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1

P wave velocity tomography of the Venezuelan region from local arrival times  

NASA Astrophysics Data System (ADS)

Arrival times from the local seismological network of Venezuela were used to estimate a three-dimensional P wave velocity model for the region between longitude 60°-74° W and latitude 6°-14° N to a depth of more than 80 km. The inversion was carried out by damped least squares, describing the media by homogeneous velocity blocks. The resolved lateral velocity variations in the first layer (0-30 km depth) showed a correlation with the main stratigraphic features of the area, while second layer (30-50 km depth) showed the influence of Moho depth variations through the region, generating a pattern well correlated to the Bouguer Anomaly Map. Lithospheric seismic velocities below the Moho appear to be influenced by the major crustal fault systems. An important low-velocity zone is present below the triple junction of the fault systems of Oca, Boconó, and Morón in northwestern Venezuela. Farther south, a similar low-velocity zone is present below the junction of the Boconó and the Santa Marta fault systems. Those are the two continental corners of the triangular Maracaibo Block. Below 80 km depth (the fourth layer) the low velocity zones show a connected pattern that follows or is adjacent to the crustal fault zones. The presence of subducted Atlantic lithosphere below the Eastern Venezuelan Basin could explain the high-velocity zone at this location. A similar interpretation emerges from the tectonic wedging model, previously proposed to explain the pronounced minimum of the gravity anomaly.

Bosch, Miguel

1997-03-01

2

Whole mantle P-wave travel time tomography  

Microsoft Academic Search

A method of tomographic inversion to obtain three-dimensional velocity perturbations in the Earth's whole mantle has been developed, and applied to more than two million P-wave arrival time data reported by International Seismology Center (ISC). The model is parameterized with 32,768 blocks; the divisions in latitude, longitude, and radius are 32, 64, and 16, respectively. Horizontal cell size is 5.6°

Hiroshi Inoue; Yoshio Fukao; Kunio Tanabe; Yosihiko Ogata

1990-01-01

3

Mantle Under the Vrancea Zone - Evidence from Dispersion of First-arriving P-Waves  

NASA Astrophysics Data System (ADS)

The Vrancea region of the south-eastern Carpathians is one of the most active seismic zones in Europe and is known for its intermediate-depth seismicity, e.g., there are strong earthquakes in a very limited seismogenic volume at intermediate-depth (70-180 km). Seismic tomography has shown a high-velocity body in that anomalous zone, extending to a depth of at least 350 km. That high-velocity body has been interpreted either as a descending lithospheric slab or as mantle lithosphere. Indeed, the regional geodynamic models proposed for this area can be split into two main model assumptions: (a) The mantle seismicity in Vrancea is associated with a descending relic oceanic lithosphere (attached or already detached from the continental crust) beneath the bending zone of the SE-Carpathians, or (b) the intermediate depth earthquakes are caused by delamination of mantle lithosphere due to continental collision and orogenic thickening. In order to shed more light on the origin of the intermediate depth seismicity in the Vrancea zone, we investigate the frequency-dependence of P-wave group arrival times of local earthquakes excited beneath this area. Dispersed P-waves have been observed in many subduction zones around the world. A most natural, and almost exclusive, explanation is based on the upper few kilometers of subducted oceanic crust that are seismically distinct from surrounding material. Such a low-velocity layer several kilometers thick acts as a waveguide, causing higher frequencies to arrive later than lower frequencies. For Vrancea, such dispersion is observed at several stations sited at the bending zone of the SE-Carpathians while signals at a reference station further northwest do not show such a behaviour. The main interest of this technique is that it provides constraints that classical seismic tomography can not give, since the low-velocity channel is too thin to be resolved by the latter technique. The presence of a tabular and inclined low-velocity suggests the presence of subducted oceanic lithosphere rather than continental lithospheric delamination as the best simple geodynamic model for the area.

Rodler, Fee-Alexandra; Bokelmann, Götz; Gerner, Andreas

2013-04-01

4

A map of relative P wave delay times across southern California  

NASA Astrophysics Data System (ADS)

Using cross correlation of band-pass-filtered waveforms, we have determined relative teleseismic P wave arrival times for the broadband stations in the Southern California Seismic Network (formerly known as TriNet). To remove as much as possible contamination of the direct P wave by near surface reflections and refractions, visible for arrivals at several stations located directly above complex three-dimensional structures, we carried out this cross correlation over only the first quarter wavelength of the P waveform, after applying a 1-2 Hz Butterworth band-pass filter. We subsequently completed a thorough visual and numerical quality control of the resulting traveltimes and were left with 12320 measurements for 144 events spanning a time period of almost 4 years, from 2000 to 2004. We present this complete data set on a topographic map of southern California (including a detailed inset map of the more densely covered LA basin area), enabling a direct investigation of data patterns. This visualization helps to develop an understanding of expected features of a future tomographic inversion of this data set.

Polet, Jascha

2007-10-01

5

Travel times and station corrections for P waves at teleseismic distances  

Microsoft Academic Search

Approximately 3300 shallow focus earthquakes and 1000 seismic stations have been used in a study of P wave travel times and station residuals, including azimuthal effects. The events were selected from a catalog containing 160,000 earthquakes, and those having uniform distance and azimuthal coverage were systematically relocated and used to refine P wave travel times and station corrections. Station corrections

Adam M. Dziewonski; Don L. Anderson

1983-01-01

6

Deep Downhole Seismic Testing at the Waste Treatment Plant Site, Hanford, WA. Volume II P-Wave Measurements in Borehole C4996 Seismic Records, Wave-Arrival Identifications and Interpreted P-Wave Velocity Profile.  

SciTech Connect

In this volume (II), all P-wave measurements are presented that were performed in Borehole C4996 at the Waste Treatment Plant (WTP) with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver. P-wave measurements were performed over the depth range of 360 to 1400 ft, typically in 10-ft intervals. However, in some interbeds, 5-ft depth intervals were used, while below about 1180 ft, depth intervals of 20 ft were used. Compression (P) waves were generated by moving the base plate of T-Rex for a given number of cycles at a fixed frequency as discussed in Section 2. This process was repeated so that signal averaging in the time domain was performed using 3 to about 15 averages, with 5 averages typically used. In addition to the LBNL 3-D geophone, called the lower receiver herein, a 3-D geophone from Redpath Geophysics was fixed at a depth of 22 ft in Borehole C4996, and a 3-D geophone from the University of Texas was embedded near the borehole at about 1.5 ft below the ground surface. This volume is organized into 12 sections as follows: Section 1: Introduction, Section 2: Explanation of Terminology, Section 3: Vp Profile at Borehole C4996, Sections 4 to 6: Unfiltered P-wave records of lower vertical receiver, reaction mass, and reference receiver, Sections 7 to 9: Filtered P-wave signals of lower vertical receiver, reaction mass and reference receiver, Section 10: Expanded and filtered P-wave signals of lower vertical receiver, and Sections 11 and 12: Waterfall plots of unfiltered and filtered lower vertical receiver signals.

Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

2007-07-06

7

Deep Downhole Seismic Testing at the Waste Treatment Plant Site, Hanford, WA. Volume I P-Wave Measurements in Borehole C4993 Seismic Records, Wave-Arrival Identifications and Interpreted P-Wave Velocity Profile.  

SciTech Connect

In this volume (I), all P-wave measurements are presented that were performed in Borehole C4993 at the Waste Treatment Plant (WTP) with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver. P-wave measurements were performed over the depth range of 370 to 1400 ft, typically in 10-ft intervals. However, in some interbeds, 5-ft depth intervals were used, while below about 1200 ft, depth intervals of 20 ft were used. Compression (P) waves were generated by moving the base plate of T-Rex for a given number of cycles at a fixed frequency as discussed in Section 2. This process was repeated so that signal averaging in the time domain was performed using 3 to about 15 averages, with 5 averages typically used. In addition to the LBNL 3-D geophone, called the lower receiver herein, a 3-D geophone from Redpath Geophysics was fixed at a depth of 22 ft in Borehole C4993, and a 3-D geophone from the University of Texas was embedded near the borehole at about 1.5 ft below the ground surface. This volume is organized into 12 sections as follows: Section 1: Introduction, Section 2: Explanation of Terminology, Section 3: Vp Profile at Borehole C4993, Sections 4 to 6: Unfiltered P-wave records of lower vertical receiver, reaction mass, and reference receiver, Sections 7 to 9: Filtered P-wave signals of lower vertical receiver, reaction mass and reference receiver, Section 10: Expanded and filtered P-wave signals of lower vertical receiver, and Sections 11 and 12: Waterfall plots of unfiltered and filtered lower vertical receiver signals.

Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

2007-07-06

8

Deep Downhole Seismic Testing at the Waste Treatment Plant Site, Hanford, WA. Volume III P-Wave Measurements in Borehole C4997 Seismic Records, Wave-Arrival Identifications and Interpreted P-Wave Velocity Profile.  

SciTech Connect

In this volume (III), all P-wave measurements are presented that were performed in Borehole C4997 at the Waste Treatment Plant (WTP) with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver. P-wave measurements were performed over the depth range of 390 to 1220 ft, typically in 10-ft intervals. However, in some interbeds, 5-ft depth intervals were used. Compression (P) waves were generated by moving the base plate of T-Rex for a given number of cycles at a fixed frequency as discussed in Section 2. This process was repeated so that signal averaging in the time domain was performed using 3 to about 15 averages, with 5 averages typically used. In addition to the LBNL 3-D geophone, called the lower receiver herein, a 3-D geophone from Redpath Geophysics was fixed at a depth of 40 ft (later relocated to 27.5 ft due to visibility in borehole after rain) in Borehole C4997, and a 3-D geophone from the University of Texas was embedded near the borehole at about 1.5 ft below the ground surface. This volume is organized into 12 sections as follows: Section 1: Introduction, Section 2: Explanation of Terminology, Section 3: Vp Profile at Borehole C4997, Sections 4 to 6: Unfiltered P-wave records of lower vertical receiver, reaction mass, and reference receiver, Sections 7 to 9: Filtered P-wave signals of lower vertical receiver, reaction mass and reference receiver, Section 10: Expanded and filtered P-wave signals of lower vertical receiver, and Sections 11 and 12: Waterfall plots of unfiltered and filtered lower vertical receiver signals.

Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

2007-06-06

9

Quantum arrival time for open systems  

SciTech Connect

We extend previous work on the arrival time problem in quantum mechanics, in the framework of decoherent histories, to the case of a particle coupled to an environment. The usual arrival time probabilities are related to the probability current, so we explore the properties of the current for general open systems that can be written in terms of a master equation of the Lindblad form. We specialize to the case of quantum Brownian motion, and show that after a time of order the localization time of the current becomes positive. We show that the arrival time probabilities can then be written in terms of a positive operator-valued measure (POVM), which we compute. We perform a decoherent histories analysis including the effects of the environment and show that time-of-arrival probabilities are decoherent for a generic state after a time much greater than the localization time, but that there is a fundamental limitation on the accuracy {delta}t, with which they can be specified which obeys E{delta}t>>({h_bar}/2{pi}). We confirm that the arrival time probabilities computed in this way agree with those computed via the current, provided there is decoherence. We thus find that the decoherent histories formulation of quantum mechanics provides a consistent explanation for the emergence of the probability current as the classical arrival time distribution, and a systematic rule for deciding when probabilities may be assigned.

Yearsley, J. M. [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom)

2010-07-15

10

Time corrections to teleseismic P delays derived from SKS splitting parameters and implications for western U.S. P-wave tomography  

NASA Astrophysics Data System (ADS)

Upper mantle anisotropy will affect teleseismic P-wave arrival times and create artifacts in isotropic travel-time tomography. Compiled SKS splitting results indicate variations in the strength and orientation of azimuthal anisotropy beneath the western U.S. We use SKS splitting parameters and a hexagonally anisotropic elastic tensor (fast symmetry axis) to estimate azimuthal anisotropy contributions to P-wave delay times and evaluate the effects on isotropic P-wave tomography. Estimated anisotropy correction times have a root-mean-square (RMS) value of 0.16 s, which is 37% of P-wave delay time RMS. The magnitude of azimuthal anisotropy, rather than its azimuth, has the strongest effect on P delay times; however, if the anisotropy symmetry axis has a plunge, P-wave travel times may be strongly affected by both magnitude and azimuth. Applying azimuthal anisotropy corrections significantly increases tomographic P-wave velocity beneath the High Lava Plains and central California coast, and decreases velocity beneath the Great Basin.

O'Driscoll, Leland J.; Humphreys, Eugene D.; Schmandt, Brandon

2011-10-01

11

FEMTOSECOND RESOLUTION BUNCH ARRIVAL TIME MONITOR  

Microsoft Academic Search

A need for femtosecond resolution beam arrival time measurements has arisen with the transition from many- picosecond-long bunches in ring-based accelerators to a few femtosecond-long bunches in high-gain free-electron lasers. Here we present an electro-optical detection scheme that uses the signal of a beam pick-up to modulate the intensity of a femtosecond laser pulse train. By detecting the energies of

F. Loehl

12

Scheduling jobs that arrive over time  

SciTech Connect

A natural and basic problem in scheduling theory is to provide good average quality of service to a stream of jobs that arrive over time. In this paper we consider the problem of scheduling n jobs that are released over time in order to minimize the average completion time of the set of jobs. In contrast to the problem of minimizing average completion time when all jobs are available at time 0, all the problems that we consider are NP-hard, and essentially nothing was known about constructing good approximations in polynomial time. We give the first constant-factor approximation algorithms for several variants of the single and parallel machine model. Many of the algorithms are based on interesting algorithmic and structural relationships between preemptive and nonpreemptive schedules and linear programming relaxations of both. Many of the algorithms generalize to the minimization of average weighted completion time as well.

Phillips, C. [Sandia National Labs., Albuquerque, NM (United States); Stein, C. [Dartmouth Coll., Hanover, NH (United States); Wein, J. [Polytechnic Univ., Brooklyn, NY (United States). Dept. of Computer Science

1995-04-06

13

On ‘arriving on time’, but what is ‘on time’?  

Microsoft Academic Search

The time-geographical concept of coupling constraints, which define when, where and for how long individuals have to join other individuals and material objects, can be useful to ‘time squeeze’ studies. Geographers have typically operationalised the ‘when’ dimension of coupling constrains through arrival times at locations in physical space or the starting time of specific activities. This paper questions this approach

Tim Schwanen

2006-01-01

14

Earthquake Travel Times: Customized Listing of Recent Arrival Times  

NSDL National Science Digital Library

The US Geological Survey Earthquake Hazards Program Web site contains the Earthquake Travel Times Customized Listing of Recent Arrival Times online calculator. The tool allows visitors to generate a listing of the times that phases from recent earthquakes arrived at their particular seismic station. After inputting the latitude and longitude of their location, the distance and magnitude of earthquakes to consider, types of phases, and other parameters, the user gets a simple but informative readout. The data includes the date and time of the earthquake, phase codes, travel time in seconds, arrival time, direction of travel, and more. Any seismologist or other researchers in similar fields should thoroughly appreciate this simple and helpful resource.

15

Passive location using time of arrival along with direction of arrival and its changing rate  

Microsoft Academic Search

Passive location is a widely investigated problem. In this paper, a pseudo-linear algorithm for moving emitters passive location and tracking based on time of arrival (TOA), direction of arrival (DOA) and DOA changing rate measurements by a non-moving observer is given. This algorithm has high convergence speed and stability, so it is of great practicability. The observability conditions of location

Li Zong-hua; Feng Dao-wang; Sun Zhong-kang; Zhou Yi-yu

2003-01-01

16

Visual discrimination thresholds for time to arrival.  

PubMed

In a seminal article, Todd (Journal of Experimental Psychology: Human Perception and Performance 7:795-810, 1981) reported a difference threshold of about 50 ms to discriminate the times of arrival of two differently sized objects that simultaneously approached head-on at constant but different velocities. Subsequent investigators, however, have often found much higher thresholds. We did one complete replication of Todd's experiment, and then modified his stimuli and experimental regime, which we hypothesized may have been responsible for some of the discrepancies reported in the literature. Unlike Todd and most other researchers, we exclusively used untrained observers. Several of our participants performed almost as well as the trained observers used by Todd and others, but the performance of most of our participants fell short of this standard. Furthermore, thresholds were affected by the experimental regimes, with large differences between objects' sizes and speeds compromising performance. Analyses of the response patterns revealed that the responses were driven mainly by the objects' relative apparent sizes. PMID:23794210

Landwehr, Klaus; Baurès, Robin; Oberfeld, Daniel; Hecht, Heiko

2013-10-01

17

Confined quantum time of arrival for the vanishing potential  

SciTech Connect

We give full account of our recent report in E. A. Galapon, R. Caballar, and R. Bahague, Phys. Rev. Lett. 93, 180406 (2004), where it is shown that formulating the free quantum time of arrival problem in a segment of the real line suggests rephrasing the quantum time of arrival problem to finding a complete set of states that evolve to unitarily arrive at a given point at a definite time. For a spatially confined particle, here it is shown explicitly that the problem admits a solution in the form of an eigenvalue problem of a class of compact and self-adjoint time of arrival operators derived by a quantization of the classical time of arrival. The eigenfunctions of these operators are numerically demonstrated to unitarily arrive at the origin at their respective eigenvalues.

Galapon, Eric A. [Theoretical Physics Group, National Institute of Physics, University of the Philippines, Diliman, Quezon City, 1101 (Philippines); Theoretical Physics, University of the Basque Country, Apdo. 644, 48080 Bilbao (Spain); Chemical Physics, University of the Basque Country, Apdo. 644, 48080 Bilbao (Spain); Caballar, Roland F.; Bahague, Ricardo [Theoretical Physics Group, National Institute of Physics, University of the Philippines, Diliman, Quezon City, 1101 (Philippines)

2005-12-15

18

Time-dependent three dimensional P-wave velocity models derived for the Geysers geothermal field  

NASA Astrophysics Data System (ADS)

The Geysers geothermal field is a source of significant small earthquake (M< 2.0) seismicity in northern California. The region has been actively monitored for seismicity, both natural and induced, since the geothermal field has been put into production. A modern digital seismic monitoring network in the area consists of 34 LBNL/Calpine (BG) borehole short-period and 12 Northern California Seismic Network (NCSN) network surface short-period seismic stations. The USGS has auto-located approximately 25,033 earthquakes (NCEDC catalog) for the years 2009 and 2010 combined from the composite seismic network. Using the auto-located solutions and a Geysers specific one-dimensional velocity model (Eberhart-Philips and Oppenheimer, 1984) as a starting point, we have simultaneously inverted for three dimensional P-wave velocities for each year's data set. Before beginning the inversion we established that the automatic S-phase picks were too unstable and thus focused only on the P-wave velocities. After culling events with initial RMS uncertainty greater than 0.06 seconds, we start with 7,403 earthquakes in 2009 and 11,199 earthquakes in 2010. The technique we use is a finite-difference travel time technique that Roecker et al. (Tectonophysics, 2006) used for the Parkfield SAFOD site. We will present the results of the simultaneous inversion for each of the 2009 and 2010 years along with plots of the seismicity relocated using these new velocity models.

Friberg, P. A.; Roecker, S. W.; Dricker, I. G.; Lisowski, S.; Hellman, S. B.

2011-12-01

19

Cascadia tremor located near plate interface constrained by S minus P wave times.  

PubMed

Nonvolcanic tremor is difficult to locate because it does not produce impulsive phases identifiable across a seismic network. An alternative approach to identifying specific phases is to measure the lag between the S and P waves. We cross-correlate vertical and horizontal seismograms to reveal signals common to both, but with the horizontal delayed with respect to the vertical. This lagged correlation represents the time interval between vertical compressional waves and horizontal shear waves. Measurements of this interval, combined with location techniques, resolve the depth of tremor sources within +/-2 kilometers. For recent Cascadia tremor, the sources locate near or on the subducting slab interface. Strong correlations and steady S-P time differences imply that tremor consists of radiation from repeating sources. PMID:19179527

La Rocca, Mario; Creager, Kenneth C; Galluzzo, Danilo; Malone, Steve; Vidale, John E; Sweet, Justin R; Wech, Aaron G

2009-01-30

20

Investigation of the lithosphere beneath the Vogelsberg volcanic complex with P-wave travel time residuals  

NASA Astrophysics Data System (ADS)

With the aim of investigating the P-wave velocity structure below the Tertiary volcano Vogelsberg, a network of 10 mobile short period seismograph stations was installed in May 1987 for a period of 20 months. P-Wave travel time residuals relative to the station Kleiner Feldberg/Taunus (TNS) were determined for 168 seismic events using the Jeffreys - Bullen travel time tables. At all stations the relative residuals showed a positive sign, indicating a low velocity zone beneath the Vogelsberg. Maxima were found in the northern part of the Vogelsberg (station VAD +0.5 s) and in the region of the Amöneburger Basin (station RAU +0.28 s). The travel time residuals were inverted using the tomographic inversion method of Aki et al. (1977). The slowness perturbations of the single blocks were calculated relative to a crustal and upper mantle model of the Rhenish Massif. The results show an intracrustal low velocity body (about -9%) striking in a Variscan direction and underlying the north-eastern part of the Vogelsberg, and another velocity minimum (about - 6%) in the region of the Am6neburger Basin. In the lower crust and the upper mantle the velocities are reduced by about 4% relative to the starting model. The Variscan alignment of the low velocity zone under the Vogelsberg correlates with results of other geological studies. It can be assumed that during the rifting phase of the Upper Rhinegraben Variscan lineations have been reactivated, favouring uprising of magma along these old structures. The position and extension of the low velocity zone correlate with the assumed sediment distributions in the area of investigation. This may account for about one-half of the observed anomaly. The reason for the velocity reduction of about 4% in the entire underground region of the Vogelsberg down to a depth of about 70 km can be explained by the intensive fracturing of the lithosphere, caused by thermal and pressure gradients during the magma eruption process.

Braun, T.; Berckhemer, H.

1993-04-01

21

Mobile TV's Time to Shine Has Arrived  

NASA Astrophysics Data System (ADS)

MoFilm, the first mobile film festival, achieved some legitimacy when multiple Academy Award-winning actor Kevin Spacey hosted the show in 2009. Spacey commented: "[I]n some countries, this might be the first time they [people] ever see a movie. … They won't see it on that big screen; they'll see it on a small one."1 According to a 2007 Gartner report, sales of cell phones skyrocketed for the first time to more than 1 billion.2 In 2008, the number of worldwide subscribers topped 4 billion, covering 60% of the world population.3 There are more mobile phones than TVs (there are 1.4 billion TVs worldwide4). Spacey concluded: "The quality of work and the simple ability at storytelling, the thing that ignites someone and inspires them to tell a story, can really come from anywhere."5

Kitson, Fred

22

Seattle Required Time-of-Arrival flight trials  

Microsoft Academic Search

The Federal Aviation Administration (FAA) conducted limited operational flight trials of Trajectory Based Operations (TBO) based upon the use of the Required Time-of-Arrival (RTA) function in modern Flight Management Systems (FMSs) October 25?31, 2010. The flight trials were conducted on the Olympia Six (OLM6) Standard Terminal Arrival (STAR) for the Seattle-Tacoma International Airport by select Alaska Airlines pilots flying Boeing

Mahesh Balakrishna; Thomas A. Becher; Paul V. MacWilliams; Joel K. Klooster; Wyatt D. Kuiper; Patrick J. Smith

2011-01-01

23

Time-of-arrival probabilities for general particle detectors  

NASA Astrophysics Data System (ADS)

We develop a general framework for the construction of probabilities for the time of arrival in quantum systems. The time of arrival is identified with the time instant when a transition in the detector's degrees of freedom takes place. Thus, its definition is embedded within the larger issue of defining probabilities with respect to time for general quantum transitions. The key point in our analysis is that we manage to reduce the problem of defining a quantum time observable to a mathematical model where time is associated to a transition from a subspace of the Hilbert space of the total system to its complementary subspace. This property makes it possible to derive a general expression for the probability for the time of transition, valid for any quantum system, with the only requirement that the time of transition is correlated with a definite macroscopic record. The framework developed here allows for the consideration of any experimental configuration for the measurement of the time of arrival, and it also applies to relativistic systems with interactions described by quantum field theory. We use the method in order to describe time-of-arrival measurements in high-energy particle reactions and for a rigorous derivation of the time-integrated probabilities in particle oscillations.

Anastopoulos, Charis; Savvidou, Ntina

2012-07-01

24

LETTER: Arrival time statistics in global disease spread  

NASA Astrophysics Data System (ADS)

Metapopulation models describing cities with different populations coupled by the travel of individuals are of great importance in the understanding of disease spread on a large scale. An important example is the Rvachev Longini model which is widely used in computational epidemiology. Few analytical results are, however, available and, in particular, little is known about paths followed by epidemics and disease arrival times. We study the arrival time of a disease in a city as a function of the starting seed of the epidemics. We propose an analytical ansatz, test it in the case of a spread on the worldwide air-transportation network, and show that it predicts accurately the arrival order of a disease in worldwide cities.

Gautreau, Aurélien; Barrat, Alain; Barthélemy, Marc

2007-09-01

25

Time-of-arrival probabilities and quantum measurements  

SciTech Connect

In this paper we study the construction of probability densities for time of arrival in quantum mechanics. Our treatment is based upon the facts that (i) time appears in quantum theory as an external parameter to the system, and (ii) propositions about the time of arrival appear naturally when one considers histories. The definition of time-of-arrival probabilities is straightforward in stochastic processes. The difficulties that arise in quantum theory are due to the fact that the time parameter of the Schroedinger's equation does not naturally define a probability density at the continuum limit, but also because the procedure one follows is sensitive on the interpretation of the reduction procedure. We consider the issue in Copenhagen quantum mechanics and in history-based schemes like consistent histories. The benefit of the latter is that it allows a proper passage to the continuous limit--there are, however, problems related to the quantum Zeno effect and decoherence. We finally employ the histories-based description to construct Positive-Operator-Valued-Measures (POVMs) for the time-of-arrival, which are valid for a general Hamiltonian. These POVMs typically depend on the resolution of the measurement device; for a free particle, however, this dependence cancels in the physically relevant regime and the POVM coincides with that of Kijowski.

Anastopoulos, Charis; Savvidou, Ntina [Department of Physics, University of Patras, 26500 Patras (Greece); Theoretical Physics Group, Imperial College, SW7 2BZ, London (United Kingdom)

2006-12-15

26

HF (High Frequency) absolute time of arrival sensing  

NASA Astrophysics Data System (ADS)

In late 1980 questions arose concerning whether the ionosphere was sufficiently stable to allow precisely measured time of arrival of skywave signals to be used for geolocation in the high frequency (HF) band between 2 and 32 MHz. The chief limitation in the accuracy of this type of system is the amount of uncertainty in the ionospheric height estimation and its temporal stability. Traditional ionospheric research resources did not address the issue in sufficient detail and time resolution to be of any assistance. In order to understand the exact nature of the ionospheric uncertainties and to quantify their extent, experimentation was proposed to sense the variation in the refraction height of the ionosphere as it relates to the time of arrival of the HF signal. The objective of this work was to determine the range of environmentally induced errors in a skywave Time Difference of Arrival (TDOA) measurement, thereby bounding the ultimate geolocation accuracy one could expect from this technique. The first experimental measurement system started operation in early 1981. This effort involved establishing a continuous absolute Time of Arrival (TOA) experiment over the one-hop midlatitude path between San Diego, California and Fort Collins, Colorado. The system is fully digital and stabilized with a cesium beam standard. This work was supplemented with vertical incidence sounder data at both ends of the path, a collateral Doppler sensing system, and coincident satellite solar data.

Rose, R. B.

1986-02-01

27

Designing a real-time ramp arrival prediction tool  

Microsoft Academic Search

Airline efficiency may be increased by the timely dissemination of accurate ramp time-of-arrival predictions for inbound aircraft. Potential benefits include improvements to gate management, ramp management, and personnel\\/equipment resource allocation. These benefits can lead to shorter aircraft turn-around times and reduced airline operating costs. Collaboration with Federal Express has identified the following criteria for a real-time prediction system: a gate

J. Legge

2004-01-01

28

Global disease spread: Statistics and estimation of arrival times  

Microsoft Academic Search

We study metapopulation models for the spread of epidemics in which different subpopulations (cities) are connected by fluxes of individuals (travelers). This framework allows one to describe the spread of a disease on a large scale and we focus here on the computation of the arrival time of a disease as a function of the properties of the seed of

Aurelien Gautreau; Alain Barrat; Marc Barthelemy

2008-01-01

29

ELECTRO-OPTIC BUNCH ARRIVAL TIME MEASUREMENT AT FLASH  

Microsoft Academic Search

Optical synchronization systems, based on mode- locked erbium-doped fiber lasers whose pulses are distributed over length stabilized fiber links, are expected to be drift free and to provide femtosecond stability for the next generation of free electron lasers. In this paper we provide a comparison between the stability of two bunch arrival time monitors working on different principles. In the

V. Arsov; M. Felber; E.-A. Knabbe; B. Lorbeer; F. Ludwig; K. Matthiesen; H. Schlarb

30

Passive radar localization by time difference of arrival  

Microsoft Academic Search

A detailed analysis for the performance of TDOA based passive radar localization systems is provided. The system considered in the analyses consists of four sensors and associated receiver blocks, samplers, and signal processors. Arrival time for the radar pulses is obtained by adaptive thresholding. Cramer-Rao bounds of TOA and TDOA are obtained. The effects of the receiver bandwidth and the

A. Dersan; Y. Tanik

2002-01-01

31

Performance of successive cancellation techniques for time of arrival estimation  

Microsoft Academic Search

Two successive cancellation methods for estimation of time or angle of arrival were presented by Krasny and Koorapaty (1986) and their performance was investigated for multipath channels with uncorrelated paths components. In this paper, the performance of the methods is investigated over channel models that have been designed to simulate real-world environments and have been extensively used for evaluating cellular

Leonid Krasny; Havish Koorapaty

2002-01-01

32

Quantum arrival and dwell times via idealized clocks  

SciTech Connect

A number of approaches to the problem of defining arrival- and dwell-time probabilities in quantum theory makes use of idealized models of clocks. An interesting question is the extent to which the probabilities obtained in this way are related to standard semiclassical results. In this paper, we explore this question using a reasonably general clock model, solved using path-integral methods. We find that, in the weak-coupling regime, where the energy of the clock is much less than the energy of the particle it is measuring, the probability for the clock pointer can be expressed in terms of the probability current in the case of arrival times, and the dwell-time operator in the case of dwell times, the expected semiclassical results. In the regime of strong system-clock coupling, we find that the arrival-time probability is proportional to the kinetic-energy density, consistent with an earlier model involving a complex potential. We argue that, properly normalized, this may be the generically expected result in this regime. We show that these conclusions are largely independent of the form of the clock Hamiltonian.

Yearsley, J. M.; Downs, D. A.; Halliwell, J. J.; Hashagen, A. K. [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom)

2011-08-15

33

Earthquake location via the direct use of arrival time catalogues  

NASA Astrophysics Data System (ADS)

For many years location using local, regional or tele-seismic arrival time data, was based on the linearized (iterative) procedure first proposed by Geiger in 1912. In the last twenty years practitioners have increasing focused on issues such as grid search optimization methods, relative hypocentre location and uncertainty analysis. All location schemes depend on knowledge of the Earth's seismic structure, often in the form of a P-and S-wave speed velocity model. Increasingly users are turning to 3-D velocity models in order to take account of lateral variations in Earth structure over the relevant distance scales. An example is hypocentre location in 3-D tomographic models. Of course the situation is somewhat circular in that many of the velocity models are themselves derived using travel time data from located earthquakes. Here we explore a new style of location method which avoids the direct use of seismic velocity models, but instead makes use of a large arrival time database of previously recorded events to provide information on laterally heterogeneous earth structure. Two alternative schemes will be outlined. The first performs location by matching the pattern of arrivals between a new event and a previously located database. The second directly uses the data base to calculate Empirical Travel Times from a station to a source region, thereby taking the place of a velocity model in the location. Results with the two approaches are very encouraging. Using large earthquake databases in this way also results in a highly flexible procedure since new arrival time information can be continually added to the database as it becomes available.

Sambridge, M.; Nicholson, T.; Gudmundsson, O.

2003-04-01

34

Travel time tomography along the EPR axis using arrivals picked from downward continued MCS shot gathers  

NASA Astrophysics Data System (ADS)

We present tomographic models for closely spaced (~200 m) multichannel seismic (MCS) profiles collected in 2008 along the axis of the East Pacific Rise (EPR) at 9°41’ - 9°57’ N during cruise MGL0812. The investigated profiles target the locations of documented hydrothermal venting as well as the area where layer 2A is believed to thin north of 9°52’ N. We downward continued shot gathers collected during this 3D MCS survey to simulate the seismic sources and receivers being located near the seafloor. This allows for extracting travel time information from near-offset refractions that are normally obscured by the seafloor reflection. 1D modeling of shot gathers shows that, despite the thinness of seismic layer 2A at the ridge axis, some refracted arrivals that turn in layer 2A arrive ahead of the seafloor reflection and can be picked on the downward continued shot gathers. Thus, the velocity structure of both seismic layers 2A and 2B is constrained well and can be solved for during the inversion. After downward continuation, arrivals can be picked across most of the shot gather, from the near offsets to offsets of approximately 5 km; this is approximately twice as much as can be picked on the original shot gathers where refractions arrive before the seafloor reflection in only the farthest 2.5-3 km of the streamer. P-wave tomography models of the uppermost crust are obtained from the observed traveltimes using a regularized non-linear inversion scheme (i.e., FAST software, Zelt & Barton [1998]). We anticipate our results will yield insight on focused hydrothermal discharge and recent eruptive events at the axis of the EPR.

Newman, K. R.; Nedimovic, M.; Delescluse, M.; Canales, J.; Carbotte, S. M.; Carton, H. D.; Mutter, J. C.

2009-12-01

35

F-Wave Decomposition for Time of Arrival Profile Estimation  

Microsoft Academic Search

F-waves are distally recorded muscle responses that result from ldquobackfiringrdquo of motor neurons following stimulation of peripheral nerves. Each F-wave response is a superposition of several motor unit responses (F-wavelets). Initial deflection of the earliest F-wavelet defines the traditional F-wave latency (FWL) and earlier F-wavelet may mask F-wavelets traveling along slower (and possibly diseased) fibers. Unmasking the time of arrival

Zhixiu Han; Xuan Kong

2007-01-01

36

Effects of arrival time errors on traveltime tomography  

NASA Astrophysics Data System (ADS)

The ISC Bulletin is the most widely used data set for traveltime tomography since it comprises the largest collection of arrival times. The large number of stations and events gives the best ray path coverage of the Earth's mantle currently available, but the data also contain a considerable amount of noise. The effects of noise are supposedly reduced by averaging delay times for similar paths, choosing a suitable parametrization and damping the tomographic inversions. In this article we focus on two types of errors in body wave arrival times and estimate their effects on global tomographic models using synthetic tests. The first type of error stems from the finite reading precision of arrival times and is equivalent to a round-off error. This yields a random contribution to delay times. We show that the reading precision inferred here often does not coincide with that reported in the Bulletin. The influence on tomography of a reading precision of 1s or better is almost insignificant since (1) its variance is very small compared to the total variance of ISC delay times and (2) less than 5 per cent of that variance maps into the tomographic model. A few stations report some arrival times with an indicated reading precision of 0.1s that are in reality only picked to the closest 10s or 1min. This results in a S/N ratio much lower than 1 and these data should be removed. The second type of error causes systematic variations of delay times as a function of time. A large amount of this error maps into the tomographic model, but, luckily, the size of the error in the input data is one order of magnitude smaller than the standard deviation of the ISC delay times. A test reveals that the rms amplitude due to these systematic errors is between 4.2 per cent (0-35km depth) and 14.4 per cent (1800-2000km depth) of the model rms amplitude. This blurs the tomographic model to some degree but does not change the overall amplitude or shape of seismic anomalies.

Röhm, Axel H. E.; Bijwaard, Harmen; Spakman, Wim; Trampert, Jeannot

2000-07-01

37

The Effects of Predator Arrival Timing on Adaptive Radiation (Invited)  

NASA Astrophysics Data System (ADS)

Much of Earth’s biodiversity is thought to have arisen by adaptive radiation, the rapid diversification of a single ancestral species to fill a wide-variety of ecological niches. Both theory and empirical evidence have long supported competition for limited resources as a primary driver of adaptive radiation. While predation has also been postulated to be an important selective force during radiation, empirical evidence is surprisingly scant and its role remains controversial. However, two recent empirical studies suggest that predation can promote divergence during adaptive radiation. Using an experimental laboratory microcosm system, we examined how predator arrival timing affects the rate and extent of diversification during adaptive radiation. We varied the introduction timing of a protozoan predator (Tetrahymena thermophila) into populations of the bacteria Pseudomonas flourescens, which is known for its ability to undergo rapid adaptive radiation in aqueous microcosms. While our results show that predator arrival timing may have a significant impact on the rate, but not extent, of diversification, these results are tenuous and should be interpreted with caution, as the protozoan predators died early in the majority of our treatments, hampering our ability for comparison across treatments. Additionally, the abundance of newly derived bacterial genotypes was markedly lower in all treatments than observed in previous experiments utilizing this microbial experimental evolution system. To address these shortcomings, we will be repeating the experiment in the near future to further explore the impact of predator arrival timing on adaptive radiation. Smooth Morph and small-Wrinkly Spreader Pseudomonas flourescens diversification in the 96 hour treatment. Day 10, diluted to 1e-5.

Borden, J.; Knope, M. L.; Fukami, T.

2009-12-01

38

The design of real-time distributed arrival time control system in a cell manufacturing  

Microsoft Academic Search

In this study a real-time distributed arrival time control system in a cell manufacturing system for JIT-oriented production environment is designed. The distributed arrival time control (DATC) system is introduced to improve the scalability and practicality of the assembly cells manufacturing systems in heterarchical manufacturing systems. The simulation experiments are implemented to present the advantage of this new control system

Bin Gao; Jun Gong; Qian Li; Jiafu Tang

2011-01-01

39

Phenotype-dependent arrival time and its consequences in a migratory bird  

Microsoft Academic Search

Arrival times for migratory animals can be viewed as the result of an optimization process of costs and benefits of early arrival, and when the cost and benefit functions of early arrival depend on phenotypic quality, this will result in phenotype-dependent optimal arrival times. This hypothesis was tested for males of the migratory and sexually size-dimorphic barn swallow Hirundo rustica.

Anders Pape Møller

1994-01-01

40

Fluctuations of photon arrival times in free atmosphere  

NASA Astrophysics Data System (ADS)

In this paper we calculate the delay of the arrival times of visible photons on the focal plane of a telescope and its fluctuations as a function of local atmospheric conditions (temperature, pressure, chemical composition, seeing values) and telescope diameter. The aim of this paper is to provide a model for delay-time fluctuations accurate to the picosecond level, as required by several very high time resolution astrophysical applications, such as the comparison of radio and optical data on giant radio bursts from optical pulsars, and Hanbury Brown Twiss Intensity Interferometry with Cerenkov light detectors The results here presented have been calculated for the European Southern Observatory telescopes in Chile (New Technology Telescope (NTT), Very Large Telescope (VLT), European Extremely Large Telescope (E-ELT), but the model can be easily applied to other sites and telescope diameters. Finally, we describe a theoretical mathematical model for calculating the Fried radius through the study of delay-time fluctuations.

Cavazzani, S.; Ortolani, S.; Barbieri, C.

2012-01-01

41

Time dependent solution of a queueing problem with correlated batch arrivals and general service time distribution  

Microsoft Academic Search

This paper considers the transient behaviour of queueing problem in which (i) the arrivals occur in batches of variable size (ii) the arrival and no arrival of a batch at two consecutive transition marks are correlated (iii) the service time distribution for each, unit is general with probability density functionD(x). TheLaplace transform of various probability generating functions of queue length

K. Murari

1972-01-01

42

Marginal picture of quantum dynamics related to intrinsic arrival times  

SciTech Connect

We introduce a marginal picture of the evolution of quantum systems, in which the representation vectors are the quantities that evolve and operators and wave packets remain static. The representation vectors can be seen as probe functions that are the evolution of a {delta} function with initial support on q=X in coordinate space. This picture of the dynamics is suited for the determination of intrinsic arrival distributions for quantum systems, providing a clear physical meaning to the 'time eigenstates' used in these calculations. We also analyze Galapon et al.'s 'confined time eigenstates' [Phys. Rev. Lett. 93, 180406 (2004)] from this point of view, and propose alternative probe functions for confined systems without the need of a quantized time.

Torres-Vega, Gabino [Physics Department, Cinvestav, Apartado Postal 14-740, 07000 Mexico City, Distrito Federal (Mexico)

2007-09-15

43

Psychophysics: how fielders arrive in time to catch the ball.  

PubMed

Tracking an object moving in three dimensions, whether as an insect pursuing a mate on the wing or as a batsman aiming to hit an approaching ball, provides the spatial and temporal information needed to intercept it. Here we show how fielders use such tracking signals to arrive at the right place in time to catch a ball - they run so that their angle of gaze elevation to the ball increases at a decreasing rate while their horizontal gaze angle to the ball increases at a constant rate (unless the distance to be run is small). Allowing the horizontal angle to increase minimizes the acceleration that the fielder must achieve to reach the interception point at the same time as the ball. PMID:14628038

McLeod, Peter; Reed, Nick; Dienes, Zoltan

2003-11-20

44

Rounding of Arrival and Departure Times in Travel Surveys: An Interpretation in Terms of Scheduled Activities  

Microsoft Academic Search

In travel surveys most respondents apply rounding of departure and arrival times to multiples of 5, 15 and 30 minutes: in the annual Dutch travel survey about 85-95 percent of all reported times are 'round' ones. We estimate rounding models for departure and arrival times. The model allows one to compute the probability that a reported arrival time m (say

Piet Rietveld

2001-01-01

45

Arrival timing and hematological parameters in Gray Catbirds ( Dumetella carolinensis )  

Microsoft Academic Search

Early arrival at the breeding grounds for migratory birds is associated with greater reproductive success. According to the\\u000a condition-dependent arrival hypothesis, only those individuals in superior physiological condition are able to bear the costs\\u000a (e.g., poor environmental conditions, limited food availability) of early arrival. Condition has usually been measured in\\u000a terms of energy reserves or mass but other physiological measures

Margret I. HatchRobert; Robert J. Smith; Jennifer C. Owen

2010-01-01

46

Simulation-based performance of assembly cells with real-time distributed arrival time control system  

Microsoft Academic Search

This paper presents the results of a simulation-based performance of assembly cells (AC) manufacturing systems with real-time distributed arrival time for JIT-oriented production environment. This research adds to the sparse body of the literature in this area. In this paper, the distributed arrival time control (DATC) systems are used to make assembly cells manufacturing systems scalable and practical in heterarchical

Gong Jun; Vittaldas V. PRABHU; Tang Jiafu

2010-01-01

47

Upper mantle anisotropy beneath Australia and Tahiti from P wave polarization: Implications for real-time earthquake location  

NASA Astrophysics Data System (ADS)

We report measurements of long-period P wave polarization (Ppol) in Australia and Tahiti made by combining modeling of the polarization deviation and harmonic analysis. The analysis of the deviation of the horizontal polarization of the P wave as a function of event back azimuth may be used to obtain information about (1) sensor misorientation, (2) dipping discontinuities, (3) seismic anisotropy, and (4) velocity heterogeneities beneath a seismic station. The results from harmonic analysis and a grid search using Snell's law suggest the presence of a dipping seismic discontinuity beneath stations CTAO and CAN in Australia. These results are consistent with published receiver function studies for these stations. The Ppol fast axis orientation is close to the N-S absolute plate motion direction at station TAU (Tasmania), which may be due to plate-motion-driven alignment of olivine crystals in the asthenosphere. Interestingly, measurements of SKS splitting at Tahiti (French Polynesia) show an apparent isotropy, whereas an inversion of Ppol observations at PPTL seismic station located in Tahiti suggests the presence of two anisotropic layers. The fast axis azimuth is oriented E-W in the upper layer, and it is close to the NW-SE orientation in the lower layer. Since Ppol orientations are used for real-time earthquake locations, especially in poorly instrumented areas such as the South Pacific, we show that the bias from anisotropy and sensor misorientation determined here can be corrected to improve the location accuracy, which yields fundamental data for rapid location necessary for effective tsunami warning.

Fontaine, Fabrice R.; Barruol, Guilhem; Kennett, Brian L. N.; Bokelmann, Goetz H. R.; Reymond, Dominique

2009-03-01

48

Change in P wave terminal force and systolic time intervals during exercise in patients with coronary artery disease.  

PubMed

P wave terminal force (Ptf) and systolic time intervals (STI) were determined non-invasively from electrocardiogram, phonocardiogram and carotid pulse wave in fifteen men with coronary artery disease, before and during exercise. Left ventricular end diastolic pressure (LVEDP) and stroke volume (SV) were determined at catheterization simultaneously with the non-invasive recordings. Pre-ejection period (PEP) shortened in eleven patients, left ventricular ejection time (LVET) shortened in eight and Ptf and PEP/LVET decreased in ten patients during exercise. Ptf was significantly correlated to LVEDP both at rest (r = -0.66) and during exercise (r = -0.79). The change in Ptf and LVEDP was less correlated (r = -0.52). The change in LVET (r = -0.50), the change in PEP (r = 0.62) and in the index PEP/LVET (r = 0.65) was correlated to the change in SV. The use of both Ptf and STI may be of value in estimating left ventricular function during exercise in patients with coronary artery disease. PMID:705243

Brubakk, O; Rossland, G A; Pedersen, O M

1978-10-01

49

Predicting the 1AU arrival times of coronal mass ejections  

Microsoft Academic Search

We describe an empirical model to predict the 1-AU arrival of coronal mass ejections (CMEs). This model is based on an effective interplanetary (IP) acceleration described by Gopalswamy et al. [2000b] that the CMEs are subject to, as they propagate from the Sun to 1 AU. We have improved this model (1) by minimizing the projection effects (using data from

Nat Gopalswamy; Alejandro Lara; Seiji Yashiro; Mike L. Kaiser

2001-01-01

50

Theoretical P-Wave Travel Times, Magnitude 6.7 Island of Hawaii, Hawaii, Sunday, October 15, 2006 at 17:07:49 UTC  

NSDL National Science Digital Library

This page from the USGS displays the predicted travel times of the P-Waves originating from the 6.7 magnitude earthquake that struck near Puako, HI on October 15th, 2006. There is a table of data as well as the map visualization.

Program, Earthquake H.; Usgs

51

A COMPARISON OF COLLAPSING AND PRECISE ARRIVAL-TIME MAPPING OF MICROSEISMICITY  

SciTech Connect

In this paper they compare the improvements in microseismic location images obtained using precise arrival times with that obtained by the collapsing technique. They first collapse the initial locations for a hydraulic-fracture data set from the Carthage Cotton Valley gas field, they then use the precise-arrival-time locations as measure for the effectiveness of the collapsing. Finally, they examine the changes when applying collapsing to the precise-arrival-time locations.

RUTLEDGE, JAMES T. [Los Alamos National Laboratory; JONES, ROB H. [Los Alamos National Laboratory

2007-01-05

52

P-wave velocity changes in freezing hard low-porosity rocks: a laboratory-based time-average model  

NASA Astrophysics Data System (ADS)

P-wave refraction seismics is a key method in permafrost research but its applicability to low-porosity rocks, that constitute alpine rock walls, has been denied in prior studies. These explain p-wave velocity changes in freezing rocks exclusively due to changing velocities of pore infill, i.e. water, air and ice. In existing models, no velocity increase is expected for low-porosity bedrock. We postulate, that mixing laws apply for high-porosity rocks, but freezing in confined space in low-porosity bedrock also alters physical rock matrix properties. In the laboratory, we measured p-wave velocities of 22 decimeter-large low-porosity (<6 %) metamorphic, magmatic and sedimentary permafrost rock samples with a natural texture (>100 micro-fissures) from 25 °C to -15 °C in 0.3 °C increments close to the freezing point. P-wave velocity increases by 7-78 % when freezing parallel to cleavage/bedding and matrix velocity increases from 5-59 % coincident to an anisotropy decrease in most samples. The expansion of rigid bedrock upon freezing is restricted and ice pressure will increase matrix velocity and decrease anisotropy while changing velocities of the pore infill are insignificant. Here, we present a modified Timur's 2-phase equation implementing changes in matrix velocity dependent on lithology and demonstrate the physical basis for refraction seismics in low-porosity bedrock.

Draebing, D.; Krautblatter, M.

2012-02-01

53

A particle filtering approach for spatial arrival time tracking in ocean acoustics.  

PubMed

The focus of this work is on arrival time and amplitude estimation from acoustic signals recorded at spatially separated hydrophones in the ocean. A particle filtering approach is developed that treats arrival times as "targets" and tracks their "location" across receivers, also modeling arrival time gradient. The method is evaluated via Monte Carlo simulations and is compared to a maximum likelihood estimator, which does not relate arrivals at neighboring receivers. The comparison demonstrates a significant advantage in using the particle filter. It is also shown that posterior probability density functions of times and amplitudes become readily available with particle filtering. PMID:21682358

Jain, Rashi; Michalopoulou, Zoi-Heleni

2011-06-01

54

Transition from discrete to continuous time-of-arrival distribution for a quantum particle  

SciTech Connect

We show that the Kijowski distribution for time of arrivals in the entire real line is the limiting distribution of the time-of-arrival distribution in a confining box as its length increases to infinity. The dynamics of the confined time-of-arrival eigenfunctions is also numerically investigated and demonstrated that the eigenfunctions evolve to have point supports at the arrival point at their respective eigenvalues in the limit of arbitrarily large confining lengths, giving insight into the ideal physical content of the Kijowsky distribution.

Galapon, Eric A. [Theoretical Physics Group, National Institute of Physics, University of the Philippines, Diliman, Quezon City, 1101 (Philippines); Departamento de Quimica Fisica, UPV-EHU, Apdo. 644, 48080 Bilbao (Spain); Theoretical Physics, The University of the Basque Country, Apdo. 644, 48080 Bilbao (Spain); Delgado, F.; Muga, J. Gonzalo [Departamento de Quimica Fisica, UPV-EHU, Apdo. 644, 48080 Bilbao (Spain); Egusquiza, Inigo [Theoretical Physics, University of the Basque Country, Apdo. 644, 48080 Bilbao (Spain)

2005-10-15

55

Predicting Bus Arrival Time on the Basis of Global Positioning System Data  

Microsoft Academic Search

The ability to obtain accurate predictions of bus arrival time on a real-time basis is a vital element to both bus operations control and passenger information systems. Several studies had been devoted to this arrival time prediction problem; however, few resulted in completely satisfactory algorithms. This paper presents a new system that can be used to predict the expected bus

Dihua Sun; Hong Luo; Liping Fu; Weining Liu; Xiaoyong Liao; Min Zhao

2007-01-01

56

Entry Times in Queues with Endogenous Arrivals: Dynamics of Play on the Individual and Aggregate Levels  

Microsoft Academic Search

This chapter considers arrival time and staying out decisions in several variants of a queueing game characterized by endogenously determined arrival times, simultaneous play, finite populations of symmetric players, discrete strategy spaces, and fixed starting and closing times of the service facility. Experimental results show 1) consistent patterns of behavior on the aggregate level in all the conditions that are

J. Neil Bearden; Amnon Rapoport; Darryl A. Seale

57

Least squares arrival time estimators for photons detected using a photomultiplier tube  

SciTech Connect

In many applications employing photodetectors, the determination of the arrival time of individual photons at the surface of the detector can be used to localize the photon source. For the case where the photon intensity is extremely low, the most common type of detector used is the photomultiplier tube. The optimal arrival time estimators for single and multiple photons arriving at the surface of a photomultiplier tube are developed in this paper. The optimal timing estimator considered is a weighted non-linear least squares estimate of the detection time for a high gain PMT with gaussian statistics. The lease squares estimator is constructed using the mean and covariance function of the photomultiplier output for different arrival times. The RMS error for the leant squares arrival time estimator was calculated and compared with the performance of other common timing estimators, including the first photoelectron timing estimators, using a Burle/RCE 8850 PMT.

Petrick, N.; Hero, A.O. III; Clinthorne, N.H.; Rogers, W.L. (Michigan Univ., Ann Arbor, MI (United States). Dept. of Electrical Engineering and Computer Science)

1992-08-01

58

Uncertainty in Phase Arrival Time Picks for Regional Seismic Events: An Experimental Design.  

National Technical Information Service (NTIS)

The detection and timing of seismic arrivals play a critical role in the ability to locate seismic events, especially at low magnitude. Errors can occur with the determination of the timing of the arrivals, whether these errors are made by automated proce...

