Sample records for topography gmrt synthesis

  1. GMRT radio detection of SN 1996aq at 617 MHz

    Microsoft Academic Search

    Sayan Chakraborti; Poonam Chandra; Alak Ray

    2009-01-01

    We report the Giant Metrewave Radio Telescope (GMRT) detection of SN 1996aq at 617 MHz, observed around 2009 March 13, 19:30 UT. The measured flux of the point source at RA 14h 22m 22.75s DEC -00d 23m 23.5s (J2000) is 1.96 +\\/- 0.17 mJy. Our synthesis map has a resolution of 5 arcseconds and rms 0.09 mJy. Follow-up observations at

  2. Next generation digital backends for the GMRT

    NASA Astrophysics Data System (ADS)

    Ajithkumar, B.; Choudhari, S. C.; Buch, K. D.; Muley, M. V.; Shelton, G. J.; Reddy, S. H.; Kudale, S.; Roy, J.; Gupta, Y.

    2013-04-01

    The GMRT Backend Group is in the process of developing wide-band digital backends as part of a major upgrade of the GMRT. The main requirements are for processing 400 MHz bandwidth signals from 30 antennas for interferometry and array mode operations, along with additional features like narrow band modes and RFI cancellation schemes. Both FPGA and GPU based designs have been explored and this paper presents the design and implementation details along with results from testing of prototype units. A comparison of the resources needed and performance achieved on FPGA and GPU based designs is presented, along with an extrapolation of these designs to a 30 station backend for the final GMRT system.

  3. Studies of novae at GMRT frequencies

    NASA Astrophysics Data System (ADS)

    Kantharia, N. G.

    2012-09-01

    The Giant Metrewave Radio Telescope (GMRT) which operates at wavelengths longer than 20 cm (frequencies ? 1.4 GHz) has been used to search for radio emission from Galactic novae systems since 2002. Of the 11 Galactic novae observed with GMRT, radio continuum emission has been detected in two of the systems whereas atomic gas associated with two systems has been imaged and studied in the 21 cm signal of H I. The two novae studied in the radio continuum with the GMRT are the remnant of GK Persei, a classical nova which had an outburst in 1901 and RS Ophiuchi, a recurrent nova following its last outburst in 2006. Combining the GMRT data on the classical nova GK Persei with VLA data at earlier epochs resulted in concluding that the nova remnant was undergoing a secular decrease in its flux density and in its adiabatic phase of evolution tep{2005A&A...435..167A}. RS Ophiuchi was observed at 1280, 610, 325 and 240 MHz with the GMRT days after its outburst and detected at all the observed frequencies. The near-simultaneous monitoring of its flux density at the low GMRT frequencies, resulted in the study of its spectral index which was indicative of synchrotron emission at all epochs tep{2007ApJ...667L.171K}. A supernova model resulted in a reasonable fit to the observed light curves; in particular the late appearance of emission at the lower GMRT frequencies due to the foreground clumpy, ionized, thermal circumbinary material. Comparison of these results with the previous outburst indicated that the densities of this clumpy medium had reduced making it optically thin to GMRT frequencies in 2006 tep{2007ApJ...667L.171K}. It is important to complement the higher radio frequency studies with observations at GMRT frequencies since these study different regions and physics of the nova system. Studies at GMRT frequencies can result in insights on the shock physics, distribution and density of the circumbinary material or planetary nebula, magnetic field generation and the spectral index evolution. Since the evolution of a nova system is faster than a supernova and novae are more numerous; these can be studied over shorter timescales. A sensitivity limit of 1 mJy can detect radio emission at GMRT frequencies upto a distance of 10 kpc, if the non-thermal luminosity of the novae system is 10^{13} W Hz^{-1}. Out of the total of about 33 novae detected in the radio bands, 9 have shown the presence of non-thermal emission in their spectra and 4 of these are recurrent in nature. GMRT frequencies are ideal to observe the non-thermal emission from the recurrent nova population as the ejecta expands driving shocks into the dense circumbinary material from the giant companion. An important motivation for studying the non-thermal radio emission from recurrent novae is to interrogate any evolutionary connection to the lack of detectable radio emission from type 1a supernova systems which recurrent novae are believed to evolve into and subsequently lend support to this model.

  4. Rate and topography of cell wall synthesis during the division cycle of Salmonella typhimurium.

    PubMed Central

    Cooper, S

    1988-01-01

    The rates of synthesis of peptidoglycan and protein during the division cycle of Salmonella typhimurium have been measured by using the membrane elution technique and differentially labeled diaminopimelic acid and leucine. The cells were labeled during unperturbed exponential growth and then bound to a nitrocellulose membrane by filtration. Newborn cells were eluted from the membrane with fresh medium. The radioactivity in the newborn cells in successive fractions was determined. As the cells are eluted from the membrane as a function of their cell cycle age at the time of labeling, the rate of incorporation of the different radioactive compounds as a function of cell cycle age can be determined. During the first part of the division cycle, the ratio of the rates of protein and peptidoglycan synthesis was constant. During the latter part of the division cycle, there was an increase in the rate of peptidoglycan synthesis relative to the rate of protein synthesis. These results support a simple, bipartite model of cell surface increase in rod-shaped cells. Before the start of constriction, the cell surface increased only by cylindrical extension. After cell constriction started, the cell surface increased by both cylinder and pole growth. The increase in surface area was partitioned between the cylinder and the pole so that the volume of the cell increased exponentially. No variation in cell density occurred because the increase in surface allowed a continuous exponential increase in cell volume that accommodated the exponential increase in cell mass. Protein was synthesized exponentially during the division cycle. The rate of cell surface increase was described by a complex equation which is neither linear nor exponential. PMID:3275624

  5. Giant metrewave radio telescope (GMRT) - Scientific objectives and design aspects

    Microsoft Academic Search

    G. Swarup

    1990-01-01

    A description is presented of the giant meterwave radio telescope (GMRT) being set up in India about 80 km north of Pune. The telescope will serve as a frontline research facility for astronomy and astrophysics. One of the important aims of the telescope is to search for the highly redshifted 21-cm line radiation from primordial neutral hydrogen clouds in order

  6. Low frequency follow up of SN 1996aq with GMRT

    Microsoft Academic Search

    Sayan Chakraborti; Poonam Chandra; Alak Ray

    2009-01-01

    We report on the follow up observations of SN 1996aq with the GMRT in 1280 MHz and 325 MHz bands, centered on 2009 March 20 (18:45 UT) and 22 (17:45 UT) respectively. The SN is detected in both observations, consistent with our previously reported position (S. Chakraborti et al. 2009, ATEL #1974). The measured fluxes are 1.05+\\/-0.09 mJy and 3.21+\\/-0.68

  7. 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.

  8. VizieR Online Data Catalog: LBDS-Lynx region GMRT 150-MHz obs. (Ishwara-Chandra+, 2010)

    NASA Astrophysics Data System (ADS)

    Ishwara-Chandra, C. H.; Sirothia, S. K.; Wadadekar, Y.; Pal, S.; Windhorst, R.

    2011-08-01

    It has been known for nearly three decades that high-redshift radio galaxies exhibit steep radio spectra, and hence ultrasteep spectrum radio sources provide candidates for high-redshift radio galaxies. Nearly all radio galaxies with z>3 have been found using this redshift-spectral index correlation. We have started a programme with the Giant Metrewave Radio Telescope (GMRT) to exploit this correlation at flux density levels about 10 to 100 times deeper than the known high-redshift radio galaxies which were identified primarily using the already available radio catalogues. In our programme, we have obtained deep, high-resolution radio observations at 150MHz with GMRT for several "deep" fields which are well studied at higher radio frequencies and in other bands of the electromagnetic spectrum, with an aim to detect candidate high-redshift radio galaxies. In this paper we present results from the deep 150-MHz observations of the LBDS-Lynx field (Leiden-Berkeley Deep Survey), which has been already imaged at 327, 610 and 1412MHz with the Westerbork Synthesis Radio Telescope and at 1400 and 4860MHz with the Very Large Array. (2 data files).

  9. Visualizing Topography

    NSDL National Science Digital Library

    Stephen Reynolds

    2006-01-01

    Topographic maps that display three-dimensional landscapes on two-dimensional surfaces can offer a great deal of spatial information in minimal space. However, it is often difficult for people to interpret the features on a topographic map. This interactive feature adapted from Stephen Reynolds's 'Visualizing Topography' website offers color-enhanced and three-dimensional visualizations to help interpret two-dimensional topographic maps. Users can introduce shading, tilt, and rotate the maps to better see the three dimensional feature being represented by the map.

  10. A software baseband receiver for pulsar astronomy at GMRT

    E-print Network

    Bhal Chandra Joshi; Sunil Ramakrishna

    2006-11-10

    A variety of pulsar studies, ranging from high precision astrometry to tests for theories of gravity, require high time resolution data. Few such observations at more than two frequencies below 1 GHz are available. Giant Meterwave Radio Telescope (GMRT) has the unique capability to provide such multi-frequency pulsar data at low observation frequencies, but the quality and time resolution of pulsar radio signals is degraded due to dispersion in the inter-stellar medium at these frequencies. Such degradation is usually taken care of by employing specialized digital hardware, which implement coherent dedispersion algorithm. In recent years, a new alternative is provided by the availability of cheap computer hardware. In this approach, the required signal processing is implemented in software using commercially off-the-shelf available computing hardware. This makes such a receiver flexible and upgradeable unlike a hardware implementation. The salient features and the modes of operation of a high time resolution pulsar instrument for GMRT based on this approach is described in this paper. The capability of the instrument is demonstrated by illustrations of test observations. We have obtained the average profile of PSR B1937+21 at 235 MHz for the first time and this profile indicates a scattering timescale of about 300 us. Lastly, the possible future extensions of this concept are discussed.

  11. SN 2008D (XRF 080109) radio detection by GMRT L-band

    Microsoft Academic Search

    Sayan Chakraborti; Alak Ray

    2008-01-01

    We report the radio detection of SN 2008D (XRF080109) in NGC 2770 by the Giant Metrewave Radio Telescope (GMRT) in the L band. GMRT observed the source as a Target of Opportunity between 2008 Jan 20 UT 16:20 and 2008 Jan 21 UT 00:05. The 16 MHz upper sideband data analysis reveals a source at RA 09h 09d 30.7s, DEC

  12. Moiré topography in odontology

    Microsoft Academic Search

    A. Moreno Yeras

    2003-01-01

    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

  13. GMRT observations of the group Holmberg 124: Evolution by tidal forces and ram pressure?

    Microsoft Academic Search

    N. G. Kantharia; S. Ananthakrishnan; R. Nityananda; Ananda Hota

    2005-01-01

    We report new radio continuum and 21 cm HI observations using the Giant Metrewave Radio Telescope (GMRT) of the group Holmberg 124 (Ho 124) comprising four late-type galaxies, namely NGC 2820, Mrk 108, NGC 2814 and NGC 2805. The three galaxies, NGC 2820, Mrk 108 and NGC 2814 which are closely located in the sky plane have clearly undergone tidal

  14. Dynamic Topography Revisited

    NASA Astrophysics Data System (ADS)

    Moresi, Louis

    2015-04-01

    Dynamic Topography Revisited Dynamic topography is usually considered to be one of the trinity of contributing causes to the Earth's non-hydrostatic topography along with the long-term elastic strength of the lithosphere and isostatic responses to density anomalies within the lithosphere. Dynamic topography, thought of this way, is what is left over when other sources of support have been eliminated. An alternate and explicit definition of dynamic topography is that deflection of the surface which is attributable to creeping viscous flow. The problem with the first definition of dynamic topography is 1) that the lithosphere is almost certainly a visco-elastic / brittle layer with no absolute boundary between flowing and static regions, and 2) the lithosphere is, a thermal / compositional boundary layer in which some buoyancy is attributable to immutable, intrinsic density variations and some is due to thermal anomalies which are coupled to the flow. In each case, it is difficult to draw a sharp line between each contribution to the overall topography. The second definition of dynamic topography does seem cleaner / more precise but it suffers from the problem that it is not measurable in practice. On the other hand, this approach has resulted in a rich literature concerning the analysis of large scale geoid and topography and the relation to buoyancy and mechanical properties of the Earth [e.g. refs 1,2,3] In convection models with viscous, elastic, brittle rheology and compositional buoyancy, however, it is possible to examine how the surface topography (and geoid) are supported and how different ways of interpreting the "observable" fields introduce different biases. This is what we will do. References (a.k.a. homework) [1] Hager, B. H., R. W. Clayton, M. A. Richards, R. P. Comer, and A. M. Dziewonski (1985), Lower mantle heterogeneity, dynamic topography and the geoid, Nature, 313(6003), 541-545, doi:10.1038/313541a0. [2] Parsons, B., and S. Daly (1983), The relationship between surface topography, gravity anomalies, and temperature structure of convection, Journal of Geophysical Research: Solid Earth (1978-2012), 88(B2), 1129-1144, doi:10.1029/JB088iB02p01129. [3] Robinson, E. M., B. Parsons, and S. F. Daly (1987), The effect of a shallow low viscosity zone on the apparent compensation of mid-plate swells, Earth and Planetary Science Letters, 82(3-4), 335-348, doi:10.1016/0012-821X(87)90207-X.

  15. Discovery of three new pulsars in a 610-MHz pulsar survey with the GMRT

    NASA Astrophysics Data System (ADS)

    Joshi, B. C.; McLaughlin, M. A.; Lyne, A. G.; Ludovici, D. A.; Pawar, N. A.; Faulkner, A. J.; Lorimer, D. R.; Kramer, M.; Davies, M. L.

    2009-09-01

    We report on the discovery of three new pulsars in the first blind survey of the north Galactic plane (45° < l < 135° |b| < 1°) with the Giant Meterwave Radio telescope (GMRT) at an intermediate frequency of 610 MHz. The survey covered 106 deg2 with a sensitivity of roughly 1 mJy to long-period pulsars (pulsars with period longer than 1 s). The three new pulsars have periods of 318, 933 and 1056 ms. Their timing parameters and flux densities, obtained in follow-up observations with the Lovell Telescope at Jodrell Bank and the GMRT, are presented. We also report on pulse nulling behaviour in one of the newly discovered pulsars, PSR J2208+5500.

  16. GMRT observation of SN 2006jc in the L-band

    Microsoft Academic Search

    Sayan Chakraborti; Alak Ray

    2008-01-01

    We report on an observation of SN 2006jc on 2008 June 27 by the Giant Metrewave Radio Telescope (GMRT) in the L-band (mean observing epoch 07.84 UT). Radio emission from the SN was not detected. The 2 sigma upper limit at the central frequency of 1397.5 MHz was 0.154 mJy at the supernova location. The corresponding map rms is 0.077

  17. No detection of L-band radio emission from SN 2007gr by GMRT

    Microsoft Academic Search

    Alak K. Ray

    2007-01-01

    Sayan Chakraborti (Tata Institute of Fundamental Research, Mumbai, (TIFR)), Poonam Chandra (Univ Virginia and National Radio Astronomical Observatory, Charlottesville), Nirupam Roy (National Centre for Radio Astrophysics (NCRA-TIFR), Pune, and Alak Ray (TIFR) report on the Target of Opportunity observation of SN 2007gr on 2007 Aug 24 by the Giant Metrewave Radio Telescope (GMRT) in the L-band between UT 0200 to

  18. GMRT observation of SN 2008ax in the L-band

    Microsoft Academic Search

    Sayan Chakraborti; Alak Ray

    2008-01-01

    We report on a Target of Opportunity (ToO) observation of SN 2008ax on 2008 Mar 25 by the Giant Metrewave Radio Telescope (GMRT) in the L-band (mean observing epoch 19.25 UT). Radio emission from the SN was not detected. The 2 sigma upper limit of the SN flux at the central frequency of 1397 MHz was 0.45 mJy. The corresponding

  19. Reanalysis of SN 2008D (XRF 080109) observation by GMRT L-band

    Microsoft Academic Search

    Sayan Chakraborti; Alak Ray

    2008-01-01

    We withdraw the claimed detection of SN 2008D (XRF080109) in NGC 2770 by the Giant Metrewave Radio Telescope (GMRT) in the L band observed on 2008 Jan 20, as reported by us in ATel #1377. The reanalyzed map noise is 0.143 mJy at 1288.75 MHz. The three sigma upper limit to the SN flux in our revised analysis is 0.43

  20. No detection of L-band radio emission from SN 2007gr by GMRT

    NASA Astrophysics Data System (ADS)

    Ray, Alak K.

    2007-08-01

    Sayan Chakraborti (Tata Institute of Fundamental Research, Mumbai, (TIFR)), Poonam Chandra (Univ Virginia and National Radio Astronomical Observatory, Charlottesville), Nirupam Roy (National Centre for Radio Astrophysics (NCRA-TIFR), Pune, and Alak Ray (TIFR) report on the Target of Opportunity observation of SN 2007gr on 2007 Aug 24 by the Giant Metrewave Radio Telescope (GMRT) in the L-band between UT 0200 to 0400.

  1. Radio non-detection of SN 2006gy with GMRT in the L-band

    Microsoft Academic Search

    Poonam Chandra; Sayan Chakraborti; Alak Ray

    2007-01-01

    SN 2006gy was observed with the GMRT on 18 May 2007 at the mean observing epoch of 6.01 UT. The L-band observation (mean frequency 1398 MHz) with a total bandwidth of 32 MHz does not detect the Supernova. The time on source was 3 hrs. The two sigma upper limit to the flux density at the position of SN 2006gy

  2. Radio monitoring of SN 2007gr by GMRT in the L-band

    Microsoft Academic Search

    Sayan Chakraborti; Poonam Chandra; Nirupam Roy; Alak Ray

    2007-01-01

    We report on a continuing Target of Opportunity (ToO) observation of SN 2007gr on 2007 Aug 25 by the Giant Metrewave Radio Telescope (GMRT) in the L-band between UT 0300 to 0500. The central frequency was 1390 MHz with a bandwidth of 32 MHz. Radio emission from the SN was not detected in this observation with a 2 sigma upper

  3. A combined GMRT/CLFST image of IC443 at 150 MHz

    E-print Network

    Mitra, D; Rao, A Pramesh

    2013-01-01

    IC443 is a relatively large Galactic (~45 arcmin) SNR with a high radio surface brightness. It has fine scale structure down to arcsec scales, and so is difficult to image on all angular scales with a single instrument. Here observations of IC443 at 151 MHz made with both the GMRT and the CLFST are combined to give a composite image of IC443 on all scales from >45 arcmin down to ~20 arcsec.

  4. A combined GMRT/CLFST image of IC443 at 150 MHz

    NASA Astrophysics Data System (ADS)

    Mitra, D.; Green, D. A.; Rao, A. Pramesh

    2014-01-01

    IC443 is a relatively large Galactic (~45 arcmin) SNR with a high radio surface brightness. It has fine scale structure down to arcsec scales, and so is difficult to image on all angular scales with a single instrument. Here observations of IC443 at 151 MHz made with both the GMRT and the CLFST are combined to give a composite image of IC443 on all scales from >45 arcmin down to ~20 arcsec.

  5. Moire topography in odontology

    NASA Astrophysics Data System (ADS)

    Moreno Yeras, A.

    2001-08-01

    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.

  6. Moiré topography in odontology

    NASA Astrophysics Data System (ADS)

    Moreno Yeras, A.

    2003-07-01

    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.

  7. SURFACE WATER & OCEAN TOPOGRAPHY

    E-print Network

    Christian, Eric

    of the Wide Swath Ocean Altimeter (WSOA) and the Shuttle Radar Topography Mission (SRTM). The Ku-band sampling for surface-water applications, near-global coverage, and the swath capabilities of the Ku-band/JPL ­ IIP98) · Enhancement of key technologies (Ka-band radar interferometry antenna design, onboard

  8. Flow Interaction with Topography

    NSDL National Science Digital Library

    2014-09-14

    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.

  9. Low Frequency Radio Observations of GRS1915+105 with GMRT

    E-print Network

    C. H. Ishwara-Chandra; A. Pramesh Rao; Mamta Pandey; R. K. Manchanda; Philippe Durouchoux

    2005-12-02

    We present the first detailed low frequency radio measurements of the galactic microquasar GRS1915+105 with GMRT. Simultaneous observations were carried out at 610 and 244 MHz. Our data does not show any signature of spectral turn over even at low radio frequency of 244 MHz. We propose that while the radio emission at high radio frequencies could predominantly come from compact jets, the emission at lower frequency originates in the lobes at the end of the jet which acts like a reservoir of low energy electrons.

  10. The Extended GMRT Radio Halo Survey. II. Further results and analysis of the full sample

    NASA Astrophysics Data System (ADS)

    Kale, R.; Venturi, T.; Giacintucci, S.; Dallacasa, D.; Cassano, R.; Brunetti, G.; Cuciti, V.; Macario, G.; Athreya, R.

    2015-07-01

    The intra-cluster medium contains cosmic rays and magnetic fields that are manifested through the large scale synchrotron sources, termed radio haloes, relics, and mini-haloes. The Extended Giant Metrewave Radio Telescope (GMRT) Radio Halo Survey (EGRHS) is an extension of the GMRT Radio Halo Survey (GRHS) designed to search for radio haloes using GMRT 610/235 MHz observations. The GRHS and EGRHS consists of 64 clusters in the redshift range 0.2-0.4 that have an X-ray luminosity larger than 5 × 1044 erg s-1 in the 0.1-2.4 keV band and declination, ? > -31° in the REFLEX and eBCS X-ray cluster catalogues. In this second paper in the series, GMRT 610/235 MHz data on the last batch of 11 galaxy clusters and the statistical analysis of the full sample are presented. A new mini-halo in RX J2129.6+0005 and candidate diffuse sources in Z5247, A2552, and Z1953 have been discovered. A unique feature of this survey are the upper limits on the detections of 1 Mpc sized radio haloes; 4 new are presented here, making a total of 31 in the survey. Of the sample, 58 clusters with adequately sensitive radio information were used to obtain the most accurate occurrence fractions so far. The occurrence fractions of radio haloes, mini-haloes and relics in our sample are ~22%, ~16% and ~5%, respectively. The P1.4 GHz-LX diagrams for the radio haloes and mini-haloes are presented. The morphological estimators - centroid shift (w), concentration parameter (c), and power ratios (P3/P0) derived from the Chandra X-ray images - are used as proxies for the dynamical states of the GRHS and EGRHS clusters. The clusters with radio haloes and mini-haloes occupy distinct quadrants in the c-w, c-P3/P0 and w-P3/P0 planes, corresponding to the more and less morphological disturbance, respectively. The non-detections span both the quadrants. Appendices are available in electronic form at http://www.aanda.org

  11. Tidal Conversion by Supercritical Topography

    E-print Network

    Balmforth, Neil J.

    Calculations are presented of the rate of energy conversion of the barotropic tide into internal gravity waves above topography on the ocean floor. The ocean is treated as infinitely deep, and the topography consists of ...

  12. Five Years of Multi-frequency Monitoring of GRB030329 Afterglow Using the GMRT and WSRT

    SciTech Connect

    Kamble, Atish; Wijers, Ralph; Rol, Evert [Astronomical Institute 'Anton Pannekoek', Kruislaan 403, 1098 SJ Amsterdam (Netherlands); Horst, A. J. van der; Kouveliotou, Chryssa [National Space Science and Technology Center, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Bhattacharya, D. [Inter University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune: 411 007 (India); Chandra, C. H. Ishwara [National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune University Campus, Pune: 411 007 (India); Resmi, L. [GRECO, Institut d'Astrophysique de Paris, 98bis, bd Arago-75014, Paris (France); Strom, R. [ASTRON, P.O. Box 2, 7990 AA Dwingeloo (Netherlands); Astronomical Institute 'Anton Pannekoek', Kruislaan 403, 1098 SJ Amsterdam (Netherlands)

    2009-05-25

    GRB 030329 displayed one of the brightest optical afterglows ever. We have followed the radio afterglow of GRB 030329 for over 5 years using the GMRT and WSRT at low radio frequencies. This is the longest as well as the lowest frequency follow up of any GRB afterglow ever.Radio observations of a GRB afterglow provide a unique probe of the physics of the blast wave at late times, when the expansion of the fireball slows down to non-relativistic speeds. Our GMRT-WSRT observations suggest that the afterglow of GRB030329 entered the non-relativistic phase around 60 days after the burst. The estimate of the fireball energy content, {approx}10{sup 51} erg, in this near-isotropic phase is much less susceptible to the collimation-related uncertainties arising in the relativistic phase. We have also been closely monitoring the evolution of the afterglow to look for possible signatures of emission from a counter jet, but no conclusive evidence has so far been found.

  13. The Dawn Topography Investigation

    NASA Technical Reports Server (NTRS)

    Raymond, C. A.; Jaumann, R.; Nathues, A.; Sierks, H.; Roatsch, T.; Preusker, E; Scholten, F.; Gaskell, R. W.; Jorda, L.; Keller, H.-U.; Zuber, M. T.; Smith, D. E.; Mastrodemos, N.; Mottola, S.

    2011-01-01

    The objective of the Dawn topography investigation is to derive the detailed shapes of 4 Vesta and 1 Ceres in order to create orthorectified image mosaics for geologic interpretation, as well as to study the asteroids' landforms, interior structure, and the processes that have modified their surfaces over geologic time. In this paper we describe our approaches for producing shape models, plans for acquiring the needed image data for Vesta, and the results of a numerical simulation of the Vesta mapping campaign that quantify the expected accuracy of our results. Multi-angle images obtained by Dawn's framing camera will be used to create topographic models with 100 m/pixel horizontal resolution and 10 m height accuracy at Vesta, and 200 m/pixel horizontal resolution and 20 m height accuracy at Ceres. Two different techniques, stereophotogrammetry and stereophotoclinometry, are employed to model the shape; these models will be merged with the asteroidal gravity fields obtained by Dawn to produce geodetically controlled topographic models for each body. The resulting digital topography models, together with the gravity data, will reveal the tectonic, volcanic and impact history of Vesta, and enable co-registration of data sets to determine Vesta's geologic history. At Ceres, the topography will likely reveal much about processes of surface modification as well as the internal structure and evolution of this dwarf planet.

  14. Gallery of Virtual Topography

    NSDL National Science Digital Library

    Stephen Reynolds

    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.

  15. The GMRT EoR experiment: limits on polarized sky brightness at 150 MHz

    NASA Astrophysics Data System (ADS)

    Pen, Ue-Li; Chang, Tzu-Ching; Hirata, Christopher M.; Peterson, Jeffrey B.; Roy, Jayanta; Gupta, Yashwant; Odegova, Julia; Sigurdson, Kris

    2009-10-01

    The Giant Metrewave Radio Telescope (GMRT) reionization effort aims to map out the large-scale structure of the Universe during the epoch of reionization (EoR). Removal of polarized Galactic emission is a difficult part of any 21 cm EoR programme, and we present new upper limits to diffuse polarized foregrounds at 150 MHz. We find no high-significance evidence of polarized emission in our observed field at mid-galactic latitude (J2000 08h26m+26). We find an upper limit on the two-dimensional angular power spectrum of diffuse polarized foregrounds of (l2Cl/2?)1/2 < 3K in frequency bins of width ?? = 1MHz at 300 < l < 1000. The three-dimensional power spectrum of polarized emission, which is most directly relevant to EoR observations, is [k3PP(k)/2?2]1/2 < 2K at k? > 0.03hMpc-1,k < 0.1hMpc-1. This can be compared to the expected EoR signal in total intensity of [k3P(k)/2?2]1/2 ~ 10mK. We find that polarized structure is substantially weaker than suggested by extrapolation from higher frequency observations, so the new low upper limits reported here reduce the anticipated impact of these foregrounds on EoR experiments. We discuss the Faraday beam and depth depolarization models and compare predictions of these models to our data. We report on a new technique for polarization calibration using pulsars, as well as a new technique to remove broad-band radio frequency interference. Our data indicate that, on the edges of the main beam at the GMRT, polarization squint creates ~3 per cent leakage of unpolarized power into polarized maps at zero rotation measure. Ionospheric rotation was largely stable during these solar minimum nighttime observations.

  16. The GMRT EoR Experiment: Limits on Polarized Sky Brightness at 150 MHz

    E-print Network

    Ue-Li Pen; Tzu-Ching Chang; Christopher M. Hirata; Jeffrey B. Peterson; Jayanta Roy; Yashwant Gupta; Julia Odegova; Kris Sigurdson

    2009-05-05

    The GMRT reionization effort aims to map out the large scale structure of the Universe during the epoch of reionization (EoR). Removal of polarized Galactic emission is a difficult part of any 21 cm EoR program, and we present new upper limits to diffuse polarized foregrounds at 150 MHz. We find no high significance evidence of polarized emission in our observed field at mid galactic latitude (J2000 08h26m+26). We find an upper limit on the 2-dimensional angular power spectrum of diffuse polarized foregrounds of [l^2 C_l/(2 PI)]^{1/2} 0.03 h/Mpc, k < 0.1 h/Mpc. This can be compared to the expected EoR signal in total intensity of [k^3 P(k)/ (2 PI^2) ]^{1/2} ~ 10 mK. We find polarized structure is substantially weaker than suggested by extrapolation from higher frequency observations, so the new low upper limits reported here reduce the anticipated impact of these foregrounds on EoR experiments. We discuss Faraday beam and depth depolarization models and compare predictions of these models to our data. We report on a new technique for polarization calibration using pulsars, as well as a new technique to remove broadband radio frequency interference. Our data indicate that, on the edges of the main beam at GMRT, polarization squint creates ~ 3% leakage of unpolarized power into polarized maps at zero rotation measure. Ionospheric rotation was largely stable during these solar minimum night time observations.

  17. Topography of Io (color)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    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

  18. Global Multi-Resolution Topography synthesis

    Microsoft Academic Search

    William B. F. Ryan; Suzanne M. Carbotte; Justin O. Coplan; Suzanne O'Hara; Andrew Melkonian; Robert Arko; Rose Anne Weissel; Vicki Ferrini; Andrew Goodwillie; Frank Nitsche; Juliet Bonczkowski; Richard Zemsky

    2009-01-01

    Seafloor bathymetric data acquired with modern swath echo sounders provide coverage for only a small fraction of the global seabed yet are of high value for studies of the dynamic processes of seafloor volcanism, tectonics, mass wasting, and sediment transport that create and shape the undersea landscape. A new method for compilation of global seafloor bathymetry that preserves the native

  19. Density, Isostasy, and Topography

    NSDL National Science Digital Library

    Anne Egger

    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.

  20. Corneal topography by keratometry

    PubMed Central

    Douthwaite, W; Evardson, W

    2000-01-01

    AIMS—To investigate the ability of a telecentric keratometer to describe the asphericity and curvature of convex ellipsoidal surfaces and human corneas.?METHODS—22 conicoidal convex surfaces and 30 human corneas were examined by conventional keratometry. Additional keratometric measurements were made when the surface was tilted in the horizontal plane relative to the instrument optical axis. This resulted in a series of radius measurements derived from different regions of the surface. These measurements were used to determine the apical radius and the p value of the horizontal meridian of each surface. The results were compared with those derived from measurements using the EyeSys videokeratoscope and form Talysurf analysis. The method was repeated on 30 human corneas and the results compared with those of a videokeratoscope.?RESULTS—For the aspheric buttons, the keratometric and the EyeSys results tended to give higher values for both apical radius and the p values than those of the Talysurf analysis. The best agreement was between the Talysurf and the keratometer where the results were not significantly different. For the human corneas, the apical radii were significantly different comparing the keratometer with the videokeratoscope but the p values were not significantly different.?CONCLUSION—The keratometric method for assessing curvature and asphericity appears to hold promise as a method for quantifying the corneal topography.?? PMID:10906088

  1. Global Topography and Tectonic Plates

    NSDL National Science Digital Library

    David Greene

    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.

  2. HI in XMD Galaxies III. GMRT observations of BCG HS0822+3542

    E-print Network

    Jayaram N. Chengalur; S. A. Pustilnik; J. -M. Martin; A. Y. Kniazev

    2006-08-04

    We present Giant Metrewave Radio Telescope (GMRT) HI 21-cm line data for the smallest known eXtremely Metal Deficient (XMD) blue compact galaxy (BCG) HS0822+3542. From HST imaging it has been suggested that HS0822+3542 actually consists of two still smaller (~ 100pc sized) ultra-compact dwarfs that are in the process of merging. The brighter of these two putative ultra compact dwarfs has an ocular appearance, similar to that seen in galaxies that have suffered a penetrating encounter with a smaller companion. From our HI imaging we find that the gas distribution and kinematics in this object are similar to that of other low mass galaxies, albeit with some evidence for tidal disturbance. On the other hand, the HI emission has an angular size ~25 times larger than that of the putative ultra-compact dwarfs. The optical emission is also offset from the centre of the HI emission. HS0822+3542 is located in the Lynx-Cancer void, but has a nearby companion LSB dwarf galaxy SAO0822+3545. In light of all this we also consider a scenario where the optical emission from HS0822+3542 comes not from two merging ultra-compact dwarfs but from multiple star forming regions in a tidally disturbed galaxy. In this model, the ocular appearance of the brighter star forming region could be the result of triggered star formation.

  3. GMRT radio continuum study of Wolf-Rayet galaxies - I. NGC 4214 and NGC 4449

    NASA Astrophysics Data System (ADS)

    Srivastava, S.; Kantharia, N. G.; Basu, Aritra; Srivastava, D. C.; Ananthakrishnan, S.

    2014-09-01

    We report low-frequency observations of Wolf-Rayet galaxies, NGC 4214 and NGC 4449 at 610, 325 and 150 MHz, using the Giant Meterwave Radio Telescope (GMRT). We detect diffuse extended emission from NGC 4214 at and NGC 4449. NGC 4449 is observed to be five times more radio luminous than NGC 4214, indicating vigorous star formation. We estimate synchrotron spectral index after separating the thermal free-free emission and obtain ?nt = -0.63 ± 0.04 (S? ? ^{? _nt}) for NGC 4214 and -0.49 ± 0.02 for NGC 4449. About 22 per cent of the total radio emission from NGC 4214 and ˜9 per cent from NGC 4449 at 610 MHz is thermal in origin. We also study the spectra of two compact star-forming regions in NGC 4214 from 325 MHz to 15 GHz and obtain ?nt = -0.32 ± 0.02 for NGC 4214-I and ?nt = -0.94 ± 0.12 for NGC 4214-II. The luminosities of these star-forming regions (˜1019 WHz-1) appear to be similar to those in circumnuclear rings in normal disc galaxies observed with similar linear resolution. We detect the supernova remnant SNR J1228+441 in NGC 4449 and estimate the spectral index of the emission between 325 and 610 MHz to be -1.8 in the epoch 2008-2009. The galaxies follow the radio-FIR correlation slopes suggesting that star formation in Wolf-Rayet galaxies, which are low-metallicity systems, are similar to that of normal disc galaxies.

  4. The Shuttle Radar Topography Mission

    Microsoft Academic Search

    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

    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.

  5. Brain Topography, 2009 Author copy

    E-print Network

    Paris-Sud XI, Université de

    1 Brain Topography, 2009 Author copy On the "dependence" of "independent" group EEG sources; an EEG Stendhal, Grenoble Institute of Tecnology, Grenoble, France. b Brain Research Laboratory, New York University Medical School, Department of Psychiatry c Brain Research center Antwerp for Innovative

  6. Deep GMRT 150 MHz observations of the LBDS-Lynx region: Ultra-Steep Spectrum Radio Sources

    E-print Network

    Ishwara-Chandra, C H; Wadadekar, Y; Pal, S; Windhorst, R

    2010-01-01

    It has been known for nearly three decades that high redshift radio galaxies exhibit steep radio spectra, and hence ultra-steep spectrum radio sources provide candidates for high-redshift radio galaxies. Nearly all radio galaxies with z > 3 have been found using this redshift-spectral index correlation. We have started a programme with GMRT to exploit this correlation at flux density levels about 10 to 100 times deeper than the known high-redshift radio galaxies which were identified primarily using the already available radio catalogues. In our programme, we have obtained deep, high resolution radio observations at 150 MHz with GMRT for several 'deep' fields which are well studied at higher radio frequencies and in other bands of the electromagnetic spectrum, with an aim to detect candidate high redshift radio galaxies. In this paper we present results from the deep 150 MHz observations of LBDS-Lynx field, which has been already imaged at 327, 610 and 1412 MHz with the WSRT and at 1400 and 4860 MHz with the ...

  7. The topography of Iapetus' leading side

    Microsoft Academic Search

    Bernd Giese; Tilmann Denk; Gerhard Neukum; Thomas Roatsch; Paul Helfenstein; Peter C. Thomas; Elizabeth P. Turtle; Alfred McEwen; Carolyn C. Porco

    2008-01-01

    We have used Cassini stereo images to study the topography of Iapetus' leading side. A terrain model derived at resolutions of 4–8 km reveals that Iapetus has substantial topography with heights in the range of ?10 km to +13 km, much more than observed on the other middle-sized satellites of Saturn so far. Most of the topography is older than

  8. Topography, Cell Response, and Nerve Regeneration

    PubMed Central

    Hoffman-Kim, Diane; Mitchel, Jennifer A.; Bellamkonda, Ravi V.

    2010-01-01

    In the body, cells encounter a complex milieu of signals, including topographical cues. Imposed topography can affect cells on surfaces by promoting adhesion, spreading, alignment, morphological changes, and changes in gene expression. Neural response to topography is complex, and depends on the dimensions and shapes of physical features. Looking toward repair of nerve injuries, strategies are being explored to engineer guidance conduits with precise surface topographies. How neurons and other cell types sense and interpret topography remains to be fully elucidated. Studies reviewed here include those of topography on cellular organization and function as well as potential cellular mechanisms of response. PMID:20438370

  9. Stem Cell Interaction with Topography

    Microsoft Academic Search

    Benjamin K. K. Teo; Soneela Ankam; Evelyn K. F. Yim

    \\u000a The growth and differentiation of stem cells are regulated by biochemical and biophysical cues in the extracellular microenvironment.\\u000a Increasing evidences have shown that substrate topography, one of the biophysical properties of the microenvironment, can\\u000a affect stem cell fate, such as the maintenance of embryonic stem cells and the differentiation of adult and embryonic stem\\u000a cells. The underlying mechanism of how

  10. The Shuttle Radar Topography Mission

    NASA Astrophysics Data System (ADS)

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

    2007-06-01

    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. Details of the development, flight operations, data processing, and products are provided for users of this revolutionary data set.

  11. Earth rotation and core topography

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

  12. Carbon Dioxide Exchange in Complex Topography

    NASA Astrophysics Data System (ADS)

    Reif, Matthias; Rotach, Mathias; Wohlfahrt, Georg; Gohm, Alexander

    2015-04-01

    On a global scale the budget of carbon dioxide (CO_2) bears a quite substantial uncertainty, which is commonly understood to be mainly due to land-surface exchange processes. In this project we investigate to what extent complex topography can amplify these land-surface exchange processes. The hypothesis is that, on the meso-scale, topography adds additional atmospheric mechanisms that drive the exchange of CO2 at the surface. This sensitivity model study investigates an idealized sine shaped valley with the atmospheric numerical model Weather Research and Forecasting (WRF) coupled to the community land model (CLM) to study the effect of complex topography on the CO2 budget compared to flat terrain. The experiment is designed to estimate the effect of the topography during maximum ecosystem exchange in summer using meteorological and ecosystem conditions at solstice, the 21. of June. Systematic variation of meteorological initial conditions, plant functional types and the topography creates an ensemble that unveils the fundamental factors that dominate the differences of CO2 between simulations with topography compared to plain surfaces in the model. The sign and magnitude of the difference between the CO2 exchange over topography and over a plain simulation are strongly dependent on the CLM plant functional type, the initial temperature, the initial relative humidity, the latitude and the area height distribution of the topography. However, in this model experiment the topography is, in the mean, a sink to the CO2 budget in the order of 5% per day.

  13. Venus topography - A harmonic analysis

    NASA Technical Reports Server (NTRS)

    Bills, B. G.; Kobrick, M.

    1985-01-01

    A model of Venusian global topography has been obtained by fitting an eighteenth-degree harmonic series to Pioneer Venus orbiter radar altimeter data. The mean radius is (6051.45 + or - 0.04) km. The corresponding mean density is (5244.8 + or 0.5) kg/cu m. The center of figure is displaced from the center of mass by (0.339 + or - 0.088) km towards (6.6 + or 10.1) deg N, (148. 8 + or - 7.7) deg. The figure of Venus is distinctly triaxial, but the orientation and magnitudes of the principal topographic axes correlate rather poorly with the gravitational principal axes. However, the higher-degree harmonics of topography and gravity are significantly correlated. The topographic variance spectrum of Venus is very similar in form to those of the moon, Mars, and especially earth. It is suggested that this spectral similarity simply reflects a statistical balance between constructional and degradational geomorphic proceses. Venus and earth are particularly similar (and differ from the moon and Mars) in that the larger bodies both exhibit a significant low degree deficit (relative to the extrapolated trend of the higher harmonics).

  14. The VVDS-VLA deep field. III. GMRT observations at 610 MHz and the radio spectral index properties of the sub-mJy population

    Microsoft Academic Search

    M. Bondi; P. Ciliegi; T. Venturi; D. Dallacasa; S. Bardelli; E. Zucca; R. M. Athreya; L. Gregorini; A. Zanichelli; O. Le Fèvre; T. Contini; B. Garilli; A. Iovino; S. Temporin; D. Vergani

    2007-01-01

    Aims:We present the low frequency (610 MHz) radio source counts of the VVDS-VLA field and investigate the radio spectral index properties of the sub-mJy population. Methods: We use new deep (rms~= 50~muJy\\/beam) observations of the VVDS-VLA field obtained at 610 MHz with the GMRT and matched in resolution (6 arcsec) with already available VLA data at 1.4 GHz on the

  15. GMRT mini-survey to search for 21-cm absorption in quasar-galaxy pairs at z ~ 0.1

    NASA Astrophysics Data System (ADS)

    Gupta, N.; Srianand, R.; Bowen, D. V.; York, D. G.; Wadadekar, Y.

    2010-10-01

    We present the results from our 21-cm absorption survey of a sample of five quasar-galaxy pairs (QGPs), with the redshift of the galaxies in the range 0.03 <= zg <= 0.18, selected from the Sloan Digital Sky Survey (SDSS). The HI 21-cm absorption was searched towards the nine sightlines with impact parameters ranging from ~10 to ~55 kpc using the Giant Metrewave Radio Telescope (GMRT). 21-cm absorption was detected only in one case, i.e. towards the quasar (zq = 2.625 SDSS J124157.54+633241.6)-galaxy (zg = 0.143 SDSS J124157.26+633237.6) pair with the impact parameter ~11 kpc. The quasar sightline in this case pierces through the stellar disc of a galaxy having near solar metallicity [i.e. (O/H)+12 = 8.7] and star formation rate uncorrected for dust attenuation of 0.1 Msolar yr-1. The quasar spectrum reddened by the foreground galaxy is well fitted with the Milky Way extinction curve (with an AV of 0.44) and the estimated HI column density is similar to the value obtained from 21-cm absorption assuming a spin temperature (TS) of 100 K. In the remaining cases, our GMRT spectra provide upper limit on N(HI) in the range (1017-1018) × TS cm-2. Combining our sample with the z <= 0.1 data available in the literature, we find the detectability of 21-cm absorption with integrated optical depth greater than 0.1 km s-1 to be 50 per cent for the impact parameter less than 20 kpc. Using the surface brightness profiles and a well-established relationship between the optical size and extent of the HI disc known for nearby galaxies, we conclude that in most of the cases of 21-cm absorption non-detection, the sightlines may not be passing through the HI gas (1? column density of a few times 1019 cm-2). We also find that in comparison to the absorption systems associated with these QGPs, z < 1 damped Lyman-? absorbers (DLAs) with 21-cm absorption detections have lower CaII equivalent widths despite having higher 21-cm optical depths and smaller impact parameters. This suggests that the current sample of DLAs may be a biased population that avoids sightlines through dusty star-forming galaxies. A systematic survey of QGPs over a wider redshift range using a large sample is needed to confirm these findings and understand the nature of 21-cm absorbers.

  16. The Extended GMRT Radio Halo Survey. I. New upper limits on radio halos and mini-halos

    NASA Astrophysics Data System (ADS)

    Kale, R.; Venturi, T.; Giacintucci, S.; Dallacasa, D.; Cassano, R.; Brunetti, G.; Macario, G.; Athreya, R.

    2013-09-01

    Context. A fraction of galaxy clusters host diffuse radio sources called radio halos, radio relics and mini-halos. These are associated with the relativistic electrons and magnetic fields present on ~Mpc scales in the intra-cluster medium. Aims: We aim to carry out a systematic radio survey of all luminous galaxy clusters selected from the REFLEX and eBCS X-ray catalogues with the Giant Metrewave Radio Telescope, to understand the statistical properties of the diffuse radio emission in galaxy clusters. Methods: We present the sample and first results from the Extended GMRT Radio Halo Survey (EGRHS), which is an extension of the GMRT Radio Halo Survey (GRHS, Venturi et al. 2007, 2008). Analysis of radio data at 610/ 235/ 325 MHz on 12 galaxy clusters are presented. Results: We report the detection of a newly discovered mini-halo in the cluster RX J1532.9+3021 at 610 MHz. The presence of a small-scale relic (~200 kpc) is suspected in the cluster Z348. We do not detect cluster-scale diffuse emission in 11 clusters. Robust upper limits on the detection of radio halo of size of 1 Mpc are determined. We also present upper limits on the detections of mini-halos in a sub-sample of cool-core clusters. The upper limits for radio halos and mini-halos are plotted in the radio power- X-ray luminosity plane and the correlations are discussed. Diffuse extended emission that is not related to the target clusters, but detected as by-products in the sensitive images of two of the cluster fields (A689 and RX J0439.0+0715) is also reported. Conclusions: Based on the information about the presence of radio halos (or upper limits), available on 48 clusters out of the total sample of 67 clusters (EGRHS+GRHS), we find that 23 ± 7% of the clusters host radio halos. The radio halo fraction rises to 31 ± 11%, when only the clusters with X-ray luminosities >8 × 1044 erg s-1 are considered. Mini-halos are found in ~50% of cool-core clusters. A qualitative examination of the X-ray images of the clusters with no diffuse radio emission indicates that a majority of these clusters do not show extreme dynamical disturbances and supports the idea that mergers play an important role in generating radio halos and relics. The analysis of the full sample will be presented in a future work. Appendix A is available in electronic form at http://www.aanda.org

  17. Phobos' shape and topography models

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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.

  18. Renormalisation of Global Mantle Dynamic Topography Predictions using Residual Topography Measurements for "Normal" Ocean Crust

    NASA Astrophysics Data System (ADS)

    Cowie, Fergus; Kusznir, Nick; Cowie, Leanne

    2015-04-01

    The best constraint on model predictions of present day mantle dynamic topography are measurements of residual topography. Residual topography is calculated by removing the isostatic effects of bathymetry, sediments, ice, crustal thickness variation and lithosphere thermal anomalies from the observed topography. Comparison of global model predictions of mantle dynamic topography with global compilations of residual topography, while showing a broadly similar pattern at long wavelengths, differ substantially in amplitude. A strong contribution to the present day surface topographic signal arises from crustal thickness variation. As a consequence it is difficult to accurately determine residual topography for continental crust and for oceanic regions with substantially thicker than average oceanic crust (e.g. oceanic crust adjacent to volcanic rifted margins, oceanic plume tracks, volcanic plateaux, micro-continents). Residual topography is best measured on ocean crust of "normal" oceanic thickness. We use global mapping of crustal thickness using gravity inversion to identify crust with thicknesses greater than that of "normal" oceanic crust in order than we can eliminate the less accurate measurements of residual topography for these thicker crustal regions. Comparison of model predicted mantle dynamic topography with residual topography measurements for the remaining regions of thinner "normal" oceanic crust shows an improved correlation but with a dynamic topography showing a positive bias with respect to residual topography and a greater amplitude. We use residual topography measurements for "normal" oceanic crust to downward shift (by approximately 600 m) and rescale (by 0.6) predicted global mantle dynamic topography. We present maps of the renormalised model predictions of global mantle topography from Steinberger (2007) and Flament et al. (2013). One consequence of renormalization is to reduce the amplitude of predicted mantle dynamic topographic uplift in the Pacific. The gravity inversion methodology includes a correction for the elevated geothermal gradient of oceanic and rifted continental margin lithosphere and sediment thickness. Caveats on this methodology are (i) that the gravity inversion methodology used to determine crustal thickness for screening out thick crust is itself dependent on mantle dynamic topography (but fortunately only weakly so) and (ii) that the renormalization procedure is biased towards oceanic regions.

  19. Enhanced Characterization of Niobium Surface Topography

    SciTech Connect

    Chen Xu, Hui Tian, Charles Reece, Michael Kelley

    2011-12-01

    Surface topography characterization is a continuing issue for the Superconducting Radio Frequency (SRF) particle accelerator community. Efforts are underway to both to improve surface topography, and its characterization and analysis using various techniques. In measurement of topography, Power Spectral Density (PSD) is a promising method to quantify typical surface parameters and develop scale-specific interpretations. PSD can also be used to indicate how chemical processes modifiesy the roughnesstopography at different scales. However, generating an accurate and meaningful topographic PSD of an SRF surface requires careful analysis and optimization. In this report, polycrystalline surfaces with different process histories are sampled with AFM and stylus/white light interferometer profilometryers and analyzed to indicate trace topography evolution at different scales. evolving during etching or polishing. Moreover, Aan optimized PSD analysis protocol will be offered to serve the SRF surface characterization needs is presented.

  20. Corneal topography measurements for biometric applications

    NASA Astrophysics Data System (ADS)

    Lewis, Nathan D.

    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.

  1. Effects of Topography on Fronts.

    NASA Astrophysics Data System (ADS)

    Williams, R. T.; Peng, Melinda S.; Zankofski, D. A.

    1992-02-01

    The hydrostatic Boussinesq equations are used to simulate the passage of fronts over a two-dimensional mountain in a cyclic domain. The fronts are forced by a confluent, periodic deformation field that moves with the uniform mean flow over the mountain. The initial conditions are selected to give a cold front confined to the lower part of the domain. Fourth-order diffusion terms are included in the numerical model to control energy cascade to the grid size scale. A numerical frontogenesis experiment with no topography produces a realistic surface front in about two days. Numerical solutions for flow over the mountain with no front are found by integrating the equations from the initial conditions, which are semigeostrophic steady-state solutions. Various mountains are considered that have the same height but different widths. The numerical solutions for wide mountains remain close to the semigeostrophic initial conditions, while for narrower mountains vertically propagating waves and a hydraulic jump develop on the lee side of the mountain. The frontal solution and the mountain solution are combined to produce the initial conditions for the basic experiments. The numerical solutions show reduced frontogenesis on the upwind slope and increased frontogenesis on the lee slope. This behavior is caused by the mountain-forced divergence on the upwind side and convergence on the lee side in agreement with the semigeostrophic solution of Zehnder and Bannon. Further experiments with no deformation forcing are carried out to correspond to the semigeostrophic passive scalar studies of Blumen and Gross. A passive scalar that represents the perturbation potential temperature is advected with the mountain solution. The frontal scale, based on the tracer field, increases on the upwind side until it reaches a maximum at the top and then decreases on the lee side, back to its original value as the front moves away from the mountain. The numerical solutions for the interactive potential temperature field have a similar behavior, although some additional blocking effects are present. For the narrower mountains the frontal structure is distorted by the gravity waves on the lee side of the mountain. These solutions resemble those of Schumann for smaller-scale mountains.

  2. Electronic Cigarette Topography in the Natural Environment

    PubMed Central

    Morabito, P. N.; Roundtree, K. A.

    2015-01-01

    This paper presents the results of a clinical, observational, descriptive study to quantify the use patterns of electronic cigarette users in their natural environment. Previously published work regarding puff topography has been widely indirect in nature, and qualitative rather than quantitative, with the exception of three studies conducted in a laboratory environment for limited amounts of time. The current study quantifies the variation in puffing behaviors among users as well as the variation for a given user throughout the course of a day. Puff topography characteristics computed for each puffing session by each subject include the number of subject puffs per puffing session, the mean puff duration per session, the mean puff flow rate per session, the mean puff volume per session, and the cumulative puff volume per session. The same puff topography characteristics are computed across all puffing sessions by each single subject and across all subjects in the study cohort. Results indicate significant inter-subject variability with regard to puffing topography, suggesting that a range of representative puffing topography patterns should be used to drive machine-puffed electronic cigarette aerosol evaluation systems. PMID:26053075

  3. Range imaging for measuring streambed topography

    Microsoft Academic Search

    Tobias K. Kohoutek; Manuel Nitsche

    2010-01-01

    The characterization of streambed topography is crucial to approach problems in fluvial hydraulics, river engineering and geomorphology. In most steep alpine environments measurement apparatus like terrestrial laser scanners or airborne Lidar systems are difficult to successfully apply, because they need free sight, elevated positions and good aerial or road access. In mountain streams this is generally not the case. We

  4. Virtual Field Trip: Temperate Deciduous Forest Topography

    E-print Network

    Hansen, Andrew J.

