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Sample records for active geodetic network

  1. VERA Geodetic Activities

    NASA Technical Reports Server (NTRS)

    Jike, Takaaki; Tamura, Yoshiaki; Shizugami, Makoto

    2013-01-01

    This report briefly describes the geodetic activities of VERA in the year 2012. The regular geodetic observations are carried out both in K- and S/X-bands. The frequency of regular observations is three times a month-twice for the VERA internal observations in K-band. The networks of the S/X sessions are JADE of GSI and IVS-T2. The raw data of the T2 and JADE sessions are electronically transferred to the Bonn, Haystack, and GSI correlators via Internet. Gravimetric observations are carried out at the VERA stations. An SG was installed at Mizusawa and placed in the vicinity of the VERA antenna in order to monitor vertical displacement at the end of 2008, and the observations continued throughout the year. Also at the VERA-Ishigakijima station, continuous operation of the SG started in 2012. The crustal movements generated by the 2011 earthquake off the Pacific coast of Tohoku continued during 2012, and displacement of the VERA-Mizusawa position by post-seismic creeping continued.

  2. Geodetic Network Design and Optimization on the Active Tuzla Fault (Izmir, Turkey) for Disaster Management

    PubMed Central

    Halicioglu, Kerem; Ozener, Haluk

    2008-01-01

    Both seismological and geodynamic research emphasize that the Aegean Region, which comprises the Hellenic Arc, the Greek mainland and Western Turkey is the most seismically active region in Western Eurasia. The convergence of the Eurasian and African lithospheric plates forces a westward motion on the Anatolian plate relative to the Eurasian one. Western Anatolia is a valuable laboratory for Earth Science research because of its complex geological structure. Izmir is a large city in Turkey with a population of about 2.5 million that is at great risk from big earthquakes. Unfortunately, previous geodynamics studies performed in this region are insufficient or cover large areas instead of specific faults. The Tuzla Fault, which is aligned trending NE–SW between the town of Menderes and Cape Doganbey, is an important fault in terms of seismic activity and its proximity to the city of Izmir. This study aims to perform a large scale investigation focusing on the Tuzla Fault and its vicinity for better understanding of the region's tectonics. In order to investigate the crustal deformation along the Tuzla Fault and Izmir Bay, a geodetic network has been designed and optimizations were performed. This paper suggests a schedule for a crustal deformation monitoring study which includes research on the tectonics of the region, network design and optimization strategies, theory and practice of processing. The study is also open for extension in terms of monitoring different types of fault characteristics. A one-dimensional fault model with two parameters – standard strike-slip model of dislocation theory in an elastic half-space – is formulated in order to determine which sites are suitable for the campaign based geodetic GPS measurements. Geodetic results can be used as a background data for disaster management systems. PMID:27873783

  3. Geodetic Network Design and Optimization on the Active Tuzla Fault (Izmir, Turkey) for Disaster Management.

    PubMed

    Halicioglu, Kerem; Ozener, Haluk

    2008-08-19

    Both seismological and geodynamic research emphasize that the Aegean Region, which comprises the Hellenic Arc, the Greek mainland and Western Turkey is the most seismically active region in Western Eurasia. The convergence of the Eurasian and African lithospheric plates forces a westward motion on the Anatolian plate relative to the Eurasian one. Western Anatolia is a valuable laboratory for Earth Science research because of its complex geological structure. Izmir is a large city in Turkey with a population of about 2.5 million that is at great risk from big earthquakes. Unfortunately, previous geodynamics studies performed in this region are insufficient or cover large areas instead of specific faults. The Tuzla Fault, which is aligned trending NE-SW between the town of Menderes and Cape Doganbey, is an important fault in terms of seismic activity and its proximity to the city of Izmir. This study aims to perform a large scale investigation focusing on the Tuzla Fault and its vicinity for better understanding of the region's tectonics. In order to investigate the crustal deformation along the Tuzla Fault and Izmir Bay, a geodetic network has been designed and optimizations were performed. This paper suggests a schedule for a crustal deformation monitoring study which includes research on the tectonics of the region, network design and optimization strategies, theory and practice of processing. The study is also open for extension in terms of monitoring different types of fault characteristics. A one-dimensional fault model with two parameters - standard strike-slip model of dislocation theory in an elastic half-space - is formulated in order to determine which sites are suitable for the campaign based geodetic GPS measurements. Geodetic results can be used as a background data for disaster management systems.

  4. Observing active deformation of volcanoes in North America: Geodetic data from the Plate Boundary Observatory and associated networks

    NASA Astrophysics Data System (ADS)

    Puskas, C. M.; Phillips, D. A.; Mattioli, G. S.; Meertens, C. M.; Hodgkinson, K. M.; Crosby, C. J.; Enders, M.; Feaux, K.; Mencin, D.; Baker, S.; Lisowski, M.; Smith, R. B.

    2013-12-01

    The EarthScope Plate Boundary Observatory (PBO), operated by UNAVCO, records deformation of the geologically diverse North America western plate boundary, with subnetworks of instruments concentrated at selected active and potentially active volcanoes. These sensors record deformation and earthquakes and allow monitoring agencies and researchers to analyze changes in ground motion and seismicity. The intraplate volcanoes at Yellowstone and Long Valley are characterized by uplift/subsidence cycles, high seismicity, and hydrothermal activity but there have been no historic eruptions at either volcano. PBO maintains dense GPS networks of 20-25 stations at each of these volcanoes, with an additional 5 boreholes at Yellowstone containing tensor strainmeters, short-period seismometers, and borehole tiltmeters. Subduction zone volcanoes in the Aleutian Arc have had multiple historic eruptions, and PBO maintains equipment at Augustine (8 GPS), Akutan (8 GPS, 4 tiltmeters), and Unimak Island (14 GPS, 8 tiltmeters). The Unimak stations are at the active Westdahl and Shishaldin edifices and the nearby, inactive Isanotski volcano. In the Cascade Arc, PBO maintains networks at Mount St. Helens (15 GPS, 4 borehole strainmeters and seismometers, 8 borehole tiltmeters), Shasta (7 GPS, 1 borehole strainmeter and seismometer), and Lassen Peak (8 GPS). Data from many of these stations in the Pacific Northwest and California are also provided as realtime streams of raw and processed data. Real-time GPS data, along with high-rate GPS data, will be an important new resource for detecting and studying future rapid volcanic deformation events and earthquakes. UNAVCO works closely with the USGS Volcano Hazards Program, archiving data from USGS GPS stations in Alaska, Cascadia, and Long Valley. The PBO and USGS networks combined provide more comprehensive coverage than PBO alone, particularly of the Cascade Arc, where the USGS maintains a multiple instruments near each volcano. Ground

  5. Geodetic Network For Crustal Deformation Control of Northernvictoria Land (antarctica)

    NASA Astrophysics Data System (ADS)

    Capra, A.; Bitelli, G.; Gandolfi, S.; Mancini, F.; Sarti, P.; Vittuari, L.

    VLNDEF (Victoria Land Network for DEFormation control) project started in 1999 with the aim to measure a network for the study of regional geodynamics of northern Victoria Land. In 1999-2000 and 2000-01 italian expeditions, a network of 25 stations with an average distance of 70 km covering the area from Terra Nova Bay, italian sta- tion in Antarctica, to the northern Oates Coast on Pacific ocean, about 700 km long and about 300 km large, was established and surveyed. The network design and stations location were based on principal faults of the area pointed out by most recent tecton- ics studies. The research activity is made within GIANT (Geodetic Infrastructure of ANTarctica) program and ANTEC (ANtarctic neoTECtonics) Group of Specialists of SCAR (Scientific Committee on Antarctic Research).The network coordinates are de- fined in most recent ITRF 2000 system through the emanation from GPS permanent station TNB1. TNB1 was included in SCAR GPS Epoch measurements campaigns and, consequently, connected to IGS network in 2000. VLNDEF includes the first italian reference network about 5000 square km around Terra Nova Bay, and a small network for Mt.Melbourne volcano monitoring. The reference network was surveyed three time, while the detail network was surveyed five time. The data were processed with different software, more recently with Bernese and Gipsy. The processing results and a preliminary approach for deformation analysis are presented.

  6. Free geometric adjustment of the DOC/DOD cooperative worldwide geodetic satellite (BC-4) network

    NASA Technical Reports Server (NTRS)

    Reilly, J. P.; Kumar, M.; Mueller, I. I.; Saxena, N.

    1973-01-01

    The application of observations from the ANNA satellite to solve geodetic problems is discussed. The establishment of a worldwide network of optical observing stations by the National Geodetic Survey is reported. The geodetic network is composed of 49 observing stations, more or less evenly distributed throughout the world. A method for using correlated satellite observations for the accurate recovery of ground station positions and applying the result to the adjustment of the National Geodetic Survey worldwide network was developed.

  7. LIBRA: An inexpensive geodetic network densification system

    NASA Technical Reports Server (NTRS)

    Fliegel, H. F.; Gantsweg, M.; Callahan, P. S.

    1975-01-01

    A description is given of the Libra (Locations Interposed by Ranging Aircraft) system, by which geodesy and earth strain measurements can be performed rapidly and inexpensively to several hundred auxiliary points with respect to a few fundamental control points established by any other technique, such as radio interferometry or satellite ranging. This low-cost means of extending the accuracy of space age geodesy to local surveys provides speed and spatial resolution useful, for example, for earthquake hazards estimation. Libra may be combined with an existing system, Aries (Astronomical Radio Interferometric Earth Surveying) to provide a balanced system adequate to meet the geophysical needs, and applicable to conventional surveying. The basic hardware design was outlined and specifications were defined. Then need for network densification was described. The following activities required to implement the proposed Libra system are also described: hardware development, data reduction, tropospheric calibrations, schedule of development and estimated costs.

  8. The International Global Network of Geodetic Fiducial Stations

    NASA Technical Reports Server (NTRS)

    LaBrecque, John

    2004-01-01

    Scientific need and technological opportunity require that we move toward implementing a global network of geodetic fiducial stations which feature co-located SLR, VLBI, GNSS, and DORIS instrumentation. Earth science of the next decade will require more accurate global change measurements of sea level topography, sea level change, polar ice mass balance, hydrological and atmospheric mass flux. and topographic deformation, real time mm scale navigation and precision time transfer on a global scale. These scientific requirements have been translated into a goal of mm scale annual stability for the terrestrial reference frame, earth orientation parameters, as well as the orbit and clock determinations tbr the GNSS systems. To meet these challenges, the four geodetic observing systems must be more tightly integrated in technology, location, and analysis. NASA strongly supports the objectives of the IGGOS initiative vis NASA's National Geodetic Observatory and INDIGO programs. The Global networks of GNSS, SLR. and VLBI observatories are for the most part poorly suited for these new demands. These important geodetic networks have evolved with little planning yet these systems are providing essential measurements to a wide swath of society. New signal structures in the GPS and the developing Galileo GNSS will soon require replacement of the GNSS receivers. The SLR network is poorly distributed globally, requires labor intensive observations and analysis, and for the most part relies upon antiquated technology. The VLBI observatories utilize large radio telescopes in remote regions that are poorly distributed globally. Co-location of these networks is sparse and co-location errors contribute significantly to the observing error spectrum. Increasing use of the S and X band by commercial and other government services will also contribute to increased observational errors. The time is upon us for an international effort to develop an optimized global geodetic fiducial network

  9. Reference networks (Control surveys). [Geodetic systems for earth crustal movement monitoring

    SciTech Connect

    Strange, W.E.; Zilkoski, D.B. )

    1991-01-01

    Control surveying activities of the National Geodetic Survey are reported for the 1987-1990 time period. The report is divided into two parts: horizontal control and vertical control. Particular attention is given to the North American Datum of 1983, high accuracy reference networks, the Global Positioning System and vertical control, vertical field surveys, and special survey projects. 44 refs.

  10. Australian geodetic VLBI network (AuScope): present and future.

    NASA Astrophysics Data System (ADS)

    Titov, Oleg

    2015-04-01

    The Australian geodetic Very Long Baseline Interferometry (VLBI) array (AuScope) consisting of three new 12-meter radio telescopes in Australia (Hobart, Katherine and Yarragadee), and a correlation facility in Perth that started operations in 2011. The daily positions of the AuScope array are estimated with a precision of a few mm, whereas their daily estimates vary within a range of 20-30 mm on the annual scale. This VLBI network also provides a substantial contribution to the improvement of the Celestial Reference Frame in the southern hemisphere. The plans for extension of the network in collaboration with the New Zealand and South Africa VLBI stations during 2015-2020 are discussed in this presentation.

  11. Designing the Next Generation Global Geodetic Network for GGOS

    NASA Astrophysics Data System (ADS)

    Pavlis, Erricos C.; Kuzmicz-Cieslak, Magdalena; König, Daniel; MacMillan, Daniel S.

    2014-05-01

    The U.S. National Research Council report "Precise Geodetic Infrastructure: National Requirements for a Shared Resource" (2010) recommended that we 'make a long-term commitment to maintain the International Terrestrial Reference Frame (ITRF) to ensure its continuity and stability'. It further determined that to ensure this, a network of about ~30 globally distributed "core" observatories with state of the art equipment was necessary and should be deployed over the next decade or so. The findings were based on simulation studies using conceptual networks where Satellite Laser Ranging (SLR) and Very Long Baseline Interferometry (VLBI) equipment of the next generation quality were deployed and operated 24/7. Since then, GGOS—the Global Geodetic Observing System, has embarked in an international effort to organize this future network, soliciting contributions from around the world, through an open solicitation "Call for Proposals—CfP". After a critical number of proposals were received, the results were evaluated and a data base was established where the likely sites are ranked in terms of the available equipment, local environment and weather, probability of completion and the relevant date, etc. The renewal process is expected to evolve smoothly over many years, from the current (legacy) state to the next generation ("GGOS-class") equipment. In order to design the optimal distribution of the proposed sites and to determine any gaps in the final network, simulations have been called for again, only this time the site locations are identical to those listed in the compiled data base, and the equipment at each site is in accordance to what is described in the data base for each point in time. The main objective of the simulations addresses the quality of the ITRF product from a network we expect to have in place about five and ten years after the NRC report (2016/2020). A secondary but equally important simulation task is the study of trade-offs when deploying new

  12. Scandinavia studies of recent crustal movements and the space geodetic baseline network

    NASA Technical Reports Server (NTRS)

    Anderson, A. J.

    1980-01-01

    A brief review of crustal movements within the Fenno-Scandia shield is given. Results from postglacial studies, projects for measuring active fault regions, and dynamic ocean loading experiments are presented. The 1979 Scandinavian Doppler Campaign Network is discussed. This network includes Doppler translocation baseline determination of future very long baseline interferometry baselines to be measured in Scandinavia. Intercomparison of earlier Doppler translocation measurements with a high precision terrestrial geodetic baseline in Scandinavia has yielded internal agreement of 6 cm over 887 km. This is a precision of better than 1 part in to the 7th power.

  13. Empirical methods of reducing the observations in geodetic networks

    NASA Astrophysics Data System (ADS)

    Kadaj, Roman

    2016-06-01

    The paper presents empirical methodology of reducing various kinds of observations in geodetic network. A special case of reducing the observation concerns cartographic mapping. For numerical illustration and comparison of methods an application of the conformal Gauss-Krüger mapping was used. Empirical methods are an alternative to the classic differential and multi-stages methods. Numerical benefits concern in particular very long geodesics, created for example by GNSS vectors. In conventional methods the numerical errors of reduction values are significantly dependent on the length of the geodesic. The proposed empirical methods do not have this unfavorable characteristics. Reduction value is determined as a difference (or especially scaled difference) of the corresponding measures of geometric elements (distances, angles), wherein these measures are approximated independently in two spaces based on the known and corresponding approximate coordinates of the network points. Since in the iterative process of the network adjustment, coordinates of the points are systematically improved, approximated reductions also converge to certain optimal values.

  14. Enhanced three-dimensional stochastic adjustment for combined volcano geodetic networks

    NASA Astrophysics Data System (ADS)

    Del Potro, R.; Muller, C.

    2009-12-01

    work we present a first effort to apply this technique to a new volcano geodetic network on Arenal volcano in Costa Rica, using triangulation, EDM and GNSS data from four campaigns. An a priori simulation, later confirmed by field measurements, of the movement detection capacity of different benchmarks within the network, shows how the network design is optimised to detect smaller displacement at the points where these are expected. Data from the four campaigns also proves the repeatability and consistency of the statistical indicators. A preliminary interpretation of the geodetic data relative to Arenal’s volcanic activity could indicate a correlation between displacement velocity and direction with the location and thickness of the recent lava flow field. This then suggests that a deflation caused by the weight of the lava field could be obscuring the effects of possible deep magmatic sources. Although this study is specific to Arenal volcano and its regional tectonic setting, we suggest that the cost-effective, high-quality results we present, prove the methodology’s potential to be incorporated into the design and analysis of volcano geodetic networks worldwide.

  15. Frednet: a continuous gps geodetic network to monitoring crustal deformation in ne Italy

    NASA Astrophysics Data System (ADS)

    Zuliani, D.; Battaglia, M.; Pascutti, D.; Murray, M.; Burgmann, R.; Michelini, A.; Marson, I.

    2003-04-01

    The Friuli Regional Deformation network (FReDNet) of continuously operating Global Positioning System (GPS) receivers monitors crustal deformation in the Friuli area and the northeast boundary of the Adriatic microplate. The Friuli area, located within the active collision zone between Eurasia and the Adriatic block, is characterized by one of the strongest clusters of seismic activity in the Adriatic microplate. Relative motions of the Adriatic block and deformation across the Friuli region are on the order of 5 mm/yr. The principal goals of the FReDNet program are to determine the distribution of deformation in this region and to estimate interseismic strain accumulation on its active faults to better assess seismic hazards. FReDNet is operated by the Centro Ricerche Sismologiche (CRS) of the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (INOGS). We began to install the initial 7 stations of FReDNet in the summer of 2002. To integrate geodetic and seismic data, we plan to co-locate some GPS stations with broadband seismometers maintained by the INOGS. FReDNet is part of a larger program of geodetic monitoring of the Adriatic microplate that includes repeating episodic measurements of geodetic points. The data and experience acquired through the FReDNet program will allow the OGS to monitor hazardous faults for emergency response management, and provide infrastructures for geodetic data management and processing.The raw and RINEX data are imported into the data archive mantained by the INOGS and immediately accessible to members of the GPS community through Internet, both by anonymous FTP and by the World Wide Web (www.crs.inogs.it/frednet).

  16. Extraction of the deterministic ingredient of a dynamic geodetic control network

    NASA Astrophysics Data System (ADS)

    Shahar, L.; Even-Tzur, G.

    2012-01-01

    A minimum constraints solution, which resolves the datum defect of a control network, is an arbitrary solution that may result in a systematic error in the estimation of the deformation parameters. This error is not derived from measurements and is usually inconsistent with the geophysical reality. A free network is affected only by errors of measurement and, therefore, a free network is an accepted way of coping with this problem. Study of deformations, which is based on the use of geodetic measurements, is usually performed today by defining a kinematic model. Such a model, when used to describe a complex geophysical environment, can lead to the partial estimation of the deterministic dynamics, which characterize the entire network. These dynamics are themselves expressed in measurements, as the adjustment systems' residuals. The current paper presents an extension of the definition of the parameters that are revalued. This extension enables the cleaning of measurements by means of the extraction of datum elements that have been defined by geodetic measurement. This cleaning minimizes the effects of these elements on the revaluated deformation. The proposed algorithm may be applied to achieve the simultaneous estimation of the physical parameters that define the geophysical activity in the network.

  17. The rotation period, direction of the north pole, and geodetic control network of Venus

    NASA Technical Reports Server (NTRS)

    Davies, M. E.; Colvin, T. R.; Rogers, P. G.; Chodas, P. W.; Sjogren, W. L.; Akim, E. L.; Stepaniants, V. A.; Vlasova, Z. P.; Zakharov, A. I.

    1992-01-01

    Three related activities that use Magellan data to derive improved estimates of the rotation period and direction of the spin axis of Venus are discussed. These are the computation of the Magellan geodetic control network, the use of measurement landmarks identified in overlapping image strips to improve the spacecraft ephemeris, and the use of common points identified on both the Venera 15/16 and the Magellan images. Since seven years separate the acquisition of the Magellan and Venera images, it should be possible to compute an accurate rotation period and possibly the spin vector of Venus.

  18. Geodetic activities of the Department of Defense under IGY programs

    SciTech Connect

    Williams, O.W.; Daugherty, K.I.

    1983-10-16

    Attention is given to the U.S. Department of Defence (DOD) activities that contributed to the International Geophysical Year's active, passive, and cooperative satellite programs. The DOD continues to support the deployment, enhancement, and application of novel technology in such areas as satellite altimetry, gravity radiometry, inertial surveying, interferometry, airborne gravimetry, inertial surveying, and CCD and laser methods for geodetic astronomy. Also noted are such major department initiatives as the Global Positioning System, which will become operational toward the end of this decade.

  19. GeoNetGIS: a Geodetic Network Geographical Information System to manage GPS networks in seismic and volcanic areas

    NASA Astrophysics Data System (ADS)

    Cristofoletti, P.; Esposito, A.; Anzidei, M.

    2003-04-01

    This paper presents the methodologies and issues involved in the use of GIS techniques to manage geodetic information derived from networks in seismic and volcanic areas. Organization and manipulation of different geodetical, geological and seismic database, give us a new challenge in interpretation of information that has several dimensions, including spatial and temporal variations, also the flexibility and brand range of tools available in GeoNetGIS, make it an attractive platform for earthquake risk assessment. During the last decade the use of geodetic networks based on the Global Positioning System, devoted to geophysical applications, especially for crustal deformation monitoring in seismic and volcanic areas, increased dramatically. The large amount of data provided by these networks, combined with different and independent observations, such as epicentre distribution of recent and historical earthquakes, geological and structural data, photo interpretation of aerial and satellite images, can aid for the detection and parameterization of seismogenic sources. In particular we applied our geodetic oriented GIS to a new GPS network recently set up and surveyed in the Central Apennine region: the CA-GeoNet. GeoNetGIS is designed to analyze in three and four dimensions GPS sources and to improve crustal deformation analysis and interpretation related with tectonic structures and seismicity. It manages many database (DBMS) consisting of different classes, such as Geodesy, Topography, Seismicity, Geology, Geography and Raster Images, administrated according to Thematic Layers. GeoNetGIS represents a powerful research tool allowing to join the analysis of all data layers to integrate the different data base which aid for the identification of the activity of known faults or structures and suggesting the new evidences of active tectonics. A new approach to data integration given by GeoNetGIS capabilities, allow us to create and deliver a wide range of maps, digital

  20. The Central Apennine Geodetic Network (CA - GeoNet): description and preliminary results

    NASA Astrophysics Data System (ADS)

    Anzidei, M.; Galvani, A.; Esposito, A.; Cristofoletti, P.; Pesci, A.; Baldi, P.; Casula, G.; Cenni, N.; Loddo, F.; Serpelloni, E.

    2003-04-01

    During the time span 1999-2002 we set up and surveyed the CA-GeoNet (Central Apennine Geodetic Network), a dense sub-regional GPS network located in one of the highest seismic areas of the Apennines (Italy), with the aim to detect the active strain rate of this sector of the chain, during inter-seismic and co-seismic epochs. The network extends across southern Umbria (Norcia area), Abrutii and southern Latium (Sora area) regions and from the Tyrrhenian to the Adriatic sea, in an area of about 130 km x 180 km. It consists of 130 vertices distributed with an average grid of 5 km over the main seismogenetic and geological structures of the area. The non permanent network is linked with the ASI and INGV permanent GPS stations. Among them, INGR, VVLO, RSTO and AQUI are deployed E-W in this area, allowing an estimation of the current strain rate component normal to the chain, from Tyrrhenian to Adriatic. Site selection was performed after an accurate geological study of the area, with the aim to set up group of stations across the typical basin and ranges seismogenetic structures of the central Apennines, to estimate the strain rate in the near field. To obtain the best accuracy during surveys, the monuments were located on significant outcrops using steel markers screwed in the rock (3D monument) or concrete pillars with deep foundations. Data analysis performed by means of Bernese 4.2 and Gamit software show accuracy at few mm level. In 2002 we re - occupied a set of selected stations across the chain. A preliminary comparison between 1999 and 2002 data for the network shows velocities up to a few mm/yr inferring preliminary items on the active deformation of the area.

  1. Recent Seismic and Geodetic Activity at Multiple Volcanoes in the Ecuadorean Andes

    NASA Astrophysics Data System (ADS)

    Hernandez, S.; Ruiz, M. C.; McCausland, W. A.; Prejean, S. G.; Mothes, P. A.; Bell, A. F.; Hidalgo, S.; Barrington, C.; Yepez, M.; Aguaiza, S.; Plain, M.

    2015-12-01

    The state of volcanic activity often fluctuates between periods of repose and unrest. The transition time between a period of repose and unrest, or vice versa for an open system, can occur within a matter of hours or days. Because of this short time scale, real-time seismic and geodetic (e.g. tiltmeter, GPS) monitoring networks are crucial for characterizing the state of activity of a volcano. In the Ecuadorean Andes, 5 volcanoes demonstrate long-term (Tungurahua, Reventador, and Guagua Pichincha) or recently reactivated (Cotopaxi, Chiles-Cerro Negro) seismic and geodetic activity. The Instituto Geofisico regularly characterizes volcano seismicity into long period, very long period, volcano-tectonic, and tremor events. Significant recent changes at these volcanoes include: rigorous reactivation of glacier-capped Cotopaxi, drumbeat seismicity absent a dome extrusion at Tungurahua, and regularly reoccurring (~7 day recurrence interval), shallow seismic swarms at Guagua Pichincha. These volcanoes locate along both the Western and Eastern Cordillera of the Ecuadorean Andes and, where data are available, manifest important variations in chemical composition, daily gas flux, and surficial deformation. We summarize the long-term geophysical parameters measured at each volcano and place recent changes in each parameter in a larger magmatic and hydrothermal context. All of the studied volcanoes present significant societal hazards to local and regional communities.

  2. The Central Apennine Geodetic Network (CA\\-GeoNet): Description and Preliminary Results

    NASA Astrophysics Data System (ADS)

    Anzidei, M.; Casula, G.; Cristofoletti, P.; Esposito, A.; Galvani, A.; Loddo, F.; Pesci, A.; Serpelloni, E.; Baldi, P.; Cenni, N.

    2002-12-01

    During the time span 1999-2001 we set up and surveyed the CA-GeoNet (Central Apennine Geodetic Network), a dense sub-regional GPS network located in one of the highest seismic areas of the Apennines (Italy), with the aim to detect the active strain rate of this sector of the chain, during inter-seismic and co-seismic epochs. The network extends across southern Umbria (Norcia area), Abrutii and southern Latium (Sora area) regions and from the Tyrrhenian to the Adriatic sea, in an area of about 130 km x 180 km. It consists of 129 vertices distributed with an average grid of 5 km over the main seismogenetic and geological structures of the area. The non permanent network is linked with the ASI and INGV permanent GPS stations. Among them, INGR, VVLO, ROSE and AQU are deployed E-W in this area, allowing a high precision estimation of the current strain rate component normal to the chain, from Tyrrhenian to Adriatic. Site selection and monumentation were performed after an accurate geological study of the area, with the aim to set up group of stations across the typical basin and ranges seismogenetic structures of the central Apennines, to estimate the strain rate in the near field. To obtain the best accuracy during surveys, the monuments were located on significant outcrops using steel markers screwed in the rock (3D monument) or concrete pillars with deep foundations. Data analysis performed by means of Bernese 4.2 and Gamit software, show accuracy within 1?2 mm in the planar and 1?5 mm in the vertical components, respectively. A preliminary comparison between 1999 and 2001 data for the Rieti and Leonessa sub-network shows horizontal displacements ranging from 5 to 15 mm.

  3. Crustal motion results derived from observations in the European geodetic VLBI network

    NASA Astrophysics Data System (ADS)

    Haas, Rüdiger; Gueguen, Erwan; Scherneck, Hans-Georg; Nothnagel, Axel; Campbell, James

    2000-10-01

    Geodetic VLBI observations have been performed with the European geodetic VLBI network since early 1990 on a regular basis. The purpose of these observations is to determine crustal motion in Europe and to establish a stable reference frame for other space geodetic techniques. Over the years the size of the network and the number of participating stations has steadily increased. Today, the network extends from the island of Sicily in the south to the island of Spitsbergen/Svalbard in the north and from the Iberian peninsula in the west to the Crimean peninsula in the east. The area covered by the network is affected by two main geodynamic processes which are post-glacial rebound effects in the northern part, and the evolution of the Alps-Apennines orogenic systems in the southern part. With nearly 10 years of VLBI observations the determination of crustal motion in Europe is carried out with high accuracy. Baseline measurements are achieved with an accuracy of a few parts per billion. We compare the evolution of baseline lengths and topocentric station displacements with geophysical models. Strain rates in Europe on a large scale are determined from the results of the VLBI analysis.

  4. Datum maintenance of the main Egyptian geodetic control networks by utilizing Precise Point Positioning "PPP" technique

    NASA Astrophysics Data System (ADS)

    Rabah, Mostafa; Elmewafey, Mahmoud; Farahan, Magda H.

    2016-06-01

    A geodetic control network is the wire-frame or the skeleton on which continuous and consistent mapping, Geographic Information Systems (GIS), and surveys are based. Traditionally, geodetic control points are established as permanent physical monuments placed in the ground and precisely marked, located, and documented. With the development of satellite surveying methods and their availability and high degree of accuracy, a geodetic control network could be established by using GNSS and referred to an international terrestrial reference frame used as a three-dimensional geocentric reference system for a country. Based on this concept, in 1992, the Egypt Survey Authority (ESA) established two networks, namely High Accuracy Reference Network (HARN) and the National Agricultural Cadastral Network (NACN). To transfer the International Terrestrial Reference Frame to the HARN, the HARN was connected with four IGS stations. The processing results were 1:10,000,000 (Order A) for HARN and 1:1,000,000 (Order B) for NACN relative network accuracy standard between stations defined in ITRF1994 Epoch1996. Since 1996, ESA did not perform any updating or maintaining works for these networks. To see how non-performing maintenance degrading the values of the HARN and NACN, the available HARN and NACN stations in the Nile Delta were observed. The Processing of the tested part was done by CSRS-PPP Service based on utilizing Precise Point Positioning "PPP" and Trimble Business Center "TBC". The study shows the feasibility of Precise Point Positioning in updating the absolute positioning of the HARN network and its role in updating the reference frame (ITRF). The study also confirmed the necessity of the absent role of datum maintenance of Egypt networks.

  5. The Global Geodetic Observing System: Space Geodesy Networks for the Future

    NASA Technical Reports Server (NTRS)

    Pearlman, Michael; Pavlis, Erricos; Ma, Chopo; Altamini, Zuheir; Noll, Carey; Stowers, David

    2011-01-01

    Ground-based networks of co-located space geodetic techniques (VLBI, SLR, GNSS. and DORIS) are the basis for the development and maintenance of the International Terrestrial Reference frame (ITRF), which is our metric of reference for measurements of global change, The Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG) has established a task to develop a strategy to design, integrate and maintain the fundamental geodetic network and supporting infrastructure in a sustainable way to satisfy the long-term requirements for the reference frame. The GGOS goal is an origin definition at 1 mm or better and a temporal stability on the order of 0.1 mm/y, with similar numbers for the scale and orientation components. These goals are based on scientific requirements to address sea level rise with confidence, but other applications are not far behind. Recent studies including one by the US National Research Council has strongly stated the need and the urgency for the fundamental space geodesy network. Simulations are underway to examining accuracies for origin, scale and orientation of the resulting ITRF based on various network designs and system performance to determine the optimal global network to achieve this goal. To date these simulations indicate that 24 - 32 co-located stations are adequate to define the reference frame and a more dense GNSS and DORIS network will be required to distribute the reference frame to users anywhere on Earth. Stations in the new global network will require geologically stable sites with good weather, established infrastructure, and local support and personnel. GGOS wil seek groups that are interested in participation. GGOS intends to issues a Call for Participation of groups that would like to contribute in the network implementation and operation. Some examples of integrated stations currently in operation or under development will be presented. We will examine necessary conditions and challenges in

  6. Feasibility of Construction of the Continuously Operating Geodetic GPS Network of Sinaloa, Mexico

    NASA Astrophysics Data System (ADS)

    Vazquez, G. E.; Jacobo, C.

    2011-12-01

    This research is based on the study and analysis of feasibility for the construction of the geodetic network for GPS continuous operation for Sinaloa, hereafter called (RGOCSIN). A GPS network of continuous operation is defined as that materialized structure physically through permanent monuments where measurements to the systems of Global Positioning (GPS) is performed continuously throughout a region. The GPS measurements in this network are measurements of accuracy according to international standards to define its coordinates, thus constituting the basic structure of geodetic referencing for a country. In this context is that in the near future the RGOCSIN constitutes a system state only accurate and reliable georeferencing in real-time (continuous and permanent operation) and will be used for different purposes; i.e., in addition to being fundamental basis for any lifting topographic or geodetic survey, and other areas such as: (1) Different construction processes (control and monitoring of engineering works); (2) Studies of deformation of the Earth's crust (before and after a seismic event); (3) GPS meteorology (weather forecasting); (4) Demarcation projects (natural and political); (5) Establishment of bases to generate mapping (necessary for the economic and social development of the state); (6) Precision agriculture (optimization of economic resources to the various crops); (7) Geographic information systems (Organization and planning activities associated with the design and construction of public services); (8) Urban growth (possible settlements in the appropriate form and taking care of the environmental aspect), among others. However there are criteria and regulations according to the INEGI (Instituto Nacional de Estadística y Geografía, http://www.inegi.org.mx/) that must be met; even for this stage of feasibility of construction that sees this project as a first phase. The fundamental criterion to be taken into account according to INEGI is a

  7. On Similarity Transformation and Geodetic Network Distortions Based on Doppler Satellite Observations

    NASA Technical Reports Server (NTRS)

    Leick, Alfred; Vangelder, Boudewijn H. W.

    1975-01-01

    Models used in geodesy to transform two sets of coordinates are studied and distortions in geodetic networks are investigated. Commonly used transformation models are first reviewed and most of them are interpreted. Differences between various models are discussed. Pitfalls in partial solutions are then considered. It is shown that only as many chords and/or directional elements can be used in the computation as are needed to completely determine the size or shape of the polyhedron implied in the set of Cartesian coordinates. Each additional element causes the normal matrix to be singular provided that all correlations between the chords are used. A number of tables and maps indicating distortions in the NAD 27, Precise Traverse M-R '72, AUS, and SAD 69 geodetic datums are also included. The residuals of the coordinates are scanned for systematic patterns after transforming each geodetic system to the NWL9D Doppler system. Also, an attempt is made to show scale distortions in the NAD 27.

  8. A Community-based Partnership for a Sustainable GNSS Geodetic Network

    NASA Astrophysics Data System (ADS)

    Dokka, R. K.

    2009-12-01

    Geodetic networks offer unparalleled opportunities to monitor and understand many of the rhythms of the Earth most vital to the sustainability of modern and future societies, i.e., crustal motions, sea-level, and the weather. For crustal deformation studies, the advantage is clear. Modern measurements allow us to document not only the permanent strains incurred over a seismic cycle, for example, but also the ephemeral strains that are critical for understanding the underlying physical mechanism. To be effective for science, however, geodetic networks must be properly designed, capitalized, and maintained over sufficient time intervals to fully capture the processes in action. Unfortunately, most networks lack interoperability and lack a business plan to ensure long term sustainability. The USA, for example, lacks a unified nation-wide GNSS network that can sustain its self over the coming years, decades, and century. Current federal priorities do not yet envision such a singular network. Publicly and privately funded regional networks exist, but tend to be parochial in scope, and optimized for a special user community, e.g., surveying, crustal motions, etc. Data sharing is common, but the lack of input at the beginning limits the functionality of the system for non-primary users. Funding for private networks depend heavily on the user demand, business cycle, and regulatory requirements. Agencies funding science networks offer no guarantee of sustained support. An alternative model (GULFNet) developed in Louisiana is meeting user needs, is sustainable, and is helping engineers, surveyors, and geologists become more spatially enabled. The common denominator among all participants is the view that accurate, precise, and timely geodetic data have tangible value for all segments of society. Although operated by a university (LSU), GULFNet is a community-based partnership between public and private sectors. GULFNet simultaneously achieves scientific goals by providing

  9. Integration of the Plate Boundary Observatory and Existing GPS Networks in Southern California: A Multi Use Geodetic Network

    NASA Astrophysics Data System (ADS)

    Walls, C.; Blume, F.; Meertens, C.; Arnitz, E.; Lawrence, S.; Miller, S.; Bradley, W.; Jackson, M.; Feaux, K.

    2007-12-01

    The ultra-stable GPS monument design developed by Southern California Geodetic Network (SCIGN) in the late 1990s demonstrates sub-millimeter errors on long time series where there are a high percentage of observations and low multipath. Following SCIGN, other networks such as PANGA and BARGEN have adopted the monument design for both deep drilled braced monuments (DDBM = 5 legs grouted 10.7 meters into bedrock/stratigraphy) and short drilled braced monuments (SDBM = 4 legs epoxied 2 meters into bedrock). A Plate Boundary Observatory (PBO) GPS station consists of a "SCIGN" style monument and state of the art NetRS receiver and IP based communications. Between the years 2003-2008 875 permanent PBO GPS stations are being built throughout the United States. Concomitant with construction of the PBO the majority of pre-existing GPS stations that meet stability specifications are being upgraded with Trimble NetRS and IP based communications to PBO standards under the EarthScope PBO Nucleus project. In 2008, with completed construction of the Plate Boundary Observatory, more than 1100 GPS stations will share common design specifications and have identical receivers with common communications making it the most homogenous geodetic network in the World. Of the 875 total Plate Boundary Observatory GPS stations, 211 proposed sites are distributed throughout the Southern California region. As of August 2007 the production status is: 174 stations built (81 short braced monuments, 93 deep drilled braced monuments), 181 permits signed, 211 permits submitted and 211 station reconnaissance reports. The balance of 37 stations (19 SDBM and 18 DDBM) will be built over the next year from Long Valley to the Mexico border in order of priority as recommended by the PBO Transform, Extension and Magmatic working groups. Fifteen second data is archived for each station and 1 Hz as well as 5 Hz data is buffered to be triggered for download in the event of an earthquake. Communications

  10. Optimization of observation plan based on the stochastic characteristics of the geodetic network

    NASA Astrophysics Data System (ADS)

    Pachelski, Wojciech; Postek, Paweł

    2016-06-01

    Optimal design of geodetic network is a basic subject of many engineering projects. An observation plan is a concluding part of the process. Any particular observation within the network has through adjustment a different contribution and impact on values and accuracy characteristics of unknowns. The problem of optimal design can be solved by means of computer simulation. This paper presents a new method of simulation based on sequential estimation of individual observations in a step-by-step manner, by means of the so-called filtering equations. The algorithm aims at satisfying different criteria of accuracy according to various interpretations of the covariance matrix. Apart of them, the optimization criterion is also amount of effort, defined as the minimum number of observations required. A numerical example of a 2-D network is illustrated to view the effectiveness of presented method. The results show decrease of the number of observations by 66% with respect to the not optimized observation plan, which still satisfy the assumed accuracy.

  11. Installation of a seafloor geodetic network offshore northern Chile (GeoSEA)

    NASA Astrophysics Data System (ADS)

    Kopp, Heidrun; Lange, Dietrich; Hannemann, Katrin; Petersen, Florian; Contreras-Reyes, Eduardo

    2016-04-01

    The seafloor stores crucial information on sub-seafloor processes, including stress, elastic strain, and earthquake and tsunami generation. This information may be extracted through the nascent scientific field of seafloor geodesy. The target of the recently installed GeoSEA array (Geodetic Earthquake Observatory on the SEAfloor) is to measure crustal deformation in mm-scale on the marine forearc and outer rise of the South American subduction system around 21°S. This segment of the Nazca-South American plate boundary has last ruptured in an earthquake in 1877 and was identified as a seismic gap prior to the 2014 Iquique/Pisagua earthquake (Mw=8.1). The southern portion of the segment remains unbroken by a recent earthquake. Seafloor geodetic measurements provide a way to monitor crustal deformation at high resolution comparable to the satellite-based GPS technique upon which terrestrial geodesy is largely based. The GeoSEA Network consists of autonomous seafloor transponders installed on 4 m high tripods, which were lowered to the seabed on the deep-sea cable of RV SONNE in December 2015. The transponders within an array intercommunicate via acoustic signals for a period of up to 3.5 years and measure acoustic distance, tilt and pressure. An additional component of the network is GeoSURF, a self-steering autonomous surface vehicle (Wave Glider), which monitors system health and is capable to upload the seafloor data to the sea surface and to transfer it via satellite. We have chosen three areas on the middle and lower slope and the outer rise for the set-up of three sub-arrays. The array in Area 1 on the middle continental slope consists of 8 transponders located in pairs on four topographic ridges, which are surface expressions of faults at depth. Area 2 is located on the outer rise seaward of the trench where 5 stations monitor extension across plate-bending related normal faults. The third area is located at water depth >5000 m on the lower continental slope

  12. Geodetic networks in Al-Hoceima, Fez-Meknes and Ouarzazate regions (Morocco) to monitor local deformations

    NASA Astrophysics Data System (ADS)

    Gil, A. J.; Ruiz, A. M.; Lacy, M. C.; Galindo-Zaldívar, J.; Anahnah, F.; Ruano, P.; Álvarez-Lobato, P. Ayarza, F.; Arboleya, A. Teixel, M. L.; Azzouz, O.; Ahmamou, A. Chalouan, M.; Kchikach, A.

    2009-04-01

    In the framework of some interdisciplinary research projects, several geodetic studies have been initiated aiming to quantify ground deformation in some areas of Morocco: the Al-Hoceima region (Rif cordillera), the Fez-Meknes region and the Ouarzazate region (Atlas Mountains). The Al-Hoceima region, located in the central part of the Rif Cordilleras, has undergone an intense seismic activity, in which the most significant events occurred in 1994 and 2004 (M= 6.3). Although seismicity data support the presence of transcurrent faults, and available radar interferometry researches evidence surface deformations, geological data suggest that main seismogentic fault zone has not a surface expression. Anyway, a set of N-S oriented normal faults (Rouadi, Al-Hoceima, Trougout) determines the present-day geomorphology and seems to continue to be active in surface. In this area, a new non-permanent GPS network consisting of 6 sites has been installed and surveyed in June 2007 and September 2008. The repeated measurements of this network may allow to exactly determine the surface expression of deep tectonic deformations in this region, and to quantify the creep and the coseismic motions in the area, that will contribute to better understand the seismic hazard. The Prerif Ridges located in the Fez-Meknes region, constitute the active mountain front of the Rif cordillera that accommodates most of the recent convergence between Eurasia and African plates. South of the ridges, the Saïss foreland basin overlies the foreland rocks corresponding to the Middle Atlas. There are evidences of Quaternary uplift of the Prerif Ridges and deformation of recent sediments as consequence of the southwards propagation of reverse faults along the mountain front. In addition, the foreland basin undergoes a roughly N-S extensional regime. The region undergoes a moderate seismic activity, with catastrophic events like that occurred in 1755 which damaged Fez and Meknes. On September 2007, a non

  13. Rank defect analysis and the realization of proper singularity in normal equations of geodetic networks

    NASA Astrophysics Data System (ADS)

    Kotsakis, C.; Chatzinikos, M.

    2017-01-01

    The singularity of input normal equations (NEQ) is a crucial element for their optimal handling in the context of terrestrial reference frame (TRF) estimation under the minimal-constraint framework. However, this element is often missing in the recovered NEQ from SINEX files after the usual deconstraining based on the stated information for the stored solutions. The same setback also occurs with the original NEQ that are formed by the least-squares processing of space geodetic data due to the datum information which is carried by various modeling choices and/or software-dependent procedures. In the absence of this datum-related singularity, it is not possible to obtain genuine minimally constrained solutions because of the interference between the input NEQ's content and the external datum conditions, a fact that may alter the geometrical information of the original measurements and can cause unwanted distortions in the estimated solution. The main goal of this paper is the formulation of a filtering scheme to enforce the proper (or desired) singularity in the input NEQ with regard to datum parameters that will be handled by the minimal-constraint setting in TRF estimation problems. The importance of this task is extensively discussed and justified with the help of several numerical examples in different GNSS networks.

  14. The combined geodetic network adjusted on the reference ellipsoid - a comparison of three functional models for GNSS observations

    NASA Astrophysics Data System (ADS)

    Kadaj, Roman

    2016-12-01

    The adjustment problem of the so-called combined (hybrid, integrated) network created with GNSS vectors and terrestrial observations has been the subject of many theoretical and applied works. The network adjustment in various mathematical spaces was considered: in the Cartesian geocentric system on a reference ellipsoid and on a mapping plane. For practical reasons, it often takes a geodetic coordinate system associated with the reference ellipsoid. In this case, the Cartesian GNSS vectors are converted, for example, into geodesic parameters (azimuth and length) on the ellipsoid, but the simple form of converted pseudo-observations are the direct differences of the geodetic coordinates. Unfortunately, such an approach may be essentially distorted by a systematic error resulting from the position error of the GNSS vector, before its projection on the ellipsoid surface. In this paper, an analysis of the impact of this error on the determined measures of geometric ellipsoid elements, including the differences of geodetic coordinates or geodesic parameters is presented. Assuming that the adjustment of a combined network on the ellipsoid shows that the optimal functional approach in relation to the satellite observation, is to create the observational equations directly for the original GNSS Cartesian vector components, writing them directly as a function of the geodetic coordinates (in numerical applications, we use the linearized forms of observational equations with explicitly specified coefficients). While retaining the original character of the Cartesian vector, one avoids any systematic errors that may occur in the conversion of the original GNSS vectors to ellipsoid elements, for example the vector of the geodesic parameters. The problem is theoretically developed and numerically tested. An example of the adjustment of a subnet loaded from the database of reference stations of the ASG-EUPOS system was considered for the preferred functional model of the GNSS

  15. The IONORING Project: Exploiting The Italian Geodetic GPS Network For Ionospheric Purposes

    NASA Astrophysics Data System (ADS)

    Spogli, L.; Cesaroni, C.; Pezzopane, M.; Alfonsi, L.; Romano, V.; Avallone, A.; Settimi, A.

    2015-12-01

    The increasing use of GNSS for navigation and precise positioning leads to the need of more and more accurate knowledge of the morphology and dynamics of the ionosphere. In fact, it is well known that the ionospheric induced delay is the main error on the GNSS precise positioning applications. On the other hand, GNSS signals propagating through the ionosphere are useful to probe the ionization of the upper atmosphere. RING (Rete Integrata GPS Nazionale) is a dense geodetic network of GPS stations managed by INGV (Istituto Nazionale di Geofisica e Vulcanologia) including about 180 receivers deployed on the whole Italian peninsula. Data acquired by the receivers were initially collected and stored to perform mainly studies focused on crustal deformations, caused both by plates movement and by earthquakes effects. The main goal of the IONORING (IONOspheric RING) project is to exploit data from the RING network to obtain ionospheric Total Electron Content (TEC) maps with very fine spatial resolution (0.1°x0.1°, lat x long) in near real-time. Ad hoc calibration and interpolation algorithms are applied to RINEX data to produce rapid and final products. The former are generated with a time lag of about 1 hour, the latter, characterized by a higher accuracy, are produced with a time lag of maximum 48 hours. These maps will be useful to support ionospheric error mitigation in precise positioning (rapid product) and to study the ionosphere morphology and dynamics during strong solar and geomagnetic storms affecting the mid-latitude ionosphere (final product). Maps and data resulting from the data-processing will be available on a dedicated web page through the electronic Space Weather upper atmosphere portal managed by INGV (www.eswua.it). In this paper, some preliminary results of the IONORING project are presented as well as the ICT interface of the project.

  16. Development of GPS/A Seafloor Geodetic Network Along Japan Trench and Onset of Its Operation

    NASA Astrophysics Data System (ADS)

    Kido, M.; Fujimoto, H.; Osada, Y.; Ohta, Y.; Yamamoto, J.; Tadokoro, K.; Okuda, T.; Watanabe, T.; Nagai, S.; Kenji, Y.

    2012-12-01

    The Tohoku-oki earthquake in 2011 revealed that an M9-class giant earthquake could occur even in the old subduction zone and that coseismic slip can reach its frontal wedge, where we considered no significant stress had been accumulated in. One of the leading figure of such finding is in situ seafloor geodetic measurement, such as GPS/A technique for horizontal displacement and pressure gauge for vertical displacement. Japan Coast Guard and Japanese university group had developed several GPS/A sites near the source region of the Tohoku-oki earthquake and detected quite large coseismic movements over 20 m in there. Displacement vectors observed these sites showed systematic variation, i.e., mainly confined in the off-Miyagi area and getting larger near the trench. However, subsequent post-seismic deformation shows inexplicable distribution. In order to elucidate this complex feature, MEXT Japan has decided to construct dense and widely-extended GPS/A network along Japan trench, including deep area (~6000m). We, Tohoku and Nagoya universities, have firstly developed high-powered seafloor transponders with an omnidirectional acoustic unit that works at 6000 m deep ocean and enable acoustic ranging over 13 km slant length. In addition, using high-energy density battery, its lifetime is expected 10 years with normal operation. Secondly, we examined the optimal distribution of GPS/A sites forming a network, taken pre-existing sites into consideration. The new network consists of 20 sites (roughly four transponders at a single site and 86 transponders in total). The distribution is dense near the area of complex post-seismic deformation and extended over 400 km to cover the adjacent area of the source region, in where induced earthquake may be expected. The largest obstacle to draw network plan is seafloor topography. Because a GPS/A site is a seafloor benchmark, its installation must be on flat and locally stable spot. Since a single GPS/A site consists of three or more

  17. Geodetic component of the monitoring of tectonic and hydrogeological activities in Kopacki Rit Nature Park

    NASA Astrophysics Data System (ADS)

    Dapo, Almin; Pribicevic, Bosko

    2013-04-01

    Based on the European and global experience, the amplitude change in the structural arrangement caused by recent tectonic movements, can be most accurately determined by repeated precise GPS measurements on specially stabilized geodetic and geodynamic points. Because of these reasons, the GPS method to determine the movements on specially stabilized points in the Nature park Kopacki rit is also applied in this project. Kopacki rit Nature Park is the biggest preserved natural flooded area on the Danube. It is spread over 23 000 hectares between the rivers Danube and Drava and is one of the biggest fluvial wetland valleys in Europe. In 1993 it was listed as one of internationally valuable wetlands according to the Ramsar Convention. By now in Kopacki rit there have been sights of about 295 bird species, more than 400 species of invertebrates and 44 types of fish. Many of them are globally endangered species like, white tailed eagle, black stork and prairie hawk. It's not rare to come across some deer herds, wild boars or others. Today's geological and geomorphological relations in the Nature park Kopacki rit are largely the result of climate, sedimentary, tectonic and anthropogenic activity in the last 10,000 years. Unfortunately the phenomenon of the Kopacki rit Nature park is in danger to be over in the near future due to those and of course man made activities on the Danube river. It is trough scientific investigations of tectonic and hydrogeological activities that scientist from University of Zagreb are trying to contribute to wider knowledge and possible solutions to this problem. In the year 2009 the first GPS campaign was conducted, and the first set of coordinates of stabilized points was determined which can be considered zero-series measurements. In 2010 a second GPS campaign was conducted and the first set of movements on the Geodynamic Network of Kopacki Rit Nature Park was determined. Processing GPS measurements from 2009 and 2010 was carried out in a

  18. How rigid is a rigid plate? Geodetic constraint from the TrigNet CGPS network, South Africa

    NASA Astrophysics Data System (ADS)

    Malservisi, Rocco; Hugentobler, Urs; Wonnacott, Richard; Hackl, Matthias

    2013-03-01

    Rigidity and continuity of the Nubia plate is a fundamental assumption for the kinematic description, the dynamic implications of its interaction with surrounding plates and ultimately an important constraint to the geodynamics processes involved in continental lithospheric rupture. Geophysical, neotectonic and geodynamics considerations suggest the possibility that the Nubia plate is not completely rigid but could be undergoing internal deformation due to the southward propagation of the East African Rift. Here, we utilize the South African TrigNet geodetic network to evaluate the amount of internal deformation within the South African region and the possibility of motion between South Africa and the rest of the African continent. Our results show that the South African region behaves rigidly, with deformation of the order of 1 nanostrain yr-1 or less. The analysis shows some higher strain rates in the eastern region, and the presence of spatially correlated residuals in the Cape Town region and the region east of Johannesburg. Although not statistically significant, the spatial coherence of those residuals could indicate tectonic activity. A comparison of the Euler vector for the South African region with previously published Euler poles for the Nubia plate as well as the analysis of the residuals of Nubia sites with respect to a `rigid' TrigNet are compatible with clockwise rotation of the South African block with respect to the African continent, consistent with a propagation of the East Africa Rift along the Okavango region.

  19. From simulation to implementation: low-cost densification of permanent GPS networks in support of geodetic applications

    NASA Astrophysics Data System (ADS)

    Chen, H.-Y.; Rizos, C.; Han, S.

    2001-10-01

    Permanent GPS networks have been established since the 1980s to support a variety of geodetic applications, ranging from local deformation monitoring to large-scale crustal motion measurement. Continuously operating GPS (CGPS) networks, consisting of geodetic-grade, dual-frequency receiver systems, generally support relative positioning to sub-centimetre accuracy, even for baselines up to several thousand kilometres in length. However, due to their comparatively high cost, the density of such GPS stations is rarely high enough to support all geodetic applications. For example, although the Geographical Survey Institute has established nearly 1000 permanent GPS stations across Japan, the average inter-station spacing is of the order of 30 km. This paper describes a method by which a sub-network of comparatively low-cost, single-frequency GPS receivers can be deployed to increase the density of typical CGPS networks. In this way it is possible to increase the spatial resolution of the measured ground deformation, while still maintaining the same level of precision as a CGPS network comprised entirely of dual-frequency GPS receivers. In order to reduce the system biases associated with single-frequency data processing, an innovative medium-range GPS positioning technique that combines the processing of single-frequency and dual-frequency data is proposed. Several data sets are analysed in order to address critical issues such as: 'Can the technique work equally well for different geographic locations across Asia, traversing large elevation changes, in various seasons?', 'Can the sub-network incorporate single-frequency receivers of different brands while maintaining similar levels of precision?', and 'Can the sub-network yield generally uniform high precision results for different baseline lengths?' The analyses undertaken by the authors confirm that the proposed technique can achieve relative accuracies similar to those obtained from dual-frequency, static

  20. Geodetic and geological evidence of active tectonics in south-western Sicily (Italy)

    NASA Astrophysics Data System (ADS)

    Barreca, G.; Bruno, V.; Cocorullo, C.; Cultrera, F.; Ferranti, L.; Guglielmino, F.; Guzzetta, L.; Mattia, M.; Monaco, C.; Pepe, F.

    2014-12-01

    Integrated geological, geodetic and marine geophysical data provide evidence of active deformation in south-western Sicily, in an area spatially coincident with the macroseismic zone of the destructive 1968 Belice earthquake sequence. Even though the sequence represents the strongest seismic event recorded in Western Sicily in historical times, focal solutions provided by different authors are inconclusive on possible faulting mechanism, which ranges from thrusting to transpression, and the seismogenic source is still undefined. Interferometric (DInSAR) observations reveal a differential ground motion on a SW-NE alignment between Campobello di Mazara and Castelvetrano (CCA), located just west of the maximum macroseismic sector. In addition, new GPS campaign-mode data acquired across the CCA alignment documents NW-SE contractional strain accumulation. Morphostructural analysis allowed to associate the alignment detected through geodetic measurements with a topographic offset of Pleistocene marine sediments. The on-land data were complemented by new high-resolution marine geophysical surveys, which indicate recent contraction on the offshore extension of the CCA alignment. The discovery of archaeological remains displaced by a thrust fault associated with the alignment provided the first likely surface evidence of coseismic and/or aseismic deformation related to a seismogenic source in the area. Results of the integrated study supports the contention that oblique thrusting and folding in response to NW-SE oriented contraction is still active. Although we are not able to associate the CCA alignment to the 1968 seismic sequence or to the historical earthquakes that destroyed the ancient Greek city of Selinunte, located on the nearby coastline, our result must be incorporated in the seismic hazard evaluation of this densely populated area of Sicily.

  1. Least squares adjustment of large-scale geodetic networks by orthogonal decomposition

    SciTech Connect

    George, J.A.; Golub, G.H.; Heath, M.T.; Plemmons, R.J.

    1981-11-01

    This article reviews some recent developments in the solution of large sparse least squares problems typical of those arising in geodetic adjustment problems. The new methods are distinguished by their use of orthogonal transformations which tend to improve numerical accuracy over the conventional approach based on the use of the normal equations. The adaptation of these new schemes to allow for the use of auxiliary storage and their extension to rank deficient problems are also described.

  2. Co-location of Space Geodetic Instruments at the "Quasar" VLBI Network Observatories

    NASA Astrophysics Data System (ADS)

    Finkelstein, A.; Ipatov, A.; Gayazov, I.; Shargorodsky, V.; Smolentsev, S.; Mitryaev, V.; Diyakov, A.; Olifirov, V.; Rahimov, I.

    2012-12-01

    This paper discusses the current status of creating the co-location stations at the observatories of the Russian VLBI network "Quasar". Satellite Laser Ranging systems "Sazhen-TM" manufactured by Research-and-Production Corporation "Precision Systems and Instruments" were installed at all observatories of the network in 2011. The main technical characteristics of the SLR system and the co-location of high-precision observational instruments at the observatories are presented in this paper.

  3. a Libration Model for Enceladus Based on Geodetic Control Point Network Analysis

    NASA Astrophysics Data System (ADS)

    Nadezhdina, I. E.; Zubarev, A. E.; Brusnikin, E. S.; Oberst, J.

    2016-06-01

    A new global control point network was derived for Enceladus, based on Cassini and Voyager-2 image data. Cassini images were taken from 2005 to 2014, for Voyager we have only one flyby in the middle of 1981. We have derived 3D Cartesian coordinates for 1128 control points as well as improved pointing data for 12 Voyager and 193 Cassini images in the Enceladus-fixed coordinate system. The point accuracies vary from 55 m to 2900 m (average point accuracy - 221 m). From tracking of the control points we detect a librational motion described by a model which includes 3 different periods and amplitudes (Rambaux et al., 2011). We determine the amplitudes for each term. Our new control point network has a higher number of point measurements and a higher accuracy than previous data (Giese et al., 2014).

  4. Operational aspects of CASA UNO '88-The first large scale international GPS geodetic network

    NASA Technical Reports Server (NTRS)

    Neilan, Ruth E.; Dixon, T. H.; Meehan, Thomas K.; Melbourne, William G.; Scheid, John A.; Kellogg, J. N.; Stowell, J. L.

    1989-01-01

    For three weeks, from January 18 to February 5, 1988, scientists and engineers from 13 countries and 30 international agencies and institutions cooperated in the most extensive GPS (Global Positioning System) field campaign, and the largest geodynamics experiment, in the world to date. This collaborative eperiment concentrated GPS receivers in Central and South America. The predicted rates of motions are on the order of 5-10 cm/yr. Global coverage of GPS observations spanned 220 deg of longitude and 125 deg of latitude using a total of 43 GPS receivers. The experiment was the first civilian effort at implementing an extended international GPS satellite tracking network. Covariance analyses incorporating the extended tracking network predicted significant improvement in precise orbit determination, allowing accurate long-baseline geodesy in the science areas.

  5. A System to Produce Precise Global GPS Network Solutions for all Geodetic GPS Stations in the World

    NASA Astrophysics Data System (ADS)

    Blewitt, G.; Kreemer, C. W.

    2010-12-01

    We have developed an end-to-end system that automatically seeks and routinely retrieves geodetic GPS data from ~5000 stations (currently) around the globe, reduces the data into unique, daily global network solutions, and produces high precision time series for station coordinates ready for time-series analysis, geophysical modeling and interpretation. Moreover, “carrier range” data are produced for all stations, enabling epoch-by-epoch tracking of individual station motions by precise point positioning for investigation of sub-daily processes, such as post-seismic after-slip and ocean tidal loading. Solutions are computed in a global reference frame aligned to ITRF, and optionally in user-specified continental-scale reference frames that can filter out common-mode signals to enhance regional strain anomalies. We describe the elements of this system, the underlying signal processing theory, the products, operational statistics, and scientific applications of our system. The system is fundamentally based on precise point positioning using JPL's GIPSY OASIS II software, coupled with ambiguity resolution and a global network adjustment of ~300,000 parameters per day using our newly developed Ambizap3 software. The system is designed to easily and efficiently absorb stations that deliver data very late, by recycling prior computations in the network adjustment, such that the resulting network solution is identical to starting from scratch. Thus, it becomes possible to trawl continuously the Internet for late arriving data, or for newly discovered data, and seamlessly update all GPS station time series using the new information content. As new stations are added to the processing archive, automated e-mail requests are made to H.-G. Scherneck's server at Chalmers University to compute ocean loading coefficients used by the station motion model. Rinex file headers are parsed and compared with alias tables in order to infer the correct receiver type and antenna

  6. Plate Boundary Observatory and related networks: GPS data analysis methods and geodetic products

    NASA Astrophysics Data System (ADS)

    Herring, Thomas A.; Melbourne, Timothy I.; Murray, Mark H.; Floyd, Michael A.; Szeliga, Walter M.; King, Robert W.; Phillips, David A.; Puskas, Christine M.; Santillan, Marcelo; Wang, Lei

    2016-12-01

    The Geodesy Advancing Geosciences and EarthScope (GAGE) Facility Global Positioning System (GPS) Data Analysis Centers produce position time series, velocities, and other parameters for approximately 2000 continuously operating GPS receivers spanning a quadrant of Earth's surface encompassing the high Arctic, North America, and Caribbean. The purpose of this review is to document the methodology for generating station positions and their evolution over time and to describe the requisite trade-offs involved with combination of results. GAGE GPS analysis involves formal merging within a Kalman filter of two independent, loosely constrained solutions: one is based on precise point positioning produced with the GIPSY/OASIS software at Central Washington University and the other is a network solution based on phase and range double-differencing produced with the GAMIT software at New Mexico Institute of Mining and Technology. The primary products generated are the position time series that show motions relative to a North America reference frame and secular motions of the stations represented in the velocity field. The position time series themselves contain a multitude of signals in addition to the secular motions. Coseismic and postseismic signals, seasonal signals from hydrology, and transient events, some understood and others not yet fully explained, are all evident in the time series and ready for further analysis and interpretation. We explore the impact of analysis assumptions on the reference frame realization and on the final solutions, and we compare within the GAGE solutions and with others.

  7. Analysis of the horizontal structure of a measurement and control geodetic network based on entropy

    NASA Astrophysics Data System (ADS)

    Mrówczyńska, Maria

    2013-06-01

    The paper attempts to determine an optimum structure of a directional measurement and control network intended for investigating horizontal displacements. For this purpose it uses the notion of entropy as a logarithmical measure of probability of the state of a particular observation system. An optimum number of observations results from the difference of the entropy of the vector of parameters ΔHX̂ (x)corresponding to one extra observation. An increment of entropy interpreted as an increment of the amount of information about the state of the system determines the adoption or rejection of another extra observation to be carried out. W pracy podjęto próbę określenia optymalnej struktury sieci kierunkowej pomiarowo-kontrolnej przeznaczonej do badań przemieszczeń poziomych. W tym celu wykorzystano pojęcie entropii jako logarytmicznej miary prawdopodobieństwa stanu określonego układu obserwacyjnego. Optymalna liczba realizowanych obserwacji wynika z różnicy entropii wektora parametrów ΔHX̂ (x) odpowiadającej jednej obserwacji nadliczbowej. Przyrost entropii interpretowany jako przyrost objętości informacji na temat stanu układu decyduje o przyjęciu względnie odrzuceniu do realizacji kolejnej obserwacji nadliczbowej.

  8. Dataworks for GNSS: Software for Supporting Data Sharing and Federation of Geodetic Networks

    NASA Astrophysics Data System (ADS)

    Boler, F. M.; Meertens, C. M.; Miller, M. M.; Wier, S.; Rost, M.; Matykiewicz, J.

    2015-12-01

    Continuously-operating Global Navigation Satellite System (GNSS) networks are increasingly being installed globally for a wide variety of science and societal applications. GNSS enables Earth science research in areas including tectonic plate interactions, crustal deformation in response to loading by tectonics, magmatism, water and ice, and the dynamics of water - and thereby energy transfer - in the atmosphere at regional scale. The many individual scientists and organizations that set up GNSS stations globally are often open to sharing data, but lack the resources or expertise to deploy systems and software to manage and curate data and metadata and provide user tools that would support data sharing. UNAVCO previously gained experience in facilitating data sharing through the NASA-supported development of the Geodesy Seamless Archive Centers (GSAC) open source software. GSAC provides web interfaces and simple web services for data and metadata discovery and access, supports federation of multiple data centers, and simplifies transfer of data and metadata to long-term archives. The NSF supported the dissemination of GSAC to multiple European data centers forming the European Plate Observing System. To expand upon GSAC to provide end-to-end, instrument-to-distribution capability, UNAVCO developed Dataworks for GNSS with NSF funding to the COCONet project, and deployed this software on systems that are now operating as Regional GNSS Data Centers as part of the NSF-funded TLALOCNet and COCONet projects. Dataworks consists of software modules written in Python and Java for data acquisition, management and sharing. There are modules for GNSS receiver control and data download, a database schema for metadata, tools for metadata handling, ingest software to manage file metadata, data file management scripts, GSAC, scripts for mirroring station data and metadata from partner GSACs, and extensive software and operator documentation. UNAVCO plans to provide a cloud VM

  9. Global geodetic observatories

    NASA Astrophysics Data System (ADS)

    Boucher, Claude; Pearlman, Mike; Sarti, Pierguido

    2015-01-01

    Global geodetic observatories (GGO) play an increasingly important role both for scientific and societal applications, in particular for the maintenance and evolution of the reference frame and those applications that rely on the reference frame for their viability. The International Association of Geodesy (IAG), through the Global Geodetic Observing System (GGOS), is fully involved in coordinating the development of these systems and ensuring their quality, perenniality and accessibility. This paper reviews the current role, basic concepts, and some of the critical issues associated with the GGOs, and advocates for their expansion to enhance co-location with other observing techniques (gravity, meteorology, etc). The historical perspective starts with the MERIT campaign, followed by the creation of international services (IERS, IGS, ILRS, IVS, IDS, etc). It provides a basic definition of observing systems and observatories and the build up of the international networks and the role of co-locations in geodesy and geosciences and multi-technique processing and data products. This paper gives special attention to the critical topic of local surveys and tie vectors among co-located systems in sites; the agreement of space geodetic solutions and the tie vectors now place one of the most significant limitations on the quality of integrated data products, most notably the ITRF. This topic focuses on survey techniques, extrapolation to instrument reference points, computation techniques, systematic biases, and alignment of the individual technique reference frames into ITRF. The paper also discusses the design, layout and implementation of network infrastructure, including the role of GGOS and the benefit that would be achieved with better standardization and international governance.

  10. Workshop Targets Development of Geodetic Transient Detection Methods

    NASA Astrophysics Data System (ADS)

    Murray-Moraleda, Jessica R.; Lohman, Rowena

    2010-02-01

    2009 SCEC Annual Meeting: Workshop on Transient Anomalous Strain Detection; Palm Springs, California, 12-13 September 2009; The Southern California Earthquake Center (SCEC) is a community of researchers at institutions worldwide working to improve understanding of earthquakes and mitigate earthquake risk. One of SCEC's priority objectives is to “develop a geodetic network processing system that will detect anomalous strain transients.” Given the growing number of continuously recording geodetic networks consisting of hundreds of stations, an automated means for systematically searching data for transient signals, especially in near real time, is critical for network operations, hazard monitoring, and event response. The SCEC Transient Detection Test Exercise began in 2008 to foster an active community of researchers working on this problem, explore promising methods, and combine effective approaches in novel ways. A workshop was held in California to assess what has been learned thus far and discuss areas of focus as the project moves forward.

  11. Suboceanic geodetic measurements

    NASA Astrophysics Data System (ADS)

    Spiess, F. N.

    1985-07-01

    This paper reviews the needs for geodetic ties among sea-floor points and between such points and others on land, as well as the environmental constraints on potential systems for making such measurements. Underwater acoustic techniques provide the best opportunities, and an essential element on which to build acoustic systems - a precision-transponder system capable of making travel-time measurements over ranges of several kilometers with an accuracy of a few microseconds - is described. Finally, three particular systems are discussed. One uses direct transmission between transponders to achieve an accuracy of 1 part in 100,000 over ranges from a few meters to about a kilometer. The second, using a larger transponder network and an intermediate vehicle, can achieve similar accuracy over ranges up to about 10 km. The third is a composite acoustic global positioning system (GPS) which should be able to achieve subdecimeter accuracy over ranges of a few hundred kilometers.

  12. Dynamics of Rifting in two Active Rift Segments in Afar - Geodetic and Structural Studies - DoRA Project

    NASA Astrophysics Data System (ADS)

    Doubre, C.; Socquet, A.; Masson, F.; Jacques, E.; Grandin, R.; Nercessian, A.; Kassim, M.; Vergne, J.; Diament, M.; Hinderer, J.; Ayele, A.; Lewi, E.; Calais, E.; Peltzer, G.; Toussaint, R.; de Chaballier, J.; Ballu, V. S.; Luck, B.; King, G. C.; Vigny, C.; Cattin, R.; Tiberi, C.; Kidane, T.; Jalludin, M.; Maggi, A.; Dorbath, C.; Manatschal, G.; Schmittbuhl, J.; Le Moigne, N.; Deroussi, S.

    2009-12-01

    The DoRA project aims to conduct complementary studies in two volcano-tectonic rifts in the Afar Depression. In Northern Afar, the Wal’is Dabbahu Rift (WD, Ethiopia) is currently undergoing a major rifting episode. This event started in September 2005 with a significant seismic activity. InSAR data revealed the injection of a 65 km-long mega-dyke that opened by up to 8 m, the slip of numerous normal faults and opening of fissures, and a rhyolitic eruption. Similarly, the Asal-Ghoubbet Rift (AG, Djibouti) was affected in 1978 by a smaller episode of rifting associated with the intrusion of a 2 m wide dyke into the crust. Since then, a large catalog of geodetic data that includes recent InSAR time series reveals the importance of non-steady deformation controlling the rift dynamics. Our goal is to gain an understanding of such volcano-tectonic segments on several time scales, including the dyking period itself and the post-event period. The study of the behavior of the AG Rift during its whole post-rifting period offers an image at t+30 years of the WD segment, while keeping in mind important structural and scale differences. First, we propose to build a complete and accurate set of geodetic data (InSAR, cGPS, GPS), covering the period under study. With a narrow temporal sample window, we will precisely describe the aseismic slip affecting the normal faults of these rifts, the periods of sudden slip and/or slip acceleration but also measure the deformation associated with probable future dyke intrusion. Second, we aim to constrain the origin of these displacements and their relation with mass transfers within the crust. Series of gravity measurements will be pursue or initiated in both rifts. Third, the recording of seismic activity is essential to constrain the relative importance of seismic and aseismic deformation. This will also help to evaluate the thickness of the seismogenic layer. Together with structural data collected during a seismic survey in the AG

  13. Corrigendum to "The 3-D strain patterns in Turkey using geodetic velocity fields from the RTK-CORS (TR) network" [J. African Earth Sci. 115 (2016) 246-270

    NASA Astrophysics Data System (ADS)

    Kutoglu, Hakan Senol; Toker, Mustafa; Mekik, Cetin

    2016-12-01

    In the article titled "The 3-D Strain patterns in Turkey using Geodetic velocity fields from the RTK-CORS (TR) Network" published in Journal of African Earth Sciences Vol. 11, pp.246-270, the black arrows on the Figs. 10 and 12 are shifted due to printing error to undesired places. The correct form of Figs. 10 and 12 are given below:

  14. Legacy and future of Kilauea's geodetic studies

    NASA Astrophysics Data System (ADS)

    Montgomery-Brown, E. D.; Miklius, A.

    2011-12-01

    Because of its extensive and detailed history of geodetic measurements, Kilauea is one of the best-studied if not also best-understood volcanic systems in the world. Hawaiian volcanoes have a long history of deformation observations. These observations range from native legends of Pele's underground travels, through initial measurements made by the Hawaiian Volcano Observatory, and finally to current ground-based and satellite observations. Many questions still remain, relating to Kilauea's dynamics, where geodetic measurements could offer fundamental insights. For example, new geodetic experiments could lead to a better understanding of the degree of magmatic and tectonic interaction, the geometries of faults at depth, the extent of offshore deformation, and the magmatic plumbing system. While it is possible to design many experiments to address these issues, we focus on three deformation targets where geodetic improvements, including finer sampling in space and time, could yield significant advancements toward understanding Kilauea's dynamics. First, by scrutinizing spatially-dense space-borne geodetic data for signs of upper east rift zone deformation and incorporating gravity and seismic data in a high resolution tomographic model, the hydraulic connection between Kilauea's summit and the rift zone could be imaged, which would provide insight into the pathways that transport magma out to the rift zones. Second, a combination of geodetic and seismic data could be used to determine the nature of possible relationships and interactions between the Hilina fault system and Kilauea's basal decollement. Such a study would have important implications for assessments of future earthquake and sector collapse hazards. Lastly, by adding seafloor geodetic measurements and seismic data to the current geodetic network on Kilauea, we could delimit the offshore extent of transient and episodic decollement deformation. In addition to multidisciplinary approaches, future geodetic

  15. Seismic and geodetic studies of the Imperial Valley, California

    SciTech Connect

    Jackson, D.D.

    1981-05-01

    The Imperial Valley exhibits perhaps the most active current tectonism in the United States; patterns of gravitational and thermal anomalies, along with geodetic measurements, strike-slip faulting, and recent volcanism suggest that the continental crust may still be spreading (Elders et al., 1972). In recent years, the United States Geological Survey and Caltech have added new seismic stations into a dense network in the Imperial Valley to study in detail the relationship between geothermal areas and earthquakes, and to understand the tectonic processes taking place there. The purposes of this study are to: (1) examine crustal structure using recently available data on P-wave arrival times of local earthquakes; (2) examine the leveling data for evidence of tectonic subsidence or uplift; and (3) study correlations between seismicity, seismic velocity, geodetic motion, geothermal activity, and local geology to provide a more consistent picture of the tectonics of the Imperial Valley.

