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1

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

PubMed Central

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 Humboldt Current System. We posit that such reductions in available foraging habitats during climatic disturbances could incur high energetic costs on these populations, ultimately affecting individual fitness and survival. PMID:25785692

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

2015-01-01

2

Validation of CryoSat-2 Classical Altimetry Data over Ocean using a GOCE Geoid to derive Absolute Dynamic Topography  

NASA Astrophysics Data System (ADS)

The ESA Earth Explorer mission CryoSat-2 provides a unique opportunity for exploring a broad variety of scientific applications in the fields of Geodesy and Oceanography. The quality assessment of CryoSat-2 data and in particular Low Rate Mode Level 2 (LRM L2) data is an essential step for a successful integration of the data products into operational usage and processing. The investigations presented in this paper are divided into two parts; on the one side the data quality analysis and on the other side the computation and use of an enhanced data product in an oceanographic application. After one year of data acquisition, the evolution of data quality is clearly visible. In this context, a comprehensive data quality analysis has been carried out, focussing mainly on cross-over difference analysis and the estimation of a present time tag bias in detail as well as other parameters, such as consistency and availability of the product. Different types of measures will be shown: Firstly, a CryoSat-2 mission internal analysis of the cross-over differences and secondly, a validation of CryoSat-2 with respect to Jason-2 as reference. As a consequence of the present deficiencies in the delivered products, a correction, to be applied to the product's data, was computed in order to gain enhanced data. To prove the feasibility of this enhancement, a case study will demonstrate the improvement of Absolute Dynamic Topography (ADT) results in an oceanic region, such as the Gulf Stream. For the ADT computation in an along track approach, geoid heights derived from the GOCE time-wise geoid model are used. The spatial resolution of the ADT is at 100km. A validation of the CryoSat-2/GOCE ADT results with other independently derived ADT estimates will be shown. A comprehensive description of the data, the techniques, the references and the models used will be included.

Horvath, A.; Dinardo, S.; Pail, R.; Gruber, T.; Benveniste, J.

2011-12-01

3

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

PubMed

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 Humboldt Current System. We posit that such reductions in available foraging habitats during climatic disturbances could incur high energetic costs on these populations, ultimately affecting individual fitness and survival. PMID:25785692

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

2015-01-01

4

Predicting dynamic topography from mantle circulation models  

NASA Astrophysics Data System (ADS)

Dynamic topography is anomalous vertical motions of Earth's surface associated with viscous flow in the mantle. Deformable boundaries, such as the surface, CMB and phase transition boundaries, within a fluid (Earth's mantle) are deflected by viscous flow. Denser than average, sinking mantle creates inward deflections of Earth's surface. Equally, upwelling flow creates bulges in the surface; large plumes are commonly thought to produce superswells, such as the anomalously high elevation of Southern Africa. Dynamic topography appears to operate on a number of length scales. Mantle density anomalies estimated from seismic tomography indicate long wavelength dynamic topography at present day of around 2 km amplitude (e.g. Conrand & Husson, 2009) whilst continental scale studies suggest vertical motions of a few hundred metres. Furthermore, time scales must be an important factor to consider when assessing dynamic topography. Stable, dense lower mantle 'piles' may contribute to dynamic surface topography; as they appear stable over reasonably long time scales, long wavelength dynamic topography may be a fairly constant feature over the recent geological past. Shorter wavelength, smaller amplitude dynamic topography may be due to more transient features of mantle convection. Studies on a continental scale reveal shorter term changes in dynamic topography of the order of a few hundred metres (e.g. Roberts & White, 2010; Heine et al., 2010). Understanding dynamic topography is complicated by the fact it is difficult to observe as the signal is often masked by isostatic effects. We use forward mantle convection models with 300 million years of recent plate motion history as the surface boundary condition to generate a present day distribution of density anomalies associated with subducted lithosphere. From the modelled temperature and density fields we calculate the normal stress at or near the surface of the model. As the models generally have a free slip surface where no vertical motion is allowed, an excess or deficit of stress exists near the surface. A pointwise force balance between this stress excess and the weight of rock above is used to calculate the anomalous elevation associated with the stress. Here we present some of the results obtained from mantle circulation models. We look at different ways of predicting dynamic topography, including the depth at which the stress field is calculated and by removing lithospheric density anomalies from the calculation. We also assess the impact of crustal thickness and isostasy on the predictions of dynamic topography.

Webb, Peter; Davies, J. Huw

2013-04-01

5

Mean dynamic topography of the Arctic Ocean  

NASA Astrophysics Data System (ADS)

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.

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

2012-01-01

6

Mean Dynamic Topography of the Arctic Ocean  

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

7

Global dynamic topography: geoscience communities requirements  

NASA Astrophysics Data System (ADS)

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 foreseen societal benefits.

Dewez, T.; Costeraste, J.

2012-04-01

8

Curvature sensor for the measurement of the static corneal topography and the dynamic tear film topography in the human eye  

NASA Astrophysics Data System (ADS)

A system to measure the topography of the first optical surface of the human eye noninvasively by using a curvature sensor is described. The static corneal topography and the dynamic topography of the tear film can both be measured, and the topographies obtained are presented. The system makes possible the study of the dynamic aberrations introduced by the tear film to determine their contribution to the overall ocular aberrations in healthy eyes, eyes with corneal pathologies, and eyes wearing contact lenses.

Gruppetta, Steve; Koechlin, Laurent; Lacombe, François; Puget, Pascal

2005-10-01

9

Lower mantle heterogeneity, dynamic topography and the geoid  

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

10

Cenozoic Tilting of the Australian Continent due to Dynamic Topography  

NASA Astrophysics Data System (ADS)

We investigate the possibility of a mantle-dynamic origin to account for the observed pattern of inundation of the Australian continent in the Cenozoic. Since the Paleocene, the Australian continent has experienced a series of regional marine incursions and regressions, which are inconsistent with the expected flooding history due to changes in eustatic sea level alone. During this time, the Australian continent has undergone no major episodes of mountain building or rifting which might account for these patterns of inundation. Since the Eocene, the Australian plate underwent rapid northward motion as the spreading rate at the South East Indian Ridge increased. As it moved northwards, the Australian plate moved away from a dynamic topography low caused by the sinking Gondwanaland slab beneath the South East Indian Ridge, and towards a dynamic topography low caused by subducted slab material in South East Asia. It is thought that these dynamic topography features at the southern and northern extremes of the Australian plate produce an underlying static and long wavelength dynamic feature over which the Australian plate has migrated through the Cenozoic. This dynamic feature should be expressed by an increase in the latitudinal asymmetry of the Australian dynamic signal. Estimates of the dynamic motion of the Australian plate since the Paleocene are made by matching observed patterns of marine incursion with models of marine inundation. Models of inundation are created by backstripping sediment from present-day topography and dynamic motion is quantified by the displacement needed to approximate the observed flooding according to eustatic sea level. We explore the trend of these displacements according to their paleo-position. Preliminary analysis suggests that the continent is influenced by a dynamic feature that is both temporally and spatially varying. We attempt to interpret the evolving dynamic topography field of Australia in the context of kinematic and 3-D dynamic models of the Australian region which provide an integrated explanation for the patterns of marine inundation in the Cenozoic.

Dicaprio, L.; Gurnis, M.; Muller, R. D.

2007-12-01

11

Static and dynamic support of western United States topography  

NASA Astrophysics Data System (ADS)

Isostatic and dynamic models of Earth's surface topography can provide important insights into the driving processes of tectonic deformation. We analyze these two estimates for the tectonically-active western United States using refined structural models derived from EarthScope USArray. For the crust, use of recent Moho depth measurements and crustal density anomalies inferred from passive source seismology improve isostatic models. However, seismically determined lithospheric thickness variations from “lithosphere-asthenosphere boundary” (LAB) maps, and lithospheric and mantle density anomalies derived from heat flow or uppermost mantle tomography, do not improve isostatic models substantially. Perhaps this is a consequence of compositional heterogeneity, a mismatch between thermal and seismological LAB, and structural complexity caused by smaller-scale dynamics. The remaining, non-isostatic (“dynamic”) component of topography is large. Topography anomalies include negative residuals likely due to active subduction of the Juan de Fuca plate, and perhaps remnants of formerly active convergence further south along the margin. Our finding of broad-scale, positive residual topography in the Basin and Range substantiates previous results, implying the presence of anomalous buoyancy there which we cannot fully explain. The Colorado Plateau does not appear dynamically anomalous at present, except at its edges. Many of the residual topography features are consistent with predictions from mantle flow computations. This suggests a convective origin, and important interactions between vigorous upper mantle convection and intraplate deformation.

Becker, Thorsten W.; Faccenna, Claudio; Humphreys, Eugene D.; Lowry, Anthony R.; Miller, Meghan S.

2014-09-01

12

Length Scale and Scaling in Both Topography Shape and Topography Dynamics  

NASA Astrophysics Data System (ADS)

Erosion processes both shapes topography and control topography dynamics so that it should be feasible to constrain the latter from the analysis of the former. During the last ten years, a bunch of studies have been done on analyzing topography in terms of erosion and transport laws. A kind of consensus has emerged around the power-law stream model which assumes that the erosion flux can be adequately described by its dependency on water flow and local topographic slope, and which gives that power laws with threshold are adequate functions to describe these dependencies, and that several processes (i.e. power-law functions) are necessary to cover the complete range of basin areas. But the consequences of these results in terms of dynamics have not been fully appraised yet. Thanks to a numerical surface-process model, we explore the relationship between form and dynamics, and especially the existence of characteristic time scales and their relationship to both structural and erosional parameters. Basically landscape erosion has a two-step evolution: an early phase which corresponds to the onset of drainage network, and a gentle back-to-equilibrium history. The former is very sensitive to initial topographic conditions and its dynamics is intimately related to drainage captures. We are mainly concerned with the latter which gives the long-term response of a continental system to any tectonic or climatic perturbation. Its characteristic time scale ? depends on the system size L in a power-law relationship which defines the nature of the continental-scale diffusion equation. For processes which depends linearly on slope (with or without threshold), this scaling can be written as: ? = ? H * (L/? aH)?, where ? H and aH are the characteristic time scale and drainage area of hillslope, L the system size, and ? the diffusion exponent which only depends on the river process. In all relevant cases, ? is smaller than 1 leading to abnormally fast diffusion. In some cases (if erosion flux is highly dependent on river flux and/or if the sediment are efficiently transported in rivers), ? is 0 and the system evolution is entirely controlled by hillslope dynamics. An analytical solution of ? has been derived with the assumptions described above. We also show that the complete analytical solution of the topography history takes the general form: h(t)=ho exp (-(t/? )?)+h? All parameters will be physically explained and related to system characteristics and erosion transport parameters.

Davy, P.

2003-12-01

13

Dynamic topography in subduction zones: insights from laboratory models  

NASA Astrophysics Data System (ADS)

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 dynamic topography and could represent the dynamic effect of the slab sinking into the asthenosphere and lowering the elevation of the upper plate.

Bajolet, Flora; Faccenna, Claudio; Funiciello, Francesca

2014-05-01

14

Effects of dynamic topography on Australian Paleogeography in the Cenozoic  

NASA Astrophysics Data System (ADS)

We have investigated the effects of dynamic topography combined with eustatic sea level variations on Australian paleogeography for the Late Cretaceous to present. Using an analytical flow model (Steinberger et al., 2001, doi: 10.1016/S0012-821X(01)00229-1 with the surface plate velocity field as boundary condition, we advect density anomalies converted from tomographic velocity anomalies (SMEAN tomographic model; Becker &Boschi, 2002, doi: 10.1029/2001GC000168) back through time. For each time step, we compute dynamic topography with a free upper boundary. This approach allows us to evaluate the spatio-temporal effects of large scale mantle convection patterns on surface processes like continental flooding and sediment deposition. The Australian continent, especially the southern Australian margin, provides a unique example for an extensive region that has been stable and fairly isolated from plate boundary processes like flexure or rift shoulder uplift for the time between 70 Ma to the present. This makes it ideal to investigate the effects of dynamic topography. Late Cretaceous and Cenozoic sedimentary deposits along the southern Australian margin indicate transgressive/regressive phases of limited extent, which can not be explained by eustatic sea level fluctuations alone. By using common estimates for the eustatic sea level in conjunction with our dynamic topography model, we have been able to reconstruct the position of the Australian paleo-shorelines, flooding patterns and water depths. We find a good agreement of our computed paleogeography with published stratigraphic data for Tertiary brown coal deposits along the southern Australian seabord (Gippsland, Murray, Otway and Bremer Basins) and stratigraphic sequences in the Murray Basin region, along the NW Australian margin and in the Eromanga Basin. Despite minor spatial discrepancies between the current model output and geological data which yet remain unresolved, our approach and modular workflow set up provides an important stepping stone to understand the influence of deep Earth processes and their impact on sediment deposition and other geomorphological processes. Due to the usage of non-proprietary data formats and open-source software it is possible to easily change the dynamic topography model input and extend the computations to incorporate the effects of sedimentation history and isostasy. We expect a further convergence of predicted paleogeography from dynamic topography models with increasing accuracy and resolution of tomographic models.

Heine, C.; M{Ü}Ller, R.; Steinberger, B.

2006-12-01

15

Dynamic Topography during Flat Subduction: Subsidence or Uplift?  

NASA Astrophysics Data System (ADS)

Since the first studies on dynamic topography and basin evolution, low-dipping subduction has been related to intracontinental, long-wavelength and high-amplitude subsidence, whereas retreating to normal subduction systems to uplift. This was proposed to explain the Cretaceous-early Cenozoic topographic evolution of the western US. However, modern flat-slab and slab-retreating segments of South America do not record such a subsidence and uplift patterns. For example, the flat slab of Peru at ˜10°SL, related to the subduction of the Nazca Ridge, underlies an elevated promontory known as the Fitzcarrald Arch. The Argentine flat-slab at ˜31°SL associated to the subduction of the Juan Fernandez Ridge underlies a high-elevated intermontane system known as the Pampean broken foreland. Both upwarping features are younger than 7 Ma and contemporaneous with the arrival of flat subduction to these segments. In order to shed light into this controversy, we calculate dynamic topography along the Andean flat-slab segments using the Hager and O'Connell (1981) instantaneous flow formulation, an accurate reconstruction of the slab geometry along the central Andes and a density contrast between the flat slabs and the country mantle close to zero (???0) in order to simulate a buoyant oceanic lithosphere. We demonstrate that dynamic subsidence develops only at the leading edge of flat subduction, where the slabs plunge >30°, whereas the flatter slabs reproduce minor or no dynamic topography signals. These results agree with geological and geophysical proxies. Along the Argentine Plains, the <7 Ma maximum sedimentary accumulation coeval with the age of the flat subduction, plus the maximum modern relief account for a accumulated relief of ˜200 m, which might be considered as an "observed dynamic subsidence" signal (given that no tectonic activity has been recorded in this region since the Cretaceous to explain this surface topography). This gives a ˜0.03 mm/yr dynamic subsidence rate that are curiously similar to the exhumations estimated by low-temperature thermochronology along the Andean foreland (Dávila, 2011).

Davila, F. M.; Lithgow-Bertelloni, C. R.

2011-12-01

16

The dynamics of the Mississippi River plume: Impact of topography, wind and offshore forcing  

E-print Network

The dynamics of the Mississippi River plume: Impact of topography, wind and offshore forcing) were employed to investigate the dynamical processes controlling the fate of the Mississippi River), The dynamics of the Mississippi River plume: Impact of topography, wind and offshore forcing on the fate

Miami, University of

17

Dynamic wetting and spreading and the role of topography  

NASA Astrophysics Data System (ADS)

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 ? and ?e 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 dependence of dynamic contact angle on time is presented. We review existing data for the spreading of small droplets of polydimethylsiloxane oil on surfaces decorated with micro-posts. On these surfaces, the initial droplet spreads with an approximately constant volume and the edge speed-dynamic contact angle relationship follows a power law v_{\\mathrm {e}} \\propto \\theta ^p . As the surface texture becomes stronger the exponent goes from p = 3 towards p = 1 in agreement with a Wenzel roughness driven spreading and a roughness modified Hoffman-de Gennes power law. Finally, we suggest that when a droplet spreads to a final partial wetting state on a rough surface, it approaches its Wenzel equilibrium contact angle in an exponential manner with a time constant dependent on roughness.

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

2009-11-01

18

Modeling the dynamic component of the geoid and topography of Venus  

E-print Network

Modeling the dynamic component of the geoid and topography of Venus M. Pauer,1,2 K. Fleming,3 and O) the density structure of Venus' mantle can be approximated by a model in which the mass anomaly distribution of the geoid and topography of Venus, J. Geophys. Res., 111, E11012, doi:10.1029/2005JE002511. 1. Introduction

Cerveny, Vlastislav

19

Hillslope glacier coupling: The interplay of topography and glacial dynamics in High Asia  

E-print Network

Hillslope glacier coupling: The interplay of topography and glacial dynamics in High Asia Dirk. Here we provide a regional synthesis of the topography and flow characteristics of 287 glaciers across High Asia using digital elevation analysis and remotely sensed glacier surface velocities. Glaciers

Bookhagen, Bodo

20

Integrated approach to estimate the ocean's time variable dynamic topography including its covariance matrix  

NASA Astrophysics Data System (ADS)

The ocean's mean dynamic topography as the difference between the sea surface and the geoid reflects many characteristics of the general ocean circulation. Consequently, it provides valuable information for evaluating or tuning ocean circulation models. However, the determination of the mean dynamic topography from satellite based gravity field and altimetric observations is not straightforward. For the integration of the dynamic topography into ocean circulation models not only the dynamic topography itself but also its inverse covariance matrix on the ocean model grid is required. We developed a rigorous combination method where both instrumental errors and omission errors are accounted for, including the determination of optimal relative weights between the observation groups. The altimetric mean sea surface is expressed as a sum of geoid heights represented in terms of spherical harmonics and the mean dynamic topography parameterized by a finite element method which can be directly related to the particular ocean model grid. The different observation groups are combined in terms of normal equations. This allows the direct determination of the normal equations of the mean dynamic topography which contain the appropriate weights for model-data misfits in least-squares ocean model inversions. The developed integrated approach can be extended by modeling the time variable component of the dynamic topography to provide estimates not only at a mean state but also at arbitrary points in time including a rigorously computed covariance matrix. The focus of this study is on the North Atlantic Ocean. We will present the conceptual design and dynamic topography estimates based on time variable data from several satellite altimeter missions in combination with GOCE and GRACE gravity field models.

Becker, Silvia; Brockmann, Jan Martin; Schuh, Wolf-Dieter

2014-05-01

21

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

NASA Astrophysics Data System (ADS)

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 geodetically derived mean dynamic topography with the full error structure in a 3D stationary inverse ocean model improves modeled oceanographic features over previous estimates.

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

2014-11-01

22

Rheology of continents and counterintuitive 3D features of the dynamic topography. (Invited)  

NASA Astrophysics Data System (ADS)

Dynamic topography is a key observable signature of the Earth's mantle convection, which is a major driving force of plate tectonics. In general view, it reflects mantle flow patterns, and hence is supposed to correlate at different extents with seismic tomography, SKS fast orientations, geodetic velocity fields and geoid anomalies. However, identification of dynamic topography had no systematic success, specifically in continents. Hence, it has been argued 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 had to be explored in 3D, which has been so far an impossible challenge due to the limited resolution and simplified representation of the lithosphere in the existing 3D models. We here present new unprecedentedly high resolution 3D experiments incorporating realistic stratified lithosphere. The results reveal strikingly disconcordant, counterintuitive features of the dynamic topography, going far beyond the inferences from previous models. In particular, weak anisotropic tectonic stress field may result 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. These 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 in tectonic-scale deformation.

Burov, E. B.; Gerya, T.

2013-12-01

23

Improving the geoid: Combining altimetry and mean dynamic topography in the California coastal ocean  

NASA Astrophysics Data System (ADS)

Satellite gravity mapping missions, altimeters, and other platforms have allowed the Earth's geoid to be mapped over the ocean to a horizontal resolution of approximately 100 km with an uncertainty of less than 10 cm. At finer resolution this uncertainty increases to greater than 10 cm. Achieving greater accuracy requires accurate estimates of the dynamic ocean topography (DOT). In this study two DOT estimates for the California Current System with uncertainties less than 10 cm are used to solve for a geoid correction field. The derived field increases the consistency between the DOTs and along-track altimetric observations, suggesting it is a useful correction to the gravitational field. The correction is large compared to the dynamic ocean topography, with a magnitude of 15 cm and significant structure, especially near the coast. The results are evidence that modern high-resolution dynamic ocean topography products can be used to improve estimates of the geoid.

Mazloff, Matthew R.; Gille, Sarah T.; Cornuelle, Bruce

2014-12-01

24

Influence of wet tropospheric correction on mesoscale dynamic topography as derived from satellite altimetry  

Microsoft Academic Search

We study the influence of the wet tropospheric correction on mesoscale dynamic topography as derived from satellite altimetry. For this purpose, we use Geosat altimeter data in the northeast Atlantic, and we process separately the tropospheric correction derived from the PERIDOT model following the technique for analyzing altimeter height profiles. We show that the humidity spatial scales are larger than

D. Jourdan; C. Boissier; A. Braun; J. F. Minster

1990-01-01

25

The Mid-Pliocene sea-level conundrum: Glacial isostasy, eustasy and dynamic topography  

NASA Astrophysics Data System (ADS)

Determining eustatic sea level during the Mid-Pliocene warm period (?3.3 to 2.9 Ma) has been a central but elusive goal in the study of past warm climates. Estimates of eustatic sea level based on geologic data span a broad range; variation that we now recognize is due in part to geographically varying post-depositional displacement caused by glacial isostatic adjustment and dynamic topography. In this study, we combine field observations and glacial isostatic adjustment modeling to estimate the dynamic topography signal in three areas that are important to paleo-sea level studies of the Mid-Pliocene warm period (South Africa, West Australia and southeastern United States). We show that dynamic topography played a significant role in the post-depositional displacement of Pliocene, and even younger Pleistocene, shorelines. In this regard, we provide a robust paleo-sea level elevation data set, corrected for glacial isostatic adjustment, that can be used to evaluate predictions from mantle flow models of dynamic topography.

Rovere, A.; Raymo, M. E.; Mitrovica, J. X.; Hearty, P. J.; O'Leary, M. J.; Inglis, J. D.

2014-02-01

26

Project EARTH-11-ABW1: Plate flexure, dynamic topography and global changes in sea-level  

E-print Network

the Late Cretaceous is a source of tectonic subsidence in sedimentary basins of the plate interior. One to plate processes such as sediment and water loading, flexure and thermal contraction and uplift fromProject EARTH-11-ABW1: Plate flexure, dynamic topography and global changes in sea-level Supervisor

Henderson, Gideon

27

Linking Observations of Dynamic Topography from Oceanic and Continental Realms around Australia  

NASA Astrophysics Data System (ADS)

In the last decade, there has been growing interest in predicting the spatial and temporal evolution of dynamic topography (i.e. the surface manifestation of mantle convection). By directly measuring Neogene and Quaternary dynamic topography around Australia's passive margins we assess the veracity of these predictions and the interplay between mantle convection and plate motion. We mapped the present dynamic topography by carefully measuring residual topography of oceanic lithosphere adjacent to passive margins. This map provides a reference with respect to which the relative record of vertical motions, preserved within the stratigraphic architecture of the margins, can be interpreted. We carefully constrained the temporal record of vertical motions along Australia's Northwest Shelf by backstripping Neogene carbonate clinoform rollover trajectories in order to minimise paleobathymetric errors. Elsewhere, we compile temporal constraints from published literature. Three principal insights emerge from our analysis. First, the present-day drawn-down residual topography of Australia, cannot be approximated by a regional tilt down towards the northeast, as previously hypothesised. The south-western and south-eastern corners of Australia are at negligible to slightly positive residual topography which slopes down towards Australia's northern margin and the Great Australian Bight. Secondly, the record of passive margin subsidence suggests drawdown across northern Australia commenced synchronously at 8±2 Ma. The amplitude of this synchronous drawdown corresponds to the amplitude of oceanic residual topography, indicating northern Australia was at an unperturbed dynamic elevation until drawdown commenced. The synchronicity of this subsidence suggests that the Australian plate has not been affected by a southward propagating wave of drawdown, despite Australia's rapid northward motion towards the subduction realm in south-east Asia. In contrast, it appears the mantle anomaly responsible for this drawdown is a relatively young, long-wavelength feature. Thirdly, there is an apparent mismatch between the current drawdown of oceanic lithosphere observed along Australia's southern margin and the onshore record of Cenozoic uplift. This disparity we attribute to the region undergoing recent uplift from a position of dynamic drawdown.

Czarnota, K.; Hoggard, M. J.; White, N.; Winterbourne, J.

2012-04-01

28

Exploiting Oceanic Residual Depth to Quantify Present-day Dynamic Topography at the Earth's Surface  

NASA Astrophysics Data System (ADS)

Convective circulation within the mantle causes vertical motions at the Earth's surface. This dynamic topography is time dependent and occurs on wavelengths of 1000s km with maximum amplitudes of ±2 km. Convective simulation models have been used extensively to make predictions of dynamic topography and have thus far out-paced observational constraints. Here, the well-established relationship between seafloor subsidence and age is used to produce a global map of residual depth anomalies in the oceanic realm. Care is taken to remove other causes of topography, including an isostatic correction for sedimentary loading that takes compaction into account, a correction for variable oceanic crustal thickness, and lithospheric thickening with age away from mid-ocean ridge spreading centres. A dataset including over 1000 seismic reflection profiles and 300 modern wide-angle refraction experiments has been amassed, primarily on old ocean floor adjacent to the continents. Calculation of residual depth yields a map of present-day dynamic topography with amplitudes significantly larger than the errors associated with the corrections. One of the most interesting results occurs along the west coast of Africa, where two full 2000 km wavelengths of dynamic topography have been captured with amplitudes ±1 km that correlate well with the long-wavelength free air gravity anomaly. Comparison with predictive models reveal poor to moderate correlations. This is a direct result of the limited resolution of the mantle tomography models used to set-up convection simulations and also the currently poor understanding of viscosity structure within the Earth. It is hoped that this residual depth dataset should provide an excellent surface boundary constraint for future convective simulation.

Hoggard, Mark; White, Nicky

2014-05-01

29

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

PubMed

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

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

2013-06-28

30

Spatial and temporal patterns of Australian dynamic topography from River Profile Modeling  

NASA Astrophysics Data System (ADS)

Despite its importance, the temporal and spatial evolution of continental dynamic topography is poorly known. Australia's isolation from active plate boundaries and its rapid northward motion within a hot spot reference frame make it a useful place to investigate the interplay between mantle convection, topography, and drainage. Offshore, dynamic topography is relatively well constrained and can be accounted for by Australia's translation over the mantle's convective circulation. To build a database of onshore constraints, we have analyzed an inventory of longitudinal river profiles, which is sensitive to uplift rate history. Using independently constrained erosional parameters, we determine uplift rates by minimizing the misfit between observed and calculated river profiles. Resultant fits are excellent and calculated uplift histories match independent geologic constraints. We infer that western and central Australia underwent regional uplift during the last 50 Myr and that the Eastern Highlands have been uplifted in two stages. The first stage from 120 to 80 Ma, coincided with rifting along the eastern margin and its existence is supported by thermochronological measurements. A second stage occurred at 80-10 Ma, formed the Great Escarpment, and coincided with Cenozoic volcanism. The relationship between topography, gravity anomalies, and shear wave tomographic models suggest that regional elevation is supported by temperature anomalies within the lithosphere's thermal boundary layer. Morphology and stratigraphy of the Eastern Highlands imply that these anomalies have been coupled to the base of the plate during Australia's northward motion over the last 70 Myr.

Czarnota, K.; Roberts, G. G.; White, N. J.; Fishwick, S.

2014-02-01

31

Infrasound wavefield modeled by coupling conduit dynamics and topography by 3D-FDTD  

NASA Astrophysics Data System (ADS)

Infrasound signal on active volcanoes has become an important tool for monitoring and understanding the explosive source dynamics. Volcano infrasound is the direct measure of pressure oscillations near open-vent and it can provide important constraints on the intensity of the eruption as well as on the source parameters including the variations of volumetric flux and exit velocity. At present, infrasonic signals recorded close to the volcano (<5 Km) have been used to model the acoustic source of volcanic explosions considering that at this distance the acoustic wavefield is relatively less affected by atmospheric structure. On the contrary, recent 2D finite-difference time-domain (FDTD) numerical modelling of infrasound propagation indicates a strong effect on the wavefield induced by the diffraction of the crater rim [Kim and Lees 2011] and by the near-source topography [Lacanna and Ripepe 2013]. However, the full three-dimensional interaction of acoustic source with conduit geometry and the topography of the volcano edifice have not been fully investigated. In order to evaluate these effects, we have developed a 3D-FDTD modelling to simulate infrasound propagation taking in account conduit dynamics and topography of the volcano. In linear acoustics, the pressure perturbations in a duct propagates as a plane wave front, which become spherical outside the vent. The radiation impedance at the vent depends on the pressure wavelength and the vent radius. In addition, the diffraction and reflection of topography contaminate the acoustic wave field and have a strong effect in reducing the amplitude and changing the waveform of the infrasonic signal also at short (<2 km) distances. Besides, the 3D numerical model allows to define in terms of Green's function the scattering effects on the acoustic wavefield caused by topography along the source-receiver path. Only by removing topographic effects from the infrasonic record and by considering the propagation inside the conduit we can quantify the source parameters with a strong impact on our understanding of the explosive dynamics.

lacanna, giorgio; ripepe, maurizio

2014-05-01

32

Investigating the Relationship Between Dynamic Topography and Sediment Flux in Africa  

NASA Astrophysics Data System (ADS)

It is generally accepted that the `basin and swell' topography of Africa is maintained by circulation within the mantle. Many swells are volcano-capped, and their topographic expression shows a close correlation with the long wavelength (>1000 km) free-air gravity anomaly, which can be regarded as a proxy for the convective pattern. Tomographic studies have revealed a region of slow seismic velocities in the lower mantle beneath the `African Superswell', a region of anomalously high elevation that stretches from the South Atlantic Ocean across southern Africa to the volcanic hot spot beneath Afar. Models based on gravity or seismology offer little constraint on the timing and development of dynamic topography since these observations are restricted to the present day. Recently, tomographic data has been combined with geomorphologically derived uplift rates from southern Africa, providing useful temporal constraints for dynamical modelling. Another way to investigate the history of dynamic topography is to interrogate the stratigraphic record. Africa is almost entirely surrounded by passive continental margins, formed during the break-up of Gondwana in the Mesozoic. Sediment has been accumulating on these margins throughout the Cenozoic, providing an indirect record of onshore vertical motions. The development of `basin and swell' topography together with epeirogenic uplift caused by the African Superswell would have had a profound effect on the drainage systems of the entire continent. 40% of the African continent is drained by just 6 rivers, which have formed large deltas on the continental shelf (i.e. Nile, Congo, Niger, Zambezi, Orange and Ogooue). Elevation of a catchment area is a primary control on the amount of sediment supplied to a major delta. Hence, by calculating the sediment flux to the deltas of Africa as a function of time, the history of vertical motions can be indirectly constrained. Analysis of several deltas reveals a widespread modification of African drainage at the start of the Neogene. The Miocene saw the establishment of the Eonile, enhanced progradation of the Niger Delta, major deposition along the West African margin following an Oligocene hiatus and renewed sedimentation in the Zambezi Delta. It has been proposed that Africa came to rest with respect to the mantle in the Oligocene, at ~30 Ma. The Early Neogene increase in sediment flux seen around Africa is consistent with the development of dynamic topography at this time. Earlier and later increases in sediment flux suggest that dynamic topography has waxed and waned over a longer time scale.

Walford, H. L.; White, N. J.

2002-12-01

33

The bottom topography and dynamics of the Obskaya and Baydaratskaya Bays, Kara Sea  

NASA Astrophysics Data System (ADS)

The development of the arctic gas fields requires a gas transport system to be laid across the Obskaya Bay and the Baydaratskaya Bay, Kara Sea. Designing, construction and safe operation of the offshore parts of the crossing demands special knowledge about a structure of the bottom topography and coastal zone dynamics. Results of investigation indicate a difference between those regions and common features of structure and evolution. Owing to a quite large scale of research it was possible to detail the bottom topography, to reveal separate elements and forms. The analyses of topography were executed to define the mechanisms and basic phases of relief formation. Accordingly, the geomorphological map describing the bottom topography by the set of parameters (major of them are morphology, morphometry, age, genesis and dynamics) has also become more detailed. Geomorphological structure of a seabed is the important source of the information on location of permafrost relicts, sites of concentration of rip currents, intensive ice bottom gouging, deformations of an underwater coastal slope and other adverse phenomena and dangerous exogenous processes. The analysis of all these data allowed making prediction of bottom topography development, to plan and carry out an engineering construction. Digital model of bottom topography is a basis for engineering constructions designing. Creation of digital models of bottom topography was carried out by the original method consisted of several stages and based on manual author's processing and interpretation of maps. Also a large amount of archival and literary materials on geophysics, geology, geomorphology and paleogeography has been involved for digital model creation with the purpose to determine the features of morphostructure and genesis of the basic elements. It is established, that the geomorphological structure of the bottom of the Baydaratskaya and Obskaya Bays reflects consecutive change of the conditions and relief formation processes in Late Pleistocene-Holocene, since a continental stage of development of the drained erosion plain down to present time, including attributes of non-uniform rise of a sea level and activity of coastal processes (underwater bluffs, ancient beach ridges et al.).

Ermolov, A.; Noskov, A.; Ogorodov, S.

2009-04-01

34

Free volume hypothetical scanning molecular dynamics method for the absolute free energy of liquids  

E-print Network

Free volume hypothetical scanning molecular dynamics method for the absolute free energy of liquids for calculating the absolute entropy, S, and free energy, F, by analyzing Boltzmann samples obtained by Monte. In this paper we remove the excluded volume EV restriction, replacing it by a "free volume" FV approach

Meirovitch, Hagai

35

Flow-topography interactions, particle transport and plankton dynamics at the Flower Garden Banks: a modeling study  

E-print Network

how flow-topography interactions at the Flower Garden Banks can exert critical control over local larval transport processes and plankton dynamics. More generally, it demonstrates the usefulness and feasibility of using numerical models as tools...

Francis, Simone

2006-04-12

36

Modeling the dynamic component of the geoid and topography of Venus  

NASA Astrophysics Data System (ADS)

We analyze the Venusian geoid and topography to determine the relative importance of isostatic, elastic and dynamic compensation mechanisms over different degree ranges. The geoid power spectrum plotted on a log-log scale shows a significant change in its slope at about degree 40, suggesting a transition from a predominantly dynamic compensation mechanism at lower degrees to an isostatic and/or elastic mechanism at higher degrees. We focus on the dynamic compensation in the lower-degree interval. We assume that (1) the flow is whole mantle in style, (2) the long-wavelength geoid and topography are of purely dynamic origin, and (3) the density structure of Venus' mantle can be approximated by a model in which the mass anomaly distribution does not vary with depth. Solving the inverse problem for viscosity within the framework of internal loading theory, we determine the families of viscosity models that are consistent with the observed geoid and topography between degrees 2 and 40. We find that a good fit to the data can be obtained not only for an isoviscous mantle without a pronounced lithosphere, as suggested in some previous studies, but also for models with a high-viscosity lithosphere and a gradual increase in viscosity with depth in the mantle. The overall viscosity increase across the mantle found for the latter group of models is only partially resolved, but profiles with a ~100-km-thick lithosphere and a viscosity increasing with depth by a factor of 10-80, hence similar to viscosity profiles expected in the Earth's mantle, are among the best fitting models.

Pauer, M.; Fleming, K.; ?adek, O.

2006-11-01

37

Enhancing the Arctic Mean Sea Surface and Mean Dynamic Topography with CryoSat-2 Data  

NASA Astrophysics Data System (ADS)

A reliable mean sea surface (MSS) is essential to derive a good mean dynamic topography (MDT) and for the estimation of short and long-term changes in the sea surface. The lack of satellite radar altimetry observations above 82 degrees latitude means that existing mean sea surface models have been unreliable in the Arctic Ocean. We here present the latest DTU mean sea surface and mean dynamic topography models that includes CryoSat-2 data to improve the reliability in the Arctic Ocean. In an attempt to extrapolate across the gap above 82 degrees latitude the previously models included ICESat data, gravimetrical geoids, ocean circulation models and various combinations hereof. Unfortunately cloud cover and the short periods of operation has a negative effect on the number of ICESat sea surface observations. DTU13MSS and DTU13MDT are the new generation of state of the art global high-resolution models that includes CryoSat-2 data to extend the satellite radar altimetry coverage up to 88 degrees latitude. Furthermore the SAR and SARin capability of CryoSat-2 dramatically increases the amount of useable sea surface returns in sea-ice covered areas compared to conventional radar altimeters like ENVISAT and ERS-1/2. With the inclusion of CryoSat-2 data the new mean sea surface is improved by more than 20 cm above 82 degrees latitude compared with the previous generation of mean sea surfaces.

Stenseng, Lars; Andersen, Ole B.; Knudsen, Per

2014-05-01

38

Interferometer for measuring the dynamic surface topography of a human tear film  

NASA Astrophysics Data System (ADS)

The anterior refracting surface of the eye is the thin tear film that forms on the surface of the cornea. Following a blink, the tear film quickly smoothes and starts to become irregular after 10 seconds. This irregularity can affect comfort and vision quality. An in vivo method of characterizing dynamic tear films has been designed based upon a near-infrared phase-shifting interferometer. This interferometer continuously measures light reflected from the tear film, allowing sub-micron analysis of the dynamic surface topography. Movies showing the tear film behavior can be generated along with quantitative metrics describing changes in the tear film surface. This tear film measurement allows analysis beyond capabilities of typical fluorescein visual inspection or corneal topography and provides better sensitivity and resolution than shearing interferometry methods. The interferometer design is capable of identifying features in the tear film much less than a micron in height with a spatial resolution of about ten microns over a 6 mm diameter. This paper presents the design of the tear film interferometer along with the considerations that must be taken when designing an interferometer for on-eye diagnostics. Discussions include eye movement, design of null optics for a range of ocular geometries, and laser emission limits for on-eye interferometry.

Primeau, Brian C.; Greivenkamp, John E.

2012-03-01

39

Using global paleogeographic datasets towards ground-truthing dynamic topography models  

NASA Astrophysics Data System (ADS)

The topography of the Earth's surface is subject to constant change due to tectonic, surface processes and mantle-driven vertical motions. While the effects of mantle convection can be approximated via convection models, there is a lack of temporally and spatially consistent data at global scale to ground-truth these models. We reverse-engineered data from published, independent global and regional paleogeographic map sets using GIS and the open-source plate tectonic modelling software GPlates and constructed a set of time-dependent, global paleo-shorelines spanning the Cretaceous Period. Within this framework, we then verify the paleoshorelines against geological maps and compute the variations between the different paleoshoreline models, creating a hybrid dataset out of the areas of highest confidence. Using this hybrid dataset, we compute the amount of change in the lateral shoreline position between individual timesteps to derive spatio-temporal patterns of relative subsidence and uplift. By taking stable cratonic blocks as our geographic base reference, we derive the tilting of these blocks and compute hypsometric curves through the amount of flooding. For our analysis we utilize a global, self-consistent set of dynamic plate polygons, sediment thickness data, and a time-dependent collection of rift basins to discriminate between areas undergoing lithospheric deformation and stable continental regions. A geospatial proximity analysis is performed to determine the spatio-temporal relationship to adjacent plate boundary types. We then compare our results with dynamic topography models.

Yeo, L. G.; Heine, C.; Müller, R. D.

2012-04-01

40

Modelling and Estimation of Dynamic Ocean Topography Within Global Geopotential Solutions  

NASA Technical Reports Server (NTRS)

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 require no "fill-in" values over areas where the DOT is undefined. We show that the PF and SH results using equal number of parameters agree quite well in overall content. In addition, PFs appear better suited for representation of high frequency signals close to the signal boundary. The development of the PF solutions for the DOT will be described and the statistics of the comparisons will be presented.

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

1998-01-01

41

The Time Dependance of Dynamic Topography: Mantle Dynamic Contributions to Local and Global Sea-Level Histories  

NASA Astrophysics Data System (ADS)

Earth's topography plays an important role in many surface processes, particularly through its influence on the water cycle and erosional processes. Our ability to predict weather patterns and surface/subsurface hydrological processes depends upon our knowledge of this field. Similarly, understanding the evolution of topography through time (paleo-topography) is critically important for the accurate modeling of past climate states such as that of the last glacial maximum. Whilst the present day topographic field can be accurately inferred over the entire globe using satellite based sensors and geodetic techniques, no equivalently comprehensive tools exist that enable access to paleo-topography. The rock record allows for limited, local estimations of deposition elevation with respect to sea level using appropriate fossils combined with sedimentological analyses. However, this method is not available in most locations as a consequence of poor-preservation of the requisite sea level indicators and in any event the accuracy of the relative sea level record is often compromised. Furthermore, just as topography itself consists of distinct dynamic and isostatic contributions, relatives sea level also consists of two contributions, respectively that due to the vertical motion of the surface of the solid Earth and that due to the changing volume of water in the global oceans. In this paper we study the time dependence of Earth's dynamic topography that has occurred over the recent past due to the action of the mantle convection process. We use a modern model of mantle mixing, an extension to three dimensions of the recently published control volume based convection model of Shahnas and Peltier (2010, JGR, vol 115, B11408). This is initialized using a mantle temperature field inferred on the basis of modern seismic tomographic imaging analysis, which enables the model to simulate the present day dynamical state of Earth's mantle. The use of this methodology enables the model to be employed to study the present state of the mantle and its evolution in the recent geological past. The predictions of the model that interest us are those of the rate of uplift and depression of the crust that contribute to records of relative sea level history over timescales sufficiently long to encompass several Late Quaternary glacial cycles. We employ a number of available local records of the time dependence of dynamical topography such as the coral based Barbados record of Peltier and Fairbanks (2006, QSR 25, pp. 3322-3337) to first demonstrate the accuracy with which the convection model is able to reconcile such observational constraints. Although several of the best available constraint data sets derive from regions in the near vicinity of active subduction zones, we proceed to apply the model's predictions to a number of (assumed to be) passive continental margins from which data have been derived that have been assumed to represent variations in eustatic sea level due to the variation of continental land ice volume such as those recently discussed by Miller et al. (2012, Geology 20, pp. 407-410). We assess the extent to which the passive continental margin assumption may have led to significant errors in the inference of global sea level rise for the mid-Pliocene interval of time centered upon 3 Ma.

Durbin, C. J.; Shahnas, M.; Peltier, W. R.

2012-12-01

42

Principal Controls Governing Vegetation Dynamics Across Varying Climates in Ecoregions with Complex Topography  

NASA Astrophysics Data System (ADS)

Remotely-sensed vegetation greenness, as measured through a photosynthetically-related index such as the enhanced vegetation index (EVI), can be extremely heterogeneous, both spatially and temporally. The driving factor behind this heterogeneity is the variability in the climate; however, a myriad of variables influence this heterogeneity, including: topography, which constrains the temperature, moisture availability, and amount of incoming radiation; soil properties, which influences the water availability, root density and length, plant morphometric characteristics, etc.; and land cover, which indicates the type of vegetation that is present. In this study, we investigate the dominant influences on the vegetation greenness across three different ecoregions (Level III CEC Ecoregions), as these regions represent natural divisions of the land with respect to vegetation dynamics and the influences on them. We employ a regression tree technique to extract patterns in the very large database created for this study and examine the patterns, or trees, for physical meaning. In all three ecoregions (the deciduous forest-dominated Blue Ridge, the evergreen forest-dominated Northern Rockies, and the shrubland-dominated Central Basin and Range), the topography is the most significant factor influencing the vegetation amount and vigor throughout the growing season. The meteorology, soil properties, and land cover follow in descending order. Thus, it is the local control on the meteorology that is the overriding influence, whereas the regional meteorologic patterns and local/regional soil properties are the next most influential. The land cover, which varies across a broad range of scales, is only influential when it differs from the dominant land cover type. The depth of the regression tree is an indicator of scale, as the greater the depth, the more the region is divided, thus the smaller the scale is. Patterns emerge in the relevance of each variable (varying somewhat from ecoregion to ecoregion and throughout the growing season): the land cover decreases exponentially with scale; the topography, meteorology, and soil properties are parabolically related to scale, although the vertex of the parabola is a minimum for topography whereas the meteorology and soil properties are inverted.

White, A. B.; Kumar, P.

2005-12-01

43

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

NASA Astrophysics Data System (ADS)

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 together with Airy isostasy have been used to predict a "synthetic" gravity derived RDA. Sediment corrected RDA for oceanic crust in the Gulf of Aden are positive (+750m) indicating anomalous uplift with respect to normal subsidence. Gravity inversion predicts normal thickness oceanic crust and a zero "synthetic" gravity derived RDA in the oceanic domain. The difference between the positive sediment corrected RDA and the zero "synthetic" gravity derived RDA, implies that the anomalous subsidence reported in the Gulf of Aden is the result of mantle dynamic uplift. For the oceanic crust outboard of Galicia Bank both the sediment corrected RDA and the "synthetic" gravity derived RDA are negative (-800m) and of similar magnitude, indicating anomalous subsidence, which is the result of anomalously thin oceanic crust, not mantle dynamic topography. We conclude that there is negligible mantle dynamic topography influencing the Galicia Bank region. In the Gulf of Lions, gravity inversion predicts thinner than average oceanic crust. Both sediment corrected RDA (-1km) and "synthetic" gravity derived RDA (-500m) are negative. The more negative sediment corrected RDA compared with the "synthetic" gravity derived RDA implies that the anomalous subsidence in the Gulf of Lions is the result of mantle dynamic subsidence as well as thinner than average oceanic crust.

Cowie, L.; Kusznir, N. J.

2012-12-01

44

Video Animation of Ocean Topography From TOPEX/POSEIDON  

NASA Technical Reports Server (NTRS)

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...

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

1993-01-01

45

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

PubMed

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. PMID:25430103

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

2014-11-01

46

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

47

Visualizing Topography  

NSDL National Science Digital Library

Explore the topography of a hill, a valley, and a cliff in this interactive activity featuring visualizations of three-dimensional topography in two dimensions. Adapted from Stephen Reynolds' Visualizing Topography.

WGBH Educational Foundation

2005-12-17

48

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

NASA Astrophysics Data System (ADS)

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.

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

2013-02-01

49

Absolute measurements of the high-frequency magnetic dynamics in Hihg- T c superconductors  

Microsoft Academic Search

We review recent measurements of the high-frequency dynamic magnetic susceptibility in the high-Tc superconducting systems La2?xSrxCuO4 and YBa2Cu3O6+x. Experiments were performed using the chopper spectrometers HET and MARI at the ISIS spallation source. We have placed our measurements on an absolute intensity scale; this allows systematic trends to be seen and comparisons with theory to be made. We find that

S. M. Hayden; G. Aeppli; P. Dai; H. A. Mook; T. G. Perring; S.-W. Cheong; Z. Fisk; F Do?an; T. E. Mason

1997-01-01

50

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

PubMed Central

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

Xue, Changying; Wong, Darice

2014-01-01

51

Impacts of topography on aspen and black spruce successional dynamics in the boreal forest  

NASA Astrophysics Data System (ADS)

The boreal forest contains over 30 percent of Earth's terrestrial carbon, stored mainly as organic matter in soils underlain by discontinuous permafrost. In interior Alaska, black spruce trees dominate these nutrient-depleted soils where the combination of cold temperatures and nutrient-poor black spruce detritus results in an accumulation of a thick layer of organic matter that is not easily decomposed. However, warming temperatures have decreased fire return intervals and resulted in permafrost recession, opening more boreal forest space to early-successional hardwoods such aspen. Because aspen and black spruce stands have a much different capacity for near-surface carbon storage, shifts in vegetation type have important implications for carbon storage in boreal forests. Yet, existing global climate models that run at resolutions of 50-100 square kilometers cannot capture vegetation dynamics that result from fire and topographic variation, where significant heterogeneity is present on scales of 1 square kilometer or less. In this study we use the Ecosystem Demography model version 2 to examine the growth and mortality dynamics of black spruce and aspen trees. Employing meteorological forcing data from the Bonanza Creek Long Term Ecological Research (BNZ-LTER) weather station (64.70°N, 148.25°W) we investigate the interdependence of permafrost depth, soil temperature, soil moisture content and plant functional type on topography. Modeled plant densities are corroborated with observed aspen and black spruce distributions at the BNZ-LTER and nearby Delta Junction, AK. We then show how an accurate spatial parameterization of aspen and black spruce trees can be used to better simulate boreal zone carbon dynamics with receding permafrost and increased fire frequency.