    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

  5. Detecting and Quantifying Topography in Neural Maps

    PubMed Central

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

    2014-01-01

    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

  6. Wettability influences cell behavior on superhydrophobic surfaces with different topographies

    Microsoft Academic Search

    B. N. Lourenco; G. Marchioli; W Song; R. L. Reis; Blitterswijk van C. A; H. B. J. Karperien; Apeldoorn van A. A; J. F. Mano

    2012-01-01

    Surface wettability and topography are recognized as critical factors influencing cell behavior on biomaterials. So far only few works have reported cell responses on surfaces exhibiting extreme wettability in combination with surface topography. The goal of this work is to study whether cell behavior on superhydrophobic surfaces is influenced by surface topography and polymer type. Biomimetic superhydrophobic rough surfaces of

  7. Experimental study of internal gravity waves generated by supercritical topography

    Microsoft Academic Search

    H. P. Zhang; B. King; Harry L. Swinney

    2007-01-01

    Oscillatory tides flowing over rough topography on the ocean floor generate internal gravity waves, which are a major source of ocean mixing. Linear inviscid theory can describe waves generated by gentle topography with slopes that are less steep than the propagation angle of the internal waves; such topography is termed subcritical. However, a clear physical picture of internal waves generated

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

    Microsoft Academic Search

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

    2003-01-01

    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

  9. The effect of topography on SAR calibration

    SciTech Connect

    Zyl, J.J. van; Chapman, B.D.; Dubois, P. (California Inst. of Tech., Pasadena, CA (United States). Jet Propulsion Lab.); Shi, Jiancheng (Univ. of California, Santa Barbara, CA (United States))

    1993-09-01

    During normal synthetic aperture radar (SAR) processing, a flat earth is assumed when performing radiometric corrections such as antenna pattern and scattering area removal. Here the authors examine the effects of topographic variations on these corrections. Local slopes will cause the actual scattering area to be different from that calculated using the flat earth assumption. It is shown that this effect, which is present for both airborne and spaceborne SAR data, may easily cause calibration errors larger than a decibel. Ignoring the topography during antenna pattern removal is expected to be negligible for spaceborne SAR's. In this paper they show how these effects can be taken into account if a digital elevation model is available for the imaged area. It is also shown that not taking the topography into account during antenna pattern removal introduces polarimetric calibration errors.

  10. TOPOAFRICA project: reconstruction and quantification of the past topography of Africa over the last 250 My

    NASA Astrophysics Data System (ADS)

    Guillocheau, F.; Braun, J.; Bourquin, S.; Gallagher, K.; Dauteuil, O.; Robin, C.; Rouby, D.; Tiercelin, J.; Chardon, D.; Godderis, Y.; Rousse, S.; Bauvais, A.; Frizon de La Motte, D.; Leturmy, P.; Donnadieu, Y.

    2009-12-01

    The goal of this project is to quantify the growth of long wavelength (x1000 km) topography over the last 250 My at the scale of a continent - Africa - and to understand (1) their relationship with the underlying mantle dynamics over such a time period and (2) their consequence over some Earth surface processes. Most studies of past topography reconstruction have focused on orogenic areas. Few efforts have been devoted to characterizing the more subtle long wavelength topography, such as the doming or plateau uplift of continental areas at the 1000 km wavelength, with a paleoelevation of few hundreds of meters to a maximum of 1000-2000m. A direct inversion of the geological data into estimates of paleotopography is difficult. Quantification of past topographies of a continent requires coupling of geological data with a sediment production (erosion) and transport numerical model. The quantification of the Meso-Cenozoic topographies of the African continent is based on uplift (mean time interval 10 my) and paleoprecipitation maps (input of the model) and siliciclastic sedimentary fluxes and thermochronological data. One of the advance of this project is to draw new-style paleogeographic reconstructions focussed on the continental environments yielding the geometry of paleocatchments, the lacustrine baselevel, the type and the flow direction of the fluvial systems… All those data are registered in database and GIS (ArcGis). Uncertainties are quantified. The uplift maps, in a first step semi-quantitative, are based on the paleogeographical changes and on synthesis of the tectonically induced-unconformities both onland and offhore (seismic) and their consequences (incised valleys, forced-regression wedges, changes of weathering types….). The paleoprecipitation maps are product by coupling climatic numerical models with a geological database (GIS) including all the climate recorders (lithology, type of clays, paleosoils; woods, pollens…). The measure of the siliciclastic sediment flux is based on a geometrical, chronostratigraphical and lithological synthesis of the peri-African (margins) and intra-African (SAG) basins. The thermochronological database is a compilation of all the data available in Africa, plus some new field collections. The new numerical model of sediment production and transport at the continental scale, TOPOSED, will form the basis of the quantitative inversion of the geological data to yield estimates of past topography. Its original aspect consists in investigating separately erosion and transport processes, and in assuming that both are controlled by slope and discharge. Studied time interval: Triassic (Induan, Ladinian, Norian), Jurassic (Sinemurian, Bajocian, Late Kimmeridgian), Cretaceous (Valanginian, Barremian, Middle Aptian, Lower to Middle Albian, Late Cenomanian, Late Coniacian-Early Santonian, Maastrichtian), Paleogene (Thanetian, Lutetian, Chattian), Neogene (Early Miocene, Early Pliocene).

  11. TOPOAFRICA project: reconstruction and quantification of the past topography of Africa over the last 250 My.

    NASA Astrophysics Data System (ADS)

    Guillocheau, François

    2010-05-01

    The goal of this project is to quantify the growth of long wavelength (x1000 km) topography over the last 250 My at the scale of a continent - Africa - and to understand (1) their relationship with the underlying mantle dynamics over such a time period and (2) their consequence over some Earth surface processes. Most studies of past topography reconstruction have focused on orogenic areas. Few efforts have been devoted to characterizing the more subtle long wavelength topography, such as the doming or plateau uplift of continental areas at the 1000 km wavelength, with a paleoelevation of few hundreds of meters to a maximum of 1000-2000m. A direct inversion of the geological data into estimates of paleotopography is difficult. Quantification of past topographies of a continent requires coupling of geological data with a sediment production (erosion) and transport numerical model. The quantification of the Meso-Cenozoic topographies of the African continent is based on uplift (mean time interval 10 my) and paleoprecipitation maps (input of the model) and siliciclastic sedimentary fluxes and thermochronological data. One of the advance of this project is to draw new-style paleogeographic reconstructions focussed on the continental environments yielding the geometry of paleocatchments, the lacustrine baselevel, the type and the flow direction of the fluvial systems… All those data are registered in database and GIS (ArcGis). Uncertainties are quantified. The uplift maps, in a first step semi-quantitative, are based on the paleogeographical changes and on synthesis of the tectonically induced-unconformities both onland and offhore (seismic) and their consequences (incised valleys, forced-regression wedges, changes of weathering types….). The paleoprecipitation maps are product by coupling climatic numerical models with a geological database (GIS) including all the climate recorders (lithology, type of clays, paleosoils; woods, pollens…). The measure of the siliciclastic sediment flux is based on a geometrical, chronostratigraphical and lithological synthesis of the peri-African (margins) and intra-African (SAG) basins. The thermochronological database is a compilation of all the data available in Africa, plus some new field collections. The new numerical model of sediment production and transport at the continental scale, TOPOSED, will form the basis of the quantitative inversion of the geological data to yield estimates of past topography. Its original aspect consists in investigating separately erosion and transport processes, and in assuming that both are controlled by slope and discharge. Studied time interval: Triassic (Induan, Ladinian, Norian), Jurassic (Sinemurian, Bajocian, Late Kimmeridgian), Cretaceous (Valanginian, Barremian, Middle Aptian, Lower to Middle Albian, Late Cenomanian, Late Coniacian-Early Santonian, Maastrichtian), Paleogene (Thanetian, Lutetian, Chattian), Neogene (Early Miocene, Early Pliocene).

  12. Topography over South America from ERS altimetry

    NASA Technical Reports Server (NTRS)

    Brenner, Anita; Frey, Herb; DiMarzio, John; Tsaoussi, Lucia

    1997-01-01

    The results of the surface topography mapping of South America during the ERS-1 geodetic mission are presented. The altimeter waveforms, the range measurement, and the internal and Doppler range corrections were obtained. The atmospheric corrections and solid tides were calculated. Comparisons between Shuttle laser altimetry and ERS-1 altimetry grid showed good agreement. Satellite radar altimetry data can be used to improve the topographic knowledge of regions for which only poor elevation data currently exist.

  13. ATM Coastal Topography-Mississippi, 2001

    USGS Publications Warehouse

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

    2009-01-01

    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.

  14. ATM Coastal Topography-Alabama 2001

    USGS Publications Warehouse

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

    2009-01-01

    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.

  15. Digital holography system for topography measurement

    NASA Astrophysics Data System (ADS)

    Amezquita, R.; Rincon, O. J.; Torres, Y. M.; Amezquita, S.

    2011-08-01

    The optical characteristics of Diffractive Optical Elements are determined by the properties of the photosensitive film on which they are produced. When working with photoresist plates, the most important property is the change in the plate's topography for different exposures. In this case, the required characterization involves a topographic measurement that can be made using digital holography. This work presents a digital holography system in which a hologram's phase map is obtained from a single recorded image. The phase map is calculated by applying a phase-shifting algorithm to a set of images that are created using a digital phase-shifting/tilteliminating procedure. Also, the curvatures, introduced by the imaging elements used in the experimental setup, are digitally compensated for using a polynomial fitting-method. The object's topography is then obtained from this modified phase map. To demonstrate the proposed procedure, the topography of patches exposed on a Shipley 1818 photoresist plate by microlithography equipment-which is currently under construction-is shown.

  16. OpenTopography: Enabling Online Access to High-Resolution Lidar Topography Data and Processing Tools

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    High-resolution topography data acquired with lidar (light detection and ranging) technology are revolutionizing the way we study the Earth's surface and overlying vegetation. These data, collected from airborne, tripod, or mobile-mounted scanners have emerged as a fundamental tool for research on topics ranging from earthquake hazards to hillslope processes. Lidar data provide a digital representation of the earth's surface at a resolution sufficient to appropriately capture the processes that contribute to landscape evolution. The U.S. National Science Foundation-funded OpenTopography Facility (http://www.opentopography.org) is a web-based system designed to democratize access to earth science-oriented lidar topography data. OpenTopography provides free, online access to lidar data in a number of forms, including the raw point cloud and associated geospatial-processing tools for customized analysis. The point cloud data are co-located with on-demand processing tools to generate digital elevation models, and derived products and visualizations which allow users to quickly access data in a format appropriate for their scientific application. The OpenTopography system is built using a service-oriented architecture (SOA) that leverages cyberinfrastructure resources at the San Diego Supercomputer Center at the University of California San Diego to allow users, regardless of expertise level, to access these massive lidar datasets and derived products for use in research and teaching. OpenTopography hosts over 500 billion lidar returns covering 85,000 km2. These data are all in the public domain and are provided by a variety of partners under joint agreements and memoranda of understanding with OpenTopography. Partners include national facilities such as the NSF-funded National Center for Airborne Lidar Mapping (NCALM), as well as non-governmental organizations and local, state, and federal agencies. OpenTopography has become a hub for high-resolution topography resources. Datasets hosted by other organizations, as well as lidar-specific software, can be registered into the OpenTopography catalog, providing users a "one-stop shop" for such information. With several thousand active users, OpenTopography is an excellent example of a mature Spatial Data Infrastructure system that is enabling access to challenging data for research, education and outreach. Ongoing OpenTopography design and development work includes the archive and publication of datasets using digital object identifiers (DOIs); creation of a more flexible and scalable high-performance environment for processing of large datasets; expanded support for satellite and terrestrial lidar; and creation of a "pluggable" infrastructure for third-party programs and algorithms. OpenTopography has successfully created a facility for sharing lidar data. In the project's next phase, we are working to enable equally easy and successful sharing of services for processing and analysis of these data.

  17. Carbon contamination topography analysis of EUV masks

    SciTech Connect

    Fan, Y.-J.; Yankulin, L.; Thomas, P.; Mbanaso, C.; Antohe, A.; Garg, R.; Wang, Y.; Murray, T.; Wuest, A.; Goodwin, F.; Huh, S.; Cordes, A.; Naulleau, P.; Goldberg, K. A.; Mochi, I.; Gullikson, E.; Denbeaux, G.

    2010-03-12

    The impact of carbon contamination on extreme ultraviolet (EUV) masks is significant due to throughput loss and potential effects on imaging performance. Current carbon contamination research primarily focuses on the lifetime of the multilayer surfaces, determined by reflectivity loss and reduced throughput in EUV exposure tools. However, contamination on patterned EUV masks can cause additional effects on absorbing features and the printed images, as well as impacting the efficiency of cleaning process. In this work, several different techniques were used to determine possible contamination topography. Lithographic simulations were also performed and the results compared with the experimental data.

  18. Bessel Function Model for Corneal Topography

    E-print Network

    Okrasi?ski, Wojciech

    2011-01-01

    In this paper we consider a new nonlinear mathematical model for corneal topography formulated as two-point boudary value problem. We derive it from first physical principles and provide some mathematical analysis. The existence and uniqeness theorems are proved as well as various estimates on exact solution. At the end we fit the simplified model based on Modified Bessel Function of the First Kind with the real corneal data consisting of matrix of 123x123 points and obtain an error of order of 1%.

  19. Welcome to Surface Topography: Metrology and Properties

    NASA Astrophysics Data System (ADS)

    Leach, Richard

    2013-11-01

    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!

  20. Dynamic surface topography influences cell function

    E-print Network

    Kiang, Jennifer Deng

    2012-01-01

    soft polyacrylamide hydrogel with magnetic nickel microwires randomly oriented in the surface of the material.Material Synthesis This topographically dynamic cell culture substrate is composed of a soft polyacrylamide hydrogel with magnetic

  1. Silk Film Topography Directs Collective Epithelial Cell Migration

    PubMed Central

    Rosenblatt, Mark I.

    2012-01-01

    The following study provides new insight into how surface topography dictates directed collective epithelial cell sheet growth through the guidance of individual cell movement. Collective cell behavior of migrating human corneal limbal-epithelial cell sheets were studied on highly biocompatible flat and micro-patterned silk film surfaces. The silk film edge topography guided the migratory direction of individual cells making up the collective epithelial sheet, which resulted in a 75% increase in total culture elongation. This was due to a 3-fold decrease in cell sheet migration rate efficiency for movement perpendicular to the topography edge. Individual cell migration direction is preferred in the parallel approach to the edge topography where localization of cytoskeletal proteins to the topography’s edge region is reduced, which results in the directed growth of the collective epithelial sheet. Findings indicate customized biomaterial surfaces may be created to direct both the migration rate and direction of tissue epithelialization. PMID:23185573

  2. Surface topography evolution and fatigue fracture in polysilicon MEMS structures

    Microsoft Academic Search

    Seyed M. Allameh; Pranav Shrotriya; Alex Butterwick; Stuart B. Brown; Wole O. Soboyejo

    2003-01-01

    This paper presents the results of an experimental study of the micromechanisms of surface topography evolution and fatigue fracture in polysilicon MEMS structures. The initial stages of fatigue are shown to be associated with stress-assisted surface topography evolution and the thickening of SiO2 layers that form on the unpassivated polysilicon surfaces and crack\\/notch faces. The differences in surface topography and

  3. A 360-Degree and -Order Model of Venus Topography

    NASA Technical Reports Server (NTRS)

    Rappaport, Nicole; Plaut, Jeffry J.

    1996-01-01

    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.

  4. A 360-degree and -order model of Venus topography

    NASA Technical Reports Server (NTRS)

    Rappaport, Nicole; Plaut, Jeffrey J.

    1994-01-01

    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.

  5. Nicotinic alteration of functional thalamocortical topography.

    PubMed

    Lee, Charles C; Yanagawa, Yuchio; Imaizumi, Kazuo

    2015-08-19

    The thalamocortical pathways form highly topographic connections from the primary sensory thalamic nuclei to the primary cortical areas. The synaptic properties of these thalamocortical connections are modifiable by activation from various neuromodulators, such as acetylcholine. Cholinergic activation can alter functional properties in both the developing and the mature nervous system. Moreover, environmental factors, such as nicotine, can activate these receptors, although the circuit-level alterations resulting from such nicotinic activation of sensory neural circuits remain largely unexplored. Therefore, we examined alterations to the functional topography of thalamocortical circuits in the developing sensory pathways of the mouse. Photostimulation by uncaging of glutamate was used to map these functional thalamocortical alterations in response to nicotinic receptor activation. As a result, we found that activation of forebrain nicotinic acetylcholine receptors results in an expansion and enhancement of functional thalamocortical topographies as assessed in brain slice preparations using laser-scanning photostimulation by uncaging of glutamate. These physiological changes were correlated with the neuroanatomical expression of nicotinic acetylcholine receptor subtypes (?7 and ?2). These circuit-level alterations may provide a neural substrate underlying the plastic development and reshaping of thalamocortical circuitry in response to nicotinic receptor activation. PMID:26164456

  6. Range imaging for measuring streambed topography

    NASA Astrophysics Data System (ADS)

    Kohoutek, Tobias K.; Nitsche, Manuel

    2010-08-01

    The characterization of streambed topography is crucial to approach problems in fluvial hydraulics, river engineering and geomorphology. In most steep alpine environments measurement apparatus like terrestrial laser scanners or airborne Lidar systems are difficult to successfully apply, because they need free sight, elevated positions and good aerial or road access. In mountain streams this is generally not the case. We describe a novel technology to acquire 3D models of nonsubmerged parts of such streambeds. The core of our range imaging system is a commercial time-of-flight video camera. The camera produces a per-pixel distance measurement using an integrated near-infrared modulated light source and an image sensor that measures the phase-shift between modulated and reflected light at each pixel. If mounted on a lightweight crane vertical above the stream, the camera can observe the streambed topography with a 3D resolution of down to 0.5 cm. However, the distance measurements degrade in accuracy under direct sunlight and when strong illumination contrasts occur. With the collected data detailed digital terrain models can be computed.

  7. Evaluation of facial palsy by moire topography

    NASA Astrophysics Data System (ADS)

    Inokuchi, Ikuo; Kawakami, Shinichiro; Maeta, Manabu; Masuda, Yu

    1991-08-01

    Society of Facial Research is used frequently. It is of great value clinically, but the method has several weak points concerning objective and quantitative assessment. This study uses moire topography to solve these problems. mA moire camera, FM3013, of the lattice irradiation type was used for measurement of the face. Five moire photographs were taken: at rest, wrinkling the forehead, closing the eyes lightly, blowing out the cheeks and grinning. The degree of facial palsy was determined by the Asymmetry Index (AI) as a measure of the degree of facial deviation. Total AI was expressed as the average AI based on calculations of the measurement in 5 photos. Severe paralysis is represented by an AI of more than 20%. Partial paralysis has a range of 20-8%. Nearly normal is judged to be less than 8%. Ten normal individuals are measured as control and show an AI of 3% or less. Moire topography is useful in assessing the recovery process because it has the benefit of making the site and grade of palsy easily achieved by the AI and the deviation in its patterns. The authors propose that the moire method is better for an objective and quantitative evaluation than the society's method.

  8. Synthetic river valleys: Creating prescribed topography for form-process inquiry and river rehabilitation design

    NASA Astrophysics Data System (ADS)

    Brown, R. A.; Pasternack, G. B.; Wallender, W. W.

    2014-06-01

    The synthesis of artificial landforms is complementary to geomorphic analysis because it affords a reflection on both the characteristics and intrinsic formative processes of real world conditions. Moreover, the applied terminus of geomorphic theory is commonly manifested in the engineering and rehabilitation of riverine landforms where the goal is to create specific processes associated with specific morphology. To date, the synthesis of river topography has been explored outside of geomorphology through artistic renderings, computer science applications, and river rehabilitation design; while within geomorphology it has been explored using morphodynamic modeling, such as one-dimensional simulation of river reach profiles, two-dimensional simulation of river networks, and three-dimensional simulation of subreach scale river morphology. To date, no approach allows geomorphologists, engineers, or river rehabilitation practitioners to create landforms of prescribed conditions. In this paper a method for creating topography of synthetic river valleys is introduced that utilizes a theoretical framework that draws from fluvial geomorphology, computer science, and geometric modeling. Such a method would be valuable to geomorphologists in understanding form-process linkages as well as to engineers and river rehabilitation practitioners in developing design surfaces that can be rapidly iterated. The method introduced herein relies on the discretization of river valley topography into geometric elements associated with overlapping and orthogonal two-dimensional planes such as the planform, profile, and cross section that are represented by mathematical functions, termed geometric element equations. Topographic surfaces can be parameterized independently or dependently using a geomorphic covariance structure between the spatial series of geometric element equations. To illustrate the approach and overall model flexibility examples are provided that are associated with mountain, lowland, and hybrid synthetic river valleys. To conclude, recommended advances such as multithread channels are discussed along with potential applications.

  9. The Influence of Topography on Volatile Transport

    NASA Astrophysics Data System (ADS)

    Stansberry, John A.; Grundy, Will; Young, Leslie

    2014-11-01

    Topography can exert important influences on volatile transport on bodies, such as Pluto and Triton, with global atmospheres supported by vapor pressure equilibrium with volatile frost on the surface. First, because local energy balance depends on the illumination angle, volatile frost will preferentially sublime from (condense on) areas tilted towards (away from) the Sun, as has been previously modelled at small spatial scales [e.g. 1]. Topographic features can also cause a completely different kind of vertical volatile transport resulting from the decrease in atmospheric pressure with altitude. On Pluto and Triton the sublimation flux from a topographic feature approximately one km high is comparable to the seasonal or inter-hemispheric sublimation flux (1 g/cm2^/year). To the extent that seasonal transport influences the distribution of volatile ices (and related characteristics such as albedo, emissivity, reflectance spectrum), topography-driven transport will exert a comparable influence around features a km or more above (or below) the global mean altitude of the frost deposits. This implies that in addition to there being a global "frost temperature" (defined by the temperature at which the frost vapor pressure equals the atmospheric pressure), there is a "frost altitude" (defined by the globally-averaged altitude of all the volatile frost). The sense of topography-driven volatile transport is to denude high areas. Consider two frost patches with equilibrium temperatures equal to the frost temperature, but at different altitudes. The high(low)-altitude patch is in contact with a lower(higher)-pressure atmosphere due to the e^(-z/H) dependence of atmospheric pressure. If the high(low)-altitude patch is above(below) the frost altitude, frost will sublime from (condense on) the high (low) frost patch, resulting in net downhill transport. We present models for the combined effects of illumination and altitude on frost transport rates for simple topographic features and discuss how these may influence the appearance of Pluto's surface as it will be seen by the New Horizons spacecraft in July 2015. [1] Yelle (1992) Science 255, 1553-1555.

  10. Assimilation of altimeter topography into oceanic models

    NASA Technical Reports Server (NTRS)

    Demey, Pierre; Menard, Yves; Pinardi, Nadia; Schroeter, J.; Verron, J.

    1991-01-01

    The primary goals of the authors are to build an intuition for assimilation techniques and to investigate the impact of variable altimeter topography on simple or complex oceanic models. In particular, applying various techniques and sensitivity studies to model and data constraints plays a key role. We are starting to use quasi-geostrophic, semigeostrophic, and primitive-equation (PE) models and to test the schemes in regions of interest to the World Ocean Circulation Experiment (WOCE), as well as in the northeast Atlantic and the Mediterranean. The impact of scatterometer wind forcing on the results is also investigated. The use of Geosat, European Remote Sensing satellite (ERS-1), and TOPEX/POSEIDON altimetry data is crucial in fine tuning the models and schemes to the selected areas of interest.

  11. EAARL topography: Dry Tortugas National Park

    USGS Publications Warehouse

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

    2008-01-01

    This lidar-derived submarine topography map was produced as a collaborative effort between the U.S. Geological Survey (USGS) Coastal and Marine Geology Program, 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 for the purposes of habitat mapping, ecological monitoring, change detection, ad event assessment (for example: bleaching, hurricanes, disease outbreaks). 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 water depth and conducting 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 managers of coastal tropical habitats.

  12. Architecture and development of olivocerebellar circuit topography

    PubMed Central

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

    2013-01-01

    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

  13. The Development and the Present Status of Moiré Topography

    Microsoft Academic Search

    Hiroshi Takasaki

    1979-01-01

    The process of the development and the present status of optical moiré topography at the University of Shizuoka are described and a historical review is presented. The main techniques described are the basic method and the grating hologram type of moiré topography.

  14. Effects of Topography on Assessing Wind Farm Impacts Using

    E-print Network

    Zhou, Liming

    Effects of Topography on Assessing Wind Farm Impacts Using MODIS Data Liming Zhou* Department) there is a pattern of LST change associated with the de- velopment of wind farms and (ii) the warming effect over wind farms reported previously is an artifact of varied surface topography. Spatial pattern and time

  15. X-ray topography utilizing non-equatorial reflections

    NASA Astrophysics Data System (ADS)

    Kingman, P. W.

    1987-03-01

    A technique for back reflection topography has been developed which uses nonequatorial reflections. The geometry of back reflection topography is analyzed in a general way, and it is shown how this analysis can be used for systematic imaging and contrast strategies. A novel camera design based upon this approach is also presented.

  16. Teleseismic traveltimes, topography and the lithospheric structure across central Mongolia

    E-print Network

    Paris-Sud XI, Université de

    Teleseismic traveltimes, topography and the lithospheric structure across central Mongolia Carole a 1000 km- long, $N-S transect across central Mongolia are used together with topography and gravity data and the lithospheric structure across central Mongolia, Geophys. Res. Lett., 35, L11301, doi:10.1029/2008GL033993. 1

  17. The Global Topography of Mars and Implications for Surface

    E-print Network

    Hauck II, Steven A.

    The Global Topography of Mars and Implications for Surface Evolution David E. Smith,1 * Maria T Zwally,1 Thomas C. Duxbury6 Elevations measured by the Mars Orbiter Laser Altimeter have yielded a high- accuracy global map of the topography of Mars. Dominant features include the low northern hemisphere

  18. Large Eddy Simulation over three-dimensional mountain topography

    Microsoft Academic Search

    M. Diebold; C. Higgins; V. Kumar; M. Lehning; M. B. Parlange

    2009-01-01

    A new generation Large-Eddy Simulation (LES) is applied to study wind fields and the influence of local topography. In this study we focus on the implementation of three-dimensional topography in our LES algorithm using an immersed boundary method. To validate the model, the LES results are compared with two sets of measured data. The first one is made of measurements

  19. Large Eddy Simulation over three-dimensional mountain topography

    Microsoft Academic Search

    M. Diebold; C. Higgins; M. Lehning; E. Bou-Zeid; M. B. Parlange

    2010-01-01

    A new generation Large-Eddy Simulation (LES) is applied to study wind fields and the influence of local topography. In this study we focus on the implementation of three-dimensional topography in our LES algorithm using an immersed boundary method. To validate the model, the LES results are compared with measurements from wind tunnel studies taken from the literature. The code is

  20. Effect of surface topography on stress concentration factor

    NASA Astrophysics Data System (ADS)

    Cheng, Zhengkun; Liao, Ridong

    2015-05-01

    Neuber rule and Arola-Ramulu model are widely used to predict the stress concentration factor of rough specimens. However, the height parameters and effective valley radius used in these two models depend strongly on the resolution of the roughness-measuring instruments and are easily introduce measuring errors. Besides, it is difficult to find a suitable parameter to characterize surface topography to quantitatively describe its effect on stress concentration factor. In order to overcome these disadvantages, profile moments are carried out to characterize surface topography, surface topography is simulated by superposing series of cosine components, the stress concentration factors of different micro cosine-shaped surface topographies are investigated by finite element analysis. In terms of micro cosine-shaped surface topography, an equation using the second profile moment to estimate the stress concentration factor is proposed, predictions for the stress concentration factor using the proposed expression are within 10% error compared with the results of finite element analysis, which are more accurate than other models. Moreover, the proposed equation is applied to the real surface topography machined by turning. Predictions for the stress concentration factor using the proposed expression are within 10% of the maximum stress concentration factors and about 5% of the effective stress concentration factors estimated from the finite element analysis for three levels of turning surface topographies under different simulated scales. The proposed model is feasible in predicting the stress concentration factors of real machined surface topographies.

  1. Mantle transition zone topography and structure beneath the Yellowstone hotspot

    E-print Network

    Dueker, Ken

    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., and K. Dueker (2004), Mantle transition zone topography and structure beneath the Yellowstone hotspot

  2. Topography of the merit function landscape in optical system design

    E-print Network

    Topography of the merit function landscape in optical system design Eco van Driel, Florian Bociort dimensions, are independent of the dimensionality of the design space so that they can provide insight into the topography of merit function landscapes of arbitrary dimensionality. Keywords: global optimization, saddle

  3. Evolution of Neogene Dynamic Topography in Madagascar

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  4. Corneal topography matching by iterative registration.

    PubMed

    Wang, Junjie; Elsheikh, Ahmed; Davey, Pinakin G; Wang, Weizhuo; Bao, Fangjun; Mottershead, John E

    2014-11-01

    Videokeratography is used for the measurement of corneal topography in overlapping portions (or maps) which must later be joined together to form the overall topography of the cornea. The separate portions are measured from different viewpoints and therefore must be brought together by registration of measurement points in the regions of overlap. The central map is generally the most accurate, but all maps are measured with uncertainty that increases towards the periphery. It becomes the reference (or static) map, and the peripheral (or dynamic) maps must then be transformed by rotation and translation so that the overlapping portions are matched. The process known as registration, of determining the necessary transformation, is a well-understood procedure in image analysis and has been applied in several areas of science and engineering. In this article, direct search optimisation using the Nelder-Mead algorithm and several variants of the iterative closest/corresponding point routine are explained and applied to simulated and real clinical data. The measurement points on the static and dynamic maps are generally different so that it becomes necessary to interpolate, which is done using a truncated series of Zernike polynomials. The point-to-plane iterative closest/corresponding point variant has the advantage of releasing certain optimisation constraints that lead to persistent registration and alignment errors when other approaches are used. The point-to-plane iterative closest/corresponding point routine is found to be robust to measurement noise, insensitive to starting values of the transformation parameters and produces high-quality results when using real clinical data. PMID:25500860

  5. Deep multi-frequency radio imaging in the Lockman Hole using the GMRT and VLA: II. The spectral index of submillimetre galaxies

    E-print Network

    Ibar, Edo; Best, P N; Coppin, K; Pope, A; Smail, Ian; Dunlop, J S

    2009-01-01

    We have employed the GMRT and the VLA to map the Lockman Hole. At 610 and 1,400 MHz, we reach noise levels of 15 and 6 uJy/beam, respectively, with well-matched resolutions (~5"). At this depth we obtained reliable detections for about half of the known submm galaxies (SMGs) in the field. For radio-identified SMGs, which are typically at z ~ 2, we measure a mean radio spectral index of alpha = -0.75 +/- 0.06 and standard deviation of 0.29, between rest-frame ~1.8 and ~4.2 GHz. The slope of their continuum emission is indistinguishable from that of local star-forming galaxies and suggests that extended optically-thin synchrotron emission dominates the radio output of SMGs. Cooling effects by synchrotron emission and Inverse Compton scattering off the CMB do not seem to affect their radio SEDs. For those SMGs judged by Spitzer mid-IR colours and spectroscopy to host obscured AGN, we find a clear deviation from the rest of the sample - they typically have steeper radio spectral indices, alpha ~< -1.0. These f...

  6. Stereo Pair: Inverted Topography, Patagonia, Argentina

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The Meseta de Somuncura is a broad plateau capped by basalt. Near its western edge is evidence of multiple volcanic events and a complex erosion history. Most notable are the long, narrow-, and winding lava flows that run across most of the right side of the image. These formed from low-viscosity lava that flowed down gullies over fairly flat terrain. Later, erosion of the landscape continued and the solidified flows were more resistant than the older surrounding rocks. Consequently, the flows became the ridges we see here. This natural process of converting gullies to ridges is called topographic inversion. See image PIA02755 (upper left corner) for a good example of topographic inversion in its earlier stages.

    Other features seen here include numerous and varied closed depressions. The regional drainage is not well integrated, and drainage ends up in salty lakes (blue if shallow, black if deep). Wind streaks indicate that winds blow toward the east (right) and blow salt grains off the lakebeds when dry. The bowtie pattern in the upper left has resulted from differing grazing practices among fenced fields.

    This cross-eyed stereoscopic image pair was generated using topographic data from the Shuttle Radar Topography Mission, combined with an enhanced Landsat 7satellite color image. The topography data are used to create two differing perspectives of a single image, one perspective for each eye. In doing so, each point in the image is shifted slightly, depending on its elevation. When stereoscopically merged, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions.

    Landsat satellites have provided visible light and infrared images of the Earth continuously since 1972. SRTM topographic data match the 30-meter (99-foot) spatial resolution of most Landsat images and provide a valuable complement for studying the historic and growing Landsat data archive. The Landsat 7 Thematic Mapper image used here was provided to the SRTM project by the United States Geological Survey, Earth Resources Observation Systems (EROS) Data Center,Sioux Falls, South Dakota.

    Elevation data used in this image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on February 11,2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense (DoD), and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise,Washington, DC.

    Size: 21.5 kilometers (13.4 miles) x 27.2 kilometers (16.9 miles) Location: 41.6 deg. South lat., 67.9 deg. West lon. Orientation: North toward upper left Image Data: Landsat bands 1,4,7 in blue, green, red Date Acquired: February 19, 2000 (SRTM), January 22, 2000 (Landsat)

  7. New Global Bathymetry and Topography Model Grids

    NASA Astrophysics Data System (ADS)

    Smith, W. H.; Sandwell, D. T.; Marks, K. M.

    2008-12-01

    A new version of the "Smith and Sandwell" global marine topography model is available in two formats. A one-arc-minute Mercator projected grid covering latitudes to +/- 80.738 degrees is available in the "img" file format. Also available is a 30-arc-second version in latitude and longitude coordinates from pole to pole, supplied as tiles covering the same areas as the SRTM30 land topography data set. The new effort follows the Smith and Sandwell recipe, using publicly available and quality controlled single- and multi-beam echo soundings where possible and filling the gaps in the oceans with estimates derived from marine gravity anomalies observed by satellite altimetry. The altimeter data have been reprocessed to reduce the noise level and improve the spatial resolution [see Sandwell and Smith, this meeting]. The echo soundings database has grown enormously with new infusions of data from the U.S. Naval Oceanographic Office (NAVO), the National Geospatial-intelligence Agency (NGA), hydrographic offices around the world volunteering through the International Hydrographic Organization (IHO), and many other agencies and academic sources worldwide. These new data contributions have filled many holes: 50% of ocean grid points are within 8 km of a sounding point, 75% are within 24 km, and 90% are within 57 km. However, in the remote ocean basins some gaps still remain: 5% of the ocean grid points are more than 85 km from the nearest sounding control, and 1% are more than 173 km away. Both versions of the grid include a companion grid of source file numbers, so that control points may be mapped and traced to sources. We have compared the new model to multi-beam data not used in the compilation and find that 50% of differences are less than 25 m, 95% of differences are less than 130 m, but a few large differences remain in areas of poor sounding control and large-amplitude gravity anomalies. Land values in the solution are taken from SRTM30v2, GTOPO30 and ICESAT data. GEBCO has agreed to adopt this model and begin updating it in 2009. Ongoing tasks include building an uncertainty model and including information from the latest IBCAO map of the Arctic Ocean.

  8. Effects of topography and woody plant canopy cover on near-ground solar radiation: Relevant energy inputs for ecohydrology and hydropedology

    NASA Astrophysics Data System (ADS)

    Zou, Chris B.; Barron-Gafford, Greg A.; Breshears, David D.

    2007-12-01

    The emerging interdisciplinary approaches of ecohydrology and hydropedology are sensitive to variation in soil-surface energy inputs, which are primarily modified by topography and woody plant canopies. Yet a synthesis of the interactive effects of these two modification types is lacking. We systematically estimated near-ground surface solar radiation inputs as modified by key attributes of topography (aspect and slope) and tree cover (degree of openness) using solar radiation modeling based on hemispherical photographs. For south aspects, reductions in annual transmission were dominated by canopy cover rather than topography, even when canopy cover was low, whereas for north aspects, canopy effects dominated the reduction in annual transmission for slopes of up to 10° at low canopy cover and up to 30° at high canopy cover. Our results provide a synthetic perspective of the nonlinear, interactive, and temporally dependent effects of slope, aspect, and amount of canopy cover on near-ground solar radiation.

  9. Shape, topography, gravity anomalies and tidal deformation of Titan

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

  10. An Improved 360 Degree and Order Model of Venus Topography

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

  11. Ocean topography experiment (TOPEX) radar altimeter

    NASA Technical Reports Server (NTRS)

    Rossi, L. C.; Hancock, D. W.; Hayne, G. S.

    1988-01-01

    A spaceflight qualified Radar Altimeter capable of achieving the TOPEX Mission measurement precision requirement of 2-centimeters, is provided and its performance (Engineering Assessment) will be evaluated after launch and continuously during its 3-year mission operational period. Information will be provided to JPL about the calibration of the TOPEX Radar Altimeter. The specifications for the required data processing algorithms which will be necessary to convert the Radar Altimeter mission telemetry data into the geophysical data will also be provided. The stringent 2 cm precision requirement for ocean topography determination from space necessitated examining existing Radar Altimeter designs for their applicability towards TOPEX. As a result, a system configuration evolved using some flight proven designs in conjunction with needed improvements which include: (1) a second frequency or channel to remove the range delay or apparent height bias caused by the electron content of the ionosphere; (2) higher transmit pulse repetition frequencies for correlation benefits at higher sea states to maintain precision; and (3) a faster microprocessor to accommodate two channels of altimetry data. Additionally, examination of past altimeter programs associated data processing algorithms was accomplished to establish the TOPEX-class Radar Altimeter data processing algorithms, and the necessary direction was outlined to begin to generate these for the TOPEX Mission.

  12. Venus topography and kilometer-scale slopes

    NASA Technical Reports Server (NTRS)

    Ford, Peter G.; Pettengill, Gordon H.

    1992-01-01

    During the first 8 months of the Magellan mission, the radar altimeter has made some three million measurements of the surface of Venus covering the latitude range from 85 deg N to 80 deg S. Methods involving range correlation, Doppler filtering, multiburst summation, and range migration are used to focus the observations and to achieve high surface resolution. Results are presented as maps of the global distribution of topography, meter-scale roughness, and power reflection coefficient. The results are similar to those reported in previous experiments (surface heights exhibit a unimodal distribution with more than 80 percent of the surface lying within 1 km of the 6051.84-km mean radius) but the higher resolution of the Magellan altimeter has disclosed several surprisingly steep features, e.g., the southwest face of the Maxwell Montes, the southern face of the Danu Montes, and the chasmata to the east of Thetis Regio, where average kilometer-scale slopes of greater than 30 deg are not uncommon. This conclusion is corroborated by close inspection of synthetic aperture radar imagery.

  13. Surface topography and rotational symmetry breaking.

    PubMed

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

    2012-07-01

    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

  14. Surface topography and rotational symmetry breaking

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    The surface electroclinic effect, which is a rotation of the molecular director in the substrate plane proportional to an electric field applied normal to the substrate, requires both a chiral environment and C2 (or lower) rotational symmetry about the field. 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.

  15. Topography on Europa....the Shadow knows

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This image of Europa was taken by the Galileo spacecraft under 'low-sun' illumination--the equivalent of taking a picture from a high altitude at sunrise or sunset. Note that in this image the topography of the terrain is emphasized. Planetary geologists use information from images acquired under a variety of lighting conditions to identify different types of structures and interpret how they formed. For example, the length of the shadow cast by a feature (e.g. a ridge or knob) is indicative of that feature's height. In this recent image, ridges and irregularly shaped knobs ranging in size from 5 kilometers across down to the limit of resolution (0.44 kilometers/pixel) can be seen. Measurements from shadow lengths indicate that features in this image range from tens of meters up to approximately one hundred meters in height.

    The Galileo spacecraft acquired this image of Europa's surface during its third orbit around Jupiter. The image covers an area approximately 40 kilometers (25 miles) by 75 kilometers (45 miles), centered near 10S, 190W.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    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.

  16. Basins of attraction on random topography.

    PubMed

    Schorghofer, N; Rothman, D H

    2001-02-01

    We investigate the consequences of fluid flowing on a continuous surface upon the geometric and statistical distribution of the flow. We find that the ability of a surface to collect water by its mere geometrical shape is proportional to the curvature of the contour line divided by the local slope. Consequently, rivers tend to lie in locations of high curvature and flat slopes. Gaussian surfaces are introduced as a model of random topography. For Gaussian surfaces the relation between convergence and slope is obtained analytically. The convergence of flow lines correlates positively with drainage area, so that lower slopes are associated with larger basins. As a consequence, we explain the observed relation between the local slope of a landscape and the area of the drainage basin geometrically. To some extent, the slope-area relation comes about not because of fluvial erosion of the landscape, but because of the way rivers choose their path. Our results are supported by numerically generated surfaces as well as by real landscapes. PMID:11308547

  17. Predicting maximum lake depth from surrounding topography.

    PubMed

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

    2011-01-01

    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

  18. The strength of contributions from topography mismatch and measurement filtering to simulated net ecosystem exchange in complex terrain

    NASA Astrophysics Data System (ADS)

    Brooks, B.; Desai, A. R.; Stephens, B. B.; Jacobson, A. R.

    2011-12-01

    Global scale carbon cycle inverse models provide invaluable information for the construction of empirically based carbon budgets based on in situ measurements. In landscapes of predominantly smooth topography inverse carbon cycle models are useful for diagnosing the magnitude and climate sensitivity of different regional carbon sinks. However, in landscapes of predominately complex topography inversion model results come with strong caveats for two reasons: 1) Coarse gridding of model topography can lead the model to sample observations at elevations far above the model surface, and 2) Transport wind fields over smoothed model representations of mountain regions are not always sufficiently resolved to inform the model about the source region for assimilated measurements. The uncertainty contributed by incorrect winds and topography mismatches (e.g., differences between the actual measurement elevation and model surface on the order of 1,000 m) is thought to be smaller for higher resolution regional inversion models (e.g., Gockede et al., 2010; Schuh et al. 2010), but these uncertainties are not well constrained for larger scale inversion systems (e.g., Peters et al., 2010), which are one of few ways for determining the relative priority of regional sinks. In this work we examine the effects on net ecosystem exchange (NEE) for a global scale inversion system when 1) topography mismatches are ameliorated, and 2) subset observations consistent with model resolution are used rather than observation-based subsets. Our focus is to use an example inversion model system, CarbonTracker (Peters et al., 2007; 2010), driven by CO2 mixing ratio measurements, including the RACCOON Network in the United States Mountain West (raccoon.ucar.edu), to quantify and compare the contribution to NEE from tower elevation mismatches and filtering strategies across biomes and and in terms of forecast skill (model data mismatch). We further compare our results to the differences in NEE over the same region from both inverse and forward models that participated in the North American Carbon Program Regional-Continental Model Synthesis.

  19. Superoleophobic Surfaces through Control of Sprayed-on Stochastic Topography

    E-print Network

    Campos, Raymond

    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 ...

  20. Geophysical implications of the longwavelength topography of Rhea

    E-print Network

    Nimmo, Francis

    of the degree 2 gravity using existing flyby data. Current models of Rhea internal structures which rely topography can complicate the interpretation of degree 2 gravity anomalies and their implications

  1. Crustal thickness and support of topography on Venus

    E-print Network

    James, Peter Benjamin

    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 ...

  2. Infragravity waves over topography: generation, dissipation, and reflection

    E-print Network

    Thomson, James M. (James McArthur)

    2006-01-01

    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 ...

  3. 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 ...

  4. Engineering microscale topographies to control the cell–substrate interface

    PubMed Central

    Nikkhah, Mehdi; Edalat, Faramarz; Manoucheri, Sam; Khademhosseini, Ali

    2013-01-01

    Cells in their in vivo microenvironment constantly encounter and respond to a multitude of signals. While the role of biochemical signals has long been appreciated, the importance of biophysical signals has only recently been investigated. Biophysical cues are presented in different forms including topography and mechanical stiffness imparted by the extracellular matrix and adjoining cells. Microfabrication technologies have allowed for the generation of biomaterials with microscale topographies to study the effect of biophysical cues on cellular function at the cell–substrate interface. Topographies of different geometries and with varying microscale dimensions have been used to better understand cell adhesion, migration, and differentiation at the cellular and sub-cellular scales. Furthermore, quantification of cell-generated forces has been illustrated with micropillar topographies to shed light on the process of mechanotransduction. In this review, we highlight recent advances made in these areas and how they have been utilized for neural, cardiac, and musculoskeletal tissue engineering application. PMID:22521491

  5. Asymmetric three-dimensional topography over mantle plumes.

    PubMed

    Burov, Evgueni; Gerya, Taras

    2014-09-01

    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. PMID:25186903

  6. Lower mantle heterogeneity, dynamic topography and the geoid

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  7. The Role of African topography in the South Asian Monsoon

    NASA Astrophysics Data System (ADS)

    Wei, H. H.; Bordoni, S.

    2014-12-01

    The Somali cross-equatorial jet is estimated to contribute up to half of the mass flux crossing the equator during the Asian monsoon season. Previous studies have argued that the Somali jet is strengthened by the East African Highlands, which act as a wall and accelerate the flow (e.g., Krishnamurti et al. 1976, Sashegyi and Geisler 1987). Besides, observational studies have shown a positive correlation between the strength of the Somali jet and the South Asian Monsoon (SAM) precipitation (e.g., Findlater 1969, Halpern and Woiceshyn 2001). These imply that the existence of the topography would relate to a stronger SAM. However, in a more recent study, Chakraborty et al. (2002) found that if the African topography is removed in a comprehensive general circulation model (GCM), the SAM strengthens. In this study, we use the GFDL AM2.1 GCM to conduct experiments with and without topography in Africa, to further examine its influence on the cross-equatorial Somali jet and the SAM. We find that when the African topography is removed, the SAM precipitation increases, consistent with the results in Chakraborty et al. (2002). Interestingly, our results also show that the cross-equatorial Somali jet does weaken in the absence of the African topography, in agreement with previous studies. The moisture budget shows that the increase in precipitation in the no-African topography experiment is primarily due to stronger wind convergence. The dynamics of the cross-equatorial Somali jet is investigated within the framework of the Potential Vorticity (PV) budget, showing the contribution of the changes in friction and diabatic heating to the circulation as the topography is removed. A backward trajectory analysis is also conducted to further examine the influence of topography on both the material tendencies of the PV budget and trajectories of parcels reaching the Indian subcontinent.

  8. SRTM Anaglyph: Inverted Topography, Patagonia, Argentina

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The Meseta de Somuncura is a broad plateau capped by basalt. Near its western edge is evidence of multiple volcanic events and a complex erosion history. Most notable are the long, narrow, and winding lava flows that run across most of the right side of the image. These formed from low-viscosity lava that flowed down gullies over fairly flat terrain. Later, erosion of the landscape continued, and the solidified flows were more resistant than the older surrounding rocks. Consequently, the flows became the ridges we see here. This natural process of converting gullies to ridges is called topographic inversion. See image PIA02755 (upper left corner) for a good example of topographic inversion in its earlier stages.

    Other features seen here include numerous and varied closed depressions. The regional drainage is not well integrated, but instead the drainage ends up in salty lakes (dark water, some with bright shores). Wind streaks indicate that winds blow toward the east (right) and blow salt grains off the lake beds when dry. The bowtie pattern in the upper left has resulted from differing grazing practices among fenced fields.

    This anaglyph was generated by first draping a Landsat Thematic Mapper image over a topographic map from the Shuttle Radar Topography Mission, then producing the two differing perspectives, one for each eye. When viewed through special glasses, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions. Anaglyph glasses cover the left eye with a red filter and the right eye with a blue filter.

    Landsat satellites have provided visible light and infrared images of the Earth continuously since 1972. SRTM topographic data match the 30-meter (99-foot) spatial resolution of most Landsat images and provide a valuable complement for studying the historic and growing Landsat data archive. The Landsat 7 Thematic Mapper image used here was provided to the SRTM project by the United States Geological Survey, Earth Resources Observation Systems (EROS) Data Center,Sioux Falls, South Dakota.

    Elevation data used in this image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on February 11,2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense (DoD), and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise,Washington, DC.

    Size: 21.5 kilometers (13.4 miles) x 27.2 kilometers (16.9 miles) Location: 41.6 deg. South lat., 67.9 deg. West lon. Orientation: North toward upper left Image Data: Landsat band 7 (short infrared) Date Acquired: February 19, 2000 (SRTM), January 22, 2000 (Landsat)

  9. Computing Granular Avalanches Over Complex Topography

    NASA Astrophysics Data System (ADS)

    Vollmoeller, P.; Dedner, A.; Ancey, C.

    2004-12-01

    Rapid Granular mass movement phenomena such as snow avalanches, rock avalanches and debris flows are natural phenomena that occur in mountainous areas throughout the world. Whereas the physical understanding of their release is quite complex, depend of many very different parameters and hence difficult to understand, the understanding of motion and stopping is less difficult and is investigated in this work using numerical simulations. Savage and Hutter (1989) proposed a one-dimensional continuum model for the numerical simulation of dry granular mixtures. It assumes an incompressible shallow flow behaviour and that the flowing mass behaves as a Mohr-Coulomb plastic material when yielding. This was extended by Gray et al. (1998) and Iverson & Denlinger on multi dimensions and by Iverson & Denlinger (2001) and Savage & Iverson (2003) for rapid two-phase flow phenomena. In this paper we are presenting a new numerical model approach for the solution of the Iverson & Denlinger equations in the case of dry rapid granular flows, with the following characteristics: - it solves the conservation laws for rapid dry granular flows. - it operates on unstructured triangular grids in the finite volume context. - it works with a dynamic adaptive grid strategy. - it operates with a higher order approximate Riemann solver and a new source term balancing technique. - it operates in a parallelized environment. We tested the numerical model against several numerical testproblems and laboratory experiments such as: - the classical lake at rest problem; - a dry granular flow down an inclined chute; - a dry granular flow down an inclined plane with and without a flow diverting obstacle; - a dry granular flow down an unregular laboratory topography .

  10. Science in Motion: Isolated Araneiform Topography

    NASA Technical Reports Server (NTRS)

    2007-01-01

    [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.

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    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.

  12. Shuttle Topography Data Inform Solar Power Analysis

    NASA Technical Reports Server (NTRS)

    2013-01-01

    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."

  13. Resolving the influences of climatology and topography on water isotopes

    NASA Astrophysics Data System (ADS)

    Auerbach, D. J.; Brandon, M. T.; Hren, M. T.

    2014-12-01

    Paleotopography records are critical to understanding geodynamic processes in ancient mountain ranges. The imprint of topography on stable isotopes of precipitation ("water isotopes") has become the most widely used method for reconstructing topography. Current approximations of how orographic lifting drives fractionation of water isotopes use 1D topography and a model based on either empirical observations or 1D Rayleigh fractionation. However, atmospheric physics tells us that the pattern and magnitude of lifting varies due to the shape of topography. We also know that the source of water isotopes and the local climatology (e.g., wind speed and direction, moist stability of the air) vary on both short and long time scales. Current approaches fail to separate the signal of topography from that of potentially large, short-term (<100 kyr) climate variations in water isotope records. We present an isotope-enabled version of the linear theory of orographic precipitation (LTOP) of Smith and Barstad (2004), which describes the response of water isotopes to topography. This model provides a first-order approximation of the water-isotope field produced by moist air flowing over complex 3D topography, which allows us to explore how the water isotope field is influenced by variations in climatology and topography. The LTOP model is attractive because of its simplicity: just 7 variables are used calculate the water isotope field, but the model still accounts for lateral flow and upwind phase tilting due to topographic barriers (to the non-linear limit). We tested this model in modern Patagonia, where there is a simple westerly pattern of atmospheric flow across a north-south mountain range. The model reproduces the strong observed fractionation and matches 166 field measurements of water isotopes in precipitation fairly well (R2 = 0.61). Sensitivity tests indicate the water isotope field is most sensitive to variations in the composition of source water (ocean), wind speed, and wind direction. Short-term climate variations are on the order of 16‰ ?D; isotope records showing less variability should be treated as unreliable. The capacity of the LTOP model to describe the observed complexity of atmospheric behavior in response to 3D topography is an important step towards future advances in paleotopography work.

  14. Gravity, Topography and the Early Evolution of the Moon

    NASA Astrophysics Data System (ADS)

    Zuber, M. T.

