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Sample records for absolute dynamic topography

  1. Evaluation of Absolute Dynamic Ocean Topography Profiles along the Brazilian Coast

    NASA Astrophysics Data System (ADS)

    Luz, R. T.; Bosch, W.; Freitas, S. R. C.; Heck, B.

    2009-04-01

    Based on a new approach, which consistently filters GRACE-based geoid undulations and altimetry-derived sea surface heights along the tracks of altimeter satellites, absolute dynamic ocean topography (DOT) profiles are estimated along the Brazilian coast. Such DOT profiles can be used to perform levelling over the sea. Connecting these profiles with Brazilian Geodetic Tide Gauge Network (RMPG) stations it would be possible to validate the current studies on the modernization of the Brazilian height system, extended over many thousand kilometers on land. The link with coastal reference sites would also allow to connect isolated height systems, e.g. north of the Amazonas River mouth. We perform long-term mean DOT-profiles of cross-calibrated altimeter satellites which operated for many years over repeated ground tracks (TOPEX, Jason-1, ERS-2). Moreover, we analyze the consistency among crossing profiles (single- and dual-satellite) in particular in areas with strong mesoscale currents. The extrapolation of DOT profiles towards selected RMPG stations is investigated. For this connection strategies are considered to overcome the degradation of coastal altimetry due to errors in ocean tide models and the land contamination of the radiometer observations.

  2. Dynamic Topography Revisited

    NASA Astrophysics Data System (ADS)

    Moresi, Louis

    2015-04-01

    Dynamic Topography Revisited Dynamic topography is usually considered to be one of the trinity of contributing causes to the Earth's non-hydrostatic topography along with the long-term elastic strength of the lithosphere and isostatic responses to density anomalies within the lithosphere. Dynamic topography, thought of this way, is what is left over when other sources of support have been eliminated. An alternate and explicit definition of dynamic topography is that deflection of the surface which is attributable to creeping viscous flow. The problem with the first definition of dynamic topography is 1) that the lithosphere is almost certainly a visco-elastic / brittle layer with no absolute boundary between flowing and static regions, and 2) the lithosphere is, a thermal / compositional boundary layer in which some buoyancy is attributable to immutable, intrinsic density variations and some is due to thermal anomalies which are coupled to the flow. In each case, it is difficult to draw a sharp line between each contribution to the overall topography. The second definition of dynamic topography does seem cleaner / more precise but it suffers from the problem that it is not measurable in practice. On the other hand, this approach has resulted in a rich literature concerning the analysis of large scale geoid and topography and the relation to buoyancy and mechanical properties of the Earth [e.g. refs 1,2,3] In convection models with viscous, elastic, brittle rheology and compositional buoyancy, however, it is possible to examine how the surface topography (and geoid) are supported and how different ways of interpreting the "observable" fields introduce different biases. This is what we will do. References (a.k.a. homework) [1] Hager, B. H., R. W. Clayton, M. A. Richards, R. P. Comer, and A. M. Dziewonski (1985), Lower mantle heterogeneity, dynamic topography and the geoid, Nature, 313(6003), 541-545, doi:10.1038/313541a0. [2] Parsons, B., and S. Daly (1983), The

  3. Inferring Cetacean Population Densities from the Absolute Dynamic Topography of the Ocean in a Hierarchical Bayesian Framework

    PubMed Central

    Pardo, Mario A.; Gerrodette, Tim; Beier, Emilio; Gendron, Diane; Forney, Karin A.; Chivers, Susan J.; Barlow, Jay; Palacios, Daniel M.

    2015-01-01

    We inferred the population densities of blue whales (Balaenoptera musculus) and short-beaked common dolphins (Delphinus delphis) in the Northeast Pacific Ocean as functions of the water-column’s physical structure by implementing hierarchical models in a Bayesian framework. This approach allowed us to propagate the uncertainty of the field observations into the inference of species-habitat relationships and to generate spatially explicit population density predictions with reduced effects of sampling heterogeneity. Our hypothesis was that the large-scale spatial distributions of these two cetacean species respond primarily to ecological processes resulting from shoaling and outcropping of the pycnocline in regions of wind-forced upwelling and eddy-like circulation. Physically, these processes affect the thermodynamic balance of the water column, decreasing its volume and thus the height of the absolute dynamic topography (ADT). Biologically, they lead to elevated primary productivity and persistent aggregation of low-trophic-level prey. Unlike other remotely sensed variables, ADT provides information about the structure of the entire water column and it is also routinely measured at high spatial-temporal resolution by satellite altimeters with uniform global coverage. Our models provide spatially explicit population density predictions for both species, even in areas where the pycnocline shoals but does not outcrop (e.g. the Costa Rica Dome and the North Equatorial Countercurrent thermocline ridge). Interannual variations in distribution during El Niño anomalies suggest that the population density of both species decreases dramatically in the Equatorial Cold Tongue and the Costa Rica Dome, and that their distributions retract to particular areas that remain productive, such as the more oceanic waters in the central California Current System, the northern Gulf of California, the North Equatorial Countercurrent thermocline ridge, and the more southern portion of

  4. Inferring cetacean population densities from the absolute dynamic topography of the ocean in a hierarchical Bayesian framework.

    PubMed

    Pardo, Mario A; Gerrodette, Tim; Beier, Emilio; Gendron, Diane; Forney, Karin A; Chivers, Susan J; Barlow, Jay; Palacios, Daniel M

    2015-01-01

    We inferred the population densities of blue whales (Balaenoptera musculus) and short-beaked common dolphins (Delphinus delphis) in the Northeast Pacific Ocean as functions of the water-column's physical structure by implementing hierarchical models in a Bayesian framework. This approach allowed us to propagate the uncertainty of the field observations into the inference of species-habitat relationships and to generate spatially explicit population density predictions with reduced effects of sampling heterogeneity. Our hypothesis was that the large-scale spatial distributions of these two cetacean species respond primarily to ecological processes resulting from shoaling and outcropping of the pycnocline in regions of wind-forced upwelling and eddy-like circulation. Physically, these processes affect the thermodynamic balance of the water column, decreasing its volume and thus the height of the absolute dynamic topography (ADT). Biologically, they lead to elevated primary productivity and persistent aggregation of low-trophic-level prey. Unlike other remotely sensed variables, ADT provides information about the structure of the entire water column and it is also routinely measured at high spatial-temporal resolution by satellite altimeters with uniform global coverage. Our models provide spatially explicit population density predictions for both species, even in areas where the pycnocline shoals but does not outcrop (e.g. the Costa Rica Dome and the North Equatorial Countercurrent thermocline ridge). Interannual variations in distribution during El Niño anomalies suggest that the population density of both species decreases dramatically in the Equatorial Cold Tongue and the Costa Rica Dome, and that their distributions retract to particular areas that remain productive, such as the more oceanic waters in the central California Current System, the northern Gulf of California, the North Equatorial Countercurrent thermocline ridge, and the more southern portion of the

  5. Mesoscale variability of the absolute dynamic topography in the Drake Passage and Scotia Sea in 1993-2014

    NASA Astrophysics Data System (ADS)

    Koshlyakov, Mikhail; Repina, Irina; Tarakanov, Roman

    2016-04-01

    Daily numerical maps of the absolute dynamics topography (ADT), which are published by the French CLS agency (www.aviso.oceanobs.com) were used for the investigation of synoptic (mesoscale) ocean eddies in the Drake Passage and Scotia Sea in 1993-2014. Parts of these maps with the closed ADT isopleths (isohypses) were detected by a precise numerical algorithm and were interpreted as places of the location of cyclonic and anticyclonic mesoscale eddies. In addition, curves of ζ²(t), where t is time and ζ (t) is disturbance of ADT relative to the mean value in 1993-2014 at a given point, were plotted at a number of points within the studied ocean region. These curves show two well pronounced time scales ("periods") of ζ²(t) fluctuations: a lesser scale of 100-500 days and a greater scale varying generally from 2 to 4.5 years manifesting as changes in the time intervals with low and high amplitudes of the lesser time scale ζ²(t) fluctuations. Comparison of the ζ²(t) curves with the ADT maps shows that these lesser scale fluctuations are related to the behavior of individual eddies: their propagation through a given point in the ocean, eddy generation or absorption of an eddy by an ACC jet. The theory of the geostrophic ocean turbulence allows us to suppose that the above mentioned greater time scale of ζ²(t) fluctuations is related to the energy exchange between the ACC jets and mesoscale eddies that appears in a given ocean region, as an alternation of the periods of intense generation of eddies by ACC jets and periods of increased reverse energy transfer from the eddies to jets. The fact revealed in this work that cyclonic (anticyclonic) eddies are adjacent from the north (south) to the ACC jets agrees with this supposition and opens the possibilities to analyze the dynamic influence of the eddy interaction with the individual ACC jets separately.

  6. Isostasy, flexure, and dynamic topography

    NASA Astrophysics Data System (ADS)

    Gvirtzman, Zohar; Faccenna, Claudio; Becker, Thorsten W.

    2016-06-01

    A fundamental scientific question is, what controls the Earth's topography? Although the theoretical principles of isostasy, flexure, and dynamic topography are widely discussed, the parameters needed to apply these principles are frequently not available. Isostatic factors controlling lithospheric buoyancy are frequently uncertain and non-isostatic factors, such as lithospheric bending towards subduction zones and dynamic topography, are hard to distinguish. The question discussed here is whether a set of simple rules that relate topography to lithospheric structure in various tectonic environments can be deduced in a way that missing parameters can be approximated; or does each area behave differently, making generalizations problematic. We contribute to this issue analyzing the Asia-Africa-Arabia-Europe domain following a top-down strategy. We compile a new crustal thickness map and remove the contribution of the crust from the observed elevation. Then, the challenge is to interpret the residual topography in terms of mantle lithosphere buoyancy and dynamics. Based on systematic relationships between tectonic environments and factors controlling topography, we argue that crustal buoyancy and mantle lithospheric density can be approximated from available geological data and that regions near mantle upwelling or downwelling are easily identified by their extreme residual topography. Yet, even for other areas, calculating lithospheric thickness from residual topography is problematic, because distinguishing variations in mantle lithosphere thickness from sub-lithospheric dynamics is difficult. Fortunately, the area studied here provides an opportunity to examine this issue. Based on the conjunction between the Afar Plume and the mid-ocean ridge in the nearby Gulf of Aden and southern Red Sea, we constrain the maximal amplitude of dynamic topography to ~ 1 km. This estimate is based on a narrow definition of dynamic topography that only includes sub

  7. Landscape response to changes in dynamic topography

    NASA Astrophysics Data System (ADS)

    Ruetenik, Gregory A.; Moucha, Robert; Hoke, Gregory D.

    2015-04-01

    Dynamic topography is characterized by broad wavelength, low amplitude undulations of the Earth's surface maintained by stresses arising from mantle convection. Earth's topography is thus an aggregate of both dynamic and isostatic topography that is modulated by surface processes and changes in topography and/or the climate can be recorded in the offshore sedimentary record. However, it is generally difficult to deconvolve this record into contributions from changes in climate, isostatic topography, and dynamic topography. Herein, we use a landscape evolution model that is capable of producing simulations at the necessary scale and resolution for quantifying landscape response to moderate changes in dynamic topography in the presence of flexural unloading and loading due to erosion and deposition. We demonstrate that moderate changes in dynamic topography coupled with flexural response imposed on a landscape with pre-existing relief and drainage divide, disequilibrates the landscape resulting in a measurable increase in erosion rates and corresponding sedimentary flux to the margin. The magnitude and timing of this erosional response to dynamic topography is dependent on several key landscape evolution parameters, most notably the erosion (advection) coefficient and effective elastic thickness. Moreover, to maximize this response, we find that changes in dynamic topography must be slow enough and long-lived for given rates of erosion otherwise the landscape will not have sufficient time to generate a response. Lastly, this anomalous flux can persist for a significant amount of time beyond the influence of dynamic topography change as the landscape strives to re-equilibrate.

  8. Flat Subduction and Dynamic Topography

    NASA Astrophysics Data System (ADS)

    Lithgow-Bertelloni, C. R.; Dávila, F. M.; Eakin, C. M.; Crameri, F.

    2014-12-01

    Mantle dynamics manifests at the surface via the horizontal motions of plates and the vertical deflections that influence topography and the non-hydrostatic geoid. The pioneering work of Mitrovica et al. (1989) and Gurnis (1990) on this dynamic topography revolutionized our understanding of sedimentary basin formation, sea level changes and continental flooding. The temporal evolution of subduction can explain the migration of basins and even the drainage reversal of the Amazon (Shephard et al., 2012; Eakin et al., 2014). Until recently, flat subduction has been seen as enhancing downward deflection of the overriding plate and increasing flooding. However, this interpretation depends crucially on the details of the morphology and density structure of the slab, which controls the loci and amplitude of the deflection. We tend to ignore morphological details in mantle dynamics because flow can smooth out short wavelength variations. We have shown instead that details matter! Using South America as a natural laboratory because of the large changes in morphology of the Nazca slab along strike, we show that downward deflection of the overriding plate and hence basin formation, do not occur over flat segments but at the leading edge, where slabs plunge back into the mantle. This is true in both Argentina and Peru. The temporal evolution from a 'normally' dipplng slab to a flat slab leads to uplift over flat segments rather than enhanced subsidence. Critical for this result is the use of a detailed morphological model of the present-day Nazca slab with a spatial resolution of 50-100 km and based on relocated seismicity and magnetotelluric results. The density structure of the slab, due to age and the presence of overthickened crust from aseismic ridge subduction is essential. Overthickened crust leads to buoyant slabs. We reproduce formation and deposition of the Acres-Solimoes basin and the evolution of the Amazon drainage basin in Peru as well as the Mar Chiquita

  9. Absolute 3D reconstruction of thin films topography in microfluidic channels by interference reflection microscopy.

    PubMed

    Huerre, A; Jullien, M-C; Theodoly, O; Valignat, M-P

    2016-03-01

    The travel of droplets, bubbles, vesicles, capsules, living cells or small organisms in microchannels is a hallmark in microfluidics applications. A full description of the dynamics of such objects requires a quantitative understanding of the complex hydrodynamic and interfacial interactions between objects and channel walls. In this paper, we present an interferometric method that allows absolute topographic reconstruction of the interspace between an object and channel walls for objects confined in microfluidic channels. Wide field microscopic imaging in reflection interference contrast mode (RICM) is directly performed at the bottom wall of microfluidic chips. Importantly, we show that the reflections at both the lower and upper surface of the microchannel have to be considered in the quantitative analysis of the optical signal. More precisely, the contribution of the reflection at the upper surface is weighted depending on the light coherence length and channel height. Using several wavelengths and illumination apertures, our method allows reconstructing the topography of thin films on channel walls in a range of 0-500 nm, with a precision as accurate as 2 nm for the thinnest films. A complete description of the protocol is exemplified for oil in water droplets travelling in channels of height 10-400 μm at a speed up to 5 mm s(-1). PMID:26830018

  10. Mean Dynamic Topography of the Arctic Ocean

    NASA Technical Reports Server (NTRS)

    Farrell, Sinead Louise; Mcadoo, David C.; Laxon, Seymour W.; Zwally, H. Jay; Yi, Donghui; Ridout, Andy; Giles, Katherine

    2012-01-01

    ICESat and Envisat altimetry data provide measurements of the instantaneous sea surface height (SSH) across the Arctic Ocean, using lead and open water elevation within the sea ice pack. First, these data were used to derive two independent mean sea surface (MSS) models by stacking and averaging along-track SSH profiles gathered between 2003 and 2009. The ICESat and Envisat MSS data were combined to construct the high-resolution ICEn MSS. Second, we estimate the 5.5-year mean dynamic topography (MDT) of the Arctic Ocean by differencing the ICEn MSS with the new GOCO02S geoid model, derived from GRACE and GOCE gravity. Using these satellite-only data we map the major features of Arctic Ocean dynamical height that are consistent with in situ observations, including the topographical highs and lows of the Beaufort and Greenland Gyres, respectively. Smaller-scale MDT structures remain largely unresolved due to uncertainties in the geoid at short wavelengths.

  11. Mean dynamic topography of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Farrell, Sinéad Louise; McAdoo, David C.; Laxon, Seymour W.; Zwally, H. Jay; Yi, Donghui; Ridout, Andy; Giles, Katharine

    2012-01-01

    ICESat and Envisat altimetry data provide measurements of the instantaneous sea surface height (SSH) across the Arctic Ocean, using lead and open water elevation within the sea ice pack. First, these data were used to derive two independent mean sea surface (MSS) models by stacking and averaging along-track SSH profiles gathered between 2003 and 2009. The ICESat and Envisat MSS data were combined to construct the high-resolution ICEn MSS. Second, we estimate the 5.5-year mean dynamic topography (MDT) of the Arctic Ocean by differencing the ICEn MSS with the new GOCO02S geoid model, derived from GRACE and GOCE gravity. Using these satellite-only data we map the major features of Arctic Ocean dynamical height that are consistent with in situ observations, including the topographical highs and lows of the Beaufort and Greenland Gyres, respectively. Smaller-scale MDT structures remain largely unresolved due to uncertainties in the geoid at short wavelengths.

  12. Global dynamic topography: geoscience communities requirements

    NASA Astrophysics Data System (ADS)

    Dewez, T.; Costeraste, J.

    2012-04-01

    The advent of free-of-charge global topographic data sets SRTM and Aster GDEM have enabled testing a host of geoscience hypotheses. This is because they first revealed the relief of previously unavailable earth landscapes, enabled quantitative geomorphometric analyses across entire landscapes and improved the resolution of measurements. Availability of such data is now considered standard, and though resolved at 30-m to 90-m pixel, which is amazing seeing where we come from, they are now regarded as mostly obsolete given the sub-meter imagery coming through web services like Google Earth. Geoscientists now appear to desire two additional features: field-scale-compatible elevation datasets (i.e. meter-scale digital models and sub-meter elevation precision) and dispose of regularly updated topography to retrieve earth surface changes, while retaining the key for success: data availability at no charge. A new satellite instrument is currently under phase 0 study at CNES, the French space agency, to fulfil these aims. The scientific community backing this demand is that of natural hazards, glaciology and to a lesser extent the biomass community. The system under study combines a native stereo imager and a lidar profiler. This combination provides spatially resolved elevation swaths together with absolute along-track elevation control point profiles. Data generated through this system, designed for revisit time better than a year, is intended to produce not only single acquisition digital surface models, colour orthoimages and small footprint full-wave-form lidar profiles to update existing topographic coverages, but also time series of them. This enables 3D change detection with centimetre-scale planimetric precision and metric vertical precision, in complement of classical spectral change appoaches. The purpose of this contribution, on behalf of the science team, is to present the mission concepts and philosophy and the scientific needs for such instrument including

  13. Evolution of Neogene Dynamic Topography in Madagascar

    NASA Astrophysics Data System (ADS)

    Paul, J. D.; Roberts, G.; White, N. J.

    2012-12-01

    Madagascar is located on the fringes of the African superswell. Its position and the existence of a +30 mGal long wavelength free-air gravity anomaly suggest that its present-day topography is maintained by convective circulation of the sub-lithospheric mantle. Residual depth anomalies of oceanic crust encompassing the island imply that Madagascar straddles a dynamic topographic gradient. In June-July 2012, we examined geologic evidence for Neogene uplift around the Malagasy coastline. Uplifted coral reef deposits, fossil beach rock, and terraces demonstrate that the northern and southern coasts are probably being uplifted at a rate of ~0.2 mm/yr. Rates of uplift clearly vary around the coastline. Inland, extensive peneplains occur at elevations of 1 - 2 km. These peneplains are underlain by 10 - 20 m thick laterite deposits, and there is abundant evidence for rapid erosion (e.g. lavaka). Basaltic volcanism also occurred during Neogene times. These field observations can be combined with an analysis of drainage networks to determine the spatial and temporal pattern of convectively driven uplift. ~100 longitudinal river profiles were extracted from a digital elevation model of Madagascar. An inverse model is then used to minimize the misfit between observed and calculated river profiles as a function of uplift rate history. During inversion, the residual misfit decreases from ~20 to ~4. Our results suggest that youthful and rapid uplift of 1-2 km occurred at rates of 0.2-0.4 mm/yr during the last ˜15 Myr. The algorithm resolves distinct phases of uplift which generate localized swells of high topography and relief (e.g. the Hauts Plateaux). Our field observations and modeling indicate that the evolution of drainage networks may contain useful information about mantle convective processes.

  14. Lower mantle heterogeneity, dynamic topography and the geoid

    NASA Technical Reports Server (NTRS)

    Hager, B. H.; Clayton, R. W.; Richards, M. A.; Comer, R. P.; Dziewonski, A. M.

    1984-01-01

    Density contrasts in the lower mantle, recently imaged using seismic tomography, drive convective flow which results in kilometers of dynamically maintained topography at the core-mantle boundary and at the Earth's surface. The total gravity field due to interior density contrasts and boundary topography predicts the largest wavelength components of the geoid remarkably well. Neglecting dynamic surface deformation leads to geoid anomalies of opposite sign than are observed.

  15. Lower mantle heterogeneity, dynamic topography and the geoid

    NASA Technical Reports Server (NTRS)

    Hager, B. H.; Clayton, R. W.; Richards, M. A.; Comer, R. P.; Dziewonski, A. M.

    1985-01-01

    Density contrasts in the lower mantle, recently imaged using seismic tomography, drive convective flow which results in kilometers of dynamically maintained topography at the core-mantle boundary and at the earth's surface. The total gravity field due to interior density constrasts and boundary topography predicts the largest wavelength components of the geoid remarkably well. Neglecting dynamic surface deformation leads to geoid anomalies of opposite sign than are observed.

  16. Mercury's Thermal Evolution, Dynamical Topography and Geoid

    NASA Astrophysics Data System (ADS)

    Ziethe, Ruth; Benkhoff, Johannes

    stagnant lid comprises roughly half the mantle after only 0.5Ga. Since the rigid lithosphere does not take part in the convection anymore, the heat coming from the interior (due to the cooling of the large core) can only be transported through the lithosphere by thermal conduction. This is a significantly less effective mechanism of heat transport than convection and hence the lithosphere forms an insulating layer. As a result, the interior is kept relatively warm.Because the mantle is relatively shallow compared to the planet's radius, and additionally the thick stagnant lid is formed relatively rapid, the convection is confined to a layer of only about 200km to 300km. Convection structures are therefore relatively small structured. The flow patterns in the early evolution show that mantle convection is characterized by numerous upwelling plumes, which are fed by the heat flow from the cooling core. These upwellings are relatively stable regarding their spatial position. As the core cools down the temperature anomalies become colder and less pronounced but not less numerous. In our calculations, a region of partial melt in the mantle forms immediately after the start of the model at a depths of roughly 220km. While in the entire lower mantle the temperature exceeds the solidus, the highest melt degrees can be found in the upwelling plumes. The partial molten region persists a significant time (up to 2.5Ga). How long the partial molten zone actually survives depends strongly on the initial conditions of the model. For instance, an outer layer with a reduced thermal conductivity would keep the lower mantle significantly warmer and a molten layer survives longer. The hot upwellings cause a surface deformation (dynamical topography) which itself causes a gravity anomaly. Due to the weak constraints of important parameters (e.g. sulfur content of the core, mantle rheology, amount and distribution of radiogenic heat sources, planetary contraction, thermal conductivity, etc

  17. Evolution of Neogene Dynamic Topography in Africa

    NASA Astrophysics Data System (ADS)

    Paul, Jonathan; Roberts, Gareth; White, Nicky

    2013-04-01

    The characteristic basins and swells of Africa's surface topography probably reflect patterns of convective circulation in the sub-lithospheric mantle. We have interrogated drainage networks to determine the spatial and temporal pattern of convectively driven uplift. ~560 longitudinal river profiles were extracted from a digital elevation model of Africa. An inverse model is then used to minimise the misfit between observed and calculated river profiles as a function of uplift rate history. During inversion, the residual misfit decreases from ~22 to ~5. Our results suggest that Africa's topography began to grow most rapidly after ~30 Ma at peak uplift rates of 0.1-0.15 mm/yr. The algorithm resolves distinct phases of uplift which generate localized swells of high topography and relief (e.g. the Angolan Dome). Uplift rate histories are shown to vary significantly from swell to swell. The calculated magnitudes, timing, and location of uplift agree well with local independent geological constraints, such as intense volcanism at Hoggar (42-39 Ma) and Afar (31-29 Ma), uplifted marine terraces, and warped peneplains. We have also calculated solid sediment flux histories for major African deltas which have persisted through time. This onshore record provides an important indirect constraint on the history of vertical motions at the surface, and agrees well with the offshore flux record, obtained from mapping isopachs of deltaic sediments. Our modelling and reconstructed sedimentary flux histories indicate that the evolution of drainage networks may contain useful information about mantle convective processes.

  18. Mercury's Thermal Evolution, Dynamical Topography and Geoid

    NASA Astrophysics Data System (ADS)

    Ziethe, Ruth; Benkhoff, Johannes

    stagnant lid comprises roughly half the mantle after only 0.5Ga. Since the rigid lithosphere does not take part in the convection anymore, the heat coming from the interior (due to the cooling of the large core) can only be transported through the lithosphere by thermal conduction. This is a significantly less effective mechanism of heat transport than convection and hence the lithosphere forms an insulating layer. As a result, the interior is kept relatively warm.Because the mantle is relatively shallow compared to the planet's radius, and additionally the thick stagnant lid is formed relatively rapid, the convection is confined to a layer of only about 200km to 300km. Convection structures are therefore relatively small structured. The flow patterns in the early evolution show that mantle convection is characterized by numerous upwelling plumes, which are fed by the heat flow from the cooling core. These upwellings are relatively stable regarding their spatial position. As the core cools down the temperature anomalies become colder and less pronounced but not less numerous. In our calculations, a region of partial melt in the mantle forms immediately after the start of the model at a depths of roughly 220km. While in the entire lower mantle the temperature exceeds the solidus, the highest melt degrees can be found in the upwelling plumes. The partial molten region persists a significant time (up to 2.5Ga). How long the partial molten zone actually survives depends strongly on the initial conditions of the model. For instance, an outer layer with a reduced thermal conductivity would keep the lower mantle significantly warmer and a molten layer survives longer. The hot upwellings cause a surface deformation (dynamical topography) which itself causes a gravity anomaly. Due to the weak constraints of important parameters (e.g. sulfur content of the core, mantle rheology, amount and distribution of radiogenic heat sources, planetary contraction, thermal conductivity, etc

  19. Zooplankton patch dynamics: daily gap formation over abrupt topography

    NASA Astrophysics Data System (ADS)

    Genin, Amatzia; Greene, Charles; Haury, Loren; Wiebe, Peter; Gal, Gideon; Kaartvedt, Stein; Meir, Eli; Fey, Connie; Dawson, Jim

    1994-05-01

    Net tow and acoustic surveys of zooplankton distributions were made over and around Sixtymile Bank (110 km southwest of San Diego, California). Gaps devoid of vertically migrating zooplankton were formed every evening above the summit of the bank. Interactions between the migrating animals, their predators, physical advection and the local topography appear to determine the gap formation and dynamics. Gaps were transported downstream during the night and appeared to disintegrate slowly through vertical swimming behavior, current shear and mixing processes. Patch dynamics following gap formation, mediated by both ocean currents and animal behavior, should augment the spatial heterogeneity of zooplankton and affect marine food webs in areas where abrupt topography features are common.

  20. Present-day dynamic and residual topography in central Anatolia

    NASA Astrophysics Data System (ADS)

    Uluocak, Ebru Şengül; Pysklywec, Russell; Göğüş, Oğuz H.

    2016-06-01

    The Central Anatolian orogenic plateau is represented by young volcanism, rapid plateau uplift, and distinctive (past and active) tectonic deformation. In this study, we consider observational data in terms of regional present-day geodynamics in the region. The residual topography of Central Anatolia was derived to define the regional isostatic conditions according to Airy isostasy and infer the potential role of "dynamic topography". Two-dimensional thermo-mechanical forward models for coupled mantle-lithosphere flow/deformation were conducted along a N-S directional profile through the region (e.g. northern/Pontides, interior, and southern/Taurides). These models were based on seismic tomography data that provide estimates about the present-day mantle thermal structure beneath the Anatolian plate. We compare the modelling results with calculated residual topography and independent data sets of geological deformation, gravity, and high surface heat flow/widespread geothermal activity. Model results suggest that there is ˜1 km of mantle flow induced dynamic topography associated with the sub-lithospheric flow driven by the seismically-inferred mantle structure. The uprising mantle may have also driven the asthenospheric source of volcanism in the north (e.g. Galatia volcanic province) and the Cappadocia volcanic province in the south while elevating the surface in the last 10 Myrs. Our dynamic topography calculations emphasize the role of vertical forcing under other orogenic plateaux underlain by relatively thin crust and low-density asthenospheric mantle.

  1. Upper-Mantle Flow Driven Dynamic Topography in Eastern Anatolia

    NASA Astrophysics Data System (ADS)

    Sengul Uluocak, Ebru; Pysklywec, Russell; Eken, Tuna; Hakan Gogus, Oguz

    2016-04-01

    Eastern Anatolia is characterized by 2 km plateau uplift -in the last 10 Myrs-, high surface heat flow distribution, shallow Curie-point depth, anomalous gravity field. Seismological observations indicate relatively high Pn and Sn attenuation and significant low seismic velocity anomalies in the region. Moreover, the surface geology is associated predominantly with volcanic rocks in which melt production through mantle upwelling (following lithospheric delamination) has been suggested. It has been long known that the topographic loading in the region cannot be supported by crustal thickness (~45 km) based on the principle of Airy isostasy. Recent global geodynamic studies carried out for evaluating the post-collisional processes imply that there is an explicit dynamic uplift in Eastern Anatolia and its adjacent regions. In this study we investigate the instantaneous dynamic topography driven by 3-D upper-mantle flow in Eastern Anatolia. For this purpose we conducted numerous thermo-mechanical models using a 2-D Arbitrary Lagrangian Eulerian (ALE) finite element method. The available P-wave tomography data extracted along 10 profiles were used to obtain depth-dependent density anomalies in the region. We present resulting dynamic topography maps and estimated 3D mantle flow velocity vectors along these 2-D cross sections for each profile. The residual topography based on crustal thickness and observed topography was calculated and compared with other independent datasets concerning geological deformation and dynamic topography predictions. The results indicate an upper mantle driven dynamic uplift correlated with the under-compensated characteristic in Eastern Anatolia. We discuss our results combined with 3D mantle flow by considering seismic anisotropy studies in the region. Initial results indicate that high dynamic uplift and the localized low Pn velocities in concurrence with Pn anisotropy structures show nearly spatial coherence in Eastern Anatolia.

  2. Mantle Flow Pattern and Dynamic Topography beneath the Eastern US

    NASA Astrophysics Data System (ADS)

    Liu, S.; King, S. D.; Adam, C. M.; Long, M. D.; Benoit, M. H.; Kirby, E.

    2015-12-01

    The complex tectonic history of the eastern US over the past billion years includes episodes of subduction and rifting associated with two complete cycles of supercontinent assembly and breakup. Both the previous global tomography models (S40RTS, SAVANI, TX2011, GyPSuM, SMEAN) and the analysis of the shear-wave splitting from the broadband seismic stations find a distinct coast-to-inland differentiation pattern in the lithosphere and upper mantle. The Mid-Atlantic Geophysical Integrative Collaboration (MAGIC) includes a dense linear seismic array from the Atlantic coast of Virginia to the western boarder of Ohio, crossing several different tectonic zones. To derive the regional mantle flow pattern along with its surface expression such as dynamic topography and aid the interpretation of the seismic observations, we are building a new geodynamic model based on ASPECT (Advanced Solver for Problems in Earth CovecTion) that uses buoyancy derived from seismic tomography along with realistic lithosphere and sub-lithosphere structure. At present, we use S40RTS and SAVANI tomography models together with the temperature-dependent viscosity to compute the mantle flow and dynamic topography. Beneath the eastern US, the upper mantle flow in our model is primarily parallel to the trend of the Appalachian belt, which is broadly consistent with the direction of the local shear-wave splitting. The dynamic topography results exhibit a coast-to-inland magnitude differentiation along the MAGIC seismic deployment. The numerical tests also show that both the magnitude and pattern of the dynamic topography are quite sensitive to the density perturbation and rigidity of the lithosphere/sub-lithosphere. Our future work involves using other tomography and viscosity models to obtain the mantle flow pattern as well as the resulting dynamic topography and geoid.

  3. Impact of lithosphere rheology on the dynamic topography

    NASA Astrophysics Data System (ADS)

    Burov, Evgueni; Gerya, Taras; Koptev, Alexander

    2014-05-01

    Dynamic topography is a key observable signature of the Earth's and planetary (e.g. Venus) mantle dynamics. In general view, it reflects complex mantle flow patterns, and hence is supposed to correlate at different extent with seismic tomography, SKS fast orientations, geodetic velocity fields and geoid anomalies. However, identification of dynamic topography had no systematic success, specifically in the Earth's continents. Here we argue that lithosphere rheology, in particular, rheological stratification of continents, results in modulation of dynamic topography, converting commonly expected long-wavelength/small amplitude undulations into short-wavelength surface undulations with wide amplitude spectrum, superimposed onto "tectonic" topography. These ideas are explored in 3D using unprecedentedly high resolution numerical experiments (grid step size 2-3 km for 1500x1500x600 km computational area) incorporating realistic rheologically stratified lithosphere. Such high resolution is actually needed to resolve small-scale crustal faulting and inter-layer coupling/uncoupling that shape surface topography. The results reveal strikingly discordant, counterintuitive features of 3D dynamic topography, going far beyond the inferences from previous models. In particular, even weak anisotropic tectonic stress field results both in large-scale small-amplitude dynamic topography and in strongly anisotropic short-wavelength (at least in one direction) dynamic topography with wide amplitude range (from 100 to 2000-3000 m), including basins and ranges and large-scale linear normal and strike-slip faults. Even very slightly pre-stressed strong lithosphere yields and localizes deformation much easier , than un-prestressed one, in response to plume impact and mantle flow. The results shed new light on the importance of lithosphere rheology and active role of lithosphere in mantle-lithosphere interactions as well as on the role of mantle flow and far-field stresses in tectonic

  4. Predicting surface dynamic topographies of stagnant lid planetary bodies

    NASA Astrophysics Data System (ADS)

    Dumoulin, C.; Čadek, O.; Choblet, G.

    2013-12-01

    Although planetary mantles are viscoelastic media, numerical models of thermal convection in a viscoelastic spherical shell are still very challenging. Here, we examine the validity of simplified mechanical and rheological frameworks classically used to approximate viscoelastic dynamic topography. We compare three simplified approaches to a linear Maxwell viscoelastic shell with a pseudo upper free-surface, considered as the reference model. A viscous model with a free-slip boundary condition at the surface correctly reproduces the final relaxed shape of the viscoelastic body but it cannot reproduce the time evolution of the viscoelastic topography. Nevertheless, characterizing the topography development is important since it can represent a significant fraction of the history for planets having a thick and rigid lithosphere (e.g. Mars). A viscous model with a pseudo free-surface, despite its time-dependency, also systematically fails to describe correctly these transient stages. An elastic filtering of the instantaneous viscous topography is required to capture the essence of the time evolution of the topography. We show that a single effective elastic thickness is needed to correctly reproduce the constant transient viscoelastic topography obtained when the lithosphere corresponds to a step-like viscosity variation, while a time-dependence of the effective elastic thickness must be considered to take account of realistic temperature-dependent viscosity variations in the lithosphere. In this case, the appropriate thickness of the elastic shell can be evaluated, at a given instant, with a simple procedure based on the local Maxwell time. Furthermore, if the elastic filtering is performed using the thin elastic shell formulation, an unrealistic degree-dependence of the thickness of the elastic shell is needed to correctly approximate the viscoelastic topography. We show that a model that fully couples a viscous body to an elastic shell of finite thickness estimated

  5. Dynamic topography in subduction zones: insights from laboratory models

    NASA Astrophysics Data System (ADS)

    Bajolet, Flora; Faccenna, Claudio; Funiciello, Francesca

    2014-05-01

    The topography in subduction zones can exhibit very complex patterns due to the variety of forces operating this setting. If we can deduce the theoretical isostatic value from density structure of the lithosphere, the effect of flexural bending and the dynamic component of topography are difficult to quantify. In this work, we attempt to measure and analyze the topography of the overriding plate during subduction compared to a pure shortening setting. We use analog models where the lithospheres are modeled by thin-sheet layers of silicone putty lying on low-viscosity syrup (asthenosphere). The model is shorten by a piston pushing an oceanic plate while a continental plate including a weak zone to localize the deformation is fixed. In one type of experiments, the oceanic plate bends and subducts underneath the continental one; in a second type the two plates are in contact without any trench, and thus simply shorten. The topography evolution is monitored with a laser-scanner. In the shortening model, the elevation increases progressively, especially in the weak zone, and is consistent with expected isostatic values. In the subduction model, the topography is characterized, from the piston to the back-wall, by a low elevation of the dense oceanic plate, a flexural bulge, the trench forming a deep depression, the highly elevated weak zone, and the continental upper plate of intermediate elevation. The topography of the upper plate is consistent with isostatic values for very early stages, but exhibits lower elevations than expected for later stages. For a same amount of shortening of the continental plate, the thickening is the same and the plate should have the same elevation in both types of models. However, comparing the topography at 20, 29 and 39% of shortening, we found that the weak zone is 0.4 to 0.6 mm lower when there is an active subduction. Theses values correspond to 2.6 to 4 km in nature. Although theses values are high, there are of the same order as

  6. The effects of abrupt topography on plankton dynamics.

    PubMed

    Zavala Sansón, L; Provenzale, A

    2009-12-01

    Plankton population dynamics in the upper layer of the ocean depends on upwelling processes that bring nutrients from deeper waters. In turn, these depend on the structure of the vertical velocity field. In coastal areas and in oceanic regions characterized by the presence of strong submarine topographic features, the variable bottom topography induces significant effects on vertical velocities and upwelling/downwelling patterns. As a consequence, large plankton and fish abundances are frequently observed above seamounts, canyons and steep continental shelves. In this work, the dynamics of an NPZ (nutrient-phytoplankton-zooplankton) system is numerically studied by coupling the ecosystem model with a quasi two-dimensional (2D) fluid model with topography. At variance with classical 2D approaches, this formulation allows for an explicit expression of the vertical motions produced when fluid columns are squeezed and stretched as they experience changes of depth. Thus, input or output of nutrients at the surface are associated with fluid motion over the bottom topography. We examine the dynamics of a cyclonic vortex over two basic topographies: a steep escarpment and a submarine mountain. We show that plankton abundance over the escarpment is modulated by the passing of topographic Rossby waves, generated by the vortex-topography interaction. In such configuration, advection effects driven by the flow over the escarpment are of limited relevance for the dynamics of biological fields. By contrast, we find that the flow resulting from the interaction of a vortex with a seamount is sufficiently strong and persistent to allow for a remarkable increase of nutrients, and a corresponding enhancement of phytoplankton and zooplankton concentrations. Over the seamount, advection effects associated with trapped flow perturbations around the summit play an essential role. PMID:19737575

  7. On the ratio of dynamic topography and gravity anomalies in a dynamic Earth

    NASA Astrophysics Data System (ADS)

    Colli, L.; Ghelichkhan, S.; Bunge, H.-P.

    2016-03-01

    Growing evidence from a variety of geologic indicators points to significant topography maintained convectively by viscous stresses in the mantle. However, while gravity is sensitive to dynamically supported topography, there are only small free-air gravity anomalies (<30 mGal) associated with Earth's long-wavelength topography. This has been used to suggest that surface heights computed assuming a complete isostatic equilibrium provide a good approximation to observed topography. Here we show that the apparent paradox is resolved by the well-established formalism of global, self-gravitating, viscously stratified Earth models. The models predict a complex relation between dynamic topography, mass, and gravity anomalies that is not summarized by a constant admittance—i.e., ratio of gravity anomalies to surface deflections—as one would infer from analytic flow solutions formulated in a half-space. Our results suggest that sizable dynamic topography may exist without a corresponding gravity signal.

  8. Dynamic wetting and spreading and the role of topography.

    PubMed

    McHale, Glen; Newton, Michael I; Shirtcliffe, Neil J

    2009-11-18

    The spreading of a droplet of a liquid on a smooth solid surface is often described by the Hoffman-de Gennes law, which relates the edge speed, v(e), to the dynamic and equilibrium contact angles θ and θ(e) through [Formula: see text]. When the liquid wets the surface completely and the equilibrium contact angle vanishes, the edge speed is proportional to the cube of the dynamic contact angle. When the droplets are non-volatile this law gives rise to simple power laws with time for the contact angle and other parameters in both the capillary and gravity dominated regimes. On a textured surface, the equilibrium state of a droplet is strongly modified due to the amplification of the surface chemistry induced tendencies by the topography. The most common example is the conversion of hydrophobicity into superhydrophobicity. However, when the surface chemistry favors partial wetting, topography can result in a droplet spreading completely. A further, frequently overlooked consequence of topography is that the rate at which an out-of-equilibrium droplet spreads should also be modified. In this report, we review ideas related to the idea of topography induced wetting and consider how this may relate to dynamic wetting and the rate of droplet spreading. We consider the effect of the Wenzel and Cassie-Baxter equations on the driving forces and discuss how these may modify power laws for spreading. We relate the ideas to both the hydrodynamic viscous dissipation model and the molecular-kinetic theory of spreading. This suggests roughness and solid surface fraction modified Hoffman-de Gennes laws relating the edge speed to the dynamic and equilibrium contact angle. We also consider the spreading of small droplets and stripes of non-volatile liquids in the capillary regime and large droplets in the gravity regime. In the case of small non-volatile droplets spreading completely, a roughness modified Tanner's law giving the dependence of dynamic contact angle on time is

  9. Solitary wave dynamics in shallow water over periodic topography.

    PubMed

    Nakoulima, Ousseynou; Zahibo, Narcisse; Pelinovsky, Efim; Talipova, Tatiana; Kurkin, Andrey

    2005-09-01

    The problem of long-wave scattering by piecewise-constant periodic topography is studied both for a linear solitary-like wave pulse, and for a weakly nonlinear solitary wave [Korteweg-de Vries (KdV) soliton]. If the characteristic length of the topographic irregularities is larger than the pulse length, the solution of the scattering problem is obtained analytically for a leading wave in the framework of linear shallow-water theory. The wave decrement in the case of the small height of the topographic irregularities is proportional to delta2, where delta is the relative height of the topographic obstacles. An analytical approximate solution is also obtained for the weakly nonlinear problem when the length of the irregularities is larger than the characteristic nonlinear length scale. In this case, the Korteweg-de Vries equation is solved for each piece of constant depth by using the inverse scattering technique; the solutions are matched at each step by using linear shallow-water theory. The weakly nonlinear solitary wave decays more significantly than the linear solitary pulse. Solitary wave dynamics above a random seabed is also discussed, and the results obtained for random topography (including experimental data) are in reasonable agreement with the calculations for piecewise topography. PMID:16253002

  10. Dynamic topography and the Cenozoic carbonate compensation depth

    NASA Astrophysics Data System (ADS)

    Campbell, S. M.; Moucha, R.; Raymo, M. E.; Derry, L. A.