A. A. Velasco C. J. Young D. N. Anderson

2001-01-01

59

Accuracy of Judging Time to Arrival: Effects of Modality, Trajectory, and Gender  

Microsoft Academic Search

Observers' accuracy in using time-to-arrival (Ta) information was examined in 4 experiments. The issues included use of visual vs. acoustic Ta information, use of acoustic Ta information by blind Ss, use of Ta information controlling for velocity, and effects of angle of approach and arrival time on judgment accuracy. Visual information was used more efficiently than audiovisual and auditory information.

William Schiff; Rivka Oldak

1990-01-01

60

A Homogeneous PCS network with Markov Call Arrival Process and Phase Type Cell Residence Time  

Microsoft Academic Search

In this paper, the arrival of calls (i.e., new and handoff calls) in a personal communications services (PCS) network is modeled by a Markov arrival process (MAP) in which we allow correlation of the interarrival times among new calls, among handoff calls, as well as between these two kinds of calls. The PCS network consists of homogeneous cells and each

Attahiru Sule Alfa; Wei Li

2002-01-01

61

Optimal time advance in terminal area arrivals: Throughput vs. fuel savings  

Microsoft Academic Search

The current operational practice in scheduling air traffic arriving at an airport is to adjust flight schedules by delay, i.e. a postponement of an aircraft's arrival at a scheduled location, to manage safely the FAA-mandated separation constraints between aircraft. To meet the observed and forecast growth in traffic demand, however, the practice of time advance (speeding up an aircraft toward

Alexander V. Sadovsky; Harry N. Swenson; William B. Haskell; Jasenka Rakas

2011-01-01

62

Passenger wait time perceptions at bus stops: empirical results and impact on evaluating real-time bus arrival information  

Microsoft Academic Search

This study quantifies the relationship between perceived and actual waiting times experienced by passengers awaiting the arrival of a bus at a bus stop. Understanding such a relationship would be useful in quantifying the value of providing real-time information to passengers on the time until the next bus is expected to arrive at a bus stop. Data on perceived and

Rabi G. Mishalani; Mark M. McCord; John Wirtz

2006-01-01

63

Localization of Wireless Emitters Based on the Time Difference of Arrival (TDOA) and Wavelet Denoising.  

National Technical Information Service (NTIS)

The localization of mobile wireless communication units using time difference of arrival (TDOA) is studied. The wavelet transform is used to increase the accuracy of TDOA estimation. Several denoising techniques based on the wavelet transform are presente...

R. D. Hippenstiel T. T. Ha U. Aktas

1999-01-01

64

Effects of fluctuations in the quantity of work arriving on waiting time, idle time and rate of losing customers  

Microsoft Academic Search

In a job shop, the intervals between job arrivals and the job processing times fluctuate and cannot be forecast. When many jobs (customers) arrive at a job shop at the same time, some customers may not place an order because they do not want to wait. To prevent such a situation, the job shop may temporarily increase the process capacity,

SEIJI KUROSU

1986-01-01

65

Sex Differences in Accuracy and Precision When Judging Time to Arrival: Data from Two Internet Studies  

Microsoft Academic Search

We report two Internet studies that investigated sex differences in the accuracy and precision of judging time to arrival.\\u000a We used accuracy to mean the ability to match the actual time to arrival and precision to mean the consistency with which each participant made their judgments. Our task was presented as a computer game in which\\u000a a toy UFO moved

Geoff SandersKamila Sinclair; Kamila Sinclair

66

Two-Step Time of Arrival Estimation for Pulse-Based Ultra-Wideband Systems  

Microsoft Academic Search

In cooperative localization systems, wireless nodes need to exchange accurate position-related information such as time-of-arrival (TOA) and angle-of-arrival (AOA), in order to obtain accu- rate location information. One alternative for providing accurate position-related information is to use ultra-wideband (UWB) signals. The high time resolution of UWB signals presents a potential for very accurate positioning based on TOA estimation. However, it

Sinan Gezici; Zafer Sahinoglu; Andreas Molisch; Hisashi Kobayashi; H. Vincent Poor

2009-01-01

67

A combined first-arrival travel time and reflection coherency optimization approach to velocity estimation  

Microsoft Academic Search

We present a nonlinear optimization method for two-dimensional velocity estimation in strongly heterogeneous media. We achieve this by designing a simulated-annealing algorithm to simultaneously maximize reflection coherency as well as minimize first-arrival travel time residuals. Relatively shallow velocity structure is constrained by first-arrival times, while coherency information from deeper reflections (if present) helps constrain deeper velocities. Prestack migration using the

Sathish K. Pullammanappallil; John N. Louie

1997-01-01

68

Population-scale drivers of individual arrival times in migratory birds.  

PubMed

1. In migratory species, early arrival on the breeding grounds can often enhance breeding success. Timing of spring migration is therefore a key process that is likely to be influenced both by factors specific to individuals, such as the quality of winter and breeding locations and the distance between them, and by annual variation in weather conditions before and during migration. 2. The Icelandic black-tailed godwit Limosa limosa islandica population is currently increasing and, throughout Iceland, is expanding into poorer quality breeding areas. Using a unique data set of arrival times in Iceland in different years for individuals of known breeding and wintering locations, we show that individuals breeding in lower quality, recently occupied and colder areas arrive later than those from traditionally occupied areas. The population is also expanding into new wintering areas, and males from traditionally occupied winter sites also arrive earlier than those occupying novel sites. 3. Annual variation in timing of migration of individuals is influenced by large-scale weather systems (the North Atlantic Oscillation), but between-individual variation is a stronger predictor of arrival time than the NAO. Distance between winter and breeding sites does not influence arrival times. 4. Annual variation in timing of migration is therefore influenced by climatic factors, but the pattern of individual arrival is primarily related to breeding and winter habitat quality. These habitat effects on arrival patterns are likely to operate through variation in individual condition and local-scale density-dependent processes. Timing of migration thus appears to be a key component of the intricate relationship between wintering and breeding grounds in this migratory system. PMID:16922847

Gunnarsson, Tómas G; Gill, Jennifer A; Atkinson, Philip W; Gélinaud, Guillaume; Potts, Peter M; Croger, Ruth E; Gudmundsson, Gudmundur A; Appleton, Graham F; Sutherland, William J

2006-09-01

69

Seattle required time of arrival (RTA) flight trials  

Microsoft Academic Search

• The 2010 Seattle RTA trials demonstrated the following: — When RTA function is engaged, the current generation of Boeing 737 avionics can meet the assigned time over the meter fix within 20 seconds under non-metering conditions (where delays are under 2 minutes). — Current generation Boeing 737 avionics can meet ATC speed and altitude constraints through use of modified

Tom Becher

2011-01-01

70

Different motion cues are used to estimate time-to-arrival for frontoparallel and looming trajectories  

PubMed Central

Estimation of time-to-arrival for moving objects is critical to obstacle interception and avoidance, as well as to timing actions such as reaching and grasping moving objects. The source of motion information that conveys arrival time varies with the trajectory of the object raising the question of whether multiple context-dependent mechanisms are involved in this computation. To address this question we conducted a series of psychophysical studies to measure observers’ performance on time-to-arrival estimation when object trajectory was specified by angular motion (“gap closure” trajectories in the frontoparallel plane), looming (colliding trajectories, TTC) or both (passage courses, TTP). We measured performance of time-to-arrival judgments in the presence of irrelevant motion, in which a perpendicular motion vector was added to the object trajectory. Data were compared to models of expected performance based on the use of different components of optical information. Our results demonstrate that for gap closure, performance depended only on the angular motion, whereas for TTC and TTP, both angular and looming motion affected performance. This dissociation of inputs suggests that gap closures are mediated by a separate mechanism than that used for the detection of time-to-collision and time-to-passage. We show that existing models of TTC and TTP estimation make systematic errors in predicting subject performance, and suggest that a model which weights motion cues by their relative time-to-arrival provides a better account of performance.

Calabro, Finnegan J.; Beardsley, Scott A.; Vaina, Lucia M.

2012-01-01

71

Multi source- multi receiver processing for arrival time optimization of microseismic borehole array data  

NASA Astrophysics Data System (ADS)

Together with a realistic velocity model and a well-designed seismic monitoring system, the quality of arrival time measurements is one of the most important factors to limit the uncertainty in the earthquake location problem. The accuracy of time picks is generally increased by exloiting the waveform similarity. This allows to calculate more precise differential arrival times which replace or improve the original arrival time picks. Typically, the waveform data are processed either event-based or receiver-based. Here, we propose to combine the receiver- oriented and the event- oriented approaches to optimize simultaneously arrival time picks for micro seismic events recorded by multi-level borehole arrays. The method extends existing concepts by cross-linking waveforms of different events in a multiplet recorded by closely spaced receivers, and the increased interconnectivity of waveforms also increases the consistency of the arrival time data. We apply the method to a hydraulic fracturing experiment, where micro seismic data were recorded by two inclined borehole arrays consisting of 30 receivers. It is shown that the picking accuracy is significantly improved compared to the original picks and also compared to the adjusted picks obtained from single receiver based processing. We also compare the improved event relocations with the original locations.

Kummerow, Joern

2013-04-01

72

Scaling Behavior of the First Arrival Time of a Random-Walking Magnetic Domain  

SciTech Connect

We report a universal scaling behavior of the first arrival time of a traveling magnetic domain wall into a finite space-time observation window of a magneto-optical microscope enabling direct visualization of a Barkhausen avalanche in real time. The first arrival time of the traveling magnetic domain wall exhibits a nontrivial fluctuation and its statistical distribution is described by universal power-law scaling with scaling exponents of 1.34 {+-} 0.07 for CoCr and CoCrPt films, despite their quite different domain evolution patterns. Numerical simulation of the first arrival time with an assumption that the magnetic domain wall traveled as a random walker well matches our experimentally observed scaling behavior, providing an experimental support for the random-walking model of traveling magnetic domain walls.

Im, M.-Y.; Lee, S.-H.; Kim, D.-H.; Fischer, P.; Shin, S.-C.

2008-02-04

73

Scaling behavior of the first arrival time of a random-walking magnetic domain.  

PubMed

We report a universal scaling behavior of the first arrival time of a traveling magnetic domain wall into a finite space-time observation window of a magneto-optical microscope enabling direct visualization of a Barkhausen avalanche in real time. The first arrival time of the traveling magnetic domain wall exhibits a nontrivial fluctuation and its statistical distribution is described by universal power-law scaling with scaling exponents of 1.34+/-0.07 for CoCr and CoCrPt films, despite their quite different domain evolution patterns. Numerical simulation of the first arrival time with an assumption that the magnetic domain wall traveled as a random walker well matches our experimentally observed scaling behavior, providing an experimental support for the random-walking model of traveling magnetic domain walls. PMID:18518241

Im, M-Y; Lee, S-H; Kim, D-H; Fischer, P; Shin, S-C

2008-04-23

74

Continuous measurement of the arrival times of x-ray photon sequence  

NASA Astrophysics Data System (ADS)

In order to record x-ray pulse profile for x-ray pulsar-based navigation and timing, this paper presents a continuous, high-precision method for measuring arrival times of photon sequence with a common starting point. In this method, a high stability atomic clock is counted to measure the coarse time of arrival photon. A high resolution time-to-digital converter is used to measure the fine time of arrival photon. The coarse times and the fine times are recorded continuously and then transferred to computer memory by way of memory switch. The pulse profile is obtained by a special data processing method. A special circuit was developed and a low-level x-ray pulse profile measurement experiment system was setup. The arrival times of x-ray photon sequence can be consecutively recorded with a time resolution of 500 ps and the profile of x-ray pulse was constructed. The data also can be used for analysis by many other methods, such as statistical distribution of photon events per time interval, statistical distribution of time interval between two photon events, photon counting histogram, autocorrelation and higher order autocorrelation.

Yan, Qiurong; Zhao, Baosheng; Sheng, Lizhi; Liu, Yong'an

2011-05-01

75

Continuous measurement of the arrival times of x-ray photon sequence  

SciTech Connect

In order to record x-ray pulse profile for x-ray pulsar-based navigation and timing, this paper presents a continuous, high-precision method for measuring arrival times of photon sequence with a common starting point. In this method, a high stability atomic clock is counted to measure the coarse time of arrival photon. A high resolution time-to-digital converter is used to measure the fine time of arrival photon. The coarse times and the fine times are recorded continuously and then transferred to computer memory by way of memory switch. The pulse profile is obtained by a special data processing method. A special circuit was developed and a low-level x-ray pulse profile measurement experiment system was setup. The arrival times of x-ray photon sequence can be consecutively recorded with a time resolution of 500 ps and the profile of x-ray pulse was constructed. The data also can be used for analysis by many other methods, such as statistical distribution of photon events per time interval, statistical distribution of time interval between two photon events, photon counting histogram, autocorrelation and higher order autocorrelation.

Yan Qiurong; Sheng Lizhi [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences 710119, Xi'an (China); Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Zhao Baosheng; Liu Yong'an [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences 710119, Xi'an (China)

2011-05-15

76

Observability of the arrival time distribution using spin-rotator as a quantum clock  

NASA Astrophysics Data System (ADS)

An experimentally realizable scheme is formulated which can test any postulated quantum mechanical approach for calculating the arrival time distribution. This is specifically illustrated by using the modulus of the probability current density for calculating the arrival/transit time distribution of spin-1/2 neutral particles at the exit point of a spin-rotator (SR) which contains a constant magnetic field. Such a calculated time distribution is then used for evaluating the distribution of spin orientations along different directions for these particles emerging from the SR. Based on this, the result of spin measurement along any arbitrary direction for such an ensemble is predicted.

Pan, Alok Kumar; Ali, Md. Manirul; Home, Dipankar

2006-04-01

77

Techniques for Measuring Arrival Times of Pulsar Signals 1: DSN Observations from 1968 to 1980.  

National Technical Information Service (NTIS)

Techniques used in the ground based observations of pulsars are described, many of them applicable in a navigation scheme. The arrival times of the pulses intercepting Earth are measured at time intervals from a few days to a few months. Low noise, wide b...

G. S. Downs P. E. Reichley

1980-01-01

78

Disclosing hidden information in the quantum Zeno effect: Pulsed measurement of the quantum time of arrival  

NASA Astrophysics Data System (ADS)

Repeated measurements of a quantum particle to check its presence in a region of space was proposed long ago [G. R. Allcock, Ann. Phys. 53, 286 (1969)] as a natural way to determine the distribution of times of arrival at the orthogonal subspace, but the method was discarded because of the quantum Zeno effect: in the limit of very frequent measurements the wave function is reflected and remains in the original subspace. We show that by normalizing the small bits of arriving (removed) norm, an ideal time distribution emerges in correspondence with a classical local-kinetic-energy distribution.

Echanobe, J.; Del Campo, A.; Muga, J. G.

2008-03-01

79

Sensitivity and consistency studies of muon arrival time distributions measured by KASCADE  

NASA Astrophysics Data System (ADS)

Using the facilities of the KASCADE Central Detector EAS muon arrival time distributions, observed with reference to the arrival time of the first locally registered muon, and their correlations with other EAS observables have been investigated at different distances R? from the shower axis. Invoking detailed Monte Carlo simulations non-parametric multivariate even-by-event analyses have been performed for an estimate of the primary mass composition. The consistency of the Monte Carlo simulations is studied by comparing the primary mass composition results inferred from observations at different R? and different muon multiplicity thresholds nth.

Badea, A. F.; Antonia, T.; Apelb, W. D.; Bekk, K.; Bercuci, A.; Blümer, H.; Bozdog, H.; Brancus, I. M.; Büttner, C.; Chilingarian, A.; Daumiller, K.; Doll, P.; Engler, J.; Feßler, F.; Gils, H. J.; Glasstetter, R.; Haeusler, R.; Haungs, A.; Heck, D.; Hörandel, J. R.; Iwan, A.; Kampert, K.-H.; Klages, H. O.; Maier, G.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Müller, M.; Obenland, R.; Oehlschläger, J.; Ostapchenkoa, S.; Petcu, M.; Rebel, H.; Risse, M.; Roth, M.; Schatz, G.; Schieler, H.; Scholz, J.; Thouw, T.; Ulrich, H.; Weber, J. H.; Weindl, A.; Wentz, J.; Wochele, J.; Zabierowski, J.

2003-07-01

80

Automatic re-picking and re-weighting of first arrival times from the Italian Seismic Network waveforms database  

NASA Astrophysics Data System (ADS)

The high resolution P-wave tomography of the Italian Peninsula and surrounding regions from crustal to upper mantle depths is the aim of a joint project between INGV (Roma) and ETH (Zurich). The project is subdivided into two steps, first of which is to establish a 3D P-wave velocity model for the crust, using both passive and active seismic sources. Getting a reliable high resolution model is of fundamental importance since the 3D crustal model will be used in the second step to correct teleseismic travel times following a method successfully applied in the last years to the Alps (Waldhauser et al. 2002). In the present work we focus on the passive sources dataset (local and regional events) to complement the CSS crustal information. Our keywords being "high-resolution" and "detailed model" we followed the idea, based on the experience of previous works in this area, that a large number of high quality pickings and a high level of consistency in the dataset represent the first goals. The Italian region (Western Mediterranean) is characterized by a high rate of seismicity including important seismic sequences. Since 1988, digital recordings for about 40,000 local and regional earthquakes are available, which INGV bulletin readings have been used in previous local earthquake tomography works. To increase the sampling power and to better locate some border events we will integrate Italian National Seismic Network data with recordings from other local and regional networks. Due to the large amount of data thus collected, a manual re-picking of all first arrivals would ask for a too long time while it would not prevent from human readings errors and inconsistencies. This would partially contrast the positive effect of a high-quality pickings. To meet the quality and consistency requests, we applied an advanced automatic re-picking procedure, the MannekenPick (MP), recently developed by F. Aldersons as a fast, reliable and "consistent" picker. We tested the whole procedure on a subset of 700 waveforms that can be considered to be representative of the Italian seismicity recordings by the INGV seismic network. In this work we present the results of these tests and of the application of MP to INGV database in "production mode". Tests and preliminary results of MP from local network data (OGS, Trieste, and ERGA, Tuscany) are included.

di Stefano, R.; Amato, A.; Aldersons, F.; Kissling, E.

2002-12-01

81

An ultrafast quantum random number generator with provably bounded output bias based on photon arrival time measurements  

NASA Astrophysics Data System (ADS)

We report the implementation of a quantum random number generator based on photon arrival times. Due to fast and high resolution timing we are able to generate the highest bitrate of any current generator based on photon arrival times. Bias in the raw data due to the exponential distribution of the arrival times is removed by postprocessing which is directly integrated in the field programmable logic of the timing electronics.

Wahl, Michael; Leifgen, Matthias; Berlin, Michael; Röhlicke, Tino; Rahn, Hans-Jürgen; Benson, Oliver

2011-04-01

82

Inversion of 3-D crustal P-wave velocity structure in Ningxia and its neighborhood by using direct, reflected and refracted waves  

Microsoft Academic Search

In this paper, simultaneous inversions for hypocentres and three-dimensional (3-D) crustral P-wave velocity structure of Ningxia\\u000a and its neighborhood are performed, by using the data of direct P wave, reflected Pm and refracted Pn phases from the Moho\\u000a discontinuity. The number of arrival-time applied to the inversion is 11 816 total, which are recorded by the Seismic Station\\u000a Network of

Yan-Long Jin; Ming-Zhi Yang; Wei-Ming Zhao; Xing-Jue Shi; Wen-Jun Xu; Guang-Quan Li

1999-01-01

83

Image processing methods for predicting the time of cloud shadow arrivals to photovoltaic systems  

Microsoft Academic Search

This document presents a combination of image processing tools used for detecting clouds from sky images and for predicting the arrival time of cloud shadows to an area of interest, for example an area of solar panels. Solar panels are used to produce energy from the sun in areas without access to electricity from central power plants and are increasingly

Yazmin Najera; Doug R. Reed; W. Mack Grady

2011-01-01

84

P-wave Velocity Structure in the Lowermost 600 km of the Mantle beneath Western Pacific Inferred from Travel Times and Amplitudes Observed with NECESSArray  

NASA Astrophysics Data System (ADS)

NECESSArray is a large-scale broadband seismic array deployed in northeastern China. Although its primary aims are to reveal the fate of subducted Pacific plate and to address several tectonic issues, it is also useful as a large aperture array to look at deep Earth. Here, we examine P-wave travel times observed with NECESSArray to determine P-wave velocity structure in the lower mantle beneath Western Pacific. Relative travel times with respect to those predicted by PREM are measured on short period seismograms from 15 earthquakes occurred in Tonga, Fiji, and Kermadec regions since Sep. 2009 to April 2010, so far, by using adaptive stacking method [Rawlinson and Kennett, 2004]. The residuals are defined as fluctuations with respect to an average of the whole array for each event. Station correction is defined as a median value of the residuals at each station. After applying the station corrections and distance corrections for the surface focus, we synthesize all the residuals and finally obtain a characteristic residual variation as a function of epicentral distance from 80 to 95 degrees. The travel time residuals show an inverted V-pattern with the maximum delay of 0.2 s at 87 degrees compared from a reference level at 80 and 95 degrees. To simply interpret this pattern through Herglotz-Wiechert inversion, we assume that the velocity structure above 600 km above the core-mantle boundary (CMB) is identical to PREM and find that the difference of the P-wave velocities from those of PREM gradually increase with depth, and reach the maximum velocity reduction of 0.15% and suddenly increase to those being identical to PREM at 270 km above the CMB. Thickness of a small velocity gradient layer at the base of the mantle is reduced to be 130 km instead of 150 km that is PREM's value. P-wave amplitudes are used as supplementary data. Station corrections for amplitude are inferred from 6 deep Fiji earthquakes in the distance range 75 to 90 degrees, in which focal mechanisms are corrected with the Global CMT solutions and theoretical amplitude variations due to elastic and anelastic structures with the reflectivity method are considered. The corrected amplitude that are sensitive to the velocity structure just the above the CMB are obtained from 3 earthquakes occurred in Kermadec islands (their latitudes vary from 29.2 S to 31.6S) in the distance range from 86 to 96 degrees. Although they are closely located each other, the data from the southernmost event indicate significantly rapid amplitude decay, and those from the northernmost event indicate moderate amplitude decay, those from the middle event show a large scatter. This observation suggests that a rapid horizontal change of the D" structure exists in the southwestern edge of the sampled region.

Tanaka, S.; Kawakatsu, H.; Chen, Y. J.; Ning, J.; Grand, S. P.; Niu, F.; Obayashi, M.; Miyakawa, K.; Idehara, K.; Tonegawa, T.; Iritani, R.; Necessarray Project Team

2011-12-01

85

p-Wave Polaron  

NASA Astrophysics Data System (ADS)

We consider a single impurity immersed in a Fermi sea close to an interspecies p-wave Feshbach resonance. We calculate its dispersion and spectral response to a radio frequency pulse. In a magnetic field, dipolar interactions split the resonance and two novel features with respect to the s-wave case appear: a third polaron branch in the excitation spectrum, in addition to the usual attractive and repulsive ones; and an anisotropic dispersion of the impurity characterized by different effective masses perpendicular and parallel to the magnetic field. The anisotropy can be tuned as a function of the field strength and the two effective masses may have opposite signs, or become smaller than the bare mass.

Levinsen, Jesper; Massignan, Pietro; Chevy, Frédéric; Lobo, Carlos

2012-08-01

86

p-Wave polaron.  

PubMed

We consider a single impurity immersed in a Fermi sea close to an interspecies p-wave Feshbach resonance. We calculate its dispersion and spectral response to a radio frequency pulse. In a magnetic field, dipolar interactions split the resonance and two novel features with respect to the s-wave case appear: a third polaron branch in the excitation spectrum, in addition to the usual attractive and repulsive ones; and an anisotropic dispersion of the impurity characterized by different effective masses perpendicular and parallel to the magnetic field. The anisotropy can be tuned as a function of the field strength and the two effective masses may have opposite signs, or become smaller than the bare mass. PMID:23006381

Levinsen, Jesper; Massignan, Pietro; Chevy, Frédéric; Lobo, Carlos

2012-08-16

87

UK 1-D regional velocity models by analysis of variance of P-wave travel times from local earthquakes  

Microsoft Academic Search

A method is presented for deriving 1-D velocity depth models from earthquake bulletin data. The models can be used as initial\\u000a models for more advanced modelling techniques such as tomographic inversion. The method is useful when there is little or\\u000a no refraction and long-range reflection survey data. The bulletin travel times are subjected to an analysis of variance, where\\u000a they

David C. Booth

2010-01-01

88

Carbon isotope turnover in blood as a measure of arrival time in migratory birds using isotopically distinct environments  

Microsoft Academic Search

Arrival time on breeding or non-breeding areas is of interest in many ecological studies exploring fitness consequences of\\u000a migratory schedules. However, in most field studies, it is difficult to precisely assess arrival time of individuals. Here,\\u000a we use carbon isotope turnover in avian blood as a technique to estimate arrival time for birds switching from one habitat\\u000a or environment to

Steffen Oppel; Abby N. Powell

2010-01-01

89

Monitoring molecular interactions using photon arrival-time interval distribution analysis  

DOEpatents

A method for analyzing/monitoring the properties of species that are labeled with fluorophores. A detector is used to detect photons emitted from species that are labeled with one or more fluorophores and located in a confocal detection volume. The arrival time of each of the photons is determined. The interval of time between various photon pairs is then determined to provide photon pair intervals. The number of photons that have arrival times within the photon pair intervals is also determined. The photon pair intervals are then used in combination with the corresponding counts of intervening photons to analyze properties and interactions of the molecules including brightness, concentration, coincidence and transit time. The method can be used for analyzing single photon streams and multiple photon streams.

Laurence, Ted A. (Livermore, CA); Weiss, Shimon (Los Angels, CA)

2009-10-06

90

Spatial polarimetric time-frequency distributions for direction-of-arrival estimations  

Microsoft Academic Search

Time-frequency distributions (TFDs) are traditionally applied to a single antenna receiver with a single polarization. Recently, spatial time-frequency distributions (STFDs) have been developed for receivers with multiple single-polarized antennas and successfully applied for direction-of-arrival (DOA) estimation of nonstationary signals. In this paper, we consider dual-polarized antenna arrays and extend the STFD to utilize the source polarization properties. The spatial polarimetric

Yimin Zhang; Baha Adnan Obeidat; Moeness G. Amin

2006-01-01

91

A Two-Step Time of Arrival Estimation Algorithm for Impulse Radio Ultra Wideband Systems  

Microsoft Academic Search

High time resolution of ultra wideband (UWB) signals facilitates very precise positioning capa- bilities based on time-of-arrival (TOA) measurements. Although the theoretical lower bound for TOA estimation can be achieved by the maximum likelihood principle, it is impractical due to the need for extremely high-rate sampling and large number of multipath components. On the other hand, the conventional correlation-based algorithm,

Sinan Gezici; Zafer Sahinoglu; Andreas F. Molisch; Hisashi Kobayashi; H. Vincent Poor

2005-01-01

92

A fast least-squares arrival time estimator for scintillation pulses  

SciTech Connect

The true weighted least-squares (WLS) arrival time estimator for scintillation pulse detection was previously found to out-perform conventional arrival time estimators such as leading-edge and constant-fraction timers, but has limited applications because of its complexity. A new diagonalized version of the weighted least-squares (DWLS) estimator has been developed which, like the true WLS, incorporates the statistical properties of the scintillation detector. The new DWLS reduces estimator complexity at the expense of fundamental timing resolution. The advantage of the DWLS implementation is that only scalar multiplications and additions are needed instead of the matrix operations used in the true WLS. It also preserves the true WLS's ability to effectively separate piled-up pulses. The DWLS estimator has been applied to pulses which approximate the response of BGO and NaI(Tl) scintillation detectors. The timing resolution obtained with the DWLS estimator is then compared to conventional analog timers along with the Cramer-Rao lower bound on achievable timing error. The DWLS out-performs the conventional arrival time estimators but does not provide optimal performance compared to the lower bound; however, it is more robust than the true WLS estimator.

Petrick, N.; Hero, A.O. III; Clinthorne, N.H.; Rogers, W.L. (Univ. of Michigan, Ann Arbor, MI (United States))

1994-08-01

93

High resolution time of arrival estimation for a cooperative sensor system  

NASA Astrophysics Data System (ADS)

Distance resolution of cooperative sensors is limited by the signal bandwidth. For the transmission mainly lower frequency bands are used which are more narrowband than classical radar frequencies. To compensate this resolution problem the combination of a pseudo-noise coded pulse compression system with superresolution time of arrival estimation is proposed. Coded pulsecompression allows secure and fast distance measurement in multi-user scenarios which can easily be adapted for data transmission purposes (Morhart and Biebl, 2009). Due to the lack of available signal bandwidth the measurement accuracy degrades especially in multipath scenarios. Superresolution time of arrival algorithms can improve this behaviour by estimating the channel impulse response out of a band-limited channel view. For the given test system the implementation of a MUSIC algorithm permitted a two times better distance resolution as the standard pulse compression.

Morhart, C.; Biebl, E. M.

2010-09-01

94

Breaking the fixed-arrival-time restriction in reaching movements of neural prosthetic devices.  

PubMed

We routinely generate reaching arm movements to function independently. For paralyzed users of upper extremity neural prosthetic devices, flexible, high-performance reaching algorithms will be critical to restoring quality-of-life. Previously, algorithms called real-time reach state equations (RSE) were developed to integrate the user's plan and execution-related neural activity to drive reaching movements to arbitrary targets. Preliminary validation under restricted conditions suggested that RSE might yield dramatic performance improvements. Unfortunately, real-world applications of RSE have been impeded because the RSE assumes a fixed, known arrival time. Recent animal-based prototypes attempted to break the fixed-arrival-time assumption by proposing a standard model (SM) that instead restricted the user's movements to a fixed, known set of targets. Here, we leverage general purpose filter design (GPFD) to break both of these critical restrictions, freeing the paralyzed user to make reaching movements to arbitrary target sets with various arrival times and definitive stopping. In silico validation predicts that the new approach, GPFD-RSE, outperforms the SM while offering greater flexibility. We demonstrate the GPFD-RSE against SM in the simulated control of an overactuated 3-D virtual robotic arm with a real-time inverse kinematics engine. PMID:21189232

Srinivasan, Lakshminarayan; da Silva, Marco

2010-12-23

95

Waiting time of handoff calls for the wireless mobile networks with dependent calls arrival processes and impatient calls  

Microsoft Academic Search

This paper studies the quasi-waiting time, the actual waiting time of the handoff calls in the buffer and the actual call holding times of new calls for the mobile wireless networks, in which the new calls arrival processes may depend on the number of calls in the target cells and the handoff calls arrival processes from the given cell to

Wei Li; Kia Makki; Niki Pissinou

2000-01-01

96

A combined first-arrival travel time and reflection coherency optimization approach to velocity estimation  

NASA Astrophysics Data System (ADS)

We present a nonlinear optimization method for two-dimensional velocity estimation in strongly heterogeneous media. We achieve this by designing a simulated-annealing algorithm to simultaneously maximize reflection coherency as well as minimize first-arrival travel time residuals. Relatively shallow velocity structure is constrained by first-arrival times, while coherency information from deeper reflections (if present) helps constrain deeper velocities. Prestack migration using the optimized velocities images reflections with greater continuity, compared with other velocity estimation methods. Using synthetic and real data we demonstrate that migrations through velocities obtained using our coherency criterion reconstruct basin-boundary structures more accurately than through those obtained using only first-arrival times. Images from shot gathers collected along COCORP Mojave line 5 across the Garlock fault in Cantil Valley, California show new evidence of links between Garlock fault branches and sub-horizontal structures in the upper crust. Imaging reflections and estimating velocities using coherency annealing is more effective and less expensive than picking reflection times from shot gathers recorded complex regions.

Pullammanappallil, Sathish K.; Louie, John N.

97

Analyses of the age of genes and the first arrival times in a finite population.  

PubMed

The age of a mutant gene is studied using the infinite allele model in which every mutant is new and selectively neutral. Based on a time reversal theory of Markov processes, we develop a method of mathematical analysis that is considerably simpler for calculating the various statistics of the age than previous methods. Formulas for the mean and variance and for the distribution of age are presented together with some examples of relevance to cases in natural populations.-Theoretical studies of the first arrival time of an allele to a specified frequency, given an initially monomorphic condition of the locus, are presented. It is shown that, beginning with an allele that has frequency p = 1 or an allele with frequency p = 1/2N, there is an initial lag phase in which there is virtually no chance of an allele with a specified intermediate frequency appearing in the population. The distribution of the first arrival time is also presented. The distribution shows several characteristics that are not immediately obvious from a consideration of only the mean and variance of first arrival time. Especially noteworthy is the existence of a very long tail to the distribution. We have also studied the distribution of the age of an allele in the population. Again, the distribution of this measure is shown to be more informative for several questions than are the mean and variance alone. PMID:17246178

Maruyama, T; Fuerst, P A

1983-12-01

98

Application of Clenshaw-Curtis Method in Confined Time of Arrival Operator Eigenvalue Problem  

NASA Astrophysics Data System (ADS)

The Clenshaw-Curtis method in discretizing a Fredholm integral operator is applied to solving the confined time of arrival operator eigenvalue problem. The accuracy of the method is measured against the known analytic solutions for the noninteracting case, and its performance compared against the well-known Nystrom method. It is found that Clenshaw-Curtis's is superior to Nystrom's. In particular, Nystrom method yields at most five correct decimal places for the eigenvalues and eigenfunctions, while Clenshaw-Curtis yields eigenvalues correct to 16 decimal places and eigenfunctions up to 15 decimal places for the same number of quadrature points. Moreover, Clenshaw-Curtis's accuracy in the eigenvalues is uniform over a determinable range of the computed eigenvalues for a given number of quadrature abscissas. Clenshaw-Curtis is then applied to the harmonic oscillator confined time of arrival operator eigenvalue problem.

Vitancol, Roberto S.; Galapon, Eric A.

99

Time difference of arrival blast localization using a network of disposable sensors  

NASA Astrophysics Data System (ADS)

Determining the location of an explosive event using a networked sensor system within an acceptable accuracy is a challenging problem. McQ has developed such a system, using a mesh network of inexpensive acoustic sensors. The system performs a three-dimensional, time-difference-of-arrival (TDOA) localization of blasts of various yields in several different environments. Localization information of the blast is provided to the end user by exfiltration over satellite communications. The system is able to perform accurately in the presence of various sources of error including GPS position, propagation effects, temperature, and error in determining the time of arrival (TOA). The system design as well as its performance are presented.

Knobler, Ronald A.; Plummer, Thomas J.

2007-05-01

100

Acoustic source localization using time-difference of arrival and neural-network analysis  

NASA Astrophysics Data System (ADS)

The developing embedded technology requires revolutions in human-machine interaction. In this paper, we propose a novel method using localization of the taping sound on the table to replace the keyboard as manual input device. The method is applicable with a quad-channel-array collection of acoustic signals, from which the time-of-arrival differences and the position information could be estimated. In practice, as our table is in a limited size and the material properties are complex, the traditional localization algorithm based on time-of-arrival differences contains a sizable margin for error. Furthermore, we use neural-network analysis to improve recognition accuracy. Then experiments and simulations are carried out to verify this signal processing algorithm.

Jiang, Nan; Dong, Jiancheng; Ying, Ren D.

2013-03-01

101

A SUB 100 FS ELECTRON BUNCH ARRIVAL-TIME MONITOR SYSTEM FOR FLASH  

Microsoft Academic Search

Abstract The stability of free-electron lasers and experiments carried out in pump-probe,configurations depends,sen- sitively on precise synchronization between,the photo- injector laser, low-level RF-systems, probe lasers, and other components,in the FEL. A precise measurement,of the arrival-time of the electron bunch with respect to the clock signal of a master oscillator is, therefore, of special importance. For this task, we propose an

A. Winter

102

A SUB 100 FS ELECTRON BUNCH ARRIVAL-TIME MONITOR SYSTEM  

Microsoft Academic Search

The stability of free-electron lasers and experiments carried out in pump-probe configurations depends sen- sitively on precise synchronization between the photo- injector laser, low-level RF-systems, probe lasers, and other components in the FEL. A precise measurement of the arrival-time of the electron bunch with respect to the clock signal of a master oscillator is, therefore, of special importance. For this

103

Control of interceptive actions is based on expectancy of time to target arrival  

Microsoft Academic Search

In this study the hypothesis that interceptive movements are controlled on the basis of expectancy of time to target arrival\\u000a was tested. The study was conducted through assessment of temporal errors and kinematics of interceptive movements to a moving\\u000a virtual target. Initial target velocity was kept unchanged in part of the trials, and in the others it was decreased 300 ms

Raymundo Machado de Azevedo Neto; Luis Augusto Teixeira

2009-01-01

104

Initial comparison of lightning mapping with operational Time-of-Arrival and Interferometric systems  

Microsoft Academic Search

The mapping of lightning radiation sources produced by the operational Time-of-Arrival National Aeronautics and Space Administration\\/Lightning Detection and Ranging (NASA\\/LDAR) system is compared with that of the Interferometric French Office National D'Etudes et de Recherches Aerospatiales (ONERA-3D) system. The comparison comprises lightning activity in three Florida storms and also individual flashes in one of these storms. Although limited in scope,

Vladislav Mazur; Earle Williams; Robert Boldi; Launa Maier; David E. Proctor

1997-01-01

105

Accurate seismic phase identification and arrival time picking of glacial icequakes  

Microsoft Academic Search

A catastrophic lake drainage event was monitored continuously using an array of 6, 4.5 Hz 3 component geophones in the Russell Glacier catchment, Western Greenland. Many thousands of events and arrival time phases (e.g., P- or S-wave) were recorded, often with events occurring simultaneously but at different locations. In addition, different styles of seismic events were identified from 'classical' tectonic

G. A. Jones; S. H. Doyle; C. Dow; B. Kulessa; A. Hubbard

2010-01-01

106

Forecasting solar wind structures and shock arrival times using an ensemble of models  

NASA Astrophysics Data System (ADS)

Forecasting the time of arrival at Earth of interplanetary shocks following solar metric type II activity is an important first step in the establishment of an operational space weather prediction system. The quality of the forecasts is of utmost importance. The performances of the shock time of arrival (STOA) and interplanetary shock propagation models (ISPM) were previously evaluated by [2000] for 36 solar events. Here we use 173 solar events between February 1997 and October 2000 to set thresholds for the Hakamada-Akasofu-Fry version 2 (HAFv.2) model and then present the results of a comparison of the performance of this model to the STOA and ISPM solar wind models. Each model predicts shock arrival time (SAT) at the Earth using real-time metric type II radio frequency drifts and coincident X-ray and optical data for input and L1 satellite observations for verification. Our evaluation of input parameters to the models showed that the accuracy of the solar metric type II radio burst observations as a measure of the initial shock velocity was compromised for those events at greater than 20° solar longitude from central meridian. The HAF model also calculates the interplanetary shock propagation imbedded in a realistic solar wind structure through which the shocks travel and interact. Standard meteorological forecast metrics are used. A variety of statistical comparisons among the three models show them to be practically equivalent in forecasting SAT. Although the HAF kinematic model performance compares favorably with ISPM and STOA, it appears to be no better at predicting SAT than ISPM or STOA. HAFv.2 takes the inhomogeneous, ambient solar wind structure into account and thereby provides a means of sorting event-driven shock arrivals from corotating interaction region (CIR) passage.

Fry, C. D.; Dryer, M.; Smith, Z.; Sun, W.; Deehr, C. S.; Akasofu, S.-I.

2003-02-01

107

On Empirical Scrutiny of the Bohmian Model Using a Spin Rotator and the Arrival/Transit Time Distribution  

NASA Astrophysics Data System (ADS)

A setup that entails nonuniqueness in the quantum prediction of the arrival/transit time distribution is analysed using the Bohmian model, implying the plausibility of two distinct calculational schemes having empirically distinguishable predictions. One of them agrees with the results obtained from the probability current density based approach that has been suggested for predicting the quantum arrival/transit time distribution.

Pan, Alok Kumar; Home, Dipankar

2012-02-01

108

Comparing seismic tomographic images from automatically- and manually-detected arrival times  

NASA Astrophysics Data System (ADS)

In this work we compare local earthquake tomographic images obtained using arrival times detected by an automatic picking procedure and by an expert seismologist. For this purpose we select a reference dataset composed of 476 earthquakes occurred in the Trentino region (north-eastern Italy) in the period 1994-2007. Local magnitudes are comprised between 0.8 and 5.3. Original recordings are mainly from the Provincia Autonoma di Trento (PAT), and from other networks operating in the surrounding areas (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - INOGS; Istituto Nazionale di Geofisica e Vulcanologia - INGV; others available via the European Integrated Data Archive). The automatic picking of P and S phases is performed through a picker engine based on the Akaike information criterion (AIC). In particular, the proposed automatic phase picker includes: (i) envelope calculation, (ii) band-pass filtering, (iii) Akaike information criterion (AIC) detector for both P- and S-arrivals, (iv) checking for impulsive arrivals, (v) evaluation of expected S onset on the basis of a preliminary location derived from the P-arrival times, and (vi) quality assessment. Simultaneously, careful manual inspection by expert seismologists is applied to the same waveform dataset, to obtain manually-repicked phase readings. Both automatic and manual procedures generate a comparable amount of readings (about 6000 P- and 5000 S-phases). These data are used for the determination of two similar 3-D propagation models for the Trentino region, applying the SIMULPS code. In order to quantitatively estimate the difference of these two models we measure their discrepancies in terms of velocity at all grid points. The small differences observed among tomographic results allow us to demonstrate that the automatic picking engine adopted in this test can be used for reprocessing large amount of seismic recordings with the aim of perform a local tomographic study with an accuracy comparable to the one obtainable with a complete manual data revision.

Spallarossa, Daniele; Scafidi, Davide; Turino, Chiara; Ferretti, Gabriele; Viganò, Alfio

2013-04-01

109

Upper mantle P-wave velocity structure beneath southern Scandinavia  

NASA Astrophysics Data System (ADS)

This study images upper mantle structure beneath different tectonic and geomorphological provinces in southern Scandinavia by P-wave travel time tomography based on teleseismic events. We present integrated results using data from several projects (CALAS, MAGNUS, SCANLIPS, CENMOVE and Tor) with a total of 202 temporary seismological stations deployed in southern Norway, southern Sweden, Denmark and the northernmost part of Germany. These stations, together with 18 permanent stations, yield a high density data coverage enabling presentation of the first high resolution 3D seismic P-wave velocity model for the upper mantle for this region, which includes areas of Baltic Shield, Scandinavian Caledonides, the entire northern part of the prominent Tornquist Zone and the Southern Scandes Mountains. P-wave arrival time residuals of up to ±1 s are observed reflecting large seismic velocity contrasts at depths. Relative regional as well as absolute global tomographic inversion is carried out and consistently show upper mantle velocity variations relative to the ak135 reference model of up to ± 2-3 % corresponding to P-wave velocity differences of about 0.4 km/s from depths of about 100 km to more than 300 km. High upper mantle velocities are observed to great depth to the east in Baltic Shield areas of southwestern Sweden. Lower velocities are found to the west and southwest beneath the Danish and North German sedimentary basins and in most of southern Norway. A well-defined, generally narrow deep boundary is observed between areas of contrasting upper mantle seismic velocity. In basin areas, low upper mantle velocities are associated with thinned lithosphere and velocity contrasts are interpreted to represent differences between deep shield lithosphere and shallow basin asthenosphere with a deep lithospheric boundary running close to the Sorgenfrei-Tornquist Zone. Differences in P-wave velocity are here likely to arise mainly from temperature differences. To the north, the boundary crosses various tectonic and geomorphologic units including shield units, the Caledonides as well as areas of high topography, and a structural and geodynamic interpretation is more complex. Reduced upper mantle velocities below southern Norway also appear to be associated with a thinner lithosphere compared to shield areas to the east. Velocity contrasts may be explained to a higher degree by both compositional and temperature differences and a geodynamic origin including both Proterozoic and Phanerozoic events. Below southern Norway, a regional contribution to buoyancy from reduced density in the upper mantle is likely to exist, but we observe no clear correlation between reduced upper mantle seismic velocity and high topography of the southern Scandes Mountains.

Medhus, A. B.; Balling, N.; Jacobsen, B. H.; England, R. W.; Kind, R.; Weidle, C.; Voss, P.; Thybo, H.

2012-04-01

110

Simulation-based performance comparison between assembly lines and assembly cells with real-time distributed arrival time control system  

Microsoft Academic Search

This paper presents the results of a simulation-based performance comparison between assembly lines (AL) and assembly cells (AC) manufacturing systems with real-time distributed arrival time for just-in-time (JIT)-oriented production environment. This research adds to the sparse body of literature in this area. The previous performance comparisons were made in smaller scalability because of the combinational problem. In addition, the comparisons

Jun Gong; Vittaldas V. Prabhu; Wenxin Liu

2011-01-01

111

Temporal dispersion of the emergence of intelligence: an inter-arrival time analysis  

NASA Astrophysics Data System (ADS)

Many reasons for why extraterrestrial intelligences might avoid communications with our civilization have been proposed. One possible scenario is that all civilizations follow the lead of some particularly distinguished civilization. This paper will examine the impact the first successful civilization could have on all other subsequent civilizations within its sphere of influence and the ramifications of this as it relates to the Fermi Paradox. Monte Carlo simulation is used to map the inter-arrival times of early civilizations and to highlight the immense epochs of time that the earliest civilizations could have had the Galaxy to themselves.

Hair, Thomas W.

2011-02-01

112

Emergency Department Arrival Times, Treatment, and Functional Recovery in Women with Acute Ischemic Stroke  

PubMed Central

Abstract Background Sex disparities have been well documented in patients with ischemic stroke. Previous studies have suggested that female sex is a risk factor for delay in arrival time to the emergency department (ED) and may contribute to ineligibility for thrombolytic therapy. With the increase in education efforts targeting women, we investigated whether ED arrival times, rates of thrombolytic use, and functional outcomes continue to differ in men and women with acute ischemic stroke (AIS). Methods This study was a retrospective database analysis of patients with AIS (2001–2008). All AIS patients presenting within 24 hours with a known time of symptom onset and a documented admission National Institutes of Health Stroke Scale (NIHSS) were included. The Modified Barthel Index (MBI) assessed patients' functional status preadmission (historical), admission, and at 3 and 12 months poststroke. Results Included in the analysis were 480 (50.6%) women and 468 (49.4%) men. Women were significantly older than men (70.6?±?0.7 vs. 65.3 years?±?0.6, p???0.001). Mean onset-to-ED time was not significantly different between the sexes (women 265?±?283 vs. men 245?±?300 minutes), nor was prestroke MBI. Logistic regression analysis demonstrated that female sex, increasing age, higher admission NIHSS, and longer onset-to-ED times all contributed to poorer functional status. Conclusions Women arrive at the ED at equivalent speed as men after AIS. Women had greater functional impairments at 3 months and 12 months poststroke despite equivalent prestroke MBI and admission NIHSS. Female sex contributes to poorer chronic functional outcomes after AIS.

Knauft, Wesley; Chhabra, Jyoti

2010-01-01

113

Predicting ambulance time of arrival to the emergency department using global positioning system and google maps.  

PubMed

Abstract Objective. To derive and validate a model that accurately predicts ambulance arrival time that could be implemented as a Google Maps web application. Methods. This was a retrospective study of all scene transports in Multnomah County, Oregon, from January 1 through December 31, 2008. Scene and destination hospital addresses were converted to coordinates. ArcGIS Network Analyst was used to estimate transport times based on street network speed limits. We then created a linear regression model to improve the accuracy of these street network estimates using weather, patient characteristics, use of lights and sirens, daylight, and rush-hour intervals. The model was derived from a 50% sample and validated on the remainder. Significance of the covariates was determined by p < 0.05 for a t-test of the model coefficients. Accuracy was quantified by the proportion of estimates that were within 5 minutes of the actual transport times recorded by computer-aided dispatch. We then built a Google Maps-based web application to demonstrate application in real-world EMS operations. Results. There were 48,308 included transports. Street network estimates of transport time were accurate within 5 minutes of actual transport time less than 16% of the time. Actual transport times were longer during daylight and rush-hour intervals and shorter with use of lights and sirens. Age under 18 years, gender, wet weather, and trauma system entry were not significant predictors of transport time. Our model predicted arrival time within 5 minutes 73% of the time. For lights and sirens transports, accuracy was within 5 minutes 77% of the time. Accuracy was identical in the validation dataset. Lights and sirens saved an average of 3.1 minutes for transports under 8.8 minutes, and 5.3 minutes for longer transports. Conclusions. An estimate of transport time based only on a street network significantly underestimated transport times. A simple model incorporating few variables can predict ambulance time of arrival to the emergency department with good accuracy. This model could be linked to global positioning system data and an automated Google Maps web application to optimize emergency department resource use. Use of lights and sirens had a significant effect on transport times. Key words: emergency medical services; prehospital emergency care. PMID:23865736

Fleischman, Ross J; Lundquist, Mark; Jui, Jonathan; Newgard, Craig D; Warden, Craig

2013-07-18

114

Ready...Go: Amplitude of the fMRI Signal Encodes Expectation of Cue Arrival Time  

PubMed Central

What happens when the brain awaits a signal of uncertain arrival time, as when a sprinter waits for the starting pistol? And what happens just after the starting pistol fires? Using functional magnetic resonance imaging (fMRI), we have discovered a novel correlate of temporal expectations in several brain regions, most prominently in the supplementary motor area (SMA). Contrary to expectations, we found little fMRI activity during the waiting period; however, a large signal appears after the “go” signal, the amplitude of which reflects learned expectations about the distribution of possible waiting times. Specifically, the amplitude of the fMRI signal appears to encode a cumulative conditional probability, also known as the cumulative hazard function. The fMRI signal loses its dependence on waiting time in a “countdown” condition in which the arrival time of the go cue is known in advance, suggesting that the signal encodes temporal probabilities rather than simply elapsed time. The dependence of the signal on temporal expectation is present in “no-go” conditions, demonstrating that the effect is not a consequence of motor output. Finally, the encoding is not dependent on modality, operating in the same manner with auditory or visual signals. This finding extends our understanding of the relationship between temporal expectancy and measurable neural signals.

Montague, P. Read; Eagleman, David M.

2009-01-01

115

From 3-Hz P Waves to 0-S-2: Real-time and deferred estimates of the moment of the Honshu event across the full frequency spectrum  

NASA Astrophysics Data System (ADS)

In the hours following the 2011 Honshu event, and as part of tsunami warning procedures at the Laboratoire de Geophysique in Papeete, Tahiti, the seismic source of the event was analyzed using a number of real-time procedures. The ultra-long period mantle magnitude algorithm suggests a static moment of 4.2E29 dyn*cm, not signifcantly different from the NEIC value obtained by W-phase inversion. The slowness parameter, THETA = -5.65, is slightly deficient, but characteristic of other large subduction events such as Nias (2005) or Peru (2001); it remains significantly larger than for slow earthquakes such as Sumatra (2004) or Mentawai (2010). Similarly, the duration of high-frequency (2-4 Hz) P waves in relation to seismic moment or estimated energy fails to document any slowness in the seismic source. These results were confirmed in the ensuing weeks by the analysis of the lowest-frequency spheroidal modes of the Earth. A dataset of 109 fits for 8 modes (including the gravest one, 0s2, and the breathing mode, 0s0) yields a remarkably flat spectrum, with an average moment of 3.5E29 dyn*cm (*/1.07). This textbook behavior of the Sendai earthquake explains the generally successful real-time modeling of its teleseismic tsunami, based on available seismic source scaling laws. On the other hand, it confirms the dichotomy, amongst mega-quakes (M sub 0 > 10 sup 29 dyn*cm) between regular events (Nias, 2005; Chile, 2010; Sendai, 2011) and slow ones (Chile, 1960; Alaska, 1964; Sumatra, 2004; and probably Rat Island, 1965), whose origin remains unexplained.

Andre, O. E.

2011-12-01

116

Arrival-time structure of the time-averaged ambient noise cross-correlation function in an oceanic waveguide.  