  16. Insights into active tectonics of eastern Taiwan from analyses of geodetic and geologic data

    NASA Astrophysics Data System (ADS)

    Huang, Wen-Jeng; Johnson, Kaj M.; Fukuda, Jun'ichi; Yu, Shui-Beih

    2010-03-01

    About 50 mm/yr of convergence between the Philippine Sea and Eurasian plates is absorbed in eastern Taiwan, and it remains unclear how the convergence is partitioned among active faults. The Longitudinal Valley fault (LVF), the most seismically active fault in eastern Taiwan, creeps at the surface in the south and not in the north; however, it is unclear how much of the fault is locked or creeping at depth. To address these problems, we model Holocene and interseismic deformation of elastic lithospheric blocks moving over a viscoelastic asthenosphere in eastern Taiwan. Through a fully probabilistic scheme, we invert GPS, interferometric synthetic aperture radar, creepmeter, and Holocene marine terrace data for block motions, fault slip rates, and distribution of interseismic creep. The data are explained with four blocks separated by three faults, Central Range fault, LVF, and an offshore fault. The model explains the essential features of interseismic and Holocene deformation. We find that 35-55 mm/yr of slip on the offshore fault is necessary to fit marine terrace uplift rates, which is a larger fraction of the plate convergence than previously recognized. The LVF has a Holocene slip rate of 20-30 mm/yr with approximately equal magnitudes of reverse-slip and left-lateral strike-slip components. Only about half of the surface area of the Longitudinal Valley fault appears to be locked. The southern segment of the LVF creeps at a rate of 5-28 mm/yr down to a depth of 15-20 km, while the northern segment is locked from the surface to a depth of 20 km.

  17. The 3-D strain patterns in Turkey using geodetic velocity fields from the RTK-CORS (TR) network

    NASA Astrophysics Data System (ADS)

    Kutoglu, Hakan Senol; Toker, Mustafa; Mekik, Cetin

    2016-03-01

    This study presents our use of GPS data to obtain and quantify the full continuous strain tensor using a 3-D velocity field in Turkey. In this study, GPS velocities improve the estimation of short-term strain tensor fields for determining the seismic hazard of Turkey. The tensorial analysis presents different aspects of deformation, such as the normal and shear strains, including their directions, the compressional and extensional strains. This analysis is appropriate for the characterizing the state of the current seismic deformation. GPS velocity data from continuous measurements (2009-2012) to estimate deformations were processed using the GAMIT/GLOBK software. Using high-rate GPS data from permanent 146 GNSS stations (RTK-CORS-TR network), the strain distribution was determined and interpolated using a biharmonic spline technique. We show the strain field patterns within axial and plane form at several critical locations, and discuss these results within the context of the seismic and tectonic deformation of Turkey. We conclude that the knowledge of the crustal strain patterns provides important information on the location of the main faults and strain accumulation for the hazard assessment. The results show an agreement between the seismic and tectonic strains confirming that there are active crustal deformations in Turkey.

  18. Actively stressed marginal networks.

    PubMed

    Sheinman, M; Broedersz, C P; MacKintosh, F C

    2012-12-07

    We study the effects of motor-generated stresses in disordered three-dimensional fiber networks using a combination of a mean-field theory, scaling analysis, and a computational model. We find that motor activity controls the elasticity in an anomalous fashion close to the point of marginal stability by coupling to critical network fluctuations. We also show that motor stresses can stabilize initially floppy networks, extending the range of critical behavior to a broad regime of network connectivities below the marginal point. Away from this regime, or at high stress, motors give rise to a linear increase in stiffness with stress. Finally, we demonstrate that our results are captured by a simple, constitutive scaling relation highlighting the important role of nonaffine strain fluctuations as a susceptibility to motor stress.

  19. A coordinate-invariant model for deforming geodetic networks: understanding rank deficiencies, non-estimability of parameters, and the effect of the choice of minimal constraints

    NASA Astrophysics Data System (ADS)

    Chatzinikos, Miltiadis; Dermanis, Athanasios

    2016-11-01

    By considering a deformable geodetic network, deforming in a linear-in-time mode, according to a coordinate-invariant model, it becomes possible to get an insight into the rank deficiency of the stacking procedure, which is the standard method for estimating initial station coordinates and constant velocities, from coordinate time series. Comparing any two out of the infinitely many least squares estimates of stacking unknowns (initial station coordinates, velocity components and transformation parameters for the reference system in each data epoch), it is proven that the two solutions differ only by a linear-in-time trend in the transformation parameters. These pass over to the initial coordinates (the constant term) and to the velocity estimates (the time coefficient part). While the difference in initial coordinates is equivalent to a change of the reference system at the initial epoch, the differences in velocity components do not comply with those predicted by the same change of reference system for all epochs. Consequently, the different velocity component estimates, obtained by introducing different sets of minimal constraints, correspond to physically different station velocities, which are therefore non-estimable quantities. The theoretical findings are numerically verified for a global, a regional and a local network, by obtaining solutions based on four different types of minimal constraints, three usual algebraic ones (inner or partial inner) and the lately introduced kinematic constraints. Finally, by resorting to the basic ideas of Felix Tisserand, it is explained why the station velocities are non-estimable quantities in a very natural way. The problem of the optimal choice of minimal constraints and, hence, of the corresponding spatio-temporal reference system is shortly discussed.

  20. A coordinate-invariant model for deforming geodetic networks: understanding rank deficiencies, non-estimability of parameters, and the effect of the choice of minimal constraints

    NASA Astrophysics Data System (ADS)

    Chatzinikos, Miltiadis; Dermanis, Athanasios

    2017-04-01

    By considering a deformable geodetic network, deforming in a linear-in-time mode, according to a coordinate-invariant model, it becomes possible to get an insight into the rank deficiency of the stacking procedure, which is the standard method for estimating initial station coordinates and constant velocities, from coordinate time series. Comparing any two out of the infinitely many least squares estimates of stacking unknowns (initial station coordinates, velocity components and transformation parameters for the reference system in each data epoch), it is proven that the two solutions differ only by a linear-in-time trend in the transformation parameters. These pass over to the initial coordinates (the constant term) and to the velocity estimates (the time coefficient part). While the difference in initial coordinates is equivalent to a change of the reference system at the initial epoch, the differences in velocity components do not comply with those predicted by the same change of reference system for all epochs. Consequently, the different velocity component estimates, obtained by introducing different sets of minimal constraints, correspond to physically different station velocities, which are therefore non-estimable quantities. The theoretical findings are numerically verified for a global, a regional and a local network, by obtaining solutions based on four different types of minimal constraints, three usual algebraic ones (inner or partial inner) and the lately introduced kinematic constraints. Finally, by resorting to the basic ideas of Felix Tisserand, it is explained why the station velocities are non-estimable quantities in a very natural way. The problem of the optimal choice of minimal constraints and, hence, of the corresponding spatio-temporal reference system is shortly discussed.

  1. Active deformation in the Northern Walker Lane: a detailed geodetic study of the Mohawk Valley and Honey Lake/Warm Springs fault systems

    NASA Astrophysics Data System (ADS)

    Bormann, J. M.; Hammond, W. C.; Kreemer, C. W.; Blewitt, G.

    2012-12-01

    The Mohawk Valley and Honey Lake/Warm Springs faults are parallel, northwest striking, dextral fault systems separated by ~50 km in the westernmost part of the Northern Walker Lane. These two faults work as a cooperative pair to accommodate 3-5 mm/yr of the total 8 mm/yr of right-lateral deformation geodetically observed across the Northern Walker Lane, however it is unclear with fault is dominant. Geologic studies of the faults result in right-lateral slip rates of 1-2.5 mm/yr on the Honey Lake fault and a minimum of 0.3 mm/yr on the Mohawk Valley fault. In contrast, previous geodetic studies estimate slip rates of ~1 mm/yr on the Honey Lake fault and ~3 mm/yr on the Mohawk Valley fault. To reconcile the discrepancy between the distribution of slip on the faults and the differences between sums of the geologically and geodetically estimated slip rates, we use new GPS data to constrain an elastic block model developed specifically to study the Mohawk Valley and Honey Lake/Warm Springs fault systems. We present a dense GPS velocity solution (~10 km average station spacing) that incorporates new data from the semi-continuous Mobile Array of GPS for Nevada Transtension network (MAGNET, http://geodesy.unr.edu/networks) operated by the University of Nevada, Reno with continuous data from the EarthScope Plate Boundary Observatory and other networks. Data collected during the summer of 2012 bring many MAGNET GPS time series in the Northern Walker Lane to near 5 years in duration. The density of our velocity field and recent advances in data processing give us unprecedented precision in the measurement of contemporary deformation in the Northern Walker Lane. We use the velocity solution to solve for slip rates on the companion fault systems and explore the effects of block model geometry assumptions and tradeoffs. Our model predicts slip rates of 2.2±0.3 mm/yr for the Mohawk Valley fault and 1.1±0.2 mm/yr for the Honey Lake fault. Block model slip rate estimates are

  2. New state-of-the art geodetic observatory on the way in the Arctic

    NASA Astrophysics Data System (ADS)

    Opseth, P. E.

    2013-12-01

    The new state-of-the-art observatory that the Norwegian Mapping Authority (NMA/Kartverket) is establishing in Ny-Aalesund, Svalbard will be a part of a global network that allows us to monitor the Earth system. In this paper we will present the value of precise measurements, the need for an infrastructure of continuously operating reference stations and software that take advantage of the infrastructure, and the value of international cooperation. NMA has a long history in operating and maintaining GNSS networks, and distributing of GNSS augmentation data. Since the first permanent GPS station was installed in 1987 we have established a network of more than 160 continuously operating reference stations (CORE) in Norway. The geodetic infrastructure, including a network of tide gauges around the Norwegian coastline, levelling and gravity measurements, allows us to establish a high-precision national network and to measure local sea-level changes of a couple of millimetres per year. NMA operates the space geodetic observatory at Ny-Aalesund, Svalbard, which now includes among others, a VLBI antenna and several GPS and GLONASS receivers. NMA is in the process of upgrading the observatory in Ny-Aalesund to a core network station within the Global Geodetic Observing System (GGOS). This means to adapt to the VLBI2010 standard and to extend our activity to integrate Satellite Laser Ranging (SLR). The construction will take five years from the start of work until the antennas are ready in 2018. Even though Norway and a few other countries are already working to upgrade their geodetic observatories, however, these efforts will not be sufficient to secure global coverage. The UN Committee of Expert on Global Geospatial Information Management (UN-GGIM) is accordingly paying growing attention to geodetic observation. Work in this committee could lead to an UN resolution on global geodetic collaboration. A UN mandate could encourage a number of other countries to make a

  3. Precise Geodetic Infrastructure: National Requirements for a Shared Resource

    NASA Astrophysics Data System (ADS)

    Minster, J. H.; Altamimi, Z.; Blewitt, G.; Carter, W. E.; Cazenave, A. A.; Dragert, H.; Herring, T.; Larson, K. M.; Ries, J. C.; Sandwell, D. T.; Wahr, J. M.; Davis, J. L.; Feary, D. A.; Shanley, L. A.; Nrc Committee On The National RequirementsPrecision Geodetic Infrastructure

    2010-12-01

    Recognizing the growing reliance of a wide range of scientific and societal endeavors on infrastructure for precise geodesy, and recognizing geodetic infrastructure as a shared national resource, NASA, USNO, NGA (DoD), NSF, NGS (NOAA), and USGS requested the National Research Council (NRC) to provide an independent assessment of the benefits provided by geodetic observations and networks, as well as a plan for the future development and support of the infrastructure needed to meet the demand for increasingly greater precision. We recommend in this study that “The United States, to maintain leadership in industry and science, and as a matter of national security, should invest in maintaining and improving the geodetic infrastructure, through upgrades in network design and construction, modernization of current observing systems, deployment of improved multi-technique observing capabilities, and funding opportunities for research, analysis, and education in global geodesy.” Today’s precise global geodetic infrastructure is fragile, and we also recommend (1) an international cooperative effort to increase the density of the international geodetic network with a goal of reaching a network of at least 24 fundamental stations; (2) a national GNSS network constructed to scientific specifications, capable of streaming high-rate data in real-time, with no restrictions on data access; (3) continued support of international geodetic services; (4) a long-term commitment to maintain the International Terrestrial Reference Frame. The astonishing advances toward higher geodetic accuracy at increasing temporal resolution are made possible only by all components of the geodetic infrastructure working together as a coherent system. The components of the geodetic infrastructure, however, are dispersed among various departments, agencies, and organizations. The nation’s precise geodetic infrastructure has not been considered holistically before now. Nevertheless, it is a

  4. Volcano-tectonic deformation in the Kivu Region, Central Africa: Results from multi-year InSAR time series analysis and continuous GNSS observations of the Kivu Geodetic Network (KivuGNet)

    NASA Astrophysics Data System (ADS)

    Geirsson, Halldor; D'Oreye, Nicolas; Smets, Benoît; Nobile, Adriano; Samsonov, Sergey; De Rauw, Dominique; Mashagiro, Niche; Kervyn, Francois

    2016-04-01

    The Kivu Region in Central Africa is a topographic dome cut by the depression of the western branch of the East African Rift, where the Nubia plate and the Victoria micro-plate are diverging by approximately 2-3 mm/yr (Stamps et al. 2008). Two closely spaced and frequently active volcanoes, Nyiragongo and Nyamulagira, are located at the plate boundary. Here, deformation signals from transient deformation events (i.e. earthquakes, eruptions, rifting episodes, intrusions or other subsurface mass movements) are intertwined with the more perpetual nature of inter-seismic strain accumulation and gradual magma accumulation. Here, we present deformation results from six years of operation of the 15- station KivuGNet (Kivu Geodetic Network) in the Kivu Region and multi-year InSAR time series of the region using the MSBAS approach (Samsonov & d'Oreye, 2012). Since 2009, KivuGNet has captured transient deformation from a) the 2010 eruption of Nyamulagira, b) the 2011-2012 eruption of Nyamulagira c) the Mw5.8 August 7, 2015 Katana earthquake at the western border of Lake Kivu. Importantly, the GPS data also show an ongoing deformation signal, which is most readily explained by long-term magma accumulation under the volcanic region. We use the GPS and InSAR deformation signals to constrain and compare source parameters of simplistic elastic models for the different time periods. Although not well constrained, most of the time periods indicate the presence of a deep (~15-30 km) magmatic source centered approximately under Nyamulagira or to the southeast of Nyamulagira, that inflates between eruptions and deflates during eruptions.

  5. GPS orbit determination at the National Geodetic Survey

    NASA Technical Reports Server (NTRS)

    Schenewerk, Mark S.

    1992-01-01

    The National Geodetic Survey (NGS) independently generates precise ephemerides for all available Global Positioning System (GPS) satellites. Beginning in 1991, these ephemerides were produced from double-differenced phase observations solely from the Cooperative International GPS Network (CIGNET) tracking sites. The double-difference technique combines simultaneous observations of two satellites from two ground stations effectively eliminating satellite and ground receiver clock errors, and the Selective Availability (S/A) signal degradation currently in effect. CIGNET is a global GPS tracking network whose primary purpose is to provide data for orbit production. The CIGNET data are collected daily at NGS and are available to the public. Each ephemeris covers a single week and is available within one month after the data were taken. Verification is by baseline repeatability and direct comparison with other ephemerides. Typically, an ephemeris is accurate at a few parts in 10(exp 7). This corresponds to a 10 meter error in the reported satellite positions. NGS is actively investigating methods to improve the accuracy of its orbits, the ultimate goal being one part in 10(exp 8) or better. The ephemerides are generally available to the public through the Coast Guard GPS Information Center or directly from NGS through the Geodetic Information Service. An overview of the techniques and software used in orbit generation will be given, the current status of CIGNET will be described, and a summary of the ephemeris verification results will be presented.

  6. Fiber networks amplify active stress

    PubMed Central

    Ronceray, Pierre; Broedersz, Chase P.

    2016-01-01

    Large-scale force generation is essential for biological functions such as cell motility, embryonic development, and muscle contraction. In these processes, forces generated at the molecular level by motor proteins are transmitted by disordered fiber networks, resulting in large-scale active stresses. Although these fiber networks are well characterized macroscopically, this stress generation by microscopic active units is not well understood. Here we theoretically study force transmission in these networks. We find that collective fiber buckling in the vicinity of a local active unit results in a rectification of stress towards strongly amplified isotropic contraction. This stress amplification is reinforced by the networks’ disordered nature, but saturates for high densities of active units. Our predictions are quantitatively consistent with experiments on reconstituted tissues and actomyosin networks and shed light on the role of the network microstructure in shaping active stresses in cells and tissue. PMID:26921325

  7. Geodetic distance measuring apparatus

    NASA Astrophysics Data System (ADS)

    Abshire, J. B.

    1980-12-01

    A geodetic distance measuring apparatus which compensates for the refractive index of the atmosphere is discussed. A mode locked laser system with a laser device and its peripheral components is utilized to derive two mutually phase locked optical wavelength signals and one phase locked microwave CW signal which respectively traverse the same distance measurement path. The optical signals are comprised of pulse type signals. Phase comparison of the two optical wavelength pulse signals is used to provide the dry air density while phase comparison of one of the optical wavelength pulse signals and the microwave CW signal issued to provide wet or water vapor density of the air. The distance to be measured corrected for the atmospheric dry air and water vapor densities in the measurement path is computed from these measurements. A time interval unit is included for measuring transit time of individual optical pulses for resolving the phase ambiguity needed with the phase measurements to give the true target distance.

  8. Fiber networks amplify active stress

    NASA Astrophysics Data System (ADS)

    Lenz, Martin; Ronceray, Pierre; Broedersz, Chase

    Large-scale force generation is essential for biological functions such as cell motility, embryonic development, and muscle contraction. In these processes, forces generated at the molecular level by motor proteins are transmitted by disordered fiber networks, resulting in large-scale active stresses. While fiber networks are well characterized macroscopically, this stress generation by microscopic active units is not well understood. I will present a comprehensive theoretical study of force transmission in these networks. I will show that the linear, small-force response of the networks is remarkably simple, as the macroscopic active stress depends only on the geometry of the force-exerting unit. In contrast, as non-linear buckling occurs around these units, local active forces are rectified towards isotropic contraction and strongly amplified. This stress amplification is reinforced by the networks' disordered nature, but saturates for high densities of active units. I will show that our predictions are quantitatively consistent with experiments on reconstituted tissues and actomyosin networks, and that they shed light on the role of the network microstructure in shaping active stresses in cells and tissue.

  9. The current state of the creation and modernization of national geodetic and cartographic resources in Poland

    NASA Astrophysics Data System (ADS)

    Doskocz, Adam

    2016-01-01

    All official data are currently integrated and harmonized in a spatial reference system. This paper outlines a national geodetic and cartographic resources in Poland. The national geodetic and cartographic resources are an important part of the spatial information infrastructure in the European Community. They also provide reference data for other resources of Spatial Data Infrastructure (SDI), including: main and detailed geodetic control networks, base maps, land and buildings registries, geodetic registries of utilities and topographic maps. This paper presents methods of producing digital map data and technical standards for field surveys, and in addition paper also presents some aspects of building Global and Regional SDI.

  10. Innovative Active Networking Services

    DTIC Science & Technology

    2004-03-01

    Integrating IKE We use the “ pluto ” implementation from Freeswan [Freeswan] as our IKE module. Pluto runs as a daemon on a Linux Network node. This base...implementation though incomplete with respect to some features of IKE is still sufficient in order to inter-operate with other pluto implementations...and many other IKE 30 implementations. Commands to pluto are given using a control interface to the daemon, called “whack”. Pluto uses either shared

  11. Insights into the 3D architecture of an active caldera ring-fault at Tendürek volcano through modeling of geodetic data

    NASA Astrophysics Data System (ADS)

    Bathke, H.; Nikkhoo, M.; Holohan, E. P.; Walter, T. R.

    2015-07-01

    The three-dimensional assessment of ring-fault geometries and kinematics at active caldera volcanoes is typically limited by sparse field, geodetic or seismological data, or by only partial ring-fault rupture or slip. Here we use a novel combination of spatially dense InSAR time-series data, numerical models and sand-box experiments to determine the three-dimensional geometry and kinematics of a sub-surface ring-fault at Tendürek volcano in Turkey. The InSAR data reveal that the area within the ring-fault not only subsides, but also shows substantial westward-directed lateral movement. The models and experiments explain this as a consequence of a 'sliding-trapdoor' ring-fault architecture that is mostly composed of outward-inclined reverse segments, most markedly so on the volcano's western flanks but includes inward-inclined normal segments on its eastern flanks. Furthermore, the model ring-fault exhibits dextral and sinistral strike-slip components that are roughly bilaterally distributed onto its northern and southern segments, respectively. Our more complex numerical model describes the deformation at Tendürek better than an analytical solution for a single rectangular dislocation in a half-space. Comparison to ring-faults defined at Glen Coe, Fernandina and Bárðarbunga calderas suggests that 'sliding-trapdoor' ring-fault geometries may be common in nature and should therefore be considered in geological and geophysical interpretations of ring-faults at different scales worldwide.

  12. Theorizing Network-Centric Activity in Education

    ERIC Educational Resources Information Center

    HaLevi, Andrew

    2011-01-01

    Networks and network-centric activity are increasingly prevalent in schools and school districts. In addition to ubiquitous social network tools like Facebook and Twitter, educational leaders deal with a wide variety of network organizational forms that include professional development, advocacy, informational networks and network-centric reforms.…

  13. The AuScope geodetic VLBI array

    NASA Astrophysics Data System (ADS)

    Lovell, J. E. J.; McCallum, J. N.; Reid, P. B.; McCulloch, P. M.; Baynes, B. E.; Dickey, J. M.; Shabala, S. S.; Watson, C. S.; Titov, O.; Ruddick, R.; Twilley, R.; Reynolds, C.; Tingay, S. J.; Shield, P.; Adada, R.; Ellingsen, S. P.; Morgan, J. S.; Bignall, H. E.

    2013-06-01

    The AuScope geodetic Very Long Baseline Interferometry array consists of three new 12-m radio telescopes and a correlation facility in Australia. The telescopes at Hobart (Tasmania), Katherine (Northern Territory) and Yarragadee (Western Australia) are co-located with other space geodetic techniques including Global Navigation Satellite Systems (GNSS) and gravity infrastructure, and in the case of Yarragadee, satellite laser ranging (SLR) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) facilities. The correlation facility is based in Perth (Western Australia). This new facility will make significant contributions to improving the densification of the International Celestial Reference Frame in the Southern Hemisphere, and subsequently enhance the International Terrestrial Reference Frame through the ability to detect and mitigate systematic error. This, combined with the simultaneous densification of the GNSS network across Australia, will enable the improved measurement of intraplate deformation across the Australian tectonic plate. In this paper, we present a description of this new infrastructure and present some initial results, including telescope performance measurements and positions of the telescopes in the International Terrestrial Reference Frame. We show that this array is already capable of achieving centimetre precision over typical long-baselines and that network and reference source systematic effects must be further improved to reach the ambitious goals of VLBI2010.

  14. LAGEOS geodetic analysis-SL7.1

    NASA Technical Reports Server (NTRS)

    Smith, D. E.; Kolenkiewicz, R.; Dunn, P. J.; Klosko, S. M.; Robbins, J. W.; Torrence, M. H.; Williamson, R. G.; Pavlis, E. C.; Douglas, N. B.; Fricke, S. K.

    1991-01-01

    Laser ranging measurements to the LAGEOS satellite from 1976 through 1989 are related via geodetic and orbital theories to a variety of geodetic and geodynamic parameters. The SL7.1 analyses are explained of this data set including the estimation process for geodetic parameters such as Earth's gravitational constant (GM), those describing the Earth's elasticity properties (Love numbers), and the temporally varying geodetic parameters such as Earth's orientation (polar motion and Delta UT1) and tracking site horizontal tectonic motions. Descriptions of the reference systems, tectonic models, and adopted geodetic constants are provided; these are the framework within which the SL7.1 solution takes place. Estimates of temporal variations in non-conservative force parameters are included in these SL7.1 analyses as well as parameters describing the orbital states at monthly epochs. This information is useful in further refining models used to describe close-Earth satellite behavior. Estimates of intersite motions and individual tracking site motions computed through the network adjustment scheme are given. Tabulations of tracking site eccentricities, data summaries, estimated monthly orbital and force model parameters, polar motion, Earth rotation, and tracking station coordinate results are also provided.

  15. Seafloor geodetic constraints on interplate coupling of the Nankai Trough megathrust zone.

    PubMed

    Yokota, Yusuke; Ishikawa, Tadashi; Watanabe, Shun-ichi; Tashiro, Toshiharu; Asada, Akira

    2016-06-16

    Interplate megathrust earthquakes have inflicted catastrophic damage on human society. Such an earthquake is predicted to occur in the near future along the Nankai Trough off southwestern Japan--an economically active and densely populated area in which megathrust earthquakes have already occurred. Megathrust earthquakes are the result of a plate-subduction mechanism and occur at slip-deficit regions (also known as 'coupling' regions), where friction prevents plates from slipping against each other and the accumulated energy is eventually released forcefully. Many studies have attempted to capture distributions of slip-deficit rates (SDRs) in order to predict earthquakes. However, these studies could not obtain a complete view of the earthquake source region, because they had no seafloor geodetic data. The Hydrographic and Oceanographic Department of the Japan Coast Guard (JHOD) has been developing a precise and sustainable seafloor geodetic observation network in this subduction zone to obtain information related to offshore SDRs. Here, we present seafloor geodetic observation data and an offshore interplate SDR-distribution model. Our data suggest that most offshore regions in this subduction zone have positive SDRs. Specifically, our observations indicate previously unknown regions of high SDR that will be important for tsunami disaster mitigation, and regions of low SDR that are consistent with distributions of shallow slow earthquakes and subducting seamounts. This is the first direct evidence that coupling conditions might be related to these seismological and geological phenomena. Our findings provide information for inferring megathrust earthquake scenarios and interpreting research on the Nankai Trough subduction zone.

  16. Mobile radio interferometric geodetic systems

    NASA Technical Reports Server (NTRS)

    Macdoran, P. F.; Niell, A. E.; Ong, K. M.; Resch, G. M.; Morabito, D. D.; Claflin, E. S.; Lockhart, T. G.

    1978-01-01

    Operation of the Astronomical Radio Interferometric Earth Surveying (ARIES) in a proof of concept mode is discussed. Accuracy demonstrations over a short baseline, a 180 km baseline, and a 380 km baseline are documented. Use of ARIES in the Sea Slope Experiment of the National Geodetic Survey to study the apparent differences between oceanographic and geodetic leveling determinations of the sea surface along the Pacific Coast is described. Intergration of the NAVSTAR Global Positioning System and a concept called SERIES (Satellite Emission Radio Interferometric Earth Surveying) is briefly reviewed.

  17. Plate motions and deformations from geologic and geodetic data

    NASA Technical Reports Server (NTRS)

    Jordan, Thomas H.

    1990-01-01

    An analysis of geodetic data in the vicinity of the Crustal Dynamics Program (CDP) site at Vandenberg Air Force Base (VNDN) is presented. The utility of space-geodetic data in the monitoring of transient strains associated with earthquakes in tectonically active areas like California is investigated. Particular interest is in the possibility that space-geodetic methods may be able to provide critical new data on deformations precursory to large seismic events. Although earthquake precursory phenomena are not well understood, the monitoring of small strains in the vicinity of active faults is a promising technique for studying the mechanisms that nucleate large earthquakes and, ultimately, for earthquake prediction. Space-geodetic techniques are now capable of measuring baselines of tens to hundreds of kilometers with a precision of a few parts in 108. Within the next few years, it will be possible to record and analyze large-scale strain variations with this precision continuously in real time. Thus, space-geodetic techniques may become tools for earthquake prediction. In anticipation of this capability, several questions related to the temporal and spatial scales associated with subseismic deformation transients are examined.

  18. The Global Space Geodesy Network: Activities Underway

    NASA Astrophysics Data System (ADS)

    Pearlman, Michael R.; Ipatov, Alexander; Long, James; Ma, Chopo; Merkowitz, Stephen; Neilan, Ruth; Noll, Carey; Pavlis, Erricos; Shargorodsky, Victor; Stowers, David; Wetzel, Scott

    2014-05-01

    Several initiatives are underway that should make substantial improvement over the next decade to the international space geodesy network as the international community works toward the GGOS 2020 goal of 32 globally distributed Core Sites with co-located VLBI, SLR, GNSS and DORIS. The Russian Space Agency and the Russian Academy of Sciences are moving forward with an implementation of six additional SLR systems and a number of GNSS receivers to sites outside Russia to expand GNSS tracking and support GGOS. The NASA Space Geodesy program has completed its prototype development phase and is now embarking on an implementation phase that is planning for deployment of 6 - 10 core sites in key geographic locations to support the global network. Additional sites are in the process of implementation in Europe and Asia. Site evaluation studies are in progress, looking at some new potential sites and there are ongoing discussions for partnership arrangements with interested agencies for new sites in South America and Africa. Work continues on the site layout design to avoid RF interference issues among co-located instruments and with external communications and media system. The placement of new and upgraded sites is guided by appropriate Observing System Simulation Experiments (OSSEs) conducted under the support of the interested international agencies. The results will help optimize the global distribution of core geodetic observatories and they will lead to the improvement of the data products from the future network. During this effort it is also recognized that co-located sites with less than the full core complement will continue to play an important and critical role in filling out the global network and strengthening the connection among the techniques. This talk will give an update on the current state of expansion of the global network and the projection for the network configuration that we forecast over the next 10 years.

  19. VLBI2010 PROOF-OF-CONCEPT GEODETIC VLBI SYSTEM

    NASA Astrophysics Data System (ADS)

    Beaudoin, C.; Niell, A. E.

    2009-12-01

    Geodetic Very Long Baseline Interferometry (VLBI) plays an important role in establishing the Terrestrial Reference Frame, measuring the Earth-orientation parameters (EOP), and understanding the properties of the Inner Core, among other geophysical phenomena. To enhance the science obtained from geodetic VLBI, NASA is funding the development of a new broadband geodetic VLBI microwave (2-12 GHz) system by the MIT Haystack Observatory, in cooperation with personnel from HTSI, NVI, and GSFC. This broadband system is intended to replace the operational S/X-band system currently deployed in the global geodetic VLBI network. The broadband capability of the new feed and receiver and the sustained data recording rate (up to 4 Gbps per band) supported by the digital back-end and Mark5C recorder will a) allow the use of relatively small (~12m) but fast slewing antennas to reduce the error due to atmosphere delay fluctuations and b) provide flexibility in frequency coverage to reduce sensitivity to external radio frequency interference, an increasing problem. A demonstration system has been implemented by installing the proof-of-concept feed, receiver, and data acquisition system on the single baseline composed of the 18m antenna in Westford MA and the 5m MV3 antenna at the Goddard Space Flight Center in Greenbelt MD. In our contribution we will describe the new geodetic VLBI system and discuss recent results. Future challenges and advances that will be needed in both hardware and software to achieve the required precision of the geodetic observables will also be presented.

  20. Active contraction of microtubule networks

    PubMed Central

    Foster, Peter J; Fürthauer, Sebastian; Shelley, Michael J; Needleman, Daniel J

    2015-01-01

    Many cellular processes are driven by cytoskeletal assemblies. It remains unclear how cytoskeletal filaments and motor proteins organize into cellular scale structures and how molecular properties of cytoskeletal components affect the large-scale behaviors of these systems. Here, we investigate the self-organization of stabilized microtubules in Xenopus oocyte extracts and find that they can form macroscopic networks that spontaneously contract. We propose that these contractions are driven by the clustering of microtubule minus ends by dynein. Based on this idea, we construct an active fluid theory of network contractions, which predicts a dependence of the timescale of contraction on initial network geometry, a development of density inhomogeneities during contraction, a constant final network density, and a strong influence of dynein inhibition on the rate of contraction, all in quantitative agreement with experiments. These results demonstrate that the motor-driven clustering of filament ends is a generic mechanism leading to contraction. DOI: http://dx.doi.org/10.7554/eLife.10837.001 PMID:26701905

  1. Workshop targets development of geodetic transient detection methods: 2009 SCEC Annual Meeting: Workshop on transient anomalous strain detection; Palm Springs, California, 12-13 September 2009

    USGS Publications Warehouse

    Murray-Moraleda, Jessica R.; Lohman, Rowena

    2010-01-01

    The Southern California Earthquake Center (SCEC) is a community of researchers at institutions worldwide working to improve understanding of earthquakes and mitigate earthquake risk. One of SCEC's priority objectives is to “develop a geodetic network processing system that will detect anomalous strain transients.” Given the growing number of continuously recording geodetic networks consisting of hundreds of stations, an automated means for systematically searching data for transient signals, especially in near real time, is critical for network operations, hazard monitoring, and event response. The SCEC Transient Detection Test Exercise began in 2008 to foster an active community of researchers working on this problem, explore promising methods, and combine effective approaches in novel ways. A workshop was held in California to assess what has been learned thus far and discuss areas of focus as the project moves forward.

  2. The Australian Geodetic Observing Program. Current Status and Future Plans

    NASA Astrophysics Data System (ADS)

    Johnston, G.; Dawson, J. H.

    2015-12-01

    Over the last decade, the Australian government has through programs like AuScope, the Asia Pacific Reference Frame (APREF), and the Pacific Sea Level Monitoring (PSLM) Project made a significant contribution to the Global Geodetic Observing Program. In addition to supporting the national research priorities, this contribution is justified by Australia's growing economic dependence on precise positioning to underpin efficient transportation, geospatial data management, and industrial automation (e.g., robotic mining and precision agriculture) and the consequent need for the government to guarantee provision of precise positioning products to the Australian community. It is also well recognised within Australia that there is an opportunity to exploit our near unique position as being one of the few regions in the world to see all new and emerging satellite navigation systems including Galileo (Europe), GPS III (USA), GLONASS (Russia), Beidou (China), QZSS (Japan) and IRNSS (India). It is in this context that the Australian geodetic program will build on earlier efforts and further develop its key geodetic capabilities. This will include the creation of an independent GNSS analysis capability that will enable Australia to contribute to the International GNSS Service (IGS) and an upgrade of key geodetic infrastructure including the national VLBI and GNSS arrays. This presentation will overview the significant geodetic activities undertaken by the Australian government and highlight its future plans.

  3. Geodetic Monitoring System Operating On Neapolitan Volcanic Area (southern Italy)

    NASA Astrophysics Data System (ADS)

    Pingue, F.; Ov-Geodesy Team

    volcanic high risk, is monitored also by dense geodetic networks using different methods: levelling, GPS, tiltmeter, tide-gauge, gravimetry, INSAR. Each of the collected data contributes to volcanic sources modelling, thus to the eruptive scenarios definition and the risk mitigation. Here the geodetic surveillance system in the Neapolitan area is described in detail and the main results obtained in the last years are shown and discussed.

  4. Combining Real-time Seismic and Geodetic Data to Improve Rapid Earthquake Information

    NASA Astrophysics Data System (ADS)

    Murray, M. H.; Neuhauser, D. S.; Gee, L. S.; Dreger, D. S.; Basset, A.; Romanowicz, B.

    2002-12-01

    The Berkeley Seismological Laboratory operates seismic and geodetic stations in the San Francisco Bay area and northern California for earthquake and deformation monitoring. The seismic systems, part of the Berkeley Digital Seismic Network (BDSN), include strong motion and broadband sensors, and 24-bit dataloggers. The data from 20 GPS stations, part of the Bay Area Regional Deformation (BARD) network of more than 70 stations in northern California, are acquired in real-time. We have developed methods to acquire GPS data at 12 stations that are collocated with the seismic systems using the seismic dataloggers, which have large on-site data buffer and storage capabilities, merge it with the seismic data stream in MiniSeed format, and continuously stream both data types using reliable frame relay and/or radio modem telemetry. Currently, the seismic data are incorporated into the Rapid Earthquake Data Integration (REDI) project to provide notification of earthquake magnitude, location, moment tensor, and strong motion information for hazard mitigation and emergency response activities. The geodetic measurements can provide complementary constraints on earthquake faulting, including the location and extent of the rupture plane, unambiguous resolution of the nodal plane, and distribution of slip on the fault plane, which can be used, for example, to refine strong motion shake maps. We are developing methods to rapidly process the geodetic data to monitor transient deformation, such as coseismic station displacements, and for combining this information with the seismic observations to improve finite-fault characterization of large earthquakes. The GPS data are currently processed at hourly intervals with 2-cm precision in horizontal position, and we are beginning a pilot project in the Bay Area in collaboration with the California Spatial Reference Center to do epoch-by-epoch processing with greater precision.

  5. Update on the activities of the GGOS Bureau of Networks and Observations

    NASA Technical Reports Server (NTRS)

    Pearlman, Michael R.; Pavlis, Erricos C.; Ma, Chopo; Noll, Carey; Thaller, Daniela; Richter, Bernd; Gross, Richard; Neilan, Ruth; Mueller, Juergen; Barzaghi, Ricardo; Bergstrand, Sten; Saunier, Jerome; Tamisiea, Mark

    2016-01-01

    The recently reorganized GGOS Bureau of Networks and Observations has many elements that are associated with building and sustaining the infrastructure that supports the Global Geodetic Observing System (GGOS) through the development and maintenance of the International Terrestrial and Celestial Reference Frames, improved gravity field models and their incorporation into the reference frame, the production of precision orbits for missions of interest to GGOS, and many other applications. The affiliated Service Networks (IVS, ILRS, IGS, IDS, and now the IGFS and the PSMSL) continue to grow geographically and to improve core and co-location site performance with newer technologies. Efforts are underway to expand GGOS participation and outreach. Several groups are undertaking initiatives and seeking partnerships to update existing sites and expand the networks in geographic areas void of coverage. New satellites are being launched by the Space Agencies in disciplines relevant to GGOS. Working groups now constitute an integral part of the Bureau, providing key service to GGOS. Their activities include: projecting future network capability and examining trade-off options for station deployment and technology upgrades, developing metadata collection and online availability strategies; improving coordination and information exchange with the missions for better ground-based network response and space-segment adequacy for the realization of GGOS goals; and standardizing site-tie measurement, archiving, and analysis procedures. This poster will present the progress in the Bureau's activities and its efforts to expand the networks and make them more effective in supporting GGOS.

  6. International Collaborations Fostering Data Discovery and Access of Geodetic Data for the Geosciences

    NASA Astrophysics Data System (ADS)

    Meertens, C. M.; Boler, F. M.; Miller, M. M.

    2014-12-01

    UNAVCO community investigators are actively engaged in using space and terrestrial geodetic techniques to study earthquake processes, mantle properties, active magmatic systems, plate tectonics, plate boundary zone deformation, intraplate deformation, glacial isostatic adjustment, and hydrologic and atmospheric processes. Since the first GPS field projects were conducted over thirty years ago, these science investigations and the UNAVCO constituency as a whole have been international and collaborative in scope and participation. Collaborations were driven by the nature of the scientific problems being addressed, the capability of the technology to make precise measurements over global scales, and inherent technical necessity for sharing of GPS tracking data across national boundaries. The International GNSS Service (IGS) was formed twenty years ago as a voluntary federation to share GPS data from now hundreds of locations around the globe to facilitate realization of global reference frames, ties to regional surveys, precise orbits, and to establish and improve best practices in analysis and infrastructure. Recently, however, numbers of regional stations have grown to the tens of thousands, typically with data that are difficult to access. UNAVCO has been working to help remove technical barriers by providing open source tools such as the Geodetic Seamless Archive Centers software to facilitate data sharing and discovery and by developing DataWorks software to manage network data. Data web services also provide the framework for UNAVCO contributions to multi-technique, inter-disciplinary, and integrative activities such as CooPEUS, GEO Supersites, EarthScope, and EarthCube. We will discuss some of UNAVCO's experiences with building and maintaining international collaborations, processes for defining and evolving best practices, technological approaches for sharing and attribution of geodetic data, and challenges to open data access.

  7. New Developments in Geodetic Data Management Systems for Fostering International Collaborations in the Geosciences

    NASA Astrophysics Data System (ADS)

    Meertens, Charles; Boler, Fran; Miller, M. Meghan

    2015-04-01

    UNAVCO community investigators are actively engaged in using space and terrestrial geodetic techniques to study earthquake processes, mantle properties, active magmatic systems, plate tectonics, plate boundary zone deformation, intraplate deformation, glacial isostatic adjustment, and hydrologic and atmospheric processes. The first GPS field projects were conducted over thirty years ago, and from the beginning these science investigations and the UNAVCO constituency as a whole have been international and collaborative in scope and participation. Collaborations were driven by the nature of the scientific problems being addressed, the capability of the technology to make precise measurements over global scales, and inherent technical necessity for sharing of GPS tracking data across national boundaries. The International GNSS Service (IGS) was formed twenty years ago as a voluntary federation to share GPS data from now hundreds of locations around the globe to facilitate realization of global reference frames, ties to regional surveys, precise orbits, and to establish and improve best practices in analysis and infrastructure. Recently, however, numbers of regional stations have grown to the tens of thousands, often with data that are difficult to access. UNAVCO has been working to help remove technical barriers by providing open source tools such as the Geodetic Seamless Archive Centers software to facilitate cross-project data sharing and discovery and by developing Dataworks software to manage network data. Data web services also provide the framework for UNAVCO contributions to multi-technique, inter-disciplinary, and integrative activities such as CoopEUS, GEO Supersites, EarthScope, and EarthCube. Within the geodetic community, metadata standards and data exchange formats have been developed and evolved collaboratively through the efforts of global organizations such as the IGS. A new generation of metadata and data exchange formats, as well as the software

  8. Damage and restoration of geodetic infrastructure caused by the 1994 Northridge, California, earthquake

    USGS Publications Warehouse

    Hodgkinson, Kathleen M.; Stein, Ross S.; Hudnut, Kenneth W.; Satalich, Jay; Richards, John H.

    1996-01-01

    We seek to restore the integrity of the geodetic network in the San Fernando, Simi, Santa Clarita Valleys and in the northern Los Angeles Basin by remeasurement of the network and identification of BMs which experienced non-tectonic displacements associated with the Northridge earthquake. We then use the observed displacement of BMs in the network to portray or predict the permanent vertical and horizontal deformation associated with the 1994 Northridge earthquake throughout the area, including sites where we lack geodetic measurements. To accomplish this, we find the fault geometry and earthquake slip that are most compatible with the geodetic and independent seismic observations of the earthquake. We then use that fault model to predict the deformation everywhere at the earth's surface, both at locations where geodetic observations exist and also where they are absent. We compare displacements predicted for a large number of numerical models of the earthquake faulting to the coseismic displacements, treating the earthquake fault as a cut or discontinuity embedded in a stiff elastic solid. This comparison is made after non-tectonic deformation has been removed from the measured elevation changes. The fault slip produces strain in the medium and deforms the ground surface. The model compatible with seismic observations that best fits the geodetic data within their uncertainties is selected. The acceptable model fault bisects the mainshock focus, and the earthquake size , magnitude, is compatible with the earthquake size measured seismically. Our fault model was used to identify geodetic monuments on engineered structures that were anomalously displaced by the earthquake.

  9. Measuring Crustal Deformation in Europe by High Precision Geodetic VLBI

    NASA Astrophysics Data System (ADS)

    Campbell, J.; Nothnagel, A.; Vennebusch, M.

    2002-06-01

    At the western tip of the Eurasian plate, the European continent is besieged by thrusting and receding neighbour plates causing deformations and ruptures of the Earth's crust evidenced by earthquakes and volcanic outbursts. Measuring the extent and progress of crustal deformation has become one of the primary tasks of geodesists and geophysicists. Realizing that Europe enjoys one of the densest networks of radio telescopes especially equipped for high precision, geodetic VLBI has provided the incentive to organise a campaign of regular geodetic VLBI observations in the European network of fixed radio telescopes. The measurements have been carried out since the late eighties at an average rate of six sessions per year. From these data, site coordinates, baseline length changes and station velocity vectors have been derived with steadily increasing accuracy. The overall picture of the observed present-day site motions emulates quite well the pattern of tectonic motions inferred from the geotectonic setting of central Europe and the western Mediterranean. Interesting details are emerging for horizontal motions of the three stations in Italy, which are strongly affected by the complex interactions between the different tectonic regimes in this area. The accuracy of the vertical components is also improving with increasing length of the observational record, allowing to detect significant trends among the relative vertical motions of the sites. The geodetic VLBI network operations have received supportive funding by the European Union under the 2nd and 4th Framework Programmes.

  10. The Contribution of the Geodetic Community (WG4) to EPOS

    NASA Astrophysics Data System (ADS)

    Fernandes, R. M. S.; Bastos, L. C.; Bruyninx, C.; D'Agostino, N.; Dousa, J.; Ganas, A.; Lidberg, M.; Nocquet, J.-M.

    2012-04-01

    WG4 - "EPOS Geodetic Data and Infrastructure" is the Working Group of the EPOS project responsible to define and prepare the integration of the existing Pan-European Geodetic Infrastructures into a unique future consistent infrastructure that supports the European Geosciences, which is the ultimate goal of the EPOS project. The WG4 is formed by representatives of the participating EPOS countries and from EUREF (European Reference Frame), which also ensures the inclusion and the contact with countries that formally are not part of the current phase of EPOS. In reality, the fact that Europe is formed by many countries (having different laws and policies) lacking an infrastructure similar to UNAVCO (which concentrates the effort of the local geo-science community) raises the difficulties to create a common geodetic infrastructure serving not only the entire geo-science community, but also many other areas of great social-economic impact. The benefits of the creation of such infrastructure (shared and easily accessed by all) are evident in order to optimize the existing and future geodetic resources. This presentation intends to detail the work being produced within the working group WG4 related with the definition of strategies towards the implementation of the best solutions that will permit to the end-users, and in particular geo-scientists, to access the geodetic data, derived solutions, and associated metadata using transparent and uniform processes. Discussed issues include the access to high-rate data in near real-time, storage and backup of historical and future data, the sustainability of the networks in order to achieve long-term stability in the observation infrastructure, seamless access to the data, open data policies, and processing tools.

  11. Geodetic measurement of deformation in California. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Sauber, Jeanne Marie

    1988-01-01

    The very long baseline interferometry (VLBI) measurements made in the western U.S. since 1979 as part of the NASA Crustal Dynamics Project provide discrete samples of the temporal and spatial deformation field. The interpretation of the VLBI-derived rates of deformation requires an examination of geologic information and more densely sampled ground-based geodetic data. In the first two of three related studies embodying this thesis triangulation and trilateration data measured on two regional networks are processed, one in the central Mojave Desert and one in the Coast Ranges east of the San Andreas fault. At the spatial scales spanned by these local geodetic networks, auxiliary geologic and geophysical data have been utilized to examine the relation between measured incremental strain and the accommodation of strain seen in local geological structures, strain release in earthquakes, and principal stress directions inferred from in situ measurements. In the third study, VLBI data from stations distributed across the Pacific - North American plate boundary zone in the western United States are processed. The VLBI data have been used to constrain the integrated rate of deformation across portions of the continental plate boundary in California and to provide a tectonic framework to interpret regional geodetic and geologic studies.

  12. Plate motions and deformations from geologic and geodetic data

    NASA Technical Reports Server (NTRS)

    Jordan, Thomas H.

    1989-01-01

    The very long baseline interferometry (VLBI) measurements made in the western U.S. since 1979 provide discrete samples of the temporal and spatial deformation field. The interpretation of the VLBI derived rates of deformation requires an examination of geologic information and more densely sampled ground based geodetic data. Triangulation and trilateration data measured on two regional networks, one in the central Mojave Desert and one in the Coast Ranges east of the San Andreas fault, were processed. At the spatial scales spanned by these local geodetic networks, auxiliary geologic and geophysical data were utilized to examine the relation between measured incremental strain and the accommodation of strain seen in local geologic structures, strain release in earthquakes, and principal stress directions inferred from in situ measurements. VLBI data was also processed from stations distributed across the Pacific-North America plate boundary zone in the western U.S. The VLBI data were used to constrain the integrated rate of deformation across portions of the continental plate boundary in California and to provide a tectonic framework to interpret regional geodetic and geologic studies.

  13. Stochastic cycle selection in active flow networks

    PubMed Central

    Woodhouse, Francis G.; Forrow, Aden; Fawcett, Joanna B.; Dunkel, Jörn

    2016-01-01

    Active biological flow networks pervade nature and span a wide range of scales, from arterial blood vessels and bronchial mucus transport in humans to bacterial flow through porous media or plasmodial shuttle streaming in slime molds. Despite their ubiquity, little is known about the self-organization principles that govern flow statistics in such nonequilibrium networks. Here we connect concepts from lattice field theory, graph theory, and transition rate theory to understand how topology controls dynamics in a generic model for actively driven flow on a network. Our combined theoretical and numerical analysis identifies symmetry-based rules that make it possible to classify and predict the selection statistics of complex flow cycles from the network topology. The conceptual framework developed here is applicable to a broad class of biological and nonbiological far-from-equilibrium networks, including actively controlled information flows, and establishes a correspondence between active flow networks and generalized ice-type models. PMID:27382186

  14. Stochastic cycle selection in active flow networks

    NASA Astrophysics Data System (ADS)

    Woodhouse, Francis; Forrow, Aden; Fawcett, Joanna; Dunkel, Jorn

    2016-11-01

    Active biological flow networks pervade nature and span a wide range of scales, from arterial blood vessels and bronchial mucus transport in humans to bacterial flow through porous media or plasmodial shuttle streaming in slime molds. Despite their ubiquity, little is known about the self-organization principles that govern flow statistics in such non-equilibrium networks. By connecting concepts from lattice field theory, graph theory and transition rate theory, we show how topology controls dynamics in a generic model for actively driven flow on a network. Through theoretical and numerical analysis we identify symmetry-based rules to classify and predict the selection statistics of complex flow cycles from the network topology. Our conceptual framework is applicable to a broad class of biological and non-biological far-from-equilibrium networks, including actively controlled information flows, and establishes a new correspondence between active flow networks and generalized ice-type models.

  15. Linking Oceanic Tsunamis and Geodetic Gravity Changes of Large Earthquakes

    NASA Astrophysics Data System (ADS)

    Fu, Yuning; Song, Y. Tony; Gross, Richard S.

    2017-03-01

    Large earthquakes at subduction zones usually generate tsunamis and coseismic gravity changes. These two independent oceanic and geodetic signatures of earthquakes can be observed individually by modern geophysical observational networks. The Gravity Recovery and Climate Experiment twin satellites can detect gravity changes induced by large earthquakes, while altimetry satellites and Deep-Ocean Assessment and Reporting of Tsunamis buoys can observe resultant tsunamis. In this study, we introduce a method to connect the oceanic tsunami measurements with the geodetic gravity observations, and apply it to the 2004 Sumatra Mw 9.2 earthquake, the 2010 Maule Mw 8.8 earthquake and the 2011 Tohoku Mw 9.0 earthquake. Our results indicate consistent agreement between these two independent measurements. Since seafloor displacement is still the largest puzzle in assessing tsunami hazards and its formation mechanism, our study demonstrates a new approach to utilizing these two kinds of measurements for better understanding of large earthquakes and tsunamis.

  16. Permanent GPS Geodetic Array in Southern California (PGGA) and GPS observations in Indonesia

    NASA Technical Reports Server (NTRS)

    Bock, Yehuds

    1994-01-01

    The Permanent GPS Geodetic Array (PGGA) is a network of permanent monitoring GPS stations in southern California devoted to the continuous measurement of crustal deformation in near real-time. The PGGA plays a unique role in studies of the kinematics of crustal deformation and the earthquake cycle in southern California because it is also providing temporally dense geodetic measurements of crustal motion over periods of minutes to variations in regional crustal strain. As it expands and matures the PGGA will play an increasingly important role in the study of active tectonics of southern California by bridging the frequency range between seismology, observatory geodesy, paleoseismology, and geology. In Indonesia GPS data is used for measurement of a large scale crustal deformation, extending from north China to the Indonesian archipelago. Indonesia offers a tremendous laboratory to study some of the processes that build continents, and mountains are active there. We began GPS observations in August 1989 on mainland Sumatra and the Mentawai Islands to study the phenomena of oblique plate convergence. We have analyzed the Indonesian data in conjunction with data collected on Christmas and Cocos Islands and at Darwin, Australia, and with the triangulation data in Sumatra.

  17. Seafloor geodetic constraints on interplate coupling of the Nankai Trough megathrust zone

    NASA Astrophysics Data System (ADS)

    Yokota, Yusuke; Ishikawa, Tadashi; Watanabe, Shun-Ichi; Tashiro, Toshiharu; Asada, Akira

    2016-06-01

    Interplate megathrust earthquakes have inflicted catastrophic damage on human society. Such an earthquake is predicted to occur in the near future along the Nankai Trough off southwestern Japan—an economically active and densely populated area in which megathrust earthquakes have already occurred. Megathrust earthquakes are the result of a plate-subduction mechanism and occur at slip-deficit regions (also known as ‘coupling’ regions), where friction prevents plates from slipping against each other and the accumulated energy is eventually released forcefully. Many studies have attempted to capture distributions of slip-deficit rates (SDRs) in order to predict earthquakes. However, these studies could not obtain a complete view of the earthquake source region, because they had no seafloor geodetic data. The Hydrographic and Oceanographic Department of the Japan Coast Guard (JHOD) has been developing a precise and sustainable seafloor geodetic observation network in this subduction zone to obtain information related to offshore SDRs. Here, we present seafloor geodetic observation data and an offshore interplate SDR-distribution model. Our data suggest that most offshore regions in this subduction zone have positive SDRs. Specifically, our observations indicate previously unknown regions of high SDR that will be important for tsunami disaster mitigation, and regions of low SDR that are consistent with distributions of shallow slow earthquakes and subducting seamounts. This is the first direct evidence that coupling conditions might be related to these seismological and geological phenomena. Our findings provide information for inferring megathrust earthquake scenarios and interpreting research on the Nankai Trough subduction zone.

  18. Global Positioning System (GPS) survey of Augustine Volcano, Alaska, August 3-8, 2000: data processing, geodetic coordinates and comparison with prior geodetic surveys

    USGS Publications Warehouse

    Pauk, Benjamin A.; Power, John A.; Lisowski, Mike; Dzurisin, Daniel; Iwatsubo, Eugene Y.; Melbourne, Tim

    2001-01-01

    Between August 3 and 8,2000,the Alaska Volcano Observatory completed a Global Positioning System (GPS) survey at Augustine Volcano, Alaska. Augustine is a frequently active calcalkaline volcano located in the lower portion of Cook Inlet (fig. 1), with reported eruptions in 1812, 1882, 1909?, 1935, 1964, 1976, and 1986 (Miller et al., 1998). Geodetic measurements using electronic and optical surveying techniques (EDM and theodolite) were begun at Augustine Volcano in 1986. In 1988 and 1989, an island-wide trilateration network comprising 19 benchmarks was completed and measured in its entirety (Power and Iwatsubo, 1998). Partial GPS surveys of the Augustine Island geodetic network were completed in 1992 and 1995; however, neither of these surveys included all marks on the island.Additional GPS measurements of benchmarks A5 and A15 (fig. 2) were made during the summers of 1992, 1993, 1994, and 1996. The goals of the 2000 GPS survey were to:1) re-measure all existing benchmarks on Augustine Island using a homogeneous set of GPS equipment operated in a consistent manner, 2) add measurements at benchmarks on the western shore of Cook Inlet at distances of 15 to 25 km, 3) add measurements at an existing benchmark (BURR) on Augustine Island that was not previously surveyed, and 4) add additional marks in areas of the island thought to be actively deforming. The entire survey resulted in collection of GPS data at a total of 24 sites (fig. 1 and 2). In this report we describe the methods of GPS data collection and processing used at Augustine during the 2000 survey. We use this data to calculate coordinates and elevations for all 24 sites surveyed. Data from the 2000 survey is then compared toelectronic and optical measurements made in 1988 and 1989. This report also contains a general description of all marks surveyed in 2000 and photographs of all new marks established during the 2000 survey (Appendix A).

  19. INEGI's Network of GPS permanent stations in Mexico

    NASA Astrophysics Data System (ADS)

    Gonzalez Franco, G. A.

    2013-05-01

    The Active National Geodetic Network administered by INEGI (Instituto Nacional de Estadística y Geografía) is a set of 24 GPS permanent stations in Mexico that was established in 1993 for a national rural cadastral project, its has been mainly used for geodetic surveys through Mexico including international borders, and has been progressing to contribute to national, regional and international reference frames through the delivering of GPS data or coordinate solutions from INEGI Processing Center to SIRGAS and NAREF. Recently GAMIT/GLOBK Processing of permanent stations in Mexico was realized from 2007-2011 to determine station's velocity. Related to natural hazards, a subset of INEGI network contributes to the project Real Time Integrated Atmosferic Water Wapor and TEC from GPS. The GPS network planned evolution consider changing to a GNSS network, adding stations to IGS, maintain the services of the present, and contribute to multidisciplinary geodetic studies through data publicly available.

  20. Detection of crustal deformation from the Landers earthquake sequence using continuous geodetic measurements

    USGS Publications Warehouse

    Bock, Y.; Agnew, D.C.; Fang, P.; Genrich, J.F.; Hager, B.H.; Herring, T.A.; Hudnut, K.W.; King, R.W.; Larsen, S.; Minster, J.-B.; Stark, K.; Wdowinski, S.; Wyatt, F.K.

    1993-01-01

    The measurement of crustal motions in technically active regions is being performed increasingly by the satellite-based Global Positioning System (GPS)1,2, which offers considerable advantages over conventional geodetic techniques3,4. Continuously operating GPS arrays with ground-based receivers spaced tens of kilometres apart have been established in central Japan5,6 and southern California to monitor the spatial and temporal details of crustal deformation. Here we report the first measurements for a major earthquake by a continuously operating GPS network, the Permanent GPS Geodetic Array (PGGA)7,9 in southern California. The Landers (magnitude Mw of 7.3) and Big Bear (Mw 6.2) earthquakes of 28 June 1992 were monitored by daily observations. Ten weeks of measurements, centred on the earthquake events, indicate significant coseismic motion at all PGGA sites, significant post-seismic motion at one site for two weeks after the earthquakes, and no significant preseismic motion. These measurements demonstrate the potential of GPS monitoring for precise detection of precursory and aftershock seismic deformation in the near and far field.

  1. Application of Space Geodetic Techniques and GIS for Crustal Deformation Monitoring in Turkey

    NASA Astrophysics Data System (ADS)

    Ozener, H.; Garagon Dogru, A.; Turgut, B.; Sabuncu, A.

    2011-12-01

    There are number of geodetic techniques for detecting crustal movements. Space-based InSAR technique measures the phase change between two phase measurements of the same ground pixel of the Earth's surface and provides a method to determine crustal deformation. The results are verified by ground-based data obtained from GPS and other seismological studies. The North Anatolian Fault (NAF), particularly western segment of it, has been investigated over two decades by means of GPS technique. It is one of the most seismically active structures in the eastern Mediterranean with a slip rate of 22 mm/year. In this study, current displacement rates obtained from sparse micro-geodetic networks at western part of NAF are presented and then we investigate the potential of InSAR to monitor crustal movements at our study regions. GPS results validate the information coming from InSAR observations. On the other hand,we have some errors due to discrepancy between the GPS and interferometric observations since they are not defining crustal deformation at the same time intervals. After quality control and processing, all datasets integrated into GIS for mapping and analysis.

  2. Korea Geodetic VLBI Station, Sejong

    NASA Technical Reports Server (NTRS)

    Donghyun, Baek; Sangoh, Yi; Hongjong, Oh; Sangchul, Han

    2013-01-01

    The Sejong VLBI station officially joined the IVS as a new Network Station in 2012. This report summarizes the activities of the Sejong station during 2012. The following are the activities at the station: 1) VLBI test observations were carried out with the Tsukuba 34-m antenna of the GSI in Japan. As a result, the Sejong antenna needs to improve its efficiency, which is currently in progress, 2) A survey to connect the VLBI reference point to GNSS and ground marks was conducted, and 3) To see the indirect effects of RFI (Radio Frequency Interference) at this place, we checked the omni-direction (AZ 0? to 360?, EL fixed at 7?) for RFI influence.

  3. Geodetic measurements with a mobile VLBI system

    NASA Technical Reports Server (NTRS)

    Niell, A. E.; Claflin, E. S.; Lockhart, T. G.; Macdoran, P. F.; Morabito, D. D.; Ong, K. M.; Resch, G. M.

    1980-01-01

    The Project ARIES 9 meter transportable antenna was used as one element of very long baseline interferometer (VLBI) to begin monitoring locations of six sites in California relative to large diameter fixed antennas at the NASA Deep Space Network, Goldstone, California, and at the Caltech Owens Valley Radio Observatory, Big Pine, California. An accuracy of about 6 cm in the horizontal components was demonstrated by comparison with measurements of the National Geodetic Survey. The root of mean square scatter of the lengths of the baselines between any pair of antennas was about 3 cm except for the Goldstone-JPL (Pasadena) baseline. In the period August 1974 to August 1977 the length of this baseline increased by 15 + or - 5 cm as JPL moved westward relative to Goldstone at the rate of 6 + or - 2 cm/year. The baseline lengths were unaffected by the uncertainties of UT1, polar motion, and tropospheric water vapor, which are the limitations to present three dimensional vector accuracies.

  4. Geodetic Imaging of the Earthquake Cycle

    NASA Astrophysics Data System (ADS)

    Tong, Xiaopeng

    In this dissertation I used Interferometric Synthetic Aperture Radar (InSAR) and Global Positioning System (GPS) to recover crustal deformation caused by earthquake cycle processes. The studied areas span three different types of tectonic boundaries: a continental thrust earthquake (M7.9 Wenchuan, China) at the eastern margin of the Tibet plateau, a mega-thrust earthquake (M8.8 Maule, Chile) at the Chile subduction zone, and the interseismic deformation of the San Andreas Fault System (SAFS). A new L-band radar onboard a Japanese satellite ALOS allows us to image high-resolution surface deformation in vegetated areas, which is not possible with older C-band radar systems. In particular, both the Wenchuan and Maule InSAR analyses involved L-band ScanSAR interferometry which had not been attempted before. I integrated a large InSAR dataset with dense GPS networks over the entire SAFS. The integration approach features combining the long-wavelength deformation from GPS with the short-wavelength deformation from InSAR through a physical model. The recovered fine-scale surface deformation leads us to better understand the underlying earthquake cycle processes. The geodetic slip inversion reveals that the fault slip of the Wenchuan earthquake is maximum near the surface and decreases with depth. The coseismic slip model of the Maule earthquake constrains the down-dip extent of the fault slip to be at 45 km depth, similar to the Moho depth. I inverted for the slip rate on 51 major faults of the SAFS using Green's functions for a 3-dimensional earthquake cycle model that includes kinematically prescribed slip events for the past earthquakes since the year 1000. A 60 km thick plate model with effective viscosity of 10 19 Pa · s is preferred based on the geodetic and geological observations. The slip rates recovered from the plate models are compared to the half-space model. The InSAR observation reveals that the creeping section of the SAFS is partially locked. This high

  5. Permanent GPS Geodetic Array in Southern California

    NASA Technical Reports Server (NTRS)

    Green, Cecil H.; Green, Ida M.

    1998-01-01

    The southern California Permanent GPS Geodetic Array (PGGA) was established in the spring of 1990 to evaluate continuous Global Positioning System (GPS) measurements as a new too] for monitoring crustal deformation. Southern California is an ideal location because of the relatively high rate of tectonic deformation, the high probability of intense seismicity, the long history of conventional and space geodetic measurements, and the availability of a well developed infrastructure to support continuous operations. Within several months of the start of regular operations, the PGGA recorded far-field coseismic displacements induced by the June 28, 1992 (M(sub w)=7.3), Landers earthquake, the largest magnitude earthquake in California in the past 40 years and the first one to be recorded by a continuous GPS array. Only nineteen months later, on 17 January 1994, the PGGA recorded coseismic displacements for the strongest earthquake to strike the Los Angeles basin in two decades, the (M(sub e)=6.7) Northridge earthquake. At the time of the Landers earthquake, only seven continuous GPS sites were operating in southern California; by the beginning of 1994, three more sites had been added to the array. However, only a pair of sites were situated in the Los Angeles basin. The destruction caused by the Northridge earthquake spurred a fourfold increase in the number of continuous GPS sites in southern California within 2 years of this event. The PGGA is now the regional component of the Southern California Integrated GPS Network (SCIGN), a major ongoing densification of continuous GPS sites, with a concentration in the Los Angeles metropolitan region. Continuous GPS provides temporally dense measurements of surface displacements induced by crustal deformation processes including interseismic, coseismic, postseismic, and aseismic deformation and the potential for detecting anomalous events such as preseismic deformation and interseismic strain variations. Although strain meters

  6. Controlling contagion processes in activity driven networks.

    PubMed

    Liu, Suyu; Perra, Nicola; Karsai, Márton; Vespignani, Alessandro

    2014-03-21

    The vast majority of strategies aimed at controlling contagion processes on networks consider the connectivity pattern of the system either quenched or annealed. However, in the real world, many networks are highly dynamical and evolve, in time, concurrently with the contagion process. Here, we derive an analytical framework for the study of control strategies specifically devised for a class of time-varying networks, namely activity-driven networks. We develop a block variable mean-field approach that allows the derivation of the equations describing the coevolution of the contagion process and the network dynamic. We derive the critical immunization threshold and assess the effectiveness of three different control strategies. Finally, we validate the theoretical picture by simulating numerically the spreading process and control strategies in both synthetic networks and a large-scale, real-world, mobile telephone call data set.

  7. An Overview of Geodetic Volcano Research in the Canary Islands

    NASA Astrophysics Data System (ADS)

    Fernández, José; González, Pablo J.; Camacho, Antonio G.; Prieto, Juan F.; Brú, Guadalupe

    2015-11-01

    The Canary Islands are mostly characterized by diffuse and scattered volcanism affecting a large area, with only one active stratovolcano, the Teide-Pico Viejo complex (Tenerife). More than 2 million people live and work in the 7,447 km2 of the archipelago, resulting in an average population density three times greater than the rest of Spain. This fact, together with the growth of exposure during the past 40 years, increases volcanic risk with respect previous eruptions, as witnessed during the recent 2011-2012 El Hierro submarine eruption. Therefore, in addition to purely scientific reasons there are economic and population-security reasons for developing and maintaining an efficient volcano monitoring system. In this scenario geodetic monitoring represents an important part of the monitoring system. We describe volcano geodetic monitoring research carried out in the Canary Islands and the results obtained. We consider for each epoch the two main existing constraints: the level of volcanic activity in the archipelago, and the limitations of the techniques available at the time. Theoretical and observational aspects are considered, as well as the implications for operational volcano surveillance. Current challenges of and future perspectives in geodetic volcano monitoring in the Canaries are also presented.

  8. Noise enhanced activity in a complex network

    NASA Astrophysics Data System (ADS)

    Choudhary, Anshul; Kohar, Vivek; Sinha, Sudeshna

    2014-09-01

    We consider the influence of local noise on a generalized network of populations having positive and negative feedbacks. The population dynamics at the nodes is nonlinear, typically chaotic, and allows cessation of activity if the population falls below a threshold value. We investigate the global stability of this large interactive system, as indicated by the average number of nodal populations that manage to remain active. Our central result is that the probability of obtaining active nodes in this network is significantly enhanced under fluctuations. Further, we find a sharp transition in the number of active nodes as noise strength is varied, along with clearly evident scaling behaviour near the critical noise strength. Lastly, we also observe noise induced temporal coherence in the active sub-network, namely, there is an enhancement in synchrony among the nodes at an intermediate noise strength.

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

    NASA Astrophysics Data System (ADS)

    Ogata, Y.

    2006-12-01

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

  10. Spontaneous network activity and synaptic development

    PubMed Central

    Kerschensteiner, Daniel

    2014-01-01

    Throughout development, the nervous system produces patterned spontaneous activity. Research over the last two decades has revealed a core group of mechanisms that mediate spontaneous activity in diverse circuits. Many circuits engage several of these mechanisms sequentially to accommodate developmental changes in connectivity. In addition to shared mechanisms, activity propagates through developing circuits and neuronal pathways (i.e. linked circuits in different brain areas) in stereotypic patterns. Increasing evidence suggests that spontaneous network activity shapes synaptic development in vivo. Variations in activity-dependent plasticity may explain how similar mechanisms and patterns of activity can be employed to establish diverse circuits. Here, I will review common mechanisms and patterns of spontaneous activity in emerging neural networks and discuss recent insights into their contribution to synaptic development. PMID:24280071

  11. Seafloor seismological/geodetic observations in the rupture area of the 2011 Tohoku-oki Earthquake

    NASA Astrophysics Data System (ADS)

    Hino, Ryota; Shinohara, Masanao; Ito, Yoshihiro

    2016-04-01

    A number of important aspects of the 2011 Tohoku-oki earthquake (Mw 9.0) were clarified by the seafloor seismological and geodetic observation above the rupture area of the earthquake. Besides the extraordinarily large coseismic displacements, various kinds of slow slip phenomena associated with intensive micro-seismicity on the plate boundary fault were identified by near field ocean bottom seismographs and seafloor geodetic observation networks. The Tohoku-oki earthquake was preceded by evident foreshock activity with a spatial expansion of this seismicity. The activity became significantly intense after the occurrence of the largest foreshock two days before the mainshock rupture. During the period, clear continuous seafloor deformation was identified caused by the aseismic slip following the largest foreshock. Another different type of aseismic slip event had occurred before this pre-imminent activity had started about a month before the largest foreshock happened. The observed increased seismicity associated with aseismic slip suggests that there must have been some chain reaction like interplay of seismic and interseismic slips before the large earthquake broke out. However, no evident deformation signals were observed indicating acceleration of fault slip immediately before the mainshock. Seafloor geodetic measurements reveals that the postseismic deformation around the rupture area of the Tohoku-oki earthquake shows complex spatial pattern and the complexity is mostly due to significant viscoelastic relaxation induced by the huge coseismic slip. The effects of viscoelastic deformation makes it difficult to identify the deformation associated with the after slip or regaining of interplate coupling and requires us to enhance the abilities of seafloor monitoring to detect the slip activities on the fault. We started an array of seismometer arrays observation including broad-band seismographs to detect and locate slow-slip events and low-frequency tremors

  12. The SCEC geodetic transient detection validation exercise

    USGS Publications Warehouse

    Lohman, Rowena B.; Murray, Jessica R.

    2013-01-01

    Over the past decade the number and size of continuously operating Global Positioning System (GPS) networks has grown substantially worldwide. A steadily increasing volume of freely available GPS measurements, combined with the application of new approaches for mining these data for signals of interest, has led to the identification of a large and diverse collection of time‐varying Earth processes. One phenomenon that has been observed is transient fault slip (also termed slow slip events or silent earthquakes) occurring over time spans of days to years (e.g., Linde et al., 1996; Hirose et al., 1999; Dragert et al., 2001; Miller et al., 2002; Kostoglodov et al., 2003; Douglas et al., 2005; Shelly et al., 2006; Ide et al., 2007; Lohman and McGuire, 2007; Schwartz and Rokosky, 2007; Szeliga et al., 2008). Such events have been widely observed in subduction zones but are also found in other tectonic settings (Linde et al., 1996; Cervelli et al., 2002; Murray and Segall, 2005; Lohman and McGuire, 2007; Montgomery‐Brown et al., 2009; Shelly, 2010; and references therein). Although retrospective study of slow‐slip events using geodetic observations is driving the formulation of new models for fault‐zone behavior and constitutive laws (e.g., Lapusta et al., 2000; Liu and Rice, 2007; Lapusta and Liu, 2009; Segall and Bradley, 2012a), much of the research on near‐real‐time detection and characterization of anomalous behaviors along fault zones has focused solely on the use of seismic tremor (e.g., Rogers and Dragert, 2003; Shelly et al., 2006; Ito et al., 2007).

  13. Geodetic results in Afar: The rifting episode of November 1978 in the Asal-Ghoubbet rift

    NASA Astrophysics Data System (ADS)

    Kasser, M.; Lepine, J. C.; Ruegg, J. C.; Tarantula, A.

    1981-01-01

    A seismo-tectonic and volcanic crisis occurred in November 1978 in the Asal-Ghoubbet rift, first subaerial section of the accreting plate boundary between the African and Arabian plates (Allard et al., 1979; Abdallah et al., 1979; Le Dain et al., 1980). The activity was located in the center of a geodetic network set up in the winter 1972-1973 by the Institut Géographique National in collaboration with the Institut de Physique du Globe de Paris. Simultaneously, a precise levelling line of about 100 km was established across the area (I.G.N., 1973). The resurveying of both the geodetic network and the levelling line was carried out after the crisis, between November 1978 and March 1979. Extensions up to 2.4 m and vertical displacements up to 0.7 m were measured. Operating techniques and results of the resurveying are described in Kasser et al. (1979) and Ruegg et al. (1979). Figure 1 shows the horizontal displacements (relating to point B and to the direction BT) and figure 2 shows the vertical displacements relating to the two external points. Tarantola et al. (1979, 1980) have shown that these results can be geodynamically interpreted by a mechanism of sudden breaking and elastic rebound after an elastic stretching of the crust due to the relative drift of the plates. The breaking is triggered by magmatic fracturing of the crust, with dykes injection from a magmatic chamber which has fed the basaltic fissurai eruption. The horizontal and vertical displacements outside the broken zone of the Inner Floor are predicted by a numerical model based on this interpretation which fit very well the experimental data.

  14. [Legal aspects of networking of medical activities].

    PubMed

    Preissler, Reinhold

    2005-04-01

    Medical networks lack a legal definition. From the viewpoint of social law, this term means a form of organization of joint-service providers in a non-specified composition for the undertaking of medical care activities; from the point of view of occupational law, this consists of a loose form of joint practice. Such medical network can conclude treatment contracts with the patients and exchange patients' medical records. A practice network can take over services as contract partner of hospitals or other institutions, in the interest of improved competition chances within the integrated care system. The joining of a third partner is basically left open by the MBO, however according to SGB V this is possible only after approval by all contract partners. In advance of a planned medical care center, is it recommended to found a physician network as starting model. Before single practices fuse into a single enterprise, management-, tax-, legal-, as well as psychological aspects must be considered.

  15. Choosing Geodetic Monuments Based on Noise in New Zealand GPS Time Series

    NASA Astrophysics Data System (ADS)

    Beavan, J.