    2015-12-01

    The carbonate compensation depth (CCD), the ocean depth at which the calcium carbonate accumulation rate goes to zero, can provide valuable insight into climatic and weathering conditions over the Cenozoic. The paleoposition of the CCD can be inferred from sediment core data. As the carbonate accumulation rate decreases linearly with depth between the lysocline and CCD, the CCD can be calculated using a linear regression on multiple sediment cores with known carbonate accumulation rates and paleodepths. It is therefore vital to have well-constrained estimates of paleodepths. Paleodepths are typically calculated using models of thermal subsidence and sediment loading and compaction. However, viscous convection-related stresses in the mantle can warp the ocean floor by hundreds of meters over broad regions and can also vary significantly over millions of years. This contribution to paleobathymetry, termed dynamic topography, can be calculated by modeling mantle flow backwards in time. Herein, we demonstrate the effect dynamic topography has on the inference of the late Cenozoic CCD with an example from the equatorial Pacific, considering sites from IODP Expeditions 320/321. The equatorial Pacific, given its large size and high productivity, is closely tied to the global carbon cycle. Accordingly, long-term changes in the equatorial Pacific CCD can be considered to reflect global changes in weathering fluxes and the carbon cycle, in addition to more regional changes in productivity and thermohaline circulation. We find that, when the dynamic topography contribution to bathymetry is accounted for, the equatorial Pacific CCD is calculated to be appreciably shallower at 30 Ma than previous estimates would suggest, implying a greater deepening of the Pacific CCD over the late Cenozoic.

  11. Dynamic wetting and spreading and the role of topography

    NASA Astrophysics Data System (ADS)

    McHale, Glen; Newton, Michael I.; Shirtcliffe, Neil J.

    2009-11-01

    The spreading of a droplet of a liquid on a smooth solid surface is often described by the Hoffman-de Gennes law, which relates the edge speed, ve, to the dynamic and equilibrium contact angles θ and θe through v_{\\mathrm {e}} \\propto \\theta (\\theta^{2}-\\theta_{\\mathrm {e}}^{2}) . When the liquid wets the surface completely and the equilibrium contact angle vanishes, the edge speed is proportional to the cube of the dynamic contact angle. When the droplets are non-volatile this law gives rise to simple power laws with time for the contact angle and other parameters in both the capillary and gravity dominated regimes. On a textured surface, the equilibrium state of a droplet is strongly modified due to the amplification of the surface chemistry induced tendencies by the topography. The most common example is the conversion of hydrophobicity into superhydrophobicity. However, when the surface chemistry favors partial wetting, topography can result in a droplet spreading completely. A further, frequently overlooked consequence of topography is that the rate at which an out-of-equilibrium droplet spreads should also be modified. In this report, we review ideas related to the idea of topography induced wetting and consider how this may relate to dynamic wetting and the rate of droplet spreading. We consider the effect of the Wenzel and Cassie-Baxter equations on the driving forces and discuss how these may modify power laws for spreading. We relate the ideas to both the hydrodynamic viscous dissipation model and the molecular-kinetic theory of spreading. This suggests roughness and solid surface fraction modified Hoffman-de Gennes laws relating the edge speed to the dynamic and equilibrium contact angle. We also consider the spreading of small droplets and stripes of non-volatile liquids in the capillary regime and large droplets in the gravity regime. In the case of small non-volatile droplets spreading completely, a roughness modified Tanner's law giving the

  12. Isostatic and dynamic support of high topography on a North Atlantic passive margin

    NASA Astrophysics Data System (ADS)

    Pedersen, Vivi K.; Huismans, Ritske S.; Moucha, Robert

    2016-07-01

    Substantial controversy surrounds the origin of high topography along passive continental margins. Here we focus on the well-documented elevated passive margin in southwestern Scandinavia, and quantify the relative contributions of crustal isostasy and dynamic topography in controlling the present topography. We find that majority of the topography is compensated by the crustal structure, suggesting a topographic age that is in accord with the 400 Myr old Caledonian orogenesis. In addition, we propose that dynamic uplift of ∼300 m has rejuvenated existing topography locally in the coastal region over the last 10 Myr. Such uplift, combined with a general sea level fall, can help explain a variety of observations that have traditionally been interpreted in favor of a peneplain uplift model. We conclude that high topography along the Scandinavian margin cannot represent remnants of a peneplain uplifted within the last 20 Myr. The topography must have been high since the Caledonian orogeny.

  13. A magmatic probe of dynamic topography beneath western North America

    NASA Astrophysics Data System (ADS)

    Klöcking, M.; White, N. J.; Maclennan, J.

    2014-12-01

    A region centered on the Yellowstone hotspot and encompassing the Colorado Plateau sits at an elevation 2 km higher than the cratonic North America. This difference broadly coincides with tomographically observed variations in lithospheric thickness: ~120 km beneath western North America, ~240 km beneath the craton. Thermochronology of the Grand Canyon area, sedimentary flux to the Gulf of Mexico, and river profile inversion all suggest that regional uplift occurred in at least two separate stages. High resolution seismic tomographic models, using USArray data, have identified a ring of low velocity material beneath the edges of the Colorado Plateau. Magmatism coincides with these low velocity zones and shows distinct phases: an overall increase in volume around 40 Ma and a change from lithospheric to asthenospheric signatures around 5 Ma. Volcanism is also observed to migrate north-east with time. Here, we attempt to integrate these different observations with lithospheric thickness. A dynamic topography model of progressive lithospheric erosion over a hot mantle plume might account for uplift as well as the temporal and spatial distribution of magmatism across western North America. Thinning of the lithosphere around the edges of the Colorado Plateau in combination with the hotter mantle potential temperature of a plume could create isostatic and dynamic uplift as well as allowing for melt production. To test this model, we have analysed around 100 samples from volcanic centers across western North America by ICP-MS for rare earth elements (REE). Most of the samples are younger than 5 Ma, and all of them have previously been analysed by XRF. Using trace element ratios such as La/Yb and Nb/Y we assess depth of melting and melt fraction, respectively. In addition, we use REE inversion modelling to estimate melt fractions as a function of depth and temperature of melting. The results are compared to existing constraints on lithospheric thickness and mantle potential

  14. Global dynamic topography observations reveal limited influence of large-scale mantle flow

    NASA Astrophysics Data System (ADS)

    Hoggard, M. J.; White, N.; Al-Attar, D.

    2016-06-01

    Convective circulation of the Earth's mantle maintains some fraction of surface topography that varies with space and time. Most predictive models show that this dynamic topography has peak amplitudes of about +/-2 km, dominated by wavelengths of 104 km. Here, we test these models against our comprehensive observational database of 2,120 spot measurements of dynamic topography that were determined by analysing oceanic seismic surveys. These accurate measurements have typical peak amplitudes of +/-1 km and wavelengths of approximately 103 km, and are combined with limited continental constraints to generate a global spherical harmonic model, the robustness of which has been carefully tested and benchmarked. Our power spectral analysis reveals significant discrepancies between observed and predicted dynamic topography. At longer wavelengths (such as 104 km), observed dynamic topography has peak amplitudes of about +/-500 m. At shorter wavelengths (such as 103 km), significant dynamic topography is still observed. We show that these discrepancies can be explained if short-wavelength dynamic topography is generated by temperature-driven density anomalies within a sub-plate asthenospheric channel. Stratigraphic observations from adjacent continental margins show that these dynamic topographic signals evolve quickly with time. More rapid temporal and spatial changes in vertical displacement of the Earth's surface have direct consequences for fields as diverse as mantle flow, oceanic circulation and long-term climate change.

  15. A Tailored Computation of the Mean Dynamic Topography for a Consistent Integration into Ocean Circulation Models

    NASA Astrophysics Data System (ADS)

    Becker, S.; Losch, M.; Brockmann, J. M.; Freiwald, G.; Schuh, W.-D.

    2014-11-01

    Geostrophic surface velocities can be derived from the gradients of the mean dynamic topography—the difference between the mean sea surface and the geoid. Therefore, independently observed mean dynamic topography data are valuable input parameters and constraints for ocean circulation models. For a successful fit to observational dynamic topography data, not only the mean dynamic topography on the particular ocean model grid is required, but also information about its inverse covariance matrix. The calculation of the mean dynamic topography from satellite-based gravity field models and altimetric sea surface height measurements, however, is not straightforward. For this purpose, we previously developed an integrated approach to combining these two different observation groups in a consistent way without using the common filter approaches (Becker et al. in J Geodyn 59(60):99-110, 2012; Becker in Konsistente Kombination von Schwerefeld, Altimetrie und hydrographischen Daten zur Modellierung der dynamischen Ozeantopographie 2012). Within this combination method, the full spectral range of the observations is considered. Further, it allows the direct determination of the normal equations (i.e., the inverse of the error covariance matrix) of the mean dynamic topography on arbitrary grids, which is one of the requirements for ocean data assimilation. In this paper, we report progress through selection and improved processing of altimetric data sets. We focus on the preprocessing steps of along-track altimetry data from Jason-1 and Envisat to obtain a mean sea surface profile. During this procedure, a rigorous variance propagation is accomplished, so that, for the first time, the full covariance matrix of the mean sea surface is available. The combination of the mean profile and a combined GRACE/GOCE gravity field model yields a mean dynamic topography model for the North Atlantic Ocean that is characterized by a defined set of assumptions. We show that including the

  16. Isostatic and dynamic support of high topography on a North Atlantic passive margin

    NASA Astrophysics Data System (ADS)

    Kathrine Pedersen, Vivi; Huismans, Ritske S.; Moucha, Robert

    2016-04-01

    Substantial controversy surrounds the origin and recent evolution of high topography along passive continental margins in the North Atlantic, with suggested age of formation ranging from early Paleozoic Caledonian orogenesis to Neogene uplift of a Mesozoic peneplain. Here we focus on the well-documented high passive margin in southwestern Scandinavia, and quantify the relative contributions of crustal isostasy and dynamic topography in controlling the present topography. We find that most topography is compensated by the crustal structure, suggesting a topographic age related to ~400 Myr old Caledonian orogenesis. In addition, we infer that dynamic uplift (~300 m) has rejuvenated existing topography locally in the coastal region within the last ~10 Myr due to mantle convection. Such uplift has, in combination with a general eustatic sea-level fall and concurrent erosion-driven isostatic rock-column uplift, the potential to increase erosion of coastal-near regions and explain observations that have traditionally been interpreted in favor of the peneplain uplift model. We conclude that high topography along the Scandinavian margin cannot represent remnants of a peneplain uplifted within the last ~20 Myr. Topography must have been high since the Caledonian orogeny.

  17. Calculating gravitationally self-consistent sea level changes driven by dynamic topography

    NASA Astrophysics Data System (ADS)

    Austermann, J.; Mitrovica, J. X.

    2015-12-01

    We present a generalized formalism for computing gravitationally self-consistent sea level changes driven by the combined effects of dynamic topography, geoid perturbations due to mantle convection, ice mass fluctuations and sediment redistribution on a deforming Earth. Our mathematical treatment conserves mass of the surface (ice plus ocean) load and the solid Earth. Moreover, it takes precise account of shoreline migration and the associated ocean loading. The new formalism avoids a variety of approximations adopted in previous models of sea level change driven by dynamic topography, including the assumption that a spatially fixed isostatic amplification of `air-loaded' dynamic topography accurately accounts for ocean loading effects. While our approach is valid for Earth models of arbitrary complexity, we present numerical results for a set of simple cases in which a pattern of dynamic topography is imposed, the response to surface mass loading assumes that Earth structure varies only with depth and that isostatic equilibrium is maintained at all times. These calculations, involving fluid Love number theory, indicate that the largest errors in previous predictions of sea level change driven by dynamic topography occur in regions of shoreline migration, and thus in the vicinity of most geological markers of ancient sea level. We conclude that a gravitationally self-consistent treatment of long-term sea level change is necessary in any effort to use such geological markers to estimate ancient ice volumes.

  18. Effect of surface topography upon micro-impact dynamics

    NASA Astrophysics Data System (ADS)

    Mohammadpour, M.; Morris, N. J.; Leighton, M.; Rahnejat, H.

    2016-03-01

    Often the effect of interactions at nano-scale determines the tribological performance of load bearing contacts. This is particularly the case for lightly loaded conjunctions where a plethora of short range kinetic interactions occur. It is also true of larger load bearing conjunctions where boundary interactions become dominant. At the diminutive scale of fairly smooth surface topography the cumulative discrete interactions give rise to the dominance of boundary effects rather than the bulk micro-scale phenomena, based on continuum mechanics. The integration of the manifold localized discrete interactions into a continuum is the pre-requisite to the understanding of characteristic boundary effects, which transcend the physical length scales and affect the key observed system attributes. These are energy efficiency and vibration refinement. This paper strives to present such an approach. It is shown that boundary and near boundary interactions can be adequately described by surface topographical measures, as well the thermodynamic conditions.

  19. Dynamic scalp topography reveals neural signs just before performance errors

    PubMed Central

    Ora, Hiroki; Sekiguchi, Tatsuhiko; Miyake, Yoshihiro

    2015-01-01

    Performance errors may cause serious consequences. It has been reported that ongoing activity of the frontal control regions across trials associates with the occurrence of performance errors. However, neural mechanisms that cause performance errors remain largely unknown. In this study, we hypothesized that some neural functions required for correct outcomes are lacking just before performance errors, and to determine this lack of neural function we applied a spatiotemporal analysis to high-density electroencephalogram signals recorded during a visual discrimination task, a d2 test of attention. To our knowledge, this is the first report of a difference in the temporal development of scalp ERP between trials with error, and correct outcomes as seen by topography during the d2 test of attention. We observed differences in the signal potential in the frontal region and then the occipital region between reaction times matched with correct and error outcomes. Our observations suggest that lapses of top-down signals from frontal control regions cause performance errors just after the lapses. PMID:26289925

  20. Geoid Anomalies and Dynamic Topography from Time Dependent, Spherical Axisymmetric Mantle Convection

    NASA Technical Reports Server (NTRS)

    Kiefer, Walter S.; Kellogg, Louise H.

    1998-01-01

    Geoid anomalies and dynamic topography are two important diagnostics of mantle convection. We present geoid and topography results for several time-dependent convection models in spherical axisymmetric geometry for Rayleigh numbers between 10(exp 6) and 10(exp 7) with depth-dependent viscosity and mixtures of bottom and internal heating. The models are strongly chaotic, with boundary layer instabilities erupting out of both thermal boundary layers. In some instances, instabilities from one boundary layer influence the development of instabilities in the other boundary layer. Such coupling between events at the top and bottom of the mantle has been suggested to play a role in a mid-Cretaceous episode of enhanced volcanism in the Pacific. These boundary layer instabilities produce large temporal variations in the geoid anomalies and dynamic nd to the topography associated with the convection. The amplitudes of these fluctuations depend on the detailed model parameter,.% it of this but fluctuations of 30-50% relative to the time-averaged geoid and topography are common. The convective planform is strongly sensitive to the specific initial conditions. Convection cells with larger aspect ratio tend to have larger fractional fluctuations in their geoid and topography amplitudes, because boundary layer instabilities have more time to develop in long cells. In some instances, we observe low-amplitude topographic highs adjacent to the topographic lows produced by cold downwellings. We discuss applications of these results to several situations, including the temporal variability of m basis. hotspots such as Hawaii, the topography of subduction zone outer rises, and the topography of coronae on Venus.

  1. Landscape Response to Changes in Dynamic Topography on the U.S. Atlantic Passive Margin

    NASA Astrophysics Data System (ADS)

    Ruetenik, G.; Moucha, R.; Hoke, G. D.

    2014-12-01

    Recent global backwards-in time models of mantle convection have resulted in vastly different interpretations of the transient state of dynamic topography on the U.S. Atlantic passive margin over the past 30 Myr (Moucha et al., 2008; Spacejovic et al., 2008; Rowley et al., 2013; Liu, 2014) . A promising way of benchmarking these geodynamic models is by reconciling them with the observed offshore sedimentary record. However, it is difficult to deconvolve the erosional response produced by changes in dynamic topography from other sources of landscape change because the erosional response is a convolution of dynamic topography changes, tectonic uplift/subsidence, flexural response to erosional unloading and depositional loading, rock properties, and climate. Herein, we present results from a new landscape evolution model that is capable of producing simulations that are required at the scale and resolution necessary to quantify the landscape response to various models of dynamic topographic change on the U.S. Atlantic passive margin in the presence of flexural unloading and loading due to erosion and deposition. We perform a sensitivity study on the effects of geodynamic modeling parameters including effective elastic thickness, climate and rock properties. We find that, while models of dynamic topography are difficult to discern from the available sedimentary record at the scale of the continent in part due to induced topologic (stream geometry) change, at the catchment scale deposition rates are vastly different through time with differing dynamic topography models. At this scale, all models show distinct peaks in deposition rates, and varying elastic thickness has a significant effect on altering the timing of peak deposition.

  2. How to approximate viscoelastic dynamic topographies of stagnant lid planetary bodies?

    NASA Astrophysics Data System (ADS)

    Dumoulin, Caroline; Čadek, Ondřej; Choblet, Gaël

    2013-04-01

    Planetary mantles are viscoelastic media. However, since numerical models of thermal convection in a viscoelastic spherical shell are still very challenging, most of the studies concerning dynamic topography of planetary surfaces generated by mantle convection use one of the following simplified rheological set-up: i) IVF (instantaneous viscous flow), ii) viscous body with a free surface, or iii) hybrid methods combining viscous deformation and elastic filtering of the topography. Justifications for the use of such approximations instead of a fully viscoelastic rheology have been made on the basis of simple tests with step-like viscosity structures, with small to moderate viscosity contrasts. However, because the rheology of planetary materials is thermally activated, the radial stratification of viscosity is more likely to be a continuous function of depth, and global viscosity contrasts might be very large. In our study, we systematically compare viscoelastic dynamic topography induced by an internal load to topographies generated by the three different simplified approaches listed above using a realistic viscosity profile for a stagnant lid associated to the lithosphere of a one plate planete. To this purpose, we compute response functions of surface topography and geoid using three different semi-spectral models that all include self-gravitation: a) a linear Maxwell body with a pseudo free upper surface, b) a viscous body with a pseudo free upper surface, and c) a viscous body with a free-slip condition at the surface. Results obtained with this last model (IVF) can then be filtered using the elastic thin shell approximation: the effective elastic thickness then corresponds to the elastic thickness that is needed to fit the viscoelastic topography with an elastic filtering of the IVF topography. We show that the effective elastic thickness varies strongly with the degree of the load, with the depth of the load, and with the duration of the loading. These

  3. Dynamic topography and gravity anomalies for fluid layers whose viscosity varies exponentially with depth

    NASA Technical Reports Server (NTRS)

    Revenaugh, Justin; Parsons, Barry

    1987-01-01

    Adopting the formalism of Parsons and Daly (1983), analytical integral equations (Green's function integrals) are derived which relate gravity anomalies and dynamic boundary topography with temperature as a function of wavenumber for a fluid layer whose viscosity varies exponentially with depth. In the earth, such a viscosity profile may be found in the asthenosphere, where the large thermal gradient leads to exponential decrease of viscosity with depth, the effects of a pressure increase being small in comparison. It is shown that, when viscosity varies rapidly, topography kernels for both the surface and bottom boundaries (and hence the gravity kernel) are strongly affected at all wavelengths.

  4. Absolute and relative choreographies in rigid body dynamics

    NASA Astrophysics Data System (ADS)

    Borisov, A. V.; Kilin, A. A.; Mamaev, I. S.

    2008-06-01

    For the classical problem of motion of a rigid body about a fixed point with zero area integral, we present a family of solutions that are periodic in the absolute space. Such solutions are known as choreographies. The family includes the well-known Delone solutions (for the Kovalevskaya case), some particular solutions for the Goryachev-Chaplygin case, and the Steklov solution. The “genealogy” of solutions of the family naturally appearing from the energy continuation and their connection with the Staude rotations are considered. It is shown that if the integral of areas is zero, the solutions are periodic with respect to a coordinate frame that rotates uniformly about the vertical (relative choreographies).

  5. Noise-driven cooperative dynamics between vegetation and topography in riparian zones

    NASA Astrophysics Data System (ADS)

    Vesipa, R.; Camporeale, C.; Ridolfi, L.

    2015-10-01

    Riparian ecosystems exhibit complex biotic and abiotic dynamics, where the triad vegetation-sediments-stream determines the ecogeomorphological features of the river landscape. Random fluctuations of the water stage are a key trait of this triad, and a number of behaviors of the fluvial environment can be understood only taking into consideration the role of noise. In order to elucidate how randomness shape riparian transects, a stochastic model that takes into account the main links between vegetation, sediments, and the stream is adopted, emphasizing the capability of vegetation to alter the plot topography. A minimalistic approach is pursued, and the probability density function of vegetation biomass is analytically evaluated in any transect plot. This probability density function strongly depends on the vegetation-topography feedback. We demonstrate how the vegetation-induced modifications of the bed topography create more suitable conditions for the survival of vegetation in a stochastically dominated environment.

  6. Dynamic topography change of the eastern United States since 3 million years ago.

    PubMed

    Rowley, David B; Forte, Alessandro M; Moucha, Robert; Mitrovica, Jerry X; Simmons, Nathan A; Grand, Stephen P

    2013-06-28

    Sedimentary rocks from Virginia through Florida record marine flooding during the mid-Pliocene. Several wave-cut scarps that at the time of deposition would have been horizontal are now draped over a warped surface with a maximum variation of 60 meters. We modeled dynamic topography by using mantle convection simulations that predict the amplitude and broad spatial distribution of this distortion. The results imply that dynamic topography and, to a lesser extent, glacial isostatic adjustment account for the current architecture of the coastal plain and proximal shelf. This confounds attempts to use regional stratigraphic relations as references for longer-term sea-level determinations. Inferences of Pliocene global sea-level heights or stability of Antarctic ice sheets therefore cannot be deciphered in the absence of an appropriate mantle dynamic reference frame. PMID:23686342

  7. Topographies and dynamics on multidimensional potential energy surfaces

    NASA Astrophysics Data System (ADS)

    Ball, Keith Douglas

    The stochastic master equation is a valuable tool for elucidating potential energy surface (PES) details that govern structural relaxation in clusters, bulk systems, and protein folding. This work develops a comprehensive framework for studying non-equilibrium relaxation dynamics using the master equation. Since our master equations depend upon accurate partition function models for use in Rice-Ramsperger-Kassel-Marcus (RRK(M) transition state theory, this work introduces several such models employing various harmonic and anharmonic approximations and compares their predicted equilibrium population distributions with those determined from molecular dynamics. This comparison is performed for the fully-delineated surfaces (KCl)5 and Ar9 to evaluate model performance for potential surfaces with long- and short-range interactions, respectively. For each system, several models perform better than a simple harmonic approximation. While no model gives acceptable results for all minima, and optimal modeling strategies differ for (KCl)5 and Ar9, a particular one-parameter model gives the best agreement with simulation for both systems. We then construct master equations from these models and compare their isothermal relaxation predictions for (KCl)5 and Ar9 with molecular dynamics simulations. This is the first comprehensive test of the kinetic performance of partition function models of its kind. Our results show that accurate modeling of transition-state partition functions is more important for (KCl)5 than for Ar9 in reproducing simulation results, due to a marked stiffening anharmonicity in the transition-state normal modes of (KCl)5. For both systems, several models yield qualitative agreement with simulation over a large temperature range. To examine the robustness of the master equation when applied to larger systems, for which full topographical descriptions would be either impossible or infeasible, we compute relaxation predictions for Ar11 using a master equation

  8. Slab flattening, dynamic topography and normal faulting in the Cordillera Blanca region (northern Peru)

    NASA Astrophysics Data System (ADS)

    Margirier, A.; Robert, X.; Laurence, A.; Gautheron, C.; Bernet, M.; Simon-Labric, T.; Hall, S. R.

    2015-12-01

    Processes driving surface uplift in the Andes are still debated and the role of subduction processes as slab flattening on surface uplift and relief building in the Andes is not well understood. Some of the highest Andean summits, the Cordillera Blanca (6768 m) and the Cordillera Negra (5187 m), are located above a present flat subduction zone (3-15°S), in northern Peru. In this area, both the geometry and timing of the flattening of the slab are well constrained (Gutscher et al., 1999; Rosenbaum et al., 2005). This region is thus a perfect target to explore the effect of slab flattening on the Andean topography and uplift. We obtained new apatite (U-Th)/He and fission-track ages from three vertical profiles located in the Cordillera Blanca and the Cordillera Negra. Time-temperature paths obtained from inverse modeling of the thermochronological data indicates a Middle Miocene cooling for both Cordillera Negra profiles. We interpret it as regional exhumation in the Cordillera Occidental starting in Middle Miocene, synchronous with the onset of the subduction of the Nazca ridge (Rosenbaum et al., 2005). We propose that the Nazca ridge subduction at 15 Ma and onset of slab flattening in northern Peru drove regional positive dynamic topography and thus enhanced exhumation in the Cordillera Occidental. This study provides new evidence of the impact subduction processes and associated dynamic topography on paleogeography and surface uplift in the Andes.

  9. Dynamic frequency-domain interferometer for absolute distance measurements with high resolution

    SciTech Connect

    Weng, Jidong; Liu, Shenggang; Ma, Heli; Tao, Tianjiong; Wang, Xiang; Liu, Cangli; Tan, Hua

    2014-11-15

    A unique dynamic frequency-domain interferometer for absolute distance measurement has been developed recently. This paper presents the working principle of the new interferometric system, which uses a photonic crystal fiber to transmit the wide-spectrum light beams and a high-speed streak camera or frame camera to record the interference stripes. Preliminary measurements of harmonic vibrations of a speaker, driven by a radio, and the changes in the tip clearance of a rotating gear wheel show that this new type of interferometer has the ability to perform absolute distance measurements both with high time- and distance-resolution.

  10. Noise-driven cooperative dynamics between vegetation and topography in riparian zones

    NASA Astrophysics Data System (ADS)

    Vesipa, Riccardo; Camporeale, Carlo; Ridolfi, Luca

    2016-04-01

    Riparian ecosystems exhibit complex biotic and abiotic dynamics, where the triad vegetation-sediments-stream determines the eco-geomorphological features of the river landscape. Random fluctuations of the water stage are a key trait of this triad, and a number of behaviors of the fluvial environment can be understood only taking into consideration the role of noise. In fact, in a given plot, vegetation biomass can grow (if the stage is below the plot elevation) or decay (if the stage is above the plot elevation). As a result, biomass exhibits significant temporal variations. In this framework, the capability of vegetation to alter the transect topography (namely, the plot elevation) is crucial. Vegetation can increase the plot elevation by a number of mechanisms (trapping of water- and wind-transported sediment particles, production of organic soil, stabilization of the soil surface). The increment of plot elevation induces the reduction of the plot-specific magnitude, frequency and duration of floods. These more favorable plot-specific hydrological conditions, in turn, induce an increment of biomass. Moreover, the higher the vegetation biomass, the higher the plot elevation increment induced by these mechanisms. In order to elucidate how the stochastically varying water stage and the vegetation-induced topographic alteration shape the bio-morphological characteristics of riparian transects, a stochastic model that takes into account the main links between vegetation, sediments and the stream was adopted. In particular, the capability of vegetation to alter the plot topography was emphasized. In modeling such interactions, the minimalistic approach was pursued. The complex vegetation-sediments-stream interactions were modeled by a set of state-depended stochastic eco-hydraulic equations. The probability density function of vegetation biomass was then analytically evaluated in any transect plot. This pdf strongly depends on the vegetation-topography feedback. We

  11. Frequency-scanning interferometry for dynamic absolute distance measurement using Kalman filter.

    PubMed

    Tao, Long; Liu, Zhigang; Zhang, Weibo; Zhou, Yangli

    2014-12-15

    We propose a frequency-scanning interferometry using the Kalman filtering technique for dynamic absolute distance measurement. Frequency-scanning interferometry only uses a single tunable laser driven by a triangle waveform signal for forward and backward optical frequency scanning. The absolute distance and moving speed of a target can be estimated by the present input measurement of frequency-scanning interferometry and the previously calculated state based on the Kalman filter algorithm. This method not only compensates for movement errors in conventional frequency-scanning interferometry, but also achieves high-precision and low-complexity dynamic measurements. Experimental results of dynamic measurements under static state, vibration and one-dimensional movement are presented. PMID:25503050

  12. Deployment dynamics of a simplified spinning IKAROS solar sail via absolute coordinate based method

    NASA Astrophysics Data System (ADS)

    Zhao, Jiang; Tian, Qiang; Hu, Hai-Yan

    2013-02-01

    The spinning solar sail of large scale has been well developed in recent years. Such a solar sail can be considered as a rigid-flexible multibody system mainly composed of a spinning central rigid hub, a number of flexible thin tethers, sail membranes, and tip masses. A simplified interplanetary kite-craft accelerated by radiation of the Sun (IKAROS) model is established in this study by using the absolute-coordinate-based (ACB) method that combines the natural coordinate formulation (NCF) describing the central rigid hub and the absolute nodal coordinate formulation (ANCF) describing flexible parts. The initial configuration of the system in the second-stage deployment is determined through both dynamic and static analyses. The huge set of stiff equations of system dynamics is solved by using the generalized-alpha method, and thus the deployment dynamics of the system can be well understood.

  13. Dynamic Passage of Topography Beneath the Southern Costa Rica Forearc seen with Seismic Stratigraphy

    NASA Astrophysics Data System (ADS)

    Edwards, J. H.; Kluesner, J. W.; Silver, E. A.

    2014-12-01

    3D seismic reflection data (CRISP) collected across the southern Costa Rica margin reveals that a thick, deforming sedimentary wedge underlies the younger slope sediments (Silver et al., this meeting). The older wedge material and younger slope sediments are separated by a high-amplitude regional unconformity. Seismic stratigraphy of the sedimentary strata overlying this regional unconformity reflects a dynamic deformation history of the margin. The younger slope sediments contain series of more localized unconformities, separating sedimentary units as thick as 1 km that reveal a dynamically changing set of inverted, overlapping basins. The geometry of these overlapping, inverted basins indicate sequential uplift events. The direction of basin thickening varies upsection, and these basins are cut by both thrust and normal faults and are deformed by folding. Structural development appears to be controlled by relief on the subducting plate interface, which induces uplift and subsidence and thereby controls the pattern of erosion and deposition. We interpret the evolution of these inverted stratigraphic packages as forming from subducting topography. Correlating these seismic-stratigraphic packages to recent drilling based on preliminary magnetostratigraphy from IODP site U1413 (Expedition 344 Scientists, 2013), allows us to date the passage of the subducting plate topography beginning ~2 Ma.

  14. Flight dynamics facility operational orbit determination support for the ocean topography experiment

    NASA Technical Reports Server (NTRS)

    Bolvin, D. T.; Schanzle, A. F.; Samii, M. V.; Doll, C. E.

    1991-01-01

    The Ocean Topography Experiment (TOPEX/POSEIDON) mission is designed to determine the topography of the Earth's sea surface across a 3 yr period, beginning with launch in June 1992. The Goddard Space Flight Center Dynamics Facility has the capability to operationally receive and process Tracking and Data Relay Satellite System (TDRSS) tracking data. Because these data will be used to support orbit determination (OD) aspects of the TOPEX mission, the Dynamics Facility was designated to perform TOPEX operational OD. The scientific data require stringent OD accuracy in navigating the TOPEX spacecraft. The OD accuracy requirements fall into two categories: (1) on orbit free flight; and (2) maneuver. The maneuver OD accuracy requirements are of two types; premaneuver planning and postmaneuver evaluation. Analysis using the Orbit Determination Error Analysis System (ODEAS) covariance software has shown that, during the first postlaunch mission phase of the TOPEX mission, some postmaneuver evaluation OD accuracy requirements cannot be met. ODEAS results also show that the most difficult requirements to meet are those that determine the change in the components of velocity for postmaneuver evaluation.

  15. Dynamic topography of visual evoked potentials and extrageniculate projection in case of Riddoch phenomenon.

    PubMed

    Tsutsui, J; Ichihashi, K; Kimura, H

    1984-01-01

    A 34-year-old woman showing the Riddoch phenomenon was studied by the technique of dynamic topography of visual evoked potential (VEP). This case had cortical blindness which developed during the process of massive intestinal hemorrhage, shock and surgery. The visual acuity was limited to hand movement, and perception of white and colored light was present, but there was no form recognition. Tracking eye movement for a flashlight was possible and optokinetic nystagmus (OKN) also appeared. CT-scan showed a diffuse low density area in the white matter of the occipital lobe. The VEPs by flash and a checkerboard of 60'-100' were detectable. Dynamic topography of the VEP showed that a strong negative deflection from the brainstem appeared at around 30 msec and this deflection expanded to the parietal region at about 90 msec. Subsequently, a positive deflection extending from the frontal region to the occipital region continued at 100 msec to 150 msec. Such a process of reaction is not observed in the normal subject. These findings suggest that the visual reaction was conducted abnormally through the extrageniculate system; from the brainstem to the parietal area and then to the occipital area. PMID:6748358

  16. Separation of dynamic and isostatic components of the Venusian gravity and topography and determination of the crustal thickness of Venus

    NASA Astrophysics Data System (ADS)

    Yang, An; Huang, Jinshui; Wei, Daiyun

    2016-09-01

    Assuming that the long-wavelength geoid and topography of Venus are supported by both mantle convection and Airy isostasy, we propose a method to separate the dynamic and isostatic components of the Venusian gravity and topography with the aid of the dynamic admittance from numerical models of mantle convection and the isostatic admittance from an Airy isostatic model. The global crustal thickness is then calculated based on the isostatic component of the gravity and topography. The results show that some highland plateaus such as Ishtar Terra and Ovda Regio have thick crust, which are largely supported by isostatic compensation. Other highland plateaus such as Thetis and Phoebe Regiones appear to have superimposed contributions from crustal thickening and dynamic support. Volcanic rises such as Atla and Beta Regiones have thin crust, which is consistent with the postulation that these volcanic rises are mainly the products of dynamic uplift caused by mantle plumes.

  17. Modelling and Estimation of Dynamic Ocean Topography Within Global Geopotential Solutions

    NASA Technical Reports Server (NTRS)

    Lemoine, Frank G.; Pavlis, Nikolaos; Wang, Y. M.; Cox, C. M.

    1998-01-01

    In this poster, we will present a report on the ongoing investigation "Improved Gravitational and Dynamic Height Models Through the use of Oceanographic Data." we have used a two year mean (1993-1994) of the Dynamic ocean Topography (DOT) field implied by the Semtner and Chervin POCM_4B model, and developed normal equations in surface spherical harmonics to degree and order 30. These normal equations, were combined with normal equations derived from TOPEX and ERS-1 altimeter data over the same time period. Combination solutions (based on satellite tracking data, altimeter data, surface gravity data and OCM data) were were developed Test solutions were obtained estimating the DOT field to 2Ox2O and 3ox3O. These solutions were tested with independent DOT values computed over 38 WOCE hydrographic sections, which contained a total of 3072 stations and represented 216000 km of travelled lines. The weighted standard deviation of the differences between the DOT obtained from the hydrographic data and and the field estimated from the joint combination solutions was computed for each of the test models, the weighted standard deviation for the baseline combination solution excluding the POCM4_B data was 9.7 cm for a DOT solution to 30x30, where introducing the POCM4_B data into the combination model reduced the standard deviation to 9.2 cm, indicating the the introduction of oceanographic information benefits the solution for the dynamic ocean topography. We will discuss the weighting schemes applied and the method of solution. Another aspect of our investigation involves testing alternate parametric representations of the dynamic height field. We looked at the alternative representations in terms of the Proudman functions (PF), and compared these to the use of spherical harmonics (SH) to represent the dynamic ocean topography, using once again the 1993 and 1994 output of the POCM4_B OCM as the reference model. A significant advantage of PF's over SH's is that the former

  18. Lithosphere Structure in Southern Africa: Mantle Density, Dynamic Topography, Moho Sharpness, and Kimberlite Magmatism

    NASA Astrophysics Data System (ADS)

    Artemieva, I. M.; Vinnik, L. P.

    2015-12-01

    In southern Africa, both the Archean and Proterozoic blocks have the topography 500-700 m higher than in any other craton worldwide, except for the Tanzanian craton. An unusually high topography may be caused by a low density of the cratonic lithospheric mantle and/or by the dynamic support of the mantle with origin below the depth of isostatic compensation (assumed to be at the lithosphere base). We use free-board constraints to examine the relative contributions of the both factors to surface topography in the cratons of southern Africa and present regional model of density structure of the lithospheric mantle. The results indicate that 0.5-1.0 km of topography requires the dynamic contribution from the sublithospheric mantle because it cannot be explained by the lithosphere structure within the petrologically permitted range of mantle densities. The calculated lithospheric mantle density values are in an overall agreement with xenolith-based data and show an overall trend in mantle density increase from Archean to younger lithospheric terranes. Notable exceptions are the Limpopo belt and the Bushveld Intrusion Complex, which have an increased mantle density, probably as a result of melt-metasomatism. The Western Cape Fold Belt has a moderately depleted mantle with density within the range expected for Phanerozoic mantle, while mantle densities beneath the Eastern Cape Fold Belt require the presence of a significant amount of eclogite in the mantle. Mantle density structure correlates with distribution of kimberlites and with seismic velocity contrast across the Moho: kimberlite-rich regions have sharp Moho and low-density (3.32-3.33 g/cc) mantle, while kimberlite-poor regions have transient Moho and denser mantle (3.34-3.35 g/cc). We explain this pattern by melt-metasomatism which affects both mantle depletion and the Moho sharpness. We also find that regions with high mantle density host non-diamondiferous kimberlites, while diamondiferous kimberlites are

  19. The eustatic chimera: isn't the Cenomanian maximum flood a dynamic topography puzzle?

    NASA Astrophysics Data System (ADS)

    Ostanciaux, E.; Robin, C.; Guillocheau, F.; Trotin, G.; Husson, L.

    2012-04-01

    More and more, dynamic topography is predicted to seriously control sea level, which challenges the concept of eustasy, but field evidence are sparse. In order to evaluate the space and time evolution of relative sea level variations, we made paleogeographic reconstructions for three consecutive stages around the presumed Cenomanian maximum flood. For that purpose, we compiled stratigraphic charts and existing paleogeographic maps to reconstruct shorelines at a global scale and infer transgressive and regressive phases. The Cenomanian transgressive phase is essentially present around the Tethys, whereas regression prevails at higher latitudes. Furthermore, diachronicity accompanies the presumed sea level high, for the trend reverses between the three stages in the northern hemisphere while it further subsides in the southern one. These reconstructions therefore suggest that an evolving degree two structure of uplift and subsidence may be more endemic of this period than uniform sea level change and thus, they better recall internal dynamics than eustasy. Indeed, flooding accompanies the Tethyan subduction zone, while regressions are located above spreading oceans. We interpret relative sea level change during the late Cretaceous as the traces of the negative dynamic subsidence above the Tehyan slab in the one hand, and in the other hand of the superplumes (African in particular) that lead to the breakup of the Atlantic. We further confront our results to the predictions of Steinberger, who provides estimates of dynamic topography since the latest Albian. We conformably observe, for instance, positive anomalies in North America, in the Baltic area, or in South Africa, but the model mostly fails to predict the observe diachronicity in vertical ground motion.

  20. Dynamic sea surface topography, gravity and improved orbit accuracies from the direct evaluation of SEASAT altimeter data

    NASA Technical Reports Server (NTRS)

    Marsh, J. G.; Lerch, F.; Koblinsky, C. J.; Klosko, S. M.; Robbins, J. W.; Williamson, R. G.; Patel, G. B.

    1989-01-01

    A method for the simultaneous solution of dynamic ocean topography, gravity and orbits using satellite altimeter data is described. A GEM-T1 based gravitational model called PGS-3337 that incorporates Seasat altimetry, surface gravimetry and satellite tracking data has been determined complete to degree and order 50. The altimeter data is utilized as a dynamic observation of the satellite's height above the sea surface with a degree 10 model of dynamic topography being recovered simultaneously with the orbit parameters, gravity and tidal terms in this model. PGS-3337 has a geoid uncertainty of 60 cm root-mean-square (RMS) globally, with the uncertainty over the altimeter tracked ocean being in the 25 cm range. Doppler determined orbits for Seasat, show large improvements, with the sub-30 cm radial accuracies being achieved. When altimeter data is used in orbit determination, radial orbital accuracies of 20 cm are achieved. The RMS of fit to the altimeter data directly gives 30 cm fits for Seasat when using PGS-3337 and its geoid and dynamic topography model. This performance level is two to three times better than that achieved with earlier Goddard earth models (GEM) using the dynamic topography from long-term oceanographic averages. The recovered dynamic topography reveals the global long wavelength circulation of the oceans with a resolution of 1500 km. The power in the dynamic topography recovery is now found to be closer to that of oceanographic studies than for previous satellite solutions. This is attributed primarily to the improved modeling of the geoid which has occurred. Study of the altimeter residuals reveals regions where tidal models are poor and sea state effects are major limitations.

  1. Multiscale Reactive Molecular Dynamics for Absolute pK a Predictions and Amino Acid Deprotonation.

    PubMed

    Nelson, J Gard; Peng, Yuxing; Silverstein, Daniel W; Swanson, Jessica M J

    2014-07-01

    Accurately calculating a weak acid's pK a from simulations remains a challenging task. We report a multiscale theoretical approach to calculate the free energy profile for acid ionization, resulting in accurate absolute pK a values in addition to insights into the underlying mechanism. Importantly, our approach minimizes empiricism by mapping electronic structure data (QM/MM forces) into a reactive molecular dynamics model capable of extensive sampling. Consequently, the bulk property of interest (the absolute pK a) is the natural consequence of the model, not a parameter used to fit it. This approach is applied to create reactive models of aspartic and glutamic acids. We show that these models predict the correct pK a values and provide ample statistics to probe the molecular mechanism of dissociation. This analysis shows changes in the solvation structure and Zundel-dominated transitions between the protonated acid, contact ion pair, and bulk solvated excess proton. PMID:25061442

  2. Age distributions and dynamically changing hydrologic systems: Exploring topography-driven flow

    NASA Astrophysics Data System (ADS)

    Gomez, J. D.; Wilson, J. L.

    2013-03-01

    Natural systems are driven by dynamic forcings that change in time as well as space, behavior that is inherited by the system flow field and results in time-varying age distributions (ADs). This work presents a review of the mathematical tools and solution approaches used to model ADs in dynamic time-varying flow systems. A simple conceptual, numerical model is then used to explore the role of flow dynamics in ADs for topography-driven flow systems. This model is an analog for regional groundwater systems and hyporheic zones. This model demonstrates that relatively small fluctuations in the forcing, even though importantly affecting the flow in the system, can have minimal effects in ADs. However, as the intensity of fluctuation increases, still within the bounds observed in natural systems, ADs in shallow parts of the system become highly sensitive to dynamic flow conditions, leading to considerable changes in the moments and modality of the distributions with time. In particular, transient flow can lead to emergence of new modes in the AD, which would not be present under steady flow conditions. The discrepancy observed between ADs under steady and transient flow conditions is explained by enhancement of mixing due to temporal variations in the flow field. ADs in deeper parts of the system are characterized by multimodality and tend to be more stable over time even for large forcing fluctuations.

  3. Anomalous Subsidence at Rifted Continental Margins: Distinguishing Mantle Dynamic Topography from Anomalous Oceanic Crustal Thickness

    NASA Astrophysics Data System (ADS)

    Cowie, L.; Kusznir, N. J.