Trugman, A. T.; Medvigy, D.

2013-12-01

52

Simulating Turbidity Current Dynamics Using Natural Topographies With and Without Clear-Water Entrainment  

NASA Astrophysics Data System (ADS)

This study uses a modified version of Parker et al. (1986)'s one-dimensional turbidity current model to simulate the dynamics of currents that traverse natural submarine topographies, in an effort to determine if such flows might plausibly traverse channel forms currently observed at the seafloor or in shallow seismic datasets. To accomplish this, we calculated flow dynamics based on 50000 sets of initial conditions that were drawn randomly between prescribed bounds, and identified those starting conditions that allowed flows to traverse the naturally observed systems. In addition to examining the along-channel runout lengths of these flows, we used flow height and maximum velocity to rule out initial conditions that created flows that would be broadly accepted as unphysical. We found that when the clear-water entrainment rules of Parker et al. (1987) were used, a small percentage of flows (2.3-9.7%) traversed the measured portion of these natural systems and maintained physically plausible peak depth-averaged velocities. However, flows meeting these criteria nonetheless reach peak heights that were many times that of the channel-bottom to levee-crest relief. Often the height of the simulated turbidity current exceeded this channel relief by as much as an order of magnitude. When clear-water entrainment was removed from the model, a larger percentage of flows traversed the measured channel geometries, and maintained more physically plausible ranges of peak depth-averaged velocities and heights. We speculate that the unphysical flows produced using clear-water entrainment may arise due to the model's neglect of flow loss through flow stripping and/or overbank collapse, or scaling problems associated with extrapolating laboratory-measured clear-water entrainment rules to the field. Future studies that aim to account for fluid mass loss by lateral collapse and extract the clear-water entrainment relationship independently of laboratory experiments may be necessary to accurately model turbidity current dynamics at the field-scale.

Traer, M. M.; Hilley, G. E.; Fildani, A.; McHargue, T.

2012-12-01

53

Estimating mean dynamic topography in boundary currents and the use of Argo trajectories  

NASA Astrophysics Data System (ADS)

A Mean Dynamic Topography (MDT) is required to estimate mean transport in the ocean, to combine with altimetry to derive instantaneous geostrophic surface velocities, and to estimate transport from shipboard hydrography. A number of MDTs are now available globally but differ most markedly in boundary currents and the Antarctic Circumpolar Current. We evaluate several MDTs in two boundary currents off New Zealand (in the subtropical western boundary current system east of the country and in the Subantarctic Front to the south) using satellite, hydrographic, and Argo observations near two altimeter tracks. Argo float trajectories are combined with estimates of shear to produce new MDTs along both altimeter tracks: sufficiently high numbers of Argo floats travel in both boundary currents to allow a useful estimate of the mean flow at 1000 m depth and conservation of potential vorticity is used to account for more realistic flow paths. In finding a MDT, we show the uncertainties in the estimates of velocity differences between 1000 m and the surface from density climatologies, while often not estimated, need to be considered. The MDT computed from the Argo trajectories is generally consistent with the CLS09 MDT in both boundary currents and, in some locations, distinctly different from the MDT using a "level of no motion" assumption. The comparison suggests velocities from Argo trajectories can be usefully combined with other observations to improve estimates of flows and MDT in boundary currents.

Bowen, Melissa; Sutton, Philip; Roemmich, Dean

2014-12-01

54

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

NASA Astrophysics Data System (ADS)

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.

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

2000-06-01

55

A new filter for the Mean Dynamic Topography of the ocean derived directly from satellite observations  

NASA Astrophysics Data System (ADS)

The Mean Dynamic Topography (MDT) of the ocean provides valuable information about the ocean's surface currents. Therefore the MDT is computed from satellite observations and then assimilated into ocean models in order to improve the ocean circulation estimates. However, the computation of the MDT from satellite observations of sea surface height and the Earth's gravity field is not straightforward and requires additional filtering of the data combination. The choice of the filter is crucial as it determines the amount of small-scale noise in the data and the resolution of the final MDT. There exist various approaches for the determination of an "optimal" filter. However, they all have in common the more or less subjective choice of the filter type and filter width. Here, a new filter is presented that is determined directly from the geodetic normal equations. By its construction, this filter accurately accounts for the correlations within the MDT data and requires no subjective choice about the filter radius. The new filtered MDT is assimilated into an inverse ocean model. Modifications in the meridional overturning circulation and in the poleward heat transports can be observed, compared to the result of the assimilation using the unfiltered MDT.

Freiwald, G.

2013-12-01

56

Under consideration for publication in J. Fluid Mech. 1 Nonlinear dynamics over rough topography  

E-print Network

is confined within a thin bottom boundary layer, so that it is through a new bottom boundary condition of nonlinear periodic and solitary waves in continuously stratified fluid over topography. The influence, and solitary waves. The present paper is similar in spirit to those of Volosov and Zdhanov. Its main novel

Vanneste, Jacques

57

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

NASA Technical Reports Server (NTRS)

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.

Rapp, Richard H.

1998-01-01

58

Dynamically consistent hydrography and absolute velocity in the eastern North Atlantic Ocean  

NASA Technical Reports Server (NTRS)

The problem of mapping a dynamically consistent hydrographic field and associated absolute geostrophic flow in the eastern North Atlantic between 24 deg and 36 deg N is related directly to the solution of the so-called thermocline equations. A nonlinear optimization problem involving Needler's P equation is solved to find the hydrography and resulting flow that minimizes the vertical mixing above about 1500 m in the ocean and is simultaneously consistent with the observations. A sharp minimum (at least in some dimensions) is found, apparently corresponding to a solution nearly conserving potential vorticity and with vertical eddy coefficient less than about 10(exp -5) sq m/s. Estimates of `residual' quantities such as eddy coefficients are extremely sensitive to slight modifications to the observed fields. Boundary conditions, vertical velocities, etc., are a product of the optimization and produce estimates differing quantitatively from prior ones relying directly upon observed hydrography. The results are generally insensitive to particular elements of the solution methodology, but many questions remain concerning the extent to which different synoptic sections can be asserted to represent the same ocean. The method can be regarded as a practical generalization of the beta spiral and geostrophic balance inverses for the estimate of absolute geostrophic flows. Numerous improvements to the methodology used in this preliminary attempt are possible.

Wunsch, Carl

1994-01-01

59

Absolute measurements of the high-frequency magnetic dynamics in high-{Tc} superconductors  

SciTech Connect

The authors review recent measurements of the high-frequency dynamic magnetic susceptibility in the high-T{sub c} superconducting systems La{sub 2{minus}x}Sr{sub x}CuO{sub 4} and YBa{sub 2}Cu{sub 3}O{sub 6+x}. Experiments were performed using the chopper spectrometers HET and MARI at the ISIS spallation source. The authors have placed their measurements on an absolute intensity scale, this allows systematic trends to be seen and comparisons with theory to be made. They find that the insulating S = 1/2 antiferromagnetic parent compounds show a dramatic renormalization in the spin wave intensity. The effect of doping on the response is to cause broadenings in wave vector and large redistributions of spectral weight in frequency.

Hayden, S.M. [Univ. of Bristol (United Kingdom). H.H. Wills Physics Lab.; Aeppli, G. [NEC Research Inst., Princeton, NJ (United States); Dai, P.; Mook, H.A. [Oak Ridge National Lab., TN (United States); Perring, T.G. [Rutherford Appleton Lab., Chilton (United Kingdom); Cheong, S.W. [Lucent Technologies, NJ (United States). Bell Labs.; Fisk, Z. [Florida State Univ., Tallahassee, FL (United States). Dept. of Physics; Dogan, F. [Univ. of Washington, Seattle, WA (United States). Dept. of Material Science and Engineering; Mason, T.E. [Univ. of Toronto, Ontario (Canada). Dept. of Physics

1997-08-07

60

Forecasting the absolute and relative shortage of physicians in Japan using a system dynamics model approach  

PubMed Central

Background In Japan, a shortage of physicians, who serve a key role in healthcare provision, has been pointed out as a major medical issue. The healthcare workforce policy planner should consider future dynamic changes in physician numbers. The purpose of this study was to propose a physician supply forecasting methodology by applying system dynamics modeling to estimate future absolute and relative numbers of physicians. Method We constructed a forecasting model using a system dynamics approach. Forecasting the number of physician was performed for all clinical physician and OB/GYN specialists. Moreover, we conducted evaluation of sufficiency for the number of physicians and sensitivity analysis. Result & conclusion As a result, it was forecast that the number of physicians would increase during 2008–2030 and the shortage would resolve at 2026 for all clinical physicians. However, the shortage would not resolve for the period covered. This suggests a need for measures for reconsidering the allocation system of new entry physicians to resolve maldistribution between medical departments, in addition, for increasing the overall number of clinical physicians. PMID:23981198

2013-01-01

61

Analysis of dynamic ocean topography using TOPEX data and orthonormal functions  

NASA Astrophysics Data System (ADS)

The representation of dynamic ocean topography (?) through spherical harmonic (SH) and orthonormal (ON) expansions was studied using TOPEX altimeter data, three potential coefficient models used to define geoid undulations, and three estimates of ? from oceanographic data and global circulation models (GCMs). The ON expansions are desirable when one wishes to study the spectral characteristics of a function in a defined domain such as the ocean. The potential coefficient models tested were JGM-2, JGM-3, and GRIM4_C4b. Each model was augmented with the OSU91A potential coefficients from degree 71 to 360. The ? models were those of Levitus [1982] and values implied by the POCM_4B (Semtner/Chervin) model and a Los Alamos National Laboratory Model POP(96) (Malone, Smith, Dukowicz). The latter two models were defined over a 2-year time period. Values of ? were computed from 2 years of TOPEX data using the three potential coefficient models. The ON expansions of ? from the TOPEX data were then compared to the estimates from the oceanographic data. The differences, to ON degree 14, with the POCM_4B model and the TOPEX results were ±14.0 cm (JGM-2), ±12.4 cm (JGM-3), and ±14.4 cm (GRIM4_C4b). A comparison with the other ? estimates using TOPEX/JGM-3 gives differences of ±14.3 cm (Levitus) and ±13.3 cm (POP (96)). The comparisons were made only to degree 14 because (1) the correlation between the ? coefficients from TOPEX data and POCM_4B fell off beyond degree 14 and (2) the geoid undulation accuracy, in the ocean region, was equal to the ? signal near degree 14. These results suggest ? estimates made above degree 14 may be contaminated by geoid undulation errors. Also suggested from the comparisons was that the TOPEX/JGM-3 estimates of ? were more reliable than those from oceanographic data to degree 8 (2500-km resolution). The ? estimates from the POCM_4B and POP(96) models, 2-year averages, agreed well north of 40°S. Below this the differences could reach 40 cm in the Antarctic Circumpolar Current (60°S, 215°). The differences between the TOPEX/JGM-3 and POCM_4B ? estimates exceeded 20 cm in a number of places (e.g., (20°N, 140°), (5°S, 130°), (60°S, 220°), (45°N, 320°)). The largest differences (-62 cm) occurred in the Banda Sea. The ? representations were used to calculate upper ocean geostrophic velocities in the east/west and north/south directions. Excluding a 10° band on either side of the equator, the difference (TOPEX versus POCM_4B) was ±2.5 cm/s with the magnitude of the total velocity being 4.8 cm/s. The difference was consistent with the error estimates of the velocities implied by the errors in the JGM-3 coefficients to degree 14. The ? estimates were also determined from four recent mean sea surface grids and the results compared to the POCM_4B model through the ON representation. The MSS grids used were the OSUMSS95, the UTCSRMSS95, the GFZ/D-PAF MSS95A, and the CNES/GRGS MSS95. The best agreement, to degree 14, was found with the OSUMSS95 (±11.1 cm) and the CSRMSS95 (±11.5 cm). The comparisons were poorer (±15 cm) when a mean sea surface was used where no mean inverted barometer correction had been applied to the gridded data. Although substantial progress has been made in the past 10 years in the determination of the Earth's gravitational potential, the accuracy limitations of geoid undulation determination still hinder the comparison and assimilation of altimeter data and oceanographic data. The need for a dedicated gravity satellite mission, to yield improved geoid undulation determinations, is clearly seen.

Rapp, Richard H.; Zhang, Changyou; Yi, Yuchan

1996-10-01

62

A Next-Generation Atmospheric Dynamics Model that Conserves Multiple Properties over Complex Topography on All Scales  

NASA Astrophysics Data System (ADS)

We present a new 3D nonhydrostatic atmospheric model that uses a 3D generalization of a mass, energy, vorticity, and potential enstrophy conserving numerical scheme for the 2D shallow water equations to solve the governing equations for 3D fluid motion (i.e. the dynamics). The model uses the altitude coordinate (as opposed to a terrain-following coordinate) in the vertical to avoid the large errors in the pressure gradient terms that can be generated near steep topography in terrain-following coordinates. The altitude coordinate allows inclusion of arbitrarily complex (and steep) topography in the model. A feature of this model not found in most others is that the numerical scheme used for the dynamics conserves domain-summed mass and energy for 3D frictionless flows and domain-summed mass, energy, vorticity, and potential enstrophy for the special case of 2D frictionless barotropic flows. These conservation properties are important to maintain because at least in 2D flows, they have been shown to preserve the correct energy cascade. To evaluate the performance of the dynamics core alone, we present simulations without physics (i.e. dry air with frictionless dynamics) on global, regional, and urban scales and a combined simulation on all three scales using nested grids. We also present a global simulation with surface heating and cooling and demonstrate that the model reproduces the basic general circulation of the atmosphere. Since the dynamics core conserves energy in the absence of external dissipation, the energy in the model tends to accumulate in the smallest scales (i.e. the grid scale) over time. To prevent this, we try several dissipation schemes and discuss the results from each. Finally, to demonstrate the scalability of the parallelized model code, we present timing results from simulations using multiple processors.

Ketefian, G. S.; Jacobson, M. Z.

2012-12-01

63

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

NASA Astrophysics Data System (ADS)

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.

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

2000-08-01

64

Constraints of the topography, gravity and volcanism on Venusian mantle dynamics and generation of plate tectonics  

NASA Astrophysics Data System (ADS)

Venus's mantle convection model was studied in a three-dimensional spherical shell domain with depth- and temperature-dependent viscosity. Numerical results show that key observations of Venus including the number of major "hotspot" volcanic systems, spectral patterns of the surface topography and geoid at long- and intermediate-wavelengths can be explained in models that have a spinel-to-post-spinel endothermic phase change of -3.5 MPa/K Clapeyron slope and averaged mantle viscosity of 2×1021 Pa s (i.e., convective Rayleigh number of 1.8×107). Our models with the endothermic phase change show relatively weak time-dependence, suggesting that the phase change may not be the primary cause for "catastrophic" resurfacing on Venus. Our calculations also show that Venus cannot have a weak asthenosphere that is similar to that on the Earth, in order to match the observations, thus supporting a key role of asthenosphere in producing plate tectonics.

Huang, Jinshui; Yang, An; Zhong, Shijie

2013-01-01

65

Comment on "Dynamic topography in South America" by Federico M. Dávila & Carolina Lithgow-Bertelloni  

NASA Astrophysics Data System (ADS)

In their article Dávila and Lithgow-Bertelloni (2013) propose that the Andes have been isostatically uncompensated throughout the Cenozoic and that additional forces induced by mantle flow were required to explain the observed topographies. Although this hypothesis seems plausible, they provide a regional model of "the Bermejo-Pampas foreland of Argentina" which implies that the deposition of the Los Llanos Formation (in La Rioja, NW Argentina) occurred during Miocene. However, this age is incongruent with the presence of a neosauropod nesting site at Sanagasta and a Cretaceous faunal assemblage in Tama both in Los Llanos Formation and well documented in recent publications. Therefore, the proposed model for "the Bermejo-Pampas foreland of Argentina" appears incorrect. Moreover, the Cretaceous exposures at Sanagasta and Tama foster the need of revising the alleged Cenozoic age of the Los Llanos Formation in La Rioja and neighboring provinces, and the tectonic models associated with this formation.

Hechenleitner, E. Martín; Fiorelli, Lucas E.; Larrovere, Mariano A.; Grellet-Tinner, Gerald; Carignano, Ana P.

2014-03-01

66

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

PubMed

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

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

2013-05-01

67

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)

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 topography that are constrained to fit a large suite of modern geophysical observables. We demonstrate that the results differ significantly from calculations in which dynamic topography is simply added to the elevation of GIA-corrected paleo-shorelines. Moreover, we apply these results to new paleo-shoreline data of Pliocene age from the US east coast, South Africa and southwest Australia to estimate peak eustatic sea level (and, thus, minimum ice volume) during the Mid Pliocene Warm Period.

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

2014-05-01

68

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

SciTech Connect

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 evolution of the crater depth as a function of fluence can be described taking into account the individual bandgap of each material.

Puerto, D.; Siegel, J.; Gawelda, W.; Galvan-Sosa, M.; Solis, J. [Laser Processing Group, Instituto de Optica-CSIC, Madrid (Spain); Ehrentraut, L. [Max-Born-Institut fuer Nichtlineare Optik und Kurzzeitspektroskopie, Berlin (Germany); Bonse, J. [Bundesanstalt fuer Materialforschung und-pruefung (BAM), Berlin (Germany)

2010-05-15

69

Absolute quantification of perfusion using dynamic susceptibility contrast MRI: pitfalls and possibilities  

Microsoft Academic Search

Absolute quantification of cerebral blood flow, cerebral blood volume and mean transit time is desirable in the determination\\u000a of tissue viability thresholds and tissue at risk in acute ischaemic stroke, as well as in cases where a global reduction\\u000a in cerebral blood flow is expected, for example, in patients with dementia or depressive disorders. Absolute values are also\\u000a useful when

Linda Knutsson; Freddy Ståhlberg; Ronnie Wirestam

2010-01-01

70

Mars Topography  

NSDL National Science Digital Library

This educational brief discusses the advances in our knowledge of Mars topography brought about by the high-resolution map produced from Mars Laser Orbiter Altimeter (MOLA) data. Individual features and regions are described along with any new insights provided by MOLA into their origins.

71

Effects of dynamic vegetation and topography on hydrological processes in semi-arid areas  

E-print Network

Ecosystems of dry climates represent a particularly interesting object for ecohydrological studies, as water is generally considered to be the key limiting resource. This work focuses on vegetation-water-energy dynamics ...

Ivanov, Valeri Yuryevich, 1974-

2006-01-01

72

Tectonic and dynamic controls on the topography and subsidence of the Argentine Pampas: The role of the flat slab  

NASA Astrophysics Data System (ADS)

We analyze the Pampean foreland (the Pampas) along the modern flat-slab segment of the south-central Andes between 31° and 33° South latitude and to the east of the Argentine “flat-slab” province, using flexural and gravity studies and computations of dynamic topography. Bouguer anomalies and flexural analysis predict a foredeep of ? 250 km width and a peripheral bulge amplitude of ? 25 m, which match the regional morphologies of the modern Argentine Pampean Plain. However, these studies do not account for the subsurface Miocene-Quaternary basin preservation, represented by sedimentary thicknesses > 400 m and with depocenters > 400 km eastward with respect to flexural models. The discrepancy suggests that two mechanisms, acting at different wavelengths, influence the Argentine Pampas. The basin preservation is likely the result of a large-scale geodynamic forcing. Models of mantle flow, driven by realistic flat-slab subduction geometry and density contrasts, reproduce the depocenter location and the wavelength of subsidence as well as most of the remaining amplitude. Nonetheless, more sophisticated studies (e.g. considering lateral viscosity variations in the mantle wedge) might help reduce the dynamic amplitudes and better reproduce the observed geological record.

Dávila, Federico M.; Lithgow-Bertelloni, Carolina; Giménez, Mario

2010-06-01

73

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

NASA Astrophysics Data System (ADS)

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.

Bakun, Andrew

2006-02-01

74

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

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

75

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

NASA Astrophysics Data System (ADS)

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 ocea?s 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.

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

2015-02-01

76

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

77

Influence of Topography and Land use Type on the Soil Organic Carbon Dynamics in Zala County, Hungary  

NASA Astrophysics Data System (ADS)

Soil organic carbon (SOC) content is an important soil property for land, plant production and environment and ecosystem management. Soil fertility and many other physio-chemical and biological properties of soils are directly/indirectly linked with carbon content of the soil. We analyze the impact of topography and land use practice on the spatial variability of top soil SOC over a mixed agricultural, forestry and grassland area from Zala County in Hungary. The spatial dynamics of SOC display a high variability over the study area. A characteristic value for the SOC of the topsoil is calculated as a weighted average of the measured SOC content of soil horizons identified within the first 30 cm of soil. Topographic features of the area are extracted from a digital elevation model (5 Ã- 5 m resolution). Information on land use type is obtained on the basis of remote sensing images and is also recorded during the field sampling campaign. Classical statistical, geostatistical and Geographical Information System (GIS) based tools have been used to study the distribution and spatial correlation features of SOC as well as its relationship with local topography and land use type. The average SOC in the study area is 1.49 % and is associated with a standard deviation of 0.73. SOC values display moderately high (i.e., 0.48) coefficient of variation (CV). SOC is typically associated with a spherical model variogram with a relatively large nugget (i.e., 0.42). The range of spatial correlation for SOC is found to be about 3.5 kilometers. The local ground slope and land use type are key parameters in determining the spatial distribution of SOC over the study area. The highest SOC content is found in a flat and low land area characterized by grass land whereas collected SOC values appear to gradually decrease with increasing values of local terrain slope. Crop lands show moderate amount of SOC. Peat excavation pits have also been recorded in the flat areas and are characterized by high SOC content. Organic matter rich top soil has been eroded from the slopes reducing the SOC content of the eroded areas. Key words: Soil organic carbon content, Digital elevation model, Geostatistics, Kriging

Adhikari, K.; Toth, G.; Guadagnini, A.; Makó, A.

2009-04-01

78

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

NASA Astrophysics Data System (ADS)

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.

Blume, Theresa; Hassler, Sibylle; Weiler, Markus

2014-05-01

79

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

NASA Astrophysics Data System (ADS)

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 explained through the bottom topography: while near the Zhuoshui mouth the bottom is very flat and shallow, the terrain adjacent to the Wu mouth is much steeper and deeper. Bottom topography and tidal inundation also play an important role in the plume dissipation: due to enhanced mixing in shallow areas subject to tidal drying/flooding of the bottom, such as the area north of the Zhoushui mouth, the salinity anomaly is generally smaller and the plume is narrower and dissipates faster than in the deeper near-mouth areas like that of Wu River. Under the NE wind conditions, the Wu and Zhuoshui plume almost merge and form a unified low salinity belt. In contrast, action of SW wind causes effective separation of river plumes. In the case of NW winds, the plumes are pressed towards the shore and trapped at the mouths, while in the case of SE wind they stretch towards the ocean. The daily mean area of the plumes under the SE wind conditions is about 6 times larger than that under the NW wind.

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

2014-05-01

80

The impact of the dynamic sea surface topography on the quasi-geoid in shallow coastal waters  

NASA Astrophysics Data System (ADS)

In this study, we examine the impact of instantaneous dynamic sea surface topography (DT) corrections to be applied to altimeter-derived sea surface slopes on the quasi-geoid in the shallow and coastal waters of the North Sea. In particular, we investigate the added value of DT corrections obtained from a shallow-water hydrodynamic model. These corrections comprise the contributions of ocean tides, wind- and pressure-driven (surge), and density-driven (baroclinic) water-level variations including the interactions between them. As a reference, we used tidal corrections derived from the global ocean tide model GOT4.7, surge corrections derived from the MOG2D model, and corrections for the time-averaged baroclinic contribution computed as differences between the DTU10 mean sea surface model and the EGG08 quasi-geoid. From a spectral analysis, we found that the baroclinic and surge parts of the DT mainly contribute to improvements in the signal-to-noise ratio (SNR) at longer wavelengths down to and that the improvements increase towards the southern North Sea. We also found that the shallow-water hydrodynamic model provides better tidal corrections compared to the GOT4.7 global ocean tide model, which are most pronounced in the southern North Sea and affect almost the entire spectrum. Very small differences (mostly below ) are observed between the quasi-geoid solutions obtained using the different sets of DT corrections. We showed that the variance component estimation provides too optimistic variance factors for the shipboard data set relative to the altimeter-derived quasi-geoid slopes. Hence, the limited impact of DT corrections is due to the fact that altimeter-derived quasi-geoid slopes hardly contribute to the estimated quasi-geoid if shipboard gravity data are included. When computing quasi-geoid solutions without shipboard gravity data, we found that less accurate or incomplete DT corrections may cause errors in the quasi-geoid with systematic spatial patterns. These systematic patterns disappear or are reduced significantly when using the DT corrections provided by the shallow-water hydrodynamic model. The main contributor to this improvement is the better tidal correction provided by the shallow-water hydrodynamic model compared to the GOT4.7 global ocean tide model. Seen the improvements of the global ocean tide models over the last two decades, we expect that in the near future global ocean tide models perform as well as dedicated regional models such as DCSM. Critical issue is, however, access to high-quality local bathymetric data.

Slobbe, D. C.; Klees, R.

2014-03-01

81

Seismic waveform inversion for core-mantle boundary topography  

NASA Astrophysics Data System (ADS)

The topography of the core-mantle boundary (CMB) is directly linked to the dynamics of both the mantle and the outer core, although it is poorly constrained and understood. Recent studies have produced topography models with mutual agreement up to degree 2. A broad-band waveform inversion strategy is introduced and applied here, with relatively low computational cost and based on a first-order Born approximation. Its performance is validated using synthetic waveforms calculated in theoretical earth models that include different topography patterns with varying lateral wavelengths, from 600 to 2500 km, and magnitudes (˜10 km peak-to-peak). The source-receiver geometry focuses mainly on the Pdiff, PKP, PcP and ScS phases. The results show that PKP branches, PcP and ScS generally perform well and in a similar fashion, while Pdiff yields unsatisfactory results. We investigate also how 3-D mantle correction influences the output models, and find that despite the disturbance introduced, the models recovered do not appear to be biased, provided that the 3-D model is correct. Using cross-correlated traveltimes, we derive new topography models from both P and S waves. The static corrections used to remove the mantle effect are likely to affect the inversion, compromising the agreement between models derived from P and S data. By modelling traveltime residuals starting from sensitivity kernels, we show how the simultaneous use of volumetric and boundary kernels can reduce the bias coming from mantle structures. The joint inversion approach should be the only reliable method to invert for CMB topography using absolute cross-correlation traveltimes.

Colombi, Andrea; Nissen-Meyer, Tarje; Boschi, Lapo; Giardini, Domenico

2014-07-01

82

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

USGS Publications Warehouse

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-weakening distance is this parameter is uniform over the fault plane, and the direction of the late part of slip of curved striations should have more weight in the estimate of initial stress direction.

Guatteri, M.; Spudich, P.

1998-01-01

83

Computation of a new Mean Dynamic Topography for the Mediterranean Sea from model outputs, altimeter measurements and oceanographic in-situ data  

NASA Astrophysics Data System (ADS)

The accurate knowledge of the ocean Mean Dynamic Topography (MDT) is a crucial issue for a number of oceanographic applications and in some areas of the Mediterranean Sea, important limitations have been found pointing to the need of an upgrade. We present a new Mean Dynamic Topography (MDT) that was computed for the Mediterranean Sea. It takes profit of improvements made possible by the use of extended datasets and refined processing. The updated dataset spans the 1993-2012 period and consists of: drifter velocities, altimetry data, hydrological profiles and model data. The methodology is similar to the previous MDT Rio et al. (2007). However, in Rio et al. (2007) no hydrological profiles had been taken into account. This has required the development of dedicated processing. A number of sensitivity studies have been carried out to obtain the most accurate MDT as possible. The main results from these sensitivity studies are the following: moderate impact to the choice of correlation scales but almost negligible sensitivity to the choice of the first guess (model solution). A systematic external validation to independent data has been made to evaluate the performance of the new MDT. Compared to previous version, SMDT-MED-2014 features shorter scales structures, which results in an altimeter velocity variance closer to the observed velocity variance and, at the same time, gives better Taylor skills.

Rio, M.-H.; Pascual, A.; Poulain, P.-M.; Menna, M.; Barceló, B.; Tintoré, J.

2014-02-01

84

Computation of a new mean dynamic topography for the Mediterranean Sea from model outputs, altimeter measurements and oceanographic in situ data  

NASA Astrophysics Data System (ADS)

The accurate knowledge of the ocean's mean dynamic topography (MDT) is a crucial issue for a number of oceanographic applications and, in some areas of the Mediterranean Sea, important limitations have been found pointing to the need of an upgrade. We present a new MDT that was computed for the Mediterranean Sea. It profits from improvements made possible by the use of extended data sets and refined processing. The updated data set spans the 1993-2012 period and consists of drifter velocities, altimetry data, hydrological profiles and model data. The methodology is similar to the previous MDT by Rio et al. (2007). However, in Rio et al. (2007) no hydrological profiles had been taken into account. This required the development of dedicated processing. A number of sensitivity studies have been carried out to obtain the most accurate MDT as possible. The main results from these sensitivity studies are the following: moderate impact to the choice of correlation scales but almost negligible sensitivity to the choice of the first guess (model solution). A systematic external validation to independent data has been made to evaluate the performance of the new MDT. Compared to previous versions, SMDT-MED-2014 (Synthetic Mean Dynamic Topography of the MEDiterranean sea) features shorter-scale structures, which results in an altimeter velocity variance closer to the observed velocity variance and, at the same time, gives better Taylor skills.

Rio, M.-H.; Pascual, A.; Poulain, P.-M.; Menna, M.; Barceló, B.; Tintoré, J.

2014-08-01

85

Does Dynamical Downscaling Introduce Novel Information in Climate Model Simulations of Recipitation Change over a Complex Topography Region?  

NASA Technical Reports Server (NTRS)

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 topography regions, GCM predictions of precipitation change with climate warming may be dry biased due to the GCM smoothing of the regional topography.

Tselioudis, George; Douvis, Costas; Zerefos, Christos

2012-01-01

86

Effects of bottom topography on dynamics of river discharges in tidal regions: case study of twin plumes in Taiwan Strait  

NASA Astrophysics Data System (ADS)

The Princeton Ocean Model is used to investigate the intratidal variability of currents and turbulent mixing and their impact on the characteristics and evolution of the plumes of two neighboring rivers, the Zhuoshui River and the Wu River, at the central eastern coast of Taiwan Strait. The two estuaries are located close to each other and their conditions are similar in many respects, and yet the two plumes exhibit significantly different behavior. We explain this through differences of the bottom topography in the areas adjacent to the two river mouths. The Zhuoshui River runs into a shallow area that is permanently exposed to strong tidal mixing, while the Wu River mouth is located in a deeper, stratified area outside the region of intense mixing. This destruction of the plume by tidal mixing is confirmed by the results of numerical modeling with POM. The spatial and temporal variability of turbulent kinetic energy and its production rate in the study region, as well as the horizontal diffusivity, are analyzed with the emphasis given to the dependence of the turbulence parameters on the bottom topography on the one hand and their influence on the river plumes on the other. Further, we use a Lagrangian particle tracking model in combination with POM to investigate the effect of the tidal wetting-and-drying (WAD) of land taking place near the Zhuoshui estuary, and demonstrate that WAD leads to significant reduction of the plume extent and surface salinity deficit near the river mouth. We use observational data from a short field campaign in the study area to tune and validate the model experiments.

Korotenko, K. A.; Osadchiev, A. A.; Zavialov, P. O.; Kao, R.-C.; Ding, C.-F.

2014-04-01

87

Absolut Vodka  

Microsoft Academic Search

This case depicts the history of an unusual brand in the "super premium" segment of the vodka market. The top-of-line positioning is supported with creative advertising, narrow distribution, point-of-purchase advertising, and expensive advertising production. Absolut has used very expensive inserts as advertisements in print vehicles during the Christmas season. The last inserts described in the case cost approximately $1 each

Paul Farris; Elizabeth Collins

88

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)

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.

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

2011-01-01

89

Determination of Absolute Configuration in Chiral Solvents with Nuclear Magnetic Resonance. A Combined Molecular Dynamics/Quantum Chemical Study.  

PubMed

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

Kessler, Ji?í; Dra?ínský, Martin; Bou?, Petr

2014-12-01

90

On the relative role of upslope and downslope topography for describing water flow path and storage dynamics  

E-print Network

, Boussinesq equation (BEq) solver. Our results show that the new smoothed dynamic topographic index and Environmental Engineering, University of Trento, Trento, Italy 2 Department of Forest Engineering, Resources

McDonnell, Jeffrey J.

91

Topography of chance  

NASA Astrophysics Data System (ADS)

We present a model of multiplicative Langevin dynamics that is based on two foundations: the Langevin equation and the notion of multiplicative evolution. The model is a nonlinear mechanism transforming a white-noise input to a dynamic-equilibrium output, using a single control: an underlying convex U-shaped potential function. The output is quantified by a stationary density which can attain a given number of shapes and a given number of randomness categories. The model generates each admissible combination of the output's shape and randomness in a universal and robust fashion. Moreover, practically all the probability distributions that are supported on the positive half-line, and that are commonly encountered and applied across the sciences, can be reverse engineered by this model. Hence, this model is a universal equilibrium mechanism, in the context of multiplicative dynamics, for the robust generation of “chance”: the model's output. In turn, the properties of the produced “chance,” the output's shape and randomness, are determined with mathematical precision by the control's landscape, its topography. Thus, a topographic map of chance is established. As a particular application, probability distributions with power-law tails are shown to be universally and robustly generated by controls on the “edge of convexity”: convex U-shaped potential functions with asymptotically linear wings.

Eliazar, Iddo I.; Cohen, Morrel H.

2013-11-01

92

Topography of chance.  

PubMed

We present a model of multiplicative Langevin dynamics that is based on two foundations: the Langevin equation and the notion of multiplicative evolution. The model is a nonlinear mechanism transforming a white-noise input to a dynamic-equilibrium output, using a single control: an underlying convex U-shaped potential function. The output is quantified by a stationary density which can attain a given number of shapes and a given number of randomness categories. The model generates each admissible combination of the output's shape and randomness in a universal and robust fashion. Moreover, practically all the probability distributions that are supported on the positive half-line, and that are commonly encountered and applied across the sciences, can be reverse engineered by this model. Hence, this model is a universal equilibrium mechanism, in the context of multiplicative dynamics, for the robust generation of "chance": the model's output. In turn, the properties of the produced "chance," the output's shape and randomness, are determined with mathematical precision by the control's landscape, its topography. Thus, a topographic map of chance is established. As a particular application, probability distributions with power-law tails are shown to be universally and robustly generated by controls on the "edge of convexity": convex U-shaped potential functions with asymptotically linear wings. PMID:24329211

Eliazar, Iddo I; Cohen, Morrel H

2013-11-01

93

Introducing Variable-Step Topography (VST) coordinates within dynamically constrained Nonhydrostatic Modeling System (NMS). Part 1: VST formulation within NMS host model framework  

NASA Astrophysics Data System (ADS)

A Variable-Step Topography (VST) surface coordinate system is introduced into a dynamically constrained, scalable, nonhydrostatic atmospheric model for reliable simulations of flows over both smooth and steep terrain without sacrificing dynamical 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 dynamically 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 dynamical constraints.

Tripoli, Gregory J.; Smith, Eric A.

2014-06-01

94

Implications of Groundwater Dynamics on Long-Term Changes of River Basin Topography and Hydrologic Response, With Application to the WE-38 Basin, Pennsylvania  

NASA Astrophysics Data System (ADS)

Numerous studies have examined the impacts of geomorphology on the hydrologic processes of river basins, but much less attention has been given to the opposite problem: the effects of hydrologic processes on the evolution of river basin topography. Fluvial erosion processes are driven by surface runoff and streamflow, which depend on precipitation rates, soil moisture dynamics, and groundwater flow. All of these processes help determine spatial and temporal patterns of runoff and streamflow in a basin. Horton runoff occurs where the infiltration capacity is exceeded by the rainfall intensity and might produce relatively uniform incision across a basin. Dunne runoff and groundwater discharge typically occur in areas adjacent to river channels, thus eroding river networks and their neighboring locations. Groundwater is expected to be especially important to patterns of erosion when the infiltration capacity is large enough to absorb significant precipitation. On the Colorado Plateau, for example, groundwater leaves significant geomorphic signatures such as amphitheater-shaped channel heads and near constant valley widths from source to outlet. In this analysis, we investigate the role that groundwater movement plays in long-term landscape evolution using a landscape evolution model that has been modified to include a more detailed representation of basin hydrology. In the model, precipitation is generated by a stochastic process that includes realistic inter-storm variation, and the precipitation is partitioned between surface runoff and groundwater recharge using specified infiltration and recharge rates. Groundwater flow is simulated by a two-dimensional Dupuit equation for a homogeneous, isotropic, unconfined aquifer with an irregular underlying impervious layer. The model is applied to the WE-38 basin, an experimental watershed in Pennsylvania. This site was selected as a study area because substantial hydrologic and geomorphic information is available including rainfall data, streamflow data, groundwater table elevations, and estimated parameters for the geomorphic processes. First, the hydrologic model is calibrated to match observed streamflow data, then the combined hydrologic/geomorphic model is used to investigate several hypothetical scenarios. The scenarios investigate the role of groundwater as the infiltration capacity, hydraulic conductivity, and impervious layer are modified. The resulting topographies are analyzed and their hydrologic behavior is characterized. The results indicate that groundwater plays an important role in shaping fluvial landscapes and thus affects the long-term evolution of hydrologic response, especially in basins with large infiltration capacities and thick aquifers.

Huang, X.; Niemann, J.

2004-12-01

95

Coupled dynamics of the co-evolution of gravel bed topography, flow turbulence and sediment transport in an experimental channel  

NASA Astrophysics Data System (ADS)

A series of flume experiments were conducted in a large experimental channel at the St. Anthony Falls Laboratory to understand the coupled dynamics of flow and bed forms above the sediment-water interface. Simultaneous high resolution measurements of velocity fluctuations, bed elevations and sediment flux at the downstream end of the channel, were made for a range of discharges. The probability density functions (pdfs) of bed elevation increments and instantaneous Reynolds stress reveal a power law tail behavior and a wavelet cross-correlation analysis depicts a strong dependence of these series across a range of scales, indicating a feedback between bed form dynamics and near-bed turbulence. These results complement our previous findings in which the signature of bed form evolution on the near-bed velocity fluctuations was confirmed via the presence of a spectral gap and two distinct power law scaling regimes in the spectral density of velocity fluctuations. We report herein a strong asymmetry in the probability distribution of bed elevation increments and instantaneous Reynolds stresses, the latter being further analyzed and interpreted via a quadrant analysis of velocity fluctuations in the longitudinal and vertical directions. We also report the presence of intermittency (multifractality) in bed elevation increments and interpret it, in view of the asymmetric nature of the pdfs, as the result of scale coupling. In other words, the geometric asymmetry at the bed form scale gets transferred down to a probabilistic asymmetry at all smaller scales indicating a local anisotropy in the energy transfer. Finally, we propose a predictive relationship between bed form averaged sediment transport rates and bed form averaged instantaneous Reynolds stress and validate it using our experimental data.

Singh, Arvind; Foufoula-Georgiou, Efi; Porté-Agel, Fernando; Wilcock, Peter R.

2012-12-01

96

Moire topography in odontology  

NASA Astrophysics Data System (ADS)

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 topography that allows the accurate measurement of different parts of the human body topography. This investigation presents the measurement of topographies 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 topography 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.

Moreno Yeras, A.

2001-08-01

97

Membrane related dynamics and the formation of actin in cells growing on micro-topographies: a spatial computational model  

PubMed Central

Background Intra-cellular processes of cells at the interface to an implant surface are influenced significantly by their extra-cellular surrounding. Specifically, when growing osteoblasts on titanium surfaces with regular micro-ranged geometry, filaments are shorter, less aligned and they concentrate at the top of the geometric structures. Changes to the cytoskeleton network, i. e., its localization, alignment, orientation, and lengths of the filaments, as well as the overall concentration and distribution of key-actors are induced. For example, integrin is distributed homogeneously, whereas integrin in activated state and vinculin, both components of focal adhesions, have been found clustered on the micro-ranged geometries. Also, the concentration of Rho, an intracellular signaling protein related to focal adhesion regulation, was significantly lower. Results To explore whether regulations associated with the focal adhesion complex can be responsible for the changed actin filament patterns, a spatial computational model has been developed using ML-Space, a rule-based model description language, and its associated Brownian-motion-based simulator. The focus has been on the deactivation of cofilin in the vicinity of the focal adhesion complex. The results underline the importance of sensing mechanisms to support a clustering of actin filament nucleations on the micro-ranged geometries, and of intracellular diffusion processes, which lead to spatially heterogeneous distributions of active (dephosphorylated) cofilin, which in turn influences the organization of the actin network. We find, for example, that the spatial heterogeneity of key molecular actors can explain the difference in filament lengths in cells on different micro-geometries partly, but to explain the full extent, further model assumptions need to be added and experimentally validated. In particular, our findings and hypothesis referring to the role, distribution, and amount of active cofilin have still 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 dynamics 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

2014-01-01

98

Toward Improved Estimation of the Dynamic Topography and Ocean Circulation in the High Latitude and Arctic Ocean: The Importance of GOCE  

NASA Astrophysics Data System (ADS)

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 dynamic topography for studies of the ocean circulation and transport estimates in the Nordic Seas and Arctic Ocean.

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.

2014-05-01

99

Expected temporal absolute gravity change across the Taiwanese Orogen, a modeling approach  

NASA Astrophysics Data System (ADS)

The island of Taiwan is located on the convergent boundary between the Philippine Sea plate and the Chinese continental margin. It offers very active mountain building and collapsing processes well illustrated by the rugged topography, rapid uplift and denudation, young tectonic landforms, active faulting and numerous earthquakes. In this paper, using simple models, we have estimated vertical movements and associated absolute gravity variations which can be expected along a profile crossing the southern part of the island and probably suffering the highest rates of rising. The two different tectonic styles proposed for the island, thin-skinned and thick-skinned, were taken into account. Horizontal and vertical movements were modeled by an elastic deformation code. Gravity variations due to these deformations are then modeled at a second step. They are dominated by plate and free-air effects, i.e. elevation of the topography, with several ?Gal yr -1. By comparison, gravity changes generated by mass transfers are weak: maximum 0.1 ?Gal yr -1 with the thin-skinned tectonic and 0.3 ?Gal yr -1 with the thick-skinned tectonic. Though elastic rheology has limitations, this modeling offers interesting results on what gravity signal can be expected from the AGTO project (Absolute Gravity in the Taiwanese Orogen), which proposes to study the dynamic of these mountain ranges using absolute gravimetry (AG) and also including relative gravimetry (RG) and GPS measurements.

Mouyen, M.; Masson, F.; Hwang, C.; Cheng, C.-C.; Cattin, R.; Lee, C. W.; Le Moigne, N.; Hinderer, J.; Malavieille, J.; Bayer, R.; Luck, B.

2009-12-01

100

Plasma radiation dynamics with the upgraded Absolute Extreme Ultraviolet tomographical system in the Tokamak à Configuration Variable  

SciTech Connect

We introduce an upgraded version of a tomographical system which is built up from Absolute Extreme Ultraviolet-type (AXUV) detectors and has been installed on the Tokamak à Configuration Variable (TCV). The system is suitable for the investigation of fast radiative processes usually observed in magnetically confined high-temperature plasmas. The upgrade consists in the detector protection by movable shutters, some modifications to correct original design errors and the improvement in the data evaluation techniques. The short-term sensitivity degradation of the detectors, which is caused by the plasma radiation itself, has been monitored and found to be severe. The results provided by the system are consistent with the measurements obtained with the usual plasma radiation diagnostics installed on TCV. Additionally, the coupling between core plasma radiation and plasma-wall interaction is revealed. This was impossible with other available diagnostics on TCV.

Tal, B.; Nagy, D.; Veres, G. [Institute for Particle and Nuclear Physics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Association EURATOM, P. O. Box 49, H-1525 Budapest (Hungary)] [Institute for Particle and Nuclear Physics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Association EURATOM, P. O. Box 49, H-1525 Budapest (Hungary); Labit, B.; Chavan, R.; Duval, B. [Ecole Polytechnique Fédérale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas, Association EURATOM-Confédération Suisse, EPFL SB CRPP, Station 13, CH-1015 Lausanne (Switzerland)] [Ecole Polytechnique Fédérale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas, Association EURATOM-Confédération Suisse, EPFL SB CRPP, Station 13, CH-1015 Lausanne (Switzerland)

2013-12-15

101

Plasma radiation dynamics with the upgraded Absolute Extreme Ultraviolet tomographical system in the Tokamak à Configuration Variable.  

PubMed

We introduce an upgraded version of a tomographical system which is built up from Absolute Extreme Ultraviolet-type (AXUV) detectors and has been installed on the Tokamak a? Configuration Variable (TCV). The system is suitable for the investigation of fast radiative processes usually observed in magnetically confined high-temperature plasmas. The upgrade consists in the detector protection by movable shutters, some modifications to correct original design errors and the improvement in the data evaluation techniques. The short-term sensitivity degradation of the detectors, which is caused by the plasma radiation itself, has been monitored and found to be severe. The results provided by the system are consistent with the measurements obtained with the usual plasma radiation diagnostics installed on TCV. Additionally, the coupling between core plasma radiation and plasma-wall interaction is revealed. This was impossible with other available diagnostics on TCV. PMID:24387434

Tal, B; Labit, B; Nagy, D; Chavan, R; Duval, B; Veres, G

2013-12-01

102

Moiré topography in odontology  

NASA Astrophysics Data System (ADS)

For several decades, measurement of optical techniques has been used in different branches of science and technology. One of these techniques is the so-called moiré topography (MT) that enables the accurate measurement of different parts of the human body topography. This investigation presents the measurement of topographies of teeth and gums using an automated system of shadow moiré and the phase shift method in an original way. The fringe patterns used to compute the shape and the shape matrix itself are presented in the article. The phase shift method ensures precisions up to the order of microns. Advantages and disadvantages of using the MT are included. Besides, some positive and negative aspects concerned with the implementation of this technique in odontology are shown in the article.

Moreno Yeras, A.

2003-07-01

103

Two-dimensional fluorescence-detected coherent spectroscopy with absolute phasing by confocal imaging of a dynamic grating and 27-step phase-cycling  

SciTech Connect

We present a novel experimental scheme for two-dimensional fluorescence-detected coherent spectroscopy (2D-FDCS) using a non-collinear beam geometry with the aid of “confocal imaging” of dynamic (population) grating and 27-step phase-cycling to extract the signal. This arrangement obviates the need for distinct experimental designs for previously developed transmission detected non-collinear two-dimensional coherent spectroscopy (2D-CS) and collinear 2D-FDCS. We also describe a novel method for absolute phasing of the 2D spectrum. We apply this method to record 2D spectra of a fluorescent dye in solution at room temperature and observe “spectral diffusion.”.

De, Arijit K., E-mail: akde@lbl.gov; Fleming, Graham R., E-mail: grfleming@lbl.gov [Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94702 (United States); Department of Chemistry, University of California at Berkeley, Berkeley, California 94702 (United States); Monahan, Daniele; Dawlaty, Jahan M. [Department of Chemistry, University of California at Berkeley, Berkeley, California 94702 (United States)

2014-05-21

104

Teaching Absolute Value Meaningfully  

ERIC Educational Resources Information Center

What is the meaning of absolute value? And why do teachers teach students how to solve absolute value equations? Absolute value is a concept introduced in first-year algebra and then reinforced in later courses. Various authors have suggested instructional methods for teaching absolute value to high school students (Wei 2005; Stallings-Roberts…

Wade, Angela

2012-01-01

105

Evolution of Shallow Isotherms Under Dynamic 3D Topography and Sampling Strategies for U-Th\\/He Dating: Examples From the Appalachian Blue Ridge and Southeastern Tibet  

Microsoft Academic Search

The effects of erosion on temperatures in the crust and the way this can complicate interpretation of cooling ages has been a venerable subject explored many times in both one and two dimensions. Unlike other thermochronological systems, the ~70 °C closure isotherm pertinent to the U-Th\\/He system will be quite sensitive to topography at scale lengths that would seem to

P. K. Zeitler; A. L. Ault; B. D. Idleman; F. J. Pazzaglia; P. O. Koons

2002-01-01

106

Flow Interaction with Topography  

NSDL National Science Digital Library

This is a foundation module in the Mesoscale Meteorology Primer series. Topics covered include an overview of factors that control whether air will go up and over a mountain or be forced around it, the role of potential and kinetic energy, the Froude number and what it tells you, and air flow blocked by topography.