    2004-12-01

    Geodetic signals of tectonic or volcanological interest recorded by geodetic instrumentation may be degraded or obscured by the presence of noise in the geodetic data. Limiting the noise is therefore important for the detection and interpretation of such signals. One source of noise is random motion occurring within the connection of the geodetic instrument to the ground. In the case of surface instruments such as GPS, the connection to the ground is through a geodetic monument. The motion of this monument, with respect to a representative volume of the Earth's near surface in its vicinity, is termed monument noise. Monument noise results from processes such as soil swelling in response to rainfall, and general rock and soil weathering effects. In this paper we investigate the noise levels within time series of continuous GPS (CGPS) positions collected on concrete pillar monuments in New Zealand. We compare these noise levels with those from drilled, braced monuments in several U.S. CGPS networks. We investigate under what conditions monument noise is the limiting noise source in the CGPS data, and attempt to provide a basis for decisions on what type of monument to deploy under certain scenarios.

  16. The Online Positioning User Service: a Web Utility for Precise Geodetic Positioning in the Geosciences

    NASA Astrophysics Data System (ADS)

    Stone, W. A.

    2014-12-01

    Geoscientists often require precise positioning capability to support research. Accurate Global Navigation Satellite System (GNSS) positioning is a specialized skill involving expertise and fraught with accuracy-compromising nuances. With the goal of providing a robust and high accuracy positioning tool and enhanced access to the United States' National Spatial Reference System (NSRS), the nation's fundamental positioning infrastructure, NOAA's National Geodetic Survey (NGS) developed the Online Positioning User Service (OPUS). OPUS is a free Web utility for processing user-submitted GNSS observations and producing geodetic coordinates referenced to both NSRS and a global reference frame. Relying on NGS' national network of GNSS Continuously Operating Reference Stations (CORS), OPUS is a powerful and user-friendly tool for production and scientific research. OPUS is widely used in geomatics professions and holds great, yet not fully tapped, potential for research geoscientists requiring accurate positional information. OPUS became operational in 2002 as a single point processing tool for multi-hour GPS occupations (OPUS-Static). Its capability has since evolved, adding the ability to process short (15 minutes) sessions (OPUS-RapidStatic) and to provide a solution sharing option. All OPUS variations have proven to be popular, with typical monthly submissions now numbering 40,000. In 2014, NGS released a network version of OPUS, OPUS-Projects, the focus of this discussion. Although other versions of OPUS process a single GNSS occupation per submission, OPUS-Projects offers rigorous geodetic network analysis and processing capability by assembling and processing GNSS observations collected over time and at multiple locations. Least squares geodetic network adjustment of included observations results in an optimal set of station coordinates, including their uncertainties and graphical statistical plots, derived from user-submitted observation data, CORS observation

  17. GEODYN- ORBITAL AND GEODETIC PARAMETER ESTIMATION

    NASA Technical Reports Server (NTRS)

    Putney, B.

    1994-01-01

    The Orbital and Geodetic Parameter Estimation program, GEODYN, possesses the capability to estimate that set of orbital elements, station positions, measurement biases, and a set of force model parameters such that the orbital tracking data from multiple arcs of multiple satellites best fits the entire set of estimation parameters. The estimation problem can be divided into two parts: the orbit prediction problem, and the parameter estimation problem. GEODYN solves these two problems by employing Cowell's method for integrating the orbit and a Bayesian least squares statistical estimation procedure for parameter estimation. GEODYN has found a wide range of applications including determination of definitive orbits, tracking instrumentation calibration, satellite operational predictions, and geodetic parameter estimation, such as the estimations for global networks of tracking stations. The orbit prediction problem may be briefly described as calculating for some later epoch the new conditions of state for the satellite, given a set of initial conditions of state for some epoch, and the disturbing forces affecting the motion of the satellite. The user is required to supply only the initial conditions of state and GEODYN will provide the forcing function and integrate the equations of motion of the satellite. Additionally, GEODYN performs time and coordinate transformations to insure the continuity of operations. Cowell's method of numerical integration is used to solve the satellite equations of motion and the variational partials for force model parameters which are to be adjusted. This method uses predictor-corrector formulas for the equations of motion and corrector formulas only for the variational partials. The parameter estimation problem is divided into three separate parts: 1) instrument measurement modeling and partial derivative computation, 2) data error correction, and 3) statistical estimation of the parameters. Since all of the measurements modeled by

  18. GeoSEA: Geodetic Earthquake Observatory on the Seafloor

    NASA Astrophysics Data System (ADS)

    Kopp, Heidrun; Lange, Dietrich; Flueh, Ernst R.; Petersen, Florian; Behrmann, Jan-Hinrich; Devey, Colin

    2014-05-01

    Space geodetic observations of crustal deformation have contributed greatly to our understanding of plate tectonic processes in general, and plate subduction in particular. Measurements of interseismic strain have documented the active accumulation of strain, and subsequent strain release during earthquakes. However, techniques such as GPS cannot be applied below the water surface because the electromagnetic energy is strongly attenuated in the water column. Evidence suggests that much of the elastic strain build up and release (and particularly that responsible for both tsunami generation and giant earthquakes) occurs offshore. To quantify strain accumulation and assess the resultant hazard potential we urgently need systems to resolve seafloor crustal deformation. Here we report on first results of sea trials of a newly implemented seafloor geodesy array. The GeoSEA (Geodetic Earthquake Observatory on the Seafloor) array consists of a seafloor transponder network comprising 35 units and a wave glider acting as a surface unit (GeoSURF) to ensure satellite correspondence, data transfer and monitor system health. Seafloor displacement occurs in the horizontal (x,y) and vertical direction (z). The vertical displacement is measured by monitoring pressure variations at the seafloor. Horizontal seafloor displacement can be measured either using an acoustic/GPS combination to provide absolute positioning (requiring a suitably equipped vessel to perform repeated cruises to provide the GPS fixes) or by long-term acoustic telemetry between different beacons fixed on the seafloor to determine relative distances by using the travel time observations to each other, which is the technique tested during our short sea trials. For horizontal direct path measurements, the system utilizes acoustic ranging techniques with a ranging precision better than 15 mm and long term stability over 2 km distances. Vertical motion is obtained from pressure gauges. Integrated inclinometers

  19. Basic research and data analysis for the national geodetic satellite program and for the earth and ocean physics applications program

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Activities related to the National Geodetic Satellite Program are reported and include a discussion of Ohio State University's OSU275 set of tracking station coordinates and transformation parameters, determination of network distortions, and plans for data acquisition and processing. The problems encountered in the development of the LAGEOS satellite are reported in an account of activities related to the Earth and Ocean Physics Applications Program. The LAGEOS problem involves transmission and reception of the laser pulse designed to make accurate determinations of the earth's crustal and rotational motions. Pulse motion, ephemeris, arc range measurements, and accuracy estimates are discussed in view of the problem. Personnel involved in the two programs are also listed, along with travel activities and reports published to date.

  20. Sloppiness in spontaneously active neuronal networks.

    PubMed

    Panas, Dagmara; Amin, Hayder; Maccione, Alessandro; Muthmann, Oliver; van Rossum, Mark; Berdondini, Luca; Hennig, Matthias H

    2015-06-03

    Various plasticity mechanisms, including experience-dependent, spontaneous, as well as homeostatic ones, continuously remodel neural circuits. Yet, despite fluctuations in the properties of single neurons and synapses, the behavior and function of neuronal assemblies are generally found to be very stable over time. This raises the important question of how plasticity is coordinated across the network. To address this, we investigated the stability of network activity in cultured rat hippocampal neurons recorded with high-density multielectrode arrays over several days. We used parametric models to characterize multineuron activity patterns and analyzed their sensitivity to changes. We found that the models exhibited sloppiness, a property where the model behavior is insensitive to changes in many parameter combinations, but very sensitive to a few. The activity of neurons with sloppy parameters showed faster and larger fluctuations than the activity of a small subset of neurons associated with sensitive parameters. Furthermore, parameter sensitivity was highly correlated with firing rates. Finally, we tested our observations from cell cultures on an in vivo recording from monkey visual cortex and we confirm that spontaneous cortical activity also shows hallmarks of sloppy behavior and firing rate dependence. Our findings suggest that a small subnetwork of highly active and stable neurons supports group stability, and that this endows neuronal networks with the flexibility to continuously remodel without compromising stability and function.

  1. Satellite-tracking and earth-dynamics research programs. [geodetic and geophysical investigations and atmospheric research using satellite drag data

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Satellite tracking and earth dynamics research programs are discussed. Geodetic and geophysical investigations are reported along with atmospheric research using satellite drag data. Satellite tracking network functions and support groups which are discussed include: network operations, communications, data-services division, moonwatch, and programming group.

  2. Motor Behavior Activates Bergmann Glial Networks

    PubMed Central

    Nimmerjahn, Axel; Mukamel, Eran A.; Schnitzer, Mark J.

    2010-01-01

    SUMMARY Although it is firmly established neuronal activity is a prime determinant of animal behavior, relationships between astrocytic excitation and animal behavior have remained opaque. Cerebellar Bergmann glia are radial astrocytes that are implicated in motor behavior and exhibit Ca2+-excitation. However, Ca2+-excitation in these cells has not previously been studied in behaving animals. Using two-photon microscopy we found that Bergmann glia exhibit three forms of Ca2+-excitation in awake behaving mice. Two of these are ongoing within the cerebellar vermis. During locomotor performance concerted Ca2+-excitation arises in networks of at least hundreds of Bergmann glia extending across several hundred microns or more. Concerted Ca2+-excitation was abolished by anesthesia or blockade of either neural activity or glutamatergic transmission. Thus, large networks of Bergmann glia can be activated by specific animal behaviors and undergo excitation of sufficient magnitude to potentially initiate macroscopic changes in brain dynamics or blood flow. PMID:19447095

  3. Position paper on active countermeasures for computer networks.

    SciTech Connect

    Van Randwyk, Jamie A.

    2003-07-01

    Computer security professionals have used passive network countermeasures for several years in order to secure computer networks. Passive countermeasures such as firewalls and intrusion detection systems are effective but their use alone is not enough to protect a network. Active countermeasures offer new ways of protecting a computer network. Corporations and government entities should adopt active network countermeasures as a means of protecting their computer networks.

  4. National Geodetic Satellite Program, Part 1

    NASA Technical Reports Server (NTRS)

    Henriksen, S. W. (Editor)

    1977-01-01

    The work performed by individual contributors to the National Geodetic Satellite Program is presented. The purpose of the organization, the instruments used in obtaining the data, a description of the data itself, the theory used in processing the data, and evaluation of the results are detailed for the participating organizations.

  5. A study program for geodetic satellite applications

    NASA Technical Reports Server (NTRS)

    Pearlman, M. R.

    1972-01-01

    The work is reported on support of the GEOS-C Program, National Geodetic Satellite program, and the Earth Physics Program. The statement of work, and a description of the GEOS-C are presented along with the trip reports, and the Earth and Ocean Physics Application program.

  6. Southern California regional earthquake probability estimated from continuous GPS geodetic data

    NASA Astrophysics Data System (ADS)

    Anderson, G.

    2002-12-01

    Current seismic hazard estimates are primarily based on seismic and geologic data, but geodetic measurements from large, dense arrays such as the Southern California Integrated GPS Network (SCIGN) can also be used to estimate earthquake probabilities and seismic hazard. Geodetically-derived earthquake probability estimates are particularly important in regions with poorly-constrained fault slip rates. In addition, they are useful because such estimates come with well-determined error bounds. Long-term planning is underway to incorporate geodetic data in the next generation of United States national seismic hazard maps, and techniques for doing so need further development. I present a new method for estimating the expected rates of earthquakes using strain rates derived from geodetic station velocities. I compute the strain rates using a new technique devised by Y. Hsu and M. Simons [Y. Hsu and M. Simons, pers. comm.], which computes the horizontal strain rate tensor ( {˙ {ɛ}}) at each node of a pre-defined regular grid, using all geodetic velocities in the data set weighted by distance and estimated uncertainty. In addition, they use a novel weighting to handle the effects of station distribution: they divide the region covered by the geodetic network into Voronoi cells using the station locations and weight each station's contribution to {˙ {ɛ}} by the area of the Voronoi cell centered at that station. I convert {˙ {ɛ}} into the equivalent seismic moment rate density (˙ {M}) using the method of \\textit{Savage and Simpson} [1997] and maximum seismogenic depths estimated from regional seismicity; ˙ {M} gives the expected rate of seismic moment release in a region, based on the geodetic strain rates. Assuming the seismicity in the given region follows a Gutenberg-Richter relationship, I convert ˙ {M} to an expected rate of earthquakes of a given magnitude. I will present results of a study applying this method to data from the SCIGN array to estimate

  7. Ny-Alesund Geodetic Observatory

    NASA Technical Reports Server (NTRS)

    Sieber, Moritz

    2013-01-01

    In 2012 the 20-m telescope at Ny-Alesund, Svalbard, operated by the Norwegian Mapping Authority (NMA), took part in 163 out of 168 scheduled sessions of the IVS program. Since spring, all data was transferred by network, and the receiver monitoring computer was replaced by a bus-coupler. In autumn, the NMA received building permission for a new observatory from the Governor of Svalbard. The bidding process and first construction work for the infrastructure will start in 2013.

  8. Mercury's interior from MESSENGER geodetic measurements

    NASA Astrophysics Data System (ADS)

    Genova, Antonio; Mazarico, Erwan; Goossens, Sander; Lemoine, Frank G.; Neumann, Gregory A.; Smith, David E.; Zuber, Maria T.; Solomon, Sean C.

    2016-04-01

    The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft completed more than 4 years of operations in orbit about Mercury. One of the main mission goals was the determination of the interior structure of Mercury enabled by geodetic observations of the topography, gravity field, rotation, and tides by the Mercury Laser Altimeter (MLA) and radio science system. MLA acquired over 25 million individual measurements of Mercury's shape that are mostly limited to the northern hemisphere because of MESSENGER's eccentric orbit. However, the lack of laser altimetry in the southern hemisphere has been partly compensated by ˜400 occultations of spacecraft radio signals. X-band radio tracking data collected by the NASA Deep Space Network (DSN) allowed the determination of Mercury's gravity field to spherical harmonic degree and order 100, the planet's obliquity, and the Love number k2. The combination of altimetry and radio measurements provides a powerful tool for the investigation of Mercury's orientation and tides, which enable a better understanding of the interior structure of the planet. The MLA measurements have been assembled into a digital elevation model (DEM) of the northern hemisphere. We then used individual altimetric measurements from the spacecraft for orbit determination, together with the radio tracking, over a continuous span of time using a batch least-squares filter. All observations were combined to recover directly the gravity field coefficients, obliquity, librations, and tides by minimizing the discrepancies between the computed observables and actual measurements. We will present the estimated 100×100 gravity field model, the obliquity, the Love number k2, and, for the first time, the tidal phase lag φ and the amplitude of the longitudinal libration from radio and altimetry data. The k2 phase provides information on Mercury's dissipation and mantle viscosity and allows a determination of the Q factor. A refinement of

  9. Historical Review of Astro-Geodetic Observations in Serbia

    NASA Astrophysics Data System (ADS)

    Ogrizovic, V.; Delcev, S.; Vasilic, V.; Gucevic, J.

    2008-10-01

    Astro-geodetic determinations of vertical deflections in Serbia began during the first years of 20th century. The first field works were led by S. Bo\\vsković. After the 2nd World War, Military Geographic Institute, Department of Geodesy from the Faculty of Civil Engineering, and Federal Geodetic Directorate continued the determinations, needed for reductions of terrestrial geodetic measurements and the astro-geodetic geoid determination. Last years improvements of the astro-geodetic methods are carried out in the area of implementing modern measurement equipment and technologies.

  10. Transmission of information in active networks

    NASA Astrophysics Data System (ADS)

    Baptista, M. S.; Kurths, J.

    2008-02-01

    Shannon’s capacity theorem is the main concept behind the theory of communication. It says that if the amount of information contained in a signal is smaller than the channel capacity of a physical media of communication, it can be transmitted with arbitrarily small probability of error. This theorem is usually applicable to ideal channels of communication in which the information to be transmitted does not alter the passive characteristics of the channel that basically tries to reproduce the source of information. For an active channel, a network formed by elements that are dynamical systems (such as neurons, chaotic or periodic oscillators), it is unclear if such theorem is applicable, once an active channel can adapt to the input of a signal, altering its capacity. To shed light into this matter, we show, among other results, how to calculate the information capacity of an active channel of communication. Then, we show that the channel capacity depends on whether the active channel is self-excitable or not and that, contrary to a current belief, desynchronization can provide an environment in which large amounts of information can be transmitted in a channel that is self-excitable. An interesting case of a self-excitable active channel is a network of electrically connected Hindmarsh-Rose chaotic neurons.

  11. Endogenous Electric Fields May Guide Neocortical Network Activity

    PubMed Central

    Fröhlich, Flavio; McCormick, David A.

    2011-01-01

    Local field potentials and the underlying endogenous electric fields (EFs) are traditionally considered to be epiphenomena of structured neuronal network activity. Recently, however, externally applied EFs have been shown to modulate pharmacologically evoked network activity in rodent hippocampus. In contrast, very little is known about the role of endogenous EFs during physiological activity states in neocortex. Here we used the neocortical slow oscillation in vitro as a model system to show that weak sinusoidal and naturalistic EFs enhance and entrain physiological neocortical network activity with an amplitude threshold within the range of in vivo endogenous field strengths. Modulation of network activity by positive and negative feedback fields based on the network activity in real-time provide direct evidence for a feedback loop between neuronal activity and endogenous EF. This significant susceptibility of active networks to EFs that only cause small changes in membrane potential in individual neurons suggests that endogenous EFs could guide neocortical network activity. PMID:20624597

  12. Analysis of variance of an underdetermined geodetic displacement problem

    SciTech Connect

    Darby, D.

    1982-06-01

    It has been suggested recently that point displacements in a free geodetic network traversing a strike-slip fault may be estimated from repeated surveys by minimizing only those displacement components normal to the strike. It is desirable to justify this procedure. We construct, from estimable quantities, a deformation parameter which is an F-statistic of the type occurring in the analysis of variance of linear models not of full rank. A test of its significance provides the criterion to justify the displacement solution. It is also interesting to study its behaviour as one varies the supposed strike of the fault. Justification of a displacement solution using data from a strike-slip fault is found, but not for data from a rift valley. The technique can be generalized to more complex patterns of deformation such as those expected near the end-zone of a fault in a dislocation model.

  13. Geodetic precession or dragging of inertial frames

    SciTech Connect

    Ashby, N. ); Shahid-Saless, B. )

    1990-08-15

    In metric theories of gravity the principle of general covariance allows one to describe phenomena by means of any convenient choice of coordinate system. In this paper it is shown that in an appropriately chosen coordinate system, geodetic precession of a gyroscope orbiting a spherically symmetric, spinning mass can be recast as a Lense-Thirring frame-dragging effect without invoking spatial curvature. The origin of this reference frame moves around the source but the frame axes point in fixed directions. The drag can be interpreted to arise from the orbital angular momentum of the source around the origin of the reference frame. In this reference frame the effects of geodetic precession and Lense-Thirring drag due to intrinsic angular momentum of the source have the same origin, namely, gravitomagnetism.

  14. Absolute Antenna Calibration at the US National Geodetic Survey

    NASA Astrophysics Data System (ADS)

    Mader, G. L.; Bilich, A. L.

    2012-12-01

    Geodetic GNSS applications routinely demand millimeter precision and extremely high levels of accuracy. To achieve these accuracies, measurement and instrument biases at the centimeter to millimeter level must be understood. One of these biases is the antenna phase center, the apparent point of signal reception for a GNSS antenna. It has been well established that phase center patterns differ between antenna models and manufacturers; additional research suggests that the addition of a radome or the choice of antenna mount can significantly alter those a priori phase center patterns. For the more demanding GNSS positioning applications and especially in cases of mixed-antenna networks, it is all the more important to know antenna phase center variations as a function of both elevation and azimuth in the antenna reference frame and incorporate these models into analysis software. Determination of antenna phase center behavior is known as "antenna calibration". Since 1994, NGS has computed relative antenna calibrations for more than 350 antennas. In recent years, the geodetic community has moved to absolute calibrations - the IGS adopted absolute antenna phase center calibrations in 2006 for use in their orbit and clock products, and NGS's CORS group began using absolute antenna calibration upon the release of the new CORS coordinates in IGS08 epoch 2005.00 and NAD 83(2011,MA11,PA11) epoch 2010.00. Although NGS relative calibrations can be and have been converted to absolute, it is considered best practice to independently measure phase center characteristics in an absolute sense. Consequently, NGS has developed and operates an absolute calibration system. These absolute antenna calibrations accommodate the demand for greater accuracy and for 2-dimensional (elevation and azimuth) parameterization. NGS will continue to provide calibration values via the NGS web site www.ngs.noaa.gov/ANTCAL, and will publish calibrations in the ANTEX format as well as the legacy ANTINFO

  15. Dry tilt network at Mount Rainier, Washington

    USGS Publications Warehouse

    Dzurisin, Daniel; Johnson, Daniel J.; Symonds, R.B.

    1984-01-01

    In addition to its primary responsibility of monitoring active Mount St. Helens, the David A. Johnston Cascades Volcano Observatory (CVO) has been charged with obtaining baseline geodetic and geochemical information at each of the other potentially active Cascade volcanoes. Dry tilt and/or trilateration networks were established during 1975-82 at Mount Baker, Mount St. Helens, Mount Hood, Mount Shasta, Lassen Peak, Crater Lake, and Long Valley caldera; coverage was extended during September 1982 to include Mount Rainier.

  16. Volcano deformation--Geodetic monitoring techniques

    USGS Publications Warehouse

    Dzurisin, Daniel; Lu, Zhong

    2007-01-01

    This book describes the techniques used by volcanologists to successfully predict several recent volcanic eruptions by combining information from various scientific disciplines, including geodetic techniques. Many recent developments in the use of state-of-the-art and emerging techniques, including Global Positioning System and Synthetic Aperture Radar Interferometry, mean that most books on volcanology are out of date, and this book includes chapters devoted entirely to these two techniques.

  17. Geodetic precession or dragging of inertial frames

    NASA Technical Reports Server (NTRS)

    Ashby, Neil; Shahid-Saless, Bahman

    1989-01-01

    In General Relativity, the Principle of General Covariance allows one to describe phenomena by means of any convenient choice of coordinate system. Here, it is shown that the geodetic precession of a gyroscope orbiting a spherically symmetric, nonrotating mass can be recast as a Lense-Thirring frame-dragging effect, in an appropriately chosen coordinate frame whose origin falls freely along with the gyroscope and whose spatial coordinate axes point in fixed directions.

  18. Global Positioning System (GPS) Geodetic Receivers,

    DTIC Science & Technology

    1982-02-08

    Subti.) S. TYPE OF REPORT A PERFo COVERED Global Positioning System ( GPS ) Geodetic N/A Receivers S. PERFORMING OrG. REPORT NUMBER I N/A AUTNORf*) S...i N meueaed idautfy b block nmAr) The NAVSTAR Global Positioning System ( GPS ) when fully developed will pro- vide world-wide, all weather, continuous... Global Positioning System ( GPS ) when fully developed will provide world-wide, all weather, continuous, highly accurate radio navigation support to

  19. Geodetic altitude to a triaxial ellipsoidal planet

    NASA Technical Reports Server (NTRS)

    Tang, Charles C. H.

    1988-01-01

    An efficient theoretical model for determining geodetic altitudes with better than millimeter accuracy is proposed, with application to the TOPEX/Poseidon project. The triaxial ellipsoidal subsurface point of a satellite is used as the initial trial solution to achieve an efficient and simple iterative solution. It is found that the second-iteration solution is exact to an accuracy of at least 10 to the -9th km.

  20. Geodetic altitude to a triaxial ellipsoidal planet

    NASA Astrophysics Data System (ADS)

    Tang, Charles C. H.

    1988-09-01

    An efficient theoretical model for determining geodetic altitudes with better than millimeter accuracy is proposed, with application to the TOPEX/Poseidon project. The triaxial ellipsoidal subsurface point of a satellite is used as the initial trial solution to achieve an efficient and simple iterative solution. It is found that the second-iteration solution is exact to an accuracy of at least 10 to the -9th km.

  1. Geodetic infrastructure at the Barcelona harbour for sea level monitoring

    NASA Astrophysics Data System (ADS)

    Martinez-Benjamin, Juan Jose; Gili, Josep; Lopez, Rogelio; Tapia, Ana; Pros, Francesc; Palau, Vicenc; Perez, Begona

    2015-04-01

    The presentation is directed to the description of the actual geodetic infrastructure of Barcelona harbour with three tide gauges of different technologies for sea level determination and contribution to regional sea level rise and understanding past and present sea level rise in the Barcelona harbour. It is intended that the overall system will constitute a CGPS Station of the ESEAS (European Sea Level) and TIGA (GPS Tide Gauge Benchmark Monitoring) networks. At Barcelona harbour there is a MIROS radar tide gauge belonging to Puertos del Estado (Spanish Harbours).The radar sensor is over the water surface, on a L-shaped structure which elevates it a few meters above the quay shelf. 1-min data are transmitted to the ENAGAS Control Center by cable and then sent each 1 min to Puertos del Estado by e-mail. The information includes wave forescast (mean period, significant wave height, sea level, etc.This sensor also measures agitation and sends wave parameters each 20 min. There is a GPS station Leica Geosystems GRX1200 GG Pro and antenna AX 1202 GG. The Control Tower of the Port of Barcelona is situated in the North dike of the so-called Energy Pier in the Barcelona harbor (Spain). This tower has different kind of antennas for navigation monitoring and a GNSS permanent station. As the tower is founded in reclaimed land, and because its metallic structure, the 50 m building is subjected to diverse movements, including periodic fluctuations due to temperature changes. In this contribution the 2009, 2011, 2012, 2013 and 2014 the necessary monitoring campaigns are described. In the framework of a Spanish Space Project, the instrumentation of sea level measurements has been improved by providing the Barcelona site with a radar tide gauge Datamar 2000C from Geonica S.L. in June 2014 near an acoustic tide gauge from the Barcelona Harbour installed in 2013. Precision levelling has been made several times in the last two years because the tower is founded in reclaimed land and

  2. Development of AN Open-Source Automatic Deformation Monitoring System for Geodetical and Geotechnical Measurements

    NASA Astrophysics Data System (ADS)

    Engel, P.; Schweimler, B.

    2016-04-01

    The deformation monitoring of structures and buildings is an important task field of modern engineering surveying, ensuring the standing and reliability of supervised objects over a long period. Several commercial hardware and software solutions for the realization of such monitoring measurements are available on the market. In addition to them, a research team at the Neubrandenburg University of Applied Sciences (NUAS) is actively developing a software package for monitoring purposes in geodesy and geotechnics, which is distributed under an open source licence and free of charge. The task of managing an open source project is well-known in computer science, but it is fairly new in a geodetic context. This paper contributes to that issue by detailing applications, frameworks, and interfaces for the design and implementation of open hardware and software solutions for sensor control, sensor networks, and data management in automatic deformation monitoring. It will be discussed how the development effort of networked applications can be reduced by using free programming tools, cloud computing technologies, and rapid prototyping methods.

  3. Breadth of Scientific Activities and Network Station Specifications in the IGS

    NASA Technical Reports Server (NTRS)

    Moore, A. W.; Springer, T. A.; Reigber, Ch.

    1999-01-01

    This presentation provides a brief overview of the scientific activities of the International GPS Service (IGS). This was an approved activity of the International Association of Geodesy (IAG) with official start of service on 1 Jan 1994. The mission of the IGS is "To provide a service to support geodetic and geophysical research activities, through GPS data and data products." The presentation explains the concept of the IGS working group, and pilot projects, and reviews the current working groups and pilot projects.

  4. Evaluation of geodetic and geologic datasets in the Northern Walker Lane-Summary and recommendations of the Workshop

    USGS Publications Warehouse

    Briggs, Richard W.; Hammond, William C.

    2010-01-01

    The Northern Walker Lane comprises a complex network of active faults in northwestern Nevada and northeastern California bound on the west by the Sierra Nevada and on the east by the extensional Basin and Range Province. Because deformation is distributed across sets of discontinuous faults, it is particularly challenging to integrate geologic and geodetic data in the NWL to assess the region's seismic hazard. Recent GPS measurements show that roughly one centimeter per year of relative displacement is accumulating across a zone about 100 km wide at the latitude of Reno, Nevada, but it is not clear where or how much of this strain might ultimately be released in damaging earthquakes. Despite decades of work in the region, the sum of documented late Pleistocene to recent slip rates is distinctly less than the GPS-measured relative displacement.

  5. A New Geodetic Research Data Management System at the Hartebeesthoek Radio Astronomy Observatory

    NASA Astrophysics Data System (ADS)

    Coetzer, G. L.; Botha, R. C.; Combrinck, L.; Fourie, S. C.

    2015-04-01

    The Hartebeesthoek Radio Astronomy Observatory (HartRAO) hosts two research programmes: radio astronomy and space geodesy. The Space Geodesy programme has four main co-located space geodetic techniques, making HartRAO a true fiducial site. The HartRAO Space Geodesy Programme is expanding its geodetic techniques to include Lunar Laser Ranging (LLR) as well as a network of seismometers, accelerometers, tide gauges, and gravimeters. These instruments will be installed across the southern African region and will generate large volumes of data that will be streamed to and stored at HartRAO. Our objective is to implement a complete Geodetic Research Data Management System (GRDMS) to handle all HartRAO's geodetic data on-site in terms of archiving, indexing, processing, and extraction. These datasets and subsequent data products will be accessible to both the scientific community and general public through an intuitive and easy to use web-based front-end. As the first step in this process, we are currently working on establishing a new data centre. This opens up the possibility for the librarian to provide data services and support by working together with researchers and information technology staff. We discuss the rationale, role players and top-level system design of this GRDMS, as well as the current status and planned products thereof.

  6. A New Unified Approach to Determine Geocenter Motion Using Space Geodetic and GRACE Gravity Data

    NASA Astrophysics Data System (ADS)

    Wu, Xiaoping; Kusche, Jürgen; Landerer, Felix W.

    2017-03-01

    Geocenter motion between the center-of-mass of the Earth system (CM) and the center-of-figure of the solid Earth surface is a critical signature of degree-1 components of global surface mass transport process that includes sea level rise, ice mass imbalance, and continental-scale hydrological change. To complement GRACE data for complete-spectrum mass transport monitoring, geocenter motion needs to be measured accurately. However, current methods of geodetic translational approach and global inversions of various combinations of geodetic deformation, simulated ocean bottom pressure, and GRACE data contain substantial biases and systematic errors. Here, we demonstrate a new and more reliable unified approach to geocenter motion determination using a recently formed satellite laser ranging based geocentric displacement time series of an expanded geodetic network of all four space geodetic techniques and GRACE gravity data. The unified approach exploits both translational and deformational signatures of the displacement data, while the addition of GRACE's near global coverage significantly reduces biases found in the translational approach and spectral aliasing errors in the inversion.

  7. Seismic active control by neutral networks

    SciTech Connect

    Tang, Yu

    1995-12-31

    A study on the application of artificial neural networks (ANNs) to active structural control under seismic loads is carried out. The structure considered is a single-degree-of-freedom (SDF) system with an active bracing device. The control force is computed by a trained neural network. The feedforward neural network architecture and an adaptive backpropagation training algorithm is used in the study. The neural net is trained to reproduce the function that represents the response-excitation relationship of the SDF system under seismic loads. The input-output training patterns are generated randomly. In the backpropagation training algorithm, the learning rate is determined by ensuring the decrease of the error function at each epoch. The computer program implemented is validated by solving the classification of the XOR problem. Then, the trained ANN is used to compute the control force according to the control strategy. If the control force exceeds the actuator`s capacity limit, it is set equal to that limit. The concept of the control strategy employed herein is to apply the control force at every time step to cancel the system velocity induced at the preceding time step so that the gradual rhythmic buildup of the response is destroyed. The ground motions considered in the numerical example are the 1940 El Centro earthquake and the 1979 Imperial Valley earthquake in California. The system responses with and without the control are calculated and compared. The feasibility and potential of applying ANNs to seismic active control is asserted by the promising results obtained from the numerical examples studied.

  8. Stiff substrates enhance cultured neuronal network activity.

    PubMed

    Zhang, Quan-You; Zhang, Yan-Yan; Xie, Jing; Li, Chen-Xu; Chen, Wei-Yi; Liu, Bai-Lin; Wu, Xiao-an; Li, Shu-Na; Huo, Bo; Jiang, Lin-Hua; Zhao, Hu-Cheng

    2014-08-28

    The mechanical property of extracellular matrix and cell-supporting substrates is known to modulate neuronal growth, differentiation, extension and branching. Here we show that substrate stiffness is an important microenvironmental cue, to which mouse hippocampal neurons respond and integrate into synapse formation and transmission in cultured neuronal network. Hippocampal neurons were cultured on polydimethylsiloxane substrates fabricated to have similar surface properties but a 10-fold difference in Young's modulus. Voltage-gated Ca(2+) channel currents determined by patch-clamp recording were greater in neurons on stiff substrates than on soft substrates. Ca(2+) oscillations in cultured neuronal network monitored using time-lapse single cell imaging increased in both amplitude and frequency among neurons on stiff substrates. Consistently, synaptic connectivity recorded by paired recording was enhanced between neurons on stiff substrates. Furthermore, spontaneous excitatory postsynaptic activity became greater and more frequent in neurons on stiff substrates. Evoked excitatory transmitter release and excitatory postsynaptic currents also were heightened at synapses between neurons on stiff substrates. Taken together, our results provide compelling evidence to show that substrate stiffness is an important biophysical factor modulating synapse connectivity and transmission in cultured hippocampal neuronal network. Such information is useful in designing instructive scaffolds or supporting substrates for neural tissue engineering.

  9. Precision gravity networks at Lassen Peak and Mount Shasta, California

    USGS Publications Warehouse

    Jachens, Robert C.; Dzurisin, Daniel; Elder, W.P.; Saltus, R.W.

    1983-01-01

    Reoccupiable precision gravity networks for the purpose of monitoring volcanic activity were established in the vicinity of Lassen Peak and Mt. Shasta. Base-line measurements were made during the summer of 1981, nearly coincident in time with other base-line geodetic measurements. The gravity surveys yielded gravity values at network stations relative to local bases with typical uncertainties of 0.007 mGal (1 computed standard error).

  10. Deep Neural Networks with Multistate Activation Functions

    PubMed Central

    Cai, Chenghao; Xu, Yanyan; Ke, Dengfeng; Su, Kaile

    2015-01-01

    We propose multistate activation functions (MSAFs) for deep neural networks (DNNs). These MSAFs are new kinds of activation functions which are capable of representing more than two states, including the N-order MSAFs and the symmetrical MSAF. DNNs with these MSAFs can be trained via conventional Stochastic Gradient Descent (SGD) as well as mean-normalised SGD. We also discuss how these MSAFs perform when used to resolve classification problems. Experimental results on the TIMIT corpus reveal that, on speech recognition tasks, DNNs with MSAFs perform better than the conventional DNNs, getting a relative improvement of 5.60% on phoneme error rates. Further experiments also reveal that mean-normalised SGD facilitates the training processes of DNNs with MSAFs, especially when being with large training sets. The models can also be directly trained without pretraining when the training set is sufficiently large, which results in a considerable relative improvement of 5.82% on word error rates. PMID:26448739

  11. Three-Dimensional Geodetic Control by Interferometry with GPS (Global Positioning System): Processing of GPS Phase Observables.

    DTIC Science & Technology

    1985-04-23

    8217 geodetic networks; three, dimensional geodesy, satellite geodesy, NAVSTAR Global Positioning System,’ GPS , interferometry 20. ABSTRACT (Continue on reverse...8217 - - .. . . . . . . . . . . . . . -t INTRODUCTION GPS interferometry is a method by which three-dimensional relative-position vectors between observing stations can be

  12. Present Geodetic Slip Rate of Being Co Fault Zone in Central Lhasa Block, Tibet

    NASA Astrophysics Data System (ADS)

    Tian, Yunfeng; Li, Yongsheng; Luo, Yi; Jiang, Wenliang; Jiang, Hongbo; Jiao, Qisong; Shen, Wenhao; Wang, Dehua; Li, Qiang; Zhang, Jingfa

    2016-08-01

    Synchronous with a series of large scale S-N rift systems in southern Tibet, the "chord" connecting the eastern and western Himalayan syntaxes, which is known as KJFZ (Karakorum Jiali Fault Zone), is supposed to experience rapid (10-20mm/a) right-lateral strike slip (Armijo et al., 1989), accommodating the E-W extension and S-N shortening of Tibetan plateau between Himalayan arc in the south and Tarim basin in the north.The Jiali fault and Beng Co fault consist of the easternmost segment of KJFZ, and they interplay with the Yadong-Gulu rift near the Gulu county.However, because of the harsh environment and the sparse modern geodetic network in this region, the recent activity of Beng Co fault zone is not well known, especially for the southeast segment (i.e. southeast the Beng Co lake). Therefore, we use both GNSS and InSAR techniques to study the current activity of Beng Co fault system.

  13. The September 16, 2015 Illapel (Mw 8.3) Earthquake: Comprehensive Analysis from Seismic and Geodetic Observations

    NASA Astrophysics Data System (ADS)

    Comte, D.; Carrizo, D.; Peyrat, S.; Russo, R. M.; Roecker, S. W.; Opazo, T.; Peña, G.; Baeza, S.; Arriaza, R.; Ortega-Culaciati, F.; Ruiz, J. A.; Contreras-Reyes, E.; Becerra, V.

    2015-12-01

    On September 16th, 2015 an Mw=8.3 struck the Illapel zone between 30°- 32.5°S along an area between the trench and the coastline, including the activation of outer-rise seismicity. The rupture area of this earthquake covers the 1943 previous large earthquake, and also seems to overlap with the northern end of the rupture of the 1971 and 1985 earthquakes. Immediately after the occurrence of the 2015 earthquake, we deployed 18 3-components short period continuous recording seismic stations to complement the coverage of the University of Chile National Seismological Center (CSN) permanent broad band seismic network and four temporary seismic stations deployed by the CSN. The short period stations will be replaced by IRIS PASCAL broad band stations through the NSF RAPID Collaborative Proposal (U. of Florida, RPI, and U. of Chile), generating an open-access data set that, along with the seismological and geodetic observations from CSN permanent networks, provide the best quality data that can be utilized immediately by a wide range of PIs and institutions around the world. Such datasets able us to pursue these main goals: 1) aftershock monitoring, focal mechanism and analysis related with the interplate rupture zone; 2) imaging the seismic structure of the 2015 Illapel rupture area; 3) characterization of the mechanical behavior of the subduction interface from geodetic observations before, during and after the earthquake, 4) identification and characterization of low frequency and/or slow slip aftershocks; characterization of seismic amplification effects and the consequent hazard determination.

  14. Geodetic and Geodynamic Studies at Department of Geodesy and Geodetic Astronomy Wut

    NASA Astrophysics Data System (ADS)

    Brzeziński, Aleksander; Barlik, Marcin; Andrasik, Ewa; Izdebski, Waldemar; Kruczyk, Michał; Liwosz, Tomasz; Olszak, Tomasz; Pachuta, Andrzej; Pieniak, Magdalena; Próchniewicz, Dominik; Rajner, Marcin; Szpunar, Ryszard; Tercjak, Monika; Walo, Janusz

    2016-06-01

    The article presents current issues and research work conducted in the Department of Geodesy and Geodetic Astronomy at the Faculty of Geodesy and Cartography at Warsaw University of Technology. It contains the most important directions of research in the fields of physical geodesy, satellite measurement techniques, GNSS meteorology, geodynamic studies, electronic measurement techniques and terrain information systems.

  15. Studies of Error Sources in Geodetic VLBI

    NASA Technical Reports Server (NTRS)

    Rogers, A. E. E.; Niell, A. E.; Corey, B. E.

    1996-01-01

    Achieving the goal of millimeter uncertainty in three dimensional geodetic positioning on a global scale requires significant improvement in the precision and accuracy of both random and systematic error sources. For this investigation we proposed to study errors due to instrumentation in Very Long Base Interferometry (VLBI) and due to the atmosphere. After the inception of this work we expanded the scope to include assessment of error sources in GPS measurements, especially as they affect the vertical component of site position and the measurement of water vapor in the atmosphere. The atmosphere correction 'improvements described below are of benefit to both GPS and VLBI.

  16. Absolute Geodetic Rotation Measurement Using Atom Interferometry

    SciTech Connect

    Stockton, J. K.; Takase, K.; Kasevich, M. A.

    2011-09-23

    We demonstrate a cold-atom interferometer gyroscope which overcomes accuracy and dynamic range limitations of previous atom interferometer gyroscopes. We show how the instrument can be used for precise determination of latitude, azimuth (true north), and Earth's rotation rate. Spurious noise terms related to multiple-path interferences are suppressed by employing a novel time-skewed pulse sequence. Extended versions of this instrument appear capable of meeting the stringent requirements for inertial navigation, geodetic applications of Earth's rotation rate determination, and tests of general relativity.

  17. Baseline mathematics and geodetics for tracking operations

    NASA Technical Reports Server (NTRS)

    James, R.

    1981-01-01

    Various geodetic and mapping algorithms are analyzed as they apply to radar tracking systems and tested in extended BASIC computer language for real time computer applications. Closed-form approaches to the solution of converting Earth centered coordinates to latitude, longitude, and altitude are compared with classical approximations. A simplified approach to atmospheric refractivity called gradient refraction is compared with conventional ray tracing processes. An extremely detailed set of documentation which provides the theory, derivations, and application of algorithms used in the programs is included. Validation methods are also presented for testing the accuracy of the algorithms.

  18. Ostrogradski Hamiltonian approach for geodetic brane gravity

    SciTech Connect

    Cordero, Ruben; Molgado, Alberto

    2010-12-07

    We present an alternative Hamiltonian description of a branelike universe immersed in a flat background spacetime. This model is named geodetic brane gravity. We set up the Regge-Teitelboim model to describe our Universe where such field theory is originally thought as a second order derivative theory. We refer to an Ostrogradski Hamiltonian formalism to prepare the system to its quantization. This approach comprize the manage of both first- and second-class constraints and the counting of degrees of freedom follows accordingly.

  19. Genetic Networks Activated by Blast Injury to the Eye

    DTIC Science & Technology

    2013-08-01

    AD_________________ Award Number: W81XWH-12-1-0255 TITLE: Genetic Networks Activated by Blast...DATES COVERED 15 July 2012 – 14 July 2013 4. TITLE AND SUBTITLE Genetic Networks Activated by Blast Injury to the Eye 5a. CONTRACT NUMBER 5b...following a blast injury to the eye. In this process the genetic networks activated by injury will be defined along with biological markers of

  20. A New Global Geodetic Strain Rate Model

    NASA Astrophysics Data System (ADS)

    Kreemer, C. W.; Klein, E. C.; Blewitt, G.; Shen, Z.; Wang, M.; Chamot-Rooke, N. R.; Rabaute, A.

    2012-12-01

    As part of the Global Earthquake Model (GEM) effort to improve global seismic hazard models, we present a new global geodetic strain rate model. This model (GSRM v. 2) is a vast improvement on the previous model from 2004 (v. 1.2). The model is still based on a finite-element type approach and has deforming cells in between the assumed rigid plates. While v.1.2 contained ~25,000 deforming cells of 0.6° by 0.5° dimension, the new models contains >136,000 cells of 0.25° by 0.2° dimension. We redefined the geometries of the deforming zones based on the definitions of Bird (2003) and Chamot-Rooke and Rabaute (2006). We made some adjustments to the grid geometry at places where seismicity and/or GPS velocities suggested the presence of deforming areas where those previous studies did not. As a result, some plates/blocks identified by Bird (2003) we assumed to deform, and the total number of plates and blocks in GSRM v.2 is 38 (including the Bering block, which Bird (2003) did not consider). GSRM v.1.2 was based on ~5,200 GPS velocities, taken from 86 studies. The new model is based on ~17,000 GPS velocities, taken from 170 studies. The GPS velocity field consists of a 1) ~4900 velocities derived by us for CPS stations publicly available RINEX data and >3.5 years of data, 2) ~1200 velocities for China from a new analysis of all CMONOC data, and 3) velocities published in the literature or made otherwise available to us. All studies were combined into the same reference frame by a 6-parameter transformation using velocities at collocated stations. Because the goal of the project is to model the interseismic strain rate field, we model co-seismic jumps while estimating velocities, ignore periods of post-seismic deformation, and exclude time-series that reflect magmatic and anthropogenic activity. GPS velocities were used to estimate angular velocities for most of the 38 rigid plates and blocks (the rest being taken from the literature), and these were used as boundary

  1. Geodetic monitoring of subrosion-induced subsidence processes in urban areas

    NASA Astrophysics Data System (ADS)

    Kersten, Tobias; Kobe, Martin; Gabriel, Gerald; Timmen, Ludger; Schön, Steffen; Vogel, Detlef

    2017-03-01

    The research project SIMULTAN applies an advanced combination of geophysical, geodetic, and modelling techniques to gain a better understanding of the evolution and characteristics of sinkholes. Sinkholes are inherently related to surface deformation and, thus, of increasing societal relevance, especially in dense populated urban areas. One work package of SIMULTAN investigates an integrated approach to monitor sinkhole-related mass translations and surface deformations induced by salt dissolution. Datasets from identical and adjacent points are used for a consistent combination of geodetic and geophysical techniques. Monitoring networks are established in Hamburg and Bad Frankenhausen (Thuringia). Levelling surveys indicate subsidence rates of about 4-5 mm per year in the main subsidence areas of Bad Frankenhausen with a local maximum of 10 mm per year around the leaning church tower. Here, the concept of combining geodetic and gravimetric techniques to monitor and characterise geological processes on and below the Earth's surface is exemplary discussed for the focus area Bad Frankenhausen. For the different methods (levelling, GNSS, relative/absolute gravimetry) stable network results at identical points are obtained by the first campaigns, i.e., the results are generally in agreement.

  2. Designing a new Geodetic Research Data Management System for the Hartebeesthoek Radio Astronomy Observatory

    NASA Astrophysics Data System (ADS)

    Coetzer, Glend Lorraine

    2015-08-01

    The Hartebeesthoek Radio Astronomy Observatory (HartRAO) participates in astronomic, astrometric and geodetic Very Long Baseline Interferometry (VLBI) observations using both 26- and 15-m diameter radio telescopes. Geodetic data from a Satellite Laser Ranger (SLR), Global Navigation Satellite System (GNSS), Met4 weather stations and a new seismic vault network must be stored at HartRAO and made available to the scientific community. Some data are e-transferred to correlators, analysis centres and space geodesy data providers, while some data are processed locally to produce basic data products. The new South African co-located seismology network of seismic and GNSS instrumentation will generate large volumes of raw data to be stored and archived at HartRAO. The current data storage systems are distributed and outdated, and management systems currently being used will also not be able to handle the additional large volumes of data. This necessitates the design and implementation of a new, modern research data management system which combines all the datasets into one database, as well as cater for current and future data volume requirements. The librarian’s expertise and knowledge will be used in the design and implementation of the new HartRAO Geodetic Research Data Management System (GRDMS). The librarian’s role and involvement in the design and implementation of the new GRDMS are presented here. Progress to date will also be discussed.

  3. Strain Rate into South American Plate by SIRGAS-CON Geodetic Observations

    NASA Astrophysics Data System (ADS)

    Marotta, G. S.; Franca, G. S.; Monico, J. G.; Fuck, R. A.

    2013-05-01

    In this study were investigated the surface strain rates computed from the direction variations and velocity values estimated from the coordinates of the continuous monitoring geodetic network called SIRGAS-CON. That investigation was done using points located in the South American plate. The determination of the strain rate was based on the Finite Element method using points defined by Delaunay triangulation (sub-networks). Each one of sub-networks was considered as an homogeneous solid body. Using these methods was possible to separate the strain from the plate movement. The results showed that there are differences of strain rate along the South American plate. From the results were suggest that near to the west board of the plate, the strain is more significant, as expected, because this region is near to one area where Nazca Plate subduct South American Plate. It was detected that the contraction region founded in this area coincides whit the region where occurs most of earthquakes of greater magnitude. Far from the board, there are some areas with anomalies of significant strain of extension and contraction that can be originated by differences of stress aligned with different geological composites. By the results, It may be concluded that large surface movements occur in regions with more heterogeneous geological structures and multiple event of rupture, that large earthquakes arising from large tectonic activity into South American Plate are concentrated in areas with contraction strain rates predominantly oriented towards northeast-southwest, that significant amounts of elastic strain can be accumulated over geological structures away from fault plate boundary and that the behavior of contractions and extensions are similar to that found by different researches involving geophysical studies. Dilation and principal components of strain rate

  4. Determination of the Deformation along the Tuzla Fault, Izmir, Turkey by Geodetic Techniques

    NASA Astrophysics Data System (ADS)

    Sabuncu, A.; Ozener, H.

    2010-12-01

    The Aegean region is the most seismically active domain in Western Anatolia which comprises Greece, the Hellenic Arc, and Western Turkey. The Aegean region is mainly under pure shear stress from an internally deforming counter-clockwise direction of the Anatolian Plate relative to the Eurasia Plate. Izmir is the third largest city in Turkey with 2.7 million population. The Tuzla Fault is lying between the town of Menderes and Cape Doganbey which has NE-SW lineament trending. It is 42 km long through the land with 3 right lateral strike slip segments. This fault has a great importance as its proximity to the city of Izmir. The study aims to perform a large scale investigation, focusing on the Tuzla Fault and its vicinity for better understanding of the region’s tectonics. A micro-geodetic network with 15 points has been established in the study area. In order to investigate the crustal deformation and relative displacements along the Tuzla Fault GPS and Precise leveling techniques were used. Observations of two GPS campaigns and two precise leveling measurements were performed in 2009 and 2010. In order to process collected data by GPS campaigns, GAMIT/GLOBK software was used. As a result of two GPS campaigns, the velocity vectors of points are rated between 21mm/yr to 25mm/yr. In addition, 6.6 mm vertical displacement was observed between two leveling benchmarks which seems critical and needs further investigation.

  5. Models of neural networks with fuzzy activation functions

    NASA Astrophysics Data System (ADS)

    Nguyen, A. T.; Korikov, A. M.

    2017-02-01

    This paper investigates the application of a new form of neuron activation functions that are based on the fuzzy membership functions derived from the theory of fuzzy systems. On the basis of the results regarding neuron models with fuzzy activation functions, we created the models of fuzzy-neural networks. These fuzzy-neural network models differ from conventional networks that employ the fuzzy inference systems using the methods of neural networks. While conventional fuzzy-neural networks belong to the first type, fuzzy-neural networks proposed here are defined as the second-type models. The simulation results show that the proposed second-type model can successfully solve the problem of the property prediction for time – dependent signals. Neural networks with fuzzy impulse activation functions can be widely applied in many fields of science, technology and mechanical engineering to solve the problems of classification, prediction, approximation, etc.

  6. Network Patch Cables Demystified: A Super Activity for Computer Networking Technology

    ERIC Educational Resources Information Center

    Brown, Douglas L.

    2004-01-01

    This article de-mystifies network patch cable secrets so that people can connect their computers and transfer those pesky files--without screaming at the cables. It describes a network cabling activity that can offer students a great hands-on opportunity for working with the tools, techniques, and media used in computer networking. Since the…

  7. Using geodetic VLBI to test Standard-Model Extension

    NASA Astrophysics Data System (ADS)

    Hees, Aurélien; Lambert, Sébastien; Le Poncin-Lafitte, Christophe

    2016-04-01

    The modeling of the relativistic delay in geodetic techniques is primordial to get accurate geodetic products. And geodetic techniques can also be used to measure the relativistic delay and get constraints on parameters describing the relativity theory. The effective field theory framework called the Standard-Model Extension (SME) has been developed in order to systematically parametrize hypothetical violations of Lorentz symmetry (in the Standard Model and in the gravitational sector). In terms of light deflexion by a massive body like the Sun, one can expect a dependence in the elongation angle different from GR. In this communication, we use geodetic VLBI observations of quasars made in the frame of the permanent geodetic VLBI monitoring program to constrain the first SME coefficient. Our results do not show any deviation from GR and they improve current constraints on both GR and SME parameters.

  8. Identities in flux: cognitive network activation in times of change.

    PubMed

    Menon, Tanya; Smith, Edward Bishop

    2014-05-01

    Using a dynamic cognitive model, we experimentally test two competing hypotheses that link identity and cognitive network activation during times of change. On one hand, affirming people's sense of power might give them confidence to think beyond the densest subsections of their social networks. Alternatively, if such power affirmations conflict with people's more stable status characteristics, this could create tension, deterring people from considering their networks' diversity. We test these competing hypotheses experimentally by priming people at varying levels of status with power (high/low) and asking them to report their social networks. We show that confirming identity-not affirming power-cognitively prepares people to broaden their social networks when the world is changing around them. The emotional signature of having a confirmed identity is feeling comfortable and in control, which mediates network activation. We suggest that stable, confirmed identities are the foundation from which people can exhibit greater network responsiveness.

  9. Workflow Modeling Using Stochastic Activity Networks

    NASA Astrophysics Data System (ADS)

    Javadi Mottaghi, Fatemeh; Abdollahi Azgomi, Mohammad

    The essence of workflow systems is workflow patterns. The aim is to use an existing powerful formal modeling language with workflow systems. Stochastic activity networks (SANs) are a powerful extension of Petri nets. Having the SAN model of a system, one can verify the functional aspects and evaluate the operational measures, both on a same model. SANs have already been used in a wide range of applications. As a new application area, we have used SANs for modeling workflow systems. The results show that the most important workflow patterns can be modeled in SANs. In addition, the resulting SAN models of workflow systems can be used for model checking and/or performance evaluation purposes using the existing tools. In this paper, we will present the results of this work. For this purpose, we will present the SAN submodels corresponding to the most important workflow patterns. Then, the proposed SAN submodels are used in a case study for workflow modeling, which will also be presented in this paper. Finally, we will present the results of the evaluation of the model using the Möbius modeling tool.

  10. Mesoscale architecture shapes initiation and richness of spontaneous network activity.

    PubMed

    Okujeni, Samora; Kandler, Steffen; Egert, Ulrich

    2017-03-14

    Spontaneous activity in the absence of external input, including propagating waves of activity, is a robust feature of neuronal networks in vivo and in vitro. The neurophysiological and anatomical requirements for initiation and persistence of such activity, however, are poorly understood, as is their role in the function of neuronal networks. Computational network studies indicate that clustered connectivity may foster the generation, maintenance and richness of spontaneous activity. Since this mesoscale architecture cannot be systematically modified in intact tissue, testing these predictions is impracticable in vivo. Here, we investigate how the mesoscale structure shapes spontaneous activity in generic networks of rat cortical neurons in vitro. In these networks, neurons spontaneously arrange into local clusters with high neurite density and form fasciculating long-range axons. We modified this structure by modulation of protein kinase C, an enzyme regulating neurite growth and cell migration. Inhibition of protein kinase C reduced neuronal aggregation and fasciculation of axons, i.e. promoted uniform architecture. Conversely, activation of protein kinase C promoted aggregation of neurons into clusters, local connectivity and bundling of long-range axons. Supporting predictions from theory, clustered networks were more spontaneously active and generated diverse activity patterns. Neurons within clusters received stronger synaptic inputs and displayed increased membrane potential fluctuations. Intensified clustering promoted the initiation of synchronous bursting events but entailed incomplete network recruitment. Moderately clustered networks appear optimal for initiation and propagation of diverse patterns of activity. Our findings support a crucial role of the mesoscale architectures in the regulation of spontaneous activity dynamics.SIGNIFICANCE STATEMENTComputational studies predict richer and persisting spatio-temporal patterns of spontaneous activity in

  11. Radio source stability and geodetic VLBI

    NASA Astrophysics Data System (ADS)

    Gattano, César; Lambert, Sébastien

    2016-04-01

    The observation of the Earth's rotation by VLBI is conditioned by the celestial reference frame that should be as stable as possible. The selection of the most stable sources therefore constitutes a major step in the construction of a celestial reference frame since their stability prevents time deformation of the axes with time. The assessment of astrometric stability, i.e., the time stability the radiocenter location as detected by the VLBI, is one of the methods that were used in previous ICRF realizations (works of M. Feissel-Vernier and ICRF2). We think the same method should be addressed for the construction of the ICRF3. We analyzed the radio source time series obtained from the analysis of the data from the permanent geodetic VLBI monitoring program of the IVS. We used several utils based on basic statistics and more advanced methods (Allan variance) in order to provide a preliminary classification of sources.

  12. Competing dynamic phases of active polymer networks

    NASA Astrophysics Data System (ADS)

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

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

  13. Brain network activity in monolingual and bilingual older adults.

    PubMed

    Grady, Cheryl L; Luk, Gigi; Craik, Fergus I M; Bialystok, Ellen

    2015-01-01

    Bilingual older adults typically have better performance on tasks of executive control (EC) than do their monolingual peers, but differences in brain activity due to language experience are not well understood. Based on studies showing a relation between the dynamic range of brain network activity and performance on EC tasks, we hypothesized that life-long bilingual older adults would show increased functional connectivity relative to monolinguals in networks related to EC. We assessed intrinsic functional connectivity and modulation of activity in task vs. fixation periods in two brain networks that are active when EC is engaged, the frontoparietal control network (FPC) and the salience network (SLN). We also examined the default mode network (DMN), which influences behavior through reduced activity during tasks. We found stronger intrinsic functional connectivity in the FPC and DMN in bilinguals than in monolinguals. Although there were no group differences in the modulation of activity across tasks and fixation, bilinguals showed stronger correlations than monolinguals between intrinsic connectivity in the FPC and task-related increases of activity in prefrontal and parietal regions. This bilingual difference in network connectivity suggests that language experience begun in childhood and continued throughout adulthood influences brain networks in ways that may provide benefits in later life.

  14. Brain Network Activity in Monolingual and Bilingual Older Adults

    PubMed Central

    Grady, Cheryl L.; Luk, Gigi; Craik, Fergus I.M.; Bialystok, Ellen

    2016-01-01

    Bilingual older adults typically have better performance on tasks of executive control (EC) than do their monolingual peers, but differences in brain activity due to language experience are not well understood. Based on studies showing a relation between the dynamic range of brain network activity and performance on EC tasks, we hypothesized that life-long bilingual older adults would show increased functional connectivity relative to monolinguals in networks related to EC. We assessed intrinsic functional connectivity and modulation of activity in task vs. fixation periods in two brain networks that are active when EC is engaged, the frontoparietal control network (FPC) and the salience network (SLN). We also examined the default mode network (DMN), which influences behavior through reduced activity during tasks. We found stronger intrinsic functional connectivity in the FPC and DMN in bilinguals than in monolinguals. Although there were no group differences in the modulation of activity across tasks and fixation, bilinguals showed stronger correlations than monolinguals between intrinsic connectivity in the FPC and task-related increases of activity in prefrontal and parietal regions. This bilingual difference in network connectivity suggests that language experience begun in childhood and continued throughout adulthood influences brain networks in ways that may provide benefits in later life. PMID:25445783

  15. Network-dependent modulation of brain activity during sleep.

    PubMed

    Watanabe, Takamitsu; Kan, Shigeyuki; Koike, Takahiko; Misaki, Masaya; Konishi, Seiki; Miyauchi, Satoru; Miyahsita, Yasushi; Masuda, Naoki

    2014-09-01

    Brain activity dynamically changes even during sleep. A line of neuroimaging studies has reported changes in functional connectivity and regional activity across different sleep stages such as slow-wave sleep (SWS) and rapid-eye-movement (REM) sleep. However, it remains unclear whether and how the large-scale network activity of human brains changes within a given sleep stage. Here, we investigated modulation of network activity within sleep stages by applying the pairwise maximum entropy model to brain activity obtained by functional magnetic resonance imaging from sleeping healthy subjects. We found that the brain activity of individual brain regions and functional interactions between pairs of regions significantly increased in the default-mode network during SWS and decreased during REM sleep. In contrast, the network activity of the fronto-parietal and sensory-motor networks showed the opposite pattern. Furthermore, in the three networks, the amount of the activity changes throughout REM sleep was negatively correlated with that throughout SWS. The present findings suggest that the brain activity is dynamically modulated even in a sleep stage and that the pattern of modulation depends on the type of the large-scale brain networks.

  16. Investigations with the Sentinel-1 Interferometric Wide Swath mode: first results and comparison with in-situ geodetic data

    NASA Astrophysics Data System (ADS)

    Borgstrom, Sven; Del Gaudio, Carlo; De Martino, Prospero; Ricciardi, Giovanni P.; Ricco, Ciro; Siniscalchi, Valeria; Prats-Iraola, Pau; Nannini, Matteo; Costantini, Mario; Minati, Federico; Walter, Thomas

    2015-04-01

    The contribution focuses on the current status of the ESA study entitled "INSARAP: Sentinel-1 InSAR Performance study with TOPS Data". The study investigates the performance of the interferometric wide swath (IW) mode of Sentinel-1, which is implemented using the terrain observation by progressive scans (TOPS) mode. In this regard, first analyses with Sentinel-1 time series will be shown, with a comparison with in-situ geodetic measurements on different test sites identified in the framework of the study, namely, Campi Flegrei/Vesuvius area in Italy, Istanbul city in Turkey, and Mexico City. The evaluation of the results will be performed by exploiting mainly continuous GPS stations located on the different sites, besides leveling measurements when also available. Also in a recent past, the comparison between InSAR and continuous GPS data, the latter projected into the radar LOS, has proven to be very effective for a cross comparison, besides InSAR Cal/Val activities, as it was for instance in the case of the recent inflation events occurred in Campi Flegrei area, marked by the well know bradyseismic phenomenon. Although continuous GPS networks are characterized by a poor space coverage in comparison with InSAR results, continuous GPS data recording allows to complement the geodetic information from InSAR sensors, limited by their revisiting time. The issue to be faced in this study is the possibility to deal with very low deformation rates in comparison with the Sentinel-1 C-band data, although the Sentinel-1 time series we expect to get from October 2014 to date should allow the identification of ground deformation in the areas of interest.

  17. Finding Quasi-Optimal Network Topologies for Information Transmission in Active Networks

    PubMed Central

    Baptista, Murilo S.; de Carvalho, Josué X.; Hussein, Mahir S.

    2008-01-01

    This work clarifies the relation between network circuit (topology) and behaviour (information transmission and synchronization) in active networks, e.g. neural networks. As an application, we show how one can find network topologies that are able to transmit a large amount of information, possess a large number of communication channels, and are robust under large variations of the network coupling configuration. This theoretical approach is general and does not depend on the particular dynamic of the elements forming the network, since the network topology can be determined by finding a Laplacian matrix (the matrix that describes the connections and the coupling strengths among the elements) whose eigenvalues satisfy some special conditions. To illustrate our ideas and theoretical approaches, we use neural networks of electrically connected chaotic Hindmarsh-Rose neurons. PMID:18941516

  18. On the Impact of GPS phase centre corrections on geodetic parameters: analytical formulation and empirical evaluation by PPP

    NASA Astrophysics Data System (ADS)

    Hiemer, Leonard; Kersten, Tobias; Schön, Steffen

    2015-04-01

    Several contributions and papers in geodesy intensively discuss the impact of the variability of GPS/GNSS absolute phase centre corrections (PCCs) directly on the positioning domain, neglecting any studies on the observation domain. Furthermore, it is very complex to evaluate in a general way the impact of several PCCs in geodetic positioning due to the different positioning concepts (e.g. PPP, relative positioning in networks) as well as implementation philosophy. Up to know, it is not clear how accurate different PCCs have to be for an individual geodetic grade antenna, in order to assume no significant and negative impact on the geodetic parameter estimation. Currently, individual calibrations have to be comparable of at least below 1mm. The poster will cover this topic by studying the observation domain as well as the geodetic position domain. The used approach is based on a pragmatic method, investigated by Geiger (1988), using generic PCC pattern. The contribution is divided into an analytical approach and an empirical approach. The analytical step discusses in detail the mathematical model and the propagation of error functions, classified by several antenna models. The empirical step evaluates these findings by practical experiments carried out with pre-defined errors on PCCs within a geodetic positioning estimation (PPP) using different software packages. We will show on the one side that some symmetrical error contributions of typical geodetic antenna designs can be described very well by this simple and pragmatic approach. The theoretical findings are compared to PPP solutions, revealing differences between the used software packages. On the other side, we show that asymmetrical error contributions are highly correlated with the satellite constellation and the geographical location. References: Geiger A. (1988): Modeling of Phase Centre Variation and its Influence on GPS-Positioning, In GPS-Techniques Applied to Geodesy and Surveying, Lecture Notes in

  19. The salience network causally influences default mode network activity during moral reasoning

    PubMed Central

    Wilson, Stephen M.; D’Esposito, Mark; Kayser, Andrew S.; Grossman, Scott N.; Poorzand, Pardis; Seeley, William W.; Miller, Bruce L.; Rankin, Katherine P.

    2013-01-01

    Large-scale brain networks are integral to the coordination of human behaviour, and their anatomy provides insights into the clinical presentation and progression of neurodegenerative illnesses such as Alzheimer’s disease, which targets the default mode network, and behavioural variant frontotemporal dementia, which targets a more anterior salience network. Although the default mode network is recruited when healthy subjects deliberate about ‘personal’ moral dilemmas, patients with Alzheimer’s disease give normal responses to these dilemmas whereas patients with behavioural variant frontotemporal dementia give abnormal responses to these dilemmas. We hypothesized that this apparent discrepancy between activation- and patient-based studies of moral reasoning might reflect a modulatory role for the salience network in regulating default mode network activation. Using functional magnetic resonance imaging to characterize network activity of patients with behavioural variant frontotemporal dementia and healthy control subjects, we present four converging lines of evidence supporting a causal influence from the salience network to the default mode network during moral reasoning. First, as previously reported, the default mode network is recruited when healthy subjects deliberate about ‘personal’ moral dilemmas, but patients with behavioural variant frontotemporal dementia producing atrophy in the salience network give abnormally utilitarian responses to these dilemmas. Second, patients with behavioural variant frontotemporal dementia have reduced recruitment of the default mode network compared with healthy control subjects when deliberating about these dilemmas. Third, a Granger causality analysis of functional neuroimaging data from healthy control subjects demonstrates directed functional connectivity from nodes of the salience network to nodes of the default mode network during moral reasoning. Fourth, this Granger causal influence is diminished in

  20. Neural network with formed dynamics of activity

    SciTech Connect

    Dunin-Barkovskii, V.L.; Osovets, N.B.

    1995-03-01

    The problem of developing a neural network with a given pattern of the state sequence is considered. A neural network structure and an algorithm, of forming its bond matrix which lead to an approximate but robust solution of the problem are proposed and discussed. Limiting characteristics of the serviceability of the proposed structure are studied. Various methods of visualizing dynamic processes in a neural network are compared. Possible applications of the results obtained for interpretation of neurophysiological data and in neuroinformatics systems are discussed.

  1. Height bias and scale effect induced by antenna gravitational deformations in geodetic VLBI data analysis

    NASA Astrophysics Data System (ADS)

    Sarti, Pierguido; Abbondanza, Claudio; Petrov, Leonid; Negusini, Monia

    2011-01-01

    The impact of signal path variations (SPVs) caused by antenna gravitational deformations on geodetic very long baseline interferometry (VLBI) results is evaluated for the first time. Elevation-dependent models of SPV for Medicina and Noto (Italy) telescopes were derived from a combination of terrestrial surveying methods to account for gravitational deformations. After applying these models in geodetic VLBI data analysis, estimates of the antenna reference point positions are shifted upward by 8.9 and 6.7 mm, respectively. The impact on other parameters is negligible. To simulate the impact of antenna gravitational deformations on the entire VLBI network, lacking measurements for other telescopes, we rescaled the SPV models of Medicina and Noto for other antennas according to their size. The effects of the simulations are changes in VLBI heights in the range [-3, 73] mm and a net scale increase of 0.3-0.8 ppb. The height bias is larger than random errors of VLBI position estimates, implying the possibility of significant scale distortions related to antenna gravitational deformations. This demonstrates the need to precisely measure gravitational deformations of other VLBI telescopes, to derive their precise SPV models and to apply them in routine geodetic data analysis.

  2. COLD MAGICS - Continuous Local Deformation Monitoring of an Arctic Geodetic Fundamental Station

    NASA Technical Reports Server (NTRS)

    Haas, Ruediger; Bergstrand, Sten

    2010-01-01

    We describe the experience gained in a project to continuously monitor the local tie at the Geodetic Observatory Ny-Alesund. A PC-controlled robotic total station was used to monitor survey prisms that were attached to survey pillars of the local network and the monuments used for geodetic VLBI and GNSS measurements. The monitoring lasted for seven days and had a temporal resolution of six minutes. The raw angle and distance measurements show clear sinusoidal signatures with a daily period, most strongly for a four-day period with 24 hours of sunshine. The derived topocentric coordinates of the survey prisms attached to the GNSS monument and the VLBI radio telescope act as approximation for the local tie. We detect clear signatures at the mm-level. With the current approach we cannot distinguish between real motion of the prisms and potential thermal influences on the instrument used for the observations. However, the project shows that continuous local tie monitoring is feasible today and in the future can and should be used for all geodetic co-location stations.

  3. Dome/Conduit inflation-deflation at Volcan de Fuego, Colima: evidence from seismic and geodetic data

    NASA Astrophysics Data System (ADS)

    Arciniega-Ceballos, A.; Cabral-Cano, E.; Castaneda, E.; Salazar-Tlaczani, L.; DeMets, C.; Marquez-Azua, B.

    2013-12-01

    Volcan de Fuego is a strato-volcano (3860 m high) in Colima Mexico, which has been presenting high explosive activity from small to large explosive events, occasionally accompanied by pyroclastic flows, periodic dome growth and destructive phases, intense fumarole activity and degassing, during the last decade. Since June 2011 a broadband seismic and geodetic network has been operating at radial distances ranging between 1.5 and 4 km from the crater. Five stations are equipped with a Nanometrics 120 s Trillium seismometer and Trimble NetR9 GPS receiver, from which three of them include a MiniDOAS gas detection system. During the period of study eruptive activity of Volcan de Fuego has been dominated by dome growth, degassing and occasional large explosions. These events are associated with the partial dome destruction and frequent ash emissions. Preliminary analyses of two-year continuous records of broadband seismic and geodesy data have revealed dome/conduit inflation-deflation phases related to conspicuous VLP tremor in the 1-20 s period band. VLP tremor has been detected in several periods since 2011 in all stations of the network. VLP tremor may be spasmodic or a persistent signal that fluctuates both in amplitude and time. Since in volcanic areas microseismicity may cover a period range of 5 to 20 s, we analyze and characterize the noise levels considering the relative amplitude with respect to the average amplitude of microseismic noise at each station. We evaluate temporal and frequency variations of volcanic activity with respect the microseismic levels. Our results indicate that the energy of the wave field in the 1-20 s period band is dominated by volcanic activity, especially in cases associated with large eruptive events. The presence of VLP tremor correlates well with inflation-deflation phases observed in the GPS time series, with total vertical displacements of 20-40 mm. This behavior is most evident in the COPN, COPE and COLW stations, which are

  4. Seafloor Geodetic Monitoring of the Central Andean Subduction Zone: The Geosea Array

    NASA Astrophysics Data System (ADS)

    Kopp, H.; Lange, D.; Contreras Reyes, E.; Behrmann, J. H.; McGuire, J. J.; Flueh, E. R.

    2014-12-01

    Seafloor geodesy has been identified as one of the central tools in marine geosciences to monitor seafloor deformation at high resolution. To quantify strain accumulation and assess the resultant hazard potential we urgently need systems to resolve seafloor crustal deformation. The GeoSEA (Geodetic Earthquake Observatory on the Seafloor) array consists of a seafloor transponder network comprising a total of 35 units and a wave glider acting as a surface unit (GeoSURF) to ensure satellite correspondence, data transfer and monitor system health. For horizontal direct path measurements, the system utilizes acoustic ranging techniques with a ranging precision better than 15 mm and long term stability over 2 km distance. Vertical motion is obtained from pressure gauges. Integrated inclinometers monitor station settlement in two horizontal directions. Travel time between instruments and the local water sound velocity will be recorded autonomously subsea without system or human intervention for up to 3.5 years. Data from the autonomous network on the seafloor can be retrieved via the integrated high-speed acoustic telemetry link without recovering the seafloor units. In late 2015 GeoSEA will be installed on the Iquique segment of the South America - Nazca convergent plate boundary to monitor crustal deformation. The Iquique seismic gap experienced the 2014 Mw 8.1 Pisagua earthquake, which apparently occurred within a local locking minimum. It is thus crucial to better resolve resolve strain in the forearc between the mainland and the trench in order to improve our understanding of forearc deformation required for hazard assessment. Mobile autonomous seafloor arrays for continuous measurement of active seafloor deformation in hazard zones have the potential to lead to transformative discoveries of plate boundary/fault zone tectonic processes and address a novel element of marine geophysical research.

  5. Google matrix of the world network of economic activities

    NASA Astrophysics Data System (ADS)

    Kandiah, Vivek; Escaith, Hubert; Shepelyansky, Dima L.

    2015-07-01

    Using the new data from the OECD-WTO world network of economic activities we construct the Google matrix G of this directed network and perform its detailed analysis. The network contains 58 countries and 37 activity sectors for years 1995 and 2008. The construction of G, based on Markov chain transitions, treats all countries on equal democratic grounds while the contribution of activity sectors is proportional to their exchange monetary volume. The Google matrix analysis allows to obtain reliable ranking of countries and activity sectors and to determine the sensitivity of CheiRank-PageRank commercial balance of countries in respect to price variations and labor cost in various countries. We demonstrate that the developed approach takes into account multiplicity of network links with economy interactions between countries and activity sectors thus being more efficient compared to the usual export-import analysis. The spectrum and eigenstates of G are also analyzed being related to specific activity communities of countries.

  6. Geodetic Estimate of Water in the Wharton Basin Upper Mantle

    NASA Astrophysics Data System (ADS)

    Masuti, S. S.; Barbot, S.; Karato, S. I.; Feng, L.; Bannerjee, P.; Natawidjaja, D.

    2015-12-01

    The formation of oceans at the Earth's surface and hence the origin of life can be directly linked to the fate of water after planetary formation, but how much water is now confined in the upper mantle remains elusive. Current estimates of water in olivine from geochemistry are between 200 and 3600 H/106 Si. Here, we exploit the water-sensitive rheology of olivine to estimate the water content in the Wharton Basin asthenosphere in the Indian Ocean. We explore the role of water stratification in the upper mantle and the transient behavior of olivine flow in the context of postseismic deformation following the 2012 Mw 8.6 Wharton Basin earthquake using geodetic data from the Sumatra GPS network. We build a model that incorporates afterslip in the brittle upper mantle and viscous flow in the asthenosphere. We introduce a formulation of the transient rheology of olivine in the form of a flow law coupled to a state evolution that characterizes the internal stress of the mineral before steady-state. We find that the Wharton Basin asthenosphere contains about 1000 H/106 Si, representing 10% of water saturation of olivine at 100 km depth. If these results can be extrapolated to other depths, this indicates an equivalent of about 0.7 ocean mass is now present in the Earth's upper mantle.