    2012-12-01

    It has been proposed that some continental rifted margins have anomalous subsidence histories and that at breakup they were elevated at shallower bathymetries than the isostatic response of classical rift models (McKenzie 1978) would predict. The existence of anomalous syn or post breakup subsidence of this form would have important implications for our understanding of the geodynamics of continental breakup and rifted continental margin formation, margin subsidence history and the evolution of syn and post breakup depositional systems. We have investigated three rifted continental margins; the Gulf of Aden, Galicia Bank and the Gulf of Lions, to determine whether the oceanic crust in the ocean-continent transition of these margins has present day anomalous subsidence and if so, whether it is caused by mantle dynamic topography or anomalous oceanic crustal thickness. Residual depth anomalies (RDA) corrected for sediment loading, using flexural backstripping and decompaction, have been calculated by comparing observed and age predicted oceanic bathymetries in order to identify anomalous oceanic bathymetry and subsidence at these margins. Age predicted bathymetric anomalies have been calculated using the thermal plate model predictions from Crosby & McKenzie (2009). Non-zero sediment corrected RDAs may result from anomalous oceanic crustal thickness with respect to the global average, or from mantle dynamic uplift. Positive RDAs may result from thicker than average oceanic crust or mantle dynamic uplift; negative RDAs may result from thinner than average oceanic crust or mantle dynamic subsidence. Gravity inversion incorporating a lithosphere thermal gravity anomaly correction and sediment thickness from 2D seismic data has been used to determine Moho depth and oceanic crustal basement thickness. The reference Moho depths used in the gravity inversion have been calibrated against seismic refraction Moho depths. The gravity inversion crustal basement thicknesses

  4. The Effect of Surface Topography on the Nonlinear Dynamics of Rossby Waves

    NASA Technical Reports Server (NTRS)

    Abarzhi, S. I.; Desjardins, O.; Pitsch, H.

    2003-01-01

    Boussinesq convection in rotating systems attracts a sustained attention of the fluid dynamics community, because it has intricate non-linear dynamics (Cross & Hohenberg 1993) and plays an important role in geophysical and astrophysical applications, such as the motion of the liquid outer core of Earth, the Red Spot in Jupiter, the giant cells in the Sun etc. (Alridge et al. 1990). A fundamental distinction between the real geo- and astrophysical problems and the idealized laboratory studies is that natural systems are inhomogeneous (Alridge et al. 1990). Heterogeneities modulate the flow and influence significantly the dynamics of convective patterns (Alridge et al. 1990; Hide 1971). The effect of modulations on pattern formation and transition to turbulence in Boussinesq convection is far from being completely understood (Cross & Hohenberg 1993; Aranson & Kramer 2002). It is generally accepted that in the liquid outer core of the Earth the transport of the angular momentum and internal heat occurs via thermal Rossby waves (Zhang et al. 2001; Kuang & Bloxham 1999). These waves been visualized in laboratory experiments in rotating liquid-filled spheres and concentric spherical shells (Zhang et al. 2001; Kuang & Bloxham 1999). The basic dynamical features of Rossby waves have been reproduced in a cylindrical annulus, a system much simpler than the spherical ones (Busse & Or 1986; Or & Busse 1987). For convection in a cylindrical annulus, the fluid motion is two-dimensional, and gravity is replaced by a centrifugal force, (Busse & Or 1986; Or & Busse 1987). Hide (1971) has suggested that the momentum and heat transport in the core might be influenced significantly by so-called bumps, which are heterogeneities on the mantle-core boundary. To model the effect of surface topography on the transport of momentum and energy in the liquid outer core of the Earth, Bell & Soward (1996), Herrmann & Busse (1998) and Westerburg & Busse (2001) have studied the nonlinear dynamics

  5. Advances in large-scale ocean dynamics from a decade of satellite altimetric measurement of ocean surface topography

    NASA Technical Reports Server (NTRS)

    Fu, L. L.; Menard, Y.

    2002-01-01

    The past decade has seen the most intensive observations of the global ocean surface topography from satellite altimeters. The Joint U.S./France TOPEX/Poseidon (T/P) Mission has become the longest radar mission ever flown in space, providing the most accurate measurements for the study of ocean dynamics since October 1992.

  6. Mantle flow and dynamic topography associated with slab window opening: Insights from laboratory models

    NASA Astrophysics Data System (ADS)

    Guillaume, Benjamin; Moroni, Monica; Funiciello, Francesca; Martinod, Joseph; Faccenna, Claudio

    2010-12-01

    We present dynamically self-consistent mantle-scale laboratory models that have been conducted to improve our understanding of the influence of slab window opening on subduction dynamics, mantle flow and associated dynamic topography over geological time scales. The adopted setup consists of a two-layer linearly viscous system simulating the subduction of a fixed plate of silicone (lithosphere) under negative buoyancy in a viscous layer of glucose syrup (mantle). Our experimental setting is also characterized by a constant-width rectangular window located at the center of a laterally confined slab, modeling the case of the interaction of a trench-parallel spreading ridge with a wide subduction zone. We found that the opening of a slab window does not produce consistent changes of the geometry and the kinematics of the slab. On the contrary, slab-induced mantle circulation, quantified both in the vertical and horizontal sections using the Feature Tracking image analysis technique, is strongly modified. In particular, rollback subduction and the opening of the slab window generate a complex mantle circulation pattern characterized by the presence of poloidal and toroidal components, with the importance of each evolving according to kinematic stages. Mantle coming from the oceanic domain floods through the slab window, indenting the supra-slab mantle zone and producing its deformation without any mixing between mantle portions. The opening of the slab window and the upwelling of sub-slab mantle produce a regional-scale non-isostatic topographic uplift of the overriding plate that would correspond to values ranging between ca. 1 and 5 km in nature. Assuming that our modeling results can be representative of the natural behavior of subduction zones, we compared them to the tectonics and volcanism of the Patagonian subduction zone. We found that the anomalous backarc volcanism that has been developing since the middle Miocene could result from the lateral flow of sub

  7. Complex dynamic substrate control: Dual-tone hydrogel photoresists allow double-dissociation of topography and modulus

    PubMed Central

    Xue, Changying; Wong, Darice

    2014-01-01

    Hydrogels are widely utilized as artificial extracellular matrices, but current materials are unable to completely recapitulate the geometric, mechanical and dynamic characteristics of natural tissues. Here, we report an approach to dynamically tune both topography and elasticity in a single photoresponsive hydrogel substrate. Upon exposure to spatially controlled doses of light, a topographically and mechanically micropatterned surface forms. Atomic force microscopy was used to investigate changes in topographical feature size and elastic moduli of the hydrogel surface as a function of irradiation time and wavelength. These photodegradable hydrogels can act as both positive and pseudo-negative photoresists, depending on exposure time and wavelength. By carefully controlling the aspect ratio (surface area to depth) of micropatterned features, unique swelling-induced ordered microstructures can be formed on the surface. These dual-tone hydrogel photoresists therefore allow dynamic tunability in both topography and elasticity, enabling the fabrication of complex and anisotropic biomaterials. PMID:24339260

  8. Contact dynamics of elasto-plastic thin beams simulated via absolute nodal coordinate formulation

    NASA Astrophysics Data System (ADS)

    Wang, Qing-Tao; Tian, Qiang; Hu, Hai-Yan

    2015-12-01

    Under the frame of multibody dynamics, the contact dynamics of elasto-plastic spatial thin beams is numerically studied by using the spatial thin beam elements of absolute nodal coordinate formulation (ANCF). The internal force of the elasto-plastic spatial thin beam element is derived under the assumption that the plastic strain of the beam element depends only on its longitudinal deformation. A new body-fixed local coordinate system is introduced into the spatial thin beam element of ANCF for efficient contact detection in the contact dynamics simulation. The linear isotropic hardening constitutive law is used to describe the elasto-plastic deformation of beam material, and the classical return mapping algorithm is adopted to evaluate the plastic strains. A multi-zone contact approach of thin beams previously proposed by the authors is also introduced to detect the multiple contact zones of beams accurately, and the penalty method is used to compute the normal contact force of thin beams in contact. Four numerical examples are given to demonstrate the applicability and effectiveness of the proposed elasto-plastic spatial thin beam element of ANCF for flexible multibody system dynamics.

  9. Contact dynamics of elasto-plastic thin beams simulated via absolute nodal coordinate formulation

    NASA Astrophysics Data System (ADS)

    Wang, Qing-Tao; Tian, Qiang; Hu, Hai-Yan

    2016-06-01

    Under the frame of multibody dynamics, the contact dynamics of elasto-plastic spatial thin beams is numerically studied by using the spatial thin beam elements of absolute nodal coordinate formulation (ANCF). The internal force of the elasto-plastic spatial thin beam element is derived under the assumption that the plastic strain of the beam element depends only on its longitudinal deformation. A new body-fixed local coordinate system is introduced into the spatial thin beam element of ANCF for efficient contact detection in the contact dynamics simulation. The linear isotropic hardening constitutive law is used to describe the elasto-plastic deformation of beam material, and the classical return mapping algorithm is adopted to evaluate the plastic strains. A multi-zone contact approach of thin beams previously proposed by the authors is also introduced to detect the multiple contact zones of beams accurately, and the penalty method is used to compute the normal contact force of thin beams in contact. Four numerical examples are given to demonstrate the applicability and effectiveness of the proposed elasto-plastic spatial thin beam element of ANCF for flexible multibody system dynamics.

  10. GOCE++ Dynamical Coastal Topography and tide gauge unification using altimetry and GOCE.

    NASA Astrophysics Data System (ADS)

    Baltazar Andersen, Ole; Knudsen, Per; Nielsen, Karina; Hughes, Chris; Woodworth, Phil; Woppelmann, Guy; Gravelle, Mederic; Bingham, Rory; Fenoblio, Luciana; Kern, Michael

    2016-04-01

    ESA has recently released a study on the potential of ocean levelling as a novel approach to the study of height system unification taking the recent development in geoid accuracy trough GOCE data into account. The suggested investigation involves the use of measurements and modelling to estimate Mean Dynamic Topography (MDT) of the ocean along a coastline which contributes/requires reconciling altimetry, tide gauge and vertical land motion. The fundamental use of the MDT computed using altimetry, ocean models or through the use of tide gauges has values of between -2 and +1 meters at different points in the ocean. However, close to the coast the determination of the MDT is problematic due to i.e., the altimeter footprint, land motion or parameterization/modelling of coastal currents. The objective of this activity is to perform a consolidated and improved understanding and modelling of coastal processes and physics responsible for sea level changes on various temporal/spatial scales. The study runs from October 2015 to march 2017 and involves elements like: Develop an approach to estimate a consistent DT at tide gauges, coastal areas, and open ocean; Validate the approach in well-surveyed areas where DT can be determined at tide gauges; Determine a consistent MDT using GOCE with consistent error covariance fields; Connect measurements of a global set of tide gauges and investigate trends

  11. New clinical instrument for the early detection of cataract using dynamic light scattering and corneal topography

    NASA Astrophysics Data System (ADS)

    Ansari, Rafat R.; Datiles, Manuel B., III; King, James F.

    2000-06-01

    A growing cataract can be detected at the molecular level using the technique of dynamic light scattering (DLS). However, the success of this method in clinical use depends upon the precise control of the scattering volume inside a patient's eye and especially during patient's repeat visits. This is important because the scattering volume (cross-over region between the scattered light and incident light) inside the eye in a high-quality DLS set-up is very small (few microns in dimension). This precise control holds the key for success in the longitudinal studies of cataract and during anti-cataract drug screening. We have circumvented these problems by fabricating a new DLS fiber optic probe with a working distance of 40 mm and by mounting it inside a cone of a corneal analyzer. This analyzer is frequently used in mapping the corneal topography during PRK (photorefractive keratectomy) and LASIK (laser in situ keratomileusis) procedures in shaping of the cornea to correct myopia. This new instrument and some preliminary clinical tests on one of us (RRA) showing the data reproducibility are described.

  12. Global mean dynamic topography based on GOCE data and Wiener filters

    NASA Astrophysics Data System (ADS)

    Gilardoni, Maddalena; Reguzzoni, Mirko; Albertella, Alberta

    2015-04-01

    A mean dynamic ocean topography (MDT) has been computed by using a GOCE-only gravity model and a given mean sea surface (MSS) obtained from satellite altimetry. Since the used gravity model, i.e. the fifth release of the time-wise solution covering the full mission lifetime, is truncated at a maximum harmonic degree of 280, the obtained MDT has to be consistently filtered. This has been done globally by using the spherical harmonic representation and following a Wiener minimization principle. This global filtering approach is convenient from the computational point of view but requires to have MDT values all over the Earth surface and therefore to fill the continents with fictitious data. The main improvements with respect to the already presented results are in the MDT filling procedure (to guarantee that the global signal has the same covariance of the one over the oceans), in the error modelling of the input MSS and in the error estimation of the filtered MDT and of the corresponding geostrophic velocities. The impact of GOCE data in the ocean circulation global modelling has been assessed by comparing the pattern of the obtained geostrophic currents with those computed by using EGM2008. Comparisons with independent circulation data based on drifters and other MDT models have been also performed with the aim of evaluating the accuracy of the obtained results.

  13. Geopotential Model Improvement Using POCM_4B Dynamic Ocean Topography Information: PGM2000A

    NASA Technical Reports Server (NTRS)

    Pavlis, N. K.; Chinn, D. S.; Cox, C. M.; Lemoine, Frank G.; Smith, David E. (Technical Monitor)

    2000-01-01

    The two-year mean (1993-1994) Dynamic Ocean Topography (DOT) field implied by the POCM_4B circulation model was used to develop normal equations for DOT, in a surface spherical harmonic representation. These normal equations were combined with normal equations from satellite tracking data, surface gravity data, and altimeter data from TOPEX/Poseidon and ERS-1. Several least-squares combination solutions were developed in this fashion, by varying parameters such as the maximum degree of the estimated DOT and the relative weights of the different data. The solutions were evaluated in terms of orbit fit residuals, GPS/Leveling-derived undulations, and independent DOT information from in situ WOCE hydrographic data. An optimal solution was developed in this fashion which was originally presented at the 1998 EGS meeting in Nice, France. This model, designated here PGM2000A, maintains the orbit and land geoid modeling performance of EGM96, while improving its marine geoid modeling capability. In addition, PGM2000A's error spectrum is considerably more realistic than those of other contemporary gravitational models and agrees well with the error spectrum of EGM96. We will present the development and evaluation of PGM2000A, with particular emphasis on the weighting of the DOT information implied by POCM_4B. We will also present an inter-comparison of PGM2000A with the GRIM5-C1 and TEG-4 models. Directions for future work and problematic areas will be identified.

  14. Video Animation of Ocean Topography From TOPEX/POSEIDON

    NASA Technical Reports Server (NTRS)

    Fu, Lee-Lueng; Leconte, Denis; Pihos, Greg; Davidson, Roger; Kruizinga, Gerhard; Tapley, Byron

    1993-01-01

    Three video loops showing various aspects of the dynamic ocean topography obtained from the TOPEX/POSEIDON radar altimetry data will be presented. The first shows the temporal change of the global ocean topography during the first year of the mission. The time-averaged mean is removed to reveal the temporal variabilities. Temporal interpolation is performed to create daily maps for the animation. A spatial smoothing is also performed to retain only the large-sale features. Gyre-scale seasonal changes are the main features. The second shows the temporal evolution of the Gulf Stream. The high resolution gravimetric geoid of Rapp is used to obtain the absolute ocean topography. Simulated drifters are used to visualize the flow pattern of the current. Meanders and rings of the current are the main features. The third is an animation of the global ocean topography on a spherical earth. The JGM-2 geoid is used to obtain the ocean topography...

  15. Retrodicting the Cenozoic evolution of the mantle: Implications for dynamic surface topography

    NASA Astrophysics Data System (ADS)

    Glišović, Petar; Forte, Alessandro; Rowley, David; Simmons, Nathan; Grand, Stephen

    2014-05-01

    Seismic tomography is the essential starting ingredient for constructing realistic models of the mantle convective flow and for successfully predicting a wide range of convection-related surface observables. However, the lack of knowledge of the initial thermal state of the mantle in the geological past is still an outstanding problem in mantle convection. The resolution of this problem requires models of 3-D mantle evolution that yield maximum consistency with a wide suite of geophysical constraints. Quantifying the robustness of the reconstructed thermal evolution is another major concern. We have carried out mantle dynamic simulations (Glišović & Forte, EPSL 2014) using a pseudo-spectral solution for compressible-flow thermal convection in 3-D spectral geometry that directly incorporate: 1) joint seismic-geodynamic inversions of mantle density structure with constraints provided by mineral physics data (Simmons et al., GJI 2009); and 2) constraints on mantle viscosity inferred by inversion of a suite of convection-related and glacial isostatic adjustment data sets (Mitrovica & Forte, EPSL 2004) characterised by Earth-like Rayleigh numbers. These time-reversed convection simulations reveal how the buoyancy associated with hot, active upwellings is a major driver of the mantle-wide convective circulation and the changes in dynamic topography at the Earth's surface. These simulations reveal, for example, a stable and long-lived superplume under the East Pacific Rise (centred under the Easter and Pitcairn hotspots) that was previously identified by Rowley et al. (AGU 2011, Nature in review) on the basis of plate kinematic data. We also present 65 Myr reconstructions of the Reunion plume that gave rise to the Deccan Traps.

  16. The Interplay Between Conformation and Absolute Configuration in Chiral Electron Dynamics of Small Diols.

    PubMed

    Daly, Steven; Tia, Maurice; Garcia, Gustavo A; Nahon, Laurent; Powis, Ivan

    2016-09-01

    A competition between chiral characteristics alternatively attributable to either conformation or to absolute configuration is identified. Circular dichroism associated with photoexcitation of the outer orbital of configurational enantiomers of 1,3- and 2,3-butanediols has been examined with a focus on the large changes in electron chiral asymmetry produced by different molecular conformations. Experimental gas-phase measurements offer support for the theoretical modeling of this chiroptical effect. A surprising prediction is that a conformationally produced pseudo-enantiomerism in 1,3-butanediol generates a chiral response in the frontier electron dynamics that outweighs the influence of the permanent configurational handedness established at the asymmetrically substituted carbon. Induced conformation, and specifically induced conformational chirality, may thus be a dominating factor in chiral molecular recognition in such systems. PMID:27445202

  17. Recognising the Different Roles and Expressions of Dynamic Mantle Flow and Plate Kinematics in the Evolution of Africa's Topography

    NASA Astrophysics Data System (ADS)

    Brown, R. W.; Wildman, M.; Beucher, R.; Chardon, D.; Rouby, D.; Stuart, F. M.; Persano, C.

    2014-12-01

    Continental elevation can be partitioned into contributions from intrinsic isostatic buoyancy forces arising from thermal, compositional and thickness variations within the crust or lithosphere and external geodynamic forces. External forces include horizontal in-plane stress and vertical forces arising from convection within the deep mantle giving rise to dynamic uplift of Earth's surface. In essence both of these are ultimately expressions of the energy driving and/or contained within the convecting lithosphere-mantle system, and so are not really separate, but their expression in the topography at the surface is often quite different. The term dynamic uplift refers to topography that is supported by the vertical stresses arising from the upward viscous flow of mantle impinging on the base of the lithosphere, and it is typically regional in extent. In recent years the importance of dynamic uplift as a major control on continental topography has been emphasised by the advances in seismology and progress in understanding the structure of the shallow as well as deep mantle. However, the difficulty of quantifying surface uplift within non-orogenic regions has hampered progress in understanding how continental topography reacts to the competing interaction between mantle process creating the topography and surface processes that destroy it. Any geomorphic response, and the resulting erosion or sedimentary signal related to these uplift events, is strongly filtered through the response times of surface processes that are responding to relatively small changes in surface gradient. But with care, the erosional history, measured over large areas, can monitor the evolution of continental scale topography and this can be very effectively measured at appropriate temporal and spatial scales using low temperature thermochronometry. This approach, combined with analysis of the offshore sedimentary record around southern Africa, has proved to be very effective at documenting the

  18. Reconcile Mantle Dynamic Models with Compositionally Distinct and Stable LLSVPs with the Observations of the Geoid and Dynamic Topography

    NASA Astrophysics Data System (ADS)

    Liu, X.; Zhong, S.

    2015-12-01

    The geoid has been well explained in mantle flow models with the buoyancy inferred from seismic models that in turn place constraints on mantle viscosity structure (e.g., Hager & Richards, 1989). These models often assume a whole-mantle convection with uniform composition and 1-D viscosity. However, seismic and geochemical observations suggest possible existence of chemically distinct piles under Africa and Pacific which extends hundreds of kilometers above the CMB (i.e., LLSVPs). As compositional heterogeneity would significantly alter the interpretation of seismic anomalies as buoyancy structure, important questions are whether a thermochemical mantle model based on seismic velocity anomalies can reconcile the geoid and how this may impact inference of mantle viscosity structure. In this study, we formulate mantle flow models that use buoyancy derived from seismic model S40RTS (Ritsema et al., 2011), assuming that the LLSVPs are stable with negative buoyancy. The models use temperature-, depth- and composition-dependent viscosity and are computed for the geoid, dynamic topography and flow velocity using CitcomS. Seismic anomalies are converted to buoyancy using thermal conversion factor cT for the whole mantle materials and composition conversion factor cc for the chemical piles defined as the domains with seismic slow anomaly <-0.5% and a maximum height of 500 km. The temperature-dependence viscosity gives rise to 3 orders of magnitude variations in viscosity, and horizontally averaged viscosity profile is consistent with the inferred 1-D viscosity from the geoid. The viscosity in the chemical piles is further reduced by a factor of Cvisc to represent the compositional effect. We measure the stability of the chemical piles by the RMS vertical velocities on the piles boundary. Our preferred thermochemical models with stable chemical piles reach similar variance reduction of geoid at ~64% to that for the uniform composition models. In the preferred model, cT is ~0

  19. Absolute Binding Free Energy Calculations Using Molecular Dynamics Simulations with Restraining Potentials

    PubMed Central

    Wang, Jiyao; Deng, Yuqing; Roux, Benoît

    2006-01-01

    The absolute (standard) binding free energy of eight FK506-related ligands to FKBP12 is calculated using free energy perturbation molecular dynamics (FEP/MD) simulations with explicit solvent. A number of features are implemented to improve the accuracy and enhance the convergence of the calculations. First, the absolute binding free energy is decomposed into sequential steps during which the ligand-surrounding interactions as well as various biasing potentials restraining the translation, orientation, and conformation of the ligand are turned “on” and “off.” Second, sampling of the ligand conformation is enforced by a restraining potential based on the root mean-square deviation relative to the bound state conformation. The effect of all the restraining potentials is rigorously unbiased, and it is shown explicitly that the final results are independent of all artificial restraints. Third, the repulsive and dispersive free energy contribution arising from the Lennard-Jones interactions of the ligand with its surrounding (protein and solvent) is calculated using the Weeks-Chandler-Andersen separation. This separation also improves convergence of the FEP/MD calculations. Fourth, to decrease the computational cost, only a small number of atoms in the vicinity of the binding site are simulated explicitly, while all the influence of the remaining atoms is incorporated implicitly using the generalized solvent boundary potential (GSBP) method. With GSBP, the size of the simulated FKBP12/ligand systems is significantly reduced, from ∼25,000 to 2500. The computations are very efficient and the statistical error is small (∼1 kcal/mol). The calculated binding free energies are generally in good agreement with available experimental data and previous calculations (within ∼2 kcal/mol). The present results indicate that a strategy based on FEP/MD simulations of a reduced GSBP atomic model sampled with conformational, translational, and orientational restraining

  20. Implications for anomalous mantle pressure and dynamic topography from lithospheric stress patterns in the North Atlantic Realm

    NASA Astrophysics Data System (ADS)

    Schiffer, Christian; Nielsen, Søren Bom

    2016-08-01

    With convergent plate boundaries at some distance, the sources of the lithospheric stress field of the North Atlantic Realm are mainly mantle tractions at the base of the lithosphere, lithospheric density structure and topography. Given this, we estimate horizontal deviatoric stresses using a well-established thin sheet model in a global finite element representation. We adjust the lithospheric thickness and the sub-lithospheric pressure iteratively, comparing modelled in plane stress with the observations of the World Stress Map. We find that an anomalous mantle pressure associated with the Iceland and Azores melt anomalies, as well as topography are able to explain the general pattern of the principle horizontal stress directions. The Iceland melt anomaly overprints the classic ridge push perpendicular to the Mid Atlantic ridge and affects the conjugate passive margins in East Greenland more than in western Scandinavia. The dynamic support of topography shows a distinct maximum of c. 1000 m in Iceland and amounts <150 m along the coast of south-western Norway and 250-350 m along the coast of East Greenland. Considering that large areas of the North Atlantic Realm have been estimated to be sub-aerial during the time of break-up, two components of dynamic topography seem to have affected the area: a short-lived, which affected a wider area along the rift system and quickly dissipated after break-up, and a more durable in the close vicinity of Iceland. This is consistent with the appearance of a buoyancy anomaly at the base of the North Atlantic lithosphere at or slightly before continental breakup, relatively fast dissipation of the fringes of this, and continued melt generation below Iceland.

  1. Prediction of Seasonal to Inter-annual Hydro-climatology including the Effects of Vegetation Dynamics and Topography over Large River Basins

    NASA Astrophysics Data System (ADS)

    Bisht, G.; Narayan, U.; Bras, R. L.

    2008-12-01

    The goal of the proposed research is to enhance the predictability of hydrology and atmospheric conditions at daily, seasonal and inter-annual time scales. Capturing the interplay between seasonally dynamic vegetation and topography occurring through the local mechanisms of radiation and soil moisture re- distribution may contribute significantly towards increasing hydro-climatological predictability at fine spatio- temporal scales. We present a coupled model that improves the representation of vegetation dynamics with complex topography using the TIN (Triangulated Irregular Network)-based Real-time Integrated Basin Simulator (tRIBS) coupled with an advanced regional atmospheric model (WRF, Weather Research Forecasting). The tRIBS-WRF coupled model has been implemented in a parallel computing framework to allow fine scale simulations over large spatial domains for multi year time periods. The simulations have been carried out for a multi year period and we analyze the accuracy of predicted hydro-climatological variables such as monthly precipitation accumulation, soil moisture and vegetation (LAI, phenology) for different cases of (i) flat topography, prescribed vegetation (ii) real topography, prescribed vegetation (iii) flat topography, dynamic vegetation and (iv) real topography, dynamic vegetation. The simulations have been performed in a semi arid region in the South Western United States with the domain centered on a well-instrumented test basin - the Walnut Gulch Experimental Watershed. Energy balance as well as soil moisture measurements from the test basin are used to evaluate the simulations. We also use MODIS NDVI observations to evaluate the simulated vegetation spatio-temporal dynamics.

  2. Easy Absolute Values? Absolutely

    ERIC Educational Resources Information Center

    Taylor, Sharon E.; Mittag, Kathleen Cage

    2015-01-01

    The authors teach a problem-solving course for preservice middle-grades education majors that includes concepts dealing with absolute-value computations, equations, and inequalities. Many of these students like mathematics and plan to teach it, so they are adept at symbolic manipulations. Getting them to think differently about a concept that they…

  3. Absolute dosimetry on a dynamically scanned sample for synchrotron radiotherapy using graphite calorimetry and ionization chambers

    NASA Astrophysics Data System (ADS)

    Lye, J. E.; Harty, P. D.; Butler, D. J.; Crosbie, J. C.; Livingstone, J.; Poole, C. M.; Ramanathan, G.; Wright, T.; Stevenson, A. W.

    2016-06-01

    The absolute dose delivered to a dynamically scanned sample in the Imaging and Medical Beamline (IMBL) on the Australian Synchrotron was measured with a graphite calorimeter anticipated to be established as a primary standard for synchrotron dosimetry. The calorimetry was compared to measurements using a free-air chamber (FAC), a PTW 31 014 Pinpoint ionization chamber, and a PTW 34 001 Roos ionization chamber. The IMBL beam height is limited to approximately 2 mm. To produce clinically useful beams of a few centimetres the beam must be scanned in the vertical direction. In practice it is the patient/detector that is scanned and the scanning velocity defines the dose that is delivered. The calorimeter, FAC, and Roos chamber measure the dose area product which is then converted to central axis dose with the scanned beam area derived from Monte Carlo (MC) simulations and film measurements. The Pinpoint chamber measures the central axis dose directly and does not require beam area measurements. The calorimeter and FAC measure dose from first principles. The calorimetry requires conversion of the measured absorbed dose to graphite to absorbed dose to water using MC calculations with the EGSnrc code. Air kerma measurements from the free air chamber were converted to absorbed dose to water using the AAPM TG-61 protocol. The two ionization chambers are secondary standards requiring calibration with kilovoltage x-ray tubes. The Roos and Pinpoint chambers were calibrated against the Australian primary standard for air kerma at the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). Agreement of order 2% or better was obtained between the calorimetry and ionization chambers. The FAC measured a dose 3–5% higher than the calorimetry, within the stated uncertainties.

  4. Absolute dosimetry on a dynamically scanned sample for synchrotron radiotherapy using graphite calorimetry and ionization chambers.

    PubMed

    Lye, J E; Harty, P D; Butler, D J; Crosbie, J C; Livingstone, J; Poole, C M; Ramanathan, G; Wright, T; Stevenson, A W

    2016-06-01

    The absolute dose delivered to a dynamically scanned sample in the Imaging and Medical Beamline (IMBL) on the Australian Synchrotron was measured with a graphite calorimeter anticipated to be established as a primary standard for synchrotron dosimetry. The calorimetry was compared to measurements using a free-air chamber (FAC), a PTW 31 014 Pinpoint ionization chamber, and a PTW 34 001 Roos ionization chamber. The IMBL beam height is limited to approximately 2 mm. To produce clinically useful beams of a few centimetres the beam must be scanned in the vertical direction. In practice it is the patient/detector that is scanned and the scanning velocity defines the dose that is delivered. The calorimeter, FAC, and Roos chamber measure the dose area product which is then converted to central axis dose with the scanned beam area derived from Monte Carlo (MC) simulations and film measurements. The Pinpoint chamber measures the central axis dose directly and does not require beam area measurements. The calorimeter and FAC measure dose from first principles. The calorimetry requires conversion of the measured absorbed dose to graphite to absorbed dose to water using MC calculations with the EGSnrc code. Air kerma measurements from the free air chamber were converted to absorbed dose to water using the AAPM TG-61 protocol. The two ionization chambers are secondary standards requiring calibration with kilovoltage x-ray tubes. The Roos and Pinpoint chambers were calibrated against the Australian primary standard for air kerma at the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). Agreement of order 2% or better was obtained between the calorimetry and ionization chambers. The FAC measured a dose 3-5% higher than the calorimetry, within the stated uncertainties. PMID:27192396

  5. Dynamic localization and negative absolute conductance in terahertz driven semiconductor superlattices

    SciTech Connect

    Keay, B.J.; Allen, S.J.; Campman, K.L.

    1995-12-31

    We report the first observation of Negative Absolute Conductance (NAC), dynamic localization and multiphoton stimulated emission assisted tunneling in terahertz driven semiconductor superlattices. Theories predicting NAC in semiconductor superlattices subjected to AC electric fields have existed for twenty years, but have never been verified experimentally. Most theories are based upon semiclassical arguments and are only valid for superlattices in the miniband or coherent tunneling regime. We are not aware of models predicting NAC in superlattices in the sequential tunneling regime, although there has been recent theoretical work on double-barrier structures. Perhaps the most remarkable result is found in the power dependence of the current-voltage (I-V) characteristics near zero DC bias. As the laser power is increased the current decreases towards zero and then becomes negative. This result implies that the electrons are absorbing energy from the laser field, producing a net current in the direction opposite to the applied voltage. NAC around zero DC bias is a particularly surprising observation considering photon-assisted tunneling is not expected to be observable between the ground states of neighboring quantum wells in a semiconductor superlattice. Contrary to this believe our results are most readily attributable to photon absorption and multiphoton emission between ground states of neighboring wells. The I-V characteristics measured in the presence of terahertz radiation at low DC bias also contain steps and plateaus analogous to photon-assisted steps observed in superconducting junctions. As many as three steps have been clearly resolved corresponding to stimulated emission into the terahertz field by a three-photon process.

  6. A quantitative assessment of the depth sensitivity of an optical topography system using a solid dynamic tissue-phantom.

    PubMed

    Correia, Teresa; Banga, Anil; Everdell, N L; Gibson, Adam P; Hebden, Jeremy C

    2009-10-21

    A solid dynamic phantom with tissue-like optical properties is presented, which contains seven discrete targets impregnated with thermochromic pigment located at different depths from the surface. Changes in absorption are obtained in response to localized heating of the targets, simulating haemodynamic changes occurring in the brain and other tissues. The depth sensitivity of a continuous wave optical topography system was assessed successfully using the phantom. Images of the targets have been reconstructed using a spatially variant regularization, and the determined spatial localization in the depth direction is shown to be accurate within an uncertainty of about 3 mm down to a depth of about 30 mm. PMID:19794240

  7. A quantitative assessment of the depth sensitivity of an optical topography system using a solid dynamic tissue-phantom

    NASA Astrophysics Data System (ADS)

    Correia, Teresa; Banga, Anil; Everdell, N. L.; Gibson, Adam P.; Hebden, Jeremy C.

    2009-10-01

    A solid dynamic phantom with tissue-like optical properties is presented, which contains seven discrete targets impregnated with thermochromic pigment located at different depths from the surface. Changes in absorption are obtained in response to localized heating of the targets, simulating haemodynamic changes occurring in the brain and other tissues. The depth sensitivity of a continuous wave optical topography system was assessed successfully using the phantom. Images of the targets have been reconstructed using a spatially variant regularization, and the determined spatial localization in the depth direction is shown to be accurate within an uncertainty of about 3 mm down to a depth of about 30 mm.

  8. The Development of a Degree 360 Expansion of the Dynamic Ocean Topography of the POCM_4B Global Circulation Model

    NASA Technical Reports Server (NTRS)

    Rapp, Richard H.

    1998-01-01

    This paper documents the development of a degree 360 expansion of the dynamic ocean topography (DOT) of the POCM_4B ocean circulation model. The principles and software used that led to the final model are described. A key principle was the development of interpolated DOT values into land areas to avoid discontinuities at or near the land/ocean interface. The power spectrum of the POCM_4B is also presented with comparisons made between orthonormal (ON) and spherical harmonic magnitudes to degree 24. A merged file of ON and SH computed degree variances is proposed for applications where the DOT power spectrum from low to high (360) degrees is needed.

  9. Physical Parameters Controlling Subduction Dynamics and Surface Topography in Self-consistent Global Models of Mantle Convection

    NASA Astrophysics Data System (ADS)

    Crameri, F.; Pears, M. I.; Lithgow-Bertelloni, C. R.; Tackley, P. J.

    2014-12-01

    Recent advances in numerical modelling allow global models of mantle convection to realistically reproduce the behaviour at convergent plate boundaries (Crameri et al., 2012a). This allows for a more extensive study of subduction that, in contrast to the numerous regional models, incorporates the complete framework of mantle convection. Here, we focus on different aspects of mantle convection including (i) slab dip variations, (ii) variations in radial mantle viscosity, and (iii) the presence of localised mantle upwellings and discuss their control on the dynamics of Earth-like plate tectonics. Additionally, we present the effect these parameter variations have on measurable quantities like dynamic topography and plate velocity. The models are calculated by the finite-volume code Stag-YY (e.g., Tackley 2008) using a multi-grid method on a fully staggered grid. Second, the sticky-air method (Matsumoto and Tomoda 1983; Schmeling et al, 2008) is applied and thus approximates a free surface when the sticky-air parameters are chosen carefully (Crameri et al., 2012b). Overall, this study demonstrates the ability of various parameters to significantly influence both subduction dynamics and surface topography. REFERENCES Crameri, F., et al. (2012a), Geophys. Res. Lett., 39(3). Crameri, F., et al. (2012b), Geophys. J. Int., 189(1). Matsumoto, T., and Y. Tomoda (1983), J. Phys. Earth, 31(3). Schmeling, H., et al. (2008), Phys. Earth Planet. Int., 171(1-4). Tackley, P. J. (2008), Phys. Earth Planet. Int., 171(1-4).

  10. Structure and Dynamics of the Polar Regions of Mars from MGS Topography and Gravity

    NASA Technical Reports Server (NTRS)

    Zuber, Maria T.; Smith, David E.; Neumann, Gregory A.; Lemoine, Frank G.

    2000-01-01

    The Mars Global Surveyor (MGS) spacecraft has been engaged in systematic mapping of Mars since insertion into Mars orbit in September, 1997. The objectives of the MGS mission are to globally map Mars as well as to quantify seasonal changes on the planet. MGS geophysical/geodetic observations of topography from the Mars Orbiter Laser Altimeter (MOLA) and gravity from the Radio Science investigation are providing significant new insights on both static and time-varying aspects of the polar regions of Mars. These observations have implications for polar processes on diurnal seasonal and climatic timescales. Thus far, MOLA has collected over 300 million precise measurements of Martian topography and cloud heights. The instrument has also provided measurements of the width of the backscattered optical pulse and of the 1064 nm reflectivity of the Martian surface and atmosphere. The along-track resolution of MOLA ground shots is approx. 300 m and the across-track spacing in the polar regions is a maximum of about four kilometers. The vertical accuracy of the topography is determined by the precision recovery of spacecraft orbits from the Radio Science investigation, which includes MOLA altimetry in the form of crossovers. This accuracy is currently approx. one meter. The gravity field is derived from X-band Doppler tracking with typical accuracy of 0.03 to 0.05 mm/s averaged over ten seconds. Current Mars gravity fields are to approximately degree and order 80 but are interpretable to the approximate degree and order 60 (spatial resolution < 180 km), which represents an estimate of the approximate coefficient limit of a field that can be produced without a power law constraint on the gravitational field inversion, which is commonly imposed for solution stability. Additional information is contained in the original extended abstract.

  11. The correction of vibration in frequency scanning interferometry based absolute distance measurement system for dynamic measurements

    NASA Astrophysics Data System (ADS)

    Lu, Cheng; Liu, Guodong; Liu, Bingguo; Chen, Fengdong; Zhuang, Zhitao; Xu, Xinke; Gan, Yu

    2015-10-01

    Absolute distance measurement systems are of significant interest in the field of metrology, which could improve the manufacturing efficiency and accuracy of large assemblies in fields such as aircraft construction, automotive engineering, and the production of modern windmill blades. Frequency scanning interferometry demonstrates noticeable advantages as an absolute distance measurement system which has a high precision and doesn't depend on a cooperative target. In this paper , the influence of inevitable vibration in the frequency scanning interferometry based absolute distance measurement system is analyzed. The distance spectrum is broadened as the existence of Doppler effect caused by vibration, which will bring in a measurement error more than 103 times bigger than the changes of optical path difference. In order to decrease the influence of vibration, the changes of the optical path difference are monitored by a frequency stabilized laser, which runs parallel to the frequency scanning interferometry. The experiment has verified the effectiveness of this method.

  12. (Photo-)thermally induced formation of dynamic surface topographies in polymer hydrogel networks.

    PubMed

    Liu, Danqing; Bastiaansen, Cees W M; den Toonder, Jaap M J; Broer, Dirk J

    2013-05-01

    In this Article, we report on our approaches to creating responsive hydrogel coatings with surfaces that can be switched between a close to flat state and a state with a predesigned topographic pattern. The trigger is either temperature or, indirectly, light. The hydrogel coatings are based on the known thermal responsive poly(N-isopropylacrylamide) utilizing its solubility change at its lower critical solution temperature (LCST) at around 32 °C. Using this material in combination with controlled cross-linking, we developed three fabrication strategies. Thermally switching symmetric surface topographies were created by careful and spatial control of the cross-link density. Sensitivity to light was created by patterns of tin oxide converting absorbed light into local heat. And to broaden the application range, we introduced a method based on volumetric effects created by a corrugated substrate. The latter method allows for the formation of asymmetric or slanted surface structures. PMID:23573907

  13. The ups and downs of North America: Evaluating the role of mantle dynamic topography since the Mesozoic

    NASA Astrophysics Data System (ADS)

    Liu, Lijun

    2015-09-01

    The driving force for transient vertical motions of Earth's surface remains an outstanding question. A main difficulty lies in the uncertain role of the underlying mantle, especially during the geological past. Here I review previous studies on both observational constraints and physical mechanisms of North American topographic evolution since the Mesozoic. I first summarize the North American vertical motion history using proxies from structural geology, geochronology, sedimentary stratigraphy, and geomorphology, based on which I then discuss the published physical models. Overall, there is a progressive consensus on the contribution of mantle dynamic topography due to buoyancy structures associated with the past subduction. At the continental scale, a largely west-to-east migrating deformation pattern suggests an eastward translation of mantle dynamic effects, consistent with models involving an eastward subduction and sinking of former Farallon slabs since the Cretaceous. Among the existing models, the inverse model based on an adjoint algorithm and time-dependent data constraints provides the most extensive explanations for the temporal changes of North American topography since the Mesozoic. At regional scales, debates still exist on the predicted surface subsidence and uplift within both the western and eastern United States, where discrepancies are likely due to differences in model setup (e.g., mantle dynamic properties and boundary conditions) and the amount of time-dependent observational constraints. Toward the development of the next-generation predictive geodynamic models, new research directions may include (1) development of enhanced data assimilation capabilities, (2) exploration of multiscale and multiphysics processes, and (3) cross-disciplinary code coupling.

  14. Sediment Transport, Complex Topography, and Hydrokinetic Turbines: Bedform Dynamics, Local Scour, and the Effect on Turbine Performance.

    NASA Astrophysics Data System (ADS)

    Guala, M.; Hill, C.; Kozarek, J. L.; Sotiropoulos, F.

    2015-12-01

    Multi-scale experiments on the interactions between axial-flow marine hydrokinetic (MHK) turbines, sediment transport and complex channel topography were performed at St. Anthony Falls Laboratory (SAFL), University of Minnesota. Model axial-flow three-bladed turbines (rotor diameters, dT = 0.15m and 0.5m) were installed in open channel flumes with both erodible and non-erodible substrates. In erodible channels, device-induced local scour was monitored over several hydraulic conditions (clear water vs. live bedload transport) and material sizes. Synchronous velocity, bed elevation and turbine performance measurements provide an indication into the effect channel topography has on device performance. A novel data acquisition imaging system provided methods for monitoring the dynamics of bedform transport as they approached and migrated past an operating axial-flow turbine. Experiments were also performed in a realistic meandering outdoor research channel with active sediment transport to investigate MHK turbine interactions with bedform migration and turbulent flow in asymmetric channels, providing new insight into turbine-sediment interactions and turbine wake behavior in curving channels. Results provide the foundation for investigating advanced turbine control strategies for optimal power production in non-stationary environments, while also providing robust data for computational model validation enabling further investigations into the interactions between energy conversion devices and the physical environment.