    2012-12-01

    The early evolution of terrestrial planets was characterized processes that shaped interiors and surfaces such as differentiation, magmatism, tectonism and impact bombardment. The Moon preserves well the record of these early processes, and due to proximity to Earth this record can be studied in unprecedented detail. Observations of the Lunar Orbiter Laser Altimeter (LOLA), an instrument on the Lunar Reconnaissance Orbiter, has collected over 5.6 billion measurements of lunar topography and has yielded the most accurate global topography model for any planet. LOLA topography enables significant advances in the quantitative characterization of planetary surfaces. Topography combined with high-resolution gravity measurements from the Gravity Recovery and Interior Laboratory (GRAIL) mission, provides the opportunity to map the lunar interior from crust to core. Spherical harmonic models of topography to degree 720 and gravity to degree 420 allow estimates of crustal thickness, density and porosity, as well as insights into the structure of the lithosphere and in particular the compensation states of major impact basins and their relationships to mare volcanism. Of great interest is the role of impact bombardment in early evolution, from the size-frequency distribution to refine relative ages, to the role of impacts in melting and re-distributing the crust. Understanding gained from the Moon can analyzed in the context of observations from other terrestrial planets to provide a holistic view of early planetary evolution.

  15. Controls on (anomalous) topography in rifted margin settings

    NASA Astrophysics Data System (ADS)

    Huismans, Ritske S.

    2015-04-01

    Contrasting end members of volcanic and non-volcanic passive margin formation show a large variability in basin shape and structure, subsidence history, and associated topographic evolution of the onshore rifted margins. The large range of structural style and associated topography of these systems imply a strong variability in the underlying thermo-mechanical conditions at the time of rifting. Rift - passive margin styles ranging from narrow to ultra wide are explained using forward numerical models with varying rheological structure, with strong crust lithosphere leading to narrow rift formation associated with highly elevated rift shoulders and conversely weak crust lithosphere resulting in highly stretched wide rifted conjugate margins and little flank morphology. In some cases rifted margins appear to indicate the formation of anomalous post rift topography. A number of mechanisms including small-scale convective removal of the lower lithosphere, lithosphere counter-flow, and dynamic topography, have been invoked to explain the anomalous topography. Forward numerical models are used to predict the magnitude and characteristic topography associated with each of these mechanisms and to evaluate their potential for explaining these apparent anomalous characteristics of rifts and rifted margins.

  16. Methods for topography artifacts compensation in scanning thermal microscopy.

    PubMed

    Martinek, Jan; Klapetek, Petr; Campbell, Anna Charvátová

    2015-08-01

    Thermal conductivity contrast images in scanning thermal microscopy (SThM) are often distorted by artifacts related to local sample topography. This is pronounced on samples with sharp topographic features, on rough samples and while using larger probes, for example, Wollaston wire-based probes. The topography artifacts can be so high that they can even obscure local thermal conductivity variations influencing the measured signal. Three methods for numerically estimating and compensating for topographic artifacts are compared in this paper: a simple approach based on local sample geometry at the probe apex vicinity, a neural network analysis and 3D finite element modeling of the probe-sample interaction. A local topography and an estimated probe shape are used as source data for the calculation in all these techniques; the result is a map of false conductivity contrast signals generated only by sample topography. This map can be then used to remove the topography artifacts from measured data or to estimate the uncertainty of conductivity measurements using SThM. The accuracy of the results and the computational demands of the presented methods are discussed. PMID:25942752

  17. Topography and functional information of plasma membrane.

    PubMed

    Sun, DeLan; Chen, JianMin; Song, YanMei; Zhu, ChuanFeng; Pan, GeBo; Wan, LiJun

    2008-02-01

    By using atomic force microscope (AFM), the topography and function of the plasmalemma surface of the isolated protoplasts from winter wheat mesophyll cells were observed, and compared with dead protoplasts induced by dehydrating stress. The observational results revealed that the plasma membrane of living protoplasts was in a state of polarization. Lipid layers of different cells and membrane areas exhibited distinct active states. The surfaces of plasma membranes were unequal, and were characterized of regionalisation. In addition, lattice structures were visualized in some regions of the membrane surface. These typical structures were assumed to be lipid molecular complexes, which were measured to be 15.8+/-0.09 nm in diameter and 1.9+/-0.3 nm in height. Both two-dimensional and three-dimensional imaging showed that the plasmalemma surfaces of winter wheat protoplasts were covered with numerous protruding particles. In order to determine the chemical nature of the protruding particles, living protoplasts were treated by proteolytic enzyme. Under the effect of enzyme, large particles became relatively looser, resulting that their width was increased and their height decreased. The results demonstrated that these particles were likely to be of protein nature. These protein particles at plasmalemma surface were different in size and unequal in distribution. The diameter of large protein particles ranged from 200 to 440 nm, with a central micropore, and the apparent height of them was found to vary from 12 to 40 nm. The diameter of mid-sized protein particles was between 40-60 nm, and a range of 1.8-5 nm was given for the apparent height of them. As for small protein particles, obtained values were 12-40 nm for their diameter and 0.7-2.2 nm for height. Some invaginated pits were also observed at the plasma membrane. They were formed by the endocytosis of protoplast. Distribution density of them at plasmalemma was about 16 pits per 15 microm(2). According to their size, we classified the invaginated pits into two types--larger pits measuring 139 nm in diameter and 7.2 nm in depth, and smaller pits measuring 96 nm in diameter and 2.3 nm in depth. On dehydration-induced dead protoplasts, the degree of polarization of plasma membranes decreased. Lipid molecular layers appeared relatively smooth, and the quantity of integral proteins reduced a lot. Invaginated pits were still detectable at the membrane surface, but due to dehydration-induced protoplast contraction, the orifice diameter of pits reduced, and their depth increased. Larger pits averagely measuring 47.4 nm in diameter and 31.9 nm in depth, and smaller pits measuring 26.5 nm in diameter and 43 nm in depth at average. The measured thickness of plasma membranes of mesophyll cells from winter wheat examined by AFM was 6.6-9.8 nm, thicker in regions covered with proteins. PMID:18239886

  18. Influence of nanophase titania topography on bacterial attachment and metabolism

    PubMed Central

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

    2008-01-01

    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

  19. A scanning radar altimeter for mapping continental topography

    NASA Technical Reports Server (NTRS)

    Dixon, T. H.

    1986-01-01

    Topographic information constitutes a fundamental data set for the Earth sciences. In the geological and geophysical sciences, topography combined with gravitational information provides an important constraint on the structure and rheologic properties of the crust and lithosphere. Detailed topography data can also be used to map offsets associated with faulting and to reveal the effects of tectonic deformation. In the polar regions, elevation data form a crucial but as yet largely unavailable resource for studying ice sheet mass balance and ice flow dynamics. The vast Antarctic ice sheet is the largest fresh water reservoir on Earth and is an important influence on ocean circulation and global climate. However, our knowledge of its stability is so limited that we cannot even specify whether the Antarctic ice sheet is growing or shrinking. It is clear that there is need for high quality global topography data. A summary of potential applications with their resolution requirements is shown.

  20. Implications of MOLA Global Roughness, Statistics, and Topography

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

  1. Ulva linza zoospore sensitivity to systematic variation of surface topography

    NASA Astrophysics Data System (ADS)

    Sheats, Julian Taylor

    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.

  2. Static and dynamic support of the Pannonian basin topography

    NASA Astrophysics Data System (ADS)

    Horváth, Ferenc; Becker, Thorsten; Faccenna, Claudio; Balázs, Attila

    2014-05-01

    Determination of isostatic gravity anomalies more than half a century ago indicated that the Pannonian basin was "overcompensated", i. e. it was more elevated than predicted by an Airy-type isostatic compensation model. In other words, the isostatic equilibrium position of this strongly attenuated crust should be well below the sea level. We have revisited this early finding in the possession of reliable data on the structure of the lithosphere-asthenosphere system (Faccenna et al. 2014) and skill to simulate the effect of upper mantle convection on the topography (Becker et al. 2014). The static component of the topography relative to a reference level can be calculated by the assumption that a lithospheric column consisting of a crustal layer and a mantle lid floats freely within the asthenosphere. The difference between the actual and calculated topography in the Pannonian basin turns out to be a robust feature with values as high as 1000 meters This residual topography is supposed to be a dynamic feature and explained in terms of instantaneous mantle flow due to temperature anomalies as inferred from regional P and S wave tomography. Dynamic topography is derived from the radial tractions acting upon a free-slip surface boundary in a Newtonian-type fluid (Becker et al. 2014). Results show a remarkably good fit between dynamic and residual topography pattern suggesting a marked convective support of the elevated Pannonian basin. Finally, we argue that mantle flow pattern in the Pannonian region is part of the Mediterranean upper mantle concvection system, which has been under the control of lithospheric subduction, rollback and eventual slab breakoff processes (Faccenna et al. 2014).

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

  4. Sound propagation over uneven ground and irregular topography

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    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.

  6. Multiwell plate tools for controlling cellular alignment with grooved topography.

    PubMed

    Londono, Camila; Soleas, John; Lücker, Petra B; Sathananthan, Suthamathy; Aitchison, J Stewart; McGuigan, Alison P

    2014-01-01

    In many tissues, cells must be aligned for proper function. This alignment can occur at the cellular and/or subcellular (protein/molecular) level. The alignment of cytoskeletal components, in fact, precedes whole cell alignment. A variety of methods exist to manipulate cytoskeletal and whole cell alignment; one of the simplest and most predictable involves seeding adherent cells onto defined substrate topography. We present here two methods to create grooved multiwell plates: one involving microfabrication, which allows for custom design of substrate topography, and a simpler, inexpensive method using commercially available diffraction gratings. We also include methods for manual and automatic quantification of cell alignment. PMID:24687428

  7. Venus gravity anomalies and their correlations with topography

    NASA Technical Reports Server (NTRS)

    Sjogren, W. L.; Bills, B. G.; Birkeland, P. W.; Esposito, P. B.; Konopliv, A. R.; Mottinger, N. A.; Ritke, S. J.; Phillips, R. J.

    1983-01-01

    This report provides a summary of the high-resolution gravity data obtained from the Pioneer Venus Orbiter radio tracking data. Gravity maps, covering a 70 deg latitude band through 360 deg of longitude, are displayed as line-of-sight and vertical gravity. Topography converted to gravity and Bouguer gravity maps are also shown in both systems. Topography to gravity ratios are made over several regions of the planet. There are markedly different ratios for the Aphrodite area as compared to the Beta and Atla areas.

  8. Role of Cigarette Sensory Cues in Modifying Puffing Topography

    PubMed Central

    Rees, Vaughan W.; Kreslake, Jennifer M.; Wayne, Geoffrey Ferris; O Connor, Richard J.; Cummings, K. Michael; Connolly, Gregory N.

    2012-01-01

    Background Human puffing topography promotes tobacco dependence by ensuring nicotine delivery, but the factors that determine puffing behavior are not well explained by existing models. Chemosensory cues generated by variations in cigarette product design features may serve as conditioned cues to allow the smoker to optimize nicotine delivery by adjusting puffing topography. Internal tobacco industry research documents were reviewed to understand the influence of sensory cues on puffing topography, and to examine how the tobacco industry has designed cigarettes, including modified risk tobacco products (MRTPs), to enhance puffing behavior to optimize nicotine delivery and product acceptability. Methods Relevant internal tobacco industry documents were identified using systematic searching with key search terms and phrases, and then snowball sampling method was applied to establish further search terms. Results Modern cigarettes are designed by cigarette manufacturers to provide sensory characteristics that not only maintain appeal, but provide cues which inform puffing intensity. Alterations in the chemosensory cues provided in tobacco smoke play an important role in modifying smoking behavior independently of the central effects of nicotine. Conclusions An associative learning model is proposed to explain the influence of chemosensory cues on variation in puffing topography. These cues are delivered via tobacco smoke and are moderated by design features and additives used in cigarettes. The implications for regulation of design features of modified risk tobacco products, which may act to promote intensive puffing while lowering risk perceptions, are discussed. PMID:22365895

  9. Towards Integrated Design of a Robust Feedback Controller and Topography

    E-print Network

    Van den Hof, Paul

    due to the dynamic uncertainties in the system. Keywords: High-speed AFM, dual-actuation, robust)] is an important tool in micro-, and nano-technology to provide images of sample topography with molecular or even with a very sharp tip, while scanning the sample or tip in a raster scan-pattern. The measurement tip

  10. Simultaneous Topography and Recognition Imaging Using Force Microscopy

    PubMed Central

    Stroh, Cordula M.; Ebner, Andreas; Geretschläger, Manfred; Freudenthaler, Günter; Kienberger, Ferry; Kamruzzahan, A. S. M.; Smith-Gill, Sandra J.; Gruber, Hermann J.; Hinterdorfer, Peter

    2004-01-01

    We present a method for simultaneously recording topography images and localizing specific binding sites with nm positional accuracy by combining dynamic force microscopy with single molecule recognition force spectroscopy. For this we used lysozyme adsorbed to mica, the functionality of which was characterized by enzyme immunoassays. The topography and recognition images were acquired using tips that were magnetically oscillated during scanning and contained antibodies directed against lysozyme. For cantilevers with low Q-factor (?1 in liquid) driven at frequencies below resonance, the surface contact only affected the downward deflections (minima) of the oscillations, whereas binding of the antibody on the tip to lysozyme on the surface only affected the upwards deflections (maxima) of the oscillations. The recognition signals were therefore well separated from the topographic signals, both in space (?z ? 5 nm) and time (?0.1 ms). Topography and recognition images were simultaneously recorded using a specially designed electronic circuit with which the maxima (Uup) and the minima (Udown) of each sinusoidal cantilever deflection period were depicted. Udown was used for driving the feedback loop to record the height (topography) image, and Uup provided the data for the recognition image. PMID:15345574

  11. Shape and Topography of Saturn's Satellites from Imaging Data

    NASA Astrophysics Data System (ADS)

    Gaskell, R. W.; Mastrodemos, N.; Rizk, B.

    2010-12-01

    Detailed global and local digital topographies of eight of Saturn's satellites are being constructed from ensembles of overlapping maplets which completely cover the visible surfaces. Each maplet is a digital representation of a piece of the surface topography and albedo constructed from imaging data with stereophotoclinometry. Multiple images projected onto the maplet provide brightness values at each pixel which are used in a least-squares estimation for slope and relative albedo. The slopes are then integrated to produce the topography solution. The central pixel of each maplet represents a control point, and the ensemble of these points is used in an estimation for their body-fixed locations, the rotational state of the body, and the position and attitude of the spacecraft. Applications of these data products include studies of cratering of icy bodies and the subsequent relaxation of the surface, while detailed shapes for the small, irregular satellites can be used to predict the surface gravity and local slope at high resolution. For a larger satellite, a precise shape determination is important because often the shape was frozen in when the body was in a different rotational state. This enables an analysis of the rotational and orbital histories of these bodies. The high resolution topography yields surface roughness, slopes, overall elevation variations, and fractal character of the surface.

  12. EAARL topography-Potato Creek watershed, Georgia, 2010

    USGS Publications Warehouse

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

    2011-01-01

    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.

  13. An anatomical and functional topography of human auditory cortical areas

    PubMed Central

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

    2014-01-01

    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

  14. Diet and Dental Topography in Pitheciine Seed Predators

    E-print Network

    Boyer, Doug M.

    Diet and Dental Topography in Pitheciine Seed Predators Justin A. Ledogar,1 * Julia M. Winchester,2 occlusal surface enamel. Data on feeding ecology show that Pithecia consumes proportionally more leaves shearing crest length, occlusal relief, surface complexity, and surface curvature relative to nonseed

  15. The effect of Gonioscopy on keratometry and corneal surface topography

    Microsoft Academic Search

    Mathew K George; Thomas Kuriakose; Brian M DeBroff; John W Emerson

    2006-01-01

    BACKGROUND: Biometric procedures such as keratometry performed shortly after contact procedures like gonioscopy and applanation tonometry could affect the validity of the measurement. This study was conducted to understand the short-term effect of gonioscopy on corneal curvature measurements and surface topography based Simulated Keratometry and whether this would alter the power of an intraocular lens implant calculated using post-gonioscopy measurements.

  16. Links between climate, erosion, uplift, and topography during intracontinental mountain

    E-print Network

    Watts, A. B. "Tony"

    of the Hangay Dome, Mongolia A. Joshua West Department of Earth Sciences, University of Southern California and Technology, Ulaanbaatar, Mongolia [1] The Hangay mountain range, a dome in central Mongolia, provides. Keywords: topography; erosion; incision; climate; epeirogenic; intracontinental; dynamic; Mongolia. Index

  17. Mars Mantle (MOHO) Topography with Mantle Elevation Texture Map

    NSDL National Science Digital Library

    NASA/Goddard Space Flight Center Scientific Visualization Studio

    This site from NASA features a rotating animation of Mars using data from Mars Orbiting Laser Altimeter (MOLA). The topography is colored to indicate elevation. Additionally, an image highlighting the mantle is colored to indicate its elevation. A flat version of this same dataset is also available.

  18. Residual topography and lithospheric structure of the Antarctic continent

    NASA Astrophysics Data System (ADS)

    Molinari, I.; Baranov, A.; Danesi, S.; Morelli, A.

    2012-12-01

    Antarctica has been the subject of considerable interest in the past few years, following the International Polar Year. The structure of its crust at a continental scale is however still known with large uncertainty. A new Moho depth map for the Antarctic continent has been recently assembled (AntMoho), merging copious information from geophysical and geological studies selected from the literature. A large volume of old and new data has been analyzed: mostly seismic experiments, as well as receiver functions and geological studies, ranging from DSS profiles acquired by Soviet Union field experiments, to recent seismic receiver function studies. AntMoho has a reference lateral resolution of 1 degree. 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. Residual topography is obtained by removing the isostatic contribution of the crust from the observed topography. Long-wavelength residual topography is interpreted as dynamic response to large scale mantle convection and density contrasts. Our calculations show that significantly different inferences on lithospheric structure and mantle dynamics may result from the variance in Moho depth recorded in the different models. A better knowledge of Moho depth and, more generally, crustal structure for Antarctica at a continent scale is a goal with likely consequences for better understanding of the complex dynamic processes acting at a regional scale.

  19. Assessment of optic disc topography with scanning laser ophthalmoscope

    Microsoft Academic Search

    Etsuo Chihara; Fusano Takahashi; Keiko Chihara

    1993-01-01

    Evaluation of the topography of the optic disc is of clinical importance to assess the degree of nerve damage. We conducted a study in 17 glaucomatous and 20 control subjects with a scanning laser ophthalmoscope (SLO; Rodenstock) and compared the results with those in conventional photographs. A tomographic image of the cup area in control subjects and the neuroretinal rim

  20. Supercritical rotating flow over topography J. G. Esler,a

    E-print Network

    Esler, Gavin

    Supercritical rotating flow over topography J. G. Esler,a O. J. Rump, and E. R. Johnson Department . The supercritical regime in which the Froude number F, the ratio of the flow speed to the interfacial gravity wave. For flows within the supercritical regime F-1 M2/3 the linear drag result is found to remain accurate up

  1. Eye Shape and Retinal Topography in Owls (Aves: Strigiformes)

    Microsoft Academic Search

    Thomas J. Lisney; Andrew N. Iwaniuk; Mischa V. Bandet; Douglas R. Wylie

    2012-01-01

    The eyes of vertebrates show adaptations to the visual environments in which they evolve. For example, eye shape is associated with activity pattern, while retinal topography is related to the symmetry or ‘openness’ of the habitat of a species. Although these relationships are well documented in many vertebrates including birds, the extent to which they hold true for species within

  2. A Spherical Harmonic Analysis of the Earth's Topography

    Microsoft Academic Search

    Georges Balmino; Kurt Lambeck; William M. Kaula

    1973-01-01

    This letter is a correction to the letter of the same title by Lee and Kaula [1967]. In 1971 two independent harmonic analyses of the topography at Meudon and Los Angeles found the results of Lee and Kaula [1967] to be incorrect. The error of the 1967 analysis has since been found to be an insufficient dimension (W. H. K.

  3. Measurement of seabed topography by multibeam sonar using CFFT

    Microsoft Academic Search

    MUTSUO OKINO; YOJI HIGASHI

    1986-01-01

    A precise ocean bottom map for ocean surveying and dredging is desired. Especially in dredging, it is essential to know the seabed topography in real time without being affected by scatterers (for example floating sand and mud) in the seawater during work. To meet these requirements, the multi-narrow-beam sonar system (MBSS) has been developed. The MBSS forms beams with the

  4. Functional Analysis of Separate Topographies of Aberrant Behavior.

    ERIC Educational Resources Information Center

    Derby, K. Mark; And Others

    1994-01-01

    A functional analysis of distinct topographies of aberrant behavior displayed by 4 individuals (ages 6-28) with moderate to profound mental retardation indicated that hypotheses of separate functions for distinct behaviors can be generated using both extended and brief functional analyses when results are graphed in the aggregate and separated by…

  5. Examining topography and stream discharge at Sherburne National Wildlife Refuge

    NSDL National Science Digital Library

    Todd Koenig Zimmerman High School ISD 728 Zimmerman, MN I will be using a modified concept of the contour mapping exercise we did at St. Thomas and the Hydrology flow lab we preformed at Coon Creek.

    In this inquiry based geologic field lab students will be estimating and measuring stream flow. Students will also map out a full scale live topography map of a dry streambed to help them estimate flow discharge. Students will use their journals to record their hypothesis, lab report questions, graphed data and evidence to backs up their observations.

  6. The Effects of Nanoscale Topography on Palladin Dynamics

    E-print Network

    Anlage, Steven

    of the grooves. ·Stress fibers also form along the direction of the grooves, and in many cases, inside understand the influence of topography Additional aspects of palladin dynamics and stress fiber formation proteins responsible for the structural and mechanical properties of cells Palladin is an actin binding

  7. Scaling and multifractal fields in the solid earth and topography

    Microsoft Academic Search

    S. Lovejoy; D. Schertzer

    2007-01-01

    Starting about thirty years ago, new ideas in nonlinear dynamics, particularly fractals and scaling, provoked an explosive growth of research both in modeling and in experimentally characterizing geosystems over wide ranges of scale. In this review we focus on scaling advances in solid earth geophysics including the topography. To reduce the review to manageable proportions, we restrict our attention to

  8. Stress distribution and topography of Tellus Regio, Venus

    NASA Technical Reports Server (NTRS)

    Williams, David R.; Greeley, Ronald

    1989-01-01

    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.

  9. Causes and Consequences of Time-Varying Dynamic Topography

    NASA Astrophysics Data System (ADS)

    White, Nicky

    2013-04-01

    Convective circulation of the Earth's mantle maintains plate motion but we know little about the spatial and temporal details of this circulation. Accurate maps of the spatial and temporal pattern of dynamic topography will profoundly affect our understanding the the relationship between surface geology and deep Earth processes. A major difficulty is the 'tyranny of isostasy'. In other words, dynamic topography is difficult to measure because crustal and lithospheric thickness and density changes are the dominant control of surface elevation. Some progress can be made along continental margins by measuring residual depth anomalies of the oldest oceanic floor on newly available seismic reflection and wide-angle profiles. These estimates of dynamic topography have amplitudes of ±1 km and wavelengths of 102-104 km. They mostly, but not always, correlate with long wavelength free-air gravity anomalies. Correlation with seismic tomographic images is much poorer. The distribution of dynamic topography throughout the rest of the oceanic realm can be supplemented by using ship-track data in regions with sparse sedimentary cover and by exploiting the mid-oceanic ridge system. On the continents, it is more difficult to measure dynamic topography with the same accuracy since the density structure of continental lithosphere is so variable but progress can be made on three fronts. First, long-wavelength gravity anomalies which straddle continental margins are an obvious and important guide. Secondly, stratal geometries across continental shelves contain information about positive and negative surface elevation changes. In several cases, 2- and 3-D seismic surveys calibrated by boreholes can be used to constrain spatial and temporal patterns of dynamic topography. In the North Atlantic Ocean, examples of buried ephemeral landscapes suggest that dynamic topography can grow and decay on timescales as short as a few million years. Recognition of positive and negative vertical motions, which cannot be accounted for by global eustasy, is encouraging and suggests that we are on the verge of creating global dynamic topographic maps which can be used to test predictive global models.

  10. Topography-driven bionano-interactions on colloidal silica nanoparticles.

    PubMed

    Paula, Amauri J; Silveira, Camila P; Martinez, Diego Stéfani T; Souza Filho, Antonio G; Romero, Fabian V; Fonseca, Leandro C; Tasic, Ljubica; Alves, Oswaldo L; Durán, Nelson

    2014-03-12

    We report here that the surface topography of colloidal mesoporous silica nanoparticles (MSNs) plays a key role on their bionano-interactions by driving the adsorption of biomolecules on the nanoparticle through a matching mechanism between the surface cavities characteristics and the biomolecules stereochemistry. This conclusion was drawn by analyzing the biophysicochemical properties of colloidal MSNs in the presence of single biomolecules, such as alginate or bovine serum albumin (BSA), as well as dispersed in a complex biofluid, such as human blood plasma. When dispersed in phosphate buffered saline media containing alginate or BSA, monodisperse spherical MSNs interact with linear biopolymers such as alginate and with a globular protein such as bovine serum albumin (BSA) independently of the surface charge sign (i.e. positive or negative), thus leading to a decrease in the surface energy and to the colloidal stabilization of these nanoparticles. In contrast, silica nanoparticles with irregular surface topographies are not colloidally stabilized in the presence of alginate but they are electrosterically stabilized by BSA through a sorption mechanism that implies reversible conformation changes of the protein, as evidenced by circular dichroism (CD). The match between the biomolecule size and stereochemistry with the nanoparticle surface cavities characteristics reflects on the nanoparticle surface area that is accessible for each biomolecule to interact and stabilize any non-rigid nanoparticles. On the other hand, in contact with variety of biomolecules such as those present in blood plasma (55%), MSNs are colloidally stabilized regardless of the topography and surface charge, although the identity of the protein corona responsible for this stabilization is influenced by the surface topography and surface charge. Therefore, the biofluid in which nanoparticles are introduced plays an important role on their physicochemical behavior synergistically with their inherent characteristics (e.g., surface topography). PMID:24524580

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

    E-print Network

    Nikurashin, Maxim (Maxim Anatolevich)

    2009-01-01

    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 ...

  12. Effects of surface-topography directionality and lubrication condition on frictional behaviour during plastic deformation

    Microsoft Academic Search

    W Rasp; C. M Wichern

    2002-01-01

    Surface-topography, friction and plasticity form a complex system at the interface of a plastic deformation operation. Surface-topography before deformation affects the frictional behaviour at the interface, which in turn affects the level and distribution of plastic deformation. The surface-topography after deformation operations is determined by a combination of the initial surface-topography, the frictional behaviour at the interface and the level

  13. The Direct Breaking of Internal Waves at Steep1 Topography2

    E-print Network

    Klymak, Jody M.

    1 The Direct Breaking of Internal Waves at Steep1 Topography2 Jody M. Klymak, Sonya Legg, Matthew H. Alford, Maarten Buijsman,3 Robert Pinkel and Jonathan D. Nash4 5 Abstract6 7 Internal waves are often steep "supercritical" topography (i.e. topography that is steeper than internal wave energy13

  14. Comparison of SRTM Topography to USGS and High Resolution Laser Altimetry Topography: Case Studies From the Oregon Coast Range

    NASA Astrophysics Data System (ADS)

    Dietrich, W. E.; Stock, J. D.; Allen, D.; Beluggi, D.; Montgomery, D. R.; Roering, J. J.

    2001-12-01

    The Shuttle Radar Topography mission (SRTM) acquired topographic data for the non-polar regions of earth at a nominal 30-m resolution. This horizontal resolution is dramatically higher than previous ~1 km data, and is likely to be used by a broad cross-section of the earth sciences community for detailed modeling of surface and coupled surface-atmospheric models. These users will need to know how SRTM topography compares with field-scale (e.g., 1-2 m) topography. We compare SRTM 30-m data to 3 sites in the forested steeplands of the Oregon Coast Range where we have acquired 2-3 m spaced topography using laser altimetry and total station surveys over areas from 2-6 km2. At each site, we have field-checked the laser altimetry with ground reconnaissance and measurements, and have identified vegetation cover. In addition, we compare the SRTM data to the existing public access data from the USGS 10- and 30-m data. We compare the coarser resolution data to high resolution data, and to re-gridded versions of the high resolution data for the following landscape metrics: 1) mean slope, 2) local slope distribution, 3) drainage density at a given area threshold, 4) relief as a function of area, 5) link magnitude distribution, and 6) slope versus area for the valley network. We also compare individual hillslope and river profiles by comparing rms error of the coarser data to fine resolution topography, and evaluate the planform errors in the coarser valley network. Our comparisons should guide user's interpretation of SRTM data where ground-truthing data are absent.

  15. Basal Topography of the South Polar Layered Deposits

    NASA Astrophysics Data System (ADS)

    Davies, C. W.; Murray, B. C.; Byrne, S.

    2004-12-01

    The ice inferred to comprise the south polar layered deposits (SPLD) represents a significant fraction of the total water reservoir of the planet. The basal topography of these deposits is currently unconstrained but may be expected to contain considerable relief based on the heavily cratered nature of the surrounding terrain. In this work we report on our efforts to characterize the overall nature of this basal topography and in so doing better constrain the volume of this important volatile reservoir. Our approach has been to measure elevations at the periphery of the SPLD (defined by [1]) and use various interpolation techniques to estimate the basal topography. We used 1300 control points from the edges and areas surrounding the SPLD and included extensive control points from within the Chasmae and other features to fit a surface beneath the SPLD. No assumptions were made about any lithospheric flexure, nor did the results suggest that possibility. We first tested a variety of surface interpolation routines on a comparable area of cratered terrain immediately adjacent to the SPLD, using the same spatial distribution of 1300 height control points as we used for the SPLD itself, and found that the topography was broadly reproducible (ignoring craters) to within a few hundred meters. The SPLD basal topography we derive can be subtracted from the current spatial topography to produce isopach maps of the layered deposits. All interpolation methods we tested (within the ArcMap 8.3) indicate a lower total SPLD volume than that previous published [Smith et al., 2001]. Our best estimate for the SPLD volume is ~1 million km3, with a formal error in volume of ~5%, corresponding to an average thickness of ~950 meters. In comparison, [2] estimated this volume to be ~1.2-1.7 million km3. The Prometheus impact basin is present as a rimmed depression, consistent with the inference by [3]. More unexpected is the presence of a broad ridge underlying nearly the entire eastern half of the SPLD, which makes those deposits relatively thin. Our isopach maps show the northwestern portion of the Ultimi lobe to be an isolated thick region, in agreement with [1]. [1] Kolb, E. J., and K. L. Tanaka (2001), Icarus, 154, 22-39. [2] Smith, D. E., et al. (2001), J. Geophys. Res., 106(E10), 23,689-23,722. [3] Byrne, S., and A. B. Ivanov (2004), J. Geophys. Res., In press.

  16. SRTM and Laser Altimeter Views of Western Washington State Topography

    NASA Astrophysics Data System (ADS)

    Harding, D. J.; Carabajal, C. C.

    2001-12-01

    Interferometric Synthetic Aperture Radar (InSAR) and laser altimeter measurements of topography provide complimentary approaches to characterize landforms. Results from the Shuttle Radar Topography Mission (SRTM) will provide an unprecedented, near-global, public-domain topography data set at 90 m resolution using a single pass C-band (5.6 cm wavelength) radar interferometer. In vegetated terrains, the C-band radar energy will penetrate part way into vegetation cover. The elevation of the resulting radar phase center, somewhere between the canopy top and underlying ground, will depend on the vegetation density, structure, and presence or absence of foliage. The high vertical accuracy and spatial resolution achieved by laser altimeters, and their capability to directly measure vegetation height and ground topography beneath vegetation cover, provides a method to evaluate InSAR representations of topography. Here a preliminary C-band SRTM digital elevation model (DEM) for a portion of western Washington State is evaluated using laser altimeter data to assess its elevation accuracy and the extent of vegetation penetration. The SRTM DEM extends from the Cascades Range westward to the Olympic Peninsula. The laser altimeter data includes two profiles acquired by the second flight of the Shuttle Laser Altimeter (SLA-02) in August, 1997, numerous transects acquired by the airborne Scanning Lidar Imager of Canopies by Echo Recovery (SLICER) in September, 1995, and comprehensive mapping in the Puget Lowland region acquired by Terrapoint, LLC for the Puget Sound Lidar Consortium in the winters of 2000 and 2001. SLA-02 and SLICER acquired waveforms that record the height distribution of illuminated surfaces within 120 m and 10 m diameter footprints, respectively. The Terrapoint elevations consist of up to four discrete returns from 1 m footprints spaced 1.5 apart, with all areas mapped twice. Methods for comparing laser altimeter and SRTM topography developed here will be applied on a global basis as Ice, Cloud and land Elevation Satellite and Vegetation Canopy Lidar laser altimeter waveform data and final SRTM products become available.

  17. Controls of climate, topography, vegetation and lithology on drainage density extracted from high resolution topography

    NASA Astrophysics Data System (ADS)

    Sangireddy, H.; Carothers, R. A.; Passalacqua, P.; Stark, C. P.

    2014-12-01

    Drainage density is a useful topographic metric that varies as a function of geomorphic processes and that serves to quantify links with topography, climate, vegetation, and lithology. Here we analyze 101 sub-basins across thirteen states in the USA using high-resolution digital terrain models (DTMs) in combination with data on the spatial variation of precipitation, soil, geology, and land cover. We test the following hypotheses: (1) Drainage density carries strong, codependent signatures of rainfall variability, soil type, and topographic relief; (2) Drainage density reflects the extent of landscape dissection on the sub-catchment scale and the subsequent processes of vegetation recovery and gullying.We employ a dimensionless drainage density (Ddd) metric defined as the ratio of likely channelized pixels in a basin to its total number of pixels, and map this metric across meter-resolution lidar DTMs using GeoNet [Passalacqua et al., 2010]. We assess the resolution-dependent scaling of Ddd and observe that it is a much weaker scaling function of DTM resolution than the dimensional formulation of drainage density (Dg), which is classically defined as the ratio of total channel length to total basin area.In order to characterize the correlation structure of drainage density with climatic parameters such as mean annual precipitation (MAP), we use a Gaussian mixture model and identify two sub-groups of landscapes that display different correlations. We observe that Ddd and MAP are negatively correlated in arid and semi-arid environments and positively correlated in humid environments. The transition occurs at a MAP around 900-1000mm/yr and coincides with the maximum observed values of soil thickness and available water content. Landscape relief has a negative correlation with Ddd in arid environments while the correlation is positive in humid climates. We discuss the implication of our results for understanding eco-geomorphic processes and for modeling landscape evolution.References:Passalacqua, P., Do Trung, T., Foufoula-Georgiou, E., Sapiro, G., & Dietrich, W. E. (2010). A geometric framework for channel network extraction from lidar: Nonlinear diffusion and geodesic paths. Journal of Geophysical Research: Earth Surface (2003-2012), 115(F1).

  18. Method and Apparatus for Creating a Topography at a Surface

    DOEpatents

    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

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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 the observed surface topography, crustal deformation, and the gravity field. Therefore, comparison of model results with observational data can help to constrain such parameters as crustal and thermal boundary layer thicknesses as well as the character of mantle flow below different Venusian features. We explore in this paper the effects of this coupling by means of a finite element modelling technique.

  20. Role of membrane stresses in the support of planetary topography

    NASA Technical Reports Server (NTRS)

    Turcotte, D. L.; Willemann, R. J.; Haxby, W. F.; Norberry, J.

    1981-01-01

    The role of membrane stresses and bending stresses in supporting topographic loads on planetary elastic lithospheres is examined. A dimensionless parameter is introduced in order to determine the ability of a spherical shell to support loads through membrane stresses. It is determined that when this parameter is large, membrane stresses can fully support topographic loads with flexure, and when it is small the influence of the membrane stresses can be neglected. Equations governing the behavior of a spherical shell are solved for a topographic load expressed in terms of spherical harmonics, and spherical harmonic expansions of the measured gravity and topography for Mars and the moon are compared with the theory. It is concluded that membrane stresses play an important role in the support of topographic loads on the moon and Mars. The correlation of observed gravitational potential anomalies with the topography on Mars is explained by membrane stresses in the elastic lithosphere.

  1. Irregular topography at the Earth's inner core boundary.

    PubMed

    Dai, Zhiyang; Wang, Wei; Wen, Lianxing

    2012-05-15

    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

  2. On the detection of underwater bottom topography by imaging radars

    NASA Technical Reports Server (NTRS)

    Alpers, W.

    1984-01-01

    A theoretical model which explains basic properties of radar imaging of underwater bottom topography in tidal channels is presented. The surface roughness modulation is described by weak hydrodynamic interaction theory in the relaxation time approximation. In contrast to previous theories on short wave modulation by long ocean waves, a different approximation is used to describe short wave modulation by tidal flow over underwater bottom topography. The modulation depth is proportional to the relaxation time of the Bragg waves. The large modulation of radar reflectivity observed in SEASAT-SAR imagery of sand banks in the Southern Bight of the North Sea are explained by assuming that the relaxation time of 34 cm Bragg waves is of the order of 30-40 seconds.

  3. [Topography of a reference plane for ultrasonic thoracometry (author's transl)].

    PubMed

    Kugener, H; Hansmann, M

    1976-10-01

    A method of ultrasonic thoracometry is reported which uses the veins of the fetal liver as landmarks. The fact that the umbilical vein running from the anterior abdominal wall to the "sinus venae portae" is visible in B-scan display is the given presupposition. In a study about topography of the vein system of the fetal liver in 50 cases the description of a so called "sinus-plane" for sonar thoracometry is given. This reference plane is shown to be identical with the "lower apertura of the fetal thorax" recommended by Hansmann and co-workers since 1971. Thereby the nowadays well established method of thoracometry in obstetrical routine work gets a more accurate definition in regard to it's topography. This is not only of theoretical interest but will improve the conditions for more accuracy and reproducibility of the method. PMID:969791

  4. Geophysical, petrological and mineral physics constraints on Earth's surface topography

    NASA Astrophysics Data System (ADS)

    Guerri, Mattia; Cammarano, Fabio; Tackley, Paul J.

    2015-04-01

    Earth's surface topography is controlled by isostatically compensated density variations within the lithosphere, but dynamic topography - i.e. the topography due to adjustment of surface to mantle convection - is an important component, specially at a global scale. In order to separate these two components it is fundamental to estimate crustal and mantle density structure and rheological properties. Usually, crustal density is constrained from interpretation of available seismic data (mostly VP profiles) based on empirical relationships such those in Brocher [2005]. Mantle density structure is inferred from seismic tomography models. Constant coefficients are used to interpret seismic velocity anomalies in density anomalies. These simplified methods are unable to model the effects that pressure and temperature variations have on mineralogical assemblage and physical properties. Our approach is based on a multidisciplinary method that involves geophysical observables, mineral physics constraints, and petrological data. Mantle density is based on the thermal interpretation of global seismic tomography models assuming various compositional structures, as in Cammarano et al. [2011]. We further constrain the top 150 km by including heat-flow data and considering the thermal evolution of the oceanic lithosphere. Crustal density is calculated as in Guerri and Cammarano [2015] performing thermodynamic modeling of various average chemical compositions proposed for the crust. The modeling, performed with the code PerpleX [Connolly, 2005], relies on the thermodynamic dataset from Holland and Powell [1998]. Compressional waves velocity and crustal layers thickness from the model CRUST 1.0 [Laske et al., 2013] offer additional constrains. The resulting lithospheric density models are tested against gravity (GOCE) data. Various crustal and mantle density models have been tested in order to ascertain the effects that uncertainties in the estimate of those features have on the modeled topography. We also test several viscosity models, either radially symmetric, the V1 profile from Mitrovica and Forte [2004], or more complex laterally varying structures. All the property fields are expanded in spherical harmonics, until degree 24, and implemented in the code StagYY [Tackley, 2008] to perform mantle instantaneous flow modeling and compute surface topography and gravitational field. Our results show the importance of constraining the crustal and mantle density structure relying on a multidisciplinary approach that involves experimentally robust thermodynamic datasets. Crustal density field has a strong effect on the isostatic component of topography. The models that we test, CRUST 1.0 and those in Guerri and Cammarano [2015], produce strong differences in the computed isostatic topography, in the range ±600 m. For the lithospheric mantle, relying on experimentally robust material properties constraints is necessary to infer a reliable density model that takes into account chemical heterogeneities. This approach is also fundamental to correctly interpret seismic models in temperature, a crucial parameter, necessary to determine the lithosphere-asthenosphere boundary, where static effects on topography leave place to dynamic ones. The comparison between results obtained with different viscosity fields, either radially symmetric or vertically and laterally varying, shows how lateral viscosity variations affect the results, in particular the modeled geoid, at different wavelengths. References: Brocher, T. M. (2005), Empirical Relations between Elastic Wavespeeds and Density in the Earth's Crust, Bulletin of the Seismological Society of America, 95(6), 2081-2092. Cammarano, F., P. J. Tackley, and L. Boschi (2011), Seismic, petrological and geodynamical constraints on thermal and compositional structure of the upper mantle: global thermochemical models, Geophys. J. Int. Connolly, J. A. D. (2005), Computation of phase equilibria by linear programming: A tool for geodynamic modeling and its application to subduction zone decarbonation, Earth and

  5. On fractional Bessel equation and the description of corneal topography

    E-print Network

    Okrasi?ski, Wojciech

    2012-01-01

    In this note we apply a modified fractional Bessel differential equation to the problem of describing corneal topography. We find the solution in terms of the power series. This solution has an interesting behavior at infinity which is a generalization of the classical results for modified Bessel function of order 0. Our model fits the real corneal geometry data with an error of order of a few per cent.

  6. White beam topography of 300 mm Si wafers

    Microsoft Academic Search

    A. N. Danilewsky; J. Wittgea; A. Rack; T. Weitkamp; R. Simon; T. Baumbach; P. McNally

    2008-01-01

    Synchrotron X-ray topography is well suited for a detailed characterisation of the real structure of single crystals and devices\\u000a based on single crystalline materials. The nature and distribution of dislocations, stacking faults, inclusions etc. as well\\u000a as long range strain from processing are of high interest especially in semiconductor wafers and electronic devices. To overcome\\u000a the limitations of the classical

  7. New Products From the Shuttle Radar Topography Mission

    Microsoft Academic Search

    Dean Gesch; Tom Farr; James Slater; Jan-Peter Muller; Sally Cook

    2006-01-01

    New data products with broad applicability to the Earth sciences are now available from the Shuttle Radar Topography Mission (SRTM). SRTM, a joint project of the National Geospatial-Intelligence Agency (NGA) and NASA, flew aboard the Space Shuttle Endeavour on an 11 day mission in February 2000 with the goal of collecting a near-global data set of high-resolution elevation data [Farr

  8. ATM Coastal Topography-Florida 2001: Western Panhandle

    USGS Publications Warehouse

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

    2009-01-01

    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 western Florida panhandle coastline, acquired October 2-4 and 7-10, 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 routinely used to create maps that represent submerged or first surface topography.

  9. ATM Coastal Topography-Texas, 2001: UTM Zone 15

    USGS Publications Warehouse

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

    2009-01-01

    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 a portion of the Texas coastline within UTM zone 15, from Matagorda Peninsula to Galveston Island, acquired October 12-13, 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.

  10. ATM Coastal Topography-Florida 2001: Eastern Panhandle

    USGS Publications Warehouse

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

    2009-01-01

    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 eastern Florida panhandle coastline, acquired October 2, 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 routinely used to create maps that represent submerged or first surface topography.

  11. ATM Coastal Topography-Texas, 2001: UTM Zone 14

    USGS Publications Warehouse

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

    2009-01-01

    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 a portion of the Texas coastline within UTM zone 14, acquired October 12-13, 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.

  12. Ocean surface topography from space (TOPEX/Poseidon Missions)

    NSDL National Science Digital Library

    Joint US and France project, the TOPEX-Poseidon satellites continuously measures sea surface height. Oceans store and transport solar heat, helping to keep Earth's climate in balance. The overall shape of the oceans' "hills" and "valleys" is called ocean surface topography, or OST. Precise knowledge of OST is essential to predict the effects of catastrophic storms. Educational resources available for all ages and backgrounds. Outstanding animation of OTS also included.

  13. Moho depth and residual topography of the Antarctic continent

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

  14. Ocean Surface Topography From Space (TOPEX/Poseidon Missions)

    NSDL National Science Digital Library

    A joint US and France project, the TOPEX-Poseidon satellites continuously measure sea surface height. The oceans store and transport solar heat, helping to keep Earth's climate in balance. The overall shape of the oceans' "hills" and "valleys" is called ocean surface topography, or OST. Precise knowledge of OST is essential to predict the effects of catastrophic storms. Educational resources available for all ages and backgrounds. Outstanding animation of OTS also included.

  15. Satellite Laser Altimeter for Measurement of Ice Sheet Topography

    Microsoft Academic Search

    Jack L. Bufton; John E. Robinson; Michael D. Femiano; Fred S. Flatow

    1982-01-01

    We describe the design and expected performance of a spaceborne laser altimeter based on a nadir-oriented laser transmitter, a 0.5-m-diam receiver telescope, and a high-accuracy satellite attitude measurement system. This instrument is designed for high-resolution mapping of polar ice sheet topography where conventional radar altimeters have difficulty. This instrument could also provide useful data on cloud-top heights and the ocean

  16. Fluorescence mapping of afferent topography in three dimensions

    Microsoft Academic Search

    Stacey L. Reeber; Samrawit A. Gebre; Roy V. Sillitoe

    Neural circuits are organized into complex topographic maps. Although several neuroanatomical and genetic tools are available\\u000a for studying circuit architecture, a limited number of methods exist for reliably revealing the global patterning of multiple\\u000a topographic projections. Here we used wheat germ agglutinin (WGA) conjugated to Alexa 555 and 488 for dual color fluorescent\\u000a mapping of parasagittal spinocerebellar topography in three

  17. Electronic cigarettes: abuse liability, topography and subjective effects

    PubMed Central

    Evans, Sarah E; Hoffman, Allison C

    2014-01-01

    Objective To review the available evidence evaluating the abuse liability, topography, subjective effects, craving and withdrawal suppression associated with e-cigarette use in order to identify information gaps and provide recommendations for future research. Methods Literature searches were conducted between October 2012 and January 2014 using five electronic databases. Studies were included in this review if they were peer-reviewed scientific journal articles evaluating clinical laboratory studies, national surveys or content analyses. Results A total of 15 peer-reviewed articles regarding behavioural use and effects of e-cigarettes published between 2010 and 2014 were included in this review. Abuse liability studies are limited in their generalisability. Topography (consumption behaviour) studies found that, compared with traditional cigarettes, e-cigarette average puff duration was significantly longer, and e-cigarette use required stronger suction. Data on e-cigarette subjective effects (such as anxiety, restlessness, concentration, alertness and satisfaction) and withdrawal suppression are limited and inconsistent. In general, study data should be interpreted with caution, given limitations associated with comparisons of novel and usual products, as well as the possible effects associated with subjects’ previous experience/inexperience with e-cigarettes. Conclusions Currently, very limited information is available on abuse liability, topography and subjective effects of e-cigarettes. Opportunities to examine extended e-cigarette use in a variety of settings with experienced e-cigarette users would help to more fully assess topography as well as behavioural and subjective outcomes. In addition, assessment of ‘real-world’ use, including amount and timing of use and responses to use, would clarify behavioural profiles and potential adverse health effects. PMID:24732159

  18. Effects of Plate Coupling and Margin Topography on Forearc Stresses

    NASA Astrophysics Data System (ADS)

    Wada, I.; Wang, K.

    2005-12-01

    The state of stress of forearc systems yields critical information on plate driving forces and the strength of subduction faults. In the outer forearc area within 100-150 km of trench, fold-and-thrust structure usually indicates horizontal, largely margin-normal, compression. However, in inner forearc regions, the state of stress is not well constrained. We infer inner forearc stresses at various subduction zones by examining earthquake focal mechanisms and fault slip data. Subduction zones examined include Northeast and Southwest Japan, Ryukyu, northern Cascadia, southern Mexico, Costa Rica, southern Peru, northern Chile, Hikurangi, and Hellenic. Stress inversion was carried out wherever appropriate. The results indicate that inner forearcs with low margin-normal compression outnumber those with high margin-normal compression. Most inner forearcs are under much less margin-normal compression than their outer forearcs, and many are under tension. Using a simple model of forearc force balance, we demonstrate that the landward stress decrease reflects an arcward decrease in the effect of plate coupling and an increase in the effect of margin topography. Plate coupling causes horizontal compression, but margin topography, with a tendency for gravitational collapse, induces horizontal tension. The abundance of low-stress inner forearcs indicates that the plate coupling force is generally too small to overcome the effect of margin topography. Finite element mechanical models show that the temporally and spatially averaged effective friction coefficient of subduction faults is usually no greater than 0.05.

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

    PubMed

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

    2005-09-01

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

  20. Permian karst topography in the Wichita uplift, southwestern Oklahoma

    SciTech Connect

    Donovan, R.N. Busbey, A.B. (Texas Christian Univ., Ft. Worth, TX (United States). Geology Dept.)

    1993-02-01

    The Wichita uplift in southwestern Oklahoma is one part of a record of Pennsylvania and early Permian deformation that affected the Southern Oklahoma aulacogen. As a result of a partial inversion, the Lower Paleozoic section of this aulacogen was sequentially stripped off an uplift between the Wichita uplift and the Anadarko basin, resulting in the exposure of ultrabasic rocks deep in the Cambrian igneous fill of the aulacogen. Following the late Paleozoic tectonism, the topography of the uplift was entombed beneath Permian sediments and remained essentially undisturbed until exhumation during the present erosional cycle. Modern erosion is gradually exposing this topography, permitting morphometric analysis of the Permian hill forms. Because of the variation of lithology in the uplift, it is possible to isolate the effects of weathering processes such as intense hydrolysis of the igneous rocks (producing, among other features, or topography) and limestone dissolution, in the form of a surface and subsurface karst imprint. The latter process resulted in a network of small caves that are essentially fissures eroded along tectonic fractures. These small caves can be found in all the exposed areas of limestone. They are particularly noteworthy for three reasons: in at least five examples they contain a complex fauna of Permian vertebrates (mostly fragmentary), speleothems in some examples contain hydrocarbon inclusions, derived from the underlying Anadarko basin, some of the caves yield evidence of post burial evolution in the form of clay infiltration from the surface and brine flushing from the underlying Anadarko basin.

  1. X-ray topography utilizing non-equatorial reflections

    NASA Astrophysics Data System (ADS)

    Kingman, P. W.

    1987-03-01

    The principal thrust of X-ray topography has been toward the study of general dislocation arrangements in quite perfect crystals. Since the early work of Barrett and Honeycombe there has been relatively little interest in deformation structures; at least in part because of the difficulty of extracting useful quantitative information about the geometry from topographs. This paper describes the general geometry of back reflection topography and shows how a systematic exploitation of the back reflection geometry can be used to maximize the information which can be obtained and optimizes the diffraction geometry for any given Bragg reflection. A camera design based upon this general approach is described, as well some specific procedures for its utilization. The basic approach to back reflection topography can be applied to any topographic arrangement. Since the present camera was intended for the study of macrostructures of crystals with high dislocation densities, it was designed to image large sample areas at low resolution. The basic analysis and procedures apply equally well to any back reflection technique. The possibility of effectively nonequatorial reflections greatly enhances the power and flexibility of the method.

  2. Changes in African topography driven by mantle convection

    NASA Astrophysics Data System (ADS)

    Moucha, Robert; Forte, Alessandro M.

    2011-10-01

    The topography of the African continent is characterized by large-scale extensional features such as the East African Rift, widespread volcanic activity, and anomalously subsided basins and uplifted domes. These enigmatic surface features have long suggested that the African continent is shaped by significant dynamic forcing originating in the underlying mantle. Here we simulate mantle convection backwards in time to reconstruct the evolution of dynamic topography of Africa over the past 30 million years. We show that the current high topography of the East African Rift system is due to the southward propagation of a topographic swell that encompassed the western margin of Arabia and the Afar region before 30 million years ago. We suggest that this dominant swell formed in response to the upwelling of the African superplume and the relative northward motion of the African tectonic plate over it. We also find that the adjacent Congo Basin has gradually subsided over the same time period in response to convective drawdown in the mantle. We conclude that much of Africa's recent geological history is driven by buoyancy forces in the mantle. Our findings have important implications for African volcanism, erosion, sediment transport and river-basin drainage patterns.

  3. Surface topography estimated by inversion of satellite gravity gradiometry observations

    NASA Astrophysics Data System (ADS)

    Ramillien, Guillaume

    2015-04-01

    An integration of mass elements is presented for evaluating the six components of the 2-order gravity tensor (i.e., second derivatives of the Newtonian mass integral for the gravitational potential) created by an uneven sphere topography consisting of juxtaposed vertical prisms. The method is based on Legendre polynomial series with the originality of taking elastic compensation of the topography by the Earth's surface into account. The speed of computation of the polynomial series increases logically with the observing altitude from the source of anomaly. Such a forward modelling can be easily used for reduction of observed gravity gradient anomalies by the effects of any spherical interface of density. Moreover, an iterative least-square inversion of the observed gravity tensor values ??? is proposed to estimate a regional set of topographic heights. Several tests of recovery have been made by considering simulated gradiometry anomaly data, and for varying satellite altitudes and a priori levels of accuracy. In the case of GOCE-type gradiometry anomalies measured at an altitude of ~300 km, the search converges down to a stable and smooth topography after 20-30 iterations while the final r.m.s. error is ~100 m. The possibility of cumulating satellite information from different orbit geometries is also examined for improving the prediction.

