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Sample records for silent slip events

  1. Simulating spontaneous aseismic and seismic slip events on evolving faults

    Science.gov (United States)

    Herrendörfer, Robert; van Dinther, Ylona; Pranger, Casper; Gerya, Taras

    2017-04-01

    Plate motion along tectonic boundaries is accommodated by different slip modes: steady creep, seismic slip and slow slip transients. Due to mainly indirect observations and difficulties to scale results from laboratory experiments to nature, it remains enigmatic which fault conditions favour certain slip modes. Therefore, we are developing a numerical modelling approach that is capable of simulating different slip modes together with the long-term fault evolution in a large-scale tectonic setting. We extend the 2D, continuum mechanics-based, visco-elasto-plastic thermo-mechanical model that was designed to simulate slip transients in large-scale geodynamic simulations (van Dinther et al., JGR, 2013). We improve the numerical approach to accurately treat the non-linear problem of plasticity (see also EGU 2017 abstract by Pranger et al.). To resolve a wide slip rate spectrum on evolving faults, we develop an invariant reformulation of the conventional rate-and-state dependent friction (RSF) and adapt the time step (Lapusta et al., JGR, 2000). A crucial part of this development is a conceptual ductile fault zone model that relates slip rates along discrete planes to the effective macroscopic plastic strain rates in the continuum. We test our implementation first in a simple 2D setup with a single fault zone that has a predefined initial thickness. Results show that deformation localizes in case of steady creep and for very slow slip transients to a bell-shaped strain rate profile across the fault zone, which suggests that a length scale across the fault zone may exist. This continuum length scale would overcome the common mesh-dependency in plasticity simulations and question the conventional treatment of aseismic slip on infinitely thin fault zones. We test the introduction of a diffusion term (similar to the damage description in Lyakhovsky et al., JMPS, 2011) into the state evolution equation and its effect on (de-)localization during faster slip events. We compare

  2. Silent slips, trips and broken hips in the under 60s: A review of the literature.

    Science.gov (United States)

    Janes, Gillian; Serrant, Laura; Sque, Magi

    2018-02-24

    This critical review of the literature regarding the recovery experiences and healthcare needs of people under 60 following a fragility hip fracture seeks to identify the associated implications for nursing practice and inform care delivery. Forty papers were included following a structured database, citation and grey literature search and filtering of results in line with specified inclusion criteria. Hip fracture is a common, serious and complex injury and an important cause of morbidity, mortality and rising healthcare costs worldwide. This review indicates that although commonly associated with the elderly, incidence and impact in the under 60s has been under-explored. Current health policy, professional and social norms almost exclusively focus on the elderly, surgical interventions and short-term outcomes, rendering the under 60s an inadvertently marginalised, relatively 'silent' sub-set of the hip fracture population. Nurses must be aware, however, of the different recovery needs of this younger group. The limited evidence available indicates these include work related needs and long term physical and psychosocial limitations in this socially and economically active group. Priorities are identified for research to inform policy and practice. Meanwhile, nurses can address the needs of this group by listening to and involving them and their families as healthcare partners. Copyright © 2018. Published by Elsevier Ltd.

  3. On the Rheology of Slow Slip Events Around Continental Moho

    Science.gov (United States)

    Gao, X.; Wang, K.; Wada, I.; He, J.

    2015-12-01

    Slow slip events (SSEs) occur in various tectonic settings but are the most abundant around the depth of upper-plate Moho in warm-slab subduction zones such as Cascadia and Nankai, accompanied with non-valcanic tremor. The paucity or absence of these near-Moho SSEs in many other subduction zones and the relationship of these SSEs with the megathrust seismogenic zone are intriguing questions of fundamental importance. We address these questions by examining Frictional-Viscous Transitions (FVTs) along subduction faults. Our key hypothesis is that there is a sharp decrease in the frictional stength of subduction faults across its intersection with the continental Moho for two reasons: (1) Enrichment of weak hydrous minerals such as talc due to the hydration of the base of the mantle wedge, and (2) elevated pore fluid pressure in the fault zone because of serpentine (antigorite) saturation of the mantle wedge corner which retards further fluid consumption and decreases permeability. Through thermal modelling using heat flow data as constraints, we found that for Cascadia, Nankai, and Hikurangi, there are two FVTs, with the first one being shallower than the Moho. At the Moho, the fault returns to the friction mode, but with slip behaviour affected by the presence of hydrous minerals and high fluid pressure. We propose this is where near-Moho SSEs occur. Farther downdip, the second FVT occurs and serves to limit the depth extent of the SSEs. Coseismic slip is limited to be shallower than the first FVT, such that frictional slip around the Moho occurs interseismically as SSEs. This mechanism also explains the occurrence of tremor, believed to represent very small SSEs, along the San Andreas fault around the Moho depth. In a way, this mechanism is akin to the "jelly-sandwich" rheology model of the continental lithosphere, but the onset of the lower slice of bread is due to a decrease in frictional strength as opposed to an increase in viscous strength. For the other

  4. Slip rate and tremor genesis in Cascadia

    Science.gov (United States)

    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.

  5. Observing and modeling the spectrum of a slow slip event: Constraints on the scaling of slow slip and tremor

    Science.gov (United States)

    Hawthorne, J. C.; Bartlow, N. M.; Ghosh, A.

    2017-12-01

    We estimate the normalized moment rate spectrum of a slow slip event in Cascadia and then attempt to reproduce it. Our goal is to further assess whether a single physical mechanism could govern slow slip and tremor events, with durations that span 6 orders of magnitude, so we construct the spectrum by parameterizing a large slow slip event as the sum of a number of subevents with various durations. The spectrum estimate uses data from three sources: the GPS-based slip inversion of Bartlow et al (2011), PBO borehole strain measurements, and beamforming-based tremor moment estimates of Ghosh et al (2009). We find that at periods shorter than 1 day, the moment rate power spectrum decays as frequencyn, where n is between 0.7 and 1.4 when measured from strain and between 1.2 and 1.4 when inferred from tremor. The spectrum appears roughly flat at periods of 1 to 10 days, as both the 1-day-period strain and tremor data and the 6-day-period slip inversion data imply a moment rate power of 0.02 times the the total moment squared. We demonstrate one way to reproduce this spectrum: by constructing the large-scale slow slip event as the sum of a series of subevents. The shortest of these subevents could be interpreted as VLFEs or even LFEs, while longer subevents might represent the aseismic slip that drives rapid tremor reverals, streaks, or rapid tremor migrations. We pick the subevent magnitudes from a Gutenberg-Richter distribution and place the events randomly throughout a 30-day interval. Then we assign each subevent a duration that scales with its moment to a specified power. Finally, we create a moment rate function for each subevent and sum all of the moment rates. We compute the summed slow slip moment rate spectra with two approaches: a time-domain numerical computation and a frequency-domain analytical summation. Several sets of subevent parameters can allow the constructed slow slip event to match the observed spectrum. One allowable set of parameters is of

  6. The Slip Behavior and Source Parameters for Spontaneous Slip Events on Rough Faults Subjected to Slow Tectonic Loading

    Science.gov (United States)

    Tal, Yuval; Hager, Bradford H.

    2018-02-01

    We study the response to slow tectonic loading of rough faults governed by velocity weakening rate and state friction, using a 2-D plane strain model. Our numerical approach accounts for all stages in the seismic cycle, and in each simulation we model a sequence of two earthquakes or more. We focus on the global behavior of the faults and find that as the roughness amplitude, br, increases and the minimum wavelength of roughness decreases, there is a transition from seismic slip to aseismic slip, in which the load on the fault is released by more slip events but with lower slip rate, lower seismic moment per unit length, M0,1d, and lower average static stress drop on the fault, Δτt. Even larger decreases with roughness are observed when these source parameters are estimated only for the dynamic stage of the rupture. For br ≤ 0.002, the source parameters M0,1d and Δτt decrease mutually and the relationship between Δτt and the average fault strain is similar to that of a smooth fault. For faults with larger values of br that are completely ruptured during the slip events, the average fault strain generally decreases more rapidly with roughness than Δτt.

  7. Episodic slow slip events in the Japan subduction zone before the 2011 Tohoku-Oki earthquake

    Science.gov (United States)

    Ito, Yoshihiro; Hino, Ryota; Kido, Motoyuki; Fujimoto, Hiromi; Osada, Yukihito; Inazu, Daisuke; Ohta, Yusaku; Iinuma, Takeshi; Ohzono, Mako; Miura, Satoshi; Mishina, Masaaki; Suzuki, Kensuke; Tsuji, Takeshi; Ashi, Juichiro

    2013-07-01

    We describe two transient slow slip events that occurred before the 2011 Tohoku-Oki earthquake. The first transient crustal deformation, which occurred over a period of a week in November 2008, was recorded simultaneously using ocean-bottom pressure gauges and an on-shore volumetric strainmeter; this deformation has been interpreted as being an M6.8 episodic slow slip event. The second had a duration exceeding 1 month and was observed in February 2011, just before the 2011 Tohoku-Oki earthquake; the moment magnitude of this event reached 7.0. The two events preceded interplate earthquakes of magnitudes M6.1 (December 2008) and M7.3 (March 9, 2011), respectively; the latter is the largest foreshock of the 2011 Tohoku-Oki earthquake. Our findings indicate that these slow slip events induced increases in shear stress, which in turn triggered the interplate earthquakes. The slow slip event source area on the fault is also located within the downdip portion of the huge-coseismic-slip area of the 2011 earthquake. This demonstrates episodic slow slip and seismic behavior occurring on the same portions of the megathrust fault, suggesting that the faults undergo slip in slow slip events can also rupture seismically.

  8. Areas prone to slow slip events impede earthquake rupture propagation and promote afterslip

    Science.gov (United States)

    Rolandone, Frederique; Nocquet, Jean-Mathieu; Mothes, Patricia A.; Jarrin, Paul; Vallée, Martin; Cubas, Nadaya; Hernandez, Stephen; Plain, Morgan; Vaca, Sandro; Font, Yvonne

    2018-01-01

    At subduction zones, transient aseismic slip occurs either as afterslip following a large earthquake or as episodic slow slip events during the interseismic period. Afterslip and slow slip events are usually considered as distinct processes occurring on separate fault areas governed by different frictional properties. Continuous GPS (Global Positioning System) measurements following the 2016 Mw (moment magnitude) 7.8 Ecuador earthquake reveal that large and rapid afterslip developed at discrete areas of the megathrust that had previously hosted slow slip events. Regardless of whether they were locked or not before the earthquake, these areas appear to persistently release stress by aseismic slip throughout the earthquake cycle and outline the seismic rupture, an observation potentially leading to a better anticipation of future large earthquakes. PMID:29404404

  9. On the micromechanics of slip events in sheared, fluid-saturated fault gouge

    Science.gov (United States)

    Dorostkar, Omid; Guyer, Robert A.; Johnson, Paul A.; Marone, Chris; Carmeliet, Jan

    2017-06-01

    We used a three-dimensional discrete element method coupled with computational fluid dynamics to study the poromechanical properties of dry and fluid-saturated granular fault gouge. The granular layer was sheared under dry conditions to establish a steady state condition of stick-slip dynamic failure, and then fluid was introduced to study its effect on subsequent failure events. The fluid-saturated case showed increased stick-slip recurrence time and larger slip events compared to the dry case. Particle motion induces fluid flow with local pressure variation, which in turn leads to high particle kinetic energy during slip due to increased drag forces from fluid on particles. The presence of fluid during the stick phase of loading promotes a more stable configuration evidenced by higher particle coordination number. Our coupled fluid-particle simulations provide grain-scale information that improves understanding of slip instabilities and illuminates details of phenomenological, macroscale observations.

  10. Temporal integration of sequential auditory events: silent period in sound pattern activates human planum temporale.

    Science.gov (United States)

    Mustovic, Henrietta; Scheffler, Klaus; Di Salle, Francesco; Esposito, Fabrizio; Neuhoff, John G; Hennig, Jürgen; Seifritz, Erich

    2003-09-01

    Temporal integration is a fundamental process that the brain carries out to construct coherent percepts from serial sensory events. This process critically depends on the formation of memory traces reconciling past with present events and is particularly important in the auditory domain where sensory information is received both serially and in parallel. It has been suggested that buffers for transient auditory memory traces reside in the auditory cortex. However, previous studies investigating "echoic memory" did not distinguish between brain response to novel auditory stimulus characteristics on the level of basic sound processing and a higher level involving matching of present with stored information. Here we used functional magnetic resonance imaging in combination with a regular pattern of sounds repeated every 100 ms and deviant interspersed stimuli of 100-ms duration, which were either brief presentations of louder sounds or brief periods of silence, to probe the formation of auditory memory traces. To avoid interaction with scanner noise, the auditory stimulation sequence was implemented into the image acquisition scheme. Compared to increased loudness events, silent periods produced specific neural activation in the right planum temporale and temporoparietal junction. Our findings suggest that this area posterior to the auditory cortex plays a critical role in integrating sequential auditory events and is involved in the formation of short-term auditory memory traces. This function of the planum temporale appears to be fundamental in the segregation of simultaneous sound sources.

  11. Automated identification and modeling aseismic slip events on Kilauea Volcano, Hawaii

    Science.gov (United States)

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

    2006-12-01

    Several aseismic slip events have been observed on the south flank of Kilauea volcano, Hawaii (Cervelli et al., Nature, 2002; Brooks et al., EPSL, 2006; Segall et al., Nature, 2006). These events are identified as spatially coherent offsets in GPS time series. We have interpreted the events as slip on a sub-horizontal surface at depths consistent with a decollement under Kilauea's south flank. In order to determine whether smaller slow slip events are present in the time series, we developed an algorithm that searches for coherent displacement patterns similar to the known slow slip events. We compute candidate displacements by taking a running difference of the mean position 6 days before and after a window of 6 days centered on the candidate time step. The candidate displacements are placed in a 3N dimensional data vector, where N is the number of stations. We then compute the angle, in the 3N dimensional data space, between the candidate displacement and a reference vector at each time step. The reference vector is a stack of displacements due to the four largest known slow slip events. Small angles indicate similar displacement patterns, regardless of amplitude. The algorithm strongly identifies four events (September 20, 1998, November 9, 2000, December 16, 2002, and January 26, 2005), each separated by approximately 2.11 years. The algorithm also identified one smaller event (March 3, 1998) that preceeded the September 1998 event by ~ 200 days, and another event (July 4, 2003) that followed the December 2002 event by ~ 200 days. These smaller, 'paired' events appear to alternate rupturing of the eastern and western parts of the south flank. Each of the slow slip events is correlated with an increase, sometimes slight, in microseismicity on the south flank of Kilauea. The temporal evolution of the microseismicity for the 2005 event is well explained by increased stress due to the slow slip (Segall et al., Nature, 2006). The microearthquakes, at depths of 6

  12. Revealing the cluster of slow transients behind a large slow slip event.

    Science.gov (United States)

    Frank, William B; Rousset, Baptiste; Lasserre, Cécile; Campillo, Michel

    2018-05-01

    Capable of reaching similar magnitudes to large megathrust earthquakes [ M w (moment magnitude) > 7], slow slip events play a major role in accommodating tectonic motion on plate boundaries through predominantly aseismic rupture. We demonstrate here that large slow slip events are a cluster of short-duration slow transients. Using a dense catalog of low-frequency earthquakes as a guide, we investigate the M w 7.5 slow slip event that occurred in 2006 along the subduction interface 40 km beneath Guerrero, Mexico. We show that while the long-period surface displacement, as recorded by Global Positioning System, suggests a 6-month duration, the motion in the direction of tectonic release only sporadically occurs over 55 days, and its surface signature is attenuated by rapid relocking of the plate interface. Our proposed description of slow slip as a cluster of slow transients forces us to re-evaluate our understanding of the physics and scaling of slow earthquakes.

  13. Fracture energy of stick-slip events in a large scale biaxial experiment

    International Nuclear Information System (INIS)

    Okubo, P.G.; Dieterich, J.H.

    1981-01-01

    The concept of apparent fracture energy for the shear failure process is employed by many authors in modeling earthquake sources as dynamically extending shear cracks. Using records of shear strain and relative displacement from stick-slip events generated along a simulated, prepared fault surface in a large (1.5m x 1.5m x 0.4m) granite block and a slip-weakening model for the fault, direct estimates of the apparent shear fracture energy of the stick-slip events have been obtained. For events generated on a finely ground fault surface, apparent fracture energy ranges from 0.06 J/m 2 at a normal stress of 1.1 MPa to 0.8 J/m 2 at a normal stress of 4.6 MPa. In contrast to estimates for tensile crack formation, we find that the apparent fracture energy of stick-slip events increases linearly with normal stress. The results for the slip-weakening model for the stick-slip events are generally consistent with constitutive fault models suggested by observations of stable sliding in smaller scale experiments

  14. Numerical Simulations of Slow Stick Slip Events with PFC, a DEM Based Code

    Science.gov (United States)

    Ye, S. H.; Young, R. P.

    2017-12-01

    Nonvolcanic tremors around subduction zone have become a fascinating subject in seismology in recent years. Previous studies have shown that the nonvolcanic tremor beneath western Shikoku is composed of low frequency seismic waves overlapping each other. This finding provides direct link between tremor and slow earthquakes. Slow stick slip events are considered to be laboratory scaled slow earthquakes. Slow stick slip events are traditionally studied with direct shear or double direct shear experiment setup, in which the sliding velocity can be controlled to model a range of fast and slow stick slips. In this study, a PFC* model based on double direct shear is presented, with a central block clamped by two side blocks. The gauge layers between the central and side blocks are modelled as discrete fracture networks with smooth joint bonds between pairs of discrete elements. In addition, a second model is presented in this study. This model consists of a cylindrical sample subjected to triaxial stress. Similar to the previous model, a weak gauge layer at a 45 degrees is added into the sample, on which shear slipping is allowed. Several different simulations are conducted on this sample. While the confining stress is maintained at the same level in different simulations, the axial loading rate (displacement rate) varies. By varying the displacement rate, a range of slipping behaviour, from stick slip to slow stick slip are observed based on the stress-strain relationship. Currently, the stick slip and slow stick slip events are strictly observed based on the stress-strain relationship. In the future, we hope to monitor the displacement and velocity of the balls surrounding the gauge layer as a function of time, so as to generate a synthetic seismogram. This will allow us to extract seismic waveforms and potentially simulate the tremor-like waves found around subduction zones. *Particle flow code, a discrete element method based numerical simulation code developed by

  15. Micromechanics and statistics of slipping events in a granular seismic fault model

    Energy Technology Data Exchange (ETDEWEB)

    Arcangelis, L de [Department of Information Engineering and CNISM, Second University of Naples, Aversa (Italy); Ciamarra, M Pica [CNR-SPIN, Dipartimento di Scienze Fisiche, Universita di Napoli Federico II (Italy); Lippiello, E; Godano, C, E-mail: dearcangelis@na.infn.it [Department of Environmental Sciences and CNISM, Second University of Naples, Caserta (Italy)

    2011-09-15

    The stick-slip is investigated in a seismic fault model made of a confined granular system under shear stress via three dimensional Molecular Dynamics simulations. We study the statistics of slipping events and, in particular, the dependence of the distribution on model parameters. The distribution consistently exhibits two regimes: an initial power law and a bump at large slips. The initial power law decay is in agreement with the the Gutenberg-Richter law characterizing real seismic occurrence. The exponent of the initial regime is quite independent of model parameters and its value is in agreement with experimental results. Conversely, the position of the bump is solely controlled by the ratio of the drive elastic constant and the system size. Large slips also become less probable in absence of fault gouge and tend to disappear for stiff drives. A two-time force-force correlation function, and a susceptibility related to the system response to pressure changes, characterize the micromechanics of slipping events. The correlation function unveils the micromechanical changes occurring both during microslips and slips. The mechanical susceptibility encodes the magnitude of the incoming microslip. Numerical results for the cellular-automaton version of the spring block model confirm the parameter dependence observed for size distribution in the granular model.

  16. Slow slip events in Guerrero, Mexico, and consequences on strain accumulation over the past 15 years.

    Science.gov (United States)

    Radiguet, M.; Cotton, F.; Cavalié, O.; Pathier, E.; Kostoglodov, V.; Vergnolle, M.; Campillo, M.; Walpersdorf, A.; Cotte, N.; Santiago, J.; Franco, S.

    2012-12-01

    Continuous Global Positioning System (cGPS) time series in Guerrero, Mexico, reveal the widespread existence of large Slow Slip Events (SSEs) at the boundary between the Cocos and North American plates. The existence of these SSEs asks the question of how seismic and aseismic slips complement each other in subduction zones. We examined the last three SSEs that occurred in 2001/2002, 2006 and 2009/2010, and their impact on the strain accumulation along the Guerrero subduction margin. We use continuous cGPS time series and InSAR images to evaluate the surface displacement during SSEs and inter-SSE periods. The slip distributions on the plate interface associated with each SSE, as well as the inter-SSE (short-term) coupling rates are evaluated by inverting these surface displacements. Our results reveal that the three analyzed SSEs have equivalent moment magnitudes of around 7.5 and their lateral extension is variable.The slip distributions for the three SSEs show that in the Guerrero gap area, the slow slip occurs at shallower depth (updip limit around 15-20 km) than in surrounding regions. The InSAR data provide additional information for the 2006 SSE. The joint inversion of InSAR and cGPS data confirms the lateral variation of the slip distribution along the trench, with shallower slip in the Guerrero seismic gap, west of Acapulco, and deeper slip further east. Inversion of inter-SSE displacement rates reveal that during the inter-SSE time intervals, the interplate coupling is high in the area where the slow slip subsequently occurs. Over a 12 year period, corresponding to three cycles of SSEs, our results reveal that the accumulated slip deficit in the Guerrero gap area is only ¼ of the slip deficit accumulated on both sides of the gap. Moreover, the regions of large slip deficit coincide with the rupture areas of recent large earthquakes. We conclude that the SSEs account for a major portion of the overall moment release budget in the Guerrero gap. If large

  17. SLOW SLIP EVENTS: PARAMETERS, CONDITIONS OF OCCURRENCE, AND FUTURE RESEARCH PROSPECTS

    Directory of Open Access Journals (Sweden)

    G. G. Kocharyan

    2014-01-01

    Full Text Available Slow slip events along faults and fractures are reviewed. Such inter-block displacements can be recorded at various scale levels and considered as transitional from quasi-stable (creep to dynamic slip (earthquake. Such events include seismogenic slip along faults at velocities by one to three orders lower than those in case of 'normal' earthquakes, as well as aseismic slip cases. Discovering such events facilitates better understanding of how energy accumulated during deformation of the crust is released.Studying conditions and the evolution of transitional regimes can provide new important information on the structure and regularities of deformation in fault zones.Data from latest publications by different authors are consolidated, and the data analysis results are presented. Over 170 slow slip events are reviewed. Based on the consolidated data and modelling results obtained by the authors, relationships between parameters of the reviewed process are established, scale relations between the events are considered, and a first-approximation analysis is conducted for impacts of geomaterial characteristics on various deformation regimes.Low-frequency earthquake foci and slow slip sites are most typically located in zones of transition from stable creep areas to seismogenic segments of the discontinuity (Fig. 3 It can be logically supposed that in such transitional zones, the interface has specific frictional properties providing for a regime that can be termed as 'conditionally stable slip'.The duration of slow deformation events is roughly proportional to the released seismic moment, while such a ratio is close to self-similarity in case of 'normal' earthquakes (Fig. 4. In case of slow slip, an area of the displaced section is larger by many factors than the corresponding value for an earthquake with the same seismic moment, while an average displacement amplitude along the fault is significantly smaller (Figures 5 and 6. Velocities of slip

  18. A viscoplastic shear-zone model for episodic slow slip events in oceanic subduction zones

    Science.gov (United States)

    Yin, A.; Meng, L.

    2016-12-01

    Episodic slow slip events occur widely along oceanic subduction zones at the brittle-ductile transition depths ( 20-50 km). Although efforts have been devoted to unravel their mechanical origins, it remains unclear about the physical controls on the wide range of their recurrence intervals and slip durations. In this study we present a simple mechanical model that attempts to account for the observed temporal evolution of slow slip events. In our model we assume that slow slip events occur in a viscoplastic shear zone (i.e., Bingham material), which has an upper static and a lower dynamic plastic yield strength. We further assume that the hanging wall deformation is approximated as an elastic spring. We envision the shear zone to be initially locked during forward/landward motion but is subsequently unlocked when the elastic and gravity-induced stress exceeds the static yield strength of the shear zone. This leads to backward/trenchward motion damped by viscous shear-zone deformation. As the elastic spring progressively loosens, the hanging wall velocity evolves with time and the viscous shear stress eventually reaches the dynamic yield strength. This is followed by the termination of the trenchward motion when the elastic stress is balanced by the dynamic yield strength of the shear zone and the gravity. In order to account for the zig-saw slip-history pattern of typical repeated slow slip events, we assume that the shear zone progressively strengthens after each slow slip cycle, possibly caused by dilatancy as commonly assumed or by progressive fault healing through solution-transport mechanisms. We quantify our conceptual model by obtaining simple analytical solutions. Our model results suggest that the duration of the landward motion increases with the down-dip length and the static yield strength of the shear zone, but decreases with the ambient loading velocity and the elastic modulus of the hanging wall. The duration of the backward/trenchward motion depends

  19. Slow Earthquake Hunters: A New Citizen Science Project to Identify and Catalog Slow Slip Events in Geodetic Data

    Science.gov (United States)

    Bartlow, N. M.

    2017-12-01

    Slow Earthquake Hunters is a new citizen science project to detect, catalog, and monitor slow slip events. Slow slip events, also called "slow earthquakes", occur when faults slip too slowly to generate significant seismic radiation. They typically take between a few days and over a year to occur, and are most often found on subduction zone plate interfaces. While not dangerous in and of themselves, recent evidence suggests that monitoring slow slip events is important for earthquake hazards, as slow slip events have been known to trigger damaging "regular" earthquakes. Slow slip events, because they do not radiate seismically, are detected with a variety of methods, most commonly continuous geodetic Global Positioning System (GPS) stations. There is now a wealth of GPS data in some regions that experience slow slip events, but a reliable automated method to detect them in GPS data remains elusive. This project aims to recruit human users to view GPS time series data, with some post-processing to highlight slow slip signals, and flag slow slip events for further analysis by the scientific team. Slow Earthquake Hunters will begin with data from the Cascadia subduction zone, where geodetically detectable slow slip events with a duration of at least a few days recur at regular intervals. The project will then expand to other areas with slow slip events or other transient geodetic signals, including other subduction zones, and areas with strike-slip faults. This project has not yet rolled out to the public, and is in a beta testing phase. This presentation will show results from an initial pilot group of student participants at the University of Missouri, and solicit feedback for the future of Slow Earthquake Hunters.

  20. Reassessing the 2006 Guerrero slow-slip event, Mexico : Implications for large earthquakes in the Guerrero Gap

    NARCIS (Netherlands)

    Bekaert, D.P.S.; Hooper, A.; Wright, T.J.

    2015-01-01

    In Guerrero, Mexico, slow-slip events have been observed in a seismic gap, where no earthquakes have occurred since 1911. A rupture of the entire gap today could result in a Mw 8.2–8.4 earthquake. However, it remains unclear how slow-slip events change the stress field in the Guerrero seismic region

  1. Revisiting Slow Slip Events Occurrence in Boso Peninsula, Japan, Combining GPS Data and Repeating Earthquakes Analysis

    Science.gov (United States)

    Gardonio, B.; Marsan, D.; Socquet, A.; Bouchon, M.; Jara, J.; Sun, Q.; Cotte, N.; Campillo, M.

    2018-02-01

    Slow slip events (SSEs) regularly occur near the Boso Peninsula, central Japan. Their time of recurrence has been decreasing from 6.4 to 2.2 years from 1996 to 2014. It is important to better constrain the slip history of this area, especially as models show that the recurrence intervals could become shorter prior to the occurrence of a large interplate earthquake nearby. We analyze the seismic waveforms of more than 2,900 events (M≥1.0) taking place in the Boso Peninsula, Japan, from 1 April 2004 to 4 November 2015, calculating the correlation and the coherence between each pair of events in order to define groups of repeating earthquakes. The cumulative number of repeating earthquakes suggests the existence of two slow slip events that have escaped detection so far. Small transient displacements observed in the time series of nearby GPS stations confirm these results. The detection scheme coupling repeating earthquakes and GPS analysis allow to detect small SSEs that were not seen before by classical methods. This work brings new information on the diversity of SSEs and demonstrates that the SSEs in Boso area present a more complex history than previously considered.

  2. Shallow very-low-frequency earthquakes accompany slow slip events in the Nankai subduction zone.

    Science.gov (United States)

    Nakano, Masaru; Hori, Takane; Araki, Eiichiro; Kodaira, Shuichi; Ide, Satoshi

    2018-03-14

    Recent studies of slow earthquakes along plate boundaries have shown that tectonic tremor, low-frequency earthquakes, very-low-frequency events (VLFEs), and slow-slip events (SSEs) often accompany each other and appear to share common source faults. However, the source processes of slow events occurring in the shallow part of plate boundaries are not well known because seismic observations have been limited to land-based stations, which offer poor resolution beneath offshore plate boundaries. Here we use data obtained from seafloor observation networks in the Nankai trough, southwest of Japan, to investigate shallow VLFEs in detail. Coincident with the VLFE activity, signals indicative of shallow SSEs were detected by geodetic observations at seafloor borehole observatories in the same region. We find that the shallow VLFEs and SSEs share common source regions and almost identical time histories of moment release. We conclude that these slow events arise from the same fault slip and that VLFEs represent relatively high-frequency fluctuations of slip during SSEs.

  3. The threat of silent earthquakes

    Science.gov (United States)

    Cervelli, Peter

    2004-01-01

    Not all earthquakes shake the ground. The so-called silent types are forcing scientists to rethink their understanding of the way quake-prone faults behave. In rare instances, silent earthquakes that occur along the flakes of seaside volcanoes may cascade into monstrous landslides that crash into the sea and trigger towering tsunamis. Silent earthquakes that take place within fault zones created by one tectonic plate diving under another may increase the chance of ground-shaking shocks. In other locations, however, silent slip may decrease the likelihood of destructive quakes, because they release stress along faults that might otherwise seem ready to snap.

  4. Segmentation of Slow Slip Events in South Central Alaska Possibly Controlled by a Subducted Oceanic Plateau

    Science.gov (United States)

    Li, Haotian; Wei, Meng; Li, Duo; Liu, Yajing; Kim, YoungHee; Zhou, Shiyong

    2018-01-01

    Recent GPS observations show that slow slip events in south central Alaska are segmented along strike. Here we review several mechanisms that might contribute to this segmentation and focus on two: along-strike variation of slab geometry and effective normal stress. We then test them by running numerical simulations in the framework of rate-and-state friction with a nonplanar fault geometry. Results show that the segmentation is most likely related to the along-strike variation of the effective normal stress on the fault plane caused by the Yakutat Plateau. The Yakutat Plateau could affect the effective normal stress by either lowering the pore pressure in Upper Cook Inlet due to less fluids release or increasing the normal stress due to the extra buoyancy caused by the subducted Yakutat Plateau. We prefer the latter explanation because it is consistent with the relative amplitudes of the effective normal stress in Upper and Lower Cook Inlet and there is very little along-strike variation in Vp/Vs ratio in the fault zone from receiver function analysis. However, we cannot exclude the possibility that the difference in effective normal stress results from along-strike variation of pore pressure due to the uncertainties in the Vp/Vs estimates. Our work implies that a structural anomaly can have a long-lived effect on the subduction zone slip behavior and might be a driving factor on along-strike segmentation of slow slip events.

  5. A Novel Event-Based Incipient Slip Detection Using Dynamic Active-Pixel Vision Sensor (DAVIS).

    Science.gov (United States)

    Rigi, Amin; Baghaei Naeini, Fariborz; Makris, Dimitrios; Zweiri, Yahya

    2018-01-24

    In this paper, a novel approach to detect incipient slip based on the contact area between a transparent silicone medium and different objects using a neuromorphic event-based vision sensor (DAVIS) is proposed. Event-based algorithms are developed to detect incipient slip, slip, stress distribution and object vibration. Thirty-seven experiments were performed on five objects with different sizes, shapes, materials and weights to compare precision and response time of the proposed approach. The proposed approach is validated by using a high speed constitutional camera (1000 FPS). The results indicate that the sensor can detect incipient slippage with an average of 44.1 ms latency in unstructured environment for various objects. It is worth mentioning that the experiments were conducted in an uncontrolled experimental environment, therefore adding high noise levels that affected results significantly. However, eleven of the experiments had a detection latency below 10 ms which shows the capability of this method. The results are very promising and show a high potential of the sensor being used for manipulation applications especially in dynamic environments.

  6. Recurrent slow slip event likely hastened by the 2011 Tohoku earthquake

    Science.gov (United States)

    Hirose, Hitoshi; Kimura, Hisanori; Enescu, Bogdan; Aoi, Shin

    2012-01-01

    Slow slip events (SSEs) are another mode of fault deformation than the fast faulting of regular earthquakes. Such transient episodes have been observed at plate boundaries in a number of subduction zones around the globe. The SSEs near the Boso Peninsula, central Japan, are among the most documented SSEs, with the longest repeating history, of almost 30 y, and have a recurrence interval of 5 to 7 y. A remarkable characteristic of the slow slip episodes is the accompanying earthquake swarm activity. Our stable, long-term seismic observations enable us to detect SSEs using the recorded earthquake catalog, by considering an earthquake swarm as a proxy for a slow slip episode. Six recurrent episodes are identified in this way since 1982. The average duration of the SSE interoccurrence interval is 68 mo; however, there are significant fluctuations from this mean. While a regular cycle can be explained using a simple physical model, the mechanisms that are responsible for the observed fluctuations are poorly known. Here we show that the latest SSE in the Boso Peninsula was likely hastened by the stress transfer from the March 11, 2011 great Tohoku earthquake. Moreover, a similar mechanism accounts for the delay of an SSE in 1990 by a nearby earthquake. The low stress buildups and drops during the SSE cycle can explain the strong sensitivity of these SSEs to stress transfer from external sources. PMID:22949688

  7. Unified law of evolution of experimental gouge-filled fault for fast and slow slip events at slider frictional experiments

    Science.gov (United States)

    Ostapchuk, Alexey; Saltykov, Nikolay

    2017-04-01

    Excessive tectonic stresses accumulated in the area of rock discontinuity are released while a process of slip along preexisting faults. Spectrum of slip modes includes not only creeps and regular earthquakes but also some transitional regimes - slow-slip events, low-frequency and very low-frequency earthquakes. However, there is still no agreement in Geophysics community if such fast and slow events have mutual nature [Peng, Gomberg, 2010] or they present different physical phenomena [Ide et al., 2007]. Models of nucleation and evolution of fault slip events could be evolved by laboratory experiments in which regularities of shear deformation of gouge-filled fault are investigated. In the course of the work we studied deformation regularities of experimental fault by slider frictional experiments for development of unified law of evolution of fault and revelation of its parameters responsible for deformation mode realization. The experiments were conducted as a classic slider-model experiment, in which block under normal and shear stresses moves along interface. The volume between two rough surfaces was filled by thin layer of granular matter. Shear force was applied by a spring which deformed with a constant rate. In such experiments elastic energy was accumulated in the spring, and regularities of its releases were determined by regularities of frictional behaviour of experimental fault. A full spectrum of slip modes was simulated in laboratory experiments. Slight change of gouge characteristics (granule shape, content of clay), viscosity of interstitial fluid and level of normal stress make it possible to obtained gradual transformation of the slip modes from steady sliding and slow slip to regular stick-slip, with various amplitude of 'coseismic' displacement. Using method of asymptotic analogies we have shown that different slip modes can be specified in term of single formalism and preparation of different slip modes have uniform evolution law. It is shown

  8. Frictional properties of the Nankai frontal thrust explain recurring shallow slow slip events

    Science.gov (United States)

    Saffer, D. M.; Ikari, M.; Kopf, A.; Roesner, A.

    2017-12-01

    Recent observations provide evidence for shallow slip reaching to the trench on subduction megathrusts, both in earthquakes and slow slip events (SSE). This is at odds with existing friction studies, which report primarily velocity-strengthening behavior (friction increases with slip velocity) for subduction fault material and synthetic analogs, which leads only to stable sliding. We report on direct shearing experiments on fault rocks from IODP Site C0007, which sampled the frontal thrust of the Nankai accretionary prism. This fault has been implicated in both coseimic slip and recurring SSE. We focus on material from 437.2 meters below seafloor, immediately above a localized shear zone near the base of the fault. In our experiments, a 25 mm diameter cylindrical specimen is loaded in an assembly of two steel plates. After application of normal stress (3, 10, or 17 MPa) and subsequent equilibration, the lower plate is driven at a constant velocity while the upper plate remains stationary; this configuration forces shear to localize between the two plates. After reaching a steady state residual friction coefficient (µss), we conducted velocity-stepping tests to measure the friction rate parameter (a-b), defined as the change in friction for a change in velocity: (a-b) = Δuss/ln(V/Vo), over a range of velocities from 0.1-100 µm s-1. We find that µss ranges from 0.26 to 0.32 and exhibits a slight decrease with normal stress. We observe velocity-weakening behavior at low normal stresses (3-10 MPa) and for low sliding velocities (30 µm s-1. At higher normal stress (17 MPa), we observe dominantly velocity-strengthening, consistent with previously reported measurements for 25 MPa normal stress. Our observation of rate weakening at slip rates matching those of SSE in the outer Nankai forearc provide a potential explanation for periodic strain accumulation and subsequent release during SSE near the trench. The observation of rate weakening behavior only at low normal

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

  11. Space geodetic observations of repeating slow slip events beneath the Bonin Islands

    Science.gov (United States)

    Arisa, Deasy; Heki, Kosuke

    2017-09-01

    The Pacific Plate subducts beneath the Philippine Sea Plate along the Izu-Bonin Trench. We investigated crustal movements at the Bonin Islands, using Global Navigation Satellite System and geodetic Very Long Baseline Interferometry data to reveal how the two plates converge in this subduction zone. These islands are located ∼100 km from the trench, just at the middle between the volcanic arc and the trench, making these islands suitable for detecting signatures of episodic deformation such as slow slip events (SSEs). During 2007-2016, we found five SSEs repeating quasi-periodically with similar displacement patterns. In estimating their fault parameters, we assumed that the fault lies on the prescribed plate boundary, and optimized the size, shape and position of the fault and dislocation vectors. Average fault slip was ∼5 cm, and the average moment magnitude was ∼6.9. We also found one SSE occurred in 2008 updip of the repeating SSE in response to an M6 class interplate earthquake. In spite of the frequent occurrence of SSEs, there is no evidence for long-term strain accumulation in the Bonin Islands that may lead to future megathrust earthquakes. Plate convergence in Mariana-type subduction zones may occur, to a large extent, episodically as repeating SSEs.

  12. Two long-term slow slip events around Tokyo Bay found by GNSS observation during 1996-2011

    Science.gov (United States)

    Tanaka, Yoshiyuki; Yabe, Suguru

    2017-03-01

    Slow slip events (SSEs) with durations ranging from days to more than a decade have been observed in plate subduction zones around the world. In the Kanto district in Japan, several SSEs have been identified based on geodetic observations. However, none of these events have had durations largely exceeding a year. In this study, we show that long-term SSEs with durations longer than 3 years occurred before the year 2000 and after 2007 on the upper interface of the Philippine Sea Plate at depths of 30-40 km. The fault model determined by inversion of global navigation satellite system data is located northeast of Tokyo Bay, where a seismic gap and low seismic wave velocities were detected by seismological observations. Moreover, the acceleration periods of the fault slip corresponded well with increases in the background seismicity for shallower earthquakes. The slip history was also temporally correlated with the long-term shear stress changes governed mainly by non-tidal variations in the ocean bottom pressure. However, the predicted slip from the long-term stress change was too small to reproduce the observed slow slips. To prove the causal relationship between the SSEs and the external stress change, more advanced modeling is necessary to confirm whether such a small slip can trigger an SSE.[Figure not available: see fulltext.

  13. Great earthquakes and slow slip events along the Sagami trough and outline of the Kanto Asperity Project

    Science.gov (United States)

    Kobayashi, R.; Yamamoto, Y.; Sato, T.; Shishikura, M.; Ito, H.; Shinohara, M.; Kawamura, K.; Shibazaki, B.

    2010-12-01

    The Kanto region is one of the most densely populated urban areas in the world. Complicated plate configurations are due to T-T-T type triple junction, island arc-island arc collision zone, and very shallow angle between axis of the Sagami trough and subducting direction. Great earthquakes along the Sagami trough have repeatedly occurred. The 1703 Genroku and 1923 (Taisho) Kanto earthquakes caused severe damages in the Tokyo metropolitan area. Intriguingly slow slip events have also repeatedly occurred in an area adjacent to the asperities of the great earthquakes, off Boso peninsula (e.g., Ozawa et al 2007). In the cases of the Nankai and Cascadia subduction zones, slow slip events occur at deeper levels than the asperity, in a transition zone between the asperity and a region of steady slip. In contrast, slow slip events in the Kanto region have occurred at relatively shallow depths, at the same level as the asperity, raising the possibility of friction controlled by different conditions to those (temperature and pressure) encountered at Nankai and Cascadia. We focus on three different types of seismic events occurring repeatedly at the almost same depth of the seismogenic zone along the Sagami trough (5-20 km) (1) The 1923 M~7.9 Taisho earthquake, located in Sagami Bay. Maximum slip is about 6 m, the recurrence interval is 200-400 yr, and the coupling rate is 80-100% (“coupling rates” = “slip amounts during earthquakes or slow-slip events” / [“rate of motion of the Philippine Sea Plate” - “recurrence interval”]) . (2) The 1703 M~8.2 Genroku earthquake, located in Sagami Bay, but also extending to the southern part of Boso Peninsula. Maximum slip is 15-20 m, the recurrence interval is ~2000 yr, and the coupling rate at the southern part of the Boso Peninsula is 10-30%. (3) Boso slow-slip events, located southeast of Boso Peninsula. Maximum slip is 15-20 cm over ~10 days, the recurrence interval is 5-6 yr, and the coupling rate is 70

  14. A viscoplastic shear-zone model for deep (15-50 km) slow-slip events at plate convergent margins

    Science.gov (United States)

    Yin, An; Xie, Zhoumin; Meng, Lingsen

    2018-06-01

    A key issue in understanding the physics of deep (15-50 km) slow-slip events (D-SSE) at plate convergent margins is how their initially unstable motion becomes stabilized. Here we address this issue by quantifying a rate-strengthening mechanism using a viscoplastic shear-zone model inspired by recent advances in field observations and laboratory experiments. The well-established segmentation of slip modes in the downdip direction of a subduction shear zone allows discretization of an interseismic forearc system into the (1) frontal segment bounded by an interseismically locked megathrust, (2) middle segment bounded by episodically locked and unlocked viscoplastic shear zone, and (3) interior segment that slips freely. The three segments are assumed to be linked laterally by two springs that tighten with time, and the increasing elastic stress due to spring tightening eventually leads to plastic failure and initial viscous shear. This simplification leads to seven key model parameters that dictate a wide range of mechanical behaviors of an idealized convergent margin. Specifically, the viscoplastic rheology requires the initially unstable sliding to be terminated nearly instantaneously at a characteristic velocity, which is followed by stable sliding (i.e., slow-slip). The characteristic velocity, which is on the order of <10-7 m/s for the convergent margins examined in this study, depends on the (1) effective coefficient of friction, (2) thickness, (3) depth, and (4) viscosity of the viscoplastic shear zone. As viscosity decreases exponentially with temperature, our model predicts faster slow-slip rates, shorter slow-slip durations, more frequent slow-slip occurrences, and larger slow-slip magnitudes at warmer convergent margins.

  15. 'Silent mentors'

    DEFF Research Database (Denmark)

    Douglas-Jones, Rachel

    2017-01-01

    Unlike cadaver donation in the West, which has to a large degree maintained the anonymity of the body used to teach medical students, the Taiwanese Tzu Chi Buddhist Silent Mentor programme at the centre of this article foregrounds the identity of the training cadaver as an essential element in me...... for medical pedagogy, body donation, and Buddhist practices prompted by this programme, putting the ‘Silent Mentors’ into conversation with the ‘new immortalities’ of this special issue....

  16. Delicate balance of magmatic-tectonic interaction at Kilauea Volcano, Hawai`i, revealed from slow slip events: Chapter 13

    Science.gov (United States)

    Montgomery-Brown, Emily; Poland, Michael; Miklius, Asta; Carey, Rebecca; Cayol, Valérie; Poland, Michael P.; Weis, Dominique

    2015-01-01

    Eleven slow slip events (SSEs) have occurred on the southern flank of Kilauea Volcano, Hawai’i, since 1997 through 2014. We analyze this series of SSEs in the context of Kilauea’s magma system to assess whether or not there are interactions between these tectonic events and eruptive/intrusive activity. Over time, SSEs have increased in magnitude and become more regular, with interevent times averaging 2.44 ± 0.15 years since 2003. Two notable SSEs that impacted both the flank and the magmatic system occurred in 2007, when an intrusion and small eruption on the East Rift Zone were part of a feedback with a SSE and 2012, when slow slip induced 2.5 cm of East Rift Zone opening (but without any change in eruptive activity). A summit inflation event and surge in East Rift Zone lava effusion was associated with a SSE in 2005, but the inferred triggering relation is not clear due to a poorly constrained slip onset time. Our results demonstrate that slow slip along Kilauea’s décollement has the potential to trigger and be triggered by activity within the volcano’s magma system. Since only three of the SSEs have been associated with changes in magmatic activity within the summit and rift zones, both the décollement and magma system must be close to failure for triggering to occur.

  17. Numerical study of the effect of earth tides on recurring short-term slow slip events

    Science.gov (United States)

    Matsuzawa, T.; Tanaka, Y.; Shibazaki, B.

    2017-12-01

    Short-term slow slip events (SSEs) in the Nankai region are affected by earth tides (e.g., Nakata et al., 2008; Ide and Tanaka, 2014; Yabe et al., 2015). The effect of tidal stress on the SSEs is also examined numerically (e.g., Hawthorne and Rubin, 2013). In our previous study (Matsuzawa et al., 2017, JpGU-AGU), we numerically simulated SSEs in the Shikoku region, and reported that tidal stress makes the variance of recurrence intervals of SSEs smaller in relatively isolated SSE regions. However, the reason of such stable recurrence was not clear. In this study, we examine the tidal effect on short-term SSEs based on a flat plate and a realistic plate model (e.g., Matsuzawa et al., 2013, GRL). We adopt a rate- and state-dependent friction law (RS-law) with cutoff velocities as in our previous studies (Matsuzawa et al., 2013). We assume that (a-b) value in the RS-law is negative within the short-term SSE region, and positive outside the region. In a flat plate model, the short-term SSE region is a circular patch with the radius of 6 km. In a realistic plate model, the short-term SSE region is based on the actual distribution of low-frequency tremor. Low effective normal stress is assumed at the depth of SSEs. Calculating stress change by earth tides as in Yabe et al., (2015), we examine the stress perturbation by two different earth tides with the period of semidiurnal (M2) and fortnight (Mf) tide in this study. In the result of a flat plate case, amplitude of SSEs becomes smaller just after the slip at whole simulated area. Recurring SSEs become clear again within one year in the case with tides (M2 or Mf), while the recurrence becomes clear after seven years in the case without tides. Interestingly, the effect of the Mf tide is similar to the case with the M2 tide, even though the amplitude of the Mf tide (0.01 kPa) is two-order smaller than that of the M2 tide. In the realistic plate model of Shikoku, clear recurrence of short-term SSEs is found earlier than the

  18. Spatial distribution of reflection intensity of the upper surface of the Philippine Sea plate, near the main slip area of the Boso Slow Slip Events

    Science.gov (United States)

    Kono, A.; Sato, T.; Shinohara, M.; Mochizuki, K.; Yamada, T.; Uehira, K.; Shimbo, T.; Machida, Y.; Hino, R.; Azuma, R.

    2017-12-01

    Off the Boso Peninsula, Japan, the Pacific plate (PAC) is subducting westward beneath the Honshu Island Arc (HIA) and the Philippine Sea plate (PHS), while the PHS is subducting northwestward under the HIA. Such tectonic interactions have caused various seismic events such as the Boso Slow Slip Events (SSEs). To better understand these seismic events, it is important to determine the structure under this region. In May 2017, we published 2D P-wave velocity structure under the survey area, and showed geometry of the upper surface of PHS (UPHS) and reflection intensity variation along it. From our result and previous studies, relatively strong reflection from the UPHS can be observed near the main slip area of Boso SSEs, and such reflective area may relate with the Boso SSEs. However, it is still insufficient to link both only from the 2D models and further work is needed to reveal spatial distribution of the strong reflection area. From July to August 2009, we conducted a marine seismic experiment using airgun as source off the east coast of the Boso Peninsula. Airgun was shot along the 4 survey lines, and 27 Ocean Bottom Seismometers (OBSs) were deployed in the survey area. In our presentation, we used 18 OBSs to determine 3D P-wave velocity structure. We estimated 3D velocity structure from airgun data recorded in the OBSs by using the FAST (Zelt and Barton, 1998). Next, we picked the reflection traveltimes likely reflected from the UPHS and applied them to the Traveltime mapping method (Fujie et al. 2006) to estimate spatial locations of the reflectors. As a result, reflections from the UPHS seem to concentrate near the main slip area of the Boso SSEs and an area where the serpentine seamount chain of the Izu-Bonin subduction zone is subducting. Acknowledgement The marine seismic experiment was conducted by R/V Hakuhou-maru of Japan Agency for Marine-Earth Science and Technology, and the OBSs were retrieved by Shincho-maru of Shin-Nihon-Kaiji co. Ltd. (Present

  19. Activated Very Low Frequency Earthquakes By the Slow Slip Events in the Ryukyu Subduction Zone

    Science.gov (United States)

    Nakamura, M.; Sunagawa, N.

    2014-12-01

    The Ryukyu Trench (RT), where the Philippine Sea plate is subducting, has had no known thrust earthquakes with a Mw>8.0 in the last 300 years. However, the rupture source of the 1771 tsunami has been proposed as an Mw > 8.0 earthquake in the south RT. Based on the dating of tsunami boulders, it has been estimated that large tsunamis occur at intervals of 150-400 years in the south Ryukyu arc (RA) (Araoka et al., 2013), although they have not occurred for several thousand years in the central and northern Ryukyu areas (Goto et al., 2014). To address the discrepancy between recent low moment releases by earthquakes and occurrence of paleo-tsunamis in the RT, we focus on the long-term activity of the very low frequency earthquakes (VLFEs), which are good indicators of the stress release in the shallow plate interface. VLFEs have been detected along the RT (Ando et al., 2012), which occur on the plate interface or at the accretionary prism. We used broadband data from the F-net of NIED along the RT and from the IRIS network. We applied two filters to all the raw broadband seismograms: a 0.02-0.05 Hz band-pass filter and a 1 Hz high-pass filter. After identification of the low-frequency events from the band-pass-filtered seismograms, the local and teleseismic events were removed. Then we picked the arrival time of the maximum amplitude of the surface wave of the VLFEs and determined the epicenters. VLFEs occurred on the RA side within 100 km from the trench axis along the RT. Distribution of the 6670 VLFEs from 2002 to 2013 could be divided to several clusters. Principal large clusters were located at 27.1°-29.0°N, 25.5°-26.6°N, and 122.1°-122.4°E (YA). We found that the VLFEs of the YA are modulated by repeating slow slip events (SSEs) which occur beneath south RA. The activity of the VLFEs increased to two times of its ordinary rate in 15 days after the onset of the SSEs. Activation of the VLFEs could be generated by low stress change of 0.02-20 kPa increase in

  20. Shallow very-low-frequency earthquakes accompanied with slow slip event along the plate boundary of the Nankai trough

    Science.gov (United States)

    Nakano, M.; Hori, T.; Araki, E.; Kodaira, S.; Ide, S.

    2017-12-01

    Recent improvements of seismic and geodetic observations have revealed the existence of a new family of slow earthquakes occurring along or close to the plate boundary worldwide. In the viewpoint of the characteristic time scales, the slow earthquakes can be classified into several groups as low-frequency tremor or tectonic tremor (LFT) dominated in several hertz, very-low-frequency earthquake (VLFE) dominated in 10 to 100 s, and short- and long-term slow-slip event (SSE) with durations of days to years. In many cases, these slow earthquakes are accompanied with other types of slow events. However, the events occurring offshore, especially beneath the toe of accretionary prism, are poorly understood because of the difficulty to detect signals. Utilizing the data captured from oceanfloor observation networks which many efforts have recently been taken to develop is necessary to improve our understandings for these events. Here, we investigated CMT analysis of shallow VLFEs using data obtained from DONET oceanfloor observation networks along the Nankai trough, southwest of Japan. We found that shallow VLFEs have almost identical history of moment release with that of synchronous SSE which occurred at the same region recently found by Araki et al. (2017). VLFE sources show updip migrations during the activity, coincident with the migration of SSE source. From these findings we conclude that these slow events share the same fault slip, and VLFE represent high-frequency fluctuations of slip during SSE. This result imply that shallow SSE along the plate interface would have occurred in the background during the shallow VLFE activities repeatedly observed along the Nankai trough, but the SSE was not reported because of difficult detections.

  1. Variable slip-rate and slip-per-event on a plate boundary fault: The Dead Sea fault in northern Israel

    Science.gov (United States)

    Wechsler, Neta; Rockwell, Thomas K.; Klinger, Yann

    2018-01-01

    We resolved displacement on buried stream channels that record the past 3400 years of slip history for the Jordan Gorge (JGF) section of the Dead Sea fault in Israel. Based on three-dimensional (3D) trenching, slip in the past millennium amounts to only 2.7 m, similar to that determined in previous studies, whereas the previous millennium experienced two to three times this amount of displacement with nearly 8 m of cumulative slip, indicating substantial short term variations in slip rate. The slip rate averaged over the past 3400 years, as determined from 3D trenching, is 4.1 mm/yr, which agrees well with geodetic estimates of strain accumulation, as well as with longer-term geologic slip rate estimates. Our results indicate that: 1) the past 1200 years appear to significantly lack slip, which may portend a significant increase in future seismic activity; 2) short-term slip rates for the past two millennia have varied by more than a factor of two and suggest that past behavior is best characterized by clustering of earthquakes. From these observations, the earthquake behavior of the Jordan Gorge fault best fits is a "weak segment model" where the relatively short fault section (20 km), bounded by releasing steps, fails on its own in moderate earthquakes, or ruptures with adjacent segments.

  2. Exercise electrocardiogram in middle-aged and older leisure time sportsmen: 100 exercise tests would be enough to identify one silent myocardial ischemia at risk for cardiac event.

    Science.gov (United States)

    Hupin, David; Edouard, Pascal; Oriol, Mathieu; Laukkanen, Jari; Abraham, Pierre; Doutreleau, Stéphane; Guy, Jean-Michel; Carré, François; Barthélémy, Jean-Claude; Roche, Frédéric; Chatard, Jean-Claude

    2018-04-15

    The importance of exercise electrocardiogram (ECG) has been controversial in the prevention of cardiac events among sportsmen. The aim of this study was to determine the frequency of silent myocardial ischemia (SMI) from an exercise ECG and its relationship with induced coronary angiographic assessment and potentially preventable cardiac events. This prospective cohort study included leisure time asymptomatic sportsmen over 35years old, referred from 2011 to 2014 in the Sports Medicine Unit of the University Hospital of Saint-Etienne. Of the cohort of 1500 sportsmen (1205 men; mean age 50.7±9.4years; physical activity level 32.8±26.8MET-h/week), 951 (63%) had at least one cardiovascular disease (CVD) risk factor. Family history, medical examination and standard resting 12-lead were collected. A total of 163 exercise ECGs (10.9%) were defined as positive, most of them due to SMI (n=129, 8.6%). SMI was an indication for coronary angiography in 23 cases, leading to 17 documented SMIs (1.1%), including 11 significant stenoses requiring revascularization. In multivariate logistic regression analysis, a high risk of CVD (OR=2.65 [CI 95%: 1.33-5.27], p=0.005) and an age >50years (OR=2.71 [CI 95%: 1.65-4.44], p<0.0001) were independently associated with confirmed SMI. The association of positive exercise ECG with significant coronary stenosis was stronger among sportsmen with CVD risk factors and older than 50years. Screening by exercise ECG can lower the risk of cardiac events in middle-aged and older sportsmen. One hundred tests would be enough to detect one silent myocardial ischemia at risk for cardiac event. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Large Contrast Between the Moment Magnitude of Tremor and the Moment Magnitude of Slip in ETS Events

    Science.gov (United States)

    Kao, H.; Wang, K.; Dragert, H.; Rogers, G. C.; Kao, J. Y.

    2009-12-01

    We have developed an algorithm to estimate the moment magnitudes (Mw) of seismic tremors that are recorded during episodic tremor and slip (ETS) events beneath the northern Cascadia margin. The tremor “cloud” during an ETS episode consists of numerous individual tremor bursts. For each tremor burst, the hypocenter is first determined by the Source-Scanning Algorithm [Kao and Shan, 2004]. From the derived source location, we calculate a set of synthetic seismograms for each station based on a fixed seismic moment but different focal mechanisms. The maximum tremor amplitude observed at each station is then compared to that of the synthetics to give an estimate of the corresponding seismic moment of the tremor burst. The seismic moment averaged over all stations is used to calculate the final tremor burst Mw. We have applied this method to local earthquakes for calibration and the results are very consistent with the magnitudes listed in the catalogue. For each of the 8 northern Cascadia ETS episodes whose GPS coverage is sufficient for slip distribution inversion, the cumulative tremor Mw for the entire tremor cloud, determined from the combined moments of all individual tremor bursts in the ETS episode, is ~3 orders less than the corresponding slip Mw in the same episode (e.g., 3.7 vs. 6.7). This result suggests that aseismic slip is the predominant mode of deformation during ETS. The majority of individual tremor bursts in northern Cascadia have Mw ranging between 1.0 and 1.7 with the mean of 1.34. Only 5% of all tremors are larger than 2.0 with the largest being ~2.5.

  4. Slow-slip events on the Whillans Ice Plain, Antarctica, described using rate-and-state friction as an ice stream sliding law

    Science.gov (United States)

    Lipovsky, Bradley Paul; Dunham, Eric M.

    2017-04-01

    The Whillans Ice Plain (WIP), Antarctica, experiences twice daily tidally modulated stick-slip cycles. Slip events last about 30 min, have sliding velocities as high as ˜0.5 mm/s (15 km/yr), and have total slip ˜0.5 m. Slip events tend to occur during falling ocean tide: just after high tide and just before low tide. To reproduce these characteristics, we use rate-and-state friction, which is commonly used to simulate tectonic faulting, as an ice stream sliding law. This framework describes the evolving strength of the ice-bed interface throughout stick-slip cycles. We present simulations that resolve the cross-stream dimension using a depth-integrated treatment of an elastic ice layer loaded by tides and steady ice inflow. Steady sliding with rate-weakening friction is conditionally stable with steady sliding occurring for sufficiently narrow ice streams relative to a nucleation length. Stick-slip cycles occur when the ice stream is wider than the nucleation length or, equivalently, when effective pressures exceed a critical value. Ice streams barely wider than the nucleation length experience slow-slip events, and our simulations suggest that the WIP is in this slow-slip regime. Slip events on the WIP show a sense of propagation, and we reproduce this behavior by introducing a rate-strengthening region in the center of the otherwise rate-weakening ice stream. If pore pressures are raised above a critical value, our simulations predict that the WIP would exhibit quasi-steady tidally modulated sliding as observed on other ice streams. This study validates rate-and-state friction as a sliding law to describe ice stream sliding styles.

  5. Silent Thyroiditis

    Science.gov (United States)

    Walker, Peter

    1984-01-01

    Silent or painless thyroiditis is a frequent cause of transient hyperthyroidism, which is characterized by recent onset of symptoms in a patient with a normal to modestly enlarged and firm thyroid gland. The hallmarks of the disease are the absence of thyroidal pain or tenderness and a markedly reduced radioiodine uptake. Histologically, the gland is characterized by an important lymphocytic infiltration, occasionally to the point of lymphoid follicle formation. However, other indices of an autoimmune cause are usually absent. The disease appears to have a predilection for the postpartum period. Relapses may occur with subsequent pregnancies. Otherwise, the course is usually benign and transient, requiring moderate doses of β-adrenergic blocking agents for symptomatic relief. No pathogenetic factors are known, but the disease may conceivably have an autoimmune basis, particularly in the postpartum patient. PMID:21278944

  6. Coupled Flow and Geomechanics Modeling of Slow Earthquakes: Application to Slow Slip Events (SSE) in the Guerrero Gap, Mexico

    Science.gov (United States)

    Alves da Silva Junior, J.; Frank, W.; Castineira, D.; Jha, B.; Juanes, R.

    2016-12-01

    Three major cycles of slow slip events (SSE) have been reported since the early 2000s in the Guerrero gap, Mexico, on the boundary between the Cocos and North American plates. Analysis of teleseismic waveforms recorded on a dense temporary seismic network in the Guerrero gap have found low S-wave velocity and high Vp/Vs ratios at the depths corresponding to the sources of SSE, implying the possible presence of fluids and thus an active dewatering process that may result in near-lithostatic pore pressure at the plate interface. Here we use coupled flow and geomechanics analysis of the Guerrero gap to model transient changes in the stress field in the subduction zone as a result of pore pressure fluctuations and potential fluid flow along the subduction interface. Our computational modeling approach couples a multiphase flow simulator with a mechanical simulator using the unconditionally stable fixed stress scheme for the sequential solution of the two-way coupling between flow and geomechanics (Jha and Juanes, 2014). We assume quasi-static mechanical deformation and neglect the inertial term in the solid momentum balance equation—an approximation that is valid to model SSE assuming aseismic slip. We represent the subducting Cocos fault as a surface embedded in a three-dimensional medium, and use zero thickness interface elements to accurately model stick-slip behavior under dynamically evolving fluid pressure and fault strength. We employ the rate- and state-dependent friction model in the evolution of the coefficient of friction. We calibrate our model using two distinct datasets—GPS data and tremor catalogs in the area of Guerrero gap—and by separately constraining the rate of water production from a model of mineral hydration with depth. Our quantitative modeling approach furnishes a mechanistic understanding of the relationship between pore pressure evolution, stress transfer and tremor migration, and helps elucidate the origin of SSE in this area.

  7. Inflation Leading to a Slow Slip Event and Volcanic Unrest at Mount Etna in 2016: Insights From CGPS Data

    Science.gov (United States)

    Bruno, V.; Mattia, M.; Montgomery-Brown, E.; Rossi, M.; Scandura, D.

    2017-12-01

    Global Positioning System (CGPS) data from Mount Etna between May 2015 and September 2016 show intense inflation and a concurrent Slow Slip Event (SSE) from 11 December 2015 to 17 May 2016. In May 2016, an eruptive phase started from the summit craters, temporarily stopping the ongoing inflation. The CGPS data presented here give us the opportunity to determine (1) the source of the inflating body, (2) the strain rate parameters highlighting shear strain rate accumulating along NE Rift and S Rift, (3) the magnitude of the SSE, and (4) possible interaction between modeled sources and other flank structures through stress calculations. By analytical inversion, we find an inflating source 5.5 km under the summit (4.4 km below sea level) and flank slip in a fragmented shallow structure accommodating displacements equivalent to a magnitude Mw6.1 earthquake. These large displacements reflect a complex mechanism of rotations indicated by the inversion of CGPS data for strain rate parameters. At the scale of the volcano, these processes can be considered precursors of seismic activity in the eastern flank of the volcano but concentrated mainly on the northern boundary of the mobile eastern flank along the Pernicana Fault and in the area of the Timpe Fault System.

  8. Transient crustal movement in the northern Izu-Bonin arc starting in 2004: A large slow slip event or a slow back-arc rifting event?

    Science.gov (United States)

    Arisa, Deasy; Heki, Kosuke

    2016-07-01

    The Izu-Bonin arc lies along the convergent boundary where the Pacific Plate subducts beneath the Philippine Sea Plate. Horizontal velocities of continuous Global Navigation Satellite System stations on the Izu Islands move eastward by up to 1 cm/year relative to the stable part of the Philippine Sea Plate suggesting active back-arc rifting behind the northern part of the arc. Here, we report that such eastward movements transiently accelerated in the middle of 2004 resulting in 3 cm extra movements in 3 years. We compare three different mechanisms possibly responsible for this transient movement, i.e. (1) postseismic movement of the 2004 September earthquake sequence off the Kii Peninsula far to the west, (2) a temporary activation of the back-arc rifting to the west dynamically triggered by seismic waves from a nearby earthquake, and (3) a large slow slip event in the Izu-Bonin Trench to the east. By comparing crustal movements in different regions, the first possibility can be shown unlikely. It is difficult to rule out the second possibility, but current evidence support the third possibility, i.e. a large slow slip event with moment magnitude of 7.5 may have occurred there.

  9. The prevalence and quality of silent, socially silent, and disclosed autobiographical memories across adulthood.

    Science.gov (United States)

    Alea, Nicole

    2010-02-01

    Two separate studies examined the prevalence and quality of silent (infrequently recalled), socially silent (i.e., recalled but not shared), and disclosed autobiographical memories. In Study 1 young and older men and women remembered positive events. Positive memories were more likely to be disclosed than to be kept socially silent or completely silent. However, socially silent and disclosed memories did not differ in memory quality: the memories were equally vivid, significant, and emotional. Silent memories were less qualitatively rich. This pattern of results was generally replicated in Study 2 with a lifespan sample for both positive and negative memories, and with additional qualitative variables. The exception was that negative memories were kept silent more often. Age differences were minimal. Women disclosed their autobiographical memories more, but men told a greater variety of people. Results are discussed in terms of the functions that memory telling and silences might serve for individuals.

  10. PBO Borehole Strainmeters: 2017 Episodic Tremor and Slip Event for Southern Vancouver Island, BC, Canada through Olympia, WA, USA

    Science.gov (United States)

    Van Boskirk, E. J.; Hodgkinson, K. M.; Gottlieb, M. H.; Johnson, W.; Henderson, D. B.; Mencin, D.; Mattioli, G. S.

    2017-12-01

    The Plate Boundary Observatory's (PBO) borehole strainmeters along the Cascadia Subduction Zone (CSZ) record the development and migration of Episodic Tremor and Slip (ETS). Along the southern Vancouver Island to Olympia, WA portion of the CSZ ETS events seem to repeat every 14 months. ETS events are non-volcanic tremor swarms that occur over periods of weeks, often migrating along segments of the subduction zone and can release the energy equivalent to a M7 or greater earthquake. Each ETS event is different; initial propagation location, ETS movement, duration, and direction all vary. Constraints provided by strainmeter observations of ETS events illuminate strain release patterns along the subducting slab interface and may help resolve questions regarding the location of the locked zone of the slab and what role ETS events play in the CSZ earthquake cycle. The 2017 CSZ ETS began in early February continuing through early April. Beginning in the northern Olympic Peninsula, near Port Angeles, it migrated south towards Olympia over the course of a week. After a two week pause it resumed under the Straits of Juan de Fuca and propagated northwest under Vancouver Island. There are 15 PBO borehole strainmeters along this segment, and ETS strain observations correlate with seismic and GPS measurements. The PBO borehole strainmeters are sensitive even over great distances from the ETS epicenters, and observe compression or extension relative to the ETS migration. Openly available PBO borehole strainmeter data used by the community has made significant contributions to understanding the ETS process, including the determination that ETS slip is tidally modulated. Data are publically available through UNAVCO and IRIS, which provide links to online tutorials and scripts. There are 32 strainmeters covering the CSZ from southern Vancouver Island, Canada to northern California, USA, and data spans back to 2005. Each site has a Gladwin tensor borehole strainmeter, a Malin three

  11. Very low frequency earthquakes (VLFEs) detected during episodic tremor and slip (ETS) events in Cascadia using a match filter method indicate repeating events

    Science.gov (United States)

    Hutchison, A. A.; Ghosh, A.

    2016-12-01

    Very low frequency earthquakes (VLFEs) occur in transitional zones of faults, releasing seismic energy in the 0.02-0.05 Hz frequency band over a 90 s duration and typically have magntitudes within the range of Mw 3.0-4.0. VLFEs can occur down-dip of the seismogenic zone, where they can transfer stress up-dip potentially bringing the locked zone closer to a critical failure stress. VLFEs also occur up-dip of the seismogenic zone in a region along the plate interface that can rupture coseismically during large megathrust events, such as the 2011 Tohoku-Oki earthquake [Ide et al., 2011]. VLFEs were first detected in Cascadia during the 2011 episodic tremor and slip (ETS) event, occurring coincidentally with tremor [Ghosh et al., 2015]. However, during the 2014 ETS event, VLFEs were spatially and temporally asynchronous with tremor activity [Hutchison and Ghosh, 2016]. Such contrasting behaviors remind us that the mechanics behind such events remain elusive, yet they are responsible for the largest portion of the moment release during an ETS event. Here, we apply a match filter method using known VLFEs as template events to detect additional VLFEs. Using a grid-search centroid moment tensor inversion method, we invert stacks of the resulting match filter detections to ensure moment tensor solutions are similar to that of the respective template events. Our ability to successfully employ a match filter method to VLFE detection in Cascadia intrinsically indicates that these events can be repeating, implying that the same asperities are likely responsible for generating multiple VLFEs.

