inertial actuation in such systems is novel, and is the focus of the DAMPER project. A May 1991 report was completed which documented the successful demonstration of inertial actuation, employed in the control of vibration in a single axis. In the 1 degree-of-freedom (1DOF) experiment a set of air bearing rails was used to suspend the payload, simulating a microgravity environment in a single horizontal axis. Digital Signal Processor (DSP) technology was used to calculate in real time, the control law between the accelerometer signals and the inertial actuators. The data obtained from this experiment verified that as much as 20 dB of rejection could be realized by this type of system. A discussion is included of recent tests performed in which vibrations were actively controlled in three axes simultaneously. In the three degree-of-freedom (3DOF) system, the air bearings were designed in such a way that the payload is free to rotate about the azimuth axis, as well as translate in the two horizontal directions. The actuator developed for the DAMPER project has applications beyond payload isolation, including structural damping and source vibration isolation. This report includes a brief discussion of these applications, as well as a commercialization plan for the actuator.

  11. Direct and Indirect Polymer-Polymer Interfacial Slip Measurements in Multilayered Films

    NASA Astrophysics Data System (ADS)

    Lee, Patrick C.; Park, Hee Eon; Macosko, Christopher W.

    2008-07-01

    Significant slip can occur during flow of two immiscible polymers due to reduced entanglements at their interface. The slip is of practical importance because of its effect on morphology and adhesion of these multi-phase materials, such as disordered two-phase blends and multilayer films. In this research, we are investigating the amount of polymer-polymer slip over a range of shear stresses from rheological measurements (i.e., indirect method) and visualization measurements (i.e., direct method) on co-extruded multilayer films. Two types of alternately layered blends were chosen: polypropylene (PP)/polystyrene (PS) and polyethylene (PE)/fluoropolymer (FP) blends. The multilayer samples of both PP/PS and PE/FP blends were prepared in a co-extrusion setup (Zhao and Macosko J. Rheol. 2002) at 200 and 210 °C, respectively, in order to match viscosity and linear viscoelasticity. To study the polymer-polymer interfacial slip over a wide stress range, three types of rheometers were used: an in-line slit-die rheometer, a rotational parallel-disk rheometer, and a sliding-plates rheometer (SPR). It was observed that the viscosity of a multilayer sample is lower than the harmonic average viscosity of two neat polymers for both PP/PS and PE/FP and decreases with the number of layers above a certain critical shear stress. Two visualization techniques, (i) the SPR with a glass top plate and (ii) a high temperature shearing cell, were utilized to prove the slip. The slip velocity (i.e., the amount of macroscopic velocity discontinuity at the interface) with respect to shear stress was calculated from each rheological and visualization methods and compared.

  12. The African hedgehog (Atelerix albiventris): Low phase I and phase II metabolism activities.

    PubMed

    Saengtienchai, Aksorn; Ikenaka, Yoshinori; Bortey-Sam, Nesta; Jermnark, Usuma; Mizukawa, Hazuki; Kawai, Yusuke K; Nakayama, Shouta M M; Ishizuka, Mayumi

    2016-12-01

    The African hedgehog, Atelerix albiventris, is a spiny mammal that has become popular as an exotic pet in many countries. To elucidate the ability of hedgehogs to metabolize xenobiotics, the animals were exposed to polycyclic aromatic hydrocarbon, pyrene. The in vivo exposure study indicated that pyrene was biotransformed to glucuronide and sulfate conjugates, such as pyrene-1-glucuronide, pyrene-1-sulfate, and pyrenediol-sulfate, and excreted in the urine. Pyrene-1-glucuronide was the main metabolite, and limited sulfate conjugate excretion was observed. The main products excreted in feces were 1-hydroxypyrene and pyrene. Based on the results of the in vivo exposure study, in vitro enzymatic kinetic experiments were performed using various substrates and compared to rats and pigs. The enzyme efficiencies of cytochrome P450 (CYP)-mediated ethoxyresorufin O-deethylase activity and warfarin 4'-, 6-, and 8-hydroxylation activity in hedgehogs were lower than those of rats. Furthermore, UDP-glucuronosyltransferase activity in hedgehogs also had a lower Km value than that in pigs. Interestingly, the enzyme efficiencies of sulfation activity toward 1-hydroxypyrene and β-estradiol in hedgehogs were significantly lower than those in pigs. These observations suggested that phenol and estrogen sulfotransferases may have limited roles in xenobiotic metabolism in hedgehogs.

  13. Geometry and late Pleistocene slip rates of the Liangdang-Jiangluo fault in the western Qinling mountains, NW China

    NASA Astrophysics Data System (ADS)

    Wen-jun, Zheng; Xing-wang, Liu; Jing-xing, Yu; Dao-yang, Yuan; Pei-zhen, Zhang; Wei-peng, Ge; Jian-zhang, Pang; Bai-yun, Liu

    2016-09-01

    Two groups of faults striking in different direction (NWW-trending and NEE-trending) within the western Qinling mountains play important roles in the tectonic deformation and the transference slip along the east end of the east Kunlun fault. We investigated the fault geometry and kinematics properties in the area. Based on the displacements of landforms and optically stimulated luminescence (OSL) dating techniques, the late Pleistocene slip rates along the Liangdang-Jiangluo fault were determined to be 0.43 ± 0.13 mm/a (thrust) and 0.71 ± 0.18 mm/a (left-lateral strike-slip). We also investigated some other faults, and obtained characteristically low slip rates. These slip rates are consistent with decadal GPS observations. Despite previous studies that point to a systematic decrease in the left-lateral slip rates from > 10 mm/a to < 2 mm/a along the eastern end of the Kunlun fault, there has been relatively little discussion about the role of the faults, that lie between the east Kunlun and west Qinling faults in accommodating the regional tectonic deformation. From the activity, geometry, and kinematics of the regional faults in the western Qinling Mountains, we concluded that the main driving force that arises from the NE-thrusting and strike slip along the east Kunlun fault dominated the deformation in the area. Our results suggest that the < 2 mm/a slip rate at the tip of the east Kunlun fault is absorbed by low slip rate faults, crustal shortening, basin formation and mountain uplift in the western Qinling mountains, and the slip is not transferred to the west Qinling fault or further north.

  14. Simple models for intermittent deformation and slip avalanches: from crystals to granular materials and earthquakes

    NASA Astrophysics Data System (ADS)

    Dahmen, K.; Ben-Zion, Y.; Uhl, J.

    2011-12-01

    Slowly sheared solid or densely packed granular materials often deform in an intermittent way with slip avalanches. The distribution of sizes follows often a power law over a broad range of sizes. In these cases, universal (i.e. detail-independent) scaling behavior governs the statistics of the slip-avalanches. Under some conditions, there are also "characteristic" statistics associated with enhanced occurrence of system-size events, and long-term mode switching between power law and characteristic behavior. These dynamic regimes can be understood with basic micromechanical model for deformation of solids with only two tuning parameter: weakening and dissipation of elastic stress transfer. For granular materials the packing fraction plays the role of the dissipation parameter and it sets the size of the largest slip avalanche. The model can reproduce observed stress-strain curves, power spectra of acoustic emissions, statistics of slip avalanches, and geometrical properties of slip, with a continuous phase transition from brittle to ductile behavior. Exact universal predictions for the power law exponents of the avalanche size distributions, durations, power spectra of acoustic emissions, and scaling functions are extracted using an analytical mean field theory and renormalization group tools. For granular materials a dynamic phase diagram with solid-like behavior and large slip avalanches at large packing fractions, and fluid-like behavior at lower packing fractions is obtained. The results agree with recent experimental observations and simulations of the statistics of dislocation dynamics in sheared crystals such as ice [1], slip avalanches in sheared granular materials [2], and avalanches in magnetic and fault systems [3,4]. [1] K. A. Dahmen, Y. Ben-Zion, and J.T. Uhl, "A micromechanical model for deformation in solids with universal predictions for stress strain curves and slip avalanches", Physical Review Letters 102, 175501/1-4 (2009). [2] K. A. Dahmen, Y

  15. GAS PHASE SELECTIVE PHOTOXIDATION OF ALCOHOLS USING LIGHT-ACTIVATED TITANIUM DIOXIDE AND MOLECULAR OXYGEN

    EPA Science Inventory

    Gas Phase Selective Oxidation of Alcohols Using Light-Activated Titanium Dioxide and Molecular Oxygen

    Gas phase selective oxidations of various primary and secondary alcohols are studied in an indigenously built stainless steel up-flow photochemical reactor using ultravi...

  16. The variations of long time period slow slip events along the Ryukyu subduction zone

    NASA Astrophysics Data System (ADS)

    Tu, Y. T.; Heki, K.

    2014-12-01

    Slow slip events (SSEs) are a type of slow earthquakes that can be observed with Global Positioning System (GPS) networks in the world. Those events are detected on intensely coupled plate boundaries such as Cascadia subduction zone (Dragert et al., 2001), western North America, Mexico (Kostoglodov et al., 2003), Alaska (Ohta et al., 2007) and Tokai and Boso areas (Ozawa et al., 2002, 2003), central Japan and are considered to have relations to large subduction thrust earthquakes. However, in southwestern Ryukyu trench where most of researchers believe that it should be a decoupled plate boundary, SSEs recur regularly and are located at a patch that is as deep as 20 to 40 km (Heki and Kataoka, 2008). For comprehending the characteristics and time variations of SSEs in this area, the GEONET GPS data of 16 years are used in this study. During 1997 to 2014, more than thirty SSEs are identified near Hateruma Island, Ryukyu. The average recurrence interval is calculated to be 6.3 months and release seismic moment is Mw 6.6 on average. However, the values of recurrence interval are not invariable. From 1997 to 2002, interval period of SSEs is 7.5 months, but during 2002 to 2008, the interval period decreases suddenly to 5.5 months. After 2008, the value restores to 7.2 months again. Furthermore, the slip amount of SSEs in this area varies with time. From 1997 to 2002, the slip is 9.5 cm/year; and during 2002 to 2008, the value slightly increases to 10.5 cm/year. However, in 2008 to 2013, the slip drops to 6.6 cm/year, but accord to the trend of cumulative slip, the slip value would increase in 2014. Considering these data, we find the slip values increase conspicuously in 2002 and 2013. Coincidentally, one Mw 7.1 thrust earthquake occurred in 2002 and earthquake swarm activity started in the Okinawa trough approximately 50km north of the SSE patch. In 2013, another earthquake swarm activity occurred in nearly the same area as the 2002 activity. This suggests that the

  17. Friction at seismic slip rates: testing thermal weakening models experimentally

    NASA Astrophysics Data System (ADS)

    Nielsen, S. B.; Spagnuolo, E.; Violay, M.; Di Toro, G.

    2013-12-01

    Recent experiments systematically explore rock friction under crustal earthquake conditions (fast slip rate 1phase can be explained either by the flash weakening model (Archard, 1958; Rice, 2006; Noda et al., 2009) or by a simple model where the strength of the slip zone is directly controlled by an Arrhenious-like thermal dependance. In the presence of melting, which occurs quite easily in silicatic rocks under coseismic conditions, the data are well explained by the frictional melt model (Nielsen et al., 2008, 2010). Frictional heating is simple to compute but requires a rather costly and inefficient convolution (even with the use of FFT) for a dynamic, extended fault simulation. Hence we desing an efficient and accurate wavenumber approximation for a solution of the temperature evolution on the fault. Finally, we propose a compact and paractical model based on a small number of memory variables for the implementation of thermal weakening friction in seismic fault simulations.

  18. Stick-slip nanofriction in cold-ion traps

    NASA Astrophysics Data System (ADS)

    Mandelli, Davide; Vanossi, Andrea; Tosatti, Erio

    2013-03-01

    Trapped cold ions are known to form linear or planar zigzag chains, helices or clusters depending on trapping conditions. They may be forced to slide over a laser induced corrugated potential, a mimick of sliding friction. We present MD simulations of an incommensurate 101 ions chain sliding subject to an external electric field. As expected with increasing corrugation, we observe the transition from a smooth-sliding, highly lubric regime to a strongly dissipative stick-slip regime. Owing to inhomogeneity the dynamics shows features reminiscent of macroscopic frictional behaviors. While the chain extremities are pinned, the incommensurate central part is initially free to slide. The onset of global sliding is preceded by precursor events consisting of partial slips of chain portions further from the center. We also look for frictional anomalies expected for the chain sliding across the linear-zigzag structural phase transition. Although the chain is too short for a proper critical behavior, the sliding friction displays a frank rise near the transition, due to opening of a new dissipative channel via excitations of transverse modes. Research partly sponsored by Sinergia Project CRSII2 136287/1.

  19. Provenance of alluvial fan deposits to constrain the mid-term offsets along a strike-slip active fault: the Elsinore fault in the Coyote Mountains, Imperial Valley, California.

    NASA Astrophysics Data System (ADS)

    Masana, Eulalia; Stepancikova, Petra; Rockwell, Thomas

    2013-04-01

    The lateral variation in rates along a fault and its constancy along time is a matter of discussion. To give light to this discussion, short, mid and long term offset distribution along a fault is needed. Many studies analyze the short-term offset distribution along a strike-slip fault that can be obtained by the analysis of offset features imprinted in the morphology of the near-fault area. We present an example on how to obtain the mid- to long-term offset values based on the composition of alluvial fans that are offset by the fault. The study area is on the southern tip of the Elsinore fault, which controls the mountain front of the Coyote Mountains (California). The Elsinore-Laguna Salada fault is part of the San Andreas fault (SAF) system, extending 250 km from the Los Angeles Basin southeastward into the Gulf of California, in Mexico. The slip-rate on the southern Elsinore fault is believed to be moderate based on recent InSAR observations, although a recent study near Fossil Canyon (southern Coyote Mountains) suggests a rate in the range of 1-2 mm/yr. For this study we processed the airborne LiDAR dataset (EarthScope Southern & Eastern California, SoCal) to map short to mid-term alluvial offsets. We reprocessed the point clouds to produce DEMs with 0.5m and 0.25m grids and we varied the insolation angles to illuminate the various fault strands and the offset features. We identified numerous offset features, such as rills, channel bars, channel walls, alluvial fans, beheaded channels and small erosional basins that varied in displacement from 1 to 350 m. For the mid- to long-term offsets of the alluvial fans we benefited from the diverse petrological composition of their sources. Moreover, we recognized that older alluvium, which is offset by greater amounts, is in some cases buried beneath younger alluvial fan deposits and separated by buried soils. To determine the source canyon of various alluvial elements, we quantified the clast assemblage of each source

  20. General Electric ATS program technical review: Phase 2 activities

    SciTech Connect

    Chance, T.; Smith, D.

    1995-10-01

    In response to the industrial and utility objectives specified for the ATS, the GE Power Generation ATS Phase 2 Program consisted of a dual approach. These were (1) development of an Industrial ATS (aircraft engine based) led by GE Aircraft Engines, and (2) development of a Utility ATS which was already underway at GEPG. Both programs required the identification and resolution of critical technical issues. Both systems were studied in Tasks 3-7, and both have resulted in designs that meet all ATS goals. The Industrial ATS as defined (130 MW) did not meet projected market power size requirements, and emphasis has remained on the Utility ATS development. The design and testing effort has been focused on the MS7001H combined cycle gas turbine, as the next product evolution in GE Power Generation`s product line. Common technology derived from the ATS Program is also being incorporated into the 50 Hz version of the ATS utility machine designated as the MS9001H.

  1. Recovery Efficiency Test Project: Phase 1, Activity report

    SciTech Connect

    Overbey, W.K. Jr.; Carden, R.S.; Kirr, J.N.

    1987-04-01

    The recovery Efficiency Test well project addressed a number of technical issues. The primary objective was to determine the increased efficiency gas recovery of a long horizontal wellbore over that of a vertical wellbore and, more specifically, what improvements can be expected from inducing multiple hydraulic fractures from such a wellbore. BDM corporation located, planned, and drilled a long radius turn horizontal well in the Devonian shale Lower Huron section in Wayne County, West Virginia, demonstrating that state-of-the-art technology is capable of drilling such wells. BDM successfully tested drilling, coring, and logging in a horizontal well using air as the circulating medium; conducted reservoir modeling studies to protect flow rates and reserves in advance of drilling operations; observed two phase flow conditions in the wellbore not observed previously; cored a fracture zone which produced gas; observed that fractures in the core and the wellbore were not systematically spaced (varied from 5 to 68 feet in different parts of the wellbore); observed that highest gas show rates reported by the mud logger corresponded to zone with lowest fracture spacing (five feet) or high fracture frequency. Four and one-half inch casting was successfully installed in the borehole and was equipped to isolate the horizontal section into eight (8) zones for future testing and stimulation operations. 6 refs., 48 figs., 10 tabs.