  4. The Relationship between Dynamic Topography and Sequence Stratigraphy

    NASA Astrophysics Data System (ADS)

    White, N. J.

    2014-12-01

    An evolving pattern of convective circulation within the mantle generates and maintains dynamic topography which is some fraction of observed topography. Spatial variations of dynamic topography are easy to measure within the oceanic realm and it is possible to exploit inventories of seismic reflection and wide-angle data to determine the dynamic topography of the oldest oceanic lithosphere that abuts passive continental margins. Results show that oceanic lithosphere has dynamic topographic anomalies of +/- 1 km with wavelengths of 500-1000 km. These substantial anomalies intersect coastal shelves and so it is expected that the development of these anomalies has affected sequence stratigraphic architecture in important ways. A series of examples will be used to illustrate how sequence stratigraphy can be profoundly influenced by changing patterns of dynamic topography. First, along the West African margin a set of dynamic topographic domes intersect the shelf edge. Onshore, the Neogene growth of these domes is recorded by emergent terraces and by drainage patterns. Offshore, an Oligo-Miocene switch from aggradation to progradation together with a series of younger disconformities have modified stratigraphic architecture along the shelf. Secondly, along the Northwest Shelf of Australia there is evidence for 700 m of dynamic drawdown of the oldest oceanic floor. Regional mapping and backstripping of clinoformal geometries within a Miocene carbonate reef complex shows that there is a dramatic switch from progradation to aggradation which cannot be attributed to glacio-eustatic variations. Instead, this switch appears to reflect growth of dynamic drawdown within the mantle. Finally, the Icelandic plume has controlled vertical motions along fringing North Atlantic margins over the last 60 Ma. Thanks to the intersecting mid-oceanic ridge, there is independent evidence that the temperature structure of this plume has fluctuated through time. These fluctuations are recorded within the detailed sequence stratigraphy of the margins where a series of ephemeral terrestrial landscapes have been mapped. Stratigraphic architecture appears to be an important repository of details about transient convective circulation which are otherwise difficult to obtain.

  5. Open questions in surface topography measurement: a roadmap

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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

  6. Large Eddy Simulation over a 3D topography:Large Eddy Simulation over a 3D topography: Comparison with the results of the field campaign

    E-print Network

    Large Eddy Simulation over a 3D topography:Large Eddy Simulation over a 3D topography: Comparison) Objectives We use the EPFL Large Eddy Simulation (LES) code coupled with Immersed Boudndary Method to model the Bolund Island (Denmark) The Bolund Island Large Eddy Simulation and Immersed Boundary Method The Bolund

  7. Effect of mesoscale topography over the Tibetan Plateau on summer precipitation in China: A regional model study

    E-print Network

    Wang, Yuqing

    Effect of mesoscale topography over the Tibetan Plateau on summer precipitation in China 2008; accepted 27 August 2008; published 8 October 2008. [1] The effect of mesoscale topography over and topography. In the sensitivity simulation, the mesoscale feature in topography over the TP was smoothed out

  8. Reconstructed Paleo-topography of the Columbia Hills, Mars

    NASA Astrophysics Data System (ADS)

    Cole, S. B.; Watters, W. A.; Aron, F.; Squyres, S. W.

    2013-12-01

    From June 2004 through March 2010, the Mars Exploration Rover Spirit conducted a detailed campaign examining the Columbia Hills of Gusev Crater. In addition to mineralogical and chemical investigations, Spirit's stereo panoramic (Pancam) and navigation (Navcam) cameras obtained over 7,000 images of geologic targets along the West Spur of the Columbia Hills and Husband Hill, the highest peak. We have analyzed the entirety of this dataset, which includes stereo coverage of several outcrop exposures with apparent bedding. We have measured the bedding plane orientations of hundreds of fine-scale (~1-100cm) features on all of the potentially in-place outcrops using Digital Terrain Models (DTMs) derived from the rover's Pancam stereo image data, and mapped these orientations on a regional HiRISE image and DTM. Assuming that the bedding material was deposited conformably on the topography at the time of emplacement, we reconstruct the paleo-topography of the Columbia Hills. Our reconstructed paleo-topography is similar to the modern shape of Husband Hill, but with steeper slopes, consistent with a substantial amount of erosion since deposition. The Columbia Hills are an irregular, nearly-triangular edifice of uncertain origin, situated near the center of the 160km-diameter crater and hypothesized to be either the remnant of a central peak structure, or overlapping crater rims. They span ~6.6 km in the northerly direction by ~3.6 km in the easterly direction, and rise 90m above the basaltic plains that fill the floor of Gusev Crater and embay the Hills. The topography is as irregular as the perimeter, and is cut by numerous valleys of varying lengths, widths, and directional trends. Along the traverse, Spirit examined several rock classes as defined by elemental abundances from the Alpha Particle X-ray Spectrometer (APXS) and identified remotely by the Miniature Thermal Emission Spectrometer (Mini-TES). Unlike the Gusev Plains, the rocks of the Columbia Hills show extensive evidence of aqueous alteration. Many of the outcrops are believed to have formed from volcanic and/or impact-related airfall material, which should drape the topography that existed at the time of emplacement. Outcrop bedding plane orientations are not consistent with the depositional material draping the current Columbia Hills edifice: dip magnitudes are steeper than the modern topographic slopes, and dip directions are not correlated with the modern topographic slope directions. There are, however, regional trends consistent with the outcrops draping an ancient underlying topography. Planes representing compositionally similar outcrops on the modern Husband Hill summit and to the northwest converge over the modern Tennessee Valley. If the paleo-structure culminated in the peak suggested by the bedding plane orientations, up to 100m of material may have been removed from the Columbia Hills.

  9. Topography and biological noise determine acoustic detectability on coral reefs

    NASA Astrophysics Data System (ADS)

    Cagua, E. F.; Berumen, M. L.; Tyler, E. H. M.

    2013-12-01

    Acoustic telemetry is an increasingly common tool for studying the movement patterns, behavior and site fidelity of marine organisms, but to accurately interpret acoustic data, the variability, periodicity and range of detectability between acoustic tags and receivers must be understood. The relative and interactive effects of topography with biological and environmental noise have not been quantified on coral reefs. We conduct two long-term range tests (1- and 4-month duration) on two different reef types in the central Red Sea to determine the relative effect of distance, depth, topography, time of day, wind, lunar phase, sea surface temperature and thermocline on detection probability. Detectability, as expected, declines with increasing distance between tags and receivers, and we find average detection ranges of 530 and 120 m, using V16 and V13 tags, respectively, but the topography of the reef can significantly modify this relationship, reducing the range by ~70 %, even when tags and receivers are in line-of-sight. Analyses that assume a relationship between distance and detections must therefore be used with care. Nighttime detection range was consistently reduced in both locations, and detections varied by lunar phase in the 4-month test, suggesting a strong influence of biological noise (reducing detection probability up to 30 %), notably more influential than other environmental noises, including wind-driven noise, which is normally considered important in open-water environments. Analysis of detections should be corrected in consideration of the diel patterns we find, and range tests or sentinel tags should be used for more than 1 month to quantify potential changes due to lunar phase. Some studies assume that the most usual factor limiting detection range is weather-related noise; this cannot be extrapolated to coral reefs.

  10. Linking topography to tonotopy in the mouse auditory thalamocortical circuit

    PubMed Central

    Hackett, Troy A.; Barkat, Tania Rinaldi; O’Brien, Barbara MJ.; Hensch, Takao K.; Polley, Daniel B.

    2011-01-01

    The mouse sensory neocortex is reported to lack several hallmark features of topographic organization such as ocular dominance and orientation columns in primary visual cortex or fine-scale tonotopy in primary auditory cortex (AI). Here, we re-examined the question of auditory functional topography by aligning ultra-dense receptive field maps from the auditory cortex and thalamus of the mouse in vivo with the neural circuitry contained in the auditory thalamocortical slice in vitro. We observed precisely organized tonotopic maps of best frequency (BF) in the middle layers of AI and the anterior auditory field (AAF) as well as in ventral and medial divisions of the medial geniculate body (MGBv, MGBm). Tracer injections into distinct zones of the BF map in AI retrogradely labeled topographically organized MGBv projections and weaker, mixed projections from MGBm. Stimulating MGBv along the tonotopic axis in the slice produced an orderly shift of voltage-sensitive dye (VSD) signals along the AI tonotopic axis, demonstrating topography in the mouse thalamocortical circuit that is preserved in the slice. However, compared to BF maps of neuronal spiking activity, the topographic order of sub-threshold VSD maps was reduced in layer IV and even further degraded in layer II/III. Therefore, the precision of AI topography varies according to the source and layer of the mapping signal. Our findings further bridge the gap between in vivo and in vitro approaches for the detailed cellular study of auditory thalamocortical circuit organization and plasticity in the genetically tractable mouse model. PMID:21414920

  11. Spatial and temporal patterns of Cenozoic dynamic topography around Australia

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    Despite its importance, the spatial and temporal pattern of dynamic topography generated by mantle convective circulation is poorly known. We present accurate estimates of dynamic topography from oceanic basins and continental margins surrounding Australia. Our starting point is measurement of residual depth anomalies on the oldest oceanic floor adjacent to the continental shelf. These anomalies were determined from a combined dataset of ~200 seismic reflection and wide-angle images of well-sedimented oceanic crust. They have amplitudes of between -1 km and +0.5 km, and their spatial variation is broadly consistent with long-wavelength free-air gravity and shallow seismic tomographic anomalies. Along the Northwest Shelf, a regional depth anomaly of -300 to -700 m intersects the adjacent continental shelf. The temporal evolution of this anomaly was determined by analyzing the stratigraphic architecture of an extensive carbonate platform, which fringes the shelf and records a dramatic switch from progradation to aggradation during Neogene times. Three-dimensional seismic mapping calibrated by boreholes was used to calculate water-loaded subsidence histories at rollover points of clinoforms along the shelf. At 9 ± 3 Ma, the rate of subsidence increases from 5 to up 75 m Myr-1, generating a subsidence anomaly of -300 to -700 m. The amplitude of this anomaly varies along the shelf and cannot be generated by glacio-eustatic sea-level variation. Instead, we propose that a regional subsidence episode, which affects both the proximal shelf and the distal oceanic basin, was generated by convective drawdown. By combining our results with other published estimates of uplift and subsidence, a map of Australia, which shows the spatial and temporal pattern of dynamic topography is presented. Most, but not all, of Australia's epeirogeny can be attributed to rapid northward motion of the Australian plate over a pre-existing pattern of convective circulation.

  12. Development of topography in 3-D continental-collision models

    NASA Astrophysics Data System (ADS)

    Pusok, A. E.; Kaus, Boris J. P.

    2015-05-01

    Understanding the formation and evolution of high mountain belts, such as the Himalayas and the adjacent Tibetan Plateau, has been the focus of many tectonic and numerical models. Here we employ 3-D numerical simulations to investigate the role that subduction, collision, and indentation play on lithosphere dynamics at convergent margins, and to analyze the conditions under which large topographic plateaus can form in an integrated lithospheric and upper mantle-scale model. Distinct dynamics are obtained for the oceanic subduction side (trench retreat, slab rollback) and the continental-collision side (trench advance, slab detachment, topographic uplift, lateral extrusion). We show that slab pull alone is insufficient to generate high topography in the upper plate, and that external forcing and the presence of strong blocks such as the Tarim Basin are necessary to create and shape anomalously high topographic fronts and plateaus. Moreover, scaling is used to predict four different modes of surface expression in continental-collision models: (I) low-amplitude homogeneous shortening, (II) high-amplitude homogeneous shortening, (III) Alpine-type topography with topographic front and low plateau, and (IV) Tibet-Himalaya-type topography with topographic front and high plateau. Results of semianalytical models suggest that the Argand number governs the formation of high topographic fronts, while the amplitude of plateaus is controlled by the initial buoyancy ratio of the upper plate. Applying these results to natural examples, we show that the Alps belong to regime (III), the Himalaya-Tibet to regime (IV), whereas the Andes-Altiplano fall at the boundary between regimes (III) and (IV).

  13. Topography of borosilicate glass reacting interface under aqueous corrosion

    NASA Astrophysics Data System (ADS)

    Delaye, J. M.; Kerrache, A.; Gin, S.

    2013-11-01

    Molecular dynamics simulations were performed to calculate the structure of a Na-borosilicate glass. The topography of an initial flat surface of this glass caused by the instantaneous release of atoms weakly bonded to the silicate network was studied, giving the minimum roughness of the surface. The resulting profiles were compared to experimental data obtained by atom probe tomography on a complex nuclear glass, after having verified that simulations are valid for the complex glass. As experimental profiles are much thicker, these comparisons support the concept that interdiffusion is a key mechanism controlling the long-term corrosion rate of nuclear glasses.

  14. EAARL Coastal Topography--Cape Canaveral, Florida, 2009: First Surface

    USGS Publications Warehouse

    Bonisteel-Cormier, J.M.; Nayegandhi, Amar; Plant, Nathaniel; Wright, C.W.; Nagle, D.B.; Serafin, K.S.; Klipp, E.S.

    2011-01-01

    These remotely sensed, geographically referenced elevation measurements of lidar-derived first-surface (FS) topography datasets were produced collaboratively by the U.S. Geological Survey (USGS), St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Kennedy Space Center, FL. This project provides highly detailed and accurate datasets of a portion of the eastern Florida coastline beachface, acquired on May 28, 2009. 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 multispectral color-infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit, which provide for sub-meter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine aircraft, but the instrument was deployed on a Pilatus PC-6. 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 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 sub-aerial topography. Specialized filtering algorithms have been implemented to determine the "bare earth" under vegetation from a point cloud of last return elevations.

  15. Gravity Field, Topography, and Interior Structure of Amalthea

    NASA Astrophysics Data System (ADS)

    Anderson, J. D.; Anabtawi, A.; Jacobson, R. A.; Johnson, T. V.; Lau, E. L.; Moore, W. B.; Schubert, G.; Taylor, A. H.; Thomas, P. C.; Weinwurm, G.

    2002-12-01

    A close Galileo flyby of Jupiter's inner moon Amalthea (JV) occurred on 5 November 2002. The final aimpoint was selected by the Galileo Radio Science Team on 5 July 2002. The closest approach distance for the selected aimpoint was 221 km from the center of mass, the latitude was - 45.23 Deg and the west longitude was 266.41 Deg (IAU/IAG/COSPAR cartographic coordinate system). In order to achieve an acceptable impact probability (0.15%), and yet fly close to Amalthea, the trajectory was selected from a class of trajectories running parallel to Amalthea's long axis. The Deep Space Network (DSN) had the capability to generate continuous coherent radio Doppler data during the flyby. Such data can be inverted to obtain information on Amalthea's gravity field. Amalthea is irregular and neither a triaxial ellipsoid nor an equilibrium body. It has a volume of about 2.4 x 106 km3, and its best-fit ellipsoid has dimensions 131x73x67 km. Its mass can be determined from the 2002 flyby, and in combination with the volume, a density can be obtained accurate to about 5%, where the error is dominated by the volume uncertainty. Similarly, gravity coefficients (Cnm Snm) can be detected up to fourth degree and order, and the second degree field (quadrupole) can be measured. Topography data are available from Voyager imaging and from images taken with Galileo's solid state imaging system at various times between February and June 1997. By combining the gravity and topography data, new information can be obtained on Amalthea's interior. For example if the gravity coefficients agree with those calculated from the topography, assuming constant density, we can conclude that Amalthea is homogeneous. On the other hand, if the gravity coefficients are smaller than predicted from topography, we can conclude that there is a concentration of mass toward Amalthea's center. We are presenting preliminary pre-publication results at the Fall meeting. This work was sponsored by the Galileo Project and was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. G.S., P.C.T., and W.B.M. acknowledge support by grants from NASA under the Planetary Geology and Geophysics program. G.W. is a visiting PhD student at JPL, May 2002 - May 2003, and acknowledges support from the Austrian Ministry for Technology and a Zonta - Amelia Earhart fellowship.

  16. EAARL Coastal Topography-Pearl River Delta 2008: First Surface

    USGS Publications Warehouse

    Nayegandhi, Amar; Brock, John C.; Wright, C. Wayne; Miner, Michael D.; Michael, D.; Yates, Xan; Bonisteel, Jamie M.

    2009-01-01

    These remotely sensed, geographically referenced elevation measurements of Lidar-derived first surface (FS) topography were produced as a collaborative effort between the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL; the University of New Orleans (UNO), Pontchartrain Institute for Environmental Sciences (PIES), New Orleans, LA; and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of a portion of the Pearl River Delta in Louisiana and Mississippi, acquired March 9-11, 2008. 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 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. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

  17. Estimating Titan Surface Topography from Cassini Synthetic Aperture RADAR Data

    NASA Astrophysics Data System (ADS)

    Stiles, B. W.; Hensley, S.; Gim, Y.; Kirk, R. L.; Zebker, H. A.; Janssen, M. A.; Johnson, W. T.; West, R. D.

    2007-12-01

    One of the more vexing dilemmas for RADAR remote sensing is the necessity to choose between altimetry and SAR imaging of a surface. Coincident surface height estimates are very useful in aiding the analysis of the unique surface features observed in the SAR imagery of Titan. Radar altimetry is optimally obtained from nadir observations, whereas SAR requires off-nadir observation in order to construct an image. Co-located nadir altimetry and SAR only occur when observations taken at different times happen to overlap. Stereo techniques can also be used to estimate topography in SAR images, but they also require multiple overlapping observations. Here we discuss a technique, SARTopo, for obtaining 10 km horizontal resolution and 75 m vertical resolution surface height estimates along each SAR swath. The height estimates comprise 1-3 cuts in each SAR pass that are 10 km wide by thousands of km long and extend along the entire long dimension of the SAR image strips. Because we obtain co-located topography along each SAR pass rather than only in regions with overlapping observations, the new technique extends the area over which we have colocated topography and SAR imagery by a couple orders of magnitude. The method is based upon Amplitude Monopulse Comparison, a technique for resolving RADAR targets developed prior to the advent of SAR. The technique requires: 1) accurate spacecraft pointing, 2) accurate spacecraft ephemeris, 3) precise knowledge of the antenna pattern of the RADAR, and 4) downlinked echo data covering the entire antenna footprint. The fourth requirement is met through synergy with Cassini SAR coverage requirements. Cassini SAR commanding and pointing is designed to utilize as much of the antenna footprint as possible in order to maximize cross-track coverage. We describe the technique and present the results for several SAR passes. We validate the technique through comparison with known features such as mountain ranges and dry lakes, and by comparison with colocated nadir altimetry and SAR stereo. In particular, we examine a strip of nadir altimetry obtained along a 1000 km strip observed by SAR a month earlier. The SARTopo height track is within 5-10 km of the nadir altimetry track for a 200 km long section. In this area, the two independent techniques agree closely. Furthermore the region contains prominent high spatial resolution topography, so it provides an excellent test of the resolution and accuracy of both techniques. SARTopo heights are also co-located and agree well with SAR stereo observations. The research described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

  18. Pre-glacial topography of the European Alps

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    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.

  19. Effect of Upper Eyelid Surgery on Corneal Topography

    Microsoft Academic Search

    Martin S. Zinkernagel; Andreas Ebneter; Dagmar Ammann-Rauch

    2007-01-01

    neal topography before surgery and at 3 months after sur- gery. Patients were divided into groups depending on the extent of surgery. In addition, the thickness of the central cornea was correlated with the change in astigmatism. Results: There were mean changes in total astigmatism of0.25diopter(D)afterptosissurgery(P=.02)and0.21D afterblepharoplastywithreductionoflargefatpads(P=.04) compared with 0.09 D in patients after skin-only blepha- roplasty.Inaddition,therewasacorrelationbetweencor- nealthicknessandchangeinastigmatismofmorethan0.2 cylinders after

  20. EAARL Topography - Vicksburg National Military Park 2008: Bare Earth

    USGS Publications Warehouse

    Nayegandhi, Amar; Brock, John C.; Wright, C. Wayne; Segura, Martha; Yates, Xan

    2008-01-01

    These remotely sensed, geographically referenced elevation measurements of Lidar-derived bare earth (BE) 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), Gulf Coast Network, Lafayette, LA; and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of the Vicksburg National Military Park in Mississippi, acquired on March 6, 2008. 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 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. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

  1. EAARL Coastal Topography-Pearl River Delta 2008: Bare Earth

    USGS Publications Warehouse

    Nayegandhi, Amar; Brock, John C.; Wright, C. Wayne; Miner, Michael D.; Yates, Xan; Bonisteel, Jamie M.

    2009-01-01

    These remotely sensed, geographically referenced elevation measurements of Lidar-derived bare earth (BE) topography were produced as a collaborative effort between the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL; the University of New Orleans (UNO), Pontchartrain Institute for Environmental Sciences (PIES), New Orleans, LA; and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of a portion of the Pearl River Delta in Louisiana and Mississippi, acquired March 9-11, 2008. 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 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. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

  2. EAARL Coastal Topography-Chandeleur Islands, Louisiana, 2010: Bare Earth

    USGS Publications Warehouse

    Nayegandhi, Amar; Bonisteel-Cormier, Jamie M.; Brock, John C.; Sallenger, A.H.; Wright, C. Wayne; Nagle, David B.; Vivekanandan, Saisudha; Yates, Xan; Klipp, Emily S.

    2010-01-01

    These remotely sensed, geographically referenced elevation measurements of lidar-derived bare-earth (BE) and submerged topography datasets were produced collaboratively by the U.S. Geological Survey (USGS), St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of a portion of the Chandeleur Islands, acquired March 3, 2010. 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 multispectral color-infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit, which provide for sub-meter 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 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 sub-aerial topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations. For more information about similar projects, please visit the Decision Support for Coastal Science and Management website.

  3. EAARL Coastal Topography - Northern Gulf of Mexico, 2007: Bare Earth

    USGS Publications Warehouse

    Smith, Kathryn E.L.; Nayegandhi, Amar; Wright, C. Wayne; Bonisteel, Jamie M.; Brock, John C.

    2009-01-01

    These remotely sensed, geographically referenced elevation measurements of Lidar-derived bare earth (BE) 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), Gulf Coast Network, Lafayette, LA; and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. The purpose of this project is to provide highly detailed and accurate datasets of select barrier islands and peninsular regions of Louisiana, Mississippi, Alabama, and Florida, acquired on June 27-30, 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 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 sub-aerial topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

  4. EAARL Coastal Topography - Northeast Barrier Islands 2007: Bare Earth

    USGS Publications Warehouse

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

    2008-01-01

    These remotely sensed, geographically referenced elevation measurements of Lidar-derived bare earth (BE) 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 northeast coastal barrier islands in New York and New Jersey, acquired April 29-30 and May 15-16, 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 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 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.

  5. River slope connects modern topography with ancient tectonics

    NASA Astrophysics Data System (ADS)

    Wendel, JoAnna

    2014-12-01

    Scientists believe that topographic features are shaped by the tectonic history of the surrounding environment. However, although models exist that relate a known tectonic history to the expected shape of the rivers, the opposite problem of finding the tectonic history that resulted in an observed river-dominated landscape remains challenging. Past researchers have used smoothing of topographic data to find averages of tectonic information or have attempted many different tectonic histories and compared their expected output against the real topography. Now, Goren et al. have expanded on these methods with two new models.

  6. The effect of Gonioscopy on keratometry and corneal surface topography

    PubMed Central

    George, Mathew K; Kuriakose, Thomas; DeBroff, Brian M; Emerson, John W

    2006-01-01

    Background Biometric procedures such as keratometry performed shortly after contact procedures like gonioscopy and applanation tonometry could affect the validity of the measurement. This study was conducted to understand the short-term effect of gonioscopy on corneal curvature measurements and surface topography based Simulated Keratometry and whether this would alter the power of an intraocular lens implant calculated using post-gonioscopy measurements. We further compared the effect of the 2-mirror (Goldmann) and the 4-mirror (Sussman) Gonioscopes. Methods A prospective clinic-based self-controlled comparative study. 198 eyes of 99 patients, above 50 years of age, were studied. Exclusion criteria included documented dry eye, history of ocular surgery or trauma, diabetes mellitus and connective tissue disorders. Auto-Keratometry and corneal topography measurements were obtained at baseline and at three follow-up times – within the first 5 minutes, between the 10th-15th minute and between the 20th-25th minute after intervention. One eye was randomized for intervention with the 2-mirror gonioscope and the other underwent the 4-mirror after baseline measurements. t-tests were used to examine differences between interventions and between the measurement methods. The sample size was calculated using an estimate of clinically significant lens implant power changes based on the SRK-II formula. Results Clinically and statistically significant steepening was observed in the first 5 minutes and in the 10–15 minute interval using topography-based Sim K. These changes were not present with the Auto-Keratometer measurements. Although changes from baseline were noted between 20 and 25 minutes topographically, these were not clinically or statistically significant. There was no significant difference between the two types of gonioscopes. There was greater variability in the changes from baseline using the topography-based Sim K readings. Conclusion Reversible steepening of the central corneal surface is produced by the act of gonioscopy as measured by Sim K, whereas no significant differences were present with Auto-K measurements. The type of Gonioscope used does not appear to influence these results. If topographically derived Sim K is used to calculate the power of the intraocular lens implant, we recommend waiting a minimum of 20 minutes before measuring the corneal curvature after gonioscopy with either Goldmann or Sussman contact lenses. PMID:16780595

  7. Large-eddy simulation of a curved open-channel flow over topography

    Microsoft Academic Search

    W. van Balen; W. S. J. Uijttewaal; K. Blanckaert

    2010-01-01

    Large-eddy simulation (LES) is performed of a curved open-channel flow over topography based on the laboratory experiment by Blanckaert [“Topographic steering, flow circulation, velocity redistribution and bed topography in sharp meander bends,” Water Resour. Res., doi:10.1029\\/2009WR008303 (in press)]. In the experiment, the large-scale bed topography had developed to a more or less stationary shape which was prescribed in the LES

  8. Large-eddy simulation of a curved open-channel flow over topography

    Microsoft Academic Search

    W. van Balen; W. S. J. Uijttewaal; K. Blanckaert

    2010-01-01

    Large-eddy simulation (LES) is performed of a curved open-channel flow over topography based on the laboratory experiment by Blanckaert [``Topographic steering, flow circulation, velocity redistribution and bed topography in sharp meander bends,'' Water Resour. Res., doi:10.1029\\/2009WR008303 (in press)]. In the experiment, the large-scale bed topography had developed to a more or less stationary shape which was prescribed in the LES

  9. Moho topography beneath the Corinth Rift area (Greece) from inversion of gravity data

    E-print Network

    Demouchy, Sylvie

    Moho topography beneath the Corinth Rift area (Greece) from inversion of gravity data C. Tiberi,1 to Miocene lithospheric instabilities. Key words: boudinage, continental rifts, gravity inversion, Greece

  10. Internal structure of Io and the global distribution of its topography

    NASA Astrophysics Data System (ADS)

    Ross, M. N.; Schubert, G.; Spohn, T.; Gaskell, R. W.

    1990-06-01

    A global topography is presently calculated for two multilayer Io models in which dissipation occurs in a viscous asthenosphere and a solid mantle: (1) a 'thermal swell' model, in which topography and heat flow are positively correlated, and (2) a 'differentiated lithosphere' model, in which topography and heat flow are negatively correlated. Both the polar topography and the hypsometric distribution of elevations in the differentiated lithosphere model are better matched with observations than the thermal swell model. The shift of the equatorial basin-swell pattern indicates a recent zonal rotation of about 25 deg for Io's lithosphere.

  11. Topography of striate-extrastriate connections in neonatally enucleated rats.

    PubMed

    Laing, Robyn J; Lasiene, Jurate; Olavarria, Jaime F

    2013-01-01

    It is known that retinal input is necessary for the normal development of striate cortex and its corticocortical connections, but there is little information on the role that retinal input plays in the development of retinotopically organized connections between V1 and surrounding visual areas. In nearly all lateral extrastriate areas, the anatomical and physiological representation of the nasotemporal axis of the visual field mirrors the representation of this axis in V1. To determine whether the mediolateral topography of striate-extrastriate projections is preserved in neonatally enucleated rats, we analyzed the patterns of projections resulting from tracer injections placed at different sites along the mediolateral axis of V1. We found that the correlation between the distance from injection sites to the lateral border of V1 and the distance of the labeling patterns in area 18a was strong in controls and much weaker in enucleates. Data from pairs of injections in the same animal revealed that the separation of area 18a projection fields for a given separation of injection sites was more variable in enucleated than in control rats. Our analysis of single and double tracer injections suggests that neonatal bilateral enucleation weakens, but not completely abolishes, the mediolateral topography in area 18a. PMID:24199194

  12. Topography of Striate-Extrastriate Connections in Neonatally Enucleated Rats

    PubMed Central

    Laing, Robyn J.; Lasiene, Jurate; Olavarria, Jaime F.

    2013-01-01

    It is known that retinal input is necessary for the normal development of striate cortex and its corticocortical connections, but there is little information on the role that retinal input plays in the development of retinotopically organized connections between V1 and surrounding visual areas. In nearly all lateral extrastriate areas, the anatomical and physiological representation of the nasotemporal axis of the visual field mirrors the representation of this axis in V1. To determine whether the mediolateral topography of striate-extrastriate projections is preserved in neonatally enucleated rats, we analyzed the patterns of projections resulting from tracer injections placed at different sites along the mediolateral axis of V1. We found that the correlation between the distance from injection sites to the lateral border of V1 and the distance of the labeling patterns in area 18a was strong in controls and much weaker in enucleates. Data from pairs of injections in the same animal revealed that the separation of area 18a projection fields for a given separation of injection sites was more variable in enucleated than in control rats. Our analysis of single and double tracer injections suggests that neonatal bilateral enucleation weakens, but not completely abolishes, the mediolateral topography in area 18a. PMID:24199194

  13. Three Dimensional Surface Topography Using LCD Pattern Transfer Method

    NASA Astrophysics Data System (ADS)

    Gatabi, Javad R.; Geerts, Wilhelmus; Aaron, Bryant; Tamir, Dan; Pandey, R. K.

    2012-03-01

    Laser lithography on curved surfaces has recently been researched due to its applicability in production processes for devices that combine integrated optical, mechanical, magnetic, and/or electronic technologies. Several laser lithography methods have been reported for pattern transfer to convex and cylindrical surfaces, but there is not a general methodology for arbitrary 3D surface lithography. This project implements an optical method for laser lithography on arbitrary 3D surfaces. An illumination pattern generated by a transparent LCD is projected through an optical microscope on top of a 3D surface and recorded by a camera. The focus quality and the distortion of the observed image depend on the local topography of the sample. The effect of the local sample topography on the projected pattern is theoretically investigated using Zemax ray-tracing software. Analysis are made for amplitude and phase modulation LCDs with different resolutions and compared with preliminary experimental results. The authors acknowledge financial support from NSF through an MRI-grant (grant: 0923506).

  14. Sentinel-3 Surface Topography Mission (STM) User Data Products

    NASA Astrophysics Data System (ADS)

    Nogueira Loddo, Carolina; Scharroo, Remko; Wilson, Hilary; Bonekamp, Hans

    2015-04-01

    The Sentinel-3 Surface Topography Mission (STM) is a key component of the Copernicus Sentinel-3 mission, set to revolutionise operational oceanography with a suite of advanced surface topography data products over ocean and sea sea-ice. In addition the STM will collect data over all earth surfaces providing improved monitoring of River and Lake stage heights and inputs to the development of Digital Elevation Models. Sentinel-3 will be the first Earth Observation mission to provide 100% SAR altimetry coverage and LRM will be maintained as a backup operating mode. In order to fully exploit the SAR capability, and validating the algorithms evolution, lower level data products (L1A, L1B and L1B-S) will be made available to the users, in addition to the level 2 products. This poster provides an overview of the S-3 STM data products that will be generated operationally within the Sentinel-3 Payload Data Ground Segment by the Instrument Processing Facilities (IPFs), and disseminated to the users.

  15. Lunar Topography: Results from the Lunar Orbiter Laser Altimeter

    NASA Technical Reports Server (NTRS)

    Neumann, Gregory; Smith, David E.; Zuber, Maria T.; Mazarico, Erwan

    2012-01-01

    The Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter (LRO) has been operating nearly continuously since July 2009, accumulating over 6 billion measurements from more than 2 billion in-orbit laser shots. LRO's near-polar orbit results in very high data density in the immediate vicinity of the lunar poles, with full coverage at the equator from more than 12000 orbital tracks averaging less than 1 km in spacing at the equator. LRO has obtained a global geodetic model of the lunar topography with 50-meter horizontal and 1-m radial accuracy in a lunar center-of-mass coordinate system, with profiles of topography at 20-m horizontal resolution, and 0.1-m vertical precision. LOLA also provides measurements of reflectivity and surface roughness down to its 5-m laser spot size. With these data LOLA has measured the shape of all lunar craters 20 km and larger. In the proposed extended mission commencing late in 2012, LOLA will concentrate observations in the Southern Hemisphere, improving the density of the polar coverage to nearly 10-m pixel resolution and accuracy to better than 20 m total position error. Uses for these data include mission planning and targeting, illumination studies, geodetic control of images, as well as lunar geology and geophysics. Further improvements in geodetic accuracy are anticipated from the use of re ned gravity fields after the successful completion of the Gravity Recovery and Interior Laboratory (GRAIL) mission in 2012.

  16. Rejuvenation of Appalachian topography due to subsidence induced differential erosion

    NASA Astrophysics Data System (ADS)

    Liu, L.

    2014-12-01

    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 are proposed to 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. Calculations show that such subsidence-induced differential erosion caused flexural-isostatic adjustments of Appalachian topography that led to the development of both relief and elevation. I propose that dynamically induced continental tilting may provide a mechanism for topographic rejuvenation in ancient orogens.

  17. SEM-EDAX investigations of use-related microstructural changes in an ammonia synthesis catalyst

    Microsoft Academic Search

    T. Egyházi; J. Scholtz; V. S. Beskov

    1984-01-01

    Changes in the topography and distribution of the chemical constituents in the microspaces of oxide type catalysts and prereduced catalysts have been investigated by scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDAX) before and after six years of use in industrial ammonia synthesis reactors.

  18. Eye shape and retinal topography in owls (Aves: Strigiformes).

    PubMed

    Lisney, Thomas J; Iwaniuk, Andrew N; Bandet, Mischa V; Wylie, Douglas R

    2012-01-01

    The eyes of vertebrates show adaptations to the visual environments in which they evolve. For example, eye shape is associated with activity pattern, while retinal topography is related to the symmetry or 'openness' of the habitat of a species. Although these relationships are well documented in many vertebrates including birds, the extent to which they hold true for species within the same avian order is not well understood. Owls (Strigiformes) represent an ideal group for the study of interspecific variation in the avian visual system because they are one of very few avian orders to contain species that vary in both activity pattern and habitat preference. Here, we examined interspecific variation in eye shape and retinal topography in nine species of owl. Eye shape (the ratio of corneal diameter to eye axial length) differed among species, with nocturnal species having relatively larger corneal diameters than diurnal species. All the owl species have an area of high retinal ganglion cell (RGC) density in the temporal retina and a visual streak of increased cell density extending across the central retina from temporal to nasal. However, the organization and degree of elongation of the visual streak varied considerably among species and this variation was quantified using H:V ratios. Species that live in open habitats and/or that are more diurnally active have well-defined, elongated visual streaks and high H:V ratios (3.88-2.33). In contrast, most nocturnal and/or forest-dwelling owls have a poorly defined visual streak, a more radially symmetrical arrangement of RGCs and lower H:V ratios (1.77-1.27). The results of a hierarchical cluster analysis indicate that the apparent interspecific variation is associated with activity pattern and habitat as opposed to the phylogenetic relationships among species. In seven species, the presence of a fovea was confirmed and it is suggested that all strigid owls may possess a fovea, whereas the tytonid barn owl (Tyto alba) does not. A size-frequency analysis of cell soma area indicates that a number of different RGC classes are represented in owls, including a population of large RGCs (cell soma area >150 µm(2)) that resemble the giant RGCs reported in other vertebrates. In conclusion, eye shape and retinal topography in owls vary among species and this variation is associated with different activity patterns and habitat preferences, thereby supporting similar observations in other vertebrates. PMID:22722085

  19. EAARL coastal topography--Alligator Point, Louisiana, 2010

    USGS Publications Warehouse

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

    2012-01-01

    This project provides highly detailed and accurate datasets of a portion of Alligator Point, Louisiana, acquired on March 5 and 6, 2010. 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 National Aeronautics and Space Administration (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 multispectral color-infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit, which provide for sub-meter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine aircraft, but the instrument was deployed on a Pilatus PC-6. 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 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 sub-aerial topography. Specialized filtering algorithms have been implemented to determine the "bare earth" under vegetation from a point cloud of last return elevations.

  20. Different Approach to the Aluminium Oxide Topography Characterisation

    SciTech Connect

    Poljacek, Sanja Mahovic; Gojo, Miroslav [Faculty of Graphic Arts, University of Zagreb, Getaldiceva 2, 10000 Zagreb (Croatia); Raos, Pero; Stoic, Antun [Mechanical Engineering Faculty, J.J. Strossmayer University of Osijek, Trg Ivane Brlic Mazuranic 2, 35000 Slavonski Brod (Croatia)

    2007-04-07

    Different surface topographic techniques are being widely used for quantitative measurements of typical industrial aluminium oxide surfaces. In this research, specific surface of aluminium oxide layer on the offset printing plate has been investigated by using measuring methods which have previously not been used for characterisation of such surfaces. By using two contact instruments and non-contact laser profilometer (LPM) 2D and 3D roughness parameters have been defined. SEM micrographs of the samples were made. Results have shown that aluminium oxide surfaces with the same average roughness value (Ra) and mean roughness depth (Rz) typically used in the printing plate surface characterisation, have dramatically different surface topographies. According to the type of instrument specific roughness parameters should be used for defining the printing plate surfaces. New surface roughness parameters were defined in order to insure detailed characterisation of the printing plates in graphic reproduction process.

  1. Ion-beam-induced topography and surface diffusion

    NASA Technical Reports Server (NTRS)

    Robinson, R. S.; Rossnagel, S. M.

    1982-01-01

    It is pointed out that the development of surface topography along with enhanced surface and bulk diffusion processes accompanying ion bombardment have generated growing interest among users of ion beams and plasmas for thin film or material processing. Interest in these processes stems both from attempts to generate topographic changes for specific studies or applications and from the need to suppress or control undesirable changes. The present investigation provides a summary of the current status of impurity-induced texturing, with emphasis on recent developments. Particular attention is given to the texturing accompanying deposition of an impurity material onto a solid surface while simultaneously etching the surface with an ion beam. A description of experimental considerations is provided, and a thermal-diffusion model is discussed along with the development of sputter cones, and aspects of impact-enhanced surface diffusion.

  2. Epidermal structure and surface topography of canine skin.

    PubMed

    Lloyd, D H; Garthwaite, G

    1982-07-01

    The stratum corneum of canine skin when measured in cryostat sections was found to have a mean thickness of 47.5 cell layers and measured 13.3 micrometers. The living epidermis was composed of three to six cell layers and measured 10.1 micrometers. Stratum corneum thickness was similar on the back and abdomen but was greater in the inguinal fold. Lipid was found in the distal intercellular spaces of the corneum to a mean depth of 34 cell layers. The surface topography of freeze dried canine skin was examined by scanning electron microscopy. The interfollicular stratum corneum was generally covered by a thin homogeneous film but in some areas hexagonal squames surrounded by amorphous globular material, which appeared to be oozing onto the surface, could be found. This material, which was also found sealing the bases of hair follicles and matting together the emerging hairs, appeared to be sebaceous lipid. PMID:7134655

  3. Eddies contribute to striations in sea surface topography

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2013-03-01

    Scientists recently observed striations in sea surface topography in all ocean basins. These striations appear as alternating mesoscale jet-like structures; they have speeds on the order of 1 centimeter per second and are typically separated by about 200 kilometers in the meridional direction. The cause of these striations has been debated. Contributing to this scientific discussion, Buckingham and Cornillon used a database of tracked eddies and a contour identification and eddy removal algorithm to show that eddies are a significant source of striations. The authors noted that a small portion of the energy was unaccounted for by propagating eddies, allowing for the existence of weak zonal flows. (Journal of Geophysical Research-Oceans, doi:10.1029/2012JC008231, 2013)

  4. Fractal structure of lunar topography: An interpretation of topographic characteristics

    NASA Astrophysics Data System (ADS)

    Cao, Wei; Cai, Zhanchuan; Tang, Zesheng

    2015-06-01

    Over the years, fractal geometry has been applied extensively in many fields of geoscience. Based on the global gridded data generated from the Lunar Reconnaissance Orbiter, we carry out our fractal measure to interpret lunar fractures by using qualitative (similar ratio) and quantitative (fractal dimension) approaches of fractal geometry. We find that most of the lunar surface exhibits fractal behavior over the given scales ranging from 1 to 256 m. Lunar maria have higher fractal dimensions than other geological units, while those of volcanic areas and highlands are lower than their surroundings. Simple and flat surfaces have low values of similar ratios and these areas indicate low surface roughness and young ages. Older-aged areas, such as the Hertzsprung basin, have low fractal dimensions and high similar ratios by their complicated topography.

  5. Topography-guided custom ablation treatment for treatment of keratoconus

    PubMed Central

    Shetty, Rohit; D’Souza, Sharon; Srivastava, Samaresh; Ashwini, R

    2013-01-01

    Keratoconus is a progressive ectatic disorder of the cornea which often presents with fluctuating refraction and high irregular astigmatism. Correcting the vision of these patients is often a challenge because glasses are unable to correct the irregular astigmatism and regular contact lenses may not fit them very well. Topography-guided custom ablation treatment (T-CAT) is a procedure of limited ablation of the cornea using excimer laser with the aim of regularizing the cornea, improving the quality of vision and possibly contact lens fit. The aim of the procedure is not to give a complete refractive correction. It has been tried with a lot of success by various groups of refractive surgeons around the world but a meticulous and methodical planning of the procedure is essential to ensure optimum results. In this paper, we attempt to elucidate the planning for a T-CAT procedure for various types of cones and asphericities. PMID:23925335

  6. Surface topography of the optic nerve head from digital images

    NASA Astrophysics Data System (ADS)

    Mitra, Sunanda; Ramirez, M.; Morales, Jose

    1992-06-01

    A novel algorithm for three-dimensional (3-D) surface representation of the optic nerve head from digitized stereo fundus images has been developed. The 3-D digital mapping of the optic nerve head is achieved by fusion of stereo depth map of a fundus image pair with a linearly stretched intensity image of the fundus. The depth map is obtained from the disparities of the features in the stereo fundus image pair, computed by a combination of cepstral analysis and a correlation-like scanning technique in the spatial domain. At present, the visualization of the optic nerve head cupping in glaucoma is clinically achieved, in most cases, by stereoscopic viewing of a fundus image pair of the suspected eye. The quantitative representation of the optic nerve head surface topography following this algorithm is not computationally intensive and should provide more useful and reproducible information than just qualitative stereoscopic viewing of the fundus.

  7. Experience-dependent changes in the topography of visual crowding

    PubMed Central

    Williamson, Kristin; Scolari, Miranda; Jeong, SuKeun; Kim, Min-Shik; Awh, Edward

    2015-01-01

    The present work examined discrimination accuracy for targets that were presented either alone in the visual field (clean displays) or embedded within a dense array of letter distractors (crowded displays). The strength of visual crowding varied strongly across the four quadrants of the visual field. Furthermore, this spatial bias in crowding was strongly influenced by the observers’ prior experience with specific distractor stimuli. Observers who were monolingual readers of English experienced amplified crowding in the upper-left quadrant, while subjects with primary reading skills in Korean, Chinese, or Japanese tended towards worse target discrimination in the lower visual field. This interaction with language experience was eliminated when non-alphanumeric stimuli were employed as distractors, suggesting that prior reading experience induced a stimulus-specific change in the topography of visual crowding from English letters. PMID:20053078

  8. SRTM Colored and Shaded Topography: Haro and Kas Hills, India

    NASA Technical Reports Server (NTRS)

    2001-01-01

    On January 26, 2001, the Kachchh region in western India suffered the most deadly earthquake in India's history. This shaded topography view of landforms northeast of the city of Bhuj depicts geologic structures that are of interest in the study the tectonic processes that may have led to that earthquake. However, preliminary field studies indicate that these structures are composed of Mesozoic rocks that are overlain by younger rocks showing little deformation. Thus these structures may be old, not actively growing, and not directly related to the recent earthquake.

    The Haro Hills are on the left and the Kas Hills are on the right. The Haro Hills are an 'anticline,' which is an upwardly convex elongated fold of layered rocks. In this view, the anticline is distinctly ringed by an erosion resistant layer of sandstone. The east-west orientation of the anticline may relate to the crustal compression that has occurred during India's northward movement toward, and collision with, Asia. In contrast, the largest of the Kas Hills appears to be a tilted (to the south) and faulted (on the north) block of layered rocks. Also seen here, the linear feature trending toward the southwest from the image center is an erosion-resistant 'dike,' which is an igneous intrusion into older 'host' rocks along a fault plane or other crack. These features are simple examples of how shaded topography can provide a direct input to geologic studies.

    In this image, colors show the elevation as measured by the Shuttle Radar Topography Mission (SRTM). Colors range from green at the lowest elevations, through yellow and red, to purple at the highest elevations. Elevations here range from near sea level to about 300 meters (about 1000 feet). Shading has been added, with illumination from the north (image top).

    Elevation data used in this image was acquired by the Shuttle Radar Topography Mission aboard the Space Shuttle Endeavour, launched on February 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense (DoD), and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise,Washington, DC.

    Size: 26.3 x 16.6 kilometers ( 16.3 x 10.3 miles) Location: 23.4 deg. North lat., 69.8 deg. East lon. Orientation: North toward the top Date Acquired: February 2000

  9. NCAR global model topography generation software for unstructured grids

    NASA Astrophysics Data System (ADS)

    Lauritzen, P. H.; Bacmeister, J. T.; Callaghan, P. F.; Taylor, M. A.

    2015-06-01

    It is the purpose of this paper to document the NCAR global model topography generation software for unstructured grids. Given a model grid, the software computes the fraction of the grid box covered by land, the gridbox mean elevation, and associated sub-grid scale variances commonly used for gravity wave and turbulent mountain stress parameterizations. The software supports regular latitude-longitude grids as well as unstructured grids; e.g. icosahedral, Voronoi, cubed-sphere and variable resolution grids. As an example application and in the spirit of documenting model development, exploratory simulations illustrating the impacts of topographic smoothing with the NCAR-DOE CESM (Community Earth System Model) CAM5.2-SE (Community Atmosphere Model version 5.2 - Spectral Elements dynamical core) are shown.

  10. New Orleans Topography, Radar Image with Colored Height

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Click on the image for the animation

    About the animation: This simulated view of the potential effects of storm surge flooding on Lake Pontchartrain and the New Orleans area was generated with data from the Shuttle Radar Topography Mission. Although it is protected by levees and sea walls against storm surges of 18 to 20 feet, much of the city is below sea level, and flooding due to storm surges caused by major hurricanes is a concern. The animation shows regions that, if unprotected, would be inundated with water. The animation depicts flooding in one-meter increments.

    About the image: The city of New Orleans, situated on the southern shore of Lake Pontchartrain, is shown in this radar image from the Shuttle Radar Topography Mission (SRTM). In this image bright areas show regions of high radar reflectivity, such as from urban areas, and elevations have been coded in color using height data also from the SRTM mission. Dark green colors indicate low elevations, rising through yellow and tan, to white at the highest elevations.

    New Orleans is near the center of this scene, between the lake and the Mississippi River. The line spanning the lake is the Lake Pontchartrain Causeway, the world's longest overwater highway bridge. Major portions of the city of New Orleans are actually below sea level, and although it is protected by levees and sea walls that are designed to protect against storm surges of 18 to 20 feet, flooding during storm surges associated with major hurricanes is a significant concern.

    Data used in this image were acquired by the Shuttle Radar Topography Mission aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter (approximately 200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between NASA, the National Geospatial-Intelligence Agency (NGA) of the U.S. Department of Defense and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Science Mission Directorate, Washington, D.C.

    Location: 30.2 degrees North latitude, 90.1 degrees East longitude Orientation: North toward the top, Mercator projection Size: 80.3 by 68.0 kilometers (49.9 by 42.3 miles) Image Data: Radar image and colored Shuttle Radar Topography Mission elevation model Date Acquired: February 2000

  11. Geologic structure of shallow maria. [topography of lunar maria

    NASA Technical Reports Server (NTRS)

    Dehon, R. A.; Waskom, J. A.

    1975-01-01

    Isopach maps and structural contour maps of the eastern mare basins (30 deg N to 30 deg S; 0 deg to 100 deg E), constructed from measurements of partially buried craters, are presented and discussed. The data, which are sufficiently scattered to yield gross thickness variations, are restricted to shallow maria with less than 1500-2000 m of mare basalts. The average thickness of basalt in the irregular maria is between 200 and 400 m. Correlations between surface topography, basalt thickness, and basin floor structure are apparent in most of the basins that were studied. The mare surface is commonly depressed in regions of thick mare basalts; mare ridges are typically located in regions of pronounced thickness changes; and arcuate mare rilles are confined to thin mare basalts. Most surface structures are attributed to shallow stresses developed within the mare basalts during consolidation and volume reduction.

  12. The Shuttle Radar Topography Mission: A Global DEM

    NASA Technical Reports Server (NTRS)

    Farr, Tom G.; Kobrick, Mike

    2000-01-01

    Digital topographic data are critical for a variety of civilian, commercial, and military applications. Scientists use Digital Elevation Models (DEM) to map drainage patterns and ecosystems, and to monitor land surface changes over time. The mountain-building effects of tectonics and the climatic effects of erosion can also be modeled with DEW The data's military applications include mission planning and rehearsal, modeling and simulation. Commercial applications include determining locations for cellular phone towers, enhanced ground proximity warning systems for aircraft, and improved maps for backpackers. The Shuttle Radar Topography Mission (SRTM) (Fig. 1), is a cooperative project between NASA and the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense. The mission is designed to use a single-pass radar interferometer to produce a digital elevation model of the Earth's land surface between about 60 degrees north and south latitude. The DEM will have 30 m pixel spacing and about 15 m vertical errors.

  13. Forecasting hurricane impact on coastal topography: Hurricane Ike

    USGS Publications Warehouse

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

    2010-01-01

    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.

  14. Observation of the floor surface topography changes in pedestrian slip resistance measurements

    Microsoft Academic Search

    In-Ju Kim; Richard Smith

    2000-01-01

    This study is concerned with the changes of the floor surface topography in the early stage of repetitive wear rubbings and the relationships between slip resistance properties and operationally defined geometric characteristics of the floor surfaces. It was assumed that: (1) alterations in surface topography will be associated with changes in the DFC; and (2) wear process will be accompanied

  15. Gravity-Driven flow of evaporating thin liquid films over substrates with topography

    E-print Network

    Jimack, Peter

    ) into the flow Figure 1: Gravity-driven flow down an inclined plane with topography of thin water films over #12;a thin layer of liquid, thickness h(x,y), flows over a topography s(x,y) on a substrate inclined inclined substrates and extends the recent numerical analysis of these flows, by (Gaskell et al 2003b

  16. Accuracy and resolution of shuttle radar topography mission data Bridget Smith and David Sandwell

    E-print Network

    Sandwell, David T.

    ascending and descending C-band swaths from the Shuttle interferometer were processed into a digitalAccuracy and resolution of shuttle radar topography mission data Bridget Smith and David Sandwell provided by the Shuttle Radar Topography Mission (SRTM) through spectral comparisons with the National

  17. Crustal structure of Mars from gravity and topography G. A. Neumann,1,2

    E-print Network

    Wieczorek, Mark

    MGS missions and the early phases of the Mars Odyssey mission. In the present study we exploitCrustal structure of Mars from gravity and topography G. A. Neumann,1,2 M. T. Zuber,1,2 M. A; accepted 11 June 2004; published 10 August 2004. [1] Mars Orbiter Laser Altimeter (MOLA) topography

  18. Corneal Topography: A review, new ANSI standards and problems to solve Stanley A. Klein

    E-print Network

    Klein, Stanley

    Corneal Topography: A review, new ANSI standards and problems to solve Stanley A. Klein School@spectacle.berkeley.edu Abstract: This review of corneal topography has three sections: 1. a brief introduction to how corneal. The presence of tear film irregularities will distort the interference pattern. Small deviations in corneal

  19. New possibilities of synchrotron radiation diffraction topography for the investigation of `exotic' magnetic domains

    Microsoft Academic Search

    J. Baruchel; P. C. de Camargo; H. Klein; I. Mazzaro; J. Nogues; A. de Oliveira

    2001-01-01

    Synchrotron radiation topography on modern sources, coupled with adequate CCD detectors, is producing (in a shorter time and with better resolution) results which could only be obtained, up to now, by using neutron topography. This is shown by two examples, carried out at the ESRF, on `exotic' antiferromagnetic domains: (1) the imaging of 180° antiferromagnetic domains in cobalt fluoride is

  20. Lithospheric topography, tilted plumes, and the track of the Snake RiverYellowstone hot spot

    E-print Network

    Shervais, John W.