PubMed

Coherent deterministic arrival times can be extracted from the derivative of the time-averaged ambient noise cross-correlation function between two receivers. These coherent arrival times are related to those of the time-domain Green's function between these two receivers and have been observed experimentally in various environments and frequency range of interest (e.g., in ultrasonics, seismology, or underwater acoustics). This nonintuitive result can be demonstrated based on a simple time-domain image formulation of the noise cross-correlation function, for a uniform distribution of noise sources in a Pekeris waveguide. This image formulation determines the influence of the noise-source distribution (in range and depth) as well as the dependence on the receiver bandwidth for the arrival-time structure of the derivative of the cross-correlation function. These results are compared with previously derived formulations of the ambient noise cross-correlation function. Practical implications of these results for sea experiments are also discussed. PMID:15704409

Sabra, Karim G; Roux, Philippe; Kuperman, W A

2005-01-01

117

Backreacting p-wave superconductors  

NASA Astrophysics Data System (ADS)

We study the gravitational backreaction of the non-abelian gauge field on the gravity dual to a 2 + 1 p-wave superconductor. We observe that as in the p + ip system a second order phase transition exists between a superconducting and a normal state. Moreover, we conclude that, below the phase transition temperature T c the lowest free energy is achieved by the p-wave solution. In order to probe the solution, we compute the holographic entanglement entropy. For both p and p + ip systems the entanglement entropy satisfies an area law. For any given entangling surface, the p-wave superconductor has lower entanglement entropy.

Arias, Raúl E.; Landea, Ignacio Salazar

2013-01-01

118

Comparative Study of Bunch Length And Arrival Time Measurements at FLASH  

SciTech Connect

Diagnostic devices to precisely measure the longitudinal electron beam profile and the bunch arrival time require elaborate new instrumentation techniques. At FLASH, two entirely different methods are used. The bunch profile can be determined with high precision by a transverse deflecting RF structure, but the method is disruptive and does not allow to monitor multiple bunches in a macro-pulse train. It is therefore complemented by two non-disruptive electrooptical devices, called EO and TEO. The EO setup uses a dedicated diagnostic laser synchronized to the machine RF. The longitudinal electron beam profile is encoded in the intensity profile of a chirped laser pulse and analyzed by looking at the spectral composition of the pulse. The second setup, TEO, utilizes the TiSa-based laser system used for pump-probe experiments. Here, the temporal electron shape is encoded into the spatial dimension of the laser pulse by an intersection angle between the laser and the electron beam at the EO-crystal. In this paper, we present a comparative study of bunch length and arrival time measurements performed simultaneously with all three experimental techniques.

Schlarb, H.; Azima, A.; Dusterer, S.; Huning, M.; Knabbe, E.A.; Roehrs, M.; Rybnikov, V.; Schmidt, B.; Steffen, B.; /DESY; Ross, M.C.; /SLAC; Schmueser, P.; Winter, A.; /Hamburg U.

2007-04-16

119

Performance Analysis of a Block-Structured Discrete-Time Retrial Queue with State-Dependent Arrivals  

Microsoft Academic Search

In this paper, we introduce a new discrete block state-dependent arrival (D-BSDA) distribution which provides fresh insights leading to a successful generalization of the discrete-time Markovian arrival\\u000a process (D-MAP). The D-BSDA distribution is related to structured Markov chains and the method of stages. The consideration of this new discrete-time\\u000a state-dependent block description gives one the ability of construct new stochastic

Jesus R. Artalejo; Quan-Lin Li

2010-01-01

120

The influence of ice-pressure on p-wave velocity in alpine low-porosity rocks: a modified time-average model  

NASA Astrophysics Data System (ADS)

Most polar and many mountainous regions are affected by permafrost. Seismic field and laboratory measurements represent a standard approach to investigate permafrost since the early 1970s. Laboratory research has focussed on arctic high-porosity sandstones, shales and carbonate rocks and results have been implemented in various seismic models (Carcione and Seriani, 1998). However, alpine rock walls consist of low-porosity bedrock and some authors deny the applicability of seismic approaches to these (McGinnis et al., 1973). Models developed in high-porosity rocks explain bulk p-wave velocity of bedrock due to changing velocities in the pore infill (ice/water/air) while the matrix velocity of bedrock remains constant. Here we show, that in low-porosity rocks matrix velocities change considerably while changes in pore velocities are insignificant. Hence, p-wave refraction seismics is applicable in low-porosity alpine rock walls. For this, we (1) present data of p-wave measurements of 23 different alpine rocks, (2) evaluate the influence of ice pressure on seismic velocities, (3) determine anisotropic decrease due to ice pressure and (4) extend Timur's (1968) 2-phase model for alpine rocks. The tested rocks derive from alpine locations in Switzerland, Germany, Austria, France and Svalbard, and German sub alpine locations. All samples possess effective porosities lower than 6 %. P-wave velocities were measured parallel and perpendicular to cleavage or bedding in a temperature range from +20° C to -15° C in a WEISS WK 180/40 high-accuracy climate chamber. Rock temperature was monitored continuously with two or three calibrated thermometers; p-waves were generated with a Geotron ultrasonic transducer and measured with a Fluke Scopemeter. (1) All rock samples show p-wave velocity increase dependent on lithology due to freezing. P-wave velocity increase is in the range of 7.33 (±3.73) % for Gneiss and 78.45 (±7.00) % for carbonate rocks parallel to cleavage/bedding; perpendicular measurements show an increase between 11.10 (±2.38) % for Gneiss and 166.01 (±56.93) % for carbonate rocks. The increase of p-wave velocity of carbonate rocks is independent of effective porosity. (2) Velocity increase due to freezing is not only derived through higher velocity of ice in relation to water; ice pressure induces an increase of the velocity of the rock matrix. Matrix velocity increases parallel to cleavage/bedding between 5.08 (±4.08) % for Gneiss and 59.44 (±9.33) % for carbonate rocks; perpendicular measurements indicate matrix velocity increase reaching from 8.95 (±4.51) % for mafic metamorphic rocks and 168.53 (±62.00) % for carbonate rocks. (3) Anisotropy decreases as a result of crack closure due to ice pressure in 15 of 23 rock samples. This effect is specially pronounced for schists. (4) We extend Timur's (1968) 2 phase equation with a lithology dependent variable to increase the matrix velocity responding to developing ice pressure while freezing. This study shows the general applicability of refraction seismics in low-porosity permafrost rocks. The expansion of rigid bedrock upon freezing is restricted and, thus, ice pressure will increase matrix velocity. Here, we present a modified "Timur (1968) 2 phase equation" implementing a 4-21 % change in matrix velocity dependent on lithology.

Dräbing, D.; Krautblatter, M.

2012-04-01

121

Timing of initial arrival at the breeding site predicts age at first reproduction in a long-lived migratory bird  

PubMed Central

In long-lived vertebrates, individuals generally visit potential breeding areas or populations during one or more seasons before reproducing for the first time. During these years of prospecting, they select a future breeding site, colony, or mate and improve various skills and their physical condition to meet the requirements of reproduction. One precondition of successful reproduction is arrival in time on the breeding grounds. Here, we study the intricate links among the date of initial spring arrival, body mass, sex, and the age of first breeding in the common tern Sterna hirundo, a long-lived migratory colonial seabird. The study is based on a unique, individual-based, long-term dataset of sexed birds, marked with transponders, which allow recording their individual arrival, overall attendance, and clutch initiation remotely and automatically year by year over the entire lifetime at the natal colony site. We show that the seasonal date of initial arrival at the breeding grounds predicts the individual age at first reproduction, which mostly occurs years later. Late first-time arrivals remain delayed birds throughout subsequent years. Our findings reveal that timing of arrival at the site of reproduction and timing of reproduction itself are coherent parameters of individual quality, which are linked with the prospects of the breeding career and may have consequences for fitness.

Becker, Peter H.; Dittmann, Tobias; Ludwigs, Jan-Dieter; Limmer, Bente; Ludwig, Sonja C.; Bauch, Christina; Braasch, Alexander; Wendeln, Helmut

2008-01-01

122

Timing of initial arrival at the breeding site predicts age at first reproduction in a long-lived migratory bird.  

PubMed

In long-lived vertebrates, individuals generally visit potential breeding areas or populations during one or more seasons before reproducing for the first time. During these years of prospecting, they select a future breeding site, colony, or mate and improve various skills and their physical condition to meet the requirements of reproduction. One precondition of successful reproduction is arrival in time on the breeding grounds. Here, we study the intricate links among the date of initial spring arrival, body mass, sex, and the age of first breeding in the common tern Sterna hirundo, a long-lived migratory colonial seabird. The study is based on a unique, individual-based, long-term dataset of sexed birds, marked with transponders, which allow recording their individual arrival, overall attendance, and clutch initiation remotely and automatically year by year over the entire lifetime at the natal colony site. We show that the seasonal date of initial arrival at the breeding grounds predicts the individual age at first reproduction, which mostly occurs years later. Late first-time arrivals remain delayed birds throughout subsequent years. Our findings reveal that timing of arrival at the site of reproduction and timing of reproduction itself are coherent parameters of individual quality, which are linked with the prospects of the breeding career and may have consequences for fitness. PMID:18711134

Becker, Peter H; Dittmann, Tobias; Ludwigs, Jan-Dieter; Limmer, Bente; Ludwig, Sonja C; Bauch, Christina; Braasch, Alexander; Wendeln, Helmut

2008-08-18

123

Expected Time of Arrival Model for School Bus Transit Using Real-Time Global Positioning System-Based Automatic Vehicle Location Data  

Microsoft Academic Search

The school bus is a major transportation mode for students in Canada. Unexpected delay of a school bus may be a major source of inconvenience for students and their parents. Accordingly, the provision of timely and reliable information on the expected arrivals of school buses would be of great benefit to them. This study develops an expected time of arrival

Eui-Hwan Chung; Amer Shalaby

2007-01-01

124

3D P-wave velocity structure beneath the Abitibi-Grenville region, eastern Canadian Shield  

NASA Astrophysics Data System (ADS)

Seismic studies of the upper mantle of the Canadian Shield have indicated a low-velocity anomaly within the cratonic lithosphere near the Ontario-Québec border, in the Abitibi-Grenville region. The lack of seismograph station coverage on the Québec side of the border previously prevented definition of the 3D geometry of this anomaly. New stations installed in the province of Québec allow us to carry out new studies of the P-wave velocity structure of the lithosphere surrounding that low-velocity anomaly, in order to better understand the complexity of the region and the interaction of the lithosphere with possible thermal anomalies in the underlying mantle. Over a hundred events have been analysed since autumn 2007. To do so, we used teleseismic P and PKP arrivals recorded at 31 stations deployed across the region, 5 belonging to UQAM’s network and 26 others belonging to the POLARIS project and the Canadian National Seismograph Network (CNSN). The relative arrival times of teleseismic P waves across the array were measured using the cross-correlation method of VanDecar & Crosson (1990). We have also calculated maps of relative arrival time residuals across the array for earthquakes coming from different back-azimuths, in order to examine systematic patterns of travel-time anomalies resulting from mantle heterogeneity. We invert the travel time data to estimate the 3D P-wave velocity structure beneath the region, using the least-squares tomographic inversion code of VanDecar (1991). Regularization and resolution tests are carried out, and we present a set of preliminary 3D upper mantle models. Depth slices and cross-sections are used to constrain the geometry of the low-velocity anomaly and surrounding upper mantle structures.

Villemaire, M.; Darbyshire, F. A.

2009-12-01

125

Probability distribution of the inter-arrival time to cellular telephony channels  

Microsoft Academic Search

This paper is focused on the statistical analysis of the call arrival process in channels of mobile telephony access networks. The approach is fully empirical, and is based on actual activity data, collected from real base stations in a working mobile network. The arrival process of the merged “fresh” (new calls) and handover traffic is proved to be smoother than

Francisco Barceló; José Ignacio Sánchez

1999-01-01

126

41 CFR 301-11.10 - Am I required to record departure/arrival dates and times on my travel claim?  

Code of Federal Regulations, 2010 CFR

...departure/arrival dates and times on my travel claim? 301-11.10...departure/arrival dates and times on my travel claim? You must record...record departure/arrival times, but you must annotate your travel claim when your travel...

2009-07-01

127

41 CFR 301-11.10 - Am I required to record departure/arrival dates and times on my travel claim?  

Code of Federal Regulations, 2010 CFR

...departure/arrival dates and times on my travel claim? 301-11.10...departure/arrival dates and times on my travel claim? You must record...record departure/arrival times, but you must annotate your travel claim when your travel...

2010-07-01

128

Propagator and multiple scattering approach to the time of arrival problem  

NASA Astrophysics Data System (ADS)

The propagator approach combined with the multiple-scattering theory is applied to the particle time of arrival (TOA) problem. This approach allows us to naturally include in the consideration the components of the particle initial wavefunction (defined at t = t0) corresponding to the positive (forward-moving term) and negative (backward-moving term) momenta. For a freely moving particle it is shown that the Allcock definition of the ideal total TOA probability disregards the backward-moving and interference terms entirely. In the presence of a measuring apparatus modeled by an imaginary step potential with the amplitude V0, the general expression for the TOA rate is obtained, the forward-moving component of which coincides with that obtained by Allcock. It is shown that when the initial particle wavefunction is well separated from the point of arrival and has a well-defined average momentum, the contribution of the backward-moving and interference terms are small and can be neglected. For a small V0, except the well-known convolution result by Allcock-Kijowski, the exponential form of the TOA rate follows at the double limit condition V0 ? 0, t - t0 ~ planck/2V0 ? ? (2V0(t - t0)/planck is finite) while the backward-moving and interference terms vanish. We show that the Allcock result for the TOA rate is valid in the entire range of V0 including the Zeno case (V0 ? ?) and the normalized TOA rate can be introduced for all values of V0 as a probability distribution. The latter is illustrated for the Gaussian wave packet.

Los, Victor F.; Los, Andrei V.

2011-05-01

129

Statistical analysis of inter-arrival times of rainfall events for Italian Sub-Alpine and Mediterranean areas  

NASA Astrophysics Data System (ADS)

In this work a set of time-series of inter-arrival times of rainfall events, at daily scale, was analysed, with the aim to verify the issue of increasing duration of dry periods. The set consists of 12 time-series recorded at rain gauges in 1926-2005, six of them belong to an Italian Sub-Alpine area (Piedmont) and six to a Mediterranean one (Sicily). In order to overcome the problem related to limited sample size for high values of inter-arrival times, the discrete probability polylog-series distribution was used to fit the empirical data from partial (20 yr) time-series. Moreover, a simple qualitative trend analysis was applied to some high quantiles of inter-arrival times as well as to the average extent of rain clusters. The preliminary analysis seems to confirm the issue of increasing duration of dry periods for both environments, which is limited to the "cold" season.

Agnese, C.; Baiamonte, G.; Cammalleri, C.; Cat Berro, D.; Ferraris, S.; Mercalli, L.

2012-09-01

130

Anxiety and P Wave Dispersion in a Healthy Young Population  

Microsoft Academic Search

Background: P wave dispersion (Pd), defined as the difference between the maximum (Pmax) and the minimum P wave duration (Pmin), and Pmax are electrocardiographic (ECG) markers that have been used to evaluate the discontinuous propagation of sinus impulses and the prolongation of atrial conduction time. Pd in normal subjects has been reported to be influenced by the autonomic tone, which

Hüseyin Uyarel; Sennur Unal Dayi; Zeynep Tartan; Ahmet Karabulut; Bülent Uzunlar; Hasan Samur; Ertan Okmen; Nese Cam

2005-01-01

131

Scattering of P Waves under the Montana Lasa  

Microsoft Academic Search

The variations of amplitude and time delay of teleseismic P waves across the Montana Lass (Large Aperture Seismic Array) were interpreted as being due to scattering by a random inhomogeneity in the earth's crust under the array. The prediction of the Chernov [1960] theory explains well the observed statistical properties of P waves with a frequency of 0.5 I-iz. The

Keiiti Aki

1973-01-01

132

A Bayesian parameter estimation approach to pulsar time-of-arrival analysis  

NASA Astrophysics Data System (ADS)

The increasing sensitivities of pulsar timing arrays to ultra-low frequency (nHz) gravitational waves promise to achieve direct gravitational wave (GW) detection within the next 5-10 years. While there are many parallel efforts being made in the improvement of telescope sensitivity, the detection of stable millisecond pulsars and the improvement of the timing software, there are reasons to believe that the methods used to accurately determine the time-of-arrival (TOA) of pulses from radio pulsars can be improved upon. More specifically, the determination of the uncertainties on these TOAs, which strongly affect the ability to detect GWs through pulsar timing, may be unreliable. We propose two Bayesian methods for the generation of pulsar TOAs starting from pulsar 'search-mode' data and pre-folded data. These methods are applied to simulated toy-model examples and in this initial work we focus on the issue of uncertainties in the folding period. The final results of our analysis are expressed in the form of posterior probability distributions on the signal parameters (including the TOA) from a single observation.

Messenger, C.; Lommen, A.; Demorest, P.; Ransom, S.

2011-03-01

133

Evaluation of methods for bolus arrival time determination using a four-dimensional MRA flow phantom.  

PubMed

In this paper an evaluation of methods determining the bolus arrival time (BAT) using a four-dimensional flow phantom to simulate 4D MR angiography is presented. Spatiotemporal 4D MRA images were acquired for analyzing the hemodynamic characteristics of cerebral vessel anomalies. Model-independent and model-dependent methods for BAT extraction are published. Generally, for the evaluation no gold standard exists and datasets with known BAT values are required. Here, a 4D flow phantom is generated based on a synthetic 3D MRA dataset with BAT values defining the time point of blood inflow for each voxel. Then, voxel-by-voxel concentration-time curves based on the gamma-variate function were computed leading to a simulated 4D MRA dataset. Additionally, partial volume effects and Gaussian noise were integrated. The simulated 4D MRA was visually inspected and regarded as similar to clinical data. Finally, phantom datasets with different vessel diameter and signal-to-noise ratio are computed. Three state-of-the-art methods were used to extract BAT values. Computed and known values were compared. The results suggest that model-dependent approaches perform better than the model-independent method. PMID:20841887

Säring, Dennis; Forkert, Nils Daniel; Illies, Till; Fiehler, Jens; Handels, Heinz

2010-01-01

134

Space weather prediction accuracy : Improved estimation of arrival times of solar wind phase fronts  

NASA Astrophysics Data System (ADS)

Most space weather phenomena, such as geomagnetic storms and substorms are associated with disturbances in the solar wind, in particular directional changes in the interplanetary magnetic field (IMF). An observational challenge in this connection is that solar wind measurments are usually taken at large distances from the Earth and have to be time shifted to be representative for the upstream conditions, where the interaction takes place. Most methods to time shift the IMF data require knowledge about the orientation of magnetic surfaces in the solar wind. The orientation can be obtained from variance analysis of the IMF. A drawback with this approach is that the variance analysis frequently give poor results or fail if Alvenic structures or magnetic islands are embedded in the solar wind plasma. In this paper, we present a wavelet based de-noising method to minimize the influence of such structures. Applications of the method shows that a better estimate of magnetic surface orientations and better prediction accuracy of the arrival time of solar wind disturbances at the Earth's magnetopause can be achieved.

Munteanu, Costel; Haaland, Stein; Mailyan, Bagrat

135

Crustal parameters estimated from P-waves of earthquakes recorded at a small array  

USGS Publications Warehouse

The P-arrival times of local and regional earthquakes that are outside of a small network of seismometers can be used to interpret crustal parameters beneath the network by employing the time-term technique. Even when the estimate of the refractor velocity is poorly determined, useful estimates of the station time-terms can be made. The method is applied to a 20 km diameter network of eight seismic stations which was operated near Castaic, California, during the winter of 1972-73. The stations were located in sedimentary basins. Beneath the network, the sedimentary rocks of the basins are known to range from 1 to more than 4 km in thickness. Relative time-terms are estimated from P-waves assumed to be propagated by a refractor in the mid-crust, and again from P-waves propagated by a refractor in the upper basement. For the range of velocities reported by others, the two sets of time-terms are very similar. They suggest that both refractors dip to the southwest, and the geology also indicates that the basement dips in this direction. In addition, the P-wave velocity estimated for the refractor of mid-crustal depths, roughly 6.7 km/sec, agrees with values reported by others. Thus, even in this region of complicated geologic structure, the method appears to give realistic results. ?? 1980 Birkha??user Verlag.

Murdock, J. N.; Steppe, J. A.

1980-01-01

136

Joint microseismic location and anisotropic tomography using differential arrival times and differential backazimuths  

NASA Astrophysics Data System (ADS)

We develop a new method to locate microseismic events induced by hydraulic fracturing with simultaneous anisotropic tomography, using differential arrival times and differential backazimuths. Compared to the existing double-difference method, our method incorporates backazimuth information to better constrain microseismic locations in the case of downhole linear seismic arrays used for monitoring induced seismicity. The tomography is constrained to a 1-D layered VTI (transversely isotropic structure with a vertical symmetry axis) structure to improve inversion stability given the limited passive seismic data. We derive analytical sensitivities for the elastic moduli (Cij) and layer thickness L, and verify the analytical results with numerical calculations. The forward modelled traveltimes and sensitivities are all calculated analytically without weak anisotropy assumption. By incorporating the relative information among events, the extended double-difference method can provide better relative locations for events and, therefore, can characterize the fractures with higher accuracy. In the two tests with synthetic data, our method provides more accurate relative locations than the traditional methods, which only use absolute information. With fast speed and high accuracy, our inversion scheme is suitable for real-time microseismic monitoring of hydraulic fracturing.

Li, Junlun; Zhang, Haijiang; Rodi, William L.; Toksoz, M. Nafi

2013-09-01

137

Estimating permeability from quasi-static deformation: Temporal variations and arrival time inversion  

SciTech Connect

Transient pressure variations within a reservoir can be treated as a propagating front and analyzed using an asymptotic formulation. From this perspective one can define a pressure 'arrival time' and formulate solutions along trajectories, in the manner of ray theory. We combine this methodology and a technique for mapping overburden deformation into reservoir volume change as a means to estimate reservoir flow properties, such as permeability. Given the entire 'travel time' or phase field, obtained from the deformation data, we can construct the trajectories directly, there-by linearizing the inverse problem. A numerical study indicates that, using this approach, we can infer large-scale variations in flow properties. In an application to Interferometric Synthetic Aperture (InSAR) observations associated with a CO{sub 2} injection at the Krechba field, Algeria, we image pressure propagation to the northwest. An inversion for flow properties indicates a linear trend of high permeability. The high permeability correlates with a northwest trending fault on the flank of the anticline which defines the field.

Vasco, D.W.; Ferretti, Alessandro; Novali, Fabrizio

2008-05-01

138

Improvement in lightning geolocation by time-of-arrival method using global ELF network data  

NASA Astrophysics Data System (ADS)

The global observation of cloud-to-ground (CG) discharges based on ELF measurements provides essential information, including vertical charge moment (Qdl) for investigations of global-scale thunderstorm activity. However, the geolocating method by direction finding of sferics in the frequency range of 1-100 Hz has a rather large error, on the order of 1000 km, even for the CGs with relatively large Qdl (>1000 C-km). Here we improve the methods for geolocation and estimation of Qdl, which are applicable to smaller CGs with Qdl down to 470 C-km, making use of the time-of-arrival method and the high correlation between Qdl and the peak amplitude of ELF sferics. The evaluated average error in geolocation, comparing with World Wide Lightning Location Network data, is 680 km. By this improved method, CGs with Qdl of <470 C-km can be detected at any location in the world. In the preliminary analysis for the year of 2004, the number of CGs whose location and Qdl are determined is about a million events per month, roughly 10-30 times compared to previous studies by ELF measurement, enabling an investigation of the day-to-day variations of the global CG distribution with transferred charge amount. The combination of accurate geolocation and the uniformity of detection show active regions in the three main areas: Africa, South America, and the Maritime Continent. In addition, minor thunderstorm areas in Japan, the Mediterranean Sea, and the Pacific Ocean can be monitored.

Yamashita, Kozo; Takahashi, Yukihiro; Sato, Mitsuteru; Kase, Hiromi

2011-02-01

139

Performance of real-time distributed arrival time control in heterarchical manufacturing systems  

Microsoft Academic Search

A highly distributed feedback control algorithm for autonomous part entities in heterarchical manufacturing systems is presented in this paper. A difference equation-based model is developed to analyze the discrete time dynamics of the resulting nonlinear control system. Control parameters are found analytically that guarantee that the system is bounded under disturbances. The dynamic response to: (i) changes in due dates;

VITTALDAS V. PRABHU

2000-01-01

140

Performance of real-time distributed arrival time control in assembly cell manufacturing systems  

Microsoft Academic Search

In recent years, assembly cells as a new manufacturing system have clearly shown that it have the ability to generate significant performance improvements over unbuffered, multi-model, linked assembly lines and multi-model assembly lines with a finite buffer of inventory between stations. However, some effective methods for scheduling in real time in this manufacturing system are sparse. In this paper, a

Jun Gong; Jiafu Tang; Qian Li

2010-01-01

141

Arrival Time Correction for Dynamic Susceptibility Contrast MR Permeability Imaging in Stroke Patients  

PubMed Central

Purpose To determine if applying an arrival time correction (ATC) to dynamic susceptibility contrast (DSC) based permeability imaging will improve its ability to identify contrast leakage in stroke patients for whom the shape of the measured curve may be very different due to hypoperfusion. Materials and Methods A technique described in brain tumor patients was adapted to incorporate a correction for delayed contrast delivery due to perfusion deficits. This technique was applied to the MRIs of 9 stroke patients known to have blood-brain barrier (BBB) disruption on T1 post contrast imaging. Regions of BBB damage were compared with normal tissue from the contralateral hemisphere. Receiver operating characteristic (ROC) analysis was performed to compare the detection of BBB damage before and after ATC. Results ATC improved the area under the curve (AUC) of the ROC from 0.53 to 0.70. The sensitivity improved from 0.51 to 0.67 and the specificity improved from 0.57 to 0.66. Visual inspection of the ROC curve revealed that the performance of the uncorrected analysis was worse than random guess at some thresholds. Conclusions The ability of DSC permeability imaging to identify contrast enhancing tissue in stroke patients improved considerably when an ATC was applied. Using DSC permeability imaging in stroke patients without an ATC may lead to false identification of BBB disruption.

Leigh, Richard; Jen, Shyian S.; Varma, Daniel D.; Hillis, Argye E.; Barker, Peter B.

2012-01-01

142

Fault zone structure determined through the analysis of earthquake arrival times  

SciTech Connect

This thesis develops and applies a technique for the simultaneous determination of P and S wave velocity models and hypocenters from a set of arrival times. The velocity models are parameterized in terms of cubic B-splines basis functions which permit the retrieval of smooth models that can be used directly for generation of synthetic seismograms using the ray method. In addition, this type of smoothing limits the rise of instabilities related to the poor resolving power of the data. V{sub P}/V{sub S} ratios calculated from P and S models display generally instabilities related to the different ray-coverages of compressional and shear waves. However, V{sub P}/V{sub S} ratios are important for correct identification of rock types and this study introduces a new methodology based on adding some coupling (i.e., proportionality) between P and S models which stabilizes the V{sub P}/V{sub S} models around some average preset value determined from the data. Tests of the technique with synthetic data show that this additional coupling regularizes effectively the resulting models.

Michelini, A.

1991-10-01

143

Resolution for a local earthquake arrival time and ambient seismic noise tomography around the Eyjafjallajökull volcano  

NASA Astrophysics Data System (ADS)

The explosive summit eruption of Eyjafjallajökull volcano from 14 April to end of May 2010 was preceded by an effusive flank eruption of the volcano (at Fimmvörðuháls) March 20th - April 12th. These eruptions culminated 18 years of recurrent volcanic unrest in the area, with extensive seismicity and high deformation rates since beginning of January 2010. A national network of seismic stations in Iceland (the SIL network), operated by he Icelandic Meteorological Office, monitored the precursors and development of the eruptions, in real time. We analyse a seismic dataset available from SIL stations in the vicinity of the eruption area, as well as data from additional portable stations that were deployed during a period of unrest in 1999 and just before and during the eruptions in 2010. The SIL system detected and located 2328 events between early March and late May 2010 in the area around Eyjafjallajökull. Here we present a preliminary evaluation of resolution for a local earthquake arrival time tomography. Adding the portable stations to the pre-existing SIL data set is crucial in order to identify more seismic events and improve the data coverage for tomography. We also present a resolution analysis for Ambient Seismic Noise Tomography (ASNT) in the area. In this method ambient seismic noise, recorded at two seismic stations, is cross-correlated. This band-limited approximation of the Green's function between two stations is used to estimate surface wave velocities. The fundamental assumptions underlying this method is that the noise is constructed from a randomly distributed wavefield, but this may be violated by volcanic tremor during the eruptions. We evaluate the robustness of inter-station correlograms as a function of time during the unrest period as well as their frequency content for evaluation of depth resolution. The results can be compared to constraints on magma movements inside the volcano based on interpretation of crustal deformation and geochemical analyses.

Benediktsdóttir, Á.; Gudmundsson, Ö.; Tryggvason, A.; Bödvarsson, R.; Brandsdóttir, B.; Vogfjörd; K.; Sigmundsson, F.

2012-04-01

144

Universal post-arrival screening for child refugees in Australia: isn't it time?  

PubMed

It is known that the refugee population in Australia is at risk of tuberculosis (TB) and children with TB infection can develop active disease with devastating consequence. Currently, in New South Wales (NSW) and possibly other Australian States and Territories, there are different and complex health-screening pathways for newly arrived refugees. This is compounded by various factors, such as social and language difficulties for refugees to access healthcare and limited pre-embarkation screening. In this Viewpoint article, we present a child refugee in Australia with TB and use this case to reason why a universal post-arrival health screening programme should be established. PMID:22320270

Patradoon-Ho, Patrick S; Ambler, Rosemary W

2010-10-06

145

A mathematical model for a polarisation based orientation measurement principle in time of arrival radio localisation systems  

Microsoft Academic Search

The determination of orientation within time of arrival radio localisation systems is a widely discussed matter within the scientific world. In most cases, this goal is reached by using additional navigation sensors. Some other techniques exist, which are utilising only carrier phase measurements. For that purpose, the antenna configuration has to be chosen adequately. In the case considered here, a

Andreas Eidloth; J. Thielecke

2010-01-01

146

The influence of photon peak arrival in the timing of plastic scintillators by means of pulsed laser and optical fibers  

Microsoft Academic Search

The influence of photon peak arrival in the laser-optical fibers timing system of a large array of plastic scintillators has been studied for different types of photomultipliers. The obtained results, helpful in properly designing the system are presented and discussed.

Pietro Benetti; Massimo Genoni; Alessandra Tomaselli

1988-01-01

147

A study of the importance of nonlinearity in the inversion of earthquake arrival time data for velocity structure  

Microsoft Academic Search

All techniques that currently exist to invert arrival time data from earthquake sources for velocity structue rest on a local linearization of the nonlinear equations relating these data to the velocity model. We have studied the limitations imposed by this approximation using synthetic data in which a one dimensional velocity model is the only varible. We have found that this

Gary L. Pavlis; Jonn R. Booker

1983-01-01

148

A Study of the Importance of Nonlinearity in the Inversion of Earthquake Arrival Time Data for Velocity Structure  

Microsoft Academic Search

All techniques that currently exist to invert arrival time data from earthquake sources for velocity structure rest on a local linearization of the nonlinear equations relating these data to the velocity model. We have studied the limitations imposed by this approximation using synthetic data in which a one dimensional velocity model is the only variable. We have found that this

Gary L. Pavlis; John R. Booker

1983-01-01

149

A Duration Analysis of the Time Taken to Find the First Job for Newly Arrived Migrants in Australia  

Microsoft Academic Search

This paper extends the traditional static focus of research on the labour market assimilation of migrants in Australia by analyzing the dynamics of job search and actual time taken to find the first job after arrival in Australia. The Longitudinal Survey of Immigrants to Australia (LSIA) covers two cohorts of recent migrants to Australia that differ considerably in immigration selection

Prem Jung Thapa; Tue Gørgens

2006-01-01

150

The Development of a General Associative Learning Account of Skill Acquisition in a Relative Arrival-Time Judgment Task  

ERIC Educational Resources Information Center

|Current theory assumes that individuals only use information from the immediate environment to perform relative arrival-time judgment tasks. This article presents a theoretical analysis of the memory requirements of this task. The authors present an analysis of the inputs to the memory system and the processes that map those inputs onto outputs.…

Loft, Shayne; Neal, Andrew; Humphreys, Michael S.

2007-01-01

151

The information from muon arrival time distributions of high-energy EAS as measured with the KASCADE detector  

NASA Astrophysics Data System (ADS)

Using the facilities of the KASCADE Central Detector extensive air showers (EAS) muon arrival time distributions, observed with reference to the arrival time of the first locally registered muon, and their correlations with other EAS observables have been experimentally investigated. The variation of adequately defined time parameters with the distance R? from the EAS axis has been measured. The experimental data enable a study of the sensitivity of such local arrival time distributions, which characterise the structure of the shower disc, to the mass composition of cosmic rays in the energy region around the knee. For that purpose, non-parametric multivariate even-by-event analyses have been performed for an estimate of the mass composition specified by three different mass groups, invoking detailed Monte Carlo simulations of the EAS development. It turns out that local muon arrival time distributions, without information on the curvature of the shower disc, display a minor sensitivity to the mass of the EAS inducing particle, at least for distances from the shower axis R?<100 m. The measurements comprise a subset of all EAS events registered by KASCADE due to the observation conditions of the arrival time distributions, with a threshold of the muon energy Eth=2.4 GeV and a minimum multiplicity nth for being accepted in the observed data samples. This subset is sensitive to variations of the integral EAS muon energy spectrum. By studying the event acceptance in the registered samples on basis of Monte Carlo simulations a test of the consistency of the Monte Carlo simulations with the data is enabled, comparing the results inferred from observations at different R? and different nth values. Within the present uncertainties the results of such a test show a remarkable agreement of the experimental findings with the Monte Carlo simulations, using the QGSJET model as generator of the high-energy hadronic interactions.

KASCADE Collaboration; Antoni, T.; Apel, W. D.; Badea, A. F.; Bekk, K.; Bercuci, A.; Blümer, H.; Bozdog, H.; Brancus, I. M.; Büttner, C.; Chilingarian, A. A.; Daumiller, K.; Doll, P.; Engler, J.; Fessler, F.; Gils, H. J.; Glasstetter, R.; Haeusler, R.; Haungs, A.; Heck, D.; Hörandel, J. R.; Iwan, A.; Kampert, K. H.; Klages, H. O.; Maier, G.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Müller, M.; Obenland, R.; Oehlschläger, J.; Ostapchenko, S.; Petcu, M.; Rebel, H.; Risse, M.; Roth, M.; Schatz, G.; Schieler, H.; Scholz, J.; Thouw, T.; Ulrich, H.; Weber, J. H.; Weindl, A.; Wentz, J.; Wochele, J.; Zabierowski, J.

2003-01-01

152

Sexual selection and spring arrival times of red-necked and Wilson's phalaropes  

Microsoft Academic Search

Seasonal changes in sex ratios during a 4-year study of red-necked phalaropes and a 3-year study of Wilson's phalaropes showed that females preceded males to breeding and\\/or courtship areas. The degree to which females preceded males may have been constrained by harsh weather, as the arrival of red-necked phalaropes was synchronous in 1983, when spring was unusually late. Neither sex

John D. Reynolds; Mark A. Colwell; Fred Cooke

1986-01-01

153

Age-Correlated Incremental Consideration of Velocity Information in Relative Time-to-Arrival Judgments  

Microsoft Academic Search

One hundred fifty-one children and 43 adults judged which of 2 cartoon birds would be the first to arrive at a common finish line. Objects moved unidirectionally along parallel trajectories, either at the same or different speeds, and disappeared at different distances from the goal. Overall, 9–10-year-old children performed as well as adults, but 4–5- and 6–8-year-olds erred significantly more

Behrang Keshavarza; Klaus Landwehra; Robin Baurèsa; Daniel Oberfelda; Heiko Hechta; Nicolas Benguiguib

2010-01-01

154

Operational warning of interplanetary shock arrivals using energetic particle data from ACE: Real-time Upstream Monitoring System  

NASA Astrophysics Data System (ADS)

We report on an operational system which provides advance warning and predictions of arrival times at Earth of interplanetary (IP) shocks that originate at the Sun. The data stream used in our prediction algorithm is real-time and comes from the Electron, Proton, and Alpha Monitor (EPAM) instrument on NASA's Advanced Composition Explorer (ACE) spacecraft. Since locally accelerated energetic storm particle (ESP) events accompany most IP shocks, their arrival can be predicted using ESP event signatures. We have previously reported on the development and implementation of an algorithm which recognizes the upstream particle signature of approaching IP shocks and provides estimated countdown predictions. A web-based system (see (http://sd-www.jhuapl.edu/UPOS/RISP/index.html) combines this prediction capability with real-time ACE/EPAM data provided by the NOAA Space Environment Center. The most recent ACE data is continually processed and predictions of shock arrival time are updated every five minutes when an event is impending. An operational display is provided to indicate advisories and countdowns for the event. Running the algorithm on a test set of historical events, we obtain a median error of about 10 hours for predictions made 24-36 hours before actual shock arrival and about 6 hours when the shock is 6-12 hours away. This system can provide critical information to mission planners, satellite operations controllers, and scientists by providing significant lead-time for approaching events. Recently, we have made improvements to the triggering mechanism as well as re-training the neural network, and here we report prediction results from the latest system.

Donegan, M.; Vandegriff, J.; Ho, G. C.; Julia, S. J.

2004-12-01

155

An Improved Technique to Predict the Time-of-Arrival of a Tumor Response in Radar-Based Breast Imaging  

Microsoft Academic Search

Radar-based microwave imaging has been proposed as a complementary modality for early-stage breast cancer screening. This paper presents an algorithm that may be used to accurately predict the time-of-arrival (TOA) of a tumor response contained in sample data acquired from a small number of antennas in a realistic scenario. The TOA information may be used by many of the existing

Douglas J. Kurrant; Elise C. Fear

2009-01-01

156

Experimental demonstration of a method to realize weak measurement of the arrival time of a single photon  

SciTech Connect

We present a realization of weak measurement for the arrival time of a single photon in virtue of the simultaneous characteristic of biphotons. Our experimental setup is based on a Hong-Ou-Mandel interferometer. A birefringent crystal is used to perform weak measurement between a preselected and a postselected measurement by two polarizers. The extreme weak values lie well outside of the eigenvalues of the observable.

Wang Qin; Sun Fangwen; Zhang Yongsheng; Jian Li; Huang Yunfeng; Guo Guangcan [Key Laboratory of Quantum Information, Department of Physics, University of Science and Technology of China, Hefei 230026 (China)

2006-02-15

157

Using soft X-ray observations to help the prediction of flare related interplanetary shocks arrival times at the Earth  

NASA Astrophysics Data System (ADS)

It is very important to predict the shock arrival times (SATs) at Earth for space weather practice. In this paper we use the energy of soft X-ray during solar flare events to help predict the SATs at Earth. We combine the soft X-ray energy and SAT prediction models previously developed by researchers to obtain two new methods. By testing the methods with the total of 585 solar flare events following the generation of a metric type II radio burst during the Solar Cycle 23 from September 1997 to December 2006, we find that the predictions of SATs at Earth could be improved by significantly increasing PODn, the proportion of events without shock detection that were correctly forecast. PODn represents a method's ability in forecasting the solar flare events without shocks arriving at the Earth, which is important for operational predictions.

Liu, H.-L.; Qin, G.

2012-04-01

158

Optical pin apparatus for measuring the arrival time and velocity of shock waves and particles  

DOEpatents

An apparatus for the detection of the arrival and for the determination of the velocity of disturbances such as shock-wave fronts and/or projectiles. Optical pins using fluid-filled microballoons as the light source and an optical fiber as a link to a photodetector have been used to investigate shock-waves and projectiles. A microballoon filled with a noble gas is affixed to one end of a fiber-optic cable, and the other end of the cable is attached to a high-speed streak camera. As the shock-front or projectile compresses the microballoon, the gas inside is heated and compressed producing a bright flash of light. The flash of light is transmitted via the optic cable to the streak camera where it is recorded. One image-converter streak camera is capable of recording information from more than 100 microballoon-cable combinations simultaneously.

Benjamin, Robert F. (315 Rover Blvd., Los Alamos, NM 87544)

1987-01-01

159

Optical pin apparatus for measuring the arrival time and velocity of shock waves and particles  

DOEpatents

An apparatus for the detection of the arrival and for the determination of the velocity of disturbances such as shock-wave fronts and/or projectiles. Optical pins using fluid-filled microballoons as the light source and an optical fiber as a link to a photodetector have been used to investigate shock-waves and projectiles. A microballoon filled with a noble gas is affixed to one end of a fiber-optic cable, and the other end of the cable is attached to a high-speed streak camera. As the shock-front or projectile compresses the microballoon, the gas inside is heated and compressed producing a bright flash of light. The flash of light is transmitted via the optic cable to the streak camera where it is recorded. One image-converter streak camera is capable of recording information from more than 100 microballoon-cable combinations simultaneously.

Benjamin, R.F.

1983-10-18

160

Optical pin apparatus for measuring the arrival time and velocity of shock waves and particles  

DOEpatents

An apparatus is disclosed for the detection of the arrival and for the determination of the velocity of disturbances such as shock-wave fronts and/or projectiles. Optical pins using fluid-filled microballoons as the light source and an optical fiber as a link to a photodetector have been used to investigate shock-waves and projectiles. A microballoon filled with a noble gas is affixed to one end of a fiber-optic cable, and the other end of the cable is attached to a high-speed streak camera. As the shock-front or projectile compresses the microballoon, the gas inside is heated and compressed producing a bright flash of light. The flash of light is transmitted via the optic cable to the streak camera where it is recorded. One image-converter streak camera is capable of recording information from more than 100 microballoon-cable combinations simultaneously. 3 figs.

Benjamin, R.F.

1987-03-10

161

Method and system of time-of-arrival estimation for ultra wideband multi-band orthogonal frequency division multiplexing signals  

US Patent & Trademark Office Database

A time-of-arrival (TOA) estimation method for multi-band orthogonal frequency division multiplexing (MB-OFDM) signals uses a simple equally-spaced channel model to recover the impulse response of the wireless channel, and locates the delay of the first channel path by minimizing the energy leakage from the first channel path. The TOA is estimated based on the delay. Such a method does not require channel information for TOA estimation at the receiver and does not require modification of the receiver structure. The method also avoids a sub-optimal solution known to occur in maximum likelihood (ML) estimation.

Xu; Huilin (Gainesville, FL); Chong; Chia-Chin (Santa Clara, CA); Guvenc; Ismail (Santa Clara, CA)

2011-09-20

162

An approach for history matching of reservoir pressure and arrival time - An example from the Ketzin pilot site, Germany  

NASA Astrophysics Data System (ADS)

The Ketzin site is the first pilot project for CO2 storage in Germany. The site is located in Brandenburg about 25 km from Berlin. Since June 2008, CO2 is injected into a saline aquifer in about 630 m to 650 m depth. The total amount of injected CO2 is much smaller (< 100.000 tons) than expected on industrial scales. However, the site is an excellent pilot project for monitoring and history matching. Beneath the injection well, two observation wells were drilled in 2007. An important task of the dynamic modelling activities is the history match of the reservoir pressure and the CO2 arrival at the observation wells. The number of degrees of freedom in a strongly heterogeneous domain is much too high for a well-posed inverse problem. Therefore, the history match requires a systematic successive procedure. What we present here is in a first step the attempt to match the pressure at the injection well since we expect the highest sensitivity to the data here. The pressure at the injection well and the first arrival time will be matched by using an inverse modelling technique. Therefore, three parameters, (1) permeability near the injection well, (2) the overall field permeability and (3) the porosity are varied. All other parameters are assumed to be known although this is a very severe restriction. In a second step the pressure at the second observation well will be matched as well. The second arrival time was observed much later than initially predicted by the models. One out of several possibilities to explain this delay is the existence of a low permeable barrier right below the top of a sand channel. The CO2 as the lighter one of the two fluid phases water and CO2 can be retained at this barrier and will start flowing beneath the barrier not before a certain threshold amount of CO2 reached the barrier.

Class, Holger; Walter, Lena

2013-04-01

163

Time resolved study of light emitted by detonation arrival at the surface of high explosives in various environments  

SciTech Connect

In search of a way to accurately measure time of arrival of detonation fronts, we have been using an electronic streak camera equipped with a light intensifier to record intensity-time histories of the light that is emitted when a detonation front emerges through the surface of high explosives in contact with various environments. Streak records at writing speeds up to 100 mm/..mu..s were obtained of detonations in air, argon, water and vacuum when the high explosive (HE) was either bare or covered with materials such as: aluminum silicofluoride (Al/sub 2/(SiF/sub 6/)/sub 3/), PETN powder, polymethyl methacrylate (PMM), glass, aluminum foils, transparent tape, black ink, potassium chloride crystals, sodium chloride crystals and lithium fluoride crystals. The result of this study is that we believe that we can measure the time of arrival of a detonation front at a bare HE surface in air to within a few nanoseconds. 12 refs., 10 figs., 1 tab.

Bahl, K.L.; Von Holle, W.G.

1988-03-24

164

Position surveillance using one active ranging satellite and time-of-arrival of a signal from an independent satellite  

NASA Astrophysics Data System (ADS)

Position surveillance using one active ranging/communication satellite and the time-of-arrival of signals from an independent satellite was shown to be feasible and practical. A towboat on the Mississippi River was equipped with a tone-code ranging transponder and a receiver tuned to the timing signals of the GOES satellite. A similar transponder was located at the office of the towing company. Tone-code ranging interrogations were transmitted from the General Electric Earth Station Laboratory through ATS-6 to the towboat and to the ground truth transponder office. Their automatic responses included digital transmissions of time-of-arrival measurements derived from the GOES signals. The Earth Station Laboratory determined ranges from the satellites to the towboat and computed position fixes. The ATS-6 lines-of-position were more precise than 0.1 NMi, 1 sigma, and the GOES lines-of-position were more precise than 1.6 NMi, 1 sigma. High quality voice communications were accomplished with the transponders using a nondirectional antenna on the towboat. The simple and effective surveillance technique merits further evaluation using operational maritime satellites.

Anderson, R. E.; Frey, R. L.; Lewis, J. R.

1980-01-01

165

Longer term trends in arrival timing of long distance migrants: the influence of abundance and population change  

Microsoft Academic Search

The first arrival dates for summer migrants in Cheshire and Wirral indicate a longer term trend towards earlier arrival since the mid 1970s, consistent with the findings of previous studies based on first arrival data from UK area bird reports. The aim of this study was to investigate the influence of abundance and population change on the apparent advancement of

Mark J. Eddowes

2011-01-01

166

P-wave propagation heterogeneity and earthquake location in the Mediterranean region  

NASA Astrophysics Data System (ADS)

We analyse P-wave traveltimes for the Mediterranean area, using both teleseismic and regional arrivals for shallow earthquakes reported in the Bulletins of the International Seismological Centre. We model delays between pairs of 0.5° × 0.5° cells, obtaining a detailed representation of the P traveltime heterogeneities. Examination of these anomalies shows the clear presence of geographically coherent patterns-consistent with known geological features-due to significant structure in the upper mantle. We present a scheme, based on an empirical heterogeneity correction (EHC) to P-wave traveltimes, to improve earthquake location. This method provides similar benefits to those of a location procedure based on ray tracing in a 3-D model, but it is simpler and computationally more efficient. The definition of the traveltime heterogeneity model, being based on a statistical procedure, bypasses most of the critical points and possible instabilities involved in model inversion. EHC relocation, applied to Mediterranean earthquakes, allows one to predict about 70 per cent of the estimated signal due to heterogeneity and produces epicentral and origin time-shifts of, respectively, 4.22 km and 0.35 s (rms). From a synthetic experiment, in which we use the proposed algorithm to retrieve known source locations, we estimate that the rms improvement achieved by the EHC relocation over a simpler, standard, 1-D location is more than 20 per cent for both epicentral mislocation and origin time-shifts.

Piromallo, Claudia; Morelli, Andrea

1998-10-01

167

An operational system for the remote location of lightning flashes using a VLF arrival time difference technique  

NASA Astrophysics Data System (ADS)

An operational system for the remote location of lightning flashes at ranges of thousands of kilometers is presented. The vertical electric fields of VLF radio atmospherics, together with time data, are observed at a network of just seven outstations dispersed over the United Kingdom and the Mediterranean. These data are forwarded to a control station, which locates individual flashes in real time using arrival time difference techniques, analogous to Loran-C, and generates regular reports for automatic distribution. The service area covered exceeds 30 deg to 70 deg N, 40 deg W to 40 deg E; flash location accuracy is 2-20 km; and approximately 400 flashes per hour can be located.

Lee, Anthony C. L.

1986-12-01

168

Three-dimensional P-wave velocity structure of Mt. Etna, Italy  

USGS Publications Warehouse

The three-dimensional P-wave velocity structure of Mt. Etna is determined to depths of 15 km by tomographic inversion of first arrival times from local earthquakes recorded by a network of 29 permanent and temporary seismographs. Results show a near-vertical low-velocity zone that extends from beneath the central craters to a depth of 10 km. This low-velocity region is coincident with a band of steeply-dipping seismicity, suggesting a magmatic conduit that feeds the summit eruptions. The most prominent structure is an approximately 8-km-diameter high-velocity body located between 2 and 12 km depth below the southeast flank of the volcano. This high-velocity body is interpreted as a remnant mafic intrusion that is an important structural feature influencing both volcanism and east flank slope stability and faulting.

Villasenor, A.; Benz, H. M.; Filippi, L.; De Luca, G.; Scarpa, R.; Patane, G.; Vinciguerra, S.

1998-01-01

169

Determination of absolute arrival times for secondary phases from combined waveform cross-correlation and differential t* measurement: Application to USArray data  

NASA Astrophysics Data System (ADS)

Automatic determination of secondary arrivals such as PP and PcP is often not performed due to processing difficulties that make designing automatic detection routines difficult. The lack of these secondary arrivals in travel time tomography, particularly for global data sets, leads to significant gaps in resolution. In this study, we develop and implement a method for automatically determining the exact time of these arrivals. We do this through the iterative application of waveform cross-correlation and differential attenuation (i.e. PP-P) deconvolution. This method is able to be applied without much input from the user and outputs both absolute arrival time and differential t* measurements. We first use cross-correlation of a known, hand-picked arrival from the Earthscope Array Network Facility with a predicted arrival for a secondary phase. These arrivals are then used in the method of Roth, et al. (1996) to determine the differential t* transfer function. We apply the transfer function to the phase with greater amplitude and re-cross-correlate to find a more exact secondary arrival time. We limit event selection by distance to ensure that there is no risk of contamination from triplication effects and limit phase selection by signal-to-noise ratio to ensure sufficient signal for cross-correlation. This method is fast and efficient in finding a large number of secondary arrivals for phases that are not usually picked during preliminary earthquake location studies. Application of this method to EarthScope data will improve both attenuation and travel-time tomography studies of the North American Plate.

Shore, P.; Heeszel, D. S.; Wysession, M. E.; Euler, G. G.

2009-12-01

170

On the possibility to discriminate the mass of the primary cosmic ray using the muon arrival times from extensive air showers: Application for Pierre Auger Observatory  

SciTech Connect

In this paper we study the possibility to discriminate the mass of the primary cosmic ray by observing the muon arrival times in ground detectors. We analyzed extensive air showers (EAS) induced by proton and iron nuclei with the same energy 8 Multiplication-Sign 10{sup 17} eV simulated with CORSIKA, and analyzed the muon arrival times at ground measured by the infill array detectors of the Pierre Auger Observatory (PAO). From the arrival times of the core and of the muons the atmospheric depth of muon generation locus is evaluated. The results suggest a potential mass discrimination on the basis of muon arrival times and of the reconstructed atmospheric depth of muon production. An analysis of a larger set of CORSIKA simulations carried out for primary energies above 10{sup 18} eV is in progress.

Arsene, N.; Rebel, H.; Sima, O. [Institute of Space Science (ISS), Bucharest-Magurele, P.O. Box MG-23 (Romania) and Physics Department, University of Bucharest, Bucharest-Magurele (Romania); Karlsruhe Institute of Technology, Karlsruhe (Germany); Physics Department, University of Bucharest, Bucharest-Magurele (Romania)

2012-11-20

171

41 CFR 301-11.10 - Am I required to record departure/arrival dates and times on my travel claim?  

Code of Federal Regulations, 2011 CFR

...record departure/arrival dates and times on my travel claim? 301-11.10 Section 301-11...Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES ALLOWABLE TRAVEL EXPENSES...

2011-07-01

172

41 CFR 301-11.10 - Am I required to record departure/arrival dates and times on my travel claim?  

Code of Federal Regulations, 2012 CFR

...record departure/arrival dates and times on my travel claim? 301-11.10 Section 301-11...Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES ALLOWABLE TRAVEL EXPENSES...