  2. Experimental Modeling of Dynamic Shallow Dip-Slip Faulting

    NASA Astrophysics Data System (ADS)

    Uenishi, K.

    2010-12-01

    In our earlier study (AGU 2005, SSJ 2005, JPGU 2006), using a finite difference technique, we have conducted some numerical simulations related to the source dynamics of shallow dip-slip earthquakes, and suggested the possibility of the existence of corner waves, i.e., shear waves that carry concentrated kinematic energy and generate extremely strong particle motions on the hanging wall of a nonvertical fault. In the numerical models, a dip-slip fault is located in a two-dimensional, monolithic linear elastic half space, and the fault plane dips either vertically or 45 degrees. We have investigated the seismic wave field radiated by crack-like rupture of this straight fault. If the fault rupture, initiated at depth, arrests just below or reaches the free surface, four Rayleigh-type pulses are generated: two propagating along the free surface into the opposite directions to the far field, the other two moving back along the ruptured fault surface (interface) downwards into depth. These downward interface pulses may largely control the stopping phase of the dynamic rupture, and in the case the fault plane is inclined, on the hanging wall the interface pulse and the outward-moving Rayleigh surface pulse interact with each other and the corner wave is induced. On the footwall, the ground motion is dominated simply by the weaker Rayleigh pulse propagating along the free surface because of much smaller interaction between this Rayleigh and the interface pulse. The generation of the downward interface pulses and corner wave may play a crucial role in understanding the effects of the geometrical asymmetry on the strong motion induced by shallow dip-slip faulting, but it has not been well recognized so far, partly because those waves are not expected for a fault that is located and ruptures only at depth. However, the seismological recordings of the 1999 Chi-Chi, Taiwan, the 2004 Niigata-ken Chuetsu, Japan, earthquakes as well as a more recent one in Iwate-Miyagi Inland

  3. Downscaling of slip distribution for strong earthquakes

    NASA Astrophysics Data System (ADS)

    Yoshida, T.; Oya, S.; Kuzuha, Y.

    2013-12-01

    We intend to develop a downscaling model to enhance the earthquake slip distribution resolution. Slip distributions have been obtained by other researchers using various inversion methods. As a downscaling model, we are discussing fractal models that include mono-fractal models (fractional Brownian motion, fBm; fractional Lévy motion, fLm) and multi-fractal models as candidates. Log - log-linearity of k (wave number) versus E (k) (power spectrum) is the necessary condition for fractality: the slip distribution is expected to satisfy log - log-linearity described above if we can apply fractal model to a slip distribution as a downscaling model. Therefore, we conducted spectrum analyses using slip distributions of 11 earthquakes as explained below. 1) Spectrum analyses using one-dimensional slip distributions (strike direction) were conducted. 2) Averaging of some results of power spectrum (dip direction) was conducted. Results show that, from the viewpoint of log - log-linearity, applying a fractal model to slip distributions can be inferred as valid. We adopt the filtering method after Lavallée (2008) to generate fBm/ fLm. In that method, generated white noises (random numbers) are filtered using a power law type filter (log - log-linearity of the spectrum). Lavallée (2008) described that Lévy white noise that generates fLm is more appropriate than the Gaussian white noise which generates fBm. In addition, if the 'alpha' parameter of the Lévy law, which governs the degree of attenuation of tails of the probability distribution, is 2.0, then the Lévy distribution is equivalent to the Gauss distribution. We analyzed slip distributions of 11 earthquakes: the Tohoku earthquake (Wei et al., 2011), Haiti earthquake (Sladen, 2010), Simeulue earthquake (Sladen, 2008), eastern Sichuan earthquake (Sladen, 2008), Peru earthquake (Konca, 2007), Tocopilla earthquake (Sladen, 2007), Kuril earthquake (Sladen, 2007), Benkulu earthquake (Konca, 2007), and southern Java

  4. Micromechanics and constitutive models for soft active materials with phase evolution

    NASA Astrophysics Data System (ADS)

    Wang, Binglian

    Soft active materials, such as shape memory polymers, liquid crystal elastomers, soft tissues, gels etc., are materials that can deform largely in response to external stimuli. Micromechanics analysis of heterogeneous materials based on finite element method is a typically numerical way to study the thermal-mechanical behaviors of soft active materials with phase evolution. While the constitutive models that can precisely describe the stress and strain fields of materials in the process of phase evolution can not be found in the databases of some commercial finite element analysis (FEA) tools such as ANSYS or Abaqus, even the specific constitutive behavior for each individual phase either the new formed one or the original one has already been well-known. So developing a computationally efficient and general three dimensional (3D) thermal-mechanical constitutive model for soft active materials with phase evolution which can be implemented into FEA is eagerly demanded. This paper first solved this problem theoretically by recording the deformation history of each individual phase in the phase evolution process, and adopted the idea of effectiveness by regarding all the new formed phase as an effective phase with an effective deformation to make this theory computationally efficient. A user material subroutine (UMAT) code based on this theoretical constitutive model has been finished in this work which can be added into the material database in Abaqus or ANSYS and can be easily used for most soft active materials with phase evolution. Model validation also has been done through comparison between micromechanical FEA and experiments on a particular composite material, shape memory elastomeric composite (SMEC) which consisted of an elastomeric matrix and the crystallizable fibre. Results show that the micromechanics and the constitutive models developed in this paper for soft active materials with phase evolution are completely relied on.

  5. Stability and phase transfer of catalytically active platinum nanoparticle suspensions

    NASA Astrophysics Data System (ADS)

    Sriram, Indira; Curtin, Alexandra E.; Chiaramonti, Ann N.; Cuchiaro, J. Hunter; Weidner, Andrew R.; Tingley, Tegan M.; Greenlee, Lauren F.; Jeerage, Kavita M.

    2015-05-01

    In this work, we present a robust synthesis protocol for platinum nanoparticles that yields a monomodal dispersion of particles that are approximately 100 nm in diameter. We determine that these particles are actually agglomerates of much smaller particles, creating a "raspberry" morphology. We demonstrate that these agglomerates are stable at room temperature for at least 8 weeks by dynamic light scattering. Furthermore, we demonstrate consistent electrocatalytic activity for methanol oxidation. Finally, we quantitatively explore the relationship between dispersion solvent and particle agglomeration; specifically, particles are found to agglomerate abruptly as solvent polarity decreases.

  6. Slip rates and ages of past earthquakes along the western Bogd and Valley-of-Lake strike slip faults (Gobi-Altay, Mongolia)

    NASA Astrophysics Data System (ADS)

    Kurtz, R.; Ritz, J. F.; Klinger, Y.; Ferry, M. A.; Davaasambuu, B.; CHOI, J. H.; Magali, R.; Bollinger, L.; Braucher, R.; Ulzibat, M.; Odonbaatar, C.; Demberel, S.

    2015-12-01

    The Gobi-Altay massif in southwestern Mongolia recorded one of the largest intracontinental earthquakes during the XXth century (04.12.57, Mw~8). This left-lateral strike-slip earthquake ruptured a 260 km-long section along the eastern part of the Bogd fault. About 100km of additional ruptures (essentially reverse) were also documented along subsidiary faults. Previous morphological and paleoseismological investigations along the eastern Bogd Fault determined a long-term slip rate of ~1 mm/yr and a mean recurrence interval of 3000-4000 years for events similar to the 1957 earthquake. The active tectonics of the western part of the Gobi-Altay massif proves to be more complex than the eastern section. Deformation is occurring along two strike-slip fault systems, the Western Bogd fault and the Valley-of-Lakes fault. This raises the question of the distribution of the deformation in space and time. In order to determine slip rates and dates of past events along the Western Bogd and Valley of Lakes faults, we carried out tectonic geomorphology and paleoseismological investigations. Preliminary results from a first expedition in 2014 allow estimating a slip rate of 0.3 mm/yr along the Valley-of-Lakes fault during the past 150 ka. Further analyses from a second expedition in summer 2015, should allow testing whether this rate remained stable through time, notably over the Holocene period. They will also enable determining the slip rate and the age of the most recent surface-rupturing event along the Western Bogd fault.

  7. Resonance Energy Transfer Relates the Gas-Phase Structure and Pharmacological Activity of Opioid Peptides.

    PubMed

    Kopysov, Vladimir; Boyarkin, Oleg V

    2016-01-11

    Enkephalins are efficient pain-relief drugs that bind to transmembrane opioid receptors. One key structural parameter that governs the pharmacological activity of these opioid peptides and is typically determined from condensed-phase structures is the distance between the aromatic rings of their Tyr and Phe residues. We use resonance energy transfer, detected by a combination of cold ion spectroscopy and mass spectrometry, to estimate the Tyr-Phe spacing for enkephalins in the gas phase. In contrast to the condensed-phase structures, these distances appear to differ substantially in enkephalins with different pharmacological efficiencies, suggesting that gas-phase structures might be a better pharmacophoric metric for ligand peptides.

  8. Effects of slip, slip rate, and shear heating on the friction of granite

    USGS Publications Warehouse

    Blanpied, M.L.; Tullis, T.E.; Weeks, J.D.

    1998-01-01

    The stability of fault slip is sensitive to the way in which frictional strength responds to changes in slip rate and in particular to the effective velocity dependence of steady state friction ????ss/?? ln V. This quantity can vary substantially with displacement, temperature and slip rate. To investigate the physical basis for this behavior and the possible influence of shear heating, we slid initially bare granite surfaces in unconfined rotary shear to displacements of hundreds of millimeters at normal stresses, ??n, of 10 and 25 MPa and at room temperature. We imposed step changes in slip rate within the range 10-2 to 103.5 ??m/s and also monitored frictional heating with thermistors embedded in the granite. The transient response of ?? to slip rate steps was fit to a rate- and state-dependent friction law using two state variables to estimate the values of several parameters in the constitutive law. The first 20 mm of slip shows rising friction and falling ????ss/?? ln V; further slip shows roughly constant friction, ????ss/?? ln V and parameter values, suggesting that a steady state condition is reached on the fault surface. At V ??? 10 ??m/s, ????ss/?? ln V = -0.004 ?? 0.001. At higher rates the response is sensitive to normal stress: At ??n = 25 MPa granite shows a transition to effective velocity strengthening (????ss/?? ln V = 0.008 ?? 0.004) at the highest slip rates tested. At 10 MPa granite shows a less dramatic change to ????ss/?? ln V ??? 0 at the highest rates. The maximum temperature measured in the granite is ???60??C at 25 MPa and 103.5 ??m/s. Temperatures are in general agreement with a numerical model of heat conduction which assumes spatially homogeneous frictional heating over the sliding surface. The simplest interpretation of our measurements of ????ss/?? ln V is that the granite is inherently veocity weakening (?????ss/??? In V 0 mimics velocity strengthening. These results have implications for the frictional behavior of faults during

  9. 'Shooting at the sun god Apollo': the Apollonian-Dionysian balance of the TimeSlips Storytelling Project.

    PubMed

    George, Daniel R

    2013-09-01

    In The Birth of Tragedy, Friedrich Nietzsche celebrated the dueling forces of reason and emotion as personified by the ancient Greek gods Apollo and Dionysus. A subtle Apollonian-Dionysian balance can be observed in TimeSlips, a group-based creative storytelling activity developed in the 1990s and increasingly used in dementia care settings worldwide. This article explains how the Apollonion-Dionysian aspects of TimeSlips are beneficial not only for persons with dementia, but also for their carers. Narrative data from medical students at Penn State College of Medicine who participated in TimeSlips at a local retirement community are shared.

  10. Coseismic Slip Variation and the Intimate Link with Fault Structure

    NASA Astrophysics Data System (ADS)

    Milliner, C. W. D.; Sammis, C. G.; Allam, A. A.; Dolan, J. F.; Hollingsworth, J.; Leprince, S.; Ayoub, F.

    2015-12-01

    Co-seismic along-strike slip heterogeneity is widely observed for many surface-rupturing earthquakes as revealed by field and high-resolution geodetic methods. However, this co-seismic slip variability is currently a poorly understood phenomenon. Key unanswered questions include: What are the characteristics and underlying causes of along-strike slip variability? Do the properties of slip variability change from fault-to-fault, along-strike or at different scales? We cross-correlate optical, pre- and post-event air photos using the program COSI-Corr to measure the near-field, surface deformation pattern of the 1992 Mw = 7.3 Landers and 1999 Mw = 7.1 Hector Mine earthquakes in high-resolution. We produce the co-seismic slip profiles of both events from over 1,500 displacement measurements and observe consistent along-strike slip variability. Although the observed slip heterogeneity seems apparently complex and disordered, a spectral analysis reveals that the slip distributions are self-affine fractal and variations of slip are not random. We find a fractal dimension of 1.68 + 0.25 and 1.58 + 0.30 for the Landers and Hector Mine earthquakes, respectively, indicating the slip distribution is rougher for the former. We show deterministically that the wavelength and amplitude of slip fluctuations of both earthquakes can be directly correlated to points of geometrical fault complexities (such as stepovers, kinks or bends) of similar size. We find the correlation of the wavelength of slip fluctuations to the size of geometrical fault complexities at all observable length scales, can explain why the complex surface rupture of the Landers earthquake has a rougher slip distribution than the geometrically simpler surface rupture of the Hector Mine event. Our results address longstanding questions concerning co-seismic slip variability, resulting in a more complete understanding of the relationship between slip distributions and fault structure.

  11. Fluid pressures at the shoe-floor-contaminant interface during slips: effects of tread and implications on slip severity.

    PubMed

    Beschorner, Kurt E; Albert, Devon L; Chambers, April J; Redfern, Mark S

    2014-01-22

    Previous research on slip and fall accidents has suggested that pressurized fluid between the shoe and floor is responsible for initiating slips yet this effect has not been verified experimentally. This study aimed to (1) measure hydrodynamic pressures during slipping for treaded and untreaded conditions; (2) determine the effects of fluid pressure on slip severity; and (3) quantify how fluid pressures vary with instantaneous resultant slipping speed, position on the shoe surface, and throughout the progression of the slip. Eighteen subjects walked on known dry and unexpected slippery floors, while wearing treaded and untreaded shoes. Fluid pressure sensors, embedded in the floor, recorded hydrodynamic pressures during slipping. The maximum fluid pressures (mean+/-standard deviation) were significantly higher for the untreaded conditions (124+/-75 kPa) than the treaded conditions (1.1+/-0.29 kPa). Maximum fluid pressures were positively correlated with peak slipping speed (r=0.87), suggesting that higher fluid pressures, which are associated with untreaded conditions, resulted in more severe slips. Instantaneous resultant slipping speed and position of sensor relative to the shoe sole and walking direction explained 41% of the fluid pressure variability. Fluid pressures were primarily observed for untreaded conditions. This study confirms that fluid pressures are relevant to slipping events, consistent with fluid dynamics theory (i.e. the Reynolds equation), and can be modified with shoe tread design. The results suggest that the occurrence and severity of unexpected slips can be reduced by designing shoes/floors that reduce underfoot fluid pressures.

  12. Hyperpolarization-activated cyclic nucleotide-gated 1 independent grid cell-phase precession in mice.

    PubMed

    Eggink, Hannah; Mertens, Paul; Storm, Eline; Giocomo, Lisa M

    2014-03-01

    Cell assemblies code information in both the temporal and spatial domain. One tractable example of temporal coding is the phenomenon of phase precession. In medial entorhinal cortex, theta-phase precession is observed in spatially specific grid cells, with grid spike-times shifting to earlier phases of the extracellular theta rhythm as the animal passes through the grid field. Although the exact mechanisms underlying spatial-temporal coding remain unknown, computational work points to single-cell oscillatory activity as a biophysical mechanism capable of producing phase precession. Support for this idea comes from observed correlations between single-cell resonance and entorhinal neurons characterized by phase precession. Here, we take advantage of the absence of single-cell theta-frequency resonance in hyperpolarization-activated cyclic nucleotide-gated (HCN) 1 knockout (KO) mice to examine the relationship between intrinsic rhythmicity and phase precession. We find phase precession is highly comparable between forebrain-restricted HCN1 KO and wild-type mice. Grid fields in HCN1 KO mice display more experience-dependent asymmetry however, consistent with reports of enhanced long-term potentiation in the absence of HCN1 and raising the possibility that the loss of HCN1 improves temporal coding via the rate-phase transformation. Combined, our results clarify the role of HCN1 channels in temporal coding and constrain the number of possible mechanisms generating phase precession. © 2013 Wiley Periodicals, Inc.