  15. Particle visualization in high-power impulse magnetron sputtering. II. Absolute density dynamics

    SciTech Connect

    Britun, Nikolay Palmucci, Maria; Konstantinidis, Stephanos; Snyders, Rony

    2015-04-28

    Time-resolved characterization of an Ar-Ti high-power impulse magnetron sputtering discharge has been performed. The present, second, paper of the study is related to the discharge characterization in terms of the absolute density of species using resonant absorption spectroscopy. The results on the time-resolved density evolution of the neutral and singly-ionized Ti ground state atoms as well as the metastable Ti and Ar atoms during the discharge on- and off-time are presented. Among the others, the questions related to the inversion of population of the Ti energy sublevels, as well as to re-normalization of the two-dimensional density maps in terms of the absolute density of species, are stressed.

  16. Absolute Summ

    NASA Astrophysics Data System (ADS)

    Phillips, Alfred, Jr.

    Summ means the entirety of the multiverse. It seems clear, from the inflation theories of A. Guth and others, that the creation of many universes is plausible. We argue that Absolute cosmological ideas, not unlike those of I. Newton, may be consistent with dynamic multiverse creations. As suggested in W. Heisenberg's uncertainty principle, and with the Anthropic Principle defended by S. Hawking, et al., human consciousness, buttressed by findings of neuroscience, may have to be considered in our models. Predictability, as A. Einstein realized with Invariants and General Relativity, may be required for new ideas to be part of physics. We present here a two postulate model geared to an Absolute Summ. The seedbed of this work is part of Akhnaton's philosophy (see S. Freud, Moses and Monotheism). Most important, however, is that the structure of human consciousness, manifest in Kenya's Rift Valley 200,000 years ago as Homo sapiens, who were the culmination of the six million year co-creation process of Hominins and Nature in Africa, allows us to do the physics that we do. .

  17. Erosion, Weathering and Stepped Topography in the Sierra Nevada, California; Quantifying the Dynamics of Hybrid (Soil-Bedrock) Landscapes

    NASA Astrophysics Data System (ADS)

    Jessup, B. S.; Miller, S. N.; Kirchner, J. W.; Riebe, C. S.

    2010-12-01

    The dynamics of granitic landscapes are regulated, in part, by bimodal weathering, which produces granular soils and expanses of bare rock ranging from meter-scale boulders to mountain-scale domes. Conceptual models for the evolution of granitic landscapes date back to Gilbert and Penck. Yet few studies have been able to realistically predict the co-occurrence of bedrock and granular soil and its implications for mountain-scale topography -- despite marked advances in quantitative landscape evolution modeling over the last few decades. Here we use terrain analysis, together with cosmogenic-nuclide measurements of erosion and weathering, to quantitatively explore Wahrhaftig's decades-old hypothesis for the development of “stepped topography” by differential weathering of bare and soil-mantled granite. According to this hypothesis, soil-mantled granite weathers much faster than bare granite; thus random erosional exposure of bare rock leads to an alternating sequence of steep, slowly weathering bedrock “steps” and gently sloped, but rapidly weathering, soil-mantled “treads”. Such treads and steps are purported to collectively account for ~2000 m of relief in the southern Sierra Nevada, California, implying that the mechanisms behind the formation of stepped topography may also account for development of mountain-scale relief in granitic landscapes. Our preliminary analysis of granitic terrain in the Sierra Nevada range suggests that steep steps often grade into gentle treads, consistent with the stepped topography hypothesis. Our data and analysis further corroborate the hypothesis with indications that bare granitic rocks erode much more slowly than their soil-mantled counterparts. This suggests that the coupling between soil production and denudation in granitic landscapes harbors a crucial tipping point; if soils are stripped to bedrock, erosion slows and soil formation is restrained to the point that bare rock can persist and rise in relief relative

  18. Multidirectional and Topography-based Dynamic-scale Varifold Representations with Application to Matching Developing Cortical Surfaces.

    PubMed

    Rekik, Islem; Li, Gang; Lin, Weili; Shen, Dinggang

    2016-07-15

    The human cerebral cortex is marked by great complexity as well as substantial dynamic changes during early postnatal development. To obtain a fairly comprehensive picture of its age-induced and/or disorder-related cortical changes, one needs to match cortical surfaces to one another, while maximizing their anatomical alignment. Methods that geodesically shoot surfaces into one another as currents (a distribution of oriented normals) and varifolds (a distribution of non-oriented normals) provide an elegant Riemannian framework for generic surface matching and reliable statistical analysis. However, both conventional current and varifold matching methods have two key limitations. First, they only use the normals of the surface to measure its geometry and guide the warping process, which overlooks the importance of the orientations of the inherently convoluted cortical sulcal and gyral folds. Second, the 'conversion' of a surface into a current or a varifold operates at a fixed scale under which geometric surface details will be neglected, which ignores the dynamic scales of cortical foldings. To overcome these limitations and improve varifold-based cortical surface registration, we propose two different strategies. The first strategy decomposes each cortical surface into its normal and tangent varifold representations, by integrating principal curvature direction field into the varifold matching framework, thus providing rich information of the orientation of cortical folding and better characterization of the complex cortical geometry. The second strategy explores the informative cortical geometric features to perform a dynamic-scale measurement of the cortical surface that depends on the local surface topography (e.g., principal curvature), thereby we introduce the concept of a topography-based dynamic-scale varifold. We tested the proposed varifold variants for registering 12 pairs of dynamically developing cortical surfaces from 0 to 6 months of age. Both

  19. The effect of rheological approximations on the dynamics and topography in 3D subduction-collision models

    NASA Astrophysics Data System (ADS)

    Pusok, Adina E.; Kaus, Boris J. P.; Popov, Anton A.

    2016-04-01

    Most of the major mountain belts and orogenic plateaus are found within the overlying plate of active or fossil subduction and/or collision zones. Moreover, they evolve differently from one another as the result of specific combinations of surface and mantle processes. These differences arise for several reasons, such as different rheological properties, different amounts of regional isostatic compensation, and different mechanisms by which forces are applied to the convergent plates. Previous 3D geodynamic models of subduction/collision processes have used various rheological approximations, making numerical results difficult to compare, since there is no clear image on the extent of these approximations on the dynamics. Here, we employ the code LaMEM to perform high-resolution long-term 3D simulations of subduction/continental collision in an integrated lithospheric and upper-mantle scale model. We test the effect of rheological approximations on mantle and lithosphere dynamics in a geometrically simplified model setup that resembles a tectonic map of the India-Asia collision zone. We use the "sticky-air" approach to allow for the development of topography and the dynamics of subduction and collision is entirely driven by slab-pull (i.e. "free subduction"). The models exhibit a wide range of behaviours depending on the rheological law employed: from linear to temperature-dependent visco-elasto-plastic rheology that takes into account both diffusion and dislocation creep. For example, we find that slab dynamics varies drastically between end member models: in viscous approximations, slab detachment is slow following a viscous thinning, while for a non-linear visco-elasto-plastic rheology, slab detachment is relatively fast, inducing strong mantle flow in the slab window. We also examine the stress states in the subducting and overriding plates and topography evolution in the upper plate, and we discuss the implications on lithosphere dynamics at convergent margins

  20. Inferences on the Emplacement Dynamics of Martian Impact Crater Ejecta: Constraints from Mola Topography

    NASA Technical Reports Server (NTRS)

    Garvin, J. B.; Baloga, S. M.

    1998-01-01

    Lobate ejecta deposits surround many of the younger impact craters on Mars. Viking Orbiter images indicate the distal parts of the ejecta blankets of these lobate craters are characterized by ramparts. In the absence of detailed topographic data for characterizing the topology of these apparently fluidized ejecta deposits, physical models have relied upon their morphologic characteristics. The most widely accepted model for the formation of such rampart ejecta deposits on Mars invokes fluidization of the ejecta to produce one or more viscous flow lobes. The availability of high-precision topographic data from the Mars Orbiter Laser Altimeter [4,51 facilitates a more quantitative examination of the physical processes involved in the formation of rampart ejecta deposits on Mars. Here we investigate the emplacement constraints that can be developed from the dimensions, topography, and morphology of martian rampart craters. The primary assumptions we have adopted are: (1) the ejecta blanket is emplaced as a continuum flow over the martian surface, rather than an airfall deposit, and (2) that the observable dimensions of the deposits are indicative of flow dimensions during emplacement.

  1. Dynamics of large-amplitude internal waves in stratified flows over topography

    NASA Astrophysics Data System (ADS)

    Prasad, Dilip

    1997-10-01

    In the first problem, the flow of a Boussinesq density- stratified fluid of large depth past the algebraic mountain ('Witch of Agnesi') is studied in the hydrostatic limit using the asymptotic theory of Kantzios & Akylas. The upstream conditions are those of constant velocity and Brunt-Vaisala frequency. On the further assumptions that the flow is steady and there is no permanent alteration of the upstream flow conditions (no upstream influence), Long's model predicts a critical amplitude of the mountain (/epsilon=0.85) above which local density inversions occur, leading to convective overturning. Linear stability analysis demonstrates that Long's steady flow is in fact unstable to infinitesimal modulations at topography amplitudes below this critical value, 0.65/ ~

  2. Future Antarctic Bed Topography and Its Implications for Ice Sheet Dynamics

    NASA Technical Reports Server (NTRS)

    Adhikari, Surendra; Ivins, Erik R.; Larour, Eric Y.; Seroussi, Helene L.; Morlighem, Mathieu; Nowicki, S.

    2014-01-01

    The Antarctic bedrock is evolving as the solid Earth responds to the past and ongoing evolution of the ice sheet. A recently improved ice loading history suggests that the Antarctic Ice Sheet (AIS) has generally been losing its mass since the Last Glacial Maximum. In a sustained warming climate, the AIS is predicted to retreat at a greater pace, primarily via melting beneath the ice shelves.We employ the glacial isostatic adjustment (GIA) capability of the Ice Sheet System Model (ISSM) to combine these past and future ice loadings and provide the new solid Earth computations for the AIS.We find that past loading is relatively less important than future loading for the evolution of the future bed topography. Our computations predict that the West Antarctic Ice Sheet (WAIS) may uplift by a few meters and a few tens of meters at years AD 2100 and 2500, respectively, and that the East Antarctic Ice Sheet is likely to remain unchanged or subside minimally except around the Amery Ice Shelf. The Amundsen Sea Sector in particular is predicted to rise at the greatest rate; one hundred years of ice evolution in this region, for example, predicts that the coastline of Pine Island Bay will approach roughly 45mmyr-1 in viscoelastic vertical motion. Of particular importance, we systematically demonstrate that the effect of a pervasive and large GIA uplift in the WAIS is generally associated with the flattening of reverse bed slope, reduction of local sea depth, and thus the extension of grounding line (GL) towards the continental shelf. Using the 3-D higher-order ice flow capability of ISSM, such a migration of GL is shown to inhibit the ice flow. This negative feedback between the ice sheet and the solid Earth may promote stability in marine portions of the ice sheet in the future.

  3. Geological Influences on Bedrock Topography and East Antarctic Ice Sheet Dynamics in the Wilkes Subglacial Basin

    NASA Astrophysics Data System (ADS)

    Ferraccioli, F.; Armadillo, E.; Young, D. A.; Blankenship, D. D.; Jordan, T. A.; Balbi, P.; Bozzo, E.; Siegert, M. J.

    2014-12-01

    The Wilkes Subglacial Basin (WSB) extends for 1,400 km from George V Land into the interior of East Antarctica and hosts several major glaciers that drain a large sector of the East Antarctic Ice Sheet (EAIS). This region is of key significance for the long-term stability of the ice sheet in East Antarctica, as it lies well below sea level and its bedrock deepens inland, making it potentially prone to marine ice sheet instability, much like areas of the West Antarctic Ice Sheet (WAIS) that are presently experiencing significant mass loss. We present new enhanced potential field images of the WSB combined with existing radar imaging to study geological controls on bedrock topography and ice flow regimes in this key sector of the ice sheet. These images reveal mayor Precambrian and Paleozoic basement faults that exert tectonic controls both on the margins of the basin and its sub-basins. Several major sub-basins can be recognised: the Eastern Basin, the Central Basins and the Western Basins. Using ICECAP aerogeophysical data we show that these tectonically controlled interior basins connect to newly identified basins underlying the Cook Ice Shelf region. This connection implies that any ocean-induced changes at the margin of the EAIS could potentially propagate rapidly further into the interior. With the aid of simple magnetic and gravity models we show that the WSB does not presently include major post Jurassic sedimentary infill. Its bedrock geology is highly variable and includes Proterozoic basement, Neoproterozoic and Cambrian sediments, intruded by Cambrian arc rocks, and cover rocks formed by Beacon sediments intruded by Jurassic Ferrar sills. Enhanced ice flow in this part of the EAIS occurs therefore in a area of mixed and spatially variable bedrock geology. This contrasts with some regions of the WAIS where more extensive sedimentary basins may represent a geological template for the onset and maintenance of fast glacial flow.

  4. Dynamics of plasma formation, relaxation, and topography modification induced by femtosecond laser pulses in crystalline and amorphous dielectrics

    SciTech Connect

    Puerto, D.; Siegel, J.; Gawelda, W.; Galvan-Sosa, M.; Solis, J.; Ehrentraut, L.; Bonse, J.

    2010-05-15

    We have studied plasma formation and relaxation dynamics along with the corresponding topography modifications in fused silica and sapphire induced by single femtosecond laser pulses (800 nm and 120 fs). These materials, representative of high bandgap amorphous and crystalline dielectrics, respectively, require nonlinear mechanisms to absorb the laser light. The study employed a femtosecond time-resolved microscopy technique that allows obtaining reflectivity and transmission images of the material surface at well-defined temporal delays after the arrival of the pump pulse which excites the dielectric material. The transient evolution of the free-electron plasma formed can be followed by combining the time-resolved optical data with a Drude model to estimate transient electron densities and skin depths. The temporal evolution of the optical properties is very similar in both materials within the first few hundred picoseconds, including the formation of a high reflectivity ring at about 7 ps. In contrast, at longer delays (100 ps-20 ns) the behavior of both materials differs significantly, revealing a longer lasting ablation process in sapphire. Moreover, transient images of sapphire show a concentric ring pattern surrounding the ablation crater, which is not observed in fused silica. We attribute this phenomenon to optical diffraction at a transient elevation of the ejected molten material at the crater border. On the other hand, the final topography of the ablation crater is radically different for each material. While in fused silica a relatively smooth crater with two distinct regimes is observed, sapphire shows much steeper crater walls, surrounded by a weak depression along with cracks in the material surface. These differences are explained in terms of the most relevant thermal and mechanical properties of the material. Despite these differences the maximum crater depth is comparable in both material at the highest fluences used (16 J/cm{sup 2}). The

  5. Sea level change since the Pliocene - a new formalism for predicting sea level in the presence of dynamic topography and isostasy

    NASA Astrophysics Data System (ADS)

    Austermann, Jacqueline; Rovere, Alessio; Moucha, Robert; Mitrovica, Jerry X.; Rowley, David B.; Forte, Alessandro M.; Raymo, Maureen E.

    2014-05-01

    Dynamic topography (DT), as reflected in local sea level change, provides a unique lens for studying the imprint of deep Earth dynamics on the Earth's surface. The elevation of paleo-shorelines over long time scales is, however, not only perturbed by DT but also by glacial isostatic adjustment (GIA) and eustatic changes in sea level. Isolating these contributions is essential for efforts to constrain past changes in ice volume or mantle convection models. Previous studies have performed this separation by modeling dynamic topography and superimposing the signal on the elevation of a GIA-corrected paleo-shoreline. However, this approach neglects deformation of the Earth in response to changes in the ocean load and geometry driven by DT. We describe a generalized, gravitationally self-consistent framework for computing sea-level changes that incorporates DT and GIA. The formalism is based on a sea-level theory developed within the GIA community that takes accurate account of viscoelastic deformation of the solid Earth, perturbations in the gravity field, migration of shorelines and the feedback into sea-level of contemporaneous (load-induced) changes in Earth rotation. Specifically, dynamic topography is introduced as a perturbation to the elevation of the solid surface that does not load the Earth because it is dynamically supported. However, water that is displaced by DT is allowed to redistribute, perturb the gravitational field and load (or unload) the ocean floor wherever the water column is increased (or decreased). The problem is complicated by plate tectonics, which (in a tectonic reference frame) leaves changes in topography and DT undefined in areas of the ocean floor where plates have been subducted. We interpolate these regions by imposing mass conservation of both the solid Earth and water on the reconstructed topography. We use the new formalism to calculate sea level change since the mid-Pliocene (3 Ma) using recent global simulations of dynamic

  6. Inherently mass-conservative version of the semi-Lagrangian Absolute Vorticity (SL-AV) atmospheric model dynamical core

    NASA Astrophysics Data System (ADS)

    Shashkin, V. V.; Tolstykh, M. A.

    2013-09-01

    The semi-Lagrangian Absolute Vorticity (SL-AV) atmospheric model is the global semi-Lagrangian hydrostatic model used for operational medium-range and seasonal forecasts at Hydrometeorological centre of Russia. The distinct feature of SL-AV dynamical core is the semi-implicit semi-Lagrangian vorticity-divergence formulation on the unstaggered grid. Semi-implicit semi-Lagrangian approach allows for long time steps while violates the global and local mass-conservation. In particular, the total mass in simulations with semi-Lagrangian models can drift significantly if no aposteriori mass-fixing algorithms are applied. However, the global mass-fixing algorithms degrade the local mass conservation. The inherently mass-conservative version of SL-AV model dynamical core presented in the article ensures global and local mass conservation without mass-fixing algorithms. The mass conservation is achieved with the introduction of the finite-volume semi-Lagrangian discretization for continuity equation based on the 3-D extension of the conservative cascade semi-Lagrangian transport scheme (CCS). The numerical experiments show that the presented new version of SL-AV dynamical core combines the accuracy and stability of the standard SL-AV dynamical core with the mass-conservation properties. The results of the mountain induced Rossby wave test and baroclinic instability test for mass-conservative dynamical core are found to be in agreement with the results available in literature.

  7. Inherently mass-conservative version of the semi-Lagrangian absolute vorticity (SL-AV) atmospheric model dynamical core

    NASA Astrophysics Data System (ADS)

    Shashkin, V. V.; Tolstykh, M. A.

    2014-02-01

    The semi-Lagrangian absolute vorticity (SL-AV) atmospheric model is the global semi-Lagrangian hydrostatic model used for operational medium-range and seasonal forecasts at the Hydrometeorological Centre of Russia. The distinct feature of the SL-AV dynamical core is the semi-implicit, semi-Lagrangian vorticity-divergence formulation on the unstaggered grid. A semi-implicit, semi-Lagrangian approach allows for long time steps but violates the global and local mass conservation. In particular, the total mass in simulations with semi-Lagrangian models can drift significantly if no a posteriori mass-fixing algorithm is applied. However, the global mass-fixing algorithms degrade the local mass conservation. The new inherently mass-conservative version of the SL-AV model dynamical core presented here ensures global and local mass conservation without mass-fixing algorithms. The mass conservation is achieved with the introduction of the finite-volume, semi-Lagrangian discretization for a continuity equation based on the 3-D extension of the conservative cascade semi-Lagrangian transport scheme (CCS). Numerical experiments show that the new version of the SL-AV dynamical core presented combines the accuracy and stability of the standard SL-AV dynamical core with the mass-conservation properties. The results of the mountain-induced Rossby-wave test and baroclinic instability test for the mass-conservative dynamical core are found to be in agreement with the results available in the literature.

  8. Sub-micron lateral topography affects endothelial migration by modulation of focal adhesion dynamics.

    PubMed

    Antonini, S; Meucci, S; Jacchetti, E; Klingauf, M; Beltram, F; Poulikakos, D; Cecchini, M; Ferrari, A

    2015-06-01

    Through the interaction with topographical features, endothelial cells tune their ability to populate target substrates, both in vivo and in vitro. Basal textures interfere with the establishment and maturation of focal adhesions (FAs) thus inducing specific cell-polarization patterns and regulating a plethora of cell activities that govern the overall endothelial function. In this study, we analyze the effect of topographical features on FAs in primary human endothelial cells. Reported data demonstrate a functional link between FA dynamics and cell polarization and spreading on structured substrates presenting variable lateral feature size. Our results reveal that gratings with 2 µm lateral periodicity maximize contact guidance. The effect is linked to the dynamical state of FAs. We argue that these results are readily applicable to the rational design of active surfaces at the interface with the blood stream. PMID:26106866

  9. Wasp-waist populations and marine ecosystem dynamics: Navigating the “ predator pit” topographies

    NASA Astrophysics Data System (ADS)

    Bakun, Andrew

    2006-02-01

    Many marine ecosystems exhibit a characteristic “wasp-waist” structure, where a single species, or at most several species, of small planktivorous fishes entirely dominate their trophic level. These species have complex life histories that result in radical variability that may propagate to both higher and lower trophic levels of the ecosystem. In addition, these populations have two key attributes: (1) they represent the lowest trophic level that is mobile, so they are capable of relocating their area of operation according to their own internal dynamics; (2) they may prey upon the early life stages of their predators, forming an unstable feedback loop in the trophic system that may, for example, precipitate abrupt regime shifts. Experience with the typical “boom-bust” dynamics of this type of population, and with populations that interact trophically with them, suggests a “predator pit” type of dynamics. This features a refuge from predation when abundance is very low, very destructive predation between an abundance level sufficient to attract interest from predators and an abundance level sufficient to satiate available predators, and, as abundance increases beyond this satiation point, decreasing specific predation mortality and population breakout. A simple formalism is developed to describe these dynamics. Examples of its application include (a) a hypothetical mechanism for progressive geographical habitat expansion at high biomass, (b) an explanation for the out-of-phase alternations of abundances of anchovies and sardines in many regional systems that appear to occur without substantial adverse interactions between the two species groups, and (c) an account of an interaction of environmental processes and fishery exploitation that caused a regime shift. The last is the example of the Baltic Sea, where the cod resource collapsed in concert with establishment of dominance of that ecosystem by the cod’s ‘wasp-waist” prey, herring and sprat.

  10. Forecasting spatial plant dynamics under future climate change in a semiarid savanna ecosystem with complex topography

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Fatichi, S.; Istanbulluoglu, E.; Vivoni, E. R.

    2011-12-01

    The space and time dynamics of savanna ecosystems in semiarid regions is tightly related to fluctuations and changes in the climate, and the competition strategies of individual plants for resources. In most parts of the southwest U.S., various General Circulation Models (GCMs) predict general warming trends with reduced annual precipitation amounts, and increased frequency of extreme droughts and wet periods in the 21st century. Despite the potential risks posed by climate change on vegetation patterns and hydrology, our ability to predict such changes at the catchment and regional scales is limited. In this study, we used a recently developed spatially explicit Cellular Automata Tree-Grass-Shrub Simulator (CATGraSS) to investigate the impacts of climate change on plant dynamics in a semiarid catchment (>3km2) located in the Sevilleta National Wildlife Refuge (SNWR) in central New Mexico, USA. In the catchment north-facing slopes are characterized by a juniper-grass savanna, and south-facing slopes by creosote bush and grass species. Initialized by LIDAR-derived tree locations and simulated grass and shrub patterns obtained from model calibration, CATGraSS is forced by a weather generator, AWE-GEN, used to downscale an ensemble of eight different GCM outputs at the study basin, producing multiple stochastic realizations of a transient climate scenario for the next hundred years. The ensemble simulations are used to examine the uncertainty in vegetation response and develop probabilistic plant distribution maps in relation to landscape morphology. This study highlights the importance of understanding local scale plant-to-plant interactions and the role of climate variability in determining climate change impacts on vegetation dynamics at varying spatial scales.

  11. Mariner 9 - An instrument of dynamical science. [for Mars gravitation and topography

    NASA Technical Reports Server (NTRS)

    Jordan, J. F.; Lorell, J.

    1975-01-01

    We review and evaluate the contributions of Mariner 9 in improving our knowledge of the dynamical characteristics of Mars and its two satellites, Phobos and Deimos. Primary results include the discovery of the large gravitational and topographical bulge in the Tharsis region, the development of a detailed gravity model representable as coefficients in a spherical harmonic expansion, the development of a topographic model exhibiting a three kilometer displacement of the center of figure from the center of mass, and the determination of the size, shape and motion of Phobos and Deimos.

  12. Interaction Between the Basin-Scale and Mesoscale Dynamics of the Black Sea: Impacts of Wind Forcing and Bottom Topography

    NASA Astrophysics Data System (ADS)

    Zatsepin, A. G.; Kremenetskiy, V. V.; Ratner, Y. B.; Stanichny, S. V.

    2008-12-01

    The general element of the classical theory of the Black Sea basin-scale circulation is the Rim current (RC) flowing cyclonically along the continental slope. Broad oceanographic application of the satellite data during the past decades has also revealed energetic mesoscale eddy-like structures that provide an effective cross- basin exchange. The aim of this report is to describe and discuss physical mechanisms of interaction between the RC and mesoscale eddies and their dependences on wind forcing and bottom topography. The study was based on the analysis of field observations and results of laboratory modeling. It was revealed by observations that in the northeastern Black Sea, having a very narrow continental slope, the topographic control of RC is weaker. The position and stability of RC is governed by the Ekman pumping. Under the strong (positive) Ekman pumping, which is more typical for the winter period, RC is a coherent and strong jet located over the continental slope. In this case, the lateral, cross-jet, exchange is relatively weak as the coastal and deep waters are separated by the dynamical front. In the alternative case of weak Ekman pumping, which is more typical for the Spring-Summer time, RC becomes unstable, meanders and breaks up into eddies producing strong lateral exchange. The effects of the wind forcing and bottom topography on the along-shore current, dynamically similar to RC, were studied in the laboratory experiment with the two-layer fluid in circular tank placed on the rotating table. It was shown that in case, when the width L of the continental slope is smaller or equal to the baroclinic Rossby deformation radius R, the influence of the bottom topography on the stability and structure of the along-shore current was negligible. After the decline or termination of the wind forcing, the along-shore current shifted in the off-shore direction, became unstable and disintegrated into eddies, providing an intensive water exchange between the

  13. A New Clinical Instrument for The Early Detection of Cataract Using Dynamic Light Scattering and Corneal Topography

    NASA Technical Reports Server (NTRS)

    Ansari, Rafat R.; Datiles, Manuel B., III; King, James F.

    2000-01-01

    A growing cataract can be detected at the molecular level using the technique of dynamic light scattering (DLS). However, the success of this method in clinical use depends upon the precise control of the scattering volume inside a patient's eye and especially during patient's repeat visits. This is important because the scattering volume (cross-over region between the scattered fight and incident light) inside the eye in a high-quality DLS set-up is very small (few microns in dimension). This precise control holds the key for success in the longitudinal studies of cataract and during anti-cataract drug screening. We have circumvented these problems by fabricating a new DLS fiber optic probe with a working distance of 40 mm and by mounting it inside a cone of a corneal analyzer. This analyzer is frequently used in mapping the corneal topography during PRK (photorefractive keratectomy) and LASIK (laser in situ keratomileusis) procedures in shaping of the cornea to correct myopia. This new instrument and some preliminary clinical tests on one of us (RRA) showing the data reproducibility are described.

  14. Improving Surface Geostrophic Current from a GOCE-Derived Mean Dynamic Topography Using Edge-Enhancing Diffusion Filtering

    NASA Astrophysics Data System (ADS)

    Sánchez-Reales, J. M.; Andersen, O. B.; Vigo, M. I.

    2016-03-01

    With increased geoid resolution provided by the gravity and steady-state ocean circulation explorer (GOCE) mission, the ocean's mean dynamic topography (MDT) can be now estimated with an accuracy not available prior to using geodetic methods. However, an altimetric-derived MDT still needs filtering in order to remove short wavelength noise unless integrated methods are used in which the three quantities are determined simultaneously using appropriate covariance functions. We studied nonlinear anisotropic diffusive filtering applied to the oceańs MDT and a new approach based on edge-enhancing diffusion (EED) filtering is presented. EED filters enable controlling the direction and magnitude of the filtering, with subsequent enhancement of computations of the associated surface geostrophic currents (SGCs). Applying this method to a smooth MDT and to a noisy MDT, both for a region in the Northwestern Pacific Ocean, we found that EED filtering provides similar estimation of the current velocities in both cases, whereas a non-linear isotropic filter (the Perona and Malik filter) returns results influenced by local residual noise when a difficult case is tested. We found that EED filtering preserves all the advantages that the Perona and Malik filter have over the standard linear isotropic Gaussian filters. Moreover, EED is shown to be more stable and less influenced by outliers. This suggests that the EED filtering strategy would be preferred given its capabilities in controlling/preserving the SGCs.

  15. Equilibrium and Dynamic Vortex States near Absolute Zero in a Weak Pinning Amorphous Film

    NASA Astrophysics Data System (ADS)

    Ochi, Aguri; Sohara, Naoya; Kaneko, Shin-ichi; Kokubo, Nobuhito; Okuma, Satoshi

    2016-04-01

    By developing and employing a mode-locking measurement with pulsed currents, we successfully determine the dynamic melting field B{c,dyn}∞ (T) for a driven vortex lattice of an amorphous MoxGe1-x film in the limit of zero temperature (T → 0) and complete a dynamic as well as a static vortex phase diagram. At T = 0, the mixed state in the absence of pinning comprises vortex-lattice and quantum-vortex-liquid (QVL) phases, and the melting field separating the two phases is identified as B{c,dyn}∞ (0). Comparison of the dynamic and static phase diagrams reveals that, when the weak pinning is introduced into the pin-free system, a disordered phase emerges just above the vortex-lattice phase and a threshold field separating the two phases is slightly suppressed from B{c,dyn}∞ (0), indicative of defect-induced disordering of the lattice. By contrast, a melting field into QVL is much enhanced from B{c,dyn}∞ (0) up to a point near the upper critical field, resulting in a significant suppression of the QVL phase. This is attributed to the stronger effective pinning at lower T, which survives quantum fluctuations.

  16. Determination of some dominant parameters of the global dynamic sea surface topography from GEOS-3 altimetry

    NASA Technical Reports Server (NTRS)

    Mather, R. S.; Lerch, F. J.; Rizos, C.; Masters, E. G.; Hirsch, B.

    1978-01-01

    The 1977 altimetry data bank is analyzed for the geometrical shape of the sea surface expressed as surface spherical harmonics after referral to the higher reference model defined by GEM 9. The resulting determination is expressed as quasi-stationary dynamic SST. Solutions are obtained from different sets of long arcs in the GEOS-3 altimeter data bank as well as from sub-sets related to the September 1975 and March 1976 equinoxes assembled with a view to minimizing seasonal effects. The results are compared with equivalent parameters obtained from the hydrostatic analysis of sporadic temperature, pressure and salinity measurements of the oceans and the known major steady state current systems with comparable wavelengths. The most clearly defined parameter (the zonal harmonic of degree 2) is obtained with an uncertainty of + or - 6 cm. The preferred numerical value is smaller than the oceanographic value due to the effect of the correction for the permanent earth tide. Similar precision is achieved for the zonal harmonic of degree 3. The precision obtained for the fourth degree zonal harmonic reflects more closely the accuracy expected from the level of noise in the orbital solutions.

  17. Extracting dynamic topography from river profiles and cosmogenic nuclide geochronology in the Middle Atlas and the High Plateaus of Morocco

    NASA Astrophysics Data System (ADS)

    Pastor, Alvar; Babault, Julien; Owen, Lewis A.; Teixell, Antonio; Arboleya, María-Luisa

    2015-11-01

    The Moulouya river system has intensely eroded the Arhbalou, Missour, and Guercif Neogene foreland basins in northeastern Morocco, having changed from net aggradation during the Miocene-early Pliocene to net incision punctuated by alluvial fan deposition at late Pliocene or early Quaternary time. This region as a whole has experienced mantle-driven, surface uplift (dynamic topography) since the late Cenozoic, being locally affected by uplift due to crustal shortening and thickening of the Middle Atlas too. Knickpoints located along the major streams of the Moulouya fluvial network, appear on both the undeformed margins of the Missour and Guercif foreland basins (High Plateaus), as well as along the thrust mountain front of the southern Middle Atlas, where they reach heights of 800-1000 m. 500-550 m of the knickpoint vertical incision might be explained by long-wavelength mantle-driven dynamic surface uplift, whereas the remaining 450-500 m in the southern Middle Atlas front and 200-300 m in the northeastern Middle Atlas front seem to be thrust-related uplift of the Jebel Bou Naceur. Be-10 terrestrial cosmogenic nuclides have been used to date two Quaternary river terraces in the Chegg Ard valley at 62 ± 14 ka and 411 ± 55 ka. The dated terraces allow the incision rates associated with the frontal structures of the Middle Atlas to be estimated at ~ 0.3 mm yr- 1. Furthermore, these ages have served to evaluate mantle-driven regional surface uplift since the middle Pleistocene in the central Missour basin, yielding values of ~ 0.1-0.2 mm yr- 1.

  18. Sea surface height and dynamic topography of the ice-covered oceans from CryoSat-2: 2011-2014

    NASA Astrophysics Data System (ADS)

    Kwok, Ron; Morison, James

    2016-01-01

    We examine 4 years (2011-2014) of sea surface heights (SSH) from CryoSat-2 (CS-2) over the ice-covered Arctic and Southern Oceans. Results are from a procedure that identifies and determines the heights of sea surface returns. Along 25 km segments of satellite ground tracks, variability in the retrieved SSHs is between ˜2 and 3 cm (standard deviation) in the Arctic and is slightly higher (˜3 cm) in the summer and the Southern Ocean. Average sea surface tilts (along these 25 km segments) are 0.01 ± 3.8 cm/10 km in the Arctic, and slightly lower (0.01 ± 2.0 cm/10 km) in the Southern Ocean. Intra-seasonal variability of CS-2 dynamic ocean topography (DOT) in the ice-covered Arctic is nearly twice as high as that of the Southern Ocean. In the Arctic, we find a correlation of 0.92 between 3 years of DOT and dynamic heights (DH) from hydrographic stations. Further, correlation of 4 years of area-averaged CS-2 DOT near the North Pole with time-variable ocean-bottom pressure from a pressure gauge and from GRACE, yields coefficients of 0.83 and 0.77, with corresponding differences of <3 cm (RMS). These comparisons contrast the length scale of baroclinic and barotropic features and reveal the smaller amplitude barotropic signals in the Arctic Ocean. Broadly, the mean DOT from CS-2 for both poles compares well with those from the ICESat campaigns and the DOT2008A and DTU13MDT fields. Short length scale topographic variations, due to oceanographic signals and geoid residuals, are especially prominent in the Arctic Basin but less so in the Southern Ocean.

  19. How topography induces reproductive asynchrony and alters gypsy moth invasion dynamics.

    PubMed

    Walter, Jonathan A; Meixler, Marcia S; Mueller, Thomas; Fagan, William F; Tobin, Patrick C; Haynes, Kyle J

    2015-01-01

    potentially be important to the population dynamics of many organisms. PMID:25039257

  20. Coseismic temporal changes of slip direction: the effect of absolute stress on dynamic rupture

    USGS Publications Warehouse

    Guatteri, Mariagiovanna; Spudich, P.

    1998-01-01

    We investigate the dynamics of rupture at low-stress level. We show that one main difference between the dynamics of high- and low-stress events is the amount of coseismic temporal rake rotation occurring at given points on the fault. Curved stations on exposed fault surfaces and earthquake dislocation models derived from ground-motion inversion indicate that the slip direction may change with time at a pointon the fault during dynamic rupture. We use a 3D boundary integral method to model temporal rake variations during dynamic rupture propagation assuming a slip-weakening friction law and isotropic friction. The points at which the slip rotates most are characterized by an initial shear stress direction substantially different from the average stress direction over the fault plane. We show that for a given value of stress drop, the level of initial shear stress (i.e., the fractional stress drop) determines the amount of rotation in slip direction. We infer that seismic events that show evidence of temporal rake rorations are characterized by a low initial shear-stress level with spatially variable direction on the fault (possibly due to changes in fault surface geometry) and an almost complete stress drop. Our models motivate a new interpretation of curved and cross-cutting striations and put new constraints on their analysis. The initial rake is in general collinear with the initial stress at the hypocenter zone, supporting the assumptions made in stress-tensor inversion from first-motion analysis. At other points on the fualt, especially away from the hypocenter, the initial slip rake may not be collinear with the initial shear stress, contradicting a common assumption of structural geology. On the other hand, the later part of slip in our models is systematically more aligned withi the average stress direction than the early slip. Our modeling suggests that the length of the straight part of curved striations is usually an upper bound of the slip

  1. Dynamic topography of the southern Central Anatolian Plateau, Turkey, and geodynamic driving mechanisms

    NASA Astrophysics Data System (ADS)

    Schildgen, T. F.; Cosentino, D.; Dudas, F. O.; Niedermann, S.; Strecker, M. R.; Echler, H.; Yildirim, C.

    2010-12-01

    Collision between Eurasia and Arabia and subsequent westward extrusion of the Anatolian microplate explains the development of major intracontinental fault systems in Anatolia that have remained active to the present-day. Concurrent, and probable episodic uplift of the Central and Eastern Anatolian plateaus (CAP and EAP), however, suggests that additional geodynamic mechanisms have contributed to the late Cenozoic morphologic development of the region. Sedimentary basins spanning the southern margin of the CAP provide insights on the timing and rates of different phases of surface uplift, giving constraints to test which geodynamic processes have contributed to surface uplift, orogenic plateau growth, and coupled landscape/climate evolution. Stratigraphic and geomorphic records of uplift and subsidence in the Mut Basin at the southern CAP margin and along the Göksu River record dynamic topographic development. Biostratigraphy and Sr isotope stratigraphy on the highest (ca. 2 km) uplifted marine sediments of the Mut basin furnish a maximum age of ca. 8 Ma for the onset of late Cenozoic uplift of the region. A Pliocene to early Pleistocene marine section, inset within the older stratigraphy at ca. 0.2 to 1.2 km elevation, reveals a history of subsidence and renewed uplift, following the initial uplift that occurred between ca. 8 Ma and Pliocene time. The most recent phase of uplift continued with possibly minor interruptions during the Quaternary, and is recorded by a series of fluvial terraces preserved between 30 and 143 m above the modern Göksu River. One terrace (143 m) reveals a 21Ne model exposure age of ca. 160 ka; ongoing exposure age determination will further constrain the uplift history. Different geodynamic mechanisms have likely contributed to surface uplift along the southern CAP margin. Initial uplift may have been associated with the predominantly sinistral Ecemis fault system that spans the southern and southeastern CAP margin. Neogene counter

  2. The dynamics of a rigid body on an absolutely rough plane

    NASA Astrophysics Data System (ADS)

    Markeev, A. P.

    1983-08-01

    An attempt is made to explain certain dynamic effects associated with the rattleback, with particular emphasis placed on the oscillations of the body near the equilibrium position or near stationary rotation. The small oscillations of the body in the neighborhood of its stationary rotation about the vertical are analyzed; an approximate system of equations describing the nonlinear oscillations of the rattleback near its equilibrium position on a plane is derived; and a complete analysis of this system is given. The results agree with experimentally observed variations of the direction of the rotation of the body about the vertical in the absence of external influence and the appearance of rotation in both directions due to oscillations about the horizontal axis.

  3. Free Energy Perturbation Hamiltonian Replica-Exchange Molecular Dynamics (FEP\\H-REMD) for absolute ligand binding free energy calculations.

    SciTech Connect

    Jiang, W.; Roux, B.

    2010-09-01

    Free Energy Perturbation with Replica Exchange Molecular Dynamics (FEP/REMD) offers a powerful strategy to improve the convergence of free energy computations. In particular, it has been shown previously that a FEP/REMD scheme allowing random moves within an extended replica ensemble of thermodynamic coupling parameters '{lambda}' can improve the statistical convergence in calculations of absolute binding free energy of ligands to proteins [J. Chem. Theory Comput. 2009, 5, 2583]. In the present study, FEP/REMD is extended and combined with an accelerated MD simulations method based on Hamiltonian replica-exchange MD (H-REMD) to overcome the additional problems arising from the existence of kinetically trapped conformations within the protein receptor. In the combined strategy, each system with a given thermodynamic coupling factor {lambda} in the extended ensemble is further coupled with a set of replicas evolving on a biased energy surface with boosting potentials used to accelerate the interconversion among different rotameric states of the side chains in the neighborhood of the binding site. Exchanges are allowed to occur alternatively along the axes corresponding to the thermodynamic coupling parameter {lambda} and the boosting potential, in an extended dual array of coupled {lambda}- and H-REMD simulations. The method is implemented on the basis of new extensions to the REPDSTR module of the biomolecular simulation program CHARMM. As an illustrative example, the absolute binding free energy of p-xylene to the nonpolar cavity of the L99A mutant of the T4 lysozyme was calculated. The tests demonstrate that the dual {lambda}-REMD and H-REMD simulation scheme greatly accelerates the configurational sampling of the rotameric states of the side chains around the binding pocket, thereby improving the convergence of the FEP computations.

  4. Mid Pliocene sea levels: A combined analysis of field data, models of glacial isostasy and dynamic topography, and eustasy. (Invited)

    NASA Astrophysics Data System (ADS)

    Rovere, A.; Raymo, M. E.; Hearty, P. J.; Austermann, J.; Mitrovica, J. X.; Michael, O.; Moucha, R.; Forte, A. M.; Rowley, D. B.

    2013-12-01

    Determining the eustatic elevation of former sea levels (SL), or equivalently ice volumes, is a central goal of paleoclimate research. SL estimates for the Mid-Pliocene warm period (MPWP, ˜3.3 to 2.9 Ma) are of particular interest as CO2 levels at that time (between 350 and 450 ppmv) were similar to today (> 400 ppmv as of May 2013). However, despite general agreement on other climate variables, SL estimates for the MPWP and the stability of polar ice sheets during this interval remain largely unconstrained. In this regard, inferring ice volumes from SL indicators of MPWP age is complicated by several factors. First, relatively few robust records of MPWP SL have been obtained from tectonically stable areas. Second, the potentially significant contaminating signals due to glacial isostatic adjustment (GIA) and dynamic topography associated with mantle convective flow (DT) have rarely, and only recently, been accounted for. Within the framework of PLIOMAX project, we are collecting accurate MPWP indicators at widely distributed sites using a combination of classic field methods, state of the art GPS and GIS techniques. Moreover, the analysis of the data involves the participation of both field geologists and geodynamic modelers. In this talk, we present data collected in three specific areas: Republic of South Africa, Western Australia and the southeastern United States. We will report on the present day elevation of MPWP shoreline indicators in each region. Moreover, we will combine this data set with a broad suite of numerical models of GIA and DT to establish current uncertainties on the estimate of eustatic SL during the MPWP, as well as comment on possible strategies for improving the accuracy of this estimate.

  5. Who is in control? Competing influences of geology, land use and topography on soil moisture and soil temperature dynamics

    NASA Astrophysics Data System (ADS)

    Blume, Theresa; Hassler, Sibylle; Weiler, Markus

    2014-05-01

    Can we identify distinct signatures of landscape elements in the event response of soil moisture and soil temperature? Moisture and temperature dynamics in soils are largely controlled by the climatic boundary conditions of rainfall, evapotranspiration and radiation. However, certain landscape features also leave characteristic finger prints on soil moisture and soil temperature time series. The extent of these influences and their time variable relative importance are important in a number of contexts, such as landscape scale prediction of soil moisture patterns or runoff generation, process predictions in ungauged basins or the improvement of hydrological model structures for the mesoscale. The competing influences of geology, land use and topography on temperature and moisture characteristics in the vadose zone are explored at the CAOS hydrological observatory in Luxemburg (http://www.caos-project.de/) with a unique experimental setup of 45 sensor clusters. These sensor clusters cover three different geologies (schist, sandstone, marls), two land use classes (forest and grassland), five different landscape positions (plateau, top-, mid- and lower hillslope as well as near stream/floodplain locations), and contrasting expositions. At each of these sensor clusters three soil moisture profiles with sensors at depths from 10 to 70 cm, four soil temperature profiles as well as air temperature, relative humidity, global radiation, rainfall/throughfall, sapflow and shallow groundwater and stream water levels were measured continuously. Time series of up to 2 years for the schist region and up to 6 months for the complete set of sites allow for a first intercomparison of characteristic event response behavior.