2012-07-01

173

Improved frequency and time of arrival estimation methods in search and rescue system based on MEO satellites  

NASA Astrophysics Data System (ADS)

This paper deals with several key points including parameter estimation such as frequency of arrival (FOA), time of arrival (TOA) estimation algorithm and signal processing techniques in Medium-altitude Earth Orbit Local User Terminals (MEOLUT) based on Cospas-Sarsat Medium-altitude Earth Orbit Search and Rescue system (MEOSAR). Based on an analytical description of distress beacon, improved TOA and FOA estimation methods have been proposed. An improved FOA estimation method which integrates bi-FOA measurement, FFT method, Rife algorithm and Gaussian window is proposed to improve the accuracy of FOA estimation. In addition, TPD algorithm and signal correlation techniques are used to achieve a high performance of TOA estimation. Parameter estimation problems are solved by proposed FOA/TOA methods under quite poor Carrier-to-Noise (C/N0). A number of simulations are done to show the improvements. FOA and TOA estimation error are lower than 0.1Hz and 11?s respectively which is very high system requirement for MEOSAR system MEOLUT.

Lin, Mo; Li, Rui; Li, Jilin

2007-11-01

174

DIRECTION OF ARRIVAL ESTIMATION IN PARTLY CALIBRATED TIME-VARYING SENSOR ARRAYS  

Microsoft Academic Search

We consider the direction finding problem in time-varying arrays composed of identically oriented subarrays displaced by unknown vector translations. A new eigenstructure-based estimator is pro- posed for such a class of partly calibrated sensor arrays.

Marius Pesavento; Alex B. Gershman Kon; Max Wong

2001-01-01

175

Direction of arrival estimation in partly calibrated time-varying sensor arrays  

Microsoft Academic Search

We consider the direction finding problem in time-varying arrays composed of identically oriented subarrays displaced by unknown vector translations. A new eigenstructure-based estimator is proposed for such a class of partly calibrated sensor arrays

Marius Pesavento; A. B. Gershman; Kon Max Wong

2001-01-01

176

Queue length and waiting time analysis of a batch arrival queue with bilevel control  

Microsoft Academic Search

Scope and Purpose—This paper concerns the analysis of a production system in which an early set-up and N-policy are employed. We model the system by Mx\\/M\\/1 queue with bilevel control and obtain the queue length and waiting time distributions. In general, with more than two control policies mixed up, obtaining the waiting time distribution is extremely complicated due to the

Ho Woo Lee; J. G. Park; B. K. Kim; Seung Hyun Yoon; Boo Yong Ahn; No Ik Park

1998-01-01

177

Image Velocity, Not Tau, Explains Arrival-Time Judgments From Global Optical Flow  

Microsoft Academic Search

The time-to-passage (TTP; i.e., the time) until an object passes an observer is optically specified by global tau, a variable that operates on the expansion rate of the angle subtended by an object relative to the observer's heading. M. K. Kaiser and L. Mowafy (1993) provided evidence for observers' sensitivity to global tau in a 3-D cloud of point lights.

Dirk Kerzel; Heiko Hecht; Nam-Gyoon Kim

1999-01-01

178

Smolt Condition and Timing of Arrival at Lower Granite Reservoir, 1988 Annual Report.  

SciTech Connect

This project monitored the daily passage of smelts during the 1988 spring outmigration at two migrant traps; one each on the Snake and Clear-water rivers. Due to the low runoff year, chinook salmon catch at the Snake River trap was very low. Steelhead trout catch was higher than normal, probably due to trap modifications and because the trap was moved to the east side of the river. Chinook salmon and steelhead trout catch at the Clearwater River trap was similar to 1987. Total cumulative recovery of PIT tagged fish at the three dams, with PIT tag detection systems was: 55% for chinook salmon, 73% for hatchery steelhead trout, and 75% for wild steelhead trout. Travel time through Lower Granite Reservoir for PIT tagged chinook salmon and steelhead trout, marked at the head of the reservoir, was affected by discharge. Statistical analysis showed that as discharge increased from 40 kcfs to 80 kcfs, chinook salmon travel time decreased three fold, and steelhead trout travel time decreased two fold. There was a statistical difference between estimates of travel time through Lower Granite Reservoir for PIT tagged and freeze branded steelhead trout, but not for chinook salmon. These differences may be related to the estimation techniques used for PIT tagged and freeze branded groups, rather than real differences in travel time.

Buettner, Edwin W.; Nelson, William R.

1989-10-01

179

Real-time shock arrival predictions during the ``Halloween 2003 epoch''  

Microsoft Academic Search

The ``Halloween'' epoch from 19 October to 20 November 2003 was marked by 19 major solar flares that were accompanied by metric type II radio bursts. Several of these flares were followed by major geomagnetic storms. The radio bursts were used in real time because they imply coronal and interplanetary transport. Most of these events were also associated with halo

M. Dryer; Z. Smith; C. D. Fry; W. Sun; C. S. Deehr; S.-I. Akasofu

2004-01-01

180

On the estimation of true speeds and arrival times of CMEs observed during 2007-2011  

NASA Astrophysics Data System (ADS)

I will present results on a study of the relationship between the speeds of a few coronal mass ejections (CMEs) measured in the corona close to the Sun and in the interplanetary medium during the ascending phase of the solar cycle 24, i.e. from 2007 to 2011. Close to the Sun, we use different techniques like forward modeling, 3D height-time and triangulation to estimate the true speeds and direction of propagation from images taken by COR1 & 2 white-light coronagraphs and also Heliospheric Imagers (HI) aboard STEREO. The 3D speeds obtained in this way are used in the CME travel time prediction models to determine the actual CME transit times from the Sun to STEREO, ACE or Wind spacecraft. These are then compared with the transit times calculated using projected CME speeds. We find CME 3D speeds give improved predictions than that obtained from projected CME speeds for most of the events. The sources of errors will be discussed and interpretation of the results in the wake of the solar minimum phase will also be highlighted.

Srivastava, Nandita

2012-07-01

181

Global lightning mapping with time of arrival method using ELF network data  

Microsoft Academic Search

ELF (less than 3 kHz) waves radiated from lightning discharges can propagate around the world many times in the Earth-ionosphere waveguide due to its extremely low attenuation. This characteristic enables us to monitor the global lightning activity with single or few ELF observation sites. Global observation of cloud-to-ground (CG) discharge based on ELF measurements provides essential information including charge moment

K. Yamashita; Y. Takahashi; M. Sato; H. Kase

2009-01-01

182

Efimov Effect for P-wave Interactions  

Microsoft Academic Search

Nonrelativistic particles with short-range interactions that produce a P-wave threshold resonance can exhibit the Efimov effect: if the inverse scattering volume 1\\/a_P and the P-wave effective range r_P are simultaneously tuned to zero, there is an infinite sequence of three-body bound states called Efimov states that have an accumulation point at the threshold. The discrete scaling factor that characterizes the

Eric Braaten; P. Hagen; H.-W. Hammer; L. Platter

2011-01-01

183

An algorithm for the localization of multiple interfering sperm whales using multi-sensor time difference of arrival.  

PubMed

In this paper an algorithm is described for the localization of individual sperm whales in situations where several near-by animals are simultaneously vocalizing. The algorithm operates on time-difference of arrival (TDOA) measurements observed at sensor pairs and assumes no prior knowledge of the TDOA-whale associations. In other words, it solves the problem of associating TDOAs to whales. The algorithm is able to resolve association disputes where a given TDOA measurement may fit to more than one position estimate and can handle spurious TDOAs. The algorithm also provides estimates of Cramer-Rao lower bound for the position estimates. The algorithm was tested with real data using TDOA estimates obtained by cross-correlating click-trains. The click-trains were generated by a separate algorithm that operated independently on each sensor to produce click-trains corresponding to a given whale and to reject click-trains from reflected propagation paths. PMID:21786881

Baggenstoss, Paul M

2011-07-01

184

Smolt Condition and Timing of Arrival at Lower Granite Reservoir, 1984 Annual Report.  

SciTech Connect

Hatcheries released 9.3 million chinook salmon and 6.3 million steelhead smolts and presmolts upriver from Lower Granite Reservoir for migration in spring, 1984. Peak passage of yearling chinook salmon occurred the third week in April at both Whitebird and Snake River traps. Passage of steelhead was still increasing when high water stopped trapping in mid-May. Average migration rate between release sites and Snake River (the head of Lower Granite Reservoir) was 13.2 miles/day and from that point on through the reservoir to the dam, 1.9 miles/day. Salmon River discharge, when considered along with other environmental factors, had the greatest effect on migration rate of smolts branded both at hatcheries and at the Whitebird trap and migrating to the head of Lower Granite Reservoir. Migration rate for steelhead released from Dworshak Hatchery and recaptured at the Clearwater trap was 34 miles/day. Survival rates to the Snake River trap of branded chinook salmon smolts released at Hells Canyon Dam, Rapid River, South Fork Salmon and Decker Flat were 52%, 65%, 68% and 35%, respectively. Classical descaling, where at least 40% of the scales are missing from at least two of five areas on the side of a smolt, ranged from 0 to 5.3% at hatcheries for chinook salmon and was less than 1% for steelhead. Scattered descaling, where at least 10% of scales are missing from at least one side of a fish, was always more extensive than was classical descaling, ranging from 2.5 times greater for Clearwater hatchery steelhead to 6.8 times greater for Clearwater wild steelhead. Mean total length of chinook salmon yearlings was the same at all the traps, i.e., 128 mm (117 mm fork length) +- 1 mm.

Scully, Richard J.; Buettner, Edwin W.

1986-02-01

185

Smolt Condition and Timing of Arrival at Lower Granite Reservoir, 1986 Annual Report.  

SciTech Connect

This project monitored the daily passage of smolts during the 1986 spring outmigration at two migrant traps, one each on the Snake and Clearwater rivers. Average migration rates for freeze-branded chinook salmon smolts were 28.2 km per day and 22.1 km per day for steelhead trout smolts between release sites and the head of Lower Granite Reservoir. The yearling chinook salmon migration begins in earnest when Salmon River discharge makes a significant rise in early to mid-April. Most yearling chinook salmon pass into Lower Granite Reservoir in April followed by passage of steelhead trout in May. Chinook salmon smolt recapture data from the Snake River trap suggest a strong dependence of migration rate on quantity of Snake and Salmon River discharge, although no statistical correlation exists at this time. Daily and seasonal descaling rates were calculated for each species at each trap. Rates were highest for hatchery steelhead trout, intermediate for yearling chinook salmon, and lowest for wild steelhead trout. Descaling rates were generally higher in 1986 than those observed in 1984 and 1985. 4 refs., 9 figs., 15 tabs.

Buettner, Edwin W.; Nelson, V. Lance

1987-09-01

186

Subduction of the Philippine Sea slab in view of P-wave anisotropy  

NASA Astrophysics Data System (ADS)

Three-dimensional (3D) structure of isotropic and anisotropic velocities in the Chugoku and Shikoku districts, southwest Japan, is retrieved from the first P-arrival times from local earthquakes by assuming P-wave azimuthal anisotropy with hexagonal-symmetry axis. The main result of isotropic velocity structure is that the Philippine Sea (PHS) slab is represented by a high-velocity body with the thickness of 20 30 km lying at the around depth of 40 km beneath the Shikoku and southern Chugoku districts. The PHS slab subduction appears to be interrupted by a small-scale low-velocity body under middle Chugoku and is not clear under north Chugoku. These features of 3D isotropic velocity structure are basically similar to those obtained in previous tomographic studies using recent seismic data. This result suggests that seismic anisotropy has no significant effect on estimation of isotropic velocity structure from the P-arrival time data. On the other hand, fast propagation directions of P-wave azimuthal anisotropy in the crust are basically in close agreement with fast polarization directions estimated from polarization anomaly of shear waves. Azimuthal anisotropy in the crust of Shikoku district is characterized by the fast propagation direction with the E W orientation trend, which is nearly parallel to trajectory of maximum principal stress acting on the southwest Japan arc and strike directions of zonal geological structure. Crustal anisotropy in the Chugoku district is consistent with the orientation of the geological structure, and not with the maximum principal stress direction. These results indicate that the crustal anisotropy is attributable not only to alignment of the stress-induced cracks but also to lineament of geological structures. We could also point out the difference in the upper mantle anisotropy between the Shikoku and Chugoku districts; i.e., P-wave velocity tends to be fast in the N S directions beneath Shikoku and southern Chugoku and in E W directions under northern Chugoku. Since the N S axis trend of P-wave anisotropy is highly correlated with high-velocity anomaly of PHS slab, it is regarded as slab anisotropy. The reason why the P-wave anisotropy shows the high propagation velocity in the E W direction beneath northern Chugoku is discussed on the example of two cases in which the PHS slab is absent and present in the upper mantle beneath the region. Although we could not locate exactly the north leading edge of the PHS slab in view of anisotropic velocity structure, if the PHS slab is defined as a high-velocity body with fast propagation axes in the directions of N S system, it turns out to exist at least beneath Shikoku to south Chugoku.

Ishise, Motoko; Oda, Hitoshi

2008-01-01

187

Simulation-based validation and arrival-time correction for Patlak analyses of Perfusion-CT scans  

NASA Astrophysics Data System (ADS)

Blood-brain-barrier (BBB) breakdown is a hypothesized mechanism for hemorrhagic transformation in acute stroke. The Patlak analysis of a Perfusion Computed Tomography (PCT) scan measures the BBB permeability, but the method yields higher estimates when applied to the first pass of the contrast bolus compared to a delayed phase. We present a numerical phantom that simulates vascular and parenchymal time-attenuation curves to determine the validity of permeability measurements obtained with different acquisition protocols. A network of tubes represents the major cerebral arteries ipsi- and contralateral to an ischemic event. These tubes branch off into smaller segments that represent capillary beds. Blood flow in the phantom is freely defined and simulated as non-Newtonian tubular flow. Diffusion of contrast in the vessels and permeation through vessel walls is part of the simulation. The phantom allows us to compare the results of a permeability measurement to the simulated vessel wall status. A Patlak analysis reliably detects areas with BBB breakdown for acquisitions of 240s duration, whereas results obtained from the first pass are biased in areas of reduced blood flow. Compensating for differences in contrast arrival times reduces this bias and gives good estimates of BBB permeability for PCT acquisitions of 90-150s duration.

Bredno, Jörg; Hom, Jason; Schneider, Thomas; Wintermark, Max

2009-02-01

188

Three-Dimensional P-Wave Velocity Image under the Carpathian Arc.  

National Technical Information Service (NTIS)

An inversion of P-wave travel time residuals from selected earthquakes in the distance range 30 deg to 98 deg to 2 seismic station networks was used to model P-wave velocity anomalies down to 250 Km depth. In the first inversion experiment a region betwee...

M. C. Oncescu V. Burlacu M. Anghel V. Smalbergher

1982-01-01

189

Arrival Time Calculation for Interplanetary Coronal Mass Ejections with Circular Fronts and Application to STEREO Observations of the 2009 February 13 Eruption  

NASA Astrophysics Data System (ADS)

One of the goals of the NASA Solar TErestrial RElations Observatory (STEREO) mission is to study the feasibility of forecasting the direction, arrival time, and internal structure of solar coronal mass ejections (CMEs) from a vantage point outside the Sun-Earth line. Through a case study, we discuss the arrival time calculation of interplanetary CMEs (ICMEs) in the ecliptic plane using data from STEREO/SECCHI at large elongations from the Sun in combination with different geometric assumptions about the ICME front shape [fixed-? (FP): a point and harmonic mean (HM): a circle]. These forecasting techniques use single-spacecraft imaging data and are based on the assumption of constant velocity and direction. We show that for the slow (350 km s-1) ICME on 2009 February 13-18, observed at quadrature by the two STEREO spacecraft, the results for the arrival time given by the HM approximation are more accurate by 12 hr than those for FP in comparison to in situ observations of solar wind plasma and magnetic field parameters by STEREO/IMPACT/PLASTIC, and by 6 hr for the arrival time at Venus Express (MAG). We propose that the improvement is directly related to the ICME front shape being more accurately described by HM for an ICME with a low inclination of its symmetry axis to the ecliptic. In this case, the ICME has to be tracked to >30° elongation to obtain arrival time errors < ± 5 hr. A newly derived formula for calculating arrival times with the HM method is also useful for a triangulation technique assuming the same geometry.

Möstl, C.; Rollett, T.; Lugaz, N.; Farrugia, C. J.; Davies, J. A.; Temmer, M.; Veronig, A. M.; Harrison, R. A.; Crothers, S.; Luhmann, J. G.; Galvin, A. B.; Zhang, T. L.; Baumjohann, W.; Biernat, H. K.

2011-11-01

190

Gamma-Ray Burst Arrival Time Localizations: Simultaneous Observations by Pioneer Venus Orbiter, Compton Gamma-Ray Observatory, and ULYSSES  

NASA Astrophysics Data System (ADS)

Between the Compton Gamma Ray Observatory (CGRO) launch in 1991 April and the Pioneer Venus Orbiter (PVO) demise in 1992 October, concurrent coverage by CGRO, PVO, and Ulysses was obtained for several hundred gamma-ray bursts (GRBs). Although most of these were below the PVO and Ulysses thresholds, 37 were positively detected by all three spacecraft, with data quality adequate for quantitative localization analysis. All were localized independently to ~2 deg accuracy by the CGRO Burst and Transient Source Experiment (BATSE), and three were also localized by COMPTEL. We computed arrival-time error boxes, whose larger dimensions range from about 2' to several degrees and whose smaller dimensions are in the arcminute range. Twelve have areas less than 10 arcmin^2, and only four have areas greater than 1 deg^2. The area of the smallest box is 0.44 arcmin^2. We find that the overall BATSE localization accuracy for these events is consistent with the most recent stated uncertainties. This work indicates that the ROSAT soft X-ray source found within a preliminary IPN error box for GB920501 (Trig 1576) (Hurley et al.) is less likely to be the GRB counterpart than previously reported.

Laros, J. G.; Hurley, K. C.; Fenimore, E. E.; Klebesadel, R. W.; Briggs, M. S.; Kouveliotou, C.; McCollough, M. L.; Fishman, G. J.; Meegan, C. A.; Cline, T. L.; Boer, M.; Niel, M.

1998-10-01

191

First measurement of scintillation photon arrival statistics using a high-granularity solid-state photosensor enabling time-stamping of up to 20,480 single photons  

Microsoft Academic Search

We propose a novel experimental method using a single-photon avalanche diode and time-to-digital convertor (SPAD-TDC) array that, for the first time, enables simultaneous measurement of the spatial and time dependence of the arrival of optical photons in a scintillation pulse with high resolution (tunable between 55 and 100 ps in time, 50 µm in space). By registering all available timing

J. R. Meijlink; C. Veerappan; S. Seifert; D. Stoppa; R. K. Henderson; E. Charbon; D. R. Schaart

2011-01-01

192

Theory and measurement of the angle of arrival and time delay of UHF radiowaves using a ring array  

Microsoft Academic Search

The knowledge of directions of arrival (DOA) of waves is fundamental in understanding the physics of the mobile communications wide-band propagation channel. We first present a measurement setup that is able to accurately measure these DOA. It is based on the evaluation of the channel complex impulse response at regularly spaced locations on a circle. We theoretically investigate a new

Jean-Pierre Rossi; Jean-Pierre Barbot; Armand J. Levy

1997-01-01

193

Automatic seismic wave arrival detection and picking with stationary analysis: Application of the KM2O-Langevin equations  

NASA Astrophysics Data System (ADS)

An automatic detection and a precise picking of the arrival times of seismic waves using digital seismograms are important for earthquake early detection systems. Here we suggest a new method for detecting and picking Pand S-wave signals automatically. Compared to methods currently in use, our method requires fewer assumption with properties of the data time series. We divide a record into intervals of equal lengths and check the "local and weak stationarity" of each interval using the theory of the KM2O-Langevin equations. The intervals are stationary when these include only background noise, but the stationarity breaks abruptly when a seismic signal arrives and the intervals include both the background noise and the P-wave. This break of stationarity makes us possible to detect P-wave arrival. We expand the method for picking of S-waves. We applied our method to earthquake data from Hi-net Japan, and 90% of P-wave auto-picks were found to be within 0.1 s of the corresponding manual picks, and 70% of S-wave picks were within 0.1 s of the manual picks. This means that our method is accurate enough to use as a part of the seismic early detection system.

Nakamula, S.; Takeo, M.; Okabe, Y.; Matsuura, M.

2007-06-01

194

Nuclear explosion locations at the Balapan, Kazakhstan, nuclear test site: the effects of high-precision arrival times and three-dimensional structure  

Microsoft Academic Search

We have investigated the potential contributions of improved arrival times (using waveform cross-correlation) and the use of three-dimensional (3-D) velocity models for seismic event location capability. Our analyses are applied to a dataset of nuclear explosions at Balapan, Kazakhstan, for which ground-truth locations and some absolute origin times are available. This ground-truth information allows us to determine excellent origin time

Clifford Thurber; Chad Trabant; Florian Haslinger; Renate Hartog

2001-01-01

195

P-wave Cooper pair splitting  

PubMed Central

Summary Background: Splitting of Cooper pairs has recently been realized experimentally for s-wave Cooper pairs. A split Cooper pair represents an entangled two-electron pair state, which has possible application in on-chip quantum computation. Likewise the spin-activity of interfaces in nanoscale tunnel junctions has been investigated theoretically and experimentally in recent years. However, the possible implications of spin-active interfaces in Cooper pair splitters so far have not been investigated. Results: We analyze the current and the cross correlation of currents in a superconductor–ferromagnet beam splitter, including spin-active scattering. Using the Hamiltonian formalism, we calculate the cumulant-generating function of charge transfer. As a first step, we discuss characteristics of the conductance for crossed Andreev reflection in superconductor–ferromagnet beam splitters with s-wave and p-wave superconductors and no spin-active scattering. In a second step, we consider spin-active scattering and show how to realize p-wave splitting using only an s-wave superconductor, through the process of spin-flipped crossed Andreev reflection. We present results for the conductance and cross correlations. Conclusion: Spin-activity of interfaces in Cooper pair splitters allows for new features in ordinary s-wave Cooper pair splitters, that can otherwise only be realized by using p-wave superconductors. In particular, it provides access to Bell states that are different from the typical spin singlet state.

Komnik, Andreas

2012-01-01

196

Magnitude estimation using high-frequency acceleration of initial P-wave  

NASA Astrophysics Data System (ADS)

Recently various methods to estimate earthquake parameters (epicentral location and magnitude) have been proposed, and some of those are applied to an earthquake early warning system. For example, the method to estimate epicentral location using single station data (the B-delta method (Odaka et al., 2003) and the Principal component analysis (Meteorological Research Institute, 1985)) is used by Japan Meteorological Agency(JMA) EEW system and the Shinkansen EEW system. Improvement of its accuracy and rapidness is discussed by Noda et al., 2011. As for estimating a magnitude from the initial phase data, the method using the maximum amplitude (Odaka et al., 2003) and the ?c method (Wu and Kanamori, 2005) are proposed. The present JMA EEW and the Shinkansen EEW system use the maximum displacement amplitude for estimating the magnitude. On the other hand, Hoshiba et al. (2010) indicated that the maximum value of acceleration amplitude tends to appear earlier than that of displacement amplitude, thus the maximum magnitude may be estimated earlier by acceleration amplitude than by displacement. In this study, we examined a method to estimate the magnitude from the amplitude of vertical acceleration in order to improve rapidness of its estimation. 10342 K-NET waveform data of 190 earthquakes (M<3.9, focal depth <150km) were used for the analysis. First, we grouped seismic waveform data according to hypocentral distances and magnitudes, then we averaged time histories of vertical acceleration of each group to examine their features. As the result, we found that the amplitude of the very initial phase (about 0.5 sec after the arrival of P-wave) mainly depends not on magnitude, but on hypocentral distances. So as to reduce the effect of hypocentral distance, we divided the high-frequency (10-20 Hz) vertical acceleration time history by the amplitude value at 0.5 sec after the arrival of P-wave, and examined statistical relationship between the normalized value and the magnitude. It was found out that correlation between the normalized value and the magnitude is significantly high. For example, the relational expression between the magnitude and the normalized value at 1.5 sec after the arrival of P-wave is A = 0.0212 * e ^ (0.9075 * M) where A and M denote the normalized value and the magnitude. To validate the accuracy of this method, we calculate differences (RMS) between the magnitude published by JMA and the magnitude estimated from the relationship obtained above. In this case, estimation error is found to be 0.6. It is obvious that high-frequency acceleration waveform is superposition of various waves radiated from fracture surface, and growth in the amplitude of observed acceleration corresponds to spreading of the fault area of rupture front. That is, it is thought that the magnitude estimated by this method using high-frequency acceleration is equivalent to the magnitude obtained by the conventional technique using low-frequency seismic data. Therefore, it would be possible to estimate the growth of the magnitude earlier by using acceleration data characterized by rapidness.

Korenaga, M.; Yamamoto, S.; Noda, S.; Iwata, N.

2011-12-01

197

The effects of pre-ejection period on post-exercise systolic blood pressure estimation using the pulse arrival time technique  

Microsoft Academic Search

Pulse arrival time (PAT) is comprised of the vascular transit time (TT) through the arterial system and the pre-ejection period\\u000a (PEP) in the heart. It has been used to predict arterial blood pressure (BP) without using a cuff. The aim of this study was\\u000a to investigate the effects of including the PEP on the accuracy of cuffless systolic BP (SBP)

Mico Yee Man Wong; Emma Pickwell-MacPherson; Yuan Ting Zhang; Jack C. Y. Cheng

2011-01-01

198

Comparison of Bolus Arrival Time Determination Methods for the Analysis of Cerebral Hemodynamics by Estimating the Impact of Temporal Resolution of 4D MRA Imaging  

Microsoft Academic Search

\\u000a In case of an early diagnosed cerebral vascular disease exact knowledge of the individual anatomy and hemodynamic situation\\u000a is needed for improved rating of the disease and therapy planning. Concentration time curves derived from 4D magnetic resonance\\u000a angiography imaging are widely used to calculate hemodynamic parameters such as the bolus arrival time (BAT). The focus of\\u000a this study is to

N. D. Forkert; D. Säring; T. Illies; J. Fiehler; H. Handels

199

Observations of high-frequency P wave earthquake and explosion spectra compared with ?-3, ?-2, and sharpe source models  

NASA Astrophysics Data System (ADS)

Observations of 10-, 20-, and 30-Hz P wave spectral amplitudes from earthquakes and explosions are compared with the Archambeau [1968, 1972] earthquake model featuring a P wave falloff of ?-3 beyond the corner frequency, a modified Brune [1970, 1971] earthquake model with ?-2 falloff, and the Sharpe [1942] explosion model which has a ?-2 falloff. The Archambeau and Sharpe models have been, in part, the basis of a proposal by Evernden et al. [1986] that high-frequency (?30 Hz) seismic energy could provide an effective solution to the problem of detection and identification of low-yield coupled and fully decoupled underground nuclear explosions. The observations of earthquakes show an increase in spectral amplitude with moment approximately in agreement with the ?-2 falloff model and, for larger moments, in disagreement with the ?-3 model. Comparison of theoretical and actual seismograms narrow-band filtered at 30 Hz shows that in part the increase in spectral amplitude of earthquakes is due to the complex and long duration of the rupture process and not because of an increase in an impulsive first arrival like that characteristic of an explosion. The 30-Hz amplitudes for explosions show much scatter, and many events have a spectral falloff greater than the ?-2 predicted by the Sharpe model. Whether this is due entirely to attenuation or is the actual source spectrum is not determined. High stress drop earthquakes are predicted to have larger spectral amplitudes than the Sharpe model. Thus any discrimination technique using high-frequency P wave spectra should probably take into account differences in pulse shape and amplitude in the time domain.

Walter, William R.; Brune, James N.; Priestley, Keith F.; Fletcher, Jon

1988-06-01

200

Three-dimensional P-wave velocity structure in the upper crust beneath Kuju Volcano, central Kyushu, Japan  

NASA Astrophysics Data System (ADS)

Kuju Volcano lies near Aso Caldera at the center of Kyushu Island, western Japan. After a few hundred years of dormancy, a phreatic explosion accompanied by a small ash eruption occurred on 11 October 1995. This study was undertaken to determine the subsurface seismic velocity structure associated with the active magmatic regime in the Kuju volcanic region. The three-dimensional, upper crustal, P-wave velocity structure beneath Kuju Volcano was determined using methods for the simultaneous inversion of P-wave arrival times from local earthquakes in and around the Kuju volcanic region for velocities and hypocentral parameters. Results reveal two shallower low-velocity anomalies located in the northern and southern parts of Kuju Volcano, consistent with the presence of significant negative Bouguer gravity anomalies. In addition, a high-velocity anomaly is located approximately 5km northwest of Mt. Kuju, one of the domes in Kuju Volcano. Beneath this high-velocity anomaly, a low-velocity anomaly is present. This velocity structure suggests a magmatic regime that has a lid consisting of cooled solid material overlying a chamber of partially molten material.

Sudo, Yasuaki; Matsumoto, Yoshihiro

201

Magnitude scaling relationship from the first P-wave arrivals on Canada's west coast  

NASA Astrophysics Data System (ADS)

The empirical magnitude scaling relationship from ground-motion period parameter ?c is derived using vertical waveforms recorded in the Cascadia Subduction Zone (CSZ) along Canada's west coast. A high-pass filtered displacement amplitude parameter, Pd, is calculated from the initial 3 s of the P waveforms and the empirical relationship between Pd and peak ground velocity, PGV, is derived using the same data set. We selected earthquakes of M >3.0 recorded during 1996-2009 by the seismic network stations in the region operated by National Resources Canada (NRCan). In total, 90 events were selected and the vertical components of the earthquakes signals were converted to ground velocity and displacement. The displacements were filtered with a one-way Butterworth high-pass filter with a cut-off frequency of 0.075 Hz. Pd and ?c are computed from the vertical seismogram components. While the average magnitude error was approximately 0.70 magnitude units when using the individual record, the error dropped to approximately 0.5 magnitude units when using the average ?c for each event. In case of PGV, the average error is approximately 0.3. These relationships may be used for initial steps in establishing an earthquake early warning system for the CSZ.

Eshaghi, A.; Tiampo, K. F.

2011-12-01

202

Skyrmion versus vortex flux lattices in p -wave superconductors  

Microsoft Academic Search

p -wave superconductors allow for topological defects known as skyrmions, in addition to the usual vortices that are possible in both s -wave and p -wave materials. In strongly type-II superconductors in a magnetic field, a skyrmion flux lattice yields a lower free energy than the Abrikosov flux lattice of vortices and should thus be realized in p -wave superconductors.

Qi Li; John Toner; D. Belitz

2009-01-01

203

Measuring the effects of remifentanil on cerebral blood flow and arterial arrival time using 3D GRASE MRI with pulsed arterial spin labelling  

Microsoft Academic Search

Arterial spin labelling (ASL) has proved to be a promising magnetic resonance imaging (MRI) technique to measure brain perfusion. In this study, volumetric three-dimensional (3D) gradient and spin echo (GRASE) ASL was used to produce cerebral blood flow (CBF) and arterial arrival time (AAT) maps during rest and during an infusion of remifentanil. Gradient and spin echo ASL perfusion-weighted images

Bradley J MacIntosh; Kyle TS Pattinson; Daniel Gallichan; Imran Ahmad; Karla L Miller; David A Feinberg; Richard G Wise; Peter Jezzard

2008-01-01

204

Anomalous delays of teleseismic P waves in Yellowstone National Park  

USGS Publications Warehouse

TELESEISMIC P waves recorded by a short-period seismic network, comprising 12 stations, in Yellowstone National Park, show anomalous delays of 1-2 s in their travel times in the central region of the park relative to the surrounding area. To explain this phenomenon, I propose that a substantial body of low velocity material is present beneath the park, with horizontal dimensions of several tens of kilometres; it may be the magma chamber associated with the volcanism of Yellowstone (ref. 1, and G. P. Eaton et al., unpublished). ?? 1975 Nature Publishing Group.

Iyer, H. M.

1975-01-01

205

Nonlinear inversion of the P-wave P-wave reflection coefficient data  

SciTech Connect

Surface seismic data are used to estimate lithologic parameters at an interface. The four unknown independent parameters at an interface are the ratio of the P-wave velocities and the ratio of the densities of upper and lower media, and the P-wave/S-wave velocity ratios in the upper and lower media respectively. The forward problem is solved by a reparameterized form of the full Zoeppritz equation for PP reflections. The inversion model is fitted to the data using a two part inversion scheme. The near offset (near normal incidence) data is initially inverted using a linearized Zoeppritz normal incidence equation to obtain estimates of the P-wave ratio and density ratio. The estimates of these two parameters are then used as initial guesses in a nonlinear full Zoeppritz inversion by a Levenberg Marquardt procedure. Partial derivatives of the reparameterized Zoeppritz equation for the Jacobian matrix are calculated analytically at each iteration. All parameters are successfully estimated from synthetic data. Poisson`s ratio of the upper and lower media can be calculated from inversion estimates of P-wave/S-wave velocity ratio. Lithologic parameters are estimated for several CDP gathers from a 3D survey of the Rabbit Hills Field in North Central Montana. A sensitivity analysis for the different parameters is performed.

Pate, A.J. [Univ. of Montana, Butte, MT (United States)

1996-06-01

206

Reactivation and mantle dynamics of North China Craton: insight from P-wave anisotropy tomography  

NASA Astrophysics Data System (ADS)

We determined the first 3-D P-wave anisotropic tomography beneath the North China Craton (NCC) using a large number of high-quality arrival-time data from local earthquakes and teleseismic events, which reveals depth-dependent azimuthal anisotropy in the crust and upper mantle down to 600 km depth. In the NCC western block, the fast velocity direction (FVD) varies from east-west in the southern part to northeast-southwest in the northern part, which may reflect either the interaction between the Yangtze block and NCC or fossil lithospheric fabrics in the craton. Under the NCC eastern block, a uniform northwest-southeast FVD is revealed in the lower part of the upper mantle (300-410 km depths) and the mantle transition zone (410-660 km depths), which may reflect horizontal and upwelling flows in the big mantle wedge (BMW) above the stagnant Pacific slab in the mantle transition zone. The NCC central block exhibits a northeast-southwest FVD, consistent with the surface tectonic orientation there, suggesting that the cold and thick (>300 km) cratonic root of the NCC western block may obstruct the northwest-southeast trending mantle flow induced by the Pacific Plate subduction, resulting in a northeast-southwest trending mantle flow under the central block. Our present results indicate that the corner flow in the BMW associated with the deep subduction of the Pacific Plate is the main cause of NCC reactivation and mantle dynamics under East China.

Tian, You; Zhao, Dapeng

2013-09-01

207

Triplicated P-wave measurements for waveform tomography of the mantle transition zone  

NASA Astrophysics Data System (ADS)

Triplicated body waves sample the mantle transition zone more extensively than any other wave type, and interact strongly with the discontinuities at 410 km and 660 km. Since the seismograms bear a strong imprint of these geodynamically interesting features, it is highly desirable to invert them for structure of the transition zone. This has rarely been attempted, due to a mismatch between the complex and band-limited data and the (ray-theoretical) modelling methods. Here we present a data processing and modelling strategy to harness such broadband seismograms for finite-frequency tomography. We include triplicated P-waves (epicentral distance range between 14 and 30°) across their entire broadband frequency range, for both deep and shallow sources. We show that is it possible to predict the complex sequence of arrivals in these seismograms, but only after a careful effort to estimate source time functions and other source parameters from data, variables that strongly influence the waveforms. Modelled and observed waveforms then yield decent cross-correlation fits, from which we measure finite-frequency traveltime anomalies. We discuss two such data sets, for North America and Europe, and conclude that their signal quality and azimuthal coverage should be adequate for tomographic inversion. In order to compute sensitivity kernels at the pertinent high body wave frequencies, we use fully numerical forward modelling of the seismic wavefield through a spherically symmetric Earth.

Stähler, S. C.; Sigloch, K.; Nissen-Meyer, T.

2012-11-01

208

Triplicated P-wave measurements for waveform tomography of the mantle transition zone  

NASA Astrophysics Data System (ADS)

Triplicated body waves sample the mantle transition zone more extensively than any other wave type, and interact strongly with the discontinuities at 410 km and 660 km. Since the seismograms bear a strong imprint of these geodynamically interesting features, it is highly desirable to invert them for structure of the transition zone. This has rarely been attemped, due to the mismatch between the complex and bandlimited data and the (ray-theoretical) modeling methods. Here we present a data processing and modeling strategy to harness such broadband seismograms for finite-frequency tomography. We include triplicated P-waves (epicentral distance range between 14 and 30°) across their entire broadband frequency range, for both deep and shallow sources. We show that it is possible to predict the complex sequence of arrivals in these seismograms, but only after a careful effort to estimate source time functions and other source parameters from data, variables that strongly influence the waveforms. Modeled and observed waveforms then yield decent cross-correlation fits, from which we measure finite-frequency traveltime anomalies. We discuss two such data sets, for North America and Europe, and conclude that their signal quality and azimuthal coverage should be adequate for tomographic inversion. In order to compute sensitivity kernels at the pertinent high body-wave frequencies, we use fully numerical forward modelling of the seismic wavefield through a spherically symmetric earth.

Stähler, S. C.; Sigloch, K.; Nissen-Meyer, T.

2012-07-01

209

Arrival time and magnitude of airborne fission products from the Fukushima, Japan, reactor incident as measured in Seattle, WA, USA.  

PubMed

We report results of air monitoring started due to the recent natural catastrophe on 11 March 2011 in Japan and the severe ensuing damage to the Fukushima Dai-ichi nuclear reactor complex. On 17-18 March 2011, we registered the first arrival of the airborne fission products (131)I, (132)I, (132)Te, (134)Cs, and (137)Cs in Seattle, WA, USA, by identifying their characteristic gamma rays using a germanium detector. We measured the evolution of the activities over a period of 23 days at the end of which the activities had mostly fallen below our detection limit. The highest detected activity from radionuclides attached to particulate matter amounted to 4.4 ± 1.3 mBq m(-3) of (131)I on 19-20 March. PMID:21719167

Leon, J Diaz; Jaffe, D A; Kaspar, J; Knecht, A; Miller, M L; Robertson, R G H; Schubert, A G

2011-06-29

210

p-wave Superconductor in a Mesoscopic Size Grain  

NASA Astrophysics Data System (ADS)

Motivated by the claim that Sr2RuO4 is a p-wave superconductor with broken time-reversal symmetry in the bulk, and many recent experimental studies of superconductors in mesoscopic size grains, we study theoretically a two-component p-wave superconductor in confined geometries, considering circular disks and rectangular samples, using both Ginzburg-Landau (GL) and quasiclassical (QC) Green function theories. For GL theory with parameters near the weak-coupling limit, we find that a sufficiently small circular disk remains normal. For zero field and intermediate sizes, a disk with sufficiently smooth boundary is in a time-reversal symmetric state, where the order parameter can be represented by a real vector forming a vortex-like structure. Only for larger grains and at lower temperatures can a broken time-reversal state be recovered. For intermediate sizes but with finite external magnetic field, the system can have possibly re-entrant phase transitions. For rectangular samples with sufficiently large aspect ratios, the superconductor near its transition temperature at zero fields has its order parameter vector parallel to the long side of the sample. Within a critical aspect ratio however, the order parameter vector forms a vortex-like structure, much like for the disk.

Yip, Sungkit; Huang, Bor-Luen

2013-03-01

211

P-wave Velocity Structures near the Inner Core Boundary in the Eastern and Western Hemispheres  

NASA Astrophysics Data System (ADS)

It is well known that the P-wave velocity structures near the inner core boundary are different in the eastern and western hemispheres. However, the detailed variations in velocity structure in each hemisphere are not well constrained yet. We examined seismic waveforms recorded at about 850 stations in Japan from 279 events occurred in and around South America and the Southern Atlantic Ocean between 2004 and 2009. The differential travel-times of PKP(BC) and PKP(DF) at epicentral distance ranges between 145° and 153° were measured by waveform cross-correlation method. To construct the P wave velocity model, we used the grid-search technique to match observed and theoretical differential travel times for selected events. As we expected, the best-fitting P wave velocity models for the eastern hemisphere are systematically different from those for the western hemisphere. Moreover, we found that there are significant variations of the P wave velocity structures in each hemisphere, especially for the western hemisphere. The one dimensional P-wave velocity models constructed for different paths can provide more constraints on the detailed P-wave velocity structures near the inner core boundary.

Yee, T.; Rhie, J.

2009-12-01

212

Queues with Negative Arrivals.  

National Technical Information Service (NTIS)

The authors single server queueing models where in addition to regular arriving customers, there are negative arrivals. A negative arrival has the effect of removing a customer from the queue. The way in which this removal is specified gives rise to sever...

E. Gelenbe K. Sigman P. Glynn

1989-01-01

213

Environmental and lunar cues are predictive of the timing of river entry and spawning-site arrival in lake sturgeon Acipenser fulvescens.  

PubMed

The associations were quantified between daily and interannual variation in the timing of a closed population of lake sturgeon Acipenser fulvescens migration and arrival at spawning sites with stream environmental and lunar covariates. Spawning data were gathered from 1262 fish in Black Lake, Michigan 2001 to 2008 and by video monitoring 2000 to 2002. Sex-specific variation in responses to external cues was also tested. Results showed that a greater number of individuals initiated migration from lake to riverine habitats at dawn and dusk relative to other times of the day. Current and lagged effects of water temperature and river discharge, and periods in the lunar cycle were important variables in models quantifying movements into the river and timing of adult arrival at spawning sites. Different suites of covariates were predictive of A. fulverscens responses during different periods of the spawning season. The timing of initiation of migration and spawning, and the importance of covariates to the timing of these events, did not differ between sexes. Stream flow and temperature covaried with other variables including day length and the lunar cycle. Anthropogenic disruption of relationships among variables may mean that environmental cues may no longer reliably convey information for Acipenseriformes and other migratory fishes. PMID:22747803

Forsythe, P S; Scribner, K T; Crossman, J A; Ragavendran, A; Baker, E A; Davis, C; Smith, K K

2012-06-12

214

Teleseismic P wave attenuation and nuclear explosion source functions inferred from Yellowknife Array data  

NASA Astrophysics Data System (ADS)

We report here the results of a comprehensive seismic attenuation investigation along the paths connecting Canada's Yellowknife seismic array (YKA) with seven active nuclear explosion testing areas. The data consist of more than 600 explosion-generated teleseismic P wave records. A dual time-frequency averaging technique is used to take advantage of the array recording characteristics without the drawback of the conventional beam-forming, excessive annihilation of high-frequency signal energies. The dual averaging technique, deployed in conjunction with a multiwindow spectral analysis method, yields smooth amplitude spectra whose falloff at high frequencies suffers little from spectral leakage due to the familiar presence of a prominent low-frequency plateau. Measured in terms of t*, the highest attenuation (0.66 s) is found along the path which originates from the Tuamotu test area; somewhat less attenuating are the two paths which depart from the Pahute Mesa (0.59 s) and Yucca Flat (0.50 s) nuclear test areas, both located within the U.S. Nevada Test Site. We find t* for these three paths to be substantially (up to 0.21 s) higher than recently published estimates (e.g., Der et al., 1985). We attribute these disparities largely to differences in spectral leakage control capability between the conventional single window and the improved multiwindow spectral analysis methods. The least attenuating paths all originate from the Soviet test areas: Novaya Zemlya (NZ), west Kazakhstan, Degelen Mountain (DM), and Shagan River (SR). The last two of these test areas, DM and SR, are both located in east Kazakhstan. The P wave signatures of the Soviet explosions are rich in high-frequency (>4.5 Hz) energies, and the YKA data (0.5-8.0 Hz) support a frequency-dependent t* whose value at high frequencies (>4.5 Hz) is as small as 0.17 s. To gain a grasp of the ramifications of the t* disparity between the multiple-window and the single-window results, we have compared explosion source time functions obtained by the multichannel deconvolution technique of Shumway and Der (1985) in order to assess their sensitivity to the input t* value. In our example involving the deconvolved source functions of five French Tuamotu explosions, we find that a 0.1-s t* difference is large enough to cause clearly discernible signature differences, in terms of the signal frequency content as well as the extractability of a secondary arrival some 0.4 s behind the first P arrival. This secondary arrival is believed to be the depth phase pP, a seismic signature of importance in both yield estimation and earthquake/explosion source discrimination. The absorption band modeling (Minster, 1978a, b) of the French Tuamotu explosion data yields 1.08±0.05 and 0.079±0.008 s for t*0 and ?m, respectively. The corresponding parameter estimates derived from the U.S. explosion data are somewhat smaller. The t*0 and ?m estimates are the smallest along the paths which depart from the four Soviet test areas. For the NZ-YKA path the t*0 and ?m estimates are 0.56±0.08 and 0.061±0.013 s, respectively. Plagued by a strong trade-off between the two model parameters, these estimates are not tightly constrained, however.

Chun, Kin-Yip; Zhu, Tianfei; West, Gordon F.

1991-07-01

215

Measure of E.C.D., time of arrival, amplitude and phase of both ground and reflected waves of LORAN-C pulses  

NASA Astrophysics Data System (ADS)

An investigation of LORAN C pulses emitted at 100 kHz by the Sylt station (Federal Republic of Germany) and received at Brussels situated at 514 km is described. The pulses are analyzed digitally. After deconvolution of the received wave, the ground wave (already measured with high precision) is subtracted to obtain the reflected wave on the ionosphere. This analysis provides accurate results for time of arrival, amplitude, phase, and ECD of both ground and reflected waves. The heights of the D layer of the ionosphere are also given.

Lievin, J. C.; Hamaide, J. P.; Scholiers, W.; Lechien, J. P.

1982-02-01

216

A Global-scale P-wave Tomography Model for Regional and Teleseismic Event Monitoring  

NASA Astrophysics Data System (ADS)

We construct a global-scale P-wave tomography model of the crust and mantle that depicts both large-scale tectonic/dynamic features, as well as detailed upper mantle heterogeneities. Fully three-dimensional ray tracing is employed to achieve accurate travel time predictions of P and Pn arrivals, necessitating the characterization of irregular and discontinuous boundaries. Therefore, we explicitly represent undulating seismic discontinuities in the crust and upper mantle within a spherical tessellation modeling framework. The tessellation-based model architecture is hierarchical in that fine node sampling is achieved by recursively subdividing a base-level tessellation. Determining the required node spacing to effectively model a given set of data is problematic, given the uneven sampling of seismic data and the differing wavelengths of actual seismic heterogeneity. To address this problem, we have developed an inversion process called Progressive Multi-level Tessellation Inversion (PMTI) that exploits the hierarchical nature of the tessellation-based design and allows the data to determine the level of model complexity. PMTI robustly images regional trends and allows localized details to emerge where resolution is sufficient. To demonstrate our complete modeling concept, we construct a velocity model based on teleseismic P and regional Pn travel time data for events occurring throughout the Middle East. Input data are a product of the statistical procedure called Bayesloc that simultaneously models all components of a multi-event system including event locations, origin times and arrival times. The initial tomographic image provides a new glimpse of the complex upper mantle velocity anomalies associated with the convergence of the Arabian and Indian plates with Eurasia. More important for event monitoring, the model accurately predicts both teleseismic and regional travel times for events occurring within the Middle East region. We present these results along with a status report on the development of a model capable of accurately predicting regional/teleseismic travel times for events worldwide. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-451511.

Simmons, N. A.; Myers, S. C.; Johannesson, G.

2010-12-01

217

Induced P-Wave Superfluidity in Asymmetric Fermi Gases  

SciTech Connect

We show that two new intraspecies P-wave superfluid phases appear in two-component asymmetric Fermi systems with short-range S-wave interactions. In the BEC limit, phonons of the molecular BEC induce P-wave superfluidity in the excess fermions. In the BCS limit, density fluctuations induce P-wave superfluidity in both the majority and the minority species. These phases may be realized in experiments with spin-polarized Fermi gases.

Bulgac, Aurel; Forbes, Michael McNeil; Schwenk, Achim [Department of Physics, University of Washington, Seattle, Washington 98195-1560 (United States)

2006-07-14

218

Absence of P-wave Reflectivity Near the D" S-wave Velocity Discontinuity in the Lowermost Mantle beneath the Cocos Plate  

NASA Astrophysics Data System (ADS)

An abrupt 1-2.5% S-wave velocity increase has been observed in the lowermost mantle beneath the Cocos plate in several studies. This is commonly attributed to the perovskite to post-perovskite phase transition. This phase transition is expected to have much weaker effects on P-wave velocities than on S-wave velocities and the depth range of the transition is expected to depend on Al and Fe content of the perovskite. We image lowermost mantle P-wave reflectivity beneath the Cocos plate using 1D stacking and 3D Kirchhoff migration. Our carefully processed data set comprises 8000 seismograms from deep South American earthquakes recorded by broadband and short-period seismic networks in western North America. Stacked P-wave source wavelets are deconvolved from the data for each event, allowing band-pass filtered signals to be combined for many events. Events are discarded if individual event-stacks do not show an impulsive PcP arrival with significant signal-to- noise ratio. Depth shifts are applied to each event to align PcP arrivals in the combined stacks. These shifts increase systematically from south to north. We observe a widespread weak P-wave reflector about 320 km above the CMB modeled well by a P-wave velocity (Vp) change of -0.2 to -0.4%, depending on the thickness of the velocity change. The depth of this relatively flat reflector is tightly constrained and is a few tens of km shallower than the local S-wave reflector, which may have regional topography of up to 100 km. We model a clear feature in the P-wave reflectivity with a change in dVp/dZ about 180 km above the CMB, accompanied by a sharp 0.2% increase in Vp. Different narrow band filters up to 2 Hz and forward modeling of double-array stacks show that this small velocity increase must occur over less than 10 km in depth. This also does not directly correspond to any significant feature in the S-wave velocity structure. The high signal-to-noise ratio of our locally binned data stacks allows us to preclude the existence of any other abrupt Vp change stronger than ±0.1 to ±0.4%. These upper bounds are influenced by the source-receiver geometry of the data and the thickness of the velocity change. A strong, positive velocity contrast, out-of-plane scatterer is observed in the migrations, and appears to originate shallower than 200 km above the CMB. Finally, we show that the PREM values for P-wave attenuation in the lowermost mantle are too low, and need to be at least three times greater locally to match our broadband observations.

Hutko, A.; Lay, T.; Revenaugh, J.; Garnero, E.

2007-12-01

219

P-wave tomography of the western United States: Insight into the Yellowstone hotspot and the Juan de Fuca slab  

NASA Astrophysics Data System (ADS)

We used 190,947 high-quality P-wave arrival times from 8421 local earthquakes and 1,098,022 precise travel-time residuals from 6470 teleseismic events recorded by the EarthScope/USArray transportable array to determine a detailed three-dimensional P-wave velocity model of the crust and mantle down to 1000 km depth under the western United States (US). Our tomography revealed strong heterogeneities in the crust and upper mantle under the western US. Prominent high-velocity anomalies are imaged beneath Idaho Batholith, central Colorado Plateau, Cascadian subduction zone, stable North American Craton, Transverse Ranges, and Southern Sierra Nevada. Prominent low-velocity anomalies are imaged at depths of 0-200 km beneath Snake River Plain, which may represent a small-scale convection beneath the western US. The low-velocity structure deviates variably from a narrow vertical plume conduit extending down to ˜1000 km depth, suggesting that the Yellowstone hotspot may have a lower-mantle origin. The Juan de Fuca slab is imaged as a dipping high-velocity anomaly under the western US. The slab geometry and its subducted depth vary in the north-south direction. In the southern parts the slab may have subducted down to >600 km depth. A "slab hole" is revealed beneath Oregon, which shows up as a low-velocity anomaly at depths of ˜100 to 300 km. The formation of the slab hole may be related to the Newberry magmatism. The removal of flat subducted Farallon slab may have triggered the vigorous magmatism in the Basin and Range and southern part of Rocky Mountains and also resulted in the uplift of the Colorado Plateau and Rocky Mountains.