  13. Mechanism and energetics of 〈c + a〉 dislocation cross-slip in hcp metals.

    PubMed

    Wu, Zhaoxuan; Curtin, W A

    2016-10-04

    Hexagonal close-packed (hcp) metals such as Mg, Ti, and Zr are lightweight and/or durable metals with critical structural applications in the automotive (Mg), aerospace (Ti), and nuclear (Zr) industries. The hcp structure, however, brings significant complications in the mechanisms of plastic deformation, strengthening, and ductility, and these complications pose significant challenges in advancing the science and engineering of these metals. In hcp metals, generalized plasticity requires the activation of slip on pyramidal planes, but the structure, motion, and cross-slip of the associated [Formula: see text] dislocations are not well established even though they determine ductility and influence strengthening. Here, atomistic simulations in Mg reveal the unusual mechanism of [Formula: see text] dislocation cross-slip between pyramidal I and II planes, which occurs by cross-slip of the individual partial dislocations. The energy barrier is controlled by a fundamental step/jog energy and the near-core energy difference between pyramidal [Formula: see text] dislocations. The near-core energy difference can be changed by nonglide stresses, leading to tension-compression asymmetry and even a switch in absolute stability from one glide plane to the other, both features observed experimentally in Mg, Ti, and their alloys. The unique cross-slip mechanism is governed by common features of the generalized stacking fault energy surfaces of hcp pyramidal planes and is thus expected to be generic to all hcp metals. An analytical model is developed to predict the cross-slip barrier as a function of the near-core energy difference and applied stresses and quantifies the controlling features of cross-slip and pyramidal I/II stability across the family of hcp metals.

  14. Mechanism and energetics of dislocation cross-slip in hcp metals

    NASA Astrophysics Data System (ADS)

    Wu, Zhaoxuan; Curtin, W. A.

    2016-10-01

    Hexagonal close-packed (hcp) metals such as Mg, Ti, and Zr are lightweight and/or durable metals with critical structural applications in the automotive (Mg), aerospace (Ti), and nuclear (Zr) industries. The hcp structure, however, brings significant complications in the mechanisms of plastic deformation, strengthening, and ductility, and these complications pose significant challenges in advancing the science and engineering of these metals. In hcp metals, generalized plasticity requires the activation of slip on pyramidal planes, but the structure, motion, and cross-slip of the associated dislocations are not well established even though they determine ductility and influence strengthening. Here, atomistic simulations in Mg reveal the unusual mechanism of dislocation cross-slip between pyramidal I and II planes, which occurs by cross-slip of the individual partial dislocations. The energy barrier is controlled by a fundamental step/jog energy and the near-core energy difference between pyramidal dislocations. The near-core energy difference can be changed by nonglide stresses, leading to tension-compression asymmetry and even a switch in absolute stability from one glide plane to the other, both features observed experimentally in Mg, Ti, and their alloys. The unique cross-slip mechanism is governed by common features of the generalized stacking fault energy surfaces of hcp pyramidal planes and is thus expected to be generic to all hcp metals. An analytical model is developed to predict the cross-slip barrier as a function of the near-core energy difference and applied stresses and quantifies the controlling features of cross-slip and pyramidal I/II stability across the family of hcp metals.

  15. Active-absorbing-state phase transition beyond directed percolation: a class of exactly solvable models.

    PubMed

    Basu, Urna; Mohanty, P K

    2009-04-01

    We introduce and solve a model of hardcore particles on a one-dimensional periodic lattice which undergoes an active-absorbing-state phase transition at finite density. In this model, an occupied site is defined to be active if its left neighbor is occupied and the right neighbor is vacant. Particles from such active sites hop stochastically to their right. We show that both the density of active sites and the survival probability vanish as the particle density is decreased below half. The critical exponents and spatial correlations of the model are calculated exactly using the matrix product ansatz. Exact analytical study of several variations of the model reveals that these nonequilibrium phase transitions belong to a new universality class different from the generic active-absorbing-state phase transition, namely, directed percolation.

  16. Ambient Tremor Triggered by Long-term Slow Slip Event in Bungo Channel, Southwest Japan

    NASA Astrophysics Data System (ADS)

    Obara, K.; Hirose, H.; Matsuzawa, T.; Tanaka, S.; Maeda, T.

    2014-12-01

    Episodic tremor and slip (ETS) is a stick-slip in the transition zone between locked and stable sliding zones on the plate interface in Southwest Japan and Cascadia. ETS episode with duration of several days usually recurs at interval of several months at each segment. On the other hand, in the Bungo channel region where is the western edge of the ETS zone in SW Japan, tremor activity continued for several months during the long-term slow slip event (SSE) in 2003 and 2010. In this paper, the relationship between long-term SSE and surrounded triggered tremor is discussed. Tremor triggered by the long-term SSE is spatially localized in the narrow width of about 10 km at the shallowest part of the tremor zone, and at the neighboring area just downdip from the source fault of the SSE. The frequency distribution of tremor along the dip direction during the SSE period is consistent with the spatial distribution of total slip estimated for 2010 SSE. Therefore, the slip of the long-term SSE penetrated in the ETS zone may generate tremor. The daily number of the activated tremor is 12-14 during the SSE; however, it is 40-50 for regular ETS episode during the inter-SSE period. On the other hand, slip rates of the long-term SSE and ETS are typically 1 mm/d and 3 mm/d, respectively. Therefore, tremor rate may be controlled by slip rate. After SSEs in 2003 and 2010, tremor activity seems to slightly increase in the east region within 50 km from the triggered tremor area. Such 7-year period variation in tremor activity is observed in only the shallower side of the tremor zone. Moreover, pattern of the long-term variation seems to slightly migrate to east during a few years. We interpret that a tiny transient slip after the long-term SSE slowly propagates between transition and locked zones. Tremor activity at the shallowest part of the tremor zone in the Bungo channel continued longer than that of regular ETS in the late 2006 during the inter-SSE period. Associated tiny GPS

  17. Evidence for Quaternary Slip on a Low Angle Normal Fault: Searles Valley, CA

    NASA Astrophysics Data System (ADS)

    Numelin, T.; Kirby, E.

    2004-12-01

    Low angle normal faults have been documented in extensional terranes worldwide, however conventional models of fault mechanics preclude slip on planes dipping less than 30 degrees. The global catalogue of earthquake focal mechanisms reveals very few occurrences of seismicity (active slip) on low angle structures, lending support to mechanical arguments against active slip on shallowly dipping planes. Recent field studies of low-angle normal faults in the Baja California and Death Valley regions of western North America, however, suggest that active slip on these structures may be more common than typically thought. Here we investigate the relationship between high angle alluvial scarps in Searles Valley and a low-angle detachment fault in order to determine if displacement on the detachment is active. The network of young and recent fault scarps along the eastern margin Searles Valley can be broadly separated into two primary segments with overlapping fault tips that form a range-scale relay zone in the vicinity of Sand Canyon. South of this relay, the active trace of the fault is marked by a series of graben developed within Late Pleistocene - Holocene alluvial fans. Within the bedrock of the Slate Range, and immediately along-strike of the graben system, is a west dipping, low-angle fault system (Sand Canyon `thrust' - Smith et al., 1968). This fault is continuous within the range for some 20 km and links with a west-dipping normal fault near Manly Pass, and is thus thought to have accommodated west directed normal-sense displacement during Plio-Quaternary time (Andrew and Walker, 2002). Mapping and structural observations at the intersection of the active fault system and the Sand Canyon fault reveals that high-angle scarps cutting Pleistocene alluvium root into a low-angle (10-15°), west-dipping gouge zone. Faults do not significantly displace the detachment surface, and thus, scarp-forming displacement must have been accommodated by slip on the detachment

  18. Depth distribution of seismic slip in oceanic lithosphere: Observations following the April 2012 great earthquakes

    NASA Astrophysics Data System (ADS)

    Aderhold, K.; Abercrombie, R. E.

    2012-12-01

    .5 earthquake showing rupture beginning on a strike-slip fault and progressing to a thrust fault possibly on the subduction interface. Significant directivity shows rupture along both N-S and E-W oriented faults in the Wharton Basin with the 2005 MW 7.2 favoring northward rupture and the 2012 MW 7.2 favoring westward rupture. We perform finite-fault slip inversions on the MW ≥ 7 events to further delineate the spatial distribution of slip and to put constraints on the strength of the oceanic lithosphere. Strike-slip earthquakes in oceanic lithosphere provide an invaluable source to study earthquake rupture dynamics. Fracture zones in the downgoing plate remain a poorly understood part of subduction zones and characterizing their activity before and after subduction contributes to a wholistic understanding of convergent plate boundaries. The extent of seismic slip—and reciprocal aseismic slip—will help determine the quantity of hydrothermally altered material at fracture zones, shown to affect the rupture of tsunamigenic earthquakes and the deformation of the overriding plate (Lin et al, 2009). Oceanic strike-slip earthquakes can be compared to continental sequences, such as on the San Andreas Fault, in order to enhance understanding of seismic cycles and rheological controls of rupture in continental lithosphere.

  19. Two-phase flow in a chemically active porous medium

    SciTech Connect

    Darmon, Alexandre Dauchot, Olivier; Benzaquen, Michael; Salez, Thomas

    2014-12-28

    We study the problem of the transformation of a given reactant species into an immiscible product species, as they flow through a chemically active porous medium. We derive the equation governing the evolution of the volume fraction of the species, in a one-dimensional macroscopic description, identify the relevant dimensionless numbers, and provide simple models for capillary pressure and relative permeabilities, which are quantities of crucial importance when tackling multiphase flows in porous media. We set the domain of validity of our models and discuss the importance of viscous coupling terms in the extended Darcy’s law. We investigate numerically the steady regime and demonstrate that the spatial transformation rate of the species along the reactor is non-monotonous, as testified by the existence of an inflection point in the volume fraction profiles. We obtain the scaling of the location of this inflection point with the dimensionless lengths of the problem. Eventually, we provide key elements for optimization of the reactor.

  20. Slip complexity in earthquake fault models.

    PubMed Central

    Rice, J R; Ben-Zion, Y

    1996-01-01

    We summarize studies of earthquake fault models that give rise to slip complexities like those in natural earthquakes. For models of smooth faults between elastically deformable continua, it is critical that the friction laws involve a characteristic distance for slip weakening or evolution of surface state. That results in a finite nucleation size, or coherent slip patch size, h*. Models of smooth faults, using numerical cell size properly small compared to h*, show periodic response or complex and apparently chaotic histories of large events but have not been found to show small event complexity like the self-similar (power law) Gutenberg-Richter frequency-size statistics. This conclusion is supported in the present paper by fully inertial elastodynamic modeling of earthquake sequences. In contrast, some models of locally heterogeneous faults with quasi-independent fault segments, represented approximately by simulations with cell size larger than h* so that the model becomes "inherently discrete," do show small event complexity of the Gutenberg-Richter type. Models based on classical friction laws without a weakening length scale or for which the numerical procedure imposes an abrupt strength drop at the onset of slip have h* = 0 and hence always fall into the inherently discrete class. We suggest that the small-event complexity that some such models show will not survive regularization of the constitutive description, by inclusion of an appropriate length scale leading to a finite h*, and a corresponding reduction of numerical grid size. Images Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:11607669

  1. IMPROVED MAGNESIUM OXIDE SLIP CASTING METHOD

    DOEpatents

    Stoddard, S.D.; Nuckolls, D.E.

    1963-12-31

    A process for making an aqueous magnesium oxide slip casting slurry comprising the steps of mixing finely ground fused magnesium oxide with water, milling the slurry for at least 30 hours at a temperature of 2-10 deg C (the low temperature during milling inhibiting the formation of hydrated magnesium oxide), discharging the slurry from the mill, adding hydrochloric acid as a deflocculent, and adding a scum inhibitor is presented. (AEC)

  2. Surface slip during large Owens Valley earthquakes

    NASA Astrophysics Data System (ADS)

    Haddon, E. K.; Amos, C. B.; Zielke, O.; Jayko, A. S.; Bürgmann, R.

    2016-06-01

    The 1872 Owens Valley earthquake is the third largest known historical earthquake in California. Relatively sparse field data and a complex rupture trace, however, inhibited attempts to fully resolve the slip distribution and reconcile the total moment release. We present a new, comprehensive record of surface slip based on lidar and field investigation, documenting 162 new measurements of laterally and vertically displaced landforms for 1872 and prehistoric Owens Valley earthquakes. Our lidar analysis uses a newly developed analytical tool to measure fault slip based on cross-correlation of sublinear topographic features and to produce a uniquely shaped probability density function (PDF) for each measurement. Stacking PDFs along strike to form cumulative offset probability distribution plots (COPDs) highlights common values corresponding to single and multiple-event displacements. Lateral offsets for 1872 vary systematically from ˜1.0 to 6.0 m and average 3.3 ± 1.1 m (2σ). Vertical offsets are predominantly east-down between ˜0.1 and 2.4 m, with a mean of 0.8 ± 0.5 m. The average lateral-to-vertical ratio compiled at specific sites is ˜6:1. Summing displacements across subparallel, overlapping rupture traces implies a maximum of 7-11 m and net average of 4.4 ± 1.5 m, corresponding to a geologic Mw ˜7.5 for the 1872 event. We attribute progressively higher-offset lateral COPD peaks at 7.1 ± 2.0 m, 12.8 ± 1.5 m, and 16.6 ± 1.4 m to three earlier large surface ruptures. Evaluating cumulative displacements in context with previously dated landforms in Owens Valley suggests relatively modest rates of fault slip, averaging between ˜0.6 and 1.6 mm/yr (1σ) over the late Quaternary.

  3. Inertial aided cycle slip detection and identification for integrated PPP GPS and INS.

    PubMed

    Du, Shuang; Gao, Yang

    2012-10-25

    The recently developed integrated Precise Point Positioning (PPP) GPS/INS system can be useful to many applications, such as UAV navigation systems, land vehicle/machine automation and mobile mapping systems. Since carrier phase measurements are the primary observables in PPP GPS, cycle slips, which often occur due to high dynamics, signal obstructions and low satellite elevation, must be detected and repaired in order to ensure the navigation performance. In this research, a new algorithm of cycle slip detection and identification has been developed. With the aiding from INS, the proposed method jointly uses WL and EWL phase combinations to uniquely determine cycle slips in the L1 and L2 frequencies. To verify the efficiency of the algorithm, both tactical-grade and consumer-grade IMUs are tested by using a real dataset collected from two field tests. The results indicate that the proposed algorithm can efficiently detect and identify the cycle slips and subsequently improve the navigation performance of the integrated system.

  4. Measurements of drag reduction by SLIPS

    NASA Astrophysics Data System (ADS)

    Samaha, Mohamed A.; Shang, Jessica; Fu, Matthew; Wang, Karen; Stone, Howard; Smits, Alexander; Hultmark, Marcus

    2014-11-01

    Slippery liquid infused porous surfaces (SLIPS) consist of an omniphobic lubricant impregnated into a micro/nanoscale textured substrate. These surfaces have been shown to repel a wide range of liquids. Several techniques to fabricate such surfaces are available in the literature. Here, we report on drag reduction and slip-length measurements using a parallel plate rheometer. Skin-friction measurements of different working fluids are performed on SLIPS with fluorinated boehmite substrates infused with different lubricants. The measurements are refined by considering the evaporation effect of the working fluids. The experiments are performed for different viscosity ratios, N (viscosity of working fluid to that of the lubricant). The effect of the gap height and strain rate on the drag reduction is also investigated. The results show that drag-reduction behavior is influenced by the viscosity ratio and the lubricant-film thickness. The observed drag reduction exists even for very thin film thicknesses. Furthermore, drag reduction is observed for different working fluids even with those having low surface tension such as ethanol. Supported under ONR Grants N00014-12-1-0875 and N00014-12-1-0962 (program manager Ki-Han Kim).