  7. Estimability of geodetic parameters from space VLBI observables

    NASA Technical Reports Server (NTRS)

    Adam, Jozsef

    1990-01-01

    The feasibility of space very long base interferometry (VLBI) observables for geodesy and geodynamics is investigated. A brief review of space VLBI systems from the point of view of potential geodetic application is given. A selected notational convention is used to jointly treat the VLBI observables of different types of baselines within a combined ground/space VLBI network. The basic equations of the space VLBI observables appropriate for convariance analysis are derived and included. The corresponding equations for the ground-to-ground baseline VLBI observables are also given for a comparison. The simplified expression of the mathematical models for both space VLBI observables (time delay and delay rate) include the ground station coordinates, the satellite orbital elements, the earth rotation parameters, the radio source coordinates, and clock parameters. The observation equations with these parameters were examined in order to determine which of them are separable or nonseparable. Singularity problems arising from coordinate system definition and critical configuration are studied. Linear dependencies between partials are analytically derived. The mathematical models for ground-space baseline VLBI observables were tested with simulation data in the frame of some numerical experiments. Singularity due to datum defect is confirmed.

  8. Local geodetic and seismic energy balance for shallow earthquake prediction

    NASA Astrophysics Data System (ADS)

    Cannavó, Flavio; Arena, Alessandra; Monaco, Carmelo

    2015-01-01

    Earthquake analysis for prediction purposes is a delicate and still open problem largely debated among scientists. In this work, we want to show that a successful time-predictable model is possible if based on large instrumental data from dense monitoring networks. To this aim, we propose a new simple data-driven and quantitative methodology which takes into account the accumulated geodetic strain and the seismically-released strain to calculate a balance of energies. The proposed index quantifies the state of energy of the selected area and allows us to evaluate better the ingoing potential seismic risk, giving a new tool to read recurrence of small-scale and shallow earthquakes. In spite of its intrinsic simple formulation, the application of the methodology has been successfully simulated in the Eastern flank of Mt. Etna (Italy) by tuning it in the period 2007-2011 and testing it in the period 2012-2013, allowing us to predict, within days, the earthquakes with highest magnitude.

  9. Global satellite triangulation and trilateration for the National Geodetic Satellite Program (solutions WN 12, 14 and 16). [study and analysis of data from artificial satellites

    NASA Technical Reports Server (NTRS)

    Mueller, I. I.; Kumar, M.; Reilly, J. P.; Saxena, N.; Soler, T.

    1973-01-01

    A multi-year study and analysis of data from satellites launched specifically for geodetic purposes and from other satellites useful in geodetic studies was conducted. The program of work included theoretical studies and analysis for the geometric determination of station positions derived from photographic observations of both passive and active satellites and from range observations. The current status of data analysis, processing and results are examined.

  10. Impact of Network Activity Levels on the Performance of Passive Network Service Dependency Discovery

    SciTech Connect

    Carroll, Thomas E.; Chikkagoudar, Satish; Arthur-Durett, Kristine M.

    2015-11-02

    Network services often do not operate alone, but instead, depend on other services distributed throughout a network to correctly function. If a service fails, is disrupted, or degraded, it is likely to impair other services. The web of dependencies can be surprisingly complex---especially within a large enterprise network---and evolve with time. Acquiring, maintaining, and understanding dependency knowledge is critical for many network management and cyber defense activities. While automation can improve situation awareness for network operators and cyber practitioners, poor detection accuracy reduces their confidence and can complicate their roles. In this paper we rigorously study the effects of network activity levels on the detection accuracy of passive network-based service dependency discovery methods. The accuracy of all except for one method was inversely proportional to network activity levels. Our proposed cross correlation method was particularly robust to the influence of network activity. The proposed experimental treatment will further advance a more scientific evaluation of methods and provide the ability to determine their operational boundaries.

  11. Effects of Full Order Geopotential Hessian on Precision Orbit Determination of Geodetic Satellites

    DTIC Science & Technology

    2014-08-01

    nutation , Earth rotation, and polar motion. OCEAN implements the majority of the conventions recommended in IERS Conventions 2010.14 For this application...fitted spacecraft in order to support geodetic research activities. Some of the supported scientific and operational data products include Earth ...Orientation Parameters, Fundamental Physical Constants, Monitoring Earth Rotation and Polar Motion, and Time-Varying Geocenter Coordinates. For a full list

  12. Integration of space geodesy: a US National Geodetic Observatory

    NASA Technical Reports Server (NTRS)

    Yunck, Thomas P.; Neilan, Ruth

    2003-01-01

    In the interest of improving the performance and efficiency of space geodesy a diverse group in the U.S., in collaboration with IGGOS, has begun to establish a unified National Geodetic Observatory (NGO).

  13. Astronomic-Geodetic Highlights from the Soviet Union,

    DTIC Science & Technology

    2007-11-02

    This report is a translation of an article in the German language periodical Austrian Journal of Geodesy , written by K. Ledersteger, published in Vienna in 1959. It concerns Astronomic-Geodetic highlights in the Soviet Union.

  14. Detecting eavesdropping activity in fiber optic networks

    NASA Astrophysics Data System (ADS)

    MacDonald, Gregory G.

    The secure transmission of data is critical to governments, military organizations, financial institutions, health care providers and other enterprises. The primary method of securing in-transit data is though data encryption. A number of encryption methods exist but the fundamental approach is to assume an eavesdropper has access to the encrypted message but does not have the computing capability to decrypt the message in a timely fashion. Essentially, the strength of security depends on the complexity of the encryption method and the resources available to the eavesdropper. The development of future technologies, most notably quantum computers and quantum computing, is often cited as a direct threat to traditional encryption schemes. It seems reasonable that additional effort should be placed on prohibiting the eavesdropper from coming into possession of the encrypted message in the first place. One strategy for denying possession of the encrypted message is to secure the physical layer of the communications path. Because the majority of transmitted information is over fiber-optic networks, it seems appropriate to consider ways of enhancing the integrity and security of the fiber-based physical layer. The purpose of this research is to investigate the properties of light, as they are manifested in single mode fiber, as a means of insuring the integrity and security of the physical layer of a fiber-optic based communication link. Specifically, the approach focuses on the behavior of polarization in single mode fiber, as it is shown to be especially sensitive to fiber geometry. Fiber geometry is necessarily modified during the placement of optical taps. The problem of detecting activity associated with the placement of an optical tap is herein approached as a supervised machine learning anomaly identification task. The inputs include raw polarization measurements along with additional features derived from various visualizations of the raw data (the inputs are

  15. Bayesian Inference Networks and Spreading Activation in Hypertext Systems.

    ERIC Educational Resources Information Center

    Savoy, Jacques

    1992-01-01

    Describes a method based on Bayesian networks for searching hypertext systems. Discussion covers the use of Bayesian networks for structuring index terms and representing user information needs; use of link semantics based on constrained spreading activation to find starting points for browsing; and evaluation of a prototype system. (64…

  16. Efficient transformations from geodetic to UTM coordinate systems

    SciTech Connect

    Toms, R.M.

    1996-08-07

    The problem of efficiently performing transformations from geocentric to geodetic coordinates has been addressed at previous DIS (Distributed Interactive Simulation) workshops. This paper extends the work presented at the 14th DIS Workshop. As a consequence of the new algorithm for geocentric to geodetic coordinate conversion, a subsequent conversion to Universal Transverse Mercator coordinates is made considerably more efficient. No additional trigonometric or square root evaluations are required and accuracy is not degraded.

  17. Criticalities in crosslinked actin networks due to myosin activity

    NASA Astrophysics Data System (ADS)

    Sheinman, Michael

    2013-03-01

    Many essential processes in cells and tissues, like motility and morphogenesis, are orchestrated by molecular motors applying internal, active stresses on crosslinked networks of actin filaments. Using scaling analysis, mean-field calculation, numerical modelling and in vitro experiments of such active networks we predict and observe different mechanical regimes exhibiting interesting critical behaviours with non-trivial power-law dependencies. Firstly, we find that the presence of active stresses can dramatically increase the stiffness of a floppy network, as was observed in reconstituted intracellular F-actin networks with myosin motors and extracellular gels with contractile cells. Uniform internal stress results in an anomalous, critical mechanical regime only in the vicinity of the rigidity percolation points of the network. However, taking into account heterogeneity of motors, we demonstrate that the motors, stiffening any floppy network, induce large non-affine fluctuations, giving rise to a critical mechanical regime. Secondly, upon increasing motor concentration, the resulting large internal stress is able to significantly enhance unbinding of the network's crosslinks and, therefore, disconnect the initially well-connected network to isolated clusters. However, during this process, when the network approaches marginal connectivity the internal stresses are expected to drop drastically such that the connectivity stabilizes. This general argument and detailed numerical simulations show that motors should drive a well connected network to a close vicinity of a critical point of marginal connectivity. Experiments clearly confirm this conclusion and demonstrate robust critical connectivity of initially well-connected networks, ruptured by the motor activity for a wide range of parameters. M. Sheinman, C.P. Broedersz and F.C. MacKintosh, Phys. Rev. Lett, in press. J. Alvarado, M. Sheinman, A. Sharma, F.C. MacKintosh and G. Koenderink, in preparation.

  18. Consistent height transformations between geodetic and meteorologic reference systems

    NASA Astrophysics Data System (ADS)

    Hobiger, T.; Boehm, J.; Boy, J.; Foster, J. H.; Gegout, P.; Haas, R.; Ichikawa, R.; MacMillan, D. S.; Ming, S.; Niell, A. E.; Nievinski, F. G.; Nordman, M.; Salstein, D. A.; Santos, M. C.; Schindelegger, M.; van Dam, T. M.; Vedel, H.; Wickert, J.; Zus, F.

    2012-12-01

    Numerical weather models (NWMs) contain valuable information that is relevant for removing the environmental signal from geodetic data. Currently no clear documentation exists regarding how to deal with the coordinate systems when carrying out the calculations in a geodetic reference frame. A "conventional" transformation model (available also as source code) would enable geodesists to handle such data easily and allow them to use data from different meteorologic data-sets. In addition, geodetic products such as GNSS derived zenith total delays are being assimilated into NWMs. Thus, the transformations that convert the meteorological data into a geodetic reference frame should also support the use of geodetic data in meteorological models. The IAG Intercomission Committee on Theory - Special Study Group 12 "Coordinate systems in numerical weather models" has been set-up to 1) deal with the differences between geodetic and meteorologic reference systems and 2) provide consistent models for transforming between the two systems. We present the first product from this effort: a conventional height transformation that transforms between ellipsoidal heights and the various height systems used in NWMs. We will discuss the choice of the gravity model, which is crucial for such a transformation, and we will present the final model that the study group believes best describes the transformation in an unambiguous and bi-directional sense.

  19. Distal gap junctions and active dendrites can tune network dynamics.

    PubMed

    Saraga, Fernanda; Ng, Leo; Skinner, Frances K

    2006-03-01

    Gap junctions allow direct electrical communication between CNS neurons. From theoretical and modeling studies, it is well known that although gap junctions can act to synchronize network output, they can also give rise to many other dynamic patterns including antiphase and other phase-locked states. The particular network pattern that arises depends on cellular, intrinsic properties that affect firing frequencies as well as the strength and location of the gap junctions. Interneurons or GABAergic neurons in hippocampus are diverse in their cellular characteristics and have been shown to have active dendrites. Furthermore, parvalbumin-positive GABAergic neurons, also known as basket cells, can contact one another via gap junctions on their distal dendrites. Using two-cell network models, we explore how distal electrical connections affect network output. We build multi-compartment models of hippocampal basket cells using NEURON and endow them with varying amounts of active dendrites. Two-cell networks of these model cells as well as reduced versions are explored. The relationship between intrinsic frequency and the level of active dendrites allows us to define three regions based on what sort of network dynamics occur with distal gap junction coupling. Weak coupling theory is used to predict the delineation of these regions as well as examination of phase response curves and distal dendritic polarization levels. We find that a nonmonotonic dependence of network dynamic characteristics (phase lags) on gap junction conductance occurs. This suggests that distal electrical coupling and active dendrite levels can control how sensitive network dynamics are to gap junction modulation. With the extended geometry, gap junctions located at more distal locations must have larger conductances for pure synchrony to occur. Furthermore, based on simulations with heterogeneous networks, it may be that one requires active dendrites if phase-locking is to occur in networks formed

  20. How to Identify Success Among Networks That Promote Active Living

    PubMed Central

    Litt, Jill; Varda, Danielle; Reed, Hannah; Retrum, Jessica; Tabak, Rachel; Gustat, Jeanette; Tompkins, Nancy O’Hara

    2017-01-01

    Objectives We evaluated organization- and network-level factors that influence organizations’ perceived success. This is important for managing interorganizational networks, which can mobilize communities to address complex health issues such as physical activity, and for achieving change. Methods In 2011, we used structured interview and network survey data from 22 states in the United States to estimate multilevel random-intercept models to understand organization- and network-level factors that explain perceived network success. Results A total of 53 of 59 “whole networks” met the criteria for inclusion in the analysis (89.8%). Coordinators identified 559 organizations, with 3 to 12 organizations from each network taking the online survey (response rate: 69.7%; range: 33%–100%). Occupying a leadership position (P < .01), the amount of time with the network (P < .05), and support from community leaders (P < .05) emerged as correlates of perceived success. Conclusions Organizations’ perceptions of success can influence decisions about continuing involvement and investment in networks designed to promote environment and policy change for active living. Understanding these factors can help leaders manage complex networks that involve diverse memberships, varied interests, and competing community-level priorities. PMID:26378863

  1. Geodetic GNSS measurements as a basis for geodynamic and glaciological research in Antarctica

    NASA Astrophysics Data System (ADS)

    Scheinert, Mirko; Dietrich, Reinhard; Knöfel, Christoph; Fritsche, Mathias; Rülke, Axel; Schröder, Ludwig; Richter, Andreas; Eberlein, Lutz

    2013-04-01

    For about twenty years our institute has been carrying out geodetic GNSS measurements and has been actively working in international collaboration for Antarctic research. Episodic GPS (and later GNSS) measurements of all contributing nations enter the "Database of the SCAR Epoch Crustal Movement Campaigns" which is being maintained at the institute in the framework of SCAR-GIANT. GNSS measurements form a basis for the realization of the International Terrestrial Reference Frame (ITRF) and its densification in Antarctica. Linked to respective products of an ongoing activity to re-process GNSS data of globally distributed stations a consistent and precise TRF realization can be reached. We will give an overview on the latest developments and the subsequent applications for geodynamic and glaciological investigations in Antarctica. Complementary to continuous GNSS observations episodic GNSS measurements have the potential to provide independent data on vertical deformations, which can be used to investigate the present-day ice-mass balance and to refine models of the glacial-isostatic adjustment. Repeated and properly referenced GNSS measurements at the ice surface yield ice-flow velocities and local ice-surface height changes. We will present latest results, e.g. for the Amundsen Sea sector, the subglacial Lake Vostok region and near-coastal regions of Dronning Maud Land or Enderby Land. Thus, it will be discussed how geodetic GNSS measurements form an important and indispensable basis for geodetic Earth system research with the focus on Antarctica.

  2. Network Interventions on Physical Activity in an Afterschool Program: An Agent-Based Social Network Study

    PubMed Central

    Zhang, Jun; Shoham, David A.; Tesdahl, Eric

    2015-01-01

    Objectives. We studied simulated interventions that leveraged social networks to increase physical activity in children. Methods. We studied a real-world social network of 81 children (average age = 7.96 years) who lived in low socioeconomic status neighborhoods, and attended public schools and 1 of 2 structured afterschool programs. The sample was ethnically diverse, and 44% were overweight or obese. We used social network analysis and agent-based modeling simulations to test whether implementing a network intervention would increase children’s physical activity. We tested 3 intervention strategies. Results. The intervention that targeted opinion leaders was effective in increasing the average level of physical activity across the entire network. However, the intervention that targeted the most sedentary children was the best at increasing their physical activity levels. Conclusions. Which network intervention to implement depends on whether the goal is to shift the entire distribution of physical activity or to influence those most adversely affected by low physical activity. Agent-based modeling could be an important complement to traditional project planning tools, analogous to sample size and power analyses, to help researchers design more effective interventions for increasing children’s physical activity. PMID:25689202

  3. On the Dynamics of the Spontaneous Activity in Neuronal Networks

    PubMed Central

    Bonifazi, Paolo; Ruaro, Maria Elisabetta; Torre, Vincent

    2007-01-01

    Most neuronal networks, even in the absence of external stimuli, produce spontaneous bursts of spikes separated by periods of reduced activity. The origin and functional role of these neuronal events are still unclear. The present work shows that the spontaneous activity of two very different networks, intact leech ganglia and dissociated cultures of rat hippocampal neurons, share several features. Indeed, in both networks: i) the inter-spike intervals distribution of the spontaneous firing of single neurons is either regular or periodic or bursting, with the fraction of bursting neurons depending on the network activity; ii) bursts of spontaneous spikes have the same broad distributions of size and duration; iii) the degree of correlated activity increases with the bin width, and the power spectrum of the network firing rate has a 1/f behavior at low frequencies, indicating the existence of long-range temporal correlations; iv) the activity of excitatory synaptic pathways mediated by NMDA receptors is necessary for the onset of the long-range correlations and for the presence of large bursts; v) blockage of inhibitory synaptic pathways mediated by GABAA receptors causes instead an increase in the correlation among neurons and leads to a burst distribution composed only of very small and very large bursts. These results suggest that the spontaneous electrical activity in neuronal networks with different architectures and functions can have very similar properties and common dynamics. PMID:17502919

  4. Hub-activated signal transmission in complex networks

    NASA Astrophysics Data System (ADS)

    Jahnke, Sven; Memmesheimer, Raoul-Martin; Timme, Marc

    2014-03-01

    A wide range of networked systems exhibit highly connected nodes (hubs) as prominent structural elements. The functional roles of hubs in the collective nonlinear dynamics of many such networks, however, are not well understood. Here, we propose that hubs in neural circuits may activate local signal transmission along sequences of specific subnetworks. Intriguingly, in contrast to previous suggestions of the functional roles of hubs, here, not the hubs themselves, but nonhub subnetworks transfer the signals. The core mechanism relies on hubs and nonhubs providing activating feedback to each other. It may, thus, induce the propagation of specific pulse and rate signals in neuronal and other communication networks.

  5. Active system area networks for data intensive computations. Final report

    SciTech Connect

    2002-04-01

    The goal of the Active System Area Networks (ASAN) project is to develop hardware and software technologies for the implementation of active system area networks (ASANs). The use of the term ''active'' refers to the ability of the network interfaces to perform application-specific as well as system level computations in addition to their traditional role of data transfer. This project adopts the view that the network infrastructure should be an active computational entity capable of supporting certain classes of computations that would otherwise be performed on the host CPUs. The result is a unique network-wide programming model where computations are dynamically placed within the host CPUs or the NIs depending upon the quality of service demands and network/CPU resource availability. The projects seeks to demonstrate that such an approach is a better match for data intensive network-based applications and that the advent of low-cost powerful embedded processors and configurable hardware makes such an approach economically viable and desirable.

  6. Cultured Neuronal Networks Express Complex Patterns of Activity and Morphological Memory

    NASA Astrophysics Data System (ADS)

    Raichman, Nadav; Rubinsky, Liel; Shein, Mark; Baruchi, Itay; Volman, Vladislav; Ben-Jacob, Eshel

    The following sections are included: * Cultured Neuronal Networks * Recording the Network Activity * Network Engineering * The Formation of Synchronized Bursting Events * The Characterization of the SBEs * Highly-Active Neurons * Function-Form Relations in Cultured Networks * Analyzing the SBEs Motifs * Network Repertoire * Network under Hypothermia * Summary * Acknowledgments * References

  7. Viking mission support. [Deep Space Network activities

    NASA Technical Reports Server (NTRS)

    Johnston, D. W. H.

    1977-01-01

    Statistics listing the Deep Space Network tracking and command support and the discrepancy report status for 1 January through 28 February 1977 are presented in tables. The initial Viking extended mission period of normal DSN support, following the nonstandard operations during the solar conjunction period is included. Operational testing subsequent to the MK III data system installations at DSS 12, 44, and 62 during this period are also discussed.

  8. Systematic fluctuation expansion for neural network activity equations.

    PubMed

    Buice, Michael A; Cowan, Jack D; Chow, Carson C

    2010-02-01

    Population rate or activity equations are the foundation of a common approach to modeling for neural networks. These equations provide mean field dynamics for the firing rate or activity of neurons within a network given some connectivity. The shortcoming of these equations is that they take into account only the average firing rate, while leaving out higher-order statistics like correlations between firing. A stochastic theory of neural networks that includes statistics at all orders was recently formulated. We describe how this theory yields a systematic extension to population rate equations by introducing equations for correlations and appropriate coupling terms. Each level of the approximation yields closed equations; they depend only on the mean and specific correlations of interest, without an ad hoc criterion for doing so. We show in an example of an all-to-all connected network how our system of generalized activity equations captures phenomena missed by the mean field rate equations alone.

  9. Geodetic measurements near Parkfield, California, 1959-1984

    NASA Astrophysics Data System (ADS)

    King, N. E.; Segall, P.; Prescott, W.

    1987-03-01

    Trilateration measurements have been made by various agencies since 1959 near Parkfield, California, in the transition zone between the central creeping section and the southern locked section of the San Andreas fault. Within the transition zone there are several creep meters and alignment arrays, four small-aperture trilateration networks, and a broad trilateration network extending 70 km southwest from the San Andreas fault to the Pacific coast. Line length changes observed after the 1966 ML = 5.6 Parkfield earthquake indicate a geodetic moment of 4.5 ± 1.0 × 1025 dyn cm. The data are consistent with either 91 ± 8 cm slip on a rupture zone which is 30 km long and extends from 3 to 8 km below the surface or 59 ± 5 cm on a 30-km-long zone 2-10 km deep. This moment estimate includes some postseismic slip and is a factor of 2-4 greater than the moment determined from seismic surface waves. The post-1966 data set is well suited to discriminate between the effects of surface and deep slip. Surface slip rates determined by creep meters, alinement arrays, and small-aperture trilateration networks decrease from 29 mm/yr at Slack Canyon to zero south of Highway 46; a gradient of roughly -0.48 ± 0.01 mm/yr/km. Deformation of a subset of the trilateration network between Cholame and San Luis Obispo is consistent with shallow slip of 2.9 ± 1.2 mm/yr from the surface to a depth of 16 km and 33.4 ± 5.5 mm/yr below 16 km. The trilateration data alone do not uniquely constrain both the transition depth from shallow to deep slip and the deep slip rate. A transition depth near 16 km is preferred because it provides the best fit to the data and because the predicted slip rate is consistent with independent estimates of the total slip rate across the San Andreas fault. This simple two-dimensional model neglects along-strike variations in the deformation. The data show no evidence for significant strike-slip deformation across faults between the San Andreas and the Pacific

  10. Sparse Neural Network Models of Antimicrobial Peptide-Activity Relationships.

    PubMed

    Müller, Alex T; Kaymaz, Aral C; Gabernet, Gisela; Posselt, Gernot; Wessler, Silja; Hiss, Jan A; Schneider, Gisbert

    2016-12-01

    We present an adaptive neural network model for chemical data classification. The method uses an evolutionary algorithm for optimizing the network structure by seeking sparsely connected architectures. The number of hidden layers, the number of neurons in each layer and their connectivity are free variables of the system. We used the method for predicting antimicrobial peptide activity from the amino acid sequence. Visualization of the evolved sparse network structures suggested a high charge density and a low aggregation potential in solution as beneficial for antimicrobial activity. However, different training data sets and peptide representations resulted in greatly varying network structures. Overall, the sparse network models turned out to be less accurate than fully-connected networks. In a prospective application, we synthesized and tested 10 de novo generated peptides that were predicted to either possess antimicrobial activity, or to be inactive. Two of the predicted antibacterial peptides showed cosiderable bacteriostatic effects against both Staphylococcus aureus and Escherichia coli. None of the predicted inactive peptides possessed antibacterial properties. Molecular dynamics simulations of selected peptide structures in water and TFE suggest a pronounced peptide helicity in a hydrophobic environment. The results of this study underscore the applicability of neural networks for guiding the computer-assisted design of new peptides with desired properties.

  11. Connectivity, excitability and activity patterns in neuronal networks

    NASA Astrophysics Data System (ADS)

    le Feber, Joost; Stoyanova, Irina I.; Chiappalone, Michela

    2014-06-01

    Extremely synchronized firing patterns such as those observed in brain diseases like epilepsy may result from excessive network excitability. Although network excitability is closely related to (excitatory) connectivity, a direct measure for network excitability remains unavailable. Several methods currently exist for estimating network connectivity, most of which are related to cross-correlation. An example is the conditional firing probability (CFP) analysis which calculates the pairwise probability (CFPi,j) that electrode j records an action potential at time t = τ, given that electrode i recorded a spike at t = 0. However, electrode i often records multiple spikes within the analysis interval, and CFP values are biased by the on-going dynamic state of the network. Here we show that in a linear approximation this bias may be removed by deconvoluting CFPi,j with the autocorrelation of i (i.e. CFPi,i), to obtain the single pulse response (SPRi,j)—the average response at electrode j to a single spike at electrode i. Thus, in a linear system SPRs would be independent of the dynamic network state. Nonlinear components of synaptic transmission, such as facilitation and short term depression, will however still affect SPRs. Therefore SPRs provide a clean measure of network excitability. We used carbachol and ghrelin to moderately activate cultured cortical networks to affect their dynamic state. Both neuromodulators transformed the bursting firing patterns of the isolated networks into more dispersed firing. We show that the influence of the dynamic state on SPRs is much smaller than the effect on CFPs, but not zero. The remaining difference reflects the alteration in network excitability. We conclude that SPRs are less contaminated by the dynamic network state and that mild excitation may decrease network excitability, possibly through short term synaptic depression.

  12. Heterogeneous interplate coupling along the Nankai Trough, Japan, detected by GPS-acoustic seafloor geodetic observation

    NASA Astrophysics Data System (ADS)

    Yokota, Yusuke; Ishikawa, Tadashi; Sato, Mariko; Watanabe, Shun-ichi; Saito, Hiroaki; Ujihara, Naoto; Matsumoto, Yoshihiro; Toyama, Shin-ichi; Fujita, Masayuki; Yabuki, Tetsuichiro; Mochizuki, Masashi; Asada, Akira

    2015-12-01

    The recurring devastating earthquake that occurs in the Nankai Trough subduction zone between the Philippine Sea plate and the Eurasian plate has the potential to cause an extremely dangerous natural disaster in the foreseeable future. Many previous studies have assumed interplate-coupling ratios for this region along the trench axis using onshore geodetic data in order to understand this recursive event. However, the offshore region that has the potential to drive a devastating tsunami cannot be resolved sufficiently because the observation network is biased to the land area. Therefore, the Hydrographic and Oceanographic Department of Japan constructed a geodetic observation network on the seafloor along the Nankai Trough using a GPS-acoustic combination technique and has used it to observe seafloor crustal movements directly above the Nankai Trough subduction zone. We have set six seafloor sites and cumulated enough data to determine the displacement rate from 2006 to January 2011. Our seafloor geodetic observations at these sites revealed a heterogeneous interplate coupling that has three particular features. The fast displacement rates observed in the easternmost area indicate strong interplate coupling (>75%) around not only the future Tokai earthquake source region but also the Paleo-Zenisu ridge. The slow displacement rates near the trench axis in the Kumano-nada Sea, a shallow part of the 1944 Tonankai earthquake source region, show a lower coupling ratio (50% to 75%). The slow displacement rate observed in the area shallower than the 1946 Nankaido earthquake source region off Cape Muroto-zaki reflects weakening interplate coupling (about 50%) probably due to a subducting seamount. Our observations above the subducting ridge and seamount indicate that the effect of a subducting seamount on an interplate-coupling region depends on various conditions such as the geometry of the seamount and the friction parameters on the plate boundary.

  13. Stimulus information stored in lasting active and hidden network states is destroyed by network bursts.

    PubMed

    Dranias, Mark R; Westover, M Brandon; Cash, Sidney; VanDongen, Antonius M J

    2015-01-01

    In both humans and animals brief synchronizing bursts of epileptiform activity known as interictal epileptiform discharges (IEDs) can, even in the absence of overt seizures, cause transient cognitive impairments (TCI) that include problems with perception or short-term memory. While no evidence from single units is available, it has been assumed that IEDs destroy information represented in neuronal networks. Cultured neuronal networks are a model for generic cortical microcircuits, and their spontaneous activity is characterized by the presence of synchronized network bursts (SNBs), which share a number of properties with IEDs, including the high degree of synchronization and their spontaneous occurrence in the absence of an external stimulus. As a model approach to understanding the processes underlying IEDs, optogenetic stimulation and multielectrode array (MEA) recordings of cultured neuronal networks were used to study whether stimulus information represented in these networks survives SNBs. When such networks are optically stimulated they encode and maintain stimulus information for as long as one second. Experiments involved recording the network response to a single stimulus and trials where two different stimuli were presented sequentially, akin to a paired pulse trial. We broke the sequential stimulus trials into encoding, delay and readout phases and found that regardless of which phase the SNB occurs, stimulus-specific information was impaired. SNBs were observed to increase the mean network firing rate, but this did not translate monotonically into increases in network entropy. It was found that the more excitable a network, the more stereotyped its response was during a network burst. These measurements speak to whether SNBs are capable of transmitting information in addition to blocking it. These results are consistent with previous reports and provide baseline predictions concerning the neural mechanisms by which IEDs might cause TCI.

  14. Goal-congruent default network activity facilitates cognitive control.

    PubMed

    Spreng, R Nathan; DuPre, Elizabeth; Selarka, Dhawal; Garcia, Juliana; Gojkovic, Stefan; Mildner, Judith; Luh, Wen-Ming; Turner, Gary R

    2014-10-15

    Substantial neuroimaging evidence suggests that spontaneous engagement of the default network impairs performance on tasks requiring executive control. We investigated whether this impairment depends on the congruence between executive control demands and internal mentation. We hypothesized that activation of the default network might enhance performance on an executive control task if control processes engage long-term memory representations that are supported by the default network. Using fMRI, we scanned 36 healthy young adult humans on a novel two-back task requiring working memory for famous and anonymous faces. In this task, participants (1) matched anonymous faces interleaved with anonymous face, (2) matched anonymous faces interleaved with a famous face, or (3) matched a famous faces interleaved with an anonymous face. As predicted, we observed a facilitation effect when matching famous faces, compared with anonymous faces. We also observed greater activation of the default network during these famous face-matching trials. The results suggest that activation of the default network can contribute to task performance during an externally directed executive control task. Our findings provide evidence that successful activation of the default network in a contextually relevant manner facilitates goal-directed cognition.

  15. Mechanisms of spontaneous activity in developing spinal networks.

    PubMed

    O'Donovan, M J; Chub, N; Wenner, P

    1998-10-01

    Developing networks of the chick spinal cord become spontaneously active early in development and remain so until hatching. Experiments using an isolated preparation of the spinal cord have begun to reveal the mechanisms responsible for this activity. Whole-cell and optical recordings have shown that spinal neurons receive a rhythmic, depolarizing synaptic drive and experience rhythmic elevations of intracellular calcium during spontaneous episodes. Activity is expressed throughout the neuraxis and can be produced by different parts of the cord and by the isolated brain stem, suggesting that it does not depend upon the details of network architecture. Two factors appear to be particularly important for the production of endogenous activity. The first is the predominantly excitatory nature of developing synaptic connections, and the second is the presence of prolonged activity-dependent depression of network excitability. The interaction between high excitability and depression results in an equilibrium in which episodes are expressed periodically by the network. The mechanism of the rhythmic bursting within an episode is not understood, but it may be due to a "fast" form of network depression. Spontaneous embryonic activity has been shown to play a role in neuron and muscle development, but is probably not involved in the initial formation of connections between spinal neurons. It may be important in refining the initial connections, but this possibility remains to be explored.

  16. A network model for activity-dependent sleep regulation.

    PubMed

    Roy, Sandip; Krueger, James M; Rector, David M; Wan, Yan

    2008-08-07

    We develop and characterize a dynamical network model for activity-dependent sleep regulation. Specifically, in accordance with the activity-dependent theory for sleep, we view organism sleep as emerging from the local sleep states of functional units known as cortical columns; these local sleep states evolve through integration of local activity inputs, loose couplings with neighboring cortical columns, and global regulation (e.g. by the circadian clock). We model these cortical columns as coupled or networked activity-integrators that transition between sleep and waking states based on thresholds on the total activity. The model dynamics for three canonical experiments (which we have studied both through simulation and system-theoretic analysis) match with experimentally observed characteristics of the cortical-column network. Most notably, assuming connectedness of the network graph, our model predicts the recovery of the columns to a synchronized state upon temporary overstimulation of a single column and/or randomization of the initial sleep and activity-integration states. In analogy with other models for networked oscillators, our model also predicts the possibility for such phenomena as mode-locking.

  17. Design and Testing of a Seafloor Geodetic System.

    NASA Astrophysics Data System (ADS)

    McIntyre, Marie C.

    A conclusion of the National Research Council's Panel on Crustal Movement Measurements was to "recommend development of a capability to measure, to a 10 cm accuracy, motions of points on the ocean floor up to several hundred kilometers offshore with respect to reference points on land." The geodetic system described in this dissertation attempts to meet this recommendation. This system locates points (benchmarks) on the seafloor relative to one another, or to a point on land, at the subdecimeter level. The underwater portion of this system is acoustic and may be tied into a global reference frame via GPS receivers at the sea surface. The first step in developing this system was to design and implement a relative positioning system on the seafloor. This approach uses acoustic ranges between precision transponders mounted on benchmarks in the seafloor. Achievement of subdecimeter level positioning required the development of precision transponders and a precision sound velocimeter, used in calculating distances from travel times. The precision transponders are interrogated from a deeply towed vehicle, on which the precision sound velocimeter is mounted. During sea tests in March 1988, controlled testing of the components of the underwater positioning system was conducted and a three transponder network was surveyed, validating the seafloor positioning system concept and establishing accuracy limits. The precision transponders were shown to be capable of determining short (100 meters) baseline lengths to within 1 cm accuracy. The sound velocimeter was shown to have a resolution and repeatability of 0.0078 m/s, better than the part in 10^5 accuracy needed to calculate ranges from travel times with centimeter level accuracies. Finally, ranging data in a network of three transponders was used, along with sound speed field measurements, to determine transponder to vehicle ranges with an rms error of 8 cm. The results of a previous computer simulation show that transponder

  18. Plasticity of recurring spatiotemporal activity patterns in cortical networks

    NASA Astrophysics Data System (ADS)

    Madhavan, Radhika; Chao, Zenas C.; Potter, Steve M.

    2007-09-01

    How do neurons encode and store information for long periods of time? Recurring patterns of activity have been reported in various cortical structures and were suggested to play a role in information processing and memory. To study the potential role of bursts of action potentials in memory mechanisms, we investigated patterns of spontaneous multi-single-unit activity in dissociated rat cortical cultures in vitro. Spontaneous spikes were recorded from networks of approximately 50 000 neurons and glia cultured on a grid of 60 extracellular substrate- embedded electrodes (multi-electrode arrays). These networks expressed spontaneous culture- wide bursting from approximately one week in vitro. During bursts, a large portion of the active electrodes showed elevated levels of firing. Spatiotemporal activity patterns within spontaneous bursts were clustered using a correlation-based clustering algorithm, and the occurrences of these burst clusters were tracked over several hours. This analysis revealed spatiotemporally diverse bursts occurring in well-defined patterns, which remained stable for several hours. Activity evoked by strong local tetanic stimulation resulted in significant changes in the occurrences of spontaneous bursts belonging to different clusters, indicating that the dynamical flow of information in the neuronal network had been altered. The diversity of spatiotemporal structure and long-term stability of spontaneous bursts together with their plastic nature strongly suggests that such network patterns could be used as codes for information transfer and the expression of memories stored in cortical networks.

  19. Pattern Formation on Networks: from Localised Activity to Turing Patterns

    PubMed Central

    McCullen, Nick; Wagenknecht, Thomas

    2016-01-01

    Networks of interactions between competing species are used to model many complex systems, such as in genetics, evolutionary biology or sociology and knowledge of the patterns of activity they can exhibit is important for understanding their behaviour. The emergence of patterns on complex networks with reaction-diffusion dynamics is studied here, where node dynamics interact via diffusion via the network edges. Through the application of a generalisation of dynamical systems analysis this work reveals a fundamental connection between small-scale modes of activity on networks and localised pattern formation seen throughout science, such as solitons, breathers and localised buckling. The connection between solutions with a single and small numbers of activated nodes and the fully developed system-scale patterns are investigated computationally using numerical continuation methods. These techniques are also used to help reveal a much larger portion of of the full number of solutions that exist in the system at different parameter values. The importance of network structure is also highlighted, with a key role being played by nodes with a certain so-called optimal degree, on which the interaction between the reaction kinetics and the network structure organise the behaviour of the system. PMID:27273339

  20. Pattern Formation on Networks: from Localised Activity to Turing Patterns

    NASA Astrophysics Data System (ADS)

    McCullen, Nick; Wagenknecht, Thomas

    2016-06-01

    Networks of interactions between competing species are used to model many complex systems, such as in genetics, evolutionary biology or sociology and knowledge of the patterns of activity they can exhibit is important for understanding their behaviour. The emergence of patterns on complex networks with reaction-diffusion dynamics is studied here, where node dynamics interact via diffusion via the network edges. Through the application of a generalisation of dynamical systems analysis this work reveals a fundamental connection between small-scale modes of activity on networks and localised pattern formation seen throughout science, such as solitons, breathers and localised buckling. The connection between solutions with a single and small numbers of activated nodes and the fully developed system-scale patterns are investigated computationally using numerical continuation methods. These techniques are also used to help reveal a much larger portion of of the full number of solutions that exist in the system at different parameter values. The importance of network structure is also highlighted, with a key role being played by nodes with a certain so-called optimal degree, on which the interaction between the reaction kinetics and the network structure organise the behaviour of the system.

  1. Poly(Capro-Lactone) Networks as Actively Moving Polymers

    NASA Astrophysics Data System (ADS)

    Meng, Yuan

    Shape-memory polymers (SMPs), as a subset of actively moving polymers, form an exciting class of materials that can store and recover elastic deformation energy upon application of an external stimulus. Although engineering of SMPs nowadays has lead to robust materials that can memorize multiple temporary shapes, and can be triggered by various stimuli such as heat, light, moisture, or applied magnetic fields, further commercialization of SMPs is still constrained by the material's incapability to store large elastic energy, as well as its inherent one-way shape-change nature. This thesis develops a series of model semi-crystalline shape-memory networks that exhibit ultra-high energy storage capacity, with accurately tunable triggering temperature; by introducing a second competing network, or reconfiguring the existing network under strained state, configurational chain bias can be effectively locked-in, and give rise to two-way shape-actuators that, in the absence of an external load, elongates upon cooling and reversibly contracts upon heating. We found that well-defined network architecture plays essential role on strain-induced crystallization and on the performance of cold-drawn shape-memory polymers. Model networks with uniform molecular weight between crosslinks, and specified functionality of each net-point, results in tougher, more elastic materials with a high degree of crystallinity and outstanding shape-memory properties. The thermal behavior of the model networks can be finely modified by introducing non-crystalline small molecule linkers that effectively frustrates the crystallization of the network strands. This resulted in shape-memory networks that are ultra-sensitive to heat, as deformed materials can be efficiently triggered to revert to its permanent state upon only exposure to body temperature. We also coupled the same reaction adopted to create the model network with conventional free-radical polymerization to prepare a dual-cure "double

  2. Creation of a global geodetic network using Mark III VLBI

    NASA Technical Reports Server (NTRS)

    Ma, Chopo; Clark, Thomas A.; Ryan, James W.

    1986-01-01

    The positions of 15 permanent VLBI stations have been determined using Mark III with one-sigma uncertainties of less than 5 cm except for three stations in the Pacific. 46070 delay/delay rate observations acquired by the Crustal Dynamics Project and Polaris/IRIS from 1980-84 were included in a least squares solution to estimate the station positions, 44 radio source positions, and earth orientation parameters.

  3. Near Real-Time Determination of Earthquake Source Parameters for Tsunami Early Warning from Geodetic Observations

    NASA Astrophysics Data System (ADS)

    Manneela, Sunanda; Srinivasa Kumar, T.; Nayak, Shailesh R.

    2016-06-01

    Exemplifying the tsunami source immediately after an earthquake is the most critical component of tsunami early warning, as not every earthquake generates a tsunami. After a major under sea earthquake, it is very important to determine whether or not it has actually triggered the deadly wave. The near real-time observations from near field networks such as strong motion and Global Positioning System (GPS) allows rapid determination of fault geometry. Here we present a complete processing chain of Indian Tsunami Early Warning System (ITEWS), starting from acquisition of geodetic raw data, processing, inversion and simulating the situation as it would be at warning center during any major earthquake. We determine the earthquake moment magnitude and generate the centroid moment tensor solution using a novel approach which are the key elements for tsunami early warning. Though the well established seismic monitoring network, numerical modeling and dissemination system are currently capable to provide tsunami warnings to most of the countries in and around the Indian Ocean, the study highlights the critical role of geodetic observations in determination of tsunami source for high-quality forecasting.

  4. Geodetic measurement of deformation in California. Ph.D. Thesis - Massachusetts Inst. of Technology

    NASA Technical Reports Server (NTRS)

    Sauber, Jeanne

    1989-01-01

    The very long baseline interferometry (VLBI) measurements made in the western U.S. since 1979 as part of the NASA Crustal Dynamics Project provide discrete samples of the temporal and spatial deformation field. The interpretation of the VLBI-derived rates of deformation requires an examination of geologic information and more densely sampled ground-based geodetic data. In the first two of three related studies, triangulation and trilateration data measured on two regional networks, one in the central Mojave Desert and one in the Coast Ranges east of the San Andreas fault, have been processed. At the spatial scales spanned by these local geodetic networks, auxiliary geologic and geophysical data have been utilized to examine the relation between measured incremental strain and the accommodation of strain seen in local geological structures, strain release in earthquakes, and principal stress directions inferred from in situ measurements. In a third study, the geocentric position vectors from a set of 77 VLBI experiments beginning in October 1982 have been used to estimate the tangential rate of change of station positions in the western U.S. in a North-America-Fixed reference frame.

  5. Modern geodetic methods for high-accuracy survey coordination on the example of magnetic exploration

    NASA Astrophysics Data System (ADS)

    Krasnoperov, R. I.; Sidorov, R. V.; Soloviev, A. A.

    2015-07-01

    The purposes and problems of the international network of geomagnetic observatories INTERMAGNET are briefly described in the work. The importance of the development of the Russian segment of the network as a part of a system for monitoring and estimating geomagnetic conditions on the Russian territory is emphasized. An example of the use of modern high-precision geodetic equipment for coor-dinate referencing of field geophysical observation is described. Factors that distort the referencing of field observations in problems of survey, engineering, and technical geophysics are listed, as well as those related to detail and high-resolution geophysical surveying and those that require a corresponding accuracy of observation point coordination. The magnetic exploration at the site of the Yamal INTERMAGNET-standard observatory serves an example to describe a technique for geodetic provision of a detailed geophysical survey by means of joint use of differential GNSS measurements and electronic tacheometry. The main advantages and disadvantages of the technique suggested are listed.

  6. Correlated errors in geodetic time series: Implications for time-dependent deformation

    USGS Publications Warehouse

    Langbein, J.; Johnson, H.

    1997-01-01

    Analysis of frequent trilateration observations from the two-color electronic distance measuring networks in California demonstrate that the noise power spectra are dominated by white noise at higher frequencies and power law behavior at lower frequencies. In contrast, Earth scientists typically have assumed that only white noise is present in a geodetic time series, since a combination of infrequent measurements and low precision usually preclude identifying the time-correlated signature in such data. After removing a linear trend from the two-color data, it becomes evident that there are primarily two recognizable types of time-correlated noise present in the residuals. The first type is a seasonal variation in displacement which is probably a result of measuring to shallow surface monuments installed in clayey soil which responds to seasonally occurring rainfall; this noise is significant only for a small fraction of the sites analyzed. The second type of correlated noise becomes evident only after spectral analysis of line length changes and shows a functional relation at long periods between power and frequency of and where f is frequency and ?? ??? 2. With ?? = 2, this type of correlated noise is termed random-walk noise, and its source is mainly thought to be small random motions of geodetic monuments with respect to the Earth's crust, though other sources are possible. Because the line length changes in the two-color networks are measured at irregular intervals, power spectral techniques cannot reliably estimate the level of I//" noise. Rather, we also use here a maximum likelihood estimation technique which assumes that there are only two sources of noise in the residual time series (white noise and randomwalk noise) and estimates the amount of each. From this analysis we find that the random-walk noise level averages about 1.3 mm/Vyr and that our estimates of the white noise component confirm theoretical limitations of the measurement technique. In

  7. Mechanisms Underlying Desynchronization of Cholinergic-Evoked Thalamic Network Activity

    PubMed Central

    Pita-Almenar, Juan Diego; Yu, Dinghui; Lu, Hui-Chen

    2014-01-01

    Synchronous neuronal activity in the thalamocortical system is critical for a number of behaviorally relevant computations, but hypersynchrony can limit information coding and lead to epileptiform responses. In the somatosensory thalamus, afferent inputs are transformed by networks of reciprocally connected thalamocortical neurons in the ventrobasal nucleus (VB) and GABAergic neurons in the thalamic reticular nucleus (TRN). These networks can generate oscillatory activity, and studies in vivo and in vitro have suggested that thalamic oscillations are often accompanied by synchronous neuronal activity, in part mediated by widespread divergence and convergence of both reticulothalamic and thalamoreticular pathways, as well as by electrical synapses interconnecting TRN neurons. However, the functional organization of thalamic circuits and its role in shaping input-evoked activity patterns remain poorly understood. Here we show that optogenetic activation of cholinergic synaptic afferents evokes near-synchronous firing in mouse TRN neurons that is rapidly desynchronized in thalamic networks. We identify several mechanisms responsible for desynchronization: (1) shared inhibitory inputs in local VB neurons leading to asynchronous and imprecise rebound bursting; (2) TRN-mediated lateral inhibition that further desynchronizes firing in the VB; and (3) powerful yet sparse thalamoreticular connectivity that mediates re-excitation of the TRN but preserves asynchronous firing. Our findings reveal how distinct local circuit features interact to desynchronize thalamic network activity. PMID:25339757

  8. Fast transient networks in spontaneous human brain activity

    PubMed Central

    Baker, Adam P; Brookes, Matthew J; Rezek, Iead A; Smith, Stephen M; Behrens, Timothy; Probert Smith, Penny J; Woolrich, Mark

    2014-01-01

    To provide an effective substrate for cognitive processes, functional brain networks should be able to reorganize and coordinate on a sub-second temporal scale. We used magnetoencephalography recordings of spontaneous activity to characterize whole-brain functional connectivity dynamics at high temporal resolution. Using a novel approach that identifies the points in time at which unique patterns of activity recur, we reveal transient (100–200 ms) brain states with spatial topographies similar to those of well-known resting state networks. By assessing temporal changes in the occurrence of these states, we demonstrate that within-network functional connectivity is underpinned by coordinated neuronal dynamics that fluctuate much more rapidly than has previously been shown. We further evaluate cross-network interactions, and show that anticorrelation between the default mode network and parietal regions of the dorsal attention network is consistent with an inability of the system to transition directly between two transient brain states. DOI: http://dx.doi.org/10.7554/eLife.01867.001 PMID:24668169

  9. BRAIN NETWORKS. Correlated gene expression supports synchronous activity in brain networks.

    PubMed

    Richiardi, Jonas; Altmann, Andre; Milazzo, Anna-Clare; Chang, Catie; Chakravarty, M Mallar; Banaschewski, Tobias; Barker, Gareth J; Bokde, Arun L W; Bromberg, Uli; Büchel, Christian; Conrod, Patricia; Fauth-Bühler, Mira; Flor, Herta; Frouin, Vincent; Gallinat, Jürgen; Garavan, Hugh; Gowland, Penny; Heinz, Andreas; Lemaître, Hervé; Mann, Karl F; Martinot, Jean-Luc; Nees, Frauke; Paus, Tomáš; Pausova, Zdenka; Rietschel, Marcella; Robbins, Trevor W; Smolka, Michael N; Spanagel, Rainer; Ströhle, Andreas; Schumann, Gunter; Hawrylycz, Mike; Poline, Jean-Baptiste; Greicius, Michael D

    2015-06-12

    During rest, brain activity is synchronized between different regions widely distributed throughout the brain, forming functional networks. However, the molecular mechanisms supporting functional connectivity remain undefined. We show that functional brain networks defined with resting-state functional magnetic resonance imaging can be recapitulated by using measures of correlated gene expression in a post mortem brain tissue data set. The set of 136 genes we identify is significantly enriched for ion channels. Polymorphisms in this set of genes significantly affect resting-state functional connectivity in a large sample of healthy adolescents. Expression levels of these genes are also significantly associated with axonal connectivity in the mouse. The results provide convergent, multimodal evidence that resting-state functional networks correlate with the orchestrated activity of dozens of genes linked to ion channel activity and synaptic function.

  10. Kinematics of the Southwestern Caribbean from New Geodetic Observations

    NASA Astrophysics Data System (ADS)

    Ruiz, G.; La Femina, P. C.; Tapia, A.; Camacho, E.; Chichaco, E.; Mora-Paez, H.; Geirsson, H.

    2014-12-01

    The interaction of the Caribbean, Cocos, Nazca, and South American plates has resulted in a complex plate boundary zone and the formation of second order tectonic blocks (e.g., the North Andean, Choco and Central America Fore Arc blocks). The Panama Region [PR], which is bounded by these plates and blocks, has been interpreted and modeled as a single tectonic block or deformed plate boundary. Previous research has defined the main boundaries: 1) The Caribbean plate subducts beneath the isthmus along the North Panama Deformed Belt, 2) The Nazca plate converges at very high obliquity with the PR and motion is assumed along a left lateral transform fault and the South Panama Deformed Belt, 3) The collision of PR with NW South America (i.e., the N. Andean and Choco blocks) has resulted in the Eastern Panama Deformed Belt, and 4) collision of the Cocos Ridge in the west is accommodated by crustal shortening, Central American Fore Arc translation and deformation across the Central Costa Rican Deformed Belt. In addition, there are several models that suggest internal deformation of this region by cross-isthmus strike-slip faults. Recent GPS observations for the PR indicates movement to the northeast relative to a stable Caribbean plate at rates of 6.9±4.0 - 7.8±4.8 mm a-1 from southern Costa Rica to eastern Panama, respectively (Kobayashi et al., 2014 and references therein). However, the GPS network did not have enough spatial density to estimate elastic strain accumulation across these faults. Recent installation and expansion of geodetic networks in southwestern Caribbean (i.e., Costa Rica, Panama, and Colombia) combined with geological and geophysical observations provide a new input to investigate crustal deformation processes in this complex tectonic setting, specifically related to the PR. We use new and existing GPS data to calculate a new velocity field for the region and to investigate the kinematics of the PR, including elastic strain accumulation on the

  11. Geodetic imaging with time series persistent scatterer InSAR

    NASA Astrophysics Data System (ADS)

    Zebker, H. A.; Shanker, A. P.

    2008-12-01

    Measuring the temporal evolution of deformation is crucial for understanding geophysical processes. InSAR methods produce detailed, spatially dense geodetic images in areas with high correlation between scattered echoes on different radar passes. Decorrelation occurs when the surface changes at wavelength scale over time. Persistent scattering (PS) methods are one way to avoid much observed decorrelation, and have proven to be useful in extracting deformation signatures from some highly decorrelating natural terrains. For slowly varying deformation fields, such as fault creep, PS approaches can image the evolution of surface movements. For episodic events such as volcanic events or even variable subsidence applications, PS networks often underestimate the deformation. The limitations of the technique appear to be mainly related to the sparseness of the data in both space and time, and are directly related to the robustness of the phase unwrapping algorithm needed to connect deformation points spatially and temporally. While early PS implementations were most successful in examining urban areas with manmade structures, and hence many bright backscattering points, the development of phase-based persistent scatterer identification approaches has permitted the method to be applicable for geophysical research. We now use a maximum likelihood phase-based method for PS identification that can find even low-amplitude PS points, greatly improving the spatial density of reliable points over that of earlier phase coherence approaches. We have applied the new detection methods to several different terrain types for various applications and present here sample PS network interferograms. We have verified several of these using either GPS or leveling data and show that the PS solutions are sometimes overly smoothed temporally, especially where the data are still poorly sampled in time. The smoothing is an artifact of our inability to properly unwrap data in three dimensions. We

  12. A study of tectonic activity in the Basin-Range Province and on the San Andreas Fault. No. 3: Kinematics of Great Basin intraplate extension from earthquake, geodetic and geologic information. Final Technical Report, 15 Apr. 1981 - 31 Jan. 1986 M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Eddington, P. K.

    1986-01-01

    Strain rates assessed from brittle fracture, associated with earthquakes, and total brittle-ductile deformation measured from geodetic data were compared to paleostrain from Quaternary geology for the intraplate Great Basin of the western United States. These data provide an assessment of the kinematics and mode of lithospheric extension that the western U.S. Cordillera has experienced in the last 5 to 10 million years. Strain and deformation rates were determined by the seismic moment tensor method using historic seismicity and fault plane solutions. Contemporary deformation of the Great Basin occurs principally along the active seismic zones. The earthquake related strain shows that the Great Basin is characterized by regional E-W extension at 8.4 mm/a in the north that diminishes to NW-SE extension of 3.5 mm/a in the south. Zones of maximum extension correspond to belts of shallow crust, high heat flow, and Quaternary basaltic volcanism, suggesting that these parameters are related through an effect such as a stress relaxation allowing bouyant uplift and ascension of magmas.

  13. Activity-Dependent Neuronal Model on Complex Networks

    PubMed Central

    de Arcangelis, Lucilla; Herrmann, Hans J.

    2012-01-01

    Neuronal avalanches are a novel mode of activity in neuronal networks, experimentally found in vitro and in vivo, and exhibit a robust critical behavior: these avalanches are characterized by a power law distribution for the size and duration, features found in other problems in the context of the physics of complex systems. We present a recent model inspired in self-organized criticality, which consists of an electrical network with threshold firing, refractory period, and activity-dependent synaptic plasticity. The model reproduces the critical behavior of the distribution of avalanche sizes and durations measured experimentally. Moreover, the power spectra of the electrical signal reproduce very robustly the power law behavior found in human electroencephalogram (EEG) spectra. We implement this model on a variety of complex networks, i.e., regular, small-world, and scale-free and verify the robustness of the critical behavior. PMID:22470347

  14. Activity flow over resting-state networks shapes cognitive task activations

    PubMed Central

    Cole, Michael W.; Ito, Takuya; Bassett, Danielle S.; Schultz, Douglas H.

    2016-01-01

    Resting-state functional connectivity (FC) has helped reveal the intrinsic network organization of the human brain, yet its relevance to cognitive task activations has been unclear. Uncertainty remains despite evidence that resting-state FC patterns are highly similar to cognitive task activation patterns. Identifying the distributed processes that shape localized cognitive task activations may help reveal why resting-state FC is so strongly related to cognitive task activations. We found that estimating task-evoked activity flow (the spread of activation amplitudes) over resting-state FC networks allows prediction of cognitive task activations in a large-scale neural network model. Applying this insight to empirical functional MRI data, we found that cognitive task activations can be predicted in held-out brain regions (and held-out individuals) via estimated activity flow over resting-state FC networks. This suggests that task-evoked activity flow over intrinsic networks is a large-scale mechanism explaining the relevance of resting-state FC to cognitive task activations. PMID:27723746

  15. Strategies for Space-Geodetic Monitoring of Infraseismic and Subseismic Transient Deformations

    NASA Technical Reports Server (NTRS)

    Jordan, Thomas H.

    1996-01-01

    The utility of space-geodetic data in elucidating infraseismic and subseismic phenomena is assessed. Existing seismological, geodetic, and other data to characterize the distribution of infraseismic and subseismic transients are used. Strategies for space-geodetic monitoring of infraseismic and subseismic transients along major plate boundaries are developed.

  16. California Health Services/Educational Activities. Consortium Network.

    ERIC Educational Resources Information Center

    White, Charles H.

    Profiles are presented of each of the 10 consortia that make up the California Health Services/Education Activities (HS/EA) network (new relationships between educational facilities where health care manpower is trained in the community settings where they practice). The first part of the booklet is a comparative analysis of (1) Area Health…

  17. Photonic network R and D activities in Japan

    NASA Astrophysics Data System (ADS)

    Kitayama, Ken-ichi; Miki, Tetsuya; Morioka, Toshio; Tsushima, Hideaki; Koga, Masafumi; Mori, Kazuyuki; Araki, Soichiro; Sato, Ken-ichi; Onaka, Hiroshi; Namiki, Shu; Aovama, Tomonori

    2005-11-01

    R and D activities on photonic networks in Japan are presented. First, milestones in current, ongoing R and D programs supported by Japanese government agencies are introduced, including long-distance and WDM fiber transmission, wavelength routing, optical burst switching, and control plane technology for IP backbone networks. Their goal was set to evolve a legacy telecommunications network to IP over WDM networks by introducing technologies for WDM and wavelength routing. We then discuss the perspectives of so-called PHASE II R and D programs for photonic networks over the next five years until 2010, by focusing on the report which has been recently issued by the Photonic Internet Forum (PIF), a consortium that has major carriers, telecom vendors, and Japanese academics as members. The PHASE II R and D programs should serve to establish a photonic platform to provide abundant bandwidth on demand, at any time on a real-time basis through the customer's initiative, to promote bandwidth-rich applications, such as grid computing, real-time digital-cinema streaming, medical and educational applications, and network storage in e-commerce.

  18. RelEx: Visualization for Actively Changing Overlay Network Specifications.

    PubMed

    Sedlmair, M; Frank, A; Munzner, T; Butz, A

    2012-12-01

    We present a network visualization design study focused on supporting automotive engineers who need to specify and optimize traffic patterns for in-car communication networks. The task and data abstractions that we derived support actively making changes to an overlay network, where logical communication specifications must be mapped to an underlying physical network. These abstractions are very different from the dominant use case in visual network analysis, namely identifying clusters and central nodes, that stems from the domain of social network analysis. Our visualization tool RelEx was created and iteratively refined through a full user-centered design process that included a full problem characterization phase before tool design began, paper prototyping, iterative refinement in close collaboration with expert users for formative evaluation, deployment in the field with real analysts using their own data, usability testing with non-expert users, and summative evaluation at the end of the deployment. In the summative post-deployment study, which entailed domain experts using the tool over several weeks in their daily practice, we documented many examples where the use of RelEx simplified or sped up their work compared to previous practices.

  19. Self-regulated homoclinic chaos in neural networks activity

    NASA Astrophysics Data System (ADS)

    Volman, Vladislav; Baruchi, Itay; Ben-Jacob, Eshel

    2004-12-01

    We compare the recorded activity of cultured neuronal networks with hybridized model simulations, in which the model neurons are driven by the recorded activity of special neurons. The latter, named `spiker' neurons, that exhibit fast firing with homoclinic chaos like characteristics, are expected to play an important role in the networks' self regulation. The cultured networks are grown from dissociated mixtures of cortical neurons and glia cells. Despite the artificial manner of their construction, the spontaneous activity of these networks exhibits rich dynamical behavior, marked by the formation of temporal sequences of synchronized bursting events (SBEs), and additional features which seemingly reflect the action of underlying regulating mechanism, rather than arbitrary causes and effects. Our model neurons are composed of soma described by the two Morris-Lecar dynamical variables (voltage and fraction of open potassium channels), with dynamical synapses described by the Tsodyks-Markram three variables dynamics. To study the recorded and simulated activities we evaluated the inter-neuron correlation matrices, and analyzed them utilizing the functional holography approach: the correlations are re-normalized by the correlation distances — Euclidean distances between the matrix columns. Then, we project the N-dimensional (for N channels) space spanned by the matrix of re-normalized correlations, or correlation affinities, onto a corresponding 3-D causal manifold (3-D Cartesian space constructed by the 3 leading principal vectors of the N-dimensional space. The neurons are located by their principal eigenvalues and linked by their original (not-normalized) correlations. This reveals hidden causal motifs: the neuron locations and their links form simple structures. Similar causal motifs are exhibited by the model simulations when feeded by the recorded activity of the spiker neurons. We illustrate that the homoclinic chaotic behavior of the spiker neurons can be

  20. Geodetic monitoring of tectonic deformation: Toward a strategy

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Issues of interest and importance to society and science are presented. The problems considered are of national concern; their solutions may contribute to a better understanding of tectonic deformation and earthquake hazards. The need for additional field data, the role of geodetic measurements, the importance of both ground and space techniques, and the need for advanced instrumentation development are discussed.

  1. A 3-D Multilateration: A Precision Geodetic Measurement System

    NASA Technical Reports Server (NTRS)

    Escobal, P. R.; Fliegel, H. F.; Jaffe, R. M.; Muller, P. M.; Ong, K. M.; Vonroos, O. H.

    1972-01-01

    A system was designed with the capability of determining 1-cm accuracy station positions in three dimensions using pulsed laser earth satellite tracking stations coupled with strictly geometric data reduction. With this high accuracy, several crucial geodetic applications become possible, including earthquake hazards assessment, precision surveying, plate tectonics, and orbital determination.

  2. Estimation of rod scale errors in geodetic leveling

    USGS Publications Warehouse

    Craymer, Michael R.; Vaníček, Petr; Castle, Robert O.

    1995-01-01

    Comparisons among repeated geodetic levelings have often been used for detecting and estimating residual rod scale errors in leveled heights. Individual rod-pair scale errors are estimated by a two-step procedure using a model based on either differences in heights, differences in section height differences, or differences in section tilts. It is shown that the estimated rod-pair scale errors derived from each model are identical only when the data are correctly weighted, and the mathematical correlations are accounted for in the model based on heights. Analyses based on simple regressions of changes in height versus height can easily lead to incorrect conclusions. We also show that the statistically estimated scale errors are not a simple function of height, height difference, or tilt. The models are valid only when terrain slope is constant over adjacent pairs of setups (i.e., smoothly varying terrain). In order to discriminate between rod scale errors and vertical displacements due to crustal motion, the individual rod-pairs should be used in more than one leveling, preferably in areas of contrasting tectonic activity. From an analysis of 37 separately calibrated rod-pairs used in 55 levelings in southern California, we found eight statistically significant coefficients that could be reasonably attributed to rod scale errors, only one of which was larger than the expected random error in the applied calibration-based scale correction. However, significant differences with other independent checks indicate that caution should be exercised before accepting these results as evidence of scale error. Further refinements of the technique are clearly needed if the results are to be routinely applied in practice.

  3. Multichannel activity propagation across an engineered axon network

    NASA Astrophysics Data System (ADS)

    Chen, H. Isaac; Wolf, John A.; Smith, Douglas H.

    2017-04-01

    Objective. Although substantial progress has been made in mapping the connections of the brain, less is known about how this organization translates into brain function. In particular, the massive interconnectivity of the brain has made it difficult to specifically examine data transmission between two nodes of the connectome, a central component of the ‘neural code.’ Here, we investigated the propagation of multiple streams of asynchronous neuronal activity across an isolated in vitro ‘connectome unit.’ Approach. We used the novel technique of axon stretch growth to create a model of a long-range cortico-cortical network, a modular system consisting of paired nodes of cortical neurons connected by axon tracts. Using optical stimulation and multi-electrode array recording techniques, we explored how input patterns are represented by cortical networks, how these representations shift as they are transmitted between cortical nodes and perturbed by external conditions, and how well the downstream node distinguishes different patterns. Main results. Stimulus representations included direct, synaptic, and multiplexed responses that grew in complexity as the distance between the stimulation source and recorded neuron increased. These representations collapsed into patterns with lower information content at higher stimulation frequencies. With internodal activity propagation, a hierarchy of network pathways, including latent circuits, was revealed using glutamatergic blockade. As stimulus channels were added, divergent, non-linear effects were observed in local versus distant network layers. Pairwise difference analysis of neuronal responses suggested that neuronal ensembles generally outperformed individual cells in discriminating input patterns. Significance. Our data illuminate the complexity of spiking activity propagation in cortical networks in vitro, which is characterized by the transformation of an input into myriad outputs over several network layers

  4. Initial Results Obtained with the First TWIN VLBI Radio Telescope at the Geodetic Observatory Wettzell.

    PubMed

    Schüler, Torben; Kronschnabl, Gerhard; Plötz, Christian; Neidhardt, Alexander; Bertarini, Alessandra; Bernhart, Simone; la Porta, Laura; Halsig, Sebastian; Nothnagel, Axel

    2015-07-30

    Geodetic Very Long Baseline Interferometry (VLBI) uses radio telescopes as sensor networks to determine Earth orientation parameters and baseline vectors between the telescopes. The TWIN Telescope Wettzell 1 (TTW1), the first of the new 13.2 m diameter telescope pair at the Geodetic Observatory Wettzell, Germany, is currently in its commissioning phase. The technology behind this radio telescope including the receiving system and the tri-band feed horn is depicted. Since VLBI telescopes must operate at least in pairs, the existing 20 m diameter Radio Telescope Wettzell (RTW) is used together with TTW1 for practical tests. In addition, selected long baseline setups are investigated. Correlation results portraying the data quality achieved during first initial experiments are discussed. Finally, the local 123 m baseline between the old RTW telescope and the new TTW1 is analyzed and compared with an existing high-precision local survey. Our initial results are very satisfactory for X-band group delays featuring a 3D distance agreement between VLBI data analysis and local ties of 1 to 2 mm in the majority of the experiments. However, S-band data, which suffer much from local radio interference due to WiFi and mobile communications, are about 10 times less precise than X-band data and require further analysis, but evidence is provided that S-band data are well-usable over long baselines where local radio interference patterns decorrelate.

  5. Initial Results Obtained with the First TWIN VLBI Radio Telescope at the Geodetic Observatory Wettzell

    PubMed Central

    Schüler, Torben; Kronschnabl, Gerhard; Plötz, Christian; Neidhardt, Alexander; Bertarini, Alessandra; Bernhart, Simone; la Porta, Laura; Halsig, Sebastian; Nothnagel, Axel

    2015-01-01

    Geodetic Very Long Baseline Interferometry (VLBI) uses radio telescopes as sensor networks to determine Earth orientation parameters and baseline vectors between the telescopes. The TWIN Telescope Wettzell 1 (TTW1), the first of the new 13.2 m diameter telescope pair at the Geodetic Observatory Wettzell, Germany, is currently in its commissioning phase. The technology behind this radio telescope including the receiving system and the tri-band feed horn is depicted. Since VLBI telescopes must operate at least in pairs, the existing 20 m diameter Radio Telescope Wettzell (RTW) is used together with TTW1 for practical tests. In addition, selected long baseline setups are investigated. Correlation results portraying the data quality achieved during first initial experiments are discussed. Finally, the local 123 m baseline between the old RTW telescope and the new TTW1 is analyzed and compared with an existing high-precision local survey. Our initial results are very satisfactory for X-band group delays featuring a 3D distance agreement between VLBI data analysis and local ties of 1 to 2 mm in the majority of the experiments. However, S-band data, which suffer much from local radio interference due to WiFi and mobile communications, are about 10 times less precise than X-band data and require further analysis, but evidence is provided that S-band data are well-usable over long baselines where local radio interference patterns decorrelate. PMID:26263991

  6. First geodetic VLBI sessions with the Chinese Deep Space Stations Jiamusi and Kashi

    NASA Astrophysics Data System (ADS)

    Xu, Dezhen; Dong, Guangliang; Wang, Guangli; Li, Haitao; Jiang, Wu

    2016-11-01

    The first three 24-h S/X dual-band geodetic VLBI sessions using two new Chinese Deep Space Stations (CDSSs), Jiamusi and Kashi, and four Chinese VLBI Stations (CVSs), Beijing, Kunming, Seshan, and Urumqi were conducted with the goal of improving the two CDSSs' positions, which were previously known to a few decimeters. Due to the limited frequency ranges of Jiamusi and Kashi, different but compatible frequencies for bandwidth synthesis were set at the CDSS and CVS stations. This paper presents the scheduling, correlation and fringe fit, and geodetic analysis of the observations. Final estimates of the station positions are obtained from the global solution using 5365 international VLBI sessions from August 3, 1979 through September 29, 2015. Position estimates for Jiamusi are accurate to 23, 35, and 41 mm in the X, Y, and Z directions, respectively, and for Kashi are accurate to 10, 20, and 16 mm. Precisions of the two CDSSs' positions are improved by a factor of 5-10 over previous values, which fully satisfies the requirements of the experiments and makes the first step towards the foundation and maintenance of the time-space reference frame based on the Chinese Deep Space Network (CDSN).

  7. Technique Errors and Limiting Factors in Laser Ranging to Geodetic Satellites

    NASA Astrophysics Data System (ADS)

    Appleby, G. M.; Luceri, V.; Mueller, H.; Noll, C. E.; Otsubo, T.; Wilkinson, M.

    2012-12-01

    The tracking stations of the International Laser Ranging Service (ILRS) global network provide to the Data Centres a steady stream of very precise laser range normal points to the primary geodetic spherical satellites LAGEOS (-1 and -2) and Etalon (-1 and -2). Analysis of these observations to determine instantaneous site coordinates and Earth orientation parameters provides a major contribution to ongoing international efforts to define a precise terrestrial reference frame, which itself supports research into geophysical processes at the few mm level of precision. For example, the latest realization of the reference frame, ITRF2008, used weekly laser range solutions from 1983 to 2009, the origin of the Frame being determined solely by the SLR technique. However, in the ITRF2008 publication, Altamimi et al (2011, Journal of Geodesy) point out that further improvement in the ITRF is partly dependent upon improving an understanding of sources of technique error. In this study we look at SLR station hardware configuration that has been subject to major improvements over the last four decades, at models that strive to provide accurate translations of the laser range observations to the centres of mass of the small geodetic satellites and at the considerable body of work that has been carried out via orbital analyses to determine range corrections for some of the tracking stations. Through this study, with specific examples, we start to put together an inventory of system-dependent technique errors that will be important information for SLR re-analysis towards the next realization of the ITRF.

  8. An Autonomous, Low Cost Platform for Seafloor Geodetic Observations

    NASA Astrophysics Data System (ADS)

    Ericksen, T.; Foster, J. H.; Bingham, B. S.; Oshiro, J.

    2014-12-01

    The Pacific GPS Facility and the Field Robotics Laboratory at the University of Hawaii have developed an approach to significantly reduce costs below ship based methods of accurately measuring short-term vertical motions of the seafloor and maintaining a continuous long-term record of seafloor pressure. Our goal has been to reduce the primary barrier preventing us from acquiring the observations we need to understand geodetic processes, and the hazards they present, at subduction zones, submarine volcanoes, and subsea landslides. To this end, we have designed a payload package for one of the University of Hawaii Wave Gliders which incorporates an acoustic telemetry package, a dual frequency geodetic-grade Global Positioning System (GPS) receiver, meteorological sensors, processing computer, and cellular communications. The Wave Glider will interrogate high accuracy pressure sensors on the seafloor to maintain a near-continuous stream of pressure and temperature data. The seafloor geodetic monument seats a sensor capable of recording pressure, temperature, and sound velocity for a deployment duration of over 5 years with an acoustic modem for communications, and an integral acoustic release for recovery and replacement of batteries. The design of the geodetic monument allows for precise repositioning of the sensor to extend the pressure record beyond a single 5+ year deployment, and includes the capability to install a mobile pressure recorder for calibration of the linear drift of the continuous pressure sensor. We will present the design of the Wave Glider payload and seafloor geodetic monument, as well as a discussion of nearshore and offshore field tests and operational procedures. An assessment of our ability to determine cm-scale vertical seafloor motions will be made by integrating the seafloor pressure measurements recovered during field testing with independent measurements of sea surface pressure and sea surface height made by the sea surface payload.

  9. Meditation leads to reduced default mode network activity beyond an active task.

    PubMed

    Garrison, Kathleen A; Zeffiro, Thomas A; Scheinost, Dustin; Constable, R Todd; Brewer, Judson A

    2015-09-01

    Meditation has been associated with relatively reduced activity in the default mode network, a brain network implicated in self-related thinking and mind wandering. However, previous imaging studies have typically compared meditation to rest, despite other studies having reported differences in brain activation patterns between meditators and controls at rest. Moreover, rest is associated with a range of brain activation patterns across individuals that has only recently begun to be better characterized. Therefore, in this study we compared meditation to another active cognitive task, both to replicate the findings that meditation is associated with relatively reduced default mode network activity and to extend these findings by testing whether default mode activity was reduced during meditation, beyond the typical reductions observed during effortful tasks. In addition, prior studies had used small groups, whereas in the present study we tested these hypotheses in a larger group. The results indicated that meditation is associated with reduced activations in the default mode network, relative to an active task, for meditators as compared to controls. Regions of the default mode network showing a Group × Task interaction included the posterior cingulate/precuneus and anterior cingulate cortex. These findings replicate and extend prior work indicating that the suppression of default mode processing may represent a central neural process in long-term meditation, and they suggest that meditation leads to relatively reduced default mode processing beyond that observed during another active cognitive task.