  12. Foreshocks and Aftershocks Detected from Stick-slip Events on a 3 m Biaxial Apparatus and their Relationship to Quasistatic Nucleation and Wear Processes

    Science.gov (United States)

    Wu, S.; Mclaskey, G.

    2017-12-01

    We investigate foreshocks and aftershocks of dynamic stick-slip events generated on a newly constructed 3 m biaxial friction apparatus at Cornell University (attached figure). In a typical experiment, two rectangular granite blocks are squeezed together under 4 or 7 MPa of normal pressure ( 4 or 7 million N on a 1 m2 fault surface), and then shear stress is increased until the fault slips 10 - 400 microns in a dynamic rupture event similar to a M -2 to M -3 earthquake. Some ruptures nucleate near the north end of the fault, where the shear force is applied, other ruptures nucleate 2 m from the north end of the fault. The samples are instrumented with 16 piezoelectric sensors, 16 eddy current sensors, and 8 strain gage rosettes, evenly placed along the fault to measure vertical ground motion, local slip, and local stress, respectively. We studied sequences of tens of slip events and identified a total of 194 foreshocks and 66 aftershocks located within 6 s time windows around the stick-slip events and analyzed their timing and locations relative to the quasistatic nucleation process. We found that the locations of the foreshocks and aftershocks were distributed all along the length of the fault, with the majority located at the ends of the fault where local normal and shear stress is highest (caused by both edge effects and the finite stiffness of the steel frame surrounding the granite blocks). We also opened the laboratory fault and inspected the fault surface and found increased wear at the sample ends. To explore the foreshocks' and aftershocks' relationship to the nucleation and afterslip, we compared the occurrence of foreshocks to the local slip rate on the laboratory fault closest to each foreshock in space and time. We found that that majority of foreshocks were generated from local slip rates between 1 and 100 microns/s, though we were not able to resolve slip rate lower than about 1 micron/s. Our experiments provide insight into how foreshocks and

  13. Tsunamis from strike-slip earthquakes in the Wharton Basin, northeast Indian Ocean: March 2016 Mw7.8 event and its relationship with the April 2012 Mw 8.6 event

    Science.gov (United States)

    Heidarzadeh, Mohammad; Harada, Tomoya; Satake, Kenji; Ishibe, Takeo; Takagawa, Tomohiro

    2017-12-01

    The Wharton Basin, off southwest Sumatra, ruptured to a large intraplate left-lateral strike-slip Mw 7.8 earthquake on 2016 March 2. The epicentre was located ∼800 km to the south of another similar-mechanism intraplate Mw 8.6 earthquake in the same basin on 2012 April 11. Small tsunamis from these strike-slip earthquakes were registered with maximum amplitudes of 0.5-1.5 cm on DARTs and 1-19 cm on tide gauges for the 2016 event, and the respective values of 0.5-6 and 6-40 cm for the 2012 event. By using both teleseismic body waves and tsunami observations of the 2016 event, we obtained optimum slip models with rupture velocity (Vr) in the range of 2.8-3.6 km s-1 belonging to both EW and NS faults. While the EW fault plane cannot be fully ruled out, we chose the best model as the NS fault plane with a Vr of 3.6 km s-1, a maximum slip of 7.7 m and source duration of 33 s. The tsunami energy period bands were 4-15 and 7-24 min for the 2016 and 2012 tsunamis, respectively, reflecting the difference in source sizes. Seismicity in the Wharton Basin is dominated by large strike-slip events including the 2012 (Mw 8.6 and 8.2) and 2016 (Mw 7.8) events, indicating that these events are possible tsunami sources in the Wharton Basin. Cumulative number and cumulative seismic-moment curves revealed that most earthquakes are of strike-slip mechanisms and the largest seismic-moment is provided by the strike-slip earthquakes in this basin.

  14. Recurrent slow slip events as a barrier to the northward rupture propagation of the 2016 Pedernales earthquake (Central Ecuador)

    Science.gov (United States)

    Vaca, Sandro; Vallée, Martin; Nocquet, Jean-Mathieu; Battaglia, Jean; Régnier, Marc

    2018-01-01

    The northern Ecuador segment of the Nazca/South America subduction zone shows spatially heterogeneous interseismic coupling. Two highly coupled zones (0.4° S-0.35° N and 0.8° N-4.0° N) are separated by a low coupled area, hereafter referred to as the Punta Galera-Mompiche Zone (PGMZ). Large interplate earthquakes repeatedly occurred within the coupled zones in 1958 (Mw 7.7) and 1979 (Mw 8.1) for the northern patch and in 1942 (Mw 7.8) and 2016 (Mw 7.8) for the southern patch, while the whole segment is thought to have rupture during the 1906 Mw 8.4-8.8 great earthquake. We find that during the last decade, the PGMZ has experienced regular and frequent seismic swarms. For the best documented sequence (December 2013-January 2014), a joint seismological and geodetic analysis reveals a six-week-long Slow Slip Event (SSE) associated with a seismic swarm. During this period, the microseismicity is organized into families of similar earthquakes spatially and temporally correlated with the evolution of the aseismic slip. The moment release (3.4 × 1018 Nm, Mw 6.3), over a 60 × 40 km area, is considerably larger than the moment released by earthquakes (5.8 × 1015 Nm, Mw 4.4) during the same time period. In 2007-2008, a similar seismic-aseismic episode occurred, with higher magnitudes both for the seismic and aseismic processes. Cross-correlation analyses of the seismic waveforms over a 15 years-long period further suggest a 2-year repeat time for seismic swarms, which also implies that SSEs recurrently affect this area. Such SSEs contribute to release the accumulated stress, likely explaining why the 2016 Pedernales earthquake did not propagate northward into the PGMZ.

  15. Estimation of the spatiotemporal evolution of slow slip events in the Tokai region, central Japan, during 1994 - 2016 using GNSS data

    Science.gov (United States)

    Sakaue, H.; Nishimura, T.; Fukuda, J.; Kato, T.

    2017-12-01

    In the Tokai region, central Japan, the long-term slow slip events (L-SSEs) observed on the subducting Philippine Sea Plate (PSP) from 2000 to 2005 and since 2013. Moreover, many short-term slow slip events (S-SSEs) have been observed in the Tokai region since 1996. Sakaue et al. (2017) reported that the spatiotemporal evolution of an L-SSE and S-SSEs on the PSP beneath the Tokai region from 2013 to 2015. This study is probably the first case that migration of slip for S-SSE (Mw GPS Research) in the Tokai region. It is well known that GNSS time series have many systematic signals that do not result from SSEs. These systematic signals include, for example, seasonal variations, cosiesmic and post-seismic deformation of the 2004 off Southeast Kii Peninsula eqrthquake and the 2011 Tohoku-oki earthquake (Mw. 9.0), crustal deformation of volcanic activity on Miyake-jima island and so on. After removing these systematic signals, we applied a modified Network Inversion Filter (NIF) [Fukuda et al., 2008]. The original NIF [Segall & Matthews, 1997] assumes a constant hyperparameter for the temporal smoothing of slip rates and thus often results in oversmoothing of slip rates. The modified NIF assumes a time-variable hyperparameter, so that changes in slip rates are effectively extracted from GNSS time series.The results indicate that not only the spatiotemporal evolutions of the 2000 Tokai L-SSE and the 2013 L-SSE but also the spatiotemporal evolution of S-SSEs are estimated. We will present a comparison of the spatiotemporal evolutions between the 2000 Tokai L-SSE and the 2013 L-SSE and possible dependence of the occurrence style of S-SSEs on the occurrence of the L-SSEs.

  16. Characteristics of aperiodic sequence of slip events caused by interaction between seismic patches and that caused be self-organized stress heterogeneity

    Science.gov (United States)

    Kato, N.

    2017-12-01

    Numerical simulations of earthquake cycles are conducted to investigate the origin of complexity of earthquake recurrence. There are two main causes of the complexity. One is self-organized stress heterogeneity due to dynamical effect. The other is the effect of interaction between some fault patches. In the model, friction on the fault is assumed to obey a rate- and state-dependent friction law. Circular patches of velocity-weakening frictional property are assumed on the fault. On the remaining areas of the fault, velocity-strengthening friction is assumed. We consider three models: Single patch model, two-patch model, and three-patch model. In the first model, the dynamical effect is mainly examined. The latter two models take into consideration the effect of interaction as well as the dynamical effect. Complex multiperiodic or aperiodic sequences of slip events occur when slip behavior changes from the seismic to aseismic, and when the degree of interaction between seismic patches is intermediate. The former is observed in all the models, and the latter is observed in the two-patch model and the three-patch model. Evolution of spatial distribution of shear stress on the fault suggests that aperiodicity at the transition from seismic to aseismic slip is caused by self-organized stress heterogeneity. The iteration maps of recurrence intervals of slip events in aperiodic sequences are examined, and they are approximately expressed by simple curves for aperiodicity at the transition from seismic to aseismic slip. In contrast, the iteration maps for aperiodic sequences caused by interaction between seismic patches are scattered and they are not expressed by simple curves. This result suggests that complex sequences caused by different mechanisms may be distinguished.

  17. Recurring extensional and strike-slip tectonics after the Neoproterozoic collisional events in the southern Mantiqueira province

    Directory of Open Access Journals (Sweden)

    Renato P. Almeida

    2012-06-01

    Full Text Available In Eastern South America, a series of fault-bounded sedimentary basins that crop out from Southern Uruguay to Southeastern Brazil were formed after the main collisional deformation of the Brasiliano Orogeny and record the tectonic events that affected the region from the Middle Ediacaran onwards. We address the problem of discerning the basin-forming tectonics from the later deformational events through paleostress analysis of more than 600 fault-slip data, mainly from the Camaquã Basin (Southern Brazil, sorted by stratigraphic level and cross-cutting relationships of superposed striations, and integrated with available stratigraphic and geochronological data. Our results show that the Camaquã Basin was formed by at least two distinct extensional events, and that rapid paleostress changes took place in the region a few tens of million years after the major collision (c.a. 630 Ma, probably due to the interplay between local active extensional tectonics and the distal effects of the continued amalgamation of plates and terranes at the margins of the still-forming Gondwana Plate. Preliminary paleostress data from the Castro Basin and published data from the Itajaí Basin suggest that these events had a regional nature.No Leste da América do Sul, um conjunto de bacias sedimentares que afloram do sul do Uruguai ao sudeste do Brasil formou-se após os eventos colisionais da Orogenia Brasiliana, registrando os eventos tectônicos que afetaram a região a partir do Mesoediacarano. O problema da distinção entre a tectônica formadora das bacias e os eventos deformacionais posteriores é aqui abordado através da análise de paleotensões de mais de 600 dados de falhas com estrias, obtidos principalmente na Bacia Camaquã (Sul do Brasil, que foram classificados por nível estratigráfico e relações de corte entre estrias sobrepostas, e intergrados a dados estratigráficos e geocronológicos disponíveis. Nossos resultados revelam que a Bacia Camaqu

  18. Silent ischaemia and hypertension

    NARCIS (Netherlands)

    Boon, D.; Piek, J. J.; van Montfrans, G. A.

    2000-01-01

    For many years now, silent ischaemia has been recognized as a distinct clinical entity, and its relevance in different patient groups has been established. However, a number of basic questions have not been answered. In explaining the pathophysiology of silent ischaemia, factors affecting both the

  19. Focal mechanisms and inter-event times of low-frequency earthquakes reveal quasi-continuous deformation and triggered slow slip on the deep Alpine Fault

    Science.gov (United States)

    Baratin, Laura-May; Chamberlain, Calum J.; Townend, John; Savage, Martha K.

    2018-02-01

    Characterising the seismicity associated with slow deformation in the vicinity of the Alpine Fault may provide constraints on the stresses acting on a major transpressive margin prior to an anticipated great (≥M8) earthquake. Here, we use recently detected tremor and low-frequency earthquakes (LFEs) to examine how slow tectonic deformation is loading the Alpine Fault late in its typical ∼300-yr seismic cycle. We analyse a continuous seismic dataset recorded between 2009 and 2016 using a network of 10-13 short-period seismometers, the Southern Alps Microearthquake Borehole Array. Fourteen primary LFE templates are used in an iterative matched-filter and stacking routine, allowing the detection of similar signals corresponding to LFE families sharing common locations. This yields an 8-yr catalogue containing 10,000 LFEs that are combined for each of the 14 LFE families using phase-weighted stacking to produce signals with the highest possible signal-to-noise ratios. We show that LFEs occur almost continuously during the 8-yr study period and highlight two types of LFE distributions: (1) discrete behaviour with an inter-event time exceeding 2 min; (2) burst-like behaviour with an inter-event time below 2 min. We interpret the discrete events as small-scale frequent deformation on the deep extent of the Alpine Fault and LFE bursts (corresponding in most cases to known episodes of tremor or large regional earthquakes) as brief periods of increased slip activity indicative of slow slip. We compute improved non-linear earthquake locations using a 3-D velocity model. LFEs occur below the seismogenic zone at depths of 17-42 km, on or near the hypothesised deep extent of the Alpine Fault. The first estimates of LFE focal mechanisms associated with continental faulting, in conjunction with recurrence intervals, are consistent with quasi-continuous shear faulting on the deep extent of the Alpine Fault.

  20. Low-grade inflammation is a risk factor for clinical stroke events in addition to silent cerebral infarcts in Japanese older hypertensives: the Jichi Medical School ABPM Study, wave 1.

    Science.gov (United States)

    Ishikawa, Joji; Tamura, Yurie; Hoshide, Satoshi; Eguchi, Kazuo; Ishikawa, Shizukiyo; Shimada, Kazuyuki; Kario, Kazuomi

    2007-03-01

    High-sensitivity C-reactive protein (hsCRP), a marker of inflammation, is associated with atherosclerosis, hypertensive target organ damage, and cardiovascular events. In the general Japanese population, the level of hsCRP is reported to be lower than that in Western countries, and the relationships among hsCRP, silent cerebral infarcts (SCIs), and clinical stroke events in older Japanese hypertensives remain unclear. We conducted brain MRI and measured hsCRP at baseline in 514 older Japanese hypertensives (clinic blood pressure > or =140/90 mm Hg, age > or =50 years old) who were enrolled in the Jichi Medical School ABPM Study, wave 1. They were followed up for an average of 41 months (range: 1 to 68 months, 1751 person-years) and the incidence of subsequent clinical stroke events was evaluated. The subjects with SCIs at baseline (n=257) had a higher hsCRP level than those without SCIs (geometric mean hsCRP [SD range]; 0.19 [0.18 to 0.21] versus 0.14 [0.13 to 0.16] mg/L, P=0.007) after adjustment for confounding factors, and the OR for the presence of SCIs was increased with the quartile of hsCRP levels. In Cox regression analysis, the patients with above median hsCRP level (> or =0.21 mg/L) (hazard ratio [HR]: 2.50, 95% CI: 1.24 to 5.00, P=0.01) and those with SCIs (HR: 4.60, 95% CI: 1.91 to 11.03, P=0.001) at baseline had independently higher risks for clinical stroke events after adjustment for age, smoking status, antihypertensive medication use, and 24-hour systolic blood pressure level. Compared with the patients with below median hsCRP level without SCIs, those with above median hsCRP level and SCIs at baseline had a higher risk for clinical stroke events (HR: 7.32, 95% CI: 2.17 to 24.76, P=0.001), although those with below median hsCRP level and SCIs (HR: 2.46, 95% CI: 0.64 to 9.47, P=0.19) and those with above median hsCRP level without SCIs (HR: 1.11, 95% CI: 0.22 to 5.55, P=0.90) did not have significant risks. High-sensitivity C-reactive protein is a

  1. Stabilizing Stick-Slip Friction

    International Nuclear Information System (INIS)

    Capozza, Rosario; Barel, Itay; Urbakh, Michael; Rubinstein, Shmuel M.; Fineberg, Jay

    2011-01-01

    Even the most regular stick-slip frictional sliding is always stochastic, with irregularity in both the intervals between slip events and the sizes of the associated stress drops. Applying small-amplitude oscillations to the shear force, we show, experimentally and theoretically, that the stick-slip periods synchronize. We further show that this phase locking is related to the inhibition of slow rupture modes which forces a transition to fast rupture, providing a possible mechanism for observed remote triggering of earthquakes. Such manipulation of collective modes may be generally relevant to extended nonlinear systems driven near to criticality.

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

    Science.gov (United States)

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

    2017-12-01

    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.

  3. Usefulness of percutaneous transluminal coronary angioplasty in silent myocardial ischemia

    International Nuclear Information System (INIS)

    Hou, Mami

    1996-01-01

    The usefulness of percutaneous transluminal coronary angioplasty (PTCA) was assessed in patients with exercise-induced asymptomatic myocardial ischemia (silent ischemia) and compared with exercise-induced symptomatic myocardial ischemia (symptomatic ischemia). Patients with single vessel coronary artery disease (51 with angina pectoris, 40 with old myocardial infarction) and evidence of stress-induced ischemia on thallium-201 single photon emission computed tomography (SPECT) underwent successful PTCA. Thirty-seven percent of angina patients and 60% of infarction patients showed asymptomatic exercise-induced ischemia. There was no significant difference in population characteristics between silent and symptomatic patients. Patients with silent angina had significantly higher percentage thallium uptake and washout rate than symptomatic patients. After PTCA, both percentage diameter stenosis and percentage thallium uptake were improved in all patients with angina irrespective of the presence or absence of symptoms. There were no significant differences in percentage thallium uptake and washout rate between patients with silent and symptomatic infarction. After PTCA, percentage diameter stenosis, percentage thallium uptake, and washout rate improved in all infarction patients irrespective of the symptoms. Zero percent of silent angina patients, 12% of symptomatic angina patients, 12% of silent infarction patients, 19% of symptomatic infarction patients had cardiac events during about 4.5 years after PTCA. The incidence of cardiac events did not significantly differ in any patient group. PTCA improved myocardial perfusion in all patients, and the incidence of cardiac events did not differ between the silent and symptomatic groups. Revascularization with PTCA is suitable for patients with silent as well as symptomatic ischemia. (author)

  4. Multiple Silent Lacunes Are Associated with Recurrent Ischemic Stroke

    DEFF Research Database (Denmark)

    Andersen, Søren Due; Skjøth, Flemming; Yavarian, Yousef

    2016-01-01

    ackground: Silent lacunes are a common finding on brain imaging in ischemic stroke patients, but the prognostic significance of these lesions is uncertain. We aimed at investigating the association of silent lacunes and the risk of ischemic stroke recurrence, death, and cardiovascular events...... in a cohort of patients with incident ischemic stroke and no atrial fibrillation (AF). Methods: We included 786 patients (mean age 59.5 (SD 14.0); 42.9% females) in a registry-based, observational cohort study on patients with first-ever ischemic stroke. On brain MRI we assessed the number of silent lacunes...... as none, single, or multiple and we calculated stratified incidence rates of the outcomes. Cox proportional hazard ratios (HRs) adjusted for age, gender, congestive heart failure, hypertension, diabetes, and vascular disease were calculated with no silent lacunes as reference. In additional analyses, we...

  5. Nonlinear dynamical triggering of slow slip

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Paul A [Los Alamos National Laboratory; Knuth, Matthew W [WISCONSIN; Kaproth, Bryan M [PENN STATE; Carpenter, Brett [PENN STATE; Guyer, Robert A [Los Alamos National Laboratory; Le Bas, Pierre - Yves [Los Alamos National Laboratory; Daub, Eric G [Los Alamos National Laboratory; Marone, Chris [PENN STATE

    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

  6. Layered Fault Rocks Below the West Salton Detachment Fault (WSDF), CA Record Multiple Seismogenic? Slip Events and Transfer of Material to a Fault Core

    Science.gov (United States)

    Axen, G. J.; Luther, A. L.; Selverstone, J.; Mozley, P.

    2011-12-01

    -size distributions reflect constrained comminution and shear localization (slopes of ~3-3.5 on log-log plots of grain size vs. no. of grains > grain size). The LCs require episodic slip events that probably record dozens of seismic cycles. Foliation likely records post- or interseismic creep. Geometric complexities among the WSDF footwall splays presumably caused episodic dilation that allowed accumulation and folding of the LCs. Mechanical processes dominated over chemical processes. A key question is why the LCs apparently were stronger than the overlying granodiorite, leading to formation of new LC layers rather than significant reworking of older layers.

  7. EFFICACY OF METOPROLOL AND DILTIAZEM IN TREATING SILENT-MYOCARDIAL-ISCHEMIA

    NARCIS (Netherlands)

    PORTEGIES, MCM; SIJBRING, P; GOBEL, JAM; VIERSMA, JW; LIE, KI

    1994-01-01

    Recent studies strongly support the prognostic importance of transient silent ischemia. Because patients with silent ischemia are at higher risk of a cardiac event, they are likely to benefit not only from control of symptoms, but also from treatment directed at prevention of ischemia. The efficacy

  8. Monitoring Progress toward Independent Silent Reading.

    Science.gov (United States)

    Franc, Lillian H.; Hildebrandt, Jeannette

    1984-01-01

    Concludes, among other things, that fluent oral reading is an important step toward reading for meaning and independent silent reading and that silent reading should be encouraged from the beginning of reading instruction. (FL)

  9. Laboratory triggering of stick-slip events by oscillatory loading in the presence of pore fluid with implications for physics of tectonic tremor

    Science.gov (United States)

    Bartlow, Noel M.; Lockner, David A.; Beeler, Nicholas M.

    2012-01-01

    The physical mechanism by which the low-frequency earthquakes (LFEs) that make up portions of tectonic (also called non-volcanic) tremor are created is poorly understood. In many areas of the world, tectonic tremor and LFEs appear to be strongly tidally modulated, whereas ordinary earthquakes are not. Anomalous seismic wave speeds, interpreted as high pore fluid pressure, have been observed in regions that generate tremor. Here we build upon previous laboratory studies that investigated the response of stick-slip on artificial faults to oscillatory, tide-like loading. These previous experiments were carried out using room-dry samples of Westerly granite, at one effective stress. Here we augment these results with new experiments on Westerly granite, with the addition of varying effective stress using pore fluid at two pressures. We find that raising pore pressure, thereby lowering effective stress can significantly increase the degree of correlation of stick-slip to oscillatory loading. We also find other pore fluid effects that become important at higher frequencies, when the period of oscillation is comparable to the diffusion time of pore fluid into the fault. These results help constrain the conditions at depth that give rise to tidally modulated LFEs, providing confirmation of the effective pressure law for triggering and insights into why tremor is tidally modulated while earthquakes are at best only weakly modulated.

  10. Evidence for slip partitioning and bimodal slip behavior on a single fault: Surface slip characteristics of the 2013 Mw7.7 Balochistan, Pakistan earthquake

    Science.gov (United States)

    Barnhart, William; Briggs, Richard; Reitman, Nadine G.; Gold, Ryan D.; Hayes, Gavin

    2015-01-01

    Deformation is commonly accommodated by strain partitioning on multiple, independent strike-slip and dip-slip faults in continental settings of oblique plate convergence. As a corollary, individual faults tend to exhibit one sense of slip – normal, reverse, or strike-slip – until whole-scale changes in boundary conditions reactivate preexisting faults in a new deformation regime. In this study, we show that a single continental fault may instead partition oblique strain by alternatively slipping in a strike-slip or a dip-slip sense during independent fault slip events. We use 0.5 m resolution optical imagery and sub-pixel correlation analysis of the 200+ km 200+km"> 2013 Mw7.7 Balochistan, Pakistan earthquake to document co-seismic surface slip characteristics and Quaternary tectonic geomorphology along the causative Hoshab fault. We find that the 2013 earthquake, which involved a ∼6:1 strike-slip to dip-slip ratio, ruptured a structurally segmented fault. Quaternary geomorphic indicators of gross fault-zone morphology reveal both reverse-slip and strike-slip deformation in the rupture area of the 2013 earthquake that varies systematically along fault strike despite nearly pure strike-slip motion in 2013. Observations of along-strike variations in range front relief and geomorphic offsets suggest that the Hoshab fault accommodates a substantial reverse component of fault slip in the Quaternary, especially along the southern section of the 2013 rupture. We surmise that Quaternary bimodal slip along the Hoshab fault is promoted by a combination of the arcuate geometry of the Hoshab fault, the frictional weakness of the Makran accretionary prism, and time variable loading conditions from adjacent earthquakes and plate interactions.

  11. Earthquake scaling laws for rupture geometry and slip heterogeneity

    Science.gov (United States)

    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. Fixed recurrence and slip models better predict earthquake behavior than the time- and slip-predictable models 1: repeating earthquakes

    Science.gov (United States)

    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.

  13. Interpretation of Microseismicity Observed From Surface and Borehole Seismic Arrays During Hydraulic Fracturing in Shale - Bedding Plane Slip Model

    Science.gov (United States)

    Stanek, F.; Jechumtalova, Z.; Eisner, L.

    2017-12-01

    We present a geomechanical model explaining microseismicity induced by hydraulic fracturing in shales developed from many datasets acquired with two most common types of seismic monitoring arrays, surface and dual-borehole arrays. The geomechanical model explains the observed source mechanisms and locations of induced events from two stimulated shale reservoirs. We observe shear dip-slip source mechanisms with nodal planes aligned with location trends. We show that such seismicity can be explained as a shearing along bedding planes caused by aseismic opening of vertical hydraulic fractures. The source mechanism inversion was applied only to selected high-quality events with sufficient signal-to-noise ratio. We inverted P- and P- and S-wave arrival amplitudes to full-moment tensor and decomposed it to shear, volumetric and compensated linear vector dipole components. We also tested an effect of noise presented in the data to evaluate reliability of non-shear components. The observed seismicity from both surface and downhole monitoring of shale stimulations is very similar. The locations of induced microseismic events are limited to narrow depth intervals and propagate along distinct trend(s) showing fracture propagation in direction of maximum horizontal stress from injection well(s). The source mechanisms have a small non-shear component which can be partly explained as an effect of noise in the data, i.e. events represent shearing on faults. We observe predominantly dip-slip events with a strike of the steeper (almost vertical) nodal plane parallel to the fracture propagation. Therefore the other possible nodal plane is almost horizontal. The rake angles of the observed mechanisms divide these dip-slips into two groups with opposite polarities. It means that we observe opposite movements on the nearly identically oriented faults. Realizing a typical structural weakness of shale in horizontal planes, we interpret observed microseismicity as a result of shearing

  14. Unusual ocular manifestations of silent sinus syndrome

    OpenAIRE

    Fonseca, Fabricio Lopes da; Mazoti, Luciana; Polati, Mariza

    2014-01-01

    Silent sinus syndrome is an acquired condition in which there is a gradual collapse of the orbital floor and inward retraction of the maxillary sinus (atelectasis of the maxillary sinus). This in turn may cause associated ocular occurrences of enophthalmos and hypotropia. This is a report of an 8 year-old boy with silent sinus syndrome and associated ocular motility disorders. The association between silent sinus syndrome and ocular motility disturbance has been recently described in the lite...

  15. Coseismic and Early Post-Seismic Slip Distributions of the 2012 Emilia (Northern Italy) Seismic Sequence: New Insights in the Faults Activation and Resulting Stress Changes on Adjacent Faults

    Science.gov (United States)

    Cheloni, D.; Giuliani, R.; D'Agostino, N.; Mattone, M.; Bonano, M.; Fornaro, G.; Lanari, R.; Reale, D.

    2015-12-01

    The 2012 Emilia sequence (main shocks Mw 6.1 May 20 and Mw 5.9 May 29) ruptured two thrust segments of a ~E-W trending fault system of the buried Ferrara Arc, along a portion of the compressional system of the Apennines that had remained silent during past centuries. Here we use the rupture geometry constrained by the aftershocks and new geodetic data (levelling, InSAR and GPS measurements) to estimate an improved coseismic slip distribution of the two main events. In addition, we use post-seismic displacements, described and analyzed here for the first time, to infer a brand new post-seismic slip distribution of the May 29 event in terms of afterslip on the same coseismic plane. In particular, in this study we use a catalog of precisely relocated aftershocks to explore the different proposed geometries of the proposed thrust segments that have been published so far and estimate the coseismic and post-seismic slip distributions of the ruptured planes responsible for the two main seismic events from a joint inversion of the geodetic data.Joint inversion results revealed that the two earthquakes ruptured two distinct planar thrust faults, characterized by single main coseismic patches located around the centre of the rupture planes, in agreement with the seismological and geological information pointing out the Ferrara and the Mirandola thrust faults, as the causative structures of the May 20 and May 29 main shocks respectively.The preferred post-seismic slip distribution related to the 29 May event, yielded to a main patch of afterslip (equivalent to a Mw 5.6 event) located westward and up-dip of the main coseismic patch, suggesting that afterslip was triggered at the edges of the coseismic asperity. We then use these co- and post-seismic slip distribution models to calculate the stress changes on adjacent fault.

  16. A Kinematic Model of Slow Slip Constrained by Tremor-Derived Slip Histories in Cascadia

    Science.gov (United States)

    Schmidt, D. A.; Houston, H.

    2016-12-01

    We explore new ways to constrain the kinematic slip distributions for large slow slip events using constraints from tremor. Our goal is to prescribe one or more slip pulses that propagate across the fault and scale appropriately to satisfy the observations. Recent work (Houston, 2015) inferred a crude representative stress time history at an average point using the tidal stress history, the static stress drop, and the timing of the evolution of tidal sensitivity of tremor over several days of slip. To convert a stress time history into a slip time history, we use simulations to explore the stressing history of a small locked patch due to an approaching rupture front. We assume that the locked patch releases strain through a series of tremor bursts whose activity rate is related to the stressing history. To test whether the functional form of a slip pulse is reasonable, we assume a hypothetical slip time history (Ohnaka pulse) timed with the occurrence of tremor to create a rupture front that propagates along the fault. The duration of the rupture front for a fault patch is constrained by the observed tremor catalog for the 2010 ETS event. The slip amplitude is scaled appropriately to match the observed surface displacements from GPS. Through a forward simulation, we evaluate the ability of the tremor-derived slip history to accurately predict the pattern of surface displacements observed by GPS. We find that the temporal progression of surface displacements are well modeled by a 2-4 day slip pulse, suggesting that some of the longer duration of slip typically found in time-dependent GPS inversions is biased by the temporal smoothing. However, at some locations on the fault, the tremor lingers beyond the passage of the slip pulse. A small percentage (5-10%) of the tremor appears to be activated ahead of the approaching slip pulse, and tremor asperities experience a driving stress on the order of 10 kPa/day. Tremor amplitude, rather than just tremor counts, is needed

  17. Underlying skills of oral and silent reading

    NARCIS (Netherlands)

    Van Den Boer, Madelon; van Bergen, Elsje; de Jong, Peter F.

    2014-01-01

    Many studies have examined reading and reading development. The majority of these studies, however, focused on oral reading rather than on the more dominant silent reading mode. Similarly, it is common practice to assess oral reading abilities rather than silent reading abilities in schools and in

  18. Silent Patent Ductus Arteriosus Aneurysm

    Directory of Open Access Journals (Sweden)

    Aline Medeiros Botta

    2002-09-01

    Full Text Available Ductus arteriosus aneurysm, a rare and potentially fatal condition, has been reported as a complication after surgical ductus arteriosus closure. Its spontaneous appearance as a septic complication, which was common in the presurgical and preantibiotic era, has been rarely reported in the contemporary literature. Persistence of silent ductus arteriosus in healthy children and adults is a frequent condition that currently has an increasing diagnostic possibility due to the availability of more accurate investigative methods, especially echocardiography. We report the case of a 1-year-old child, in whom no previous heart disease was known, who developed a giant aneurysm of the ductus arteriosus during a staphylococcal infection. This complication appeared after craniotomy for emptying an accidental subdural hematoma. This report associates the persistence of ductus arteriosus with a complication considered rare, which has a rapidly fatal evolution.

  19. Modeling of rock friction 2. Simulation of preseismic slip

    International Nuclear Information System (INIS)

    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 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

  20. Imbricated slip rate processes during slow slip transients imaged by low-frequency earthquakes

    Science.gov (United States)

    Lengliné, O.; Frank, W.; Marsan, D.; Ampuero, J. P.

    2017-12-01

    Low Frequency Earthquakes (LFEs) often occur in conjunction with transient strain episodes, or Slow Slip Events (SSEs), in subduction zones. Their focal mechanism and location consistent with shear failure on the plate interface argue for a model where LFEs are discrete dynamic ruptures in an otherwise slowly slipping interface. SSEs are mostly observed by surface geodetic instruments with limited resolution and it is likely that only the largest ones are detected. The time synchronization of LFEs and SSEs suggests that we could use the recorded LFEs to constrain the evolution of SSEs, and notably of the geodetically-undetected small ones. However, inferring slow slip rate from the temporal evolution of LFE activity is complicated by the strong temporal clustering of LFEs. Here we apply dedicated statistical tools to retrieve the temporal evolution of SSE slip rates from the time history of LFE occurrences in two subduction zones, Mexico and Cascadia, and in the deep portion of the San Andreas fault at Parkfield. We find temporal characteristics of LFEs that are similar across these three different regions. The longer term episodic slip transients present in these datasets show a slip rate decay with time after the passage of the SSE front possibly as t-1/4. They are composed of multiple short term transients with steeper slip rate decay as t-α with α between 1.4 and 2. We also find that the maximum slip rate of SSEs has a continuous distribution. Our results indicate that creeping faults host intermittent deformation at various scales resulting from the imbricated occurrence of numerous slow slip events of various amplitudes.

  1. SLIP CASTING METHOD

    Science.gov (United States)

    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.

  2. A Model for Low-Frequency Earthquake Slip in Cascadia

    Science.gov (United States)

    Chestler, S.; Creager, K.

    2017-12-01

    Low-Frequency Earthquakes (LFEs) are commonly used to identify when and where slow slip occurred, especially for slow slip events that are too small to be observed geodetically. Yet, an understanding of how slip occurs within an LFE family patch, or patch on the plate interface where LFEs repeat, is limited. How much slip occurs per LFE and over what area? Do all LFEs within an LFE family rupture the exact same spot? To answer these questions, we implement a catalog of 39,966 LFEs, sorted into 45 LFE families, beneath the Olympic Peninsula, WA. LFEs were detected and located using data from approximately 100 3-component stations from the Array of Arrays experiment. We compare the LFE family patch area to the area within the LFE family patch that slips through LFEs during Cascadia Episodic Tremor and Slip (ETS) events. Patch area is calculated from relative LFE locations, solved for using the double difference method. Slip area is calculated from the characteristic moment (mean of the exponential moment-frequency distribution) and number LFEs for each family and geodetically measured ETS slip. We find that 0.5-5% of the area within an LFE family patch slips through LFEs. The rest must deform in some other manner (e.g., ductile deformation). We also explore LFE slip patterns throughout the entire slow slip zone. Is LFE slip uniform? Does LFE slip account for all geodetically observed slow slip? Double difference relocations reveal that LFE families are 2 km patches where LFE are clustered close together. Additionally, there are clusters of LFE families with diameters of 4-15 km. There are gaps with no observable, repeating LFEs between LFE families in clusters and between clusters of LFE families. Based on this observation, we present a model where LFE slip is heterogeneous on multiple spatial scales. Clusters of LFE families may represent patches with higher strength than the surrounding areas. Finally, we find that LFE slip only accounts for a small fraction ( 0

  3. Constraining the roughness degree of slip heterogeneity

    KAUST Repository

    Causse, Mathieu

    2010-05-07

    This article investigates different approaches for assessing the degree of roughness of the slip distribution of future earthquakes. First, we analyze a database of slip images extracted from a suite of 152 finite-source rupture models from 80 events (Mw = 4.1–8.9). This results in an empirical model defining the distribution of the slip spectrum corner wave numbers (kc) as a function of moment magnitude. To reduce the “epistemic” uncertainty, we select a single slip model per event and screen out poorly resolved models. The number of remaining models (30) is thus rather small. In addition, the robustness of the empirical model rests on a reliable estimation of kc by kinematic inversion methods. We address this issue by performing tests on synthetic data with a frequency domain inversion method. These tests reveal that due to smoothing constraints used to stabilize the inversion process, kc tends to be underestimated. We then develop an alternative approach: (1) we establish a proportionality relationship between kc and the peak ground acceleration (PGA), using a k−2 kinematic source model, and (2) we analyze the PGA distribution, which is believed to be better constrained than slip images. These two methods reveal that kc follows a lognormal distribution, with similar standard deviations for both methods.

  4. Characteristics of silent countingin synchronized swimmers

    Directory of Open Access Journals (Sweden)

    Sergey V. Leonov

    2012-01-01

    Full Text Available This article describes the temporal characteristics of silent counting as used duringa competition by the Russian youth team of synchronized swimmers. Theathletes listened to the music that accompanied their performance at the competition.Diff erent indices of silent counting were defi ned, such as the beginningand cessation of diff erent periods of counting, counting frequency, the stabilityof the temporal structure of silent counting, the degree of synchronization of silentcounting at diff erent moments during the sports program. We studied therelationship of these characteristics of counting with expert estimates of the athletes’sense of tempo, coordination of movements, and choreographic abilities.

  5. Unusual ocular manifestations of silent sinus syndrome

    Directory of Open Access Journals (Sweden)

    Fabricio Lopes da Fonseca

    2014-01-01

    Full Text Available Silent sinus syndrome is an acquired condition in which there is a gradual collapse of the orbital floor and inward retraction of the maxillary sinus (atelectasis of the maxillary sinus. This in turn may cause associated ocular occurrences of enophthalmos and hypotropia. This is a report of an 8 year-old boy with silent sinus syndrome and associated ocular motility disorders. The association between silent sinus syndrome and ocular motility disturbance has been recently described in the literature. However, this is an infrequent association, mainly in childhood.

  6. Transluminal coronary angioplasty in the treatment of silent ischemia

    International Nuclear Information System (INIS)

    Bergin, P.; Myler, R.K.; Shaw, R.E.; Stertzer, S.H.; Clark, D.A.; Ryan, C.; Murphy, M.C.

    1988-01-01

    Fifty-four asymptomatic patients with positive thallium exercise tests underwent coronary angiography followed by coronary angioplasty (PTCA), as the primary therapy for silent ischemia. The procedure was technically successful in 89% of these patients. Emergency bypass graft surgery was necessary in 2 (3.6%) and q-wave myocardial infarction occurred in 1 (1.8%) of these. All fifty-four patients have been followed for a mean of 35 months since angioplasty. Of the 48 patients with initially successful PTCA, 12 had either clinical restenosis (9/14 or 19%) or a new lesion (3/48 or 6%) during follow-up, which required a repeat PTCA. At the longest follow-up, 46 (85%) had been successfully treated with on or more PTCA procedures. Two patients (3.6%) had sustained late q-wave myocardial infarction and two additional patients reported angina pectoris. There were no deaths. Angioplasty as a primary therapy for silent ischemia appears efficacious, with success and restenosis rates comparable to those in the symptomatic population. Event-free survival is improved, compared with natural history data for patients with silent ischemia from other studies. Prudent risk/benefit analysis may help to define subgroups most likely to benefit from this intervention

  7. A Model for Low-Frequency Earthquake Slip

    Science.gov (United States)

    Chestler, S. R.; Creager, K. C.

    2017-12-01

    Using high-resolution relative low-frequency earthquake (LFE) locations, we calculate the patch areas (Ap) of LFE families. During episodic tremor and slip (ETS) events, we define AT as the area that slips during LFEs and ST as the total amount of summed LFE slip. Using observed and calculated values for AP, AT, and ST, we evaluate two end-member models for LFE slip within an LFE family patch. In the ductile matrix model, LFEs produce 100% of the observed ETS slip (SETS) in distinct subpatches (i.e., AT ≪ AP). In the connected patch model, AT = AP, but ST ≪ SETS. LFEs cluster into 45 LFE families. Spatial gaps (˜10 to 20 km) between LFE family clusters and smaller gaps within LFE family clusters serve as evidence that LFE slip is heterogeneous on multiple spatial scales. We find that LFE slip only accounts for ˜0.2% of the slip within the slow slip zone. There are depth-dependent trends in the characteristic (mean) moment and in the number of LFEs during both ETS events (only) and the entire ETS cycle (Mcets and NTets and Mcall and NTall, respectively). During ETS, Mc decreases with downdip distance but NT does not change. Over the entire ETS cycle, Mc decreases with downdip distance, but NT increases. These observations indicate that deeper LFE slip occurs through a larger number (800-1,200) of small LFEs, while updip LFE slip occurs primarily during ETS events through a smaller number (200-600) of larger LFEs. This could indicate that the plate interface is stronger and has a higher stress threshold updip.

  8. RETRAN dynamic slip model

    International Nuclear Information System (INIS)

    McFadden, J.H.; Paulsen, M.P.; Gose, G.C.

    1981-01-01

    A time dependent equation for the slip velocity in a two-phase flow condition has been incorporated into a developmental version of the RETRAN computer code. This model addition has been undertaken to remove a limitation in RETRAN-01 associated with the homogeneous equilibrium mixture model. In this paper, the development of the slip model is summarized and the corresponding constitutive equations are discussed. Comparisons of RETRAN analyses with steady-state void fraction data and data from the Semiscale S-02-6 small break test are also presented

  9. RETRAN dynamic slip model

    International Nuclear Information System (INIS)

    McFadden, J.H.; Paulsen, M.P.; Gose, G.C.

    1981-01-01

    Thermal-hydraulic codes in general use for system calculations are based on extensive analyses of loss-of-coolant accidents following the postulated rupture of a large coolant pipe. In this study, time-dependent equation for the slip velocity in a two-phase flow condition has been incorporated into the RETRAN-02 computer code. This model addition was undertaken to remove a limitation in RETRAN-01 associated with the homogeneous equilibrium mixture model. The dynamic slip equation was derived from a set of two-fluid conservation equations. 18 refs

  10. “Silent” Diabetes and Clinical Outcome After Treatment With Contemporary Drug-Eluting Stents : The BIO-RESORT Silent Diabetes Study

    NARCIS (Netherlands)

    von Birgelen, Clemens; Kok, Marlies M.; Sattar, Naveed; Zocca, Paolo; Doelman, Cees; Kant, Gert D.; Löwik, Marije M.; van der Heijden, Liefke C.; Sen, Hanim; van Houwelingen, Gert K.; Stoel, Martin G.; Louwerenburg, J. (Hans) W.; Hartmann, Marc; de Man, Frits H.A.F.; Linssen, Gerard C.M.; Doggen, Carine J.M.; Tandjung, Kenneth

    2018-01-01

    Objectives: This study sought to assess the prevalence and clinical impact of silent diabetes and pre-diabetes in “nondiabetic” percutaneous coronary intervention (PCI) all-comers. Background: Patients with undetected and thus untreated (silent) diabetes may have higher event risks after PCI with

  11. Inorganic glass ceramic slip rings

    Science.gov (United States)

    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.

  12. Fluid Pressures at the Shoe-Floor-Contaminant Interface During Slips: Effects of Tread & Implications on Slip Severity

    Science.gov (United States)

    Beschorner, Kurt E.; Albert, Devon L.; Chambers, April J.; Redfern, Mark S.

    2018-01-01

    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. PMID:24267270

  13. Myocardial perfusion in silent myocardial ischemia

    International Nuclear Information System (INIS)

    Narita, Michihiro; Kurihara, Tadashi; Murano, Kenichi; Usami, Masahisa

    1989-01-01

    To investigate myocardial perfusion in silent myocardial ischemia, we performed exercise stress myocardial tomography with thallium-201 (Tl) in 85 patients with coronary artery disease (CAD). Exercise stress myocardial tomography was obtained both immediately after exercise and three hours later. Patients were classified into two groups according to the presence (Symptomatic Group, n=36) or absence (Silent Group, n=49) of chest pain during exercise stress. Clinical features (age, gender and history of myocardial infarction) and arteriographically determined severity of CAD were the same in both groups. The extent of myocardial ischemia (% Ischemia) estimated by exercise stress myocardial tomography was the same in each group (30±10 % in Silent Group, 28±12 % in Symptomatic Group, NS). The severity of exercise-induced myocardial ischemia was expressed as a minimal value of myocardial Tl washout rate (minimal WOR) of each patient. Although exercise heart rate was identical in both groups, minimal WOR in Silent Group was significantly higher than that of Symptomatic Group (4±10% vs -16±14%, p<0.001). The study in patients who exhibited both silent and symptomatic ischemia showed the same results. These findings suggest that the severity of ischemia is a fundamental factor in determining the presence or absence of pain during exercise induced ischemia. (author)

  14. Stick-slip substructure in rapid tape peeling

    KAUST Repository

    Thoroddsen, Sigurdur T.

    2010-10-15

    The peeling of adhesive tape is known to proceed with a stick-slip mechanism and produces a characteristic ripping sound. The peeling also produces light and when peeled in a vacuum, even X-rays have been observed, whose emissions are correlated with the slip events. Here we present direct imaging of the detachment zone when Scotch tape is peeled off at high speed from a solid surface, revealing a highly regular substructure, during the slip phase. The typical 4-mm-long slip region has a regular substructure of transverse 220 μm wide slip bands, which fracture sideways at speeds over 300 m/s. The fracture tip emits waves into the detached section of the tape at ∼100 m/s, which promotes the sound, so characteristic of this phenomenon.

  15. Stick-slip substructure in rapid tape peeling

    KAUST Repository

    Thoroddsen, Sigurdur T; Nguyen, H. D.; Takehara, K.; Etoh, T. G.

    2010-01-01

    The peeling of adhesive tape is known to proceed with a stick-slip mechanism and produces a characteristic ripping sound. The peeling also produces light and when peeled in a vacuum, even X-rays have been observed, whose emissions are correlated with the slip events. Here we present direct imaging of the detachment zone when Scotch tape is peeled off at high speed from a solid surface, revealing a highly regular substructure, during the slip phase. The typical 4-mm-long slip region has a regular substructure of transverse 220 μm wide slip bands, which fracture sideways at speeds over 300 m/s. The fracture tip emits waves into the detached section of the tape at ∼100 m/s, which promotes the sound, so characteristic of this phenomenon.

  16. No slip gravity

    Science.gov (United States)

    Linder, Eric V.

    2018-03-01

    A subclass of the Horndeski modified gravity theory we call No Slip Gravity has particularly interesting properties: 1) a speed of gravitational wave propagation equal to the speed of light, 2) equality between the effective gravitational coupling strengths to matter and light, Gmatter and Glight, hence no slip between the metric potentials, yet difference from Newton's constant, and 3) suppressed growth to give better agreement with galaxy clustering observations. We explore the characteristics and implications of this theory, and project observational constraints. We also give a simple expression for the ratio of the gravitational wave standard siren distance to the photon standard candle distance, in this theory and others, and enable a direct comparison of modified gravity in structure growth and in gravitational waves, an important crosscheck.

  17. Replacing dark energy by silent virialisation

    Science.gov (United States)

    Roukema, Boudewijn F.

    2018-02-01

    Context. Standard cosmological N-body simulations have background scale factor evolution that is decoupled from non-linear structure formation. Prior to gravitational collapse, kinematical backreaction (𝒬𝒟) justifies this approach in a Newtonian context. Aims: However, the final stages of a gravitational collapse event are sudden; a globally imposed smooth expansion rate forces at least one expanding region to suddenly and instantaneously decelerate in compensation for the virialisation event. This is relativistically unrealistic. A more conservative hypothesis is to allow non-collapsed domains to continue their volume evolution according to the 𝒬𝒟 Zel'dovich approximation (QZA). We aim to study the inferred average expansion under this "silent" virialisation hypothesis. Methods: We set standard (MPGRAFIC) EdS 3-torus (T3) cosmological N-body initial conditions. Using RAMSES, we partitioned the volume into domains and called the DTFE library to estimate the per-domain initial values of the three invariants of the extrinsic curvature tensor that determine the QZA. We integrated the Raychaudhuri equation in each domain using the INHOMOG library, and adopted the stable clustering hypothesis to represent virialisation (VQZA). We spatially averaged to obtain the effective global scale factor. We adopted an early-epoch-normalised EdS reference-model Hubble constant H1EdS = 37.7 km s-1 /Mpc and an effective Hubble constant Heff,0 = 67.7 km s-1 /Mpc. Results: From 2000 simulations at resolution 2563, we find that reaching a unity effective scale factor at 13.8 Gyr (16% above EdS), occurs for an averaging scale of L13.813 = 2.5-0.1+0.1 Mpc/heff. Relativistically interpreted, this corresponds to strong average negative curvature evolution, with the mean (median) curvature functional Ωℛ𝒟 growing from zero to about 1.5-2 by the present. Over 100 realisations, the virialisation fraction and super-EdS expansion correlate strongly at

  18. Events

    Directory of Open Access Journals (Sweden)

    Igor V. Karyakin

    2016-02-01

    Full Text Available The 9th ARRCN Symposium 2015 was held during 21st–25th October 2015 at the Novotel Hotel, Chumphon, Thailand, one of the most favored travel destinations in Asia. The 10th ARRCN Symposium 2017 will be held during October 2017 in the Davao, Philippines. International Symposium on the Montagu's Harrier (Circus pygargus «The Montagu's Harrier in Europe. Status. Threats. Protection», organized by the environmental organization «Landesbund für Vogelschutz in Bayern e.V.» (LBV was held on November 20-22, 2015 in Germany. The location of this event was the city of Wurzburg in Bavaria.

  19. Purely Magnetic Silent Universes do not Exist

    Science.gov (United States)

    Vu, K. T.; Carminati, J.

    2008-09-01

    We present a new Maple package called STeM (Symbolic Tetrad Manipulation). Using STeM, we outline, using a formalism which is a hybrid of the NP and Orthonormal ones, the proof of the nonexistence of purely magnetic silent universes.

  20. Relativistic numerical cosmology with silent universes

    Science.gov (United States)

    Bolejko, Krzysztof

    2018-01-01

    Relativistic numerical cosmology is most often based either on the exact solutions of the Einstein equations, or perturbation theory, or weak-field limit, or the BSSN formalism. The silent universe provides an alternative approach to investigate relativistic evolution of cosmological systems. The silent universe is based on the solution of the Einstein equations in 1  +  3 comoving coordinates with additional constraints imposed. These constraints include: the gravitational field is sourced by dust and cosmological constant only, both rotation and magnetic part of the Weyl tensor vanish, and the shear is diagnosable. This paper describes the code simsilun (free software distributed under the terms of the reposi General Public License), which implements the equations of the silent universe. The paper also discusses applications of the silent universe and it uses the Millennium simulation to set up the initial conditions for the code simsilun. The simulation obtained this way consists of 16 777 216 worldlines, which are evolved from z  =  80 to z  =  0. Initially, the mean evolution (averaged over the whole domain) follows the evolution of the background ΛCDM model. However, once the evolution of cosmic structures becomes nonlinear, the spatial curvature evolves from ΩK =0 to ΩK ≈ 0.1 at the present day. The emergence of the spatial curvature is associated with ΩM and Ω_Λ being smaller by approximately 0.05 compared to the ΛCDM.

  1. The Silent Spring of Rachel Carson.

    Science.gov (United States)

    Kerstetter, Ned

    1996-01-01

    Presents a lesson plan examining Rachel Carson's call to arms concerning the harmful consequences of pesticides. Students view a video documentary on Carson's work and read a synopsis of her book, "Silent Spring." Assessment is provided by various activities including writing assignments, creating posters, and editorial cartoons. (MJP)

  2. Malaria - Africa's silent tsunami | IDRC - International Development ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    2011-01-12

    Jan 12, 2011 ... Less well known is the continuous “silent tsunami” of malaria in Africa ... This means almost 3 lives per minute lost from an easily preventable and treatable disease. It was gratifying to see the beginnings of similar passion to deal with ... often in shapes, sizes, and colours unpopular in African households.

  3. Silent Film in the German Classroom.

    Science.gov (United States)

    Caldwell, David

    In addition to using films in the German classroom to introduce students to German culture and history, it is important to show and study the film as film. This procedure emphasizes the importance of the film as a part of creative arts in Germany and demands student participation in observation and discussion. Many German silent films are…

  4. Frictional melting and stick-slip behavior in volcanic conduits

    Science.gov (United States)

    Kendrick, Jackie Evan; Lavallee, Yan; Hirose, Takehiro; di Toro, Giulio; Hornby, Adrian Jakob; Hess, Kai-Uwe; Dingwell, Donald Bruce

    2013-04-01

    Dome-building eruptions have catastrophic potential, with dome collapse leading to devastating pyroclastic flows with almost no precursory warning. During dome growth, the driving forces of the buoyant magma may be superseded by controls along conduit margins; where brittle fracture and sliding can lead to formation of lubricating cataclasite and gouge. Under extreme friction, pseudotachylyte may form at the conduit margin. Understanding the conduit margin processes is vital to understanding the continuation of an eruption and we postulate that pseudotachylyte generation could be the underlying cause of stick-slip motion and associated seismic "drumbeats", which are so commonly observed at dome-building volcanoes. This view is supported by field evidence in the form of pseudotachylytes identified in lava dome products at Soufrière Hills (Montserrat) and Mount St. Helens (USA). Both eruptions were characterised by repetitive, periodic seismicity and lava spine extrusion of highly viscous magma. High velocity rotary shear (HVR) experiments demonstrate the propensity for melting of the andesitic and dacitic material (from Soufrière Hills and Mount St. Helens respectively) at upper conduit stress conditions (HVR experiments which mimic rapid velocity fluctuations in stick-slip behavior demonstrate velocity-weakening behavior of melt, with a tendency for unstable slip. During ascent, magma may slip and undergo melting along the conduit margin. In the process the shear resistance of the slip zone is increased, acting as a viscous brake halting slip (the "stick" of stick-slip motion). Sufficient buoyancy-driven pressures from ascending magma below eventually overcome resistance to produce a rapid slip event (the "slip") along the melt-bearing slip zone, which is temporarily lubricated due to velocity-weakening. New magma below experiences the same slip event more slowly (as the magma decompresses) to produce a viscous brake and the process is repeated. This allows a

  5. Velocity- and slip-dependent weakening on the Tohoku plate boundary fault: shallow coseismic slip facilitated by foreshock afterslip

    Science.gov (United States)

    Ito, Y.; Ikari, M.; Ujiie, K.; Kopf, A.

    2016-12-01

    Understanding of role of slow earthquakes as they relate to the occurrence of both megathrust earthquakes and tsunami earthquakes is necessary to mitigate these disasters in the near future. Laboratory shearing experiments is one of important approach to evaluate these relationships. Here, we use powdered gouge samples from JFAST (IODP Expedition 343) Hole C0019E, core sample 17R-1, which is the plate boundary fault zone in the Japan Trench subduction zone. In this region, both large coseismic slip during the 2011 Tohoku-Oki earthquake as well as discrete slow slip events (SSE) have occurred. Experiments were conducted in a single-direct shear apparatus under normal stress of 16 MPa, with total shear displacements of up to 16 mm. We evaluate both the velocity- and slip-dependence of friction by extracting the velocity-dependent friction parameters a, b, and Dc, and measuring the rate of change in friction coefficient with shear displacement as the slip-dependence of friction. We report that in friction experiments using the Tohoku fault zone samples, an increase in sliding velocity exceeding that of earthquake afterslip can induce a change from steady-state frictional strength or slip hardening friction to slip-weakening frictional behavior. Our results show that the slip weakening is observed when the slip velocity exceeds 1 x 10-6 m/s during our experiments, while steady-state frictional strength or slip hardening is observed below 1x10-6 m/s. In the Japan Trench region, two slow events were observed at the downdip edge of the mainshock coseismic slip zone (< 30 m) were observed. These are an episodic SSE with a slip velocity of 0.1 x 10-6, and afterslip after the largest foreshock with a slip velocity of 2 x 10-6 m/s. This suggests that the afterslip may have facilitated the large coseismic slip during the mainshock on the plate boundary fault of the Tohoku-Oki earthquake.

  6. Triggered surface slips in the Salton Trough associated with the 1999 Hector Mine, California, earthquake

    Science.gov (United States)

    Rymer, M.J.; Boatwright, J.; Seekins, L.C.; Yule, J.D.; Liu, J.

    2002-01-01

    Surface fracturing occurred along the southern San Andreas, Superstition Hills, and Imperial faults in association with the 16 October 1999 (Mw 7.1) Hector Mine earthquake, making this at least the eighth time in the past 31 years that a regional earthquake has triggered slip along faults in the Salton Trough. Fractures associated with the event formed discontinuous breaks over a 39-km-long stretch of the San Andreas fault, from the Mecca Hills southeastward to Salt Creek and Durmid Hill, a distance from the epicenter of 107 to 139 km. Sense of slip was right lateral; only locally was there a minor (~1 mm) vertical component of slip. Dextral slip ranged from 1 to 13 mm. Maximum slip values in 1999 and earlier triggered slips are most common in the central Mecca Hills. Field evidence indicates a transient opening as the Hector Mine seismic waves passed the southern San Andreas fault. Comparison of nearby strong-motion records indicates several periods of relative opening with passage of the Hector Mine seismic wave-a similar process may have contributed to the field evidence of a transient opening. Slip on the Superstition Hills fault extended at least 9 km, at a distance from the Hector Mine epicenter of about 188 to 196 km. This length of slip is a minimum value, because we saw fresh surface breakage extending farther northwest than our measurement sites. Sense of slip was right lateral; locally there was a minor (~1 mm) vertical component of slip. Dextral slip ranged from 1 to 18 mm, with the largest amounts found distributed (or skewed) away from the Hector Mine earthquake source. Slip triggered on the Superstition Hills fault commonly is skewed away from the earthquake source, most notably in 1968, 1979, and 1999. Surface slip on the Imperial fault and within the Imperial Valley extended about 22 km, representing a distance from the Hector Mine epicenter of about 204 to 226 km. Sense of slip dominantly was right lateral; the right-lateral component of slip

  7. Surface slip during large Owens Valley earthquakes

    KAUST Repository

    Haddon, E. K.; Amos, C. B.; Zielke, Olaf; Jayko, A. S.; Burgmann, R.

    2016-01-01

    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 approximate to 1.0 to 6.0 m and average 3.31.1 m (2 sigma). Vertical offsets are predominantly east-down between approximate to 0.1 and 2.4 m, with a mean of 0.80.5 m. The average lateral-to-vertical ratio compiled at specific sites is approximate to 6:1. Summing displacements across subparallel, overlapping rupture traces implies a maximum of 7-11 m and net average of 4.41.5 m, corresponding to a geologic M-w approximate to 7.5 for the 1872 event. We attribute progressively higher-offset lateral COPD peaks at 7.12.0 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 approximate to 0.6 and 1.6 mm/yr (1 sigma) over the late Quaternary.

  8. Surface slip during large Owens Valley earthquakes

    KAUST Repository

    Haddon, E. K.

    2016-01-10

    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 approximate to 1.0 to 6.0 m and average 3.31.1 m (2 sigma). Vertical offsets are predominantly east-down between approximate to 0.1 and 2.4 m, with a mean of 0.80.5 m. The average lateral-to-vertical ratio compiled at specific sites is approximate to 6:1. Summing displacements across subparallel, overlapping rupture traces implies a maximum of 7-11 m and net average of 4.41.5 m, corresponding to a geologic M-w approximate to 7.5 for the 1872 event. We attribute progressively higher-offset lateral COPD peaks at 7.12.0 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 approximate to 0.6 and 1.6 mm/yr (1 sigma) over the late Quaternary.

  9. Silent stroke and advance in neuroimaging

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Yasushi; Sadoshima, Seizo; Hasuo, Kanehiro; Saku, Yoshisuke; Fujishima, Masatoshi (Kyushu Univ., Fukuoka (Japan). Faculty of Medicine)

    1990-10-01

    Recently, silent strokes are more frequently demonstrated by CT and MRI with the advance of neuroimaging. The infarcted lesions unrelated to the neurological symptoms were detected in 8, 30, 28, 34, 60, 63% of the patients with cerebral infarction in 1977-78, 1982, 1985, 1986, 1987, 1988, respectively, by CT and/or MRI, and the asymptomatic patients with incidentally diagnosed cerebral infarction were amounted to 16% (8 of 51 cases) in 1988. Of the recent 50 patients with cerebral infarction examined by CT and MRI, asymptomatic cerebrovascular lesions were detected in 25 (50%) by CT and in 35 (70%) by MRI. MRI also revealed asymptomatic old hemorrhage in 7 (14%). The clinical significance of silent stroke was discussed. (author).

  10. Scoring an Abstract Contemporary Silent Film

    OpenAIRE

    Frost, Crystal

    2014-01-01

    I composed an original digital audio film score with full sound design for a contemporary silent film called Apple Tree. The film is highly conceptual and interpretive and required a very involved, intricate score to successfully tell the story. In the process of scoring this film, I learned new ways to convey an array of contrasting emotions through music and sound. After analyzing the film's emotional journey, I determined that six defining emotions were the foundation on which to build an ...

  11. Teen Depression and Suicide, A SILENT CRISIS.

    Science.gov (United States)

    Kroning, Maureen; Kroning, Kayla

    2016-01-01

    Adolescent depression is a serious problem affecting 10.7% of all teens and 29.9% of high school students; 17% of high school students have contemplated suicide. Yet, depression in teens is often unrecognized. This article relays the tragic death of a 17-year-old, along with symptoms of depression and suicide in adolescents; DSM-5 criteria for depression; treatments including protective factors, psychotherapy, and medications; and imparts interventions for addressing this huge but silent crisis.

  12. Creep and slip: Seismic precursors to the Nuugaatsiaq landslide (Greenland)

    Science.gov (United States)

    Poli, Piero

    2017-09-01

    Precursory signals to material's failure are predicted by numerical models and observed in laboratory experiments or using field data. These precursory signals are a marker of slip acceleration on weak regions, such as crustal faults. Observation of these precursory signals of catastrophic natural events, such as earthquakes and landslides, is necessary for improving our knowledge about the physics of the nucleation process. Furthermore, observing such precursory signals may help to forecast these catastrophic events or reduce their hazard. I report here the observation of seismic precursors to the Nuugaatsiaq landslide in Greenland. Time evolution of the detected precursors implies that an aseismic slip event is taking place for hours before the landslide, with an exponential increase of slip velocity. Furthermore, time evolution of the precursory signals' amplitude sheds light on the evolution of the fault physics during the nucleation process.

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

    Science.gov (United States)

    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.

  14. Slips of the Pun

    DEFF Research Database (Denmark)

    Balle, Søren Hattesen

    ’ at the same time, the second one of which gets told as a result of a simple slip of a pun. If one story of the poem is the poet-speaker’s hermeneutic quest for the possible meaningfulness of a past love affair, the other – somewhat less conspicuously – introduces his attempt to remember and recover the bodily...... matter in the end. At any rate, the reader is left wondering how literally he ought to take the poet-speaker’s punning prediction that he and his lover “’ll/Stay in touch”. And what about the reader’s own attempt to ‘make sense’ of Ashbery’s puns? To which extent does he or she become engaged in a sexual...... relationship with them if one extends Ashbery’s playing with word to what goes one in the reader’s interpretive act? Ashbery’s friend and fellow poet Kenneth Koch once said of the former’s poetry that “it wants to go to bed with you”....

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

    NARCIS (Netherlands)

    Collettini, C.; Niemeijer, A.; Viti, C.; Smith, S.A.F.; Marone, C.

    2011-01-01

    Recent high-resolution GPS and seismological data reveal that tectonic faults exhibit complex, multi-modeslipbehavior 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

  16. Recurrent Silent Thyroiditis as a Sequela of Postpartum Thyroiditis

    Science.gov (United States)

    Kim, Paul

    2014-01-01

    Thyroiditis encompasses a group of disorders characterized by thyroid inflammation. Though clinically indistinguishable from silent thyroiditis, postpartum thyroiditis occurs in women within 12 months after delivery. Recurrent postpartum thyroiditis in subsequent pregnancies is common, but recurrent silent thyroiditis is rare. We reported a case of patient with recurrent episodes of thyroiditis, unrelated to pregnancy, after an episode of postpartum thyroiditis. It is of interest that postpartum thyroiditis and silent thyroiditis could occur closely to each other; however, the link between these disorders is not well established. This report is to remind physicians of the possibility of recurrent silent thyroiditis in women with a history of postpartum thyroiditis. PMID:24987536

  17. Silent ischemia and beta-blockade

    DEFF Research Database (Denmark)

    Egstrup, K

    1991-01-01

    and should also be directed at the other coronary artery risk factors of the patients. The effects of beta-blockers, which reduce the duration and frequency of silent ischemic episodes, is well described. The effect is most pronounced in the morning, when the frequency of ischemia is highest......, and the mechanism of action seems mainly mediated through a reduction in myocardial oxygen demand. beta-Blockers have shown effectiveness in both effort-induced angina and mixed angina, and increased anti-ischemic potency may be achieved by combination therapy with a calcium antagonist. Abrupt withdrawal of beta-blockers...

  18. An introduction to silent speech interfaces

    CERN Document Server

    Freitas, João; Dias, Miguel Sales; Silva, Samuel

    2017-01-01

    This book provides a broad and comprehensive overview of the existing technical approaches in the area of silent speech interfaces (SSI), both in theory and in application. Each technique is described in the context of the human speech production process, allowing the reader to clearly understand the principles behind SSI in general and across different methods. Additionally, the book explores the combined use of different data sources, collected from various sensors, in order to tackle the limitations of simpler SSI approaches, addressing current challenges of this field. The book also provides information about existing SSI applications, resources and a simple tutorial on how to build an SSI.

  19. Slow Slip and Earthquake Nucleation in Meter-Scale Laboratory Experiments

    Science.gov (United States)

    Mclaskey, G.

    2017-12-01

    The initiation of dynamic rupture is thought to be preceded by a quasistatic nucleation phase. Observations of recent earthquakes sometimes support this by illuminating slow slip and foreshocks in the vicinity of the eventual hypocenter. I describe laboratory earthquake experiments conducted on two large-scale loading machines at Cornell University that provide insight into the way earthquake nucleation varies with normal stress, healing time, and loading rate. The larger of the two machines accommodates a 3 m long granite sample, and when loaded to 7 MPa stress levels, we observe dynamic rupture events that are preceded by a measureable nucleation zone with dimensions on the order of 1 m. The smaller machine accommodates a 0.76 m sample that is roughly the same size as the nucleation zone. On this machine, small variations in nucleation properties result in measurable differences in slip events, and we generate both dynamic rupture events (> 0.1 m/s slip rates) and slow slip events ( 0.001 to 30 mm/s slip rates). Slow events occur when instability cannot fully nucleate before reaching the sample ends. Dynamic events occur after long healing times or abrupt increases in loading rate which suggests that these factors shrink the spatial and temporal extents of the nucleation zone. Arrays of slip, strain, and ground motion sensors installed on the sample allow us to quantify seismic coupling and study details of premonitory slip and afterslip. The slow slip events we observe are primarily aseismic (less than 1% of the seismic coupling of faster events) and produce swarms of very small M -6 to M -8 events. These mechanical and seismic interactions suggest that faults with transitional behavior—where creep, small earthquakes, and tremor are often observed—could become seismically coupled if loaded rapidly, either by a slow slip front or dynamic rupture of an earthquake that nucleated elsewhere.

  20. Eye Movement during Silent and Oral Reading: How Can we Compensate the Loss of Multisensory Process during Silent Reading?

    Directory of Open Access Journals (Sweden)

    Maiko Takahashi

    2011-10-01

    Full Text Available While reading texts orally, we process the multisensory language information. Accordingly, in the context of reading aloud, we process the visually presented text and produce the auditory information of the text through articulatory movement. These multisensory processing activities are assumed to facilitate the memory and comprehension of textual information. Conversely, while reading silently, we process only the visual information of the text. Although we cannot use the multisensory language information while reading silently, several researchers have found that there is little difference between the degree of comprehension based on silent and oral reading for adult readers. The purpose of this study is to explain how we compensate the loss of multisensory process during silent reading by comparing the visual processing process during silent and oral reading. By conducting two experiments, we measured and compared the eye movement during silent and oral reading. The results showed that silent reading took shorter time for comprehension than oral reading, and readers had more visual fixation points and read back frequently during reading silently than orally. These reading strategies during silent reading seemed to compensate the loss of multisensory process and support the text comprehension.