COMET

2001-01-01

107

TOPOGRAPHIES LAW / DROIT  

E-print Network

THE LAYERS OF LAW TOPOGRAPHIES DU DROIT Faculty of Law Faculté de droit LAW / DROIT AUTOMNE FALL/ 2011 #12;2 FOCUS | LAW ­ FALL / AUTOMNE 2011 ­ MCGILL UNIVERSITY FALL/AUTOMNE 2011 RédactRices en chef Sebastiao, Development Coordinator, alumnioffice.law@mcgill.ca Telephone: 514.398.3679 Focus Law est publié

Fabry, Frederic

108

Phobos' shape and topography models  

NASA Astrophysics Data System (ADS)

The global shape and the dynamic environment are fundamental properties of a body. Other properties such as volume, bulk density, and models for the dynamic 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 dynamic models for Phobos were derived from a polyhedron representation of the DTM. The DTM, spherical harmonic function model, and dynamic models, have been refined and represent Phobos' dynamic and geometric topography 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.

Willner, K.; Shi, X.; Oberst, J.

2014-11-01

109

Crustal thickness and support of topography on Venus  

E-print Network

The topography of a terrestrial planet can be supported by several mechanisms: (1) crustal thickness variations, (2) density variations in the crust and mantle, (3) dynamic support, and (4) lithospheric stresses. Each of ...

James, Peter Benjamin

110

Gallery of Virtual Topography  

NSDL National Science Digital Library

The Gallery of Virtual Topography features virtual depictions of topography, including 3D perspectives and QuickTime Virtual Reality (QTVR) movies, created from Digital Elevation Models (DEM's). The site showcases QTVR object movies where the user can spin a 3D terrain to view it from different perspectives. It also includes static 3D-perspective images (JPEG files) of the 3D terrains for those users with slower Internet connections. Some movies and images depict only the form of the landscape, but in others topographic contours are draped over the landscape to better illustrate how contours portray different types of topography (cliffs versus badlands, for example). Some animations illustrate the significance of contours, by allowing the user to progressively fill the landscape up with water to see the water interact with different topographic features. The site also contains a topographic contour map for each 3D terrain, so that instructors can develop student exercises, such as locating points on a map and constructing topographic profiles. Some QTVR movies contain numbered topographic features just for this purpose.

Stephen Reynolds

111

Evolution of Shallow Isotherms Under Dynamic 3D Topography and Sampling Strategies for U-Th/He Dating: Examples From the Appalachian Blue Ridge and Southeastern Tibet  

NASA Astrophysics Data System (ADS)

The effects of erosion on temperatures in the crust and the way this can complicate interpretation of cooling ages has been a venerable subject explored many times in both one and two dimensions. Unlike other thermochronological systems, the ~70 °C closure isotherm pertinent to the U-Th/He system will be quite sensitive to topography at scale lengths that would seem to require a 3D approach to sampling, data interpretation, and modeling. As we illustrate with models and data from two end members, these complications in the temperature field are relevant to both older, more slowly eroding settings as well as active, rapidly exhuming settings where extreme erosion rates are in play. Solution of the transient heat flow equation in three dimensions identifies the thermal and temporal structures predicted for these two end-members. In older, more slowly eroding regions, such as the Appalachian Blue Ridge, relief is lower but the longer time scales and larger topographic wavelength conspire to allow non-trivial deflection of shallow isotherms that can thwart simple sampling strategies based on 2D age-elevation transects. In mountains such as Nanga Parbat and Namche Barwa in the Himalaya and the Southern Alps in New Zealand, rapid exhumation leaves shallow isotherms pushed well up into topography and sub-parallel to the topographic surface. Although the situation is complex, 3D modeling can help identify experimental and sampling strategies that permit interesting questions to be addressed in mountain-scale landscape evolution, such as the degree of lateral migration of mountainous topography. One simple approach is to generate predictive age-residual maps where the modeled 70 °C closure surface is subtracted from the DEM used in generating the 3D model. This reveals locations where sampling can yield ages with useful variation, as in the southern Appalachians where existing age-elevation transects have not been particularly revealing on their own in reconstructions of the post-orogenic evolution of that landscape.

Zeitler, P. K.; Ault, A. L.; Idleman, B. D.; Pazzaglia, F. J.; Koons, P. O.

2002-12-01

112

Corneal topography system  

NASA Astrophysics Data System (ADS)

A new corneal topography system is described which combines proven grid projection and stereo triangulation techniques with an innovative user interface which simplifies the data capture process. Principles of the imaging, measurement, and calibration processes used with the system are presented. The device generates a complete topographic model of the anterior corneal surface with spatial resolution of 0.2 millimeters and elevation accuracy of 2 microns. System applications include pre- and post-operative assessment of refractive surgery patients, contact lens fitting including specification of custom RGP lenses, and excimer surgery planning and simulation. The innovative features of the system are described along with preliminary results of accuracy evaluations.

Cambier, James L.; Gao, Yan

1998-03-01

113

Implications of MOLA Global Roughness, Statistics, and Topography  

NASA Technical Reports Server (NTRS)

New insights are emerging as the ongoing high-quality measurements of the Martian surface topography 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 topography 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 absolute accuracy of topography 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.

Aharonson, O.; Zuber, M. T.; Neumann, G. A.

1999-01-01

114

Excited State Structure and Dynamics from Absolute Resonance Raman Intensities: the Photochemistry and Photophysics of 1,3,5-CYCLOOCTATRIENE, Cyclobutene and Nile Blue.  

NASA Astrophysics Data System (ADS)

Resonance Raman spectra of 1,3,5-cyclooctatriene and cyclobutene are obtained and analyzed using fully-thermalized time-correlator theory to detail the initial nuclear dynamics of disrotatory photochemical ring-opening reactions. For 1,3,5-cyclooctatriene, intense resonance Raman scattering is detected in the normal modes corresponding to ethylenic stretching (1610 and 1640 cm^{-1} ) and carbon-ring twist-boat planarization (140 and 404 cm^{-1}) coordinates. No intensity is observed in modes which project onto the disrotatory ring-opening motion, such as the non-totally symmetric CH_2 twist fundamental or its overtone. Also, no intensity is observed in the symmetric CH_2 twist, which corresponds to conrotatory ring-opening motion. Absolute resonance Raman intensities and the absorption spectrum of cyclooctatriene are modeled to quantitate the excited-state equilibrium geometry displacements along the Franck-Condon active modes as well as the homogeneous and inhomogeneous linewidths. Analysis of the fluorescence quantum yield gives an excited-state lifetime of ~30 fs presumably caused by fast internal conversion to a low-lying A_1 state. These results indicate that the femtosecond nuclear dynamics of the initial steps of this photochemical reaction are along the twist-boat planarization coordinates and not the disrotatory reaction coordinate. The ring-opening presumably occurs after the planarization step and is directed by the doubly-excited character in the 2A_1 electronic state. The 200-nm resonance Raman spectrum of cyclobutene shows resonance enhancement of single (984 and 1110 cm^{-1}) and double bond stretching fundamentals, the 2150 cm ^{-1} overtone of the b _2 CH_2 twisting mode, the 656 cm^{-1} overtone of the b_2 out-of-plane ring pucker, and the 902 cm^{-1} fundamental of the b_1 in-plane ring bending mode. These intensities indicate that the initial evolution of the optically-excited molecule is along the Woodward -Hoffmann-predicted disrotatory ring-opening reaction coordinate. Comparison of these results with the excited-state dynamics of other pericyclic systems suggests that pericyclic rearrangements occur only once a planar skeletal structure is established and that the bond rearrangement occurs predominantly on the low-lying, optically-forbidden 2A_1 excited state. Although not considered in the Woodward-Hoffmann analysis, this state correlates directly to the sound electronic states of the photoproducts in these systems. Resonance Raman spectra of Nile Blue have also been obtained and analyzed to quantitate the excited-state equilibrium geometry displacements of 40 resonance Raman active modes. The absolute Raman cross sections permit the absorption lineshape to be separated into its homogeneous (350 cm^{-1} HWHM) and inhomogeneous (313 cm^{-1} HWHM) components. This analysis yields a 25-fs electronic dephasing time which compares well to results obtained through direct femtosecond photon echo measurements; it is proposed that the origin of this dephasing is the low -frequency solvent bath modes which are coupled to the electronic transition.

Lawless, Mary Katherine

115

Absolute nuclear material assay  

DOEpatents

A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute 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.

Prasad, Manoj K. (Pleasanton, CA); Snyderman, Neal J. (Berkeley, CA); Rowland, Mark S. (Alamo, CA)

2012-05-15

116

RADAR Reveals Titan Topography  

NASA Technical Reports Server (NTRS)

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 topography will be included in our presentation. Data obtained in the Ta encounter include a SAR image swath

Kirk, R. L.; Callahan, P.; Seu, R.; Lorenz, R. D.; Paganelli, F.; Lopes, R.; Elachi, C.

2005-01-01

117

Topography of Io (color)  

NASA Technical Reports Server (NTRS)

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 topography 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 topography 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.

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.

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).

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

1997-01-01

118

Support of long-wavelength topography on Mercury inferred from MESSENGER measurements of gravity and topography  

NASA Astrophysics Data System (ADS)

To explore the mechanisms of support of surface topography on Mercury, we have determined the admittances and correlations of topography 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 dynamic flow. We find that long-wavelength (spherical harmonic degree l < 15) surface topography 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 dynamic 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 topography.

James, Peter B.; Zuber, Maria T.; Phillips, Roger J.; Solomon, Sean C.

2015-02-01

119

Absolute colorimetric characterization of a DSLR camera  

NASA Astrophysics Data System (ADS)

A simple but effective technique for absolute colorimetric camera characterization is proposed. It offers a large dynamic range requiring just a single, off-the-shelf target and a commonly available controllable light source for the characterization. The characterization task is broken down in two modules, respectively devoted to absolute luminance estimation and to colorimetric characterization matrix estimation. The characterized camera can be effectively used as a tele-colorimeter, giving an absolute estimation of the XYZ data in cd=m2. The user is only required to vary the f - number of the camera lens or the exposure time t, to better exploit the sensor dynamic range. The estimated absolute tristimulus values closely match the values measured by a professional spectro-radiometer.

Guarnera, Giuseppe Claudio; Bianco, Simone; Schettini, Raimondo

2014-03-01

120

Density, Isostasy, and Topography  

NSDL National Science Digital Library

Show caption HideA critical component of this activity involves sharing team data with the entire class, done the old-fashioned way on the chalkboard. Details This activity begins with an exploration of a topographic map of the earth, ending with the question: Why is the distribution of topography on the earth bimodal? The students then collect two forms of data. They measure the density of the most common rocks that make up oceanic crust (basalt), continental crust (granite), and the mantle (peridotite). They also measure the density of several different kinds of wood, and how high each kind floats in a tub of water. In each case, they work in teams of two or three and then the entire class shares their data. Based on the data from the wood, they derive an equation that relates the density of the wood to the height at which the block floats in the water - the isostasy equation. They then substitute density values for real rocks into their equation to derive thicknesses for average continental and oceanic crust, and apply their knowledge in order to draw a cross-section of the crust across South America. This activity gives students a real, hands-on and mathematical understanding of the principle of isostasy.

Anne Egger

121

Lake Topography and Wind Waves Determining Seasonal-Spatial Dynamics of Total Suspended Matter in Turbid Lake Taihu, China: Assessment Using Long-Term High-Resolution MERIS Data  

PubMed Central

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 topography, 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 dynamics were controlled by the lake topography, wind-driven sediment resuspension and SAV distribution. PMID:24846206

Zhang, Yunlin; Shi, Kun; Liu, Xiaohan; Zhou, Yongqiang; Qin, Boqiang

2014-01-01

122

Estimating Absolute Site Effects  

SciTech Connect

The authors use previously determined direct-wave attenuation functions as well as stable, coda-derived source excitation spectra to isolate the absolute S-wave site effect for the horizontal and vertical components of weak ground motion. They used selected stations in the seismic network of the eastern Alps, and find the following: (1) all ''hard rock'' sites exhibited deamplification phenomena due to absorption at frequencies ranging between 0.5 and 12 Hz (the available bandwidth), on both the horizontal and vertical components; (2) ''hard rock'' site transfer functions showed large variability at high-frequency; (3) vertical-motion site transfer functions show strong frequency-dependence, and (4) H/V spectral ratios do not reproduce the characteristics of the true horizontal site transfer functions; (5) traditional, relative site terms obtained by using reference ''rock sites'' can be misleading in inferring the behaviors of true site transfer functions, since most rock sites have non-flat responses due to shallow heterogeneities resulting from varying degrees of weathering. They also use their stable source spectra to estimate total radiated seismic energy and compare against previous results. they find that the earthquakes in this region exhibit non-constant dynamic stress drop scaling which gives further support for a fundamental difference in rupture dynamics between small and large earthquakes. To correct the vertical and horizontal S-wave spectra for attenuation, they used detailed regional attenuation functions derived by Malagnini et al. (2002) who determined frequency-dependent geometrical spreading and Q for the region. These corrections account for the gross path effects (i.e., all distance-dependent effects), although the source and site effects are still present in the distance-corrected spectra. The main goal of this study is to isolate the absolute site effect (as a function of frequency) by removing the source spectrum (moment-rate spectrum) from the distance-corrected S-wave spectra. Typically, removing the S-wave source spectrum is difficult because of inadequate corrections for the source radiation pattern, directivity and random interference. In addition to complexities near the source, 2-D and 3-D structure beneath the recording site will result in an azimuth-dependent site effect. Since the direct wave only samples a narrow range in take-off and back-azimuth angles, multi-station averaging is needed to minimize the inherent scatter. To minimize these complicating effects, they apply the coda methodology outlined by Mayeda et al., (2003) to obtain stable moment-rate spectra. This methodology provides source amplitude and derived source spectra that are a factor of 3-to-4 times more stable than those derived from direct waves. Since the coda is commonly thought of as scattered energy that samples all ray parameters and back-azimuths, it is not very sensitive to the source radiation pattern and 3-D structure. This property makes it an excellent choice for use in obtaining average properties of the source, site and path effects in a region. Due to the characteristics of the techniques used in this study, all the inverted quantities are azimuthally averaged, since the aximuthal information is lost in the processing.

Malagnini, L; Mayeda, K M; Akinci, A; Bragato, P L

2004-07-15

123

Eosinophil count - absolute  

MedlinePLUS

An absolute eosinophil count is a blood test that measures the number of white blood cells called eosinophils. Eosinophils become active when you have certain allergic diseases, infections, and other medical conditions.

124

Global Topography and Tectonic Plates  

NSDL National Science Digital Library

The goal of this activity is to investigate global topographic and tectonic features, especially the tectonic plates and their boundaries. Using a double-page size digital topographic map of the Earth that includes both land and sea floor topography, students are asked to draw plate boundaries, deduce plate motions and interactions, and explore the connections between topography and tectonic processes at the global scale.

David Greene

125

Absolute Biodiesel Potential Country Name  

E-print Network

Absolute Biodiesel Potential Country Name Production Cost ($/liter) Potential Biodiesel Volume,234 0% 0% #12;Absolute Biodiesel Potential Country Name Production Cost ($/liter) Potential Biodiesel;Absolute Biodiesel Potential Country Name Production Cost ($/liter) Potential Biodiesel Volume (liters

Wisconsin at Madison, University of

126

Asymmetric three-dimensional topography over mantle plumes  

NASA Astrophysics Data System (ADS)

The role of mantle-lithosphere interactions in shaping surface topography has long been debated. In general, it is supposed that mantle plumes and vertical mantle flows result in axisymmetric, long-wavelength topography, which strongly differs from the generally asymmetric short-wavelength topography created by intraplate tectonic forces. However, identification of mantle-induced topography 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' topography (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 topography 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 topography 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 dynamic topography, mantle-lithosphere interactions, and continental break-up processes above mantle plumes.

Burov, Evgueni; Gerya, Taras

2014-09-01

127

Deep versus shallow origin of gravity anomalies, topography and volcanism on Earth, Venus and Mars  

E-print Network

Deep versus shallow origin of gravity anomalies, topography and volcanism on Earth, Venus and Mars Available online xxxx Keywords: Earth Venus, Interior Mars, Interior Volcanism a b s t r a c t The relation dynamics of planets. From the power spectra of gravity and topography on Earth, Venus and Mars we infer

Steinberger, Bernhard

128

Satellite remote sensing of landscape freeze/thaw state dynamics for complex Topography and Fire Disturbance Areas Using multi-sensor radar and SRTM digital elevation models  

NASA Technical Reports Server (NTRS)

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 dynamics 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.

Podest, Erika; McDonald, Kyle; Kimball, John; Randerson, James

2003-01-01

129

The Shuttle Radar Topography Mission  

Microsoft Academic Search

The Shuttle Radar Topography Mission produced the most complete, highest-resolution digital elevation model of the Earth. The project was a joint endeavor of NASA, the National Geospatial-Intelligence Agency, and the German and Italian Space Agencies and flew in February 2000. It used dual radar antennas to acquire interferometric radar data, processed to digital topographic data at 1 arc sec resolution.

Tom G. Farr; Paul A. Rosen; Edward Caro; Robert Crippen; Riley Duren; Scott Hensley; Michael Kobrick; Mimi Paller; Ernesto Rodriguez; Ladislav Roth; David Seal; Scott Shaffer; Joanne Shimada; Jeffrey Umland; Marian Werner; Michael Oskin; Douglas Burbank; Douglas Alsdorf

2007-01-01

130

Absolute configuration of neostenine  

NASA Astrophysics Data System (ADS)

Heavy atoms bromine and iodine were incorporated into the neostenine ( 1) skeleton through reductive cleavage of the lactone ring, followed by acylation with 4-bromobenzoyl chloride, and salt formation with methyl iodide, respectively. The absolute configuration of the seven chiral centers C1, C9, C9a, C10, C11, C1 and C13 in 1 were assigned as S, S, R, R, R, R, and S, respectively, based on the Flack parameters in X-ray structure refinement, and results from the two heavy atom derivatives are consistent with each other. As many Stemona alkaloids share the same lactone and pyrrolo[1,2-?]azepine nucleus as those in 1, the facile method reported in this paper can be applied for the determination of absolute configurations of similar alkaloids.

Jiang, Ren-Wang; Ye, Wencai; Shaw, Pang-Chui; But, Paul Pui-Hay; Mak, Thomas C. W.

2010-03-01

131

Estimating Absolute Site Effects  

Microsoft Academic Search

The authors use previously determined direct-wave attenuation functions as well as stable, coda-derived source excitation spectra to isolate the absolute S-wave site effect for the horizontal and vertical components of weak ground motion. They used selected stations in the seismic network of the eastern Alps, and find the following: (1) all ''hard rock'' sites exhibited deamplification phenomena due to absorption

L. Malagnini; K M Mayeda; A Akinci; P L Bragato

2004-01-01

132

Vacillating jets: baroclinic turbulence and topography  

NASA Astrophysics Data System (ADS)

Observations from satellite altimetry and output from high-resolution ocean models indicate that the Southern Ocean is characterised by an intricate web of narrow, meandering, filamentary jets. These jets undergo spontaneous formation, merger and splitting events, and rapid latitude shifts over periods of weeks to months. The role of topography in controlling jet variability is explored using a doubly-periodic, forced-dissipative, two-layer quasi-geostrophic model. The system is forced by a baroclinically-unstable, vertically-sheared mean flow in a domain that is large enough to accommodate multiple jets. The dependence of (i) meridional jet spacing, (ii) time scales of jet variability and (iii) large-scale, domain-averaged transport properties on changes in the length scale and steepness of simple sinusoidal topographical features is analysed. The Rhines scale ?? measures the meridional extent of eddy mixing by a single jet, and the ratio ??/?T, where ?T is the topographic length scale, determines jet behaviour. Multiple, steady jets with fixed meridional spacing are observed when ?? ? ?T or when ?? ? ?T. However when ?? < ?T, a pattern of perpetual jet formation and jet merger dominates the time evolution of the system. This unsteady structure significantly alters the large-scale energetics and transport properties, leading to a reduction in transport by a factor of two if the topography consists of zonally-invariant ridges, and an increase in transport by an order of magnitude or more if the topography consists of two-dimensional sinusoidal bumps. For certain parameters, bumpy topography gives rise to periodic oscillations in jet structure between purely-zonal and topographically-steered states. In these cases, transport is dominated by bursts of mixing associated with the shifts between the two regimes. Unsteady jet behaviour depends crucially on the feedback between changes in mean flow orientation, caused by topographic steering, and the conversion of potential energy to kinetic energy through baroclinic instability, as well as on asymmetric Reynolds stresses created by topographical modifications to the large-scale potential vorticity gradient. It is likely that these processes play a role in the dynamic nature of Southern Ocean jets.

Thompson, A. F.

2009-04-01

133

Gravity and topography. [of planet Mars  

NASA Technical Reports Server (NTRS)

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, dynamical 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 topography, inferences are made about the degree and depth of compensation in the interior and stresses in the lithosphere.

Esposito, P. B.; Banerdt, W. B.; Lindal, G. F.; Sjogren, W. L.; Slade, M. A.; Bills, B. G.; Smith, D. E.; Balmino, G.

1992-01-01

134

Mapping of sea bottom topography  

NASA Technical Reports Server (NTRS)

Under suitable conditions the bottom topography of shallow seas is visible in remote sensing radar imagery. Two experiments were performed to establish which remote sensing technique or combination yields optimal imaging of bottom topography and which hydro-meteorological conditions are favorable. A further goal is to gain experience with these techniques. Two experiments were performed over an area in the North Sea near the measuring platform Meetpost Noordwijk (MPN). The bottom topography in the test area is dominated by sand waves. The crests of the sand waves are perpendicular to the coast line and the dominating (tidal-)current direction. A 4x4 sq km wide section of the test area was studied in more detail. The first experiment was undertaken on 16 Aug. 1989. During the experiment the following remote sensing instruments were used: Landsat-Thematic Mapper, and NASA/JPL Airborne Imaging Radar (AIR). The hydro-meteorological conditions; current, wind, wave, and air and water temperature were monitored by MPN, a ship of Rijkswaterstaat (the OCTANS), and a pitch-and-roll WAVEC-buoy. The second experiment took place on 12 July 1992. During this experiment data were collected with the NASA/JPL polarimetric synthetic aperture radar (SAR), and a five-band helicopter-borne scatterometer. Again the hydro-meteorological conditions were monitored at MPN and the OCTANS. Furthermore, interferometric radar data were collected.

Calkoen, C. J.; Wensink, G. J.; Hesselmans, G. H. F. M.

1992-01-01

135

Earth rotation and core topography  

NASA Technical Reports Server (NTRS)

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 topography 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 topography. The purpose of work supported by NAG5-819 was to study further the problem of CMB topography, using geodesy, fluid mechanics, geomagnetics, and seismology. This is a final report.

Hager, Bradford H.; Clayton, Robert W.; Spieth, Mary Ann

1988-01-01

136

The Role of Topography in Glacial Inception  

NASA Astrophysics Data System (ADS)

We test the influence of model topography on glacial inception using a coupled atmosphere-slab ocean version of NCAR’s Community Climate System Model (CCSM3). Simulations employ a modern orbital configuration and greenhouse gas concentrations representing both recent (year 1990) and hypothetically lower present-day values in accordance with Ruddiman’s Early Anthropogenic Hypothesis (240 ppm CO2 and 450 ppb CH4). The model is run at two different resolutions: a relatively coarse horizontal configuration (T42, approximately 2.8 degrees) and comparatively fine resolution (T85, approximately 1.4 degrees). Although under contemporary greenhouse forcing the extent of permanent boreal snow cover in the two model configurations is similar, imposing lower concentrations of CO2 and CH4 generates much more extensive glacial inception in the T85 experiment (150% increase) than in the T42 version (80% increase). Furthermore, the spatial patterns of glacial inception differ considerably. Only the T85 resolution produces widespread permanent snow cover over the Rocky Mountains and on Baffin Island, consistent with geologic evidence for ice sheet nucleation in northeastern Canada. Although much of the enhanced sensitivity in the higher-resolution simulations is directly attributable to the colder and wetter conditions around elevated topography, some of the response also appears to be driven dynamically and remotely as a function of the simulated elevation of Greenland. The colder conditions over and downstream of the Greenland Ice Sheet in the modern T85 simulation promote a smaller cooling locally under lowered greenhouse forcing that seems to activate a wave-1 dynamical response in the atmospheric pressure field. The resulting circulation anomalies favor stronger upslope wind flow from the Pacific Ocean over the northern Rocky Mountains, enhancing the regional development of a permanent snow pack. Although these experiments are driven by greenhouse forcing rather than historical orbital variations, we believe that our findings apply to the general mechanisms of glacial inception.

Vavrus, S. J.; Philippon-Berthier, G.; Kutzbach, J. E.; Ruddiman, W. F.

2009-12-01

137

NOVA: Absolute Zero  

NSDL National Science Digital Library

On a hot day, some might wish they could get the temperature down a bit. They might not wish it to be as cold as, say absolute zero, but there are many scientists who are interested in doing just that. For those who are curious, absolute zero clocks in at around minus 460 degrees Fahrenheit. This engaging website is meant to serve as a complementary resource to the two-part series that recently aired on NOVA on this engaging topic. Visitors can start by watching a short preview of the program, and then continuing on to look over some of the special interactive features on the site. All told, there are ten different features, including "A Sense of Scale", "How Low Can You Go?", and "Milestones in Cold Research". The "Milestones in Cold Research" is a great place to start, as it's an interactive timeline that chronicles the "netherworld of extraordinarily low temperatures" as investigated by everyone from Galileo to current researchers. Of course, there are also more playful features here, such as "The Ice Trade", which asks users to dispatch ships loaded with natural ice to Florida, Brazil, and India.

138

Absolute flow field estimation for the Nordic seas from combined gravimetric, altimetric, and in situ data  

NASA Astrophysics Data System (ADS)

In the Nordic seas, we combine a computation of absolute surface current flow derived from geodetic data with in situ historical hydrographic data to estimate the absolute volume, heat, and salt transports as a function of depth. Our mean dynamic topography (MDT) is calculated from marine, airborne and satellite gravimetry, combined with satellite altimetry, using a new algorithm called the iterative combination method (ICM). Residual noise in the gravimetric geoid is the limit on MDT resolution and is suppressed using a Gaussian filter with a width at half-peak amplitude of 59 km. Detailed and coherent flow paths for surface geostrophic currents are clearly identified. ICM MDT was used as fixed boundary condition to transform historical hydrography into absolute estimates of volume, heat, and salt transport, replacing the assumption of an isobaric surface at a predetermined depth. For the inflow of Atlantic Water (potential temperature ? > 6°C) through the Faroe-Shetland Channel into the Nordic seas, we obtain time-averaged fluxes between 1993 and 1996 of 3.5 Sv (volume), 121 TW (heat), and 124 × 106 kg s-1 (salt), very close to reported observations from acoustic Doppler current profiler moorings and conductivity-temperature-depth data. For the Svinøy section, we obtain a northward transport of Atlantic Water (S > 35.0, T > 5.0°C) of 3.9 Sv in the eastern branch of the Norwegian Atlantic Current comparable with reported measurements of 4.2 Sv. Similarly good agreement is found for the Hornbanki and Iceland-Faroe Ridge sections and for monitoring Atlantic Water outflow across the Barents Sea Opening to the Arctic shelf.

Hunegnaw, A.; Siegismund, F.; Hipkin, R.; Mork, K. A.

2009-02-01

139

Effect of topography on sulfate redistribution in Cumulonimbus cloud development.  

PubMed

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 topography on the sulfate redistribution in a clean and a polluted environment, the complex topography 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 dynamics, while cloud microphysics and precipitation determine wet removal of the chemical species. In simulations with realistic topography, 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 topography. 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 topography conditions affect the sulfate redistribution in the sense of greater possibilities of transport. Numerical simulations without real topography give an artificial increase of deposited sulfur mass of about 25-30 %. PMID:24243093

Vujovi?, Dragana; Vu?kovi?, Vladan; Curi?, Mla?en

2014-03-01

140

Simultaneous inversion for mantle shear velocity and the topography of transition zone discontinuities  

NASA Astrophysics Data System (ADS)

A method is presented for the simultaneous inversions of shear velocity in the mantle and the topography of transition zone discontinuities. Each travel time residual, corrected for crust and free surface topography, 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 topography. We expand the lateral variations in velocity and the topography 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 topography 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 topography 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 absolute 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%.

Gu, Y. J.; Dziewonski, A. M.

2001-05-01

141

Comparison of Sum Absolute QRST Integral, and Temporal Variability in Depolarization and Repolarization, Measured by Dynamic Vectorcardiography Approach, in Healthy Men and Women  

PubMed Central

Background Recently we showed the predictive value of sum absolute 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

Tereshchenko, Larisa G.

2013-01-01

142

Absolute Equilibrium Entropy  

NASA Technical Reports Server (NTRS)

The entropy associated with absolute 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.

Shebalin, John V.

1997-01-01

143

Quantifying turbidity current interactions with topography  

E-print Network

This thesis advances our understanding of how transport properties of turbidity currents are mediated by interactions with seafloor topography, specifically channelized surfaces. Turbidity currents are responsible for ...

Straub, Kyle M

2007-01-01

144

Topography Simulation for Nanometer Semiconductor Process  

NASA Astrophysics Data System (ADS)

In this paper, we propose a novel scheme for simulating the topography of nanometer semiconductor processes. Since the proposed scheme considers only the surface cells moving forward and backward during etching or deposition, the simulator does not suffer from an increased memory requirement due to the complexity of the high aspect-ratio structure built on the wafer. This method consists of steps for calculating the front surface moving forward and backward and converting the cell structure into a tetrahedral mesh structure for subsequent numerical simulation. This method mitigates the excessive memory requirement through a dynamic allocating scheme wherein only topographical data at the surface cell are taken into account. A spillover algorithm is also implemented in the simulator so that any excessive etching or deposition which is more than the rate acceptable at the exposed cell during a single time step is reconsidered in the adjacent cells. Our proposed scheme was verified for structures with complex geometry, such as a thin film transistor-liquid crystal display (TFT-LCD) structure, a read only memory (ROM) or a dynamic random access memory (DRAM) cell.

Lee, Jun?Gu; Yoon, Sukin; Won, Taeyoung

2006-04-01

145

sup 13 N ammonia myocardial imaging at rest and with exercise in normal volunteers. Quantification of absolute myocardial perfusion with dynamic positron emission tomography  

SciTech Connect

Positron emission tomography (PET) was applied to the measurement of myocardial perfusion using the perfusion tracer 13N-labeled ammonia. 13N ammonia was delivered intravenously to 13 healthy volunteers both at rest and during supine bicycle exercise. Dynamic PET imaging was obtained in three cross-sectional planes for 10 minutes commencing with each injection. The left ventricle was divided into eight sectors, and a small region of interest was assigned to the left ventricular blood pool to obtain the arterial input function. The net extraction of 13N ammonia was obtained for each sector by dividing the tissue 13N concentration at 10 minutes by the integral of the input function from the time of injection to 10 minutes. With this approach for calculating net extractions, rest and exercise net extractions were not significantly different from each other. To obviate possible overestimation of the true 13N ammonia input function by contamination by 13N-labeled compounds other than 13N ammonia or by spillover from myocardium into blood pool, the net extractions were calculated using only the first 90 seconds of the blood and tissue time-activity curves. This approach for calculating net extractions yielded significant differences between rest and exercise, with an average ratio of exercise to rest of 1.38 +/- 0.34. Nonetheless, the increase was less than predicted from the average 2.7-2.8-fold increase in double product at peak exercise or the 1.7-fold increase in double product at 1 minute after exercise. However, when the first 90 seconds of dynamic data were fit with a two compartment tracer kinetic model, average perfusion rates of 0.75 +/- 0.43 ml/min/g at rest and 1.50 +/- 0.74 ml/min/g with exercise were obtained. This average increase in perfusion of 2.2-fold corresponded to similar average increases in double product.

Krivokapich, J.; Smith, G.T.; Huang, S.C.; Hoffman, E.J.; Ratib, O.; Phelps, M.E.; Schelbert, H.R. (UCLA School of Medicine (USA))

1989-11-01

146

Fast Parallel Absolute Irreducibility Testing  

Microsoft Academic Search

e present a fast parallel deterministic algorithm for testing multivariate integral polyno- - c mials for absolute irreducibility, that is irreducibility over the complex numbers. More pre isely, we establish that the set of absolutely irreducible integral polynomials belongs to the e i complexity class NC of Boolean circuits of polynomial size and logarithmic depth. Therefor t also belongs to

Erich Kaltofen

1985-01-01

147

Bathymetry, Topography, and Relief Data  

NSDL National Science Digital Library

This extensive site from NOAA's National Geophysical Data Center provides a collection of bathymetry, topography, and relief data from a variety of sources and environments including coastlines, the Great Lakes, and the seafloor. The site also features the National Ocean Service (NOS) hydrographic database. Some images and data can be downloaded at no charge, while others may be purchased on CD-ROM or DVD. The site can be searched for downloadable data using the GEODAS Data Search and Retrieval System. Data products from NOS surveys, including Descriptive Reports (DRs), smooth sheet images, survey data images, textual gridded data, and sidescan sonar mosaics, are available for download using the National Ocean Service Hydrographic Survey Data Map Service, an ArcIMS interactive map and data discovery tool.

National Geophysical Data Center

148

Venus - Global gravity and topography  

NASA Astrophysics Data System (ADS)

A new gravity field determination that has been produced combines both the Pioneer Venus Orbiter (PVO) and the Magellan Doppler radio data. Comparisons between this estimate, a spherical harmonic model of degree and order 21, and previous models show that significant improvements have been made. Results are displayed as gravity contours overlaying a topographic map. We also calculate a new spherical harmonic model of topography based on Magellan altimetry, with PVO altimetry included where gaps exist in the Magellan data. This model is also of degree and order 21, so in conjunction with the gravity model, Bouguer and isostatic anomaly maps can be produced. These results are very consistent with previous results, but reveal more spatial resolution in the higher latitudes.

McNamee, J. B.; Borderies, N. J.; Sjogren, W. L.

1993-05-01

149

Corneal topography of posterior keratoconus.  

PubMed

Posterior keratoconus is an unusual abnormality of the cornea generally classified as one of the anterior chamber cleavage anomalies. It is characterized clinically by the presence of a circumscribed or generalized corneal thinning with posterior depression of the cornea and is considered distinct from keratoconus. Although patients with posterior keratoconus may have visual complaints clearly related to their abnormal corneas, the surface topography of these corneas has not been studied in detail. Keratometry and photokeratoscopy provide an incomplete picture of the surface geometry of posterior keratoconus. We utilized computer assisted topographic analysis to study the cornea of a patient with posterior keratoconus. The Topographic Modeling System demonstrated that the patient's cornea showed a central steepened "cone" coincident with the area of circumscribed posterior keratoconus as well as paracentral flattening. This report documents the topographic abnormality in this rare disorder. PMID:1424657

Mannis, M J; Lightman, J; Plotnik, R D

1992-07-01

150

Large scale topography of Io  

NASA Technical Reports Server (NTRS)

To investigate the large scale topography 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.

Gaskell, R. W.; Synnott, S. P.

1987-01-01

151

Mercury's global shape and topography from MESSENGER limb images  

NASA Astrophysics Data System (ADS)

We derive models for the global shape and topography of Mercury from limb images obtained by the MESSENGER spacecraft during flybys and from orbit. Crossover heights of 225 individual limb profiles were adjusted by least-squares techniques to establish a rigid global topographic network. Mercury is confirmed to possess an equatorial ellipticity and a polar oblateness. Several large impact basins and craters can be identified in the topographic model, including one basin that was earlier proposed but unconfirmed. Comparisons with absolute height data from laser altimetry indicate that the limb model appears to overestimate planetary radius by ~900 m on average. Limb profiles and local digital terrain models derived from stereo-photogrammetry show good agreement.

Elgner, Stephan; Stark, Alexander; Oberst, Jürgen; Perry, Mark E.; Zuber, Maria T.; Robinson, Mark S.; Solomon, Sean C.

2014-11-01

152

Moho depth and residual topography of the Antarctic continent  

NASA Astrophysics Data System (ADS)

A new Moho depth map for the Antarctic continent has been recently assembled (ANTMoho), merging information retrieved from geophysical and geological studies selected from the literature. A large volume of old and new data have been analyzed: from active seismic prospection,including DSS profiles acquired by Soviet Union field experiments, to recent passive seismic receiver function and geological studies. ANTMoho has a reference lateral resolution of 1 degree. The oldest Archean and Proterozoic crust of East Antarctica has a thickness of 36-56 km (with an average of about 41 km). The continental crust of the Transantarctic Mountains, the Antarctic Peninsula and Wilkes Basin has a thickness of 30-40 km (with an average Moho of about 30 km). The youngest rifted continental crust of the West Antarctic Rift System has a thickness of 16-28 km (with an average Moho of about 26 km). The mean Moho depth of the whole model is 33.8 km. We compare this new model to other available for the whole continent (Bassin et al., 2000; Block et al., 2009) and study the possible geodynamic consequences calculating the residual topography -- an indicator of dynamic response to large-scale mantle flow. We adopt the semianalytical methodology implemented in the HC code (developed and maintained by Prof. T. Becker). The spatial resolution is limited by the L=127 of the input model. The Transantarctic Mountains appear not to be isostatically compensated, such as the neighboring Wilkes Subglacial Basin. East Antarctica on a large scale does not show significant uncompensated topography. There are however some smaller-scale residual topography features, that correlate with sub-glacial topography and that may indicate some limitation in resolution or laterally-variable crustal density. Better knowledge of crustal structure is therefore an important tool for better understanding of the complex dynamic processes acting at a regional scale.

Baranov, Alexey; Molinari, Irene; Morelli, Andrea; Danesi, Stefania

2013-04-01

153

Predicting Maximum Lake Depth from Surrounding Topography  

PubMed Central

Information about lake morphometry (e.g., depth, volume, size, etc.) aids understanding of the physical and ecological dynamics 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 topography 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

Hollister, Jeffrey W.; Milstead, W. Bryan; Urrutia, M. Andrea

2011-01-01

154

Absolute judgments of odor intensity  

Microsoft Academic Search

Results obtained with the method of absolute judgment suggest that a relatively unpracticed S can identify correctly three levels of intensity of an odorant and that a well-practiced S can identify about four levels.

Trygg Engen; Carl Pfaffmann

1959-01-01

155

Cryogenic, Absolute, High Pressure Sensor  

NASA Technical Reports Server (NTRS)

A pressure sensor is provided for cryogenic, high pressure applications. A highly doped silicon piezoresistive pressure sensor is bonded to a silicon substrate in an absolute pressure sensing configuration. The absolute pressure sensor is bonded to an aluminum nitride substrate. Aluminum nitride has appropriate coefficient of thermal expansion for use with highly doped silicon at cryogenic temperatures. A group of sensors, either two sensors on two substrates or four sensors on a single substrate are packaged in a pressure vessel.

Chapman, John J. (Inventor); Shams. Qamar A. (Inventor); Powers, William T. (Inventor)

2001-01-01

156

Maps of Mars Global Topography  

NASA Technical Reports Server (NTRS)

Maps of Mars' global topography. The projections are Mercator to 70o latitude and stereographic at the poles with the south pole at left and north pole at right. Note the elevation difference between the northern and southern hemispheres. The Tharsis volcano-tectonic province is centered near the equator in the longitude range 220o E to 300o E and contains the vast east-west trending Valles Marineris canyon system and several major volcanic shields including Olympus Mons (18o N, 225o E), Alba Patera (42o N, 252o E), Ascraeus Mons (12o N, 248o E), Pavonis Mons (0o, 247o E), and Arsia Mons (9o S, 239o E). Regions and structures discussed in the text include Solis Planum (25o S, 270o E), Lunae Planum (10o N, 290o E), and Claritas Fossae (30o S, 255o E). Major impact basins include Hellas (45o S, 70o E), Argyre (50o S, 320o E), Isidis (12o N, 88o E), and Utopia (45o N, 110o E). This analysis uses an areocentric coordinate convention with east longitude positive.

1999-01-01

157

Absolute Calibration Using the MSX Reference Spheres  

NASA Astrophysics Data System (ADS)

MSX conducted five absolute calibration experiments against emissive reference spheres between 25 August 1996 and 20 February 1997. The 2 cm diameter, T6061 Al spheres are coated with Martin Black. The thermal properties of the spheres are well known and their emissivities and reflectivities were accurately measured in the laboratory. The spheres were ejected at an elevation angle of 15 degrees above the MSX velocity vector in the orbital plane; the velocities were measured at the time of ejection. The geometric parameters of the spheres at the time of measurement were determined from orbital dynamics. The energy balance equation between the thermal input from the direct Sunlight, Sunlight reflected by the Earth and upwelling Earthshine and the total flux emitted by the sphere is solved to derive the instantaneous temperature of the sphere. The MSX in-band fluxes are then calculated from the blackbody at the temperature of the sphere predicted by the model modified by the wavelength dependent infrared emissivity at the distance of the sphere plus infrared Earthshine and Sunlight reflected by the sphere. The weighted results for the five spheres agree to within the uncertainties with the SPIRIT III responsivities determined from the absolute fluxes for infrared standard stars derived by Cohen et al. The MSX calibration against the reference spheres thus validate the absolute fluxes for the standard stars to <2%.

Price, S. D.; Paxson, C.; Murdock, T. L.

2004-12-01

158

Topography of the Moon from the Clementine Lidar  

NASA Technical Reports Server (NTRS)

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 Topography Model 2 (GLTM 2). This topographic field has an absolute 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 topography 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 topography 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 topography 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 for the absence of significant farside maria except for S.P.-Aitken, whose depth and lack of mare require significant internal compositional and/or thermal heterogeneity. A macroscale surface roughness map shows that roughness at length scales of 10(exp 1) - 10(exp 2) km correlates with elevation and surface age.

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

1997-01-01

159

Sensory properties of menthol and smoking topography  

PubMed Central

Although there is a great deal known about menthol as a flavoring agent in foods and confections, less is known about the particular sensory properties of menthol cigarette smoke. Similarly, although smoking topography (the unique way an individual smokes a cigarette) has been well studied using non-menthol cigarettes, there is relatively less known about how menthol affects smoking behavior. The objective of this review is to assess the sensory properties of menthol tobacco smoke, and smoking topography associated with menthol cigarettes. The cooling, analgesic, taste, and respiratory effects of menthol are well established, and studies have indicated that menthol’s sensory attributes can have an influence on the positive, or rewarding, properties associated smoking, including ratings of satisfaction, taste, perceived smoothness, and perceived irritation. Despite these sensory properties, the data regarding menthol’s effect on smoking topography are inconsistent. Many of the topography studies have limitations due to various methodological issues. PMID:21624149

2011-01-01

160

Evaluating Marie Byrd Land stability using an improved basal topography  

NASA Astrophysics Data System (ADS)

Prior understanding of the ice-sheet setting in Marie Byrd Land (MBL) was derived primarily from geologic and geochemical studies of the current nunataks, with very few geophysical surveys imaging the ice covered regions. The geologic context suggested that the ice rests on a broad regional high, in contrast to the deep basins and trenches that characterize the majority of West Antarctica. This assumed topography would favor long-term stability for the West Antarctic Ice Sheet (WAIS) in MBL. Airborne geophysical data collected in 2009 reveal a much deeper bed than previously estimated, including a significant trough underlying DeVicq Glacier and evidence for extensive glacial erosion. Using these data, we produce a new map of subglacial topography, with which we model the sensitivity of WAIS to a warming ocean using the ice-sheet model of Pollard and DeConto (2012b). We compare the results to estimates of ice loss during WAIS collapse using the previously defined subglacial topography, to determine the impact of the newly discovered subglacial features. Our results indicate that the topographic changes are not sufficient to destabilize the northern margin of MBL currently feeding the Getz Ice Shelf; the majority of ice loss occurs from flow toward the Siple Coast. However, despite only slight dynamic differences, using the new bed as a boundary condition results in an additional 8 cm of sea-level rise during major glacial retreat, an increase of just over 2%. Precise estimation of past and future ice retreat, as well as a complete understanding of the geologic history of the region, will require a higher resolution picture of the bed topography around the Executive Committee mountains.

Holschuh, N.; Pollard, D.; Alley, R. B.; Anandakrishnan, S.

2014-12-01

161

Topography of the synaptosomal membrane  

PubMed Central

The composition and disposition of the constituent polypeptides of rat cerebral cortical synaptosomal membranes were analyzed on SDS acrylamide gels. Of 20 bands readily detected, 11 account for greater than 93% of the total protein analyzed. These are: (molecu25); 3 (175); 4 (doublet, 137); 5 (doublet, 97); 6 (68); 7 (61); 8 (54); 9 (44); 10 (37); and 11 (33). Bands 5 and 8-10 are the most prominent and account for greater than 60% of the protein mass or 0.67 of its molecular fraction. By lactoperoxidase iodination, the bulk of the proteins in bands 3, 5, 6, and 8 and a portion of band 11 appear to be located on the external (junctional) face of the membrane of intact synaptosomes; proteins in bands 1, 2, 7, 9, and 10 appear to be localized on the internal (synaptoplasmic) face and become labeled only when synaptosomes are lysed. Further confirmation of the topographical distribution is provided by evidence that bands 3-6, 8, and 11 contain glycoproteins susceptible to labeling in intact synaptosomes by oxidation with galactose oxidase or periodate followed by reduction with NaB3H4. Evidence is provided for significant contributions by tubulin- and actin-like molecules to bands 8 and 9, respectively, suggesting that a substantial fraction of the tubulin in the synaptosomal membrane is disposed externally (accessible to iodination) whereas most, if not all, of the actin appears to exhibit the opposite topography. Similar though weaker inferences can also be drawn with regard to the location of tropomyosin and troponin. Preliminary evidence is provided that postsynaptic densities exhibit a protein and iodination profile distinct from that of the synpatosomal membrane. PMID:1033185

1976-01-01

162

Corneal topography measurements for biometric applications  

NASA Astrophysics Data System (ADS)

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 topography 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 topography measured. Human subject topography 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. Topography data was collected from 59 subjects and modeled using Zernike polynomials, which provide for a simple method of compressing topography 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 topography measurements. Reasonably accurate results, between three to eight percent simultaneous false match and false non-match rates, were achieved.

Lewis, Nathan D.

163

Numerical modeling and analysis of the effect of complex Greek topography on tornadogenesis  

NASA Astrophysics Data System (ADS)

Tornadoes have been reported in Greece over recent decades in specific sub-geographical areas and have been associated with strong synoptic forcing. While it has been established that meteorological conditions over Greece are affected at various scales by the significant variability of topography, the Ionian Sea to the west and the Aegean Sea to the east, there is still uncertainty regarding topography's importance on tornadic generation and development. The aim of this study is to investigate the role of topography in significant tornadogenesis events that were triggered under strong synoptic scale forcing over Greece. Three tornado events that occurred over the last years in Thebes (Boeotia, 17 November 2007), Vrastema (Chalkidiki, 12 February 2010) and Vlychos (Lefkada, 20 September 2011) were selected for numerical experiments. These events were associated with synoptic scale forcing, while their intensities were T4-T5 (on the TORRO scale), causing significant damage. The simulations were performed using the non-hydrostatic weather research and forecasting model (WRF), initialized by European Centre for Medium-Range Weather Forecasts (ECMWF) gridded analyses, with telescoping nested grids that allow for the representation of atmospheric circulations ranging from the synoptic scale down to the mesoscale. In the experiments, the topography of the inner grid was modified by: (a) 0% (actual topography) and (b) -100% (without topography), making an effort to determine whether the occurrence of tornadoes - mainly identified by various severe weather instability indices - could be indicated by modifying topography. The principal instability variables employed consisted of the bulk Richardson number (BRN) shear, the energy helicity index (EHI), the storm-relative environmental helicity (SRH), and the maximum convective available potential energy (MCAPE, for parcels with maximum ?e). Additionally, a model verification was conducted for every sensitivity experiment accompanied by analysis of the absolute vorticity budget. Numerical simulations revealed that the complex topography constituted an important factor during the 17 November 2007 and 12 February 2010 events, based on EHI, SRH, BRN, and MCAPE analyses. Conversely, topography around the 20 September 2011 event was characterized as the least significant factor based on EHI, SRH, BRN, and MCAPE analyses.