  10. The Seismic Broad Band Western Mediterranean (wm) Network and the Obs Fomar Pool: Current state and Obs activities.

    NASA Astrophysics Data System (ADS)

    Pazos, Antonio; Davila, Jose Martin; Buforn, Elisa; Bezzeghoud, Mourad; Harnafi, Mimoun; Mattesini, Mauricio; Caldeira, Bento; Hanka, Winfried; El Moudnib, Lahcen; Strollo, Angelo; Roca, Antoni; Lopez de Mesa, Mireya; Dahm, Torsten; Cabieces, Roberto

    2016-04-01

    The Western Mediterranean (WM) seismic network started in 1996 as an initiative of the Royal Spanish Navy Observatory (ROA) and the Universidad Complutense de Madrid (UCM), with the collaboration of the GeoForschungsZentrum (GFZ) of Potsdam. A first broad band seismic station (SFUC) was installed close to Cádiz (South Spain). Since then, additional stations have been installed in the Ibero-Moghrebian region. In 2005, the "WM" code was assigned by the FDSN and new partners were jointed: Evora University (UEVO, Portugal), the Scientifique Institute of Rabat (ISRABAT, Morocco), and GFZ. Now days, the WM network is composed by 15 BB stations, all of them with Streckaisen STS-2 or STS-2.5 sensors, Quanterra or Earthdata digitizers and SeiscomP. Most them have co-installed a permanent geodetic GPS stations, and some them also have an accelerometer. There are 10 stations deployed in Spanish territory (5 in the Iberian peninsula, 1 in Balearic islands and 4 in North Africa Spanish places) with VSAT or Internet communications, 2 in Portugal (one of them without real time), and 3 in Morocco (2 VSAT and 1 ADSL). Additionally, 2 more stations (one in South Spain and one in Morocco) will be installed along this year. Additionally ROA has deployed a permanent real time VBB (CMG-3T: 360s) station at the Alboran Island. Due to the fact that part of the seismic activity is located at marine areas, and also because of the poor geographic azimuthal coverage at some zones provided by the land stations (specially in the SW of the San Vicente Cape area), ROA and UCM have acquired six broad band "LOBSTERN" OBS, manufactured by KUM (Kiel, Germany), conforming the OBS FOMAR pool. Three of them with CMG-40T sensor and the other with Trillium 120. These OBS were deployed along the Gibraltar strait since January to November 2014 to study the microseismicity in the Gibraltar strait area. In September 2015 FOMAR network has been deployed in SW of the San Vicente Cape for 8 months as a part of

  11. Geodetic slip rate estimates for the Alhama de Murcia and Carboneras faults in the SE Betics, Spain

    NASA Astrophysics Data System (ADS)

    Khazaradze, Giorgi; Echeverria, Anna; Masana, Eulàlia

    2016-04-01

    The Alhama de Murcia and the Carboneras faults are the most prominent geologic structures within the Eastern Betic Shear Zone (EBSZ), located in SE Spain. Using continuous and campaign GPS observations conducted during the last decade, we were able to confirm the continuing tectonic activity of these faults by quantifying their geodetic slip-rates and comparing the estimated values with the geological (including paleoseismological) observations. We find that the bulk of the observed deformation is concentrated around the Alhama de Murcia (AMF) and the Palomares (PF) faults. The geodetic horizontal slip rate (reverse-sinistral) of 1.5±0.3 mm/yr calculated for the AMF and PF fault system is in good agreement with geological observations at the AMF, as well as, the focal mechanism of the 2011 Lorca earthquake, suggesting a main role of the AMF. We also find that the geodetic slip rate of the Carboneras fault zone (CFZ) is almost purely sinistral strike-slip with a rate of 1.3±0.2 mm/yr along N48° direction, very similar to 1.1 mm/yr geologic slip-rate, estimated from recent onshore and offshore paleoseismic and geomorphologic studies. The fact the geodetic and the geologic slip-rates are similar at the AMF and CF faults, suggests that both faults have been tectonically active since Quaternary, slipping at approximately at constant rate of 1.1 to 1.8 mm/yr. Since the existing GPS data cannot discern whether the CFZ is slipping seismically or aseismically, we have intended to relate the on-going seismic activity to the slip-rates estimated using GPS. For this reason we compared seismic and geodetic strain rates, where the latter are larger than seismic strain rates, suggesting the presence of aseismic processes in the area. Nevertheless, due to the large earthquake recurrence intervals, we may be underestimating the seismic strain rates. The direction of the P and T average stress axes are in good agreement with geodetic principal strain rate axes. To summarize, in

  12. Multiview fusion for activity recognition using deep neural networks

    NASA Astrophysics Data System (ADS)

    Kavi, Rahul; Kulathumani, Vinod; Rohit, Fnu; Kecojevic, Vlad

    2016-07-01

    Convolutional neural networks (ConvNets) coupled with long short term memory (LSTM) networks have been recently shown to be effective for video classification as they combine the automatic feature extraction capabilities of a neural network with additional memory in the temporal domain. This paper shows how multiview fusion can be applied to such a ConvNet LSTM architecture. Two different fusion techniques are presented. The system is first evaluated in the context of a driver activity recognition system using data collected in a multicamera driving simulator. These results show significant improvement in accuracy with multiview fusion and also show that deep learning performs better than a traditional approach using spatiotemporal features even without requiring any background subtraction. The system is also validated on another publicly available multiview action recognition dataset that has 12 action classes and 8 camera views.

  13. Actin network architecture can determine myosin motor activity.

    PubMed

    Reymann, Anne-Cécile; Boujemaa-Paterski, Rajaa; Martiel, Jean-Louis; Guérin, Christophe; Cao, Wenxiang; Chin, Harvey F; De La Cruz, Enrique M; Théry, Manuel; Blanchoin, Laurent

    2012-06-08

    The organization of actin filaments into higher-ordered structures governs eukaryotic cell shape and movement. Global actin network size and architecture are maintained in a dynamic steady state through regulated assembly and disassembly. Here, we used experimentally defined actin structures in vitro to investigate how the activity of myosin motors depends on network architecture. Direct visualization of filaments revealed myosin-induced actin network deformation. During this reorganization, myosins selectively contracted and disassembled antiparallel actin structures, while parallel actin bundles remained unaffected. The local distribution of nucleation sites and the resulting orientation of actin filaments appeared to regulate the scalability of the contraction process. This "orientation selection" mechanism for selective contraction and disassembly suggests how the dynamics of the cellular actin cytoskeleton can be spatially controlled by actomyosin contractility.

  14. Dynamical state of the network determines the efficacy of single neuron properties in shaping the network activity.

    PubMed

    Sahasranamam, Ajith; Vlachos, Ioannis; Aertsen, Ad; Kumar, Arvind

    2016-05-23

    Spike patterns are among the most common electrophysiological descriptors of neuron types. Surprisingly, it is not clear how the diversity in firing patterns of the neurons in a network affects its activity dynamics. Here, we introduce the state-dependent stochastic bursting neuron model allowing for a change in its firing patterns independent of changes in its input-output firing rate relationship. Using this model, we show that the effect of single neuron spiking on the network dynamics is contingent on the network activity state. While spike bursting can both generate and disrupt oscillations, these patterns are ineffective in large regions of the network state space in changing the network activity qualitatively. Finally, we show that when single-neuron properties are made dependent on the population activity, a hysteresis like dynamics emerges. This novel phenomenon has important implications for determining the network response to time-varying inputs and for the network sensitivity at different operating points.

  15. 3D actin network centerline extraction with multiple active contours.

    PubMed

    Xu, Ting; Vavylonis, Dimitrios; Huang, Xiaolei

    2014-02-01

    Fluorescence microscopy is frequently used to study two and three dimensional network structures formed by cytoskeletal polymer fibers such as actin filaments and actin cables. While these cytoskeletal structures are often dilute enough to allow imaging of individual filaments or bundles of them, quantitative analysis of these images is challenging. To facilitate quantitative, reproducible and objective analysis of the image data, we propose a semi-automated method to extract actin networks and retrieve their topology in 3D. Our method uses multiple Stretching Open Active Contours (SOACs) that are automatically initialized at image intensity ridges and then evolve along the centerlines of filaments in the network. SOACs can merge, stop at junctions, and reconfigure with others to allow smooth crossing at junctions of filaments. The proposed approach is generally applicable to images of curvilinear networks with low SNR. We demonstrate its potential by extracting the centerlines of synthetic meshwork images, actin networks in 2D Total Internal Reflection Fluorescence Microscopy images, and 3D actin cable meshworks of live fission yeast cells imaged by spinning disk confocal microscopy. Quantitative evaluation of the method using synthetic images shows that for images with SNR above 5.0, the average vertex error measured by the distance between our result and ground truth is 1 voxel, and the average Hausdorff distance is below 10 voxels.

  16. Optimal stimulus scheduling for active estimation of evoked brain networks

    NASA Astrophysics Data System (ADS)

    Kafashan, MohammadMehdi; Ching, ShiNung

    2015-12-01

    Objective. We consider the problem of optimal probing to learn connections in an evoked dynamic network. Such a network, in which each edge measures an input-output relationship between sites in sensor/actuator-space, is relevant to emerging applications in neural mapping and neural connectivity estimation. Approach. We show that the problem of scheduling nodes to a probe (i.e., stimulate) amounts to a problem of optimal sensor scheduling. Main results. By formulating the evoked network in state-space, we show that the solution to the greedy probing strategy has a convenient form and, under certain conditions, is optimal over a finite horizon. We adopt an expectation maximization technique to update the state-space parameters in an online fashion and demonstrate the efficacy of the overall approach in a series of detailed numerical examples. Significance. The proposed method provides a principled means to actively probe time-varying connections in neuronal networks. The overall method can be implemented in real time and is particularly well-suited to applications in stimulation-based cortical mapping in which the underlying network dynamics are changing over time.

  17. Scalable wavelet-based active network detection of stepping stones

    NASA Astrophysics Data System (ADS)

    Gilbert, Joseph I.; Robinson, David J.; Butts, Jonathan W.; Lacey, Timothy H.

    2012-06-01

    Network intrusions leverage vulnerable hosts as stepping stones to penetrate deeper into a network and mask malicious actions from detection. Identifying stepping stones presents a significant challenge because network sessions appear as legitimate traffic. This research focuses on a novel active watermark technique using discrete wavelet transformations to mark and detect interactive network sessions. This technique is scalable, resilient to network noise, and difficult for attackers to discern that it is in use. Previously captured timestamps from the CAIDA 2009 dataset are sent using live stepping stones in the Amazon Elastic Compute Cloud service. The client system sends watermarked and unmarked packets from California to Virginia using stepping stones in Tokyo, Ireland and Oregon. Five trials are conducted in which the system sends simultaneous watermarked samples and unmarked samples to each target. The live experiment results demonstrate approximately 5% False Positive and 5% False Negative detection rates. Additionally, watermark extraction rates of approximately 92% are identified for a single stepping stone. The live experiment results demonstrate the effectiveness of discerning watermark traffic as applied to identifying stepping stones.

  18. Geodetic observations in Iceland: divergent plate boundary influenced by a hotspot

    NASA Astrophysics Data System (ADS)

    Ofeigsson, Benedikt Gunnar; Hreinsdóttir, Sigrun; Sigmundsson, Freysteinn; Arnadottir, Thora; Vogfjord, Kristin; Geirsson, Halldor; Einarsson, Pall; Jonsson, Sigurjon; Villemin, Thierry; Fjalar Sigurdsson, Sigurdur; Roberts, Matthew; Sturkell, Erik; Lafemina, Peter C.; Bennett, Richard; Voelksen, Christof; Valsson, Gudmundur; Sigurdsson, Thorarinn

    2013-04-01

    The mid Atlantic ridge, separating the Eurasian and North American tectonic plates, is mostly buried below the Atlantic. There are, however, a few places where subaerial exposure of the mid-oceanic rift system allows geodetic observations of the deformation associated with the plate boundary. Iceland is the largest portion of the system emerged above sea level, a consequence of excessive volcanism caused by the interaction of a mantle plume with the mid-oceanic ridge. Iceland is therefore a unique site to study processes associated with divergent plate boundaries, and the effects of the plume-ridge interaction. A network of continuous GPS stations have been operating in Iceland since 1995 when the first station was installed in Reykjavik. Since then, stations have been added to the network at different points in time, with over 70 stations presently in operation. The network has been used e.g. for studies of deformation associated with the divergent plate boundary, micro-plate formation due to rift jumps, the plate-spreading deformation cycle associated with rifting episodes, strain rates and stress accumulation on transform zones connecting the ridge segments and deformation due to magmatic processes. In addition the GPS network is used in studies of the deformation associated with mass variations of Iceland's glaciers. The continuous GPS network serves as monitoring tool in Iceland, both for volcanic and seismic hazards but also as a research tool. In the recent Futurvolc project, which partly builds on EPOS, the data from the continuous GPS network along with data from the seismic network and InSAR observations, will serve as the main input in joint analyses of long and short term magma movements in volcanic regions. The establishment of the continuous GPS network in Iceland has provided an ideal tool to further increase our understanding of the geodynamic processes associated with divergent plate boundaries and plume-ridge interaction as well as establishing a

  19. CRAFFT: An Activity Prediction Model based on Bayesian Networks.

    PubMed

    Nazerfard, Ehsan; Cook, Diane J

    2015-04-01

    Recent advances in the areas of pervasive computing, data mining, and machine learning offer unique opportunities to provide health monitoring and assistance for individuals facing difficulties to live independently in their homes. Several components have to work together to provide health monitoring for smart home residents including, but not limited to, activity recognition, activity discovery, activity prediction, and prompting system. Compared to the significant research done to discover and recognize activities, less attention has been given to predict the future activities that the resident is likely to perform. Activity prediction components can play a major role in design of a smart home. For instance, by taking advantage of an activity prediction module, a smart home can learn context-aware rules to prompt individuals to initiate important activities. In this paper, we propose an activity prediction model using Bayesian networks together with a novel two-step inference process to predict both the next activity features and the next activity label. We also propose an approach to predict the start time of the next activity which is based on modeling the relative start time of the predicted activity using the continuous normal distribution and outlier detection. To validate our proposed models, we used real data collected from physical smart environments.

  20. A Comparative Study of the Applied Methods for Estimating Deflection of the Vertical in Terrestrial Geodetic Measurements

    PubMed Central

    Vittuari, Luca; Tini, Maria Alessandra; Sarti, Pierguido; Serantoni, Eugenio; Borghi, Alessandra; Negusini, Monia; Guillaume, Sébastien

    2016-01-01

    This paper compares three different methods capable of estimating the deflection of the vertical (DoV): one is based on the joint use of high precision spirit leveling and Global Navigation Satellite Systems (GNSS), a second uses astro-geodetic measurements and the third gravimetric geoid models. The working data sets refer to the geodetic International Terrestrial Reference Frame (ITRF) co-location sites of Medicina (Northern, Italy) and Noto (Sicily), these latter being excellent test beds for our investigations. The measurements were planned and realized to estimate the DoV with a level of precision comparable to the angular accuracy achievable in high precision network measured by modern high-end total stations. The three methods are in excellent agreement, with an operational supremacy of the astro-geodetic method, being faster and more precise than the others. The method that combines leveling and GNSS has slightly larger standard deviations; although well within the 1 arcsec level, which was assumed as threshold. Finally, the geoid model based method, whose 2.5 arcsec standard deviations exceed this threshold, is also statistically consistent with the others and should be used to determine the DoV components where local ad hoc measurements are lacking. PMID:27104544

  1. Generalized activity equations for spiking neural network dynamics

    PubMed Central

    Buice, Michael A.; Chow, Carson C.

    2013-01-01

    Much progress has been made in uncovering the computational capabilities of spiking neural networks. However, spiking neurons will always be more expensive to simulate compared to rate neurons because of the inherent disparity in time scales—the spike duration time is much shorter than the inter-spike time, which is much shorter than any learning time scale. In numerical analysis, this is a classic stiff problem. Spiking neurons are also much more difficult to study analytically. One possible approach to making spiking networks more tractable is to augment mean field activity models with some information about spiking correlations. For example, such a generalized activity model could carry information about spiking rates and correlations between spikes self-consistently. Here, we will show how this can be accomplished by constructing a complete formal probabilistic description of the network and then expanding around a small parameter such as the inverse of the number of neurons in the network. The mean field theory of the system gives a rate-like description. The first order terms in the perturbation expansion keep track of covariances. PMID:24298252

  2. Dopamine depresses cholinergic oscillatory network activity in rat hippocampus.

    PubMed

    Weiss, Torsten; Veh, Rüdiger W; Heinemann, Uwe

    2003-11-01

    The dopaminergic neuronal system is implicated in cognitive processes in a variety of brain regions including the mesolimbic system. We have investigated whether dopamine also affects synchronized network activity in the hippocampus, which has been ascribed to play a pivotal role in memory formation. Gamma frequency (20-80 Hz) oscillations were induced by the cholinergic agonist carbachol. Oscillatory activity was examined in area CA3 of Wistar rat hippocampal slices, employing field potential and intracellular recordings. Application of carbachol initiated synchronized population activity in the gamma band at 40 Hz. Induced gamma activity persisted over hours and required GABAA receptors. Dopamine reversibly decreased the integrated gamma band power of the carbachol rhythm by 62%, while its frequency was not changed. By contrast, individual pyramidal cells recorded during carbachol-induced field gamma activity exhibited theta frequency (5-15 Hz) membrane potential oscillations that were not altered by dopamine. The dopamine effect on the field gamma activity was mimicked by the D1 receptor agonist SKF-383393 and partially antagonized by the D1 antagonist SCH-23390. Conversely, the D2 receptor agonist quinpirole failed to depress the oscillations, and the D2 antagonist sulpiride did not prevent the suppressive dopamine effect. The data indicate that dopamine strongly depresses cholinergic gamma oscillations in area CA3 of rat hippocampus by activation of D1-like dopamine receptors and that this effect is most likely mediated via impairment of interneurons involved in generation and maintenance of the carbachol-induced network rhythm.

  3. Geodetic measurement of tectonic deformation in the southern Alps and Provence, France, 1947-1994

    NASA Astrophysics Data System (ADS)

    Ferhat, Gilbert; Feigl, Kurt L.; Ritz, Jean-François; Souriau, Annie

    1998-06-01

    Active deformation at the boundary between the Eurasia and Africa plates varies in style. The belt between the Alpine mountain range and the Mediterranean Sea, for example, differs markedly in its western and eastern parts. In the western part, around southeast France, the mountains are higher, but the seismicity lower, than in the eastern part, around northern Italy and Greece. Yet the inter-plate convergence rate of 6 mm/yr varies by less than 15% between these two areas. To better understand the behaviour of this complex plate boundary, we use geodesy to map the spatial distribution of the deformation. In this paper, we focus on southeast France, a tectonic crossroads between three different domains (Alps, Ligurian Sea, and Massif Central) which exhibits a moderate level of seismicity. Here, the geodetic measurements imply low rates of horizontal deformation. By combining historical triangulation measurements mostly from 1947 to 1983 with Global Positioning System (GPS) surveys in 1993 and 1994, we estimate the rate of angular shear in triangular subnetworks covering the study area. The estimated strain rates in thirteen of nineteen triangles are smaller than their (1 standard deviation) uncertainties of about 0.1 microradian/yr. This value bounds the rate of deformation for a 100-km wide zone in Provence, between Marseilles to the south and the Ventoux massif to the north. The geodetic estimates place an upper bound of 1 to 2 mm/yr on the slip rates of two seismically active structures, the Durance fault and the Nı̂mes fault, assuming a fault zone ˜20 km wide in each case. We also find strain rates as high as 0.20±0.07 microradian/yr in three subnetworks near the epicentre of the magnitude 5.3 Haute-Ubaye earthquake in 1959, in a region which includes the higher summits. This may be interpreted either as pure shear with compression oriented NE-SW across this region or right-lateral simple shear along NNW-SSE-trending faults. Given that this earthquake is

  4. The effect of the neural activity on topological properties of growing neural networks.

    PubMed

    Gafarov, F M; Gafarova, V R

    2016-09-01

    The connectivity structure in cortical networks defines how information is transmitted and processed, and it is a source of the complex spatiotemporal patterns of network's development, and the process of creation and deletion of connections is continuous in the whole life of the organism. In this paper, we study how neural activity influences the growth process in neural networks. By using a two-dimensional activity-dependent growth model we demonstrated the neural network growth process from disconnected neurons to fully connected networks. For making quantitative investigation of the network's activity influence on its topological properties we compared it with the random growth network not depending on network's activity. By using the random graphs theory methods for the analysis of the network's connections structure it is shown that the growth in neural networks results in the formation of a well-known "small-world" network.

  5. DORIS data analysis at Geodetic Observatory Pecný using single-satellite and multi-satellite geodetic solutions

    NASA Astrophysics Data System (ADS)

    Štěpánek, Petr; Douša, Jan; Filler, Vratislav; Hugentobler, Urs

    2010-12-01

    The DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) data are processed in the framework of the International DORIS Service (IDS) at several analysis centers. Each analysis center follows its own processing strategy and models. This manuscript presents the results of the processing based on a development version 5.0 of the Bernese GPS Software at the Geodetic Observatory Pecný analysis center (GOP). The complete period 1993.0-2009.0 was processed applying the free-network approach in order to estimate main parameters namely station and polar motion coordinates. A significant improvement has been achieved in the estimated station coordinates and polar parameters by processing the data from the satellites equipped with the second generation of the DORIS receiver, SPOT-5 and Envisat, launched in 2002. The RMS of polar coordinates in 2003.0-2008.0 shows a decreasing trend over the entire analyzed time period. The transformation parameters between the DORIS solution and ITRF2005 were subjected to a spectral analysis, confirming the domination of the annual and semiannual periodicity. The behavior of the terrestrial reference frame scale is quite stable with a few exceptions. The analysis of a major scale shift at the end of 2004 revealed SPOT-5 and Envisat satellites as the source of the problem. However, the termination of the TOPEX/Poseidon DORIS data processing at the end of 2004 did not influence significantly the overall scale level. Another objective of the paper is a detailed analysis of relations between the value of the observation residuals and the length of the observation Doppler count interval. A simple empirical model considering the observation noise as a sum of the constant and time-dependent terms is propounded and discussed. The estimated troposphere total zenith delays are compared to the corresponding values derived from GNSS (IGS PPP products) and the source of the differences as well as their systematic behavior and

  6. An Autonomous, Low Cost Platform for Seafloor Geodetic Observations

    NASA Astrophysics Data System (ADS)

    Ericksen, T.; Foster, J. H.; Bingham, B. S.; Oshiro, J.

    2015-12-01

    The Pacific GPS Facility and the Field Robotics Laboratory at the University of Hawaii have developed an approach to significantly reduce the costs of accurately measuring short-term vertical motions of the seafloor and maintaining a continuous long-term record of seafloor pressure. Traditional ship-based methods of acquiring these measurements are often prohibitively expensive. Our goal has been to reduce the primary barrier preventing us from acquiring the observations we need to understand geodetic processes, and the hazards they present, at subduction zones, submarine volcanoes, and subsea landslides. To this end, we have designed a payload package for the University of Hawaii Wave Glider which incorporates an acoustic telemetry package, a dual frequency geodetic-grade Global Positioning System (GPS) receiver, meteorological sensors, processing computer, and cellular communications. The Wave Glider is able to interrogate high accuracy pressure sensors on the seafloor to maintain a near-continuous stream of ocean bottom pressure and temperature data. The Wave Glider also functions as an integral part of the seafloor geodetic observing system, recording accurate sea surface elevations and barometric pressure; direct measurements of two of the primary sources of seafloor pressure change. The seafloor geodetic monument seats a sensor capable of recording pressure, temperature, and sound velocity for a deployment duration of over 5 years with an acoustic modem for communications, and an integral acoustic release for recovery and replacement of batteries. The design of the geodetic monument allows for precise repositioning of the sensor to extend the pressure record beyond a single 5+ year deployment, and includes the capability to install a mobile pressure recorder for calibration of the linear drift of the continuous pressure sensor. We will present the results of our field tests and an assessment of our ability to determine cm-scale vertical seafloor motions by

  7. Structural damage detection using active members and neural networks

    NASA Astrophysics Data System (ADS)

    Manning, R. A.

    1994-06-01

    The detection of damage in structures is a topic which has considerable interest in many fields. In the past many methods for detecting damage in structures has relied on finite element model refinement methods. This note presents a structural damage methodology in which only active member transfer function data are used in conjunction with an artificial neural network to detect damage in structures. Specifically, the method relies on training a neural network using active member transfer function pole/zero information to classify damaged structure measurements and to predict the degree of damage in the structure. The method differs from many of the past damage detection algorithms in that no attempt is made to update a finite element model or to match measured data with new finite element analyses of the structure in a damaged state.

  8. Broken Detailed Balance of Filament Dynamics in Active Networks

    NASA Astrophysics Data System (ADS)

    Gladrow, J.; Fakhri, N.; MacKintosh, F. C.; Schmidt, C. F.; Broedersz, C. P.

    2016-06-01

    Myosin motor proteins drive vigorous steady-state fluctuations in the actin cytoskeleton of cells. Endogenous embedded semiflexible filaments such as microtubules, or added filaments such as single-walled carbon nanotubes are used as novel tools to noninvasively track equilibrium and nonequilibrium fluctuations in such biopolymer networks. Here, we analytically calculate shape fluctuations of semiflexible probe filaments in a viscoelastic environment, driven out of equilibrium by motor activity. Transverse bending fluctuations of the probe filaments can be decomposed into dynamic normal modes. We find that these modes no longer evolve independently under nonequilibrium driving. This effective mode coupling results in nonzero circulatory currents in a conformational phase space, reflecting a violation of detailed balance. We present predictions for the characteristic frequencies associated with these currents and investigate how the temporal signatures of motor activity determine mode correlations, which we find to be consistent with recent experiments on microtubules embedded in cytoskeletal networks.

  9. Multiscale Transient Signal Detection: Localizing Transients in Geodetic Data Through Wavelet Transforms and Sparse Estimation Techniques

    NASA Astrophysics Data System (ADS)

    Riel, B.; Simons, M.; Agram, P.

    2012-12-01

    Transients are a class of deformation signals on the Earth's surface that can be described as non-periodic accumulation of strain in the crust. Over seismically and volcanically active regions, these signals are often challenging to detect due to noise and other modes of deformation. Geodetic datasets that provide precise measurements of surface displacement over wide areas are ideal for exploiting both the spatial and temporal coherence of transient signals. We present an extension to the Multiscale InSAR Time Series (MInTS) approach for analyzing geodetic data by combining the localization benefits of wavelet transforms (localizing signals in space) with sparse optimization techniques (localizing signals in time). Our time parameterization approach allows us to reduce geodetic time series to sparse, compressible signals with very few non-zero coefficients corresponding to transient events. We first demonstrate the temporal transient detection by analyzing GPS data over the Long Valley caldera in California and along the San Andreas fault near Parkfield, CA. For Long Valley, we are able to resolve the documented 2002-2003 uplift event with greater temporal precision. Similarly for Parkfield, we model the postseismic deformation by specific integrated basis splines characterized by timescales that are largely consistent with postseismic relaxation times. We then apply our method to ERS and Envisat InSAR datasets consisting of over 200 interferograms for Long Valley and over 100 interferograms for Parkfield. The wavelet transforms reduce the impact of spatially correlated atmospheric noise common in InSAR data since the wavelet coefficients themselves are essentially uncorrelated. The spatial density and extended temporal coverage of the InSAR data allows us to effectively localize ground deformation events in both space and time with greater precision than has been previously accomplished.

  10. Transform Faults and Lithospheric Structure: Insights from Numerical Models and Shipboard and Geodetic Observations

    NASA Astrophysics Data System (ADS)

    Takeuchi, Christopher S.

    In this dissertation, I study the influence of transform faults on the structure and deformation of the lithosphere, using shipboard and geodetic observations as well as numerical experiments. I use marine topography, gravity, and magnetics to examine the effects of the large age-offset Andrew Bain transform fault on accretionary processes within two adjacent segments of the Southwest Indian Ridge. I infer from morphology, high gravity, and low magnetization that the extremely cold and thick lithosphere associated with the Andrew Bain strongly suppresses melt production and crustal emplacement to the west of the transform fault. These effects are counteracted by enhanced temperature and melt production near the Marion Hotspot, east of the transform fault. I use numerical models to study the development of lithospheric shear zones underneath continental transform faults (e.g. the San Andreas Fault in California), with a particular focus on thermomechanical coupling and shear heating produced by long-term fault slip. I find that these processes may give rise to long-lived localized shear zones, and that such shear zones may in part control the magnitude of stress in the lithosphere. Localized ductile shear participates in both interseismic loading and postseismic relaxation, and predictions of models including shear zones are within observational constraints provided by geodetic and surface heat flow data. I numerically investigate the effects of shear zones on three-dimensional postseismic deformation. I conclude that the presence of a thermally-activated shear zone minimally impacts postseismic deformation, and that thermomechanical coupling alone is unable to generate sufficient localization for postseismic relaxation within a ductile shear zone to kinematically resemble that by aseismic fault creep (afterslip). I find that the current record geodetic observations of postseismic deformation do not provide robust discriminating power between candidate linear and

  11. A proposed concept for a crustal dynamics information management network

    NASA Technical Reports Server (NTRS)

    Lohman, G. M.; Renfrow, J. T.

    1980-01-01

    The findings of a requirements and feasibility analysis of the present and potential producers, users, and repositories of space-derived geodetic information are summarized. A proposed concept is presented for a crustal dynamics information management network that would apply state of the art concepts of information management technology to meet the expanding needs of the producers, users, and archivists of this geodetic information.

  12. NOS/NGS activities to support development of radio interferometric surveying techniques

    NASA Technical Reports Server (NTRS)

    Carter, W. E.; Dracup, J. F.; Hothem, L. D.; Robertson, D. S.; Strange, W. E.

    1980-01-01

    National Geodetic Survey activities towards the development of operational geodetic survey systems based on radio interferometry are reviewed. Information about the field procedures, data reduction and analysis, and the results obtained to date is presented.

  13. An Assessment of Overt Malicious Activity Manifest in Residential Networks

    DTIC Science & Technology

    2011-07-07

    also monitor for network-level signatures aimed at detecting three malware families, Zlob, Conficker, and Zeus . To take advantage of the long...compromise by flagging activity related to known malware families. To do so, we focused on Zlob, Conficker, and Zeus . The Zlob malware family [24] changes... Zeus Domainblocklist [25] to identify local systems infected with Zeus . Since the list does not only contain seemingly random domain names but also

  14. Local Jurisdictions and Active Shooters: Building Networks, Building Capacities

    DTIC Science & Technology

    2010-12-01

    AND ACTIVE SHOOTERS: BUILDING NETWORKS, BUILDING CAPACITIES by Tracy L. Frazzano December 2010 Thesis Advisors: Sam Clovis , Jr...SCHOOL December 2010 Author: Tracy L. Frazzano Approved by: Sam H. Clovis ., Jr. Thesis Advisor Lauren Fernandez Co-Advisor...thesis in and of itself, so I will try and limit it as best I can. To my advisors, Lauren Fernandez and Samuel Clovis , I would like to thank you for

  15. Ultrananocrystalline diamond thin films functionalized with therapeutically active collagen networks.

    SciTech Connect

    Huang, H.; Chen, M.; Bruno, P.; Lam, R.; Robinson, E.; Gruen, D.; Ho, D.; Materials Science Division; Northwestern Univ.

    2009-01-01

    The fabrication of biologically amenable interfaces in medicine bridges translational technologies with their surrounding biological environment. Functionalized nanomaterials catalyze this coalescence through the creation of biomimetic and active substrates upon which a spectrum of therapeutic elements can be delivered to adherent cells to address biomolecular processes in cancer, inflammation, etc. Here, we demonstrate the robust functionalization of ultrananocrystalline diamond (UNCD) with type I collagen and dexamethasone (Dex), an anti-inflammatory drug, to fabricate a hybrid therapeutically active substrate for localized drug delivery. UNCD oxidation coupled with a pH-mediated collagen adsorption process generated a comprehensive interface between the two materials, and subsequent Dex integration, activity, and elution were confirmed through inflammatory gene expression assays. These studies confer a translational relevance to the biofunctionalized UNCD in its role as an active therapeutic network for potent regulation of cellular activity toward applications in nanomedicine.

  16. Energy-aware activity classification using wearable sensor networks

    NASA Astrophysics Data System (ADS)

    Dong, Bo; Montoye, Alexander; Moore, Rebecca; Pfeiffer, Karin; Biswas, Subir

    2013-05-01

    This paper presents implementation details, system characterization, and the performance of a wearable sensor network that was designed for human activity analysis. Specific machine learning mechanisms are implemented for recognizing a target set of activities with both out-of-body and on-body processing arrangements. Impacts of energy consumption by the on-body sensors are analyzed in terms of activity detection accuracy for out-of-body processing. Impacts of limited processing abilities for the on-body scenario are also characterized in terms of detection accuracy, by varying the background processing load in the sensor units. Impacts of varying number of sensors in terms of activity classification accuracy are also evaluated. Through a rigorous systems study, it is shown that an efficient human activity analytics system can be designed and operated even under energy and processing constraints of tiny on-body wearable sensors.

  17. Energy-aware Activity Classification using Wearable Sensor Networks

    PubMed Central

    Dong, Bo; Montoye, Alexander; Moore, Rebecca; Pfeiffer, Karin; Biswas, Subir

    2014-01-01

    This paper presents implementation details, system characterization, and the performance of a wearable sensor network that was designed for human activity analysis. Specific machine learning mechanisms are implemented for recognizing a target set of activities with both out-of-body and on-body processing arrangements. Impacts of energy consumption by the on-body sensors are analyzed in terms of activity detection accuracy for out-of-body processing. Impacts of limited processing abilities for the on-body scenario are also characterized in terms of detection accuracy, by varying the background processing load in the sensor units. Impacts of varying number of sensors in terms of activity classification accuracy are also evaluated. Through a rigorous systems study, it is shown that an efficient human activity analytics system can be designed and operated even under energy and processing constraints of tiny on-body wearable sensors. PMID:25075266

  18. Network feedback regulates motor output across a range of modulatory neuron activity.

    PubMed

    Spencer, Robert M; Blitz, Dawn M

    2016-06-01

    Modulatory projection neurons alter network neuron synaptic and intrinsic properties to elicit multiple different outputs. Sensory and other inputs elicit a range of modulatory neuron activity that is further shaped by network feedback, yet little is known regarding how the impact of network feedback on modulatory neurons regulates network output across a physiological range of modulatory neuron activity. Identified network neurons, a fully described connectome, and a well-characterized, identified modulatory projection neuron enabled us to address this issue in the crab (Cancer borealis) stomatogastric nervous system. The modulatory neuron modulatory commissural neuron 1 (MCN1) activates and modulates two networks that generate rhythms via different cellular mechanisms and at distinct frequencies. MCN1 is activated at rates of 5-35 Hz in vivo and in vitro. Additionally, network feedback elicits MCN1 activity time-locked to motor activity. We asked how network activation, rhythm speed, and neuron activity levels are regulated by the presence or absence of network feedback across a physiological range of MCN1 activity rates. There were both similarities and differences in responses of the two networks to MCN1 activity. Many parameters in both networks were sensitive to network feedback effects on MCN1 activity. However, for most parameters, MCN1 activity rate did not determine the extent to which network output was altered by the addition of network feedback. These data demonstrate that the influence of network feedback on modulatory neuron activity is an important determinant of network output and feedback can be effective in shaping network output regardless of the extent of network modulation.

  19. Geodetic subsidence rate in coastal Louisiana

    NASA Astrophysics Data System (ADS)

    Abdollahzadeh, M.; Dixon, T. H.; Malservisi, R.

    2013-12-01

    Southern coastal Louisiana is experiencing significant subsidence, leading to land loss and increasing the risk of storm-related flooding. Several processes contribute to this subsidence, with differing spatial and temporal variations. Here we report on regional subsidence as measured by a network of continuously recording, high precision GPS stations, and attempt to characterize it. Our results show that the short-term subsidence rate of parts of the Mississippi delta is considerably higher than surrounding coastal areas. Sediment compaction, low-angle faulting and regional subsidence associated with mass loading appear to be the major factors controlling subsidence in the delta. The coastal regions outside of the delta undergo slower subsidence, probably related to factors such as fluid withdrawal (ground water, petroleum and natural gas extraction).

  20. Geodetic measurement of deformation in the Ventura basin region, southern California

    NASA Technical Reports Server (NTRS)

    Donnellan, Andrea; Hager, Bradford H.; King, Robert W.; Herring, Thomas A.

    1993-01-01

    We have measured the deformation in the Ventura basin region, southern California, with Global Positioning System (GPS) measurements carried out over 4.6 years between 1987 and 1992. The deformation within our network is spatically variable on scales of tens of kilometers, with strain rates reaching 0.6 +/- 1 micro-rad/yr in the east-central basin. Blocklike rotations are observed south and northwest of the basin where the maximum shear strain rates are an order of magnitude lower (0.06 +/- 1 micro-rad/yr to the south). We also observed clockwise rotations of 1 deg - 7 deg/m.y. Shear strain rates determined by comparing angle changes from historical triangulation spanning several decades and GPS measurements give consistent, though less precise, results. The geodetic rates of shortening across the basin and Western Transverse Ranges are lower than those estimated from geological observations, but the patterns of deformation from the two methods agree qualitatively.

  1. The geodetic signature of the M8.0 Oct. 9, 1995, Jalisco subduction earthquake

    USGS Publications Warehouse

    Melbourne, T.; Carmichael, I.; DeMets, C.; Hudnut, K.; Sanchez, O.; Stock, J.; Suarez, G.; Webb, F.

    1997-01-01

    The October, 1995 Mw 8.0 Jalisco subduction earthquake has provided a thorough geodetic observation of the coseismic subduction process. An 11 station regional GPS network located directly onshore of the rupture demonstrates consistent vertical subsidence verified by tide gauge data and southwest-directed extension, with measured displacements reaching 1 meter. Unusually shallow and non-uniform faulting is required to explain the displacements. We determine that up to 5 meters of slip occurred within the upper 15 km of the thrust fault zone and 2 meters possibly as shallow as 8 km, and that slip was likely distributed in two main patches. The paucity of continental sediments in this subduction zone could be responsible for the anomalously shallow faulting.

  2. Geodetic measurement of deformation in the Ventura basin region, southern California

    SciTech Connect

    Donnellan, A.; Hager, B.H.; King, R.W.; Herring, T.A. |

    1993-12-01

    We have measured the deformation in the Ventura basin region, southern California, with Global Positioning System (GPS) measurements carried out over 4.6 years between 1987 and 1992. The deformation within our network is spatically variable on scales of tens of kilometers, with strain rates reaching 0.6 +/- 1 micro-rad/yr in the east-central basin. Blocklike rotations are observed south and northwest of the basin where the maximum shear strain rates are an order of magnitude lower (0.06 +/- 1 micro-rad/yr to the south). We also observed clockwise rotations of 1 deg - 7 deg/m.y. Shear strain rates determined by comparing angle changes from historical triangulation spanning several decades and GPS measurements give consistent, though less precise, results. The geodetic rates of shortening across the basin and Western Transverse Ranges are lower than those estimated from geological observations, but the patterns of deformation from the two methods agree qualitatively.

  3. A study of epidemic spreading on activity-driven networks

    NASA Astrophysics Data System (ADS)

    Zou, Yijiang; Deng, Weibing; Li, Wei; Cai, Xu

    2016-03-01

    The epidemic spreading was explored on activity-driven networks (ADNs), accounting for the study of dynamics both on and of the ADN. By employing the susceptible-infected-susceptible (SIS) model, two aspects were considered: (1) the infection rate of susceptible agent (depending on the number of its infected neighbors) evolves due to the temporal structure of ADN, rather than being a constant number; (2) the susceptible and infected agents generate unequal links while being activated, namely, the susceptible agent gets few contacts with others in order to protect itself. Results show that, in both cases, the larger epidemic threshold and smaller outbreak size were obtained.

  4. Multivariate neural network operators with sigmoidal activation functions.

    PubMed

    Costarelli, Danilo; Spigler, Renato

    2013-12-01

    In this paper, we study pointwise and uniform convergence, as well as order of approximation, of a family of linear positive multivariate neural network (NN) operators with sigmoidal activation functions. The order of approximation is studied for functions belonging to suitable Lipschitz classes and using a moment-type approach. The special cases of NN operators, activated by logistic, hyperbolic tangent, and ramp sigmoidal functions are considered. Multivariate NNs approximation finds applications, typically, in neurocomputing processes. Our approach to NN operators allows us to extend previous convergence results and, in some cases, to improve the order of approximation. The case of multivariate quasi-interpolation operators constructed with sigmoidal functions is also considered.

  5. Using Active Networking to Detect and Troubleshoot Issues in Tactical Data Networks

    DTIC Science & Technology

    2014-06-01

    MASTER OF SCIENCE IN SYSTEMS TECHNOLOGY (COMMAND, CONTROL, AND COMMUNICATIONS) from the NAVAL POSTGRADUATE SCHOOL June 2014 Author: Kevin McMullen...Style Sheets D3 Data-Driven Documents DOM Document Object Model EKMS Electronic Key Management System FDDI Fiber Distributed Data Interface FIPS Federal...Enduring Freedom OSI open systems interconnection PLAN Programming Language for Active Networks PPP Point-to-Point Protocol RCT regimental combat

  6. Tera-node Network Technology (TASK 4) Network Infrastructure Activities (NIA) final report

    SciTech Connect

    Postel, John; Bannister, Joe

    2000-03-15

    The TNT project developed software technologies in scalable personal telecommunications (SPT), Reservation Protocol 2 (RSVP2), Scalable Computing Infrastructure (SCOPE), and Network Infrastructure Activities (NIA). SPT = developed many innovative protocols to support the use of videoconferencing applications on the Internet. RSVP2 = developed a new reference model and further standardization of RSVP. SCOPE = developed dynamic resource discovery techniques and distributed directory services in support of resource allocation for large distributed systems and computations. NIA = provided policy, operational, and support to the transitioning Internet.

  7. Geodetic positioning using a global positioning system of satellites

    NASA Technical Reports Server (NTRS)

    Fell, P. J.

    1980-01-01

    Geodetic positioning using range, integrated Doppler, and interferometric observations from a constellation of twenty-four Global Positioning System satellites is analyzed. A summary of the proposals for geodetic positioning and baseline determination is given which includes a description of measurement techniques and comments on rank deficiency and error sources. An analysis of variance comparison of range, Doppler, and interferometric time delay to determine their relative geometric strength for baseline determination is included. An analytic examination to the effect of a priori constraints on positioning using simultaneous observations from two stations is presented. Dynamic point positioning and baseline determination using range and Doppler is examined in detail. Models for the error sources influencing dynamic positioning are developed. Included is a discussion of atomic clock stability, and range and Doppler observation error statistics based on random correlated atomic clock error are derived.

  8. Cartografical And Geodetical Aspects Of The Krakus Mound In Cracow

    NASA Astrophysics Data System (ADS)

    Banasik, Piotr

    2015-12-01

    In this work the fate of the Krakus Mound, the oldest of all existing Krakow's mounds, has been presented. The work was carried out based on selected iconographic, cartographic and geodetic documents. Using as an example old views, panoramas of the city and maps, various functions that the Krakus Mound was fulfilling over its long history were shown. An attempt was made to document the military significance of this mound and the surrounding hills. The particular astro-geodetic importance of the Krakus Mound on the scale of the city and southern Poland region was widely discussed. The Krakus Mound also inscribed itself in the history of the use of GPS technology as well as research on the local determination of the geoid in the area of Krakow.

  9. Monitoring of stability of ASG-EUPOS network coordinates

    NASA Astrophysics Data System (ADS)

    Figurski, M.; Szafranek, K.; Wrona, M.

    2009-04-01

    ASG-EUPOS (Active Geodetic Network - European Position Determination System) is the national system of precise satellite positioning in Poland, which increases a density of regional and global GNSS networks and is widely used by public administration, national institutions, entrepreneurs and citizens (especially surveyors). In near future ASG-EUPOS is to take role of main national network. Control of proper activity of stations and realization of ETRS'89 is a necessity. User of the system needs to be sure that observations quality and coordinates accuracy are high enough. Coordinates of IGS (International GNSS Service) and EPN (European Permanent Network) stations are precisely determined and any changes are monitored all the time. Observations are verified before they are archived in regional and global databases. The same applies to ASG-EUPOS. This paper concerns standardization of GNSS observations from different stations (uniform adjustment), examination of solutions correctness according to IGS and EPN standards and stability of solutions and sites activity

  10. A small change in neuronal network topology can induce explosive synchronization transition and activity propagation in the entire network.

    PubMed

    Wang, Zhenhua; Tian, Changhai; Dhamala, Mukesh; Liu, Zonghua

    2017-04-03

    We here study explosive synchronization transitions and network activity propagation in networks of coupled neurons to provide a new understanding of the relationship between network topology and explosive dynamical transitions as in epileptic seizures and their propagations in the brain. We model local network motifs and configurations of coupled neurons and analyze the activity propagations between a group of active neurons to their inactive neuron neighbors in a variety of network configurations. We find that neuronal activity propagation is limited to local regions when network is highly clustered with modular structures as in the normal brain networks. When the network cluster structure is slightly changed, the activity propagates to the entire network, which is reminiscent of epileptic seizure propagation in the brain. Finally, we analyze intracranial electroencephalography (IEEG) recordings of a seizure episode from a epilepsy patient and uncover that explosive synchronization-like transition occurs around the clinically defined onset of seizure. These findings may provide a possible mechanism for the recurrence of epileptic seizures, which are known to be the results of aberrant neuronal network structure and/or function in the brain.

  11. PersonA: Persuasive social network for physical Activity.

    PubMed

    Ayubi, Soleh U; Parmanto, Bambang

    2012-01-01

    Advances in physical activity (PA) monitoring devices provide ample opportunities for innovations in the way the information produced by these devices is used to encourage people to have more active lifestyles. One such innovation is expanding the current use of the information from self-management to social support. We developed a Persuasive social network for physical Activity (PersonA) that combines automatic input of physical activity data, a smartphone, and a social networking system (SNS). This paper describes the motivation for and overarching design of the PersonA and its functional and non-functional features. PersonA is designed to intelligently and automatically receive raw PA data from the sensors in the smartphone, calculate the data into meaningful PA information, store the information on a secure server, and show the information to the users as persuasive and real-time feedbacks or publish the information to the SNS to generate social support. The implementation of self-monitoring, social support, and persuasive concepts using currently available technologies has the potential for promoting healthy lifestyle, greater community participation, and higher quality of life. We also expect that PersonA will enable health professionals to collect in situ data related to physical activity. The platform is currently being used and tested to improve PA level of three groups of users in Pittsburgh, PA, USA.

  12. Taurine activates GABAergic networks in the neocortex of immature mice

    PubMed Central

    Sava, Bogdan A.; Chen, Rongqing; Sun, Haiyan; Luhmann, Heiko J.; Kilb, Werner

    2014-01-01

    Although it has been suggested that taurine is the main endogenous neurotransmitter acting on glycine receptors, the implications of glycine receptor-mediated taurine actions on immature neocortical networks have not been addressed yet. To investigate the influence of taurine on the excitability of neuronal networks in the immature neocortex, we performed whole-cell patch-clamp recordings from visually identified pyramidal neurons and interneurons in coronal slices from C57Bl/6 and GAD67-green fluorescent protein (GFP) transgenic mice (postnatal days 2–4). In 46% of the pyramidal neurons bath-application of taurine at concentrations ≥ 300 μM significantly enhanced the frequency of postsynaptic currents (PSCs) by 744.3 ± 93.8% (n = 120 cells). This taurine-induced increase of PSC frequency was abolished by 0.2 μM tetrodotoxin (TTX), 1 μM strychnine or 3 μM gabazine, but was unaffected by the glutamatergic antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and (±) R(-)-3-(2-carboxypiperazine-4-yl)-propyl-1-phosphonic acid (CPP), suggesting that taurine specifically activates GABAergic network activity projecting to pyramidal neurons. Cell-attached recordings revealed that taurine enhanced the frequency of action potentials (APs) in pyramidal neurons, indicating an excitatory action of the GABAergic PSCs. In order to identify the presynaptic targets of taurine we demonstrate that bath application of taurine induced in GAD67-GFP labeled interneurons an inward current that is mainly mediated by glycine receptors and can generate APs in these cells. We conclude from these results that taurine can enhance network excitability in the immature neocortex by selectively activating GABAergic interneurons via interactions with glycine receptors. PMID:24550782

  13. Geodetic Observatory Wettzell - 20-m Radio Telescope and Twin Telescope

    NASA Technical Reports Server (NTRS)

    Neidhardt, Alexander; Kronschnabl, Gerhard; Schatz, Raimund

    2013-01-01

    In the year 2012, the 20-m radio telescope at the Geodetic Observatory Wettzell, Germany again contributed very successfully to the International VLBI Service for Geodesy and Astrometry observing program. Technical changes, developments, improvements, and upgrades were made to increase the reliability of the entire VLBI observing system. In parallel, the new Twin radio telescope Wettzell (TTW) got the first feedhorn, while the construction of the HF-receiving and the controlling system was continued.

  14. Extracting Independent Local Oscillatory Geophysical Signals by Geodetic Tropospheric Delay

    NASA Technical Reports Server (NTRS)

    Botai, O. J.; Combrinck, L.; Sivakumar, V.; Schuh, H.; Bohm, J.

    2010-01-01

    Zenith Tropospheric Delay (ZTD) due to water vapor derived from space geodetic techniques and numerical weather prediction simulated-reanalysis data exhibits non-linear and non-stationary properties akin to those in the crucial geophysical signals of interest to the research community. These time series, once decomposed into additive (and stochastic) components, have information about the long term global change (the trend) and other interpretable (quasi-) periodic components such as seasonal cycles and noise. Such stochastic component(s) could be a function that exhibits at most one extremum within a data span or a monotonic function within a certain temporal span. In this contribution, we examine the use of the combined Ensemble Empirical Mode Decomposition (EEMD) and Independent Component Analysis (ICA): the EEMD-ICA algorithm to extract the independent local oscillatory stochastic components in the tropospheric delay derived from the European Centre for Medium-Range Weather Forecasts (ECMWF) over six geodetic sites (HartRAO, Hobart26, Wettzell, Gilcreek, Westford, and Tsukub32). The proposed methodology allows independent geophysical processes to be extracted and assessed. Analysis of the quality index of the Independent Components (ICs) derived for each cluster of local oscillatory components (also called the Intrinsic Mode Functions (IMFs)) for all the geodetic stations considered in the study demonstrate that they are strongly site dependent. Such strong dependency seems to suggest that the localized geophysical signals embedded in the ZTD over the geodetic sites are not correlated. Further, from the viewpoint of non-linear dynamical systems, four geophysical signals the Quasi-Biennial Oscillation (QBO) index derived from the NCEP/NCAR reanalysis, the Southern Oscillation Index (SOI) anomaly from NCEP, the SIDC monthly Sun Spot Number (SSN), and the Length of Day (LoD) are linked to the extracted signal components from ZTD. Results from the synchronization

  15. Crowdsourced Contributions to the Nation's Geodetic Elevation Infrastructure

    NASA Astrophysics Data System (ADS)

    Stone, W. A.

    2014-12-01

    NOAA's National Geodetic Survey (NGS), a United States Department of Commerce agency, is engaged in providing the nation's fundamental positioning infrastructure - the National Spatial Reference System (NSRS) - which includes the framework for latitude, longitude, and elevation determination as well as various geodetic models, tools, and data. Capitalizing on Global Navigation Satellite System (GNSS) technology for improved access to the nation's precise geodetic elevation infrastructure requires use of a geoid model, which relates GNSS-derived heights (ellipsoid heights) with traditional elevations (orthometric heights). NGS is facilitating the use of crowdsourced GNSS observations collected at published elevation control stations by the professional surveying, geospatial, and scientific communities to help improve NGS' geoid modeling capability. This collocation of published elevation data and newly collected GNSS data integrates together the two height systems. This effort in turn supports enhanced access to accurate elevation information across the nation, thereby benefiting all users of geospatial data. By partnering with the public in this collaborative effort, NGS is not only helping facilitate improvements to the elevation infrastructure for all users but also empowering users of NSRS with the capability to do their own high-accuracy positioning. The educational outreach facet of this effort helps inform the public, including the scientific community, about the utility of various NGS tools, including the widely used Online Positioning User Service (OPUS). OPUS plays a key role in providing user-friendly and high accuracy access to NSRS, with optional sharing of results with NGS and the public. All who are interested in helping evolve and improve the nationwide elevation determination capability are invited to participate in this nationwide partnership and to learn more about the geodetic infrastructure which is a vital component of viable spatial data for

  16. Plate motions and deformations from geologic and geodetic data

    NASA Technical Reports Server (NTRS)

    Jordan, T. H.

    1986-01-01

    A satellite laser ranging experiment conducted by NASA since 1972 has measured the relative motion between the North America and Pacific plates in California. Based on these measurements, the 896-km distance between San Diego and Quincy, California, is shortening at 62 + or - 9 mm/yr. This geodetic estimate is consistent with the rate of motion between the two plates, calculated from geological data to be 53 + or - 3 mm/yr averaged over the past few million years.

  17. Plate motions and deformations from geologic and geodetic data

    NASA Astrophysics Data System (ADS)

    Jordan, T. H.

    A satellite laser ranging experiment conducted by NASA since 1972 has measured the relative motion between the North America and Pacific plates in California. Based on these measurements, the 896-km distance between San Diego and Quincy, California, is shortening at 62 + or - 9 mm/yr. This geodetic estimate is consistent with the rate of motion between the two plates, calculated from geological data to be 53 + or - 3 mm/yr averaged over the past few million years.

  18. A Consistent Geodetic Reference System for GPS (Global Positioning System).

    DTIC Science & Technology

    1987-02-27

    reliable and accurate Operational Control System (OCS) is a prerequisite for successful Global Positioning System ( GPS ) navigation performance. The OCS...DDOR Doubly differenced (between station pair and Navstar pair) phase data GPS Global Positioning System MIT Massachusetts Institute of Technology...FWft SOTR4as-2 A Consistent Geodetic Reference System for GPS A. S. LIU Systems and Computer Engineering Division Engineering Group The Aerospace

  19. Geodetic antenna calibration test in the Antarctic environment

    USGS Publications Warehouse

    Grejner-Brzezinska, A.; Vazquez, E.; Hothem, L.

    2006-01-01

    TransAntarctic Mountain DEFormation (TAMDEF) Monitoring Network is the NSF-sponsored OSU and USGS project, aimed at measuring crustal motion in the Transantarctic Mountains of Victoria Land using GPS carrier phase measurements. Station monumentation, antenna mounts, antenna types, and data processing strategies were optimized to achieve mm-level estimates for the rates of motion. These data contributes also to regional Antarctic frame definition. Significant amount of data collected over several years allow the investigation of unique aspects of GPS geodesy in Antarctica, to determine how the error spectrum compares to the mid-latitude regions, and to identify the optimum measurement and data processing schemes for Antarctic conditions, in order to test the predicted rates of motion (mm-level w.r.t. time). The data collection for the TAMDEF project was initiated in 1996. The primary antenna used has been the Ashtech L1/L2 Dorne Margolin (D/M) choke ring. A few occupations involved the use of a Trimble D/M choke ring. The data were processed using the antenna calibration data available from the National Geodetic Survey (NGS). The recent developments in new antenna designs that are lighter in weight and lower in cost are being considered as a possible alternative to the bulkier and more expensive D/M choke ring design. In November 2003, in situ testing of three alternative models of L1/L2 antennas was conducted at a site located in the vicinity of McMurdo Station, Antarctica (S77.87, E166.56). The antenna models used in this test were: Ashtech D/M choke ring, Trimble D/M choke ring, Trimble Zephyr, and the NovAtel GPS-702. Two stations, spaced within 30 meters, were used in the test. Both had the characteristics similar to the stations of the TAMDEF network, i.e., the UNAVCO fixed-height, force-centered level mounts with a constant antenna offset were used, ensuring extreme stability of the antenna/ mount/pin set up. During each of the four 3-day test data collection

  20. The Contribution of Raised Intraneuronal Chloride to Epileptic Network Activity

    PubMed Central

    Alfonsa, Hannah; Merricks, Edward M.; Codadu, Neela K.; Cunningham, Mark O.; Deisseroth, Karl; Racca, Claudia

    2015-01-01

    Altered inhibitory function is an important facet of epileptic pathology. A key concept is that GABAergic activity can become excitatory if intraneuronal chloride rises. However, it has proved difficult to separate the role of raised chloride from other contributory factors in complex network phenomena, such as epileptic pathology. Therefore, we asked what patterns of activity are associated with chloride dysregulation by making novel use of Halorhodopsin to load clusters of mouse pyramidal cells artificially with Cl−. Brief (1–10 s) activation of Halorhodopsin caused substantial positive shifts in the GABAergic reversal potential that were proportional to the charge transfer during the illumination and in adult neocortical pyramidal neurons decayed with a time constant of τ = 8.0 ± 2.8s. At the network level, these positive shifts in EGABA produced a transient rise in network excitability, with many distinctive features of epileptic foci, including high-frequency oscillations with evidence of out-of-phase firing (Ibarz et al., 2010). We show how such firing patterns can arise from quite small shifts in the mean intracellular Cl− level, within heterogeneous neuronal populations. Notably, however, chloride loading by itself did not trigger full ictal events, even with additional electrical stimulation to the underlying white matter. In contrast, when performed in combination with low, subepileptic levels of 4-aminopyridine, Halorhodopsin activation rapidly induced full ictal activity. These results suggest that chloride loading has at most an adjunctive role in ictogenesis. Our simulations also show how chloride loading can affect the jitter of action potential timing associated with imminent recruitment to an ictal event (Netoff and Schiff, 2002). PMID:25995461

  1. Application of neural networks to seismic active control

    SciTech Connect

    Tang, Yu

    1995-07-01

    An exploratory study on seismic active control using an artificial neural network (ANN) is presented in which a singledegree-of-freedom (SDF) structural system is controlled by a trained neural network. A feed-forward neural network and the backpropagation training method are used in the study. In backpropagation training, the learning rate is determined by ensuring the decrease of the error function at each training cycle. The training patterns for the neural net are generated randomly. Then, the trained ANN is used to compute the control force according to the control algorithm. The control strategy proposed herein is to apply the control force at every time step to destroy the build-up of the system response. The ground motions considered in the simulations are the N21E and N69W components of the Lake Hughes No. 12 record that occurred in the San Fernando Valley in California on February 9, 1971. Significant reduction of the structural response by one order of magnitude is observed. Also, it is shown that the proposed control strategy has the ability to reduce the peak that occurs during the first few cycles of the time history. These promising results assert the potential of applying ANNs to active structural control under seismic loads.

  2. Beyond Statistical Significance: Implications of Network Structure on Neuronal Activity

    PubMed Central

    Vlachos, Ioannis; Aertsen, Ad; Kumar, Arvind

    2012-01-01

    It is a common and good practice in experimental sciences to assess the statistical significance of measured outcomes. For this, the probability of obtaining the actual results is estimated under the assumption of an appropriately chosen null-hypothesis. If this probability is smaller than some threshold, the results are deemed statistically significant and the researchers are content in having revealed, within their own experimental domain, a “surprising” anomaly, possibly indicative of a hitherto hidden fragment of the underlying “ground-truth”. What is often neglected, though, is the actual importance of these experimental outcomes for understanding the system under investigation. We illustrate this point by giving practical and intuitive examples from the field of systems neuroscience. Specifically, we use the notion of embeddedness to quantify the impact of a neuron's activity on its downstream neurons in the network. We show that the network response strongly depends on the embeddedness of stimulated neurons and that embeddedness is a key determinant of the importance of neuronal activity on local and downstream processing. We extrapolate these results to other fields in which networks are used as a theoretical framework. PMID:22291581

  3. Innovation diffusion on time-varying activity driven networks

    NASA Astrophysics Data System (ADS)

    Rizzo, Alessandro; Porfiri, Maurizio

    2016-01-01

    Since its introduction in the 1960s, the theory of innovation diffusion has contributed to the advancement of several research fields, such as marketing management and consumer behavior. The 1969 seminal paper by Bass [F.M. Bass, Manag. Sci. 15, 215 (1969)] introduced a model of product growth for consumer durables, which has been extensively used to predict innovation diffusion across a range of applications. Here, we propose a novel approach to study innovation diffusion, where interactions among individuals are mediated by the dynamics of a time-varying network. Our approach is based on the Bass' model, and overcomes key limitations of previous studies, which assumed timescale separation between the individual dynamics and the evolution of the connectivity patterns. Thus, we do not hypothesize homogeneous mixing among individuals or the existence of a fixed interaction network. We formulate our approach in the framework of activity driven networks to enable the analysis of the concurrent evolution of the interaction and individual dynamics. Numerical simulations offer a systematic analysis of the model behavior and highlight the role of individual activity on market penetration when targeted advertisement campaigns are designed, or a competition between two different products takes place.

  4. Voluntary control of intracortical oscillations for reconfiguration of network activity

    PubMed Central

    Corlier, Juliana; Valderrama, Mario; Navarrete, Miguel; Lehongre, Katia; Hasboun, Dominique; Adam, Claude; Belaid, Hayat; Clémenceau, Stéphane; Baulac, Michel; Charpier, Stéphane; Navarro, Vincent; Le Van Quyen, Michel

    2016-01-01

    Voluntary control of oscillatory activity represents a key target in the self-regulation of brain function. Using a real-time closed-loop paradigm and simultaneous macro- and micro-electrode recordings, we studied the effects of self-induced intracortical oscillatory activity (4–8 Hz) in seven neurosurgical patients. Subjects learned to robustly and specifically induce oscillations in the target frequency, confirmed by increased oscillatory event density. We have found that the session-to-session variability in performance was explained by the functional long-range decoupling of the target area suggesting a training-induced network reorganization. Downstream effects on more local activities included progressive cross-frequency-coupling with gamma oscillations (30–120 Hz), and the dynamic modulation of neuronal firing rates and spike timing, indicating an improved temporal coordination of local circuits. These findings suggest that effects of voluntary control of intracortical oscillations can be exploited to specifically target plasticity processes to reconfigure network activity, with a particular relevance for memory function or skill acquisition. PMID:27808225

  5. Platelet Serotonin Transporter Function Predicts Default-Mode Network Activity

    PubMed Central

    Kasess, Christian H.; Meyer, Bernhard M.; Hofmaier, Tina; Diers, Kersten; Bartova, Lucie; Pail, Gerald; Huf, Wolfgang; Uzelac, Zeljko; Hartinger, Beate; Kalcher, Klaudius; Perkmann, Thomas; Haslacher, Helmuth; Meyer-Lindenberg, Andreas; Kasper, Siegfried; Freissmuth, Michael; Windischberger, Christian; Willeit, Matthäus; Lanzenberger, Rupert; Esterbauer, Harald; Brocke, Burkhard; Moser, Ewald; Sitte, Harald H.; Pezawas, Lukas

    2014-01-01

    Background The serotonin transporter (5-HTT) is abundantly expressed in humans by the serotonin transporter gene SLC6A4 and removes serotonin (5-HT) from extracellular space. A blood-brain relationship between platelet and synaptosomal 5-HT reuptake has been suggested, but it is unknown today, if platelet 5-HT uptake can predict neural activation of human brain networks that are known to be under serotonergic influence. Methods A functional magnetic resonance study was performed in 48 healthy subjects and maximal 5-HT uptake velocity (Vmax) was assessed in blood platelets. We used a mixed-effects multilevel analysis technique (MEMA) to test for linear relationships between whole-brain, blood-oxygen-level dependent (BOLD) activity and platelet Vmax. Results The present study demonstrates that increases in platelet Vmax significantly predict default-mode network (DMN) suppression in healthy subjects independent of genetic variation within SLC6A4. Furthermore, functional connectivity analyses indicate that platelet Vmax is related to global DMN activation and not intrinsic DMN connectivity. Conclusion This study provides evidence that platelet Vmax predicts global DMN activation changes in healthy subjects. Given previous reports on platelet-synaptosomal Vmax coupling, results further suggest an important role of neuronal 5-HT reuptake in DMN regulation. PMID:24667541

  6. Default-mode-like network activation in awake rodents.

    PubMed

    Upadhyay, Jaymin; Baker, Scott J; Chandran, Prasant; Miller, Loan; Lee, Younglim; Marek, Gerard J; Sakoglu, Unal; Chin, Chih-Liang; Luo, Feng; Fox, Gerard B; Day, Mark

    2011-01-01

    During wakefulness and in absence of performing tasks or sensory processing, the default-mode network (DMN), an intrinsic central nervous system (CNS) network, is in an active state. Non-human primate and human CNS imaging studies have identified the DMN in these two species. Clinical imaging studies have shown that the pattern of activity within the DMN is often modulated in various disease states (e.g., Alzheimer's, schizophrenia or chronic pain). However, whether the DMN exists in awake rodents has not been characterized. The current data provides evidence that awake rodents also possess 'DMN-like' functional connectivity, but only subsequent to habituation to what is initially a novel magnetic resonance imaging (MRI) environment as well as physical restraint. Specifically, the habituation process spanned across four separate scanning sessions (Day 2, 4, 6 and 8). At Day 8, significant (p<0.05) functional connectivity was observed amongst structures such as the anterior cingulate (seed region), retrosplenial, parietal, and hippocampal cortices. Prior to habituation (Day 2), functional connectivity was only detected (p<0.05) amongst CNS structures known to mediate anxiety (i.e., anterior cingulate (seed region), posterior hypothalamic area, amygdala and parabracial nucleus). In relating functional connectivity between cingulate-default-mode and cingulate-anxiety structures across Days 2-8, a significant inverse relationship (r = -0.65, p = 0.0004) was observed between these two functional interactions such that increased cingulate-DMN connectivity corresponded to decreased cingulate anxiety network connectivity. This investigation demonstrates that the cingulate is an important component of both the rodent DMN-like and anxiety networks.

  7. Pre-stimulus BOLD-network activation modulates EEG spectral activity during working memory retention.

    PubMed

    Kottlow, Mara; Schlaepfer, Anthony; Baenninger, Anja; Michels, Lars; Brandeis, Daniel; Koenig, Thomas

    2015-01-01

    Working memory (WM) processes depend on our momentary mental state and therefore exhibit considerable fluctuations. Here, we investigate the interplay of task-preparatory and task-related brain activity as represented by pre-stimulus BOLD-fluctuations and spectral EEG from the retention periods of a visual WM task. Visual WM is used to maintain sensory information in the brain enabling the performance of cognitive operations and is associated with mental health. We tested 22 subjects simultaneously with EEG and fMRI while performing a visuo-verbal Sternberg task with two different loads, allowing for the temporal separation of preparation, encoding, retention and retrieval periods. Four temporally coherent networks (TCNs)-the default mode network (DMN), the dorsal attention, the right and the left WM network-were extracted from the continuous BOLD data by means of a group ICA. Subsequently, the modulatory effect of these networks' pre-stimulus activation upon retention-related EEG activity in the theta, alpha, and beta frequencies was analyzed. The obtained results are informative in the context of state-dependent information processing. We were able to replicate two well-known load-dependent effects: the frontal-midline theta increase during the task and the decrease of pre-stimulus DMN activity. As our main finding, these two measures seem to depend on each other as the significant negative correlations at frontal-midline channels suggested. Thus, suppressed pre-stimulus DMN levels facilitated later task related frontal midline theta increases. In general, based on previous findings that neuronal coupling in different frequency bands may underlie distinct functions in WM retention, our results suggest that processes reflected by spectral oscillations during retention seem not only to be "online" synchronized with activity in different attention-related networks but are also modulated by activity in these networks during preparation intervals.

  8. Antituberculosis activity of the molecular libraries screening center network library.

    PubMed

    Maddry, Joseph A; Ananthan, Subramaniam; Goldman, Robert C; Hobrath, Judith V; Kwong, Cecil D; Maddox, Clinton; Rasmussen, Lynn; Reynolds, Robert C; Secrist, John A; Sosa, Melinda I; White, E Lucile; Zhang, Wei

    2009-09-01

    There is an urgent need for the discovery and development of new antitubercular agents that target novel biochemical pathways and treat drug-resistant forms of the disease. One approach to addressing this need is through high-throughput screening of drug-like small molecule libraries against the whole bacterium in order to identify a variety of new, active scaffolds that will stimulate additional biological research and drug discovery. Through the Molecular Libraries Screening Center Network, the NIAID Tuberculosis Antimicrobial Acquisition and Coordinating Facility tested a 215,110-compound library against Mycobacterium tuberculosis strain H37Rv. A medicinal chemistry survey of the results from the screening campaign is reported herein.

  9. Environmental Monitoring Networks Optimization Using Advanced Active Learning Algorithms

    NASA Astrophysics Data System (ADS)

    Kanevski, Mikhail; Volpi, Michele; Copa, Loris

    2010-05-01

    The problem of environmental monitoring networks optimization (MNO) belongs to one of the basic and fundamental tasks in spatio-temporal data collection, analysis, and modeling. There are several approaches to this problem, which can be considered as a design or redesign of monitoring network by applying some optimization criteria. The most developed and widespread methods are based on geostatistics (family of kriging models, conditional stochastic simulations). In geostatistics the variance is mainly used as an optimization criterion which has some advantages and drawbacks. In the present research we study an application of advanced techniques following from the statistical learning theory (SLT) - support vector machines (SVM) and the optimization of monitoring networks when dealing with a classification problem (data are discrete values/classes: hydrogeological units, soil types, pollution decision levels, etc.) is considered. SVM is a universal nonlinear modeling tool for classification problems in high dimensional spaces. The SVM solution is maximizing the decision boundary between classes and has a good generalization property for noisy data. The sparse solution of SVM is based on support vectors - data which contribute to the solution with nonzero weights. Fundamentally the MNO for classification problems can be considered as a task of selecting new measurement points which increase the quality of spatial classification and reduce the testing error (error on new independent measurements). In SLT this is a typical problem of active learning - a selection of the new unlabelled points which efficiently reduce the testing error. A classical approach (margin sampling) to active learning is to sample the points closest to the classification boundary. This solution is suboptimal when points (or generally the dataset) are redundant for the same class. In the present research we propose and study two new advanced methods of active learning adapted to the solution of

  10. Active traffic management on road networks: a macroscopic approach.

    PubMed

    Kurzhanskiy, Alex A; Varaiya, Pravin

    2010-10-13

    Active traffic management (ATM) is the ability to dynamically manage recurrent and non-recurrent congestion based on prevailing traffic conditions in order to maximize the effectiveness and efficiency of road networks. It is a continuous process of (i) obtaining and analysing traffic measurement data, (ii) operations planning, i.e. simulating various scenarios and control strategies, (iii) implementing the most promising control strategies in the field, and (iv) maintaining a real-time decision support system that filters current traffic measurements to predict the traffic state in the near future, and to suggest the best available control strategy for the predicted situation. ATM relies on a fast and trusted traffic simulator for the rapid quantitative assessment of a large number of control strategies for the road network under various scenarios, in a matter of minutes. The open-source macrosimulation tool Aurora ROAD NETWORK MODELER is a good candidate for this purpose. The paper describes the underlying dynamical traffic model and what it takes to prepare the model for simulation; covers the traffic performance measures and evaluation of scenarios as part of operations planning; introduces the framework within which the control strategies are modelled and evaluated; and presents the algorithm for real-time traffic state estimation and short-term prediction.

  11. GNSS geodetic techniques for time and frequency transfer applications

    NASA Astrophysics Data System (ADS)

    Lahaye, François; Cerretto, Giancarlo; Tavella, Patrizia

    2011-01-01

    We performed an initial analysis of the pseudorange data of the GIOVE-B satellite, one of the two experimental Galileo satellites currently in operation, for time transfer.The time transfer technique specified herein does not refer to the definition of Galileo Common View as set up by the European Space Agency, the Royal Observatory of Belgium and Timing Expert, nor the Common View GPS standard practice for BIPM.1 For this specific aim, software was developed to process the GIOVE-B raw pseudoranges and broadcast navigation messages collected by the Galileo Experimental Sensor Stations (GESS) tracking network, yielding station clock phase errors with respect to the Experimental Galileo System Time (EGST). The software also allows processing the Global Positioning System (GPS) P1 and P2 pseudorange data with broadcast navigation message collected at the same stations to obtain the station clock phase errors with respect to the GPS system time (GPST). Differencing these solutions between stations provides two independent means of GNSS time transfer. We compared these time transfer results with Precise Point Positioning (PPP) method applied to GPS data in combined carrier-phase and pseudorange mode as well as in pseudorange-only mode to show their relative merits. The PPP solutions in combined carrier-phase and pseudorange mode showed the least instability of the methods tested herein at all scales, at few parts in 1015 at 1 day for the stations processed, following a tau-½ interval dependency. Conversely, the PPP solutions in pseudorange-only mode are an order of magnitude worst (few parts in 1014 at 1 day for the stations processed) following a tau-1 power-law, but slightly better than the single-satellite raw GPS time transfer solutions obtained using the developed software, since the PPP least-squares solution effectively averages the pseudorange noise. The pseudorange noise levels estimated from PPP pseudorange residuals and from clock solution comparisons are

  12. On Comparing Precision Orbit Solutions of Geodetic Satellites Given Several Atmospheric Density Models

    DTIC Science & Technology

    2014-08-01

    Preprint) AAS 15-752 ON COMPARING PRECISION ORBIT SOLUTIONS OF GEODETIC SATELLITES GIVEN SEVERAL ATMOSPHERIC DENSITY MODELS John G. Warner∗, Krysta...tool. High precision laser ranging data to geodetic satellites were used as test cases to evaluate the solution accuracy and predictive capabilities...2014 2. REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE On Comparing Precision Orbit Solutions of Geodetic Satellites Given Several

  13. Experiment S-213 selenocentric geodetic reference system

    NASA Technical Reports Server (NTRS)

    Doyle, F. J.; Elassal, A. A.; Lucas, J. R.

    1976-01-01

    Development and implementation of a photogrammetric system was undertaken to provide accurate selenodetic positions and topographic mapping of all areas overflown by orbital spacecraft. The system was installed in the scientific instrument module (SIM) bay of the Apollo command service module (CSM). In theory, this system provided everything a photogrammetrist could want: the position of each exposure station would be obtained from Earth-based tracking; the orientation of each photograph could be computed from the synchronized stellar exposure and the lock-angles determined by preflight calibration; and the scale of each stereomodel would be obtained directly from the altimeter data. Operationally, the data acquisition was adequate, but less than optimum. Systematic errors are believed to be the result of the primitive orbit determination procedures in use at the time of the Apollo 15 mission, inadequate models of the lunar gravity field, and spacecraft oscillations induced by uncoupled thrusting and various activities of the astronauts.

  14. Boscovich: his geodetic and cartographic studies.

    NASA Astrophysics Data System (ADS)

    Crippa, B.; Forcella, V.; Mussio, L.

    The name of Ruggero Giuseppe Boscovich has many spellings: the Croatian Boscovič, linked to his Dalmatian origin, becomes Boscowich in German. Ruggero Giuseppe Boscovich lived and worked in many cities: Rome, Pavia, Venice, Paris, London, Warsaw, Saint Petersburg and Constantinople, where he carried out diplomatic missions. He was a Jesuit and studied mathematics, physics, astronomy, geodesy, and cartography. His studies in geodesy and cartography were developed in Italy: he measured the meridian between Rome and Rimini, he worked on the new map of the Papal State and he designed the Brera Observatory. In the first part of the present work, we present Boscovich's activities from a chronological point of view. In the second part, we focus on two specific arguments, related to geodesy and cartography: the new map of the Papal State and an attempt to rebuild the associated triangulation.