  1. Silent Bodies: Japanese taciturnity and image thinking

    Directory of Open Access Journals (Sweden)

    Ana Došen

    2017-03-01

    Full Text Available A nonverbal transmission and an implicit way of communication are highly encouraged in Japanese society. The reason for this “silence prerogative” is often found in historical facts of lengthy feudal era or in ancient philosophies and religions such as Buddhism and Confucianism and their various concepts which privilege taciturn way of communication. Moreover, the unspoken comprehension is often complemented by the attitude which equates truthfulness with silence. This paper explores the silence as a communicative act in the domain of Japanese art, where the body takes over the place of the language. In traditional Japanese theatrical performance, such as noh, words are often inadequate to convey emotion and therefore the aesthetics of emptiness, understatement and abstraction is transcended by the masks with "nonmoving lips". Drawing on theoretical perspectives from both East and West, I argue that the silent bodies operate as deliberate and integral determinants of Japanese non-silent art forms – especially in cinema and theatre. In the Eastern thought, visual perception is fundamental in cognition of the world, whereas auditory discernment is secondary to "image-thinking" (Yuasa. Accustomed to taciturnity, Japanese audience effectively corresponds to the performance and "completes" it in silence.

  2. Evidence Based Prevention of Occupational Slips, Trips and Falls

    DEFF Research Database (Denmark)

    Jensen, Olaf Chresten

    2009-01-01

    It is estimated that about one third of the compensated occupational injuries and half of the most serious occupational injuries in merchant seafaring are related to slips, trips and falls (STF)-events. Among the elderly, STF is the risk factor that causes the largest number of inpatient days...

  3. Silent Conversations in the Labyrinth of Artistic Research and Practice

    Science.gov (United States)

    Eis, Andrea

    2013-01-01

    This essay explores silent conversations with the past, but also navigates through the labyrinth of artistic process, with its manifold passages of research, chance occurrence and aesthetic experimentation. The double metaphors of silent conversations and labyrinths apply to the essay and the artwork within it, to the research and to the practice.…

  4. Slip-dependent weakening on shallow plate boundary fault in the Japan subduction zone: shallow coseismic slip facilitated by foreshock afterslip

    Science.gov (United States)

    Ito, Yoshi; Ikari, Matt; Ujiie, Kohtaro; Kopf, Achim

    2017-04-01

    Understanding of role of slow earthquakes as they relate to the occurrence of both megathrust earthquakes and tsunami earthquakes is necessary to mitigate these disasters in the near future. Laboratory shearing experiments is one of important approach to evaluate these relationships. Here, we use powdered gouge samples from JFAST (IODP Expedition 343) Hole C0019E, core sample 17R-1, which is the plate boundary fault zone in the Japan Trench subduction zone. In this region, both large coseismic slip during the 2011 Tohoku-Oki earthquake as well as discrete slow slip events (SSE) have occurred. Experiments were conducted in a single-direct shear apparatus under normal stress of 16 MPa, with total shear displacements of up to 16 mm. We evaluate the slip-dependence of friction by extracting the velocity-dependent friction parameters a, b, and Dc , and also measure the rate of change in friction coefficient with shear displacement as the slip-dependence of friction. We report that in friction experiments using the Tohoku fault zone samples, an increase in sliding velocity exceeding that of earthquake afterslip can induce a change from steady-state frictional strength or slip hardening friction to slip-weakening frictional behavior. Our results show that the slip weakening is observed when the slip velocity exceeds 3.7 × 10-6 m/s during our experiments, while steady-state frictional strength or slip hardening is observed below 1 × 10-6 m/s. In the Japan Trench region, two slow events prior to the mainshock were observed in the mainshock area with a coseismic slip exceeding 30 m . One event is an episodic SSE with a slip velocity of 0.1 × 10-6 , and the other is afterslip after the largest Tohoku earthquake foreshock with a slip velocity exceeding 2 × 10-6 m/s. Our experiments show that slip-weakening friction should be expected at the afterslip rate, suggesting that the afterslip may have facilitated the large coseismic slip during the mainshock on the plate boundary

  5. Slip of Spreading Viscoplastic Droplets.

    Science.gov (United States)

    Jalaal, Maziyar; Balmforth, Neil J; Stoeber, Boris

    2015-11-10

    The spreading of axisymmetric viscoplastic droplets extruded slowly on glass surfaces is studied experimentally using shadowgraphy and swept-field confocal microscopy. The microscopy furnishes vertical profiles of the radial velocity using particle image velocimetry (PIV) with neutrally buoyant tracers seeded in the fluid. Experiments were conducted for two complex fluids: aqueous solutions of Carbopol and xanthan gum. On untreated glass surfaces, PIV demonstrates that both fluids experience a significant amount of effective slip. The experiments were repeated on glass that had been treated to feature positive surface charges, thereby promoting adhesion between the negatively charged polymeric constituents of the fluids and the glass surface. The Carbopol and xanthan gum droplets spread more slowly on the treated surface and to a smaller radial distance. PIV demonstrated that this reduced spreading was associated with a substantial reduction in slip. For Carbopol, the effective slip could be eliminated entirely to within the precision of the PIV measurements; the reduction in slip was less effective for xanthan gum, with a weak slip velocity remaining noticeable.

  6. Sensitivity of tsunami wave profiles and inundation simulations to earthquake slip and fault geometry for the 2011 Tohoku earthquake

    KAUST Repository

    Goda, Katsuichiro; Mai, Paul Martin; Yasuda, Tomohiro; Mori, Nobuhito

    2014-01-01

    In this study, we develop stochastic random-field slip models for the 2011 Tohoku earthquake and conduct a rigorous sensitivity analysis of tsunami hazards with respect to the uncertainty of earthquake slip and fault geometry. Synthetic earthquake slip distributions generated from the modified Mai-Beroza method captured key features of inversion-based source representations of the mega-thrust event, which were calibrated against rich geophysical observations of this event. Using original and synthesised earthquake source models (varied for strike, dip, and slip distributions), tsunami simulations were carried out and the resulting variability in tsunami hazard estimates was investigated. The results highlight significant sensitivity of the tsunami wave profiles and inundation heights to the coastal location and the slip characteristics, and indicate that earthquake slip characteristics are a major source of uncertainty in predicting tsunami risks due to future mega-thrust events.

  7. Sensitivity of tsunami wave profiles and inundation simulations to earthquake slip and fault geometry for the 2011 Tohoku earthquake

    KAUST Repository

    Goda, Katsuichiro

    2014-09-01

    In this study, we develop stochastic random-field slip models for the 2011 Tohoku earthquake and conduct a rigorous sensitivity analysis of tsunami hazards with respect to the uncertainty of earthquake slip and fault geometry. Synthetic earthquake slip distributions generated from the modified Mai-Beroza method captured key features of inversion-based source representations of the mega-thrust event, which were calibrated against rich geophysical observations of this event. Using original and synthesised earthquake source models (varied for strike, dip, and slip distributions), tsunami simulations were carried out and the resulting variability in tsunami hazard estimates was investigated. The results highlight significant sensitivity of the tsunami wave profiles and inundation heights to the coastal location and the slip characteristics, and indicate that earthquake slip characteristics are a major source of uncertainty in predicting tsunami risks due to future mega-thrust events.

  8. Surface slip during large Owens Valley earthquakes

    Science.gov (United States)

    Haddon, E.K.; Amos, C.B.; Zielke, O.; Jayko, Angela S.; Burgmann, R.

    2016-01-01

    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.

  9. Silent Localization of Underwater Sensors Using Magnetometers

    Directory of Open Access Journals (Sweden)

    Jonas Callmer

    2010-01-01

    Full Text Available Sensor localization is a central problem for sensor networks. If the sensor positions are uncertain, the target tracking ability of the sensor network is reduced. Sensor localization in underwater environments is traditionally addressed using acoustic range measurements involving known anchor or surface nodes. We explore the usage of triaxial magnetometers and a friendly vessel with known magnetic dipole to silently localize the sensors. The ferromagnetic field created by the dipole is measured by the magnetometers and is used to localize the sensors. The trajectory of the vessel and the sensor positions are estimated simultaneously using an Extended Kalman Filter (EKF. Simulations show that the sensors can be accurately positioned using magnetometers.

  10. Effective slip lengths for flows over surfaces with nanobubbles: the effects of finite slip

    International Nuclear Information System (INIS)

    Hendy, S C; Lund, N J

    2009-01-01

    We consider effective slip lengths for flows of simple liquids over surfaces contaminated by gaseous nanobubbles. In particular, we examine whether the effects of finite slip over the liquid-bubble interface are important in limiting effective slip lengths over such surfaces. Using an expression that interpolates between the perfect slip and finite slip regimes for flow over bubbles, we conclude that for the bubble dimensions and coverages typically reported in the literature the effects of finite slip are secondary, reducing effective slip lengths by only 10%. Further, we find that nanobubbles do not significantly increase slip lengths beyond those reported for bare hydrophobic surfaces.

  11. Analysing earthquake slip models with the spatial prediction comparison test

    KAUST Repository

    Zhang, L.; Mai, Paul Martin; Thingbaijam, Kiran Kumar; Razafindrakoto, H. N. T.; Genton, Marc G.

    2014-01-01

    Earthquake rupture models inferred from inversions of geophysical and/or geodetic data exhibit remarkable variability due to uncertainties in modelling assumptions, the use of different inversion algorithms, or variations in data selection and data processing. A robust statistical comparison of different rupture models obtained for a single earthquake is needed to quantify the intra-event variability, both for benchmark exercises and for real earthquakes. The same approach may be useful to characterize (dis-)similarities in events that are typically grouped into a common class of events (e.g. moderate-size crustal strike-slip earthquakes or tsunamigenic large subduction earthquakes). For this purpose, we examine the performance of the spatial prediction comparison test (SPCT), a statistical test developed to compare spatial (random) fields by means of a chosen loss function that describes an error relation between a 2-D field (‘model’) and a reference model. We implement and calibrate the SPCT approach for a suite of synthetic 2-D slip distributions, generated as spatial random fields with various characteristics, and then apply the method to results of a benchmark inversion exercise with known solution. We find the SPCT to be sensitive to different spatial correlations lengths, and different heterogeneity levels of the slip distributions. The SPCT approach proves to be a simple and effective tool for ranking the slip models with respect to a reference model.

  12. Analysing earthquake slip models with the spatial prediction comparison test

    KAUST Repository

    Zhang, L.

    2014-11-10

    Earthquake rupture models inferred from inversions of geophysical and/or geodetic data exhibit remarkable variability due to uncertainties in modelling assumptions, the use of different inversion algorithms, or variations in data selection and data processing. A robust statistical comparison of different rupture models obtained for a single earthquake is needed to quantify the intra-event variability, both for benchmark exercises and for real earthquakes. The same approach may be useful to characterize (dis-)similarities in events that are typically grouped into a common class of events (e.g. moderate-size crustal strike-slip earthquakes or tsunamigenic large subduction earthquakes). For this purpose, we examine the performance of the spatial prediction comparison test (SPCT), a statistical test developed to compare spatial (random) fields by means of a chosen loss function that describes an error relation between a 2-D field (‘model’) and a reference model. We implement and calibrate the SPCT approach for a suite of synthetic 2-D slip distributions, generated as spatial random fields with various characteristics, and then apply the method to results of a benchmark inversion exercise with known solution. We find the SPCT to be sensitive to different spatial correlations lengths, and different heterogeneity levels of the slip distributions. The SPCT approach proves to be a simple and effective tool for ranking the slip models with respect to a reference model.

  13. Slip flow in graphene nanochannels

    DEFF Research Database (Denmark)

    . Kannam, Sridhar; Billy, Todd; Hansen, Jesper Schmidt

    2011-01-01

    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)10.1103/PhysRevE.84.016313]. 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...

  14. Seismic and Aseismic Slip on the Cascadia Megathrust

    Science.gov (United States)

    Michel, S. G. R. M.; Gualandi, A.; Avouac, J. P.

    2017-12-01

    Our understanding of the dynamics governing aseismic and seismic slip hinges on our ability to image the time evolution of fault slip during and in between earthquakes and transients. Such kinematic descriptions are also pivotal to assess seismic hazard as, on the long term, elastic strain accumulating around a fault should be balanced by elastic strain released by seismic slip and aseismic transients. In this presentation, we will discuss how such kinematic descriptions can be obtained from the analysis and modelling of geodetic time series. We will use inversion methods based on Independent Component Analysis (ICA) decomposition of the time series to extract and model the aseismic slip (afterslip and slow slip events). We will show that this approach is very effective to identify, and filter out, non-tectonic sources of geodetic strain such as the strain due to surface loads, which can be estimated using gravimetric measurements from GRACE, and thermal strain. We will discuss in particular the application to the Cascadia subduction zone.

  15. Modification of hormonal secretion in clinically silent pituitary adenomas.

    Science.gov (United States)

    Daems, Tania; Verhelst, Johan; Michotte, Alex; Abrams, Pascale; De Ridder, Dirk; Abs, Roger

    2009-01-01

    Silent pituitary adenomas are a subtype of adenomas characterized by positive immunoreactivity for one or more hormones classically secreted by normal pituitary cells but without clinical expression, although in some occasions enhanced or changed secretory activity can develop over time. Silent corticotroph adenomas are the classical example of this phenomenon. A series of about 500 pituitary adenomas seen over a period of 20 years were screened for modification in hormonal secretion. Biochemical and immunohistochemical data were reviewed. Two cases were retrieved, one silent somatotroph adenoma and one thyrotroph adenoma, both without specific clinical features or biochemical abnormalities, which presented 20 years after initial surgery with evidence of acromegaly and hyperthyroidism, respectively. While the acromegaly was controlled by a combination of somatostatin analogs and growth hormone (GH) receptor antagonist therapy, neurosurgery was necessary to manage the thyrotroph adenoma. Immunohistochemical examination demonstrated an increase in the number of thyroid stimulating hormone (TSH)-immunoreactive cells compared to the first tissue. Apparently, the mechanisms responsible for the secretory modifications are different, being a change in secretory capacity in the silent somatotroph adenoma and a quantitative change in the silent thyrotroph adenoma. These two cases, one somatotroph and one thyrotroph adenoma, are an illustration that clinically silent pituitary adenomas may in rare circumstances evolve over time and become active, as previously demonstrated in silent corticotroph adenomas.

  16. The complex evolution of transient slip revealed by precise tremor locations in western Shikoku, Japan

    Science.gov (United States)

    Shelly, D. R.; Beroza, G. C.; Ide, S.

    2007-12-01

    Transient slow slip events are increasingly being recognized as important components of strain release on faults and may substantially impact the earthquake cycle. Surface-based geodetic instruments provide estimates of the overall slip distribution in larger transients but are unable to capture the detailed evolution of such slip, either in time or space. Accompanying some of these slip transients is a relatively weak, extended duration seismic signal, known as non-volcanic tremor, which has recently been shown to be generated by a sequence of shear failures occurring as part of the slip event. By precisely locating the tremor, we can track some features of slip evolution with unprecedented resolution. Here, we analyze two weeklong episodes of tremor and slow slip in western Shikoku, Japan. We find that these slip transients do not evolve in a smooth and steady fashion but contain numerous sub-events of smaller size and shorter duration. In addition to along-strike migration rates of about 10 km/day observed previously, much faster migration also occurs, usually in the slab dip direction, at rates of 25-150 km/hour over distances of up to 20 km. We observe such migration episodes in both the up-dip and down-dip directions. These episodes may be most common on certain portions of the plate boundary that generate strong tremor in intermittent bursts. The surrounding regions of the fault may slip more continuously, driving these stronger patches to repeated failures. Tremor activity has a strong tidal periodicity, possibly reflecting the modulation of slow slip velocity by tidal stresses.

  17. Simulating the Evolving Behavior of Secondary Slow Slip Fronts

    Science.gov (United States)

    Peng, Y.; Rubin, A. M.

    2017-12-01

    High-resolution tremor catalogs of slow slip events reveal secondary slow slip fronts behind the main front that repetitively occupy the same source area during a single episode. These repetitive fronts are most often observed in regions with high tremor density. Their recurrence intervals gradually increase from being too short to be tidally modulated (tens of minutes) to being close to tidal periods (about 12 or 24 hours). This could be explained by a decreasing loading rate from creep in the surrounding regions (with few or no observable tremor events) as the main front passes by. As the recurrence intervals of the fronts increase, eventually they lock in on the tidal periods. We attempt to simulate this numerically using a rate-and-state friction law that transitions from velocity-weakening at low slip speeds to velocity strengthening at high slip speeds. Many small circular patches with a cutoff velocity an order of magnitude higher than that of the background are randomly placed on the fault, in order to simulate the average properties of the high-density tremor zone. Preliminary results show that given reasonable parameters, this model produces similar propagation speeds of the forward-migrating main front inside and outside the high-density tremor zone, consistent with observations. We will explore the behavior of the secondary fronts that arise in this model, in relation to the local density of the small tremor-analog patches, the overall geometry of the tremor zone and the tides.

  18. Slip activity of persistent slip bands in polycrystalline nickel

    International Nuclear Information System (INIS)

    Weidner, A.; Beyer, R.; Blochwitz, C.; Holste, C.; Schwab, A.; Tirschler, W.

    2006-01-01

    The appearance of glide localizations after cyclic deformation in the saturation stage was investigated for polycrystalline nickel. It was shown that persistent slip bands (PSBs) are formed in a wide range of grain orientations. Concerning the grain size it was found, that the probability for the appearance of PSBs is higher for larger grains. The local slip activity of the formed PSBs was studied after half-cycle deformation using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The fraction of grains with glide-active PSBs and the glide-active PSB volume itself is very small after the half-cycle loading. The obtained local shear strain amplitudes are quite high and vary in the range of 0.2-5%. They are comparable with those found in nickel single crystals at the same loading procedure

  19. Using Vocal and Silent Reading Approaches for the Enhancement ...

    African Journals Online (AJOL)

    Nekky Umera

    An International Multi-Disciplinary Journal. Vol. 3 (1) ... expresses his thoughts and feelings in such a way that the person can be ... creative, critical and evaluative. .... In the first week, the research assistants taught the oral and silent reading.

  20. Silent store detection and recording in memory storage

    Energy Technology Data Exchange (ETDEWEB)

    Bose, Pradip; Cher, Chen-Yong; Nair, Ravi

    2017-03-14

    An aspect includes receiving a write request that includes a memory address and write data. Stored data is read from a memory location at the memory address. Based on determining that the memory location was not previously modified, the stored data is compared to the write data. Based on the stored data matching the write data, the write request is completed without writing the write data to the memory and a corresponding silent store bit, in a silent store bitmap is set. Based on the stored data not matching the write data, the write data is written to the memory location, the silent store bit is reset and a corresponding modified bit is set. At least one of an application and an operating system is provided access to the silent store bitmap.

  1. Silent store detection and recording in memory storage

    Energy Technology Data Exchange (ETDEWEB)

    Bose, Pradip; Cher, Chen-Yong; Nair, Ravi

    2017-03-07

    An aspect includes receiving a write request that includes a memory address and write data. Stored data is read from a memory location at the memory address. Based on determining that the memory location was not previously modified, the stored data is compared to the write data. Based on the stored data matching the write data, the write request is completed without writing the write data to the memory and a corresponding silent store bit, in a silent store bitmap is set. Based on the stored data not matching the write data, the write data is written to the memory location, the silent store bit is reset and a corresponding modified bit is set. At least one of an application and an operating system is provided access to the silent store bitmap.

  2. Silent Circulation of Ross River Virus in French Polynesia

    Directory of Open Access Journals (Sweden)

    Maite Aubry

    2015-08-01

    Discussion: Our results support the existence of autochthonous RRV transmission and suggest that this pathogen has silently circulated in French Polynesia. These findings raise the question of possible undetected circulation of RRV in other Pacific Island Countries and Territories.

  3. Current practice for diagnosis and management of silent atrial fibrillation

    DEFF Research Database (Denmark)

    Dobreanu, Dan; Svendsen, Jesper Hastrup; Lewalter, Thorsten

    2013-01-01

    for the diagnosis and management of silent AF. This survey is based on an electronic questionnaire sent to the European Heart Rhythm Association Research Network partners. Responses were received from 33 centres in 16 countries. The preferred screening methods for silent AF in patients with rhythm control...... for such patients. Most responders preferred rate control over rhythm control in patients with silent AF, although some favoured pulmonary vein isolation in young patients. However, oral anticoagulant therapy in patients at high thromboembolic risk was considered mandatory by most, provided that at least one......Although it is well known that silent atrial fibrillation (AF) is associated with morbidity and mortality rates similar to those of symptomatic AF, no specific strategy for screening and management of this form of AF has been advocated. The purpose of this survey was to identify current practices...

  4. Silent Synapse-Based Circuitry Remodeling in Drug Addiction.

    Science.gov (United States)

    Dong, Yan

    2016-05-01

    Exposure to cocaine, and likely other drugs of abuse, generates α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor-silent glutamatergic synapses in the nucleus accumbens. These immature synaptic contacts evolve after drug withdrawal to redefine the neurocircuital properties. These results raise at least three critical questions: (1) what are the molecular and cellular mechanisms that mediate drug-induced generation of silent synapses; (2) how are neurocircuits remodeled upon generation and evolution of drug-generated silent synapses; and (3) what behavioral consequences are produced by silent synapse-based circuitry remodeling? This short review analyzes related experimental results, and extends them to some speculations. © The Author 2015. Published by Oxford University Press on behalf of CINP.

  5. How Silent is the Right to Silence?

    Directory of Open Access Journals (Sweden)

    Katherine Biber

    2012-11-01

    Full Text Available A long-held and fundamental principle of our criminal justice system is that people accused of crimes have a right to silence, arising from the presumption of innocence. Rules of evidence try to protect this ‘right’ during trial, by ensuring that juries understand that adverse inferences cannot be drawn from the silence of the accused. Silence, in court, can mean nothing, and we are not to speculate about what might motivate an accused person to remain silent, or what they might have said had they spoken. However, an examination of the jurisprudence in this area shows that the law is often not dealing with actual silence; sometimes when the law refers to the ‘right to silence’, it seems to mean a ‘refusal to hear’. In other instances, there is actual silence, and yet the law refuses to subject that silence to any critical interpretation, insisting that we cannot infer anything from it. While we have learned, from theatre, music, linguistics, religion and psychology, to develop sophisticated means for interpreting silence, the law demands that we set aside these interpretive tools, hearing silence that isn’t there, and inferring nothing about something.

  6. Silent communication: toward using brain signals.

    Science.gov (United States)

    Pei, Xiaomei; Hill, Jeremy; Schalk, Gerwin

    2012-01-01

    From the 1980s movie Firefox to the more recent Avatar, popular science fiction has speculated about the possibility of a persons thoughts being read directly from his or her brain. Such braincomputer interfaces (BCIs) might allow people who are paralyzed to communicate with and control their environment, and there might also be applications in military situations wherever silent user-to-user communication is desirable. Previous studies have shown that BCI systems can use brain signals related to movements and movement imagery or attention-based character selection. Although these systems have successfully demonstrated the possibility to control devices using brain function, directly inferring which word a person intends to communicate has been elusive. A BCI using imagined speech might provide such a practical, intuitive device. Toward this goal, our studies to date addressed two scientific questions: (1) Can brain signals accurately characterize different aspects of speech? (2) Is it possible to predict spoken or imagined words or their components using brain signals?

  7. Silent synapses in neuromuscular junction development.

    Science.gov (United States)

    Tomàs, Josep; Santafé, Manel M; Lanuza, Maria A; García, Neus; Besalduch, Nuria; Tomàs, Marta

    2011-01-01

    In the last few years, evidence has been found to suggest that some synaptic contacts become silent but can be functionally recruited before they completely retract during postnatal synapse elimination in muscle. The physiological mechanism of developmental synapse elimination may be better understood by studying this synapse recruitment. This Mini-Review collects previously published data and new results to propose a molecular mechanism for axonal disconnection. The mechanism is based on protein kinase C (PKC)-dependent inhibition of acetylcholine (ACh) release. PKC activity may be stimulated by a methoctramine-sensitive M2-type muscarinic receptor and by calcium inflow though P/Q- and L-type voltage-dependent calcium channels. In addition, tropomyosin-related tyrosine kinase B (trkB) receptor-mediated brain-derived neurotrophic factor (BDNF) activity may oppose the PKC-mediated ACh release depression. Thus, a balance between trkB and muscarinic pathways may contribute to the final functional suppression of some neuromuscular synapses during development. © 2010 Wiley-Liss, Inc.

  8. Recurrent Silent Thyroiditis as a Sequela of Postpartum Thyroiditis

    OpenAIRE

    Hanseree, Preaw; Salvador, Vincent Bryan; Sachmechi, Issac; Kim, Paul

    2014-01-01

    Thyroiditis encompasses a group of disorders characterized by thyroid inflammation. Though clinically indistinguishable from silent thyroiditis, postpartum thyroiditis occurs in women within 12 months after delivery. Recurrent postpartum thyroiditis in subsequent pregnancies is common, but recurrent silent thyroiditis is rare. We reported a case of patient with recurrent episodes of thyroiditis, unrelated to pregnancy, after an episode of postpartum thyroiditis. It is of interest that postpar...

  9. Complex evolution of transient slip derived from precise tremor locations in western Shikoku, Japan

    Science.gov (United States)

    Shelly, David R.; Beroza, Gregory C.; Ide, Satoshi

    2007-10-01

    Transient slip events, which occur more slowly than traditional earthquakes, are increasingly being recognized as important components of strain release on faults and may substantially impact the earthquake cycle. Surface-based geodetic instruments provide estimates of the overall slip distribution in larger transients but are unable to capture the detailed evolution of such slip, either in time or in space. Accompanying some of these slip transients is a relatively weak, extended duration seismic signal, known as nonvolcanic tremor, which has recently been shown to be generated by a sequence of shear failures occurring as part of the slip event. By precisely locating the tremor, we can track some features of slip evolution with unprecedented resolution. Here, we analyze two weeklong episodes of tremor and slow slip in western Shikoku, Japan. We find that these slip transients do not evolve in a smooth and steady fashion but contain numerous subevents of smaller size and shorter duration. In addition to along-strike migration rates of ˜10 km/d observed previously, much faster migration also occurs, usually in the slab dip direction, at rates of 25-150 km/h over distances of up to ˜20 km. We observe such migration episodes in both the updip and downdip directions. These episodes may be most common on certain portions of the plate boundary that generate strong tremor in intermittent bursts. The surrounding regions of the fault may slip more continuously, driving these stronger patches to repeated failures. Tremor activity has a strong tidal periodicity, possibly reflecting the modulation of slow slip velocity by tidal stresses.

  10. The role of bed-parallel slip in the development of complex normal fault zones

    Science.gov (United States)

    Delogkos, Efstratios; Childs, Conrad; Manzocchi, Tom; Walsh, John J.; Pavlides, Spyros

    2017-04-01

    Normal faults exposed in Kardia lignite mine, Ptolemais Basin, NW Greece formed at the same time as bed-parallel slip-surfaces, so that while the normal faults grew they were intermittently offset by bed-parallel slip. Following offset by a bed-parallel slip-surface, further fault growth is accommodated by reactivation on one or both of the offset fault segments. Where one fault is reactivated the site of bed-parallel slip is a bypassed asperity. Where both faults are reactivated, they propagate past each other to form a volume between overlapping fault segments that displays many of the characteristics of relay zones, including elevated strains and transfer of displacement between segments. Unlike conventional relay zones, however, these structures contain either a repeated or a missing section of stratigraphy which has a thickness equal to the throw of the fault at the time of the bed-parallel slip event, and the displacement profiles along the relay-bounding fault segments have discrete steps at their intersections with bed-parallel slip-surfaces. With further increase in displacement, the overlapping fault segments connect to form a fault-bound lens. Conventional relay zones form during initial fault propagation, but with coeval bed-parallel slip, relay-like structures can form later in the growth of a fault. Geometrical restoration of cross-sections through selected faults shows that repeated bed-parallel slip events during fault growth can lead to complex internal fault zone structure that masks its origin. Bed-parallel slip, in this case, is attributed to flexural-slip arising from hanging-wall rollover associated with a basin-bounding fault outside the study area.

  11. Transformation of fault slip modes in laboratory experiments

    Science.gov (United States)

    Martynov, Vasilii; Alexey, Ostapchuk; Markov, Vadim

    2017-04-01

    Slip mode of crust fault can vary because of many reasons. It's well known that fault structure, material of fault gouge, pore fluid et al. in many ways determines slip modes from creep and slow slip events to mega-earthquakes [1-3]. Therefore, the possibility of fault slip transformation due to external action is urgent question. There is popular and developing approach of fluid injection into central part of fault. The phenomenon of earthquakes induced due to pumping of water was investigated on small and large scales [4, 5]. In this work the laboratory experiments were conducted to study the evolution of the experimental fault slip when changing the properties of the interstitial fluid. The scheme of experiments is the classical slider-model set-up, in which the block under the shear force slips along the interface. In our experiments the plexiglas block 8x8x3 cm3 in size was put on the plexiglas base. The contact of the blocks was filled with a thin layer (about 3 mm thick) of a granular material. The normal load varied from 31 to 156 kPa. The shear load was applied through a spring with stiffness 60 kN/m, and the rate of spring deformation was 20 or 5 mcm/s. Two parameters were recorded during experiments: the shear force acting on the upper block (with an accuracy of 1 N) and its displacement relatively the base (with an accuracy of 0.1 μm). The gouge was composed of quartz sand (97.5%) and clay (2.5%). As a moisturizer were used different fluids with viscosity varying from 1 to 103 mPa x s. Different slip modes were simulated during slider-experiments. In our experiments slip mode is the act of instability manifested in an increase of slip velocity and a drop of shear stress acting on a movable block. The amplitude of a shear stress drop and the peak velocity of the upper block were chosen as the characteristics of the slip mode. In the laboratory experiments, slip events of one type can be achieved either as regularly recurring (regular mode) or as random

  12. Evidence for presynaptically silent synapses in the immature hippocampus

    International Nuclear Information System (INIS)

    Yoon, Jae Young; Choi, Sukwoo

    2017-01-01

    Silent synapses show NMDA receptor (NMDAR)-mediated synaptic responses, but not AMPAR-mediated synaptic responses. A prevailing hypothesis states that silent synapses contain NMDARs, but not AMPARs. However, alternative presynaptic hypotheses, according to which AMPARs are present at silent synapses, have been proposed; silent synapses show slow glutamate release via a fusion pore, and glutamate spillover from the neighboring synaptic terminals. Consistent with these presynaptic hypotheses, the peak glutamate concentrations at silent synapses have been estimated to be ≪170 μM, much lower than those seen at functional synapses. Glutamate transients predicted based on the two presynaptic mechanisms have been shown to activate only high-affinity NMDARs, but not low-affinity AMPARs. Interestingly, a previous study has developed a new approach to distinguish between the two presynaptic mechanisms using dextran, an inert macromolecule that reduces the diffusivity of released glutamate: postsynaptic responses through the fusion pore mechanism, but not through the spillover mechanism, are potentiated by reduced glutamate diffusivity. Therefore, we reasoned that if the fusion pore mechanism underlies silent synapses, dextran application would reveal AMPAR-mediated synaptic responses at silent synapses. In the present study, we recorded AMPAR-mediated synaptic responses at the CA3-CA1 synapses in neonatal rats in the presence of blockers for NMDARs and GABAARs. Bath application of dextran revealed synaptic responses at silent synapses. GYKI53655, a selective AMPAR-antagonist, completely inhibited the unsilenced synaptic responses, indicating that the unsilenced synaptic responses are mediated by AMPARs. The dextran-mediated reduction in glutamate diffusivity would also lead to the activation of metabotropic glutamate receptors (mGluRs), which might induce unsilencing via the activation of unknown intracellular signaling. Hence, we determined whether mGluR-blockers alter

  13. "Luck's always to blame": silent wounds of a penetrating gunshot trauma sustained 20 years ago.

    Science.gov (United States)

    Tomos, Ioannis; Manali, Effrosyni D; Argentos, Stylianos; Raptakis, Thomas; Papiris, Spyros A

    2015-01-01

    Gunshot tracheal injuries represent life-threatening events and usually necessitate emergent surgical intervention. We report a case of an exceptional finding of a patient with retained ballistic fragments in the soft tissues of the thorax, proximal to the right subclavian artery and the trachea, carrying silently his wounds for two decades without any medical or surgical intervention. The bullet pellet on the upper part of the trachea seen accidentally in the chest computed tomography, was also found during bronchoscopy. In short "luck's always to blame".

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

    Science.gov (United States)

    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 (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 breaks over a 54-km-long stretch of the fault, from the Indio Hills southeastward to Durmid Hill. Sense of slip was right

  15. Episodic tremor and slip explained by fluid-enhanced microfracturing and sealing

    Science.gov (United States)

    Bernaudin, M.; Gueydan, F.

    2017-12-01

    A combination of non-volcanic tremor and transient slow slip events behaviors is commonly observed at plate interface, between locked/seismogenic zone at low depths and stable/ductile creep zone at larger depths. This association defines Episodic Tremor and Slip, systematically highlighted by over-pressurized fluids and near failure shear stress conditions. Here we propose a new mechanical approach that provides for the first time a mechanical and field-based explanation of the observed association between non-volcanic tremor and slow slip events. In contrast with more classical rate-and-state models, this physical model uses a ductile rheology with grain size sensitivity, fluid-driven microfracturing and sealing (e.g. grain size reduction and grain growth) and related pore fluid pressure fluctuations. We reproduce slow slip events by transient ductile strain localization as a result of fluid-enhanced microfracturing and sealing. Moreover, occurrence of macrofracturing during transient strain localization and local increase in pore fluid pressure well simulate non-volcanic tremor. Our model provides therefore a field-based explanation of episodic tremor and slip and moreover predicts the depth and temperature ranges of their occurrence in subduction zones. It implies furthermore that non-volcanic tremor and slow slip events are physically related.

  16. Listening in on Friction: Stick-Slip Acoustical Signatures in Velcro

    Science.gov (United States)

    Hurtado Parra, Sebastian; Morrow, Leslie; Radziwanowski, Miles; Angiolillo, Paul

    2013-03-01

    The onset of kinetic friction and the possible resulting stick-slip motion remain mysterious phenomena. Moreover, stick-slip dynamics are typically accompanied by acoustic bursts that occur temporally with the slip event. The dry sliding dynamics of the hook-and-loop system, as exemplified by Velcro, manifest stick-slip behavior along with audible bursts that are easily micrphonically collected. Synchronized measurements of the friction force and acoustic emissions were collected as hooked Velcro was driven at constant velocity over a bed of looped Velcro in an anechoic chamber. Not surprising, the envelope of the acoustic bursts maps well onto the slip events of the friction force time series and the intensity of the bursts trends with the magnitude of the difference of the friction force during a stick-slip event. However, the analysis of the acoustic emission can serve as a sensitive tool for revealing some of the hidden details of the evolution of the transition from static to kinetic friction. For instance, small acoustic bursts are seen prior to the Amontons-Coulomb threshold, signaling precursor events prior to the onset of macroscopically observed motion. Preliminary spectral analysis of the acoustic emissions including intensity-frequency data will be presented.

  17. Preliminary soil-slip susceptibility maps, southwestern California

    Science.gov (United States)

    Morton, Douglas M.; Alvarez, Rachel M.; Campbell, Russell H.; Digital preparation by Bovard, Kelly R.; Brown, D.T.; Corriea, K.M.; Lesser, J.N.

    2003-01-01

    This group of maps shows relative susceptibility of hill slopes to the initiation sites of rainfall-triggered soil slip-debris flows in southwestern California. As such, the maps offer a partial answer to one part of the three parts necessary to predict the soil-slip/debris-flow process. A complete prediction of the process would include assessments of “where”, “when”, and “how big”. These maps empirically show part of the “where” of prediction (i.e., relative susceptibility to sites of initiation of the soil slips) but do not attempt to show the extent of run out of the resultant debris flows. Some information pertinent to “when” the process might begin is developed. “When” is determined mostly by dynamic factors such as rainfall rate and duration, for which local variations are not amenable to long-term prediction. “When” information is not provided on the maps but is described later in this narrative. The prediction of “how big” is addressed indirectly by restricting the maps to a single type of landslide process—soil slip-debris flows. The susceptibility maps were created through an iterative process from two kinds of information. First, locations of sites of past soil slips were obtained from inventory maps of past events. Aerial photographs, taken during six rainy seasons that produced abundant soil slips, were used as the basis for soil slip-debris flow inventory. Second, digital elevation models (DEM) of the areas that were inventoried were used to analyze the spatial characteristics of soil slip locations. These data were supplemented by observations made on the ground. Certain physical attributes of the locations of the soil-slip debris flows were found to be important and others were not. The most important attribute was the mapped bedrock formation at the site of initiation of the soil slip. However, because the soil slips occur in surficial materials overlying the bedrocks units, the bedrock formation can only serve as

  18. Is Slow Slip a Cause or a Result of Tremor?

    Science.gov (United States)

    Luo, Y.; Ampuero, J. P.

    2017-12-01

    While various modeling efforts have been conducted to reproduce subsets of observations of tremor and slow-slip events (SSE), a fundamental but yet unanswered question is whether slow slip is a cause or a result of tremor. Tremor is commonly regarded as driven by SSE. This view is mainly based on observations of SSE without detected tremors and on (frequency-limited) estimates of total tremor seismic moment being lower than 1% of their concomitant SSE moment. In previous studies we showed that models of heterogeneous faults, composed of seismic asperities embedded in an aseismic fault zone matrix, reproduce quantitatively the hierarchical patterns of tremor migration observed in Cascadia and Shikoku. To address the title question, we design two end-member models of a heterogeneous fault. In the SSE-driven-tremor model, slow slip events are spontaneously generated by the matrix (even in the absence of seismic asperities) and drive tremor. In the Tremor-driven-SSE model the matrix is stable (it slips steadily in the absence of asperities) and slow slip events result from the collective behavior of tremor asperities interacting via transient creep (local afterslip fronts). We study these two end-member models through 2D quasi-dynamic multi-cycle simulations of faults governed by rate-and-state friction with heterogeneous frictional properties and effective normal stress, using the earthquake simulation software QDYN (https://zenodo.org/record/322459). We find that both models reproduce first-order observations of SSE and tremor and have very low seismic to aseismic moment ratio. However, the Tremor-driven-SSE model assumes a simpler rheology than the SSE-driven-tremor model and matches key observations better and without fine tuning, including the ratio of propagation speeds of forward SSE and rapid tremor reversals and the decay of inter-event times of Low Frequency Earthquakes. These modeling results indicate that, in contrast to a common view, SSE could be a result

  19. Direct effects of smoking on the heart: silent ischemic disturbances of coronary flow

    International Nuclear Information System (INIS)

    Deanfield, J.E.; Shea, M.J.; Wilson, R.A.; Horlock, P.; de Landsheere, C.M.; Selwyn, A.P.

    1986-01-01

    Cigarette smoking is strongly associated with ischemic heart disease and acute coronary events. The effect of smoking a single cigarette on regional myocardial perfusion was studied in 13 chronic smokers with typical stable angina pectoris using positron emission tomography and rubidium-82 ( 82 Rb). Findings were compared with the effects of physical exercise. After exercise, 8 patients (61%) had angina, ST depression and abnormal regional myocardial perfusion. Uptake of 82 Rb increased from 49 +/- 8 to 60 +/- 7 in remote myocardium, but decreased from 46 +/- 3 to 37 +/- 5 in an ischemic area. The remaining 5 patients (39%) had homogeneous increases in 82 Rb uptake without angina or ST depression. After smoking, 6 of the 8 patients with positive exercise test responses had a decrease in 82 Rb uptake, from 47 +/- 3 to 35 +/- 6 in the same segment of myocardium affected during exercise. However, in contrast to exercise, the events during smoking were largely silent. The absolute decreases in regional 82 Rb uptake after smoking occurred at significantly lower levels of myocardial oxygen demand than after exercise. This suggests that an impairment of coronary blood supply is responsible. Thus, in smokers with coronary artery disease, each cigarette can cause profound silent disturbances of regional myocardial perfusion that are likely to occur frequently during daily life. Such repeated insults may represent an important mechanism linking smoking with coronary events

  20. Self-similar slip distributions on irregular shaped faults

    Science.gov (United States)

    Herrero, A.; Murphy, S.

    2018-06-01

    We propose a strategy to place a self-similar slip distribution on a complex fault surface that is represented by an unstructured mesh. This is possible by applying a strategy based on the composite source model where a hierarchical set of asperities, each with its own slip function which is dependent on the distance from the asperity centre. Central to this technique is the efficient, accurate computation of distance between two points on the fault surface. This is known as the geodetic distance problem. We propose a method to compute the distance across complex non-planar surfaces based on a corollary of the Huygens' principle. The difference between this method compared to others sample-based algorithms which precede it is the use of a curved front at a local level to calculate the distance. This technique produces a highly accurate computation of the distance as the curvature of the front is linked to the distance from the source. Our local scheme is based on a sequence of two trilaterations, producing a robust algorithm which is highly precise. We test the strategy on a planar surface in order to assess its ability to keep the self-similarity properties of a slip distribution. We also present a synthetic self-similar slip distribution on a real slab topography for a M8.5 event. This method for computing distance may be extended to the estimation of first arrival times in both complex 3D surfaces or 3D volumes.

  1. Controls of earthquake faulting style on near field landslide triggering : the role of coseismic slip

    OpenAIRE

    Tatard, Lucile; Grasso, J. R.

    2013-01-01

    We compare the spatial distributions of seven databases of landslides triggered by M-w=5.6-7.9 earthquakes, using distances normalized by the earthquake fault length. We show that the normalized landslide distance distributions collapse, i.e., the normalized distance distributions overlap whatever the size of the earthquake, separately for the events associated with dip-slip, buried-faulting earthquakes, and surface-faulting earthquakes. The dip-slip earthquakes triggered landslides at larger...

  2. Misbheaving Faults: The Expanding Role of Geodetic Imaging in Unraveling Unexpected Fault Slip Behavior

    Science.gov (United States)

    Barnhart, W. D.; Briggs, R.

    2015-12-01

    Geodetic imaging techniques enable researchers to "see" details of fault rupture that cannot be captured by complementary tools such as seismology and field studies, thus providing increasingly detailed information about surface strain, slip kinematics, and how an earthquake may be transcribed into the geological record. For example, the recent Haiti, Sierra El Mayor, and Nepal earthquakes illustrate the fundamental role of geodetic observations in recording blind ruptures where purely geological and seismological studies provided incomplete views of rupture kinematics. Traditional earthquake hazard analyses typically rely on sparse paleoseismic observations and incomplete mapping, simple assumptions of slip kinematics from Andersonian faulting, and earthquake analogs to characterize the probabilities of forthcoming ruptures and the severity of ground accelerations. Spatially dense geodetic observations in turn help to identify where these prevailing assumptions regarding fault behavior break down and highlight new and unexpected kinematic slip behavior. Here, we focus on three key contributions of space geodetic observations to the analysis of co-seismic deformation: identifying near-surface co-seismic slip where no easily recognized fault rupture exists; discerning non-Andersonian faulting styles; and quantifying distributed, off-fault deformation. The 2013 Balochistan strike slip earthquake in Pakistan illuminates how space geodesy precisely images non-Andersonian behavior and off-fault deformation. Through analysis of high-resolution optical imagery and DEMs, evidence emerges that a single fault map slip as both a strike slip and dip slip fault across multiple seismic cycles. These observations likewise enable us to quantify on-fault deformation, which account for ~72% of the displacements in this earthquake. Nonetheless, the spatial distribution of on- and off-fault deformation in this event is highly spatially variable- a complicating factor for comparisons

  3. Silent Revolution in Research for Sustainability

    Directory of Open Access Journals (Sweden)

    Bruce Alder

    2016-06-01

    Full Text Available Is research ‘fit-for-purpose’ for realizing sustainable development? More than two decades after the Brundtland report and UNCED Earth summit, the world has now adopted Sustainable Development Goals(SDGs. Rather than a cause for celebration, this delay should encourage reflection on the role of research in society. Why is it so difficult to realize sustainability in practice? The answer lies in the fact that universities and research centres persist with 19th century methods of data gathering, scholarly analysis, and journal articles. Today’s world needs science in real-time, whether to detect drought, confront Ebola, or assist refugees. Research needs to work faster and embrace 21st century practices including data science, open access, and infographics.A silent revolution is occurring in the ways of organizing and conducting research, enabled by new technology and encouraging work that tackles the key challenges facing society. A variety of new arrangements have come into existence that promote international collaboration, including Horizon 2020 with its emphasis on societal challenges, the Bill & Melinda Gates Foundation which has inspired a family of grand challenges funds on health and development, and the Future Earth joint program of research for global sustainability. These arrangements not only control billions of dollars in research funding, they also influence the strategies of national research councils and international organizations. The result is no less than a transformation in the incentives that reward how researchers invest their time and effort.Why is a revolution needed? Within research, substantial growth in knowledge production coincided with fragmentation among disciplines. One can easily find expertise and publications in soil science or agronomy, yet integrated efforts on food security and climate adaptation remain scarce. Beyond research, society remains largely uninformed, as academics avoid engaging in public

  4. Silent (painless) thyroiditis. Evidence of a geographic variation in frequency

    International Nuclear Information System (INIS)

    Vitug, A.C.; Goldman, J.M.

    1985-01-01

    Recent reports suggest that 14% to 23% of thyrotoxic patients have silent (painless) thyroiditis, a newly described syndrome characterized by transient thyrotoxicosis with a low radioactive iodine uptake. A three-year review at a Brooklyn (NY) hospital showed only one definite and three possible cases of silent thyroiditis among 86 thyrotoxic patients. At most, 4% to 5% of thyrotoxic patients had silent thyroiditis. The authors suggest a geographic variation in this syndrome. Most cases and the largest series are from Japan and the Great Lakes area of North America. The latter may be related to increased iodine intake over many years in a previously endemic area of hypoiodidism and goiter, although other local factors may also be involved

  5. Silent (painless) thyroiditis. Evidence of a geographic variation in frequency

    Energy Technology Data Exchange (ETDEWEB)

    Vitug, A.C.; Goldman, J.M.

    1985-03-01

    Recent reports suggest that 14% to 23% of thyrotoxic patients have silent (painless) thyroiditis, a newly described syndrome characterized by transient thyrotoxicosis with a low radioactive iodine uptake. A three-year review at a Brooklyn (NY) hospital showed only one definite and three possible cases of silent thyroiditis among 86 thyrotoxic patients. At most, 4% to 5% of thyrotoxic patients had silent thyroiditis. The authors suggest a geographic variation in this syndrome. Most cases and the largest series are from Japan and the Great Lakes area of North America. The latter may be related to increased iodine intake over many years in a previously endemic area of hypoiodidism and goiter, although other local factors may also be involved.

  6. Silent method for mathematics instruction: An overview of teaching subsets

    Science.gov (United States)

    Sugiman, Apino, Ezi

    2017-05-01

    Generally, teachers use oral communication for teaching mathematics. Taking an opposite perspective, this paper describes how instructional practices for mathematics can be carried out namely a silent method. Silent method uses body language, written, and oral communication for classroom interaction. This research uses a design research approach consisting of four phases: preliminary, prototyping and developing the instruction, and assessment. There are four stages of silent method. The first stage is conditioning stage in which the teacher introduces the method and makes agreement about the `rule of the game'. It is followed by the second one, elaborating stage, where students guess and explore alternative answers. The third stage is developing mathematical thinking by structuring and symbolizing. Finally, the method is ended by reinforcing stage which aims at strengthening and reflecting student's understanding. In this paper, every stage is described on the basis of practical experiences in a real mathematics classroom setting.

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

    Science.gov (United States)

    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.

  8. Re‐estimated effects of deep episodic slip on the occurrence and probability of great earthquakes in Cascadia

    Science.gov (United States)

    Beeler, Nicholas M.; Roeloffs, Evelyn A.; McCausland, Wendy

    2013-01-01

    Mazzotti and Adams (2004) estimated that rapid deep slip during typically two week long episodes beneath northern Washington and southern British Columbia increases the probability of a great Cascadia earthquake by 30–100 times relative to the probability during the ∼58 weeks between slip events. Because the corresponding absolute probability remains very low at ∼0.03% per week, their conclusion is that though it is more likely that a great earthquake will occur during a rapid slip event than during other times, a great earthquake is unlikely to occur during any particular rapid slip event. This previous estimate used a failure model in which great earthquakes initiate instantaneously at a stress threshold. We refine the estimate, assuming a delayed failure model that is based on laboratory‐observed earthquake initiation. Laboratory tests show that failure of intact rock in shear and the onset of rapid slip on pre‐existing faults do not occur at a threshold stress. Instead, slip onset is gradual and shows a damped response to stress and loading rate changes. The characteristic time of failure depends on loading rate and effective normal stress. Using this model, the probability enhancement during the period of rapid slip in Cascadia is negligible (stresses of 10 MPa or more and only increases by 1.5 times for an effective normal stress of 1 MPa. We present arguments that the hypocentral effective normal stress exceeds 1 MPa. In addition, the probability enhancement due to rapid slip extends into the interevent period. With this delayed failure model for effective normal stresses greater than or equal to 50 kPa, it is more likely that a great earthquake will occur between the periods of rapid deep slip than during them. Our conclusion is that great earthquake occurrence is not significantly enhanced by episodic deep slip events.

  9. Geodetically resolved slip distribution of the 27 August 2012 Mw=7.3 El Salvador earthquake

    Science.gov (United States)

    Geirsson, H.; La Femina, P. C.; DeMets, C.; Hernandez, D. A.; Mattioli, G. S.; Rogers, R.; Rodriguez, M.

    2013-12-01

    On 27 August 2012 a Mw=7.3 earthquake occurred offshore of Central America causing a small tsunami in El Salvador and Nicaragua but little damage otherwise. This is the largest magnitude earthquake in this area since 2001. We use co-seismic displacements estimated from episodic and continuous GPS station time series to model the magnitude and spatial variability of slip for this event. The estimated surface displacements are small (earthquake. We use TDEFNODE to model the displacements using two different modeling approaches. In the first model, we solve for homogeneous slip on free rectangular fault(s), and in the second model we solve for distributed slip on the main thrust, realized using different slab models. The results indicate that we can match the seismic moment release, with models indicating rupture of a large area, with a low magnitude of slip. The slip is at shallow-to-intermediate depths on the main thrust off the coast of El Salvador. Additionally, we observe a deeper region of slip to the east, that reaches towards the Gulf of Fonseca between El Salvador and Nicaragua. The observed tsunami additionally indicates near-trench rupture off the coast of El Salvador. The duration of the rupturing is estimated from seismic data to be 70 s, which indicates a slow rupture process. Since the geodetic moment we obtain agrees with the seismic moment, this indicates that the earthquake was not associated with aseismic slip.

  10. Dual megathrust slip behaviors of the 2014 Iquique earthquake sequence

    Science.gov (United States)

    Meng, Lingsen; Huang, Hui; Bürgmann, Roland; Ampuero, Jean Paul; Strader, Anne

    2015-02-01

    The transition between seismic rupture and aseismic creep is of central interest to better understand the mechanics of subduction processes. A Mw 8.2 earthquake occurred on April 1st, 2014 in the Iquique seismic gap of northern Chile. This event was preceded by a long foreshock sequence including a 2-week-long migration of seismicity initiated by a Mw 6.7 earthquake. Repeating earthquakes were found among the foreshock sequence that migrated towards the mainshock hypocenter, suggesting a large-scale slow-slip event on the megathrust preceding the mainshock. The variations of the recurrence times of the repeating earthquakes highlight the diverse seismic and aseismic slip behaviors on different megathrust segments. The repeaters that were active only before the mainshock recurred more often and were distributed in areas of substantial coseismic slip, while repeaters that occurred both before and after the mainshock were in the area complementary to the mainshock rupture. The spatiotemporal distribution of the repeating earthquakes illustrates the essential role of propagating aseismic slip leading up to the mainshock and illuminates the distribution of postseismic afterslip. Various finite fault models indicate that the largest coseismic slip generally occurred down-dip from the foreshock activity and the mainshock hypocenter. Source imaging by teleseismic back-projection indicates an initial down-dip propagation stage followed by a rupture-expansion stage. In the first stage, the finite fault models show an emergent onset of moment rate at low frequency ( 0.5 Hz). This indicates frequency-dependent manifestations of seismic radiation in the low-stress foreshock region. In the second stage, the rupture expands in rich bursts along the rim of a semi-elliptical region with episodes of re-ruptures, suggesting delayed failure of asperities. The high-frequency rupture remains within an area of local high trench-parallel gravity anomaly (TPGA), suggesting the presence of

  11. Fast Slip Velocity in a High-Entropy Alloy

    Science.gov (United States)

    Rizzardi, Q.; Sparks, G.; Maaß, R.

    2018-04-01

    Due to fluctuations in nearest-neighbor distances and chemistry within the unit cell, high-entropy alloys are believed to have a much higher resistance to dislocation motion than pure crystals. Here, we investigate the coarse-grained dynamics of a number of dislocations being active during a slip event. We found that the time-resolved dynamics of slip is practically identical in Au and an Al0.3CoCrFeNi high-entropy alloy, but much faster than in Nb. Differences between the FCC-crystals are seen in the spatiotemporal velocity profile, with faster acceleration and slower velocity relaxation in the high-entropy alloy. Assessing distributions that characterize the intermittently evolving plastic flow reveals material-dependent scaling exponents for size, duration, and velocity-size distributions. The results are discussed in view of the underlying dislocation mobility.

  12. Preliminary slip history of the 2002 Denali earthquake

    Science.gov (United States)

    Ji, C.; Helmberger, D.; Wald, D.

    2002-12-01

    Rapid slip histories for the 2002 Denali earthquake were derived from the IRIS global data before geologists arrived in the field. We were able to predict many of the features they observed. Three models were produced indicating a step-wise improvement in matching the waveform data applying a formalism discussed in Ji et al. (2002). The first model referred to as Phase I is essentially an automated solution where a simple fault plane (300 km long) is fixed agreeing with CMT (Harvard) solution (strike 298 dip =86) assuming the PDE epicenter. The fit to the initial P waves does not work since they do not display a strike-slip polarity pattern. Thus, to continue we added a thrusting event (Phase II) following roughly the fault geometry of the Denali fault based on DEM topography map. While this produced some improvements, major misfits still remained. Before proceeding with Phase III, we did some homework on a foreshock, the Mw=6.7 Nenana event. After modeling this strike-slip event as a distributed fault, we used this relatively simple event to calibrate paths where shifts in P-waves and SH-waves ranged up to 4 and 8 sec respectively. Applying these corrections revealed some discrepancies in the rupture initiation. To produce a consistent picture requires 4 fault segments A, B, C and D. A weak rupture may initiate on a strike-slip Denali fault branch A at a depth of 10 km where a low angle thrust fault plane B intersects A. After about 2 sec, a major event occurred on plane B (strike=221, dip=35) and dominated the rupture of next 8 sec. When rupture B reaches the surface at about 10 sec after initiation, the major portion of the Denali fault (segment C) ruptured eastward with a relatively fast velocity (3 km/sec) producing a large slip concentration (up to 9 m at a depth of 10 km). The surface slip is about 7 km at a 20 km long segment. This feature is near the intersection of the Denali fault and the Totichunda fault (branch D). The rupture on D is relatively

  13. Fault slip and earthquake recurrence along strike-slip faults — Contributions of high-resolution geomorphic data

    KAUST Repository

    Zielke, Olaf

    2015-01-01

    Understanding earthquake (EQ) recurrence relies on information about the timing and size of past EQ ruptures along a given fault. Knowledge of a fault\\'s rupture history provides valuable information on its potential future behavior, enabling seismic hazard estimates and loss mitigation. Stratigraphic and geomorphic evidence of faulting is used to constrain the recurrence of surface rupturing EQs. Analysis of the latter data sets culminated during the mid-1980s in the formulation of now classical EQ recurrence models, now routinely used to assess seismic hazard. Within the last decade, Light Detection and Ranging (lidar) surveying technology and other high-resolution data sets became increasingly available to tectono-geomorphic studies, promising to contribute to better-informed models of EQ recurrence and slip-accumulation patterns. After reviewing motivation and background, we outline requirements to successfully reconstruct a fault\\'s offset accumulation pattern from geomorphic evidence. We address sources of uncertainty affecting offset measurement and advocate approaches to minimize them. A number of recent studies focus on single-EQ slip distributions and along-fault slip accumulation patterns. We put them in context with paleoseismic studies along the respective faults by comparing coefficients of variation CV for EQ inter-event time and slip-per-event and find that a) single-event offsets vary over a wide range of length-scales and the sources for offset variability differ with length-scale, b) at fault-segment length-scales, single-event offsets are essentially constant, c) along-fault offset accumulation as resolved in the geomorphic record is dominated by essentially same-size, large offset increments, and d) there is generally no one-to-one correlation between the offset accumulation pattern constrained in the geomorphic record and EQ occurrence as identified in the stratigraphic record, revealing the higher resolution and preservation potential of

  14. Dynamics of fault slip near the stability transition combining laboratory and numerical experiments

    Science.gov (United States)

    Mele Veedu, D.; Giorgetti, C.; Scuderi, M. M.; Barbot, S.; Marone, C.; Collettini, C.

    2017-12-01

    Frictional stability controls the seismogenic potential of faults. Laboratory (1) and theoretical (2) studies document and predict the conditions under which fault slip is seismic or aseismic. However, the full gamut of fault slip behavior near the stable/unstable boundary is still poorly known. Here, we combine insight from laboratory and numerical experiments to identify the wide spectrum of frictional instabilities around that transition, including slow-slip events, period-multiplying events, and chaos. We present a synoptic picture of the dynamics of fault slip in a bifurcation diagram obtained from a series of laboratory and numerical experiments. We compare the laboratory observations with spring-slider and finite-fault numerical models. In the laboratory, we vary the stiffness of the system by modulating the stress field around the experimental fault. In the numerical experiments, we vary the characteristic weakening distance to explore a range of critical nucleation sizes. Contrarily to previously found (3), complex fault dynamics can be obtained with a rate-and-state constitutive law with a single state variable. While the dynamics of fault slip is complicated on large faults by the presence of morphological and rheological heterogeneities, the range of instabilities identified in the laboratory is reminiscent of the variety of slow and fast earthquakes found along subduction zones (4). The accord between laboratory data and theoretical models affords more realistic predictions of fault behavior at slow slip speeds. (1) Scuderi et al., (2016), (2) Ruina (1983), (3) Gu & Wong (1994), (4) Obara & Kato (2016)

  15. The role of water in slip casting

    Science.gov (United States)

    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.

  16. Implications of basal micro-earthquakes and tremor for ice stream mechanics: Stick-slip basal sliding and till erosion

    Science.gov (United States)

    Barcheck, C. Grace; Tulaczyk, Slawek; Schwartz, Susan Y.; Walter, Jacob I.; Winberry, J. Paul

    2018-03-01

    The Whillans Ice Plain (WIP) is unique among Antarctic ice streams because it moves by stick-slip. The conditions allowing stick-slip and its importance in controlling ice dynamics remain uncertain. Local basal seismicity previously observed during unstable slip is a clue to the mechanism of ice stream stick-slip and a window into current basal conditions, but the spatial extent and importance of this basal seismicity are unknown. We analyze data from a 2010-2011 ice-plain-wide seismic and GPS network to show that basal micro-seismicity correlates with large-scale patterns in ice stream slip behavior: Basal seismicity is common where the ice moves the least between unstable slip events, with small discrete basal micro-earthquakes happening within 10s of km of the central stick-slip nucleation area and emergent basal tremor occurring downstream of this area. Basal seismicity is largely absent in surrounding areas, where inter-slip creep rates are high. The large seismically active area suggests that a frictional sliding law that can accommodate stick-slip may be appropriate for ice stream beds on regional scales. Variability in seismic behavior over inter-station distances of 1-10 km indicates heterogeneity in local bed conditions and frictional complexity. WIP unstable slips may nucleate when stick-slip basal earthquake patches fail over a large area. We present a conceptual model in which basal seismicity results from slip-weakening frictional failure of over-consolidated till as it is eroded and mobilized into deforming till.

  17. Possible deep fault slip preceding the 2004 Parkfield earthquake, inferred from detailed observations of tectonic tremor

    Science.gov (United States)

    Shelly, David R.

    2009-01-01

    Earthquake predictability depends, in part, on the degree to which sudden slip is preceded by slow aseismic slip. Recently, observations of deep tremor have enabled inferences of deep slow slip even when detection by other means is not possible, but these data are limited to certain areas and mostly the last decade. The region near Parkfield, California, provides a unique convergence of several years of high-quality tremor data bracketing a moderate earthquake, the 2004 magnitude 6.0 event. Here, I present detailed observations of tectonic tremor from mid-2001 through 2008 that indicate deep fault slip both before and after the Parkfield earthquake that cannot be detected with surface geodetic instruments. While there is no obvious short-term precursor, I find unidirectional tremor migration accompanied by elevated tremor rates in the 3 months prior to the earthquake, which suggests accelerated creep on the fault ∼16 km beneath the eventual earthquake hypocenter.

  18. Slip in the 1857 and earlier large earthquakes along the Carrizo Plain, San Andreas Fault.

    Science.gov (United States)

    Zielke, Olaf; Arrowsmith, J Ramón; Grant Ludwig, Lisa; Akçiz, Sinan O

    2010-02-26

    The moment magnitude (Mw) 7.9 Fort Tejon earthquake of 1857, with a approximately 350-kilometer-long surface rupture, was the most recent major earthquake along the south-central San Andreas Fault, California. Based on previous measurements of its surface slip distribution, rupture along the approximately 60-kilometer-long Carrizo segment was thought to control the recurrence of 1857-like earthquakes. New high-resolution topographic data show that the average slip along the Carrizo segment during the 1857 event was 5.3 +/- 1.4 meters, eliminating the core assumption for a linkage between Carrizo segment rupture and recurrence of major earthquakes along the south-central San Andreas Fault. Earthquake slip along the Carrizo segment may recur in earthquake clusters with cumulative slip of approximately 5 meters.

  19. Triggered surface slips in southern California associated with the 2010 El Mayor-Cucapah, Baja California, Mexico, earthquake

    Science.gov (United States)

    Rymer, Michael J.; Treiman, Jerome A.; Kendrick, Katherine J.; Lienkaemper, James J.; Weldon, Ray J.; Bilham, Roger; Wei, Meng; Fielding, Eric J.; Hernandez, Janis L.; Olson, Brian P.E.; Irvine, Pamela J.; Knepprath, Nichole; Sickler, Robert R.; Tong, Xiaopeng; Siem, Martin E.

    2011-01-01

    The April 4, 2010 (Mw7.2), El Mayor-Cucapah, Baja California, Mexico, earthquake is the strongest earthquake to shake the Salton Trough area since the 1992 (Mw7.3) Landers earthquake. Similar to the Landers event, ground-surface fracturing occurred on multiple faults in the trough. However, the 2010 event triggered surface slip on more faults in the central Salton Trough than previous earthquakes, including multiple faults in the Yuha Desert area, the southwestern section of the Salton Trough. In the central Salton Trough, surface fracturing occurred along the southern San Andreas, Coyote Creek, Superstition Hills, Wienert, Kalin, and Imperial Faults and along the Brawley Fault Zone, all of which are known to have slipped in historical time, either in primary (tectonic) slip and/or in triggered slip. Surface slip in association with the El Mayor-Cucapah earthquake is at least the eighth time in the past 42 years that a local or regional earthquake has triggered slip along faults in the central Salton Trough. In the southwestern part of the Salton Trough, surface fractures (triggered slip) occurred in a broad area of the Yuha Desert. This is the first time that triggered slip has been observed in the southwestern Salton Trough.

  20. Electro-optical hybrid slip ring

    Science.gov (United States)

    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

  1. Silent, indirect strategic processes in small and medium sized enterprises

    DEFF Research Database (Denmark)

    Larsen, Mette Vinther; Madsen, Charlotte Øland; Rasmussen, Jørgen Gulddahl

    Based on empirical data we in this paper explore day-to-day strategising with an emphasis on phronesis. This way we shed some light on the nearly silent, quiet, indirect strategic change processes as they are practiced and reflected upon by leaders in small companies in their daily practice...

  2. Correlation between increased platelet ADP aggregability and silent brain infarcts

    International Nuclear Information System (INIS)

    Ono, Kenichiro; Arimoto, Hirohiko; Shirotani, Toshiki

    2012-01-01

    The purpose of this study was to investigate the correlation between platelet aggregability and silent brain infarcts. The study subjects were 445 people (264 men, 181 women; mean age, 53±14 years) with no neurologic signs, history of brain tumor, trauma, cerebrovascular disease, or antiplatelet medications. Adenosine diphosphate (ADP)-induced platelet aggregation was measured by the aggregation-size analytic method. Platelet aggregability was classified into 9 classes. The presence of headache/vertigo, hypertension, diabetes mellitus, hyperlipidemia, or smoking was elicited by questioning or blood sampling. A head MRI scan was performed, and if marked atherosclerosis or obvious stenosis in the intracranial vessels was detected, it was defined as a positive MR angiography (MRA) finding. Silent brain infarcts were detected in 26.3% of subjects. Hyperaggregability defined as that above class 6, 7, and 8 was present in 43.8%, 30.8%, and 15.7% of subjects, respectively. The risk factors for silent brain infarcts by multiple logistic regression analysis were aging, hypertension, positive MRA findings, and hyperaggregability. Platelet ADP hyperaggregability might be a risk factor for silent brain infarcts. (author)

  3. Compositionality for Markov reward chains with fast and silent transitions

    NARCIS (Netherlands)

    Markovski, J.; Sokolova, A.; Trcka, N.; Vink, de E.P.

    2009-01-01

    A parallel composition is defined for Markov reward chains with stochastic discontinuity, and with fast and silent transitions. In this setting, compositionality with respect to the relevant aggregation preorders is established. For Markov reward chains with fast transitions the preorders are

  4. Stopping the Silent Killer: Hepatitis B Among Asian Americans

    Centers for Disease Control (CDC) Podcasts

    This podcast discusses an underappreciated health threat to many Asians and Pacific Islanders in the United States: chronic infection with the hepatitis B virus. Dr. John Ward, director of CDC's Division of Viral Hepatitis, and Dr. Sam So, founder of the Asian Liver Center at Stanford University, address the importance of testing, vaccination, and care to prevent serious health consequences from this "silent" disease.

  5. Hydrocoele: A Silent Disability Affecting Quality of Life in Katakwi ...

    African Journals Online (AJOL)

    Background: Katakwi district is one of the rural districts in eastern Uganda in Teso Sub Region. The district is heavily infested with filarial worms a major cause for hydrocoele and elephantiasis if the infection is left untreated. Hydrocoele in Katakwi district are still a big cause of silent morbidity though it's an operable ...

  6. Health Education Films of the Silent Era: A Historical Analysis

    Science.gov (United States)

    Sofalvi, Alan

    2011-01-01

    Films have been used to present health messages throughout the history of the medium. The purpose of this article is to describe pictures from the silent film era that were designed to educate people about health issues. Films still available in at least one format were reviewed. Published reviews were also used to obtain information about these…

  7. silent no more: sexual violence in conflict as a challenge

    African Journals Online (AJOL)

    Rights (FIDH), Violence Against Women in Syria: Breaking the Silence, Briefing. Paper Based on an .... not perceived as the church's concern”, Silent No More, p. 8. .... travel all night to retrieve the bodies and bury them with dignity.23 In the.

  8. Perspectives on the "Silent Period" for Emergent Bilinguals in England

    Science.gov (United States)

    Bligh, Caroline; Drury, Rose

    2015-01-01

    This article draws together the research findings from two ethnographic studies as a means to problematize the "silent period" as experienced by young bilingual learners in two English speaking early-years settings in England. Most teachers and senior early-years practitioners in England are monolingual English speakers. The children…

  9. Human Schedule Performance, Protocol Analysis, and the "Silent Dog" Methodology

    Science.gov (United States)

    Cabello, Francisco; Luciano, Carmen; Gomez, Inmaculada; Barnes-Holmes, Dermot

    2004-01-01

    The purpose of the current experiment was to investigate the role of private verbal behavior on the operant performances of human adults, using a protocol analysis procedure with additional methodological controls (the "silent dog" method). Twelve subjects were exposed to fixed ratio 8 and differential reinforcement of low rate 3-s schedules. For…

  10. Buried shallow fault slip from the South Napa earthquake revealed by near-field geodesy.

    Science.gov (United States)

    Brooks, Benjamin A; Minson, Sarah E; Glennie, Craig L; Nevitt, Johanna M; Dawson, Tim; Rubin, Ron; Ericksen, Todd L; Lockner, David; Hudnut, Kenneth; Langenheim, Victoria; Lutz, Andrew; Mareschal, Maxime; Murray, Jessica; Schwartz, David; Zaccone, Dana

    2017-07-01

    Earthquake-related fault slip in the upper hundreds of meters of Earth's surface has remained largely unstudied because of challenges measuring deformation in the near field of a fault rupture. We analyze centimeter-scale accuracy mobile laser scanning (MLS) data of deformed vine rows within ±300 m of the principal surface expression of the M (magnitude) 6.0 2014 South Napa earthquake. Rather than assuming surface displacement equivalence to fault slip, we invert the near-field data with a model that allows for, but does not require, the fault to be buried below the surface. The inversion maps the position on a preexisting fault plane of a slip front that terminates ~3 to 25 m below the surface coseismically and within a few hours postseismically. The lack of surface-breaching fault slip is verified by two trenches. We estimate near-surface slip ranging from ~0.5 to 1.25 m. Surface displacement can underestimate fault slip by as much as 30%. This implies that similar biases could be present in short-term geologic slip rates used in seismic hazard analyses. Along strike and downdip, we find deficits in slip: The along-strike deficit is erased after ~1 month by afterslip. We find no evidence of off-fault deformation and conclude that the downdip shallow slip deficit for this event is likely an artifact. As near-field geodetic data rapidly proliferate and will become commonplace, we suggest that analyses of near-surface fault rupture should also use more sophisticated mechanical models and subsurface geomechanical tests.