Tian, You; Zhao, Dapeng

2012-06-01

220

A P wave velocity model of Earth's core  

NASA Astrophysics Data System (ADS)

Present Earth core models derived from the retrieval of global Earth structure are based on absolute travel times, mostly from the International Seismological Centre (ISC), and/or free-oscillation eigenfrequencies. Many core phase data are left out of these constructions, e.g., PKP differential travel times, amplitude ratios, and waveforms. This study is an attempt to utilize this additional information to construct a model of core P wave velocity which is consistent with the different types of core phase data available. In conjunction with our waveform modeling we used 150 differential time measurements and 87 amplitude ratio measurements, which were the highest-quality observations chosen from a large population of Global Digital Seismograph Network (GDSN) records. As a result of fitting these various data sets, a one-dimensional P wave velocity model of the core, PREM2, is proposed. This model, modified from the Preliminary Reference Earth Model (PREM) (Dziewonski and Anderson, 1981), shows a better fit to the combined data set than any of the existing core models. Major features of the model include a sharp velocity discontinuity at the inner core boundary (ICB), with a large jump (0.78 km/s), and a low velocity gradient at the base of the fluid core. The velocity is nearly constant over the lower 100 km of the outer core. The model features a depth-dependent Q? structure in the inner core such that a constant t* for the inner core fits the amplitude ratios and waveforms of short-period waves moderately well. This means the top of the inner core is more attenuating than the deeper part of the inner core. In addition, the P velocity in the lowermost mantle is reduced from that of PREM as a baseline adjustment for the observed separations of the DF and AB branches of PKP at large distances.

Song, Xiaodong; Helmberger, Don V.

1995-06-01

221

Anomalous quantum mass flow of atoms in p -wave resonance  

Microsoft Academic Search

I analyze an atomic Fermi gas with a planar p -wave interaction, motivated by the experimentally observed anisotropy in p -wave Feshbach resonances. An axial superfluid state is verified. A domain wall object is discovered to be a new topological defect of this superfluid and an explicit solution has been found. Gapless quasiparticles appear as bound states on the wall,

W. Vincent Liu

2005-01-01

222

Teleseismic P-wave tomogram of the Yellowstone plume  

NASA Astrophysics Data System (ADS)

Inversion of a new data set of teleseismic P-wave travel-times from three PASSCAL seismic deployments around the Yellowstone hotspot reveals a 100 km diameter upper mantle plume that extends from the Yellowstone volcanic caldera to 500 km depth and dips 20° to the northwest. A monotonic decrease in the velocity perturbation of the plume from -3.2% at 100 km to -0.9% at 450 km is consistent with a uniform thermal anomaly of 180°C. Where the plume crosses the 410 km discontinuity, previous research shows a depression in the 410 km discontinuity consistent with a warm plume (Fee and Dueker, 2004). Additionally, a region of high velocities extends to 250 km beneath the Wind River basin in NW Wyoming that may represent a convective downwelling of the lithosphere.

Yuan, Huaiyu; Dueker, Ken

2005-04-01

223

P wave tomography of the mantle under the Alpine-Mediterranean area  

NASA Astrophysics Data System (ADS)

We study the upper mantle P wave velocity structure below the Euro-Mediterranean area, down to 1000 km depth, by seismic travel time tomography. We invert summary residuals constructed with both regional and teleseismic first arrival data reported by the International Seismological Centre (ISC) (1964-1995), introducing some alternative strategies in the travel time tomographic approach and a new scheme to correct teleseismic data for global mantle structure. Our high-resolution model PM0.5 is parameterized with three-dimensional (3-D) linear splines on a grid of nodes with 0.5° spacing in both horizontal directions and 50 km vertical spacing. We obtain about 26% root-mean-square (RMS) reduction of residuals by inversion in addition to roughly 31% reduction after summary rays formation and selection. Sensitivity analyses are performed through several test inversions to explore the resolution characteristics of the model at different spatial scales. The distribution of large-scale fast anomalies suggests that two different stages of a convection process presently coexist in very close regions. The mantle dynamics of western central Europe is dominated by blockage of subducted slabs at the 660 km discontinuity and ponding of seismically fast material in the transition zone. Contrarily, in the eastern Mediterranean, fast velocity material sinks into the lower mantle, suggesting that the flow of the cold downwelling here is not blocked by the 660 km discontinuity. On a smaller scale, the existence of tears in the subducted slab (lithospheric detachment) all along both margins of the Adriatic plate, as proposed by some authors, is not supported by our tomographic images.

Piromallo, Claudia; Morelli, Andrea

2003-02-01

224

Estimating the value of containment strategies in delaying the arrival time of an influenza pandemic: A case study of travel restriction and patient isolation  

NASA Astrophysics Data System (ADS)

With a simple phenomenological metapopulation model, which characterizes the invasion process of an influenza pandemic from a source to a subpopulation at risk, we compare the efficiency of inter- and intrapopulation interventions in delaying the arrival of an influenza pandemic. We take travel restriction and patient isolation as examples, since in reality they are typical control measures implemented at the inter- and intrapopulation levels, respectively. We find that the intrapopulation interventions, e.g., patient isolation, perform better than the interpopulation strategies such as travel restriction if the response time is small. However, intrapopulation strategies are sensitive to the increase of the response time, which might be inevitable due to socioeconomic reasons in practice and will largely discount the efficiency.

Wang, Lin; Zhang, Yan; Huang, Tianyi; Li, Xiang

2012-09-01

225

On the waiting time of arriving aircrafts and the capacity of airports with one or two runways  

Microsoft Academic Search

In this paper we examine a model for the landing procedure of aircrafts at an airport. The characteristic feature here is that due to air turbulence the safety distance between two landing aircrafts depends on the types of these two machines. Hence, an efficient routing of the aircraft to two runways may reduce their waiting time.First, we use M\\/SM\\/1 queues

Nicole Bäuerle; O. Engelhardt-funke; M. Kolonko

2007-01-01

226

The transient analysis of the queue-length distribution in the batch arrival system with N-policy, multiple vacations and setup times  

NASA Astrophysics Data System (ADS)

A batch arrival queueing system of the MX/G/1 type with unlimited queue is considered. After each busy period the server begins a multiple vacation period, consisting of independent single vacations, when the service process is blocked. The server begins successive single vacations as far as at the end of one of them the number of customers waiting in the queue equals at least N. The service of the first customer after the vacation period is preceded by a setup time. The analysis of the queue-size distribution on the first vacation cycle is directed to the analysis of the same characteristic in the corresponding ''usual'' system with unremovable server on its first busy period. The renewal-theory approach is used to obtain results in the general case. As main result the explicit representation for the LT of queue-size distribution is derived for the original system.

Kempa, Wojciech M.

2010-10-01

227

Effect of Birth Asphyxia on P Wave Dispersion.  

PubMed

OBJECTIVES: To evaluate the cardiac conduction system using P wave dispersion on electrocardiogram and its relationship with the short term mortality and development of arrhythmia in asphyxiated neonates. METHODS: Thirty term babies with evidence of asphyxia and without any congenital abnormalities were consecutively evaluated as cases. They were compared with thirty healthy term babies without asphyxia. Twelve-lead surface electrocardiography was obtained from all the patients and the controls, and P wave dispersion was calculated according to its definition as the difference between P maximum duration and P minimum duration in 12-lead electrocardiogram. RESULTS: A statically significant difference of P wave dispersion was observed between the patients and the control group (0.027?±?0.011 mm/s and 0.016?±?0.006 mm/s, respectively; P value?=?0.0001). The P wave dispersion had a statistically significant correlation with the grade of asphyxia (P?=?0.004, r?=?0.62), the P wave dispersion had no statistically significant correlation with Apgar scores, short term arrhythmia, and troponin I level in asphyxiated neonates (P?P wave dispersion increased in asphyxiated neonates and correlated with grade of asphyxia; however, the increased P wave dispersion was not correlated with the short term mortality, arrhythmia and troponin I level of the asphyxiated neonates. PMID:23640697

Amoozgar, Hamid; Barekati, Monirosadat; Farhani, Nahal; Pishva, Narjes

2013-05-01

228

P-wave morphology: underlying mechanisms and clinical implications.  

PubMed

Increasing awareness of atrial fibrillation (AF) and its impact on public health revives interest in identification of noninvasive markers of predisposition to AF and ECG-based risk stratification. P-wave duration is generally accepted as the most reliable noninvasive marker of atrial conduction, and its prolongation has been associated with history of AF. However, patients with paroxysmal AF without structural heart disease may not have any impressive P-wave prolongation, thus suggesting that global conduction slowing is not an obligatory requirement for development of AF. P-wave morphology is therefore drawing increasing attention as it reflects the three-dimensional course of atrial depolarization propagation and detects local conduction disturbances. The factors that determine P-wave appearance include (1) the origin of the sinus rhythm that defines right atrial depolarization vector, (2) localization of left atrial breakthrough that defines left atrial depolarization vector, and (3) the shape and size of atrial chambers. However, it is often difficult to distinguish whether P-wave abnormalities are caused by atrial enlargement or interatrial conduction delay. Recent advances in endocardial mapping technologies have linked certain P-wave morphologies with interatrial conduction patterns and the function of major interatrial conduction routes. The value of P-wave morphology extends beyond cardiac arrhythmias associated with atrial conduction delay and can be used for prediction of clinical outcome of a wide range of cardiovascular disorders, including ischemic heart disease and congestive heart failure. PMID:22816534

Platonov, Pyotr G

2012-07-01

229

3D P-wave velocity structure around the rupture area of the 2003 Tokachi-oki earthquake (Mw=8.0) in the margin of the Kuril trench  

NASA Astrophysics Data System (ADS)

We determined the three dimensional P-wave velocity structure in the rupture area of the 2003 Tokachi-oki earthquake (Mw=8.0) by using P-wave travel time data of the aftershocks and relocated the hypocenters simultaneously. In the area off the southeastern coast of Hokkaido, Japan, the large earthquakes occurred repeatedly because the Pacific plate is subducting beneath Hokkaido island in the North American plate. After Yamanaka and Kikuchi (2003), the 2003 Tokachi-oki earthquake re-ruptured the same asperity on September 26, 2003, as the 1952 Tokachi-oki earthquake (Mw=8.1). In order to investigate the aftershock activity in the rupture area, we deployed 47 Ocean Bottom Seismometers (OBSs) immediately after the main earthquake. By using the travel time data from the OBS network, the accurate aftershock distribution was obtained [Shinohara et al (2004), Yamada et al (2005)]. In this study, we picked P arrival times of the aftershocks selected carefully as the best data set for a seismic tomographic inversion. And then we estimated 3D P-wave velocity structure by applying the P travel time data to the simultaneous inversion method [Thurber (1983, 1993), Eberhart-Phillips (1986, 1990)]. Although we couldn't image the overall structure of the subducting Pacific plate because of the shallow seismicity, the subducting plate is imaged as velocity anomalies dipping toward northwest. It is suggested from the result of the hypocenters relocated in the consequence of the inversion that the dip angle of the subducting plate increases at around the distance of 100km from the trench axis. It is also suggested that the dip angle is larger at the northeastern part than the southwestern part of the study area. The fault slip distribution of the 2003 Tokachi-oki earthquake seems to be unrelated to the P-wave velocity (Vp) structure obtained here. In the meantime, S-wave velocity (Vs) structure was not obtained because of the ambiguous S-wave forms and the undefined S-wave arrival times due to the surficial unconsolidated sedimentary layers at the stations. Vp/Vs structure in the rupture area is considered to be related to the source process of the large earthquake. In order to obtain Vp/Vs structure, we need to merge the arrival data of the OBSs with those of the land stations to lessen influence of sedimentary layers.

Machida, Y.; Takanami, T.; Murai, Y.; Shinohara, M.; Yamada, T.; Kanazawa, T.; Hirata, N.; Sakai, S.; Mochizuki, K.; Shiobara, H.; Hino, R.; Nishino, M.; Shimizu, H.; Uehira, K.; Kaneda, Y.; Suyehiro, K.; Watanabe, T.; Takahashi, N.; Sato, T.; Araki, E.; Mikada, H.; Uhira, K.

2006-12-01

230

Effects of instantons on [ital P]-wave multiquark systems  

SciTech Connect

We study noncentral parts of the flavor-singlet interquark interactions induced by the instanton--light-quark coupling and their effects on the [ital P]-wave multiquark systems: the negative parity nonstrange baryons and the relative [ital P]-wave two-nucleon systems. It is found that the noncentral force from the instanton induced interaction reduces that from the one-gluon exchange in the excited [ital P]-wave nucleons. This cancellation does not occur in the spin-orbit force between nucleons, where the flavor-symmetric [ital q]-[ital q] interaction plays a dominant role.

Takeuchi, S. (Department of Public Health and Environmental Science, School of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo, Tokyo 113 (Japan))

1994-10-17

231

The signal averaged P wave in atrioventricular block--evidence for abnormal atrial conduction?  

PubMed

The incidence of atrial fibrillation in patients with atrioventricular block (AVB) appears increased over that for the unpaced population even if atrioventricular synchrony is maintained by dual chamber pacing. To assess whether atrial fibrillation in these patients might be due to concurrent abnormality in atrial activation we performed signal averaged P wave (SAPW) recordings in 15 patients with dual chamber pacemakers implanted for AVB and compared the results to those from 21 unpaced controls. The median (range) age was 69 (53-89) years for patients and 60 (51-78) years for controls. Eleven patients and 12 controls were male. All patients were pacing in VDD mode at the time of study. SAPW recordings were obtained using our previously reported selective P wave averaging system. We measured P wave duration after high pass filtering at 40 Hz, the rate of change of P wave voltage over time (spatial velocity) and low and high frequency spectral energy after Fourier transformation of the P wave signal. We found increased P wave duration, mean spatial velocity and lower frequency energy in patients with AVB compared to controls [duration, 144 (5) vs. 134 (2) ms, p<0.05; mean spatial velocity, 5.6 (0.4) vs. 4.6 (0.1) mV/s, p<0.05; energy 20-150 Hz, 57.4 (8.2) vs. 36.3 (2.8) muV2.s, p<0.01. All values mean (SEM)]. These results suggest that the increased incidence of atrial fibrillation in patients paced for AVB may be related to intrinsic abnormalities of atrial activation and not solely to the pacing mode. Ensuring sequential atrioventricular pacing in these patients may not completely abolish the increased incidence of atrial fibrillation. PMID:9510489

Stafford, P J; Cooper, J; Baker, S; deBono, D P; Vincent, R; Garratt, C J

1998-01-31

232

Skyrmion Flux Lattices in p,-wave Superconductors  

Microsoft Academic Search

In p,-wave superconductors, topological excitations known as skyrmions are allowed, in addition to the usual vortices. In strongly type-II materials in an external magnetic field, a skyrmion flux lattice is expected to be energetically favored compared to a vortex flux lattice [1]. We analytically calculate the energy, magnetization curves (B(H)), and elasticity of skyrmion flux lattices in p,-wave superconductors near

Qi Li; John Toner; Dietrich Belitz

2007-01-01

233

p-wave holographic insulator/superconductor phase transition  

SciTech Connect

Using a five-dimensional anti-de Sitter (AdS) soliton in an Einstein-Yang-Mills theory with SU(2) gauge group, we study p-wave holographic insulator/superconductor phase transition. To explore the phase structure of the model, we consider the system in the probe limit as well as fully back-reacted solutions. We will also study the zero temperature limit of the p-wave holographic superconductor in four dimensions.

Akhavan, Amin [School of physics, Institute for Research in Fundamental Sciences (IPM) P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Department of Physics, Sharif University of Technology P.O. Box 11365-9161, Tehran (Iran, Islamic Republic of); Alishahiha, Mohsen [School of physics, Institute for Research in Fundamental Sciences (IPM) P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)

2011-04-15

234

Brain natriuretic peptide and P wave duration in dialysis patients  

Microsoft Academic Search

Objectives  P wave duration and dispersion, defined as the difference between the maximum and minimum P duration, are regarded as very\\u000a important non-invasive ECG markers for assessing atrial arrhythmia risk. Plasma brain natriuretic peptide (BNP) level is an\\u000a independent predictor of recurrence of atrial fibrillation. We compared the effects of hemodialysis (HD) and continuous ambulatory\\u000a peritoneal dialysis (CAPD) on P wave

M. Cagatay Taskapan; Soner Senel; Ozkan Ulutas; Yuksel Aksoy; Ibrahim Sahin; Feridun Kosar; Hulya Taskapan

2007-01-01

235

Teleseismic P wave attenuation and nuclear explosion source functions inferred from Yellowknife array data  

Microsoft Academic Search

We report here the results of a comprehensive seismic attenuation investigation along the paths connecting Canada's Yellowknife seismic array (YKA) with seven active nuclear explosion testing areas. The data consist of more than 600 explosion-generated teleseismic P wave records. A dual time-frequency averaging technique is used to take advantage of the array recording characteristics without the drawback of the conventional

Kin-Yip Chun; Tianfei Zhu; Gordon F. West

1991-01-01

236

Reference-based linear curve fitting for bolus arrival time estimation in 4D MRA and MR perfusion-weighted image sequences.  

PubMed

The bolus arrival time (BAT) based on an indicator dilution curve is an important hemodynamic parameter. As the direct estimation of this parameter is generally problematic, various parametric models have been proposed that describe typical physiological shapes of indicator dilution curves, but it remains unclear which model describes the real physiological background. This article presents a method that indirectly incorporates physiological information derived from the data available. For this, a patient-specific hemodynamic reference curve is extracted, and the corresponding reference BAT is determined. To estimate a BAT for a given signal curve, the reference curve is fitted linearly to the signal curve. The parameters of the fitting process are then used to transfer the reference BAT to the signal curve. The validation of the method proposed based on Monte Carlo simulations showed that the approach presented is capable of improving the BAT estimation precision compared with standard BAT estimation methods by up to 59% while at the same time reduces the computation time. A major benefit of the method proposed is that no assumption about the underlying distribution of indicator dilution has to be made, as it is implicitly modeled in the reference curve. PMID:20740654

Forkert, Nils Daniel; Fiehler, Jens; Ries, Thorsten; Illies, Till; Möller, Dietmar; Handels, Heinz; Säring, Dennis

2011-01-01

237

The effects of pre-ejection period on post-exercise systolic blood pressure estimation using the pulse arrival time technique.  

PubMed

Pulse arrival time (PAT) is comprised of the vascular transit time (TT) through the arterial system and the pre-ejection period (PEP) in the heart. It has been used to predict arterial blood pressure (BP) without using a cuff. The aim of this study was to investigate the effects of including the PEP on the accuracy of cuffless systolic BP (SBP) estimation using the PAT technique in post-exercise recovery. Experiments were conducted on 22 normotensive participants. PAT, TT and PEP were determined from simultaneous measurements of the electrocardiogram, photoplethysmogram and impedance cardiogram. Moderate exercise induced significant (p < 0.05) increases in SBP and heart rate and significant (p < 0.05) decreases in PEP and PAT. Diastolic blood pressure and TT only varied insignificantly (p > 0.05). SBP was moderately correlated with PEP (r = -0.61) and PAT (r = -0.81). PAT and PEP were moderately correlated (r = 0.67). When SBP was estimated using least-squares methods, the differences between the measured and predicted SBP using PEP, PAT and TT were 0.0 ± 6.6, 0.0 ± 4.9 and 0.0 ± 9.3 mmHg, respectively. The findings suggested that PAT gives the best SBP prediction and PEP has some potential to predict blood pressure. The inclusion of PEP in the PAT measurement is necessary to facilitate accurate cuffless blood pressure prediction after exercise. PMID:20824282

Wong, Mico Yee Man; Pickwell-MacPherson, Emma; Zhang, Yuan Ting; Cheng, Jack C Y

2010-09-08

238

Visualization of segmental arterialization with arrival time parametric imaging using Sonazoid-enhanced ultrasonography in portal vein thrombosis: A case report  

PubMed Central

A 55-year-old male was admitted in mid-April 2011 with a fever of >39°C and pain in the lower right abdomen. A medical examination revealed sepsis originating from colonic diverticulitis. Abdominal B-mode ultrasonography (US) performed on admission detected thrombi in the superior mesenteric vein and in the right branch of the hepatic portal vein. Arrival time parametric imaging (At-PI) using Sonazoid-enhanced US showed arterialization of the entire right lobe of the liver. The treatment for the sepsis and portal thrombi that had been started upon admission dissolved the thrombi by day 22, with the exception of one thrombus in the P8 branch of the portal vein. At-PI performed on the same day confirmed arterialization in segment 8, but portal vein dominance was restored elsewhere. When the blood inflow from the hepatic portal vein was reduced, the hepatic arterial blood flow was increased to compensate for the reduction in the total blood supply. The At-PI functions used in the Sonazoid-enhanced US were simple yet effective in visualizing the changes in the hepatic hemodynamics caused by the portal thrombus.

WAKUI, NORITAKA; TAKAYAMA, RYUJI; MATSUKIYO, YASUSHI; SHINOHARA, MIE; KOBAYASHI, SHUNSUKE; KANEKAWA, TAKENORI; NAKANO, SHIGERU; NAGAI, HIDENARI; KUDO, TAKAHIDE; MARUYAMA, KENICHI; SUMINO, YASUKIYO

2013-01-01

239

A near-optimal low complexity sensor fusion technique for accurate indoor localization based on ultrasound time of arrival measurements from low-quality sensors  

NASA Astrophysics Data System (ADS)

A fusion-based localization technique for location-based services in indoor environments is introduced herein, based on ultrasound time-of-arrival measurements from multiple off-the-shelf range estimating sensors which are used in a market-available localization system. In-situ field measurements results indicated that the respective off-the-shelf system was unable to estimate position in most of the cases, while the underlying sensors are of low-quality and yield highly inaccurate range and position estimates. An extensive analysis is performed and a model of the sensor-performance characteristics is established. A low-complexity but accurate sensor fusion and localization technique is then developed, which consists inof evaluating multiple sensor measurements and selecting the one that is considered most-accurate based on the underlying sensor model. Optimality, in the sense of a genie selecting the optimum sensor, is subsequently evaluated and compared to the proposed technique. The experimental results indicate that the proposed fusion method exhibits near-optimal performance and, albeit being theoretically suboptimal, it largely overcomes most flaws of the underlying single-sensor system resulting in a localization system of increased accuracy, robustness and availability.

Mitilineos, Stelios A.; Argyreas, Nick D.; Thomopoulos, Stelios C. A.

2009-05-01

240

P wave dispersion is prolonged in patients with Wilson's disease  

PubMed Central

AIM: To investigate the P wave dispersion as a non-invasive marker of intra-atrial conduction disturbances in patients with Wilson’s disease. METHODS: We compared Wilson’s disease patients (n = 18) with age matched healthy subjects (n = 15) as controls. The diagnosis was based on clinical symptoms, laboratory tests (ceruloplasmin, urinary and hepatic copper concentrations). P wave dispersion, a measurement of the heterogeneity of atrial depolarization, was measured as the difference between the duration of the longest and the shortest P-waves in 12 lead electrocardiography. RESULTS: All the patients were asymptomatic on cardiological examination and have sinusal rhythm in electrocardiography. Left ventricular and left atrial diameters, left ventricular ejection fraction and left ventricular mass index were similar in both groups. The Wilson’s disease patients had a significantly higher P wave dispersion compared with the controls (44.7 ± 5.8 vs 25.7 ± 2.5, P < 0.01). CONCLUSION: There was an increase in P wave dispersion in cardiologically asymptomatic Wilson’s disease patients which probably represents an early stage of cardiac involvement.

Arat, Nurcan; Kacar, Sabite; Golbasi, Zehra; Akdogan, Meral; Sokmen, Yeliz; Kuran, Sedef; Idilman, Ramazan

2008-01-01

241

Velocity contrast across the 1944 rupture zone of the North Anatolian fault east of Ismetpasa from analysis of teleseismic arrivals  

NASA Astrophysics Data System (ADS)

We use differences between arrival times of teleseismic events at sets of stations crossing the North Anatolian fault east of Ismetpasa, where shallow creep has been observed, to detect and quantify a contrast of seismic velocities across the fault. Waveform cross correlations are utilized to calculate phase delays of P waves with respect to expected teleseismic arrivals with incident angles corresponding to the generating events. Compiled delay times associated with 121 teleseismic events indicate about 4.3% average P wave velocity contrast across the fault over the top 36 km, with faster velocity on the north side. The estimated contrast is about 8.3% if the velocity contrast is limited to the top 18 km. The sense of velocity contrast is consistent with the overall tectonic setting and inference made for the examined fault section based on theoretical expectations for bimaterial ruptures and observed asymmetry of rock damage across the fault. Our data indicate lack of significant microseismicity near the fault, suggesting that creep in the area is limited to the depth section above the seismogenic zone.

Ozakin, Yaman; Ben-Zion, Yehuda; Aktar, Mustafa; Karabulut, Hayrullah; Peng, Zhigang

2012-04-01

242

Supercurrent in a p-wave holographic superconductor  

SciTech Connect

The p-wave and p+ip-wave holographic superconductors with fixed DC supercurrent are studied by introducing a nonvanishing vector potential. We find that close to the critical temperature T{sub c} of zero current, the numerical results of both the p-wave model and the p+ip model are the same as those of Ginzburg-Landau (GL) theory; for example, the critical current is j{sub c}{approx}(T{sub c}-T){sup 3/2} and the phase transition in the presence of a DC current is a first-order transition. Beside the similar results between both models, the p+ip superconductor shows isotropic behavior for the supercurrent, while the p-wave superconductor shows anisotropic behavior for the supercurrent.

Zeng Huabi [Department of Physics, Nanjing University, Nanjing 210093 (China); Sun Weimin; Zong Hongshi [Department of Physics, Nanjing University, Nanjing 210093 (China); Joint Center for Particle, Nuclear Physics and Cosmology, Nanjing 210093 (China)

2011-02-15

243

Detection of the electrocardiogram P-wave using wavelet analysis  

NASA Astrophysics Data System (ADS)

Since wavelet analysis is an effective tool for analyzing transient signals, we studied its feature extraction and representation properties for events in electrocardiogram (EKG) data. Significant features of the EKG include the P-wave, the QRS complex, and the T-wave. For this paper the feature that we chose to focus on was the P-wave. Wavelet analysis was used as a preprocessor for a backpropagation neural network with conjugate gradient learning. The inputs to the neural network were the wavelet transforms of EKGs at a particular scale. The desired output was the location of the P-wave. The results were compared to results obtained without using the wavelet transform as a preprocessor.

Anant, Kan S.; Dowla, Farid U.; Rodrigue, Garry H.

1994-03-01

244

Detection of the electrocardiogram P-wave using wavelet analysis  

SciTech Connect

Since wavelet analysis is an effective tool for analyzing transient signals, we studied its feature extraction and representation properties for events in electrocardiogram (EKG) data. Significant features of the EKG include the P-wave, the QRS complex, and the T-wave. For this paper the feature that we chose to focus on was the P-wave. Wavelet analysis was used as a pre-processor for a backpropagation neural network with conjugate gradient learning. The inputs to the neural network were the wavelet transforms of EKGs at a particular scale. The desired output was the location of the P-wave. The results were compared to results obtained without using the wavelet transform as a pre-processor.

Anant, K.S.; Rodrigue, G.H. [California Univ., Davis, CA (United States). Dept. of Applied Science]|[Lawrence Livermore National Lab., CA (United States); Dowla, F.U. [Lawrence Livermore National Lab., CA (United States)

1994-01-01

245

Further evidence for the `Lay discontinuity' beneath northern Siberia and the North Atlantic from short-period P-waves recorded in France  

NASA Astrophysics Data System (ADS)

We analyze data from the French Laboratoire de Detection Geophysique (LDG) network of digital short-period seismic stations. The P-waves from several earthquakes in the Kuril-Okhotsk region display clear secondary arrivals in the 75-85° range, which are not explained by smooth lower mantle models. The move-out of the arrivals across the network indicates a deep mantle origin. We interpret them as waves reflected off, or transmitted at, the 'Lay discontinuity', about 300 km above the core-mantle boundary. The bounce points at this discontinuity are located beneath northern Siberia, slightly to the northwest of the region for which a similar structure has been reported. We propose tools for investigating the lateral variations of the D? structure on the scale 100-1000 km. The method we propose is based on the deconvolution of the data, or convolution of synthetics, by a source time function derived from the data. We show that the method helps identification of the waves that interact with the 'Lay discontinuity', and enables a more objective mapping of its lateral variations. Evidence for bumps a few kilometers high on the lateral scale of a few tens of kilometers is proposed. We also probe a spot of the lower mantle beneath the North Atlantic. A detailed analysis of the waveforms from a Chiapas earthquake suggests that the 'Lay discontinuity' is also present in that part of the world.

Houard, Sylvain; Nataf, Henri-Claude

1992-08-01

246

Automated determination of P-wave polarization at the GRSN  

NASA Astrophysics Data System (ADS)

Polarization analysis of P-waves has been applied for identification of seismic phases (Earle, 1999), for earthquake location (Dyer et al., 1999), measurements of seismic anisotropy (Schulte-Pelkum, 2001), and determination of velocity models. In isotropic, lateral homogeneous media, P-wave polarization is confined to the vertical-radial plane; deviations of horizontal polarization direction from the great-circle propagation direction can be due to smooth lateral velocity heterogeneities, dipping discontinuities, and seismic anisotropy. In order to distinguish between these different causes, P-wave polarization parameters have to be determined for a large number of events in different source regions. Here we present the results of the polarization analysis of P-waves recorded at the GRSN for events in the distance range between 5° and 90°. For a consistent and efficient processing of a large data set we developed an automated procedure for the determination of the P-wave incidence angle and backazimuth. Details of the algorithm are described and results are shown as a function of backazimuth and frequency. We select events with a SNR > 2 at various epicentral distances and avoid the contamination of the P-wave with depth phases. The P-wave polarization parameters are calculated in a moving window using eigenvectors and eigenvalues of the covariance matrix of 3 component records (Jurkevics,1988). The length of the moving window is dependent on epicentral distance and the corner frequency of the band pass filter applied prior the computation of covariance matrix. We also estimate a quality factor and an uncertainty for the polarization parameters in terms of ratio between the intermediate and smallest eigenvalues. An automated picking of the P-wave polarization has been developed based on a characteristic function, defined in terms of amplitude, signal to noise ratios, polarization parameters and their comparison with the predicted ones calculated for the IASP91 model (Kennett, 2005). Especially for lower frequencies results between the stations are comparable. For higher frequencies and local events the spatial variation of the parameters is larger. Interestingly, indications for a dependency on frequency are found in certain distance ranges for incidence angles as well as azimuthal deviations. For comparison we apply the f-k analysis (Capon, 1969) to determine the propagation direction.

Cristiano, L.; Meier, T.; Weidle, C.; Krüger, F.

2012-04-01

247

Coexistence of p-wave cooper pairing and ferromagnetism  

NASA Astrophysics Data System (ADS)

A two-band model for coexistence of p-wave superconductivity with localized ferromagnetism is studied using the equation of motion approach. It shows that ferromagnetic and superconducting states enhance each other but in a different way from that of the one-band model. The Curie temperature is not only determined by the exchange interactions between localized spins, but also can be increased with the coupling between electrons and spins, and with the p-wave Cooper-pairing interaction. These results are complementary to those of the one-band model, which suggest that the Curie temperature is unlikely to ever be below the superconducting transition temperature.

Yan, Xu; Gu, Qiang

2013-10-01

248

P-wave locking in the postventricular atrial refractory period of cardiac resynchronization devices. Management with the Biotronik system.  

PubMed

Electrical desynchronization in cardiac resynchronization therapy (CRT) occurs when sinus P waves are continually locked in the postventricular atrial refractory period (PVARP). This process is characterized by sequences of a P wave as an atrial event in the PVARP followed by a conducted and sensed ventricular event. Such sequences are more common in patients with a prolonged PR interval, often initiated by premature ventricular complexes (PVC) and terminated by PVCs or slowing of the sinus rate. Specific algorithms automatically identify a recurring pattern of P wave locking in the PVARP, whereupon they shorten the PVARP temporarily until atrial tracking is restored with the programmed sensed AV interval. The Biotronik family of Lumax CRT devices use an AV control window which is not an algorithm that "unlocks" P waves trapped in the PVARP. Rather, it prevents P waves from becoming trapped in the PVARP. A ventricular sensed event occurring within the AV control interval does not start a PVARP so that P wave locking cannot occur when the AV conduction time is shorter than the AV control interval. PMID:22527755

Barold, S S; Stroobandt, R X; Herweg, B; Kucher, A

2012-06-01

249

Teleseismic P-wave Velocity Tomography Beneath The Arabian Peninsula  

Microsoft Academic Search

We have imaged tomographically the three-dimensional velocity structure of the upper mantle beneath the Arabian Peninsula using teleseismic P-waves. The data came from the Saudi Arabian National Digital Seismic Network (SANDSN) operated by King Abdulaziz City for Science and Technology (KACST) and three permanent stations (RAYN, EIL and MRNI). The KACST network consists of 38 stations (27 broadband and 11

A. A. Nyblade; A. Rodgers; A. Al-Amri

2004-01-01

250

P Wave Polarity During Pacing in Pulmonary Veins  

Microsoft Academic Search

Introduction: Recent studies have demonstrated that premature depolarizations that trigger atrial fibrillation often arise in pulmonary veins. The purpose of this study was to evaluate whether P wave polarity is helpful in distinguishing which of the 4 pulmonary veins is the site of orgin of a premature depolarization.

Hung-Fat Tse; Chu-Pak Lau; Kathy L. Lee; Frank Pelosi; Hakan Oral; Bradley P. Knight; S. Adam Strickberger; Fred Morady

2001-01-01

251

INTEGRATING P-WAVE AND S-WAVE SEISMIC DATA TO IMPROVE CHARACTERIZATION OF OIL RESERVOIRS  

SciTech Connect

During this period, the principal investigator wrote an abstract and research accomplishments which was published in the journal of the historically black colleges and universities and other minority institutions contract review meeting of June 2003. Interpretations and analysis of data from the study area shows that incident full-elastic seismic wavefield reflected four different wave modes, P, fast-S (SH) , slow-S (SV) and C. These four wave modes image unique geologic stratigraphy and facies and at the same time reflect independent stratal surfaces. It was also observed that P-wave and S-wave do not always reflect from the same stratal boundaries. At inline coordinate 2100 and crossline coordinates of 10,380, 10430, 10480 and 10,520 the P-wave stratigraphy shows coherency at time slice 796 m/s and C-wave stratigraphy shows coherency at time slice 1964 m/s at the same inline coordinate and crossline coordinates of 10,400 to 10470. At inline coordinate 2800 and crossline coordinate 10,650, P-wave stratigraphy shows coherency at time slice 792 m/s and C-wave stratigraphy shows coherency at time slice 1968 m/s.

Innocent J. Aluka

2004-01-12

252

Predicting interplanetary shock arrivals at Earth, Mars, and Venus: A real-time modeling experiment following the solar flares of 5–14 December 2006  

Microsoft Academic Search

A 3-D, kinematic, solar wind model (Hakamada-Akasofu-Fry version 2 (HAFv.2)) is used to predict interplanetary shock arrivals at Venus, Earth, and Mars during a sequence of significant solar events that occurred in the interval 5–14 December 2006. Mars and Venus were on the opposite side of the Sun from Earth during this period. The shocks from the first two east

S. M. P. McKenna-Lawlor; M. Dryer; C. D. Fry; Z. K. Smith; D. S. Intriligator; W. R. Courtney; C. S. Deehr; W. Sun; K. Kecskemety; K. Kudela; J. Balaz; S. Barabash; Y. Futaana; M. Yamauchi; R. Lundin

2008-01-01

253

Mantle Attenuation Estimated from Regional and Teleseismic P-waves of Deep Earthquakes and Surface Explosions  

NASA Astrophysics Data System (ADS)

We estimated the network-averaged mantle attenuation t*(total) of 0.5 s beneath the North Korea test site (NKTS) by use of P-wave spectra and normalized spectral stacks from the 25 May 2009 declared nuclear test (mb 4.5; IDC). This value was checked using P-waves from seven deep (580-600 km) earthquakes (4.8 < M w < 5.5) in the Jilin-Heilongjiang, China region that borders with Russia and North Korea. These earthquakes are 200-300 km from the NKTS, within 200 km of the Global Seismic Network seismic station in Mudanjiang, China (MDJ) and the International Monitoring System primary arrays at Ussuriysk, Russia (USRK) and Wonju, Republic of Korea (KSRS). With the deep earthquakes, we split the t*(total) ray path into two segments: a t*(u), that represents the attenuation of the up-going ray from the deep hypocenters to the local-regional receivers, and t*(d), that represents the attenuation along the down-going ray to teleseismic receivers. The sum of t*(u) and t*(d) should be equal to t*(total), because they both share coincident ray paths. We estimated the upper-mantle attenuation t*(u) of 0.1 s at stations MDJ, USRK, and KSRS from individual and stacks of normalized P-wave spectra. We then estimated the average lower-mantle attenuation t*(d) of 0.4 s using stacked teleseismic P-wave spectra. We finally estimated a network average t*(total) of 0.5 s from the stacked teleseismic P-wave spectra from the 2009 nuclear test, which confirms the equality with the sum of t*(u) and t*(d). We included constraints on seismic moment, depth, and radiation pattern by using results from a moment tensor analysis and corner frequencies from modeling of P-wave spectra recorded at local distances. We also avoided finite-faulting effects by excluding earthquakes with complex source time functions. We assumed ?2 source models for earthquakes and explosions. The mantle attenuation beneath the NKTS is clearly different when compared with the network-averaged t* of 0.75 s for the western US and is similar to values of approximately 0.5 s for the Semipalatinsk test site within the 0.5-2 Hz range.

Ichinose, G.; Woods, M.; Dwyer, J.

2013-01-01

254

Holographic p-wave superconductors from Gauss-Bonnet gravity  

SciTech Connect

We study the holographic p-wave superconductors in a five-dimensional Gauss-Bonnet gravity with an SU(2) Yang-Mills gauge field. In the probe approximation, we find that when the Gauss-Bonnet coefficient grows, the condensation of the vector field becomes harder, both the perpendicular and parallel components, with respect to the direction of the condensation, of the anisotropic conductivity decrease. We also study the mass of the quasiparticle excitations, the gap frequency and the DC conductivities of the p-wave superconductor. All of them depend on the Gauss-Bonnet coefficient. In addition, we observe a strange behavior for the condensation and the relation between the gap frequency and the mass of quasiparticles when the Gauss-Bonnet coefficient is larger than 9/100, which is the upper bound for the Gauss-Bonnet coefficient from the causality of the dual field theory.

Cai Ronggen; Nie Zhangyu; Zhang Haiqing [Key Laboratory of Frontiers in Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, P.O. Box 2735, Beijing 100190 (China)

2010-09-15

255

Interaction Between Domain Walls in Chiral p-Wave Superfluids  

NASA Astrophysics Data System (ADS)

We calculate microscopically the interaction energy of domain walls separating degenerate ground states in a chiral p-wave fermionic superfluid. The interaction is mediated by the quasiparticles experiencing Andreev scattering at the domain walls. As a by-product, we derive a useful general expression for the free energy of an arbitrary nonuniform texture of the order parameter in terms of the quasiparticle scattering matrix.

Przedborski, M. A.; Samokhin, K. V.

2013-10-01

256

Decays rates for S- and P-wave bottomium  

SciTech Connect

The authors use the Bodwin-Braaten-Lepage factorization scheme to separate the long- and short-distance factors that contribute to the decay rates of {Upsilon}, {eta}{sub b} (S-wave) and {chi}{sub b},h{sub b} (P-wave). The long distance matrix elements are calculated on the lattice in the quenched approximation using a non-relativistic formulation of the b quark dynamics.

Bodwin, G.T.; Kim, S.; Sinclair, D.K.

1994-11-01

257

Electrocardiographic P-wave characteristics in patients with psoriasis vulgaris  

PubMed Central

Purpose Psoriasis vulgaris is one of the most common skin disorders. Patients with psoriasis carry an excessive risk of atrial fibrillation (AF). The differences between the maximum (Pmax) and the minimum (Pmin) P-wave duration on ECG are defined as P-wave dispersion (PWD). Prolongation of PWD is an independent risk factor for the development of AF. The aim of this the study was to investigate P-wave duration and PWD in patients with psoriasis. Methods Sixty-one adult patients with psoriasis vulgaris (group 1) and 58 age and sex-matched healthy individuals (group 2) were included in this study. ECG recordings were obtained, and the P-wave variables were calculated. Results were reported as mean ± standard deviation and percentages. Continuous variables were analysed using Student's t test. A value of P < 0.05 was considered statistically signi?cant. Results Pmax and PWD were significantly higher in group 1 than in group 2 (108.8 ± 21.3 ms versus 93.3 ± 13.0 ms, P < 0.001; 67.4 ± 22.9 ms versus 45.0 ± 19.6 ms, P < 0.001, respectively). Also, Pmin was significantly lower in group 1 (41.3 ± 12.3 ms versus 48.3 ± 14.3 ms, P = 0.04). The psoriasis disease activity score and hsCRP correlated with PWD (P < 0.01). Conclusions Atrial conduction of sinus impulses was impaired in patients with psoriasis vulgaris. It was more prominent in patients with severe disease. Physicians caring for patients with psoriasis vulgaris should screen them for AF development.

Erdogan, Ercan; Tasal, Abdurrrahman; Vatankulu, Mehmet Akif; Kul, Seref; Sevgili, Emrah; Ertas, Gokhan; Dizman, Didem; Onsun, Nahide; Uysal, Omer

2013-01-01

258

Models of the upper mantle beneath the central North Island, New Zealand, from speeds and anisotropy of subhorizontal P waves (Pn)  

NASA Astrophysics Data System (ADS)

The central North Island of New Zealand shows significant variations in Pn wave speeds over small distances, ranging from 8.5 ± 0.2 km/s to 7.4 ± 0.1 km/s over a distance of 150 km. A combination of national network seismometers, local volcanic seismic monitoring networks, and temporary deployments are used to collect arrival times from local events, during the period of 1990-2006. The data set consists of approximately 11,200 Pn observations from 3000 local earthquakes at 91 seismograph sites. We have created a method that allows us to model the predominant wavelength features of P wave speeds in the uppermost mantle, as well as estimating values of mantle anisotropy and irregularities in the crust beneath stations, using least squares collocation. The resulting model shows distinct variations in uppermost mantle Pn velocities. Velocities of less than 7.5 km/s are found beneath the back-arc extension region of the Central Volcanic Region, and under the Taranaki Volcanic Region, indicating the presence of water and partial melt. The region to the east shows extremely high velocities of 8.3-8.5 km/s, where the P waves are traveling within the subducting Pacific slab. Slightly lower than normal mantle velocities of 7.8-8.1 km/s are found in the western North Island, suggesting a soft mantle. Pn anisotropy estimates throughout the North Island show predominately trench-parallel fast directions, ceasing to nulls in the west. Anisotropy measurements indicate the strain history of the mantle. Null anisotropy measurements suggest an undisturbed mantle, suggesting that mantle beneath the western North Island is young.

Seward, A. M.; Henderson, C. M.; Smith, E. G. C.

2009-01-01

259

Scattered P'P' waves observed at short distances  

USGS Publications Warehouse

We detect previously unreported 1 Hz scattered waves at epicentral distances between 30° and 50° and at times between 2300 and 2450 s after the earthquake origin. These waves likely result from off-azimuth scattering of PKPbc to PKPbc in the upper mantle and crust and provide a new tool for mapping variations in fine-scale (10 km) mantle heterogeneity. Array beams from the Large Aperture Seismic Array (LASA) clearly image the scattered energy gradually emerging from the noise and reaching its peak amplitude about 80 s later, and returning to the noise level after 150 s. Stacks of transverse versus radial slowness (?t, ?r) show two peaks at about (2, -2) and (-2,-2) s/°, indicating the waves arrive along the major arc path (180° to 360°) and significantly off azimuth. We propose a mantle and surface PKPbc to PKPbc scattering mechanism for these observations because (1) it agrees with the initiation time and distinctive slowness signature of the scattered waves and (2) it follows a scattering path analogous to previously observed deep-mantle PK•KP scattering (Chang and Cleary, 1981). The observed upper-mantle scattered waves and PK•KP waves fit into a broader set of scattered waves that we call P?•d•P?, which can scatter from any depth, d, in the mantle.

Earle, Paul S.; Rost, Sebastian; Shearer, Peter M.; Thomas, Christine

2011-01-01

260

Crust and upper mantle P wave velocity structure beneath Valles Caldera, New Mexico: Results from the Jemez teleseismic tomography experiment  

NASA Astrophysics Data System (ADS)

New results are presented from the teleseismic component of the Jemez Tomography Experiment conducted across Valles caldera in northern New Mexico. We invert 4872 relative P wave arrival times recorded on 50 portable stations to determine velocity structure to depths of 40 km. The three principle features of our model for Valles caldera are: (1) near-surface low velocities of -17% beneath the Toledo embayment and the Valle Grande, (2) midcrustal low velocities of -23% in an ellipsoidal volume underneath the northwest quadrant of the caldera, and (3) a broad zone of low velocities (-15%) in the lower crust or upper mantle. Crust shallower than 20 km is generally fast to the northwest of the caldera and slow to the southeast. Near-surface low velocities are interpreted as thick deposits of Bandelier tuff and postcaldera volcaniclastic rocks. Lateral variation in the thickness of these deposits supports increased caldera collapse to the southeast, beneath the Valle Grande. We interpret the midcrustal low-velocity zone to contain a minimum melt fraction of 10%. While we cannot rule out the possibility that this zone is the remnant 1.2 Ma Bandelier magma chamber, the eruption history and geochemistry of the volcanic rocks erupted in Valles caldera following the Bandelier tuff make it more likely that magma results from a new pulse of intrusion, indicating that melt flux into the upper crust beneath Valles caldera continues. The low-velocity zone near the crust-mantle boundary is consistent with either partial melt in the lower crust or mafic rocks without partial melt in the upper mantle. In either case, this low-velocity anomaly indicates that underplating by mantle-derived melts has occurred.

Steck, Lee K.; Thurber, Clifford H.; Fehler, Michael C.; Lutter, William J.; Roberts, Peter M.; Baldridge, W. Scott; Stafford, Darrik G.; Sessions, Robert

1998-10-01

261

An automated full waveform logging system for high-resolution P-wave profiles in marine sediments  

NASA Astrophysics Data System (ADS)

An automated, PC-based logging system has been developed to investigate marine sediment cores by full waveform transmission seismograms. High-resolution P-wave velocity and amplitude attenuation profiles are simultaneously derived from the transmission data to characterize the acoustic properties of the sediment column. A pair of ultrasonic, piezoelectric wheel probes is used to generate and record the transmission signals travelling radially through the sediment core. Both unsplit and split cores are allowed. Mounted in a carriage driven by a stepping motor via a shaft the probes automatically move along the core liner, stopping at equidistant spacings to provide a quasi-continuous inspection of the core by the transmission data. The axial travel distance and the core diameter are determined by digital measuring tools. First arrivals are picked automatically from the transmission seismograms using either a threshold in the seismogram's envelope or a cross-correlation algorithm taking the ‘zero-offset’ signal of both wheel probes into account. Combined with the core diameter these first arrivals lead to a P-wave velocity profile with a relative precision of 1 to 2 m s-1. Simultaneously, the maximum peak-to-peak amplitudes of the transmission seismograms are evaluated to get a first idea on the amplitude attenuation along the sediment core. Two examples of gravity cores taken during a recent cruise of R.V. METEOR in the Western Equatorial Atlantic are presented. They yield that the P-wave profiles can be used for locating strong and fine-scale lithological changes, e.g. turbidite layers and slight variations in the sand, silt or clay content. In addition, the transmission seismograms and their amplitude spectra obviously seem to reveal a correlation between the relative amount of low-frequency spectral components and the sediment grain size, and thus provide a tool for the determination of additional, related physical or sedimentological parameters in future investigations.

Breitzke, Monika; Spie?, Volkhard

1993-11-01

262

Three-dimensional P-wave Velocity Structure of the Bear Valley Region of Central California  

NASA Astrophysics Data System (ADS)

The three-dimensional P-wave velocity structure of the Bear Valley region of central California is determined by applying a circular ray-tracing technique to 1735 P-wave arrivals from 108 locally recorded earthquakes. Comparison of the results obtained from one-dimensional and laterally varying starting models shows that many of the features in the structure determined are fairly insensitive to the choice of the starting model. Velocities associated with the Gabilan granites southwest of the San Andreas Fault are slightly higher than those in the Franciscan formation to the northeast, and these two features are separated in the southern part of the region by a narrow fault zone with very low velocities. In the southeastern part of the region, where the Gabilan granites do not abut the San Andreas Fault, the low velocities of the fault zone cross over to the southwestern side of the fault. They also appear to extend to depths of at least 15km, thus locally reversing the contrast across the San Andreas Fault that prevails farther to the northwest. In the northwestern part of the region, the low velocities of the fault zone split and follow the surface traces of the San Andreas and Calaveras Faults, but do not appear to extend to depths much deeper than about 6km. There also appears to be a well-defined contrast in structure in the middle of the Santa Clara Valley, suggesting the existence of a fault in the basement of the valley that may be a southern extension of the Sargent Fault into this region. Relocated hypocenters beneath the San Andreas Fault cluster in a zone that dips about 80° southwest and intersects the surface trace of the fault in the southern part of region.

Lin, C.-H.; Roecker, S. W.

263

Laboratory monitoring of P waves in partially saturated sand  

NASA Astrophysics Data System (ADS)

Energy dissipation is observed on seismic data when a wave propagates through a porous medium, involving different frequency regimes depending on the nature of rock and fluid types. We focus here on the role of partial fluid saturation in unconsolidated porous media, looking in particular at P-wave phase velocity and attenuation. The study consists in running an experiment in a sand-filled tank partially saturated with water. Seismic propagation in the tank is generated in the kHz range by hitting a steel ball on a granite plate. Seismic data are recorded by buried accelerometers and injecting or extracting water controls the partial saturation. Several imbibition/drainage cycles were performed between the water and gas residual saturations. A Continuous Wavelet Transform applied on seismic records allowed us to extract the direct P wave at each receiver. We observe an hysteresis in phase velocities and inverse quality factors between imbibition and drainage. Phase velocities and inverse quality factors are then jointly inverted to get a final poro-viscoelastic model of the partially saturated sand that satisfactorily reproduces the data. The model formulation consists in generalizing the Biot theory to effective properties of the fluid and medium (permeability and bulk modulus) to properly explain the phase velocity variation as a function of the saturation. The strong level of attenuation measured experimentally is further explained by an anelastic effect due to grain to grain sliding, adding to Biot's losses. This study shows that fluid distribution at microscopic scale has strong influence on the attenuation of direct P waves at macroscopic scale and confirms that seismic prospection may be a powerful tool for the characterization of transport phenomena in porous media.

Barrière, Julien; Bordes, Clarisse; Brito, Daniel; Sénéchal, Pascale; Perroud, Hervé

2012-12-01

264

Impact of Phase Transitions on P Wave Velocities  

SciTech Connect

In regions where a high pressure phase is in equilibrium with a low pressure phase, the bulk modulus defined by the P-V relationship is greatly reduced. Here we evaluate the effect of such transitions on the P wave velocity. A model, where cation diffusion is the rate limiting factor, is used to project laboratory data to the conditions of a seismic wave propagating in the two-phase region. We demonstrate that for the minimum expected effect there is a significant reduction of the seismic velocity, as large as 10% over a narrow depth range.

D Weidner; L Li

2011-12-31

265

Impact of Phase Transitions on P Wave Velocities  

SciTech Connect

In regions where a high pressure phase is in equilibrium with a low pressure phase, the bulk modulus defined by the P-V relationship is greatly reduced. Here we evaluate the effect of such transitions on the P wave velocity. A model, where cation diffusion is the rate limiting factor, is used to project laboratory data to the conditions of a seismic wave propagating in the two-phase region. We demonstrate that for the minimum expected effect there is a significant reduction of the seismic velocity, as large as 10% over a narrow depth range.

Weidner, D.; Li, L

2010-01-01

266

p-Wave Cold Collisions in an Optical Lattice Clock  

SciTech Connect

We study ultracold collisions in fermionic ytterbium by precisely measuring the energy shifts they impart on the atoms' internal clock states. Exploiting Fermi statistics, we uncover p-wave collisions, in both weakly and strongly interacting regimes. With the higher density afforded by two-dimensional lattice confinement, we demonstrate that strong interactions can lead to a novel suppression of this collision shift. In addition to reducing the systematic errors of lattice clocks, this work has application to quantum information and quantum simulation with alkaline-earth atoms.