  15. A future geodetic monitoring system for vertical land motion in the Perth basin, Australia

    NASA Astrophysics Data System (ADS)

    Filmer, Mick; Featherstone, Will; Morgan, Linda; Schenk, Andreas

    2013-04-01

    Vertical land movement (VLM) affects many regions around the world and can have various causes, such as tectonics, glacial isostatic adjustment and resource extraction. Geodetic monitoring systems are employed in different configurations to identify VLM to provide knowledge for hazard mapping, risk assessment and land planning. We describe results from historical geodetic observations, and efforts to establish a monitoring system in the Western Australian city of Perth, which is subject to VLM, most probably caused by groundwater extraction over the past ~100 years. The most direct evidence of VLM in Perth is provided by two continuously operating GNSS (CGNSS) stations HIL1 (from 1997) and PERT (from 1992). However, these stations provide estimates only at discrete locations. In addition, the data from HIL1 is subject to frequent equipment changes and PERT ceased operation in early 2012. The CGNSS VLM rates reach ~-6 mm/yr, but are not linear over time and appear to be highly correlated with the rates of groundwater extraction. Limited sequences of interferometric synthetic aperture radar (InSAR) images are available over short periods between 1992-2009, and although these suggest spatially variable VLM rates reaching -5 mm/yr at some locations, the uncertainty from the small number of images suggest that these results should be treated cautiously. If it remains necessary to extract groundwater for Perth (possibly at increased rates), an ongoing monitoring programme is needed. This should be based on combined GNSS, InSAR and levelling observation programmes. Historical levelling data from the early 1970s is currently being extracted from hardcopy archives into digital file format for analysis and adjustment. These data will be used to establish an original reference network for later geodetic observations comprising repeat levelling campaigns connected to periodic GNSS campaigns and CGNSS stations, but most importantly, a regular and structured acquisition of In

  16. Dysregulated but not decreased salience network activity in schizophrenia

    PubMed Central

    White, Thomas P.; Gilleen, James; Shergill, Sukhwinder S.

    2013-01-01

    Effective estimation of the salience of environmental stimuli underlies adaptive behavior, while related aberrance is believed to undermine rational thought processes in schizophrenia. A network including bilateral frontoinsular cortex (FIC) and dorsal anterior cingulate cortex (dACC) has been observed to respond to salient stimuli using functional magnetic resonance imaging (fMRI). To test the hypothesis that activity in this salience network (SN) is less discriminately modulated by contextually-relevant stimuli in schizophrenia than in healthy individuals, fMRI data were collected in 20 individuals with schizophrenia and 13 matched controls during performance of a modified monetary incentive delay (MID) task. After quantitatively identifying spatial components representative of the FIC and dACC features of the SN, two principal analyses were conducted. In the first, modulation of SN activity by salience was assessed by measuring response to trial outcome. First-level general linear models were applied to individual-specific time-courses of SN activity identified using spatial independent component analysis (ICA). This analysis revealed a significant salience-by-performance-by-group interaction on the best-fit FIC component's activity at trial outcome, whereby healthy individuals but not individuals with schizophrenia exhibited greater distinction between the response to hits and misses in high salience trials than in low salience trials. The second analysis aimed to ascertain whether SN component amplitude differed between the study groups over the duration of the experiment. Independent-samples T-tests on back-projected, percent-signal-change scaled SN component images importantly showed that the groups did not differ in the overall amplitude of SN expression over the entire dataset. These findings of dysregulated but not decreased SN activity in schizophrenia provide physiological support for mechanistic conceptual frameworks of delusional thought formation

  17. The influence of cooling, crystallisation and re-melting on the interpretation of geodetic signals in volcanic systems

    NASA Astrophysics Data System (ADS)

    Caricchi, Luca; Biggs, Juliet; Annen, Catherine; Ebmeier, Susanna

    2014-02-01

    Deformation of volcanic edifices is typically attributed to the movement of magma within the volcanic plumbing system, but a wide range of magmatic processes are capable of producing significant volume variations and may also produce deformation. In order to understand the evolution of magmatic systems prior to eruption and correctly interpret monitoring signals, it is necessary to quantify the patterns and timescales of surface deformation that processes such as crystallisation, degassing and expansion of the hydrothermal system can produce. We show how the combination of petrology and thermal modelling can be applied to geodetic observations to identify the processes occurring in a magmatic reservoir during volcanic unrest. Thermal modelling and petrology were used to determine the timescales and volumetric variations associated with cooling, crystallisation and gas exsolution. These calculations can be performed rapidly and highlight the most likely processes responsible for the variation of a set of monitoring parameters. We then consider the magnitude and timescales of deformation produced by other processes occurring within the vicinity of an active magma system. We apply these models to a time series of geodetic data spanning the period between the 1997 and 2008 eruptions of Okmok volcano, Aleutians, examining scenarios involving crystallisation, degassing and remelting of the crystallising shallow magmatic body and including a viscoelastic shell or hydrothermal system. The geodetic observations are consistent with the injection of a water-saturated basalt, followed by minor crystallisation and degassing. Other scenarios are not compatible either with the magnitude or rate of the deformation signals.

  18. Seafloor Geodetic Investigation of Shallow Slow Slip Events at the Hikurangi Subduction Margin, New Zealand

    NASA Astrophysics Data System (ADS)

    Webb, Spahr C.; Wallace, Laura M.; Ito, Yoshihiro; Mochizuki, Kimihiro; Hino, Ryota; Henrys, Stuart; Schwartz, Susan; Sheehan, Anne

    2016-04-01

    Shallow slow slip events (<10-15 km depth) are well-documented at the northern Hikurangi subduction margin, New Zealand. During the Hikurangi Ocean Bottom Investigation of Tremor and Slow Slip (HOBITSS) project, we deployed and successfully recovered a dense network (<10 km spacing) of 24 Absolute Pressure Gauges (APG) and 15 Ocean Bottom Seismometers (OBS) to investigate vertical seafloor deformation and seismicity related to shallow slow slip. The HOBITSS network was deployed for one year from May 2014 to June 2015, in a region directly above an area of large, shallow slow slip events offshore Gisborne, New Zealand. A large slow slip event occurred directly beneath the HOBITSS network in September/October of 2014. The APG data reveal the detailed distribution of seafloor deformation above a shallow (< 10 km depth) offshore subduction thrust for the first time ever. We show evidence that slow slip events can occur very close to the trench and within 2km of the seafloor, where very low pressures and temperatures exist. APGs are a viable tool to detect detailed vertical deformation (on the order of 1-4 cm) of the seafloor and thus enable geodetic investigations of shallow SSEs and other similar-sized transient deformation events at offshore plate boundaries.

  19. Photonic Network R&D Activities in Japan-Current Activities and Future Perspectives

    NASA Astrophysics Data System (ADS)

    Kitayama, Ken-Ichi; Miki, Tetsuya; Morioka, Toshio; Tsushima, Hideaki; Koga, Masafumi; Mori, Kazuyuki; Araki, Soichiro; Sato, Ken-Ichi; Onaka, Hiroshi; Namiki, Shu; Aoyama, Tomonori

    2005-10-01

    R&D activities on photonic networks in Japan are presented. First, milestones in current ongoing R&D programs supported by Japanese government agencies are introduced, including long-distance and wavelength division multiplexing (WDM) fiber transmission, wavelength routing, optical burst switching (OBS), and control-plane technology for IP backbone networks. Their goal was set to evolve a legacy telecommunications network to IP-over-WDM networks by introducing technologies for WDM and wavelength routing. We then discuss the perspectives of so-called PHASE II R&D programs for photonic networks over the next 5 years until 2010, by focusing on the report that has been recently issued by the Photonic Internet Forum (PIF), a consortium that has major carriers, telecom vendors, and Japanese academics as members. The PHASE II R&D programs should serve to establish a photonic platform to provide abundant bandwidth on demand, at any time on a real-time basis, through the customer's initiative to promote bandwidth-rich applications, such as grid computing, real-time digital-cinema streaming, medical and educational applications, and network storage in e-commerce.

  20. Stock Price Change Rate Prediction by Utilizing Social Network Activities

    PubMed Central

    Mitsubuchi, Takashi; Sakurai, Akito

    2014-01-01

    Predicting stock price change rates for providing valuable information to investors is a challenging task. Individual participants may express their opinions in social network service (SNS) before or after their transactions in the market; we hypothesize that stock price change rate is better predicted by a function of social network service activities and technical indicators than by a function of just stock market activities. The hypothesis is tested by accuracy of predictions as well as performance of simulated trading because success or failure of prediction is better measured by profits or losses the investors gain or suffer. In this paper, we propose a hybrid model that combines multiple kernel learning (MKL) and genetic algorithm (GA). MKL is adopted to optimize the stock price change rate prediction models that are expressed in a multiple kernel linear function of different types of features extracted from different sources. GA is used to optimize the trading rules used in the simulated trading by fusing the return predictions and values of three well-known overbought and oversold technical indicators. Accumulated return and Sharpe ratio were used to test the goodness of performance of the simulated trading. Experimental results show that our proposed model performed better than other models including ones using state of the art techniques. PMID:24790586

  1. Dynamic Control of Synchronous Activity in Networks of Spiking Neurons

    PubMed Central

    Hutt, Axel; Mierau, Andreas; Lefebvre, Jérémie

    2016-01-01

    Oscillatory brain activity is believed to play a central role in neural coding. Accumulating evidence shows that features of these oscillations are highly dynamic: power, frequency and phase fluctuate alongside changes in behavior and task demands. The role and mechanism supporting this variability is however poorly understood. We here analyze a network of recurrently connected spiking neurons with time delay displaying stable synchronous dynamics. Using mean-field and stability analyses, we investigate the influence of dynamic inputs on the frequency of firing rate oscillations. We show that afferent noise, mimicking inputs to the neurons, causes smoothing of the system’s response function, displacing equilibria and altering the stability of oscillatory states. Our analysis further shows that these noise-induced changes cause a shift of the peak frequency of synchronous oscillations that scales with input intensity, leading the network towards critical states. We lastly discuss the extension of these principles to periodic stimulation, in which externally applied driving signals can trigger analogous phenomena. Our results reveal one possible mechanism involved in shaping oscillatory activity in the brain and associated control principles. PMID:27669018

  2. Incorporating GPS geodetic data into the undergraduate classroom to improve data and information literacy

    NASA Astrophysics Data System (ADS)

    Jansma, P. E.; Mattioli, G. S.

    2002-12-01

    As part of an NSF-funded project, we are incorporating Global Positioning System (GPS) geodesy into the classroom to improve data and information literacy among undergraduate students. Our objectives are: to introduce statistical concepts essential for the interpretation of large datasets; to promote communication skills; to enhance critical thinking; and to build teamwork. GPS geodesy is ideal for illustrating data literacy concepts. Data precision and accuracy depend upon several factors, including type of equipment, environmental conditions, length of occupations, monument design, site location, configuration of the geodetic network, and processing strategies. All of these can be varied, allowing the students to learn the trade-offs among cost, time, and quality and to determine the most efficient methodology for specific problems. In addition, precision, accuracy, and errors govern the interpretations that can be made and the potential to distinguish among competing models. Our focus is a semester-long course that uses GPS geodesy in real-world applications and also requires integration of GPS data into oral presentations and written reports. Students work in teams on "cases" that pose hypotheses for testing. The cases are derived from our on-going research projects and take advantage of on-line continuous GPS (CGPS) data as well as our archived campaign data. The case studies are: 1) Microplate tectonics in the northeastern Caribbean; 2) Inflation/deflation cycles of the Soufriere Hills volcano, Montserrat; and 3) Contribution of monument instability to the overall error in geodetic data from the New Madrid Seismic Zone. All course materials will be on-line and available for the community.

  3. Constraints on Crustal Viscosity from Geodetic Observations

    NASA Astrophysics Data System (ADS)

    Houseman, Gregory

    2015-04-01

    Laboratory measurements of the ductile deformation of crustal rocks demonstrate a range of crystal deformation mechanisms that may be represented by a viscous deformation law, albeit one in which the effective viscosity may vary by orders of magnitude, depending on temperature, stress, grain size, water content and other factors. In such measurements these factors can be separately controlled and effective viscosities can be estimated more or less accurately, though the measured deformation occurs on much shorter time scales and length scales than are typical of geological deformation. To obtain bulk measures of the in situ crustal viscosity law for actual geological processes, estimated stress differences are balanced against measured surface displacement or strain rates: at the continental scale, surface displacement and strain rates can be effectively measured using GPS, and stress differences can be estimated from the distribution of gravitational potential energy; this method has provided constraints on a depth-averaged effective viscosity for the lithosphere as a whole in regions that are actively deforming. Another technique measures the post-seismic displacements that are interpreted to occur in the aftermath of a large crustal earthquake. Stress-differences here are basically constrained by the co-seismic deformation and the elastic rigidity (obtained from seismic velocity) and the strain rates are again provided by GPS. In this technique the strain is a strong function of position relative to the fault, so in general the interpretation of this type of data depends on a complex calculation in which various simplifying assumptions must be made. The spatial variation of displacement history on the surface in this case contains information about the spatial variation of viscosity within the crust. Recent post-seismic studies have shown the potential for obtaining measurements of both depth variation and lateral variation of viscosity in the crust beneath

  4. An Autonomous, Low Cost Platform for Seafloor Geodetic Observations

    NASA Astrophysics Data System (ADS)

    Ericksen, T.; Foster, J. H.; Bingham, B. S.

    2013-12-01

    The high cost of acquiring geodetic data from the sea floor has limited the observations available to help us understand and model the behavior of seafloor geodetic processes. To address this problem, the Pacific GPS Facility at the University of Hawaii is developing a cost effective approach for accurately measuring short-term vertical motions of the seafloor and maintaining a continuous long-term record of seafloor pressure without the requirement for costly ship time. There is a recognized need to vastly increase our underwater geodetic observing capacity. Most of the largest recorded earthquakes and most devastating tsunamis are generated at subduction zones underwater. Similarly, many volcanoes are partly (e.g. Santorini) or completely (e.g. Loihi) submerged, and are not well observed and understood. Furthermore, landslide features ring many ocean basins, and huge debris deposits surround many volcanic oceanic islands. Our approach will lower the cost of collecting sea-floor geodetic data, reducing the barriers preventing us from acquiring the information we need to observe and understand these types of structures and provide a direct societal benefit in improving hazard assessment. The capability is being developed by equipping one of the University of Hawaii Wave Gliders with an integrated acoustic telemetry package, a dual frequency geodetic-grade Global Positioning System (GPS) receiver, processing unit, and cellular communications. The Wave Glider will interrogate high accuracy pressure sensors on the sea floor to maintain a near-continuous stream of pressure and temperature data, but seafloor pressure data includes contribution from a variety of sources and on its own may not provide the accuracy required for geodetic investigations. Independent measurements of sea surface pressure and sea surface height can be used to remove these contributions from the observed sea floor pressure timeseries. We will integrate our seafloor pressure measurements with air

  5. Modulation of Rhythmic Activity in Mammalian Spinal Networks Is Dependent on Excitability State

    PubMed Central

    2017-01-01

    Neuromodulators play an important role in activating rhythmically active motor networks; however, what remains unclear are the network interactions whereby neuromodulators recruit spinal motor networks to produce rhythmic activity. Evidence from invertebrate systems has demonstrated that the effect of neuromodulators depends on the pre-existing state of the network. We explored how network excitation state affects the ability of dopamine to evoke rhythmic locomotor activity in the neonatal mouse isolated spinal cord. We found that dopamine can evoke unique patterns of motor activity that are dependent on the excitability state of motor networks. Different patterns of motor activity ranging from tonic, nonrhythmic activity to multirhythmic, nonlocomotor activity to locomotor activity were produced by altering global motor network excitability through manipulations of the extracellular potassium and bath NMDA concentration. A similar effect was observed when network excitation was manipulated during an unstable multirhythm evoked by a low concentration (15 µm) of 5-HT, suggesting that our results are not neuromodulator specific. Our data show in vertebrate systems that modulation is a two-way street and that modulatory actions are largely influenced by the network state. The level of network excitation can account for variability between preparations and is an additional factor to be considered when circuit elements are removed from the network. PMID:28144626

  6. Detection of silent cells, synchronization and modulatory activity in developing cellular networks.

    PubMed

    Hjorth, Johannes J J; Dawitz, Julia; Kroon, Tim; Pires, Johny; Dassen, Valerie J; Berkhout, Janna A; Emperador Melero, Javier; Nadadhur, Aish G; Alevra, Mihai; Toonen, Ruud F; Heine, Vivi M; Mansvelder, Huibert D; Meredith, Rhiannon M

    2016-04-01

    Developing networks in the immature nervous system and in cellular cultures are characterized by waves of synchronous activity in restricted clusters of cells. Synchronized activity in immature networks is proposed to regulate many different developmental processes, from neuron growth and cell migration, to the refinement of synapses, topographic maps, and the mature composition of ion channels. These emergent activity patterns are not present in all cells simultaneously within the network and more immature "silent" cells, potentially correlated with the presence of silent synapses, are prominent in different networks during early developmental periods. Many current network analyses for detection of synchronous cellular activity utilize activity-based pixel correlations to identify cellular-based regions of interest (ROIs) and coincident cell activity. However, using activity-based correlations, these methods first underestimate or ignore the inactive silent cells within the developing network and second, are difficult to apply within cell-dense regions commonly found in developing brain networks. In addition, previous methods may ignore ROIs within a network that shows transient activity patterns comprising both inactive and active periods. We developed analysis software to semi-automatically detect cells within developing neuronal networks that were imaged using calcium-sensitive reporter dyes. Using an iterative threshold, modulation of activity was tracked within individual cells across the network. The distribution pattern of both inactive and active, including synchronous cells, could be determined based on distance measures to neighboring cells and according to different anatomical layers.

  7. Assessment of optimally filtered recent geodetic mean dynamic topographies

    NASA Astrophysics Data System (ADS)

    Siegismund, F.