Matsangouras, I. T.; Pytharoulis, I.; Nastos, P. T.

2014-07-01

164

Absolute Performance of AUSGeoid09 in Mountainous Regions  

NASA Astrophysics Data System (ADS)

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 absolute sense in the Mid Hunter and Snowy Mountains regions of New South Wales. Absolute (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 absolute 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 topography 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.

Sussanna, Vittorio; Janssen, Volker; Gibbings, Peter

2014-09-01

165

Against "Absolutely Everything"! Georey Hellman  

E-print Network

- ence and cannot be made sense of. This avoids the trap of sayi, even make sense? How could one possibly doubt it? According to Lewis [1991, 68], the skeptical position-constructively a¢ rm) existence, and can one ultimately avoid falling back on absolutely unrestricted quanti

Hellman, Geoffrey

166

Absolute transition probabilities of phosphorus.  

NASA Technical Reports Server (NTRS)

Use of a gas-driven shock tube to measure the absolute 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.-

Miller, M. H.; Roig, R. A.; Bengtson, R. D.

1971-01-01

167

Feinberg on Absolute Legal Rights  

ERIC Educational Resources Information Center

Although the author wished that there were absolute rights, as Joel Feinberg has argued there are, he presented an argument to the contrary. Among the points he attempted to establish was that there is no hard and fast distinction between legal rights and legal privileges as Feinberg has maintained. (Author/RK)

James, Gene G.

1976-01-01

168

Open questions in surface topography measurement: a roadmap  

NASA Astrophysics Data System (ADS)

Control of surface topography has always been of vital importance for manufacturing and many other engineering and scientific disciplines. However, despite over one hundred years of quantitative surface topography measurement, there are still many open questions. At the top of the list of questions is ‘Are we getting the right answer?’ This begs the obvious question ‘How would we know?’ There are many other questions relating to applications, the appropriateness of a technique for a given scenario, or the relationship between a particular analysis and the function of the surface. In this first ‘open questions’ article we have gathered together some experts in surface topography measurement and asked them to address timely, unresolved questions about the subject. We hope that their responses will go some way to answer these questions, address areas where further research is required, and look at the future of the subject. The first section ‘Spatial content characterization for precision surfaces’ addresses the need to characterise the spatial content of precision surfaces. Whilst we have been manufacturing optics for centuries, there still isn’t a consensus on how to specify the surface for manufacture. The most common three methods for spatial characterisation are reviewed and compared, and the need for further work on quantifying measurement uncertainties is highlighted. The article is focussed on optical surfaces, but the ideas are more pervasive. Different communities refer to ‘figure, mid-spatial frequencies, and finish’ and ‘form, waviness, and roughness’, but the mathematics are identical. The second section ‘Light scattering methods’ is focussed on light scattering techniques; an important topic with in-line metrology becoming essential in many manufacturing scenarios. The potential of scattering methods has long been recognized; in the ‘smooth surface limit’ functionally significant relationships can be derived from first principles for statistically stationary, random surfaces. For rougher surfaces, correlations can be found experimentally for specific manufacturing processes. Improvements in computational methods encourage us to revisit light scattering as a powerful and versatile tool to investigate surface and thin film topographies, potentially providing information on both topography and defects over large areas at high speed. Future scattering techniques will be applied for complex film systems and for sub-surface damage measurement, but more research is required to quantify and standardise such measurements. A fundamental limitation of all topography measurement systems is their finite spatial bandwidth, which limits the slopes that they can detect. The third section ‘Optical measurements of surfaces containing high slope angles’ discusses this limitation and potential methods to overcome it. In some cases, a rough surface can allow measurement of slopes outside the classical optics limit, but more research is needed to fully understand this process. The last section ‘What are the challenges for high dynamic range surface measurement?’ presents the challenge facing metrologists by the use of surfaces that need measurement systems with very high spatial and temporal bandwidths, for example, those found in roll-to-roll manufacturing. High resolution, large areas and fast measurement times are needed, and these needs are unlikely to be fulfilled by developing a single all-purpose instrument. A toolbox of techniques needs to be developed which can be applied for any specific manufacturing scenario. The functional significance of surface topography has been known for centuries. Mirrors are smooth. Sliding behaviour depends on roughness. We have been measuring surfaces for centuries, but we still face many challenges. New manufacturing paradigms suggest that we need to make rapid measurements online that relate to the functional performance of the surface. This first ‘open questions’ collection addresses a subset of the challenges facing the surface metrology commun

Leach, Richard; Evans, Christopher; He, Liangyu; Davies, Angela; Duparré, Angela; Henning, Andrew; Jones, Christopher W.; O’Connor, Daniel

2015-03-01

169

Effects of patterned topography on biofilm formation  

NASA Astrophysics Data System (ADS)

Bacterial biofilms are a population of bacteria attached to each other and irreversibly to a surface, enclosed in a matrix of self-secreted polymers, among others polysaccharides, proteins, DNA. Biofilms cause persisting infections associated with implanted medical devices and hospital acquired (nosocomial) infections. Catheter-associated urinary tract infections (CAUTIs) are the most common type of nosocomial infections accounting for up to 40% of all hospital acquired infections. Several different strategies, including use of antibacterial agents and genetic cues, quorum sensing, have been adopted for inhibiting biofilm formation relevant to CAUTI surfaces. Each of these methods pertains to certain types of bacteria, processes and has shortcomings. Based on eukaryotic cell topography interaction studies and Ulva linza spore studies, topographical surfaces were suggested as a benign control method for biofilm formation. However, topographies tested so far have not included a systematic variation of size across basic topography shapes. In this study patterned topography was systematically varied in size and shape according to two approaches 1) confinement and 2) wetting. For the confinement approach, using scanning electron microscopy and confocal microscopy, orienting effects of tested topography based on staphylococcus aureus (s. aureus) (SH1000) and enterobacter cloacae (e. cloacae) (ATCC 700258) bacterial models were identified on features of up to 10 times the size of the bacterium. Psuedomonas aeruginosa (p. aeruginosa) (PAO1) did not show any orientational effects, under the test conditions. Another important factor in medical biofilms is the identification and quantification of phenotypic state which has not been discussed in the literature concerning bacteria topography characterizations. This was done based on antibiotic susceptibility evaluation and also based on gene expression analysis. Although orientational effects occur, phenotypically no difference was observed between the patterned topography tested. Another potential strategy for biofilm control through patterned topography is based on the design of robust non-wetting surfaces with undercut feature geometries, characterized by 1) breakthrough pressure and 2) triple phase contact line model. It was found that height and presence of undercut had statistically significant effects, directly proportional to breakthrough pressures, whereas extent of undercut did not. A predictive triple phase contact line model was also developed. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)

Vasudevan, Ravikumar

2011-12-01

170

CMB topography and electrical conductivity as additional constraints for the lowermost mantle thermo-chemical structure  

NASA Astrophysics Data System (ADS)

A variety of seismic observations, including tomographic models, indicate that the lowermost mantle is strongly heterogeneous. Seismic observations further support a thermo-chemical origin for the large scale heterogeneities. In particular, the large low-shear wave velocity provinces (LLSVP) observed by global tomographic images are better explained by a combination of thermal and chemical anomalies. Despite the accuracy of seismic information, uncertainties and trade-off still prevent the determination of a detailed lower mantle thermo-chemical structure. For instance, the nature of chemical heterogeneities and the exact role played by the post-perovskite phase transition are still debated. Additional constraints are needed to discriminate between the possible models of structure and dynamics of the lower mantle. Here, we consider two potential additional constraints, the electrical conductivity and the dynamic topography at the core-mantle boundary (CMB). Unlike density and seismic velocities, electrical conductivity increases with temperature. In addition, it strongly varies with the iron and silicate content. Using appropriate mineral physics data, we calculated a 3D distribution of electrical conductivity in lower mantle from the thermo-chemical structure inferred by probabilistic tomography, which maps iron and silicate excess in the LLSVP. In the lowermost mantle, we observe a belt of high conductivity, with maximum values around 20 S/m located in the LLSVP. Such a belt may trigger electric currents in the lowermost mantle and induce magnetic field variations with period of one year or more. It may thus be seen by global models of electrical conductivity. Unfortunately, such models do not sample yet regions deeper than 2000 km. A second, independent constraint we explored is the dynamic topography at the CMB. We used stagYY to calculate the dynamic topography associated with several models of thermo-chemical convection, and observe strong differences depending on the model. In models that include large thermo-chemical reservoirs, corresponding to the LLSVP seen by seismic tomography, the CMB dynamic topography is dominated by ridges about 5 km high along the borders of the reservoirs. The spherical harmonic power spectra is dominated by degrees 8 to 10. By contrast, in isochemical models, the dynamic topography focuses at the foot of plumes, where it reaches about 20 km, and is dominated by low (2 and 3) spherical harmonic degrees. Again, the CMB topography may have some implications for the dynamics of the outer core, and the details of the magnetic field. Further developments in seismology may also give a better image of the CMB topography.

Deschamps, F.; Yin, Y.; Tackley, P. J.

2013-12-01

171

The Absolute Spectrum Polarimeter (ASP)  

NASA Technical Reports Server (NTRS)

The Absolute Spectrum Polarimeter (ASP) is an Explorer-class mission to map the absolute 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.

Kogut, A. J.

2010-01-01

172

Absolute calibration of optical flats  

DOEpatents

The invention uses the phase shifting diffraction interferometer (PSDI) to provide a true point-by-point measurement of absolute 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 absolute phase error of the optical flat is obtained.

Sommargren, Gary E.

2005-04-05

173

Detecting and Quantifying Topography in Neural Maps  

PubMed Central

Topographic maps are an often-encountered feature in the brains of many species, yet there are no standard, objective procedures for quantifying topography. Topographic maps are typically identified and described subjectively, but in cases where the scale of the map is close to the resolution limit of the measurement technique, identifying the presence of a topographic map can be a challenging subjective task. In such cases, an objective topography detection test would be advantageous. To address these issues, we assessed seven measures (Pearson distance correlation, Spearman distance correlation, Zrehen's measure, topographic product, topological correlation, path length and wiring length) by quantifying topography in three classes of cortical map model: linear, orientation-like, and clusters. We found that all but one of these measures were effective at detecting statistically significant topography even in weakly-ordered maps, based on simulated noisy measurements of neuronal selectivity and sparse sampling of the maps. We demonstrate the practical applicability of these measures by using them to examine the arrangement of spatial cue selectivity in pallid bat A1. This analysis shows that significantly topographic arrangements of interaural intensity difference and azimuth selectivity exist at the scale of individual binaural clusters. PMID:24505279

Yarrow, Stuart; Razak, Khaleel A.; Seitz, Aaron R.; Seriès, Peggy

2014-01-01

174

Virtual Field Trip: Temperate Deciduous Forest Topography  

E-print Network

Virtual Field Trip: Temperate Deciduous Forest #12;Topography #12;Landform and Soils #12;Climate #12;Climate #12;Vegetation Structure #12;Vegetation Structure #12;Disturbance and Forest Growth Rates and Askins 1995 #12;Presettlement forest Clearing for homestead: 1740 Height of forest clearing: 1830 Farm

Hansen, Andrew J.

175

Ocean Surface Topography from Space - Science  

NSDL National Science Digital Library

This site, from the Jet Propulsion Laboratory at the California Institute of Technology, describes the scientific applications of ocean surface topography from missions such as TOPEX/Poseidon and Jason-1. Other topics include uses of the collected data, such as evaluations of ocean circulation, tides, weather and climate patterns, and other trends.

Jet Propulsion Laboratory

176

The evolution of topography on a comet  

Microsoft Academic Search

The authors have developed a simple model of an infinite cylindrical trench on a comet. The energy balance equation has been modified to include physical processes which are relevant with topography present, and includes shadowing, radiative heating from the opposing walls, and the condensation energy of sublimed gas molecules striking the walls instead of escaping to space. The model is

J. E. Colwell; B. M. Jakosky

1987-01-01

177

Structural Characterization of Doped GaSb Single Crystals by X-ray Topography  

SciTech Connect

We characterized GaSb single crystals containing different dopants (Al, Cd and Te), grown by the Czochralski method, by x-ray topography and high angular resolution x-ray diffraction. Lang topography revealed dislocations parallel and perpendicular to the crystal's surface. Double-crystal GaSb 333 x-ray topography shows dislocations and vertical stripes than can be associated with circular growth bands. We compared our high-angular resolution x-ray diffraction measurements (rocking curves) with the findings predicted by the dynamical theory of x-ray diffraction. These measurements show that our GaSb single crystals have a relative variation in the lattice parameter ({Delta}d/d) on the order of 10{sup -5}. This means that they can be used as electronic devices (detectors, for example) and as x-ray monochromators.

Honnicke, M.G.; Mazzaro, I.; Manica, J.; Benine, E.; M da Costa, E.; Dedavid, B. A.; Cusatis, C.; Huang, X. R.

2009-09-13

178

Floquet representation of absolute phase and pulse-shape effects on laser-driven molecular photodissociation  

Microsoft Academic Search

Using a recent reformulation of Floquet theory [S. GuérinH. R. Jauslin, Adv. Chem. Phys.12520031], we discuss the dynamical role of the absolute phase in the photofragmentation of molecules subjected to laser pulses. We show how the dependence of Floquet states on an absolute phase is related to the complexity of the dressed molecular scheme and to the multiphoton character of

T. T. Nguyen-Dang; C. Lefebvre; H. Abou-Rachid; O. Atabek

2005-01-01

179

Bias in Absolute Magnitude Determination from Parallaxes  

E-print Network

Relations are given for the correction of bias when mean absolute magnitudes are derived by the method of reduced parallaxes. The bias in the case of the derivation of the absolute magnitudes of individual objects is also considered.

Michael Feast

2002-08-29

180

Sea bottom topography imaging with SAR  

NASA Technical Reports Server (NTRS)

It is well known that under favorable meteorological and hydrodynamical conditions the bottom topography of shallow seas can be mapped with airborne or spaceborne imaging radar. This phenomenon was observed for the first time in 1969 by de Loor and co-workers in Q-band Side Looking Airborne Radar (SLAR) imagery of sandwaves in the North Sea. It is now generally accepted that the imaging mechanism consists of three steps: (1) interaction between (tidal) current and bottom topography causes spatial modulations in the surface current velocity; (2) modulations in the surface current velocity give rise to variations in the spectrum of wind-generated waves, as described by the action balance equation; and (3) variations in the wave spectrum show up as intensity modulations in radar imagery. In order to predict radar backscatter modulations caused by sandwaves, an imaging model, covering the three steps, was developed by the Dutch Sea Bottom Topography Group. This model and some model results will be shown. On 16 Aug. 1989 an experiment was performed with the polarimetric P-, L-, and C-band synthetic aperture radar (SAR) of NASA/JPL. One scene was recorded in SAR mode. On 12 Jul. 1991 another three scenes were recorded, of which one was in the ATI-mode (Along-Track Interferometer). These experiments took place in the test area of the Sea Bottom Topography Group, 30 km off the Dutch coast, where the bottom topography is dominated by sand waves. In-situ data were gathered by a ship in the test area and on 'Measuring Platform Noordwijk', 20 km from the center of the test area. The radar images made during the experiment were compared with digitized maps of the bottom. Furthermore, the profiles of radar backscatter modulation were compared with the results of the model. During the workshop some preliminary results of the ATI measurements will be shown.

Vanderkooij, M. W. A.; Wensink, G. J.; Vogelzang, J.

1992-01-01

181

The influence of topography and vegetation self-organization over resource fluxes in wetland ecosystems  

NASA Astrophysics Data System (ADS)

While it is recognized that topography and vegetation self-organization (SO) are both first order controls over ecosystem dynamics, the discrete contributions that these two controls have over ecosystem functioning have not been studied in any rigorous way. This work is focused on systematically isolating the separate and combined impacts of topography and SO over vegetation dynamics. We simulate the steady state and transient dynamics of nitrogen-limited patterned peat vegetation observed in the bogs of northern Siberia. We do so across a realistic range of land slopes, nutrient limitation values, and rainfall amounts. Simulation results show that on relatively shallow slopes, vegetation SO is a primary control over the spatial arrangement of vegetation, and that such self-organized arrangements yield the most efficient capture of ecosystem resources. However, as slope increases, and or resource limitation is low, topography begins to exert its control over the temporal and spatial dynamics. As will be discussed, these results suggest a simple continuum framework, valid across biomes, for understanding the interplay between these two first order controls. Specifically, as resources (e.g., water, nutrients) increase, ecosystem dynamics shift towards topographic control, while when resources are reduced, ecosystem dynamics shift towards vegetation SO control.

Stieglitz, Marc; Cheng, Yiwei; Truk, Greg; Engel, Victor; Ross, Joshua

2014-05-01

182

Astronomy Ranking Task: Apparent and Absolute Magnitude  

E-print Network

Astronomy Ranking Task: Apparent and Absolute Magnitude Exercise #3 Description: The figure below shows five stars (A - E) as they appear in the night sky from Earth. The absolute magnitude number: ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ D. Ranking Instructions: Rank the absolute magnitude number (from greatest to least) of each star (A

Farritor, Shane

183

What is wrong with absolute individual fitness?  

E-print Network

What is wrong with absolute individual fitness? David Sloan Wilson Departments of Biology is that fit- ness is a relative concept. It does not matter how well an organism survives and reproduces, only arguments are framed in terms of absolute individual fitness. The absolute fitness criterion (AFC) can

Wilson, David. S.

184

Compressor performance, absolutely! M. R. Titchener  

E-print Network

Compressor performance, absolutely! M. R. Titchener Dept of CS, U. of Auck., N.Z. (Email: mark the absolute performance of existing string compressors may be measured. Kolmogorov (1958) recognised://tcode.auckland.ac.nz/~corpus has been used to evaluate the `absolute' performance of a series of popular compressors. The results

Titchener, Mark R.

185

Pre-glacial topography of the European Alps  

NASA Astrophysics Data System (ADS)

We present a reconstruction of the Alpine topography prior to Quaternary glaciation, based on the assumption that the pre-glacial topography of the Alps was a fluvial landscape in equilibrium with tectonic and isostatic rock uplift. Amongst the models that have been proposed, the stream-power law has been profitably used for modeling the dynamics of fluvial bedrock channel incision: dz-= U - KAmSn dt (1) where dz/dt (m a-1) is the time rate of change of channel elevation, U(m a-1) is rock-uplift rate, A(m) is upstream drainage area, S is local channel gradient, K is a dimensionless coefficient of erosion and m and n are positive constants related to basin hydrology and erosion process. Under steady-state conditions (dz/dt = 0), equation (1) can be solved to yield an expression for equilibrium channel gradient: 1 ( U-)n - (m) S = K A n (2) where the ratios U/K and m/n are generally referred to as the steepness and concavity index, respectively. Particular focus is put on the spatial variability of the steepness index over the Alpine mountain belt. Assuming a constant concavity index, the pre-glacial topography of the Alps is obtained through an inversion technique that resolves local slopes (as described in eq. 2) by minimizing the misfit between the elevations of the actual and modeled channel heads. Comparing the present-day and reconstructed pre-glacial topography, we infer patterns and magnitudes of exhumation and rock uplift produced by Quaternary glaciation in the Alps. We find a correspondence between rock type and pre-glacial channel steepness which may indicate that rock erodibility has a significant importance in determining the pre-glacial fluvial network elevation. Our results also provide insight into patterns of glacial erosion and associated isostatic adjustment, and provide estimates of the increase of valley-scale topographic relief and decrease of mean elevation that glaciation seems to have produced in the Alps.

Sternai, P.; Herman, F.; Champagnac, J.-D.; Fox, M.; Salcher, B.; Willett, S. D.

2012-04-01

186

Absolute calibration of optical tweezers  

SciTech Connect

As a step toward absolute calibration of optical tweezers, a first-principles theory of trapping forces with no adjustable parameters, corrected for spherical aberration, is experimentally tested. Employing two very different setups, we find generally very good agreement for the transverse trap stiffness as a function of microsphere radius for a broad range of radii, including the values employed in practice, and at different sample chamber depths. The domain of validity of the WKB ('geometrical optics') approximation to the theory is verified. Theoretical predictions for the trapping threshold, peak position, depth variation, multiple equilibria, and 'jump' effects are also confirmed.

Viana, N.B.; Mazolli, A.; Maia Neto, P.A.; Nussenzveig, H.M.; Rocha, M.S.; Mesquita, O.N. [LPO-COPEA and Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590 (Brazil); Departamento de Fisica, Instituto de Ciencias ExatasUniversidade Federal de Minas Gerais, Belo Horizonte, MG, 30123-970 (Brazil)

2006-03-27

187

Gravity and topography of Venusian highlands: Implications for formation mechanisms  

NASA Astrophysics Data System (ADS)

Gravity and topography data are used to determine the apparent compensation depths (ADC's) of thirteen venusian regions. The depths are interpreted in terms of the likely tectonic origins of each area. First, three geologically distinct regions are studied in detail by inverting Pioneer Venus line of sight gravity data to obtain a model of vertical gravity over Bell Regio (possible hot spot), Tellus Regio (tessera terrain), and Leda Planitia (plains). The admittance spectra, the geoid to topography ratio (GTR), and the ADC for each region are found. Each area has a distinct gravity signature. The shallow ADC at Tellus Regio (approximately 25 km) indicates that crustal compensation, possibly with some thermal compensation, is most likely. The large ADC (approximately 175 km) and GTR (20 m/km) along with an unusual admittance spectra at Bell Regio indicate that some dynamic compensation is necessary; crustal or thermal compensation may also be present. Leda Planitia has an intermediate ADC (approximately 65 km), which indicates either thermal or crustal compensation. Second, ADC's and GTR's for 12 venusian highland regions are estimated directly from the topography and line of sight gravity data. These features are: Asteria, Atla, Bell, Beta, Ovda, Phoebe, Tellus, Thetis, and Ulfrun Regiones; Nokomis, Gula, and Sappho Montes. The ADC's range is 50-270 km; the GTR's range is 7-31 m/km. Two distinct GTR groups are apparent. The lower GTR group is best modeled by compensation due to thermal thinning of the lithosphere; some minor component of dynamic or crustal compensation may also be present. A fit to the upper GTR group requires dynamic compensation; a lesser contribution from thermal or crustal compensation may also be present. Upper mantle convection without a low viscosity zone can fit the data. Although the convection parameters are not well constrained, the best fit occurs for a conductive lid thickness of 105 km and a Rayleigh number of 105. These results indicate that hot spots are likely to make a significant contribution to heat loss on Venus.

Smrekar, Suzanne Elizabeth

188

Absolute Neutron Emission Measurement in Burning Plasma Experiments  

NASA Astrophysics Data System (ADS)

The absolute measurement of neutron emission rate from the whole plasma is a very important diagnostics as a fusion power monitor in fusion experimental devices with D-T or D-T operations. Here measurement techniques of time-resolved and time-integrated absolute neutron emission on the present tokamaks and ITER are reviewed. In the present tokamaks, fission chamber installed outside the vacuum vessel are very popular in the absolute neutron emission rate measurement. As well as conventional neutron monitors installed outside the vacuum vessel, in-vessel neutron monitors using micro fission chamber are proposed for the absolute neutron emission rate measurement in ITER. The neutron activation system provides time-integrated measurements of the total neutron yield with high accuracy by using well known neutron reaction cross sections, which is useful to maintain a robust measure of fusion energy production with stability and wide dynamic range. The calibration of the relation between the neutron emission rate in the whole plasma and the output of neutron monitor is the most important issue in the absolute neutron emission rate measurements. The calibration of the neutron detectors has been performed by moving a neutron source such as a 252Cf neutron or a small accelerator-based neutron generator. For the calibration in ITER, the neutron generator with neutron emission rate of 1011 s-1 or stronger is required to obtain high accuracy.

Nishitani, Takeo; Ishikawa, Masao; Kondoh, Takashi; Kusama, Yoshinori; Asai, Keisuke; Sasao, Mmamiko

2008-03-01

189

Absolute Neutron Emission Measurement in Burning Plasma Experiments  

SciTech Connect

The absolute measurement of neutron emission rate from the whole plasma is a very important diagnostics as a fusion power monitor in fusion experimental devices with D-T or D-T operations. Here measurement techniques of time-resolved and time-integrated absolute neutron emission on the present tokamaks and ITER are reviewed. In the present tokamaks, fission chamber installed outside the vacuum vessel are very popular in the absolute neutron emission rate measurement. As well as conventional neutron monitors installed outside the vacuum vessel, in-vessel neutron monitors using micro fission chamber are proposed for the absolute neutron emission rate measurement in ITER. The neutron activation system provides time-integrated measurements of the total neutron yield with high accuracy by using well known neutron reaction cross sections, which is useful to maintain a robust measure of fusion energy production with stability and wide dynamic range. The calibration of the relation between the neutron emission rate in the whole plasma and the output of neutron monitor is the most important issue in the absolute neutron emission rate measurements. The calibration of the neutron detectors has been performed by moving a neutron source such as a {sup 252}Cf neutron or a small accelerator-based neutron generator. For the calibration in ITER, the neutron generator with neutron emission rate of 10{sup 11} s{sup -1} or stronger is required to obtain high accuracy.

Nishitani, Takeo; Ishikawa, Masao; Kondoh, Takashi; Kusama, Yoshinori [Japan Atomic Energy Agency, Naka, Ibaraki-ken, 311-0193 (Japan); Asai, Keisuke [Nagoya University, Chikusa-ku, Nagoya, 464-8603 (Japan); Sasao, Mmamiko [Tohoku University, Aoba-ku, Sendai, 980-8579 (Japan)

2008-03-12

190

The Belize margin revisited. 2. Origin of Holocene antecedent topography  

Microsoft Academic Search

The importance of antecedent topography in dictating Holocene facies patterns has been generally recognized. There is, however, disagreement as to origin or lithology of the antecedent topography, particularly with respect to the siliciclastic or carbonate nature of the underlying topography and structural patterns. To help resolve these problems, published and unpublished information have been compiled to produce a structural fabric

Edward G. Purdy; Eberhard Gischler; Anthony J. Lomando

2003-01-01

191

Spatial Fourier Transform Analysis of Polishing Pad Surface Topography  

NASA Astrophysics Data System (ADS)

The spatial Fourier transform analysis is proposed to quantitatively evaluate the irregular topography of the conditioned chemical mechanical polishing (CMP) pad surface. We discuss the power spectrum in the spatial wavelengths of the surface topographies corresponding to polishing time. We conclude that the spatial wavelength of less than 5 µm in the topography yielded high material removal rates.

Khajornrungruang, Panart; Kimura, Keiichi; Okuzono, Takahisa; Suzuki, Keisuke; Kushida, Takashi

2012-05-01

192

Absolute MR thermometry using nanocarriers.  

PubMed

Accurate time-resolved temperature mapping is crucial for the safe use of hyperthermia-mediated drug delivery. We here propose a magnetic resonance imaging temperature mapping method in which drug delivery systems serve not only to improve tumor targeting, but also as an accurate and absolute nano-thermometer. This method is based on the temperature-dependent chemical shift difference between water protons and the protons in different groups of drug delivery systems. We show that the chemical shift of the protons in the ethylene oxide group in polyethylene glycol (PEG) is temperature-independent, whereas the proton resonance of water decreases with increasing temperature. The frequency difference between both resonances is linear and does not depend on pH and physiological salt conditions. In addition, we show that the proton resonance of the methyl group in N-(2-hydroxypropyl)-methacrylamide (HPMA) is temperature-independent. Therefore, PEGylated liposomes, polymeric mPEG-b-pHPMAm-Lac2 micelles and HPMA copolymers can provide a temperature-independent reference frequency for absolute magnetic resonance (MR) thermometry. Subsequently, we show that multigradient echo MR imaging with PEGylated liposomes in situ allows accurate, time-resolved temperature mapping. In conclusion, nanocarrier materials may serve as highly versatile tools for tumor-targeted drug delivery, acting not only as hyperthermia-responsive drug delivery systems, but also as accurate and precise nano-thermometers. PMID:24706612

Deckers, Roel; Sprinkhuizen, Sara M; Crielaard, Bart J; Ippel, Johannes H; Boelens, Rolf; Bakker, Chris J G; Storm, Gert; Lammers, Twan; Bartels, Lambertus W

2014-01-01

193

Description of two-process surface topography  

NASA Astrophysics Data System (ADS)

After two machining processes, a large number of surface topography measurements were made using Talyscan 150 stylus measuring equipment. The measured samples were divided into two groups. The first group contained two-process surfaces of random nature, while the second group used random-deterministic textures of random plateau parts and portions of deterministic valleys. For comparison, one-process surfaces were also analysed. Correlation and regression analysis was used to study the dependencies among surface texture parameters in 2D and 3D systems. As the result of this study, sets of parameters describing multi-process surface topography were obtained for two-process surfaces of random and of random-deterministic types.

Grabon, W.; Pawlus, P.

2014-04-01

194

ATM Coastal Topography-Alabama 2001  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived first surface (FS) topography were produced collaboratively by the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of the Alabama coastline, acquired October 3-4, 2001. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative scanning Lidar instrument originally developed by NASA, and known as the Airborne Topographic Mapper (ATM), was used during data acquisition. The ATM system is a scanning Lidar system that measures high-resolution topography of the land surface, and incorporates a green-wavelength laser operating at pulse rates of 2 to 10 kilohertz. Measurements from the laser ranging device are coupled with data acquired from inertial navigation system (INS) attitude sensors and differentially corrected global positioning system (GPS) receivers to measure topography of the surface at accuracies of +/-15 centimeters. The nominal ATM platform is a Twin Otter or P-3 Orion aircraft, but the instrument may be deployed on a range of light aircraft. Elevation measurements were collected over the survey area using the ATM system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for pre-survey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is routinely used to create maps that represent submerged or first surface topography.

Nayegandhi, Amar; Yates, Xan; Brock, John C.; Sallenger, A.H.; Bonisteel, Jamie M.; Klipp, Emily S.; Wright, C. Wayne

2009-01-01

195

Diffraction imaging (topography) with monochromatic synchrotron radiation  

NASA Technical Reports Server (NTRS)

Structural information of special interest to crystal growers and device physicists is now available from high resolution monochromatic synchrotron diffraction imaging (topography). In the review, the importance of superior resolution in momentum transfer and in space is described, and illustrations are taken from a variety of crystals: gallium arsenide, cadmium telluride, mercuric iodide, bismuth silicon oxide, and lithium niobate. The identification and understanding of local variations in crystal growth processes are shown. Finally, new experimental opportunities now available for exploitation are indicated.

Steiner, Bruce; Kuriyama, Masao; Dobbyn, Ronald C.; Laor, Uri

1988-01-01

196

Karst Topography: Teacher's Guide and Paper Model  

NSDL National Science Digital Library

This lesson uses paper models to help students understand karst processes, why caves develop in limestone, and how karst topography develops. Introductory materials explain how ground- or surface waters can dissolve limestone, some features of karst landscapes (sinkholes, disappearing streams), and some features of caves (stalagmites, stalactites, flowstone). A teacher's guide provides patterns and instructions for building the models, and a glossary and references are included.

197

ATM Coastal Topography-Mississippi, 2001  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of lidar-derived first-surface (FS) topography were produced collaboratively by the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of the Mississippi coastline, from Lakeshore to Petit Bois Island, acquired September 9-10, 2001. The datasets are made available for use as a management tool to research scientists and natural-resource managers. An innovative scanning lidar instrument originally developed by NASA, and known as the Airborne Topographic Mapper (ATM), was used during data acquisition. The ATM system is a scanning lidar system that measures high-resolution topography of the land surface and incorporates a green-wavelength laser operating at pulse rates of 2 to 10 kilohertz. Measurements from the laser-ranging device are coupled with data acquired from inertial navigation system (INS) attitude sensors and differentially corrected global positioning system (GPS) receivers to measure topography of the surface at accuracies of +/-15 centimeters. The nominal ATM platform is a Twin Otter or P-3 Orion aircraft, but the instrument may be deployed on a range of light aircraft. Elevation measurements were collected over the survey area using the ATM system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of lidar data in an interactive or batch mode. Modules for presurvey flight-line definition, flight-path plotting, lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is used routinely to create maps that represent submerged or first-surface topography.

Nayegandhi, Amar; Yates, Xan; Brock, John C.; Sallenger, A.H.; Klipp, Emily S.; Wright, C. Wayne

2009-01-01

198

Topography measurement of specular and diffuse surfaces  

NASA Astrophysics Data System (ADS)

We measured the topography of lens by using a technique of diffuse reflection (fringe projection technique) and by a method based on specular reflection technique (similar to Placido disk system). The obtained results with both techniques are compared with those obtained with a spherometer. The retrieval of the three-dimensional shape of the lens is an issue of great interest for wide medical application, particularly in ophthalmology.

Serrano García, David Ignacio; Martínez García, Amalia; Rayas-Alvarez, Juan Antonio

2010-08-01

199

Impacts of Topography on Sea Level Change  

NSDL National Science Digital Library

This lesson is comprised of three activities (three class periods). Students use web-based animations to explore the impacts of ice melt and changes to sea level. Students are introduced to topographic maps by doing a hands-on activity to model the contours of an island. Students examine the relationship between topography and sea level change by mapping changing shorelines using a topographic map.

2007-01-01

200

The topography of the nuclear fission barrier  

Microsoft Academic Search

Fission theory first developed within the framework of the liquid drop model. Shell model concepts were introduced into fission\\u000a theory much later than they were in nuclear structure theory, but then with spectacular success in explaining striking experimental\\u000a results then emerging in actinide fission. In the last two decades the complex topography of the fission barrier that is the\\u000a result

J E Lynn

1989-01-01

201

Absolute radiance re-calibration of FIRST  

NASA Astrophysics Data System (ADS)

The FIRST (Far-InfraRed Spectroscopy of the Troposphere) instrument is a 10 to 100 micron spectrometer with 0.64 micron resolution designed to measure the complete mid and far-infrared radiance of the Earth's Atmosphere. FIRST has been successfully used to obtain high-quality atmospheric radiance data from the ground and from a high-altitude balloon. A Fourier transform interferometer is used to provide the spectral resolution and two on-board blackbodies are used for calibration. This paper discusses the recent re-calibration of FIRST at Space Dynamics Laboratory for absolute radiance accuracy. The calibration used the LWRICS (Long Wave Infrared Calibration Source) blackbody, which NIST testing shows to be accurate to the ~100 mK level in brightness temperature. There are several challenges to calibrating FIRST, including the large dynamic range, out of phase light, and drift in the interferogram phase. The accuracy goal for FIRST was 0.2 K over most of the 10 to 100 micron range, and results show FIRST meets this goal for a range of target temperatures.

Latvakoski, Harri; Mlynczak, Martin; Johnson, David; Cageao, Rich; Swasey, Jason; Johnson, Kendall

2012-10-01

202

Adaptive Topographies and Equilibrium Selection in an Evolutionary Game  

PubMed Central

It has long been known in the field of population genetics that adaptive topographies, in which population equilibria maximise mean population fitness for a trait regardless of its genetic bases, do not exist. Whether one chooses to model selection acting on a single locus or multiple loci does matter. In evolutionary game theory, analysis of a simple and general game involving distinct roles for the two players has shown that whether strategies are modelled using a single ‘locus’ or one ‘locus’ for each role, the stable population equilibria are unchanged and correspond to the fitness-maximising evolutionary stable strategies of the game. This is curious given the aforementioned population genetical results on the importance of the genetic bases of traits. Here we present a dynamical systems analysis of the game with roles detailing how, while the stable equilibria in this game are unchanged by the number of ‘loci’ modelled, equilibrium selection may differ under the two modelling approaches. PMID:25706762

Osinga, Hinke M.; Marshall, James A. R.

2015-01-01

203

Adaptive topographies and equilibrium selection in an evolutionary game.  

PubMed

It has long been known in the field of population genetics that adaptive topographies, in which population equilibria maximise mean population fitness for a trait regardless of its genetic bases, do not exist. Whether one chooses to model selection acting on a single locus or multiple loci does matter. In evolutionary game theory, analysis of a simple and general game involving distinct roles for the two players has shown that whether strategies are modelled using a single 'locus' or one 'locus' for each role, the stable population equilibria are unchanged and correspond to the fitness-maximising evolutionary stable strategies of the game. This is curious given the aforementioned population genetical results on the importance of the genetic bases of traits. Here we present a dynamical systems analysis of the game with roles detailing how, while the stable equilibria in this game are unchanged by the number of 'loci' modelled, equilibrium selection may differ under the two modelling approaches. PMID:25706762

Osinga, Hinke M; Marshall, James A R

2015-01-01

204

EAARL topography: Assateague Island National Seashore  

USGS Publications Warehouse

This Web site contains 58 lidar-derived bare earth topography maps and GIS files for the Assateague Island National Seashore. These lidar-derived topography maps were produced as a collaborative effort between the U.S. Geological Survey (USGS) Coastal and Marine Geology Program, FISC St. Petersburg, Florida, the National Park Service (NPS) South Florida/Caribbean Network Inventory and Monitoring Program, and the National Aeronautics and Space Administration (NASA) Wallops Flight Facility. One objective of this research is to create techniques to survey coral reefs and barrier islands for the purposes of geomorphic change studies, habitat mapping, ecological monitoring, change detection, and event assessment. As part of this project, data from an innovative instrument under development at the NASA Wallops Flight Facility, the NASA Experimental Airborne Advanced Research Lidar (EAARL) are being used. This sensor has the potential to make significant contributions in this realm for measuring subaerial and submarine topography wthin cross-environment surveys. High spectral resolution, water-column correction, and low costs were found to be key factors in providing accurate and affordable imagery to costal resource managers.

Brock, John C.; Wright, C. Wayne; Patterson, Matt; Nayegandhi, Amar; Travers, Laurinda J.

2007-01-01

205

Corneal topography of excimer laser photorefractive keratectomy.  

PubMed

The application of the 193 nm excimer laser for keratorefractive surgery promises to deliver a higher degree of precision and predictability than traditional procedures such as radial keratotomy. The development and evaluation of keratorefractive surgery have benefited from the parallel advances made in the field of corneal topography analysis. We used the Computed Anatomy Topography Modeling System (TMS-1) to analyze a Louisiana State University (LSU) Eye Center series of patients who had photorefractive keratectomy for the treatment of myopia with the VISX Twenty/Twenty excimer laser system. The excimer ablations were characterized by a relatively uniform distribution of surface powers within the treated zone. In the few cases that exhibited marked refractive regression, corneal topography analysis showed correlative changes. With topographical analysis, centration of the ablations relative to the center of the pupil could be evaluated. Marked improvement in centration occurred in the patients of LSU Series IIB in which the procedure to locate the point on the cornea directly over the pupil's center during surgery was refined. Corneal topographical analysis provides objective measures of keratorefractive surgical results and is able to measure the precise tissue removal effect of excimer laser ablation without the uncertainties caused by measuring visual acuity alone. Our observations forecast the need for improved aids to center the laser ablations and for the development of a course of treatment to prevent post-ablation stromal remodeling. PMID:8450433

Klyce, S D; Smolek, M K

1993-01-01

206

EAARL topography: George Washington Birthplace National Monument  

USGS Publications Warehouse

This Web site contains Lidar-derived topography (first return and bare earth) maps and GIS files for George Washington Birthplace National Monument in Virginia. These lidar-derived topography maps were produced as a collaborative effort between the U.S. Geological Survey (USGS) Coastal and Marine Geology Program, FISC St. Petersburg, the National Park Service (NPS), Northeast Coastal and Barrier Network, Inventory and Monitoring Program, and the National Aeronautics and Space Administration (NASA) Wallops Flight Facility. One objective of this research is to create techniques to survey coral reefs and barrier islands for the purposes of geomorphic change studies, habitat mapping, ecological monitoring, change detection, and event assessment. As part of this project, data from an innovative instrument under development at the NASA Wallops Flight Facility, the NASA Experimental Airborne Advanced Research Lidar (EAARL) are being used. This sensor has the potential to make significant contributions in this realm for measuring subaerial and submarine topography wthin cross-environment surveys. High spectral resolution, water-column correction, and low costs were found to be key factors in providing accurate and affordable imagery to coastal resource managers.

Brock, John C.; Wright, C. Wayne; Patterson, Matt; Nayegandhi, Amar; Patterson, Judd

2007-01-01

207

EAARL topography: Cape Cod National Seashore  

USGS Publications Warehouse

This Web site contains 90 Lidar-derived bare earth topography maps and GIS files for the Cape Cod National Seashore. These Lidar-derived topography maps were produced as a collaborative effort between the U.S. Geological Survey (USGS) Florida Integrated Science Center (FISC) St. Petersburg, Florida, the National Park Service (NPS), Northeast Coastal and Barrier Network, Inventory and Monitoring Program, and the National Aeronautics and Space Administration (NASA) Wallops Flight Facility. One objective of this research is to create techniques to survey coral reefs and barrier islands for the purposes of geomorphic change studies, habitat mapping, ecological monitoring, change detection, and event assessment. As part of this project, data from an innovative instrument under development at the NASA Wallops Flight Facility, the NASA Experimental Airborne Advanced Research Lidar (EAARL) are being used. This sensor has the potential to make significant contributions in this realm for measuring subaerial and submarine topography wthin cross-environment surveys. High spectral resolution, water-column correction, and low costs were found to be key factors in providing accurate and affordable imagery to coastal resource managers.

Brock, John C.; Wright, C. Wayne; Patterson, Matt; Nayegandhi, Amar; Travers, Laurinda J.

2007-01-01

208

An absolute Johnson noise thermometer  

E-print Network

We developed an absolute Johnson noise thermometer (JNT), an instrument to measure the thermodynamic temperature of a sensing resistor, with traceability to voltage, resistance and frequency quantities. The temperature is measured in energy units, and can be converted to SI units (kelvin) with the accepted value of the Boltzmann constant kb; or, conversely, it can be employed to perform measurements at the triple point of water, and obtain a determination of kb. The thermometer is composed of a correlation spectrum analyzer an a calibrated noise source, both constructed around commercial mixed-signal boards. The calibrator generates a pseudorandom noise, by digital synthesis and amplitude scaling with inductive voltage dividers; the signal spectrum is a frequency comb covering the measurement bandwidth. JNT measurements at room temperature are compatible with those of a standard platinum resistance thermometer within the combined uncertainty of 60 ppm. A path towards future improvements of JNT accuracy is also sketched.

Luca Callegaro; Vincenzo D'Elia; Marco Pisani; Alessio Pollarolo

2009-01-30

209

Dependence of Eemian Greenland temperature reconstructions on the ice sheet topography  

NASA Astrophysics Data System (ADS)

The influence of a reduced Greenland Ice Sheet (GrIS) on Greenland's surface climate during the Eemian interglacial is studied using a set of simulations with different GrIS realizations performed with a comprehensive climate model. We find a distinct impact of changes in the GrIS topography on Greenland's surface air temperatures (SAT) even when correcting for changes in surface elevation, which influences SAT through the lapse rate effect. The resulting lapse-rate-corrected SAT anomalies are thermodynamically driven by changes in the local surface energy balance rather than dynamically caused through anomalous advection of warm/cold air masses. The large-scale circulation is indeed very stable among all sensitivity experiments and the Northern Hemisphere (NH) flow pattern does not depend on Greenland's topography in the Eemian. In contrast, Greenland's surface energy balance is clearly influenced by changes in the GrIS topography and this impact is seasonally diverse. In winter, the variable reacting strongest to changes in the topography is the sensible heat flux (SHF). The reason is its dependence on surface winds, which themselves are controlled to a large extent by the shape of the GrIS. Hence, regions where a receding GrIS causes higher surface wind velocities also experience anomalous warming through SHF. Vice-versa, regions that become flat and ice-free are characterized by low wind speeds, low SHF, and anomalous low winter temperatures. In summer, we find surface warming induced by a decrease in surface albedo in deglaciated areas and regions which experience surface melting. The Eemian temperature records derived from Greenland proxies, thus, likely include a temperature signal arising from changes in the GrIS topography. For the Eemian ice found in the NEEM core, our model suggests that up to 3.1 °C of the annual mean Eemian warming can be attributed to these topography-related processes and hence is not necessarily linked to large-scale climate variations.

Merz, N.; Born, A.; Raible, C. C.; Fischer, H.; Stocker, T. F.

2014-06-01

210

Dependence of Eemian Greenland temperature reconstructions on the ice sheet topography  

NASA Astrophysics Data System (ADS)

The influence of a reduced Greenland ice sheet (GrIS) on Greenland's surface climate during the Eemian interglacial is studied using a comprehensive climate model. We find a distinct impact of changes in the GrIS topography on Greenland's surface air temperatures (SAT) even when correcting for changes in surface elevation which influences SAT through the lapse rate effect. The resulting lapse rate corrected SAT anomalies are thermodynamically driven by changes in the local surface energy balance rather than dynamically caused through anomalous advection of warm/cold air masses. The large-scale circulation is indeed very stable among all sensitivity experiments and the NH flow pattern does not depend on Greenland's topography in the Eemian. In contrast, Greenland's surface energy balance is clearly influenced by changes in the GrIS topography and this impact is seasonally diverse. In winter, the variable reacting strongest to changes in the topography is the sensible heat flux (SHFLX). The reason is its dependence on surface winds, which themselves are controlled to a large extent by the shape of the GrIS. Hence, regions where a receding GrIS causes higher surface wind velocities also experience anomalous warming through SHFLX. Vice-versa, regions that become flat and ice-free are characterized by low wind speeds, low SHFLX and anomalous cold winter temperatures. In summer, we find surface warming induced by a decrease in surface albedo in deglaciated areas and regions which experience surface melting. The Eemian temperature records derived from Greenland proxies, thus, likely include a temperature signal arising from changes in the GrIS topography. For the NEEM ice core site, our model suggests that up to 3.2 °C of the annual mean Eemian warming can be attributed to these topography-related processes and hence is not necessarily linked to large-scale climate variations.

Merz, N.; Born, A.; Raible, C. C.; Fischer, H.; Stocker, T. F.

2013-12-01

211

CZARNOTA ET AL.:DYNAMIC TOPOGRAPHY AROUND AUSTRALIA Residual Topography Estimates From Wide Angle Seismic  

E-print Network

maximum LSD57 Curray et al. (1977) 108.150 -14.950 -34 -87 -153 maximum LSD58 Curray et al. (1977) 115.550 -13.783 -472 -554 -651 maximum LSD59 Curray et al. (1977) 118.433 -13.517 -370 -451 -546 maximum MSN12

Cambridge, University of

212

The Reliability of Puff Topography and Subjective Responses During Ad lib Smoking of a Single Cigarette  

PubMed Central

Introduction: Acute smoking behavior (i.e., puff topography) and subjective responses during the ad lib smoking of a single cigarette in the laboratory may provide useful measures of smoking reinforcement and reward, respectively. However, the reliability of such measures is not clear, leaving uncertain the utility of a single assessment of smoking behavior as an individual difference measure. Methods: Dependent smokers (N = 94) smoked normally prior to each of 4 laboratory sessions during which they were instructed to smoke 1 cigarette of their preferred brand in ad libitum and unblinded fashion and then rate it for subjective effects. Puff topography (puff number, total volume, and maximum volume) was assessed via portable Clinical Research Support System device. Subjective reward and perception were assessed by visual analog scales of “liking” and “how strong,” respectively. The reliability of puff topography and subjective measures was determined across days by intra-class correlations (ICCs). Differences due to sex and nicotine dependence (high and low Fagerström Test for Nicotine Dependence score) were also examined. Results: Reliability was highly significant for each measure. ICCs were .70 for total puff volume, .60 for maximum puff volume, .73 for puff number, .64 for liking, and .78 for how strong. Reliability generally did not differ by sex or dependence, but absolute values for total volume and maximum puff volume were greater in men and in high dependent smokers. Liking was also greater in high dependent smokers. Conclusions: Puff topography and subjective measures during the ad lib smoking of a single cigarette are highly reliable. Smoking responses during a single ad lib smoking session may be useful in identifying stable individual differences in smoking reinforcement and reward. PMID:22039077

Karelitz, Joshua L.; Giedgowd, Grace E.; Conklin, Cynthia A.