    Lithospheric topography, tilted plumes, and the track of the Snake River­Yellowstone hot spot John; published 24 September 2008. [1] The trace of the Snake River­Yellowstone hot spot is the world's best), Lithospheric topography, tilted plumes, and the track of the Snake River­Yellowstone hot spot, Tectonics, 27

  1. Coremantle boundary topography as a possible constraint on lower mantle chemistry and dynamics

    E-print Network

    Rhoads, James

    Core­mantle boundary topography as a possible constraint on lower mantle chemistry and dynamics November 2009 Editor: Y. Ricard Keywords: mantle convection core­mantle boundary CMB topography) in the lowermost mantle beneath the central Pacific and Africa is not well constrained. We explore numerical

  2. Representation of Topography by Shaved Cells in a Height Coordinate Ocean Model

    Microsoft Academic Search

    Alistair Adcroft; Chris Hill; John Marshall

    1997-01-01

    Height coordinate ocean models commonly represent topography as a ''staircase'' of discontinuous steps that are fitted to the model grid. Here the ramifications of an alternative approach are studied in which ''shaved cells'' are used to represent irregular topography. The problem is formulated using the finite-volume method and care is taken to ensure that the discrete forms have appropriate conservation

  3. The effect of atmospheric CO 2 and ice sheet topography on LGM climate

    Microsoft Academic Search

    S. J. Kim

    2004-01-01

    The role of reduced atmospheric CO 2 concentration and ice sheet topography plus its associated land albedo on the LGM climate is investigated using a coupled atmosphere-ocean-sea ice climate system model. The surface cooling induced by the reduced CO 2 concentration is larger than that by the ice sheet topography plus other factors by about 30% for the surface air

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

    E-print Network

    Steinberger, Bernhard

    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

  5. Modeling the dynamic component of the geoid and topography of Venus

    E-print Network

    Cerveny, Vlastislav

    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

  6. Large Eddy Simulation and Snow Transport over three-dimensional topography

    Microsoft Academic Search

    M. Diebold; C. W. Higgins; M. Lehning; M. B. Parlange

    2010-01-01

    A new generation Large-Eddy Simulation (LES) is applied to study wind fields and the influence of local topography. In this study we first focus on the implementation of three-dimensional topography in our LES algorithm using an immersed boundary method. To validate this model, the LES results are compared with measurements from wind tunnel studies taken from the literature. Simulations and

  7. Plasma molding over surface topography: Energy and angular distribution of ions extracted out of large holes

    E-print Network

    Economou, Demetre J.

    Plasma molding over surface topography: Energy and angular distribution of ions extracted out of large holes Chang-Koo Kim and Demetre J. Economoua) Plasma Processing Laboratory, Department of Chemical November 2001 Plasma molding over surface topography was investigated by measuring the energy and angular

  8. The role of topography in promoting fractal patchiness in a carbonate shelf landscape

    E-print Network

    Purkis, Sam

    using high-resolution terrain models built using bathymetric LiDAR soundings of the shallow Puerto Rico Topography Á Fractional Brownian motion Á LiDAR Á Remote sensing Introduction A reef's surface topography such as the spatiotemporal Communicated by Geology Editor Dr. Bernhard Riegl S. J. Purkis (&) Á K. E. Kohler National Coral

  9. SEASAT-Derived Ocean Surface Topography: Comparison With Coincident Kuroshio Hydrographic Data

    Microsoft Academic Search

    H. Michael Byrne; Patricia E. Pullen

    1983-01-01

    During the SEASAT repeat-orbit period, a CTD and deep (1800 m) XBT hydrographic experiment was conducted across the Kuroshio to obtain cotemporaneous surface topography measurements for comparison with the altimeter-derived surface height measurements. The results showed that the altimeter could detect and measure the change in sea surface topography caused by movement of the Kuroshio and the cold rings that

  10. Reflectivity and topography of cells grown on glass-coverslips measured with

    E-print Network

    Ovryn, Ben

    Reflectivity and topography of cells grown on glass-coverslips measured with phase-shifted laser by sub-cellular structures from the reflection at the coverslip-buffer interface. The method offers the topography and reflection from calibration spheres and from stress fibers and adhesions in both fixed

  11. Deducing crack history in an aged boiler tube from fracture surface topography

    Microsoft Academic Search

    T. Kobayashi; D. A. Shockey; G. Ogundele; D. D. McNabb; D. Sidey

    1994-01-01

    A new fractographic technique, Fracture Surface Topography Analysis (FRASTA), was applied to a crack in a boiler tube of a fossil-fired power plant in an attempt to determine when in its 22-year service history the crack initiated and the rate at which it grew. By comparing the topographies of the conjugate crack surfaces, the authors estimated that the crack nucleated

  12. Internal wave generation from rough topography D. A. Aguilar and B. R. Sutherlanda

    E-print Network

    Sutherland, Bruce

    Internal wave generation from rough topography D. A. Aguilar and B. R. Sutherlanda Department examine internal wave generation above and in the lee of finite-amplitude periodic topography having various degrees of roughness. We show that internal waves are generated not only by flow over the hills

  13. The effects of topography on magma chamber deformation models: Application to Mt. Etna and radar interferometry

    Microsoft Academic Search

    Charles A. Williams; Geoff Wadge

    1998-01-01

    We have used a three-dimensional elastic finite element model to examine the effects of topography on the surface deformation predicted by models of magma chamber deflation. We used the topography of Mt. Etna to control the geometry of our model, and compared the finite element results to those predicted by an analytical solution for a pressurized sphere in an elastic

  14. Maximum-likelihood Theory for the Inversion of Gravity and Topography

    E-print Network

    Maximum-likelihood Theory for the Inversion of Gravity and Topography Frederik J Simons Princeton University Sofia C. Olhede University College London #12;Topography 2/25 #12;The free-air gravity anomaly 3/25 #12;The Bouguer-air gravity anomaly 4/25 #12;The standard model 5/25 0 800 1600 2400 -16 -8 0 8

  15. A laboratory study of low-mode internal tide scattering by finite-amplitude topography

    E-print Network

    Dauxois, Thierry

    A laboratory study of low-mode internal tide scattering by finite-amplitude topography Thomas concerning the scattering of a low-mode internal tide by finite-amplitude Gaussian topography. Experiments produces significant reflection of the internal tide and transfer of energy from low to high modes. © 2009

  16. A new insight into the North Atlantic Ocean seafloor topography

    NASA Astrophysics Data System (ADS)

    Niedzielski, Tomasz; Priede, Imants G.

    2010-05-01

    This paper demonstrates a new analysis of the North Atlantic seafloor topography with the particular emphasis on the Mid-Atlantic Ridge. The approach comprises a large-scale investigation of North Atlantic and the global ocean seafloor morphology as well as local-scale investigations on two representative transects across the Mid-Atlantic Ridge at 54°N and 49°N . The large-scale analysis is based on the General Bathymetric Chart of the Oceans (GEBCO), whereas the local-scale analysis is from multi-beam data collected during the ECOMAR cruise of the RRS James Cook (JC011) in 2007, processed and filtered using MB System software. Various Geographic Information System (GIS) techniques and standard statistical measures are employed. The bathyal zone (depth of 800-3500 m) of the North Atlantic is divided into three groups: ocean margin bathyal zone, Mid-Atlantic Ridge bathyal zone, and sea mounts bathyal zone. The Mid-Atlantic Ridge accounts for a large fraction of the total available bathyal habitat for marine organisms in the North Atlantic Ocean. This fraction increases with depth so that from approximately 2600m, 0.5 and 0.6 of available area is on the ridge. GIS-based analysis of the two transects across the ridge using high-resolution multi-beam charts allows the identification of different kinds of habitats including extensive flat areas covered with soft sediments, steep rocky escarpments and intermediate areas with different slope characteristics. We hypothesise that topography of the Mid Atlantic Ridge makes a major contribution to abundance and biodiversity of bathyal life in the North Atlantic Ocean.

  17. Density constraints of lunar upper crust from gravity and topography

    NASA Astrophysics Data System (ADS)

    Huang, Q.; Wieczorek, M. A.; Ping, J.

    2011-12-01

    Remote sensing and in situ measurements have shown that there are large lateral and vertical variations in the composition of the lunar crust. These crustal density diversities can be investigated using newly obtained global gravity and topography data. We applied a localized spectral admittance technique to various crustal regions by windowing the free-air gravity and surface topography with the band-limited localization windows of Wieczorek and Simons (2005, 2007). These admittances were interpreted using a geophysical model that includes both surface and subsurface loads that are supported by an elastic lithosphere. By varying the crustal density, elastic thickness and loading ratio in certain ranges, the best fitting bulk densities for a number of homogeneous regions were constrained to vary laterally from 2590 kg m-3 to 3010 kg m-3, with a mean value of 2700 kg m-3. Assuming the composition of the upper crust is uniform, the porosity of the upper crust could be determined if the pore-free surface density is known. Based on the known compositions of lunar rocks and estimated mineralogical norms, we found that the pore-free densities of lunar rocks were highly correlated with FeO and TiO2 abundance. The rock density can vary from 2884 to 3038 kg m-3 in estimated regions by using the iron and titanium abundances from Lunar Prospector gamma-ray spectrometer. We calculated the porosity of each region and found a mean value of ~7.4±3.4%, with permissible values from 0 to 14%. Furthermore, we took into account the vertical variation of crust density, and developed a novel technique that the density profile of the crust could be inverted using higher resolution gravity models. Since all these analyses are challenging using the recent Kaguya gravity models, higher resolution gravity data expected from NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission would place tight constrains on both the lateral and vertical density variations of the lunar crust.

  18. Including Topography and Vegetation Attributes for Developing Pedotransfer Functions

    NASA Astrophysics Data System (ADS)

    Sharma, S. K.; Mohanty, B. P.; Zhu, J.

    2006-12-01

    With the advent of advanced geographical informational systems (GIS) and remote sensing technologies in recent years, topographic (elevation, slope, aspect, and flow accumulation) and vegetation attributes are routinely available from digital elevation models (DEMs) and normalized difference vegetation index (NDVI) at different spatial (remote sensor footprint, watershed, regional) scales. Based on the correlation of soil distribution and vegetation growth patterns across a topographically heterogeneous landscape, this study explores the use of topographic and vegetation attributes in addition to pedologic attributes to develop pedotransfer functions (PTFs) for estimating soil hydraulic properties in the Southern Great Plains of the USA. The extensive Southern Great Plains 1997 (SGP97) hydrology experiment database was used to derive these functions by using artificial neural networks. Eighteen models combining bootstrapping technique with artificial neural networks were developed in a hierarchical manner to predict the soil water contents at eight different soil water potentials (theta at 5, 10, 333, 500, 1000, 3000, 8000, and 15000 cm) and the van Genuchten hydraulic parameters (teta residual, theta saturated, a, n). The performance of the neural network models was evaluated using the Spearman correlation coefficient between the observed and the predicted values and root mean square error (RMSE). Although variability exists within bootstrapped replications, improvements (of different levels of statistical significance) were achieved with certain input combinations of basic soil properties, topography and vegetation information compared with using only the basic soil properties as inputs. Topography (DEM) and vegetation (NDVI) attributes at finer scales were useful to capture the variations within the soil mapping units for the SGP97 region dominated by perennial grass cover

  19. Influence of topography on density of grassland passerines in pastures

    USGS Publications Warehouse

    Renfrew, R.B.; Ribic, C.A.

    2002-01-01

    Pastures provide substantial habitat for grassland birds of management concern in the Driftless Area of southwestern Wisconsin. The rolling topography in this region is characterized by lowland valleys surrounded by relatively steep and often wooded slopes which are set apart from more expansive treeless uplands. We hypothesized that there would be lower densities of area sensitive grassland passerines in lowland grasslands compared to upland grasslands because of their preference for larger more open grasslands. To test this hypothesis and assess how well pasture area and vegetation structure predicted grassland passerine density compared to upland/lowland status, we conducted point counts of birds in 60 pastures in May-June 1997 and 1998. Upland pastures generally supported greater densities of grassland passerines than lowland pastures. Densities of Savannah sparrow (Passerculus sandwichensis) and bobolink (Dolichonyx oryzivorus) were significantly higher in upland pastures than in lowland pastures. Grasshopper sparrow (Ammodramus savannarum) density was significantly higher on uplands in one of the study years. The density of eastern meadowlark (Sturnella magna), western meadowlark (S. neglecta) and sedge wren (Cistothorus platensis) did not differ significandy between uplands and lowlands. Grassland passerine density was also predicted by pasture size and vegetation structure. Densities of bobolink and grasshopper sparrow were higher in larger pastures. Bobolink and Savannah sparrow occurred on pastures with greater vegetation height-density and less bare ground; bobolink also preferred shallower litter depths. Lowland pastures supported grassland bird species of management concern and should not be neglected. However, we recommend that pasture management for grassland passerines in areas of variable topography favor relatively large upland pastures that will contain higher densities of species of management concern.

  20. An inversion of geoid and topography for mantle and crustal structure on Mars

    NASA Technical Reports Server (NTRS)

    Kiefer, Walter; Bills, Bruce; Frey, Herb; Nerem, Steve; Roark, Jim; Zuber, Maria

    1993-01-01

    Mars has the largest amplitude geoid anomalies and surface topography known on the terrestrial planets. A number of prior studies have analyzed Martian gravity anomalies and topography in terms of isostasy and flexure of the crust and lithosphere. Other studies have emphasized the role of mantle convection in producing gravity anomalies and topography in some regions of Mars. Geoid and topography observations for simultaneous estimates of density anomalies in the crust and mantle of Mars are inverted. In performing this study, a recent degree 50 spherical harmonic expansion of the Martian gravity field (GMM-l) and a corresponding resolution expansion of the USGS Mars topography model are used. However, our analysis is restricted to harmonic degrees up to L equals 25, which are better determined than the higher harmonics. This provides a half-wavelength horizontal resolution of 425 km.

  1. Surface topography of cylindrical gear wheels after smoothing in abrasive mass, honing and shot peening

    NASA Astrophysics Data System (ADS)

    Michalski, J.; Pawlus, P.; ?elasko, W.

    2011-08-01

    The present paper presents the analysis of surface topography of gear teeth as the result of final machining processes. Teeth of multiple cylindrical gears shaped by grinding were smoothed in abrasive mass, honed or shot peened. The measurement of gears were made using coordinate measuring machine and 3D surface topography stylus instrument. The following deviations were studied; pitch deviation, total pitches deviations, variation of teeth thickness and deviation of gear radial run-out. Changes in teeth surface topography during machining process were determined. 3D surface topography parameters, surface directionality as well as areal autocorrelation and power spectral density functions were taken into consideration. As the results of the analysis, the best surface topography with regard to gear operational properties was recommended.

  2. Radiation and Dissipation of Internal Waves Generated by Geostrophic Motions Impinging on Small-Scale Topography: Theory

    E-print Network

    Nikurashin, Maxim

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

  3. Combustion synthesis

    Microsoft Academic Search

    Kashinath C Patil; Singanahally T Aruna; Sambandan Ekambaram

    1997-01-01

    Many innovative self-propagating high-temperature synthesis (SHS) techniques such as filtration, combustion, the centrifugal thermite process, field activated combustion, solid-state metathesis, flame synthesis and simultaneous SHS and densification have been developed for the synthesis of ‘advanced materials’. A novel gas producing self-propagating process initiated at low temperature using redox compounds and mixtures has been used for the preparation of fine particle

  4. UNIVERSITYOF HAWAI'I lIl3RARY INTERNAL TIDE SCATTERING AT M1DOCEAN TOPOGRAPHY

    E-print Network

    Luther, Douglas S.

    UNIVERSITYOF HAWAI'I lIl3RARY INTERNAL TIDE SCATTERING AT M1DOCEAN TOPOGRAPHY A DISSERTATION The scattering ofmode-oneM, internal tides from I) idealized Gaussian topography and 2) the Line Islands Ridge is examined with a primitive equation numerical model. Internal tide scattering at topography leads to a loss

  5. Anomalous Accretionary Margin Topography Formed By Repeated Earthquakes

    NASA Astrophysics Data System (ADS)

    Furlong, Kevin P.

    2014-05-01

    It has long been recognized that accretionary margins of major subduction zones undergo substantial deformation. However even with the large amounts of shortening accommodated within the margin, for most subduction zones, there is an extended submarine portion to the accretionary, highly-deformed upper-plate between the trench and the coast. This is a vexing situation since this submarine section typically overlies the actual locked or coupled patch of the plate interface. The result of this is added difficulty in directly observing processes related to the plate interface coupling - such processes as micro-seismicity and the actual patterns of plate coupling. There are a few locations globally in which there are sub-aerially exposed terranes that lie closer to the trench and overlie the inferred coupled or seismogenic portion of the plate interface. Such regions have taken on significance in subduction zone studies as they provide locations to observe the plate interface coupling effects in the near-field. In particular the Pacific coast of Costa Rica provides such a location, and there has been substantial geologic, geophysical, and geodetic research exploiting the positions of these near-trench peninsulas (Nicoya, Osa, and Burica). These sites provide near-field access to plate-interface processes, but whether they represent typical subduction zone behavior remains an open question as the deformational processes or inherited structures that have produced this anomalous topography are not well constrained. Simply put, if the existence of these sub-aerial, near-trench terranes is a result of anomalous behavior on the plate interface (as has been suggested), then their utility in providing high-fidelity near-field insight into the plate interface properties and processes is substantially reduced. Here we propose a new mechanism that could be responsible for the formation of both the Nicoya and Osa Peninsulas in the past, and is currently producing a third peninsula - the Burica Peninsula at the intersection of the Panama fracture zone and the margin. Specifically we propose that the anomalous topography along the Pacific coast of Costa Rica has been produced by repeated, great subduction earthquakes that have ruptured across the boundary separating the Cocos and Nazca plates - the subducted continuation of the Panama fracture zone. The pattern of upper-plate shortening generated by such a process (documented in the 2007 Mw 8.1 Solomon Islands earthquake, which produced co-seismic localized uplift above the subducted transform plate boundary) convolved with the migration history of the Panama triple junction (PTJ) is proposed as the mechanism to produce substantial along-margin, long-lived accretionary margin topography. Specifically we argue that repeated great subduction earthquakes that rupture across fundamental plate boundary structures can produce substantial, long-lived upper plate deformation above the inter-seismically coupled plate interface.

  6. Breaking Gravity Waves Over Large-Scale Topography

    NASA Astrophysics Data System (ADS)

    Doyle, J. D.; Shapiro, M. A.

    2002-12-01

    The importance of mountain waves is underscored by the numerous studies that document the impact on the atmospheric momentum balance, turbulence generation, and the creation of severe downslope winds. As stably stratified air is forced to rise over topography, large amplitude internal gravity waves may be generated that propagate vertically, amplify and breakdown in the upper troposphere and lower stratosphere. Many of the numerical studies reported on in the literature have used two- and three-dimensional models with simple, idealized initial states to examine gravity wave breaking. In spite of the extensive previous work, many questions remain regarding gravity wave breaking in the real atmosphere. Outstanding issues that are potentially important include: turbulent mixing and wave overturning processes, mountain wave drag, downstream effects, and the mesoscale predictability of wave breaking. The current limit in our knowledge of gravity wave breaking can be partially attributed to lack of observations. During the Fronts and Atlantic Storm-Track Experiment (FASTEX), a large amplitude gravity wave was observed in the lee of Greenland on 29 January 1997. Observations taken collected during FASTEX presented a unique opportunity to study topographically forced gravity wave breaking and to assess the ability of high-resolution numerical models to predict the structure and evolution of such phenomena. Measurements from the NOAA G-4 research aircraft and high-resolution numerical simulations are used to study the evolution and dynamics of the large-amplitude gravity wave event that took place during the FASTEX. Vertical cross section analysis of dropwindsonde data, with 50-km horizontal spacing, indicates the presence of a large amplitude breaking gravity wave that extends from above the 150-hPa level to 500 hPa. Flight-level data indicate a horizontal shear of over 10-3 s-1 across the breaking wave with 25 K potential temperature perturbations. This breaking wave may have important implications for momentum flux parameterization in mesoscale models, stratospheric-tropospheric exchange dynamics as well as the dynamic sources and sinks of the ozone budget. Additionally, frequent breaking waves over Greenland are a known commercial and military aviation hazard. NRL's nonhydrostatic COAMPS^{TM}$ model is used with four nested grids with horizontal resolutions of 45 km, 15 km, 5 km and 1.67 km and 65 vertical levels to simulate the gravity wave event. The model simulation captures the temporal evolution and horizontal structure of the wave. However, the model underestimates the vertical amplitude of the wave. The model simulation suggests that the breaking wave may be triggered as a consequence of vertically propagating internal gravity waves emanating from katabatic flow near the extreme slopes of eastern Greenland. Additionally, a number of simulations that make use of a horizontally homogeneous initial state and both idealized and actual Greenland topography are performed. These simulations highlight the sensitivity of gravity wave amplification and breaking to the planetary rotation, slope of the Greenland topography, representation of turbulent mixing, and surface processes.

  7. Impacts of mean dynamic topography on a regional ocean assimilation system

    NASA Astrophysics Data System (ADS)

    Yan, C.; Zhu, J.; Tanajura, C. A. S.

    2015-06-01

    An ocean assimilation system was developed for the Pacific-Indian oceans with the aim of assimilating altimetry data, sea surface temperature, and in-situ measurements from ARGO, XBT, CTD, and TAO. The altimetry data assimilation requires the addition of the mean dynamic topography to the altimetric sea level anomaly to match the model sea surface height. The mean dynamic topography is usually computed from the model long-term mean sea surface height, and is also available from gravimeteric satellite data. In this study, different mean dynamic topographies are used to examine their impacts on the sea level anomaly assimilation. Results show that impacts of the mean dynamic topography cannot be neglected. The mean dynamic topography from the model long-term mean sea surface height without assimilating in-situ observations results in worsened subsurface temperature and salinity estimates. The gravimeter-based mean dynamic topography results in an even worse estimate. Even if all available observations including in-situ measurements, sea surface temperature measurements, and altimetry data are assimilated, the estimates are still not improved. This further indicates that the other types of observations do not compensate for the shortcoming due to the altimetry data assimilation. The mean dynamic topography computed from the model's long-term mean sea surface height after assimilating in-situ observations presents better results.

  8. Modelling formation of complex topography by the seagrass Posidonia oceanica

    NASA Astrophysics Data System (ADS)

    Kendrick, Gary A.; Marbà, Núria; Duarte, Carlos M.

    2005-12-01

    Posidonia oceanica is a slow growing seagrass species that extends via growing rhizomes that grow only centimetres both horizontally and vertically each year. Posidonia oceanica forms topographically complex biogenic reefs of dead rhizome and sediments that are up to 4 m in height that are called "matte". This study investigates the role of slow horizontal and vertical growth of rhizomes in the formation of topographic complexity in P. oceanica matte using agent-based modelling. The simulated infilling of landscapes by P. oceanica was run over 600 iterations (years) for 10 random starts of 150 agents each. Initial infilling rates were very slow and P. oceanica had limited cover after a century of growth. Growth accelerated after 100 years but plateaued after 400 years such that after 600 years only two-thirds of the landscape was occupied by P. oceanica. The pattern of spread of agents was initially random in direction but after larger patches were formed spread was radial from these patches. The seagrass landscape was initially highly fragmented with many small separate patches made up of a few agents each, with a Landscape Division index close to 1. Between 300 and 600 years Landscape Division declined sharply to 0.42, indicating patches had coalesced into larger more continuous meadows forming a less fragmented landscape. Perimeter to area ratio of seagrass patches declined exponentially from >1 to approximately 0.2 over 600 years of simulation. The matte developed from growth of patches and its greatest height occurred in more continuously occupied cells of the grid. The topography of the reef that occupied two-thirds of the landscape after six centuries of growth could be described as a pattern of channels between reef plateaus elevated 1-2 m above channels. These results demonstrate that development in P. oceanica meadows of three-dimensional structure, in the formation of biogenic reefs, can be explained by, and is an emergent property of, slow horizontal and vertical rhizome growth rates combined with the time it takes for the accumulation of rhizomes in any region of the landscape. As such, the model provides a parsimonious explanation for the development of complex matte topography.

  9. Topography on Titan : New Results on Large and Small Scales

    NASA Astrophysics Data System (ADS)

    Lorenz, R. D.; Cassini Radar Team

    2011-12-01

    Although topographic coverage of Titan is and will remain sparse, some significant results have been obtained from global, regional and local measurements, via stereo, radarclinometry (shape-from-shading), autostereo (deviation from an assumed symmetric shape due to the inclined incidence), altimetry and SARtopo (monopulse) techniques. The global ellipsoidal shape (Zebker et al., 2009) provides important geophysical constraints on the interior. Hypsometry (Lorenz et al., 2011) provides insight into the balance of constructional and erosive processes and the strength of the lithosphere. Some local observations to be summarized in the talk include the measurement of mountains, the quantification of slopes that divert dunes and that drive fluid flow in river networks, as well as depth measurement of several impact craters and the assessment of candidate cryovolcanic structures. A recent new observation is a long altimetry pass T77 along the equator at the western edge of Xanadu, acquired both to constrain Titan's global shape and to understand the surface slopes and properties that may maintain the striking contrast between the dune fields of Shangri-La and the rugged and radiometrically anomalous Xanadu region. T77 also featured a SAR observation of the Ksa impact structure (discovered in SAR on T17), allowing a stereo DEM to be constructed. A feature shared by Earth and Titan is the ephemeral topography of liquids on the surface. Titan's lakes and seas likely vary in depth on geological (Myr-Gyr) and astronomical (~10 kyr) timescales : the depth of Ontario Lacus has been observed to vary on a seasonal timescale (~1 m/yr). Periodic changes of the order of 0.2-5m may occur diurnally, forced by Saturn gravitational tides. Finally, waves may be generated, at least during the windy season (which for Titan's north may be just about to begin) which can be constrained by radar and optical scattering measurements. Looking to the future, a Phase A study of the Titan Mare Explorer (TiME) mission, to float in Ligeia Mare in 2023, raises the prospect of seabed topography measurement via an acoustic depth sounder (sonar).

  10. Characterization of energetic topography of heterogeneous surfaces through the analysis of thermal desorption spectra

    NASA Astrophysics Data System (ADS)

    Gargiulo, M. V.; Sales, J. L.; Ciacera, M.; Zgrablich, G.

    2002-04-01

    Monte Carlo simulations of thermal programmed desorption spectra (TPDS) are obtained and analyzed for general heterogeneous surfaces characterized by a dual-site-bond model, where the adsorptive energy topography is described in terms of a correlation length l0. It is shown that the behavior of TPDS is such that the ambiguity arising in the characterization of the energetic topography through adsorption isotherms, where adsorbate-adsorbate interactions and topography effects compete with each other, is resolved in such a way that TPDS provide a more powerful characterization method.

  11. X-Ray Topography of Tetragonal Lysozyme Grown by the Temperature-Controlled Technique

    NASA Technical Reports Server (NTRS)

    Stojanoff, V.; Siddons, D. P.; Monaco, Lisa A.; Vekilov, Peter; Rosenberger, Franz

    1997-01-01

    Growth-induced defects in lysozyme crystals were observed by white-beam and monochromatic X-ray topography at the National Synchrotron Light Source (NSLS) at the Brookhaven National Laboratory (BNL). The topographic methods were non-destructive to the extent that traditional diffraction data collection could be performed to high resolution after topography. It was found that changes in growth parameters, defect concentration as detected by X-ray topography, and the diffraction quality obtainable from the crystals were all strongly correlated. In addition, crystals with fewer defects showed lower mosaicity and higher diffraction resolution as expected.

  12. Development of material measures for performance verifying surface topography measuring instruments

    NASA Astrophysics Data System (ADS)

    Leach, Richard; Giusca, Claudiu; Rickens, Kai; Riemer, Oltmann; Rubert, Paul

    2014-04-01

    The development of two irregular-geometry material measures for performance verifying surface topography measuring instruments is described. The material measures are designed to be used to performance verify tactile and optical areal surface topography measuring instruments. The manufacture of the material measures using diamond turning followed by nickel electroforming is described in detail. Measurement results are then obtained using a traceable stylus instrument and a commercial coherence scanning interferometer, and the results are shown to agree to within the measurement uncertainties. The material measures are now commercially available as part of a suite of material measures aimed at the calibration and performance verification of areal surface topography measuring instruments.

  13. Crater Topography on Titan: Implications for Landscape Evolution

    NASA Technical Reports Server (NTRS)

    Neish, Catherine D.; Kirk, R.L.; Lorenz, R. D.; Bray, V. J.; Schenk, P.; Stiles, B. W.; Turtle, E.; Mitchell, K.; Hayes, A.

    2013-01-01

    We present a comprehensive review of available crater topography measurements for Saturn's moon Titan. In general, the depths of Titan's craters are within the range of depths observed for similarly sized fresh craters on Ganymede, but several hundreds of meters shallower than Ganymede's average depth vs. diameter trend. Depth-to-diameter ratios are between 0.0012 +/- 0.0003 (for the largest crater studied, Menrva, D approximately 425 km) and 0.017 +/- 0.004 (for the smallest crater studied, Ksa, D approximately 39 km). When we evaluate the Anderson-Darling goodness-of-fit parameter, we find that there is less than a 10% probability that Titan's craters have a current depth distribution that is consistent with the depth distribution of fresh craters on Ganymede. There is, however, a much higher probability that the relative depths are uniformly distributed between 0 (fresh) and 1 (completely infilled). This distribution is consistent with an infilling process that is relatively constant with time, such as aeolian deposition. Assuming that Ganymede represents a close 'airless' analogue to Titan, the difference in depths represents the first quantitative measure of the amount of modification that has shaped Titan's surface, the only body in the outer Solar System with extensive surface-atmosphere exchange.

  14. Representing the influence of subgrid topography on hydrology

    SciTech Connect

    Leung, L.R.; Ghan, S.J.

    1993-10-01

    Estimates of the impact of global climate change on land surface hydrology require climate information on scales far smaller than those explicitly resolved by global climate models of today and the foreseeable future. To bridge the gap between what is required and what is resolved, we propose a subgrid-scale parameterization of the influence of topography on clouds, precipitation, and land surface hydrology. The parameterization represents subgrid variations in surface elevation in terms of discrete elevation classes. Separate cloud and surface processes are calculated for each elevation class. The simulated surface temperature, precipitation, snowpack, and soil moisture for each elevation class can then be distributed according to the spatial distribution of surface elevation within each grid cell. The scheme is being applied to the Pacific Northwest Laboratory`s climate version of the Penn State/NCAR Mesoscale Model. Validation is being addressed by driving the model with observed lateral boundary conditions for the Pacific Northwest and comparing with surface observations. Preliminary results from the simulation will be presented.

  15. Assessing Gravity Estimates to Improve Dynamic Ocean Topography

    NASA Astrophysics Data System (ADS)

    Gille, S. T.; Krzemien, T.; Mazloff, M. R.; Cornuelle, B. D.

    2013-12-01

    Dynamic ocean topography (DOT), which defines the streamlines of ocean circulation, can be computed from the difference between mean sea surface (MSS) measurements (e.g. from satellite altimetry) and the Earth's geoid (from gravity observations). Uncertainties in the geoid translate into uncertainties in DOT, and this is particularly an issue for smaller length-scales. We estimate these uncertainties at various length-scales by comparing GRACE and GOCE-based geoid products with MSS and DOT products. Geoid and mean sea surface height fields are then combined to constrain the DOT in an assimilating ocean model, the Southern Ocean State Estimate (SOSE). Uncertainties in the small-scale geoid are accounted for with a prescribed error variance. The large-scale geoid errors are accounted for by solving for a smooth error field representing misfit to geoid model estimates. This error field minimizes the impact of correlated errors in the geoid on the optimization, while providing a metric for evaluating the consistency estimate of SOSE relative to the geoid products. For the EGM08 and TIMR3 geoid fields, our analysis for the Southern Ocean shows that error variances tend to be largest in small-scale regions associated with large topographic features. Error covariance magnitudes imply regional differences between the two products.

  16. OCT 3-D surface topography of isolated human crystalline lenses

    PubMed Central

    Sun, Mengchan; Birkenfeld, Judith; de Castro, Alberto; Ortiz, Sergio; Marcos, Susana

    2014-01-01

    Quantitative 3-D Optical Coherence Tomography was used to measure surface topography of 36 isolated human lenses, and to evaluate the relationship between anterior and posterior lens surface shape and their changes with age. All lens surfaces were fitted to 6th order Zernike polynomials. Astigmatism was the predominant surface aberration in anterior and posterior lens surfaces (accounting for ~55% and ~63% of the variance respectively), followed by spherical terms, coma, trefoil and tetrafoil. The amount of anterior and posterior surface astigmatism did not vary significantly with age. The relative angle between anterior and posterior surface astigmatism axes was on average 36.5 deg, tended to decrease with age, and was >45 deg in 36.1% lenses. The anterior surface RMS spherical term, RMS coma and 3rd order RMS decreased significantly with age. In general, there was a statistically significant correlation between the 3rd and 4th order terms of the anterior and posterior surfaces. Understanding the coordination of anterior and posterior lens surface geometries and their topographical changes with age sheds light into the role of the lens in the optical properties of the eye and the lens aging mechanism. PMID:25360371

  17. Wind-Related Topography in Phoenix's Region of Mars (Animation)

    NASA Technical Reports Server (NTRS)

    2008-01-01

    [figure removed for brevity, see original site] Click on image for animation

    This movie shifts from a global zoom indicating the Phoenix landing area on Mars to a topographical map indicating relative elevations in the landing region. The elevations could affect wind patterns at the site.

    In particular, Phoenix is in a broad, shallow valley. The edge of the valley, about 150 meters (500 feet) above the floor, may provide enough of a slope to the east of Phoenix to explain winds coming from the east during nights at the site. Cooler, denser air could be sinking down the slope and toward the lander.

    Atmospheric scientists on the Phoenix team are analyzing wind patterns to distiguish effects of nearby topography from larger-scale movement of the atmosphere in the polar region.

    The elevation information for this topographical mapping comes from the Mars Orbiter Laser Altimeter on NASA's Mars Global Surveyor orbiter. The blue-coded area is the valley floor. Orange and yellow indicate relatively higher elevations.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver. JPL managed the Mars Global Surveyor mission for the NASA Science Mission Directorate.

  18. New Products From the Shuttle Radar Topography Mission

    NASA Astrophysics Data System (ADS)

    Gesch, Dean; Farr, Tom; Slater, James; Muller, Jan-Peter; Cook, Sally

    2006-05-01

    New data products with broad applicability to the Earth sciences are now available from the Shuttle Radar Topography Mission (SRTM). SRTM, a joint project of the National Geospatial-Intelligence Agency (NGA) and NASA, flew aboard the Space Shuttle Endeavour on an 11 day mission in February 2000 with the goal of collecting a near-global data set of high-resolution elevation data [Farr and Kobrick, 2000]. Data from the mission have been available to researchers for several years, but newly available products offer enhanced usability and applicability. Final products include elevation data resulting from a substantial editing effort by the NGA in which water bodies and coastlines were well defined and data artifacts known as spikes and wells (single pixel errors) were removed. This second version of the SRTM data set, also referred to as `finished' data, represents a significant improvement over earlier versions that had nonflat water bodies, poorly defined coastlines, and numerous noise artifacts. The edited data are available at a one-arc-second resolution (approximately 30 meters) for the United States and its territories, and at a three-arc-second resolution (approximately 90 meters) for non-U.S. areas.

  19. Corneal topography reinterpretation through separate analysis of the projected rings

    NASA Astrophysics Data System (ADS)

    Espinosa, Julian; Roig, Ana B.; Mas, David; Hernández, Consuelo; Illueca, Carlos

    2012-06-01

    We present a new algorithm to process captured images of reflected Placido rings. Up to our knowledge, conventional topographers transform from Cartesian to polar coordinates and vice-versa, thus extrapolating corneal data and introducing noise and image artefacts. Moreover, captured data are processed by the device according to proprietary algorithms and offering a final map of corneal curvature. Corneal topography images consists of concentric rings of approximately elliptical shape. Our proposal consists of considering the information that provides each separate ring. A snake-annealing-like method permits identifying the ring even with discontinuities due to eye-lashes and reflections. By analysing the geometrical parameters of rings (centre, semi-axis and orientation), one can obtain information about small morphological micro-fluctuations and local astigmatisms. These parameters can be obtained with sub-pixel accuracy so the method results of high precision. The method can be easily adapted to work on any topographer, so that it can provide additional information about the cornea at no additional cost.

  20. Determining Titan surface topography from Cassini SAR data

    USGS Publications Warehouse

    Stiles, Bryan W.; Hensley, Scott; Gim, Yonggyu; Bates, David M.; Kirk, Randolph L.; Hayes, Alex; Radebaugh, Jani; Lorenz, Ralph D.; Mitchell, Karl L.; Callahan, Philip S.; Zebker, Howard; Johnson, William T.K.; Wall, Stephen D.; Lunine, Jonathan I.; Wood, Charles A.; Janssen, Michael; Pelletier, Frederic; West, Richard D.; Veeramacheneni, Chandini

    2009-01-01

    A technique, referred to as SARTopo, has been developed for obtaining surface height estimates with 10 km horizontal resolution and 75 m vertical resolution of the surface of Titan along each Cassini Synthetic Aperture Radar (SAR) swath. We describe the technique and present maps of the co-located data sets. A global map and regional maps of Xanadu and the northern hemisphere hydrocarbon lakes district are included in the results. A strength of the technique is that it provides topographic information co-located with SAR imagery. Having a topographic context vastly improves the interpretability of the SAR imagery and is essential for understanding Titan. SARTopo is capable of estimating surface heights for most of the SAR-imaged surface of Titan. Currently nearly 30% of the surface is within 100 km of a SARTopo height profile. Other competing techniques provide orders of magnitude less coverage. We validate the SARTopo technique through comparison with known geomorphological features such as mountain ranges and craters, and by comparison with co-located nadir altimetry, including a 3000 km strip that had been observed by SAR a month earlier. In this area, the SARTopo and nadir altimetry data sets are co-located tightly (within 5-10 km for one 500 km section), have similar resolution, and as expected agree closely in surface height. Furthermore the region contains prominent high spatial resolution topography, so it provides an excellent test of the resolution and precision of both techniques.

  1. Discriminant analysis of functional optical topography for schizophrenia diagnosis

    NASA Astrophysics Data System (ADS)

    Chuang, Ching-Cheng; Nakagome, Kazuyuki; Pu, Shenghong; Lan, Tsuo-Hung; Lee, Chia-Yen; Sun, Chia-Wei

    2014-01-01

    Abnormal prefrontal function plays a central role in the cognition deficits of schizophrenic patients; however, the character of the relationship between discriminant analysis and prefrontal activation remains undetermined. Recently, evidence of low prefrontal cortex (PFC) activation in individuals with schizophrenia has also been found during verbal fluency tests (VFT) and other cognitive tests with several neuroimaging methods. The purpose of this study is to assess the hemodynamic changes of the PFC and discriminant analysis between schizophrenia patients and healthy controls during VFT task by utilizing functional optical topography. A total of 99 subjects including 53 schizophrenic patients and 46 age- and gender-matched healthy controls were studied. The results showed that the healthy group had larger activation in the right and left PFC than in the middle PFC. Besides, the schizophrenic group showed weaker task performance and lower activation in the whole PFC than the healthy group. The result of the discriminant analysis showed a significant difference with P value <0.001 in six channels (CH 23, 29, 31, 40, 42, 52) between the schizophrenic and healthy groups. Finally, 68.69% and 71.72% of subjects are correctly classified as being schizophrenic or healthy with all 52 channels and six significantly different channels, respectively. Our findings suggest that the left PFC can be a feature region for discriminant analysis of schizophrenic diagnosis.

  2. Substrate topography determines neuronal polarization and growth in vitro.

    PubMed

    Micholt, Liesbeth; Gärtner, Annette; Prodanov, Dimiter; Braeken, Dries; Dotti, Carlos G; Bartic, Carmen

    2013-01-01

    The establishment of neuronal connectivity depends on the correct initial polarization of the young neurons. In vivo, developing neurons sense a multitude of inputs and a great number of molecules are described that affect their outgrowth. In vitro, many studies have shown the possibility to influence neuronal morphology and growth by biophysical, i.e. topographic, signaling. In this work we have taken this approach one step further and investigated the impact of substrate topography in the very early differentiation stages of developing neurons, i.e. when the cell is still at the round stage and when the first neurite is forming. For this purpose we fabricated micron sized pillar structures with highly reproducible feature sizes, and analyzed neurons on the interface of flat and topographic surfaces. We found that topographic signaling was able to attract the polarization markers of mouse embryonic neurons -N-cadherin, Golgi-centrosome complex and the first bud were oriented towards topographic stimuli. Consecutively, the axon was also preferentially extending along the pillars. These events seemed to occur regardless of pillar dimensions in the range we examined. However, we found differences in neurite length that depended on pillar dimensions. This study is one of the first to describe in detail the very early response of hippocampal neurons to topographic stimuli. PMID:23785482

  3. Substrate Topography Determines Neuronal Polarization and Growth In Vitro

    PubMed Central

    Micholt, Liesbeth; Gärtner, Annette; Prodanov, Dimiter; Braeken, Dries; Dotti, Carlos G.; Bartic, Carmen

    2013-01-01

    The establishment of neuronal connectivity depends on the correct initial polarization of the young neurons. In vivo, developing neurons sense a multitude of inputs and a great number of molecules are described that affect their outgrowth. In vitro, many studies have shown the possibility to influence neuronal morphology and growth by biophysical, i.e. topographic, signaling. In this work we have taken this approach one step further and investigated the impact of substrate topography in the very early differentiation stages of developing neurons, i.e. when the cell is still at the round stage and when the first neurite is forming. For this purpose we fabricated micron sized pillar structures with highly reproducible feature sizes, and analyzed neurons on the interface of flat and topographic surfaces. We found that topographic signaling was able to attract the polarization markers of mouse embryonic neurons -N-cadherin, Golgi-centrosome complex and the first bud were oriented towards topographic stimuli. Consecutively, the axon was also preferentially extending along the pillars. These events seemed to occur regardless of pillar dimensions in the range we examined. However, we found differences in neurite length that depended on pillar dimensions. This study is one of the first to describe in detail the very early response of hippocampal neurons to topographic stimuli. PMID:23785482

  4. Automated object-based classification of topography from SRTM data

    NASA Astrophysics Data System (ADS)

    Dr?gu?, Lucian; Eisank, Clemens

    2012-03-01

    We introduce an object-based method to automatically classify topography from SRTM data. The new method relies on the concept of decomposing land-surface complexity into more homogeneous domains. An elevation layer is automatically segmented and classified at three scale levels that represent domains of complexity by using self-adaptive, data-driven techniques. For each domain, scales in the data are detected with the help of local variance and segmentation is performed at these appropriate scales. Objects resulting from segmentation are partitioned into sub-domains based on thresholds given by the mean values of elevation and standard deviation of elevation respectively. Results resemble reasonably patterns of existing global and regional classifications, displaying a level of detail close to manually drawn maps. Statistical evaluation indicates that most of classes satisfy the regionalization requirements of maximizing internal homogeneity while minimizing external homogeneity. Most objects have boundaries matching natural discontinuities at regional level. The method is simple and fully automated. The input data consist of only one layer, which does not need any pre-processing. Both segmentation and classification rely on only two parameters: elevation and standard deviation of elevation. The methodology is implemented as a customized process for the eCognition® software, available as online download. The results are embedded in a web application with functionalities of visualization and download.

  5. Anomalous sea surface structures as an object of statistical topography

    NASA Astrophysics Data System (ADS)

    Klyatskin, V. I.; Koshel, K. V.

    2015-06-01

    By exploiting ideas of statistical topography, we analyze the stochastic boundary problem of emergence of anomalous high structures on the sea surface. The kinematic boundary condition on the sea surface is assumed to be a closed stochastic quasilinear equation. Applying the stochastic Liouville equation, and presuming the stochastic nature of a given hydrodynamic velocity field within the diffusion approximation, we derive an equation for a spatially single-point, simultaneous joint probability density of the surface elevation field and its gradient. An important feature of the model is that it accounts for stochastic bottom irregularities as one, but not a single, perturbation. Hence, we address the assumption of the infinitely deep ocean to obtain statistic features of the surface elevation field and the squared elevation gradient field. According to the calculations, we show that clustering in the absolute surface elevation gradient field happens with the unit probability. It results in the emergence of rare events such as anomalous high structures and deep gaps on the sea surface almost in every realization of a stochastic velocity field.

  6. Single cell electric impedance topography: Mapping membrane capacitance

    PubMed Central

    Dharia, Sameera; Ayliffe, Harold E.

    2010-01-01

    Single-cell electric impedance topography (sceTopo), a technique introduced here, maps the spatial distribution of capacitance (i.e. displacement current) associated with the membranes of isolated, living cells. Cells were positioned in the center of a circular recording chamber surrounded by eight electrodes. Electrodes were evenly distributed on the periphery of the recording chamber. Electric impedance measured between adjacent electrode pairs (10 kHz–5 MHz) was used to construct topographical maps of the spatial distribution of membrane capacitance. Xenopus Oocytes were used as a model cell to develop sceTopo because these cells consist of two visually distinguishable hemispheres, each with distinct membrane composition and structure. Results showed significant differences in the imaginary component of the impedance between the two oocyte hemispheres. In addition, the same circumferential array was used to map the size of the extracellular electrical shunt path around the cell, providing a means to estimate the location and shape of the cell in the recording chamber. PMID:19904403

  7. Single cell electric impedance topography: mapping membrane capacitance.

    PubMed

    Dharia, Sameera; Ayliffe, Harold E; Rabbitt, Richard D

    2009-12-01

    Single-cell electric impedance topography (sceTopo), a technique introduced here, maps the spatial distribution of capacitance (i.e. displacement current) associated with the membranes of isolated, living cells. Cells were positioned in the center of a circular recording chamber surrounded by eight electrodes. Electrodes were evenly distributed on the periphery of the recording chamber. Electric impedance measured between adjacent electrode pairs (10 kHz-5 MHz) was used to construct topographical maps of the spatial distribution of membrane capacitance. Xenopus Oocytes were used as a model cell to develop sceTopo because these cells consist of two visually distinguishable hemispheres, each with distinct membrane composition and structure. Results showed significant differences in the imaginary component of the impedance between the two oocyte hemispheres. In addition, the same circumferential array was used to map the size of the extracellular electrical shunt path around the cell, providing a means to estimate the location and shape of the cell in the recording chamber. PMID:19904403

  8. Crater topography on Titan: Implications for landscape evolution

    NASA Astrophysics Data System (ADS)

    Neish, C. D.; Kirk, R. L.; Lorenz, R. D.; Bray, V. J.; Schenk, P.; Stiles, B. W.; Turtle, E.; Mitchell, K.; Hayes, A.; Cassini Radar Team

    2013-03-01

    We present a comprehensive review of available crater topography measurements for Saturn’s moon Titan. In general, the depths of Titan’s craters are within the range of depths observed for similarly sized fresh craters on Ganymede, but several hundreds of meters shallower than Ganymede’s average depth vs. diameter trend. Depth-to-diameter ratios are between 0.0012 ± 0.0003 (for the largest crater studied, Menrva, D ? 425 km) and 0.017 ± 0.004 (for the smallest crater studied, Ksa, D ? 39 km). When we evaluate the Anderson-Darling goodness-of-fit parameter, we find that there is less than a 10% probability that Titan’s craters have a current depth distribution that is consistent with the depth distribution of fresh craters on Ganymede. There is, however, a much higher probability that the relative depths are uniformly distributed between 0 (fresh) and 1 (completely infilled). This distribution is consistent with an infilling process that is relatively constant with time, such as aeolian deposition. Assuming that Ganymede represents a close ‘airless’ analogue to Titan, the difference in depths represents the first quantitative measure of the amount of modification that has shaped Titan’s surface, the only body in the outer Solar System with extensive surface-atmosphere exchange.

  9. Crustal structure of Mars from gravity and topography

    NASA Technical Reports Server (NTRS)

    Neumann, G. A.; Zuber, M. T.; Wieczorek, M. A.; McGovern, P. J.; Lemoine, F. G.; Smith, D. E.

    2004-01-01

    Mars Orbiter Laser Altimeter (MOLA) topography and gravity models from 5 years of Mars Global Surveyor (MGS) spacecraft tracking provide a window into the structure of the Martian crust and upper mantle. We apply a finite-amplitude terrain correction assuming uniform crustal density and additional corrections for the anomalous densities of the polar caps, the major volcanos, and the hydrostatic flattening of the core. A nonlinear inversion for Moho relief yields a crustal thickness model that obeys a plausible power law and resolves features as small as 300 km wavelength. On the basis of petrological and geophysical constraints, we invoke a mantle density contrast of 600 kg m-3; with this assumption, the Isidis and Hellas gravity anomalies constrain the global mean crustal thickness to be >45 km. The crust is characterized by a degree 1 structure that is several times larger than any higher degree harmonic component, representing the geophysical manifestation of the planet's hemispheric dichotomy. It corresponds to a distinction between modal crustal thicknesses of 32 km and 58 km in the northern and southern hemispheres, respectively. The Tharsis rise and Hellas annulus represent the strongest components in the degree 2 crustal thickness structure. A uniform highland crustal thickness suggests a single mechanism for its formation, with subsequent modification by the Hellas impact, erosion, and the volcanic construction of Tharsis. The largest surviving lowland impact, Utopia, post-dated formation of the crustal dichotomy. Its crustal structure is preserved, making it unlikely that the northern crust was subsequently thinned by internal processes.

  10. SAR Image Coregistration Based on Topography and Deformation

    NASA Astrophysics Data System (ADS)

    Yun, S.; Kim, S.; Rosen, P.

    2008-12-01

    L-band repeat-pass InSAR has been getting scientists' attention for its penetration depth through dense vegetation, revealing the ground deformation under the canopy of forest. This makes it possible to achieve a good coverage of volcanic activities in tropical areas such as Hawaii, Galapagos, and Indonesia. Another advantage of L-band InSAR is its tolerance to a large baseline. The critical baseline scales with the wavelength, and practically a baseline of over 1 km often produces interferograms. However, the large baseline causes parallax in the presence of topography, which appears as pixel shift between master and slave images that sometimes leads to a severe decorrelation. Using ALOS PALSAR data of Java Island, Indonesia, and intermediate files produced by ROI_PAC, we correct this parallax before forming an interferogram to improve the interferometric coherence. We also test an automatic implementation of the 'rubber sheeting" coregistration (e.g. Yun et al., GRL, 2007) for localized large deformation that cannot be explained by polynomial fitting.

  11. Dust as a potential tracer for the flow over topography

    NASA Astrophysics Data System (ADS)

    Alpert, Pinhas; Barkan, Yossi

    2015-04-01

    The distribution of mineral dust around topographical obstacles is examined, using the dimensionless Froude number (Fr) that describes different flow regimes in a fluid. Flow around a peak with a close-to-circular shape in dusty environment like the Sahara and the Sahel was examined in order to investigate the distribution of the dust around the obstacle in different flow regimes as expressed by the Fr number. The Total Ozone Mapping Spectrometer Aerosol Index (TOMS-AI) daily Aerosol Index, and the u and v wind components were used for the years 1979-1992, i.e. 14 years. It is first shown by the TOMS-AI data that the shape of the dust distribution around the circular peak is in good agreement with the shape of the peak itself. Additionally good correlation exists between the vertical distribution of the dust above the peak and the Froude Number in its vicinity. This method allows for the first time the investigation of flow above and around topographical obstacles in the open space employing dust as the flow-tracer. References: J. Barkan and P. Alpert, "Dust as a potential tracer for the flow over topography", Intern. J. Geosci., (in press) 2015. J. Barkan and P. Alpert, "A unique case-study of near-circular Saharan dust transport over the Atlantic Ocean", Atmospheric and Climate Sciences (ACS), 4, 164-170, 2014.

  12. STS-99 Shuttle Radar Topography Mission Stability and Control

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  13. Skylab earth resources experiment package /EREP/ - Sea surface topography experiment

    NASA Technical Reports Server (NTRS)

    Vonbun, F. O.; Marsh, J. G.; Mcgoogan, J. T.; Leitao, C. D.; Vincent, S.; Wells, W. T.