    2013-01-01

    AbstractRecent geoids from the Gravity Recovery and Climate Experiment (GRACE) and the Gravity field and steady state Ocean Circulation Explorer satellite mission (GOCE) contain useful short-scale information for the construction of a <span class="hlt">geodetic</span> ocean mean dynamic topography (MDT). The <span class="hlt">geodetic</span> MDT is obtained from subtracting the geoid from a mean sea surface (MSS) as measured by satellite altimetry. A gainful use of the MDT and an adequate assessment needs an optimal filtering. This is accomplished here by defining a cutoff length scale dmax for the geoid and applying a Gaussian filter with half-width radius r on the MDT. A series of MDTs (GRACE, GOCE, and combined satellite-only (GOCO) solutions) is tested, using different sets of filter parameters dmax and r. Optimal global and regional dependent filter parameters are estimated. To find optimal parameters and to assess the resulting MDTs, the geostrophic surface currents induced by the filtered <span class="hlt">geodetic</span> MDT are compared to corrected near-surface currents obtained from the Global Drifter Program (GDP). The global optimal cutoff degree and order (d/o) dmax (half-width radius r of the spatial Gaussian filter) is 160 (1.1°) for GRACE; 180 (1.1-1.2°) for 1st releases of GOCE (time- and space-wise methods) and GOCO models; and 210 (1.0 degree) for 2nd and 3rd releases of GOCE and GOCO models. The cutoff d/o is generally larger (smaller) and the filter length smaller (larger) for regions with strong, small-scale (slow, broad scale) currents. The smallest deviations from the drifter data are obtained with the GOCO03s geoid model, although deviations of other models are only slightly higher.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730012612','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730012612"><span>Refraction effects of atmosphere on <span class="hlt">geodetic</span> measurements to celestial bodies</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Joshi, C. S.</p> <p>1973-01-01</p> <p>The problem is considered of obtaining accurate values of refraction corrections for <span class="hlt">geodetic</span> measurements of celestial bodies. The basic principles of optics governing the phenomenon of refraction are defined, and differential equations are derived for the refraction corrections. The corrections fall into two main categories: (1) refraction effects due to change in the direction of propagation, and (2) refraction effects mainly due to change in the velocity of propagation. The various assumptions made by earlier investigators are reviewed along with the basic principles of improved models designed by investigators of the twentieth century. The accuracy problem for various quantities is discussed, and the conclusions and recommendations are summarized.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.G33A0676M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.G33A0676M"><span>Seafloor <span class="hlt">geodetic</span> reference station branched from submarine cable</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mochizuki, M.; Asada, A.; Ura, T.; Asakawa, K.; Yokobiki, T.; Iwase, R.; Goto, T.; Sato, M.; Nagahashi, K.; Tanaka, T.</p> <p>2008-12-01</p> <p>We launched a project supported by the Japan Society for the Science Promotion as the Grants in Aid for Scientific Research. In this project, we are aiming at developing new-generation seafloor <span class="hlt">geodetic</span> observation system that conquers difficulties inherent with the current system. Central idea of this project is to utilize techniques of underwater robot (Autonomous Underwater Vehicle) and submarine cable to make measurements in place of using the research vessels. Combination of underwater robot and submarine cable make it possible to provide permanent seafloor reference point, to conduct the observation with selecting favorable condition of sea and GPS satellite distributions, to make much more frequent observations and to enable flexible planning of observation in response to sudden <span class="hlt">geodetic</span> events. Prototype of the on-board system which should be installed on an AUV was finished. Several trials had been done with the system in the sea. The results from them showed that the new on-board system will reach to the higher level in performance than the current system in the near future. And then we started to dedicate ourselves mainly to developing new seafloor transponder. The current seafloor transponder system is stand-alone one which runs on internal batteries. We expect five to ten years for the lifetime of the current seafloor transponder, even though it depends on how often we perform measurements with the transponder. Replacement of the seafloor transponder will be needed when we target seafloor crustal deformation that has long time cycle more than several decades. Continuity of seafloor <span class="hlt">geodetic</span> observation will be stopped. New seafloor transponder which we have been developing is one which can be connected to a submarine cable by wet-mate connectors. Power is supplied through submarine cable and then the new seafloor transponder will be a permanent reference station for seafloor <span class="hlt">geodetic</span> survey. Submarine cable can supply accurate GPS time (1pps) and clock</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ESASP.739E..89S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ESASP.739E..89S"><span>Current and Future <span class="hlt">Geodetic</span> Satellite Missions for Global Change Monitoring</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sneeuw, Nico; Li, Jiancheng; Cai, Jiangqing; Jiang, Weiping; Xu, Xinyu; Chu, Yonghai; Jin, Taoyong; Chao, Nengfang; Elmi, Omid; Tourian, Mohammad J.</p> <p>2016-08-01</p> <p>Global change deals with large- and small-scale processes that modify the Earth's atmosphere, land and ocean. Using innovative <span class="hlt">geodetic</span> space-borne sensor systems, dedicated gravity field and altimeter satellites monitor these processes over a range of spatial and temporal scales. The integrated analysis of these geometric and gravimetric Earth observation data shall improve the knowledge of system processes of the changing Earth. We here report on valuable contributions from satellite altimetry and satellite gravimetry to Earth system science in general and to hydrology in particular.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760012443','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760012443"><span>On differential transformations between Cartesian and curvilinear (<span class="hlt">geodetic</span>) coordinates</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Soler, T.</p> <p>1976-01-01</p> <p>Differential transformations are developed between Cartesian and curvilinear orthogonal coordinates. Only matrix algebra is used for the presentation of the basic concepts. After defining the reference systems used the rotation (R), metric (H), and Jacobian (J) matrices of the transformations between cartesian and curvilinear coordinate systems are introduced. A value of R as a function of H and J is presented. Likewise an analytical expression for J(-1) as a function of H(-2) and R is obtained. Emphasis is placed on showing that differential equations are equivalent to conventional similarity transformations. Scaling methods are discussed along with ellipsoidal coordinates. Differential transformations between elipsoidal and <span class="hlt">geodetic</span> coordinates are established.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986EOSTr..67..691B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986EOSTr..67..691B"><span><span class="hlt">Geodetic</span> Refraction: Effects of Electromagnetic Wave Propagation Through the Atmosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bossy, L.; Paquet, P.</p> <p></p> <p>The atmospheric refraction has always been one of the main perturbations of classical terrestrial geodesy. For the future, and taking into account that a precision of a few centimeters is attainable over distances of few thousand kilometers, the monitoring of the atmospheric perturbation also requires a strong improvement for space applications that are mainly based on radio techniques. This is the reason why, for 2 decades, the interest in refraction studies has increased, as reflected in this monograph, which is entirely devoted to the properties of the atmospheric effects on various <span class="hlt">geodetic</span> measurements and to their evaluation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10072366','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10072366"><span>The origin of spontaneous <span class="hlt">activity</span> in developing <span class="hlt">networks</span> of the vertebrate nervous system.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>O'Donovan, M J</p> <p>1999-02-01</p> <p>Spontaneous neuronal <span class="hlt">activity</span> has been detected in many parts of the developing vertebrate nervous system. Recent studies suggest that this <span class="hlt">activity</span> depends on properties that are probably shared by all developing <span class="hlt">networks</span>. Of particular importance is the high excitability of recurrently connected, developing <span class="hlt">networks</span> and the presence of <span class="hlt">activity</span>-induced transient depression of <span class="hlt">network</span> excitability. In the spinal cord, it has been proposed that the interaction of these properties gives rise to spontaneous, periodic <span class="hlt">activity</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26089794','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26089794"><span>Self-organization of synchronous <span class="hlt">activity</span> propagation in neuronal <span class="hlt">networks</span> driven by local excitation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bayati, Mehdi; Valizadeh, Alireza; Abbassian, Abdolhossein; Cheng, Sen</p> <p>2015-01-01</p> <p>Many experimental and theoretical studies have suggested that the reliable propagation of synchronous neural <span class="hlt">activity</span> is crucial for neural information processing. The propagation of synchronous firing <span class="hlt">activity</span> in so-called synfire chains has been studied extensively in feed-forward <span class="hlt">networks</span> of spiking neurons. However, it remains unclear how such neural <span class="hlt">activity</span> could emerge in recurrent neuronal <span class="hlt">networks</span> through synaptic plasticity. In this study, we investigate whether local excitation, i.e., neurons that fire at a higher frequency than the other, spontaneously <span class="hlt">active</span> neurons in the <span class="hlt">network</span>, can shape a <span class="hlt">network</span> to allow for synchronous <span class="hlt">activity</span> propagation. We use two-dimensional, locally connected and heterogeneous neuronal <span class="hlt">networks</span> with spike-timing dependent plasticity (STDP). We find that, in our model, local excitation drives profound <span class="hlt">network</span> changes within seconds. In the emergent <span class="hlt">network</span>, neural <span class="hlt">activity</span> propagates synchronously through the <span class="hlt">network</span>. This <span class="hlt">activity</span> originates from the site of the local excitation and propagates through the <span class="hlt">network</span>. The synchronous <span class="hlt">activity</span> propagation persists, even when the local excitation is removed, since it derives from the synaptic weight matrix. Importantly, once this connectivity is established it remains stable even in the presence of spontaneous <span class="hlt">activity</span>. Our results suggest that synfire-chain-like <span class="hlt">activity</span> can emerge in a relatively simple way in realistic neural <span class="hlt">networks</span> by locally exciting the desired origin of the neuronal sequence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016cosp...41E1220M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016cosp...41E1220M"><span>Current Situation of AFREF and First Results from GNSS <span class="hlt">Networks</span> in Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mahmoud, Salah; Farah, Hussein; Wonnacott, Richard</p> <p>2016-07-01</p> <p>The African <span class="hlt">Geodetic</span> Reference Frame (AFREF) is conceived as a unified <span class="hlt">geodetic</span> reference frame for Africa. It will be the fundamental basis for the national three-dimensional reference <span class="hlt">networks</span> fully consistent and homogeneous with the International Terrestrial Reference Frame (ITRF). When fully implemented, its backbone will consist of a <span class="hlt">network</span> of continuous, permanent GPS stations such that a user anywhere in Africa would have free access to, and would be at most 1000km from, such stations. Full implementation will include a unified vertical datum and support for efforts to establish a precise African geoid, in concert with the African Geoid project <span class="hlt">activities</span>. The realization of AFREF has vast potentials for geodesy, mapping, surveying, geoinformation, natural hazards mitigation, earth sciences, etc. Its implementation will provide a major springboard for the transfer and enhancement of skills in surveying and geodesy and especially GPS technology and applications. AFREF is, therefore, an African initiative to unify the <span class="hlt">geodetic</span> reference frames of Africa based on the ITRF through a <span class="hlt">network</span> of GNSS base stations at a spacing such users will be at most within ~1000 km of a base station. First Reference Frame Solution of about 80 <span class="hlt">geodetic</span> GPS stations in Africa has been started in February 2013 at some processing centers in Europe and Africa. Results of independent solutions being developed by various African scientific teams: Hart RAO, South Africa; Ardhi University, Tanzania and SEGAL, University of Beria Interior, Portugal, show an accuracy of aligned ITRF 2008 using 42 IGS stations in E and N components with 3.0 mm and in U component 7.5 mm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA574395','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA574395"><span>Emulation of the <span class="hlt">Active</span> Immune Response in a Computer <span class="hlt">Network</span></span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2009-01-15</p> <p>Dynamics of the Estimation Process 53 15 Dual <span class="hlt">Network</span> Interface for concurrent execution of testbed experiments and lab management 57 16 Hardware Testbed...Two Physical Nodes 62 20 <span class="hlt">Network</span> Security Testbed Management Software Stack 63 21 Virtual <span class="hlt">Network</span> Topology for Worm Propagation Experiment Generated...system could be reformulated in terms of the characteristics of computer <span class="hlt">networks</span> and interpreted as a set of instructions to a <span class="hlt">network</span> manager . This</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.7064F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.7064F"><span>Current status of the EPOS WG4 - GNSS and Other <span class="hlt">Geodetic</span> Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fernandes, Rui; Bastos, Luisa; Bruyninx, Carine; D'Agostino, Nicola; Dousa, Jan; Ganas, Athanassios; Lidberg, Martin; Nocquet, Jean-Mathieu</p> <p>2014-05-01</p> <p>WG4 - "EPOS <span class="hlt">Geodetic</span> Data and Other <span class="hlt">Geodetic</span> Data" is the Working Group of the EPOS project in charge of defining and preparing the integration of the existing Pan-European <span class="hlt">Geodetic</span> Infrastructures that will support European Geosciences, which is the ultimate goal of the EPOS project. The WG4 is formed by representatives of the participating EPOS countries (23) but it is also open to the entire <span class="hlt">geodetic</span> community. In fact, WG4 also already includes members from countries that formally are not integrating EPOS in this first step. The <span class="hlt">geodetic</span> component of EPOS (WG4) is dealing essentially with Research Infrastructures focused on continuous operating GNSS (cGNSS) in the current phase. The option of concentrating the efforts on the presently most generalized <span class="hlt">geodetic</span> tool supporting research on Solid Earth was decided in order to optimize the existing resources. Nevertheless, WG4 will continue to pursue the development of tools and methodologies that permit the access of the EPOS community to other <span class="hlt">geodetic</span> information (e.g., gravimetry). Furthermore, although the focus is on Solid Earth applications, other research and technical applications (e.g., reference frames, meteorology, space weather) can also benefit from the efforts of WG4 EPOS towards the optimization of the <span class="hlt">geodetic</span> resources in Europe. We will present and discuss the plans for the implementation of the thematic and core services (TCS) for <span class="hlt">geodetic</span> data within EPOS and the related business plan. We will focus on strategies towards the implementation of the best solutions that will permit to the end-users, and in particular geo-scientists, to access the <span class="hlt">geodetic</span> data, derived solutions, and associated metadata using transparent and uniform processes. Five pillars have been defined proposed for the TCS: Dissemination, Preservation, Monitoring, and Analysis of <span class="hlt">geodetic</span> data plus the Support and Governance Infrastructure. Current proposals and remaining open questions will be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016E%26ES...40a2003Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016E%26ES...40a2003Z"><span>A Wolf Pack Algorithm for <span class="hlt">Active</span> and Reactive Power Coordinated Optimization in <span class="hlt">Active</span> Distribution <span class="hlt">Network</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhuang, H. M.; Jiang, X. J.</p> <p>2016-08-01</p> <p>This paper presents an <span class="hlt">active</span> and reactive power dynamic optimization model for <span class="hlt">active</span> distribution <span class="hlt">network</span> (ADN), whose control variables include the output of distributed generations (DGs), charge or discharge power of energy storage system (ESS) and reactive power from capacitor banks. To solve the high-dimension nonlinear optimization model, a new heuristic swarm intelligent method, namely wolf pack algorithm (WPA) with better global convergence and computational robustness, is adapted so that the <span class="hlt">network</span> loss minimization can be achieved. In this paper, the IEEE33-bus system is used to show the effectiveness of WPA technique compared with other techniques. Numerical tests on the modified IEEE 33-bus system show that WPA for <span class="hlt">active</span> and reactive multi-period optimization of ADN is exact and effective.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5368652','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5368652"><span>Organization of prefrontal <span class="hlt">network</span> <span class="hlt">activity</span> by respiration-related oscillations</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Biskamp, Jonatan; Bartos, Marlene; Sauer, Jonas-Frederic</p> <p>2017-01-01</p> <p>The medial prefrontal cortex (mPFC) integrates information from cortical and sub-cortical areas and contributes to the planning and initiation of behaviour. A potential mechanism for signal integration in the mPFC lies in the synchronization of neuronal discharges by theta (6–12 Hz) <span class="hlt">activity</span> patterns. Here we show, using in vivo local field potential (LFP) and single-unit recordings from awake mice, that prominent oscillations in the sub-theta frequency band (1–5 Hz) emerge during awake immobility in the mPFC. These oscillation patterns are distinct from but phase-locked to hippocampal theta <span class="hlt">activity</span> and occur synchronized with nasal respiration (hence termed prefrontal respiration rhythm [PRR]). PRR <span class="hlt">activity</span> modulates the amplitude of prefrontal gamma rhythms with greater efficacy than theta oscillations. Furthermore, single-unit discharges of putative pyramidal cells and GABAergic interneurons are entrained by prefrontal PRR and nasal respiration. Our data thus suggest that PRR <span class="hlt">activity</span> contributes to information processing in the prefrontal neuronal <span class="hlt">network</span>. PMID:28349959</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUSM.G33A..10C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUSM.G33A..10C"><span>Antarctic VLNDEF <span class="hlt">Network</span> for Regional Deformation Control in Absolute Reference Frame: Problems and Possible Solution.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Capra, A.; Gandolfi, S.; Mancini, F.; Negusini, M.; Vittuari, L.</p> <p>2004-05-01</p> <p>VLNDEF (Victoria Land <span class="hlt">Network</span> for DEFormationn control) <span class="hlt">Geodetic</span> Program addresses the crustal deformation control of the Northern Victoria Land (Antarctica) by means of <span class="hlt">geodetic</span> GPS measurements. The project is within the <span class="hlt">activity</span> of GIANT (<span class="hlt">Geodetic</span> Infrastructure of Antarctica) SCAR Program and was established within the actions of ANTEC (ANTarctic NeoTECtonics) Group of Specialists. During 1999-2000 and 2000-2001 Italian expeditions a <span class="hlt">network</span> of 27 stations was established and completely surveyed over an area extending from the southernmost points at 70 degrees latitude south to the Oates Coast region at 76°S, corresponding to a wideness of 700 km along the south-north and 300 km in the west to east directions. The average distance between stations is about of 70-80 km. During the field <span class="hlt">activities</span> in the 2002-03 expedition the whole <span class="hlt">network</span> was surveyed. During those expeditions long time sessions of connection between VLNDEF and TAMDEF <span class="hlt">networks</span> performed. TAMDEF is a USA NSF program for crustal deformation control on southern Victoria Land. The dataset has been processed using different package such as Bernese and Gipsy in order to compare solutions and fix the better approach for the transition between reference frame. The first solution was initially constrained in the ITRF97 solution using the TNB1 GPS permanent station coordinate provided by the SCAR GPS Epoch solution. The approach to crustal deformation determination is relevant in terms of relative regional deformation, among the <span class="hlt">network</span> stations, and the absolute deformation study, through the connection to international reference frame. Particularly important is the study of for VLNDEF in order to integrated evaluation with other continental and regional <span class="hlt">networks</span>, as SCAR GPS Epoch and TAMDEF.Some aspects related to the data processing in the Antarctic region and the use of the ITRF2000 as reference frame will be discussed in the paper in addition to the analysis of the deformation in the area.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.G33B0686G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.G33B0686G"><span>Reanalysis of CORS and Global GPS Data at the National <span class="hlt">Geodetic</span> Survey</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Griffiths, J.; Rohde, J. R.; Ray, J.; Cline, M.; Dillinger, W. H.; Dulaney, R. L.; Hilla, S.; Kass, W. G.</p> <p>2008-12-01</p> <p>We present current results and preliminary interpretations from an ongoing project at the National <span class="hlt">Geodetic</span> Survey (NGS) to reanalyze Global Positioning System (GPS) data collected since 1994 at stations of the International GNSS Service (IGS) global tracking <span class="hlt">network</span> and at stations of the U.S. Continuously Operating Reference Stations (CORS) <span class="hlt">network</span>. Reanalysis of the global data is expected to be complete by January 2009, while the reanalysis of the CORS data will take much longer, perhaps until late 2011. The reanalysis is accomplished in two stages. The first stage is designed to obtain a consistent set of GPS satellite orbits, Earth Rotation Parameters (ERPs) and a time series of global station coordinates expressed in the current IGS Terrestrial Reference Frame, i.e., IGS05. The second stage is designed to obtain a time- series of station coordinates for the much denser CORS <span class="hlt">network</span>. An important aspect to this two-stage approach is that a relatively uniform global <span class="hlt">network</span> is used to determine the satellite orbits, ERPs and terrestrial frame, which are then fixed and used to position the CORS <span class="hlt">network</span> accurately and consistently within the same framework. Both stages of the analysis use a) the PAGES software from NGS to preprocess and reduce the RINEX observations, and b) the CATREF software from Institut Géographique National to obtain regularized station coordinates and secular velocities. The CATREF software provides the added benefit of allowing weekly Helmert frame alignments to the long-term frame and detection of station discontinuities and other frame distortions in both the global and CORS solutions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT.......267M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT.......267M"><span>Enzymatic <span class="hlt">activity</span> preservation through entrapment within degradable hydrogel <span class="hlt">networks</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mariani, Angela Marie</p> <p></p> <p>This dissertation aimed to design and develop a "biogel;" a reproducible, abiotic, and biocompatible polymer hydrogel matrix, that prolongs enzymatic stability allowing for rapid production of biomolecules. The researched entrapment method preserves enzyme <span class="hlt">activity</span> within an amicable environment while resisting <span class="hlt">activity</span> reduction in the presence of increased pH environmental challenges. These biogels can be used in a number of applications including repeated production of small molecules and in biosensors. Five main objectives were accomplished: 1) Biogels capable of maintaining enzymatic functionality post-entrapment procedures were fabricated; 2) Biogel <span class="hlt">activity</span> dependence on crosslinker type and crosslink density was determined; 3) Biogel composition effects on sustained <span class="hlt">activity</span> after storage were compared; 4) Biogel <span class="hlt">activity</span> dependence on charged monomer moieties was evaluated, and 5) Combined optimization knowledge gained from the first four objectives was utilized to determine the protection of enzymes within hydrogels when challenged with an increased pH above 8. Biogels were fabricated by entrapping β-galactosidase (lactase) enzyme within acrylamide (ACR) gels crosslinked with poly(ethylene glycol) diacrylate (PEGDA, degradable through hydrolysis) or N,N'-methylenebisacrylamide (BIS, non-degradable). Initial hydrogel entrapment reduced <span class="hlt">activity</span> to 40% in ACR/PEGDA gels, compared to a 75% reduction in initial <span class="hlt">activity</span> of ACR/BIS biogels. Once entrapped, these enzymes resist <span class="hlt">activity</span> reduction in the presence of environmental challenges, such as altering the pH from 7 to above 8. When biogels were challenged at a pH of 8, <span class="hlt">activity</span> retention positively correlated to PEGDA crosslinker density; increasing from 48% to 91% retention in 30 to 40 mole % PEGDA biogels as compared to solution based control which retained only 23%. Retention of <span class="hlt">activity</span> when perturbed from pH 7 is advantageous for biogel applications including the repeated production of desired small</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGeod..88..941W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGeod..88..941W"><span>M-estimation with probabilistic models of <span class="hlt">geodetic</span> observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wiśniewski, Z.</p> <p>2014-10-01</p> <p>The paper concerns -estimation with probabilistic models of <span class="hlt">geodetic</span> observations that is called estimation. The special attention is paid to estimation that includes the asymmetry and the excess kurtosis, which are basic anomalies of empiric distributions of errors of <span class="hlt">geodetic</span> or astrometric observations (in comparison to the Gaussian errors). It is assumed that the influence function of estimation is equal to the differential equation that defines the system of the Pearson distributions. The central moments , are the parameters of that system and thus, they are also the parameters of the chosen influence function. The estimation that includes the Pearson type IV and VII distributions ( method) is analyzed in great detail from a theoretical point of view as well as by applying numerical tests. The chosen distributions are leptokurtic with asymmetry which refers to the general characteristic of empirical distributions. Considering -estimation with probabilistic models, the Gram-Charlier series are also applied to approximate the models in question ( method). The paper shows that estimation with the application of probabilistic models belongs to the class of robust estimations; method is especially effective in that case. It is suggested that even in the absence of significant anomalies the method in question should be regarded as robust against gross errors while its robustness is controlled by the pseudo-kurtosis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004cosp...35..830S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004cosp...35..830S"><span><span class="hlt">Geodetic</span> Mobil Solar Spectrometer for JASON Altimeter Satellite Calibration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Somieski, A.; Buerki, B.; Geiger, A.; Kahle, H.-G.; Becker-Ross, H.; Florek, S.; Okruss, M.</p> <p></p> <p>Atmospheric water vapor is a crucial factor in achieving highest accuracies for space <span class="hlt">geodetic</span> measurements. Water vapor causes a delay of the propagation time of the altimeter satellite signal, which propagates into errors for the determination of surface heights. Knowledge of the precipitable water vapor (PW) enables a tropospheric correction of the satellite signal. Therefore, different remote sensing techniques have been pursued to measure the PW continuously. The prototype <span class="hlt">Geodetic</span> Mobil Solar Spectrometer (GEMOSS) was developed at the Geodesy and Geodynamics Laboratory (GGL, ETH Zurich) in cooperation with the Institute of Spectrochemistry and Applied Spectroscopy (ISAS) (Berlin, Germany). A new optical approach allows the simultaneous measurement of numerous single absorption lines of water vapor in the wide range between 728 nm and 915 nm. The large number of available absorption lines increases the accuracy of the absolute PW retrievals considerably. GEMOSS has been deployed during two campaigns in Greece in the framework of the EU-project GAVDOS, which deals with the calibration of the altimeter satellite JASON. During the overfly of JASON, the ground-based determination of PW enables the correction of the satellite measurements due to tropospheric water vapor. Comparisons with radiometer and radiosondes data allow to assess the accuracy and reliability of GEMOSS. The instrumental advancement of GEMOSS is presented together with the results of the campaigns carried out.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930071961&hterms=satellite+orbit&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dsatellite%2Borbit','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930071961&hterms=satellite+orbit&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dsatellite%2Borbit"><span>Atmospheric gravitational influence on <span class="hlt">geodetic</span> satellite orbits - Starlette analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chao, B. F.; Chan, Joseph C.</p> <p>1992-01-01</p> <p>The atmosphere is constantly in motion. The changing gravitational force due to the air mass movement will slightly perturb the orbit of a satellite. As the instrument accuracy for <span class="hlt">geodetic</span> satellites improves, failure to model this perturbation can result in significant systematic errors in the orbit determination. The latter, in turn, will degrade the Earth's gravity solutions. A direct modeling technique to analyze the atmospheric gravitational influence on <span class="hlt">geodetic</span> satellite is developed. We use the global surface pressure data from the ECMWF Initial Analysis Database to compute the gravitational force due to atmospheric perturbation exerted on given satellite as a function of time during selected orbital arcs. Satellite Laser Ranging (SLR) tracking data for selected Starlette (altitude 900 km) orbital arcs are used to test the computed force model. Although only a slight reduction in the rms residuals is observed when the atmospheric gravitational perturbation is included in the force model for data reduction of the SLR data, significant improvement is obtained in the predictability of the satellite orbit. Comprehensive studies involving more definitive test criteria and more refined models are still needed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhyA..432..354H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhyA..432..354H"><span>Epidemic process on <span class="hlt">activity</span>-driven modular <span class="hlt">networks</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Han, Dun; Sun, Mei; Li, Dandan</p> <p>2015-08-01</p> <p>In this paper, we propose two novel models of epidemic spreading by considering the <span class="hlt">activity</span>-driven and the <span class="hlt">network</span> modular. Firstly, we consider the susceptible-infected-susceptible (SIS) contagion model and derive analytically the epidemic threshold. The results indicate that the epidemic threshold only involves with the value of the spread rate and the recovery rate. In addition, the asymptotic refractory density of infected nodes in the different communities exhibits different trends with the change of the modularity-factor. Then, the infected-driven vaccination model is presented. Simulation results illustrate that the final density of vaccination will increase with the increase of the response strength of vaccination. Moreover, the final infected density in the original-infected-community shows different trends with the change of the response strength of vaccination and the spreading rate. The infected-driven vaccination is a good way to control the epidemic spreading.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4882550','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4882550"><span>Natural lecithin promotes neural <span class="hlt">network</span> complexity and <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Latifi, Shahrzad; Tamayol, Ali; Habibey, Rouhollah; Sabzevari, Reza; Kahn, Cyril; Geny, David; Eftekharpour, Eftekhar; Annabi, Nasim; Blau, Axel; Linder, Michel; Arab-Tehrany, Elmira</p> <p>2016-01-01</p> <p>Phospholipids in the brain cell membranes contain different polyunsaturated fatty acids (PUFAs), which are critical to nervous system function and structure. In particular, brain function critically depends on the uptake of the so-called “essential” fatty acids such as omega-3 (n-3) and omega-6 (n-6) PUFAs that cannot be readily synthesized by the human body. We extracted natural lecithin rich in various PUFAs from a marine source and transformed it into nanoliposomes. These nanoliposomes increased neurite outgrowth, <span class="hlt">network</span> complexity and neural <span class="hlt">activity</span> of cortical rat neurons in vitro. We also observed an upregulation of synapsin I (SYN1), which supports the positive role of lecithin in synaptogenesis, synaptic development and maturation. These findings suggest that lecithin nanoliposomes enhance neuronal development, which may have an impact on devising new lecithin delivery strategies for therapeutic applications. PMID:27228907</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2792876','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2792876"><span>Antituberculosis <span class="hlt">Activity</span> of the Molecular Libraries Screening Center <span class="hlt">Network</span> Library</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>MADDRY, JOSEPH A.; ANANTHAN, SUBRAMANIAM; GOLDMAN, ROBERT C.; HOBRATH, JUDITH V.; KWONG, CECIL D.; MADDOX, CLINTON; RASMUSSEN, LYNN; REYNOLDS, ROBERT C.; SECRIST, JOHN A.; SOSA, MELINDA I.; WHITE, E. LUCILE; ZHANG, WEI</p> <p>2009-01-01</p> <p>SUMMARY There is an urgent need for the discovery and development of new antitubercular agents that target novel biochemical pathways and treat drug-resistant forms of the disease. One approach to addressing this need is through high-throughput screening of drug-like small molecule libraries against the whole bacterium in order to identify a variety of new, <span class="hlt">active</span> scaffolds that will stimulate additional biological research and drug discovery. Through the Molecular Libraries Screening Center <span class="hlt">Network</span>, the NIAID Tuberculosis Antimicrobial Acquisition and Coordinating Facility tested a 215,110-compound library against M. tuberculosis strain H37Rv. A medicinal chemistry survey of the results from the screening campaign is reported herein. PMID:19783214</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA106786','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA106786"><span>DMA Support to a Unified <span class="hlt">Geodetic</span> Datum for the African Continent</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1981-11-01</p> <p>The third major <span class="hlt">geodetic</span> arc is in the northern part of the continent. It joins Marrakech to Alexandria. This North African Arc encompasses the...African <span class="hlt">geodetic</span> chains. One, in the northwest, extends about 14 degrees between Dakar and Marrakech through Mauritania and Western Sahara. A second</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012CG.....46..229C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012CG.....46..229C"><span>Transforming geocentric cartesian coordinates to <span class="hlt">geodetic</span> coordinates by using differential search algorithm</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Civicioglu, Pinar</p> <p>2012-09-01</p> <p>In order to solve numerous practical navigational, <span class="hlt">geodetic</span> and astro-<span class="hlt">geodetic</span> problems, it is necessary to transform geocentric cartesian coordinates into <span class="hlt">geodetic</span> coordinates or vice versa. It is very easy to solve the problem of transforming <span class="hlt">geodetic</span> coordinates into geocentric cartesian coordinates. On the other hand, it is rather difficult to solve the problem of transforming geocentric cartesian coordinates into <span class="hlt">geodetic</span> coordinates as it is very hard to define a mathematical relationship between the <span class="hlt">geodetic</span> latitude (φ) and the geocentric cartesian coordinates (X, Y, Z). In this paper, a new algorithm, the Differential Search Algorithm (DS), is presented to solve the problem of transforming the geocentric cartesian coordinates into <span class="hlt">geodetic</span> coordinates and its performance is compared with the performances of the classical methods (i.e., Borkowski, 1989; Bowring, 1976; Fukushima, 2006; Heikkinen, 1982; Jones, 2002; Zhang, 2005; Borkowski, 1987; Shu, 2010 and Lin, 1995) and Computational-Intelligence algorithms (i.e., ABC, JDE, JADE, SADE, EPSDE, GSA, PSO2011, and CMA-ES). The statistical tests realized for the comparison of performances indicate that the problem-solving success of DS algorithm in transforming the geocentric cartesian coordinates into <span class="hlt">geodetic</span> coordinates is higher than those of all classical methods and Computational-Intelligence algorithms used in this paper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/EJ1126525.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/EJ1126525.pdf"><span>Development of a Mathematical Model to Assess the Accuracy of Difference between <span class="hlt">Geodetic</span> Heights</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Gairabekov, Ibragim; Kliushin, Evgenii; Gayrabekov, Magomed-Bashir; Ibragimova, Elina; Gayrabekova, Amina</p> <p>2016-01-01</p> <p>The article includes the results of theoretical studies of the accuracy of <span class="hlt">geodetic</span> height survey and marks points on the Earth's surface using satellite technology. The dependence of the average square error of <span class="hlt">geodetic</span> heights difference survey from the distance to the base point was detected. It is being proved that by using satellite…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110011834','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110011834"><span>c5++ - Multi-Technique Analysis Software for Next Generation <span class="hlt">Geodetic</span> Instruments</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hobiger, Thomas; Gotoh, Tadahiro; Otsubo, toshimichi; Kubooka, Toshihiro; Sekido, Mamoru; Takiguchi, Hiroshi; Takeuchi, Hiroshi</p> <p>2010-01-01</p> <p>Processing of space <span class="hlt">geodetic</span> techniques should be carried out with consistent and utmost up-todate physical models. Therefore, c5++ is being developed, which will act as a framework under which dedicated space <span class="hlt">geodetic</span> applications can be created. Due to its nature, combination of different techniques as well as automated processing of VLBI experiments will become possible with c5++.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvE..94a2407Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvE..94a2407Y"><span>Size-dependent regulation of synchronized <span class="hlt">activity</span> in living neuronal <span class="hlt">networks</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yamamoto, Hideaki; Kubota, Shigeru; Chida, Yudai; Morita, Mayu; Moriya, Satoshi; Akima, Hisanao; Sato, Shigeo; Hirano-Iwata, Ayumi; Tanii, Takashi; Niwano, Michio</p> <p>2016-07-01</p> <p>We study the effect of <span class="hlt">network</span> size on synchronized <span class="hlt">activity</span> in living neuronal <span class="hlt">networks</span>. Dissociated cortical neurons form synaptic connections in culture and generate synchronized spontaneous <span class="hlt">activity</span> within 10 days in vitro. Using micropatterned surfaces to extrinsically control the size of neuronal <span class="hlt">networks</span>, we show that synchronized <span class="hlt">activity</span> can emerge in a <span class="hlt">network</span> as small as 12 cells. Furthermore, a detailed comparison of small (˜20 cells), medium (˜100 cells), and large (˜400 cells) <span class="hlt">networks</span> reveal that synchronized <span class="hlt">activity</span> becomes destabilized in the small <span class="hlt">networks</span>. A computational modeling of neural <span class="hlt">activity</span> is then employed to explore the underlying mechanism responsible for the size effect. We find that the generation and maintenance of the synchronized <span class="hlt">activity</span> can be minimally described by: (1) the stochastic firing of each neuron in the <span class="hlt">network</span>, (2) enhancement in the <span class="hlt">network</span> <span class="hlt">activity</span> in a positive feedback loop of excitatory synapses, and (3) Ca-dependent suppression of bursting <span class="hlt">activity</span>. The model further shows that the decrease in total synaptic input to a neuron that drives the positive feedback amplification of correlated <span class="hlt">activity</span> is a key factor underlying the destabilization of synchrony in smaller <span class="hlt">networks</span>. Spontaneous neural <span class="hlt">activity</span> plays a critical role in cortical information processing, and our work constructively clarifies an aspect of the structural basis behind this.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27575164','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27575164"><span>Size-dependent regulation of synchronized <span class="hlt">activity</span> in living neuronal <span class="hlt">networks</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yamamoto, Hideaki; Kubota, Shigeru; Chida, Yudai; Morita, Mayu; Moriya, Satoshi; Akima, Hisanao; Sato, Shigeo; Hirano-Iwata, Ayumi; Tanii, Takashi; Niwano, Michio</p> <p>2016-07-01</p> <p>We study the effect of <span class="hlt">network</span> size on synchronized <span class="hlt">activity</span> in living neuronal <span class="hlt">networks</span>. Dissociated cortical neurons form synaptic connections in culture and generate synchronized spontaneous <span class="hlt">activity</span> within 10 days in vitro. Using micropatterned surfaces to extrinsically control the size of neuronal <span class="hlt">networks</span>, we show that synchronized <span class="hlt">activity</span> can emerge in a <span class="hlt">network</span> as small as 12 cells. Furthermore, a detailed comparison of small (∼20 cells), medium (∼100 cells), and large (∼400 cells) <span class="hlt">networks</span> reveal that synchronized <span class="hlt">activity</span> becomes destabilized in the small <span class="hlt">networks</span>. A computational modeling of neural <span class="hlt">activity</span> is then employed to explore the underlying mechanism responsible for the size effect. We find that the generation and maintenance of the synchronized <span class="hlt">activity</span> can be minimally described by: (1) the stochastic firing of each neuron in the <span class="hlt">network</span>, (2) enhancement in the <span class="hlt">network</span> <span class="hlt">activity</span> in a positive feedback loop of excitatory synapses, and (3) Ca-dependent suppression of bursting <span class="hlt">activity</span>. The model further shows that the decrease in total synaptic input to a neuron that drives the positive feedback amplification of correlated <span class="hlt">activity</span> is a key factor underlying the destabilization of synchrony in smaller <span class="hlt">networks</span>. Spontaneous neural <span class="hlt">activity</span> plays a critical role in cortical information processing, and our work constructively clarifies an aspect of the structural basis behind this.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27574315','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27574315"><span>How <span class="hlt">networks</span> communicate: propagation patterns in spontaneous brain <span class="hlt">activity</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mitra, Anish; Raichle, Marcus E</p> <p>2016-10-05</p> <p>Initially regarded as 'noise', spontaneous (intrinsic) <span class="hlt">activity</span> accounts for a large portion of the brain's metabolic cost. Moreover, it is now widely known that infra-slow (less than 0.1 Hz) spontaneous <span class="hlt">activity</span>, measured using resting state functional magnetic resonance imaging of the blood oxygen level-dependent (BOLD) signal, is correlated within functionally defined resting state <span class="hlt">networks</span> (RSNs). However, despite these advances, the temporal organization of spontaneous BOLD fluctuations has remained elusive. By studying temporal lags in the resting state BOLD signal, we have recently shown that spontaneous BOLD fluctuations consist of remarkably reproducible patterns of whole brain propagation. Embedded in these propagation patterns are unidirectional 'motifs' which, in turn, give rise to RSNs. Additionally, propagation patterns are markedly altered as a function of state, whether physiological or pathological. Understanding such propagation patterns will likely yield deeper insights into the role of spontaneous <span class="hlt">activity</span> in brain function in health and disease.This article is part of the themed issue 'Interpreting blood oxygen level-dependent: a dialogue between cognitive and cellular neuroscience'.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23071431','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23071431"><span>Functional modules, structural topology, and optimal <span class="hlt">activity</span> in metabolic <span class="hlt">networks</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Resendis-Antonio, Osbaldo; Hernández, Magdalena; Mora, Yolanda; Encarnación, Sergio</p> <p>2012-01-01</p> <p>Modular organization in biological <span class="hlt">networks</span> has been suggested as a natural mechanism by which a cell coordinates its metabolic strategies for evolving and responding to environmental perturbations. To understand how this occurs, there is a need for developing computational schemes that contribute to integration of genomic-scale information and assist investigators in formulating biological hypotheses in a quantitative and systematic fashion. In this work, we combined metabolome data and constraint-based modeling to elucidate the relationships among structural modules, functional organization, and the optimal metabolic phenotype of Rhizobium etli, a bacterium that fixes nitrogen in symbiosis with Phaseolus vulgaris. To experimentally characterize the metabolic phenotype of this microorganism, we obtained the metabolic profile of 220 metabolites at two physiological stages: under free-living conditions, and during nitrogen fixation with P. vulgaris. By integrating these data into a constraint-based model, we built a refined computational platform with the capability to survey the metabolic <span class="hlt">activity</span> underlying nitrogen fixation in R. etli. Topological analysis of the metabolic reconstruction led us to identify modular structures with functional <span class="hlt">activities</span>. Consistent with modular <span class="hlt">activity</span> in metabolism, we found that most of the metabolites experimentally detected in each module simultaneously increased their relative abundances during nitrogen fixation. In this work, we explore the relationships among topology, biological function, and optimal <span class="hlt">activity</span> in the metabolism of R. etli through an integrative analysis based on modeling and metabolome data. Our findings suggest that the metabolic <span class="hlt">activity</span> during nitrogen fixation is supported by interacting structural modules that correlate with three functional classifications: nucleic acids, peptides, and lipids. More fundamentally, we supply evidence that such modular organization during functional nitrogen fixation is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19830025016','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19830025016"><span>On the <span class="hlt">geodetic</span> applications of simultaneous range-differencing to LAGEOS</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pablis, E. C.</p> <p>1982-01-01</p> <p>The possibility of improving the accuracy of <span class="hlt">geodetic</span> results by use of simultaneously observed ranges to Lageos, in a differencing mode, from pairs of stations was studied. Simulation tests show that model errors can be effectively minimized by simultaneous range differencing (SRD) for a rather broad class of <span class="hlt">network</span> satellite pass configurations. The methods of least squares approximation are compared with monomials and Chebyshev polynomials and the cubic spline interpolation. Analysis of three types of orbital biases (radial, along- and across track) shows that radial biases are the ones most efficiently minimized in the SRC mode. The degree to which the other two can be minimized depends on the type of parameters under estimation and the geometry of the problem. Sensitivity analyses of the SRD observation show that for baseline length estimations the most useful data are those collected in a direction parallel to the baseline and at a low elevation. Estimating individual baseline lengths with respect to an assumed but fixed orbit not only decreases the cost, but it further reduces the effects of model biases on the results as opposed to a <span class="hlt">network</span> solution. Analogous results and conclusions are obtained for the estimates of the coordinates of the pole.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24928353','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24928353"><span>Enhanced excitatory synaptic <span class="hlt">network</span> <span class="hlt">activity</span> following transient group I metabotropic glutamate <span class="hlt">activation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pan, Y-Z; Rutecki, P A</p> <p>2014-09-05</p> <p>Prolonged <span class="hlt">activation</span> of group I metabotropic glutamate receptors (mGluRs) using the agonist (S)-3,5-dihydroxyphenylglycine (DHPG) produces long-lasting changes in the CA3 region of the hippocampal slice. Changes in CA3 pyramidal neuron excitability that follow DHPG exposure result in abnormal <span class="hlt">network</span> <span class="hlt">activity</span> manifest by epileptiform <span class="hlt">activity</span> that consists of interictal and longer lasting ictal epileptiform discharges. In this study we evaluated changes in synaptic <span class="hlt">activity</span> of CA3 neurons in rat hippocampal slices that occurred after exposure to DHPG. Whole-cell voltage-clamp recordings were made from visually identified CA3 neurons in control artificial cerebrospinal fluid at times greater than 1h after DHPG exposure. Compared to control slices, neurons from slices exposed to DHPG showed enhanced amplitude and frequency of spontaneously occurring excitatory postsynaptic currents (EPSCs) without a concurrent change in inhibitory postsynaptic current (IPSC) amplitude or frequency. Miniature EPSCs were not affected by DHPG exposure but mIPSCs occurred less frequently and were of reduced amplitude. IPSCs recorded in the presence of ionotropic glutamate receptor blockade occurred less frequently in neurons that had been exposed to DHPG. Monosynaptic-evoked IPSPs were also reduced in amplitude in neurons that had been exposed to DHPG. Taken together, these findings demonstrated an enhanced <span class="hlt">network</span> excitability of the CA3 region and failure of compensatory synaptic inhibition. We propose that prolonged <span class="hlt">activation</span> of group I mGluR that may occur under conditions of pathological glutamate release results in long-lasting changes in CA3 synaptic <span class="hlt">network</span> <span class="hlt">activity</span> and epileptiform <span class="hlt">activity</span> driven by excessive synaptic excitation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110011879','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110011879"><span>The State and Development Direction of the <span class="hlt">Geodetic</span> VLBI Station in Korea</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ju, Hyunhee; Kim, Myungho; Kim, Suchul; Park, Jinsik; Kondo, Tetsuro; Kim, Tuhwan; Oh, Hongjong; Yi, Sangoh</p> <p>2010-01-01</p> <p>A permanent <span class="hlt">geodetic</span> VLBI station with a 22-m diameter antenna will be newly constructed in Korea by the National Geographic Information Institute (NGII) under the project Korea VLBI system for Geodesy (KVG) that aims at maintaining the Korean <span class="hlt">geodetic</span> datum accurately on the International Terrestrial Reference Frame (ITRF). KVG can receive 2, 8, 22, and 43 GHz bands simultaneously in order to conduct <span class="hlt">geodetic</span> and astronomical VLBI observations with Korea astronomical VLBI stations along with <span class="hlt">geodetic</span> observations with IVS stations. This simultaneous four-band receiving capability is a unique feature of the KVG system. The KVG has started officially in October 2008. A new <span class="hlt">geodetic</span> VLBI station will be constructed at Sejong city (about 120 km south of Seoul and about 20 km north-northwest of Daejeon) and construction of all systems will be completed in 2011.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Personal+AND+financial+AND+business&pg=3&id=EJ720313','ERIC'); return false;" href="http://eric.ed.gov/?q=Personal+AND+financial+AND+business&pg=3&id=EJ720313"><span>Who Can You Turn to? Tie <span class="hlt">Activation</span> within Core Business Discussion <span class="hlt">Networks</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Renzulli, Linda A.; Aldrich, Howard</p> <p>2005-01-01</p> <p>We examine the connection between personal <span class="hlt">network</span> characteristics and the <span class="hlt">activation</span> of ties for access to resources during routine times. We focus on factors affecting business owners' use of their core <span class="hlt">network</span> ties to obtain legal, loan, financial and expert advice. Owners rely more on core business ties when their core <span class="hlt">networks</span> contain a high…</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3772553','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3772553"><span>Both novelty and expertise increase action observation <span class="hlt">network</span> <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Liew, Sook-Lei; Sheng, Tong; Margetis, John L.; Aziz-Zadeh, Lisa</p> <p>2013-01-01</p> <p>Our experiences with others affect how we perceive their actions. In particular, <span class="hlt">activity</span> in bilateral premotor and parietal cortices during action observation, collectively known as the action observation <span class="hlt">network</span> (AON), is modulated by one's expertise with the observed actions or individuals. However, conflicting reports suggest that AON <span class="hlt">activity</span> is greatest both for familiar and unfamiliar actions. The current study examines the effects of different types and amounts of experience (e.g., visual, interpersonal, personal) on AON <span class="hlt">activation</span>. fMRI was used to scan 16 healthy participants without prior experience with individuals with amputations (novices), 11 experienced occupational therapists (OTs) who had varying amounts of experience with individuals with amputations, and one individual born with below-elbow residual limbs (participant CJ), as they viewed video clips of goal-matched actions performed by an individual with residual limbs and by an individual with hands. Participants were given increased visual exposure to actions performed by both effectors midway through the scanning procedure. Novices demonstrated a large AON response to the initial viewing of an individual with residual limbs compared to one with hands, but this signal was attenuated after they received visual exposure to both effectors. In contrast, OTs, who had moderate familiarity with residual limbs, demonstrated a lower AON response upon initial viewing—similar to novices after they received visual exposure. At the other extreme, CJ, who has extreme familiarity with residual limbs both visually and motorically, shows a largely increased left-lateralized AON response, exceeding that of novices and experienced OTs, when viewing the residual limb compared to hand actions. These results suggest that a nuanced model of AON engagement is needed to explain how cases of both extreme experience (CJ) and extreme novelty (novices) can result in the greatest AON <span class="hlt">activity</span>. PMID:24062656</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPhCS.604a2007G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPhCS.604a2007G"><span>Recent Progress in Some <span class="hlt">Active</span> Topics on Complex <span class="hlt">Networks</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gu, J.; Zhu, Y.; Guo, L.; Jiang, J.; Chi, L.; Li, W.; Wang, Q. A.; Cai, X.</p> <p>2015-04-01</p> <p>Complex <span class="hlt">networks</span> have been extensively studied across many fields, especially in interdisciplinary areas. It has since long been recognized that topological structures and dynamics are important aspects for capturing the essence of complex <span class="hlt">networks</span>. The recent years have also witnessed the emergence of several new elements which play important roles in <span class="hlt">network</span> study. By combining the results of different research orientations in our group, we provide here a review of the recent advances in regards to spectral graph theory, opinion dynamics, interdependent <span class="hlt">networks</span>, graph energy theory and temporal <span class="hlt">networks</span>. We hope this will be helpful for the newcomers of those fields to discover new intriguing topics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4610572','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4610572"><span><span class="hlt">Active</span> Low Intrusion Hybrid Monitor for Wireless Sensor <span class="hlt">Networks</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Navia, Marlon; Campelo, Jose C.; Bonastre, Alberto; Ors, Rafael; Capella, Juan V.; Serrano, Juan J.</p> <p>2015-01-01</p> <p>Several systems have been proposed to monitor wireless sensor <span class="hlt">networks</span> (WSN). These systems may be <span class="hlt">active</span> (causing a high degree of intrusion) or passive (low observability inside the nodes). This paper presents the implementation of an <span class="hlt">active</span> hybrid (hardware and software) monitor with low intrusion. It is based on the addition to the sensor node of a monitor node (hardware part) which, through a standard interface, is able to receive the monitoring information sent by a piece of software executed in the sensor node. The intrusion on time, code, and energy caused in the sensor nodes by the monitor is evaluated as a function of data size and the interface used. Then different interfaces, commonly available in sensor nodes, are evaluated: serial transmission (USART), serial peripheral interface (SPI), and parallel. The proposed hybrid monitor provides highly detailed information, barely disturbed by the measurement tool (interference), about the behavior of the WSN that may be used to evaluate many properties such as performance, dependability, security, etc. Monitor nodes are self-powered and may be removed after the monitoring campaign to be reused in other campaigns and/or WSNs. No other hardware-independent monitoring platforms with such low interference have been found in the literature. PMID:26393604</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26393604','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26393604"><span><span class="hlt">Active</span> Low Intrusion Hybrid Monitor for Wireless Sensor <span class="hlt">Networks</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Navia, Marlon; Campelo, Jose C; Bonastre, Alberto; Ors, Rafael; Capella, Juan V; Serrano, Juan J</p> <p>2015-09-18</p> <p>Several systems have been proposed to monitor wireless sensor <span class="hlt">networks</span> (WSN). These systems may be <span class="hlt">active</span> (causing a high degree of intrusion) or passive (low observability inside the nodes). This paper presents the implementation of an <span class="hlt">active</span> hybrid (hardware and software) monitor with low intrusion. It is based on the addition to the sensor node of a monitor node (hardware part) which, through a standard interface, is able to receive the monitoring information sent by a piece of software executed in the sensor node. The intrusion on time, code, and energy caused in the sensor nodes by the monitor is evaluated as a function of data size and the interface used. Then different interfaces, commonly available in sensor nodes, are evaluated: serial transmission (USART), serial peripheral interface (SPI), and parallel. The proposed hybrid monitor provides highly detailed information, barely disturbed by the measurement tool (interference), about the behavior of the WSN that may be used to evaluate many properties such as performance, dependability, security, etc. Monitor nodes are self-powered and may be removed after the monitoring campaign to be reused in other campaigns and/or WSNs. No other hardware-independent monitoring platforms with such low interference have been found in the literature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4009070','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4009070"><span>Predicting Single-Neuron <span class="hlt">Activity</span> in Locally Connected <span class="hlt">Networks</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Azhar, Feraz; Anderson, William S.</p> <p>2014-01-01</p> <p>The characterization of coordinated <span class="hlt">activity</span> in neuronal populations has received renewed interest in the light of advancing experimental techniques that allow recordings from multiple units simultaneously. Across both in vitro and in vivo preparations, nearby neurons show coordinated responses when spontaneously <span class="hlt">active</span> and when subject to external stimuli. Recent work (Truccolo, Hochberg, & Donoghue, 2010) has connected these coordinated responses to behavior, showing that small ensembles of neurons in arm-related areas of sensorimotor cortex can reliably predict single-neuron spikes in behaving monkeys and humans. We investigate this phenomenon using an analogous point process model, showing that in the case of a computational model of cortex responding to random background inputs, one is similarly able to predict the future state of a single neuron by considering its own spiking history, together with the spiking histories of randomly sampled ensembles of nearby neurons. This model exhibits realistic cortical architecture and displays bursting episodes in the two distinct connectivity schemes studied. We conjecture that the baseline predictability we find in these instances is characteristic of locally connected <span class="hlt">networks</span> more broadly considered. PMID:22845824</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.S43D..05W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.S43D..05W"><span>Challenges in Defining Seismogenic Zone Using <span class="hlt">Geodetic</span> and Structural Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, K.; Hyndman, R. D.</p> <p>2004-12-01</p> <p>The coseismic fault slip area in recent subduction earthquakes can be determined from seismological, tsumani, and <span class="hlt">geodetic</span> observations. The coseismic rupture appears to be limited generally by a temperature around 125° C at the updip end and a temperature around 350° C or the intersection of the plate interface with the forearc Moho at the downdip end, with significant along-strike variations. Defining the seismogenic zone from interseismic deformation is much more challenging, because of the fewer available observation methods and the poorly understood earthquake cycle deformation process. It is reasonable to expect the rupture zone to be locked in the interseismic period, but the updip and downdip limits of mechanical locking do not usually have clear simple <span class="hlt">geodetic</span> signatures. Fault motion outside the locked zone is not simply determined by frictional properties and fault stress. Surface deformation changes through the earthquake cycle due to both transient fault slip and viscoelastic stress relaxation. If an elastic dislocation model is used to explain decade- and century-scale viscoelastic interseismic deformation, a more gradual downdip tapering of locking is required to fit <span class="hlt">geodetic</span> observations long after the most recent earthquake. Rate- and state-dependent friction and nonlinear mantle rock rheology are both important candidates in explaining transient afterslip of duration of days to a few years downdip of coseismic rupture, although their distinction is obscured by strain localization in nonlinear deformation. Newtonian rheology is arguably applicable a few fault dimensions from the rupture zone and several years after the earthquake. Cascadia and Nankai episodic "silent" slips indicate that the forearc material at 30-40 km depths is able to accumulate and release elastic strain energy. It has been proposed that such slip may be shear deformation of a band of km's thickness above the subducting slab (and that the shear band terminates seismogenic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860017269','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860017269"><span>Plate motions and deformations from geologic and <span class="hlt">geodetic</span> data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jordan, T. H.</p> <p>1986-01-01</p> <p>Research effort on behalf of the Crustal Dynamics Project focused on the development of methodologies suitable for the analysis of space-<span class="hlt">geodetic</span> data sets for the estimation of crustal motions, in conjunction with results derived from land-based <span class="hlt">geodetic</span> data, neo-tectonic studies, and other geophysical data. These methodologies were used to provide estimates of both global plate motions and intraplate deformation in the western U.S. Results from the satellite ranging experiment for the rate of change of the baseline length between San Diego and Quincy, California indicated that relative motion between the North American and Pacific plates over the course of the observing period during 1972 to 1982 were consistent with estimates calculated from geologic data averaged over the past few million years. This result, when combined with other kinematic constraints on western U.S. deformation derived from land-based geodesy, neo-tectonic studies, and other geophysical data, places limits on the possible extension of the Basin and Range province, and implies significant deformation is occurring west of the San Andreas fault. A new methodology was developed to analyze vector-position space-<span class="hlt">geodetic</span> data to provide estimates of relative vector motions of the observing sites. The algorithm is suitable for the reduction of large, inhomogeneous data sets, and takes into account the full position covariances, errors due to poorly resolved Earth orientation parameters and vertical positions, and reduces baises due to inhomogeneous sampling of the data. This methodology was applied to the problem of estimating the rate-scaling parameter of a global plate tectonic model using satellite laser ranging observations over a five-year interval. The results indicate that the mean rate of global plate motions for that interval are consistent with those averaged over several million years, and are not consistent with quiescent or greatly accelerated plate motions. This methodology was also</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986mit..reptQ....J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986mit..reptQ....J"><span>Plate motions and deformations from geologic and <span class="hlt">geodetic</span> data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jordan, T. H.</p> <p>1986-06-01</p> <p>Research effort on behalf of the Crustal Dynamics Project focused on the development of methodologies suitable for the analysis of space-<span class="hlt">geodetic</span> data sets for the estimation of crustal motions, in conjunction with results derived from land-based <span class="hlt">geodetic</span> data, neo-tectonic studies, and other geophysical data. These methodologies were used to provide estimates of both global plate motions and intraplate deformation in the western U.S. Results from the satellite ranging experiment for the rate of change of the baseline length between San Diego and Quincy, California indicated that relative motion between the North American and Pacific plates over the course of the observing period during 1972 to 1982 were consistent with estimates calculated from geologic data averaged over the past few million years. This result, when combined with other kinematic constraints on western U.S. deformation derived from land-based geodesy, neo-tectonic studies, and other geophysical data, places limits on the possible extension of the Basin and Range province, and implies significant deformation is occurring west of the San Andreas fault. A new methodology was developed to analyze vector-position space-<span class="hlt">geodetic</span> data to provide estimates of relative vector motions of the observing sites. The algorithm is suitable for the reduction of large, inhomogeneous data sets, and takes into account the full position covariances, errors due to poorly resolved Earth orientation parameters and vertical positions, and reduces baises due to inhomogeneous sampling of the data. This methodology was applied to the problem of estimating the rate-scaling parameter of a global plate tectonic model using satellite laser ranging observations over a five-year interval. The results indicate that the mean rate of global plate motions for that interval are consistent with those averaged over several million years, and are not consistent with quiescent or greatly accelerated plate motions. This methodology was also</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JAESc..82...21D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JAESc..82...21D"><span><span class="hlt">Geodetic</span> and seismological investigation of crustal deformation near Izmir (Western Anatolia)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dogru, Asli; Gorgun, Ethem; Ozener, Haluk; Aktug, Bahadir</p> <p>2014-03-01</p> <p>The Aegean region including western Turkey, mainland Greece, and the Hellenic Arc is the most seismological and geodynamical <span class="hlt">active</span> domain in the Alpine Himalayan Belt. In this study, we processed 3 years of survey-mode GPS data and present the analysis of a combination of <span class="hlt">geodetic</span> and seismological data around Izmir, which is the third most populated city in Turkey. The velocities obtained from 15 sites vary between 25 mm/yr and 28 mm/yr relative to the Eurasian plate. The power law exponent of earthquake size distribution (b-value) ranges from 0.8 to 2.8 in the Izmir region between 26.2°E and 27.2°E. The lowest b-value zones are found along Karaburun Fault (b = 0.8) and, between Seferihisar and Tuzla Faults (b = 0.8). A localized stress concentration is expected from numerical models of seismicity along geometrical locked fault patches. Therefore, areas with lowest b-values are considered to be the most likely location for a strong earthquake, a prediction that is confirmed by the 2005 Mw = 5.9 Seferihisar earthquake sequences, with epicentres located to the south of the Karaburun Fault. The north-south extension of the Izmir area is corroborated by extension rates up to 140 nanostrain/yr as obtained from our GPS data. We combined the 3-year GPS velocity field with the published velocity field to determine the strain rate pattern in the area. The spatial distribution of b-value reflects the normal background due to the tectonic framework and is corroborated by the <span class="hlt">geodetic</span> data. b-Values correlate with strain pattern. This relationship suggests that decrease of b-values signifies accumulating strain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.V31E4799P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.V31E4799P"><span>Investigating the long-term <span class="hlt">geodetic</span> response to magmatic intrusions at volcanoes in northern California</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parker, A. L.; Biggs, J.; Annen, C.; Houseman, G. A.; Yamasaki, T.; Wright, T. J.; Walters, R. J.; Lu, Z.</p> <p>2014-12-01</p> <p>Ratios of intrusive to extrusive <span class="hlt">activity</span> at volcanic arcs are thought to be high, with estimates ranging between 5:1 and 30:1. Understanding the <span class="hlt">geodetic</span> response to magmatic intrusion is therefore fundamental to large-scale studies of volcano deformation, providing insight into the dynamics of the inter-eruptive period of the volcano cycle and the building of continental crust. In northern California, we identify two volcanoes - Medicine Lake Volcano (MLV) and Lassen Volcanic Center (LaVC) - that exhibit long-term (multi-decadal) subsidence. We test the hypothesis that deformation at these volcanoes results from processes associated with magmatic intrusions. We first constrain the spatial and temporal characteristics of the deformation fields, establishing the first time-series of deformation at LaVC using InSAR data, multi-temporal analysis techniques and global weather models. Although the rates of deformation at the two volcanoes are similar (~1 cm/yr), our results show that the ratio of vertical to horizontal displacements is significantly different, suggesting contrasting source geometries. To test the origin of deformation, we develop modeling strategies to investigate thermal and viscoelastic processes associated with magmatic intrusions. The first model we develop couples analytical <span class="hlt">geodetic</span> models to a numerical model of volume loss due to cooling and crystallization based upon temperature-melt fraction relationships from petrological experiments. This model provides evidence that magmatic intrusion at MLV has occurred more recently than the last eruption ~1 ka. The second model we test uses a finite element approach to simulate the time-dependent viscoelastic response of the crust to magmatic intrusion. We assess the magnitude and timescales of ground deformation that may result from these processes, exploring the model parameter space before applying the models to our InSAR observations of subsidence in northern California.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.G21A..04R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.G21A..04R"><span>Real-time GPS positioning of the Pacific Northwest <span class="hlt">Geodetic</span> Array</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rabak, I.; Santillan, V. M.; Scrivner, C. W.; Melbourne, T. I.</p> <p>2009-12-01</p> <p>The Pacific Northwest <span class="hlt">Geodetic</span> Array (PANGA) is now comprised of nearly 130 continuously operating GPS receivers located throughout the Cascadia subduction zone. The stations straddle <span class="hlt">active</span> crustal faults, volcanoes and landslides, they span the megathrust forearc and tsunamigenic regions along the Pacific coast, and they monitor ageing man-made structures such as dams, levees and elevated freeways. All data are streamed in real-time into CWU where they are processed in real-time into station position and tropospheric water content within a reference frame defined in central Washington. To disseminate these streams, we currently provide 16 station position streams via an interface to Google Maps to present geographically the three component real-time plots in 5 min, 1 hour, and 24 hour time periods. The user's web browser makes repeated requests at a refresh rate of 5 seconds and after the initial request it only requests new data points from the web server. The 5 min real-time plot is updated every second. The web server provides the data streams in a compact JSON (JavaScript Object Notation) form and data plotting is handled by the user's web browser. The data streams are parsed into JavaScript arrays and plotted using the new HTML5 "canvas" element. This approach produces faster response times for the data streams, and by reducing the load on the web server, allows distribution to large numbers of users. Data are also available via a dedicated Ntrip/TCP-IP socket interface. These real-time data are now being used to monitor <span class="hlt">geodetic</span> displacements caused by earthquakes, volcanic eruptions and landslides; current efforts to develop real-time finite fault inversions and automated alarm systems will be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860052286&hterms=conformity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dconformity','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860052286&hterms=conformity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dconformity"><span>Landsat Thematic Mapper <span class="hlt">geodetic</span> accuracy - Implications for geocoded map compatibility</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bryant, N. A.; Zobrist, A. L.; Walker, R. E.; Gokhmann, B.</p> <p>1985-01-01</p> <p>The <span class="hlt">geodetic</span> accuracy and geometric fidelity of corrected thematic mapper (TM) imagery are evaluated. The positional accuracy requirements for the TM are for a single band to within 0.5 pixels of true earth-surface locations at any point over 90 percent of the image and for interband registration to within 0.3 pixel tolerance over 90 percent of the data. Landsat 4 and 5 TM data are analyzed to investigate: (1) single band geometric integrity, (2) 30 m resolution interband registration; (3) image to image conformity; (4) image to ground conformity; and (5) image projective geometry conformity to a mapped earth geometry. The procedures used to study these characteristics are described. The data reveal that Landsat TM digital data met or exceed map accuracy standards for horizontal control.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19760049323&hterms=lippincott&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dlippincott','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19760049323&hterms=lippincott&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dlippincott"><span>A very-long-baseline interferometer system for <span class="hlt">geodetic</span> applications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Whitney, A. R.; Rogers, A. E. E.; Hinteregger, H. F.; Knight, C. A.; Levine, J. I.; Lippincott, S.; Clark, T. A.; Shapiro, I. I.; Robertson, D. S.</p> <p>1976-01-01</p> <p>A very-long-baseline interferometer system was designed and built for <span class="hlt">geodetic</span> applications. Each interferometer terminal records a 360-kHz spectral band of noise from a compact extragalactic radio source. The center frequency of the spectral band can be selected to sample sequentially bands covering a much wider frequency range to obtain subnanosecond accuracy in group-delay measurements. A tunnel-diode pulse generator is used to calibrate the delays in the receiver. The necessary sets of algorithms and computer programs have been developed to analyze the data and have allowed the system to be employed to make accurate determinations of vector baselines, radio-source positions, polar motion, and universal time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.5789M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.5789M"><span>Finite volume method for <span class="hlt">geodetic</span> boundary value problem</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Medľa, Matej; Mikula, Karol; Macák, Marek</p> <p>2016-04-01</p> <p>We present new finite volume numerical scheme for solving the <span class="hlt">Geodetic</span> boundary value problem on non-uniform logically rentangular grids together with new second-order upwind treatment of the oblique derivative. First the logically rectangular grid is built above the Earth topography by evolving surface approach. Then the Laplace equation is solved on such grid by using the finite volume method in which the normal derivative on finite volume boundary face is split into derivative in tangential direction and a derivative in direction of the vector connecting representative points of neigbouring finite volumes. The oblique derivative boundary condition is understood as a stationary advection equation and second-order upwind method is developed for its discretization. The numerical experiments will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23813685','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23813685"><span>How yawning switches the default-mode <span class="hlt">network</span> to the attentional <span class="hlt">network</span> by <span class="hlt">activating</span> the cerebrospinal fluid flow.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Walusinski, Olivier</p> <p>2014-03-01</p> <p>Yawning is a behavior to which little research has been devoted. However, its purpose has not yet been demonstrated and remains controversial. In this article, we propose a new theory involving the brain <span class="hlt">network</span> that is functional during the resting state, that is, the default mode <span class="hlt">network</span>. When this <span class="hlt">network</span> is <span class="hlt">active</span>, yawning manifests a process of switching to the attentional system through its capacity to increase circulation of cerebrospinal fluid (CSF), thereby increasing clearance of somnogenic factors (prostaglandin D(2), adenosine, and others) accumulating in the cerebrospinal fluid.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.G13A0510L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.G13A0510L"><span>A Stable <span class="hlt">Geodetic</span> Reference Frame within the COCONET Footprint to Enable High-Accuracy Ground Deformation Study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, H.; Wang, G.; Yu, J.</p> <p>2014-12-01</p> <p>COCONET(Continuously Operating Caribbean GPS Observational <span class="hlt">Network</span>) is a multidisciplinary research infrastructure focused on improving the ability to understand, predict, and prepare for multiple natural hazards in the Caribbean, Central America, and Northern Andes. GPS data alone cannot provide accurate ground deformation information over time and space. A precise regional reference frame is needed in interpolating GPS observations to address regional and local ground deformations. Failure to use a precise reference frame would cause unintended negative consequences. The mainly purpose of this study is to establish a stable <span class="hlt">geodetic</span> reference frame within the COCONet footprint (abbreviated as "COCONet-RF") and to provide positional time series and velocities (relative to COCONet-RF) of all permanent GPS stations within the COCONet footprint to the public. The GIPSY software package was used to calculate position within IGS08. The local reference frame was realized by a 14-parameter Helmert transformation technique. It will be periodically updated in order to synchronize with the update of the IGS reference frame. This stable COCONer-RF would provide a higher accuracy <span class="hlt">geodetic</span> infrastructure for delineating the magnitude and spatial and temporal variations of ground deformations associated with landslides, faulting, subsidence, and volcanoes. Researchers who are not familiar with GPS data processing and reference transformation will be able to directly integrate COCONET products into their specific research.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ISPAr41B8.1169S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ISPAr41B8.1169S"><span>Detection of Coastline Deformation Using Remote Sensing and <span class="hlt">Geodetic</span> Surveys</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sabuncu, A.; Dogru, A.; Ozener, H.; Turgut, B.</p> <p>2016-06-01</p> <p>The coastal areas are being destroyed due to the usage that effect the natural balance. Unconsciously sand mining from the sea for nearshore nourishment and construction uses are the main ones. Physical interferences for mining of sand cause an ecologic threat to the coastal environment. However, use of marine sand is inevitable because of economic reasons or unobtainable land-based sand resources. The most convenient solution in such a protection-usage dilemma is to reduce negative impacts of sand production from marine. This depends on the accurate determination of criteriaon production place, style, and amount of sand. With this motivation, nearshore geodedic surveying studies performed on Kilyos Campus of Bogazici University located on the Black Sea coast, north of Istanbul, Turkey between 2001-2002. The study area extends 1 km in the longshore. <span class="hlt">Geodetic</span> survey was carried out in the summer of 2001 to detect the initial condition for the shoreline. Long-term seasonal changes in shoreline positions were determined biannually. The coast was measured with post-processed kinematic GPS. Besides, shoreline change has studied using Landsat imagery between the years 1986-2015. The data set of Landsat 5 imageries were dated 05.08.1986 and 31.08.2007 and Landsat 7 imageries were dated 21.07.2001 and 28.07.2015. Landcover types in the study area were analyzed on the basis of pixel based classification method. Firstly, unsupervised classification based on ISODATA (Iterative Self Organizing Data Analysis Technique) has been applied and spectral clusters have been determined that gives prior knowledge about the study area. In the second step, supervised classification was carried out by using the three different approaches which are minimum-distance, parallelepiped and maximum-likelihood. All pixel based classification processes were performed with ENVI 4.8 image processing software. Results of <span class="hlt">geodetic</span> studies and classification outputs will be presented in this paper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993AAS...182.3503S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993AAS...182.3503S"><span><span class="hlt">Geodetic</span> VLBI Observations with the Hat Creek Telescope</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shaffer, D. B.; NASA/Gsfc Geodetic VLBI Group</p> <p>1993-05-01</p> <p><span class="hlt">Geodetic</span> VLBI observations made with the Hat Creek 85' antenna were important contributions to the NASA Crustal Dynamics Program (CDP). Among other things, the CDP studied motions of the Earth's crustal plates and deformation in the vicinity of the San Andreas Fault in California. The 85' antenna was one of the three fundamental anchor points in California east of the San Andreas fault that were used from 1983 to 1991 to determine the motions at various mobile VLBI sites along the San Andreas and to determine the Pacific plate motions at Vandenberg Air Force Base and Ft. Ord (California) and Kauai (Hawaii). The Hat Creek site itself was found to be moving 10.6 +/- 0.4 (one sigma ) mm/yr to the WNW (PA 305deg ) with respect to a ``stable" eastern North America. Hat Creek is located near the western edge of the Northern Basin and Range province. Its motion is thought to be a combination of WNW extension across the Basin and Range, and a small component of NW elastic deformation due to the interaction between the North American and Pacific plates. <span class="hlt">Geodetic</span> VLBI measurements from Hat Creek to the nearby Quincy and the more distant Ely (Nevada) and Platteville (Colorado) mobile sites were the key measurements in defining the extension rate for the Northern Basin and Range as 8 +/- 2 mm/yr (PA ~ 300deg ). Hat Creek was also the anchor point for measuring a 5 cm northward seismic displacement at the Ft. Ord mobile site due to the Loma Prieta earthquake. We will show the motion of California and Pacific basin sites for which Hat Creek contributed important data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1610068H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1610068H"><span><span class="hlt">Geodetic</span> constraints on volcanic plume height at Grímsvötn volcano, Iceland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hreinsdóttir, Sigrún; Sigmundsson, Freysteinn; Roberts, Matthew; Björnsson, Halldór; Grapenthin, Ronni; Arason, Pórdur; Árnadóttir, Thóra; Hólmjárn, Jósef; Geirsson, Halldór; Bennett, Richard; Gudmundsson, Magnús; Oddsson, Björn; Ófeigsson, Benedikt; Villemin, Thierry; Jónsson, Torsteinn; Sturkell, Erik; Höskuldsson, Ármann; Larsen, Gudrún; Thordarson, Thor; Óladóttir, Bergrún</p> <p>2014-05-01</p> <p>In 2011 a VEI 4 explosive eruption took place at Grímsvötn volcano, Iceland. Grímsvötn is a subglacial basaltic volcano beneath the Vatnajökull ice cap. It is Iceland's most frequently erupting volcano, with recent eruptions in 1983, 1998, 2004, and 2011. The volcano has a low seismic velocity anomaly down to about 3 km depth, interpreted as a magma chamber. A continuous GPS station and a tiltmeter are located on a nunatak, Mount Grímsfjall, which protrudes from the ice at the southern rim of the caldera. The 21-28 May 2011 eruption was Grímsvötn's largest since 1873, resulting in airspace closure in northern Europe and the cancellation of about 900 passenger flights. The eruption was preceded by gradual inflation following the 2004 eruption and progressive increase in seismicity. Kinematic 1 Hz solutions were derived for the position of the GPS station in the hours immediately before and during the 2011 eruption. The onset of deformation preceded the eruption by one hour and reached maximum of 0.57 m within 48 hours. Throughout the eruption the GPS station moved consistently in direction N38.4+/-0.5W, opposite to the direction of movements during the 2004-2011 inter eruptive phase. The deformation characteristics suggest that the signal was mostly due to pressure change in a source at 1.7 +/- 0.2 km depth. We use the <span class="hlt">geodetic</span> measurements to infer co-eruptive pressure change in the magma chamber using the Mogi model. The rate of pressure drop is then used to estimate the magma flow rate from the chamber. Numerous studies have shown that plume height in explosive eruptions can be related to magma discharge. Using an empirical relationship between the volcanic plume height and magma flow rate (Mastin et al., 2009) we estimate the evolution of the plume height from the <span class="hlt">geodetic</span> data. Two weather radars monitored the height of the volcanic plume during the eruption. A strong initial plume with peaks at 20-25 km was followed by a declining, pulsating <span class="hlt">activity</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatSR...517830B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatSR...517830B"><span>Muscle <span class="hlt">networks</span>: Connectivity analysis of EMG <span class="hlt">activity</span> during postural control</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boonstra, Tjeerd W.; Danna-Dos-Santos, Alessander; Xie, Hong-Bo; Roerdink, Melvyn; Stins, John F.; Breakspear, Michael</p> <p>2015-12-01</p> <p>Understanding the mechanisms that reduce the many degrees of freedom in the musculoskeletal system remains an outstanding challenge. Muscle synergies reduce the dimensionality and hence simplify the control problem. How this is achieved is not yet known. Here we use <span class="hlt">network</span> theory to assess the coordination between multiple muscles and to elucidate the neural implementation of muscle synergies. We performed connectivity analysis of surface EMG from ten leg muscles to extract the muscle <span class="hlt">networks</span> while human participants were standing upright in four different conditions. We observed widespread connectivity between muscles at multiple distinct frequency bands. The <span class="hlt">network</span> topology differed significantly between frequencies and between conditions. These findings demonstrate how muscle <span class="hlt">networks</span> can be used to investigate the neural circuitry of motor coordination. The presence of disparate muscle <span class="hlt">networks</span> across frequencies suggests that the neuromuscular system is organized into a multiplex <span class="hlt">network</span> allowing for parallel and hierarchical control structures.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.5800D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.5800D"><span><span class="hlt">Geodetic</span> Leveling Data In Northern-central Apennines (italy): Vertical <span class="hlt">Geodetic</span> Strain Versus Seismicity and Seismogenic Structures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>D'Anastasio, E.; de Martini, P. M.; Selvaggi, G.; Pantosti, D.; Marchioni, A.</p> <p></p> <p>For over 120 years the Istituto Geografico Militare d'Italia (IGM) has repeatedly mea- sured the elevation of selected routes running along and across the Italian peninsula. Some of these routes have been measured three times during a time span of over a century, thus yielding a fundamental contribution to the quantification of vertical tec- tonic strains. Through the years, the main national first order leveling lines, for which the measurement accuracy is particularly good, have captured long-wavelength trends, interpreted as regional uplift or doming of volcanic areas, together with coseismic el- evation changes associated with large earthquakes. The scope of this contribution is to present our methodology in the analysis of the regional <span class="hlt">geodetic</span> signal and to stimu- late the discussion on its possible relations with the instrumental/historical seismicity and with known major seismogenic structures. As a first step of this project we have studied in detail four transects across the northern-central Apennines, using seven lev- eling lines for a total length of about 750 km. For each route we have at least a 20 years-long record and a benchmark's density higher than 0.3/km. The most important errors, both random and systematic, will be discussed together with IGM's standard for first order leveling lines and with the probable total error we adopted as a good measure of the overall uncertainty. Being very arduous to determine absolute heights for any benchmark in Italy, we decided to adopt a procedure involving relative eleva- tion changes, where the westernmost point (on the Thyrrenian side) of each transect is assumed stable. The observed elevation changes stand significantly above the detec- tion threshold of the <span class="hlt">geodetic</span> instruments and show regional long-wavelength signal. Along three of the four transects, a relative maximum elevation change rate of about 1 mm/yr has been observed. A preliminary comparison of the <span class="hlt">geodetic</span> signals with instrumental and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1008305','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1008305"><span>Biophysical Model of Cortical <span class="hlt">Network</span> <span class="hlt">Activity</span> and the Influence of Electrical Stimulation</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2015-11-13</p> <p>parameters for seizure disruption using neural <span class="hlt">network</span> simulations, Biological Cybernetics (08 2007) W.S. Anderson, P. Kudela, S. Weinberg, G.K...Bergey, P.J. Franaszczuk. Phase-dependent stimulation effects on bursting <span class="hlt">activity</span> in a neural <span class="hlt">network</span> cortical simulation, Epilepsy Research (07 2008...Epilepsy Research (06 2011) WS Anderson, F Azhar. Predicting Single-Neuron <span class="hlt">Activity</span> in Locally Connected <span class="hlt">Networks</span> , Neural Computation (05 2011</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1711093G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1711093G"><span>Characterization of Ground Displacement Sources from Variational Bayesian Independent Component Analysis of Space <span class="hlt">Geodetic</span> Time Series</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gualandi, Adriano; Serpelloni, Enrico; Elina Belardinelli, Maria; Bonafede, Maurizio; Pezzo, Giuseppe; Tolomei, Cristiano</p> <p>2015-04-01</p> <p>, giving a more reliable estimate of them. Here we introduce the vbICA technique and present its application on synthetic data that simulate a GPS <span class="hlt">network</span> recording ground deformation in a tectonically <span class="hlt">active</span> region, with synthetic time-series containing interseismic, coseismic, and postseismic deformation, plus seasonal deformation, and white and coloured noise. We study the ability of the algorithm to recover the original (known) sources of deformation, and then apply it to a real scenario: the Emilia seismic sequence (2012, northern Italy), which is an example of seismic sequence occurred in a slowly converging tectonic setting, characterized by several local to regional anthropogenic or natural sources of deformation, mainly subsidence due to fluid withdrawal and sediments compaction. We apply both PCA and vbICA to displacement time-series recorded by continuous GPS and InSAR (Pezzo et al., EGU2015-8950).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED390024.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED390024.pdf"><span><span class="hlt">Active</span> Readers--What Benefits Do They Gain from an Educational Telecommunications <span class="hlt">Network</span>?</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Jacobs, Gloria; DiMauro, Vanessa</p> <p></p> <p>"<span class="hlt">Active</span> readers" are silent members of telecommunications <span class="hlt">networks</span> who read but do not contribute. Often derided as lurkers, <span class="hlt">active</span> readers benefit from their <span class="hlt">network</span> participation and in turn professionally benefit others. A study, still in progress, is interviewing 20 silent participants of the LabNet community who have posted fewer…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27562484','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27562484"><span>Cooperative wireless <span class="hlt">network</span> control based health and <span class="hlt">activity</span> monitoring system.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Prakash, R; Ganesh, A Balaji; Girish, Siva V</p> <p>2016-10-01</p> <p>A real-time cooperative communication based wireless <span class="hlt">network</span> is presented for monitoring health and <span class="hlt">activity</span> of an end-user in their environment. The cooperative communication offers better energy consumption and also an opportunity to aware the current location of a user non-intrusively. The link between mobile sensor node and relay node is dynamically established by using Received Signal Strength Indicator (RSSI) and Link Quality Indicator (LQI) based on adaptive relay selection scheme. The study proposes a Linear Acceleration based Transmission Power Decision Control (LA-TPDC) algorithm to further enhance the energy efficiency of cooperative communication. Further, the occurrences of false alarms are carefully prevented by introducing three stages of sequential warning system. The real-time experiments are carried-out by using the nodes, namely mobile sensor node, relay nodes and a destination node which are indigenously developed by using a CC430 microcontroller integrated with an in-built transceiver at 868 MHz. The wireless node performance characteristics, such as energy consumption, Signal-Noise ratio (SNR), Bit Error Rate (BER), Packet Delivery Ratio (PDR) and transmission offset are evaluated for all the participated nodes. The experimental results observed that the proposed linear acceleration based transmission power decision control algorithm almost doubles the battery life time than energy efficient conventional cooperative communication.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4230731','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4230731"><span>Dynamics on <span class="hlt">Networks</span>: The Role of Local Dynamics and Global <span class="hlt">Networks</span> on the Emergence of Hypersynchronous Neural <span class="hlt">Activity</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Schmidt, Helmut; Petkov, George; Richardson, Mark P.; Terry, John R.</p> <p>2014-01-01</p> <p>Graph theory has evolved into a useful tool for studying complex brain <span class="hlt">networks</span> inferred from a variety of measures of neural <span class="hlt">activity</span>, including fMRI, DTI, MEG and EEG. In the study of neurological disorders, recent work has discovered differences in the structure of graphs inferred from patient and control cohorts. However, most of these studies pursue a purely observational approach; identifying correlations between properties of graphs and the cohort which they describe, without consideration of the underlying mechanisms. To move beyond this necessitates the development of computational modeling approaches to appropriately interpret <span class="hlt">network</span> interactions and the alterations in brain dynamics they permit, which in the field of complexity sciences is known as dynamics on <span class="hlt">networks</span>. In this study we describe the development and application of this framework using modular <span class="hlt">networks</span> of Kuramoto oscillators. We use this framework to understand functional <span class="hlt">networks</span> inferred from resting state EEG recordings of a cohort of 35 adults with heterogeneous idiopathic generalized epilepsies and 40 healthy adult controls. Taking emergent synchrony across the global <span class="hlt">network</span> as a proxy for seizures, our study finds that the critical strength of coupling required to synchronize the global <span class="hlt">network</span> is significantly decreased for the epilepsy cohort for functional <span class="hlt">networks</span> inferred from both theta (3–6 Hz) and low-alpha (6–9 Hz) bands. We further identify left frontal regions as a potential driver of seizure <span class="hlt">activity</span> within these <span class="hlt">networks</span>. We also explore the ability of our method to identify individuals with epilepsy, observing up to 80 predictive power through use of receiver operating characteristic analysis. Collectively these findings demonstrate that a computer model based analysis of routine clinical EEG provides significant additional information beyond standard clinical interpretation, which should ultimately enable a more appropriate mechanistic stratification of people</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010TCD.....4.1151F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010TCD.....4.1151F"><span>Comparison of direct and <span class="hlt">geodetic</span> mass balances on a multi-annual time scale</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fischer, A.</p> <p>2010-07-01</p> <p>Glacier mass balance is measured with the direct or the <span class="hlt">geodetic</span> method. In this study, the <span class="hlt">geodetic</span> mass balances of six Austrian glaciers in 19 periods between 1953 and 2006 are compared to the direct mass balances in the same periods. The mean annual <span class="hlt">geodetic</span> mass balance for all periods is -0.5 m w.e./year. The mean difference between the <span class="hlt">geodetic</span> and the direct data is -0.7 m w.e., the minimum -7.3 m w.e. and the maximum 5.6 m w.e. The accuracy of <span class="hlt">geodetic</span> mass balance resulting from the accuracy of the DEMs ranges from 2 m w.e. for photogrammetric data to 0.002 m w.e. for LIDAR data. Basal melt, seasonal snow cover and density changes of the surface layer contribute up to 0.7 m w.e. for the period of 10 years to the difference to the direct method. The characteristics of published data of Griesgletscher, Gulkana Glacier, Lemon Creek glacier, South Cascade, Storbreen, Storglaciären, and Zongo Glacier is similar to these Austrian glaciers. For 26 analyzed periods with an average length of 18 years the mean difference between the <span class="hlt">geodetic</span> and the direct data is -0.4 m w.e., the minimum -7.2 m w.e. and the maximum 3.6 m w.e. Longer periods between the acquisition of the DEMs do not necessarily result in a higher accuracy of the <span class="hlt">geodetic</span> mass balance. Specific glaciers show specific trends of the difference between the direct and the <span class="hlt">geodetic</span> data according to their type and state. In conclusion, <span class="hlt">geodetic</span> and direct mass balance data are complementary, but differ systematically.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.G21A0753P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.G21A0753P"><span><span class="hlt">Geodetic</span> Time Series: An Overview of UNAVCO Community Resources and Examples of Time Series Analysis Using GPS and Strainmeter Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Phillips, D. A.; Meertens, C. M.; Hodgkinson, K. M.; Puskas, C. M.; Boler, F. M.; Snett, L.; Mattioli, G. S.</p> <p>2013-12-01</p> <p>We present an overview of time series data, tools and services available from UNAVCO along with two specific and compelling examples of <span class="hlt">geodetic</span> time series analysis. UNAVCO provides a diverse suite of <span class="hlt">geodetic</span> data products and cyberinfrastructure services to support community research and education. The UNAVCO archive includes data from 2500+ continuous GPS stations, borehole geophysics instruments (strainmeters, seismometers, tiltmeters, pore pressure sensors), and long baseline laser strainmeters. These data span temporal scales from seconds to decades and provide global spatial coverage with regionally focused <span class="hlt">networks</span> including the EarthScope Plate Boundary Observatory (PBO) and COCONet. This rich, open access dataset is a tremendous resource that enables the exploration, identification and analysis of time varying signals associated with crustal deformation, reference frame determinations, isostatic adjustments, atmospheric phenomena, hydrologic processes and more. UNAVCO provides a suite of time series exploration and analysis resources including static plots, dynamic plotting tools, and data products and services designed to enhance time series analysis. The PBO GPS <span class="hlt">network</span> allow for identification of ~1 mm level deformation signals. At some GPS stations seasonal signals and longer-term trends in both the vertical and horizontal components can be dominated by effects of hydrological loading from natural and anthropogenic sources. Modeling of hydrologic deformation using GLDAS and a variety of land surface models (NOAH, MOSAIC, VIC and CLM) shows promise for independently modeling hydrologic effects and separating them from tectonic deformation as well as anthropogenic loading sources. A major challenge is to identify where loading is dominant and corrections from GLDAS can apply and where pumping is the dominant signal and corrections are not possible without some other data. In another arena, the PBO strainmeter <span class="hlt">network</span> was designed to capture small short</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...636228V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...636228V"><span>Simultaneous multi-patch-clamp and extracellular-array recordings: Single neuron reflects <span class="hlt">network</span> <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vardi, Roni; Goldental, Amir; Sardi, Shira; Sheinin, Anton; Kanter, Ido</p> <p>2016-11-01</p> <p>The increasing number of recording electrodes enhances the capability of capturing the network’s cooperative <span class="hlt">activity</span>, however, using too many monitors might alter the properties of the measured neural <span class="hlt">network</span> and induce noise. Using a technique that merges simultaneous multi-patch-clamp and multi-electrode array recordings of neural <span class="hlt">networks</span> in-vitro, we show that the membrane potential of a single neuron is a reliable and super-sensitive probe for monitoring such cooperative <span class="hlt">activities</span> and their detailed rhythms. Specifically, the membrane potential and the spiking <span class="hlt">activity</span> of a single neuron are either highly correlated or highly anti-correlated with the time-dependent macroscopic <span class="hlt">activity</span> of the entire <span class="hlt">network</span>. This surprising observation also sheds light on the cooperative origin of neuronal burst in cultured <span class="hlt">networks</span>. Our findings present an alternative flexible approach to the technique based on a massive tiling of <span class="hlt">networks</span> by large-scale arrays of electrodes to monitor their <span class="hlt">activity</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5099952','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5099952"><span>Simultaneous multi-patch-clamp and extracellular-array recordings: Single neuron reflects <span class="hlt">network</span> <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Vardi, Roni; Goldental, Amir; Sardi, Shira; Sheinin, Anton; Kanter, Ido</p> <p>2016-01-01</p> <p>The increasing number of recording electrodes enhances the capability of capturing the network’s cooperative <span class="hlt">activity</span>, however, using too many monitors might alter the properties of the measured neural <span class="hlt">network</span> and induce noise. Using a technique that merges simultaneous multi-patch-clamp and multi-electrode array recordings of neural <span class="hlt">networks</span> in-vitro, we show that the membrane potential of a single neuron is a reliable and super-sensitive probe for monitoring such cooperative <span class="hlt">activities</span> and their detailed rhythms. Specifically, the membrane potential and the spiking <span class="hlt">activity</span> of a single neuron are either highly correlated or highly anti-correlated with the time-dependent macroscopic <span class="hlt">activity</span> of the entire <span class="hlt">network</span>. This surprising observation also sheds light on the cooperative origin of neuronal burst in cultured <span class="hlt">networks</span>. Our findings present an alternative flexible approach to the technique based on a massive tiling of <span class="hlt">networks</span> by large-scale arrays of electrodes to monitor their <span class="hlt">activity</span>. PMID:27824075</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19810018627','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19810018627"><span>Development of a composite <span class="hlt">geodetic</span> structure for space construction, phase 2</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1981-01-01</p> <p>Primary physical and mechanical properties were defined for pultruded hybrid HMS/E-glass P1700 rod material used for the fabrication of <span class="hlt">geodetic</span> beams. Key properties established were used in the analysis, design, fabrication, instrumentation, and testing of a <span class="hlt">geodetic</span> parameter cylinder and a lattice cone closeout joined to a short cylindrical <span class="hlt">geodetic</span> beam segment. Requirements of structural techniques were accomplished. Analytical procedures were refined and extended to include the effect of rod dimensions for the helical and longitudinal members on local buckling, and the effect of different flexural and extensional moduli on general instability buckling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19750003343','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19750003343"><span>GEODYN system description, volume 1. [computer program for estimation of orbit and <span class="hlt">geodetic</span> parameters</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chin, M. M.; Goad, C. C.; Martin, T. V.</p> <p>1972-01-01</p> <p>A computer program for the estimation of orbit and <span class="hlt">geodetic</span> parameters is presented. The areas in which the program is operational are defined. The specific uses of the program are given as: (1) determination of definitive orbits, (2) tracking instrument calibration, (3) satellite operational predictions, and (4) <span class="hlt">geodetic</span> parameter estimation. The relationship between the various elements in the solution of the orbit and <span class="hlt">geodetic</span> parameter estimation problem is analyzed. The solution of the problems corresponds to the orbit generation mode in the first case and to the data reduction mode in the second case.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10751456','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10751456"><span>Modeling of spontaneous <span class="hlt">activity</span> in developing spinal cord using <span class="hlt">activity</span>-dependent depression in an excitatory <span class="hlt">network</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tabak, J; Senn, W; O'Donovan, M J; Rinzel, J</p> <p>2000-04-15</p> <p>Spontaneous episodic <span class="hlt">activity</span> is a general feature of developing neural <span class="hlt">networks</span>. In the chick spinal cord, the <span class="hlt">activity</span> comprises episodes of rhythmic discharge (duration 5-90 sec; cycle rate 0.1-2 Hz) that recur every 2-30 min. The <span class="hlt">activity</span> does not depend on specialized connectivity or intrinsic bursting neurons and is generated by a <span class="hlt">network</span> of functionally excitatory connections. Here, we develop an idealized, qualitative model of a homogeneous, excitatory recurrent <span class="hlt">network</span> that could account for the multiple time-scale spontaneous <span class="hlt">activity</span> in the embryonic chick spinal cord. We show that cycling can arise from the interplay between excitatory connectivity and fast synaptic depression. The slow episodic behavior is attributable to a slow <span class="hlt">activity</span>-dependent <span class="hlt">network</span> depression that is modeled either as a modulation of cellular excitability or as synaptic depression. Although the two descriptions share many features, the model with a slow synaptic depression accounts better for the experimental observations during blockade of excitatory synapses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24414334','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24414334"><span>Studying modulation on simultaneously <span class="hlt">activated</span> SSVEP neural <span class="hlt">networks</span> by a cognitive task.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wu, Zhenghua</p> <p>2014-01-01</p> <p>Since the discovery of steady-state visually evoked potential (SSVEP), it has been used in many fields. Numerous studies suggest that there exist three SSVEP neural <span class="hlt">networks</span> in different frequency bands. An obvious phenomenon has been observed, that the amplitude and phase of SSVEP can be modulated by a cognitive task. Previous works have studied this modulation on separately <span class="hlt">activated</span> SSVEP neural <span class="hlt">networks</span> by a cognitive task. If two or more SSVEP neural <span class="hlt">networks</span> are <span class="hlt">activated</span> simultaneously in the process of a cognitive task, is the modulation on different SSVEP neural <span class="hlt">networks</span> the same? In this study, two different SSVEP neural <span class="hlt">networks</span> were <span class="hlt">activated</span> simultaneously by two different frequency flickers, with a working memory task irrelevant to the flickers being conducted at the same time. The modulated SSVEP waves were compared with each other and to those only under one flicker in previous studies. The comparison results show that the cognitive task can modulate different SSVEP neural <span class="hlt">networks</span> with a similar style.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21628565','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21628565"><span>Enhancement of CA3 hippocampal <span class="hlt">network</span> <span class="hlt">activity</span> by <span class="hlt">activation</span> of group II metabotropic glutamate receptors.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ster, Jeanne; Mateos, José María; Grewe, Benjamin Friedrich; Coiret, Guyllaume; Corti, Corrado; Corsi, Mauro; Helmchen, Fritjof; Gerber, Urs</p> <p>2011-06-14</p> <p>Impaired function or expression of group II metabotropic glutamate receptors (mGluRIIs) is observed in brain disorders such as schizophrenia. This class of receptor is thought to modulate <span class="hlt">activity</span> of neuronal circuits primarily by inhibiting neurotransmitter release. Here, we characterize a postsynaptic excitatory response mediated by somato-dendritic mGluRIIs in hippocampal CA3 pyramidal cells and in stratum oriens interneurons. The specific mGluRII agonists DCG-IV or LCCG-1 induced an inward current blocked by the mGluRII antagonist LY341495. Experiments with transgenic mice revealed a significant reduction of the inward current in mGluR3(-/-) but not in mGluR2(-/-) mice. The excitatory response was associated with periods of synchronized <span class="hlt">activity</span> at theta frequency. Furthermore, cholinergically induced <span class="hlt">network</span> oscillations exhibited decreased frequency when mGluRIIs were blocked. Thus, our data indicate that hippocampal responses are modulated not only by presynaptic mGluRIIs that reduce glutamate release but also by postsynaptic mGluRIIs that depolarize neurons and enhance CA3 <span class="hlt">network</span> <span class="hlt">activity</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.G11A0617V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.G11A0617V"><span>Pseudorage Multipath Estimation and Analysis at the GPS Rgna <span class="hlt">Network</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vazquez, G. E.; Barron, M. A.</p> <p>2010-12-01</p> <p>A research study was conducted to evaluate the amount of pseudorange multipath at GPS sites in the National <span class="hlt">Active</span> <span class="hlt">Geodetic</span> <span class="hlt">Network</span> (RGNA) that is administrated by the National Institute of Statistics, Geography and Informatics (INEGI) of México, which supports three dimensional positioning for public users. The RGNA <span class="hlt">Network</span> consists of 20 GPS stations located throughout México, where double difference <span class="hlt">geodetic</span>-grade receivers collect GPS data continuously the 365 days of the year. It is well known that, despite carefully selected locations, the GPS stations are to some extent, affected by the presence of multipath. Furthermore, it is very feasible that for RGNA users that relied on precise measurements of pseudorange observables, the existence of pseudorange multipath could affect any type of related application for a short period of time. Thus, in order to identify the most and the least affected stations, the pseudorange multipath (MP1 and MP2) and the daily root mean square (rms-MP1 and rms-MP2) variations were estimated and analyzed at each GPS site of the RGNA <span class="hlt">Network</span>. The GPS data processing was performed using the public software TEQC (Test of Quality Check) by UNAVCO and the pseudorange multipath analysis is presented at each site over a year basis (in terms of time-series) considering the data span from year 2005 (doy 265) to year 2010 (doy 300).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22999229','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22999229"><span>Social <span class="hlt">networks</span> of experientially similar others: formation, <span class="hlt">activation</span>, and consequences of <span class="hlt">network</span> ties on the health care experience.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gage, Elizabeth A</p> <p>2013-10-01</p> <p>Research documents that interactions among experientially similar others (individuals facing a common stressor) shape health care behavior and ultimately health outcomes. However, we have little understanding of how ties among experientially similar others are formed, what resources and information flows through these <span class="hlt">networks</span>, and how <span class="hlt">network</span> embeddedness shapes health care behavior. This paper uses in-depth interviews with 76 parents of pediatric cancer patients to examine <span class="hlt">network</span> ties among experientially similar others after a serious medical diagnosis. Interviews were conducted between August 2009 and May 2011. Findings demonstrate that many parents formed ties with other families experiencing pediatric cancer, and that information and resources were exchanged during the everyday <span class="hlt">activities</span> associated with their child's care. <span class="hlt">Network</span> flows contained emotional support, caregiving strategies, information about second opinions, health-related knowledge, and strategies for navigating the health care system. Diffusion of information, resources, and support occurred through explicit processes (direct information and support exchanges) and implicit processes (parents learning through observing other families). <span class="hlt">Network</span> flows among parents shaped parents' perceptions of the health care experience and their role in their child's care. These findings contribute to the social <span class="hlt">networks</span> and social support literatures by elucidating the mechanisms through which <span class="hlt">network</span> ties among experientially similar others influence health care behavior and experiences.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.S13A1056B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.S13A1056B"><span>Seismological and <span class="hlt">Geodetic</span> Observations of the 15th August 2007 Pisco, Peru Earthquake.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Biggs, J.; Psencik, K.; Norabuena, E.; Robinson, D.; Dixon, T.</p> <p>2007-12-01</p> <p>On 15th August 2007, a M8.0 earthquake occurred on the interface between the Nazca and South American Plates causing widespread damage in the towns of Chincha Alta, Ica and Pisco, with 514 casualties and 35,500 buildings reported destroyed. The 2007 Pisco earthquake occurred in a region between two large recent earthquakes: the 1996 M7.7 Nazca earthquake to the south and, in 1974, a M8.1 earthquake to the north. The existing local GPS <span class="hlt">network</span> was resurveyed within 2 weeks of the earthquake and significant displacements measured at 8-10 sites. Co-seismic and postseismic InSAR data has been collected from several satellites, including Envisat, ERS-2, Radarsat and ALOS. In the two weeks following the mainshock, 42 aftershocks were recorded teleseismicly with magnitudes in the range 4-6.3. We will present results from the analysis of this <span class="hlt">geodetic</span> data along with seismological analysis of teleseismic recordings of the mainshock and aftershocks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010JGRB..115.3401K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010JGRB..115.3401K"><span>Inverting <span class="hlt">geodetic</span> time series with a principal component analysis-based inversion method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kositsky, A. P.; Avouac, J.-P.</p> <p>2010-03-01</p> <p>The Global Positioning System (GPS) system now makes it possible to monitor deformation of the Earth's surface along plate boundaries with unprecedented accuracy. In theory, the spatiotemporal evolution of slip on the plate boundary at depth, associated with either seismic or aseismic slip, can be inferred from these measurements through some inversion procedure based on the theory of dislocations in an elastic half-space. We describe and test a principal component analysis-based inversion method (PCAIM), an inversion strategy that relies on principal component analysis of the surface displacement time series. We prove that the fault slip history can be recovered from the inversion of each principal component. Because PCAIM does not require externally imposed temporal filtering, it can deal with any kind of time variation of fault slip. We test the approach by applying the technique to synthetic <span class="hlt">geodetic</span> time series to show that a complicated slip history combining coseismic, postseismic, and nonstationary interseismic slip can be retrieved from this approach. PCAIM produces slip models comparable to those obtained from standard inversion techniques with less computational complexity. We also compare an afterslip model derived from the PCAIM inversion of postseismic displacements following the 2005 8.6 Nias earthquake with another solution obtained from the extended <span class="hlt">network</span> inversion filter (ENIF). We introduce several extensions of the algorithm to allow statistically rigorous integration of multiple data sources (e.g., both GPS and interferometric synthetic aperture radar time series) over multiple timescales. PCAIM can be generalized to any linear inversion algorithm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060044421&hterms=Group+work&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DGroup%2Bwork','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060044421&hterms=Group+work&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DGroup%2Bwork"><span>GGOS working group on ground <span class="hlt">networks</span> and communications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pearlman, M.; Altamimi, Z.; Beck, N.; Forsberg, R.; Gurtner, W.; Kenyon, S.; Behrend, D.; Lemoine, F. G.; Ma, C.; Noll, C. E.; Pavlis, E. C.; Malkin, Z.; Moore, A.; Webb, F. H.; Neilan, R.; Ries, J. C.; Rothacher, M.; Willis, P.</p> <p>2005-01-01</p> <p><span class="hlt">Activities</span> of this Working Group include the investigation of the status quo and the development of a plan for full <span class="hlt">network</span> integration to support improvements in terrestrial reference frame establishment and maintenance, Earth orientation and gravity field monitoring, precision orbit determination, and other <span class="hlt">geodetic</span> and gravimetric applications required for the long-term observation of global change. This integration process includes the development of a <span class="hlt">network</span> of fundamental stations with as many co-located techniques as possible, with precisely determined intersystem vectors. This <span class="hlt">network</span> would exploit the strengths of each technique and minimize the weaknesses where possible. This paper discusses the organization of the working group, the work done to date, and future tasks.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGeod.tmp...99K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGeod.tmp...99K"><span>GPS code phase variations (CPV) for GNSS receiver antennas and their effect on <span class="hlt">geodetic</span> parameters and ambiguity resolution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kersten, Tobias; Schön, Steffen</p> <p>2016-12-01</p> <p>Precise navigation and <span class="hlt">geodetic</span> coordinate determination rely on accurate GNSS signal reception. Thus, the receiver antenna properties play a crucial role in the GNSS error budget. For carrier phase observations, a spherical radiation pattern represents an ideal receiver antenna behaviour. Deviations are known as phase centre corrections. Due to synergy of carrier and code phase, similar effects on the code exist named code phase variations (CPV). They are mainly attributed to electromagnetic interactions of several <span class="hlt">active</span> and passive elements of the receiver antenna. Consequently, a calibration and estimation strategy is necessary to determine the shape and magnitudes of the CPV. Such a concept was proposed, implemented and tested at the Institut für Erdmessung. The applied methodology and the obtained results are reported and discussed in this paper. We show that the azimuthal and elevation-dependent CPV can reach maximum magnitudes of 0.2-0.3 m for <span class="hlt">geodetic</span> antennas and up to maximum values of 1.8 m for small navigation antennas. The obtained values are validated by dedicated tests in the observation and coordinate domain. As a result, CPV are identified to be antenna- related properties that are independent from location and time of calibration. Even for <span class="hlt">geodetic</span> antennas when forming linear combinations the CPV effect can be amplified to values of 0.4-0.6 m. Thus, a significant fractional of the Melbourne-Wübbena linear combination. A case study highlights that incorrect ambiguity resolution can occur due to neglecting CPV corrections. The impact on the coordinates which may reach up to the dm level is illustrated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24525260','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24525260"><span>Social <span class="hlt">network</span> <span class="hlt">activation</span>: the role of health discussion partners in recovery from mental illness.