  11. Buried shallow fault slip from the South Napa earthquake revealed by near-field geodesy

    Science.gov (United States)

    Brooks, Benjamin A.; Minson, Sarah E.; Glennie, Craig L.; Nevitt, Johanna M.; Dawson, Tim; Rubin, Ron; Ericksen, Todd L.; Lockner, David; Hudnut, Kenneth; Langenheim, Victoria; Lutz, Andrew; Mareschal, Maxime; Murray, Jessica; Schwartz, David; Zaccone, Dana

    2017-01-01

    Earthquake-related fault slip in the upper hundreds of meters of Earth’s surface has remained largely unstudied because of challenges measuring deformation in the near field of a fault rupture. We analyze centimeter-scale accuracy mobile laser scanning (MLS) data of deformed vine rows within ±300 m of the principal surface expression of the M (magnitude) 6.0 2014 South Napa earthquake. Rather than assuming surface displacement equivalence to fault slip, we invert the near-field data with a model that allows for, but does not require, the fault to be buried below the surface. The inversion maps the position on a preexisting fault plane of a slip front that terminates ~3 to 25 m below the surface coseismically and within a few hours postseismically. The lack of surface-breaching fault slip is verified by two trenches. We estimate near-surface slip ranging from ~0.5 to 1.25 m. Surface displacement can underestimate fault slip by as much as 30%. This implies that similar biases could be present in short-term geologic slip rates used in seismic hazard analyses. Along strike and downdip, we find deficits in slip: The along-strike deficit is erased after ~1 month by afterslip. We find no evidence of off-fault deformation and conclude that the downdip shallow slip deficit for this event is likely an artifact. As near-field geodetic data rapidly proliferate and will become commonplace, we suggest that analyses of near-surface fault rupture should also use more sophisticated mechanical models and subsurface geomechanical tests. PMID:28782026

  12. Using Early Silent Film to Teach French: The Language of "Cinema Muet."

    Science.gov (United States)

    Bloom, Michelle E.

    1995-01-01

    Discusses the use of early silent films in second-language classrooms, focusing on the experiences of one instructor in using early French silents in elementary and intermediate French courses. Sample lesson plans and information on the availability of French silents are also provided. (Contains 17 references.) (MDM)

  13. Oral Reading Fluency as a Predictor of Silent Reading Fluency at Secondary and Postsecondary Levels

    Science.gov (United States)

    Seok, Soonhwa; DaCosta, Boaventura

    2014-01-01

    This research investigated oral reading fluency as a predictor of silent reading fluency at the secondary and postsecondary levels. Several measures were used, including the Gray Oral Reading Test, the Test of Silent Word Reading Fluency, the Test of Silent Contextual Reading Fluency, and the Reading Observation Scale. A total of 223 students…

  14. Nanomechanics of slip avalanches in amorphous plasticity

    Science.gov (United States)

    Cao, Penghui; Dahmen, Karin A.; Kushima, Akihiro; Wright, Wendelin J.; Park, Harold S.; Short, Michael P.; Yip, Sidney

    2018-05-01

    Discrete stress relaxations (slip avalanches) in a model metallic glass under uniaxial compression are studied using a metadynamics algorithm for molecular simulation at experimental strain rates. The onset of yielding is observed at the first major stress drop, accompanied, upon analysis, by the formation of a single localized shear band region spanning the entire system. During the elastic response prior to yielding, low concentrations of shear transformation deformation events appear intermittently and spatially uncorrelated. During serrated flow following yielding, small stress drops occur interspersed between large drops. The simulation results point to a threshold value of stress dissipation as a characteristic feature separating major and minor avalanches consistent with mean-field modeling analysis and mechanical testing experiments. We further interpret this behavior to be a consequence of a nonlinear interplay of two prevailing mechanisms of amorphous plasticity, thermally activated atomic diffusion and stress-induced shear transformations, originally proposed by Spaepen and Argon, respectively. Probing the atomistic processes at widely separate strain rates gives insight to different modes of shear band formation: percolation of shear transformations versus crack-like propagation. Additionally a focus on crossover avalanche size has implications for nanomechanical modeling of spatially and temporally heterogeneous dynamics.

  15. Event maps in a stick-slip system

    DEFF Research Database (Denmark)

    Galvanetto, Ugo; Knudsen, Carsten

    1997-01-01

    This paper describes a one-dimensional map generated by a two degree-of-freedom mechanical system that undergoes self-sustained oscillations induced by dry friction. The iterated map allows a much simpler representation and a better understanding of some dynamic features of the system. Some appli...

  16. Characteristics and habitat of deep vs. shallow slow slip events

    Science.gov (United States)

    Wipperfurth, S. A.; Sramek, O.; Roskovec, B.; Mantovani, F.; McDonough, W. F.

    2016-12-01

    Models integrating geophysics and geochemistry allow for characterization of the Earth's heat budget and geochemical evolution. Global lithospheric geophysical models are now constrained by surface and body wave data and are classified into several unique tectonic types. Global lithospheric geochemical models have evolved from petrological characterization of layers to a combination of petrologic and seismic constraints. Because of these advances regarding our knowledge of the lithosphere, it is necessary to create an updated chemical and physical reference model. We are developing a global lithospheric reference model based on LITHO1.0 (segmented into 1°lon x 1°lat x 9-layers) and seismological-geochemical relationships. Uncertainty assignments and correlations are assessed for its physical attributes, including layer thickness, Vp and Vs, and density. This approach yields uncertainties for the masses of the crust and lithospheric mantle. Heat producing element abundances (HPE: U, Th, and K) are ascribed to each volume element. These chemical attributes are based upon the composition of subducting sediment (sediment layers), composition of surface rocks (upper crust), a combination of petrologic and seismic correlations (middle and lower crust), and a compilation of xenolith data (lithospheric mantle). The HPE abundances are correlated within each voxel, but not vertically between layers. Efforts to provide correlation of abundances horizontally between each voxel are discussed. These models are used further to critically evaluate the bulk lithosphere heat production in the continents and the oceans. Cross-checks between our model and results from: 1) heat flux (Artemieva, 2006; Davies, 2013; Cammarano and Guerri, 2017), 2) gravity (Reguzzoni and Sampietro, 2015), and 3) geochemical and petrological models (Rudnick and Gao, 2014; Hacker et al. 2015) are performed.

  17. Deafening silence? Time to reconsider whether organisations are silent or deaf when things go wrong.

    Science.gov (United States)

    Jones, Aled; Kelly, Daniel

    2014-09-01

    Several public inquiries into healthcare failings in the UK have noted that employees of failing organizations attempt to raise concerns about shortcomings in care, often over a prolonged period of time, only for those concerns to be ignored. However, healthcare literature has largely focused on how organizations and their employees are silent in the face of such failings, positioning employees as daring not to speak in response to serious workplace problems or issues. We argue that only focussing on organizational silence is a critical mistake which misrepresents actual events and overly-simplifies the complexities of workplace culture. The disregard shown by academics, practitioners and policy makers to employee voice strategies, which do not amount to whistle-blowing, but equally cannot either be defined as "silence", results in signals being ignored that can be effective in preventing and ending wrongdoing by others. In addition to understanding silence we suggest therefore that better understanding of why organizations are deaf to, or disregard, employee concerns are needed. We propose that a virtuous cycle is possible, whereby the introduction of systems that result in better listening and valuing of employee concerns reinforces a culture of speaking up and, in turn, organizational learning. Similarly, organizations that disregard employees concerns are destined not to learn, ultimately falling silent and failing. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  18. Documentation of programs that compute 1) static tilts for a spatially variable slip distribution, and 2) quasi-static tilts produced by an expanding dislocation loop with a spatially variable slip distribution

    Science.gov (United States)

    McHugh, Stuart

    1976-01-01

    The material in this report is concerned with the effects of a vertically oriented rectangular dislocation loop on the tilts observed at the free surface of an elastic half-space. Part I examines the effect of a spatially variable static strike-slip distribution across the slip surface. The tilt components as a function of distance parallel, or perpendicular, to the strike of the slip surface are displayed for different slip-versus-distance profiles. Part II examines the effect of spatially and temporally variable slip distributions across the dislocation loop on the quasi-static tilts at the free surface of an elastic half space. The model discussed in part II may be used to generate theoretical tilt versus time curves produced by creep events.

  19. Dynamical stability of slip-stacking particles

    Energy Technology Data Exchange (ETDEWEB)

    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.

  20. Seismic slip on clay nano-foliation

    Science.gov (United States)

    Aretusini, S.; Pluemper, O.; Passelègue, F. X.; Spagnuolo, E.; Di Toro, G.

    2017-12-01

    Deformation processes active at seismic slip rates (ca. 1 m/s) on smectite-rich slipping zones are not well understood, although they likely control the mechanical behaviour of: i) subduction zone faults affected by tsunamigenic earthquakes (e.g. Japan Trench affected by Tohoku-Oki 2011 earthquake), ii) plate-boundary faults (e.g. San Andreas Fault), and iii) landslide decollements (e.g. 1963 Vajont landslide). Here we present a set of rotary experiments performed on water-dampened 2 mm thick clay-rich (70% wt. smectite and 30% wt. opal) gouge layers sheared at slip rates V ranging from 0.01 to 1.3 m/s, for 3 m of displacement under 5 MPa normal stress. Microstructural analyses were conducted on pre- and post-sheared gouges using focused ion beam scanning electron and transmission electron microscopy. All sheared gouges were slip weakening in the first 0.1 m of displacement, with friction coefficient decreasing from 0.3-0.45 to 0.5-0.15. Then, with progressive slip, gouges evolved to slip-strengthening (final friction coefficient of 0.35-0.48) at V ≤0.1 m/s and slip-neutral (final friction of 0.05) at V=1.3 m/s. Despite the large difference in the imposed slip rate and frictional behaviour, the slipping zone always consisted of a nano-foliation defined by sub-micrometric smectite crystals wrapping opal grains. The nano-foliated layer thickness decreased from 1.5 mm at V≤0.1 m/s to 0.15 mm at V=1.3 m/s. The presence of a similar nano-foliation in all the smectite-rich wet gouges suggests the activation of similar deformation processes, dominated by frictional slip on grain boundary and basal planes. The variation of deformed thickness with slip rate shows that dynamic weakening, occurring only at seismic slip rates, is controlled by strain localization.

  1. Three mile island. The silent disaster.

    Science.gov (United States)

    Smith, J S; Fisher, J H

    1981-04-24

    From Wednesday, March 28, 1979, to Wednesday, April 4, 1979, Dauphin County, Pennsylvania, was in a state of near-panic in response to the Three Mile Island nuclear accident. The Dauphin County Office of Emergency Preparedness quickly attempted to develop a plan to evacuate not only the population of an area 20 miles in radius from the plant but the short-term and long-term care medical facilities as well. For medical evacuation, a system of classification of patients was defined and matched to needed transportation. Furthermore, a critical coordinating link was established with the Hospital Association of Pennsylvania to identify and categorize relocation beds in receiving hospitals far from the incident site in the event of evacuation. Just as this incident was unusual, so too were the planning activities unique since they were never before conceived or accomplished.

  2. Three Mile Island. The silent disaster

    International Nuclear Information System (INIS)

    Smith, J.S. Jr.; Fisher, J.H.

    1981-01-01

    From Wednesday, March 28, 1979, to Wednesday, April 4, 1979, Dauphin County, Pennsylvania, was in a state of near-panic in response to the Three Mile Island nuclear accident. The Dauphin County Office of Emergency Preparedness quickly attempted to develop a plan to evacuate not only the population of an area 20 miles in radius from the plant but the short-term and long-term care medical facilities as well. For medical evacuation, a system of classification of patients was defined and matched to needed transportation. Furthermore, a critical coordinating link was established with the Hospital Association of Pennsylvania to identify and categorize relocation beds in receiving hospitals far from the incident site in the event of evacuation. Just as this incident was unusual, so too were the planning activities unique since they were never before conceived or accomplished

  3. Slip-mediated dewetting of polymer microdroplets

    Science.gov (United States)

    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

  4. Nonequilibrium Chromosome Looping via Molecular Slip Links

    Science.gov (United States)

    Brackley, C. A.; Johnson, J.; Michieletto, D.; Morozov, A. N.; Nicodemi, M.; Cook, P. R.; Marenduzzo, D.

    2017-09-01

    We propose a model for the formation of chromatin loops based on the diffusive sliding of molecular slip links. These mimic the behavior of molecules like cohesin, which, along with the CTCF protein, stabilize loops which contribute to organizing the genome. By combining 3D Brownian dynamics simulations and 1D exactly solvable nonequilibrium models, we show that diffusive sliding is sufficient to account for the strong bias in favor of convergent CTCF-mediated chromosome loops observed experimentally. We also find that the diffusive motion of multiple slip links along chromatin is rectified by an intriguing ratchet effect that arises if slip links bind to the chromatin at a preferred "loading site." This emergent collective behavior favors the extrusion of loops which are much larger than the ones formed by single slip links.

  5. Grain scale observations of stick-slip dynamics in fluid saturated granular fault gouge

    Science.gov (United States)

    Johnson, P. A.; Dorostkar, O.; Guyer, R. A.; Marone, C.; Carmeliet, J.

    2017-12-01

    We are studying granular mechanics during slip. In the present work, we conduct coupled computational fluid dynamics (CFD) and discrete element method (DEM) simulations to study grain scale characteristics of slip instabilities in fluid saturated granular fault gouge. The granular sample is confined with constant normal load (10 MPa), and sheared with constant velocity (0.6 mm/s). This loading configuration is chosen to promote stick-slip dynamics, based on a phase-space study. Fluid is introduced in the beginning of stick phase and characteristics of slip events i.e. macroscopic friction coefficient, kinetic energy and layer thickness are monitored. At the grain scale, we monitor particle coordination number, fluid-particle interaction forces as well as particle and fluid kinetic energy. Our observations show that presence of fluids in a drained granular fault gouge stabilizes the layer in the stick phase and increases the recurrence time. In saturated model, we observe that average particle coordination number reaches higher values compared to dry granular gouge. Upon slip, we observe that a larger portion of the granular sample is mobilized in saturated gouge compared to dry system. We also observe that regions with high particle kinetic energy are correlated with zones of high fluid motion. Our observations highlight that spatiotemporal profile of fluid dynamic pressure affects the characteristics of slip instabilities, increasing macroscopic friction coefficient drop, kinetic energy release and granular layer compaction. We show that numerical simulations help characterize the micromechanics of fault mechanics.

  6. Pattern Recognition of Signals for the Fault-Slip Type of Rock Burst in Coal Mines

    Directory of Open Access Journals (Sweden)

    X. S. Liu

    2015-01-01

    Full Text Available The fault-slip type of rock burst is a major threat to the safety of coal mining, and effectively recognizing its signals patterns is the foundation for the early warning and prevention. At first, a mechanical model of the fault-slip was established and the mechanism of the rock burst induced by the fault-slip was revealed. Then, the patterns of the electromagnetic radiation, acoustic emission (AE, and microseismic signals in the fault-slip type of rock burst were proposed, in that before the rock burst occurs, the electromagnetic radiation intensity near the sliding surface increases rapidly, the AE energy rises exponentially, and the energy released by microseismic events experiences at least one peak and is close to the next peak. At last, in situ investigations were performed at number 1412 coal face in the Huafeng Mine, China. Results showed that the signals patterns proposed are in good agreement with the process of the fault-slip type of rock burst. The pattern recognition can provide a basis for the early warning and the implementation of relief measures of the fault-slip type of rock burst.

  7. Why Sociology Is Silent Concerning Borders

    Directory of Open Access Journals (Sweden)

    S.E. Nikolov

    2015-08-01

    Full Text Available Border in sociological sense means a barrier that separates social groups, strata, their values, and the difference between ways of life between particular social groups. Such groups may be separated by many dividing lines, or borders: social/living conditions, opportunities/prospects, legal rights/customs, viewpoints, and so on. Sometimes mobility does not permit other than individual, or small-group, crossing of these borders. It seems really strange why border topic is almost completely absent from the sociology. It is so pertinent to the fate and shaping of various social groups, depending from the location of the border. We think of a boundary whenever we think of an entity demarcated from its surroundings. Events, too, have boundaries – temporal ones: their beginning, climax, final. All our lives are bounded in the continuum between our births and our deaths. A philosopher would imply also that even imaginary, abstract entities, such as concepts or layouts, have boundaries of their own. One may say that condition for all this boundary/border talk is coherent, and whether it reproduces the world around us’ structure, or the organizing activity of our intellect, are matters of deep philosophical controversy. Borders are difficult to disappear totally even within the European Union, providing some obstacles to the freedom of movement to those left still outside the Schengen agreement.

  8. Anamnesis and the Silent Narrator in Plato and John

    Directory of Open Access Journals (Sweden)

    George L. Parsenios

    2017-03-01

    Full Text Available The Gospel of John is often compared to the dialogues of Plato by those who connect Johannine theology and Platonic philosophy. The comparison operates on the level of ideas. The present paper does not ignore issues of theology and philosophy but grounds a comparison of John and Plato first and foremost on the literary level. In several key places in John 1, 3, and 14, the Johannine narrator recedes from view and is unexpectedly silent where one would expect a narrator’s comment to organize the conversations and interactions between characters in John. Plato also renders the voice of the narrator silent in a dialogue like the Theaetetus. This paper argues that John and Plato both suppress the narrator’s voice in order to further their anamnetic efforts and to make later generations not only readers but participants in their original conversations.

  9. Velocities of dislocation groups in very thin neutron-irradiated copper single crystals measured by slip line cinematography

    Energy Technology Data Exchange (ETDEWEB)

    Potthoff, H.H. (Technische Univ. Braunschweig (Germany, F.R.). Inst. fuer Metallphysik und Nukleare Festkoerperphysik)

    1983-05-16

    Slip line development on very thin flat single crystals of neutron-irradiated Cu (thickness down to only 15 to 20 ..mu..m, orientation for single glide, yield region, room temperature) is recorded by high-speed cinematography during tensile deformation. In such very thin crystals glide dislocations on the slip plane must be arranged in a rather simple way. Drops in tensile load occuring during initiation of single slip lines at the Lueders band front indicate that in the beginning of a slip line development dislocation groups traverse the whole glide plane in very short times. Evaluating the data measured for the slip line growth v/sub s/ >= 10 cm/s is found for screw dislocations and v/sub e/ >= v/sub s/ for edge dislocations. For later stages on thin crystals and for all stages on thick crystals (>= several 100 ..mu..m) slip line development is much slower and slip line show many cross slip events which then appear to control the mean velocity of the dislocations.

  10. Velocities of dislocation groups in very thin neutron-irradiated copper single crystals measured by slip line cinematography

    International Nuclear Information System (INIS)

    Potthoff, H.H.

    1983-01-01

    Slip line development on very thin flat single crystals of neutron-irradiated Cu (thickness down to only 15 to 20 μm, orientation for single glide, yield region, room temperature) is recorded by high-speed cinematography during tensile deformation. In such very thin crystals glide dislocations on the slip plane must be arranged in a rather simple way. Drops in tensile load occuring during initiation of single slip lines at the Lueders band front indicate that in the beginning of a slip line development dislocation groups traverse the whole glide plane in very short times. Evaluating the data measured for the slip line growth v/sub s/ >= 10 cm/s is found for screw dislocations and v/sub e/ >= v/sub s/ for edge dislocations. For later stages on thin crystals and for all stages on thick crystals (>= several 100 μm) slip line development is much slower and slip line show many cross slip events which then appear to control the mean velocity of the dislocations. (author)

  11. Silent Warning: Understanding the National Terrorism Advisory System

    Science.gov (United States)

    2014-12-01

    NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release; distribution is unlimited SILENT WARNING...PERFORMING OR GANIZATION NA:i\\ti E (S) AND ADDRESS(ES) Naval Postgraduate School Monterey, CA 93943-5000 9. SP ONSORING /MONIT ORING AGENCY NAME(S) AND...Homeland Sectu’ity Advisory System, Boston Marathon bombing, Christmas Day bomber, tmderwear bomber, hum cane , cotmteiteiTO!’ism, CT AB

  12. Incidence and implications of silent hydronephrosis following percutaneous nephrolithotomy
.

    Science.gov (United States)

    Dagrosa, Lawrence; Moses, Rachel; Pais, Vernon M

    2017-01-01

    While routine renal imaging following ureteroscopy for urinary calculi has been recommended to screen for asymptomatic "silent" obstruction, the rate of silent obstruction following percutaneous nephrolithotomy (PCNL) remains poorly defined, and no consensus recommendations exist on routine postoperative imaging. At our institution, we sought to assess the incidence of silent hydronephrosis (SH), as a screen for obstruction, following PCNL. The records of all 162 patients who met study inclusion criteria were reviewed. Of this group, 112 patients presented for their scheduled renal ultrasonography 4 - 6 weeks following stent removal to screen for SH. Asymptomatic patients found to have ultrasonographic evidence of hydronephrosis were further analyzed. SH was noted in 16% (18/112) of patients. Two required subsequent ureteroscopic stone extraction (1.8%), one of which also underwent endoureterotomy for a ureteral stricture. Four patients (22%) had stable hydronephrosis and declined functional imaging, 2 patients (11%) had a known partial ureteropelvic junction obstruction and declined intervention. SH resolved spontaneously in 50% (9/18) with a mean time to resolution of 6.3 months. There was no difference in stone complexity based on Guy's stone score between groups, 2.8 (± 0.92) vs. 2.4 (± 1.03), p = 0.34. Although not statistically significant, patients with SH were more likely to have had residual stone fragments postoperatively, 39% (7/18) vs. 19% (18/94), p = 0.067. SH following, PCNL was identified in 16% of this screened population, with the majority requiring no intervention. However, SH may be attributed to residual stone or stricture, which may have been otherwise unrecognized in up to 2% of patients undergoing PCNL. Consideration should be given for routine postoperative ultrasound to screen for silent obstruction following PCNL.
.

  13. Analytical approximations for stick-slip vibration amplitudes

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel; Fidlin, A.

    2003-01-01

    , the amplitudes, and the base frequencies of friction-induced stick¿slip and pure-slip oscillations. For stick¿slip oscillations, this is accomplished by using perturbation analysis for the finite time interval of the stick phase, which is linked to the subsequent slip phase through conditions of continuity...

  14. Prevalence of silent gastrointestinal complications in maintenance renal transplant population

    Directory of Open Access Journals (Sweden)

    Teplitsky Susan

    2010-01-01

    Full Text Available This study aims to determine the prevalence of silent GI complications within a stable renal transplant population and to investigate whether the conversion to enteric-coated myco-phenolate sodium (EC-MPS, Myfortic; would improve symptom scores. This was a single-center, open-label, non-randomized, prospective study. Patients without any history of GI com-plaints were evaluated by means of the gastrointestinal symptom rating scale (GSRS, with subse-quent switch to EC-MPS in a group of patients. Silent complications were defined as patients who voiced no GI complaints at clinic visits despite a score of ≥ 2 on GSRS scale. A total of 236 stable patients participated in the trial. The prevalence of baseline scores ≥ 2 was relatively high with abdominal pain 29.66%, reflux 37.28%, indigestion 50%, constipation 58.47% and diarrhea 33.4%. Of 236 patients, 80 were converted to EC-MPS. There was statistically significant improvement on all scales in the subgroup of patients with GSRS score ≥ 2 (P< 0.05. In conclusion, the GSRS scale identified a high percentage of silent gastrointestinal complications in this renal transplant population. The converted patients with higher GSRS scores reported a sustained improvement.

  15. Assessing reading fluency in Kenya: Oral or silent assessment?

    Science.gov (United States)

    Piper, Benjamin; Zuilkowski, Stephanie Simmons

    2015-04-01

    In recent years, the Education for All movement has focused more intensely on the quality of education, rather than simply provision. Many recent and current education quality interventions focus on literacy, which is the core skill required for further academic success. Despite this focus on the quality of literacy instruction in developing countries, little rigorous research has been conducted on critical issues of assessment. This analysis, which uses data from the Primary Math and Reading Initiative (PRIMR) in Kenya, aims to begin filling this gap by addressing a key assessment issue - should literacy assessments in Kenya be administered orally or silently? The authors compared second-grade students' scores on oral and silent reading tasks of the Early Grade Reading Assessment (EGRA) in Kiswahili and English, and found no statistically significant differences in either language. They did, however, find oral reading rates to be more strongly related to reading comprehension scores. Oral assessment has another benefit for programme evaluators - it allows for the collection of data on student errors, and therefore the calculation of words read correctly per minute, as opposed to simply words read per minute. The authors therefore recommend that, in Kenya and in similar contexts, student reading fluency be assessed via oral rather than silent assessment.

  16. Rape Survivors' Experiences of the Silent Protest: Implications for Promoting Healing and Resilience.

    Science.gov (United States)

    Padmanabhanunni, Anita; Edwards, David

    2016-05-01

    This article examines the experiences of nine rape survivors who participated in the Silent Protest, an annual protest march at Rhodes University that aims to highlight the sexual abuse of women, validate the harm done, and foster solidarity among survivors. Participants responded to a semi-structured interview focusing on the context of their rape and its impact, and their experiences of participation in the Protest In the first phase of data analysis, synoptic case narratives were written. In the second, themes from participants' experience were identified using interpretative phenomenological analysis. In the third, the data were examined in light of questions around the extent to which participation contributed to healing. Participants reported experiences of validation and empowerment but the majority were suffering from posttraumatic stress disorder. In some cases, participation had exacerbated self-blame and avoidant coping. Recommendations are made about the provision of psychoeducation and counseling at such events. © The Author(s) 2015.

  17. Seismic potential of weak, near-surface faults revealed at plate tectonic slip rates.

    Science.gov (United States)

    Ikari, Matt J; Kopf, Achim J

    2017-11-01

    The near-surface areas of major faults commonly contain weak, phyllosilicate minerals, which, based on laboratory friction measurements, are assumed to creep stably. However, it is now known that shallow faults can experience tens of meters of earthquake slip and also host slow and transient slip events. Laboratory experiments are generally performed at least two orders of magnitude faster than plate tectonic speeds, which are the natural driving conditions for major faults; the absence of experimental data for natural driving rates represents a critical knowledge gap. We use laboratory friction experiments on natural fault zone samples at driving rates of centimeters per year to demonstrate that there is abundant evidence of unstable slip behavior that was not previously predicted. Specifically, weak clay-rich fault samples generate slow slip events (SSEs) and have frictional properties favorable for earthquake rupture. Our work explains growing field observations of shallow SSE and surface-breaking earthquake slip, and predicts that such phenomena should be more widely expected.

  18. Differences in autonomic nerve function in patients with silent and symptomatic myocardial ischaemia.

    Science.gov (United States)

    Shakespeare, C. F.; Katritsis, D.; Crowther, A.; Cooper, I. C.; Coltart, J. D.; Webb-Peploe, M. W.

    1994-01-01

    BACKGROUND--Autonomic neuropathy provides a mechanism for the absence of symptoms in silent myocardial ischaemia, but characterisation of the type of neuropathy is lacking. AIM--To characterise and compare autonomic nerve function in patients with silent and symptomatic myocardial ischaemia. METHODS AND RESULTS--The Valsalva manoeuvre, heart rate variation (HRV) in response to deep breathing and standing, lower body negative pressure, isometric handgrip, and the cold pressor test were performed by patients with silent (n = 25) and symptomatic (n = 25) ambulatory ischaemia and by controls (n = 21). No difference in parasympathetic efferent function between patients with silent and symptomatic ischaemia was recorded, but both had significantly less HRV in response to standing than the controls (p < 0.005 for silent and p < 0.01 for symptomatic). Patients with silent ischaemia showed an increased propensity for peripheral vasodilatation compared with symptomatic patients (p < 0.02) and controls (p < 0.04). Impaired sympathetic function was found in patients with pure silent ischaemia (n = 4) compared with the remaining patients with silent ischaemia whose pain pathways were presumed to be intact. CONCLUSIONS--Patients with silent ischaemia and pain pathways presumed to be intact have an enhanced peripheral vasodilator response, and if this applied to the coronary vasculature it could provide a mechanism for limiting ischaemia to below the pain threshold. Patients with pure silent ischaemia have evidence of sympathetic autonomic dysfunction. Images PMID:8297687

  19. Magnetic resonance imaging at primary diagnosis cannot predict subsequent contralateral slip in slipped capital femoral epiphysis

    Energy Technology Data Exchange (ETDEWEB)

    Wensaas, Anders [Akershus University Hospital, Department of Orthopaedic Surgery, Loerenskog (Norway); Wiig, Ola; Terjesen, Terje [Oslo University Hospital, Department of Orthopaedic Surgery, Rikshospitalet (Norway); Castberg Hellund, Johan; Khoshnewiszadeh, Behzad [Oslo University Hospital, Department of Radiology and Nuclear Medicine, Ullevaal (Norway)

    2017-12-15

    Prophylactic fixation of the contralateral hip in slipped capital femoral epiphysis (SCFE) is controversial, and no reliable method has been established to predict subsequent contralateral slip. The main purpose of this study was to evaluate if magnetic resonance imaging (MRI) performed at primary diagnosis could predict future contralateral slip. Twenty-two patients with unilateral SCFE were included, all had MRI of both hips taken before operative fixation. Six different parameters were measured on the MRI: the MRI slip angle, the greatest focal widening of the physis, the global widening of the physis measured at three locations (the midpoint of the physis and 1 cm lateral and medial to the midpoint), periphyseal (epiphyseal and metaphyseal) bone marrow edema, the presence of pathological joint effusion, and the amount of joint effusion measured from the lateral edge of the greater trochanter. Mean follow-up was 33 months (range, 16-63 months). Six patients were treated for contralateral slip during the follow-up time and a comparison of the MRI parameters of the contralateral hip in these six patients and in the 16 patients that remained unilateral was done to see if subsequent contralateral slip was possible to predict at primary diagnosis. All MRI parameters were significantly altered in hips with established SCFE compared with the contralateral hips. However, none of the MRI parameters showed any significant difference between patients who had a subsequent contralateral slip and those that remained unilateral. MRI taken at primary diagnosis could not predict future contralateral slip. (orig.)

  20. The prevention of slipping accidents: a review and discussion of work related to the methodology of measuring slip resistance

    OpenAIRE

    Leclercq , Sylvie

    1999-01-01

    International audience; The recommendations made after the analysis of accidents following an incident of slipping often include the use of anti-slip footwear and/or the installation of an anti-slip floor covering. Such recommendations make it necessary to study biomechanical and tribologic phenomena that occur during slipping, in particular in order to develop criteria for the evaluation of the slip resistance of footwear and floor surfaces. Consequently, research which deals with the preven...

  1. Seismic wave triggering of nonvolcanic tremor, episodic tremor and slip, and earthquakes on Vancouver Island

    Science.gov (United States)

    Rubinstein, Justin L.; Gomberg, Joan; Vidale, John E.; Wech, Aaron G.; Kao, Honn; Creager, Kenneth C.; Rogers, Garry

    2009-02-01

    We explore the physical conditions that enable triggering of nonvolcanic tremor and earthquakes by considering local seismic activity on Vancouver Island, British Columbia during and immediately after the arrival of large-amplitude seismic waves from 30 teleseismic and 17 regional or local earthquakes. We identify tremor triggered by four of the teleseismic earthquakes. The close temporal and spatial proximity of triggered tremor to ambient tremor and aseismic slip indicates that when a fault is close to or undergoing failure, it is particularly susceptible to triggering of further events. The amplitude of the triggering waves also influences the likelihood of triggering both tremor and earthquakes such that large amplitude waves triggered tremor in the absence of detectable aseismic slip or ambient tremor. Tremor and energy radiated from regional/local earthquakes share the same frequency passband so that tremor cannot be identified during these smaller, more frequent events. We confidently identify triggered local earthquakes following only one teleseism, that with the largest amplitude, and four regional or local events that generated vigorous aftershock sequences in their immediate vicinity. Earthquakes tend to be triggered in regions different from tremor and with high ambient seismicity rates. We also note an interesting possible correlation between large teleseismic events and episodic tremor and slip (ETS) episodes, whereby ETS events that are "late" and have built up more stress than normal are susceptible to triggering by the slight nudge of the shaking from a large, distant event, while ETS events that are "early" or "on time" are not.

  2. Asymmetrical slip propensity: required coefficient of friction.

    Science.gov (United States)

    Seo, Jung-suk; Kim, Sukwon

    2013-07-31

    Most studies in performing slips and falls research reported their results after the ipsilateral leg of subjects (either right foot or left foot) was guided to contact the contaminated floor surface although many studies indicated concerns for asymmetries of legs in kinematic or kinetic variables. Thus, the present study evaluated if dominant leg's slip tendency would be different from non-dominant leg's slip tendency by comparing the Required Coefficient of Friction (RCOF) of the two lower limbs. Forty seven health adults participated in the present study. RCOF was measured when left or right foot of subjects contacted the force platforms respectively. Paired t-test was performed to test if RCOF and heel velocity (HCV) of dominant legs was different from that of non-dominant legs. It was suggested that the asymmetry in RCOFs and HCV between the two lower limbs existed. The RCOFs of non-dominant legs were higher than that of dominant legs. The results indicated that asymmetry in slip propensity, RCOF, was existed in lower extremity. The results from the study suggested that it would be benefit to include a variable, such as asymmetry, in slips and falls research.

  3. Slip patterns and preferred dislocation boundary planes

    DEFF Research Database (Denmark)

    Winther, G.

    2003-01-01

    The planes of deformation induced extended planar dislocation boundaries are analysed in two different co-ordinate systems, namely the macroscopic system defined by the deformation axes and the crystallographic system given by the crystallographic lattice. The analysis covers single and polycryst......The planes of deformation induced extended planar dislocation boundaries are analysed in two different co-ordinate systems, namely the macroscopic system defined by the deformation axes and the crystallographic system given by the crystallographic lattice. The analysis covers single...... and polycrystals of fcc metals in three deformation modes (rolling, tension and torsion). In the macroscopic system, boundaries lie close to the macroscopically most stressed planes. In the crystallographic system, the boundary plane depends on the grain/crystal orientation. The boundary planes in both co......-ordinate systems are rationalised based on the slip. The more the slip is concentrated on a slip plane, the closer the boundaries lie to this. The macroscopic preference arises from the macroscopic directionality of the slip. The established relations are applied to (a) prediction of boundary planes from slip...

  4. Interseismic Coupling, Co- and Post-seismic Slip: a Stochastic View on the Northern Chilean Subduction Zone

    Science.gov (United States)

    Jolivet, R.; Duputel, Z.; Simons, M.; Jiang, J.; Riel, B. V.; Moore, A. W.; Owen, S. E.

    2017-12-01

    Mapping subsurface fault slip during the different phases of the seismic cycle provides a probe of the mechanical properties and the state of stress along these faults. We focus on the northern Chile megathrust where first order estimates of interseismic fault locking suggests little to no overlap between regions slipping seismically versus those that are dominantly aseismic. However, published distributions of slip, be they during seismic or aseismic phases, rely on unphysical regularization of the inverse problem, thereby cluttering attempts to quantify the degree of overlap between seismic and aseismic slip. Considering all the implications of aseismic slip on our understanding of the nucleation, propagation and arrest of seismic ruptures, it is of utmost importance to quantify our confidence in the current description of fault coupling. Here, we take advantage of 20 years of InSAR observations and more than a decade of GPS measurements to derive probabilistic maps of inter-seismic coupling, as well as co-seismic and post-seismic slip along the northern Chile subduction megathrust. A wide InSAR velocity map is derived using a novel multi-pixel time series analysis method accounting for orbital errors, atmospheric noise and ground deformation. We use AlTar, a massively parallel Monte Carlo Markov Chain algorithm exploiting the acceleration capabilities of Graphic Processing Units, to derive the probability density functions (PDF) of slip. In northern Chile, we find high probabilities for a complete release of the elastic strain accumulated since the 1877 earthquake by the 2014, Iquique earthquake and for the presence of a large, independent, locked asperity left untapped by recent events, north of the Mejillones peninsula. We evaluate the probability of overlap between the co-, inter- and post-seismic slip and consider the potential occurrence of slow, aseismic slip events along this portion of the subduction zone.

  5. Quantifying slip balance in the earthquake cycle: Coseismic slip model constrained by interseismic coupling

    KAUST Repository

    Wang, Lifeng

    2015-11-11

    The long-term slip on faults has to follow, on average, the plate motion, while slip deficit is accumulated over shorter time scales (e.g., between the large earthquakes). Accumulated slip deficits eventually have to be released by earthquakes and aseismic processes. In this study, we propose a new inversion approach for coseismic slip, taking interseismic slip deficit as prior information. We assume a linear correlation between coseismic slip and interseismic slip deficit, and invert for the coefficients that link the coseismic displacements to the required strain accumulation time and seismic release level of the earthquake. We apply our approach to the 2011 M9 Tohoku-Oki earthquake and the 2004 M6 Parkfield earthquake. Under the assumption that the largest slip almost fully releases the local strain (as indicated by borehole measurements, Lin et al., 2013), our results suggest that the strain accumulated along the Tohoku-Oki earthquake segment has been almost fully released during the 2011 M9 rupture. The remaining slip deficit can be attributed to the postseismic processes. Similar conclusions can be drawn for the 2004 M6 Parkfield earthquake. We also estimate the required time of strain accumulation for the 2004 M6 Parkfield earthquake to be ~25 years (confidence interval of [17, 43] years), consistent with the observed average recurrence time of ~22 years for M6 earthquakes in Parkfield. For the Tohoku-Oki earthquake, we estimate the recurrence time of~500-700 years. This new inversion approach for evaluating slip balance can be generally applied to any earthquake for which dense geodetic measurements are available.

  6. Quantifying slip balance in the earthquake cycle: Coseismic slip model constrained by interseismic coupling

    KAUST Repository

    Wang, Lifeng; Hainzl, Sebastian; Mai, Paul Martin

    2015-01-01

    The long-term slip on faults has to follow, on average, the plate motion, while slip deficit is accumulated over shorter time scales (e.g., between the large earthquakes). Accumulated slip deficits eventually have to be released by earthquakes and aseismic processes. In this study, we propose a new inversion approach for coseismic slip, taking interseismic slip deficit as prior information. We assume a linear correlation between coseismic slip and interseismic slip deficit, and invert for the coefficients that link the coseismic displacements to the required strain accumulation time and seismic release level of the earthquake. We apply our approach to the 2011 M9 Tohoku-Oki earthquake and the 2004 M6 Parkfield earthquake. Under the assumption that the largest slip almost fully releases the local strain (as indicated by borehole measurements, Lin et al., 2013), our results suggest that the strain accumulated along the Tohoku-Oki earthquake segment has been almost fully released during the 2011 M9 rupture. The remaining slip deficit can be attributed to the postseismic processes. Similar conclusions can be drawn for the 2004 M6 Parkfield earthquake. We also estimate the required time of strain accumulation for the 2004 M6 Parkfield earthquake to be ~25 years (confidence interval of [17, 43] years), consistent with the observed average recurrence time of ~22 years for M6 earthquakes in Parkfield. For the Tohoku-Oki earthquake, we estimate the recurrence time of~500-700 years. This new inversion approach for evaluating slip balance can be generally applied to any earthquake for which dense geodetic measurements are available.

  7. Silent pituitary macroadenoma co-secreting growth hormone and thyroid stimulating hormone.

    Science.gov (United States)

    Sen, Orhan; Ertorer, M Eda; Aydin, M Volkan; Erdogan, Bulent; Altinors, Nur; Zorludemir, Suzan; Guvener, Nilgun

    2005-04-01

    Silent pituitary adenomas are a group of tumors showing heterogenous morphological features with no hormonal function observed clinically. To date no explanation has been provided as to why these tumors remain "silent". We report a case of a silent macroadenoma with both growth hormone (GH) and thyroid stimulating hormone (TSH) staining and secretion but with no clinical manifestations, in particular, the absence of features of acromegaly or hyperthyroidism. The relevant literature is reviewed.

  8. Using an Earthquake Simulator to Model Tremor Along a Strike Slip Fault

    Science.gov (United States)

    Cochran, E. S.; Richards-Dinger, K. B.; Kroll, K.; Harrington, R. M.; Dieterich, J. H.

    2013-12-01

    We employ the earthquake simulator, RSQSim, to investigate the conditions under which tremor occurs in the transition zone of the San Andreas fault. RSQSim is a computationally efficient method that uses rate- and state- dependent friction to simulate a wide range of event sizes for long time histories of slip [Dieterich and Richards-Dinger, 2010; Richards-Dinger and Dieterich, 2012]. RSQSim has been previously used to investigate slow slip events in Cascadia [Colella et al., 2011; 2012]. Earthquakes, tremor, slow slip, and creep occurrence are primarily controlled by the rate and state constants a and b and slip speed. We will report the preliminary results of using RSQSim to vary fault frictional properties in order to better understand rupture dynamics in the transition zone using observed characteristics of tremor along the San Andreas fault. Recent studies of tremor along the San Andreas fault provide information on tremor characteristics including precise locations, peak amplitudes, duration of tremor episodes, and tremor migration. We use these observations to constrain numerical simulations that examine the slip conditions in the transition zone of the San Andreas Fault. Here, we use the earthquake simulator, RSQSim, to conduct multi-event simulations of tremor for a strike slip fault modeled on Cholame section of the San Andreas fault. Tremor was first observed on the San Andreas fault near Cholame, California near the southern edge of the 2004 Parkfield rupture [Nadeau and Dolenc, 2005]. Since then, tremor has been observed across a 150 km section of the San Andreas with depths between 16-28 km and peak amplitudes that vary by a factor of 7 [Shelly and Hardebeck, 2010]. Tremor episodes, comprised of multiple low frequency earthquakes (LFEs), tend to be relatively short, lasting tens of seconds to as long as 1-2 hours [Horstmann et al., in review, 2013]; tremor occurs regularly with some tremor observed almost daily [Shelly and Hardebeck, 2010; Horstmann

  9. A geodetic matched filter search for slow slip with application to the Mexico subduction zone

    Science.gov (United States)

    Rousset, B.; Campillo, M.; Lasserre, C.; Frank, W. B.; Cotte, N.; Walpersdorf, A.; Socquet, A.; Kostoglodov, V.

    2017-12-01

    Since the discovery of slow slip events, many methods have been successfully applied to model obvious transient events in geodetic time series, such as the widely used network strain filter. Independent seismological observations of tremors or low-frequency earthquakes and repeating earthquakes provide evidence of low-amplitude slow deformation but do not always coincide with clear occurrences of transient signals in geodetic time series. Here we aim to extract the signal corresponding to slow slips hidden in the noise of GPS time series, without using information from independent data sets. We first build a library of synthetic slow slip event templates by assembling a source function with Green's functions for a discretized fault. We then correlate the templates with postprocessed GPS time series. Once the events have been detected in time, we estimate their duration T and magnitude Mw by modeling a weighted stack of GPS time series. An analysis of synthetic time series shows that this method is able to resolve the correct timing, location, T, and Mw of events larger than Mw 6 in the context of the Mexico subduction zone. Applied on a real data set of 29 GPS time series in the Guerrero area from 2005 to 2014, this technique allows us to detect 28 transient events from Mw 6.3 to 7.2 with durations that range from 3 to 39 days. These events have a dominant recurrence time of 40 days and are mainly located at the downdip edges of the Mw>7.5 slow slip events.

  10. Modeling and Analyzing the Slipping of the Ball Screw

    Directory of Open Access Journals (Sweden)

    Nannan Xu

    Full Text Available AbstractThis paper aims to set up the ball systematic slipping model and analyze the slipping characteristics caused by different factors for a ball screw operating at high speeds. To investigate the ball screw slipping mechanism, transformed coordinate system should be established firstly. Then it is used to set up mathematical modeling for the ball slipping caused by the three main reasons and the speed of slipping can be calculated. Later, the influence of the contact angle, helix angle and screw diameter for ball screw slipping will be analyzed according to the ball slipping model and slipping speeds equation and the slipping analysis will be obtained. Finally, curve of slipping analysis and that of mechanical efficiency of the ball screw analysis by Lin are compared, which will indirectly verify the correctness of the slipping model. The slipping model and the curve of slipping analysis established in this paper will provide theory basis for reducing slipping and improving the mechanical efficiency of a ball screw operating at high speeds.

  11. Tremor-genic slow slip regions may be deeper and warmer and may slip slower than non-tremor-genic regions

    Science.gov (United States)

    Montgomery-Brown, Emily; Syracuse, Ellen M.

    2015-01-01

    Slow slip events (SSEs) are observed worldwide and often coincide with tectonic tremor. Notable examples of SSEs lacking observed tectonic tremor, however, occur beneath Kīlauea Volcano, Hawaii, the Boso Peninsula, Japan, near San Juan Bautista on the San Andreas Fault, California, and recently in Central Ecuador. These SSEs are similar to other worldwide SSEs in many ways (e.g., size or duration), but lack the concurrent tectonic tremor observed elsewhere; instead, they trigger swarms of regular earthquakes. We investigate the physical conditions that may distinguish these non-tremor-genic SSEs from those associated with tectonic tremor, including slip velocity, pressure, temperature, fluids, and fault asperities, although we cannot eliminate the possibility that tectonic tremor may be obscured in highly attenuating regions. Slip velocities of SSEs at Kīlauea Volcano (∼10−6 m/s) and Boso Peninsula (∼10−7 m/s) are among the fastest SSEs worldwide. Kīlauea Volcano, the Boso Peninsula, and Central Ecuador are also among the shallowest SSEs worldwide, and thus have lower confining pressures and cooler temperatures in their respective slow slip zones. Fluids also likely contribute to tremor generation, and no corresponding zone of high vp/vs has been noted at Kīlauea or Boso. We suggest that the relatively faster slip velocities at Kīlauea Volcano and the Boso Peninsula result from specific physical conditions that may also be responsible for triggering swarms of regular earthquakes adjacent to the slow slip, while different conditions produce slower SSE velocities elsewhere and trigger tectonic tremor.

  12. Slipping slender bodies and enhanced flagellar locomotion

    Science.gov (United States)

    Man, Yi; Lauga, Eric

    2017-11-01

    In the biological world, many cells exploit slender appendages to swim, include numerous species of bacteria, algae and spermatozoa. A classical method to describe the flow field around such appendages is slender-body theory (SBT), which is often used to study flagellar motility in Newtonian fluids. However, biology environments are often rheologically complex due to the presence of polymers. These polymers generically phase-separate near rigid boundaries where low-viscosity fluid layers lead to effective slip on the surface. In this talk, we present an analytical derivation of SBT in the case where the no-slip boundary condition on the appendage is replaced by a Navier slip boundary condition. Our results demonstrate in particular a systematic reduction of the resistance coefficient of the slender filaments in their tangential direction, which leads to enhanced flagellar locomotion.

  13. Frictional processes in smectite-rich gouges sheared at slow to high slip rates

    Science.gov (United States)

    Aretusini, Stefano; Mittempergher, Silvia; Gualtieri, Alessandro; Di Toro, Giulio

    2015-04-01

    The slipping zones of shallow sections of megathrusts and of large landslides are often smectite-rich (e.g., montmorillonite type). Consequently, similar "frictional" processes operating at high slip rates (> 1 m/s) might be responsible of the large slips estimated in megathrust (50 m for the 2011 Tohoku Mw 9.1 earthquake) and measured in large landslides (500 m for the 1963 Vajont slide, Italy). At present, only rotary shear apparatuses can reproduce simultaneously the large slips and slip rates of these events. Noteworthy, the frictional processes proposed so far (thermal and thermochemical pressurization, etc.) remain rather obscure. Here we present preliminary results obtained with the ROtary Shear Apparatus (ROSA) installed at Padua University. Thirty-one experiments were performed at ambient conditions on pure end-members of (1) smectite-rich standard powders (STx-1b: ~68 wt% Ca-montmorillonite, ~30 wt% opal-CT and ~2 wt% quartz), (2) quartz powders (qtz) and (3) on 80:20 = Stx-1b:qtz mixtures. The gouges were sandwiched between two (1) hollow (25/15 mm external/internal diameter) or (2) solid (25 mm in diameter) stainless-steel made cylinders and confined by inner and outer Teflon rings (only outer for solid cylinders). Gouges were sheared at a normal stress of 5 MPa, slip rates V from 300 μm/s to 1.5 m/s and total slip of 3 m. The deformed gouges were investigated with quantitative (Rietveld method with internal standard) X-ray powder diffraction (XRPD) and Scanning Electron Microscopy (SEM). In the smectite-rich standard endmember, (1) for 300 μm/s ≤ V ≤ 0.1 m/s, initial friction coefficient (μi) was 0.6±0.05 whereas the steady-state friction coefficient (μss) was velocity and slip strengthening (μss 0.85±0.05), (2) for 0.1 m/s 0.8 m/s, velocity and slip weakening (μi = 0.7±0.1 and μss = 0.25±0.05). In the 80:20 Stx-1b:qtz mixtures, (1) for 300 μm/s ≤ V ≤ 0.1 m/s, μi ranged was 0.7±0.05 and increased with slip to μss = 0.77±0

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

    Science.gov (United States)

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

    2012-12-01

    The lack of clear geological markers of seismic faulting represents a major limitation in our current comprehension of earthquake physics. At present pseudotachylytes (i.e. friction-induced melts) are the only unambiguously identified indicator of ancient seismicity in exhumed fault zones, but pseudotachylytes are not found in many rock types, including carbonates. We report the occurrence of small-displacement, mirror-like slip surfaces from a fault zone cutting dolostones. A combination of field observations and rotary shear friction experiments suggests that such slip surfaces: 1) are formed only at seismic slip rates, and 2) could potentially be used to estimate power dissipation during individual slip events. The Foiana Line (FL) is a major NNE-SSW-trending sinistral transpressive fault in the Italian Southern Alps. The outcropping fault zone consists of a rotary-shear experiments using SHIVA (INGV, Rome) were performed on 3 mm thick layers of dolomite gouge (grain size friction coefficient (μ) from a peak value of ~0.7 to a steady-state value of ~0.25. The gouge starts to weaken above a threshold velocity in the range 0.19-0.49 m/s following a 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

  15. The influence of testing apparatus stiffness on the source properties of laboratory stick-slip

    Science.gov (United States)

    Kilgore, B. D.; McGarr, A.; Beeler, N. M.; Lockner, D. A.

    2016-12-01

    Stick-slip experiments were performed to determine the influence of the testing apparatus stiffness on source properties, to develop methods to relate stick-slip to natural earthquakes, and to examine the hypothesis of McGarr [2012] that the product of unloading stiffness, k, and slip duration, T, is both scale-independent and approximately constant for both laboratory and natural earthquakes. A double-direct shear load frame was used with Sierra White Granite samples at 2 MPa normal stress, and a remote loading rate of 0.2 µm/s. The stiffness of the test apparatus was varied by more than an order of magnitude by inserting disk springs into the shear loading column adjacent to the granite samples. Servo-controlling slip at a point between the forcing ram and the shear force load cell, produced repeatable slip events. Slip and slip duration decrease as k increases, as they do for natural earthquakes. In contrast to earthquakes, stress drop and slip rate decrease with increasing k, and the product kT for these experiments is not constant, but decreases with k. These data, collected over a range of k, do not conform to McGarr's [2012] hypothesis. However, analysis of stick-slip studies from other testing apparatuses is consistent with McGarr's hypothesis; kT is scale-independent, similar to that of earthquakes, equal to the ratio of static stress drop to average slip velocity, and similar to the ratio of shear modulus to wavespeed of rock. These properties result from conducting experiments over a range of sample sizes, using rock samples with the same elastic properties as the Earth, and using testing machines whose stiffnesses decrease, and characteristic periods increase with scale. A consequence of our experiments and analysis is that extrapolation of lab scale earthquake source properties to the Earth is more difficult than previously thought, requiring an accounting for the properties of the testing machines and additional research beyond that reported here.

  16. Vaporization of fault water during seismic slip

    Science.gov (United States)

    Chen, Jianye; Niemeijer, André R.; Fokker, Peter A.

    2017-06-01

    Laboratory and numerical studies, as well as field observations, indicate that phase transitions of pore water might be an important process in large earthquakes. We present a model of the thermo-hydro-chemo-mechanical processes, including a two-phase mixture model to incorporate the phase transitions of pore water, occurring during fast slip (i.e., a natural earthquake) in order to investigate the effects of vaporization on the coseismic slip. Using parameters from typical natural faults, our modeling shows that vaporization can indeed occur at the shallow depths of an earthquake, irrespective of the wide variability of the parameters involved (sliding velocity, friction coefficient, gouge permeability and porosity, and shear-induced dilatancy). Due to the fast kinetics, water vaporization can cause a rapid slip weakening even when the hydrological conditions of the fault zone are not favorable for thermal pressurization, e.g., when permeability is high. At the same time, the latent heat associated with the phase transition causes the temperature rise in the slip zone to be buffered. Our parametric analyses reveal that the amount of frictional work is the principal factor controlling the onset and activity of vaporization and that it can easily be achieved in earthquakes. Our study shows that coseismic pore fluid vaporization might have played important roles at shallow depths of large earthquakes by enhancing slip weakening and buffering the temperature rise. The combined effects may provide an alternative explanation for the fact that low-temperature anomalies were measured in the slip zones at shallow depths of large earthquakes.

  17. The Rachel Carson Letters and the Making of Silent Spring

    Directory of Open Access Journals (Sweden)

    John Paull

    2013-06-01

    Full Text Available Environment, conservation, green, and kindred movements look back to Rachel Carson’s 1962 book Silent Spring as a milestone. The impact of the book, including on government, industry, and civil society, was immediate and substantial, and has been extensively described; however, the provenance of the book has been less thoroughly examined. Using Carson’s personal correspondence, this paper reveals that the primary source for Carson’s book was the extensive evidence and contacts compiled by two biodynamic farmers, Marjorie Spock and Mary T. Richards, of Long Island, New York. Their evidence was compiled for a suite of legal actions (1957-1960 against the U.S. Government and that contested the aerial spraying of dichlorodiphenyltrichloroethane (DDT. During Rudolf Steiner’s lifetime, Spock and Richards both studied at Steiner’s Goetheanum, the headquarters of Anthroposophy, located in Dornach, Switzerland. Spock and Richards were prominent U.S. anthroposophists, and established a biodynamic farm under the tutelage of the leading biodynamics exponent of the time, Dr. Ehrenfried Pfeiffer. When their property was under threat from a government program of DDT spraying, they brought their case, eventually lost it, in the process spent US$100,000, and compiled the evidence that they then shared with Carson, who used it, and their extensive contacts and the trial transcripts, as the primary input for Silent Spring. Carson attributed to Spock, Richards, and Pfeiffer, no credit whatsoever in her book. As a consequence, the organics movement has not received the recognition, that is its due, as the primary impulse for Silent Spring, and it is, itself, unaware of this provenance.

  18. Assessment of Silent T1-weighted head imaging at 7 T

    Energy Technology Data Exchange (ETDEWEB)

    Costagli, Mauro; Tiberi, Gianluigi; Tosetti, Michela [Imago7 Foundation, Pisa (Italy); IRCCS Stella Maris, Laboratory of Medical Physics and Biotechnologies for Magnetic Resonance, Pisa (Italy); Symms, Mark R. [GE Applied Science Laboratory, Pisa (Italy); Angeli, Lorenzo [University of Pisa, Department of Translational Research and New Technologies in Medicine and Surgery, Pisa (Italy); Kelley, Douglas A.C. [GE Healthcare Technologies, San Francisco, CA (United States); Biagi, Laura [IRCCS Stella Maris, Laboratory of Medical Physics and Biotechnologies for Magnetic Resonance, Pisa (Italy); Farnetani, Andrea [University of Ferrara, Engineering Department, Ferrara (Italy); Materiacustica s.r.l., Ferrara (Italy); Rua, Catarina [University of Pisa, Department of Physics, Pisa (Italy); Donatelli, Graziella [Azienda Ospedaliero-Universitaria Pisana (AOUP), Neuroradiology Unit, Department of Diagnostic and Interventional Radiology, Pisa (Italy); Cosottini, Mirco [Imago7 Foundation, Pisa (Italy); University of Pisa, Department of Translational Research and New Technologies in Medicine and Surgery, Pisa (Italy)

    2016-06-15

    This study aimed to assess the performance of a ''Silent'' zero time of echo (ZTE) sequence for T1-weighted brain imaging using a 7 T MRI system. The Silent sequence was evaluated qualitatively by two neuroradiologists, as well as quantitatively in terms of tissue contrast, homogeneity, signal-to-noise ratio (SNR) and acoustic noise. It was compared to conventional T1-weighted imaging (FSPGR). Adequacy for automated segmentation was evaluated in comparison with FSPGR acquired at 7 T and 1.5 T. Specific absorption rate (SAR) was also measured. Tissue contrast and homogeneity in Silent were remarkable in deep brain structures and in the occipital and temporal lobes. Mean tissue contrast was significantly (p < 0.002) higher in Silent (0.25) than in FSPGR (0.11), which favoured automated tissue segmentation. On the other hand, Silent images had lower SNR with respect to conventional imaging: average SNR of FSPGR was 2.66 times that of Silent. Silent images were affected by artefacts related to projection reconstruction, which nevertheless did not compromise the depiction of brain tissues. Silent acquisition was 35 dB(A) quieter than FSPGR and less than 2.5 dB(A) louder than ambient noise. Six-minute average SAR was <2 W/kg. The ZTE Silent sequence provides high-contrast T1-weighted imaging with low acoustic noise at 7 T. (orig.)

  19. Insights into the causal relationship between slow slip and tectonic tremor in Guerrero, Mexico

    Science.gov (United States)

    Villafuerte, Carlos; Cruz-Atienza, Víctor M.

    2017-08-01

    Similar to other subduction zones, tectonic tremors (TTs) and slow-slip events (SSEs) take place in the deep segment of the plate interface in Guerrero, Mexico. However, their spatial correlation in this region is not as clear as the episodic tremor and slip observed in Cascadia and Japan. In this study we provide insights into the causal relationship between TTs and SSEs in Guerrero by analyzing the evolution of the deformation fields induced by the long-term 2006 SSE together with new locations of TTs and low-frequency earthquakes (LFEs). Unlike previous studies we find that the SSE slip rate modulates the TT and LFE activity in the whole tremor region. This means that the causal relationship between the SSE and the TT activity directly depends on the stressing rate history of the tremor asperities that is modulated by the surrounding slip rate. We estimated that the frictional strength of the asperities producing tremor downdip in the sweet spot is around 3.2 kPa, which is 2.3 times smaller than the corresponding value updip in the transient zone, partly explaining the overwhelming tremor activity of the sweet spot despite that the slow slip there is smaller. Based on the LFE occurrence-rate history during the interlong-term SSE period, we determined that the short-term SSEs in Guerrero take place further downdip (about 35 km) than previously estimated, with maximum slip of about 8 mm in the sweet spot. This new model features a continuum of slow slip extending across the entire tremor region of Guerrero.

  20. Large-magnitude Dextral Slip on the Wairarapa Fault, New Zealand

    Science.gov (United States)

    Rodgers, D. W.; Little, T.

    2004-12-01

    Dextral slip associated with an 1855 Ms 8.0+ event on the Wairarapa fault near Wellington, New Zealand was reported to be 12+/-1 m along a rupture length of at least 148km (Grapes, 1999), one of the largest single-event strike-slip offsets documented worldwide. Initial results from a new study involving detailed neotectonic mapping and microtopographic surveys of offset landforms (including many beheaded, inactive streams) strongly suggest that dextral slip was as much as 50% greater than previously measured. 1855 surface ruptures were mapped with certainty where a linear scarp characterized by steep slopes (30-90°) and exposed alluvium cuts across active or inactive stream channels. The fifteen individual strands comprising the Wairarapa fault zone that we have mapped to date are 1200+/-700 m long and typically left-stepping. Slip in the stepover zones between these strands is distributed amongst two or more ruptures and intervening anticlines, a situation that causes along-strike variations in slip and which locally complicates the interpretation of 1855 displacement. We focused on seven of the best-preserved sites where low-discharge streams are disrupted by the fault zone, including five that had been previously attributed by Grapes (1999) to coseismic slip during the 1855 earthquake. One of these (Pigeon Bush) includes two sequentially displaced, now beheaded linear stream channels, oriented perpendicular to the fault scarp, that preserve distinct offsets with respect to a single deeply incised, originally contiguous gorge on the opposite side of the fault. To quantify the minimum fault displacements at each site, we made 1:500 scale topographic maps employing n = 2,000-10,000 points collected with GPS and laser instrumentation. Measured dextral slip values, here attributed to the 1855 earthquake, include 16.4+/-1.0m (Hinaburn), 12.9+/-2.0m (Cross Creek), 17.2+/-2.5m (Lake Meadows), 18.7+/-1.0m (Pigeon Bush), 13.0+/-1.5m (Pigeon Bush 2), 15.1+/-1.0m (Pigeon

  1. Recent Progress on Modeling Slip Deformation in Shape Memory Alloys

    Science.gov (United States)

    Sehitoglu, H.; Alkan, S.

    2018-03-01

    This paper presents an overview of slip deformation in shape memory alloys. The performance of shape memory alloys depends on their slip resistance often quantified through the Critical Resolved Shear Stress (CRSS) or the flow stress. We highlight previous studies that identify the active slip systems and then proceed to show how non- Schmid effects can be dominant in shape memory slip behavior. The work is mostly derived from our recent studies while we highlight key earlier works on slip deformation. We finally discuss the implications of understanding the role of slip on curtailing the transformation strains and also the temperature range over which superelasticity prevails.

  2. Recent Progress on Modeling Slip Deformation in Shape Memory Alloys

    Science.gov (United States)

    Sehitoglu, H.; Alkan, S.

    2018-03-01

    This paper presents an overview of slip deformation in shape memory alloys. The performance of shape memory alloys depends on their slip resistance often quantified through the Critical Resolved Shear Stress (CRSS) or the flow stress. We highlight previous studies that identify the active slip systems and then proceed to show how non-Schmid effects can be dominant in shape memory slip behavior. The work is mostly derived from our recent studies while we highlight key earlier works on slip deformation. We finally discuss the implications of understanding the role of slip on curtailing the transformation strains and also the temperature range over which superelasticity prevails.

  3. Prognostic significance of silent myocardial ischemia on a thallium stress test

    International Nuclear Information System (INIS)

    Heller, L.I.; Tresgallo, M.; Sciacca, R.R.; Blood, D.K.; Seldin, D.W.; Johnson, L.L.

    1990-01-01

    The clinical significance of silent ischemia is not fully known. The purpose of this study was to determine whether the presence or absence of angina during a thallium stress test positive for ischemia was independently predictive of an adverse outcome. Two hundred thirty-four consecutive patients with ischemia on a thallium stress test were identified. Ischemia was defined as the presence of defect(s) on the immediate postexercise scans not in the distribution of prior infarctions that redistributed on 4-hour scans. During the test 129 patients had angina, defined as characteristic neck, jaw, arm, back or chest discomfort, while the remaining 105 patients had no angina. Follow-up ranged from 2 to 8.2 years (mean 5.2 +/- 2.1) and was successfully obtained in 156 patients. Eighty-two of the 156 patients had angina (group A) and 74 had silent ischemia (group S). Group A patients were significantly older (62 +/- 8 vs 59 +/- 8 years, p less than 0.05). There was no significant difference between the 2 groups in terms of sex, history of prior infarction or presence of left main/3-vessel disease. A larger percentage of patients in group A were receiving beta blockers (60 vs 41%, p less than 0.05) and nitrates (52 vs 36%, 0.05 less than p less than 0.10). There was a large number of cardiac events (myocardial infarction, revascularization and death) in both groups (37 of 82 [45%] in group A; 28 of 72 [38%] in group S) but no statistically significant difference between the groups. Similarly, life-table analysis revealed no difference in mortality between the 2 groups

  4. Unravelling the Mysteries of Slip Histories, Validating Cosmogenic 36Cl Derived Slip Rates on Normal Faults

    Science.gov (United States)

    Goodall, H.; Gregory, L. C.; Wedmore, L.; Roberts, G.; Shanks, R. P.; McCaffrey, K. J. W.; Amey, R.; Hooper, A. J.

    2017-12-01

    The cosmogenic isotope chlorine-36 (36Cl) is increasingly used as a tool to investigate normal fault slip rates over the last 10-20 thousand years. These slip histories are being used to address complex questions, including investigating slip clustering and understanding local and large scale fault interaction. Measurements are time consuming and expensive, and as a result there has been little work done validating these 36Cl derived slip histories. This study aims to investigate if the results are repeatable and therefore reliable estimates of how normal faults have been moving in the past. Our approach is to test if slip histories derived from 36Cl are the same when measured at different points along the same fault. As normal fault planes are progressively exhumed from the surface they accumulate 36Cl. Modelling these 36Cl concentrations allows estimation of a slip history. In a previous study, samples were collected from four sites on the Magnola fault in the Italian Apennines. Remodelling of the 36Cl data using a Bayesian approach shows that the sites produced disparate slip histories, which we interpret as being due to variable site geomorphology. In this study, multiple sites have been sampled along the Campo Felice fault in the central Italian Apennines. Initial results show strong agreement between the sites we have processed so far and a previous study. This indicates that if sample sites are selected taking the geomorphology into account, then 36Cl derived slip histories will be highly similar when sampled at any point along the fault. Therefore our study suggests that 36Cl derived slip histories are a consistent record of fault activity in the past.

  5. Hydro-Mechanical Modelling of Slow Slip Phenomena at the Subduction Interface.

    Science.gov (United States)

    Petrini, C.; Gerya, T.; Madonna, C.; van Dinther, Y.

    2016-12-01

    Subduction zones experience a spectrum of slip phenomena, ranging from large devastating megathrust earthquakes to aseismic slow slip events. Slow slip events, lasting hours to years and being perceptible only by instruments, are believed to have the capability to induce large earthquakes. It is also repeatedly proposed that such slow events are controlled by fluid-rock interactions along the subduction interface, thus calling for development of fully coupled seismo-hydro-mechanical modeling approaches to identify their physics and controlling parameters. We present a newly developed finite difference visco-elasto-plastic numerical code with marker-in-cell technique, which fully couples mechanical deformation and fluid flow. We use this to investigate how the presence of fluids in the pore space of a (de)compacting rock matrix affects elastic stress accumulation and release along a fluid-bearing subduction interface. The model simulates the spontaneous occurrence of quasi-periodic slow slip phenomena along self-consistently forming highly localized shearbands, which accommodate shear displacement between two plates. The produced elastic rebound events show a slip velocity on the order of cm/yr, which is in good agreement with measured data. The governing gradual strength decrease along the slowly propagating shear bands is related to a drop in total pressure caused by shear localization at nearly constant (slightly decreasing) fluid pressure. Gradual reduction of the difference between the total and fluid pressure decreases brittle/plastic strength of fluid-bearing rocks along the shear bands, thus providing a dynamic feedback mechanism for the accumulated elastic stress release at the subduction interface.

  6. Premonitory acoustic emissions and stick-slip in natural and smooth-faulted Westerly granite

    Science.gov (United States)

    Thompson, B.D.; Young, R.P.; Lockner, David A.

    2009-01-01

    A stick-slip event was induced in a cylindrical sample of Westerly granite containing a preexisting natural fault by loading at constant confining pressure of 150 MPa. Continuously recorded acoustic emission (AE) data and computer tomography (CT)-generated images of the fault plane were combined to provide a detailed examination of microscale processes operating on the fault. The dynamic stick-slip event, considered to be a laboratory analog of an earthquake, generated an ultrasonic signal that was recorded as a large-amplitude AE event. First arrivals of this event were inverted to determine the nucleation site of slip, which is associated with a geometric asperity on the fault surface. CT images and AE locations suggest that a variety of asperities existed in the sample because of the intersection of branch or splay faults with the main fault. This experiment is compared with a stick-slip experiment on a sample prepared with a smooth, artificial saw-cut fault surface. Nearly a thousand times more AE were observed for the natural fault, which has a higher friction coefficient (0.78 compared to 0.53) and larger shear stress drop (140 compared to 68 MPa). However at the measured resolution, the ultrasonic signal emitted during slip initiation does not vary significantly between the two experiments, suggesting a similar dynamic rupture process. We propose that the natural faulted sample under triaxial compression provides a good laboratory analogue for a field-scale fault system in terms of the presence of asperities, fault surface heterogeneity, and interaction of branching faults. ?? 2009.