2012-01-01

213

Mantle flow modeling of the anomalous topography in the south-east Carpathians  

NASA Astrophysics Data System (ADS)

The neotectonic evolution of the Carpathians is dominated by collisions of irregular continental fragments and accretion of nappe stacks due to the Alpine orogenic activity. The geological record indicates that the uplift of the Carpathian fold thrust belt and subsidence of the adjacent Focsani (foredeep) basin occurred coevally in the aftermath of Alpine collision. Recent seismological studies indicate a distinct high velocity body (Vrancea slab) beneath the Focsani basin (42 km thick crust) and low velocity upper mantle beneath the high Carpathians (35 km crustal thickness). A suite of models has been proposed to explain the pattern of anomalous surface topography in the region; however no models have considered the role of underlying mantle dynamics/flow. Here we test that whether the observed anomalous uplift/subsidence in the southeastern corner of the Carpathians - with a > 1 km elevation- and adjacent 13 km deep Focsani basin may have been formed due to the dynamical effects of mantle flow. A conversion of seismic tomography velocity anomalies to temperature field was performed as an input into a series of 2-D thermo-mechanical numerical models. Based on the simple isostasy formula, we quantify the residual topography calculations (non-isostatic component of topography) to further reconcile them with our dynamic modeling interpretations. Our results suggest that active mantle flow beneath the Carpathians may possibly explain the current topographic anomalies (e.g., dynamic uplift/subsidence) beneath this region.

?engül Uluocak, Ebru; Gö?Ü?, O?uz H.; Komut, Tolga; Pysklywec, Russell N.

2014-05-01

214

Study of the Taiwanese Orogen from Absolute Gravity Data  

NASA Astrophysics Data System (ADS)

The island of Taiwan is located on the convergent boundary between the Philippine Sea Plate and the Chinese continental margin. In south-central Taiwan, the collision between the Luzon volcanic arc and the Chinese continental margin has caused intense crustal thickening and shortening in the rising mountain range. The mountain building processes are very alive and well illustrated by the rugged topography, rapid uplift and denudation, young tectonic landforms, active faulting and numerous earthquakes. The project AGTO proposes to study this natural laboratory of building of the mountain ranges using absolute gravimetry (AG). It also includes relative gravimetry (RG), GPS measurements and modelling. The target area is the southern part of the Island, for the Luzon volcanic arc to the east (Lutao island) to the western coastal plain (Tainan county), crossing the Coastal and Central ranges. This region probably suffers the highest rates of rising (between 1 and 2 cm/year of vertical movement in the Central range documented by permanent GPS measurements). Two AG measurements of the nine AGTO gravity bases have been performed respectively in November 2006 and November 2008. We will present these data and compare with models. Using simple models, we have estimated vertical movements and gravity field's variations which can be expected near the AG sites. Gravity variations due to the deformations are dominated by plate and free air effects, i.e. elevation of the topography. By comparison with these effects, those generated by mass transfers are weak: maximum 0.1 microgal/yr with the thin-skinned tectonic and 0.4 microgal/yr with the thick-skinned tectonic.

Masson, F.; Mouyen, M.; Hwang, C.; Cheng, C.; Lee, C.; Le Moigne, N.; Hinderer, J.; Cattin, R.; Luck, B.; Bayer, R.; Malavieille, J.

2008-12-01

215

Frequency spectra of absolute optical instruments  

NASA Astrophysics Data System (ADS)

We analyse frequency spectra of absolute optical instruments and show that they have very specific properties: the eigenfrequencies form tight groups that are almost equidistantly spaced. We prove this by theoretical analysis and demonstrate by numerically calculated spectra of various examples of absolute instruments. We also show that in rotationally and spherically symmetric absolute instruments a source, its image and the centre of the device must lie on a straight line.

Tyc, Tomáš; Danner, Aaron

2012-08-01

216

Topography and subduction geometry in the central Andes: Clues to the mechanics of a noncollisional orogen  

NASA Technical Reports Server (NTRS)

The central Andeean orogen between 12 deg and 32 deg S latitude exhibits a high degree of spatial order: principally an extraordinary bilateral symmetry that is common to the Earth's surface, the underlying Wadati-Benioff zone, and the Nazca/South America plate kinematics, which has been stable since the mid-Tertiary. This spatial order must reflect the physical mechanisms of mountain building in this noncollisional orogen. The shapes of the topography and subduction zone can be reduced to symmetric and antisummeric components relative to any verical symmetry plane; the particular plaen which minimizes the antisymmetry (and maximizes the symmetry) is well resolved and is essentially coincident with the stable Euler equator of Nacza/South America relative motion since the mid-Tertiary. That the topography, subduction geometry, and persistent mid-Tertiary plate kinematics share common spatial and geometric elements suggests that he distribution of topography in this orogen depends strongly on the dynamics of subduction. Other factors that might affect the topography and underlying tectonics, such as climate and inherited strutura fabric, which have different spatial characterisitcs, must be of less significance at a continental scale. Furthermore, the small components of asymmetry among the various elements of the orogen appear to be mutually relate in a simple way; it is possible that this coupled asymmetry is associated with a late Teriary change in plate kinematics. These observations suggest that there is a close connection between plate tectonics and the form of the Earth's surface in this noncollisional setting. It follows hta the distribution of topography near convergent plate boundaries may provide a powerful constraing for understanding the dynamics of subduction.

Gephart, John W.

1994-01-01

217

On topography and geoid from 2-D stagnant lid convection calculations  

NASA Astrophysics Data System (ADS)

Temperature-dependent convection in the stagnant lid regime with a Frank-Kamenetskii and Arrhenius viscosity formulation are compared. When properly scaled, the Nusselt number and root-mean-square velocity of the fluid for the two viscosity formulations are similar but the surface stresses and hence predicted dynamic topography and geoid differ significantly. The Arrhenius viscosity formulation results are insensitive to a viscosity cutoff at the high viscosity limit as long as the cutoff is 104 times the basal viscosity. The condition number for stagnant lid convection matrices using a penalty formulation is smaller than the penalty number times viscosity contrast value (a reasonable estimate of the condition number), explaining why large viscosity contrast convection problems with the penalty method agree with other formulations and analytic solutions. The difference in magnitude between the maximum and minimum dynamic topography could be used to constrain the magnitude of the viscosity contrast across the stagnant lid in planetary bodies.

King, Scott D.

2009-03-01

218

Reconstituting ring-rafts in bud-mimicking topography of model membranes  

PubMed Central

During vesicular trafficking and release of enveloped viruses, the budding and fission processes dynamically remodel the donor cell membrane in a protein- or a lipid-mediated manner. In all cases, in addition to the generation or relief of the curvature stress, the buds recruit specific lipids and proteins from the donor membrane through restricted diffusion for the development of a ring-type raft domain of closed topology. Here, by reconstituting the bud topography in a model membrane, we demonstrate the preferential localization of cholesterol- and sphingomyelin-enriched microdomains in the collar band of the bud-neck interfaced with the donor membrane. The geometrical approach to the recapitulation of the dynamic membrane reorganization, resulting from the local radii of curvatures from nanometre-to-micrometre scales, offers important clues for understanding the active roles of the bud topography in the sorting and migration machinery of key signalling proteins involved in membrane budding. PMID:25058275

Ryu, Yong-Sang; Lee, In-Ho; Suh, Jeng-Hun; Park, Seung Chul; Oh, Soojung; Jordan, Luke R.; Wittenberg, Nathan J.; Oh, Sang-Hyun; Jeon, Noo Li; Lee, Byoungho; Parikh, Atul N.; Lee, Sin-Doo

2014-01-01

219

Macromolecular Topography Leaps into the Digital Age  

NASA Technical Reports Server (NTRS)

A low-cost, real-time digital topography system is under development which will replace x-ray film and nuclear emulsion plates. The imaging system is based on an inexpensive surveillance camera that offers a 1000x1000 array of 8 im square pixels, anti-blooming circuitry, and very quick read out. Currently, the system directly converts x-rays to an image with no phosphor. The system is small and light and can be easily adapted to work with other crystallographic equipment. Preliminary images have been acquired of cubic insulin at the NSLS x26c beam line. NSLS x26c was configured for unfocused monochromatic radiation. Six reflections were collected with stills spaced from 0.002 to 0.001 degrees apart across the entire oscillation range that the reflections were in diffracting condition. All of the reflections were rotated to the vertical to reduce Lorentz and beam related effects. This particular CCD is designed for short exposure applications (much less than 1 sec) and so has a relatively high dark current leading to noisy raw images. The images are processed to remove background and other system noise with a multi-step approach including the use of wavelets, histogram, and mean window filtering. After processing, animations were constructed with the corresponding reflection profile to show the diffraction of the crystal volume vs. the oscillation angle as well as composite images showing the parts of the crystal with the strongest diffraction for each reflection. The final goal is to correlate features seen in reflection profiles captured with fine phi slicing to those seen in the topography images. With this development macromolecular topography finally comes into the digital age.

Lovelace, J.; Bellamy, H.; Snell, E. H.; Borgstahl, G.

2003-01-01

220

Absolute instabilities of standing pulses  

NASA Astrophysics Data System (ADS)

We analyse instabilities of standing pulses in reaction-diffusion systems that are caused by an absolute instability of the homogeneous background state. Specifically, we investigate the impact of pitchfork, Turing and oscillatory bifurcations of the rest state on the standing pulse. At a pitchfork bifurcation, the standing pulse continues through the bifurcation point, where it selects precisely one of the two bifurcating equilibria. At a Turing instability, symmetric pulses emerge that are spatially asymptotic to the bifurcating spatially periodic Turing patterns. These pulses exist for any wavenumber inside the Eckhaus stability band. Oscillatory instabilities of the background state lead to genuinely time-periodic pulses that emit small wave trains with a unique selected wavenumber. We analyse these three bifurcations by studying the standing-wave and modulated-wave equations: in this setup, pulses correspond to homoclinic orbits to equilibria that undergo reversible bifurcations. We use blow-up techniques to show that the relevant stable and unstable manifolds can be continued across the bifurcation point and to investigate both the existence and stability of the bifurcating waves.

Sandstede, Björn; Scheel, Arnd

2005-01-01

221

Improving HST Pointing & Absolute Astrometry  

NASA Astrophysics Data System (ADS)

Accurate absolute astrometry is becoming increasingly important in an era of multi-mission archives and virtual observatories. Hubble Space Telescope's (HST's) Guidestar Catalog II (GSC2) has reduced coordinate error to around 0.25 arcsecond, a factor 2 or more compared with GSC1. With this reduced catalog error, special attention must be given to calibrate and maintain the Fine Guidance Sensors (FGSs) and Science Instruments (SIs) alignments in HST to a level well below this in order to ensure that the accuracy of science product's astrometry keywords and target positioning are limited only by the catalog errors. After HST Servicing Mission 4, such calibrations' improvement in "blind" pointing accuracy will allow for more efficient COS acquisitions. Multiple SIs and FGSs each have their own footprints in the spatially shared HST focal plane. It is the small changes over time in primarily the whole-body positions & orientations of these instruments & guiders relative to one another that is addressed by this work. We describe the HST Cycle 15 program CAL/OTA 11021 which, along with future variants of it, determines and maintains positions and orientations of the SIs and FGSs to better than 50 milli- arcseconds and 0.04 to 0.004 degrees of roll, putting errors associated with the alignment sufficiently below GSC2 errors. We present recent alignment results and assess their errors, illustrate trends, and describe where and how the observer sees benefit from these calibrations when using HST.

Lallo, Matthew; Nelan, E.; Kimmer, E.; Cox, C.; Casertano, S.

2007-05-01

222

Prelaunch absolute radiometric calibration of LANDSAT-4 protoflight Thematic Mapper  

NASA Technical Reports Server (NTRS)

Results are summarized and analyzed from several prelaunch tests with a 122 cm integrating sphere used as part of the absolute radiometric calibration experiments for the protoflight TM sensor carried on the LANDSAT-4 satellite. The calibration procedure is presented and the radiometric sensitivity of the TM is assessed. The internal calibrator and dynamic range after calibration are considered. Tables show dynamic range after ground processing, spectral radiance to digital number and digital number to spectral radiance values for TM bands 1, 2, 3, 4, 5, 7 and for channel 4 of band 6.

Barker, J. L.; Ball, D. L.; Leung, K. C.; Walker, J. A.

1984-01-01

223

EAARL Coastal Topography - Sandy Hook 2007  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived topography were produced as a collaborative effort between the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL; the National Park Service (NPS), Northeast Coastal and Barrier Network, Kingston, RI; and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of Gateway National Recreation Area's Sandy Hook Unit in New Jersey, acquired on May 16, 2007. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative airborne Lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL) was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) Lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive Lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multi-spectral color infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers and an integrated miniature digital inertial measurement unit, which provide for submeter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine Cessna 310 aircraft, but the instrument may be deployed on a range of light aircraft. A single pilot, a Lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for pre-survey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is routinely used to create maps that represent submerged or first surface topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

Nayegandhi, Amar; Brock, John C.; Wright, C. Wayne; Stevens, Sara; Yates, Xan; Bonisteel, Jamie M.

2008-01-01

224

Welcome to Surface Topography: Metrology and Properties  

NASA Astrophysics Data System (ADS)

I am delighted to welcome readers to this inaugural issue of Surface Topography: Metrology and Properties (STMP). In these days of citation indexes and academic reviews, it is a tough, and maybe a brave, job to start a new journal. But the subject area has never been more active and we are seeing genuine breakthroughs in the use of surfaces to control functional performance. Most manufactured parts rely on some form of control of their surface characteristics. The surface is usually defined as that feature on a component or device, which interacts with either the environment in which it is housed (or in which the device operates), or with another surface. The surface topography and material characteristics of a part can affect how fluids interact with it, how the part looks and feels and how two bearing parts will slide together. The need to control, and hence measure, surface features is becoming increasingly important as we move into a miniaturized world. Surface features can become the dominant functional features of a part and may become large in comparison to the overall size of an object. Research into surface texture measurement and characterization has been carried out for over a century and is now more active than ever, especially as new areal surface texture specification standards begin to be introduced. The range of disciplines for which the function of a surface relates to its topography is very diverse; from metal sheet manufacturing to art restoration, from plastic electronics to forensics. Until now, there has been no obvious publishing venue to bring together all these applications with the underlying research and theory, or to unite those working in academia with engineering and industry. Hence the creation of Surface Topography: Metrology and Properties . STMP will publish the best work being done across this broad discipline in one journal, helping researchers to share common themes and highlighting and promoting the extraordinary benefits this field yields across an array of applications in the modern world. To this end, we have gathered leading experts from across our scope to form our inaugural editorial board. Their broad subject knowledge and experience will help to guide the journal and ensure we meet our goal of high-quality research, published quickly, across the breadth of the subject. We are committed to providing a rapid and yet rigorous peer review process. As a launch promotion, all STMP's published content will be free to readers during 2013. The editorial board and I hope you will be as excited by the possibilities of this new journal as we are, and that you will choose to both submit your research and read STMP in the months and years to come. We look forward to reading your papers!

Leach, Richard

2013-11-01

225

Interpreting layer thickness advection in terms of eddy-topography interaction  

NASA Astrophysics Data System (ADS)

A parameterization for the spatial pattern of the eddy induced thickness advection parameter estimated from a dynamically consistent data assimilation procedure is presented. Values of the thickness advection parameter are predominantly negative (positive) over seamounts, and positive (negative) over the deep ocean in the southern (northern) hemisphere along strong currents; its magnitude is large at high latitudes but low in the tropical regions. Those characteristics motivate a parameterization based on the Coriolis parameter, the bottom depth and an eddy length scale. As a parameterization for an eddy streamfunction, the associated bolus velocities advect density anti-cyclonically (cyclonically) around seamounts (troughs). Although the parameterization has the same form as Holloway’s streamfunction for the Neptune effect, and is also related to eddy-topography interactions, Holloway’s streamfunction is in contrast applied to the momentum equation. The parameterization is independently confirmed by the flux-mean gradient relation from the output of a high resolution model. The effect of the proposed scheme is investigated using a channel model with idealized bottom topographies and a global ocean circulation model with realistic bottom topography. In agreement with the high resolution model, our scheme generates cold (warm) domes and cyclonic circulations over seamounts (troughs), which is consistent with the eddy movement in presence of the topographic ? effect. This provides a different mechanism for eddy-topography interaction than the Neptune effect, which generates circulations of opposing sign.

Liu, Chuanyu; Köhl, Armin; Stammer, Detlef

2014-09-01

226

A 360-Degree and -Order Model of Venus Topography  

NASA Technical Reports Server (NTRS)

This report presents the most recent spherical harmonic topography model of Venus developed at Jet Propulsion Laboratory. It was produced by a spherical harmonic analysis of the most complete set of Magellan altimetry data, augmented by Pioneer Venus and Venera data. The harmonic coefficients of the topography were computed to degree and order 360. Compared to previous topography models, this one has the highest correlation with the gravity field of Venus.

Rappaport, Nicole; Plaut, Jeffry J.

1996-01-01

227

A 360-degree and -order model of Venus topography  

NASA Technical Reports Server (NTRS)

This report presents the most recent spherical harmonic topography model of Venus developed at Jet Propulsion Laboratory. It was produced by a spherical harmonic analysis of the most complete set of Magellan altimetry data, augmented by Pioneer Venus and Venera data. The harmonic coefficients of the topography were computed to degree and order 360. Compared to previous topography models, this one has the highest correlation with the gravity field of Venus.

Rappaport, Nicole; Plaut, Jeffrey J.

1994-01-01

228

Optic nerve head topography and static perimetry in glaucoma diagnostics  

NASA Astrophysics Data System (ADS)

Analysis of the optic nerve head topography and static perimetry, are important in glaucoma diagnostics. Topography of the optic nerve head by Topographic Scanning Systems, carries a lot of planimetric and volumetric values. In this paper, results of optic nerve head topography and static perimetry of 116 primary open angle glaucoma cases, are discussed. Estimating correlation between topographic and perimetric data, the most valuable parameter of the topographic method is carried out. Its values in different stages of glaucoma are given.

Rzendkowski, Marek; Janiec, Slawomir; Momot-Kawalska, Barbara; Blazejewska-Meller, Grazyna

1998-10-01

229

Introducing the Mean Absolute Deviation "Effect" Size  

ERIC Educational Resources Information Center

This paper revisits the use of effect sizes in the analysis of experimental and similar results, and reminds readers of the relative advantages of the mean absolute deviation as a measure of variation, as opposed to the more complex standard deviation. The mean absolute deviation is easier to use and understand, and more tolerant of extreme…

Gorard, Stephen

2015-01-01

230

Astronomy Ranking Task: Apparent and Absolute Magnitude  

E-print Network

Astronomy Ranking Task: Apparent and Absolute Magnitude Exercise #4 Description: The table below provides partial magnitude and distance information for five stars (A - E). Star Name Apparent Magnitude Absolute Magnitude Distance from Earth (parsecs) A -1 3 B 5 1 C 0 10 D 1 10,000 E 3 3 A. Ranking

Farritor, Shane

231

COMMUNICATIONS Determination of absolute photoionization cross sections  

E-print Network

product branching ratios in scattering experiments, absolute photo- ionization cross sections are requiredCOMMUNICATIONS Determination of absolute photoionization cross sections for vinyl and propargyl cross sections for vinyl and propargyl radicals at 10 eV of 11.1 2.2 and 8.3 1.6 Mb, respectively. From

Neumark, Daniel M.

232

Frequency spectra of absolute optical instruments  

NASA Astrophysics Data System (ADS)

We analyze frequency spectra of optical devices called absolute optical instruments. We show that they have very specific properties: the eigenfrequencies form tight, almost equidistantly spaced groups. We prove this by theoretical analysis and demonstrate by numerically calculated spectra of various examples of absolute instruments.

Tyc, Tomáš; Danner, Aaron

2012-09-01

233

A puzzle about the Scandinavian topography  

NASA Astrophysics Data System (ADS)

In this contribution we analyze the topography of Scandinavia with a method recently used to assess the age and the stage of topographical evolution of the Alps (Hergarten, Wagner & Stüwe, EPSL 297:453, 2010). The method considers the mean (channel) slope at fixed catchment size as a function of the elevation. For continental Europe (without Scandinavia) we found a linear relationship without any offset up to elevations of several hundred meters, which means that slope is directly proportional to elevation. This relationship also holds for smaller parts of Europe such as the region directly draining to the Atlantic Ocean or the Mediterranean region, although the reason for this phenomenon remains unclear. In contrast, the region of Norway draining to the Atlantic Ocean west of Norway's southernmost point shows a different behavior. The slope-elevation relation follows is a straight line, too, but with a significant offset of about 500 m. Extrapolating this relation towards negative elevations suggests that zero slope would be achieved about 500 m below sea level. A possible interpretation of this vertical shift in topography might be that 500 m of glacial subsidence are still left at Norway's coast of the Atlantic Ocean. But on the other hand, analyzing the part of Scandinavia draining to Skagerrak, Kattegat and Baltic Sea yields a linear slope-elevation relationship without any vertical shift, although this region should include the center of Scandinavia's glacial subsidence.

Hergarten, S.; Stüwe, K.

2012-04-01

234

Hydrothermal circulation in fault slots with topography  

NASA Astrophysics Data System (ADS)

There are numerous cases where the circulation of hydrothermal fluid is likely to be confined within a permeable fault slot. Examples are (1) the Lost City Hydrothermal Field (LCHF) at 30 N in the Atlantic, which is likely to be controlled by large E-W faults related to the Atlantis transform fault and mass wasting on the southern wall of the Atlantis Massif, and (2) large normal faults bounding the Hess Deep rift in the East Pacific, which contain intense hydrothermal metamorphic assemblages in lower crustal gabbros formed at 200-350 ° C. This type of circulation could occur anywhere where steep faults cut the oceanic crust, including large near-axis normal faults, transform faults and faults at subduction bend zones, and could be the major way in which the upper mantle and lower crust are hydrated. It is therefore important to constrain the controls on temperature conditions of alteration and hence mineral assemblages. Previous 2-D modelling of the LCHF shows that seafloor topography and permeability structure combine together to localise the field near the highest point of the Atlantis Massif. Our new models are 3-D, based on a 10km cube with seafloor topography of ~ 2km affecting both the fault slot and impermeable wall rocks. We have used Comsol multiphysics in this modelling, with a constant basal heatflow corresponding to the near conductive thermal gradient measured in IODP Hole 1309D, 5km north of the LCHF, and a constant temperature seafloor boundary condition. The wall rocks of the slot have a permeability of 10-17 m2 while permeability in the slot is varied between 10-14 and 10-15 m2. Initial conditions are a conductive thermal structure corresponding to the basal heatflow at steady state. Generic models not based on any particular known topography quickly stabilise a hydrothermal system in the fault slot with a single upflow zone close to the model edge with highest topography. In models with a depth of circulation in the fault slot of about 6 km, after an initial period of higher temperature venting which removes heat from the initial condition, venting temperature is approximately 200 ° C with a permeability of 3x10-15 m2. This falls to about 170 ° C with a permeability of 5x10-15 m2. Temperatures can be reduced by restricting the depth of hydrothermal circulation. These temperatures correspond to prehnite-chlorite assemblages seen in fault rocks at Hess Deep, but are higher than those observed at the LCHF. Work is continuing to vary permeability, fault slot geometry and topography to better match the conditions in the Atlantis Massif, and to model the effects of dyke intrusion into the fault zone as observed at Hess Deep.

Titarenko, Sofya; McCaig, Andrew

2014-05-01

235

Origin of bending in uncoated microcantilever - Surface topography?  

SciTech Connect

We provide direct experimental evidence to show that difference in surface topography on opposite sides of an uncoated microcantilever induces bending, upon exposure to water molecules. Examination on opposite sides of the microcantilever by atomic force microscopy reveals the presence of localized surface features on one side, which renders the induced stress non-uniform. Further, the root mean square inclination angle characterizing the surface topography shows a difference of 73° between the opposite sides. The absence of deflection in another uncoated microcantilever having similar surface topography confirms that in former microcantilever bending is indeed induced by differences in surface topography.

Lakshmoji, K.; Prabakar, K.; Tripura Sundari, S., E-mail: sundari@igcar.gov.in; Jayapandian, J.; Tyagi, A. K.; Sundar, C. S. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)

2014-01-27

236

Absolute instability of the Gaussian wake profile  

NASA Technical Reports Server (NTRS)

Linear parallel-flow stability theory has been used to investigate the effect of viscosity on the local absolute instability of a family of wake profiles with a Gaussian velocity distribution. The type of local instability, i.e., convective or absolute, is determined by the location of a branch-point singularity with zero group velocity of the complex dispersion relation for the instability waves. The effects of viscosity were found to be weak for values of the wake Reynolds number, based on the center-line velocity defect and the wake half-width, larger than about 400. Absolute instability occurs only for sufficiently large values of the center-line wake defect. The critical value of this parameter increases with decreasing wake Reynolds number, thereby indicating a shrinking region of absolute instability with decreasing wake Reynolds number. If backflow is not allowed, absolute instability does not occur for wake Reynolds numbers smaller than about 38.

Hultgren, Lennart S.; Aggarwal, Arun K.

1987-01-01

237

New Interpretation of Inertial Force and Natural Existence of Absolute Background  

E-print Network

We reinvestigate the formalism of classical particle dynamics according to the basic requirement of causal consistency, and obtain a new particle dynamical equation. In the application of this new particle dynamical equation, the new formula is more in line with the empirical laws from classical mechanics experiments than Newton's second law, but inertial reference frames are no longer required and inertial forces are no longer introduced by hand. The new dynamical equation can be straightforwardly applied in any reference frame which is irrotational with respect to the absolute background of (the whole space of) the universe, namely a moderately general principle of relativity is realized on particle dynamics. The nature of the inertial force is nothing but the real forces acting on the reference object. As far as the framework of classical mechanics is concerned, the essence of this work is nothing but an error existing in the formalism of Newton's second law being corrected. However, it may be more important that the derivation of this new particle dynamics equation strongly suggests the existence of an absolute background for the whole space of the universe. In physical concepts, the absolute background for space must be distinguished from the relative scales of space in order to be mostly compatible with the physical logic in Einstein's special relativity and general relativity. Certainly, the absolute background of space is also able to be understood as the implicit part of Newton's absolute view of space-time, but the former is more natural and more accurate in natural philosophy.

ChiYi Chen

2015-01-04

238

STS-99 Shuttle Radar Topography Mission Stability and Control  

NASA Technical Reports Server (NTRS)

The Shuttle Radar Topography Mission (SRTM) flew aboard Space Shuttle Endeavor February 2000 and used interferometry to map 80% of the Earth's landmass. SRTM employed a 200-foot deployable mast structure to extend a second antenna away from the main antenna located in the Shuttle payload bay. Mapping requirements demanded precision pointing and orbital trajectories from the Shuttle on-orbit Flight Control System (PCS). Mast structural dynamics interaction with the FCS impacted stability and performance of the autopilot for attitude maneuvers and pointing during mapping operations. A damper system added to ensure that mast tip motion remained with in the limits of the outboard antenna tracking system while mapping also helped to mitigate structural dynamic interaction with the FCS autopilot. Late changes made to the payload damper system, which actually failed on-orbit, required a redesign and verification of the FCS autopilot filtering schemes necessary to ensure rotational control stability. In-flight measurements using three sensors were used to validate models and gauge the accuracy and robustness of the pre-mission notch filter design.

Hamelin, Jennifer L.; Jackson, Mark C.; Kirchwey, Christopher B.; Pileggi, Roberto A.

2001-01-01

239

Verification of Geosat sea surface topography in the Gulf Stream extension with surface drifting buoys and hydrographic measurements  

Microsoft Academic Search

Altimeter data from Geosat have been analyzed in the Gulf Stream extension area. Horizontal maps of the sea surface height anomaly relative to an annual mean for various 17-day intervals were constructed using an objective mapping procedure. The mean sea level was approximated by the dynamic topography from climatological hydrographic data. Geostrophic surface velocities derived from the composite maps (mean

J. Willebrand; R. H. Käse; D. Stammer; H.-H. Hinrichsen; W. Krauss

1990-01-01

240

Rejuvenation of Appalachian topography caused by subsidence-induced differential erosion  

NASA Astrophysics Data System (ADS)

In ancient orogens, such as the Appalachian Mountains in the eastern United States, the difference between the high and low points--topographic relief--can continue to increase long after the tectonic forces that created the range have become inactive. Climatic forcing and mantle-induced dynamic uplift could drive formation of relief, but clear evidence is lacking in the Appalachian Mountains. Here I use a numerical simulation of dynamic topography in North America, combined with reconstructions of the sedimentation history from the Gulf of Mexico, to show that rejuvenation of topographic relief in the Appalachian Mountains since the Palaeogene period could have been caused by mantle-induced dynamic subsidence associated with sinking of the subducted Farallon slab. Specifically, I show that patterns of continental erosion and the eastward migration of sediment deposition centres in the Gulf of Mexico closely follow the locus of predicted dynamic subsidence. Furthermore, pulses of rapid sediment deposition in the Gulf of Mexico and western Atlantic correlate with enhanced erosion in the Appalachian Mountains during the Miocene epoch, caused by dynamic tilting of the continent. The model predicts that such subsidence-induced differential erosion caused flexural-isostatic adjustments of Appalachian topography that led to the development of 400 m of relief and more than 200 m of elevation. I propose that dynamically induced continental tilting may provide a mechanism for topographic rejuvenation in ancient orogens.

Liu, Lijun

2014-07-01

241

Global relativity establishes absolute time and a universal frame of reference  

Microsoft Academic Search

It has been known for several decades that the rest energy of all matter in space is essentially equal to the total gravitational energy in space. The Dynamic Universe model introduced in this paper studies the equality as a dynamic zero-energy balance of motion and gravitation in spherically closed space. In such a solution time is absolute, the fourth dimension

Tuomo Suntola

242

Temporal and spatial distribution of exhumed topography  

NASA Technical Reports Server (NTRS)

Perhaps the greatest chance for exhumation, or burial, of a landscape by terrestrial processes exists near the boundaries of the climatic belts. In the Southern Hemisphere, there is comparatively little land area within Budel's zone of extra-tropical valley formation, which contains most of the examples of exhumed topography in the Northern Hemisphere. The only examples of resurrected landforms that occur within Budel's tropical zone are located near the boundary of this zone, where climate may have changed during the Pleistocene. The ages of exhumed landforms sampled are not equally distributed through geologic time. Most of the exhumed features were created either during the Precambrian or the Tertiary periods which are commonly cited as episodes of significant landform development.

Rhodes, D. D.

1984-01-01

243

Forecasting Hurricane Impact on Coastal Topography  

NASA Astrophysics Data System (ADS)

Extreme storms can have a profound impact on coastal topography and thus on ecosystems and human-built structures within coastal regions. For instance, landfalls of several recent major hurricanes have caused significant changes to the U.S. coastline, particularly along the Gulf of Mexico. Some of these hurricanes (e.g., Ivan in 2004, Katrina and Rita in 2005, and Gustav and Ike in 2008) led to shoreline position changes of about 100 meters. Sand dunes, which protect the coast from waves and surge, eroded, losing several meters of elevation in the course of a single storm. Observations during these events raise the question of how storm-related changes affect the future vulnerability of a coast.

Plant, Nathaniel G.; Stockdon, Hilary F.; Sallenger, Asbury H.; Turco, Michael J.; East, Jeffery W.; Taylor, Arthur A.; Shaffer, Wilson A.

2010-02-01

244

Architecture and development of olivocerebellar circuit topography  

PubMed Central

The cerebellum has a simple tri-laminar structure that is comprised of relatively few cell types. Yet, its internal micro-circuitry is anatomically, biochemically, and functionally complex. The most striking feature of cerebellar circuit complexity is its compartmentalized topography. Each cell type within the cerebellar cortex is organized into an exquisite map; molecular expression patterns, dendrite projections, and axon terminal fields divide the medial-lateral axis of the cerebellum into topographic sagittal zones. Here, we discuss the mechanisms that establish zones and highlight how gene expression and neural activity contribute to cerebellar pattern formation. We focus on the olivocerebellar system because its developmental mechanisms are becoming clear, its topographic termination patterns are very precise, and its contribution to zonal function is debated. This review deconstructs the architecture and development of the olivocerebellar pathway to provide an update on how brain circuit maps form and function. PMID:23293588

Reeber, Stacey L.; White, Joshua J.; George-Jones, Nicholas A.; Sillitoe, Roy V.

2013-01-01

245

Secondary standard stars for absolute spectrophotometry  

NASA Technical Reports Server (NTRS)

Based on an adopted absolute spectral energy distribution for the primary standard star Alpha Lyrae, absolute fluxes are given for the four very metal-deficient F type subdwarfs HD 19445, HD 84937, BD + 26.2606 deg, and BD + 17.4703 deg. Somewhat inferior data are also given for HD 140283. The data are given for 40-A bands and cover the wavelength range from 3080 A to 12,000 A. The four stars, all near magnitude 9 and distributed around the sky, are intended as secondary standards for absolute spectrophotometry.

Oke, J. B.; Gunn, J. E.

1983-01-01

246

Bedrock topography beneath the Red Lake peatlands  

SciTech Connect

Detailed hydrologic investigations of peat landforms in the Red Lake Peatlands have revealed that groundwater flow is significantly related to the type of landform and vegetation community present at a given site. Hydrogeologic modeling of shallow groundwater systems suggests that bedrock topography is an important, perhaps the vital, boundary condition controlling groundwater flow. Determination of depth to bedrock beneath different peat landforms is necessary to test the hydrogeologic models and obtain a better understanding of the processes which produce them. Direct determination of bedrock depth in peatlands is hampered by the difficult conditions and high costs of boring. In addition, environmental impacts from boring activities would probably be substantial in these sensitive ecosystems. Shallow seismic methods appear to be the most promising approach to obtain the necessary data. Unfortunately the 2+ meters of peat covering Lake Agassiz sediments overlying the bedrock is not only a poor substrate for geophone emplacement, but is a strong attenuator of seismic waves. These difficulties have been overcome by constructing a tool which allows the geophones to be emplaced beneath the peat and into the top of the sediments. The shotgun cartridge source is also located beneath the peat. This combination results in very good seismic records, far better than those possible with surface sources and geophones. The results from a preliminary survey along a 600m line show that there are significant variations in bedrock topography below the peat. In a distance of less than 500m, depth to bedrock changes by about 30%, from about 55m to about 40m. This is similar to variations indicated by the models.

Miller, P.; Shaw, G.H. (Union Coll., Schenectady, NY (United States). Geology Dept.); Glaser, P. (Univ. of Minnesota, Minneapolis, MN (United States). Limnological Research Center); Siegel, D. (Syracuse Univ., NY (United States). Dept. of Geology)

1992-01-01

247

Mantle transition zone topography and structure beneath the Yellowstone hotspot  

E-print Network

Mantle transition zone topography and structure beneath the Yellowstone hotspot David Fee and Ken of the 410 and 660 km discontinuities beneath the Yellowstone hotspot are constrained using common conversion, providing no evidence for a lower mantle plume currently beneath the hotspot. The topography suggests

Dueker, Ken

248

PAR Corneal Topography System (PAR CTS): the clinical application of close-range photogrammetry.  

PubMed

The PAR Corneal Topography System (CTS) is a computer-driven corneal imaging system which uses close-range photogrammetry (rasterphotogrammetry) to measure and produce a topographic map of the corneal surface. The PAR CTS makes direct point-by-point measurements of surface elevation using a stereo-triangulation technique. The CTS uses a grid pattern composed of horizontal and vertical lines spaced about 0.2 mm (200 microns) apart. Each grid intersection comprises a surface feature which can be located in multiple images and used to generate an (x,y,z) coordinate. Unlike placido disc-based videokeratoscopes, the PAR CTS requires neither a smooth reflective surface nor precise spatial alignment for accurate imaging. In addition to surface elevation, the PAR CTS computes axial and tangential curvatures and refractive power. Difference maps are available in all curvatures, refractive power, and in absolute elevation. PMID:8587772

Belin, M W; Cambier, J L; Nabors, J R; Ratliff, C D

1995-11-01

249

Enabling Access to High-Resolution Lidar Topography for Earth Science Research  

NASA Astrophysics Data System (ADS)

High-resolution topography data acquired with lidar (light detection and ranging a.k.a. laser scanning) technology are revolutionizing the way we study the geomorphic processes acting along the Earth's surface. These data, acquired from either an airborne platform or from a tripod-mounted scanner, are emerging as a fundamental tool for research on a variety of topics ranging from earthquake hazards to ice sheet dynamics. Lidar topography data allow earth scientists to study the processes that contribute to landscape evolution at resolutions not previously possible yet essential for their appropriate representation. These datasets also have significant implications for earth science education and outreach because they provide an accurate digital representation of landforms and geologic hazards. However, along with the potential of lidar topography comes an increase in the volume and complexity of data that must be efficiently managed, archived, distributed, processed and integrated in order for them to be of use to the community. A single lidar data acquisition may generate terabytes of data in the form of point clouds, digital elevation models (DEMs), and derivative imagery. This massive volume of data is often difficult to manage and poses significant distribution challenges when trying to allow access to the data for a large scientific user community. Furthermore, the datasets can be technically challenging to work with and may require specific software and computing resources that are not readily available to many users. The U.S. National Science Foundation (NSF)-funded OpenTopography Facility (http://www.opentopography.org) is an online data access and processing system designed to address the challenges posed by lidar data, and to democratize access to these data for the scientific user community. OpenTopography provides free, online access to lidar data in a number of forms, including raw lidar point cloud data, standard DEMs, and easily accessible Google Earth visualizations. OpenTopography uses cyberinfrastructure resources to allow users, regardless of their level of expertise, to access lidar data products that can be applied to their research. In addition to data access, the system uses customized algorithms and high-performance computing resources to allow users to perform on-the-fly data processing tasks such as the generation of custom DEMs. OpenTopography's primarily focus is on large, community-oriented, scientific data sets, such as those acquired by the NSF-funded EarthScope project. We are actively expanding our holdings through collaborations with researchers and data providers to include data from a wide variety of landscapes and geologic domains. Ultimately, the goal is for OpenTopography to be the primary clearing house for Earth science-oriented high-resolution topography. This presentation will provide an overview of the OpenTopography Facility, including available data, processing capabilities and resources, examples from scientific use cases, and a snapshot of system and data usage thus far. We will also discuss current development activities related to deploying high-performance algorithms for hydrologic processing of DEMs, geomorphic change detection analysis, and the incorporation of full waveform lidar data into the system.

Crosby, Christopher; Nandigam, Viswanath; Arrowsmith, Ramon; Baru, Chaitan

2010-05-01

250

A New Gimmick for Assigning Absolute Configuration.  

ERIC Educational Resources Information Center

A five-step procedure is provided to help students in making the assignment absolute configuration less bothersome. Examples for both single (2-butanol) and multi-chiral carbon (3-chloro-2-butanol) molecules are included. (JN)

Ayorinde, F. O.

1983-01-01

251

New absolute magnitude calibrations for detached binaries  

E-print Network

Lutz-Kelker bias corrected absolute magnitude calibrations for the detached binary systems with main-sequence components are presented. The absolute magnitudes of the calibrator stars were derived at intrinsic colours of Johnson-Cousins and 2MASS (Two Micron All Sky Survey) photometric systems. As for the calibrator stars, 44 detached binaries were selected from the Hipparcos catalogue, which have relative observed parallax errors smaller than 15% ($\\sigma_{\\pi}/\\pi\\leq0.15$). The calibration equations which provide the corrected absolute magnitude for optical and near-infrared pass bands are valid for wide ranges of colours and absolute magnitudes: $-0.18magnitude calibrations of this study can be used as a convenient statistical tool to estimate the true distances of detached binaries out of Hipparcos' distance limit.

S. Bilir; T. Ak; E. Soydugan; F. Soydugan; E. Yaz; N. Filiz Ak; Z. Eker; O. Demircan; M. Helvaci

2008-06-07

252

Influence of planetary-scale topography on the diurnal thermal tide during the 1971 Martian dust storm  

NASA Technical Reports Server (NTRS)

Data obtained with the Mariner 9 infrared spectroscopy experiment during the Martian Dust Storm of 1971 to 1972 are examined for evidence of topographic influence on the atmospheric thermal structure. Temperature perturbations which are well correlated with the planetary scale topography are found superposed on the large amplitude diurnal thermal tide. Applications of tidal theory to the data indicate that the observed perturbations result from the kinematic interaction of the westward traveling diurnal wave with the large scale components of topography. The dominant mode is excited by the wave-number two topography component and is a vertically evanescent eastward traveling wave with an equivalent depth comparable to the atmospheric scale height. The principle dynamic effect of this mode is the enhancement of the amplitude of the near-surface diurnal wind to over 40m/sec in limited areas near 30 deg south latitude. It appears likely that dust was injected into the atmosphere in these regions during the storm.

Conrath, B. J.

1976-01-01

253

The absolute magnitudes of Type IA supernovae  

Microsoft Academic Search

Absolute magnitudes in the B, V, and I bands are derived for nine well-observed Type Ia supernovae, using host galaxy distances estimated via the surface brightness fluctuations or Tully-Fisher methods. These data indicate that there is a significant intrinsic dispersion in the absolute magnitudes at maximum light of Type Ia supernovae, amounting to +\\/- 0.8 mag in B, +\\/- 0.6

M. M. Phillips

1993-01-01

254

Absolute calibration of imaging atmospheric Cherenkov telescopes  

E-print Network

A calibrated laser pulse propagating through the atmosphere produces a flash of Rayleigh scattered light with an intensity that can be calculated very accurately when atmospheric conditions are good. This is used in a technique developed for the absolute calibration of ultra high energy cosmic ray fluorescence telescopes, and it can also be applied to imaging atmospheric Cherenkov telescopes (IACTs). In this paper we present the absolute calibration system being constructed and tested for the VERITAS project.

N. Shepherd; J. H. Buckley; O. Celik; J. Holder; S. LeBohec; H. Manseri; F. Pizlo; M. Roberts

2005-07-04

255

Dynamical diffraction imaging (topography) with X-ray synchrotron radiation  

NASA Technical Reports Server (NTRS)

By contrast to electron microscopy, which yields information on the location of features in small regions of materials, X-ray diffraction imaging can portray minute deviations from perfect crystalline order over larger areas. Synchrotron radiation-based X-ray optics technology uses a highly parallel incident beam to eliminate ambiguities in the interpretation of image details; scattering phenomena previously unobserved are now readily detected. Synchrotron diffraction imaging renders high-resolution, real-time, in situ observations of materials under pertinent environmental conditions possible.

Kuriyama, M.; Steiner, B. W.; Dobbyn, R. C.

1989-01-01

256

Absolute Being vs Relative Becoming  

E-print Network

Contrary to our immediate and vivid sensation of past, present, and future as continually shifting non-relational modalities, time remains as tenseless and relational as space in all of the established theories of fundamental physics. Here an empirically adequate generalized theory of the inertial structure is discussed in which proper time is causally compelled to be tensed within both spacetime and dynamics. This is accomplished by introducing the inverse of the Planck time at the conjunction of special relativity and Hamiltonian mechanics, which necessitates energies and momenta to be invariantly bounded from above, and lengths and durations similarly bounded from below, by their respective Planck scale values. The resulting theory abhors any form of preferred structure, and yet captures the transience of now along timelike worldlines by causally necessitating a genuinely becoming universe. This is quite unlike the scenario in Minkowski spacetime, which is prone to a block universe interpretation. The minute deviations from the special relativistic effects such as dispersion relations and Doppler shifts predicted by the generalized theory remain quadratically suppressed by the Planck energy, but may nevertheless be testable in the near future, for example via observations of oscillating flavor ratios of ultrahigh energy cosmic neutrinos, or of altering pulse rates of extreme energy binary pulsars.

Joy Christian

2007-04-23

257

Topography and Volcanoes on Io (color)  

NASA Technical Reports Server (NTRS)

The images used to create this enhanced color composite of Io were acquired by NASA's Galileo spacecraft during its seventh orbit (G7) of Jupiter. Low sun angles near the terminator (day-night boundary near the left side of the image) offer lighting conditions which emphasize the topography or relief on the volcanic satellite. The topography appears very flat near the active volcanic centers such as Loki Patera (the large dark horse-shoe shaped feature near the terminator) while a variety of mountains and plateaus exist elsewhere. The big reddish-orange ring in the lower right is formed by material deposited from the eruption of Pele, Io's largest volcanic plume.

North is to the top of this 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 6.1 kilometers per picture element. The images were taken on April 4th, 1997 at a range of 600,000 kilometers.

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).

Concurrent results from Galileo's exploration of Io appear in the October 15th, 1997 issue of Geophysical Research Letters. The papers are: Temperature and Area Constraints of the South Volund Volcano on Io from the NIMS and SSI Instruments during the Galileo G1 Orbit, by A.G. Davies, A.S. McEwen, R. Lopes-Gautier, L. Keszthelyi, R.W. Carlson and W.D. Smythe. High-temperature hot spots on Io as seen by the Galileo Solid-State Imaging (SSI) experiment, by A. McEwen, D. Simonelli, D. Senske, K. Klassen, L. Keszthelyi, T. Johnson, P. Geissler, M. Carr, and M. Belton. Io: Galileo evidence for major variations in regolith properties, by D. Simonelli, J. Veverka, and A. McEwen.

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

1997-01-01

258

Mask topography effect in chromeless phase lithography  

NASA Astrophysics Data System (ADS)

Different types of phase-shift masks (PSM) in combination with the proper illumination condition are widely used to allow 193nm lithography to print ever-decreasing pitches with a sufficient process window. A viable option for the 65nm node is Chromeless Phase Lithography (CPL), which combines a chromeless phase shift mask and 193nm off-axis illumination. It has been demonstrated that CPL has a high flexibility for through pitch imaging. Also concerning mask making CPL masks showed advantages over alternating and attenuated PSM [1]. This paper discusses how the mask quality and its topography influence the imaging performance of CPL. It is shown that mask topography is an important factor for CPL, as the imaging relies also on the quartz depth differences in the mask. The wafer image is sensitive to phase variations induced by the quartz etch depth and the sidewall profile. Their impact is separately studied using rigorous 3D mask electro-magnetic field simulations (Sigma-C Solid-CM). Correlation of experimental results to simulation explains that the observed pitch-dependent tilt in the Bossung curves is mainly related to the 3D character of the mask. In search for a global compensation valid through pitch, the simulation study also evaluates the effect of other contributors such as lens aberrations in the optical system, assist features and half-toning Cr zebra lines in the design. However, as the tilt is inherent to the CPL mask fabrication, a compensation of the Bossung tilt effect can only be obtained for specific combinations of all sources, as will be shown. We concentrate on the imaging of 70nm lines and 100nm contact holes in pitches ranging from dense up to isolated. The wafers are exposed on an ASML PAS5500/1100 ArF scanner working with a 0.75NA projection lens and various types of off-axis illumination. The wafers are evaluated on a top-down CD SEM (KLA-Tencor 8250XR).

Philipsen, Vicky; Bekaert, Joost; Vandenberghe, Geert; Jonckheere, Rik; Van Den Broeke, Douglas; Socha, Robert

2004-12-01

259

Characterizing smoking topography of cannabis in heavy users  

PubMed Central

Rationale Little is known about the smoking topography characteristics of heavy cannabis users. Such measures may be able to predict cannabis use-related outcomes and could be used to validate self-reported measures of cannabis use. Objectives The current study was conducted to measure cannabis smoking topography characteristics during periods of ad libitum use and to correlate topography assessments with measures of self-reported cannabis use, withdrawal and craving during abstinence, and cognitive task performance. Methods Participants (N=20) completed an inpatient study in which they alternated between periods of ad libitum cannabis use and abstinence. Measures of self-reported cannabis use, smoking topography, craving, withdrawal, and sleep measures were collected. Results Participants smoked with greater intensity (e.g., greater volume, longer duration) on initial cigarette puffs with a steady decline on subsequent puffs. Smoking characteristics were significantly correlated with severity of withdrawal, notably sleep quality and architecture, and craving during abstinence, suggesting dose-related effects of cannabis use on these outcomes. Smoking characteristics generally were not significantly associated with cognitive performance. Smoking topography measures were significantly correlated with self-reported measures of cannabis use, indicating validity of these assessments, but topography measures were more sensitive than self-report in predicting cannabis-related outcomes. Conclusions A dose–effect relationship between cannabis consumption and outcomes believed to be clinically important was observed. With additional research, smoking topography assessments may become a useful clinical tool. PMID:21922170

Stitzer, Maxine L.; Vandrey, Ryan

2013-01-01

260

Jasminum flexile flower absolute from India--a detailed comparison with three other jasmine absolutes.  