    1976-01-01

    The S-193 Skylab radar altimeter was operated in a round-the-world pass on Jan. 31, 1974. The main purpose of this experiment was to test and 'measure' the variation of the sea surface topography using the Goddard Space Flight Center (GSFC) geoid model as a reference. This model is based upon 430,000 satellite and 25,000 ground gravity observations. Variations of the sea surface on the order of -40 to +60 m were observed along this pass. The 'computed' and 'measured' sea surfaces have an rms agreement on the order of 7 m. This is quite satisfactory, considering that this was the first time the sea surface has been observed directly over a distance of nearly 35,000 km and compared to a computed model. The Skylab orbit for this global pass was computed using the Goddard Earth Model (GEM 6) and S-band radar tracking data, resulting in an orbital height uncertainty of better than 5 m over one orbital period.

  14. Leveraging High Resolution Topography for Education and Outreach: Updates to OpenTopography to make EarthScope and Other Lidar Datasets more Prominent in Geoscience Education

    NASA Astrophysics Data System (ADS)

    Kleber, E.; Crosby, C. J.; Arrowsmith, R.; Robinson, S.; Haddad, D. E.

    2013-12-01

    The use of Light Detection and Ranging (lidar) derived topography has become an indispensable tool in Earth science research. The collection of high-resolution lidar topography from an airborne or terrestrial platform allows landscapes and landforms to be represented at sub-meter resolution and in three dimensions. In addition to its high value for scientific research, lidar derived topography has tremendous potential as a tool for Earth science education. Recent science education initiatives and a community call for access to research-level data make the time ripe to expose lidar data and derived data products as a teaching tool. High resolution topographic data fosters several Disciplinary Core Ideas (DCIs) of the Next Generation Science Standards (NGS, 2013), presents respective Big Ideas of the new community-driven Earth Science Literacy Initiative (ESLI, 2009), teaches to a number National Science Education Standards (NSES, 1996), and Benchmarks for Science Literacy (AAAS, 1993) for science education for undergraduate physical and environmental earth science classes. The spatial context of lidar data complements concepts like visualization, place-based learning, inquiry based teaching and active learning essential to teaching in the geosciences. As official host to EarthScope lidar datasets for tectonically active areas in the western United States, the NSF-funded OpenTopography facility provides user-friendly access to a wealth of data that is easily incorporated into Earth science educational materials. OpenTopography (www.opentopography.org), in collaboration with EarthScope, has developed education and outreach activities to foster teacher, student and researcher utilization of lidar data. These educational resources use lidar data coupled with free tools such as Google Earth to provide a means for students and the interested public to visualize and explore Earth's surface in an interactive manner not possible with most other remotely sensed imagery. The education section of the OpenTopography portal has recently been strengthened with the addition of several new resources and the re-organization of existing content for easy discovery. New resources include a detailed frequently asked questions (FAQ) section, updated 'How-to' videos for downloading data from OpenTopography and additional webpages aimed at students, educators and researchers leveraging existing and updated resources from OpenTopography, EarthScope and other organizations. In addition, the OpenLandform catalog, an online collection of classic geologic landforms depicted in lidar, has been updated to include additional tectonic landforms from EarthScope lidar datasets.

  15. Topography effects in the 1999 Athens earthquake : engineering issues in seismology

    E-print Network

    Assimaki, Dominic, 1975-

    2004-01-01

    It is well known that irregular topography can substantially affect the amplitude and frequency characteristics of seismic motion. Macroseismic observations of destructive earthquakes often show higher damage intensity at ...

  16. The Formation of Nonzonal Jets over Sloped Topography EMMA J. D. BOLAND

    E-print Network

    Thompson, Andrew

    The Formation of Nonzonal Jets over Sloped Topography EMMA J. D. BOLAND The University of Cambridge barotropic and baroclinic Corresponding author address: Emma Boland, DAMTP, Centre for Mathematical Sciences

  17. The effect of topography on the wavelet response of seismic arrays 

    E-print Network

    Al-Shuhail, Abdullatif Abdulrahman

    1993-01-01

    Analyzing seismic arrays using their responses to wavelets provides a more convenient and direct method of analysis than using their conventional time-harmonic responses. In this study, the effect of topography on the wavelet response of seismic...

  18. The effect of topography on the wavelet response of seismic arrays

    E-print Network

    Al-Shuhail, Abdullatif Abdulrahman

    1993-01-01

    Analyzing seismic arrays using their responses to wavelets provides a more convenient and direct method of analysis than using their conventional time-harmonic responses. In this study, the effect of topography on the wavelet response of seismic...

  19. Emplacement of Long Lava Flows: Detailed Topography of the Carrizozo Basalt Lava Flow, New Mexico

    NASA Technical Reports Server (NTRS)

    Zimbelman, J. R; Johnston, A. K.

    2000-01-01

    The Carrizozo flow in south-central New Mexico was examined to obtain detailed topography for a long basaltic lava flow. This information will be helpful in evaluating emplacement models for long lava flows.

  20. 2D/3D Topography Comparisons of 10 Consecutively Manufactured Chisels and Punches

    E-print Network

    Perkins, Richard A.

    2D/3D Topography Comparisons of 10 Consecutively Manufactured Chisels and Punches Through the Cross Manufactured Punches · Punch ­ Impression Toolmark Creation · Punch ­ Measurement and Analysis · Conclusions 3 (striated toolmarks) and punches (impression toolmarks). · Can consecutively manufactured tools still

  1. Large Eddy Simulation and Snow Transport over three-dimensional topography

    NASA Astrophysics Data System (ADS)

    Diebold, M.; Higgins, C. W.; Lehning, M.; Parlange, M. B.

    2010-12-01

    A new generation Large-Eddy Simulation (LES) is applied to study wind fields and the influence of local topography. In this study we first focus on the implementation of three-dimensional topography in our LES algorithm using an immersed boundary method. To validate this model, the LES results are compared with measurements from wind tunnel studies taken from the literature. Simulations and comparison with data from real topographies are done as well. This code is used to model snow transport over a mountainous topography. For this, our Large Eddy Simulation code is coupled with a saltation model and a Lagrangian stochastic model, which is used to account for suspension. The snow deposition patterns are then investigated.

  2. Cell Adhesion on Polyelectrolyte Multilayer Coated Polydimethylsiloxane Surfaces with Varying Topographies

    E-print Network

    Lee, Ilsoon

    Cell Adhesion on Polyelectrolyte Multilayer Coated Polydimethylsiloxane Surfaces with Varying types (fibroblasts, HeLa, and primary hepatocytes) cultured on various polydimethylsiloxane (PDMS on polydimethylsiloxane (PDMS) surfaces with varying topographies. PDMS is a silicon-based organic polymer that can

  3. The Impact of Finite-Amplitude Bottom Topography on Internal Wave Generation in the Southern Ocean

    E-print Network

    Nikurashin, Maxim

    Direct observations in the Southern Ocean report enhanced internal wave activity and turbulence in a kilometer-thick layer above rough bottom topography collocated with the deep-reaching fronts of the Antarctic Circumpolar ...

  4. Study of the tear topography dynamics using a lateral shearing interferometer

    NASA Astrophysics Data System (ADS)

    Dubra, Alfredo; Paterson, Carl; Dainty, Christopher

    2004-12-01

    The dynamics of the pre-corneal tear film topography are studied on 21 subjects with a purpose-built lateral shearing interferometer. Interesting tear topography features such as post-blink undulation, break-up, eyelid-produced bumps/ridges, bubbles and rough pre-contact lens tear surfaces were recorded. Using the calculated tear topography maps, the effects of the tear dynamics in visual performance, refractive surgery and ophthalmic adaptive optics are discussed in terms of wavefront RMS. The potential of lateral shearing interferometry for clinical applications such as dry eye diagnosis and contact lens performance studies is illustrated by the recorded topography features such as post-blink undulation, break-up, eyelid-produced bumps/ridges, bubbles and rough tear surfaces in front of contact lenses.

  5. A laboratory study of low-mode internal tide scattering by finite-amplitude topography

    E-print Network

    Peacock, Thomas

    We present the first laboratory experimental results concerning the scattering of a low-mode internal tide by finite-amplitude Gaussian topography. Experiments performed at the Coriolis Platform in Grenoble used a recently ...

  6. An Analysis of the Effect of Topography on the Martian Hadley Cells

    E-print Network

    Plumb, R. Alan

    Previous work with Mars general circulation models (MGCMs) has shown that the north–south slope in Martian topography causes asymmetries in the Hadley cells at equinox and in the annual average. To quantitatively solve for ...

  7. Karst Topography: Teacher's Guide to Accompany Black and White and Color Paper Models

    NSDL National Science Digital Library

    Tau Alpha

    Using paper patterns, students are able to construct a model that depicts Karst topography, including typical features such as caves, limestone bedrock, sink holes, and springs. The accompanying Teachers Guide provides extensive background information about the dissolutional processes that form caves. Information is also provided about unique animals found in caves and the importance of understanding Karst topography in city planning and water resource issues.

  8. Quantitative characterization of the surface topography of rolled sheets by laser scanning microscopy and fourier transformation

    Microsoft Academic Search

    Liv Gjønnes

    1996-01-01

    The surface of twin-roll cast aluminum sheets undergoes dramatic changes during cold rolling. This is mainly due to variables\\u000a in the roll gap, topography of the rolls, lubrication, material properties, and in particular the initial structure and topography\\u000a of the cast sheet. Therefore, it is important to have means to quantitatively describe the changes in the surface structure\\u000a of each

  9. Where asylum-seekers wait: feminist counter-topographies of sites between states

    Microsoft Academic Search

    Alison Mountz

    2011-01-01

    This article examines topographies and counter-topographies of power operating transnationally across a range of sites inhabited by asylum-seekers en route between nation-states. In locations such as tunnels, detention centers and islands, journeys across time and space are truncated in myriad ways. For asylum-seekers, temporality is often conceptualized as waiting, limbo or suspension. These temporal zones map onto corresponding spatial ambiguities

  10. A thermomechanical study of the effects of mold topography on the solidification of Aluminum alloys

    Microsoft Academic Search

    Lijian Tan; Nicholas Zabaras

    2005-01-01

    A thermomechanical study of the effects of mold topography on the solidification of Aluminum alloys at early times is provided. The various coupling mechanisms between the solid-shell and mold deformation and heat transfer at the mold\\/solid-shell interface during the early stages of Aluminum solidification on molds with uneven topographies are investigated. The air-gap nucleation time, the stress evolution and the

  11. 7 The Numerical Wind Atlas for Ire-7.1 Topography for Ireland

    E-print Network

    7 The Numerical Wind Atlas for Ire- land 7.1 Topography for Ireland The topography of Ireland of British Island as it might influence the flow field in the northeast of Ireland. Table 4. Maximum terrain for the maps of Ireland used by KAMM. x 10 km 5 km 2.5 km Grid size 48 × 54 90 × 108 180 × 212 points Max. h

  12. The origin of the Iberian microplate high topography

    NASA Astrophysics Data System (ADS)

    Quintana, L.; Pulgar, J. A.; Alonso, J. L.; Fernandez Viejo, G.

    2013-12-01

    The Iberian microplate is about 1100 km width, 3500 km long, and experienced contraction during the Cenozoic convergence of the Eurasian and African plates. In this process two main mountain ranges were created in the boundaries of the microplate: the Cantabrian-Pyrenean range in the north and the Betic-Rif orogenic system in the south, with a maximun height of 3479 m over sea level. However, in the interior of the microplate there is also several ranges and plateaus, with maximun heights of 2592 m. The origin of these interior high topography is controversial and has been explained by means of several procesess as: a) transference of displacement from the south border of the microplate, b) lithospheric folding, or c) more complex deep mantle related processes. In this work we investigate the relation between the northern border range of the microplate and some Iberian interior reliefs as: a) the Spanish Central System range, located in the central part of the microplate, with peaks over 2500 m, and b) the North-Iberian meseta, situated between these two ranges, and with average heights of 750 m. In order to solve this relation we have built a crustal-scale cross-section, through the northern half of the Iberian microplate, by using field geological mapping, subsoil information and deep geophysical data. The section acroos the central part of the Cantabrian range shows the well-known Iberian microplate continental subduction beneath the Eurasian plate, with a prominent crustal root that reaches up to 45 km depth. In this section an important difference between the upper and lower crust shortening values has been found. Thus, the upper crust has been shortened 97 km while the lower crust 122 km. The section across de Central System range shows a slightly thickened crust. In this range also exist a difference in the shortening values between upper and lower crust, but in the contrary sense than the Cantabrian range. Thus, the Central System range has been shortened between 24-50 km in the upper crust, while the lower crust shows minor shortening. To solve this controversy, we propose that the Cantabrian and the Central System ranges are connected through a middle crustal detachment, 300 km long, beneath the North-Iberian meseta. Thus the default of shortening of the Central System lower crust is balanced by the excess of shortening of the Cantabrian lower crust subduction. At the same time we propose that the middle crustal detachment is not horizonal but rather a very low angle ramp dipping to the north. With this geometry we explain also the uplift of the North-Iberian meseta.We conclude that the mechanism that best explain the origin of the Iberian microplate interior high topography is the transference of displacement from the border ranges to the interior ones of the microplate.

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

    NASA Astrophysics Data System (ADS)

    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

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  15. Erosion of Terrestrial Rift Flank Topography: A Quantitative Study

    NASA Technical Reports Server (NTRS)

    Weissel, Jeffrey K.

    1999-01-01

    Many rifted or passive continental margins feature a seaward-facing erosional escarpment which abruptly demarcates deeply weathered, low relief, interior uplands from a deeply incised, high relief coastal zone. It is generally accepted that these escarpments originate at the time of continental rifting and propagate inland through the elevated rift flank topography at rates on the order of 1 km/Myr over the course of a margin's history. Considering the length of passive margins worldwide and an average rift flank plateau height of several hundred meters, it is clear that sediment eroded from passive margins is an important component of the mass flux from continents to oceans through geologic time. The overall goal of the research reported here is to develop a quantitative understanding of the kinematics of escarpment propagation across passive margins and the underlying geological processes responsible for this behavior. Plateau-bounding escarpments in general exhibit two basic forms depending on the direction of surface water drainage on the plateau interior relative to the escarpment. Where surface water flows away from the escarpment, the escarpment takes the form of subdued embayments and promontories, such that its overall trend remains fairly straight as it evolves with time. Where upland streams flow across the escarpment, it takes the form of dramatic, narrow gorges whose heads appear to propagate up the plateau drainage systems as large-scale knickpoints. From work on the Colorado Plateau, Schmidt (1987) noted that the Colorado River is located much closer to the Grand Canyon's south rim, a drainage divide escarpment, than to the north rim, which is a gorge-like escarpment. The main implication is that the gorge-like form might be associated with higher long-term average erosion rates compared to the drainage divide escarpment type.

  16. Scaling and multifractal fields in the solid earth and topography

    NASA Astrophysics Data System (ADS)

    Lovejoy, S.; Schertzer, D.

    2007-08-01

    Starting about thirty years ago, new ideas in nonlinear dynamics, particularly fractals and scaling, provoked an explosive growth of research both in modeling and in experimentally characterizing geosystems over wide ranges of scale. In this review we focus on scaling advances in solid earth geophysics including the topography. To reduce the review to manageable proportions, we restrict our attention to scaling fields, i.e. to the discussion of intensive quantities such as ore concentrations, rock densities, susceptibilities, and magnetic and gravitational fields. We discuss the growing body of evidence showing that geofields are scaling (have power law dependencies on spatial scale, resolution), over wide ranges of both horizontal and vertical scale. Focusing on the cases where both horizontal and vertical statistics have both been estimated from proximate data, we argue that the exponents are systematically different, reflecting lithospheric stratification which - while very strong at small scales - becomes less and less pronounced at larger and larger scales, but in a scaling manner. We then discuss the necessity for treating the fields as multifractals rather than monofractals, the latter being too restrictive a framework. We discuss the consequences of multifractality for geostatistics, we then discuss cascade processes in which the same dynamical mechanism repeats scale after scale over a range. Using the binomial model first proposed by de Wijs (1951) as an example, we discuss the issues of microcanonical versus canonical conservation, algebraic ("Pareto") versus long tailed (e.g. lognormal) distributions, multifractal universality, conservative and nonconservative multifractal processes, codimension versus dimension formalisms. We compare and contrast different scaling models (fractional Brownian motion, fractional Levy motion, continuous (in scale) cascades), showing that they are all based on fractional integrations of noises built up from singularity basis functions. We show how anisotropic (including stratified) models can be produced simply by replacing the usual distance function by an anisotropic scale function, hence by replacing isotropic singularities by anisotropic ones.

  17. PRK in patients with a keratoconic topography picture. The concept of a physiological 'displaced apex syndrome'.

    PubMed Central

    Doyle, S J; Hynes, E; Naroo, S; Shah, S

    1996-01-01

    AIMS/BACKGROUND: Keratoconus is generally held to be an absolute contraindication for photorefractive keratectomy (PRK). Corneas with inferior steepening on corneal topography are widely thought to have subclinical keratoconus. We were not convinced that this is always the case, as there seems to be a group of patients with a stable inferior steepening pattern on topography who show no other characteristics of clinical keratoconus. We thus decided to offer PRK to some of these patients under strictly defined criteria. METHOD: Four myopic patients with a topography pattern of inferior steepening were submitted to PRK. They were selected on the basis of being aged over 35, with a stable refraction, no slit-lamp signs of keratoconus, and a corrected vision of not less than 6/7 (0.9) with a spherical spectacle correction. They gave fully informed consent that this was an experimental procedure. RESULTS: The refractive results at 6 months after operation were within the range one would expect for PRK on corneas with a regular 'bow-tie' topography and similar level of myopia. No unusual problems were encountered. CONCLUSION: We feel that the corneal topography pattern of inferior steepening is not always a contraindication for PRK. The concept of a physiological 'displaced apex syndrome' is discussed and illustrated by corneal topography in different positions of gaze. Images PMID:8664226

  18. The differential regulation of osteoblast and osteoclast activity by surface topography of hydroxyapatite coatings.

    PubMed

    Costa, Daniel O; Prowse, Paul D H; Chrones, Tom; Sims, Stephen M; Hamilton, Douglas W; Rizkalla, Amin S; Dixon, S Jeffrey

    2013-10-01

    The behavior of bone cells is influenced by the surface chemistry and topography of implants and scaffolds. Our purpose was to investigate how the topography of biomimetic hydroxyapatite (HA) coatings influences the attachment and differentiation of osteoblasts, and the resorptive activity of osteoclasts. Using strategies reported previously, we directly controlled the surface topography of HA coatings on polycaprolactone discs. Osteoblasts and osteoclasts were incubated on HA coatings having distinct isotropic topographies with submicrometer and micro-scale features. Osteoblast attachment and differentiation were greater on more complex, micro-rough HA surfaces (Ra ~2 ?m) than on smoother topographies (Ra ~1 ?m). In contrast, activity of the osteoclast marker tartrate-resistant acid phosphatase was greater on smoother than on micro-rough surfaces. Furthermore, scanning electron microscopy revealed the presence of resorption lacunae exclusively on smoother HA coatings. Inhibition of resorption on micro-rough surfaces was associated with disruption of filamentous actin sealing zones. In conclusion, HA coatings can be prepared with distinct topographies, which differentially regulate responses of osteoblasts, as well as osteoclastic activity and hence susceptibility to resorption. Thus, it may be possible to design HA coatings that induce optimal rates of bone formation and degradation specifically tailored for different applications in orthopedics and dentistry. PMID:23830579

  19. A Systematic Study of Topography Effect of ERT Based on 3-D Modeling and Inversion

    NASA Astrophysics Data System (ADS)

    Lu, De-Bao; Zhou, Qi-You; Junejo, S. A.; Xiao, An-Lin

    2015-06-01

    In this study, a quick method using a digital elevation model (DEM) to obtain real terrain points for generating tetrahedral mesh has been developed, based on TetGen. Then three-dimensional (3-D) forward modeling and inversion, based on the patching method of electrical resistivity tomography (ERT) and which have been compared favorably with those obtained using other software, were used to study topography effect. Asystematic research of apparent resistivity features of different topographies with pole-pole array and Wenner array has been conducted in this study. Based on that, the solutions for removing topography effect are given to the two-dimensional (2-D) survey and the 3-D survey, respectively. Comparing to the inversion result, the solution for the 2-D survey can effectively remove topography influence. A 3-D inversion algorithm incorporating topography is proposed at the same time. Two synthetic models incorporating real topography with fault and ellipse anomalies were created to test the 3-D inversion algorithm, and the results show that the relative image error is less than 30 % and the correlation coefficient is more than 90 %.

  20. French Polynesia Hotspot Swells Explained By Dynamic Topography

    NASA Astrophysics Data System (ADS)

    Adam, C.; Yoshida, M.; Isse, T.; Suetsugu, D.; Shiobara, H.; Sugioka, H.; Kanazawa, T.; Fukao, Y.; Barruol, G.

    2007-12-01

    Situated on the South Pacific Superswell, French Polynesia is a region characterized by numerous geophysical anomalies among which a high volcanism concentration. Seven hotspots are required to explain the observed chains, volcanism ages and geochemical trends. Many open questions still remain on the origin of these hotspot chains: are they created by passive uplift of magma due to discontinuities in the structure of the lithosphere or by the ascent of mantle plumes? In this case, at which depth do these plumes initiate in the mantle? Many geophysical observations (bathymetry, gravity, magnetism, volcanism ages..) are used to understand the unique phenomenon occurring on this region. The most useful information may come from tomography models since they provide a 3D view of the mantle. Until recently, the tomography models over the region were quite inaccurate because of the sparse location of the seismic stations. The deployment of two new seismic stations networks (BBOBS and temporary island stations) has lately remedied this failing. The resulting tomography model obtained through the inversion of Rayleigh waves provides the most accurate view of the shallowest part of the mantle (depths ? 240 km) beneath French Polynesia. Indeed, for the first time the accuracy of a tomography model is good enough to provide information about plume phenomenology in this complex region. In order to quantify the plumes effect on the seafloor, we compute the dynamic topography through an instantaneous flow model. The general trend of the observed depths anomalies (highs and lows) is well recovered. For example the amplitude, location and extension of the swells associated with the Society, Macdonald and Rarotonga are accurately described by the dynamic model. We also find that dynamic uplift is associated with the Tuamotu archipelago which means that a part of the observed swell is due to the present day action of plumes. Since no volcanism ages are available over this chain, this new information may be quite important in understanding the archipelago origin. Another interesting result is that Arago, which is supposed to be an active hotspot along the Cook-Austral chain is situated on a bathymetric low which is well recovered by the dynamic model. Since this region is associated with downwelling flows, this makes us question its hotspot origin.

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

    NASA Technical Reports Server (NTRS)

    Kiefer, Walter S.; Kellogg, Louise H.

    1998-01-01

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

  2. The Laser Vegetation Imaging Sensor (LVIS): An Airborne Laser Altimeter for Mapping Vegetation and Topography

    NASA Technical Reports Server (NTRS)

    Bryan, J.; Rabine, David L.

    1998-01-01

    The Laser Vegetation Imaging Sensor (LVIS) is an airborne laser altimeter designed to quickly and extensively map surface topography as well as the relative heights of other reflecting surfaces within the laser footprint. Since 1997, this instrument has primarily been used as the airborne simulator for the Vegetation Canopy Lidar (VCL) mission, a spaceborne mission designed to measure tree height, vertical structure and ground topography (including sub-canopy topography). LVIS is capable of operating from 500 m to 10 km above ground level with footprint sizes from 1 to 60 m. Laser footprints can be randomly spaced within the 7 degree telescope field-of-view, constrained only by the operating frequency of the ND:YAG Q-switched laser (500 Hz). A significant innovation of the LVIS altimeter is that all ranging, waveform recording, and range gating are performed using a single digitizer, clock base, and detector. A portion of the outgoing laser pulse is fiber-optically fed into the detector used to collect the return signal and this entire time history of the outgoing and return pulses is digitized at 500 Msamp/sec. The ground return is then located using software digital signal processing, even in the presence of visibly opaque clouds. The surface height distribution of all reflecting surfaces within the laser footprint can be determined, for example, tree height and ground elevation. To date, the LVIS system has been used to monitor topographic change at Long Valley caldera, CA, as part of NASA's Topography and Surface Change program, and to map tree structure and sub-canopy topography at the La Selva Biological Research Station in Costa Rica, as part of the pre-launch calibration activities for the VCL mission. We present results that show the laser altimeter consistently and accurately maps surface topography, including sub-canopy topography, and vegetation height and structure. These results confirm the measurement concept of VCL and highlight the benefits of airborne prototypes of spaceborne instruments.

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

    NASA Astrophysics Data System (ADS)

    Dumoulin, Caroline; ?adek, Ond?ej; Choblet, Gaël

    2013-04-01

    Planetary mantles are viscoelastic media. However, since numerical models of thermal convection in a viscoelastic spherical shell are still very challenging, most of the studies concerning dynamic topography of planetary surfaces generated by mantle convection use one of the following simplified rheological set-up: i) IVF (instantaneous viscous flow), ii) viscous body with a free surface, or iii) hybrid methods combining viscous deformation and elastic filtering of the topography. Justifications for the use of such approximations instead of a fully viscoelastic rheology have been made on the basis of simple tests with step-like viscosity structures, with small to moderate viscosity contrasts. However, because the rheology of planetary materials is thermally activated, the radial stratification of viscosity is more likely to be a continuous function of depth, and global viscosity contrasts might be very large. In our study, we systematically compare viscoelastic dynamic topography induced by an internal load to topographies generated by the three different simplified approaches listed above using a realistic viscosity profile for a stagnant lid associated to the lithosphere of a one plate planete. To this purpose, we compute response functions of surface topography and geoid using three different semi-spectral models that all include self-gravitation: a) a linear Maxwell body with a pseudo free upper surface, b) a viscous body with a pseudo free upper surface, and c) a viscous body with a free-slip condition at the surface. Results obtained with this last model (IVF) can then be filtered using the elastic thin shell approximation: the effective elastic thickness then corresponds to the elastic thickness that is needed to fit the viscoelastic topography with an elastic filtering of the IVF topography. We show that the effective elastic thickness varies strongly with the degree of the load, with the depth of the load, and with the duration of the loading. These results naturally depend on the ratio between the mantle and the lithospheric thicknesses. We show that, in the case of Mars, it is not possible to approximate viscoelastic topographies generated by a stable plume using the elastic filtering of viscous dynamic topographies.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    The ocean's 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. The sea surface is directly observed by satellite radar altimetry while the geoid cannot be observed directly. The satellite-based gravity field determination requires different measurement principles (satellite-to-satellite tracking (e.g. GRACE), satellite-gravity-gradiometry (GOCE)). In addition, hydrographic measurements (salinity, temperature and pressure; near-surface velocities) provide information on the dynamic topography. The observation types have different representations and spatial as well as temporal resolutions. Therefore, the determination of the dynamic topography is not straightforward. Furthermore, the integration of the dynamic topography into ocean circulation models requires not only the dynamic topography itself but also its inverse covariance matrix on the ocean model grid. We developed a rigorous combination method in which the dynamic topography is parameterized in space as well as in time. The altimetric sea surface heights are expressed as a sum of geoid heights represented in terms of spherical harmonics and the dynamic topography parameterized by a finite element method which can be directly related to the particular ocean model grid. Besides the difficult task of combining altimetry data with a gravity field model, a major aspect is the consistent combination of satellite data and in-situ observations. The particular characteristics and the signal content of the different observations must be adequately considered requiring the introduction of auxiliary parameters. Within our model the individual observation groups are combined in terms of normal equations considering their full covariance information; i.e. a rigorous variance/covariance propagation from the original measurements to the final product is accomplished. In conclusion, the developed integrated approach allows for estimating the dynamic topography and its inverse covariance matrix on arbitrary grids in space and time. The inverse covariance matrix contains the appropriate weights for model-data misfits in least-squares ocean model inversions. 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 seven satellite altimeter missions (Jason-1, Jason-2, Topex/Poseidon, Envisat, ERS-2, GFO, Cryosat2) in combination with the latest GOCE gravity field model and in-situ data from the Argo floats and near-surface drifting buoys.

  5. Numerical modeling and analysis of the effect of Greek complex topography on tornado genesis

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    Tornadoes have been reported in Greece over the last decades in specific sub-geographical areas and have been associated with strong synoptic forcing. It is well known that meteorological conditions over Greece are affected at various scales by the significant variability of topography, the Ionian Sea at the west and the Aegean Sea at the east. However, 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 tornado genesis events that were triggered under strong synoptic scale forcing over Greece. Three tornado events that occurred over the last years in Thiva (Boeotia, 17 November 2007), Vrastema (Chalkidiki, 12 February 2010) and Vlychos (Lefkada, 20 September 2011) have been selected for numerical experiments. These events were associated with synoptic scale forcing, while their intensity was T4-T5 (Torro scale) and caused significant damage. The simulations were performed using the non-hydrostatic Weather Research and Forecasting model (WRF), initialized with ECMWF gridded analyses, with telescoping nested grids that allow the representation of atmospheric circulations ranging from the synoptic scale down to the meso scale. In the experiments the topography of the inner grid was modified by: (a) 0% (actual topography) and (b) -100% (without topography). The aim was to determine whether the occurrence of tornadoes - mainly identified by various severe weather instability indices - could be indicated by modifying topography. The main utilized instability variables concerned the Bulk Richardson number shear (BRN), the energy helicity index (EHI), the storm-relative environmental helicity (SRH) and the maximum convective available potential energy (MCAPE, for parcel with maximum theta-e). Additional a verification of model was conducted for every sensitivity experiment accompanied with analysis absolute vorticity budget. Numerical simulations revealed that the complex topography was denoted as an important factor during 17 November 2007 and 12 February 2010 events, based on EHI and BRN analyses. Topography around 20 September 2011 event was characterized as the least factor based on EHI, SRH, BRN analyses.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

  7. Discerning the role of topography and ion exchange in cell response of bioactive tissue engineering scaffolds.

    PubMed

    Engel, Elisabeth; Del Valle, Sergio; Aparicio, Conrado; Altankov, George; Asin, Luis; Planell, Josep A; Ginebra, Maria-Pau

    2008-08-01

    Surface topography is known to have an influence on osteoblast activity. However, in the case of bioactive materials, topographical changes can affect also ion exchange properties. This makes the problem more complex, since it is often difficult to separate the strictly topographical effects from the effects of ionic fluctuations in the medium. The scope of this paper is to analyze the simultaneous effect of topography and topography-mediated ion exchange on the initial cellular behavior of osteoblastic-like cells cultured on bioactive tissue engineering substrates. Two apatitic substrates with identical chemical composition but different micro/nanostructural features were obtained by low-temperature setting of a calcium phosphate cement. MG63 osteoblastic-like cells were cultured either in direct contact with the substrates or with their extracts. A strong and permanent decrease of calcium concentration in the culture medium, dependent on substrate topography, was detected. A major effect of the substrate microstructure on cell proliferation was observed, explained in part by the topography-mediated ion exchange, but not specifically by the ionic Ca(2+) fluctuations. Cell differentiation was strongly enhanced when cells were cultured on the finer substrate. This effect was not explained by the chemical modification of the medium, but rather suggested a strictly topographical effect. PMID:18680388

  8. Biodiversity of Jinggangshan Mountain: The Importance of Topography and Geographical Location in Supporting Higher Biodiversity

    PubMed Central

    Liu, Gang; Huang, Fang-Fang; Liu, Jin-Gang; Liao, Wen-Bo; Wang, Ying-Yong; Ren, Si-Jie; Chen, Chun-Quan; Peng, Shao-Lin

    2015-01-01

    Diversity is mainly determined by climate and environment. In addition, topography is a complex factor, and the relationship between topography and biodiversity is still poorly understood. To understand the role of topography, i.e., altitude and slope, in biodiversity, we selected Jinggangshan Mountain (JGM), an area with unique topography, as the study area. We surveyed plant and animal species richness of JGM and compared the biodiversity and the main geographic characteristics of JGM with the adjacent 4 mountains. Gleason’s richness index was calculated to assess the diversity of species. In total, 2958 spermatophyte species, 418 bryophyte species, 355 pteridophyte species and 493 species of vertebrate animals were recorded in this survey. In general, the JGM biodiversity was higher than that of the adjacent mountains. Regarding topographic characteristics, 77% of JGM’s area was in the mid-altitude region and approximately 40% of JGM’s area was in the 10°–20° slope range, which may support more vegetation types in JGM area and make it a biodiversity hotspot. It should be noted that although the impact of topography on biodiversity was substantial, climate is still a more general factor driving the formation and maintenance of higher biodiversity. Topographic conditions can create microclimates, and both climatic and topographic conditions contribute to the formation of high biodiversity in JGM. PMID:25763820

  9. Topography compensation for haptization of a mesh object and its stiffness distribution.

    PubMed

    Yim, Sunghoon; Jeon, Seokhee; Choi, Seungmoon

    2015-01-01

    This work was motivated by the need for perceptualizing nano-scale scientific data, e.g., those acquired by a scanning probe microscope, where collocated topography and stiffness distribution of a surface can be measured. Previous research showed that when the topography of a surface with spatially varying stiffness is rendered using the conventional penalty-based haptic rendering method, the topography perceived by the user could be significantly distorted from its original model. In the worst case, a higher region with a smaller stiffness value can be perceived to be lower than a lower region with a larger stiffness value. This problem was explained by the theory of force constancy: the user tends to maintain an invariant contact force when s/he strokes the surface to perceive its topography. In this paper, we present a haptization algorithm that can render the shape of a mesh surface and its stiffness distribution with high perceptual accuracy. Our algorithm adaptively changes the surface topography on the basis of the force constancy theory to deliver adequate shape information to the user while preserving the stiffness perception. We also evaluated the performance of the proposed haptization algorithm in comparison to the constraint-based algorithm by examining relevant proximal stimuli and carrying out a user experiment. Results demonstrated that our algorithm could improve the perceptual accuracy of shape and reduce the exploration time, thereby leading to more accurate and efficient haptization. PMID:25794366

  10. The Importance of Basal Topography for Greenland Ice Sheet Margin Hydrology

    NASA Astrophysics Data System (ADS)

    Moustafa, S.; Rennermalm, A. K.; Smith, L. C.; Pitcher, L. H.; Chu, V. W.

    2012-12-01

    Nearly half of the Greenland ice sheet's total mass loss is controlled by surface mass balance, primarily driven by meltwater runoff exiting at its margin via supra-, en-, and sub-glacial drainage networks into fjords and pro-glacial lakes and rivers. Despite the importance of meltwater runoff, Greenland's hydrologic drainage patterns are not well understood. This is partly due to a scarcity of ice sheet meltwater runoff observations and detailed information about supra- and sub-glacial topography, which are responsible for dictating runoff flow patterns. However, such data are available locally in southwest Greenland for the Akuliarusiarsuup Kuua (AK) River watershed. In this study, NASA IceBridge supra-glacial (Airborne Topographic Mapper (ATM)) and sub-glacial (Multichannel Coherent Radar Depth Sounder (MCoRDS)) topography and in situ hydrologic data from 2009-2012 are used to study three nested riverine systems within the AK River watershed ranging from 8 to 101 km2. Examination of relationships between drainage patterns modeled from topographic data and actual ice sheet runoff losses provide insight into drainage basin delineation accuracy, scale-dependency, and surface and sub-glacial topography controls on ice sheet margin hydrology. Finally, an assessment is made to determine the importance of incorporating basal topography within meltwater runoff models versus surface topography alone.

  11. Transylvanian heat flow in the presence of topography, paleoclimate and groundwater flow

    NASA Astrophysics Data System (ADS)

    ?erban, Delia Zemira; Nielsen, Søren B.; Demetrescu, Cri?an

    2001-07-01

    The Transylvanian Depression (TD) is located in the inner part of the Carpathian orogen and shows a marked heat flux low of 30 mW m -2 in the centre, increasing to 60 mW m -2 towards the margins. It is the purpose of the paper to asses the possibility that the observed heat flux in the TD is a consequence of disturbances of the shallow geothermal gradient caused by topography, topographically driven ground water flow and climatic changes. The thermal effects of topography, topographically driven groundwater flow and paleoclimate have been investigated using two-dimensional finite element models. The results show that topography can induce a decrease in heat flux at hill crests and an increase at the bottom of valleys. Topographically driven ground water flow accentuates the effect above ˜1000 m and decreases it below. For the characteristic amplitude and wavelength of topography in Transylvania the heat flux corrections for the cumulated effect of topography and water flow are maximum 1 mW m -2, which is insignificant. Paleoclimate potentially has a large thermal effect. Temperature variations associated with the last glaciation can produce a significantly increasing gradient with depth, which is present in the majority of measured wells. Inversion of six wells confirmed that the curvature in the temperature profiles is consistent with the climatic cooling of the last glaciation. The paleoclimatic effect may induce heat flow corrections in the range 3-7 mW m -2.

  12. Controlled surface topography regulates collective 3D migration by epithelial-mesenchymal composite embryonic tissues.

    PubMed

    Song, Jiho; Shawky, Joseph H; Kim, YongTae; Hazar, Melis; LeDuc, Philip R; Sitti, Metin; Davidson, Lance A

    2015-07-01

    Cells in tissues encounter a range of physical cues as they migrate. Probing single cell and collective migratory responses to physically defined three-dimensional (3D) microenvironments and the factors that modulate those responses are critical to understanding how tissue migration is regulated during development, regeneration, and cancer. One key physical factor that regulates cell migration is topography. Most studies on surface topography and cell mechanics have been carried out with single migratory cells, yet little is known about the spreading and motility response of 3D complex multi-cellular tissues to topographical cues. Here, we examine the response to complex topographical cues of microsurgically isolated tissue explants composed of epithelial and mesenchymal cell layers from naturally 3D organized embryos of the aquatic frog Xenopus laevis. We control topography using fabricated micropost arrays (MPAs) and investigate the collective 3D migration of these multi-cellular systems in these MPAs. We find that the topography regulates both collective and individual cell migration and that dense MPAs reduce but do not eliminate tissue spreading. By modulating cell size through the cell cycle inhibitor Mitomycin C or the spacing of the MPAs we uncover how 3D topographical cues disrupt collective cell migration. We find surface topography can direct both single cell motility and tissue spreading, altering tissue-scale processes that enable efficient conversion of single cell motility into collective movement. PMID:25933063

  13. Submillimeter-Scale Topography of the Lunar Regolith

    NASA Astrophysics Data System (ADS)

    Helfenstein, Paul; Shepard, Michael K.

    1999-09-01

    We have applied computer stereophotogrammetry to Apollo Lunar Surface Closeup Camera (ALSCC) pictures of the lunar surface to construct the first-ever digital topographic relief maps of undisturbed lunar soil over spatial scales from 85 ?m to 8.5 cm. Using elevation histograms, fractal analysis, and Hapke's photometric roughness model we show that Apollo 14 (Fra Mauro) Imbrium ejecta is rougher than average Apollo 11 (Mare Tranquilitatis) and Apollo 12 (Oceanus Procellarum) mare surfaces at submillimeter to decimeter size-scales. We confirm the early result of K. Lumme et al. (1985, Earth Moon Planets33, 19-29) that the cumulative distribution of elevations for lunar soil is typically well described by Gaussian statistics. However, cumulative distributions are insensitive to asymmetries in the shapes of elevation histograms: Of 11 discrete elevation histograms we measured, about half exhibit significant deviations from Gaussian behavior. We also confirm Lumme et al.'s finding that the roughnesses of all lunar surfaces increase with decreasing size-scale. We further show that the scale dependence of roughness is well represented by fractal statistics. The rates of change of roughness with size scale, represented by fractal dimension D, are remarkably similar among terrians. After correcting for the contribution of large-scale roughness, our average value of D=2.31±0.06 falls within the range 2.0?D?2.4 reported from lunar radar studies. The amplitude of roughness, which we characterize with the rms slope angle at 1-mm scale, varies significantly among terrains. For lunar mare, the average rms slope angle is 16°±4°3 and that for Fra Mauro regolith is 25°±1°. By comparison to radar data, we suggest that the roughness of Fra Mauro (Imbrium ejecta) regolith is similar to that of lunar highland terrains. We find that the Gaussian slope distribution assumed in B. W. Hapke's model (1984, Icarus59, 41-59) adequately describes typical lunar regolith surfaces. A revised form of Hapke's equation that models realistic particle phase functions and the coherent backscatter opposition effect was fitted to disk-resolved lunar photometric observations and yields estimates of overline?=27±1° for highland and overline?=24±1° for mare regolith. These values of overline? as well as the implied relative highland:mare photometric roughness ratio are best matched in our elevation data by the cummulative contributions of surface topography covering all scales greater than 0.1 mm. Less than 5% of the photometrically detected roughness of lunar regolith is contributed by surface relief at scales larger than 8 cm. This conclusion implies that values of overline? derived from whole-disk and disk-resolved photometry, respectively, may be taken to represent the same physical quantity. In addition, particulate samples used in goniophotometric measurements should not be assumed to be photometrically smooth (i.e., overline?=0°), as is often done in laboratory applications of Hapke's photometric model. The predicted photometric roughness at size scales of 0.1 mm and less significantly exceed photometric estimates and suggests that there exists a measurable size scale below which topographic relief either is not photometrically detectable or is not represented in the Hapke model as macroscopic roughness.

  14. Molecular response of Escherichia coli adhering onto nanoscale topography

    NASA Astrophysics Data System (ADS)

    Rizzello, Loris; Galeone, Antonio; Vecchio, Giuseppe; Brunetti, Virgilio; Sabella, Stefania; Pompa, Pier Paolo

    2012-10-01

    Bacterial adhesion onto abiotic surfaces is an important issue in biology and medicine since understanding the bases of such interaction represents a crucial aspect in the design of safe implant devices with intrinsic antibacterial characteristics. In this framework, we investigated the effects of nanostructured metal substrates on Escherichia coli adhesion and adaptation in order to understand the bio-molecular dynamics ruling the interactions at the interface. In particular, we show how highly controlled nanostructured gold substrates impact the bacterial behavior in terms of morphological changes and lead to modifications in the expression profile of several genes, which are crucially involved in the stress response and fimbrial synthesis. These results mainly demonstrate that E. coli cells are able to sense even slight changes in surface nanotopography and to actively respond by activating stress-related pathways. At the same time, our findings highlight the possibility of designing nanoengineered substrates able to trigger specific bio-molecular effects, thus opening the perspective of smartly tuning bacterial behavior by biomaterial design.

  15. Geoid and topography for infinite Prandtl number convection in a spherical shell

    NASA Technical Reports Server (NTRS)

    Bercovici, D.; Schubert, G.; Zebib, A.

    1988-01-01

    Geoid anomalies and surface and lower-boundary topographies are calculated for numerically generated thermal convection for an infinite Prandtl number, Boussinesq, axisymmetric spherical fluid shell with constant gravity and viscosity, for heating both entirely from below and entirely from within. Convection solutions are obtained for Rayleigh numbers Ra up to 20 times the critical Ra in heating from below and 27 times critical for heating from within. Geoid parallels surface undulations, and boundary deformation generally increases with increasing cell wavelength. Dimensionless geoid and topography in heating from below are about 5 times greater than in heating from within. Values for heating from within correlate more closely with geophysical data than values from heating from below, suggesting a predominance of internal heating in the mantle. The study emphasizes that dynamically induced topography and geoid are sensitive to the mode of heating in the earth's mantle.

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

    SciTech Connect

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

    2009-09-13

    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.

  17. Development of a surface topography instrument for automotive textured steel plate

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Wang, Shenghuai; Chen, Yurong; Xie, Tiebang

    2010-08-01

    The surface topography of automotive steel plate is decisive to its stamping, painting and image clarity performances. For measuring this kind of surface topography, an instrument has been developed based on the principle of vertical scanning white light microscopy interference principle. The microscopy interference system of this instrument is designed based on the structure of Linnik interference microscopy. The 1D worktable of Z direction is designed and introduced in details. The work principle of this instrument is analyzed. In measuring process, the interference microscopy is derived as a whole and the measured surface is scanned in vertical direction. The measurement accuracy and validity is verified by templates. Surface topography of textured steel plate is also measured by this instrument.

  18. Venus - Comparison of gravity and topography in the vicinity of Beta Regio

    NASA Technical Reports Server (NTRS)

    Reasenberg, R. D.; Goldberg, Z. M.; Shapiro, I. I.

    1982-01-01

    The Doppler tracking data obtained from the Pioneer Venus Orbiter when it passed near Beta Regio yielded a peak vertical anomaly of 150 mGal when analyzed by our two stage procedure. A comparison of maps of the gravity and topography at comparable resolution shows a striking correlation. A scatter plot shows that the observed gravity anomaly is approximately 0.4 of that expected from uncompensated topography of half the mean density of Venus. However, the spectral admittance shows that the gravity anomalies can not be explained either by Airy compensation at fixed depth or by a model comprising an elastic plate atop an inviscid fluid. The gravity and topography variations may signify deep compensation or dynamic support for Beta Regio and more shallow compensation for other features.

  19. Wind Energy Forecasting Utilizing High Resolution Topography in the WRF Model

    NASA Astrophysics Data System (ADS)

    Beechler, B. E.; Zupanski, D.

    2012-12-01

    Local topography has considerable effects on the dynamics of low-level winds. Many wind farms take advantage of the local landscape when deciding where to place their turbines. In this study we attempt to better model these unique local features by representing them more accurately. The current default WRF topography has a maximum resolution of 30 arc seconds which at mid-latitudes is roughly 1 kilometer whereas the USGS database currently covers 95% of the United States at 30 meter resolution. In this study the 1/3 arc second national elevation database (NED13) is interfaced with the WRF model using a tool developed specifically to make this process simple and the effects of modeling with the updated topography are investigated.

  20. Topography-Dependent Eikonal Traveltime Tomography for Upper Crustal Structure Beneath an Irregular Surface

    NASA Astrophysics Data System (ADS)

    Ma, Ting; Zhang, Zhongjie

    2015-06-01

    Seismic modeling of the crust with nonflat topography can be made by first-arrival traveltime tomography, which faces the challenge of an irregular free surface. A feasible way to deal with this problem consists of expanding the physical space by overlapping a low velocity layer above the irregular surface in order to have a flat topography, besides using the classical eikonal equation solver for traveltime computation. However, the undesirable consequences of this method include seismic ray deviations due to the transition from an irregular surface that is the free boundary to an inner discontinuity lying in the expanded computational space. An alternative solution, called irregular surface flattening, which involves the transformation between curvilinear and Cartesian coordinate systems, has been recently proposed through the formulation of the topography-dependent eikonal equation (TDEE) and a new solver for forward modeling of traveltimes. Based on the solution of this equation, we present topography-dependent eikonal traveltime tomography (hereafter TDETT) for seismic modeling of the upper crust. First-arrival traveltimes are calculated using the TDEE solver and the raypaths with the minimum traveltime that can be found by following the steepest traveltime gradient from the receiver to the source. By solving an algebraic equation system that connects the slowness perturbations with the already determined traveltimes, these variables can be obtained making use of the back-projection algorithm. This working scheme is evaluated through three numerical examples with different topographic complexities that are conducted from synthetic data and a fourth example with somewhat more complicated topography and real data acquired in northeastern Tibet. The comparison of the results obtained by both methods, i.e., physical space expansion above the irregular surface and irregular surface flattening, fully validates the tomography scheme that is proposed to construct seismic velocity models with nonflat topography.

  1. Fast integral rigorous modeling applied to wafer topography effect prediction on 2x nm bulk technologies

    NASA Astrophysics Data System (ADS)

    Michel, J.-C.; Le Denmat, J.-C.; Tishchenko, A.; Jourlin, Y.

    2014-03-01

    Reflection by wafer topography and underlying layers during optical lithography can cause unwanted overexposure in the resist [1]. In most cases, the use of bottom anti reflective coating limits this effect. However, this solution is not always suitable because of process complexity, cost and cycle time penalty, as for ionic implantation lithography process in 28nm bulk technology. As a consequence, computational lithography solutions are currently under development to simulate and correct wafer topographical effects [2], [3]. For ionic implantation source drain (SD) photolithography step, wafer topography influences resulting in implant pattern variation are various: active silicon areas, Poly patterns, Shallow Trench Isolation (STI) and topographical transitions between these areas. In 28nm bulk SD process step, the large number of wafer stack variations involved in implant pattern modulation implies a complex modeling of optical proximity effects. Furthermore, those topography effects are expected to increase with wafer stack complexity through technology node downscaling evolution. In this context, rigorous simulation can bring significant value for wafer topography modeling evolution in R and D process development environment. Unfortunately, classical rigorous simulation engines are rapidly run time and memory limited with pattern complexity for multiple under layer wafer topography simulation. A presentation of a fast rigorous Maxwell's equation solving algorithm integrated into a photolithography proximity effects simulation flow is detailed in this paper. Accuracy, run time and memory consumption of this fast rigorous modeling engine is presented through the simulation of wafer topography effects during ionic implantation SD lithography step in 28nm bulk technology. Also, run time and memory consumption comparison is shown between presented fast rigorous modeling and classical rigorous RCWA method through simulation of design of interest. Finally, integration opportunity of such fast rigorous modeling method into OPC flow is discussed in this paper.

  2. Dependence of Eemian Greenland temperature reconstructions on the ice sheet topography

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    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.

  3. Dependence of Eemian Greenland temperature reconstructions on the ice sheet topography

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  4. A laboratory study of low-mode internal tide scattering by finite-amplitude topography

    E-print Network

    Peacock, Thomas; Didelle, Henri; Viboud, Samuel; Dauxois, Thierry

    2015-01-01

    We present the first laboratory experimental results concerning the scattering of a low-mode internal tide by a gaussian topography. Experiments performed at the Coriolis Platform in Grenoble used a recently-conceived internal wave generator as a means of producing a high-quality mode-1 wave field. The evolution of the wave field in the absence and presence of a supercritical Gaussian was studied by performing spatiotemporal modal decompositions of velocity field data obtained using Particle Image Velocimetry (PIV). The results support predictions that large-amplitude supercritical topography produces significant reflection of the internal tide and transfer of energy from low to high modes.

  5. Submarine topography and sediments of the lower continental slope off East-Central Mexico 

    E-print Network

    Baie, Lyle Frederick

    1967-01-01

    SUBMARINE TOPOGRAPHY AND SEDIMENTS OF THE LOWER CONTINENTAL SLOPE OFF EAST-CENTRAL MEXICO A Thesis By LYLE FREDRICK BAIE Submitted to the Graduate College of the Texas A&M University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE August 1967 Major Subject: GEOLOGICAL OCEANOGRAPHY SUBMARINE TOPOGRAPHY AND SEDIMENTS OF THE LOWER CONTINENTAL SLOPE OFF EAST-CENTRAL MEXICO A Thesis By LYLE FREDRICK BAIE Approved as to style and content fy: airman o x t Me e...

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

    NASA Technical Reports Server (NTRS)

    Revenaugh, Justin; Parsons, Barry

    1987-01-01

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

  7. Angle resolved ion scattering spectroscopy at surfaces of pure liquids: topography and orientation of molecules.

    PubMed

    Andersson, Gunther

    2005-08-01

    The topography of a liquid surface has not been the subject of experimental research because of a lack of experimental methods. The hereby outlined investigation shows how the topography of a liquid surface can be classified through the angular mode of neutral impact collision ion scattering spectroscopy. It further shows how concentration depth profiles with a high depth resolution are gained. These can be used as the basis to determine quantitatively the orientation of molecules. The substances investigated are the polar solvents formamide and benzyl alcohol. PMID:16189615

  8. Preliminary Investigation of EarthScope EARS Derived MOHO Topography and Large Scale Faye Gravity Anomaly

    NASA Astrophysics Data System (ADS)

    Crain, K.; Holland, A. A.

    2013-12-01

    This is a preliminary investigation using the EarthScope EARS receiver functions in combination with the Faye gravity anomaly. This includes both qualitative and quantitative comparison of the large scale Faye anomaly with an expected 3D geology interpretation for the southern mid-continent U.S.A. The 3D geology interpretation consists of expected 3D topographies based on National Elevation Data, published formation elevations, measured and published basement topography with geology, and the expected MOHO topography calculated using the EARS estimated crustal thickness. The EARS automated receiver functions provides a large data set of automatically generated receiver functions and models of bulk crustal properties. These bulk crustal properties include crustal thickness, and Vp/Vs given an assumed Vp. The results from this automatic determination can be evaluated through the H-K stacking, and are often a good method to identify where there may be complex structure or poor quality data. Some a priori information is used to constrain the EARS crustal model. The observed Faye gravity anomaly is calculated using the observed gravity value at their observation location from the PACES gravity database and their extracted elevation from the national elevation data set. Then the expected Faye gravity is modeled using the expected 3D geology interpretation. The observed and modeled Faye gravity, along with the expected 3D geologic interpretation with its topographies and geology and their expected uncertainties are used in a simple 3D density inversion to evaluate the consistency of the estimated with the expected crust / MOHO interface. Areas with complex crustal geology and or inconsistent EARS data are identified as areas of higher uncertainty and require further study. Even areas with agreement between the expected MOHO topography and the Faye anomaly have interesting geology implications. For example: in central Oklahoma the 14 km deep Anadarko basin has a positive Faye anomaly associated with it without surface topography at the same location there is a positive qualitative correlation with the EARS derived MOHO topography. The Faye gravity and MOHO topography may imply an extension of the Mid-Continent Rift through Kansas to the Southern Oklahoma Aulacogen and possibly further south and requires further investigation.