  7. Electrocardiographically and symptomatically silent myocardial ischemia during exercise testing

    International Nuclear Information System (INIS)

    Kurata, Chinori; Tawarahara, Kei; Sakata, Kazuyuki; Taguchi, Takahisa; Fukumoto, Yoshihiro; Kobayashi, Akira; Yamazaki, Noboru; Tanaka, Hiroshi

    1991-01-01

    Certain patients with coronary artery disease (CAD) may have neither ST depression nor chest pain during exercise despite the presence of myocardial ischemia. The frequency and characteristics of such electrocardiographically and symptomatically silent ischemia were studied in 171 patients with both angiographically documented CAD and scintigraphically documented ischemia. Fifty-six (33%) of 171 patients had neither ST depression nor chest pain (Group N), and 115 (67%) had ST depression and/or chest pain (Group P). The two groups were similar with respect to age, gender, the prevalence of prior infarction, and peak systolic blood pressure. Group N patients, however, had a higher mean peak heart rate and rate-pressure product, less severe scintigraphic ischemia, a lower lung thallium-201 uptake, and a smaller number of diseased vessels. Stepwise discriminant analysis showed a history of effort angina, lung thallium-201 uptake, and scintigraphic severity of ischemia to be significant discriminators between Groups N and P. In conclusion, electrocardiographically and symptomatically silent ischemia may be common during exercise in patients with CAD, and less severe ischemia may be one of important determinants. (author)

  8. Analysis of P and Pdiff Coda Arrivals for Water Reverberations to Evaluate Shallow Slip Extent in Large Megathrust Earthquakes

    Science.gov (United States)

    Rhode, A.; Lay, T.

    2017-12-01

    Determining the up-dip rupture extent of large megathrust ruptures is important for understanding their tsunami excitation, frictional properties of the shallow megathrust, and potential for separate tsunami earthquake occurrence. On land geodetic data have almost no resolution of the up-dip extent of faulting and teleseismic observations have limited resolution that is strongly influenced by typically poorly known shallow seismic velocity structure near the toe of the accretionary prism. The increase in ocean depth as slip on the megathrust approaches the trench has significant influence on the strength and azimuthal distribution of water reverberations in the far-field P wave coda. For broadband P waves from large earthquakes with dominant signal periods of about 10 s, water reverberations generated by shallow fault slip under deep water may persist for over a minute after the direct P phases have passed, giving a clear signal of slip near the trench. As the coda waves can be quickly evaluated following the P signal, recognition of slip extending to the trench and associated enhanced tsunamigenic potential could be achieved within a few minutes after the P arrival, potentially contributing to rapid tsunami hazard assessment. We examine the broadband P wave coda at distances from 80 to 120° for a large number of recent major and great earthquakes with independently determined slip distributions and known tsunami excitation to evaluate the prospect for rapidly constraining up-dip rupture extent of large megathrust earthquakes. Events known to have significant shallow slip, at least locally extending to the trench (e.g., 2016 Illapel, Chile; 2010 Maule, 2010 Mentawai) do have relatively enhanced coda levels at all azimuths, whereas events that do not rupture the shallow megathrust (e.g., 2007 Sumatra, 2014 Iquique, 2003 Hokkaido) do not. Some events with slip models lacking shallow slip show strong coda generation, raising questions about the up-dip resolution of

  9. Estimated combined steady state tyre slip characteristics

    NARCIS (Netherlands)

    Fernandez, A.L.A.; Pauwelussen, J.P.

    2001-01-01

    Excessive behaviour of vehicles is often the subject of study, motivated by either the development of active safety systems uch as ESP, or the improvement of vehicle performance such as for racecars. In all of these cases, combined slip needs to be taken into account. In many cases however, the full

  10. Hydrodynamic slip length as a surface property

    Science.gov (United States)

    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.

  11. Stress near geometrically complex strike-slip faults - Application to the San Andreas fault at Cajon Pass, southern California

    Science.gov (United States)

    Saucier, Francois; Humphreys, Eugene; Weldon, Ray, II

    1992-01-01

    A model is presented to rationalize the state of stress near a geometrically complex major strike-slip fault. Slip on such a fault creates residual stresses that, with the occurrence of several slip events, can dominate the stress field near the fault. The model is applied to the San Andreas fault near Cajon Pass. The results are consistent with the geological features, seismicity, the existence of left-lateral stress on the Cleghorn fault, and the in situ stress orientation in the scientific well, found to be sinistral when resolved on a plane parallel to the San Andreas fault. It is suggested that the creation of residual stresses caused by slip on a wiggle San Andreas fault is the dominating process there.

  12. Stick-slip Cycles and Tidal Modulation of Ice Stream Flow

    Science.gov (United States)

    Lipovsky, B.; Dunham, E. M.

    2016-12-01

    The reactivation of a single dormant Antarctic ice stream would double the continent's mass imbalance. Despite importance of understanding the likelihood of such an event, direct observation of the basal processes that lead to the activation and stagnation of streaming ice are minimal. As the only ice stream undergoing stagnation, the Whillans Ice Plain (WIP) occupies a central role in our understanding of these subglacial processes. Complicating matters is the observation, from GPS records, that the WIP experiences most of its motion during episodes of rapid sliding. These sliding events are tidally modulated and separated by 12 hour periods of quiescence. We conduct numerical simulations of ice stream stick-slip cycles. Our simulations include rate- and state-dependent frictional sliding, tidal forcing, inertia, upstream loading in a cross-stream, thickness-averaged formulation. Our principal finding is that ice stream motion may respond to ocean tidal forcing with one of two end member behaviors. In one limit, tidally modulated slip events have rupture velocities that approach the shear wave speed and slip events have a duration that scales with the ice stream width divided by the shear wave speed. In the other limit, tidal modulation results in ice stream sliding velocities with lower amplitude variation but at much longer timescales, i.e. semi-diurnal and longer. This latter behavior more closely mimics the behavior of several active ice streams (Bindschadler, Rutford). We find that WIP slip events exist between these two end member behaviors: rupture velocities are far below the inertial limit yet sliding occurs only episodically. The continuum of sliding behaviors is governed by a critical ice stream width over which slip event nucleate. When the critical width is much longer than the ice stream width, slip events are unable to nucleate. The critical width depends on the subglacial effective pressure, ice thickness, and frictional and elastic constitutive

  13. Next generation GNSS single receiver cycle slip reliability

    NARCIS (Netherlands)

    Teunissen, P.J.G.; De Bakker, P.F.

    2009-01-01

    In this contribution we study the multi-frequency, carrier-phase slip detection capabilities of a single receiver. Our analysis is based on an analytical expression that we present for themulti-frequencyminimal detectable carrier phase cycle slip.

  14. Development of compact slip detection sensor using dielectric elastomer

    Science.gov (United States)

    Choi, Jae-young; Hwang, Do-Yeon; Kim, Baek-chul; Moon, Hyungpil; Choi, Hyouk Ryeol; Koo, Ja Choon

    2015-04-01

    In this paper, we developed a resistance tactile sensor that can detect a slip on the surface of sensor structure. The presented sensor device has fingerprint-like structures that are similar with the role of the humans finger print. The resistance slip sensor that the novel developed uses acrylo-nitrile butadiene rubber (NBR) as a dielectric substrate and graphene as an electrode material. We can measure the slip as the structure of sensor makes a deformation and it changes the resistance through forming a new conductive route. To manufacture our sensor, we developed a new imprint process. By using this process, we can produce sensor with micro unit structure. To verify effectiveness of the proposed slip detection, experiment using prototype of resistance slip sensor is conducted with an algorithm to detect slip and slip is successfully detected. We will discuss the slip detection properties.

  15. Seismic Slip on an Oblique Detachment Fault at Low Angles

    Science.gov (United States)

    Janecke, S. U.; Steely, A. N.; Evans, J. P.

    2008-12-01

    fault when the detachment was active, when it produced voluminous pseudotachylyte during eartquakes, and when the supradetachment basin above it received a large volume of sediment eroded from the pseudotachylyte-bearing parts of the damage zone. To interpret the pseudotachylyte as the product of slip across a detachment when it was dipping at least 45 degrees requires a sequence of events that is so unlikely that we reject it. There must have been seismic slip at low dip angles across the West Salton detachment fault. Our conclusion agrees with prior studies by John and Axen in the Chemehuevi and Whipple metamorphic core complex and increases the published catalogue of detachment faults that sport pseudotachylytes. These data document that low-angle normal faults are seismogenic, and that conditions that allow pseudotachylytes to form may occur at shallow levels in the crust.

  16. Time-dependent inversions of slow slip at the Hikurangi subduction zone, New Zealand, using numerical Green's functions

    Science.gov (United States)

    Williams, C. A.; Wallace, L. M.; Bartlow, N. M.

    2017-12-01

    Slow slip events (SSEs) have been observed throughout the world, and the existence of these events has fundamentally altered our understanding of the possible ranges of slip behavior at subduction plate boundaries. In New Zealand, SSEs occur along the Hikurangi Margin, with shallower events in the north and deeper events to the south. In a recent study, Williams and Wallace (2015) found that static SSE inversions that consider elastic property variations provided significantly different results than those based on an elastic half-space. For deeper events, the heterogeneous models predicted smaller amounts of slip, while for shallower events the heterogeneous model predicted larger amounts of slip. In this study, we extend our initial work to examine the temporal variations in slip. We generate Green's functions using the PyLith finite element code (Aagaard et al., 2013) to allow consideration of elastic property variations provided by the New Zealand-wide seismic velocity model (Eberhart-Phillips et al., 2010). These Green's functions are then integrated to provide Green's functions compatible with the Network Inversion Filter (NIF, Segall and Matthews,1997; McGuire and Segall, 2003; Miyazaki et al.,2006). We examine 12 SSEs occurring along the Hikurangi Margin during 2010 and 2011, and compare the results using heterogeneous Green's functions with those of Bartlow et al. (2014), who examined the same set of SSEs with the NIF using a uniform elastic half-space model. The use of heterogeneous Green's functions should provide a more accurate picture of the slip distribution and evolution of the SSEs. This will aid in understanding the correlations between SSEs and seismicity and/or tremor and the role of SSEs in the accommodation of plate motion budgets in New Zealand.

  17. Spatial Comparisons of Tremor and Slow Slip as a Constraint on Fault Strength in the Northern Cascadia Subduction Zone

    Science.gov (United States)

    Hall, K.; Schmidt, D. A.; Houston, H.

    2017-12-01

    We measure displacement vectors from about 50 or more PANGA 3-component GPS stations to analyze six large ETS events from 2007 - 2016 in northern Cascadia, and invert for slip on a realistic plate interface. Our previous results indicated that significant slip of up to 2 cm occurs 10 to 15 km up-dip of the western edge of tremor beneath the Olympic Peninsula. This far up-dip aseismic slip persists in several of the ETS events. We also find that this offset appears to vary along-strike with a greater offset beneath the Olympic Peninsula and up into the Strait of Juan de Fuca in comparison to lower Puget Sound. To explain this, we explore how properties (temperature and permeability) of the overlying structure may influence fault strength. In our conceptual model, the observation that slip inferred from GPS can extend updip of tremor suggests that updip of the observed edge of tremor, seismogenic patches that could produce tremor and low frequency earthquakes (LFEs) are too strong to fail from the relatively minor amount of far up-dip slow slip. This is consistent with the observation that, within the ETS zone, down-dip LFEs occur frequently, whereas up-dip LFEs occur only during the largest ETS events and are unaffected by tidal stresses until the later stages of an ETS event. This suggests that the up-dip seismogenic patches have a larger discrepancy between their strength and stress states, and therefore require larger stress perturbations (such as those from a propagating ETS slip pulse) to trigger seismic failure. We consider whether lateral variations in overlying structure may explain the along-strike variations in far up-dip aseismic slip. There is an abrupt change in lithology from the meta-sediments of the Olympic accretionary complex to the mafic basalts of the Crescent terrane. The juxtaposition of these different lithologies could potentially explain the along-strike variations in far up-dip aseismic slip. We propose to explore whether relative changes

  18. Silent ischemic brain lesions after transcatheter aortic valve replacement : lesion distribution and predictors

    NARCIS (Netherlands)

    Samim, Mariam; Hendrikse, Jeroen; van der Worp, H. Bart; Agostoni, Pierfrancesco; Nijhoff, Freek; Doevendans, Pieter A.; Stella, Pieter R.

    Silent ischemic brain lesions and ischemic stroke are known complications of transcatheter aortic valve replacement (TAVR). We aimed to investigate the occurrence and distribution of TAVR-related silent ischemic brain lesions using diffusion-weighted magnetic resonance imaging (DWI). Consecutive

  19. Morphology and Spelling in French Students with Dyslexia: The Case of Silent Final Letters

    Science.gov (United States)

    Quémart, Pauline; Casalis, Séverine

    2017-01-01

    Spelling is a challenge for individuals with dyslexia. Phoneme-to-grapheme correspondence rules are highly inconsistent in French, which make them very difficult to master, in particular for dyslexics. One recurrent manifestation of this inconsistency is the presence of silent letters at the end of words. Many of these silent letters perform a…

  20. The Keefe Inventory of Silent Reading: A Window into the Reading Process.

    Science.gov (United States)

    Keefe, Donald

    1993-01-01

    Contains part of the Keefe Inventory of Silent Reading, a silent informal reading inventory. Presents a case study of a student to whom it was administered, including analysis of this individual's reading ability and description of the specific strategies used with this individual on the basis of the results of the inventory. (RS)

  1. Does phonological recoding occur during silent reading and is it necessary for orthographic learning?

    NARCIS (Netherlands)

    de Jong, P.F.; Bitter, D.J.L.; van Setten, M.; Marinus, E.

    2009-01-01

    Two studies were conducted to test the central claim of the self-teaching hypothesis (i.e., phonological recoding is necessary for orthographic learning) in silent reading. The first study aimed to demonstrate the use of phonological recoding during silent reading. Texts containing pseudowords were

  2. (In-)Secure messaging with the Silent Circle instant messaging protocol

    NARCIS (Netherlands)

    Verschoor, S.R.; Lange, T.

    2016-01-01

    Silent Text, the instant messaging application by the company Silent Circle, provides its users with end-to-end encrypted communication on the Blackphone and other smartphones. The underlying protocol, SCimp, has received many extensions during the update to version 2, but has not been subjected to

  3. Distinct transmitter release properties determine differences in short-term plasticity at functional and silent synapses.

    Science.gov (United States)

    Cabezas, Carolina; Buño, Washington

    2006-05-01

    Recent evidence suggests that functional and silent synapses are not only postsynaptically different but also presynaptically distinct. The presynaptic differences may be of functional importance in memory formation because a proposed mechanism for long-term potentiation is the conversion of silent synapses into functional ones. However, there is little direct experimentally evidence of these differences. We have investigated the transmitter release properties of functional and silent Schaffer collateral synapses and show that on the average functional synapses displayed a lower percentage of failures and higher excitatory postsynaptic current (EPSC) amplitudes than silent synapses at +60 mV. Moreover, functional but not silent synapses show paired-pulse facilitation (PPF) at +60 mV and thus presynaptic short-term plasticity will be distinct in the two types of synapse. We examined whether intraterminal endoplasmic reticulum Ca2+ stores influenced the release properties of these synapses. Ryanodine (100 microM) and thapsigargin (1 microM) increased the percentage of failures and decreased both the EPSC amplitude and PPF in functional synapses. Caffeine (10 mM) had the opposite effects. In contrast, silent synapses were insensitive to both ryanodine and caffeine. Hence we have identified differences in the release properties of functional and silent synapses, suggesting that synaptic terminals of functional synapses express regulatory molecular mechanisms that are absent in silent synapses.

  4. Aseismic and seismic slip induced by fluid injection from poroelastic and rate-state friction modeling

    Science.gov (United States)

    Liu, Y.; Deng, K.; Harrington, R. M.; Clerc, F.

    2016-12-01

    Solid matrix stress change and pore pressure diffusion caused by fluid injection has been postulated as key factors for inducing earthquakes and aseismic slip on pre-existing faults. In this study, we have developed a numerical model that simulates aseismic and seismic slip in a rate-and-state friction framework with poroelastic stress perturbations from multi-stage hydraulic fracturing scenarios. We apply the physics-based model to the 2013-2015 earthquake sequences near Fox Creek, Alberta, Canada, where three magnitude 4.5 earthquakes were potentially induced by nearby hydraulic fracturing activity. In particular, we use the relocated December 2013 seismicity sequence to approximate the fault orientation, and find the seismicity migration spatiotemporally correlate with the positive Coulomb stress changes calculated from the poroelastic model. When the poroelastic stress changes are introduced to the rate-state friction model, we find that slip on the fault evolves from aseismic to seismic in a manner similar to the onset of seismicity. For a 15-stage hydraulic fracturing that lasted for 10 days, modeled fault slip rate starts to accelerate after 3 days of fracking, and rapidly develops into a seismic event, which also temporally coincides with the onset of induced seismicity. The poroelastic stress perturbation and consequently fault slip rate continue to evolve and remain high for several weeks after hydraulic fracturing has stopped, which may explain the continued seismicity after shut-in. In a comparison numerical experiment, fault slip rate quickly decreases to the interseismic level when stress perturbations are instantaneously returned to zero at shut-in. Furthermore, when stress perturbations are removed just a few hours after the fault slip rate starts to accelerate (that is, hydraulic fracturing is shut down prematurely), only aseismic slip is observed in the model. Our preliminary results thus suggest the design of fracturing duration and flow

  5. Cohesion-Induced Stabilization in Stick-Slip Dynamics of Weakly Wet, Sheared Granular Fault Gouge

    Science.gov (United States)

    Dorostkar, Omid; Guyer, Robert A.; Johnson, Paul A.; Marone, Chris; Carmeliet, Jan

    2018-03-01

    We use three-dimensional discrete element calculations to study stick-slip dynamics in a weakly wet granular layer designed to simulate fault gouge. The granular gouge is constituted by 8,000 spherical particles with a polydisperse size distribution. At very low liquid content, liquids impose cohesive and viscous forces on particles. Our simulations show that by increasing the liquid content, friction increases and granular layer shows higher recurrence time between slip events. We also observe that slip events exhibit larger friction drop and layer compaction in wet system compared to dry. We demonstrate that a small volume of liquid induces cohesive forces between wet particles that are responsible for an increase in coordination number leading to a more stable arrangement of particles. This stabilization is evidenced with 2 orders of magnitude lower particle kinetic energy in wet system during stick phase. Similar to previous experimental studies, we observe enhanced frictional strength for wet granular layers. In experiments, the physicochemical processes are believed to be the main reason for such behavior; we show, however, that at low confining stresses, the hydromechanical effects of induced cohesion are sufficient for observed behavior. Our simulations illuminate the role of particle interactions and demonstrate the conditions under which induced cohesion plays a significant role in fault zone processes, including slip initiation, weakening, and failure.

  6. Evidence for Truncated Exponential Probability Distribution of Earthquake Slip

    KAUST Repository

    Thingbaijam, Kiran Kumar; Mai, Paul Martin

    2016-01-01

    Earthquake ruptures comprise spatially varying slip on the fault surface, where slip represents the displacement discontinuity between the two sides of the rupture plane. In this study, we analyze the probability distribution of coseismic slip, which provides important information to better understand earthquake source physics. Although the probability distribution of slip is crucial for generating realistic rupture scenarios for simulation-based seismic and tsunami-hazard analysis, the statistical properties of earthquake slip have received limited attention so far. Here, we use the online database of earthquake source models (SRCMOD) to show that the probability distribution of slip follows the truncated exponential law. This law agrees with rupture-specific physical constraints limiting the maximum possible slip on the fault, similar to physical constraints on maximum earthquake magnitudes.We show the parameters of the best-fitting truncated exponential distribution scale with average coseismic slip. This scaling property reflects the control of the underlying stress distribution and fault strength on the rupture dimensions, which determines the average slip. Thus, the scale-dependent behavior of slip heterogeneity is captured by the probability distribution of slip. We conclude that the truncated exponential law accurately quantifies coseismic slip distribution and therefore allows for more realistic modeling of rupture scenarios. © 2016, Seismological Society of America. All rights reserverd.

  7. Evidence for Truncated Exponential Probability Distribution of Earthquake Slip

    KAUST Repository

    Thingbaijam, Kiran K. S.

    2016-07-13

    Earthquake ruptures comprise spatially varying slip on the fault surface, where slip represents the displacement discontinuity between the two sides of the rupture plane. In this study, we analyze the probability distribution of coseismic slip, which provides important information to better understand earthquake source physics. Although the probability distribution of slip is crucial for generating realistic rupture scenarios for simulation-based seismic and tsunami-hazard analysis, the statistical properties of earthquake slip have received limited attention so far. Here, we use the online database of earthquake source models (SRCMOD) to show that the probability distribution of slip follows the truncated exponential law. This law agrees with rupture-specific physical constraints limiting the maximum possible slip on the fault, similar to physical constraints on maximum earthquake magnitudes.We show the parameters of the best-fitting truncated exponential distribution scale with average coseismic slip. This scaling property reflects the control of the underlying stress distribution and fault strength on the rupture dimensions, which determines the average slip. Thus, the scale-dependent behavior of slip heterogeneity is captured by the probability distribution of slip. We conclude that the truncated exponential law accurately quantifies coseismic slip distribution and therefore allows for more realistic modeling of rupture scenarios. © 2016, Seismological Society of America. All rights reserverd.

  8. Performance analysis of a microcontroller based slip power recovery ...

    African Journals Online (AJOL)

    Slip power recovery wound rotor induction motor drives are used in high power, limited speed range applications where control of slip power provides the variable speed drive system. In this paper, the steady state performance analysis of conventional slip power recovery scheme using static line commutated inverter in the ...

  9. Silent left ventricular dysfunction during routine activity after thrombolytic therapy for acute myocardial infarction

    International Nuclear Information System (INIS)

    Kayden, D.S.; Wackers, F.J.; Zaret, B.L.

    1990-01-01

    To investigate prospectively the occurrence and significance of postinfarction transient left ventricular dysfunction, 33 ambulatory patients who underwent thrombolytic therapy after myocardial infarction were monitored continuously for 187 +/- 56 min during normal activity with a radionuclide left ventricular function detector at the time of hospital discharge. Twelve patients demonstrated 19 episodes of transient left ventricular dysfunction (greater than 0.05 decrease in ejection fraction, lasting greater than or equal to 1 min), with no change in heart rate. Only two episodes in one patient were associated with chest pain and electrocardiographic changes. The baseline ejection fraction was 0.52 +/- 0.12 in patients with transient left ventricular dysfunction and 0.51 +/- 0.13 in patients without dysfunction (p = NS). At follow-up study (19.2 +/- 5.4 months), cardiac events (unstable angina, myocardial infarction or death) occurred in 8 of 12 patients with but in only 3 of 21 patients without transient left ventricular dysfunction (p less than 0.01). During submaximal supine bicycle exercise, only two patients demonstrated a decrease in ejection fraction greater than or equal to 0.05 at peak exercise; neither had a subsequent cardiac event. These data suggest that transient episodes of silent left ventricular dysfunction at hospital discharge in patients treated with thrombolysis after myocardial infarction are common and associated with a poor outcome. Continuous left ventricular function monitoring during normal activity may provide prognostic information not available from submaximal exercise test results

  10. Discrete element modeling of triggered slip in faults with granular gouge: application to dynamic earthquake triggering

    International Nuclear Information System (INIS)

    Ferdowsi, B.

    2014-01-01

    Recent seismological observations based on new, more sensitive instrumentation show that seismic waves radiated from large earthquakes can trigger other earthquakes globally. This phenomenon is called dynamic earthquake triggering and is well-documented for over 30 of the largest earthquakes worldwide. Granular materials are at the core of mature earthquake faults and play a key role in fault triggering by exhibiting a rich nonlinear response to external perturbations. The stick-slip dynamics in sheared granular layers is analogous to the seismic cycle for earthquake fault systems. In this research effort, we characterize the macroscopic scale statistics and the grain-scale mechanisms of triggered slip in sheared granular layers. We model the granular fault gouge using three dimensional discrete element method simulations. The modeled granular system is put into stick-slip dynamics by applying a conning pressure and a shear load. The dynamic triggering is simulated by perturbing the spontaneous stick-slip dynamics using an external vibration applied to the boundary of the layer. The influences of the triggering consist in a frictional weakening during the vibration interval, a clock advance of the next expected large slip event and long term effects in the form of suppression and recovery of the energy released from the granular layer. Our study suggests that above a critical amplitude, vibration causes a significant clock advance of large slip events. We link this clock advance to a major decline in the slipping contact ratio as well as a decrease in shear modulus and weakening of the granular gouge layer. We also observe that shear vibration is less effective in perturbing the stick-slip dynamics of the granular layer. Our study suggests that in order to have an effective triggering, the input vibration must also explore the granular layer at length scales about or less than the average grain size. The energy suppression and the subsequent recovery and increased

  11. Silent Flange Coupling Design Used for the Schenck Eddy Current Dynamometer

    Science.gov (United States)

    Schinteie, D.; Croitorescu, V.

    2016-11-01

    The silent flange used for coupling different machines/systems to an eddy current dynamometer represents one of the modular components each test-bench should use. By introducing a silent flange into a dynamometer, the coupling steps are easier and faster. For an appropriate design, the silent flange was analyzed using dedicated software during different operation procedures and scenarios, for materials that allow easy manufacturing. This study shows that the design for this silent flange model has no danger of failure due to the small deformation and the values for the equivalent stresses. The silent flange coupling is suitable for the dynamometer for his high positioning accuracy, the zero backlash and the fact that there is no motion between the shafts.

  12. Low fetal hemoglobin percentage is associated with silent brain lesions in adults with homozygous sickle cell disease

    OpenAIRE

    Calvet, David; Tuilier, Titien; Mélé, Nicolas; Turc, Guillaume; Habibi, Anoosha; Abdallah, Nassim Ait; Majhadi, Loubna; Hemery, François; Edjlali, Myriam; Galacteros, Frédéric; Bartolucci, Pablo

    2017-01-01

    Low %HbF is independently associated with silent WMCs on brain imaging in adults with SCD.Our results highlight the potential use of therapeutic strategies inducing HbF expression in SCD patients with silent white matter changes.

  13. Soundless Speech/ Wordless Writing: Language and German Silent Cinema

    Directory of Open Access Journals (Sweden)

    Marc Silberman

    2010-12-01

    Full Text Available Speech / Wordless Writing: Language and German Silent Cinema Marc Silberman If language loses its communicative and interpretative functions in direct proportion to the loss of its referential grounding, then the modernist crisis is simultaneously a crisis of its signifying practices. This means that the evolution of the silent cinema is a particularly rich site to examine the problematic relationship of language and image. This essay presents several expressionist films as a specific response to this crisis in order to describe the diverse cinematic forms of resistance to the word, to articulated speech. While some film makers developed the silence of the silent film into a “gestural language” that dramatized light and movement, others reproduced the film figures’ silent speech by means of graphically stylized intertitles. My thesis is that the expressionist cinema maintained an idealistic notion of the film as a pure work of art that aimed at a unified composition of all elements and missed the opportunity to explore the rich semiotic possibilities of the new technological medium with its hybrid, synergetic forms and provocative force. Hence, the expressionist cinema marks a transition or even the endpoint of a long process of reflection about the communicative possibilities of language that shifted to a fundamentally new level with the invention of sound cinema at the end of the 1920s. Parole muette / écriture sans mot: Le langage et le cinéma allemand muet Marc Silberman Le langage, dit-on, perd de ses functions communicatrices et interpretatives en proportion directe à la perte de sa force référentielle. On dira que la crise moderniste est également une crise des pratiques signifiantes. Ce qui revient à dire aussi que l’évolution du cinéma muet serait une site particulièrement riche pour examiner les problématiques du langage vs. l’image. Cet essai présente quelques films expressionnistes comme réactions à la crise

  14. Plasma remediation of trichloroethylene in silent discharge plasmas

    International Nuclear Information System (INIS)

    Evans, D.; Rosocha, L.A.; Anderson, G.K.; Coogan, J.J.; Kushner, M.J.

    1993-01-01

    Plasma destruction of toxins, and volatile organic compounds in particular, from gas streams is receiving increased attention as an energy efficient means to remediate those compounds. In this regard, remediation of trichloroethylene (TCE) in silent discharge plasmas has been experimentally and theoretically investigated. We found that TCE can be removed from Ar/O 2 gas streams at atmospheric pressure with an energy efficiency of 15--20 ppm/(mJ/cm 3 ), or 2--3 kW h kg -1 . The majority of the Cl from TCE is converted to HCl, Cl 2 , and COCl 2 , which can be removed from the gas stream by a water bubbler. The destruction efficiency of TCE is smaller in humid mixtures compared to dry mixtures due to interception of reactive intermediates by OH radicals

  15. Scaling of silent electrical discharge reactors for hazardous organics destruction

    International Nuclear Information System (INIS)

    Coogan, J.J.; Rosocha, L.A.; Brower, M.J.; Kang, M.; Schmidt, C.A.

    1993-01-01

    Silent electrical discharges are used to produce highly reactive free radicals that destroy hazardous compounds entrained in gaseous effluents at ambient gas temperatures and pressures. We have carried out destruction experiments at Los Alamos on a range of volatile organic compounds (VOCs), including trichloroethylene (TCE), carbon tetrachloride, perchloroethylene (PCE), and chlorofluorocarbons (CFCs). We have measured a ''nine-factor'', the amount of energy required to reduce the VOC concentration by a factor of ten. For practical reactor power densities, the ''nine-factor'' can be used to predict the destruction an removal efficiency (DRE) in terms of gas flow rate and the number of reactor modules. This report proposes a modular, stackable architecture for scaling up the reactor throughput

  16. [Silent myocardial ischemia in patients with transient ischemic attacks].

    Science.gov (United States)

    Sánchez Valiente, S; Mostacero, E; del Río, A; Morales, F

    1994-10-01

    Given evidence that ischemic heart disease is the most frequent cause of death in patients with cerebrovascular disease, we used ergometrics to screen 80 patients with TIA for silent myocardial ischemia (SMI) at the neurological unit of Hospital Clínico Universitario in Zaragoza, Spain. The patients were compared with a control group of 80 with no signs of heart disease. Neither the patients nor the controls had ever shown clinical signs of coronary ischemia and their baseline electrocardiograms were normal. Stress test results were positive in 25 (31%) of the TIA patients, and in 4 (5%) (p Hiperlipidemia (75% testing positive versus 43% negative, p < 0.01) and diabetes (31% testing positive versus 13% negative, p < 0.01) were the risk factors statistically related with a positive stress test.

  17. Myocardial perfusion imaging for detection of silent myocardial ischemia

    International Nuclear Information System (INIS)

    Beller, G.A.

    1988-01-01

    Despite the widespread use of the exercise stress test in diagnosing asymptomatic myocardial ischemia, exercise radionuclide imaging remains useful for detecting silent ischemia in numerous patient populations, including those who are totally asymptomatic, those who have chronic stable angina, those who have recovered from an episode of unstable angina or an uncomplicated myocardial infarction, and those who have undergone angioplasty or received thrombolytic therapy. Studies show that thallium scintigraphy is more sensitive than exercise electrocardiography in detecting ischemia, i.e., in part, because perfusion defects occur more frequently than ST depression and before angina in the ischemic cascade. Thallium-201 scintigraphy can be performed to differentiate a true- from a false-positive exercise electrocardiographic test in patients with exercise-induced ST depression and no angina. The development of technetium-labeled isonitriles may improve the accuracy of myocardial perfusion imaging. 11 references

  18. Reducing the silent burden of impaired mental health.

    Science.gov (United States)

    Jané-Llopis, Eva; Anderson, Peter; Stewart-Brown, Sarah; Weare, Katherine; Wahlbeck, Kristian; McDaid, David; Cooper, Cary; Litchfield, Paul

    2011-08-01

    Mental and behavioral disorders account for about one third of the world's disability caused by all ill health among adults, with unipolar depressive disorders set to be the world's number one cause of illhealth and premature death in 2030, affecting high- and low-income countries. There is a range of evidence-based cost-effective interventions that can be implemented in parenting, at schools, at the workplace, and in older age that can promote health and well-being, reduce mental disorders, lead to improved productivity, and increase resilience to cope with many of the stressors in the world. These facts need to be better communicated to policymakers to ensure that the silent burden of impaired mental health is adequately heard and reduced.

  19. Stopping the Silent Killer: Hepatitis B Among Asian Americans

    Centers for Disease Control (CDC) Podcasts

    2008-04-18

    This podcast discusses an underappreciated health threat to many Asians and Pacific Islanders in the United States: chronic infection with the hepatitis B virus. Dr. John Ward, director of CDC's Division of Viral Hepatitis, and Dr. Sam So, founder of the Asian Liver Center at Stanford University, address the importance of testing, vaccination, and care to prevent serious health consequences from this "silent" disease.  Created: 4/18/2008 by National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention (NCHHSTP), Division of Viral Hepatitis (DVH) and Office of Dispute Resolution and Equal Employment Opportunity, Office of the Director (OD).   Date Released: 5/1/2008.

  20. Relation between boundary slip mechanisms and waterlike fluid behavior

    Science.gov (United States)

    Ternes, Patricia; Salcedo, Evy; Barbosa, Marcia C.

    2018-03-01

    The slip of a fluid layer in contact with a solid confining surface is investigated for different temperatures and densities using molecular dynamic simulations. We show that for an anomalous waterlike fluid the slip goes as follows: for low levels of shear, defect slip appears and is related to the particle exchange between the fluid layers; at high levels of shear, global slip occurs and is related to the homogeneous distribution of the fluid in the confining surfaces. The oscillations in the transition velocity from defect to global slip are shown to be associated with changes in the layering distribution in the anomalous fluid.

  1. Treatment of hazardous organic wastes using silent discharge plasmas

    International Nuclear Information System (INIS)

    Rosocha, L.A.; Anderson, G.K.; Bechtold, L.A.; Coogan, J.J.; Heck, H.G.; Kang, M.; McCulla, W.H.; Tennant, R.A.; Wantuck, P.J.

    1992-01-01

    During the past two decades, interest in applying non-equilibrium plasmas to the removal of hazardous chemicals from gaseous media has been growing, in particular from heightened concerns over the pollution of our environment and a growing body of environmental regulations. At the Los Alamos National Laboratory, we are currently engaged in a project to develop non-equilibrium plasma technology for hazardous waste treatment. Our present focus is on dielectric-barrier discharges, which are historically called silent electrical discharges. This type of plasma is also named a silent discharge plasma (SDP). We have chosen this method due to its potential for high energy efficiency, its scientific and technological maturity, and its scalability. The SDP process has been demonstrated to be reliable and economical for the industrial-scale synthesis of ozone, where municipal water treatment plants frequently require the on-site generation of thousands of kilograins per day (Eliasson ampersand Kogelschatz). The related methods of corona processing are presently the focus of work at other institutions, particularly for flue gas processing. Both SDP and corona processes are characterized by the production of large quantities of highly reactive free radicals, especially atomic oxygen O(3P) and the hydroxyl OH, in the gaseous medium and their subsequent reaction with contaminants. Our primary objective is to convert hazardous or toxic chemicals into non-hazardous compounds or into materials which are more amenable to treatment. In the ideal case, the hazardous wastes are destructively oxidized to simpler, non-hazardous compounds plus CO2 and H2O. Sometimes the reaction products are still potentially hazardous, but are easily treated by conventional methods to yield non-hazardous products

  2. Spatio-temporal foreshock activity during stick-slip experiments of large rock samples

    Science.gov (United States)

    Tsujimura, Y.; Kawakata, H.; Fukuyama, E.; Yamashita, F.; Xu, S.; Mizoguchi, K.; Takizawa, S.; Hirano, S.

    2016-12-01

    Foreshock activity has sometimes been reported for large earthquakes, and has been roughly classified into the following two classes. For shallow intraplate earthquakes, foreshocks occurred in the vicinity of the mainshock hypocenter (e.g., Doi and Kawakata, 2012; 2013). And for intraplate subduction earthquakes, foreshock hypocenters migrated toward the mainshock hypocenter (Kato, et al., 2012; Yagi et al., 2014). To understand how foreshocks occur, it is useful to investigate the spatio-temporal activities of foreshocks in the laboratory experiments under controlled conditions. We have conducted stick-slip experiments by using a large-scale biaxial friction apparatus at NIED in Japan (e.g., Fukuyama et al., 2014). Our previous results showed that stick-slip events repeatedly occurred in a run, but only those later events were preceded by foreshocks. Kawakata et al. (2014) inferred that the gouge generated during the run was an important key for foreshock occurrence. In this study, we proceeded to carry out stick-slip experiments of large rock samples whose interface (fault plane) is 1.5 meter long and 0.5 meter wide. After some runs to generate fault gouge between the interface. In the current experiments, we investigated spatio-temporal activities of foreshocks. We detected foreshocks from waveform records of 3D array of piezo-electric sensors. Our new results showed that more than three foreshocks (typically about twenty) had occurred during each stick-slip event, in contrast to the few foreshocks observed during previous experiments without pre-existing gouge. Next, we estimated the hypocenter locations of the stick-slip events, and found that they were located near the opposite end to the loading point. In addition, we observed a migration of foreshock hypocenters toward the hypocenter of each stick-slip event. This suggests that the foreshock activity observed in our current experiments was similar to that for the interplate earthquakes in terms of the

  3. On thermal stability in incompressible slip flow

    International Nuclear Information System (INIS)

    Bestman, A.R.

    1990-12-01

    The paper considers the classical problem of the stability of a layer of fluid heated from below, but in the case when the density is low and there is slip flow at the bounding walls. The eigenvalue problem which ensures is tackled by taking cognisance of the orthogonality of Bessel function of the first kind. It is observed that the Rayleigh number for the onset of instability, for the case of marginal stability, is increased by gas rarefication. (author). 2 refs

  4. Slip processing of high Tc superconductors

    International Nuclear Information System (INIS)

    Sinha, R.K.; Sinha, R.K.

    1991-01-01

    Slip-processing technique has been used to fabricate tapes and alumina-supported films of superconducting YBa 2 Cu 3 Osub(7-x). Good densification and connectivity are revealed by scanning electron microscopy. Both the tape and film show superconductivity well above the liquid nitrogen temperature with a transition range of 3deg and 5degK respectively. (author). 10 refs., 4 figs

  5. Dynamic slip of polydisperse linear polymers using partitioned plate

    Science.gov (United States)

    Ebrahimi, Marzieh; Konaganti, Vinod Kumar; Hatzikiriakos, Savvas G.

    2018-03-01

    The slip velocity of an industrial grade high molecular weight high-density polyethylene (HDPE) is studied in steady and dynamic shear experiments using a stress/strain controlled rotational rheometer equipped with a parallel partitioned plate geometry. Moreover, fluoroalkyl silane-based coating is used to understand the effect of surface energy on slip in steady and dynamic conditions. The multimode integral Kaye-Bernstein-Kearsley-Zapas constitutive model is applied to predict the transient shear response of the HDPE melt obtained from rotational rheometer. It is found that a dynamic slip model with a slip relaxation time is needed to adequately predict the experimental data at large shear deformations. Comparison of the results before and after coating shows that the slip velocity is largely affected by surface energy. Decreasing surface energy by coating increases slip velocity and decreases the slip relaxation time.

  6. Oscillatory Stokes Flow Past a Slip Cylinder

    Science.gov (United States)

    Palaniappan, D.

    2013-11-01

    Two-dimensional transient slow viscous flow past a circular cylinder with Navier slip boundary conditions is considered in the limit of low-Reynolds number. The oscillatory Stokes flow problem around a cylinder is solved using the stream function method leading to an analytic solution in terms of modified Bessel functions of the second kind. The corresponding steady-state behavior yields the familiar paradoxical result first detected by Stokes. It is noted that the two key parameters, viz., the frequency λ, and the slip coefficient ξ have a significant impact on the flow field in the vicinity of the cylinder contour. In the limit of very low frequency, the flow is dominated by a term containing a well-known biharmonic function found by Stokes that has a singular behavior at infinity. Local streamlines for small times show interesting flow patterns. Attached eddies due to flow separation - observed in the no-slip case - either get detached or pushed away from the cylinder surface as ξ is varied. Computed asymptotic results predict that the flow exhibits inviscid behavior far away from the cylinder in the frequency range 0 < λ << 1 . Although the frequency of oscillations is finite, our exact solutions reveal fairly rapid transitions in the flow domain. Research Enhancement grant, TAMUCC.

  7. Slip length crossover on a graphene surface

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Zhi, E-mail: liangz3@rpi.edu [Rensselaer Nanotechnology Center, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Keblinski, Pawel, E-mail: keplip@rpi.edu [Rensselaer Nanotechnology Center, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    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.

  8. Slip cast coating of alumina crucibles

    International Nuclear Information System (INIS)

    Haroun, N.A.; El-Masry, M.A.A.

    1980-01-01

    The development of a process for coating alumina crucibles with MgO protective coat in a two-step slip casting operation is described. The best milling conditions for the alumina used were wet ball milling for 24 hr. MgO had to be calcined at 1200 0 C to minimize hydration. Optimum slip casting conditions for alumina and magnesia were found to be L/S I and pH 3-6 or 9-II for the former, and L/S 3 (alcohol) and pH 8.5-10 for the latter. Sintering of Al 2 O 3 and MgO in the temperature range 1150-500 0 C was investigated. Additions of NiO and MgO lowered the sintered densities at lower temperatures but improved the densification at 1500 0 C. Near theoretical density Al 2 O 3 and MgO crucibles were obtained. A two-step slip casting technique was developed to coat Al 2 O 3 with MgO. Certain slow firing schedules could eliminate the otherwise observed coat-crucible separation and cracks. (author)

  9. The evolving interaction of low-frequency earthquakes during transient slip.

    Science.gov (United States)

    Frank, William B; Shapiro, Nikolaï M; Husker, Allen L; Kostoglodov, Vladimir; Gusev, Alexander A; Campillo, Michel

    2016-04-01

    Observed along the roots of seismogenic faults where the locked interface transitions to a stably sliding one, low-frequency earthquakes (LFEs) primarily occur as event bursts during slow slip. Using an event catalog from Guerrero, Mexico, we employ a statistical analysis to consider the sequence of LFEs at a single asperity as a point process, and deduce the level of time clustering from the shape of its autocorrelation function. We show that while the plate interface remains locked, LFEs behave as a simple Poisson process, whereas they become strongly clustered in time during even the smallest slow slip, consistent with interaction between different LFE sources. Our results demonstrate that bursts of LFEs can result from the collective behavior of asperities whose interaction depends on the state of the fault interface.

  10. A terrestrial lidar-based workflow for determining three-dimensional slip vectors and associated uncertainties

    Science.gov (United States)

    Gold, Peter O.; Cowgill, Eric; Kreylos, Oliver; Gold, Ryan D.

    2012-01-01

    Three-dimensional (3D) slip vectors recorded by displaced landforms are difficult to constrain across complex fault zones, and the uncertainties associated with such measurements become increasingly challenging to assess as landforms degrade over time. We approach this problem from a remote sensing perspective by using terrestrial laser scanning (TLS) and 3D structural analysis. We have developed an integrated TLS data collection and point-based analysis workflow that incorporates accurate assessments of aleatoric and epistemic uncertainties using experimental surveys, Monte Carlo simulations, and iterative site reconstructions. Our scanning workflow and equipment requirements are optimized for single-operator surveying, and our data analysis process is largely completed using new point-based computing tools in an immersive 3D virtual reality environment. In a case study, we measured slip vector orientations at two sites along the rupture trace of the 1954 Dixie Valley earthquake (central Nevada, United States), yielding measurements that are the first direct constraints on the 3D slip vector for this event. These observations are consistent with a previous approximation of net extension direction for this event. We find that errors introduced by variables in our survey method result in <2.5 cm of variability in components of displacement, and are eclipsed by the 10–60 cm epistemic errors introduced by reconstructing the field sites to their pre-erosion geometries. Although the higher resolution TLS data sets enabled visualization and data interactivity critical for reconstructing the 3D slip vector and for assessing uncertainties, dense topographic constraints alone were not sufficient to significantly narrow the wide (<26°) range of allowable slip vector orientations that resulted from accounting for epistemic uncertainties.

  11. Seismogenic frictional melting in the magmatic column as the driving force of stick-slip motion

    Science.gov (United States)

    Kendrick, J. E.; Lavallee, Y.; Hirose, T.; Di Toro, G.; Hornby, A.; De Angelis, S.; Henton De Angelis, S.; Ferk, A.; Hess, K.; Leonhardt, R.; Dingwell, D. B.

    2013-12-01

    Lava dome eruptions subjected to high extrusion rates commonly evolve from endogenous to exogenous growth and limits to their structural stability hold catastrophic potential as explosive eruption triggers. In the conduit strain localisation in magma, accompanied by seismogenic failure, marks the onset of brittle magma ascent dynamics. The rock record of exogenous dome structures preserves vestiges of cataclastic processes and of thermal anomalies, key to unravelling subsurface processes. A combined structural, thermal and magnetic investigation of shear bands from Mount St. Helens (MSH) and Soufrière Hills volcano (SHV) reveal evidence of faulting and frictional melting within the magmatic column. High velocity rotary shear (HVR) experiments demonstrate the propensity for melting of andesitic and dacitic material (from SHV and MSH respectively) at upper conduit stress conditions. Such melting events may be linked to the step-wise extrusion of magma accompanied by repetitive long-period (LP) seismicity. Using a source duration calculated from the waveforms at seismic stations around SHV, and slip distance per drumbeat calculated from extrusion rate, frictional melting of SHV andesite in a high velocity rotary shear apparatus can be achieved at small slip distances (HVR experiments which mimic rapid velocity fluctuations in stick-slip behavior demonstrate velocity-weakening behavior of melt, with a tendency for unstable slip. We postulate that pseudotachylyte generation could be the underlying cause of stick-slip motion and associated seismic 'drumbeats', which are so commonly observed at dome-building volcanoes, allowing for a fixed spatial locus and the occurrence of 'families' of similar seismic events. We conclude that, given the ease with which melting is achieved in volcanic rocks, and considering the high ambient temperatures in volcanic conduits, frictional melting is a highly probable consequence of viscous magma ascent.

  12. Fatigue strain mapping via digital image correlation for Ni-based superalloys: The role of thermal activation on cube slip

    International Nuclear Information System (INIS)

    Mello, Alberto W.; Nicolas, Andrea; Sangid, Michael D.

    2017-01-01

    A deformation mechanism map for a Ni-based superalloy is presented during cyclic loading at low (300 °C), intermediate (550 °C), and high (700 °C) temperatures for low (0.7%) and high (1.0%) applied strain amplitudes. Strain mapping is performed via digital image correlation (DIC) during interrupted fatigue experiments at elevated temperatures at 1, 10, 100 and 1000 cycles, for each specified loading and temperature condition. The DIC measurements are performed in a scanning electron microscope, which allows high-resolution measurements of heterogeneous slip events and a vacuum environment to ensure stability of the speckle pattern for DIC at high temperatures. The cumulative fatigue experiments show that the slip bands are present in the first cycle and intensify with number of cycles; resulting in highly localized strain accumulation. The strain mapping results are combined with microstructure characterization via electron backscatter diffraction. The combination of crystal orientations and high-resolution strain measurements was used to determine the active slip planes. At low temperatures, slip bands follow the {111} octahedral planes. However, as temperature increases, both the {111} octahedral and {100} cubic slip planes accommodate strain. The activation of cubic slip via cross-slip within the ordered intermetallic γ’ phase has been well documented in Ni-based superalloys and is generally accepted as the mechanism responsible for the anomalous yield phenomenon. The results in this paper represent an important quantifiable study of cubic slip system activity at the mesoscale in polycrystalline γ-γ’ Ni-based superalloys, which is a key advancement to calibrate the thermal activation components of polycrystalline deformation models.

  13. Fatigue strain mapping via digital image correlation for Ni-based superalloys: The role of thermal activation on cube slip

    Energy Technology Data Exchange (ETDEWEB)

    Mello, Alberto W.; Nicolas, Andrea; Sangid, Michael D., E-mail: msangid@purdue.edu

    2017-05-17

    A deformation mechanism map for a Ni-based superalloy is presented during cyclic loading at low (300 °C), intermediate (550 °C), and high (700 °C) temperatures for low (0.7%) and high (1.0%) applied strain amplitudes. Strain mapping is performed via digital image correlation (DIC) during interrupted fatigue experiments at elevated temperatures at 1, 10, 100 and 1000 cycles, for each specified loading and temperature condition. The DIC measurements are performed in a scanning electron microscope, which allows high-resolution measurements of heterogeneous slip events and a vacuum environment to ensure stability of the speckle pattern for DIC at high temperatures. The cumulative fatigue experiments show that the slip bands are present in the first cycle and intensify with number of cycles; resulting in highly localized strain accumulation. The strain mapping results are combined with microstructure characterization via electron backscatter diffraction. The combination of crystal orientations and high-resolution strain measurements was used to determine the active slip planes. At low temperatures, slip bands follow the {111} octahedral planes. However, as temperature increases, both the {111} octahedral and {100} cubic slip planes accommodate strain. The activation of cubic slip via cross-slip within the ordered intermetallic γ’ phase has been well documented in Ni-based superalloys and is generally accepted as the mechanism responsible for the anomalous yield phenomenon. The results in this paper represent an important quantifiable study of cubic slip system activity at the mesoscale in polycrystalline γ-γ’ Ni-based superalloys, which is a key advancement to calibrate the thermal activation components of polycrystalline deformation models.

  14. Migraine with aura and silent brain infarcts lack of mediation of patent foramen ovale.

    Science.gov (United States)

    Calviere, L; Tall, P; Massabuau, P; Bonneville, F; Larrue, V

    2013-12-01

    Population-based studies have shown a heightened prevalence of clinically silent brain infarcts in subjects who have migraine with aura (MA). We sought to determine whether this association could be confirmed in young patients with cryptogenic ischemic stroke, and explored the role of patent foramen ovale (PFO) as a potential underlying mechanism. Patients were selected from a registry of young patients consecutively treated for ischemic stroke in a tertiary university hospital among those without definite cause of stroke. Patients with PFO were matched for age and gender with patients with normal atrial septum. Migraine and MA were evaluated after patient selection and matching. Silent brain infarcts were independently evaluated on MRI. We included 100 patients [60 men; mean age (SD), 44.8 years (8.3)], 50 patients with PFO. We found silent brain infarcts in 36 patients and MA in 13 patients. MA was more frequent in patients with silent brain infarcts than in patients without silent brain infarcts (25.0% vs. 6.3%; OR, 5; 95% CI, 1.4-17.6; P = 0.01). Traditional cardiovascular risk factors were not associated with silent brain infarcts. PFO was neither associated with MA (OR, 1.7; 95% CI, 0.5-5.3) nor silent brain infarcts (OR, 0.7; 95% CI, 0.3-1.5). The association of MA with silent brain infarcts was not altered after adjustment for PFO. Findings suggest that silent brain infarcts in young patients with cryptogenic stroke is associated with MA. We found no evidence for a mediating effect of PFO on this association. © 2013 The Author(s) European Journal of Neurology © 2013 EFNS.

  15. Screening for silent myocardial ischemia caseof diabetics : interest of myocardial perfusion scintigraphy

    International Nuclear Information System (INIS)

    Bahri, Haifa

    2007-01-01

    Silent myocardial ischemia is a major cause of morbidity and mortality in diabetic patients. Its diagnosis by noninvasive means such as myocardial SPECT would improve the management of these patients. The purpose of this study is to assess the frequency of silent myocardial ischemia in asymptomatic diabetics and their evolution. As a result, the myocardial SPECT is a reliable tool for screening for silent myocardial ischemia in diabetic patients. Its prognostic value allows to stratify the cardiac risk and guide therapeutic management. Its integration into a screening strategy in Tunisia seems limited by its low availability and cost. The latter could be reduced by better patient selection.

  16. Morphology and slip rate of the Hurunui section of the Hope Fault, South Island, New Zealand

    International Nuclear Information System (INIS)

    Langridge, R.M.; Berryman, K.R.

    2005-01-01

    The Hurunui section of the Hope Fault is a newly defined, 42 km long geomorphic fault section which extends from Harper Pass to the Hope-Boyle River confluence. Reconnaissance mapping along the Hurunui section from Hope Shelter to Harper Pass provided new data on its location, geomorphology, displacement, and slip rate. More than 200 previously published field observations of dextrally and vertically displaced landforms along the fault provide data on the distribution of displacement along the fault trace. Five radiocarbon dates found in association with offset geomorphic features are presented and two new measures of dextral slip rate are calculated. At McKenzie Stream, a late Holocene fan complex is cut by the Hope Fault. Young abandoned and active channels on this surface show dextral offsets of up to 22 ± 2 m along a south-facing scarp with a height of up to 5 m. Woody litter from a unit in this complex has yielded a radiocarbon age of 2331 ± 55 yr BP and a corresponding minimum horizontal slip rate of 8.1-11.0 mm/yr. At Macs Knob, large dextral deflections of stream catchments are linked to episodes of glacial resetting of the landscape. Correlation of the offset of 'Macs stream' (166 ± 17 m) with a post-Aranuian age peat (10,782 ± 60 yr BP) yields a maximum horizontal slip rate of 13.0 ± 1.5 mm/yr. The single-event dextral displacement, based on offset stream channels at McKenzie fan, is 3.2-3.8 m (av. c. 3.4 m). The ratio of dextral to vertical slip is c. 7 ± 2:1, indicating that the Hope Fault has a dominantly strike-slip sense of motion. The average recurrence interval for the last 5-7 events (i.e., to produce 19-24 m slip at McKenzie fan) is 310-490 yr. The age of the most recent surface-rupturing earthquake at this site is not known, though felt effects, fault scaling, and landscape arguments indicate it was not the AD 1888 North Canterbury earthquake. (author). 48 refs., 10 figs., 2 tabs

  17. Characterization of Aftershock Sequences from Large Strike-Slip Earthquakes Along Geometrically Complex Faults

    Science.gov (United States)

    Sexton, E.; Thomas, A.; Delbridge, B. G.

    2017-12-01

    Large earthquakes often exhibit complex slip distributions and occur along non-planar fault geometries, resulting in variable stress changes throughout the region of the fault hosting aftershocks. To better discern the role of geometric discontinuities on aftershock sequences, we compare areas of enhanced and reduced Coulomb failure stress and mean stress for systematic differences in the time dependence and productivity of these aftershock sequences. In strike-slip faults, releasing structures, including stepovers and bends, experience an increase in both Coulomb failure stress and mean stress during an earthquake, promoting fluid diffusion into the region and further failure. Conversely, Coulomb failure stress and mean stress decrease in restraining bends and stepovers in strike-slip faults, and fluids diffuse away from these areas, discouraging failure. We examine spatial differences in seismicity patterns along structurally complex strike-slip faults which have hosted large earthquakes, such as the 1992 Mw 7.3 Landers, the 2010 Mw 7.2 El-Mayor Cucapah, the 2014 Mw 6.0 South Napa, and the 2016 Mw 7.0 Kumamoto events. We characterize the behavior of these aftershock sequences with the Epidemic Type Aftershock-Sequence Model (ETAS). In this statistical model, the total occurrence rate of aftershocks induced by an earthquake is λ(t) = λ_0 + \\sum_{i:t_i

  18. Episodic Tremor and Slip Explained by Fluid-Enhanced Microfracturing and Sealing

    Science.gov (United States)

    Bernaudin, M.; Gueydan, F.

    2018-04-01

    Episodic tremor and slow-slip events at the deep extension of plate boundary faults illuminate seismic to aseismic processes around the brittle-ductile transition. These events occur in volumes characterized by overpressurized fluids and by near failure shear stress conditions. We present a new modeling approach based on a ductile grain size-sensitive rheology with microfracturing and sealing, which provides a mechanical and field-based explanation of such phenomena. We also model pore fluid pressure variation as a function of changes in porosity/permeability and strain rate-dependent fluid pumping. The fluid-enhanced dynamic evolution of microstructures defines cycles of ductile strain localization and implies increase in pore fluid pressure. We propose that slow-slip events are ductile processes related to transient strain localization, while nonvolcanic tremor corresponds to fracturing of the whole rock at the peak of pore fluid pressure. Our model shows that the availability of fluids and the efficiency of fluid pumping control the occurrence and the P-T conditions of episodic tremor and slip.

  19. A geophone wireless sensor network for investigating glacier stick-slip motion

    Science.gov (United States)

    Martinez, Kirk; Hart, Jane K.; Basford, Philip J.; Bragg, Graeme M.; Ward, Tyler; Young, David S.

    2017-08-01

    We have developed an innovative passive borehole geophone system, as part of a wireless environmental sensor network to investigate glacier stick-slip motion. The new geophone nodes use an ARM Cortex-M3 processor with a low power design capable of running on battery power while embedded in the ice. Only data from seismic events was stored, held temporarily on a micro-SD card until they were retrieved by systems on the glacier surface which are connected to the internet. The sampling rates, detection and filtering levels were determined from a field trial using a standard commercial passive seismic system. The new system was installed on the Skalafellsjökull glacier in Iceland and provided encouraging results. The results showed that there was a relationship between surface melt water production and seismic event (ice quakes), and these occurred on a pattern related to the glacier surface melt-water controlled velocity changes (stick-slip motion). Three types of seismic events were identified, which were interpreted to reflect a pattern of till deformation (Type A), basal sliding (Type B) and hydraulic transience (Type C) associated with stick-slip motion.

  20. A geodetic matched-filter search for slow slip with application to the Mexico subduction zone

    Science.gov (United States)

    Rousset, B.; Campillo, M.; Lasserre, C.; Frank, W.; Cotte, N.; Walpersdorf, A.; Socquet, A.; Kostoglodov, V.

    2017-12-01

    Since the discovery of slow slip events, many methods have been successfully applied to model obvious transient events in geodetic time series, such as the widely used network strain filter. Independent seismological observations of tremors or low frequency earthquakes and repeating earthquakes provide evidence of low amplitude slow deformation but do not always coincide with clear occurrences of transient signals in geodetic time series. Here, we aim to extract the signal corresponding to slow slips hidden in the noise of GPS time series, without using information from independent datasets. We first build a library of synthetic slow slip event templates by assembling a source function with Green's functions for a discretized fault. We then correlate the templates with post-processed GPS time series. Once the events have been detected in time, we estimate their duration T and magnitude Mw by modelling a weighted stack of GPS time series. An analysis of synthetic time series shows that this method is able to resolve the correct timing, location, T and Mw of events larger than Mw 6.0 in the context of the Mexico subduction zone. Applied on a real data set of 29 GPS time series in the Guerrero area from 2005 to 2014, this technique allows us to detect 28 transient events from Mw 6.3 to 7.2 with durations that range from 3 to 39 days. These events have a dominant recurrence time of 40 days and are mainly located at the down dip edges of the Mw > 7.5 SSEs.

  1. Detecting Silent Data Corruptions in Aerospace-Based Computing Using Program Invariants

    Directory of Open Access Journals (Sweden)

    Junchi Ma

    2016-01-01

    Full Text Available Soft error caused by single event upset has been a severe challenge to aerospace-based computing. Silent data corruption (SDC is one of the results incurred by soft error. SDC occurs when a program generates erroneous output with no indications. SDC is the most insidious type of results and very difficult to detect. To address this problem, we design and implement an invariant-based system called Radish. Invariants describe certain properties of a program; for example, the value of a variable equals a constant. Radish first extracts invariants at key program points and converts invariants into assertions. It then hardens the program by inserting the assertions into the source code. When a soft error occurs, assertions will be found to be false at run time and warn the users of soft error. To increase the coverage of SDC, we further propose an extension of Radish, named Radish_D, which applies software-based instruction duplication mechanism to protect the uncovered code sections. Experiments using architectural fault injections show that Radish achieves high SDC coverage with very low overhead. Furthermore, Radish_D provides higher SDC coverage than that of either Radish or pure instruction duplication.

  2. Silent ischemia in patients after the acute myocardial infarction

    International Nuclear Information System (INIS)

    Samarzija, M.

    1991-01-01

    The purpose of this study was to determine the frequency and importance of silent ischemia in patients (pts) after acute myocardial infarction (AMI) as well as to establish diagnostic and prognostic values of exercise stress test (EST), Holter (H) monitoring and thallium-201 (Tl) scintigraphy. All the tests were performed 2-4 months following the AMI. The criterion for diagnostic myocardial ischemia on EST and H is 1 mm or more of horizontal or down-sloping ST depression. Additional criteria for Holter imply that the ischemic episode should last one minute and be separated from other episodes by at least one minute. Planar thallium images were performed 5-10 minutes after the stress test; the delayed images were obtained after 3-6 hours. Visual and quantitative methods were employed in the analysis of Tl-scintigraphy. Scintigraphy was considered positive if exercise-induced perfusion defects showed redistribution. The study included 74 asymptomatic patients after the AMI. The patients were divided into two groups by results of quantitative Tl-scintigraphy: Group I - 44 pts with silent ischemia, Group II - 30 pts without ischemia. In Group I, out of 44 pts, 9 had a positive exercise stress test, 4 showed a painless ST depression on Holter and 7 had both tests positive, whereas 24 pts had only scintigraphy positive. In Group II one patient had positive EST and H. Sensitivity and specificity were determined by results of coronary arteriography performed on 33 pts: EST (Se=40%, Sp=80%), H (Se=21%, Sp=100%) and scintigraphy (Se=93%, Sp=80%). During the follow-up period lasting at least 12 months, in Group I 3 pts died, 1 developed a new myocardial infarction and 15 pts had painful ischemic occurrences. In Group II only 3 pts developed symptoms of angina pectoris. Tl-scintigraphy was the only non-invasive test showing significant correlation with the follow-up outcomes. The diagnostic and prognostic superiority of Tl-scintigraphy justifies its value as an initial

  3. Silent ischemia in patients after uncomplicated myocardial infarction

    International Nuclear Information System (INIS)

    Samarzija, M.; Tezak, S.

    1994-01-01

    The purpose of this study was to determine the frequency and importance of silent ischemia in patients (pts) after the acute myocardial infarction (A MI) as well as to establish diagnostic and prognostic value of exercise stress test (EST), Holter (H) monitoring and thallium-201 (Tl) scintigraphy. All the three tests were performed 2-4 months following the AMI. The criterion for diagnosing myocardial ischemia on EST and H is 1 mm or more of horizontal or down-sloping ST depression. Additional criteria for Holter imply the ischemic episode should last one minute and be separated from other episodes by at least one minute. Planar thallium images were performed 5-10 minute after the stress test; the delayed images were obtained after 3-6 hours. Visual and quantitative methods were employed in the analysis of TI-scintigraphy. Scintigraphy was considered positive if exercise- induced perfusion defects showed redistribution. The study included 74 asymptomatic patients after the AMI. The patients were divided into two groups by results of quantitative Tl-scintigraphy: Group I - 44 pts with silent ischemia, Group II - 30 pts without ischemia. In Group I, out of 44 pts, 9 had a positive exercise stress, 4 showed a painless ST depression on Holter and 7 had both tests positive, whereas 24 pts had only scintigraphy positive. In Group II one patient had positive EST and H. Sensitivity and specificity were determined by results of coronary arteriography performed on 33 pts: EST (Se=40%, Sp=80%), H (Se=219, Sp=100%) and scintigraphy (Se=93%, Sp =80%). During the follow-up period lasting at least 12 months, in Group I 3 pts died, 1 developed a new myocardial infarction and 15 pts had painful ischemic occurrences. In Group II only 3 pts developed symptoms of angina pectoris. Tl-scintigraphy was the only non-invasive test showing significant correlation with the follow-up outcomes. The diagnostic and prognostic superiority of Tl-scintigraphy justifies its value as the initial

  4. Slip control for LIM propelled transit vehicles

    Science.gov (United States)

    Wallace, A. K.; Parker, J. H.; Dawson, G. E.

    1980-09-01

    Short stator linear induction motors, with an iron-backed aluminum sheet reaction rail and powered by a controlled inverter, have been selected as the propulsion system for transit vehicles in an intermediate capacity system (12-20,000 pphpd). The linear induction motor is capable of adhesion independent braking and acceleration levels which permit safe, close headways. In addition, simple control is possible allowing moving block automatic train control. This paper presents a slip frequency control scheme for the LIM. Experimental results for motoring and braking obtained from a test vehicle are also presented. These values are compared with theoretical predictions.

  5. The evolution of the Gutenberg-Richter, b-value, throughout periodic and aperiodic stick-slip cycles

    Science.gov (United States)

    Bolton, D. C.; Riviere, J.; Marone, C.; Johnson, P. A.

    2017-12-01

    The Gutenberg-Richter earthquake size statistic, b value, is a useful proxy for documenting the state of stress on a fault and understanding precursory phenomena preceding dynamic failure. It has been shown that the b value varies systematically as a function of position within the seismic cycle. Frictional studies on intact rock samples with saw-cut faults have shown that b value decreases continuously preceding failure. For intact rock samples, the spatiotemporal changes in b value are thought to be related to the evolution of asperities and micro-cracks. However, few studies have shown how b value evolves spatially and temporally for fault zones containing gouge and wear materials. We hypothesize that the micromechanical mechanisms acting within fault gouge, such as creation and destruction of force chains, grain rolling, sliding, jamming and fracturing play an important role in the evolution of b value and that they may have distinct signatures during periodic and aperiodic cycles of stick-slip frictional motion. We report results from experiments conducted on simulated fault gouge using a biaxial deformation apparatus in a double-direct shear configuration. Acoustic emissions (AEs) are recorded at 4 MHz from 36 P-polarized piezoelectric transducers, which are embedded in steel blocks located adjacent to the fault zone. We compute the frequency-magnitude distribution of detected AEs using a moving window in events where each window is overlapped by 75%. We report on the evolution of b value as a function of normal stress and gouge layer thickness. For periodic slip events, b value reaches a maximum value immediately after a slip event and decreases continuously until the next failure. Aperiodic slip events show similar trends in b-value initially, however unlike periodic slip events, b value reaches a steady state value before failure occurs. In addition, for periodic slip events the magnitude of the change in b value scales inversely with gouge layer thickness

  6. Boundary Slip and Surface Interaction: A Lattice Boltzmann Simulation

    International Nuclear Information System (INIS)

    Yan-Yan, Chen; Hua-Bing, Li; Hou-Hui, Yi

    2008-01-01

    The factors affecting slip length in Couette geometry flows are analysed by means of a two-phase mesoscopic lattice Boltzmann model including non-ideal fluid-fluid and fluid-wall interactions. The main factors influencing the boundary slip are the strength of interactions between fluid-fluid and fluid-wall particles. Other factors, such as fluid viscosity, bulk pressure may also change the slip length. We find that boundary slip only occurs under a certain density (bulk pressure). If the density is large enough, the slip length will tend to zero. In our simulations, a low density layer near the wall does not need to be postulated a priori but emerges naturally from the underlying non-ideal mesoscopic dynamics. It is the low density layer that induces the boundary slip. The results may be helpful to understand recent experimental observations on the slippage of micro flows

  7. Closed central slip injuries--a missed diagnosis?

    LENUS (Irish Health Repository)

    Nugent, N

    2011-09-01

    The extensor apparatus of the finger is a complex structure and injury can lead to significant digital dysfunction. Closed central slip injuries may be missed or diagnosis delayed because of lack of an open wound and often no radiographic abnormality, and can result in boutonniere deformities if untreated. This study aimed to quantify the number of patients attending with closed central slip injuries and to ascertain if the initial diagnosis was correct. The number of patients presenting to us over a 6 month period was recorded. The original diagnosis, time to diagnosis of central slip injury and the presence\\/absence of a boutonniere deformity were recorded. Ten patients were included in the study. Seven (70%) injuries were due to sport. Eight (80%) had a delayed diagnosis of central slip injury. Six (60%) had previously presented to general practitioners or emergency departments. Seven (70%) had boutonniere deformities. Closed central slip injuries can be missed. Simple clinical tests can diagnose central slip disruption.