  5. Earthquake slip on oceanic transform faults.

    PubMed

    Abercrombie, R E; Ekström, G

    2001-03-01

    Oceanic transform faults are one of the main types of plate boundary, but the manner in which they slip remains poorly understood. Early studies suggested that relatively slow earthquake rupture might be common; moreover, it has been reported that very slow slip precedes some oceanic transform earthquakes, including the 1994 Romanche earthquake. The presence of such detectable precursors would have obvious implications for earthquake prediction. Here we model broadband seismograms of body waves to obtain well-resolved depths and rupture mechanisms for 14 earthquakes on the Romanche and Chain transform faults in the equatorial Atlantic Ocean. We found that earthquakes on the longer Romanche transform are systematically deeper than those on the neighbouring Chain transform. These depths indicate that the maximum depth of brittle failure is at a temperature of approximately 600 degrees C in oceanic lithosphere. We find that the body waves from the Romanche 1994 earthquake can be well modelled with relatively deep slip on a single fault, and we use the mechanism and depth of this earthquake to recalculate its source spectrum. The previously reported slow precursor can be explained as an artefact of uncertainties in the assumed model parameters.

  6. Slip length crossover on a graphene surface

    SciTech Connect

    Liang, Zhi; Keblinski, Pawel

    2015-04-07

    Using equilibrium and non-equilibrium molecular dynamics simulations, we study the flow of argon fluid above the critical temperature in a planar nanochannel delimited by graphene walls. We observe that, as a function of pressure, the slip length first decreases due to the decreasing mean free path of gas molecules, reaches the minimum value when the pressure is close to the critical pressure, and then increases with further increase in pressure. We demonstrate that the slip length increase at high pressures is due to the fact that the viscosity of fluid increases much faster with pressure than the friction coefficient between the fluid and the graphene. This behavior is clearly exhibited in the case of graphene due to a very smooth potential landscape originating from a very high atomic density of graphene planes. By contrast, on surfaces with lower atomic density, such as an (100) Au surface, the slip length for high fluid pressures is essentially zero, regardless of the nature of interaction between fluid and the solid wall.

  7. Tremor and the Depth Extent of Slip in Large Earthquakes

    NASA Astrophysics Data System (ADS)

    BEroza, G. C.; Brown, J. R.; Ide, S.

    2013-05-01

    We survey the evidence for the distribution of tremor and mainshock slip. In Southwest Japan, where tremor is well located, it outlines the down-dip edge of slip in the 1944 and 1946 Nankai earthquakes. In Alaska and the Aleutians, tremor location and slip distributions in slip are subject to greater uncertainty, but within that uncertainty they are consistent with the notion that tremor outlines the down-dip limit of mainshock slip. In Mexico, tremor locations and the extent of rupture in large (M > 7) earthquakes are also uncertain, but show a similar relationship. Taken together, these observations suggest that tremor may provide important information on the depth extent of rupture in large earthquakes where there have been no large earthquakes to test that hypothesis. If applied to the Cascadia subduction zone, it suggests slip will extend farther inland than previously assumed. If applied to the San Andreas Fault, it suggests slip will extend deeper than has previously been assumed.

  8. Minimum cycle slip airborne differential carrier phase GPS antenna

    NASA Technical Reports Server (NTRS)

    Wright, Charles Wayne (Inventor)

    2005-01-01

    An antenna system is disclosed including a GPS antenna which is driven by an articulator in an opposite direction to aircraft roll. Aircraft roll is sensed by an onboard navigation system and translation module sends a signal to a processor which provides a drive signal to the articulator. As the aircraft rolls in one direction, the antenna is driven oppositely to maintain the vertical orientation of the antenna.

  9. Activity of Sulfa Drugs and Their Combinations against Stationary Phase B. burgdorferi In Vitro.

    PubMed

    Feng, Jie; Zhang, Shuo; Shi, Wanliang; Zhang, Ying

    2017-03-22

    Lyme disease is a most common vector-borne disease in the US. Although the majority of Lyme patients can be cured with the standard two- to four-week antibiotic treatment, at least 10%-20% of patients continue to suffer from prolonged post-treatment Lyme disease syndrome (PTLDS). While the cause for this is unclear, one possibility is that persisting organisms are not killed by current Lyme antibiotics. In our previous studies, we screened an FDA drug library and an NCI compound library on B. burgdorferi and found some drug hits including sulfa drugs as having good activity against B. burgdorferi stationary phase cells. In this study, we evaluated the relative activity of three commonly used sulfa drugs, sulfamethoxazole (Smx), dapsone (Dps), sulfachlorpyridazine (Scp), and also trimethoprim (Tmp), and assessed their combinations with the commonly prescribed Lyme antibiotics for activities against B. burgdorferi stationary phase cells. Using the same molarity concentration, dapsone, sulfachlorpyridazine and trimethoprim showed very similar activity against stationary phase B. burgdorferi enriched in persisters; however, sulfamethoxazole was the least active drug among the three sulfa drugs tested. Interestingly, contrary to other bacterial systems, Tmp did not show synergy in drug combinations with the three sulfa drugs at their clinically relevant serum concentrations against B. burgdorferi. We found that sulfa drugs combined with other antibiotics were more active than their respective single drugs and that four-drug combinations were more active than three-drug combinations. Four-drug combinations dapsone + minocycline + cefuroxime + azithromycin and dapsone + minocycline + cefuroxime + rifampin showed the best activity against stationary phase B. burgdorferi in these sulfa drug combinations. However, these four-sulfa-drug-containing combinations still had considerably less activity against B. burgdorferi stationary phase cells than the Daptomycin + cefuroxime

  10. Activity of Sulfa Drugs and Their Combinations against Stationary Phase B. burgdorferi In Vitro

    PubMed Central

    Feng, Jie; Zhang, Shuo; Shi, Wanliang; Zhang, Ying

    2017-01-01

    Lyme disease is a most common vector-borne disease in the US. Although the majority of Lyme patients can be cured with the standard two- to four-week antibiotic treatment, at least 10%–20% of patients continue to suffer from prolonged post-treatment Lyme disease syndrome (PTLDS). While the cause for this is unclear, one possibility is that persisting organisms are not killed by current Lyme antibiotics. In our previous studies, we screened an FDA drug library and an NCI compound library on B. burgdorferi and found some drug hits including sulfa drugs as having good activity against B. burgdorferi stationary phase cells. In this study, we evaluated the relative activity of three commonly used sulfa drugs, sulfamethoxazole (Smx), dapsone (Dps), sulfachlorpyridazine (Scp), and also trimethoprim (Tmp), and assessed their combinations with the commonly prescribed Lyme antibiotics for activities against B. burgdorferi stationary phase cells. Using the same molarity concentration, dapsone, sulfachlorpyridazine and trimethoprim showed very similar activity against stationary phase B. burgdorferi enriched in persisters; however, sulfamethoxazole was the least active drug among the three sulfa drugs tested. Interestingly, contrary to other bacterial systems, Tmp did not show synergy in drug combinations with the three sulfa drugs at their clinically relevant serum concentrations against B. burgdorferi. We found that sulfa drugs combined with other antibiotics were more active than their respective single drugs and that four-drug combinations were more active than three-drug combinations. Four-drug combinations dapsone + minocycline + cefuroxime + azithromycin and dapsone + minocycline + cefuroxime + rifampin showed the best activity against stationary phase B. burgdorferi in these sulfa drug combinations. However, these four-sulfa-drug–containing combinations still had considerably less activity against B. burgdorferi stationary phase cells than the Daptomycin

  11. Variability in AIRS CO2 during active and break phases of Indian summer monsoon.

    PubMed

    Revadekar, J V; Ravi Kumar, K; Tiwari, Yogesh K; Valsala, Vinu

    2016-01-15

    Due to human activities, the atmospheric concentration of Carbon Dioxide (CO2) has been rising extensively since the Industrial Revolution. Indian summer monsoon (ISM) has a dominant westerly component from ocean to land with a strong tendency to ascend and hence may have role in CO2 distribution in lower and middle troposphere over Indian sub-continent. A substantial component of ISM variability arises from the fluctuations on the intra-seasonal scale between active and break phases which correspond to strong and weak monsoon circulation. In view of the above, an attempt is made in this study to examine the AIRS/AQUA satellite retrieved CO2 distribution in response to atmospheric circulation with focus on active and break phase. Correlation analysis indicates the increase in AIRS CO2 linked with strong monsoon circulation. Study also reveals that anomalous circulation pattern during active and break phase show resemblance with high and low values of AIRS CO2. Homogeneous monsoon regions of India show substantial increase in CO2 levels during active phase. Hilly regions of India show strong contrast in CO2 and vertical velocity during active and break phases.

  12. Modeling of rock friction 2. Simulation of preseismic slip

    USGS Publications Warehouse

    Dieterich, J.H.

    1979-01-01

    The constitutive relations developed in the companion paper are used to model detailed observations of preseismic slip and the onset of unstable slip in biaxial laboratory experiments. The simulations employ a deterministic plane strain finite element model to represent the interactions both within the sliding blocks and between the blocks and the loading apparatus. Both experiments and simulations show that preseismic slip is controlled by initial inhomogeneity of shear stress along the sliding surface relative to the frictional strength. As a consequence of the inhomogeneity, stable slip begins at a point on the surface and the area of slip slowly expands as the external loading increases. A previously proposed correlation between accelerating rates of stable slip and growth of the area of slip is supported by the simulations. In the simulations and in the experiments, unstable slip occurs shortly after a propagating slip event traverses the sliding surface and breaks out at the ends of the sample. In the model the breakout of stable slip causes a sudden acceleration of slip rates. Because of velocity dependency of the constitutive relationship for friction, the rapid acceleration of slip causes a decrease in frictional strength. Instability occurs when the frictional strength decreases with displacement at a rate that exceeds the intrinsic unloading characteristics of the sample and test machine. A simple slider-spring model that does not consider preseismic slip appears to approximate the transition adequately from stable sliding to unstable slip as a function of normal stress, machine stiffness, and surface roughness for small samples. However, for large samples and for natural faults the simulations suggest that the simple model may be inaccurate because it does not take into account potentially large preseismic displacements that will alter the friction parameters prior to instability. Copyright ?? 1979 by the American Geophysical Union.

  13. EFFECT OF VAPOR-PHASE BIOREACTOR OPERATION ON BIOMASS ACCUMULATION, DISTRIBUTION, AND ACTIVITY. (R826168)

    EPA Science Inventory

    Excess biomass accumulation and activity loss in vapor-phase bioreactors (VPBs) can lead to unreliable long-term operation. In this study, temporal and spatial variations in biomass accumulation, distribution and activity in VPBs treating toluene-contaminated air were monitored o...

  14. Differential control of active and silent phases in relaxation models of neuronal rhythms.

    PubMed

    Tabak, Joël; O'Donovan, Michael J; Rinzel, John

    2006-12-01

    Rhythmic bursting activity, found in many biological systems, serves a variety of important functions. Such activity is composed of episodes, or bursts (the active phase, AP) that are separated by quiescent periods (the silent phase, SP). Here, we use mean field, firing rate models of excitatory neural network activity to study how AP and SP durations depend on two critical network parameters that control network connectivity and cellular excitability. In these models, the AP and SP correspond to the network's underlying bistability on a fast time scale due to rapid recurrent excitatory connectivity. Activity switches between the AP and SP because of two types of slow negative feedback: synaptic depression-which has a divisive effect on the network input/output function, or cellular adaptation-a subtractive effect on the input/output function. We show that if a model incorporates the divisive process (regardless of the presence of the subtractive process), then increasing cellular excitability will speed up the activity, mostly by decreasing the silent phase. Reciprocally, if the subtractive process is present, increasing the excitatory connectivity will slow down the activity, mostly by lengthening the active phase. We also show that the model incorporating both slow processes is less sensitive to parameter variations than the models with only one process. Finally, we note that these network models are formally analogous to a type of cellular pacemaker and thus similar results apply to these cellular pacemakers.

  15. Slip of polydisperse polymers: Molecular weight distribution above and below the plane of slip

    NASA Astrophysics Data System (ADS)

    Sabzevari, Seyed Mostafa; Strandman, Satu; Wood-Adams, Paula Marie

    2015-04-01

    When strong slip occurs during the drag flow of highly entangled polybutadienes (PBD) in a sliding plate rheometer equipped with stainless steel parallel plates, a thin film of polymer debris remains on the substrate after the slip. This debris is assumed to be formed by the disentanglement process that occurs in strong slip at a distance of about one molecular size from the plate. In order to evaluate the composition of the debris we collected it with tetrahydrofuran and subjected it to gel permeation chromatography. It was found that the molecular weight distribution (MWD) of the debris is significantly different from that of the bulk. Moreover, in mixtures prepared from long and short PBDs with distinctly different molecular weight distributions, the MWD of the debris was found to be richer in low molecular weight components and leaner in the high molecular weight components compared to the bulk. This information is important since it reveals the compositional difference between the bulk and interfacial layer above and below the plane of slip. The difference in MWD is likely a consequence of the strong slip in which some of long chains are pulled away from the surface-adsorbed chains by the flow leaving a debris lean in the high molecular weight component.

  16. Effective slip for flow in a rotating channel bounded by stick-slip walls

    NASA Astrophysics Data System (ADS)

    Ng, Chiu-On

    2016-12-01

    This paper aims to look into how system rotation may modify the role played by boundary slip in controlling flow through a rotating channel bounded by stick-slip walls. A semianalytical model is developed for pressure-driven flow in a slit channel that rotates about an axis perpendicular to its walls, which are superhydrophobic surfaces patterned with periodic alternating no-shear and no-slip stripes. The cases where the flow is driven by a pressure gradient parallel or normal to the stripes are considered. The effects of the no-shear area fraction on the velocities and effective slip lengths for the primary and secondary flows are investigated as functions of the rotation rate and the channel height. It is mathematically proved that the secondary flow rate is exactly the same in the two cases, irrespective of whether the primary flow is parallel or normal to the wall stripes. For any rotation speed, there is an optimal value of the no-shear area fraction at which the primary flow rate is maximum. This is a consequence of two competing effects: the no-shear part of the wall may serve to reduce the wall resistance, thereby enhancing the flow especially at low rotation, but it also weakens the formation of the near-wall Ekman layer, which is responsible for pumping the flow especially at high rotation. Wall slip in a rotating environment is to affect flow in the Ekman layer, but not flow in the geostrophic core.

  17. Effective slip for flow in a rotating channel bounded by stick-slip walls.

    PubMed

    Ng, Chiu-On

    2016-12-01

    This paper aims to look into how system rotation may modify the role played by boundary slip in controlling flow through a rotating channel bounded by stick-slip walls. A semianalytical model is developed for pressure-driven flow in a slit channel that rotates about an axis perpendicular to its walls, which are superhydrophobic surfaces patterned with periodic alternating no-shear and no-slip stripes. The cases where the flow is driven by a pressure gradient parallel or normal to the stripes are considered. The effects of the no-shear area fraction on the velocities and effective slip lengths for the primary and secondary flows are investigated as functions of the rotation rate and the channel height. It is mathematically proved that the secondary flow rate is exactly the same in the two cases, irrespective of whether the primary flow is parallel or normal to the wall stripes. For any rotation speed, there is an optimal value of the no-shear area fraction at which the primary flow rate is maximum. This is a consequence of two competing effects: the no-shear part of the wall may serve to reduce the wall resistance, thereby enhancing the flow especially at low rotation, but it also weakens the formation of the near-wall Ekman layer, which is responsible for pumping the flow especially at high rotation. Wall slip in a rotating environment is to affect flow in the Ekman layer, but not flow in the geostrophic core.

  18. Slow Slip Events on a 760 mm Long Granite Sample

    NASA Astrophysics Data System (ADS)

    Mclaskey, G.; Yamashita, F.