Lemke, N. D.; Sherman, J. A.; Oates, C. W.; Ludlow, A. D. [National Institute of Standards and Technology, Boulder, Colorado 80305 (United States); Stecher, J. von; Rey, A. M. [JILA, NIST, and University of Colorado, Department of Physics, Boulder, Colorado 80309 (United States)

2011-09-02

267

Instanton induced interaction in the {ital P}-wave baryons  

SciTech Connect

We study spin-dependence of the interquark interactions induced by the instanton-light quark coupling and their effects on the excited baryon spectrum and multiquark systems. It is found that the spin-orbit force from the instanton induced interaction reduces that from the one-gluon exchange in the flavor-octet {ital P}-wave baryons. This cancellation does not occur in the spin-orbit force between nucleons, where the flavor symmetric q-q interaction plays a dominant role. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Takeuchi, S. [Department of Public Health and Environmental Science, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo, Tokyo 113 (Japan)

1995-05-10

268

P Wave Residuals as a Function of Azimuth, 2. Undulations of the Mantle Low-Velocity Layer as an Explanation  

Microsoft Academic Search

In an earlier paper Bolt and Nuttli presented evidence that the P wave delay times, relative to Berkeley, at a number of seismographic stations in central and northern California, ex!fibit a significant dependence on azimuth of wave approach. Numerical analysis of these data indicates that their amplitudes are too large to be accounted for by crustal structure only. The data

Otto W. Nuttli; Bruce A. Bolt

1969-01-01

269

Revealing the architecture of the upper boundary of the Philippine Sea Plate beneath the northern tip of the Izu-Tanzawa Collision Zone, Central Japan, using later-phase of P waves  

NASA Astrophysics Data System (ADS)

In Izu-Tanzawa Collision Zone (ITCZ), Izu arc collides with Japan arc due to subduction of the Philippine Sea plate (PHP). Recent studies by Kikuchi (2008) and Arai et al. (2009) have revealed that the upper boundary of PHP has a complex geometry in this area. High seismicity near the top boundary of PHP is reported in the front (northern) edge of the ITCZ, which is the transition zone from collision to subduction of PHP, whereas an aseismic zone is located on the western part of the high seismicity region. This spatial variation of seismicity is probably related to the shape of PHP caused by the difference between collisional vs. subductive movements. To better correlate the spatial distribution of seismicity and the plate configuration, we attempt to find a discontinuous surface near the upper boundary of PHP using later phases of P waves. We used seismic-waveform data from the website of Hi-net seismic network. In the high seismicity region, clear later phases of P waves (X phases) are observed in vertical component seismograms recorded at the stations above the high seismicity region. The X phases arrive 0.5s to 2.0s after P arrivals. Time difference between P and X arrivals (X-P times) increases with distances between the plate boundary and the hypocenters. Similarly, X-P times increase as the distances from the northwestern edge of the high seismicity region to the hypocenters increase. These observations suggest two possibilities for the origin of the X phases: (1) a converted wave at the upper boundary of PHP or (2) a reflected wave from the edge of the high seismicity region. First we searched a suitable plane for which calculated X-P times can match the observed X-P times, by assuming the X phases are converted waves. We found that two converted planes located at different depths would best explain all observed X-P times simultaneously; the depth of the estimated plane in the western side of the high seismicity zone is deeper than that of the eastern side. Next, we determined reflection points for which the observed X-P times can fit: estimated reflection points were concentrated in the northwestern edge of the high seismicity region. In either case, generation points of X phases are located near the top boundary of PHP and it would be expected that the detailed structure near the top boundary of the PHP could be clarified using these later phases. Acknowledgement: We thank the National Research Institute for Earth Science and Disaster Prevention of Japan for providing the Hi-net data.

Shuri, Y.; Tsumura, N.

2010-12-01

270

A New P-wave Frequency Dependent Magnitude Estimation Technique  

NASA Astrophysics Data System (ADS)

A new procedure for estimating Mb is suggested which is analogous to the new procedure being proposed by Russell and Bonner (2005) for the estimation of surface wave magnitudes. The measurement process involves the use of narrow pass band Butterworth filters on broad band station data that isolate the amplitude of the P waves at each particular frequency. The amplitude-period data are then used to estimate magnitudes with corrections for both the filtering process and frequency dependent attenuation. The magnitudes generally vary smoothly with frequency and the maximum value is selected for each station's Mb. The technique offers a number of advantages over tradition Mb measurement procedures. These include an inherently increasing window length with increasing period. This allows the technique to utilize longer period data for large events. In selecting the maximum Mb from the frequency-magnitude data the effects of the corner frequency on the event magnitude are also avoided. New work by Veith (2005) defines both the frequency dependent attenuation for P waves and an improved worldwide regional magnitude correction curve. While the need for region specific correction curves is evident, the worldwide average curve together with the frequency dependent attenuation corrections offers significantly improved regional Mb estimates, particularly when combined with this new analysis technique.

Veith, K. F.; Rivers, W.; Wagner, R.

2005-12-01

271

Original Article Assessment of the P Wave Dispersion and Duration in Elite Women Basketball Players  

Microsoft Academic Search

Background: P wave dispersion is an independent predictor of atrial fibrillation. P wave dispersion is associated with inhomogeneous and discontinuous propagation of sinus impulses. The purpose of this study was to investigate P wave dispersion and transthoracic echocardiographic findings in elite women basketball players. Methods: We recruited 27 well-trained woman athletes with a training history of many years (11.9 ±

Gokhan Metin; Mustafa Yildiz; Bulent Bayraktar; Ilker Yucesir; Hasan Kasap; Lutfi Cakar

272

Newly Arrived West Indian Adolescents  

Microsoft Academic Search

This study explores patterns of adjustment among newly arrived West Indian adolescents. In particular, it focuses on the concurrent developmental and cultural transitions of immigration and adolescence. Barriers to adjustment and patterns of identity formation are explored and discussed within the context of a typological developmental model. Findings of this study are based on the responses of 25 newly arrived

Annette M. Mahoney

2002-01-01

273

P-wave anisotropy in the lower lithosphere  

Microsoft Academic Search

Long-range controlled source seismic experiments yield detailed information about the velocity depth structure of the lower lithosphere. Between Ireland and Northern Britain three such profiles sample almost the same portion of the subcrustal lithosphere. Three zones with steep velocity gradients have been detected between 30 km and 90 km depth. Both the pattern and velocity of the arrivals are incompatible

C. J. Bean; A. W. B. Jacob

1990-01-01

274

First high resolution P wave velocity structure beneath Tenerife Island, (Canary Islands, Spain)  

NASA Astrophysics Data System (ADS)

3D velocity structure distribution has been imaged for first time using high resolution traveltime seismic tomography of the active volcano of Tenerife Island (Canary Islands, Spain). It is located in the Atlantic Ocean. In this island is situated the Teide stratovolcano (3718 m high) that is part of the Cañadas-Teide-Pico Viejo volcanic complex. Las Cañadas is a caldera system more than 20 kilometers wide where at least four distinct caldera processes have been identified. Evidence for many explosive eruptions in the volcanic complex has been found; the last noticeable explosive eruption (sub-plinean) occurred at Montaña Blanca around 2000 years ago. During the last 300 years, six effusive eruptions have been reported, the last of which took place at Chinyero Volcano on 18 November 1909. In January 2007, a seismic active experiment was carried out as part of the TOM-TEIDEVS project. About 6850 air gun shots were fired on the sea and recorded on a dense local seismic land network consisting of 150 independent (three component) seismic stations. The good quality of the recorded data allowed identifying P-wave arrivals up to offsets of 30-40 km obtaining more than 63000 traveltimes used in the tomographic inversion. The images have been obtained using ATOM-3D code (Koulakov, 2009). This code uses ray bending algorithms in the ray tracing for the forward modelling and in the inversion step it uses gradient methods. The velocity models show a very heterogeneous upper crust that is usual in similar volcanic environment. The tomographic images points out the no-existence of a magmatic chamber near to the surface and below Pico Teide. The ancient Las Cañadas caldera borders are clearly imaged featuring relatively high seismic velocity. Moreover, we have found a big low velocity anomaly in the northwest dorsal of the island. The last eruption took place in 1909 in this area. Furthermore, in the southeast another low velocity anomaly has been imaged. Several resolution and accuracy tests were carried out to quantify the reliability of the final velocity models. Checkerboard tests show that the well-resolved are located up to 6-8 km depth. Also we carried out synthetic tests in which we successfully reproduce single anomalies observed in the velocity models. Especially we have study carefully the low velocity anomalies found in the NW and SE, which have been recovered successfully. The jack-knife technique have been used and our results are stable if we remove the 50% of the data for different stations, but if we reject all the data for some stations, the velocity models can change. These tests assure the uniqueness of the first 3D velocity model that characterizes the internal structure of the Tenerife Island. As main conclusions of our work we can remark: a) This is the first 3-D velocity image of the area; b) we have observed low velocity anomalies near to surface that could be associated to the presence of magma, water reservoirs and volcanic landslides; c) high velocity anomalies could be related to ancient volcanic episodes or basement structures; d) our results could help to resolve many questions relate to the evolution of the volcanic system, as the presence or not of big landslides, calderic explosions or others; e) this image is a very important tool to improve the knowledge of the volcanic hazard, and therefore volcanic risk. We would like to highlight the importance of take into account the risk of eruption in other areas besides Pico Teide-Las Cañadas system.

Garcia-Yeguas, Araceli; Ivan, Koulakov; Ibañez Jesus, M.; Valenti, Sallarès.

2010-05-01

275

Rupture Process of the 2007 Noto Hanto Earthquake Inferred From Local P-wave Records: Second hypocenter, Initial Rupture, Main Rupture, Asperity and Killer Pulse  

NASA Astrophysics Data System (ADS)

The 2007 Noto Hanto earthquake (Mjma6.9; Mw6.7) occurred on 25 March 2007 (JST) in the Noto Peninsula area of central Japan, which shook strongly the near-source region. Many strong-motion stations recorded the seismic motion near the source region. In this study we analyzed the P-wave part of such records. In the waveform a typical characteristic can be seen. That is an emergent onset. The strong-motion records at local stations except the three nearest stations show nearly two seconds of small but increasing amplitude arrival (hereafter, called "initial rupture phase") followed by the onset of the main energy release (hereafter, called "main rupture phase"). Such an emergent onset is seen on strong-motion records of other earthquakes (e.g., the 2000 Western Tottori earthquake; the 2005 West Off Fukuoka Prefecture earthquake; the 2007 Niigataken Chuetsu-oki earthquake). For the three nearest stations, S wave may have masked the main rupture phase with the lager amplitudes. The P- wave part of the records has another remarkable feature. In the first P onset part of the initial rupture phase two events can be seen. The difference between the two arrivals is about 0.5 s. Using a master-event technique (Takenaka et al., 2006, EPS) we determined the location of the second event (hereafter called "the second hypocenter") relative to the location of the first event (i.e. hypocenter), and then estimated the relative location and time of the onset of the main rupture with respect to the second hypocenter. We furthermore mapped the asperity area on the main fault plane using a source imaging technique based on the back-projection (Yamamoto and Takenaka, 2006, AGU Fall Meeting). From these analyses, we derived the following rupture history of this earthquake: The initial rupture plane and the main rupture plane are different as suggested by the focal mechanism solutions of the P-wave polarities (JMA, 2007) and the CMT (F-net, NIED, 2007). The rupture first propagated toward the direction of strike of the initial rupture plane for 0.5 seconds and changed to the main rupture plane, where this changing point is the second hypocenter. It located at about 1 km apart from the hypocenter. The rupture then restarted toward the direction of Wajima City along the main rupture plane. The main rupture (breaking of the asperity) began at a time of 2.4 s after the second hypocenter onset at a position of 1.0 km and 1.4 km in the strike and updip directions, respectively, from the second hypocenter. The asperity distributes along an updip and strike direction from the second hypocenter and the imaging peak locates around the coast near Monzen-cho, Wajima city in the Noto Peninsula. This estimated rupture history is consistent with damage distribution and spatial pattern of the observed killer pulse (forward rupture directivity pulse) in S-wave portion of the strong-motion records. (Acknowledgements) We used the strong-motion records supplied by the National Institute for Earth Science and Disaster Prevention (NIED; K-NET, KiK-net, F-net), and the Japan Meteorological Agency (JMA).

Yamamoto, Y.; Takenaka, H.

2007-12-01

276

Prediction in Markovian bulk arrival queues  

Microsoft Academic Search

This paper deals with the statistical analysis of bulk arrival queues from a Bayesian point of view. The focus is on prediction of the usual measures of performance of the system in equilibrium. Posterior predictive distribution of the number of customers in the system is obtained through its probability generating function. Posterior distribution of the waiting time, in the queue

Carmen Armero; David Conesa

2000-01-01

277

Systematics of S- and P-wave radiation widths  

SciTech Connect

The question of calculating differences in s- and p-wave radiation widths as a valid evaluation tool is explored. A purely statistical approach such as that provided by the Brink-Axel formula depends upon two factors: 1) an adequate description of the giant dipole resonance shape at energies well below the resonance, and 2) an adequate description of the level densities between the ground state and the excitation of the compound nucleus near the neutron separation energy. Some success has been obtained in certain regions of the periodic table with this simple approach, e.g., in the actinides where all nuclei exhibit similar rigid permanent deformations. However, if the method is to be used as a general evaluation procedure throughout the periodic table and particularly in regions where the radiative transition probabilities are enhanced by direct processes, it appears that much more nuclear structure information needs to be incorporated into the calculations.

Moore, M.S.

1980-09-22

278

P-Wave hyperons in nonperturbative quark dynamics  

SciTech Connect

We carry out an investigation of the P-wave hyperons {lambda} {sigma}, and {xi} employing the field correlator method in QCD. This method allows us to derive the effective Hamiltonian (EH) approach successfully applied to the meson and ground-state baryon spectra. The EH is written in the form of the nonrelativistic three-quark Hamiltonian with perturbative Coulomb-like and nonperturbative string interactions and the specific mass term. We solve the three-quark problem using the hyperspherical approach. With only two parameters, the string tension {sigma} and the strong coupling constant {alpha}{sub s}, a unified quantitative description of the ground and excited hyperon states is achieved. In particular, we predict that all the hyperon states have the similar cost (in {delta}) {approx}460 MeV.

Driga, O. N., E-mail: driga@itep.ru; Narodetskii, I. M., E-mail: naro@itep.ru; Veselov, A. I. [Institute for Theoretical and Experimental Physics (Russian Federation)], E-mail: veselov@itep.ru

2008-02-15

279

Quantum Computing with p-Wave Superfluid Vortices  

NASA Astrophysics Data System (ADS)

It is shown that Majorana fermions trapped in three vortices in a p-wave superfluid implement a qubit for universal quantum computing. Several similar ideas have already been proposed: Ivanov [Phys. Rev. Lett. 86 (2001) 268] and Zhang et al. [Phys. Rev. Lett. 99 (2007) 220502] have proposed schemes in which a qubit is implemented with two and four Majorana fermions, respectively, where a qubit operation is performed by exchanging the positions of Majorana fermions. The set of gates thus obtained is a discrete subset of the relevant unitary group. We propose, in this paper, a new scheme, where three Majorana fermions form a qubit. We show that continuous 1-qubit gate operations are possible by exchanging the positions of Majorana fermions complemented with dynamical phase change. Two-qubit gates are realized through the use of the coupling between Majorana fermions belonging to different qubits.

Ohmi, Tetsuo; Nakahara, Mikio

2010-10-01

280

Topological Quantum Computing with p-Wave Superfluid  

NASA Astrophysics Data System (ADS)

It is shown that Majorana fermions trapped in three p-wave superfluid vortices form a qubit in a topological quantum computing (TQC). Several similar ideas have already been proposed, in which a qubit operation is performed by braiding the world lines of these two or four Majorana fermions. Naturally the set of quantum gates thus obtained is a discrete subset of the relevant unitary group. We propose a new scheme, where three Majorana fermions form a qubit. We show that continuous qubit operations are made possible by braiding the Majorana fermions complemented with dynamical phase factors. Furthermore, it is possible to introduce entanglement between two such qubits by geometrical manipulation of some vortices involved.

Nakahara, Mikio; Ohmi, Tetsuo

2010-03-01

281

Crustal structure of Deception Island volcano from P wave seismic tomography: Tectonic and volcanic implications  

NASA Astrophysics Data System (ADS)

Deception Island (62°59'S, 60°41'W) is an active volcano located in the Bransfield Strait between the Antarctic Peninsula and the South Shetland Islands. The island is composed of rocks that date from <0.75 Ma to historical eruptions (1842, 1967, 1969, and 1970), and nowadays most of its activity is represented by vigorous hydrothermal circulation, slight resurgence of the inner bay floor, and intense seismicity, with frequent volcano-tectonic and long-period events. In January 2005 an extensive seismic survey took place in and around the island to collect high-quality data for a high-resolution P wave velocity tomography study. A total of 95 land and 14 ocean bottom seismometers were deployed, and more than 6600 air gun shots were fired. As a result of this experiment, more than 70,000 travel time data were used to obtain the velocity model, which resolves strong P wave velocity contrasts down to 5 km depth. The joint interpretation of the Vp distribution together with the results of geological, geochemical, and other geophysical (magnetic and gravimetric) measurements allows us to map and interpret several volcanic features of the island and surroundings. The most striking feature is the low P wave velocity beneath the caldera floor which represents the seismic image of an extensive region of magma beneath a sediment-filled basin. Another low-velocity zone to the east of Deception Island corresponds to seafloor sedimentary deposits, while high velocities to the northwest are interpreted as the crystalline basement of the South Shetland Islands platform. In general, in the tomographic image we observe NE-SW and NW-SE distributions of velocity contrasts that are compatible with the regional tectonic directions and suggest that the volcanic evolution of Deception Island is strongly conditioned by the Bransfield Basin geodynamics.

Zandomeneghi, Daria; Barclay, Andrew; Almendros, Javier; IbañEz Godoy, Jesús M.; Wilcock, William S. D.; Ben-Zvi, Tami

2009-06-01

282

Tomographic imaging of local earthquake delay times for three-dimensional velocity variation in western Washington  

Microsoft Academic Search

Tomographic inversion is applied to delay times from local earthquakes to image three dimensional velocity variations in the Puget Sound region of western Washington. The 37,500 square km region is represented by nearly cubic blocks of 5 km per side. P-wave arrival time observations from 4,387 crustal earthquakes, with depths of 0 to 40 km, were used as sources producing

Jonathan M. Lees; Robert S. Crosson

1990-01-01

283

Derivation of site-specific relationships between hydraulic parameters and p-wave velocities based on hydraulic and seismic tomography  

NASA Astrophysics Data System (ADS)

In this study, hydraulic and seismic tomographic measurements were used to derive a site-specific relationship between the geophysical parameter p-wave velocity and the hydraulic parameters, diffusivity and specific storage. Our field study includes diffusivity tomograms derived from hydraulic travel time tomography, specific storage tomograms, derived from hydraulic attenuation tomography, and p-wave velocity tomograms, derived from seismic tomography. The tomographic inversion was performed in all three cases with the Simultaneous Iterative Reconstruction Technique algorithm, using a ray tracing technique with curved trajectories. The experimental set up was designed such that the p-wave velocity tomogram overlaps the hydraulic tomograms by half. The experiments were performed at a well-characterized sand and gravel aquifer, located in the Leine River valley near Göttingen, Germany. Access to the shallow subsurface was provided by direct-push technology. The high spatial resolution of hydraulic and seismic tomography was exploited to derive representative site-specific relationships between the hydraulic and geophysical parameters, based on the area where geophysical and hydraulic tests were performed. The transformation of the p-wave velocities into hydraulic properties was undertaken using a k-means cluster analysis. Results demonstrate that the combination of hydraulic and geophysical tomographic data is a promising approach to improve hydrogeophysical site characterization.

Brauchler, R.; Doetsch, J.; Dietrich, P.; Sauter, M.

2012-03-01

284

A correlation between Schmidt hammer rebound numbers with impact strength index, slake durability index and P-wave velocity  

NASA Astrophysics Data System (ADS)

The main objective of this study was to establish statistical relationship between Schmidt hammer rebound numbers with impact strength index (ISI), slake durability index (SDI) and P-wave velocity. These are important properties to characterize a rock mass and are being widely used in geological and geotechnical engineering. Due to its importance, Schmidt hammer rebound number is considered as one of the most important property for the determination of other properties, like ISI, SDI and P-wave velocity. Determination of these properties in the laboratory is time consuming and tedious as well as requiring expertise, whereas Schmidt hammer rebound number can be easily obtained on site which in addition is non-destructive. So, in this study, an attempt has been made to determine these index properties in the laboratory and each index property was correlated with Schmidt hammer rebound values. Empirical equations have been developed to predict ISI, SDI and P-wave velocity using rebound values. It was found that Schmidt hammer rebound number shows linear relation with ISI and SDI, whereas exponential relation with P-wave velocity. To check the sensitivity of empirical relations, Student's t test was done to verify the correlation between rebound values and other rock index properties.

Sharma, P. K.; Khandelwal, Manoj; Singh, T. N.

2011-01-01

285

Derivation of site-specific relationships between hydraulic parameters and p-wave velocities based on hydraulic and seismic tomography  

SciTech Connect

In this study, hydraulic and seismic tomographic measurements were used to derive a site-specific relationship between the geophysical parameter p-wave velocity and the hydraulic parameters, diffusivity and specific storage. Our field study includes diffusivity tomograms derived from hydraulic travel time tomography, specific storage tomograms, derived from hydraulic attenuation tomography, and p-wave velocity tomograms, derived from seismic tomography. The tomographic inversion was performed in all three cases with the SIRT (Simultaneous Iterative Reconstruction Technique) algorithm, using a ray tracing technique with curved trajectories. The experimental set-up was designed such that the p-wave velocity tomogram overlaps the hydraulic tomograms by half. The experiments were performed at a wellcharacterized sand and gravel aquifer, located in the Leine River valley near Göttingen, Germany. Access to the shallow subsurface was provided by direct-push technology. The high spatial resolution of hydraulic and seismic tomography was exploited to derive representative site-specific relationships between the hydraulic and geophysical parameters, based on the area where geophysical and hydraulic tests were performed. The transformation of the p-wave velocities into hydraulic properties was undertaken using a k-means cluster analysis. Results demonstrate that the combination of hydraulic and geophysical tomographic data is a promising approach to improve hydrogeophysical site characterization.

Brauchler, R.; Doetsch, J.; Dietrich, P.; Sauter, M.

2012-01-10

286

High resolution 3D P wave velocity structure beneath Tenerife Island (Canary Islands, Spain) based on tomographic inversion of active-source data  

NASA Astrophysics Data System (ADS)

We present a high resolution 3 dimensional (3D) P wave velocity model for Tenerife Island, Canaries, covering the top of Teide volcano (3,718 m a.s.l.) down to around 8 km below sea level (b.s.l). The tomographic inversion is based on a large data set of travel times obtained from a 3D active seismic experiment using offshore shots (air guns) recorded at more than 100 onshore seismic stations. The obtained seismic velocity structure is strongly heterogeneous with significant (up to 40%) lateral variations. The main volcanic structure of the Las Cañadas-Teide-Pico Viejo Complex (CTPVC) is characterized by a high P wave velocity body, similar to many other stratovolcanoes. The presence of different high P wave velocity regions inside the CTPVC may be related to the geological and volcanological evolution of the system. The presence of high P wave velocities at the center of the island is interpreted as evidence for a single central volcanic source for the formation of Tenerife. Furthermore, reduced P wave velocities are found in a small confined region in CTPVC and are more likely related to hydrothermal alteration, as indicated by the existence of fumaroles, than to the presence of a magma chamber beneath the system. In the external regions, surrounding CTPVC a few lower P wave velocity regions can be interpreted as fractured zones, hydrothermal alterations, porous materials and thick volcaniclastic deposits.

GarcíA-Yeguas, Araceli; Koulakov, Ivan; IbáñEz, Jesús M.; Rietbrock, A.

2012-09-01

287

Lung function tests and a `vertical' P wave axis in the electrocardiogram  

Microsoft Academic Search

Chapman, T. T. (1974).Thorax, 29, 106-109. Lung function tests and a `vertical' P wave axis in the electrocardiogram. The relationship between a vertical P wave axis and impaired lung function was studied in 1,144 patients with chronic non-specific lung disease. There was a significant relationship between a vertical P wave axis and reduction in forced expiratory volume (FEV1), FEV1 as

T. T. Chapman

1974-01-01

288

Stabilization of the p-Wave Superfluid State in an Optical Lattice  

Microsoft Academic Search

It is hard to stabilize the p-wave superfluid state of cold atomic gas in free space due to inelastic collisional losses. We consider the p-wave Feshbach resonance in an optical lattice, and show that it is possible to have a stable p-wave superfluid state where the multiatom collisional loss is suppressed through the quantum Zeno effect. We derive the effective

Y.-J. Han; Y.-H. Chan; W. Yi; A. J. Daley; S. Diehl; P. Zoller; L.-M. Duan

2009-01-01

289

Stabilization of the p-wave superfluid state in an optical lattice  

Microsoft Academic Search

It is hard to stabilize the p-wave superfluid state of cold atomic gas in free space due to inelastic collisional losses. We consider the p-wave Feshbach resonance in an optical lattice, and show that it is possible to have a stable p-wave superfluid state where the multi-atom collisional loss is suppressed through the quantum Zeno effect. We derive the effective

Yang-Hao Chan; Yong-Jian Han; Wei Yi; Andrew Daley; Sebastian Diehl; Peter Zoller; Luming Duan

2010-01-01

290

Effects of autonomic stimulation and blockade on signal-averaged P wave duration  

Microsoft Academic Search

Objectives. This study sought to evaluate the effects of autonomic stimulation and blockade on the signal-averaged P wave duration.Background. Signal-averaged P wave duration has been shown to have prognostic implications for patients prone to develop atrial fibrillation, but autonomic influences on the signal-averaged P wave duration have not been studied.Methods. In 14 healthy volunteers (8 men, 6 women; mean [±SD

Asim N. Cheema; Mirza W. Ahmed; Alan H. Kadish; Jeffrey J. Goldberger

1995-01-01

291

Seismic Tomography of the Sacramento -- San Joaquin River Delta: Joint P-wave/Gravity and Ambient Noise Methods  

NASA Astrophysics Data System (ADS)

The Sacramento -- San Joaquin River Delta (SSJRD) is an area that has been identified as having high seismic hazard but has resolution gaps in the seismic velocity models of the area due to a scarcity of local seismic stations and earthquakes. I present new three-dimensional (3D) P-wave velocity (Vp) and S-wave velocity (Vs) models for the SSJRD which fill in the sampling gaps of previous studies. I have created a new 3D seismic velocity model for the SSJRD, addressing an identified need for higher resolution velocity models in the region, using a new joint gravity/body-wave tomography algorithm. I am able to fit gravity and arrival-time residuals jointly using an empirical density-velocity relationship to take advantage of existing gravity data in the region to help fill in the resolution gaps of previous velocity models in the area. I find that the method enhances the ability to resolve the relief of basin structure relative to seismic-only tomography at this location. I find the depth to the basement to be the greatest in the northwest portion of the SSJRD and that there is a plateau in the basement structure beneath the southeast portion of the SSJRD. From my findings I infer that the SSJRD may be prone to focusing effects and basin amplification of ground motion. A 3D, Vs model for the SSJRD and surrounding area was created using ambient noise tomography. The empirical Green's functions are in good agreement with published cross-correlations and match earthquake waveforms sharing similar paths. The group velocity and shear velocity maps are in good agreement with published regional scale models. The new model maps velocity values on a local scale and successfully recovers the basin structure beneath the Delta. From this Vs model I find the maximum depth of the basin to reach approximately 15 km with the Great Valley Ophiolite body rising to a depth of 10 km east of the SSJRD. We consider our basement-depth estimates from the Vp model to be more robust than from the Vs model.

Teel, Alexander C.

292

Crustal P-Wave Speed Structure Under Mount St. Helens From Local Earthquake Tomography  

NASA Astrophysics Data System (ADS)

We used local earthquake data to model the P-wave speed structure of Mount St. Helens with the aim of improving our understanding of the active magmatic system. Our study used new data recorded by a dense array of 19 broadband seismographs that were deployed during the current eruption together with permanent network data recorded since the May 18, 1980 eruption. Most earthquakes around Mount St. Helens during the last 25 years were clustered in a narrow vertical column beneath the volcano from the surface to a depth of about 10 km. Earthquakes also occurred in a well-defined zone extending to the NNW from the volcano known as the St. Helens Seismic Zone (SHZ). During the current eruption, earthquakes have been confined to within 3 km of the surface beneath the crater floor. These earthquakes apparently radiate little shear-wave energy and the shear arrivals are usually contaminated by surface waves. Thus, we focused on developing an improved P- wave speed model. We used two data sources: (1) the short-period, vertical-component Pacific Northwest Seismograph Network and (2) new data recorded on a temporary array between June 2005 and February 2006. We first solved for a minimum one-dimensional model, incorporating the Moho depth found during an earlier wide-aperture refraction study. The three-dimensional model was solved simultaneously with hypocenter locations using the computer code SIMULPS14, extended for full three-dimensional ray shooting. We modified the code to force raypaths to remain below the ground surface. We began with large grid spacing and progressed to smaller grid spacing where the earthquakes and stations were denser. In this way we achieve a 40 km by 40 km regional model as well as a 10 km by 10 km fine-scale model directly beneath Mount St. Helens. The large-scale model is consistent with mapped geology and other geophysical data in the vicinity of Mount St. Helens. For example, there is a zone of relatively low velocities (-2% to -5% lower than background model) from 3 to at least 10 km depth extending NNW from the volcano parallel to the SHZ. The low-wave- speed zone coincides with a linear magnetic low, the western edge of a magnetotelluric conductive anomaly, and a localized gravity low. The coincidence of the volcano and these anomalies indicates this preexisting zone of weakness may control the location of Mount St. Helens, as has been suggested by previous investigators. Prominent high-wave-speed anomalies (+3% to +6% relative to background) on either side of this zone are due to plutons, which are also imaged with other geophysical data. Fine-scale modeling of the upper crust directly beneath Mount St. Helens reveals subtle structures not seen in the larger-scale model. The key structure is a cylindrical volume with speeds almost 10% slower than the background model extending from 6 to at least 10 km depth. The vertical, cylindrical volume of earthquakes, which reaches from the surface to more than 10 km depth, splits around this low-wave-speed volume creating an aseismic zone coincident with the low P-wave speeds. We interpret this volume as a melt-rich reservoir surrounded by hot rock.

Waite, G. P.; Moran, S. C.

2006-12-01

293

P-wave [cs][cs] tetraquark state: Y(4260) or Y(4660)?  

SciTech Connect

The mass of a P-wave cs-scalar-diquark cs-scalar-antidiquark state is computed in the framework of QCD sum rules. The result 4.69{+-}0.36 GeV is in good agreement with the experimental value of Y(4660) but higher than Y(4260)'s, which supports the P-wave [cs][cs] configuration for Y(4660) while disfavors the interpretation of Y(4260) as the P-wave [cs][cs] state. In the same picture, the mass of P-wave [bs][bs] is predicted to be 11.19{+-}0.49 GeV.

Zhang Jianrong; Huang Mingqiu [Department of Physics, National University of Defense Technology, Hunan 410073 (China)

2011-02-01

294

Stabilization of the p-Wave Superfluid State in an Optical Lattice  

SciTech Connect

It is hard to stabilize the p-wave superfluid state of cold atomic gas in free space due to inelastic collisional losses. We consider the p-wave Feshbach resonance in an optical lattice, and show that it is possible to have a stable p-wave superfluid state where the multiatom collisional loss is suppressed through the quantum Zeno effect. We derive the effective Hamiltonian for this system, and calculate its phase diagram in a one-dimensional optical lattice. The results show rich phase transitions between the p-wave superfluid state and different types of insulator states induced either by interaction or by dissipation.

Han, Y.-J.; Chan, Y.-H.; Duan, L.-M. [Department of Physics and MCTP, University of Michigan, Ann Arbor, Michigan 48109 (United States); Yi, W.; Daley, A. J.; Diehl, S.; Zoller, P. [Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, Austria and Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck (Austria)

2009-08-14

295

Radio-frequency spectroscopy of {sup 6}Li p-wave molecules: Towards photoemission spectroscopy of a p-wave superfluid  

SciTech Connect

We study rf spectroscopy of a lithium gas with the goal to explore the possibilities for photoemission spectroscopy of a strongly interacting p-wave Fermi gas. Radio-frequency spectra of quasibound p-wave molecules and of free atoms in the vicinity of the p-wave Feshbach resonance located at 159.15 G are presented. The spectra are free of detrimental final-state effects. The observed relative magnetic-field shifts of the molecular and atomic resonances confirm earlier measurements realized with direct rf association. Furthermore, evidence of molecule production by adiabatically ramping the magnetic field is observed. Finally, we propose the use of a one-dimensional optical lattice to study anisotropic superfluid gaps as most direct proof of p-wave superfluidity.

Maier, R. A. W.; Marzok, C.; Zimmermann, C.; Courteille, Ph. W. [Physikalisches Institut, Eberhard Karls Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany); Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Caixa Postal 369, Sao Carlos-SP 13560-970 (Brazil)

2010-06-15

296

A statistical study of the performance of the Hakamada-Akasofu-Fry version 2 numerical model in predicting solar shock arrival times at Earth during different phases of solar cycle 23  

NASA Astrophysics Data System (ADS)

The performance of the Hakamada Akasofu-Fry, version 2 (HAFv.2) numerical model, which provides predictions of solar shock arrival times at Earth, was subjected to a statistical study to investigate those solar/interplanetary circumstances under which the model performed well/poorly during key phases (rise/maximum/decay) of solar cycle 23. In addition to analyzing elements of the overall data set (584 selected events) associated with particular cycle phases, subsets were formed such that those events making up a particular sub-set showed common characteristics. The statistical significance of the results obtained using the various sets/subsets was generally very low and these results were not significant as compared with the hit by chance rate (50%). This implies a low level of confidence in the predictions of the model with no compelling result encouraging its use. However, the data suggested that the success rates of HAFv.2 were higher when the background solar wind speed at the time of shock initiation was relatively fast. Thus, in scenarios where the background solar wind speed is elevated and the calculated success rate significantly exceeds the rate by chance, the forecasts could provide potential value to the customer. With the composite statistics available for solar cycle 23, the calculated success rate at high solar wind speed, although clearly above 50%, was indicative rather than conclusive. The RMS error estimated for shock arrival times for every cycle phase and for the composite sample was in each case significantly better than would be expected for a random data set. Also, the parameter "Probability of Detection, yes" (PODy) which presents the Proportion of Yes observations that were correctly forecast (i.e. the ratio between the shocks correctly predicted and all the shocks observed), yielded values for the rise/maximum/decay phases of the cycle and using the composite sample of 0.85, 0.64, 0.79 and 0.77, respectively. The statistical results obtained through detailed analysis of the available data provided insights into how changing circumstances on the Sun and in interplanetary space can affect the performance of the model. Since shock arrival predictions are widely utilized in making commercially significant decisions re. protecting space assets, the present detailed archival studies can be useful in future operational decision making during solar cycle 24. It would be of added value in this context to use Briggs-Rupert methodology to estimate the cost to an operator of acting on an incorrect forecast.

McKenna-Lawlor, S. M. P.; Fry, C. D.; Dryer, M.; Heynderickx, D.; Kecskemety, K.; Kudela, K.; Balaz, J.

2012-02-01

297

Monitoring of the ultrasonic P-wave velocity in early-age concrete with embedded piezoelectric transducers  

NASA Astrophysics Data System (ADS)

This note deals with the use of embedded piezoelectric transducers to monitor the ultrasonic P-wave velocity evolution during the setting and hardening phases of concrete subsequent to casting time. The main advantage of the technique is the possibility of overcoming the limitations of traditional methods which prevent the application of specific mechanical boundary conditions during the measurement. The embedded transducers are based on the ‘smart aggregates’ concept previously developed at the University of Houston, Texas. Two piezoelectric transducers are embedded in a prismatic mold and the evolution of the P-wave velocity is recorded for the first 24 h in concrete after the casting time. The results are very promising and show a good agreement with classical ultrasonic tests using external transducers.

Dumoulin, Cédric; Karaiskos, Grigoris; Carette, Jérôme; Staquet, Stéphanie; Deraemaeker, Arnaud

2012-04-01

298

The attenuation of P waves propagating in central Arizona, approximately 2400 km from the upper mantle is extremely low in the Cen- Lake Superior. . tral Lowlands and Great Plains. During the The northeast part of the recording line Lake Superior seismic experiment in the 1963 traverses a region that has been relatively International Upper Mantle Experiment, un- stable since Cambrian time, aboutBy (King, usually high amplitudes were observed; seismic 1933). From the Canadian Shield, one of the  

Microsoft Academic Search

Seismic-refraction measurements indicate that P waves travel with an apparent velocity of about 8.5 km\\/sec at depths greater than about 100 km, at least from central Nebraska to south-central Arizona. The attenuation of P waves propagating in the upper mantle is ex- tremely low in the Central Lowlands and the Great Plains. The data do not indicate the existence of

J. C. ROLLER

1966-01-01

299

Fluid pressure arrival time tomography: Estimation and assessment in the presence of inequality constraints, with an application to a producing gas field at Krechba, Algeria  

SciTech Connect

Deformation in the overburden proves useful in deducing spatial and temporal changes in the volume of a producing reservoir. Based upon these changes we estimate diffusive travel times associated with the transient flow due to production, and then, as the solution of a linear inverse problem, the effective permeability of the reservoir. An advantage an approach based upon travel times, as opposed to one based upon the amplitude of surface deformation, is that it is much less sensitive to the exact geomechanical properties of the reservoir and overburden. Inequalities constrain the inversion, under the assumption that the fluid production only results in pore volume decreases within the reservoir. We apply the formulation to satellite-based estimates of deformation in the material overlying a thin gas production zone at the Krechba field in Algeria. The peak displacement after three years of gas production is approximately 0.5 cm, overlying the eastern margin of the anticlinal structure defining the gas field. Using data from 15 irregularly-spaced images of range change, we calculate the diffusive travel times associated with the startup of a gas production well. The inequality constraints are incorporated into the estimates of model parameter resolution and covariance, improving the resolution by roughly 30 to 40%.

Rucci, A.; Vasco, D.W.; Novali, F.

2010-04-01

300

Fabrics of the lithospheric mantle beneath the Northern Apennines - first results on P-wave anisotropy from RETREAT experiment (Italy)  

Microsoft Academic Search

We analyze travel time deviations of teleseismic P waves, particularly their variations with back-azimuth and incidence angle recorded during the RETREAT (REtreating-TRench, Extension and Accretion Tectonics) passive seismic experiment (2003-2006, Margheriti et al., Annals of Geophys. 2006) as a part of the multidisciplinary international project aiming at developing a self-consistent dynamic model of syn-convergent extension in the Northern Apennines. Stations

Helena Munzarova; Jaroslava Plomerova; Ludek Vecsey

2010-01-01

301

An efficient hybrid pseudospectral/finite-difference scheme for solving the TTI pure P-wave equation  

NASA Astrophysics Data System (ADS)

The pure P-wave equation for modelling and migration in tilted transversely isotropic (TTI) media has attracted more and more attention in imaging seismic data with anisotropy. The desirable feature is that it is absolutely free of shear-wave artefacts and the consequent alleviation of numerical instabilities generally suffered by some systems of coupled equations. However, due to several forward-backward Fourier transforms in wavefield updating at each time step, the computational cost is significant, and thereby hampers its prevalence. We propose to use a hybrid pseudospectral (PS) and finite-difference (FD) scheme to solve the pure P-wave equation. In the hybrid solution, most of the cost-consuming wavenumber terms in the equation are replaced by inexpensive FD operators, which in turn accelerates the computation and reduces the computational cost. To demonstrate the benefit in cost saving of the new scheme, 2D and 3D reverse-time migration (RTM) examples using the hybrid solution to the pure P-wave equation are carried out, and respective runtimes are listed and compared. Numerical results show that the hybrid strategy demands less computation time and is faster than using the PS method alone. Furthermore, this new TTI RTM algorithm with the hybrid method is computationally less expensive than that with the FD solution to conventional TTI coupled equations.

Zhan, Ge; Pestana, Reynam C.; Stoffa, Paul L.

2013-04-01

302

Earthquake Location and Upper Mantle Structure From P Wave Polarization in French Polynesia and Australia: Preliminary Results  

NASA Astrophysics Data System (ADS)

We report measurements of long-period P wave polarization in French Polynesia and in Australia. The 3D character of particle motion of P waves provides complementary and independent constraints on the upper mantle structure beneath a given station to that from shear-wave splitting. Analysis of the deviation of horizontal polarization and the vertical polarization angle as a function of event backazimuth are used to obtain information about: i) sensor misorientation, ii) seismic anisotropy, and iii) velocity heterogeneities. The measurements are realized with a method proposed by Schulte-Pelkum and others. Despite the availability of 15 years of data, the two permanent stations on Tahiti do not show any evidence of shear-wave splitting (Fontaine and others) whereas P wave polarization observations do. Using the latter technique the fast axis azimuth is oriented N118°E close to the direction of the present Pacific plate motion. At Rikitea, in the Gambier Islands, the fast axis azimuth is N109°E. This suggests that SKS waves sample either a complex upper mantle structure induced by the recent magmatism on Tahiti or a vertical mantle upwelling, while P waves identify an azimuthal anisotropy in the asthenosphere with a lateral offset, since the incidence angles are much larger than the SKS waves. Australia is ideally located for P wave polarization analysis due to the favourable distribution of seismicity around this continent. Moreover, some relatively dense networks of broadband seismometers were installed throughout the Australian region during the last decade that may give the possibility to discriminate between velocity perturbations and seismic anisotropy beneath some stations. In Tahiti, the tsunami warning centre uses only one seismic station in real-time to determine the earthquake location. The horizontal polarization of P waves deviates up to 10° depending on the backazimuth of the event. The introduction in the automatic earthquake location of a term for correction of the deviation of the direction of particle motion would improve the precision of the location and thus the accuracy of the tsunami warning system.

Fontaine, F. R.; Barruol, G.; Kennett, B. L.; Bokelmann, G. H.; Reymond, D.

2006-12-01

303

P wave dispersion is prolonged in patients with Wilson’s disease  

Microsoft Academic Search

AIM: To investigate the P wave dispersion as a non- invasive marker of intra-atrial conduction disturbances in patients with Wilson's disease. METHODS: We compared Wilson's disease patients (n = 18) with age matched healthy subjects (n = 15) as controls. The diagnosis was based on clinical symptoms, laboratory tests (ceruloplasmin, urinary and hepatic copper concentrations). P wave dispersion, a measurement

Nurcan Arat; Sabite Kacar; Zehra Golbasi; Meral Akdogan; Yeliz Sokmen; Sedef Kuran; Ramazan Idilman; Türkiye Yüksek

2008-01-01

304

Anomalous quantum mass flow of atoms in p-wave resonance  

Microsoft Academic Search

I analyze an atomic Fermi gas with a planar p-wave interaction, motivated by the experimentally observed anisotropy in p-wave Feshbach resonances. An axial superfluid state is verified. A domain wall object is discovered to be a new topological defect of this superfluid and an explicit solution has been found. Gapless quasiparticles appear as bound states on the wall, dispersing in

W. Vincent

2005-01-01

305

Upper mantle Q and thermal structure beneath Tanzania, East Africa from teleseismic P wave spectra  

Microsoft Academic Search

We measure P wave spectral amplitude ratios from deep-focus earthquakes recorded at broadband seismic stations of the Tanzania network to estimate regional variation of sublithospheric mantle attenuation beneath the Tanzania craton and the eastern branch of the East African Rift. One-dimensional profiles of QP adequately explain the systematic variation of P wave attenuation in the sublithospheric upper mantle: QP ?

Anupama Venkataraman; Andrew A. Nyblade; Jeroen Ritsema

2004-01-01

306

Upper mantle Q and thermal structure beneath Tanzania, East Africa from teleseismic P wave spectra  

Microsoft Academic Search

We measure P wave spectral amplitude ratios from deep-focus earthquakes recorded at broadband seismic stations of the Tanzania network to estimate regional variation of sublithospheric mantle attenuation beneath the Tanzania craton and the eastern branch of the East African Rift. One-dimensional profiles of QP adequately explain the systematic variation of P wave attenuation in the sublithospheric upper mantle: QP ~

Anupama Venkataraman; Andrew A. Nyblade; Jeroen Ritsema

2004-01-01

307

P Wave Indices, Obesity, and the Metabolic Syndrome: The Atherosclerosis Risk in Communities Study  

Microsoft Academic Search

Atrial fibrillation and obesity are increasing in prevalence and are interrelated epidemics. There has been limited assessment of how obesity and the metabolic syndrome impact P wave indices, established electrocardiographic predictors of atrial fibrillation. We conducted a cross-sectional analysis to determine the association of obesity and the components of the metabolic syndrome with P wave indices in the population-based Atherosclerosis

Jared W. Magnani; Faye L. Lopez; Elsayed Z. Soliman; Richard F. Maclehose; Richard S. Crow; Alvaro Alonso

2012-01-01

308

X(3915) and X(4350) as New Members in the P-Wave Charmonium Family  

SciTech Connect

The analysis of the mass spectrum and the calculation of the strong decay of P-wave charmonium states strongly purport to explain the newly observed X(3915) and X(4350) as new members in the P-wave charmonium family, i.e., chi{sub c0}{sup '} for X(3915) and chi{sub c2}{sup ''} for X(4350). Under the P-wave charmonium assignment to X(3915) and X(4350), the J{sup PC} quantum numbers of X(3915) and X(4350) must be 0{sup ++} and 2{sup ++} respectively, which provide important criteria to test the P-wave charmonium explanation for X(3915) and X(4350) proposed by this Letter. The decay behavior of the remaining two P-wave charmonium states with the second radial excitation is predicted, and an experimental search for them is suggested.

Liu Xiang; Sun Zhifeng [School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Research Center for Hadron and CSR Physics, Lanzhou University and Institute of Modern Physics of CAS, Lanzhou 730000 (China); Luo Zhigang [School of Physics, Peking University, Beijing 100871 (China)

2010-03-26

309

Chronic carbon monoxide exposure increases electrocardiographic P-wave and QT dispersion.  

PubMed

We investigated the association between chronic carbon monoxide (CO) exposure and electrocardiographic maximum/minimum P-wave duration (Pmax/Pmin), P-wave dispersion (Pd), maximum/minimum QT interval (QTmax/QTmin), and QT and corrected QT dispersion (QTd/cQTd), which are known as predictors of atrial fibrillation, ventricular arrhythmias, and sudden death. We obtained electrocardiograms of 48 apparently healthy male indoor barbecue workers (age mean +/- SD; 33.6 +/- 9.4) who were working in various restaurants for at least 3 yr and 51 age-matched healthy men (age mean +/- SD; 35.1 +/- 6.7). Average working time of the indoor barbecue workers in their jobs was 15.6 +/- 7.1 yr. P-wave parameters were analyzable in 39 barbecue workers and 40 control subjects and QT intervals were analyzable in 44 barbecue workers and 47 control subjects. Clinical characteristics of indoor barbecue workers and the control group were comparable in terms of age, sex, body mass index, blood pressure, heart rate, Pmin, and QTmin. However, COHb levels, Pmax, Pd, QTmax, QTd, and cQTd measurements were higher in indoor barbecue workers than in the control group (6.48 +/- 1.43 vs. 2.19 +/- 1.30, p < .001; 106.15 +/- 7.47 vs. 101.50 +/- 6.62, p < .005; 30.51 +/- 7.59 vs. 24.50 +/- 6.77, p < .001; 406.59 +/- 17.64 vs. 390.85 +/- 13.15, P < .001; 48.40 +/- 8.87 vs. 34.89 +/- 5.85, P < .001; 53.64 +/- 9.14 vs. 37.77 +/- 6.71, P < .001, respectively). In Pearson correlation analysis there were significant correlations between COHb level and Pd, QTmax, QTd, and cQTd (r = .315 P < .005; r = .402, P < .001, r = .573, P < .001, r = .615, P < .001, respectively). In conclusion, the present study is the first to assess and find an association between chronic CO exposure and electrocardiographic Pd and QTd/cQTd. PMID:18645728

Sari, Ibrahim; Zengin, Suat; Ozer, Orhan; Davutoglu, Vedat; Yildirim, Cuma; Aksoy, Mehmet

2008-07-01

310

Converted-wave PS arrivals in tilted TI media: Analysis of ray-paths and amplitudes  

NASA Astrophysics Data System (ADS)

Converted-waves, i.e., downgoing P-waves that convert upon reflection to S-waves, excited by a compressional source and recorded by horizontal geophones provide a measure of media properties that relate to rock type and fluid saturation. Other uses that have arisen from measuring, analyzing and interpreting PS-waves, include improved structural imaging in formations with occurrence of gas and analysis of seismic anisotropy for estimating fracture density and orientation. Addressing anisotropy in the seismic processing flow is paramount due to the strong influence of this phenomenon in the wave path. Furthermore, analyses of both traveltimes and amplitudes that include anisotropic parameters provide a better picture of the subsurface. Anisotropy types used to describe common geologic scenarios include vertical and horizontal transversely isotropy (VTI and HTI, respectively). Presence of horizontal shale formations is a common cause of the VTI type, while a single vertical fracture system is a typical example of the HTI. Another degree of complexity is to consider a tilted symmetry axis corresponding to a formation with thin layers that are dipping, or the presence of non-vertical fractures. These media, described as tilted TI, have important observable effects on the converted-wave arrivals: i) asymmetry of the wave-path; ii) shear-wave splitting; and iii) non-zero amplitudes at zero offset. Based on numerical modeling, effects of the tilt in the simmetry axis on arrival times, travel path, and amplitudes of the converted waves are analyzed. Ultimate objectives of the work include quantifying these effects on converted-wave data processing, and investigating the reflected wavefield signature for retrieving tilt angle in situations where the stress field induces thin layering or fractures with a tilted symmetry axis.

Ramos-Martinez, J.; Calderon-Macias, C.

2005-05-01

311

Retrospective Tests of an Earthquake Forecasting Model in Japan Based on P-Wave Velocity Anomalies  

NASA Astrophysics Data System (ADS)

We constructed an earthquake forecasting model of long-term probability based on P-wave velocity perturbations from a standard layered model for Japan. We considered the perturbations as a predictive parameter that may be useful for assessing regional seismogenesis. We evaluated the distance between two distributions of parameters, the background distribution (parameters over the entire space domain), and the conditional distribution (parameters at earthquake epicenters) then used this distance to measure the reliability of the predictive parameters. We selected 198 epicenters of earthquakes with magnitudes of 5.0 and larger for 1961 to 2008 to estimate the conditional distribution. More than 3000 points were selected at every point on a 0.1° x 0.1° grid for the background distribution. P-wave variations were considered at four different depths (10, 15, 20, and 25km at each point) for both distributions. Both distributions were approximated by normal distributions with four variables. The distance between two distributions could be analytically estimated to be 0.3, which suggests that an average probability of the proposed model (VP4L model) over the 198 earthquakes is 1.35 times higher than that of a stationary uniform Poisson (SUP) model. To confirm this assessment, we conducted N-, L- and R-tests of the VP4L model, where the SUP model was adopted for comparisons. The retrospective test demonstrated that the observed scores of N- and L-tests are consistent with those expected from the VP4L model. However, the average probability gain calculated from the R-score is about 1.19, which is less than the assessed value. We will start the prospective test to see how the model would perform in a truly prospective test.

Imoto, M.; Matsubara, M.; Yamamoto, N.

2010-12-01

312

Seismic characterization of fracture orientation in the Austin Chalk using azimuthal P-wave AVO  

NASA Astrophysics Data System (ADS)

The Austin Chalk is a naturally fractured reservoir. Horizontal drilling, to intersect more fractures, is the most efficient method to develop this reservoir. Information about the predominant fracture orientation in the subsurface is essential before horizontal drilling. This information may be provided by cores, well logs, outcrop, or seismic data. In this study, I apply the azimuthal P-wave AVO method suggested by Ruger and Tsvankin (1997) on 2-D P-wave seismic data in Gonzales County, Texas, in order to determine the fracture azimuth in the Austin Chalk. The data also include oil production from horizontal wells and various types of well logs from vertical wells in the study area. The raw seismic data was imaged through a processing sequence that preserved the relative changes of amplitudes with offset. The stacked sections of some seismic lines showed that the top of the Austin Chalk reflector is laterally inconsistent. This is interpreted as an indication of fractured zones in the subsurface. This interpretation was strengthened by well logs that indicated fracturing in nearby wells. The AVO gradient of every CDP in a seismic line was determined. The median AVO gradient of all the CDPs in a seismic line was chosen to represent the whole line. The median AVO gradients of the lines and their corresponding line azimuths were used repeatedly to solve the azimuthal AVO equation, of Ruger and Tsvankin (1997), for the fracture azimuth using a combination of three different lines every time. The resultant fracture-azimuth solutions clustered about two, nearly perpendicular, azimuths: N58E and S31E. To resolve the inherently ambiguous solutions, the results from the production and well log data were used. Since the production and well log data indicated the presence of NE-trending fractures, I chose the N58E direction as the fracture azimuth. This result agreed with the results of other studies in surrounding areas, using different methods, about the fracture azimuth in the Austin Chalk.