PubMed

Jasminum flexile flower absolute from the south of India and the corresponding vacuum headspace (VHS) sample of the absolute were analyzed using GC and GC-MS. Three other commercially available Indian jasmine absolutes from the species: J. sambac, J. officinale subsp. grandiflorum, and J. auriculatum and the respective VHS samples were used for comparison purposes. One hundred and twenty-one compounds were characterized in J. flexile flower absolute, with methyl linolate, benzyl salicylate, benzyl benzoate, (2E,6E)-farnesol, and benzyl acetate as the main constituents. A detailed olfactory evaluation was also performed. PMID:19831037

Braun, Norbert A; Kohlenberg, Birgit; Sim, Sherina; Meier, Manfred; Hammerschmidt, Franz-Josef

2009-09-01

261

The effect of topography on the seismic wavefield  

NASA Astrophysics Data System (ADS)

Active tectonic settings exhibit deformation manifested by earthquakes and by strong topographic variations due to erosion and uplift. Seismic waves from these earthquakes will clearly be influenced by the topographic variations, but it is challenging to isolate the effects of topography from the effects of variations in 3D seismic wave-speed structure. Here we design a realistic numerical experiment to investigate the effects of topography on the regional seismic wavefield. We choose southern California as a target region. We perform several sets of 3D seismic wavefield simulations for 137 earthquake sources ranging from Mw 3.4 to 5.4. We test the influence of topography within a homogeneous model and a layered model, and for each model we establish the shortest resolvable period for each path between a source and station. By examining the path-specific shortest resolvable periods, we are able to make some generalizations. Topography has the strongest influence on surface waves, particularly for waveforms with travel paths that are nodal to the source radiation; in these directions, the wave amplitudes are relatively low, so any multi-pathing or scattering effects due to topography are more easily identified. The topographic effects are stronger for shorter periods and for longer paths. The influence of topography on the seismic waveforms arises from both the change in the topographic surface, but also the change in the wave-speed structure that arises from perturbing the topography for a 1D (or 3D) wave-speed model. These generalizations of the influence of topography provide a basis for further numerical investigations or for where to search within a regional set of observations for the topographic effects. Topography should be included within simulation-based seismic imaging applications, especially those at high frequencies, in order to eliminate the possibility of attributing topographically-caused waveforms to subsurface variations in structure.

Miller, Ulrika

262

Inversion of topography in Martian highland terrains  

SciTech Connect

Ring furrows are flat-floored trenches, circulate in plan view, forming rings 7 to 50 km in diameter. Typically, ring furrows, which are 0.5 km deep and 2 to 10 km wide, surround a central, flat-topped, circular mesa or plateau. The central plateau is about the same elevation or lower than the plain outside the ring. Ring furrows are unique features of the dissected martian uplands. Related landforms range from ring furrows with fractured central plateaus to circular mesas without encircling moats. Ring furrows are superposed on many types of materials, but they are most common cratered plateau-type materials that are interpreted as volcanic flow material overlying ancient cratered terrain. The ring shape and size suggest that they are related to craters partially buried by lava flows. Ring furrows were formed by preferential removal of exposed rims of partially buried craters. Evidence of overland flow of water is lacking except within the channels. Ground ice decay and sapping followed by fluvial erosion are responsible for removal of the less resistant rim materials. Thus, differential erosion has caused a reversal of topography in which the originally elevated rim is reduced to negative relief.

De Hon, R.A.

1985-01-01

263

Surface topography and rotational symmetry breaking.  

PubMed

The surface electroclinic effect, which is a rotation of the molecular director in the substrate plane proportional to an electric field E applied normal to the substrate, requires both a chiral environment and C(2) (or lower) rotational symmetry about E. The two symmetries typically are created in tandem by manipulating the surface topography, a process that conflates their effects. Here we use a pair of rubbed polymer-coated substrates in a twist geometry to obtain our main result, viz., that the strengths of two symmetries, in this case the rub-induced breaking of C(?) rotational symmetry and chiral symmetry, can be separated and quantified. Experimentally we observe that the strength of the reduced rotational symmetry arising from the rub-induced scratches, which is proportional to the electroclinic response, scales linearly with the induced topographical rms roughness and increases with increasing rubbing strength of the polymer. Our results also suggest that the azimuthal anchoring strength coefficient is relatively insensitive to the strength of the rubbing. PMID:23005441

Basu, Rajratan; Nemitz, Ian R; Song, Qingxiang; Lemieux, Robert P; Rosenblatt, Charles

2012-07-01

264

Corneal topography changes after vitreoretinal surgery.  

PubMed

The authors report the results of a prospective study to assess corneal topography changes after vitreoretinal surgery procedures. Computer-assisted videokeratography using a Topographic Modeling System-1 (TMS-1) were prospectively performed before and after vitreoretinal surgery (vitrectomy with or without scleral buckling) in 12 eyes (patients) with varied vitreoretinal pathology, including cytomegalovirus (CMV) retinitis, CMV-related retinal detachment, retinal detachment with and without proliferative vitreoretinopathy, trauma, acute retinal necrosis, and macular hole. Preoperative and postoperative surface regularity index (SRI), surface asymmetry index (SAI), and induced astigmatism were determined. Patients were followed for an average of 6 months (range: 2-15 months). Mean preoperative SRI was 0.52 (0.05-1.06) and postoperative SRI was 0.73 (0.25-1.36). Mean preoperative SAI was 0.43 (0.22-0.93) and postoperative SAI was 0.56 (0.21-0.99). Mean induced astigmatism was 0.7 diopters. Our study suggests that the central corneal optical quality (SRI) and the asymmetricity of the anterior corneal curvature (SAI) deteriorates after vitreoretinal surgery. PMID:11300644

Azar-Arevalo, O; Arevalo, J F

2001-01-01

265

An Improved 360 Degree and Order Model of Venus Topography  

NASA Technical Reports Server (NTRS)

We present an improved 360 degree and order spherical harmonic solution for Venus' topography. The new model uses the most recent set of Venus altimetry data with spacecraft positions derived from a recent high resolution gravity model. Geometric analysis indicates that the offset between the center of mass and center of figure of Venus is about 10 times smaller than that for the Earth, the Moon, or Mars. Statistical analyses confirm that the RMS topography follows a power law over the central part of the spectrum. Compared to the previous topography model, the new model is more highly correlated with Venus' harmonic gravity field.

Rappaport, Nicole J.; Konopliv, Alex S.; Kucinskas, Algis B.; Ford, Peter G.

1999-01-01

266

Shape, topography, gravity anomalies and tidal deformation of Titan  

NASA Astrophysics Data System (ADS)

Gravity measurements and elevation data from the Cassini mission have been used to create shape, global topography and gravity anomaly models of Titan that enable an improved understanding of its outer ice I shell structure. We provide constraints on the averaged ice shell thickness and its long-wavelength lateral variations, as well as the density of the subsurface ocean using gravity anomalies, the tidal Love number k2 measurement and long-wavelength topography. We found that Titan’s surface topography is consistent with an approximate isostatically compensated ice shell of variable thickness, likely in a thermally conductive or in a subcritical convective state, overlying a relatively dense subsurface ocean.

Mitri, Giuseppe; Meriggiola, Rachele; Hayes, Alex; Lefevre, Axel; Tobie, Gabriel; Genova, Antonio; Lunine, Jonathan I.; Zebker, Howard

2014-07-01

267

Determination of ¹?N-incorporation into plant proteins and their absolute quantitation: a new tool to study nitrogen flux dynamics and protein pool sizes elicited by plant-herbivore interactions.  

PubMed

Herbivory leads to changes in the allocation of nitrogen among different pools and tissues; however, a detailed quantitative analysis of these changes has been lacking. Here, we demonstrate that a mass spectrometric data-independent acquisition approach known as LC-MS(E), combined with a novel algorithm to quantify heavy atom enrichment in peptides, is able to quantify elicited changes in protein amounts and (15)N flux in a high throughput manner. The reliable identification/quantitation of rabbit phosphorylase b protein spiked into leaf protein extract was achieved. The linear dynamic range, reproducibility of technical and biological replicates, and differences between measured and expected (15)N-incorporation into the small (SSU) and large (LSU) subunits of ribulose-1,5-bisphosphate-carboxylase/oxygenase (RuBisCO) and RuBisCO activase 2 (RCA2) of Nicotiana attenuata plants grown in hydroponic culture at different known concentrations of (15)N-labeled nitrate were used to further evaluate the procedure. The utility of the method for whole-plant studies in ecologically realistic contexts was demonstrated by using (15)N-pulse protocols on plants growing in soil under unknown (15)N-incorporation levels. Additionally, we quantified the amounts of lipoxygenase 2 (LOX2) protein, an enzyme important in antiherbivore defense responses, demonstrating that the approach allows for in-depth quantitative proteomics and (15)N flux analyses of the metabolic dynamics elicited during plant-herbivore interactions. PMID:22905865

Ullmann-Zeunert, Lynn; Muck, Alexander; Wielsch, Natalie; Hufsky, Franziska; Stanton, Mariana A; Bartram, Stefan; Böcker, Sebastian; Baldwin, Ian T; Groten, Karin; Svatoš, Aleš

2012-10-01

268

Pyroclastic density currents and local topography as seen with the conveyer model  

NASA Astrophysics Data System (ADS)

Pyroclastic density currents (PDCs) are multiphase flows generated during explosive volcanic eruptions, and they move down the volcano, and over the surrounding topography. The flow-topography interaction can play a fundamental role in the sedimentary processes, and in the resulting deposit facies architecture, as well as can play a dramatic role in the flow behavior, and in the associated volcanic hazard. This paper aims at discussing the PDC-topography interaction theme from the viewpoint of both deposits and flow structure, by accounting for appropriate literature, and revising the concepts in light of the theoretical conveyer model of Doronzo and Dellino (2013) on sedimentation and deposition in particulate density currents. First the effects, then the causes of the flow-topography interaction are discussed, in order to follow the historical development of theme concepts. The discussion is relative in terms of inertial and forced currents, which are defined on the basis of a dimensionless quantity (SD) representing the conservation of mass. Momentum equation relating depositional unit thickness, flow shear velocity, and density contrast shows that the flow is the cause of PDC motion, whereas the density contrast sustains the momentum, and the deposits are the process effect. In particular, the flow structure is described into three parts, flow-substrate boundary zone, boundary layer (lower part), and wake region (upper part) of the current. The facies architecture of PDC deposits, and the volcanic hazard depend on fluid dynamic and hydraulic behavior represented, in light of the conveyer model, by the balance of sedimentation and deposition rates through transport and erosion (“sedimentation-deposition” ratio, SD). This balance acts between flow-substrate boundary zone and boundary layer. The paper discussion mainly applies to small-to-intermediate volume eruptions. Field and modeling examples of Vulcano tuff cone and Colli Albani maar (Italy) constrain the conveyer model, whereas the literature of very large, ignimbrite-forming eruptions, and stratovolcanism is accounted for theme completeness. The main findings are some relative guidelines on PDC-topography interaction that can be used when modeling the flow, and interpreting the pyroclastic deposits: low SD is typical of inertial currents, whereas high SD is typical of forced currents, which can vary depending on topography.

Doronzo, Domenico M.; Dellino, Pierfrancesco

2014-05-01

269

Traveltime computation and imaging from rugged topography in 3D TTI media  

NASA Astrophysics Data System (ADS)

Foothill areas with rugged topography are of great potential for oil and gas seismic exploration, but subsurface imaging in these areas is very challenging. Seismic acquisition with larger offset and wider azimuth is necessary for seismic imaging in complex areas. However, the scale anisotropy in this case must be taken into account. To generalize the pre-stack depth migration (PSDM) to 3D transversely isotropic media with vertical symmetry axes (VTI) and tilted symmetry axes (TTI) from rugged topography, a new dynamic programming approach for the first-arrival traveltime computation method is proposed. The first-arrival time on every uniform mesh point is calculated based on Fermat's principle with simple calculus techniques and a systematic mapping scheme. In order to calculate the minimum traveltime, a set of nonlinear equations is solved on each mesh point, where the group velocity is determined by the group angle. Based on the new first-arrival time calculation method, the corresponding PSDM and migration velocity analysis workflow for 3D anisotropic media from rugged surface is developed. Numerical tests demonstrate that the proposed traveltime calculation method is effective in both VTI and TTI media. The migration results for 3D field data show that it is necessary to choose a smooth datum to remove the high wavenumber move-out components for PSDM with rugged topography and take anisotropy into account to achieve better images.

Liu, Shaoyong; Wang, Huazhong; Yang, Qinyong; Fang, Wubao

2014-02-01

270

An iterative inverse method to estimate basal topography and initialize ice flow models  

NASA Astrophysics Data System (ADS)

We evaluate an inverse approach to reconstruct distributed bedrock topography and simultaneously initialize an ice flow model. The inverse method involves an iterative procedure in which an ice dynamical model (PISM) is run multiple times over a prescribed period, while being forced with space- and time-dependent climate input. After every iteration bed heights are adjusted using information of the remaining misfit between observed and modeled surface topography. The inverse method is first applied in synthetic experiments with a constant climate forcing to verify convergence and robustness of the approach in three dimensions. In a next step, the inverse approach is applied to Nordenskiöldbreen, Svalbard, forced with height- and time-dependent climate input since 1300 AD. An L-curve stopping criterion is used to prevent overfitting. Validation against radar data reveals a high correlation (up to R = 0.89) between modeled and observed thicknesses. Remaining uncertainties can mainly be ascribed to inaccurate model physics, in particular, uncertainty in the description of sliding. Results demonstrate the applicability of this inverse method to reconstruct the ice thickness distribution of glaciers and ice caps. In addition to reconstructing bedrock topography, the method provides a direct tool to initialize ice flow models for forecasting experiments.

van Pelt, W. J. J.; Oerlemans, J.; Reijmer, C. H.; Pettersson, R.; Pohjola, V. A.; Isaksson, E.; Divine, D.

2013-06-01

271

Molecular iodine absolute frequencies. Final report  

SciTech Connect

Fifty specified lines of {sup 127}I{sub 2} were studied by Doppler-free frequency modulation spectroscopy. For each line the classification of the molecular transition was determined, hyperfine components were identified, and one well-resolved component was selected for precise determination of its absolute frequency. In 3 cases, a nearby alternate line was selected for measurement because no well-resolved component was found for the specified line. Absolute frequency determinations were made with an estimated uncertainty of 1.1 MHz by locking a dye laser to the selected hyperfine component and measuring its wave number with a high-precision Fabry-Perot wavemeter. For each line results of the absolute measurement, the line classification, and a Doppler-free spectrum are given.

Sansonetti, C.J. [National Inst. of Standards and Technology, Gaithersburg, MD (United States)

1990-06-25

272

Absolute calibration in vivo measurement systems  

SciTech Connect

Lawrence Livermore National Laboratory (LLNL) is currently investigating a new method for obtaining absolute calibration factors for radiation measurement systems used to measure internally deposited radionuclides in vivo. Absolute calibration of in vivo measurement systems will eliminate the need to generate a series of human surrogate structures (i.e., phantoms) for calibrating in vivo measurement systems. The absolute calibration of in vivo measurement systems utilizes magnetic resonance imaging (MRI) to define physiological structure, size, and composition. The MRI image provides a digitized representation of the physiological structure, which allows for any mathematical distribution of radionuclides within the body. Using Monte Carlo transport codes, the emission spectrum from the body is predicted. The in vivo measurement equipment is calibrated using the Monte Carlo code and adjusting for the intrinsic properties of the detection system. The calibration factors are verified using measurements of existing phantoms and previously obtained measurements of human volunteers. 8 refs.

Kruchten, D.A.; Hickman, D.P.

1991-02-01

273

Quantitative standards for absolute linguistic universals.  

PubMed

Absolute linguistic universals are often justified by cross-linguistic analysis: If all observed languages exhibit a property, the property is taken to be a likely universal, perhaps specified in the cognitive or linguistic systems of language learners and users. In many cases, these patterns are then taken to motivate linguistic theory. Here, we show that cross-linguistic analysis will very rarely be able to statistically justify absolute, inviolable patterns in language. We formalize two statistical methods--frequentist and Bayesian--and show that in both it is possible to find strict linguistic universals, but that the numbers of independent languages necessary to do so is generally unachievable. This suggests that methods other than typological statistics are necessary to establish absolute properties of human language, and thus that many of the purported universals in linguistics have not received sufficient empirical justification. PMID:24117660

Piantadosi, Steven T; Gibson, Edward

2014-01-01

274

Mantle dynamics and geodesy  

NASA Technical Reports Server (NTRS)

Both completed work and work that is still in progress are presented. The completed work presented includes: (1) core-mantle boundary topography; (2) absolute value for mantle viscosity; (3) code development; (4) lateral heterogeneity of subduction zone rheology; and (5) planning for the Coolfront meeting. The work presented that is still in progress includes: (1) geoid anomalies for a chemically stratified mantle; and (2) geoid anomalies with lateral variations in viscosity.

Albee, Arden

1990-01-01

275

Absolute versus temporal anomaly and percent of saturation soil moisture spatial variability for six networks worldwide  

NASA Astrophysics Data System (ADS)

The analysis of the spatial-temporal variability of soil moisture can be carried out considering the absolute (original) soil moisture values or relative values, such as the percent of saturation or temporal anomalies. Over large areas, soil moisture data measured at different sites can be characterized by large differences in their minimum, mean, and maximum absolute values, even though in relative terms their temporal patterns are very similar. In these cases, the analysis considering absolute compared with percent of saturation or temporal anomaly soil moisture values can provide very different results with significant consequences for their use in hydrological applications and climate science. In this study, in situ observations from six soil moisture networks in Italy, Spain, France, Switzerland, Australia, and United States are collected and analyzed to investigate the spatial soil moisture variability over large areas (250-150,000 km2). Specifically, the statistical and temporal stability analyses of soil moisture have been carried out for absolute, temporal anomaly, and percent of saturation values (using two different formulations for temporal anomalies). The results highlight that the spatial variability of the soil moisture dynamic (i.e., temporal anomalies) is significantly lower than that of the absolute soil moisture values. The spatial variance of the time-invariant component (temporal mean of each site) is the predominant contribution to the total spatial variance of absolute soil moisture data. Moreover, half of the networks show a minimum in the spatial variability for intermediate conditions when the temporal anomalies are considered, in contrast with the widely recognized behavior of absolute soil moisture data. The analyses with percent saturation data show qualitatively similar results as those for the temporal anomalies because of the applied normalization which reduces spatial variability induced by differences in mean absolute soil moisture only. Overall, we find that the analysis of the spatial-temporal variability of absolute soil moisture does not apply to temporal anomalies or percent of saturation values.

Brocca, L.; Zucco, G.; Mittelbach, H.; Moramarco, T.; Seneviratne, S. I.

2014-07-01

276

EAARL coastal topography--North Shore, Lake Pontchartrain, Louisiana, 2010  

USGS Publications Warehouse

This DVD contains lidar-derived coastal topography GIS datasets of a portion of the north shore of Lake Pontchartrain, Louisiana. These datasets were acquired on February 28, March 1, and March 5, 2010.

Bonisteel-Cormier, J.M.; Nayegandhi, Amar; Fredericks, Xan; Wright, C.W.; Brock, J.C.; Nagle, D.B.; Vivekanandan, Saisudha; Barras, J.A.

2012-01-01

277

Influence of local topography on precision irrigation management  

Technology Transfer Automated Retrieval System (TEKTRAN)

Precision irrigation management is currently accomplished using spatial information about soil properties through soil series maps or electrical conductivity (EC measurements. Crop yield, however, is consistently influenced by local topography, both in rain-fed and irrigated environments. Utilizing ...

278

Calculation of irrotational wind pattern with application to Cleveland topography  

NASA Technical Reports Server (NTRS)

Small perturbation theory is applied to compute the deflection of the wind blowing across land that has an irregular topography. As an illustration, the method is applied first to the flow around a single hill of Gaussian profile. Then calculations are made for the irregular topography on the east side of Cleveland where the elevation changes by several hundred feet. It was found that the topography produced small wind deflections that would not be of practical importance in air pollution dispersion studies. The calculations were for a neutrally stable atmosphere. Although they are not investigated here, other factors such as thermal stratification of the atmosphere, diurnal variations, and convection currents resulting from the proximity of Lake Erie and the city heat island effect are expected to be more significant than the influence of topography.

Siegel, R.

1972-01-01

279

23. SPILLWAY NO. 1 LOWER END TOPOGRAPHY AND SECTIONS. ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

23. SPILLWAY NO. 1 - LOWER END TOPOGRAPHY AND SECTIONS. February 1934. Reference BS-150. - Cushman No. 1 Hydroelectric Power Plant, Spillway, North Fork of Skokomish River, 5 miles West of Hood Canal, Hoodsport, Mason County, WA

280

THE INFLUENCE OF TOPOGRAPHY AND TEMPERATURE ON QUERCUS ILICIFOLIA SUCCESSION  

E-print Network

and tree oak plot. I found that colder microclimates are created by the effects of the low topography ecosystem. It is opportunistic and an early successional species that is maintained by disturbances. Scrub

Vallino, Joseph J.

281

Geoid height versus topography for oceanic plateaus and swells  

NASA Technical Reports Server (NTRS)

Gridded geoid height data (Marsh et al.l, 1986) and gridded bathymetry data (Van Wykhouse, 1973) are used to estimate the average compensation depths of 53 oceanic swells and plateaus. The relationship between geoid height and topography is examined using Airy and thermal compensation models. It is shown that geoid height is linearly related to topography between wavelengths of 400 and 4000 m as predicted by isostatic compensation models. The geoid/topography ratio is dependent on the average depth of compensation. The intermediate geoid/topography ratios of most thermal swells are interpreted as a linear combination of the decaying thermal swell signature and that of the persisting Airy-compensated volcanic edifice.

Sandwell, David T.; Mackenzie, Kevin R.

1989-01-01

282

Superoleophobic Surfaces through Control of Sprayed-on Stochastic Topography  

E-print Network

The liquid repellency and surface topography characteristics of coatings comprising a sprayed-on mixture of fluoroalkyl-functional precipitated silica and a fluoropolymer binder were examined using contact and sliding angle ...

Campos, Raymond

283

Surface topography and the impact on fatigue performance  

NASA Astrophysics Data System (ADS)

Areal characterization was applied to plain fatigue specimens manufactured from a nickel-based superalloy, Alloy 720Li, to determine the impact of machined/finished surface topography on fatigue performance of this material. Samples were subjected to fatigue testing in the as-turned and shot peened conditions to study the interaction between residual stresses and topography in influencing the fatigue performance. The turning process was deliberately manipulated to produce three distinct finishes which were subsequently given an identical shot peening, resulting in six grades of surface topography. Surface topography was found to influence fatigue even in the presence of peened compressive residual stresses by promoting crack initiation at valley sites. Both the roughness amplitude and spatial characteristics of the surface were found to be important when correlating to fatigue performance.

Ardi, D. T.; Li, Y. G.; Chan, K. H. K.; Blunt, L.; Bache, M. R.

2015-03-01

284

Infragravity waves over topography: generation, dissipation, and reflection  

E-print Network

Ocean surface infragravity waves (periods from 20 to 200 s) observed along the southern California coast are shown to be sensitive to the bottom topography of the shelf region, where propagation is linear, and of the ...

Thomson, James M. (James McArthur)

2006-01-01

285

Spatially explicit simulation of peatland hydrology and carbon dioxide exchange: Influence of mesoscale topography  

NASA Astrophysics Data System (ADS)

Carbon dynamics in peatlands are controlled, in large part, by their wetness as defined by water table depth and volumetric liquid soil moisture content. A common type of peatland is raised bogs that typically have a multiple-layer canopy of vascular plants over a Sphagnum moss ground cover. Their convex form restricts water supply to precipitation and water is shed toward the margins, usually by lateral subsurface flow. The hydraulic gradient for lateral subsurface flow is governed by the peat surface topography at the mesoscale (˜200 m to 5 km). To investigate the influence of mesoscale topography on wetness, evapotranspiration (ET), and gross primary productivity (GPP) in a bog during the snow-free period, we compare the outputs of a further developed version of the daily Boreal Ecosystem Productivity Simulator (BEPS) with observations made at the Mer Bleue peatland, located near Ottawa, Canada. Explicitly considering mesoscale topography, simulated total ET and GPP correlate well with measured ET (r = 0.91) and derived gross ecosystem productivity (GEP; r = 0.92). Both measured ET and derived GEP are simulated similarly well when mesoscale topography is neglected, but daily simulated values are systematically underestimated by about 10% and 12% on average, respectively, due to greater wetness resulting from the lack of lateral subsurface flow. Owing to the differences in moss surface conductances of water vapor and carbon dioxide with increasing moss water content, the differences in the spatial patterns of simulated total ET and GPP are controlled by the mesotopographic position of the moss ground cover.

Sonnentag, O.; Chen, J. M.; Roulet, N. T.; Ju, W.; Govind, A.

2008-06-01

286

Science in Motion: Isolated Araneiform Topography  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] Figure 1

Have you ever found that to describe something you had to go to the dictionary and search for just the right word?

The south polar terrain is so full of unearthly features that we had to visit Mr. Webster to find a suitable term. 'Araneiform' means 'spider-like'. These are channels that are carved in the surface by carbon dioxide gas. We do not have this process on Earth.

The channels are somewhat radially organized (figure 1) and widen and deepen as they converge. In the past we've just refered to them as 'spiders.' 'Isolated araneiform topography' means that our features look like spiders that are not in contact with each other.

Observation Geometry Image PSP_003087_0930 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on 24-Mar-2007. The complete image is centered at -87.1 degrees latitude, 126.3 degrees East longitude. The range to the target site was 244.4 km (152.8 miles). At this distance the image scale is 24.5 cm/pixel (with 1 x 1 binning) so objects 73 cm across are resolved. The image shown here has been map-projected to 25 cm/pixel . The image was taken at a local Mars time of 08:22 PM and the scene is illuminated from the west with a solar incidence angle of 81 degrees, thus the sun was about 9 degrees above the horizon. At a solar longitude of 206.4 degrees, the season on Mars is Northern Autumn.

2007-01-01

287

Phase contrast in Simultaneous Topography and Recognition imaging.  

PubMed

The operation of a force microscope in Simultaneous Topography and Recognition (TREC) imaging mode is analyzed by means of numerical simulations. Both topography and recognition signals are analyzed by using a worm-like chain force as the specific interaction between the functionalized tip probe and the sample. The special feedback mechanism in this mode is shown to couple the phase signal to the presence of molecular recognition interactions even in absence of dissipation. PMID:19523768

Fuss, M C; Sahagún, E; Köber, M; Briones, F; Luna, M; Sáenz, J J

2009-08-01

288

Astronomy Ranking Task: Apparent and Absolute Magnitude  

E-print Network

Astronomy Ranking Task: Apparent and Absolute Magnitude Exercise #1 Description: The figure below is equipped with identical headlights. A. Ranking Instructions: Rank the distance (from greatest to least) that each car is from you. Ranking Order: Greatest 1 _______ 2 _______ 3 _______ 4 _______ Least Or

Farritor, Shane

289

Absolute configuration of remisporines A & B.  

PubMed

The absolute configuration of remisporine B was determined based on a comparison of experimental and calculated electronic circular dichroism (ECD) spectra. Density functional theory (DFT) was used to calculate the ECD spectra varying the parameter controlling the number of calculated electronic transitions. Mapping the reaction surface provided support for the proposed Diels-Alder dimerization of remisporine A to form remisporine B. PMID:25735997

Sherer, Edward C; Cheeseman, James R; Williamson, R Thomas

2015-04-14

290

Absolute head media spacing measurement in situ  

Microsoft Academic Search

For the nanometer-spaced head disk interface, the demand for precision flying height (FH) measurement increases. The conventional optical FH testing technology is facing physical challenges, and the industry is seeking the alternative technology for nanometer FH test. This work proposes to use logarithmic harmonic ratio of reproduced waveform versus testing frequency to derive absolute head media spacing (HMS) in situ.

Zhi-Min Yuan; Bo Liu

2006-01-01

291

Astronomy Ranking Task: Apparent and Absolute Magnitude  

E-print Network

Astronomy Ranking Task: Apparent and Absolute Magnitude Exercise #2 Description: The figure below magnitude. Ranking Order: Greatest 1 _______ 2 _______ 3 _______ 4 _______ 5 _______ Least Or, the apparent magnitude number would be the same for each star. ______ (indicate with check mark). Carefully explain your

Farritor, Shane

292

The amount of information in absolute judgments  

Microsoft Academic Search

The distribution of an O's absolute judgments, in which he identifies a stimulus as having a particular value, may indicate how much information he obtained about which of several alternative stimuli occurred at a particular time. The amount of information conveyed to O can be measured in bits This measure may give an estimate of the minimum number of stimulus

W. R. Garner; Harold W. Hake

1951-01-01

293

Absolute partial photoionization cross sections of ozone.  

SciTech Connect

Despite the current concerns about ozone, absolute partial photoionization cross sections for this molecule in the vacuum ultraviolet (valence) region have been unavailable. By eclectic re-evaluation of old/new data and plausible assumptions, such cross sections have been assembled to fill this void.

Berkowitz, J.; Chemistry

2008-04-01

294

Absolute instability of a viscous hollow jet  

Microsoft Academic Search

An investigation of the spatiotemporal stability of hollow jets in unbounded coflowing liquids, using a general dispersion relation previously derived, shows them to be absolutely unstable for all physical values of the Reynolds and Weber numbers. The roots of the symmetry breakdown with respect to the liquid jet case, and the validity of asymptotic models are here studied in detail.

Alfonso M. Gañán-Calvo

2007-01-01

295

An Absolute Electrometer for the Physics Laboratory  

ERIC Educational Resources Information Center

A low-cost, easy-to-use absolute electrometer is presented: two thin metallic plates and an electronic balance, usually available in a laboratory, are used. We report on the very good performance of the device that allows precise measurements of the force acting between two charged plates. (Contains 5 footnotes, 2 tables, and 6 figures.)

Straulino, S.; Cartacci, A.

2009-01-01

296

Teaching Absolute Value Inequalities to Mature Students  

ERIC Educational Resources Information Center

This paper gives an account of a teaching experiment on absolute value inequalities, whose aim was to identify characteristics of an approach that would realize the potential of the topic to develop theoretical thinking in students enrolled in prerequisite mathematics courses at a large, urban North American university. The potential is…

Sierpinska, Anna; Bobos, Georgeana; Pruncut, Andreea

2011-01-01

297

Absolute pitch: perception, coding, and controversies  

E-print Network

Absolute pitch: perception, coding, and controversies Daniel J. Levitin and Susan E. Rogers are converging to shed light on the nature of processing, categorization and memory for pitch in humans and animals. Although most people are unable to name or place pitch values in consistent, well

Levitin, Daniel

298

Visualization of High-Resolution LiDAR Topography in Google Earth  

NASA Astrophysics Data System (ADS)

The growing availability of high-resolution LiDAR (Light Detection And Ranging) topographic data has proven to be revolutionary for Earth science research. These data allow scientists to study the processes acting on the Earth’s surfaces at resolutions not previously possible yet essential for their appropriate representation. In addition to their utility for research, the data have also been recognized as powerful tools for communicating earth science concepts for education and outreach purposes. Unfortunately, the massive volume of data produced by LiDAR mapping technology can be a barrier to their use. To facilitate access to these powerful data for research and educational purposes, we have been exploring the use of Keyhole Markup Language (KML) and Google Earth to deliver LiDAR-derived visualizations. The OpenTopography Portal (http://www.opentopography.org/) is a National Science Foundation-funded facility designed to provide access to Earth science-oriented LiDAR data. OpenTopography hosts a growing collection of LiDAR data for a variety of geologic domains, including many of the active faults in the western United States. We have found that the wide spectrum of LiDAR users have variable scientific applications, computing resources, and technical experience and thus require a data distribution system that provides various levels of access to the data. For users seeking a synoptic view of the data, and for education and outreach purposes, delivering full-resolution images derived from LiDAR topography into the Google Earth virtual globe is powerful. The virtual globe environment provides a freely available and easily navigated viewer and enables quick integration of the LiDAR visualizations with imagery, geographic layers, and other relevant data available in KML format. Through region-dependant network linked KML, OpenTopography currently delivers over 20 GB of LiDAR-derived imagery to users via simple, easily downloaded KMZ files hosted at the Portal. This method provides seamlessly access to hillshaded imagery for both bare earth and first return terrain models with various angles of illumination. Seamless access to LiDAR-derived imagery in Google Earth has proven to be the most popular product available in the OpenTopography Portal. The hillshade KMZ files have been downloaded over 3000 times by users ranging from earthquake scientists to K-12 educators who wish to introduce cutting edge real world data into their earth science lessons. OpenTopography also provides dynamically generated KMZ visualizations of LiDAR data products produced when users choose to use the OpenTopography point cloud access and processing system. These Google Earth compatible products allow users to quickly visualize the custom terrain products they have generated without the burden of loading the data into a GIS environment. For users who have installed the Google Earth browser plug-in, these visualizations can be launched directly from the OpenTopography results page and viewed directly in the browser.

Crosby, C. J.; Nandigam, V.; Arrowsmith, R.; Blair, J. L.

2009-12-01

299

Shuttle Topography Data Inform Solar Power Analysis  

NASA Technical Reports Server (NTRS)

The next time you flip on a light switch, there s a chance that you could be benefitting from data originally acquired during the Space Shuttle Program. An effort spearheaded by Jet Propulsion Laboratory (JPL) and the National Geospatial-Intelligence Agency (NGA) in 2000 put together the first near-global elevation map of the Earth ever assembled, which has found use in everything from 3D terrain maps to models that inform solar power production. For the project, called the Shuttle Radar Topography Mission (SRTM), engineers at JPL designed a 60-meter mast that was fitted onto Shuttle Endeavour. Once deployed in space, an antenna attached to the end of the mast worked in combination with another antenna on the shuttle to simultaneously collect data from two perspectives. Just as having two eyes makes depth perception possible, the SRTM data sets could be combined to form an accurate picture of the Earth s surface elevations, the first hight-detail, near-global elevation map ever assembled. What made SRTM unique was not just its surface mapping capabilities but the completeness of the data it acquired. Over the course of 11 days, the shuttle orbited the Earth nearly 180 times, covering everything between the 60deg north and 54deg south latitudes, or roughly 80 percent of the world s total landmass. Of that targeted land area, 95 percent was mapped at least twice, and 24 percent was mapped at least four times. Following several years of processing, NASA released the data to the public in partnership with NGA. Robert Crippen, a member of the SRTM science team, says that the data have proven useful in a variety of fields. "Satellites have produced vast amounts of remote sensing data, which over the years have been mostly two-dimensional. But the Earth s surface is three-dimensional. Detailed topographic data give us the means to visualize and analyze remote sensing data in their natural three-dimensional structure, facilitating a greater understanding of the features and processes taking place on Earth."

2013-01-01

300

Evolution of Topography in Glaciated Mountain Ranges  

NASA Technical Reports Server (NTRS)

This thesis examines the response of alpine landscapes to the onset of glaciation. The basic approach is to compare fluvial and glacial laudscapes, since it is the change from the former to the latter that accompanies climatic cooling. This allows a detailed evaluation of hypotheses relating climate change to tectonic processes in glaciated mountain belts. Fieldwork was carried out in the eastern Sierra Nevada, California, and the Sangre de Cristo Range, Colorado, alongside digital elevation model analyses in the western US, the Southern Alps of New Zealand, and the Himalaya of northwestern Pakistan. hypothesis is overstated in its appeal to glacial erosion as a major source of relief production and subsequent peak uplift. Glaciers in the eastern Sierra Nevada and the western Sangre de Cristos have redistributed relief, but have produced only modest relief by enlarging drainage basins at the expense of low-relief topography. Glaciers have lowered valley floors and ridgelines by similar amounts, limiting the amount of "missing mass' that can be generated, and causing a decrease in drainage basin relief. The principal response of glaciated landscapes to rapid rock uplift is the development of towering cirque headwalls. This represents considerable relief production, but is not caused by glacial erosion alone. Large valley glaciers can maintain their low gradient regardless of uplift rate, which supports the "glacial buzzsaw" hypothesis. However, the inability of glaciers to erode steep hillslopes as rapidly can cause mean elevations to rise. Cosmogenic isotope dating is used to show that (i) where plucking is active, the last major glaciation removed sufficient material to reset the cosmogenic clock; and (ii) former glacial valley floors now stranded near the crest of the Sierra Nevada are at varying stages of abandonment, suggesting a cycle of drainage reorganiszation and relief inversion due to glacial erosion similar to that observed in river networks. Glaciated landscapes are quite distinct from their fluvial counterparts in both landforms and processes. Given the scarcity of purely fluvial, active mountain ranges, it is essential that glacial erosion be considered amongst the processes sculpting active orogenic belts.

Brocklehurst, Simon H.

2002-01-01

301

Comparison of soil moisture dynamics across different land covers  

NASA Astrophysics Data System (ADS)

The spatial and temporal variability of soil moisture and its dependency on local or regional scale characteristics, such as soil texture, land cover and topography as well as weather and climate anomalies, is a fundamental feature for environmental applications. In a recent study based on a network of grassland stations in Switzerland (Mittelbach and Seneviratne 2012), it was shown that the spatio-temporal variability of absolute soil moisture is clearly distinct from the spatio-temporal variability of temporal soil moisture anomalies, and that regional-scale patterns of soil moisture dynamics could clearly be identified at the scale of Switzerland. However, it has not yet been investigated whether these conclusions apply across land cover types. In the current study, we investigate differences in soil moisture dynamics at paired grassland-forest sites and their dependency either on dynamic or static site properties. The analysis is based on three-year continuous soil moisture measurements at three paired grassland and nearby forest sites of the SwissSMEX (http://www.iac.ethz.ch/url/research/SwissSMEX) soil moisture network. The three paired sites are located in different climatic regions of Switzerland. They are characterized by similar meteorological conditions but within the pairs differences in topography (elevation, slope, aspect) and soil properties are found. At all sites continuous measurements of soil moisture are available in four different depths, from 5 cm to 50 cm. The analyses of daily mean soil moisture at the single depths and integrated over the 50 cm soil column reveal different behaviour with respect to absolute soil moisture levels and temporal soil moisture dynamics between grassland and forest sites during the whole three-year period. Focusing on the recession of soil moisture during precipitation-free periods, a seasonal dependency is observed with strongest recession in summer for both land covers. However, a different behaviour is found in spring and autumn. While stronger recession is found over grassland in spring, the forest sites indicate stronger recession in autumn, with most pronounced differences at deeper depths. This investigation thus suggests that differences in soil moisture dynamics across land cover types depend on the dynamics of the vegetation cover and less on static site properties. Reference: Mittelbach, H., and S.I. Seneviratne, 2012: A new perspective on the spatio-temporal variability of soil moisture: temporal dynamics versus time invariant contributions. Hydrol. Earth Syst. Sci., 16, 2169-2179.

Mittelbach, Heidi; Henschel, Florian; Seneviratne, Sonia I.

2013-04-01

302

Simulation of surface topography of big aspheric fabrication by ultra-precision diamond turning based on tool swing feeding  

NASA Astrophysics Data System (ADS)

In the respect of ultra-precision manufacturing of axisymmetric surface, the machine tool with tool swing feeding which has less interpolation error sources compared to the conventional ultra-precision diamond turning machine tool with T-structureis worth studying.Therefore,based on the dynamic simulation modeling and multi-body dynamics theory,in this paper, we establish the control model,and tool path for Ultra-precision machine.Then we got the model for surface topography with differentinput parameters like spindle speed, feedrate, tool parameters and so on. Taking the spherical optics part with diameter of 300 mm, for example, we input the process parameters and get its surface topography, then evaluate its surface quality by surface roughness value (Ra) and surface shape accuracy(PV) .

Yao, Honghui; Li, Zengqiang; Sun, Tao

2014-08-01

303

Circum-Arctic mantle structure and long-wavelength topography since the Jurassic  

NASA Astrophysics Data System (ADS)

The circum-Arctic is one of the most tectonically complex regions of the world, shaped by a history of ocean basin opening and closure since the Early Jurassic. The region is characterized by contemporaneous large-scale Cenozoic exhumation extending from Alaska to the Atlantic, but its driving force is unknown. We show that the mantle flow associated with subducted slabs of the South Anuyi, Mongol-Okhotsk, and Panthalassa oceans have imparted long-wavelength deflection on overriding plates. We identify the Jurassic-Cretaceous South Anuyi slab under present-day Greenland in seismic tomography and numerical mantle flow models. Under North America, we propose the "Farallon" slab results from Andean-style ocean-continent convergence around ~30°N and from a combination of ocean-continent and intraoceanic subduction north of 50°N. We compute circum-Arctic dynamic topography through time from subduction-driven convection models and find that slabs have imparted on average <1-16 m/Myr of dynamic subsidence across the region from at least 170 Ma to ~50 Ma. With the exception of Siberia, the main phase of circum-Arctic dynamic subsidence has been followed either by slowed subsidence or by uplift of <1-6 m/Myr on average to present day. Comparing these results to geological inferences suggest that subduction-driven dynamic topography can account for rapid Middle to Late Jurassic subsidence in the Slave Craton and North Slope (respectively, <15 and 21 m/Myr, between 170 and 130 Ma) and for dynamic subsidence (<7 m/Myr, ~170-50 Ma) followed by dynamic uplift (<6 m/Myr since 50 Ma) of the Barents Sea region. Combining detailed kinematic reconstructions with geodynamic modeling and key geological observations constitutes a powerful tool to investigate the origin of vertical motion in remote regions.

Shephard, G. E.; Flament, N.; Williams, S.; Seton, M.; Gurnis, M.; Müller, R. D.

2014-10-01

304

Absolutely continuous spectrum implies ballistic transport for quantum particles in a random potential on tree graphs  

SciTech Connect

We discuss the dynamical implications of the recent proof that for a quantum particle in a random potential on a regular tree graph absolutely continuous (ac) spectrum occurs non-perturbatively through rare fluctuation-enabled resonances. The main result is spelled in the title.

Aizenman, Michael [Departments of Physics and Mathematics, Princeton University, Princeton, New Jersey 08544 (United States); Warzel, Simone [Zentrum Mathematik, TU Munich, Boltzmannstr. 3, 85747 Garching (Germany)

2012-09-15

305

Absolutely continuous spectrum implies ballistic transport for quantum particles in a random potential on tree graphs  

E-print Network

We discuss the dynamical implications of the recent proof that for a quantum particle in a random potential on a regular tree graph absolutely continuous spectrum occurs non-perturbatively through rare fluctuation-enabled resonances. The main result is spelled in the title.

Michael Aizenman; Simone Warzel

2012-05-20

306

Predicting Maximum Lake Depth from Surrounding Topography  

EPA Science Inventory

Lake volume aids understanding of the physical and ecological dynamics of lakes, yet is often not readily available. The data needed to calculate lake volume (i.e. bathymetry) are usually only collected on a lake by lake basis and are difficult to obtain across broad regions. ...

307

Absolute height measurement of specular surfaces with modified active fringe reflection photogrammetry  

NASA Astrophysics Data System (ADS)

Deflectometric methods have been studied for more than a decade for slope measurement of specular freeform surfaces through utilization of the deformation of a sample pattern after reflection from a tested sample surface. Usually, these approaches require two-directional fringe patterns to be projected on a LCD screen or ground glass and require slope integration, which leads to some complexity for the whole measuring process. This paper proposes a new mathematical measurement model for measuring topography information of freeform specular surfaces, which integrates a virtual reference specular surface into the method of active fringe reflection photogrammetry and presents a straight-forward relation between height of the tested surface and phase signals. This method only requires one direction of horizontal or vertical sinusoidal fringe patterns to be projected from a LCD screen, resulting in a significant reduction in capture time over established methods. Assuming the whole system has been precalibrated during the measurement process, the fringe patterns are captured separately via the virtual reference and detected freeform surfaces by a CCD camera. The reference phase can be solved according to the spatial geometric relation between the LCD screen and the CCD camera. The captured phases can be unwrapped with a heterodyne technique and optimum frequency selection method. Based on this calculated unwrapped-phase and that proposed mathematical model, absolute height of the inspected surface can be computed. Simulated and experimental results show that this methodology can conveniently calculate topography information for freeform and structured specular surfaces without integration and reconstruction processes.

Ren, Hongyu; Jiang, Xiangqian; Gao, Feng; Zhang, Zonghua

2014-07-01

308

Corneal topography from spectral optical coherence tomography (sOCT).  

PubMed

We present a method to obtain accurate corneal topography from a spectral optical coherence tomography (sOCT) system. The method includes calibration of the device, compensation of the fan (or field) distortion introduced by the scanning architecture, and image processing analysis for volumetric data extraction, segmentation and fitting. We present examples of three-dimensional (3-D) surface topography measurements on spherical and aspheric lenses, as well as on 10 human corneas in vivo. Results of sOCT surface topography (with and without fan-distortion correction) were compared with non-contact profilometry (taken as reference) on a spherical lens, and with non-contact profilometry and state-of-the art commercial corneal topography instruments on aspheric lenses and on subjects. Corneal elevation maps from all instruments were fitted by quadric surfaces (as well as by tenth-order Zernike polynomials) using custom routines. We found that the discrepancy in the estimated radius of curvature from nominal values in artificial corneas decreased from 4.6% (without fan distortion correction) to 1.6% (after fan distortion correction), and the difference in the asphericity decreased from 130% to 5%. In human corneas, the estimated corneal radius of curvature was not statistically significantly different across instruments. However, a Bland-Altman analysis showed consistent differences in the estimated asphericity and corneal shape between sOCT topographies without fan distortion correction and the rest of the measurements. PMID:22162814

Ortiz, Sergio; Siedlecki, Damian; Pérez-Merino, Pablo; Chia, Noelia; de Castro, Alberto; Szkulmowski, Maciej; Wojtkowski, Maciej; Marcos, Susana

2011-12-01

309

Absolute and relative quantification of RNA modifications via biosynthetic isotopomers  

PubMed Central

In the resurging field of RNA modifications, quantification is a bottleneck blocking many exciting avenues. With currently over 150 known nucleoside alterations, detection and quantification methods must encompass multiple modifications for a comprehensive profile. LC–MS/MS approaches offer a perspective for comprehensive parallel quantification of all the various modifications found in total RNA of a given organism. By feeding 13C-glucose as sole carbon source, we have generated a stable isotope-labeled internal standard (SIL-IS) for bacterial RNA, which facilitates relative comparison of all modifications. While conventional SIL-IS approaches require the chemical synthesis of single modifications in weighable quantities, this SIL-IS consists of a nucleoside mixture covering all detectable RNA modifications of Escherichia coli, yet in small and initially unknown quantities. For absolute in addition to relative quantification, those quantities were determined by a combination of external calibration and sample spiking of the biosynthetic SIL-IS. For each nucleoside, we thus obtained a very robust relative response factor, which permits direct conversion of the MS signal to absolute amounts of substance. The application of the validated SIL-IS allowed highly precise quantification with standard deviations <2% during a 12-week period, and a linear dynamic range that was extended by two orders of magnitude. PMID:25129236

Kellner, Stefanie; Ochel, Antonia; Thüring, Kathrin; Spenkuch, Felix; Neumann, Jennifer; Sharma, Sunny; Entian, Karl-Dieter; Schneider, Dirk; Helm, Mark

2014-01-01

310

Gravity, Topography, and Magnetic Field of Mercury from Messenger  

NASA Technical Reports Server (NTRS)

On 18 March 2011, the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft was inserted into a 12-hour, near-polar orbit around Mercury, with an initial periapsis altitude of 200 km, initial periapse latitude of 60 deg N, and apoapsis at approximately 15,200 km altitude in the southern hemisphere. This orbit has permitted the mapping of regional gravitational structure in the northern hemisphere, and laser altimetry from the MESSENGER spacecraft has yielded a geodetically controlled elevation model for the same hemisphere. The shape of a planet combined with gravity provides fundamental information regarding its internal structure and geologic and thermal evolution. Elevations in the northern hemisphere exhibit a unimodal distribution with a dynamic range of 9.63 km, less than that of the Moon (19.9 km), but consistent with Mercury's higher surface gravitational acceleration. After one Earth-year in orbit, refined models of gravity and topography have revealed several large positive gravity anomalies that coincide with major impact basins. These candidate mascons have anomalies that exceed 100 mGal and indicate substantial crustal thinning and superisostatic uplift of underlying mantle. An additional uncompensated 1000-km-diameter gravity and topographic high at 68 deg N, 33 deg E lies within Mercury's northern volcanic plains. Mercury's northern hemisphere crust is generally thicker at low latitudes than in the polar region. The low-degree gravity field, combined with planetary spin parameters, yields the moment of inertia C/MR2 = 0.353 +/- 0.017, where M=3.30 x 10(exp 23) kg and R=2440 km are Mercury's mass and radius, and a ratio of the moment of inertia of Mercury's solid outer shell to that of the planet of Cm/C = 0.452 +/- 0.035. One proposed model for Mercury's radial density distribution consistent with these results includes silicate crust and mantle layers overlying a dense solid (possibly Fe-S) layer, a liquid Fe-rich outer core of radius 2030 +/- 37 km, and an assumed solid inner core. Magnetic field measurements indicate a northward offset of Mercury's axial magnetic dipole from the geographic equator by 479 +/-3 km and provide evidence for a regional-scale magnetic field approximately collocated with the northern volcanic plains of possible crustal origin. These results from MESSENGER indicate a complex and asymmetric evolution of internal structure and dynamics in this end-member inner planet.