    2015-12-01

    We describe slow slip events and dynamic rupture events generated on a newly constructed large-scale biaxial friction apparatus at Cornell University that provide insights into the mechanisms of aseismic and seismic slip. We find that, under nominally similar experimental conditions, the 760 mm long granite sample sometimes slips in dynamic stick-slip events and sometimes relieves accumulated shear stress through slow slip events. To provide insights into this curious behavior and the underlying mechanisms, fault slip and shear stress are each measured at 8 locations along the 760 mm long fault. This allows us to map slow slip fronts and the nucleation and propagation of dynamic fault rupture. The granite sample is also instrumented with an array of piezoelectric sensors that are the laboratory equivalent of a seismic network. When the sample is loaded relatively slowly, at 0.03 MPa/s, slow slip occurs on large sections of the fault and the slow slipping region soon expands to the sample boundary. In this case, stress is released in a slow slip event with peak slip velocities < 2 mm/s. Alternatively, when one end of the sample is loaded rapidly (4 MPa/s), or the sample is allowed to heal in stationary contact for a few minutes, slow slip initiates near the load point and accelerates to slip velocities exceeding 200 mm/s before the slow slipping region expands all the way to the sample boundary. This produces a dynamic slip event (stick-slip). The dynamic slip events radiate seismic waves equivalent to a M = -2.5 earthquake. In contrast, the laboratory-generated slow slip events are predominantly aseismic and produce only bursts of tiny and discrete seismic events (M = -6) reminiscent of swarms of microseismicity. The experiments illustrate how a single fault can slide slowly and aseismically or rapidly and dynamically depending on stress state and loading conditions. We compare the behavior observed on this Cornell apparatus to the behavior of other large

  19. Detailed history of slip along the Sunda mega-thrust

    NASA Astrophysics Data System (ADS)

    Simão, Nuno; Lindsay, Anthony; Murphy, Shane; McCloskey, John; Bhloscaidh, Mairead Nic; Nalbant, Suleyman

    2013-04-01

    We undertook a reconstruction of more than 200 years of deformation on the Sunda mega-thrust using the history of vertical displacement recorded in the stratigraphy of coral micro-atolls. This reconstruction gave an unprecedented opportunity to understand the distributions of slip on the recent series of great earthquakes and its relationship with coupling. We have seen with the recent earthquakes that, whilst the slip-coupling relationship may be complex and certainly depends on the pre-stress, the greatest slip generally occurs in areas of high coupling. We have also seen that the spatial distributions of the greatest slip reveals tessellation between earthquakes. Using Monte Carlo techniques, we compare ground deformation produced by different fractal slip distributions with micro-atoll coral data to estimate slip distributions for the 1797 and 1833 historical earthquakes. The resulting slip estimations have a more realistic spatial distribution and provide a better fit to the micro-atoll data than previously published solutions. Preliminary results seem to imply that the 1797 and 1833 ruptures reveal a level of complementarity, where the greatest values of slip tessellate with the greatest slip values observed in the two great earthquakes of 2007 and the earthquake of 2010. In addition, the spatial stacking of all slips from all available earthquake slip distributions reveals a strong correlation with the spatial distribution of the coupling. Discrepancies in the spatial slip-coupling correlation, although strongly influenced by the uncertainties of the slip distributions, and with the 1797 and 1833 earthquakes playing a stronger role, can still be used as a way to pin-point possible areas of slip deficit when compared with the spatial distribution of coupling. This seems to imply that correspondence between the slip probability in 1797 and 1833 and present-day earthquakes slip and coupling appears to show the same basic relationship indicating that the broad

  20. Soft-bed experiments beneath Engabreen, Norway: Regelation, infiltration, basal slip and bed deformation

    USGS Publications Warehouse

    Iverson, N.R.; Hooyer, T.S.; Fischer, U.H.; Cohen, D.; Moore, P.L.; Jackson, M.; Lappegard, G.; Kohler, J.

    2007-01-01

    To avoid some of the limitations of studying soft-bed processes through boreholes, a prism of simulated till (1.8 m ?? 1.6 m ?? 0.45 m) with extensive instrumentation was constructed in a trough blasted in the rock bed of Engabreen, a temperate glacier in Norway. Tunnels there provide access to the bed beneath 213 m of ice. Pore-water pressure was regulated in the prism by pumping water to it. During experiments lasting 7-12 days, the glacier regelated downward into the prism to depths of 50-80 mm, accreting ice-infiltrated till at rates predicted by theory. During periods of sustained high pore-water pressure (70-100% of overburden), ice commonly slipped over the prism, due to a water layer at the prism surface. Deformation of the prism was activated when this layer thinned to a sub-millimeter thickness. Shear strain in the till was pervasive and decreased with depth. A model of slip by ploughing of ice-infiltrated till across the prism surface accounts for the slip that occurred when effective pressure was sufficiently low or high. Slip at low effective pressures resulted from water-layer thickening that increased non-linearly with decreasing effective pressure. If sufficiently widespread, such slip over soft glacier beds, which involves no viscous deformation resistance, may instigate abrupt increases in glacier velocity.

  1. Radar Determination of Fault Slip and Location in Partially Decorrelated Images

    NASA Astrophysics Data System (ADS)

    Parker, Jay; Glasscoe, Margaret; Donnellan, Andrea; Stough, Timothy; Pierce, Marlon; Wang, Jun

    2016-09-01

    Faced with the challenge of thousands of frames of radar interferometric images, automated feature extraction promises to spur data understanding and highlight geophysically active land regions for further study. We have developed techniques for automatically determining surface fault slip and location using deformation images from the NASA Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR), which is similar to satellite-based SAR but has more mission flexibility and higher resolution (pixels are approximately 7 m). This radar interferometry provides a highly sensitive method, clearly indicating faults slipping at levels of 10 mm or less. But interferometric images are subject to decorrelation between revisit times, creating spots of bad data in the image. Our method begins with freely available data products from the UAVSAR mission, chiefly unwrapped interferograms, coherence images, and flight metadata. The computer vision techniques we use assume no data gaps or holes; so a preliminary step detects and removes spots of bad data and fills these holes by interpolation and blurring. Detected and partially validated surface fractures from earthquake main shocks, aftershocks, and aseismic-induced slip are shown for faults in California, including El Mayor-Cucapah (M7.2, 2010), the Ocotillo aftershock (M5.7, 2010), and South Napa (M6.0, 2014). Aseismic slip is detected on the San Andreas Fault from the El Mayor-Cucapah earthquake, in regions of highly patterned partial decorrelation. Validation is performed by comparing slip estimates from two interferograms with published ground truth measurements.

  2. Flexural-slip generated bedding-parallel veins from central Victoria, Australia

    NASA Astrophysics Data System (ADS)

    Fowler, T. J.

    1996-12-01

    Thin continuous laminated bedding-parallel quartz veins (BPVs) with slip-striated and fibred vein walls occur within slates, or at their contact with sandstones, on the limbs of chevron folds in the Bendigo-Castlemaine goldfields, southeastern Australia. Two microstructural Types of BPV (I and II) have been previously recognized, and are confirmed in this study. Both types are concluded to have formed during and/or after crenulation cleavage (the first tectonic axial planar structure) in the wallrock slates, and during flexural-slip folding. Type I BPVs consist of syntaxial phyllosilicate inclusion trails, parallel to bedding, enclosing inclined inclusion bands, the latter formed by detachment of wallrock phyllosilicate particles from the walls of pressure solution-segmented discordant tension veins. Type I BPVs are formed by bedding-parallel shear, and grow in width by propagation of the discordant veins into the BPV walls. Type II veins are composed of quartz bands separated by wallrock slate seams which have split away from the vein wall during dilatant shear opening. They incorporate numerous torn-apart fragments of crenulated wallrock slate. Type I BPV inclusion band average spacing of 0.5 mm probably represents the magnitude of slip increments during stick-slip flexural-slip folding activity.

  3. Simultaneous teleseismic and geodetic observations of the stick-slip motion of an Antarctic ice stream.

    PubMed

    Wiens, Douglas A; Anandakrishnan, Sridhar; Winberry, J Paul; King, Matt A

    2008-06-05

    Long-period seismic sources associated with glacier motion have been recently discovered, and an increase in ice flow over the past decade has been suggested on the basis of secular changes in such measurements. Their significance, however, remains uncertain, as a relationship to ice flow has not been confirmed by direct observation. Here we combine long-period surface-wave observations with simultaneous Global Positioning System measurements of ice displacement to study the tidally modulated stick-slip motion of the Whillans Ice Stream in West Antarctica. The seismic origin time corresponds to slip nucleation at a region of the bed of the Whillans Ice Stream that is likely stronger than in surrounding regions and, thus, acts like an 'asperity' in traditional fault models. In addition to the initial pulse, two seismic arrivals occurring 10-23 minutes later represent stopping phases as the slip terminates at the ice stream edge and the grounding line. Seismic amplitude and average rupture velocity are correlated with tidal amplitude for the different slip events during the spring-to-neap tidal cycle. Although the total seismic moment calculated from ice rigidity, slip displacement, and rupture area is equivalent to an earthquake of moment magnitude seven (M(w) 7), seismic amplitudes are modest (M(s) 3.6-4.2), owing to the source duration of 20-30 minutes. Seismic radiation from ice movement is proportional to the derivative of the moment rate function at periods of 25-100 seconds and very long-period radiation is not detected, owing to the source geometry. Long-period seismic waves are thus useful for detecting and studying sudden ice movements but are insensitive to the total amount of slip.

  4. Effects of Fluid Flow on Slip Evolution in a Thermoporoelastic Medium: Implications for Seismic Moment Evolution

    NASA Astrophysics Data System (ADS)

    Suzuki, T.; Yamashita, T.

    2015-12-01

    We have constructed a framework associated with the interaction among heat, fluid pressure and inelastic pore creation, and found three nondimensional parameters, Su, Su' and Ta, which are related to the dilatancy effect, fluid flow effect and the upper limit of the dilatancy, respectively. Without fluid flow, they were found to generate two qualitatively different slip behaviors, acceleration case and spontaneous slip cessation case. In particular, the acceleration case shows the initial deceleration and later acceleration approaching the final high-speed slip. Between the deceleration and acceleration phases, we observe a transient state featured by low and approximately constant slip velocity. We employ the fluid flow effect here and give some implications for understanding the temporal evolution of seismic moments. For example, Ide et al. (2007) found that ordinary earthquakes and slow earthquakes have different forms of temporal evolutions of the seismic moments. In addition, Duputel et al. (2013) observed examples showing exceptional moment evolution behavior even among ordinary earthquakes. Yamashita and Suzuki (2011) successfully modeled the former result by introducing slip-induced dilatancy coupled with fluid flow, while the modeling of the latter remains unaccomplished. If we introduce the fluid flow, we observe only the acceleration case and the duration of the transient state is longer than that without the fluid flow. This can be a model for a slow earthquake if we assume a 2-D model, and the seismic moment of such an earthquake evolves in almost a quadratic function in time. On the other hand, for the acceleration case without the fluid flow, the seismic moment evolution is almost a cubic function. Moreover, for the spontaneous slip cessation case, it evolves with a quadratic or linear function. The framework explaining all the behaviors mentioned above has been obtained. Quantitative investigation on the nondimensional parameters will also be done.

  5. Principal Slip Zones in Carbonate: Microstructural Characterization and Implications for the Seismic Cycle

    NASA Astrophysics Data System (ADS)

    Smith, Steven; Billi, Andrea; di Toro, Giulio

    2010-05-01

    Main shocks in central Italy, such as the L'Aquila Mw 6.3 earthquake on 6 April 2009, and associated foreshock and aftershock sequences, often nucleate within, and rupture through, carbonate-bearing rocks within the upper-crust. One way to understand the mechanical behaviour of such rocks during the passage of earthquake ruptures is to study the Principal Slip Zones (PSZs) of exhumed faults. The PSZs are thought to accommodate a majority of displacement during individual earthquake slip events, and potentially contain a rich variety of information about earthquake-related processes and, more generally, deformation mechanisms throughout the seismic cycle. At present, however, there are no reliable microstructural or geochemical indicators of seismic slip in carbonate rocks. We present detailed field and microstructural observations of the PSZs of large-displacement, seismically active normal fault zones in the central Apennines of Italy. The fault zones are exhumed from <3km depth and cut 3-5km thick sequences of platform limestone. Samples were collected from individual PSZs containing polished slip surfaces with both small (centimetres to metres) and large (metres to hundreds of metres) displacements, including the main PSZ that defines the active Quaternary fault scarp. Small displacement slipping zones are characterized by typical cataclastic fabrics, including angular grains cross-cut by brittle fractures, and a gradual decrease in grain-size towards the polished slip surface. In contrast, large-displacement slipping zones always contain a continuous, texturally-distinct layer up to 2-3mm in thickness that lies immediately beneath the polished slip surface. This layer is itself internally zoned; up to 6 distinct zones can be present, each between 200-300µm in thickness, and recognized on the basis of grain-size, colour, and textural variations. In some cases, the zones developed at the expense of one another. 100-200µm-thick, syn-tectonic calcite veins

  6. Suppression of strike-slip fault systems

    NASA Astrophysics Data System (ADS)

    Curren, I. S.

    2012-12-01

    In orogens elongated parallel to a great circle about the Euler pole for the two bounding plates, theory requires simple-shear deformation in the form of distributed deformation or velocity discontinuities across strike-slip faults. This type of deformation, however, does not develop at all plate boundaries requiring toroidal motion. Using the global plate boundary model, PB2002 [Bird, 2003], as the basis for identifying areas where expected simple-shear deformation is absent or underdeveloped, it was also possible to identify two potential causes for this behavior: (1) the presence of extensive fracturing at right angles to the shear plane and (2) regional cover of flood basalts or andesites with columnar joints. To test this hypothesis, a new plane-stress finite-strain model was developed to study the effects of such pre-existing structures on the development of simple shear in a clay cake. A homogenous kaolinite-water mixture was poured into a deforming parallelogram box and partially dried to allow for brittle and plastic deformation at and below the surface of the clay, respectively. This was floated on a dense fluid foundation, effectively removing basal friction, and driven by a motor in a sinistral direction from the sides of the box. Control experiments produced classic Riedel model fault assemblages and discrete, through-going primary deformation zones (PDZs); experiments with pre-existing structures developed the same, though subdued and distributed, fault assemblages but did not develop through-going PDZs. Although formation of strike-slip faults was underdeveloped at the surface in clay with pre-existing structures, offset within the clay cake (measured, with respect to a fixed point, by markers on the clay surface) as a fraction of total offset of the box was consistently larger than that of the control experiments. This suggests that while the extent of surface faulting was lessened in clay with pre-existing structures, slip was still occurring at

  7. Approach run increases preactivation and eccentric phases muscle activity during drop jumps from different drop heights.

    PubMed

    Ruan, Mianfang; Li, Li

    2010-10-01

    The purpose of this study was to investigate the effects of a horizontal approach run and drop height on the activation of lower extremity muscles during drop jumps. Ten participants performed drop jumps from drop heights of 15, 30, 45 and 60cm with zero (standing), one, two, and three approach run steps. The EMG activities of the Gluteus Maximus (GM), Rectus Femoris (RF), Biceps Femoris (BF), Vastus Lateralis (VL), Tibialis Anterior (TA), Gastrocnemius (GA) and Soleus (SO) were recorded, full-wave rectified, and averaged (aEMG) during the preactivation (50ms before touchdown), downward, and push-off phases. Increasing drop height did not enhance the muscle activation level of any examined muscles except GA. During the preactivation phase, the aEMG of all muscles except TA increased with the number of approach run steps. The aEMG of RF, BF, VL, and SO also increased with the number of approach run steps during the downward phase, while no aEMG changes were observed during the push-off phase. These results suggest that a horizontal approach run preceding the drop jump is an effective strategy for increasing the muscle preactivation level, which contributes to a higher level of muscle activity during the eccentric contraction phase and could potentially contribute to the reported higher power output during the concentric contraction phase.

  8. Muscle activation patterns in acceleration-based phases during reach-to-grasp movement

    PubMed Central

    Tokuda, Keisuke; Lee, Bumsuk; Shiihara, Yasufumi; Takahashi, Kazuhiro; Wada, Naoki; Shirakura, Kenji; Watanabe, Hideomi

    2016-01-01

    [Purpose] An earlier study divided reaching activity into characteristic phases based on hand velocity profiles. By synchronizing muscle activities and the acceleration profile, a phasing approach for reaching movement, based on hand acceleration profiles, was attempted in order to elucidate the roles of individual muscle activities in the different phases of the acceleration profile in reaching movements. [Subjects and Methods] Ten healthy volunteer subjects participated in this study. The aim was to electromyographically evaluate muscles around the shoulder, the upper trapezius, the anterior deltoid, the biceps brachii, and the triceps brachii, most of which have been used to evaluate arm motion, as well as the acceleration of the upper limb during simple reaching movement in the reach-to-grasp task. [Results] Analysis showed the kinematic trajectories of the acceleration during a simple biphasic profile of the reaching movement could be divided into four phases: increasing acceleration (IA), decreasing acceleration (DA), increasing deceleration (ID), and decreasing deceleration (DD). Muscles around the shoulder showed different activity patterns, which were closely associated with these acceleration phases. [Conclusion] These results suggest the important role of the four phases, derived from the acceleration trajectory, in the elucidation of the muscular mechanisms which regulate and coordinate the muscles around the shoulder in reaching movements. PMID:27942129

  9. Physiologically motivated multiplex Kuramoto model describes phase diagram of cortical activity.

    PubMed

    Sadilek, Maximilian; Thurner, Stefan

    2015-05-21

    We derive a two-layer multiplex Kuramoto model from Wilson-Cowan type physiological equations that describe neural activity on a network of interconnected cortical regions. This is mathematically possible due to the existence of a unique, stable limit cycle, weak coupling, and inhibitory synaptic time delays. We study the phase diagram of this model numerically as a function of the inter-regional connection strength that is related to cerebral blood flow, and a phase shift parameter that is associated with synaptic GABA concentrations. We find three macroscopic phases of cortical activity: background activity (unsynchronized oscillations), epileptiform activity (highly synchronized oscillations) and resting-state activity (synchronized clusters/chaotic behaviour). Previous network models could hitherto not explain the existence of all three phases. We further observe a shift of the average oscillation frequency towards lower values together with the appearance of coherent slow oscillations at the transition from resting-state to epileptiform activity. This observation is fully in line with experimental data and could explain the influence of GABAergic drugs both on gamma oscillations and epileptic states. Compared to previous models for gamma oscillations and resting-state activity, the multiplex Kuramoto model not only provides a unifying framework, but also has a direct connection to measurable physiological parameters.