  8. Using Low-Frequency Earthquakes to Investigate Slow Slip Processes and Plate Interface Structure Beneath the Olympic Peninsula, WA

    Science.gov (United States)

    Chestler, Shelley

    This dissertation seeks to further understand the LFE source process, the role LFEs play in generating slow slip, and the utility of using LFEs to examine plate interface structure. The work involves the creation and investigation of a 2-year-long catalog of low-frequency earthquakes beneath the Olympic Peninsula, Washington. In the first chapter, we calculate the seismic moments for 34,264 low-frequency earthquakes (LFEs) beneath the Olympic Peninsula, WA. LFE moments range from 1.4x1010- 1.9x1012 N-m (M W=0.7-2.1). While regular earthquakes follow a power-law moment-frequency distribution with a b-value near 1 (the number of events increases by a factor of 10 for each unit increase in MW), we find that while for large LFEs the b-value is ˜6, for small LFEs it is families, or spots on the plate interface where LFEs repeat, can also be fit by exponential distributions. An exponential moment-frequency distribution implies a scale-limited source process. We consider two end-member models where LFE moment is limited by (1) the amount of slip or (2) slip area. We favor the area-limited model. Based on the observed exponential distribution of LFE moment and geodetically observed total slip we estimate that the total area that slips within an LFE family has a diameter of 300 m. Assuming an area-limited model, we estimate the slips, sub-patch diameters, stress drops, and slip rates for LFEs during ETS events. We allow for LFEs to rupture smaller sub-patches within the LFE family patch. Models with 1-10 sub-patches produce slips of 0.1-1 mm, sub-patch diameters of 80-275 m, and stress drops of 30-1000 kPa. While one sub-patch is often assumed, we believe 3-10 sub-patches are more likely. In the second chapter, using high-resolution relative low-frequency earthquake (LFE) locations, we calculate the patch areas (Ap) of LFE families. During Episodic Tremor and Slip (ETS) events, we define AT as the area that slips during LFEs and ST as the total amount of summed LFE slip

  9. Kids Speak: Preferred Parental Behavior at Youth Sport Events

    Science.gov (United States)

    Omli, Jens; Wiese-Bjornstal, Diane M.

    2011-01-01

    News reports (e.g., Abrams, 2008) and scholarly research (e.g., Wiersma & Fifer, 2005) have indicated increasing concern that parent-spectator behavior at youth sport events may be problematic. Multiple strategies have been used to influence spectator behavior in youth sport contexts (e.g., "Silent Sundays"). However, it is unlikely that…

  10. Silent angels the genetic and clinical aspects of Rett syndrome

    Directory of Open Access Journals (Sweden)

    Dziwota Ewelina

    2016-12-01

    Full Text Available Rett syndrome is a neurodevelopmental genetic disorder and, because of some behavioral characteristics, individuals affected by the disease are known as silent angels. Girls with Rett syndrome perform stereotyped movements, they have learning difficulties, their reaction time is prolonged, and they seem alienated in the environment. These children require constant pediatric, neurological and orthopedic care. In the treatment of Rett syndrome physical therapy, music therapy, hydrotherapy, hippotherapy, behavioral methods, speech therapy and diet, are also used. In turn, psychological therapy of the syndrome is based on the sensory integration method, using two or more senses simultaneously. In 80% of cases, the syndrome is related to mutations of the MECP2 gene, located on chromosome X. The pathogenesis of Rett syndrome is caused by the occurrence of a non-functional MeCP2 protein, which is a transcription factor of many genes, i.e. Bdnf, mef2c, Sgk1, Uqcrc1. Abnormal expression of these genes reveals a characteristic disease phenotype. Clinical symptoms relate mainly to the nervous, respiratory, skeletal and gastrointestinal systems. Currently causal treatment is not possible. However, researchers are developing methods by which, perhaps in the near future, it will be possible to eliminate the mutations in the MECP2 gene, and this will give a chance to the patient for normal functioning.

  11. The silent mass extinction of insect herbivores in biodiversity hotspots.

    Science.gov (United States)

    Fonseca, Carlos Roberto

    2009-12-01

    Habitat loss is silently leading numerous insects to extinction. Conservation efforts, however, have not been designed specifically to protect these organisms, despite their ecological and evolutionary significance. On the basis of species-host area equations, parameterized with data from the literature and interviews with botanical experts, I estimated the number of specialized plant-feeding insects (i.e., monophages) that live in 34 biodiversity hotspots and the number committed to extinction because of habitat loss. I estimated that 795,971-1,602,423 monophagous insect species live in biodiversity hotspots on 150,371 endemic plant species, which is 5.3-10.6 monophages per plant species. I calculated that 213,830-547,500 monophagous species are committed to extinction in biodiversity hotspots because of reduction of the geographic range size of their endemic hosts. I provided rankings of biodiversity hotspots on the basis of estimated richness of monophagous insects and on estimated number of extinctions of monophagous species. Extinction rates were predicted to be higher in biodiversity hotspots located along strong environmental gradients and on archipelagos, where high spatial turnover of monophagous species along the geographic distribution of their endemic plants is likely. The results strongly support the overall strategy of selecting priority conservation areas worldwide primarily on the basis of richness of endemic plants. To face the global decline of insect herbivores, one must expand the coverage of the network of protected areas and improve the richness of native plants on private lands.

  12. Silent Sinus Syndrome: A Retrospective Review of 11 Cases

    Directory of Open Access Journals (Sweden)

    Karima DARGHAL

    2014-06-01

    Full Text Available Objective: The purpose of this study is to describe the clinical and radiological features of SSS, and to review therapeutic possibilities and their outcomes.Patients and Methods: Retrospective observational case series in the department of Arthur Vernes Institute between Mars 2007 and  Novembre 2012. Clinical records, including ophthalmology and otolaryngology evaluations as well as computed tomography scans and operative reports, were carefully examined. A literature review for relevant studies was performed to examine similar cases.Results: Eleven cases of  SSS were identified. Nine men and two women (sex ratio 4.5, aged between 23 and 54 years (mean, 30 years. there was 3 to 4 mm enophthalmos in 10 cases (90.9%, and hypoglobus in all cases, with no effect on visual function. In all 11 cases, the maxillary roof (orbital floor was drawn downwards, and the one or more walls of the maxilla were concave. In 4 cases septal deviation was present. 8 patients (72.7% underwent endoscopic sinus surgery, while 3 refused it. Septoplasty was performed in 4 cases (36.3%.Conclusion: The silent sinus syndrome is a rare entity. It mainly presents as unilateral enophthalmos in younger people and has very characteristic clinical and radiologic signs.This case series reports our diagnostic and therapeutic experience with this syndrome.

  13. Silent Spring, the 50th anniversary of Rachel Carson's book.

    Science.gov (United States)

    Pimentel, David

    2012-09-27

    David Pimentel is a professor of ecology and agricultural sciences at Cornell University, Ithaca, NY 14853-0901. His Ph.D. is from Cornell University and had postdoctoral research at the University of Chicago, MIT, and fellowship at Oxford University (England). He was awarded a distinguished honorary degree from the University of Massachusetts. His research spans the fields of energy, population ecology, biological pest control, pesticides, sustainable agriculture, land and water conservation, livestock, and environmental policy. Pimentel has published more than 700 scientific papers and 37 books and has served on many national and government committees including the National Academy of Sciences; President's Science Advisory Council; U.S Department of Agriculture; U.S. Department of Energy; U.S. Department of Health, Education and Welfare; Office of Technology Assessment of the U.S. Congress; and the U.S. State Department. He is currently Editorial Advisor for BMC Ecology. In this article, he reflects on 50 years since the publication of Rachel Carson's influential book, Silent Spring.

  14. Sonographically determined clues to the symptomatic or silent cholelithiasis

    International Nuclear Information System (INIS)

    Saba, S.; Iqbal, Z.

    2007-01-01

    To determine an association between sonographically determined contractility with the symptomatic or silent nature of gallstone. Adult gallstone patients without (group I) and with biliary symptoms (group II) were compared with age and gender-matched controls. Demographic data, body mass index, risk factors, size, number and mobility of gallstone, gallbladder wall thickness (GBWT), volume and Ejection Fraction (EF) were determined on ultrasound before and after a standardized fatty meal (BFM and AFM). Demographic data, risk factors and gallstone characteristics were analyzed by Pearson Chi-square test and the gallbladder characteristics were analyzed by One-way ANOVA and Post Hoc tests by multiple comparisons on SPSS 11 with significance p=0.05. The gallbladder contractility as measured by changes in wall thickness and volume changes BFM and AFM, and ejection fraction was similar in controls and asymptomatic cholelithiasis groups and significantly reduced in symptomatic patients (p<.001). Multiparity (p=0.002), female gender (p=0.018), age less than 50 years (0.05), impacted calculi (p=0.001), multiple calculi (<.001) and calculi 5 mm (p<0.001) were associated with pain. A sluggishly emptying gallbladder was more significantly associated with symptomatic cholelithiasis compared to controls and asymptomatic cholelithiasis state in this series. Consideration of age, gender, impaction of calculi, number and size of calculi is important in causing symptom state and management options. (author)

  15. Construction of the Cylindrical Ozone Generator by Silent Discharge Method

    International Nuclear Information System (INIS)

    Agus Purwadi; Widdi Usada; Suryadi; Isyuniarto; Sri Sukmajaya

    2002-01-01

    It has been constructed the ozone generator by silent discharge method. Anode and cathode of discharge tube were made of stainless steel (SS) in the cylinder form with diameters of 22 mm and 25 mm, the length of 100 mm and 110 mm, the equal thickness of 1 mm respectively. The dielectric was made of cylinder glass with diameter of 23 cm, the length of 105 cm and the thickness of 1 mm. The testing of apparatus was carried out by using discharge voltage of 12.5 kV and frequency of 1.5 kHz. Identification of the ozone gas formation was marked by the existing of special ozone smell and the separated of iodine molecule (yellow colour) from the potassium iodide solution which contaminated gas out put from the ozonizer. By using absorbing method can be shown that the ozone production rate was 0.196 mg/s by using oxygen gas input and 0.065 mg/s by using ordinary air input. (author)

  16. Silent Aortic Dissection Presenting as Transient Locked-In Syndrome

    Science.gov (United States)

    Nadour, Wadih; Goldwasser, Brian; Biederman, Robert W.; Taffe, Kevin

    2008-01-01

    Acute aortic dissection is a medical emergency. Without prompt recognition and treatment, the mortality rate is high. An atypical presentation makes timely diagnosis difficult, especially if the patient is experiencing no characteristic pain. Many patients with aortic dissection are reported to have presented with various neurologic manifestations, but none with only a presentation of transient locked-in syndrome. Herein, we report a case of completely painless aortic dissection in a woman who presented with a transient episode of anarthria, quadriplegia, and preserved consciousness. On physical examination, she had a 40-point difference in blood pressure between her left and right arms, and a loud diastolic murmur. The diagnosis of acute aortic dissection was reached via a combination of radiography, computed tomography, echocardiography, and a high index of clinical suspicion. The patient underwent emergency surgery and ultimately experienced a successful outcome. To our knowledge, this is the 1st report of aortic dissection that presented solely as locked-in syndrome. We suggest that silent aortic dissection be added to the differential diagnosis for transient locked-in syndrome. PMID:18941610

  17. Slip reactivation during the 2011 Tohoku earthquake: Dynamic rupture and ground motion simulations

    Science.gov (United States)

    Galvez, P.; Dalguer, L. A.

    2013-12-01

    The 2011 Mw9 Tohoku earthquake generated such as vast geophysical data that allows studying with an unprecedented resolution the spatial-temporal evolution of the rupture process of a mega thrust event. Joint source inversion of teleseismic, near-source strong motion and coseismic geodetic data , e.g [Lee et. al, 2011], reveal an evidence of slip reactivation process at areas of very large slip. The slip of snapshots of this source model shows that after about 40 seconds the big patch above to the hypocenter experienced an additional push of the slip (reactivation) towards the trench. These two possible repeating slip exhibited by source inversions can create two waveform envelops well distinguished in the ground motion pattern. In fact seismograms of the KiK-Net Japanese network contained this pattern. For instance a seismic station around Miyagi (MYGH10) has two main wavefronts separated between them by 40 seconds. A possible physical mechanism to explain the slip reactivation could be a thermal pressurization process occurring in the fault zone. In fact, Kanamori & Heaton, (2000) proposed that for large earthquakes frictional melting and fluid pressurization can play a key role of the rupture dynamics of giant earthquakes. If fluid exists in a fault zone, an increase of temperature can rise up the pore pressure enough to significantly reduce the frictional strength. Therefore, during a large earthquake the areas of big slip persuading strong thermal pressurization may result in a second drop of the frictional strength after reaching a certain value of slip. Following this principle, we adopt for slip weakening friction law and prescribe a certain maximum slip after which the friction coefficient linearly drops down again. The implementation of this friction law has been done in the latest unstructured spectral element code SPECFEM3D, Peter et. al. (2012). The non-planar subduction interface has been taken into account and place on it a big asperity patch inside

  18. Progressive slip after removal of screw fixation in slipped capital femoral epiphysis: two case reports

    NARCIS (Netherlands)

    Engelsma, Y.; Morgenstern, P.; van der Sluijs, J.A.; Witbreuk, M.M.

    2012-01-01

    Introduction. In slipped capital femoral epiphysis the femoral neck displaces relative to the head due to weakening of the epiphysis. Early recognition and adequate surgical fixation is essential for a good functional outcome. The fixation should be secured until the closure of the epiphysis to

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

    Science.gov (United States)

    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

  20. Agreement of the silent partnership – tax and legal consequences of its conclusion and execution

    OpenAIRE

    Monika Zieniewicz

    2016-01-01

    The institution of the silent partnership is not currently regulated by any legal act in the Polish legal system, although its importance in practice is not in doubt. As every action made in the economic sphere and economic execution of the contract is associated with specific effects on the basis of the tax laws. However, due to the lack of statutory regulation of the institution of silent partnership problematic is the question of determining the effects of tax legislation. Therefore, speci...

  1. Experimental investigation of flow and slip transition in nanochannels

    Science.gov (United States)

    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.

  2. Slipped capital femoral epiphysis: A modern treatment protocol

    Directory of Open Access Journals (Sweden)

    Slavković Nemanja

    2009-01-01

    Full Text Available The treatment of a patient with slipped capital femoral epiphysis begins with an early diagnosis and accurate classification. On the basis of symptom duration, clinical findings and radiographs, slipped capital femoral epiphysis is classified as pre-slip, acute, acute-on-chronic and chronic. The long-term outcome of slipped capital femoral epiphysis is directly related to severity and the presence or absence of avascular necrosis and/or chondrolysis. Therefore, the first priority in the treatment of slipped capital femoral epiphysis is to avoid complications while securing the epiphysis from further slippage. Medical treatment of patients with acute and acute-on-chronic slipped capital femoral epiphysis, as well as those presented in pre-slip stage, is the safest, although time-consuming. Manipulations, especially forced and repeated, are not recommended due to higher avascular necrosis risk. The use of intraoperative fluoroscopy to assist in the placement of internal fixation devices has markedly increased the success of surgical treatment. Controversy remains as to whether the proximal femoral epiphysis in severe, chronic slipped capital femoral epiphysis should be realigned by extracapsular osteotomies or just fixed in situ. The management protocol for slipped capital femoral epiphysis depends on the experience of the surgeon, motivation of the patient and technical facilities.

  3. Multiparameter Monitoring and Prevention of Fault-Slip Rock Burst

    OpenAIRE

    Hu, Shan-chao; Tan, Yun-liang; Ning, Jian-guo; Guo, Wei-Yao; Liu, Xue-sheng

    2017-01-01

    Fault-slip rock burst is one type of the tectonic rock burst during mining. A detailed understanding of the precursory information of fault-slip rock burst and implementation of monitoring and early warning systems, as well as pressure relief measures, are essential to safety production in deep mines. This paper first establishes a mechanical model of stick-slip instability in fault-slip rock bursts and then reveals the failure characteristics of the instability. Then, change rule of mining-i...

  4. Stochastic Wheel-Slip Compensation Based Robot Localization and Mapping

    Directory of Open Access Journals (Sweden)

    SIDHARTHAN, R. K.

    2016-05-01

    Full Text Available Wheel slip compensation is vital for building accurate and reliable dead reckoning based robot localization and mapping algorithms. This investigation presents stochastic slip compensation scheme for robot localization and mapping. Main idea of the slip compensation technique is to use wheel-slip data obtained from experiments to model the variations in slip velocity as Gaussian distributions. This leads to a family of models that are switched depending on the input command. To obtain the wheel-slip measurements, experiments are conducted on a wheeled mobile robot and the measurements thus obtained are used to build the Gaussian models. Then the localization and mapping algorithm is tested on an experimental terrain and a new metric called the map spread factor is used to evaluate the ability of the slip compensation technique. Our results clearly indicate that the proposed methodology improves the accuracy by 72.55% for rotation and 66.67% for translation motion as against an uncompensated mapping system. The proposed compensation technique eliminates the need for extro receptive sensors for slip compensation, complex feature extraction and association algorithms. As a result, we obtain a simple slip compensation scheme for localization and mapping.

  5. The written voice: implicit memory effects of voice characteristics following silent reading and auditory presentation.

    Science.gov (United States)

    Abramson, Marianne

    2007-12-01

    After being familiarized with two voices, either implicit (auditory lexical decision) or explicit memory (auditory recognition) for words from silently read sentences was assessed among 32 men and 32 women volunteers. In the silently read sentences, the sex of speaker was implied in the initial words, e.g., "He said, ..." or "She said...". Tone in question versus statement was also manipulated by appropriate punctuation. Auditory lexical decision priming was found for sex- and tone-consistent items following silent reading, but only up to 5 min. after silent reading. In a second study, similar lexical decision priming was found following listening to the sentences, although these effects remained reliable after a 2-day delay. The effect sizes for lexical decision priming showed that tone-consistency and sex-consistency were strong following both silent reading and listening 5 min. after studying. These results suggest that readers create episodic traces of text from auditory images of silently read sentences as they do during listening.

  6. Source study of the Jan Mayen transform fault strike-slip earthquakes

    Science.gov (United States)

    Rodríguez-Pérez, Q.; Ottemöller, L.

    2014-07-01

    Seismic source parameters of oceanic transform zone earthquakes have been relatively poorly studied. Previous studies showed that this type of earthquakes has unique characteristics such as not only the relatively common occurrence of slow events with weak seismic radiation at high frequencies but also the occurrence of some events that have high apparent stress indicating strong high frequency radiation. We studied 5 strike-slip earthquakes in the Jan Mayen fracture zone with magnitudes in the range of 5.9 centroid time delay compared to other oceanic transform fault earthquakes.

  7. Strike-slip tectonics during rift linkage

    Science.gov (United States)

    Pagli, C.; Yun, S. H.; Ebinger, C.; Keir, D.; Wang, H.

    2017-12-01

    The kinematics of triple junction linkage and the initiation of transforms in magmatic rifts remain debated. Strain patterns from the Afar triple junction provide tests of current models of how rifts grow to link in area of incipient oceanic spreading. Here we present a combined analysis of seismicity, InSAR and GPS derived strain rate maps to reveal that the plate boundary deformation in Afar is accommodated primarily by extensional tectonics in the Red Sea and Gulf of Aden rifts, and does not require large rotations about vertical axes (bookshelf faulting). Additionally, models of stress changes and seismicity induced by recent dykes in one sector of the Afar triple junction provide poor fit to the observed strike-slip earthquakes. Instead we explain these patterns as rift-perpendicular shearing at the tips of spreading rifts where extensional strains terminate against less stretched lithosphere. Our results demonstrate that rift-perpendicular strike-slip faulting between rift segments achieves plate boundary linkage during incipient seafloor spreading.

  8. Quaternary Slip History for the Agua Blanca Fault, northern Baja California, Mexico

    Science.gov (United States)

    Gold, P. O.; Behr, W. M.; Rockwell, T. K.; Fletcher, J. M.

    2017-12-01

    The Agua Blanca Fault (ABF) is the primary structure accommodating San Andreas-related right-lateral slip across the Peninsular Ranges of northern Baja California. Activity on this fault influences offshore faults that parallel the Pacific coast from Ensenada to Los Angeles and is a potential threat to communities in northern Mexico and southern California. We present a detailed Quaternary slip history for the ABF, including new quantitative constraints on geologic slip rates, slip-per-event, the timing of most recent earthquake, and the earthquake recurrence interval. Cosmogenic 10Be exposure dating of clasts from offset fluvial geomorphic surfaces at 2 sites located along the western, and most active, section of the ABF yield preliminary slip rate estimates of 2-4 mm/yr and 3 mm/yr since 20 ka and 2 ka, respectively. Fault zone geomorphology preserved at the younger site provides evidence for right-lateral surface displacements measuring 2.5 m in the past two ruptures. Luminescence dating of an offset alluvial fan at a third site is in progress, but is expected to yield a slip rate relevant to the past 10 kyr. Adjacent to this third site, we excavated 2 paleoseismic trenches across a sag pond formed by a right step in the fault. Preliminary radiocarbon dates indicate that the 4 surface ruptures identified in the trenches occurred in the past 6 kyr, although additional dating should clarify earthquake timing and the mid-Holocene to present earthquake recurrence interval, as well as the likely date of the most recent earthquake. Our new slip rate estimates are somewhat lower than, but comparable within error to, previous geologic estimates based on soil morphology and geodetic estimates from GPS, but the new record of surface ruptures exposed in the trenches is the most complete and comprehensively dated earthquake history yet determined for this fault. Together with new and existing mapping of tectonically generated geomorphology along the ABF, our constraints

  9. Short-and-long-term Slip Rates Along the Carboneras Fault in the Betic Cordillera, Spain

    Science.gov (United States)

    Khazaradze, G.; López, R.; Pallàs, R.; Ortuño, M.; Bordonau, J.; Masana, E.

    2017-12-01

    We present the new results from our long-standing studies to understand the geodynamic behavior of the Carboneras fault, located in the SE Betic Cordilleras of Spain. Specifically, we quantify the geodetic and geologic slip rates for the onland section of the fault. As a result of our previous GPS observations, we have been able to confirm the continuing tectonic activity of the Carboneras fault: we were able to quantify that the geodetic slip rate of the fault equals 1.3±0.2 mm/yr, expressed mainly as a left-lateral strike slip motion (Echeverria et al., 2015). In autumn 2017, with the purpose of revealing a detailed nature of the crustal deformation and its partitioning between different structures, 3 new continuous GPS stations will be established along the fault-perpendicular profile. In addition, since summer 2016, we have conducted surveys of the nearby CuaTeNeo and IGN Regente campaign points. We have also established and measured several new geodetic points in the vicinity of the fault, with the aim of increasing the spatial coverage around it. The GPS measured, short-term slip rates are in surprising agreement with the estimates of the long-term, geologic slip rates based on paleoseismic studies, which indicate a minimum strike-slip rate of 1.31 mm/yr and dip-slip rate of 0.05 mm/yr since 110.3 ka (Moreno et al. 2015). In order to increase the paleoseismic event database, several new sites have been identified along the fault, where further paleoseismic trenching surveys will be performed within the coming year or two. At the site of Tostana, located at the central part of the fault, in winter 2017 seven trenches have been opened and clear evidence of past earthquakes has been encountered. These new data, combined with the findings of the recent geomorphological study of river offsets (Ferrater, 2016) and new GPS observations, should improve the reliability of the existent deformation data and therefore, will help to better understand the seismic hazard

  10. Paleoseismic evidence of characteristic slip on the Western segment of the North Anatolian fault, Turkey

    Science.gov (United States)

    Klinger, Yann; Sieh, K.; Altunel, E.; Akoglu, A.; Barka, A.; Dawson, Tim; Gonzalez, Tania; Meltzner, A.; Rockwell, Thomas

    2003-01-01

    We have conducted a paleoseismic investigation of serial fault rupture at one site along the 110-km rupture of the North Anatolian fault that produced the Mw 7.4 earthquake of 17 August 1999. The benefit of using a recent rupture to compare serial ruptures lies in the fact that the location, magnitude, and slip vector of the most recent event are all very well documented. We wished to determine whether or not the previous few ruptures of the fault were similar to the recent one. We chose a site at a step-over between two major strike-slip traces, where the principal fault is a normal fault. Our two excavations across the 1999 rupture reveal fluvial sands and gravels with two colluvial wedges related to previous earthquakes. Each wedge is about 0.8 m thick. Considering the processes of collapse and subsequent diffusion that are responsible for the formation of a colluvial wedge, we suggest that the two paleoscarps were similar in height to the 1999 scarp. This similarity supports the concept of characteristic slip, at least for this location along the fault. Accelerator mass spectrometry (AMS) radiocarbon dates of 16 charcoal samples are consistent with the interpretation that these two paleoscarps formed during large historical events in 1509 and 1719. If this is correct, the most recent three ruptures at the site have occurred at 210- and 280-year intervals.

  11. Witnessing a Large-scale Slipping Magnetic Reconnection along a Dimming Channel during a Solar Flare

    Energy Technology Data Exchange (ETDEWEB)

    Jing, Ju; Lee, Jeongwoo; Xu, Yan; Liu, Chang; Wang, Haimin [Center for Solar-Terrestrial Research, New Jersey Institute of Technology, Newark, NJ 07102-1982 (United States); Liu, Rui [CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Sciences, University of Science and Technology of China, Hefei 230026 (China); Cheung, Mark C. M. [Lockheed Martin Solar and Astrophysics Laboratory, Palo Alto, CA 94304 (United States); Zhu, Chunming, E-mail: ju.jing@njit.edu [Department of Physics, Montana State University, Bozeman, MT 59717 (United States)

    2017-06-20

    We report the intriguing large-scale dynamic phenomena associated with the M6.5 flare (SOL2015-06-22T18:23) in NOAA active region 12371, observed by RHESSI , Fermi , and the Atmospheric Image Assembly (AIA) and Magnetic Imager (HMI) on the Solar Dynamics Observatory ( SDO ). The most interesting feature of this event is a third ribbon (R3) arising in the decay phase, propagating along a dimming channel (seen in EUV passbands) toward a neighboring sunspot. The propagation of R3 occurs in the presence of hard X-ray footpoint emission and is broadly visible at temperatures from 0.6 MK to over 10 MK through the differential emission measure analysis. The coronal loops then undergo an apparent slipping motion following the same path of R3, after a ∼80 minute delay. To understand the underlying physics, we investigate the magnetic configuration and the thermal structure of the flaring region. Our results are in favor of a slipping-type reconnection followed by the thermodynamic evolution of coronal loops. In comparison with those previously reported slipping reconnection events, this one proceeds across a particularly long distance (∼60 Mm) over a long period of time (∼50 minutes) and shows two clearly distinguished phases: the propagation of the footpoint brightening driven by nonthermal particle injection and the apparent slippage of loops governed by plasma heating and subsequent cooling.

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

    Science.gov (United States)

    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

  13. Prognostic importance of silent myocardial ischemia detected by intravenous dipyridamole thallium myocardial imaging in asymptomatic patients with coronary artery disease

    International Nuclear Information System (INIS)

    Younis, L.T.; Byers, S.; Shaw, L.; Barth, G.; Goodgold, H.; Chaitman, B.R.

    1989-01-01

    One hundred seven asymptomatic patients who underwent intravenous dipyridamole thallium imaging were evaluated to determine prognostic indicators of subsequent cardiac events over an average follow-up period of 14 +/- 10 months. Univariate analysis of 18 clinical, scintigraphic and angiographic variables revealed that a reversible thallium defect, a combined fixed and reversible thallium defect, number of segmental thallium defects and extent of coronary artery disease were significant predictors of subsequent cardiac events. Of the 13 patients who died or had a nonfatal infarction, 12 had a reversible thallium defect. Stepwise logistic regression analysis selected a reversible thallium defect as the only significant predictor of cardiac events. When death or myocardial infarction was the outcome variable, a combined fixed and reversible thallium defect was the only predictor of outcome. In patients without previous myocardial infarction, the cardiac event rate was significantly greater in those with an abnormal versus normal thallium scan (55% versus 12%, p less than 0.001). Thus, intravenous dipyridamole thallium scintigraphy is a useful noninvasive test to risk stratify asymptomatic patients with coronary artery disease. A reversible thallium defect most likely indicates silent myocardial ischemia in a sizable fraction of patients in this clinical subset and is associated with an unfavorable prognosis

  14. Effects of acoustic waves on stick-slip in granular media and implications for earthquakes

    Science.gov (United States)

    Johnson, P.A.; Savage, H.; Knuth, M.; Gomberg, J.; Marone, Chris

    2008-01-01

    It remains unknown how the small strains induced by seismic waves can trigger earthquakes at large distances, in some cases thousands of kilometres from the triggering earthquake, with failure often occurring long after the waves have passed. Earthquake nucleation is usually observed to take place at depths of 10-20 km, and so static overburden should be large enough to inhibit triggering by seismic-wave stress perturbations. To understand the physics of dynamic triggering better, as well as the influence of dynamic stressing on earthquake recurrence, we have conducted laboratory studies of stick-slip in granular media with and without applied acoustic vibration. Glass beads were used to simulate granular fault zone material, sheared under constant normal stress, and subject to transient or continuous perturbation by acoustic waves. Here we show that small-magnitude failure events, corresponding to triggered aftershocks, occur when applied sound-wave amplitudes exceed several microstrain. These events are frequently delayed or occur as part of a cascade of small events. Vibrations also cause large slip events to be disrupted in time relative to those without wave perturbation. The effects are observed for many large-event cycles after vibrations cease, indicating a strain memory in the granular material. Dynamic stressing of tectonic faults may play a similar role in determining the complexity of earthquake recurrence. ??2007 Nature Publishing Group.

  15. Influence of limb temperature on cutaneous silent periods.

    Science.gov (United States)

    Kofler, Markus; Valls-Solé, Josep; Vasko, Peter; Boček, Václav; Štetkárová, Ivana

    2014-09-01

    The cutaneous silent period (CSP) is a spinal inhibitory reflex mediated by small-diameter afferents (A-delta fibers) and large-diameter efferents (alpha motoneurons). The effect of limb temperature on CSPs has so far not been assessed. In 27 healthy volunteers (11 males; age 22-58 years) we recorded median nerve motor and sensory action potentials, median nerve F-wave and CSPs induced by noxious digit II stimulation in thenar muscles in a baseline condition at room temperature, and after randomly submersing the forearm in 42 °C warm or 15 °C cold water for 20 min each. In cold limbs, distal and proximal motor and sensory latencies as well as F-wave latencies were prolonged. Motor and sensory nerve conduction velocities were reduced. Compound motor and sensory nerve action potential amplitudes did not differ significantly from baseline. CSP onset and end latencies were more delayed than distal and proximal median nerve motor and sensory latencies, whereas CSP duration was not affected. In warm limbs, opposite but smaller changes were seen in nerve conduction studies and CSPs. The observed CSP shift "en bloc" towards longer latencies without affecting CSP duration during limb cooling concurs with slower conduction velocity in both afferent and efferent fibers. Disparate conduction slowing in afferents and efferents, however, suggests that nociceptive EMG suppression is mediated by fibers of different size in the afferent than in the efferent arm, indirectly supporting the contribution of A-delta fibers as the main afferent input. Limb temperature should be taken into account when testing CSPs in the clinical setting, as different limb temperatures affect CSP latencies more than large-diameter fiber conduction function. Copyright © 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  16. Immunological profile of silent brain infarction and lacunar stroke.

    Directory of Open Access Journals (Sweden)

    Paola Sarchielli

    Full Text Available Neuroinflammation is believed to be involved in the pathophysiological mechanisms of silent brain infarcts (SBI. However, the immunological profile of SBI has been scarcely investigated. In the context of a national research project named SILENCE, aimed at investigating clinical, biochemical and pathogenic features of SBI, we have measured the plasma profile of some inflammatory-related molecules in SBI patients (n = 21, patients with recent lacunar infarcts (LI, n = 28 and healthy controls (n = 31, consecutively enrolled in four Italian centres. A panel of chemokines (MIG, CTACK, IL16, SDF1a, MCP1, growth factors (SCF, SCGFb, HGF, IL3, immunoglobulin-type adhesion molecules (ICAM1, VCAM1, proinflammatory cytokines (IL18, INFa2, MIF, IL12p40, cell surface receptors on T-cells (IL2Ra, and inductors of apoptosis (TRAIL was assessed in plasma samples by Luminex xMAP™ technology. Immunological parameters were compared using non-parametric statistics and performance to distinguish SBI and LI was evaluated by receiver operating characteristic (ROC analysis. Plasma levels of ICAM1 were significantly higher in both SBI and LI patients as compared to controls (SBI≥LI>Ctrl. A different trend was observed for IL16 (SBICtrl, SCF (LICtrl and SCGFb (SBI>LICtrl and IL18 when compared to LI patients (Ctrl≤SBI>LI. All the other immunological markers did not significantly differ among groups. According to ROC analysis, the best predictor for SBI condition was the chemokine MIG (AUC = 0.84, sensitivity 86%, specificity 77%, while SCF had the best performance in distinguishing LI patients (AUC = 0.84, sensitivity 86%, specificity 68%. These results confirm the involvement of inflammatory processes in cerebrovascular disorders, particularly in SBI, a very common age-related condition. The differences in plasma profile of inflammatory molecules may underlie different pathological mechanisms in SBI and LI patients.

  17. Mass media effect on vaccines uptake during silent polio outbreak.

    Science.gov (United States)

    Sagy, Iftach; Novack, Victor; Gdalevich, Michael; Greenberg, Dan

    2018-03-14

    During 2013, isolation of a wild type 1 poliovirus from routine sewage sample in Israel, led to a national OPV campaign. During this period, there was a constant cover of the outbreak by the mass media. To investigate the association of media exposure and OPV and non-OPV vaccines uptake during the 2013 silent polio outbreak in Israel. We received data on daily immunization rates during the outbreak period from the Ministry of Health (MoH). We conducted a multivariable time trend analysis to assess the association between daily media exposure and vaccines uptake. Analysis was stratified by ethnicity and socio-economic status (SES). During the MoH supplemental immunization activity, 138,799 OPV vaccines were given. There was a significant association between media exposure and OPV uptake, most prominent in a lag of 3-5 days from the exposure among Jews (R.R 1.79C.I 95% 1.32-2.41) and high SES subgroups (R.R 1.71C.I 95% 1.27-2.30). These subgroups also showed increased non-OPV uptake in a lag of 3-5 days from the media exposure, in all vaccines except for MMR. Lower SES and non-Jewish subgroups did not demonstrate the same association. Our findings expand the understanding of public behaviour during outbreaks. The public response shows high variability within specific subgroups. These findings highlight the importance of tailored communication strategies for each subgroup. Copyright © 2018 Elsevier Ltd. All rights reserved.

  18. Modelling the tuned criticality in stick-slip friction during metal cutting

    International Nuclear Information System (INIS)

    Wang, Q; Ye, G G; Dai, L H; Lu, C

    2015-01-01

    Cutting is a ubiquitous process in nature and man-made systems. Here we demonstrate that, based on morphological patterns observed in experiments, the friction behaviour of metal cutting exhibits a criticality with cutting speed as a tuned parameter. The corresponding stick-slip events can be described by a power law distribution. A dynamic thermo-mechanical model is developed to investigate how such a tuned criticality occurs. It is shown that, in terms of the linear stability analysis, stick-slip friction is due to the thermo-mechanical instability and dynamical interaction between shear dissipation and nonlinear friction. Moreover, there is a secondary transition from a criticality state to a limit cycle that is dominated by the inertia effect, which is similar to the frequency lock phenomenon in a forced Duffing oscillator. (paper)

  19. Prediction of fluid velocity slip at solid surfaces

    DEFF Research Database (Denmark)

    Hansen, Jesper Schmidt; Todd, Billy; Daivis, Peter

    2011-01-01

    methods, it allows us to directly compute the intrinsic wall-fluid friction coefficient rather than an empirical friction coefficient that includes all sources of friction for planar shear flow. The slip length predicted by our method is in excellent agreement with the slip length obtained from direct...

  20. Multiparameter Monitoring and Prevention of Fault-Slip Rock Burst

    Directory of Open Access Journals (Sweden)

    Shan-chao Hu

    2017-01-01

    Full Text Available Fault-slip rock burst is one type of the tectonic rock burst during mining. A detailed understanding of the precursory information of fault-slip rock burst and implementation of monitoring and early warning systems, as well as pressure relief measures, are essential to safety production in deep mines. This paper first establishes a mechanical model of stick-slip instability in fault-slip rock bursts and then reveals the failure characteristics of the instability. Then, change rule of mining-induced stress and microseismic signals before the occurrence of fault-slip rock burst are proposed, and multiparameter integrated early warning methods including mining-induced stress and energy are established. Finally, pressure relief methods targeting large-diameter boreholes and coal seam infusion are presented in accordance with the occurrence mechanism of fault-slip rock burst. The research results have been successfully applied in working faces 2310 of the Suncun Coal Mine, and the safety of the mine has been enhanced. These research results improve the theory of fault-slip rock burst mechanisms and provide the basis for prediction and forecasting, as well as pressure relief, of fault-slip rock bursts.

  1. A Transformational Approach to Slip-Slide Factoring

    Science.gov (United States)

    Steckroth, Jeffrey

    2015-01-01

    In this "Delving Deeper" article, the author introduces the slip-slide method for solving Algebra 1 mathematics problems. This article compares the traditional method approach of trial and error to the slip-slide method of factoring. Tools that used to be taken for granted now make it possible to investigate relationships visually,…

  2. Earthquake source properties from instrumented laboratory stick-slip

    Science.gov (United States)

    Kilgore, Brian D.; McGarr, Arthur F.; Beeler, Nicholas M.; Lockner, David A.; Thomas, Marion Y.; Mitchell, Thomas M.; Bhat, Harsha S.

    2017-01-01

    Stick-slip experiments were performed to determine the influence of the testing apparatus on source properties, develop methods to relate stick-slip to natural earthquakes and examine the hypothesis of McGarr [2012] that the product of stiffness, k, and slip duration, Δt, is scale-independent and the same order as for earthquakes. The experiments use the double-direct shear geometry, Sierra White granite at 2 MPa normal stress and a remote slip rate of 0.2 µm/sec. To determine apparatus effects, disc springs were added to the loading column to vary k. Duration, slip, slip rate, and stress drop decrease with increasing k, consistent with a spring-block slider model. However, neither for the data nor model is kΔt constant; this results from varying stiffness at fixed scale.In contrast, additional analysis of laboratory stick-slip studies from a range of standard testing apparatuses is consistent with McGarr's hypothesis. kΔt is scale-independent, similar to that of earthquakes, equivalent to the ratio of static stress drop to average slip velocity, and similar to the ratio of shear modulus to wavespeed of rock. These properties result from conducting experiments over a range of sample sizes, using rock samples with the same elastic properties as the Earth, and scale-independent design practices.

  3. Stability Analysis of Static Slip-Energy Recovery Drive via ...

    African Journals Online (AJOL)

    The stability of the sub synchronous static slip energy recovery scheme for the speed control of slip-ring induction motor is presented. A set of nonlinear differential equations which describe the system dynamics are derived and linearized about an operating point using perturbation technique. The Eigenvalue analysis of the ...

  4. Slipping and rolling on an inclined plane

    International Nuclear Information System (INIS)

    Aghamohammadi, Cina; Aghamohammadi, Amir

    2011-01-01

    In the first part of the paper, using a direct calculation two-dimensional motion of a particle sliding on an inclined plane is investigated for general values of friction coefficient (μ). A parametric equation for the trajectory of the particle is also obtained. In the second part of the paper, the motion of a sphere on the inclined plane is studied. It is shown that the evolution equation for the contact point of a sliding sphere is similar to that of a point particle sliding on an inclined plane whose friction coefficient is 7/2 μ. If μ > 2/7 tan θ, for any arbitrary initial velocity and angular velocity, the sphere will roll on the inclined plane after some finite time. In other cases, it will slip on the inclined plane. In the case of rolling, the centre of the sphere moves on a parabola. Finally the velocity and angular velocity of the sphere are exactly computed.

  5. Analysis of slipped capital femoral epiphysis

    International Nuclear Information System (INIS)

    Magid, D.; Fishman, E.K.; Sponseller, P.D.; Griffin, P.P.

    1988-01-01

    CT with multiplanar reconstruction (CT/MPR) was used to assess 25 adolescents with known or suspected slipped capital femoral epiphysis (SCFE). CT/MPR localizes the epiphysis in three planes, establishing its relationship to the acetabulum and the metaphyseal neck. MPR facilitates measurements of head-neck angles, residusal head-neck contact, and relative retrovision. CT/MPR may establish the true age of the epiphyseal failure and can reveal subtle SCFE in the face of normal plain films. Patients often present with confusing histories; clues to the true age of failure include subtle signs of healing, remodeling, or new bone buttressing. Characterization of acute versus chronic conditions influences preoperative planning. Postoperatively, CT/MPR confirms early results and follows epiphyseal fusion and remodelling. It also detects complications, such as pin or graft migration avascular necrosis (AVN), or chondrolysis

  6. Learning and Prediction of Slip from Visual Information

    Science.gov (United States)

    Angelova, Anelia; Matthies, Larry; Helmick, Daniel; Perona, Pietro

    2007-01-01

    This paper presents an approach for slip prediction from a distance for wheeled ground robots using visual information as input. Large amounts of slippage which can occur on certain surfaces, such as sandy slopes, will negatively affect rover mobility. Therefore, obtaining information about slip before entering such terrain can be very useful for better planning and avoiding these areas. To address this problem, terrain appearance and geometry information about map cells are correlated to the slip measured by the rover while traversing each cell. This relationship is learned from previous experience, so slip can be predicted remotely from visual information only. The proposed method consists of terrain type recognition and nonlinear regression modeling. The method has been implemented and tested offline on several off-road terrains including: soil, sand, gravel, and woodchips. The final slip prediction error is about 20%. The system is intended for improved navigation on steep slopes and rough terrain for Mars rovers.

  7. Axisymmetric Tornado Simulations with a Semi-Slip Boundary

    Directory of Open Access Journals (Sweden)

    Brian H. Fiedler

    2017-12-01

    Full Text Available The structure of natural tornadoes and simulated analogs are sensitive to the lower boundary condition for friction. Three-dimensional numerical simulations of storms require a choice for turbulence parameterizations and resolution of wind near the lower boundary. This article explores some of the consequences of choices of a surface drag coefficient on the structure of a mature simulated tornado, using a conventional axisymmetric model. The surface drag parameterization is explored over the range of the semi-slip condition, including the extremes of no-slip and free-slip. A moderate semi-slip condition allows for an extreme pressure deficit, but without the unrealistic vortex breakdown of the no-slip condition.

  8. Influence of movement regime of stick-slip process on the size distribution of accompanying acoustic emission characteristics

    Science.gov (United States)

    Matcharashvili, Teimuraz; Chelidze, Tamaz; Zhukova, Natalia; Mepharidze, Ekaterine; Sborshchikov, Alexander

    2010-05-01

    Many scientific works on dynamics of earthquake generation are devoted to qualitative and quantitative reproduction of behavior of seismic faults. Number of theoretical, numerical or physical models are already designed for this purpose. Main assumption of these works is that the correct model must be capable to reproduce power law type relation for event sizes with magnitudes greater than or equal to a some threshold value, similar to Gutenberg-Richter (GR) law for the size distribution of earthquakes. To model behavior of a seismic faults in laboratory conditions spring-block experimental systems are often used. They enable to generate stick-slip movement, intermittent behavior occurring when two solids in contact slide relative to each other driven at a constant velocity. Wide interest to such spring-block models is caused by the fact that stick-slip is recognized as a basic process underlying earthquakes generation along pre-existing faults. It is worth to mention, that in stick slip experiments reproduction of power law, in slip events size distribution, with b values close or equal to the one found for natural seismicity is possible. Stick-slip process observed in these experimental models is accompanied by a transient elastic waves propagation generated during the rapid release of stress energy in spring-block system. Oscillations of stress energy can be detected as a characteristic acoustic emission (AE). Accompanying stick slip AE is the subject of intense investigation, but many aspects of this process are still unclear. In the present research we aimed to investigate dynamics of stick slip AE in order to find whether its distributional properties obey power law. Experiments have been carried out on spring-block system consisting of fixed and sliding plates of roughly finished basalt samples. The sliding block was driven with a constant velocity. Experiments have been carried out for five different stiffness of pulling spring. Thus five different regimes

  9. How informative are slip models for aftershock forecasting?

    Science.gov (United States)

    Bach, Christoph; Hainzl, Sebastian

    2013-04-01

    Coulomb stress changes (ΔCFS) have been recognized as a major trigger mechanism for earthquakes, in particular aftershock distributions and the spatial patterns of ΔCFS are often found to be correlated. However, the Coulomb stress calculations are based on slip inversions and the receiver fault mechanisms which both contain large uncertainties. In particular, slip inversions are usually non-unique and often differ strongly for the same earthquakes. Here we want to address the information content of those inversions with respect to aftershock forecasting. Therefore we compare the slip models to randomized fractal slip models which are only constrained by fault information and moment magnitude. The uncertainty of the aftershock mechanisms is considered by using many receiver fault orientations, and by calculating ΔCFS at several depth layers. The stress change is then converted into an aftershock probability map utilizing a clock advance model. To estimate the information content of the slip models, we use an Epidemic Type Aftershock Sequence (ETAS) model approach introduced by Bach and Hainzl (2012), where the spatial probability density of direct aftershocks is related to the ΔCFS calculations. Besides the directly triggered aftershocks, this approach also takes secondary aftershock triggering into account. We quantify our results by calculating the information gain of the randomized slip models relative to the corresponding published slip model. As case studies, we investigate the aftershock sequences of several well-known main shocks such as 1992 Landers, 1999 Hector Mine, 2004 Parkfield, 2002 Denali. First results show a huge difference in the information content of slip models. For some of the cases up to 90% of the random slip models are found to perform better than the originally published model, for some other cases only few random models are found performing better than the published slip model.

  10. PROCESSING OF CONCENTRATED AQUEOUS ZIRCONIA-BIOGLASS SLIPS BY SLIP CASTING

    Directory of Open Access Journals (Sweden)

    Beltina Leon

    2017-03-01

    Full Text Available 3 mol% yttria-partially stabilized zirconia (Y-TZP powder and a sol-gel derived CaO- P₂O₅- SiO₂ (64S bioglass, were used to produce Y-TZP- bioglass slip cast compacts. The rheological properties of concentrated aqueous Y-TZP- 64S suspensions prepared with two different glass contents: 10.5 vol% and 19.9 vol%, and ammonium polyacrylate (NH₄PA as dispersant, were investigated and compared with those of Y-TZP. The density of green cast samples was related to the degree of slip dispersion. The substitution of Y-TZP by 64S glass in the mixtures resulted in greater adsorption of NH₄PA; however, the viscosity and yield stress values of Y-TZP-64S slips were higher than those of Y-TZP ones for the solid loadings studied. The increase in the glass content from 10.5 to 19.9 vol% increased the viscosity and yield stress values. The presence of 64S glass in the mixtures resulted in a less dense packing of cast samples.

  11. Spatiotemporal evolution of premonitory fault slip prior to stick-slip instability: New insight into the earthquake preparation

    Science.gov (United States)

    Zhuo, Y. Q.; Liu, P.; Guo, Y.; Ji, Y.; Ma, J.

    2017-12-01

    Premonitory fault slip, which begins with quasistatic propagation followed by quasidynamic propagation, may be a key clue bridging the "stick" state and "slip" state of a fault. More attentions have been paid for a long time to the temporal resolution of measurement than the spatial resolution, leading to the incomplete interpretation for the spatial evolution of premonitory slip, particularly during the quasistatic phase. In the present study, measurement of the quasistatic propagation of premonitory slip is achieved at an ultrahigh spatial resolution via a digital image correlation method. Multiple premonitory slip zones are observed and found to be controlled spatially by the fault contact heterogeneity, particularly the strong contact patches that prevent the propagation of premonitory slip and accumulate strain. As a result, premonitory slip is accelerated within constrained week contact spaces and consequently triggers the breakout of quasidynamic propagation. The results provide new insights into the quasistatic propagation of premonitory slip and may offer new interpretations for the earthquake nucleation process. This work is fund by the National Natural Science Foundation of China (Grant No. 41572181), the Basic Scientific Funding of Chinese National Nonprofit Institutes (Grant No. IGCEA1415, IGCEA1525), and the Early-Stage Work of Key Breakthrough Plan in Seismology from China Earthquake Administration.

  12. Single Event Upsets in the ATLAS IBL Front End ASICs

    CERN Document Server

    Rozanov, Alexander; The ATLAS collaboration

    2018-01-01

    During operation at instantaneous luminosities of up to 2.1 10^{34} cm^{-2} s^{-1} the front end chips of the ATLAS innermost pixel layer (IBL) experienced single event upsets affecting its global registers as well as the settings for the individual pixels, causing, among other things loss of occupancy, noisy pixels, and silent pixels. A quantitative analysis of the single event upsets as well as the operational issues and mitigation techniques will be presented.

  13. Single Event Upsets in the ATLAS IBL Front End ASICs

    CERN Document Server

    Rozanov, Alexandre; The ATLAS collaboration

    2018-01-01

    During operation at instantaneous luminosities of up to 2.1 1034 cm2 s−1 frontend chips of the ATLAS innermost pixel layer (IBL) experienced single event upsets affecting its global registers as well as the settings for the individual pixels, causing, amongst other things loss of occupancy, noisy pixels, and silent pixels. A quantitative analysis of the single event upsets as well as the operational issues and mitigation techniques are presented.

  14. Silent circulation of St. Louis encephalitis virus prior to an encephalitis outbreak in Cordoba, Argentina (2005.

    Directory of Open Access Journals (Sweden)

    Luis Adrian Díaz

    2012-01-01

    Full Text Available St. Louis encephalitis virus is a complex zoonoses. In 2005, 47 laboratory-confirmed and probable clinical cases of SLEV infection were reported in Córdoba, Argentina. Although the causes of 2005 outbreak remain unknown, they might be related not only to virological factors, but also to ecological and environmental conditions. We hypothesized that one of the factors for SLE reemergence in Córdoba, Argentina, was the introduction of a new SLEV genotype (SLEV genotype III, with no previous activity in the area. In order to evaluate this hypothesis we carried out a molecular characterization of SLEV detections from mosquitoes collected between 2001 and 2004 in Córdoba city. A total of 315 mosquito pools (11,002 individuals including 12 mosquitoes species were analyzed. Overall, 20 pools (8 mosquitoes species were positive for SLEV. During this study, genotypes II, V and VII were detected. No mosquito pool infected with genotype III was detected before the 2005 outbreak. Genotype V was found every year and in the 8 sampled sites. Genotypes II and VII showed limited temporal and spatial activities. We cannot dismiss the association of genotype II and V as etiological agents during the outbreak. However, the silent circulation of other SLEV strains in Córdoba city before the 2005 outbreak suggests that the introduction of genotype III was an important factor associated to this event. Not mutually exclusive, other factors such as changes in avian hosts and mosquitoes vectors communities, driven by climatic and environmental modifications, should also be taken into consideration in further studies.

  15. 45. Ezetimibe and statins yields on silent holter ambulatory myocardial ischemia

    Directory of Open Access Journals (Sweden)

    W. Kadro

    2016-07-01

    Full Text Available Further cholestrol lowering may affect silent ischemia detected on holter monitoring. Cholesterol lowering is associated with a reduction in cardiovascular morbidity and mortality. Statins are the main drugs for cholesterol lowering. Ezetimibe when added to statins gives further reduction in cholesterol but its long-term effect on cardiovascular morbidity and mortality and ischemic events is not known. This study sought to determine whether further cholesterol lowering with ezitimibe will also results in a reduction of myocardial ischemia during daily life. We enrolled 50 patients with proven stable coronary artery disease (CAD and at least one episode of ST-segment depression on ambulatory ECG monitoring. All of them were receiving optimal therapy for CAD including statin therapy for cholesterol reduction. 25 patients were randomized to continue their statin therapy (Statin only group and 25 to recieve statin plus ezitimibe 10 mg/day (ezitimibe group. Serum cholesterol and LDL cholesterol levels and ambulatory monitoring were repeated after 4–6 months of therapy. The two groups were comparable with respect to baseline characteristics, number of episodes of ST-segment depression, and baseline serum cholesterol levels. The ezitimibe group had lower mean total and LDL cholesterol levels at study end and experienced a significant reduction in the number of episodes of ST-segment depression compared with the statin only group. ST-segment depression was completely resolved in 13 of 25 patients (52% in the ezitimibe group versus 3 of 25 (12% in the statin only group. The ezitimibe group exhibited a highly significant reduction in ambulatory ischemia (P < .001. By logistic regression, treatment with ezitimibe was an independent predictor of ischemia resolution. Further cholesterol lowering with ezitimibe can result in reduction or resolution of myocardial ischemia recorded as episodes of ST-segment depression in ambulatory monitoring of the ECG.

  16. Left ventricular function abnormalities as a manifestation of silent myocardial ischemia.

    Science.gov (United States)

    Lambert, C R; Conti, C R; Pepine, C J

    1986-11-01

    A large body of evidence exists indicating that left ventricular dysfunction is a common occurrence in patients with severe coronary artery disease and represents silent or asymptomatic myocardial ischemia. Such dysfunction probably occurs early in the time course of every ischemic episode in patients with coronary artery disease whether symptoms are eventually manifested or not. The pathophysiology of silent versus symptomatic left ventricular dysfunction due to ischemia appears to be identical. Silent ischemia-related left ventricular dysfunction can be documented during spontaneous or stress-induced perturbations in the myocardial oxygen supply/demand ratio. It also may be detected by nitroglycerin-induced improvement in ventricular function or by salutary changes in wall motion following revascularization. Silent left ventricular dysfunction is a very early occurrence during ischemia and precedes electrocardiographic abnormalities. In this light, its existence should always be kept in mind when dealing with patients with ischemic heart disease. It can be hypothesized that because silent ischemia appears to be identical to ischemia with symptoms in a pathophysiologic sense, prognosis and treatment in both cases should be the same.

  17. Clinical study of correlation of pre-senile and senile depressive stage with silent cerebral infarction

    International Nuclear Information System (INIS)

    Fujikawa, Tokumi; Yamawaki, Shigeto; Fujita, Yasunobu; Shibata, Youko; Touhouda, Yoshikuni.

    1992-01-01

    The relationship between the pre-senile/senile depressive state and silent cerebral infarction was examined by MRI. Consecutive 56 depressive patients aged 50 years or older underwnt MRI. MRI revealed silent cerebral infarction in 60.3% of patients in whom depression occurred at the age of less than 65 years. The complication rate was significantly higher in these patients than the younger patients (60.9% vs 20%). Complications of silent cerebral infarction were found in 53.6% for patients in whom depression occurred at the age of less than 65 years and symptoms were deteriorated at the age of 65 years or older and in 100% for patients in whom it occurred at the age of 65 years or older and hospitalization was simultaneously required. These figures were remarkably higher than the age-related complication rate of silent cerebral infarction in non-depressive normal persons. This suggested that approximately half of depressive patients of pre-senile onset and majority of depressive patients of senile onset might have parenchymal involvement due to silent cerebral infarction. Both perforating-type and cortical-type infarcts were found. This has a implication for the involvement of multiple infarct-related foci in depressive state. For cortical-type infarcts, partial lesions were predominant, followed by frontal and temporal lesions. The incidence of left frontal infarcts was significanly higher than that of right frontal infarcts. Infarcts in both the parietal and left frontal lobes may be responsible for depressive state. (N.K.)

  18. The Right to Remain Silent in Criminal Trial

    Directory of Open Access Journals (Sweden)

    Gianina Anemona Radu

    2013-05-01

    Full Text Available A person's right not to incriminate oneself or to remain silent and not contribute to their own incrimination is a basic requirement of due process, although the right not to testify against oneself is not expressly guaranteed. This legal right is intended to protect the accused/ the defendant against the authorities’ abusive coercion. The scope of the right not to incriminate oneself is related to criminal matter under the Convention, and thus susceptible or applicable to criminal proceedings concerning all types of crimes as a guarantee to a fair trial. The European Court of Justice ruled that despite the fact that art. 6 paragraph 2 of the Convention does not expressly mention the right not to incriminate oneself and the right not to contribute to their own incrimination (nemo tenetur are ipsum accusare these are generally recognized international rules that are in consistence with the notion of “fair trial” stipulated in art. 6. By virtue of the right to silence, the person charged with a crime is free to answer the questions or not, as he/she believes it is in his/her interest. Therefore, the right to silence involves not only the right not to testify against oneself, but also the right of the accused/ defendant not to incriminate oneself. Thus, the accused/defendant cannot be compelled to assist in the production of evidence and cannot be sanctioned for failing to provide certain documents or other evidence. Obligation to testify against personal will, under the constraint of a fine or any other form of coercion constitutes an interference with the negative aspect of the right to freedom of expression which must be necessary in a democratic society. It is essential to clarify certain issues as far as this right is concerned. First of all, the statutory provision in question is specific to adversarial systems, which are found mainly in Anglo-Saxon countries and are totally different from that underlying the current Romanian Criminal

  19. Quasi-dynamic versus fully dynamic simulations of earthquakes and aseismic slip with and without enhanced coseismic weakening

    Science.gov (United States)

    Thomas, Marion Y.; Lapusta, Nadia; Noda, Hiroyuki; Avouac, Jean-Philippe

    2014-03-01

    Physics-based numerical simulations of earthquakes and slow slip, coupled with field observations and laboratory experiments, can, in principle, be used to determine fault properties and potential fault behaviors. Because of the computational cost of simulating inertial wave-mediated effects, their representation is often simplified. The quasi-dynamic (QD) approach approximately accounts for inertial effects through a radiation damping term. We compare QD and fully dynamic (FD) simulations by exploring the long-term behavior of rate-and-state fault models with and without additional weakening during seismic slip. The models incorporate a velocity-strengthening (VS) patch in a velocity-weakening (VW) zone, to consider rupture interaction with a slip-inhibiting heterogeneity. Without additional weakening, the QD and FD approaches generate qualitatively similar slip patterns with quantitative differences, such as slower slip velocities and rupture speeds during earthquakes and more propensity for rupture arrest at the VS patch in the QD cases. Simulations with additional coseismic weakening produce qualitatively different patterns of earthquakes, with near-periodic pulse-like events in the FD simulations and much larger crack-like events accompanied by smaller events in the QD simulations. This is because the FD simulations with additional weakening allow earthquake rupture to propagate at a much lower level of prestress than the QD simulations. The resulting much larger ruptures in the QD simulations are more likely to propagate through the VS patch, unlike for the cases with no additional weakening. Overall, the QD approach should be used with caution, as the QD simulation results could drastically differ from the true response of the physical model considered.

  20. STUDY OF IMMUNITY TO POLIOVIRUSES ON CERTAIN "SILENT" TERRITORIES OF RUSSIA

    Directory of Open Access Journals (Sweden)

    N. I. Romanenkova

    2011-01-01

    Full Text Available Abstract. The degree of immunity to polioviruses of three serotypes among children of different ages was analysed on certain "controlled" and "silent" territories of Russia in different periods of Polio Eradication Initiative. It was shown that the levels of immunity of children’s population to polioviruses on "controlled" and "silent" territories had no significant difference. It was stated that on the phase which preceded the certification for the absence of circulation of wild polioviruses, when the National Immunisation Days were conducted in the country, the percentage of eronegative children to polioviruses of different serotypes was low on all the territories of Russia. After Russia as a part of the WHO European region was certified as a polio free country and mass immunisation was stopped thepercentage of seronegative children increased, especially to poliovirus of serotype 3, both on the "controlled" and on the "silent" territories.

  1. Agreement of the silent partnership – tax and legal consequences of its conclusion and execution

    Directory of Open Access Journals (Sweden)

    Monika Zieniewicz

    2016-12-01

    Full Text Available The institution of the silent partnership is not currently regulated by any legal act in the Polish legal system, although its importance in practice is not in doubt. As every action made in the economic sphere and economic execution of the contract is associated with specific effects on the basis of the tax laws. However, due to the lack of statutory regulation of the institution of silent partnership problematic is the question of determining the effects of tax legislation. Therefore, special attention is needed to determine the issue of these effects on the basis of income tax, tax on goods and services, transfer tax and the tax on inheritance and donations, as well as the question of liability for the tax liabilities of the silent partnership.

  2. The clinical dilemma of "silent desensitization" in aspirin-exacerbated respiratory disease.

    Science.gov (United States)

    White, Andrew A; Bosso, John V; Stevenson, Donald D

    2013-01-01

    Aspirin desensitization is a treatment option for patients with aspirin-exacerbated respiratory disease (AERD). Some patients with an excellent history of aspirin or nonsteroidal anti-inflammatory drug (NSAID) reactions have negative aspirin challenges/desensitization. This study discusses the clinical entity of silent desensitization in AERD and the dilemma that this presents to the practicing allergist/immunologist. We discuss a series of patients with a strong history of NSAID reactions who initially underwent a negative challenge/silent desensitization. These patients were subsequently proven to have AERD after a second positive aspirin challenge. Silent desensitization is an uncommon but important outcome to recognize in AERD. Clinicians performing aspirin desensitization should understand that this can occur and consider a second confirmatory aspirin challenge in some patients.

  3. Slip, trip and fall accidents occurring during the delivery of mail.

    Science.gov (United States)

    Bentley, T A; Haslam, R A

    1998-12-01

    This study sought to identify causal factors for slip, trip and fall accidents occurring during the delivery of mail. Analysis of in-house data produced information about accident circumstances for 1734 fall cases. The most common initiating events in delivery falls were slips and trips. Slips most often occurred on snow, ice or grass, while trips tended to involve uneven pavements, obstacles and kerbs. Nearly one-fifth of falls occurred on steps, with step falls requiring longer absence from work than falls on the level. Half of all falls occurred during November-February and three-quarters of falls occurred between 7 and 9 a.m. Incidence rates for female employees were 50% higher than for their male colleagues. Accident-independent methods included interviews with safety personnel and managers, discussion groups with delivery employees, and a questionnaire survey of employees and managers. These techniques provided data on risk factors related to the task, behaviour, footwear and equipment. Arising from these accident-independent investigations, it is suggested that unsafe working practices, such as reading addresses while walking and taking shortcuts, increase the risk of falls. Organizational issues include management safety activities, training and equipment provision. Measures are discussed that might lead to a reduction in the incidence of delivery fall accidents.

  4. Stick-slip friction and wear of articular joints

    Science.gov (United States)

    Lee, Dong Woog; Banquy, Xavier; Israelachvili, Jacob N.

    2013-01-01

    Stick-slip friction was observed in articular cartilage under certain loading and sliding conditions and systematically studied. Using the Surface Forces Apparatus, we show that stick-slip friction can induce permanent morphological changes (a change in the roughness indicative of wear/damage) in cartilage surfaces, even under mild loading and sliding conditions. The different load and speed regimes can be represented by friction maps—separating regimes of smooth and stick-slip sliding; damage generally occurs within the stick-slip regimes. Prolonged exposure of cartilage surfaces to stick-slip sliding resulted in a significant increase of surface roughness, indicative of severe morphological changes of the cartilage superficial zone. To further investigate the factors that are conducive to stick-slip and wear, we selectively digested essential components of cartilage: type II collagen, hyaluronic acid (HA), and glycosaminoglycans (GAGs). Compared with the normal cartilage, HA and GAG digestions modified the stick-slip behavior and increased surface roughness (wear) during sliding, whereas collagen digestion decreased the surface roughness. Importantly, friction forces increased up to 2, 10, and 5 times after HA, GAGs, and collagen digestion, respectively. Also, each digestion altered the friction map in different ways. Our results show that (i) wear is not directly related to the friction coefficient but (ii) more directly related to stick-slip sliding, even when present at small amplitudes, and that (iii) the different molecular components of joints work synergistically to prevent wear. Our results also suggest potential noninvasive diagnostic tools for sensing stick-slip in joints. PMID:23359687

  5. Factors associated with worker slipping in limited-service restaurants.

    Science.gov (United States)

    Courtney, Theodore K; Verma, Santosh K; Huang, Yueng-Hsiang; Chang, Wen-Ruey; Li, Kai Way; Filiaggi, Alfred J

    2010-02-01

    Slips, trips and falls (STF) are responsible for a substantial injury burden in the global workplace. Restaurant environments are challenged by STF. This study assessed individual and work environment factors related to slipping in US limited-service restaurant workers. Workers in 10 limited-service restaurants in Massachusetts were recruited to participate. Workers' occupational slip and/or fall history within the past 4 weeks was collected by multilingual written questionnaires. Age, gender, job tenure, work hours per week and work shift were also collected. Shoe type, condition and gross shoe contamination were visually assessed. Floor friction was measured and each restaurant's overall mean coefficient of friction (COF) was calculated. The logistic generalised estimating equations model was used to compute adjusted odds ratios (OR). Of 125 workers, 42 reported one or more slips in the past 4 weeks with two reporting a resultant fall. Results from multivariable regression showed that higher restaurant mean COF was significantly associated with a decreased risk of self-reported slipping (OR 0.59, 95% CI 0.42 to 0.82). From the highest to the lowest COF restaurant, the odds of a positive slip history increased by a factor of more than seven. Younger age, male gender, lower weekly work hours and the presence of gross contamination on worker's shoe sole were also associated with increased odds of slip history. Published findings of an association between friction and slipping and falling in actual work environments are rare. The findings suggest that effective intervention strategies to reduce the risk of slips and falls in restaurant workers could include increasing COF and improving housekeeping practices.

  6. Perception of slipperiness and prospective risk of slipping at work

    Science.gov (United States)

    Courtney, Theodore K; Verma, Santosh K; Chang, Wen-Ruey; Huang, Yueng-Hsiang; Lombardi, David A; Brennan, Melanye J; Perry, Melissa J

    2013-01-01

    Objectives Falls are a leading cause of injury at work, and slipping is the predominant cause of falling. Prior research has suggested a modest correlation between objective measures (such as coefficient of friction, COF) and subjective measures of slipperiness (such as worker perceptions) in the workplace. However, the degree of association between subjective measures and the actual risk of slipping at the workplace is unknown. This study examined the association between perception of slipperiness and the risk of slipping. Methods 475 workers from 36 limited-service restaurants participated in a 12-week prospective cohort study. At baseline, demographic information was collected, participants rated floor slipperiness in eight areas of the restaurant, and work environment factors, such as COF, were measured. Restaurant-level and area-level mean perceptions of slipperiness were calculated. Participants then reported their slip experience at work on a weekly basis for the next 12 weeks. The associations between perception of slipperiness and the rate of slipping were assessed. Results Adjusting for age, gender, body mass index, education, primary language, mean COF, use of slip-resistant shoes, and restaurant chain, each 1-point increase in mean restaurant-level perception of slipperiness (4-point scale) was associated with a 2.71 times increase in the rate of slipping (95% CI 1.25 to 5.87). Results were similar for area-level perception within the restaurant (rate ratios (RR) 2.92, 95% CI 2.41 to 3.54). Conclusions Perceptions of slipperiness and the subsequent rate of slipping were strongly associated. These findings suggest that safety professionals, risk managers and employers could use aggregated worker perceptions of slipperiness to identify slipping hazards and, potentially, to assess intervention effectiveness. PMID:22935953

  7. Spectrum of Slip Processes on the Subduction Interface in a Continuum Framework Resolved by Rate-and State Dependent Friction and Adaptive Time Stepping

    Science.gov (United States)

    Herrendoerfer, R.; van Dinther, Y.; Gerya, T.

    2015-12-01

    fraction of characteristic slip distance over maximum slip velocity, we are able to resolve stick-slip events and increase computational speed. In this better resolved framework, we examine the role of aseismic slip on the megathrust cycle and its dependence on subduction velocity.

  8. Numerical Simulation of Methane Slip in Dual Fuel Marine Engines

    OpenAIRE

    Han, Jaehyun; Jensen, Michael Vincent; Pang, Kar Mun; Walther, Jens Honore; Schramm, Jesper; Bae, Choongsik

    2017-01-01

    The methane slip is the problematic issue for the engines using natural gas(NG). Because methane is more powerful greenhouse gas (GHG) than CO2, understanding of the methane slip during gas exchange process of the engines is essential. In this study, the influence of the gas pipe geometry and the valve timings on the methane slip was investigated. MAN L28/32DF engine was modeled to simulate the gas exchange process of the four stroke NG-diesel dual fuel engines. The mesh size of the model was...

  9. Simulation of engine auxiliary drive V-belt slip motion. Part 1. Development of belt slip model; Engine hoki V belt slip kyodo no simulation. 1. Belt slip model no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Kurisu, T [Mazda Motor Corp., Hiroshima (Japan)

    1997-10-01

    V-belts are widely used for driving auxiliary components of an engine. Inadequet design of such belt system sometimes results in troubles such as belt squeak, side rubber separation and/or bottom rubber crack. However, there has been no design tools which can predict belt slip quantitatively. The author developed a motion simulation program of Auxiliary Drive V-Belt System considering belt slip. The program showed good prediction accuracy for belt slip motion. This paper describes the simulation model. 1 ref., 12 figs.