Neumann, Gregory A.; Solomon, Sean C.; Zuber, Maria T.; Phillips, Roger J.; Barnouin, Olivier; Ernst, Carolyn; Goosens, Sander; Hauck, Steven A., II; Head, James W., III; Johnson, Catherine L.; Lemoine, Frank G.; Margot, Jean-Luc; McNutt, Ralph; Mazarico, Erwan M.; Oberst, Jurgen; Peale, Stanley J.; Perry, Mark; Purucker, Michael E.; Rowlands, David D.; Torrence, Mark H.

2012-01-01

311

Absolute absorption spectroscopy based on molecule interferometry  

E-print Network

We propose a new method to measure the absolute photon absorption cross section of neutral molecules in a molecular beam. It is independent of our knowledge of the particle beam density, nor does it rely on photo-induced fragmentation or ionization. The method is based on resolving the recoil resulting from photon absorption by means of near-field matter-wave interference, and it thus applies even to very dilute beams with low optical densities. Our discussion includes the possibility of internal state conversion as well as fluorescence. We assess the influence of various experimental uncertainties and show that the measurement of absolute absorption cross sections is conceivable with high precision and using existing technologies.

Stefan Nimmrichter; Klaus Hornberger; Hendrik Ulbricht; Markus Arndt

2008-11-07

312

Absolute quantification method for protein concentration.  

PubMed

A fast and accurate assay to determine the absolute concentration of proteins is described based on direct measurement of droplet entrapped oligomer formation in electrospray. Here we demonstrate the approach using electrospray differential mobility analysis (ES-DMA), which can distinguish monomers and dimers from higher order oligomers. A key feature of the method is that it allows determination of the absolute number concentration of proteins eliminating the need for protein-specific calibration. The method was demonstrated by measuring the concentration of a NIST Standard Reference Material 927e (bovine serum albumin), a high-purity immunoglobulin G 1?, and a formulated Rituximab. The method may be applied to any electrospray source, regardless of diagnostic tool (e.g., MS or ion-mobility, etc.), provided the electrospray is operated in a droplet-fission mode. PMID:25412350

Li, Mingdong; Tan, Jiaojie; Tarlov, Michael J; Zachariah, Michael R

2014-12-16

313

Asteroid absolute magnitudes and slope parameters  

NASA Technical Reports Server (NTRS)

A new listing of absolute magnitudes (H) and slope parameters (G) has been created and published in the Minor Planet Circulars; this same listing will appear in the 1992 Ephemerides of Minor Planets. Unlike previous listings, the values of the current list were derived from fits of data at the V band. All observations were reduced in the same fashion using, where appropriate, a single basis default value of 0.15 for the slope parameter. Distances and phase angles were computed for each observation. The data for 113 asteroids was of sufficiently high quality to permit derivation of their H and G. These improved absolute magnitudes and slope parameters will be used to deduce the most reliable bias-corrected asteroid size-frequency distribution yet made.

Tedesco, Edward F.

1991-01-01

314

Absolute absorption spectroscopy based on molecule interferometry  

E-print Network

We propose a new method to measure the absolute photon absorption cross section of neutral molecules in a molecular beam. It is independent of our knowledge of the particle beam density, nor does it rely on photo-induced fragmentation or ionization. The method is based on resolving the recoil resulting from photon absorption by means of near-field matter-wave interference, and it thus applies even to very dilute beams with low optical densities. Our discussion includes the possibility of internal state conversion as well as fluorescence. We assess the influence of various experimental uncertainties and show that the measurement of absolute absorption cross sections is conceivable with high precision and using existing technologies.

Nimmrichter, Stefan; Ulbricht, Hendrik; Arndt, Markus

2008-01-01

315

Absolute and relative dosimetry for ELIMED  

SciTech Connect

The definition of detectors, methods and procedures for the absolute and relative dosimetry of laser-driven proton beams is a crucial step toward the clinical use of this new kind of beams. Hence, one of the ELIMED task, will be the definition of procedures aiming to obtain an absolute dose measure at the end of the transport beamline with an accuracy as close as possible to the one required for clinical applications (i.e. of the order of 5% or less). Relative dosimetry procedures must be established, as well: they are necessary in order to determine and verify the beam dose distributions and to monitor the beam fluence and the energetic spectra during irradiations. Radiochromic films, CR39, Faraday Cup, Secondary Emission Monitor (SEM) and transmission ionization chamber will be considered, designed and studied in order to perform a fully dosimetric characterization of the ELIMED proton beam.

Cirrone, G. A. P.; Schillaci, F.; Scuderi, V. [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and Institute of Physics Czech Academy of Science, ELI-Beamlines project, Na Slovance 2, Prague (Czech Republic)] [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and Institute of Physics Czech Academy of Science, ELI-Beamlines project, Na Slovance 2, Prague (Czech Republic); Cuttone, G.; Candiano, G.; Musumarra, A.; Pisciotta, P.; Romano, F. [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania (Italy)] [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania (Italy); Carpinelli, M. [INFN Sezione di Cagliari, c/o Dipartimento di Fisica, Università di Cagliari, Cagliari (Italy)] [INFN Sezione di Cagliari, c/o Dipartimento di Fisica, Università di Cagliari, Cagliari (Italy); Leonora, E.; Randazzo, N. [INFN-Sezione di Catania, Via Santa Sofia 64, Catania (Italy)] [INFN-Sezione di Catania, Via Santa Sofia 64, Catania (Italy); Presti, D. Lo [INFN-Sezione di Catania, Via Santa Sofia 64, Catania, Italy and Università di Catania, Dipartimento di Fisica e Astronomia, Via S. Sofia 64, Catania (Italy)] [INFN-Sezione di Catania, Via Santa Sofia 64, Catania, Italy and Università di Catania, Dipartimento di Fisica e Astronomia, Via S. Sofia 64, Catania (Italy); Raffaele, L. [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and INFN-Sezione di Catania, Via Santa Sofia 64, Catania (Italy)] [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and INFN-Sezione di Catania, Via Santa Sofia 64, Catania (Italy); Tramontana, A. [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and Università di Catania, Dipartimento di Fisica e Astronomia, Via S. Sofia 64, Catania (Italy)] [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and Università di Catania, Dipartimento di Fisica e Astronomia, Via S. Sofia 64, Catania (Italy); Cirio, R.; Sacchi, R.; Monaco, V. [INFN, Sezione di Torino, Via P.Giuria, 1 10125 Torino, Italy and Università di Torino, Dipartimento di Fisica, Via P.Giuria, 1 10125 Torino (Italy)] [INFN, Sezione di Torino, Via P.Giuria, 1 10125 Torino, Italy and Università di Torino, Dipartimento di Fisica, Via P.Giuria, 1 10125 Torino (Italy); Marchetto, F.; Giordanengo, S. [INFN, Sezione di Torino, Via P.Giuria, 1 10125 Torino (Italy)] [INFN, Sezione di Torino, Via P.Giuria, 1 10125 Torino (Italy)

2013-07-26

316

Absolute and relative dosimetry for ELIMED  

NASA Astrophysics Data System (ADS)

The definition of detectors, methods and procedures for the absolute and relative dosimetry of laser-driven proton beams is a crucial step toward the clinical use of this new kind of beams. Hence, one of the ELIMED task, will be the definition of procedures aiming to obtain an absolute dose measure at the end of the transport beamline with an accuracy as close as possible to the one required for clinical applications (i.e. of the order of 5% or less). Relative dosimetry procedures must be established, as well: they are necessary in order to determine and verify the beam dose distributions and to monitor the beam fluence and the energetic spectra during irradiations. Radiochromic films, CR39, Faraday Cup, Secondary Emission Monitor (SEM) and transmission ionization chamber will be considered, designed and studied in order to perform a fully dosimetric characterization of the ELIMED proton beam.

Cirrone, G. A. P.; Cuttone, G.; Candiano, G.; Carpinelli, M.; Leonora, E.; Lo Presti, D.; Musumarra, A.; Pisciotta, P.; Raffaele, L.; Randazzo, N.; Romano, F.; Schillaci, F.; Scuderi, V.; Tramontana, A.; Cirio, R.; Marchetto, F.; Sacchi, R.; Giordanengo, S.; Monaco, V.

2013-07-01

317

From Hubble's NGSL to Absolute Fluxes  

NASA Technical Reports Server (NTRS)

Hubble's Next Generation Spectral Library (NGSL) consists of R-l000 spectra of 374 stars of assorted temperature, gravity, and metallicity. Each spectrum covers the wavelength range, 0.18-1.00 microns. The library can be viewed and/or downloaded from the website, http://archive.stsci.edu/prepds/stisngsll. Stars in the NGSL are now being used as absolute flux standards at ground-based observatories. However, the uncertainty in the absolute flux is about 2%, which does not meet the requirements of dark-energy surveys. We are therefore developing an observing procedure that should yield fluxes with uncertainties less than 1 % and will take part in an HST proposal to observe up to 15 stars using this new procedure.

Heap, Sara R.; Lindler, Don

2012-01-01

318

Consistent thermostatistics forbids negative absolute temperatures  

NASA Astrophysics Data System (ADS)

Over the past 60 years, a considerable number of theories and experiments have claimed the existence of negative absolute temperature in spin systems and ultracold quantum gases. This has led to speculation that ultracold gases may be dark-energy analogues and also suggests the feasibility of heat engines with efficiencies larger than one. Here, we prove that all previous negative temperature claims and their implications are invalid as they arise from the use of an entropy definition that is inconsistent both mathematically and thermodynamically. We show that the underlying conceptual deficiencies can be overcome if one adopts a microcanonical entropy functional originally derived by Gibbs. The resulting thermodynamic framework is self-consistent and implies that absolute temperature remains positive even for systems with a bounded spectrum. In addition, we propose a minimal quantum thermometer that can be implemented with available experimental techniques.

Dunkel, Jörn; Hilbert, Stefan

2014-01-01

319

Absolute enantioselective separation: optical activity ex machina.  

PubMed

The paper describes methodology of using three independent macroscopic factors affecting molecular orientation to accomplish separation of a racemic mixture without the presence of any other chiral compounds, i. e., absolute enantioselective separation (AES) which is an extension of a concept of applying these factors to absolute asymmetric synthesis. The three factors may be applied simultaneously or, if their effects can be retained, consecutively. The resulting three mutually orthogonal or near orthogonal directors constitute a true chiral influence and their scalar triple product is the measure of the chirality of the system. AES can be executed in a chromatography-like microfluidic process in the presence of an electric field. It may be carried out on a chemically modified flat surface, a monolithic polymer column made of a mesoporous material, each having imparted directional properties. Separation parameters were estimated for these media and possible implications for the natural homochirality are discussed. PMID:16342798

Bielski, Roman; Tencer, Michal

2005-11-01

320

Probing absolute spin polarization at the nanoscale.  

PubMed

Probing absolute values of spin polarization at the nanoscale offers insight into the fundamental mechanisms of spin-dependent transport. Employing the Zeeman splitting in superconducting tips (Meservey-Tedrow-Fulde effect), we introduce a novel spin-polarized scanning tunneling microscopy that combines the probing capability of the absolute values of spin polarization with precise control at the atomic scale. We utilize our novel approach to measure the locally resolved spin polarization of magnetic Co nanoislands on Cu(111). We find that the spin polarization is enhanced by 65% when increasing the width of the tunnel barrier by only 2.3 Å due to the different decay of the electron orbitals into vacuum. PMID:25423049

Eltschka, Matthias; Jäck, Berthold; Assig, Maximilian; Kondrashov, Oleg V; Skvortsov, Mikhail A; Etzkorn, Markus; Ast, Christian R; Kern, Klaus

2014-12-10

321

The absolute bioavailability of caffeine in man  

Microsoft Academic Search

The absolute bioavailability of orally administered caffeine was investigated in 10 healthy adult male volunteers, aged 18.8 to 30.0 years. The subjects were administered a 5 mg\\/kg dose of caffeine as either an aqueous oral solution or an intravenous infusion, on separate occasions about 1 week apart, in a randomized crossover fashion. Plasma samples were collected over the 24-h period

J. Blanchard; S. J. A. Sawers

1983-01-01

322

The Risks of Absolute Medical Confidentiality  

Microsoft Academic Search

Some ethicists argue that patient confidentiality is absolute and thus should never be broken. I examine these arguments that\\u000a when critically scrutinised, become porous. I will explore the concept of patient confidentiality and argue that although,\\u000a this is a very important medical and bioethical issue, this needs to be wisely delivered to reduce third party harm or even\\u000a detriment to

M. A. Crook

323

Teaching absolute value inequalities to mature students  

Microsoft Academic Search

This paper gives an account of a teaching experiment on absolute value inequalities, whose aim was to identify characteristics\\u000a of an approach that would realize the potential of the topic to develop theoretical thinking in students enrolled in prerequisite\\u000a mathematics courses at a large, urban North American university. The potential is demonstrated in an epistemological analysis\\u000a of the topic. It

Anna Sierpinska; Georgeana Bobos; Andreea Pruncut

324

The absolute spectrophotometric catalog by Anita Cochran  

NASA Astrophysics Data System (ADS)

The absolute spectrophotometric catalog by Anita Cochran is presented in a machine-readable form. The catalog systematizes observations acquired at the McDonald Observatory in 1977-1978. The data are compared with other sources, in particular, the calculated broadband stellar magnitudes are compared with photometric observations by other authors, to show that the observational data given in the catalog are reliable and suitable for a variety of applications. Observations of variable stars of different types make Cochran's catalog especially valuable.

Burnashev, V. I.; Burnasheva, B. A.; Ruban, E. V.; Hagen-Torn, E. I.

2014-06-01

325

Absolute detector calibration using twin beams  

E-print Network

A method for the determination of absolute quantum detection efficiency is suggested based on the measurement of photocount statistics of twin beams. The measured histograms of joint signal-idler photocount statistics allow to eliminate an additional noise superimposed on an ideal calibration field composed of only photon pairs. This makes the method superior above other approaches presently used. Twin beams are described using a paired variant of quantum superposition of signal and noise.

Jan Perina Jr; Ondrej Haderka; Vaclav Michalek; Martin Hamar

2012-05-09

326

Modeling Floods in Athabasca Valles, Mars, Using CTX Stereo Topography  

NASA Astrophysics Data System (ADS)

Among the most remarkable landforms on Mars are the outflow channels, which suggest the occurrence of catastrophic water floods in the past. Athabasca Valles has long been thought to be the youngest of these channels [1-2], although it has recently become clear that the young crater age applies to a coating lava flow [3]. Simulations with a 2.5-dimensional flood model have provided insight into the details of flood dynamics but have also demonstrated that the Digital Elevation Model (DEM) from the Mars Orbiter Laser Altimeter (MOLA) Mission Experiment Gridded Data Records includes significant artifacts at this latitude at the scales relevant for flood modeling [4]. In order to obtain improved topography, we processed stereo images from the Context Camera (CTX) of the Mars Reconnaissance Orbiter (MRO) using methods developed for producing topographic models of the Moon with images from the Lunar Reconnaissance Orbiter Camera, a derivative of the CTX camera. Some work on flood modeling with CTX stereo has been published by [5], but we will present several advances, including corrections to the published CTX optical distortion model and improved methods to combine the stereo and MOLA data. The limitations of current methods are the accuracy of control to MOLA and the level of error introduced when the MRO spacecraft is not in a high-stability mode during stereo imaging, leading to jitter impacting the derived topography. Construction of a mosaic of multiple stereo pairs, controlled to MOLA, allows us to consider flow through the cluster of streamlined islands in the upper part of the channel [6], including what is suggested to be the best example of flood-formed subaqueous dunes on Mars [7]. We will present results from running a flood model [4, 8] through the high-resolution (100 m/post) DEM covering the streamlined islands and subaqueous dunes, using results from a lower-resolution model as a guide to the inflow. By considering a range of flow levels below estimated peak flow, we can examine the flow behavior at the site of the apparent subaqueous dunes and, in particular, assess whether the flow in this area is uniquely conducive to the formation of such bedforms [e.g., 9]. [1] Berman D. C. and Hartmann W. K. (2002) Icarus 159, 1-17. [2] Burr D. M. et al. (2002) Icarus 159, 53-73. [3] Jaeger W. L. et al. (2010) Icarus 205, 230-243. [4] Keszthelyi L. P. et al. (2007) GRL 34, L21206. [5] McIntyre et al. (2012) JGR 117, E03009. [6] Burr D. (2005) Geomorphology 69, 242-252. [7] Burr D. M. et al. (2004) Icarus 171, 68-83. [8] Denlinger R. P. and O'Connell D. R. H. (2008) J. Hyd. Eng. 134, 1590-1602. [9] Kleinhans M. G. (2005) JGR 110, E12003.

Dundas, C. M.; Keszthelyi, L. P.; Denlinger, R. P.; Thomas, O. H.; Galuszka, D.; Hare, T. M.; Kirk, R. L.; Howington-Kraus, E.; Rosiek, M.

2012-12-01

327

Ocean and laboratory observations on waves over topography  

NASA Astrophysics Data System (ADS)

This thesis addresses the observation, analysis and dynamics of waves as being trapped, generated and focused by sloping topography. ---Shelf waves with diurnal tidal frequency off Greenland--- Tidal analysis has been carried out on current measurements at a “cross-shelf” transect off Greenland at 71 N. The diurnal tides manifest themselves mainly as a barotropic continental shelf wave, travelling southward along the shelf slope. This follows from the amplitude distribution of the diurnal tidal components and from the rotation sense of the tidal ellipses at different cross-slope locations, as calculated with simple two-dimensional models. The well organized cross-slope pattern of the velocity amplitudes is absent in observations further north near 75 N. These observations suggest that the local vanishing of the group velocity, which is caused by topography, is of importance for the existence and local amplification of these continental shelf waves with diurnal tidal frequency. ---Tidal and residual currents near the shelf break in Biscay--- Internal-wave energy in continuously stratified fluids propagates in the vertical plane, at an angle set by the wave, buoyancy and Coriolis frequencies. Repeated Acoustic Doppler Current Profiler observations on three transects, crossing the shelf edge, now directly reveal this beam-wise propagation of internal tides in the Bay of Biscay. This confirms previous suggestions based on observations sampled more sparsely in space. The present observation is made by bin-wise harmonic analysis of horizontal currents, leading to the spatial resolution of barotropic and baroclinic semi-diurnal tidal and (time-averaged) residual flows. The observed baroclinic tide compares favourably to that produced by a two-dimensional numerical model. The observations reveal details of the internal tidal beam, including its spatial amplitude distribution, presence of amphidromes and direction of phase propagation. The cross-isobath structure of the along-slope barotropic mean flow shows a localized maximum near the shelf break. Over two transects it agrees in sign and magnitude with a theoretical tidally-rectified flow. The baroclinic, cross-isobath mean flow shows a strong near-bottom downwelling flow, compensated by an on-shelf directed flow in the upper part. The along-shelf mean flow displays subsurface-intensification attributed here to frictional modification of a tidally-rectified flow that is bottom-trapped due to stratification. ---Internal wave focusing revisited--- An experiment which discussed the appearance of an internal wave attractor in a uniformly-stratified, free-surface fluid (Maas et al. 1997) is revisited. This is done in order to give a more detailed and more accurate description of the underlying focusing process. Evolution of the attractor can now be quantified. For the tank with one sloping sidewall, and for the parameter regime (density stratification, forcing frequency) studied, the inverse exponential growth rate determined at several locations in the fluid turns out to be 122 seconds always. Only the start and duration of the growth differs: away from the attractor region it appears later and is of shorter duration. Here, these features are interpreted by employing a new theoretical basis that incorporates an external forcing via a surface boundary condition (an infinitesimal barotropic seiche) and that describes the solution in terms of propagating waves.

Lam, F. P. A.

2007-01-01

328

Sea-Surface Topography and Precise Geodesy From Aircraft: Applications to Coastal Oceanography  

NASA Astrophysics Data System (ADS)

Highly dynamic coastal ocean processes occur at temporal and spatial scales that cannot be captured by present or planned satellite altimeters. Space-borne gravity missions such as CHAMP, GRACE and GOCE also provide time-varying gravity and a geoidal msl reference surface at resolution that is too coarse for many coastal applications. The Naval Research Laboratory and the Naval Oceanographic Office have been testing airborne measurement techniques, gravity and altimetry, to determine sea-surface height and height anomaly at the short scales required for littoral regions. We have developed a precise local gravimetric geoid over a test region in the northern Gulf of Mexico from historical gravity data and recent airborne gravity surveys. The local geoid provides a msl reference surface with a resolution of about 10-15 km. A series of altimetry reflights over the region with time scales of 1 day to 1 year reveal a highly dynamic environment with coherent and rapidly varying sea-surface height anomalies. Although wind-driven topography may also be a factor, airborne expendable bathy-thermograph (AXBT) data collected at the same time show apparent correlation with wave-like temperature anomalies propagating up the continental slope of the Desoto Canyon. The observed variability may be responsible for some part of the long-term average topography calculated by differencing the gravimetric geoid with a satellite altimetry msl reference.

Brozena, J. M.; Childers, V. A.; Jacobs, G.; Blaha, J.; Ball, D.

2002-12-01

329

A downscaling method for simulating deep current interactions with topography - Application to the Sigsbee Escarpment  

NASA Astrophysics Data System (ADS)

A nesting approach is applied to dynamically downscale the deep circulation from a basin-scale model in regions of complicated topography where deep dynamics may be poorly resolved. The method is applied to nest a high vertical and horizontal resolution Navy Coastal Ocean Model (NCOM) domain covering the north-central Gulf of Mexico within a HYbrid Coordinate Ocean Model (HYCOM) Gulf of Mexico domain. The northwestern Gulf of Mexico has a very steep topographic feature, the Sigsbee Escarpment, over which localized bottom-intensified currents with short cross-isobath length scales have been observed in water depths between 1500 m and 3000 m. It has been hypothesized that these intense currents are related to the presence of the Loop Current or Loop Current Eddies, strong upper ocean mesoscale circulation features in the Gulf. A modeling system is required that can resolve the short length scales of topography and the currents, resolve the vertical trapping of the currents, and realistically simulate the mesoscale upper and deep ocean circulation features. The multi-model nesting approach described here simulates these intense currents with characteristics very similar to observations, and demonstrates the connectivity to the larger scale ocean circulation features.

Morey, Steven L.; Dukhovskoy, Dmitry S.

2013-09-01

330

Effects of lunar topography on the near-surface dusty-plasma environment  

NASA Astrophysics Data System (ADS)

Due to interactions with the solar wind and ultraviolet radiation, the lunar surface develops a complex plasma environment, especially around features like craters and boulders. Various phenomena have been observed on the lunar surface, including dust levitation and horizontal dust transport. Dust levitation and transport could result in dust ponding, as has been observed on asteroid 433 Eros. To understand these phenomena a three-dimensional particle-in-cell (PIC) code was ran using the high-performance code, VORPAL©. The plasma environment was modeled above various topographies, including: (1) a flat surface; (2) a crater with a diameter of seven meters; (3) a 1x1x1 meter block; and (4) a system including a crater and a block. All four scenarios were modeled with changing solar angles to simulate a full days worth of plasma conditions. Dust dynamics were then modeled with a test particle approach, where individual dust grains are introduced into the PIC-modeled plasma environment. We simulated multiple lunar days of dust dynamics in order to detect net transport of the dust. To do this, we stepped through time while interpolating between solar angles to obtain plasma conditions and continuously eject charged grains off the surface to interact with the electric fields. A comparison of the effects of the various surface topographies on the dust and plasma environment will be presented.

Piquette, M. R.; Horanyi, M.; Likhanskii, A.

2013-12-01

331

Plasma Molding over Surface Topography: IED and IAD over Steps  

NASA Astrophysics Data System (ADS)

Plasma molding over surface topography finds applications in MEMS microfabrication, plasma extraction through grids, and plasma contact with internal reactor parts (e.g., wafer chuck edge). The flux, energy and angular distributions of ions incident on the target are of primary importance in these applications. These quantities depend critically on the shape of the meniscus (plasma-sheath boundary) formed over the surface topography. We have developed a 2-D simulation tool to calculate the flux, energy and angular distribution of ions (and fast neutrals) impinging on surface topography in contact with a high density plasma. Plasma molding over a step has been analyzed in detail. Simulation results will be compared to experimental data as a function of distance from the step obtained at Sandia National Labs.

Economou, Demetre; Kim, Doosik

2001-10-01

332

SPC Shape and Topography of Vesta from DAWN Imaging Data  

NASA Astrophysics Data System (ADS)

The DAWN spacecraft has now left Vesta, leaving a legacy of more than 16000 clear filter images of the asteroid. During the last month of Dawn's stay at Vesta, the sun slowly crept northward, enabling the spacecraft to view topography closer to the north pole. We have used these images with our stereophotoclinometry (SPC) software to construct topography for most of Vesta's surface to 50 meter resolution, and below about 60 degrees south to 20 meter resolution. We present this topography as a 1/64 degree gridded map (about 70 m resolution), as a stereographic projection of the south polar region at 25 m resolution and as a global shape model with 1.57 million vectors. In addition, we present solutions for the s/c position and camera pointing at all imaging times during DAWN's entire stay at Vesta.

Gaskell, Robert W.

2012-10-01

333

Influence of nanophase titania topography on bacterial attachment and metabolism  

PubMed Central

Surfaces with nanophase compared to conventional (or nanometer smooth) topographies are known to have different properties of area, charge, and reactivity. Previously published research indicates that the attachment of certain bacteria (such as Pseudomonas fluorescens 5RL) is higher on surfaces with nanophase compared to conventional topographies, however, their effect on bacterial metabolism is unclear. Results presented here show that the adhesion of Pseudomonas fluorescens 5RL and Pseudomonas putida TVA8 was higher on nanophase than conventional titania. Importantly, in terms of metabolism, bacteria attached to the nanophase surfaces had higher bioluminescence rates than on the conventional surfaces under all nutrient conditions. Thus, the results from this study show greater select bacterial metabolism on nanometer than conventional topographies, critical results with strong consequences for the design of improved biosensors for bacteria detection. PMID:19337418

Park, Margaret R; Banks, Michelle K; Applegate, Bruce; Webster, Thomas J

2008-01-01

334

Surface topography prediction on laser processed tool steel  

NASA Astrophysics Data System (ADS)

In laser surface treatment the laser beam is used as energy source for surface modification improving aspects such as mechanical properties, tribology or surface texture. Modeling tools have special interest in processes with many variables, like laser surface processing, in order to minimize the tryout testing to find the optimal process parameters. The work presented here focuses on the prediction of the final topography in laser polishing process. By FFT analysis of the surface profile it is possible to get the different frequency components of the initial topography. On the other hand, thermal field simulation was carried out to evaluate the melt duration. Matching this with the spatial frequency damping during process, the reconstruction of the processed topography was obtained.

Ukar, E.; Lamikiz, A.; Martínez, S.; López de Lacalle, L. N.

2012-04-01

335

Introduction to Special Section on Tectonics and Topography  

NASA Astrophysics Data System (ADS)

This special section on tectonics and topography developed from an American Geophysical Union Chapman Conference convened in the late summer of 1992 in Snowbird, Utah. The intent of the gathering was to assemble a diverse group of Earth scientists working on ultimately the same problem: the interaction between crustal and surficial processes or, euphemistically, tectonics and topography. Through numerous and enthusiastic conversations, it became clear to us prior to the Chapman Conference that many people were working on the interaction between tectonics and topography but about half of these were either unaware of the others or were aghast at the way in which the others simplified their subject (and vice versa for the other half!). To our delight, the conference brought forth a wonderful array of scientists from virtually all subdisciplines of geology, and the desire for mutual help and a sympathetic ear was palpable.

Merritts, Dorothy; Ellis, Michael

1994-06-01

336

Sintered silver joints via controlled topography of electronic packaging subcomponents  

DOEpatents

Disclosed are sintered silver bonded electronic package subcomponents and methods for making the same. Embodiments of the sintered silver bonded EPSs include topography modification of one or more metal surfaces of semiconductor devices bonded together by the sintered silver joint. The sintered silver bonded EPSs include a first semiconductor device having a first metal surface, the first metal surface having a modified topography that has been chemically etched, grit blasted, uniaxial ground and/or grid sliced connected to a second semiconductor device which may also include a first metal surface with a modified topography, a silver plating layer on the first metal surface of the first semiconductor device and a silver plating layer on the first metal surface of the second semiconductor device and a sintered silver joint between the silver plating layers of the first and second semiconductor devices which bonds the first semiconductor device to the second semiconductor device.

Wereszczak, Andrew A.

2014-09-02

337

Ulva linza zoospore sensitivity to systematic variation of surface topography  

NASA Astrophysics Data System (ADS)

The use of surface topographical microstructure is abundant in nature. The lotus plant uses a fractal-like topography to create a highly non-wetting surface that self-cleans as water drops take dirt particles with them as they roll off. Analysis of how topography affects surface interactions offers a unique opportunity to attack a problem that affects our economy and societal health significantly. The attachment of biological material to manmade surfaces can be looked at as fouling or directed adhesion. Marine fouling on ship hulls costs the United States $600 million each year due to increased fuel usage caused by drag. Hospital-acquired methicillin-resistant Staphylococcus aureus infections cause thousands of deaths annually as a result of colonization of hospital surfaces. The lack of biocompatible synthetic surfaces for implants such as vascular grafts lead to restenosis as cells are unable to develop a natural interaction with the graft surface. In each circumstance there is much to learn about the complicated attachment process. This work expands the investigation of the role of topography in the attachment of the green fouling algae Ulva linza to poly(dimethylsiloxane) surfaces. Spore attachment density was correlated to the Wenzel roughness ratio on low surface energy, high-modulus poly(dimethylsiloxane)-grafted-silicon topographies. The role of topography on a scale less than the size of a spore was investigated on nano-roughened poly(dimethylsiloxane) elastomer surfaces. For a specific group of patterns, the spatial distribution of spores attached to topographies was quantitatively analyzed and shown to correlate with feature dimensions.

Sheats, Julian Taylor

338

The Absolute Calibration of the EUV Imaging Spectrometer on Hinode  

E-print Network

We investigate the absolute calibration of the EUV Imaging Spectrometer (EIS) on Hinode by comparing EIS full-disk mosaics with irradiance observations from the EUV Variability Experiment (EVE) on the Solar Dynamics Observatory. We also use ultra-deep (>10^5s) exposures of the quiet corona above the limb combined with a simple differential emission measure model to establish new effective area curves that incorporate information from the most recent atomic physics calculations. We find that changes to the EIS instrument sensitivity are a complex function of both time and wavelength. We find that the sensitivity is decaying exponentially with time and that the decay constants vary with wavelength. The EIS short wavelength channel shows significantly longer decay times than the long wavelength channel.

Warren, Harry P; Landi, Enrico

2013-01-01

339

Airborne Lidar Simulator for the Lidar Surface Topography (LIST) Mission  

NASA Technical Reports Server (NTRS)

In 2007, the National Research Council (NRC) completed its first decadal survey for Earth science at the request of NASA, NOAA, and USGS. The Lidar Surface Topography (LIST) mission is one of fifteen missions recommended by NRC, whose primary objectives are to map global topography and vegetation structure at 5 m spatial resolution, and to acquire global surface height mapping within a few years. NASA Goddard conducted an initial mission concept study for the LIST mission in 2007, and developed the initial measurement requirements for the mission.

Yu, Anthony W.; Krainak, Michael A.; Abshire, James B.; Cavanaugh, John; Valett, Susan; Ramos-Izquierdo, Luis

2010-01-01

340

Venus gravity and topography: 60th degree and order model  

NASA Technical Reports Server (NTRS)

We have combined the most recent Pioneer Venus Orbiter (PVO) and Magellan (MGN) data with the earlier 1978-1982 PVO data set to obtain a new 60th degree and order spherical harmonic gravity model and a 120th degree and order spherical harmonic topography model. Free-air gravity maps are shown over regions where the most marked improvement has been obtained (Ishtar-Terra, Alpha, Bell and Artemis). Gravity versus topography relationships are presented as correlations per degree and axes orientation.

Konopliv, A. S.; Borderies, N. J.; Chodas, P. W.; Christensen, E. J.; Sjogren, W. L.; Williams, B. G.; Balmino, G.; Barriot, J. P.

1993-01-01

341

Sound propagation over uneven ground and irregular topography  

NASA Technical Reports Server (NTRS)

Theoretical, computational, and experimental techniques were developed for predicting the effects of irregular topography on long range sound propagation in the atmosphere. Irregular topography is understood to imply a ground surface that: (1) is not idealizable as being perfectly flat, or (2) that is not idealizable as having a constant specific acoustic impedance. The focus is on circumstances where the propagation is similar to what might be expected for noise from low altitude air vehicles flying over suburban or rural terrain, such that rays from the source arrive at angles close to grazing incidence.

Berthelot, Yves H.; Pierce, Allan D.; Kearns, James A.; Zhou, Ji-Xun

1988-01-01

342

Sound propagation over uneven ground and irregular topography  

NASA Technical Reports Server (NTRS)

The goal of this research is to develop theoretical, computational, and experimental techniques for predicting the effects of irregular topography on long range sound propagation in the atmosphere. Irregular topography is understood to imply a ground surface that is not idealizable as being perfectly flat or that is no idealizable as having a constant specific acoustic impedance. The focus is on circumstances where the propagation is similar to what might be expected for noise from low-altitude air vehicles flying over suburban or rural terrain, such that rays from the source arrive at angles close to grazing incidence.

Berthelot, Yves H.; Pierce, Allan D.; Main, Geoffrey L.; Zhou, Ji-Xun; Kearns, James A.

1988-01-01

343

Sound propagation over uneven ground and irregular topography  

NASA Technical Reports Server (NTRS)

The development of theoretical, computational, and experimental techniques for predicting the effects of irregular topography on long range sound propagation in the atmosphere is discussed. Irregular topography here is understood to imply a ground surface that (1) is not idealizable as being perfectly flat or (2) that is not idealizable as having a constant specific acoustic impedance. The study focuses on circumstances where the propagation is similar to what might be expected for noise from low-altitude air vehicles flying over suburban or rural terrain, such that rays from the source arrive at angles close to grazing incidence.

Pierce, A. D.; Main, G. L.; Kearns, J. A.; Benator, D. R.; Parish, J. R., Jr.

1986-01-01

344

Assessing the quality of topography from stereo-photoclinometry  

NASA Astrophysics Data System (ADS)

Stereo-photoclinometry (SPC) has been used extensively to determine the shape and topography of various asteroids from image data. This technique will be used as one of two main approaches for determining the shape and topography of the asteroid Bennu, the target of the Origins Spectral Interpretation Resource Identification Security-Regolith Explorer (OSIRIS-REx) mission. The purpose of this study is to evaluate the quality of SPC products derived from the Near-Earth Asteroid Rendezvous (NEAR) mission, whose suite of imaging data resembles that to be collected by OSIRIS-REx. We make use of the NEAR laser range-finder (NLR) to independently assess SPC's accuracy and precision.

Barnouin, O.; Gaskell, R.; Kahn, E.; Ernst, C.; Daly, M.; Bierhaus, E.; Johnson, C.; Clark, B.; Lauretta, D.

2014-07-01

345

The Impact of Weather & Topography on Landslide Development  

NSDL National Science Digital Library

The Real World Learning Objects Resource Library has provided this activity to demonstrate the role of weather and topography in environmental disasters. Students will use real GIS data to analyze the relationship between weather, topography and landslides. Background materials and worksheets are provided in the â??Content Materialsâ? section, and the procedure for students to follow is clearly outlined. Additional materials that students may find helpful are located in the â??Supplementary Resourcesâ? section. This is an excellent resource for environmental science and earth science teachers that can be used in the classroom or as a homework assignment.

Kimbler, Frank

346

Geoid, topography, and convection-driven crustal deformation on Venus  

NASA Technical Reports Server (NTRS)

High-resolution Magellan images and altimetry of Venus reveal a wide range of styles and scales of surface deformation that cannot readily be explained within the classical terrestrial plate tectonic paradigm. The high correlation of long-wavelength topography and gravity and the large apparent depths of compensation suggest that Venus lacks an upper-mantle low-viscosity zone. A key difference between Earth and Venus may be the degree of coupling between the convecting mantle and the overlying lithosphere. Mantle flow should then have recognizable signatures in the relationships between surface topography, crustal deformation, and the observed gravity field.

Simons, Mark; Hager, Bradford H.; Solomon, Sean C.

1992-01-01

347

Temporal Dynamics of Microbial Rhodopsin Fluorescence Reports Absolute Membrane Voltage  

E-print Network

coli (7), Ã?90 mV to Ã?65 mV in cardiomyocytes and neurons, to near 0 mV in undifferentiated stem cells slower shifts in resting voltage, such as occur during embry- onic development (17), stem cell membrane voltage is a fundamentally important property of a living cell; its value is tightly coupled

Cohen, Adam E.

348

Dynamic space converts relativity into absolute time and dis- tance  

Microsoft Academic Search

A confusing feature in the theory of relativity is the use of time and distance as parameters in explaining the constancy of the velocity of light and the reduced frequencies of atomic clocks in fast motion and in high gravitational field. It is well known that a radio signal passing a mass cen- ter is delayed compared to a signal

Tuomo Suntola

349

Using, Seeing, Feeling, and Doing Absolute Value for Deeper Understanding  

ERIC Educational Resources Information Center

Using sticky notes and number lines, a hands-on activity is shared that anchors initial student thinking about absolute value. The initial point of reference should help students successfully evaluate numeric problems involving absolute value. They should also be able to solve absolute value equations and inequalities that are typically found in…

Ponce, Gregorio A.

2008-01-01

350

Mixed Integer Linear Programming Method for Absolute Value Equations  

Microsoft Academic Search

We formulate the NP-hard absolute value equation as linear complementary problem when the singular values of A exceed one, and we proposed a mixed integer linear programming method to absolute value equation problem. The effectiveness of the method is demonstrated by its ability to solve random problems. Index Terms—absolute value equation; linear complementary problem; mixed integer linear programming. The basic

Longquan Yong

2009-01-01

351

Absolute instruments and perfect imaging in geometrical optics  

E-print Network

Absolute instruments and perfect imaging in geometrical optics Tom´as Tyc, Lenka Herz symmetric absolute instruments that provide perfect imaging in the sense of geometrical optics. We derive to propose several new absolute instruments, in particular a lens providing a stigmatic image of an optically

Tyc, Tomas

352

Absolute neutron measurements in neutron decay  

NASA Astrophysics Data System (ADS)

Neutrons undergo ?-decay to produce a proton, an electron and an anti-neutrino. The decay rate plays an important role in particle physics and in cosmology, and since the late 1940s, numerous attempts have been made at the most precise measurement of this rate. The difficulty in detecting neutrons has kept this a challenging experimental problem. This work, based at the NIST reactor, is concerned with a decay rate measurement method in which simultaneous measurements are made of the decay protons and the neutrons in a well-defined volume of neutron beam. From the two, the lifetime can be determined by employing the differential form of the radioactive decay law, dN/dt = -N/? n. The precision goal of the NIST measurement is a part in a thousand; at this time, the largest source of uncertainty is in the determination of the neutron density in the beam. In order to improve on this, we compare the device at the 0.1% level against an absolute detector with unit efficiency for neutron detection. This absolute neutron detector operates by measuring the thermal power produced by neutron capture reactions in a neutron absorber. The primary challenges to this technique are: (1)the accurate detection of very small amounts of power (less than a ?Watt) produced in the particular beam used for this measurement, and (2)the demonstration that all of the kinetic energy of the reaction products appear as heat in the target. Such small energy deposits are detectable with a cryogenic radiometer operating at liquid helium temperatures and we have achieved the required precision goal for the instrument: the measurement uncertainty in the neutron rate over a period of a day is below 0.1% for a neutron rate of 3 × 10 5 s-1. The verification of the absolute accuracy of the radiometer is in progress.

Chowdhuri, Zema

353

Absolute Radiometric Calibration of EUNIS-06  

NASA Technical Reports Server (NTRS)

The Extreme-Ultraviolet Normal-Incidence Spectrometer (EUNIS) is a soundingrocket payload that obtains imaged high-resolution spectra of individual solar features, providing information about the Sun's corona and upper transition region. Shortly after its successful initial flight last year, a complete end-to-end calibration was carried out to determine the instrument's absolute radiometric response over its Longwave bandpass of 300 - 370A. The measurements were done at the Rutherford-Appleton Laboratory (RAL) in England, using the same vacuum facility and EUV radiation source used in the pre-flight calibrations of both SOHO/CDS and Hinode/EIS, as well as in three post-flight calibrations of our SERTS sounding rocket payload, the precursor to EUNIS. The unique radiation source provided by the Physikalisch-Technische Bundesanstalt (PTB) had been calibrated to an absolute accuracy of 7% (l-sigma) at 12 wavelengths covering our bandpass directly against the Berlin electron storage ring BESSY, which is itself a primary radiometric source standard. Scans of the EUNIS aperture were made to determine the instrument's absolute spectral sensitivity to +- 25%, considering all sources of error, and demonstrate that EUNIS-06 was the most sensitive solar E W spectrometer yet flown. The results will be matched against prior calibrations which relied on combining measurements of individual optical components, and on comparisons with theoretically predicted 'insensitive' line ratios. Coordinated observations were made during the EUNIS-06 flight by SOHO/CDS and EIT that will allow re-calibrations of those instruments as well. In addition, future EUNIS flights will provide similar calibration updates for TRACE, Hinode/EIS, and STEREO/SECCHI/EUVI.

Thomas, R. J.; Rabin, D. M.; Kent, B. J.; Paustian, W.

2007-01-01

354

Absolute Physical Calibration in the Infrared  

E-print Network

We determine an absolute calibration for the MIPS 24 microns band and recommend adjustments to the published calibrations for 2MASS, IRAC, and IRAS photometry to put them on the same scale. We show that consistent results are obtained by basing the calibration on either an average A0V star spectral energy distribution (SED), or by using the absolutely calibrated SED of the sun in comparison with solar-type stellar photometry (the solar analog method). After the rejection of a small number of stars with anomalous SEDs (or bad measurements), upper limits of ~ 1.5% (rms) are placed on the intrinsic infrared SED variations in both A dwarf and solar-type stars. These types of stars are therefore suitable as general-purpose standard stars in the infrared. We provide absolutely calibrated SEDs for a standard zero magnitude A star and for the sun to allow extending this work to any other infrared photometric system. They allow the recommended calibration to be applied from 1 to 25 microns with an accuracy of ~2 %, and with even higher accuracy at specific wavelengths such as 2.2, 10.6, and 24 microns, near which there are direct measurements. However, we confirm earlier indications that Vega does not behave as a typical A0V star between the visible and the infrared, making it problematic as the defining star for photometric systems. The integration of measurements of the sun with those of solar-type stars also provides an accurate estimate of the solar SED from 1 through 30 microns, which we show agrees with theoretical models.

G. H. Rieke; M. Blaylock; L. Decin; C. Engelbracht; P. Ogle; E. Avrett; J. Carpenter; R. M. Cutri; L. Armus; K. Gordon; R. O. Gray; J. Hinz; K. Su; Christopher N. A. Willmer

2008-06-11

355

Achieving Climate Change Absolute Accuracy in Orbit  

NASA Technical Reports Server (NTRS)

The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission will provide a calibration laboratory in orbit for the purpose of accurately measuring and attributing climate change. CLARREO measurements establish new climate change benchmarks with high absolute radiometric accuracy and high statistical confidence across a wide range of essential climate variables. CLARREO's inherently high absolute accuracy will be verified and traceable on orbit to Système Internationale (SI) units. The benchmarks established by CLARREO will be critical for assessing changes in the Earth system and climate model predictive capabilities for decades into the future as society works to meet the challenge of optimizing strategies for mitigating and adapting to climate change. The CLARREO benchmarks are derived from measurements of the Earth's thermal infrared spectrum (5-50 micron), the spectrum of solar radiation reflected by the Earth and its atmosphere (320-2300 nm), and radio occultation refractivity from which accurate temperature profiles are derived. The mission has the ability to provide new spectral fingerprints of climate change, as well as to provide the first orbiting radiometer with accuracy sufficient to serve as the reference transfer standard for other space sensors, in essence serving as a "NIST [National Institute of Standards and Technology] in orbit." CLARREO will greatly improve the accuracy and relevance of a wide range of space-borne instruments for decadal climate change. Finally, CLARREO has developed new metrics and methods for determining the accuracy requirements of climate observations for a wide range of climate variables and uncertainty sources. These methods should be useful for improving our understanding of observing requirements for most climate change observations.

Wielicki, Bruce A.; Young, D. F.; Mlynczak, M. G.; Thome, K. J; Leroy, S.; Corliss, J.; Anderson, J. G.; Ao, C. O.; Bantges, R.; Best, F.; Bowman, K.; Brindley, H.; Butler, J. J.; Collins, W.; Dykema, J. A.; Doelling, D. R.; Feldman, D. R.; Fox, N.; Huang, X.; Holz, R.; Huang, Y.; Jennings, D.; Jin, Z.; Johnson, D. G.; Jucks, K.; Kato, S.; Kratz, D. P.; Liu, X.; Lukashin, C.; Mannucci, A. J.; Phojanamongkolkij, N.; Roithmayr, C. M.; Sandford, S.; Taylor, P. C.; Xiong, X.

2013-01-01

356

Controls of initial topography on temporal and spatial patterns of glacial erosion  

NASA Astrophysics Data System (ADS)

Here we investigate the influence of initial pre-glacial topography on spatial and temporal patterns of glacial erosion using numerical surface process modelling, including a higher order ice sheet model. First, we consider glacier dynamics when simulating glaciation in two real landscapes, representing plateau-type topography (southeast Australia) and characteristic steady-state fluvial topography (southern Taiwan). We find that the different initial landscape configurations result in distinctly different ice configurations and patterns of basal sliding. The sliding patterns are controlled by ice configuration and the resulting basal shear stresses and by the thermal properties at the base of the ice. We then investigate how these characteristic patterns of basal sliding control glacial erosion and long-term landscape evolution using synthetic representations of the two landscapes. The two landscape configurations result in markedly different spatial and temporal patterns of glacial erosion. However, the resulting landscapes may have similar morphology, irrespective of initial landscapes and glacial erosion patterns being significantly different. The numerical experiments also suggest that, in addition to basal temperature, basal shear stress is important in restricting long-term glacial erosion, which is relevant for the preservation of landforms during glaciations. Specifically, pre-glacial landforms may be eroded although they are initially protected by cold-based ice, when the ice configuration promotes significant basal shear stress (glacial erosion) at the edge of a plateau-like landscape. In contrast, pre-glacial landforms may be preserved irrespective of the ice being warm-based, when low gradients in the ice surface act to limit basal shear stress.

Pedersen, Vivi K.; Huismans, Ritske S.; Herman, Frédéric; Egholm, David L.

2014-10-01

357

High-resolution ice thickness and bed topography of a land-terminating section of the Greenland Ice Sheet  

NASA Astrophysics Data System (ADS)

We present ice thickness and bed topography maps with high spatial resolution (250 to 500 m) of a and-terminating section of the Greenland Ice Sheet derived from combined ground-based and airborne radar surveys. The data have a total area of ~12000 km2 and cover the whole ablation area of the outlet glaciers of Isunnguata Sermia, Russell, Leverett, Ørkendalen and Isorlersuup up to the long-term mass balance equilibrium line altitude at ~1600 m above sea level. The bed topography shows highly variable subglacial trough systems, and the trough of the Isunnguata Sermia Glacier is over-deepened and reaches an elevation of several hundreds of meters below sea level. The ice surface is smooth and only reflects the bedrock topography in a subtle way, resulting in a highly variable ice thickness. The southern part of our study area consists of higher bed elevations compared to the northern part. The covered area is one of the most studied regions of the Greenland Ice Sheet with studies of mass balance, dynamics, and supraglacial lakes, and our combined dataset can be valuable for detailed studies of ice sheet dynamics and hydrology. The compiled datasets of ground-based and airborne radar surveys are accessible for reviewers (password protected) at doi.pangaea.de/10.1594/pangaea.830314 and will be freely available in the final revised paper.