  10. Long-term slip deficit and the forecasting of slip in future earthquakes

    NASA Astrophysics Data System (ADS)

    McCloskey, John; NicBhloscaidh, Mairead; Simao, Nuno

    2014-05-01

    In the last decade a series of devastating earthquakes have between them killed more than three-quarters of a million people. None of the events were formally forecast and have been repeatedly referred to a seismological 'surprises'. Here we argue that while earthquakes within the wide swath of diffuse deformation comprising the Alpine-Himalayan belt pose a set of particularly difficult set of challenges, earthquakes which are driven by high strain-rates at plate boundaries and which have relatively short nominal recurrence times might be forecast if the data exists to perform long-term slip deficit modelling and stress reconstruction. We show that two instrumentally recorded event on the Sumatran margin in 2007 and 2010 occurred in regions of high slip deficit identified by reconstruction of slip in historical earthquakes in 1797 and 1833 under the Mentawai Islands using more than 200 years of geodetic data recorded in the stratigraphy of coral micro-atolls growing there. In the presentation we will describe the data and a new Bayesian-Monte Carlo slip reconstruction technique. The technique is based on the stochastic forward modelling of many slip distributions each using the same set of elastic Green's functions to estimate, by superposition of contributions from each fault cell, the vertical displacement at the coral locations resulting from each simulated event. Every solution, weighted by its goodness of fit to the data, is added to a stack whose final values contain an estimate of the most likely distribution of slip in the historical earthquakes. Further, we estimate the Kullback-Liebler divergence over the fault area providing a non-arbitrary assessment of the spatial distribution of information gain, identifying regions of low- and high- model confidence. We then model the long-term slip deficit on the megathrust assuming a zero of stress immediately after the 1652 Mentawai Islands earthquake. We use the resulting slip deficit field to compute the entire

  11. Earthquake scaling laws for rupture geometry and slip heterogeneity

    NASA Astrophysics Data System (ADS)

    Thingbaijam, Kiran K. S.; Mai, P. Martin; Goda, Katsuichiro

    2016-04-01

    We analyze an extensive compilation of finite-fault rupture models to investigate earthquake scaling of source geometry and slip heterogeneity to derive new relationships for seismic and tsunami hazard assessment. Our dataset comprises 158 earthquakes with a total of 316 rupture models selected from the SRCMOD database (http://equake-rc.info/srcmod). We find that fault-length does not saturate with earthquake magnitude, while fault-width reveals inhibited growth due to the finite seismogenic thickness. For strike-slip earthquakes, fault-length grows more rapidly with increasing magnitude compared to events of other faulting types. Interestingly, our derived relationship falls between the L-model and W-model end-members. In contrast, both reverse and normal dip-slip events are more consistent with self-similar scaling of fault-length. However, fault-width scaling relationships for large strike-slip and normal dip-slip events, occurring on steeply dipping faults (δ~90° for strike-slip faults, and δ~60° for normal faults), deviate from self-similarity. Although reverse dip-slip events in general show self-similar scaling, the restricted growth of down-dip fault extent (with upper limit of ~200 km) can be seen for mega-thrust subduction events (M~9.0). Despite this fact, for a given earthquake magnitude, subduction reverse dip-slip events occupy relatively larger rupture area, compared to shallow crustal events. In addition, we characterize slip heterogeneity in terms of its probability distribution and spatial correlation structure to develop a complete stochastic random-field characterization of earthquake slip. We find that truncated exponential law best describes the probability distribution of slip, with observable scale parameters determined by the average and maximum slip. Applying Box-Cox transformation to slip distributions (to create quasi-normal distributed data) supports cube-root transformation, which also implies distinctive non-Gaussian slip

  12. Comprehensive understanding of a deep transition zone from an unstable- to stable-slip regime of the megathrust interplate earthquake

    NASA Astrophysics Data System (ADS)

    Kato, A.; Iidaka, T.; Ikuta, R.; Yoshida, Y.; Katsumata, K.; Iwasaki, T.; Sakai, S.; Yamaoka, K.; Watanabe, T.; Kunitomo, T.; Yamazaki, F.; Tsumura, N.; Nozaki, K.; Okubo, M.; Suzuki, S.; Hirata, N.; Zhang, H.; Thurber, C. H.

    2009-12-01

    Most slow slips have occurred in the deep transition zone from an unstable- to stable-slip regime. Detailed knowledge about a deep transition zone is essentially important to understand the mechanism of the slow slips, and the stress concentration process to the source region of the megathrust interplate earthquake. We have conducted a very dense seismic observation in the Tokai-region from the April to the August in 2008 through a linear deployment of 75 portable stations, in Japan. The array extended from the bottom part of the source region of the Tokai earthquake to deep low-frequency earthquakes (LFE, ~ 35 km depth) including the long-term slow-slip region (~ 25 km depth). Here we present a high-resolution tomographic imaging of seismic velocities and highly-accurate hypocenters including LFEs, using first arrival data from the dense seismograph deployment. We manually picked the first arrivals of P- and S- waves from each waveform for about 700 earthquakes including about 20 LFEs observed by the dense array. Then, we applied the TomoDD-code [Zhang and Thurber, 2003] to the arrival data set, adding an accurate double-difference data estimated by a waveform cross-correlation technique. A low velocity (Vp, Vs) layer with high Poisson’s ratio is clearly imaged, and tilts to the northwestward with a low dip angle, which corresponds to the subducting oceanic crust of the Philippine Sea Slab. Although seismicity within the oceanic crust is significantly low, few earthquakes occur within the oceanic crust. The LFEs are linearly aligned along the top surface of the subducting oceanic crust at depths from 30 to 40 km. The Poisson’s ratio within the oceanic crust does not show significant depth-dependent increase beneath the linear alignment of LFEs. This result argues against a depth section of Poisson’s ratio obtained in the SW Japan [Shelly et al., 2006]. Beneath the LFEs, active cluster of slab earthquakes are horizontally distributed. At the depths greater

  13. Reduced parasympathetic activity during sleep in the symptomatic phase of severe premenstrual syndrome

    PubMed Central

    Baker, Fiona C.; Colrain, Ian M; Trinder, John

    2008-01-01

    Objective Severe premenstrual syndrome (PMS) is a common, distressing disorder in women that manifests during the premenstrual (late-luteal) phase of the ovulatory menstrual cycle. There is some evidence that altered autonomic function may be an important component of PMS but few studies have used heart rate variability (HRV), as a sensitive marker of autonomic activity, in severe PMS and findings are conflicting. Methods We investigated HRV during sleep, a state relatively free of external disruptions, in nine women with severe PMS and twelve controls. Results The normal-to-normal (NN) RR-interval was shorter during the sleep period in women with PMS than in controls in both the follicular and late-luteal phases of the menstrual cycle. The standard deviation of all NN intervals (SDNN), a measure of total variability in the inter-beat interval, was lower during the sleep period in the late-luteal phase than in the follicular phase in women with PMS. The square root of the mean of the sum of the squares of differences between adjacent NN intervals (rMSSD), a measure reflecting high frequency activity, showed a similar pattern. High frequency power, a marker of parasympathetic activity, was lower during non-rapid eye movement (non-REM) and REM sleep in the late-luteal phase than in the follicular phase in women with severe PMS. Controls had a shorter NN-interval, but similar HRV measures, in the late-luteal phase compared with the follicular phase. Conclusion These results suggest that women with severe PMS have decreased parasympathetic activity during sleep in association with their premenstrual symptoms compared to when they are symptom-free. PMID:18582607

  14. Seismic slip recorded in tourmaline fault mirrors from Elba Island (Italy)

    NASA Astrophysics Data System (ADS)

    Viti, C.; Brogi, A.; Liotta, D.; Mugnaioli, E.; Spiess, R.; Dini, A.; Zucchi, M.; Vannuccini, G.

    2016-05-01

    This paper reports the first example of fault mirrors developed in an unusual protolith, consisting of tourmaline crystals with interstitial goethite. The deformation mechanisms active in the fault zone have been investigated from the outcrop to the nanoscale, aiming to identify possible traces of frictional heating at seismic slip rate, as observed for other fault mirrors in different protoliths. The investigation revealed the superposition of two main deformational stages. The first was dominated by brittle processes and produced a cataclastic/ultracataclastic principal slip zone, a few mm thick; the second was associated with seismic slip and produced a sharp discontinuity (the principal slip surface) within the cataclastic/ultracataclastic zone. The mirror-like coating, a few microns thick, occurs on the principal slip surface, and is characterized by 1) absence of interstitial goethite; 2) occurrence of truncated tourmaline crystals; 3) highly variable grain size, from 200 μm to 200 nm; 4) tourmaline close packing with interlobate grain boundaries, and 5) tourmaline random crystallographic orientation. Micro and nanostructural investigations indicate the occurrence of thermally-activated processes, involving both interstitial goethite and tourmaline. In particular, close to the principal slip surface, goethite is completely decomposed, and produced an amorphous porous material, with local topotactic recrystallization of hematite. Tourmaline clasts are typically characterized by strongly lobate boundaries, indicative of reaction and partial decomposition at grain boundaries. TEM observations revealed the occurrence of tourmaline nanograins, a few tens of nm in size, characterized by rounded shape and fading amorphous boundaries, that cannot be obtained by brittle processes. Lastly, the peculiar interlobate microstructure of the mirror surface is interpreted as the result of grain boundary recrystallization processes taking place by deformation at high

  15. Shallow Slip Localization Along Megathrusts: Investigating the Role of Scaly Fabric

    NASA Astrophysics Data System (ADS)

    Vannucchi, P.

    2015-12-01

    Scaly fabric is classically interpreted as a low strain-rate structure, resulting from progressive shearing with episodic formation and destruction of oriented and flattened clay layers and aggregates. Scientific Ocean drilling of the Japan Trench in response to the 2011 Tohoku-Oki EQ sampled the active plate-boundary décollement zone in a place of known, large, and very recent displacement. The visual inspection of core material from the plate boundary décollement reveals a clay layer with scaly fabric, cut by a sharp discontinuity that may be the record of co-seismic slip (Chester et al., 2013). This result brought to the need to re-evaluate the role and the characteristics of scaly fabric. Scaly fabric is the typical meso/microstructure marking the location of slip concentration in all the active décollements cored near the trench (i.e. Barbados, Nankai, Costa Rica, Japan Trench) and in analogue fossil examples cropping out onland. Scaly fabric tends to form self-similar patterns, and usually areas with smaller phacoids are interpreted as more deformed. We know that scaliness develops in the early stages of deformation, that the slip surfaces defining the phacoids are sharp and they do not occur randomly, that they grow and coalesce forming a progressively finer anastomosing network, and that eventually the anastomoising slip surfaces are "enhanced" or "cut" by straight slip surfaces. Advances in identifying detailed evolutionary history of slip localization from scaly fabric to discrete surfaces have been paralleled by laboratory experiments. Here we try to summarize direct and indirect information on physical properties of clay layers deformed at shallow depth and, possibly, their links to the seismic cycle. These challenges include future work on the role of scaly fabric on earthquake deformation along faults.

  16. The Rolling with Slipping Experiment in the Virtual Physics Laboratory--Context-Based Teaching Material

    ERIC Educational Resources Information Center

    Maidana, Nora L.; da Fonseca, Monaliza; Barros, Suelen F.; Vanin, Vito R.

    2016-01-01

    The Virtual Laboratory was created as a complementary educational activity, with the aim of working abstract concepts from an experimental point of view. In this work, the motion of a ring rolling and slipping in front of a grid printed panel was recorded. The frames separated from this video received a time code, and the resulting set of images…

  17. Major and minor slip-events in frictional stick-slip

    NASA Astrophysics Data System (ADS)

    Tsekenis, Georgios; Tatar, Demet; Rubinstein, Shmuel; Weitz, David; Aziz, Michael; Spaepen, Frans

    Several universal phenomena characterize friction that are independent of the materials involved such as the logarithmic aging of the static friction coefficient and the logarithmic velocity weakening of the dynamic friction coefficient. We study dry friction between rough surfaces with programmed statistical profiles. By measuring the displacement field at the frictional interface we observe stick-slip behavior which reveals two kinds of slip: major events that tend to grow large and unbounded and minor events that usually stay small and bounded. Research supported by Harvard MRSEC Program under NSF contracts DMR-0820484, DMR-1420570.

  18. Coseismic slip distribution of the 1923 Kanto earthquake, Japan

    USGS Publications Warehouse

    Pollitz, F.F.; Nyst, M.; Nishimura, T.; Thatcher, W.

    2005-01-01

    The slip distribution associated with the 1923 M = 7.9 Kanto, Japan, earthquake is reexamined in light of new data and modeling. We utilize a combination of first-order triangulation, second-order triangulation, and leveling data in order to constrain the coseismic deformation. The second-order triangulation data, which have not been utilized in previous studies of 1923 coseismic deformation, are associated with only slightly smaller errors than the first-order triangulation data and expand the available triangulation data set by about a factor of 10. Interpretation of these data in terms of uniform-slip models in a companion study by Nyst et al. shows that a model involving uniform coseismic slip on two distinct rupture planes explains the data very well and matches or exceeds the fit obtained by previous studies, even one which involved distributed slip. Using the geometry of the Nyst et al. two-plane slip model, we perform inversions of the same geodetic data set for distributed slip. Our preferred model of distributed slip on the Philippine Sea plate interface has a moment magnitude of 7.86. We find slip maxima of ???8-9 m beneath Odawara and ???7-8 m beneath the Miura peninsula, with a roughly 2:1 ratio of strike-slip to dip-slip motion, in agreement with a previous study. However, the Miura slip maximum is imaged as a more broadly extended feature in our study, with the high-slip region continuing from the Miura peninsula to the southern Boso peninsula region. The second-order triangulation data provide good evidence for ???3 m right-lateral strike slip on a 35-km-long splay structure occupying the volume between the upper surface of the descending Philippine Sea plate and the southern Boso peninsula. Copyright 2005 by the American Geophysical Union.

  19. Revisiting the question: Does high-latitude solar activity lead low-latitude solar activity in time phase?

    SciTech Connect

    Kong, D. F.; Qu, Z. N.; Guo, Q. L.

    2014-05-01

    Cross-correlation analysis and wavelet transform methods are used to investigate whether high-latitude solar activity leads low-latitude solar activity in time phase or not, using the data of the Carte Synoptique solar filaments archive from 1919 March to 1989 December. From the cross-correlation analysis, high-latitude solar filaments have a time lead of 12 Carrington solar rotations with respect to low-latitude ones. Both the cross-wavelet transform and wavelet coherence indicate that high-latitude solar filaments lead low-latitude ones in time phase. Furthermore, low-latitude solar activity is better correlated with high-latitude solar activity of the previous cycle than with that of the following cycle, which is statistically significant. Thus, the present study confirms that high-latitude solar activity in the polar regions is indeed better correlated with the low-latitude solar activity of the following cycle than with that of the previous cycle, namely, leading in time phase.

  20. Dissecting eukaryotic cells by coherent phase microscopy: quantitative analysis of quiescent and activated T lymphocytes

    NASA Astrophysics Data System (ADS)

    Tychinsky, Vladimir P.; Kretushev, Alexander V.; Vyshenskaya, Tatiana V.; Shtil, Alexander A.