  9. GLUTATHIONE SYNTHESIS

    PubMed Central

    Lu, Shelly C.

    2012-01-01

    BACKGROUND Glutathione (GSH) is present in all mammalian tissues as the most abundant non-protein thiol that defends against oxidative stress. GSH is also a key determinant of redox signaling, vital in detoxification of xenobiotics, regulates cell proliferation, apoptosis, immune function, and fibrogenesis. Biosynthesis of GSH occurs in the cytosol in a tightly regulated manner. Key determinants of GSH synthesis are the availability of the sulfur amino acid precursor, cysteine, and the activity of the rate-limiting enzyme, glutamate cysteine ligase (GCL), which is composed of a catalytic (GCLC) and a modifier (GCLM) subunit. The second enzyme of GSH synthesis is GSH synthetase (GS). SCOPE OF REVIEW This review summarizes key functions of GSH and focuses on factors that regulate the biosynthesis of GSH, including pathological conditions where GSH synthesis is dysregulated. MAJOR CONCLUSIONS GCL subunits and GS are regulated at multiple levels and often in a coordinated manner. Key transcription factors that regulate the expression of these genes include NF-E2 related factor 2 (Nrf2) via the antioxidant response element (ARE), AP-1, and nuclear factor kappa B (NF?B). There is increasing evidence that dysregulation of GSH synthesis contributes to the pathogenesis of many pathological conditions. These include diabetes mellitus, pulmonary and liver fibrosis, alcoholic liver disease, cholestatic liver injury, endotoxemia and drug-resistant tumor cells. GENERAL SIGNIFICANCE GSH is a key antioxidant that also modulates diverse cellular processes. A better understanding of how its synthesis is regulated and dysregulated in disease states may lead to improvement in the treatment of these disorders. PMID:22995213

  10. The GMRT: System Parameters and Current Status

    E-print Network

    Udgaonkar, Jayant B.

    , albeit for only one polarisation per band. 1.2 Electronics At the focus of each antenna, each feed has 2 Overview 2 1.1 Antennas & Feeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 Electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.3 Software based

  11. Effects of digital elevation model map scale and data resolution on a topography-based watershed model

    Microsoft Academic Search

    David M. Wolock; Curtis V. Price

    1994-01-01

    The effects of digital elevation model (DEM) map scale and data resolution on watershed model predictions of hydrologic characteristics were determined for TOPMODEL, a topography-based watershed model. The effects of topography on watershed hydrology are represented in TOPMODEL as the distribution of ln (a\\/tan B), where ln is the Napierian logarithm, a is the upslope area per unit contour length,

  12. IEEE GEOSCIENCE AND REMOTE SENSING LETTERS, VOL. X, NO. X, NOVEMBER 200X 1 Digital Topography Models for Martian Surfaces

    E-print Network

    Vilalta, Ricardo

    is at the center of our current solar system explo- ration efforts. In particular, there are presently three an analysis of Martian topography data. The Martian topography data was gathered by the Mars Orbiter Laser notion of the DEM. Individual pixels in the DTM carry an array of local and regional topographical

  13. Abstract--Novel technologies like substrate transfer technology can introduce severe topography on otherwise flat silicon wafers.

    E-print Network

    Technische Universiteit Delft

    on otherwise flat silicon wafers. Since optical lithography is usually performed on ultra flat wafers, the alignment system is not optimized for high topography wafers. In this work, an experimental procedure is presented to measure the alignment offset of an ASML PAS5000/50 waferstepper on high topography wafers

  14. Impact of Hillslope-Scale Organization of Topography, Soil Moisture, Soil Temperature, and Vegetation on Modeling Surface Microwave Radiation Emission

    Microsoft Academic Search

    Alejandro N. Flores; Valeriy Y. Ivanov; Dara Entekhabi; Rafael L. Bras

    2009-01-01

    Microwave radiometry will emerge as an important tool for global remote sensing of near-surface soil moisture in the coming decade. In this modeling study, we find that hillslope-scale topography (tens of meters) influences microwave brightness temperatures in a way that produces bias at coarser scales (kilometers). The physics underlying soil moisture remote sensing suggests that the effects of topography on

  15. Impacts of Typhoon Track and Island Topography on the Heavy Rainfalls in Taiwan Associated with Morakot (2009)

    E-print Network

    2009-01-01

    Impacts of Typhoon Track and Island Topography on the Heavy Rainfalls in Taiwan Associated rainfall and flooding event in Taiwan induced by Typhoon Morakot (2009). It is found that a good rainfall, interaction of the typhoon circulation with complex topography in southern Taiwan plays a domi- nant role

  16. Internal wave and boundary current generation by tidal flow over topography Amadeus Dettner, Harry L. Swinney, and M. S. Paoletti

    E-print Network

    Texas at Austin. University of

    Internal wave and boundary current generation by tidal flow over topography Amadeus Dettner, Harry turbulence and small-scale internal waves above deep-ocean topography Phys. Fluids 25, 106604 (2013); 10.1063/1.4826888 Topographically induced internal solitary waves in a pycnocline: Secondary generation and selection criteria Phys

  17. A stress interpretation scheme applied to lunar gravity and topography data

    E-print Network

    A stress interpretation scheme applied to lunar gravity and topography data F. Chambat1 and B to be directly related to the deviatoric stresses without any rheological assumptions. In this approach a new set above the corresponding equipotential surfaces and (2) the stress difference. The method is applied

  18. Clinical Correlation between Placido, Scheimpflug and LED Color Reflection Topographies in Imaging of a Scarred Cornea.

    PubMed

    Kanellopoulos, Anastasios John; Asimellis, George

    2014-09-01

    This case report aims to evaluate safety, efficacy and feasibility of anterior surface imaging by a novel point-source reflection topographer, in comparison to four other corneal imaging modalities. A 17-year-old female patient, clinically diagnosed with chronic herpetic keratitis in her left eye was imaged by a novel multicolored-spot reflection topography system. We comparatively investigated elevation and curvature maps between the novel topographer and established Placido disk topography and Scheimpflug tomography systems. Pachymetry maps were compared between the Scheimpflug system and anterior-segment optical coherence tomography system. The Placido system failed to properly register the abnormal anterior surface due to incomplete mire registration, while the Scheimpflug topometry device imaged the anterior surface properly, but not the posterior (due to media opacity), and thus pachymetry was highly irregular and erroneous in this case. Imaging of corneas infected with herpes simplex virus keratitis has been rare; we have not identified any such documentation in the peer review literature in the last 10 years. This novel multicolored-spot reflection topography imaging may offer successful corneal imaging in cases where established clinical topography systems may fail to produce accurate reconstruction of the corneal shape. This is an important case demonstrating exceptional clinical feasibility in such rare cases offered by a newly introduced technology in ophthalmic imaging. PMID:25408671

  19. Integrated Surface Topography Characterization of Variously Polished Niobium for Superconducting Particle Accelerators

    SciTech Connect

    Hui Tian, Charles Reece, Michael Kelley, G. Ribeill

    2009-05-01

    As superconducting niobium radio-frequency (SRF) cavities approach fundamental material limits, there is increased interest in understanding the details of topographical influences on realized performance limitations. Micro-and nano-roughness are implicated in both direct geometrical field enhancements as well as complications of the composition of the 50 nm surface layer in which the super-currents flow. Interior surface chemical polishing (BCP/EP) to remove mechanical damage leaves surface topography, including pits and protrusions of varying sharpness. These may promote RF magnetic field entry, locally quenching superconductivity, so as to degrade cavity performance. A more incisive analysis of surface topography than the widely-used average roughness is needed. In this study, a power spectral density (PSD) approach based on Fourier analysis of surface topography data acquired by both stylus profilometry and atomic force microscopy (AFM) is being used to distinguish the scale-dependent smoothing effects. The topographical evolution of the Nb surface as a function of different steps of EP is reported, resulting in a novel qualitative and quantitative description of Nb surface topography.

  20. Contact-mode AFM control with modified surface topography learning observer and PTC

    Microsoft Academic Search

    Hiroshi Fujimoto; Takashi Oshima

    2008-01-01

    Atomic force microscope (AFM) is the instrument that can measure the surface of samples on the nano-scale. Most of the controllers of commercial AFMs are designed by classic control theory. However, sophisticated control theory has been applied in recent academic papers. Authors have already proposed a surface topography learning observer (STLO) based on disturbance observer theory. However, this method is

  1. Managing Construction Operations Visually: 3-D Techniques for Complex Topography and Restricted Visibility

    ERIC Educational Resources Information Center

    Rodriguez, Walter; Opdenbosh, Augusto; Santamaria, Juan Carlos

    2006-01-01

    Visual information is vital in planning and managing construction operations, particularly, where there is complex terrain topography and salvage operations with limited accessibility and visibility. From visually-assessing site operations and preventing equipment collisions to simulating material handling activities to supervising remotes sites…

  2. Effects of topography on tropical lower montane forests under different geological conditions on Mount Kinabalu, Borneo

    Microsoft Academic Search

    Masaaki Takyu; Shin-Ichiro Aiba; Kanehiro Kitayama

    2002-01-01

    Species composition and forest structure change with topography.However, mechanisms for topographical vegetation changes are still not wellunderstood, because a topographical gradient is a complex environmentalgradientinclusive of many factors. The foot of Mt. Kinabalu is covered with three typesof geological substrates, i.e. Quaternary and Tertiary sedimentary rocks andultrabasic (serpentine) rock. Quaternary and Tertiary sedimentaryrocks are different in site age, but controlled

  3. EAARL coastal topography-Gateway National Recreation Area, New Jersey and New York, 2009

    USGS Publications Warehouse

    Nayegandhi, Amar; Vivekanandan, Saisudha; Brock, John C.; Stevens, Sara; Wright, C. Wayne; Bonisteel, Jamie M.; Nagle, David B.; Yates, Xan; Klipp, Emily S.

    2010-01-01

    This DVD contains lidar-derived bare-earth (BE) and first-surface (FS) topography GIS datasets of a portion of the Gateway National Recreation Area in New Jersey and New York. These datasets were acquired July 8-9, 2009.

  4. Scaling and parameterization of clear-sky solar radiation over complex topography

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Solar radiation at the land surface is influenced by slope, aspect, shadows, and obstruction of the sky, all of which vary over a wide range of length scales in regions of complex topography, with important consequences for the surface energy balance. Atmospheric models, however, generally assume t...

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

    E-print Network

    Paris-Sud XI, Université de

    High Resolution SAR Interferometry: influence of local topography in the context of glacier Spatiale - Bucuresti, ROMANIA - Tel/fax +4021 457 44 71 Abstract-- SAR interferometric data offers become mandatory with the increase of the SAR resolution. In this paper, an original 2-step method

  6. Mare Crisium area topography - A comparison of earth-based radar and Apollo mapping camera results

    Microsoft Academic Search

    S. H. Zisk

    1978-01-01

    An earth-based radar topography (ERT) map has been constructed of the Mare Crisium area. Systematic and random sources of error are discussed. A comparison between the ERT map and Lunar Topographic Orthophotomaps shows a random mean discrepancy of less than 100 m between the two maps, except for small-scale (20 km or less in diameter) features, where systematic smoothing reduces

  7. Lunar topography: statistical analysis at 10-1 kilometer scale roughness

    Microsoft Academic Search

    Y. Yokota; J. Haruyama; C. Honda; T. Morota; M. Ohtake

    2006-01-01

    Lunar topography reflects the impact history of the terrain We will report a comparison of statistic values about lunar topographic roughness such as the fractal dimension at 10-1 kilometer-scale among several regions in lunar highlands Though one popular method to estimate absolute age of the lunar terrain is the crater counting method it is difficult to estimate absolute ages of

  8. Clinical Correlation between Placido, Scheimpflug and LED Color Reflection Topographies in Imaging of a Scarred Cornea

    PubMed Central

    Kanellopoulos, Anastasios John; Asimellis, George

    2014-01-01

    This case report aims to evaluate safety, efficacy and feasibility of anterior surface imaging by a novel point-source reflection topographer, in comparison to four other corneal imaging modalities. A 17-year-old female patient, clinically diagnosed with chronic herpetic keratitis in her left eye was imaged by a novel multicolored-spot reflection topography system. We comparatively investigated elevation and curvature maps between the novel topographer and established Placido disk topography and Scheimpflug tomography systems. Pachymetry maps were compared between the Scheimpflug system and anterior-segment optical coherence tomography system. The Placido system failed to properly register the abnormal anterior surface due to incomplete mire registration, while the Scheimpflug topometry device imaged the anterior surface properly, but not the posterior (due to media opacity), and thus pachymetry was highly irregular and erroneous in this case. Imaging of corneas infected with herpes simplex virus keratitis has been rare; we have not identified any such documentation in the peer review literature in the last 10 years. This novel multicolored-spot reflection topography imaging may offer successful corneal imaging in cases where established clinical topography systems may fail to produce accurate reconstruction of the corneal shape. This is an important case demonstrating exceptional clinical feasibility in such rare cases offered by a newly introduced technology in ophthalmic imaging. PMID:25408671

  9. Retinal Ganglion Cell Topography of Five Species of Ground-Foraging Birds

    Microsoft Academic Search

    Tracy Dolan; Esteban Fernández-Juricic

    2010-01-01

    Birds that forage on the ground have been studied extensively in relation to behavioral trade-offs between foraging and scanning for predators; however, we know little about the topography of their retinas, which can influence how they gather visual information. We characterized the density of retinal ganglion cells across the retina and estimated visual acuity of four Passeriformes (European starling Sturnus

  10. pinyon-juniper cover and topography in the central Great Basin, Nevada

    Microsoft Academic Search

    Bethany A. Bradley; Erica Fleishman

    Aim Increasing geographical range and density of conifers is a major form of land-cover change in the western United States, affecting fire frequency, biogeochemistry and possibly biodiversity. However, the extent and magnitude of the change are uncertain. This study aimed to quantify the relationship between changing conifer cover and topography. Location The central Great Basin in the state of Nevada,

  11. Scaling and parametrization of clear-sky solar radiation over complex topography

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Solar radiation at the land surface is influenced by slope, aspect, shadows and obstruction of the sky, all of which vary over a wide range of length scales in regions of complex topography, with important consequences for the surface energy balance. Atmospheric models, however, generally assume the...

  12. EAARL topography-Three Mile Creek and Mobile-Tensaw Delta, Alabama, 2010

    USGS Publications Warehouse

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

    2011-01-01

    This DVD contains lidar-derived first-surface (FS) and bare-earth (BE) topography GIS datasets of a portion of the Mobile-Tensaw Delta region and Three Mile Creek in Alabama. These datasets were acquired on March 6, 2010.

  13. Topography of the Moho undulations in France from gravity data: their age and origin

    Microsoft Academic Search

    J. P. Lefort; B. N. P. Agarwal

    2002-01-01

    The complete gravity data set from France and part of the neighboring countries has been analyzed to compute the topography of the Moho undulations. This work is based on an improved filtering technique and an appropriate assumed density contrast between the crust and the upper mantle. Comparison with deep seismic refraction data reveals that this relief map expresses the continuity

  14. Breast muscle topography and its relationship to muscularity in Pekin ducklings

    E-print Network

    Paris-Sud XI, Université de

    Note Breast muscle topography and its relationship to muscularity in Pekin ducklings Karima A muscles (m. pectoralis superficialis, m. pectoralis profundus) were used to exam- ine their usefulness as predictors or indices of total carcass muscle weight. As much as 65 % of the variation in total carcass

  15. The Topography of Mars by the Mars Orbiter Laser Altimeter (MOLA)

    NSDL National Science Digital Library

    NASA

    This NASA website features an interactive map of Mars. Users can click on the map to obtain a detailed image showing the MOLA topography for the selected region. Images are 10 x 10 degrees with an elevation scale bar in meters at the bottom. The site can be used for in-class activities, exercises, and/or class presentations.

  16. 3D SEM for surface topography quantification - a case study on dental surfaces

    NASA Astrophysics Data System (ADS)

    Glon, F.; Flys, O.; Lööf, P.-J.; Rosén, B.-G.

    2014-03-01

    3D analysis of surface topography is becoming a more used tool for industry and research. New ISO standards are being launched to assist in quantifying engineering surfaces. The traditional optical measuring instrumentation used for 3D surface characterization has been optical interferometers and confocal based instrumentation. However, the resolution here is limited in the lateral dimension to the wavelength of visible light to about 500 nm. The great advantage using the SEM for topography measurements is the high flexibility to zoom from low magnifications and locating interesting areas to high magnification of down to nanometer large surface features within seconds. This paper presents surface characterization of dental implant micro topography. 3D topography data was created from SEM images using commercial photogrammetric software. A coherence scanning interferometer was used for reference measurements to compare with the 3D SEM measurements on relocated areas. As a result of this study, measurements emphasizes that the correlation between the accepted CSI measurements and the new technology represented by photogrammetry based on SEM images for many areal characterization parameters are around or less than 20%. The importance of selecting sampling and parameter sensitivity to varying sampling is high-lighted. Future work includes a broader study of limitations of the photogrammetry technique on certified micro-geometries and more application surfaces at different scales.

  17. Topography affected landscape fire history patterns in southern Arizona, USA Jose M. Iniguez a,

    E-print Network

    Topography affected landscape fire history patterns in southern Arizona, USA Jose M. Iniguez a, AZ 86001, United States b Laboratory of Tree-Ring Research, 105 West Stadium, University of Arizona frequent surface fires burned in forests of the western United States prior to Euro-American settlement

  18. Upgraded X-ray topography and microtomography beamline at the Kurchatov synchrotron radiation source

    SciTech Connect

    Senin, R. A., E-mail: senin_ra@rrcki.ru; Khlebnikov, A. S.; Vyazovetskova, A. E.; Blinov, I. A.; Golubitskii, A. O.; Kazakov, I. V.; Vorob'ev, A. A. [National Research Centre 'Kurchatov Institute' (Russian Federation); Buzmakov, A. V.; Asadchikov, V. E.; Shishkov, V. A. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Mukhamedzhanov, E. Kh.; Kovalchuk, M. V. [National Research Centre 'Kurchatov Institute' (Russian Federation)

    2013-05-15

    An upgraded X-ray Topography and Microtomography (XRT-MT) station is described, the parameters of the optical schemes and detectors are given, and the experimental possibilities of the station are analyzed. Examples of tomographic reconstructions are reported which demonstrate spatial resolutions of 2.5 and 10 {mu}m at fields of view of 2.5 and 10 mm, respectively.

  19. Species-specific engineered antifouling topographies: correlations between the settlement of algal zoospores and barnacle cyprids

    Microsoft Academic Search

    James F. Schumacher; Nick Aldred; Maureen E. Callow; John A. Finlay; James A. Callow; Anthony S. Clare; Anthony B. Brennan

    2007-01-01

    Novel, non-toxic antifouling technologies are focused on the manipulation of surface topography to deter settlement of the dispersal stages of fouling organisms. This study investigated the effect of the aspect ratio (feature height\\/feature width) of topographical features engineered in polydimethylsiloxane, on the settlement of cyprids of Balanus amphitrite and zoospores of Ulva linza. The correlation of relative aspect ratios to

  20. Spectral analysis of tsunami waves: Separation of source and topography effects

    Microsoft Academic Search

    Alexander B. Rabinovich

    1997-01-01

    A new approach is proposed to separate the influence of source and topography in observed tsunami spectra and to reconstruct the initial source spectrum. The method assumes a linear tide gauge response to external forcing and is based on comparative analysis of tsunami and background spectra. Evaluation of the ratio of tsunami to background spectra gives functional characteristics that are

  1. Effects of grazing, topography, and precipitation on the structure of a semiarid grassland

    Microsoft Academic Search

    Daniel G. Milchunas; William K. Lauenroth; Philip L. Chapman; Mohammad K. Kazempour

    1989-01-01

    Structural aspects of the shortgrass steppe plant community, functional groups, and species populations were examined in response to long-term heavy grazing and exclosure from grazing, contiguous wet or dry years, and an environmental gradient of topography. Of the three factors, relatively greater differences in community similarity were observed between catena positions, particularly on the ungrazed treatments. Grazing was intermediate between

  2. Functions of Maladaptive Behavior in Intellectual and Developmental Disabilities: Behavior Categories and Topographies

    ERIC Educational Resources Information Center

    Rojahn, Johannes; Zaja, Rebecca H.; Turygin, Nicole; Moore, Linda; van Ingen, Daniel J.

    2012-01-01

    Research has shown that different maladaptive behavior categories may be maintained by different contingencies. We examined whether behavior categories or behavior topographies determine functional properties. The "Questions about Behavioral Function" with its five subscales ("Attention", "Escape", "Nonsocial", "Physical", and "Tangible") was…

  3. A novel approach to characterizing the surface topography of niobium superconducting radio frequency (SRF) accelerator cavities

    SciTech Connect

    Hui Tian, Guilhem Ribeill, Chen Xu, Charles E. Reece, Michael J. Kelley

    2011-03-01

    As superconducting niobium radio-frequency (SRF) cavities approach fundamental material limits, there is increased interest in understanding the details of topographical influences on realized performance limitations. Micro- and nano-roughness are implicated in both direct geometrical field enhancements as well as complications of the composition of the 50 nm surface layer in which the super-currents typically flow. Interior surface chemical treatments such as buffered chemical polishing (BCP) and electropolishing (EP) used to remove mechanical damage leave surface topography, including pits and protrusions of varying sharpness. These may promote RF magnetic field entry, locally quenching superconductivity, so as to degrade cavity performance. A more incisive analysis of surface topography than the widely used average roughness is needed. In this study, a power spectral density (PSD) approach based on Fourier analysis of surface topography data acquired by both stylus profilometry and atomic force microscopy (AFM) is introduced to distinguish the scale-dependent smoothing effects, resulting in a novel qualitative and quantitative description of Nb surface topography. The topographical evolution of the Nb surface as a function of different steps of well-controlled EP is discussed. This study will greatly help to identify optimum EP parameter sets for controlled and reproducible surface levelling of Nb for cavity production.

  4. Topography of the core-mantle boundary and lateral homogeneity of the liquid core

    Microsoft Academic Search

    Andrea Morelli; Adam M. Dziewonski

    1987-01-01

    Separate inversions of travel-time residuals of waves reflected from and transmitted through the core-mantle boundary yield similar results in terms of spherical harmonic expansion of its topography up to degree and order four. This indicates the absence of detectable lateral heterogeneity in the liquid core. The relief of the boundary is + or - 6 km but its flattening, determined

  5. Sensitivities Kernels of Seismic Traveltimes and Amplitudes for Quality Factor and Boundary Topography

    NASA Astrophysics Data System (ADS)

    Hsieh, M.; Zhao, L.; Ma, K.

    2010-12-01

    Finite-frequency approach enables seismic tomography to fully utilize the spatial and temporal distributions of the seismic wavefield to improve resolution. In achieving this goal, one of the most important tasks is to compute efficiently and accurately the (Fréchet) sensitivity kernels of finite-frequency seismic observables such as traveltime and amplitude to the perturbations of model parameters. In scattering-integral approach, the Fréchet kernels are expressed in terms of the strain Green tensors (SGTs), and a pre-established SGT database is necessary to achieve practical efficiency for a three-dimensional reference model in which the SGTs must be calculated numerically. Methods for computing Fréchet kernels for seismic velocities have long been established. In this study, we develop algorithms based on the finite-difference method for calculating Fréchet kernels for the quality factor Q? and seismic boundary topography. Kernels for the quality factor can be obtained in a way similar to those for seismic velocities with the help of the Hilbert transform. The effects of seismic velocities and quality factor on either traveltime or amplitude are coupled. Kernels for boundary topography involve spatial gradient of the SGTs and they also exhibit interesting finite-frequency characteristics. Examples of quality factor and boundary topography kernels will be shown for a realistic model for the Taiwan region with three-dimensional velocity variation as well as surface and Moho discontinuity topography.

  6. Soil resources and topography shape local tree community structure in tropical forests

    PubMed Central

    Baldeck, Claire A.; Harms, Kyle E.; Yavitt, Joseph B.; John, Robert; Turner, Benjamin L.; Valencia, Renato; Navarrete, Hugo; Davies, Stuart J.; Chuyong, George B.; Kenfack, David; Thomas, Duncan W.; Madawala, Sumedha; Gunatilleke, Nimal; Gunatilleke, Savitri; Bunyavejchewin, Sarayudh; Kiratiprayoon, Somboon; Yaacob, Adzmi; Supardi, Mohd N. Nur; Dalling, James W.

    2013-01-01

    Both habitat filtering and dispersal limitation influence the compositional structure of forest communities, but previous studies examining the relative contributions of these processes with variation partitioning have primarily used topography to represent the influence of the environment. Here, we bring together data on both topography and soil resource variation within eight large (24–50 ha) tropical forest plots, and use variation partitioning to decompose community compositional variation into fractions explained by spatial, soil resource and topographic variables. Both soil resources and topography account for significant and approximately equal variation in tree community composition (9–34% and 5–29%, respectively), and all environmental variables together explain 13–39% of compositional variation within a plot. A large fraction of variation (19–37%) was spatially structured, yet unexplained by the environment, suggesting an important role for dispersal processes and unmeasured environmental variables. For the majority of sites, adding soil resource variables to topography nearly doubled the inferred role of habitat filtering, accounting for variation in compositional structure that would previously have been attributable to dispersal. Our results, illustrated using a new graphical depiction of community structure within these plots, demonstrate the importance of small-scale environmental variation in shaping local community structure in diverse tropical forests around the globe. PMID:23256196

  7. A Topography of Collaboration: Methodology, Identity and Community in Self-Study of Practice Research

    ERIC Educational Resources Information Center

    Hamilton, Mary Lynn; Pinnegar, Stefinee

    2013-01-01

    Through the use of the metaphoric tool of topography, two educational researchers explore the development of their understanding of collaboration in self-study of teacher education practices research. The researchers communicate their perceptions through the presentation of four topographic moments. Each topographic moment is represented by a poem…

  8. Balance of chemistry, topography, and mechanics at the cellbiomaterial interface: Issues and challenges for

    E-print Network

    this goal, we can attack this problem by considering the factors that surface scientists can control of creating surfaces with well-defined chemistry and topography combined with sensitive surface characterization techniques have unquestionably deepened our understanding of surface chemical and topographical

  9. On the incorporation of sea surface topography in establishing vertical control

    Microsoft Academic Search

    G. Fotopoulos; I. N. Tziavos; M. G. Sideris

    One of the major sources of distortion in vertical control networks is caused by neglecting sea surface topography (SST) at tide gauge stations. Often, the orthometric height is fixed to zero at these stations without applying proper corrections for the deviation of the mean sea surface from the equipotential surface represented by the geoid. In view of the significant improvements

  10. The Relationship of the MOLA Topography of Mars to the Mean Atmospheric Pressure

    NASA Technical Reports Server (NTRS)

    Smith, David E.; Zuber, Maria T.

    1999-01-01

    The MOLA topography of Mars is based on a new mean radius of the planet and new equipotential surface for the areoid. The mean atmospheric pressure surface of 6.1mbars that has been used in the past as a reference level for topography does not apply to the zero level of MOLA elevations. The MOLA mean radius of the planet is 3389508 meters and the mean equatorial radius is 339600 meters. The areoid of the zero level of the MOLA altimetry is defined to be the potential surface with the same potential as the mean equatorial radius. The MOLA topography differs from the USGS digital elevation data by approximately 1.6 km, with MOLA higher. The average pressure on the MOLA reference surface for Ls =0 is approximately 5.1 mbars and has been derived from occultation data obtained from the tracking of Viking, Mariner, and MGS spacecraft and interpolated with the aid of the Ames Mars GCM. The new topography and the new occultation data are providing a more reliable relationship between elevation and surface pressure.

  11. Effects of Topography and Soil Depth on Runon and Focused Infiltration: Upper Split Wash Watershed, Nevada

    Microsoft Academic Search

    D. A. Woolhiser; R. W. Fedors; S. A. Stothoff

    2001-01-01

    A modeling study of surface and near surface hydrology of a small watershed, upper Split Wash, overlying the potential Yucca Mountain (YM), Nevada high level nuclear waste repository was carried out. The objective was to evaluate the interaction of topography and soil depth across a small watershed and the hillslope process of runoff-runon. Zones of focused infiltration can result from

  12. Puffing Topography and Interpersonal Bonding Behavior Observed Among Recovering Drug Addicts Versus General Smokers

    E-print Network

    Zhou, Yaoqi

    Puffing Topography and Interpersonal Bonding Behavior Observed Among Recovering Drug Addicts Versus Department of Oral Biology, Indiana University School of Dentistry; 2 Fairbanks Addiction Hospital and interpersonal bonding behaviors of recovering drug addicts to that of general smokers in a natural setting

  13. Calculation of Intraocular Lens Power Using Orbscan II Quantitative Area Topography After Corneal Refractive Surgery

    Microsoft Academic Search

    Carlos G. Arce; Eduardo S. Soriano; Robert W. Weisenthal; Stephen M. Hamilton; Karolinne M. Rocha; Juan B. Alzamora; Eduardo J. Maidana; Vijayalakshmi L. Vadrevu; Kenneth Himmel; Paulo Schor; Mauro Campos

    2009-01-01

    PURPOSE: To present the prospective application of the Orbscan II central 2-mm total-mean corneal power obtained by quantitative area topography in intraocular lens (IOL) calculation after refractive surgery. METHODS: Calculated and achieved refraction and the difference between them were studied in 77 eyes of 61 patients with previous radial keratotomy (RK), RK and additional surgeries, myopic LASIK, myopic pho- torefractive

  14. SAR interferometry at Venus for topography and change detection Franz J. Meyer a,b,n

    E-print Network

    Sandwell, David T.

    SAR interferometry at Venus for topography and change detection Franz J. Meyer a,b,n , David T 1 March 2012 Received in revised form 4 October 2012 Accepted 5 October 2012 Keywords: Venus of Venus in the early 1990's, techniques of synthetic aperture radar interferometry (InSAR) have become

  15. Effects of Topography on Earthquake Ground Motions Observed During the 2004 Parkfield Earthquake

    NASA Astrophysics Data System (ADS)

    Wang, G.; Tang, G.; Burbach, G. N.; Jackson, C. R.; Lin, Q.

    2005-05-01

    During recent earthquakes such as 1994 Northridge, 1999 Izmit, 1999 Chi-Chi events, unusually large ground motions were recorded near the crests of ridges. Some concentrated patterns of structural damage relative to topography were also observed. These observations have suggested that surface topography significantly affect ground motions. However, the effects of topography often mix with the effects of path and geologic conditions. In order to properly quantify the topographic effects, crest motions must be evaluated relative to comparable free-field motions under same site conditions. The September 28, 2004 Parkfield earthquake (Mw 6) supplied an unprecedented opportunity of studying the topographic effects. It is an anticipated event that came 15 years later than predicted date. Very densed instruments had been installed in this region to capture the anticipated event. A large number of records are available from instruments installed on hills close to the epicenter. We will study the effects of topography on strong ground motions in this work. The main purpose of this study is to isolate the influence of the topographic effects from the effects of wave propagation, geologic amplification, as well as soil-structure interaction.

  16. Vegetation height estimation from Shuttle Radar Topography Mission and National Elevation Datasets

    Microsoft Academic Search

    Josef Kellndorfer; Wayne Walker; Leland Pierce; Craig Dobson; Jo Ann Fites; Carolyn Hunsaker; John Vona; Michael Clutter

    2004-01-01

    A study was conducted to determine the feasibility of obtaining estimates of vegetation canopy height from digital elevation data collected during the 2000 Shuttle Radar Topography Mission (SRTM). The SRTM sensor mapped 80% of the Earth's land mass with a C-band Interferometric Synthetic Aperture Radar (InSAR) instrument, producing the most complete digital surface map of Earth. Due to the relatively

  17. Full chip implant correction with wafer topography OPC modeling in 2x nm bulk technologies

    NASA Astrophysics Data System (ADS)

    Michel, J.-C.; Le Denmat, J.-C.; Sungauer, E.; Robert, F.; Yesilada, E.; Armeanu, A.-M.; Entradas, J.; Sturtevant, J. L.; Do, T.; Granik, Y.

    2013-09-01

    Ionic implantation photolithography step considered to be non critical started to be influenced by unwanted overexposure by wafer topography with technology node downscaling evolution [1], [2]. Starting from 2xnm technology nodes, implant patterns modulated on wafer by classical implant proximity effects are also influenced by wafer topography which can cause drastic pattern degradation [2], [3]. This phenomenon is expected to be attenuated by the use of anti-reflecting coating but it increases process complexity and involves cost and cycle time penalty. As a consequence, computational lithography solutions are currently under development in order to correct wafer topographical effects on mask [3]. For ionic implantation source Drain (SD) on Silicon bulk substrate, wafer topography effects are the consequence of active silicon substrate, poly patterns, STI stack, and transitions between patterned wafer stack. In this paper, wafer topography aware OPC modeling flow taking into account stack effects for bulk technology is presented. Quality check of this full chip stack aware OPC model is shown through comparison of mask computational verification and known systematic defectivity on wafer. Also, the integration of topographical OPC model into OPC flow for chip scale mask correction is presented with quality and run time penalty analysis.

  18. Human Corneal Limbal-Epithelial Cell Response to Varying Silk Film Geometric Topography In Vitro

    PubMed Central

    Lawrence, Brian D.; Pan, Zhi; Liu, Aihong; Kaplan, David L.; Rosenblatt, Mark I.

    2012-01-01

    Silk fibroin films are a promising class of biomaterials that have a number of advantages for use in ophthalmic applications due to their transparent nature, mechanical properties and minimal inflammatory response upon implantation. Freestanding silk films with parallel line and concentric ring topographies were generated for in vitro characterization of human corneal limbal-epithelial (HCLE) cell response upon differing geometric patterned surfaces. Results indicated that silk film topography significantly affected initial HCLE culture substrate attachment, cellular alignment, cell-to-cell contact formation, actin cytoskeleton alignment, and focal adhesion (FA) localization. Most notably, parallel line patterned surfaces displayed a 36%–54% increase on average in initial cell attachment, which corresponded to an over 2-fold increase in FA localization when compared to other silk film surfaces and controls. In addition, distinct localization of FA formation was observed along the edges for all patterned silk film topographies. In conclusion, silk film feature topography appears to help direct corneal epithelial cell response and cytoskeleton development, especially in regards to FA distribution, in vitro. PMID:22705042

  19. Morphological decomposition of the surface topography of an internal combustion engine cylinder to characterize wear

    Microsoft Academic Search

    Etienne Decencière; Dominique Jeulin

    2001-01-01

    A surface topography decomposition methodology is presented. It decomposes a surface into three elements: reference surface (waviness and form); superficial roughness (related to friction and wear); and valleys (related to lubricant circulation and reservoirs). It is applied to cylinder liners from an internal combustion V6 engine from in order to remove form and waviness components. The study of the resulting

  20. Double lateral shearing interferometer for the quantitative measurement of tear film topography

    E-print Network

    Dainty, Chris

    topography features: postblink tear undulation, tear breakup, eyelid-produced bumps and ridges, bubbles of these is refractive surgery in its different techniques: photorefractive keratectomy (PRK), laser-assisted in situ surgery and high-resolution retinal imaging instruments. It is likely that the largest source

  1. Satellites images, digitized topography, and the recognition of the Xela Caldera, Quezaltenango Valley, Guatemala

    Microsoft Academic Search

    D. Foley; A. McEwen; W. Duffield; G. Heiken

    1992-01-01

    The authors propose, based on reconnaissance geology studies and interpretation of landforms as depicted by Landsat Thematic Mapper (TM) images combined with digitized topography, that the Quezaltenango basin of Guatemala is part of a caldera. The Quezaltenango basin is an elliptical depression, about 12 by 25 km and about 500 m deep. The proposed Xela Caldera extends beyond the basin

  2. Global digital topography mapping with a synthetic aperture scanning radar altimeter

    Microsoft Academic Search

    C. Elachi; K. E. Im; F. Li; E. Rodriguez

    1990-01-01

    Global digital topography data of the land surface is of importance in a variety of geoscientific and application disciplines. Such a database, with a spatial resolution of 150 to 500 m and height accuracy of 5 m or better can be acquired from an orbiting platform using a synthetic aperture scanning radar altimeter. Near-global coverage can be achieved within 14

  3. LINKING BENTHIC ALGAL BIOMASS TO STREAM SUBSTRATUM TOPOGRAPHY1 Justin N. Murdock2

    E-print Network

    Kaufman, Glennis A.

    effect on benthic algal development. Considerable research has been conducted on the effectsLINKING BENTHIC ALGAL BIOMASS TO STREAM SUBSTRATUM TOPOGRAPHY1 Justin N. Murdock2 and Walter K of substrata significantly influence benthic algal development. We explored the relationships among substratum

  4. De-striping of MODIS Optical Bands for Ice Sheet Mapping and Topography

    Microsoft Academic Search

    T. M. Haran; M. A. Fahnestock; T. A. Scambos

    2002-01-01

    Over the past 20 years, optical band data from the Advanced Very High Resolution Radiometer (AVHRR) sensor with a spatial resolution of 1100 meters and a radiometric resolution of 10 bits (1 part in 1024) have been used to map both surface features and topography in great detail over large regions of the earth's ice sheets. The Moderate Resolution Imaging

  5. Soil resources and topography shape local tree community structure in tropical forests.

    PubMed

    Baldeck, Claire A; Harms, Kyle E; Yavitt, Joseph B; John, Robert; Turner, Benjamin L; Valencia, Renato; Navarrete, Hugo; Davies, Stuart J; Chuyong, George B; Kenfack, David; Thomas, Duncan W; Madawala, Sumedha; Gunatilleke, Nimal; Gunatilleke, Savitri; Bunyavejchewin, Sarayudh; Kiratiprayoon, Somboon; Yaacob, Adzmi; Supardi, Mohd N Nur; Dalling, James W

    2013-02-22

    Both habitat filtering and dispersal limitation influence the compositional structure of forest communities, but previous studies examining the relative contributions of these processes with variation partitioning have primarily used topography to represent the influence of the environment. Here, we bring together data on both topography and soil resource variation within eight large (24-50 ha) tropical forest plots, and use variation partitioning to decompose community compositional variation into fractions explained by spatial, soil resource and topographic variables. Both soil resources and topography account for significant and approximately equal variation in tree community composition (9-34% and 5-29%, respectively), and all environmental variables together explain 13-39% of compositional variation within a plot. A large fraction of variation (19-37%) was spatially structured, yet unexplained by the environment, suggesting an important role for dispersal processes and unmeasured environmental variables. For the majority of sites, adding soil resource variables to topography nearly doubled the inferred role of habitat filtering, accounting for variation in compositional structure that would previously have been attributable to dispersal. Our results, illustrated using a new graphical depiction of community structure within these plots, demonstrate the importance of small-scale environmental variation in shaping local community structure in diverse tropical forests around the globe. PMID:23256196

  6. Vegetation height derivation from Shuttle Radar Topography Mission data in southeast Georgia, USA

    Microsoft Academic Search

    J. M. Kellndorfer; W. S. Walker; M. C. Dobson; M. Vona; M. Clutter

    2004-01-01

    A study was conducted to determine the extent to which data from the 2000 Shuttle Radar Topography Mission (SRTM) can be used to estimate vegetation canopy height in conjunction with an existing bald Earth DEM as provided by the National Elevation Dataset (NED). Intensively managed slash pine stands with canopy heights ranging from 11 to 21 m were biometrically surveyed

  7. Rheology and Structure of Planetary Near-Surface Materials from Landform Topography

    Microsoft Academic Search

    David Gerard Jankowski

    1995-01-01

    The topography of landforms observed in spacecraft images of planetary bodies is used to infer the rheologies of the materials comprising them. Rheologic models are then used to infer information about the subsurface composition, structure, and physical state. A quantitative analysis of error sources in one -dimensional planetary photo-clinometry is presented. Slope errors are investigated for a variety of viewing

  8. Large-amplitude internal wave generation in the lee of step-shaped topography

    E-print Network

    Sutherland, Bruce

    1 Large-amplitude internal wave generation in the lee of step-shaped topography B. R. Sutherland University of Alberta, Edmonton, Canada. Short title: LARGE-AMPLITUDE INTERNAL WAVE GENERATION . . . #12 downstream of the base of the step, and internal waves, which propagate vertically away from the step

  9. Fine-scale modeling of the boundary layer wind field over steep topography

    Microsoft Academic Search

    N. Raderschall; M. Lehning; C. Schär

    2008-01-01

    This paper describes the adaptation of wind fields to steep and complex terrain using fine-scale numerical modeling. The work is motivated by the need of high-resolution flow fields to predict snow transport and snow cover development for avalanche warning purposes. Applying the nonhydrostatic and compressible atmospheric prediction model Advanced Regional Prediction System (ARPS) to steep alpine topography, the boundary layer

  10. An examination of topography and density anomalies as a cause of stress 

    E-print Network

    Marten, Robert Francis

    1986-01-01

    . 6181 6101 Ra I E E 60Z I a 5991 5951 5351. 55, 0 lao le. o 59. 0 Col a t I t u d e Fig. 14. Stress eigenvectors for the case of fully compensated topography. See text for explanation of the symbols used. 31 STRESS E]GENVECTORS Aeletlve...

  11. Topography of the complete corticopontine projection: From experiments to principal maps

    Microsoft Academic Search

    Trygve B. Leergaard; Jan G. Bjaalie

    2007-01-01

    The mammalian brain is characterized by orderly spatial distribution of its cellular components, commonly referred to as topographical organization. The topography of cortical and subcortical maps is thought to represent functional or computational properties. In the present investigation, we have studied map transformations and organizing principles in the projections from the cerebral cortex to the pontine nuclei, with emphasis on

  12. Calibration of the geometrical characteristics of areal surface topography measuring instruments

    NASA Astrophysics Data System (ADS)

    Giusca, C. L.; Leach, R. K.; Helery, F.; Gutauskas, T.

    2011-08-01

    The use of areal surface topography measuring instruments has increased significantly over the past ten years as industry starts to embrace the use of surface structuring to affect the function of a component. This has led to a range of areal surface topography measuring instruments being developed and becoming available commercially. For such instruments to be used as part of quality control during production, it is essential for them to be calibrated according to international standards. The ISO 25178 suite of specification standards on areal surface topography measurement presents a series of tests that can be used to calibrate the metrological characteristics of an areal surface topography measuring instrument. Calibration artefacts and test procedures have been developed that are compliant with ISO 25178. The material measures include crossed gratings, resolution artefacts and pseudorandom surfaces. Traceability is achieved through the NPL Areal Instrument - a primary stylus-based instrument that uses laser interferometers to measure the displacement of the stylus tip. Good practice guides on areal calibration have also been drafted for stylus instruments, coherence scanning interferometers, scanning confocal microscopes and focus variation instruments.

  13. Basement Surface Faulting and Topography for Savannah River Site and Vicinity

    SciTech Connect

    Cumbest, R.J.

    1998-12-17

    This report integrates the data from more than 60 basement borings and over 100 miles of seismic reflection profiling acquired on the Savannah River Site to map the topography of the basement (unweathered rock) surface and faulting recorded on this surface.

  14. Links between topography, wind, deflation, lakes and dust: The case of the Bodele Depression, Chad

    E-print Network

    Washington, Richard

    Links between topography, wind, deflation, lakes and dust: The case of the Bode´le´ Depression, Chad R. Washington,1 M. C. Todd,2 G. Lizcano,1 I. Tegen,3 C. Flamant,4 I. Koren,5 P. Ginoux,6 S, the Last Glacial Maximum, was probably sufficient to create the shallow lake in which diatoms lived during

  15. Thickness of the Martian crust: Improved constraints from geoid-to-topography ratios

    Microsoft Academic Search

    Mark A. Wieczorek; Maria T. Zuber

    2004-01-01

    (1) The average crustal thickness of the southern highlands of Mars was investigated by calculating geoid-to-topography ratios (GTRs) and interpreting these in terms of an Airy compensation model appropriate for a spherical planet. We show that (1) if GTRs were interpreted in terms of a Cartesian model, the recovered crustal thickness would be underestimated by a few tens of kilometers,

  16. Thickness of the Martian crust: Improved constraints from geoid-to-topography ratios

    Microsoft Academic Search

    Mark A. Wieczorek; Maria T. Zuber

    2004-01-01

    The average crustal thickness of the southern highlands of Mars was investigated by calculating geoid-to-topography ratios (GTRs) and interpreting these in terms of an Airy compensation model appropriate for a spherical planet. We show that (1) if GTRs were interpreted in terms of a Cartesian model, the recovered crustal thickness would be underestimated by a few tens of kilometers, and

  17. The wide swath ocean altimeter: algorithm and technology developments for improved ocean topography measurements

    NASA Technical Reports Server (NTRS)

    Pollard, Brian D.; Rodriguez, Ernesto; Kitiyakara, Amirit; Akins, Torry

    2001-01-01

    The Wide Swath Ocean Altimeter (WSOA) is a recently proposed interferometric instrument that would provide nearly complete global ocean topography measurements from a single platform. Several new algorithm and technology developments improve the expected WSOA performance, and facilitate the feasibility of including WSOA on a next generation altimeter mission. Those developments are discussed in this paper.

  18. Toward comprehensive Titan digital topography construction: A technical demonstration with stereogrammetry and photo/radarclinometry

    NASA Astrophysics Data System (ADS)

    Kim, J.; Wan, W.; Lee, S.; Choi, Y.

    2014-12-01

    Topographic reconstruction is a high priority task for the solid planet and satellite exploration missions. Laser/radar altimetry and stereo analyses have been widely used for this purpose and achieve high quality 3D topographic data over various planetary surfaces such as Venus, Mercury, Moon and Mars. However, in contrast with inner planet and satellite, the base data sets to compose digital topography over outer planets and satellites are very limited. Titan, the largest satellite of Saturn has also too limited data inventory to achieve sufficient spatial resolution in topographic data, in spite of increasing interests about the detailed topography owing to the recent interesting discoveries on methane fluvial system, aeolian geomorphologies and possible tectonic activity. Therefore the endeavours to increase the coverage of digital topography employing radargrammetry (Kirk et al. 2009), radar altimetry (Elachi, et al. 2005) and SARtopo (Stiles et al. 2009) have been actively conducted. Although these efforts result in the construction of a global topographic map, the consequent spatial resolutions of global topography are still poor (Lorentz et al. 2013). In this study, we tried to improve the coverage and the quality of Titan digital terrain model employing approaches as follows; 1) A semi-automated stereo matching scheme manipulating low signal-to-noise SAR image pair incorporating adaptive filtering and base topography, 2) the geodetic control improvement of stereo SAR pair based on altimetric measurements, 3) introduction of radarclinometry to refine the topography from stereo analyses. Especially together with the technical improvements to exploit SAR stereo pair, the possibility to mine height information from Visual Infrared Mapping Spectrometer (VIMS) was actively explored by the means of hybrid stereogrammetry between VIMS and SAR image pairs and photoclinometry. The developed scheme was applied for a few testing areas especially over Xanadu which is the largest topographic feature over Titan and well covered by SAR and VIMS. The constructed topography revealed many interesting geomorphic features such as drainage networks and rugged terrains in detail. To fully demonstrate the potential of these approaches, technical details will be continuously improved.

  19. Control of marine biofouling and medical biofilm formation with engineered topography

    NASA Astrophysics Data System (ADS)

    Schumacher, James Frederick

    Biofouling is the unwanted accumulation and growth of cells and organisms on clean surfaces. This process occurs readily on unprotected surfaces in both the marine and physiological environments. Surface protection in both systems has typically relied upon toxic materials and biocides. Metallic paints, based on tin and copper, have been extremely successful as antifouling coatings for the hulls of ships by killing the majority of fouling species. Similarly, antibacterial medical coatings incorporate metal-containing compounds such as silver or antibiotics that kill the bacteria. The environmental concerns over the use of toxic paints and biocides in the ocean, the developed antibiotic resistance of bacterial biofilms, and the toxicity concerns with silver suggest the need for non-toxic and non-kill solutions for these systems. The manipulation of surface topography on non-toxic materials at the size scale of the fouling species or bacteria is one approach for the development of alternative coatings. These surfaces would function simply as a physical deterrent of settlement of fouling organisms or a physical obstacle for the adequate formation of a bacterial biofilm without the need to kill the targeted microorganisms. Species-specific topographical designs called engineered topographies have been designed, fabricated and evaluated for potential applications as antifouling marine coatings and material surfaces capable of reducing biofilm formation. Engineered topographies fabricated on the surface of a non-toxic, polydimethylsiloxane elastomer, or silicone, were shown to significantly reduce the attachment of zoospores of a common ship fouling green algae (Ulva) in standard bioassays versus a smooth substrate. Other engineered topographies were effective at significantly deterring the settlement of the cyprids of barnacles (Balanus amphitrite). These results indicate the potential use of engineered topography applied to non-toxic materials as an environmentally friendly coating for antifouling applications in the ocean. In addition, a biomaterial-grade silicone modified with a tailored engineered topography significantly inhibited the bacterial biofilm growth from Staphylococcus aureus for up to 14 days exposure without the use of bactericidal agents. Mature biofilms were present on equivalently exposed smooth silicone surfaces. Engineered surface topographies present a promising means of blocking biofilm development on medical surfaces and reducing the rate of related infections.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  1. Non-Equilibrium Topography in the southern Central Range of Taiwan

    NASA Astrophysics Data System (ADS)

    Ouimet, W. B.; Byrne, T. B.; Huang, C.

    2012-12-01

    The relatively constant width of the Taiwan orogen and consistent elevation of the drainage divide has led numerous workers to argue for a topographic steady state where the influx of material along the front and the base of the collision is balanced by erosion. In general, this simple framework for evaluating the process of mountain building has been adequate to explain some first order features of Taiwan such as regional cooling patterns from low temperature thermochronometers, but there a number of observations that are difficult to explain based on the simple paradigm of a southward propagating collision and growth of steady state topography in Taiwan over the last 5 Ma. Here, we document and analyze large areas (20-100 sq km) of anomalously low relief in the higher elevations of the southern Central Range of Taiwan. These areas of low relief straddle the topographic crest of the range, have outlet elevations ranging from 1800-2500 meters, and are fringed by steep channels with relatively high stream gradient indexes. Field work confirms that these low relief areas are characterized by low hillslope angles draped by clay rich lateritic soils not seen in lower reaches, with few landslides and low-gradient, alluviated streams. This was in sharp contrast with the landslide-dominated hillslopes and steep bedrock channels that characterized topography directly adjacent to this subdued, low relief topography. The observed transition from low-relief topography to steeper lower reaches does not display significant variations in lithology (it is all slate), or rainfall (annual or that experienced during Typhoon Morakot). We hypothesize that these areas of subdued, low-relief topography are eroding slowly and represent a relict landscape that formed prior to a recent acceleration in rock uplift rate. We have sampled stream sediment for 10Be analysis to test this hypothesis and determine the erosion rates associated with the low-relief topography, as well as adjacent deeply dissected, high-relief topography. Overall, our data and analysis suggests that, although the collision may be propagating southward at a regional scale, the deformational, thermal and exhumational processes have apparently been punctuated by transient events not previously recognized in the evolution of Taiwan.

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

    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.