  10. Rate-Dependent Slip of Newtonian Liquid at Smooth Surfaces

    International Nuclear Information System (INIS)

    Zhu, Yingxi; Granick, Steve

    2001-01-01

    Newtonian fluids were placed between molecularly smooth surfaces whose spacing was vibrated at spacings where the fluid responded as a continuum. Hydrodynamic forces agreed with predictions from the no-slip boundary condition only provided that flow rate (peak velocity normalized by spacing) was low, but implied partial slip when it exceeded a critical level, different in different systems, correlated with contact angle (surface wettability). With increasing flow rate and partially wetted surfaces, hydrodynamic forces became up to 2--4 orders of magnitude less than expected by assuming the no-slip boundary condition that is commonly stated in textbooks

  11. Detection of slip from multiple sites in an artificial finger

    Energy Technology Data Exchange (ETDEWEB)

    Muridan, N; Chappell, P H; Cranny, A; White, N M [Electronic Systems and Devices Group, School of Electronics and Computer Science, University of Southampton, SO17 1BJ (United Kingdom); Cotton, D P J, E-mail: nm07r@ecs.soton.ac.u [Nanoscience Centre, University of Cambridge, Cambridge (United Kingdom)

    2009-07-01

    A Piezoelectric thick-film sensor is a good candidate for the extraction of information from object slip in hand prosthesis. Five slip sensors were fabricated on different linkages of an artificial hand. The signals from each sensor were compared to the output from the sensor mounted on the fingertip. An analysis of the output signals from all the sensors indicates that the linkage sensors also produce similar output signals to the fingertip sensor. In the next phase of the research, velocity and acceleration of the slipped object will be considered in the analysis.

  12. Local void and slip model used in BODYFIT-2PE

    International Nuclear Information System (INIS)

    Chen, B.C.J.; Chien, T.H.; Kim, J.H.; Lellouche, G.S.

    1983-01-01

    A local void and slip model has been proposed for a two-phase flow without the need of fitting any empirical parameters. This model is based on the assumption that all bubbles have reached their terminal rise velocities in the two-phase region. This simple model seems to provide reasonable calculational results when compared with the experimental data and other void and slip models. It provides a means to account for the void and slip of a two-phase flow on a local basis. This is particularly suitable for a fine mesh thermal-hydraulic computer program such as BODYFIT-2PE

  13. Fault-Slip Data Analysis and Cover Versus Basement Fracture Patterns - Implications for Subsurface Technical Processes in Thuringia, Germany

    Science.gov (United States)

    Kasch, N.; Kley, J.; Navabpour, P.; Siegburg, M.; Malz, A.

    2014-12-01

    Recent investigations in Thuringia, Central Germany, focus on the potential for carbon sequestration, groundwater supply and geothermal energy. We report on the results of an integrated fault-slip data analysis to characterize the geometries and kinematics of systematic fractures in contrasting basement and cover rock lithologies. The lithostratigraphy of the area comprises locally exposed crystalline rocks and intermittently overlying Permian volcanic and clastic sedimentary rocks, together referred to as basement. A Late Permian sequence of evaporites, carbonates and shale constitutes the transition to the continuous sedimentary cover of Triassic age. Major NW-SE-striking fault zones and minor NNE-SSW-striking faults affect this stratigraphic succession. These characteristic narrow deforming areas ( 15 km) non-deforming areas suggesting localized zones of mechanical weakness, which can be confirmed by the frequent reactivation of single fault strands. Along the major fault zones, the basement and cover contain dominant inclined to sub-vertical NW-SE-striking fractures. These fractures indicate successive normal, dextral strike-slip and reverse senses of slip, evidencing events of NNE-SSW extension and contraction. Another system of mostly sub-vertical NNW-SSE- and NE-SW-striking conjugate strike-slip faults mainly developed within the cover implies NNE-SSW contraction and WNW-ESE extension. Earthquake focal mechanisms and in-situ stress measurements reveal a NW-SE trend for the modern SHmax. Nevertheless, fractures and fault-slip indicators are rare in the non-deforming areas, which characterizes Thuringia as a dual domain of (1) large unfractured areas and (2) narrow zones of high potential for technical applications. Our data therefore provide a basis for estimation of slip and dilation tendency of the contrasting fractures in the basement and cover under the present-day stress field, which must be taken into account for different subsurface technical

  14. Magmatic control along a strike-slip volcanic arc: The central Aeolian arc (Italy)

    Science.gov (United States)

    Ruch, J.; Vezzoli, L.; De Rosa, R.; Di Lorenzo, R.; Acocella, V.

    2016-02-01

    The regional stress field in volcanic areas may be overprinted by that produced by magmatic activity, promoting volcanism and faulting. In particular, in strike-slip settings, the definition of the relationships between the regional stress field and magmatic activity remains elusive. To better understand these relationships, we collected stratigraphic, volcanic, and structural field data along the strike-slip central Aeolian arc (Italy): here the islands of Lipari and Vulcano separate the extensional portion of the arc (to the east) from the contractional one (to the west). We collected >500 measurements of faults, extension fractures, and dikes at 40 sites. Most structures are NNE-SSW to NNW-SSE oriented, eastward dipping, and show almost pure dip-slip motion, consistent with an E-W extension direction, with minor dextral and sinistral shear. Our data highlight six eruptive periods during the last 55 ka, which allow considering both islands as a single magmatic system, in which tectonic and magmatic activities steadily migrated eastward and currently focus on a 10 km long × 2 km wide active segment. Faulting appears to mostly occur in temporal and spatial relation with magmatic events, supporting that most of the observable deformation derives from transient magmatic activity (shorter term, days to months), rather than from steady longer-term regional tectonics (102-104 years). More in general, the central Aeolian case shows how magmatic activity may affect the structure and evolution of volcanic arcs, overprinting any strike-slip motion with magma-induced extension at the surface.

  15. Magmatic control along a strike-slip volcanic arc: The central Aeolian arc (Italy)

    KAUST Repository

    Ruch, Joel

    2016-01-23

    The regional stress field in volcanic areas may be overprinted by that produced by magmatic activity, promoting volcanism and faulting. In particular, in strike-slip settings, the definition of the relationships between the regional stress field and magmatic activity remains elusive. To better understand these relationships, we collected stratigraphic, volcanic and structural field data along the strike-slip Central Aeolian arc (Italy): here the islands of Lipari and Vulcano separate the extensional portion of the arc (to the east) from the contractional one (to the west). We collected >500 measurements of faults, extension fractures and dikes at 40 sites. Most structures are NNE-SSW to NNW-SSE oriented, eastward dipping, and show almost pure dip-slip motion; consistent with an E-W extension direction, with minor dextral and sinistral shear. Our data highlight six eruptive periods during the last 55 ka, which allow considering both islands as a single magmatic system, in which tectonic and magmatic activity steadily migrated eastward and currently focus on a 10 km long x 2 km wide active segment. Faulting appears to mostly occur in temporal and spatial relation with magmatic events, supporting that most of the observable deformation derives from transient magmatic activity (shorter-term, days to months), rather than from steady longer-term regional tectonics (102-104 years). More in general, the Central Aeolian case shows how magmatic activity may affect the structure and evolution of volcanic arcs, overprinting any strike-slip motion with magma-induced extension at the surface.

  16. Laboratory study of electromagnetic initiation of slip

    Directory of Open Access Journals (Sweden)

    V. Chikhladze

    2002-06-01

    Full Text Available Recently Russian seismologists reported the triggering effect of MHD soundings on microseismic activity in the Central Asia test area.The paper focuses on an experimental test of the possibility of triggering the mechanical instability of a system that is close to critical state by a series of electromagnetic pulses.The mechanical system consisted of two pieces of rock;the upper piece can slip on the fixed supporting sample if the latter one is tilted up to the critical angle.In this state,the triggering of mechanical instability by some weak impact such as electrical pulse became more probable.The slope of support in the experiment is an analogue of tectonic stress in natural conditions.The preliminary experiments,carried out in a dry environment,at the humidity of atmosphere 30-50%,show that a strong EM-pulse induces sliding of a sample of rock (granite,basalt,labradoriteplaced on the supporting sample which is inclined at the slope close to,but less than,the critical angle with a probability 0.07.

  17. Prevalence of symptomatic and silent stress-induced perfusion defects in diabetic patients with suspected coronary artery disease referred for myocardial perfusion scintigraphy

    International Nuclear Information System (INIS)

    Prior, John O.; Calcagni, Maria-Lucia; Bischof Delaloye, Angelika; Monbaron, David; Ruiz, Juan; Koehli, Melanie

    2005-01-01

    Silent myocardial ischaemia - as evaluated by stress-induced perfusion defects on myocardial perfusion scintigraphy (MPS) in patients without a history of chest pain - is frequent in diabetes and is associated with increased rates of cardiovascular events. Its prevalence has been determined in asymptomatic diabetic patients, but remains largely unknown in diabetic patients with suspected coronary artery disease (CAD) in the clinical setting. In this study we therefore sought (a) to determine the prevalence of symptomatic and silent perfusion defects in diabetic patients with suspected CAD and (b) to characterise the eventual predictors of abnormal perfusion. The patient population comprised 133 consecutive diabetic patients with suspected CAD who had been referred for MPS. Studies were performed with exercise (41%) or pharmacological stress testing (1-day protocol, 99m Tc-sestamibi, 201 Tl or both). We used semi-quantitative analysis (20-segment polar maps) to derive the summed stress score (SSS) and the summed difference score (SDS). Abnormal MPS (SSS≥4) was observed in 49 (37%) patients (SSS=4.9±8.4, SDS=2.4±4.7), reversible perfusion defects (SDS≥2) in 40 (30%) patients [SSS=13.3±10.9; SDS=8.0±5.6; 20% moderate to severe (SDS>4), 7% multivessel] and fixed defects in 21 (16%) patients. Results were comparable between patients with and patients without a history of chest pain. Of 75 patients without a history of chest pain, 23 (31%, 95% CI=21-42%) presented reversible defects (SSS=13.9±11.3; SDS=7.4±1.2), indicative of silent ischaemia. Reversible defects were associated with inducible ST segment depression during MPS stress (odds ratio (OR)=3.2, p<0.01). Fixed defects were associated with erectile dysfunction in males (OR=3.7, p=0.02) and lower aspirin use (OR=0.25, p=0.02). Silent stress-induced perfusion defects occurred in 31% of the patients, a rate similar to that in patients with a history of chest pain. MPS could identify these patients with a

  18. Prevalence of symptomatic and silent stress-induced perfusion defects in diabetic patients with suspected coronary artery disease referred for myocardial perfusion scintigraphy

    Energy Technology Data Exchange (ETDEWEB)

    Prior, John O.; Calcagni, Maria-Lucia; Bischof Delaloye, Angelika [Centre Hospitalier Universitaire Vaudois (CHUV University Hospital), Division of Nuclear Medicine, Lausanne (Switzerland); Monbaron, David; Ruiz, Juan [Centre Hospitalier Universitaire Vaudois (CHUV University Hospital), Division of Endocrinology, Diabetology and Metabolism, Lausanne (Switzerland); Koehli, Melanie [Centre Hospitalier Universitaire Vaudois (CHUV University Hospital), Division of Nuclear Medicine, Lausanne (Switzerland); Centre Hospitalier Universitaire Vaudois (CHUV University Hospital), Division of Endocrinology, Diabetology and Metabolism, Lausanne (Switzerland)

    2005-01-01

    Silent myocardial ischaemia - as evaluated by stress-induced perfusion defects on myocardial perfusion scintigraphy (MPS) in patients without a history of chest pain - is frequent in diabetes and is associated with increased rates of cardiovascular events. Its prevalence has been determined in asymptomatic diabetic patients, but remains largely unknown in diabetic patients with suspected coronary artery disease (CAD) in the clinical setting. In this study we therefore sought (a) to determine the prevalence of symptomatic and silent perfusion defects in diabetic patients with suspected CAD and (b) to characterise the eventual predictors of abnormal perfusion. The patient population comprised 133 consecutive diabetic patients with suspected CAD who had been referred for MPS. Studies were performed with exercise (41%) or pharmacological stress testing (1-day protocol, {sup 99m}Tc-sestamibi, {sup 201}Tl or both). We used semi-quantitative analysis (20-segment polar maps) to derive the summed stress score (SSS) and the summed difference score (SDS). Abnormal MPS (SSS{>=}4) was observed in 49 (37%) patients (SSS=4.9{+-}8.4, SDS=2.4{+-}4.7), reversible perfusion defects (SDS{>=}2) in 40 (30%) patients [SSS=13.3{+-}10.9; SDS=8.0{+-}5.6; 20% moderate to severe (SDS>4), 7% multivessel] and fixed defects in 21 (16%) patients. Results were comparable between patients with and patients without a history of chest pain. Of 75 patients without a history of chest pain, 23 (31%, 95% CI=21-42%) presented reversible defects (SSS=13.9{+-}11.3; SDS=7.4{+-}1.2), indicative of silent ischaemia. Reversible defects were associated with inducible ST segment depression during MPS stress (odds ratio (OR)=3.2, p<0.01). Fixed defects were associated with erectile dysfunction in males (OR=3.7, p=0.02) and lower aspirin use (OR=0.25, p=0.02). Silent stress-induced perfusion defects occurred in 31% of the patients, a rate similar to that in patients with a history of chest pain. MPS could identify

  19. Slip reactivation model for the 2011 Mw9 Tohoku earthquake: Dynamic rupture, sea floor displacements and tsunami simulations.

    Science.gov (United States)

    Galvez, P.; Dalguer, L. A.; Rahnema, K.; Bader, M.

    2014-12-01

    The 2011 Mw9 Tohoku earthquake has been recorded with a vast GPS and seismic network given unprecedented chance to seismologists to unveil complex rupture processes in a mega-thrust event. In fact more than one thousand near field strong-motion stations across Japan (K-Net and Kik-Net) revealed complex ground motion patterns attributed to the source effects, allowing to capture detailed information of the rupture process. The seismic stations surrounding the Miyagi regions (MYGH013) show two clear distinct waveforms separated by 40 seconds. This observation is consistent with the kinematic source model obtained from the inversion of strong motion data performed by Lee's et al (2011). In this model two rupture fronts separated by 40 seconds emanate close to the hypocenter and propagate towards the trench. This feature is clearly observed by stacking the slip-rate snapshots on fault points aligned in the EW direction passing through the hypocenter (Gabriel et al, 2012), suggesting slip reactivation during the main event. A repeating slip on large earthquakes may occur due to frictional melting and thermal fluid pressurization effects. Kanamori & Heaton (2002) argued that during faulting of large earthquakes the temperature rises high enough creating melting and further reduction of friction coefficient. We created a 3D dynamic rupture model to reproduce this slip reactivation pattern using SPECFEM3D (Galvez et al, 2014) based on a slip-weakening friction with sudden two sequential stress drops . Our model starts like a M7-8 earthquake breaking dimly the trench, then after 40 seconds a second rupture emerges close to the trench producing additional slip capable to fully break the trench and transforming the earthquake into a megathrust event. The resulting sea floor displacements are in agreement with 1Hz GPS displacements (GEONET). The seismograms agree roughly with seismic records along the coast of Japan.The simulated sea floor displacement reaches 8-10 meters of

  20. A Comparison of Reading Rates, Comprehension, and Stamina in Oral and Silent Reading of Fourth-Grade Students

    Science.gov (United States)

    Trainin, Guy; Hiebert, Elfrieda H.; Wilson, Kathleen M.

    2015-01-01

    This study examined the relationships between silent and oral reading fluency and comprehension. Findings indicated that fourth grade students had consistent levels of comprehension in both reading modes. Students of all reading levels showed a similar pattern across the segments of a text set in both oral and silent reading--a gradual increase in…

  1. Silent infarction on a second CT scan in 91 patients without manifest stroke in the Dutch TIA trial

    NARCIS (Netherlands)

    Herderscheê, D.; Hijdra, A.; Algra, A.; Kappelle, L. J.; Koudstaal, P. J.; van Gijn, J.

    1994-01-01

    The frequency of silent infarction is an important issue because it is a marker of vascular disease. We studied the occurrence of silent infarction in a sample of patients from the Dutch TIA trial, in which patients were randomized between 30 and 283 mg of aspirin. A total of 91 patients with TIA or

  2. Shape fabric development in rigid clast populations under pure shear: The influence of no-slip versus slip boundary conditions

    Science.gov (United States)

    Mulchrone, Kieran F.; Meere, Patrick A.

    2015-09-01

    Shape fabrics of elliptical objects in rocks are usually assumed to develop by passive behavior of inclusions with respect to the surrounding material leading to shape-based strain analysis methods belonging to the Rf/ϕ family. A probability density function is derived for the orientational characteristics of populations of rigid ellipses deforming in a pure shear 2D deformation with both no-slip and slip boundary conditions. Using maximum likelihood a numerical method is developed for estimating finite strain in natural populations deforming for both mechanisms. Application to a natural example indicates the importance of the slip mechanism in explaining clast shape fabrics in deformed sediments.

  3. Electrical Potentials Observed During Frictional Stick-Slip - A Semiconductor Mechanism

    Science.gov (United States)

    Leeman, J.; Scuderi, M.; Marone, C.; Saffer, D. M.

    2013-12-01

    Electromagnetic phenomena are commonly reported during and after large earthquakes. Various lines of evidence including charring of plant roots, magnetic remnant signatures in pseudotachylite, and visible earthquake lights indicate a strong electrical potential separation during co-seismic rupture. Suggested explanations have included triboelectricity, piezoelectricity, and streaming potentials. The 'semiconductor effect', or migration of electron holes, has been proposed as an alternative explanation and studied extensively in solids. We present evidence of a similar migration effect in a granular material that exhibits repeated frictional stick-slip events under a variety of conditions. Soda-lime glass beads were sheared in a double-direct shear configuration in a biaxial loading frame. Glass beads exhibit consistent, repetitive stick-slip and rate/state friction effects that are similar to rock. Layers of 5 mm thickness were sheared under a constant normal load of 4MPa, at load point velocities of 1, 30, and 100 μm/s. This was done for mono-disperse particle size distributions of 100-150 μm and 420-500 μm. Tests were conducted at room humidity, at 100% humidity, and under submerged conditions. During shearing, the electrical potential of the surface was monitored relative to the system ground with a non-contact electrostatic volt meter (ESVM) manufactured by Trek Incorporated. During stick-slip events, we observe electrical potential anomalies that appear to be related to failure of force chains supporting the shear load. Two distinct types of behavior are delineated by the attainment of steady state frictional sliding. In the pre-steady state phase, as shear stress is increasing, layers are observed to charge during stick-slip and the potential of the entire system rises. When shear stress rises to the level of steady state frictional sliding, the system begins to discharge, with superimposed anomalies characterized by potential drops of several volts that

  4. Stick-slip and Torsional Friction Factors in Inclined Wellbores

    Directory of Open Access Journals (Sweden)

    Aarsnes Ulf Jakob F.

    2018-01-01

    The model is shown to have a good match with the surface and downhole behavior of two deviated wellbores for depths ranging from 1500 to 3000 meters. In particular, the model replicates the amplitude and period of the oscillations, in both the topside torque and the downhole RPM, as caused by the along-string stick slip. It is further shown that by using the surface behavior of the drill-string during rotational startup, an estimate of the static and dynamic friction factors along the wellbore can be obtained, even during stick-slip oscillations, if axial tension in the drillstring is considered. This presents a possible method to estimate friction factors in the field when off-bottom stick slip is encountered, and points in the direction of avoiding stick slip through the design of an appropriate torsional start-up procedure without the need of an explicit friction test.

  5. Wheel slip dump valve for railway braking system

    Science.gov (United States)

    Zhang, Xuan; Zhang, LiHao; Li, QingXuan; Shi, YanTao

    2017-09-01

    As we all know, pneumatic braking system plays an important role in the safety of the whole vehicle. In the anti slip braking system, the pressure of braking cylinder can be adjusted by the quick power response of wheel slip dump valve, so that the lock situation won’t occur during vehicle service. During the braking of railway vehicles, the braking force provided by braking disc reduces vehicle’s speed. But the locking slip will happen due to the oversize of braking force or the reduction of sticking coefficient between wheel and rail. It will cause not only the decline of braking performance but also the increase of braking distance. In the meanwhile, it will scratch the wheel and influence the stable running of vehicles. Now, the speed of passenger vehicle has been increased. In order to shorten the braking distance as far as possible, sticking stickiness must be fully applied. So the occurrence probability of wheel slip is increased.

  6. Non-slipping domains of a pulled spool

    International Nuclear Information System (INIS)

    Wagner, Clemens; Vaterlaus, Andreas

    2014-01-01

    We have investigated the pulled spool by considering pulling angles up to 360 ∘ . Our focus was on downward pulling forces with pulling angles in the range of 180 ∘ to 360 ∘ . In this range we have found a domain of pulling angles where the spool never starts to slip independent of the strength of the pulling force. The size of the domain depends on the static friction coefficient and on the moment of inertia of the spool. The non-slipping domain is mainly formed around the critical angle where the static friction force becomes zero. For low static friction the non-slipping domain decays into two different domains. We have determined the limiting angles of the non-slipping domains and explored the transitions from a single domain to two separated domains in parameter space. (paper)

  7. Assessment of slip factor models at off-design condition

    International Nuclear Information System (INIS)

    Yoon, Sung Ho; Baek, Je Hyun

    2000-01-01

    Slip factor is defined as an empirical factor being multiplied to theoretical energy transfer for the estimation of real work input of a centrifugal compressor. Researchers have tried to develop a simple empirical model, for a century, to predict a slip factor. However most these models were developed on the condition of design point assuming inviscid flow. So these models often fail to predict a correct slip factor at off-design condition. In this study, we summarized various slip factor models and compared these models with experimental and numerical data at off-design condition. As a result of this study, Wiesner's and Paeng and Chung's models are applicable for radial impeller, but all the models are not suitable for backswept impeller. Finally, the essential avenues for future study is discussed

  8. Improvement of ozone yield by a multi-discharge type ozonizer using superposition of silent discharge plasma

    International Nuclear Information System (INIS)

    Song, Hyun-Jig; Chun, Byung-Joon; Lee, Kwang-Sik

    2004-01-01

    In order to improve ozone generation, we experimentally investigated the silent discharge plasma and ozone generation characteristics of a multi-discharge type ozonizer. Ozone in a multi-discharge type ozonizer is generated by superposition of a silent discharge plasma, which is simultaneously generated in separated discharge spaces. A multi-discharge type ozonizer is composed of three different kinds of superposed silent discharge type ozonizers, depending on the method of applying power to each electrode. We observed that the discharge period of the current pulse for a multi discharge type ozonizer can be longer than that of silent discharge type ozonizer with two electrodes and one gap. Hence, ozone generation is improved up to 17185 ppm and 783 g/kwh in the case of the superposed silent discharge type ozonizer for which an AC high voltages with a 180 .deg. phase difference were applied to the internal electrode and the external electrode, respectively, with the central electrode being grounded.

  9. Serratia marcescens harboring SME-4 in Brazil: A silent threat.

    Science.gov (United States)

    Cayô, Rodrigo; Leme, Rodrigo Cuiabano Paes; Streling, Ana Paula; Matos, Adriana Pereira; Nodari, Carolina Silva; Chaves, Jessica Reis Esteves; Brandão, Jorge Luiz Ferreira; de Almeida, Maíra Fernandes; Carrareto, Valério; de Castro Pereira, Marco Aurélio; de Almeida, Jean Pierre Aquino; Ferreira, Demian Candido; Gales, Ana Cristina

    2017-04-01

    The intrinsic polymyxin resistance displayed by Serratia marcescens makes the acquisition of carbapenemase encoding genes a worrisome event. This study report a SME-4-producing S. marcescens isolate causing septic shock in Brazil. The insertion of novel resistance determinants and their consequent spread in our territory is noteworthy. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Foreshocks during the nucleation of stick-slip instability

    Science.gov (United States)

    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.

  11. Entropy Stability and the No-Slip Wall Boundary Condition

    KAUST Repository

    Svä rd, Magnus; Carpenter, Mark H.; Parsani, Matteo

    2018-01-01

    We present an entropy stable numerical scheme subject to no-slip wall boundary conditions. To enforce entropy stability only the no-penetration boundary condition and a temperature condition are needed at a wall, and this leads to an L bound on the conservative variables. In this article, we take the next step and design a finite difference scheme that also bounds the velocity gradients. This necessitates the use of the full no-slip conditions.

  12. Entropy Stability and the No-Slip Wall Boundary Condition

    KAUST Repository

    Svärd, Magnus

    2018-01-18

    We present an entropy stable numerical scheme subject to no-slip wall boundary conditions. To enforce entropy stability only the no-penetration boundary condition and a temperature condition are needed at a wall, and this leads to an L bound on the conservative variables. In this article, we take the next step and design a finite difference scheme that also bounds the velocity gradients. This necessitates the use of the full no-slip conditions.

  13. Molecular Dynamics Simulations of Slip on Curved Surfaces

    Directory of Open Access Journals (Sweden)

    Ross D.A.

    2016-07-01

    Full Text Available We present Molecular Dynamics (MD simulations of liquid water confined within nanoscale geometries, including slit-like and cylindrical graphitic pores. These equilibrium results are used for calculating friction coefficients, which in turn can be used to calculate slip lengths. The slip length is a material property independent of the fluid flow rate. It is therefore a better quantity for study than the fluid velocity at the wall, also known as the slip velocity. Once the slip length has been found as a function of surface curvature, it can be used to parameterise Lattice Boltzmann (LB simulations. These larger scale simulations are able to tell us about how fluid transport is affected by slip in complex geometries; not just limited to single pores. Applications include flow and transport in nano-porous engine valve deposits and gas shales. The friction coefficient is found to be a function of curvature and is higher for fluid on convex surfaces and lower for concave surfaces. Both concave and convex surfaces approach the same value of the friction coefficient, which is constant above some critical radius of curvature, here found to be 7.4 ± 2.9 nm. The constant value of the friction coefficient is 10,000 ± 600 kg m−2 s−1, which is equivalent to a slip length of approximately 67 ± 4 nm.

  14. A flexible slip sensor using triboelectric nanogenerator approach

    Science.gov (United States)

    Wang, Xudong; Liang, Jiaming; Xiao, Yuxiang; Wu, Yichuan; Deng, Yang; Wang, Xiaohao; Zhang, Min

    2018-03-01

    With the rapid development of robotic technology, tactile sensors for robots have gained great attention from academic and industry researchers. Tactile sensors for slip detection are essential for human-like steady control in dexterous robot hand. In this paper, we propose and demonstrate a flexible slip sensor based on triboelectric nanogenerator with a seesaw structure. The sensor is composed of two porous PDMS layers separated by an inverted trapezoid structure with a height of 500 μm. In order to customize the sensitivity of the sensor, porous PDMS was fabricated by mixing PDMS with deionized water thoroughly and then removing water with heat. Laser-induced porous graphene and aluminium are served as the pair of contact materials. To detect slip from different directions, two sets of the electrode pair were used. Experimental results show a distinct difference between static state and the moment when a slip happens was detected. In addition, the output voltage of the sensors increased as the increase of slip velocity from 0.25 mm/s to 2.5 mm/s. The flexible slip sensor proposed here shows the potential applications in smart robotics and prosthesis.

  15. Development of roller type side slip tester; Roller shiki side slip tester no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Nishiyama, S [Hiroshima City Industrial Technology Institute, Hiroshima (Japan); Harada, S; Harada, K

    1997-10-01

    This paper presents a new development of roller type side slip tester (RTSSI). The test equipment consists of four parts, which are developed in this research. These are a roller part, a control part, a remote control part and a CRT part. In this study, we especially investigated the mechanism and performance between tire and roller. We analyzed the amount of side slip with various toe angles. The developed tester is examined under the conditions that is considered in industrial applications. We investigated the influences of toe angle, size of tire, pressure of tire, coefficient of friction between tire and roller, pushing force of tire, revolution velocity of roller, axle load and so on. The validity of the developed RTSST is confirmed under these conditions. It was found that the RTSST can be used in practical use. Some measurement results are presented in the form of parametric plots. And we also compared measurements data between the RTSST and that of flat type using several automobiles. 4 refs., 8 figs., 4 tabs.

  16. Micromechanical Model for Deformation in Solids with Universal Predictions for Stress-Strain Curves and Slip Avalanches

    International Nuclear Information System (INIS)

    Dahmen, Karin A.; Ben-Zion, Yehuda; Uhl, Jonathan T.

    2009-01-01

    A basic micromechanical model for deformation of solids with only one tuning parameter (weakening ε) is introduced. The model can reproduce observed stress-strain curves, acoustic emissions and related power spectra, event statistics, and geometrical properties of slip, with a continuous phase transition from brittle to ductile behavior. Exact universal predictions are extracted using mean field theory and renormalization group tools. The results agree with recent experimental observations and simulations of related models for dislocation dynamics, material damage, and earthquake statistics.

  17. Fault slip and earthquake recurrence along strike-slip faults — Contributions of high-resolution geomorphic data

    KAUST Repository

    Zielke, Olaf; Klinger, Yann; Arrowsmith, J. Ramon

    2015-01-01

    to contribute to better-informed models of EQ recurrence and slip-accumulation patterns. After reviewing motivation and background, we outline requirements to successfully reconstruct a fault's offset accumulation pattern from geomorphic evidence. We address

  18. Dual silent communication system development based on subvocal speech and Raspberry Pi

    Directory of Open Access Journals (Sweden)

    José Daniel Ramírez-Corzo

    2016-09-01

    Additionally, in this article we show the speech subvocal signals’ recording system realization. The average accuracy percentage was 72.5 %, and includes a total of 50 words by class, this is 200 signals. Finally, it demonstrated that using the Raspberry Pi it is possible to set a silent communication system, using subvocal. speech signals.

  19. Silent hepatitis E virus infection in Dutch blood donors, 2011 to 2012

    NARCIS (Netherlands)

    Slot, E.; Hogema, B. M.; Riezebos-Brilman, A.; Kok, T. M.; Molier, M.; Zaaijer, H. L.

    2013-01-01

    In Europe, the dynamics of endemic hepatitis E virus (HEV) infection remain enigmatic. We studied the presence of silent HEV infection among Dutch blood donors. Using donations collected throughout the Netherlands in 2011 and 2012, 40,176 donations were tested for HEV RNA in 459 pools of 48 or 480

  20. The Effect of Background Music While Silent Reading on EFL Learners’ Reading Comprehension

    Directory of Open Access Journals (Sweden)

    sakineh sahebdel

    2014-05-01

    Full Text Available This study attempted to determine the effect of background music while silent reading on Iranian EFL learners’ reading comprehension. The participants were 57 Iranian EFL learners between the ages of 14 and 16 in two 3rd grade high schoolclasses at pre-intermediate proficiency level. Before treatment,both experimental and control groups took a reading comprehension pretest. In the experimental group, the researchers played Mozart sonatas as background music and asked them to read the passage silently and then answer the reading comprehension questions. In the control group, the procedure was the same, but no music was played while silent reading by the students. After ten sessions, the students of both groups were asked to answer another independent but parallel form of reading section of PET as their post-test. The independent samples t-testresultsindicated that the experimental group outperformed the control group in reading comprehension posttest, and listening to background music while silent reading had a significantly positive effect on Iranian EFL learners’ reading comprehension. The results of the present study have implications for EFL students, teachers, and teacher educators as well as syllabus designers and materials developers.

  1. Characterisation of silent and active genes for a variable large protein of Borrelia recurrentis

    Directory of Open Access Journals (Sweden)

    Scragg Ian G

    2002-10-01

    Full Text Available Abstract Background We report the characterisation of the variable large protein (vlp gene expressed by clinical isolate A1 of Borrelia recurrentis; the agent of the life-threatening disease louse-borne relapsing fever. Methods The major vlp protein of this isolate was characterised and a DNA probe created. Use of this together with standard molecular methods was used to determine the location of the vlp1B. recurrentis A1 gene in both this and other isolates. Results This isolate was found to carry silent and expressed copies of the vlp1B. recurrentis A1 gene on plasmids of 54 kbp and 24 kbp respectively, whereas a different isolate, A17, had only the silent vlp1B. recurrentis A17 on a 54 kbp plasmid. Silent and expressed vlp1 have identical mature protein coding regions but have different 5' regions, both containing different potential lipoprotein leader sequences. Only one form of vlp1 is transcribed in the A1 isolate of B. recurrentis, yet both 5' upstream sequences of this vlp1 gene possess features of bacterial promoters. Conclusion Taken together these results suggest that antigenic variation in B. recurrentis may result from recombination of variable large and small protein genes at the junction between lipoprotein leader sequence and mature protein coding region. However, this hypothetical model needs to be validated by further identification of expressed and silent variant protein genes in other B. recurrentis isolates.

  2. Origin of the low-level EMG during the silent period following transcranial magnetic stimulation

    DEFF Research Database (Denmark)

    Butler, Jane E; Petersen, Nicolas C; Herbert, Robert D

    2012-01-01

    OBJECTIVE: The cortical silent period refers to a period of near silence in the electromyogram (EMG) after transcranial magnetic stimulation (TMS) of the motor cortex during contraction. However, low-level EMG of unknown origin is often present. We hypothesised that it arises through spinal...

  3. Silent Films and Strange Stories: Theory of Mind, Gender, and Social Experiences in Middle Childhood

    Science.gov (United States)

    Devine, Rory T.; Hughes, Claire

    2013-01-01

    In this study of two hundred and thirty 8- to 13-year-olds, a new "Silent Films" task is introduced, designed to address the dearth of research on theory of mind in older children by providing a film-based analogue of F. G. E. Happe's (1994) Strange Stories task. Confirmatory factor analysis showed that all items from both tasks loaded…

  4. Veratridine activates a silent sodium-channel in rat isolated aorta

    NARCIS (Netherlands)

    WERMELSKIRCHEN, D; WILFFERT, B; NEBEL, U; LEIDIG, A; WIRTH, A; Peters, Thies

    1992-01-01

    To investigate the existence of silent Na+ channels, isolated rat aorta was treated with veratridine (0.1 mM) and the resulting Ca2+ uptake was determined. After 30-min incubation the total tissue uptake of Ca2+ and Ca2+ uptake increased from 2.325 +/- 0.017 to 2.614 +/- 0.080 nmol/mg wet weight

  5. Cervical Cancer as a silent killer: A rare case report with review of literature

    Directory of Open Access Journals (Sweden)

    Deeksha Pandey

    2015-01-01

    Full Text Available Advanced-stage cervical cancer almost always presents either with abnormal vaginal bleeding or with foul-smelling vaginal discharge. We present here a rare case, where a postmenopausal lady presented almost silently with stage IVA cervical cancer. Fortunately, timely referral, correct diagnosis, and multispecialty team work could save her life.

  6. Direct and Indirect Effects of Print Exposure on Silent Reading Fluency

    Science.gov (United States)

    Mano, Quintino R.; Guerin, Julia M.

    2018-01-01

    Print exposure is an important causal factor in reading development. Little is known, however, of the mechanisms through which print exposure exerts an effect onto reading. To address this gap, we examined the direct and indirect effects of print exposure on silent reading fluency among college students (n = 52). More specifically, we focused on…

  7. BOOK REVIEW: ARE YOU AN ADVOCATE, TACIT SUPPORTER, CRITICAL SKEPTIC, OR SILENT SKEPTIC?

    Science.gov (United States)

    "Silent Sperm," "You're not half the man your grandfather was," "Assault on the Male," "Gender Benders,"-perhaps no other public health concern has given rise to the number of memorable sound bites than has the issue of whether environmental contaminants are causing adverse healt...

  8. Measuring the cortical silent period can increase diagnostic confidence for amyotrophic lateral sclerosis.

    NARCIS (Netherlands)

    Schelhaas, H.J.; Arts, I.M.P.; Overeem, S.; Houtman, C.J.; Janssen, H.; Kleine, B.U.; Munneke, M.; Zwarts, M.J.

    2007-01-01

    We evaluated a modified measurement of the cortical silent period (CSP) as a simple procedure to add further confidence in the diagnostic work-up for ALS. Thirty-seven consecutive patients with a suspicion of having ALS were included together with 25 healthy volunteers, and followed until a final

  9. Definition dependent properties of the cortical silent period in upper-extremity muscles, a methodological study

    NARCIS (Netherlands)

    Kuijk, A.A. van; Bakker, C.D.; Hendriks, J.C.M.; Geurts, A.C.; Stegeman, D.F.; Pasman, J.W.

    2014-01-01

    BACKGROUND: To explore if stimulus-response (S-R) characteristics of the silent period (SP) after transcranial magnetic stimulation (TMS) are affected by changing the SP definition and by changing data presentation in healthy individuals. This information would be clinically relevant to predict

  10. Definition dependent properties of the cortical silent period in upper-extremity muscles, a methodological study

    NARCIS (Netherlands)

    van Kuijk, A.A.; Bakker, C,; Hendriks, J.J.A.; Geurts, A.H.; Stegeman, D.F.; Pasman, J.W.

    2014-01-01

    Background: To explore if stimulus-response (S-R) characteristics of the silent period (SP) after transcranial magnetic stimulation (TMS) are affected by changing the SP definition and by changing data presentation in healthy individuals. This information would be clinically relevant to predict

  11. Neural responses to silent lipreading in normal hearing male and female subjects

    NARCIS (Netherlands)

    Ruytjens, Liesbet; Albers, Frans; van Dijk, Pim; Wit, Hero; Willemsen, Antoon

    In the past, researchers investigated silent lipreading in normal hearing subjects with functional neuroimaging tools and showed how the brain processes visual stimuli that are normally accompanied by an auditory counterpart. Previously, we showed activation differences between males and females in

  12. Scintigraphic diagnosis of silent aspiration following double-sided lung transplantation

    International Nuclear Information System (INIS)

    Toenshoff, G.; Stock, U.; Bohuslavizki, K.H.; Brenner, W.; Costard-Jaeckle, A.; Cremer, J.; Clausen, M.

    1996-01-01

    We present a case of a 25 year old patient who underwent double-sided lung transplantation and suffered from recurrent pneumonia. Silent aspiration was suspected clinically. Aspiration was proved by scintigraphy enabling to discriminate between direct oro-pulmonal aspiration and aspiration after gastro-esophageal reflux. (orig.) [de

  13. Whatever Happened to the Silent Scientific Revolution?--Research, Theory and Practice in Distance Education.

    Science.gov (United States)

    Morgan, Alistair

    The point of departure for this article is the title of a book edited by David Fetterman, "Qualitative Approaches to Educational Evaluation--The Silent Scientific Revolution." This article addresses the question of how the shift to a qualitative, phenomenological approach has impinged on research and evaluation in distance education.…

  14. Locating the origin of stick slip instabilities in sheared granular layers

    Science.gov (United States)

    Korkolis, Evangelos; Niemeijer, André

    2017-04-01

    Acoustic emission (AE) monitoring is a non-invasive technique widely used to evaluate the state of materials and structures. We have developed a system that can locate the source of AE events associated with unstable sliding (stick-slip) of sheared granular layers during laboratory friction experiments. Our aim is to map the spatial distribution of energy release due to permanent microstructural changes, using AE source locations as proxies. This will allow us to determine the distribution of applied work in a granular medium, which will be useful in developing constitutive laws that describe the frictional behavior of such materials. The AE monitoring system is installed on a rotary shear apparatus. This type of apparatus is used to investigate the micromechanical processes responsible for the macroscopic frictional behavior of granular materials at large shear displacements. Two arrays of 8 piezoelectric sensors each are installed into the ring-shaped steel pistons that confine our samples. The sensors are connected to a high-speed, multichannel oscilloscope that can record full waveforms. The apparatus is also equipped with a system that continuously records normal and lateral (shear) loads and displacements, as well as pore fluid pressure. Thus, we can calculate the frictional and volumetric response of our granular aggregates, as well as the location of AE sources. Here, we report on the results of room temperature experiments on granular aggregates consisting of glass beads or segregated mixtures of glass beads and calcite, at up to 5 MPa normal stress and sliding velocities between 1 and 100 μm/s. Under these conditions, glass beads exhibit unstable sliding behavior accompanied by significant AE activity, whereas calcite exhibits stable sliding and produces no AEs. We recorded a range of unstable sliding behaviors, from fast, regular stick slip at high normal stress (> 4 MPa) and sliding velocities below 20 μm/s, to irregular stick slip at low normal

  15. How Long Is Long Enough? Estimation of Slip-Rate and Earthquake Recurrence Interval on a Simple Plate-Boundary Fault Using 3D Paleoseismic Trenching

    Science.gov (United States)

    Wechsler, N.; Rockwell, T. K.; Klinger, Y.; Agnon, A.; Marco, S.

    2012-12-01

    Models used to forecast future seismicity make fundamental assumptions about the behavior of faults and fault systems in the long term, but in many cases this long-term behavior is assumed using short-term and perhaps non-representative observations. The question arises - how long of a record is long enough to represent actual fault behavior, both in terms of recurrence of earthquakes and of moment release (aka slip-rate). We test earthquake recurrence and slip models via high-resolution three-dimensional trenching of the Beteiha (Bet-Zayda) site on the Dead Sea Transform (DST) in northern Israel. We extend the earthquake history of this simple plate boundary fault to establish slip rate for the past 3-4kyr, to determine the amount of slip per event and to study the fundamental behavior, thereby testing competing rupture models (characteristic, slip-patch, slip-loading, and Gutenberg Richter type distribution). To this end we opened more than 900m of trenches, mapped 8 buried channels and dated more than 80 radiocarbon samples. By mapping buried channels, offset by the DST on both sides of the fault, we obtained for each an estimate of displacement. Coupled with fault crossing trenches to determine event history, we construct earthquake and slip history for the fault for the past 2kyr. We observe evidence for a total of 9-10 surface-rupturing earthquakes with varying offset amounts. 6-7 events occurred in the 1st millennium, compared to just 2-3 in the 2nd millennium CE. From our observations it is clear that the fault is not behaving in a periodic fashion. A 4kyr old buried channel yields a slip rate of 3.5-4mm/yr, consistent with GPS rates for this segment. Yet in spite of the apparent agreement between GPS, Pleistocene to present slip rate, and the lifetime rate of the DST, the past 800-1000 year period appears deficit in strain release. Thus, in terms of moment release, most of the fault has remained locked and is accumulating elastic strain. In contrast, the

  16. Half-cycle slip activity of persistent slip bands at different stages of fatigue life of polycrystalline nickel

    Czech Academy of Sciences Publication Activity Database

    Weidner, A.; Man, Jiří; Tirschler, W.; Klapetek, P.; Blochwitz, C.; Polák, Jaroslav; Skrotzki, W.

    2008-01-01

    Roč. 492, č. 1-2 (2008), s. 118-127 ISSN 0921-5093 R&D Projects: GA ČR GA106/06/1096 Institutional research plan: CEZ:AV0Z20410507 Keywords : persistent slip band * slip activity * half-cycle deformation * atomic force microscopy * scanning electron microscopy * nickel Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.806, year: 2008

  17. Is lithostatic loading important for the slip behavior and evolution of normal faults in the Earth's crust?

    International Nuclear Information System (INIS)

    Kattenhorn, Simon A.; Pollard, David D.

    1999-01-01

    Normal faults growing in the Earth's crust are subject to the effects of an increasing frictional resistance to slip caused by the increasing lithostatic load with depth. We use three-dimensional (3-D) boundary element method numerical models to evaluate these effects on planar normal faults with variable elliptical tip line shapes in an elastic solid. As a result of increasing friction with depth, normal fault slip maxima for a single slip event are skewed away from the fault center toward the upper fault tip. There is a correspondingly greater propagation tendency at the upper tip. However, the tall faults that would result from such a propagation tendency are generally not observed in nature. We show how mechanical interaction between laterally stepping fault segments significantly competes with the lithostatic loading effect in the evolution of a normal fault system, promoting lateral propagation and possibly segment linkage. Resultant composite faults are wider than they are tall, resembling both 3-D seismic data interpretations and previously documented characteristics of normal fault systems. However, this effect may be greatly complemented by the influence of a heterogeneous stratigraphy, which can control fault nucleation depth and inhibit fault propagation across the mechanical layering. Our models demonstrate that although lithostatic loading may be an important control on fault evolution in relatively homogeneous rocks, the contribution of lithologic influences and mechanical interaction between closely spaced, laterally stepping faults may predominate in determining the slip behavior and propagation tendency of normal faults in the Earth's crust. (c) 1999 American Geophysical Union

  18. Constraining the Distribution of Vertical Slip on the South Heli Shan Fault (Northeastern Tibet) From High-Resolution Topographic Data

    Science.gov (United States)

    Bi, Haiyun; Zheng, Wenjun; Ge, Weipeng; Zhang, Peizhen; Zeng, Jiangyuan; Yu, Jingxing

    2018-03-01

    Reconstruction of the along-fault slip distribution provides an insight into the long-term rupture patterns of a fault, thereby enabling more accurate assessment of its future behavior. The increasing wealth of high-resolution topographic data, such as Light Detection and Ranging and photogrammetric digital elevation models, allows us to better constrain the slip distribution, thus greatly improving our understanding of fault behavior. The South Heli Shan Fault is a major active fault on the northeastern margin of the Tibetan Plateau. In this study, we built a 2 m resolution digital elevation model of the South Heli Shan Fault based on high-resolution GeoEye-1 stereo satellite imagery and then measured 302 vertical displacements along the fault, which increased the measurement density of previous field surveys by a factor of nearly 5. The cumulative displacements show an asymmetric distribution along the fault, comprising three major segments. An increasing trend from west to east indicates that the fault has likely propagated westward over its lifetime. The topographic relief of Heli Shan shows an asymmetry similar to the measured cumulative slip distribution, suggesting that the uplift of Heli Shan may result mainly from the long-term activity of the South Heli Shan Fault. Furthermore, the cumulative displacements divide into discrete clusters along the fault, indicating that the fault has ruptured in several large earthquakes. By constraining the slip-length distribution of each rupture, we found that the events do not support a characteristic recurrence model for the fault.

  19. Effects of layered crust on the coseismic slip inversion and related CFF variations: Hints from the 2012 Emilia Romagna earthquake

    Science.gov (United States)

    Nespoli, Massimo; Belardinelli, Maria E.; Anderlini, Letizia; Bonafede, Maurizio; Pezzo, Giuseppe; Todesco, Micol; Rinaldi, Antonio P.

    2017-12-01

    The 2012 Emilia Romagna (Italy) seismic sequence has been extensively studied given the occurrence of two mainshocks, both temporally and spatially close to each other. The recent literature accounts for several fault models, obtained with different inversion methods and different datasets. Several authors investigated the possibility that the second event was triggered by the first mainshock with elusive results. In this work, we consider all the available InSAR and GPS datasets and two planar fault geometries, which are based on both seismological and geological constraints. We account for a layered, elastic half-space hosting the dislocation and compare the slip distribution resulting from the inversion and the related changes in Coulomb Failure Function (CFF) obtained with both a homogeneous and layered half-space. Finally, we focus on the interaction between the two main events, discriminating the contributions of coseismic and early postseismic slip of the mainshock on the generation of the second event and discuss the spatio-temporal distribution of the seismic sequence. When accounting for both InSAR and GPS geodetic data we are able to reproduce a detailed coseismic slip distribution for the two mainshocks that is in accordance with the overall aftershock seismicity distribution. Furthermore, we see that an elastic medium with depth dependent rigidity better accounts for the lack of the shallow seismicity, amplifying, with respect to the homogeneous case, the mechanical interaction of the two mainshocks.

  20. What causes an icy fault to slip? Investigating strike-slip failure conditions on Ganymede at Dardanus and Tiamat Sulcus.

    Science.gov (United States)

    Cameron, M. E.; Smith-Konter, B. R.; Burkhard, L. M.; Collins, G. C.; Seifert, F.; Pappalardo, R. T.

    2015-12-01

    Ganymede exhibits two geologically distinct terrains known as dark and light (grooved) terrain. The mechanism for a transition from dark to light terrain remains unclear; however, inferences of strike-slip faulting and distributed shear zones suggest that strike-slip tectonism may be important to the structural development of Ganymede's surface and in this transition. Here we investigate the role of tidal stresses on Ganymede in the formation and evolution of strike-slip structures in both dark and grooved terrains. Using numerical code SatStress, we calculate both diurnal and non-synchronous rotation (NSR) tidal stresses at Ganymede's surface. Specifically, we investigate the role of fault friction and orbital eccentricity in the development of ~45 km of right-lateral offset at Dardanus Sulcus and a possible case of study with a detailed morphological mapping of strike-slip morphologies (en echelon structures, strike-slip duplexes, laterally offset pre-existing features, and possible strained craters) at Nun Sulcus and several other locations. These structures serve as example regions to provide improved constraints for global stress mechanisms responsible for strike-slip fault evolution on Ganymede.

  1. Silent Atrial Fibrillation in Elderly Pacemaker Users: A Randomized Trial Using Home Monitoring.

    Science.gov (United States)

    Lima, Ceb; Martinelli, M; Peixoto, G L; Siqueira, S F; Wajngarten, Maurício; Silva, Rodrigo Tavares; Costa, Roberto; Filho, Roberto; Ramires, José Antônio Franchini

    2016-05-01

    Pacemaker with remote monitoring (PRM) may be useful for silent atrial fibrillation (AF) detection. The aims of this study were to evaluate the incidence of silent AF, the role of PRM, and to determine predictors of silent AF occurrence. Three hundred elderly patients with permanent pacemaker (PPM) were randomly assigned to the remote group (RG) or control group (CG). All patients received PPM with remote monitoring capabilities. Primary end point was AF occurrence rate and the secondary end points were time to AF detection and number of days with AF. During the average follow-up of 15.7±7.7 months, AF episodes were detected in 21.6% (RG = 24% vs CG = 19.3%, P = 0.36]. There was no difference in the time to detect the first AF episode. However, the median time to detect AF recurrence in the RG was lower than that in the CG (54 days vs 100 days, P = 0.004). The average number of days with AF was 16.0 and 51.2 in the RG and CG, respectively (P = 0.028). Predictors of silent AF were left atrial diameter (odds ratio [OR] 1.2; 95% CI = 1.1-1.3; P pacemaker; left atrial diameter and diastolic dysfunction were predictors of its occurrence. AF monitoring by means of pacemaker is a valuable tool for silent AF detection and continuous remote monitoring allows early AF recurrence detection and reduces the number of days with AF. © 2015 Wiley Periodicals, Inc.

  2. Sounds from seeing silent motion: Who hears them, and what looks loudest?

    Science.gov (United States)

    Fassnidge, Christopher J; Freeman, Elliot D

    2018-03-09

    Some people hear what they see: car indicator lights, flashing neon shop signs, and people's movements as they walk may all trigger an auditory sensation, which we call the visual-evoked auditory response (vEAR or 'visual ear'). We have conducted the first large-scale online survey (N > 4000) of this little-known phenomenon. We analysed the prevalence of vEAR, what induces it, and what other traits are associated with it. We assessed prevalence by asking whether respondents had previously experienced vEAR. Participants then rated silent videos for vividness of evoked auditory sensations, and answered additional trait questions. Prevalence appeared higher relative to other typical synaesthesias. Prior awareness and video ratings were associated with greater frequency of other synaesthesias, including flashes evoked by sounds, and musical imagery. Higher-rated videos often depicted meaningful events that predicted sounds (e.g., collisions). However, even videos containing abstract flickering or moving patterns could also elicit higher ratings, despite having no predictable association with sounds. Such videos had higher levels of raw 'motion energy' (ME), which we quantified using a simple computational model of motion processing in early visual cortex. Critically, only respondents reporting prior awareness of vEAR tended to show a positive correlation between video ratings and ME. This specific sensitivity to ME suggests that in vEAR, signals from visual motion processing may affect audition relatively directly without requiring higher-level interpretative processes. Our other findings challenge the popular assumption that individuals with synaesthesia are rare and have ideosyncratic patterns of brain hyper-connectivity. Instead, our findings of apparently high prevalence and broad associations with other synaesthesias and traits are jointly consistent with a common dependence on normal variations in physiological mechanisms of disinhibition or excitability of

  3. Slip transmission in bcc FeCr polycrystal

    Energy Technology Data Exchange (ETDEWEB)

    Patriarca, Luca, E-mail: luca.patriarca@polimi.it [Politecnico di Milano, Department of Mechanical Engineering, Via La Masa 34, I-20156 Milano (Italy); Abuzaid, Wael; Sehitoglu, Huseyin [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206W. Green St., Urbana, IL 61801 (United States); Maier, Hans J. [Institut für Werkstoffkunde, Leibniz Universität Hannover, An der Universität 2, D-30823 Garbsen (Germany)

    2013-12-20

    Grain boundaries induce heterogeneities in the deformation response of polycrystals. Studying these local variations in response, measured through high resolution strain measurement techniques, is important and can improve our understanding of fatigue damage initiation in the vicinity of grain boundaries and material hardening. In this work, strain fields across grain boundaries were measured using advanced digital image correlation techniques. In conjunction with strain measurements, grain orientations from electron back-scattered diffraction were used to establish the dislocation reactions at each boundary, providing the corresponding residual Burgers vectors due to slip transmission across the interfaces. A close correlation was found between the magnitude of the residual Burgers vector and the local strain change across the boundary. When the residual Burgers vector magnitude (with respect to the lattice spacing) exceeds 1.0, the high strains on one side of the boundary are paired with low strains across the boundary, indicating the difficulties for slip dislocations to penetrate the grain interfaces. When the residual Burgers vector approaches zero, the strain fields vary smoothly across the boundary due to limited resistance to slip transmission. The results suggest that the residual Burgers vector magnitude, which relates to the GB (Grain Boundary) resistance to slip transmission, enables a quantitative analysis of the accumulation of strain at the microstructural level and the development of strain heterogeneities across grain boundaries. The results are presented for FeCr bcc alloy which exhibits single slip per grain making the measurements and dislocation reactions rather straightforward. The work points to the need to incorporate details of slip dislocation–grain boundary interaction (slip transmission) in modeling research.

  4. Spatiotemporal distribution of interplate slip following the 2003 Tokachi-oki earthquake deduced from ocean bottom pressure gauges and onland GNSS data

    Science.gov (United States)

    Itoh, Y.; Nishimura, T.; Ariyoshi, K.; Matsumoto, H.

    2017-12-01

    The 2003 Tokachi-oki earthquake (Mw 8.0) is an interplate earthquake along the Kurile trench. Its co- and post-seismic deformation has been observed by onland GNSS [e.g., Miyazaki et al. 2004] and modeled with afterslip and/or viscoelastic relaxation [e.g., Itoh and Nishimura 2016]. In the offshore region, two ocean bottom pressure gauges (OBPs) are operated by JAMSTEC since July 1999 [Hirata et al. 2002] and they have continuously observed the pre-, co- and post-seismic pressure change of the 2003 event [Baba et al. 2006]. The observed pressure change can be interpreted as vertical displacement, and the resolution of slip beneath the seafloor far from the land was improved by incorporating these pressure data into onland GNSS data [Baba et al. 2006]. However, no previous studies used postseismic pressure data for several years to estimate an interplate slip. Because, in this region, an M8 class event similar to the 2003 event has occurred in 1952, it is important to clarify a healing process of an interplate coupling which may lead to a next M8 class event in terms of the earthquake cycle. Itoh and Nishimura [2017, JpGU-AGU Joint Meeting] estimated it but used only onland GNSS data. In this study, we use both onland GNSS and OBP data. For OBP data analysis, we first removed the tidal component using BAYTAP08 [Tamura et al. 1991; Tamura and Agnew 2008]. Next, we corrected the temporal fluctuation of data correlating with temperature [Baba et al. 2006]. We estimated the linear trend before the 2003 event using the corrected time series from 2002 Jan. 1 to 2003 Sep. 1 and remove the estimated trend from the data after the 2003 event. Here, we assumed a non-linear drift could be ignored. Finally, we down-sampled the remained time series with an interval of 1 month. For the onland GNSS data, we used the same data set of Itoh and Nishimura [2017, JpGU-AGU Joint Meeting]. We constructed the model consisting of coseismic slip of the 2003 and M6-7 events in the postseismic

  5. How material contrast around subduction faults may control coseismic slip and rupture dynamics: tsunami applications for the case study of Tohoku

    Science.gov (United States)

    Scala, Antonio; Murphy, Shane; Romano, Fabrizio; Lorito, Stefano; Festa, Gaetano; Volpe, Manuela; Piatanesi, Alessio

    2017-04-01

    Recent megathrust tsunamigenic events, e.g. Maule 2010 (M8.8) and Tohoku 2011 (M9.0), generated huge tsunami waves as a consequence of high slip in the shallow part of the respective subduction zone. Other events, (e.g. the recent Mentawai 2010, M7.8, or the historical Meiji 1896, M8.2), referred to as tsunami earthquakes, produced unexpectedly large tsunami waves, probably due to large slip at shallow depth over longer rupture durations compared to deeper thrust events. Subduction zone earthquakes originate and propagate along bimaterial interfaces separating materials having different elastic properties, e.g. continental and oceanic crust, a stiffer deep mantle wedge, shallow compliant accretionary prism etc. Bimaterial interfaces have been showed, through observations (seismological and laboratory) and theoretical studies, to affect the rupture: introducing a preferred rupture direction as well as asymmetric rupture velocities and shear stress redistributions. Such features are predominantly due to the break of symmetry between the two sides of the interface in turn ascribable to the complex coupling between the frictional interfacial sliding and the slip-induced normal stress perturbations. In order to examine the influence of material contrast on a fault plane on the seismic source and tsunami waves, we modelled a Tohoku-like subduction zone to perform a large number of 2D along-dip rupture dynamics simulations in the framework of linear slip weakening both for homogeneous and bimaterial fault. In this latter model, the rupture acts as the interface between the subducting oceanic crust and the overriding layers (accretionary prism, continental crust and mantle wedge), varying the position of the shear stress asperity acting as nucleation patch. Initial results reveal that ruptures in homogeneous media produce earthquakes with large slip at depth compared to the case where bi-material interface is included. However the opposite occurs for events nucleating at

  6. Effect of face fracturing on shear wave coda quality factor estimated from acoustic emission events

    CSIR Research Space (South Africa)

    Kgarume, T

    2013-10-01

    Full Text Available by the number of events. It was found that the Qc dependency on frequency follows a power law. For face events, the power law is given by ( ) 99.006.0 ffQ = and ( ) 58.1003.0 ffQ = for fault slip events. Qc derived from face events was found to be lower than... to be n = 0.99, resulting in the relation: ( ) 99.006.0 ffQ = . For fault slip events, n = 1.58, resulting in the relation: ( ) 58.1003.0 ffQ = . The lower degree of dependency suggests that fractures ahead of the stope face tend to reduce...

  7. An Earthquake Swarm Search Implemented at Major Convergent Margins to Test for Associated Aseismic Slip

    Science.gov (United States)

    Holtkamp, S. G.; Pritchard, M. E.; Lohman, R. B.; Brudzinski, M. R.

    2009-12-01

    Recent geodetic analysis indicates earthquake swarms may be associated with slow slip such that earthquakes may only represent a fraction of the moment release. To investigate this potential relationship, we have developed a manual search approach to identify earthquake swarms from a seismicity catalog. Our technique is designed to be insensitive to spatial and temporal scales and the total number of events, as seismicity rates vary in different fault zones. Our first application of this technique on globally recorded earthquakes in South America detects 35 possible swarms of varying spatial scale, with 18 in the megathrust region and 8 along the volcanic arc. Three swarms in the vicinity of the arc appear to be triggered by the Mw=8.5 2001 Peru earthquake, and are examined for possible triggering mechanisms. Coulomb stress modeling suggests that static stress changes due to the earthquake are insufficient to trigger activity, so a dynamic or secondary triggering mechanism is more likely. Volcanic swarms are often associated with ground deformation, either associated with fluid movement (e.g. dike intrusion or chamber inflation or deflation) or fault movement, although these processes are sometimes difficult to differentiate. The only swarm along the arc with sufficient geodetic data that we can process and model is near Ticsani Volcano in Peru. In this case, a swarm of events southeast of the volcano precedes a more typical earthquake sequence beneath the volcano, and evidence for deformation is found in the location of the swarm, but there is no evidence for aseismic slip. Rather, we favor a model where the swarm is associated with deflation of a magma body to the southeast that triggered the earthquake sequence by promoting movement on a fault beneath Ticsani. Since swarms on the subduction interface may indicate aseismic moment release, with a direct impact on hazard, we examine potential relations between swarms and megathrust ruptures. We find evidence that

  8. Relating stick-slip friction experiments to earthquake source parameters

    Science.gov (United States)

    McGarr, Arthur F.

    2012-01-01

    Analytical results for parameters, such as static stress drop, for stick-slip friction experiments, with arbitrary input parameters, can be determined by solving an energy-balance equation. These results can then be related to a given earthquake based on its seismic moment and the maximum slip within its rupture zone, assuming that the rupture process entails the same physics as stick-slip friction. This analysis yields overshoots and ratios of apparent stress to static stress drop of about 0.25. The inferred earthquake source parameters static stress drop, apparent stress, slip rate, and radiated energy are robust inasmuch as they are largely independent of the experimental parameters used in their estimation. Instead, these earthquake parameters depend on C, the ratio of maximum slip to the cube root of the seismic moment. C is controlled by the normal stress applied to the rupture plane and the difference between the static and dynamic coefficients of friction. Estimating yield stress and seismic efficiency using the same procedure is only possible when the actual static and dynamic coefficients of friction are known within the earthquake rupture zone.

  9. Numerical study of effects of accommodation coefficients on slip phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Young Jae; Kwon, Oh Joon [KAIST, Daejeon (Korea, Republic of)

    2015-05-15

    An unstructured mesh Navier-Stokes solver employing a Maxwell slip boundary condition was developed. The present flow solver was applied to the simulation of flows around an axisymmetric hollow cylinder in a Mach 10.4 free stream, known as Calspan-UB Research Center (CUBRC) Run 14 case, and the velocity slip and the temperature jump on the cylinder surface were investigated. The effect of tangential momentum and thermal accommodation coefficients used in the Maxwell condition was also investigated by adjusting their values. The results show that the reverse flow region is developed on the body surface due to the interaction between the shock and the boundary layer. Also, the shock impingement makes pressure high. The flow properties on the surface agree well with the experimental data, and the velocity slip and the temperature jump vary consistently with the local Knudsen number change. The accommodation coefficients affect the slip phenomena and the size of the flow region. The slip phenomena become larger when both tangential momentum and thermal accommodation coefficients are decreased. However, the range of the reverse flow region decreases when the momentum accommodation coefficient is decreased. The characteristics of the momentum and thermal accommodation coefficients also are overlapped when they are altered together.

  10. Technological control of slip casting by the method of PMR

    International Nuclear Information System (INIS)

    Rozental', O.M.; Toropov, Yu.S.; Sobolev, A.S.; Pliner, S.Yu.; Demina, T.E.; Permikina, I.M.

    1980-01-01

    The method of proton magnetic resonance (PMR) is suggested for operational chemico-technological control of slip casting made of oxides of metals in the technology of technical ceramics. PMR spectra of finely dispersed slip casting made of aluminium and zirconium oxides (0.9 mol. of the ZrO 2 shake + 0.1 V 2 O 3 ) are analysed. It is shown that the quality of slip casting out of aqueous suspensions of aluminium and zirconium oxides is abruptly reduced if dP/dW (P - parameter of the PMR line shape, W - humidity) decrease. It is established that slip casting made of zirconium oxide should not be kept in the air more than 5 days, and that of aluminium oxide, more than 3 days at room temperature and should not be exposed to high (> 105 deg C) temperatures. The quality of slip casting is reduced in the regime of too energetic electrosedimentation the optimum regime of electrosedimentation is approximately 5/3 under the conditions of the above experiment

  11. Dynamic Behavior of Fault Slip Induced by Stress Waves

    Directory of Open Access Journals (Sweden)

    Guang-an Zhu

    2016-01-01

    Full Text Available Fault slip burst is a serious dynamic hazard in coal mining. A static and dynamic analysis for fault slip was performed to assess the risk of rock burst. A numerical model FLAC3D was established to understand the stress state and mechanical responses of fault rock system. The results obtained from the analysis show that the dynamic behavior of fault slip induced by stress waves is significantly affected by mining depth, as well as dynamic disturbance intensity and the distance between the stope and the fault. The isolation effect of the fault is also discussed based on the numerical results with the fault angle appearing to have the strongest influence on peak vertical stress and velocity induced by dynamic disturbance. By taking these risks into account, a stress-relief technology using break-tip blast was used for fault slip burst control. This technique is able to reduce the stress concentration and increase the attenuation of dynamic load by fracturing the structure of coal and rock. The adoption of this stress-relief method leads to an effective reduction of fault slip induced rock burst (FSIRB occurrence.

  12. Dislocation cross-slip in fcc solid solution alloys

    International Nuclear Information System (INIS)

    Nöhring, Wolfram Georg; Curtin, W.A.

    2017-01-01

    Cross-slip is a fundamental process of screw dislocation motion and plays an important role in the evolution of work hardening and dislocation structuring in metals. Cross-slip has been widely studied in pure FCC metals but rarely in FCC solid solutions. Here, the cross-slip transition path in solid solutions is calculated using atomistic methods for three representative systems of Ni-Al, Cu-Ni and Al-Mg over a range of solute concentrations. Studies using both true random alloys and their corresponding average-alloy counterparts allow for the independent assessment of the roles of (i) fluctuations in the spatial solute distribution in the true random alloy randomness and (ii) average alloy properties such as stacking fault energy. The results show that the solute fluctuations dominate the activation energy barrier, i.e. there are large sample-to-sample variations around the average activation barrier. The variations in activation barrier correlate linearly with the energy difference between the initial and final states. The distribution of this energy difference can be computed analytically in terms of the solute/dislocation interaction energies. Thus, the distribution of cross-slip activation energies can be accurately determined from a parameter-free analytic model. The implications of the statistical distribution of activation energies on the rate of cross-slip in real alloys are then identified.

  13. Soil slips and debris flows on terraced slopes

    Science.gov (United States)

    Crosta, G. B.; Dal Negro, P.; Frattini, P.

    Terraces cover large areas along the flanks of many alpine and prealpine valleys. Soil slips and soil slips-debris flows are recurrent phenomena along terraced slopes. These landslides cause damages to people, settlements and cultivations. This study investigates the processes related to the triggering of soil slip-debris flows in these settings, analysing those occurred in Valtellina (Central Alps, Italy) on November 2000 after heavy prolonged rainfalls. 260 landslides have been recognised, mostly along the northern valley flank. About 200 soil slips and slumps occurred in terraced areas and a third of them evolved into debris flows. Field work allowed to recognise the settings at soil slip-debris flow source areas. Landslides affected up to 2.5 m of glacial, fluvioglacial and anthropically reworked deposits overlying metamorphic basement. Laboratory and in situ tests allowed to characterise the geotechnical and hydraulic properties of the terrains involved in the initial failure. Several stratigraphic and hydrogeologic factors have been individuated as significant in determining instabilities on terraced slopes. They are the vertical changes of physical soil properties, the presence of buried hollows where groundwater convergence occurs, the rising up of perched groundwater tables, the overflow and lateral infiltration from superficial drainage network, the runoff concentration by means of pathways and the insufficient drainage of retaining walls.

  14. History-dependent friction and slow slip from time-dependent microscopic junction laws studied in a statistical framework.

    Science.gov (United States)

    Thøgersen, Kjetil; Trømborg, Jørgen Kjoshagen; Sveinsson, Henrik Andersen; Malthe-Sørenssen, Anders; Scheibert, Julien

    2014-05-01

    To study how macroscopic friction phenomena originate from microscopic junction laws, we introduce a general statistical framework describing the collective behavior of a large number of individual microjunctions forming a macroscopic frictional interface. Each microjunction can switch in time between two states: a pinned state characterized by a displacement-dependent force and a slipping state characterized by a time-dependent force. Instead of tracking each microjunction individually, the state of the interface is described by two coupled distributions for (i) the stretching of pinned junctions and (ii) the time spent in the slipping state. This framework allows for a whole family of microjunction behavior laws, and we show how it represents an overarching structure for many existing models found in the friction literature. We then use this framework to pinpoint the effects of the time scale that controls the duration of the slipping state. First, we show that the model reproduces a series of friction phenomena already observed experimentally. The macroscopic steady-state friction force is velocity dependent, either monotonic (strengthening or weakening) or nonmonotonic (weakening-strengthening), depending on the microscopic behavior of individual junctions. In addition, slow slip, which has been reported in a wide variety of systems, spontaneously occurs in the model if the friction contribution from junctions in the slipping state is time weakening. Next, we show that the model predicts a nontrivial history dependence of the macroscopic static friction force. In particular, the static friction coefficient at the onset of sliding is shown to increase with increasing deceleration during the final phases of the preceding sliding event. We suggest that this form of history dependence of static friction should be investigated in experiments, and we provide the acceleration range in which this effect is expected to be experimentally observable.

  15. De novo amplification within a silent human cholinesterase gene in a family subjected to prolonged exposure to organophosphorus insecticides

    International Nuclear Information System (INIS)

    Prody, C.A.; Dreyfus, P.; Soreq, H.; Zamir, R.; Zakut, H.