Lindbäck, K.; Pettersson, R.; Doyle, S. H.; Helanow, C.; Jansson, P.; Savstrup Kristensen, S.; Stenseng, L.; Forsberg, R.; Hubbard, A. L.

2014-03-01

358

Least absolute deviation (LAD) image matching  

NASA Astrophysics Data System (ADS)

The robust estimator properties of the L,-norm or least absolute deviation (LAD) is shown to provide better subpixel matching accuracy in the presence of outlier points than the least squares method widely employed for image matching applications. Two LAD algorithms are compared with each other and with the least squares (LS) method and the iteratively reweighted least squares (IRLS) method. Results indicate that the Barrodale-Roberts LAD algorithm can be used advantageously in conjunction with or in place of the IRLS and LS algorithms.

Calitz, M. F.; Rüther, H.

359

Absolute Priority for a Vehicle in VANET  

NASA Astrophysics Data System (ADS)

In today's world, traffic jams waste hundreds of hours of our life. This causes many researchers try to resolve the problem with the idea of Intelligent Transportation System. For some applications like a travelling ambulance, it is important to reduce delay even for a second. In this paper, we propose a completely infrastructure-less approach for finding shortest path and controlling traffic light to provide absolute priority for an emergency vehicle. We use the idea of vehicular ad-hoc networking to reduce the imposed travelling time. Then, we simulate our proposed protocol and compare it with a centrally controlled traffic light system.

Shirani, Rostam; Hendessi, Faramarz; Montazeri, Mohammad Ali; Sheikh Zefreh, Mohammad

360

Absolute Calibration of the Auger Fluorescence Detectors  

E-print Network

Absolute calibration of the Pierre Auger Observatory fluorescence detectors uses a light source at the telescope aperture. The technique accounts for the ombined effects of all detector components in a single measurement. The calibrated 2.5 m diameter light source fills the aperture, providing uniform illumination to each pixel. The known flux from the light source and the response of the acquisition system give the required calibration for each pixel. In the lab, light source uniformity is studied using CCD images and the intensity is measured relative to NIST-calibrated photodiodes. Overall uncertainties are presently 12%, and are dominated by systematics.

P. Bauleo; J. Brack; L. Garrard; J. Harton; R. Knapik; R. Meyhandan; A. C. Rovero; A. Tamashiro; D. Warner; for the Auger Collaboration

2005-07-14

361

Extracting Topographic Features From Shuttle Radar Topography Mission (SRTM) Images  

Microsoft Academic Search

Abstract This report addresses the problem of extracting topographic features from Shuttle Radar Topography Mission (SRTM) imagery. The features are used for Earth science applications and include slope, curvature, aspect, flow direction, flow accumulation and compound,topographic index (CTI). The objective of our work is (1) to support topographic feature extraction similar to the onein ArcGIS, (2) to provide extraction of

Wei-wen Feng; Peter Bajcsy

362

Dental topography of platyrrhines and prosimians: convergence and contrasts.  

PubMed

Dental topographic analysis is the quantitative assessment of shape of three-dimensional models of tooth crowns and component features. Molar topographic curvature, relief, and complexity correlate with aspects of feeding behavior in certain living primates, and have been employed to investigate dietary ecology in extant and extinct primate species. This study investigates whether dental topography correlates with diet among a diverse sample of living platyrrhines, and compares platyrrhine topography with that of prosimians. We sampled 111 lower second molars of 11 platyrrhine genera and 121 of 20 prosimian genera. For each tooth we calculated Dirichlet normal energy (DNE), relief index (RFI), and orientation patch count (OPCR), quantifying surface curvature, relief, and complexity respectively. Shearing ratios and quotients were also measured. Statistical analyses partitioned effects of diet and taxon on topography in platyrrhines alone and relative to prosimians. Discriminant function analyses assessed predictive diet models. Results indicate that platyrrhine dental topography correlates to dietary preference, and platyrrhine-only predictive models yield high rates of accuracy. The same is true for prosimians. Topographic variance is broadly similar among platyrrhines and prosimians. One exception is that platyrrhines display higher average relief and lower relief variance, possibly related to lower relative molar size and functional links between relief and tooth longevity distinct from curvature or complexity. Explicitly incorporating phylogenetic distance matrices into statistical analyses of the combined platyrrhine-prosimian sample results in loss of significance of dietary effects for OPCR and SQ, while greatly increasing dietary significance of RFI. PMID:24318939

Winchester, Julia M; Boyer, Doug M; St Clair, Elizabeth M; Gosselin-Ildari, Ashley D; Cooke, Siobhán B; Ledogar, Justin A

2014-01-01

363

An anatomical and functional topography of human auditory cortical areas  

PubMed Central

While advances in magnetic resonance imaging (MRI) throughout the last decades have enabled the detailed anatomical and functional inspection of the human brain non-invasively, to date there is no consensus regarding the precise subdivision and topography of the areas forming the human auditory cortex. Here, we propose a topography of the human auditory areas based on insights on the anatomical and functional properties of human auditory areas as revealed by studies of cyto- and myelo-architecture and fMRI investigations at ultra-high magnetic field (7 Tesla). Importantly, we illustrate that—whereas a group-based approach to analyze functional (tonotopic) maps is appropriate to highlight the main tonotopic axis—the examination of tonotopic maps at single subject level is required to detail the topography of primary and non-primary areas that may be more variable across subjects. Furthermore, we show that considering multiple maps indicative of anatomical (i.e., myelination) as well as of functional properties (e.g., broadness of frequency tuning) is helpful in identifying auditory cortical areas in individual human brains. We propose and discuss a topography of areas that is consistent with old and recent anatomical post-mortem characterizations of the human auditory cortex and that may serve as a working model for neuroscience studies of auditory functions. PMID:25120426

Moerel, Michelle; De Martino, Federico; Formisano, Elia

2014-01-01

364

EAARL topography-Potato Creek watershed, Georgia, 2010  

USGS Publications Warehouse

This DVD contains lidar-derived first-surface (FS) and bare-earth (BE) topography GIS datasets of a portion of the Potato Creek watershed in the Apalachicola-Chattahoochee-Flint River basin, Georgia. These datasets were acquired on February 27, 2010.

Bonisteel-Cormier, J.M.; Nayegandhi, Amar; Fredericks, Xan; Jones, J.W.; Wright, C.W.; Brock, J.C.; Nagle, D.B.

2011-01-01

365

EAARL coastal topography-Virginia, post-Nor'Ida, 2009  

USGS Publications Warehouse

This DVD contains lidar-derived first-surface (FS) and bare-earth (BE) topography GIS datasets of a portion of the Virginia coastline beachface. These datasets were acquired post-Nor'Ida on November 27, 2009, November 29, 2009, and December 1, 2009.

Bonisteel-Cormier, J.M.; Nayegandhi, Amar; Fredericks, Xan; Klipp, E.S.; Nagle, D.B.; Vivekanandan, Saisudha; Wright, C.W.; Sallenger, A.H.; Brock, J.C.

2011-01-01

366

Stress distribution and topography of Tellus Regio, Venus  

NASA Technical Reports Server (NTRS)

The Tellus Regio area of Venus represents a subset of a narrow latitude band where Pioneer Venus Orbiter (PVO) altimetry data, line-of-sight (LOS) gravity data, and Venera 15/16 radar images have all been obtained with good resolution. Tellus Regio also has a wide variety of surface morphologic features, elevations ranging up to 2.5 km, and a relatively low LOS gravity anomaly. This area was therefore chosen in order to examine the theoretical stress distributions resulting from various models of compensation of the observed topography. These surface stress distributions are then compared with the surface morphology revealed in the Venera 15/16 radar images. Conclusions drawn from these comparisons will enable constraints to be put on various tectonic parameters relevant to Tellus Regio. The stress distribution is calculated as a function of the topography, the equipotential anomaly, and the assumed model parameters. The topography data is obtained from the PVO altimetry. The equipotential anomaly is estimated from the PVO LOS gravity data. The PVO LOS gravity represents the spacecraft accelerations due to mass anomalies within the planet. These accelerations are measured at various altitudes and angles to the local vertical and therefore do not lend themselves to a straightforward conversion. A minimum variance estimator of the LOS gravity data is calculated, taking into account the various spacecraft altitudes and LOS angles and using the measured PVO topography as an a priori constraint. This results in an estimated equivalent surface mass distribution, from which the equipotential anomaly is determined.

Williams, David R.; Greeley, Ronald

1989-01-01

367

Smoking topography in tobacco chippers and dependent smokers  

Microsoft Academic Search

Although most cigarette smokers exhibit signs of tobacco dependence, a subset of this population, referred to as tobacco chippers, does not show characteristic signs of dependence. Few studies have attempted to characterize differences between these groups of smokers. The purpose of the present study was to examine smoking topography in chippers (CH) and dependent smokers (DS). Topographical variables including puff

Saul Shiffman

1996-01-01

368

Analysis of Multiple Manding Topographies during Functional Communication Training  

Microsoft Academic Search

We evaluated the effects of reinforcing multiple manding topographies during functional communication training (FCT) to decrease problem behavior for three preschool-age children. During Phase 1, a functional analysis identified conditions that maintained problem behavior for each child. During Phase 2, the children's parents taught them to request positive reinforcers (attention or toys) via vocal manding, manual signing, or touching a

2009-01-01

369

BIOLOGICAL CYBERNETICS, 69, 109-118. Topography And Ocular Dominance  

E-print Network

of activity presented simultaneously in both eyes. An important aspect of this model is that ocular dominanceBIOLOGICAL CYBERNETICS, 69, 109-118. Topography And Ocular Dominance: A Model Exploring Positive Edinburgh EH8 9LW UNITED KINGDOM ¡ ¢ £ ¤ ¥ ¦ § ¨ ¦ © £ ¦ Abstract The map from eye to brain

Sejnowski, Terrence J.

370

Mass and Local Topography Measurements of Itokawa by Hayabusa  

Microsoft Academic Search

The ranging instrument aboard the Hayabusa spacecraft measured the surface topography of asteroid 25143 Itokawa and its mass. A typical rough area is similar in roughness to debris located on the interior wall of a large crater on asteroid 433 Eros, which suggests a surface structure on Itokawa similar to crater ejecta on Eros. The mass of Itokawa was estimated

Shinsuke Abe; Tadashi Mukai; Naru Hirata; Olivier S. Barnouin-Jha; Andrew F. Cheng; Hirohide Demura; Robert W. Gaskell; Tatsuaki Hashimoto; Kensuke Hiraoka; Takayuki Honda; Takashi Kubota; Masatoshi Matsuoka; Takahide Mizuno; Ryosuke Nakamura; Daniel J. Scheeres; Makoto Yoshikawa

2006-01-01

371

NEW PHOTORESIST COATING METHOD FOR HIGH TOPOGRAPHY SURFACES  

E-print Network

-grooves, and cavities. Thus, the conformal photoresist coating of wafers with 3D microstructures becomes a critical step with high topography on silicon or glass surface because of defects generated in the resist layer during. Electrodeposition of photoresist has been reported as a useful method for 3-D stacks of chips [3] but it requires

Peter, Yves-Alain

372

Topography of Extracellular Matrix Mediates Vascular Morphogenesis and Migration Speeds  

E-print Network

Topography of Extracellular Matrix Mediates Vascular Morphogenesis and Migration Speeds Amy L for wound healing, muscle repair, morphogenesis, new blood vessel growth, and cancer invasion. In this study on Vascular Morphogenesis 2 Introduction The extracellular matrix (ECM) is a major component of the extravascu

Jiang, Yi

373

Ultrastructural basement membrane topography of the bladder epithelium  

Microsoft Academic Search

The basement membrane underlies epithelium and separates it from deeper tissues. Recent studies suggest that nanoscale topography of the surface of basement membrane may modulate adhesion, migration, proliferation and differentiation of overlying epithelium. This study was performed to elucidate nanoscale topographic features of basement membrane of the bladder. Bladder tissues were obtained from three adult female rhesus macaques. A process

George A. Abrams; Christopher J. Murphy; Zun-Yi Wang; Paul F. Nealey; Dale E. Bjorling

2003-01-01

374

Towards Integrated Design of a Robust Feedback Controller and Topography  

E-print Network

, a positioning stage is used which can position the tip relative to the sample in all three spatial directions)] is an important tool in micro-, and nano-technology to provide images of sample topography with molecular or even of the vertical feedback loop without sacrificing effective positioning range, by using a combination of a long

Van den Hof, Paul

375

THE SURFACE WATER AND OCEAN TOPOGRAPHY (SWOT) MISSION  

Microsoft Academic Search

Satellite altimetry has revolutionized the study of the global oceans for the past two decades by providing unprecedented observations of the ocean surface topography at scales larger than about 200 km and made significant advances in our understanding of global ocean circulation and sea level change. However, the coarse cross-track sampling and measurement precision have prevented resolving scales shorter than

Douglas Alsdorf; Erensto Rodriguez; Rosemary Morrow; Nelly Mognard; Juliette Lambin; Parag Vaze; Thierry Lafon

376

SWOT: The Surface Water & Ocean Topography Satellite Mission  

E-print Network

SWOT: The Surface Water & Ocean Topography Satellite Mission Doug Alsdorf Byrd Polar Research, lake, and river water storage as a regulator of biogeochemical cycles of Oceans ECCO-2 MIT JPL ocean current model Although altimetry data have significantly advanced the study

377

Influence of lunar topography on simulated surface temperature  

NASA Astrophysics Data System (ADS)

The surface temperature of the Moon is one of the essential parameters for the lunar exploration, especially to evaluate the Moon thermophysical features. The distribution of the temperature is heavily influenced by the Moon topography, which, however, is rarely studied in the state-of-art surface temperature models. Therefore, this paper takes the Moon topography into account to improve the surface temperature model, Racca model. The main parameters, such as slopes along the longitude and latitude directions, are estimated with the topography data from Chang'E-1 satellite and the Horn algorithm. Then the effective solar illumination model is then constructed with the slopes and the relative position to the subsolar point. Finally, the temperature distribution over the Moon surface is obtained with the effective illumination model and the improved Racca model. The results indicate that the distribution of the temperature is very sensitive to the fluctuation of the Moon surface. The change of the surface temperature is up to 150 K in some places compared to the result without considering the topography. In addition, the variation of the surface temperature increases with the distance from the subsolar point and the elevation, along both latitude and longitude directions. Furthermore, the simulated surface temperature coincides well with the brightness temperature in 37 GHz observed by the microwave sounder onboard Chang'E-2 satellite. The corresponded emissivity map not only eliminates the influence of the topography, but also hints the inherent properties of the lunar regolith just below the surface. Last but not the least, the distribution of the permanently shadowed regions (PSRs) in the lunar pole area is also evaluated with the simulated surface temperature result.

Zhiguo, Meng; Yi, Xu; Zhanchuan, Cai; Shengbo, Chen; Yi, Lian; Hang, Huang

2014-11-01

378

Allometric scaling of infraorbital surface topography in Homo.  

PubMed

Infraorbital morphology is often included in phylogenetic and functional analyses of Homo. The inclusion of distinct infraorbital configurations, such as the "canine fossa" in Homo sapiens or the "inflated" maxilla in Neandertals, is generally based on either descriptive or qualitative assessments of this morphology, or simple linear chord and subtense measurements. However, the complex curvilinear surface of the infraorbital region has proven difficult to quantify through these traditional methods. In this study, we assess infraorbital shape and its potential allometric scaling in fossil Homo (n=18) and recent humans (n=110) with a geometric morphometric method well-suited for quantifying complex surface topographies. Our results indicate that important aspects of infraorbital shape are correlated with overall infraorbital size across Homo. Specifically, individuals with larger infraorbital areas tend to exhibit relatively flatter infraorbital surface topographies, taller and narrower infraorbital areas, sloped inferior orbital rims, anteroinferiorly oriented maxillary body facies, posteroinferiorly oriented maxillary processes of the zygomatic, and non-everted lateral nasal margins. In contrast, individuals with smaller infraorbital regions generally exhibit relatively depressed surface topographies, shorter and wider infraorbital areas, projecting inferior orbital rims, posteroinferiorly oriented maxillary body facies, anteroinferiorly oriented maxillary processes, and everted lateral nasal margins. These contrasts form a continuum and only appear dichotomized at the ends of the infraorbital size spectrum. In light of these results, we question the utility of incorporating traditionally polarized infraorbital morphologies in phylogenetic and functional analyses without due consideration of continuous infraorbital and facial size variation in Homo. We conclude that the essentially flat infraorbital surface topography of Neandertals is not unique and can be explained, in part, as a function of possessing large infraorbital regions, the ancestral condition for Homo. Furthermore, it appears likely that the diminutive infraorbital region of anatomically modern Homo sapiens is a primary derived trait, with related features such as depressed infraorbital surface topography expressed as correlated secondary characters. PMID:19118866

Maddux, Scott D; Franciscus, Robert G

2009-02-01

379

A method for absolute calibration of compasses  

NASA Astrophysics Data System (ADS)

In order to reference the speed and direction of ocean currents, currentmeters are fitted with a magnetic compass. The manufacturers of currentmeters provide users so-called autocalibration procedures and software to allow for the verification of the good working order and rectification of the bias of compass magnetic field sensors. Nevertheless, these tests do not make it possible to correct all the errors that can alter field measurements and particularly the nonlinear effects. In order to calculate corrections and estimate the accuracy of the 'autocalibration' procedure, an absolute calibration method has been devised, based on the GPS positioning of two geodetic reference points and on the measurement of angles and distances between one of these points and the instrument being tested. The standard uncertainty of this method has been assessed as 0.64°. It is below the compass accuracy and makes it possible to underscore the bias resulting from the 'autocalibration' operations and to evaluate corrections. This method, which can be extended to other equipment, is a solution for absolute compass calibrations.

LeMenn, Marc; LeGoff, Michel

2007-05-01

380

Absolute configuration of 7-epi-sesquithujene.  

PubMed

7-epi-sesquithujene (1) is a bicyclic sesquiterpene isolated from phoebe oil, an essential oil of the Brazilian walnut tree, Phoebe porosa. It is also produced by stressed ash trees and has been shown to elicit strong electrophysiological responses on emerald ash borer, Agrilus planipennis, antennae. In the course of the development of a synthetic 7-epi-sesquithujene lure for field testing against the emerald ash borer, we found that the absolute configuration of this compound had not been determined. We isolated >95% pure 7-epi-sesquithujene from phoebe oil via successive fractionation and conventional and argentation (HPLC) chromatographies. The specific optical rotation of this compound matched that of a synthetic product of known configuration. We also synthesized two other stereoisomers of sesquithujene and developed a chiral GC method to separate all four. Based on the specific rotation, stereoselective syntheses, and chiral GC analyses, 7-epi-sesquithujene present in phoebe oil and white ash was found to have the 2S,6S,7R absolute configuration. PMID:21574561

Khrimian, Ashot; Cossé, Allard A; Crook, Damon J

2011-06-24

381

Standardization of the cumulative absolute velocity  

SciTech Connect

EPRI NP-5930, A Criterion for Determining Exceedance of the Operating Basis Earthquake,'' was published in July 1988. As defined in that report, the Operating Basis Earthquake (OBE) is exceeded when both a response spectrum parameter and a second damage parameter, referred to as the Cumulative Absolute Velocity (CAV), are exceeded. In the review process of the above report, it was noted that the calculation of CAV could be confounded by time history records of long duration containing low (nondamaging) acceleration. Therefore, it is necessary to standardize the method of calculating CAV to account for record length. This standardized methodology allows consistent comparisons between future CAV calculations and the adjusted CAV threshold value based upon applying the standardized methodology to the data set presented in EPRI NP-5930. The recommended method to standardize the CAV calculation is to window its calculation on a second-by-second basis for a given time history. If the absolute acceleration exceeds 0.025g at any time during each one second interval, the earthquake records used in EPRI NP-5930 have been reanalyzed and the adjusted threshold of damage for CAV was found to be 0.16g-set.

O'Hara, T.F.; Jacobson, J.P. (Yankee Atomic Electric Co., Bolton, MA (United States))

1991-12-01

382

Radiation and dissipation of internal waves generated by geostrophic motions impinging on small-scale topography  

E-print Network

Observations and inverse models suggest that small-scale turbulent mixing is enhanced in the Southern Ocean in regions above rough topography. The enhancement extends 1 km above the topography suggesting that mixing is ...

Nikurashin, Maxim (Maxim Anatolevich)

2009-01-01

383

High Resolution Global Topography of Eros from NEAR Imaging and LIDAR Data  

NASA Technical Reports Server (NTRS)

Principal Data Products: Ensemble of L-maps from SPC, Spacecraft state, Asteroid pole and rotation. Secondary Products: Global topography model, inertia tensor, gravity. Composite high resolution topography. Three dimensional image maps.

Gaskell, Robert W.; Konopliv, A.; Barnouin-Jha, O.; Scheeres, D.

2006-01-01

384

Tectonic geomorphology and hydrocarbon induced topography of the Mid-Channel Anticline, Santa Barbara Basin, California  

E-print Network

Tectonic geomorphology and hydrocarbon induced topography of the Mid-Channel Anticline, Santa The geomorphology of the western sector of the Mid-Channel Anticline (MCA), Santa Barbara, southern California. Keywords: Active folding; Tectonic geomorphology; Hydrocarbon induced topography 1. Introduction

Keller, Ed

385

Origins of topography in the western U.S.: Mapping crustal and upper mantle density variations using a uniform seismic velocity model  

NASA Astrophysics Data System (ADS)

To investigate the physical basis for support of topography in the western U.S., we construct a subcontinent scale, 3-D density model using ~1000 estimated crustal thicknesses and S velocity profiles to 150 km depth at each of 947 seismic stations. Crustal temperature and composition are considered, but we assume that mantle velocity variations are thermal in origin. From these densities, we calculate crustal and mantle topographic contributions. Typical 2? uncertainty of topography is ~500 m, and elevations in 84% of the region are reproduced within error. Remaining deviations from observed elevations are attributed to melt, variations in crustal quartz content, and dynamic topography; compositional variations in the mantle, while plausible, are not necessary to reproduce topography. Support for western U.S. topography is heterogeneous, with each province having a unique combination of mechanisms. Topography due to mantle buoyancy is nearly constant (within ~250 m) across the Cordillera; relief there (>2 km) results from variations in crustal chemistry and thickness. Cold mantle provides ~1.5 km of ballast to the thick crust of the Great Plains and Wyoming craton. Crustal temperature variations and dynamic pressures have smaller magnitude and/or more localized impacts. Positive gravitational potential energy (GPE) anomalies (~2 × 1012N/m) calculated from our model promote extension in the northern Basin and Range and near the Sierra Nevada. Negative GPE anomalies (-3 × 1012N/m) along the western North American margin and Yakima fold and thrust belt add compressive stresses. Stresses derived from lithospheric density variations may strongly modulate tectonic stresses in the western U.S. continental interior.

Levandowski, Will; Jones, Craig H.; Shen, Weisen; Ritzwoller, Michael H.; Schulte-Pelkum, Vera

2014-03-01

386

A method of calculating the total flow from a given sea surface topography  

NASA Technical Reports Server (NTRS)

Using a simple dynamical model of a wind-driven ocean circulation of the Stommel type, and an analytical basis developed to objectively analyze the sea surface height residuals from an altimeter and, in the process, to determine the total flow instead of just the near surface geostrophic component associated with the given sea surface topography. The method is based on first deriving the solution to the forced problem for a given wind stress required to develop a hypothetical true or perfect data field and to establishing the basis for the objective analysis. The stream function and the surface height field for the forced problem are developed in terms of certain characteristic functions with the same expansion coefficients for both fields. These characteristic functions are simply the solutions for a homogeneous elliptic equation for the stream function and the solutions of an inhomogeneous balance equation for the height field. For the objective analysis, using a sample of randomly selected height values from the true data field, the height field characteristic functions are used to fit the given topography in a least squares sense. The resulting expansion coefficients then permit the synthesis of the total flow field via the stream function characteristic modes and the solution is perfectly well behaved even along the equator. The method of solution is easily adaptable to realistic ocean basis by straight forward numerical methods. The analytical basis of the theory and the results for an ideal rectangular basin on a beta plane are described.

Rao, Desiraju B.; Steenrod, Stephen D.; Sanchez, Braulio V.

1987-01-01

387

Influence of Extracellular Matrix Proteins and Substratum Topography on Corneal Epithelial Cell Alignment and Migration  

PubMed Central

The basement membrane (BM) of the corneal epithelium presents biophysical cues in the form of topography and compliance that can impact the phenotype and behaviors of cells and their nuclei through modulation of cytoskeletal dynamics. In addition, it is also well known that the intrinsic biochemical attributes of BMs can modulate cell behaviors. In this study, the influence of the combination of exogenous coating of extracellular matrix proteins (ECM) (fibronectin-collagen [FNC]) with substratum topography was investigated on cytoskeletal architecture as well as alignment and migration of immortalized corneal epithelial cells. In the absence of FNC coating, a significantly greater percentage of cells aligned parallel with the long axis of the underlying anisotropically ordered topographic features; however, their ability to migrate was impaired. Additionally, changes in the surface area, elongation, and orientation of cytoskeletal elements were differentially influenced by the presence or absence of FNC. These results suggest that the effects of topographic cues on cells are modulated by the presence of surface-associated ECM proteins. These findings have relevance to experiments using cell cultureware with biomimetic biophysical attributes as well as the integration of biophysical cues in tissue-engineering strategies and the development of improved prosthetics. PMID:23488816

Raghunathan, VijayKrishna; McKee, Clayton; Cheung, Wai; Naik, Rachel; Nealey, Paul F.; Russell, Paul

2013-01-01

388

0 PROLOGUE --ABSOLUTE VALUE INEQUALITIES 1 0.1 Absolute Value Inequalities . . . . . . . . . . . . . . . . . . . . 1  

E-print Network

the relevant material about the manipulation of absolute value inequalities. The main point will be this: to solve an inequality like |2x - 5| picture rather than just trying to do algebra. Some algebraic manipulation is unavoidable, but to avoid manipulative errors, geometric insight

Sarkar, Amites

389

A preliminary evaluation of ocean topography from the TOPEX/POSEIDON mission  

NASA Technical Reports Server (NTRS)

We have analyzed 50 ten-day cycles of TOPEX/POSEIDON (T/P) altimeter data to evaluate the ocean dynamic topography and its temporal variations. We have employed data from both the U.S. and French altimeters along with the NASA precision orbits in this analysis. Errors in the diurnal and semidiurnal components of the Cartwright-Ray tide model have been significantly reduced using a correction developed from a combination of JGM-2 and OSU91A was employed, as well as a geoid model based solely on OSU91A. The long wavelengths of the comparisons to historical data, although geoid error still corrupts the dynamic topography for wavelengths shorter than 2500 km. The root mean square (RMS) variability is similar to previous results from Geosat, with bakground 'noise' approaching 3 cm RMS. The computed annual and semiannual variations are also similar to previous Geosat results, although the hemispheric distribution of the annual heating cycle is much better presented in the T/P results. They also compare reasonably well with the Levitus hydrographic compilation in the northern hemisphere, although the T/P variations generally have larger amplitudes. Ten-day average maps of variations in sea level compare well with simulations measurements at ocean tide gauges, with RMS differences of less than 4 cm and correlations greater than 0.6 for most of the island gauges. Time-longitude plots of these sea level variations at different latitudes in the Pacific clearly show the presence of equatorial Kelvin waves and Rossby waves, with the wave speeds agreeing well with theoretical and observed values. Measurement of variations in global sea level over cycles 2-51 have an RMS variability of 6.3 mm and a rate of change of -3.5 +/- 8 mm/yr, the uncertainty primarily due to insufficient averaging of the interannual and periodic sea level variations. These results show that the accuracy of the T/P measurements of sea level has dramatically improved over previous missions, with estimated time variable errors of 4 cm or less. Although geographically correlated orbit errors have also been reduced to the few centimeter level, further improvement in determinations of the mean dynamic topography will be difficult to obtain until a more accurate model of the marine geoid is available.

Nerem, R. S.; Schrama, E. J.; Koblinsky, C. J.; Beckley, B.

1994-01-01

390

Evaluation of a pre-treatment assessment to select mand topographies for functional communication training  

Microsoft Academic Search

Recent research has suggested that variables related to specific mand topographies targeted during functional communication training (FCT) can affect treatment outcomes. These include effort, novelty of mands, previous relationships with problem behavior, and preference. However, there is little extant research on procedures for identifying which mand topographies to incorporate into FCT. In the current study, a mand topography assessment was

Joel E. Ringdahl; Terry S. Falcomata; Tory J. Christensen; Sandie M. Bass-Ringdahl; Alison Lentz; Anuradha Dutt; Jessica Schuh-Claus

2009-01-01

391

Topography and the water cycle in a temperate middle mountain environment: the need for interdisciplinary experiments  

Microsoft Academic Search

Two main characteristics of mountainous regions are the large topography-driven lateral redistributions of water and energy, and the considerable topography-related heterogeneities on all scales. These features are difficult to estimate, to incorporate into hydrologic models and to aggregate on the general circulation model grid scale. On the local scale, the topography controls the spatial patterns of water and energy inputs,

Bruno Ambroise

1995-01-01

392

High Resolution SAR Interferometry: influence of local topography in the context of glacier monitoring  

E-print Network

High Resolution SAR Interferometry: influence of local topography in the context of glacier the opportu- nity to measure temperate glacier surface topography and displacement between the two for glacier activity monitoring, by providing regular measure- ments such as surface topography, velocity

Paris-Sud XI, Université de

393

Combined absolute and relative gravity measurement for microgravity monitoring in Aso volcanic field  

NASA Astrophysics Data System (ADS)

Absolute measurement with a portable A10-017 absolute gravimeter at some benchmarks in the Aso volcanic field are valuable for reducing uncertainties of regional gravity variations and will be useful for delineating the long term trends of gravity changes. A10 absolute gravimeter is a new generation of portable absolute instrument and has accuracy 10 microGal. To further the development of a high precision gravity data, we also conducted measurement using two relative gravimeter (Scintrex CG-5 [549] and LaCoste type G-1016) to be combined with an A10 absolute gravimeter. The using absolute gravimeter along with relative gravimeter can reduce drift correction factor and improve the result of gravity change data in microgravity monitoring. Microgravity monitoring is a valued tool for mapping the redistribution of subsurface mass and for assessing changes in the fluid as a dynamic process in volcanic field. Gravity changes enable the characterization of subsurface processes: i.e., the mass of the intrusion or hydrothermal flow. A key assumption behind gravity monitoring is that changes in earth's gravity reflect mass-transport processes at depth [1]. The absolute gravity network was installed at seven benchmarks using on May 2010, which re-occupied in October 2010, and June 2011. The relative gravity measurements were performed at 28 benchmarks in one month before the eruption on May 2011 and then followed by series of gravity monitoring after the eruption in every three to five months. Gravity measurements covered the area more than 60 km2 in the west side of Aso caldera. Some gravity benchmarks were measured using both absolute and relative gravimeter and is used as the reference benchmarks. In longer time period, the combined gravity method will improve the result of gravity change data for monitoring in the Aso volcanic field. As a result, the gravity changes detected the hydrothermal flow in the subsurface which has a correlation to water level fluctuation in the crater. Large residual gravity changes between the surveys of absolute and relative gravimeter are found at benchmarks around Nakadake crater. Keywords: Microgravity monitoring, Aso volcanic field References [1] Battaglia, M., J. Gottsmann, D. Carbone, and J. Fernandez, 2008, 4D volcano gravimetry: Geophysics, vol. 73 no.6, p. WA3-WA18.

Sofyan, Yayan; Nishijima, Jun; Yoshikawa, Shin; Fujimitsu, Yasuhiro; Kagiyama, Tsuneomi; Fukuda, Yoichi

2014-05-01

394

Absolute measurements of fast neutrons using yttrium.  

PubMed

Yttrium is presented as an absolute neutron detector for pulsed neutron sources. It has high sensitivity for detecting fast neutrons. Yttrium has the property of generating a monoenergetic secondary radiation in the form of a 909 keV gamma-ray caused by inelastic neutron interaction. It was calibrated numerically using MCNPX and does not need periodic recalibration. The total yttrium efficiency for detecting 2.45 MeV neutrons was determined to be f(n) approximately 4.1x10(-4) with an uncertainty of about 0.27%. The yttrium detector was employed in the NX2 plasma focus experiments and showed the neutron yield of the order of 10(8) neutrons per discharge. PMID:20815606

Roshan, M V; Springham, S V; Rawat, R S; Lee, P; Krishnan, M

2010-08-01

395

Absolute instability of a viscous hollow jet  

NASA Astrophysics Data System (ADS)

An investigation of the spatiotemporal stability of hollow jets in unbounded coflowing liquids, using a general dispersion relation previously derived, shows them to be absolutely unstable for all physical values of the Reynolds and Weber numbers. The roots of the symmetry breakdown with respect to the liquid jet case, and the validity of asymptotic models are here studied in detail. Asymptotic analyses for low and high Reynolds numbers are provided, showing that old and well-established limiting dispersion relations [J. W. S. Rayleigh, The Theory of Sound (Dover, New York, 1945); S. Chandrasekhar, Hydrodynamic and Hydromagnetic Stability (Dover, New York, 1961)] should be used with caution. In the creeping flow limit, the analysis shows that, if the hollow jet is filled with any finite density and viscosity fluid, a steady jet could be made arbitrarily small (compatible with the continuum hypothesis) if the coflowing liquid moves faster than a critical velocity.

Gañán-Calvo, Alfonso M.

2007-02-01

396

Absolute instability of a viscous hollow jet.  

PubMed

An investigation of the spatiotemporal stability of hollow jets in unbounded coflowing liquids, using a general dispersion relation previously derived, shows them to be absolutely unstable for all physical values of the Reynolds and Weber numbers. The roots of the symmetry breakdown with respect to the liquid jet case, and the validity of asymptotic models are here studied in detail. Asymptotic analyses for low and high Reynolds numbers are provided, showing that old and well-established limiting dispersion relations [J. W. S. Rayleigh, The Theory of Sound (Dover, New York, 1945); S. Chandrasekhar, Hydrodynamic and Hydromagnetic Stability (Dover, New York, 1961)] should be used with caution. In the creeping flow limit, the analysis shows that, if the hollow jet is filled with any finite density and viscosity fluid, a steady jet could be made arbitrarily small (compatible with the continuum hypothesis) if the coflowing liquid moves faster than a critical velocity. PMID:17358457

Gañán-Calvo, Alfonso M

2007-02-01

397

Absolute radiometric calibration of the Thematic Mapper  

NASA Technical Reports Server (NTRS)

Calibration data for the solar reflective bands of the Landsat-5 TM obtained from five in-flight absolute radiometric calibrations from July 1984-November 1985 at White Sands, New Mexico are presented and analyzed. Ground reflectance and atmospheric data were utilized to predict the spectral radiance at the entrance pupil of the TM and the average number of digital counts in each TM band. The calibration of each of the TM solar reflective bands was calculated in terms of average digital counts/unit spectral radiance for each band. It is observed that for the 12 reflectance-based measurements the rms variation from the means as a percentage of the mean is + or - 1.9 percent; for the 11 measurements in the IR bands, it is + or - 3.4 percent; and the rms variation for all 23 measurements is + or - 2.8 percent.

Slater, P. N.; Biggar, S. F.; Holm, R. G.; Jackson, R. D.; Mao, Y.

1986-01-01

398

MAGSAT: Vector magnetometer absolute sensor alignment determination  

NASA Technical Reports Server (NTRS)

A procedure is described for accurately determining the absolute alignment of the magnetic axes of a triaxial magnetometer sensor with respect to an external, fixed, reference coordinate system. The method does not require that the magnetic field vector orientation, as generated by a triaxial calibration coil system, be known to better than a few degrees from its true position, and minimizes the number of positions through which a sensor assembly must be rotated to obtain a solution. Computer simulations show that accuracies of better than 0.4 seconds of arc can be achieved under typical test conditions associated with existing magnetic test facilities. The basic approach is similar in nature to that presented by McPherron and Snare (1978) except that only three sensor positions are required and the system of equations to be solved is considerably simplified. Applications of the method to the case of the MAGSAT Vector Magnetometer are presented and the problems encountered discussed.

Acuna, M. H.

1981-01-01

399

Absolute measurements of fast neutrons using yttrium  

SciTech Connect

Yttrium is presented as an absolute neutron detector for pulsed neutron sources. It has high sensitivity for detecting fast neutrons. Yttrium has the property of generating a monoenergetic secondary radiation in the form of a 909 keV gamma-ray caused by inelastic neutron interaction. It was calibrated numerically using MCNPX and does not need periodic recalibration. The total yttrium efficiency for detecting 2.45 MeV neutrons was determined to be f{sub n}{approx}4.1x10{sup -4} with an uncertainty of about 0.27%. The yttrium detector was employed in the NX2 plasma focus experiments and showed the neutron yield of the order of 10{sup 8} neutrons per discharge.

Roshan, M. V.; Springham, S. V.; Rawat, R. S.; Lee, P.; Krishnan, M. [National Institute of Education, Nanyang Technological University, Singapore, 637616 (Singapore)

2010-08-15

400

Measured and modelled absolute gravity in Greenland  

NASA Astrophysics Data System (ADS)

Present day changes in the ice volume in glaciated areas like Greenland will change the load on the Earth and to this change the lithosphere will respond elastically. The Earth also responds to changes in the ice volume over a millennial time scale. This response is due to the viscous properties of the mantle and is known as Glaical Isostatic Adjustment (GIA). Both signals are present in GPS and absolute gravity (AG) measurements and they will give an uncertainty in mass balance estimates calculated from these data types. It is possible to separate the two signals if both gravity and Global Positioning System (GPS) time series are available. DTU Space acquired an A10 absolute gravimeter in 2008. One purpose of this instrument is to establish AG time series in Greenland and the first measurements were conducted in 2009. Since then are 18 different Greenland GPS Network (GNET) stations visited and six of these are visited more then once. The gravity signal consists of three signals; the elastic signal, the viscous signal and the direct attraction from the ice masses. All of these signals can be modelled using various techniques. The viscous signal is modelled by solving the Sea Level Equation with an appropriate ice history and Earth model. The free code SELEN is used for this. The elastic signal is modelled as a convolution of the elastic Greens function for gravity and a model of present day ice mass changes. The direct attraction is the same as the Newtonian attraction and is calculated as this. Here we will present the preliminary results of the AG measurements in Greenland. We will also present modelled estimates of the direct attraction, the elastic and the viscous signals.

Nielsen, E.; Forsberg, R.; Strykowski, G.

2012-12-01

401

MARQUIS: a multiplex method for absolute quantification of peptides and posttranslational modifications.  

PubMed

Absolute quantification of protein expression and posttranslational modifications by mass spectrometry has been challenging due to a variety of factors, including the potentially large dynamic range of phosphorylation response. To address these issues, we have developed MARQUIS-Multiplex Absolute Regressed Quantification with Internal Standards-a novel mass spectrometry-based approach using a combination of isobaric tags and heavy-labelled standard peptides, to construct internal standard curves for peptides derived from key nodes in signal transduction networks. We applied MARQUIS to quantify phosphorylation dynamics within the EGFR network at multiple time points following stimulation with several ligands, enabling a quantitative comparison of EGFR phosphorylation sites and demonstrating that receptor phosphorylation is qualitatively similar but quantitatively distinct for each EGFR ligand tested. MARQUIS was also applied to quantify the effect of EGFR kinase inhibition on glioblastoma patient-derived xenografts. MARQUIS is a versatile method, broadly applicable and extendable to multiple mass spectrometric platforms. PMID:25581283

Curran, Timothy G; Zhang, Yi; Ma, Daniel J; Sarkaria, Jann N; White, Forest M

2015-01-01

402

A study on Ganymede's surface topography: Perspectives for radar sounding  

NASA Astrophysics Data System (ADS)

Radar sounding of Jovian icy satellites has great potential to address specific science questions such as the presence of subsurface liquid water. Radargrams acquired over Mars polar caps allow observing clear echoes up to kilometers depth. However, Jovian icy satellites display dramatically different surface topographies. In order to assess possible issues arising from such surface topographies on radar sounding, we performed a study on different DEMs (Digital Elevation Models) obtained on Ganymede. Topographic data are derived using stereo and photoclinometric analysis of Galileo and Voyager images at resolutions of 16-629 m. Main results are presented in this paper. Overall we found that Ganymede's surface is quite rough, with mean slopes at 630 m scale varying from 3.5° to 8°, smoothest terrains being found within sulcii. This will be a major challenge for the design of radar sounders and parameters should be chosen accordingly in order to correctly sound this planetary body. Previous studies have shown similar concern for Europa.

Berquin, Y.; Kofman, W.; Herique, A.; Alberti, G.; Beck, P.

2013-03-01

403

Effect of extraocular muscle surgery on corneal topography.  

PubMed

A computerized videokeratoscopy system was used to evaluate changes in corneal topography after muscle surgery in 36 eyes of 18 rabbits. Topographic analysis revealed a significant flattening of the cornea in the superior and superotemporal octants after superior rectus recession (mean +/- SE, -1.78 +/- 0.16 diopters) compared with control eyes undergoing a sham procedure (-0.17 +/- 0.18 D; P less than .05). Excision of all rectus muscles caused a generalized corneal flattening (-1.42 +/- 0.13 D; P less than .001). A computerized, finite element model of the globe, including the rectus muscles, demonstrated corneal deformation as a result of extraocular muscle tension; recession of an extraocular muscle in this model caused corneal flattening in the quadrant of the recessed muscle. These data suggest that corneal topography is affected by extraocular muscle tension, corroborating clinical reports of refractive change after strabismus surgery. PMID:2043078

Kwito, S; Sawusch, M R; McDonnell, P J; Gritz, D C; Moreira, H; Evensen, D

1991-06-01

404

Method and Apparatus for Creating a Topography at a Surface  

DOEpatents

Methods and apparatus whereby an optical interferometer is utilized to monitor and provide feedback control to an integrated energetic particle column, to create desired topographies, including the depth, shape and/or roughness of features, at a surface of a specimen. Energetic particle columns can direct energetic species including, ions, photons and/or neutral particles to a surface to create features having in-plane dimensions on the order of 1 micron, and a height or depth on the order of 1 nanometer. Energetic processes can include subtractive processes such as sputtering, ablation, focused ion beam milling and, additive processes, such as energetic beam induced chemical vapor deposition. The integration of interferometric methods with processing by energetic species offers the ability to create desired topographies at surfaces, including planar and curved shapes.

Adams, David P. (Albuquerque, NM); Sinclair, Michael B. (Albuquerque, NM); Mayer, Thomas M. (Albuquerque, NM); Vasile, Michael J. (Albuquerque, NM); Sweatt, William C. (Albuquerque, NM)

2008-11-11

405

Defect Analysis in Crystals using X-ray Topography  

SciTech Connect

A brief review of X-ray topography - a nondestructive method for direct observation and characterization of defects in single crystals - is presented here. The origin and development of this characterization method and the different techniques derived from it are described. Emphasis is placed on synchrotron X-ray topography and its application in studying various crystal imperfections. Mechanisms of contrast formation on X-ray topographs are discussed, with emphasis on contrast associated with dislocations. Determination of Burgers vectors and line directions of dislocations from analysis of X-ray topographs is explained. Contrast from inclusions is illustrated, and their differentiation from dislocations is demonstrated with the aid of simulated topographs. Contrast arising from the deformation fields associated with cracks is also briefly covered.

Raghothamachar,B.; Dhanaraj, G.; Bai, J.; Dudley, M.

2006-01-01

406

Topography, relief, climate and glaciers: a global prespective  

NASA Astrophysics Data System (ADS)

The examination of the relationship between Earth's topography and present and past climate (i.e. long-term elevation of glaciers Equilibrium Line Altitude) reveals that the elevation of mountain ranges may be limited or controlled by glaciations. This is of prime importance, because glacial condition would lead to a limit the mountain development, hence the accumulation of gravitational energy and prevent the development of further glacial conditions as well as setting the erosion in (peri)glacial environments. This study examines the relationships between topography and the global Equilibrium Line Altitude of alpine glaciers around the world (long term snowline, i.e. the altitude where the ice mass balance is null). Two main observations can be drawn: 1) The distance between the (averaged and maximum) topography, and the ELA decreases pole ward the poles, and even become reversed (mean elevation above to ELA) at high latitude. Correlatively, the elevation of very large portion of land at mid-latitude cannot be related to glaciations, simply because it was never glaciated (large distance between topography and long-term mean ELA). The maximum distance between the ELA and the topography is greater close to the equator and decreases poleward. In absence of glacial and periglacial erosion, this trend cannot have its origin in glacial and periglacial processes. Moreover, the ELA elevation shows a significant (1000 - 1500m) depression in the intertropical zone. This depression of the ELA is not reflected at all in the topography. 2) The distribution of relief on Earth, if normalized by the mean elevation of mountain ranges (as a proxy for available space to create relief) shows a latitudinal band of greater relief between 40° and 60° (or between ELA of 500m to 2500m a.s.l.). This mid-latitude relatively greater relief challenges the straightforward relationship between glaciations, erosion and topography. Oppositely, it suggests that glacier may be more efficient agent in temperate area, with important amplitude between glacial and interglacial climate. This is consistent with the view of a very variable glacier erodibility that can erode and protect the landscape, as well as with studies documenting a bimodal location of the preferred glacial erosion, at relatively high elevation (around the long-term ELA), and at much lower elevation (close to the glacial maximum lower reaches), thanks to efficient water lubrication of the glacier bases that greatly enhance the sliding velocity. These findings show that the relation between the mountain topography and the long term snowline is not as straightforward as previously proposed. Beside the role of tectonic forcing highlighted by several authors, the importance of the glacial erosion appears to be crucial at mid latitude, but more complex at both high and low latitude. Moreover, the relief at mid latitude appears to be higher, hence suggesting a positive correlation between relief and topographic control of glacier on the landscape.

Champagnac, Jean-Daniel; Valla, Pierre; Herman, fred

2014-05-01

407

Irregular topography at the Earth's inner core boundary.  

PubMed

Compressional seismic wave reflected off the Earth's inner core boundary (ICB) from earthquakes occurring in the Banda Sea and recorded at the Hi-net stations in Japan exhibits significant variations in travel time (from -2 to 2.5 s) and amplitude (with a factor of more than 4) across the seismic array. Such variations indicate that Earth's ICB is irregular, with a combination of at least two scales of topography: a height variation of 14 km changing within a lateral distance of no more than 6 km, and a height variation of 4-8 km with a lateral length scale of 2-4 km. The characteristics of the ICB topography indicate that small-scale variations of temperature and/or core composition exist near the ICB, and/or the ICB topographic surface is being deformed by small-scale forces out of its thermocompositional equilibrium position and is metastable. PMID:22547788

Dai, Zhiyang; Wang, Wei; Wen, Lianxing

2012-05-15

408

Irregular topography at the Earth’s inner core boundary  

PubMed Central

Compressional seismic wave reflected off the Earth’s inner core boundary (ICB) from earthquakes occurring in the Banda Sea and recorded at the Hi-net stations in Japan exhibits significant variations in travel time (from -2 to 2.5 s) and amplitude (with a factor of more than 4) across the seismic array. Such variations indicate that Earth’s ICB is irregular, with a combination of at least two scales of topography: a height variation of 14 km changing within a lateral distance of no more than 6 km, and a height variation of 4–8 km with a lateral length scale of 2–4 km. The characteristics of the ICB topography indicate that small-scale variations of temperature and/or core composition exist near the ICB, and/or the ICB topographic surface is being deformed by small-scale forces out of its thermocompositional equilibrium position and is metastable. PMID:22547788

Dai, Zhiyang; Wang, Wei; Wen, Lianxing

2012-01-01

409

Gravity studies at Etna volcano: a comparison between relative and absolute gravity measurements  

NASA Astrophysics Data System (ADS)

The INGV has been operating at Mt Etna a discrete gravity network since 1986 and three continuous gravi