Al-Shuhail, Abdullatif Adulrahman

313

Effect of crack aperture on P-wave velocity and dispersion  

NASA Astrophysics Data System (ADS)

We experimentally studied the effect of crack aperture on P-wave velocity, amplitude, anisotropy and dispersion. Experimental models were constructed based on Hudson's theory. Six crack models were embedded with equal-radius penny-shaped crack inclusions in each layer. The P-wave velocity and amplitude were measured parallel and perpendicular to the layers of cracks at frequencies of 0.1 MHz to 1 MHz. The experiments show that as the crack aperture increases from 0.1 mm to 0.34 mm, the amplitude of the P-waves parallel to the crack layers decreases linearly with increasing frequency and the P-wave velocity dispersion varies from 1.5% to 2.1%, whereas the amplitude of the P-wave perpendicular to the crack layers decreases quadratically with increasing frequency and the velocity dispersion varies from 1.9% to 4.7%. The variation in the velocity dispersion parallel and perpendicular to the cracks intensifies the anisotropy dispersion of the P-waves in the crack models (6.7% to 83%). The P-wave dispersion strongly depends on the scattering characteristics of the crack apertures.

Wei, Jian-Xin; Di, Bang-Rang; Ding, Pin-Bo

2013-06-01

314

Systematic determination of earthquake rupture directivity and fault planes from analysis of long-period P-wave spectra  

NASA Astrophysics Data System (ADS)

If an earthquake has a primarily unilateral rupture, the pulse width observed on seismograms will vary depending on the angle between the rupture direction and the takeoff vector to the station. We have developed a method to estimate the amount of pulse broadening from the spectrum and apply it to a long-period database of large, globally distributed earthquakes that occurred between 1988 and 2000. We select vertical-component P-waves at epicentral distances of 20°-98°. We compute the spectrum from a 64-s-long window around each P-wave arrival. Each spectrum is the product of source, receiver and propagation response functions as well as local source- and receiver-side effects. Since there are multiple receivers for each source and multiple sources for each receiver, we can estimate and remove the source- and receiver-side terms by stacking the appropriate P log spectra. For earthquakes deeper than ~200 km, source effects dominate the residual spectra. We use our pulse-width estimates to determine the best rupture direction and to identify which nodal plane of the Harvard centroid moment tensor (CMT) solution is most consistent with this rupture direction for 66 events. In about 30 per cent of the cases, one of the two nodal planes produces a much better fit to the data and can be identified as the true fault plane. When results from previous studies are available for comparison, our rupture directions are usually consistent with their results, particularly for earthquakes with simple rupture histories.

Warren, Linda M.; Shearer, Peter M.

2006-01-01

315

Evidence for back scattering of near-podal seismic P'P' waves from the 150-220 km zone in Earth's upper mantle  

SciTech Connect

The deepest and most inaccessible parts of Earth's interior--the core and core-mantle boundary regions can be studied from compressional waves that turn in the core and are routinely observed following large earthquakes at epicentral distances between 145{sup o} and 180{sup o} (also called P', PKIKP or PKP waves). P'P' (PKPPKP) are P' waves that travel from a hypocenter through the Earth's core, reflect from the free surface and travel back through the core to a recording station on the surface. P'P' waves are sometimes accompanied by precursors, which were reported first in the 1960s as small-amplitude arrivals on seismograms at epicentral distances of about 50{sup o}-70{sup o}. Most prominent of these observed precursors were explained by P'P' waves generated by earthquakes or explosions that did not reach the Earth's surface but were reflected from the underside of first order velocity discontinuities at 410 and 660 km in the upper mantle mantle. Here we report the discovery of hitherto unobserved near-podal P'P' waves (at epicentral distance less than 10{sup o}) and very prominent precursors preceding the main energy by as much as 55 seconds. We interpret these precursors as a back scattered energy from undocumented structure in the upper mantle, in a zone between 150 and 220 km depth beneath Earth's surface. From these observations, we identify a frequency dependence of Q (attenuation quality factor) in the lithosphere that can be modeled by a flat relaxation spectrum below about 0.05-0.1 Hz and increasing with as the first power of frequency above this value, confirming pioneering work by B. Gutenberg.

Tkalcic, H; Flanagan, M P; Cormier, V F

2005-07-15

316

Drought in Africa caused delayed arrival of European songbirds.  

PubMed

Despite an overall advancement in breeding area arrival, one of the latest spring arrivals in northwest Europe since 1950 of several trans-Saharan songbird species occurred in 2011. Year-round tracking of red-backed shrikes and thrush nightingales revealed that the cause of the delay was a prolongation of stopover time during spring migration at the Horn of Africa, which was affected by extreme drought. Our results help to establish a direct link at the individual level between changes in local climate during migration and arrival and breeding condition in Europe thousands of kilometers further north. PMID:23224549

Tøttrup, A P; Klaassen, R H G; Kristensen, M W; Strandberg, R; Vardanis, Y; Lindström, Å; Rahbek, C; Alerstam, T; Thorup, K

2012-12-01

317

Application of first-arrival tomography to characterize a quick clay landslide site in Southwest Sweden  

NASA Astrophysics Data System (ADS)

First-arrival traveltime tomography was applied to high-resolution seismic data acquired over a known quick-clay landslide scar near the Göta River in southwest Sweden in order to reveal the geometry and physical properties of clay-related normally consolidated sediments. Investigated area proved to be a challenging environment for tomographic imaging because of large P-wave velocity variations, ranging from 500 to 6000 m/s, and relatively steeply-dipping bedrock. Despite these challenges, P-wave velocity models were obtained down to ca. 150 m for two key 2D seismic profiles (each about 500-m long) intersecting over the landslide scar. The models portrait the sandwich-like structure of marine clays and coarse-grained consolidated sediments, but the estimated resolution (20 m) is too small to distinguish thin layers within this structure. Modelled velocity structures match well the results of reflection seismic processing and resistivity tomography available along the same profiles.

Adamczyk, Anna; Malinowski, Micha?; Malehmir, Alireza

2013-10-01

318

The effects of spall on teleseismic P-waves: An investigation with theoretical seismograms  

NASA Astrophysics Data System (ADS)

The effects of spall on teleseismic P-wave seismograms are investigated using theoretical seismograms calculated with an extended reflectivity method. The equivalent point-source used to model the spall process has been derived following the work of Day et al. [1983] with the modification of a spall rise-time which is introduced to account for the time necessary to bring the total spalled mass into ballistic flight. The effect of spall is studied by the superposition of synthetic seismograms for a pure explosion source with synthetic seismograms for a pure spall source. The source signal for the pure explosion is the von Seggern-Blandford reduced displacement potential. The model parameters for explosion and spall sources used are representative for the Pahute Mesa (NTS) nuclear explosion HARZER and have been determined from close-in (distance 2-7 km) and regional seismograms [Johnson, 1988; Patton, 1988]. Additionally, spall model parameters calculated from scaling relations which have been derived independently of the HARZER event are used. The result of this part of the study is that spall can contribute significantly to the waveforms of teleseismic P-waves. This conclusion still holds if certain ranges for the parameters of both the explosion and spall models are introduced. The effect of spall is to increase the peak-to-peak amplitudes and to enhance the higher frequencies compared to the predictions for the explosion without spall. However, the interference pattern in the composite explosion/spall seismograms is generally complicated and depends critically on the kinematic spall characteristics like the spall dwell- and rise-time. For the spall scaling relations considered here Sobel'ls [1978] and Patton's [1989, 1990] relations predict essential contributions of spall to teleseismic P-waveforms; only that of Viecelli [1973] predicts a minor effect on teleseismic P-waveforms. Finally, a comparison of the theoretical seismograms with observations of HARZER at teleseismic distances (SRO stations MAJO and GRFO) is made. From this comparison it is found that an explosion source without spall explains reasonably well both the maximum peak-to-peak amplitudes and the general frequency content of the data if an earth model with a dissipation time t* of 0.75 s is assumed. Therefore it is argued that the spall-model parameters momentum and spall mass used for the HARZER calculations might be up to an order of magnitude too large.

Schlittenhardt, Jörg

319

When Did the First Americans Arrive?  

NSDL National Science Digital Library

Who were the first Americans, when did they arrive, and from where did they come? With limited evidence, scientists have long proposed a hypothesis that linked the migration route and the timing of the migration of these ancient people to the end of the last ice age. This video segment, adapted from a NOVA television broadcast, describes how archaeologists have uncovered new evidence suggesting that the first Americans may have been able to migrate down the coast of North America, rather than waiting for an ice-free corridor to develop, implying that migration could have occurred earlier than previously thought. The segment is five minutes forty seconds in length.

2010-09-15

320

The short-term health of Canada's new immigrant arrivals: evidence from LSIC  

Microsoft Academic Search

Objectives. The objectives of the current paper are to address the timing of declines in health after arrival in the host country, and to document differences in health status by immigrant arrival group (economic immigrants, family reunification, and refugees).Design. Statistics Canada's Longitudinal Survey of Immigrants to Canada captures health and other attributes of a cohort of immigrant arrivals to Canada

Bruce Newbold

2009-01-01

321

The Multiple Runway Planner (MRP): Modeling and Analysis for Arrival Planning  

Microsoft Academic Search

The multiple runway planner (MRP) is a tool that has been developed at Boeing for system effectiveness analysis of arrival sequencing, scheduling, and runway assignment. Given a set of arrivals, with pre-determined meter fix assignments and estimated times of arrival (ETA), the algorithm determines runway assignments and preferred sequences and schedules at the fixes and at the assigned runways. Separation

Matthew E. Berge; Aslaug Haraldsdottir; J. Scharl

2006-01-01

322

Direction of Arrival Estimation Using the Parameterized Spatial Correlation Matrix  

Microsoft Academic Search

The estimation of the direction-of-arrival (DOA) of one or more acoustic sources is an area that has generated much interest in recent years, with applications like automatic video camera steering and multiparty stereophonic teleconferencing entering the market. DOA estimation algorithms are hindered by the effects of background noise and reverberation. Methods based on the time-differences-of-arrival (TDOA) are commonly used to

Jacek Dmochowski; Jacob Benesty; Sofiène Affes

2007-01-01

323

Spatial variations of P wave attenuation in the mantle beneath North America  

Microsoft Academic Search

We estimate the spatial variation of the seismic parameter t* using teleseismic (epicentral distance = 30°–85°) P wave spectra of about 200 deep (focal depths > 200 km) earthquakes recorded by 378 broadband seismometers in the United States and Canada. Relative P wave spectral ratios up to 1 Hz for about 63,000 station pairs with high signal-to-noise ratio and impulsive

Yong Keun Hwang; Jeroen Ritsema; Saskia Goes

2009-01-01

324

Skyrmionic state and stable half-quantum vortices in chiral p-wave superconductors  

NASA Astrophysics Data System (ADS)

Observability of half-quantum vortices and skyrmions in p-wave superconductors is an outstanding open question. Under the most common conditions, fractional flux vortices are not thermodynamically stable in bulk samples. Here we show that in chiral p-wave superconductors, there is a regime where, in contrast, lattices of integer-flux vortices are not thermodynamically stable. Instead, skyrmions made of spatially separated half-quantum vortices are the topological defects produced by an applied external field.

Garaud, Julien; Babaev, Egor

2012-08-01

325

Anomalous quantum mass flow of atoms in p-wave resonance  

Microsoft Academic Search

I analyze an atomic Fermi gas with a planar p-wave interaction, motivated by\\u000athe experimentally observed anisotropy in p-wave Feshbach resonances. An axial\\u000asuperfluid state is verified. A domain wall object is discovered to be a new\\u000atopological defect of this superfluid and an explicit solution has been found.\\u000aGapless quasiparticles appear as bound states on the wall, dispersing in

W. Vincent Liu

2005-01-01

326

P-wave pion absorption on two nucleons and low-energy pion-nucleus scattering  

Microsoft Academic Search

The P-wave pion-nucleus optical potential ~varrho2(R) which derives from P-wave pion absorption on two nucleons is constructed using several piNN absorption models with pion- (and varrho-) rescattering through the 33-resonance. A local-laplacian optical-model study of pi-12C scattering in the energy interval 60 MeV <=Tpi<= 120 MeV including this additional absorptive potential indicates sizeable but parameter-sensitive increases in the reaction cross

R. Rockmore; E. Kanter; P. Goode

1978-01-01

327

P-wave velocity variation in the upper mantle beneath Tibetan Plateau  

NASA Astrophysics Data System (ADS)

We produced a P-wave model of the upper mantle beneath Tibeatan Plateau from a combination of International Seismological Centre (ISC) P and pP data, processed by Engdahl et al. (1998), P data of the Annual Bulletin of Chinese Earthquake (ABCE) [IG-CSB, 1990-1998], and travel times of P phases recorded at temporary arrays around Tibetan Plateau, including arrays operated by (a) MIT and the Chengdu Institute of Geology and Mineral Resources (MIT-CIGMR) - 09/2003-09/2004; (b) Lehigh university and CIGMR - 07/2003-10/2004; (c) the INDEPTH (InterNational DEep Profiling of Tibet and the Himalaya) project - 05/1994-10/1994, 07/1997-06/1999; and (d) various French and Chinese groups - 07/1991-06/1992. Incorporating the travel times of phases recorded at arrays allow us to constrain upper mantle structure with much greater resolution and confidence than before, and the preliminary models reveal intriguing variations in P-wavespeed in the upper mantle beneath Tibetan Plateau. Our images suggest that the Indian lithosphere subducts from the foreland basin and underlies only the southwestern margin of the Tibetan Plateau, implying that much of the Tibetan Plateau is not underlain by Indian but by Asian lithosphere. Some of the seismically slow structures beneath the eastern part of the plateau may connect to structures, and presumably, processes in the upper mantle beneath the South China Sea.

Li, C.; van der Hilst, R.; Chen, Z.; Anne, M.

2005-12-01

328

Deep seafloor arrivals in long range ocean acoustic propagation.  

PubMed

Ocean bottom seismometer observations at 5000?m depth during the long-range ocean acoustic propagation experiment in the North Pacific in 2004 show robust, coherent, late arrivals that are not readily explained by ocean acoustic propagation models. These "deep seafloor" arrivals are the largest amplitude arrivals on the vertical particle velocity channel for ranges from 500 to 3200?km. The travel times for six (of 16 observed) deep seafloor arrivals correspond to the sea surface reflection of an out-of-plane diffraction from a seamount that protrudes to about 4100?m depth and is about 18?km from the receivers. This out-of-plane bottom-diffracted surface-reflected energy is observed on the deep vertical line array about 35?dB below the peak amplitude arrivals and was previously misinterpreted as in-plane bottom-reflected surface-reflected energy. The structure of these arrivals from 500 to 3200?km range is remarkably robust. The bottom-diffracted surface-reflected mechanism provides a means for acoustic signals and noise from distant sources to appear with significant strength on the deep seafloor. PMID:24116525

Stephen, Ralph A; Thompson Bolmer, S; Udovydchenkov, Ilya A; Worcester, Peter F; Dzieciuch, Matthew A; Andrew, Rex K; Mercer, James A; Colosi, John A; Howe, Bruce M

2013-10-01

329

Detecting voids in masonry by cooperatively inverting P-wave and georadar traveltimes  

NASA Astrophysics Data System (ADS)

Collecting different geophysical data sets at the same object and site offers the opportunity to reduce uncertainties and ambiguities in data analysis and interpretation. To be effective, the different available data sets should be linked during the model-generation process, e.g. by cooperative inversion. In this study, we apply a recently developed zonal cooperative inversion approach based on fuzzy c-means cluster analysis to a non-destructive testing experiment. After briefly reviewing the fundamentals of the inversion strategy, we present a synthetic study investigating the potential of the method to detect air-filled voids in masonry by using ultrasonic and georadar traveltime data. Then, we present and discuss laboratory experiments including the results of cooperatively inverted ultrasonic and georadar traveltimes collected at a masonry test specimen. The geometry of the specimen is known and is thus an ideal test object for a first-time real application of the novel zonal cooperative inversion procedure. Compared to the results of separate inversions of ultrasonic and georadar traveltimes, the zonal cooperative inversion allows for an improved delineation of the size and position of the cavities. The P-wave and georadar velocities determined for the model regions corresponding to the cavities are also improved.

Paasche, Hendrik; Wendrich, Astrid; Tronicke, Jens; Trela, Christiane

2008-09-01

330

Imaging the Juan de Fuca plate beneath southern Oregon using teleseismic P wave residuals  

USGS Publications Warehouse

Images the Juan de Fuca plate in southern Oregon using seismic tomography. P wave travel time residuals from a 366-km-long seismic array operated in southern Oregon in 1982 are inverted. The southeast striking array extended from the Coast ranges to the Modoc Plateau and crossed the High Cascades at Crater Lake, Oregon. Three features under the array were imaged: one high-velocity zone and two low-velocity zones. The high-velocity zone is 3-4% faster than the surrounding upper mantle. It dips steeply at 65?? to the east beneath the Cascade Range and extends down to at least 200 km. It is proposed that this high-velocity feature is subducted Juan de Fuca plate. Two low-velocity zones were also imaged, both of which are 3-4% slower than the surrounding earth structure. The southeastern low-velocity zone may be caused by partially molten crust underlying the Crater Lake volcano region. -from Authors

Harris, R. A.; Iyer, H. M.; Dawson, P. B.

1991-01-01

331

What Do s- and p-Wave Neutron Average Radiative Widths Reveal  

SciTech Connect

A first observation of two resonance-like structures at mass numbers 92 and 112 in the average capture widths of the p-wave neutron resonances relative to the s-wave component is interpreted in terms of a spin-orbit splitting of the 3p single-particle state into P{sub 3/2} and P{sub 1/2} components at the neutron separation energy. A third structure at about A = 124, which is not correlated with the 3p-wave neutron strength function, is possibly due to the Pygmy Dipole Resonance. Five significant results emerge from this investigation: (i) The strength of the spin-orbit potential of the optical-model is determined as 5.7 {+-} 0.5 MeV, (ii) Non-statistical effects dominate the p-wave neutron-capture in the mass region A = 85 - 130, (iii) The background magnitude of the p-wave average capture-width relative to that of the s-wave is determined as 0.50 {+-} 0.05, which is accounted for quantitatively in tenns of the generalized Fermi liquid model of Mughabghab and Dunford, (iv) The p-wave resonances arc partially decoupled from the giant-dipole resonance (GDR), and (v) Gamma-ray transitions, enhanced over the predictions of the GDR, are observed in the {sup 90}Zr - {sup 98}Mo and Sn-Ba regions.

Mughabghab, S.F.

2010-04-30

332

Increased QT dispersion and P wave dispersion in major depressive disorder  

PubMed Central

BACKGROUND: QT and P wave dispersion parameters can indicate abnormalities in autonomic nervous system and cardiac functioning. OBJECTIVES: To determine QT and P wave dispersion in patients with major depressive disorder compared with healthy volunteers. METHODS: Fifty newly diagnosed patients with major depressive disorder and 50 age- and sex-matched healthy volunteers underwent 12-lead electrocardiography. QT interval, QT dispersion, heart rate-corrected QT dispersion and P wave dispersions were calculated manually by a blinded specialist. RESULTS: Groups were comparable in terms of age, sex, body mass index, smoking status, metabolic diseases and left ventricular ejection fraction. The major depressive disorder group had significantly higher QT dispersion (58.5±9.9 versus 41.7±3.8; P<0.001), heart rate-corrected QT dispersion (62.5±10.0 versus 45.2±4.3; P<0.001) and P wave dispersion (46.9±4.8 versus 41.5±5.1; P<0.001). CONCLUSION: Increased QT dispersion, heart-rate corrected QT dispersion and P wave dispersion in major depressive disorder patients may be indicative of autonomic imbalance and increased risk of cardiac morbidity and mortality.

Tosu, Aydin Rodi; Demir, Serafettin; Kaya, Yuksel; Selcuk, Murat; Asker, Muntecep; Ozdemir, Mahmut; Tenekecioglu, Erhan

2013-01-01

333

Evaluation of strength of heterogeneity in the lithosphere from peak amplitude analyses of teleseismic short-period vector P waves  

NASA Astrophysics Data System (ADS)

We quantitatively characterize the regional variations in the strength of heterogeneity in the lithosphere of the globe by analysing the observed seismogram envelopes of teleseismic P waves in the frequency band of 0.5-4Hz. We apply a theoretical scattering model based on the Markov approximation for a plane P wave propagating through the random medium characterized by a Gaussian autocorrelation function. Since this model presumes the vertical incidence of an impulsive plane wavelet, we first analyse teleseismic P waves from deep earthquakes occurring along the western Pacific regions. We measure the ratios of peak intensity of transverse components to that of the sum of the three components, and determine the quantity of randomness ?2 z/a, where ?, a and z are fractional fluctuation, correlation distance and thickness of a heterogeneous structure, respectively. Although source time functions of shallow earthquakes are too complex to directly apply the scattering model, a good correlation between the ratios of peak amplitude and the normalized transverse amplitude, which is the square root of the energy partition of the P-coda waves into the transverse component, enables us to use the shallow earthquakes that occur widely around the world. As a result, the quantity ?2 z/a extends from 1.15 × 10-4 to 6.34 × 10-2 at 0.5-1 Hz, 2.02 × 10-3 to 1.89 × 10-1 at 1-2 Hz and 1.49 × 10-4 to 1.89 × 10-1 at 2-4 Hz, which are in agreement with the results of previous studies using different methods. The spatial distribution of randomness almost agrees with various tectonic settings and roughly correlates with lateral variations of Lg coda Q and shear wave velocity perturbations at 80 km depth, suggesting that lateral heterogeneity extends from the shallow crust to uppermost mantle.

Kubanza, Mungiya; Nishimura, Takeshi; Sato, Haruo

2007-10-01

334

Upper mantle Q and thermal structure beneath Tanzania, East Africa from teleseismic P wave spectra  

NASA Astrophysics Data System (ADS)

We measure P wave spectral amplitude ratios from deep-focus earthquakes recorded at broadband seismic stations of the Tanzania network to estimate regional variation of sublithospheric mantle attenuation beneath the Tanzania craton and the eastern branch of the East African Rift. One-dimensional profiles of QP adequately explain the systematic variation of P wave attenuation in the sublithospheric upper mantle: QP ~ 175 beneath the cratonic lithosphere, while it is ~ 80 beneath the rifted lithosphere. By combining the QP values and a model of P wave velocity perturbations, we estimate that the temperature beneath the rifted lithosphere (100-400 km depth) is 140-280 K higher than ambient mantle temperatures, consistent with the observation that the 410 km discontinuity in this region is depressed by 30-40 km.

Venkataraman, Anupama; Nyblade, Andrew A.; Ritsema, Jeroen

2004-08-01

335

Proximity effect in ferromagnet/triplet p-wave superconductor structures  

NASA Astrophysics Data System (ADS)

The superconducting proximity effect in normal metal/insulator/ferromagnet/triplet p-wave superconductor (N/I/FP) structures is studied based on an extended Blonder Tinkham Klapwijk (BTK) theory. Three kinds of pairings for the P side are chosen: p, p, p+ip waves. The transition from the “0” to “?” state is found in the conductance spectra with increasing the thickness of F or the ferromagnetic exchange energy. The large amplitude of the normalized conductance suggests the possible coexistence of the ferromagnetism and p-wave superconductivity in a small region near the F/P interface induced by the proximity effect.

Li, Hong; Yang, Wei; Yang, Xinjian; Qin, Minghui

2007-02-01

336

Spatial and Temporal Variations in t s \\/t p and in P Wave Residuals at Blue Mountain Lake, New York: Application to Earthquake Prediction  

Microsoft Academic Search

Renewed earthquake activity at Blue Mountain Lake (BML), New York, in July 1973 provided an excellent opportunity to monitor the travel time ratio of $ to P waves (ts\\/t,) in real time and to test the ts\\/t, technique as a predictive tool. From a mean value of 1.73 on July 30, 1973, ts\\/t, decreased to about 1.5 over the next

Yash P. Aggarwal; Lynn R. Sykes; David W. Simpson; Paul G. Richards

1975-01-01

337

Subduction in the southern Caribbean: Images from finite-frequency P wave tomography  

NASA Astrophysics Data System (ADS)

The eastern boundary of the Caribbean plate is marked by subduction of the Atlantic under the Lesser Antilles. The southeastern plate boundary is characterized by a strike-slip margin, while different configurations of subduction of the southwest Caribbean under South America have been proposed. We investigate the slab geometry in the upper mantle using multiple-frequency, teleseismic P wave tomography. Waveforms from P and PKPdf phases from 285 (Mb > 5.0) events occurring at epicentral distances from 30° to 90° and greater than 150° were bandpass filtered and cross-correlated to obtain up to three sets of delay times for each event. The delay times were inverted using approximate first Fresnel zone sensitivity kernels. Our results show the subducting Atlantic slab, as well as a second slab in the west of the study area that we interpret as a subducting fragment of the Caribbean plate. Both slabs have steep dips where imaged and can be traced to depths greater than 600 km. These results are consistent with transition zone boundary topography as determined by receiver function analysis. The Atlantic slab extends continent-ward south of the plate bounding strike-slip margin. We interpret this extension as continental margin lithospheric mantle that is detaching from beneath South America and subducting along with the oceanic Atlantic slab. The steep subduction of the Caribbean occurs ˜500 km landward from the trench, implying an initial stage of shallow subduction as far to the east as the Lake Maracaibo-Mérida Andes region, as has been inferred from intermediate depth seismicity.

Bezada, M. J.; Levander, A.; Schmandt, B.

2010-12-01

338

Hybrid theory of P-wave electron-Li2+ elastic scattering and photoabsorption in two-electron systems  

NASA Astrophysics Data System (ADS)

In previous papers [Bhatia, Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.85.052708 85, 052708 (2012); Bhatia, Phys. Rev. A10.1103/PhysRevA.86.032709 86, 032709 (2012)] electron-hydrogen and electron-He+ P-wave scattering phase shifts were calculated using the hybrid theory. This method is extended to the singlet and triplet electron-Li2+ P-wave scattering in the elastic region, where the correlation functions are of Hylleraas type. The short-range and long-range correlations are included in the Schrödinger equation at the same time, by using a combination of a modified method of polarized orbitals and the optical potential formalism. Phase shifts are compared to those obtained by other methods. The present calculation requires very few correlation functions to obtain accurate results which are rigorous lower bounds to the exact phase shifts. The continuum functions obtained in this method are used to calculate photodetachment and photoionization cross sections of two-electron systems H-, He, and Li+. Cross sections of the metastable 1,3S states of He, and Li+ are also calculated. These cross sections are calculated in the elastic region and compared with previous calculations. Using these cross sections, the Maxwellian-averaged radiative-recombination rates at various electron temperatures are also calculated.

Bhatia, A. K.

2013-04-01

339

Relationship of P-wave seismic attributes, azimuthal anisotropy, and commercial gas pay in 3-D P-wave multiazimuth data, Rulison field, Piceance Basin, Colorado  

SciTech Connect

This case history is one of three field projects funded by the US Department of Energy a part of its ongoing research effort aimed to expand current levels of drilling and production efficiency in naturally-fractured tight-gas reservoirs. The original states goal for the 3-D P-wave seismic survey was to evaluate and map fracture azimuth and relative fracture density throughout a naturally-fractured gas reservoir interval. At Rulison field, this interval is the Cretaceous Mesaverde, approximately 2,500 ft (760 m) of lenticular sands, silts, and shales. Three-dimensional full-azimuth P-wave data were acquired for the evaluation of azimuthal anisotropy and the relationship of the anisotropy to commercial pay in the target interval. The methodology is based on the evaluation of two restricted-azimuth orthogonal (source receiver azimuth) 3-D P-wave volumes aligned with the natural principal axes of the azimuthal anisotropy, as estimated from velocity analysis of multiazimuth prestack gathers. The Dix interval velocity, as well as the interval amplitude variation with offset (AVO) gradient, was calculated for both azimuths for the gas-saturated Mesaverde interval. The two seismic attributes best correlated with commercial gas pay (at a 21-well control set) were (1) values greater than 4% azimuthal variation in the interval velocity ratio (source-receiver azimuth N60E/N30W) of the target interval (the gas-saturated Mesaverde), and (2) the sum of the interval AVO gradients (N60E + N30W). The sum of the interval AVO gradients is an attribute sensitive to the presence of gas, but not diagnostic of an azimuthal variation in the amplitude. The two-azimuth interval velocity anisotropy mapped over the survey area suggests spatial variations in the orientation of the maximum horizontal stress field and the open (to flow) fracture system.

Lynn, H.B.; Campagna, D.; Simon, K.M.; Beckham, W.E.

1999-08-01

340

Confinement-induced p-wave resonances from s-wave interactions  

SciTech Connect

We show that a purely s-wave interaction in three dimensions (3D) can induce higher partial-wave resonances in mixed dimensions. We develop two-body scattering theories in all three cases of 0D-3D, 1D-3D, and 2D-3D mixtures and determine the positions of higher partial-wave resonances in terms of the 3D s-wave scattering length assuming a harmonic confinement potential. We also compute the low-energy scattering parameters in the p-wave channel (scattering volume and effective momentum) that are necessary for the low-energy effective theory of the p-wave resonance. We point out that some of the resonances observed in the Florence group experiment [Phys. Rev. Lett. 104, 153202 (2010)] can be interpreted as the p-wave resonances in the 2D-3D mixed dimensions. Our study paves the way for a variety of physics, such as Anderson localization of matter waves under p-wave resonant scatterers.

Nishida, Yusuke [Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Tan, Shina [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

2010-12-15

341

The role of P wave in prediction of atrial fibrillation after coronary artery surgery  

Microsoft Academic Search

Atrial fibrillation (AF) is a common arrhythmia after coronary artery bypass surgery (CABG). The purpose of this study was to determine the role of P wave duration, amplitude and dispersion in the prediction of AF after CABG. This study included 120 patients undergoing elective CABG. Clinical characteristics, 12-lead electrocardiogram (ECG), echocardiogram and coronary angiogram were obtained in all patients. We

Che-Ming Chang; Shih-Huang Lee; Ming-Jen Lu; Chia-Hsun Lin; Hung-Hsing Chao; Jun-Jack Cheng; Peiliang Kuan; Chi-Ren Hung

1999-01-01

342

Structure and consequences of vortex-core states in p-wave superfluids  

Microsoft Academic Search

We study the properties of the subgap states in p-wave superfluids, which occur at energies below the bulk gap and are localized inside the cores of vortices. We argue that their presence affects the topological protection of the zero modes. Transitions between the subgap states, including the zero modes and at energies much smaller than the gap, can alter the

G. Möller; N. R. Cooper; V. Gurarie

2011-01-01

343

Zonal cooperative inversion of crosshole P-wave, S-wave, and georadar traveltime data sets  

Microsoft Academic Search

In this study, we use and extend a recently developed zonal cooperative inversion approach and apply it to the inversion of three independent geophysical field data sets. We invert crosshole P-wave, S-wave, and georadar data sets acquired in sand and gravel dominated unconsolidated sediments to detect and characterize different sedimentary units relevant for an engineering or hydrological site characterization. The

Steffen Linder; Hendrik Paasche; Jens Tronicke; Ernst Niederleithinger; Thomas Vienken

2010-01-01

344

Higher P-Wave Dispersion in Migraine Patients with Higher Number of Attacks  

PubMed Central

Objective and Aim. An imbalance of the sympathetic system may explain many of the clinical manifestations of the migraine. We aimed to evaluate P-waves as a reveal of sympathetic system function in migraine patients and healthy controls. Materials and Methods. Thirty-five episodic type of migraine patients (complained of migraine during 5 years or more, BMI < 30?kg/m2) and 30 controls were included in our study. We measured P-wave durations (minimum, maximum, and dispersion) from 12-lead ECG recording during pain-free periods. ECGs were transferred to a personal computer via a scanner and then used for magnification of x400 by Adobe Photoshop software. Results. P-wave durations were found to be similar between migraine patients and controls. Although P WD (P-wave dispersion) was similar, the mean value was higher in migraine subjects. P WD was positively correlated with P max (P < 0.01). Attacks number per month and male gender were the factors related to the P WD (P < 0.01). Conclusions. Many previous studies suggested that increased sympathetic activity may cause an increase in P WD. We found that P WD of migraine patients was higher than controls, and P WD was related to attacks number per month and male gender. Further studies are needed to explain the chronic effects of migraine.

Kocer, A.; Ery?lmaz, M.; Tutkan, H.; Ercan, N.; Kucukbayrak, Z. S.

2012-01-01

345

Effective field theory for halo nuclei: shallow p-wave states  

Microsoft Academic Search

Halo nuclei are a promising new arena for studies based on effective field theory (EFT). We develop an EFT for shallow p-wave states and discuss the application to elastic n? scattering. In contrast to the s-wave case, both the scattering length and effective range enter at leading order. We also discuss the prospects of using EFT in the description of

C. A. Bertulani; H.-W. Hammer; U. van Kolck

2002-01-01

346

Destructive interference of s and p waves in 180°C ? ? p elastic scattering  

Microsoft Academic Search

The differential cross section for ??p elastic scattering shows a pronounced dip at 180° and incident pion laboratory energies around 57 MeV. This is due to the cancellation of the real parts of the s- and p-wave hadronic scattering amplitudes. The first observation of this dip is reported and the potential of exploiting the destructive interference phenomenon is discussed.

M. Janousch; A. Badertscher; P. F. A. Goudsmit; H. J. Leisi; E. Matsinos; P. Weber; Z. G. Zhao

1997-01-01

347

Deconvolution of Teleseismic P-Waves Using the SV Autocorrelation Method with Application to the P-Wave Structure Beneath the Hi-CLIMB Array in Tibet  

NASA Astrophysics Data System (ADS)

The analysis of seismic receiver functions has become an effective approach for determining crust and upper mantle structure. In the traditional receiver function method, the vertical component is used to deconvolve the radial component, where the vertical component is assumed to be equivalent to the source wavelet. However, in the approach of Dasgupta and Nowack (2006), the deconvolution of three-component teleseismic P-waves is performed by using the autocorrelation of P to SV scattered waves (SVA method). In this approach, three-component seismic data (in the vertical-radial-transverse frame) is transformed into P- SV-SH frame (Kennett, 1991) with the effects of the free surface also taken into account. The P to SV scattering is assumed to be random and white so that the autocorrelation of the SV component is equivalent to the autocorrelation of the source wavelet. This is similar to the assumption used for predictive deconvolution using P to P scattering in exploration geophysics. A minimum-phase source wavelet is estimated from the autocorrelation of the SV component and this wavelet can be used to deconvolve the teleseismic P-wave (unrotated radial and vertical components). However, the radial and vertical components must be transformed to minimum phase before the deconvolution. This can be done since under conditions typical of a teleseismic incident wave, the P-wave impulse response of receiver-side stratification will be minimum phase (Bostock, 2004). In this way we can get both deconvolved P to P and P to SV scattered components. The approach is first tested with synthetic data in which random velocity fluctuations are added to a 1-D deterministic crust and upper mantle structure. The approach is then applied to deconvolve teleseismic P-wave components (radial and vertical) for data from stations of the Hi-CLIMB seismic array which were deployed across the Himalayan-Tibetan collision zone. The SV-autocorrelation method is used for different earthquake events for each station and then the results of a group of events are stacked. The Moho depths obtained for the PpPmp phase on the deconvolved vertical component are then compared to those obtained from the Ps phases for selected stations beneath the Hi-CLIMB array.

Roy, S.; Nowack, R. L.

2008-12-01

348

Impact of hemodialysis on P-wave amplitude, duration, and dispersion  

PubMed Central

Atrial fibrillation (AF) is a frequent arrhythmia in patients undergoing hemodialysis (HD). P wave duration (PWdu) and P wave dispersion (PWdi) have been shown to be predictors of emerging AF in different clinical conditions. We sought to study the impact of HD on PWdu, PWdi, and P wave amplitude in a cohort of patients undergoing HD. Seventeen patients (8 men, 31±10 years) were studied. Echocardiography parameters, the sum of the amplitude of P waves in all 12 ECG leads (SP), mean PWdu, and PWdi, along with a host of other parameters (body weight, heart rate, electrolytes and hemoglobin/hematochrit) were measured 1/2h, before and after, HD. SP increased (11.8±3.9 vs 15.3±4.0 mm, p = 0.004), mean PWdu remained stable (82.7±11.1 vs 81.6±10.5 ms, p = 0.606), PWdi decreased (51.7±19.1 vs 41.7±19.1 ms, p = 0.03), and left atrial dimension decreased (37.96±3.90 vs 30.62±3.38 mm, p = 0.0001), after HD. The change in PWdi correlated with fluid removed by HD (r = -0.55, p = 0.022). Re-measurements of P-wave parameters in a random group of 11 of the 17 patients revealed augmented SP (p = 0.01), and stable mean PWdu (p = 0.36), and PWdi (p = 0.31), after HD. Fluid removed by HD leads to an increase in SP, a stable mean PWdu, and decrease (or stability on re-measurement in a subgroup of patients) in PWdi. Stability of PWdu may be due to the effects of augmentation of the P-wave amplitude and the reduction of the left atrial volume, cancelling each other. Variability of PWdi may stem from the occasional impossibility to measure PWdu (or measure it correctly) in minute P-waves in certain ECG leads, which in turn profoundly affects the PWdi.

Drighil, Abdenasser; Madias, John E; Mosalami, Hanane El; Badaoui, Nadia El; Mouine, Bahija; Fadili, Wafae; Ramdani, Beenyouness; Bennis, Ahmed

2007-01-01

349

Impact of hemodialysis on P-wave amplitude, duration, and dispersion.  

PubMed

Atrial fibrillation (AF) is a frequent arrhythmia in patients undergoing hemodialysis (HD). P wave duration (PWdu) and P wave dispersion (PWdi) have been shown to be predictors of emerging AF in different clinical conditions. We sought to study the impact of HD on PWdu, PWdi, and P wave amplitude in a cohort of patients undergoing HD. Seventeen patients (8 men, 31+/-10 years) were studied. Echocardiography parameters, the sum of the amplitude of P waves in all 12 ECG leads (SP), mean PWdu, and PWdi, along with a host of other parameters (body weight, heart rate, electrolytes and hemoglobin/hematochrit) were measured 1/2h, before and after, HD. SP increased (11.8+/-3.9 vs 15.3+/-4.0 mm, p = 0.004), mean PWdu remained stable (82.7+/-11.1 vs 81.6+/-10.5 ms, p = 0.606), PWdi decreased (51.7+/-19.1 vs 41.7+/-19.1 ms, p = 0.03), and left atrial dimension decreased (37.96+/-3.90 vs 30.62+/-3.38 mm, p = 0.0001), after HD. The change in PWdi correlated with fluid removed by HD (r = -0.55, p = 0.022). Re-measurements of P-wave parameters in a random group of 11 of the 17 patients revealed augmented SP (p = 0.01), and stable mean PWdu (p = 0.36), and PWdi (p = 0.31), after HD. Fluid removed by HD leads to an increase in SP, a stable mean PWdu, and decrease (or stability on re-measurement in a subgroup of patients) in PWdi. Stability of PWdu may be due to the effects of augmentation of the P-wave amplitude and the reduction of the left atrial volume, cancelling each other. Variability of PWdi may stem from the occasional impossibility to measure PWdu (or measure it correctly) in minute P-waves in certain ECG leads, which in turn profoundly affects the PWdi. PMID:17538700

Drighil, Abdenasser; Madias, John E; El Mosalami, Hanane; El Badaoui, Nadia; Mouine, Bahija; Fadili, Wafae; Ramdani, Beenyouness; Bennis, Ahmed

2007-04-01

350

Arrival Generators for Queueing Simulations.  

National Technical Information Service (NTIS)

The paper presents two methods for modeling cyclic inputs to a congested system in a discrete event digital simulation. Specifically, it is assumed that the interarrival times follow a probability distribution whose parameters are functions of time. Assum...

G. S. Fishman E. P. C. Kao

1974-01-01

351

High-precision earthquake location and three-dimensional P wave velocity determination at Redoubt Volcano, Alaska  

Microsoft Academic Search

Redoubt Volcano, Alaska poses significant volcanic hazard to the Cook Inlet region and overlying flight paths. During and following the most recent eruption in 1989–1990 the Alaska Volcano Observatory deployed up to 10 seismometers to improve real-time monitoring capabilities at Redoubt and continues to produce an annual earthquake catalog with associated arrival times for this volcano. We compute a three-dimensional

Heather R. DeShon; Clifford H. Thurber; Charlotte Rowe

2007-01-01

352

Travel-time tomography of the Abitibi-Grenville region, eastern Canada  

NASA Astrophysics Data System (ADS)

Seismic studies of the Canadian Shield have indicated certain structural anomalies within the cratonic lithosphere. A low-velocity anomaly has been imaged near the Ontario-Québec border, in the Abitibi-Grenville province, but its 3D geometry was poorly-defined due to a lack of seismograph station coverage on the Québec side of the border. With the help of the 5 new seismograph stations installed in western Québec in 2007, 26 others belonging to the POLARIS project and the Canadian National Seismograph Network (CNSN), and a data set of travel time picks from the ABI-96 teleseismic experiment (Rondenay et al., 2000), we analyse the P-wave velocity structure of the lithosphere in order to better understand the complexity of the region and the interaction of the lithosphere with thermal anomalies in the underlying mantle. Several analysis steps have been carried out. We first measured the relative arrival times of teleseismic P waves across the array, using the cross-correlation method of VanDecar & Crosson (1990). We present the results of an analysis of azimuthal variations of these arrival times for representative stations across the array. We have also calculated maps of relative arrival time residuals across the array for earthquakes coming from different back- azimuths, in order to examine systematic patterns of travel-time anomalies resulting from mantle heterogeneity. Finally, we have inverted the travel time data to estimate a preliminary model of the 3D P-wave velocity structure beneath the region, using a standard tomographic inversion technique.

Villemaire, M.; Darbyshire, F. A.

2009-05-01

353

Travel-time Tomography of the Abitibi-Grenville Region, Eastern Canada  

NASA Astrophysics Data System (ADS)

Seismic studies of the Canadian Shield have indicated certain structural anomalies within the cratonic lithosphere. A low-velocity anomaly has been imaged near the Ontario-Quebec border, in the Abitibi- Grenville province, but its 3D geometry was poorly-defined due to a lack of seismograph station coverage on the Quebec side of the border. With the help of the 5 new seismograph stations installed in western Quebec in 2007, 26 others belonging to the POLARIS project and the Canadian National Seismograph Network (CNSN), and a data set of travel time picks from the ABI-96 teleseismic experiment (Rondenay et al., 2000), we analyse the P-wave velocity structure of the lithosphere in order to better understand the complexity of the region and the interaction of the lithosphere with thermal anomalies in the underlying mantle. Several analysis steps have been carried out. We first measured the relative arrival times of teleseismic P waves across the array, using the cross-correlation method of VanDecar & Crosson (1990). We present the results of an analysis of azimuthal variations of these arrival times for representative stations across the array. We have also calculated maps of relative arrival time residuals across the array for earthquakes coming from different back-azimuths, in order to examine systematic patterns of travel-time anomalies resulting from mantle heterogeneity. Finally, we have inverted the travel time data to estimate a preliminary model of the 3D P-wave velocity structure beneath the region, using a standard tomographic inversion technique.

Villemaire, M.; Darbyshire, F. A.

2008-12-01

354

Process Arrival Pattern and Shared Memory Aware Alltoall on InfiniBand  

NASA Astrophysics Data System (ADS)

Recent studies have shown that processes in real applications can arrive at the collective calls at different times. This imbalanced process arrival pattern can significantly affect the performance of the collective operations. MPI_Alltoall() is a communication-intensive collective operation that is used in many parallel scientific applications. Its efficient implementation under different process arrival patterns is critical to the performance of applications that use them frequently. In this paper, we propose novel RDMA-based process arrival pattern aware MPI_Alltoall() algorithms over InfiniBand clusters. We extend the algorithms to be shared memory aware for small to medium size messages. The micro-benchmark and application results indicate that the proposed algorithms outperform the native implementation as well as their non-process arrival pattern aware counterparts when processes arrive at different times.

Qian, Ying; Afsahi, Ahmad

355

Binary-Representation-Based Genetic Algorithm for Aircraft Arrival Sequencing and Scheduling  

Microsoft Academic Search

Arrival sequencing and scheduling (ASS) at airports is an NP-hard problem. Much effort has been made to use permutation-representation-based genetic algorithms (GAs) to tackle this problem, whereas this paper attempts to design an efficient GA based on a binary representation of arriving queues. Rather than using the order and\\/or arriving time of each aircraft in the queue to construct chromosomes

Xiao-bing Hu; Ezequiel A. Di Paolo

2008-01-01

356

Automatic detection and rapid determination of earthquake magnitude by wavelet multiscale analysis of the primary arrival  

NASA Astrophysics Data System (ADS)

Earthquake early warning systems save lives. It is of great importance that networked systems of seismometers be equipped with reliable tools to make rapid determinations of earthquake magnitude in the few to tens of seconds before the damaging ground motion occurs. A new fully automated algorithm based on the discrete wavelet transform detects as well as analyzes the incoming first arrival with unmatched accuracy and precision, estimating the final magnitude to within a single unit from the first few seconds of the P wave. The curious observation that such brief segments of the seismogram may contain information about the final magnitude even of very large earthquakes, which occur on faults that may rupture over tens of seconds, is central to a debate in the seismological community which we hope to stimulate but cannot attempt to address within the scope of this paper. Wavelet coefficients of the seismogram can be determined extremely rapidly and efficiently by the fast lifting wavelet transform. Extracting amplitudes at individual scales is a very simple procedure, involving a mere handful of lines of computer code. Scale-dependent thresholded amplitudes derived from the wavelet transform of the first 3--4 seconds of an incoming seismic P arrival are predictive of earthquake magnitude, with errors of one magnitude unit for seismograms recorded up to 150 km away from the earthquake source. Our procedure is a simple yet extremely efficient tool for implementation on low-power recording stations. It provides an accurate and precise method of autonomously detecting the incoming P wave and predicting the magnitude of the source from the scale-dependent character of its amplitude well before the arrival of damaging ground motion. Provided a dense array of networked seismometers exists, our procedure should become the tool of choice for earthquake early warning systems worldwide.

Dando, B.; Simons, F. J.; Allen, R. M.

2006-12-01

357

8 CFR 232.3 - Arriving aliens.  

Code of Federal Regulations, 2011 CFR

8 Aliens and Nationality 1 2013-01-01 2013-01-01 false Arriving aliens. 232.3 Section 232.3 Aliens and Nationality DEPARTMENT OF HOMELAND SECURITY IMMIGRATION REGULATIONS DETENTION OF ALIENS FOR PHYSICAL...

2013-01-01

358

Drive to Arrive-Series One.  

National Technical Information Service (NTIS)

Drive to Arrive-Series 1 is the first of five installments of short public service announcements utilizing country music artists to spokespersons. The series covers personally owned vehicle (POV) safety issues and concerns. Topics include speed, fatigue, ...

2002-01-01

359

New Crew Members Arrive at Station  

NASA Video Gallery

The Expedition 28 crew expanded to six members with the arrival of Flight Engineers Mike Fossum, Sergei Volkov and Satoshi Furukawa. The new trio docked to the International Space Station in the Soyuz TMA-02M spacecraft June 9, 2011.

Mark Garcia

2011-06-09

360

Webb Mirrors Arrive at NASA Goddard  

NASA Video Gallery

James Webb Space Telescope's secondary mirror, along with a primary mirror segment arrived at NASA's Goddard Space Flight Center in Greenbelt, Md., on Nov. 5, 2012. Credit: NASA's Goddard Space Flight Center > Related story > Download high-res video

Robert Garner

2012-11-27

361

Wake Turbulence Mitigation for Arrivals (WTMA).  

National Technical Information Service (NTIS)

The preliminary Wake Turbulence Mitigation for Arrivals (WTMA) concept of operations is described in this paper. The WTMA concept provides further detail to work initiated by the Wake Vortex Avoidance System Concept Evaluation Team and is an evolution of ...

A. C. Trujillo D. M. Williams G. W. Lohr

2008-01-01

362

Zero field Hall effect in chiral p-wave superconductors near the Kosterlitz-Thouless transition  

NASA Astrophysics Data System (ADS)

A theory of vortex dynamics developed by Ambegaokar, Halperin, Nelson, and Siggia is employed to study two-dimensional chiral p-wave superconducting systems. Due to unequal values of drag coefficients of opposite vorticity specific to chiral p-wave cases, we find that a ``convective'' term, in addition to diffusivity, should enter the dynamical equations governing vortex pair unbinding process. As a consequence, we find a matrix form dielectric function and a new contribution to Hall conductance ?xy automatically follows even in zero magnetic field. We predict both the Hall conductance and power dissipation show a peak across the Kosterlitz-Thouless transition temperature. Their frequency dependence is also discussed. It is found that a set of frequency-dependent length scales, which controls the truncation of renormalization process, depends on both the convective and diffusive motion of vortices.

Kit Chung, Chun; Kato, Yusuke

2013-03-01

363

Attenuation of P-Waves by Wave-Induced Fluid Flow  

SciTech Connect

Analytical expressions for three P-wave attenuation mechanisms in rocks are given and numerically-compared. The mechanisms are: (1) Biot loss, in which flow occurs at the scale of the wavelength between the peaks and troughs of a P wave; (2) squirt loss, in which flow occurs at the grain scale between microcracks the grains and the adjacent pores; and (3) mesoscopic loss, in which flow occurs at intermediate scales between the various lithological bodies that are present in an averaging volume of earth material. Each mechanism is of importance over different frequency bands. Typically, Biot loss is only important at the highest of ultrasonic frequencies (> 1 MHz), squirt-loss (when it occurs) is important in the range of 10 kHz to 1 MHz, while mesoscale loss dominates at the lower frequencies (<10 kHz) employed in seismology.

Pride, S R; Berryman, J G

2002-03-29

364

Permeability and P-wave velocity change in granitic rocks under freeze–thaw cycles  

Microsoft Academic Search

An extensive experimental investigation of microstructural changes in granites under freeze–thaw cycles using permeability and P-wave velocity measurements is described. Two types of natural granite rocks are considered and tested under dry and saturated conditions. The specimens were subjected to 200 heating–cooling cycles (??20°C\\/?+?20°C); each cycle had a duration of 24 h. The results indicate that the ageing process decreases the

M. Takarli; W. Prince

2007-01-01

365

Effect of tectonic stress release on explosion P-wave signatures  

Microsoft Academic Search

The influence of induced tectonic stress release on the short-period teleseismic P-wave signature of underground nuclear explosions is studied. Primary attention is directed to the first few cycles of the record from which body-wave magnitude (m\\/sub b\\/) is determined. Computational models for both the explosion and the superimposed tectonic release double couple are employed and theoretical seismograms are computed. Interest

Bache

1976-01-01

366

Decay constants of P-wave heavy-light mesons from unquenched lattice QCD  

Microsoft Academic Search

We review some decays that require knowledge of the decay constants of 0+ heavy-light mesons. We compute the decay constants of P-wave heavy-light mesons from unquenched lattice QCD, with two degenerate flavours of sea quarks, at a single lattice spacing. The lightest sea quark mass used in the calculation is a third of the strange quark mass. For the charm-strange

G. Herdoiza; C. McNeile; C. Michael

2006-01-01

367

First-order ray tracing for qP waves in inhomogeneous, weakly anisotropic media  

Microsoft Academic Search

We propose approximate ray-tracing equations for qP-waves propagating in smooth, inhomogeneous, weakly anisotropic media. For their derivation, we use perturbation theory, in which deviations of anisotropy from isotropy are considered to be the first-order quan- tities. The proposed ray-tracing equations and corre- sponding traveltimes are of the first order. Accuracy of the traveltimes can be increased by calculating a second-

Ivan P

368

Automatic discrimination of underwater acoustic signals generated by teleseismic P-waves: A probabilistic approach  

NASA Astrophysics Data System (ADS)

We propose a new probabilistic scheme for the automatic recognition of underwater acoustic signals generated by teleseismic P-waves recorded by hydrophones in the ocean. The recognition of a given signal is based on the relative distribution of its power among different frequency bands. The signal's power distribution is compared with a statistical model developed by analyzing relative power distributions of many signals of the same origin and a numerical criterion is calculated, which can serve as a measure of the probability for the signal to belong to the statistical model. Our recognition scheme was applied to 6-month-long continuous records of seven ocean bottom hydrophones (OBH) deployed in the Ligurian Sea. A maximum of 94% of all detectable teleseismic P-waves recorded during the deployment of the OBHs were recognized correctly with no false recognitions. The proposed recognition method will be implemented in autonomous underwater robots dedicated to detect and transmit acoustic signals generated by teleseismic P-waves.