  3. Combined varenicline and naltrexone treatment reduces smoking topography intensity in heavy-drinking smokers.

    PubMed

    Roche, Daniel J O; Bujarski, Spencer; Hartwell, Emily; Green, ReJoyce; Ray, Lara A

    2015-07-01

    Heavy drinking smokers constitute a distinct sub-population of smokers for whom traditional smoking cessation therapies may not be effective. Recent evidence suggested that combined varenicline (VAR) and naltrexone (NTX) therapy may be more efficacious than either monotherapy alone in reducing smoking and drinking-related behavior in this population. The manner in which individuals smoke a cigarette (i.e., smoking topography) may be predictive of smoking cessation outcomes, yet the effects of smoking pharmacotherapies on puffing behavior have not been thoroughly examined. Therefore, the current double-blind medication study examined the effects of VAR alone (1mg BID), low dose NTX alone (25mg QD), the combination of VAR+NTX, and placebo on smoking topography measures in heavy drinking, non-treatment seeking daily smokers (n=120). After a 9-day titration period, participants completed a laboratory session in which they smoked their first cigarette of the day using a smoking topography device following 12h of nicotine abstinence and consumption of an alcoholic beverage (BrAC=0.06g/dl). The primary measures were puff count, volume, duration, and velocity and inter-puff interval (IPI). Independent of medication group, puff velocity and IPI increased, while puff volume and duration decreased, over the course of the cigarette. The active medication groups, vs. the placebo group, had significantly blunted puff duration and velocity slopes over the course of the cigarette, and this effect was particularly evident in the VAR+NTX group. Additionally, the VAR+NTX group demonstrated lower average IPI than the monotherapy groups and lower average puff volume than all other groups. These results suggest that smoking pharmacotherapies, particularly the combination of VAR+NTX, alter smoking topography in heavy drinking smokers, producing a pattern of less intense puffing behavior. As smoking topography has been predictive of the ability to quit smoking, future studies should examine how smoking pharmacotherapies' effects on puffing behavior relate to smoking cessation outcomes. PMID:25933795

  4. Mediterranean summer climate and the importance of Middle-East Topography

    NASA Astrophysics Data System (ADS)

    Simpson, Isla; Seager, Richard; Shaw, Tiffany; Ting, Mingfang

    2015-04-01

    In summer, the atmospheric circulation over the Mediterranean is characterized by localized intense subsidence and low level northerlies over the central- to eastern portion of the basin. Here, simulations with the Community Atmosphere Model, version 5 are used to investigate the influence of the elevated terrain of North Africa and the Middle East on this summertime circulation. This builds on previous work that recognized a role for North African topography in localizing the Mediterranean subsidence. By flattening the two regions of elevated terrain in the model it is demonstrated that, while they both conspire to produce about 30% of the summertime subsidence, contrary to previous work, the mountains of the Middle-East dominate in this topographic contribution by far. This topography, consisting primarily of the Zagros Mountain range, alters the circulation throughout the depth of the troposphere over the Mediterranean, and further East. The model results suggest that about 20% of the Mediterranean summertime moisture deficit can be attributed to this mountain induced circulation. This topography, therefore, plays an important role in the climate of the Mediterranean and the large scale circulation over the rest of Eurasia during the summer. Further stationary wave modelling reveals that the mountain influence is produced via mechanical forcing of the flow. The greatest influence of the topography occurs when the low level incident flow is easterly, as happens during the summer, primarily due to the presence of condensational heating over Asia. During other seasons, when the low level incident flow is westerly, the influence of Middle-East topography on the Mediterranean is negligible.

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

    NASA Astrophysics Data System (ADS)

    lacanna, giorgio; ripepe, maurizio

    2014-05-01

    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.

  6. Promoting scientific collaboration and research through integrated social networking capabilities within the OpenTopography Portal

    NASA Astrophysics Data System (ADS)

    Nandigam, V.; Crosby, C. J.; Baru, C.

    2009-04-01

    LiDAR (Light Distance And Ranging) topography data offer earth scientists the opportunity to study the earth's surface at very high resolutions. As a result, the popularity of these data is growing dramatically. However, the management, distribution, and analysis of community LiDAR data sets is a challenge due to their massive size (multi-billion point, mutli-terabyte). We have also found that many earth science users of these data sets lack the computing resources and expertise required to process these data. We have developed the OpenTopography Portal to democratize access to these large and computationally challenging data sets. The OpenTopography Portal uses cyberinfrastructure technology developed by the GEON project to provide access to LiDAR data in a variety of formats. LiDAR data products available range from simple Google Earth visualizations of LiDAR-derived hillshades to 1 km2 tiles of standard digital elevation model (DEM) products as well as LiDAR point cloud data and user generated custom-DEMs. We have found that the wide spectrum of LiDAR users have variable scientific applications, computing resources and technical experience and thus require a data system with multiple distribution mechanisms and platforms to serve a broader range of user communities. Because the volume of LiDAR topography data available is rapidly expanding, and data analysis techniques are evolving, there is a need for the user community to be able to communicate and interact to share knowledge and experiences. To address this need, the OpenTopography Portal enables social networking capabilities through a variety of collaboration tools, web 2.0 technologies and customized usage pattern tracking. Fundamentally, these tools offer users the ability to communicate, to access and share documents, participate in discussions, and to keep up to date on upcoming events and emerging technologies. The OpenTopography portal achieves the social networking capabilities by integrating various software technologies and platforms. These include the Expression Engine Content Management System (CMS) that comes with pre-packaged collaboration tools like blogs and wikis, the Gridsphere portal framework that contains the primary GEON LiDAR System portlet with user job monitoring capabilities and a java web based discussion forum (Jforums) application all seamlessly integrated under one portal. The OpenTopography Portal also provides integrated authentication mechanism between the various CMS collaboration tools and the core gridsphere based portlets. The integration of these various technologies allows for enhanced user interaction capabilities within the portal. By integrating popular collaboration tools like discussion forums and blogs we can promote conversation and openness among users. The ability to ask question and share expertise in forum discussions allows users to easily find information and interact with users facing similar challenges. The OpenTopography Blog enables our domain experts to post ideas, news items, commentary, and other resources in order to foster discussion and information sharing. The content management capabilities of the portal allow for easy updates to information in the form of publications, documents, and news articles. Access to the most current information fosters better decision-making. As has become the standard for web 2.0 technologies, the OpenTopography Portal is fully RSS enabled to allow users of the portal to keep track of news items, forum discussions, blog updates, and system outages. We are currently exploring how the information captured by user and job monitoring components of the Gridsphere based GEON LiDAR System can be harnessed to provide a recommender system that will help users to identify appropriate processing parameters and to locate related documents and data. By seamlessly integrating the various platforms and technologies under one single portal, we can take advantage of popular online collaboration tools that are either stand alone or software platform restricted. The availability of these coll

  7. Texture Synthesis Michael Kazhdan

    E-print Network

    Kazhdan, Michael

    Texture Synthesis Michael Kazhdan (600.357 / 600.457) An Image Synthesizer. Perlin, 1985 Texture Synthesis by Non-Parametric Sampling. Efros and Leung, 1999 Wang Tiles for Image and Texture Generation. Cohen et al., 2003 #12;Overview · Texture synthesis Introduction Procedural texture synthesis Image

  8. Modeling the shallow gravity-driven flows as saturated binary mixtures over temporally varying topography

    NASA Astrophysics Data System (ADS)

    Tai, Yih-Chin; Kuo, Chih-Yu

    2010-05-01

    Based on the "shallow water models over arbitrary topography" by Bouchut and Westdickenberg [2004], and the "Coulomb-mixture theory" by Iversion and Denlinger [2001], we propose a saturated binary mixture model over temporally varying topography, where the effects of the entrainment and deposition are considered. Due to the deposition or erosion processes, the interface between the moving material and the stagnant base is a non-material singular surface that moves with its own velocity. Its motion is thus determined by the mass exchange between the flowing layer and the ground. Through the introduction of the unified coordinate method (e.g. Hui [2004, 2007]) and dimension analysis, the leading-order depth-integrated mass and momentum equations are presented in the time-dependent and topography-fitted curvilinear coordinate system, where the evolving curvature effect is neatly included in the total derivative operator of the variable topography-fitted coordinates. The motion of the basal interface is postulated by function of basal friction coefficient, sliding velocity, local thickness of the flowing layer and a threshold kinetic energy. A shock-capturing numerical scheme is implemented to solve the derived equation system (e.g. Tai and Kuo [2008] or Tai and Lin [2008]). And the key features are investigated and illustrated by the numerical results. References: [1] F. Bouchut and M. Westdickenberg, "Gravity driven shallow water models for arbitrary topography." Commun. Math. Sci. 2, 359-389 (2004). [2] R.M. Iverson and R.P. Denlinger, "Flow of variably fluidized granular masses across three-dimensional terrain. Part 1 Coulomb mixture theory." J. Geophysical Research, 106, 537-552 (2001). [3] W.H. Hui, "A unified coordinates approach to computational Fluid dynamics." J. Comput. and Applied Math., 163, 15-28 (2004). [4] W.H. Hui. "The unified coordinate system in computational fluid dynamics." Commun. Comput. Phys., 2(4), 577-610 (2007). [5] Y.C. Tai and C.Y. Kuo, "A new model of granular flows over general topography with erosion and deposition." Acta Mechanica, 199, 71-96 (2008). [6] Y.C. Tai and Y.C. Lin, "A focused view of the behavior of granular flows down a confined inclined chute into horizontal run-out zone." Phys. Fluids, 20, 123302 (2008).

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

    NASA Astrophysics Data System (ADS)

    Doronzo, Domenico M.; Dellino, Pierfrancesco

    2014-05-01

    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.

  10. How long do U-shaped valleys last? The lifespan of glacial topography set by tectonics.

    NASA Astrophysics Data System (ADS)

    Prasicek, Günther; Larsen, Isaac; Montgomery, David

    2015-04-01

    More than 10 kyr after the last major glaciation the topography of mountain ranges world-wide remains dominated by characteristic glacial landforms such as U-shaped valleys, but the transition from a glacial to a fluvial landscape is poorly constrained and it remains unclear how long glacial morphology persists following deglaciation. The longevity of glacial topography influences glacial extent and erosion in subsequent glaciations and hence the cumulative impact of Pleistocene glacial cycles on the evolution of mountain ranges. We tested whether tectonic forcing and erosional response control the timescale over which glacial topography persists into inter-glacial periods in the western Southern Alps of New Zealand and other mountain ranges worldwide, including the syntaxes of the Himalaya and Taiwan. We quantified the degree of glacial imprint by exploiting the conventional interpretation of V-shaped fluvial and U-shaped glacial valleys. Valley cross sections were automatically extracted from digital terrain models and power-laws were fitted to each cross section to quantify the shape of the valley flanks. A power-law exponent of 1 characterizes the straight valley flanks of a V-shaped cross section and greater exponents are indicative of progressively more U-shaped valleys. Our results show that tectonic forcing is a first-order control on landscape evolution and on the persistence of glacial morphology worldwide. In Earth's most rapidly uplifting mountain ranges the lifespan of glacial topography is on the order of one interglacial period, preventing the development of a cumulative glacial signal. In contrast, in most alpine landscapes more than 100 kyr are required for the transformation from glacial back to fluvial topography and glacial landforms have not or have only partially been erased during the current interglacial. Thus we suggest, emphasizing the influence of glacially preconditioned topography on glacial extent and erosion, that tectonic forcing governs the impact of climate depressions on active orogens beyond controlling their vertical extent, by also altering the spatial and temporal pattern of erosion during subsequent glacial periods via a link between rock uplift and valley cross-sectional shape.

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

    PubMed Central

    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

    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

  12. Sounds and silence: An optical topography study of language recognition at birth

    NASA Astrophysics Data System (ADS)

    Peña, Marcela; Maki, Atsushi; Kovaic, Damir; Dehaene-Lambertz, Ghislaine; Koizumi, Hideaki; Bouquet, Furio; Mehler, Jacques

    2003-09-01

    Does the neonate's brain have left hemisphere (LH) dominance for speech? Twelve full-term neonates participated in an optical topography study designed to assess whether the neonate brain responds specifically to linguistic stimuli. Participants were tested with normal infant-directed speech, with the same utterances played in reverse and without auditory stimulation. We used a 24-channel optical topography device to assess changes in the concentration of total hemoglobin in response to auditory stimulation in 12 areas of the right hemisphere and 12 areas of the LH. We found that LH temporal areas showed significantly more activation when infants were exposed to normal speech than to backward speech or silence. We conclude that neonates are born with an LH superiority to process specific properties of speech.

  13. The decay of the spectrum of the gravitational potential and the topography for the earth

    NASA Technical Reports Server (NTRS)

    Rapp, R. H.

    1989-01-01

    The spectrum of the earth's gravitational potential and topography, as represented by spherical harmonic expansions to degree 180, have been computed. Modeling the decay in the form of (A x l) exp-Beta, values of A and Beta for several degree (l) ranges were computed. For degree range 5-180, Beta was 2.54 for the potential and 2.16 for equivalent rock topography. The potential decay was somewhat slower than that implied by Kaula's rule. However, at high degree ranges, the Beta values were larger agreeing better with recent determinations from terrestrial gravity data and geoid undulations implied by satellite altimetric data. The values imply that the potential decays faster at higher l values.

  14. The Effect of Nano-Scale Topography on Keratinocyte Phenotype and Wound Healing Following Burn Injury

    PubMed Central

    Rea, Suzanne M.; Stevenson, Andrew W.; Wood, Fiona M.; Fear, Mark W.

    2012-01-01

    Topographic modulation of tissue response is an important consideration in the design and manufacture of a biomaterial. In developing new tissue therapies for skin, all levels of architecture, including the nanoscale need to be considered. Here we show that keratinocyte phenotype is affected by nanoscale changes in topography with cell morphology, proliferation, and migration influenced by the pore size in anodic aluminum oxide membranes. A membrane with a pore size of 300?nm, which enhanced cell phenotype in vitro, was used as a dressing to cover a partial thickness burn injury in the pig. Wounds dressed with the membrane showed evidence of advanced healing with significantly less organizing granulation tissue and more mature epidermal layers than control wounds dressed with a standard burns dressing. The results demonstrate the importance of nanoscale topography in modulating keratinocyte phenotype and skin wound healing. PMID:21988618

  15. Gravity/topography admittance inversion on Venus using niching genetic algorithms

    NASA Astrophysics Data System (ADS)

    Lawrence, Kristin P.; Phillips, Roger J.

    2003-10-01

    We used niching genetic algorithms (NGAs) to invert localized Venus gravity/topography admittance over lowland regions Atalanta and Lavinia Planitiae, as well as volcanic rise Atla Regio for comparison. Assuming both top (topography) and bottom (mantle density anomalies) loads, we calculated theoretical admittance using thin elastic shell models. We inverted admittance for crustal thickness, elastic lithosphere thickness, mantle density anomaly thickness, and ratio (pz) of mantle density anomaly to topographic load. NGA inversion provides an efficient means of finding globally optimal and sub-optimal solutions. Error analyses of all three regions show that pz is a robust estimate; there is significant trade-off between elastic lithosphere and mantle anomaly thicknesses, while crustal thickness is ill-constrained. Optimal models suggest that mantle density anomalies are ~+1 to 2% underlying lowland regions and ~-3 to -4% underlying Atla Regio.

  16. Assimilation of geodetic dynamic ocean topography with ensemble based Kalman filter

    NASA Astrophysics Data System (ADS)

    Janjic, T.; Albertella, A.; Schroeter, J.; Savcenko, R.; Rummel, R.; Bosch, W.

    2012-04-01

    We use the geodetic method to obtain the dynamical ocean topography (DOT). This method combines the multi-mission-altimeter sea surface height and the GRACE/GOCE gravity field. Using the new global filtering approach, the spectral consistency of both fields is achieved by filtering the sea surface height and the geoid. The new global filtering approach reduces the artificats near the coast lines. Further, results of assimilation of multi-mission-altimeter data and the GRACE/GOCE gravity data into the finite element ocean model (FEOM) are investigated. By assimilating only absolute dynamical topography data using the ensemble Kalman filter and time varying observation error covariances, we were able to improve modeled fields. Results are closer to observations which were not used for assimilation and lie outside the area covered by altimetry in the Southern Ocean (e.g. temperature of surface drifters or deep temperatures in the Weddell Sea area.)

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

    NASA Astrophysics Data System (ADS)

    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

    2014-07-01

    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.

  18. Surface topography regulates wnt signaling through control of primary cilia structure in mesenchymal stem cells

    PubMed Central

    McMurray, R. J.; Wann, A. K. T.; Thompson, C. L.; Connelly, J. T.; Knight, M. M.

    2013-01-01

    The primary cilium regulates cellular signalling including influencing wnt sensitivity by sequestering ?-catenin within the ciliary compartment. Topographic regulation of intracellular actin-myosin tension can control stem cell fate of which wnt is an important mediator. We hypothesized that topography influences mesenchymal stem cell (MSC) wnt signaling through the regulation of primary cilia structure and function. MSCs cultured on grooves expressed elongated primary cilia, through reduced actin organization. siRNA inhibition of anterograde intraflagellar transport (IFT88) reduced cilia length and increased active nuclear ?-catenin. Conversely, increased primary cilia assembly in MSCs cultured on the grooves was associated with decreased levels of nuclear active ?-catenin, axin-2 induction and proliferation, in response to wnt3a. This negative regulation, on grooved topography, was reversed by siRNA to IFT88. This indicates that subtle regulation of IFT and associated cilia structure, tunes the wnt response controlling stem cell differentiation. PMID:24346024

  19. Buried topography of Utopia, Mars - Persistence of a giant impact depression

    NASA Astrophysics Data System (ADS)

    McGill, G. E.

    1989-03-01

    Knobs, partially buried craters, ring fractures, and some mesas permit a qualitative determination of the topography buried beneath younger northern plains materials. These features are widely distributed in the Utopia area but are absent in a large, roughly circular region centered at about 48 deg N, 240 deg W. This implies the existence of a circular depression about 3300 km in diameter buried beneath Utopia Planitia that is interpreted to represent the central part of a very large impact basin. The presence of buried curved massifs around part of this depression, and a roughly coincident mascon, lend further support. Present topography, areal geology, and paleotopography of buried surfaces all point to the persistence of this major depression for almost the entire history of Mars.

  20. X-ray topography of a natural twinned diamond of unusual pseudo-tetrahedral morphology

    NASA Astrophysics Data System (ADS)

    Fritsch, Emmanuel; Moore, Moreton; Rondeau, Benjamin; Waggett, Richard G.

    2005-06-01

    The internal morphology of a natural twinned diamond was investigated using X-ray section topography. The diamond consisted of two crystals joined along a {1 1 1} plane whose remote ends were triangular {1 1 1} faces with sizes approximately 4 mm on the edge. A coating of fibrous growth obscured the morphology of the good quality diamond inside. Although the coat displayed re-entrant surfaces near the twin plane along three edges of the crystal, X-ray topography showed the inner crystal to protrude outwards along these same edges. The good quality inner core displayed the classical "spinel law" twinned octahedral morphology whereas the fibrous rim showed a typical sphalerite-like twinned tetrahedral morphology. A possible growth mechanism which could account for this is discussed.

  1. Relationship Between Patterned Wafer Topography Evolution and STI CMP Motor Current Endpoint Signals

    Microsoft Academic Search

    D. Boning; X. Xie; J. Sorooshian; A. Philipossian; D. Stein; D. Hetherington

    Chemical Mechanical Planarization (CMP) has become the enabling planarization method for Shallow Trench Isolation (STI) in sub-0.25 micrometer technologies. While CMP is able to reduce topography over longer lateral distances than earlier techniques, it continues to suffer from pattern dependencies that can result in dishing and erosion in STI structures. This shortcoming becomes dramatically worse with substantial over-polish times, thereby

  2. Topography adjacent to Signal Corps Radar (S.C.R.) 296 Station 5, ...

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

    Topography adjacent to Signal Corps Radar (S.C.R.) 296 Station 5, showing conditions before construction, May 28, 1943, this drawing shows the Bonita Ridge access road retaining wall and general conditions at Bonita Ridge before the construction of Signal Corps Radar (S.C.R.) 296 Station 5 - Fort Barry, Signal Corps Radar 296, Station 5, Transmitter Building Foundation, Point Bonita, Marin Headlands, Sausalito, Marin County, CA

  3. Mare Crisium area topography - A comparison of earth-based radar and Apollo mapping camera results

    NASA Technical Reports Server (NTRS)

    Zisk, S.

    1978-01-01

    An earth-based radar topography (ERT) map has been constructed of the Mare Crisium area. Systematic and random sources of error are discussed. A comparison between the ERT map and Lunar Topographic Orthophotomaps shows a random mean discrepancy of less than 100 m between the two maps, except for small-scale (20 km or less in diameter) features, where systematic smoothing reduces the ERT elevation contrast

  4. Functional networks in motor sequence learning: abnormal topographies in Parkinson's disease.

    PubMed

    Nakamura, T; Ghilardi, M F; Mentis, M; Dhawan, V; Fukuda, M; Hacking, A; Moeller, J R; Ghez, C; Eidelberg, D

    2001-01-01

    We examined the neural circuitry underlying the explicit learning of motor sequences in normal subjects and patients with early stage Parkinson's disease (PD) using 15O-water (H2 15O) positron emission tomography (PET) and network analysis. All subjects were scanned while learning motor sequences in a task emphasizing explicit learning, and during a kinematically controlled motor execution reference task. Because different brain networks are thought to subserve target acquisition and retrieval during motor sequence learning, we used separate behavioral indices to quantify these aspects of learning during the PET experiments. In the normal cohort, network analysis of the PET data revealed a significant covariance pattern associated with acquisition performance. This topography was characterized by activations in the left dorsolateral prefrontal cortex (PFdl), rostral supplementary motor area (preSMA), anterior cingulate cortex, and in the left caudate/putamen. A second independent covariance pattern was associated with retrieval performance. This topography was characterized by bilateral activations in the premotor cortex (PMC), and in the right precuneus and posterior parietal cortex. The normal learning-related topographies failed to predict acquisition performance in PD patients and predicted retrieval performance less accurately in the controls. A separate network analysis was performed to identify discrete learning-related topographies in the PD cohort. In PD patients, acquisition performance was associated with a covariance pattern characterized by activations in the left PFdl, ventral prefrontal, and rostral premotor regions, but not in the striatum. Retrieval performance in PD patients was associated with a covariance pattern characterized by activations in the right PFdl, and bilaterally in the PMC, posterior parietal cortex, and precuneus. These results suggest that in early stage PD sequence learning networks are associated with additional cortical activation compensating for abnormalities in basal ganglia function. PMID:11198104

  5. Relationship between ocean velocity and motionally induced electrical signals: 2. In the presence of sloping topography

    Microsoft Academic Search

    Zoltan B. Szuts

    2010-01-01

    Motionally induced electric fields and electric currents in the ocean depend to first order solely on the vertical dimension. We investigate the significance of two-dimensional (2-D) perturbations that arise in the presence of sloping topography. The full electric response is calculated for a schematic geometry that contains a topographic slope, has a two-layer ocean with a layer of sediment beneath,

  6. ATM Coastal Topography-Louisiana, 2001: UTM Zone 15 (Part 1 of 2)

    USGS Publications Warehouse

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

    2010-01-01

    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 a portion of the Louisiana coastline beach face within UTM Zone 15, from Isles Dernieres to Grand Isle, acquired September 7 and 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.

  7. ATM Coastal Topography - Louisiana, 2001: UTM Zone 16 (Part 2 of 2)

    USGS Publications Warehouse

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

    2009-01-01

    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 a portion of the Louisiana coastline beach face within UTM Zone 16, from Grand Isle to the Chandeleur Islands, acquired September 7 and 9, 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.

  8. Quantifying rapid changes in coastal topography using modern mapping techniques and GIS

    Microsoft Academic Search

    HELENA MITASOVA; THOMAS G. DRAKE; DAVID BERNSTEIN

    ABSTRACT Innovative methodology based on a combination of Real Time Kinematic GPS (RTK-GPS), lidar, and open source GIS was developed to gain a better understanding of rapid changes in coastal topography. Improved spatial interpolation techniques were implemented,to produce detailed topographic surfaces from lidar and RTK-GPS data. The methodology,is demonstrated for two North Carolina areas: Jockey's Ridge State Park, and Bald

  9. Neolithic settlement distributions as a function of sea level controlled topography in the Yangtze delta, China

    Microsoft Academic Search

    Daniel Jean Stanley; Zhongyuan Chen

    1996-01-01

    Combined geological and archaeological data sets indicate that sea level controlled topography best explains the timing of Neolithic settlement onto the southern Yangtze delta plain, almost 1500 yr later than inland China. Information on settlement patterns of the three major Neolithic cultures (Ma-Jia-Bang, Song-Ze, Liang-Zhu), dated from ca. 5500 to 2200 B.C., is provided by petrologic study of habitat bases

  10. Promoting scientific collaboration and research through integrated social networking capabilities within the OpenTopography Portal

    Microsoft Academic Search

    V. Nandigam; C. J. Crosby; C. Baru

    2009-01-01

    LiDAR (Light Distance And Ranging) topography data offer earth scientists the opportunity to study the earth's surface at very high resolutions. As a result, the popularity of these data is growing dramatically. However, the management, distribution, and analysis of community LiDAR data sets is a challenge due to their massive size (multi-billion point, mutli-terabyte). We have also found that many

  11. Australian plate motion and topography linked to fossil New Guinea slab below Lake Eyre

    NASA Astrophysics Data System (ADS)

    Schellart, W. P.; Spakman, W.

    2015-07-01

    Unravelling causes for absolute plate velocity change and continental dynamic topography change is challenging because of the interdependence of large-scale geodynamic driving processes. Here, we unravel a clear spatio-temporal relation between latest Cretaceous-Early Cenozoic subduction at the northern edge of the Australian plate, Early Cenozoic Australian plate motion changes and Cenozoic topography evolution of the Australian continent. We present evidence for a ?4000 km wide subduction zone, which culminated in ophiolite obduction and arc-continent collision in the New Guinea-Pocklington Trough region during subduction termination, coinciding with cessation of spreading in the Coral Sea, a ?5 cm/yr decrease in northward Australian plate velocity, and slab detachment. Renewed northward motion caused the Australian plate to override the sinking subduction remnant, which we detect with seismic tomography at 800-1200 km depth in the mantle under central-southeast Australia at a position predicted by our absolute plate reconstructions. With a numerical model of slab sinking and mantle flow we predict a long-wavelength subsidence (negative dynamic topography) migrating southward from ?50 Ma to present, explaining Eocene-Oligocene subsidence of the Queensland Plateau, ?330 m of late Eocene-early Oligocene subsidence in the Gulf of Carpentaria, Oligocene-Miocene subsidence of the Marion Plateau, and providing a first-order fit to the present-day, ?200 m deep, topographic depression of the Lake Eyre Basin and Murray-Darling Basin. We propound that dynamic topography evolution provides an independent means to couple geological processes to a mantle reference frame. This is complementary to, and can be integrated with, other approaches such as hotspot and slab reference frames.

  12. Sensitivity of SS precursors to topography on the upper-mantle 660-km discontinuity

    Microsoft Academic Search

    Emmanuel Chaljub; Albert Tarantola

    1997-01-01

    The sensitivity of SS precursors to the presence of topography on the 660-km discontinuity is addressed using an axisymmetric finite difference approximation to the SH wave propagation in the Earth mantle. Numerical experiments are lead to quantify the bias in both wavelength and amplitude committed in estimating depth information on the upper-mantle discontinuities from ray inversion of SdS arrival times.

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

    Microsoft Academic Search

    Christopher Crosby; Viswanath Nandigam; Ramon Arrowsmith; Chaitan Baru

    2010-01-01

    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

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

    Microsoft Academic Search

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

    1994-01-01

    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

  15. Determination of surface roughness and topography of dental resin-based nanocomposites using AFM analysis

    PubMed Central

    Lainovi?, Tijana; Viloti?, Marko; Blaži?, Larisa; Kakaš, Damir; Markovi?, Dubravka; Ivaniševi?, Aljoša

    2013-01-01

    The aim of this study was to determine surface roughness and topography of polished dental resin-based nanocomposites. Four representative dental resin-based nanocomposites were tested in the study: two nanohybrids (Filtek Z550 and Tetric EvoCeram) and two nanofilled (Filtek Ultimate Body and Filtek Ultimate Translucent); and two reference materials: one microfilled (Gradia Direct) and one microhybrid (Filtek Z250). Polymerized cylindrical specimens (4 mm x 2 mm) were polished with multi-step polishing system-Super Snap. Immediately after the polishing, topography of each specimen was examined by Veeco di CP-II Atomic Force Microscope. Specimen’s surface has been scanned in 6 points in contact mode with CONT20A-CP tips. 1 Hz scan rate and 256 x 256 resolution were used to obtain topography on a 90 ?m x 90 ?m scanning area. Measured topography data were processed by Image Processing and Data Analysis V2.1.15 software. Following parameters were compared among specimens: average roughness and maximum peak-to-valley distance. All of the tested materials had similar average surface roughness after finishing and polishing procedure. The lowest values occurred in the material Filtek Ultimate Body, and the highest in the Filtek Z550. When interpreting maximum peak-to-valley distance the larger differences in values (up to 100%) occurred in Filtek Z550, Filtek Z250 and Filtek Ultimate Body, which is a result of the deep polishing channels and tracks. Type, size, distribution of fillers and filler loading in tested materials, didn’t influence average roughness values, but had an impact on maximum peak-to-valley distance values. PMID:23448609

  16. Retrieving 3-D Topography by Using a Single-Antenna Squint-Mode Airborne SAR

    Microsoft Academic Search

    Oleksandr O. Bezvesilniy; Ievgeniia V. Dukhopelnykova; Volodymyr V. Vynogradov; Dmytro M. Vavriv

    2007-01-01

    In this paper, a novel method is proposed for retrieving 3-D topography of the ground surface by using a single-antenna squint-mode airborne synthetic aperture radar (SAR). The main idea of the method is based on the fact that the spatial 3-D location of a target can be found as the intersection of the range sphere, the Doppler cone, and the

  17. Winds on Mars during the Viking season - Predictions based on a general circulation model with topography

    Microsoft Academic Search

    J. B. Pollack; C. B. Leovy; Y. H. Mintz; W. van Camp

    1976-01-01

    The Arakawa-Mintz general circulation model of the earth has been applied to Mars at the season of the Viking Lander mission. Allowance has been made for the effects of the large Martian topography. The calculated wind fields exhibit significant zonally symmetric, topographically forced, and diurnal tidal components. Average wind speeds of 20-25 m\\/sec were found at three possible landing sites,

  18. Fabrication of microfluidic mixers with varying topography in glass using the powder-blasting process

    Microsoft Academic Search

    Abdeljalil Sayah; Pierre-Antoine Thivolle; Virendra K. Parashar; Martin A. M. Gijs

    2009-01-01

    The powder-blasting method is used to fabricate structures with a three-dimensional topography in glass using elastomeric masks. The relation between the mask opening width and the erosion depth is exploited to fabricate microstructures with varying depth in a single micropatterning step. As an application, planar three-dimensional micro-mixers were fabricated, which consist of a repeating convergent microfluidic nozzle structure. Three different

  19. A topography-based scaling algorithm for soil hydraulic parameters at hillslope scales: Field testing

    NASA Astrophysics Data System (ADS)

    Jana, Raghavendra B.; Mohanty, Binayak P.

    2012-02-01

    Soil hydraulic parameters were upscaled from a 30 m resolution to a 1 km resolution using a new aggregation scheme (described in the companion paper) where the scale parameter was based on the topography. When soil hydraulic parameter aggregation or upscaling schemes ignore the effect of topography, their application becomes limited at hillslope scales and beyond, where topography plays a dominant role in soil deposition and formation. Hence the new upscaling algorithm was tested at the hillslope scale (1 km) across two locations: (1) the Little Washita watershed in Oklahoma, and (2) the Walnut Creek watershed in Iowa. The watersheds were divided into pixels of 1 km resolution and the effective soil hydraulic parameters obtained for each pixel. Each pixel/domain was then simulated using the physically based HYDRUS-3-D modeling platform. In order to account for the surface (runoff/on) and subsurface fluxes between pixels, an algorithm to route infiltration-excess runoff onto downstream pixels at daily time steps and to update the soil moisture states of the downstream pixels was applied. Simulated soil moisture states were compared across scales, and the coarse scale values compared against the airborne soil moisture data products obtained during the hydrology experiment field campaign periods (SGP97 and SMEX02) for selected pixels with different topographic complexities, soil distributions, and land cover. Results from these comparisons show good correlations between simulated and observed soil moisture states across time, topographic variations, location, elevation, and land cover. Stream discharge comparisons made at two gauging stations in the Little Washita watershed also provide reasonably good results as to the suitability of the upscaling algorithm used. Based only on the topography of the domain, the new upscaling algorithm was able to provide coarse resolution values for soil hydraulic parameters which effectively captured the variations in soil moisture across the watershed domains.

  20. A load distribution model for hypoid gears using ease-off topography and shell theory

    Microsoft Academic Search

    M. Kolivand; A. Kahraman

    2009-01-01

    A computationally efficient load distribution model is proposed for both face-milled and face-hobbed hypoid gears produced by Formate and generate processes. Tooth surfaces are defined directly from the cutter parameters and machine settings. A novel methodology based on the ease-off topography is used to determine the unloaded contact patterns. The proposed ease-off methodology finds the instantaneous contact curve through a

  1. Global digital topography mapping with a synthetic aperture scanning radar altimeter

    NASA Technical Reports Server (NTRS)

    Elachi, C.; Im, K. E.; Rodriguez, E.

    1990-01-01

    Global digital topography data of the land surface is of importance in a variety of geoscientific and application disciplines. Such a database, with a spatial resolution of 150 to 500 m and height accuracy of 5 m or better can be acquired from an orbiting platform using a synthetic aperture scanning radar altimeter. Near-global coverage can be achieved within 14 days from an orbiting platform in a polar or near-polar orbit.

  2. Combining altimetric\\/gravimetric and ocean model mean dynamic topography models in the GOCINA region

    Microsoft Academic Search

    Per Knudsen; Ole B. Andersen; René Forsberg; Henning P. Föh; Arne V. Olesen; Anne L. Vest; Dag Solheim; Ove D. Omang; Roger Hipkin; Addisu Hunegnaw; Keith Haines; Rory Bingham; Jean-Philippe Drecourt; Johnny A. Johannessen; Helge Drange; Frank Siegismund; Fabrice Hernandez; Gilles Larnicol; Marie-Helene Rio; Philippe Schaeffer

    Initially, existing mean dynamic topography (MDT) models were collected and reviewed. The models were corrected for the differences\\u000a in averaging period using the annual anomalies computed from satellite altimetry. Then a composite MDT was derived as the\\u000a mean value in each grid node together with a standard deviation to represent its error. A new synthetic MDT was obtained from\\u000a the

  3. Global rate and spectral characteristics of internal gravity wave generation by geostrophic flow over topography

    NASA Astrophysics Data System (ADS)

    Scott, R. B.; Goff, J. A.; Naveira Garabato, A. C.; Nurser, A. J. G.

    2011-09-01

    The rate of generation of internal gravity waves in the lee of small length scale topography by geostrophic flow in the World Ocean was estimated using linear theory with corrections for finite amplitude topography. Several global data sets were combined for the calculation including an ocean circulation model for the near-bottom geostrophic flow statistics, over 500 abyssal current meter records, historical climatological data for the buoyancy frequency, and two independent estimates of the small scale topographic statistical properties. The first topography estimate was based on an empirically-derived relationship between paleo-spreading rates and abyssal hill roughness, with corrections for sedimentation. The second estimate was based on small-scale (<100 km) roughness of satellite altimetry-derived gravity field, using upward continuation relationships to derive estimates of abyssal hill roughness at the seafloor at scales less than approximately 20 km. The lee wave generation rate was found to be between 0.34 to 0.49 TW. The Southern Hemisphere produced 92% of the lee wave energy, with the Southern Ocean dominating. Strength of the bottom flow was the most important factor in producing the global pattern of generation rate, except in the Indian Ocean where extremely rough topography produced strong lee wave generation despite only moderate bottom flows. The results imply about one half of the mechanical power input to the ocean general circulation from the extra-equatorial wind stress of the World Ocean results from abyssal lee wave generation. Topographic length scales between 176 m and 2.5 km (horizontal wavelengths between 1 and 16 km) accounted for 90% of the globally integrated generation.

  4. Dependence of Eemian Greenland temperature reconstructions on the ice sheet topography

    NASA Astrophysics Data System (ADS)

    Merz, Niklaus; Born, Andreas; Raible, Christoph; Fischer, Hubertus; Stocker, Thomas

    2014-05-01

    The impact of a reduced Greenland ice sheet (GrIS) on Greenland's surface climate during the Eemian interglacial is investigated employing the CCSM4 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 driven by changes in the surface energy balance. 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 increased 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 results have implications for the interpretation of Eemian temperature reconstructions based on Greenland proxy archives such as the NEEM ice core. Changing the GrIS topography acts as a local forcing for Greenland's climate, whereas the effect on the climate outside of Greenland is small and mostly negligible. 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 linked to large-scale climate variations.

  5. Project GEOS-C. [designed to measure the topography of ocean surface and the sea state

    NASA Technical Reports Server (NTRS)

    1975-01-01

    An oceanographic-geodetic satellite, designated Geodynamics Experimental Ocean Satellite-C (GEOS-C), an earth-orbiting spacecraft designed to measure precisely the topography of the ocean surface and the sea state (wave height, wave period, wave propagation direction) is described. Launch operations, spacecraft description, and mission objectives are included along with a brief flight history of the NASA satellite geodesy program. Principal investigations to be performed by the GEOS-C mission are discussed.

  6. EAARL Coastal Topography-Western Florida, Post-Hurricane Charley, 2004: First Surface

    USGS Publications Warehouse

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

    2009-01-01

    This DVD contains lidar-derived first-surface (FS) topography GIS datasets of a portion of the western Florida coastline beachface, acquired post-Hurricane Charley on August 16 and 18, 2004. Click on a tile number (1 - 68) to view the corresponding 1-meter-resolution images and links to each data directory. Click on the red tile in the index map to view the 3-meter-resolution mosaic and link to the corresponding directory.

  7. Cell surface topography is a regulator of molecular interactions during chemokine-induced neutrophil spreading.

    PubMed

    Lomakina, Elena B; Marsh, Graham; Waugh, Richard E

    2014-09-16

    Adhesive interactions between neutrophils and endothelium involve chemokine-induced neutrophil spreading and subsequent crawling on the endothelium to sites of transmigration. We investigated the importance of cell topography in this process using immunofluorescence, scanning electron microscopy, and live-cell imaging using total internal reflectance microscopy to observe redistribution of key membrane proteins, both laterally and relative to surface topography, during neutrophil spreading onto glass coated with interleukin 8. During formation of the lamellipod, L-selectin is distributed on microvilli tips along the top of the lamellipodium, whereas the interleukin 8 receptors CXCR1 and CXCR2 and the integrin LFA-1 (?L?2) were present at the interface between the lamellipodium and the substrate. Total internal reflection fluorescence imaging indicated that LFA-1 and both chemokine receptors redistributed into closer contact with the substrate as the cells spread onto the surface and remodeled their topography. A geometric model of the surface remodeling with nonuniform distribution of molecules and a realistic distribution of microvilli heights was matched to the data, and the fits indicated a 1000-fold increase in the concentration of chemokine receptors and integrins available for bond formation at the interface. These observations imply that topographical remodeling is a key mechanism for regulating cell adhesion and surface-induced activation of cells. PMID:25229138

  8. Integrated Analysis of Climate, Soil, Topography and Vegetative Growth in Iberian Viticultural Regions

    PubMed Central

    Fraga, Helder; Malheiro, Aureliano C.; Moutinho-Pereira, José; Cardoso, Rita M.; Soares, Pedro M. M.; Cancela, Javier J.; Pinto, Joaquim G.; Santos, João A.

    2014-01-01

    The Iberian viticultural regions are convened according to the Denomination of Origin (DO) and present different climates, soils, topography and management practices. All these elements influence the vegetative growth of different varieties throughout the peninsula, and are tied to grape quality and wine type. In the current study, an integrated analysis of climate, soil, topography and vegetative growth was performed for the Iberian DO regions, using state-of-the-art datasets. For climatic assessment, a categorized index, accounting for phenological/thermal development, water availability and grape ripening conditions was computed. Soil textural classes were established to distinguish soil types. Elevation and aspect (orientation) were also taken into account, as the leading topographic elements. A spectral vegetation index was used to assess grapevine vegetative growth and an integrated analysis of all variables was performed. The results showed that the integrated climate-soil-topography influence on vine performance is evident. Most Iberian vineyards are grown in temperate dry climates with loamy soils, presenting low vegetative growth. Vineyards in temperate humid conditions tend to show higher vegetative growth. Conversely, in cooler/warmer climates, lower vigour vineyards prevail and other factors, such as soil type and precipitation acquire more important roles in driving vigour. Vines in prevailing loamy soils are grown over a wide climatic diversity, suggesting that precipitation is the primary factor influencing vigour. The present assessment of terroir characteristics allows direct comparison among wine regions and may have great value to viticulturists, particularly under a changing climate. PMID:25251495

  9. Design and construction of a novel tribometer with online topography and wear measurement

    SciTech Connect

    Korres, Spyridon; Dienwiebel, Martin [Karlsruhe Institute of Technology, IZBS, Kaiserstr. 12, 76131 Karlsruhe (Germany) and Fraunhofer-Institute for Mechanics of Materials IWM, Woehlerstr. 11, 79108 Freiburg (Germany)

    2010-06-15

    We present a novel experimental platform that links topographical and material changes with the friction and wear behavior of oil-lubricated metal surfaces. This concept combines state-of-the-art methods for the analysis of the surface topography on the micro- and nanoscale with the online measurement of wear. At the same time, it allows for frictional and lateral force detection. Information on the topography of one of the two surfaces is gathered in situ with a three-dimensional (3D) holography microscope at a maximum frequency of 15 frames/s and higher resolution images are provided at defined time intervals by an atomic force microscope. The wear measurement is conducted online by means of radio nuclide technique. The quantitative measurement of the lateral and frictional forces is conducted with a custom-built 3D force sensor. The surfaces can be lubricated with an optically transparent oil or water. The stability and precision of the setup have been tested in a model experiment. The results show that the exact same position can be relocated and examined after each load cycle. Wear and topography measurements were performed with a radioactive labeled iron pin sliding against an iron plate.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    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.

  11. Surface undulations of Antarctic ice streams tightly controlled by bedrock topography

    NASA Astrophysics Data System (ADS)

    De Rydt, J.; Gudmundsson, G. H.; Corr, H. F. J.; Christoffersen, P.

    2013-03-01

    Full Stokes flow-line models predict that fast-flowing ice streams transmit information about their bedrock topography most efficiently to the surface for basal undulations with length scales between 1 and 20 times the mean ice thickness. This typical behaviour is independent of the precise values of the flow law and sliding law exponents, and should be universally observable. However, no experimental evidence for this important theoretical prediction has been obtained so far, hence ignoring an important test for the physical validity of current-day ice flow models. In our work we use recently acquired airborne radar data for the Rutford Ice Stream and Evans Ice Stream, and we show that the surface response of fast-flowing ice is highly sensitive to bedrock irregularities with wavelengths of several ice thicknesses. The sensitivity depends on the slip ratio, i.e. the ratio between mean basal sliding velocity and mean deformational velocity. We find that higher values of the slip ratio generally lead to a more efficient transfer, whereas the transfer is significantly dampened for ice that attains most of its surface velocity by creep. Our findings underline the importance of bedrock topography for ice stream dynamics on spatial scales up to 20 times the mean ice thickness. Our results also suggest that local variations in the flow regime and surface topography at this spatial scale cannot be explained by variations in basal slipperiness.

  12. Surface undulations of Antarctic ice streams tightly controlled by bedrock topography

    NASA Astrophysics Data System (ADS)

    De Rydt, Jan; Hilmar Gudmundsson, G.; Corr, Hugh F. G.; Christoffersen, Poul

    2013-04-01

    Ice dynamics models predict that fast-flowing ice streams transmit information about their bedrock topography most efficiently to the surface for basal undulations with length scales between 1 and 20 times the mean ice thickness. This typical behaviour is independent on the precise values of the flow law and sliding law exponents, and should be universally observable. However, no experimental evidence for this important theoretical prediction has been obtained so far, hence ignoring an important test for the physical validity of current-day ice flow models. In our work we use recently acquired airborne radar data for the Rutford Ice Stream and Evans Ice Stream, and we show that the surface response of fast-flowing ice is highly sensitive to bedrock irregularities with wavelengths of several ice thicknesses. The sensitivity depends on the slip ratio, i.e., the ratio between mean basal sliding velocity and mean deformational velocity. We find that higher values of the slip ratio generally lead to a more efficient transfer, whereas the transfer is significantly dampened for ice that attains most of its surface velocity by creep. Our findings underline the importance of bedrock topography for ice stream dynamics on spatial scales up to 20 times the mean ice thickness. Our results also suggest that local variations in the flow regime and surface topography at this spatial scale cannot be explained by variations in basal slipperiness.

  13. Spatial cross-correlation of Antarctic Sea ice and seabed topography

    NASA Technical Reports Server (NTRS)

    Deveaux, Richard D.; Phelan, Michael J.

    1990-01-01

    A time series of derived sea ice concentrations as observed about Antarctica by the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) satellite in 1983 is considered. The degree of spatial cross correlation between these data and seabed topography is quantified. The approach is to implement a statistical image processing filter designed to extract local patterns of spatial cross correlation over the entire sea ice field as it undergoes daily changes. Throughout the sea ice, it was found that large scale variations in sea ice concentration correlate systematically with variations in the topography of the seabed. Generally speaking, high concentrations of sea ice occur over deep ocean, whereas areas of encavement, early dissipation and polynya formation develop over topographic features of high elevation. The latter was studied in detail with respect to the features Maud Rise, Astrid Ridge and the continental shelf in the Cosmonaut and Ross Seas. In each case, it is shown that an encavement in sea ice, a polynya, or both develops in the vicinity of the feature in question. As these results are quantified in terms of spatial cross correlation, a potential role is inferred for seabed topography in such fluctuations in the sea ice about Antarctica.

  14. Land cover and topography affect the land transformation caused by wind facilities.

    PubMed

    Diffendorfer, Jay E; Compton, Roger W

    2014-01-01

    Land transformation (ha of surface disturbance/MW) associated with wind facilities shows wide variation in its reported values. In addition, no studies have attempted to explain the variation across facilities. We digitized land transformation at 39 wind facilities using high resolution aerial imagery. We then modeled the effects of turbine size, configuration, land cover, and topography on the levels of land transformation at three spatial scales. The scales included strings (turbines with intervening roads only), sites (strings with roads connecting them, buried cables and other infrastructure), and entire facilities (sites and the roads or transmission lines connecting them to existing infrastructure). An information theoretic modeling approach indicated land cover and topography were well-supported variables affecting land transformation, but not turbine size or configuration. Tilled landscapes, despite larger distances between turbines, had lower average land transformation, while facilities in forested landscapes generally had the highest land transformation. At site and string scales, flat topographies had the lowest land transformation, while facilities on mesas had the largest. The results indicate the landscape in which the facilities are placed affects the levels of land transformation associated with wind energy. This creates opportunities for optimizing wind energy production while minimizing land cover change. In addition, the results indicate forecasting the impacts of wind energy on land transformation should include the geographic variables affecting land transformation reported here. PMID:24558449

  15. Accurate acoustic and elastic beam migration without slant stack for complex topography

    NASA Astrophysics Data System (ADS)

    Huang, Jianping; Yuan, Maolin; Liao, Wenyuan; Li, Zhenchun; Yue, Yubo

    2015-06-01

    Recent trends in seismic exploration have led to the collection of more surveys, often with multi-component recording, in onshore settings where both topography and subsurface targets are complex, leading to challenges for processing methods. Gaussian beam migration (GBM) is an alternative to single-arrival Kirchhoff migration, although there are some issues resulting in unsatisfactory GBM images. For example, static correction will give rise to the distortion of wavefields when near-surface elevation and velocity vary rapidly. Moreover, Green’s function compensated for phase changes from the beam center to receivers is inaccurate when receivers are not placed within some neighborhood of the beam center, that is, GBM is slightly inflexible for irregular acquisition system and complex topography. As a result, the differences of both the near-surface velocity and the surface slope from the beam center to the receivers and the poor spatial sampling of the land data lead to inaccuracy and aliasing of the slant stack, respectively. In order to improve the flexibility and accuracy of GBM, we propose accurate acoustic, PP and polarity-corrected PS beam migration without slant stack for complex topography. The applications of this method to one-component synthetic data from a 2D Canadian Foothills model and a Zhongyuan oilfield fault model, one-component field data and an unseparated multi-component synthetic data demonstrate that the method is effective for structural and relatively amplitude-preserved imaging, but significantly more time-consuming.

  16. Ground surface temperature scenarios in complex high-mountain topography based on regional climate model results

    NASA Astrophysics Data System (ADS)

    Salzmann, Nadine; NöTzli, Jeannette; Hauck, Christian; Gruber, Stephan; Hoelzle, Martin; Haeberli, Wilfried

    2007-06-01

    Climate change can have severe impacts on the high-mountain cryosphere, such as instabilities in rock walls induced by thawing permafrost. Relating climate change scenarios produced from global climate models (GCMs) and regional climate models (RCMs) to complex high-mountain environments is a challenging task. The qualitative and quantitative impact of changes in climatic conditions on local to microscale ground surface temperature (GST) and the ground thermal regime is not readily apparent. This study assesses a possible range of changes in the GST (?GST) in complex mountain topography. To account for uncertainties associated with RCM output, a set of 12 different scenario climate time series (including 10 RCM-based and 2 incremental scenarios) was applied to the topography and energy balance (TEBAL) model to simulate average ?GST for 36 different topographic situations. Variability of the simulated ?GST is related primarily to the emission scenarios, the RCM, and the approach used to apply RCM results to the impact model. In terms of topography, significant influence on GST simulation was shown by aspect because it modifies the received amount of solar radiation at the surface. North faces showed higher sensitivity to the applied climate scenarios, while uncertainties are higher for south faces. On the basis of the results of this study, use of RCM-based scenarios is recommended for mountain permafrost impact studies, as opposed to incremental scenarios.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  18. The fluctuating topography and acceleration statistics in a turbulent channel flow

    NASA Astrophysics Data System (ADS)

    Chiristos Vassilicos, John; Chen, Lu; Hu, Zhiwei

    2009-11-01

    Dallas, Vassilicos & Hewitt (PRE, 2009) characterised the turbulent channel flow topography of the fluctuating velocity field in terms of its stagnation points and quantified this topography by observing that, in the intermediate layer, the number density of stagnation points is inversely proportional to wall-distance. Our DNS of turbulent channel flow confirm this observation at skin friction Reynolds numbers 360 and 720. This spatial structure of the fluctuating velocity's topography partly determines the mean flow profile. We then study, in the intermediate layer, the motion of stagnation points which depends on the acceleration field. The mean streamwise acceleration equals the square of the skin friction velocity divided by the half width, the mean spanwise acceleration is zero and the mean wall-normal acceleration equals the vertical gradient of the mean square vertical fluctuating velocity. The local and convective acceleration terms tend to cancel each other and their rms values are equal only if the terms involving products of mean and fluctuating velocity terms are taken into account. When these terms are excluded, the rms of all three acceleration components are inversely proportional to wall-distance. Consequently,the rms of the streamwise stagnation point velocity is inversely proportional to wall-distance but the rms of this velocity's two other components are independent of it.

  19. Assimilation of geodetic dynamical ocean topography data into ocean circulation model

    NASA Astrophysics Data System (ADS)

    Janjic, Tijana; Schroeter, Jens; Albertella, Alberta; Bosch, Wolfgang; Rummel, Reiner; Savcenko, Roman

    Estimation of ocean circulation via assimilation of satellite measurements of dynamical ocean topography (DOT) into the global finite-element ocean model (FEOM) is investigated. The DOT was obtained by means of geodetic approach from carefully cross-calibrated multi-mission-altimeter data and GRACE gravity fields. The spectral consistency was achieved by means of the filtering applied on sea surface and geoid. Since the dynamical ocean topography is obtained from data types coming from different sources, different techniques can be employed for their assimilation into ocean circulation models. For example, the data can be combined and interpolated onto the model grid before they are used in assimilation. In this case special care needs to be taken concerning the specification of observational error statistics. The assimilation is performed by employing the local SEIK filter and various functions for observations error covariance are used. Finally we consider the effects of assimilation on potential temperature field and on steric height changes. Analysed potential temperature is compared with ARGO data. We also compared the standard deviation of the observations and standard deviation of the steric height calculated from the analysis. In many regions of the world ocean there is a good correspondence between these two fields. However also structures that are not present in the observations appear in the steric height standard deviations. Keywords: dynamical ocean topography, data assimilation Session: A2.6

  20. Integrated Analysis of Climate, Soil, Topography and Vegetative Growth in Iberian Viticultural Regions

    NASA Astrophysics Data System (ADS)

    Fraga, Helder; Malheiro, Aureliano C.; Moutinho-Pereira, José; Cardoso, Rita M.; Soares, Pedro M. M.; Cancela, Javier J.; Pinto, Joaquim G.; Santos, João A.

    2015-04-01

    The Iberian viticultural regions are convened according to the Denomination of Origin (DO) and present different climates, soils, topography and management practices. All these elements influence the vegetative growth of different varieties throughout the peninsula, and are tied to grape quality and wine type. In the current study, an integrated analysis of climate, soil, topography and vegetative growth was performed for the Iberian DO regions, using state-of-the-art datasets. For climatic assessment, a categorized index, accounting for phenological/thermal development, water availability and grape ripening conditions was computed. Soil textural classes were established to distinguish soil types. Elevation and aspect (orientation) were also taken into account, as the leading topographic elements. A spectral vegetation index was used to assess grapevine vegetative growth and an integrated analysis of all variables was performed. The results showed that the integrated climate-soil-topography influence on vine performance is evident. Most Iberian vineyards are grown in temperate dry climates with loamy soils, presenting low vegetative growth. Vineyards in temperate humid conditions tend to show higher vegetative growth. Conversely, in cooler/warmer climates, lower vigour vineyards prevail and other factors, such as soil type and precipitation acquire more important roles in driving vigour. Vines in prevailing loamy soils are grown over a wide climatic diversity, suggesting that precipitation is the primary factor influencing vigour. The present assessment of terroir characteristics allows direct comparison among wine regions and may have great value to viticulturists, particularly under a changing climate.