  6. On the effect of the Post-perovskite phase change on global mantle flow, geoid and dynamic topography

    NASA Astrophysics Data System (ADS)

    Shahraki, Meysam; Schmeling, Harro; Kaban, Mikhail; Petrunin, Alexei

    2014-05-01

    In the lowermost parts of mantle, the D" layer is a profoundly important layer as it involves the process of heat and mass transfer between core and mantle. However, the physical nature of this layer is an issue of active debate. The seismic data represent a rapid increase and decrease of the shear velocity, especially beneath Circum-Pacific margins, in the D" layer. Indeed, such abrupt velocity discontinuity is not expected for this hot layer. The discovery of the perovskite (pv) to Post-perovskite (pPv) phase transformation has led to dramatic increase in our understanding of the structure of the D" layer, since it is thought to produce such seismic discontinuity. Here, we have investigate the influence of the phase transformation of pv to pPv on the geoid undulation as one of the most important geophysical observable, using 3D spherical shell mantle circulation models based on a seismic tomography model (S40RTS) and strongly lateral viscosity variations in the D" layer and the mantle above. We demonstrate that the geoid anomalies are strongly affected by the presence of pPv in the lowermost mantle. While the geoid heights over subduction zones are increased by considering a strong pPv compared to then surrounding mantle, a weak pPv reduces the geoid height, and a better fit to the observed geoid is obtained. We show that, applying a weak pPv viscosity of at least three orders of magnitude any higher viscosity contrast does not affect the geoid any further. We also investigate the effects of weak pPv combined with a different tomography model, a different pPv density contrast, the presence or absence of a global thermal-boundary-layer (TBL) and the presence or absence of lateral viscosity variations in the lower mantle. Keywords: Post-perovskite, phase transitions, geoid, dynamic topography

  7. Nuclear depolarization and absolute sensitivity in magic-angle spinning cross effect dynamic nuclear polarization.

    PubMed

    Mentink-Vigier, Frédéric; Paul, Subhradip; Lee, Daniel; Feintuch, Akiva; Hediger, Sabine; Vega, Shimon; De Paëpe, Gaël

    2015-09-14

    Over the last two decades solid state Nuclear Magnetic Resonance has witnessed a breakthrough in increasing the nuclear polarization, and thus experimental sensitivity, with the advent of Magic Angle Spinning Dynamic Nuclear Polarization (MAS-DNP). To enhance the nuclear polarization of protons, exogenous nitroxide biradicals such as TOTAPOL or AMUPOL are routinely used. Their efficiency is usually assessed as the ratio between the NMR signal intensity in the presence and the absence of microwave irradiation εon/off. While TOTAPOL delivers an enhancement εon/off of about 60 on a model sample, the more recent AMUPOL is more efficient: >200 at 100 K. Such a comparison is valid as long as the signal measured in the absence of microwaves is merely the Boltzmann polarization and is not affected by the spinning of the sample. However, recent MAS-DNP studies at 25 K by Thurber and Tycko (2014) have demonstrated that the presence of nitroxide biradicals combined with sample spinning can lead to a depolarized nuclear state, below the Boltzmann polarization. In this work we demonstrate that TOTAPOL and AMUPOL both lead to observable depolarization at ≈110 K, and that the magnitude of this depolarization is radical dependent. Compared to the static sample, TOTAPOL and AMUPOL lead, respectively, to nuclear polarization losses of up to 20% and 60% at a 10 kHz MAS frequency, while Trityl OX63 does not depolarize at all. This experimental work is analyzed using a theoretical model that explains how the depolarization process works under MAS and gives new insights into the DNP mechanism and into the spin parameters, which are relevant for the efficiency of a biradical. In light of these results, the outstanding performance of AMUPOL must be revised and we propose a new method to assess the polarization gain for future radicals. PMID:26235749

  8. Comparing the effects of rheology on the dynamics and topography of 3D subduction-collision models

    NASA Astrophysics Data System (ADS)

    Pusok, Adina E.; Kaus, Boris; Popov, Anton

    2015-04-01

    Most of the major mountain belts and orogenic plateaus are found within the overlying plate of active or fossil subduction and/or collision zones. It is well known that they evolve differently from one another as the result of specific combinations of surface and mantle processes. The differences among the structures and evolutions of mountain belts arise for several reasons, such as different strengths of materials, different amounts of regional isostatic compensation, and different mechanisms by which forces are applied to the convergence plates. All these possible controlling factors can change with space and time. Of all the mountain belts and orogenic plateaus, the most striking example is the India-Asia collision zone, which gave rise to the Himalayas and the Tibetan Plateau, the largest region of elevated topography and anomalously thick crust on Earth. Understanding the formation and evolution of such a highly elevated region has been the focus of many tectonic and numerical models. While some of these models (i.e. thin sheet model) have successfully illustrated some of the basic physics of continental collision, none can simultaneously represent active processes such as subduction, underthrusting, channel flow or extrusion, for which fully 3D models are required. Here, we employed the 3D code LaMEM to investigate the role that subduction, continental collision and indentation play on lithosphere dynamics at convergent margins, and the implications they have for the Asian tectonics. Our model setup resembles a simplified tectonic map of the India-Asia collision zone and we performed long-term 3D simulations to analyse the dynamics and the conditions under which large topographic plateaus, such as the Tibetan Plateau can form in an integrated lithospheric and upper-mantle scale model. Results of models with linear viscous rheologies show different modes between the oceanic subduction side (continuous subduction, trench retreat and slab roll-back) and the

  9. Influence of bottom topography on dynamics of river plumes in semi-enclosed domains: Case study in Taiwan Strait

    NASA Astrophysics Data System (ADS)

    Zavialov, Peter; Korotenko, Konstantin; Osadchiev, Alexander; Kao, Ruei-Chi; Ding, Chung-Feng

    2014-05-01

    This paper summarizes the results of a Russian-Taiwan research project focused on the role of continental discharges into the Taiwan Strait, an important channel in the western Pacific Ocean transporting water between the South China Sea and the East China Sea. Another critically important hydrographic feature in the area is the discharge of freshwater from multiple rivers of the western coast of Taiwan. With its long-term average discharge rate of 210 m3/s, the Zhuoshui River is the biggest of the rivers bringing a large amount of pollutants and nutrients into the Strait. The northern extremity of Zhuoshui River's plume often merges with that of the Wu River (also known as Dudu River) whose average discharge rate is about 120 m3/s. Oceanic waters in the area experience significant anthropogenic pressures, traceable to the distance of a few km offshore and tens of km along the shore. This is manifested, in particular, in strongly elevated concentrations of copper, iron, and other trace metals. The corresponding quantitative estimates are obtained. The newly obtained in situ data from a field campaign were also used to implement 2 numerical models aimed at simulating the pathways of the continental waters in the study region. One of them, based on the Princeton Ocean Model, was coupled with a regional barotropic tidal model for the Taiwan Strait. The other one, a fully Lagrangian model STRiPE is based on applying a complete set of momentum equations to individual "particles" of river water released into the ocean. Both models demonstrated reasonable good agreement with the in situ data and each other. The bathymetry, tides and winds significantly affect the dynamics of the Wu and Zhuoshui river plumes, acting together in a complex interactive manner. The Zhuoshui River plume stretches in a narrow alongshore belt both to the south and north from the river mouth while the larger, round-shaped Wu River's plume elongates mostly north of its mouth. The difference is

  10. Introducing variable-step topography (VST) coordinates within dynamically constrained nonhydrostatic modeling system (NMS). Part 2: VST performance on orthodox obstacle flows

    NASA Astrophysics Data System (ADS)

    Tripoli, Gregory J.; Smith, Eric A.

    2014-06-01

    In this second part of a two-part sequence of papers, the performance metrics and quantitative advantages of a new VST surface coordinate system, implemented within a dynamically constrained, nonhydrostatic, cloud mesoscale atmospheric model, are evaluated in conjunction with seven orthodox obstacle flow problems. [The first part presented a full formulation of the VST model, prefaced by a description of the framework of the newly re-tooled nonhydrostatic modeling system (NMS) operating within integral constraints based on the conservation of the foremost quantities of mass, energy and circulation.] The intent behind VST is to create a vertical surface coordinate system boundary underpinning a nonhydrostatic atmosphere capable of reliable simulations of flows over both smooth and steep terrain without sacrificing dynamical integrity over either type of surface. Model simulation results are analyzed for six classical fluid dynamics problems involving flows relative to obstacles with known analytical or laboratory-simulated solutions, as well as for a seventh noteworthy mountain wave breaking problem that has well-studied numerical solutions. For cases when topography becomes excessively severe or poorly resolved numerically, atmospheric models using transform (terrain-following) coordinates produce noteworthy errors rendering a stable integration only if the topography is smoothed. For cases when topography is slowly varying (smooth or subtle), models using discrete-step coordinates also produce noteworthy errors relative to known solutions. Alternatively, the VST model demonstrates that both limitations of the two conventional approaches, for the entire range of slope severities, can be overcome. This means that VST is ideally suited for a scalable, nonhydrostatic atmospheric model, safeguarded with physically realistic dynamical constraints.

  11. The structure and dynamics of coherent vortex tubes in rotating shear turbulence of zero-mean-absolute vorticity.

    NASA Astrophysics Data System (ADS)

    Tanaka, Mitsuru; Yanase, Shinichiro

    2010-05-01

    The effect of the system rotation on shear flow turbulence is one of the central issues of fluid mechanics in relation to geophysical and astrophysical phenomena as well as engineering applications such as turbo machinery, so is still being vigorously investigated. If a turbulent shear flow is rotated as a whole about the axis parallel to the mean-shear vorticity, the flow structure is significantly influenced by the magnitude and direction of vorticity associated with the mean shear relative to those of the system rotation. The flow field is called either cyclonic or anti-cyclonic accordingly as vorticities associated with the mean shear and the system rotation are parallel or anti-parallel. Turbulence has a tendency to keep its two-dimensional structure along the system rotation both for cyclonic and for an anti-cyclonic regions for rapid system rotation, whereas the two-dimensional structure is unstable and easily broken down to three-dimensional in an anti-cyclonic region if the system rotation is relatively slow to the mean-shear vorticity. If the flow field is anti-cyclonic and the mean-shear vorticity cancels out that of the system rotation, the mean absolute vorticity is zero in the flow field, and then it is called the zero-mean-absolute-vorticity state (ZAVS). ZAVS, which is neutral to the above-mentioned instability, is observed in many rotating shear flow turbulence. One of the most remarkable features of ZAVS turbulence is the generation of very coherent quasi-streamwise vortex tubes which are not observed in other cases of rotating or nonrotating turbulence. Though the importance of the role of vortex tubes in shear flow turbulence is generally recognized, it is not easy to study their dynamics due to the interactions between vortex tubes and vortex-shear layers which are generated from the background mean-shear vorticity. In ZAVS, on the other hand, it is rather easy to investigate vortex tubes in turbulence because they are stable and long

  12. Determination of absolute configuration in chiral solvents with nuclear magnetic resonance. A combined molecular dynamics/quantum chemical study.

    PubMed

    Kessler, Jiří; Dračínský, Martin; Bouř, Petr

    2015-05-28

    Nuclear magnetic resonance (NMR) spectroscopy is omnipresent in chemical analysis. However, chirality of a molecule can only be detected indirectly by NMR, e.g., by monitoring its interaction with another chiral object. In the present study, we investigate the spectroscopic behavior of chiral molecules placed into a chiral solvent. In this case, the solvent-solute interaction is much weaker, but the application range of such NMR analysis is wider than for a specific chemical shift agent. Two alcohols and an amine were used as model systems, and differences in NMR chemical shifts dependent on the solute-solvent chirality combination were experimentally detected. Combined quantum mechanic/molecular mechanic (QM/MM) computations were applied to reveal the underlying solute-solvent interactions. NMR shielding was calculated using the density functional theory (DFT). While the experimental observations could not be reproduced quantitatively, the modeling provided a qualitative agreement and detailed insight into the essence of solvent-solute chiral interactions. The potentials of mean force (PMF) obtained using molecular dynamics (MD) and the weighted histogram analysis method (WHAM) indicate that the chiral interaction brings about differences in conformer ratios, which are to a large extent responsible for the NMR shifts. The MD results also predicted slight changes in the solvent structure, including the radial distribution function (RDF), to depend on the solvent/solute chirality combination. Apart from the conformer distribution, an effective average solvent electrostatic field was tested as another major factor contributing to the chiral NMR effect. The possibility to simulate spectral effects of chiral solvents from the first-principles opens up the way to NMR spectroscopic determination of the absolute configuration for a larger scale of compounds, including those not forming specific complexes. PMID:25411905

  13. Constraining the Absolute Orientation of eta Carinae's Binary Orbit: A 3-D Dynamical Model for the Broad [Fe III] Emission

    NASA Technical Reports Server (NTRS)

    Madura, T. I.; Gull, T. R.; Owocki, S. P.; Groh, J. H.; Okazaki, A. T.; Russell, C. M. P.

    2011-01-01

    We present a three-dimensional (3-D) dynamical model for the broad [Fe III] emission observed in Eta Carinae using the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS). This model is based on full 3-D Smoothed Particle Hydrodynamics (SPH) simulations of Eta Car's binary colliding winds. Radiative transfer codes are used to generate synthetic spectro-images of [Fe III] emission line structures at various observed orbital phases and STIS slit position angles (PAs). Through a parameter study that varies the orbital inclination i, the PA(theta) that the orbital plane projection of the line-of-sight makes with the apastron side of the semi-major axis, and the PA on the sky of the orbital axis, we are able, for the first time, to tightly constrain the absolute 3-D orientation of the binary orbit. To simultaneously reproduce the blue-shifted emission arcs observed at orbital phase 0.976, STIS slit PA = +38deg, and the temporal variations in emission seen at negative slit PAs, the binary needs to have an i approx. = 130deg to 145deg, Theta approx. = -15deg to +30deg, and an orbital axis projected on the sky at a P A approx. = 302deg to 327deg east of north. This represents a system with an orbital axis that is closely aligned with the inferred polar axis of the Homunculus nebula, in 3-D. The companion star, Eta(sub B), thus orbits clockwise on the sky and is on the observer's side of the system at apastron. This orientation has important implications for theories for the formation of the Homunculus and helps lay the groundwork for orbital modeling to determine the stellar masses.

  14. Absolute Zero

    NASA Astrophysics Data System (ADS)

    Donnelly, Russell J.; Sheibley, D.; Belloni, M.; Stamper-Kurn, D.; Vinen, W. F.

    2006-12-01

    Absolute Zero is a two hour PBS special attempting to bring to the general public some of the advances made in 400 years of thermodynamics. It is based on the book “Absolute Zero and the Conquest of Cold” by Tom Shachtman. Absolute Zero will call long-overdue attention to the remarkable strides that have been made in low-temperature physics, a field that has produced 27 Nobel Prizes. It will explore the ongoing interplay between science and technology through historical examples including refrigerators, ice machines, frozen foods, liquid oxygen and nitrogen as well as much colder fluids such as liquid hydrogen and liquid helium. A website has been established to promote the series: www.absolutezerocampaign.org. It contains information on the series, aimed primarily at students at the middle school level. There is a wealth of material here and we hope interested teachers will draw their student’s attention to this website and its substantial contents, which have been carefully vetted for accuracy.

  15. Constraining the absolute orientation of η Carinae's binary orbit: a 3D dynamical model for the broad [Fe III] emission

    NASA Astrophysics Data System (ADS)

    Madura, T. I.; Gull, T. R.; Owocki, S. P.; Groh, J. H.; Okazaki, A. T.; Russell, C. M. P.