    1989-01-01

    A 100-fold DNA amplification in the CHE gene, coding for serum butyrylcholinesterase (BtChoEase), was found in a farmer expressing silent CHE phenotype. Individuals homozygous for this gene display a defective serum BtChoEase and are particularly vulnerable to poisoning by agricultural organophosphorus insecticides, to which all members of this family had long been exposed. DNA blot hybridization with regional BtChoEase cDNA probes suggested that the amplification was most intense in regions encoding central sequences within BtChoEase cDNA, whereas distal sequences were amplified to a much lower extent. This is in agreement with the onion skin model, based on amplification of genes in cultured cells and primary tumors. The amplification was absent in the grandparents but present at the same extent in one of their sons and in a grandson, with similar DNA blot hybridization patterns. In situ hybridization experiments localized the amplified sequences to the long arm of chromosome 3, close to the site where the authors previously mapped the CHE gene. Altogether, these observations suggest that the initial amplification event occurred early in embryogenesis, spermatogenesis, or oogenesis, where the CHE gene is intensely active and where cholinergic functioning was indicated to be physiologically necessary. These findings demonstrate a de novo amplification in apparently healthy individuals within an autosomal gene producing a target protein to an inhibitor

  16. Prevalence of silent myocardial ischaemia during exercise stress testing. Its relation to effort tolerance and myocardial perfusion abnormalities.

    Science.gov (United States)

    Fragasso, G; Sciammarella, M G; Rossetti, E E; Xuereb, R G; Xuereb, M; Bonetti, F; Carandente, O M; Margonato, A; Chierchia, S L

    1992-07-01

    The number of underperfused myocardial segments, the extent of coronary artery disease and the severity of impairment of coronary flow reserve were compared in 147 consecutive patients exhibiting painful or painless ischaemic ST segment depression on exercise testing. Of 147 patients, only 61 (41%) experienced angina (group 1) whilst 86 (59%) did not (group 2). In the two groups coronary disease was comparable for both extent and distribution, and neither the location of transient perfusion defects nor their relation to areas of old myocardial necrosis appeared to influence the presence or absence of chest pain. However, exercise duration, exercise time and rate-pressure product at the beginning of ischaemia were lower in group 1. Furthermore, a greater proportion of asymptomatic patients had only one ischaemic segment on 99mTc-MIBI perfusion scintigraphy. We conclude that: (1) in patients with effort angina and coronary disease, the incidence of electrocardiographic silent ischaemic events induced by exercise is similar to that observed in studies based on continuous ECG monitoring. (2) Exertional angina is more frequently associated with greater ischaemic areas and with more severe degrees of impairment of residual coronary flow reserve. (3) The presence of an old myocardial infarction does not appear to influence the incidence of ischaemic cardiac pain.

  17. SLIP VELOCITY IN PULSED DISC AND DOUGHNUT EXTRACTION COLUMN

    Directory of Open Access Journals (Sweden)

    Mohammad Outokesh

    2011-09-01

    Full Text Available In the present work, slip velocity has been measured in a 76 mm diameter pulsed disc and doughnut extraction column for four different liquid-liquid systems. The effects of operating variables including pulsation intensity and dispersed and continuous phase flow rates on slip velocity have been investigated. The existence of three different operational regimes, namely mixersettler, transition, and emulsion regimes, was observed when the energy input was changed. Empirical correlations are derived for prediction of the slip velocity in terms of operating variables, physical properties of the liquid systems, and column geometry for different regimes. Good agreement between prediction and experiments was found for all operating conditions that were investigated.

  18. Slip-stick excitation and travelling waves excite silo honking

    Directory of Open Access Journals (Sweden)

    Warburton Katarzyna

    2017-01-01

    Full Text Available Silo honking is the harmonic sound generated by the discharge of a silo filled with a granular material. In industrial storage silos, the acoustic emission during discharge of PET-particles forms a nuisance for the environment and may ultimately result in structural failure. This work investigates the phenomenon experimentally using a laboratory-scale silo, and successfully correlates the frequency of the emitted sound with the periodicity of the mechanical motion of the grains. The key driver is the slip-stick interaction between the wall and the particles, characterized as a wave moving upwards through the silo. A quantitative correlation is established for the first time between the frequency of the sound, measured with an electret microphone, and the slip-frequency, measured with a high-speed camera. In the lower regions of the tube, both the slip-stick motion and the honking sound disappear.

  19. Slip analysis of squeezing flow using doubly stratified fluid

    Science.gov (United States)

    Ahmad, S.; Farooq, M.; Javed, M.; Anjum, Aisha

    2018-06-01

    The non-isothermal flow is modeled and explored for squeezed fluid. The influence of velocity, thermal and solutal slip effects on transport features of squeezed fluid are analyzed through Darcy porous channel when fluid is moving due to squeezing of upper plate towards the stretchable lower plate. Dual stratification effects are illustrated in transport equations. A similarity analysis is performed and reduced governing flow equations are solved using moderated and an efficient convergent approach i.e. Homotopic technique. The significant effects of physical emerging parameters on flow velocity, temperature and fluid concentration are reporting through various plots. Graphical explanations for drag force, Nusselt and Sherwood numbers are stated and examined. The results reveal that minimum velocity field occurs near the plate, whereas it increases far away from the plate for strong velocity slip parameter. Furthermore, temperature and fluid concentration significantly decreases with increased slip effects. The current analysis is applicable in some advanced technological processes and industrial fluid mechanics.

  20. Numerical Simulation of Methane Slip in Dual Fuel Marine Engines

    DEFF Research Database (Denmark)

    Han, Jaehyun; Jensen, Michael Vincent; Pang, Kar Mun

    2017-01-01

    estimations. The simulations with various gas pipe geometries were conducted. It seemed that the effect of the change in injection direction is more dominant than the change in the gas hole configuration. The favorable injection direction for minimum amount of methane slip was discovered as the direction...... which helps developing the flow of methane far from the exhaust ports. The effects of various valve timing settings were also simulated. The advancement of the exhaust valve closing was more efficient than the retardation of the intake valve opening. A little retardation of the intake valve opening even......The methane slip is the problematic issue for the engines using natural gas(NG). Because methane is more powerful greenhouse gas (GHG) than CO2, understanding of the methane slip during gas exchange process of the engines is essential. In this study, the influence of the gas pipe geometry...

  1. Slip-stick excitation and travelling waves excite silo honking

    Science.gov (United States)

    Warburton, Katarzyna; Porte, Elze; Vriend, Nathalie

    2017-06-01

    Silo honking is the harmonic sound generated by the discharge of a silo filled with a granular material. In industrial storage silos, the acoustic emission during discharge of PET-particles forms a nuisance for the environment and may ultimately result in structural failure. This work investigates the phenomenon experimentally using a laboratory-scale silo, and successfully correlates the frequency of the emitted sound with the periodicity of the mechanical motion of the grains. The key driver is the slip-stick interaction between the wall and the particles, characterized as a wave moving upwards through the silo. A quantitative correlation is established for the first time between the frequency of the sound, measured with an electret microphone, and the slip-frequency, measured with a high-speed camera. In the lower regions of the tube, both the slip-stick motion and the honking sound disappear.

  2. Effects of Spine Motion on Foot Slip in Quadruped Bounding

    Directory of Open Access Journals (Sweden)

    Dongliang Chen

    2018-01-01

    Full Text Available Translation and bend of the spine in the sagittal plane during high-speed quadruped running were investigated. The effect of the two spine motions on slip between the foot and the ground was also explored. First, three simplified sagittal plane models of quadruped mammals were studied in symmetric bounding. The first model’s trunk allowed no relative motion, the second model allowed only trunk bend, and the third model allowed both bend and translation. Next, torque was introduced to equivalently replace spine motion and the possibility of foot slip of the three models was analyzed theoretically. The results indicate that the third model has the least possibility of slip. This conclusion was further confirmed by simulation experiments. Finally, the conclusion was verified by the reductive model crawling robot.

  3. Friction, slip and structural inhomogeneity of the buried interface

    International Nuclear Information System (INIS)

    Dong, Y; Wu, J; Martini, A; Li, Q

    2011-01-01

    An atomistic model of metallic contacts using realistic interatomic potentials is used to study the connection between friction, slip and the structure of the buried interface. Incommensurability induced by misalignment and lattice mismatch is modeled with contact sizes that are large enough to observe superstructures formed by the relative orientations of the surfaces. The periodicity of the superstructures is quantitatively related to inhomogeneous shear stress distributions in the contact area, and a reduced order model is used to clarify the connection between friction and structural inhomogeneity. Finally, the movement of atoms is evaluated before, during and after slip in both aligned and misaligned contacts to understand how the interfacial structure affects the mechanisms of slip and the corresponding frictional behavior

  4. Quantitative numerical method for analysing slip traces observed by AFM

    International Nuclear Information System (INIS)

    Veselý, J; Cieslar, M; Coupeau, C; Bonneville, J

    2013-01-01

    Atomic force microscopy (AFM) is used more and more routinely to study, at the nanometre scale, the slip traces produced on the surface of deformed crystalline materials. Taking full advantage of the quantitative height data of the slip traces, which can be extracted from these observations, requires however an adequate and robust processing of the images. In this paper an original method is presented, which allows the fitting of AFM scan-lines with a specific parameterized step function without any averaging treatment of the original data. This yields a quantitative and full description of the changes in step shape along the slip trace. The strength of the proposed method is established on several typical examples met in plasticity by analysing nano-scale structures formed on the sample surface by emerging dislocations. (paper)

  5. Limits of recovery against slip-induced falls while walking.

    Science.gov (United States)

    Yang, Feng; Bhatt, Tanvi; Pai, Yi-Chung

    2011-10-13

    Slip-induced falls in gait often have devastating consequences. The purposes of this study were 1) to select the determinants that can best discriminate the outcomes (recoveries or falls) of an unannounced slip induced in gait (and to find their corresponding threshold, i.e., the limits of recovery, which can clearly separate these two outcomes), and 2) to verify these results in a subset of repeated-slip trials. Based on the data collected from 69 young subjects during a slip induced in gait, nine different ways of combining the center of mass (COM) stability, the hip height, and its vertical velocity were investigated with the aid of logistic regression. The results revealed that the COM stability (s) and limb support (represented by the quotient of hip vertical velocity to hip height, S(hip)) recorded at the instant immediately prior to the recovery step touchdown were sufficiently sensitive to account for all (100%) variance in falls, and specific enough to account for nearly all (98.3%) variability in recoveries. This boundary (S(hip)=-0.22s-0.25), which quantifies the risk of falls in the stability-limb support quotient (s-S(hip)) domain, was fully verified using second-slip and third-slip trials (n=76) with classification of falls at 100% and recoveries at 98.6%. The severity of an actual fall is likely to be greater further below the boundary, while the likelihood of a fall diminishes above it. Finally, the slope of the boundary also indicates the tradeoff between the stability and limb support, whereby high stability can compensate for the insufficiency in limb support, or vice versa. Copyright © 2011 Elsevier Ltd. All rights reserved.

  6. Active strike-slip faulting in El Salvador, Central America

    Science.gov (United States)

    Corti, Giacomo; Carminati, Eugenio; Mazzarini, Francesco; Oziel Garcia, Marvyn

    2005-12-01

    Several major earthquakes have affected El Salvador, Central America, during the Past 100 yr as a consequence of oblique subduction of the Cocos plate under the Caribbean plate, which is partitioned between trench-orthogonal compression and strike-slip deformation parallel to the volcanic arc. Focal mechanisms and the distribution of the most destructive earthquakes, together with geomorphologic evidence, suggest that this transcurrent component of motion may be accommodated by a major strike-slip fault (El Salvador fault zone). We present field geological, structural, and geomorphological data collected in central El Salvador that allow the constraint of the kinematics and the Quaternary activity of this major seismogenic strike-slip fault system. Data suggest that the El Salvador fault zone consists of at least two main ˜E-W fault segments (San Vicente and Berlin segments), with associated secondary synthetic (WNW-ESE) and antithetic (NNW-SSE) Riedel shears and NW-SE tensional structures. The two main fault segments overlap in a dextral en echelon style with the formation of an intervening pull-apart basin. Our original geological and geomorphologic data suggest a late Pleistocene Holocene slip rate of ˜11 mm/yr along the Berlin segment, in contrast with low historical seismicity. The kinematics and rates of deformation suggested by our new data are consistent with models involving slip partitioning during oblique subduction, and support the notion that a trench-parallel component of motion between the Caribbean and Cocos plates is concentrated along E-W dextral strike-slip faults parallel to the volcanic arc.

  7. Investigation of Floor Surface Finishes for Optimal Slip Resistance Performance

    Directory of Open Access Journals (Sweden)

    In-Ju Kim

    2018-03-01

    Full Text Available Background: Increasing the slip resistance of floor surfaces would be desirable, but there is a lack of evidence on whether traction properties are linearly correlated with the topographic features of the floor surfaces or what scales of surface roughness are required to effectively control the slipperiness of floors. Objective: This study expands on earlier findings on the effects of floor surface finishes against slip resistance performance and determines the operative ranges of floor surface roughness for optimal slip resistance controls under different risk levels of walking environments. Methods: Dynamic friction tests were conducted among three shoes and nine floor specimens under wet and oily environments and compared with a soapy environment. Results: The test results showed the significant effects of floor surface roughness on slip resistance performance against all the lubricated environments. Compared with the floor-type effect, the shoe-type effect on slip resistance performance was insignificant against the highly polluted environments. The study outcomes also indicated that the oily environment required rougher surface finishes than the wet and soapy ones in their lower boundary ranges of floor surface roughness. Conclusion: The results of this study with previous findings confirm that floor surface finishes require different levels of surface coarseness for different types of environmental conditions to effectively manage slippery walking environments. Collected data on operative ranges of floor surface roughness seem to be a valuable tool to develop practical design information and standards for floor surface finishes to efficiently prevent pedestrian fall incidents. Keywords: floor surface finishes, operational levels of floor surface roughness, slip resistance, wet, soapy and oily environments

  8. Factors associated with use of slip-resistant shoes in US limited-service restaurant workers.

    Science.gov (United States)

    Verma, Santosh K; Courtney, Theodore K; Corns, Helen L; Huang, Yueng-Hsiang; Lombardi, David A; Chang, Wen-Ruey; Brennan, Melanye J; Perry, Melissa J

    2012-06-01

    Slips and falls are a leading cause of injury at work. Several studies have indicated that slip-resistant shoes can reduce the risk of occupational slips and falls. Few studies, however, have examined the determinants of slip-resistant shoe use. This study examined the individual and workplace factors associated with slip-resistant shoe use. 475 workers from 36 limited-service restaurants in the USA participated in a study of workplace slipping. Demographic and job characteristic information about each participant was collected. Restaurant managers provided information on whether slip-resistant shoes were provided and paid for by the employer and whether any guidance was given regarding slip-resistant shoe use when they were not provided. Kitchen floor coefficient of friction was measured. Slip-resistant status of the shoes was determined by noting the presence of a 'slip-resistant' marking on the sole. Poisson regression with robust SE was used to calculate prevalence ratios. 320 participants wore slip-resistant shoes (67%). In the multivariate analysis, the prevalence of slip-resistant shoe use was lowest in 15-19-year age group. Women were more likely to wear slip-resistant shoes (prevalence ratio 1.18, 95% CI 1.07 to 1.31). The prevalence of slip-resistant shoe use was lower when no guidance regarding slip-resistant shoes was given as compared to when they were provided by the employer (prevalence ratio 0.66, 95% CI 0.55 to 0.79). Education level, job tenure and the mean coefficient of friction had no significant effects on the use of slip-resistant shoes. Provision of slip-resistant shoes was the strongest predictor of their use. Given their effectiveness and low cost, employers should consider providing slip-resistant shoes at work.

  9. Co-seismic slip, post-seismic slip, and largest aftershock associated with the 1994 Sanriku-haruka-oki, Japan, earthquake

    Science.gov (United States)

    Yagi, Yuji; Kikuchi, Masayuki; Nishimura, Takuya

    2003-11-01

    We analyzed continuous GPS data to investigate the spatio-temporal distribution of co-seismic slip, post-seismic slip, and largest aftershock associated with the 1994 Sanriku-haruka-oki, Japan, earthquake (Mw = 7.7). To get better resolution for co-seismic and post-seismic slip distribution, we imposed a weak constraint as a priori information of the co-seismic slip determined by seismic wave analyses. We found that the post-seismic slip during 100 days following the main-shock amount to as much moment release as the main-shock, and that the sites of co-seismic slip and post-seismic slip are partitioning on a plate boundary region in complimentary fashion. The major post-seismic slip was triggered by the mainshock in western side of the co-seismic slip, and the extent of the post-seismic slip is almost unchanged with time. It rapidly developed a shear stress concentration ahead of the slip area, and triggered the largest aftershock.

  10. Case of slipped capital femoral epiphysis following radiation

    Energy Technology Data Exchange (ETDEWEB)

    Terada, Hiroshi; Usui, Hiroshi; Nakamura, Yutaka; Chiba, Masahiro; Yamaji, Shushin; Oba, Yoshihiro

    1987-06-01

    A 12-year-old boy presented with pain of the right hip joint and claudication. At the age of 7 months, the patient had received prophylactic irradiation of 30 Gy to the pelvic area including lumbar vertebrae and bilateral hip joints following extirpation of the right undescended testicle for embryonal carcinoma. Roentgenograph showed slipped capial femoral epiphysis. A review of the literature suggests that bone growth and hormonal changes in the early stage of puberty are involved, in addition to radiation damaged epiphyseal cartilage, in the pathophysiologic mechanisms of radiation induced slipped capital femoral epiphysis. (Namekawa, K.).

  11. Passive, Silent and Revolutionary: The 'Arab Spring' Revisited.

    Science.gov (United States)

    Brownlee, Billie Jeanne; Ghiabi, Maziyar

    2016-01-01

    To counter the trend toward mechanization of research and aridity of critical analysis, this article makes a case for an interdisciplinary quest. To borrow Felix Guattari and Gilles Deleuze's phrase, we are convinced that 'everything is political, but every politics is simultaneously a macropolitics and a micropolitics.' With an eye to open-ended research questions, this article attempts to build a body of theoretical, political and anthropological considerations, which, it is hoped, could function as a case of enquiry into the mechanics of power, revolt and revolution. The objective is to draw comparative and phenomenological lines between the events of the 2011 'Arab Spring,' in its local ecologies of protest, with its global reverberations as materialized in the slogans, acts and ideals of Greek and Spanish Indignados and the UK and US occupy movements. In order to do so, it proposes to clarify terminological ambiguities and to bring into the analytical scenario new subjects, new means and new connections. The article resolves to lay the ground for a scholarship of silence, by which the set of unheard voices, hidden actions and defiant tactics of the ordinary, through extraordinary people, find place in the interpretation of phenomena such as revolts and revolutions.

  12. An investigation of the reduction of carbon dioxide in a silent electric discharge

    Science.gov (United States)

    Luce, R. S.; Greenough, B. (Editor)

    1978-01-01

    The reduction of CO2 to O2 and CO in a silent electric discharge was studied. It was found that current alone (in the ionized plasma induced by the silent electric discharge) was reponsible for the CO2 reduction process. Voltage and frequency were important only in so far as they induced current in the plasma. Pressure and temperature were of minimum influence in the process. The large power consumption in the process was recognized as resulting from the low power factor of the reactor vessel which electrically behaved like a capacitor. The power factor was subsequently improved by adding an inductive element to make the reactor vessel capacitance part of a resonant circuit. It was found that the CO2 reduction process was most efficient in terms of power vs reduction rate when a voltage was employed that was only slightly higher than that needed to induce the plasma.

  13. When Spiders Bite: The Use, Misuse, and Unintended Consequences of ``Silent Information''

    Science.gov (United States)

    Keenan, Thomas P.

    Spiders are the workhorses of the Internet, silently (and almost invisibly) traversing the online world, 24 hours a day, looking for information that may be of interest to someone. It is being archived, organized, and sold, usually without the knowledge or consent of the subject of the information. Serious consequences are starting to appear, such as the withdrawal of three candidates from the October 2008 Canadian Federal election because of previous online indiscretions. While these were intentional if mis-guided postings, information made available without our consent can have equally devastating effects. Advances in artificial intelligence, as well as the increasing tendency to post more and more information, such as videos, will make the gathering, aggregation, and republishing of this “silent information” an increasingly important issue that must be addressed from the technical, social, ethical and legal perspectives, and sooner rather than later.

  14. Dynamic wind turbine models in power system simulation tool DIgSILENT

    DEFF Research Database (Denmark)

    Hansen, Anca Daniela; Iov, F.; Sørensen, Poul Ejnar

    , connection of the wind turbine at different types of grid and storage systems. Different control strategies have been developed and implemented for these wind turbine concepts, their performance in normal or fault operation being assessed and discussed by means of simulations. The described control......This report presents a collection of models and control strategies developed and implemented in the power system simulation tool PowerFactory DIgSILENT for different wind turbine concepts. It is the second edition of Risø-R-1400(EN) and it gathers and describes a whole wind turbine model database...... of the interaction between the mechanical structure of the wind turbine and the electrical grid during different operational modes. The report provides thus a description of the wind turbines modelling, both at a component level and at a system level. The report contains both the description of DIgSILENT built...

  15. Typical and atypical (silent) subacute thyroiditis in a wife and husband

    International Nuclear Information System (INIS)

    Morrison, J.; Caplan, R.H.

    1978-01-01

    Typical subacute thyroiditis was diagnosed in a woman. Three weeks later, signs and symptoms of hyperthyroidism developed in her husband. Although the right lobe of his thyroid gland was slightly enlarged, pain and tenderness were absent throughout the course of his illness. The free thyroxine equivalent (FTE) value and the sedimentation rate were elevated; the low uptake of radioactive iodine by the thyroid gland was consistent with ''silent'' subacute thyroiditis. We postulate that a common etiology, probably viral, was operative in both cases. Nine additional cases of hyperthyroidism with low levels of thyroidal uptake of radioactive iodine are described. The thyroid glands of these patients were normal or slightly enlarged. Antithyroglobulin antibody levels determined in seven patients were not substantially elevated. The clinical course of these patients was characteristic of ''silent'' subacute thyroiditis. Although the origin of the syndrome remains unclear, the disease is self-limited and therapy, if any, is supportive

  16. Typical and atypical (silent) subacute thyroiditis in a wife and husband

    Energy Technology Data Exchange (ETDEWEB)

    Morrison, J.; Caplan, R.H.

    1978-01-01

    Typical subacute thyroiditis was diagnosed in a woman. Three weeks later, signs and symptoms of hyperthyroidism developed in her husband. Although the right lobe of his thyroid gland was slightly enlarged, pain and tenderness were absent throughout the course of his illness. The free thyroxine equivalent (FTE) value and the sedimentation rate were elevated; the low uptake of radioactive iodine by the thyroid gland was consistent with ''silent'' subacute thyroiditis. We postulate that a common etiology, probably viral, was operative in both cases. Nine additional cases of hyperthyroidism with low levels of thyroidal uptake of radioactive iodine are described. The thyroid glands of these patients were normal or slightly enlarged. Antithyroglobulin antibody levels determined in seven patients were not substantially elevated. The clinical course of these patients was characteristic of ''silent'' subacute thyroiditis. Although the origin of the syndrome remains unclear, the disease is self-limited and therapy, if any, is supportive.

  17. Distance and Azimuthal Dependence of Ground‐Motion Variability for Unilateral Strike‐Slip Ruptures

    KAUST Repository

    Vyas, Jagdish Chandra

    2016-06-21

    We investigate near‐field ground‐motion variability by computing the seismic wavefield for five kinematic unilateral‐rupture models of the 1992 Mw 7.3 Landers earthquake, eight simplified unilateral‐rupture models based on the Landers event, and a large Mw 7.8 ShakeOut scenario. We include the geometrical fault complexity and consider different 1D velocity–density profiles for the Landers simulations and a 3D heterogeneous Earth structure for the ShakeOut scenario. For the Landers earthquake, the computed waveforms are validated using strong‐motion recordings. We analyze the simulated ground‐motion data set in terms of distance and azimuth dependence of peak ground velocity (PGV). Our simulations reveal that intraevent ground‐motion variability Graphic is higher in close distances to the fault (<20  km) and decreases with increasing distance following a power law. This finding is in stark contrast to constant sigma‐values used in empirical ground‐motion prediction equations. The physical explanation of a large near‐field Graphic is the presence of strong directivity and rupture complexity. High values of Graphic occur in the rupture‐propagation direction, but small values occur in the direction perpendicular to it. We observe that the power‐law decay of Graphic is primarily controlled by slip heterogeneity. In addition, Graphic, as function of azimuth, is sensitive to variations in both rupture speed and slip heterogeneity. The azimuth dependence of the ground‐motion mean μln(PGV) is well described by a Cauchy–Lorentz function that provides a novel empirical quantification to model the spatial dependency of ground motion. Online Material: Figures of slip distributions, residuals to ground‐motion prediction equations (GMPEs), distance and azimuthal dependence, and directivity predictor of ground‐motion variability for different source models.

  18. Evidence for fluid-triggered slip in the 2009 Mount Rainier, Washington earthquake swarm

    Science.gov (United States)

    Shelly, David R.; Moran, Seth C.; Thelen, Weston A.

    2013-01-01

    A vigorous swarm of over 1000 small, shallow earthquakes occurred 20–22 September 2009 beneath Mount Rainier, Washington, including the largest number of events ever recorded in a single day at Rainier since seismic stations were installed on the edifice in 1989. Many events were only clearly recorded on one or two stations on the edifice, or they overlapped in time with other events, and thus only ~200 were locatable by manual phase picking. To partially overcome this limitation, we applied waveform-based event detection integrated with precise double-difference relative relocation. With this procedure, detection and location goals are accomplished in tandem, using cross-correlation with continuous seismic data and waveform templates constructed from cataloged events. As a result, we obtained precise locations for 726 events, an improvement of almost a factor of 4. These event locations define a ~850 m long nearly vertical structure striking NNE, with episodic migration outward from the initial hypocenters. The activity front propagates in a manner consistent with a diffusional process. Double-couple-constrained focal mechanisms suggest dominantly near-vertical strike-slip motion on either NNW or ENE striking faults, more than 30° different than the strike of the event locations. This suggests the possibility of en echelon faulting, perhaps with a component of fault opening in a fracture-mesh-type geometry. We hypothesize that the swarm was initiated by a sudden release of high-pressure fluid into preexisting fractures, with subsequent activity triggered by diffusing fluid pressure in combination with stress transfer from the preceding events.

  19. Resetting of Quartz OSL (optically stimulated luminescence) Signals by Frictional Heating in Experimentally Sheared Gouges at Seismic Slip Rates.

    Science.gov (United States)

    Kim, J. H.; Choi, J. H.; Chauhan, N.; Lee, S.; Hirose, T.; Ree, J. H.

    2014-12-01

    Recent studies on natural and experimental seismic faults have revealed that frictional heating plays an important role in earthquake dynamics as well as in producing mineralogical and microstructural signatures of seismic faulting. Here, we report changes in OSL signals in quartz by frictional heating in experimental fault gouges. The gouges (80% of quartz and 20% of bentonite by weight) with a thickness of 1 mm were sheared between sandstone cylinders (diameter: 25 mm) at a normal stress of 1 MPa and slip rate of 1.31 m/s. The quartz grains from a sand dune on the western coast of South Korea were sieved to select size fractions between 90 and 250 μm. The equivalent dose (De) of the undeformed quartz grains was 8.0 ± 0.3 Gy. Upon displacement, the friction abruptly increases to the 1st peak (with friction coefficient μ ≈ 0.75) followed by slip weakening. Then the fault zones show two more peak frictions (μ ≈ 0.53~0.75) and finally reach a steady-state friction (μ ≈ 0.2~0.35). The fault can be divided into three zones based grain size (thus slip rate); slip localization (SLZ), intermediate slip-rate (ISZ) and low slip-rate (LSZ) zones. SLZ develops adjacent to the moving side of the sandstone cylinder with P-foliation and shear band. The size of quartz (Dq) in ISZ and LSZ is 5-30 μm and 50-250 μm, respectively. SEM and TEM analyses indicate that the fault gouge of SLZ consists of subangular quartz clasts (Dq ≈ 3 μm) and matrix of nano-scale quartz, unidentified silicate minerals and amorphous material. The fault zones were sectioned into six layers (~160 µm thick for each layer) parallel to the fault zone boundary for OSL analyses. Quartz grains from all the layers except the one immediately adjacent to the stationary side of the sandstone cylinder show De of 'effectively' 0 Gy indicating a full resetting of OSL signals. The partial resetting of OSL signal in the layer adjacent to the stationary side of the cylinder indicates the temperature (T

  20. Slip-accumulation patterns and earthquake recurrences along the Talas-Fergana Fault - Contributions of high-resolution geomorphic offsets.

    Science.gov (United States)

    Rizza, M.; Dubois, C.; Fleury, J.; Abdrakhmatov, K.; Pousse, L.; Baikulov, S.; Vezinet, A.

    2017-12-01

    In the western Tien-Shan Range, the largest intracontinental strike-slip fault is the Karatau-Talas Fergana Fault system. This dextral fault system is subdivided into two main segments: the Karatau fault to the north and the Talas-Fergana fault (TFF) to the south. Kinematics and rates of deformation for the TFF during the Quaternary period are still debated and are poorly constrained. Only a few paleoseismological investigations are availabe along the TFF (Burtman et al., 1996; Korjenkov et al., 2010) and no systematic quantifications of the dextral displacements along the TFF has been undertaken. As such, the appraisal of the TFF behavior demands new tectonic information. In this study, we present the first detailed analysis of the morphology and the segmentation of the TFF and an offset inventory of morphological markers along the TFF. To discuss temporal and spatial recurrence patterns of slip accumulated over multiple seismic events, our study focused on a 60 km-long section of the TFF (Chatkal segment). Using tri-stereo Pleiades satellite images, high-resolution DEMs (1*1 m pixel size) have been generated in order to (i) analyze the fine-scale fault geometry and (ii) thoroughly measure geomorphic offsets. Photogrammetry data obtained from our drone survey on high interest sites, provide higher-resolution DEMs of 0.5 * 0.5 m pixel size.Our remote sensing mapping allows an unprecedented subdivision - into five distinct segments - of the study area. About 215 geomorphic markers have been measured and offsets range from 4.5m to 180 m. More than 80% of these offsets are smaller than 60 m, suggesting landscape reset during glacial maximum. Calculations of Cumulative Offset Probability Density (COPD) for the whole 60 km-long section as well as for each segments support distinct behavior from a segment to another and thus variability in slip-accumulation patterns. Our data argue for uniform slip model behavior along this section of the TFF. Moreover, we excavated a

  1. Psychosis and Silent Celiac Disease in a Down Syndrome Adolescent: A Case Report

    Directory of Open Access Journals (Sweden)

    Amparo Morant

    2011-01-01

    Full Text Available Celiac disease is an autoimmune systemic disorder. It presents gastrointestinal and nongastrointestinal manifestations as well as associated conditions. We report a 16-year-old Down syndrome girl who presented psychosis symptomatology, and she was diagnosed as having silent celiac disease. Olanzapine treatment and gluten-free diet were satisfactory. It is necessary to consider celiac disease in Down syndrome patients with psychiatric symptoms, mainly psychotic symptomatology.

  2. Silent reading of music and texts; eye movements and integrative reading mechanisms

    OpenAIRE

    Cara, Michel André; Gómez, Gabriela

    2016-01-01

    This study investigates to what extent structural units defined by physical and structural markers elicit different eye movement patterns when reading contrasting stimuli of music and verbal texts. Eye movements were tracked and compared in ten musicians undergoing Bachelor’s degrees as they silently read six texts and six pieces of music for piano: the music was contemporary, in modal style, and the style of the texts was informative and literary. Participants were music students at Universi...

  3. Harmonic Domain Modelling of Transformer Core Nonlinearities Using the DIgSILENT PowerFactory Software

    OpenAIRE

    Bak, Claus Leth; Bak-Jensen, Birgitte; Wiechowski, Wojciech

    2008-01-01

    This paper demonstrates the results of implementation and verification of an already existing algorithm that allows for calculating saturation characteristics of singlephase power transformers. The algorithm was described for the first time in 1993. Now this algorithm has been implemented using the DIgSILENT Programming Language (DPL) as an external script in the harmonic domain calculations of a power system analysis tool PowerFactory [10]. The algorithm is verified by harmonic measurements ...

  4. Dynamic wind turbine models in power system simulation tool DIgSILENT

    OpenAIRE

    Hansen, A.D.; Jauch, C.; Sørensen, Poul Ejnar; Iov, F.; Blaabjerg, F.

    2004-01-01

    The present report describes the dynamic wind turbine models implemented in the power system simulation tool DIgSILENT (Version 12.0). The developed models are a part of the results of a national research project, whose overall objective is to create amodel database in different simulation tools. This model database should be able to support the analysis of the interaction between the mechanical structure of the wind turbine and the electrical grid during different operational modes. The repo...

  5. Cumulus-specific genes are transcriptionally silent following somatic cell nuclear transfer in a mouse model*

    OpenAIRE

    Tong, Guo-qing; Heng, Boon-chin; Ng, Soon-chye

    2007-01-01

    This study investigated whether four cumulus-specific genes: follicular stimulating hormone receptor (FSHr), hyaluronan synthase 2 (Has2), prostaglandin synthase 2 (Ptgs2) and steroidogenic acute regulator protein (Star), were correctly reprogrammed to be transcriptionally silent following somatic cell nuclear transfer (SCNT) in a murine model. Cumulus cells of C57×CBA F1 female mouse were injected into enucleated oocytes, followed by activation in 10 µmol/L strontium chloride for 5 h and sub...

  6. Direct speech quotations promote low relative-clause attachment in silent reading of English.

    Science.gov (United States)

    Yao, Bo; Scheepers, Christoph

    2018-07-01

    The implicit prosody hypothesis (Fodor, 1998, 2002) proposes that silent reading coincides with a default, implicit form of prosody to facilitate sentence processing. Recent research demonstrated that a more vivid form of implicit prosody is mentally simulated during silent reading of direct speech quotations (e.g., Mary said, "This dress is beautiful"), with neural and behavioural consequences (e.g., Yao, Belin, & Scheepers, 2011; Yao & Scheepers, 2011). Here, we explored the relation between 'default' and 'simulated' implicit prosody in the context of relative-clause (RC) attachment in English. Apart from confirming a general low RC-attachment preference in both production (Experiment 1) and comprehension (Experiments 2 and 3), we found that during written sentence completion (Experiment 1) or when reading silently (Experiment 2), the low RC-attachment preference was reliably enhanced when the critical sentences were embedded in direct speech quotations as compared to indirect speech or narrative sentences. However, when reading aloud (Experiment 3), direct speech did not enhance the general low RC-attachment preference. The results from Experiments 1 and 2 suggest a quantitative boost to implicit prosody (via auditory perceptual simulation) during silent production/comprehension of direct speech. By contrast, when reading aloud (Experiment 3), prosody becomes equally salient across conditions due to its explicit nature; indirect speech and narrative sentences thus become as susceptible to prosody-induced syntactic biases as direct speech. The present findings suggest a shared cognitive basis between default implicit prosody and simulated implicit prosody, providing a new platform for studying the effects of implicit prosody on sentence processing. Copyright © 2018 Elsevier B.V. All rights reserved.

  7. Phenotypically silent Cre recombination within the postnatal ventricular conduction system.

    Science.gov (United States)

    Bhattacharyya, Samadrita; Bhakta, Minoti; Munshi, Nikhil Vilas

    2017-01-01

    The cardiac conduction system (CCS) is composed of specialized cardiomyocytes that initiate and maintain cardiac rhythm. Any perturbation to the normal sequence of electrical events within the heart can result in cardiac arrhythmias. To understand how cardiac rhythm is established at the molecular level, several genetically modified mouse lines expressing Cre recombinase within specific CCS compartments have been created. In general, Cre driver lines have been generated either by homologous recombination of Cre into an endogenous locus or Cre expression driven by a randomly inserted transgene. However, haploinsufficiency of the endogenous gene compromises the former approach, while position effects negatively impact the latter. To address these limitations, we generated a Cre driver line for the ventricular conduction system (VCS) that preserves endogenous gene expression by targeting the Contactin2 (Cntn2) 3' untranslated region (3'UTR). Here we show that Cntn23'UTR-IRES-Cre-EGFP/+ mice recombine floxed alleles within the VCS and that Cre expression faithfully recapitulates the spatial distribution of Cntn2 within the heart. We further demonstrate that Cre expression initiates after birth with preservation of native Cntn2 protein. Finally, we show that Cntn23'UTR-IRES-Cre-EGFP/+ mice maintain normal cardiac mechanical and electrical function. Taken together, our results establish a novel VCS-specific Cre driver line without the adverse consequences of haploinsufficiency or position effects. We expect that our new mouse line will add to the accumulating toolkit of CCS-specific mouse reagents and aid characterization of the cell-autonomous molecular circuitry that drives VCS maintenance and function.

  8. Risk factors associated with the occurrence of silent pulmonary embolism in patients with deep venous thrombosis of the lower limb.

    Science.gov (United States)

    Li, Fenghe; Wang, Xuehu; Huang, Wen; Ren, Wei; Cheng, Jun; Zhang, Mao; Zhao, Yu

    2014-08-01

    The aim of our study is to investigate the prevalence of silent pulmonary embolism in patients with deep venous thrombosis in the lower limbs and to evaluate the associated risk factors. A total of 322 patients with acute deep venous thrombosis confirmed by CT venography or Doppler ultrasonography were studied. The diagnosis of silent pulmonary embolism was established by computed tomography pulmonary arteriography (CTPA). The association between covariates and the prevalence of silent pulmonary embolism in patients with deep venous thrombosis in lower limbs were assessed using chi-square test and multivariable regression. The incidence of silent pulmonary embolism was 33.5% (108 in 322 patients) in all patients with deep venous thrombosis in lower limbs. Chi-square test showed male gender, the right lower limb, proximal location of the thrombus, unprovoked venous thrombosis and coexisting heart diseases were related to a higher incidence of silent pulmonary embolism in patients with deep venous thrombosis in lower limbs. The multivariate regression analysis confirmed that the risk factors associated with silent pulmonary embolism in deep venous thrombosis patients included the right side and proximal location of the thrombus (odds ratio: 2.023, 95% CI: 1.215-3.368; odds ratio: 3.610, 95% CI: 1.772-7.354), unprovoked venous thrombosis (odds ratio: 2.037, 95% CI: 1.188-3.493), coexisting heart diseases (odds ratio: 4.507, 95% CI: 2.667-7.618). Silent pulmonary embolism occurred frequently in patients with deep venous thrombosis in lower limbs. The right side, the proximal location of the thrombus, unprovoked venous thrombosis and coexisting heart diseases increased the risk for the occurrence of silent pulmonary embolism. © The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  9. Gated single photon emission computer tomography for the detection of silent myocardial ischemia

    International Nuclear Information System (INIS)

    Pena Q, Yamile; Coca P, Marco Antonio; Batista C, Juan Felipe; Fernandez-Britto, Jose; Quesada P, Rodobaldo; Pena C; Andria

    2009-01-01

    Background: Asymptomatic patients with severe coronary atherosclerosis may have a normal resting electrocardiogram and stress test. Aim: To assess the yield of Gated Single Photon Emission Computer Tomography (SPECT) for the screening of silent myocardial ischemia in type 2 diabetic patients. Material and methods: Electrocardiogram, stress test and gated-SPECT were performed on 102 type 2 diabetic patients aged 60 ± 8 years without cardiovascular symptoms. All subjects were also subjected to a coronary angiography, whose results were used as gold standard. Results: Gated-SPECT showed myocardial ischemia on 26.5% of studied patients. The sensibility, specificity, accuracy, positive predictive value and negative predictive value were 92.3%, 96%, 95%, 88.8%, 97.3%, respectively. In four and six patients ischemia was detected on resting electrocardiogram and stress test, respectively. Eighty percent of patients with doubtful resting electrocardiogram results and 70% with a doubtful stress test had a silent myocardial ischemia detected by gated-SPECT. There was a good agreement between the results of gated-SPECT and coronary angiography (k =0.873). Conclusions: Gated-SPECT was an useful tool for the screening of silent myocardial ischemia

  10. The prevalence and the clinical characteristics of silent myocardial ischemia detected by stress thallium scintigraphy

    International Nuclear Information System (INIS)

    Matsuo, Hitoshi; Watanabe, Sachiro; Nishida, Yoshio

    1992-01-01

    The prevalence of silent myocardial ischemia was retrospectively assessed in a group of 100 consecutive patients with angiographically proved coronary artery disease, and diagnostic ECG, by symptom-limited exercise thallium-201 scintigraphy. Twenty-four patients had no evidence of ischemia despite adequate exercise level. So among 76 patients with exercise induced ischemia, only 33 patients (43%) stopped exercise due to anginal pain (symptomatic ischemia: Group 3). And 43 patients with asymptomatic ischemia composed of 23 patients (30%) with ECG change (Group 2B) and 20 patients (26%) without ECG change (Group 2A). Patients background including the history of old myocardial infarction and diabetes mellitus, were similar among Group 2A, 2B, and Group 3. Our Major observation was that the extent and severity of quantified SPECT perfusion defects was nearly identified between 3 groups. Thus in this study group, there was a rather high prevalence rate of silent ischemia (57%) by exercise thallium-201 criteria. Patients with silent ischemia, associated with positive and negative exercise ECG findings, and those with exercise angina had similar background and comparable amount of jeopardized myocardium. (author)

  11. Detecting Silent Data Corruption for Extreme-Scale Applications through Data Mining

    Energy Technology Data Exchange (ETDEWEB)

    Bautista-Gomez, Leonardo [Argonne National Lab. (ANL), Argonne, IL (United States); Cappello, Franck [Argonne National Lab. (ANL), Argonne, IL (United States)

    2014-01-16

    Supercomputers allow scientists to study natural phenomena by means of computer simulations. Next-generation machines are expected to have more components and, at the same time, consume several times less energy per operation. These trends are pushing supercomputer construction to the limits of miniaturization and energy-saving strategies. Consequently, the number of soft errors is expected to increase dramatically in the coming years. While mechanisms are in place to correct or at least detect some soft errors, a significant percentage of those errors pass unnoticed by the hardware. Such silent errors are extremely damaging because they can make applications silently produce wrong results. In this work we propose a technique that leverages certain properties of high-performance computing applications in order to detect silent errors at the application level. Our technique detects corruption solely based on the behavior of the application datasets and is completely application-agnostic. We propose multiple corruption detectors, and we couple them to work together in a fashion transparent to the user. We demonstrate that this strategy can detect the majority of the corruptions, while incurring negligible overhead. We show that with the help of these detectors, applications can have up to 80% of coverage against data corruption.

  12. Harmony hurts: participation and silent conflict at an Indonesian fish pond.

    Science.gov (United States)

    Tam, Chui-Ling

    2006-07-01

    Participatory environmental and resource management is premised on open communication to reach consensus. However, deliberate and open communication cannot adequately address silent conflict. This begs two questions. First, how is the existence of covert communication and silent conflict to be recognized and addressed? Second, how are the wider social relations and traditions that encompass communication and conflict to be described and explained? These questions revolve around communicative power. Communication of environmental knowledge is deeply embedded in social power structures, with direct implications for participatory resource planning and implementation. Ethnographic research conducted at a failed community-managed fish farming project in Southeast Sulawesi, Indonesia shows that a culture of harmony and respect for authority can silence environmental conflict in the hierarchical "community." Three propositions are offered. First, communication amnesia and exclusion jeopardize participation. Second, cultures of harmony and silent conflict shape planning processes and outcomes. Third, the weak use manipulation and communication strategy to acquire a "voice" while preserving harmony. These propositions address five unresolved issues in participatory resource management: analysis of groups, contextuality, social relationships, nonparticipants, and informal communication. Power, tradition, and social networks affect the valuing of knowledge relative to the power of different individuals and institutions to communicate priorities, values, and needs. These factors are critical to the inclusion of both participants and nonparticipants.

  13. Silent and a audible stereotypes: The constitution of "ethnic character" in Serbian epic poetry

    Directory of Open Access Journals (Sweden)

    Đerić Gordana

    2005-01-01

    Full Text Available The article deals with the explanatory relevance of the concept of stereotype in one of its original meanings - as a "mental image". This meaning of the term is the starting point for further differentiations, such as: between linguistic and behavioral stereotypes (in the sense of nonverbal, expected responses; universal and particular stereotypes; self representative and introspective stereotypes; permanent and contemporary stereotypes; and finally, what is most important for our purposes, the difference between silent and audible stereotypes. These distinctions, along with the functions of stereotype, are discussed in the first part of the paper. In the second part, the relations of silent and audible stereotypes are tested against the introduction of "innovative vocabularies" in popular lore. In other words, the explanatory power of this differentiation is checked through an analysis of unconventional motives in Serbian epic poems. The goal of the argument is to clarify the procedure of self creation of masculinity as a relevant feature of the "national character" through "tactic games" of silent and audible stereotypes. The examination of these "poetic strategies" serves a twofold purpose: to illustrate the process of constructing particular features of the "ethno type", on one hand, and to check hypotheses and models which are taken as frameworks in analyzing stereotypes, on the other.

  14. Estimation of cortical silent period following transcranial magnetic stimulation using a computerised cumulative sum method.

    Science.gov (United States)

    King, Nicolas K K; Kuppuswamy, Annapoorna; Strutton, Paul H; Davey, Nick J

    2006-01-15

    The cortical silent period (CSP) following transcranial magnetic stimulation (TMS) of the motor cortex can be used to measure intra-cortical inhibition and changes in a number of important pathologies affecting the central nervous system. The main drawback of this technique has been the difficulty in accurately identifying the onset and offset of the cortical silent period leading to inter-observer variability. We developed an automated method based on the cumulative sum (Cusum) technique to improve the determination of the duration and area of the cortical silent period. This was compared with experienced raters and two other automated methods. We showed that the automated Cusum method reliably correlated with the experienced raters for both duration and area of CSP. Compared with the automated methods, the Cusum also showed the strongest correlation with the experienced raters. Our results show the Cusum method to be a simple, graphical and powerful method of detecting low-intensity CSP that can be easily automated using standard software.

  15. Silent reading of direct versus indirect speech activates voice-selective areas in the auditory cortex.

    Science.gov (United States)

    Yao, Bo; Belin, Pascal; Scheepers, Christoph

    2011-10-01

    In human communication, direct speech (e.g., Mary said: "I'm hungry") is perceived to be more vivid than indirect speech (e.g., Mary said [that] she was hungry). However, for silent reading, the representational consequences of this distinction are still unclear. Although many of us share the intuition of an "inner voice," particularly during silent reading of direct speech statements in text, there has been little direct empirical confirmation of this experience so far. Combining fMRI with eye tracking in human volunteers, we show that silent reading of direct versus indirect speech engenders differential brain activation in voice-selective areas of the auditory cortex. This suggests that readers are indeed more likely to engage in perceptual simulations (or spontaneous imagery) of the reported speaker's voice when reading direct speech as opposed to meaning-equivalent indirect speech statements as part of a more vivid representation of the former. Our results may be interpreted in line with embodied cognition and form a starting point for more sophisticated interdisciplinary research on the nature of auditory mental simulation during reading.

  16. Detection of silent cells, synchronization and modulatory activity in developing cellular networks.

    Science.gov (United States)

    Hjorth, Johannes J J; Dawitz, Julia; Kroon, Tim; Pires, Johny; Dassen, Valerie J; Berkhout, Janna A; Emperador Melero, Javier; Nadadhur, Aish G; Alevra, Mihai; Toonen, Ruud F; Heine, Vivi M; Mansvelder, Huibert D; Meredith, Rhiannon M

    2016-04-01

    Developing networks in the immature nervous system and in cellular cultures are characterized by waves of synchronous activity in restricted clusters of cells. Synchronized activity in immature networks is proposed to regulate many different developmental processes, from neuron growth and cell migration, to the refinement of synapses, topographic maps, and the mature composition of ion channels. These emergent activity patterns are not present in all cells simultaneously within the network and more immature "silent" cells, potentially correlated with the presence of silent synapses, are prominent in different networks during early developmental periods. Many current network analyses for detection of synchronous cellular activity utilize activity-based pixel correlations to identify cellular-based regions of interest (ROIs) and coincident cell activity. However, using activity-based correlations, these methods first underestimate or ignore the inactive silent cells within the developing network and second, are difficult to apply within cell-dense regions commonly found in developing brain networks. In addition, previous methods may ignore ROIs within a network that shows transient activity patterns comprising both inactive and active periods. We developed analysis software to semi-automatically detect cells within developing neuronal networks that were imaged using calcium-sensitive reporter dyes. Using an iterative threshold, modulation of activity was tracked within individual cells across the network. The distribution pattern of both inactive and active, including synchronous cells, could be determined based on distance measures to neighboring cells and according to different anatomical layers. © 2015 Wiley Periodicals, Inc.

  17. Silent cerebral infarction, income, and grade retention among students with sickle cell anemia

    Science.gov (United States)

    King, Allison A.; Rodeghier, Mark J.; Panepinto, Julie Ann; Strouse, John J.; Casella, James F.; Quinn, Charles T.; Dowling, Michael M.; Sarnaik, Sharada A.; Thompson, Alexis A.; Woods, Gerald M.; Minniti, Caterina P.; Redding-Lallinger, Rupa C.; Kirby-Allen, Melanie; Kirkham, Fenella J.; McKinstry, Robert; Noetzel, Michael J.; White, Desiree A.; Kwiatkowski, Janet K.; Howard, Thomas H.; Kalinyak, Karen A.; Inusa, Baba; Rhodes, Melissa M.; Heiny, Mark E.; Fuh, Ben; Fixler, Jason M.; Gordon, Mae O.; DeBaun, Michael R.

    2014-01-01

    Children with sickle cell anemia have a higher-than-expected prevalence of poor educational attainment. We test two key hypotheses about educational attainment among students with sickle cell anemia, as measured by grade retention and use of special education services: (1) lower household per capita income is associated with lower educational attainment; (2) the presence of a silent cerebral infarct is associated with lower educational attainment. We conducted a multicenter, cross-sectional study of cases from 22 U.S. sites included in the Silent Infarct Transfusion Trial. During screening, parents completed a questionnaire that included sociodemographic information and details of their child’s academic status. Of 835 students, 670 were evaluable; 536 had data on all covariates and were used for analysis. The students’ mean age was 9.4 years (range: 5–15) with 52.2% male; 17.5% of students were retained one grade level and 18.3% received special education services. A multiple variable logistic regression model identified that lower household per capita income (odds ratio [OR] of quartile 1 = 6.36, OR of quartile 2 = 4.7, OR of quartile 3 = 3.87; P = 0.001 for linear trend), age (OR = 1.3; P sickle cell anemia, household per capita income is associated with grade retention, whereas the presence of a silent cerebral infarct is not. Future educational interventions will need to address both the medical and socioeconomic issues that affect students with sickle cell anemia. PMID:25042018

  18. The influence of slip velocity and temperature on permeability during and after high-velocity fault slip

    Science.gov (United States)

    Tanikawa, W.; Mukoyoshi, H.; Tadai, O.; Hirose, T.; Lin, W.

    2011-12-01

    Fluid transport properties in fault zones play an important role in dynamic processes during large earthquakes. If the permeability in a fault zone is low, high pore-fluid pressures caused by thermal pressurization (Sibson, 1973) or shear-induced compaction (Blanpied et al., 1992) can lead to an apparent reduction of fault strength. Changes in porosity and permeability of fault rocks within a fault zone during earthquakes and the subsequent progressive recovery of these properties may have a large influence on earthquake recurrence (Sleep and Blanpied, 1992). A rotary shear apparatus was used to investigate changes of fluid transport properties in a fault zone by real-time measurement of gas flow rates during and after shearing of hollow sandstone and granite cylinders at various slip rates. Our apparatus measures permeability parallel to the slip plane in both the slip zone and wall rocks. In all cases, permeability decreased rapidly with an increase of friction, but recovered soon after slip, reaching a steady state within several tens of minutes. The rate of reduction of permeability increased with increasing slip velocity. Permeability did not recover to pre-slip levels after low-velocity tests but recovered to exceed them after high-velocity tests. Frictional heating of gases at the slip surface increased gas viscosity, which increased gas flow rate to produce an apparent permeability increase. The irreversible permeability changes of the low-velocity tests were caused by gouge formation due to wearing and smoothing of the slip surface. The increase of permeability after high-velocity tests was caused by mesoscale fracturing in response to rapid temperature rise. Changes of pore fluid viscosity contributed more to changes of flow rate than did permeability changes caused by shear deformation, although test results from different rocks and pore fluids might be different. References Blanpied, M.L., Lockner, D.A., Byerlee, J.D., 1992. An earthquake mechanism

  19. Chronic and acute anemia and extracranial internal carotid stenosis are risk factors for silent cerebral infarcts in sickle cell anemia.

    Science.gov (United States)

    Bernaudin, Françoise; Verlhac, Suzanne; Arnaud, Cécile; Kamdem, Annie; Vasile, Manuela; Kasbi, Florence; Hau, Isabelle; Madhi, Fouad; Fourmaux, Christine; Biscardi, Sandra; Epaud, Ralph; Pondarré, Corinne

    2015-03-05

    Early transcranial Doppler (TCD) screening of the Créteil sickle cell anemia (SCA)-newborn cohort, and rapid initiation of transfusion programs, resulted in successful prevention of overt strokes, but a high cumulative risk of silent cerebral infarcts (SCI) remained, suggesting that TCD screening does not identify all patients with SCA at risk for SCI. We hypothesized that episodes of hypoperfusion/hypoxia, as observed during acute chest syndromes or acute anemic events (AAE), and extracranial internal carotid artery (eICA) stenoses, detectable via submandibular Doppler sonography and cervical magnetic resonance angiography (MRA), could also be risk factors for SCI. This study includes 189 stroke-free patients with SCA from the Créteil newborn cohort (1992-2010) followed longitudinally by magnetic resonance imaging/MRA, including cervical MRA at the last assessment. All patients with abnormal TCD and/or intracranial stenoses were placed on a transfusion program. Mean follow-up was 9.9 years (range, 2.2-19.9 years; 1844 patient-years). Annual rates of clinical events were calculated. The cumulative risk for SCI was 39.1% (95% confidence interval [CI], 23.5%-54.7%) by age 18 years, with no plateau. We confirm that baseline hemoglobin level lower than 7 g/dL before age 3 years is a highly significant predictive risk factor for SCI (hazard ratio, 2.97; 95% CI, 1.43-6.17; P = .004). Furthermore, we show that AAE rate (odds ratio, 2.64 per unit increase; 95% CI, 1.09-6.38; P = .031) and isolated eICA stenosis (odds ratio, 3.19; 95% CI, 1.18-8.70; P = .023) are significant and independent risk factors for SCI. © 2015 by The American Society of Hematology.

  20. Pedestrians in wintertime-effects of using anti-slip devices.

    Science.gov (United States)

    Berggård, Glenn; Johansson, Charlotta

    2010-07-01

    Pedestrians slipping and falling is a major safety problem around the world, not least in countries with long winters such as Sweden. About 25000-30000 people need medical care every year for treatment of fall injuries in Sweden. Use of appropriate shoes and anti-slip devices are examples of individual measures that have been suggested to prevent slipping and falling. An intervention study was performed during the period February to April 2008. The study, which focused on healthy adults in northern Sweden, examined the effect of using anti-slip devices on daily walking journeys and prevention of slip and falls. The respondents were divided into three groups: an Intervention Group, a Control Group, with similar distribution of gender and age, and a Comparison Group. Four questionnaires were distributed: (1) background, (2) daily diary of distance walked and occurrence of incidents or accidents reported weekly, (3) detailed incident or fall report and (4) experiences of using anti-slip devices for those who used these devices during the trial period. Half of the respondents stated that they had previous experience of using anti-slip devices. In this study, 52% of the respondents used anti-slip devices. Anti-slip devices improve the walking capability during wintertime. Among those using appropriate anti-slip devices, the average daily walking distance was found to be statistically significantly longer compared to people not using anti-slip devices. This study indicates that an increase in daily walking distance can be made without increasing the risk of slips/falls when using anti-slip devices. The study also indicates that by using appropriate anti-slip devices and having information about when and where to use them, based on their design, people avoid having slips and falls. The respondents experienced in using anti-slip devices in this study will continue to use them and will also recommend others to use anti-slip devises. Copyright 2010 Elsevier Ltd. All rights

  1. Deformation twinning in zinc-aluminium single crystals after slip

    International Nuclear Information System (INIS)

    Lukac, P.; Kral, F.; Trojanova, Z.; Kral, R.

    1993-01-01

    Deformation twinning in Zn-Al single crystals deformed by slip in the basal system is examined. The influence of temperature and the content of aluminium in zinc on the twinning stress is investigated in the temperature range from 198 to 373 K. It is shown that the twinning stress rises with increasing temperature and increases with the concentration of Al atoms. (orig.)

  2. Atomistic Determination of Cross-Slip Pathway and Energetics

    DEFF Research Database (Denmark)

    Rasmussen, Torben; Jacobsen, Karsten Wedel; Leffers, Torben

    1997-01-01

    plane. The transition state and activation energy for cross slip as well as the energies of the involved dislocation constrictions are determined. One constriction has a negative energy compared to parallel partials. The energy vs splitting width for recombination of parallel partials into a perfect...

  3. Analysis of slip flow heat transfer between two unsymmetrically

    Indian Academy of Sciences (India)

    This paper presents an analytical investigation to study the heat transfer and fluid flow characteristics in the slip flow region for hydrodynamically and thermally fully developed flow between parallel plates.Both upper and lower plates are subjected to asymmetric heat flux boundary conditions. The effect of first ordervelocity ...

  4. Investigation of torque control using a variable slip induction generator

    Energy Technology Data Exchange (ETDEWEB)

    Bossanyi, E A; Gamble, C R

    1991-07-01

    An investigation of the possibilities of using a variable slip induction generator to control wind turbine transmission torque has been carried out. Such a generator consists of a wound rotor induction generator with its rotor winding connected to an external variable resistance circuit. By controlling the external resistance, the torque-slip characteristic of the generator can be modified, allowing efficient, low-slip operation below rated wind speed and compliant, high-slip operation above rated, where the additional losses are of no consequence but the resulting compliance allows a much reduced duty to be specified for the transmission and gearbox. A number of hardware options have been investigated for the variable resistance rotor circuit, the main options being either a rectifier and DC chopper or an AC regulator. Both of these options use semiconductor switching devices, for which the relative merits of thyristors, MOSFETs, GTOs and transistors have been investigated. A favoured scheme consisting of an AC regulator using GTOs has been provisionally selected. This choice uses some non-standard equipment but is expected to give negligible problems with harmonics. A comprehensive simulation model has been set up and used to investigate the behaviour of the whole system. (author).

  5. On the Modeling of Contact Interfaces with Frictional Slips

    Directory of Open Access Journals (Sweden)

    Ligia Munteanu

    2013-09-01

    Full Text Available The paper analyses the contact interfaces between the scatterers and the matrix into the sonic composites, in the presence of the frictional slips. The sonic composite is a sonic liner designed in order to provide suppression of unwanted noise for jet engines, with emphases on the nacelle of turbofan engines for commercial aircraft.

  6. A temperature dependent slip factor based thermal model for friction ...

    Indian Academy of Sciences (India)

    thermal modelling of FSW process by assuming the slip factor as a function of any one of the parameters such as ... Normal load, Fn. 31138 N .... source was moved in discrete steps of 1 mm to simulate the linear motion of the tool. At each load.

  7. Wenchuan Ms8.0 earthquake coseismic slip distribution inversion

    Directory of Open Access Journals (Sweden)

    Hongbo Tan

    2015-05-01

    Full Text Available By using GPS and gravity data before and after the Wenchuan Ms8.0 earthquake and combining data from geological surveys and geophysical inversion studies, an initial coseismic fault model is constructed. The dip angle changes of the fault slip distribution on the fault plane are inversed, and the inversion results show that the shape of the fault resembles a double-shovel. The Yingxiu–Beichuan Fault is approximately 330 km long, the surface fault dip angle is 65.1°, which gradually reduces with increasing depth to 0° at the detachment layer at a depth of 19.62 km. The Guanxian–Jiangyou Fault is approximately 90 km long, and its dip angle at the surface is 55.3°, which gradually reduces with increasing depth; the fault joins the Yingxiu–Beichuan Fault at 13.75 km. Coseismic slip mainly occurs above a depth of 19 km. There are five concentrated rupture areas, Yingxiu, Wenchuan, Hanwang, Beichuan, and Pingwu, which are consistent with geological survey results and analyses of the aftershock distribution. The rupture mainly has a thrust component with a small dextral strike–slip component. The maximum slip was more than 10 m, which occurred near Beichuan and Hanwang. The seismic moment is 7.84 × 1020 Nm (Mw7.9, which is consistent with the seismological results.

  8. Break-Even Point for a Proof Slip Operation

    Science.gov (United States)

    Anderson, James F.

    1972-01-01

    Break-even analysis is applied to determine what magnitude of titles added per year is sufficient to utilize economically Library of Congress proof slips and a Xerox 914 copying machine in the cataloging operation of a library. A formula is derived, and an example of its use is given. (1 reference) (Author/SJ)

  9. Slip sliding away: Promoting ethical behaviours in soccer ...

    African Journals Online (AJOL)

    Slip sliding away: Promoting ethical behaviours in soccer. ... African Journal for Physical Activity and Health Sciences ... after the 2010 Soccer World Cup, has led to increased demands on sport organisations, coaches and players ... While the natural law steers individuals to act morally, a performance ethic motivates many ...

  10. A temperature dependent slip factor based thermal model for friction

    Indian Academy of Sciences (India)

    This paper proposes a new slip factor based three-dimensional thermal model to predict the temperature distribution during friction stir welding of 304L stainless steel plates. The proposed model employs temperature and radius dependent heat source to study the thermal cycle, temperature distribution, power required, the ...

  11. Mechanical properties of very thin cover slip glass disk

    Indian Academy of Sciences (India)

    Unknown

    Mechanical properties of very thin cover slip glass disk. A SEAL, A K DALUI, M BANERJEE, A K MUKHOPADHYAY* and K K PHANI. Central Glass and Ceramic Research Institute, Kolkata 700 032, India. Abstract. The biaxial flexural strength, Young's modulus, Vicker's microhardness and fracture toughness data for very ...

  12. Shear Stress-Relative Slip Relationship at Concrete Interfaces

    Directory of Open Access Journals (Sweden)

    Keun-Hyeok Yang

    2016-01-01

    Full Text Available This study develops a simple and rational shear stress-relative slip model of concrete interfaces with monolithic castings or smooth construction joints. In developing the model, the initial shear cracking stress and relative slip amount at peak stress were formulated from a nonlinear regression analysis using test data for push-off specimens. The shear friction strength was determined from the generalized equations on the basis of the upper-bound theorem of concrete plasticity. Then, a parametric fitting analysis was performed to derive equations for the key parameters determining the shapes of the ascending and descending branches of the shear stress-relative slip curve. The comparisons of predictions and measurements obtained from push-off tests confirmed that the proposed model provides superior accuracy in predicting the shear stress-relative slip relationship of interfacial shear planes. This was evidenced by the lower normalized root mean square error than those in Xu et al.’s model and the CEB-FIB model, which have many limitations in terms of the roughness of the substrate surface along an interface and the magnitude of equivalent normal stress.

  13. Constraining slip rates and spacings for active normal faults

    Science.gov (United States)

    Cowie, Patience A.; Roberts, Gerald P.

    2001-12-01

    Numerous observations of extensional provinces indicate that neighbouring faults commonly slip at different rates and, moreover, may be active over different time intervals. These published observations include variations in slip rate measured along-strike of a fault array or fault zone, as well as significant across-strike differences in the timing and rates of movement on faults that have a similar orientation with respect to the regional stress field. Here we review published examples from the western USA, the North Sea, and central Greece, and present new data from the Italian Apennines that support the idea that such variations are systematic and thus to some extent predictable. The basis for the prediction is that: (1) the way in which a fault grows is fundamentally controlled by the ratio of maximum displacement to length, and (2) the regional strain rate must remain approximately constant through time. We show how data on fault lengths and displacements can be used to model the observed patterns of long-term slip rate where measured values are sparse. Specifically, we estimate the magnitude of spatial variation in slip rate along-strike and relate it to the across-strike spacing between active faults.

  14. Chaotic mixing in a planar, curved channel using periodic slip

    International Nuclear Information System (INIS)

    Garg, P.; Picardo, J. R.; Pushpavanam, S.

    2015-01-01

    We propose a novel strategy for designing chaotic micromixers using curved channels confined between two flat planes. The location of the separatrix between the Dean vortices, induced by centrifugal forces, is dependent on the location of the maxima of axial velocity. An asymmetry in the axial velocity profile can change the location of the separatrix. This is achieved physically by introducing slip alternatingly at the top and bottom walls. This leads to streamline crossing and Lagrangian chaos. An approximate analytical solution of the velocity field is obtained using perturbation theory. This is used to find the Lagrangian trajectories of fluid particles. Poincare sections taken at periodic locations in the axial direction are used to study the extent of chaos. We study two microchannel designs, called circlet and serpentine, in which the Dean vortices in adjacent half cells are co-rotating and counter-rotating, respectively. The extent of mixing, at low Re and low slip length, is shown to be greater in the serpentine case. Wide channels are observed to have much better mixing than tall channels; an important observation not made for separatrix flows till now. Eulerian indicators are used to gauge the extent of mixing, with varying slip length, and it is shown that an optimum slip length exists which maximizes the mixing in a particular geometry. Once the parameter space of relatively high mixing is identified, detailed variance computations are carried out to identify the detailed features

  15. Chaotic mixing in a planar, curved channel using periodic slip

    Science.gov (United States)

    Garg, P.; Picardo, J. R.; Pushpavanam, S.

    2015-03-01

    We propose a novel strategy for designing chaotic micromixers using curved channels confined between two flat planes. The location of the separatrix between the Dean vortices, induced by centrifugal forces, is dependent on the location of the maxima of axial velocity. An asymmetry in the axial velocity profile can change the location of the separatrix. This is achieved physically by introducing slip alternatingly at the top and bottom walls. This leads to streamline crossing and Lagrangian chaos. An approximate analytical solution of the velocity field is obtained using perturbation theory. This is used to find the Lagrangian trajectories of fluid particles. Poincare sections taken at periodic locations in the axial direction are used to study the extent of chaos. We study two microchannel designs, called circlet and serpentine, in which the Dean vortices in adjacent half cells are co-rotating and counter-rotating, respectively. The extent of mixing, at low Re and low slip length, is shown to be greater in the serpentine case. Wide channels are observed to have much better mixing than tall channels; an important observation not made for separatrix flows till now. Eulerian indicators are used to gauge the extent of mixing, with varying slip length, and it is shown that an optimum slip length exists which maximizes the mixing in a particular geometry. Once the parameter space of relatively high mixing is identified, detailed variance computations are carried out to identify the detailed features.

  16. Assemblage of strike-slip faults and tectonic extension and ...

    Indian Academy of Sciences (India)

    12

    the formation, evolution and distribution of these strike-slip faults have important. 80 ...... function of coal-derived gas study for natural gas industry development in China; .... Bohai-Zhangjiakou seismotectonic zone based on 3D visco-elastic ...

  17. Wheel slip control with torque blending using linear and nonlinear model predictive control

    Science.gov (United States)

    Basrah, M. Sofian; Siampis, Efstathios; Velenis, Efstathios; Cao, Dongpu; Longo, Stefano

    2017-11-01

    Modern hybrid electric vehicles employ electric braking to recuperate energy during deceleration. However, currently anti-lock braking system (ABS) functionality is delivered solely by friction brakes. Hence regenerative braking is typically deactivated at a low deceleration threshold in case high slip develops at the wheels and ABS activation is required. If blending of friction and electric braking can be achieved during ABS events, there would be no need to impose conservative thresholds for deactivation of regenerative braking and the recuperation capacity of the vehicle would increase significantly. In addition, electric actuators are typically significantly faster responding and would deliver better control of wheel slip than friction brakes. In this work we present a control strategy for ABS on a fully electric vehicle with each wheel independently driven by an electric machine and friction brake independently applied at each wheel. In particular we develop linear and nonlinear model predictive control strategies for optimal performance and enforcement of critical control and state constraints. The capability for real-time implementation of these controllers is assessed and their performance is validated in high fidelity simulation.

  18. Direct measurement of wall slip and slip layer thickness of non-Brownian hard-sphere suspensions in rectangular channel flows

    Science.gov (United States)

    Jesinghausen, Steffen; Weiffen, Rene; Schmid, Hans-Joachim

    2016-09-01

    Wall slip is a long-known phenomenon in the field of rheology. Nevertheless, the origin and the evolution are not completely clear yet. Regarding suspensions, the effect becomes even more complicated, because different mechanisms like pure slip or slip due to particle migration have to be taken into account. Furthermore, suspensions themselves show many flow anomalies and the isolation of slip is complicated. In order to develop working physical models, further insight is necessary. In this work,