    2012-07-01

    We present a concept for quantitative characterization of a functional state of an individual eukaryotic cell based on interference imaging. The informative parameters of the phase images of quiescent and mitogen-activated T lymphocytes included the phase thickness, phase volume, the area, and the size of organelles. These parameters were obtained without a special hypothesis about cell structure. Combinations of these parameters generated a ``phase portrait'' of the cell. A simplified spherical multilayer optic model of a T lymphocyte was used to calculate the refractivity profile, to identify structural elements of the image with the organelles, and to interpret the parameters of the phase portrait. The values of phase image parameters underwent characteristic changes in the course of mitogenic stimulation of T cells; thereby, the functional state of individual cells can be described using these parameters. Because the values of the components of the phase portrait are measured in absolute units, it is possible to compare the parameters of images obtained with different interference microscopes. Thus, the analysis of phase portraits provides a new and perspective approach for quantitative, real-time analysis of subcellular structure and physiologic state of an individual cell.

  1. Principal Slip Zones in Limestone: Microstructural Characterization and Implications for the Seismic Cycle (Tre Monti Fault, Central Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Smith, Steven A. F.; Billi, Andrea; Toro, Giulio Di; Spiess, Richard

    2011-12-01

    Earthquakes in central Italy, and in other areas worldwide, often nucleate within and rupture through carbonates in the upper crust. During individual earthquake ruptures, most fault displacement is thought to be accommodated by thin principal slip zones. This study presents detailed microstructural observations of the slip zones of the seismically active Tre Monti normal fault zone. All of the slip zones cut limestone, and geological constraints indicate exhumation from <2 km depth, where ambient temperatures are ≪100°C. Scanning electron microscope observations suggest that the slip zones are composed of 100% calcite. The slip zones of secondary faults in the damage zone contain protocataclastic and cataclastic fabrics that are cross-cut by systematic fracture networks and stylolite dissolution surfaces. The slip zone of the principal fault has much more microstructural complexity, and contains a 2-10 mm thick ultracataclasite that lies immediately beneath the principal slip surface. The ultracataclasite itself is internally zoned; 200-300 μm-thick ultracataclastic sub-layers record extreme localization of slip. Syn-tectonic calcite vein networks spatially associated with the sub-layers suggest fluid involvement in faulting. The ultracataclastic sub-layers preserve compelling microstructural evidence of fluidization, and also contain peculiar rounded grains consisting of a central (often angular) clast wrapped by a laminated outer cortex of ultra-fine-grained calcite. These "clast-cortex grains" closely resemble those produced during layer fluidization in other settings, including the basal detachments of catastrophic landslides and saturated high-velocity friction experiments on clay-bearing gouges. An overprinting foliation is present in the slip zone of the principal fault, and electron backscatter diffraction analyses indicate the presence of a weak calcite crystallographic preferred orientation (CPO) in the fine-grained matrix. The calcite c-axes are

  2. Transpressional segment boundaries in strike-slip fault systems offshore southern California: Implications for fluid expulsion and cold seep habitats

    NASA Astrophysics Data System (ADS)

    Maloney, Jillian M.; Grupe, Benjamin M.; Pasulka, Alexis L.; Dawson, Katherine S.; Case, David H.; Frieder, Christina A.; Levin, Lisa A.; Driscoll, Neal W.

    2015-05-01

    The importance of tectonics and fluid flow in controlling cold seep habitats has long been appreciated at convergent margins but remains poorly understood in strike-slip systems. Here we present geophysical, geochemical, and biological data from an active methane seep offshore from Del Mar, California, in the inner California borderlands (ICB). The location of this seep appears controlled by localized transpression associated with a step in the San Diego Trough fault zone and provides an opportunity to examine the interplay between fluid expulsion and restraining step overs along strike-slip fault systems. These segment boundaries may have important controls on seep locations in the ICB and other margins characterized by strike-slip faulting (e.g., Greece, Sea of Marmara, and Caribbean). The strike-slip fault systems offshore southern California appear to have a limited distribution of seep sites compared to a wider distribution at convergent plate boundaries, which may influence seep habitat diversity and connectivity.

  3. Method for providing slip energy control in permanent magnet electrical machines

    DOEpatents

    Hsu, John S.

    2006-11-14

    An electric machine (40) has a stator (43), a permanent magnet rotor (38) with permanent magnets (39) and a magnetic coupling uncluttered rotor (46) for inducing a slip energy current in secondary coils (47). A dc flux can be produced in the uncluttered rotor when the secondary coils are fed with dc currents. The magnetic coupling uncluttered rotor (46) has magnetic brushes (A, B, C, D) which couple flux in through the rotor (46) to the secondary coils (47c, 47d) without inducing a current in the rotor (46) and without coupling a stator rotational energy component to the secondary coils (47c, 47d). The machine can be operated as a motor or a generator in multi-phase or single-phase embodiments and is applicable to the hybrid electric vehicle. A method of providing a slip energy controller is also disclosed.

  4. The Berry phase and the Aharonov-Bohm effect on optical activity.

    PubMed

    Tan, C Z

    2008-09-15

    The helical crystal structure in optically active media acts as the natural micro-solenoids for the electromagnetic waves passing through them, producing the longitudinal magnetic field in the direction of the axis of helices. Magnetic flux through the helical structure is quantized. The Berry phase is induced by rotation of the electrons around the helical structure. Optical rotation is related to the difference in the accumulative Berry phase between the right-, and the left-circularly polarized waves, which is proportional to the magnetic flux through the helical structure, according to the Aharonov-Bohm effect. The optical activity is the natural Faraday effect and the natural Aharonov-Bohm effect.

  5. Modeling the Thermodynamics of Mixed Organic-Inorganic Aerosols to Predict Water Activities and Phase Equilibria

    NASA Astrophysics Data System (ADS)

    Zuend, A.; Marcolli, C.; Luo, B.; Peter, T.

    2008-12-01

    Tropospheric aerosol particles contain mixtures of inorganic salts, acids, water, and a large variety of organic compounds. Interactions between these substances in liquid mixtures lead to discrepancies from ideal thermodynamic behavior. While the thermodynamics of aqueous inorganic systems at atmospheric temperatures are well established, little is known about the physicochemistry of mixed organic-inorganic particles. Salting-out and salting-in effects result from organic-inorganic interactions and are used to improve industrial separation processes. In the atmosphere, they may influence the aerosol phases. Liquid-liquid phase separations into a mainly polar (aqueous) and a less polar organic phase may considerably influence the gas/particle partitioning of semi-volatile substances compared to a single phase estimation. Moreover, the phases present in the aerosol define the reaction medium for heterogeneous and multiphase chemistry occurring in aerosol particles. A correct description of these phases is needed when gas- or cloud-phase reaction schemes are adapted to aerosols. Non-ideal thermodynamic behavior in mixtures is usually described by an expression for the excess Gibbs energy. We present the group-contribution model AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients), which explicitly accounts for molecular interactions between solution constituents, both organic and inorganic, to calculate activities, chemical potentials and the total Gibbs energy of mixed systems. This model allows to compute vapor-liquid (VLE), liquid-liquid (LLE) and solid-liquid (SLE) equilibria within one framework. Focusing on atmospheric applications we considered eight different cations, five anions and a wide range of alcohols/polyols as organic compounds. With AIOMFAC, the activities of the components within an aqueous electrolyte solution are very well represented up to high ionic strength. We show that the semiempirical middle

  6. Accurate means of detecting and characterizing abnormal patterns of ventricular activation by phase image analysis

    SciTech Connect

    Botvinick, E.H.; Frais, M.A.; Shosa, D.W.; O'Connell, J.W.; Pacheco-Alvarez, J.A.; Scheinman, M.; Hattner, R.S.; Morady, F.; Faulkner, D.B.

    1982-08-01

    The ability of scintigraphic phase image analysis to characterize patterns of abnormal ventricular activation was investigated. The pattern of phase distribution and sequential phase changes over both right and left ventricular regions of interest were evaluated in 16 patients with normal electrical activation and wall motion and compared with those in 8 patients with an artificial pacemaker and 4 patients with sinus rhythm with the Wolff-Parkinson-White syndrome and delta waves. Normally, the site of earliest phase angle was seen at the base of the interventricular septum, with sequential change affecting the body of the septum and the cardiac apex and then spreading laterally to involve the body of both ventricles. The site of earliest phase angle was located at the apex of the right ventricle in seven patients with a right ventricular endocardial pacemaker and on the lateral left ventricular wall in one patient with a left ventricular epicardial pacemaker. In each case the site corresponded exactly to the position of the pacing electrode as seen on posteroanterior and left lateral chest X-ray films, and sequential phase changes spread from the initial focus to affect both ventricles. In each of the patients with the Wolff-Parkinson-White syndrome, the site of earliest ventricular phase angle was located, and it corresponded exactly to the site of the bypass tract as determined by endocardial mapping. In this way, four bypass pathways, two posterior left paraseptal, one left lateral and one right lateral, were correctly localized scintigraphically. On the basis of the sequence of mechanical contraction, phase image analysis provides an accurate noninvasive method of detecting abnormal foci of ventricular activation.

  7. Multiplate magnetorheological fluid limited slip differential clutch

    NASA Astrophysics Data System (ADS)

    Kavlicoglu, Barkan M.; Gordaninejad, Faramarz; Evrensel, Cahit A.; Fuchs, Alan; Korol, George

    2003-08-01

    This study focuses on the design and characterization of a multi-plate magneto-rheological fluid (MRF) limited slip differential (LSD) clutch. Three-dimensional electromagnetic finite element analyzes are performed to optimize the MRF LSD clutch design. The torque transfer capacity of the clutch is predicted utilizing Bingham-Plastic constitutive model of the MRF. The MRF LSD clutch is tested at different velocities and applied magnetic fields. The clutch heating is also examined under different operating conditions to determine the thermal effects on the torque transfer performance of the multi-plate clutch.

  8. Fixed recurrence and slip models better predict earthquake behavior than the time- and slip-predictable models 1: repeating earthquakes

    USGS Publications Warehouse

    Rubinstein, Justin L.; Ellsworth, William L.; Chen, Kate Huihsuan; Uchida, Naoki

    2012-01-01

    The behavior of individual events in repeating earthquake sequences in California, Taiwan and Japan is better predicted by a model with fixed inter-event time or fixed slip than it is by the time- and slip-predictable models for earthquake occurrence. Given that repeating earthquakes are highly regular in both inter-event time and seismic moment, the time- and slip-predictable models seem ideally suited to explain their behavior. Taken together with evidence from the companion manuscript that shows similar results for laboratory experiments we conclude that the short-term predictions of the time- and slip-predictable models should be rejected in favor of earthquake models that assume either fixed slip or fixed recurrence interval. This implies that the elastic rebound model underlying the time- and slip-predictable models offers no additional value in describing earthquake behavior in an event-to-event sense, but its value in a long-term sense cannot be determined. These models likely fail because they rely on assumptions that oversimplify the earthquake cycle. We note that the time and slip of these events is predicted quite well by fixed slip and fixed recurrence models, so in some sense they are time- and slip-predictable. While fixed recurrence and slip models better predict repeating earthquake behavior than the time- and slip-predictable models, we observe a correlation between slip and the preceding recurrence time for many repeating earthquake sequences in Parkfield, California. This correlation is not found in other regions, and the sequences with the correlative slip-predictable behavior are not distinguishable from nearby earthquake sequences that do not exhibit this behavior.

  9. Slip statistics of dislocation avalanches under different loading modes.

    PubMed

    Maass, R; Wraith, M; Uhl, J T; Greer, J R; Dahmen, K A

    2015-04-01

    Slowly compressed microcrystals deform via intermittent slip events, observed as displacement jumps or stress drops. Experiments often use one of two loading modes: an increasing applied stress (stress driven, soft), or a constant strain rate (strain driven, hard). In this work we experimentally test the influence of the deformation loading conditions on the scaling behavior of slip events. It is found that these common deformation modes strongly affect time series properties, but not the scaling behavior of the slip statistics when analyzed with a mean-field model. With increasing plastic strain, the slip events are found to be smaller and more frequent when strain driven, and the slip-size distributions obtained for both drives collapse onto the same scaling function with the same exponents. The experimental results agree with the predictions of the used mean-field model, linking the slip behavior under different loading modes.

  10. Vehicular Slip Ratio Control Using Nonlinear Control Theory

    NASA Astrophysics Data System (ADS)

    Ikeda, Yuichi; Nakajima, Takashi; Chida, Yuichi

    In this paper, we discuss integrated vehicle slip ratio control under both deceleration and acceleration without the need for controller switching, and also propose a design method for such an integrated slip ratio controller based on the slip ratio dynamics. When a vehicle switches from acceleration to deceleration and vice versa, the slip ratio varies discontinuously. Here, the slip ratio is approximated to a continuous function by using a sigmoid function. And a controller is then designed by using feedback linearization based on the approximated slip ratio. The stability of the designed control system is proven by Lyapunov stability theorem. Furthermore, we propose a robust control method based on a disturbance observer and sliding mode control theory. Finally, the effectiveness of the proposed control method is verified through numerical simulation.

  11. Stick-slip instabilities and shear strain localization in amorphous materials.

    PubMed

    Daub, Eric G; Carlson, Jean M

    2009-12-01

    We study the impact of strain localization on the stability of frictional slipping in dense amorphous materials. We model the material using shear transformation zone (STZ) theory, a continuum approximation for plastic deformation in amorphous solids. In the STZ model, the internal state is quantified by an effective disorder temperature, and the effective temperature dynamics capture the spontaneous localization of strain. We study the effect of strain localization on stick-slip instabilities by coupling the STZ model to a noninertial spring slider system. We perform a linear stability analysis to generate a phase diagram that connects the small scale physics of strain localization to the macroscopic stability of sliding. Our calculations determine the values of spring stiffness and driving velocity where steady sliding becomes unstable and we confirm our results through numerical integration. We investigate both homogeneous deformation, where no shear band forms, and localized deformation, where a narrow shear band spontaneously forms and accommodates all of the deformation. Our results show that at a given velocity, strain localization leads to unstable frictional sliding at a much larger spring stiffness compared to homogeneous deformation, and that localized deformation cannot be approximated by a homogeneous model with a narrower material. We also find that strain localization provides a physical mechanism for irregular stick-slip cycles in certain parameter ranges. Our results quantitatively connect the internal physics of deformation in amorphous materials to the larger scale frictional dynamics of stick-slip.

  12. Stress inversion of heterogeneous fault-slip data with unknown slip sense - an OFA clustering technique tested on artificial and real data

    NASA Astrophysics Data System (ADS)

    Hansen, J.-A.; Bergh, S. G.; Osmundsen, P. T.; Redfield, T.

    2012-04-01

    Mesozoic to early Cenozoic brittle fault zones are exposed in crystalline basement rocks in the Lofoten and Vesterålen area, North Norway. These fault zones contain abundant striated fracture planes, and may convey important information about the kinematic and dynamic evolution of adjacent fault-bounded rift basins offshore. However, determining slip sense is difficult as offset markers are rare and one has to rely on fault plane morphology. The fault-slip data does, in addition, show clear evidence of being heterogeneous. The linear part of Fry's σ-space inversion method do not depend on slip sense and may, in conjunction with the Objective Function Algorithm (OFA), be used to separate heterogeneous fault-slip data and calculate respective stress tensors. However, tests on artificial data show that the inversions corresponding with the lowest obtained value of the objective function give erroneous results when errors are introduced in the dataset. The method also fails in determining the number of superimposed tensors. We show that by contouring principal stress orientations from the OFA after e.g. 1000 runs, using all solutions with an objective function value below mean and different initial subdivisions, we get more reliable orientations for the principal stresses active during faulting. The method can also be used to evaluate the number of superimposed tensors in the heterogeneous dataset as an overestimation of tensors does not generate significant artificial clusters of principal stress orientations. We refer to this technique as OFA clustering. Initial results using OFA clustering on field data from the Lofoten and Vesterålen area give principal stress orientations in agreement with plate reconstructions and the orientations of the main boundary faults offshore. Since no pre-classification of the fault-slip data is needed, all data points are used with no filtering, and slip sense is not required, the OFA clustering technique is a robust method for

  13. Precarious rock evidence for low near-source accelerations for trans-tensional strike-slip earthquakes

    NASA Astrophysics Data System (ADS)

    Brune, James N.