    2012-03-01

    We present a three-dimensional (3D) dynamical model for the broad [Fe III] emission observed in η Carinae using the Hubble Space Telescope/Space Telescope Imaging Spectrograph (STIS). This model is based on full 3D smoothed particle hydrodynamics simulations of η Car's binary colliding winds. Radiative transfer codes are used to generate synthetic spectroimages of [Fe III] emission-line structures at various observed orbital phases and STIS slit position angles (PAs). Through a parameter study that varies the orbital inclination i, the PA θ that the orbital plane projection of the line of sight makes with the apastron side of the semimajor axis and the PA on the sky of the orbital axis, we are able, for the first time, to tightly constrain the absolute 3D orientation of the binary orbit. To simultaneously reproduce the blueshifted emission arcs observed at orbital phase 0.976, STIS slit PA =+38° and the temporal variations in emission seen at negative slit PAs, the binary needs to have an i≈ 130° to 145°, θ≈-15° to +30° and an orbital axis projected on the sky at a PA ≈ 302° to 327° east of north. This represents a system with an orbital axis that is closely aligned with the inferred polar axis of the Homunculus nebula, in 3D. The companion star, ηB, thus orbits clockwise on the sky and is on the observer's side of the system at apastron. This orientation has important implications for theories for the formation of the Homunculus and helps lay the groundwork for orbital modelling to determine the stellar masses. Footnotes<label>1</label>Low- and high-ionization refer here to atomic species with ionizations potentials (IPs) below and above the IP of hydrogen, 13.6 eV.<label>2</label>Measured in degrees from north to east.<label>3</label>θ is the same as the angle φ defined in fig. 3 of O08.<label>4</label>The outer edge looks circular only because this marks the edge of the spherical computational domain of the SPH simulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140001041','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140001041"><span id="translatedtitle">Does <span class="hlt">Dynamical</span> Downscaling Introduce Novel Information in Climate Model Simulations of Recipitation Change over a Complex <span class="hlt">Topography</span> Region?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tselioudis, George; Douvis, Costas; Zerefos, Christos</p> <p>2012-01-01</p> <p>Current climate and future climate-warming runs with the RegCM Regional Climate Model (RCM) at 50 and 11 km-resolutions forced by the ECHAM GCM are used to examine whether the increased resolution of the RCM introduces novel information in the precipitation field when the models are run for the mountainous region of the Hellenic peninsula. The model results are inter-compared with the resolution of the RCM output degraded to match that of the GCM, and it is found that in both the present and future climate runs the regional models produce more precipitation than the forcing GCM. At the same time, the RCM runs produce increases in precipitation with climate warming even though they are forced with a GCM that shows no precipitation change in the region. The additional precipitation is mostly concentrated over the mountain ranges, where orographic precipitation formation is expected to be a dominant mechanism. It is found that, when examined at the same resolution, the elevation heights of the GCM are lower than those of the averaged RCM in the areas of the main mountain ranges. It is also found that the majority of the difference in precipitation between the RCM and the GCM can be explained by their difference in topographic height. The study results indicate that, in complex <span class="hlt">topography</span> regions, GCM predictions of precipitation change with climate warming may be dry biased due to the GCM smoothing of the regional <span class="hlt">topography</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010EGUGA..1212575G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010EGUGA..1212575G&link_type=ABSTRACT"><span id="translatedtitle">Mantle convection, <span class="hlt">topography</span> and geoid</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Golle, Olivia; Dumoulin, Caroline; Choblet, Gaël.; Cadek, Ondrej</p> <p>2010-05-01</p> <p>The internal evolution of planetary bodies often include solid-state convection. This phenomenon may have a large impact on the various interfaces of these bodies (<span class="hlt">dynamic</span> <span class="hlt">topography</span> occurs). It also affects their gravity field (and the geoid). Since both geoid and <span class="hlt">topography</span> can be measured by a spacecraft, and are therefore available for several planetary bodies (while seismological measurements are still lacking for all of them but the Moon and the Earth), these are of the first interest for the study of internal structures and processes. While a classical approach now is to combine gravity and altimetry measurements to infer the internal structure of a planet [1], we propose to complement it by the reverse problem, i.e., producing synthetic geoid and <span class="hlt">dynamic</span> <span class="hlt">topography</span> from numerical models of convection as proposed by recent studies (e.g. for the CMB <span class="hlt">topography</span> of the Earth,[2]). This procedure first include a simple evaluation of the surface <span class="hlt">topography</span> and geoid from the viscous flow obtained by the 3D numerical tool OEDIPUS [3] modeling convection in a spherical shell. An elastic layer will then be considered and coupled to the viscous model - one question being whether the elastic shell shall be included 'on top' of the convective domain or within it, in the cold 'lithospheric' outer region. What we will present here corresponds to the first steps of this work: the comparison between the response functions of the <span class="hlt">topography</span> and the geoid obtained from the 3D convection program to the results evaluated by a spectral method handling radial variations of viscosity [4]. We consider the effect of the elastic layer whether included in the convective domain or not. The scale setting in the context of a full thermal convection model overlaid by an elastic shell will be discussed (thickness of the shell, temperature at its base...). References [1] A.M. Wieczorek, (2007), The gravity and <span class="hlt">topography</span> of the terrestrial planets, Treatise on Geophysics, 10, 165-206. [2</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19920037750&hterms=asthenosphere&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dasthenosphere','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19920037750&hterms=asthenosphere&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dasthenosphere"><span id="translatedtitle">Geoid anomalies and <span class="hlt">dynamic</span> <span class="hlt">topography</span> from convection in cylindrical geometry - Applications to mantle plumes on earth and Venus</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kiefer, Walter S.; Hager, Bradford H.</p> <p>1992-01-01</p> <p>A variety of evidence suggests that at least some hotspots are formed by quasi-cylindrical mantle plumes upwelling from deep in the mantle. Such plumes are modeled in cylindrical, axisymmetric geometry with depth-dependent, Newtonian viscosity. Cylindrical and sheet-like, Cartesian upwellings have significantly different geoid and <span class="hlt">topography</span> signatures. However, Rayleigh number-Nusselt number systematics in the two geometries are quite similar. The geoid anomaly and topographic uplift over a plume are insensitive to the viscosity of the surface layer, provided that it is at least 1000 times the interior viscosity. Increasing the Rayleigh number or including a low-viscosity asthenosphere decreases the geoid anomaly and the topographic uplift associated with an upwelling plume.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.T13B2380N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.T13B2380N"><span id="translatedtitle"><span class="hlt">Dynamic</span> <span class="hlt">topography</span> of the western Great Plains: landscape evidence for mantle-driven uplift associated with the Jemez lineament of NE New Mexico and SE Colorado</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nereson, A. L.; Karlstrom, K. E.; McIntosh, W. C.; Heizler, M. T.; Kelley, S. A.; Brown, S. W.</p> <p>2011-12-01</p> <p><span class="hlt">Dynamic</span> <span class="hlt">topography</span> results when viscous stresses created by flow within the mantle are transmitted through the lithosphere and interact with, and deform, the Earth's surface. Because <span class="hlt">dynamic</span> <span class="hlt">topography</span> is characterized by low amplitudes and long wavelengths, its subtle effects may be best recorded in low-relief areas such as the Great Plains of the USA where they can be readily observed and measured. We apply this concept to a unique region of the western Great Plains in New Mexico and Colorado where basalt flows of the Jemez lineament (Raton-Clayton and Ocate fields) form mesas (inverted <span class="hlt">topography</span>) that record the evolution of the Great Plains surface through time. This study uses multiple datasets to evaluate the mechanisms which have driven the evolution of this landscape. Normalized channel steepness index (ksn) analysis identifies anomalously steep river gradients across broad (50-100 km) convexities within a NE- trending zone of differential river incision where higher downstream incision rates in the last 1.5 Ma suggest headwater uplift. At 2-8 Ma timescales, 40Ar/39Ar ages of basalt-capped paleosurfaces in the Raton-Clayton and Ocate volcanic fields indicate that rates of denudation increase systematically towards the NW from a NE-trending zone of approximately zero denudation (that approximately coincides with the high ksn zone), also suggestive of regional warping above the Jemez lineament. Onset of more rapid denudation is observed in the Raton-Clayton field beginning at ca. 3.6 Ma. Furthermore, two 300-400-m-high NE-trending erosional escarpments impart a staircase-like topographic profile to the region. Tomographic images from the EarthScope experiment show that NE-trending topographic features of this region correspond to an ~8 % P-wave velocity gradient of similar trend at the margin of the low-velocity Jemez mantle anomaly. We propose that the erosional landscapes of this unique area are, in large part, the surface expression of <span class="hlt">dynamic</span> mantle</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GGG....16.1771V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GGG....16.1771V"><span id="translatedtitle"><span class="hlt">Dynamics</span> of intraoceanic subduction initiation: 2. Suprasubduction zone ophiolite formation and metamorphic sole exhumation in context of <span class="hlt">absolute</span> plate motions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van Hinsbergen, Douwe J. J.; Peters, Kalijn; Maffione, Marco; Spakman, Wim; Guilmette, Carl; Thieulot, Cedric; Plümper, Oliver; Gürer, Derya; Brouwer, Fraukje M.; Aldanmaz, Ercan; Kaymakcı, Nuretdin</p> <p>2015-06-01</p> <p>Analyzing subduction initiation is key for understanding the coupling between plate tectonics and the underlying mantle. Here we focus on suprasubduction zone (SSZ) ophiolites and how their formation links to intraoceanic subduction initiation in an <span class="hlt">absolute</span> plate motion frame. SSZ ophiolites form the majority of exposed oceanic lithosphere fragments and are widely recognized to have formed during intraoceanic subduction initiation. Structural, petrological, geochemical, and plate kinematic constraints on their kinematic evolution show that SSZ crust forms at fore-arc spreading centers at the expense of a mantle wedge, thereby flattening the nascent slab. This leads to the typical inverted pressure gradients found in metamorphic soles that form at the subduction plate contact below and during SSZ crust crystallization. Former spreading centers are preserved in forearcs when subduction initiates along transform faults or off-ridge oceanic detachments. We show how these are reactivated when subduction initiates in the <span class="hlt">absolute</span> plate motion direction of the inverting weakness zone. Upon inception of slab pull due to, e.g., eclogitization, the sole is separated from the slab, remains welded to the thinned overriding plate lithosphere, and can become intruded by mafic dikes upon asthenospheric influx into the mantle wedge. We propound that most ophiolites thus formed under special geodynamic circumstances and may not be representative of normal oceanic crust. Our study highlights how far-field geodynamic processes and <span class="hlt">absolute</span> plate motions may force intraoceanic subduction initiation as key toward advancing our understanding of the entire plate tectonic cycle.</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_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" 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_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26737346','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26737346"><span id="translatedtitle">A million-plus neuron model of the hippocampal dentate gyrus: Dependency of spatio-temporal network <span class="hlt">dynamics</span> on <span class="hlt">topography</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hendrickson, Phillip J; Yu, Gene J; Song, Dong; Berger, Theodore W</p> <p>2015-01-01</p> <p>This paper describes a million-plus granule cell compartmental model of the rat hippocampal dentate gyrus, including excitatory, perforant path input from the entorhinal cortex, and feedforward and feedback inhibitory input from dentate interneurons. The model includes experimentally determined morphological and biophysical properties of granule cells, together with glutamatergic AMPA-like EPSP and GABAergic GABAA-like IPSP synaptic excitatory and inhibitory inputs, respectively. Each granule cell was composed of approximately 200 compartments having passive and active conductances distributed throughout the somatic and dendritic regions. Modeling excitatory input from the entorhinal cortex was guided by axonal transport studies documenting the topographical organization of projections from subregions of the medial and lateral entorhinal cortex, plus other important details of the distribution of glutamatergic inputs to the dentate gyrus. Results showed that when medial and lateral entorhinal cortical neurons maintained Poisson random firing, dentate granule cells expressed, throughout the million-cell network, a robust, non-random pattern of spiking best described as spatiotemporal "clustering". To identify the network property or properties responsible for generating such firing "clusters", we progressively eliminated from the model key mechanisms such as feedforward and feedback inhibition, intrinsic membrane properties underlying rhythmic burst firing, and/or topographical organization of entorhinal afferents. Findings conclusively identified topographical organization of inputs as the key element responsible for generating a spatio-temporal distribution of clustered firing. These results uncover a functional organization of perforant path afferents to the dentate gyrus not previously recognized: <span class="hlt">topography</span>-dependent clusters of granule cell activity as "functional units" that organize the processing of entorhinal signals. PMID:26737346</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4878386','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4878386"><span id="translatedtitle">A Million-Plus Neuron Model of the Hippocampal Dentate Gyrus: Dependency of Spatio-Temporal Network <span class="hlt">Dynamics</span> on <span class="hlt">Topography</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>Hendrickson, Phillip J.; Yu, Gene J.; Song, Dong; Berger, Theodore W.</p> <p>2016-01-01</p> <p>This paper describes a million-plus granule cell compartmental model of the rat hippocampal dentate gyrus, including excitatory, perforant path input from the entorhinal cortex, and feedforward and feedback inhibitory input from dentate interneurons. The model includes experimentally determined morphological and biophysical properties of granule cells, together with glutamatergic AMPA-like EPSP and GABAergic GABAA-like IPSP synaptic excitatory and inhibitory inputs, respectively. Each granule cell was composed of approximately 200 compartments having passive and active conductances distributed throughout the somatic and dendritic regions. Modeling excitatory input from the entorhinal cortex was guided by axonal transport studies documenting the topographical organization of projections from subregions of the medial and lateral entorhinal cortex, plus other important details of the distribution of glutamatergic inputs to the dentate gyrus. Results showed that when medial and lateral entorhinal cortical neurons maintained Poisson random firing, dentate granule cells expressed, throughout the million-cell network, a robust, non-random pattern of spiking best described as spatiotemporal “clustering”. To identify the network property or properties responsible for generating such firing “clusters”, we progressively eliminated from the model key mechanisms such as feedforward and feedback inhibition, intrinsic membrane properties underlying rhythmic burst firing, and/or topographical organization of entorhinal afferents. Findings conclusively identified topographical organization of inputs as the key element responsible for generating a spatio-temporal distribution of clustered firing. These results uncover a functional organization of perforant path afferents to the dentate gyrus not previously recognized: <span class="hlt">topography</span>-dependent clusters of granule cell activity as “functional units” that organize the processing of entorhinal signals. PMID:26737346</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790013321','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790013321"><span id="translatedtitle">Problems in determining sea surface <span class="hlt">topography</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Whitehead, J. A., Jr.</p> <p>1978-01-01</p> <p>Anticipated problems for determining ocean <span class="hlt">dynamics</span> signals from sea surface <span class="hlt">topography</span> are discussed. The needs for repeated tracks are listed if oceanic tides or ocean turbulence are to be determined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T13D..07P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T13D..07P"><span id="translatedtitle">Effects of rheology on the <span class="hlt">dynamics</span> and development of <span class="hlt">topography</span> in 3D numerical simulations of continental collision, with an application to the India-Asia collision zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pusok, A. E.; Kaus, B.; Popov, A.</p> <p>2014-12-01</p> <p>The Himalayas and the adjacent Tibetan Plateau represent the largest region of elevated <span class="hlt">topography</span> and anomalously thick crust on Earth. Understanding the formation and evolution of the region has been the focus of many tectonic and numerical models. While some of these models (i.e. thin sheet model) have successfully illustrated some of the basic physics of continental collision, none can simultaneously represent active processes such as subduction, underthrusting, channel flow or extrusion, for which fully 3D models are required. Here, we employed the 3D code LaMEM to investigate the role that subduction, continental collision and indentation play on lithosphere <span class="hlt">dynamics</span> at convergent margins, and the implications they have for the Asian tectonics. Our model setup resembles a simplified tectonic map of the India-Asia collision zone and we performed a large number of 3D simulations to analyse the <span class="hlt">dynamics</span> and the conditions under which large topographic plateaus, such as the Tibetan Plateau can form in an integrated lithospheric and upper-mantle scale model. Results of models with linear viscous rheologies show different modes between the oceanic subduction side (continuous subduction, trench retreat and slab roll-back) and the continental collision side (trench advance, slab detachment, topographic uplift and lateral extrusion of material). Despite the complex <span class="hlt">dynamics</span> and the great variation in slab shape across the subduction-collision zone, which are consistent with tomographic observations, we note that slab-pull alone is insufficient to generate high <span class="hlt">topography</span> in the upper plate. Several studies suggested that external forces (i.e. ridge push, plume push or slab suction) must be important in order to sustain the on-going convergence of India towards Eurasia. We show that external forcing and the presence of strong blocks such as the Tarim Basin within the Asian lithosphere are necessary to create and shape anomalously high topographic fronts and plateaus</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014DyAtO..66...28T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014DyAtO..66...28T"><span id="translatedtitle">Introducing Variable-Step <span class="hlt">Topography</span> (VST) coordinates within <span class="hlt">dynamically</span> constrained Nonhydrostatic Modeling System (NMS). Part 1: VST formulation within NMS host model framework</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tripoli, Gregory J.; Smith, Eric A.</p> <p>2014-06-01</p> <p>A Variable-Step <span class="hlt">Topography</span> (VST) surface coordinate system is introduced into a <span class="hlt">dynamically</span> constrained, scalable, nonhydrostatic atmospheric model for reliable simulations of flows over both smooth and steep terrain without sacrificing <span class="hlt">dynamical</span> integrity over either type of surface. Backgrounds of both terrain-following and step coordinate model developments are presented before justifying the turn to a VST approach within an appropriately configured host model. In this first part of a two-part sequence of papers, the full formulation of the VST model, prefaced by a description of the framework of its apposite host, i.e., a re-tooled Nonhydrostatic Modeling System (NMS), are presented. [The second part assesses the performance and benefits of the new VST coordinate system in conjunction with seven orthodox obstacle flow problems.] The NMS is a 3-dimensional, nonhydrostatic cloud-mesoscale model, designed for integrations from plume-cloud scales out to regional-global scales. The derivative properties of VST in conjunction with the NMS's newly designed <span class="hlt">dynamically</span> constrained core are capable of accurately capturing the deformations of flows by any type of terrain variability. Numerical differencing schemes needed to satisfy critical integral constraints, while also effectively enabling the VST lower boundary, are described. The host model constraints include mass, momentum, energy, vorticity and enstrophy conservation. A quasi-compressible closure cast on multiple-nest rotated spherical grids is the underlying framework used to study the advantages of the VST coordinate system. The principle objective behind the VST formulation is to combine the advantages of both terrain-following and step coordinate systems without suffering either of their disadvantages, while at the same time creating a vertical surface coordinate setting suitable for a scalable, nonhydrostatic model, safeguarded with physically realistic <span class="hlt">dynamical</span> constraints.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003AGUFM.B31C0321P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AGUFM.B31C0321P"><span id="translatedtitle">Satellite Remote Sensing of Landscape Freeze/Thaw State <span class="hlt">Dynamics</span> for Complex <span class="hlt">Topography</span> and Fire Disturbance Areas Using Multi-Sensor Radar and SRTM Digital Elevation Models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Podest, E.; McDonald, K.; Kimball, J.; Randerson, J. T.</p> <p>2003-12-01</p> <p>The annual freeze/thaw cycle drives the length of the growing season in the boreal forest, and is a major factor determining annual productivity and associated exchange of CO2 with the atmosphere. Variations in freeze/thaw processes are spatially and temporally complex in boreal environments, particularly in areas of complex <span class="hlt">topography</span> and in fire disturbance regimes. We investigate the spatial and temporal characteristics of seasonal freeze/thaw <span class="hlt">dynamics</span> in complex boreal landscapes, as derived from radar backscatter measured with ERS (C-band, VV polarization, 200m resolution) and JERS-1 (L-band, HH polarization, 100m resolution) Synthetic Aperture Radars (SARs), and with the SeaWinds scatterometer (Ku-band, 25km resolution). C- and L-band backscatter are applied to characterize freeze/thaw transitions for a chronosequence of recovering burn sites near Delta Junction, Alaska, and for a region of complex <span class="hlt">topography</span> on the Kenai Peninsula, Alaska. We characterize differences in radar-derived freeze/thaw state, examining transitions over complex terrain and landscape disturbance regimes. In areas of complex terrain, we explore freeze/thaw <span class="hlt">dynamics</span> related to elevation, slope aspect and varying landcover. In the burned regions, we explore the timing of seasonal freeze/thaw transition as related to the recovering landscape, relative to that of a nearby control site. We apply in situ biophysical measurements, including flux tower measurements to validate and interpret the remotely sensed parameters. A multi-scale analysis is performed relating high-resolution SAR backscatter and moderate resolution scatterometer measurements to assess trade-offs in spatial and temporal resolution in the remotely sensed fields. A temporal change discriminator is applied to classify time series radar imagery to classify the landscape freeze-thaw state. We apply a 30m-resolution digital elevation model (DEM) derived from Shuttle Radar <span class="hlt">Topography</span> Mission (SRTM) data to orthorectify the time</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004PhRvE..70a1911O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004PhRvE..70a1911O"><span id="translatedtitle">Spatially uniform and nonuniform analyses of electroencephalographic <span class="hlt">dynamics</span>,with application to the <span class="hlt">topography</span> of the alpha rhythm</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>O'Connor, S. C.; Robinson, P. A.</p> <p>2004-07-01</p> <p>Corticothalamic <span class="hlt">dynamics</span> are investigated using a model in which spatial nonuniformities are incorporated via the coupling of spatial eigenmodes. Comparison of spectra generated using the nonuniform analysis with those generated using a uniform one demonstrates that, for most frequencies, local activity is only weakly dependent on activity elsewhere in the cortex; however, dispersion of low-wave-number activity ensures that distant <span class="hlt">dynamics</span> influence local <span class="hlt">dynamics</span> at low frequencies (below approximately 2Hz ), and at the alpha frequency (approximately 10Hz ), where propagating signals are inherently weakly damped, and wavelengths are large. When certain model parameters have similar spatial profiles, as is expected from physiology, the low-frequency discrepancies tend to cancel, and the uniform analysis with local parameter values is an adequate approximation to the full nonuniform one across the whole spectrum, at least for large-scale nonuniformities. After comparing the uniform and nonuniform analyses, we consider one possible application of the nonuniform analysis: studying the phenomenon of occipital alpha dominance, whereby the alpha frequency and power are greater at the back of the head (occipitally) than at the front. In order to infer realistic nonuniformities in the model parameters, the uniform version of the model is first fitted to data recorded from 98 normal subjects in a waking, eyes-closed state. This yields a set of parameters at each of five electrode sites along the midline. The inferred parameter nonuniformities are consistent with anatomical and physiological constraints. Introducing these spatial profiles into the full nonuniform model then quantitatively reproduces observed site-dependent variations in the alpha power and frequency. The results confirm that the frequency shift is mainly due to a decrease in the corticothalamic propagation delay, but indicate that the delay nonuniformity cannot account for the observed occipital increase in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AnPhy.326.1941A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AnPhy.326.1941A"><span id="translatedtitle">The analysis of space-time structure in QCD vacuum II: <span class="hlt">Dynamics</span> of polarization and <span class="hlt">absolute</span> X-distribution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alexandru, Andrei; Draper, Terrence; Horváth, Ivan; Streuer, Thomas</p> <p>2011-08-01</p> <p>We propose a framework for quantitative evaluation of <span class="hlt">dynamical</span> tendency for polarization in an arbitrary random variable that can be decomposed into a pair of orthogonal subspaces. The method uses measures based on comparisons of given <span class="hlt">dynamics</span> to its counterpart with statistically independent components. The formalism of previously considered X-distributions is used to express the aforementioned comparisons, in effect putting the former approach on solid footing. Our analysis leads to the definition of a suitable correlation coefficient with clear statistical meaning. We apply the method to the <span class="hlt">dynamics</span> induced by pure-glue lattice QCD in local left-right components of overlap Dirac eigenmodes. It is found that, in finite physical volume, there exists a non-zero physical scale in the spectrum of eigenvalues such that eigenmodes at smaller (fixed) eigenvalues exhibit convex X-distribution (positive correlation), while at larger eigenvalues the distribution is concave (negative correlation). This chiral polarization scale thus separates a regime where <span class="hlt">dynamics</span> enhances chirality relative to statistical independence from a regime where it suppresses it, and gives an objective definition to the notion of "low" and "high" Dirac eigenmode. We propose to investigate whether the polarization scale remains non-zero in the infinite volume limit, in which case it would represent a new kind of low energy scale in QCD.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015E%26PSL.421..107S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015E%26PSL.421..107S"><span id="translatedtitle">Australian plate motion and <span class="hlt">topography</span> linked to fossil New Guinea slab below Lake Eyre</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schellart, W. P.; Spakman, W.</p> <p>2015-07-01</p> <p>Unravelling causes for <span class="hlt">absolute</span> plate velocity change and continental <span class="hlt">dynamic</span> <span class="hlt">topography</span> change is challenging because of the interdependence of large-scale geodynamic driving processes. Here, we unravel a clear spatio-temporal relation between latest Cretaceous-Early Cenozoic subduction at the northern edge of the Australian plate, Early Cenozoic Australian plate motion changes and Cenozoic <span class="hlt">topography</span> evolution of the Australian continent. We present evidence for a ∼4000 km wide subduction zone, which culminated in ophiolite obduction and arc-continent collision in the New Guinea-Pocklington Trough region during subduction termination, coinciding with cessation of spreading in the Coral Sea, a ∼5 cm/yr decrease in northward Australian plate velocity, and slab detachment. Renewed northward motion caused the Australian plate to override the sinking subduction remnant, which we detect with seismic tomography at 800-1200 km depth in the mantle under central-southeast Australia at a position predicted by our <span class="hlt">absolute</span> plate reconstructions. With a numerical model of slab sinking and mantle flow we predict a long-wavelength subsidence (negative <span class="hlt">dynamic</span> <span class="hlt">topography</span>) migrating southward from ∼50 Ma to present, explaining Eocene-Oligocene subsidence of the Queensland Plateau, ∼330 m of late Eocene-early Oligocene subsidence in the Gulf of Carpentaria, Oligocene-Miocene subsidence of the Marion Plateau, and providing a first-order fit to the present-day, ∼200 m deep, topographic depression of the Lake Eyre Basin and Murray-Darling Basin. We propound that <span class="hlt">dynamic</span> <span class="hlt">topography</span> evolution provides an independent means to couple geological processes to a mantle reference frame. This is complementary to, and can be integrated with, other approaches such as hotspot and slab reference frames.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23489583','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23489583"><span id="translatedtitle">Neuronal correlates of decisions to speak and act: Spontaneous emergence and <span class="hlt">dynamic</span> <span class="hlt">topographies</span> in a computational model of frontal and temporal areas.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Garagnani, Max; Pulvermüller, Friedemann</p> <p>2013-10-01</p> <p>The neural mechanisms underlying the spontaneous, stimulus-independent emergence of intentions and decisions to act are poorly understood. Using a neurobiologically realistic model of frontal and temporal areas of the brain, we simulated the learning of perception-action circuits for speech and hand-related actions and subsequently observed their spontaneous behaviour. Noise-driven accumulation of reverberant activity in these circuits leads to their spontaneous ignition and partial-to-full activation, which we interpret, respectively, as model correlates of action intention emergence and action decision-and-execution. Importantly, activity emerged first in higher-association prefrontal and temporal cortices, subsequently spreading to secondary and finally primary sensorimotor model-areas, hence reproducing the <span class="hlt">dynamics</span> of cortical correlates of voluntary action revealed by readiness-potential and verb-generation experiments. This model for the first time explains the cortical origins and <span class="hlt">topography</span> of endogenous action decisions, and the natural emergence of functional specialisation in the cortex, as mechanistic consequences of neurobiological principles, anatomical structure and sensorimotor experience. PMID:23489583</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/456978','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/456978"><span id="translatedtitle">Fluorescence of excited charge-transfer complexes and <span class="hlt">absolute</span> <span class="hlt">dynamics</span> of radical-ion pairs in acetonitrile</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gould, I.R.; Farid, S.</p> <p>1992-09-17</p> <p>An analysis of the <span class="hlt">dynamics</span> of the radical-ion pairs of a series of 2,6,9,10-tetracyanoanthracene acceptor/alkylbenzene donor systems in acetonitrile is described in this paper. This analysis is carried out by using a combination of time-resolved emission and absorption spectroscopies and measurements of {Phi} {sub ions} from the contact radical-ion pair (CRIP) and the solvent-separated radical-ion pair (SSRIP).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3023343','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3023343"><span id="translatedtitle">Combining Steady-State and <span class="hlt">Dynamic</span> Methods for Determining <span class="hlt">Absolute</span> Signs of Hyperfine Interactions: Pulsed ENDOR Saturation and Recovery (PESTRE)</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Doan, Peter E.</p> <p>2010-01-01</p> <p>The underlying causes of asymmetric intensities in Davies pulsed ENDOR spectra that are associated with the signs of the hyperfine interaction are reinvestigated. The intensity variations in these asymmetric ENDOR patterns are best described as shifts in an apparent baseline intensity that occurs <span class="hlt">dynamically</span> following on-resonance ENDOR transitions. We have developed an extremely straightforward multi-sequence protocol that is capable of giving the sign of the hyperfine interaction by probing a single ENDOR transition, without reference to its partner transition. This technique, Pulsed ENDOR Saturatation and Recovery (PESTRE) monitors <span class="hlt">dynamic</span> shifts in the ‘baseline’ following measurements at a single RF frequency (single ENDOR peak), rather than observing anomalous ENDOR intensity differences between the two branches of an ENDOR response. These baseline shifts, referred to as <span class="hlt">dynamic</span> reference levels (DRLs), can be directly tied to the electron spin manifold from which that ENDOR transition arises. The application of this protocol is demonstrated on 57Fe ENDOR of a 2Fe-2S ferredoxin. We use the 14N ENDOR transitions of the S = 3/2 [Fe(II)NO]2+ center of the non-heme iron enzyme, anthranilate dioxygenase (AntDO) to examine the details of the relaxation model using PESTRE. PMID:21075026</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/19253361','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19253361"><span id="translatedtitle"><span class="hlt">Absolute</span> quantification of cerebral blood flow in neurologically normal volunteers: <span class="hlt">dynamic</span>-susceptibility contrast MRI-perfusion compared with computed tomography (CT)-perfusion.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ziegelitz, Doerthe; Starck, Göran; Mikkelsen, Irene K; Tullberg, Mats; Edsbagge, Mikael; Wikkelsö, Carsten; Forssell-Aronson, Eva; Holtås, Stig; Knutsson, Linda</p> <p>2009-07-01</p> <p>To improve the reproducibility of arterial input function (AIF) registration and <span class="hlt">absolute</span> cerebral blood flow (CBF) quantification in <span class="hlt">dynamic</span>-susceptibility MRI-perfusion (MRP) at 1.5T, we rescaled the AIF by use of a venous output function (VOF). We compared CBF estimates of 20 healthy, elderly volunteers, obtained by computed tomography (CT)-perfusion (CTP) and MRP on two consecutive days. MRP, calculated without the AIF correction, did not result in any significant correlation with CTP. The rescaled MRP showed fair to moderate correlation with CTP for the central gray matter (GM) and the whole brain. Our results indicate that the method used for correction of partial volume effects (PVEs) improves MRP experiments by reducing AIF-introduced variance at 1.5T. PMID:19253361</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=VALUE+AND+ABSOLUTE&id=EJ1000865','ERIC'); return false;" href="http://eric.ed.gov/?q=VALUE+AND+ABSOLUTE&id=EJ1000865"><span id="translatedtitle">Teaching <span class="hlt">Absolute</span> Value Meaningfully</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>Wade, Angela</p> <p>2012-01-01</p> <p>What is the meaning of <span class="hlt">absolute</span> value? And why do teachers teach students how to solve <span class="hlt">absolute</span> value equations? <span class="hlt">Absolute</span> value is a concept introduced in first-year algebra and then reinforced in later courses. Various authors have suggested instructional methods for teaching <span class="hlt">absolute</span> value to high school students (Wei 2005; Stallings-Roberts…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4363941','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4363941"><span id="translatedtitle">Membrane related <span class="hlt">dynamics</span> and the formation of actin in cells growing on micro-<span class="hlt">topographies</span>: a spatial computational model</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>2014-01-01</p> <p> to be verified in wet-lab experiments. Conclusion Letting cells grow on surface structures is a possibility to shed new light on the intricate mechanisms that relate membrane and actin related <span class="hlt">dynamics</span> in the cell. Our results demonstrate the need for declarative expressive spatial modeling approaches that allow probing different hypotheses, and the central role of the focal adhesion complex not only for nucleating actin filaments, but also for regulating possible severing agents locally. PMID:25200251</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SGeo...35..661J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SGeo...35..661J"><span id="translatedtitle">Toward Improved Estimation of the <span class="hlt">Dynamic</span> <span class="hlt">Topography</span> and Ocean Circulation in the High Latitude and Arctic Ocean: The Importance of GOCE</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Johannessen, J. A.; Raj, R. P.; Nilsen, J. E. Ø.; Pripp, T.; Knudsen, P.; Counillon, F.; Stammer, D.; Bertino, L.; Andersen, O. B.; Serra, N.; Koldunov, N.</p> <p>2014-05-01</p> <p>The Arctic plays a fundamental role in the climate system and shows significant sensitivity to anthropogenic climate forcing and the ongoing climate change. Accelerated changes in the Arctic are already observed, including elevated air and ocean temperatures, declines of the summer sea ice extent and sea ice thickness influencing the albedo and CO2 exchange, melting of the Greenland Ice Sheet and increased thawing of surrounding permafrost regions. In turn, the hydrological cycle in the high latitude and Arctic is expected to undergo changes although to date it is challenging to accurately quantify this. Moreover, changes in the temperature and salinity of surface waters in the Arctic Ocean and Nordic Seas may also influence the flow of dense water through the Denmark Strait, which are found to be a precursor for changes in the Atlantic meridional overturning circulation with a lead time of around 10 years (Hawkins and Sutton in Geophys Res Lett 35:L11603, 2008). Evidently changes in the Arctic and surrounding seas have far reaching influences on regional and global environment and climate variability, thus emphasizing the need for advanced quantitative understanding of the ocean circulation and transport variability in the high latitude and Arctic Ocean. In this respect, this study combines in situ hydrographical data, surface drifter data and direct current meter measurements, with coupled sea ice-ocean models, radar altimeter data and the latest GOCE-based geoid in order to estimate and assess the quality, usefulness and validity of the new GOCE-derived mean <span class="hlt">dynamic</span> <span class="hlt">topography</span> for studies of the ocean circulation and transport estimates in the Nordic Seas and Arctic Ocean.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1413998B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1413998B"><span id="translatedtitle">Open<span class="hlt">Topography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Baru, C.; Arrowsmith, R.; Crosby, C.; Nandigam, V.; Phan, M.; Cowart, C.</p> <p>2012-04-01</p> <p>Open<span class="hlt">Topography</span> is a cyberinfrastructure-based facility for online access to high-resolution <span class="hlt">topography</span> and tools. The project is an outcome of the Geosciences Network (GEON) project, which was a research project funded several years ago in the US to investigate the use of cyberinfrastructure to support research and education in the geosciences. Open<span class="hlt">Topography</span> provides online access to large LiDAR point cloud datasets along with services for processing these data. Users are able to generate custom DEMs by invoking DEM services provided by Open<span class="hlt">Topography</span> with custom parameter values. Users can track the progress of their jobs, and a private myOpenTopo area retains job information and job outputs. Data available at Open<span class="hlt">Topography</span> are provided by a variety of data acquisition groups under joint agreements and memoranda of understanding (MoU). These include national facilities such as the National Center for Airborne Lidar Mapping, as well as local, state, and federal agencies. Open<span class="hlt">Topography</span> is also being designed as a hub for high-resolution <span class="hlt">topography</span> resources. Datasets and services available at other locations can also be registered here, providing a "one-stop shop" for such information. We will describe the Open<span class="hlt">Topography</span> system architecture and its current set of features, including the service-oriented architecture, a job-tracking database, and social networking features. We will also describe several design and development activities underway to archive and publish datasets using digital object identifiers (DOIs); create a more flexible and scalable high-performance environment for processing of large datasets; extend support for satellite-based and terrestrial lidar as well as synthetic aperture radar (SAR) data; and create a "pluggable" infrastructure for third-party services. Open<span class="hlt">Topography</span> has successfully created a facility for sharing lidar data. In the next phase, we are developing a facility that will also enable equally easy and successful sharing of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://medlineplus.gov/ency/article/003649.htm','NIH-MEDLINEPLUS'); return false;" href="https://medlineplus.gov/ency/article/003649.htm"><span id="translatedtitle">Eosinophil count - <span class="hlt">absolute</span></span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>Eosinophils; <span class="hlt">Absolute</span> eosinophil count ... the white blood cell count to give the <span class="hlt">absolute</span> eosinophil count. ... than 500 cells per microliter (cells/mcL). Normal value ranges may vary slightly among different laboratories. Talk ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001SPIE.4419...50M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001SPIE.4419...50M"><span id="translatedtitle">Moire <span class="hlt">topography</span> in odontology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moreno Yeras, A.</p> <p>2001-08-01</p> <p>For several decades measurement optical techniques have been used in different branches of Science and Technology and in medicine. One of these techniques is the so-called Moire <span class="hlt">topography</span> that allows the accurate measurement of different parts of the human body <span class="hlt">topography</span>. This investigation presents the measurement of <span class="hlt">topographies</span> of teeth and gums using an automated system of shadow moire, with which precision can be reached up to the order of the microns by the phase shift instrumentation in an original way. Advantages and disadvantages of using the Moire <span class="hlt">topography</span> and its comparison with other techniques used in the optical metrology are presented. Also, some positive and negative aspects of the implementation of this technique are shown in dentistry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=inspection+AND+techniques&pg=3&id=EJ096841','ERIC'); return false;" href="http://eric.ed.gov/?q=inspection+AND+techniques&pg=3&id=EJ096841"><span id="translatedtitle">X Ray <span class="hlt">Topography</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>Balchin, A. A.</p> <p>1974-01-01</p> <p>Discusses some aspects in X-ray <span class="hlt">topography</span>, including formation of dislocations, characteristics of stacking faults, x-ray contrast in defect inspection, Berg-Barrett technique, and Lang traversing crystal and Borrmann's methods. (CC)</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_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" 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_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JHyd..510..124L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JHyd..510..124L"><span id="translatedtitle">Effects of <span class="hlt">topography</span> and soil depth on saturated-zone <span class="hlt">dynamics</span> in steep hillslopes explored using the three-dimensional Richards' equation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liang, Wei-Li; Uchida, Taro</p> <p>2014-03-01</p> <p>The generation of subsurface saturation has large implications for hydrological response in a catchment. Although rainfall-runoff responses have been observed worldwide in many catchments, the spatiotemporal patterns of soil-water movement and subsurface saturation processes in hillslopes and catchments are not yet fully understood because of the small number of observations and their limited areal extent. Numerical simulation allows for exploration of the entire subsurface saturation process in a hillslope or basin. In this study, as a virtual experiment we used a three-dimensional Richards' equation and detailed observational data of <span class="hlt">topography</span> and soil depth to examine the <span class="hlt">dynamics</span> of subsurface saturated-zone generation in steep hillslopes in a catchment during a storm event. Such a simulation approach had not been previously applied for a catchment-scale area. In order to identify the effects of topographic factors on saturation development, we excluded the influence of the heterogeneity of hydraulic properties and used three generalized hydraulic parameter sets that were previously proposed for environments similar to our site. The resulting waveforms of discharges in the three simulations were quite different and unexpected, which was predominately attributed to the combination of soil and bedrock hydraulic conductivity characteristics. However, common appearances in spatial and temporal variations in the generations of saturated zones were found in the three simulations. Subsurface saturation predominately developed at the soil-bedrock interface where saturated zones were generated fragmentarily and locally at first and then connected to flow downslope, flowing from the upper or middle slope areas to the lower slope area. The fragmentary development of saturated zones in the early stage during the storm event was controlled by soil depth; subsequently, the lateral transfer of saturation was controlled by the topographic wetness index at the soil</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhyA..439....1O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhyA..439....1O"><span id="translatedtitle"><span class="hlt">Absolute</span> negative mobility of interacting Brownian particles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ou, Ya-li; Hu, Cai-tian; Wu, Jian-chun; Ai, Bao-quan</p> <p>2015-12-01</p> <p>Transport of interacting Brownian particles in a periodic potential is investigated in the presence of an ac force and a dc force. From Brownian <span class="hlt">dynamic</span> simulations, we find that both the interaction between particles and the thermal fluctuations play key roles in the <span class="hlt">absolute</span> negative mobility (the particle noisily moves backwards against a small constant bias). When no the interaction acts, there is only one region where the <span class="hlt">absolute</span> negative mobility occurs. In the presence of the interaction, the <span class="hlt">absolute</span> negative mobility may appear in multiple regions. The weak interaction can be helpful for the <span class="hlt">absolute</span> negative mobility, while the strong interaction has a destructive impact on it.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JVGR..310..172S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JVGR..310..172S"><span id="translatedtitle">The oscillation model of hydrothermal <span class="hlt">dynamics</span> beneath Aso volcano, southwest Japan after small eruption on May 2011: A new understanding model using repeated <span class="hlt">absolute</span> and relative gravity measurement</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sofyan, Yayan; Nishijima, Jun; Fujimitsu, Yasuhiro; Yoshikawa, Shin; Kagiyama, Tsuneomi; Ohkura, Takahiro</p> <p>2016-01-01</p> <p>At the end of 2010, the seismic activity in Aso volcano intensely increased and water level in the Nakadake crater decreased until early in 2011, then was followed by a small eruption in May 2011. After the eruption and heavy rain, the volcanic activity subsided to calm period, crater bottom was refilled with water, and water level increased in the Nakadake crater. The next tremor reappeared in 2014 and tracked to eruption in November 2014. This eruptive pattern and water level variation in the crater repeatedly appeared on the surface, and it should be related to the hydrothermal <span class="hlt">dynamics</span> beneath Aso volcano. We initiated the gravity measurements in relation to hydrothermal <span class="hlt">dynamics</span> in the subsurface of Aso volcano using Scintrex CG-5 (549) and LaCoste Romberg type G-1016 relative gravimeter at 28 benchmarks in April 2011, one month before the eruption. The repeated gravity measurements continue to monitor Aso volcano with a series of the measurement after the eruption in every three months to a half year. We analyze the gravity variation from 2011 to 2014 between the time of the phreatic and strombolian eruption. The measurements covered the area more than 60 km2 in the west side of Aso caldera. A new gravity network was also installed in May 2010 at seven benchmarks using A10-017 <span class="hlt">absolute</span> gravimeter, which re-occupied in October 2010, June 2011 and two benchmarks in June 2014. As a result, the gravity changes distinguish hydrothermal <span class="hlt">dynamic</span> in the subsurface, which has a direct correlation to water level fluctuation in the crater, after the first eruption and before the second discharge. The monitoring data notice large gravity changes between the surveys at benchmarks around Nakadake crater and Kusasenri area. The simple 3D inversion models of the 4-D gravity data deduce the density contrast distribution beneath Aso volcano. The inversion and mass change result generate the oscillation typical as a new understanding model. The variation of the mass shows a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1042637','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1042637"><span id="translatedtitle"><span class="hlt">Absolute</span> nuclear material assay</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.</p> <p>2012-05-15</p> <p>A method of <span class="hlt">absolute</span> nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an <span class="hlt">absolute</span> nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an <span class="hlt">absolute</span> nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/993087','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/993087"><span id="translatedtitle"><span class="hlt">Absolute</span> nuclear material assay</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.</p> <p>2010-07-13</p> <p>A method of <span class="hlt">absolute</span> nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an <span class="hlt">absolute</span> nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an <span class="hlt">absolute</span> nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1714981I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1714981I"><span id="translatedtitle">Post-fire Vegetation Regeneration <span class="hlt">Dynamics</span> to <span class="hlt">Topography</span> and Burn Severity in two contrasting ecosystems: the Case of the Montane Cordillera Ecozones of Western Canada & that of a Typical Mediterranean site in Greece</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ireland, Gareth; Petropoulos, George P.; Kalivas, Dionissios; Griffirths, Hywel M.; Louka, Panagiota</p> <p>2015-04-01</p> <p>Altering land cover <span class="hlt">dynamics</span> is currently regarded as the single most important variable of global change affecting ecological systems. Wildfires are an integral part of many terrestrial ecosystems and are considered to dramatically affect land cover <span class="hlt">dynamics</span> at a variety of spatial and temporal scales. In this context, knowledge of the spatio-temporal distribution of post-fire vegetation recovery <span class="hlt">dynamics</span> is of key importance. In this study, we explore the relationships between vegetation recovery <span class="hlt">dynamics</span> to <span class="hlt">topography</span> and burn severity for two different ecosystems using a chronosequence of Landsat TM data images analysis. One of our experimental sites is the Okanagan Mountain Park, located in the Montane Cordillera Ecozones of western Canada at which a fire occurred in 2003. The other is Mt. Parnitha, located in Greece, representing a typical Mediterranean setting. The spatio-temporal patterns of regrowth for 8 years following the fire events were quantified based on the analysis of 2 widely used indices, the Normalized Difference Vegetation Index (NDVI) and the Regeneration Index (RI). Burn severity was derived from the differenced Normalized Burn Ratio (dNBR) index computed from the Landsat TM images. Topographical information for the studied area was obtained from the ASTER global operational product. Relationships of vegetation regrowth to both <span class="hlt">topography</span> and burn severity was quantified using a series of additional statistical metrics. In overall, results indicated noticeable differences in the recovery rates of both ecosystems to the pre-fire patterns. Re-growth rates appeared to be somewhat higher in north-facing slopes in comparison to south facing ones for both experimental sites, in common with other similar studies in different ecosystems. Lastly, areas of lower burn severity exhibited a higher recovery rate compared to areas of high severity burns. Results are presented in detail and an explanation of the main observation trends is also attempted to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NPGeo..22..713L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NPGeo..22..713L"><span id="translatedtitle">Universal multifractal Martian <span class="hlt">topography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Landais, F.; Schmidt, F.; Lovejoy, S.</p> <p>2015-11-01</p> <p>In the present study, we investigate the scaling properties of the <span class="hlt">topography</span> of Mars. Planetary topographic fields are well known to roughly exhibit (mono)fractal behavior. Indeed, the fractal formalism reproduces much of the variability observed in <span class="hlt">topography</span>. Still, a single fractal dimension is not enough to explain the huge variability and intermittency. Previous studies have claimed that fractal dimensions might be different from one region to another, excluding a general description at the planetary scale. In this article, we analyze the Martian topographic data with a multifractal formalism to study the scaling intermittency. In the multifractal paradigm, the apparent local variation of the fractal dimension is interpreted as a statistical property of multifractal fields. We analyze the <span class="hlt">topography</span> measured with the Mars Orbiter Laser altimeter (MOLA) at 300 m horizontal resolution, 1 m vertical resolution. We adapted the Haar fluctuation method to the irregularly sampled signal. The results suggest a multifractal behavior from the planetary scale down to 10 km. From 10 to 300 m, the <span class="hlt">topography</span> seems to be simple monofractal. This transition indicates a significant change in the geological processes governing the Red Planet's surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NPGD....2.1007L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NPGD....2.1007L"><span id="translatedtitle">Universal multifractal Martian <span class="hlt">topography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Landais, F.; Schmidt, F.; Lovejoy, S.</p> <p>2015-07-01</p> <p>In the present study, we investigate the scaling properties of the <span class="hlt">topography</span> of Mars. Planetary topographic fields are well known to roughly exhibit (mono)fractal behavior. Indeed, the fractal formalism is reproduces much of the variability observed in <span class="hlt">topography</span>. Still, a single fractal dimension is not enough to explain the huge variability and intermittency. Previous studies have claimed that fractal dimensions might be different from one region to an other, excluding a general description at the planetary scale. In this article, we are analyzing the Martian topographic data with a multifractal formalism to study the scaling intermittency. In the multifractal paradigm, the apparent local variation of the fractal dimension is interpreted as a statistical property of multifractal fields. We analyze the <span class="hlt">topography</span> measured with the laser altimeter MOLA at 300 m horizontal resolution, 1 m vertical resolution. We adapted the Haar fluctuation method to the the irregularly sampled signal. The results suggest a multifractal behavior from planetary scale down to 10 km. From 10 km to 300 m, the <span class="hlt">topography</span> seems to be simple monofractal. This transition indicates a significant change in the geological processes governing the Red Planet's surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014P%26SS..102...51W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014P%26SS..102...51W"><span id="translatedtitle">Phobos' shape and <span class="hlt">topography</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>Willner, K.; Shi, X.; Oberst, J.</p> <p>2014-11-01</p> <p>The global shape and the <span class="hlt">dynamic</span> environment are fundamental properties of a body. Other properties such as volume, bulk density, and models for the <span class="hlt">dynamic</span> environment can subsequently be computed based on such models. Stereo-photogrammetric methods were applied to derive a global digital terrain model (DTM) with 100 m/pixel resolution using High Resolution Stereo Camera images of the Mars Express mission and Viking Orbiter images. In a subsequent least-squares fit, coefficients of the spherical harmonic function to degree and order 45 are computed. The <span class="hlt">dynamic</span> models for Phobos were derived from a polyhedron representation of the DTM. The DTM, spherical harmonic function model, and <span class="hlt">dynamic</span> models, have been refined and represent Phobos' <span class="hlt">dynamic</span> and geometric <span class="hlt">topography</span> with much more detail when compared to Shi et al. (2012) and Willner et al. (2010) models, respectively. The volume of Phobos has been re-determined to be in the order of 5741 km3 with an uncertainty of only 0.6% of the total volume. This reduces the bulk density to 1.86±0.013 g/cm3 in comparison to previous results. Assuming a homogeneous mass distribution a forced libration amplitude for Phobos of 1.14° is computed that is in better agreement with observations by Willner et al. (2010) than previous estimates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19780061113&hterms=ferrari&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dferrari','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19780061113&hterms=ferrari&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dferrari"><span id="translatedtitle">Mars <span class="hlt">topography</span> harmonics and geophysical implications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bills, B. G.; Ferrari, A. J.</p> <p>1978-01-01</p> <p>The paper describes an improved model of Martian global <span class="hlt">topography</span> which has been obtained by fitting a sixteenth-degree harmonic series to occultation, radar, spectral, and photogrammetric measurements. Empirical elevation data based on photographic data are used to supplement the observations in areas without data. Values for the mean radius, the mean density, and the displacement of the center of the figure from the center of mass are presented. The reported geometric flattening is too great and the reported <span class="hlt">dynamic</span> flattening is too small for Mars to be homogeneous and hydrostatic. Maps of the data distribution, global <span class="hlt">topography</span>, and Bouguer gravity anomaly are interpreted in terms of a crustal thickness map which is consistent with gravity, <span class="hlt">topography</span>, and recent preliminary Viking seismic results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140010845','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140010845"><span id="translatedtitle">The Dawn <span class="hlt">Topography</span> Investigation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Raymond, C. A.; Jaumann, R.; Nathues, A.; Sierks, H.; Roatsch, T.; Preusker, E; Scholten, F.; Gaskell, R. W.; Jorda, L.; Keller, H.-U.; Zuber, M. T.; Smith, D. E.; Mastrodemos, N.; Mottola, S.</p> <p>2011-01-01</p> <p>The objective of the Dawn <span class="hlt">topography</span> investigation is to derive the detailed shapes of 4 Vesta and 1 Ceres in order to create orthorectified image mosaics for geologic interpretation, as well as to study the asteroids' landforms, interior structure, and the processes that have modified their surfaces over geologic time. In this paper we describe our approaches for producing shape models, plans for acquiring the needed image data for Vesta, and the results of a numerical simulation of the Vesta mapping campaign that quantify the expected accuracy of our results. Multi-angle images obtained by Dawn's framing camera will be used to create topographic models with 100 m/pixel horizontal resolution and 10 m height accuracy at Vesta, and 200 m/pixel horizontal resolution and 20 m height accuracy at Ceres. Two different techniques, stereophotogrammetry and stereophotoclinometry, are employed to model the shape; these models will be merged with the asteroidal gravity fields obtained by Dawn to produce geodetically controlled topographic models for each body. The resulting digital <span class="hlt">topography</span> models, together with the gravity data, will reveal the tectonic, volcanic and impact history of Vesta, and enable co-registration of data sets to determine Vesta's geologic history. At Ceres, the <span class="hlt">topography</span> will likely reveal much about processes of surface modification as well as the internal structure and evolution of this dwarf planet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23586876','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23586876"><span id="translatedtitle"><span class="hlt">Absolute</span> biological needs.