Sukhovich, Alexey; Irisson, Jean-Olivier; Simons, Frederik J.; Ogé, Anthony; Hello, Yann; Deschamps, Anne; Nolet, Guust

2011-09-01

369

Thermal structure beneath Tanzania from attenuation measurements using teleseismic P wave spectra  

NASA Astrophysics Data System (ADS)

Using P wave spectral amplitude ratios from deep-focus earthquakes recorded at broadband seismic stations of the Tanzania PASSCAL network, we estimate the regional variation of sublithospheric mantle attenuation beneath the Tanzania craton and the eastern branch of the East African Rift. To constrain the thermal anomaly beneath the eastern rift, we analyze P wave attenuation beneath the Tanzania seismic network and the adjacent rift system in combination with velocity anomalies determined from seismic tomography. We conclude that the observed variation in t* can be explained by variation in Qp in the sublithospheric mantle and obtain values of Qp ˜175 beneath the cratonic lithosphere and Qp ˜80 beneath the rifted lithosphere. By combining the Qp values and a model of P wave velocity perturbations, we estimate that the temperature beneath the rifted lithosphere (100-400km depth) is 140-280K higher than ambient mantle temperatures, consistent with the observation that the 410km discontinuity in this region is depressed by 30-40km.

Ritsema, J.; Venkataraman, A.; Nyblade, A.

2004-12-01

370

P-wave velocity structure of the uppermost mantle beneath Hawaii from traveltime tomography  

USGS Publications Warehouse

We examine the P-wave velocity structure beneath the island of Hawaii using P-wave residuals from teleseismic earthquakes recorded by the Hawaiian Volcano Observatory seismic network. The station geometry and distribution of events makes it possible to image the velocity structure between ~ 40 and 100 km depth with a lateral resolution of ~ 15 km and a vertical resolution of ~ 30 km. For depths between 40 and 80 km, P-wave velocities are up to 5 per cent slower in a broad elongated region trending SE-NW that underlies the island between the two lines defined by the volcanic loci. No direct correlation between the magnitude of the lithospheric anomaly and the current level of volcanic activity is apparent, but the slow region is broadened at ~ 19.8??N and narrow beneath Kilauea. In the case of the occanic lithosphere beneath Hawaii, slow seismic velocities are likely to be related to magma transport from the top of the melting zone at the base of the lithosphere to the surface. Thermal modelling shows that the broad elongated low-velocity zone cannot be explained in terms of conductive heating by one primary conduit per volcano but that more complicated melt pathways must exist.

Tilmann, F. J.; Benz, H. M.; Priestley, K. F.; Okubo, P. G.

2001-01-01

371

Renormalization in the three-body problem with resonant p-wave interactions  

NASA Astrophysics Data System (ADS)

Resonant p-wave interactions can be described by a minimal zero-range model defined by a truncated effective range expansion so that the only two-body interaction parameters are the inverse scattering volume 1/ap and the p-wave effective range rp. This minimal model can be formulated as a local quantum field theory with a p-wave interaction between atom fields and a molecular field. In the two-atom sector, the model is renormalizable, but it has unphysical behavior at high energies because there are negative-probability states with momentum scale rp. In the sector with three atoms, two of which are identical, renormalization in some parity and angular momentum channels involves an ultraviolet limit cycle, indicating asymptotic discrete scale invariance. The Efimov effect occurs in the unitary limit ap-1/3,rp?0, but this limit is unphysical because there are low-energy states with negative probability. The minimal model can be of physical relevance only at energies small compared to the energy scale set by rp where the effects of negative-probability states are suppressed.

Braaten, Eric; Hagen, P.; Hammer, H.-W.; Platter, L.

2012-07-01

372

Suppression of surface p-wave superconductivity in disordered topological insulators  

NASA Astrophysics Data System (ADS)

The paper proposes a self-consistent Green function description of the induced surface superconductivity in a disordered three-dimensional topological insulator (TI) coupled to an s-wave superconductor. We recover earlier results regarding the induced spin-triplet p-wave pairing, showing that a mixture of p- and s-wave pair correlations appears as a result of broken spin-rotation symmetry on the helical surface of the TI. Unlike the s-wave pairing, the p-wave component is found to be suppressed in dirty TIs in which the elastic mean-free path is much smaller than the superconducting coherence length. The suppression is due to the generic nonlocality of the spin-triplet correlations, which makes them strongly dependent on the mean-free path in a disordered system. In dirty TIs the induced superconductivity is predicted to be predominantly s-wave like. In cleaner TIs, however, the p-wave component may reach a magnitude comparable to (but not larger than) the s-wave pairing.

Tkachov, G.

2013-06-01

373

QT and P wave dispersion and heart rate variability in patients with Dravet syndrome.  

PubMed

SCN1A mutations are found in up to 80 % of patients with Dravet syndrome (DS), and the sudden unexpected death in epilepsy (SUDEP) rate is higher in DS than in most forms of severe epilepsy. The aim of this study is to examine the autonomic cardiac function and the risk of arrhythmia in DS patients by evaluating QT and P wave dispersion and heart rate variability (HRV) using standard electrocardiography (ECG) and 24-h ECG. The study group consisted of 15 patients (9 boys and 6 girls aged 3.5-17 years) who were genetically diagnosed with DS. The control group comprised 20 healthy subjects, 13 boys and 7 girls aged 4-17 years. P wave dispersion (44.6 ± 3.5 ms), QT dispersion (58.8 ± 7.5 ms) and QTc dispersion (70.8 ± 7.4 ms) were significantly higher in DS patients as compared to the control group (p < 0.001 for all values). However, there was no significant difference in PR, QT or QTc length between the groups. 24-h Holter ECG showed that all HRV parameters were significantly lower in patients with DS. The decreased HRV and increased P wave and QT dispersion seen in DS patients are important signs of autonomic dysfunction with increased adrenergic tone. To determine whether autonomic dysfunction is correlated with SUDEP in DS, long-term electrocardiographic monitoring and wider prospective studies are necessary. PMID:23065439

Ergul, Yakup; Ekici, Baris; Tatli, Burak; Nisli, Kemal; Ozmen, Meral

2012-10-13

374

Does pet arrival trigger prosocial behaviors in individuals with autism?  

PubMed

Alteration of social interactions especially prosocial behaviors--an important aspect of development--is one of the characteristics of autistic disorders. Numerous strategies or therapies are used to improve communication skills or at least to reduce social impairments. Animal-assisted therapies are used widely but their relevant benefits have never been scientifically evaluated. In the present study, we evaluated the association between the presence or the arrival of pets in families with an individual with autism and the changes in his or her prosocial behaviors. Of 260 individuals with autism--on the basis of presence or absence of pets--two groups of 12 individuals and two groups of 8 individuals were assigned to: study 1 (pet arrival after age of 5 versus no pet) and study 2 (pet versus no pet), respectively. Evaluation of social impairment was assessed at two time periods using the 36-items ADI-R algorithm and a parental questionnaire about their child-pet relationships. The results showed that 2 of the 36 items changed positively between the age of 4 to 5 (t(0)) and time of assessment (t(1)) in the pet arrival group (study 1): "offering to share" and "offering comfort". Interestingly, these two items reflect prosocial behaviors. There seemed to be no significant changes in any item for the three other groups. The interactions between individuals with autism and their pets were more--qualitatively and quantitatively--reported in the situation of pet arrival than pet presence since birth. These findings open further lines of research on the impact of pet's presence or arrival in families with an individual with autism. Given the potential ability of individuals with autism to develop prosocial behaviors, related studies are needed to better understand the mechanisms involved in the development of such child-pet relationship. PMID:22870246

Grandgeorge, Marine; Tordjman, Sylvie; Lazartigues, Alain; Lemonnier, Eric; Deleau, Michel; Hausberger, Martine

2012-08-01

375

Seasonality and structural breaks: NZ visitor arrivals and 9\\/11  

Microsoft Academic Search

We analyse monthly short term visitor arrival time series for New Zealand, to assess the effect of the 11 September 2001 terrorist attacks. We demonstrate that while some historical events have had a marked structural effect on trends in those arrivals, 9\\/11 was not one of these. Our conclusions are drawn on the basis of an initial nonparametric analysis, followed

John Haywood; John Randal

376

Give me a break? New Zealand visitor arrivals and the effects of 9\\/11  

Microsoft Academic Search

We analyse monthly short-term visitor arrival time series for New Zealand, to assess the effect of the 11 September 2001 terrorist attacks on the number of visitors to New Zealand. Somewhat misleading reports from the media concerning these data are highlighted. We demonstrate that while some historical events have had a marked structural effect on trends in visitor arrivals to

John HaywoodJohn Randal

377

Optimal Arrival Flight Sequencing and Scheduling Using Discrete Airborne Delays  

Microsoft Academic Search

An algorithm for optimal arrival flight sequencing and spacing in a near-terminal area is proposed. The optimization problem and algorithm proposed in this paper are developed for a decision-support tool for air-traffic control, which uses discrete delay times as optimization variables. The algorithm is applicable to various scenarios with situational and operational constraints such as maximum position shift (MPS) constraints

Yeonju Eun; Inseok Hwang; Hyochoong Bang

2010-01-01

378

Deep seafloor arrivals: an unexplained set of arrivals in long-range ocean acoustic propagation.  

PubMed

Receptions, from a ship-suspended source (in the band 50-100 Hz) to an ocean bottom seismometer (about 5000 m depth) and the deepest element on a vertical hydrophone array (about 750 m above the seafloor) that were acquired on the 2004 Long-Range Ocean Acoustic Propagation Experiment in the North Pacific Ocean, are described. The ranges varied from 50 to 3200 km. In addition to predicted ocean acoustic arrivals and deep shadow zone arrivals (leaking below turning points), "deep seafloor arrivals," that are dominant on the seafloor geophone but are absent or very weak on the hydrophone array, are observed. These deep seafloor arrivals are an unexplained set of arrivals in ocean acoustics possibly associated with seafloor interface waves. PMID:19640024

Stephen, Ralph A; Bolmer, S Thompson; Dzieciuch, Matthew A; Worcester, Peter F; Andrew, Rex K; Buck, Linda J; Mercer, James A; Colosi, John A; Howe, Bruce M

2009-08-01

379

Isotopic identification of the parity-violating neutron p-wave resonance at energy E0=3.2 eV in Xe  

NASA Astrophysics Data System (ADS)

Two-dimensional pulse height and time-of-flight (TOF) spectra were measured at the IBR-30 pulsed neutron source to make the isotopic identification of the parity-violating p-wave resonance at E0=3.2 eV recently observed in Xe. Analysis of the TOF spectra corresponding to the characteristic low-energy gamma-rays established the 131Xe isotope as the origin of the 3.2-eV resonance. This new finding poses a challenge for the development of a polarized solid 131Xe target for a test of time-reversal invariance with neutrons.

Skoy, V. R.; Sharapov, E. I.; Gundorin, N. A.; Popov, Yu. P.; Prokofichev, Yu. V.; Roberson, N. R.; Mitchell, G. E.

1996-06-01

380

Entanglement entropy in holographic p-wave superconductor/insulator model  

NASA Astrophysics Data System (ADS)

We continue our study of entanglement entropy in the holographic superconducting phase transitions. In this paper we consider the holographic p-wave superconductor/insulator model, where as the back reaction increases, the transition is changed from second order to first order. We find that unlike the s-wave case, there is no additional first order transition in the superconducting phase. We calculate the entanglement entropy for two strip geometries. One is parallel to the super current, and the other is orthogonal to the super current. In both cases, we find that the entanglement entropy monotonically increases with respect to the chemical potential.

Cai, Rong-Gen; Li, Li; Li, Li-Fang; Su, Ru-Keng

2013-06-01

381

Induced p-wave superfluidity in strongly interacting imbalanced Fermi gases  

SciTech Connect

The induced interaction among the majority spin species, due to the presence of the minority species, is computed for the case of a population-imbalanced resonantly interacting Fermi gas. It is shown that this interaction leads to an instability, at low temperatures, of the recently observed polaron Fermi liquid phase of strongly imbalanced Fermi gases to a p-wave superfluid state. We find that the associated transition temperature, while quite small in the weakly interacting BCS regime, is experimentally accessible in the strongly interacting unitary regime.

Patton, Kelly R.; Sheehy, Daniel E. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)

2011-05-15

382

Creating p-wave superfluids and topological excitations in optical lattices  

SciTech Connect

We propose to realize a p-wave superfluid using bosons mixed with a single species of fermions in a deep optical lattice. We analyze with a self-consistent method its excitation spectrum in presence of a vortex, and we point out the range of interaction strengths in which the zero-energy mode with topological character exists on a finite optical lattice. Lattice effects are strongest close to fermionic half filling: here the linearity of the low-lying spectrum is lost, and a new class of extended zero-energy modes with checkerboard structure and d-wave symmetry appears.

Massignan, P. [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels, Barcelona (Spain); Grup de Fisica Teorica, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Spain); Sanpera, A. [Grup de Fisica Teorica, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Spain); ICREA-Institucio Catalana de Recerca i Estudis Avancats, E-08010 Barcelona (Spain); Lewenstein, M. [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels, Barcelona (Spain); ICREA-Institucio Catalana de Recerca i Estudis Avancats, E-08010 Barcelona (Spain)

2010-03-15

383

Condensates of p-Wave Pairs Are Exact Solutions for Rotating Two-Component Bose Gases  

SciTech Connect

We derive exact analytical results for the wave functions and energies of harmonically trapped two-component Bose-Einstein condensates with weakly repulsive interactions under rotation. The isospin symmetric wave functions are universal and do not depend on the matrix elements of the two-body interaction. The comparison with the results from numerical diagonalization shows that the ground state and low-lying excitations consist of condensates of p-wave pairs for repulsive contact interactions, Coulomb interactions, and the repulsive interactions between aligned dipoles.

Papenbrock, T [UTK/ORNL/GSI-Darmstadt/Inst. für Kernphysik, Tech. Univ. Darmstadt-Germany; Reimann, S. M. [Lund University, Sweden; Kavoulakis, G. M. [Technological Educational Institute of Crete, Heraklion, Greece

2012-01-01

384

Tomographic imaging of the P-wave velocity structure beneath the Kamchatka peninsula  

NASA Astrophysics Data System (ADS)

A total of 5270 shallow and intermediate-depth earthquakes recorded by the 32 stations of the regional seismic network of the Geophysical Service of Russia are used to assess the P-wave velocity structure beneath the Kamchatka peninsula in the Western Pacific. The tomographic inversion is carried out in three steps. First, a 1-D tomographic problem is solved in order to obtain an initial velocity model. Based on the 1-D velocity model, 3-D tomographic inversions with homogeneous and heterogeneous starting models are obtained. The Conrad (15 km depth) and Moho (35 km depth) discontinuities determined from the 1-D tomographic inversion, and the upper boundary of the subducting slab are taken into account in the heterogeneous starting model for the traveltimes and ray-path determinations. Both velocity structure and hypocentral locations are determined simultaneously in the inversion. The spacing of the grid nodes is a half-degree in the horizontal direction and 20-50 km in the vertical direction. A detailed P-wave tomographic image is determined down to a depth of 200 km. The resulting tomographic image has a prominent low-velocity anomaly that shows a maximum decrease in P-wave velocity of approximately 6 per cent at 30 km depth beneath a chain of active volcanoes. At depth, low-velocity anomalies are also observed in the mantle wedge extending down to a depth of approximately 150 km. These anomalies are apparently associated with the volcanic activity. The sedimentary basin of the Central Kamchatsky graben, to the west of the volcanic front, and the accretionary prism at the trench correlate with shallow low-velocity anomalies. High-velocity anomalies observed at a depth of 10 km may be associated with the location of metamorphic basements in the Ganalsky-Valaginskoe uplift and upper crust of Shipunsky cape. The results also suggest that the subducted Pacific plate has P-wave velocities approximately 2-7 per cent higher than those of the surrounding mantle and a thickness of approximately 70 km.

Gorbatov, A.; Domínguez, J.; Suárez, G.; Kostoglodov, V.; Zhao, D.; Gordeev, E.

1999-05-01

385

Evasion of HSR in S-wave charmonium decaying to P-wave light hadrons  

NASA Astrophysics Data System (ADS)

The S-wave charmonium decaying to a P-wave and S-wave light hadron pairs are supposed to be suppressed by the helicity selection rule in the perturbative QCD framework. With an effective Lagrangian method, we show that the intermediate charmed meson loops can provide a possible mechanism for the evasion of the helicity selection rule, and result in sizeable decay branching ratios in some of those channels. The theoretical predictions can be examined by the forthcoming BES-III data in the near future.

Li, Gang; Liu, Xiao-Hai; Zhao, Qiang

2013-09-01

386

Cardiopulmonary arrest on arrival due to penetrating trauma  

PubMed Central

INTRODUCTION The aim of this study was to clarify the outcome of patients with cardiopulmonary arrest on arrival due to penetrating trauma (PT-CPA) and to establish the treatment strategy. PATIENTS AND METHODS The clinical course of 29 patients with PT-CPA over the past 10 years was examined. We have taken three approaches to these patients: (i) an aggressive treatment strategy; (ii) an in-hospital system supporting this aggressive resuscitation; and (iii) the pre-hospital emergency medical service (EMS) system in our city. RESULTS Although the return of spontaneous circulation (ROSC) was established in 59% of patients, only 17% survived for 7 days, 14% were discharged, and 7% were neurologically intact. Of 10 patients showing pulseless electrical activity (PEA) on the scene, ROSC was established in 100% and 30% were discharged; however, of 12 patients showing asystole, ROSC was established in 33% and no patient could be discharged. There was no difference in the time interval from the arrival at the emergency department to ROSC between discharged patients and patients who died. The time interval from collapse to arrival at the emergency department in discharged patients and patients who went to the intensive care unit was shorter than that of patients who died in the emergency department with and without ROSC. CONCLUSIONS We cannot decide to give up and terminate resuscitation in any PT-CPA patients and cannot define salvageable patients. However, our data show that 30-min resuscitation is thought to be relevant and that we should not give up on resuscitation because of the time interval without ROSC after arrival at the hospital.

Moriwaki, Yoshihiro; Sugiyama, Mitsugi; Toyoda, Hiroshi; Kosuge, Takayuki; Tahara, Yoshio; Suzuki, Noriyuki

2010-01-01

387

NASA Dual Precipitation Radar Arrives at Goddard  

NASA Video Gallery

The Dual-frequency Precipitation Radar (DPR) built by the Japan Aerospace Exploration Agency (JAXA) for the Global Precipitation Measurement (GPM) mission's Core Observatory arrived on Friday, March 16 and was unloaded today at NASA's Goddard Space Flight Center, Greenbelt, Md. Comprised of two radars, the DPR is one of two instruments that will fly on the Core Observatory.

gsfcvideo

2012-03-20

388

Magnitude determination using initial P waves for Cascadia Subduction Zone in Canada's west cost  

NASA Astrophysics Data System (ADS)

The critical goal of earthquake early warning (EEW) is determining the overall size of an earthquake and the expected strong ground motion from the first few seconds of the P wave. We explore a practical approach to earthquake early warning in the Cascadia subduction zone in Canada's west coast by determining earthquake early warning parameter ?c from the initial 3 s of the P waveforms recorded at the National Resource Canada (NRCan) seismic network stations for earthquakes with M > 4.0 We selected 75 earthquakes with that has been recorded during 1986-2010 by Seismic Network stations in the region operated by NRCan. The vertical components of earthquakes signals were converted to ground velocity and displacement. The displacements are filtered with a one-way Butterworth high-pass filter with a cut-off frequency of 0.075 Hz. From the vertical components, ?c is computed. We found the relationship between ?c and magnitude (M) for this region, therefore earthquake size, can be estimated using only with 3 of seconds of signal from the P wave while the rupture itself is still propagating and final dimension of rupture is far from complete.

Eshaghi, A.; Tiampo, K. F.

2010-12-01

389

The effect of diabetic autonomic neuropathy on P-wave duration, dispersion and atrial fibrillation  

PubMed Central

Introduction Atrial fibrillation (AF) is the most common sustained arrhythmia. Diabetic autonomic neuropathy (DAN) is a frequent complication of diabetes mellitus and has a negative impact on the cardiovascular system. There are no data about the occurrence of paroxysmal atrial fibrillation (PAF) in the population with DAN. Material and methods We analysed the data of 100 patients with PAF. The study population was divided into three groups: group I: 28 patients with diabetes mellitus (DM) and DAN, group II: 34 patients with DM without DAN, and group III: 38 patients without DM. P-wave duration (FPD) and dispersion (PWD) were measured during sinus rhythm and AF episodes were counted during 12 months of follow-up. Results Recurrence of PAF was higher in group I (47 episodes/year) compared to groups II and III (26 and 22 episodes/year) – p<0.01. The FPD was longer in group I (137.4 ±12.0 ms vs. 126 ±23.0 ms in II group and 129 ±18.3 ms in group III; p<0.001). The PWD was longer in patients with DAN (53 ±19 ms vs. 36 ±18 ms and 34 ± 20 ms, p<0.001). Conclusions The results showed that the presence of DAN caused a significant increase in P-wave duration and dispersion, which might be responsible for the recurrence of AF.

Bissinger, Andrzej; Grycewicz, Tomasz; Grabowicz, Wlodzimierz; Lubinski, Andrzej

2011-01-01

390

The opposite polarity of the PQ segment compared to the P wave isointegral maps.  

PubMed

The aim of our work was to study the opposite polarity of the PQ segment to the P wave body surface potential maps in different groups of patients. We constructed isointegral maps (IIM) in 26 healthy controls (C), 16 hypertensives (HT), 26 patients with arterial hypertension and left ventricular hypertrophy (LVH) and 15 patients with myocardial infarction (MI). We analyzed values and positions of map extrema and compared the polarity of maps using the correlation coefficient. The IIM P maxima appeared mainly over the precordium, the minima mainly in the right subclavicular area. The highest maxima were in the MI group, being significantly higher than in the HT and LVH groups. No differences concerning any values of other extrema were significant. The IIM PQ maxima were distributed over the upper half of the chest; the minima mainly over the middle sternum. A statistically significant opposite polarity between the IIM P and IIM PQ was found in 80 % of cases. The opposite polarity of the P wave and the PQ segment was proved in isointegral body surface maps. The extrema occurred in areas not examined by the standard chest leads. This has to be considered for diagnostic purposes. PMID:21812513

Kozlíková, K; Martinka, J; Murín, J; Bulas, J

2011-08-01

391

Component azimuths of the CEArray stations estimated from P-wave particle motion  

NASA Astrophysics Data System (ADS)

The recently built China Digital Seismic Network consists of the China National Digital Seismic Network (CNDSN), 31 regional seismic networks and several small aperture arrays with more than 1 000 stations including 850+ broadband stations. It forms a gigantic seismic array that provides an unprecedented opportunity to study the Earth's deep interior besides its routine task of seismic monitoring. Many modern seismic studies rely on rotation of vertical and horizontal components in order to separate different types of seismic waves. Knowledge of the orientations of the two horizontal components thus is important to perform a correction rotation. We analyzed particle motions of teleseismic P waves recorded by the network and used them to estimate the north-component azimuth of each station. An SNR-weighted-multi-event method was introduced to obtain component azimuths that best explain the P-wave particle motions of all the events recorded at a station. The method provides robust estimates including a measurement error calculated from background noise levels. We found that about one third of the stations have some sort of problems, including misorientation of the two horizontal components, mislabeling and polarity reversal in one or more components. These problems need to be taken into account for any rotation based seismic studies.

Niu, Fenglin; Li, Juan

2011-02-01

392

P-Wave to Rayleigh-wave conversion coefficients for wedge corners; model experiments  

USGS Publications Warehouse

An analytic solution is not available for the diffraction of elastic waves by wedges; however, numerical solutions of finite-difference type are available for selected wedge angles. The P- to Rayleigh-wave conversion coefficients at wedge tips have been measured on two-dimensional seismic models for stress-free wedges with wedge angles, ??0, of 10, 30, 60, 90 and 120??. The conversion coefficients show two broad peaks and a minimum as a function of the angle between the wedge face and the direction of the incident P-wave. The minimum occurs for the P wave incident parallel to the wedge face and one maximum is near an incidence angle of 90?? to the wedge face. The amplitude of this maximum, relative to the other, decreases as the wedge angle increases. The asymmetry of the conversion coefficients, CPR(??; ??0), relative to parallel incidence (?? = 0) increases as the wedge angle increases. The locations of the maxima and the minimum as well as the asymmetry can be explained qualitatively. The conversion coefficients are measured with an accuracy of ??5% in those regions where there are no interfering waves. A comparison of the data for the 10?? wedge with the theoretical results for a half plane (0?? wedge) shows good correlation. ?? 1978.

Gangi, A. F.; Wesson, R. L.

1978-01-01

393

Experimental study on p-wave neutron strength functions for light nuclei  

NASA Astrophysics Data System (ADS)

Broad energy distributions in fast neutron beams have been achieved by appropriate filtering of the236U fission radiation provided from the RENT converter facility at the FRM research reactor. Transmission measurements in such beams result in average cross sections to which resonance reactions and shape elastic scattering contribute. We used a silicon (124.5 cm) filtered beam with a median energy of 143 keV (width 20 keV) and beams with 1.3 MeV (0.55 to 3 MeV) and 2.1 MeV (1 to 5.5 MeV) obtained through different filter combinations of lead and polyethylene. The relative high energies and the broad spectra made it possible to determine experimentally the contributions of s- and p-wave resonance reactions to the average cross section even for light nuclei. Using the three different beams we determined the average cross sections for the elements in the mass region A=9 to 65. Analysing the measured cross sections by means of the R matrix formalism provided a complete set of p-wave strength functions and distant level parameters. Moreover, single particle shell effects in the cross sections were observed. In conclusion we obtained informations on the 2 P and the 3 S size resonances and about the validity of the optical model for neutron reactions with light nuclei.

Koester, L.; Waschkowski, W.; Meier, J.; Rau, G.; Salehi, M.

1988-12-01

394

Controlling arrival for the machine repair problem with switching failure  

NASA Astrophysics Data System (ADS)

This study investigates the warm-standby machine repair problem which involves a controlling arrival policy and switching failure probability. It involves operating machines with S warm standbys and one single server. The failure times and repair times are assumed to follow an exponential distribution. For such system, some system performance measures are derived and a steady-state expected cost function per unit time is developed. By using Quasi-Newton method followed direct search method, we can find the joint optimal parameter values at maximum profit such that the availability constraint is satisfied.

Chang, Fu-Min; Ke, Jau-Chuan; Liou, Cheng-Hwai

2013-02-01

395

Evaluating predictions of ICME arrival at Earth and Mars  

NASA Astrophysics Data System (ADS)

We present a study of interplanetary coronal mass ejection (ICME) propagation to Earth and Mars. Because of the significant space weather hazard posed by ICMEs, understanding and predicting their arrival and impact at Mars is important for current and future robotic and manned missions to the planet. We compare running ENLILv2.6 with coronal mass ejection (CME) input parameters from both a manual and an automated method. We analyze shock events identified at Mars in Mars Global Surveyor data in 2001 and 2003, when Earth and Mars were separated by <80° in heliocentric longitude. The shocks identified at Mars were also identified at Earth, and the majority of the shock sources were identified through the Solar and Heliospheric Observatory-Large Angle and Spectrometric Coronagraph catalogue. We find that arrival times predicted by the two methods at both planets are statistically similar, dynamic pressures predicted when using the automated method are better, and the automated method tends to underestimate both CME width and speed. Using the location of the related flare as the CME direction did not improve results. In addition, changing the CME speed toward the plane-of-sky speed at 20 RS improves the match to observations, mainly because the speed found by the automated method is underestimated. The time lapse between the shock arrival at Earth and Mars, for the events studied here, is shorter than expected from simulations, and the presence of high speed streams can enable an ICME to arrive almost simultaneously at Earth and Mars. This work will be applied to improve the input parameter methods for ENLIL.

Falkenberg, T. V.; Taktakishvili, A.; Pulkkinen, A.; Vennerstrom, S.; Odstrcil, D.; Brain, D.; Delory, G.; Mitchell, D.

2011-09-01

396

Isotopic identification of the parity-violating neutron p-wave resonance at energy E0=3.2 eV in Xe  

Microsoft Academic Search

Two-dimensional pulse height and time-of-flight (TOF) spectra were measured at the IBR-30 pulsed neutron source to make the isotopic identification of the parity-violating p-wave resonance at E0=3.2 eV recently observed in Xe. Analysis of the TOF spectra corresponding to the characteristic low-energy gamma-rays established the 131Xe isotope as the origin of the 3.2-eV resonance. This new finding poses a challenge

V. R. Skoy; E. I. Sharapov; N. A. Gundorin; Yu. P. Popov; Yu. V. Prokofichev; N. R. Roberson; G. E. Mitchell

1996-01-01

397

Isotopic identification of the parity-violating neutron {ital p}-wave resonance at energy {ital E}â=3.2 eV in Xe  

Microsoft Academic Search

Two-dimensional pulse height and time-of-flight (TOF) spectra were measured at the IBR-30 pulsed neutron source to make the isotopic identification of the parity-violating {ital p}-wave resonance at {ital E}â=3.2 eV recently observed in Xe. Analysis of the TOF spectra corresponding to the characteristic low-energy gamma-rays established the ¹³¹Xe isotope as the origin of the 3.2-eV resonance. This new finding poses

V. R. Skoy; E. I. Sharapov; N. A. Gundorin; Y. P. Popov; Y. V. Prokofichev; N. R. Roberson; G. E. Mitchell

1996-01-01

398

Time-resolved velocity tomography at Mount Etna (Italy) volcano during 2000-2008  

NASA Astrophysics Data System (ADS)

The continuous volcanic and seismic activity at Mount Etna makes this volcano an important laboratory for seismological and geophysical studies. We used repeated three-dimensional tomography (4D tomography) to detect variations in elastic parameters during different volcanic cycles in the period November 2000-May 2008, that includes several flank eruptions. The use of a large number of permanent seismic stations and the abundance of local earthquakes, occurring both before and during the eruptions, guarantee consistent and high-resolution velocity models. First, we performed a tomographic inversion of the whole data set to define the 3D P-wave velocity (VP) and the structure of the P- to S-wave velocity ratio (VP/VS). A total of ca. 3,000 well constrained earthquakes (root mean square time residuals ? 0.4 s; horizontal and vertical hypocentral location errors ? 1.5 km; azimuthal gap of the stations ? 180°), ca. 40,000 P-wave arrivals, and ca. 9,000 S-wave arrivals were inverted to model a grid, 2 km by 2 km by 1 km spaced, with the use of SIMULPS-14 software. Then, on the basis of geophysical and geochemical observations indicating some cyclic recharging and discharging (eruptions) phases, we inverted different sub-periods to investigate time variations in the elastic parameters. The observed time changes of velocity-oriented anomalies suggest that four-dimensional tomography could provide a basis for more efficient volcano monitoring and short- and midterm eruption forecasting.

Barberi, G.; Cocina, O.; Chiarabba, C.; De Gori, P.; Patane', D.

2012-04-01

399

Tunneling conductance in topological insulator ferromagnet/p-wave superconductor junctions  

NASA Astrophysics Data System (ADS)

The tunneling conductance in topological insulator (TI) ferromagnet/p-wave superconductor (FM/pS) junction is studied based on the Blonder-Tinkham-Klapwijk (BTK) theory. The Fermi energy mismatch between FM and pS as well as the finite quasiparticle lifetime are considered. Three kinds of pairings px, py, and px+ipy-waves for pS are chosen. It is found that the spectrum strongly depend on the magnetic gap, the gate potential, the quasiparticle lifetime as well as the type of the pair potential symmetry. The pair potential symmetry drastically affects the formation of the zero-energy bound states dependent on the magneto effect or the Fermi energy mismatch effect. The finite quasiparticle lifetime effect can suppress the Andreev resonant scattering process at eV=?0 and smear the dips in the conductance.

Li, Hong; Yang, Xinjian

2012-09-01

400

Hyperfine structure of S- and P-wave states in muonic-helium ion  

SciTech Connect

Corrections of order {alpha}{sup 5} and {alpha}{sup 6} to the hyperfine structure of S- and P-wave energy levels of the muonic-helium ion are calculated. Electron-vacuum-polarization effects, corrections for the nuclear structure, and recoil effects are taken into account. The numerical values obtained for respective hyperfine splitting, -1334.73 meV (1S), -166.64 meV (2S), -58 712.90 {mu}eV (2P{sub 1/2}), and -24 290.69 {mu}eV (2P{sub 3/2}), can be viewed as a reliable estimate for a comparison with experimental data, and the hyperfine-structure interval of {Delta}{sub 12} = 8{Delta}E{sup hfs}(2S) - {Delta}E{sup hfs}(1S) = 1.59 meV can be used to test QED predictions.

Martynenko, A. P., E-mail: mart@ssu.samara.ru; Elekina, E. N. [Samara State University (Russian Federation)

2010-12-15

401

Three-Body Bound States in Atomic Mixtures With Resonant p-Wave Interaction  

NASA Astrophysics Data System (ADS)

We employ the Born-Oppenheimer approximation to find the effective potential in a three-body system consisting of a light particle and two heavy ones when the heavy-light short-range interaction potential has a resonance corresponding to a nonzero orbital angular momentum. In the case of an exact resonance in the p-wave scattering amplitude, the effective potential is attractive and long range; namely, it decreases as the third power of the interatomic distance. Moreover, we show that the range and power of the potential, as well as the number of bound states, are determined by the mass ratio of the particles and the parameters of the heavy-light short-range potential.

Efremov, Maxim A.; Plimak, Lev; Ivanov, Misha Yu.; Schleich, Wolfgang P.

2013-09-01

402

Three-Body Bound States in Atomic Mixtures With Resonant p-Wave Interaction.  

PubMed

We employ the Born-Oppenheimer approximation to find the effective potential in a three-body system consisting of a light particle and two heavy ones when the heavy-light short-range interaction potential has a resonance corresponding to a nonzero orbital angular momentum. In the case of an exact resonance in the p-wave scattering amplitude, the effective potential is attractive and long range; namely, it decreases as the third power of the interatomic distance. Moreover, we show that the range and power of the potential, as well as the number of bound states, are determined by the mass ratio of the particles and the parameters of the heavy-light short-range potential. PMID:24074084

Efremov, Maxim A; Plimak, Lev; Ivanov, Misha Yu; Schleich, Wolfgang P

2013-09-10

403

Study of light-cone distribution amplitudes for p-wave heavy mesons  

NASA Astrophysics Data System (ADS)

In this paper, a study of light-cone distribution amplitudes for p-wave heavy mesons is presented in both general and heavy quark frameworks. Within the light-front approach, the leading twist light-cone distribution amplitudes, ?M(u) and their relevant decay constants of heavy scalar, axial-vector, and tensor mesons, fM, are formulated. The relations of some decay constants can be simplified when the heavy quark limit is taken into account. After fixing the parameters which appear in a Gaussian wave function, the corresponding decay constants are calculated and compared with those of other theoretical approaches. The curves and the first six ? moments of ?M(u) are plotted and estimated. These results all endorse the requirements of heavy quark symmetry.

Hwang, Chien-Wen

2012-11-01

404

Engineering p-wave interactions in ultracold atoms using nanoplasmonic traps  

NASA Astrophysics Data System (ADS)

Engineering strong p-wave interactions between fermions is one of the challenges in modern quantum physics. Such interactions are responsible for a plethora of fascinating quantum phenomena, such as topological quantum liquids and exotic superconductors. Here we propose a method to generate these fermionic interactions by combining recent developments in nanoplasmonics with progress in realizing laser-induced gauge fields. Nanoplasmonics allows for strong confinement, leading to a geometric resonance in the atom-atom scattering. In combination with the laser coupling of the atomic states, this is shown to result in the desired interaction. We illustrate how this scheme can be used for the stabilization of strongly correlated fractional quantum Hall states in ultracold fermionic gases.

Juliá-Díaz, B.; Graß, T.; Dutta, O.; Chang, D. E.; Lewenstein, M.

2013-07-01

405

Low-energy S- and P-wave Positronium-Hydrogen Collisions  

NASA Astrophysics Data System (ADS)

Positronium-atom scattering is of experimental interest. We have investigated low-energy positronium-hydrogen scattering, a fundamental four-body Coulomb process. We computed the S- and P-wave phase shifts using a number of variants of the Kohn variational method. For the S-wave, we implemented various techniques to overcome linear dependence problems. Our results compare favorably with earlier Kohn variational calculations [1]. We determined the S-wave scattering length and effective range using a quantum defect theory for the van der Waals interaction [2]. [4pt] [1] P. Van Reeth and J. W. Humberston, J. Phys. B 36, 1923 (2003), Nucl. Intrum. and Methods Phys. Res. B 221, 140 (2004).[0pt] [2] Bo Gao, Phys. Rev. A 58, 4222 (1998).

Woods, Denton; Ward, S. J.; van Reeth, P.

2012-06-01

406

Regional difference in small-scale heterogeneities in the crust and upper mantle in Japan derived by the analysis of high-frequency P-wave  

NASA Astrophysics Data System (ADS)

In order to understand distribution properties of small-scale heterogeneities in the crust and upper mantle structure, we analyze three-component seismograms recorded by Hi-net in Japan. We examined relative strength of the P-wave in the transverse (T) component and its change as a function of frequency and propagation distances, which is strongly relating to the strength of seismic wave scattering in the lithosphere. We analyzed 53,220 Hi-net record from 310 shallow (h<30km) crustal earthquakes with MJMA =2.0-5.3. The three-component seismograms are firstly applied by band-pass filter with pass band frequency of f=1-2, 2-4, 4-8, 8-16, 16-32 Hz and then the Hilbert transform is used to synthesize envelope of each component. Then, the energy partition (EP) of P wave in the T component relative to total P-wave energy is evaluated around the P wave in 3-sec time window. The estimated EP value is almost constant 0.2 in high-frequencies (8-16 Hz) at shorter distance, while it is 0.07 in low-frequencies (1-2 Hz). We found clearly frequency-change property of EP value. But at larger distance over 150 km, EP values gradually increase with increasing distance. In high-frequencies (8-16, 16-32 Hz), especially EP values asymptotically reach from 0.2 to 0.33, equi-partitioning of P-wave energy into three components. This may because Pn-phase dominates in larger hypocentral distances. In order to examine difference in the EP in each area of Japan which would be relating to the strength of crustal heterogeneities in each area we divided the area of Japan into three regions, fore-arc side of Tohoku, back-arc side of Tohoku and Chugoku-Shikoku area. The difference in EP value in each area is clearly found in the high-frequency (4-8 Hz) band, where larger EP (0.2) was obtained at back-arc side of Tohoku relative to smaller EP (0.1) at fore-arc side of Tohoku and Chugoku-Shikoku. This is consistent with the results of Carcole and Sato (2009) who estimated the strength of crustal heterogeneities based on the multi lapse time-window analysis. In order to clarify the cause of such regional difference of EP, we conduct 3-D FDM simulations using stochastic random media. The model covers a zone 204.8 km by 204.8 km by 64.0 km descretized with 0.1 km in horizontal direction and 0.05 km in vertical direction. The small-scale heterogeneity in the lithosphere is constructed by velocity fluctuation from average velocity. The fluctuation is characterized by von Karman-type ACF with the correlation length a, the rms value e and decay order k. We assume average background velocities of P-wave and S-wave are VP = 5.8 km and VS = 3.36 km, respectively. We employ an explosive point source into the model. The FDM simulations were conducted on the Earth Simulator at JAMSTEC. We conducted a number of FDM simulation using different model parameters of stochastic random media for different e (= 0.03, 0.05, 0.07, 0.09) and fixed a and k (a = 5km, k = 0.5). The simulation results confirm EP value increases linearly with increasing e. We also found that larger EP obtained in the back-arc side of Tohoku can be explained by 4% larger e relative to those of other regions.

Takemura, S.; Furumura, T.

2010-12-01

407

P-wave Tomographic Image Across the Central Transverse Ranges Region From Inversion of Local Earthquake and Active Source Data, Southern California  

NASA Astrophysics Data System (ADS)

The central Transverse Ranges region is considered as a place that has documented significant evidence of tectonic history of southern California. To investigate such a region associated with extensive Cenozoic tectonic activities, we apply a new deformable-layer tomography approach to determine layers of varying thickness as a direct product of tomographic imaging. 1,546 P-wave first arrival data from local earthquakes and 10,869 from active shots of Los Angles Regional Seismic Experiment (LARSE) I have been used together to invert the velocity structure along a northeastern trending 2-D profile across the Central Transverse Ranges region. The combined data result in highly dense ray path distribution, especially within the upper crust. In addition, Moho depths from previous study have been incorporated into the inversion to improve solving the model in the deep and sparsely sampled areas. The tomographic inversion procedure implemented in this study is as follows: first, a long wavelength model is constructed by inverting local earthquake arrivals only with sparse Moho constraints; second, this tomographic model is refined by adding surface seismic arrivals and introducing lateral velocity variations within layers. Along the profile, our tomographic image shows high resolution, detailed near-surface geological features besides those long-wavelength features resolved in the previous studies. The existence of the San Andreas Fault is clearly evidenced, which is characterized by a vertical low-velocity zone to at least 20-km depth. The sedimentary basin boundaries are observed unconformably lying above the high velocity basement. Near the northern edge of the Los Angeles Basin and southern foothills of the San Gabriel Mountains in the upper crust, the high velocity gradient units on two sides of this high velocity feature represent that the transition from sedimentary rocks to crystalline rocks is abrupt, which could be indicative of the major basin-bounding faults, such as the Whittier fault and the Sierra Madre fault zones. Our new tomographic image represented by both layers and cells has provided new insights across the Central Transverse Ranges region, and the resolution of the tomographic solution has been greatly improved by using local earthquake data and surface seismic data jointly.

Li, L.; Zhou, H.

2007-12-01

408

Application of back-propagation neural networks to identification of seismic arrival types  

NASA Astrophysics Data System (ADS)

A back-propagation neural network (BPNN) approach is developed to identify P- and S-arrivals from three-component recordings of local earthquake data. The BPNN is trained by selecting trace segments of P- and S-waves and noise bursts converted into an attribute space based on the degree of polarization (DOP). After training, the network can automatically identify the type of arrival on earthquake recordings. Compared with manual analysis, a BPNN trained with nine groups of DOP segments can correctly identify 82.3% of the P-arrivals and 62.6% of the S-arrivals from one seismic station, and when trained with five groups from a training dataset selected from another seismic station, it can correctly identify 76.6% of the P-arrivals and 60.5% of S-arrivals. This approach is adaptive and needs only the onset time of arrivals as input, although its performance cannot be improved by simply adding more training datasets due to the complexity of DOP patterns. Our experience suggests that other information or another network may be necessary to improve its performance.

Dai, Hengchang; MacBeth, Colin

1997-05-01

409

Signal averaged P wave compared with standard electrocardiography or echocardiography for prediction of atrial fibrillation after coronary bypass grafting.  

PubMed Central

OBJECTIVE: To define the clinical value of the signal averaged P wave (SAPW) and to compare it with the standard electrocardiogram (ECG), echocardiogram, and clinical assessment for the prediction of atrial fibrillation after coronary bypass grafting (CABG). DESIGN: Prospective validation cohort study. SETTING: Regional cardiothoracic centre. PATIENTS: 201 unselected patients undergoing first elective CABG were recruited over six months. Patients requiring concomitant valve surgery were excluded. MAIN OUTCOME MEASURES: Age, sex, cardiothoracic ratio, and cardioactive drugs were noted. P wave specific SAPW recordings, ECG, and M mode echocardiograms from which left atrial diameter was measured were performed within 24 hours of surgery. Filtered P wave duration (SAPWD), spatial velocity, and energy were calculated from the SAPW. From the ECG, lead II P wave duration, P terminal force in lead V1, total P wave duration, and isoelectric interval were measured. Patients had Holter monitoring for 48 hours postoperatively and daily ECGs until discharge. RESULTS: Two patients died (1%) and 10 were unsuitable for analysis (5%). Of the remaining 189, 51 (27%) had atrial fibrillation (AF) lasting > 1 hour at a mean of 2 (0.5 to 7) days after CABG. Of the variables examined, only SAPWD (AF group 148 (SD 12), v 142 (14) ms, P = 0.008) and male sex (AF group 96%, v 78%, P < 0.01) were significantly different. A prospectively defined SAPWD of > 141 ms predicted atrial fibrillation with positive and negative predictive accuracies of 34% and 83%. Logistic regression analysis identified both male sex and SAPWD as significant independent predictors of postoperative atrial fibrillation. CONCLUSIONS: Signal averaged P wave duration was a better predictor of atrial fibrillation after coronary bypass grafting than standard electrocardiographic or echocardiographic criteria. The predictive value of this test is such that it is likely to be useful in the design of prospective trials of prophylactic antiarrhythmic treatment but is of limited use using current techniques in the clinical management of individual patients.

Stafford, P. J.; Kolvekar, S.; Cooper, J.; Fothergill, J.; Schlindwein, F.; deBono, D. P.; Spyt, T. J.; Garratt, C. J.

1997-01-01

410

Predicted signatures of p-wave superfluid phases and Majorana zero modes of fermionic atoms in rf absorption  

SciTech Connect

We study the superfluid phases of quasi-two-dimensional atomic Fermi gases interacting via a p-wave Feshbach resonance. We calculate the absorption spectra of these phases under a hyperfine transition for both nonrotating and rotating superfluids. We show that one can identify the different phases of the p-wave superfluid from the absorption spectrum. The absorption spectrum shows clear signatures of the existence of Majorana zero modes at the cores of vortices of the weakly pairing p{sub x}+ip{sub y} phase.

Grosfeld, Eytan; Stern, Ady; Ilan, Roni [Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100 (Israel); Cooper, Nigel R. [T.C.M. Group, Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

2007-09-01

411

9 CFR 93.804 - Declaration upon arrival.  

Code of Federal Regulations, 2013 CFR

...CONVEYANCE AND SHIPPING CONTAINERS Elephants, Hippopotami, Rhinoceroses, and Tapirs...Declaration upon arrival. Upon arrival of an elephant, hippopotamus, rhinoceros, or...broker; (g) The region from which the elephant, hippopotamus, rhinoceros, or...

2013-01-01

412

9 CFR 93.804 - Declaration upon arrival.  

Code of Federal Regulations, 2010 CFR

...AND SHIPPING CONTAINERS Elephants, Hippopotami, Rhinoceroses, and Tapirs § 93...arrival. Upon arrival of an elephant, hippopotamus, rhinoceros, or tapir at a port...The region from which the elephant, hippopotamus, rhinoceros, or tapir was...

2009-01-01

413

9 CFR 93.804 - Declaration upon arrival.  

Code of Federal Regulations, 2010 CFR

...CONVEYANCE AND SHIPPING CONTAINERS Elephants, Hippopotami, Rhinoceroses, and Tapirs...Declaration upon arrival. Upon arrival of an elephant, hippopotamus, rhinoceros, or...broker; (g) The region from which the elephant, hippopotamus, rhinoceros, or...

2010-01-01

414

7 CFR 319.75-6 - Arrival notification.  

Code of Federal Regulations, 2013 CFR

...Continued) ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE FOREIGN QUARANTINE NOTICES Khapra Beetle § 319.75-6 Arrival notification. Promptly upon arrival of any restricted article at a port of entry, the...

2013-01-01

415

P-wave monitoring of an unconsolidated and partially saturated porous medium : an experimental study  

NASA Astrophysics Data System (ADS)

Nowadays, it is well admitted that hydrogeological properties of porous media (porosity, fluid saturation and permeability) can influence seismic properties. In geophysics, the major theory which links hydrogeological and seismic parameters is poroelasticity proposed by Biot (1956). The Biot relaxation process is due to the relative displacement of fluid in comparison to the solid which causes a significant attenuation of seismic waves, notably in unconsolidated and highly permeable media. Laboratory experiments are necessary to better understand the effects of fluids on velocity dispersion and attenuation of seismic waves but few ones are done in the low frequency range (1Hz to 10 kHz) where the wavelength is greater than heterogeneities size. In order to analyse the role of partial saturation on direct P-waves phase velocity and attenuation, we performed a laboratory experiment in the kiloHertz range to avoid scale effects between field studies and traditional ultrasonic laboratory measurements. This experiment consists in a sand-filled tank equiped with accelerometers and water capacitance probes, where seismic propagation is generated by hitting a steel ball on a granite plate. Several imbibition/drainage cycles were performed between the water and gas residual saturations. Seismic data were processed by a Continuous Wavelet Transform using the complex Morlet wavelet which was numerically validated using a viscoelastic 2D code for wave propagation (Specfem2D). Phase velocity of direct P-wave decreases with the increase of water content, that is quite consistent with Biot-Gassmann-Wood (BGW) limit of the Biot's theory both for imbibition and drainage. This behaviour indicates that the fluid mixture (gaz and water) can be averaged as an effective fluid, which is typical of field seismic applications. In this experiment, attenuation is very strong and cannot be fully explained by the macroscopic fluid flow of Biot's theory. It is necessary to introduce a viscoelastic contribution linked to the grain to grain overall losses, which are described by a constant Q-model. Moreover, hysteresis between imbibition and drainage are observed and explained by introducing an effective permeability of the mixture depending on water and gas relative permeabilities.

Barriere, J.; Bordes, C.; Sénéchal, P.; Brito, D.; Perroud, H.

2012-04-01

416

High-Resolution P-Wave Tomography at the Global Scale: Multi-Resolution Inversions of an Updated Database  

NASA Astrophysics Data System (ADS)

The teleseismic P-wave travel time database compiled by the International Seismological Centre (ISC), based on records from stations all over the globe, provides the most important constraint to our knowledge of the Earth's mantle P-velocity structure. Bob Engdahl and his co-workers have systematically "reprocessed" ISC data, relocating sources and re-identifying phases by a non-linear algorithm. A few years ago, M. Antolik and his co-workers at Harvard have proved that Engdahl's residuals could be further corrected, after relocating seismic sources with a procedure that accounts for the presence of lateral heterogeneities in the Earth's structure. The database thus compiled by Antolik has been succesfully employed in tomographic modeling studies by authors at Harvard, and a comparison of results from Engdahl's and Antolik's residuals was published in a 2000 JGR article by Boschi and Dziewonski. More than half-a-decade later, the size of Engdahl's database has almost doubled. We apply Antolik's relocation method to the updated travel-time database, and "invert" the resulting set of corrected residuals to find new tomographic images. Do the new images, thus derived, contain more information about the Earth than the ones already found in the literature? We attempt to quantify the improvement in model quality that the new data should grant, conducting tomographic inversions with parameterizations of different nominal resolution, and applying Akaike criterion to determine to what extent a growth in the number of free parameters reflects a growth in the information content of models. We measure the propagation of observation errors into the solution, and the fictitious coupling between model coefficients, computing covariance and resolution matrices associated with the inverse problem in question. We explore the possibility of parameterizing the Earth's mantle with voxel grids of nonuniform density, as a way of by-passing the selection of an "appropriate" value for the regularization (roughness- minimization) parameter.

Boschi, L.; Soldati, G.; Antolik, M.

2006-12-01

417

Ultrasonic P-wave and S-wave attenuation in partially frozen porous material saturated with brine  

NASA Astrophysics Data System (ADS)

Ultrasonic wave transmission measurements were conducted in order to examine the influence of ice-brine coexisting system grown in porous material on ultrasonic P- and S-waves. We observed the variations of a transmitted wave with a frequency content of 150-1000 kHz through a liquid system to a solid-liquid coexistence system, changing its temperature from 20°C to -15°C. We quantitatively estimated attenuation for porous materials with two different porosities (37.3 and 48.2 %) during the freezing of salty water in porous material by considering different distances between the source and receiver transducers. This paper is concerned with attenuation at ultrasonic frequencies of 500-1000 kHz for P-waves and 100-400 kHz for S-waves. The waveform analyses indicate that the attenuation curves reach their peak at a temperature of -3°C and gradually decrease with decreasing temperature. We found a positive correlation between the attenuation of ultrasonic waves and the existence of unfrozen brine estimated by the pulsed nuclear magnetic resonance (NMR) technique. Thus, the laboratory experiments of the present study demonstrated that ultrasonic waves with such a frequency range are significantly affected by the existence of a solid-liquid coexistence system in the porous material. In terms of a plausible mechanism for attenuation, we must consider the physical interactions between pore fluid and ice, that is, the pore microstructure and permeability in such system is important.