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Perry, Brea L; Pescosolido, Bernice A</p> <p>2015-01-01</p> <p>In response to health problems, individuals may strategically <span class="hlt">activate</span> their social <span class="hlt">network</span> ties to help manage crisis and uncertainty. While it is well-established that social relationships provide a crucial safety net, little is known about who is chosen to help during an episode of illness. Guided by the <span class="hlt">Network</span> Episode Model, two aspects of consulting others in the face of mental illness are considered. First, we ask who <span class="hlt">activates</span> ties, and what kinds of ties and <span class="hlt">networks</span> they attempt to leverage for discussing health matters. Second, we ask about the utility of <span class="hlt">activating</span> health-focused <span class="hlt">network</span> ties. Specifically, we examine the consequences of <span class="hlt">network</span> <span class="hlt">activation</span> at time of entry into treatment for individuals' quality of life, social satisfaction, ability to perform social roles, and mental health functioning nearly one year later. Using interview data from the longitudinal Indianapolis <span class="hlt">Network</span> Mental Health Study (INMHS, N = 171), we focus on a sample of new patients with serious mental illness and a group with less severe disorders who are experiencing their first contact with the mental health treatment system. Three findings stand out. First, our results reveal the nature of agency in illness response. Whether under a rational choice or habitus logic, individuals appear to evaluate support needs, identifying the best possible matches among a larger group of potential health discussants. These include members of the core <span class="hlt">network</span> and those with prior mental health experiences. Second, selective <span class="hlt">activation</span> processes have implications for recovery. Those who secure adequate <span class="hlt">network</span> resources report better outcomes than those who injudiciously <span class="hlt">activate</span> <span class="hlt">network</span> ties. Individuals who <span class="hlt">activate</span> weaker relationships and those who are unsupportive of medical care experience poorer functioning, limited success in fulfilling social roles, and lower social satisfaction and quality of life later on. Third, the evidence suggests that social <span class="hlt">networks</span> matter above and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21852971','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21852971"><span>Sustained <span class="hlt">activity</span> in hierarchical modular neural <span class="hlt">networks</span>: self-organized criticality and oscillations.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Sheng-Jun; Hilgetag, Claus C; Zhou, Changsong</p> <p>2011-01-01</p> <p>Cerebral cortical brain <span class="hlt">networks</span> possess a number of conspicuous features of structure and dynamics. First, these <span class="hlt">networks</span> have an intricate, non-random organization. In particular, they are structured in a hierarchical modular fashion, from large-scale regions of the whole brain, via cortical areas and area subcompartments organized as structural and functional maps to cortical columns, and finally circuits made up of individual neurons. Second, the <span class="hlt">networks</span> display self-organized sustained <span class="hlt">activity</span>, which is persistent in the absence of external stimuli. At the systems level, such <span class="hlt">activity</span> is characterized by complex rhythmical oscillations over a broadband background, while at the cellular level, neuronal discharges have been observed to display avalanches, indicating that cortical <span class="hlt">networks</span> are at the state of self-organized criticality (SOC). We explored the relationship between hierarchical neural <span class="hlt">network</span> organization and sustained dynamics using large-scale <span class="hlt">network</span> modeling. Previously, it was shown that sparse random <span class="hlt">networks</span> with balanced excitation and inhibition can sustain neural <span class="hlt">activity</span> without external stimulation. We found that a hierarchical modular architecture can generate sustained <span class="hlt">activity</span> better than random <span class="hlt">networks</span>. Moreover, the system can simultaneously support rhythmical oscillations and SOC, which are not present in the respective random <span class="hlt">networks</span>. The mechanism underlying the sustained <span class="hlt">activity</span> is that each dense module cannot sustain <span class="hlt">activity</span> on its own, but displays SOC in the presence of weak perturbations. Therefore, the hierarchical modular <span class="hlt">networks</span> provide the coupling among subsystems with SOC. These results imply that the hierarchical modular architecture of cortical <span class="hlt">networks</span> plays an important role in shaping the ongoing spontaneous <span class="hlt">activity</span> of the brain, potentially allowing the system to take advantage of both the sensitivity of critical states and the predictability and timing of oscillations for efficient information</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24999907','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24999907"><span>Low attentional engagement makes attention <span class="hlt">network</span> <span class="hlt">activity</span> susceptible to emotional interference.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mäki-Marttunen, Verónica; Pickard, Natasha; Solbakk, Anne-Kristin; Ogawa, Keith H; Knight, Robert T; Hartikainen, Kaisa M</p> <p>2014-09-10</p> <p>The aim of this study was to investigate whether emotion-attention interaction depends on attentional engagement. To investigate emotional modulation of attention <span class="hlt">network</span> <span class="hlt">activation</span>, we used a functional MRI paradigm consisting of a visuospatial attention task with either frequent (high-engagement) or infrequent (low-engagement) targets and intermittent emotional or neutral distractors. The attention task recruited a bilateral frontoparietal <span class="hlt">network</span> with no emotional interference on <span class="hlt">network</span> <span class="hlt">activation</span> when the attentional engagement was high. In contrast, when the attentional engagement was low, the unpleasant stimuli interfered with the <span class="hlt">activation</span> of the frontoparietal attention <span class="hlt">network</span>, especially in the right hemisphere. This study provides novel evidence for low attentional engagement making attention control <span class="hlt">network</span> <span class="hlt">activation</span> susceptible to emotional interference.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23267078','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23267078"><span>Blink-related momentary <span class="hlt">activation</span> of the default mode <span class="hlt">network</span> while viewing videos.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nakano, Tamami; Kato, Makoto; Morito, Yusuke; Itoi, Seishi; Kitazawa, Shigeru</p> <p>2013-01-08</p> <p>It remains unknown why we generate spontaneous eyeblinks every few seconds, more often than necessary for ocular lubrication. Because eyeblinks tend to occur at implicit breakpoints while viewing videos, we hypothesized that eyeblinks are <span class="hlt">actively</span> involved in the release of attention. We show that while viewing videos, cortical <span class="hlt">activity</span> momentarily decreases in the dorsal attention <span class="hlt">network</span> after blink onset but increases in the default-mode <span class="hlt">network</span> implicated in internal processing. In contrast, physical blackouts of the video do not elicit such reciprocal changes in brain <span class="hlt">networks</span>. The results suggest that eyeblinks are <span class="hlt">actively</span> involved in the process of attentional disengagement during a cognitive behavior by momentarily <span class="hlt">activating</span> the default-mode <span class="hlt">network</span> while deactivating the dorsal attention <span class="hlt">network</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.9947T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.9947T"><span>The potential role of real-time <span class="hlt">geodetic</span> observations in tsunami early warning</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tinti, Stefano; Armigliato, Alberto</p> <p>2016-04-01</p> <p> experimental or testing stage and haven't been implemented yet in any standard TWS operations. Nonetheless, this is seen to be the future and the natural TWS evolving enhancement. In this context, improvement of the real-time estimates of tsunamigenic earthquake focal mechanism is of fundamental importance to trigger the appropriate computational chain. Quick discrimination between strike-slip and thrust-fault earthquakes, and equally relevant, quick assessment of co-seismic on-fault slip distribution, are exemplary cases to which a real-time <span class="hlt">geodetic</span> monitoring system can contribute significantly. Robust inversion of <span class="hlt">geodetic</span> data can help to reconstruct the sea floor deformation pattern especially if two conditions are met: the source is not too far from <span class="hlt">network</span> stations and is well covered azimuthally. These two conditions are sometimes hard to satisfy fully, but in certain regions, like the Mediterranean and the Caribbean sea, this is quite possible due to the limited size of the ocean basins. Close cooperation between the Global <span class="hlt">Geodetic</span> Observing System (GGOS) community, seismologists, tsunami scientists and TWS operators is highly recommended to obtain significant progresses in the quick determination of the earthquake source, which can trigger a timely estimation of the ensuing tsunami and a more reliable and detailed assessment of the tsunami size at the coast.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20728555','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20728555"><span>Stimulus-free thoughts induce differential <span class="hlt">activation</span> in the human default <span class="hlt">network</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Preminger, Son; Harmelech, Tal; Malach, Rafael</p> <p>2011-01-15</p> <p>Despite extensive research of the Default <span class="hlt">network</span>, a set of regions which tend to reduce their <span class="hlt">activity</span> relative to rest in response to stimulus-driven tasks, its function is still debated. Specifically, it is still not clear to what extent the <span class="hlt">activation</span> profile of this <span class="hlt">network</span> is driven by processes related to external stimulation (inhibitory or anticipatory), or is driven by specific thought contents. To address this question, we examined the ability of thoughts, generated in the absence of external stimulation, to modulate default <span class="hlt">network</span> <span class="hlt">activation</span>. In a set of experiments, several types of long lasting stimulus-free thoughts were elicited by brief (<1s) auditory cues. Sustained (40s) brain <span class="hlt">activations</span>, far outlasting the cue, were demonstrated during these stimulus-free conditions. Importantly, brain <span class="hlt">activity</span> in the default <span class="hlt">network</span> showed a striking modulation associated with stimulus-free thought content. More specifically, a preferential <span class="hlt">activation</span> was observed in essentially the entire default <span class="hlt">network</span> during volitional-prospection thoughts when compared to the other stimulus-free thought conditions. Furthermore, several regions of the default <span class="hlt">network</span> showed long-lasting above rest <span class="hlt">activations</span> during the volitional-prospection condition. Our results demonstrate that default <span class="hlt">network</span> <span class="hlt">activation</span> can be modulated in the absence of external stimuli, thus pointing to the importance of thought-content in default-<span class="hlt">network</span> specialization. Furthermore, together with previous research, these results support the notion that intrinsically oriented processing is a core specialization of the default <span class="hlt">network</span>. Finally, our stimulus-free experimental paradigm introduces a new method for studying default <span class="hlt">network</span> functionality.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19800010867','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19800010867"><span>Development of a composite <span class="hlt">geodetic</span> structure for space construction, phase 1A</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1980-01-01</p> <p>The development of a <span class="hlt">geodetic</span> beam and beam builder for on orbit construction of large truss type space structures is discussed. The <span class="hlt">geodetic</span> beam is a lightweight, open lattice structure composed of an equilateral gridwork of crisscrossing rods. The beam provides a high degree of stiffness and minimizes structural distortion, due to temperature gradients, through the incorporation of a new graphite and glass reinforced thermoplastic composite material with a low coefficient of thermal expansion. A low power consuming, high production rate, beam builder automatically fabricates the <span class="hlt">geodetic</span> beams in space using rods preprocessed on Earth. Three areas of the development are focused upon; (1) <span class="hlt">geodetic</span> beam designs for local attachment of equipment or beam to beam joining in a parallel or crossing configurations, (2) evaluation of long life pultruded rods capable of service temperatures higher than possible with the HMS/P1700 rod material, and (3) evalaution of high temperature joint encapsulant materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..4310663J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..4310663J"><span>Reconciling seismicity and <span class="hlt">geodetic</span> locking depths on the Anza section of the San Jacinto fault</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jiang, Junle; Fialko, Yuri</p> <p>2016-10-01</p> <p>Observations from the Anza section of the San Jacinto Fault in Southern California reveal that microseismicity extends to depths of 15-18 km, while the <span class="hlt">geodetically</span> determined locking depth is less than 10 km. This contrasts with observations from other major faults in the region and also with predictions of fault models assuming a simple layered distribution of frictional properties with depth. We suggest that an anomalously shallow <span class="hlt">geodetic</span> fault locking may result from a transition zone at the bottom of seismogenic layer with spatially heterogeneous frictional properties. Numerical models of faults that incorporate stochastic heterogeneity at transitional depths successfully reproduce the observed depth relation between seismicity and <span class="hlt">geodetic</span> locking, as well as complex spatiotemporal patterns of microseismicity with relatively scarce repeating earthquakes. Our models predict propagation of large earthquakes to the bottom of the transition zone, and ubiquitous aseismic transients below the locked zone, potentially observable using high-precision <span class="hlt">geodetic</span> techniques.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22757540','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22757540"><span>Coherent periodic <span class="hlt">activity</span> in excitatory Erdös-Renyi neural <span class="hlt">networks</span>: the role of <span class="hlt">network</span> connectivity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tattini, Lorenzo; Olmi, Simona; Torcini, Alessandro</p> <p>2012-06-01</p> <p>In this article, we investigate the role of connectivity in promoting coherent <span class="hlt">activity</span> in excitatory neural <span class="hlt">networks</span>. In particular, we would like to understand if the onset of collective oscillations can be related to a minimal average connectivity and how this critical connectivity depends on the number of neurons in the <span class="hlt">networks</span>. For these purposes, we consider an excitatory random <span class="hlt">network</span> of leaky integrate-and-fire pulse coupled neurons. The neurons are connected as in a directed Erdös-Renyi graph with average connectivity <k> scaling as a power law with the number of neurons in the <span class="hlt">network</span>. The scaling is controlled by a parameter γ, which allows to pass from massively connected to sparse <span class="hlt">networks</span> and therefore to modify the topology of the system. At a macroscopic level, we observe two distinct dynamical phases: an asynchronous state corresponding to a desynchronized dynamics of the neurons and a regime of partial synchronization (PS) associated with a coherent periodic <span class="hlt">activity</span> of the <span class="hlt">network</span>. At low connectivity, the system is in an asynchronous state, while PS emerges above a certain critical average connectivity <k>(c). For sufficiently large <span class="hlt">networks</span>, <k>(c) saturates to a constant value suggesting that a minimal average connectivity is sufficient to observe coherent <span class="hlt">activity</span> in systems of any size irrespectively of the kind of considered <span class="hlt">network</span>: sparse or massively connected. However, this value depends on the nature of the synapses: reliable or unreliable. For unreliable synapses, the critical value required to observe the onset of macroscopic behaviors is noticeably smaller than for reliable synaptic transmission. Due to the disorder present in the system, for finite number of neurons we have inhomogeneities in the neuronal behaviors, inducing a weak form of chaos, which vanishes in the thermodynamic limit. In such a limit, the disordered systems exhibit regular (non chaotic) dynamics and their properties correspond to that of a homogeneous</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012Chaos..22b3133T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012Chaos..22b3133T"><span>Coherent periodic <span class="hlt">activity</span> in excitatory Erdös-Renyi neural <span class="hlt">networks</span>: The role of <span class="hlt">network</span> connectivity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tattini, Lorenzo; Olmi, Simona; Torcini, Alessandro</p> <p>2012-06-01</p> <p>In this article, we investigate the role of connectivity in promoting coherent <span class="hlt">activity</span> in excitatory neural <span class="hlt">networks</span>. In particular, we would like to understand if the onset of collective oscillations can be related to a minimal average connectivity and how this critical connectivity depends on the number of neurons in the <span class="hlt">networks</span>. For these purposes, we consider an excitatory random <span class="hlt">network</span> of leaky integrate-and-fire pulse coupled neurons. The neurons are connected as in a directed Erdös-Renyi graph with average connectivity <k> scaling as a power law with the number of neurons in the <span class="hlt">network</span>. The scaling is controlled by a parameter γ, which allows to pass from massively connected to sparse <span class="hlt">networks</span> and therefore to modify the topology of the system. At a macroscopic level, we observe two distinct dynamical phases: an asynchronous state corresponding to a desynchronized dynamics of the neurons and a regime of partial synchronization (PS) associated with a coherent periodic <span class="hlt">activity</span> of the <span class="hlt">network</span>. At low connectivity, the system is in an asynchronous state, while PS emerges above a certain critical average connectivity <k>c. For sufficiently large <span class="hlt">networks</span>, <k>c saturates to a constant value suggesting that a minimal average connectivity is sufficient to observe coherent <span class="hlt">activity</span> in systems of any size irrespectively of the kind of considered <span class="hlt">network</span>: sparse or massively connected. However, this value depends on the nature of the synapses: reliable or unreliable. For unreliable synapses, the critical value required to observe the onset of macroscopic behaviors is noticeably smaller than for reliable synaptic transmission. Due to the disorder present in the system, for finite number of neurons we have inhomogeneities in the neuronal behaviors, inducing a weak form of chaos, which vanishes in the thermodynamic limit. In such a limit, the disordered systems exhibit regular (non chaotic) dynamics and their properties correspond to that of a homogeneous fully</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA590678','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA590678"><span>Efficient Strategies for <span class="hlt">Active</span> Interface-Level <span class="hlt">Network</span> Topology Discovery</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2013-09-01</p> <p>production system to probe 500 randomly selected Internet subnetworks and gather real -world <span class="hlt">network</span> maps . As compared to datasets from existing measurement...load while producing reliable <span class="hlt">network</span> topology maps . Although SCP has been shown to work well in simulation over real -data from CAIDA’s Archipelago...testing of SCP to perform real , production, Internet mapping . We find that, as originally proposed, SCP has a critical flaw stemming load-balancing</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFM.G52A0966M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFM.G52A0966M"><span>Trials for better precision of seafloor <span class="hlt">geodetic</span> observation system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mochizuki, M.; Sato, M.; Fujita, M.; Yoshida, Z.; Yabuki, T.; Asada, A.</p> <p>2002-12-01</p> <p>Institute of Industrial Science, University of Tokyo, and Hydrographic Department, Japan, have been developing seafloor <span class="hlt">geodetic</span> observation system and conducting observations using the system. Precise acoustic ranging and kinematic GPS positioning techniques are combined into the system. Seafloor reference station which consists of four mirror type transponders is deployed on the seafloor and measures its position in reference to GPS stations on land and ship. Fourteen seafloor <span class="hlt">geodetic</span> reference stations have been distributed on the forearc areas of Japan island arc. Subsea crustal deformation due to subducting two oceanic plates of the Pacific and the Philippine sea can be monitored by using the seafloor reference stations. Although we obtained satisfactory results with the already existing system, we come up with possible improvements of the system as we accumulate the experience of the observations using the system. Trials to improve the system are always done. In this poster, we will present two of such trials. 1. To improve the stability of the rigid pole connecting the GPS antenna and the ship-board transducer. The bending of the GPS pole was found by examining the offsets in the acoustic ranging residuals. Acoustic ranging is made with condition that the ship drifts over sea surface. Drag force generated between surface current and the pole makes the pole itself bend. The pole was replaced by new, more rigid pole to overcome the problem. Also, we monitor amount of bending of the pole, that is, the offset between the GPS antenna and the transducer, using tiltmeter through the observation. 2. To reduce the acoustic ranging error due to shape of the transducer. Coded sinusoidal acoustic wave with 15cm wave length is used as the ranging signal. This wave length is comparable to the dimension of the cylindrical transducers employed both on the ship-board system and on the seafloor transponder. Transducer can not be regarded as a point considering the wave</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T13F2699W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T13F2699W"><span>Stress coupling in the seismic cycle indicated from <span class="hlt">geodetic</span> measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, L.; Hainzl, S.; Zoeller, G.; Holschneider, M.</p> <p>2012-12-01</p> <p>The seismic cycle includes several phases, the interseismic, coseismic and postseismic phase. In the interseismic phase, strain gradually builds up around the overall locked fault in tens to thousands of years, while it is coseismically released in seconds. In the postseismic interval, stress relaxation lasts months to years, indicated by evident aseismic deformations which have been indicated to release comparable or even higher strain energy than the main shocks themselves. Benefiting from the development of <span class="hlt">geodetic</span> observatory, e.g., Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) in the last two decades, the measurements of surface deformation have been significantly improved and become valuable information for understanding the stress evolution on the large fault plane. In this study, we utilize the GPS/InSAR data to investigate the slip deficit during the interseismic phase, the coseismic slip and the early postseismic creep on the fault plane. However, it is already well-known that slip inversions based only on the surface measurements are typically non-unique and subject to large uncertainties. To reduce the ambiguity, we utilize the assumption of stress coupling between interseismic and coseismic phases, and between coseismic and postseismic phases. We use a stress constrained joint inversion in Bayesian approach (Wang et al., 2012) to invert simultaneously for (1) interseismic slip deficit and coseismic slip, and (2) coseismic slip and postseismic creep. As case studies, we analyze earthquakes occurred in well-instrumented regions such as the 2004 M6.0 Parkfield earthquake, the 2010 M8.7 earthquake and the 2011 M9.1 Tohoku-Oki earthquake. We show that the inversion with the stress-coupling constraint leads to better constrained slip distributions. Meanwhile, the results also indicate that the assumed stress coupling is reasonable and can be well reflected from the available <span class="hlt">geodetic</span> measurements. Reference: Lifeng</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SPIE.9097E..03G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SPIE.9097E..03G"><span>Sensing <span class="hlt">network</span> for electromagnetic fields generated by seismic <span class="hlt">activities</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gershenzon, Naum I.; Bambakidis, Gust; Ternovskiy, Igor V.</p> <p>2014-06-01</p> <p>The sensors <span class="hlt">network</span> is becoming prolific and play now increasingly more important role in acquiring and processing information. Cyber-Physical Systems are focusing on investigation of integrated systems that includes sensing, <span class="hlt">networking</span>, and computations. The physics of the seismic measurement and electromagnetic field measurement requires special consideration how to design electromagnetic field measurement <span class="hlt">networks</span> for both research and detection earthquakes and explosions along with the seismic measurement <span class="hlt">networks</span>. In addition, the electromagnetic sensor <span class="hlt">network</span> itself could be designed and deployed, as a research tool with great deal of flexibility, the placement of the measuring nodes must be design based on systematic analysis of the seismic-electromagnetic interaction. In this article, we review the observations of the co-seismic electromagnetic field generated by earthquakes and man-made sources such as vibrations and explosions. The theoretical investigation allows the distribution of sensor nodes to be optimized and could be used to support existing geological <span class="hlt">networks</span>. The placement of sensor nodes have to be determined based on physics of electromagnetic field distribution above the ground level. The results of theoretical investigations of seismo-electromagnetic phenomena are considered in Section I. First, we compare the relative contribution of various types of mechano-electromagnetic mechanisms and then analyze in detail the calculation of electromagnetic fields generated by piezomagnetic and electrokinetic effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890062474&hterms=ambiguity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dambiguity','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890062474&hterms=ambiguity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dambiguity"><span>Carrier phase ambiguity resolution for the Global Positioning System applied to <span class="hlt">geodetic</span> baselines up to 2000 km</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Blewitt, Geoffrey</p> <p>1989-01-01</p> <p>A technique for resolving the ambiguities in the GPS carrier phase data (which are biased by an integer number of cycles) is described which can be applied to <span class="hlt">geodetic</span> baselines up to 2000 km in length and can be used with dual-frequency P code receivers. The results of such application demonstrated that a factor of 3 improvement in baseline accuracy could be obtained, giving centimeter-level agreement with coordinates inferred by very-long-baseline interferometry in the western United States. It was found that a method using pseudorange data is more reliable than one using ionospheric constraints for baselines longer than 200 km. It is recommended that future GPS <span class="hlt">networks</span> have a wide spectrum of baseline lengths (ranging from baselines shorter than 100 km to those longer than 1000 km) and that GPS receivers be used which can acquire dual-frequency P code data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15037355','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15037355"><span>Absolute exponential stability of recurrent neural <span class="hlt">networks</span> with Lipschitz-continuous <span class="hlt">activation</span> functions and time delays.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cao, Jinde; Wang, Jun</p> <p>2004-04-01</p> <p>This paper investigates the absolute exponential stability of a general class of delayed neural <span class="hlt">networks</span>, which require the <span class="hlt">activation</span> functions to be partially Lipschitz continuous and monotone nondecreasing only, but not necessarily differentiable or bounded. Three new sufficient conditions are derived to ascertain whether or not the equilibrium points of the delayed neural <span class="hlt">networks</span> with additively diagonally stable interconnection matrices are absolutely exponentially stable by using delay Halanay-type inequality and Lyapunov function. The stability criteria are also suitable for delayed optimization neural <span class="hlt">networks</span> and delayed cellular neural <span class="hlt">networks</span> whose <span class="hlt">activation</span> functions are often nondifferentiable or unbounded. The results herein answer a question: if a neural <span class="hlt">network</span> without any delay is absolutely exponentially stable, then under what additional conditions, the neural <span class="hlt">networks</span> with delay is also absolutely exponentially stable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26026598','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26026598"><span>Young adolescents' perceived <span class="hlt">activity</span> space risk, peer <span class="hlt">networks</span>, and substance use.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mason, Michael; Mennis, Jeremy; Way, Thomas; Light, John; Rusby, Julie; Westling, Erika; Crewe, Stephanie; Flay, Brian; Campbell, Leah; Zaharakis, Nikola; McHenry, Chantal</p> <p>2015-07-01</p> <p>Adolescent substance use is a developmentally contingent social practice that is constituted within the routine social-environment of adolescents' lives. Few studies have examined peer <span class="hlt">networks</span>, perceived <span class="hlt">activity</span> space risk (risk of substance use at routine locations), and substance use. We examined the moderating influence of peer <span class="hlt">network</span> characteristics on the relationship between perceived <span class="hlt">activity</span> space risk and substance use among a sample of 250 urban adolescents. Significant interactions were found between peer <span class="hlt">networks</span> and perceived <span class="hlt">activity</span> space risk on tobacco and marijuana use, such that protective peer <span class="hlt">networks</span> reduced the effect of <span class="hlt">activity</span> place risk on substance use. A significant 3-way interaction was found on marijuana use indicating that gender moderated peer <span class="hlt">network</span>'s effect on <span class="hlt">activity</span> space risk. Conditional effect analysis found that boys' peer <span class="hlt">networks</span> moderated the effect of perceived <span class="hlt">activity</span> space risk on marijuana use, whereas for girls, the effect of perceived <span class="hlt">activity</span> space risk on marijuana use was not moderated by their peer <span class="hlt">networks</span>. These findings could advance theoretical models to inform social-environmental research among adolescents.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.V43B3139W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.V43B3139W"><span>Magma-tectonic interactions in Kīlauea's Southwest Rift Zone in 2006 through coupled <span class="hlt">geodetic</span>/seismological analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wauthier, C.; Roman, D. C.; Poland, M. P.</p> <p>2015-12-01</p> <p>For much of the first 20 years of Kīlauea's 1983-present Pu'u 'Ō'ō eruption, deformation was characterized by subsidence at the volcano's summit and along both the East Rift Zone (ERZ) and Southwest Rift Zone (SWRZ). At the end of 2003, however, Kīlauea's summit began a 4-year period of inflation due to a surge in magma supply to the volcano. In 2006, the SWRZ also experienced atypical inflation, which was last observed in 1981-82 during a series of dike intrusions. To investigate the <span class="hlt">active</span> magma sources and their interactions with faulting in the SWRZ during 2006, we integrate contemporary <span class="hlt">geodetic</span> data from InSAR and GPS with double-couple fault-plane solutions for volcano-tectonic earthquakes and Coulomb stress modeling. According to the rate of deformation measured in daily GPS data, two distinct periods can be defined, spanning January to 15 March 2006 (period 1) and 16 March to 30 September 2006 (period 2). <span class="hlt">Geodetic</span> models suggest that, during period 1, deformation, due to pressurization of magma in a vertical prolate-spheroidal conduit, in the south caldera area. In addition, a major seismic swarm occurred in both the SWRZ and ERZ. Our preliminary results also suggest that, during period 2, magma was still overpressurizing the same prolate-spheroid but a subhorizontal sill also intruded further to the southwest in the seismic SWRZ (SSWRZ). The beginning of period 2 also corresponds to a switch from subsidence to inflation of the SWRZ. Faulting in the upper ERZ is primarily strike-slip, with no obvious change in FPS orientation between periods 1 and 2. In contrast, faulting in the upper SSWRZ occurs as dip-slip motion on near-vertical faults. SSWRZ FPS show a mix of orientations including NW- and NE-striking faults, which along with relative earthquake locations, suggest a series of right-stepping fault segments, particularly during period 2. Calculated Coulomb stress changes indicate that faulting in the upper SSWRZ may result from stresses produced by</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.2873H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.2873H"><span><span class="hlt">Geodetic</span> monitoring strategy at the geothermal sites of Soultz-sous-Forêts and Rittershoffen (Upper Rhine Graben, France)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heimlich, Christine; Masson, Frédéric; Gourmelen, Noël</p> <p>2014-05-01</p> <p>The European Cenozoic rift system, and in particular the Upper Rhine Graben offers a high potential of deep geothermal energy due to the well known geothermal anomaly and to the number of subsurface temperature data from oil exploration in the Upper Rhine Graben. One example is the Soultz-sous-Forêts Enhance Geothermal System (EGS) located in the French part of the Upper Rhine Graben. The Soultz-sous-Forêts EGS started in 1987 as a deep geothermal research site. The wells are drilled in naturally fractured and altered granites from 3200 to 5260 m depth located in the vicinity of quasi North-South faults. It is the first EGS site connected to the electric <span class="hlt">network</span>, its electric production capacity is of 1.5MWe. A second EGS site, ECOGI, is in development near the village of Rittershoffen located at 7 km from Soultz-sous-Forêts. The objective of ECOGI is to produce 24MWth energy for an industrial use with a doublet configuration of wells at depths around 2500 and 3000 meters. Both EGS sites benefit of the natural circulation of geothermal water. Some challenges in geothermal power plant are to understand the long-term behavior of the geothermal system and the induced seismicity. In the Soultz-sous-Forêts plant, borehole measures give evidences of aseismic slip (Bailleux et al., 2013). And previous <span class="hlt">geodetic</span> monitoring studies of other deep geothermal plants show subsidence and horizontal displacements due to geothermal exploitation (e.g. Massonnet et al., 1997; Nishijima et al., 2005; Fialko and Simons, 2000). The ability of geodesy tools to provide information about dynamic behaviour and the change in the local stress field around the geothermal site make them a suitable method to meet these challenges. Therefore, we establish a long-term <span class="hlt">geodetic</span> monitoring system of the two geothermal sites. This work presents the monitoring strategy and the preliminary results. We install a <span class="hlt">network</span> of continuous GNSS and INSAR data are in acquisition. Our aim is to monitor</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4128701','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4128701"><span>DOC2B and Munc13-1 Differentially Regulate Neuronal <span class="hlt">Network</span> <span class="hlt">Activity</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lavi, Ayal; Sheinin, Anton; Shapira, Ronit; Zelmanoff, Daniel; Ashery, Uri</p> <p>2014-01-01</p> <p>Alterations in the levels of synaptic proteins affect synaptic transmission and synaptic plasticity. However, the precise effects on neuronal <span class="hlt">network</span> <span class="hlt">activity</span> are still enigmatic. Here, we utilized microelectrode array (MEA) to elucidate how manipulation of the presynaptic release process affects the <span class="hlt">activity</span> of neuronal <span class="hlt">networks</span>. By combining pharmacological tools and genetic manipulation of synaptic proteins, we show that overexpression of DOC2B and Munc13-1, proteins known to promote vesicular maturation and release, elicits opposite effects on the <span class="hlt">activity</span> of the neuronal <span class="hlt">network</span>. Although both cause an increase in the overall number of spikes, the distribution of spikes is different. While DOC2B enhances, Munc13-1 reduces the firing rate within bursts of spikes throughout the <span class="hlt">network</span>; however, Munc13-1 increases the rate of <span class="hlt">network</span> bursts. DOC2B's effects were mimicked by Strontium that elevates asynchronous release but not by a DOC2B mutant that enhances spontaneous release rate. This suggests for the first time that increased asynchronous release on the single-neuron level promotes bursting <span class="hlt">activity</span> in the <span class="hlt">network</span> level. This innovative study demonstrates the complementary role of the <span class="hlt">network</span> level in explaining the physiological relevance of the cellular <span class="hlt">activity</span> of presynaptic proteins and the transformation of synaptic release manipulation from the neuron to the <span class="hlt">network</span> level. PMID:23537531</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.3408A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.3408A"><span>Determination of recent horizontal crustal movements and deformations of African and Eurasian plates in western Mediterranean region using <span class="hlt">geodetic</span>-GPS computations extended to 2006 (from 1997) related to NAFREF and AFREF frames.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Azzouzi, R.</p> <p>2009-04-01</p> <p> Western Mediterranean and especially on Morocco. Exploiting parameters of positions and dispersions of these stations within the 1997-2003 period, the motion and the interaction types of interaction between African and Eurasian tectonic plates can be estimated. Similarly, the crustal dynamic parameters of tension of these sites will be computed. The time occupation on repeated observations sites is at least 72 hours. The measurements are continuous on permanent stations. The precise ephemerides are used in GPS computations. The post-treatments are done using commercial and scientific softwares. The coordinates obtained for two consecutive periods to and t within a period of 8 years will be used by programs established for this purpose to estimate crustal dynamic parameters of tension as well as to evaluate the appropriate movements. Even crustal dynamic parameters will be determined on each sites of the GPS-Geodynamics <span class="hlt">network</span>, whose interest of seismic investigations is very important. This will allow best knowledge of substantial seismic <span class="hlt">activities</span> of the surrounding zones. It can be deduced by measuring the motions and their parameter tensions using GPS. These estimations will contribute on the earthquake prediction by supervising the strain accumulation and its release in the <span class="hlt">active</span> areas. For the <span class="hlt">geodetically</span> aspect the GPS-Geodynamics sites computed in the ITRF frame can be used with other similar ounces' of Africa country and some well selected and convenient IGS, EUREF stations..to determine first the NAFREF and the AFRER frames.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JGRB..112.6410V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JGRB..112.6410V"><span>Twenty-five years of <span class="hlt">geodetic</span> measurements along the Tadjoura-Asal rift system, Djibouti, East Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vigny, Christophe; de Chabalier, Jean-Bernard; Ruegg, Jean-Claude; Huchon, Philippe; Feigl, Kurt L.; Cattin, Rodolphe; Asfaw, Laike; Kanbari, Khaled</p> <p>2007-06-01</p> <p>Since most of Tadjoura-Asal rift system sits on dry land in the Afar depression near the triple junction between the Arabia, Somalia, and Nubia plates, it is an ideal natural laboratory for studying rifting processes. We analyze these processes in light of a time series of <span class="hlt">geodetic</span> measurements from 1978 through 2003. The surveys used triangulation (1973), trilateration (1973, 1979, and 1981-1986), leveling (1973, 1979, 1984-1985, and 2000), and the Global Positioning System (GPS, in 1991, 1993, 1995, 1997, 1999, 2001, and 2003). A <span class="hlt">network</span> of about 30 GPS sites covers the Republic of Djibouti. Additional points were also measured in Yemen and Ethiopia. Stations lying in the Danakil block have almost the same velocity as Arabian plate, indicating that opening near the southern tip of the Red Sea is almost totally accommodated in the Afar depression. Inside Djibouti, the Asal-Ghoubbet rift system accommodates 16 ± 1 mm/yr of opening perpendicular to the rift axis and exhibits a pronounced asymmetry with essentially null deformation on its southwestern side and significant deformation on its northeastern side. This rate, slightly higher than the large-scale Arabia-Somalia motion (13 ± 1 mm/yr), suggests transient variations associated with relaxation processes following the Asal-Ghoubbet seismovolcanic sequence of 1978. Inside the rift, the deformation pattern exhibits a clear two-dimensional pattern. Along the rift axis, the rate decreases to the northwest, suggesting propagation in the same direction. Perpendicular to the rift axis, the focus of the opening is clearly shifted to the northeast, relative to the topographic rift axis, in the "Petit Rift," a rift-in-rift structure, containing most of the <span class="hlt">active</span> faults and the seismicity. Vertical motions, measured by differential leveling, show the same asymmetric pattern with a bulge of the northeastern shoulder. Although the inner floor of the rift is subsiding with respect to the shoulders, all sites within the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.3857T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.3857T"><span><span class="hlt">Geodetic</span> constraints to the source mechanism of the 2011-2013 unrest at Campi Flegrei (Italy) caldera</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Trasatti, Elisa; Polcari, Marco; Bonafede, Maurizio; Stramondo, Salvatore</p> <p>2016-04-01</p> <p>Campi Flegrei (Italy) is a nested caldera and together with Vesuvius is one of the Italian GEO Geohazard Supersites (GSNL). The area is characterized by one of the highest volcanic hazard of the world, due to the very high density of inhabitants (1800/km²), the persistent <span class="hlt">activity</span> of the system and the explosive character of volcanism. A major unrest episode took place in 1982-84, when the town of Pozzuoli, located at the caldera center, was uplifted by 1.80 m. Minor uplifts of few centimeters, seismic swarms and degassing episodes took place in 1989, 2000 and 2004-06. Since 2005 Campi Flegrei is uplifting, reaching a ground velocity of 9 cm/yr in 2012, showing that the caldera is in a critical state on the verge of instability. In this work, we present results from SAR Interferometry and <span class="hlt">geodetic</span> data modelling at Campi Flegrei in the framework of the EU's FP7 MED-SUV Project. We exploit two COSMO-SkyMed data sets to map the deformation field during 2011-2013. The spatial distributions of the cumulative displacement from COSMO-SkyMed ascending/descending orbits show similar behaviors, confirming the bell-shaped pattern of the deformation at least within the inner rim of the caldera. The resulting data, together with GPS data from the Neapolitan Volcanoes Continuous GPS <span class="hlt">network</span> (NeVoCGPS) is fitted through a geophysical inversion process using finite element forward models to account for the 3D heterogeneous medium. The best fit model is a north dipping mixed-mode dislocation source lying at ~5 km depth. The driving mechanism is ascribable to magma input into the source of the large 1982-1984 unrest (since similar source characteristics were inferred) that generates initial inflation followed by additional shear slip accompanying the extension of crack tips. The history and the current state of the system indicate that Campi Flegrei is able to erupt again. Constraining the defomation source may have important implications in terms of civil protection and the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.9896A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.9896A"><span>Assessment of the accuracy of global <span class="hlt">geodetic</span> satellite laser ranging observations 1993-2013</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Appleby, Graham; Rodriguez, Jose</p> <p>2014-05-01</p> <p>We continue efforts to estimate the intrinsic accuracy of range measurements made by the major satellite laser ranging stations of the ILRS <span class="hlt">Network</span> using normal point observations of the primary <span class="hlt">geodetic</span> satellites LAGEOS and LAGEOS-II. In a novel, but risky, approach we carry out weekly, loosely constrained, reference frame solutions for satellite initial state vectors, station coordinates and daily EOPs (X-pole, Y-pole and LoD), as well as estimating range bias for all the stations. We apply known range errors a-priori from the table developed and maintained through the efforts of the ILRS Analysis Working Group and apply station- and time-specific satellite centre of mass corrections (Appleby and Otsubo, 2014), both corrections that are currently implemented in the standard ILRS reference frame products. Our approach, to solve simultaneously for station coordinates and possible range bias for all the stations, has the strength that any bias results are independent of the coordinates taken for example from ITRF2008; thus the approach has the potential to discover bias that may have become absorbed primarily in station height had the coordinates been determined on the assumption of zero bias. A serious complication of the approach is that correlations will inevitably exist between station height and range bias. However, for the major stations of the <span class="hlt">Network</span>, and using LAGEOS and LAGEOS-II observations simultaneously in our weekly solutions, we are developing techniques and testing their sensitivity in performing a partial separation between these parameters at the expense of an increase in the variance of the stations' height time series. In this paper we discuss the results in terms of potential impact on coordinate solutions, including the reference frame scale, and in the context of preparations for ITRF2013.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1713483F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1713483F"><span><span class="hlt">Geodetic</span> integration of Sentinel-1A IW data using PSInSAR in Hungary</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Farkas, Péter; Hevér, Renáta; Grenerczy, Gyula</p> <p>2015-04-01</p> <p>ESA's latest Synthetic Aperture Radar (SAR) mission Sentinel-1 is a huge step forward in SAR interferometry. With its default acquisition mode called the Interferometric Wide Swath Mode (IW) areas through all scales can be mapped with an excellent return time of 12 days (while only the Sentinel-1A is in orbit). Its operational data policy is also a novelty, it allows scientific users free and unlimited access to data. It implements a new type of ScanSAR mode called Terrain Observation with Progressive Scan (TOPS) SAR. It has the same resolution as ScanSAR but with better signal-to-noise ratio distribution. The bigger coverage is achieved by rotation of the antenna in the azimuth direction, therefore it requires very precise co-registration because even errors under a pixel accuracy can introduce azimuth phase variations caused by differences in Doppler-centroids. In our work we will summarize the benefits and the drawbacks of the IW mode. We would like to implement the processing chain of GAMMA Remote Sensing of such data for mapping surface motion with special attention to the co-registration step. Not only traditional InSAR but the advanced method of Persistent Scatterer InSAR (PSInSAR) will be performed and presented as well. PS coverage, along with coherence, is expected to be good due to the small perpendicular and temporal baselines. We would also like to integrate these measurements into national <span class="hlt">geodetic</span> <span class="hlt">networks</span> using common reference points. We have installed trihedral corner reflectors at some selected sites to aid precise collocation. Thus, we aim to demonstrate that Sentinel-1 can be effectively used for surface movement detection and monitoring and it can also provide valuable information for the improvement of our <span class="hlt">networks</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EPJB...89...26Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EPJB...89...26Z"><span>Modelling temporal <span class="hlt">networks</span> of human face-to-face contacts with public <span class="hlt">activity</span> and individual reachability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Yi-Qing; Cui, Jing; Zhang, Shu-Min; Zhang, Qi; Li, Xiang</p> <p>2016-02-01</p> <p>Modelling temporal <span class="hlt">networks</span> of human face-to-face contacts is vital both for understanding the spread of airborne pathogens and word-of-mouth spreading of information. Although many efforts have been devoted to model these temporal <span class="hlt">networks</span>, there are still two important social features, public <span class="hlt">activity</span> and individual reachability, have been ignored in these models. Here we present a simple model that captures these two features and other typical properties of empirical face-to-face contact <span class="hlt">networks</span>. The model describes agents which are characterized by an attractiveness to slow down the motion of nearby people, have event-triggered <span class="hlt">active</span> probability and perform an <span class="hlt">activity</span>-dependent biased random walk in a square box with periodic boundary. The model quantitatively reproduces two empirical temporal <span class="hlt">networks</span> of human face-to-face contacts which are testified by their <span class="hlt">network</span> properties and the epidemic spread dynamics on them.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26493108','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26493108"><span>Fitness, but not physical <span class="hlt">activity</span>, is related to functional integrity of brain <span class="hlt">networks</span> associated with aging.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Voss, Michelle W; Weng, Timothy B; Burzynska, Agnieszka Z; Wong, Chelsea N; Cooke, Gillian E; Clark, Rachel; Fanning, Jason; Awick, Elizabeth; Gothe, Neha P; Olson, Erin A; McAuley, Edward; Kramer, Arthur F</p> <p>2016-05-01</p> <p>Greater physical <span class="hlt">activity</span> and cardiorespiratory fitness are associated with reduced age-related cognitive decline and lower risk for dementia. However, significant gaps remain in the understanding of how physical <span class="hlt">activity</span> and fitness protect the brain from adverse effects of brain aging. The primary goal of the current study was to empirically evaluate the independent relationships between physical <span class="hlt">activity</span> and fitness with functional brain health among healthy older adults, as measured by the functional connectivity of cognitively and clinically relevant resting state <span class="hlt">networks</span>. To build context for fitness and physical <span class="hlt">activity</span> associations in older adults, we first demonstrate that young adults have greater within-<span class="hlt">network</span> functional connectivity across a broad range of cortical association <span class="hlt">networks</span>. Based on these results and previous research, we predicted that individual differences in fitness and physical <span class="hlt">activity</span> would be most strongly associated with functional integrity of the <span class="hlt">networks</span> most sensitive to aging. Consistent with this prediction, and extending on previous research, we showed that cardiorespiratory fitness has a positive relationship with functional connectivity of several cortical <span class="hlt">networks</span> associated with age-related decline, and effects were strongest in the default mode <span class="hlt">network</span> (DMN). Furthermore, our results suggest that the positive association of fitness with brain function can occur independent of habitual physical <span class="hlt">activity</span>. Overall, our findings provide further support that cardiorespiratory fitness is an important factor in moderating the adverse effects of aging on cognitively and clinically relevant functional brain <span class="hlt">networks</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26523082','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26523082"><span>Tidal Love and Shida numbers estimated by <span class="hlt">geodetic</span> VLBI.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Krásná, Hana; Böhm, Johannes; Schuh, Harald</p> <p>2013-10-01</p> <p>Frequency-dependent Love and Shida numbers, which characterize the Earth response to the tidal forces, were estimated in a global adjustment of all suitable <span class="hlt">geodetic</span> Very Long Baseline Interferometry (VLBI) sessions from 1984.0 to 2011.0. Several solutions were carried out to determine the Love and Shida numbers for the tidal constituents at periods in the diurnal band and in the long-period band in addition to values of the Love and Shida numbers common for all tides of degree two. Adding up all twelve diurnal tidal waves that were estimated, the total differences in displacement with respect to the theoretical conventional values of the Love and Shida numbers calculated from an Earth model reach 1.73 ± 0.29 mm in radial direction and 1.15 ± 0.15 mm in the transverse plane. The difference in the radial deformation following from the estimates of the zonal Love numbers is largest for the semi-annual tide Ssa with 1.07 ± 0.19 mm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoJI.202..763S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoJI.202..763S"><span><span class="hlt">Geodetic</span> secular velocity errors due to interannual surface loading deformation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Santamaría-Gómez, Alvaro; Mémin, Anthony</p> <p>2015-08-01</p> <p><span class="hlt">Geodetic</span> vertical velocities derived from data as short as 3 yr are often assumed to be representative of linear deformation over past decades to millennia. We use two decades of surface loading deformation predictions due to variations of atmospheric, oceanic and continental water mass to assess the effect on secular velocities estimated from short time-series. The interannual deformation is time-correlated at most locations over the globe, with the level of correlation depending mostly on the chosen continental water model. Using the most conservative loading model and 5-yr-long time-series, we found median vertical velocity errors of 0.5 mm yr-1 over the continents (0.3 mm yr-1 globally), exceeding 1 mm yr-1 in regions around the southern Tropic. Horizontal velocity errors were seven times smaller. Unless an accurate loading model is available, a decade of continuous data is required in these regions to mitigate the impact of the interannual loading deformation on secular velocities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4599447','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4599447"><span>Tidal Love and Shida numbers estimated by <span class="hlt">geodetic</span> VLBI☆</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Krásná, Hana; Böhm, Johannes; Schuh, Harald</p> <p>2013-01-01</p> <p>Frequency-dependent Love and Shida numbers, which characterize the Earth response to the tidal forces, were estimated in a global adjustment of all suitable <span class="hlt">geodetic</span> Very Long Baseline Interferometry (VLBI) sessions from 1984.0 to 2011.0. Several solutions were carried out to determine the Love and Shida numbers for the tidal constituents at periods in the diurnal band and in the long-period band in addition to values of the Love and Shida numbers common for all tides of degree two. Adding up all twelve diurnal tidal waves that were estimated, the total differences in displacement with respect to the theoretical conventional values of the Love and Shida numbers calculated from an Earth model reach 1.73 ± 0.29 mm in radial direction and 1.15 ± 0.15 mm in the transverse plane. The difference in the radial deformation following from the estimates of the zonal Love numbers is largest for the semi-annual tide Ssa with 1.07 ± 0.19 mm. PMID:26523082</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900011223','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900011223"><span>Thin-plate spline quadrature of <span class="hlt">geodetic</span> integrals</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Vangysen, Herman</p> <p>1989-01-01</p> <p>Thin-plate spline functions (known for their flexibility and fidelity in representing experimental data) are especially well-suited for the numerical integration of <span class="hlt">geodetic</span> integrals in the area where the integration is most sensitive to the data, i.e., in the immediate vicinity of the evaluation point. Spline quadrature rules are derived for the contribution of a circular innermost zone to Stoke's formula, to the formulae of Vening Meinesz, and to the recursively evaluated operator L(n) in the analytical continuation solution of Molodensky's problem. These rules are exact for interpolating thin-plate splines. In cases where the integration data are distributed irregularly, a system of linear equations needs to be solved for the quadrature coefficients. Formulae are given for the terms appearing in these equations. In case the data are regularly distributed, the coefficients may be determined once-and-for-all. Examples are given of some fixed-point rules. With such rules successive evaluation, within a circular disk, of the terms in Molodensky's series becomes relatively easy. The spline quadrature technique presented complements other techniques such as ring integration for intermediate integration zones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1614072D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1614072D"><span>Tidal investigations at Borowa Gora <span class="hlt">Geodetic</span>-Geophysical Observatory</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dykowski, Przemyslaw; Sekowski, Marcin</p> <p>2014-05-01</p> <p>In 2009 three LaCoste&Romberg model G gravimeters owed by the Institute of Geodesy and Cartography (IGiK) were equipped with a modern type of feedback system (LRFB-300) which gives a wide range of possibilities for gravimetric measurements. One of the modified LCR gravimeters (G1036) is used for continuous tidal recordings in Borowa Gora <span class="hlt">Geodetic</span> - Geophysical Observatory of IGiK, is situated north of Warsaw. Good quality data is now collected from February of 2012. A set of Linux shell scripts have been developed to provide reliable readout recordings (via bluetooth) as well as automatic handling of any exceptional situations. The system runs with the LCR-G1036 from the beginning of February 2012, and since then the completeness of the recording visibly improved compared to previous recordings reaching nearly 98%. The tidal observation have been calibrated several times during the course of recordings, four times with the A10-020 and once with the FG5-230. Also some results concerning the calibration of the tidal recordings with relative meters is presented. A special period (end of 2013) is emphasized where the A10-020 performs measurements every hour for a two weeks alongside three LCR meters. The local tidal model is developed and presented with comparison to the model used in absolute gravity determinations with the A10-020 at Borowa Gora and on the stations of the gravity control.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMNG23A3795G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMNG23A3795G"><span>Detection of Aseismic <span class="hlt">Geodetic</span> Transients Using k-Nearest Neighbors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Granat, R. A.</p> <p>2014-12-01</p> <p>Observation and detection of aseismic transient signals in <span class="hlt">geodetic</span> data is an important part of improving understanding of the earthquake cycle. Recent work, conducted as part of the Southern California Earthquake Center's transient detection exercise, showed that transient detection results were improved by using multiple detection methods and by localizing results to specified geographical regions. While geographical regions can be defined on the basis of a priori science domain knowledge, regions defined in such a way are vulnerable to edge effects (i.e., observations collected near the region boundary are less reliable) and are not easily extendable to new regions or measurement modalities where a priori understanding is limited. We present an approach to overcoming these challenges that utilizes a k-nearest neighbor approach to defining geographical regions for GPS stations. In this approach, each station has its own individual region, defined by a chosen number k closest neighboring stations rather than any predefined geographical boundary. In this general framework, a weighting function controls the contributions of neighboring stations to the transient detection, while a distance function (e.g., Vincenty's method) controls which k stations are considered neighbors. The "proper" k depends both on the transient detection method and the weighting function; it can be defined by the user directly or optimized using hyperparameter optimization. For transient detection using multiple detection methods, this framework nests readily within an ensemble classifier.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.7343P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.7343P"><span>Comparison of AuScope VLBI and GPS <span class="hlt">geodetic</span> data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Plank, Lucia; Santamaría-Gómez, Alvaro; Lovell, James</p> <p>2015-04-01</p> <p>The AuScope <span class="hlt">geodetic</span> Very Long Baseline Interferometry (VLBI) array consists of three telescopes on Australian territory, each of them co-located with Global Navigation Satellite Systems (GNSS) tracking stations. The high cadence VLBI observing program gives baselines and station coordinates of good quality, with baseline length repeatabilities (WRMS) of a few millimetres for the Australian baselines. In this contribution we present the latest VLBI results of regional and global experiments and compare them to baselines and site coordinates derived from GNSS data. For a thorough comparison, we use similar models for both, the VLBI and the GNSS data processing. Investigations of common tropospheric parameters and clock terms, as well as validations against the local ties as determined in the 2014 local surveys will supplement this study. Additional insight into the topic of technique specific errors is expected from the analysis of dedicated experiments with the two co-located telescopes at Hobart, the 26m legacy antenna and the new 12m dish.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/110235','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/110235"><span>An efficient algorithm for geocentric to <span class="hlt">geodetic</span> coordinate conversion</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Toms, R.M.</p> <p>1995-09-01</p> <p>The problem of performing transformations from geocentric to <span class="hlt">geodetic</span> coordinates has received an inordinate amount of attention in the literature. Numerous approximate methods have been published. Almost none of the publications address the issue of efficiency and in most cases there is a paucity of error analysis. Recently there has been a surge of interest in this problem aimed at developing more efficient methods for real time applications such as DIS. Iterative algorithms have been proposed that are not of optimal efficiency, address only one error component and require a small but uncertain number of relatively expensive iterations for convergence. In this paper a well known rapidly convergent iterative approach is modified to eliminate intervening trigonometric function evaluations. A total error metric is defined that accounts for both angular and altitude errors. The initial guess is optimized to minimize the error for one iteration. The resulting algorithm yields transformations correct to one centimeter for altitudes out to one million kilometers. Due to the rapid convergence only one iteration is used and no stopping test is needed. This algorithm is discussed in the context of machines that have FPUs and legacy machines that utilize mathematical subroutine packages.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26685516','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26685516"><span>The Premedieval Origin of Portolan Charts: New <span class="hlt">Geodetic</span> Evidence.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nicolai, Roel</p> <p>2015-09-01</p> <p>Portolan charts are highly realistic medieval charts that show remarkably accurate coastlines of the Mediterranean and the Black Sea. They emerged suddenly, without any predecessors or a clear developmental path, in Italy during the thirteenth century. There is broad scholarly agreement that these charts are original creations of European medieval culture. However, corroborating evidence is lacking, and a convincing explanation of the method of their construction has so far not been provided. In this essay it is demonstrated by means of <span class="hlt">geodetic</span> analysis that the overall shape of the coastlines corresponds closely to that on a modern map based on the Mercator projection. It is further demonstrated that this correspondence cannot possibly be due to chance. Consequently, the existence of a Mercator or Mercator-like map projection on portolan charts is incompatible with the assumed medieval origin of these charts. Portolan charts are far more sophisticated than has hitherto been recognized. Their construction was well beyond the capabilities of cartographers from either medieval Europe or the Arabic-Islamic world. This conclusion serves to reopen the question of the origins of the geometric data and the construction methods that until now have appeared to underlie medieval portolan charts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995PhRvE..51..738G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995PhRvE..51..738G"><span>Time structure of the <span class="hlt">activity</span> in neural <span class="hlt">network</span> models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gerstner, Wulfram</p> <p>1995-01-01</p> <p>Several neural <span class="hlt">network</span> models in continuous time are reconsidered in the framework of a general mean-field theory which is exact in the limit of a large and fully connected <span class="hlt">network</span>. The theory assumes pointlike spikes which are generated by a renewal process. The effect of spikes on a receiving neuron is described by a linear response kernel which is the dominant term in a weak-coupling expansion. It is shown that the resulting ``spike response model'' is the most general renewal model with linear inputs. The standard integrate-and-fire model forms a special case. In a <span class="hlt">network</span> structure with several pools of identical spiking neurons, the global states and the dynamic evolution are determined by a nonlinear integral equation which describes the effective interaction within and between different pools. We derive explicit stability criteria for stationary (incoherent) and oscillatory (coherent) solutions. It is shown that the stationary state of noiseless systems is ``almost always'' unstable. Noise suppresses fast oscillations and stabilizes the system. Furthermore, collective oscillations are stable only if the firing occurs while the synaptic potential is increasing. In particular, collective oscillations in a <span class="hlt">network</span> with delayless excitatory interaction are at most semistable. Inhibitory interactions with short delays or excitatory interactions with long delays lead to stable oscillations. Our general results allow a straightforward application to different <span class="hlt">network</span> models with spiking neurons. Furthermore, the theory allows an estimation of the errors introduced in firing rate or ``graded-response'' models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18490486','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18490486"><span>A community-organizing approach to promoting physical <span class="hlt">activity</span> in older adults: the southeast senior physical <span class="hlt">activity</span> <span class="hlt">network</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cheadle, Allen; Egger, Ruth; LoGerfo, James P; Walwick, Julie; Schwartz, Sheryl</p> <p>2010-03-01</p> <p>This article describes a community organizing approach to promoting physical <span class="hlt">activity</span> among underserved older adults in southeast Seattle: the Southeast Senior Physical <span class="hlt">Activity</span> <span class="hlt">Network</span> (SESPAN). The organizing strategy involves <span class="hlt">networking</span> with a variety of community-based organizations, with two broad objectives: (a) program objective-to make connections between two (or more) community-based organizations to create senior physical <span class="hlt">activity</span> programs where none existed before; and (b) coalition objective-to build a broader <span class="hlt">network</span> or coalition of groups and organizations to assist in making larger scale environmental and policy changes. <span class="hlt">Networking</span> among organizations led to the creation of a number of potentially sustainable walking and exercise programs that are reaching previously underserved communities within Southeast Seattle. In addition, a major community event led to the establishment of a health coalition that has the potential to continue to generate new broad-based programs and larger scale environmental changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4758040','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4758040"><span>AST: <span class="hlt">Activity</span>-Security-Trust driven modeling of time varying <span class="hlt">networks</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wang, Jian; Xu, Jiake; Liu, Yanheng; Deng, Weiwen</p> <p>2016-01-01</p> <p><span class="hlt">Network</span> modeling is a flexible mathematical structure that enables to identify statistical regularities and structural principles hidden in complex systems. The majority of recent driving forces in modeling complex <span class="hlt">networks</span> are originated from <span class="hlt">activity</span>, in which an <span class="hlt">activity</span> potential of a time invariant function is introduced to identify agents’ interactions and to construct an <span class="hlt">activity</span>-driven model. However, the new-emerging <span class="hlt">network</span> evolutions are already deeply coupled with not only the explicit factors (e.g. <span class="hlt">activity</span>) but also the implicit considerations (e.g. security and trust), so more intrinsic driving forces behind should be integrated into the modeling of time varying <span class="hlt">networks</span>. The agents undoubtedly seek to build a time-dependent trade-off among <span class="hlt">activity</span>, security, and trust in generating a new connection to another. Thus, we reasonably propose the <span class="hlt">Activity</span>-Security-Trust (AST) driven model through synthetically considering the explicit and implicit driving forces (e.g. <span class="hlt">activity</span>, security, and trust) underlying the decision process. AST-driven model facilitates to more accurately capture highly dynamical <span class="hlt">network</span> behaviors and figure out the complex evolution process, allowing a profound understanding of the effects of security and trust in driving <span class="hlt">network</span> evolution, and improving the biases induced by only involving <span class="hlt">activity</span> representations in analyzing the dynamical processes. PMID:26888717</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26888717','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26888717"><span>AST: <span class="hlt">Activity</span>-Security-Trust driven modeling of time varying <span class="hlt">networks</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Jian; Xu, Jiake; Liu, Yanheng; Deng, Weiwen</p> <p>2016-02-18</p> <p><span class="hlt">Network</span> modeling is a flexible mathematical structure that enables to identify statistical regularities and structural principles hidden in complex systems. The majority of recent driving forces in modeling complex <span class="hlt">networks</span> are originated from <span class="hlt">activity</span>, in which an <span class="hlt">activity</span> potential of a time invariant function is introduced to identify agents' interactions and to construct an <span class="hlt">activity</span>-driven model. However, the new-emerging <span class="hlt">network</span> evolutions are already deeply coupled with not only the explicit factors (e.g. <span class="hlt">activity</span>) but also the implicit considerations (e.g. security and trust), so more intrinsic driving forces behind should be integrated into the modeling of time varying <span class="hlt">networks</span>. The agents undoubtedly seek to build a time-dependent trade-off among <span class="hlt">activity</span>, security, and trust in generating a new connection to another. Thus, we reasonably propose the <span class="hlt">Activity</span>-Security-Trust (AST) driven model through synthetically considering the explicit and implicit driving forces (e.g. <span class="hlt">activity</span>, security, and trust) underlying the decision process. AST-driven model facilitates to more accurately capture highly dynamical <span class="hlt">network</span> behaviors and figure out the complex evolution process, allowing a profound understanding of the effects of security and trust in driving <span class="hlt">network</span> evolution, and improving the biases induced by only involving <span class="hlt">activity</span> representations in analyzing the dynamical processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...621352W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...621352W"><span>AST: <span class="hlt">Activity</span>-Security-Trust driven modeling of time varying <span class="hlt">networks</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Jian; Xu, Jiake; Liu, Yanheng; Deng, Weiwen</p> <p>2016-02-01</p> <p><span class="hlt">Network</span> modeling is a flexible mathematical structure that enables to identify statistical regularities and structural principles hidden in complex systems. The majority of recent driving forces in modeling complex <span class="hlt">networks</span> are originated from <span class="hlt">activity</span>, in which an <span class="hlt">activity</span> potential of a time invariant function is introduced to identify agents’ interactions and to construct an <span class="hlt">activity</span>-driven model. However, the new-emerging <span class="hlt">network</span> evolutions are already deeply coupled with not only the explicit factors (e.g. <span class="hlt">activity</span>) but also the implicit considerations (e.g. security and trust), so more intrinsic driving forces behind should be integrated into the modeling of time varying <span class="hlt">networks</span>. The agents undoubtedly seek to build a time-dependent trade-off among <span class="hlt">activity</span>, security, and trust in generating a new connection to another. Thus, we reasonably propose the <span class="hlt">Activity</span>-Security-Trust (AST) driven model through synthetically considering the explicit and implicit driving forces (e.g. <span class="hlt">activity</span>, security, and trust) underlying the decision process. AST-driven model facilitates to more accurately capture highly dynamical <span class="hlt">network</span> behaviors and figure out the complex evolution process, allowing a profound understanding of the effects of security and trust in driving <span class="hlt">network</span> evolution, and improving the biases induced by only involving <span class="hlt">activity</span> representations in analyzing the dynamical processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/EJ1090942.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/EJ1090942.pdf"><span>"Who Do You Talk to about Your Teaching?": <span class="hlt">Networking</span> <span class="hlt">Activities</span> among University Teachers</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Pataraia, Nino; Falconer, Isobel; Margaryan, Anoush; Littlejohn, Allison; Fincher, Sally</p> <p>2014-01-01</p> <p>As the higher education environment changes, there are calls for university teachers to change and enhance their teaching practices to match. <span class="hlt">Networking</span> practices are known to be deeply implicated in studies of change and diffusion of innovation, yet academics' <span class="hlt">networking</span> <span class="hlt">activities</span> in relation to teaching have been little studied. This paper…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/EJ1114908.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/EJ1114908.pdf"><span>Students' <span class="hlt">Network</span> Project <span class="hlt">Activities</span> in the Context of the Information Educational Medium of Higher Education Institution</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Samerkhanova, Elvira K.; Krupoderova, Elena P.; Krupoderova, Klimentina R.; Bahtiyarova, Lyudmila N.; Ponachugin, Alexander V.</p> <p>2016-01-01</p> <p>The purpose of the research is justifying didactic possibilities of the use of <span class="hlt">network</span> services for the organization of information for the learning environment of college, where students carry out their project <span class="hlt">activities</span>, and where effective <span class="hlt">networking</span> between students and teachers takes place. The authors consider didactic possibilities of…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/FR-2010-12-03/pdf/2010-29869.pdf','FEDREG'); return false;" href="https://www.gpo.gov/fdsys/pkg/FR-2010-12-03/pdf/2010-29869.pdf"><span>75 FR 75593 - Financial Crimes Enforcement <span class="hlt">Network</span>; Confidentiality of Suspicious <span class="hlt">Activity</span> Reports</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR">Federal Register 2010, 2011, 2012, 2013, 2014</a></p> <p></p> <p>2010-12-03</p> <p>... 31 CFR Part 103 RIN 1506-AA99 Financial Crimes Enforcement <span class="hlt">Network</span>; Confidentiality of Suspicious <span class="hlt">Activity</span> Reports AGENCY: The Financial Crimes Enforcement <span class="hlt">Network</span> (``FinCEN''), Treasury. ACTION: Final... functions to promote the integrity of financial markets and mitigate risks of financial crime....</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=186005&keyword=dmso&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=84796068&CFTOKEN=71073114','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=186005&keyword=dmso&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=84796068&CFTOKEN=71073114"><span>DELTAMETHRIN AND ESFENVALERATE INHIBIT SPONTANEOUS <span class="hlt">NETWORK</span> <span class="hlt">ACTIVITY</span> IN RAT CORTICAL NEURONS IN VITRO.</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>Understanding pyrethroid actions on neuronal <span class="hlt">networks</span> will help to establish a mode of action for these compounds, which is needed for cumulative risk decisions under the Food Quality Protection Act of 1996. However, pyrethroid effects on spontaneous <span class="hlt">activity</span> in <span class="hlt">networks</span> of inter...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880044565&hterms=The_Gulf_of_California&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DThe_Gulf_of_California','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880044565&hterms=The_Gulf_of_California&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DThe_Gulf_of_California"><span>A few parts in 10 to the 8th <span class="hlt">geodetic</span> baseline repeatablity in the Gulf of California using the Global Positioning System</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tralli, David M.; Dixon, Timothy H.</p> <p>1988-01-01</p> <p>GPS <span class="hlt">geodetic</span> measurements of 350-650 km baselines across the Pacific-North America plate boundary in the Gulf of California are presented. The analysis employs a four-station U.S. fiducial <span class="hlt">network</span> and combined carrier phase and pseudorange data. Water vapor radiometer data at the Gulf sites are used to calibrate the GPS signal for wet tropospheric path delays. Residual tropospheric delays are modeled as first-order exponentially correlated stochastic processes. The measurement precision for horizontal components is a few parts in 10 to the 8th or better.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27875137','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27875137"><span>Visualizing the Hidden <span class="hlt">Activity</span> of Artificial Neural <span class="hlt">Networks</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rauber, Paulo E; Fadel, Samuel G; Falcao, Alexandre X; Telea, Alexandru C</p> <p>2017-01-01</p> <p>In machine learning, pattern classification assigns high-dimensional vectors (observations) to classes based on generalization from examples. Artificial neural <span class="hlt">networks</span> currently achieve state-of-the-art results in this task. Although such <span class="hlt">networks</span> are typically used as black-boxes, they are also widely believed to learn (high-dimensional) higher-level representations of the original observations. In this paper, we propose using dimensionality reduction for two tasks: visualizing the relationships between learned representations of observations, and visualizing the relationships between artificial neurons. Through experiments conducted in three traditional image classification benchmark datasets, we show how visualization can provide highly valuable feedback for <span class="hlt">network</span> designers. For instance, our discoveries in one of these datasets (SVHN) include the presence of interpretable clusters of learned representations, and the partitioning of artificial neurons into groups with apparently related discriminative roles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhyA..468..614Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhyA..468..614Z"><span>Effects of <span class="hlt">active</span> links on epidemic transmission over social <span class="hlt">networks</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhu, Guanghu; Chen, Guanrong; Fu, Xinchu</p> <p>2017-02-01</p> <p>A new epidemic model with two infection periods is developed to account for the human behavior in social <span class="hlt">network</span>, where newly infected individuals gradually restrict most of future contacts or are quarantined, causing infectivity change from a degree-dependent form to a constant. The corresponding dynamics are formulated by a set of ordinary differential equations (ODEs) via mean-field approximation. The effects of diverse infectivity on the epidemic dynamics ​are examined, with a behavioral interpretation of the basic reproduction number. Results show that such simple adaptive reactions largely determine the impact of <span class="hlt">network</span> structure on epidemics. Particularly, a theorem proposed by Lajmanovich and Yorke in 1976 is generalized, so that it can be applied for the analysis of the epidemic models with multi-compartments especially <span class="hlt">network</span>-coupled ODE systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhA...49B5601Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhA...49B5601Z"><span>Noise influence on spike <span class="hlt">activation</span> in a Hindmarsh-Rose small-world neural <span class="hlt">network</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhe, Sun; Micheletto, Ruggero</p> <p>2016-07-01</p> <p>We studied the role of noise in neural <span class="hlt">networks</span>, especially focusing on its relation to the propagation of spike <span class="hlt">activity</span> in a small sized system. We set up a source of information using a single neuron that is constantly spiking. This element called initiator x o feeds spikes to the rest of the <span class="hlt">network</span> that is initially quiescent and subsequently reacts with vigorous spiking after a transitional period of time. We found that noise quickly suppresses the initiator’s influence and favors spontaneous spike <span class="hlt">activity</span> and, using a decibel representation of noise intensity, we established a linear relationship between noise amplitude and the interval from the initiator’s first spike and the rest of the <span class="hlt">network</span> <span class="hlt">activation</span>. We studied the same process with <span class="hlt">networks</span> of different sizes (number of neurons) and found that the initiator x o has a measurable influence on small <span class="hlt">networks</span>, but as the <span class="hlt">network</span> grows in size, spontaneous spiking emerges disrupting its effects on <span class="hlt">networks</span> of more than about N = 100 neurons. This suggests that the mechanism of internal noise generation allows information transmission within a small neural neighborhood, but decays for bigger <span class="hlt">network</span> domains. We also analyzed the Fourier spectrum of the whole <span class="hlt">network</span> membrane potential and verified that noise provokes the reduction of main θ and α peaks before transitioning into chaotic spiking. However, <span class="hlt">network</span> size does not reproduce a similar phenomena; instead we recorded a reduction in peaks’ amplitude, a better sharpness and definition of Fourier peaks, but not the evident degeneration to chaos observed with increasing external noise. This work aims to contribute to the understanding of the fundamental mechanisms of propagation of spontaneous spiking in neural <span class="hlt">networks</span> and gives a quantitative assessment of how noise can be used to control and modulate this phenomenon in Hindmarsh-Rose (H-R) neural <span class="hlt">networks</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17293055','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17293055"><span>Prefrontal cortical <span class="hlt">network</span> <span class="hlt">activity</span>: Opposite effects of psychedelic hallucinogens and D1/D5 dopamine receptor <span class="hlt">activation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lambe, E K; Aghajanian, G K</p> <p>2007-03-30</p> <p>The fine-tuning of <span class="hlt">network</span> <span class="hlt">activity</span> provides a modulating influence on how information is processed and interpreted in the brain. Here, we use brain slices of rat prefrontal cortex to study how recurrent <span class="hlt">network</span> <span class="hlt">activity</span> is affected by neuromodulators known to alter normal cortical function. We previously determined that glutamate spillover and stimulation of extrasynaptic N-methyl-d-aspartic acid (NMDA) receptors are required to support hallucinogen-induced cortical <span class="hlt">network</span> <span class="hlt">activity</span>. Since microdialysis studies suggest that psychedelic hallucinogens and dopamine D1/D5 receptor agonists have opposite effects on extracellular glutamate in prefrontal cortex, we hypothesized that these two families of psychoactive drugs would have opposite effects on cortical <span class="hlt">network</span> <span class="hlt">activity</span>. We found that <span class="hlt">network</span> <span class="hlt">activity</span> can be enhanced by 2,5-dimethoxy-4-iodoamphetamine (DOI) (a psychedelic hallucinogen that is a partial agonist of 5-HT(2A/2C) receptors) and suppressed by the selective D1/D5 agonist SKF 38393. This suppression could be mimicked by direct <span class="hlt">activation</span> of adenylyl cyclase with forskolin or by addition of a cAMP analog. These findings are consistent with previous work showing that <span class="hlt">activation</span> of adenylyl cyclase can upregulate neuronal glutamate transporters, thereby decreasing synaptic spillover of glutamate. Consistent with this hypothesis, a low concentration of the glutamate transporter inhibitor threo-beta-benzoylaspartic acid (TBOA) restored electrically-evoked recurrent <span class="hlt">activity</span> in the presence of a selective D1/D5 agonist, whereas recurrent <span class="hlt">activity</span> in the presence of a low level of the GABA(A) antagonist bicuculline was not resistant to suppression by the D1/D5 agonist. The tempering of <span class="hlt">network</span> UP states by D1/D5 receptor <span class="hlt">activation</span> may have implications for the proposed use of D1/D5 agonists in the treatment of schizophrenia.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19393237','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19393237"><span>Human embryonic stem cell-derived neuronal cells form spontaneously <span class="hlt">active</span> neuronal <span class="hlt">networks</span> in vitro.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Heikkilä, Teemu J; Ylä-Outinen, Laura; Tanskanen, Jarno M A; Lappalainen, Riikka S; Skottman, Heli; Suuronen, Riitta; Mikkonen, Jarno E; Hyttinen, Jari A K; Narkilahti, Susanna</p> <p>2009-07-01</p> <p>The production of functional human embryonic stem cell (hESC)-derived neuronal cells is critical for the application of hESCs in treating neurodegenerative disorders. To study the potential functionality of hESC-derived neurons, we cultured and monitored the development of hESC-derived neuronal <span class="hlt">networks</span> on microelectrode arrays. Immunocytochemical studies revealed that these <span class="hlt">networks</span> were positive for the neuronal marker proteins beta-tubulin(III) and microtubule-associated protein 2 (MAP-2). The hESC-derived neuronal <span class="hlt">networks</span> were spontaneously <span class="hlt">active</span> and exhibited a multitude of electrical impulse firing patterns. Synchronous bursts of electrical <span class="hlt">activity</span> similar to those reported for hippocampal neurons and rodent embryonic stem cell-derived neuronal <span class="hlt">networks</span> were recorded from the differentiated cultures until up to 4 months. The dependence of the observed neuronal <span class="hlt">network</span> <span class="hlt">activity</span> on sodium ion channels was examined using tetrodotoxin (TTX). Antagonists for the glutamate receptors NMDA [D(-)-2-amino-5-phosphonopentanoic acid] and AMPA/kainate [6-cyano-7-nitroquinoxaline-2,3-dione], and for GABAA receptors [(-)-bicuculline methiodide] modulated the spontaneous electrical <span class="hlt">activity</span>, indicating that pharmacologically susceptible neuronal <span class="hlt">networks</span> with functional synapses had been generated. The findings indicate that hESC-derived neuronal cells can generate spontaneously <span class="hlt">active</span> <span class="hlt">networks</span> with synchronous communication in vitro, and are therefore suitable for use in developmental and drug screening studies, as well as for regenerative medicine.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JGRB..11710406B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JGRB..11710406B"><span>Space-<span class="hlt">geodetic</span> evidence for multiple magma reservoirs and subvolcanic lateral intrusions at Fernandina Volcano, Galápagos Islands</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bagnardi, Marco; Amelung, Falk</p> <p>2012-10-01</p> <p>Using Interferometric Synthetic Aperture Radar (InSAR) measurements of the surface deformation at Fernandina Volcano, Galápagos (Ecuador), acquired between January 2003 and September 2010, we study the structure and the dynamics of the shallow magmatic system of the volcano. Through the analysis of spatial and temporal variations of the measured line-of-sight displacement we identify multiple sources of deformation beneath the summit and the southern flank. At least two sources are considered to represent permanent zones of magma storage given their persistent or recurrent <span class="hlt">activity</span>. Elastic deformation models indicate the presence of a flat-topped magma reservoir at ˜1.1 km below sea level and an oblate-spheroid cavity at ˜4.9 km b.s.l. The two reservoirs are hydraulically connected. This inferred structure of the shallow storage system is in agreement with previous <span class="hlt">geodetic</span> studies and previous petrological analysis of both subaerial and submarine lavas. The almost eight-year-long observation interval provides for the first time <span class="hlt">geodetic</span> evidence for two subvolcanic lateral intrusions from the central storage system (in December 2006 and August 2007). Subvolcanic lateral intrusions could provide the explanation for enigmatic volcanic events at Fernandina such as the rapid uplift at Punta Espinoza in 1927 and the 1968 caldera collapse without significant eruption.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.7561Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.7561Z"><span>Field Installation and Real-Time Data Processing of the New Integrated Seismo<span class="hlt">Geodetic</span> System with Real-Time Acceleration and Displacement Measurements for Earthquake Characterization Based on High-Rate Seismic and GPS Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zimakov, Leonid; Jackson, Michael; Passmore, Paul; Raczka, Jared; Alvarez, Marcos; Barrientos, Sergio</p> <p>2015-04-01</p> <p>We will discuss and show the results obtained from an integrated Seismo<span class="hlt">Geodetic</span> System, model SG160-09, installed in the Chilean National <span class="hlt">Network</span>. The SG160-09 provides the user high rate GNSS and accelerometer data, full epoch-by-epoch measurement integrity and, using the Trimble Pivot™ Seismo<span class="hlt">Geodetic</span> App, the ability to create combined GNSS and accelerometer high-rate (200Hz) displacement time series in real-time. The SG160-09 combines seismic recording with GNSS <span class="hlt">geodetic</span> measurement in a single compact, ruggedized package. The system includes a low-power, 220-channel GNSS receiver powered by the latest Trimble-precise Maxwell™6 technology and supports tracking GPS, GLONASS and Galileo signals. The receiver incorporates on-board GNSS point positioning using Real-Time Precise Point Positioning (PPP) technology with satellite clock and orbit corrections delivered over IP <span class="hlt">networks</span>. The seismic recording element includes an ANSS Class A, force balance triaxial accelerometer with the latest, low power, 24-bit A/D converter, which produces high-resolution seismic data. The SG160-09 processor acquires and packetizes both seismic and <span class="hlt">geodetic</span> data and transmits it to the central station using an advanced, error-correction protocol with back fill capability providing data integrity between the field and the processing center. The SG160-09 has been installed in the seismic station close to the area of the Iquique earthquake of April 1, 2014, in northern Chile, a seismically prone area at the current time. The hardware includes the SG160-09 system, external Zephyr <span class="hlt">Geodetic</span>-2 GNSS antenna, and high-speed Internet communication media. Both acceleration and displacement data was transmitted in real-time to the National Seismological Center in Santiago for real-time data processing using Earthworm / Early Bird software. Command/Control of the field station and real-time GNSS position correction are provided via the Pivot software suite. Data from the SG160-09 system was</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Tectp.666..211B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Tectp.666..211B"><span><span class="hlt">Geodetic</span> implications on block formation and geodynamic domains in the South Shetland Islands, Antarctic Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Berrocoso, M.; Fernández-Ros, A.; Prates, G.; García, A.; Kraus, S.</p> <p>2016-01-01</p> <p>The South Shetland Islands archipelago is dynamically complex due to its tectonic surroundings. Most islands are part of a formerly <span class="hlt">active</span> volcanic arc, although Deception, Penguin and Bridgeman Islands, as well as several submarine volcanoes, are characterized by <span class="hlt">active</span> back-arc volcanism. <span class="hlt">Geodetic</span> benchmarks were deployed and the movement of the lithosphere to which they were fixed measured to provide geodynamic insight for the South Shetland Islands, Bransfield Basin and Antarctic Peninsula area based on surface deformation. These benchmarks' data add spatial and temporal coverage to previous results. The results reveal two different geodynamic patterns, each confined to a distinct part of the South Shetland Islands archipelago. The inferred absolute horizontal velocity vectors for the benchmarks in the northeastern part of the archipelago are consistent with the opening of the Bransfield Basin, while benchmark vectors in the southwestern part of the archipelago are similar to those of the benchmarks on the Antarctic Peninsula. In between, Snow, Deception and Livingston Islands represent a transition zone. In this area, the horizontal velocity vectors relative to the Antarctic plate shift northeastwards from N to NW. Furthermore, the South Shetland Islands benchmarks, except for that at Gibbs (Elephant) Islands, indicate subsidence, which might be a consequence of the slab roll-back at the South Shetland Trench. In contrast, the uplift revealed by the Antarctic Peninsula benchmarks suggests glacial isostatic adjustment after the Larson B ice-shelf breakup.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060042432&hterms=learn+english&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dlearn%2Benglish','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060042432&hterms=learn+english&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dlearn%2Benglish"><span>SAN-RL: combining spreading <span class="hlt">activation</span> <span class="hlt">networks</span> and reinforcement learning to learn configurable behaviors</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>White, J.; Gaines, D. M.; Wilkes, M.; Kusumalnukool, K.; Thongchai, S.; Kawamura, K.</p> <p>2001-01-01</p> <p>This approach provides the agent with a causal structure, the spreading <span class="hlt">activation</span> <span class="hlt">network</span>, relating goals to the actions that can achieve those goals. This enables the agent to select actions relative to the goal priorities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007ITEIS.127.1619T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007ITEIS.127.1619T"><span><span class="hlt">Activity</span> Changes Induced by Spatio-Temporally Correlated Stimuli in Cultured Cortical <span class="hlt">Networks</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takayama, Yuzo; Moriguchi, Hiroyuki; Jimbo, Yasuhiko</p> <p></p> <p><span class="hlt">Activity</span>-dependent plasticity probably plays a key role in learning and memory in biological information processing systems. Though long-term potentiation and depression have been extensively studied in the filed of neuroscience, little is known on the mechanisms for integrating these modifications on <span class="hlt">network</span>-wide <span class="hlt">activity</span> changes. In this report, we studied effects of spatio-temporally correlated stimuli on the neuronal <span class="hlt">network</span> <span class="hlt">activity</span>. Rat cortical neurons were cultured on substrates with 64 embedded micro-electrodes and the evoked responses were extracellularly recorded and analyzed. We compared spatio-temporal patterns of the responses between before and after repetitive application of correlated stimuli. After the correlated stimuli, the <span class="hlt">networks</span> showed significantly different responses from those in the initial states. The modified <span class="hlt">activity</span> reflected structures of the repeatedly applied correlated stimuli. The results suggested that spatiotemporally correlated inputs systematically induced modification of synaptic strengths in neuronal <span class="hlt">networks</span>, which could serve as an underlying mechanism of associative memory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4830439','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4830439"><span>Topic-Aware Physical <span class="hlt">Activity</span> Propagation in a Health Social <span class="hlt">Network</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Phan, Nhathai; Ebrahimi, Javid; Kil, Dave; Piniewski, Brigitte; Dou, Dejing</p> <p>2016-01-01</p> <p>Modeling physical <span class="hlt">activity</span> propagation, such as physical exercise level and intensity, is the key to preventing the conduct that can lead to obesity; it can also help spread wellness behavior in a social <span class="hlt">network</span>. PMID:27087794</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22408506','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22408506"><span>Cross-layer <span class="hlt">active</span> predictive congestion control protocol for wireless sensor <span class="hlt">networks</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wan, Jiangwen; Xu, Xiaofeng; Feng, Renjian; Wu, Yinfeng</p> <p>2009-01-01</p> <p>In wireless sensor <span class="hlt">networks</span> (WSNs), there are numerous factors that may cause <span class="hlt">network</span> congestion problems, such as the many-to-one communication modes, mutual interference of wireless links, dynamic changes of <span class="hlt">network</span> topology and the memory-restrained characteristics of nodes. All these factors result in a <span class="hlt">network</span> being more vulnerable to congestion. In this paper, a cross-layer <span class="hlt">active</span> predictive congestion control scheme (CL-APCC) for improving the performance of <span class="hlt">networks</span> is proposed. Queuing theory is applied in the CL-APCC to analyze data flows of a single-node according to its memory status, combined with the analysis of the average occupied memory size of local <span class="hlt">networks</span>. It also analyzes the current data change trends of local <span class="hlt">networks</span> to forecast and <span class="hlt">actively</span> adjust the sending rate of the node in the next period. In order to ensure the fairness and timeliness of the <span class="hlt">network</span>, the IEEE 802.11 protocol is revised based on waiting time, the number of the node's neighbors and the original priority of data packets, which dynamically adjusts the sending priority of the node. The performance of CL-APCC, which is evaluated by extensive simulation experiments. is more efficient in solving the congestion in WSNs. Furthermore, it is clear that the proposed scheme has an outstanding advantage in terms of improving the fairness and lifetime of <span class="hlt">networks</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15872094','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15872094"><span>Endogenous <span class="hlt">activation</span> of kainate receptors regulates glutamate release and <span class="hlt">network</span> <span class="hlt">activity</span> in the developing hippocampus.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lauri, Sari E; Segerstråle, Mikael; Vesikansa, Aino; Maingret, Francois; Mulle, Christophe; Collingridge, Graham L; Isaac, John T R; Taira, Tomi</p> <p>2005-05-04</p> <p>Kainate receptors (KARs) are highly expressed throughout the neonatal brain, but their function during development is unclear. Here, we show that the maturation of the hippocampus is associated with a switch in the functional role of presynaptic KARs. In a developmental period restricted to the first postnatal week, endogenous L-glutamate tonically <span class="hlt">activates</span> KARs at CA3 glutamatergic synapses to regulate release in an action potential-independent manner. At synapses onto pyramidal cells, KARs inhibit glutamate release via a G-protein and PKC-dependent mechanism. In contrast, at glutamatergic terminals onto CA3 interneurons, presynaptic KARs can facilitate release in a G-protein-independent mechanism. In both cell types, however, KAR <span class="hlt">activation</span> strongly upregulates inhibitory transmission. We show that, through the interplay of these novel diverse mechanisms, KARs strongly regulate the characteristic synchronous <span class="hlt">network</span> <span class="hlt">activity</span> observed in the neonatal hippocampus. By virtue of this, KARs are likely to play a central role in the development of hippocampal synaptic circuits.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4877528','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4877528"><span>Spontaneous Neuronal <span class="hlt">Activity</span> in Developing Neocortical <span class="hlt">Networks</span>: From Single Cells to Large-Scale Interactions</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Luhmann, Heiko J.; Sinning, Anne; Yang, Jenq-Wei; Reyes-Puerta, Vicente; Stüttgen, Maik C.; Kirischuk, Sergei; Kilb, Werner</p> <p>2016-01-01</p> <p>Neuronal <span class="hlt">activity</span> has been shown to be essential for the proper formation of neuronal circuits, affecting developmental processes like neurogenesis, migration, programmed cell death, cellular differentiation, formation of local and long-range axonal connections, synaptic plasticity or myelination. Accordingly, neocortical areas reveal distinct spontaneous and sensory-driven neuronal <span class="hlt">activity</span> patterns already at early phases of development. At embryonic stages, when immature neurons start to develop voltage-dependent channels, spontaneous <span class="hlt">activity</span> is highly synchronized within small neuronal <span class="hlt">networks</span> and governed by electrical synaptic transmission. Subsequently, spontaneous <span class="hlt">activity</span> patterns become more complex, involve larger <span class="hlt">networks</span> and propagate over several neocortical areas. The developmental shift from local to large-scale <span class="hlt">network</span> <span class="hlt">activity</span> is accompanied by a gradual shift from electrical to chemical synaptic transmission with an initial excitatory action of chloride-gated channels <span class="hlt">activated</span> by GABA, glycine and taurine. Transient neuronal populations in the subplate (SP) support temporary circuits that play an important role in tuning early neocortical <span class="hlt">activity</span> and the formation of mature neuronal <span class="hlt">networks</span>. Thus, early spontaneous <span class="hlt">activity</span> patterns control the formation of developing <span class="hlt">networks</span> in sensory cortices, and disturbances of these <span class="hlt">activity</span> patterns may lead to long-lasting neuronal deficits. PMID:27252626</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4889937','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4889937"><span>NetDecoder: a <span class="hlt">network</span> biology platform that decodes context-specific biological <span class="hlt">networks</span> and gene <span class="hlt">activities</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>da Rocha, Edroaldo Lummertz; Ung, Choong Yong; McGehee, Cordelia D.; Correia, Cristina; Li, Hu</p> <p>2016-01-01</p> <p>The sequential chain of interactions altering the binary state of a biomolecule represents the ‘information flow’ within a cellular <span class="hlt">network</span> that determines phenotypic properties. Given the lack of computational tools to dissect context-dependent <span class="hlt">networks</span> and gene <span class="hlt">activities</span>, we developed NetDecoder, a <span class="hlt">network</span> biology platform that models context-dependent information flows using pairwise phenotypic comparative analyses of protein–protein interactions. Using breast cancer, dyslipidemia and Alzheimer's disease as case studies, we demonstrate NetDecoder dissects subnetworks to identify key players significantly impacting cell behaviour specific to a given disease context. We further show genes residing in disease-specific subnetworks are enriched in disease-related signalling pathways and information flow profiles, which drive the resulting disease phenotypes. We also devise a novel scoring scheme to quantify key genes—<span class="hlt">network</span> routers, which influence many genes, key targets, which are influenced by many genes, and high impact genes, which experience a significant change in regulation. We show the robustness of our results against parameter changes. Our <span class="hlt">network</span> biology platform includes freely available source code (http://www.NetDecoder.org) for researchers to explore genome-wide context-dependent information flow profiles and key genes, given a set of genes of particular interest and transcriptome data. More importantly, NetDecoder will enable researchers to uncover context-dependent drug targets. PMID:26975659</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26975659','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26975659"><span>NetDecoder: a <span class="hlt">network</span> biology platform that decodes context-specific biological <span class="hlt">networks</span> and gene <span class="hlt">activities</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>da Rocha, Edroaldo Lummertz; Ung, Choong Yong; McGehee, Cordelia D; Correia, Cristina; Li, Hu</p> <p>2016-06-02</p> <p>The sequential chain of interactions altering the binary state of a biomolecule represents the 'information flow' within a cellular <span class="hlt">network</span> that determines phenotypic properties. Given the lack of computational tools to dissect context-dependent <span class="hlt">networks</span> and gene <span class="hlt">activities</span>, we developed NetDecoder, a <span class="hlt">network</span> biology platform that models context-dependent information flows using pairwise phenotypic comparative analyses of protein-protein interactions. Using breast cancer, dyslipidemia and Alzheimer's disease as case studies, we demonstrate NetDecoder dissects subnetworks to identify key players significantly impacting cell behaviour specific to a given disease context. We further show genes residing in disease-specific subnetworks are enriched in disease-related signalling pathways and information flow profiles, which drive the resulting disease phenotypes. We also devise a novel scoring scheme to quantify key genes-<span class="hlt">network</span> routers, which influence many genes, key targets, which are influenced by many genes, and high impact genes, which experience a significant change in regulation. We show the robustness of our results against parameter changes. Our <span class="hlt">network</span> biology platform includes freely available source code (http://www.NetDecoder.org) for researchers to explore genome-wide context-dependent information flow profiles and key genes, given a set of genes of particular interest and transcriptome data. More importantly, NetDecoder will enable researchers to uncover context-dependent drug targets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23032193','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23032193"><span>Development of coherent neuronal <span class="hlt">activity</span> patterns in mammalian cortical <span class="hlt">networks</span>: common principles and local hetereogeneity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Egorov, Alexei V; Draguhn, Andreas</p> <p>2013-01-01</p> <p>Many mammals are born in a very immature state and develop their rich repertoire of behavioral and cognitive functions postnatally. This development goes in parallel with changes in the anatomical and functional organization of cortical structures which are involved in most complex <span class="hlt">activities</span>. The emerging spatiotemporal <span class="hlt">activity</span> patterns in multi-neuronal cortical <span class="hlt">networks</span> may indeed form a direct neuronal correlate of systemic functions like perception, sensorimotor integration, decision making or memory formation. During recent years, several studies--mostly in rodents--have shed light on the ontogenesis of such highly organized patterns of <span class="hlt">network</span> <span class="hlt">activity</span>. While each local <span class="hlt">network</span> has its own peculiar properties, some general rules can be derived. We therefore review and compare data from the developing hippocampus, neocortex and--as an intermediate region--entorhinal cortex. All cortices seem to follow a characteristic sequence starting with uncorrelated <span class="hlt">activity</span> in uncoupled single neurons where transient <span class="hlt">activity</span> seems to have mostly trophic effects. In rodents, before and shortly after birth, cortical <span class="hlt">networks</span> develop weakly coordinated multineuronal discharges which have been termed synchronous plateau assemblies (SPAs). While these patterns rely mostly on electrical coupling by gap junctions, the subsequent increase in number and maturation of chemical synapses leads to the generation of large-scale coherent discharges. These patterns have been termed giant depolarizing potentials (GDPs) for predominantly GABA-induced events or early <span class="hlt">network</span> oscillations (ENOs) for mostly glutamatergic bursts, respectively. During the third to fourth postnatal week, cortical areas reach their final <span class="hlt">activity</span> patterns with distinct <span class="hlt">network</span> oscillations and highly specific neuronal discharge sequences which support adult behavior. While some of the mechanisms underlying maturation of <span class="hlt">network</span> <span class="hlt">activity</span> have been elucidated much work remains to be done in order to fully</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5114006','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5114006"><span>Analyzing heterogeneity in the effects of physical <span class="hlt">activity</span> in children on social <span class="hlt">network</span> structure and peer selection dynamics</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Henry, Teague; Gesell, Sabina B.; Ip, Edward H.</p> <p>2016-01-01</p> <p>Background Social <span class="hlt">networks</span> influence children and adolescents’ physical <span class="hlt">activity</span>. The focus of this paper is to examine the differences in the effects of physical <span class="hlt">activity</span> on friendship selection, with eye to the implications on physical <span class="hlt">activity</span> interventions for young children. <span class="hlt">Network</span> interventions to increase physical <span class="hlt">activity</span> are warranted but have not been conducted. Prior to implementing a <span class="hlt">network</span> intervention in the field, it is important to understand potential heterogeneities in the effects that <span class="hlt">activity</span> level have on <span class="hlt">network</span> structure. In this study, the associations between <span class="hlt">activity</span> level and cross sectional <span class="hlt">network</span> structure, and <span class="hlt">activity</span> level and change in <span class="hlt">network</span> structure are assessed. Methods We studied a real-world friendship <span class="hlt">network</span> among 81 children (average age 7.96 years) who lived in low SES neighborhoods, attended public schools, and attended one of two structured aftercare programs, of which one has existed and the other was new. We used the exponential random graph model (ERGMs) and its longitudinal extension to evaluate the association between <span class="hlt">activity</span> level and various demographic factors in having, forming, and dissolving friendship. Due to heterogeneity between the friendship <span class="hlt">networks</span> within the aftercare programs, separate analyses were conducted for each <span class="hlt">network</span>. Results There was heterogeneity in the effect of physical <span class="hlt">activity</span> on both cross sectional <span class="hlt">network</span> structure and the formation and dissolution processes, both across time and between <span class="hlt">networks</span>. Conclusions <span class="hlt">Network</span> analysis could be used to assess the unique structure and dynamics of a social <span class="hlt">network</span> before an intervention is implemented, so as to optimize the effects of the <span class="hlt">network</span> intervention for increasing childhood physical <span class="hlt">activity</span>. Additionally, if peer selection processes are changing within a <span class="hlt">network</span>, a static <span class="hlt">network</span> intervention strategy for childhood physical <span class="hlt">activity</span> could become inefficient as the <span class="hlt">network</span> evolves. PMID:27867518</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26221627','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26221627"><span>An Optimal CDS Construction Algorithm with <span class="hlt">Activity</span> Scheduling in Ad Hoc <span class="hlt">Networks</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Penumalli, Chakradhar; Palanichamy, Yogesh</p> <p>2015-01-01</p> <p>A new energy efficient optimal Connected Dominating Set (CDS) algorithm with <span class="hlt">activity</span> scheduling for mobile ad hoc <span class="hlt">networks</span> (MANETs) is proposed. This algorithm achieves energy efficiency by minimizing the Broadcast Storm Problem [BSP] and at the same time considering the node's remaining energy. The Connected Dominating Set is widely used as a virtual backbone or spine in mobile ad hoc <span class="hlt">networks</span> [MANETs] or Wireless Sensor <span class="hlt">Networks</span> [WSN]. The CDS of a graph representing a <span class="hlt">network</span> has a significant impact on an efficient design of routing protocol in wireless <span class="hlt">networks</span>. Here the CDS is a distributed algorithm with <span class="hlt">activity</span> scheduling based on unit disk graph [UDG]. The node's mobility and residual energy (RE) are considered as parameters in the construction of stable optimal energy efficient CDS. The performance is evaluated at various node densities, various transmission ranges, and mobility rates. The theoretical analysis and simulation results of this algorithm are also presented which yield better results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4220781','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4220781"><span>Friendship <span class="hlt">networks</span> and physical <span class="hlt">activity</span> and sedentary behavior among youth: a systematized review</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2013-01-01</p> <p>Background Low levels of physical <span class="hlt">activity</span> and increased participation in sedentary leisure-time <span class="hlt">activities</span> are two important obesity-risk behaviors that impact the health of today’s youth. Friend’s health behaviors have been shown to influence individual health behaviors; however, current evidence on the specific role of friendship <span class="hlt">networks</span> in relation to levels of physical <span class="hlt">activity</span> and sedentary behavior is limited. The purpose of this review was to summarize evidence on friendship <span class="hlt">networks</span> and both physical <span class="hlt">activity</span> and sedentary behavior among children and adolescents. Method After a search of seven scientific databases and reference scans, a total of thirteen articles were eligible for inclusion. All assessed the association between friendship <span class="hlt">networks</span> and physical <span class="hlt">activity</span>, while three also assessed sedentary behavior. Results Overall, higher levels of physical <span class="hlt">activity</span> among friends are associated with higher levels of physical <span class="hlt">activity</span> of the individual. Longitudinal studies reveal that an individual’s level of physical <span class="hlt">activity</span> changes to reflect his/her friends’ higher level of physical <span class="hlt">activity</span>. Boys tend to be influenced by their friendship <span class="hlt">network</span> to a greater extent than girls. There is mixed evidence surrounding a friend’s sedentary behavior and individual sedentary behavior. Conclusion Friends’ physical <span class="hlt">activity</span> level appears to have a significant influence on individual’s physical <span class="hlt">activity</span> level. Evidence surrounding sedentary behavior is limited and mixed. Results from this review could inform effective public health interventions that harness the influence of friends to increase physical <span class="hlt">activity</span> levels among children and adolescents. PMID:24289113</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013FrME....8..109L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013FrME....8..109L"><span>Frequency domain <span class="hlt">active</span> vibration control of a flexible plate based on neural <span class="hlt">networks</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Jinxin; Chen, Xuefeng; He, Zhengjia</p> <p>2013-06-01</p> <p>A neural-<span class="hlt">network</span> (NN)-based <span class="hlt">active</span> control system was proposed to reduce the low frequency noise radiation of the simply supported flexible plate. Feedback control system was built, in which neural <span class="hlt">network</span> controller (NNC) and neural <span class="hlt">network</span> identifier (NNI) were applied. Multi-frequency control in frequency domain was achieved by simulation through the NN-based control systems. A pre-testing experiment of the control system on a real simply supported plate was conducted. The NN-based control algorithm was shown to perform effectively. These works lay a solid foundation for the <span class="hlt">active</span> vibration control of mechanical structures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920021735','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920021735"><span>The optimization of force inputs for <span class="hlt">active</span> structural acoustic control using a neural <span class="hlt">network</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cabell, R. H.; Lester, H. C.; Silcox, R. J.</p> <p>1992-01-01</p> <p>This paper investigates the use of a neural <span class="hlt">network</span> to determine which force actuators, of a multi-actuator array, are best <span class="hlt">activated</span> in order to achieve structural-acoustic control. The concept is demonstrated using a cylinder/cavity model on which the control forces, produced by piezoelectric actuators, are applied with the objective of reducing the interior noise. A two-layer neural <span class="hlt">network</span> is employed and the back propagation solution is compared with the results calculated by a conventional, least-squares optimization analysis. The ability of the neural <span class="hlt">network</span> to accurately and efficiently control actuator <span class="hlt">activation</span> for interior noise reduction is demonstrated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990106580&hterms=activity+Physics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dactivity%2BPhysics','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990106580&hterms=activity+Physics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dactivity%2BPhysics"><span>Large-Scale Coronal Heating from "Cool" <span class="hlt">Activity</span> in the Solar Magnetic <span class="hlt">Network</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Falconer, D. A.; Moore, R. L.; Porter, J. G.; Hathaway, D. H.</p> <p>1999-01-01</p> <p>In Fe XII images from SOHO/EIT, the quiet solar corona shows structure on scales ranging from sub-supergranular (i.e., bright points and coronal <span class="hlt">network</span>) to multi-supergranular (large-scale corona). In Falconer et al 1998 (Ap.J., 501, 386) we suppressed the large-scale background and found that the <span class="hlt">network</span>-scale features are predominantly rooted in the magnetic <span class="hlt">network</span> lanes at the boundaries of the supergranules. Taken together, the coronal <span class="hlt">network</span> emission and bright point emission are only about 5% of the entire quiet solar coronal Fe XII emission. Here we investigate the relationship between the large-scale corona and the <span class="hlt">network</span> as seen in three different EIT filters (He II, Fe IX-X, and Fe XII). Using the median-brightness contour, we divide the large-scale Fe XII corona into dim and bright halves, and find that the bright-half/dim half brightness ratio is about 1.5. We also find that the bright half relative to the dim half has 10 times greater total bright point Fe XII emission, 3 times greater Fe XII <span class="hlt">network</span> emission, 2 times greater Fe IX-X <span class="hlt">network</span> emission, 1.3 times greater He II <span class="hlt">network</span> emission, and has 1.5 times more magnetic flux. Also, the cooler <span class="hlt">network</span> (He II) radiates an order of magnitude more energy than the hotter coronal <span class="hlt">network</span> (Fe IX-X, and Fe XII). From these results we infer that: 1) The heating of the <span class="hlt">network</span> and the heating of the large-scale corona each increase roughly linearly with the underlying magnetic flux. 2) The production of <span class="hlt">network</span> coronal bright points and heating of the coronal <span class="hlt">network</span> each increase nonlinearly with the magnetic flux. 3) The heating of the large-scale corona is driven by widespread cooler <span class="hlt">network</span> <span class="hlt">activity</span> rather than by the exceptional <span class="hlt">network</span> <span class="hlt">activity</span> that produces the <span class="hlt">network</span> coronal bright points and the coronal <span class="hlt">network</span>. 4) The large-scale corona is heated by a nonthermal process since the driver of its heating is cooler than it is. This work was funded by the Solar Physics Branch of NASA's office of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.G24A..01F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.G24A..01F"><span><span class="hlt">Geodetic</span> Constraints on the Tectonics of Alaska and the North Pacific (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Freymueller, J. T.</p> <p>2009-12-01</p> <p>Alaska is one of the most tectonically <span class="hlt">active</span> areas in the world, hosting a combination of subduction, arc volcanism, continental terrane collision and accretion, and large-scale deformation of the continental lithosphere. The general outline of Alaska tectonics was sketched extremely well by George Plafker and others by the 1980s, but many important details, and particularly rates of motion, are now known primarily through modern space <span class="hlt">geodetic</span> measurements. In addition to steady tectonic deformation of the continent, the observed crustal deformation includes significant components due to earthquake cycle deformation, both steady and transient postseismic, volcanic inflation and eruption, and glacial isostatic adjustment. <span class="hlt">Geodetic</span> data and the combination of plate configuration and geography have allowed us to study a wide variety of problems in the kinematics and dynamics