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>McLeod, Stephen</p> <p>2014-07-01</p> <p><span class="hlt">Absolute</span> needs (as against instrumental needs) are independent of the ends, goals and purposes of personal agents. Against the view that the only needs are instrumental needs, David Wiggins and Garrett Thomson have defended <span class="hlt">absolute</span> needs on the grounds that the verb 'need' has instrumental and <span class="hlt">absolute</span> senses. While remaining neutral about it, this article does not adopt that approach. Instead, it suggests that there are <span class="hlt">absolute</span> biological needs. The <span class="hlt">absolute</span> nature of these needs is defended by appeal to: their objectivity (as against mind-dependence); the universality of the phenomenon of needing across the plant and animal kingdoms; the impossibility that biological needs depend wholly upon the exercise of the abilities characteristic of personal agency; the contention that the possession of biological needs is prior to the possession of the abilities characteristic of personal agency. Finally, three philosophical usages of 'normative' are distinguished. On two of these, to describe a phenomenon or claim as 'normative' is to describe it as value-dependent. A description of a phenomenon or claim as 'normative' in the third sense does not entail such value-dependency, though it leaves open the possibility that value depends upon the phenomenon or upon the truth of the claim. It is argued that while survival needs (or claims about them) may well be normative in this third sense, they are normative in neither of the first two. Thus, the idea of <span class="hlt">absolute</span> need is not inherently normative in either of the first two senses. PMID:23586876</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009ECSS...85..593K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009ECSS...85..593K"><span id="translatedtitle">Exploring LiDAR data for mapping the micro-<span class="hlt">topography</span> and tidal hydro-<span class="hlt">dynamics</span> of mangrove systems: An example from southeast Queensland, Australia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Knight, Jon M.; Dale, Pat E. R.; Spencer, John; Griffin, Lachlan</p> <p>2009-12-01</p> <p>The aim was to explore the use of Light Detection and Ranging (LiDAR) data to map the micro-<span class="hlt">topography</span> of an intertidal wetland in southeast Queensland Australia. The driver for this was the need to identify and map the habitats of the immature stages of an aedine disease vector mosquito ( Aedes vigilax (Skuse)). We derived a high resolution digital elevation model (DEM) data set at a vertical resolution of 0.05 m from LiDAR data. The relative accuracy of the DEM across the site was tested by comparing water depth predictions derived from the DEM against in-situ water depth readings from pressure sensors over a 10-day tidal cycle, which included high spring tides. We found that the field observations of micro-topographic units important for mosquito management matched those delineated from the DEM. The micro-<span class="hlt">topography</span> included a low berm or central ridge that was more or less continuous across the site, a shallow back basin and fringing mangroves. The fringing mangroves had unimpeded connection to the tidal source, however the central ridge blocked tidal water from the back basin for all but the highest tides. Eggshell survey indicated that the back basin was the area suitable for immature mosquitoes. We conclude that LiDAR data has application for understanding and mapping the structure of mangrove wetlands. We have also demonstrated (in a small area) that LiDAR is useful for modelling the effect of sea level changes on the coastal fringe. LiDAR may be the only method to inform research on changes to land use and ecosystems caused by sea level change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT.......187S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT.......187S"><span id="translatedtitle">Investigations of Titan's <span class="hlt">topography</span> and surface roughness</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sharma, Priyanka</p> <p></p> <p>Saturn's moon, Titan is a geomorphologically active planetary object, and its surface is influenced by multiple processes like impact cratering, fluvial and aeolian erosion, lacustrine processes, tectonics, cryovolcanism and mantling. Disentangling the processes that compete to shape Titan's landscape is difficult in the absence of global <span class="hlt">topography</span> data. In this thesis, I utilize techniques in topographic statistics, fractal theory, study of terrestrial analogs and landscape evolution modeling to characterize Titan's <span class="hlt">topography</span> and surface roughness and investigate the relative roles of surface processes in sculpting its landscape. I mapped the shorelines of 290 North Polar Titanian lakes using the Cassini Synthetic Aperture Radar dataset. The fractal dimensions of the shorelines were calculated via the divider/ruler method and box-counting method, at length scales of (1--10) km and found to average 1.27 and 1.32, respectively. The inferred power-spectral exponent of Titan's <span class="hlt">topography</span> was found to be ≤ 2, which is lower than the values obtained from the global <span class="hlt">topography</span> of the Earth or Venus. In order to interpret fractal dimensions of Titan's shorelines in terms of the surficial processes at work, I repeated a similar statistical analysis with 114 terrestrial analogous lakes formed by different processes, using C-band radar backscatter data from the Shuttle Radar <span class="hlt">Topography</span> Mission (SRTM). I found different lake generation mechanisms on Earth produce 'statistically different' shorelines; however, no specific set of processes could be identified for forming Titanian lake basins. Using the Cassini RADAR altimetry data, I investigated Titan's global surface roughness and calculated median <span class="hlt">absolute</span> slopes, average relief and Hurst exponent (H) for the surface of Titan. I detected a clear trend with latitude in these roughness parameters. Equatorial regions had the smallest slopes, lowest values of H and smallest intra-footprint relief, compared to the mid</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012SPIE.8209E..1US','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012SPIE.8209E..1US"><span id="translatedtitle">Toward optical coherence <span class="hlt">topography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sayegh, Samir; Jiang, Yanshui</p> <p>2012-03-01</p> <p>Commercial OCT systems provide pachymetry measurements. Full corneal topographic information of anterior and posterior corneal surfaces for use in cataract surgery and refractive procedures is a desirable goal and would add to the usefulness of anterior and posterior segment evaluation. While substantial progress has been made towards obtaining "average" central corneal power (D Huang), power in different meridians and <span class="hlt">topography</span> are still missing. This is usually reported to be due to eye movement. We analyze the role of centration, eye movements and develop a model that allows for the formulation of criteria for obtaining reliable topographic data within ¼ diopter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1231575','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1231575"><span id="translatedtitle">The <span class="hlt">absolute</span> path command</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Moody, A.</p> <p>2012-05-11</p> <p>The ap command traveres all symlinks in a given file, directory, or executable name to identify the final <span class="hlt">absolute</span> path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it can provide the <span class="hlt">absolute</span> path to a relative directory from the current working directory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1231575-absolute-path-command','SCIGOV-ESTSC'); return false;" href="http://www.osti.gov/scitech/biblio/1231575-absolute-path-command"><span id="translatedtitle">The <span class="hlt">absolute</span> path command</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech/">Energy Science and Technology Software Center (ESTSC)</a></p> <p></p> <p>2012-05-11</p> <p>The ap command traveres all symlinks in a given file, directory, or executable name to identify the final <span class="hlt">absolute</span> path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it canmore » provide the <span class="hlt">absolute</span> path to a relative directory from the current working directory.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4315668','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4315668"><span id="translatedtitle"><span class="hlt">Absolute</span> Quantitation of Myocardial Blood Flow in Human Subjects with or without Myocardial Ischemia using <span class="hlt">Dynamic</span> Flurpiridaz F 18 Positron Emission Tomography</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Packard, René R. S.; Huang, Sung-Cheng; Dahlbom, Magnus; Czernin, Johannes; Maddahi, Jamshid</p> <p>2015-01-01</p> <p><span class="hlt">Absolute</span> quantitation of myocardial blood flow (MBF) by positron emission tomography (PET) is an established method of analyzing coronary artery disease (CAD) but subject to the various shortcomings of available radiotracers. Flurpiridaz F 18 is a novel PET radiotracer which exhibits properties of an ideal tracer. Methods A new <span class="hlt">absolute</span> perfusion quantitation method with Flurpiridaz was developed, taking advantage of the early kinetics and high first-pass extraction by the myocardium of this radiotracer, and the first in human measurements of MBF performed in 7 normal subjects and 8 patients with documented CAD. PET images with time-activity curves were acquired at rest and during adenosine stress. Results In normal subjects, regional MBF between coronary artery territories did not differ significantly, leading to a mean global MBF of 0.73 mL/min/g at rest and 2.53 mL/min/g during stress, with a mean global myocardial flow reserve (MFR) of 3.70. CAD vascular territories with <50% stenosis demonstrated a mean MBF of 0.73 at rest and 2.02 during stress, leading to a mean MFR of 2.97. CAD vascular territories with ≥50% stenosis exhibited a mean MBF of 0.86 at rest and 1.43 during stress, leading to a mean MFR of 1.86. Differences in stress MBF and MFR between normal and CAD territories, as well as between <50% and ≥50% stenosis vascular territories, were significant (P<0.01). Conclusion <span class="hlt">Absolute</span> quantitation of MBF in humans with the novel PET radiotracer Flurpiridaz is feasible over a wide range of cardiac flow in the presence or absence of stress-inducible myocardial ischemia. The significant decrease in stress MBF and ensuing MFR in CAD territories allows a clear distinction between vascular territories exhibiting stress-inducible myocardial ischemia and those with normal perfusion. PMID:25071096</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20000110271&hterms=MOLA&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DMOLA','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20000110271&hterms=MOLA&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DMOLA"><span id="translatedtitle">Implications of MOLA Global Roughness, Statistics, and <span class="hlt">Topography</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Aharonson, O.; Zuber, M. T.; Neumann, G. A.</p> <p>1999-01-01</p> <p>New insights are emerging as the ongoing high-quality measurements of the Martian surface <span class="hlt">topography</span> by Mars Orbiter Laser Altimeter (MOLA) on board the Mars Global Surveyor (MGS) spacecraft increase in coverage, resolution, and diversity. For the first time, a global characterization of the statistical properties of <span class="hlt">topography</span> is possible. The data were collected during the aerobreaking hiatus, science phasing, and mapping orbits of MGS, and have a resolution of 300-400 m along track, a range resolution of 37.5 cm, a range precision of 1-10 m for surface slopes up to 30 deg., and an <span class="hlt">absolute</span> accuracy of <span class="hlt">topography</span> of 13 m. The spacecraft's orbit inclination dictates that nadir observations have latitude coverage of about 87.1S to 87.1N; the addition of observations obtained during a period of off-nadir pointing over the north pole extended coverage to 90N. Additional information is contained in the original extended abstract.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050170605','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050170605"><span id="translatedtitle">RADAR Reveals Titan <span class="hlt">Topography</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kirk, R. L.; Callahan, P.; Seu, R.; Lorenz, R. D.; Paganelli, F.; Lopes, R.; Elachi, C.</p> <p>2005-01-01</p> <p>The Cassini Titan RADAR Mapper is a K(sub u)-band (13.78 GHz, lambda = 2.17 cm) linear polarized RADAR instrument capable of operating in synthetic aperture (SAR), scatterometer, altimeter and radiometer modes. During the first targeted flyby of Titan on 26 October, 2004 (referred to as Ta) observations were made in all modes. Evidence for topographic relief based on the Ta altimetry and SAR data are presented here. Additional SAR and altimetry observations are planned for the T3 encounter on 15 February, 2005, but have not been carried out at this writing. Results from the T3 encounter relevant to <span class="hlt">topography</span> will be included in our presentation. Data obtained in the Ta encounter include a SAR image swath</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_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" 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_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=PIA00740&hterms=Dark+web&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DDark%2Bweb','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=PIA00740&hterms=Dark+web&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DDark%2Bweb"><span id="translatedtitle"><span class="hlt">Topography</span> of Io (color)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1997-01-01</p> <p>The images used to create this color composite of Io were acquired by Galileo during its ninth orbit (C9) of Jupiter and are part of a sequence of images designed to map the <span class="hlt">topography</span> or relief on Io and to monitor changes in the surface color due to volcanic activity. Obtaining images at low illumination angles is like taking a picture from a high altitude around sunrise or sunset. Such lighting conditions emphasize the <span class="hlt">topography</span> of the volcanic satellite. Several mountains up to a few miles high can be seen in this view, especially near the upper right. Some of these mountains appear to be tilted crustal blocks. Most of the dark spots correspond to active volcanic centers.<p/>North is to the top of the picture which merges images obtained with the clear, red, green, and violet filters of the solid state imaging (CCD) system on NASA's Galileo spacecraft. . The resolution is 8.3 kilometers per picture element. The image was taken on June 27, 1997 at a range of 817,000 kilometers by the solid state imaging (CCD) system on NASA's Galileo spacecraft.<p/>The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).<p/>This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4028274','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4028274"><span id="translatedtitle">Lake <span class="hlt">Topography</span> and Wind Waves Determining Seasonal-Spatial <span class="hlt">Dynamics</span> of Total Suspended Matter in Turbid Lake Taihu, China: Assessment Using Long-Term High-Resolution MERIS Data</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhang, Yunlin; Shi, Kun; Liu, Xiaohan; Zhou, Yongqiang; Qin, Boqiang</p> <p>2014-01-01</p> <p>Multiple comprehensive in situ bio-optical investigations were conducted from 2005 to 2010 and covered a large variability of total suspended matter (TSM) in Lake Taihu to calibrate and validate a TSM concentration estimation model based on Medium Resolution Imaging Spectrometer (MERIS) data. The estimation model of the TSM concentration in Lake Taihu was developed using top-of-atmosphere (TOA) radiance of MERIS image data at band 9 in combination with a regional empirical atmospheric correction model, which was strongly correlated with the in situ TSM concentration (r2 = 0.720, p<0.001, and n = 73). The relative root mean square error (RRMSE) and mean relative error (MRE) were 36.9% and 31.6%, respectively, based on an independent validation dataset that produced reliable estimations of the TSM concentration. The developed algorithm was applied to 50 MERIS images from 2003 to 2011 to obtain a high spatial and temporal heterogeneity of TSM concentrations in Lake Taihu. Seasonally, the highest and lowest TSM concentrations were found in spring and autumn, respectively. Spatially, TSM concentrations were high in the southern part and center of the lake and low in Xukou Bay, East Lake Taihu. The lake <span class="hlt">topography</span>, including the water depth and distance from the shore, had a significant effect on the TSM spatial distribution. A significant correlation was found between the daily average wind speed and TSM concentration (r2 = 0.685, p<0.001, and n = 50), suggesting a critical role of wind speed in the TSM variations in Lake Taihu. In addition, a low TSM concentration was linked to the appearance of submerged aquatic vegetation (SAV). Therefore, TSM <span class="hlt">dynamics</span> were controlled by the lake <span class="hlt">topography</span>, wind-driven sediment resuspension and SAV distribution. PMID:24846206</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26022836','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26022836"><span id="translatedtitle"><span class="hlt">Absolutely</span> relative or relatively <span class="hlt">absolute</span>: violations of value invariance in human decision making.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Teodorescu, Andrei R; Moran, Rani; Usher, Marius</p> <p>2016-02-01</p> <p>Making decisions based on relative rather than <span class="hlt">absolute</span> information processing is tied to choice optimality via the accumulation of evidence differences and to canonical neural processing via accumulation of evidence ratios. These theoretical frameworks predict invariance of decision latencies to <span class="hlt">absolute</span> intensities that maintain differences and ratios, respectively. While information about the <span class="hlt">absolute</span> values of the choice alternatives is not necessary for choosing the best alternative, it may nevertheless hold valuable information about the context of the decision. To test the sensitivity of human decision making to <span class="hlt">absolute</span> values, we manipulated the intensities of brightness stimuli pairs while preserving either their differences or their ratios. Although asked to choose the brighter alternative relative to the other, participants responded faster to higher <span class="hlt">absolute</span> values. Thus, our results provide empirical evidence for human sensitivity to task irrelevant <span class="hlt">absolute</span> values indicating a hard-wired mechanism that precedes executive control. Computational investigations of several modelling architectures reveal two alternative accounts for this phenomenon, which combine <span class="hlt">absolute</span> and relative processing. One account involves accumulation of differences with activation dependent processing noise and the other emerges from accumulation of <span class="hlt">absolute</span> values subject to the temporal <span class="hlt">dynamics</span> of lateral inhibition. The potential adaptive role of such choice mechanisms is discussed. PMID:26022836</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JGRE..120..287J&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JGRE..120..287J&link_type=ABSTRACT"><span id="translatedtitle">Support of long-wavelength <span class="hlt">topography</span> on Mercury inferred from MESSENGER measurements of gravity and <span class="hlt">topography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>James, Peter B.; Zuber, Maria T.; Phillips, Roger J.; Solomon, Sean C.</p> <p>2015-02-01</p> <p>To explore the mechanisms of support of surface <span class="hlt">topography</span> on Mercury, we have determined the admittances and correlations of <span class="hlt">topography</span> and gravity in Mercury's northern hemisphere from measurements obtained by NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. These admittances and correlations can be interpreted in the context of a number of theoretical scenarios, including flexural loading and <span class="hlt">dynamic</span> flow. We find that long-wavelength (spherical harmonic degree l < 15) surface <span class="hlt">topography</span> on Mercury is primarily supported through a combination of crustal thickness variations and deep mass anomalies. The deep mass anomalies may be interpreted either as lateral variations in mantle density or as relief on compositional interfaces. Domical topographic swells are associated with high admittances and are compensated at 300-400 km depth in the lower reaches of Mercury's mantle. Quasi-linear topographic rises are primarily associated with shallow crustal compensation and are weakly correlated with positive mass anomalies in the mantle. The center of the Caloris basin features some of the thinnest crust on the planet, and the basin is underlain by a large negative mass anomaly. We also explore models of <span class="hlt">dynamic</span> flow in the presence of compositional stratification above the liquid core. If there is substantial compositional stratification in Mercury's solid outer shell, relaxation of perturbed compositional interfaces may be capable of creating and sustaining long-wavelength <span class="hlt">topography</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=PIA01217&hterms=solid+state+lighting&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsolid%2Bstate%2Blighting','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=PIA01217&hterms=solid+state+lighting&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsolid%2Bstate%2Blighting"><span id="translatedtitle"><span class="hlt">Topography</span> of Io</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1997-01-01</p> <p>This image of Io was acquired by Galileo during its ninth orbit (C9) of Jupiter as part of a sequence of images designed to cover Io at low illumination angles to map the landforms. Obtaining images at such illuminations is like taking a picture from a high altitude around sunrise or sunset. Such lighting conditions emphasize the <span class="hlt">topography</span> of the volcanic satellite. Several mountains up to a few miles high can be seen in this view, especially near the upper right. Some of these mountains appear to be tilted crustal blocks.<p/>North is to the top of the picture. The resolution is 8.3 kilometers per picture element. The image was taken on June 27, 1997 at a range of 817,000 kilometers by the solid state imaging (CCD) system on NASA's Galileo spacecraft.<p/>The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.<p/>This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110013051','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110013051"><span id="translatedtitle">Electronic <span class="hlt">Absolute</span> Cartesian Autocollimator</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Leviton, Douglas B.</p> <p>2006-01-01</p> <p>An electronic <span class="hlt">absolute</span> Cartesian autocollimator performs the same basic optical function as does a conventional all-optical or a conventional electronic autocollimator but differs in the nature of its optical target and the manner in which the position of the image of the target is measured. The term <span class="hlt">absolute</span> in the name of this apparatus reflects the nature of the position measurement, which, unlike in a conventional electronic autocollimator, is based <span class="hlt">absolutely</span> on the position of the image rather than on an assumed proportionality between the position and the levels of processed analog electronic signals. The term Cartesian in the name of this apparatus reflects the nature of its optical target. Figure 1 depicts the electronic functional blocks of an electronic <span class="hlt">absolute</span> Cartesian autocollimator along with its basic optical layout, which is the same as that of a conventional autocollimator. Referring first to the optical layout and functions only, this or any autocollimator is used to measure the compound angular deviation of a flat datum mirror with respect to the optical axis of the autocollimator itself. The optical components include an illuminated target, a beam splitter, an objective or collimating lens, and a viewer or detector (described in more detail below) at a viewing plane. The target and the viewing planes are focal planes of the lens. Target light reflected by the datum mirror is imaged on the viewing plane at unit magnification by the collimating lens. If the normal to the datum mirror is parallel to the optical axis of the autocollimator, then the target image is centered on the viewing plane. Any angular deviation of the normal from the optical axis manifests itself as a lateral displacement of the target image from the center. The magnitude of the displacement is proportional to the focal length and to the magnitude (assumed to be small) of the angular deviation. The direction of the displacement is perpendicular to the axis about which the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950048057&hterms=schlumberger&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dschlumberger','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950048057&hterms=schlumberger&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dschlumberger"><span id="translatedtitle">The length-scaling properties of <span class="hlt">topography</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Weissel, Jeffrey K.; Pratson, Lincoln F.; Malinverno, Alberto</p> <p>1994-01-01</p> <p>The scaling properties of synthetic topographic surfaces and digital elevation models (DEMs) of <span class="hlt">topography</span> are examined by analyzing their 'structure functions,' i.e., the qth order powers of the <span class="hlt">absolute</span> elevation differences: delta h(sub q) (l) = E((<span class="hlt">absolute</span> value of h(x + l) - h(x))(exp q)). We find that the relation delta h(sub 1 l) approximately equal cl(exp H) describes well the scaling behavior of natural topographic surfaces, as represented by DEMs gridded at 3 arc sec. Average values of the scaling exponent H between approximately 0.5 and 0.7 characterize DEMs from Ethiopia, Saudi Arabia, and Somalia over 3 orders of magnitude range in length scale l (approximately 0.1-150 km). Differences in appparent topographic roughness among the three areas most likely reflect differences in the amplitude factor c. Separate determination of scaling properties in the x and y coordinate directions allows us to assess whether scaling exponents are azimuthally dependent (anisotropic) or whether they are isotropic while the surface itself is anisotropic over a restricted range of length scale. We explore ways to determine whether topographic surfaces are characterized by simple or multiscaling properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/921934','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/921934"><span id="translatedtitle"><span class="hlt">ABSOLUTE</span> POLARIMETRY AT RHIC.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>OKADA; BRAVAR, A.; BUNCE, G.; GILL, R.; HUANG, H.; MAKDISI, Y.; NASS, A.; WOOD, J.; ZELENSKI, Z.; ET AL.</p> <p>2007-09-10</p> <p>Precise and <span class="hlt">absolute</span> beam polarization measurements are critical for the RHIC spin physics program. Because all experimental spin-dependent results are normalized by beam polarization, the normalization uncertainty contributes directly to final physics uncertainties. We aimed to perform the beam polarization measurement to an accuracy Of {Delta}P{sub beam}/P{sub beam} < 5%. The <span class="hlt">absolute</span> polarimeter consists of Polarized Atomic Hydrogen Gas Jet Target and left-right pairs of silicon strip detectors and was installed in the RHIC-ring in 2004. This system features proton-proton elastic scattering in the Coulomb nuclear interference (CNI) region. Precise measurements of the analyzing power A{sub N} of this process has allowed us to achieve {Delta}P{sub beam}/P{sub beam} = 4.2% in 2005 for the first long spin-physics run. In this report, we describe the entire set up and performance of the system. The procedure of beam polarization measurement and analysis results from 2004-2005 are described. Physics topics of AN in the CNI region (four-momentum transfer squared 0.001 < -t < 0.032 (GeV/c){sup 2}) are also discussed. We point out the current issues and expected optimum accuracy in 2006 and the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3579786','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3579786"><span id="translatedtitle">Comparison of Sum <span class="hlt">Absolute</span> QRST Integral, and Temporal Variability in Depolarization and Repolarization, Measured by <span class="hlt">Dynamic</span> Vectorcardiography Approach, in Healthy Men and Women</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Tereshchenko, Larisa G.</p> <p>2013-01-01</p> <p>Background Recently we showed the predictive value of sum <span class="hlt">absolute</span> QRST integral (SAI QRST) and repolarization lability for risk stratification of sudden cardiac death (SCD) in heart failure patients. The goal of this study was to compare SAI QRST and metrics of depolarization and repolarization variability in healthy men and women. Methods Orthogonal ECGs were recorded at rest for 10 minutes in 160 healthy men and women (mean age 39.6±14.6, 80 men). Mean spatial TT′ angle, and normalized variances of T loop area, of spatial T vector amplitude, of QT interval and Tpeak-Tend area were measured for assessment of repolarization lability. Normalized variances of spatial QRS vector and QRS loop area characterized variability of depolarization. In addition, variability indices (VI) were calculated to adjust for normalized heart rate variance. SAI QRST was measured as the averaged arithmetic sum of areas under the QRST curve. Results Men were characterized by shorter QTc (430.3±21.7 vs. 444.7±22.2 ms; P<0.0001) and larger SAI QRST (282.1±66.7 vs.204.9±58.5 mV*ms; P<0.0001). Repolarization lability negatively correlated with spatial T vector amplitude. Adjusted by normalized heart rate variance, QT variability index was significantly higher in women than in men (−1.54±0.38 vs. −1.70±0.33; P = 0.017). However, in multivariate logistic regression after adjustment for body surface area, QTc, and spatial T vector amplitude, healthy men had 1.5–3 fold higher probability of having larger repolarization lability, as compared to healthy women (T vector amplitude variability index odds ratio 3.88(95%CI 1.4–11.1; P = 0.012). Conclusions Healthy men more likely than women have larger repolarization lability. PMID:23451181</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992JChPh..96..339T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992JChPh..96..339T"><span id="translatedtitle">Reaction <span class="hlt">dynamics</span> of D+H2 --> DH+H: Effects of potential energy surface <span class="hlt">topography</span> and usefulness of the constant centrifugal potential approximation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takada, Shoji; Ohsaki, Akihiko; Nakamura, Hiroki</p> <p>1992-01-01</p> <p>Two findings are reported for the D+H2→DH+H reaction on the basis of the exact quantum mechanical calculation for J=0, where J is total angular momentum. First, with use of the Liu-Siegbahn-Truhlar-Horowitz (LSTH) surface and the Varandas surface, we demonstrate that a rather small difference in potential energy surface (PES) induces a surprisingly large effect on reaction <span class="hlt">dynamics</span>. Two origins of the discrepancy are pointed out and analyzed: (1) Noncollinear conformation in the reaction zone contributes to the reaction significantly despite the fact that the minimum energy path and the saddle point are located in the collinear configuration. (2) A difference in the distant part of PES also causes a discrepancy in the reaction <span class="hlt">dynamics</span> indirectly, although this effect is much smaller than (1). Secondly, we investigate the validity of the constant centrifugal potential approximation (CCPA) based on the accurate results for J=0. The use of CCPA to estimate total cross section and rate constant is again proved to have practical utility as in the cases of the sudden and adiabatic approximations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19940007593&hterms=analysis+variance&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Danalysis%2Bvariance','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19940007593&hterms=analysis+variance&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Danalysis%2Bvariance"><span id="translatedtitle">Spectral analysis of the gravity and <span class="hlt">topography</span> of Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bills, Bruce G.; Frey, Herbert V.; Kiefer, Walter S.; Nerem, R. Steven; Zuber, Maria T.</p> <p>1993-01-01</p> <p>New spherical harmonic models of the gravity and <span class="hlt">topography</span> of Mars place important constraints on the structure and <span class="hlt">dynamics</span> of the interior. The gravity and <span class="hlt">topography</span> models are significantly phase coherent for harmonic degrees n less than 30 (wavelengths greater than 700 km). Loss of coherence below that wavelength is presumably due to inadequacies of the models, rather than a change in behavior of the planet. The gravity/<span class="hlt">topography</span> admittance reveals two very different spectral domains: for n greater than 4, a simple Airy compensation model, with mean depth of 100 km, faithfully represents the observed pattern; for degrees 2 and 3, the effective compensation depths are 1400 and 550 km, respectively, strongly arguing for <span class="hlt">dynamic</span> compensation at those wavelengths. The gravity model has been derived from a reanalysis of the tracking data for Mariner 9 and the Viking Orbiters, The <span class="hlt">topography</span> model was derived by harmonic analysis of the USGS digital elevation model of Mars. Before comparing gravity and <span class="hlt">topography</span> for internal structure inferences, we must ensure that both are consistently referenced to a hydrostatic datum. For the gravity, this involves removal of hydrostatic components of the even degree zonal coefficients. For the <span class="hlt">topography</span>, it involves adding the degree 4 equipotential reference surface, to get spherically referenced values, and then subtracting the full degree 50 equipotential. Variance spectra and phase coherence of orthometric heights and gravity anomalies are addressed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20060043634&hterms=Topography&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DTopography','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20060043634&hterms=Topography&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DTopography"><span id="translatedtitle">Satellite remote sensing of landscape freeze/thaw state <span class="hlt">dynamics</span> for complex <span class="hlt">Topography</span> and Fire Disturbance Areas Using multi-sensor radar and SRTM digital elevation models</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Podest, Erika; McDonald, Kyle; Kimball, John; Randerson, James</p> <p>2003-01-01</p> <p>We characterize differences in radar-derived freeze/thaw state, examining transitions over complex terrain and landscape disturbance regimes. In areas of complex terrain, we explore freezekhaw <span class="hlt">dynamics</span> related to elevation, slope aspect and varying landcover. In the burned regions, we explore the timing of seasonal freeze/thaw transition as related to the recovering landscape, relative to that of a nearby control site. We apply in situ biophysical measurements, including flux tower measurements to validate and interpret the remotely sensed parameters. A multi-scale analysis is performed relating high-resolution SAR backscatter and moderate resolution scatterometer measurements to assess trade-offs in spatial and temporal resolution in the remotely sensed fields.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16463910','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16463910"><span id="translatedtitle">Implants as <span class="hlt">absolute</span> anchorage.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rungcharassaeng, Kitichai; Kan, Joseph Y K; Caruso, Joseph M</p> <p>2005-11-01</p> <p>Anchorage control is essential for successful orthodontic treatment. Each tooth has its own anchorage potential as well as propensity to move when force is applied. When teeth are used as anchorage, the untoward movements of the anchoring units may result in the prolonged treatment time, and unpredictable or less-than-ideal outcome. To maximize tooth-related anchorage, techniques such as differential torque, placing roots into the cortex of the bone, the use of various intraoral devices and/or extraoral appliances have been implemented. Implants, as they are in direct contact with bone, do not possess a periodontal ligament. As a result, they do not move when orthodontic/orthopedic force is applied, and therefore can be used as "<span class="hlt">absolute</span> anchorage." This article describes different types of implants that have been used as orthodontic anchorage. Their clinical applications and limitations are also discussed. PMID:16463910</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040110742','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040110742"><span id="translatedtitle"><span class="hlt">Absolute</span> Equilibrium Entropy</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Shebalin, John V.</p> <p>1997-01-01</p> <p>The entropy associated with <span class="hlt">absolute</span> equilibrium ensemble theories of ideal, homogeneous, fluid and magneto-fluid turbulence is discussed and the three-dimensional fluid case is examined in detail. A sigma-function is defined, whose minimum value with respect to global parameters is the entropy. A comparison is made between the use of global functions sigma and phase functions H (associated with the development of various H-theorems of ideal turbulence). It is shown that the two approaches are complimentary though conceptually different: H-theorems show that an isolated system tends to equilibrium while sigma-functions allow the demonstration that entropy never decreases when two previously isolated systems are combined. This provides a more complete picture of entropy in the statistical mechanics of ideal fluids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21611867','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21611867"><span id="translatedtitle"><span class="hlt">Absolute</span> neutrino mass measurements</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wolf, Joachim</p> <p>2011-10-06</p> <p>The neutrino mass plays an important role in particle physics, astrophysics and cosmology. In recent years the detection of neutrino flavour oscillations proved that neutrinos carry mass. However, oscillation experiments are only sensitive to the mass-squared difference of the mass eigenvalues. In contrast to cosmological observations and neutrino-less double beta decay (0v2{beta}) searches, single {beta}-decay experiments provide a direct, model-independent way to determine the <span class="hlt">absolute</span> neutrino mass by measuring the energy spectrum of decay electrons at the endpoint region with high accuracy.Currently the best kinematic upper limits on the neutrino mass of 2.2eV have been set by two experiments in Mainz and Troitsk, using tritium as beta emitter. The next generation tritium {beta}-experiment KATRIN is currently under construction in Karlsruhe/Germany by an international collaboration. KATRIN intends to improve the sensitivity by one order of magnitude to 0.2eV. The investigation of a second isotope ({sup 137}Rh) is being pursued by the international MARE collaboration using micro-calorimeters to measure the beta spectrum. The technology needed to reach 0.2eV sensitivity is still in the R and D phase. This paper reviews the present status of neutrino-mass measurements with cosmological data, 0v2{beta} decay and single {beta}-decay.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AIPC.1382...49W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AIPC.1382...49W"><span id="translatedtitle"><span class="hlt">Absolute</span> neutrino mass measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wolf, Joachim</p> <p>2011-10-01</p> <p>The neutrino mass plays an important role in particle physics, astrophysics and cosmology. In recent years the detection of neutrino flavour oscillations proved that neutrinos carry mass. However, oscillation experiments are only sensitive to the mass-squared difference of the mass eigenvalues. In contrast to cosmological observations and neutrino-less double beta decay (0v2β) searches, single β-decay experiments provide a direct, model-independent way to determine the <span class="hlt">absolute</span> neutrino mass by measuring the energy spectrum of decay electrons at the endpoint region with high accuracy. Currently the best kinematic upper limits on the neutrino mass of 2.2eV have been set by two experiments in Mainz and Troitsk, using tritium as beta emitter. The next generation tritium β-experiment KATRIN is currently under construction in Karlsruhe/Germany by an international collaboration. KATRIN intends to improve the sensitivity by one order of magnitude to 0.2eV. The investigation of a second isotope (137Rh) is being pursued by the international MARE collaboration using micro-calorimeters to measure the beta spectrum. The technology needed to reach 0.2eV sensitivity is still in the R&D phase. This paper reviews the present status of neutrino-mass measurements with cosmological data, 0v2β decay and single β-decay.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25186903','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25186903"><span id="translatedtitle">Asymmetric three-dimensional <span class="hlt">topography</span> over mantle plumes.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Burov, Evgueni; Gerya, Taras</p> <p>2014-09-01</p> <p>The role of mantle-lithosphere interactions in shaping surface <span class="hlt">topography</span> has long been debated. In general, it is supposed that mantle plumes and vertical mantle flows result in axisymmetric, long-wavelength <span class="hlt">topography</span>, which strongly differs from the generally asymmetric short-wavelength <span class="hlt">topography</span> created by intraplate tectonic forces. However, identification of mantle-induced <span class="hlt">topography</span> is difficult, especially in the continents. It can be argued therefore that complex brittle-ductile rheology and stratification of the continental lithosphere result in short-wavelength modulation and localization of deformation induced by mantle flow. This deformation should also be affected by far-field stresses and, hence, interplay with the 'tectonic' <span class="hlt">topography</span> (for example, in the 'active/passive' rifting scenario). Testing these ideas requires fully coupled three-dimensional numerical modelling of mantle-lithosphere interactions, which so far has not been possible owing to the conceptual and technical limitations of earlier approaches. Here we present new, ultra-high-resolution, three-dimensional numerical experiments on <span class="hlt">topography</span> over mantle plumes, incorporating a weakly pre-stressed (ultra-slow spreading), rheologically realistic lithosphere. The results show complex surface evolution, which is very different from the smooth, radially symmetric patterns usually assumed as the canonical surface signature of mantle upwellings. In particular, the <span class="hlt">topography</span> exhibits strongly asymmetric, small-scale, three-dimensional features, which include narrow and wide rifts, flexural flank uplifts and fault structures. This suggests a dominant role for continental rheological structure and intra-plate stresses in controlling <span class="hlt">dynamic</span> <span class="hlt">topography</span>, mantle-lithosphere interactions, and continental break-up processes above mantle plumes. PMID:25186903</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A41C3058W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A41C3058W"><span id="translatedtitle">The Role of African <span class="hlt">topography</span> in the South Asian Monsoon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wei, H. H.; Bordoni, S.</p> <p>2014-12-01</p> <p>The Somali cross-equatorial jet is estimated to contribute up to half of the mass flux crossing the equator during the Asian monsoon season. Previous studies have argued that the Somali jet is strengthened by the East African Highlands, which act as a wall and accelerate the flow (e.g., Krishnamurti et al. 1976, Sashegyi and Geisler 1987). Besides, observational studies have shown a positive correlation between the strength of the Somali jet and the South Asian Monsoon (SAM) precipitation (e.g., Findlater 1969, Halpern and Woiceshyn 2001). These imply that the existence of the <span class="hlt">topography</span> would relate to a stronger SAM. However, in a more recent study, Chakraborty et al. (2002) found that if the African <span class="hlt">topography</span> is removed in a comprehensive general circulation model (GCM), the SAM strengthens. In this study, we use the GFDL AM2.1 GCM to conduct experiments with and without <span class="hlt">topography</span> in Africa, to further examine its influence on the cross-equatorial Somali jet and the SAM. We find that when the African <span class="hlt">topography</span> is removed, the SAM precipitation increases, consistent with the results in Chakraborty et al. (2002). Interestingly, our results also show that the cross-equatorial Somali jet does weaken in the absence of the African <span class="hlt">topography</span>, in agreement with previous studies. The moisture budget shows that the increase in precipitation in the no-African <span class="hlt">topography</span> experiment is primarily due to stronger wind convergence. The <span class="hlt">dynamics</span> of the cross-equatorial Somali jet is investigated within the framework of the Potential Vorticity (PV) budget, showing the contribution of the changes in friction and diabatic heating to the circulation as the <span class="hlt">topography</span> is removed. A backward trajectory analysis is also conducted to further examine the influence of <span class="hlt">topography</span> on both the material tendencies of the PV budget and trajectories of parcels reaching the Indian subcontinent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016SGeo...37..339P&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016SGeo...37..339P&link_type=ABSTRACT"><span id="translatedtitle">Toward a High-Resolution Monitoring of Continental Surface Water Extent and <span class="hlt">Dynamics</span>, at Global Scale: from GIEMS (Global Inundation Extent from Multi-Satellites) to SWOT (Surface Water Ocean <span class="hlt">Topography</span>)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prigent, Catherine; Lettenmaier, Dennis P.; Aires, Filipe; Papa, Fabrice</p> <p>2016-03-01</p> <p>Up to now, high-resolution mapping of surface water extent from satellites has only been available for a few regions, over limited time periods. The extension of the temporal and spatial coverage was difficult, due to the limitation of the remote sensing technique [e.g., the interaction of the radiation with vegetation or cloud for visible observations or the temporal sampling with the synthetic aperture radar (SAR)]. The advantages and the limitations of the various satellite techniques are reviewed. The need to have a global and consistent estimate of the water surfaces over long time periods triggered the development of a multi-satellite methodology to obtain consistent surface water all over the globe, regardless of the environments. The Global Inundation Extent from Multi-satellites (GIEMS) combines the complementary strengths of satellite observations from the visible to the microwave, to produce a low-resolution monthly dataset (0.25^circ × 0.25^circ) of surface water extent and <span class="hlt">dynamics</span>. Downscaling algorithms are now developed and applied to GIEMS, using high-spatial-resolution information from visible, near-infrared, and synthetic aperture radar (SAR) satellite images, or from digital elevation models. Preliminary products are available down to 500-m spatial resolution. This work bridges the gaps and prepares for the future NASA/CNES Surface Water Ocean <span class="hlt">Topography</span> (SWOT) mission to be launched in 2020. SWOT will delineate surface water extent estimates and their water storage with an unprecedented spatial resolution and accuracy, thanks to a SAR in an interferometry mode. When available, the SWOT data will be adopted to downscale GIEMS, to produce a long time series of water surfaces at global scale, consistent with the SWOT observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=effect+AND+assimilation&pg=7&id=EJ735377','ERIC'); return false;" href="http://eric.ed.gov/?q=effect+AND+assimilation&pg=7&id=EJ735377"><span id="translatedtitle"><span class="hlt">Absolute</span> Identification by Relative Judgment</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>Stewart, Neil; Brown, Gordon D. A.; Chater, Nick</p> <p>2005-01-01</p> <p>In unidimensional <span class="hlt">absolute</span> identification tasks, participants identify stimuli that vary along a single dimension. Performance is surprisingly poor compared with discrimination of the same stimuli. Existing models assume that identification is achieved using long-term representations of <span class="hlt">absolute</span> magnitudes. The authors propose an alternative…</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_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" 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_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=VALUE+AND+ABSOLUTE&id=EJ765743','ERIC'); return false;" href="http://eric.ed.gov/?q=VALUE+AND+ABSOLUTE&id=EJ765743"><span id="translatedtitle">Be Resolute about <span class="hlt">Absolute</span> Value</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>Kidd, Margaret L.</p> <p>2007-01-01</p> <p>This article explores how conceptualization of <span class="hlt">absolute</span> value can start long before it is introduced. The manner in which <span class="hlt">absolute</span> value is introduced to students in middle school has far-reaching consequences for their future mathematical understanding. It begins to lay the foundation for students' understanding of algebra, which can change…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1815060L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1815060L"><span id="translatedtitle">Statistics of <span class="hlt">topography</span> : multifractal approach to describe planetary <span class="hlt">topography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Landais, Francois; Schmidt, Frédéric; Lovejoy, Shaun</p> <p>2016-04-01</p> <p>In the last decades, a huge amount of topographic data has been obtained by several techniques (laser and radar altimetry, DTM…) for different bodies in the solar system. In each case, topographic fields exhibit an extremely high variability with details at each scale, from millimeters to thousands of kilometers. In our study, we investigate the statistical properties of the <span class="hlt">topography</span>. Our statistical approach is motivated by the well known scaling behavior of <span class="hlt">topography</span> that has been widely studied in the past. Indeed, scaling laws are strongly present in geophysical field and can be studied using fractal formalism. More precisely, we expect multifractal behavior in global topographic fields. This behavior reflects the high variability and intermittency observed in topographic fields that can not be generated by simple scaling models. In the multifractal formalism, each statistical moment exhibits a different scaling law characterized by a function called the moment scaling function. Previous studies were conducted at regional scale to demonstrate that <span class="hlt">topography</span> present multifractal statistics (Gagnon et al., 2006, NPG). We have obtained similar results on Mars (Landais et al. 2015) and more recently on different body in the the solar system including the Moon, Venus and Mercury. We present the result of different multifractal approaches performed on global and regional basis and compare the fractal parameters from a body to another.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.3382H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.3382H"><span id="translatedtitle">Controls on (anomalous) <span class="hlt">topography</span> in rifted margin settings</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huismans, Ritske S.</p> <p>2015-04-01</p> <p>Contrasting end members of volcanic and non-volcanic passive margin formation show a large variability in basin shape and structure, subsidence history, and associated topographic evolution of the onshore rifted margins. The large range of structural style and associated <span class="hlt">topography</span> of these systems imply a strong variability in the underlying thermo-mechanical conditions at the time of rifting. Rift - passive margin styles ranging from narrow to ultra wide are explained using forward numerical models with varying rheological structure, with strong crust lithosphere leading to narrow rift formation associated with highly elevated rift shoulders and conversely weak crust lithosphere resulting in highly stretched wide rifted conjugate margins and little flank morphology. In some cases rifted margins appear to indicate the formation of anomalous post rift <span class="hlt">topography</span>. A number of mechanisms including small-scale convective removal of the lower lithosphere, lithosphere counter-flow, and <span class="hlt">dynamic</span> <span class="hlt">topography</span>, have been invoked to explain the anomalous <span class="hlt">topography</span>. Forward numerical models are used to predict the magnitude and characteristic <span class="hlt">topography</span> associated with each of these mechanisms and to evaluate their potential for explaining these apparent anomalous characteristics of rifts and rifted margins.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870011267','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870011267"><span id="translatedtitle">Linear baroclinic instability in the presence of large scale <span class="hlt">topography</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Reynolds, Nathaniel Dunton</p> <p>1987-01-01</p> <p>The effect of a planetary-scale, wavenumber 2 <span class="hlt">topography</span> on baroclinically active disturbances is investigated for a channel domain in a two-layer, quasi-geostrophic context. When the lower-layer zonal velocity is nonzero, the <span class="hlt">topography</span> influences the disturbances by forcing a stationary wave, and the <span class="hlt">topography</span> and the forced wave influence the growth rates and the spatial structures of the time-dependent solutions. The case of zero zonal velocity in the lower layer was also investigated, for which no forced wave exists. Asymptotic forms of the equations, valid when the topographic effect (governed by the ratio of the nondimensional topographic height to the rotational Froude number) is small, are used to obtain both the stationary and time-dependent solutions. The latter are also obtained using a numerical approach, in which is determined the eigenvalues and eigenfunctions of a matrix representing the <span class="hlt">dynamical</span> equations. Agreement is good between the two approaches. Recent laboratory experiments with a baroclinic annulus in which there is a false bottom with wavenumber 2 <span class="hlt">topography</span>, are used to select governing parameters. The simultaneous presence of a stationary forced wave of wavenumber 2 and a time-dependent baroclinic wave of wavenumber 4, which has wavenumber 2 and 6 sidebands due to the <span class="hlt">topography</span>, yields a flow field that exhibits some principal features of the laboratory experiments. The position of the forced wave and the location of an excursion in latitude of the storm track show qualitative resemblance to those features observed in the atmosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890001054','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890001054"><span id="translatedtitle">Earth rotation and core <span class="hlt">topography</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hager, Bradford H.; Clayton, Robert W.; Spieth, Mary Ann</p> <p>1988-01-01</p> <p>The NASA Geodynamics program has as one of its missions highly accurate monitoring of polar motion, including changes in length of day (LOD). These observations place fundamental constraints on processes occurring in the atmosphere, in the mantle, and in the core of the planet. Short-timescale (t less than or approx 1 yr) variations in LOD are mainly the result of interaction between the atmosphere and the solid earth, while variations in LOD on decade timescales result from the exchange of angular momentum between the mantle and the fluid core. One mechanism for this exchange of angular momentum is through topographic coupling between pressure variations associated with flow in the core interacting with <span class="hlt">topography</span> at the core-mantel boundary (CMB). Work done under another NASA grant addressing the origin of long-wavelength geoid anomalies as well as evidence from seismology, resulted in several models of CMB <span class="hlt">topography</span>. The purpose of work supported by NAG5-819 was to study further the problem of CMB <span class="hlt">topography</span>, using geodesy, fluid mechanics, geomagnetics, and seismology. This is a final report.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5927137','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5927137"><span id="translatedtitle">Stresses in a submarine <span class="hlt">topography</span> under ocean waves</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mei, C.C.; McTigue, D.F.</p> <p>1984-09-01</p> <p>The problem of submarine slope stability is of interest to both offshore engineering and geology. In an uneven <span class="hlt">topography</span>, the weight above a horizontal plane induces two-dimensional variation in the static stress field. The action of wave pressure, which changes with depth, further introduces excess pore pressure and <span class="hlt">dynamic</span> stresses in the sea bottom. In the present paper, we combine a simple analytical theory for the static stress by the present authors, and the recent solution by Mei and Foda for wave-induced stresses in a plane poro-elastic sea bed to account for mild bottom slope and wave shoaling, and obtain the effective stress field in a submarine <span class="hlt">topography</span> under sea waves. Sample results are given for a ridge and a canyon. In particular, the <span class="hlt">dynamic</span> pore pressure and the combined static and <span class="hlt">dynamic</span> effective stresses are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5268545','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5268545"><span id="translatedtitle">Stresses in a submarine <span class="hlt">topography</span> under ocean waves</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mei, C.C.; McTigue, D.F.</p> <p>1984-01-01</p> <p>The problem of submarine slope stability is of interest to both offshore engineering and geology. In an uneven <span class="hlt">topography</span>, the weight above a horizontal plane induces two-dimensional variation in the static stress field. The action of wave pressure, which changes with depth, further introduces excess pore pressure and <span class="hlt">dynamic</span> stresses in the sea bottom. In the present paper, we combine a simple analytical theory for the static stress by the present authors, and the recent solution by Mei and Foda for wave-induced stresses in a plane poro-elastic sea bed to account for mild bottom slope and wave shoaling, to obtain the effective stress field in a submarine <span class="hlt">topography</span> under sea waves. Sample results are given for a ridge and a canyon. In particular the <span class="hlt">dynamic</span> pore pressure and the combined static and <span class="hlt">dynamic</span> effective stresses are presented. 10 references, 11 figures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930043862&hterms=Mars+planet&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DMars%2Bplanet','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930043862&hterms=Mars+planet&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DMars%2Bplanet"><span id="translatedtitle">Gravity and <span class="hlt">topography</span>. [of planet Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Esposito, P. B.; Banerdt, W. B.; Lindal, G. F.; Sjogren, W. L.; Slade, M. A.; Bills, B. G.; Smith, D. E.; Balmino, G.</p> <p>1992-01-01</p> <p>The paper summarizes the fundamental gravity field constants for Mars and a brief historical review of early determinations and current-day accurate estimates. These include the planetary gravitational constant, global figure, <span class="hlt">dynamical</span> oblateness, mean density, and rotational period. Topographic results from data acquired from the 1967 opposition to the most recent, 1988, opposition are presented. Both global and selected local topographic variations and features are discussed. The inertia tensor and the nonhydrostatic component of Mars are examined in detail. The dimensionless moment of inertia about the rotational axis is 0.4 for a body of uniform density and 0.37621 if Mars were in hydrostatic equilibrium. By comparing models of both gravity and <span class="hlt">topography</span>, inferences are made about the degree and depth of compensation in the interior and stresses in the lithosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25500860','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25500860"><span id="translatedtitle">Corneal <span class="hlt">topography</span> matching by iterative registration.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Junjie; Elsheikh, Ahmed; Davey, Pinakin G; Wang, Weizhuo; Bao, Fangjun; Mottershead, John E</p> <p>2014-11-01</p> <p>Videokeratography is used for the measurement of corneal <span class="hlt">topography</span> in overlapping portions (or maps) which must later be joined together to form the overall <span class="hlt">topography</span> of the cornea. The separate portions are measured from different viewpoints and therefore must be brought together by registration of measurement points in the regions of overlap. The central map is generally the most accurate, but all maps are measured with uncertainty that increases towards the periphery. It becomes the reference (or static) map, and the peripheral (or <span class="hlt">dynamic</span>) maps must then be transformed by rotation and translation so that the overlapping portions are matched. The process known as registration, of determining the necessary transformation, is a well-understood procedure in image analysis and has been applied in several areas of science and engineering. In this article, direct search optimisation using the Nelder-Mead algorithm and several variants of the iterative closest/corresponding point routine are explained and applied to simulated and real clinical data. The measurement points on the static and <span class="hlt">dynamic</span> maps are generally different so that it becomes necessary to interpolate, which is done using a truncated series of Zernike polynomials. The point-to-plane iterative closest/corresponding point variant has the advantage of releasing certain optimisation constraints that lead to persistent registration and alignment errors when other approaches are used. The point-to-plane iterative closest/corresponding point routine is found to be robust to measurement noise, insensitive to starting values of the transformation parameters and produces high-quality results when using real clinical data. PMID:25500860</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3016849','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3016849"><span id="translatedtitle"><span class="hlt">Topography</span>, Cell Response, and Nerve Regeneration</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hoffman-Kim, Diane; Mitchel, Jennifer A.; Bellamkonda, Ravi V.</p> <p>2010-01-01</p> <p>In the body, cells encounter a complex milieu of signals, including topographical cues. Imposed <span class="hlt">topography</span> can affect cells on surfaces by promoting adhesion, spreading, alignment, morphological changes, and changes in gene expression. Neural response to <span class="hlt">topography</span> is complex, and depends on the dimensions and shapes of physical features. Looking toward repair of nerve injuries, strategies are being explored to engineer guidance conduits with precise surface <span class="hlt">topographies</span>. How neurons and other cell types sense and interpret <span class="hlt">topography</span> remains to be fully elucidated. Studies reviewed here include those of <span class="hlt">topography</span> on cellular organization and function as well as potential cellular mechanisms of response. PMID:20438370</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPSC...10..514S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPSC...10..514S"><span id="translatedtitle">Estimation of Ganymede's <span class="hlt">Topography</span>, Rotation and Tidal Deformation - a Study of Synthetic Ganymede Laser Altimeter Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steinke, T.; Stark, A.; Steinbrügge, G.; Hussmann, H.; Oberst, J.</p> <p>2015-10-01</p> <p>We implement an iterative least-squares inversion routine to study the estimation of several <span class="hlt">dynamic</span> Ganymede rotation parameters by laser altimetry. Based on spherical harmonic expansions of the global <span class="hlt">topography</span> we use simulated Ganymede Laser Al-timeter observations representing the synthetic <span class="hlt">topography</span> of the satellite. Besides the static <span class="hlt">topography</span> we determine the <span class="hlt">dynamical</span> parameters, such as the rotation rate, the amplitudes of physical librations, the spin pole orientation, and the tidal deformation. This parameters may strengthen implications for a liquid ocean beneath Ganymede's icy shell and, in addition, constrain geodetic frame parameters essential for various space-borne experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27581485','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27581485"><span id="translatedtitle">Transient <span class="hlt">absolute</span> robustness in stochastic biochemical networks.