    2003-05-01

    This paper describes precarious rock evidence for low ground motions associated with extensional sections of strike-slip faults. Recent evidence from physical and numerical models and data regressions has indicated that ground motion for extensional strike-slip regions may be lower than for strike-slip faults with a large fault-normal tectonic stress component, and for thrust faults in general. Data from compressional strike-slip and thrust earthquakes dominates the database used in most regression curves for ground acceleration, and in the calculation of current probabilistic seismic hazard maps. Therefore, estimates of ground accelerations on these seismic hazard maps may be too high for sites near extensional sections of strike-slip faults. This paper discusses precariously balanced rock data from three areas near extensional sections of strike-slip faulting: (1) the region of the Honey fault, California, with an active Holocene fault, (2) the Red Rock Canyon region of the Garlock fault, near a dilatational step-over, and (3) the region just south of Beaumont, California, near the Hemet dilatational step-over in the San Jacinto fault. These are all active strike-slip faults, with at least a few large earthquakes in the Holocene, and, in the case of the San Jacinto example, historic large earthquakes ( M=7). Thus, the precarious rocks at these sites are evidence of relatively low ground motions associated with extensional strike-slip faulting. The results of this study could be very important in developing more detailed seismic hazard maps in the future.

  14. Geology of the Çaldıran Fault, Eastern Turkey: Age, slip rate and implications on the characteristic slip behaviour

    NASA Astrophysics Data System (ADS)

    Selçuk, Azad Sağlam; Erturaç, M. Korhan; Nomade, Sebastien

    2016-06-01

    The Çaldıran Fault is a strike slip fault with a dextral slip in East Anatolia. The activity on this fault was marked by the November, 24 1976 earthquake (Mw: 7.1) which produced an ~ 50 km long surface rupture and caused 3840 fatalities, which was close to half of the population living along the fault at that time. Together with the North Tabriz Fault in Iran, it is regarded as the southern boundary of the Caucasus Block. The fault has an average annual slip rate of 8.1 from 10.8 mm yr- 1, as derived from elastic block modelling. We present results from a detailed morphotectonic survey along the fault. The Çaldıran Fault is comprised of three segments, each of which is eparated by bend structures that bend towards the SW with a total change in strike of 20° from east to west. The offsets of lithological contact markers show that the long-term geological slip rate for the Çaldıran fault is approximately 3.27 ± 0.17 mm yr- 1for a duration of approximately 290 ka. The cumulative offset of the fault was determined from an analysis of a dome-shaped rhyolitic volcano which constrained the age of the fault to the Middle-Late Pleistocene. An analysis of small-scale morphological offset markers indicates a characteristic slip behaviour of the Çaldıran Fault for the last 3 events with an average offset of 2.6 m.

  15. Temperature Estimates for the Slow Slip Region on the Decollement Underlying the South Flank of Kilauea

    NASA Astrophysics Data System (ADS)

    Spinelli, G. A.

    2013-12-01

    Eleven slow slip events on the decollement beneath the south flank of Kilauea volcano have been documented geodetically since 1998 (Brooks et al., 2006; Montgomery-Brown et al., 2009; 2013). Tectonic tremor has not been observed associated with these events, in contrast to most slow slip events in subduction zones (Montgomery-Brown et al., 2013). The slow slip events occur on the decollement at ~8 km depth, and updip of the 'normal' earthquakes on the fault. Constraining temperatures on Kilauea's decollement allows comparisons between its slow slip events and those in subduction zones. Kilauea's slow slip events (~8 km depth) are significantly shallower than most subduction zone slow slip events. I estimate temperatures in a 2-D cross-section through the south flank of Kilauea by combining methods used in subduction zone thermal models (Wang et al., 1995) with elements of intrusion cooling models of volcanoes (e.g., Civetta et al., 2004). Temperatures in the cross-section are controlled by: 1) heat sources from friction on the decollement, radioactive decay, and volcanic activity, and 2) heat transport by conduction, advection of the volcanic pile to the southeast over the underlying oceanic lithosphere, and advective heat transport associated with groundwater flow. I examine the thermal effects of a range of effective friction coefficients on the fault from 0-0.2. I determine the potential effects of groundwater flow in the upper ~1-2 km of the onshore and near-offshore volcanic pile (e.g., Kauahikaua, 1993; Buttner and Huenges, 2003) on decollement temperatures. Finally, I examine how heat input from Kilauea volcano may result in higher decollement temperatures than at the same depth on plate boundary faults in subduction zones.

  16. Magnetic activity and radial electric field during I-phase in ASDEX Upgrade plasmas

    NASA Astrophysics Data System (ADS)

    Birkenmeier, Gregor; Cavedon, Marco; Conway, Garrard; Manz, Peter; Puetterich, Thomas; Stroth, Ulrich; ASDEX Upgrade Team Team

    2016-10-01

    At the transition from the low (L-mode) to the high (H-mode) confinement regime, so called limit-cycle oscillations (LCOs) can occur at the edge of a fusion plasma. During the LCO evolution, which is also called I-phase, the relative importance of background flows and turbulence-generated zonal flows can change, and it is still unclear whether a large contribution of zonal flows is a necessary condition for triggering the H-mode. At ASDEX Upgrade, I-phases have been studied in a wide range of parameters. The modulation of flows and gradients during I-phase is accompanied by a strong magnetic activity with a specific poloidal and toroidal structure. The magnetic activity increases during the development of an edge pedestal during I-phase, and is preceded by type-III ELM-like precursors. During all phases of the I-phase, the radial electric field Er is found to be close to the neoclassical prediction of the electric field Er , neo. These results suggest that zonal flows do not contribute significantly to the LCO dynamics, and the burst like behavior is reminiscent of a critical-gradient driven instability like edge localized modes. These observations on ASDEX Upgrade seem to be inconsistent with LCO models based on an interaction between zonal flows and turbulence.

  17. [Slipped capital femoral epiphysis associated with hyperparathyroidism. A case report].

    PubMed

    Khiari, Karima; Cherif, Lotfi; Ben Abdallah, Nejib; Maazoun, Imen; Hadj Ali, Insaf; Bentaarit, Chokri; Turki, Sami; Ben Maïz, Hedi

    2003-12-01

    Slippage of the upper femoral epiphysis can occur in association with multiple endocrine imbalances. A case of slipped femoral epiphysis with primary hyperparathyroidism is reported. The patient was an adolescent, 16 Years of age, who presented bilateral slipped epiphysis. Investigation showed that he had hypercalcemia (3.1 mmol/l) related to primary hyperparathyroidism. A parathyroid adenoma was removed. Outcome was favorable and the slipped femoral epiphyses did not require a specific treatment.

  18. Coronal Dynamic Activities in the Declining Phase of a Solar Cycle

    NASA Astrophysics Data System (ADS)

    Jang, Minhwan; Woods, T. N.; Hong, Sunhak; Choe, G. S.

    2016-12-01

    It has been known that some solar activity indicators show a double-peak feature in their evolution through a solar cycle, which is not conspicuous in sunspot number. In this Letter, we investigate the high solar dynamic activity in the declining phase of the sunspot cycle by examining the evolution of polar and low-latitude coronal hole (CH) areas, splitting and merging events of CHs, and coronal mass ejections (CMEs) detected by SOHO/LASCO C3 in solar cycle 23. Although the total CH area is at its maximum near the sunspot minimum, in which polar CHs prevail, it shows a comparable second maximum in the declining phase of the cycle, in which low-latitude CHs are dominant. The events of CH splitting or merging, which are attributed to surface motions of magnetic fluxes, are also mostly populated in the declining phase of the cycle. The far-reaching C3 CMEs are also overpopulated in the declining phase of the cycle. From these results we suggest that solar dynamic activities due to the horizontal surface motions of magnetic fluxes extend far in the declining phase of the sunspot cycle.

  19. Superficial shoulder muscle co-activations during lifting tasks: Influence of lifting height, weight and phase.

    PubMed

    Blache, Y; Dal Maso, F; Desmoulins, L; Plamondon, A; Begon, M

    2015-04-01

    This study aimed to assess the level of co-activation of the superficial shoulder muscles during lifting movement. Boxes containing three different loads (6, 12, and 18 kg) were lifted by fourteen subjects from the waist to shoulder or eye level. The 3D kinematics and electromyograms of the three deltoids, latissimus dorsi and pectoralis major were recorded. A musculoskeletal model was used to determine direction of the moment arm of these muscles. Finally an index of muscle co-activation named the muscle focus was used to evaluate the effects of lifting height, weight lifted and phase (pulling, lifting and dropping phases) on superficial shoulder muscle coactivation. The muscle focus was lower (more co-contraction) during the dropping phase compared to the two other phases (-13%, p<0.001). This was explained by greater muscle activations and by a change in the direction of the muscle moment arm as a function of glenohumeral joint position. Consequently, the function of the shoulder superficial muscles varied with respect to the glenohumeral joint position. To increase the superficial muscle coactivation during the dropping phase may be a solution to increase glenohumeral joint stiffness.

  20. Canadian and Siberian Boreal Fire Activity during ARCTAS Spring and Summer Phases

    NASA Astrophysics Data System (ADS)

    Stocks, B. J.; Fromm, M. D.; Soja, A. J.; Servranckx, R.; Lindsey, D.; Hyer, E.

    2009-12-01

    The summer phase of ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) was designed specifically around forest fire activity in the Canadian boreal forest, and located in areas of northern Canada where summer forest fires are ubiquitous. Lightning fires are most often allowed to burn naturally in these regions, and a number of large free-burning fires in northern Saskatchewan in late June/early July 2008 provided excellent targets during the summer phase of ARCTAS. Smoke generated by a large number of early spring fires in Kazakhstan and southern Siberia unexpectedly made a significant contribution to arctic haze during the Alaska-based spring phase of ARCTAS, Numerous smoke plumes were sampled during the spring phase of ARCTAS, creating interest in the origin and characteristics of the fires in the source regions of East Asia. This presentation is designed to connect aircraft and satellite smoke chemistry/transport measurements with ground-based measurements of fire activity during the spring and summer phases of ARCTAS. The Canadian Forest Fire Danger Rating System (CFFDRS) is used to determine forest fire danger conditions in regions of fire activity, and these measurements are in turn used to project fire behavior characteristics. Fuel consumption, spread rates, and frontal fire intensity are calculated using the CFFDRS. Energy release rates at ground level are related to convection/smoke column development and smoke injection heights.

  1. Automated co-alignment of coherent fiber laser arrays via active phase-locking.

    PubMed

    Goodno, Gregory D; Weiss, S Benjamin

    2012-07-02

    We demonstrate a novel closed-loop approach for high-precision co-alignment of laser beams in an actively phase-locked, coherently combined fiber laser array. The approach ensures interferometric precision by optically transducing beam-to-beam pointing errors into phase errors on a single detector, which are subsequently nulled by duplication of closed-loop phasing controls. Using this approach, beams from five coherent fiber tips were simultaneously phase-locked and position-locked with sub-micron accuracy. Spatial filtering of the sensed light is shown to extend the control range over multiple beam diameters by recovering spatial coherence despite the lack of far-field beam overlap.

  2. Cloud droplet activation through oxidation of organic aerosol influenced by temperature and particle phase state

    NASA Astrophysics Data System (ADS)

    Slade, Jonathan H.; Shiraiwa, Manabu; Arangio, Andrea; Su, Hang; Pöschl, Ulrich; Wang, Jian; Knopf, Daniel A.

    2017-02-01

    Chemical aging of organic aerosol (OA) through multiphase oxidation reactions can alter their cloud condensation nuclei (CCN) activity and hygroscopicity. However, the oxidation kinetics and OA reactivity depend strongly on the particle phase state, potentially influencing the hydrophobic-to-hydrophilic conversion rate of carbonaceous aerosol. Here, amorphous Suwannee River fulvic acid (SRFA) aerosol particles, a surrogate humic-like substance (HULIS) that contributes substantially to global OA mass, are oxidized by OH radicals at different temperatures and phase states. When oxidized at low temperature in a glassy solid state, the hygroscopicity of SRFA particles increased by almost a factor of two, whereas oxidation of liquid-like SRFA particles at higher temperatures did not affect CCN activity. Low-temperature oxidation appears to promote the formation of highly-oxygenated particle-bound fragmentation products with lower molar mass and greater CCN activity, underscoring the importance of chemical aging in the free troposphere and its influence on the CCN activity of OA.

  3. Inverting measurements of surface slip on the Superstition Hills fault

    USGS Publications Warehouse

    Boatwright, J.; Budding, K.E.; Sharp, R.V.

    1989-01-01

    We derive and test a set of inversions of surface-slip measurements based on the empirical relation u(t)=uf/(1 + T/t)c proposed by Sharp and Saxton (1989) to estimate the final slip uf, the power-law exponent c, and the power-law duration T. At short times, Sharp's relation behaves like the simple power law, u(t)~u1tc, where u1 is the initial slip, that is, the slip at 1 day after the earthquake. At long times, the slip approaches the final slip asymptotically. The inversions are designed in part to exploit the accuracy of measurements of differential slip; that is, measurements of surface slip which are made relative to a set of nails or stakes emplaced after the earthquake. We apply the inversions to slip measurements made at 53 sites along the Superstition Hills fault for the 11 months following the M=6.2 and 6.6 earthqakes of 24 November 1987. -from Authors

  4. Experimental investigation of flow and slip transition in nanochannels

    NASA Astrophysics Data System (ADS)

    Li, Zhigang; Li, Long; Mo, Jingwen

    2014-11-01

    Flow slip in nanochannels is sought in many applications, such as sea water desalination and molecular separation, because it can enhance fluid transport, which is essential in nanofluidic systems. Previous findings about the slip length for simple fluids at the nanoscale appear to be controversial. Some experiments and simulations showed that the slip length is independent of shear rate, which agrees with the prediction of classic slip theories. However, there is increasing work showing that slip length is shear rate dependent. In this work, we experimentally investigate the Poiseuille flows in nanochannels. It is found that the flow rate undergoes a transition between two linear regimes as the shear rate is varied. The transition indicates that the non-slip boundary condition is valid at low shear rate. When the shear rate is larger than a critical value, slip takes place and the slip length increases linearly with increasing shear rate before approaching a constant value. The results reported in this work can help advance the understanding of flow slip in nanochannels. This work was supported by the Research Grants Council of the Hong Kong Special Administrative Region under Grant Nos. 615710 and 615312. J. Mo was partially supported by the Postgraduate Scholarship through the Energy Program at HKUST.

  5. Transient slip episode in central and southwest Japan.

    NASA Astrophysics Data System (ADS)

    Miyazaki, S.; Segall, P.; McGuire, J. J.; Kato, T.; Hatanaka, Y.

    2007-05-01

    We have studied transient slip episodes in central and southwest Japan, where the Philippine Sea plate is subducting at the annual rate of ~ 6.5cm/yr. A slow thrust slip event occurred in Bungo Channel, in southwest Japan, and anomalous displacements were found in at multiple GPS time series for stations in Shikoku and Kyushu islands. We analyzed those GPS data with time-dependent inversion method, and found that the slip initiated at a deeper part (~ 40km) of the plate boundary. The acceleration and following decelelation took longer than one year. The second event is the 2000 Tokai slow slip event, which initialed in early 2000. We also applied the same time-dependent inversion method to infer the space-time distribution of slip and slip-rate at the plate boundary. The slip initiated at the deeper part of the plate boundary (~ 40km), and migrated upward to the depth of ~ 30km. This event lasted for longer than 5 years. Having cumulative slip at each epoch, we are able to calculate shear stress change with dislocation theory. We examined velocity-dependence of the shear stress change to compare with a numerical simulation based on rate-state friction. The observed stress-velocity path is similar to what obtained for high-speed rupture, suggesting that slow slip events occurred in velocity weakening friction. This makes a clear contrast to what we obtained for the afterslip for the 2003 Tokachi-oki earthquake.

  6. Slip to the Trench for Great Subduction Earthquakes

    NASA Astrophysics Data System (ADS)

    Mori, J. J.

    2015-12-01

    The 2011 Tohoku-oki earthquake had the largest ever recorded fault slip (40 to 60 meters) on the shallow portion of the subduction zone close to the trench. This large displacement was largely unexpected for this region and was mainly responsible for the very large and damaging tsunami along the northeast coast of Honshu. We investigate the possibility of large slip to the trench in great earthquakes for other subduction zones around the world. Since the trench region is generally far offshore, it is often difficu