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Enciso, German A</p> <p>2016-08-01</p> <p><span class="hlt">Absolute</span> robustness allows biochemical networks to sustain a consistent steady-state output in the face of protein concentration variability from cell to cell. This property is structural and can be determined from the topology of the network alone regardless of rate parameters. An important question regarding these systems is the effect of discrete biochemical noise in the <span class="hlt">dynamical</span> behaviour. In this paper, a variable freezing technique is developed to show that under mild hypotheses the corresponding stochastic system has a transiently robust behaviour. Specifically, after finite time the distribution of the output approximates a Poisson distribution, centred around the deterministic mean. The approximation becomes increasingly accurate, and it holds for increasingly long finite times, as the total protein concentrations grow to infinity. In particular, the stochastic system retains a transient, <span class="hlt">absolutely</span> robust behaviour corresponding to the deterministic case. This result contrasts with the long-term <span class="hlt">dynamics</span> of the stochastic system, which eventually must undergo an extinction event that eliminates robustness and is completely different from the deterministic <span class="hlt">dynamics</span>. The transiently robust behaviour may be sufficient to carry out many forms of robust signal transduction and cellular decision-making in cellular organisms. PMID:27581485</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24243093','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24243093"><span id="translatedtitle">Effect of <span class="hlt">topography</span> on sulfate redistribution in Cumulonimbus cloud development.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vujović, Dragana; Vučković, Vladan; Curić, Mlađen</p> <p>2014-03-01</p> <p>An aqueous chemical module is created and included into a complex three-dimensional atmospheric cloud-resolving mesoscale model. In the chemical module, oxidation of S(IV) by ozone and hydrogen peroxide in cloud-water and rainwater, as important process of the sulfate production is included. To examine the impact of <span class="hlt">topography</span> on the sulfate redistribution in a clean and a polluted environment, the complex <span class="hlt">topography</span> of Serbia is included in the model. Numerical simulations of an isolated summer Cumulonimbus cloud shows that thunderstorms generate very strong vertical sulfate redistribution from the planetary boundary layer to the upper troposphere. This redistribution is sensitive to cloud <span class="hlt">dynamics</span>, while cloud microphysics and precipitation determine wet removal of the chemical species. In simulations with realistic <span class="hlt">topography</span>, the chemical species are transported over larger distances close to the surface, while in the upper atmosphere, there is no difference compared to the simulations without <span class="hlt">topography</span>. The sensitivity tests of cloud chemistry to the physical processes are made. Omission of nucleation and impact scavenging of aerosols in the model simulations shows that 75.8 and 62.5 % of total sulfur mass deposited in the base experiment for the clean and the polluted environment, respectively, is the result of other processes. Exclusion of oxidation accounted for 19.2 and 37.7 % of total sulfur deposited for clean and polluted environment. Ignoring the ice phase almost not change mass of deposited sulfur: there is an increase of 2.9 and 1.5 % for clean and polluted atmosphere, respectively. Real <span class="hlt">topography</span> conditions affect the sulfate redistribution in the sense of greater possibilities of transport. Numerical simulations without real <span class="hlt">topography</span> give an artificial increase of deposited sulfur mass of about 25-30 %. PMID:24243093</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMED11B3407G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMED11B3407G"><span id="translatedtitle">The <span class="hlt">Topography</span> Tub Learning Activity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Glesener, G. B.</p> <p>2014-12-01</p> <p>Understanding the basic elements of a topographic map (i.e. contour lines and intervals) is just a small part of learning how to use this abstract representational system as a resource in geologic mapping. Interpretation of a topographic map and matching its features with real-world structures requires that the system is utilized for visualizing the shapes of these structures and their spatial orientation. To enrich students' skills in visualizing <span class="hlt">topography</span> from topographic maps a spatial training activity has been developed that uses 3D objects of various shapes and sizes, a sighting tool, a plastic basin, water, and transparencies. In the first part of the activity, the student is asked to draw a topographic map of one of the 3D objects. Next, the student places the object into a plastic tub in which water is added to specified intervals of height. The shoreline at each interval is used to reference the location of the contour line the student draws on a plastic inkjet transparency directly above the object. A key part of this activity is the use of a sighting tool by the student to assist in keeping the pencil mark directly above the shoreline. It (1) ensures the accurate positioning of the contour line and (2) gives the learner experience with using a sight before going out into the field. Finally, after the student finishes drawing the contour lines onto the transparency, the student can compare and contrast the two maps in order to discover where improvements in their visualization of the contours can be made. The teacher and/or peers can also make suggestions on ways to improve. A number of objects with various shapes and sizes are used in this exercise to produce contour lines representing the different types of <span class="hlt">topography</span> the student may encounter while field mapping. The intended outcome from using this visualization training activity is improvement in performance of visualizing <span class="hlt">topography</span> as the student moves between the topographic representation and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1989SPIE.1036...99Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1989SPIE.1036...99Y"><span id="translatedtitle">Precision Measurement Of Corneal <span class="hlt">Topography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yoder, Paul R.; Macri, Timothy F.; Telfair, William B.; Bennett, Peter S.; Martin, Clifford A.; Warner, John W.</p> <p>1989-05-01</p> <p>We describe a new electro-optical device being developed to provide precise measurements of the three-dimensional <span class="hlt">topography</span> of the human cornea. This device, called a digital keratoscope, is intended primarily for use in preparing for and determining the effect of corneal surgery procedures such as laser refractive keratectomy, radial keratotomy or corneal transplant on the refractive power of the cornea. It also may serve as an aid in prescribing contact lenses. The basic design features of the hardware and of the associated computer software are discussed, the means for alignment and calibration are described and typical results are given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AGUSM...S21B02G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AGUSM...S21B02G"><span id="translatedtitle">Simultaneous inversion for mantle shear velocity and the <span class="hlt">topography</span> of transition zone discontinuities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gu, Y. J.; Dziewonski, A. M.</p> <p>2001-05-01</p> <p>A method is presented for the simultaneous inversions of shear velocity in the mantle and the <span class="hlt">topography</span> of transition zone discontinuities. Each travel time residual, corrected for crust and free surface <span class="hlt">topography</span>, is modeled as resulting from contributions from three-dimensional shear velocity perturbations to a spherical Earth model and boundary undulations to the 410 and 660 km discontinuities. This approach minimizes tradeoffs between velocity and <span class="hlt">topography</span>. We expand the lateral variations in velocity and the <span class="hlt">topography</span> of each discontinuity using 362 spherical B-splines; we expand the radial variations using 14 cubic B-splines. To increase the reliability of the measurements, particularly in the undersampled southern hemisphere, we re-examine the <span class="hlt">topography</span> of the 410- and 660 km discontinuities from more than 21,000 SH-component records. This new data set is significantly larger than those used earlier studies of SS precursors. The long-wavelength features of our new <span class="hlt">topography</span> maps of the 410- and 660-km discontinuities are compatible with results of earlier studies: the large-scale patterns are dominated by low degree spherical harmonics, particularly at degrees 1 and 2. We also include an independent measurement of the global transition zone thickness for additional constraints on the structure in the transition zone. The best-fit model from the joint inversion reduces the variance of the <span class="hlt">absolute</span> and differential travel times of S, SS and ScS by 40 to 70 %, and the differential travel times of SS precursors by up to 90%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.H54C..04I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.H54C..04I"><span id="translatedtitle">Aspects of Radiation Budget, Subsurface Lateral Moisture Exchange, and Vegetation Function in Areas of Complex <span class="hlt">Topography</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ivanov, V. Y.; Bras, R. L.; Istanbulluoglu, E.; Vivoni, E. R.</p> <p>2004-12-01</p> <p>There is evidence that <span class="hlt">topography</span> strongly affects the state, function, and distribution of vegetation by controlling incoming solar radiation and lateral redistribution of soil moisture. However, numerical experiments studying the effects that a <span class="hlt">topography</span> can have on vegetation have oversimplified the treatment of <span class="hlt">topography</span> and/or the representation of vegetation. We investigate the control of <span class="hlt">topography</span> on vegetation state and stress via detailed modeling of radiation and soil moisture budgets across the varied terrain of a watershed. A detailed vegetation-hydrology model parameterizes the processes of canopy radiative transfer and rainfall interception and couples the processes of infiltration and evapotranspiration to photosynthesis via moisture uptake through a root systems with varied profiles. The model is applied on a continuous basis to synthetic watersheds of <span class="hlt">topography</span> dominated by either convex or concave hillslopes. The numerical analysis is carried out for several plant functional types and soils. Inferences from the spatially-distributed <span class="hlt">dynamics</span> are used to examine topographic niches favorable to vegetation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012Tectp.526....5H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012Tectp.526....5H&link_type=ABSTRACT"><span id="translatedtitle">Unraveling <span class="hlt">topography</span> around subduction zones from laboratory models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Husson, Laurent; Guillaume, Benjamin; Funiciello, Francesca; Faccenna, Claudio; Royden, Leigh H.</p> <p>2012-03-01</p> <p>The relief around subduction zones results from the interplay of <span class="hlt">dynamic</span> processes that may locally exceed the (iso)static contributions. The viscous dissipation of the energy in and around subduction zones is capable of generating kilometer scale vertical ground movements. In order to evaluate <span class="hlt">dynamic</span> <span class="hlt">topography</span> in a self-consistent subduction system, we carried out a set of laboratory experiments, wherein the lithosphere and mantle are simulated by means of Newtonian viscous materials, namely silicone putty and glucose syrup. Models are kept in their most simple form and are made of negative buoyancy plates, of variable width and thickness, freely plunging into the syrup. The surface of the model and the top of the slab are scanned in three dimensions. A forebulge systematically emerges from the bending of the viscous plate, adjacent to the trench. With a large wavelength, <span class="hlt">dynamic</span> pressure offsets the foreside and backside of the slab by ~ 500 m on average. The suction, that accompanies the vertical descent of the slab depresses the surface on both sides. At a distance equal to the half-width of the slab, the topographic depression amounts to ~ 500 m on average and becomes negligible at a distance that equals the width of the slab. In order to explore the impact of slab rollback on the <span class="hlt">topography</span>, the trailing edge of the plates is alternatively fixed to (fixed mode) and freed from (free mode) the end wall of the tank. Both the pressure and suction components of the <span class="hlt">topography</span> are ~ 30% lower in the free mode, indicating that slab rollback fosters the <span class="hlt">dynamic</span> subsidence of upper plates. Our models are compatible with first order observations of the <span class="hlt">topography</span> around the East Scotia, Tonga, Kermadec and Banda subduction zones, which exhibit anomalous depths of nearly 1 km as compared to adjacent sea floor of comparable age.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19720027445&hterms=isolated+neutral&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Disolated%2Bneutral','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19720027445&hterms=isolated+neutral&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Disolated%2Bneutral"><span id="translatedtitle"><span class="hlt">Absolute</span> transition probabilities of phosphorus.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Miller, M. H.; Roig, R. A.; Bengtson, R. D.</p> <p>1971-01-01</p> <p>Use of a gas-driven shock tube to measure the <span class="hlt">absolute</span> strengths of 21 P I lines and 126 P II lines (from 3300 to 6900 A). Accuracy for prominent, isolated neutral and ionic lines is estimated to be 28 to 40% and 18 to 30%, respectively. The data and the corresponding theoretical predictions are examined for conformity with the sum rules.-</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMNG23A1772O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMNG23A1772O"><span id="translatedtitle">Spectral <span class="hlt">Topography</span> Generation for Arbitrary Grids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oh, T. J.</p> <p>2015-12-01</p> <p>A new <span class="hlt">topography</span> generation tool utilizing spectral transformation technique for both structured and unstructured grids is presented. For the source global digital elevation data, the NASA Shuttle Radar <span class="hlt">Topography</span> Mission (SRTM) 15 arc-second dataset (gap-filling by Jonathan de Ferranti) is used and for land/water mask source, the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) 30 arc-second land water mask dataset v5 is used. The original source data is coarsened to a intermediate global 2 minute lat-lon mesh. Then, spectral transformation to the wave space and inverse transformation with wavenumber truncation is performed for isotropic <span class="hlt">topography</span> smoothness control. Target grid <span class="hlt">topography</span> mapping is done by bivariate cubic spline interpolation from the truncated 2 minute lat-lon <span class="hlt">topography</span>. Gibbs phenomenon in the water region can be removed by overwriting ocean masked target coordinate grids with interpolated values from the intermediate 2 minute grid. Finally, a weak smoothing operator is applied on the target grid to minimize the land/water surface height discontinuity that might have been introduced by the Gibbs oscillation removal procedure. Overall, the new <span class="hlt">topography</span> generation approach provides spectrally-derived, smooth <span class="hlt">topography</span> with isotropic resolution and minimum damping, enabling realistic <span class="hlt">topography</span> forcing in the numerical model. <span class="hlt">Topography</span> is generated for the cubed-sphere grid and tested on the KIAPS Integrated Model (KIM).</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_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" 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_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.usgs.gov/imap/1726/plate-2.pdf','USGSPUBS'); return false;" href="http://pubs.usgs.gov/imap/1726/plate-2.pdf"><span id="translatedtitle">Bedrock <span class="hlt">topography</span> of northwest Iowa</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hansen, R.E.; Runkle, D.L.</p> <p>1986-01-01</p> <p>Bedrock in Iowa (Hershey, 1969) generally is overlain by deposits of glacial drive and alluvium. The drift, consisting of glacial till and glacial outwash, ranges in thickness from zero to more than 500 feet in western Iowa; the alluvium in stream valleys ranges in thickness from less than 1 foot to more than 70 feet. The configuration of the bedrock surface is the result of a complex system of ancient drainage courses that were developed during a long period of preglacial erosion. This map, for a 12 county area in west-central Iowa, is the eighth in a series of nine reports that will provide statewide coverage of the bedriock <span class="hlt">topography</span> of Iowa. </p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870014110','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870014110"><span id="translatedtitle">Large scale <span class="hlt">topography</span> of Io</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gaskell, R. W.; Synnott, S. P.</p> <p>1987-01-01</p> <p>To investigate the large scale <span class="hlt">topography</span> of the Jovian satellite Io, both limb observations and stereographic techniques applied to landmarks are used. The raw data for this study consists of Voyager 1 images of Io, 800x800 arrays of picture elements each of which can take on 256 possible brightness values. In analyzing this data it was necessary to identify and locate landmarks and limb points on the raw images, remove the image distortions caused by the camera electronics and translate the corrected locations into positions relative to a reference geoid. Minimizing the uncertainty in the corrected locations is crucial to the success of this project. In the highest resolution frames, an error of a tenth of a pixel in image space location can lead to a 300 m error in true location. In the lowest resolution frames, the same error can lead to an uncertainty of several km.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JAGeo...8..195S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JAGeo...8..195S"><span id="translatedtitle"><span class="hlt">Absolute</span> Performance of AUSGeoid09 in Mountainous Regions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sussanna, Vittorio; Janssen, Volker; Gibbings, Peter</p> <p>2014-09-01</p> <p>The Australian Height Datum (AHD) is the current national vertical datum for Australia, and AUSGeoid09 is the latest quasigeoid model used to compute (normal-orthometric)AHDheights fromGlobalNavigation Satellite System (GNSS) derived ellipsoidal heights. While previous studies have evaluated the AUSGeoid09 model across Australia, such studies have not focused on mountainous regions in particular. This paper investigates the performance of AUSGeoid09 in an <span class="hlt">absolute</span> sense in the Mid Hunter and Snowy Mountains regions of New South Wales. <span class="hlt">Absolute</span> (i.e. single point) comparisons were undertaken between AUSGeoid09-derived heights and published AHD heights. The performance of AUSGeoid09 was evaluated relative to its predecessor AUSGeoid98. In both study areas, an overall improvement is evident when applying AUSGeoid09 to compute AHD heights in an <span class="hlt">absolute</span> sense. In the MidHunter, AUSGeoid09 provided a substantial improvement over its predecessor, clearly demonstrating the benefits of its new geometric component on GNSS-derived AHD height determination. In the Snowy Mountains, moderate improvement over AUSGeoid98 was evident. However, a slope was detected for AUSGeoid09 residuals, and it appears that the geometric component may have overcompensated for sea surface <span class="hlt">topography</span> in this area. While this appraisal of AUSGeoid09 performance in mountainous regions is encouraging, it has been shown that some discrepancies still remain between AUSGeoid09-derived heights and AHD. Eventually, a new vertical datum will be necessary to ensure homogeneity across Australia.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PhRvA..94a3808D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PhRvA..94a3808D&link_type=ABSTRACT"><span id="translatedtitle">Optomechanics for <span class="hlt">absolute</span> rotation detection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Davuluri, Sankar</p> <p>2016-07-01</p> <p>In this article, we present an application of optomechanical cavity for the <span class="hlt">absolute</span> rotation detection. The optomechanical cavity is arranged in a Michelson interferometer in such a way that the classical centrifugal force due to rotation changes the length of the optomechanical cavity. The change in the cavity length induces a shift in the frequency of the cavity mode. The phase shift corresponding to the frequency shift in the cavity mode is measured at the interferometer output to estimate the angular velocity of <span class="hlt">absolute</span> rotation. We derived an analytic expression to estimate the minimum detectable rotation rate in our scheme for a given optomechanical cavity. Temperature dependence of the rotation detection sensitivity is studied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20100014902&hterms=asp&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dasp','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20100014902&hterms=asp&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dasp"><span id="translatedtitle">The <span class="hlt">Absolute</span> Spectrum Polarimeter (ASP)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kogut, A. J.</p> <p>2010-01-01</p> <p>The <span class="hlt">Absolute</span> Spectrum Polarimeter (ASP) is an Explorer-class mission to map the <span class="hlt">absolute</span> intensity and linear polarization of the cosmic microwave background and diffuse astrophysical foregrounds over the full sky from 30 GHz to 5 THz. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r much greater than 1O(raised to the power of { -3}) and Compton distortion y < 10 (raised to the power of{-6}). We describe the ASP instrument and mission architecture needed to detect the signature of an inflationary epoch in the early universe using only 4 semiconductor bolometers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1175308','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1175308"><span id="translatedtitle"><span class="hlt">Absolute</span> calibration of optical flats</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Sommargren, Gary E.</p> <p>2005-04-05</p> <p>The invention uses the phase shifting diffraction interferometer (PSDI) to provide a true point-by-point measurement of <span class="hlt">absolute</span> flatness over the surface of optical flats. Beams exiting the fiber optics in a PSDI have perfect spherical wavefronts. The measurement beam is reflected from the optical flat and passed through an auxiliary optic to then be combined with the reference beam on a CCD. The combined beams include phase errors due to both the optic under test and the auxiliary optic. Standard phase extraction algorithms are used to calculate this combined phase error. The optical flat is then removed from the system and the measurement fiber is moved to recombine the two beams. The newly combined beams include only the phase errors due to the auxiliary optic. When the second phase measurement is subtracted from the first phase measurement, the <span class="hlt">absolute</span> phase error of the optical flat is obtained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PhRvS..14l3501X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhRvS..14l3501X"><span id="translatedtitle">Enhanced characterization of niobium surface <span class="hlt">topography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xu, Chen; Tian, Hui; Reece, Charles E.; Kelley, Michael J.</p> <p>2011-12-01</p> <p>Surface <span class="hlt">topography</span> characterization is a continuing issue for the superconducting radio frequency (SRF) particle accelerator community. Efforts are under way to both improve surface <span class="hlt">topography</span> and its characterization and analysis using various techniques. In measurement of <span class="hlt">topography</span>, power spectral density (PSD) is a promising method to quantify typical surface parameters and develop scale-specific interpretations. PSD can also be used to indicate how the process modifies <span class="hlt">topography</span> at different scales. However, generating an accurate and meaningful topographic PSD of an SRF surface requires careful analysis and optimization. In this report, niobium surfaces with different process histories are sampled with atomic force microscopy and stylus profilometry and analyzed to trace <span class="hlt">topography</span> evolution at different scales. An optimized PSD analysis protocol to serve SRF needs is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoJI.203.1263K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoJI.203.1263K"><span id="translatedtitle">High surface <span class="hlt">topography</span> related to upper mantle flow beneath Eastern Anatolia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Komut, Tolga</p> <p>2015-11-01</p> <p>Eastern Anatolia region between north-south colliding Arabian and Eurasian plates has no significant crustal root and shallow (upper) mantle flow beneath seems to be vertically supporting its high <span class="hlt">topography</span>. It has a high surface heat flow and the underlying mantle is characterized by low seismic velocity zones. Using a mantle density/temperature variation field derived from P-wave seismic velocity, current shallow mantle flow and resultant <span class="hlt">dynamic</span> <span class="hlt">topography</span> of Eastern Anatolia and adjacent Arabian foreland and Caucasus areas were calculated along a vertical section. The section crosses the tectonic boundaries interrelated with slab bodies (high seismic velocity/cold regions) and the low velocity zones above the slabs. According to the modelling experiments, the surface <span class="hlt">topography</span> of Eastern Anatolia seems to be supported by shallow mantle flow <span class="hlt">dynamics</span>. On the other hand, residual <span class="hlt">topography</span> for the region was calculated using high resolution crustal thickness data. Positive residual <span class="hlt">topography</span> that suggests an undercompensated state of Eastern Anatolia is in concordance with the <span class="hlt">dynamic</span> <span class="hlt">topography</span> anomaly. The modelled local shallow mantle flow support due to the density contrast between hot (low velocity) zones and underlying cold slab bodies beneath the area may be the present-day snapshot of the mantle flow uplift in Eastern Anatolia presence of which was previously suggested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://geology.er.usgs.gov/eespteam/terrainmodeling/ds_136.htm','USGSPUBS'); return false;" href="http://geology.er.usgs.gov/eespteam/terrainmodeling/ds_136.htm"><span id="translatedtitle"><span class="hlt">Topography</span> and Landforms of Ecuador</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Chirico, Peter G.; Warner, Michael B.</p> <p>2005-01-01</p> <p>EXPLANATION The digital elevation model of Ecuador represented in this data set was produced from over 40 individual tiles of elevation data from the Shuttle Radar <span class="hlt">Topography</span> Mission (SRTM). Each tile was downloaded, converted from its native Height file format (.hgt), and imported into a geographic information system (GIS) for additional processing. Processing of the data included data gap filling, mosaicking, and re-projection of the tiles to form one single seamless digital elevation model. For 11 days in February of 2000, NASA, the National Geospatial-Intelligence Agency (NGA), the German Aerospace Center (DLR), and the Italian Space Agency (ASI) flew X-band and C-band radar interferometry onboard the Space Shuttle Endeavor. The mission covered the Earth between 60?N and 57?S and will provide interferometric digital elevation models (DEMs) of approximately 80% of the Earth's land mass when processing is complete. The radar-pointing angle was approximately 55? at scene center. Ascending and descending orbital passes generated multiple interferometric data scenes for nearly all areas. Up to eight passes of data were merged to form the final processed SRTM DEMs. The effect of merging scenes averages elevation values recorded in coincident scenes and reduces, but does not completely eliminate, the amount of area with layover and terrain shadow effects. The most significant form of data processing for the Ecuador DEM was gap-filling areas where the SRTM data contained a data void. These void areas are a result of radar shadow, layover, standing water, and other effects of terrain, as well as technical radar interferometry phase unwrapping issues. To fill these gaps, topographic contours were digitized from 1:50,000 - scale topographic maps which date from the mid-late 1980's (Souris, 2001). Digital contours were gridded to form elevation models for void areas and subsequently were merged with the SRTM data through GIS and remote sensing image-processing techniques</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011GeoRL..3816611V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011GeoRL..3816611V"><span id="translatedtitle">Stochastic variability of oceanic flows above <span class="hlt">topography</span> anomalies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Venaille, A.; Le Sommer, J.; Molines, J.-M.; Barnier, B.</p> <p>2011-08-01</p> <p>We describe a stochastic variability mechanism which is genuinely internal to the ocean, i.e., not due to fluctuations in atmospheric forcing. The key ingredient is the existence of closed contours of bottom <span class="hlt">topography</span> surrounded by a stirring region of enhanced eddy activity. This configuration leads to the formation of a robust but highly variable vortex above the <span class="hlt">topography</span> anomaly. The vortex <span class="hlt">dynamics</span> integrates the white noise forcing of oceanic eddies into a red noise signal for the large scale volume transport of the vortex. The strong interannual fluctuations of the transport of the Zapiola anticyclone (˜100 Sv) in the Argentine basin are argued to be partly due to such eddy-driven stochastic variability, on the basis of a 310 years long simulation of a comprehensive global ocean model run driven by a repeated-year forcing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3184154','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3184154"><span id="translatedtitle">Predicting Maximum Lake Depth from Surrounding <span class="hlt">Topography</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>Hollister, Jeffrey W.; Milstead, W. Bryan; Urrutia, M. Andrea</p> <p>2011-01-01</p> <p>Information about lake morphometry (e.g., depth, volume, size, etc.) aids understanding of the physical and ecological <span class="hlt">dynamics</span> of lakes, yet is often not readily available. The data needed to calculate measures of lake morphometry, particularly lake depth, are usually collected on a lake-by-lake basis and are difficult to obtain across broad regions. To span the gap between studies of individual lakes where detailed data exist and regional studies where access to useful data on lake depth is unavailable, we developed a method to predict maximum lake depth from the slope of the <span class="hlt">topography</span> surrounding a lake. We use the National Elevation Dataset and the National Hydrography Dataset – Plus to estimate the percent slope of surrounding lakes and use this information to predict maximum lake depth. We also use field measured maximum lake depths from the US EPA's National Lakes Assessment to empirically adjust and cross-validate our predictions. We were able to predict maximum depth for ∼28,000 lakes in the Northeastern United States with an average cross-validated RMSE of 5.95 m and 5.09 m and average correlation of 0.82 and 0.69 for Hydrological Unit Code Regions 01 and 02, respectively. The depth predictions and the scripts are openly available as supplements to this manuscript. PMID:21984945</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/910204','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/910204"><span id="translatedtitle"><span class="hlt">Absolute</span> Measurement of Electron Cloud Density</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Covo, M K; Molvik, A W; Cohen, R H; Friedman, A; Seidl, P A; Logan, G; Bieniosek, F; Baca, D; Vay, J; Orlando, E; Vujic, J L</p> <p>2007-06-21</p> <p>Beam interaction with background gas and walls produces ubiquitous clouds of stray electrons that frequently limit the performance of particle accelerator and storage rings. Counterintuitively we obtained the electron cloud accumulation by measuring the expelled ions that are originated from the beam-background gas interaction, rather than by measuring electrons that reach the walls. The kinetic ion energy measured with a retarding field analyzer (RFA) maps the depressed beam space-charge potential and provides the <span class="hlt">dynamic</span> electron cloud density. Clearing electrode current measurements give the static electron cloud background that complements and corroborates with the RFA measurements, providing an <span class="hlt">absolute</span> measurement of electron cloud density during a 5 {micro}s duration beam pulse in a drift region of the magnetic transport section of the High-Current Experiment (HCX) at LBNL.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720024184','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720024184"><span id="translatedtitle"><span class="hlt">Absolute</span> calibration of ultraviolet filter photometry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bless, R. C.; Fairchild, T.; Code, A. D.</p> <p>1972-01-01</p> <p>The essential features of the calibration procedure can be divided into three parts. First, the shape of the bandpass of each photometer was determined by measuring the transmissions of the individual optical components and also by measuring the response of the photometer as a whole. Secondly, each photometer was placed in the essentially-collimated synchrotron radiation bundle maintained at a constant intensity level, and the output signal was determined from about 100 points on the objective. Finally, two or three points on the objective were illuminated by synchrotron radiation at several different intensity levels covering the <span class="hlt">dynamic</span> range of the photometers. The output signals were placed on an <span class="hlt">absolute</span> basis by the electron counting technique described earlier.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.usgs.gov/fs/2009/3087/','USGSPUBS'); return false;" href="http://pubs.usgs.gov/fs/2009/3087/"><span id="translatedtitle">Shuttle Radar <span class="hlt">Topography</span> Mission (SRTM)</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>U.S. Geological Survey</p> <p>2009-01-01</p> <p>Under an agreement with the National Aeronautics and Space Administration (NASA) and the Department of Defense's National Geospatial-Intelligence Agency (NGA), the U.S. Geological Survey (USGS) is distributing elevation data from the Shuttle Radar <span class="hlt">Topography</span> Mission (SRTM). The SRTM is a joint project of NASA and NGA to map the Earth's land surface in three dimensions at an unprecedented level of detail. As part of space shuttle Endeavour's flight during February 11-22, 2000, the SRTM successfully collected data over 80 percent of the Earth's land surface for most of the area between latitudes 60 degrees north and 56 degrees south. The SRTM hardware included the Spaceborne Imaging Radar-C (SIR-C) and X-band Synthetic Aperture Radar (X-SAR) systems that had flown twice previously on other space shuttle missions. The SRTM data were collected with a technique known as interferometry that allows image data from dual radar antennas to be processed for the extraction of ground heights.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.usgs.gov/fs/2003/0071/report.pdf','USGSPUBS'); return false;" href="http://pubs.usgs.gov/fs/2003/0071/report.pdf"><span id="translatedtitle">Shuttle Radar <span class="hlt">Topography</span> Mission (SRTM)</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>U.S. Geological Survey</p> <p>2003-01-01</p> <p>Under an agreement with the National Aeronautics and Space Administration (NASA) and the Department of Defense's National Imagery and Mapping Agency (NIMA), the U.S. Geological Survey (USGS) is now distributing elevation data from the Shuttle Radar <span class="hlt">Topography</span> Mission (SRTM). The SRTM is a joint project between NASA and NIMA to map the Earth's land surface in three dimensions at a level of detail unprecedented for such a large area. Flown aboard the NASA Space Shuttle Endeavour February 11-22, 2000, the SRTM successfully collected data over 80 percent of the Earth's land surface, for most of the area between 60? N. and 56? S. latitude. The SRTM hardware included the Spaceborne Imaging Radar-C (SIR-C) and X-band Synthetic Aperture Radar (X-SAR) systems that had flown twice previously on other space shuttle missions. The SRTM data were collected specifically with a technique known as interferometry that allows image data from dual radar antennas to be processed for the extraction of ground heights.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950027808&hterms=Binocular+vision&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DBinocular%2Bvision','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950027808&hterms=Binocular+vision&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DBinocular%2Bvision"><span id="translatedtitle"><span class="hlt">Topography</span> from shading and stereo</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Horn, Berthold P.; Caplinger, Michael</p> <p>1993-01-01</p> <p>Methods exploiting photometric information in images that have been developed in machine vision can be applied to planetary imagery. Present techniques, however, focus on one visual cue, such as shading or binocular stereo, and produce results that are either not very accurate in an <span class="hlt">absolute</span> sense or provide information only at few points on the surface. We plan to integrate shape from shading, binocular stereo and photometric stereo to yield a robust system for recovering detailed surface shape and surface reflectance information. Such a system will be useful in producing quantitative information from the vast volume of imagery being received, as well as in helping visualize the underlying surface. The work will be carried out on a popular computing platform so that it will be easily accessible to other workers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930016614&hterms=Binocular+vision&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DBinocular%2Bvision','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930016614&hterms=Binocular+vision&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DBinocular%2Bvision"><span id="translatedtitle"><span class="hlt">Topography</span> from shading and stereo</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Horn, Berthold P.; Caplinger, Michael</p> <p>1992-01-01</p> <p>Methods exploiting photometric information in images that have been developed in machine vision can be applied to planetary imagery. Present techniques, however, focus on one visual cue, such as shading or binocular stereo, and produce results that are either not very accurate in an <span class="hlt">absolute</span> sense or provide information only at few points on the surface. We plan to integrate shape from shading, binocular stereo and photometric stereo to yield a robust system for recovering detailed surface shape and surface reflectance information. Such a system will be useful in producing quantitative information from the vast volume of imagery being received, as well as in helping visualize the underlying surface. The work will be carried out on a popular computing platform so that it will be easily accessible to other workers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790013324','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790013324"><span id="translatedtitle">The AFGL <span class="hlt">absolute</span> gravity program</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hammond, J. A.; Iliff, R. L.</p> <p>1978-01-01</p> <p>A brief discussion of the AFGL's (Air Force Geophysics Laboratory) program in <span class="hlt">absolute</span> gravity is presented. Support of outside work and in-house studies relating to gravity instrumentation are discussed. A description of the current transportable system is included and the latest results are presented. These results show good agreement with measurements at the AFGL site by an Italian system. The accuracy obtained by the transportable apparatus is better than 0.1 microns sq sec 10 microgal and agreement with previous measurements is within the combined uncertainties of the measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AGUSM...B41C08F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AGUSM...B41C08F"><span id="translatedtitle">The Shuttle Radar <span class="hlt">Topography</span> Mission</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Farr, T. G.; Kobrick, M.</p> <p>2001-05-01</p> <p>The Shuttle Radar <span class="hlt">Topography</span> Mission (SRTM), which flew successfully aboard Endeavour in February 2000, is a cooperative project between NASA and the National Imagery and Mapping Agency (NIMA). The mission was designed to use a single-pass radar interferometer to produce a digital elevation model of the Earth's land surface between about 60 degrees north and 56 degrees south latitude. The DEM will have 30 m horizontal resolution and about 15 m vertical errors. Two ortho-rectified C-band image mosaics are also planned. SRTM used a modification of the radar instrument that comprised the Spaceborne Radar Laboratory that flew twice on the Shuttle Endeavour in 1994. To collect the interferometric data, a 60 m mast, additional C-band antenna, and improved tracking and navigation devices were added. A second X-band antenna was also added by the German Space Agency, and produced higher resolution topographic measurements in strips nested within the full, C-band coverage. First results indicate that the radars and ancillary instruments worked very well. Data played back to the ground during the flight were processed to DEMs and products released hours after acquisition. An extensive program for calibration and verification of the SRTM data is now underway. When complete later this year, systematic processing of the data will begin, with final products emerging a continent at a time. Data processing will be completed by the end of 2002. Products will be transferred to the US Geological Survey's EROS Data Center for civilian archive and distribution. NIMA will handle Department of Defense distribution. * Work performed under contract to NASA.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AGUFM.G22B0214F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AGUFM.G22B0214F"><span id="translatedtitle">The Shuttle Radar <span class="hlt">Topography</span> Mission</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Farr, T. G.; Kobrick, M.</p> <p>2001-12-01</p> <p>The Shuttle Radar <span class="hlt">Topography</span> Mission (SRTM), which flew successfully aboard Endeavour in February 2000, is a cooperative project between NASA, the National Imagery and Mapping Agency, and the German and Italian Space Agencies. The mission was designed to use a single-pass radar interferometer to produce a digital elevation model of the Earth's land surface between about 60 degrees north and 56 degrees south latitude. The DEM will have 30 m horizontal resolution and better than 15 m vertical errors. Two ortho-rectified C-band image mosaics are also planned. Data processing will be completed by the end of 2002. SRTM used a modification of the radar instrument that comprised the Spaceborne Radar Laboratory that flew twice on the Shuttle Endeavour in 1994. To collect the interferometric data, a 60 m mast, additional C-band antenna, and improved tracking and navigation devices were added. A second X-band antenna was also added by the German Space Agency, and produced higher resolution topographic measurements in strips nested within the full, C-band coverage. First results indicate that the radars and ancillary instruments worked very well. Data played back to the ground during the flight were processed to DEMs and products released hours after acquisition. An extensive program for calibration and verification of the SRTM data is now underway. When complete later this year, systematic processing of the data will begin, with final products emerging a continent at a time. Products will be transferred to the US Geological Survey's EROS Data Center for civilian archive and distribution. NIMA will handle Department of Defense distribution. * Work performed under contract to NASA.</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_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" 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_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMIN31C1015M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMIN31C1015M"><span id="translatedtitle">The Glacier and Land Ice Surface <span class="hlt">Topography</span> Interferometer: An Airborne Proof-of-concept Mapping Sensor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moller, D.; Hensley, S.; Chuang, C.; Fisher, C.; Muellerschoen, R.; Milligan, L.; Sadowy, G.; Rignot, E. J.</p> <p>2009-12-01</p> <p>In May 2009 a new radar technique for mapping ice surface <span class="hlt">topography</span> was demonstrated in a Greenland campaign as part of the NASA International Polar Year activities. This was achieved by integrating a Ka-band single-pass interferometric synthetic radar on the NASA Dryden Gulfstream III for a coordinated deployment. Although the technique of using radar interferometry for mapping terrain has been demonstrated before, this is the first such application at millimeter-wave frequencies. This proof-of-concept demonstration was motivated by the Glacier and Land Ice Surface <span class="hlt">Topography</span> Interferometer (GLISTIN) Instrument Incubator Program and furthermore, highly leveraged existing ESTO hardware and software assets (the Unmanned Airborne Vehicle Synthetic Aperture Radar (UAVSAR) and processor and the PR2 (precipitation radar 2) RF assembly and power amplifier). Initial Ka-band test flights occurred in March and April of 2009 followed by the Greenland deployment. Instrument performance indicates swath widths over the ice between 5-7km, with height precisions ranging from 30cm-3m at a posting of 3m x 3m. However, for this application the electromagnetic wave will penetrate an unknown amount into the snow cover thus producing an effective bias that must be calibrated. This penetration will be characterized as part of this program and is expected to vary as a function of snow wetness and radar incidence angle. To evaluate this, we flew a coordinated collection with the NASA Wallops Airborne Topographic Mapper on a transect from Greenland’s Summit its West coast. This flight included two field calibration sites at Colorado Institute for Research in Environmental Science’s Swiss Camp and the National Science Foundation’s Summit station. Additional collections entailed flying a grid over Jakobshavn glacier which were repeated after 6 days to reveal surface <span class="hlt">dynamics</span>. In this time frame we were able to observe horizontal motion of over 1km on the glacier. While developed for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013JGRE..118..908B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013JGRE..118..908B&link_type=ABSTRACT"><span id="translatedtitle">Convection-driven compaction as a possible origin of Enceladus's long wavelength <span class="hlt">topography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Besserer, J.; Nimmo, F.; Roberts, J. H.; Pappalardo, R. T.</p> <p>2013-05-01</p> <p>The long wavelength surface <span class="hlt">topography</span> of Enceladus shows depressions about 1 km in depth and ˜102 km wide. One possible cause of this <span class="hlt">topography</span> is spatially variable amounts of compaction of an initially porous ice shell, driven by spatial variations in heat flux. Here, we show that the heat flux variations associated with convection in the shell can quantitatively match the observed features. We develop a simple model of viscous compaction that includes the effect of porosity on thermal conductivity, and find that an initial shell porosity of at least 20-25% is required to develop the observed <span class="hlt">topography</span> over ˜1 Ga. This mechanism produces topographic depressions, not rises, above convective upwellings, and does not generate detectable gravity anomalies. Unlike transient <span class="hlt">dynamic</span> <span class="hlt">topography</span>, it can potentially leave a permanent record of ancient convective processes in the shallow lithospheres of icy satellites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980018849','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980018849"><span id="translatedtitle"><span class="hlt">Topography</span> of the Moon from the Clementine Lidar</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Smith, David E.; Zuber, Maria T.; Neumann, Gregory A.; Lemoine, Frank G.</p> <p>1997-01-01</p> <p>Range measurements from the lidar instrument carried aboard the Clementine spacecraft have been used to produce an accurate global topographic model of the Moon. This paper discusses the function of the lidar; the acquisition, processing, and filtering of observations to produce a global topographic model; and the determination of parameters that define the fundamental shape of the Moon. Our topographic model: a 72nd degree and order spherical harmonic expansion of lunar radii, is designated Goddard Lunar <span class="hlt">Topography</span> Model 2 (GLTM 2). This topographic field has an <span class="hlt">absolute</span> vertical accuracy of approximately 100 m and a spatial resolution of 2.5 deg. The field shows that the Moon can be described as a sphere with maximum positive and negative deviations of approx. 8 km, both occurring on the farside, in the areas of the Korolev and South Pole-Aitken (S.P.-Aitken) basins. The amplitude spectrum of the <span class="hlt">topography</span> shows more power at longer wavelengths as compared to previous models, owing to more complete sampling of the surface, particularly the farside. A comparison of elevations derived from the Clementine lidar to control point elevations from the Apollo laser altimeters indicates that measured relative topographic heights generally agree to within approx. 200 in over the maria. While the major axis of the lunar gravity field is aligned in the Earth-Moon direction, the major axis of <span class="hlt">topography</span> is displaced from this line by approximately 10 deg to the cast and intersects the farside 24 deg north of the equator. The magnitude of impact basin <span class="hlt">topography</span> is greater than the lunar flattening (approx. 2 km) and equatorial ellipticity (approx. 800 m), which imposes a significant challenge to interpreting the lunar figure. The floors of mare basins are shown to lie close to an equipotential surface, while the floors of unflooded large basins, except for S.P.-Aitken, lie above this equipotential. The radii of basin floors are thus consistent with a hydrostatic mechanism</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1815003A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1815003A"><span id="translatedtitle">The influence of deep mantle heterogeneity on the rhythms and scales of surface <span class="hlt">topography</span> evolution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arnould, Maëlis; Coltice, Nicolas; Flament, Nicolas</p> <p>2016-04-01</p> <p>Earth's surface, the interface between external processes and internal <span class="hlt">dynamics</span> (lithosphere motions and mantle convection), is continuously reorganised. A large part of Earth's <span class="hlt">topography</span> is generated by mantle motions and lithospheric stresses [1], which impacts for instance the global sea-level, the <span class="hlt">dynamics</span> of sedimentary basins and the geoid. Studying how surface <span class="hlt">topography</span> evolves in both space and time thus not only provides information on the rhythms and scales of evolution of those processes, but would also be a tool for the study of the mantle motions and properties from which it originates [2]. In this study, we propose to characterise the spatial and temporal scales of evolution of surface <span class="hlt">topography</span> in 2D spherical annulus numerical models of mantle convection developing a plate-like behaviour. We use the geodynamical code StagYY [3] to first determine a mantle convection regime generating a surface <span class="hlt">topography</span> with Earth-like amplitudes and realistic mantle <span class="hlt">dynamics</span> at first order (e.g. high Rayleigh number, reasonable lithosphere thickness, pseudo-plastic lithosphere rheology generating plate tectonics). We then use this convection regime to investigate how the presence of stable deep-rooted thermochemical heterogeneities influence the rhythms of evolution of surface <span class="hlt">topography</span>. We analyse our results to identify how the timescales of evolution are connected with the lengthscales of <span class="hlt">topography</span>, in light of the tectonic histories produced by the models. References: [1] M. Gurnis, Long-term controls of eustatic and epeirogenic motions by mantle convection, GSA Today, 2(7):141-157, 1992. [2] B.H. Hager, R.W. Clayton, M.A. Richards, R.P. Comer, and A.M. Dziewonski, Lower mantle heterogeneity, <span class="hlt">dynamic</span> <span class="hlt">topography</span> and the geoid, Nature, 313:541-545, 1985. [3] J.W. Hernlund and P.J. Tackley, Modeling mantle convection in the spherical annulus, Phys. Earth Planet. Interiors, 171(1):48-54, 2008.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1031324','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1031324"><span id="translatedtitle">Enhanced Characterization of Niobium Surface <span class="hlt">Topography</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chen Xu, Hui Tian, Charles Reece, Michael Kelley</p> <p>2011-12-01</p> <p>Surface <span class="hlt">topography</span> characterization is a continuing issue for the Superconducting Radio Frequency (SRF) particle accelerator community. Efforts are underway to both to improve surface <span class="hlt">topography</span>, and its characterization and analysis using various techniques. In measurement of <span class="hlt">topography</span>, Power Spectral Density (PSD) is a promising method to quantify typical surface parameters and develop scale-specific interpretations. PSD can also be used to indicate how chemical processes modifiesy the roughnesstopography at different scales. However, generating an accurate and meaningful topographic PSD of an SRF surface requires careful analysis and optimization. In this report, polycrystalline surfaces with different process histories are sampled with AFM and stylus/white light interferometer profilometryers and analyzed to indicate trace <span class="hlt">topography</span> evolution at different scales. evolving during etching or polishing. Moreover, Aan optimized PSD analysis protocol will be offered to serve the SRF surface characterization needs is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMEP52A..07M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMEP52A..07M"><span id="translatedtitle">Cenozoic migration of <span class="hlt">topography</span> in the North American Cordillera</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mix, H. T.; Mulch, A.; Chamberlain, C. P.</p> <p>2010-12-01</p> <p>Continental <span class="hlt">topography</span> is the result of complex interactions among mantle convection, continental <span class="hlt">dynamics</span>, as well as climatic and erosional processes. Therefore, topographic evolution of mountain belts and continental interiors reflects directly upon the coupling between mantle and surface processes. It has recently been proposed that the modern <span class="hlt">topography</span> of western North America is partly controlled by the removal of the subducting Farallon Plate and replacement of lithospheric mantle by hot asthenosphere, creating surface uplift of the Colorado Plateau, the southwestern United States and northern Mexico, while concomitant subsidence characterizes the central United States. How the <span class="hlt">topography</span> of the Cenozoic North American Cordillera evolved in the past is largely unknown, yet currently debated tectonic models each have a predictable topographic response. We examined Cenozoic surface uplift patterns of western North America based on a record of ~3000 stable isotope proxy data. This data set is consistent with Eocene north to south surface uplift in the Cordillera, culminating in the assembly of an Eocene-Oligocene highland 3-4 km in elevation. The diachronous record of surface uplift and associated magmatism further supports tectonic models calling for the convective removal of mantle lithosphere or removal of the Farallon slab by buckling along an east-west axis. The Eocene-Oligocene development of similar-to-present day rainout patterns along the flanks of the Cordilleran orogen is therefore unlikely to be the result of late Mesozoic crustal thickening and associated development of an Andean-style Altiplano.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JCAP...08..060V&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JCAP...08..060V&link_type=ABSTRACT"><span id="translatedtitle">Cosmology with negative <span class="hlt">absolute</span> temperatures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vieira, J. P. P.; Byrnes, Christian T.; Lewis, Antony</p> <p>2016-08-01</p> <p>Negative <span class="hlt">absolute</span> temperatures (NAT) are an exotic thermodynamical consequence of quantum physics which has been known since the 1950's (having been achieved in the lab on a number of occasions). Recently, the work of Braun et al. [1] has rekindled interest in negative temperatures and hinted at a possibility of using NAT systems in the lab as dark energy analogues. This paper goes one step further, looking into the cosmological consequences of the existence of a NAT component in the Universe. NAT-dominated expanding Universes experience a borderline phantom expansion (w < ‑1) with no Big Rip, and their contracting counterparts are forced to bounce after the energy density becomes sufficiently large. Both scenarios might be used to solve horizon and flatness problems analogously to standard inflation and bouncing cosmologies. We discuss the difficulties in obtaining and ending a NAT-dominated epoch, and possible ways of obtaining density perturbations with an acceptable spectrum.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PhDT.......154L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhDT.......154L"><span id="translatedtitle">Corneal <span class="hlt">topography</span> measurements for biometric applications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lewis, Nathan D.</p> <p></p> <p>The term biometrics is used to describe the process of analyzing biological and behavioral traits that are unique to an individual in order to confirm or determine his or her identity. Many biometric modalities are currently being researched and implemented including, fingerprints, hand and facial geometry, iris recognition, vein structure recognition, gait, voice recognition, etc... This project explores the possibility of using corneal <span class="hlt">topography</span> measurements as a trait for biometric identification. Two new corneal topographers were developed for this study. The first was designed to function as an operator-free device that will allow a user to approach the device and have his or her corneal <span class="hlt">topography</span> measured. Human subject <span class="hlt">topography</span> data were collected with this device and compared to measurements made with the commercially available Keratron Piccolo topographer (Optikon, Rome, Italy). A third topographer that departs from the standard Placido disk technology allows for arbitrary pattern illumination through the use of LCD monitors. This topographer was built and tested to be used in future research studies. <span class="hlt">Topography</span> data was collected from 59 subjects and modeled using Zernike polynomials, which provide for a simple method of compressing <span class="hlt">topography</span> data and comparing one topographical measurement with a database for biometric identification. The data were analyzed to determine the biometric error rates associated with corneal <span class="hlt">topography</span> measurements. Reasonably accurate results, between three to eight percent simultaneous false match and false non-match rates, were achieved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JGRD..117.3112H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JGRD..117.3112H"><span id="translatedtitle">Shortwave radiation parameterization scheme for subgrid <span class="hlt">topography</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Helbig, N.; LöWe, H.</p> <p>2012-02-01</p> <p><span class="hlt">Topography</span> is well known to alter the shortwave radiation balance at the surface. A detailed radiation balance is therefore required in mountainous terrain. In order to maintain the computational performance of large-scale models while at the same time increasing grid resolutions, subgrid parameterizations are gaining more importance. A complete radiation parameterization scheme for subgrid <span class="hlt">topography</span> accounting for shading, limited sky view, and terrain reflections is presented. Each radiative flux is parameterized individually as a function of sky view factor, slope and sun elevation angle, and albedo. We validated the parameterization with domain-averaged values computed from a distributed radiation model which includes a detailed shortwave radiation balance. Furthermore, we quantify the individual topographic impacts on the shortwave radiation balance. Rather than using a limited set of real <span class="hlt">topographies</span> we used a large ensemble of simulated <span class="hlt">topographies</span> with a wide range of typical terrain characteristics to study all topographic influences on the radiation balance. To this end slopes and partial derivatives of seven real <span class="hlt">topographies</span> from Switzerland and the United States were analyzed and Gaussian statistics were found to best approximate real <span class="hlt">topographies</span>. Parameterized direct beam radiation presented previously compared well with modeled values over the entire range of slope angles. The approximation of multiple, anisotropic terrain reflections with single, isotropic terrain reflections was confirmed as long as domain-averaged values are considered. The validation of all parameterized radiative fluxes showed that it is indeed not necessary to compute subgrid fluxes in order to account for all topographic influences in large grid sizes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.C31E0569M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.C31E0569M"><span id="translatedtitle">Satellite Altimetric Mappings of Arctic Sea Surface <span class="hlt">Topography</span>: An Evaluation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McAdoo, D. C.; Farrell, S. L.; Laxon, S. W.; Zwally, H. J.; Yi, D.; Coakley, B.; Cochran, J. R.</p> <p>2008-12-01</p> <p>Increasingly precise mappings of sea surface <span class="hlt">topography</span> (SST) in the Arctic Ocean are being derived from near-polar satellite altimeters such as the laser system - Geoscience Laser Altimeter System (GLAS) - onboard NASA's ICESat and the radar systems onboard ESA's ERS-2 and Envisat. These mappings of sea surface <span class="hlt">topography</span> (SST) have important oceanographic and geodetic applications. For example, because the geoid does conform closely to sea surface <span class="hlt">topography</span> we can use altimetric SST measurements to estimate gravity (e.g., see the ARCtic Satellite-only (ARCS) field, McAdoo et al. 2008) particularly in regions lacking "true" surface gravity observations. Also, by differencing mappings of mean SST with a gravimetric geoid - particularly a geoid underpinned by a GRACE mean field model - we can estimate the <span class="hlt">dynamic</span> ocean <span class="hlt">topography</span> (DOT) and circulation of the Arctic Ocean. However, accurate estimates of DOT (e.g. accuracies better than a decimeter) require that we have very precise knowledge of the geoid and mean SST. Comparing a mean SST derived from ICESat/GLAS data spanning several years with a corresponding mean SST derived from ERS-2 data reveals short- wavelength differences or discrepancies of order 40 - 60 cm in certain areas of the Arctic Ocean such as the Chukchi Borderland. In order to attribute a portion of these discrepancies to laser or radar altimeter measurement error, we convert these mean SST fields to equivalent gravity fields and compare with gravity observations from several of the unclassified SCICEX/U.S. Navy submarine cruises (Edwards and Coakley, 2003; http://www.ldeo.columbia.edu/res/pi/SCICEX/ ). This comparison enables us to quantify short-wavelength errors in both laser and radar altimetric mean SST models.</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_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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